Effects of higher dietary protein intake on energy balance and metabolic control in children with long-chain 3-hydroxy acyl-CoA dehydrogenase (LCHAD) or trifunctional protein (TFP) deficiency

Successful management of rhabdomyolysis with triheptanoin in a child with severe long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency

Early-onset long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency is a fatty acid β-oxidation disorder with a poor prognosis. Triheptanoin, an anaplerotic oil with odd-chain fatty acids can improve the disease course. The female patient presented here was diagnosed at the age of 4 months, and treatment was started as fat restriction, frequent feeding, and standard medium-chain triglyceride supplementation. In follow-up, she had frequent rhabdomyolysis episodes (∼8 per year). At the age of six, she had 13 episodes in 6 months, and triheptanoin was started as part of a compassionate use program. Following unrelated hospital stays due to multisystem inflammatory syndrome in children and a bloodstream infection, she had only 3 rhabdomyolysis episodes, and hospitalized days decreased from 73 to 11 during her first year with triheptanoin. Triheptanoin drastically decreased the frequency and severity of rhabdomyolysis, but progression of retinopathy was not altered.

Anthropometric Parameters in Patients with Fatty Acid Oxidation Disorders: A Case-Control Study, Systematic Review and Meta-Analysis

This study compared the anthropometric parameters of patients with fatty acid oxidation disorders (FAOD) and healthy controls, showing an increased prevalence of abnormal body weight (overweight and obesity) in the FAOD group. First, differences in BMI, BMI percentiles and z-scores, and weight and weight percentiles were compared in a cohort of 39 patients with FAOD and 156 healthy controls, as well as between patients born before and after the introduction of a populational newborn screening programme (NBS) in 2014 in Poland. We also performed a systematic literature review yielding 12 studies mentioning anthropometric parameters in 80 FAOD patients and 121 control subjects, followed by a meta-analysis of data from 8 studies and our cohort. There were significant differences in body weight percentiles (p = 0.001), BMI (p = 0.022), BMI percentiles (p = 0.003) and BMI z-scores (p = 0.001) between FAOD patients and controls in our cohort but not between pre- and post-newborn-screening patients. The meta-analysis did not show any differences in weight and BMI in all tested subgroups, i.e., all FAOD patients vs. controls, medium-chain acyl-CoA dehydrogenase (MCADD) patients vs. controls and patients with FAOD types other than MCAD vs. controls. These results, however, should be interpreted with caution due to the overall low quality of evidence as assessed by GRADE, the small sample sizes and the significant heterogeneity of the included data.

Charcot-Marie-Tooth Disease With Episodic Rhabdomyolysis Due to Two Novel Mutations in the β Subunit of Mitochondrial Trifunctional Protein and Effective Response to Modified Diet Therapy

A 29-year-old female experienced chronic progressive peripheral neuropathy since childhood and was diagnosed with Charcot–Marie–Tooth disease (CMT) at age 15. She developed recurrent, fever-induced rhabdomyolysis (RM) at age 24. EMG studies showed decreased amplitude of compound muscle action potential, declined motor conductive velocity, and absence of sensor nerve action potential. Acylcarnitine analysis revealed elevated C16-OH, C18-OH, and C18:1-OH. Muscle biopsy showed scattered foci of necrotic myofibers invaded by macrophages, occasional regenerating fibers, and remarkable muscle fiber type grouping. Whole-exome sequencing identified two novel heterozygous mutations: c.490G>A (p.G164S) and c.686G>A (p.R229Q) in HADHB gene encoding the β-subunit of mitochondrial trifunctional protein (MTP). Reduction of long-chain fatty acid via dietary restrictions alleviated symptoms effectively. Our study indicates that the defect of the MTP β-subunit accounts for both CMT and RM in the same patient and expands the clinical spectrum of disorders caused by the HADHB mutations. Our systematic review of all MTPD patients with dietary treatment indicates that the effect of dietary treatment is related to the age of onset and the severity of symptoms.

Dietary management and major clinical events in patients with long-chain fatty acid oxidation disorders enrolled in a phase 2 triheptanoin study

Background & aims:

Long-chain fatty acid oxidation disorders (LC-FAOD) are rare, life-threatening, autosomal recessive disorders that lead to energy depletion and major clinical events (MCEs), such as acute metabolic crises of hypoglycemia, cardiomyopathy, and rhabdomyolysis. The aim of this study was to report a post hoc analysis of diet diary data from the phase 2 UX007-CL201 study (NCT01886378).

Methods:

In the single-arm, open-label, phase 2 UX007-CL201 study, the safety and efficacy of 78 weeks of treatment with triheptanoin, an odd-carbon, medium-chain triglyceride consisting of three 7-carbon fatty acids on a glycerol backbone, was investigated in subjects with LC-FAOD versus a retrospective 78-week period when subjects were optimally managed under published dietary guidelines. Subject dietary reports were collected to analyze the relationship between diet, triheptanoin treatment, and MCEs. Referring metabolic physicians completed a survey on patient management and clinical outcomes before and after initiation of triheptanoin. Before initiating triheptanoin, subjects received a mean daily caloric intake (DCI) of 17.4% from medium-chain triglycerides (MCT). During the study, subjects received a mean of 27.5% DCI from triheptanoin. Protein (13.7% vs 14.5% DCI), long-chain fat (13.1% vs 10.5% DCI), and carbohydrate (55.3% vs 47.1% DCI) intake were consistent between the pre-triheptanoin and triheptanoin treatment periods, respectively.

Results:

Following 78 weeks of treatment, mean annualized MCE rate decreased by 48.1% (p = 0.021) and mean annualized MCE event-day rate decreased by 50.3% (p = 0.028). A weak association existed between improvement in annualized MCE rate and change in percent DCI from MCT (Spearman rank correlation: r = −0.38; 95% CI: −0.675, 0.016). However, there was large variability in the association and no specific pattern of change for larger or smaller changes in dose. Seventy-two percent of physicians reported that triheptanoin had a clinically meaningful benefit on medical management of their patients.

Conclusions:

Treatment with triheptanoin at the protocol-specified dose decreased the rate of MCEs in patients with LC-FAOD independently from other dietary changes between the pre-triheptanoin and triheptanoin treatment periods.

Trial registration:ClinicalTrials.gov identifier: NCT01886378.

Clinical manifestations and management of fatty acid oxidation disorders

Fatty acid oxidation disorders (FAOD) are a group of rare, autosomal recessive, metabolic disorders caused by variants of the genes for the enzymes and proteins involved in the transport and metabolism of fatty acids in the mitochondria. Those affected by FAOD are unable to convert fatty acids into tricarboxylic acid cycle intermediates such as acetyl-coenzyme A, resulting in decreased adenosine triphosphate and glucose for use as energy in a variety of high-energy-requiring organ systems. Signs and symptoms may manifest in infants but often also appear in adolescents or adults during times of increased metabolic demand, such as fasting, physiologic stress, and prolonged exercise. Patients with FAOD present with a highly heterogeneous clinical spectrum. The most common clinical presentations include hypoketotic hypoglycemia, liver dysfunction, cardiomyopathy, rhabdomyolysis, and skeletal myopathy, as well as peripheral neuropathy and retinopathy in some subtypes. Despite efforts to detect FAOD through newborn screening and manage patients early, symptom onset can be sudden and serious, even resulting in death. Therefore, it is critical to identify quickly and accurately the key signs and symptoms of patients with FAOD to manage metabolic decompensations and prevent serious comorbidities.

Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach

The nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD) is the fourth in a series of web-based guidelines focusing on the diet treatment for inherited metabolic disorders and follows previous publication of guidelines for maple syrup urine disease (2014), phenylketonuria (2016) and propionic acidemia (2019). The purpose of this guideline is to establish harmonization in the treatment and monitoring of individuals with VLCAD of all ages in order to improve clinical outcomes. Six research questions were identified to support guideline development on: nutrition recommendations for the healthy individual, illness management, supplementation, monitoring, physical activity and management during pregnancy. This report describes the methodology used in its development including review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; expert input through two Delphi surveys and a nominal group process; and external review from metabolic physicians and dietitians. It includes the summary statements of the nutrition management recommendations for each research question, followed by a standardized rating based on the strength of the evidence. Online, open access of the full published guideline allows utilization by health care providers, researchers and collaborators who advise, advocate and care for individuals with VLCAD and their families and can be accessed from the Genetic Metabolic Dietitians International (https://GMDI.org) and Southeast Regional Genetics Network (https://southeastgenetics.org/ngp) websites.

Higher dietary protein intake preserves lean body mass, lowers liver lipid deposition, and maintains metabolic control in participants with long-chain fatty acid oxidation disorders

Medical nutrition therapy for long-chain fatty acid oxidation disorders (LC-FAODs) currently emphasizes fasting avoidance, restricted dietary long-chain fatty acid intake, supplementation with medium chain triglycerides, and increased carbohydrate intake. We hypothesize that increasing dietary protein intake relative to carbohydrate intake would preserve metabolic control yet induce physical benefits including reduced hepatic lipogenesis. Therefore, we compared two dietary approaches with similar fat intake but different carbohydrate to protein ratios in participants diagnosed with LC-FAODs. Thirteen participants were enrolled and randomized into either a high-protein (PRO) or a high-carbohydrate (CHO) diet for 4 months. Baseline and 4-month assessments included body composition, ectopic lipid deposition, and resting energy expenditure. End of study assessments also included total energy expenditure, metabolic responses to oral feedings, and whole-body fatty acid oxidation capacity. At the end of the dietary intervention, both groups had similar energy expenditure, fat and glucose oxidation rates, and glucolipid responses to mixed meal and oral glucose loads. Neither dietary group experienced worsening symptoms related to their LC-FAOD. Compared to the CHO group, the PRO group exhibited increased blood levels of short-chain acylcarnitines, reduced intrahepatic lipid content, and maintained lean body mass while the CHO group lost lean mass. In patients with LC-FAODs, increasing protein intake maintained metabolic control, reduced liver fat without risk of metabolic decompensation, and helped preserve lean body mass. We propose that a modest increase in dietary protein along with fasting avoidance and fat restriction may improve body composition and energy expenditure in patients with LC-FAODs.

Exome Sequencing Provides Evidence of Polygenic Adaptation to a Fat-Rich Animal Diet in Indigenous Siberian Populations

Siberia is one of the coldest environments on Earth and has great seasonal temperature variation. Long-term settlement in northern Siberia undoubtedly required biological adaptation to severe cold stress, dramatic variation in photoperiod, and limited food resources. In addition, recent archeological studies show that humans first occupied Siberia at least 45,000 years ago; yet our understanding of the demographic history of modern indigenous Siberians remains incomplete. In this study, we use whole-exome sequencing data from the Nganasans and Yakuts to infer the evolutionary history of these two indigenous Siberian populations. Recognizing the complexity of the adaptive process, we designed a model-based test to systematically search for signatures of polygenic selection. Our approach accounts for stochasticity in the demographic process and the hitchhiking effect of classic selective sweeps, as well as potential biases resulting from recombination rate and mutation rate heterogeneity. Our demographic inference shows that the Nganasans and Yakuts diverged ∼12,000-13,000 years ago from East-Asian ancestors in a process involving continuous gene flow. Our polygenic selection scan identifies seven candidate gene sets with Siberian-specific signals. Three of these gene sets are related to diet, especially to fat metabolism, consistent with the hypothesis of adaptation to a fat-rich animal diet. Additional testing rejects the effect of hitchhiking and favors a model in which selection yields small allele frequency changes at multiple unlinked genes.

Role of 3-Hydroxy Fatty Acid-Induced Hepatic Lipotoxicity in Acute Fatty Liver of Pregnancy

Acute fatty liver of pregnancy (AFLP), a catastrophic illness for both the mother and the unborn offspring, develops in the last trimester of pregnancy with significant maternal and perinatal mortality. AFLP is also recognized as an obstetric and medical emergency. Maternal AFLP is highly associated with a fetal homozygous mutation (1528G>C) in the gene that encodes for mitochondrial long-chain hydroxy acyl-CoA dehydrogenase (LCHAD). The mutation in LCHAD results in the accumulation of 3-hydroxy fatty acids, such as 3-hydroxy myristic acid, 3-hydroxy palmitic acid and 3-hydroxy dicarboxylic acid in the placenta, which are then shunted to the maternal circulation leading to the development of acute liver injury observed in patients with AFLP. In this review, we will discuss the mechanistic role of increased 3-hydroxy fatty acid in causing lipotoxicity to the liver and in inducing oxidative stress, mitochondrial dysfunction and hepatocyte lipoapoptosis. Further, we also review the role of 3-hydroxy fatty acids in causing placental damage, pancreatic islet β-cell glucolipotoxicity, brain damage, and retinal epithelial cells lipoapoptosis in patients with LCHAD deficiency.

The Relationship between Dietary Intake, Growth, and Body Composition in Inborn Errors of Intermediary Protein Metabolism

OBJECTIVES

To examine relationships between dietary intake, growth and body composition patterns in patients with inborn errors of intermediary protein metabolism and to determine a safe protein:energy ratio (P:E ratio) associated with optimal growth outcomes.

STUDY DESIGN

Retrospective longitudinal data of growth and dietary intake in patients (n = 75) with isovaleric acidemia (IVA; n = 7), methylmalonic acidemia/propionic acidemia (MMA/PA; n = 14), urea cycle defects (UCD; n = 44), classical maple syrup urine disease (MSUD; n = 10) were collected. Prospective longitudinal data of growth, dietary intake, and body composition from 21 patients: IVA (n = 5), MMA/PA (n = 6), UCD (n = 7), and MSUD (n = 3) were collected at clinic visits.

RESULTS

Fifty-two of 75 (66%), 49 of 74 (68%), and 44 of 65 (68%) patients had a z-score of 0 (±1) for lifetime weight, height, and body mass index, respectively. Patients with MMA/PA had the lowest median height and weight z-scores, and MSUD patients had highest median body mass index z-score at all ages. In IVA, MMA/PA, and UCD, total natural protein intake met or exceeded the Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO)/United Nations University (UNU) recommended safe levels. Median percentage fat mass was 17.6% in IVA, 20.7% in MMA/PA, 19.4% in UCD, and 17.8% in MSUD. There was a significant negative correlation between percentage fat mass and total protein intake in IVA, MMA/PA, and UCD (r = -0.737; P = .010). The correlation between the P:E ratio and growth variables in IVA, MMA/PA, and UCD suggest a safe P:E ratio (>1.5 to < 2.9) g protein:100 kcal/day.

CONCLUSION

Growth outcomes in inborn errors of intermediary protein metabolism are not always ideal. Most patients with IVA, MMA/PA, and UCD consume sufficient natural protein to meet FAO/WHO/UNU recommendations. A P:E ratio range of (>1.5 to < 2.9)g protein/100 kcal/day correlates with optimal growth outcomes.

VLCAD deficiency: Follow-up and outcome of patients diagnosed through newborn screening in Victoria

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency is an inherited metabolic disorder of fatty acid oxidation. Treatment practices of the disorder have changed over the past 10-15years since this disorder was included in newborn screening programs and patients were diagnosed pre-symptomatically. A genotype-phenotype correlation has been suggested but the discovery of novel mutations make this knowledge limited. Herein, we describe our experience in treating patients (n=22) diagnosed through newborn screening and mutational confirmation and followed up over a median period of 104months. We report five novel mutations. In 2013 we formalised our treatment protocol, which essentially follows a European consensus paper from 2009 and our own experience. The prescribed low natural fat diet is relaxed for patients who are asymptomatic when reaching age 5years but medium-chain triglyceride oil is recommended before and after physical activity regardless of age. Metabolic stability, growth, development and cardiac function are satisfactory in all patients. There were no episodes of encephalopathy or hypoglycaemia but three patients had episodes of muscle pain with our without rhabdomyolysis. Body composition studies showed a negative association between dietary protein intake and percent body fat. Larger patient cohort and longer follow up time are required for further elucidation of genotype-phenotype correlations and for establishing the role of dietary protein in metabolic stability and long-term healthier body composition in patients with VLCAD deficiency.

Earlier diagnosis and strict diets improve the survival rate and clinical course of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

AIM

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a severe metabolic disease that, without treatment, often leads to premature death or serious handicap. The aim of this study was to evaluate the clinical course of LCHADD with the homozygous 1528G>C (E510Q) mutation when patients underwent strict dietary treatment.

METHODS

From 1997 to 2010, 16 patients with LCHADD were diagnosed in Finland. They were followed up, and data were prospectively collected as they emerged. Clinical data before diagnosis were retrospectively collected from hospital records. This cohort was compared with an earlier cohort of patients diagnosed from 1976 to 1996.

RESULTS

The disease presented from birth to five months of age with failure to thrive, hypotonia, hepatomegaly, metabolic acidosis, cardiomyopathy and hypoketotic hypoglycaemia. In this cohort, the therapeutic delay was 0-30 days and the survival rate at the end of the study was 62.5% compared with 10-year survival rate of 14.3% for the earlier cohort. The survivors were in good overall condition, but some of them had developed mild retinopathy or mild neuropathy.

CONCLUSION

Earlier diagnosis and stricter dietary regimes improved the survival rates and clinical course of patients with LCHADD in Finland. However, improvements in therapy are still needed to prevent the development of long-term complications, such as retinopathy and neuropathy.

Deletion of Cyclophilin D Impairs β-Oxidation and Promotes Glucose Metabolism

Cyclophilin D (CypD) is a mitochondrial matrix protein implicated in cell death, but a potential role in bioenergetics is not understood. Here, we show that loss or depletion of CypD in cell lines and mice induces defects in mitochondrial bioenergetics due to impaired fatty acid β-oxidation. In turn, CypD loss triggers a global compensatory shift towards glycolysis, with transcriptional upregulation of effectors of glucose metabolism, increased glucose consumption and higher ATP production. In vivo, the glycolytic shift secondary to CypD deletion is associated with expansion of insulin-producing β-cells, mild hyperinsulinemia, improved glucose tolerance, and resistance to high fat diet-induced liver damage and weight gain. Therefore, CypD is a novel regulator of mitochondrial bioenergetics, and unexpectedly controls glucose homeostasis, in vivo.

Increased and early lipolysis in children with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency during fast

Children with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHAD) have a defect in the degradation of long-chain fatty acids and are at risk of hypoketotic hypoglycemia and insufficient energy production as well as accumulation of toxic fatty acid intermediates. Knowledge on substrate metabolism in children with LCHAD deficiency during fasting is limited. Treatment guidelines differ between centers, both as far as length of fasting periods and need for night feeds are concerned. To increase the understanding of fasting intolerance and improve treatment recommendations, children with LCHAD deficiency were investigated with stable isotope technique, microdialysis, and indirect calometry, in order to assess lipolysis and glucose production during 6 h of fasting. We found an early and increased lipolysis and accumulation of long chain acylcarnitines after 4 h of fasting, albeit no patients developed hypoglycemia. The rate of glycerol production, reflecting lipolysis, averaged 7.7 ± 1.6 µmol/kg/min, which is higher compared to that of peers. The rate of glucose production was normal for age; 19.6 ± 3.4 µmol/kg/min (3.5 ± 0.6 mg/kg/min). Resting energy expenditure was also normal, even though the respiratory quotient was increased indicating mainly glucose oxidation. The results show that lipolysis and accumulation of long chain acylcarnitines occurs before hypoglycemia in fasting children with LCHAD, which may indicate more limited fasting tolerance than previously suggested.

New ways of defining protein and energy relationships in inborn errors of metabolism

Dietary restrictions required to manage individuals with inborn errors of metabolism (IEM) are essential for metabolic control, however may result in an increased risk to both short and long-term nutritional status. Dietary factors most likely to influence nutritional status include energy intake, protein quality and quantity, micronutrient intake and the frequency and extent to which the diet must be altered during periods of increased physical or metabolic stress. Patients on the most restrictive diets, including those with intakes consisting of low levels of natural protein or those with recurrent illness or frequent metabolic decompensation carry the most nutritional risk. Due to the difficulties in determining condition specific requirements, dietary intake recommendations and nutritional monitoring tools used in patients with IEM are the same as, or extrapolated from, those used in healthy populations. As a consequence, evidence is lacking for the safest dietary prescriptions required to manage these patients long term, as tolerance to dietary therapy is generally described in terms of metabolic stability rather than long term nutritional and health outcomes. As the most frequent therapeutic dietary manipulation in IEM is alteration in dietary protein, and as protein status is critically dependent on adequate energy provision, the use of a Protein to Energy ratio (P:E ratio) as an additional tool will better define the relationship between these critical components. This could accurately define dietary quality and ensure that not only an adequate, but also a safe and balanced intake is provided.

Use of propofol for short duration procedures in children with long chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) or trifunctional protein (TFP) deficiencies

The medication propofol, commonly used for anesthesia, has been avoided in patients with mitochondrial fatty acid oxidation disorders (FAODs) due to concerns that it contains long-chain fatty acids (LCFAs), and because of reports of severe side effects in some critically ill patients receiving high-dose propofol infusions that mimic some of the symptoms regularly found in FAOD patients. In this secondary analysis, we examined the outcomes of 8 children with long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency or trifunctional protein (TFP) deficiency who were repeatedly sedated for an electroretinogram (ERG) as part of a longitudinal study of the progression of chorioretinopathy commonly found in this population. A total of 39 sedated ERG procedures were completed using propofol for sedation. The propofol dosing, estimated total energy needs of the subject, and inpatient dietary intake recording were completed in 32 of these procedures. The LCFAs in the propofol provided approximately 1.0% of the average total daily energy needs. The sedation with propofol resulted in no adverse side effects and was safely used in this short duration procedure.

A method for measuring fatty acid oxidation in C. elegans

The nematode C. elegans has during the past decade proven to be a valuable model organism to identify and examine molecular mechanisms regulating lipid storage and metabolism. While the primary approach has been to identify genes and pathways conferring alterations in lipid accumulation, only a few recent studies have recognized the central role of fatty acid degradation in cellular lipid homeostasis. In the present study, we show how complete oxidation of fatty acids can be determined in live C. elegans by examining oxidation of tritium-labeled fatty acids to tritiated H₂O that can be measured by scintillation counting. Treating animals with sodium azide, an inhibitor of the electron transport chain, reduced ³H₂O production to approximately 15%, while boiling of animals prior to assay completely blocked the production of labeled water. We demonstrate that worms fed different bacterial strains exhibit different fatty acid oxidation rates. We show that starvation results in increased fatty acid oxidation, which is independent of the transcription factor NHR-49. On the contrary, fatty acid oxidation is reduced to approximately 70% in animals lacking the worm homolog of the insulin receptor, DAF-2. Hence, the present methodology can be used to delineate the role of specific genes and pathways in the regulation of β-oxidation in C. elegans.

Impaired amino acid metabolism contributes to fasting-induced hypoglycemia in fatty acid oxidation defects

The importance of mitochondrial fatty acid β-oxidation (FAO) as a glucose-sparing process is illustrated by patients with inherited defects in FAO, who may present with life-threatening fasting-induced hypoketotic hypoglycemia. It is unknown why peripheral glucose demand outpaces hepatic gluconeogenesis in these patients. In this study, we have systematically addressed the fasting response in long-chain acyl-CoA dehydrogenase-deficient (LCAD KO) mice. We demonstrate that the fasting-induced hypoglycemia in LCAD KO mice was initiated by an increased glucose requirement in peripheral tissues, leading to rapid hepatic glycogen depletion. Gluconeogenesis did not compensate for the increased glucose demand, which was not due to insufficient hepatic glucogenic capacity but rather caused by a shortage in the supply of glucogenic precursors. This shortage in supply was explained by a suppressed glucose-alanine cycle, decreased branched-chain amino acid metabolism and ultimately impaired protein mobilization. We conclude that during fasting, FAO not only serves to spare glucose but is also indispensable for amino acid metabolism, which is essential for the maintenance of adequate glucose production.

Growth in Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is an inborn error of fatty acid metabolism that affects the degradation of long chain fatty acids and causes insufficient energy production and accumulation of toxic intermediates. The treatment consists of a diet low in fat, with supplementation of medium-chain triglycerides that bypass the metabolic block. In addition, frequent feeds and extra carbohydrates are given during febrile illnesses to reduce lipolysis. Hence, this diet differs from the general dietary recommendations for growing children. Furthermore, the Swedish dietary instructions for fat intake in LCHAD deficiency are given in grams, which differ from most guidelines that recommend fat intake as percentage shares of total caloric intake.

AIMS

To assess growth in patients with LCHAD deficiency, in relation to dietary treatment and to evaluate if overweight/obesity is more common than in the normal population.

RESULTS

The growth velocity showed acceleration after diagnosis and the start of treatment, followed by a period of stable or decelerated growth. The majority of the patients developed overweight to a greater extent than children without LCHAD deficiency. Several patients also went through a phase of obesity. Data on final height (FH) showed that three out of five patients had grown according to their genetic potential.

CONCLUSIONS

Regular and frequent follow-up and careful monitoring of weight are essential to avoid the development of overweight and obesity. The Swedish dietary instructions defining fat intake in total grams per day may be an alternative approach to achieve a moderate total caloric intake.

Successful weight loss in two adult patients diagnosed with late-onset long-chain Fatty Acid oxidation defect

Patients with long-chain fatty acid oxidation defect (LCFAOD) cannot tolerate fasting and are restricted in their physical activity, hence their increased risk of obesity. Experts therefore advise avoidance of catabolic situations and discourage weight reduction in these patients.Two patients with late-diagnosed LCFAOD undergoing treatment at two academic centers successfully lost weight under supervision of a metabolic dietitian. Patient 1 (male, 47 years) diagnosed with CPT 2 deficiency lost 10 kg body weight in a 3-month period with the help of an energy and LCT-restricted, MCT- and carbohydrate-rich diet in combination with an exercise program. CK levels, C16, C18, and C18:1 levels of his acylcarnitine profile and his blood pressure decreased during the period of weight reduction. Patient 2 (male, 39 years) has a VLCAD deficiency. Dietary advice was energy and LCT restriction, MCT and carbohydrate-enriched food with raw cornstarch added during the night. Patient 2 lost almost 40 kg body weight to 87.6 kg (BMI 25.1) in 2 years. CK, insulin, TG, and ALAT blood levels decreased.

CONCLUSION

Weight reduction without loss of metabolic control seems possible in late-onset LCFAOD patients. No metabolic crisis occurred in these two patients, while the positive effects of weight reduction were clear. The residual enzyme function in late-onset LCFAOD may be one of the reasons that metabolic decompensation was prevented. In addition, dietary adjustments to prevent excessive fatty acid oxidation likely contributed as well. Therefore, expert supervision by a dietician specialized in metabolic diseases is recommended. Concise SentenceContrary to the current literature, weight loss in patients with late-diagnosed LCFAOD can be successful. A description of two FOAD patients who lost weight without encountering negative side effects at two academic centers is given.

Variability in the clinical management of fatty acid oxidation disorders: results of a survey of Canadian metabolic physicians

INTRODUCTION

There is little robust empirical evidence on which to base treatment recommendations for fatty acid oxidation disorders. While consensus guidelines are important, understanding areas where there is a lack of consensus is also critical to inform priorities for future evaluative research.

METHODS

We surveyed Canadian metabolic physicians on the treatment of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency, long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency, and mitochondrial trifunctional protein (MTP) deficiency. We ascertained physicians' opinions on the use of different interventions for the long-term management of patients as well as for the management of acute illness, focusing on identifying interventions characterized by high variability in opinions. We also investigated factors influencing treatment decisions.

RESULTS

We received 18 responses (response rate 45%). Participants focused on avoidance of fasting and increased meal frequency as interventions for the management of MCAD deficiency. For the long-chain disorders, avoidance of fasting remained the most consistently endorsed intervention, with additional highly endorsed treatments differing for VLCAD versus LCHAD/MTP deficiency. L-carnitine supplementation and restriction of dietary fat were characterized by high variability in physicians' opinions, as were several interventions specific to long-chain disorders. Social factors and patient characteristics were important influences on treatment decisions.

CONCLUSIONS

Based on our findings we suggest that high priority treatments for rigorous effectiveness studies could include L-carnitine supplementation (MCAD and LCHAD/MTP deficiencies), restriction of dietary fat, and, for the long-chain disorders, feeding practices for breastfed infants and the use of various supplements (essential fatty acids, carbohydrates, cornstarch, multivitamins).

Genetic determinants of hepatic steatosis in man

Hepatic steatosis is one of the most common liver disorders in the general population. The main cause of hepatic steatosis is nonalcoholic fatty liver disease (NAFLD), representing the hepatic component of the metabolic syndrome, which is characterized by type 2 diabetes, obesity, and dyslipidemia. Insulin resistance and excess adiposity are considered to play key roles in the pathogenesis of NAFLD. Although the risk factors for NAFLD are well established, the genetic basis of hepatic steatosis is largely unknown. Here we review recent progress on genomic variants and their association with hepatic steatosis and discuss the potential impact of these genetic studies on clinical practice. Identifying the genetic determinants of hepatic steatosis will lead to a better understanding of the pathogenesis and progression of NAFLD.

Clinical and biochemical monitoring of patients with fatty acid oxidation disorders

Evidence-based guidelines for monitoring patients with disorders in fatty acid oxidation (FAO) are lacking, and most protocols are based on expert statements. Here, we describe our protocol for Danish patients. Clinical monitoring is the most important measure and has the main aims of checking growth, development and diet and of bringing families to the clinic regularly to remind them of their child's risk and review how they cope and adjust, e.g. to an acute intercurrent illness. Most of these measures are simple and can be carried out during a routine out-patient visit; we seldom do more complicated assessments by a neuropsychologist, speech therapist, or physical and occupational therapists. Paraclinical measurements are not used for short-chain and medium-chain disorders; electrocardiography (including 24 h monitoring) and echocardiography are done for most patients with long-chain and carnitine transporter deficiencies. Eye examination is done in all, and liver ultrasonography in some patients with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase/tri-functional protein (LCHAD/TFP) deficiencies. Biochemical follow-up includes determination of free carnitine and acylcarnitines. Free carnitine is measured to monitor carnitine supplementation in patients with multiple acyl-coenzyme A dehydrogenase deficiency (MADD) and carnitine transporter deficiency (CTD) and to follow metabolic control and disclose deficiency states in other FAO disorders. We are evaluating long-chain acylcarnitines in patients with long-chain disorders; so far there does not seem to be any clear-cut benefit in following these levels. An erythrocyte fatty acid profile is done in patients with long-chain disorders to test for essential fatty acid and docosahexanoic acid (DHA) deficiencies. The measurement of creatine kinase is helpful in long-chain disorders. Ongoing follow-up and education of the patient is important throughout life to prevent disease morbidity or death from metabolic crises.

Inborn errors of energy metabolism associated with myopathies

Inherited neuromuscular disorders affect approximately one in 3,500 children. Structural muscular defects are most common; however functional impairment of skeletal and cardiac muscle in both children and adults may be caused by inborn errors of energy metabolism as well. Patients suffering from metabolic myopathies due to compromised energy metabolism may present with exercise intolerance, muscle pain, reversible or progressive muscle weakness, and myoglobinuria. In this review, the physiology of energy metabolism in muscle is described, followed by the presentation of distinct disorders affecting skeletal and cardiac muscle: glycogen storage diseases types III, V, VII, fatty acid oxidation defects, and respiratory chain defects (i.e., mitochondriopathies). The diagnostic work-up and therapeutic options in these disorders are discussed.

Adipocyte accumulation of long-chain fatty acids in obesity is multifactorial, resulting from increased fatty acid uptake and decreased activity of genes involved in fat utilization

BACKGROUND

The obesity epidemic causes significant morbidity and mortality. Knowledge of cellular function and gene expression in obese adipose tissue will yield insights into obesity pathogenesis and suggest therapeutic targets. The aim of this work is to study the processes determining fat accumulation in adipose tissue from obese patients.

METHODS

Omental fat was collected from two cohorts of obese bariatric surgery patients and sex-matched normal-weight donors. Isolated adipocytes were compared for cell size, volume, and long-chain fatty acid (LCFA) uptake. Omental fat RNAs were screened by 10K microarray (cohort 1: three obese, three normal) or Whole Genome microarray (cohort 2: seven obese, four normal). Statistical differences in gene and pathway expression were identified in cohort 1 using the GeneSifter Software (Geospiza) with key results confirmed in cohort 2 samples by microarray, quantitative real-time polymerase chain reaction, and pathway analysis.

RESULTS

Obese omental adipocytes had increased surface area, volume, and V (max) for saturable LCFA uptake. Dodecenoyl-coenzyme A delta isomerase, central to LCFA metabolism, was approximately 1.6-fold underexpressed in obese fat in cohorts 1 and 2. Additionally, the Kyoto Encyclopedia of Genes and Genomics pathway analysis identified oxidative phosphorylation and fatty acid metabolism pathways as having coordinate, nonrandom downregulation of gene expression in both cohorts.

CONCLUSIONS

In obese omental fat, saturable adipocyte LCFA uptake was greater than in controls, and expression of key genes involved in lipolysis, beta-oxidation, and metabolism of fatty acids was reduced. Thus, both increased uptake and reduced metabolism of LCFAs contribute to the accumulation of LCFAs in obese adipocytes.

EFFECT OF FEEDING, EXERCISE AND GENOTYPE ON PLASMA 3-HYDROXYACYLCARNITINES IN CHILDREN WITH LCHAD DEFICIENCY

Chronic complications observed in patients with long-chain 3-hydroxyacylCoA dehydrogenase (LCHAD) or trifunctional protein (TFP) deficiency may be mediated by the accumulation of 3-hydroxy fatty acids or 3-hydroxyacylcarnitines. To understand variation in metabolite accumulation, their concentrations were measured by tandem mass spectrometry before and after a mixed meal and moderate intensity exercise. Subjects who were homozygous or heterozygous for the common mutation (c.1528G>C) in the TFP alpha subunit (LCHAD deficiency) had significantly higher 3-hydroxyacylcarnitines than subjects with TFP deficiency. Feeding a mixed meal significantly suppressed and exercise significantly increased plasma 3-hydroxyacylcarnitines concentrations.

Treatment recommendations in long-chain fatty acid oxidation defects: consensus from a workshop

Published data on treatment of fatty acid oxidation defects are scarce. Treatment recommendations have been developed on the basis of observations in 75 patients with long-chain fatty acid oxidation defects from 18 metabolic centres in Central Europe. Recommendations are based on expert practice and are suggested to be the basis for further multicentre prospective studies and the development of approved treatment guidelines. Considering that disease complications and prognosis differ between different disorders of long-chain fatty acid oxidation and also depend on the severity of the underlying enzyme deficiency, treatment recommendations have to be disease-specific and depend on individual disease severity. Disorders of the mitochondrial trifunctional protein are associated with the most severe clinical picture and require a strict fat-reduced and fat-modified (medium-chain triglyceride-supplemented) diet. Many patients still suffer acute life-threatening events or long-term neuropathic symptoms despite adequate treatment, and newborn screening has not significantly changed the prognosis for these severe phenotypes. Very long-chain acyl-CoA dehydrogenase deficiency recognized in neonatal screening, in contrast, frequently has a less severe disease course and dietary restrictions in many patients may be loosened. On the basis of the collected data, recommendations are given with regard to the fat and carbohydrate content of the diet, the maximal length of fasting periods and the use of l-carnitine in long-chain fatty acid oxidation defects.