Enhanced glycolysis and GSK3 inactivation promote brain metabolic adaptations following neuronal mitochondrial stress

Unraveling the Role of Wnt Signaling Pathway in the Pathogenesis of Autism Spectrum Disorder (ASD): A Systematic Review

Autism spectrum disorder (ASD), or simply autism, is a neurodevelopmental disorder characterized by social communication deficit, restricted interests, and repetitive behavior. Several studies suggested a link between autism and the dysregulation of the Wnt signaling pathway which is mainly involved in cell fate determination, cell migration, cell polarity, neural patterning, and organogenesis. Despite the absence of effective therapy, significant progress has been made in understanding the pathogenesis of ASD. Neuropharmacological studies showed that drugs acting on the Wnt pathway like Canagliflozin can alleviate autistic-like behavior in animal models. Hence, this pathway could potentially be a futuristic therapeutic target to mitigate autism's symptoms. This systematic review aims to collect and analyze evidence that elucidates how alterations in the Wnt pathway may contribute to the pathogenesis of autism in animal models at the molecular, cellular, and physiological levels. Comprehensive searches were conducted across multiple databases, including PubMed, Web of Science, Embase, and Scopus to identify relevant studies up to March 2024. The inclusion criteria encompassed experimental studies that focused on the link between autism and this pathway, and the quality assessment was ensured by SYRCLE's risk of bias tools. Collectively, the included articles highlighted the possible implication of this pathway in the abnormalities found in autism, which impacted processes such as energy metabolism, oxidative stress, and neurogenesis. These alterations could underlie autistic behavior by affecting synaptic transmission and mitochondrial function.

Tissue-specific adaptations to cytochrome c oxidase deficiency shape physiological outcomes

It becomes increasingly clear that the tissue specificity of mitochondrial diseases might in part rely on their ability to compensate for mitochondrial defects, contributing to the heterogeneous nature of mitochondrial diseases. Here, we investigated tissue-specific responses to cytochrome c oxidase (CIV or COX) deficiency using a mouse model with heart and skeletal muscle-specific depletion of the COX assembly factor COX10. At three weeks of age, both tissues exhibit pronounced CIV depletion but respond differently to oxidative phosphorylation (OXPHOS) impairment. Heart-specific COX10 depletion caused severe dilated cardiomyopathy, while skeletal muscle experiences less damage. Cardiac CIV deficiency triggered extensive metabolic remodelling and stress response activation, potentially worsening cardiomyopathy, whereas skeletal muscle showed no stress response or significant metabolic changes. Our findings highlight distinct tissue capacities for managing CIV deficiency, explaining how identical primary defects can lead to different phenotypic outcomes and contribute to the heterogeneous progression of mitochondrial diseases.

Brain Glycogen-Its Metabolic Role in Neuronal Health and Neurological Disorders-An Extensive Narrative Review

Background: Brain glycogen is imperative for neuronal health, as it supports energy demands and metabolic processes. This review examines the pathways involved in glycogen storage and utilization in the central nervous system, emphasizing their role in both physiology and pathology. It explores how alterations in glycogen metabolism contribute to neurological disorders, including neurodegenerative diseases, epilepsy, and metabolic conditions while highlighting the bidirectional interaction between neurons and glia in maintaining brain homeostasis. Methods: A comprehensive search of articles published between 2015 and 2025 was conducted using the following databases: ScienceDirect, Scopus, Wiley, Web of Science, Medline, and PubMed. The selection of relevant studies was based on their focus on brain glycogen metabolism and its role in neurological conditions, with studies that did not meet the inclusion criteria being excluded. Results: The metabolic processes of brain glycogen are subject to rigorous regulation by astrocyte-neuron interactions, thereby ensuring metabolic homeostasis and energy availability. The dysregulation of glycogen storage and mobilization has been implicated in the development of synaptic dysfunction, excitotoxicity, and neurodegeneration in a variety of disorders. For instance, aberrant glycogen accumulation in diseases such as Lafora disease has been associated with severe neurodegeneration, while impaired glycogen mobilization has been shown to exacerbate energy deficits in Alzheimer's and epilepsy. Conclusions: Targeting brain glycogen metabolism represents a promising approach for therapeutic intervention in neurological disorders. However, the translation of these strategies to human models remains challenging, particularly with regard to the long-term safety and specificity of glycogen-targeted therapies.

Downregulated expression of lactate dehydrogenase in adult oligodendrocytes and its implication for the transfer of glycolysis products to axons

Oligodendrocytes and astrocytes are metabolically coupled to neuronal compartments. Pyruvate and lactate can shuttle between glial cells and axons via monocarboxylate transporters. However, lactate can only be synthesized or used in metabolic reactions with the help of lactate dehydrogenase (LDH), a tetramer of LDHA and LDHB subunits in varying compositions. Here we show that mice with a cell type-specific disruption of both Ldha and Ldhb genes in oligodendrocytes lack a pathological phenotype that would be indicative of oligodendroglial dysfunctions or lack of axonal metabolic support. Indeed, when combining immunohistochemical, electron microscopical, and in situ hybridization analyses in adult mice, we found that the vast majority of mature oligodendrocytes lack detectable expression of LDH. Even in neurodegenerative disease models and in mice under metabolic stress LDH was not increased. In contrast, at early development and in the remyelinating brain, LDHA was readily detectable in immature oligodendrocytes. Interestingly, by immunoelectron microscopy LDHA was particularly enriched at gap junctions formed between adjacent astrocytes and at junctions between astrocytes and oligodendrocytes. Our data suggest that oligodendrocytes metabolize lactate during development and remyelination. In contrast, for metabolic support of axons mature oligodendrocytes may export their own glycolysis products as pyruvate rather than lactate. Lacking LDH, these oligodendrocytes can also "funnel" lactate through their "myelinic" channels between gap junction-coupled astrocytes and axons without metabolizing it. We suggest a working model, in which the unequal cellular distribution of LDH in white matter tracts facilitates a rapid and efficient transport of glycolysis products among glial and axonal compartments.