Search Results (47)

Considered by some to be the largest metabolic organ of the body, the functional integrity of skeletal muscle is highly dependent on its exceptional plasticity, which is primarily governed by mitochondrial quality control. The signaling axis composed of AMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) serves as a critical hub that senses cellular energy status, coordinates mitochondrial biogenesis, regulates muscle fiber type switching, and maintains protein homeostasis. This review systematically delineates the structural functions and synergistic regulatory network of the AMPK/SIRT1/PGC-1α signaling axis. It further elucidates the regulatory roles of this pathway under physiological conditions—such as exercise adaptation and muscle fiber-type transformation—and its dysregulated mechanisms in the pathogenesis of various skeletal muscle disorders, including sarcopenia, disuse atrophy, cachexia, neurogenic atrophy, muscular dystrophy, and type 2 diabetes mellitus-related myopathy. Building on this foundation, this review critically analyzes current multifaceted therapeutic strategies targeting this pathway, encompassing exercise and physical therapy, nutritional and natural products, and small molecule drugs, as well as gene and cell-based therapies. Finally, this review delves into the challenges facing clinical translation in this field, such as the complexity of the signaling network, individual variability, and bioavailability issues. It also proposes future research directions focused on developing precision intervention tools, establishing effective biomarker systems, and exploring combination intervention strategies. Collectively, the AMPK/SIRT1/PGC-1α signaling axis is central to maintaining skeletal muscle metabolic homeostasis, and targeting this pathway provides a robust theoretical foundation and broad application prospects for the prevention and treatment of skeletal muscle-related diseases. Full article

Background: Heimler syndrome (HS) is a rare autosomal recessive disorder representing the mildest end of the peroxisome biogenesis disorder spectrum. It is caused by hypomorphic mutations in peroxisomal assembly genes, most commonly PEX1 and PEX6, and is characterized by sensorineural hearing loss, amelogenesis imperfecta, and retinal dystrophy. Due to phenotypic overlap with other inherited sensory disorders, particularly Usher syndrome, diagnosis of this condition is frequently delayed. Methods: We investigated two unrelated Saudi families presenting with congenital hearing loss and retinal dystrophy who were initially diagnosed with Usher syndrome. Detailed clinical evaluation, including comprehensive ophthalmologic and audiologic assessments, was performed. Whole-exome sequencing (WES) was conducted to identify the underlying genetic cause, followed by variant filtering and in silico pathogenicity prediction. Results: We identified a novel homozygous missense variant, p.Val97Gly (V97G), in the PEX6 gene that co-segregated with the disease phenotype in both families. This variant was absent from major population databases, including dbSNP, the 1000 Genomes Project, ExAC, and gnomAD, and was predicted to be deleterious by multiple in silico prediction tools. Clinically, affected individuals presented with congenital sensorineural hearing loss, pigmentary retinal dystrophy with electrophysiological evidence of cone–rod dysfunction, enamel abnormalities consistent with amelogenesis imperfecta, and mild dysmorphic facial features, supporting a diagnosis within the Heimler syndrome spectrum. Conclusions: Our findings expand the mutational spectrum of PEX6 and highlight Heimler syndrome as an important differential diagnosis in patients presenting with Usher-like phenotypes. To the best of our knowledge, this study represents the first report of the PEX6 p.Val97Gly variant associated with Heimler syndrome in a Saudi population, underscoring the value of whole-exome sequencing for accurate diagnosis and genetic counseling in individuals with inherited sensory disorders. Full article

Rhizomelic chondrodysplasia punctata type 1 (RCDP1) is a peroxisomal disorder characterized by skeletal shortening, intellectual disability, seizures, cataracts, and reduced lifespans. RCDP1 is caused by biallelic loss-of-function variants in PEX7, which encodes a protein required for importing select enzymes into the peroxisome matrix, including those essential for ether lipid synthesis (e.g., plasmalogens) and the branched-chain fatty acid catabolism. Plasmalogen deficiency is a hallmark of RCDP1 and other peroxisomal disorders, including RCDP types 2-5 (RCDP2-5) and Zellweger spectrum disorders (ZSD). Here, we performed comprehensive metabolomic profiling of clinical samples from RCDP patients and Pex7-deficient mouse models. We identified profound neurometabolic disturbances in the cerebral cortex and cerebellum of Pex7-deficient mice involving multiple lipid classes, including phosphatidylethanolamines (PEs), phosphatidylcholines (PCs), acylcarnitines, and sphingomyelins. Notably, many of these neurometabolic alterations were absent in patient and Pex7-deficient mouse plasma, indicating that plasma-based profiling can underrepresent the extent of CNS lipid remodeling. Overall, these findings reveal novel insights into neurometabolic adaptations to plasmalogen deficiency and suggest the potential involvement of additional pathways that may contribute to neurological dysfunction in RCDP. Full article

Introduction: Infantile Refsum disease (IRD) is considered one of the milder phenotypes within the Zellweger Spectrum Disorders (ZSDs), a group of peroxisomal biogenesis disorders characterized by a generalized impairment of peroxisomal function. Pathognomonic features of IRD are growth retardation, hearing and cognitive impairment, neuromuscular problems, and craniofacial anomalies. Due to the relatively short lifespan, severe dental anomalies have not been previously reported in association with this disorder. This case report describes a rare manifestation of multiple impacted teeth and near complete edentulism in an adult patient diagnosed with Infantile Refsum disease (IRD). Material and Methods: The patient, a 24-year-old female, presented with a skeletal Class III malocclusion, severe maxillary hypoplasia, and complete impaction of the permanent dentition. The diagnosis of Infantile Refsum disease (IRD) was genetically confirmed and was associated with both neurological and dermatological manifestations. Conclusions: This case underscores that severe disturbances in tooth eruption and impaction may represent underrecognized manifestations of metabolic and genetic disorders such as Infantile Refsum disease (IRD). Dental professionals should remain vigilant to the potential association between systemic conditions and delayed or failed tooth eruption, emphasizing the need for interdisciplinary management and further investigation. Full article

Astrocytes and microglia constitute nearly half of all central nervous system cells and are indispensable for its proper function. Both exhibit striking morphological and functional heterogeneity, adopting either neuroprotective (A2, M2) or proinflammatory (A1, M1) phenotypes in response to cytokines, pathogen-associated molecular patterns (PAMPs)/damage-associated molecular patterns (DAMPs), toll-like receptor 4 (TLR4) activation, and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signaling. Crucially, many of these phenotypic transitions arise during the earliest stages of neurodegeneration, when glial dysfunction precedes overt neuronal loss and may act as a primary driver of disease onset. This review critically examines glial-centered hypotheses of neurodegeneration, with emphasis on their roles in early disease phases: (i) microglial polarization from an M2 neuroprotective state to an M1 proinflammatory state; (ii) NLRP3 inflammasome assembly via P2X purinergic receptor 7 (P2X7R)-mediated K⁺ efflux; (iii) a self-amplifying astrocyte–microglia–neuron inflammatory feedback loop; (iv) impaired microglial phagocytosis and extracellular-vesicle–mediated propagation of β-amyloid (Aβ) and tau; (v) astrocytic scar formation driven by aquaporin-4 (AQP4), matrix metalloproteinase-9 (MMP-9), glial fibrillary acidic protein (GFAP)/vimentin, connexins, and janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling; (vi) cellular reprogramming of astrocytes and NG2 glia into functional neurons; and (vii) mitochondrial dysfunction in glia, including Dynamin-related protein 1/Mitochondrial fission protein 1 (Drp1/Fis1) fission imbalance and dysregulation of the sirtuin 1/peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Sirt1/PGC-1α) axis. Promising therapeutic strategies target pattern-recognition receptors (TLR4, NLRP3/caspase-1), cytokine modulators (interleukin-4 (IL-4), interleukin-10 (IL-10)), signaling cascades (JAK2–STAT, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphoinositide 3-kinase–protein kinase B (PI3K–AKT), adenosine monophosphate-activated protein kinase (AMPK)), microglial receptors (triggering receptor expressed on myeloid cells 2 (TREM2)/spleen tyrosine kinase (SYK)/ DNAX-activating protein 10 (DAP10), siglec-3 (CD33), chemokine C-X3-C motif ligand 1/ CX3C motif chemokine receptor 1 (CX3CL1/CX3CR1), Cluster of Differentiation 200/ Cluster of Differentiation 200 receptor 1 (CD200/CD200R), P2X7R), and mitochondrial biogenesis pathways, with a focus on normalizing glial phenotypes rather than simply suppressing pathology. Interventions that restore neuroglial homeostasis at the earliest stages of disease may hold the greatest potential to delay or prevent progression. Given the complexity of glial phenotypes and molecular isoform diversity, a comprehensive, multitargeted approach is essential for mitigating Alzheimer’s disease and related neurodegenerative disorders. This review not only synthesizes pathogenesis but also highlights therapeutic opportunities, offering what we believe to be the first concise overview of the principal hypotheses implicating glial cells in neurodegeneration. Rather than focusing on isolated mechanisms, our goal is a holistic perspective—integrating diverse glial processes to enable comparison across interconnected pathological conditions. Full article

Mitochondrial dysfunction is a key factor in the pathophysiology of major depressive disorder (MDD) and treatment-resistant depression (TRD), connecting oxidative stress, neuroinflammation, and reduced neuroplasticity. Physical exercise induces specific mitochondrial changes linked to improvements in mental health. The aim of this paper was to examine emerging evidence regarding the effects of physical exercise on mitochondrial function and treatment-resistant depression, highlighting the clinical importance of the use of mitochondrial biomarkers to personalize exercise prescriptions for patients with depression, particularly those who cannot tolerate standard treatments. Physical exercise improves mitochondrial function, enhances biogenesis and neuroplasticity, and decreases oxidative stress and neuroinflammation. Essential signaling pathways, including brain-derived neurotrophic factor, AMP-activated protein kinase, active peroxisome proliferator-activated receptor-γ coactivator-1α, and Ca²⁺/calmodulin-dependent protein kinase, support these effects. Most studies have concentrated on the impact of low- and moderate-intensity aerobic exercise on general health. However, new evidence suggests that resistance exercise and high-intensity interval training also promote healthy mitochondrial adaptations, although the specific exercise intensity required to achieve this goal remains to be determined. There is strong evidence that exercise is an effective treatment for MDD, particularly for TRD, by promoting specific mitochondrial adaptations. However, key gaps remain in our understanding of the optimal exercise dose and which patient subgroups are most likely to benefit from it (Graphical Abstract). Full article

Peroxisomes are cellular organelles involved in multiple metabolic processes, including lipid oxidation, lipid synthesis, and the metabolism of reactive oxygen species. Peroxisomal disorders arise from defects in peroxisomal biogenesis or peroxisomal enzymes. Patients with severe peroxisomal disorders often present with a range of distinctive physical features and congenital malformations, such as neuronal migration defects, renal cysts, and bony stippling in the patellae and long bones. Liver disease has also been reported in some patients with peroxisomal biogenesis disorders, although the exact molecular mechanisms underlying its development remain unclear. Metabolic dysfunction-associated steatotic liver disease (MASLD) is now recognised as one of the most prevalent causes of chronic liver disease globally, due to its widespread incidence and potential for serious complications. This review aims to highlight the possible involvement of peroxisomal defects in the pathogenesis of MASLD. Full article

Alzheimer’s disease (AD), the most common form of dementia, is a progressive neurodegenerative disorder characterized by memory loss and cognitive decline. In addition to its two major pathological hallmarks, extracellular amyloid beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs), recent evidence highlights the critical roles of mitochondrial dysfunction and neuroinflammation in disease progression. Aβ impairs mitochondrial function, which, in part, can subsequently trigger inflammatory cascades, creating a vicious cycle of neuronal damage. Estrogen receptors (ERs) are widely expressed throughout the brain, and the sex hormone 17β-estradiol (E2) exerts neuroprotection through both anti-inflammatory and mitochondrial mechanisms. While E2 exhibits neuroprotective properties, its mechanisms against Aβ toxicity remain incompletely understood. In this study, we investigated the neuroprotective effects of E2 against Aβ-induced mitochondrial dysfunction and neuroinflammation in primary cortical neurons, with a particular focus on the role of AMP-activated protein kinase (AMPK). We found that E2 treatment significantly increased phosphorylated AMPK and upregulated the expression of mitochondrial biogenesis regulator peroxisome proliferator-activated receptor gamma coactivator-1 α (PGC-1α), leading to improved mitochondrial respiration. In contrast, Aβ suppressed AMPK and PGC-1α signaling, impaired mitochondrial function, activated the pro-inflammatory nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), and reduced neuronal viability. E2 pretreatment also rescued Aβ-induced mitochondrial dysfunction, suppressed NF-κB activation, and, importantly, prevented the decline in neuronal viability. However, the pharmacological inhibition of AMPK using Compound C (CC) abolished these protective effects, resulting in mitochondrial collapse, elevated inflammation, and cell death, highlighting AMPK’s critical role in mediating E2’s actions. Interestingly, while NF-κB inhibition using BAY 11-7082 partially restored mitochondrial respiration, it failed to prevent Aβ-induced cytotoxicity, suggesting that E2’s full neuroprotective effects rely on broader AMPK-dependent mechanisms beyond NF-κB suppression alone. Together, these findings establish AMPK as a key mediator of E2’s protective effects against Aβ-driven mitochondrial dysfunction and neuroinflammation, providing new insights into estrogen-based therapeutic strategies for AD. Full article

Type 2 diabetes mellitus represents a major global health burden and is often preceded by a prediabetic state characterized by insulin resistance and metabolic dysfunction. Mitochondrial alterations, oxidative stress, and disturbances in lipid metabolism are central to the prediabetes pathophysiology. Melatonin, a pleiotropic indolamine, is known to regulate metabolic and mitochondrial processes; however, its therapeutic potential in prediabetes remains poorly understood. This study investigated the effects of melatonin on energy metabolism, oxidative stress, and mitochondrial function in a rat model of prediabetes induced by chronic sucrose intake and low-dose streptozotocin administration. Following prediabetes induction, animals were treated with melatonin (20 mg/kg) for four weeks. Biochemical analyses were conducted to evaluate glucose and lipid metabolism, and mitochondrial function was assessed via gene expression, enzymatic activity, and oxidative stress markers. Additionally, hepatic mitochondrial dynamics were examined by quantifying key regulators genes associated with biogenesis, fusion, and fission. Prediabetic animals exhibited dyslipidemia, hepatic lipid accumulation, increased fat depots, and impaired glucose metabolism. Melatonin significantly reduced serum glucose, triglycerides, and total cholesterol levels, while enhancing the hepatic high-density lipoprotein content. It also stimulated β-oxidation by upregulating hydroxyacyl-CoA dehydrogenase and citrate synthase activity. Mitochondrial dysfunction in prediabetic animals was evidenced by the reduced expression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha and mitochondrial transcription factor A, both of which were markedly upregulated by melatonin. The indolamine also modulated mithocondrial dynamics by regulating fusion and fission markers, including mitosuin 1 and 2, optic atrophy protein, and dynamin-related protein. Additionally, melatonin mitigated oxidative stress by enhancing the activity of superoxide dismutase and catalase while reducing lipid peroxidation. These findings highlight melatonin’s protective role in prediabetes by improving lipid and energy metabolism, alleviating oxidative stress, and restoring mitochondrial homeostasis. This study provides novel insights into the therapeutic potential of melatonin in addressing metabolic disorders, particularly in mitigating mitochondrial dysfunction associated with prediabetes. Full article

Background/Objectives: Zellweger spectrum disorder (ZSD), a rare genetic disease characterized by defects in peroxisome biogenesis, results in dysfunction of all organ systems, including feeding difficulties, gastrointestinal bleeding, and reduced overall growth. Despite this nutritional impact, no published studies have assessed dietary intake in ZSD. The purpose of this study was to determine nutrient intake in individuals with ZSD or a related peroxisomal disorder using two methods of dietary assessment as provided by family caregivers. Methods: Family caregivers participated in multiple 24 h dietary recall interviews and completed 3-day food records for their child with ZSD or a related single-enzyme peroxisomal disorder over a 6-month period. Results: Twenty-one subjects (eleven orally fed and ten enterally fed), ranging from 1 to 33 years of age, were included in the study. Energy and nutrient intake as reported by dietary recall vs. 3-day food record were highly correlated for all nutrients (r² = 0.998, p < 0.0001). Mean nutrient intakes for subjects generally achieved or exceeded DRI requirements, except for fiber (about 50% of DRI). Conclusions: These results show that dietary assessment is feasible in individuals with ZSD using caregiver input, regardless of feed modality, and that dietary intake is consistent across different methods of assessment. These findings may be applicable in dietary assessments for individuals with ZSD and similar genetic disorders and a methodological consideration in clinical interventions. Full article

Peroxisomes are ubiquitous, dynamic, oxidative organelles with key functions in cellular lipid metabolism and redox homeostasis. They have been linked to healthy ageing, neurodegeneration, cancer, the combat of pathogens and viruses, and infection and immune responses. Their biogenesis relies on several peroxins (encoded by PEX genes), which mediate matrix protein import, membrane assembly, and peroxisome multiplication. Defects in peroxins or peroxisomal enzymes can result in severe disorders, including developmental and neurological abnormalities. The drive to understand the role of peroxisomes in human health and disease, as well as their functions in tissues and organs or during development, has led to the establishment of vertebrate models. The zebrafish (Danio rerio) has become an attractive vertebrate model organism to investigate peroxisomal functions. Here, we provide an overview of the visualisation of peroxisomes in zebrafish, as well as the peroxisomal metabolic functions and peroxisomal protein inventory in comparison to human peroxisomes. We then present zebrafish models which have been established to investigate peroxisomal disorders. These include model zebrafish for peroxisome biogenesis disorders/Zellweger Spectrum disorders, and single enzyme deficiencies, particularly adrenoleukodystrophy and fatty acid beta-oxidation abnormalities. Finally, we highlight zebrafish models for deficiencies of dually targeted peroxisomal/mitochondrial proteins. Advantages for the investigation of peroxisomes during development and approaches to the application of zebrafish models for drug screening are discussed. Full article

Radiation liver injury is a common complication of hepatocellular carcinoma radiotherapy. It is mainly caused by irreversible damage to the DNA of hepatocellular cells directly by radiation, which seriously interferes with metabolism and causes cell death. AdipoRon can maintain lipid metabolism and stabilize blood sugar by activating adiponectin receptor 1 (AdipoR1). However, the role of AdipoRon/AdipoR1 in the regulation of ionizing radiation (IR)-induced mitochondrial damage remains unclear. In this study, we aimed to elucidate the roles of AdipoRon/AdipoR1 in IR-induced mitochondrial damage in normal hepatocyte cells. We found that AdipoRon treatment rescued IR-induced liver damage in mice and mitochondrial damage in normal hepatocytes in vivo and in vitro. AdipoR1 deficiency exacerbated IR-induced oxidative stress, mitochondrial dynamics, and biogenesis disorder. Mechanistically, the absence of AdipoR1 inhibits the activity of adenosine monophosphate-activated protein kinase α (AMPKα), subsequently leading to disrupted mitochondrial dynamics by decreasing mitofusin (MFN) and increasing dynamin-related protein 1 (DRP1) protein expression. It also controls mitochondrial biogenesis by suppressing the peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC1α) and transcription factor A (TFAM) signaling pathway, ultimately resulting in impaired mitochondrial function. To sum up, AdipoRon/AdipoR1 maintain mitochondrial function by regulating mitochondrial dynamics and biogenesis through the AdipoR1-AMPKα signaling pathway. This study reveals the significant role of AdipoR1 in regulating IR-induced mitochondrial damage in hepatocytes and offers a novel approach to protecting against damage caused by IR. Full article

Peroxisomes are organelles involved in many cellular metabolic functions, including the degradation of very-long-chain fatty acids (VLCFAs; C ≥ 22), the initiation of ether-phospholipid synthesis, and the metabolism of reactive oxygen species. All of these processes are essential for the maintenance of cellular lipid and redox homeostasis, and their perturbation can trigger inflammatory response in immune cells, including in the central nervous system (CNS) resident microglia and astrocytes. Consistently, peroxisomal disorders, a group of congenital diseases caused by a block in peroxisomal biogenesis or the impairment of one of the peroxisomal enzymes, are associated with neuroinflammation. Peroxisomal function is also dysregulated in many neurodegenerative diseases and during brain aging, both of which are associated with neuroinflammation. This suggests that deciphering the role of peroxisomes in neuroinflammation may be important for understanding both congenital and age-related brain dysfunction. In this review, we discuss the current advances in understanding the role and function of peroxisomes in neuroinflammation. Full article

Peroxisome proliferator-activated receptors (PPARs) may play an important role in the pathomechanism/pathogenesis of Alzheimer’s disease (AD) and several other neurological/neuropsychiatric disorders. AD leads to progressive alterations in the redox state, ion homeostasis, lipids, and protein metabolism. Significant alterations in molecular processes and the functioning of several signaling pathways result in the degeneration and death of synapses and neuronal cells, leading to the most severe dementia. Peroxisome proliferator-activated receptor alpha (PPAR-α) is among the processes affected by AD; it regulates the transcription of genes related to the metabolism of cholesterol, fatty acids, other lipids and neurotransmission, mitochondria biogenesis, and function. PPAR-α is involved in the cholesterol transport to mitochondria, the substrate for neurosteroid biosynthesis. PPAR-α-coding enzymes, such as sulfotransferases, which are responsible for neurosteroid sulfation. The relation between PPAR-α and cholesterol/neurosteroids may have a significant impact on the course and progression of neurodegeneration/neuroprotection processes. Unfortunately, despite many years of intensive studies, the pathogenesis of AD is unknown and therapy for AD and other neurodegenerative diseases is symptomatic, presenting a significant goal and challenge today. This review presents recent achievements in therapeutic approaches for AD, which are targeting PPAR-α and its relation to cholesterol and neurosteroids in AD and neuropsychiatric disorders. Full article

It has been proposed that procedures which upregulate mitochondrial biogenesis and autophagy by replacing damaged mitochondria with healthy ones may prevent the development of several heart diseases. A member of serine and threonine kinases, adenosine monophosphate-activated protein kinase (AMPK), could play essential roles in the autophagy and/or mitophagy. AMPK is widely distributed in various cells, which might play diverse regulatory roles in different tissues and/or organs. In fact, changes in the kinase function of AMPK due to alteration of activity have been linked with diverse pathologies including cardiac disorders. AMPK can regulate mitochondrial biogenesis via peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) signaling and also improve oxidative mitochondrial metabolism through inhibition of mechanistic/mammalian target of rapamycin (mTOR) pathway, which may also modulate the autophagy/mitophagy through autophagy activating kinase 1 (ULK1) and/or transforming growth factor beta (TGF-β) signaling. Therefore, the modulation of AMPK in autophagy/mitophagy pathway might probably be thought as a therapeutic tactic for several cardiac disorders. As kinases are amongst the most controllable proteins, in general, the design of small molecules targeting kinases might be an eye-catching avenue to modulate cardiac function. Some analyses of the molecular biology underlying mitophagy suggest that nutraceuticals and/or drugs including specific AMPK modulator as well as physical exercise and/or dietary restriction that could modulate AMPK may be useful against several heart diseases. These observations may virtually be limited to preclinical studies. Come to think of these, however, it is speculated that some nutraceutical regimens might have positive potential for managing some of cardiac disorders. Full article