Riceberry rice (Oryza sativa L.) is a new pigmented variety of rice from Thailand. Despite its high anthocyanin content, its effect on adipogenesis and adipocyte function remains unexplored. We investigated whether Riceberry rice extract (RBE) impacted cell proliferation by examining viability and cell cycle, using preadipocyte 3T3-L1 cells. To test RBE’s effect on adipocyte formation, cells were cultured in adipogenic medium supplemented with extract and adipocyte number and triglyceride levels were quantified. Furthermore, Akt1 phosphorylation along with RT-qPCR and intracellular calcium imaging were performed to obtain an insight into its mechanism of action. The effect of RBE on adipocyte function was investigated using glucose uptake and lipolysis assays. Treatment of cells with RBE decreased preadipocyte number without cytotoxicity despite inducing cell cycle arrest (p < 0.05). During adipogenic differentiation, RBE supplementation reduced adipocyte number and triglyceride accumulation by downregulating transcription factors (e.g., PPARγ, C/EBPα, and C/EBPβ) and their target genes (p < 0.05). The Akt1 phosphorylation was decreased by RBE but insignificance, however, the extract failed to increase intracellular calcium signals. Finally, the treatment of adipocytes with RBE reduced glucose uptake by downregulating Glut4 mRNA expression and enhanced isoproterenol-induced lipolysis (p < 0.05). These findings suggest that RBE could potentially be used in the treatment of obesity by inhibiting adipocyte formation and proliferation.

Cyanidin-3-rutinoside (C3R) is an anthocyanin with anti-diabetic properties found in red-purple fruits. However, the molecular mechanisms of C3R on Ca²⁺-dependent insulin secretion remains unknown. This study aimed to identify C3R's mechanisms of action in pancreatic β-cells. Rat INS-1 cells were used to elucidate the effects of C3R on insulin secretion, intracellular Ca²⁺ signaling, and gene expression. The results showed that C3R at 60, 100, and 300 µM concentrations significantly increased insulin secretion via intracellular Ca²⁺ signaling. The exposure of cells with C3R concentrations up to 100 μM did not affect cell viability. Pretreatment of cells with nimodipine (voltage-dependent Ca²⁺ channel (VDCC) blocker), U73122 (PLC inhibitor), and 2-APB (IP₃ receptor blocker) inhibited the intracellular Ca²⁺ signals by C3R. Interestingly, C3R increased intracellular Ca²⁺ signals and insulin secretion after depletion of endoplasmic reticulum Ca²⁺ stores by thapsigargin. However, insulin secretion was abolished under extracellular Ca²⁺-free conditions. Moreover, C3R upregulated mRNA expression for Glut2 and Kir_6.2 genes. These findings indicate that C3R stimulated insulin secretion by promoting Ca²⁺ influx via VDCCs and activating the PLC-IP₃ pathway. C3R also upregulates the expression of genes necessary for glucose-induced insulin secretion. This is the first study describing the molecular mechanisms by which C3R stimulates Ca²⁺-dependent insulin secretion from pancreatic β-cells. These findings contribute to our understanding on how anthocyanins improve hyperglycemia in diabetic patients.

Riceberry rice containing anthocyanins is a new pigmented variety of rice from Thailand with various biological activities such as antioxidant, anti‐inflammatory, anti‐hyperglycemia, and anti‐cancer. The present study aimed to investigate the effects of Riceberry rice extract (RBE) on adipogenic differentiation in mice 3T3‐L1 cells. RBE was obtained using water followed by freeze dryer lyophilization. Then, total phenolic compounds, total anthocyanin contents, and major anthocyanins in RBE were analyzed. The 3T3‐L1 preadipocytes were cultured in differentiation media and supplemented with RBE 1, 10, 20 and 50 μg/ml concentrations. After 8 days of incubation, cell viability, mature adipocyte number, triglyceride levels, and glucose uptake were determined. The mRNA expression of transcription factors and adipogenic genes including PPARγ, C/EBPα, FasN, ACC, aP2, AdipoQ, Leptin, Resistin, InsR, and Glut4 were also examined. The results revealed that RBE contained total phenolic compounds (63.33±2.4 mg gallic acid equivalent/g extract) and total anthocyanin (10.13±0.14 mg cyanidin‐3‐glucoside/g extract). The anthocyanins detected were cyanidin‐3‐glucoside and peonidin‐3‐glucoside. In 3T3‐L1 cells, RBE significantly reduced the number of mature adipocytes and triglyceride accumulation in a concentration‐dependent manner. In addition, the treatment of 3T3‐L1 cells with the various RBE concentrations did not cause cytotoxicity. Furthermore, the mRNA expression of major transcription factors, PPARγ and C/EBPα were significantly downregulated by RBE (20 and 50 μg/ml) in both early phase (day 3) and late phase (day 8) of adipogenesis. At 50 μg/ml RBE, there was a significant reduction in mRNA expression levels of all adipogenic genes. Interestingly, RBE (10, 20 and 50 μg/ml) significantly reduced glucose uptake into adipocytes via downregulated InsR and Glut4 mRNA expression. These findings suggest that RBE could potentially be used as an anti‐obesity agent by inhibiting adipogenesis and reducing glucose uptake in adipocytes. Support or Funding Information: Dutsadi Phiphat Scholarship from Chulalongkorn University, LSU‐SVM CORP