Endurance athletes, insulin secretion and muscle quality.
OBJECTIVE
To study how muscle ubiquinone content (MUQ) and percentage slow twitch (%ST) of muscle fibres in the thighs of male healthy subjects with a low or high insulin response to glucose infusion tests (GIT) affected blood glucose control (BGC).


METHODS
People with a low insulin response were recruited from sedentary low insulin responders (LIRs) or endurance trained LIRs. A group of men with high insulin response (HIRs) was used for comparison. In addition to GIT, glucose metabolism was estimated with somatostatin-insulin-glucose infusion tests (SIGIT; insulin sensitivity).


RESULTS
Sedentary LIRs and HIRs had low exercise capacities and an increased BGC with increased exercise capacity. BGC in sedentary LIRs, in contrast to HIRs increased with MUQ and/or %ST. Only trained LIRs showed an elevated peripheral insulin receptor sensitivity despite a decreasing MUQ with %ST. This relationship indicated muscle metabolic lesions in trained LIRs with a high %ST and additional compensatory BGC mechanisms in trained LIRs.


CONCLUSIONS
BGC in HIRs was maintained with insulin and an exercise-regulated insulin sensitivity, BGC in sedentary LIRs with a good muscle membrane and metabolic control due to adequate MUQ depots, and BGC in trained LIRs with an elevated insulin sensitivity. Trained LIRs rich in %ST had a low MUQ indicative of muscle lesions such as from 'overuse injury'.
Karlsson
J
J
OBLA AB, Vaxholm, Sweden.
Rønneberg
H R
HR
D000328:Adult; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D018657:Muscle Fibers, Slow-Twitch; D009132:Muscles / Q000737:chemistry / Q000502:physiology*; D010807:Physical Endurance; D013178:Sports Medicine; D014451:Ubiquinone / Q000032:analysis
D007328:Insulin; D014451:Ubiquinone