Vitamin D and Cardiometabolic Risk Factors and Diseases

1

Running title: Mousa, A., et al. Vitamin D and Cardiometabolic Syndrome

Vitamin D and Cardiometabolic Risk Factors and Diseases

Aya Mousaa, Negar Naderpoor

a,b, Helena J Teede

a,b,c, Maximilian PJ de Courten

d , Robert

Scragge , Barbora de Courten

a,b

a Monash Centre for Health Research and Implementation, School of Public Health and

Preventive Medicine, Monash University, MHRP, 43-51 Kanooka Grove, Clayton VIC 3168

Australia

bDiabetes and Vascular Medicine Unit, Monash Health, Locked Bag 29, Clayton, VIC 3168,

Australia

cRobinson Research Institute, Discipline of Obstetrics and Gynaecology, University of

Adelaide, Adelaide SA 5005, Australia

dCentre for Chronic Diseases, College of Health and Biomedicine, Victoria University,

Melbourne, Australia

eSchool of Population Health, The University of Auckland, New Zealand

Funding sources:

Negar Naderpoor, Helena Teede and Barbora de Courten are supported by the Australian

National Health and Medical Research Council.

Conflicts of Interests

The authors declare that they have no conflict of interest.

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Acknowledgements

Aya Mousa is a recipient of the Australian Postgraduate Award scholarship provided by

Monash University. Negar Naderpoor, Helena Teede and Barbora de Courten are supported

by the Australian National Health and Medical Research Council.

Corresponding author:

A/Prof. Barbora de Courten, MD PhD MPH FRACP

Monash Centre for Health, Research and Implementation, School of Public health and

Preventive Medicine, Monash University

43-51 Kanooka Grove, Clayton,

Melbourne, VIC 3168, Australia

Telephone: +61 3 9594 7086

Email: [email protected]

3

Abstract

Obesity, type 2 diabetes, and cardiovascular disease (CVD) are the most common preventable

causes of morbidity and mortality worldwide. Insulin resistance, which is a shared feature in

these conditions, is also strongly linked to the development of polycystic ovary syndrome

(PCOS), which is the most common endocrine disease in women of reproductive age and a

major cause of infertility.

Vitamin D deficiency has reached epidemic proportions worldwide, primarily due to the shift

to sedentary, indoor lifestyles and sun avoidance behaviours to protect against skin cancer. In

recent years, vitamin D deficiency has been implicated in the aetiology of type 2 diabetes,

PCOS and CVD, and has been shown to be associated with their risk factors including

obesity, insulin resistance, hypertension, as well as chronic low-grade inflammation.

Treating vitamin D deficiency may offer a feasible and cost-effective means of reducing

cardiometabolic risk factors at a population level in order to prevent the development of type

2 diabetes and CVD. However, not all intervention studies show that vitamin D

supplementation improves these risk factors. Importantly, there is significant heterogeneity in

existing studies with regards to doses and drug regimens used, populations studied (ie vitamin

D deficient or sufficient), and the lengths of supplementation, and only few studies have

directly studied the effect of vitamin D on insulin secretion and resistance with the use of

clamp methods. Therefore, there is a need for well-designed large scale trials to clarify the

role of vitamin D supplementation in the prevention of type 2 diabetes, PCOS, and CVD.

Keywords: vitamin D, obesity, insulin resistance, polycystic ovary syndrome, inflammation,

cardiovascular disease, diabetes.

Word Count: 7,285

Number of figures: 1

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1. Background:

From a physiological perspective, the main role of vitamin D has been in regulating calcium

and phosphorus homeostasis to promote healthy mineralization of bone. However, recent

evidence is shifting recognition of the role of vitamin D towards extra-skeletal properties,

particularly in relation to cardiometabolic risk factors and diseases. These potential metabolic

effects have gained much attention over the past decade and vitamin D has been implicated in

the pathophysiology of obesity, insulin resistance, type 2 diabetes, polycystic ovary syndrome

(PCOS), and cardiovascular disease (CVD) as well as in modulating chronic low-grade

inflammation, now a well-established risk factor in many chronic diseases.

Type 2 diabetes is a global health problem. At least 366 million people have diabetes, and

this figure is likely to rise to 552 million by 2030, largely due to an increase in the prevalence

of obesity underpinned by changes in lifestyle 1. The greater prevalence of obesity and

diabetes contributes to high morbidity and mortality from diabetes complications including

CVD, which is the primary cause of death in those with diabetes, with considerable

associated healthcare costs 2.

There is increased recognition of the possible role of vitamin D in type 2 diabetes and CVD,

and of its potential contribution to this health burden as vitamin D deficiency is now

prevalent worldwide. This is largly due to sedentary indoor lifestyles, use of sunscreen and

protective clothing to reduce the risk of skin cancer 3. Vitamin D deficiency is defined as

plasma 25(OH)D <50nmol/L, although there is currently no consensus on the optimal levels

of vitamin D to maintain health 4. Nevertheless, it is of concern that 20-60% and 10-40% of

the UK and US populations, respectively, have vitamin D levels <50nmol/L 5. In Australia,

despite the sunny climate, vitamin D deficiency is prevalent in 50% of women and 31% of

men living at latitudes >350south

6.

5

Adequate levels of vitamin D are primarily achieved via cutaneous synthesis upon exposure

to ultraviolet (UV) B radiation, and can also be derived from diet and supplements in the

form of cholecalciferol or ergocalciferol 7. However, with current restrictions around sun

exposure due to fear of skin cancer, it is difficult to obtain adequate levels of vitamin D

through sun exposure, and few foods are naturally high in vitamin D, or vitamin D-fortified 3.

The use of supplements has thus been advocated as a more practical option for countering the

widespread deficiency, especially since this is in line with current public health measures for

sun avoidance and skin cancer protection 8.

Following ingestion or synthesis, vitamin D is hydroxylated by the liver into 25-hydroxy

vitamin D after which it undergoes a second hydroxylation in the kidney by 25(OH)D-1α-

hydroxylase (CYP27B1) to form 1,25-dihydroxy vitamin D3 (calcitriol), the biologically

active form of vitamin D 9. Calcitriol exerts its biological effects by acting as a steroid

hormone, and by binding to a nuclear vitamin D receptor (VDR) in target tissues. It has been

recently found that nearly all tissue cells express the VDR, including pancreatic β-cells and

cardiomyocytes, which supports the notion that vitamin D is likely to exert diverse effects,

outside of the musculoskeletal domain 10

.

While there is currently no universal consensus on the adequate intake of vitamin D, the

recommended dietary allowance (RDA) for adults (19-50 years) has been defined as 5μg/day

(200 IU/day) in Australia based on the amount required to maintain 25(OH)D at ≥27.5

nmol/L in circumstances of minimal UV exposure 11

. This increases to 10μg/day in older

people to compensate for reduced vitamin D production in the skin with aging 11

. However,

the US Institute of Medicine has recently increased the RDA for adults aged 19-70 years to

15μg/day (600 IU/day) 12

. While a safe upper limit has not yet been formally established,

6

there are concerns about toxicity from mega-doses of vitamin D. For example, one trial

administering a single oral dose of 12,500 ug (500,000 IU) annually of vitamin D reported a

significant increase in the rate of falls and fractures over a 5 year period 13

, a risk that may be

avoided by fractionating this dose into more frequent physiological administrations 14

.

Importantly, 25(OH)D intakes ≤800 IU/day might be sufficient to achieve bone health, but

may not be sufficient to observe cardiometoblic effects of vitamin D. In addition, the balance

between adequate replacement and avoidance of risks is yet to be established 15

.

2. Vitamin D and Obesity

Observational Studies

Overweight and obesity are defined as abnormal or excessive fat accumulation i.e. body mass

index (BMI) ≥25kg/m2 for overweight and BMI≥30kg/m

2 for obese. The worldwide

prevalence of overweight adults (18 years and older) is 39% while the prevalence of obesity

is 13%, which translates to more than 1.9 billion overweight adults, of which over 600

million are obese 16

. Obesity is preventable through healthy diet and regular exercise, but

once obesity develops, intensive weight loss strategies, exercise programs and medications

are needed for its treatment 16

. Obesity is a common risk factor for many chronic diseases

including type 2 diabetes and cardiovascular disease17

and is associated with chronic low-

grade inflammation 18

.

Recent studies have suggested that the rising prevalence of vitamin D deficiency may in part

be driven by increasing obesity rates 19

. Large nationally representative observational studies

including the National Health and Nutrition Survey (NHANES) have described an

association between overweight and/or obesity and vitamin D deficiency across all age

groups 19

. Recently, a meta-analysis of 34 cross-sectional studies found a significant, albeit

weak, association between serum 25(OH)D levels and BMI, with an observed 4% reduction

7

in 25(OH)D with every 10% increase in BMI 20

. A bi-directional Mendelian randomization

analysis of 21 prospective studies with 42,024 participants supports this finding, reporting

that higher BMI leads to lower 25(OH)D 21

. This association remained consistent across

gender, age, and ethnicity, and the authors concluded that obesity was a causal factor for

developing vitamin D deficiency. Importantly, the reverse was not found as lower vitamin D

levels did not appear to lead to a higher BMI, thus suggesting that increasing vitamin D levels

is unlikely to promote weight loss or influence weight regulation 21

.

Intervention Studies

Randomised trials support the observational data that while obesity may influence vitamin D

status, low vitamin D does not prevent obesity. A meta-analysis of 18 trials measuring several

anthropometric outcomes, including fat mass and BMI, found no significant decrease in BMI

following vitamin D supplementation 22

. There was also no change in percentage of body fat,

body weight, or lean fat mass, however several factors may have contributed to the negative

findings. Two-thirds of trials had durations of ≤6 months, with one-third lasting ≤3months,

and only half of all included trials supplemented ≥2,000 IU/ day of vitamin D. Also, of the

seventeen trials, seven included participants who were not vitamin D deficient

(25(OH)D >50nmol/L), 3 trials included participants with borderline deficiency (25(OH)D=

45-50nmol/L) and only 3 trials included participants with 25(OH)D <30nmol/L.

Overall, the review on the impact of vitamin D on BMI is limited by significant heterogeneity

in study design, participant characteristics, and cut-off points defining vitamin D deficiency

as well as inadequate dosages and durations of vitamin D therapy22

. In support of this, a

subsequent RCT combined caloric restriction and exercise with vitamin D supplementation of

2,000IU/day for 1 year, and found that only those who became replete (25(OH)D ≥80nmol/L)

had lost more weight (-8.8kg versus -5.6kg; P = 0.05), and had a reduced waist circumference

8

(-6.6cm versus -2.5cm; P = 0.02), and percentage body fat (-4.7 versus -2.6, P = 0.04),

compared to the diet and exercise only group 23

. Despite the apparently consistent

relationship between vitamin D and obesity in observational studies, results from randomised

trials remain equivocal, and further trials using higher vitamin D doses and longer follow-up

periods are needed to confirm the extent and direction of this association. Overall,

particularly given the results of the recent Mendelian randomisation study 21

, the evidence

favours obesity being a determinant of vitamin D deficiency, rather than vitamin D status

altering risk of developing obesity.

3. Vitamin D and Type 2 Diabetes Risk:


Type 2 diabetes is characterised by an inadequate response to insulin known as insulin

resistance and relative or absolute insulin deficiency. It has reached epidemic proportions due

to the increasing prevalence of obesity and is a leading cause of morbidity and mortality

mainly due to diabetes complications including CVD 24

. The prevalence of diabetes in 2013

was 382 million people worldwide with type 2 diabetes accounting for approximately 85% of

cases 25

. Recent studies have linked low vitamin D levels with type 2 diabetes risk factors and

type 2 diabetes itself 26

.

Cross-sectional studies show that people with type 2 diabetes have on average lower plasma

25(OH)D concentrations compared to healthy people 27

, and low plasma 25(OH)D has been

associated with higher fasting serum glucose 28-30

and higher haemoglobin A1c (HbA1c) 31, 32

as well as insulin resistance 30, 33

, and decreased first and second phase insulin secretion 34, 35

.

In prospective studies, low serum 25(OH)D levels have been associated with the

development of insulin resistance 29

and incident type 2 diabetes 36

. A recent meta-analysis of

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21 prospective studies by Song et al.36

reported that decreased plasma 25(OH)D

concentrations were associated with a higher incidence of type 2 diabetes, irrespective of sex,

duration of follow-up, sample size, diabetes diagnostic criteria, or 25(OH)D assay method.

Each 10 nmol/L increment in 25(OH)D levels was linearly associated with a 4% lower risk of

developing type 2 diabetes 36

.

Mendelian randomisation analyses of the association between vitamin D and type 2 diabetes

risk are not consistent. A study by Ye et al. 37

found that two single nucleotide

polymorphisms (SNPs) responsible for 25(OH)D metabolism were not associated with

fasting or 2 hour glucose, fasting insulin, or HBA1c, but two other SNPs responsible for

25(OH)D synthesis had a significant causal association with fasting insulin; however none

were associated with type 2 diabetes risk. Another Mendelian analysis found that genetic

variation in the DHCR7 gene (responsible for endogenous vitamin D production in the skin)

was significantly associated with an increased risk of type 2 diabetes (P=0.04), but variation

in CYP2R1 (responsible for liver conversion of vitamin D to 25(OH)D) was not 38

.

Conversely, Buijsse et al.39

found that both synthesis and metabolism allele scores were not

related to type 2 diabetes risk. A limitation of these studies is that the SNP effects on

circulating 25(OH)D are relatively small, thus large sample sizes are needed to detect effects

with sufficient accuracy 39

. Overall, observational studies appear to support an association

between vitamin D and diabetes risk, but the results of genetic studies are conflicting.


A recent meta-analysis conducted by Seida et al.40

identified 35 randomised trials ranging

between 4 weeks to 7 years duration, 200 IU/day to 450,000 IU/year of vitamin D3

supplementation, and totalling 43,407 study participants including healthy, pre-diabetic, and

type 2 diabetic individuals. The meta-analysis found no effect for vitamin D on HbA1c,

10

fasting glucose, insulin resistance (homeostatic model assessment for insulin resistance:

HOMA-IR), insulin secretion (HOMA of β-cell function), or progression to diabetes.

However, once the studies administering large single doses were omitted, vitamin D

supplementation improved insulin resistance in patients with type 2 diabetes but not in

individuals without diabetes. Importantly, Seida et al.40

also excluded trials that used the

hyperinsulinaemic-euglycaemic clamp, the gold-standard method for measuring insulin

sensitivity 40

. Additionally, vitamin D levels of participants in the included trials were also

not specified; hence it was not clear if participants were vitamin D deficient at baseline.

Furthermore, 3 trials included in the meta-analysis supplemented only ≤800 IU/day of

vitamin D, which is unlikely to sufficiently raise vitamin D levels 41-43

. As such, the lack of

findings in trials examining vitamin D and type 2 diabetes may be attributable to considerable

heterogeneity between trials, not restricting participant inclusion criteria to vitamin D

deficient individuals, and/or providing vitamin D doses which were insufficient in raising

plasma 25(OH)D to optimal levels to demonstrate any effects. It is clear that good quality

intervention trials with gold standard measures of glucose metabolism are vital to address

these key knowledge gaps.

4. Vitamin D and Polycystic Ovary Syndrome:


Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of

reproductive age and is underpinned by insulin resistance and hyperandrogenism with key

clinical reproductive and metabolic features 44

. Insulin resistance has an important role in the

aetiology of PCOS as it drives development of other PCOS features including

hyperandrogenism, obesity, glucose intolerance, type 2 diabetes, and it increases

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cardiovascular risk factors and diseases 44

. Lower levels of vitamin D have been reported in

women with PCOS compared to controls even after adjustment for BMI and age 45, 46

. In a

study in Scotland, the prevalence of severe vitamin D deficiency (25OHD <25 nmol/L) was

44.0% in women with PCOS compared to 11.2% in women without PCOS 47

. However,

observational studies on vitamin D levels in women with PCOS compared with non-PCOS

women have yielded inconsistent results 48

. In a study of 206 women with PCOS, 72.8% had

vitamin D levels below 74.88 nmol/L, and women with combined PCOS and metabolic

syndrome had lower vitamin D levels compared to women with PCOS without metabolic

syndrome (43.2 versus 64.4 nmol/L respectively) 49

. Vitamin D was also associated with

features of metabolic syndrome in PCOS women 49

. Some studies have shown that obese

women with PCOS also have lower vitamin D levels compared with lean women with PCOS

50-52, whereas others found no difference in vitamin D levels between obese versus lean

women with PCOS 53

.

Similar to findings from general populations, a significant correlation has been demonstrated

between low vitamin D levels and insulin resistance in women with PCOS 47, 49, 50, 52, 54

. The

association between 25(OH)D level and insulin resistance measured by HOMA-IR and

quantitative insulin sensitivity check index (QUICKI) remained significant after adjustment

for BMI and WHR 47, 49, 54, 55

. A recent systematic review which included 18 studies (1,893

women with PCOS and 717 control women) reported a negative association between

25(OH)D levels and HOMA-IR in both women with PCOS and controls with 0.27 and 0.19

lower HOMA-IR in women with PCOS and controls, respectively, for every 10nmol/L higher

serum 25(OH)D 56

. An uncontrolled study evaluating the association of vitamin D deficiency

with insulin sensitivity by the gold-standard hyperinsulinaemic-euglycaemic clamp and body

composition measured by Dual-energy X-ray absorptiometry (DEXA) in 38 women with

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PCOS found a positive correlation between 25(OH)D levels and insulin sensitivity but this

was not significant after adjusting for adiposity 51

.

Another study by Mazloumi et al 45

, involving 103 women with PCOS and 103 controls,

found a positive relationship between vitamin D, calcium, and adiponectin concentrations.

Low levels of adiponectin, previously documented in PCOS 57

, are associated with insulin

resistance 58

. However, the association between PCOS and low adiponectin levels in the

study by Mazloomi et al. 45

was not significant after adjustment for vitamin D level. Authors

proposed that the hypoadiponectinaemia might be secondary to vitamin D deficiency.

Studies investigating the correlation between vitamin D and hyperandrogenism in PCOS have

also reported inconsistent results. Vitamin D deficiency has been associated with lower sex

hormone binding globulin (SHBG) and higher free androgen index, testosterone and

dehydroepiandrosterone sulfate (DHEAS) levels in women with PCOS 47, 50, 52

. Some studies

however found no association between vitamin D and androgens or gonadotropins 53

.

Vitamin D levels have also been found to be lower in PCOS associated with hirsutism

compared to PCOS without hirsutism 49

.

There is also accumulating evidence on the effect of vitamin D on ovarian function and

reproduction. The VDR is found in ovaries, endometrium and placenta, and low vitamin D

has been associated with decreased ovarian reserve 46

. In one study for example, women with

ovulatory dysfunction and PCOS had lower vitamin D levels than women with other causes

of infertility and this was independent of BMI 59

.


Two double-blinded placebo controlled randomised clinical trials (RCTs) have been

conducted to date, and they both showed no change in insulin sensitivity in non-diabetic

13

women with PCOS following vitamin D supplementation 60, 61

. One of these RCTs

investigated the effect of a large dose of vitamin D (12,000 IU/day) for 12 weeks 60

, and the

other provided 50,000 IU vitamin D every 20 days for 2 months 61

. Most participants in the

former trial and all in the latter had vitamin D deficiency (25(OH)D <50nmol/L). There was

no significant change in QUICKI, insulin sensitivity index, HOMA-IR, fasting glucose or

insulin levels 60

.

Similarly, a single arm open label trial involving overweight women with PCOS and vitamin

D deficiency also demonstrated no change in insulin sensitivity after 3 months of calcium

(530mg/d) and vitamin D (daily dose of 3533 IU for the first five participants, increased to

8533 IU for the other seven participants) 62

. The relatively short duration of these trials could

be the reason for not finding an effect on insulin sensitivity following vitamin D

supplementation. However, one single arm trial with a single oral dose of 300,000 IU vitamin

D resulted in a significant reduction of HOMA-IR in obese women with PCOS after three

weeks 63

. Decrease in fasting and stimulated glucose levels post oral glucose tolerance test

was reported following weekly 20,000 IU of vitamin D for six months in another

uncontrolled study, however HOMA-IR remained unchanged 64

.

Despite some evidence indicating increased endometrial thickness 65

and improved

menstruation 64, 66

and follicle maturation 66

from vitamin D supplementation, there is no

evidence of improved pregnancy rate spontaneously or after intra uterine insemination

following vitamin D supplementation alone or in combination with calcium in PCOS 65, 66

.

One uncontrolled study involving 13 women with PCOS and chronic anovulation (nine with

amenorrhea/ oligomenorrhea) reported normal menstruations for 7 out of 9 women within 2

months of calcium and vitamin D replacement, while another 4 women maintained their usual

menstruation 67

.

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Evidence of the effect of vitamin D supplementation on androgen and lipid levels mainly

comes from non-randomised, single arm trials on overweight and obese women with PCOS,

and the few RCTs that have been conducted so far are limited by small sample sizes and short

durations with no RCT lasting longer than 6 months. Findings from one single-arm open

label trial involving 12 overweight and vitamin D deficient women with PCOS showed a

reduction in total testosterone and androstenedione levels after calcium and vitamin D

supplementation for 3 months62

, whereas other studies have found no effect of vitamin D

supplementation on androgen levels in women with PCOS 60, 63, 64

. For example, a high daily

dose of vitamin D supplementation (12,000 IU/day) for 12 weeks in a double blinded

placebo-controlled RCT involving 11 women with PCOS and 11 controls showed no

significant change of total and free testosterone 60

.

There is some evidence indicating the effect of vitamin D supplementation to reduce

triglycerides (TG)64, 68, 69

and total cholesterol 64, 68, 70

in women with PCOS. One double

blinded placebo-controlled RCT showed a significant reduction of total cholesterol, TG and

very low-density lipoprotein (VLDL), but no change of high-density lipoprotein (HDL) or

low-density lipoprotein (LDL) following vitamin D supplementation (50000 IU every 20

days) for two months 68

. Another RCT showed no change of lipid levels after high doses of

vitamin D supplementation (12,000 IU daily) for three months 60

.

Overall, the data across a range of endpoints is inconclusive in this heterogeneous high

metabolic risk group and further research with larger sample sizes and longer durations are

needed to establish the role of vitamin D in PCOS.

5. Vitamin D and Cardiovascular Disease Risk:

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Observational Studies:

Several large nationally representative cross-sectional studies including the NHANES 71

and

the Tromsø Study72

have examined the relationship between vitamin D levels and blood

pressure (BP) and/or hypertension, and found that vitamin D deficiency was associated with

an increased prevalence of hypertension or pre-hypertension. A recent review conducted by

Carbone et al.73

identified 35 cross-sectional studies, of which only seven found no

association between vitamin D and BP or hypertension. Importantly, five of these seven

studies included participants who were not vitamin D deficient (≥50nmol), and one was

borderline (median =48nmol/L). It has been suggested that cardiovascular risk factors may be

more prominent in vitamin D deficient subjects. This is supported by a cross-sectional study

by Burgaz et al. 74

, which found that men with 25(OH)D levels below 37.5nmol/L had a

three-fold increased prevalence of confirmed hypertension74

, while another study of 381

vitamin D deficient men and women (25(OH)D = 31.0±12.5 nmol/L) found a significant

inverse association between low 25(OH)D values and the prevalence of pre-hypertension 75

.

Pittas et al.76

performed a meta-analysis on 4 prospective studies ranging between 7 and 10

years follow up, in which one study used self-reported vitamin D intake, while three

measured plasma vitamin D concentrations. All four studies reported hypertension by self-

report. A significant inverse association between low vitamin D levels and incident

hypertension after 7-8 years was reported when comparing the lowest and highest vitamin D

concentrations (<37 to 50nmol/L versus >75-80nmol, respectively) 76

. A more recent meta-

analysis of 11 prospective studies, 4 of which assessed dietary vitamin D intake and the

remaining seven assessed blood 25(OH)D concentrations, found that subjects in higher

vitamin D concentration tertiles had a 30% lower risk of developing hypertension compared

to those in lower tertiles (risk ratio=0.70, P<0.05)77

. A pooled dose–response analysis of five

studies also found that each 32 nmol/L increase in 25(OH)D levels was associated with a

16

12% lower risk of hypertension77

. These findings are supported by Mendelian randomization

analyses examining genes responsible for 25(OH)D synthesis or substrate availability

(CYP2R1 and DHCR7) in large samples (n >140,000) 78

. These analyses found that each

25(OH)D-increasing allele of the synthesis score was associated with a -0.10 mm Hg and -

0.08 mm Hg in systolic and diastolic BP, respectively (P <0.05), and reduced odds of

hypertension (OR per allele, 0·98; P=0.001) 78

.

Both cross-sectional and prospective studies investigating the effect of vitamin D on lipid

profiles have had divergent results. While some studies found positive relationships between

vitamin D and HDL75, 79-85

, and an inverse relationship between vitamin D and total

cholesterol and TG 34, 81

, others have not 30, 86-90

.

Prospective studies investigating vitamin D and overall CVD risk were recently reviewed in a

meta-analysis of 19 studies conducted between 2005 and 2012, with 6,123 CVD cases in

65,994 participants 91

. Low 25(OH)D levels (<60nmol/L) were associated with increased

CVD risk , specifically with increased total and CVD mortality. The increased CVD risk

seemed to plateau when vitamin D levels reached 60nmol/L, thus suggesting that while

vitamin D deficiency may increase CVD risk, higher levels may not further decrease risk.

Collectively, existing observational data suggests that CVD risk is increased only when

25(OH)D levels are low (<60 nmol/L).

Links between vitamin D and CVD risk have also been explored in Mendelian randomisation

studies, with some conflicting results. One study examining genetic variants in DHCR7 and

CYP2R1 found that genetically low 25(OH)D concentrations were not associated with

increased cardiovascular mortality 92

, and another study found that neither genotype score nor

the 4 SNPs examined were related to risk of myocardial infarction or overall CVD risk 93

.

However, Levin et al. 94

found a SNP within the VDR which significantly altered the

17

association between low 25(OH)D and CVD outcomes, and thus identified subgroups of

individuals with genotypes that make them more or less susceptible to CVD risk when their

vitamin D levels are low. Current genetic studies are however lacking, and until well-

designed large-scale studies and RCTs are conducted, such associations cannot be confirmed

nor denied.

Intervention Studies:

Few randomised trials have been conducted to investigate the effect of vitamin D

supplementation on cardiovascular risk markers or CVD incidence. However, several large-

scale trials are currently underway which include cardiovascular risk factors and CVD

development or CVD event incidence as primary outcomes, including the VITAL trial in the

United States, FIND trial in Finland, D-Health Study in Australia, and the ViDA trial in New

Zealand 95

.

A meta-analysis by Pittas et al. 76

of 10 RCTs concluded that there was no effect of vitamin D

supplementation on CVD risk factors including BP or incident hypertension. A more recent

review by Kunutsor et al. 96

found 16 trials comprising 1,879 participants, and ranging from 5

weeks to 12 months duration, with 800-1,870 IU/day of vitamin D supplementation.

Following meta-analysis, the authors found similar results to those of the Pittas group 76

, but

a significant reduction in diastolic BP (-1.3mmHg, P<0.05) was observed in six trials of

participants with pre-existing cardiometabolic disease.

Importantly, a limited number of the reviewed trials investigated BP as a primary outcome,

and only few studies focused on vitamin D-deficient individuals. In one study that did not

initially find significant changes in BP following supplementation of 3,000 IU/day vitamin D

for 20 weeks, subgroup analysis of only the vitamin D-deficient subjects did show decreased

systolic and diastolic BP by 4/3 mm Hg(P=0.05/0.01) in the vitamin D group as compared to

18

placebo 97

. This is supported by one of the largest RCTs of hypertensive patients (n = 283)

with vitamin D deficiency that supplemented 1000-4000IU/day of vitamin D for 3 months,

and found that for each 2.5nmol/L increase in plasma 25(OH)D, there was a 0.2 mmHg

reduction in systolic BP (P=0.02) 98

.

With regards to vitamin D supplementation and dyslipidemia, a systematic review conducted

by Jorde and Grimnes identified 10 placebo-controlled randomised trials investigating

vitamin D and lipids, and found that some trials showed positive, while others showed

negative effects of vitamin D supplementation on HDL, LDL, total cholesterol, and TG 99

.

Only one trial in 165 healthy, overweight and vitamin D deficient participants (mean= 30

nmol/L) showed significant results with an 8% increase in LDL and a 16% decrease in TG in

the vitamin D group (3,320 IU /day for 1yr) compared to placebo 100

.

Few randomised trials have examined the effect of vitamin D on the incidence of CVD or

CVD-related events. A systematic review conducted by Elamin et al.101

found 51 trials, of

which 30 trials reported effects of vitamin D supplementation on CVD-related mortality, but

only 6 on myocardial infarction, 6 on stroke, and 5 on peripheral vascular disease. Meta-

analyses showed no effect of vitamin D on any of these outcomes, although a non-significant

reduction in mortality was observed in those receiving vitamin D (risk ratio= 0.96, P= 0.08).

Importantly, many of the included trials were not designed to evaluate cardiovascular

outcomes and were thus likely underpowered. Also, 6 of the trials included participants who

were not vitamin D deficient, while another 12 trials did not report or were unclear on

baseline vitamin D status. This is of relevance as participants without vitamin D deficiency

are less likely to benefit from vitamin D supplementation 101

.

Potential cardiovascular benefits of vitamin D may also be obscured due to confounding

baseline characteristics that were unaccounted for such as diet, exercise and smoking status,

19

or due to the co-administration of calcium in many of these trials which may have masked

any benefits of vitamin D, and perhaps even had a detrimental cardiovascular effect 102

. This

is supported by a more recent review where Zitterman et al.4 concluded that vitamin D

supplementation is not likely to reduce CVD risk by more than 15%, a level that may not be

detectable in current data. The general consensus reached by these and previous reviews 76, 96

is that existing trials are of poor to moderate quality at best, and although the role of vitamin

D in CVD prevention is promising, higher quality randomised trials are needed to adequately

test its potential 76, 96, 99

.

6. Proposed Inter-relationships and Mechanisms for Vitamin D in the Pathophysiology

of Cardiometabolic Risk Factors & Disease:

Several hypotheses have been proposed around the inter-relationships between obesity and

vitamin D and the potential mechanisms by which vitamin D may affect the development and

progression of cardiometabolic risk factors and disease [Figure 1].

Vitamin D and Obesity:

A simple explanation for the relationship between vitamin D and obesity can be attributed to

lifestyle and behavioural differences. Low dietary intake of both calcium and vitamin D have

been reported in obese individuals 103

. Obese individuals may also be less likely to engage in

outdoor activities, and those who do spend time outdoors tend to expose less skin to the sun

than non-obese individuals. Both these aspects result in less exposure to sunlight and

decreased vitamin D synthesis in the skin 22

. However, the differences in sun exposure though

difficult to measure do not fully explain the variance in vitamin D concentrations between

obese and non-obese individuals 104

. Another possible mechanism of vitamin D deficiency in

obesity is that sequestration of the fat-soluble vitamin in adipose tissue mass and/or a slower

20

rate of synthesis of 25(OH)D by the steatotic liver in obese individuals, may result in

decreased bioavailability and thus lower vitamin D levels 104

. Others have also found

impairments in 25(OH)D hydroxylation in obesity 17

.

A more indirect mechanism by which vitamin D may affect obesity is via its regulation of

parathyroid hormone (PTH) and calcium. Low vitamin D levels result in increased PTH,

which in turn stimulates the influx of calcium into adipocytes. Intracellular calcium in these

cells can enhance lipogenesis and thus excess PTH may promote weight gain 104, 105

.

Consistent with this notion, a positive association between PTH and BMI, and a reduction in

PTH following weight loss have been reported 106, 107

.

Vitamin D and Type 2 Diabetes:

In vitro studies have proposed that vitamin D affects both insulin sensitivity and secretion 108-

110. With regards to insulin sensitivity, vitamin D increases transcriptional activation and

expression of the insulin receptor gene, thereby improving insulin sensitivity via facilitating

both basal- and insulin- mediated glucose transport and oxidation 108-110

.

Vitamin D actions on PTH are also thought to be indirectly involved in the development of

insulin resistance, metabolic syndrome, and diabetes. As mentioned, low vitamin D levels

result in high PTH levels, and this excess PTH in some studies has been linked to decreased

insulin sensitivity111

, while Reis et al.90

suggest that clinical investigations have consistently

associated hyperparathyroidism with a two- to four-fold increased risk of diabetes. Proposed

mechanisms suggest that PTH may interfere with both insulin secretion and insulin action.

PTH has been suggested to decrease insulin mediated glucose uptake by liver, muscle, and

adipose cells by reducing the number of glucose transporters (both GLUT1 and GLUT4)

available in cell membranes, while PTH has also been shown to suppress insulin release 112

.

21

Collectively, current data suggests that vitamin D deficiency, and the subsequent excess in

PTH may inhibit insulin signalling and exert negative effects on insulin sensitivity, however

more mechanistic studies are needed to further clarify these biological pathways in humans.

Extra and intracellular calcium levels, which are regulated by vitamin D, have been shown to

influence both insulin sensitivity and secretion. Vitamin D enhances insulin action and signal

transduction by regulating extracellular calcium to ensure normal calcium influx through cell

membranes 27

. This in turn prevents interference with normal insulin release, given that

insulin secretion is a calcium-dependent process 27

. Vitamin D also increases β-cell insulin

secretion by elevating intracellular calcium, which is an essential mechanism involved in β-

cell glycolysis and the signalling of circulating glucose 113

.

The vitamin D binding protein (DBP) and the VDR, which are present in pancreatic islets,

influence the bioavailability and the distribution of vitamin D in tissues 114, 115

. The DBP and

VDR have been suggested to play a role in β-cell function 114, 115

. Genomic effects of vitamin

D via the VDR have been proposed, whereby increased expression of the VDR has been

linked to stimulation of insulin release in pancreatic β-cells, and enhanced insulin

responsiveness for glucose transport 114

.

Chronic low-grade inflammation is an important risk factor for cardiometabolic diseases,

particularly because cytokine-mediated β-cell apoptosis is a central feature in the

development and progression of type 2 diabetes 116

. Vitamin D influences inflammatory

responses through multiple mechanisms. Vitamin D modulates cytokine secretion by

inhibition of the proliferation and stimulatory abilities of T-cells and monocytes 117

. In fact,

vitamin D has been shown to down-regulate pro-inflammatory cytokines, including CRP,

tumor necrosis factor–alpha (TNF-α), interleukin (IL)-6, IL-1, and IL-8, and up-regulate anti-

22

inflammatory cytokines such as IL-10 118

. This is supported by a clinical trial where vitamin

D supplementation for one year reduced circulating IL-6 concentrations in obese subjects 119

.

Interestingly, vitamin D has also been associated with increased circulating adiponectin, a

peptide hormone with favourable effects on chronic low-grade inflammation, and glucose and

lipid metabolism. This action of vitamin D is thought to occur partly via down-regulating IL-

6 since IL-6 has been shown to inhibit adiponectin gene expression 119, 120

.

In vitro data show that the VDR is present in most inflammatory cells, supporting the role of

vitamin D in inflammatory responses 10

. Absence of the VDR also seems to be associated

with increased nuclear factor- kappa B (NFB) activity, a transcription factor which has a

key role in regulating immune responses to infection and that has been implicated in the

pathophysiology of insulin resistance and type 2 diabetes 121

. Conversely, NFB translocation

appears to be arrested, and its activity weakened by vitamin D 121

.

Vitamin D also up-regulates osteocalcin, a protein secreted by osteoblasts that is important

for bone mineralisation, but has also been implicated in the regulation of glucose metabolism

via effects on both insulin sensitivity and secretion 122, 123

. Osteocalcin stimulates adiponectin

expression and release of adiponectin from adipose tissue 120

, but also has effects on insulin

secretion via increases in GLP-1 122, 123

.

Advanced glycation end products (AGEs), a key factor in the pathogenesis of diabetes

complications, have been recently implicated in the pathophysiology of insulin resistance 124,

125. Harmful effects of AGEs include increases in inflammation and oxidative stress as well

as direct effects on β-cells, all of which are important risk factors for the development and

progression of diabetes 124-126

. In vitro studies suggest that the addition of vitamin D to

various cells, including endothelial cells, appeared to hamper AGEs-induced NFB activity

23

121, 127, 128. In addition, vitamin D was also found to exert protective effects by increasing the

circulating soluble receptor for AGEs (sRAGE), thereby reducing AGEs 129

.

Vitamin D and PCOS

Obesity, insulin resistance and chronic low-grade inflammation have important roles in the

development of PCOS and progression of its complications. As such, the mechanisms by

which vitamin D impacts on obesity, insulin resistance and chronic inflammation that have

been discussed above, also apply to PCOS.

In addition to these, PCOS is characterised by hyperandrogenism and oligo/anovulation. One

indirect mechanism proposed for the role of vitamin D deficiency in PCOS is by reducing

SHBG and thereby increasing free androgen levels. However, the association between

vitamin D and SHBG is not significant in most studies after adjusting for BMI 130

.

Furthermore, vitamin D deficiency is linked to hyperandrogenism through increasing PTH

which has been positively associated with testosterone level independent of BMI in women

with PCOS 131

. A role for calcium has also been established in relation to oocyte maturation

and the initial phase of egg development at fertilisation in both animal and human studies.

Abnormalities in calcium homeostasis and PTH levels secondary to vitamin D deficiency

may thus be responsible for arrested follicular development and menstrual dysfunction in

women with PCOS 67

.

Gene polymorphisms in the VDR are also proposed to have a role in the development of

PCOS with some genotypes being associated with more insulin resistance or

hyperandrogenism 46

. VDR-null mutant mice have been shown to have uterine hypoplasia

and impaired folliculogenesis suggesting a role for VDR in reproduction 132

. In addition,

AGEs and anti-Mullerian hormone (AMH) are elevated in women with PCOS, the latter

being due to abnormal ovarian folliculogenesis 129, 133

. It has been shown that both AGEs and

24

AMH levels are higher in anovulatory compared to ovulatory PCOS. As such, they may

interact in the anovulatory mechanisms in women with PCOS 133

. Vitamin D reduces AGEs

129, as has been mentioned earlier, but it has also been shown to normalise serum AMH in

women with PCOS and vitamin D deficiency 134

.

Despite the above proposed mechanisms, there remains a clear need for further research in

this unique insulin resistant disorder to clearly establish the mechanisms and potential

therapeutic benefit of vitamin D in PCOS.

Vitamin D and Cardiovascular Disease

Low vitamin D has been implicated as having an important role in development of CVD risk

factors via several mechanisms. Vitamin D has been shown to induce genes that are

protective against atherosclerosis and myocardial damage 135, 136

, and it also appears to

suppress cardiac hypertrophy 137, 138

. Another suggested mechanism is an increased activation

of the renin-angiotensin-aldosterone system (RAAS). Low vitamin D has been associated

with increased circulating angiotensin-II concentrations 137

, and blunted renal plasma flow

response to angiotensin-II infusion in normotensive subjects 73

. Vitamin D is therefore

believed to improve cardiac function and reduce blood pressure, primarily by down-

regulating the RAAS and reducing plasma levels of angiotensin II, which decreases

angiotensin II-induced vasoconstriction, and reduces renin via calcium regulation 139

. This is

supported by randomised trials where improved blood pressure was observed in individuals

following vitamin D supplementation, however this was restricted only to individuals with

baseline vitamin D deficiency 97, 98.

High renin concentrations have also been independently

associated with the progression of thrombosis and left ventricular hypertrophy, along with

having an independent effect on CVD-related morbidity and mortality 140

.

25

Additional mechanisms contributing to the protective effects of vitamin D against

atherosclerosis are increased production of a matrix protein which inhibits cellular vascular

calcification73

, enhances expression of anticoagulant glycoproteins, while down-regulating

expression of critical coagulation factors, and prevents foam cell formation and LDL

cholesterol uptake by macrophages 141

. Vitamin D has also been shown to directly promote

HDL particle formation and regulate serum apolipoprotein A-1 levels, both of which

contribute to increased cholesterol transport and overall improved lipid profiles 81

. In addition,

higher vitamin D and thus higher calcium levels are proposed to reduce hepatic triglyceride

formation and secretion 99

. Calcium acts to form insoluble soaps to prevent absorption of

dietary fat and binds to bile acids, which increases the hepatic conversion of cholesterol to

bile acids, thus reducing overall cholesterol levels 142

.

Vitamin D deficiency also elevates PTH levels as mentioned earlier, and this has been

associated with low HDL cholesterol as well as impaired endothelial function, arterial

stiffness and hypertension 73,90

. Suggested mechanisms for these actions include increased

aldosterone secretion via direct stimulation of sympathetic activity by PTH, and the indirect

mechanism of PTH whereby it alters calcium transport in various tissues, including vascular

smooth muscle, which may contribute to hypertension, among other CVD risks 73,90

.

In vitro activation of the VDR has also been shown to stimulate nitric oxide production in

endothelial cells and improve angiogenic features of endothelial progenitor cells, while

regulating the proliferation, migration, mineralization, and thrombogenic protein expression

of vascular smooth muscle cells 73

. Similarly, the VDR also improves lipid metabolism by

reducing acetylated LDL cholesterol uptake 79

. VDR polymorphisms have been associated

with an increased genetic susceptibility to CVD risks including hypertension73

.

26

Given the presence of the VDR in inflammatory cells, vitamin D also appears to exert

protective features against CVD via inflammatory and oxidative stress pathways. Chronic

low-grade inflammation and advanced glycation have both been suggested to play important

roles in the pathogenesis of CVD 4, 143

. Vitamin D reduces both chronic low-grade

inflammation and AGEs as discussed earlier. In addition, human in vitro studies have found

that vitamin D reduces the effect of AGEs on endothelial cells, thereby decreasing arterial

stiffness and endothelial dysfunction 128

. Consistent with this, AGEs and NFB activity has

been associated with diastolic pressure and pulse pressure in healthy normotensive adults 126,

143. Collectively, present data show promising explanations of mechanisms involved in the

effects of vitamin D on cardiovascular risk factors, however further research is needed to

clarify the extent by which vitamin D may be a protective agent against CVD risk factors and

disease.

7. Limitations of the Current Literature

Current knowledge around the benefits of vitamin D in relation to cardiometabolic health

remains contentious. Equivocal findings from both observational and interventional studies

are affected by several factors including the lack of defined knowledge around appropriate

dosages or optimal concentrations of vitamin D, and the duration of supplementation

necessary to appreciate any cardiometabolic effects. It is also unclear whether vitamin D is

only effective in certain subgroups, and whether a certain threshold exists at which vitamin D

ceases to incur additional benefits. However, it has been postulated that vitamin D

supplementation only exhibits beneficial effects in those who are deficient (25(OH)D <50

nmol/L), and only if supplemented in adequate dosages (>2000 IU /day) and for sufficient

durations for development of the outcome, all of which are factors needing proper

consideration in the design and execution of future trials in this field of research 76, 96, 99

.

27

Previous trials have been limited by poor participant compliance, insufficient dosages, and

small sample sizes, many of which included participants who were not vitamin D deficient.

The relatively short durations of these trials have also not allowed sufficient time to observe

development of these chronic diseases. Many trials have also co-administered vitamin D with

calcium, and since high calcium levels are now known to increase CVD risk, this may have

masked any potential benefits of vitamin D 4. Thus while existing research outlines a

potential role for vitamin D in improving cardiometabolic health, more conclusive evidence

is needed to confirm the true effects of vitamin D and to determine the mechanistic pathways

by which it can work as a protective agent against these diseases.

8. Conclusions and Future Directions

Cardiometabolic risk factors and diseases including obesity, PCOS, type 2 diabetes, and CVD

are associated with significant morbidity and mortality, as well as increasing healthcare costs.

Most importantly, they are preventable conditions, but while lifestyle interventions for

treatment of obesity and other cardiometabolic risk factors are an important part of

preventative strategies, they are expensive, difficult to implement, and unlikely to succeed on

their own. Therefore, alongside existing lifestyle interventions, there is an urgent need to

identify and test safe and effective interventions that can be easily implemented at a

population level to prevent these conditions and reduce their complications.

In recent years, vitamin D deficiency has attracted significant attention as a potential

contributing factor to the development of cardiometabolic diseases. Vitamin D deficiency is

now pandemic across most populations, given the shift to sedentary, indoor lifestyles, and sun

safety concerns. However, with the use of supplements, vitamin D deficiency can be easily

28

treated on a population-wide level. Despite current research suggesting the involvement of

vitamin D in the pathogenesis of obesity, type 2 diabetes, PCOS, and CVD; there remains

unanswered questions and continued debate regarding the potential use of vitamin D

supplementation as a wide-scale prevention strategy. Large, well-designed, and robust

interventional trials in vitamin D deficient individuals with sufficient vitamin D doses are

necessary to clarify the role of vitamin D in mitigating the current burden of chronic disease.

If such trials establish a protective role for vitamin D in cardiometabolic health, treating

vitamin D deficiency via population-wide strategies could be a feasible and cost-effective

means of successfully preventing and treating type 2 diabetes, PCOS, and CVD on a global

scale.

9. Author Contributions

AyaMousa, Negar Naderpoor, and Barbora de Courten drafted the manuscript. Helena Teede,

Maximilian de Courten, and Robert Scragg contributed to reviewing and editing the

manuscript. All authors read and approved the final manuscript.

29

10. Abbreviations

RCT = Randomised controlled trial

BMI = Body mass index

CVD = Cardiovascular disease

PCOS = Polycystic ovary syndrome

OGTT = Oral glucose tolerance test

IVGTT = Intravenous glucose tolerance test

HOMA-IR = Homeostasis model assessment for insulin resistance

QUICKI = Quanititative insulin sensitivity check index

BP = Blood pressure

HDL/ LDL = High- / Low- density lipoprotein cholesterol

TG = Triglycerides

RAAS = Renin-angiotensin-aldosterone system

VDR = Vitamin D receptor

PTH = Parathyroid hormone

HbA1c = Haemoglobin A1c

IU = International units

CRP = C-reactive protein

MIF = Macrophage migration inhibitory factor

IL = Interleukin

MCP-1 = Monocyte chemotactic protein-1

NFB = Nuclear factor kappa-B

TNF-α = Tumour necrose factor-alpha

AGEs = Advanced glycation end products

AMH = Anti-mullerian hormone

SHBG = Sex hormone binding globulin

DHEAS = Dehydroepiandrosterone sulfate

25(OH)D = 25-hydroxy vitamin D

NHMRC = National Health and Medical Research Council

SPHPM = School of Public Health and Preventive Medicine

MUHREC = Monash University Human Research Ethics Committee

30

MCHRI = Monash Centre for Health Research and Implementation

References

1. Chen L, Magliano DJ, Zimmet PZ. The worldwide epidemiology of type 2 diabetes mellitus--

present and future perspectives. Nature reviews Endocrinology. 2012 Apr;8(4):228-36. PubMed

PMID: 22064493. Epub 2011/11/09. eng.

2. Zhang P, Zhang X, Brown J, Vistisen D, Sicree R, Shaw J, et al. Global healthcare

expenditure on diabetes for 2010 and 2030. Diabetes Research and Clinical Practice.87(3):293-301.

3. Holick MF. Vitamin D status: measurement, interpretation, and clinical application. Annals of

epidemiology. 2009 Feb;19(2):73-8. PubMed PMID: 18329892. Pubmed Central PMCID:

Pmc2665033. Epub 2008/03/11. eng.

4. Zittermann A. Vitamin D and cardiovascular disease. Anticancer research. 2014

Sep;34(9):4641-8. PubMed PMID: 25202039. Epub 2014/09/10. eng.

5. Prentice A. Vitamin D deficiency: a global perspective. Nutr Rev. 2008 Oct;66(10 Suppl

2):S153-64. PubMed PMID: 18844843. Epub 2008/12/05. eng.

6. Gagnon C, Lu ZX, Magliano DJ, Dunstan DW, Shaw JE, Zimmet PZ, et al. Serum 25-

hydroxyvitamin D, calcium intake, and risk of type 2 diabetes after 5 years: results from a national,

population-based prospective study (the Australian Diabetes, Obesity and Lifestyle study). Diabetes

care. 2011 May;34(5):1133-8. PubMed PMID: 21430082. Pubmed Central PMCID: Pmc3114481.

Epub 2011/03/25. eng.

7. Wang C. Role of vitamin d in cardiometabolic diseases. Journal of diabetes research.

2013;2013:243934. PubMed PMID: 23671861. Pubmed Central PMCID: Pmc3647592. Epub

2013/05/15. eng.

8. Sinclair C. Risks and benefits of sun exposure: implications for public health practice based

on the Australian experience. Prog Biophys Mol Biol. 2006 Sep;92(1):173-8. PubMed PMID:

16580055. Epub 2006/04/04. eng.

9. Norman AW, Bouillon R. Vitamin D nutritional policy needs a vision for the future. Exp Biol

Med (Maywood). 2010 Sep;235(9):1034-45. PubMed PMID: 20667908. Epub 2010/07/30. eng.

10. Veldman CM, Cantorna MT, DeLuca HF. Expression of 1,25-dihydroxyvitamin D(3)

receptor in the immune system. Archives of biochemistry and biophysics. 2000 Feb 15;374(2):334-8.

PubMed PMID: 10666315. Epub 2000/02/10. eng.

11. Australian Government, Department of Health and Aging, Council. NHaMR. Nutrient

reference values for Australia and New Zealand. Executive Summary. Canberra: NHMRC; 2006.

12. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK, et al. The 2011 report

on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians

need to know. The Journal of clinical endocrinology and metabolism. 2011 Jan;96(1):53-8. PubMed

PMID: 21118827. Pubmed Central PMCID: Pmc3046611. Epub 2010/12/02. eng.

13. Sanders KM, Stuart AL, Williamson EJ, Simpson JA, Kotowicz MA, Young D, et al. Annual

high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial. JAMA.

2010 May 12;303(18):1815-22. PubMed PMID: 20460620. Epub 2010/05/13. eng.

14. Brown JP. Administration of annual oral high-dose vitamin D to community-dwelling older

women in autumn and winter months increases risk of falls and fractures. Evidence Based Medicine.

2010 December 1, 2010;15(6):175-6.

15. Holick MF. Vitamin D deficiency in 2010: Health benefits of vitamin D and sunlight: a D-

bate. Nat Rev Endocrinol. 2011 Feb;7(2):73-5. PubMed PMID: 21263437. Epub 2011/01/26. eng.

16. Organization WH. Obesity and overweight. World Health Organization; 2015 [updated

January 2015; cited 2015 10/02/2015]; Available from:

http://www.who.int/mediacentre/factsheets/fs311/en/.

17. Vanlint S. Vitamin D and Obesity. Nutrients. 2013 03/20, 02/16/received03/12/revised

03/14/accepted;5(3):949-56. PubMed PMID: PMC3705328.

http://www.who.int/mediacentre/factsheets/fs311/en/

31

18. Vozarova B, Weyer C, Hanson K, Tataranni PA, Bogardus C, Pratley RE. Circulating

interleukin-6 in relation to adiposity, insulin action, and insulin secretion. Obesity research. 2001

Jul;9(7):414-7. PubMed PMID: 11445664. Epub 2001/07/11. eng.

19. Pourshahidi LK. Vitamin D and obesity: current perspectives and future directions. Proc Nutr

Soc. 2014 Oct 31:1-10. PubMed PMID: 25359323. Epub 2014/11/02. Eng.

20. Saneei P, Salehi-Abargouei A, Esmaillzadeh A. Serum 25-hydroxy vitamin D levels in

relation to body mass index: a systematic review and meta-analysis. Obesity reviews : an official

journal of the International Association for the Study of Obesity. 2013 May;14(5):393-404. PubMed

PMID: 23331724. Epub 2013/01/22. eng.

21. Vimaleswaran KS, Berry DJ, Lu C, Tikkanen E, Pilz S, Hiraki LT, et al. Causal relationship

between obesity and vitamin D status: bi-directional Mendelian randomization analysis of multiple

cohorts. PLoS medicine. 2013;10(2):e1001383. PubMed PMID: 23393431. Pubmed Central PMCID:

Pmc3564800. Epub 2013/02/09. eng.

22. Pathak K, Soares MJ, Calton EK, Zhao Y, Hallett J. Vitamin D supplementation and body

weight status: a systematic review and meta-analysis of randomized controlled trials. Obesity reviews :

an official journal of the International Association for the Study of Obesity. 2014 Jun;15(6):528-37.


23. Mason C, Xiao L, Imayama I, Duggan C, Wang CY, Korde L, et al. Vitamin D3

supplementation during weight loss: a double-blind randomized controlled trial. The American

journal of clinical nutrition. 2014 May;99(5):1015-25. PubMed PMID: 24622804. Pubmed Central

PMCID: Pmc3985208. Epub 2014/03/14. eng.

24. Glintborg D, Hermann AP, Andersen M. Bone mineral density and vitamin D in PCOS and

hirsutism. Expert Review of Endocrinology & Metabolism. 2013 2013/09//

//;8:449+. English.

25. Forouhi NG, Wareham NJ. Epidemiology of diabetes. Medicine (Abingdon, England : UK

ed). 2014 Dec;42(12):698-702. PubMed PMID: 25568613. Pubmed Central PMCID: Pmc4282306.

Epub 2015/01/09. Eng.

26. Afzal S, Bojesen SE, Nordestgaard BG. Low 25-hydroxyvitamin D and risk of type 2 diabetes:

a prospective cohort study and metaanalysis. Clinical chemistry. 2013 Feb;59(2):381-91. PubMed

PMID: 23232064. Epub 2012/12/13. eng.

27. Pittas A, Lau J, Hu F, Dawson-Hughes B. The role of Vitamin D and calcium in type 2

diabetes: a systematic review and meta-analysis. The Journal of clinical endocrinology and

metabolism. 2007;92:2017-29.

28. Need AG, O'Loughlin PD, Horowitz M, Nordin BE. Relationship between fasting serum

glucose, age, body mass index and serum 25 hydroxyvitamin D in postmenopausal women. Clinical

endocrinology. 2005 Jun;62(6):738-41. PubMed PMID: 15943837. Epub 2005/06/10. eng.

29. Forouhi NG, Luan J, Cooper A, Boucher BJ, Wareham NJ. Baseline serum 25-hydroxy

vitamin d is predictive of future glycemic status and insulin resistance: the Medical Research Council

Ely Prospective Study 1990-2000. Diabetes. 2008 Oct;57(10):2619-25. PubMed PMID: 18591391.

eng.

30. Liu E, Meigs JB, Pittas AG, McKeown NM, Economos CD, Booth SL, et al. Plasma 25-

hydroxyvitamin d is associated with markers of the insulin resistant phenotype in nondiabetic adults.

The Journal of nutrition. 2009 Feb;139(2):329-34. PubMed PMID: 19106328. Pubmed Central


31. Hypponen E, Power C. Vitamin D status and glucose homeostasis in the 1958 British birth

cohort: the role of obesity. Diabetes Care. 2006 Oct;29(10):2244-6. PubMed PMID: 17003300. Epub

2006/09/28. eng.

32. Pinelli NR, Jaber LA, Brown MB, Herman WH. Serum 25-hydroxy vitamin d and insulin

resistance, metabolic syndrome, and glucose intolerance among Arab Americans. Diabetes Care. 2010

Jun;33(6):1373-5. PubMed PMID: 20332348. Pubmed Central PMCID: 2875457. Epub 2010/03/25.

eng.

32

33. Chonchol M, Scragg R. 25-Hydroxyvitamin D, insulin resistance, and kidney function in the

Third National Health and Nutrition Examination Survey. Kidney international. 2007 Jan;71(2):134-9.


34. Chiu KC, Chu A, Go VL, Saad MF. Hypovitaminosis D is associated with insulin resistance

and beta cell dysfunction. The American journal of clinical nutrition. 2004 May;79(5):820-5. PubMed

PMID: 15113720. Epub 2004/04/29. eng.

35. Ou HY, Karnchanasorn R, Lee LZ, Chiu KC. Interaction of BMI with vitamin D and insulin

sensitivity. European journal of clinical investigation. 2011 Nov;41(11):1195-201. PubMed PMID:

21434896. Epub 2011/03/26. eng.

36. Song Y, Wang L, Pittas AG, Del Gobbo LC, Zhang C, Manson JE, et al. Blood 25-hydroxy

vitamin D levels and incident type 2 diabetes: a meta-analysis of prospective studies. Diabetes care.

2013 May;36(5):1422-8. PubMed PMID: 23613602. Pubmed Central PMCID: Pmc3631862. Epub

2013/04/25. eng.

37. Ye Z, Sharp SJ, Burgess S, Scott RA, Imamura F, Langenberg C, et al. Association between

circulating 25-hydroxyvitamin D and incident type 2 diabetes: a mendelian randomisation study. The

lancet Diabetes & endocrinology. 2015 Jan;3(1):35-42. PubMed PMID: 25281353. Pubmed Central


38. Afzal S, Brondum-Jacobsen P, Bojesen SE, Nordestgaard BG. Vitamin D concentration,

obesity, and risk of diabetes: a mendelian randomisation study. The lancet Diabetes & endocrinology.

2014 Apr;2(4):298-306. PubMed PMID: 24703048. Epub 2014/04/08. eng.

39. Buijsse B, Boeing H, Hirche F, Weikert C, Schulze MB, Gottschald M, et al. Plasma 25-

hydroxyvitamin D and its genetic determinants in relation to incident type 2 diabetes: a prospective

case-cohort study. European journal of epidemiology. 2013 Sep;28(9):743-52. PubMed PMID:

24002339. Epub 2013/09/05. eng.

40. Seida JC, Mitri J, Colmers IN, Majumdar SR, Davidson MB, Edwards AL, et al. Clinical

review: Effect of vitamin D3 supplementation on improving glucose homeostasis and preventing

diabetes: a systematic review and meta-analysis. The Journal of clinical endocrinology and

metabolism. 2014 Oct;99(10):3551-60. PubMed PMID: 25062463. Epub 2014/07/26. eng.

41. Avenell A, Cook JA, MacLennan GS, McPherson GC. Vitamin D supplementation and type 2

diabetes: a substudy of a randomised placebo-controlled trial in older people (RECORD trial,

ISRCTN 51647438). Age and ageing. 2009 Sep;38(5):606-9. PubMed PMID: 19617604. Epub

2009/07/21. eng.

42. de Boer IH, Tinker LF, Connelly S, Curb JD, Howard BV, Kestenbaum B, et al. Calcium plus

vitamin D supplementation and the risk of incident diabetes in the Women's Health Initiative.

Diabetes care. 2008 Apr;31(4):701-7. PubMed PMID: 18235052. Pubmed Central PMCID:

Pmc3046029. Epub 2008/02/01. eng.

43. Pittas A, Harris S, Stark P, B. D-H. The effects of calcium and vitamin d supplementation on

blood glucose and markers of inflammation in nondiabetic adults. Diabetes Care 2007;30(4):980-6.

44. Teede HJ, Hutchison SK, Zoungas S. The management of insulin resistance in polycystic

ovary syndrome. Trends in endocrinology and metabolism: TEM. 2007 Sep;18(7):273-9. PubMed

PMID: 17698366.

45. Mazloomi S, Sharifi F, Hajihosseini R, Kalantari S, Mazloomzadeh S. Association between

Hypoadiponectinemia and Low Serum Concentrations of Calcium and Vitamin D in Women with

Polycystic Ovary Syndrome. ISRN endocrinology. 2012;2012:949427. PubMed PMID: 22363895.

Pubmed Central PMCID: PMC3265215. Epub 2012/03/01. eng.

46. Nestler JE, Reilly ER, Cheang KI, Bachmann LM, Downs RW, Jr. A pilot study: effects of

decreasing serum insulin with diazoxide on vitamin D levels in obese women with polycystic ovary

syndrome. Transactions of the American Clinical and Climatological Association. 2012;123:209-19;

discussion 19-20. PubMed PMID: 23303986. Pubmed Central PMCID: Pmc3540606. Epub

2013/01/11. eng.

47. Li HW, Brereton RE, Anderson RA, Wallace AM, Ho CK. Vitamin D deficiency is common

and associated with metabolic risk factors in patients with polycystic ovary syndrome. Metabolism:

clinical and experimental. 2011 Oct;60(10):1475-81. PubMed PMID: 21550088. Epub 2011/05/10.

eng.

33

48. Mahmoudi T. Genetic variation in the vitamin D receptor and polycystic ovary syndrome risk.

Fertility and sterility. 2009 Oct;92(4):1381-3. PubMed PMID: 19501823. Epub 2009/06/09. eng.

49. Wehr E, Pilz S, Schweighofer N, Giuliani A, Kopera D, Pieber TR, et al. Association of

hypovitaminosis D with metabolic disturbances in polycystic ovary syndrome. European journal of

endocrinology / European Federation of Endocrine Societies. 2009 Oct;161(4):575-82. PubMed

PMID: 19628650. Epub 2009/07/25. eng.

50. Yildizhan R, Kurdoglu M, Adali E, Kolusari A, Yildizhan B, Sahin HG, et al. Serum 25-

hydroxyvitamin D concentrations in obese and non-obese women with polycystic ovary syndrome.

Archives of gynecology and obstetrics. 2009 Oct;280(4):559-63. PubMed PMID: 19214546. Epub

2009/02/14. eng.

51. Muscogiuri G, Policola C, Prioletta A, Sorice G, Mezza T, Lassandro A, et al. Low levels of

25(OH)D and insulin-resistance: 2 unrelated features or a cause-effect in PCOS? Clinical nutrition

(Edinburgh, Scotland). 2012 Aug;31(4):476-80. PubMed PMID: 22260937. Epub 2012/01/21. eng.

52. Hahn S, Haselhorst U, Tan S, Quadbeck B, Schmidt M, Roesler S, et al. Low serum 25-

hydroxyvitamin D concentrations are associated with insulin resistance and obesity in women with

polycystic ovary syndrome. Experimental and clinical endocrinology & diabetes : official journal,

German Society of Endocrinology [and] German Diabetes Association. 2006 Nov;114(10):577-83.


53. Velija-Asimi Z. Evaluation of the association of vitamin D deficiency with gonadotropins and

sex hormone in obese and non-obese women with polycystic ovary syndrome. Medicinski glasnik :

official publication of the Medical Association of Zenica-Doboj Canton, Bosnia and Herzegovina.

2014 Feb;11(1):170-6. PubMed PMID: 24496360. Epub 2014/02/06. eng.

54. Wehr E, Trummer O, Giuliani A, Gruber HJ, Pieber TR, Obermayer-Pietsch B. Vitamin D-

associated polymorphisms are related to insulin resistance and vitamin D deficiency in polycystic

ovary syndrome. European journal of endocrinology / European Federation of Endocrine Societies.

2011 May;164(5):741-9. PubMed PMID: 21389086. Epub 2011/03/11. eng.

55. Patra SK, Nasrat H, Goswami B, Jain A. Vitamin D as a predictor of insulin resistance in

polycystic ovarian syndrome. Diabetes & metabolic syndrome. 2012 Jul-Sep;6(3):146-9. PubMed

PMID: 23158978. Epub 2012/11/20. eng.

56. Krul-Poel YH, Snackey C, Louwers Y, Lips P, Lambalk CB, Laven JS, et al. The role of

vitamin D in metabolic disturbances in polycystic ovary syndrome: a systematic review. European

journal of endocrinology / European Federation of Endocrine Societies. 2013 Dec;169(6):853-65.


57. Sharifi F, Hajihosseini R, Mazloomi S, Amirmogaddami H, Nazem H. Decreased adiponectin

levels in polycystic ovary syndrome, independent of body mass index. Metabolic syndrome and

related disorders. 2010 Feb;8(1):47-52. PubMed PMID: 19929617. Epub 2009/11/26. eng.

58. Kern PA, Di Gregorio GB, Lu T, Rassouli N, Ranganathan G. Adiponectin expression from

human adipose tissue: relation to obesity, insulin resistance, and tumor necrosis factor-alpha

expression. Diabetes. 2003 Jul;52(7):1779-85. PubMed PMID: 12829646. Epub 2003/06/28. eng.

59. Pal L, Shu, J., Zeitlian, G., Hickmon, C. Vitamin D insufficiency in reproductive years may

be contributory to ovulatory infertility and PCOS. Fetility and Sterility. 2008;90(S14).

60. Raja-Khan N, Shah J, Stetter CM, Lott ME, Kunselman AR, Dodson WC, et al. High-dose

vitamin D supplementation and measures of insulin sensitivity in polycystic ovary syndrome: a

randomized, controlled pilot trial. Fertility and sterility. 2014 Jun;101(6):1740-6. PubMed PMID:

24636395. Epub 2014/03/19. eng.

61. Ardabili HR, Gargari BP, Farzadi L. Vitamin D supplementation has no effect on insulin

resistance assessment in women with polycystic ovary syndrome and vitamin D deficiency. Nutrition

research (New York, NY). 2012 Mar;32(3):195-201. PubMed PMID: 22464806. Epub 2012/04/03.

eng.

62. Pal L, Berry A, Coraluzzi L, Kustan E, Danton C, Shaw J, et al. Therapeutic implications of

vitamin D and calcium in overweight women with polycystic ovary syndrome. Gynecological

endocrinology : the official journal of the International Society of Gynecological Endocrinology. 2012

Dec;28(12):965-8. PubMed PMID: 22780885. Pubmed Central PMCID: PMC3743962. Epub

2012/07/12. eng.

34

63. Selimoglu H, Duran C, Kiyici S, Ersoy C, Guclu M, Ozkaya G, et al. The effect of vitamin D

replacement therapy on insulin resistance and androgen levels in women with polycystic ovary

syndrome. Journal of endocrinological investigation. 2010 Apr;33(4):234-8. PubMed PMID:

19820295. Epub 2009/10/13. eng.

64. Wehr E, Pieber TR, Obermayer-Pietsch B. Effect of vitamin D3 treatment on glucose

metabolism and menstrual frequency in polycystic ovary syndrome women: a pilot study. Journal of

endocrinological investigation. 2011 Nov;34(10):757-63. PubMed PMID: 21613813. Epub

2011/05/27. eng.

65. Asadi M, Matin N, Frootan M, Mohamadpour J, Qorbani M, Tanha FD. Vitamin D improves

endometrial thickness in PCOS women who need intrauterine insemination: a randomized double-

blind placebo-controlled trial. Archives of gynecology and obstetrics. 2014 Apr;289(4):865-70.


66. Firouzabadi R, Aflatoonian A, Modarresi S, Sekhavat L, MohammadTaheri S. Therapeutic

effects of calcium & vitamin D supplementation in women with PCOS. Complementary therapies in

clinical practice. 2012 May;18(2):85-8. PubMed PMID: 22500844. Epub 2012/04/17. eng.

67. Thys-Jacobs S, Donovan D, Papadopoulos A, Sarrel P, Bilezikian JP. Vitamin D and calcium

dysregulation in the polycystic ovarian syndrome. Steroids. 1999 6//;64(6):430-5.

68. Rahimi-Ardabili H, Pourghassem Gargari B, Farzadi L. Effects of vitamin D on

cardiovascular disease risk factors in polycystic ovary syndrome women with vitamin D deficiency.

Journal of endocrinological investigation. 2013 Jan;36(1):28-32. PubMed PMID: 22453059. Epub

2012/03/29. eng.

69. Kotsa K, Yavropoulou MP, Anastasiou O, Yovos JG. Role of vitamin D treatment in glucose

metabolism in polycystic ovary syndrome. Fertility and sterility. 2009 Sep;92(3):1053-8. PubMed

PMID: 18930208. Epub 2008/10/22. eng.

70. Thomson RL, Spedding S, Brinkworth GD, Noakes M, Buckley JD. Seasonal effects on

vitamin D status influence outcomes of lifestyle intervention in overweight and obese women with

polycystic ovary syndrome. Fertility and sterility. 2013 May;99(6):1779-85. PubMed PMID:

23357457. Epub 2013/01/30. eng.

71. Martins D, Wolf M, Pan D, Zadshir A, Tareen N, Thadhani R, et al. Prevalence of

cardiovascular risk factors and the serum levels of 25-hydroxyvitamin D in the United States: data

from the Third National Health and Nutrition Examination Survey. Archives of internal medicine.

2007 Jun 11;167(11):1159-65. PubMed PMID: 17563024. Epub 2007/06/15. eng.

72. Jorde R, Figenschau Y, Emaus N, Hutchinson M, Grimnes G. Serum 25-Hydroxyvitamin D

Levels Are Strongly Related to Systolic Blood Pressure But Do Not Predict Future Hypertension.

Hypertension. 2010 March 1, 2010;55(3):792-8.

73. Carbone F, Mach F, Vuilleumier N, Montecucco F. Potential pathophysiological role for the

vitamin D deficiency in essential hypertension. World journal of cardiology. 2014 May 26;6(5):260-

76. PubMed PMID: 24944756. Pubmed Central PMCID: Pmc4062123. Epub 2014/06/20. eng.

74. Burgaz A, Byberg L, Rautiainen S, Orsini N, Hakansson N, Arnlov J, et al. Confirmed

hypertension and plasma 25(OH)D concentrations amongst elderly men. Journal of internal medicine.

2011 Feb;269(2):211-8. PubMed PMID: 21091810. Epub 2010/11/26. eng.

75. Gannage-Yared MH, Chedid R, Khalife S, Azzi E, Zoghbi F, Halaby G. Vitamin D in relation

to metabolic risk factors, insulin sensitivity and adiponectin in a young Middle-Eastern population.

European journal of endocrinology / European Federation of Endocrine Societies. 2009

Jun;160(6):965-71. PubMed PMID: 19289535. Epub 2009/03/18. eng.

76. Pittas AG, Chung M, Trikalinos T, Mitri J, Brendel M, Patel K, et al. Systematic review:

Vitamin D and cardiometabolic outcomes. Annals of internal medicine. 2010 Mar 2;152(5):307-14.

PubMed PMID: 20194237. Pubmed Central PMCID: Pmc3211092. Epub 2010/03/03. eng.

77. Kunutsor SK, Apekey TA, Steur M. Vitamin D and risk of future hypertension: meta-analysis

of 283,537 participants. European journal of epidemiology. 2013 Mar;28(3):205-21. PubMed PMID:

23456138. Epub 2013/03/05. eng.

78. Vimaleswaran KS, Cavadino A, Berry DJ, Jorde R, Dieffenbach AK, Lu C, et al. Association

of vitamin D status with arterial blood pressure and hypertension risk: a mendelian randomisation

study. The lancet Diabetes & endocrinology. 2014 Sep;2(9):719-29. PubMed PMID: 24974252. Epub

2014/06/30. eng.

35

79. Al-Daghri NM, Alkharfy KM, Al-Saleh Y, Al-Attas OS, Alokail MS, Al-Othman A, et al.

Modest reversal of metabolic syndrome manifestations with vitamin D status correction: a 12-month

prospective study. Metabolism: clinical and experimental. 2012 May;61(5):661-6. PubMed PMID:

22075268. Epub 2011/11/15. eng.

80. Antonenko LV, Kholodova Iu D, Apukhovskaia LI, Voziian PA, Solodova EV, Kvashnina

LV. [Structural-functional changes in plasma lipoproteins during vitamin D-deficient rickets in

children]. Ukrainskii biokhimicheskii zhurnal. 1990 May-Jun;62(3):54-9. PubMed PMID: 2396322.

Epub 1990/05/01. Strukturno-funktsional'nye izmeneniia lipoproteinov plazmy krovi pri vitamin-D-

defitsitnom rakhite u detei. rus.

81. Auwerx J, Bouillon R, Kesteloot H. Relation between 25-hydroxyvitamin D3, apolipoprotein

A-I, and high density lipoprotein cholesterol. Arteriosclerosis and thrombosis : a journal of vascular

biology / American Heart Association. 1992 Jun;12(6):671-4. PubMed PMID: 1350464. Epub

1992/06/01. eng.

82. Boucher BJ, Mannan N, Noonan K, Hales CN, Evans SJ. Glucose intolerance and impairment

of insulin secretion in relation to vitamin D deficiency in east London Asians. Diabetologia. 1995

Oct;38(10):1239-45. PubMed PMID: 8690178. Epub 1995/10/01. eng.

83. Johnson MD, Nader NS, Weaver AL, Singh R, Kumar S. Relationships between 25-

hydroxyvitamin D levels and plasma glucose and lipid levels in pediatric outpatients. The Journal of

pediatrics. 2010 Mar;156(3):444-9. PubMed PMID: 19926097. Epub 2009/11/21. eng.

84. Kumar J, Muntner P, Kaskel FJ, Hailpern SM, Melamed ML. Prevalence and associations of

25-hydroxyvitamin D deficiency in US children: NHANES 2001-2004. Pediatrics. 2009

Sep;124(3):e362-70. PubMed PMID: 19661054. Pubmed Central PMCID: Pmc3749840. Epub

2009/08/08. eng.

85. Williams DM, Fraser A, Lawlor DA. Associations of vitamin D, parathyroid hormone and

calcium with cardiovascular risk factors in US adolescents. Heart (British Cardiac Society). 2011

Feb;97(4):315-20. PubMed PMID: 21193684. Pubmed Central PMCID: Pmc3931194. Epub

2011/01/05. eng.

86. Botella-Carretero JI, Alvarez-Blasco F, Villafruela JJ, Balsa JA, Vazquez C, Escobar-

Morreale HF. Vitamin D deficiency is associated with the metabolic syndrome in morbid obesity.

Clinical nutrition (Edinburgh, Scotland). 2007 Oct;26(5):573-80. PubMed PMID: 17624643. Epub

2007/07/13. eng.

87. Hypponen E, Boucher BJ, Berry DJ, Power C. 25-hydroxyvitamin D, IGF-1, and metabolic

syndrome at 45 years of age: a cross-sectional study in the 1958 British Birth Cohort. Diabetes. 2008

Feb;57(2):298-305. PubMed PMID: 18003755. Epub 2007/11/16. eng.

88. Maki KC, Rubin MR, Wong LG, McManus JF, Jensen CD, Marshall JW, et al. Serum 25-

hydroxyvitamin D is independently associated with high-density lipoprotein cholesterol and the

metabolic syndrome in men and women. Journal of clinical lipidology. 2009 Aug;3(4):289-96.


89. Melamed ML, Michos ED, Post W, Astor B. 25-hydroxyvitamin D levels and the risk of

mortality in the general population. Archives of internal medicine. 2008 Aug 11;168(15):1629-37.

PubMed PMID: 18695076. Pubmed Central PMCID: Pmc2677029. Epub 2008/08/13. eng.

90. Reis JP, von Muhlen D, Kritz-Silverstein D, Wingard DL, Barrett-Connor E. Vitamin D,

parathyroid hormone levels, and the prevalence of metabolic syndrome in community-dwelling older

adults. Diabetes care. 2007 Jun;30(6):1549-55. PubMed PMID: 17351276. Epub 2007/03/14. eng.

91. Wang L, Song Y, Manson JE, Pilz S, Marz W, Michaelsson K, et al. Circulating 25-hydroxy-

vitamin D and risk of cardiovascular disease: a meta-analysis of prospective studies. Circulation

Cardiovascular quality and outcomes. 2012 Nov;5(6):819-29. PubMed PMID: 23149428. Pubmed

Central PMCID: Pmc3510675. Epub 2012/11/15. eng.

92. Afzal S, Brøndum-Jacobsen P, Bojesen SE, Nordestgaard BG. Genetically low vitamin D

concentrations and increased mortality: mendelian randomisation analysis in three large cohorts. BMJ.

2014;349.

93. Jorde R, Schirmer H, Wilsgaard T, Joakimsen RM, Mathiesen EB, Njølstad I, et al.

Polymorphisms Related to the Serum 25-Hydroxyvitamin D Level and Risk of Myocardial Infarction,

Diabetes, Cancer and Mortality. The Tromsø Study. PloS one. 2012 05/23

36

02/10/received

04/17/accepted;7(5):e37295. PubMed PMID: PMC3359337.

94. Levin GP, Robinson-Cohen C, de Boer IH, Houston DK, Lohman K, Liu Y, et al. Genetic

variants and associations of 25-hydroxyvitamin D concentrations with major clinical outcomes.

JAMA : the journal of the American Medical Association. 2012 Nov 14;308(18):1898-905. PubMed

PMID: 23150009. Pubmed Central PMCID: Pmc3645444. Epub 2012/11/15. eng.

95. Meyer HE, Holvik K, Lips P. Should vitamin D supplements be recommended to prevent

chronic diseases? BMJ. 2015;350.

96. Kunutsor SK, Burgess S, Munroe PB, Khan H. Vitamin D and high blood pressure: causal

association or epiphenomenon? European journal of epidemiology. 2014 Jan;29(1):1-14. PubMed

PMID: 24374742. Epub 2014/01/01. eng.

97. Larsen T, Mose FH, Bech JN, Hansen AB, Pedersen EB. Effect of cholecalciferol

supplementation during winter months in patients with hypertension: a randomized, placebo-

controlled trial. American journal of hypertension. 2012 Nov;25(11):1215-22. PubMed PMID:

22854639. Epub 2012/08/03. eng.

98. Forman JP, Scott JB, Ng K, Drake BF, Suarez EG, Hayden DL, et al. Effect of Vitamin D

Supplementation on Blood Pressure in Blacks. Hypertension. 2013 April 1, 2013;61(4):779-85.

99. Jorde R, Grimnes G. Vitamin D and metabolic health with special reference to the effect of

vitamin D on serum lipids. Progress in lipid research. 2011 Oct;50(4):303-12. PubMed PMID:

21640757. Epub 2011/06/07. eng.

100. Zittermann A, Frisch S, Berthold HK, Gotting C, Kuhn J, Kleesiek K, et al. Vitamin D

supplementation enhances the beneficial effects of weight loss on cardiovascular disease risk markers.

The American journal of clinical nutrition. 2009 May;89(5):1321-7. PubMed PMID: 19321573. Epub

2009/03/27. eng.

101. Elamin MB, Abu Elnour NO, Elamin KB, Fatourechi MM, Alkatib AA, Almandoz JP, et al.

Vitamin D and cardiovascular outcomes: a systematic review and meta-analysis. The Journal of

clinical endocrinology and metabolism. 2011 Jul;96(7):1931-42. PubMed PMID: 21677037. Epub

2011/06/17. eng.

102. Zittermann A, Kuhn J, Dreier J, Knabbe C, Gummert JF, Borgermann J. Vitamin D status and

the risk of major adverse cardiac and cerebrovascular events in cardiac surgery. European heart

journal. 2013 May;34(18):1358-64. PubMed PMID: 23315905. Epub 2013/01/15. eng.

103. Kamycheva E, Joakimsen RM, Jorde R. Intakes of calcium and vitamin d predict body mass

index in the population of Northern Norway. The Journal of nutrition. 2003 Jan;133(1):102-6.


104. Cheng S, Massaro JM, Fox CS, Larson MG, Keyes MJ, McCabe EL, et al. Adiposity,

Cardiometabolic Risk, and Vitamin D Status: The Framingham Heart Study. Diabetes. 2010 10/15

07/10/received

09/22/accepted;59(1):242-8. PubMed PMID: PMC2797928.

105. Snijder MB, van Dam RM, Visser M, Deeg DJ, Dekker JM, Bouter LM, et al. Adiposity in

relation to vitamin D status and parathyroid hormone levels: a population-based study in older men

and women. The Journal of clinical endocrinology and metabolism. 2005 Jul;90(7):4119-23. PubMed

PMID: 15855256. Epub 2005/04/28. eng.

106. Andersen T, McNair P, Hyldstrup L, Fogh-Andersen N, Nielsen TT, Astrup A, et al.

Secondary hyperparathyroidism of morbid obesity regresses during weight reduction. Metabolism:

clinical and experimental. 1988 May;37(5):425-8. PubMed PMID: 3367788. Epub 1988/05/01. eng.

107. Kamycheva E, Sundsfjord J, Jorde R. Serum parathyroid hormone level is associated with

body mass index. The 5th Tromso study. European journal of endocrinology / European Federation of

Endocrine Societies. 2004 Aug;151(2):167-72. PubMed PMID: 15296470. Epub 2004/08/07. eng.

108. Dunlop TW, Vaisanen S, Frank C, Molnar F, Sinkkonen L, Carlberg C. The human

peroxisome proliferator-activated receptor delta gene is a primary target of 1alpha,25-

dihydroxyvitamin D3 and its nuclear receptor. Journal of molecular biology. 2005 Jun 3;349(2):248-

60. PubMed PMID: 15890193. Epub 2005/05/14. eng.

37

109. Maestro B, Campion J, Davila N, Calle C. Stimulation by 1,25-dihydroxyvitamin D3 of

insulin receptor expression and insulin responsiveness for glucose transport in U-937 human

promonocytic cells. Endocrine journal. 2000 Aug;47(4):383-91. PubMed PMID: 11075718. Epub

2000/11/15. eng.

110. Maestro B, Molero S, Bajo S, Davila N, Calle C. Transcriptional activation of the human

insulin receptor gene by 1,25-dihydroxyvitamin D(3). Cell biochemistry and function. 2002

Sep;20(3):227-32. PubMed PMID: 12125099. Epub 2002/07/19. eng.

111. Cheung PS, Thompson NW, Brothers TE, Vinik AI. Effect of hyperparathyroidism on the

control of diabetes mellitus. Surgery. 1986 Dec;100(6):1039-47. PubMed PMID: 3538462. Epub

1986/12/01. eng.

112. Teegarden D, Donkin SS. Vitamin D: emerging new roles in insulin sensitivity. Nutrition

research reviews. 2009 Jun;22(1):82-92. PubMed PMID: 19555519. Epub 2009/06/27. eng.

113. Palomer X, Gonzalez-Clemente JM, Blanco-Vaca F, Mauricio D. Role of vitamin D in the

pathogenesis of type 2 diabetes mellitus. Diabetes, obesity & metabolism. 2008 Mar;10(3):185-97.


114. Krul-Poel Y, Wijland H, Stam F, ten Boekel E, Lips P, Simsek S. Study protocol: a

randomised placebo-controlled clinical trial to study the effect of vitamin D supplementation on

glycaemic control in type 2 Diabetes Mellitus SUNNY trial. BMC Endocr Disord. 2014

2014/07/17;14(1):1-8. English.

115. Wang G, Li Y, Li L, Yu F, Cui L, Ba Y, et al. Association of the vitamin D binding protein

polymorphisms with the risk of type 2 diabetes mellitus: a meta-analysis. BMJ open.

2014;4(11):e005617. PubMed PMID: 25371416. Pubmed Central PMCID: Pmc4225232. Epub

2014/11/06. eng.

116. Kharroubi I, Ladriere L, Cardozo AK, Dogusan Z, Cnop M, Eizirik DL. Free fatty acids and

cytokines induce pancreatic beta-cell apoptosis by different mechanisms: role of nuclear factor-

kappaB and endoplasmic reticulum stress. Endocrinology. 2004 Nov;145(11):5087-96. PubMed

PMID: 15297438. Epub 2004/08/07. eng.

117. Wolden-Kirk H, Overbergh L, Christesen HT, Brusgaard K, Mathieu C. Vitamin D and

diabetes: its importance for beta cell and immune function. Molecular and cellular endocrinology.

2011 Dec 5;347(1-2):106-20. PubMed PMID: 21889571. Epub 2011/09/06. eng.

118. Guillot X, Semerano L, Saidenberg-Kermanac'h N, Falgarone G, Boissier MC. Vitamin D

and inflammation. Joint, bone, spine : revue du rhumatisme. 2010 Dec;77(6):552-7. PubMed PMID:

21067953.

119. Beilfuss J, Berg V, Sneve M, Jorde R, Kamycheva E. Effects of a 1-year supplementation

with cholecalciferol on interleukin-6, tumor necrosis factor-alpha and insulin resistance in overweight

and obese subjects. Cytokine. 2012 12//;60(3):870-4.

120. Vaidya A, Williams JS, Forman JP. THE INDEPENDENT ASSOCIATION BETWEEN 25-

HYDROXYVITAMIN D AND ADIPONECTIN AND ITS RELATION WITH BMI IN TWO

LARGE COHORTS: the NHS and the HPFS. Obesity (Silver Spring, Md). 2012 07/14;20(1):186-91.

PubMed PMID: PMC3461263.

121. Harant H, Andrew PJ, Reddy GS, Foglar E, Lindley IJ. 1alpha,25-dihydroxyvitamin D3 and a

variety of its natural metabolites transcriptionally repress nuclear-factor-kappaB-mediated interleukin-

8 gene expression. European journal of biochemistry / FEBS. 1997 Nov 15;250(1):63-71. PubMed

PMID: 9431991. Epub 1998/02/07. eng.

122. Mizokami A, Yasutake Y, Gao J, Matsuda M, Takahashi I, Takeuchi H, et al. Osteocalcin

induces release of glucagon-like peptide-1 and thereby stimulates insulin secretion in mice. PloS one.

2013;8(2):e57375. PubMed PMID: 23437377. Pubmed Central PMCID: Pmc3577726. Epub

2013/02/26. eng.

123. Winhofer Y, Handisurya A, Tura A, Bittighofer C, Klein K, Schneider B, et al. Osteocalcin is

related to enhanced insulin secretion in gestational diabetes mellitus. Diabetes care. 2010

Jan;33(1):139-43. PubMed PMID: 19808925. Pubmed Central PMCID: Pmc2797959. Epub

2009/10/08. eng.

124. Mark AB, Poulsen MW, Andersen S, Andersen JM, Bak MJ, Ritz C, et al. Consumption of a

diet low in advanced glycation end products for 4 weeks improves insulin sensitivity in overweight

women. Diabetes care. 2014 Jan;37(1):88-95. PubMed PMID: 23959566. Epub 2013/08/21. eng.

38

125. Vlassara H, Cai W, Crandall J, Goldberg T, Oberstein R, Dardaine V, et al. Inflammatory

mediators are induced by dietary glycotoxins, a major risk factor for diabetic angiopathy. Proceedings

of the National Academy of Sciences. 2002 November 26, 2002;99(24):15596-601.

126. Singh R, Barden A, Mori T, Beilin L. Advanced glycation end-products: a review.

Diabetologia. 2001 Feb;44(2):129-46. PubMed PMID: 11270668. Epub 2001/03/29. eng.

127. Cohen-Lahav M, Shany S, Tobvin D, Chaimovitz C, Douvdevani A. Vitamin D decreases

NFkappaB activity by increasing IkappaBalpha levels. Nephrology, dialysis, transplantation : official

publication of the European Dialysis and Transplant Association - European Renal Association. 2006

Apr;21(4):889-97. PubMed PMID: 16455676. Epub 2006/02/04. eng.

128. Talmor Y, Golan E, Benchetrit S, Bernheim J, Klein O, Green J, et al. Calcitriol blunts the

deleterious impact of advanced glycation end products on endothelial cells. American journal of

physiology Renal physiology. 2008 May;294(5):F1059-64. PubMed PMID: 18353875. Epub

2008/03/21. eng.

129. Irani M, Minkoff H, Seifer DB, Merhi Z. Vitamin D increases serum levels of the soluble

receptor for advanced glycation end products in women with PCOS. The Journal of clinical

endocrinology and metabolism. 2014 May;99(5):E886-90. PubMed PMID: 24606102. Epub

2014/03/13. eng.

130. Thomson RL, Spedding S, Buckley JD. Vitamin D in the aetiology and management of

polycystic ovary syndrome. Clinical endocrinology. 2012 Sep;77(3):343-50. PubMed PMID:

22574874. Epub 2012/05/12. eng.

131. Panidis D, Balaris C, Farmakiotis D, Rousso D, Kourtis A, Balaris V, et al. Serum

parathyroid hormone concentrations are increased in women with polycystic ovary syndrome. Clinical

chemistry. 2005 Sep;51(9):1691-7. PubMed PMID: 16037412. Epub 2005/07/23. eng.

132. Yoshizawa T, Handa Y, Uematsu Y, Takeda S, Sekine K, Yoshihara Y, et al. Mice lacking

the vitamin D receptor exhibit impaired bone formation, uterine hypoplasia and growth retardation

after weaning. Nature genetics. 1997 Aug;16(4):391-6. PubMed PMID: 9241280. Epub 1997/08/01.

eng.

133. Diamanti-Kandarakis E, Piouka A, Livadas S, Piperi C, Katsikis I, Papavassiliou AG, et al.

Anti-mullerian hormone is associated with advanced glycosylated end products in lean women with

polycystic ovary syndrome. European journal of endocrinology / European Federation of Endocrine

Societies. 2009 May;160(5):847-53. PubMed PMID: 19208775. Epub 2009/02/12. eng.

134. Irani M, Seifer D, Minkoff H, Merhi Z. Vitamin d normalizes abnormally elevated serum

antimullerian hormone levels usually noted in women with polycystic ovary syndrome. Obstetrics and

gynecology. 2014 May;123 Suppl 1:189S. PubMed PMID: 24770121. Epub 2014/04/29. eng.

135. Li YC, Qiao G, Uskokovic M, Xiang W, Zheng W, Kong J. Vitamin D: a negative endocrine

regulator of the renin–angiotensin system and blood pressure. The Journal of Steroid Biochemistry

and Molecular Biology. 2004 5//;89–90(0):387-92.

136. Pludowski P, Holick MF, Pilz S, Wagner CL, Hollis BW, Grant WB, et al. Vitamin D effects

on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility,

pregnancy, dementia and mortality-a review of recent evidence. Autoimmunity reviews. 2013

Aug;12(10):976-89. PubMed PMID: 23542507. Epub 2013/04/02. eng.

137. Baz-Hecht M, Goldfine AB. The impact of vitamin D deficiency on diabetes and

cardiovascular risk. Current opinion in endocrinology, diabetes, and obesity. 2010 Apr;17(2):113-9.


138. O'Connell TD, Berry JE, Jarvis AK, Somerman MJ, Simpson RU. 1,25-Dihydroxyvitamin D3

regulation of cardiac myocyte proliferation and hypertrophy. The American journal of physiology.

1997 Apr;272(4 Pt 2):H1751-8. PubMed PMID: 9139959. Epub 1997/04/01. eng.

139. Resnick LM, Muller FB, Laragh JH. Calcium-regulating hormones in essential hypertension.

Relation to plasma renin activity and sodium metabolism. Annals of internal medicine. 1986

Nov;105(5):649-54. PubMed PMID: 3532893. Epub 1986/11/01. eng.

140. Verma S, Gupta M, Holmes DT, Xu L, Teoh H, Gupta S, et al. Plasma renin activity predicts

cardiovascular mortality in the Heart Outcomes Prevention Evaluation (HOPE) study. European heart

journal. 2011 Sep;32(17):2135-42. PubMed PMID: 21415069. Epub 2011/03/19. eng.

141. Oh J, Weng S, Felton SK, Bhandare S, Riek A, Butler B, et al. 1,25(OH)2 vitamin d inhibits

foam cell formation and suppresses macrophage cholesterol uptake in patients with type 2 diabetes

39

mellitus. Circulation. 2009 Aug 25;120(8):687-98. PubMed PMID: 19667238. Pubmed Central


142. Reid IR, Mason B, Horne A, Ames R, Clearwater J, Bava U, et al. Effects of calcium

supplementation on serum lipid concentrations in normal older women: a randomized controlled trial.

The American journal of medicine. 2002 Apr 1;112(5):343-7. PubMed PMID: 11904107. Epub

2002/03/21. eng.

143. Sourris KC, Lyons JG, Dougherty SL, Chand V, Straznicky NE, Schlaich MP, et al. Plasma

advanced glycation end products (AGEs) and NF-kappaB activity are independent determinants of

diastolic and pulse pressure. Clinical chemistry and laboratory medicine : CCLM / FESCC. 2014 Jan

1;52(1):129-38. PubMed PMID: 23525877. Epub 2013/03/26. eng.

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Titles of Figures

Figure 1. Proposed mechanisms of vitamin D deficiency in cardiometabolic diseases:

Diagram illustrating the suggested mechanistic pathways by which vitamin D can affect

risk factors associated with the development of cardiometabolic conditions including

PCOS, diabetes and cardiovascular disease.

Documents

Vitamin D and Cardiometabolic Risk Factors and Diseases