Lupin gamma conglutin protein: effect on Slc2a2, Gck and Pdx-1 gene expression and GLUT2 levels in diabetic rats

Recently, lupin seed (Lupinus albus L., Fabaceae) products have emerged as a functional food due to their nutritional and health benefits. Numerous reports have demonstrated the hypoglycemic effects of lupin's gamma conglutin protein; nonetheless, its mechanism of action remains elusive. To understand the role of this protein on glucose metabolism, we evaluated the effect of administering L. albus’ gamma conglutin on Slc2a2, Gck, and Pdx-1 gene expression as well as GLUT2 protein tissue levels in streptozotocin-induced diabetic rats. While consuming their regular diet, animals received a daily gamma conglutin dose (120 mg/kg per body weight) for seven consecutive days. Serum glucose levels were measured at the beginning and at the end of the experimental period. At the end of the trial, we quantified gene expression in pancreatic and hepatic tissues as well as GLUT2 immunopositivity in Langerhans islets. Gamma conglutin administration lowered serum glucose concentration by 17.7%, slightly increased Slc2a2 and Pdx-1 mRNA levels in pancreas, up-regulated Slc2a2 expression in the liver, but it had no effect on hepatic Gck expression. After gamma conglutin administration, GLUT2 immunopositivity in Langerhans islets of diabetic animals resembled that of healthy rats. In conclusion, our results indicate that gamma conglutin up-regulates Slc2a2 gene expression in liver and normalizes GLUT2 protein content in pancreas of streptozotocin-induced rats.