Carbohydrate depletion has profound effects on the muscle amino acid and glucose metabolism during hyperinsulinaemia

Aim: We investigated the effect of carbohydrate availability and euglycaemi c hyperinsulinaemia on intramuscular and plasma amino acids in 14 healthy m en (age 26.5 +/- 0.9 years, b.m.i. 22.9 +/- 0.5 kg/m(2)). Methods: Insulin was infused (1.5 mU/kg/min) for 240 min both after a carbo hydrate depleting exercise and after carbohydrate loading. Muscle samples w ere taken before and after hyperinsulinaemia. Plasma and intramuscular amin o acid concentrations were measured. Results: Insulin-mediated glucose disposal was similar after carbohydrate d epletion (65.2 +/- 1.9 mmol/kg/min) and loading (66.9 +/- 2.8 mmol/kg/min). Carbohydrate depletion was associated with decreased alanine and increased branched chain amino acid (BCAA) concentrations in muscle and plasma. Bloo d lactate was lower after carbohydrate depletion (477 +/- 25 mmol/l) than l oading (850 +/- 76 mmol/l, p < 0.001). In carbohydrate depletion, hyperinsu linaemia resulted in a greater increase in intramuscular (from 927 +/- 48 n mol/g muscle to 2029 +/- 104 nmol/g muscle, p < 0.001), than plasma (from 1 97 +/- 6.7 mu mol/l to 267 +/- 11 mu mol/l, p < 0.001) alanine. After carbo hydrate loading muscle alanine did not rise significantly (from 1546 +/- 11 2 nmol/g muscle to 1781 +/- 71 nmol/g muscle) whereas plasma alanine decrea sed (from 339 +/- 26 <mu>mol/l to 272 +/- 13 mu mol/l, p < 0.05). Conclusions: (1) Carbohydrate availability has profound effects on the inte rrelationship between glucose and amino acid metabolism and on the form of storage for glucose-derived carbons. (2) For most amino acids changes in pl asma levels of amino acids are not related to changes in concentrations of intramuscular amino acids during hyperinsulinaemia.