The dual PPARα/γ agonist, ragaglitazar, improves insulin sensitivity and metabolic profile equally with pioglitazone in diabetic and dietary obese ZDF rats

Abstract

1 In 6- and 10-week-old obesity-prone (fa/fa) Zucker diabetic fatty (ZDF) rats, effects of prevention and intervention therapies, respectively, were compared between PPARα/γ agonist, ragaglitazar (RAGA) and separate PPARγ and α agonists, pioglitazone (PIO) and bezafibrate (BF). 2 In a separate study, lean (+/+) ZDF rats fed highly palatable chow to induce dietary obesity and insulin resistance were treated similarly. To test insulin-secretory capacity, all animals underwent a hyperglycaemic clamp. 3 Insulin sensitivity was improved equally by RAGA and PIO in fa/fa rats subjected to both prevention and intervention treatments (e.g., prevention HOMA-IR: -71 and -72%, respectively), as was hyperglycaemia (both -68%). BF had no effect on either parameter in any study. Plasma lipids were markedly reduced (by 48-77%) by RAGA in all studies, equivalent to PIO, but to a greater extent than BF. 4 RAGA improved β-cell function (HOMA-β) more than three-fold with prevention and intervention therapies, whereas PIO showed improvement only in intervention therapy. Consistent with improved insulin sensitivity, glucose infusion rate during the clamp was 60% higher in RAGA-treated animals subjected to prevention therapy, but there was little additional insulin-secretory response, suggesting that insulin secretion was already maximal. 5 Thus, RAGA and PIO equally improve metabolic profile in ZDF rats, particularly when administered early in the course of diabetes. They also improve β-cell function, although this is better demonstrated through indices incorporating fasting insulin and glucose concentrations than through the hyperglycaemic clamp technique in this model. © 2005 Nature Publishing Group All rights reserved.