Peroxisome proliferator activated receptor δ (PPARδ) agonist but not PPARα corrects carnitine palmitoyl transferase 2 deficiency in human muscle cells

Type 2 carnitine palmitoyl transferase (CPT2) is involved in the transfer of long-chain fatty acid into the mitochondria. CPT2- deficient patients carry gene mutations associated with different clinical presentations, correlating with various levels of fatty acid oxidation ( FAO) and residual CPT2 enzyme activity. We tested the hypothesis that pharmacological stimulation of peroxisome proliferator-activated receptors ( PPAR) can stimulate FAO in CPT2- deficient muscle cells. Accordingly, we show that a 48-h treatment of CPT2- deficient myoblasts by bezafibrate restored FAO in patient cells. Specific agonists of PPAR delta (GW delta 0742), and, to a lower extent, PPAR alpha (GW alpha 7647) also stimulated FAO in control myoblasts. However, when tested in CPT2- deficient myoblasts, only the delta-agonist was able to restore FAO, whereas the alpha-agonist had no effect. GW delta 0742 increased CPT2 mRNA levels, whereas no change in CPT2 transcripts was found in response to GW alpha 7647. Bezafibrate and GW delta 0742 increased residual CPT2 activity and normalized long-chain acylcarnitine production by deficient cells. Finally, CPT1-B mRNA was also stimulated after PPAR agonist treatment, and this likely takes part in drug-induced increase of FAO in control muscle cells. In conclusion, this study clearly suggests that PPARs could be therapeutic targets for correction of inborn beta-oxidation defects in human muscle. Furthermore, these data also illustrate a selective control of beta-oxidation enzyme gene expression by PPAR delta, with no contribution of PPAR alpha.