IN-VIVO NMR EVIDENCE FOR MODERATE GLUCOSE ACCUMULATION IN HUMAN SKELETAL-MUSCLE DURING HYPERGLYCEMIA

In vivo NMR evidence for moderate glucose accumulation in human skelet al muscle during hyperglycemia. Am. J. Physiol. 271 (Endocrinol. Metab . 34): E434-E438, 1996.-Although the absence of intracellular (IC) fre e glucose is direct evidence of glucose transport being the rate-limit ing step for muscle glucose disposal at euglycemia, the scarcity of da ta in humans during hyperglycemia precludes any definitive conclusion. In the present study, C-13 and P-31 in vivo nuclear magnetic resonanc e (NMR) data from two separate groups of subjects were combined to mea sure IC free glucose in the human skeletal muscle. When these noninvas ive tools were used with an infusion of [1-C-13]glucose, a steady-stat e concentration of 1.2 +/- 0.2 mmol IC glucose/l IC water was observed at the end of a 2-h hyperglycemic clamp with somatostatin infusion, d uring which glycemia was maintained at approximate to 22 mmol/l and in sulinemia at approximate to 5 mU/l. Despite this moderate glucose accu mulation, the persistence of a large transmembrane glucose gradient su ggests that the posttransport steps do not play a significant role in the control of muscle glucose disposal in these specific conditions, r elevant to insulinopenic diabetic patients.