The long noncoding RNA Bsr in the genomically imprinted Dlk1-Dio3 region is suppressed in newborn rat pancreas by gestational obesity

Background: Fetal metabolic programming imposed by maternal obesity and impaired glucose tolerance predisposes the offspring to metabolic disease and beta cell dysfunction as adults. The aim of this study was to assess the whole pancreas RNA changes in neonatal offspring exposed to fetal programming. Methods: The outcome of fetal programming on offspring was tested using the selectively bred Diet Induced Obese (DIO) and the Diet Resistant (DR) strains. DIO and DR rats were fed either chow or high fat, high sucrose (high energy, HE) diet during gestation and the differences in pancreas RNA expression at two days after birth were measured by microarray. Pancreas sections were stained and analyzed for alpha and beta cell numbers. Neonatal islets were treated with cytotoxic cytokines and RNA measured by RT-Q-PCR. Results: Morphometric analyses revealed significant differences in alpha and beta cell numbers per pancreas or per islet by HE diet. Microarray analyses revealed 11 fold downregulation of the long noncoding RNA Bsr in whole pancreas by HE feeding of DIO rat dams. MicroRNAs from the same locus, the Dlk1- Dio3 imprinted region, were also decreased by HE diet. Moreover, treatment of isolated neonatal islets with inflammatory cytokines, IL-1β and IFN-γ, led to reduction of Bsr transcript in a time and dose dependent manner. Conclusions: Our data suggest that fetal programming of Bsr may play a role in beta cell dysfunction in obesity and type 2 diabetes.

Localization of microRNA-375 in perinatal rat pancreas

MicroRNA (miRNA)-375 is highly expressed in the pancreatic endocrine islets. Maintaining appropriate miR-375 levels is very important for beta cell development, function and proliferation. The aim of the current study was to investigate the regulation and localization of miR-375 in rat perinatal pancreas at embryonic day 20 (E20), postnatal day 0 (D0) and day 2 (D2). Expression levels of miR-375 were measured by in situ hybridization on fixed neonatal rat pancreas. Interestingly, while miR-375 was detectable at robust levels at all three time points, the major site of expression of miR-375 at D0 and D2 was in pancreatic exocrine cells. Our data show that miR-375 has a dynamic change of expression in pancreatic exocrine tissue during the perinatal period. Moreover, these findings indicate that pancreatic endocrine cells may not always be the major source of expression of miR-375 in pancreas. We suggest that the marked change of miR-375 levels in exocrine cells following birth could regulate processes involved in the adaptation of the exocrine pancreas to digestion of external nutrients derived from milk.

Combined Immuno-FISH confirms islet-specific miRNAs

Combined immuno-FISH offers an important tool for understanding the localization of mature microRNAs with reference to other proteins within the same cell. This procedure has been previously demonstrated by our team and the method has been described earlier [1, 2].