[Expression of TSG-6 gene during 3T3-L1 preadipocyte differentiation and regulative role of tumor necrosis factor-alpha].

Objective: Tumor necrosis factor alpha-stimulated gene-6 (TSG-6 gene) differentially expressed in adipose tissue of obese and normal human subjects or rats. To explore the relationship between the differential expression of TSG-6 and adipocyte differentiation, adipogenesis and obesity, the present study aimed to investigate the changes of TSG-6 gene expression during 3T3-L1 preadipocyte differentiation and to analyze the regulative role of TNF-alpha on TSG-6 gene expression in matured 3T3-L1 adipocytes.

Methods: 3T3-L1 preadipocytes were cultured in vitro and differentiated into the matured adipocytes. TNF-alpha in different concentrations (0.1 ng/ml, 1.0 ng/ml, 10.0 ng/ml) was added into the culture medium of fully differentiated adipocytes (day 10) for various times (0.5 h, 2 h, 6 h, 12 h, 24 h). Total RNA from these adipocytes was extracted and the levels of TSG-6 gene mRNA expression were evaluated by RT-PCR.

Results: (1) In preadipocytes, the level of TSG-6 gene mRNA expression remained low. In the presence of dexamethasone (Dex), MIX and insulin, with the 3T3-L1 preadipocytes being differentiated into the matured adipocytes, the level of TSG-6 gene mRNA expression was upregulated and reached the higher level in fully differentiated adipocytes. There is a significant difference between any two detected phases in the levels of TSG-6 gene mRNA expression (P < 0.05), except that the levels of TSG-6 gene mRNA expression did not increase obviously on day 0 to day 2, day 3 to day 5, day 4 to day 6 and day 7 to day 10 (P > 0.05). (2) Treatment of day 10 3T3-L1 adipocytes with TNF-alpha of different concentrations (0.1 ng/ml, 1.0 ng/ml, 10.0 ng/ml) resulted in a significant decrease in the level of TSG-6 gene mRNA expression. The inhibition effect of TNF-alpha on TSG-6 gene mRNA expression generally tended to be reinforced with the increasing concentrations of TNF-alpha and the elongation of time course, except for the period of 6 - 24 h after the stimulation of 10.0 ng/ml TNF-alpha. When 0.1 ng/ml TNF-alpha was applied, the level of TSG-6 gene expression decreased by 33.73% at 6 h, 97.39% at 12 h. While 1.0 ng/ml TNF-alpha was used, the level of TSG-6 gene expression decreased by 78.68% at 6 h, which remained until 24 h. At a concentration of TNF-alpha up to 10.0 ng/ml, the level of TSG-6 gene expression decreased by 96.27% at 2 h. TSG-6 gene expression was almost fully inhibited.

Conclusion: (1) TSG-6 gene may be involved in adipocyte differentiation and adipogenesis. (2) TNF-alpha can downregulate the mRNA expression of TSG-6 gene in matured adipocytes. The inhibitory effect of TNF-alpha on TSG-6 gene expression is generally dose-correlated.