Role of nucleolar protein NOM1 in pancreatic islet β cell apoptosis in diabetes.

Diabetes is a metabolic disease that results from impairment in insulin secretion. The present study aimed to investigate the potential role of NOM1 in the function of pancreatic islet β cells and insulin secretion. MIN6 cells isolated from mice were transfected with siRNA-NOM1 to assess the influence of NOM1 on the expression of the cell apoptosis-associated proteins, such as caspase-3. In addition, MIN6 cells were cultured in medium containing different glucose concentrations in order to assess the sensitivity of MIN6 cells to glucose. The effect of NOM1 expression and glucose on MIN6 cell proliferation was also analyzed using an MTT assay. Furthermore, the mRNA expression levels of insulin 1 and 2 in MIN6 cells were detected using reverse transcription-quantitative polymerase chain reaction, while the expression levels of various cell apoptosis-associated proteins, Bcl-2 and Bax, were analyzed using western blot analysis. Compared with the control group, downregulation NOM1 and high glucose concentration of 25 mM significantly increased the cleaved caspase-3 level in MIN6 cells (P<0.05). In addition, downregulation of NOM1 significantly inhibited the MIN6 cell proliferation ability and reduced the insulin 2 mRNA expression (P<0.05). NOM1 knockdown also resulted in significantly increased Bax2 level and decreased Bcl-2 level in MIN6 cells (P<0.05). However no significant difference in insulin mRNA expression was observed between the control and siRNA-NOM1-transfected group (P>0.05). In conclusion, the present study suggested that NOM1 expression may be affected by blood glucose, and that NOM1 may be associated with pancreatic islet β cell apoptosis. In addition, NOM1 may serve a pivotal role in diabetes by affecting insulin synthesis and secretion in pancreatic islet β cells.