Linoleate-Enrichment of Mitochondrial Cardiolipin Molecular Species Is Developmentally Regulated and a Determinant of Metabolic Phenotype

Simple Summary Cardiolipin is a very important structural phospholipid within the mitochochondrial membrane. Cardiolipin's composition is different in various tissues but the importance of this variation has not been studied. This study aims to elucidate how mitochondrial cardiolipin composition correlates with metabolic activity in the rat heart and liver and how altering composition is sufficient to shift fatty acid use in heart cells. Cardiolipin (CL), the major mitochondrial phospholipid, regulates the activity of many mitochondrial membrane proteins. CL composition is shifted in heart failure with decreases in linoleate and increases in oleate side chains, but whether cardiolipin composition directly regulates metabolism is unknown. This study defines cardiolipin composition in rat heart and liver at three distinct ages to determine the influence of CL composition on beta-oxidation (ss-OX). CL species, expression of ss-OX and glycolytic genes, and carnitine palmitoyltransferase (CPT) activity were characterized in heart and liver from neonatal, juvenile, and adult rats. Ventricular myocytes were cultured from neonatal, juvenile, and adult rats and cardiolipin composition and CPT activity were measured. Cardiolipin composition in neonatal rat ventricular cardiomyocytes (NRVMs) was experimentally altered and mitochondrial respiration was assessed. Linoleate-enrichment of CL was observed in rat heart, but not liver, with increasing age. ss-OX genes and CPT activity were generally higher in adult heart and glycolytic genes lower, as a function of age, in contrast to liver. Palmitate oxidation increased in NRVMs when CL was enriched with linoleate. Our results indicate (1) CL is developmentally regulated, (2) linoleate-enrichment is associated with increased ss-OX and a more oxidative mitochondrial phenotype, and (3) experimentally induced linoleate-enriched CL in ventricular myocytes promotes a shift from pyruvate metabolism to fatty acid ss-OX.

Automated summary

This study investigates the relationship between mitochondrial cardiolipin composition and metabolic activity in the rat heart and liver, as well as the impact of altering composition on fatty acid utilization in heart cells. The results show that the enrichment of linoleate in cardiac mitochondria is associated with increased beta-oxidation and mitochondrial respiration. This study provides important insights into the regulatory mechanisms of cardiac metabolism by mitochondrial composition.