Mechanisms of anthocyanin-enrich Riceberry rice extract (Oryza sativa L.) on the regulation of nutrient metabolisms and adipogenesis

Abstract

Riceberry rice, a new pigmented rice variety from Thailand, contained high anthocyanin content and expressed various biological activities. This study aimed to investigate the anti-obesity effects of Riceberry rice extract (RBE) in 3T3-L1 preadipocytes and to identify the mechanism of RBE and its phytochemicals on insulin secretion from pancreatic INS-1 cells. In 3T3-L1 cells, RBE inhibited preadipocyte proliferation by inducing cell cycle arrest without causing cytotoxicity. During adipogenesis, RBE downregulated transcription factor and adipogenic gene expression leading to the decrease in adipocyte number and triglyceride accumulation. Moreover, RBE reduced glucose uptake by downregulating glucose transporter 4 gene expression and enhanced lipolysis. RBE and its phytochemicals had no effect on intracellular calcium signaling in both preadipocytes and pancreatic β-cells. However, cyanidin-3-rutinoside (C3R) which synthesized from rutin presenting in RBE stimulated insulin secretion by promoting calcium influx via L-type voltage-dependent calcium channels (VDCCs) and activating the PLC-IP3 pathway. Furthermore, C3R upregulated glucose-induced insulin secretion gene expression without cytotoxicity. These findings support the benefits of anthocyanins on the prevention of obesity, diabetes, and metabolic syndrome.