Ammonia role in glial dysfunction in methylmalonic acidemia

Neurodegenerative biomarkers and inflammation in patients with propionic and methylmalonic acidemias: effect of L-carnitine treatment

Propionic and methylmalonic acidemias (PAcidemia and MMAcidemia, respectively) are genetic disorders characterized by acute metabolic decompensation and neurological complications. L-carnitine (LC) is effective in reducing toxic metabolites that are related to the pathophysiology of these diseases. Therefore we investigated biomarkers of inflammation (cytokines and C-reactive protein (CRP)), neurodegeneration (BDNF, NCAM-1 and cathepsin-D) and biomolecules oxidation (sulfhydryl content and thiobarbituric acid-reactive species (TBARS)), as well as carnitine concentrations in untreated patients with PAcidemia and MMAcidemia, in patients under treatment with LC and a protein-restricted diet for until 2 years and in patients under the same treatment for more than 2 years. It was verified an increase of CRP, IL-6, IL-8, TNF-α, IL-10, NCAM-1 and cathepsin-D in untreated patients compared to controls. On the other hand, reduced levels of TNF-α, CRP, IL-10, NCAM-1 and cathepsin-D were found in plasma from treated patients, as well as increased concentrations of LC. Furthermore, oxidative biomarkers were increased in untreated patients and were normalized with the prolonged treatment with LC. In conclusion, this work shows, for the first time, that inflammatory and neurodegenerative peripheral biomarkers are increased in patients with PAcidemia and MMAcidemia and that treatment with LC is effective to protect against these alterations.

The Efficacy and Outcomes of Renal Replacement Therapy in Pediatric Metabolic Disorders

Background/Objectives: This study aims to evaluate the efficacy and outcomes of renal replacement therapy (RRT) in pediatric patients with metabolic diseases, specifically focusing on the impact of hemodialysis (HD) and peritoneal dialysis (PD) on clinical parameters, toxin reduction, and long-term survival. Methods: This retrospective study included 10 pediatric patients (eight females and two males) treated at a pediatric nephrology department between 2020 and 2023. Patients diagnosed with metabolic disorders, including maple syrup urine disease (MSUD), methylmalonic acidemia (MMA), and glycogen storage disease (GSD), underwent RRT. Clinical data, demographic information, and biochemical parameters were collected and analyzed. Results: Among the patients, 50% were diagnosed with MSUD, 30% with MMA, and 20% with GSD. RRT, including HD and PD, was administered to manage acute metabolic crises. HD was particularly effective in rapidly reducing toxic metabolite levels. Patients treated with HD showed significant reductions in leucine and ammonium levels, with median reductions of 94.5% and 86%, respectively. Overall, 60% of the patients demonstrated long-term survival, highlighting the critical role of RRT in managing metabolic crises. In conclusion, RRT, including HD and PD, is crucial in managing pediatric metabolic disorders by effectively reducing toxic metabolite levels and improving clinical outcomes. Conclusions: The results of this study are consistent with previous research, highlighting the critical role of RRT in the acute management of metabolic crises and supporting its adoption as a standard treatment method.

Methylmalonic acid induces inflammatory response and redox homeostasis disruption in C6 astroglial cells: potential glioprotective roles of melatonin and resveratrol

Methylmalonic acidemia is a neurometabolic disorder biochemically characterized by the accumulation of methylmalonic acid (MMA) in different tissues, including the central nervous system (CNS). In this sense, it has been shown that high levels of this organic acid have a key role in the progressive neurological deterioration in patients. Astroglial cells actively participate in a wide range of CNS functions, such as antioxidant defenses and inflammatory response. Considering the role of these cells to maintain brain homeostasis, in the present study, we investigated the effects of MMA on glial parameters, focusing on redox homeostasis and inflammatory process, as well as putative mediators of these events in C6 astroglial cells. MMA decreased cell viability, glutathione levels, and antioxidant enzyme activities, increased inflammatory response, and changed the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), nuclear factor kappa B (NFκB), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and adenosine receptors, suggesting that these transcriptional factors and proteins may underlie the glial responses induced by MMA. Moreover, we also demonstrated the protective roles of melatonin and resveratrol against MMA-induced inflammation and decrease in glutathione levels. In summary, our findings support the hypothesis that astroglial changes are associated with pathogenesis of methylmalonic acidemia. In addition, we showed that these cells might be potential targets for preventive/therapeutic strategies by using molecules, such as melatonin and resveratrol, which mediated glioprotection in this inborn error of metabolism.

Case report: Is exchange transfusion a possible treatment for metabolic decompensation in neonates with methylmalonic aciduria in the setting of limited resources?

Hyperammonemia is a serious complication of methylmalonic acidemia, with high mortality and permanent neurological sequelae in survivors. Primary hospitals are often the first admission hospitals for these children but are limited by their experience and facilities to provide rapid and effective treatment, increasing the risk of death in children with methylmalonic acidemia's metabolic crisis. In this report, we reported a case of a 7-day-old male neonate with decompensated methylmalonic acidemia, who underwent automatic peripheral arteriovenous exchange transfusion. The serum ammonia level of the boy decreased significantly post exchange transfusion. Therefore, we put forward the suggestion of exchange transfusion for hyperammonemia, in combination with medical therapy, in children with inborn errors of metabolism as an initial treatment option in primary hospitals if a rapid transfer to a center with dialysis facilities is not possible.

Sustained glial reactivity induced by glutaric acid may be the trigger to learning delay in early and late phases of development: Involvement of p75NTR receptor and protection by N-acetylcysteine

Degeneration of striatal neurons and cortical atrophy are pathological characteristics of glutaric acidemia type I (GA-I), a disease characterized by accumulation of glutaric acid (GA). The mechanisms that lead to neuronal loss and cognitive impairment are still unclear. The purpose of this study was to verify if acute exposure to GA during the neonatal period is sufficient to trigger apoptotic processes and lead to learning delay in early and late period. Besides, whether N-acetylcysteine (NAC) would protect against impairment induced by GA. Pups mice received a dose of GA (2.5 μmol/ g) or saline, 12 hs after birth, and were treated with NAC (250 mg/kg) or saline, up to 21th day of life. Although GA exhibited deficits in the procedural and working memories in 21 and 40-day-old mice, NAC protected against cognitive impairment. In striatum and cortex, NAC prevented glial cells activation (GFAP and Iba-1), decreased NGF, Bcl-2 and NeuN, the increase of lipid peroxidation and PARP induced by GA in both ages. NAC protected against increased p75NTR induced by GA, but not in cortex of 21-day-old mice. Thus, we showed that the integrity of striatal and cortical pathways has an important role for learning and suggested that sustained glial reactivity in neonatal period can be an initial trigger for delay of cognitive development. Furthermore, NAC protected against cognitive impairment induced by GA. This work shows that early identification of the alterations induced by GA is important to avoid future clinical complications and suggest that NAC could be an adjuvant treatment for this acidemia.

Involvement of the Cholinergic Parameters and Glial Cells in Learning Delay Induced by Glutaric Acid: Protection by N-Acetylcysteine

Dysfunction of basal ganglia neurons is a characteristic of glutaric acidemia type I (GA-I), an autosomal recessive inherited neurometabolic disease characterized by deficiency of glutaryl-CoA dehydrogenase (GCDH) and accumulation of glutaric acid (GA). The affected patients present clinical manifestations such as motor dysfunction and memory impairment followed by extensive striatal neurodegeneration. Knowing that there is relevant striatal dysfunction in GA-I, the purpose of the present study was to verify the performance of young rats chronically injected with GA in working and procedural memory test, and whether N-acetylcysteine (NAC) would protect against impairment induced by GA. Rat pups were injected with GA (5 μmol g body weight^-1, subcutaneously; twice per day; from the 5th to the 28th day of life) and were supplemented with NAC (150 mg/kg/day; intragastric gavage; for the same period). We found that GA injection caused delay procedural learning; increase of cytokine concentration, oxidative markers, and caspase levels; decrease of antioxidant defenses; and alteration of acetylcholinesterase (AChE) activity. Interestingly, we found an increase in glial cell immunoreactivity and decrease in the immunoreactivity of nuclear factor-erythroid 2-related factor 2 (Nrf2), nicotinic acetylcholine receptor subunit alpha 7 (α7nAChR), and neuronal nuclei (NeuN) in the striatum. Indeed, NAC administration improved the cognitive performance, ROS production, neuroinflammation, and caspase activation induced by GA. NAC did not prevent neuronal death, however protected against alterations induced by GA on Iba-1 and GFAP immunoreactivities and AChE activity. Then, this study suggests possible therapeutic strategies that could help in GA-I treatment and the importance of the striatum in the learning tasks.