Journal of Critical Care (2012) 27, 400–409

Serial changes in adiponectin and resistin in critically illpatients with sepsis: Associations with sepsis phase,severity, and circulating cytokine levels☆,☆☆

Dimitra A. Vassiliadi MDa,b,⁎, Marinella Tzanela MDb, Anastasia Kotanidou MDa,Stylianos E. Orfanos MD c, Nikitas Nikitas MDc, Apostolos Armaganidis MDc,Michalis Koutsilieris MD, PhDd, Charis Roussos MD, PhDa,Stylianos Tsagarakis MD, PhD, FRCPb, Ioanna Dimopoulou MDc

aFirst Department of Critical Care Medicine, Evangelismos Hospital and M. Simou Laboratory, Athens, GreecebDepartment of Endocrinology, Diabetes and Metabolism, Evangelismos Hospital, Athens, GreececSecond Critical Care Department, Attikon University Hospital, Athens, GreecedDepartment of Experimental Physiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece

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Keywords:Adiponectin;Resistin;Cytokines;Sepsis;Severe sepsis;Septic shock;SOFA score;APACHE II score

AbstractPurpose: The aim of the present study was to describe the variation in adiponectin and resistin levels, 2adipokines with opposing effects on metabolism, in mechanically ventilated patients with sepsis andtheir relationships to disease severity and cytokine levels.Materials and Methods: An observational prospective study was conducted in a secondary/tertiary unit.Forty-one mechanically ventilated patients diagnosed as having sepsis were included in the study. TheAcute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scoreswere estimated. Adiponectin, resistin, and cytokines were measured upon sepsis diagnosis and every 3to 4 days thereafter until day 30. Adiponectin and resistin were also measured in 40 controls.Results: The patients had higher adiponectin (10.9 ± 6.1 μg/mL vs 6.0 ± 2.9 μg/mL, P b .001) andresistin (24.7 ng/mL vs 3.8 ng/mL, P b .001) levels compared with the controls. Adiponectin increasedand resistin decreased significantly over time in the entire cohort. Resistin correlated with AcutePhysiology and Chronic Health Evaluation II, Sequential Organ Failure Assessment, interleukin (IL)-6,IL-8, and IL-10 and was significantly higher in severe sepsis/septic shock compared with sepsis. Nocorrelations between adiponectin and clinical scores were noted.Conclusions: Adiponectin and resistin change reciprocally during the course of sepsis. Resistin relatesto the severity of sepsis and the degree of inflammatory response. Adiponectin and resistin may play acritical role in the metabolic adaptations observed in sepsis.© 2012 Elsevier Inc. All rights reserved.

☆ Conflict of interest statement: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.☆☆ This research did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sector.⁎ Corresponding author. Endocrine Unit, Second Department of Internal Medicine, Attikon University Hospital, 12462 Athens, Greece. Tel.: +30

105832584; fax: +30 2105832590.E-mail address: dimitra.vas@gmail.com (D.A. Vassiliadi).

883-9441/$ – see front matter © 2012 Elsevier Inc. All rights reserved.oi:10.1016/j.jcrc.2012.04.007

401Adipokines in critically ill patients with sepsis

1. Introduction We also examined their relations to serum cytokines and

Profound alterations in metabolic pathways occur duringsepsis [1]. Changes that occur during the first hours to daysare considered part of an acute adaptive metabolic response[2]. Advances in intensive care medicine and mechanical lifesupport have led to extended immediate survival of thesepatients who enter a prolonged phase of dependency on vitalorgan support. This phase is characterized by different andpossibly less effective coping mechanisms whose patho-physiology is complex and remains largely unknown. Agreater understanding of the mechanisms underlying themetabolic changes in this protracted phase of sepsis holdspromise for the development of new therapeutic strategies.The endocrine system consists of a major component of theadaptive response to stress. Alterations of hypothalamic-pituitary adrenal, growth hormone, and thyroid axes in boththe acute and the chronic phases of critical illness have beencharacterized to some extent [2], However, with theexception of leptin [3-5], the release patterns of adiposetissue–derived hormones, referred as adipokines, have notbeen thoroughly investigated in patients with sepsis.Adipokines regulate metabolism and mediate multipleinteractions with the immune and endocrine systems [6,7].In addition, alterations in adipokine levels may represent aconsequence of the inflammatory response [8], whereascertain adipokines such as resistin can also be derived fromimmune cells [7].

Adiponectin and resistin are 2 recently describedadipokines that have been implicated in the regulation ofvarious metabolic processes [6]. Adiponectin is derivedalmost exclusively from the adipose tissue and is regarded asan insulin-sensitizing hormone with anti-inflammatoryproperties [6,9]. Resistin was introduced as the hormonethat links obesity with insulin resistance [10]. However, inhumans, as opposed to murine species, circulating resistin isderived mainly from immune cells [11] and probablycontributes to inflammation-induced insulin resistance[12].So far, most of the current data on the role of theseadipokines in critical illness are derived from animal models[9,12,13] or experimental studies of human acute endotox-emia [8,11,14]. A number of clinical studies have addressedthe circulating levels of these adipokines upon admission tothe intensive care unit (ICU) in mixed populations [15-17].The pathophysiologic mechanisms involved in sepsis,however, differ from other noninfectious causes of criticalillness, and only few investigations have specifically targetedpatients with sepsis [18,19]. Moreover, data on serialmeasurements, covering both the acute and the chronicphases of sepsis, are very limited [4,19,20].

Given the opposing effects of adiponectin and resistin onmetabolism, our primary objective was to study the kineticsof these adipokines during the acute and, particularly, theprotracted phases of sepsis. Therefore, we aimed to analyzethose patients who exhibited the full spectrum of changesfrom acute sepsis to chronic sepsis and subsequent recovery.

whether changes of these adipokines relate to the severityof sepsis.

2. Materials and methods

2.1. Study population

We prospectively enrolled 65 consecutive patientsadmitted to the ICU of “Evangelismos” General Hospitalduring the period February 2003 to February 2004. Somepatients of this cohort have been included in previouspublications [21,22]. All patients fulfilled the criteria ofsepsis, as established by the American College of ChestPhysicians/Society of Critical Care Medicine consensusconference [23]. The inclusion criteria were as follows:diagnosis of sepsis within the last 24 hours; age above 18years; no history of psychiatric, endocrine, or metabolicdisease; exclusion of pregnancy in premenopausal women;no HIV infection; no history of antitumor medication orradiation; and no treatment with steroids, thyroxine, ordopamine before and/or during the study. We analyzed onlysamples collected from patients with at least 7-day durationof sepsis (aiming to study the acute and chronic phases ofsepsis). Of the initial 65 patients, 6 died and 6 weredischarged before completing 7 days in the ICU, whereas 12received glucocorticoids. Thus, we studied 41 patients (34men, 7 women; mean age, 52.0 ± 19.4 years; range, 18-72years) (Fig. 1). None of the patients received intensiveinsulin therapy. Once admitted to the ICU and gastrointes-tinal track function permitting, all patients were administeredcontinuous total or partial parenteral and/or enteral nutritionwith the same standard composition.

The control group for adiponectin and resistin levelsconsisted of 40 apparently healthy overnight-fasted blooddonors (12 women, 28 men; mean age, 51.2 ± 7.3 years).There was no difference in the male-to-female ratio or theage between controls and patients.

2.2. Study protocol

This is an observational prospective study. The hospital'sethics committee approved the study, and all subjects or theirrelatives gave informed consent. The following data wererecorded: age, sex, admission diagnosis, sepsis stage, site ofinfection, pathogens, and ICU outcome (30-day mortalityrate). Patients were classified as having sepsis, severe sepsis,and septic shock according to the definitions established bythe American College of Chest Physicians/Society of CriticalCare Medicine consensus conference [23]. Blood samplesfor measurements of adiponectin, resistin, interleukin (IL)-6,IL-8, and IL-10 were collected in the morning, on the day ofsepsis diagnosis (day 1), and on days 3, 7, 10, 14, 18, 22, 26,and 30, or upon termination of mechanical ventilation or

Fig. 1 Flowchart of the patients' population.

402 D.A. Vassiliadi et al.

death. The clinical severity of sepsis was evaluated usingthe Acute Physiology and Chronic Health Evaluation(APACHE) II and the Sequential Organ Failure Assessment(SOFA) on all the aforementioned time points. Insulinresistance was assessed by the Homeostasis ModelAssessment (HOMA) index and was calculated using thefollowing formula: [fasting insulin (IU/mL) × fastingglucose (mg/dL)]/405] [24].

2.3. Measurements

Glucose was measured using a standard laboratorymethod. Insulin was assayed using an immunoradiometricassay (Biosource Europe SA, Nivelles, Belgium), with alower detection limit of 1 μIU/mL and an intra-assaycoefficients of variation (CVs) of 2.2% at 6.6 ± 0.1 μIU/mLand 1.6% at 53.3 ± 0.8 μIU/mL. Adiponectin was measuredusing a human adiponectin enzyme-linked immunosorbentassay, a quantitative sandwich enzyme immunoassay(Quantikine; R&D Systems Inc, Oxfordshire, UK). Theminimum detectable limit of the assay ranges from 0.079 to0.891 ng/mL (mean, 0.246 ng/mL); the intra-assay CVs are2.5% at 0.0198 μg/mL, 3.4% at 0.0699 μg/mL, and 4.7% at0.143 μg/mL. The reference range of the assay is 0.865 to21.424 μg/mL (mean ± SD, 6.641 ± 3.665 μg/mL).

Resistin was measured using human resistin enzyme-linked immunosorbent assay, a biotin-labeled antibody-based sandwich enzyme immunoassay (BioVendor GmbH,Heidelberg, Germany). The minimum detectable limit of the

assay is 0.1 ng/mL; the intra-assay CVs for resistin are 2.8%at 7.5 ng/mL and 3.4% at 11.35 ng/mL. The reference rangeof the assay is 8.1 ± 4.0 ng/mL (mean ± SD; n = 123).

Concentrations of IL-6, IL-8, and IL-10 in sera wereestimated in duplicate after staining with monoclonal anti-bodies and passage through FACSCalibur (Becton Dickinson,Cockeysville, MD). Lowest limits of detection were 3 pg/mLfor IL-6, 3 pg/mL for IL-8, and 3 pg/mL for IL-10.

2.4. Statistical analysis

Statistical packages SPSS 15.0 (SPSS, Chicago, Illinois)and Sigma Plot 11.0 (Systat Software Inc. [SSI], San Jose,CA) were used for data analysis. Continuous variables arereported as mean ± SD or as medians and interquartile range(IQR). Normality was checked with the Shapiro-Wilk test.Logarithmic transformation was applied to normalize databefore using parametric tests. t Test or Mann-Whitneynonparametric test was applied to compare adipokine levelsbetween patients and controls. Mixed-effect models wereused to assess changes in concentrations of adiponectin andresistin (transformed in a logarithmic scale) over time and toassess differences in adiponectin and resistin profiles bysepsis stage (sepsis vs severe sepsis/septic shock) and by 30-day mortality. For pairwise multiple comparison procedures,the Bonferroni confidence interval adjustment was applied.To assess changes in adiponectin and resistin levels between2 time points (at sepsis onset or day 1 vs last measurementbefore termination of mechanical ventilation or death), in

403Adipokines in critically ill patients with sepsis

survivors and nonsurvivors separately, we applied the paired-samples t test for adiponectin and the Wilcoxon signed ranktest for resistin. All correlations between variables were testedusing Spearman correlation coefficient. A P b .05 wasconsidered statistically significant in all analyses.

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3. Results

3.1. Patients' characteristics

The characteristics of the entire cohort (N = 41), includingsex, age, clinical severity scores, adipokines, glucose,insulin, HOMA index, and cytokine levels, are shown inTable 1. There were 9 medical cases (n = 9) including brainhemorrhage (n = 4), pancreatitis (n = 2), suicide attempt (n =1), lung hemorrhage (n = 1), and pneumonia (n = 1); 15patients with trauma; and 17 surgical cases consisting ofmajor gastrointestinal operations (n = 10), cardiovascularoperations (n = 1), lung operations (n = 3), and otheroperations (n = 3). The most common site of infection waspneumonia (n = 18), followed by intra-abdominal infections(n = 16) and various other infections (n = 7). Pathogens wereidentified in 33 patients: gram-negative bacteria in 28 (16Acinetobacter species, 6 Enterobacter species, 4 Pseudo-monas aeruginosa, 1 Klebsiella pneumoniae, and 1 Steno-trophomonas maltophilia) and gram-positive in 5 patients (3Staphylococcus aureus, 1 Staphylococcus epidermidis, and 1Enterococcus). Sepsis stages included sepsis (n = 15), severesepsis (n = 16), and septic shock (n = 10). Of the 41 patientswith sepsis studied, 11 died in the ICU (within 7-26 daysfrom sepsis onset), yielding a 30-day mortality rate of 27%.In particular, the 30-day mortality rate was 7%, 31%, and50% for sepsis, severe sepsis, and septic shock, respectively.Of the 30 survivors, 25 patients have been extubated at

Table 1 Patients' clinical and laboratory characteristics on theday of admission in the ICU

All patients (N = 41)

Sex 7 F/34 MAge (y) 52.0 ± 19.4SOFA a 10.0 (7.0-12.0)APACHE II b 19.0 ± 6.5Adiponectin (μg/mL) b 10.9 ± 6.1Resistin (ng/mL) a 24.7 (18.4-41.1)Glucose (mg/dL) b 159.1 ± 47.9Insulin (μIU/mL) a 25.7 (16.1-49.8)HOMA index a 10.8 (6.6-26.7)IL-6 (pg/mL) a 265 (110–473)IL-8 (pg/mL) a 135 (68–225)IL-10 (pg/mL) a 12 (5–23)

F, female; M, male.a Median and IQR in parentheses.b Mean ± SD.

various time points, whereas 5 patients remained intubatedupon completion of the protocol, that is, for more than 30days (Fig. 1). The number of patients requiring norepineph-rine administration on each time point is shown in Fig. 2.

3.2. Adipokines in patients with sepsis and controls

On day 1, patients with sepsis compared with healthycontrols had a significantly higher mean adiponectin level(10.9 ± 6.1 μg/mL vs 6.0 ± 2.9 μg/mL, P b .001), along withhigher median resistin level (24.7 ng/mL [IQR, 18.4-41.1 ng/mL] vs 3.8 ng/mL [IQR 3.2-5.5 ng/mL], P b .001).

3.3. Adipokine levels during the acute and chronicphases of sepsis

Mixed-model analysis showed that adiponectin increasedsignificantly from the acute to the prolonged phase of sepsis

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ig. 2 A, Adiponectin levels increased during the course ofepsis in the whole cohort (P = .01). Pairwise multiple comparisonsvealed that the difference was significant between days 1 and 7,0, 14, and 18 (all P b .01). B, Resistin levels decreased during theourse of sepsis in the whole cohort (P b .001). Pairwise multipleomparisons revealed that the difference was significant betweenays 26 and 1, 3, and 10 (all P b .05). Presented values are means ±EM. N, number of patients in the respective days; V, number ofatients requiring vasopressors (ie, norepinephrine) in the respec-

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ig. 3 A, Adiponectin levels in patients with sepsis comparedith patients with severe sepsis and septic shock. Significantifferent patterns are seen in the 2 groups (P b .001); adiponectincreased in patients with sepsis (P = .01), whereas they remainedonstant in patients with severe sepsis/septic shock. B, Patients withepsis had significantly lower resistin levels compared with patientsith severe sepsis and septic shock throughout the course of sepsisb .002). Presented values are means ± SEM. N, number of

atients in the respective days.

404 D.A. Vassiliadi et al.

(P = .01) in the entire cohort of patients (Fig. 2A). Pairwisemultiple comparisons revealed that the differences weresignificant between days 1 and 7, 10, 14, and 18 (all P b .01).In contrast, resistin (log transformed) decreased significantlylate in the course of sepsis (P b .001; Fig. 2B). Pairwisemultiple comparisons revealed that the differences weresignificant between days 26 and 1, 3, and 10 (all P b .05).

3.4. Adipokines and sepsis stages and/or severity

Subgroup analysis according to the stages of sepsisrevealed a higher adiponectin level in patients with severesepsis (11.8 ± 6.4 μg/mL, P = .001) and septic shock (12.2 ±6.6 μg/mL, P b .01), whereas patients with sepsis hadsimilar levels (8.8 ± 5.0 μg/mL; P, nonsignificant) comparedwith the controls (6.0 ± 2.9 μg/mL). The controls had asignificantly lower median resistin level compared withpatients with sepsis (3.8 ng/mL vs 18.6 ng/mL, P b .001),severe sepsis (3.8 ng/mL vs 35.1 ng/mL, P b .001), andseptic shock (3.8 ng/mL vs 35.0 ng/mL, P b .001).

According to mixed-model analysis, there was nodifference in adiponectin between patients having sepsisand those with severe sepsis/septic shock (P = .20).However, adiponectin levels displayed different patterns inthe 2 groups (P b .001), with an increment with time inpatients with sepsis (P = .01), whereas they remainedconstant in patients with severe sepsis/septic shock (Fig. 3A).

According to mixed-model analysis, resistin (log trans-formed) was significantly lower in sepsis compared withsevere sepsis/septic shock throughout the course of sepsis(P b .002; Fig. 3B).

On day 1, there were no correlations between adiponectinand APACHE II (ρ = 0.2, P = .3) or SOFA score (ρ = 0.2,P = .4). In contrast, resistin correlated significantly with bothAPACHE II (ρ = 0.5, P = .01) and SOFA scores (ρ = 0.6,P b .001; Fig. 4A, B).

3.5. Correlations between cytokines and adipokines

Adiponectin correlated inversely with IL-8 during theprolonged phase of sepsis (Table 2).

The correlations of sepsis-associated cytokines IL-6 andIL-8 to resistin levels on day 1 are shown in Fig. 4 (C, D),whereas correlations for all days are given in Table 3. Therewere positive correlations between IL-6, IL-8, and resistin atmost time points. Interleukin-10 correlated with resistin onlyon day 1 (ρ = 0.4, P = .01).

No correlation between adipokines and CRP levels orwhite blood cell count was found.

3.6. Adipokine levels and clinical outcome

Mixed-model analysis showed that there were nodifferences in adiponectin (P = .9) and resistin (P = .3)between survivors and nonsurvivors during the study period.

Fwdincsw(Pp

In a subgroup of patients (n = 25) who showed clinicalimprovement and organ dysfunction resolution within thestudy period, that is, those who were extubated within the 30days of the study protocol and after excluding those whowere still intubated after the completion of the study (n = 5),adiponectin increased significantly from day 1 to the lastperformed measurement (10.3 ± 5.1 μg/mL vs 14.4 ± 7.8 μg/mL, P = .003) (Fig. 5A), whereas resistin decreasedsignificantly (23 ng/mL vs 15 ng/mL, P b .001; Fig. 5B).In these patients, a parallel significant decrease in clinicalseverity scores including APACHE II (day 1: 18 ± 7 vs lastday: 10 ± 7, P b .001) and SOFA (day 1: 7 [IQR, 6-13] vslast day: 5 [IQR, 3-7], P b .001), as well as IL-6, IL-8, andIL-10 levels, was seen. The pattern of changes ofadiponectin, resistin, SOFA score, IL-6, IL-8, and IL-10 isshown in Fig. 6. All parameters changed significantly withtime (adiponectin, P b .001; resistin, P = .02; SOFA score,P b .001; IL-6, P b .001; IL-8; P b .001; IL-10, P b .001), asshown by mixed-model analysis.

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405Adipokines in critically ill patients with sepsis

In patients who died, no significant change was seenregarding adiponectin (day 1: 11.9 ± 7.7 μg/mL vs last

Table 2 Correlations (ρ) between adiponectin and IL-8 levelsin all patients

Adiponectin

Day 1 Day 3 Day 7 Day 10 Day 14 Day 18

IL-8Day 1 ρ 0.01 −0.10 −0.08 −0.35 −0.17 −0.22

P .95 .58 .66 .08 .48 .37Day 3 ρ −0.04 −0.13 −0.10 −0.32 −0.24 −0.26

P .81 .48 .58 .12 .31 .32Day 7 ρ −0.07 −0.21 −0.17 −0.33 −0.55 −0.46

P .70 .23 .33 .11 .01 .06Day10

ρ −0.12 −0.21 −0.20 −0.40 −0.57 −0.64P .55 .28 .31 .05 .01 .01

Day14

ρ −0.41 −0.46 −0.55 −0.53 −0.59 −0.46P .08 .05 .01 .04 .01 .09

Day18

ρ −0.38 −0.37 −0.45 −0.59 −0.55 −0.70P .16 .18 .09 .04 .04 .01

Bold denotes statistically significant correlations.

measurement: 13.2 ± 8.3 μg/mL, P = .4) and resistin levels(day 1: 29.8 ng/mL vs last measurement: 28 ng/mL, P = .3).

3.7. Metabolic parameters and adipokines

Glucose levels on the first day correlated with insulin levels(ρ = 0.7,P = .001), SOFA score (ρ = 0.5,P = .02), and age (ρ =0.5, P = .01). On the first day, nonsurvivors compared withsurvivors had higher glucose levels (214 ± 24 mg/dL vs 143 ±41 mg/dL, P = .01) and HOMA index (28 ± 8 vs 19 ± 24, P =.003) but similar insulin levels (42.3 ± 27.4 vs 38.6 ± 40.8, P =.4). There was no correlation of adiponectin with glucose,insulin, or HOMA levels during acute sepsis. An inverserelationship was found, however, with both insulin levels andHOMA on the day before outcome (r = −0.5 [P b .01] and r =−0.6 [P b .01], respectively). Resistin did not correlate withany of those parameters.

4. Discussion

In the present study, we focused on critically ill patientswith sepsis and described the pattern of the circulating

Table 3 Correlations (ρ) between resistin and IL-6 and IL-8 levels in all patients

Resistin

Day 1 Day 3 Day 7 Day 10 Day 14 Day 18

IL-6Day 1 ρ 0.66 0.46 0.43 0.11 0.07 0.03

P b.001 b.001 .01 .57 .77 .91Day 3 ρ 0.56 0.38 0.43 0.20 0.14 −0.06

P b.001 .02 .01 .33 .55 .81Day 7 ρ 0.47 0.48 0.59 0.47 0.67 0.54

P b.001 b.001 b.001 .01 b.001 .02Day 10 ρ 0.29 0.28 0.42 0.46 0.79 0.77

P .13 .14 .02 .01 b.001 b.001Day 14 ρ 0.36 0.48 0.71 0.59 0.75 0.77

P .13 .04 b.001 .01 b.001 b.001Day 18 ρ 0.29 0.28 0.46 0.27 0.46 0.50

P .30 .33 .08 .33 .07 .06IL-8Day 1 ρ 0.46 0.37 0.31 0.15 0.12 0.08

P b.001 .03 .06 .45 .60 .72Day 3 ρ 0.39 0.22 0.24 0.21 0.21 0.17

P .02 .21 .15 .30 .35 .49Day 7 ρ 0.54 0.43 0.44 0.22 0.46 0.30

P b.001 .01 .01 .26 .04 .21Day 10 ρ 0.38 0.38 0.32 0.33 0.55 0.51

P .05 .05 .08 .09 .01 .03Day 14 ρ 0.57 0.49 0.62 0.38 0.62 0.47

P .01 .03 b.001 .11 b.001 .05Day 18 ρ 0.67 0.51 0.53 0.35 0.42 0.47

P .01 .06 .03 .21 .10 .08

Bold denotes statistically significant correlations.

Initial levels Last measurement

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406 D.A. Vassiliadi et al.

adiponectin and resistin levels during a lengthy time periodcovering both the acute and protracted phases, withparticular interest on the changes that are observed uponrecovery. Our data indicate that in the acute phase, patientswith sepsis have increased adiponectin and resistin levels.A further increase in adiponectin and a reciprocal decreasein resistin levels during the prolonged phase of sepsis werenoted. In addition, we found that resistin is associated withsepsis severity and that its levels reflect the magnitude ofthe inflammatory response. No such associations werefound for adiponectin, indicating different mechanisms inthe underlying regulation and/or origin of these adipokinesduring the process of sepsis.

In view of adiponectin's anti-inflammatory, insulin-sensitizing properties, and its protective role in vascularendothelial cell function [6], increased adiponectin levels atthe onset of sepsis may represent a beneficial, compensatorymechanism. In fact, in a study by Keller et al [14], injectionof endotoxin abolished the decrease in adiponectin levels dueto prolonged fasting observed during saline infusion. Incontrast to our results, however, studies [4,16,18,20] onpatients with sepsis reported either decreased [18,20] orsimilar [4,16] levels of adiponectin compared with controls.These discrepancies may be caused by differences regardingthe studied subjects. Our control subjects were in a fasting

state that has been shown to acutely reduce adiponectinlevels [14]. Of note, our analysis showed that adiponectinlevels may differ according to sepsis stages. We observedincreased adiponectin levels in patients with either severesepsis or septic shock but not in sepsis. In accordance withour data, a recent study in children with various stages ofsepsis [25] reported increased plasma high-molecular-weightadiponectin and resistin levels in those with septic shock. Inmost previous studies, with the exception of Hillenbrand et al[18], patients were not stratified based on sepsis stages, andthus, it is unclear whether patients with severe sepsis orseptic shock were investigated. In Hillebrand et al [18],cohort patients were significantly older and with aconsiderably higher proportion of male subjects comparedwith controls. Moreover, in most studies, diabetic patientsand patients who received glucocorticoids were not exclud-ed. In our study, we opted for a selected population ofpatients with sepsis who did not receive glucocorticoids, a

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Fig. 6 Changes in adiponectin, resistin, SOFA score, IL-6, IL-8, and IL-10 in the 25 patients with organ dysfunction resolution. Allparameters changed significantly with time (adiponectin, P b .001; resistin, P = .02; SOFA score, P b .001; IL-6, P b .001; IL-8, P b .001; IL-10, P b .001) as shown by mixed-model analysis. Presented values are means ± SEM.

407Adipokines in critically ill patients with sepsis

factor that may have an impact on adipokine levels [26]. Onadmission, adiponectin levels were similar in survivors andnonsurvivors. Data on whether adiponectin levels in theacute phase of sepsis may predict survival are contradictory[16,20]. Our study, however, included only selected patientswith protracted sepsis, and thus, no conclusions regardingmortality prediction can be drawn.

An interesting finding of the present study was the gradualincrease in adiponectin concentrations over time, observed inthe entire population of patients with sepsis, representingeventually a beneficial adaptive response. In previousstudies, the adiponectin secretion pattern during sepsis hasnot been thoroughly characterized. A similar pattern was alsorecently reported in a cohort of protracted critical illness of

408 D.A. Vassiliadi et al.

pulmonary origin [4] and in 8 patients recovering fromsubarachnoidal hemorrhage [27]. In contrast, in the study byVenkatesh et al [20], adiponectin levels did not changesignificantly in critically ill subjects; however, the study waslimited to days 3 and 7 days of critical illness, so that theearly and protracted phases were not assessed. Moreover,only 9 patients with sepsis were included, a number too smallto permit a separate analysis of this particular population.Although it remains controversial whether a dysregulation ofadiponectin secretion exists initially in sepsis, our findingsgive ground that in the protracted phase of sepsis, there is anaugmentation of adiponectin secretion. The mechanismsunderlying these changes are not well understood. Onepossibility is that circulating cytokines modulate adipocyterelease of adiponectin. In vitro experiments have shown adose-dependent inhibitory effect of tumor necrosis factor αin adiponectin secretion mediated through the activation ofnuclear factor κB [6]. In our study, however, no correlationwas observed between cytokines and adiponectin levelsduring the acute phase of sepsis. In this line, it should benoted that in a study of experimental human endotoxemia,the marked rise of circulating proinflammatory cytokines hadno significant acute effect on adiponectin levels [8].Nevertheless, in the protracted course of sepsis, we observedan inverse relationship between adiponectin and IL-8 thatmay reflect a negative effect of adiponectin on IL-8 [28].

Our study, along with previously published data [15,19],confirms that resistin should be regarded as an acute-phaseprotein because it was markedly raised in patients with sepsiscompared with healthy subjects and it correlated with theclinical severity scores and other markers of inflammation.Interestingly, resistin levels were related to sepsis stages; thatis, patients having severe sepsis/septic shock had a higherresistin level compared with patients with sepsis. Only fewstudies investigated the circulating pattern of resistin in theprotracted phase of sepsis. Sunden-Cullberg et al [19]measured resistin levels in patients with sepsis for a periodof 2 weeks; they reported increased resistin levels thatremained unchanged over time. However, our study showeda progressive decline from the acute to chronic phases ofsepsis that was more pronounced in those who demonstratedorgan dysfunction resolution and recovery from sepsis. Apossible explanation, in line with our results, is that as theinflammatory process subsides, resistin levels fall.

Our findings are consistent with a reciprocal secretorypattern of adiponectin and resistin, with adiponectin showinga rise and resistin showing a decline upon recovery fromsepsis, a finding that has not been documented before.Interestingly, these 2 adipokines have opposing actions intheir metabolic and immune actions and may, thus,contribute significantly to the metabolic adaptations thatare observed in the process of sepsis and the modulation ofinflammatory responses. It is plausible that during the acutephase, resistin, along with several other cytokines andhormones, induces an insulin resistance state, which directsglucose to the defence machinery. Conversely, during the

prolonged phase, resistin decreases, and along with theadiponectin rise, the interior milieu moves toward a phase ofimproved insulin sensitivity. Besides its metabolic effects,adiponectin has immune-modulating properties; it has aninhibitory effect on nuclear factor κB [6] and also modulatesthe secretion of IL-8 [28]. In our cohort, adiponectin levelswere inversely related to IL-8 after the acute phase of sepsis,and therefore, it could be speculated that the adiponectin risemay well be a contributing factor in the control of theinflammatory processes.

The strengths of our study should be emphasized: weconducted a monocenter study that ensures that all subjectsreceived the same care standards, and we studied a cohort ofmechanically ventilated patients with sepsis having the entirerange of sepsis severity (sepsis, severe sepsis, and septicshock). Also, this is the first study to investigate the parallelchanges of both adiponectin and resistin over time; serialmeasurements were carried out for an extended time period,examining the acute and chronic phases of sepsis. Moreover,we excluded patients who required glucocorticoids becausethey have a significant effect on adipokine and cytokinelevels. On the other hand, for this reason, our cohortrepresents a selected population of patients with sepsisbecause those with a short course of sepsis, either due torapid recovery or due to early death, were not included, aswell as those treated with steroids, which may have created abias toward excluding the most severely ill patients. Thismay account for the discrepancies with the few other studiesthat have included a mixture of critically ill patients with abroad spectrum of severity. Also, for the aforementionedreasons, our study was not designed to investigate theassociation between adipokine levels and outcome predic-tion. Also, the study was performed under controlledconditions of nutrient administration; although both adipo-kines do not seem to be affected by the dietary composition[29], fasting has been shown to acutely decrease adiponectinlevels [14], whereas it probably has no effect on resistinlevels [30].

Limitations of our study include the limited number ofstudied patients and that data on several somatometricparameters and, in particular, body mass index (BMI) orvisceral fat were not available for most of the patientsincluded in this cohort. For practical reasons, body weight isnot routinely available in the setting of critically ill,mechanically ventilated patients, and the generous adminis-tration of intravenous fluids makes measurements unreliable.Lack of BMI data is of relevance regarding the analysis ofadiponectin levels because it is known that there is a negativecorrelation between BMI and adiponectin levels, at least innoncritically ill subjects [6], whereas there are contradictingdata regarding patients with sepsis [18,31]. Nevertheless,inclusion of BMI may have provided some additional usefulinformation. In contrast, the relationship of resistin withadiposity is not clear [30], and previous studies [15,19,31] incritically ill patients have shown no correlation of resistinlevels and BMI.

409Adipokines in critically ill patients with sepsis

5. Conclusions

In the present study, we demonstrated that adiponectinrises and resistin declines during the course of sepsis incritically ill patients. Resistin relates to the severity of sepsisand the degree of the inflammatory response. Taken together,the observed changes in adiponectin and resistin levels maycontribute to the metabolic adaptations observed during theacute and prolonged phases of sepsis.

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