Disappearance of bovine insulin from plasma in diabetic and normal subjects

Relationships between insulin secretion, insulin action, and fasting plasma glucose concentration in nondiabetic and noninsulin-dependent diabetic subjects

The relationships between insulin secretion, insulin action, and fasting plasma glucose concentration (FPG) were examined in 34 southwest American Indians (19 nondiabetics, 15 noninsulin-dependent diabetics) who had a broad range of FPG (88-310 mg/100 ml). Fasting, glucose-stimulated, and meal-stimulated plasma insulin concentrations were negatively correlated with FPG in diabetics but not in nondiabetics. In contrast, fasting and glucose-stimulated plasma C-peptide concentrations did not decrease with increasing FPG in either group and 24-h urinary C-peptide excretion during a diet of mixed composition was positively correlated with FPG for all subjects (r = 0.36, P less than 0.05). Fasting free fatty acid (FFA) was correlated with FPG in nondiabetics (r = 0.49, P less than 0.05) and diabetics (r = 0.77, P less than 0.001). Fasting FFA was also correlated with the isotopically determined endogenous glucose production rate in the diabetics (r = 0.54, P less than 0.05). Endogenous glucose production was strongly correlated with FPG in the diabetics (r = 0.90, P less than 0.0001), but not in the nondiabetics. Indirect calorimetry showed that FPG was also negatively correlated with basal glucose oxidation rates (r = -0.61, P less than 0.001), but positively with lipid oxidation (r = 0.74, P less than 0.001) in the diabetics. Insulin action was measured as total insulin-mediated glucose disposal, glucose oxidation, and storage rates, using the euglycemic clamp with simultaneous indirect calorimetry at plasma insulin concentrations of 135 +/- 5 and 1738 +/- 59 microU/ml. These parameters of insulin action were significantly, negatively correlated with FPG in the nondiabetics at both insulin concentrations, but not in the diabetics although all the diabetics had markedly decreased insulin action. We conclude that decreased insulin action is present in the noninsulin-dependent diabetics in this population and marked hyperglycemia occurs with the addition of decreased peripheral insulin availability. Decreased peripheral insulin availability leads to increased FFA concentrations and lipid oxidation rates (and probably also increased concentrations of gluconeogenic precursors) that together stimulate gluconeogenesis, hepatic glucose production, and progressive hyperglycemia.

C-peptide secretion and insulin antibodies as determinants of stability in diabetes mellitus

The relative significance of residual beta-cell secretory activity and human insulin antibodies in determining diabetic stability has been examined in 35 diabetic subjects. The response of plasma C-peptide immunoreactivity following 50 g oral glucose has been used as an index of beta-cell function. Glucose-stimulated C-peptide secretion was observed in 58% of stable diabetics, but in no labile diabetics. When present, C-peptide secretion following a glucose load in diabetics was of smaller amplitude and slower in onset, but more prolonged than in normal subjects. In secretors, stability of diabetes was significantly correlated with the magnitude of the C-peptide response. As a group, labile diabetics had lower insulin antibody levels than stable patients, but stability and antibody levels were not correlated in individual patients. In non-secretors there was no difference in antibody levels between the stable and labile groups. Neither the equilibrium binding affinities nor the dissociation rate constants differed significantly for antibodies from stable and labile diabetics. Thus stability of diabetes depends upon residual beta-cell secretory activity, but not on the concentration or binding characteristics of insulin antibodies.

Effect of "fractionated" insulins on total plasma insulin binding capacity and insulin requirements in severe diabetes

Serial observations of insulin requirement and total plasma insulin binding capacity have been carried out on six xevere diabetics whose treatment was changed from standard soluble and isophane (NPH) insulins to "fractionated" preparations (Nordisk Insulin Ltd). No correlation was found between initial insulin dose and binding capacity, but changes in these two functions during the study period were closely correlated, both for the group as a whole and for individual patients in whom falls in insulin dose occurred. It is concluded that highly purified insulins could be valuable in the treatment of insulin-resistant cases, that their use is frequently associated with a gradual reduction in insulin dose, and that estimation of total plasma insulin binding capacity may indicate which patients are most likely to benefit from fractionated insulin. No sudden change in insulin requirement was seen on changing to purified insulin preparations.

Serum insulin, insulin antibodies and insulin requirement in the first period of insulin treatment in non-insulin resistant diabetics

Twelve insulin-sensitive diabetics were studied for 200 days after the initiation of mixed beef-pork NPH insulin. Normalization of the fasting blood glucose was not accompanied by any elevation in the pre-treatment fasting immunoreactive insulin level. Insulin antibodies appeared in 2 patients on the second week of insulin treatment, in 6 others within 87 days. In 4 patients no antibodies were found 200 days after the start of insulin. The appearance of antibodies was accompanied in two patients by a decrease in insulin requirement, in others there was no change. When antibodies were present, the total maximum insulin binding capacity was 4 to 12 U/l, but the total insulin constituted only 3 to 36% of the binding capacity. Insulin wastage caused by the destruction of the immune complexes was calculated to be 0.35 to 5.6 U/die only, and this explains the negligible effect of insulin antibodies on insulin requirement in non-resistant patients.