Effects of pioglitazone and/or simvastatin on circulating TNFα and adiponectin levels in insulin resistance

Abstract

The current study investigated the effects of 14-day pioglitazone (PIO) and/or simvastatin (SIM) treatments on serum adiponectin (Adp) and TNFα levels (markers of adipocyte dysfunction), as well as on metabolic perturbations that arise from prolonged (8 week) consumption of a high fructose (HFD; 60%) diet in a rat model of pre-diabetic insulin resistance. The HFD induced a deranged lipid profile that was associated with adipose tissue hypertrophy, increased ratios of visceral and epididymal fats to body weight, and fatty liver. These perturbations were associated with hypo-adiponectinemia (50.8%) and increased serum TNFα (6.5-fold) levels. Treatment with PIO ameliorated the altered blood and hepatic glucose metabolism via an Adp-dependent mechanism; PIO also mitigated the changes in blood TNFα and led to a hyperelevation of Adp levels. SIM amended hepatic and overall lipid metabolism, regulated TNFα, but failed to alter the glucose intolerance or significantly impact on the HFD-altered Adp levels. Coadministration of SIM + PIO was superior in improving overall metabolic parameters compared to each monotherapy. Cotreatment was optimal in reestablishing insulin resistance, most efficacious in improving serum lipid profiles, normalizing percentage ratios of epididymal and visceral fats to body weight, and augmenting Adp/reducing TNFα levels relative to that in the HFD group or with HFD + each drug alone. The results here show that use of either monotherapy or a combined SIM + PIO approach might, from a clinical perspective, provide an ability to delay progression to Type 2 diabetes and its associated inflammatory/cardiovascular effects.