Glucose kinetics in human obesity.

The kinetics of glucose utilization have been studied in 325 normal subjects, and 150 obese patients free from diabetes or other endocrine diseases. The investigation included measurements in the basal state by isotope dilution technique, determinations of glucose utilization rate induced by endogenous insulinic response (intravenous glucose load and tolbutamide) and by administration of various doses of exogenous insulin. — Results showed that whatever the test used, the disappearance rate constants (slope values or fractional disappearance rate) and the total uptakes (absolute value) of the obese patients were systematically lower than the corresponding values in the normal subjects. This metabolic abnormality is not favoured by ageing, but is not due to a diminished ability of the pancreas to release insulin: basal levels of plasma insulin and rises induced by glucose and by tolbutamide were significantly higher in obese patients. — The deficiency is better revealed by increasing the utilization rate by insulinic stimulation: the greater the slope value, the larger the impairment. In fact, there is a straight line relationship showing direct proportionality between the impairment of the glucose utilization rate constant and the velocity of the process, irrespective of the amount of insulin present or added. This feature strongly suggests in human obesity that the metabolic disturbance primarily affects the glucose uptake process itself rather than the action of insulin.