Effects Of BRL37344on Lipolysis Metabolism And Leptin, Tumor Necrosis Factor-α Expression In3T3-L1Adipocytes

Objective:Obesity is an epidemic disease that threatens to inundate health care resources by increasing the incidence of diabetes mellitus, hypertension, coronary heart disease and cancer. However, the etiology and pathogenesis of obesity are not entirely understood. Direct and effective means of obesity treatment have been received more attentions. Selective β3-adrenergic receptor agonists, which have potential weight loss effects in rodents through stimulating the lipolysis of white adipose tissue and non-shivering thermogenesis of brown adipose tissue, offer perspective on anti-obesity drug research. Adipose tissue as an active endocrine organ secretes a wide range of proteins termed adipokines which play a prominent role in the maintenance of the energy metabolic balance of organism. This study was designed to investigate the effects of BRL37344, a kind of selective β3-adrenergic receptor agonist, on lipolysis metabolism and leptin, tumor necrosis factor-a expression in mature3T3-L1adipocytes, further to clarify its anti-obesity effect and explore the mechanism at the celluar level.Methods:The3T3-L1preadipocytes were cultured at37℃,5%CO2, then differentiated into mature adipocytes with differentiation medium containing insulin, dexamethasone and3-isobutyl-l-methylxanthine. Morphology and extracting stained intracytoplasmic lipid with oil red O all verified their adipocyte identity. These cells were incubated with BRL37344at different concentrations (0,10-9,10-7mol/L)and durations (0,12,24,48h). The cells and corresponding conditioned media were collected and stored at-80℃. Lipolysis was quantified by glycerol released in the medium which was determined by use of a colorimetric assay. Leptin and TNF-a mRNA expression were assayed by reverse transcription-polymerase chain reaction. The contents of leptin and TNF-a in the medium were detected by enzyme linked immunosorbent assay. Data and figures in the text were expressed as means±SE. Statistical analysis was undertaken using t-text and variance analysis for comparison of control versus treatment groups. The threshold for significance was P<0.05.Results:1. Glycerol accumulation in the culture medium increased significantly in a concentration and time dependent manner after BRL37344treatment, especially10-7mol/L for48h in which glycerol production increased by95～102%compared with control group(P<0.01).2. BRL37344with every concentration in the experiment (10-9,10-7mol/L) could inhibit leptin, TNF-a gene expression and secretion significantly, and it showed a dose-dependent relationship. BRL37344at doses of10-1mol/L supressed leptin, TNF-a mRNA level to the maximum extent for48h by97%(P<0.01)、130%(P<0.01), as well as leptin, TNF-a secretion for48h by48%(P<0.01)、95%(P<0.01), respectively.3. The leptin, TNF-a gene expression and secretion, which had no significant change for12h, began to reduce after intervention of10-7mol/L BRL37344for24h, and reached a minimum level after48hours intervention, in which leptin, TNF-a mRNA reduced by119%(P<0.01)、158%(P<0.01), as well as leptin, TNF-a secretion reduced by50%(P<0.01),92%(P<0.01), respectively.Conclusion:Selective β3-adrenergic receptor agonist BRL37344promotes lipolysis and suppresses leptin, TNF-a expression and secretion in mature3T3-L1adipocytes in a concentration and time manner, therefore, anti-obesity activity of BRL37344is involved in the enhancing effects on lipolysis and leptin, TNF-a sensitivity. Direct interactions between BRL37344with lipolysis signaling and endocrine function of adipocytes may thus be instrumental for this compound’s effects.