Effect of Eplerenone on Endothelial Function in Metabolic Syndrome

Patients with the metabolic syndrome (MetSyn) are at increased risk for cardiovascular mortality and morbidity.

This increased cardiovascular risk is attributed to metabolic dysregulations like impaired glucose tolerance or diabetes mellitus and dyslipidemia, abdominal obesity and arterial hypertension, which promote oxidative stress and inflammation and together cause an atherogenic environment. MetSyn is now a well established cardiovascular risk factor and prevalence and incidence of MetSyn in the western world are constantly rising with 19.8 percent prevalence in Germany 4.

Aldosterone is predominantly synthesized in the adrenal glands. In addition, local aldosterone synthesis has been found in the heart and vasculature and aldosterone synthesis in adipocytes is discussed. Aldosterone exerts its effects via the mineralocorticoid receptor (MR). Besides the well described MR in the distal tubule of the kidney MR have also been detected in other organs such as the vasculature and a paracrine mode of action is discussed. Recently it has been described, that MR can be activated independent of aldosterone in hypertensive and obese rats 1. Aldosterone promoted end organ damage is mainly found in the cardiovascular system and the kidney. Inflammation and activation of different factors promotes fibroblast growth and matrix production resulting in myocardial fibrosis, vascular remodelling and renal fibrosis. Aldosterone appears to be involved in all steps of this process by synthesis of reactive oxygen species, induction of inflammation and growth factors like TGF-Beta and connective tissue growth factor. Taken together aldosterone - as the MetSyn- is an independent cardiovascular risk factor 5.

MetSyn and aldosterone are cardiovascular risk factors and it is of crucial importance to note that there is a connection between MetSyn and aldosterone. In clinical studies it was clearly demonstrated that Renin and Aldosterone in patients with MetSyn are elevated 6. Similar results have been obtained in animal studies where obesity induced arterial hypertension increased renin and aldosterone levels 7-9. In a cross sectional study with 397 participants the impact of aldosterone on the onset of arterial hypertension and MetSyn was analysed. In this study blood pressure was associated with aldosterone levels and aldosterone was correlated with waist circumference, insulin, HOMA index and an unfavourable lipid profile 10.

Other cross sectional studies show a direct correlation of aldosterone levels and impaired glucose metabolism in patients with and without the MetSyn 10;11. Taken together, aldosterone influences essential parameters of the MetSyn. Coincidentally parameters of the MetSyn are stimulus for an increased aldosterone synthesis, i.e. visceral adipocytes 12.

In large scale clinical trials - RALES, EPHESUS, 4E 2;3;13 - inhibition of MR has proven to be beneficial in patients with congestive heart failure and post myocardial infarction and this result has been confirmed for diabetic patients, who are known to have an increased cardiovascular risk. In addition, these diabetic patients had significant less hypoglycaemic episodes, indicating an association of MR inhibition and glucose metabolism. Despite the promising data of MR inhibition on cardiovascular mortality and morbidity there is only very limited data on the impact of MR inhibition on metabolic, endocrine, and inflammatory parameters in patients with MetSyn, who have not yet suffered from cardiovascular events.

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