Effects of pioglitazone on nitric oxide bioavailability measured using a catheter-type nitric oxide sensor in angiotensin II-infusion rabbit

The impact of pioglitazone on ADMA and oxidative stress markers in patients with type 2 diabetes

AIMS

To determine whether pioglitazone 30 mg daily reduces levels of ADMA in adult patients with diabetes, and whether there is improvement in markers of oxidative stress.

METHODS

Prospective randomized cross-over placebo-controlled study of 36 adults age 40-75 years with type 2 diabetes recruited from a single academic health center. Intervention was for 12 weeks, followed by a 4-week wash-out period, followed by a second 12-week cross-over treatment period. The main outcome was comparison of the change in ADMA levels in the two treatment periods. Secondary outcomes included change in NOx and F2-isoprostanes.

RESULTS

Thirty-six patients were enrolled in the study, 31 completed the protocol; the study enrollment met the sample size required to detect a change of 18% in levels. There were no differences in ADMA, NOx and F2-isoprostanes levels in the two treatment periods. Non-study medication changes or changes in dose were infrequent, and a statin was added during the study period in only one patient.

CONCLUSIONS

Despite previous animal data that showed an effect of pioglitazone on ADMA, the current study in human patients did not demonstrate any differences in ADMA, NOx, or F2-isoprostane levels. The results do not favor that pioglitazone has a significant impact on ADMA levels in human patients with diabetes.

Angiotensin-(1-7) prevents diabetes-induced attenuation in PPAR-gamma and catalase activities

The mechanisms by which angiotensin-(1-7) [Ang-(1-7)] exerts its beneficial effects on end-organ damage associated with diabetes and hypertension are not well understood. The purpose of this study was A) to compare the effects of apocynin with Ang-(1-7) on renal vascular dysfunction and NADPH oxidase activity in a combined model of diabetes and hypertension and B) to further determine whether chronic treatment with Ang-(1-7) can modulate renal catalase, and peroxisome proliferator activated receptor- gamma (PPAR-gamma) levels in streptozotocin-induced diabetes in both normotensive Wistar Kyoto rats (WKY) and in spontaneously hypertensive rats (SHR). Apocynin or Ang-(1-7) treatment for one month starting at the onset of diabetes similarly attenuated elevation of renal NADPH oxidase activity in the diabetic SHR kidney and reduced the degree of proteinuria and hyperglycemia, but had little or modest effect on reducing mean arterial pressure. Both drugs also attenuated the diabetes-induced increase in renal vascular responsiveness to endothelin-1. Induction of diabetes in WKY and SHR animals resulted in significantly reduced renal catalase activity and in PPAR-gamma mRNA and protein levels. Treatment with Ang-(1-7) significantly prevented diabetes-induced reduction in catalase activity and the reduction in PPAR-gamma mRNA and protein levels in both animal models. Taken together, these data suggest that activation of Ang-(1-7)-mediated signaling could be an effective way to prevent the elevation of NADPH oxidase activity and inhibition of PPAR-gamma and catalase activities in diabetes and/or hypertension.