Advantages and limitations of renin inhibition with aliskiren

In the current context of renin-angiotensin-aldosterone system (RAAS) blockade, angiotensin (Ang) converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), or their combination, have proved to be effective in providing cardiovascular and renal protection. However, renin inhibition has long been recognized as the preferred site for blockade of the RAAS because renin represents the first, highly-regulated and rate-limiting step of the system. Up to now, the first orally active renin inhibitors initially tested in humans did not meet the necessary all the criteria (specificity, potency, and pharmacokinetic profile) to become clinically useful drugs. The synthesis of aliskiren, a potent alkane carboxamide renin inhibitor, now provides an orally active compound which, according to its pharmacological profile in normotensive subjects and in patients with hypertension, diabetic nephropathy or heart failure suggests that this drug may be of value for the treatment of patients with cardiovascular and renal disorders. However, long-term studies are needed to demonstrate the efficacy of aliskiren in these clinical settings. The results of the Aliskiren Trial in Type 2 Diabetes Using Cardiorenal Disease Endpoints (ALTITUDE) trial which has already included 8600 patients with type 2 diabetes, proteinuria and a high cardiovascular risk and compared the effects of aliskiren vs. a placebo on a composite endpoint including renal and cardiovascular morbidity and mortality should be provided in 2012.     

Protein Z: a new regulator of coagulation in arterial vessels?

Protein Z (PZ) is a vitamin K dependent factor identified in human plasma in 1984 whose physiological function was poorly understood. It was recently shown that protein Z is implicated in the down-regulation of coagulation by forming a complex with a plasma proteinase inhibitor called protein Z-dependent protease inhibitor (ZPI) which inhibits activated factor Xa on phospholipid surfaces. In the absence of an additional challenge, the disruption of PZ gene in mice is asymptomatic, but the association with the factor VLeiden mutation leads to a near complete mortality during the neonatal period with microvascular thrombosis. Unexpectedly, in humans, a relationship between protein Z deficiency and ischemic strokes, was firstly evidenced, but not confirmed by all the epidemiological study. Additional studies suggest that protein Z deficiency could be also a risk factor for acute coronary syndromes, early fetal losses, and increased the arterial risk in antiphospholipid syndrome. This review analyzes the different studies so far published and discusses the different results obtained in order to understand whether or not protein Z deficiency could be considered as an arterial ischemic risk factor.