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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. ARC Key Centre of Teaching and Research. University of Wollongong.

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Gregory E Peoples, Peter L McLennan, Alice J Owen

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  1. Skeletal muscle incorporation of n-3 fatty acids increases oxygen efficiency and reduces fatigue during repetitive muscle contractions in the rat autoperfused contracting hindlimb ARC Key Centre of Teaching and Research University of Wollongong Gregory E Peoples, Peter L McLennan, Alice J Owen Smart Foods Centre, Department of Biomedical Science University of Wollongong

  2. 1.n-3 PUFA highly oxidisable fish oil feeding = tissue incorporation but no clinical evidence of associated adverse health effects 2.Exercise Creates oxidation Muscle fatigue / soreness but Regular exercise reduces muscle soreness / fatigue Oxidation Paradox

  3. 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]

  4. Skeletal muscle shows some similar incorporation patterns to heart membrane Fatty Acid Control Fish Oil 20:4n-6 RBC 19.01 + 1.17 18.72 + 2.53 Arachidonic 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*

  5. Hypothesis • Skeletal muscle oxygen consumption is modulated by dietary fish oil • Skeletal muscle fatigue is modulated by dietary fish oil

  6. Rat Autoperfused Hindlimb Preparation Systemic BP Ventilator Hindlimb venous return Perfusion pressure 5 6 Stimulator Pump 10 10 0 0 4 5 5 0 0 0 0 3 - - 0 0 25 25 50 50 75 75 10 10 12 12 5 5 0 0 0 0 0 0 00 00 50 50 0 0 7 Gastrocnemius Muscle Tension Arterial & venous sampling

  7. 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

  8. Rat hindlimb perfusion & Phospholipid analysis Dietary Period

  9. Rat autoperfused hindlimb in vivo - Developed tension during repetitive twitch stimulation

  10. Skeletal muscle (red and white) DHA profiles for SF, n-6 and n-3 groups after 8 weeks diet. a,b indicates p<0.05 between diets

  11. Repeat bout stimulus Arterial and Venous Blood Samples R1 E1 R2 E2 R3 E3 30 minutes 10 minutes 30 minutes 10 minutes 30 minutes 10 minutes Stimulation: 7-1V, 1Hz, 0.05ms twitch duration

  12. Single bout prolonged stimulus Arterial and Venous Blood Samples 30 minutes rest 30 minutes contraction Flow: 2ml/minute 7-12V, 2Hz, 0.05ms

  13. Muscle Twitch

  14. Muscle Twitch

  15. Single bout prolonged hypoxic stimulus Arterial and Venous Blood Samples 30 minutes rest Flow: 1ml/minute 30 minutes contraction Flow: 2ml/minute 7-12V, 2Hz, 0.05ms ~14% O2

  16. Twitch tension development: Normoxia v Hypoxia *p<0.05 for diets **p<0.05 for time

  17. 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.

  18. 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.

  19. 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.

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