Polyphenols extracted from grape powder induce lipogenesis and glucose uptake during differentiation of murine preadipocytes




Torabi, Sheida
DiMarco, Nancy M.

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Experimental Biology and Medicine


Assessing the effects of grapes and grape powder extracted polyphenols on lipogenesis and glucose uptake in adipocytes may clarify the risk/benefit of recommending them to individuals with obesity and insulin resistance. We investigated the effect of grape powder extracted polyphenols (GPEP) on intracellular fat accumulation and glucose uptake during differentiation of 3T3-F442A preadipocytes. Total polyphenols were extracted and measured based on gallic acid equivalents (GAE). There were 2167mg of GAE polyphenols in 100 g of grape powder. 3T3-F442A cells were incubated with GPEP, extracted from 125–500 mg GP/mL of media, until day 8 of differentiation when the cells were collected for different assays. AdipoRedTM assay and Oil Red O staining showed that GPEP induced, in a dose-dependent manner, an increase in intracellular triacylglycerol (TAG) content of adipocytes. Concomitantly, grape powder extracted polyphenols increased, in a dose-dependent manner, glucose uptake by 3T3-F442A cells, and there was a strong positive correlation between glucose uptake and the amount of TAG accumulation (r¼0.826, n¼24, P 0.001). No changes in cell viability was measured by Trypan Blue staining, suggesting that these effects were independent of cytotoxicity. Western-blot showed that GPEP upregulated protein level of glucose transport protein 4 (GLUT4), p-PKB/Akt, and p- AMPK in 3T3-F442A adipocytes. LY294002 (10 mmol/L), a phosphatidyl-inositol 3 kinase inhibitor (PI3K), reversed the effects of grape powder extracted polyphenols on cellular lipid content and glucose uptake. Furthermore, quantitative real-time polymerase chain reaction showed that GPEP increased mRNA expression of GLUT4, fatty acid synthase, lipoprotein lipase, adiponectin, and peroxisome proliferator-activated receptor g, while it decreased mRNA expression of leptin and Insig-1. Our results indicate that GPEP may induce adipocyte differentiation via upregulation of GLUT4, PI3K and adipogenic genes. Future research may be directed toward obese individuals with insulin resistance or individuals with diabetes.


This article was published with the assistance of the Texas Woman's University Libraries Open Access Fund. The original article can be found at: https://doi.org/10.1177/1535370216645213


California Table Grape Commission, Grape powder, Polyphenols, 3T3-F442A, Adipocyte, Differentiation, Glucose uptake, LY294002, Phosphatidyl-inositol 3 kinase, Akt, Proliferator-activated receptor g, Glucose transport protein 4, Adiponectin, AMP-activated protein kinase


This is the publisher’s version of an article that is available at https://doi.org/10.1177/1535370216645213. Recommended citation: Torabi, S., & DiMarco, N. M. (2016). Original research: Polyphenols extracted from grape powder induce lipogenesis and glucose uptake during differentiation of murine preadipocytes. Experimental Biology and Medicine, 241(16), 1776–1785. This item has been deposited in accordance with publisher copyright and licensing terms and with the author’s permission.