Carbohydrate depletion has profound effects on the muscle amino acid and glucose metabolism during hyperinsulinaemia.
OBJECTIVE
We investigated the effect of carbohydrate availability and euglycaemic hyperinsulinaemia on intramuscular and plasma amino acids in 14 healthy men (age 26.5 +/- 0.9 years, b.m.i. 22.9 +/- 0.5 kg/m2).


METHODS
Insulin was infused (1.5 mU/kg/min) for 240 min both after a carbohydrate depleting exercise and after carbohydrate loading. Muscle samples were taken before and after hyperinsulinaemia. Plasma and intramuscular amino acid concentrations were measured.


RESULTS
Insulin-mediated glucose disposal was similar after carbohydrate depletion (65.2 +/- 1.9 micromol/kg/min) and loading (66.9 +/- 2.8 micromol/kg/min). Carbohydrate depletion was associated with decreased alanine and increased branched chain amino acid (BCAA) concentrations in muscle and plasma. Blood lactate was lower after carbohydrate depletion (477 +/- 25 micromol/l) than loading (850 +/- 76 micromol/l, p < 0.001). In carbohydrate depletion, hyperinsulinaemia resulted in a greater increase in intramuscular (from 927 +/- 48 nmol/g muscle to 2029 +/- 104 nmol/g muscle, p < 0.001), than plasma (from 197 +/- 6.7 micromol/l to 267 +/- 11 micromol/l, p < 0.001) alanine. After carbohydrate loading muscle alanine did not rise significantly (from 1546 +/- 112 nmol/g muscle to 1781 +/- 71 nmol/g muscle) whereas plasma alanine decreased (from 339 +/- 26 micromol/l to 272 +/- 13 micromol/l, p < 0.05).


CONCLUSIONS
(1) Carbohydrate availability has profound effects on the interrelationship between glucose and amino acid metabolism and on the form of storage for glucose-derived carbons. (2) For most amino acids changes in plasma levels of amino acids are not related to changes in concentrations of intramuscular amino acids during hyperinsulinaemia.
Ebeling
P
P
Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland. pertti_ebeling@yahoo.com
Tuominen
J A
JA
Laipio
M L
ML
Virtanen
M A
MA
Koivisto
E
E
Koivisto
V A
VA
D000328:Adult; D000409:Alanine / Q000097:blood / Q000378:metabolism; D000596:Amino Acids / Q000097:blood / Q000378:metabolism*; D000597:Amino Acids, Branched-Chain / Q000097:blood / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D002241:Carbohydrates / Q000172:deficiency*; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D015444:Exercise / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism*; D007328:Insulin / Q000008:administration & dosage; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*
D000596:Amino Acids; D000597:Amino Acids, Branched-Chain; D001786:Blood Glucose; D002241:Carbohydrates; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D019344:Lactic Acid; D005947:Glucose; D000409:Alanine