Co-ordinated regulation of neurogenin-3 expression in the maternal and fetal pancreas during pregnancy.

OBJECTIVE: Several studies have shown increased beta cell mass during pregnancy in both rodents and humans. Proliferation of existing beta cells seems to be the predominant mechanism in rodents, whereas the mechanism in humans is unclear. We hypothesized that neogenesis contributes to the increased beta cell mass in pregnancy and that circulating factors are involved. SAMPLES: Pancreatic tissue from mice and rat and serum from pregnant women. METHOD: Morphometric analysis of pancreas of pregnant and nonpregnant mice was carried out by immunocytochemical staining for the neogenic marker neurogenin-3. Messenger RNA levels of neurogenin-3 and the transcription factor musculoaponeurotic fibrosarcoma oncogene family protein B in fetal rat pancreas cells, cultured with serum from pregnant women, were measured by quantitative polymerase chain reaction. MAIN OUTCOME MEASURES: The number of neurogenin-3-positive cells present in pregnant mice was increased compared with nonpregnant mice. Neurogenin-3 and musculoaponeurotic fibrosarcoma oncogene family protein B mRNA was detected in fetal rat pancreas exposed to serum from pregnant women. RESULTS: In pregnant mice we found a 3.6-fold increase in beta cell volume at day 18 compared with nonpregnant mice and a 3.5-fold increase in neurogenin-3 volume at day 14, mainly located in the acinar compartment where it was eightfold higher than in nonpregnant mice. In fetal rat pancreatic cells exposed to serum from pregnant women we found a marked increase in both neurogenin-3 and musculoaponeurotic fibrosarcoma oncogene family protein B mRNA levels in fibroblast-like cells. CONCLUSION: These results suggest that neogenesis contributes to the increased beta cell mass in pregnancy and that circulating factors are involved in beta cell formation in both the maternal and fetal pancreas during pregnancy.

Impact of fetal and neonatal environment on beta cell function and development of diabetes.

The global epidemic of diabetes is a serious threat against health and healthcare expenses. Although genetics is important it does not explain the dramatic increase in incidence, which must involve environmental factors. Two decades ago the concept of the thrifty phenotype was introduced, stating that the intrauterine environment during pregnancy has an impact on the gene expression that may persist until adulthood and cause metabolic diseases like obesity and type 2 diabetes. As the pancreatic beta cells are crucial in the regulation of metabolism this article will describe the influence of normal pregnancy on the beta cells in both the mother and the fetus and how various conditions like diabetes, obesity, overnutrition and undernutrition during and after pregnancy may influence the ability of the offspring to adapt to changes in insulin demand later in life. The influence of environmental factors including nutrients and gut microbiota on appetite regulation, mitochondrial activity and the immune system that may affect beta cell growth and function directly and indirectly is discussed. The possible role of epigenetic changes in the transgenerational transmission of the adverse programming may be the most threatening aspect with regard to the global diabetes epidemics. Finally, some suggestions for intervention are presented.

Trefoil factors are expressed in human and rat endocrine pancreas: differential regulation by growth hormone.

Trefoil factors (TFFs) 1, 2, and 3 are expressed in mucosal epithelia. TFFs are particular abundant in the intestine in which they play a crucial role in maintenance and restitution of the epithelium. Because pancreas developmentally arises from the primitive foregut, we explored the expression of TFFs in the pancreas in man and rat. Immunocytochemical staining of adult human pancreas showed abundant TFF3 immunoreactivity in pancreatic islets and some duct cells, whereas weak TFF1 and no TFF2 staining were detected. In the islets TFF3 localized to most insulin and some glucagon and pancreatic polypeptide-producing cells. TFF3 immunoreactivity was colocalized with insulin and glucagon in distinct cell clusters in human fetal pancreas at wk 14 and in the newborn rat pancreas. In isolated human and rat islets, TFF3 and TFF1 mRNA was identified by RT-PCR, and TFF3 protein was detected in human pancreas and islets by ELISA. Exposure of neonatal rat islets or insulinoma cells to GH, a known beta-cell growth factor, resulted in markedly increased TFF3 but decreased TFF1 mRNA levels. The effect of GH on TFF3 expression was confirmed by Western blot. Culture of neonatal rat islets in the presence of TFF3 resulted in attachment and migration of the islet cells, but no effects on proliferation, insulin secretion or cytokine-induced apoptosis were seen. These data demonstrate expression of TFFs in the endocrine pancreas, but their possible functions remain unknown.