Thermogenic response to insulin and glucose infusions in man: a model to evaluate the different components of the thermic effect of carbohydrate.

The thermogenic response to an insulin and glucose infusion was determined in 10 healthy lean volunteers using a euglycemic clamp technique in conjunction with respiratory exchange measurements. The progressive rise in resting metabolic rate (RMR) from 4.295 +/- 0.360 kJ/min during the baseline to 4.771 +/- 0.410 kJ/min during the 90--120 min period of the euglycemic clamp (p less than 0.01) correlated with the progressive increase in the glucose infusion rate (r = 0.836, p less than 0.01), with the glucose storage rate (r = 0.812, p less than 0.01), but not with the significant rise in insulin of norepinephrine concentrations. Storage of nutrients, as well as increased sympathetic nervous system (SNS) activity are known to increase RMR. Two thirds to three quarters of the observed increment in RMR following the insulin and glucose infusion in this study can be accounted for by the metabolic processing of the infused glucose for storage purposes. The rest of the thermogenic response (24--35%) must be explained by other mechanisms such as increased SNS activity.