title: Leg citrate metabolism at rest and during exercise in relation to diet and substrate utilization in man.
abstract: Previously we have demonstrated a lower rate of carbohydrate utilization in skeletal muscle after a fat than after a carbohydrate rich diet both at rest and during exercise. To test the hypothesis of citrate as a regulator of glycolysis (1) arterial-femoral venous (a-fv) differences for oxygen, citrate, pyruvate and lactate and (2) muscle citrate and glucose-6-phosphate (G-6-P) were determined at rest and after 5 and 25 min of submaximal bicycle exercise. Citrate release and muscle citrate concentration were higher after fat than after carbohydrate diet at rest and 5 min exercise, but did not differ between diets at 25 min exercise. Lactate release and muscle lactate concentration were lower after fat diet at 5 and 25 min exercise. Pyruvate release at 5 min exercise was higher after fat diet. The G-6-P concentration was higher at rest, insignificantly higher after 5 min exercise and lower at 25 min exercise after the fat diet. The findings support the notion that at rest and 5 min exercise fat diet induced inhibition of glycolysis might be mediated through increased intramuscular citrate acting on phosphofructokinase. In addition, the greater pyruvate release at 5 min exercise after fat diet in spite of a smaller lactate release, indicates a decreased pyruvate dehydrogenase activity and/or NADH to NAD ratio after fat diet. The inhibition of glycolysis at 25 min exercise after fat diet on the other hand does not seem to be citrate mediated.
mesh_terms: D000328:Adult; D002951:Citrates / Q000378:metabolism*; D019343:Citric Acid; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004041:Dietary Fats / Q000008:administration & dosage*; D004734:Energy Metabolism; D005260:Female; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000378:metabolism; D006019:Glycolysis; D006339:Heart Rate; D006801:Humans; D007773:Lactates / Q000378:metabolism; D007866:Leg / Q000098:blood supply; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D005082:Physical Exertion; D011773:Pyruvates / Q000378:metabolism; D012039:Regional Blood Flow; D012119:Respiration
chemical_list: D002951:Citrates; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005958:Glucosephosphates; D007773:Lactates; D011773:Pyruvates; D019343:Citric Acid; D019298:Glucose-6-Phosphate