Modulation of Adipocyte Function by Dietary Omega-

3 Fatty AcidsCarla Taylor, PhD

Departments of Human Nutritional Sciences

and Physiology, University of Manitoba

& Canadian Centre for Agri-food Research in Health & Medicine,

St. Boniface Research Centre

The Omega-3 Fatty Acid Family

Eicosapentaenoic acid (EPA)20:5 n-3

Docosahexaenoic acid (DHA)22:6 n-3

α-Linolenic acid (ALA)18:3 n-3

Polyunsaturated Fatty Acid Metabolism

δ-6-des

Omega-3 Fatty Acids

Alpha-linolenic acidALA 18:3 n-3

Stearidonic acid18:4 n-3

Eicosatetraenoic acid20:4 n-3

Eicosapentaenoic acidEPA 20:5 n-3

Docosapentaenoic acid

DPA 22:5 n-3

ω3 Tetracosahexenoic acid 24:6 n-3

Omega-6 Fatty Acids

Linoleic acidLA 18:2 n-6

Gamma-linolenic acidGLA 18:3 n-6

Dihomo γ-linolenic acid

DGLA 20:3 n-6

Arachidonic acidAA 20:4 n-6

Adrenic acid22:4 n-6

Δ6 desaturase

elongase

Δ5 desaturase

elongase

Δ6 desaturase

Adapted from Sprecher (2000)

Docosahexaenoic acidDHA 22:6 n-3

ω6 Docosapentaenoic acid

22:5 n-6

ω3 Tetracosapentaenoic

acid 24:5 n-3

ω6 Tetracosatetrenoic

acid24:4 n-6ω6

Tetracosapentaenoic acid

24:5 n-6

elongase

peroxisomalbeta-oxidation

Membrane fluidity

Protein localization

Ion channel function Signalling

events

EicosanoidsProstaglandinsLeukotrienes

Endocannabinoids

Extracellular and

Nuclear Receptors

Membrane

Components

Substrates for

Signalling Molecules

Receptor-mediated Signalling

Physiological Roles of Omega-3 Fatty Acids

Various Organs

Adiponectin

Omentin

Visfatin

Vaspin

Resistin

Leptin

Chemerin

Adipose tissue an endocrine organ

Healthy Adipose tissue

Dysfunctional Adipose tissue

Obesity

Macrophage

Blood vessele

Research Question:What are the effects of dietary intervention with plant-based omega-3 fatty acids (ALA) on adipocyte size and adipose tissue function in an obese model?

Experimental Design

Omega-3 fatty acid diet

(faALA, n=7)

Control diet

(faCTL, n=7)

Control diet

(lnCTL, n=7)

Baseline

(faBASE, n=7)

17 week oldlean (ln) Zucker

rats

17 week old fa/fa (fa) Zucker

rats

8 weeks

Rats were 25 week old at end of dietary treatments

8 weeks

Source: http://www.canola-council.org/properties.html

ALA

Fatty acid profile of the experimental diets

Fatty Acid % Composition* ALA diet CTL diet Saturated Fat 12.2 15.8

C16:0 7.5 10.5

C18:0 3.9 4.2

Monounsaturated fat 19.1 22.5

C18:1 18.8 22.1

Polyunsaturated fat 67.3 59.9

C18:2 (n6) 33.4 51.6

C18:3 (n3) 33.7 8.0

Polyunsaturated:saturated fat ratio

5.5 3.8

Omega-6:omega-3 ratio 1.0 6.4

Both diets contained

8.5 g fat/100 g diet

Soybeanoil

50:50Flaxseed oil& soybeanoil

LA

ALA

n6/n3 ratio *g/100 g total fatty

acids

Body weight, feed intake and obesity were unchanged

0

250

500

750

1000

lnCTL

faCTL

faALA

0

50

100

150

200

250

Wk 1 Wk 2 Wk 3 Wk 4 Wk 5 Wk 6 Wk 7 Wk 8

lnCTL

faCTL

faALA

0

4

8

12

lnCTL faCTL faALA faBASE

Visceral adipose depots (g/100 g bwt)

Weekly feed intake (g)

Weekly body weights (g)

a

b bb

Columns with different letters areSignificantly different (P<0.05)

The faALA group had smaller adipocytes

The faALA group had lower levels of leptin in adipose tissue

Adiponectin = Anti-inflammatory adipokineLeptin = Pro-inflammatory adipokine

The faALA group had lower levels of IL-10 & TNF-α in adipose

Interleukin-10 (IL-10) = Anti-inflammatory cytokineTumor necrosis factor-α (TNF-α) = Pro-inflammatory cytokine

The faALA group had a 5-fold reduction in adipose MCP-1 (to lean levels)

MCP-1 = monocyte chemoattractant factor-1

Macrophages infiltrating adipose tissue were unchanged.

The faALA group had fewer T-cells in adipose tissue

Summary

• Plant-based omega-3 (ALA) in fa/fa Zucker rat model:

• 5-fold reduction in MCP-1 in adipose tissue

• 75% lower levels of TNF-α and IL-10 in adipose tissue

• less T-cell infiltration in adipose tissue

• smaller adipocyte size despite no change in adipose mass or body weight.

Next Steps• Comparison of plant-based omega-3 (ALA) with marine-based

omega-3 (EPA vs DHA) in fa/fa Zucker rat model

• Oxylipins and 3T3-L1 adipocytes

Polyunsaturated Fatty Acid MetabolismOmega-3 Fatty

AcidsAlpha-linolenic acid

ALA 18:3 n-3

Stearidonic acid18:4 n-3

Eicosatetraenoic acid20:4 n-3

Eicosapentaenoic acidEPA 20:5 n-3

Docosapentaenoic acid

DPA 22:5 n-3

ω3 Tetracosahexenoic acid 24:6 n-3

Omega-6 Fatty Acids

Linoleic acidLA 18:2 n-6

Gamma-linolenic acidGLA 18:3 n-6

Dihomo γ-linolenic acid

DGLA 20:3 n-6

Arachidonic acidAA 20:4 n-6

Adrenic acid22:4 n-6

“Less” inflammator

y

“More”inflammator

y

Δ6 desaturase

elongase

Δ5 desaturase

elongase

Δ6 desaturase

Adapted from Sprecher (2000)

Docosahexaenoic acidDHA 22:6 n-3

ω6 Docosapentaenoic acid

22:5 n-6

ω3 Tetracosapentaenoic

acid 24:5 n-3

ω6 Tetracosatetrenoic

acid24:4 n-6ω6

Tetracosapentaenoic acid

24:5 n-6

elongase

peroxisomalbeta-oxidation

Oxylipins

Oxylipins

Arachidonic acid20:4 n-6

Linoleic acid18:2 n-6

α-Linolenic acid18:3 n-3

9-HOTrE

9-HODE

13-HODE

15-HETE

5-HETE

PGE2

5-LOX

5-LOX

5-LOX

15-LOX

15-LOX

COXOxylipins

3T3-L1Pre-adipocyte

2-3 Days

Confluence

2 Days

Day 6 Day 4

Start ofdifferentiation

Day 8

Fullydifferentiated

INS, DEX, IBMX

Day 0

Growth arrested

Day 2

INS

Mitotic clonal expansion

Oxylipins (30 nM)

Oxylipins (30 nM)

Harvest

Oxylipins (30 nM)

Oxylipins (30 nM)

preadipocyte adipocyte

PGE2

15-HETE

13-HODE

5-HETE

9-HODE

9-HOTrE

Oxylipin treatment affects differentiation of 3T3-L1 adipocytes.

AA PGE2

AA 15-HETE

LA 13-HODE

5-HETE AA

9-HODE LA

9-HOTrE ALA

0

20

40

60

80

100

120

#*#*#*#*#*

*Li

pid

Con

tent

(%

veh

icle

con

trol

)

#

Oxylipins from AA (5- and 15-HETE), LA (9- and 13-HODE), and ALA (9-HOTrE):

•inhibit lipid droplet formation & perilipin (PLIN)•inhibit fatty acid synthase (FAS)

•affect lipid metabolism: • hormone sensitive lipase (HSL)• adipose triglyceride lipase (ATGL)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

*

Re

lative

Ba

nd

In

ten

sity

FAS

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

**

*

#

*

Re

lative

Ba

nd

In

ten

sity

HSL

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

#

*

*

*

*

*

*

Rela

tive B

and I

nte

nsity

ATGL

Lipid droplets

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

*

#

*

Re

lative B

an

d I

nte

nsity

PLIN

*, significantly different from preadipocytes; #, significantly different from vehicle

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

#

#

*

Re

lative

Ba

nd

In

ten

sity

Acrp

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

#

*

*

Re

lative

Ba

nd

In

ten

sity

TNFa

Inflammatory markers:

PGE2 from AA (omega-6 fatty acid) and 9-HOTrE from ALA (omega-3 fatty acid) reduced ACRP (adiponectin), an anti-inflammatory marker

5-HETE from AA (omega-6 fatty acid) reduced TNFα (tumor necrosis-alpha), a pro-inflammatory marker*, significantly different from preadipocytes#, significantly different from vehicle

Summary

• First comparison of bioactivity of LA and ALA oxylipins versus classical AA oxylipins

• Important physiological effects

• Oxylipins derived from omega-6 fatty acids are not necessarily pro-inflammatory and those from omega-3 fatty acids are not necessarily anti-inflammatory

• Focus on adipocytes & implications for obesity

Trainees•Maria Baranowski•Jennifer Enns•Shannon Neumann•Leslee Tworek

Collaborators•Peter Zahradka•Harold Aukema

Funding & Scholarships•Agri-food Research Development Initiative•Natural Sciences and Engineering Research Council•Manitoba Health Research Council•Manitoba Institute of Child Health•NSERC CREATE FAST program

Thank you

Obesity

Adipose tissue mass = ↑adipocyte size

A. Noto et al. / Metabolism Clinical and Experimental 56 (2007) 1601–1611

(hypertrophy)

Lean rat

fa/fa rat

Adipogenesis

(hyperplasia)

+ ↑adipocyte number

Affects metabolicAltered phenotype

& endocrine properties

Overnutrition

Adiponectin

Ad ipon ectin

Dysfunctiona l ad ipocyteNorm al ad ipocyte

insulin resistanceatherosclerosis

inflammationhypertension

insulin sensitiveanti-atheroscleroticanti-inflammatoryanti-hypertensive

LeptinTNFIL-6CRPAngiotensinogen

Increased CV riskDecreased CV risk

LeptinTNFIL-6CRPAngiotensinogen

Lifestyle and pharmacological

interventions