The Emerging Potential of the Apelin-APJ System in Heart Failure

• The apelin-APJ system is a novel neurohormonal pathway with vasodilator, inotropic, and aquaretic properties as well an apparent antagonistic relationship with the renin-angiotensin system.
• It is down-regulated in HF, and there is a growing interest around the therapeutic potential of up-regulating this system in acute and chronic HF.
• Early data suggest that apelin infusion is safe in HF and that its vasodilator action is maintained.
• Further work is required to ascertain the effects of potentiation of the apelin-APJ system in acute and chronic HF.

The apelin-APJ system is a novel neurohormonal pathway, with studies to date suggesting that it may be of pathophysiologic relevance in heart failure and may indeed be a viable therapeutic target in this syndrome. This interest is driven primarily by the demonstration of its vasodilator, inotropic, and aquaretic actions as well as its apparent antagonistic relationship with the renin-angiotensin system. However, its promise is heightened further by the observation that, unlike other and more established cardioprotective pathways, it appears to be down-regulated in heart failure, suggesting that augmentation of this axis may have a powerful effect on the heart failure syndrome. We review the literature regarding the apelin-APJ system in heart failure and suggest areas requiring further research.