Abstract
Long-chain fatty acid oxidation disorders (LC-FAODs) cause energy deficits in heart and skeletal muscle that are only partially corrected by current medium-chain lipid therapies such as triheptanoin. We find that heart and muscle lack medium-chain acyl-CoA synthetases, limiting the capacity for β-oxidation of medium-chain fatty acids. Instead, heart and muscle mitochondria robustly respire on medium-chain acylcarnitines. The mitochondrial matrix enzyme carnitine acetyltransferase (CrAT) efficiently converts orally delivered octanoylcarnitine (C8-carnitine) to octanoyl-CoA for energy generation. C8-carnitine exhibits twice the oral bioavailability of triheptanoin and distributes to muscle and heart. A single oral dose significantly enhances grip strength and treadmill endurance while attenuating lactic acidosis in 2 mouse models of LC-FAODs. Thus, medium-chain acylcarnitines overcome a previously unrecognized metabolic bottleneck in LC-FAOD muscle and may represent an alternative to triglyceride-based therapies for bioenergetic disorders.
Authors
Keaton J. Solo, Yuxun Zhang, Sivakama S. Bharathi, Bob B. Zhang, Adam C. Richert, Alexandra V. Schmidt, Clinton Van’t Land, Olivia D’Annibale, Timothy C. Wood, Eric S. Goetzman
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