Combination therapy with PPARγ and PPARα agonists increases glucose-stimulated insulin secretion in db/db mice

Although peroxisome proliferator-activated receptor (PPAR)γ agonists ameliorate insulin resistance, they sometimes cause body weight gain, and the effect of PPAR agonists on insulin secretion is unclear. We evaluated the effects of combination therapy with a PPARγ agonist, pioglitazone, and a PPARα agonist, bezafibrate, and a dual agonist, KRP-297, for 4 wk in male C57BL/6J mice and db/db mice, and we investigated glucose-stimulated insulin secretion (GSIS) by in situ pancreatic perfusion. Body weight gain in db/db mice was less with KRP-297 treatment than with pioglitazone or pioglitazone + bezafibrate treatment. Plasma glucose, insulin, triglyceride, and nonesterified fatty acid levels were elevated in untreated db/db mice compared with untreated C57BL/6J mice, and these parameters were significantly ameliorated in the PPARγ agonist-treated groups. Also, PPARγ agonists ameliorated the diminished GSIS and insulin content, and they preserved insulin and GLUT2 staining in db/db mice. GSIS was further increased by PPARγ and -α agonists. We conclude that combination therapy with PPARγ and PPARα agonists may be more useful with respect to body weight and pancreatic GSIS in type 2 diabetes with obesity.