The effects of l-alanine supplementation in late-onset glycogen storage disease type II

Nutritional co-therapy with 1,3-butanediol and multi-ingredient antioxidants enhances autophagic clearance in Pompe disease

Alglucosidase alpha is an orphan drug approved for enzyme replacement therapy (ERT) in Pompe disease (PD); however, its efficacy is limited in skeletal muscle because of a partial blockage of autophagic flux that hinders intracellular trafficking and enzyme delivery. Adjunctive therapies that enhance autophagic flux and protect mitochondrial integrity may alleviate autophagic blockage and oxidative stress and thereby improve ERT efficacy in PD. In this study, we compared the benefits of ERT combined with a ketogenic diet (ERT-KETO), daily administration of an oral ketone precursor (1,3-butanediol; ERT-BD), a multi-ingredient antioxidant diet (ERT-MITO; CoQ10, α-lipoic acid, vitamin E, beetroot extract, HMB, creatine, and citrulline), or co-therapy with the ketone precursor and multi-ingredient antioxidants (ERT-BD-MITO) on skeletal muscle pathology in GAA-KO mice. We found that two months of 1,3-BD administration raised circulatory ketone levels to ≥1.2 mM, attenuated autophagic buildup in type 2 muscle fibers, and preserved muscle strength and function in ERT-treated GAA-KO mice. Collectively, ERT-BD was more effective vs. standard ERT and ERT-KETO in terms of autophagic clearance, dampening of oxidative stress, and muscle maintenance. However, the addition of multi-ingredient antioxidants (ERT-BD-MITO) provided the most consistent benefits across all outcome measures and normalized mitochondrial protein expression in GAA-KO mice. We therefore conclude that nutritional co-therapy with 1,3-butanediol and multi-ingredient antioxidants may provide an alternative to ketogenic diets for inducing ketosis and enhancing autophagic flux in PD patients.

L-alanine supplementation in Pompe disease (IOPD): a potential therapeutic implementation for patients on ERT? A case report

Background

Pompe disease (PD) is a disorder of glycogen metabolism conditioning a progressive and life conditioning myopathy. Enzyme replacement therapy (ERT) is currently the best treatment option for PD, but is not resolutive. While other potential therapeutic approaches have been reported before, these have never been tried as co- treatments. L-alanine oral supplementation (LAOS) has been proven to reduce muscle breakdown: we hereby report the first case of supplementation on a PD patient on ERT.

Case presentation

F. is a 9 y.o. infantile onset Pompe Disease (IOPD) girl ERT-treated since age 1 developing a progressive myopathy. We started her on LAOS and performed assessments at baseline, 6 and 9 months. At baseline, F.’s weight, height and BMI were within normal ranges, while body composition showed low fat mass -FM and high resting energy expenditure—REE levels. After LAOS, a progressive FM increase and REE reduction could be observed both at 6 and 9 months.

Conclusions

ERT is not curative for PD patients thus additional treatments could be considered to improve outcomes. Our patient showed physical signs of inability to accumulate energy when exclusively on ERT, while FM increase and REE reduction occurred when supplemented with LAOS, likely reflecting anabolic pathways’ implementation. This is the first case reporting potential LAOS benefits in PD-on ERT patients. Longitudinal case control studies are yet needed to evaluate possible efficacy of combined LAOS And ERT treatment in PD patients.

Mitochondrial enzyme GPT2 regulates metabolic mechanisms required for neuron growth and motor function in vivo

The metabolic needs for postnatal growth of the human nervous system are vast. Recessive loss-of-function mutations in the mitochondrial enzyme glutamate pyruvate transaminase 2 (GPT2) in humans cause postnatal undergrowth of brain, and cognitive and motor disability. We demonstrate that GPT2 governs critical metabolic mechanisms in neurons required for neuronal growth and survival. These metabolic processes include neuronal alanine synthesis and anaplerosis, the replenishment of tricarboxylic acid (TCA) cycle intermediates. We performed metabolomics across postnatal development in Gpt2-null mouse brain to identify the trajectory of dysregulated metabolic pathways: alterations in alanine occur earliest; followed by reduced TCA cycle intermediates and reduced pyruvate; followed by elevations in glycolytic intermediates and amino acids. Neuron-specific deletion of GPT2 in mice is sufficient to cause motor abnormalities and death pre-weaning, a phenotype identical to the germline Gpt2-null mouse. Alanine biosynthesis is profoundly impeded in Gpt2-null neurons. Exogenous alanine is necessary for Gpt2-null neuronal survival in vitro, but is not needed for Gpt2-null astrocytes. Dietary alanine supplementation in Gpt2-null mice enhances animal survival, and improves the metabolic profile of Gpt2-null brain, but does not alone appear to correct motor function. In surviving Gpt2-null animals, we observe smaller upper and lower motor neurons in vivo. We also observe selective death of lower motor neurons in vivo with worsening motor behavior with age. In conclusion, these studies of the pathophysiology of GPT2 Deficiency have identified metabolic mechanisms required for neuronal growth and that potentially underlie selective neuronal vulnerabilities in motor neurons.

Nutrition in adult patients with selected lysosomal storage diseases

Lysosomal storage disorders (LSDs) are a group of clinically heterogeneous disorders affecting the function of lysosomes and are characterized by an accumulation of undigested substrates within several cell types. In recent years there have been substantial advances in supportive care and drug treatment for some LSDs, leading to improved patient survival, as seen in Gaucher, Pompe and Fabry disease and some Mucopolysaccharidoses; however, many symptoms still persist. Thus it is now even more important to improve patients' quality of life and reduce symptoms and comorbidities. One potential way of achieving this goal is through adjunct nutritional therapy, which is challenging as patients may be overweight with associated consequences, or malnourished, or underweight. Furthermore, drugs used to treat LSDs can modify the metabolic status and needs of patients. There are currently not enough data to make specific dietary recommendations for individual LSDs; however, suggestions can be made for managing clinical manifestations of the diseases, as well as treatment-associated adverse events. The metabolic and nutritional status of adult patients must be regularly assessed and individualized dietary plans may be created to cater to a patient's specific needs. Damage to the autophagic process is a common feature in LSDs that is potentially sensitive to dietary manipulation and needs to be assessed in clinical studies.

Effect of alanine supplementation on oxalate synthesis

The Primary Hyperoxalurias (PH) are rare disorders of metabolism leading to excessive endogenous synthesis of oxalate and recurring calcium oxalate kidney stones. Alanine glyoxylate aminotransferase (AGT), deficient in PH type 1, is a key enzyme in limiting glyoxylate oxidation to oxalate. The affinity of AGT for its co-substrate, alanine, is low suggesting that its metabolic activity could be sub-optimal in vivo. To test this hypothesis, we examined the effect of L-alanine supplementation on oxalate synthesis in cell culture and in mouse models of Primary Hyperoxaluria Type 1 (Agxt KO), Type 2 (Grhpr KO) and in wild-type mice. Our results demonstrated that increasing L-alanine in cells decreased synthesis of oxalate and increased viability of cells expressing GO and AGT when incubated with glycolate. In both wild type and Grhpr KO male and female mice, supplementation with 10% dietary L-alanine significantly decreased urinary oxalate excretion ~30% compared to baseline levels. This study demonstrates that increasing the availability of L-alanine can increase the metabolic efficiency of AGT and reduce oxalate synthesis.

Diagnosis and treatment of late-onset Pompe disease in the Middle East and North Africa region: consensus recommendations from an expert group

Background

Pompe disease is a rare autosomal recessive disorder caused by a deficiency of the lysosomal enzyme alpha-glucosidase responsible for degrading glycogen. Late-onset Pompe disease has a complex multisystem phenotype characterized by a range of symptoms.

Methods

An expert panel from the Middle East and North Africa (MENA) region met to create consensus-based guidelines for the diagnosis and treatment of late-onset Pompe disease for the MENA region, where the relative prevalence of Pompe disease is thought to be high but there is a lack of awareness and diagnostic facilities.

Results

These guidelines set out practical recommendations and include algorithms for the diagnosis and treatment of late-onset Pompe disease. They detail the ideal diagnostic workup, indicate the patients in whom enzyme replacement therapy should be initiated, and provide guidance on appropriate patient monitoring.

Conclusions

These guidelines will serve to increase awareness of the condition, optimize patient diagnosis and treatment, reduce disease burden, and improve patient outcomes.

Fat and carbohydrate metabolism during exercise in late-onset Pompe disease

Pompe disease is caused by absence of the lysosomal enzyme acid alpha-glucosidase. It is generally assumed that intra-lysosomal hydrolysis of glycogen does not contribute to skeletal muscle energy production during exercise. However, this hypothesis has never been tested in vivo during exercise. We examined the metabolic response to exercise in patients with late-onset Pompe disease, in order to determine if a defect in energy metabolism may play a role in the pathogenesis of Pompe disease. We studied six adult patients with Pompe disease and 10 healthy subjects. The participants underwent ischemic forearm exercise testing, and peak work capacity was determined. Fat and carbohydrate metabolism during cycle exercise was examined with a combination of indirect calorimetry and stable isotope methodology. Finally, the effects of an IV glucose infusion on heart rate, ratings of perceived exertion, and work capacity during exercise were determined. We found that peak oxidative capacity was reduced in the patients to 17.6 vs. 38.8 ml kg(-1) min(-1) in healthy subjects (p = 0.002). There were no differences in the rate of appearance and rate of oxidation of palmitate, or total fat and carbohydrate oxidation, between the patients and the healthy subjects. None of the subjects improved exercise tolerance by IV glucose infusion. In conclusion, peak oxidative capacity is reduced in Pompe disease. However, skeletal muscle fat and carbohydrate use during exercise was normal. The results indicate that a reduced exercise capacity is caused by muscle weakness and wasting, rather than by an impaired skeletal muscle glycogenolytic capacity. Thus, it appears that acid alpha-glucosidase does not play a significant role in the production of energy in skeletal muscle during exercise.

Changes in nutritional status and body composition during enzyme replacement therapy in adult-onset type II glycogenosis

BACKGROUND

In adult glycogen storage disease type II (GSDII), a single-gene mutation causes reduction of the lysosomal enzyme acid alpha-glucosidse. This produces a chronic proximal myopathy with respiratory involvement. Enzyme replacement treatment (ERT) has recently become available and is expected to improve muscle strength. This should result in increased lean body mass. In this study we evaluate body composition and nutritional status in GSDII, and assess whether these parameters changed during treatment.

METHODS

Seventeen patients with late-onset GSDII, aged 52.6 +/- 16.8 years, received ERT for >18 months. Dietary habits and metabolic profiles of glucids, lipids, and proteins were assessed. Body composition was calculated using anthropometry and bioelectrical impedence analysis.

RESULTS

On inclusion, we found increased fat mass (FM) in five patients in severe disease stage; all had normal body mass index (BMI). FM correlated inversely, and lean mass (LM) directly, with creatine kinase, prealbumin and albumin levels. After treatment, BMI and FM significantly increased, while LM only showed a trend toward increase. Prealbumin and albumin levels increased as early as after the first months of ERT.

DISCUSSION

Body mass index value may underestimate FM in patients in severe stage of disease, due to altered body composition. In severely affected patients, laboratory parameters revealed a relative protein malnutrition, that was reversed by ERT, this reflecting restoration of normal muscle metabolic pathways. Increased BMI may indicate a reduction in energy consumption during exercise or respiration, along with clinical improvement.

The effects of alanine ingestion on metabolic responses to exercise in cyclists

The influence of alanine on plasma amino acid concentrations and fuel substrates as well as cycling performance was examined. Four solutions [6% alanine (ALA); 6% sucrose (CHO); 6% alanine and 6% sucrose (ALA-CHO); an artificially sweetened placebo (PLC)] were tested using a double-blind, randomised, cross-over design. During each trial, ten cyclists ingested 500 mL of test solution 30 min before exercise and 250 mL after 15, 30, and 45 min of exercise. Participants cycled for 45 min at 75% VO(2)max followed by a 15-min performance trial. Blood was collected before beverage consumption and prior to the performance trial. Alanine concentration was increased (p < 0.05) by approximately tenfold for ALA and ALA-CHO and less than twofold for CHO and PLC. Alanine ingestion increased concentrations of most gluconeogenic amino acids. Overall, alanine supplementation tended to produce favourable metabolic effects, but did not influence performance.

Newborn screening for Pompe disease: synthesis of the evidence and development of screening recommendations

BACKGROUND

Pompe disease is a lysosomal storage disorder that leads to the accumulation of glycogen and subsequently to muscle weakness, organ damage, and death. Pompe disease is detectable through newborn screening, and treatment has become available recently.

OBJECTIVE

Our goal was to review systematically all available evidence regarding screening for infantile Pompe disease to help policy makers determine whether Pompe disease should be added to their state's newborn screening battery.

METHODS

We searched online databases, including Medline, clinicaltrials.gov, and the Computer Retrieval of Information on Scientific Projects database, as well as Web sites maintained by federal organizations (eg, the Food and Drug Administration) and other nonprofit or private organizations (eg, the March of Dimes and Genzyme Corp), by using the terms "glycogen storage disease type II," "Pompe disease," and "Pompe's disease." We also obtained preliminary findings from a screening program in Taiwan. Data were critically appraised and extracted by 2 investigators, one who is an expert in systematic review methods and the other who is an expert in Pompe disease.

RESULTS

The prevalence of Pompe disease has been estimated to be approximately 1 case per 40,000. Small studies suggest that enzyme therapy is highly efficacious in infantile Pompe disease and that earlier intervention leads to improved outcomes. Screening cannot distinguish between infantile and late-onset Pompe disease. The current screening program in Taiwan has a high false-positive rate; however, the threshold was purposely set low to ensure that no case would be missed.

CONCLUSIONS

Pilot studies of screening are needed to identify the most efficacious strategy for screening and determine how to manage cases of late-onset Pompe disease before screening for Pompe disease is adopted widely by newborn screening programs.

Anaplerotic diet therapy in inherited metabolic disease: therapeutic potential

Beginning with phenylketonuria, dietary therapy for inborn errors has focused primarily on the restriction of the precursor to an affected catabolic pathway in an attempt to limit the production of potential toxins. Anaplerotic therapy is based on the concept that there may exist an energy deficit in these diseases that might be improved by providing alternative substrate for both the citric acid cycle (CAC) and the electron transport chain for enhanced ATP production. This article focuses on this basic problem, as it may relate to most catabolic disorders, and provides our current experience involving inherited diseases of mitochondrial fat oxidation, glycogen storage, and pyruvate metabolism using the anaplerotic compound triheptanoin. The observations have led to a realization that 'inter-organ' signalling and 'nutrient sensors' such as adenylate monophosphate mediated-protein kinase (AMPK) and mTOR (mammalian target of rapamycin) appear to play a significant role in the intermediary metabolism of these diseases. Activated AMPK turns on catabolic pathways to augment ATP production while turning off synthetic pathways that consume ATP. Information is provided regarding the inter-organ requirements for more normal metabolic function during crisis and how anaplerotic therapy using triheptanoin, as a direct source of substrate to the CAC for energy production, appears to be a more successful approach to an improved quality of life for these patients.

The effect of L-alanine therapy in a patient with adult onset glycogen storage disease type II

Adult-onset glycogen storage disease type II (GSD II) (McKusick 232300) is a progressive disabling myopathy. At present there is no treatment of proven clinical efficacy. Enzyme replacement therapy may in the future provide benefit but it will be costly and is not yet freely available. L-Alanine, a simple and relatively cheap therapy, has been shown to reduce protein degradation in GSD II patients but has not previously been assessed for clinical benefit in a controlled study. In this study L-alanine was assessed in a double blind, placebo-controlled, crossover n = 1 study. Assessments consisted of spirometry, cardiopulmonary exercise testing, quality of life measurements, biochemical markers and assessment by the criterion 4-component model of body composition. Alanine therapy was associated with a 15% gain in total body protein. However, the patient showed no functional improvement and reported feeling worse after treatment. Further controlled studies in a small group may be warranted, but not widespread use of this therapy.

Modification of the natural history of adult-onset acid maltase deficiency by nutrition and exercise therapy

Adult-onset acid maltase deficiency is an inherited lysosomal skeletal-muscle disease characterized by progressive myopathy and respiratory failure, for which there is no known therapy. In an uncontrolled, prospective study, we evaluated whether adherence to high-protein and low-carbohydrate nutrition and exercise therapy (NET) can slow the progressive deterioration of muscle function in this disease. Thirty-four patients have been treated with NET for periods of 2-10 years (mean 4.5 +/- 2.5). Pre-NET rate of muscle function deterioration, as measured by the Walton scale, was compared to post-NET rate. Twenty-six patients were deemed to be consistently compliant with NET. Difference between pre-NET slope of muscle function deterioration to that of post-NET slope in compliant patients was -0.29 (95% CI -0.19, 0.39) (P < 0.0001). We conclude that compliance with NET can slow deterioration of muscle function and improve the natural history of adult-onset acid maltase deficiency. Muscle Nerve, 2006.

Benign course of glycogen storage disease type IIb in two brothers: Nature or nurture?

Two brothers with the childhood variant of type II glycogenosis (GSD-IIb) treated with nutrition and exercise therapy (NET) from a young age showed an unusually benign course. Muscle biopsy from the older brother, which showed characteristic vacuolar glycogen accumulation at age 2, had reverted to normal by age 16. A muscle biopsy from the younger brother was normal at 5 years. It is uncertain whether this anomalous evolution was spontaneous (nature) or due to the symptomatic therapy (nurture), but NET should be considered in patients with GSD-IIb until enzyme replacement or gene therapy become generally available.

L-alanine supplementation in late infantile glycogen storage disease type II

We report a male with late infantile glycogen storage disease type II (Pompe's disease) who presented at 12 months of age with muscular hypotonia and developmental delay. Oral supplementation with L-alanine has been administered for 5 years. Progression of skeletal myopathy was slow, and cardiomyopathy resolved almost completely. L-alanine may be a valuable supplement for infants with glycogen storage disease type II.