gregory e peoples, peter l mclennan, alice j owen

Skeletal muscle incorporation of n-3 fatty acids increases oxygen efficiency and

reduces fatigue during repetitive muscle contractions in the rat autoperfused

contracting hindlimb

Gregory E Peoples, Peter L McLennan, Alice J OwenSmart Foods Centre, Department of Biomedical Science

University of Wollongong

ARC Key Centre of Teaching and Research University of Wollongong

ARC Key Centre of Teaching and Research


Oxidation Paradox1. n-3 PUFA• highly oxidisable• fish oil feeding

= tissue incorporationbut

• no clinical evidence of associated adverse health effects

2. Exercise• Creates oxidation• Muscle fatigue / soreness

but• Regular exercise reduces

muscle soreness / fatigue



Membrane incorporation of long chain n-3 PUFA

1. Composition of cell membrane is reflective of dietary fatty acid profile

2. In heart, membrane n-3 PUFA incorporation

• reduces ventricular arrhythmia

• lowers myocardial oxygen consumption

• reduces heart rate

[isolated hearts indicate direct intra-cardiac effects]



Fatty Acid Control Fish Oil

20:4n-6 RBC 19.01 + 1.17 18.72 + 2.53Arachidonic Acid Heart 22.73 + 2.11 13.16 + 1.70*

Skeletal 11.08 + 3.37 7.14 + 1.54*

22:6n-3 RBC 1.92 + 0.21 5.91 + 0.80*DHA Heart 9.66 + 0.42 23.72 + 2.6*

Skeletal 11.4 + 1.9 18.40 + 4.15*

Skeletal muscle shows some similar incorporation patterns to heart membrane



Hypothesis

• Skeletal muscle oxygen consumption is modulated by dietary fish oil

• Skeletal muscle fatigue is modulated by dietary fish oil



Rat Autoperfused Hindlimb Preparation

Pump

SystemicBP

4

5 6

3 7

Ventilator

0 25

0 500 75

0 1000 12

50 -50 0 50 100

Stimulator

GastrocnemiusMuscle Tension

Perfusionpressure

Hindlimb venous return

0 25

0 500 75

0 1000 12

50 -50 0 50 100

Arterial & venous sampling



Baseline measures following 30minutes perfusion without contraction

Minute ventilation (ml/min) 130±10

PaO2 (mmHg) ~100

SaO2 (%) 98±0.2

(a-v)O2 (ml/100ml) 4.8±0.5

Hindlimb VO2 (µmol/g/min) 0.31±0.03

Arterial glucose (mM) 6.2±0.34

Arterial lactate (mM) 1.7±0.09

Hindlimb perfusion pressure (mmHg) 102±5



Dietary Period

8 w eeks

S atu ra ted F a t D ie tS F

8 week s

S u n flower S eed O il D ie tn -6

8 w eeks

F ish O il D ie tn -3

M ale w is ta r ra ts2 w eek s w ash ou t d ie t (O live O il)

Rat hindlimb perfusion & Phospholipid analysis



Rat autoperfused hindlimb in vivo - Developed tension during repetitive

twitch stimulation

0 50 100 150 200 250 300 350 400

0255075

100125150175200

peak

1/2 peak

time (s)

Forc

e Di

spla

cem

ent (

g)



Skeletal muscle (red and white) DHA profiles for SF, n-6 and n-3 groups after 8 weeks diet.

Red White0

10

20

30a a

b

b

bb

SFn-6n-3

DH

A: P

erce

ntag

e of

Tota

l

a,b indicates p<0.05 between diets



Repeat bout stimulus

10 minutes 10 minutes 10 minutes

Arterial and Venous Blood Samples

30 minutes

30 minutes

30 minutes

R1 E1 R2 E2 R3 E3

Stimulation: 7-1V, 1Hz, 0.05ms twitch duration



Single bout prolonged stimulus


30 minutes rest 30 minutes contraction

Flow: 2ml/minute

7-12V, 2Hz, 0.05ms



Muscle Twitch

Peak Contraction

0.0 0.1 0.2 0.3 0.4-20

020406080

100120140160180200

Time (s)

Forc

e D

ispl

acem

ent (

g)



Muscle Twitch

Peak Contraction

0.0 0.1 0.2 0.3 0.4-20

020406080

100120140160180200

Time (s)

Forc

e D

ispl

acem

ent (

g) 50% Fatigue

0.0 0.1 0.2 0.3 0.4-20

020406080

100120140160180200

Time (s)Fo

rce

Dis

plac

emen

t (g)



Single bout prolonged hypoxic stimulus


30 minutes rest

Flow: 1ml/minute

30 minutes contraction

Flow: 2ml/minute

7-12V, 2Hz, 0.05ms

~14% O2



Twitch tension development:

Normoxia v Hypoxia

*p<0.05 for diets

**p<0.05 for time

0.5 1 2.5 5 10 15 20 25 30

0

50

100

150NormoxiaHypoxia

*

**

Time (minutes)

Twitc

h Te

nsio

n (g

/g)

0.5 1 2.5 5 10 15 20 25 30

0

1

2

3NormoxiaHypoxia

*

**

Time (minutes)

Oxy

gen

Con

sum

ptio

n(

mol

/g/m

in)



Summary

Fish oil feeding

1. Increased skeletal muscle membrane incorporation of n-3 PUFA, specifically DHA.

During Normoxia:

2. Reduced fatigue during 10 and 30minutes muscle stimulation.

3. Maintained lower relative rise time, fall time, contraction duration and maximum rate of tension development and relaxation throughout 30minutes muscle stimulation.

4. Increased efficiency of oxygen use in relation to muscle twitch tension development.

5. Improved recovery of muscle contraction.

6. Reduced muscle oxygen consumption during recovery.



Summary

Fish oil feeding

During Hypoxia:

7. Reduced fatigue during 30minutes muscle stimulation.

8. Increased efficiency of oxygen use in relation to muscle twitch tension development (v saturated fat).

9. Improved caffeine induced recovery of muscle contraction.



Conclusion

• Dietary fish oil enhances fatigue resistance in skeletal muscle.

• Dietary fish oil may be beneficial in reducing oxygen flux during muscle contraction potentially reducing oxidative stress and protecting muscle during hypoxia.

gregory e peoples, peter l mclennan, alice j owen

Documents

minutes muscle stimulation

muscle contraction potent

membrane n

minutes perfusion

reduced fatigue

oxygen flux

myocardial oxygen consumption

conclusiondietary fish