Combinations of genistein, EGCG and/or resveratrol synergistically inhibit pre-adipocyte differentiation by suppressing PPAR-γ/C/EBP-α pathway
Obesity is the focus of many public health efforts in the United States. Although it appears to level off between 2003 and 2010, the prevalence of obesity in the United States is very high, with 34.9% of adults and 17% of children obese in 2012. While a number of anti-obesity drugs are currently available on the market or undergoing clinical development, the potential of natural products for preventing and treating obesity is considered as an excellent alternative strategy for developing effective, safe and cost-effective anti-obesity agents because of the potential hazardous side effect and high cost of the current anti-obesity drugs. Indeed, a number of studies have been carried out to investigate the anti-obesity effect of plants-derived compounds like soy bean genistein (G) , green tea epigallocatechin-3-gallate (EGCG or E), and grape resveratrol (R). However, the anti-obesity effect of these compounds are still controversial in human studies because the high dosages working in cells and animals can not be reached in humans by consuming the food or supplements. Therefore, the goal of this study is to test whether the combinations of G, E and/or R synergistically or additively inhibit pre-adicpocyte differentiation and to further define its molecular mechanisms. Individual or combinations of G (30µM), E (30µM) and/or R (30µM) were treated in differentiated 3T3-L1 cells for 10 days, and G (15µM), E (15µM) and/or R (15µM) were treated in differentiated human primary pre-adipocytes (HPAs) for 15 days. Cell differentiation was evaluated by intracellular lipid accumulation, which was measured by a Synergy H1 microplate reader after Oil O red staining and dissolved in 100% isopropanol. Total proteins extracted from the cells were subjected to Western Blot to measure specific protein expression. Our results shown that combinations of G, R or E significantly inhibited pre-adipocyte differentiation both in 3T3-L1 cells (E+G,73.0% of control, P<.05); R+G, 89.0% of control, P<.01; G+E, 62.0.0% of control, P>.05; G+E+R, 39.3% of control, p<0.01) and HPAs (E+G,70.0% of control, P<.05; R+G, 77% of control, P<.01; G+E, 85% of control, P>.05; G+E+R, 60% of control, p<0.01). We also observed a similar pattern that combinations of G, E and/or R synergistically reduced expressions of CCAAT-binding proteins alpha (C/EBPα) and peroxisome proliferator activated receptor gamma (PPAR-γ), the two key pre-adipocyte differentiation regulators, both in differentiated 3T3-L1 cells and HPAs, suggesting that the synergistic anti-adipogenic effect of G, E and/or R may be mediated by the PPAR-γ and C/EBPα signaling pathways. Moreover, combined G, E and/or R synergistically reduced protein expression of fatty acid binding protein 4 (FABP4) , a key molecule in fat drop accumulation in a very similar pattern of these compounds in inhibiting differentiation in 3T3-L1 cells. This synergistic anti-adipogenic effect of combinations of G, E and/or R may be mediated by the common or different signaling pathways including AMP-activated kinase, mitogen-activated protein kinase and PPAR-γ/C/EBPα although more studies are still needed. The results from this study provide potential approach to prevent obesity by consuming variety of foods with anti-obesity bioactive compounds.
"Combinations of genistein, EGCG and/or resveratrol synergistically inhibit pre-adipocyte differentiation by suppressing PPAR-γ/C/EBP-α pathway"
ETD Collection for Tennessee State University.