Cyanidin inhibits adipogenesis in 3T3-L1 preadipocytes by activating the PLC-IP3 pathway.

Cyanidin is the most abundant anthocyanin found in red-purple plants and possesses anti-obesity properties. However, its mechanism of action in adipocytes remains unknown. The objective of this study was to elucidate how cyanidin inhibits adipocyte formation in 3T3-L1 preadipocytes. Cells were cultured in adipogenic differentiation medium supplemented with cyanidin and examined for adipogenesis, cell viability, and adipocyte gene expression using Oil Red O staining, MTT assay, and RT-qPCR. Real-time Ca2+ imaging analysis was performed in living cells to elucidate cyanidin's mechanism of action. The results demonstrated that cyanidin (1-50 µM) supplementation to the adipogenic medium inhibited adipogenesis by downregulating adipogenic marker gene expression (PPARγ, C/EBPα, adiponectin, and aP2) without affecting cell viability after 4 days of treatment. Stimulation of cells with cyanidin (30-100 µM) increased intracellular Ca2+ in a concentration dependent manner with peak calcium increases at 50 µM. Pretreatment of cells with the phospholipase C (PLC) inhibitor U73122, inositol triphosphate (IP3) receptor blocker 2-APB, and depletion of endoplasmic reticulum Ca2+ stores by thapsigargin abolished the Ca2+ increases by cyanidin. These findings suggested that cyanidin inhibits adipocyte formation by activating the PLC-IP3 pathway and intracellular Ca2+ signaling. Our study is the first report describing the mechanism underlying the anti-obesity effect of cyanidin.

Cyanidin-3-rutinoside stimulated insulin secretion through activation of L-type voltage-dependent Ca2+ channels and the PLC-IP3 pathway in pancreatic ß-cells.

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 ß-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 Kir6.2 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 ß-cells. These findings contribute to our understanding on how anthocyanins improve hyperglycemia in diabetic patients.

Anthocyanin-Enriched Riceberry Rice Extract Inhibits Cell Proliferation and Adipogenesis in 3T3-L1 Preadipocytes by Downregulating Adipogenic Transcription Factors and Their Targeting Genes.

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/EBPß) 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.