at SciVerse ScienceDirect

Biochimie xxx (2013) 1e8

Contents lists available

Biochimie

journal homepage: www.elsevier .com/locate/biochi

Review

Regulation of mitochondrial fatty acid b-oxidation in human:What can we learn from inborn fatty acid b-oxidation deficiencies?

Jean Bastin*

INSERM U747, Université Paris Descartes, UFR Biomédicale des Saints-Pères, 45, rue des Saints-Pères, 75270 Paris Cedex 06, France

a r t i c l e i n f o

Article history:Received 14 March 2013Accepted 30 May 2013Available online xxx

Keywords:Mitochondrial fatty acid b-oxidationInborn enzyme defectsNewborn screeningPharmacological therapyPPARFibrates

* Tel.: þ33 1 42862219; fax: þ33 1 42863868.E-mail address: jean.bastin@inserm.fr.

0300-9084/$ e see front matter � 2013 Published byhttp://dx.doi.org/10.1016/j.biochi.2013.05.012

Please cite this article in press as: J. Bastin, Racid b-oxidation deficiencies?, Biochimie (2

a b s t r a c t

The mitochondrial fatty acid b-oxidation (FAO) pathway plays a crucial role in ATP production in manytissues with high-energy demand. This is highlighted by the diverse and possibly severe clinical mani-festations of inborn fatty acid b-oxidation deficiencies. More than fifteen genetic FAO enzyme defectshave been described to date, forming a large group of rare diseases. Inborn FAO disorders are charac-terized by a high genetic heterogeneity, with a variety of gene mutations resulting in complete or partialloss-of-function of the corresponding enzyme. The panel of observed phenotypes varies from multi-organ failure in the neonate with fatal outcome, up to milder late onset manifestations associatedwith significant disabilities. Diagnosis of FAO disorders has markedly improved over the last decades, butfew treatments are available. The clinical, biochemical, and molecular analysis of these disorders pro-vided new, and sometimes unexpected, data on the organization and regulation of mitochondrial FAO inhumans, in various tissues, and at various stages of development. This will be illustrated by examples ofFAO defects affecting enzymes of long-chain fatty acid import into the mitochondria, or Lynen helixenzymes. The involvement of the transcriptional network regulating FAO gene expression, in particularthe PGC-1a/PPAR axis, as a target for pharmacological therapy of these genetic disorders, will also bediscussed.

� 2013 Published by Elsevier Masson SAS.

1. Introduction

The mitochondrial fatty acid b-oxidation (FAO) represents amajor source of energy in numerous tissues including liver, heart,and skeletal muscle. This metabolic pathway plays a pivotal role formaintaining energy homeostasis in situations such as fasting orprolonged exercise that require glucose sparing and major energysupply. In these situations, adipose tissue lipolysis provides freefatty acids to target tissues. Hepatic FAO also fuels the production ofketone bodies, which represent a major energy source for extra-hepatic tissues, and in particular for brain and heart, whenglucose becomes limiting [1]. The use of fatty acids as energysubstrate requires about 25 different enzymes and transport pro-teins [2], which carry out the cellular uptake and activation of fattyacids, their import into the mitochondria, and the b-oxidation steps(or Lynen helix) [3]. The basic reactions of Lynen helix weredescribed more than fifty years ago, but a large number of newcomponents have been identified since then, and our under-standing of the overall FAO process is still incomplete.

Elsevier Masson SAS.

egulation of mitochondrial fa013), http://dx.doi.org/10.101

The first FAO enzyme defect, described in 1973, opened the wayto the discovery of more than 15 other genetic defects in thispathway, which are all autosomal recessive disorders [1,4e6]. FAOdisorders encompass a wide spectrum of clinical manifestations,which primarily affect tissues that strongly depend on fatty acidsfor energy production i.e. liver, heart, and skeletal muscle. However,the observed phenotypes are highly heterogeneous, ranging frommulti-organ failure in the newborn with a high mortality rate [7],up to adult-onset mild phenotypes [1]. In addition to a largenumber of disease-causing genes, molecular analysis also revealeda great variety of mutations. Null mutations, which fully disrupt theexpression of mutated gene, are often encountered in the mostsevere disease presentations [8]. Nevertheless, a majority of pa-tients exhibit missense mutations, with unpredictable effects onenzyme structure and activity, and often poorly understood geno-type/phenotype correlations [4]. It is nowwidely admitted that thediversity of phenotypes associated to FAO deficiencies cannot beexplained on the basis of genetics only. Importantly, clinical man-ifestations of FAO disorders vary according to different physiolog-ical or nutritional factors, and are often aggravated by metabolicstress conditions such as fasting, exposure to cold, or muscularexercise [4,5,9,10]. All these conditions are known to trigger majorchanges in the mitochondrial utilization of fatty acids, mediated by

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012

J. Bastin / Biochimie xxx (2013) 1e82

various metabolic signaling pathways targeting the FAO pathway. Ittherefore appears that the mechanisms regulating mitochondrialFAO activity in various tissues play a role in modulating the clinicalexpression of FAO deficiencies. Conversely, the expression patternof inborn FAO disorders can provide interesting insights into therole of FAO in various tissues under different physiological condi-tions, or at various stages of development, and its regulation. Wewill illustrate these issues on a few selected examples of well-characterized FAO disorders affecting the mitochondrial b-oxida-tion of medium-chain or long-chain fatty acids.

2. MCAD deficiency: asymptomatic throughout life or rapidlyfatal, why?

MCAD (MIM 607008, Medium-Chain-Acyl-CoA Dehydrogenase)is a homotetrameric flavoenzyme located in the mitochondrialmatrix, which catalyzes the initial step of medium-chain fatty acid(MCFA, 6e12 carbons) b-oxidation. In adult rodents or human,medium-chain fatty acids are minor components of the normaldiet, and mainly originate from chain-shortening of dietary long-chain fatty acids (LCFA, 14e20 carbons) by b-oxidation within themitochondria. In suckling mammals, in contrast, the maternal milkrepresents a high-fat diet particularly rich in medium-chain fattyacids, which are actively synthesized by the mammary gland[11,12]. The importance of these substrates in the energy meta-bolism of the neonate was long unsuspected, until the first de-scriptions of fatal presentations of MCAD deficiency, in the 80’s[13]. MCAD deficiency is now recognized as the most commonFAO disorder in Caucasian populations. Its prevalence is estimatedbetween 1/10,000 and 1/27,000 in European countries i.e. similar tothat of phenylketonuria, a condition for which expanded newbornscreening was implemented in the 60’s [7,14e17].

MCAD deficiency generally presents as episodes of hypoketotichypoglycemia during catabolic stress conditions, eventuallyevolving toward life-threatening metabolic decompensation with

Fig. 1. Physiopathology of severe neon

Please cite this article in press as: J. Bastin, Regulation of mitochondrial faacid b-oxidation deficiencies?, Biochimie (2013), http://dx.doi.org/10.101

encephalopathy. The disease is usually asymptomatic outside acuteepisodes [14,18]. MCAD deficiency is generally diagnosed in new-borns or infants aged between a few months and two years, andvery rarely in adults [18]. Diagnosis is based on symptoms and onthe detection of specific biomarkers such as elevated plasma levelsof octanoylcarnitine, or urinary medium-chain dicarboxylic acids[14]. MCAD deficiency is associated to a significant risk of deathsince as many as 20e30% of patients die during their first metaboliccrisis. Furthermore, 20e40% of survivors will exhibit permanentneurological damages. Nevertheless, adverse outcomes can betreated by correction of hypoglycemia, followed by appropriateclinical management to avoid fasting periods [18,19].

Overall, the physiopathology of the disease is primarilyexplained by hepatic dysfunction (Fig. 1). Liver involvement is inpart related to the specific digestion pattern of medium-chaincompared to long-chain fatty acids. Indeed, MCFA absorbed fromthe small intestine are directly transferred as free fatty acidsthrough the portal vein to the liver, in contrast to LCFA that areincorporated as triglycerides into chylomicrons, to enter thelymphatic system [20]. The liver, in contrast to other tissues, istherefore particularly exposed to dietary changes in MCFA supply.Accordingly, in the presence of MCAD deficiency in the neonate, thehigh MCFA supply through maternal milk probably leads to a liver-specific accumulation of toxic CoA or carnitine MCFA derivatives inthe immature liver. Because newborns and young children haveproportionately higher cerebral glucose requirements than adults,the physiological response to fasting, in particular in the liver, playsa pivotal role in themaintenance of energy balance during postnataldevelopment [21]. Impairment of b-oxidation in the liver cannegatively affect ATP supply for neoglucogenesis, and acetylCoAproduction for ketone bodies synthesis and for urea cycle activity(Fig. 1). Ultimately, deficient MCFA b-oxidation during fasting pe-riods can therefore result in very low systemic levels of glucose andketone bodies, combined with toxic effects of hyperammonemia, asituation that can have severe consequences on brain energy

atal fatty acid oxidation disorders.

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012

J. Bastin / Biochimie xxx (2013) 1e8 3

metabolism and functions, and accounts for the development ofencephalopathy [1,9]. This scheme also explains why adverse out-comes associated toMCADdeficiency can be relativelyeasily treatedby intravenous glucose infusion, or can be prevented by avoidingfasting and maintaining a high dietary glucose supply.

Analysis of MCAD gene mutations, more than 70 to date, in-dicates a prevalence of missense over “null” (nonsense, prematurestop, insertions or deletions) mutations. 80e90% of symptomaticpatients are homozygous for the c.985A>G mutation, with a highproportion of the remaining patients harboring this mutation at theheterozygous state [14]. The relative ease of detection of this dis-ease by biochemical and molecular analysis, together with the ef-ficacy of treatment, led to introduce population-based newbornscreening for MCAD deficiency in many developed countries, basedon high-throughput analysis of acylcarnitines pattern in “Guthrie”dried blood spots, by electrospray tandem mass spectrometry (ESI-MSeMS) [22,23]. Newborns found positive for octanoyl-L-carnitineare then analyzed for mutations of MCAD gene. Newborn screeningof MCAD deficiency was initiated around the 2000’s, and repre-sented one of the largest programs for screening and prevention ofa new genetic metabolic disorder. The results obtained from largecohorts of newborns (z500,000 in Denmark [14], Australia [24], orCanada [25],>1 million in Germany [26], England [17] or USA [16]),revealed an incidence of MCAD deficiency much higher than ex-pected on the basis of clinically detected patients, and a broaderand more complex spectrum of mutations [14,27e29]. Overall, ahigh proportion of MCAD-deficient detected newborns wereasymptomatic at the time of diagnosis. They were then generallysubjected to preventive therapy based on avoidance of fasting andhigh carbohydrate intake, implemented through instructions pro-vided to the parents by dieticians, and most of them remainedasymptomatic so far [14,16,18,19]. It became progressively clear thatnewborn screening for MCAD deficiency markedly reduces the riskof death or severe metabolic decompensation in screenedcompared to unscreened population, illustrating a remarkableexample of successful preventive medicine against a potentiallysevere neonatal disorder [7,14,15,30].

Despite the large amount of data gathered on the presentationandmolecular basis of MCAD deficiency, a number of questions stillremain unanswered. For example, the reasons why MCAD defi-ciency does not generally affect extra-hepatic tissues with highfatty acid utilization, like heart or skeletal muscle, are unclear. Moreimportantly for patient management, the variability of clinicalmanifestations of MCAD deficiency is still poorly understood. Thisis true, in particular for the common c.985A>G mutation, sinceindividuals harboring this mutation at the homozygous state canpresent life-threatening symptoms, but can also eventually remainasymptomatic throughout life, and the risk of disease associated tothis genotype is at present not well-characterized [14]. Overall,among the many other mutations described in patients who pre-sented symptoms, there is no clear correlation between MCADgenotype and disease severity [14,24,27]. The high variability andthe possible absence of symptoms in genetically deficient patientsstill remain enigmatic, but several hypotheses have been proposedto account for these observations. First, this could suggest thatMCFA b-oxidation only plays a minor role in energy balance, andthat incomplete b-oxidation of LCFA is sufficient tomaintain energybalance in most situations, and in most tissues [9]. It can also bethought that compensatory mechanisms allow an increased utili-zation of other energy substrates, in particular glucose [31]. Somedata support this notion of metabolic flexibility in heart, howeverchanges in cardiac substrate utilization are also suspected tocontribute to pathogenesis in this tissue [32e34]. Finally, it is alsoconceivable that some levels of residual MCFA b-oxidation capac-ities do exist in some MCAD-deficient patients, and several

Please cite this article in press as: J. Bastin, Regulation of mitochondrial faacid b-oxidation deficiencies?, Biochimie (2013), http://dx.doi.org/10.101

observations come in support of this hypothesis. First, MCAD genemissense mutations do not necessarily result in complete enzymeloss-of-function, and functional analysis of MCAD mutant enzymesoften revealed misfolded proteins with detectable levels of residualenzyme activity [27,28]. Similarly, in vitro studies in lymphocytesdemonstrated low but detectable residual octanoyl-CoA oxidationcapacities in a significant proportion of MCAD-deficient genotypes[29]. Finally, some MCAD deficient patients were found unaffectedby periods of overnight fasting, with normal ketone bodies pro-duction and MCFA oxidation [21]. Some authors explain these ob-servations by a possible functional overlap between the MCAD andother AcylCoA dehydrogenases, allowing the oxidation of MCFA- byLCFA-specific isoforms [15]. This could eventually be true in mice[35], but appears unlikely in human, due to the particular isoforminvolved in the initiation of human LCFA b-oxidation (MIM 609575,Very-long-chain acyl-CoA dehydrogenase, VLCAD, see next para-graph), which exhibits very little activity toward medium-chainfatty acids [3].

Overall, considering the very large potential for tissue-specific ordevelopmental regulation of MCAD expression [36], we think thatcompensatorymechanisms in deficient cellsmight allow to cope forenzyme deficiency, and to support basal metabolic needs. Inparticular, activation of endogenous metabolic signaling networksthat control MCAD gene expression could mediate up-regulation ofresidual protein and enzyme activity, in order to maintain MCFAoxidation capacities despite genetic alterations in enzyme activity.In keeping with this, MCAD was one of the first mitochondrial en-zymes shown to be regulated at the gene expression level by a va-riety of transcription factors, including Hepatocyte nuclear factor 4(HNF4), Peroxisome proliferator activated receptor (PPAR), thyroidhormone receptor (TR), Estrogen receptor (ER) and Estrogen relatedreceptor alpha (ERRa) [37e39]. These nuclear receptors play anessential role in the regulation of MCAD mRNA abundance, proteinlevel and enzyme activity in different tissues, under various physi-ological states, and at various stages of development, triggeringlarge adaptive changes inMCADgene expression and FAO capacitiesas a function of energy demand. Furthermore, the activity of thesetranscription factors is itself controlled by the PPARg-co-activator1alpha (PGC-1a) [40], and this highly dynamic transcriptional reg-ulatory network plays a key role in regulating energy productionthrough FAO in liver, heart or muscle [32,41,42].

A possible involvement of PPAR in the response to FAO blockadewas clearly suggested by studies run in mice receiving low doses ofetomoxir, a pharmacological inhibitor of mitochondrial FAO.Indeed, whereas this treatment did not induce any symptoms inwild-type mice, it triggered a severe metabolic decompensation inPPAR alpha gene knockout mice (PPARa�/�), with symptoms thatmimicked those observed in FAO-deficient newborns i.e. hepaticand cardiac steatosis, hypoglycemia and lethargy, eventually lead-ing to death [43]. Accordingly, it appears that FAO dysfunction canlead to the activation of PPARa signaling pathway, probably medi-ated by the accumulation of non-metabolized fatty acids acting asendogenous ligands [44]. In support of this, it was recently shownthat activation of the PPARa/PGC-1a axis by endogenous lipids isessential for maintenance of mitochondrial functions in cardiacmyocytes [45]. These mechanisms could form the basis forcompensatory up-regulation of MCAD and other FAO enzymes invarious tissues with high fatty acid utilization, in response to apartial b-oxidation blockade. In the absence of this regulatoryresponse, i.e. in PPARa�/� mice, severe energy deficiency and or-gan failure would occur, leading to eventually fatal metabolicdecompensation [43]. To what extent these regulatory mechanismsoperate in MCAD deficient patients, and could be involved in thenormalization of MCFA b-oxidation, is difficult to assess. However,it is most likely that MCAD deficiency, like other FAO disorders,

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012

β

Fig. 2. Diversity of phenotypes of CPT2 deficiency.

J. Bastin / Biochimie xxx (2013) 1e84

triggers long-term compensatory mechanisms that are central tothe physiopathology of the disorder, as suggested by studies of FAOgene knockout animal models [31,46,47].

3. The FAO regulatory network contains therapeutic targetsfor correction of inborn FAO disorders

Interestingly, there is evidence that activation of PPAR signalingpathway can induce a correction of genetic defects of LCFA b-oxidation, as exemplified in the case of Carnitine Palmitoyl-Transferase 2 (CPT2) or VLCAD deficiency. The CPT2 (MIM600650) belongs to a group of four carnitine acyltransferases, withdifferent localization and roles in fatty acid oxidation, and in theregulation of acylCoA pools [48,49]. CPT2 is associated to the innermitochondrial membrane, and catalyzes the conversion of long-chain acyl-carnitines, produced by the activity of CPT1 (Carnitinepalmitoyltransferase 1), back to long-chain acyl-CoAs. In human,these long-chain-CoA esters serve as substrates for the VLCAD,which catalyzes the first step of mitochondrial LCFA b-oxidation[3,50]. The VLCAD belongs to a group of nine acylCoA de-hydrogenases (ACAD) with different substrate specificity, includingfour isoforms devoted to straight-chain fatty acid b-oxidation, withdifferent chain-length specificities (very long-, long-, medium-, andshort-chain-fatty acids) [51]. There are major differences betweenmice and human in this group of ACAD [35]. In particular, whereasboth long chain (LCAD, MIM 609576) and very long chain (VLCAD)acyl-CoA dehydrogenases react with LCFA in mice, this functionaloverlap does not exist in human [35,52]. Indeed, human LCAD ex-hibits very low activity vis-à-vis long-chain fatty acids, and, inaddition, is expressed at very low levels in human tissues with highfatty acid utilization [53]. In line with this, molecular analysis ofpatients found deficient for long-chain acylCoA dehydrogenaseactivity revealed mutations in the VLCAD, but never in the LCAD,gene [1,54,55]. Thus, severe mutations in the VLCAD gene lead tocomplete LCFA b-oxidation deficiency in human [56], which is notobserved in VLCAD�/� mice [35].

CPT2 and VLCAD deficiencies are among the most commondefects of mitochondrial long-chain fatty acid b-oxidation [1,8,48].Each of these disorders can present several phenotypes that vary inseverity, tissue involvement and age of onset. A few cases of fetalmalformations with brain dysgenesis and renal cysts have beenreported as the most severe presentation of CPT2 deficiency [48].The neonatal form of CPT2 deficiency, which associates liverinsufficiency, cardiomyopathy and peripheral myopathy, is a severedisease due to cardiac conduction disorders that expose patientsto death during the neonatal period or infancy (Fig. 2) [57,58].A similar severe phenotype has been described for VLCAD defi-ciency, associating Reye-syndrome like metabolic crisis, cardiacarrhythmia, and death before one year of age (Fig. 1). Anotherpresentation of VLCAD deficiency manifests as recurrent episodesof hepatic coma after fasting, without heart involvement, in infancy[8,59]. Finally, the majority of patients diagnosed with CPT2 orVLCAD deficiency present the so-called “mild” phenotype, charac-terized by isolated myopathy of adolescence or adult-onset (Fig. 2)[8,49,60,61]. Typical manifestations of this metabolic myopathy aremuscle stiffness and myalgia with attacks of rhabdomyolysis trig-gered by exercise [8,48,62]. Rhabdomyolysis can occasionally resultin severe episodes of acute renal insufficiency, and, rarely, in patientdeath [63,64].

Interestingly, the onset of symptoms of the muscular forms ofCPT2 or VLCAD deficiency in teenagers correlates with the prefer-ential use of oxidative metabolism for energy production duringthe pubertal period, and with a particular dependence on FAO tosustain muscular exercise during adolescence [65,66]. Altogether,these two enzyme defects illustrate the possibly severe phenotypes

Please cite this article in press as: J. Bastin, Regulation of mitochondrial faacid b-oxidation deficiencies?, Biochimie (2013), http://dx.doi.org/10.101

associated with deficiencies in LCFA b-oxidation, which may causedeath early in life, together with the existence of milder myopathicforms, with later onset.

Currently, more than 70 mutations of the CPT2 gene have beendescribed, of which about two thirds are missense mutations,including the common Ser113Leu substitution, whereas the rest aremostly null mutations [49,60,61]. VLCAD deficiency also exhibits ahigh genetic heterogeneity withmore than 80mutations described,in majority missense mutations [8,67]. In contrast to medium- orshort-chain FAO defects, CPT2 or VLCAD deficiency exhibit somelevel of genotypeephenotype correlation. Indeed, homozygous nullmutations leading to complete absence of mRNA and mutatedenzyme are invariably found associated with the most severepresentations of these disorders [8,67]. In line with this, analysis offibroblasts from patients carrying null mutations of CPT2 or VLCADgene [56,68,69] always reveals undetectable LCFA b-oxidation ca-pacities (Fig. 2). This is consistently associated with severe cardio-myopathy andmajor cardiac dysfunction early in life (Figs. 1 and 2),and clearly indicates that, even though the adult heart exhibitssome level of metabolic flexibility [33] i.e. can temporarily useglucose or ketone bodies in place of fatty acids for energy pro-duction, the postnatal development of LCFA b-oxidation is a pre-requisite for normal development of cardiac functions, and thatLCFA are indispensable to provide ATP for cardiac contractionduring this period.

Overall, the diversity of phenotypes and symptoms possiblyassociated to LCFA defects still remain partly unexplained. CPT2deficiency was the first FAO disorder in which the relations be-tween clinical presentation, biochemical phenotype, and genotype,could at least in part, be clarified. Indeed, results obtained from acohort of 20 CPT2-deficient patients demonstrated that the levelsof palmitate oxidation measured in patient cells were undetectablein cells from patients with the severe phenotype, whereas low butsignificant levels could consistently be measured in cells from pa-tients with the adult-onset muscular phenotype (Fig. 2). Thisindicated that clinical severity of CPT2 deficiency correlated tosome extent with the biochemical phenotype [70]. From this andother more recent studies, it became clear that the milder clinicalpresentation of CPT2 deficiency was always associated to genemutations that allow the production of low levels of mutatedenzyme with residual enzyme activity, resulting in the expression

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012

J. Bastin / Biochimie xxx (2013) 1e8 5

of residual LCFA b-oxidation capacities in the patient muscle[10,60,71].

In the case of VLCAD deficiency, the existence of residualmetabolic capacities associated to the mild disease phenotype isnow generally admitted, but did not initially appear as clearly as inthe case of CPT2 deficiency. In particular, assessment of FAO inpatients fibroblasts did not always allow to distinguish between themild and the severe disease presentations, under standard cultureconditions [69]. However, under pharmacological stimulation (seebelow), cells from patients with the mild phenotype return to near-normal FAO capacities, while, in contrast, cells from severelyaffected patients remain extremely deficient, due to mutationscritically affecting VLCAD enzyme stability and activity [59,69,72].Analysis of plasma acylcarnitines in VLCAD-deficient patients madepossible to diagnose the different forms of the disease with a goodspecificity, and formed the basis of newborn screening for VLCADdeficiency [73,74], which is presently performed in a number ofcountries [16,75]. This allowed providing data on the estimatedincidence of the disease (1/31,500). Overall, and as for MCADdeficiency, implementation of newborn screening for VLCAD defi-ciency quite often resulted in the detection of asymptomatic in-dividuals who were generally submitted to preventive measures,and did not subsequently develop any disease symptoms, until now[16,75,76].

Despite marked advances in molecular analysis, and as observedfor MCAD deficiency, the nature of the mutations of the CPT2 orVLCAD gene does not, by itself, allow to fully predict the onset andseverity of disease manifestations. Indeed, the symptoms associ-ated to CPT2 or VLCAD are often episodic, and the disease can beasymptomatic outside acute episodes [60,75]. Furthermore, it isestablished that clinical manifestations of CPT2 or VLCAD defi-ciency can be triggered, or aggravated, by various environmental orphysiological stress factors. Thus, Reye-like syndrome can occur inresponse to short fasting periods in newborns with the severepresentations of CPT2 or VLCAD deficiency [48,72]. In parallel, pa-tients with the myopathic form of these disorders often experiencemyalgia and episodes of rhabdomyolysis not only after exercise, butalso in response to cold, short fasting periods, febrile illness, orpsychological stress. Accordingly, there is a clear correlation be-tween the appearance ofmuscular symptoms and the occurrence ofphysiological conditions that trigger an increase in FAO.

The complexity of phenotypes associated to CPT2 or VLCADdeficiencymakes the therapeutic options more complex than in thecase of MCAD deficiency. The neonatal form of CPT2 deficiencycannot be treated and is almost invariably fatal. The situation isslightly more favorable for neonates diagnosed with the severeform of VLCAD deficiency, despite a high mortality. Indeed, pre-vention of catabolic stress by a high glucose formula enriched inmedium-chain fatty acids has been reported to prevent the mostseveremanifestations of the disease, at least in some cases [77e79].Other approaches include carnitine supplementation in order toconvert potentially toxic long-chain acyl-CoAs to acylcarnitines.However, the role of carnitine supplements in FAO defects remainscontroversial and of unproven value due to the absence ofcontrolled trials [80]. Finally most adult CPT2- or VLCAD-deficientpatients do not follow any treatment and constantly manage toadapt their lifestyle to their muscular handicap.

Nevertheless, recent studies showed that pharmacologicaltreatments based on the stimulation of residual FAO capacitiesrepresented, at least for some forms of CPT2 or VLCAD deficiency, apromising approach. These were initially developed on a rationaleof target-based therapy, similar to that used for drug developmentin common metabolic diseases. Indeed, the above-mentioned ob-servations on the physiopathology of CPT2 deficiency led us tohypothesize that pharmacological activation of the PPAR signaling

Please cite this article in press as: J. Bastin, Regulation of mitochondrial faacid b-oxidation deficiencies?, Biochimie (2013), http://dx.doi.org/10.101

pathway might be of therapeutic value in FAO disorders. There arethree PPAR isoforms called PPARa, PPARd (also called b or b/d), andPPARg. As mentioned previously, numerous studies in animalmodels had established the key role of the PPARa and/or PPARdsignaling pathway(s) in up-regulating the FAO in rodents. Surpris-ingly, however, there were very few data to objectivize FAO controlby the PPAR system in human before studies on correction of CPT2-,or VLCAD-deficiency by bezafibrate in patient cells becameavailable.

Our initial experiments aimed at comparing the effects of fourfibrate derivatives known to act as PPAR activators, and widelyprescribed as hypolipidemic drugs (fenofibrate, gemfibrozil,ciprofibrate, and bezafibrate). Only bezafibrate was able to restorenormal FAO capacities in fibroblasts from patients with themuscular presentation of CPT2 deficiency, whereas the other drugshad no effects [68]. Furthermore, no response to bezafibrate wasobserved in fibroblasts from severely affected neonates. We thendemonstrated that exposure to bezafibrate also resulted in a com-plete correction of FAO capacities in myoblasts and myotubes fromCPT2-deficient patients [71]. A compared analysis of the responseto PPARa (GW7647) and PPARd (GW0742) high affinity agonists wasthen performed in the patients’ muscle cells, which brought newinsights on FAO regulation, and on the observed pharmacologicalresponse to fibrates. Indeed, correction of FAO capacities in CPT2-deficient muscle cells was only obtained after treatment by thePPARd agonist, whereas the alpha-specific agonist was ineffective[71]. The key role of PPARd in the control of FAOwas then confirmedin various animal studies [81,82]. This PPARd-specific responseexplained the specificity of bezafibrate effects, compared to otherfibrates, in CPT2-deficient cells. Indeed, in contrast to most fibratesthat act as exclusive agonists of PPARa, bezafibrate is the only dualagonist capable to activate both PPARa and PPARd [83]. Accordingly,correction of CPT2 deficiency by bezafibrate was entirely related tothe unique ability of this fibrate to activate PPARd. This pharma-cological approach was then extended to the VLCAD deficiency[56,69]. The potential of bezafibrate was tested in cells from pa-tients representing a wide panel of genotypes and missense mu-tations, corresponding to the three phenotypes of the disease. Inbrief, the results showed that, as for CPT2 deficiency, the respon-siveness to bezafibrate was related to the transcriptional up-regulation of residual of VLCAD protein and enzyme activity, inresponse to PPAR activation. Indeed, two thirds of tested cell linesexhibited a significant induction of VLCAD protein levels (1.5e2-fold), enzyme activity (up to 7.7-fold), and FAO capacities (up to3-fold) in response to bezafibrate [69]. Interestingly, these studiessuggested a partial response of VLCAD-deficient fibroblasts tofenofibrate, a PPARa agonist, but complete restoration of FAO valueswas only obtained using bezafibrate. This suggests that correctionof VLCAD deficiency might involve dual activation of PPARa andPPARd by bezafibrate. Altogether, this ex-vivo approach thereforeclearly suggested a therapeutic potential of bezafibrate in patientswith the muscular form of CPT2- or VLCAD deficiency.

The efficacy of bezafibrate in patients with the muscular form ofCPT2 deficiency was then tested in a pilot clinical trial. Briefly, sixpatients received bezafibrate at the dose of 3 � 200 mg tablets perday, i.e. the normal drug dosage when used as hypolipidemicagent [10,84]. This study revealed a marked increase in the oxida-tion of palmitoyl-L-carnitine, the specific CPT2 substrate, in patientmuscle mitochondria, following a 6-month treatment by bezafi-brate. Clinical improvement in patient condition appeared from theresults of SF36 quality of life questionnaire, and was characterizedby a decline in muscle pain associated with an increase in thetolerance to exercise. In parallel, treatment by bezafibrate resultedin an overall decrease in the number of rhabdomyolysis episodes inall the patients. This was the first drug trial in this disorder, and,

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012

J. Bastin / Biochimie xxx (2013) 1e86

clearly suggested a therapeutic benefit of bezafibrate in myopathicCPT2-deficient patients. These data also further documented theregulation of FAO in human skeletal muscle, and its in vivo phar-macology, indicating that bezafibrate induced a PPARd-mediatedstimulation of this pathway in this tissue. In line with these ob-servations, additional data supporting stimulatory effects of beza-fibrate on FAO, and on hepatic ketone bodies production, wererecently reported in different studies [85e89].

Altogether, these data support the hypothesis that new thera-peutic approaches of genetic FAO deficiencies could be achieved bypharmacological targeting of endogenous regulatory network thatcontrol the expression levels of enzymes and proteins in the FAOpathway. Information gathered from FAO-deficient cells might behighly valuable to progress on these issues. In this regard, PPAR/fibrate is not the only system that opens new avenues for therapy ofFAO disorders. Recent work also points to the potential of resver-atrol, and of some of its major metabolites, unpublished data forcorrection of CPT2- or VLCAD-deficiency in patient cells [90]. Theregulatory mechanisms targeted by resveratrol are however muchmore complex than in the case of bezafibrate, possibly involvingactivation of one or several sirtuins (NADþ-dependent histonedeacetylases), and/or the activation of AMP-activated protein ki-nase. This could result in a PGC-1a-dependent activation of FAOenzyme gene transcription, involving various nuclear receptors.

To conclude, it is presently admitted that regulation of mito-chondrial FAO could be a key issue to understand the physiopa-thology of common cardiovascular [32,33] or metabolic diseases[91]. Accordingly, the development of pharmacological agentsspecifically targeting FAO is a promising field of research that mightlead to numerous applications for the treatment of rare and com-mon diseases.

References

[1] P. Rinaldo, D. Matern, M.J. Bennett, Fatty acid oxidation disorders, AnnualReview of Physiology 64 (2002) 477e502.

[2] J. Vockley, D.A. Whiteman, Defects of mitochondrial beta-oxidation: a growinggroup of disorders, Neuromuscular Disorders 12 (2002) 235e246.

[3] R.J. Wanders, J.P. Ruiter, L. IJLst, H.R. Waterham, S.M. Houten, The enzymologyof mitochondrial fatty acid beta-oxidation and its application to follow-upanalysis of positive neonatal screening results, Journal of Inherited Meta-bolic Disease 33 (2010) 479e494.

[4] N. Gregersen, B.S. Andresen, C.B. Pedersen, R.K. Olsen, T.J. Corydon, P. Bross,Mitochondrial fatty acid oxidation defects e remaining challenges, Journal ofInherited Metabolic Disease 31 (2008) 643e657.

[5] S.E. Olpin, Fatty acid oxidation defects as a cause of neuromyopathic disease ininfants and adults, Clinical Laboratory 51 (2005) 289e306.

[6] R.J. Wanders, P. Vreken, M.E. den Boer, F.A. Wijburg, A.H. van Gennip, L. IJLst,Disorders of mitochondrial fatty acyl-CoA beta-oxidation, Journal of InheritedMetabolic Disease 22 (1999) 442e487.

[7] J. Baruteau, P. Sachs, P. Broue, M. Brivet, H. Abdoul, C. Vianey-Saban, H. Ogierde Baulny, Clinical and biological features at diagnosis in mitochondrial fattyacid beta-oxidation defects: a French pediatric study of 187 patients, Journalof Inherited Metabolic Disease (2012).

[8] N. Gregersen, B.S. Andresen, M.J. Corydon, T.J. Corydon, R.K. Olsen, L. Bolund,P. Bross, Mutation analysis in mitochondrial fatty acid oxidation defects:exemplified by acyl-CoA dehydrogenase deficiencies, with special focus ongenotypeephenotype relationship, Human Mutation 18 (2001) 169e189.

[9] M.J. Bennett, Pathophysiology of fatty acid oxidation disorders, Journal ofInherited Metabolic Disease 33 (2010) 533e537.

[10] J.P. Bonnefont, J. Bastin, P. Laforet, F. Aubey, A. Mogenet, S. Romano,D. Ricquier, S. Gobin-Limballe, A. Vassault, A. Behin, B. Eymard, J.L. Bresson,F. Djouadi, Long-term follow-up of bezafibrate treatment in patients with themyopathic form of carnitine palmitoyltransferase 2 deficiency, Clinical Phar-macology & Therapeutics 88 (2010) 101e108.

[11] O. Genzel-Boroviczeny, J. Wahle, B. Koletzko, Fatty acid composition of humanmilk during the 1st month after term and preterm delivery, European Journalof Pediatrics 156 (1997) 142e147.

[12] E.M. Novak, S.M. Innis, Impact of maternal dietary n-3 and n-6 fatty acids onmilk medium-chain fatty acids and the implications for neonatal liver meta-bolism, American Journal of Physiology, Endocrinology and Metabolism 301(2011) E807eE817.

[13] N. Gregersen, R. Lauritzen, K. Rasmussen, Suberylglycine excretion in theurine from a patient with dicarboxylic aciduria, Clinica Chimica Acta, Inter-national Journal of Clinical Chemistry 70 (1976) 417e425.

Please cite this article in press as: J. Bastin, Regulation of mitochondrial faacid b-oxidation deficiencies?, Biochimie (2013), http://dx.doi.org/10.101

[14] B.S. Andresen, A.M. Lund, D.M. Hougaard, E. Christensen, B. Gahrn,M. Christensen, P. Bross, A. Vested, H. Simonsen, K. Skogstrand, S. Olpin,N.J. Brandt, F. Skovby, B. Norgaard-Pedersen, N. Gregersen, MCAD deficiencyin Denmark, Molecular Genetics and Metabolism 106 (2012) 175e188.

[15] F. Feillet, H. Ogier, D. Cheillan, C. Aquaviva, F. Labarthe, J. Baruteau, B. Chabrol,P. de Lonlay, V. Valayanopoulos, R. Garnotel, D. Dobbelaere, G. Briand,E. Jeannesson, A. Vassault, C. Vianey-Saban, Medium-chain acyl-CoA-dehydrogenase (MCAD) deficiency: French consensus for neonatalscreening, diagnosis, and management, Archives de pediatrie: organe officielde la Societe francaise de pediatrie 19 (2012) 184e193.

[16] M. Lindner, G.F. Hoffmann, D. Matern, Newborn screening for disorders offatty-acid oxidation: experience and recommendations from an expertmeeting, Journal of Inherited Metabolic Disease 33 (2010) 521e526.

[17] J. Oerton, J.M. Khalid, G. Besley, R.N. Dalton, M. Downing, A. Green,M. Henderson, S. Krywawych, J. Leonard, B.S. Andresen, C. Dezateux, Newbornscreening for medium chain acyl-CoA dehydrogenase deficiency in England:prevalence, predictive value and test validity based on 1.5 million screenedbabies, Journal of Medical Screening 18 (2011) 173e181.

[18] U.A. Schatz, R. Ensenauer, The clinical manifestation of MCAD deficiency:challenges towards adulthood in the screened population, Journal of InheritedMetabolic Disease 33 (2010) 513e520.

[19] B. Wilcken, Fatty acid oxidation disorders: outcome and long-term prognosis,Journal of Inherited Metabolic Disease 33 (2010) 501e506.

[20] Y.Q. You, P.R. Ling, J.Z. Qu, B.R. Bistrian, Effects of medium-chain triglycerides,long-chain triglycerides, or 2-monododecanoin on fatty acid composition inthe portal vein, intestinal lymph, and systemic circulation in rats, JPEN,Journal of Parenteral and Enteral Nutrition 32 (2008) 169e175.

[21] J.H. Walter, Tolerance to fast: rational and practical evaluation in children withhypoketonaemia, Journal of Inherited Metabolic Disease 32 (2009) 214e217.

[22] D.H. Chace, S.L. Hillman, J.L. Van Hove, E.W. Naylor, Rapid diagnosis of MCADdeficiency: quantitative analysis of octanoylcarnitine and other acylcarnitinesin newborn blood spots by tandem mass spectrometry, Clinical Chemistry 43(1997) 2106e2113.

[23] B. Wilcken, V. Wiley, J. Hammond, K. Carpenter, Screening newborns forinborn errors of metabolism by tandem mass spectrometry, New EnglandJournal of Medicine 348 (2003) 2304e2312.

[24] L. Waddell, V. Wiley, K. Carpenter, B. Bennetts, L. Angel, B.S. Andresen,B. Wilcken, Medium-chain acyl-CoA dehydrogenase deficiency: genotypeebiochemical phenotype correlations, Molecular Genetics and Metabolism 87(2006) 32e39.

[25] S. Kennedy, B.K. Potter, K. Wilson, L. Fisher, M. Geraghty, J. Milburn,P. Chakraborty, The first three years of screening for medium chain acyl-CoAdehydrogenase deficiency (MCADD) by newborn screening ontario, BMC Pe-diatrics 10 (2010) 82.

[26] M. Lindner, G. Gramer, G. Haege, J. Fang-Hoffmann, K.O. Schwab, U. Tacke,F.K. Trefz, E. Mengel, U. Wendel, M. Leichsenring, P. Burgard, G.F. Hoffmann,Efficacy and outcome of expanded newborn screening for metabolic diseasese report of 10 years from South-West Germany, Orphanet Journal of RareDiseases 6 (2011) 44.

[27] B.S. Andresen, S.F. Dobrowolski, L. O’Reilly, J. Muenzer, S.E. McCandless,D.M. Frazier, S. Udvari, P. Bross, I. Knudsen, R. Banas, D.H. Chace, P. Engel,E.W. Naylor, N. Gregersen, Medium-chain acyl-CoA dehydrogenase (MCAD)mutations identified by MS/MS-based prospective screening of newbornsdiffer from those observed in patients with clinical symptoms: identificationand characterization of a new, prevalent mutation that results in mild MCADdeficiency, American Journal of Human Genetics 68 (2001) 1408e1418.

[28] E.M. Maier, S.W. Gersting, K.F. Kemter, J.M. Jank, M. Reindl, D.D. Messing,M.S. Truger, C.P. Sommerhoff, A.C. Muntau, Protein misfolding is the molec-ular mechanism underlying MCADD identified in newborn screening, HumanMolecular Genetics 18 (2009) 1612e1623.

[29] M. Sturm, D. Herebian, M. Mueller, M.D. Laryea, U. Spiekerkoetter, Functionaleffects of different medium-chain acyl-CoA dehydrogenase genotypes andidentification of asymptomatic variants, PLoS One 7 (2012) e45110.

[30] U. Spiekerkoetter, Mitochondrial fatty acid oxidation disorders: clinical pre-sentation of long-chain fatty acid oxidation defects before and after newbornscreening, Journal of Inherited Metabolic Disease 33 (2010) 527e532.

[31] S. Tucci, D. Herebian, M. Sturm, A. Seibt, U. Spiekerkoetter, Tissue-specificstrategies of the very-long chain acyl-CoA dehydrogenase-deficient (VLCAD�/�) mouse to compensate a defective fatty acid beta-oxidation, PLoS One 7(2012) e45429.

[32] G. Aubert, R.B. Vega, D.P. Kelly, Perturbations in the gene regulatory pathwayscontrolling mitochondrial energy production in the failing heart, Biochimicaet biophysica acta 1833 (2013) 840e847.

[33] V. Lionetti, W.C. Stanley, F.A. Recchia, Modulating fatty acid oxidation in heartfailure, Cardiovascular Research 90 (2011) 202e209.

[34] M.N. Sack, D.P. Kelly, The energy substrate switch during development ofheart failure: gene regulatory mechanisms (Review), International Journal ofMolecular Medicine 1 (1998) 17e24.

[35] M. Chegary, H. Brinke, J.P. Ruiter, F.A. Wijburg, M.S. Stoll, P.E. Minkler, M. vanWeeghel, H. Schulz, C.L. Hoppel, R.J. Wanders, S.M. Houten, Mitochondriallong chain fatty acid beta-oxidation in man and mouse, Biochimica et bio-physica acta 1791 (2009) 806e815.

[36] B.E. Hainline, D.J. Kahlenbeck, J. Grant, A.W. Strauss, Tissue specific anddevelopmental expression of rat long-and medium-chain acyl-CoA de-hydrogenases, Biochimica et biophysica acta 1216 (1993) 460e468.

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012

J. Bastin / Biochimie xxx (2013) 1e8 7

[37] M.E. Carter, T. Gulick, D.D. Moore, D.P. Kelly, A pleiotropic element in theMCAD gene promoter mediates transcriptional regulation by multiple nuclearreceptor transcription factors and defines novel receptor-DNA binding motifs,Molecular and Cellular Biology 14 (1994) 4360e4372.

[38] T.C. Leone, S. Cresci, M.E. Carter, Z. Zhang, D.S. Lala, A.W. Strauss, D.P. Kelly,The human medium chain acyl-CoA dehydrogenase gene promoter consists ofa complex arrangement of nuclear receptor response elements and Sp1binding sites, Journal of Biological Chemistry 270 (1995) 16308e16314.

[39] R.B. Vega, D.P. Kelly, A role for estrogen-related receptor alpha in the controlof mitochondrial fatty acid beta-oxidation during brown adipocyte differen-tiation, Journal of Biological Chemistry 272 (1997) 31693e31699.

[40] J.M. Huss, R.P. Kopp, D.P. Kelly, Peroxisome proliferator-activated receptorcoactivator-1alpha (PGC-1alpha) coactivates the cardiac-enriched nuclearreceptors estrogen-related receptor-alpha and -gamma. Identification ofnovel leucine-rich interaction motif within PGC-1alpha, Journal of BiologicalChemistry 277 (2002) 40265e40274.

[41] B.N. Finck, D.P. Kelly, PGC-1 coactivators: inducible regulators of energymetabolism in health and disease, Journal of Clinical Investigation 116 (2006)615e622.

[42] Z. Gerhart-Hines, J.T. Rodgers, O. Bare, C. Lerin, S.H. Kim, R. Mostoslavsky,F.W. Alt, Z. Wu, P. Puigserver, Metabolic control of muscle mitochondrialfunction and fatty acid oxidation through SIRT1/PGC-1alpha, The EMBOJournal 26 (2007) 1913e1923.

[43] F. Djouadi, C.J. Weinheimer, J.E. Saffitz, C. Pitchford, J. Bastin, F.J. Gonzalez,D.P. Kelly, A gender-related defect in lipid metabolism and glucose homeo-stasis in peroxisome proliferator-activated receptor alpha-deficient mice,Journal of Clinical Investigation 102 (1998) 1083e1091.

[44] T.C. Leone, C.J. Weinheimer, D.P. Kelly, A critical role for the peroxisomeproliferator-activated receptor alpha (PPARalpha) in the cellular fastingresponse: the PPARalpha-null mouse as a model of fatty acid oxidation dis-orders, Proceedings of the National Academy of Sciences of the United Statesof America 96 (1999) 7473e7478.

[45] D.P. Kelly, Novel communication between myocyte lipid storage and fatburning unveiled, Circulation Research 110 (2012) 655e657.

[46] H. Herrema, T.G. Derks, T.H. van Dijk, V.W. Bloks, A. Gerding, R. Havinga,U.J. Tietge, M. Muller, G.P. Smit, F. Kuipers, D.J. Reijngoud, Disturbed hepaticcarbohydrate management during high metabolic demand in medium-chainacyl-CoA dehydrogenase (MCAD)-deficient mice, Hepatology 47 (2008)1894e1904.

[47] U. Spiekerkoetter, P.A. Wood, Mitochondrial fatty acid oxidation disorders:pathophysiological studies in mouse models, Journal of Inherited MetabolicDisease 33 (2010) 539e546.

[48] J.P. Bonnefont, F. Djouadi, C. Prip-Buus, S. Gobin, A. Munnich, J. Bastin,Carnitine palmitoyltransferases 1 and 2: biochemical, molecular and medicalaspects, Molecular Aspects of Medicine 25 (2004) 495e520.

[49] P.J. Isackson, M.J. Bennett, G.D. Vladutiu, Identification of 16 new disease-causing mutations in the CPT2 gene resulting in carnitine palmitoyltransfer-ase II deficiency, Molecular Genetics and Metabolism 89 (2006) 323e331.

[50] T. Aoyama, M. Souri, S. Ushikubo, T. Kamijo, S. Yamaguchi, R.I. Kelley,W.J. Rhead, K. Uetake, K. Tanaka, T. Hashimoto, Purification of human very-long-chain acyl-coenzyme A dehydrogenase and characterization of its defi-ciency in seven patients, Journal of Clinical Investigation 95 (1995) 2465e2473.

[51] J.J. Kim, R. Miura, Acyl-CoA dehydrogenases and acyl-CoA oxidases. Structuralbasis for mechanistic similarities and differences, European Journal ofBiochemistry/FEBS 271 (2004) 483e493.

[52] K.B. Cox, D.A. Hamm, D.S. Millington, D. Matern, J. Vockley, P. Rinaldo,C.A. Pinkert, W.J. Rhead, J.R. Lindsey, P.A. Wood, Gestational, pathologic andbiochemical differences between very long-chain acyl-CoA dehydrogenasedeficiency and long-chain acyl-CoA dehydrogenase deficiency in the mouse,Human Molecular Genetics 10 (2001) 2069e2077.

[53] A.C. Maher, A.W. Mohsen, J. Vockley, M.A. Tarnopolsky, Low expression oflong-chain acyl-CoA dehydrogenase in human skeletal muscle, MolecularGenetics and Metabolism 100 (2010) 163e167.

[54] B.S. Andresen, P. Bross, C. Vianey-Saban, P. Divry, M.T. Zabot, C.R. Roe,M.A. Nada, A. Byskov, T.A. Kruse, S. Neve, K. Kristiansen, I. Knudsen,M.J. Corydon, N. Gregersen, Cloning and characterization of human very-long-chain acyl-CoA dehydrogenase cDNA, chromosomal assignment of the geneand identification in four patients of nine different mutations within theVLCAD gene, Human Molecular Genetics 5 (1996) 461e472.

[55] T. Aoyama, Y. Uchida, R.I. Kelley, M. Marble, K. Hofman, J.H. Tonsgard,W.J. Rhead, T. Hashimoto, A novel disease with deficiency of mitochondrialvery-long-chain acyl-CoA dehydrogenase, Biochemical and BiophysicalResearch Communications 191 (1993) 1369e1372.

[56] F. Djouadi, F. Aubey, D. Schlemmer, J.P. Ruiter, R.J. Wanders, A.W. Strauss,J. Bastin, Bezafibrate increases very-long-chain acyl-CoA dehydrogenaseprotein and mRNA expression in deficient fibroblasts and is a potentialtherapy for fatty acid oxidation disorders, Human Molecular Genetics 14(2005) 2695e2703.

[57] J.P. Bonnefont, F. Taroni, P. Cavadini, C. Cepanec, M. Brivet, J.M. Saudubray,J.P. Leroux, F. Demaugre, Molecular analysis of carnitine palmitoyltransferaseII deficiency with hepatocardiomuscular expression, American Journal ofHuman Genetics 58 (1996) 971e978.

[58] F. Demaugre, J.P. Bonnefont, M. Colonna, C. Cepanec, J.P. Leroux,J.M. Saudubray, Infantile form of carnitine palmitoyltransferase II deficiency

Please cite this article in press as: J. Bastin, Regulation of mitochondrial faacid b-oxidation deficiencies?, Biochimie (2013), http://dx.doi.org/10.101

with hepatomuscular symptoms and sudden death. Physiopathologicalapproach to carnitine palmitoyltransferase II deficiencies, Journal of ClinicalInvestigation 87 (1991) 859e864.

[59] B.S. Andresen, S. Olpin, B.J. Poorthuis, H.R. Scholte, C. Vianey-Saban,R. Wanders, L. Ijlst, A. Morris, M. Pourfarzam, K. Bartlett, E.R. Baumgartner,J.B. deKlerk, L.D. Schroeder, T.J. Corydon, H. Lund, V. Winter, P. Bross,L. Bolund, N. Gregersen, Clear correlation of genotype with disease phenotypein very-long-chain acyl-CoA dehydrogenase deficiency, American Journal ofHuman Genetics 64 (1999) 479e494.

[60] A. Anichini, M. Fanin, C. Vianey-Saban, D. Cassandrini, C. Fiorillo, C. Bruno,C. Angelini, Genotypeephenotype correlations in a large series of patients withmuscle type CPT II deficiency, Journal of Neurology Research 33 (2011) 24e32.

[61] S. Corti, A. Bordoni, D. Ronchi, O. Musumeci, M. Aguennouz, A. Toscano,C. Lamperti, N. Bresolin, G.P. Comi, Clinical features and new molecularfindings in carnitine palmitoyltransferase II (CPT II) deficiency, Journal of theNeurological Sciences 266 (2008) 97e103.

[62] M. Deschauer, T. Wieser, S. Zierz, Muscle carnitine palmitoyltransferase IIdeficiency: clinical and molecular genetic features and diagnostic aspects,Archives of Neurology 62 (2005) 37e41.

[63] I. Handig, E. Dams, F. Taroni, S. Van Laere, T. de Barsy, P.J. Willems, Inheritanceof the S113L mutation within an inbred family with carnitine palmitoyl-transferase enzyme deficiency, Human Genetics 97 (1996) 291e293.

[64] K.J. Kelly, J.S. Garland, T.T. Tang, A.L. Shug, M.J. Chusid, Fatal rhabdomyolysisfollowing influenza infection in a girl with familial carnitine palmitoyl-transferase deficiency, Pediatrics 84 (1989) 312e316.

[65] M.C. Riddell, The endocrine response and substrate utilization during exercise inchildren and adolescents, Journal of Applied Physiology 105 (2008) 725e733.

[66] M.C. Riddell, V.K. Jamnik, K.E. Iscoe, B.W. Timmons, N. Gledhill, Fat oxidationrate and the exercise intensity that elicits maximal fat oxidation decreaseswith pubertal status in young male subjects, Journal of Applied Physiology105 (2008) 742e748.

[67] N. Gregersen, P. Bross, B.S. Andresen, Genetic defects in fatty acid beta-oxidation and acyl-CoA dehydrogenases. Molecular pathogenesis and geno-typeephenotype relationships, European Journal of Biochemistry/FEBS 271(2004) 470e482.

[68] F. Djouadi, J.P. Bonnefont, L. Thuillier, V. Droin, N. Khadom, A. Munnich,J. Bastin, Correction of fatty acid oxidation in carnitine palmitoyltransferase 2-deficient cultured skin fibroblasts by bezafibrate, Pediatric Research 54 (2003)446e451.

[69] S. Gobin-Limballe, F. Djouadi, F. Aubey, S. Olpin, B.S. Andresen, S. Yamaguchi,H. Mandel, T. Fukao, J.P. Ruiter, R.J. Wanders, R. McAndrew, J.J. Kim, J. Bastin,Genetic basis for correction of very-long-chain acyl-coenzyme A dehydroge-nase deficiency by bezafibrate in patient fibroblasts: toward a genotype-basedtherapy, American Journal of Human Genetics 81 (2007) 1133e1143.

[70] L. Thuillier, H. Rostane, V. Droin, F. Demaugre, M. Brivet, N. Khadom, C. Prip-Buus, S. Gobin, J.M. Saudubray, J.P. Bonnefont, Correlation between genotype,metabolic data, and clinical presentation in carnitine palmitoyltransferase 2deficiency, Human Mutation 5 (2003) 493e501.

[71] F. Djouadi, F. Aubey, D. Schlemmer, J. Bastin, Peroxisome proliferator activatedreceptor {delta} (PPAR{delta}) agonist but not PPAR{alpha} corrects carnitinepalmitoyltransferase 2 deficiency in human muscle cells, Journal of ClinicalEndocrinology and Metabolism 90 (2005) 1791e1797.

[72] S. Gobin-Limballe, R.P. McAndrew, F. Djouadi, J.J. Kim, J. Bastin, Comparedeffects of missense mutations in very-long-chain acyl-CoA dehydrogenasedeficiency: combined analysis by structural, functional and pharmacologicalapproaches, Biochimica et biophysica acta 1802 (2010) 478e484.

[73] A. Boneh, B.S. Andresen, N. Gregersen, M. Ibrahim, N. Tzanakos, H. Peters,J. Yaplito-Lee, J.J. Pitt, VLCAD deficiency: pitfalls in newborn screening andconfirmation of diagnosis by mutation analysis, Molecular Genetics andMetabolism 88 (2006) 166e170.

[74] M. Liebig, I. Schymik, M. Mueller, U. Wendel, E. Mayatepek, J. Ruiter,A.W. Strauss, R.J. Wanders, U. Spiekerkoetter, Neonatal screening for verylong-chain acyl-CoA dehydrogenase deficiency: enzymatic and molecularevaluation of neonates with elevated C14:1-carnitine levels, Pediatrics 118(2006) 1065e1069.

[75] G.L. Arnold, J. Van Hove, D. Freedenberg, A. Strauss, N. Longo, B. Burton,C. Garganta, C. Ficicioglu, S. Cederbaum, C. Harding, R.G. Boles, D. Matern,P. Chakraborty, A. Feigenbaum, A Delphi clinical practice protocol for themanagement of very long chain acyl-CoA dehydrogenase deficiency, Molec-ular Genetics and Metabolism 96 (2009) 85e90.

[76] U. Spiekerkoetter, B. Sun, T. Zytkovicz, R. Wanders, A.W. Strauss, U. Wendel,MS/MS-based newborn and family screening detects asymptomatic patientswith very-long-chain acyl-CoA dehydrogenase deficiency, Journal of Pediat-rics 143 (2003) 335e342.

[77] C. Angelini, A. Federico, H. Reichmann, A. Lombes, P. Chinnery, D. Turnbull,Task force guidelines handbook: EFNS guidelines on diagnosis and manage-ment of fatty acid mitochondrial disorders, European Journal of Neurology 13(2006) 923e929.

[78] C.R. Roe, L. Sweetman, D.S. Roe, F. David, H. Brunengraber, Treatment ofcardiomyopathy and rhabdomyolysis in long-chain fat oxidation disordersusing an anaplerotic odd-chain triglyceride, Journal of Clinical Investigation110 (2002) 259e269.

[79] J. Vockley, R.H. Singh, D.A. Whiteman, Diagnosis and management of defectsof mitochondrial beta-oxidation, Current Opinion in Clinical Nutrition andMetabolic Care 5 (2002) 601e609.

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012

J. Bastin / Biochimie xxx (2013) 1e88

[80] U. Spiekerkoetter, J. Bastin, M. Gillingham, A. Morris, F. Wijburg, B. Wilcken,Current issues regarding treatment of mitochondrial fatty acid oxidationdisorders, Journal of Inherited Metabolic Disease 33 (2010) 555e561.

[81] G.D. Barish, V.A. Narkar, R.M. Evans, PPAR delta: a dagger in the heart of themetabolic syndrome, Journal of Clinical Investigation 116 (2006) 590e597.

[82] E. Ehrenborg, A. Krook, Regulation of skeletal muscle physiology and meta-bolism by peroxisome proliferator-activated receptor delta, PharmacologicalReviews 61 (2009) 373e393.

[83] J.M. Peters, T. Aoyama, A.M. Burns, F.J. Gonzalez, Bezafibrate is a dual ligandfor PPARalpha and PPARbeta: studies using null mice, Biochimica et bio-physica acta 1632 (2003) 80e89.

[84] J.P. Bonnefont, J. Bastin, A. Behin, F. Djouadi, Bezafibrate for treatment of aninborn mitochondrial ß-oxidation defect, New England Journal of Medicine360 (2009) 838e840.

[85] R. Ensenauer, R. Fingerhut, S.C. Schriever, B. Fink, M. Becker, N.C. Sellerer,P. Pagel, A. Kirschner, T. Dame, B. Olgemoller, W. Roschinger, A.A. Roscher, Insitu assay of fatty acid beta-oxidation by metabolite profiling following per-meabilization of cell membranes, Journal of Lipid Research 53 (2012) 1012e1020.

[86] H. Li, S. Fukuda, Y. Hasegawa, H. Kobayashi, J. Purevsuren, Y. Mushimoto,S. Yamaguchi, Effect of heat stress and bezafibrate on mitochondrial beta-oxidation: comparison between cultured cells from normal and

Please cite this article in press as: J. Bastin, Regulation of mitochondrial faacid b-oxidation deficiencies?, Biochimie (2013), http://dx.doi.org/10.101

mitochondrial fatty acid oxidation disorder children using in vitro probeacylcarnitine profiling assay, Brain & Development 32 (2010) 362e370.

[87] J. Tremblay-Mercier, D. Tessier, M. Plourde, M. Fortier, D. Lorrain,S.C. Cunnane, Bezafibrate mildly stimulates ketogenesis and fatty acid meta-bolism in hypertriglyceridemic subjects, Journal of Pharmacology andExperimental Therapeutics 334 (2010) 341e346.

[88] S. Yamaguchi, H. Li, J. Purevsuren, K. Yamada, M. Furui, T. Takahashi,Y. Mushimoto, H. Kobayashi, Y. Hasegawa, T. Taketani, T. Fukao, S. Fukuda,Bezafibrate can be a new treatment option for mitochondrial fatty acidoxidation disorders: evaluation by in vitro probe acylcarnitine assay, Molec-ular Genetics and Metabolism 107 (2012) 87e91.

[89] M. Yao, D. Yao, M. Yamaguchi, J. Chida, D. Yao, H. Kido, Bezafibrate upre-gulates carnitine palmitoyltransferase II expression and promotes mito-chondrial energy crisis dissipation in fibroblasts of patients with influenza-associated encephalopathy, Molecular Genetics and Metabolism 104 (2011)265e272.

[90] J. Bastin, A. Lopes-Costa, F. Djouadi, Exposure to resveratrol triggers phar-macological correction of fatty acid utilization in human fatty acid oxidation-deficient fibroblasts, Human Molecular Genetics 20 (2011) 2048e2057.

[91] L. Zhang, W. Keung, V. Samokhvalov, W. Wang, G.D. Lopaschuk, Role of fattyacid uptake and fatty acid beta-oxidation in mediating insulin resistance inheart and skeletal muscle, Biochimica et biophysica acta 1801 (2010) 1e22.

tty acid b-oxidation in human: What can we learn from inborn fatty6/j.biochi.2013.05.012