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

Abstract

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 2167 mg 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. AdipoRed TM assay and Oil Red O stainingshowed 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 (r ¼ 0.826, n ¼ 24, 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.

Insulin Mimetic Properties of Extracts Prepared from Bellis perennis

“…We used HPLC-MS for the identification and quantitation of potential active compounds. As polyphenolics are frequently associated with potential anti-diabetic effects in conjunction with elevated GLUT4 translocation [ 47 , 48 , 49 ], our main focus was on phytochemicals. To date, there is only limited information on the polyphenolic contents of Bellis perennis .…”

Effect of diets supplemented with linseed alone or combined with vitamin E and selenium or with plant extracts, on Longissimus thoracis transcriptome in growing-finishing Italian Large White pigs

“…Only the study from Kamei et al [ 67 ] considers the effect of a diet supplemented with fat and maple syrup (rich in polyphenols) on mouse liver, evidencing similarly to our study an overexpression of ELOVL6 and SCD . Torabi and DiMarco [ 68 ] reported that also polyphenols supplementation alone increased the expression of lipogenic genes in rat preadipocyte cultures. Moreover, considering that some studies reported also an upregulation of lipogenic genes following n -3 PUFA supplementation [ 8 , 22 ] we hypothesize that the combined n -3 PUFA and polyphenols supplementation may trigger the expression of lipogenic genes.…”

Inflammation and Oxidative Stress in an Obese State and the Protective Effects of Gallic Acid

“…Besides tea ( Camellia sinensis ), fruits that have been shown to contain high levels of gallic acid or its derivative compounds include avocado, ellagitannin-enriched polyphenolic extract, Eugenia dysenterica DC., freeze-dried jaboticaba peel, grape powder, herbal mixture, Limonium spp . (Plumbaginaceae), Mangifera indica L., mango, mulberry water, Nelumbo nucifera leaf, Norton grape pomace, number ten supplement, Ocimum basilicum , pineapple, pomegranate peels, Psidium guajava L., Pedro Sato, Paluma and Século XXI, Pu-erh tea, Punica granatum , Ribes nigrum L , Rubus suavissimus , and Terminalia bellirica [11,15,19,98,99,102,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,142,143,145].…”

“…Blackcurrant ( Ribes nigrum ) supplemented in diet for eight weeks reduced body weight gain and improved glucose metabolism in HFD fed mice [11]. Although limitations in decreasing oxidative stress in obese female mice have been observed [120], several beneficial effects for grapes ( Vitis vinifera ) extracts have been identified by other researchers in cultured adipocytes and obese rodents [120,129,130]. The beneficial effects include the capacity of this grape extract to reduce plasma C-reactive protein levels, improve glucose uptake and insulin signaling, which may be related to enhanced expression of perilipin-1, fatty acid binding protein 4, GLUT4, as well as PI3K.…”