Glucose ingestion and substrate utilization during exercise in boys with IDDM

This study was intended to compare exogenous [C-13]glucose (Glu,) oxidation in boys with insulin-dependent diabetes mellitus (IDDM) and healthy boys o f similar age, weight, and maximal Oz uptake. In a control trial with water intake (CT) and in a C-13-enriched glucose trial (GT), subjects cycled for 60 min (58.8 +/- 0.9% maximal O-2 uptake) while the utilization of total g lucose, total fat, and Glu,,, was assessed. In CT, total glucose was 84.7 /- 9.2 vs. 91.3 +/- 6.6 g/60 min (not significantly different) and total fa t was 13.3 +/- 2.2 vs. 11.1 +/- 1.7 g/60 min (not significantly different) in IDDM vs, healthy boys, respectively. In GT, Glu, was 10.4 +/- 1.7 vs. 14 .8 +/- 1.1 g/60 min, corresponding to 9.0 +/- 1.0 vs. 12.4 +/-: 0.5% of the total energy supply in IDDM and healthy boys, respectively (P < 0.05). End ogenous glucose was spared in both groups by 12.6 +/- 3.5% (P < 0.05). Bloo d glucose and plasma insulin concentrations were two- to threefold higher i n IDDM vs. healthy boys in both trials. In conclusion, Glu,,, is impaired i n exercising boys with IDDM, even when plasma insulin levels are elevated.