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

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.

Exercise training alone or in combination with high-protein diet in patients with late onset Pompe disease: results of a cross over study

Background

Late onset Pompe disease (LOPD) is a lysosomal neuromuscular disorder which can progressively impair the patients’ exercise tolerance, motor and respiratory functions, and quality of life. The available enzyme replacement therapy (ERT) does not completely counteract disease progression. We investigated the effect of exercise training alone, or associated with a high-protein diet, on the exercise tolerance, muscle and pulmonary functions, and quality of life of LOPD patients on long term ERT.

Methods

The patients were asked to participate to a crossover randomized study comprehending a control period (free diet, no exercise) followed by 2 intervention periods: exercise or exercise + diet, each lasting 26 weeks and separated by 13 weeks washout periods. Exercise training included moderate-intensity aerobic exercise on a cycle ergometer, stretching and balance exercises, strength training. The diet was composed by 25–30% protein, 30–35% carbohydrate and 35–40% fat. Before and after each period patients were assessed for: exercise tolerance test on a cycle-ergometer, serum muscle enzymes, pulmonary function tests and SF36 questionnaire for quality of life. Compliance was evaluated by training and dietary diaries. Patients were contacted weekly by researchers to optimize adherence to treatments.

Results

Thirteen LOPD patients, median age 49 ± 11 years, under chronic ERT (median 6.0 ± 4.0 years) were recruited. Peak aerobic power (peak pulmonary O₂ uptake) decreased after control, whereas it increased after exercise, and more markedlyafter exercise + diet. Serum levels of lactate dehydrogenase (LDH) significantly decreased after exercise + diet; both creatine kinase (CK) and LDH levels were significantly reduced after exercise + diet compared to exercise. Pulmonary function showed no changes after control and exercise, whereas a significant improvement of forced expiratory volume in 1 sec (FEV1) was observed after exercise + diet. SF36 showed a slight improvement in the “mental component” scale after exercise, and a significant improvement in “general health” and “vitality” after exercise + diet. The compliance to prescriptions was higher than 70% for both diet and exercise.

Conclusions

Exercise tolerance (as evaluated by peak aerobic power) showed a tendency to decrease in LOPD patients on long term ERT. Exercise training, particularly if combined with high-protein diet, could reverse this decrease and result in an improvement, which was accompanied by improved quality of life. The association of the two lifestyle interventions resulted also in a reduction of muscle enzyme levels and improved pulmonary function.

Patient and observer reported outcome measures to evaluate health-related quality of life in inherited metabolic diseases: a scoping review

BACKGROUND

Health-related Quality of Life (HrQoL) is a multidimensional measure, which has gained clinical and social relevance. Implementation of a patient-centred approach to both clinical research and care settings, has increased the recognition of patient and/or observer reported outcome measures (PROMs or ObsROMs) as informative and reliable tools for HrQoL assessment. Inherited Metabolic Diseases (IMDs) are a group of heterogeneous conditions with phenotypes ranging from mild to severe and mostly lacking effective therapies. Consequently, HrQoL evaluation is particularly relevant.

OBJECTIVES

We aimed to: (1) identify patient and/or caregiver-reported HrQoL instruments used among IMDs; (2) identify the main results of the application of each HrQoL tool and (3) evaluate the main limitations of HrQoL instruments and study design/methodology in IMDs.

METHODS

A scoping review was conducted using methods outlined by Arksey and O'Malley. Additionally, we critically analysed each article to identify the HrQoL study drawbacks.

RESULTS

Of the 1954 studies identified, 131 addressed HrQoL of IMDs patients using PROMs and/or ObsROMs, both in observational or interventional studies. In total, we identified 32 HrQoL instruments destined to self- or proxy-completion; only 2% were disease-specific. Multiple tools (both generic and disease-specific) proved to be responsive to changes in HrQoL; the SF-36 and PedsQL questionnaires were the most frequently used in the adult and pediatric populations, respectively. Furthermore, proxy data often demonstrated to be a reliable approach complementing self-reported HrQoL scores. Nevertheless, numerous limitations were identified especially due to the rarity of these conditions.

CONCLUSIONS

HrQoL is still not frequently assessed in IMDs. However, our results show successful examples of the use of patient-reported HrQoL instruments in this field. The importance of HrQoL measurement for clinical research and therapy development, incites to further research in HrQoL PROMs' and ObsROMs' creation and validation in IMDs.

Glycogen metabolism in humans

In the human body, glycogen is a branched polymer of glucose stored mainly in the liver and the skeletal muscle that supplies glucose to the blood stream during fasting periods and to the muscle cells during muscle contraction. Glycogen has been identified in other tissues such as brain, heart, kidney, adipose tissue, and erythrocytes, but glycogen function in these tissues is mostly unknown. Glycogen synthesis requires a series of reactions that include glucose entrance into the cell through transporters, phosphorylation of glucose to glucose 6-phosphate, isomerization to glucose 1-phosphate, and formation of uridine 5'-diphosphate-glucose, which is the direct glucose donor for glycogen synthesis. Glycogenin catalyzes the formation of a short glucose polymer that is extended by the action of glycogen synthase. Glycogen branching enzyme introduces branch points in the glycogen particle at even intervals. Laforin and malin are proteins involved in glycogen assembly but their specific function remains elusive in humans. Glycogen is accumulated in the liver primarily during the postprandial period and in the skeletal muscle predominantly after exercise. In the cytosol, glycogen breakdown or glycogenolysis is carried out by two enzymes, glycogen phosphorylase which releases glucose 1-phosphate from the linear chains of glycogen, and glycogen debranching enzyme which untangles the branch points. In the lysosomes, glycogen degradation is catalyzed by α-glucosidase. The glucose 6-phosphatase system catalyzes the dephosphorylation of glucose 6-phosphate to glucose, a necessary step for free glucose to leave the cell. Mutations in the genes encoding the enzymes involved in glycogen metabolism cause glycogen storage diseases.

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.