Diabetes, Vol 39, Issue 11 1373-1380, Copyright © 1990 by American Diabetes Association
Effect of insulin on oxidation of intracellularly and extracellularly derived glucose in patients with NIDDM. Evidence for primary defect in glucose transport and/or phosphorylation but not oxidation
PC Butler, EJ Kryshak, M Marsh and RA Rizza
Department of Medicine, Mayo Clinic, Rochester, MN 55905.
Insulin-stimulated glucose oxidation is decreased in patients with
non-insulin-dependent diabetes mellitus (NIDDM). It is not known whether
this decrease is due to a primary defect in the oxidative pathway or is
secondary to impaired glucose transport and/or phosphorylation. To address
this issue, glucose oxidation was measured under steady-state conditions at
low (approximately 270 pmol) and high (approximately 17 mumol) insulin
concentrations in seven patients with NIDDM and seven healthy nondiabetic
subjects matched for sex, age, and obesity. Glucose oxidation was measured
simultaneously by indirect calorimetry and the isotopedilution technique.
Although glucose oxidation and nonoxidative storage were lower (P less than
0.05) in diabetic than nondiabetic subjects during the low- and high-dose
insulin infusions, oxidation of intracellularly derived glucose, estimated
by subtracting the rate of oxidation measured isotopically (i.e., glucose
oxidation derived from the extracellular space) from that measured by
indirect calorimetry (i.e., total glucose oxidation), did not differ in
diabetic and nondiabetic subjects during the low-dose insulin infusion (3.3
+/- 0.1 vs. 3.0 +/- 0.1 mumol.kg-1.min-1). Both techniques provided
identical estimates of glucose oxidation during the high-dose insulin
infusion. Impaired oxidation of extracellularly but not intracellularly
derived glucose strongly suggests that the cause of decreased glucose
oxidation in patients with NIDDM is secondary to impaired glucose transport
and/or phosphorylation rather than a primary abnormality in the oxidative
pathway.