Vitamin E supplementation and caloric restriction promotes regulation of insulin secretion and glycemic homeostasis by different mechanisms in rats.

Vitamin E and caloric restriction have antioxidant effects in mammals. The aim of this study was to evaluate effects of vitamin E supplementation and caloric restriction upon insulin secretion and glucose homeostasis in rats. Male Wistar rats were distributed among the following groups: C, control group fed ad libitum; R, food quantity reduction of 40%; CV, control group supplemented with vitamin E [30 mg·kg-1·day-1]; and RV, food-restricted group supplemented with vitamin E. The experiments ran for 21 days. Glucose tolerance and insulin sensitivity was higher in the CV, R, and RV groups. Insulin secretion stimulated with different glucose concentrations was lower in the R and RV groups, compared with C and CV. In the presence of glucose and secretagogues, insulin secretion was higher in the CV group and was lower in the R and RV groups. An increase in insulin receptor occurred in the fat pad and muscle tissue of groups CV, R, and RV. Levels of hepatic insulin receptor and phospho-Akt protein were higher in groups R and RV, compared with C and CV, while muscle phospho-Akt was increased in the CV group. There was a reduction in hepatic RNA levels of the hepatocyte growth factor gene and insulin degrading enzyme in the R group, and increased levels of insulin degrading enzyme in the CV and RV groups. Thus, vitamin E supplementation and caloric restriction modulate insulin secretion by different mechanisms to maintain glucose homeostasis.

ARHGAP21 as a master regulator of multiple cellular processes.

The cellular cytoskeleton is involved with multiple biological processes and is tightly regulated by multiple proteins and effectors. Among these, the RhoGTPases family is one of the most important players. RhoGTPAses are, in turn, regulated by many other elements. In the past decade, one of those regulators, the RhoGAP Rho GTPase Activating Protein 21 (ARHGAP21), has been overlooked, despite being implied as having an important role on many of those processes. In this paper, we aimed to review the available literature regarding ARHGAP21 to highlight its importance and the mechanisms of action that have been found so far for this still unknown protein involved with cell adhesion, migration, Golgi regulation, cell trafficking, and even insulin secretion.