Pharmacological inhibition of carnitine palmitoyltransferase 1 restores mitochondrial oxidative phosphorylation in human trifunctional protein deficient fibroblasts

Biochim Biophys Acta Mol Basis Dis. 2017 Jun;1863(6):1292-1299. doi: 10.1016/j.bbadis.2017.04.005. Epub 2017 Apr 6.

Abstract

Background: Mitochondrial Trifunctional Protein deficiency (TFPD) is a severe genetic disease characterized by altered energy metabolism and accumulation of long-chain (LC) acylcarnitines in blood and tissues. This accumulation could impair the mitochondrial oxidative phosphorylation (OxPhos), contributing to the non-optimal outcome despite conventional diet therapy with medium-chain triglycerides (MCT).

Method: Acylcarnitine and OxPhos parameters were measured in TFPD-fibroblasts obtained from 8 children and cultured in medium mimicking fasting (LCFA) or conventional treatment (MCT), with or without Etomoxir (ETX) an inhibitor of carnitine palmitoyltransferase 1 (CPT1) activity, and were compared to results obtained with fibroblasts from 5 healthy-control children. The effects of various acylcarnitines were also tested on control fibroblasts.

Results: In the LCFA-condition, TFPD-fibroblasts demonstrated a large accumulation of LC-acylcarnitines associated with decreased O2-consumption (63±3% of control, P<0.001) and ATP production (67±5%, P<0.001) without modification of coupling efficiency. A dose-dependent decrease in O2-consumption was reproduced in control fibroblasts by addition of increasing dose of LC-acylcarnitines, while it was almost preserved with MC-acylcarnitines. The MCT-condition reduced LC-acylcarnitine accumulation and partially improved O2-consumption (80±3%, P<0.01) in TFPD-fibroblasts. The addition of ETX in both LCFA- and MCT-conditions normalized acylcarnitine profiles and restored O2-consumption and ATP production at the same levels than control.

Conclusion: Accumulation of LC-acylcarnitines plays a major role in the pathophysiology of TFPD, reducing OxPhos capacities. These deleterious effects could be partially prevented by MCT-therapy and totally corrected by ETX. Inhibition of CPT1 may be view as a new therapeutic target for patients with a severe form of TFPD.

Keywords: Acylcarnitines; Etomoxir; Long-chain 3-hydroxyacyl-CoA dehydrogenase; Mitochondria; Mitochondrial trifunctional protein deficiency; Oxidative phosphorylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cardiomyopathies / metabolism*
  • Cardiomyopathies / pathology
  • Carnitine O-Palmitoyltransferase / antagonists & inhibitors*
  • Carnitine O-Palmitoyltransferase / metabolism
  • Epoxy Compounds / pharmacology*
  • Female
  • Fibroblasts / metabolism*
  • Fibroblasts / pathology
  • Humans
  • Infant
  • Infant, Newborn
  • Lipid Metabolism, Inborn Errors / metabolism*
  • Lipid Metabolism, Inborn Errors / pathology
  • Male
  • Mitochondria / metabolism*
  • Mitochondria / pathology
  • Mitochondrial Myopathies / metabolism*
  • Mitochondrial Myopathies / pathology
  • Mitochondrial Trifunctional Protein / deficiency*
  • Mitochondrial Trifunctional Protein / drug effects
  • Mitochondrial Trifunctional Protein / metabolism
  • Nervous System Diseases / metabolism*
  • Nervous System Diseases / pathology
  • Oxidative Phosphorylation / drug effects*
  • Rhabdomyolysis / metabolism*
  • Rhabdomyolysis / pathology

Substances

  • Epoxy Compounds
  • Mitochondrial Trifunctional Protein
  • Carnitine O-Palmitoyltransferase
  • etomoxir

Supplementary concepts

  • Trifunctional Protein Deficiency With Myopathy And Neuropathy