Fullerton, M. O.; Phillips, L. C.; Redgrave, R. E.; Haufroid, V.; Merces, G.; Kerridge, S. T.; Richardson, G. D.; Mercier, N.; Roland, D.; Dewulf, J. P.; Burn, J.; Bamforth, S. D.; Phillips, H. M.

Abstract Background and Aims The sodium-dependent multivitamin transporter, encoded by SLC5A6, mediates cellular uptake of the vitamins, biotin and pantothenic acid, both of which are essential cofactors for energy metabolism. Here, we report two families with SLC5A6 mutations presenting with early-onset dilated cardiomyopathy (DCM). To investigate the link between vitamin deficiency and DCM, we generated a novel cardiac-specific Slc5a6 knockout (Slc5a6cKO) mouse model and tested the therapeutic potential of vitamin supplementation. Methods Cardiac function in Slc5a6cKO mice was assessed by cardiac magnetic resonance imaging and ECG measurements. Histological, biochemical, and proteomic analyses were conducted to identify structural and metabolic changes. The impact of dietary biotin and pantothenic acid supplementation on disease progression was evaluated. Results Slc5a6cKO mice developed progressive cardiac dysfunction, manifesting as DCM with cardiac dilation, cardiomyocyte hypertrophy, fibrosis, impaired Coenzyme A synthesis, and metabolic imbalance, culminating in premature death by 26 weeks. Proteomic analysis revealed early mitochondrial metabolic disruption and extracellular matrix protein upregulation at 8 weeks, preceding overt cardiac dysfunction. Strikingly, vitamin supplementation from preconception onwards, prevented the cardiac phenotype, preserving cardiac structure, function, morphology and survival. This parallels the clinical outcome in one patient who received early vitamin treatment, compared to another who required a heart transplant following delayed vitamin treatment. Conclusions This study establishes a direct link between SLC5A6-mediated vitamin transport, mitochondrial function, and cardiac health. It highlights how vitamin deficiency contributes to DCM pathogenesis and supports early vitamin supplementation as a potential therapeutic strategy for metabolic cardiomyopathies.