Regulation of fat-carbohydrate interaction in skeletal muscle during intense aerobic cycling.
Six male subjects received either a saline (control) or Intralipid infusion during 30 min rest and 15 min cycling at 85% maximal O2 uptake (VO2max) to examine the regulation of fat-carbohydrate interaction (glucose-fatty acid cycle) in skeletal muscle. Muscle biopsies were sampled immediately before and at 3 and 15 min of exercise in both trials. A muscle biopsy was also taken at -30 min rest in the Intralipid trial. Intralipid infusion significantly elevated plasma free fatty acids above control during rest (0.21 +/- 0.04 to 0.94 +/- 0.09 mM) and exercise (5 min: 1.27 +/- 0.15 mM; 15 min: 1.42 +/- 0.13 mM). Muscle glycogen degradation was significantly lower in the Intralipid trial (109.7 +/- 29.3 vs. 194.7 +/- 32.1 mmol/kg dry muscle). Muscle lactate accumulation after 15 min was similar in both trials (control, 60.7 +/- 12.2 and Intralipid, 60.9 +/- 12.4 mmol/kg dry muscle). Muscle citrate increased at rest during Intralipid (0.32 +/- 0.06 to 0.58 +/- 0.06 mmol/kg dry muscle) but was not different between trials at 3 min (control, 0.73 +/- 0.07 and Intralipid, 0.68 +/- 0.06 mmol/kg dry muscle) and 15 min of cycling. Resting acetyl-CoA was unaffected by Intralipid and increased similarly in both trials at 3 min of cycling (control, 59.0 +/- 10.3 and Intralipid, 50.7 +/- 13.6 mumol/kg dry muscle) and remained unchanged at 15 min. Pyruvate dehydrogenase activity increased five- to sevenfold during exercise and was similar in both trials (15 min: control, 2.42 +/- 0.30 and Intralipid, 2.79 +/- 0.41 mmol.min-1 x kg wet wt-1).(ABSTRACT TRUNCATED AT 250 WORDS)
Dyck
D J
DJ
School of Human Biology, University of Guelph, Ontario, Canada.
Putman
C T
CT
Heigenhauser
G J
GJ
Hultman
E
E
Spriet
L L
LL
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000108:Acetylcarnitine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D002951:Citrates / Q000378:metabolism; D004837:Epinephrine / Q000097:blood; D015444:Exercise; D005217:Fat Emulsions, Intravenous / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005947:Glucose / Q000378:metabolism*; D005990:Glycerol / Q000494:pharmacology; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008297:Male; D009132:Muscles / Q000098:blood supply / Q000378:metabolism* / Q000502:physiology; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption; D010725:Phosphocreatine / Q000378:metabolism; D013997:Time Factors
D002951:Citrates; D005217:Fat Emulsions, Intravenous; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D010725:Phosphocreatine; D000108:Acetylcarnitine; D000105:Acetyl Coenzyme A; D000255:Adenosine Triphosphate; D006003:Glycogen; D005947:Glucose; D005990:Glycerol; D009638:Norepinephrine; D004837:Epinephrine