Abnormal expression of HADH, an enzyme of fatty acid oxidation, affects tumor development and prognosis (Review).

Tumor occurrence and progression are closely associated with abnormal energy metabolism and energy metabolism associated with glucose, proteins and lipids. The reprogramming of energy metabolism is one of the hallmarks of cancer. As a form of energy metabolism, fatty acid metabolism includes fatty acid uptake, de novo synthesis and ß­oxidation. In recent years, the role of abnormal fatty acid ß­oxidation in tumors has gradually been recognized. Mitochondrial trifunctional protein (MTP) serves an important role in fatty acid ß­oxidation and HADH (two subtypes: α subunit, HADHA and ß subunit, HADHB) are important subunits of MTP. HADH participates in the steps of 2, 3 and 4 fatty acid ß­oxidation. However, there is no review summarizing the specific role of HADH in tumors. Therefore, the present study focused on HADH as the main indicator to explore the changes in fatty acid ß­oxidation in several types of tumors. The present review summarized the changes in HADH in 11 organs (cerebrum, oral cavity, esophagus, liver, pancreas, stomach, colorectum, lymph, lung, breast, kidney), the effect of up­ and downregulation and the relationship of HADH with prognosis. In summary, HADH can be either a suppressor or a promoter depending on where the tumor is located, which is closely associated with prognostic assessment. HADHA and HADHB have similar prognostic roles in known and comparable tumors.

Spermidine activates mitochondrial trifunctional protein and improves antitumor immunity in mice.

Spermidine (SPD) delays age-related pathologies in various organisms. SPD supplementation overcame the impaired immunotherapy against tumors in aged mice by increasing mitochondrial function and activating CD8+ T cells. Treatment of naïve CD8+ T cells with SPD acutely enhanced fatty acid oxidation. SPD conjugated to beads bound to the mitochondrial trifunctional protein (MTP). In the MTP complex, synthesized and purified from Escherichia coli, SPD bound to the α and ß subunits of MTP with strong affinity and allosterically enhanced their enzymatic activities. T cell-specific deletion of the MTP α subunit abolished enhancement of programmed cell death protein 1 (PD-1) blockade immunotherapy by SPD, indicating that MTP is required for SPD-dependent T cell activation.

Protein folding and unfolding: proline cis-trans isomerization at the c subunits of F1 FO -ATPase might open a high conductance ion channel.

The c subunits, which constitute the c-ring apparatus of the F1 FO -ATPase, could be the main components of the mitochondrial permeability transition pore (mPTP). The well-known modulator of the mPTP formation and opening is the cyclophilin D (CyPD), a peptidyl-prolyl cis-trans isomerase. On the loop, which connects the two hairpin α-helix of c subunit, is present the unique proline residue (Pro40 ) that could be a biological target of CyPD. Indeed, the proline cis-trans isomerization might provide the switch that interconverts the open/closed states of the pore by pulling out the c-ring lipid plug.

Oxylipin metabolism is controlled by mitochondrial ß-oxidation during bacterial inflammation.

Oxylipins are potent biological mediators requiring strict control, but how they are removed en masse during infection and inflammation is unknown. Here we show that lipopolysaccharide (LPS) dynamically enhances oxylipin removal via mitochondrial ß-oxidation. Specifically, genetic or pharmacological targeting of carnitine palmitoyl transferase 1 (CPT1), a mitochondrial importer of fatty acids, reveal that many oxylipins are removed by this protein during inflammation in vitro and in vivo. Using stable isotope-tracing lipidomics, we find secretion-reuptake recycling for 12-HETE and its intermediate metabolites. Meanwhile, oxylipin ß-oxidation is uncoupled from oxidative phosphorylation, thus not contributing to energy generation. Testing for genetic control checkpoints, transcriptional interrogation of human neonatal sepsis finds upregulation of many genes involved in mitochondrial removal of long-chain fatty acyls, such as ACSL1,3,4, ACADVL, CPT1B, CPT2 and HADHB. Also, ACSL1/Acsl1 upregulation is consistently observed following the treatment of human/murine macrophages with LPS and IFN-γ. Last, dampening oxylipin levels by ß-oxidation is suggested to impact on their regulation of leukocyte functions. In summary, we propose mitochondrial ß-oxidation as a regulatory metabolic checkpoint for oxylipins during inflammation.

HADHB, a fatty acid beta-oxidation enzyme, is a potential prognostic predictor in malignant lymphoma.

In haematological malignancies, such as malignant lymphoma, reprogramming of fatty acid metabolism favours tumour cell survival and drug resistance. Hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha (HADHA), an enzyme involved in fatty acid beta-oxidation (FAO), is overexpressed in high-grade lymphoma and is a predictor of poor prognosis in diffuse large B-cell lymphoma (DLBCL). HADHB forms a heterodimer with HADHA and functions as an FAO enzyme together with HADHA; however, the relevance of its expression in malignant lymphoma is unknown. In this study, we investigated the roles and antitumour effects of HADHB expression in malignant lymphoma. Immunohistochemical analysis showed that HADHB was frequently overexpressed in the high-grade lymphoma subtype. HADHB overexpression was observed in 68% (87/128) of DLBCL cases and was an independent predictor of poor prognosis (p=0.001). In vitro analysis demonstrated that HADHB knockdown suppressed cell proliferation in LCL-K and MD901 cells (p<0.05). Additionally, treatment with the FAO inhibitor, ranolazine, increased cell death in control cells compared with that in HADHB knockdown LCL-K and MD901 cells (p<0.01). Cell death was also suppressed by the ferroptosis inhibitor, ferrosatin-1, in LCL-K and MD901 cells (p<0.05). Collectively, these findings provide basic evidence for the development of new cell death-based therapies for refractory malignant lymphoma. We plan to perform prospective studies and preclinical studies using animal models to confirm these results.

MTP deficiency caused by HADHB mutations: Pathophysiology and clinical manifestations.

Mutations in the HADHB gene lead to Mitochondrial Trifunctional Protein (MTP) deficiency. MTP deficiency is a rare autosomal recessive disorder affecting long-chain fatty acid oxidation. Patients affected by MTP deficiency are unable to metabolize long-chain fatty-acids and suffer a variety of symptoms exacerbated during fasting. The three phenotypes associated with complete MTP deficiency are an early-onset cardiomyopathy and early death, an intermediate form with recurrent hypoketotic hypoglycemia and a sensorimotor neuropathy with episodic rhabdomyolysis with small amount of residual enzyme activities. This review aims to discuss the pathophysiological mechanisms and clinical manifestations of each phenotype, which appears different and linked to HADHB expression levels. Notably, the pathophysiology of the sensorimotor neuropathy is relatively unknown and we provide a hypothesis on the qualitative aspect of the role of acylcarnitine buildup in Schwann cells in MTP deficiency patients. We propose that acylcarnitine may exit the Schwann cell and alter membrane properties of nearby axons leading to axonal degeneration based on recent findings in different metabolic disorders.

Comprehensive miRNA and DNA Microarray Analyses Reveal the Response of Hepatic miR-203 and Its Target Gene to Protein Malnutrition in Rats.

Adequate protein nutrition is essential for good health. Effects of protein malnutrition in animals have been widely studied at the mRNA level with the development of DNA microarray technology. Although microRNAs (miRNAs) have attracted attention for their function in regulating gene expression and have been studied in several disciplines, fewer studies have clarified the effects of protein malnutrition on miRNA alterations. The present study aimed to elucidate the relationship between protein malnutrition and miRNAs. Six-week old Wistar male rats were fed a control diet (20% casein) or a low-protein diet (5% casein) for two weeks, and their livers were subjected to both DNA microarray and miRNA array analysis. miR-203 was downregulated and its putative target Hadhb (hydroxyacyl-CoA dehydrogenase ß subunit), known to regulate ß-oxidation of fatty acids, was upregulated by the low-protein diet. In an in vitro experiment, miR-203 or its inhibitor were transfected in HepG2 cells, and the pattern of Hadhb expression was opposite to that of miR-203 expression. In addition, to clarifying the hepatic miRNA profile in response to protein malnutrition, these results showed that a low-protein diet increased Hadhb expression through downregulation of miR-203 and induced ß-oxidation of fatty acids.

Mitochondrial trifunctional protein deficiency as a polyneuropathy etiology in childhood.

BACKGROUND: The mitochondrial trifunctional protein (MTP) is a multienzyme complex of the fatty acid betaoxidation cycle. Mitochondrial trifunctional protein deficiency (MTPD), a rare condition that leads to failure of converting certain fats to energy is characterized by decreased activity of three enzymes in the enzyme complex. Signs and symptoms of MTPD may present during infancy or later in life; those that begin after infancy include hypotonia, muscle pain, rhabdomyolysis, and peripheral neuropathy. We report a Turkish boy diagnosed with MTPD after being investigated for polyneuropathy of unknown origin since infancy. CASE: A 5.5-year-old male patient was admitted to our clinic with complaints of weakness in the arms and legs, physical inactivity compared to his peers, fatigue, weakness and, difficulty in climbing stairs since infancy. Electroneuromyography (ENMG) analysis showed moderate symmetric distal sensorimotor and axonal neuropathy. On the background of chronic polyneuropathy, the patient had acute relapsing episodes with progressively worsening severity in the follow-up period until 12.5 years of age. Whole exome sequencing (WES) was performed in the patient and, revealed that the patient had a homozygous c.1390G > A (p.Gly464Ser) pathogenic variant of the HADHB gene. Although rhabdomyolysis is a well defined accompanying clinical feature of MTPD, it was not present in our patient who only had worsening muscle weakness during attacks. CONCLUSION: On the background of chronic polyneuropathy and acute relapsing episodes triggered by fasting or illnesses and rhabdomyolysis physicians should suspect disorders of the fatty acid beta-oxidation cycle.

A long noncoding RNA regulates inflammation resolution by mouse macrophages through fatty acid oxidation activation.

Proper resolution of inflammation is vital for repair and restoration of homeostasis after tissue damage, and its dysregulation underlies various noncommunicable diseases, such as cardiovascular and metabolic diseases. Macrophages play diverse roles throughout initial inflammation, its resolution, and tissue repair. Differential metabolic reprogramming is reportedly required for induction and support of the various macrophage activation states. Here we show that a long noncoding RNA (lncRNA), lncFAO, contributes to inflammation resolution and tissue repair in mice by promoting fatty acid oxidation (FAO) in macrophages. lncFAO is induced late after lipopolysaccharide (LPS) stimulation of cultured macrophages and in Ly6Chi monocyte-derived macrophages in damaged tissue during the resolution and reparative phases. We found that lncFAO directly interacts with the HADHB subunit of mitochondrial trifunctional protein and activates FAO. lncFAO deletion impairs resolution of inflammation related to endotoxic shock and delays resolution of inflammation and tissue repair in a skin wound. These results demonstrate that by tuning mitochondrial metabolism, lncFAO acts as a node of immunometabolic control in macrophages during the resolution and repair phases of inflammation.

Seizure-induced impairment in neuronal ketogenesis: Role of zinc-α2-glycoprotein in mitochondria.

Ketone bodies (KBs) were known to suppress seizure. Untraditionally, neurons were recently reported to utilize fatty acids and produce KBs, but the effect of seizure on neuronal ketogenesis has not been researched. Zinc-α2-glycoprotein (ZAG) was reported to suppress seizure via unclear mechanism. Interestingly, ZAG was involved in fatty acid ß-oxidation and thus may exert anti-epileptic effect by promoting ketogenesis. However, this promotive effect of ZAG on neuronal ketogenesis has not been clarified. In this study, we performed immunoprecipitation and mass spectrometry to identify potential interaction partners with ZAG. The mechanisms of how ZAG translocated into mitochondria were determined by quantitative coimmunoprecipitation after treatment with apoptozole, a heat shock cognate protein 70 (HSC70) inhibitor. ZAG level was modulated by lentivirus in neurons or adeno-associated virus in rat brains. Seizure models were induced by magnesium (Mg2+ )-free artificial cerebrospinal fluid in neurons or intraperitoneal injection of pentylenetetrazole kindling in rats. Ketogenesis was determined by cyclic thio-NADH method in supernatant of neurons or brain homogenate. The effect of peroxisome proliferator-activated receptor γ (PPARγ) on ZAG expression was examined by Western blot, quantitative real-time polymerase chain reaction (qRT-PCR) and chromatin immunoprecipitation qRT-PCR. We found that seizure induced ketogenesis deficiency via a ZAG-dependent mechanism. ZAG entered mitochondria through a HSC70-dependent mechanism, promoted ketogenesis by binding to four ß-subunits of long-chain L-3-hydroxyacyl-CoA dehydrogenase (HADHB) and alleviated ketogenesis impairment in a neuronal seizure model and pentylenetetrazole-kindled epileptic rats. Additionally, PPARγ activation up-regulated ZAG expression by binding to promoter region of AZGP1 gene and promoted ketogenesis through a ZAG-dependent mechanism.

Targeting viperin to the mitochondrion inhibits the thiolase activity of the trifunctional enzyme complex.

Understanding the mechanisms by which viruses evade host cell immune defenses is important for developing improved antiviral therapies. In an unusual twist, human cytomegalovirus co-opts the antiviral radical SAM enzyme viperin (virus-inhibitory protein, endoplasmic reticulum-associated, interferon-inducible) to enhance viral infectivity. This process involves translocation of viperin to the mitochondrion, where it binds the ß-subunit (HADHB) of the mitochondrial trifunctional enzyme complex that catalyzes thiolysis of ß-ketoacyl-CoA esters as part of fatty acid ß-oxidation. Here we investigated how the interaction between these two enzymes alters their activities and affects cellular ATP levels. Experiments with purified enzymes indicated that viperin inhibits the thiolase activity of HADHB, but, unexpectedly, HADHB activates viperin, leading to synthesis of the antiviral nucleotide 3'-deoxy-3',4'-didehydro-CTP. Measurements of enzyme activities in lysates prepared from transfected HEK293T cells expressing these enzymes mirrored the findings obtained with purified enzymes. Thus, localizing viperin to mitochondria decreased thiolase activity, and coexpression of HADHB significantly increased viperin activity. Furthermore, targeting viperin to mitochondria also increased the rate at which HADHB is retrotranslocated out of mitochondria and degraded, providing an additional mechanism by which viperin reduces HADHB activity. Targeting viperin to mitochondria decreased cellular ATP levels by more than 50%, consistent with the enzyme disrupting fatty acid catabolism. These results provide biochemical insight into the mechanism by which human cytomegalovirus subverts viperin; they also provide a biochemical rationale for viperin's recently discovered role in regulating thermogenesis in adipose tissues.

Identification and functional characterization of mutations within HADHB associated with mitochondrial trifunctional protein deficiency.

Mitochondrial trifunctional protein (MTP) deficiency is a rare autosomal recessive disorder with several phenotypes. Neuromyopathic form of MTP deficiency is characterized by infantile or juvenile-onset, progressive peripheral neuropathy and rhabdomyolysis. To date, only one Chinese patient harboring homozygous c. 739C>T (p.R247C) in HADHB has been reported. Here, using whole exome sequencing (WES), we identified a compound heterozygote of c.407T>C (p.M136T) and c.421G>A (p.A141T) within HADHB in a Chinese MTP deficiency patient of neuromyopathic form. In vitro cell functional studies were performed to evaluate the effect of mutations on MTP complex expression and subcellular location, which revealed that p.M136T and p.A141T mutations compromised MTP complex stability but not altered subcellular localization, resulting in lower protein level at 37 °C but higher at 30 °C. These results indicated that both mutations were pathogenic through a loss-of-function mechanism and temperature-sensitive leading to their correlation with the mild phenotype. The current study broadens the genetic spectrum of HADHB and highlights the importance of screening fatty acid oxidation deficiency-related gene mutations among patients with intermittent rhabdomyolysis, as in the patient reported here, although extremely rare.

HADHA and HADHB gene associated phenotypes - Identification of rare variants in a patient cohort by Next Generation Sequencing.

The heterooctameric mitochondrial trifunctional protein (MTP), composed of four α- and ß-subunits harbours three enzymes that each perform a different function in mitochondrial fatty acid ß-oxidation. Pathogenic variants in the MTP genes (HADHA and HADHB) cause MTP deficiency, a rare autosomal recessive metabolic disorder characterized by phenotypic heterogeneity ranging from severe, early-onset, cardiac disease to milder, later-onset, myopathy and neuropathy. Since metabolic myopathies and neuropathies are a group of rare genetic disorders and their associated muscle symptoms may be subtle, the diagnosis is often delayed. Here we evaluated data of 161 patients with myopathy and 242 patients with neuropathy via next generation sequencing (NGS) and report the diagnostic yield in three patients of this cohort by the detection of disease-causing variants in the HADHA or HADHB gene. The mitigated phenotypes of this treatable disease were missed by the newborn screening, highlighting the importance of phenotype-based NGS analysis in patients with rare and clinically very variable disorders such as MTP deficiency.

Expression of miR-33 from an SREBP2 intron inhibits the expression of the fatty acid oxidation-regulatory genes CROT and HADHB in chicken liver.

1. Limiting the growth of adipose tissue in chickens is a major issue in the poultry industry. In chickens, de novo synthesis of lipids occurs primarily in the liver. Thus, it is necessary to understand how fatty acid accumulation in the liver is controlled. The miR-33 is an intronic microRNA (miRNA) of the chicken sterol regulatory element binding transcription factor 2 (SREBF2), which is a master switch in activating many genes involved in the uptake and synthesis of cholesterol, triglycerides, fatty acids and phospholipids. 2. In the current study, the genes CROT and HADHB known to encode enzymes critical for fatty acid oxidation were predicted to be potential targets of miR-33 in chickens via the miRNA target prediction programs 'miRanda' and 'TargetScan'. Co-transfection and dual-luciferase reporter assays showed that the expression of luciferase reporter gene linked to the 3'-untranslated region (3'UTR) of the chicken CROT and HADHB mRNA was down-regulated by overexpression of the chicken miR-33 (P < 0.05). This down-regulation was completely abolished when the predicted miR-33 target sites in the CROT and HADHB 3'UTR were mutated. 3. Transfecting miR-33 mimics into the LMH cells led to a decrease in the mRNA expression of CROT and HADHB (P < 0.01), and this transfection had a similar effect on the proteins (P < 0.05). In contrast, the expression of CROT in primary chicken hepatocytes was up-regulated after transfection with the miR-33 inhibitor LNA-anti-miR-33 (P < 0.05). 4. Using quantitative RT-PCR, it was shown that the expression of miR-33 was increased in the chicken liver from day 0 to day 49 of age, whereas the CROT and HADHB mRNA levels decreased during the same period. 5. These findings support the conclusion that miR-33 might play an important role in lipid metabolism in the chicken liver by negatively regulating the expression of the CROT and HADHB genes, which encode enzymes critical for lipid oxidation.

HADHB mutations cause infantile-onset axonal Charcot-Marie-Tooth disease: A report of two cases.

Mitochondrial trifunctional protein deficiency (MTPD) is a rare disorder caused by mutations in the HADHA and HADHB genes. Here, we report on two Han Chinese patients with HADHB mutation-associated infantile axonal Charcot-Marie-Tooth disease (IACMT). Both patients were unrelated. Case 1 was a 19-year-old man, and case 2 was a 5-year-old boy. Both had delayed motor development and slowly-progressing distal muscle weakness with areflexia and foot deformities. The electrophysiology findings were compatible with axonal polyneuropathy in both patients. Blood tandem mass spectrometry showed increased concentrations of multiple acylcarnitines. Nerve biopsies showed axonal neuropathy with a moderate loss of myelinated fibers. Gene analysis identified two compound heterozygous mutations (c.184A>G/c.340A>G and c.488G>A/c.1175C>T, respectively) in the HADHB gene. The c.488G>A mutation was novel. This study broadens the phenotype of MTPD and suggests that the genetic testing of patients suffering from IACMT should include the HADHB gene.
.

Integrated analyses of multi-omics reveal global patterns of methylation and hydroxymethylation and screen the tumor suppressive roles of HADHB in colorectal cancer.

Background: DNA methylation is an important epigenetic modification, associated with gene expression. 5-Methylcytosine and 5-hydroxymethylcytosine are two epigenetic hallmarks that maintain the equilibrium of epigenetic reprogramming. Disequilibrium in genomic methylation leads to carcinogenesis. The purpose of this study was to elucidate the epigenetic mechanisms of DNA methylation and hydroxymethylation in the carcinogenesis of colorectal cancer. Methods: Genome-wide patterns of DNA methylation and hydroxymethylation in six paired colorectal tumor tissues and corresponding normal tissues were determined using immunoprecipitation and sequencing. Transcriptional expression was determined by RNA sequencing (RNA-Seq). Groupwise differential methylation regions (DMR), differential hydroxymethylation regions (DhMR), and differentially expressed gene (DEG) regions were identified. Epigenetic biomarkers were screened by integrating DMR, DhMR, and DEGs and confirmed using functional analysis. Results: We identified a genome-wide distinct hydroxymethylation pattern that could be used as an epigenetic biomarker for clearly differentiating colorectal tumor tissues from normal tissues. We identified 59,249 DMRs, 187,172 DhMRs, and 948 DEGs by comparing between tumors and normal tissues. After cross-matching genes containing DMRs or DhMRs with DEGs, we screened seven genes that were aberrantly regulated by DNA methylation in tumors. Furthermore, hypermethylation of the HADHB gene was persistently found to be correlated with downregulation of its transcription in colorectal cancer (CRC). These findings were confirmed in other patients of colorectal cancer. Tumor functional analysis indicated that HADHB reduced cancer cell migration and invasiveness. These findings suggested its possible role as a tumor suppressor gene (TSG). Conclusion: This study reveals the global patterns of methylation and hydroxymethylation in CRC. Several CRC-associated genes were screened with multi-omic analysis. Aberrant methylation and hydroxymethylation were found to be in the carcinogenesis of CRC.

Nuclear Receptor Nur77 Facilitates Melanoma Cell Survival under Metabolic Stress by Protecting Fatty Acid Oxidation.

Fatty acid oxidation (FAO) is crucial for cells to overcome metabolic stress by providing ATP and NADPH. However, the mechanism by which FAO is regulated in tumors remains elusive. Here we show that Nur77 is required for the metabolic adaptation of melanoma cells by protecting FAO. Glucose deprivation activates ERK2 to phosphorylate and induce Nur77 translocation to the mitochondria, where Nur77 binds to TPß, a rate-limiting enzyme in FAO. Although TPß activity is normally inhibited by oxidation under glucose deprivation, the Nur77-TPß association results in Nur77 self-sacrifice to protect TPß from oxidation. FAO is therefore able to maintain NADPH and ATP levels and prevent ROS increase and cell death. The Nur77-TPß interaction further promotes melanoma metastasis by facilitating circulating melanoma cell survival. This study demonstrates a novel regulatory function of Nur77 with linkage of the FAO-NADPH-ROS pathway during metabolic stress, suggesting Nur77 as a potential therapeutic target in melanoma.

Genetic Dissection of the Impact of miR-33a and miR-33b during the Progression of Atherosclerosis.

As an important regulator of macrophage cholesterol efflux and HDL biogenesis, miR-33 is a promising target for treatment of atherosclerosis, and numerous studies demonstrate that inhibition of miR-33 increases HDL levels and reduces plaque burden. However, important questions remain about how miR-33 impacts atherogenesis, including whether this protection is primarily due to direct effects on plaque macrophages or regulation of lipid metabolism in the liver. We demonstrate that miR-33 deficiency in Ldlr-/- mice promotes obesity, insulin resistance, and hyperlipidemia but does not impact plaque development. We further assess how loss of miR-33 or addition of miR-33b in macrophages and other hematopoietic cells impact atherogenesis. Macrophage-specific loss of miR-33 decreases lipid accumulation and inflammation under hyperlipidemic conditions, leading to reduced plaque burden. Therefore, the pro-atherogenic effects observed in miR-33-deficient mice are likely counterbalanced by protective effects in macrophages, which may be the primary mechanism through which anti-miR-33 therapies reduce atherosclerosis.

Clinical and molecular investigation of 14 Japanese patients with complete TFP deficiency: a comparison with Caucasian cases.

Mitochondrial trifunctional protein (TFP) deficiency is an inherited metabolic disorder of mitochondrial fatty-acid oxidation. Isolated long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is often reported in Caucasian countries due to a common mutation. However, the molecular and clinical basis of complete TFP deficiency has not been extensively reported. In this study, 14 Japanese cases (13 families) with complete TFP deficiency, including 9 previously reported cases, were analyzed to clarify the clinical and molecular characteristics of TFP deficiency. The clinical types of the 14 patients were as follows: 12 cases of neonatal (n=7) or myopathic (n=5) types and 2 cases of intermediate type. Peripheral neuropathy was found in four cases and hypocalcemia due to hypoparathyroidism, which is rarely reported in Caucasian patients, had developed in four cases. Maternal hemolysis, elevated liver enzymes and low platelet count syndrome and acute fatty liver of pregnancy were noted in two and one mothers, respectively. Fourteen mutations were identified in 26 alleles in Japanese patients, including two novel mutations (HADHA: c.361C>T, and HADHA-HADHB: g.26233880_ 26248855del), although no common mutations were found. This study suggests that the molecular and clinical aspects of Japanese patients with TFP deficiencies differ from those of Caucasian patients.

Mitochondrial trifunctional protein deficiency: an adult patient with similar progress to Charcot-Marie-Tooth disease.

A 45-year-old man presented to us due to slowly progressive muscle weakness and sensory disturbances in his lower limbs since his 40's. He reported multiple episodes of exercise-induced severe muscle fatigue and brown urine in his childhood, which disappeared by age 20. A nerve conduction study showed peripheral axonal neuropathy and then Charcot-Marie-Tooth disease (CMT) was considered as the most likely diagnosis; however, exome sequencing failed to identify a mutation in the known genes of CMTs. Since age 55, he recurrently developed severe rhabdomyolysis that required hospitalization. On suspicion of lipid metabolism disorders, we performed serum acylcarnitine analysis, and which revealed mildly elevated long-chain fatty acids. We re-examined variants obtained via exome sequencing and found a mutation in HADHB. Mitochondrial trifunctional protein (MTP) deficiency is a rare autosomal recessive disorder of mitochondrial fatty acid beta-oxidation caused by HADHA or HADHB mutation. It can be a life-threatening multiorgan disorder with early infantile onset, but it can also present in childhood or adolescence with peripheral neuropathy and recurrent rhabdomyolysis. This case of adult-diagnosed MTP deficiency was characterized by slowly progressive peripheral neuropathy masquerading CMT in addition to muscular symptoms. MTP deficiency should be considered in patients with the combination of peripheral neuropathy and recurrent rhabdomyolysis.