L-Arginine supplementation improves insulin sensitivity and beta cell function in the offspring of diabetic rats through AKT and PDX-1 activation

Abstract

Maternal hyperglycemia can result in defects in glucose metabolism and pancreatic beta-cell function in offspring. The purpose of this study was to evaluate the impact of maternal diabetes mellitus on pancreatic islets, muscle and adipose tissue of the offspring, with or without oral L-Arginine supplementation. The induction of diabetes was performed using streptozotocin (60 mg/kg). Animals were studied at 3 months of age and treatment (sucrose or L-Arginine) was administered from weaning. We observed that L-Arg improved insulin sensitivity in the offspring of diabetic mothers (DA), reflected by higher insulin-induced phosphorylation of Akt in muscle and adipose tissue. Insulin resistance is associated with increased oxidative stress and the NADPH oxidase enzyme plays an important role. Our results showed that the augmented interaction of p47(PHOX) with gp91(PHOX) subunits of the enzyme in skeletal muscle tissue in the offspring of diabetic rats (DV) was abolished after L-Arg treatment in DA rats. Maternal diabetes caused alterations in the islet functionality of the offspring leading to increased insulin secretion at both low (2.8 mM) and high (16.7 mM) concentrations of glucose. L-Arg reverses this effect, suggesting that it may be an important modulator in the insulin secretory process. In addition it is possible that L-Arg exerts its effects directly onto essential molecules for the maintenance and survival of pancreatic islets, decreasing protein expression of p47(PHOX) while increasing Akt phosphorylation and PDX-1 expression. The mechanism by which L-Arg exerts its beneficial effects may involve nitric oxide bioavailability since treatment restored NO levels in the pancreas.