School of BiosciencesJohn Harwood

Bruce Caterson

Clare Hughes

How may dietary n-3 polyunsaturated fatty acids

alleviate Alzheimer's disease?

Alzheimer’s Research Network - May 23rd 2008

School of Psychology

Mark Good

Cécile Bascoul

3

2

1

DHA is a polyunsaturated fatty acid (22:6n-3)

In rat brain, DHA constitutes > 17% of the total fatty acids(Horrocks and Farooqui, 2004)

Source: fatty fish

DHA precursors: EPA (20:5n-3) and ALA (18:3n-3)

Docosahexaenoic acid (DHA)

Constituent of phospholipids of the cells plasma membrane

Positive effects of DHA on AD

In mouse/rat models:

DHA Aβ in AD mouse model.

DHA impairment of learning and memory in Aβ-infused rats.

In human:

DHA in hippocampus of AD patients.

Dietary n-3 fatty acids or fish risk of AD.

Methods Experiment on mice WT and Tg2576 (APPsw)

Behavioural changes

Biochemical changes

WTTg WTTg

Normal diet

+ 5% DHA + 5% control oil

Foraging experiment

?

1 error = 1 return

• Males + females• Diets at 4 months• 12 months of age

ALZHEIMER’S MOUSE NORMAL MOUSE

8 min 30s8 errors

1 min 35s1 error

Average mean errors(mean ± SEM)

Foraging experiment

0

2

4

6

8

10

12

14

Tg oil WT oil Tg DHA WT DHA

Ave

rag

e m

ean

err

ors

ANOVA:Significant progression with sessions (p = 0.003) Significant effect of genotype (p = 0.013)Non-significant effect of diet (p = 0.132)

(n = 12) (n = 10) (n = 11) (n = 10)

Main fatty acids in cortex

0%

5%

10%

15%

20%

25%

30%

16:0 18:0 18:1n-9 18:1n-7 20:4n-6 22:4n-6 22:6n-3(DHA)

Fatty acids

Tg oil (n=6)

WT oil (n=6)

Tg DHA (n=6)

WT DHA (n=6)

Main fatty acids: > 2% of total fatty acids

(mean ± SD)

DHA is incorporated in cortex, cerebellum and hippocampus

Individual phospholipids - TLC

1st

2nd

PE

PC

PSSph

DPG

Mouse brain lipids

PI

0%5%

10%15%20%25%30%35%40%45%50%

16:0(palmitic)

18:0(stearic)

18:1n-9 18:1n-7 20:4n-6 (AA) 22:4n-6 22:6n-3(DHA)

Fatty acids

Tg oil (n = 4)

WT oil (n = 4)

Tg DHA (n = 4)

WT DHA (n = 4)

Fatty acids over 2% of the total fatty acids

Main fatty acids in cortex phosphatidylinositol (PI)(mean ± SD)

sn-1 (16:0)

sn-2 (18:0)PI head group

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

X 16:0(palmitic)

X X 18:0(stearic)

18:1n-9 20:4n-6(AA)

22:4n-6 22:6n-3(DHA)

Fatty acids

Tg oil (n = 4)

WT oil (n = 4)

Tg DHA (n = 4)

WT DHA (n = 4)

Main fatty acids in cortex phosphatidylethanolamine (PE)(mean ± SD)

Fatty acids over 2% of the total fatty acids

sn-1 (18:0)

sn-2 (DHA)PE head group

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

16:0

a/16

:0

16:0

p/18

:1

16:1

e/18

:1

16:1

a/18

:1

16:0

a/18

:1

18:0

a/16

:0

16:0

p/20

:4

18:1

p/18

:1

18:0

p/18

:1

18:0

p/18

:0

16:0

a/20

:4

18:1

a/18

:1

18:0

a/18

:1

18:0

a/18

:0

16:0

p/22

:6

17:2

/20:

4

16:0

e/22

:6

16:0

p/22

:5

18:0

p/20

:4

16:0

p/22

:4

18:0

e/20

:4

18:1

p/20

:2

18:1

p/20

:1

17:1

/20:

1

18:0

/20:

6

16:0

a/22

:6

16:0

a/22

:5

18:1

a/20

:4

18:0

a/20

:4

18:0

a/20

:3

18:0

a/20

:1

17:2

/22:

6

18:0

a/20

:0

18:0

p/22

:6

18:0

e/22

:6

18:0

p/22

:5

18:0

p/22

:4

18:1

a/22

:6

18:0

a/22

:6

18:0

a/22

:4

Transitions

Tg oil

WT oil

Tg DHA

WT DHA

**

* *

*

* *

*

Mass SpectrometryPE molecular species in cortex

(mean ± SEM)

Mean fold change of expression of IL-6 in female

0123456

cortex hippocampus

Tg oil

Tg DHA

WT oil

WT DHA

In female, significant effect of genotype (p = 0.02), diet (p = 0.02) and brain area (p = 0.01).

In male, non-significant effect of genotype (p = 0.18), diet (p = 0.50) and brain area (p = 0.66).

Q-PCR analysis

(mean ± SD)

Immunohistochemistry: Aβ 1-40 (21 months of age)

Tg DHA 135

Tg oil 189 Tg oil 180

Tg DHA 149

Tg oil 173

Tg DHA 159

Tg oil

Tg DHA

Conclusions

DHA is incorporated in the brain, mainly in PE.

Cognitive improvement with DHA rich diet

may be due to a reduced inflammation.