Effects of transgenic endothelin-2 overexpression on diabetic cardiomyopathy in rats

P>Background Transgenic overexpression of human endothelin-2 in rats was used to characterize the contribution of endothelin to diabetic cardiomyopathy. Materials and methods Diabetes mellitus was induced by streptozotocin in transgenic rats and transgene-negative controls. Nondiabetic animals were included as well to form a 4-group study design. Heart morphological and molecular alterations were analysed following 6 months of hyperglycaemia. Results Plasma endothelin concentrations were significantly higher in both transgenic groups than in wild-type groups (nondiabetic: 3 center dot 5 +/- 0 center dot 4 vs. 2 center dot 1 +/- 0 center dot 2, P < 0 center dot 05; diabetic: 4 center dot 5 +/- 0 center dot 4 vs. 2 center dot 5 +/- 0 center dot 4 fmol mL-1, P < 0 center dot 01). Diabetes induced cardiac hypertrophy in both wild-type and transgenic rats and showed the highest myocardial interstitial tissue volume density in diabetic transgenic rats (1 center dot 5 +/- 0 center dot 07%) as compared with nondiabetic transgenic (1 center dot 1 +/- 0 center dot 03%), nondiabetic wild-type (0 center dot 8 +/- 0 center dot 01%) and diabetic wild-type rats (1 center dot 1 +/- 0 center dot 03%; P < 0 center dot 01 for all comparisons). A similar pattern with the most severe changes in the enothelin-2 transgenic, diabetic animals was observed for hypertrophy of the large coronary arteries and the small intramyocardial arterioles respectively. Cardiac mRNA expression of endothelin-1, endothelin receptors type A and B were altered in some degree by diabetes or transgenic overexpression of endothelin-2, but not in a uniform manner. Blood pressure did not differ between any of the four groups. Conclusions Overexpression of the human endothelin-2 gene in rats aggravates diabetic cardiomyopathy by more severe coronary and intramyocardial vessel hypertrophy and myocardial interstitial fibrosis. This transgenic intervention provides further and independent support for a detrimental, blood pressure-independent role of endothelins in diabetic cardiac changes.