Cardiac anaplerosis in health and disease: food for thought

Abstract

There has been a resurgence of interest for the field of cardiac metabolism catalysed by the increased need for new therapeutic targets for patients with heart failure. The primary focus of research in this area to date has been on the impact of substrate selection for oxidative energy metabolism; however, anaplerotic metabolism also has significant interest for its potential cardioprotective role. Anaplerosis refers to metabolic pathways that replenish the citric acid cycle intermediates, which are essential to energy metabolism; however, our understanding of the role and regulation of this process in the heart, particularly under pathophysiological conditions, is very limited. Therefore, the goal of this article is to provide a foundation for future directions of research on cardiac anaplerosis and heart disease. We include an overview of anaplerotic metabolism, a critical evaluation of current methods available for its quantitation in the intact heart, and a discussion of its role and regulation both in health and disease as it is currently understood based mostly on animal studies. We also consider genetic diseases affecting anaplerotic pathways in humans and acute intervention studies with anaplerotic substrates in the clinics. Finally, as future perspectives, we will share our thoughts about potential benefits and practical considerations on modalities of interventions targeting anaplerosis in heart disease, including heart failure.

Figure 1

Overview of pathways and reactions that are related to anaplerosis and CAC intermediate efflux. Dotted lines indicate pathways/reactions participating to CAC intermediate entry (red) or removal (blue) or both (green), whereas an asterisk indicates CAC intermediates and amino acids that participate specifically to the malate–aspartate shuttle. Numbers refer to the enzymes catalysing the following pathways/reactions that will be referred to in the text: 1, pyruvate decarboxylation (PDC); 2 and 3, pyruvate carboxylation (PC) by pyruvate carboxylase and malic enzyme, respectively; 4 and 5, transaminase, 6: succinyl-CoA thiokinase; 7, 3-oxoacid-CoA transferase; 8, mitochondrial tricarboxylate transporter; 9, aconitase; 10, α-ketoglutarate dehydrogenase. AcAc, acetoacetate; BCAA, branched-chain amino acids (valine, isoleucine); OAA, oxaloacetate.