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International audience; Mitochondrial trifunctional protein (MTP) deficiency caused by HADHA or HADHB gene mutations exhibits substantial molecular, biochemical, and clinical heterogeneity and ranks among the more severe fatty acid oxidation (FAO) disorders, without pharmacological treatment. Since bezafibrate has been shown to potentially correct other FAO disorders in patient cells, we analyzed its effects in 26 MTP-deficient patient fibroblasts representing 16 genotypes. Overall, the patient cell lines exhibited variable, complex, biochemical profiles and pharmacological responses. HADHA-deficient fibroblasts showed markedly reduced alpha subunit protein levels together with decreased beta-subunit abundance, exhibited a -86 to -96% defect in LCHAD activity, and produced large amounts of C14 and C16 hydroxyacylcarnitines. In control fibroblasts, exposure to bezafibrate (400 μM for 48 h) increased the abundance of HADHA and HADHB mRNAs, immune-detectable alpha and beta subunit proteins, activities of LCHAD and LCKAT, and stimulated FAO capacities, clearly indicating that MTP is pharmacologically up-regulated by bezafibrate in human fibroblasts. In MTP-deficient patient fibroblasts, which were found markedly FAO-deficient, bezafibrate improved FAO capacities in six of 26 (23%) cases, including three cell lines heterozygous for the common c1528G > C mutation. Altogether, our results strongly suggest that, due to variable effects of HADHA and HADHB mutations on MTP abundance and residual activity, improvement of MTP deficiency in response to bezafibrate was achieved in a subset of responsive genotypes.

International audience; Carnitine palmitoyltransferase 2 (CPT2) deficiency is a rare mitochondrial fatty acid oxidation (FAO) disorder characterized by myalgia, exercise intolerance, and rhabdomyolysis. We evaluate the efficacy of bezafibrate (BZ), a hypolipidemic drug, as a treatment for this form of CPT2 deficiency. A pilot trial was conducted with BZ in six patients for 6 months. There was a follow-up period of 3 years. The oxidation rates of the long-chain fatty acid derivative palmitoyl-CoA, measured in the mitochondria of the patients' muscles, were markedly lower than normal before treatment and increased significantly (+39 to +206%; P = 0.028) in all patients after BZ treatment. The evaluation of the therapeutic effects by the patients themselves (using the Short Form Health Survey (SF-36)), as well as by the physicians, indicated an improvement in the condition of the patients; there was an increase in physical activity and a decline in muscular pain. The results suggest that BZ has a therapeutic effect in the muscular form of CPT2 deficiency.

To the Editor: Carnitine palmitoyltransferase II (CPT2) deficiency is a rare autosomal recessive disorder of mitochondrial fatty acid oxidation. The most common form of this disorder is characteriz...

International audience; Context: The mitochondrial respiratory chain (RC) disorders are the largest group of inborn errors of metabolism and still remain without treatment in most cases.Objective: We tested whether bezafibrate, a drug acting as a peroxisome proliferator-activated receptor (PPAR) agonist, could stimulate RC capacities.Design: Fibroblasts or myoblasts from controls or patients deficient in complex I (CI), complex III (CIII), or complex IV (CIV) were cultured with or without bezafibrate.Main outcome measures: Enzyme activities, mRNA and protein expression, and respiration rates were measured.Results: In control cells, bezafibrate increased the CI, CIII, and CIV enzyme activities (+42 to +52%), as well as RC mRNAs (+40 to +120%) and RC protein levels (+50 to +150%). Nine of 14 patient cell lines tested exhibited a significant increase in the activity of the deficient RC complex after bezafibrate treatment (+46 to +133%), and full pharmacological correction could be achieved in seven cell lines. Similar effects were obtained using a PPARdelta agonist. These changes were related to a drug-induced increase in the mutated mRNAs and RC protein levels. Finally, the molecular mechanisms by which the PPAR pathway could induce the expression of genes encoding structural subunits or ancillary proteins of the RC apparatus, leading to stimulate the activity and protein levels of RC complex, likely involved the PPARgamma coactivator-1alpha.Conclusions: This study suggests a rationale for a possible correction of moderate RC disorders due to mutations in nuclear genes, using existing drugs, and brings new insights into the role of PPAR in the regulation of the mitochondrial RC in human cells.

International audience; Very-long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency is an inborn mitochondrial fatty-acid b-oxidation (FAO) defect associated with a broad mutational spectrum, with phenotypes ranging from fatal cardiopathy in infancy to adolescent-onset myopathy, and for which there is no established treatment. Recent data suggest that bezafibrate could improve the FAO capacities in b-oxidation-deficient cells, by enhancing the residual level of mutant enzyme activity via gene-expression stimulation. Since VLCAD-deficient patients frequently harbor missense mutations with unpredictable effects on enzyme activity, we investigated the response to bezafibrate as a function of genotype in 33 VLCAD-deficient fibroblasts representing 45 different mutations. Treatment with bezafibrate (400 mM for 48 h) resulted in a marked increase in FAO capacities, often leading to restoration of normal values, for 21 genotypes that mainly corresponded to patients with the myopathic phenotype. In contrast, bezafibrate induced no changes in FAO for 11 genotypes corresponding to severe neonatal or infantile phenotypes. This pattern of response was not due to differential inductions of VLCAD messenger RNA, as shown by quantitative real-time polymerase chain reaction, but reflected variable increases in measured VLCAD residual enzyme activity in response to bezafibrate. Genotype cross-analysis allowed the identification of alleles carrying missense mutations, which could account for these different pharmacological profiles and, on this basis, led to the characterization of 9 mild and 11 severe missense mutations. Altogether, the responses to bezafibrate reflected the severity of the metabolic blockage in various genotypes, which appeared to be correlated with the phenotype, thus providing a new approach for analysis of genetic heterogeneity. Finally, this study emphasizes the potential of bezafibrate, a widely prescribed hypolipidemic drug, for the correction of VLCAD deficiency and exemplifies the integration of molecular information in a therapeutic strategy.

International audience; Inherited defect in very-long-chain acyl-CoA dehydrogenase (VLCAD), a mitochondrial enzyme catalyzing the initial step of long-chain fatty acid beta-oxidation (FAO), is one of the most frequent FAO enzyme defects. VLCAD deficiency is associated with clinical manifestations varying in severity, tissue involvement and age of onset. The molecular basis of VLCAD deficiency has been elucidated but therapeutic approaches are quite limited. In this study, we tested the hypothesis that fibrates, acting as agonist of peroxisome proliferator-activated receptors (PPARs), might stimulate FAO in VLCAD-deficient cells. We demonstrate that addition of bezafibrate or fenofibric acid in the culture medium induced a dose-dependent (up to 3-fold) increase in palmitate oxidation capacities in cells from patients with the myopathic form of VLCAD deficiency, but not in cells from severely affected patients. Complete normalization of cell FAO capacities could be achieved after exposure to 500 microm bezafibrate for 48 h. Cell therapy of VLCAD deficiency was related to drug-induced increases in VLCAD mRNA (+44 to +150%; P

International audience; 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 PPARdelta (GWdelta 0742), and, to a lower extent, PPARalpha (GWalpha 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. GWdelta 0742 increased CPT2 mRNA levels, whereas no change in CPT2 transcripts was found in response to GWalpha 7647. Bezafibrate and GWdelta 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 PPARdelta, with no contribution of PPARalpha.

International audience; Carnitine palmitoyltransferase 2 (CPTII) deficiency is among the most common inborn errors of mitochondrial fatty acid ␤-oxidation (FAO). Clinical phenotype varies in relation to the metabolic block, as assessed by studies of FAO in patient fibroblasts. Thus, fibroblasts from patients with mild manifestations have appreciable residual CPTII enzyme activity, in contrast to those from severely affected patients. In the present study, we hypothesized that the hypolipidemic drug bezafibrate, acting as an activator of the peroxisome proliferator-activated receptor ␣ might stimulate FAO in CPTII-deficient cells. Data obtained show that bezafibrate treatment of mild-type CPTII-deficient cells resulted in a time-and dose-dependant increase in CPTII mRNA (from ϩ47% to ϩ66%) and residual enzyme activity (from ϩ54% to 135%), and led to normalization of 3 H-palmitate and 3 H-myristate cellular oxidation rates. Bezafibrate did not correct FAO in fibroblasts from patients with severe phenotype. This study establishes for the first time that peroxisome prolif-erator-activated receptor activators, acting via stimulation of gene expression, can stimulate CPTII residual activity to a level sufficient to allow normal FAO flux in deficient human fibro-blasts, and suggests that this approach should be tested in other inborn errors of mitochondrial ␤-oxidation. (Pediatr Res 54: 446-451, 2003)

Summary Increased mitochondrial biogenesis by activation of PPAR- or AMPK/PGC-1α-dependent homeostatic pathways has been proposed as a treatment for mitochondrial disease. We tested this hypothesis on three recombinant mouse models characterized by defective cytochrome c-oxidase (COX) activity: a knockout (KO) mouse for Surf1, a knockout/knockin mouse for Sco2, and a muscle-restricted KO mouse for Cox15. First, we demonstrated that double-recombinant animals overexpressing PGC-1α in skeletal muscle on a Surf1 KO background showed robust induction of mitochondrial biogenesis and increase of mitochondrial respiratory chain activities, including COX. No such effect was obtained by treating both Surf1−/− and Cox15−/− mice with the pan-PPAR agonist bezafibrate, which instead showed adverse effects in either model. Contrariwise, treatment with the AMPK agonist AICAR led to partial correction of COX deficiency in all three models, and, importantly, significant motor improvement up to normal in the Sco2KO/KI mouse. These results open new perspectives for therapy of mitochondrial disease., Highlights ► AICAR partially corrects COX deficiency in three mouse models ► Bezafibrate, a pan-PPAR activator, failed to correct COX deficiency in vivo ► Motor performance improves under AICAR in one mouse model ► Activation of the AMPK/Pgc1α axis can correct OXPHOS defects in vivo

International audience; Exposure to fibrates leads to normalization of fatty acid oxidation (FAO) in fibroblasts from patients with myopathic forms of CPT2 deficiency or VLCAD deficiency. Correction of FAO is related to a drug-induced increase of residual enzyme activity, and this could provide a new treatment strategy for these disorders.