Splanchnic and muscle metabolism during exercise in NIDDM patients

To characterize splanchnic and muscle metabolism during exercise in non-insulin-dependent diabetes mellitus (NIDDM), eight male nonobese patients and seven healthy control subjects (CON) were studied during 40 min of bicycle exercise at 60% of maximal oxygen uptake. Biopsies were obtained from the quadriceps femoris muscle at rest and immediately after exercise. Arterial glucose concentration in NIDDM had declined by 10% (P < 0.01) at the end of exercise, whereas in CON it had risen by 21% (P < 0.05). Leg glucose uptake rose from 0.19 +/- 0.06 mmol/min at rest to 2.25 +/- 0.61 mmol/min at the end of exercise in NIDDM and from 0.13 +/- 0.05 to 1.17 +/- 0.34 mmol/min in CON. Splanchnic glucose output increased from 0.52 +/- 0.06 to 2.37 +/- 0.26 mmol/min in NIDDM and from 0.79 +/- 0.12 to 2.44 +/- 0.38 mmol/min in CON. Leg lactate output during exercise was twofold higher in NIDDM. Muscle contents of lactate and glycogen were similar in both groups at rest, whereas after exercise lactate tended to be higher (19.5 +/- 1.7 vs. 12.7 +/- 5.9 mmol/kg dry wt) and glycogen lower (154 +/- 35 vs. 251 +/- 41 mmol glucosyl units/kg dry wt) in NIDDM. Whole body respiratory exchange ratio during exercise was higher in NIDDM (0.84 +/- 0.02 vs. 0.78 +/- 0.02, P < 0.05). Exercise-induced changes in other muscle metabolites were similar in NIDDM and CON. These data indicate that the decline in blood glucose during exercise in nonobese NIDDM is due to enhanced peripheral glucose utilization rather than to an attenuated increase in splanchnic glucose output.