Role of (−)-epigallocatechin-3-gallate in cell viability, lipogenesis, and retinol-binding protein 4 expression in adipocytes

Abstract

(-)-Epigallocatechin-3-gallate (EGCG), a bioactive compound of green tea, is known to combat obesity by reducing the viability and lipid accumulation of adipocytes. In this study, we evaluated the mechanism and clinical relevance on those actions of EGCG. We measured the viability of 3T3-L1 preadipocytes and adipocytes by the 3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide assay. Lipid accumulation was measured by Oil Red O staining. Intracellular accumulation of reactive oxygen species (ROS) was determined using a flow cytometer. Cellular glucose uptake was determined with 2-deoxy-[(3)H]-glucose. The protein levels of peroxisome proliferator-activated receptor (PPAR)-γ and adiponectin in 3T3-L1 adipocytes, as well as the protein level and secretion of plasma retinol-binding protein (RBP4) in human adipocytes, were measured by western blot. EGCG at concentrations higher than 10 μM induced ROS generation and decreased the viability and lipid accumulation of adipocytes. It also decreased the expression of PPAR-γ and adiponectin. At concentrations readily achievable in human plasma via green tea intake (≤10 μM), EGCG inhibited cellular glucose uptake and enhanced the expression and secretion of RBP4 in adipocytes. Pharmacological doses of EGCG showed cytotoxic effects in preadipocytes and adipocytes. EGCG-mediated glucose uptake inhibition in adipocytes may be clinically relevant and is probably linked to the increase in the expression and secretion of RBP4. Because secreted RBP4 from adipocytes inhibits muscular glucose uptake and enhance hepatic glucose output, the systemic effect of EGCG associated with its effect on RBP4 secretion should be further determined, as it may negatively regulate whole-body insulin sensitivity, contrary to general belief.

Momordica charantia Seed Extract Reduces Pre-Adipocyte Viability, Affects Lactate Dehydrogenase Release, and Lipid Accumulation in 3T3-L1 Cells

“…37,38 A decrease in Oil red O lipid staining has been reported to coincide with the observed decreases in PPARg expression in 3T3-L1 cell treated with a variety of natural product extracts. [39][40][41] Conversely, when lipid accumulation was increased PPARg expression was also reported increased. 42 Although not directly measured in this study it seems evident that the triterpenoids contained in the BMS extract decrease lipid accumulation and thus likely would reduce PPARg expression.…”

Green tea and type 2 diabetes

“…However, the concentrations of EGCG required to decrease the number of preadipocytes and adipocytes are too high to be consumed by humans without considerable side effects 15, 16, 17. Although green tea catechins have the molecular structure to scavenge oxygen-free radicals, their effectiveness in biological systems has not been clarified.…”

“…Cell viability is impaired significantly when preadipocytes are treated with 50 μM EGCG, but recover by treatment with the antioxidant vitamin E 15 . This means that this concentration of EGCG may act as a pro-oxidant 18 .…”

Effect of Green Tea (−)-Epigallocatechin Gallate on Adipocytes

“…EGCG at 10 mM inhibited insulin-induced increases in cell number by 34% and the triglyceride content by 54% during a nine-day period of differentiation (Kao et al, 2000b. EGCG at 5e200 mM reduces amounts of lipid accumulation in differentiating 3T3-L1 adipocytes (Furuyashiki et al, 2004;Hwang et al, 2005;Kim et al, 2010;Moon et al, 2007;Sung et al, 2010). EGCG at 5e200 mM reduces amounts of lipid accumulation in differentiating 3T3-L1 adipocytes (Furuyashiki et al, 2004;Hwang et al, 2005;Kim et al, 2010;Moon et al, 2007;Sung et al, 2010).…”