Objective: This study was designed to (1) investigate the expression profiles of resistin in db/db mice and its dynamic association with metabolic parameters; and (2) evaluate the effects of Rosiglitazone on production of resistin.
Methods: Db/db mice and their lean litter mates were used for this study. Epididymal fat tissue was excised from mice of different age (from 5 to 12 weeks) for ex vivo incubation. Resistin,along with adiponectin,in serum and conditioned culture medium of epididymal fat pads were measured with immunoassays. The gene expression of resistin was determined by real-time PCR. Rosiglitazone or the vehicle (PBS) was administered into db/db mice by daily intra-gastric gavage. Differentiated 3T3-L1 adipocytes were used for in vitro evaluation.
Results: The secretion of resistin from the fat pads in db/db mice was significantly lower than that in lean mice (P<0.01). The mRNA expression of the resistin gene in fat tissue of db/db mice at the age of 5 weeks was decreased by 60.5% compared to lean controls (p<0.05). Serum levels of resistin were comparable between the obese and lean groups, perhaps due to the increased total fat mass in db/db mice. Correlation analysis showed that serum resistin levels were positively correlated to resistin secretion from fat pads(r = 0.844,P = 0.000), while negatively associated with the body weight (r = -0.515, P = 0.000) and fasting glucose level (r = -0.357, P = 0.002). Notably, treatment with rosiglitazone increased the serum resistin levels by 66.4%(P<0.05)in db/db mice. In 3T3-L1 adipocytes, Rosiglitazone (10 uM) markedly enhanced the secretion of resistin by 120% (P<0.01) and its gene expression by 78.1% (P<0.05).
Conclusion: Both resistin gene expression and its secretion from the epididymal adipose tissue were decreased in db/db obese mice, while the insulin-sensitizing drug rosiglitazone increased resistin production. Our results do not support the role of resistin as an etiological link between obesity and diabetes.