Hormone-fuel metabolism during exercise of insulin-dependent diabetic patients treated with an artificial B-cell unit

Summary The effects of restoration of glucose homeostasis on hormone-fuel metabolism of diabetic individuals during exercise (40% maximal O₂ consumption) were determined by monitoring fuel oxidation rates and levels of substrates and hormones in nine normal subjects and five insulin-dependent diabetic patients while on conventional insulin therapy and after 3 days on artificial B-cell directed glucose regulation. The non-protein respiratory quotient (npRQ) and carbohydrate oxidation rate of the conventionally-treated diabetic subjects (0.908±0.002 and 538±5 mg/m²·min) were lower and the lipid oxidation rate (101±2 mg/m²·min) was significantly higher than those of the normal group during the bicycle exercise (0.937±0.004, 582±8, and 70±4 mg/m²·min, respectively). After 3 days of artificial B-cell insulin therapy, the npRQ and carbohydrate oxidation rate of the exercising diabetics significantly increased to 0.965±0.004 and 693±13 mg/m²·min, while the lipid oxidation rate declined to 39±4 mg/m²·min (p<0.001). We conclude that artificial B-cell directed insulin therapy increases carbohydrate oxidation and decreases lipid oxidation in exercising insulin-dependent diabetic subjects. However, if restoration of metabolic response identical to that of exercising normals is desired, the excess in carbohydrate oxidation coincident with elevated blood lactate and pyruvate levels suggest that the artificial B-cell therapy may not have been completely optimal, probably due to the hyperinsulinization of the diabetic patients. Research supported by NIH grants AM 15191 and AM 20530, Howard Hughes Medical Institute (U.S.A.), and FAPESP (Brazil) (n ^o 78/1131)