The effect of short-term intravenous insulin administration on the glucagon response to a carbohydrate meal in adult onset and juvenile type diabetes

These experiments were designed to determine whether the abnormal glucagon response of diabetics to a glucose meal can be restored to normal by the short-term administration of exogenous insulin in amounts sufficient to produce normal and above normal plasma insulin levels. The immunoreactive glucagon (IRG) response of nine nondiabetics to oral glucose was compared with that of ten juvenile and ten adult type diabetics. In the absence of exogenous insulin, the IRG response of diabetics was strikingly different from the nondiabetics, rising paradoxically, whereas in nondiabetics there was a decline in IRG. When plasma insulin levels were raised to normal by infusion of insulin (0.06 U/kg for 2 hr), the abnormal IRG response of adult type diabetics was not improved; the IRG response of the juvenile type patients was improved, but remained abnormal. Raising plasma insulin briefly to greater than normal concentrations inproved the IRG response during the glucose meal in both groups, but in the adult group total IRG suppression was still only half that of the nondiabetics; in the juvenile type group it was reduced to the nondiabetic level, but at glucose and insulin levels far above those of nondiabetics. The results are compatible with the view that the glucose-sensing function of the A-cells is, at least in part, mediated by or requires insulin. In juvenile diabetics, the abnormality is corrected by raising plasma insulin to above normal levels; adult onset diabetics appear to be less sensitive even to large doses of insulin during a carbohydrate load.