Procine recombinant NK-lysin inhibits hepatocellular carcinoma metastasis by downregulating FKBP3 and inhibiting oxidative phosphorylation and glycolysis: a proteomic analysis / 南方医科大学学报

OBJECTIVE@#To investigate the potential mechanisms that mediate the inhibitory effect of porcine recombinant NKlysin (prNK-lysin) against liver cancer cell metastasis.@*METHODS@#HPLC-tandem mass spectrometry was used to identify the differentially expressed proteins in prNK-lysin-treated hepatocellular carcinoma SMMOL/LC-7721 cells in comparison with the control and PBS-treated cells. GO functional annotation and KEGG pathway analysis of the differentially expressed proteins were performed using GO and KEGG databases. RT-qPCR was used to determine the mRNA expression levels of polypeptide-N-acetylgalactosaminotransferase 13 (GALNT13), transmembrane protein 51 (TMEM51) and FKBP prolyl isomerase 3 (FKBP3) in the cells, and the protein expression of FKBP3 was verified using Western blotting.@*RESULTS@#Proteomic analysis identified 1989 differentially expressed proteins in prNK-lysin-treated cells compared with the control cells, and 2753 compared with PBS-treated cells. Fifteen proteins were differentially expressed between PBS-treated and the control cells, and 1909 were differentially expressed in prNK- lysin group compared with both PBS and control groups. These differentially expressed proteins were involved mainly in the viral process, translational initiation and RNA binding and were enriched mainly in ribosome, protein process in endoplasmic reticulum, and RNA transport pathways. RT-qPCR showed that compared with the control group, prNK-lysin treatment significantly increased the mRNA expressions of GALNT13 (P < 0.05) and TMEM51 (P < 0.01) and lowered FKBP3 mRNA expression (P < 0.05). Western blotting also showed a significantly decreased expression of FKBP3 protein in prNK-lysin-treated cells (P < 0.001).@*CONCLUSION@#Treatment with prNK-lysin causes significant changes in protein expression profile of SMMOL/LC-7721 cells and inhibits hepatocellular carcinoma metastasis by downregulating FKBP3 protein and affecting the cellular oxidative phosphorylation and glycolysis pathways.

Berberine targets the electron transport chain complex I and reveals the landscape of OXPHOS dependency in acute myeloid leukemia with IDH1 mutation / 中国天然药物

Metabolic reprogramming, a newly recognized trait of tumor biology, is an intensively studied prospect for oncology medicines. For numerous tumors and cancer cell subpopulations, oxidative phosphorylation (OXPHOS) is essential for their biosynthetic and bioenergetic functions. Cancer cells with mutations in isocitrate dehydrogenase 1 (IDH1) exhibit differentiation arrest, epigenetic and transcriptional reprogramming, and sensitivity to mitochondrial OXPHOS inhibitors. In this study, we report that berberine, which is widely used in China to treat intestinal infections, acted solely at the mitochondrial electron transport chain (ETC) complex I, and that its association with IDH1 mutant inhibitor (IDH1mi) AG-120 decreased mitochondrial activity and enhanced antileukemic effect in vitro andin vivo. Our study gives a scientific rationale for the therapy of IDH1 mutant acute myeloid leukemia (AML) patients using combinatory mitochondrial targeted medicines, particularly those who are resistant to or relapsing from IDH1mi.

Markers of mitochondrial energy metabolism and their potential relationships with fatigue in human adults: a scoping review

This scoping review aimed to synthesize the best available evidence of the associations between molecular and genetic markers of mitochondrial metabolism and fatigue in human adults. The research question guiding this review was, "Are there potential relationships between mitochondrial metabolism markers and fatigue?" The literature search used three terms (mitochondria; fatigue; energy metabolism), which yielded 263 manuscripts and 22 theses/dissertations. The studies included in the review had to meet three criteria: (1) Include adult participants (≥18 years of age); (2) Show a relationship between mitochondrial energy metabolism and fatigue; (3) Be published in English, Spanish, or Portuguese. Of the 17 articles included for a full-text review, some had a cross-sectional design (6/17, 35%), and more than half (12/17, 70%) were published between 2015 and 2020. The predominant population studied were patients diagnosed with chronic fatigue syndrome (9/17, 53%). Most studies (15/17, 88%) assessed fatigue with validated instruments. Mitochondrial markers associated with fatigue are a) mitochondrial transport pathways and respiratory chain, b) mutations in mitochondrial DNA, and c) energy disorders in cells of the immune system, such as natural killer cells. Mitochondrial metabolic activities, such as the production and transport of ATP, are significant components that may help understand the etiology of fatigue. Future directions should include longitudinal study designs, characterization of fatigue phenotypes, and the identification of markers involved in production and transport pathways. The clinical relevance in this field can lead to interventions targeting mitochondrial markers to reduce or prevent fatigue.

Effect of glutamine metabolism on chemoresistance and its mechanism in tumors / 浙江大学学报·医学版

The metabolic reprogramming of tumor cells is characterized by increased uptake of various nutrients including glutamine. Glutamine metabolism provides the required substances for glycolysis and oxidative phosphorylation and affects the homeostasis of carbohydrate，fat and protein metabolism to induce the chemoresistance of tumor cells. Combination of chemotherapeutic agents with inhibitors specific to different components of glutamine metabolic pathway has obtained favorable clinical results on various tumors. Glutamine metabolic pathway plays a role in drug resistance of tumor cells in various ways. Firstly，the dynamic change of glutamine transporters can directly affect intracellular glutamine content thereby causing drug resistance; secondly，tumor stromal cells including adipocyte，fibroblast and metabolite from tumor microenvironment would give rise to immune-mediated drug resistance; thirdly，the expression and activity of key enzymes in glutamine metabolism also has a critical role in drug resistance of tumors. This article reviews the effects of glutamine metabolic pathway in the development of tumor chemoresistance，in terms of transporters，tumor microenvironment and metabolic enzymes，to provide insight for improving the therapeutic efficacy for drug-resistant tumors.

Imbalance of Gut Streptococcus, Clostridium, and Akkermansia Determines the Natural Course of Atopic Dermatitis in Infant

PURPOSE: The roles of gut microbiota on the natural course of atopic dermatitis (AD) are not yet fully understood. We investigated whether the composition and function of gut microbiota and short-chain fatty acids (SCFAs) at 6 months of age could affect the natural course of AD up to 24 months in early childhood.METHODS: Fecal samples from 132 infants were analyzed using pyrosequencing, including 84 healthy controls, 22 transient AD and 26 persistent AD subjects from the Cohort for Childhood Origin of Asthma and Allergic Diseases (COCOA) birth cohort. The functional profile of the gut microbiome was analyzed by whole-metagenome sequencing. SCFAs were measured using gas chromatography-mass spectrometry.RESULTS: Low levels of Streptococcus and high amounts of Akkermansia were evident in transient AD cases, and low Clostridium, Akkermansia and high Streptococcus were found in children with persistent AD. The relative abundance of Streptococcus positively correlated with scoring of AD (SCORAD) score, whereas that of Clostridium negatively correlated with SCORAD score. The persistent AD group showed decreased gut microbial functional genes related to oxidative phosphorylation compared with healthy controls. Butyrate and valerate levels were lower in transient AD infants compared with healthy and persistent AD infants.CONCLUSIONS: Compositions, functions and metabolites of the early gut microbiome are related to natural courses of AD in infants.

Metabolic Reprogramming by the Excessive AMPK Activation Exacerbates Antigen-Specific Memory CD8⁺ T Cell Differentiation after Acute Lymphocytic Choriomeningitis Virus Infection

During virus infection, T cells must be adapted to activation and lineage differentiation states via metabolic reprogramming. Whereas effector CD8⁺ T cells preferentially use glycolysis for their rapid proliferation, memory CD8⁺ T cells utilize oxidative phosphorylation for their homeostatic maintenance. Particularly, enhanced AMP-activated protein kinase (AMPK) activity promotes the memory T cell response through different pathways. However, the level of AMPK activation required for optimal memory T cell differentiation remains unclear. A new metformin derivative, IM156, formerly known as HL156A, has been reported to ameliorate various types of fibrosis and inhibit in vitro and in vivo tumors by inducing AMPK activation more potently than metformin. Here, we evaluated the in vivo effects of IM156 on antigen-specific CD8⁺ T cells during their effector and memory differentiation after acute lymphocytic choriomeningitis virus infection. Unexpectedly, our results showed that in vivo treatment of IM156 exacerbated the memory differentiation of virus-specific CD8⁺ T cells, resulting in an increase in short-lived effector cells but decrease in memory precursor effector cells. Thus, IM156 treatment impaired the function of virus-specific memory CD8⁺ T cells, indicating that excessive AMPK activation weakens memory T cell differentiation, thereby suppressing recall immune responses. This study suggests that metabolic reprogramming of antigen-specific CD8⁺ T cells by regulating the AMPK pathway should be carefully performed and managed to improve the efficacy of T cell vaccine.

O metabolismo energético mitocondrial e a síndrome da fadiga crônica: uma scoping review / The mitochondrial energy metabolism and chronic fatigue syndrome: a scoping review

Nessa dissertação foi realizada uma scoping review com objetivo de buscar na literatura o que existe, até o presente momento, para explicar a relação entre o metabolismo mitocondrial com a síndrome da fadiga crônica (SFC). A SFC se apresenta de forma diferente para cada indivíduo, o que torna complexo seu entendimento, uma vez que não foram identificados biomarcadores específicos para auxiliar em um diagnóstico definitivo que favoreça uma intervenção adequada e tratamentos mais eficazes. Diferentes mecanismos biológicos são estudados, sendo que alterações no metabolismo mitocondrial têm sido foco de pesquisas recentes. Tais alterações podem ser a causa de fadiga severa e estudos sobre SFC mostraram que entre os principais indicadores da disfunção mitocondrial, envolvidos com a menor produção de ATP, está o comprometimento das vias de fosforilação oxidativa. O método utilizado nessa revisão, scoping review, é utilizado para investigar conceitos-chave subjacentes a uma nova área de pesquisa, bem como esclarecer definições de trabalhos, analisando o título e resumo de artigos para seleciona-los. Como critérios de inclusão ficaram determinados: (1) estudos clínicos que registram pacientes adultos (>= 18 anos de idade); (2) mostram uma relação entre questões do metabolismo e bioenergética mitocondrial com síndrome da fadiga crônica; (3) são escritos em português, inglês ou espanhol; (4) artigos publicados nos últimos 10 anos. E de exclusão: (1) utilizaram modelos animai; (2) relatos de casos, editoriais, cartas, revisões de literatura, resumos e dissertações de reuniões; (3) literatura cinzenta. Entre os descritores comuns, utilizados para realizar a busca nas bases de dados estão: mitochondria OR mitochondrial, fatigue, bioenergy OR bioenergetic OR energy metabolism. O estudo foi guiado pela seguinte questão: ""Alterações no metabolismo energético mitocondrial estão relacionados com a origem e prevalência da síndrome da fadiga crônica?". Após utilizar a estratégia de busca, específica para cada uma das quatro bases de dados (PubMed, EMBASE, SCOPUS e Web of Science), foram encontrados 228 artigos, os quais foram exportados para o software Rayyan QCRI e removidos aqueles que se encontravam em duplicata. Este software permitiu que dois revisores executassem, de forma independente, a leitura dos títulos e resumos de 150 artigos e 27 foram selecionados para a leitura na íntegra, por atenderem aos critérios supracitados. Dentre esses últimos, apenas 10 relatavam alterações no metabolismo mitocondrial relacionadas à SFC. As alterações compreendem modificações nas vias de transporte mitocondrial e na cadeia respiratória; mutações no DNA mitocondrial e, até mesmo, disfunções energéticas em células do sistema imune, como as natural-killer. Foram encontrados dados de pesquisas em diversas áreas clínicas, tais como: cardiologia, oncologia e distúrbios musculares, os quais podem colaborar para trazer luz às causas biológicas dessa síndrome. Desta forma, tornou-se ainda mais evidente a conexão entre distúrbios na bioenergética mitocondrial, como uma menor capacidade de transporte de oxigênio por meio das vias de transporte, ou até mesmo, a insuficiência mitocondrial para produção de ATP, com a SFC. De acordo com os estudos que compuseram a amostra final desta revisão (n=10), o metabolismo mitocondrial e suas principais atividades, como a produção e transporte de ATP, são um alvo potencial para auxiliar na compreensão de incógnitas existentes sobre a SFC. Esses resultados são promissores para a enfermagem, sobretudo na área da ciência dos sintomas, com impacto na qualidade de vida e no manejo personalizado de sintomas em diferentes condições crônicas, especialmente na SFC

In this dissertation a scoping review was carried out with the objective of searching in the literature what exists to date to explain the relationship between mitochondrial metabolism and chronic fatigue syndrome (CFS). SFC presents itself differently for each individual, which makes complex their understanding, since no specific biomarkers were identified to aid in a definitive diagnosis that favors an appropriate intervention and more effective treatments. Different biological mechanisms are studied, and changes in mitochondrial metabolism have been the focus of recent research. Such alterations may be the cause of severe fatigue and studies on CFS have shown that among the main indicators of mitochondrial dysfunction, involved in the lower production of ATP, is the involvement of oxidative phosphorylation pathways. The method used in this review, scoping review, is used to investigate key concepts underlying a new research area, as well as clarifying definitions of papers, analyzing the title and abstract articles to select them. As inclusion criteria were determined: (1) clinical studies that register adult patients (>= 18 years of age); (2) show a relationship between metabolism and bioenergetic mitochondrial issues with chronic fatigue syndrome; (3) written in Portuguese, English or Spanish; (4) articles published in the last 10 years. The exclusion criteria: (1) used animal models; (2) case reports, editorials, letters, literature reviews, abstracts and dissertations; (3) gray literature. Among the common descriptors used to perform the search in the databases are: mitochondria OR mitochondrial, fatigue, bioenergy OR bioenergetic OR energy metabolism. The study was guided by the following question: "" Changes in mitochondrial energy metabolism are related to the origin and prevalence of chronic fatigue syndrome? ". After using the search strategy, specific to each of the four databases (PubMed, EMBASE, SCOPUS and Web of Science), 228 articles were found, which were exported to the Rayyan QCRI software and removed from those that were in duplicate. This software allowed two reviewers to independently perform the reading of the titles and abstracts of 150 articles and 27 were selected for reading in full, because they meet the aforementioned criteria. Among the latter, only 10 reported changes in mitochondrial metabolism related to CFS. The changes comprise modifications in mitochondrial transport pathways and respiratory chain; mutations in mitochondrial DNA, and even energy dysfunctions in cells of the immune system, such as natural killer. Research data have been found in several clinical areas, such as: cardiology, oncology and muscular disorders, which can collaborate to bring light to the biological causes of this syndrome. Thus, the connection between disturbances in mitochondrial bioenergetics, such as reduced oxygen transport capacity, or even mitochondrial insufficiency for ATP production, with CFS became even more evident. According to the studies that compose the final sample of this review (n = 10), mitochondrial metabolism and its main activities, such as the production and transport of ATP, are a potential target to aid in the understanding of existing unknowns about CFS. These results are promising for nursing, especially in the area of symptom science, with an impact on quality of life and personalized management of symptoms in different chronic conditions, especially CFS

Regulation of Systemic Glucose Homeostasis by T Helper Type 2 Cytokines

Obesity results in an inflammatory microenvironment in adipose tissue, leading to the deterioration of tissue protective mechanisms. Although recent studies suggested the importance of type 2 immunity in an anti-inflammatory microenvironment in adipose tissue, the regulatory effects of T helper 2 (Th2) cytokines on systemic metabolic regulation are not fully understood. Recently, we identified the roles of the Th2 cytokine (interleukin 4 [IL-4] and IL-13)-induced adipokine, growth differentiation factor 15 (GDF15), in adipose tissue in regulating systemic glucose metabolism via signal transducer and activator of transcription 6 (STAT6) activation. Moreover, we showed that mitochondrial oxidative phosphorylation is required to maintain these macrophage-regulating autocrine and paracrine signaling pathways via Th2 cytokine-induced secretion of GDF15. In this review, we discuss how the type 2 immune response and Th2 cytokines regulate metabolism in adipose tissue. Specifically, we review the systemic regulatory roles of Th2 cytokines in metabolic disease and the role of mitochondria in maintenance of type 2 responses in adipose tissue homeostasis.

Angiotensin II and TGF-β1 Induce Alterations in Human Amniotic Fluid-Derived Mesenchymal Stem Cells Leading to Cardiomyogenic Differentiation Initiation

BACKGROUND AND OBJECTIVES: Human amniotic fluid-derived mesenchymal stem cells (AF-MSCs) may be a valuable source for cardiovascular tissue engineering and cell therapy. The aim of this study is to verify angiotensin II and transforming growth factor-beta 1 (TGF-β1) as potential cardiomyogenic differentiation inducers of AF-MSCs. METHODS AND RESULTS: AF-MSCs were obtained from amniocentesis samples from second-trimester pregnant women, isolated and characterized by the expression of cell surface markers (CD44, CD90, CD105 positive; CD34 negative) and pluripotency genes (OCT4, SOX2, NANOG, REX1). Cardiomyogenic differentiation was induced using different concentrations of angiotensin II and TGF-β1. Successful initiation of differentiation was confirmed by alterations in cell morphology, upregulation of cardiac genes-markers NKX2-5, TBX5, GATA4, MYH6, TNNT2, DES and main cardiac ion channels genes (sodium, calcium, potassium) as determined by RT-qPCR. Western blot and immunofluorescence analysis revealed the increased expression of Connexin43, the main component of gap junctions, and Nkx2.5, the early cardiac transcription factor. Induced AF-MSCs switched their phenotype towards more energetic and started utilizing oxidative phosphorylation more than glycolysis for energy production as assessed using Agilent Seahorse XF analyzer. The immune analysis of chromatin-modifying enzymes DNMT1, HDAC1/2 and Polycomb repressive complex 1 and 2 (PRC1/2) proteins BMI1, EZH2 and SUZ12 as well as of modified histones H3 and H4 indicated global chromatin remodeling during the induced differentiation. CONCLUSIONS: Angiotensin II and TGF-β1 are efficient cardiomyogenic inducers of human AF-MSCs; they initiate alterations at the gene and protein expression, metabolic and epigenetic levels in stem cells leading towards cardiomyocyte-like phenotype formation.

Association of mitochondrial haplogroup F with physical performance in korean population

Athletic performance is a complex multifactorial trait involving genetic and environmental factors. The heritability of an athlete status was reported to be about 70% in a twin study, and at least 155 genetic markers are known to be related with athlete status. Mitochondrial DNA (mtDNA) encodes essential proteins for oxidative phosphorylation, which is related to aerobic capacity. Thus, mtDNA is a candidate marker for determining physical performance. Recent studies have suggested that polymorphisms of mtDNA are associated with athlete status and/or physical performance in various populations. Therefore, we analyzed mtDNA haplogroups to assess their association with the physical performance of Korean population. The 20 mtDNA haplogroups were determined using the SNaPshot assay. Our result showed a significant association of the haplogroup F with athlete status (odds ratio, 3.04; 95% confidence interval, 1.094 to 8.464; p = 0.012). Athletes with haplogroup F (60.64 ± 3.04) also demonstrated a higher Sargent jump than athletes with other haplogroups (54.28 ± 1.23) (p = 0.041). Thus, our data imply that haplogroup F may play a crucial role in the physical performance of Korean athletes. Functional studies with larger sample sizes are necessary to further substantiate these findings.

Role of the Pyruvate Dehydrogenase Complex in Metabolic Remodeling: Differential Pyruvate Dehydrogenase Complex Functions in Metabolism

Mitochondrial dysfunction is a hallmark of metabolic diseases such as obesity, type 2 diabetes mellitus, neurodegenerative diseases, and cancers. Dysfunction occurs in part because of altered regulation of the mitochondrial pyruvate dehydrogenase complex (PDC), which acts as a central metabolic node that mediates pyruvate oxidation after glycolysis and fuels the Krebs cycle to meet energy demands. Fine-tuning of PDC activity has been mainly attributed to post-translational modifications of its subunits, including the extensively studied phosphorylation and de-phosphorylation of the E1α subunit of pyruvate dehydrogenase (PDH), modulated by kinases (pyruvate dehydrogenase kinase [PDK] 1-4) and phosphatases (pyruvate dehydrogenase phosphatase [PDP] 1-2), respectively. In addition to phosphorylation, other covalent modifications, including acetylation and succinylation, and changes in metabolite levels via metabolic pathways linked to utilization of glucose, fatty acids, and amino acids, have been identified. In this review, we will summarize the roles of PDC in diverse tissues and how regulation of its activity is affected in various metabolic disorders.

The Pentose Phosphate Pathway as a Potential Target for Cancer Therapy

During cancer progression, cancer cells are repeatedly exposed to metabolic stress conditions in a resource-limited environment which they must escape. Increasing evidence indicates the importance of nicotinamide adenine dinucleotide phosphate (NADPH) homeostasis in the survival of cancer cells under metabolic stress conditions, such as metabolic resource limitation and therapeutic intervention. NADPH is essential for scavenging of reactive oxygen species (ROS) mainly derived from oxidative phosphorylation required for ATP generation. Thus, metabolic reprogramming of NADPH homeostasis is an important step in cancer progression as well as in combinational therapeutic approaches. In mammalian, the pentose phosphate pathway (PPP) and one-carbon metabolism are major sources of NADPH production. In this review, we focus on the importance of glucose flux control towards PPP regulated by oncogenic pathways and the potential therein for metabolic targeting as a cancer therapy. We also summarize the role of Snail (Snai1), an important regulator of the epithelial mesenchymal transition (EMT), in controlling glucose flux towards PPP and thus potentiating cancer cell survival under oxidative and metabolic stress.

Cancer Energy Metabolism: Shutting Power off Cancer Factory

In 1923, Dr. Warburg had observed that tumors acidified the Ringer solution when 13 mM glucose was added, which was identified as being due to lactate. When glucose is the only source of nutrient, it can serve for both biosynthesis and energy production. However, a series of studies revealed that the cancer cell consumes glucose for biosynthesis through fermentation, not for energy supply, under physiological conditions. Recently, a new observation was made that there is a metabolic symbiosis in which glycolytic and oxidative tumor cells mutually regulate their energy metabolism. Hypoxic cancer cells use glucose for glycolytic metabolism and release lactate which is used by oxygenated cancer cells. This study challenged the Warburg effect, because Warburg claimed that fermentation by irreversible damaging of mitochondria is a fundamental cause of cancer. However, recent studies revealed that mitochondria in cancer cell show active function of oxidative phosphorylation although TCA cycle is stalled. It was also shown that blocking cytosolic NADH production by aldehyde dehydrogenase inhibition, combined with oxidative phosphorylation inhibition, resulted in up to 80% decrease of ATP production, which resulted in a significant regression of tumor growth in the NSCLC model. This suggests a new theory that NADH production in the cytosol plays a key role of ATP production through the mitochondrial electron transport chain in cancer cells, while NADH production is mostly occupied inside mitochondria in normal cells.

Deficiency of Sphingosine-1-Phosphate Reduces the Expression of Prohibitin and Causes β-Cell Impairment via Mitochondrial Dysregulation

BACKGROUND: Emerging evidence suggests that sphingolipids may be involved in type 2 diabetes. However, the exact signaling defect through which disordered sphingolipid metabolism induces β-cell dysfunction remains unknown. The current study demonstrated that sphingosine-1-phosphate (S1P), the product of sphingosine kinase (SphK), is an essential factor for maintaining β-cell function and survival via regulation of mitochondrial action, as mediated by prohibitin (PHB). METHODS: We examined β-cell function and viability, as measured by mitochondrial function, in mouse insulinoma 6 (MIN6) cells in response to manipulation of cellular S1P and PHB levels. RESULTS: Lack of S1P induced by sphingosine kinase inhibitor (SphKi) treatment caused β-cell dysfunction and apoptosis, with repression of mitochondrial function shown by decreases in cellular adenosine triphosphate content, the oxygen consumption rate, the expression of oxidative phosphorylation complexes, the mitochondrial membrane potential, and the expression of key regulators of mitochondrial dynamics (mitochondrial dynamin-like GTPase [OPA1] and mitofusin 1 [MFN1]). Supplementation of S1P led to the recovery of mitochondrial function and greatly improved β-cell function and viability. Knockdown of SphK2 using small interfering RNA induced mitochondrial dysfunction, decreased glucose-stimulated insulin secretion (GSIS), and reduced the expression of PHB, an essential regulator of mitochondrial metabolism. PHB deficiency significantly reduced GSIS and induced mitochondrial dysfunction, and co-treatment with S1P did not reverse these trends. CONCLUSION: Altogether, these data suggest that S1P is an essential factor in the maintenance of β-cell function and survival through its regulation of mitochondrial action and PHB expression.

Mitochondrial dysfunction reduces the activity of KIR2.1 K⁺ channel in myoblasts via impaired oxidative phosphorylation

Myoblast fusion depends on mitochondrial integrity and intracellular Ca²⁺ signaling regulated by various ion channels. In this study, we investigated the ionic currents associated with [Ca²⁺]i regulation in normal and mitochondrial DNA-depleted (ρ0) L6 myoblasts. The ρ0 myoblasts showed impaired myotube formation. The inwardly rectifying K⁺ current (I(Kir)) was largely decreased with reduced expression of KIR2.1, whereas the voltage-operated Ca²⁺ channel and Ca²⁺-activated K⁺ channel currents were intact. Sustained inhibition of mitochondrial electron transport by antimycin A treatment (24 h) also decreased the I(Kir). The ρ0 myoblasts showed depolarized resting membrane potential and higher basal [Ca²⁺]ᵢ. Our results demonstrated the specific downregulation of I(Kir) by dysfunctional mitochondria. The resultant depolarization and altered Ca²⁺ signaling might be associated with impaired myoblast fusion in ρ0 myoblasts.

Mitochondrial proteomic profile of complex IV deficiency fibroblasts: rearrangement of oxidative phosphorylation complex/supercomplex and other metabolic pathways / Perfil proteómico mitocondrial de los fibroblastos con deficiencia del complejo IV: reordenamiento del complejo/supercomplejo de la fosforilación oxidativa y otras vías metabólicas

Abstract: Background: Mitochondriopathies are multisystem diseases affecting the oxidative phosphorylation (OXPHOS) system. Skin fibroblasts are a good model for the study of these diseases. Fibroblasts with a complex IV mitochondriopathy were used to determine the molecular mechanism and the main affected functions in this disease. Methods: Skin fibroblast were grown to assure disease phenotype. Mitochondria were isolated from these cells and their proteome extracted for protein identification. Identified proteins were validated with the MitoMiner database. Results: Disease phenotype was corroborated on skin fibroblasts, which presented a complex IV defect. The mitochondrial proteome of these cells showed that the most affected proteins belonged to the OXPHOS system, mainly to the complexes that form supercomplexes or respirosomes (I, III, IV, and V). Defects in complex IV seemed to be due to assembly issues, which might prevent supercomplexes formation and efficient substrate channeling. It was also found that this mitochondriopathy affects other processes that are related to DNA genetic information flow (replication, transcription, and translation) as well as beta oxidation and tricarboxylic acid cycle. Conclusions: These data, as a whole, could be used for the better stratification of these diseases, as well as to optimize management and treatment options.

Resumen: Introducción: Las mitocondriopatías son enfermedades multisistémicas que afectan el funcionamiento de la fosforilación oxidativa (OXPHOS). Un buen modelo de estudio para estas enfermedades es el cultivo primario de fibroblastos. En este trabajo se utilizaron fibroblastos con mitocondriopatía del complejo IV para determinar cuáles son las principales funciones afectadas en esta enfermedad. Métodos: Se realizaron cultivos primarios de fibroblastos para corroborar el fenotipo de la enfermedad. Las mitocondrias se aislaron de estas células y se extrajo su proteoma para su identificación. Las proteínas identificadas se validaron con la base de datos de MitoMiner. Resultados: Los fibroblastos conservaron el fenotipo de la enfermedad que incluye un defecto del complejo IV. El proteoma mitocondrial de estas células mostró que las proteínas más afectadas pertenecen al sistema de OXPHOS, principalmente los complejos que forman supercomplejos o respirosomas (I, III, IV y V). El defecto en el complejo IV al parecer se debió a problemas de ensamblaje que pueden evitar la formación de los supercomplejos y la eficiente canalización de sustratos. También se observó que esta mitocondriopatía afecta otros procesos relacionados con el flujo de información genética del DNA (replicación, transcripción y traducción), así como con la beta oxidación y el ciclo de los ácidos tricarboxílicos (TCA). Conclusiones: En conjunto, estos datos podrían utilizarse para una mejor clasificación de estas enfermedades, así como para la optimización de las opciones de manejo y tratamiento.

Effects of exercise on obesity-induced mitochondrial dysfunction in skeletal muscle

Obesity is known to induce inhibition of glucose uptake, reduction of lipid metabolism, and progressive loss of skeletal muscle function, which are all associated with mitochondrial dysfunction in skeletal muscle. Mitochondria are dynamic organelles that regulate cellular metabolism and bioenergetics, including ATP production via oxidative phosphorylation. Due to these critical roles of mitochondria, mitochondrial dysfunction results in various diseases such as obesity and type 2 diabetes. Obesity is associated with impairment of mitochondrial function (e.g., decrease in O₂ respiration and increase in oxidative stress) in skeletal muscle. The balance between mitochondrial fusion and fission is critical to maintain mitochondrial homeostasis in skeletal muscle. Obesity impairs mitochondrial dynamics, leading to an unbalance between fusion and fission by favorably shifting fission or reducing fusion proteins. Mitophagy is the catabolic process of damaged or unnecessary mitochondria. Obesity reduces mitochondrial biogenesis in skeletal muscle and increases accumulation of dysfunctional cellular organelles, suggesting that mitophagy does not work properly in obesity. Mitochondrial dysfunction and oxidative stress are reported to trigger apoptosis, and mitochondrial apoptosis is induced by obesity in skeletal muscle. It is well known that exercise is the most effective intervention to protect against obesity. Although the cellular and molecular mechanisms by which exercise protects against obesity-induced mitochondrial dysfunction in skeletal muscle are not clearly elucidated, exercise training attenuates mitochondrial dysfunction, allows mitochondria to maintain the balance between mitochondrial dynamics and mitophagy, and reduces apoptotic signaling in obese skeletal muscle.

Exosome-derived microRNAs in cancer metabolism: possible implications in cancer diagnostics and therapy

Malignant progression is greatly affected by dynamic cross-talk between stromal and cancer cells. Exosomes are secreted nanovesicles that have key roles in cell–cell communication by transferring nucleic acids and proteins to target cells and tissues. Recently, MicroRNAs (miRs) and their delivery in exosomes have been implicated in physiological and pathological processes. Tumor-delivered miRs, interacting with stromal cells in the tumor microenvironment, modulate tumor progression, angiogenesis, metastasis and immune escape. Altered cell metabolism is one of the hallmarks of cancer. A number of different types of tumor rely on mitochondrial metabolism by triggering adaptive mechanisms to optimize their oxidative phosphorylation in relation to their substrate supply and energy demands. Exogenous exosomes can induce metabolic reprogramming by restoring the respiration of cancer cells and supress tumor growth. The exosomal miRs involved in the modulation of cancer metabolism may be potentially utilized for better diagnostics and therapy.

The First Korean case of combined oxidative phosphorylation deficiency-17 diagnosed by clinical and molecular investigation / 소아과

Combined oxidative phosphorylation deficiency-17 (COXPD-17) is very rare and is caused by homozygous or compound heterozygous mutations in the ELAC2 gene on chromosome 17p12. The ELAC2 gene functions as a mitochondrial tRNA processing gene, and only 4 different pathogenic mutations have been reported in ELAC2-associated mitochondrial dysfunction involving oxidative phosphorylation. Affected patients show various clinical symptoms and prognosis, depending on the genotype. We report a novel mutation in the ELAC2 gene (c.95C>G [p.Pro32Arg], het), in an infant with COXPD-17 who presented with encephalopathy including central apnea and intractable epilepsy, and growth and developmental retardation. During hospitalization, consistently elevated serum lactic acid levels were noted, indicative of mitochondrial dysfunction. The patient suddenly died of shock of unknown cause at 5 months of age. This is the first case report of COXPD-17 in Korea and was diagnosed based on clinical characteristics and genetic analysis.

Inhibition of HIF1α and PDK Induces Cell Death of Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most common and aggressive form of brain tumors. GBMs, like other tumors, rely relatively less on mitochondrial oxidative phosphorylation (OXPHOS) and utilize more aerobic glycolysis, and this metabolic shift becomes augmented under hypoxia. In the present study, we investigated the physiological significance of altered glucose metabolism and hypoxic adaptation in the GBM cell line U251 and two newly established primary GBMs (GBM28 and GBM37). We found that these three GBMs exhibited differential growth rates under hypoxia compared to those under normoxia. Under normoxia, the basal expressions of HIF1α and the glycolysis-associated genes, PDK1, PDK3, and GLUT1, were relatively low in U251 and GBM28, while their basal expressions were high in GBM37. Under hypoxia, the expressions of these genes were enhanced further in all three GBMs. Treatment with dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase (PDK), induced cell death in GBM28 and GBM37 maintained under normoxia, whereas DCA effects disappeared under hypoxia, suggesting that hypoxic adaptation dominated DCA effects in these GBMs. In contrast, the inhibition of HIF1α with chrysin suppressed the expression of PDK1, PDK3, and GLUT1 and markedly promoted cell death of all GBMs under both normoxia and hypoxia. Interestingly, however, GBMs treated with chrysin under hypoxia still sustained higher viability than those under normoxia, and chrysin and DCA co-treatment was unable to eliminate this hypoxia-dependent resistance. Together, these results suggest that hypoxic adaptation is critical for maintaining viability of GBMs, and targeting hypoxic adaptation can be an important treatment option for GBMs.