We investigated in vitro the pancreatic B-cell response of hyperinsulinemic animals compared to that of controls with the aim of clarifying if the hyperinsulinemia is related to an alteration of the islet insulin secretion. Hyperinsulinemia was induced by pregnancy (observation at 19.5 days) and electrolytic lesions of the hypothalamic nucleus ventromedialis (2 days after lesion). The kinetics of the glucose dose/response curves (measured during a 60 min incubation period) differed markedly in the two hyperinsulinemic conditions. Whereas the islets from pregnant rats were characterized by a lowered glucose threshold, an enhanced half-maximal and maximal secretion rate, those of lesioned rats showed only an increased half-maximal and maximal secretion response in spite of a comparable islet insulin content. When culturing islets of hyperinsulinemic animals up to 6 days, the insulin secretion of those prepared from VMH-lesioned rats behaved identically to controls, whereas the islets of pregnant rats maintained their enhanced sensitivity at a glucose concentration of 5 mmol/l. These results confirm that the pancreatic B-cell response contributed significantly to the hyperinsulinemia, but different mechanisms are likely to be responsible for the altered B-cell secretion.

Animals↗

PubMedDate not supplied

Investigations on isolated islets in vitro. IX. Influence of food deprivation and glucose refeeding in vitro on insulin secretion.

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Animals↗

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Age-dependent insulin secretion of the endocrine pancreas in vitro from fetuses of diabetic and nondiabetic patients.

Fetal hyperinsulinemia is assumed to play a key role in the pathogenesis of diabetic fetopathy. To investigate the role of enhanced fetal B-cell mass as one cause of fetal hyperinsulinemia during diabetic pregnancy, we studied human fetal pancreatic slices from diabetic women (FDW) with poor metabolic control and nondiabetic women (FNDW) between 11 and 26 wk of pregnancy, morphometrically and by in vitro incubation experiments. Abortions had been performed due to different medical indications. We found a good correlation between the calculated B-cell mass and the gestational age in both FDW and FNDW, but the increase in FDW was much more pronounced. Such a correlation was also found in vitro regarding the insulin response to glucose and IBMX. The FDW had significantly higher values than FNDW of the same age range. In contrast to this, we found in two diabetic patients with tight metabolic control during the whole pregnancy results similar to those in FNDW. Therefore, we assume that it could be possible to prevent fetal hyperinsulinemia and perhaps even diabetic fetopathy in diabetic women by tight metabolic control during the whole pregnancy, but further investigations are necessary.

Diabetes Mellitus, Type 1↗