New in vitro model derived from brain-specific Mut-/- mice confirms cerebral ammonium accumulation in methylmalonic aciduria

OVA-Induced Food Allergy Leads to Neurobehavioral Changes in Mice and the Potential Role of Gut Microbiota and Metabolites Dysbiosis

The neurobehavioral changes in food allergy mice have not been comprehensively studied, and the mechanism underlying them remains unclear. Our study aims to fully investigate neurobehavioral changes in OVA (ovalbumin)-sensitized food allergy mice and explore the potential mechanism via the gut microbiota-brain axis. We established the food allergy mouse (C57BL/6J male) model with OVA, evaluating the anaphylactic symptoms and the levels of Th2 signature cytokine and allergy-related antibodies in serum. Using behavioral tests, we measured anxiety, depression, social behavior, repetitive behavior, attention, and spatial memory in control and OVA mice. In addition, we analyzed the prefrontal cortex for measuring inflammation-related indicators and gathered serum for untargeted metabolomics analysis and feces for 16S rDNA sequencing. OVA mice exhibited anaphylactic symptoms and significantly elevated serum IgE and Th2 signature cytokine levels. In addition to anxiety-like, depression-like, and repetitive behaviors, OVA mice also displayed less social interest and damaged attention. TNF-α, IL-1β, and IL-6 levels and the activation of microglia in the prefrontal cortex of OVA mice were significantly increased, which might explain the neuronal damage. Using multi-omics technology, amino acid metabolism disruption, particularly carboxylic acids and derivatives, was observed in OVA mice, which was remarkably correlated with the altered abundance of gut microbiota related to food allergy. Behaviors in OVA-induced food allergy mice were extensively impaired. The disruption of amino acid metabolism associated with gut microbiota dysbiosis in OVA mice might play a pivotal role in impairing neural immune homeostasis and neuronal damage, which could be responsible for behavioral abnormalities.

Treatment of metabolic disorders using genomic technologies: Lessons from methylmalonic acidemia

Hereditary methylmalonic acidemia (MMA) caused by deficiency of the enzyme methylmalonyl-CoA mutase (MMUT) is a relatively common and severe organic acidemia. The recalcitrant nature of the condition to conventional dietary and medical management has led to the use of elective liver and combined liver-kidney transplantation in some patients. However, liver transplantation is intrinsically limited by organ availability, the risks of surgery, procedural and life-long management costs, transplant comorbidities, and a remaining underlying risk of complications related to MMA despite transplantation. Here, we review pre-clinical studies that present alternative approaches to solid organ transplantation as a treatment for MMUT MMA, including adeno-associated viral gene addition therapy, mRNA therapy, and genome editing, with and without nuclease enhancement.

Physical and Neurological Development of a Girl Born to a Mother with Methylmalonic Acidemia and Kidney Transplantation and Review of the Literature

Background: actual literature suggests that children of methylmalonic acidemia patients are mostly healthy, but data are only partial, especially regarding long-term outcome. Therefore, our aim was to evaluate the possible long-term neurological effects of fetal exposure to high levels of methylmalonic acid in a child of a renal transplant recipient. Methods: we retrospectively evaluated the clinical and neurological records of a girl whose mother is a kidney transplant recipient affected by methylmalonic acidemia. Subsequently, we compared our results with the ones already published. Results: the girl’s weight and stature were within the normal range in the first years of life but, starting from 4 years of age, she became progressively overweight. Regarding the neurodevelopment aspects, for the first time we performed a complete and seriated neuropsychological evaluation, highlighting a mild but significant weakness in the verbal domain, with a worsening trend at three-year revaluation. Conclusions: since children of MMA patients are exposed to methylmalonic acid, the efforts of the physicians caring for these children should be directed on careful evaluation of growth, prevention of obesity and regular neurological examination together with structured neuropsychological tests to achieve a better insight in possible complications of pregnancy in patients suffering from this condition.

Milestones in treatments for inborn errors of metabolism: Reflections on Where chemistry and medicine meet

From Sir Archibald Garrod's initial description of the tetrad of albinism, alkaptonuria, cystinuria, and pentosuria to today, the field of medicine dedicated to inborn errors of metabolism has evolved from disease identification and mechanistic discovery to the development of therapies designed to subvert biochemical defects. In this review, we highlight major milestones in the treatment and diagnosis of inborn errors of metabolism, starting with dietary therapy for phenylketonuria in the 1950s and 1960s, and ending with current approaches in genetic manipulation.

Determination of Cytokines and Oxidative Stress Biomarkers in Cognitive Impairment Induced by Methylmalonic Acidemia

OBJECTIVE

Methylmalonic acidemia (MMA) is the most common organic acidemia in children. Many patients with MMA suffered from cognitive impairments. The aim of this study was to identify the significance of cytokines and oxidative stress biomarkers in MMA-induced cognitive impairment.

METHODS

We enrolled 64 children with combined MMA and homocystinuria and 64 age- and sex-matched healthy volunteers. Participants were subsequently classified as with or without cognitive impairments using a uniform neuropsychological assessment test. Serum samples were collected. The serum levels of cytokines and oxidative stress biomarkers were measured using the ELISA or chemical methods.

RESULTS

Compared to control group, the serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, malondialdehyde (MDA), and nitric oxide (NO) in the MMA patients increased markedly (p < 0.05); glutathione (GSH) and superoxide dismutase (SOD) decreased obviously (p < 0.01). The levels of IL-6, TNF-α, NO, and MDA in the serum were negatively associated with DQ or IQ scores. The levels of GSH and SOD in the serum were positively correlated with DQ or IQ scores. After receiver operating characteristic curve analysis, NO was the most useful individual marker for distinguishing the cognitive dysfunction, corresponding to the area under ROC curve (AUC) of 0.82 (95% CI, 0.74-0.91), sensitivity of 76.60%, and specificity of 80.25%. GSH and MDA were also useful for diagnosis of MMA-induced cognitive dysfunction, corresponding to the AUC of 0.80 (95% CI, 0.70-0.89), and 0.73 (95% CI, 0.63-0.82), respectively. The sensitivity and specificity of GSH were 72.34 and 80.25%, respectively. The sensitivity and specificity of MDA were 85.11 and 51.85%, respectively.

CONCLUSIONS

The high-concentration methylmalonic acid in the blood induced immune cells to release pro-inflammatory cytokines such as TNF-α and IL-6. These cytokines and high-concentration methylmalonic acid stimulated the immune cells to produce reactive oxygen species (ROS) and reactive nitrogen species (RNS). The serum methylmalonic acid, cytokines, ROS, and RNS were across the blood-brain barrier and induced cognitive impairment. The small molecule substances such as serum NO, MDA, and GSH participated in the process of neuroinflammation and oxidative stress injury induced by MMA and could be useful for distinguishing the cognitive impairment.

Impaired mitophagy links mitochondrial disease to epithelial stress in methylmalonyl-CoA mutase deficiency

Deregulation of mitochondrial network in terminally differentiated cells contributes to a broad spectrum of disorders. Methylmalonic acidemia (MMA) is one of the most common inherited metabolic disorders, due to deficiency of the mitochondrial methylmalonyl-coenzyme A mutase (MMUT). How MMUT deficiency triggers cell damage remains unknown, preventing the development of disease-modifying therapies. Here we combine genetic and pharmacological approaches to demonstrate that MMUT deficiency induces metabolic and mitochondrial alterations that are exacerbated by anomalies in PINK1/Parkin-mediated mitophagy, causing the accumulation of dysfunctional mitochondria that trigger epithelial stress and ultimately cell damage. Using drug-disease network perturbation modelling, we predict targetable pathways, whose modulation repairs mitochondrial dysfunctions in patient-derived cells and alleviate phenotype changes in mmut-deficient zebrafish. These results suggest a link between primary MMUT deficiency, diseased mitochondria, mitophagy dysfunction and epithelial stress, and provide potential therapeutic perspectives for MMA.