Effects of Rosiglitazone on Inflammation in Otsuka Long-Evans Tokushima Fatty Rats

BACKGROUND Inflammation plays a role in the response to metabolic stress in type 2 diabetes. However, the effects of rosiglitazone on inflammation of skeletal muscle have not been fully examined in type 2 diabetes. METHODS We investigated the effects of the insulin-sensitizing anti-diabetic agent, rosiglitazone, on the progression of skeletal muscle inflammation in Otsuka Long-Evans Tokushima Fatty (OLETF) type 2 diabetic rats. We examined the expression of serologic markers (serum glucose, insulin and free fatty acid) and inflammatory cytokines (tumor-necrosis factor-alpha, interleukin [IL]-1beta and IL-6) in OLETF rats from early to advanced diabetic stage (from 28 to 40 weeks of age). RESULTS Serum glucose and insulin concentrations were significantly decreased in rosiglitazone-treated OLETF rats compared to untreated OLETF rats. Rosiglitazone treatment significantly decreased the concentrations of serum inflammatory cytokines from 28 to 40 weeks of age. The mRNA expression of various cytokines in skeletal muscle was reduced in rosiglitazone-treated OLETF rats compared with untreated OLETF rats. Furthermore, rosiglitazone treatment resulted in the downregulation of ERK1/2 phosphorylation and NF-kappaB expression in the skeletal muscle of OLETF rats. CONCLUSION These results suggest that rosiglitazone may improve insulin sensitivity with its anti-inflammatory effects on skeletal muscle.