Biochemical correlates of neuropsychiatric illness in maple syrup urine disease

Neonatal Screening for Inherited Metabolic Diseases in 2016

The scope of newborn screening (NBS) programs is continuously expanding. NBS programs are secondary prevention interventions widely recognized internationally in the "field of Public Health." These interventions are aimed at early detection of asymptomatic children affected by certain diseases, with the objective to establish a definitive diagnosis and apply the proper treatment to prevent further complications and sequelae and ensure a better quality of life. The most significant event in the history of neonatal screening was the discovery of phenylketonuria in 1934. This disease has been the paradigm of inherited metabolic diseases. The next paradigm was the introduction of tandem mass spectrometry in the NBS programs that make possible the simultaneous measurement of several metabolites and consequently, the detection of several diseases in one blood spot and in an unique analysis. We aim to review the current situation of neonatal screening in 2016 worldwide and show scientific evidence of the benefits for some diseases. We will also discuss future challenges. It should be taken into account that any consideration to expand an NBS panel should involve a rigorous process of decision-making that balances benefits against the risks of harm.

Serum Markers of Neurodegeneration in Maple Syrup Urine Disease

Maple syrup urine disease (MSUD) is an inherited disorder caused by deficient activity of the branched-chain α-keto acid dehydrogenase complex involved in the degradation pathway of branched-chain amino acids (BCAAs) and their respective α-keto-acids. Patients affected by MSUD present severe neurological symptoms and brain abnormalities, whose pathophysiology is poorly known. However, preclinical studies have suggested alterations in markers involved with neurodegeneration. Because there are no studies in the literature that report the neurodegenerative markers in MSUD patients, the present study evaluated neurodegenerative markers (brain-derived neurotrophic factor (BDNF), cathepsin D, neural cell adhesion molecule (NCAM), plasminogen activator inhibitor-1 total (PAI-1 (total)), platelet-derived growth factor AA (PDGF-AA), PDGF-AB/BB) in plasma from 10 MSUD patients during dietary treatment. Our results showed a significant decrease in BDNF and PDGF-AA levels in MSUD patients. On the other hand, NCAM and cathepsin D levels were significantly greater in MSUD patients compared to the control group, while no significant changes were observed in the levels of PAI-1 (total) and PDGF-AB/BB between the control and MSUD groups. Our data show that MSUD patients present alterations in proteins involved in the neurodegenerative process. Thus, the present findings corroborate previous studies that demonstrated that neurotrophic factors and lysosomal proteases may contribute, along with other mechanisms, to the intellectual deficit and neurodegeneration observed in MSUD.

NMR-Based Metabonomic Analysis of Physiological Responses to Starvation and Refeeding in the Rat

Starvation is a postabsorptive condition derived from a limitation on food resources by external factors. Energy homeostasis is maintained under this condition by using sources other than glucose via adaptive mechanisms. After refeeding, when food is available, other adaptive processes are linked to energy balance. However, less has been reported about the physiological mechanisms present as a result of these conditions, considering the rat as a supraorganism. Metabolic profiling using (1)H nuclear magnetic resonance spectroscopy was used to characterize the physiological metabolic differences in urine specimens collected under starved, refed, and recovered conditions. In addition, because starvation induced lack of faecal production and not all animals produced faeces during refeeding, 24 h pooled faecal water samples were also analyzed. Urinary metabolites upregulated by starvation included 2-butanamidoacetate, 3-hydroxyisovalerate, ketoleucine, methylmalonate, p-cresyl glucuronide, p-cresyl sulfate, phenylacetylglycine, pseudouridine, creatinine, taurine, and N-acetyl glycoprotein, which were related to renal and skeletal muscle function, β-oxidation, turnover of proteins and RNA, and host-microbial interactions. Food-derived metabolites, including gut microbial cometabolites, and tricarboxylic acid cycle intermediates were upregulated under refed and recovered conditions, which characterized anabolic urinary metabotypes. The upregulation of creatine and pantothenate indicated an absorptive state after refeeding. Fecal short chain fatty acids, 3-(3-hydroxyphenyl)propionate, lactate, and acetoin provided additional information about the combinatorial metabolism between the host and gut microbiota. This investigation contributes to allow a deeper understanding of physiological responses associated with starvation and refeeding.

Living related versus deceased donor liver transplantation for maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited disorder of branched chain ketoacid (BCKA) oxidation associated with episodic and chronic brain disease. Transplantation of liver from an unrelated deceased donor restores 9-13% whole-body BCKA oxidation capacity and stabilizes MSUD. Recent reports document encouraging short-term outcomes for MSUD patients who received a liver segment from mutation heterozygous living related donors (LRDT). To investigate effects of living related versus deceased unrelated grafts, we studied four Brazilian MSUD patients treated with LRDT who were followed for a mean 19 ± 12 postoperative months, and compared metabolic and clinical outcomes to 37 classical MSUD patients treated with deceased donor transplant. Patient and graft survival for LRDT were 100%. Three of 4 MSUD livers were successfully domino transplanted into non-MSUD subjects. Following LRDT, all subjects resumed a protein-unrestricted diet as mean plasma leucine decreased from 224 ± 306 μM to 143 ± 44 μM and allo-isoleucine decreased 91%. We observed no episodes of hyperleucinemia during 80 aggregate postoperative patient-months. Mean plasma leucine:isoleucine:valine concentration ratios were ~2:1:4 after deceased donor transplant compared to ~1:1:1.5 following LRDT, resulting in differences of predicted cerebral amino acid uptake. Mutant heterozygous liver segments effectively maintain steady-state BCAA and BCKA homeostasis on an unrestricted diet and during most catabolic states, but might have different metabolic effects than grafts from unrelated deceased donors. Neither living related nor deceased donor transplant affords complete protection from metabolic intoxication, but both strategies represent viable alternatives to nutritional management.

In Vivo NMR Studies of the Brain with Hereditary or Acquired Metabolic Disorders

Metabolic disorders, whether hereditary or acquired, affect the brain, and abnormalities of the brain are related to cellular integrity; particularly in regard to neurons and astrocytes as well as interactions between them. Metabolic disturbances lead to alterations in cellular function as well as microscopic and macroscopic structural changes in the brain with diabetes, the most typical example of metabolic disorders, and a number of hereditary metabolic disorders. Alternatively, cellular dysfunction and degeneration of the brain lead to metabolic disturbances in hereditary neurological disorders with neurodegeneration. Nuclear magnetic resonance (NMR) techniques allow us to assess a range of pathophysiological changes of the brain in vivo. For example, magnetic resonance spectroscopy detects alterations in brain metabolism and energetics. Physiological magnetic resonance imaging (MRI) detects accompanying changes in cerebral blood flow related to neurovascular coupling. Diffusion and T1/T2-weighted MRI detect microscopic and macroscopic changes of the brain structure. This review summarizes current NMR findings of functional, physiological and biochemical alterations within a number of hereditary and acquired metabolic disorders in both animal models and humans. The global view of the impact of these metabolic disorders on the brain may be useful in identifying the unique and/or general patterns of abnormalities in the living brain related to the pathophysiology of the diseases, and identifying future fields of inquiry.

Evolution of maple syrup urine disease in patients diagnosed by newborn screening versus late diagnosis

Maple syrup urine disease (MSUD) is a rare metabolic disorder for which the newborn screening (NBS) is possible but it has not been yet implemented for most Spanish regions. In the present study, we assess the clinical features and outcome of 14 MSUD Spanish patients with similar treatment protocol diagnosed either by NBS or by clinical symptoms. Eight patients were detected by NBS, four classic and four moderate MSUD. The average age at detection was 4.6 days, the mean plasmatic concentration of leucine at diagnosis was 1807 μM; the average number of days with leucine >1000 μM was 0.7 (0-4) and the mean number of total hospitalizations was 1.6 (0-5). Mean follow-up time was 70 months. They had good evolution: all remain asymptomatic, but 2 patients have attention deficit and hyperactivity disorder. Six patients with late diagnosis of classic MSUD were followed during 41 months. All presented with acute encephalopathy during the first month of life, mean leucine levels of 2355 μM, mean number of days with leucine >1000 μM of 6.6 (1-13) and mean number of total hospitalizations of 5.3 (4-7). Only two patients have a psychomotor development index in the lower limit (80 and 83). For all patients a good genotype-phenotype correlation was found and four novel mutations were identified: p.A311H, p.T84S, p.T397L, pL398P. Our study support that NBS improves prognosis of MSUD patients. But early diagnosis and an aggressive treatment together with a close monitoring of leucine levels improve neurological evolution in MSUD patients, even for those not detected by NBS.

A 26-hour system of highly sensitive whole genome sequencing for emergency management of genetic diseases

While the cost of whole genome sequencing (WGS) is approaching the realm of routine medical tests, it remains too tardy to help guide the management of many acute medical conditions. Rapid WGS is imperative in light of growing evidence of its utility in acute care, such as in diagnosis of genetic diseases in very ill infants, and genotype-guided choice of chemotherapy at cancer relapse. In such situations, delayed, empiric, or phenotype-based clinical decisions may meet with substantial morbidity or mortality. We previously described a rapid WGS method, STATseq, with a sensitivity of >96 % for nucleotide variants that allowed a provisional diagnosis of a genetic disease in 50 h. Here improvements in sequencing run time, read alignment, and variant calling are described that enable 26-h time to provisional molecular diagnosis with >99.5 % sensitivity and specificity of genotypes. STATseq appears to be an appropriate strategy for acutely ill patients with potentially actionable genetic diseases.

A critical reappraisal of dietary practices in methylmalonic acidemia raises concerns about the safety of medical foods. Part 1: isolated methylmalonic acidemias

PURPOSE

Medical foods for methylmalonic and propionic acidemias (MMA/PA) contain minimal valine, isoleucine, methionine and threonine, but have been formulated with increased leucine. We aimed to assess the effects of imbalanced branched-chain amino acid intake on metabolic and growth parameters in a cohort of MMA patients ascertained via a natural history study.

METHODS

Cross-sectional anthropometric and body composition measurements were correlated with diet content and disease-related biomarkers in 61 patients with isolated MMA (46 mut, 9 cblA and 6 cblB).

RESULTS

Patients with MMA tolerated close to the recommended daily allowance (RDA) of complete protein (mut⁰: 99.45 ± 32.05% RDA). However, 85% received medical foods, the protein-equivalent in which often exceeded complete protein intake (35%). Medical food consumption resulted in low plasma valine and isoleucine concentrations, prompting paradoxical supplementation with these propiogenic amino acids. Weight and height–for age Z-scores correlated negatively with the leucine/valine intake ratio (r=−0.453, P=0.014, R²=0.209 and r=−0.341, P=0.05, R²=0.123, respectively).

CONCLUSION

Increased leucine intake in patients with MMA resulted in iatrogenic amino acid deficiencies and was associated with adverse growth outcomes. Medical foods for propionate oxidation disorders need to be redesigned and studied prospectively, to ensure efficacy and safety.

TRIAL REGISTRATION

This clinical study is registered in www.clinicaltrials.gov with the ID: NCT00078078. Study URL: http://clinicaltrials.gov/ct2/show/NCT00078078

Inherited Metabolic Disorders: Aspects of Chronic Nutrition Management

The introduction of newborn screening and the development of new therapies have led to an expanding population of patients with inherited metabolic disorders, and these patients are now entering adulthood. Dietary therapy is the mainstay of treatment for many of these disorders, and thus, trained metabolic dietitians are critical members of the multidisciplinary team required for management of such patients. The main goals of dietary therapy in inborn errors of metabolism are the maintenance of normal growth and development while limiting offending metabolites and providing deficient products. Typically, the offending metabolite is either significantly reduced or removed completely from the diet and then reintroduced in small quantities until blood levels are within the normal range. Such treatment is required in infancy, childhood, and adulthood and requires careful monitoring of micronutrient and macronutrient intake throughout the life span. The goal of this review is to highlight the basic principles of chronic nutrition management of the inborn errors of protein, carbohydrate, and fat metabolism.

Chronic activation of mTOR complex 1 by branched chain amino acids and organ hypertrophy

The mitochondrial branched chain aminotransferase-deficient mouse model (BCATm KO), which exhibits elevated plasma and tissue branched chain amino acids (BCAAs), was used to study the effect of BCAAs on mammalian target of rapamycin complex 1 (mTORC1) regulation of organ size. BCATm is the first enzyme in the BCAA catabolic pathway. BCATm KO mouse exhibited hypertrophy of heart, kidneys, and spleen. On the other hand, the mass of the gastrocnemius was reduced relative to body mass. Feeding the mice with a diet supplemented with rapamycin prevented the enlargement of the heart and spleen, suggesting that mTORC1 is the mediator of these effects. Consistently, enlargement of these organs was accompanied by the activation of mTORC1 complex as evidenced by enhanced levels of S6 and 4E-BP1 phosphorylation. HSP20, HSP27 and GAPDH were also increased in the heart but not gastrocnemius, consistent with mTORC1 activation. Liver, however, displayed no weight difference between the KO and the wild-type mice despite the highest activation level of mTORC1 complex. These observations suggest that the anabolic effect of mTORC1 activation at the organ level by BCAAs and inhibition by rapamycin are complex phenomenon and tissue-specific. In addition, it suggests that rapamycin can be used to counter hypertrophy of the organs when activation of mTORC1 is the underlying cause.

Quality of life, psychological adjustment, and adaptive functioning of patients with intoxication-type inborn errors of metabolism - a systematic review

Background

In recent decades, considerable progress in diagnosis and treatment of patients with intoxication-type inborn errors of metabolism (IT-IEM) such as urea cycle disorders (UCD), organic acidurias (OA), maple syrup urine disease (MSUD), or tyrosinemia type 1 (TYR 1) has resulted in a growing group of long-term survivors. However, IT-IEM still require intense patient and caregiver effort in terms of strict dietetic and pharmacological treatment, and the threat of metabolic crises is always present. Furthermore, crises can affect the central nervous system (CNS), leading to cognitive, behavioural and psychiatric sequelae. Consequently, the well-being of the patients warrants consideration from both a medical and a psychosocial viewpoint by assessing health-related quality of life (HrQoL), psychological adjustment, and adaptive functioning. To date, an overview of findings on these topics for IT-IEM is lacking. We therefore aimed to systematically review the research on HrQoL, psychological adjustment, and adaptive functioning in patients with IT-IEM.

Methods

Relevant databases were searched with predefined keywords. Study selection was conducted in two steps based on predefined criteria. Two independent reviewers completed the selection and data extraction.

Results

Eleven articles met the inclusion criteria. Studies were of varying methodological quality and used different assessment measures. Findings on HrQoL were inconsistent, with some showing lower and others showing higher or equal HrQoL for IT-IEM patients compared to norms. Findings on psychological adjustment and adaptive functioning were more consistent, showing mostly either no difference or worse adjustment of IT-IEM patients compared to norms. Single medical risk factors for HrQoL, psychological adjustment, or adaptive functioning have been addressed, while psychosocial risk factors have not been addressed.

Conclusion

Data on HrQoL, psychological adjustment, and adaptive functioning for IT-IEM are sparse. Studies are inconsistent in their methodological approaches, assessment instruments and norm populations. A disease-specific standard assessment procedure for HrQoL is not available. Psychosocial risk factors for HrQoL, psychological adjustment, or adaptive functioning have not been investigated. Considering psychosocial variables and their corresponding risk factors for IT-IEM would allow evaluation of outcomes and treatments as well as the planning of effective social and psychological interventions to enhance the patients’ HrQoL.

Brain-blood amino acid correlates following protein restriction in murine maple syrup urine disease

Background

Conventional therapy for patients with maple syrup urine disease (MSUD) entails restriction of protein intake to maintain acceptable levels of the branched chain amino acid, leucine (LEU), monitored in blood. However, no data exists on the correlation between brain and blood LEU with protein restriction, and whether correction in blood is reflected in brain.

Methods

To address this question, we fed intermediate MSUD mice diets of 19% (standard) and 6% protein, with collection of sera (SE), striata (STR), cerebellum (CE) and cortex (CTX) for quantitative amino acid analyses.

Results

LEU and valine (VAL) levels in all brain regions improved on average 28% when shifting from 19% to 6% protein, whereas the same improvements in SE were on average 60%. Isoleucine (ILE) in brain regions did not improve, while the SE level improved 24% with low-protein consumption. Blood-branched chain amino acids (LEU, ILE, and VAL in sera (SE)) were 362-434 μM, consistent with human values considered within control. Nonetheless, numerous amino acids in brain regions remained abnormal despite protein restriction, including glutamine (GLN), aspartate (ASP), glutamate (GLU), gamma-aminobutyric acid (GABA), asparagine (ASN), citrulline (CIT) and serine (SER). To assess the specificity of these anomalies, we piloted preliminary studies in hyperphenylalaninemic mice, modeling another large neutral aminoacidopathy. Employing an identical dietary regimen, we found remarkably consistent abnormalities in GLN, ASP, and GLU.

Conclusions

Our results suggest that blood amino acid analysis may be a poor surrogate for assessing the outcomes of protein restriction in the large neutral amino acidopathies, and further indicate that chronic neurotransmitter disruptions (GLU, GABA, ASP) may contribute to long-term neurocognitive dysfunction in these disorders.

Branched-chain amino acid metabolism: from rare Mendelian diseases to more common disorders

Branched-chain amino acid (BCAA) metabolism plays a central role in the pathophysiology of both rare inborn errors of metabolism and the more common multifactorial diseases. Although deficiency of the branched-chain ketoacid dehydrogenase (BCKDC) and associated elevations in the BCAAs and their ketoacids have been recognized as the cause of maple syrup urine disease (MSUD) for decades, treatment options for this disorder have been limited to dietary interventions. In recent years, the discovery of improved leucine tolerance after liver transplantation has resulted in a new therapeutic strategy for this disorder. Likewise, targeting the regulation of the BCKDC activity may be an alternative potential treatment strategy for MSUD. The regulation of the BCKDC by the branched-chain ketoacid dehydrogenase kinase has also been implicated in a new inborn error of metabolism characterized by autism, intellectual disability and seizures. Finally, there is a growing body of literature implicating BCAA metabolism in more common disorders such as the metabolic syndrome, cancer and hepatic disease. This review surveys the knowledge acquired on the topic over the past 50 years and focuses on recent developments in the field of BCAA metabolism.

Behavioral responses in rats submitted to chronic administration of branched-chain amino acids

Maple syrup urine disease (MSUD) is an inborn metabolism error caused by a deficiency of branched-chain α-keto acid dehydrogenase complex activity. This blockage leads to an accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine, and valine, as well as their corresponding α-keto and α-hydroxy acids. Previous reports suggest that MSUD patients are at high risk for chronic neuropsychiatric problems. Therefore, in this study, we assessed variables that suggest depressive-like symptoms (anhedonia as measured by sucrose intake, immobility during the forced swimming test and body and adrenal gland weight) in rats submitted to chronic administration of BCAA during development. Furthermore, we determined if these parameters were sensitive to imipramine and N-acetylcysteine/deferoxamine (NAC/DFX). Our results demonstrated that animals subjected to chronic administration of branched-chain amino acids showed a decrease in sucrose intake without significant changes in body weight. We also observed an increase in adrenal gland weight and immobility time during the forced swimming test. However, treatment with imipramine and NAC/DFX reversed these changes in the behavioral tasks. In conclusion, this study demonstrates a link between MSUD and depression in rats. Moreover, this investigation reveals that the antidepressant action of NAC/DFX and imipramine might be associated with their capability to maintain pro-/anti-oxidative homeostasis.

Adipose transplant for inborn errors of branched chain amino acid metabolism in mice

Liver transplantation appears to be quite beneficial for treatment of maple syrup urine disease (MSUD, an inherited disorder of branched chain amino acid metabolism); however, there is a limited availability of donor livers worldwide and the first year costs of liver transplants are quite high. Recent studies have suggested that intact adipose tissue, already widely used in reconstructive surgery, may have an underappreciated high capacity for branched chain amino acid (BCAA) metabolism. Here we examined the potential for adipose tissue transplant to lower circulating BCAAs in two models of defective BCAA metabolism, BCATm and PP2Cm [branched chain keto acid dehydrogenase complex (BCKDC) phosphatase] knockout (KO) mice. After 1-2g fat transplant, BCATm and PP2Cm KO mice gained or maintained body weight 3weeks after surgery and consumed similar or more food/BCAAs the week before phlebotomy. Transplant of fat into the abdominal cavity led to a sterile inflammatory response and nonviable transplanted tissue. However when 1-2g of fat was transplanted subcutaneously into the back, either as small (0.1-0.3g) or finely minced pieces introduced with an 18-ga. needle, plasma BCAAs decreased compared to Sham operated mice. In two studies on BCATm KO mice and one study on PP2Cm KO mice, fat transplant led to 52-81% reductions in plasma BCAAs compared to baseline plasma BCAA concentrations of untreated WT type siblings. In PP2Cm KO mice, individual BCAAs in plasma were also significantly reduced by fat transplant, as were the alloisoleucine/Phe ratios. Therefore, subcutaneous fat transplantation may have merit as an adjunct to dietary treatment of MSUD. Additional studies are needed to further refine this approach.