Glycine increases mRNA adiponectin and diminishes pro-inflammatory adipokines expression in 3T3-L1 cells

Obesity and,type 2 diabetes course with chronic low-grade inflammation, where adiponectin is down-regulated and pro-inflammatory markers, like interleukin (IL)-6, tumor necrosis factor alpha (TNF-alpha), and C-reactive protein (CRP), are up-regulated. A treatment option to improve the micro- and macro-complications in type 2 diabetes is the use of glycine, which has been demonstrated previously to increase the expression of anti-inflammatory cytokine IL-10 in monocytes and down-regulate the expression of TNF-alpha in monocytes and Kupffer cells. Recently, our group demonstrated that glycine decreases the pro-inflammatory plasmatic cytokines in type 2 diabetes. The aim of this study was to test the effect of glycine on adipokines expression in 3T3-L1 cells. Cells were grown and differentiated in the presence of 10 mM glycine. After 2 days of confluence, cells were differentiated to adipocytes in the same medium supplemented with insulin, dexamethasone, and 3-isobutyl-1-methylxanthine. The RNA was extracted at days 0 and 8 of differentiation (fibroblasts and mature adipocyte phenotypes, respectively). The expression of PPAR-gamma (peroxisome proliferator-activated receptor-gamma), adiponectin, resistin, IL-6 and TNF-alpha were analyzed by real-time PCR. We demonstrated that when 3T3-L1 cells were treated with glycine, IL-6, resistin and TNF-alpha mRNA expression was decreased, but surprisingly adiponectin and PPAR-gamma were up-regulated. In all cases the values were statistically significant (P<0.05) between glycine treatment and controls. These results show that glycine improves the pro-inflammatory profile and up-regulates adiponectin gene expression. Therefore, glycine could be useful as a modulator of the pro-inflammatory state observed in obesity and type 2 diabetes. (C) 2008 Elsevier B.V. All rights reserved.