Aldosterone, hypertension and heart failure: insights from clinical trials

Two clinical trials will be reviewed, RALES1 and ILLUMINATE.2 In RALES, low-dose spironolactone in addition to standard of care, produced a 30% improvement in survival in progressive heart failure, commonly assumed to reflect deleterious effects of aldosterone, with spironolactone competing with aldosterone for cardiac mineralocorticoid receptors. Recent evidence, however, points to cortisol rather than aldosterone as the hormone activating cardiac mineralocorticoid receptors, under conditions of tissue damage, and spironolactone as acting by mechanisms other than receptor blockade. ILLUMINATE compared the effects of torcetrapib, a cholesterol ester transport protein inhibitor, in combination with atorvastatin vs. atorvastatin alone, and was terminated after excess mortality was found in the torcetrapib arm. Subjects receiving torcetrapib showed effects consistent with increased aldosterone secretion, subsequently confirmed on patient samples and in vitro. In animal experiments, the pressor effect of torcetrapib was abolished by adrenalectomy but not by administration of trilostane, an inhibitor of aldosterone secretion. Although aldosterone (and probably cortisol) excess is involved in the off-target effects of torcetrapib, they may also involve secretion of endogenous oubain from the adrenal glomerulosa. This possibility may explain the enigma of aldosterone being homeostatic in chronic sodium deficiency, but deleterious in the presence of inappropriate sodium levels.