The Effect Of Glucose On Expression Of Adiponectin Gene In 3T3-L1 Adipocyte

BackgroundObesity is commonly associated with insulin resistance and hyperinsulinemia and is a major risk factor for the development of type 2 diabetes and cardiovascular disease. Adipose tissue is now known as an endocrine and paracrine organ to express and secrete a variety of metabolites,hormones,and cytokines have been implicated in metabolism balance and the development of insulin resistant and cardiovascular disease, such as leptin, tumor necrosis factor-a ,resistin. The molecular basis for the link between obesity, diabetes, and cardiovascular disease remains poorly understood. More recently, a novel adipose-specific protein, adiponectin, has been discovered. Adiponectin is abundant in the circulation in humans,thus accounting for approximately 0.01% of total plasma protein. Plasma adiponectin concentrations were found to be decreased in individuals with obesity,type 2 diabetes, and cardiovascular disease. The gene encoding adiponectin is located on human chromosome 3q27,which strongly linked to type 2 diabetes and the metabolic syndrome in European individuals. Several studies have been conformed that plasma adiponectin concentration was negative correlated with waist-to-thigh ratio, BMI, fast plasma insulin, insulin resistance, fast glucose concentration, plasma triglyceride, in contrast, positively with M-low rate(insulin sensitivity).In a multivariate analysis, fast plasma insulin concentration, M-rate, and waist-to-thigh ratio, were significant independent determinates of adiponectinemia. Together these data suggest the close relationship between the expression of adiponectin, plasma adiponectin concentration and insulin sensitivity, plasma insulin concentration. In the current study, in order to study the relationship between the high glucose and adiponectin expression, we examined the effect of glucose on the adiponectin mRNA expression in 3T3-L1 adipocytes in vitro.Materials and methodsThe marine preadipocyte cell line 3T3 - LI adipocyte (was provided by Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences) were grown in DMEM containing 5.5mM glucose as normal anchoring cells. Confluent preadipocytes were cultured for 2 days in culture medium further supplemented with 10 g/ml insulin, 0.5mM isobutylmethylxanthine and 0.25 u M dexamethasone and 2 days in culture medium with 10 g/ml insulin. After additional 4 to 6 days in culture medium , more than 90% of the cells had accumulated fat droplets.Glucose was dissolved with ddH2O and diluted to desiredconcentrations with culture medium. The major working solution concentration of glucose was from 5.5 mM to 45 mM. The time of glucose effecting on 3T3-L1 is 48 hours. Then adiponectin gene expression was measured by semi-quantitative RT-PCR, the adiponectin mRNA levels was controlled with those of - actin.ResultsTreatment of 3T3-L1 cells with different glucose concentration for 48 hours suppressed adiponectin gene expression. Furthmore, at the lower glucose concentration (lower than 20 mM) , the suppressed effect of glucose on adiponectin gene expression is not significant. When the glucose concentration is 20mM or much higher, the adiponectin gene expression have been significantly suppressed(p< 0.05), if the glucose concentration is 45 mM,the suppressive effect is very significant(p< 0.01).ConclusionsOur results suggested that higher glucose concentration could significantly inhibit the expression of adiponectin gene in 3T3-L1 adipocyte. The inhibition effect of higher glucose concentration maybe is due to the insulin resistance.