Rice Bran Phenolic Extracts Modulate Insulin Secretion and Gene Expression Associated with β-Cell Function

Oxidative stress is known to modulate insulin secretion and initiate gene alterations resulting in impairment of beta-cell function and type 2 diabetes mellitus (T2DM). Rice bran (RB) phenolic extracts contain bioactive properties that may target metabolic pathways associated with the pathogenesis of T2DM. This study aimed to examine the effect of stabilized RB phenolic extracts on the expression of genes associated with beta-cell function such as glucose transporter 2 (Glut2), pancreatic and duodenal homeobox 1 (Pdx1), sirtuin 1 (Sirt1), mitochondrial transcription factor A (Tfam), and insulin 1 (Ins1) in addition to evaluating its impact on glucose-stimulated insulin secretion. It was observed that treatment with different concentrations of RB phenolic extracts (25-250 mu g/mL) significantly increased the expression ofGlut2,Pdx1,Sirt1, Tfam,andIns1genes and glucose-stimulated insulin secretion under both normal and high glucose conditions. RB phenolic extracts favourably modulated the expression of genes involved in beta-cell dysfunction and insulin secretion via several mechanisms such as synergistic action of polyphenols targeting signalling molecules, decreasing free radical damage by its antioxidant activity, and stimulation of effectors or survival factors of insulin secretion.