Comparison of gene transcription between subcutaneous and visceral adipose tissue in Chinese adults

Obese individuals with fat stored in visceral adipose tissue (VAT) generally suffer greater adverse metabolic consequences than those with fat stored predominantly in subcutaneous adipose tissue (SAT), but its molecular basis is not completely understood. We isolated paired samples of SAT and VAT from 15 lean and 15 obese subjects and systematically compared the transcription level of genes that may determine fat distribution and metabolic sequelae between SAT and VAT using quantitative real-time PCR. We found that, leptin levels were lower in VAT than SAT, for both lean and obese subjects. In lean subjects, tumor necrosis factor-alpha (TNF-alpha) was expressed equally in both fat depots, while toll-like receptor 4 (TLR4) and glucocorticoid receptor (GR) showed significantly lower expression in VAT than SAT. In obese subjects, TNF-alpha and TLR4 expression were significantly higher in VAT than SAT, yet GR expression did not differ in these areas. For all subjects, VAT 11beta-hydroxysteroid dehydrogenate type 1 (11beta-HSD1) level was significantly correlated with BMI. GR expression level was significantly correlated with TLR4 expression level. Cultured adipocytes showed higher TLR4 mRNA level after differentiation, and higher TNF-alpha level after treatment with free fatty acids. These results suggest that there are depot-specific differences in leptin, TNF-alpha, TLR4 and GR transcriptions in humans. TLR4 signaling and higher 11beta-HSD1 and GR levels in VAT may contribute predominantly to inflammatory factor production and subsequent metabolic sequelae in obese human.