Cardiac peroxisome-proliferator-activated receptor expression in hypertension co-existing with diabetes

Hypertension and DM (diabetes mellitus) are common chronic disorders that often co-exist. DM and PPAR (peroxisome-proliferator-activated receptor)-γ agonists may directly impair heart function. However, the effects of DM and PPAR-γ agonists on hypertensive myocardium are not known. Hence the aim of the present study was to investigate whether DM and a PPAR-γ agonist [RGZ (rosiglitazone)] modulated the effects of hypertension on myocardial expression of PPAR isoforms. Cardiac PPAR isoforms, TNF (tumour necrosis factor)-α and IL (interleukin)-6 were evaluated by real-time PCR and Western blotting in SHRs (spontaneously hypertensive rats), diabetic SHRs, diabetic SHRs treated with RGZ (5 mg/kg of body weight) and control WKY (Wistar–Kyoto) rats. Cardiac NADPH oxidase activity was quantified using a SOD (superoxide dismutase)-sensitive cytochrome c reduction assay. When compared with hearts from control WKY rats, hearts from SHRs had decreased PPAR-α and PPAR-δ mRNA and protein levels (39 and 44% respectively for PPAR-α, and 37 and 42% respectively for PPAR-δ), but had increased PPAR-γ mRNA and protein levels (1.9- and 1.4-fold respectively). The hypertension-induced changes in mRNA and protein of cardiac PPAR isoforms were enhanced in diabetic SHRs, which were attenuated in diabetic SHRs treated with RGZ. Cardiac TNF-α and IL-6 protein levels and NADPH oxidase activities were increased in SHRs and were increased further in diabetic SHRs. RGZ treatment decreased TNF-α and IL-6 protein levels and NADPH oxidase activities in hearts from diabetic SHRs. In conclusion, these findings suggest that DM and the PPAR-γ agonist modulated the hypertensive effects on cardiac PPAR isoform expression.