Cumulative effect of cardiovascular risk factors on regulation of AMPK/SIRT1-PGC-1α-SIRT3 pathway in the human erectile tissue

Abstract

Cardiovascular disease risk factors (CVDRF), especially diabetes mellitus (DM), disrupts oxidative stress response. This condition underlies endothelial dysfunction, early manifested in men as erectile dysfunction. Current study aims to elucidate the impact of CVDRF in the oxidation responsive AMPK/SIRT1-PGC-1α-SIRT3 pathway and related miRNAs in human corpus cavernosum. Human penile tissue fragments from individuals submitted to programmed urological surgeries (n=27), aged 43-63 years, were clustered depending on the presence of CVDRF; control group included samples from patients without CVDRF, groups A and B included samples from patients with DM and additional CVDRF, totalizing ≤2 CVDRF (group A) and ≥3 CVDRF (group B). Dual immunolabelling of SIRT3, SOD2 or GPX1 with α-actin in tissue sections was carried out. The assessment of expression levels of NOX1, phospho-AMPKα, total AMPKα, SIRT1, PGC-1α, SIRT3, SOD2 and GPX1 was performed by Western blotting and of miR-200a, miR-34a, miR-421 and miR-206 by real-time PCR. Phospho-AMPKα and SIRT3 expression was found significantly increased in group B relatively to other groups, suggesting a marked influence of CVDRF, additional to DM, in the regulation of these enzymes. NOX1 was also increased in group B relatively to controls. Only an increasing tendency was observed in phospho-AMPKα/total AMPKα ratio, SIRT1 and PGC-1α expression in groups A and B when compared with controls. Concerning anti-oxidant enzymes, GPX1 expression was found incremented in group A but, SOD2 expression was decreased in groups A and B, comparatively with controls. Group B presented significantly diminished levels of miR-421 and miR-200a, but only a decreasing trend on miR-34 and miR-206 expression was observed. Taken together, our findings demonstrated that besides DM, additional CVDRF presented a cumulative effect in the cellular response to oxidative unbalance, contributing to AMPK/SIRT1-PGC-1α-SIRT3 pathway activation. SOD2, a major mitochondrial anti-oxidant defence, didn´t follow the same variation.