High glucose-induced oxidative stress increases the copy number of mitochondrial DNA in human mesangial cells

Mitochondrial DNA copy number alterations: Key players in the complexity of glioblastoma (Review)

Renowned as a highly invasive and lethal tumor derived from neural stem cells in the central nervous system, glioblastoma (GBM) exhibits substantial histopathological variation and genomic complexity, which drive its rapid progression and therapeutic resistance. Alterations in mitochondrial DNA (mtDNA) copy number (CN) serve a crucial role in GBM development and progression, affecting various aspects of tumor biology, including energy production, oxidative stress regulation and cellular adaptability. Fluctuations in mtDNA levels, whether elevated or diminished, can impair mitochondrial function, potentially disrupting oxidative phosphorylation and amplifying reactive oxygen species generation, thereby fueling tumor growth and influencing treatment responses. Understanding the mechanisms of mtDNA‑CN variations, and their interplay with genetic and environmental elements in the tumor microenvironment, is essential for advancing diagnostic and therapeutic strategies. Targeting mtDNA alterations could strengthen treatment efficacy, mitigate resistance and ultimately enhance the prognosis of patients with this aggressive brain tumor. The present review summarizes the existing literature on mtDNA alterations, specifically emphasizing variations in mtDNA‑CN and their association with GBM by surveying articles published between 1996 and 2024, sourced from databases such as Scopus, PubMed and Google Scholar. In addition, the review provides a brief overview of mitochondrial genome architecture, knowledge regarding the regulation of mtDNA integrity and CN, and how mitochondria significantly impact GBM tumorigenesis. This review further presents information on therapeutic approaches for restoring mtDNA‑CN that contribute to optimized mitochondrial function and improved health outcomes.

Differential Expression of Nuclear-Encoded Mitochondrial Protein Genes of ATP Synthase Across Different Tissues of Female Buffalo

The physiological well-being of buffaloes, encompassing phenotypic traits, reproductive health, and productivity, depends on their energy status. Mitochondria, the architects of energy production, orchestrate a nuanced interplay between nuclear and mitochondrial domains. Oxidative phosphorylation complexes and associated proteins wield significant influence over metabolic functions, energy synthesis, and organelle dynamics, often linked to tissue-specific pathologies. The unexplored role of ATP synthase in buffalo tissues prompted a hypothesis: in-depth exploration of nuclear-derived mitochondrial genes, notably ATP synthase, reveals distinctive tissue-specific diversity. RNA extraction and sequencing of buffalo tissues (kidney, heart, brain, and ovary) enabled precise quantification of nuclear-derived mitochondrial protein gene expression. The analysis unveiled 24 ATP synthase transcript variants, each with unique tissue-specific patterns. Kidney, brain, and heart exhibited elevated gene expression compared to ovaries, with 10, 8, and 19 up-regulated genes, respectively. The kidney showed 3 and 12 down-regulated genes compared to the brain and heart. The heart-brain comparison highlighted ten highly expressed genes in ATP synthase functions. Gene ontology and pathway analyses revealed enriched functions linked to ATP synthesis and oxidative phosphorylation, offering a comprehensive understanding of energy production in buffalo tissues. This analysis enhances understanding of tissue-specific gene expression, emphasizing the influence of energy demands. Revealing intricate links between mitochondrial gene expression and tissue specialization in buffaloes, it provides nuanced insights into tissue-specific expression of nuclear-encoded mitochondrial protein genes, notably ATP synthase, advancing the comprehension of buffalo tissue biology.

Quantifying the effects of the mitochondrial genome on milk production traits in dairy cows: Empirical results and modeling challenges

Substantial advances in livestock traits have been achieved primarily through selection strategies targeting variation in the nuclear genome, with little attention given to mitogenome variation. We analyzed the influence of the mitogenome on milk production traits of Holstein cattle in Croatia based on strategically generated next-generation sequencing data for 109 cows pedigree-linked to 7,115 milk production records (milk, fat, and protein yield) from 3,006 cows (first 5 lactations). Because little is known about the biology of the relationship between mitogenome variation and production traits, our quantitative genetic modeling was complex. Thus, the proportion of total variance explained by mitogenome inheritance was estimated using 5 different models: (1) a cytoplasmic model with maternal lineages (CYTO), (2) a haplotypic model with mitogenome sequences (HAPLO), (3) an amino acid model with unique amino acid sequences (AMINO), (4) an evolutionary model based on a phylogenetic analysis using Bayesian Evolutionary Analysis Sampling Trees phylogenetic analysis (EVOL), and (5) a mitogenome SNP model (SNPmt). The polygenic autosomal and X chromosome additive genetic effects based on pedigree were modeled, together with the effects of herd-year-season interaction, permanent environment, location, and age at first calving. The estimated proportions of phenotypic variance explained by mitogenome in 4 different models (CYTO, HAPLO, AMINO, and SNPmt) were found to be substantial given the size of mitogenome, ranging from 5% to 7% for all 3 milk traits. At the same time, a negligible proportion of the phenotypic variance was explained by mitogenome with the EVOL model. Similarly, in all models, no proportion of phenotypic variance was explained by the X chromosome. Although our results should be confirmed in other dairy cattle populations, including a large number of sequenced mitogenomes and nuclear genomes, the potential of utilizing mitogenome information in animal breeding is promising, especially as the acquisition of complete genome sequences becomes cost-effective.

Association between blood mitochondrial DNA copy number and mental disorders: A bidirectional two-sample mendelian randomization study

BACKGROUND

Mitochondria is essential for cellular energy production, oxidative stress, and apoptosis. Mitochondrial DNA (mtDNA) encodes essential proteins for mitochondrial function. Although several studies have explored the association between changes in mtDNA copy number (mtDNA-CN) and risk of mental disorders, the results remain debated. This study used a bidirectional two-sample Mendelian randomization (MR) analysis to examine the genetic causality between mtDNA-CN and mental disorders.

METHODS

Genome-wide association study (GWAS) data for mtDNA-CN were sourced from UK biobank, involving 383,476 European cases. GWAS data for seven mental disorders-attention deficit/hyperactivity disorder, autism spectrum disorder (ASD), schizophrenia, bipolar disorder, major depressive disorder, anxiety, and obsessive-compulsive disorder-were primarily obtained from the Psychiatric Genomics Consortium. Causal associations were assessed using inverse variance weighting, with sensitivity analyses via the weighted median and MR-Egger methods. Reverse MR considered the seven mental disorders as exposures. All analyses were replicated with additional mtDNA-CN GWAS data from 465,809 individuals in the Heart and Ageing Research in Genomic Epidemiology consortium and the UK Biobank.

RESULTS

Forward MR observed a 27 % decrease in the risk of ASD per standard deviation increase in genetically determined blood mtDNA-CN (OR = 0.73, 95%CI: 0.58-0.92, p = 0.002), with no causal effects on other disorders. Additionally, reverse MR did not indicate a causal association between any of the mental disorders and mtDNA-CN. Validation analyses corroborated these findings, indicating their robustness.

CONCLUSIONS

Our study supports the potential causal association between mtDNA-CN and the risk of ASD, suggesting that mtDNA-CN could serve as a promising biomarker for early screening of ASD.

Role of mitochondrial dysfunction in kidney disease: Insights from the cGAS-STING signaling pathway

ABSTRACT

Over the past decade, mitochondrial dysfunction has been investigated as a key contributor to acute and chronic kidney disease. However, the precise molecular mechanisms linking mitochondrial damage to kidney disease remain elusive. The recent insights into the cyclic guanosine monophosphate-adenosine monophosphate (GMP-AMP) synthetase (cGAS)-stimulator of interferon gene (STING) signaling pathway have revealed its involvement in many renal diseases. One of these findings is that mitochondrial DNA (mtDNA) induces inflammatory responses via the cGAS-STING pathway. Herein, we provide an overview of the mechanisms underlying mtDNA release following mitochondrial damage, focusing specifically on the association between mtDNA release-activated cGAS-STING signaling and the development of kidney diseases. Furthermore, we summarize the latest findings of cGAS-STING signaling pathway in cell, with a particular emphasis on its downstream signaling related to kidney diseases. This review intends to enhance our understanding of the intricate relationship among the cGAS-STING pathway, kidney diseases, and mitochondrial dysfunction.

Long-term effects of warm water immersion on kidney tissue damage in diabetic rats

Objectives

This study aimed to investigate the effects of Warm Water Immersion (WWI) on inflammation, kidney function, and kidney tissue damage in rats with diabetes mellitus (DM).

Materials and Methods

Forty male rats were divided into four groups: Healthy Control (HC), Diabetic Control (DC), Diabetic Rats treated with WWI (DW), and Healthy Rats treated with WWI (HW). Daily 15-minute WWI sessions at 43 °C were administered for eight weeks. Various parameters including lipids, fasting blood sugar (FBS), HbA1C, insulin, advanced glycation end products (AGEs), HSP70, glomerular filtration rate (GFR), urinary albumin excretion, creatinine, blood urea nitrogen (BUN), oxidative stress, anti-oxidant parameters, and gene expression of RAGE, VEGF, and TGFß1 were assessed. Histological examination of kidney tissue was also conducted.

Results

Significant reductions in FBS, AGEs, glutathione, superoxide dismutase (SOD), and nitric oxide (NO) levels were observed in the DW group compared to DC. Expression of RAGE, VEGF, and TGFß1 genes decreased in DW. Triglycerides, total cholesterol, and LDL cholesterol were lower in DW. Insulin, HDL cholesterol, catalase, total anti-oxidant capacity (TAC), and tissue HSP70 were higher in DW. Histological assessment revealed reduced kidney damage in DW compared to DC.

Conclusion

WWI for eight weeks shows promise in mitigating diabetic nephropathy in rats, suggesting its potential as a non-invasive adjunctive therapy for managing diabetes complications.

Licochalcone A alleviates abnormal glucolipid metabolism and restores energy homeostasis in diet-induced diabetic mice

Licochalcone A (LCA) is a bioactive chalcone compound identified in licorice. This study aimed to investigate the effects of LCA on glucolipid metabolism and energy homeostasis, as well as the underlying mechanisms. Blood glucose levels, oral glucose tolerance, serum parameters, and histopathology were examined in high-fat-high-glucose diet (HFD)-induced diabetic mice, with metformin as a positive control. Additionally, changes in key markers related to glucolipid metabolism and mitochondrial function were analyzed to comprehensively assess LCA's effects on metabolism. The results showed that LCA alleviated metabolic abnormalities in HFD-induced diabetic mice, which were manifested by suppression of lipogenesis, promotion of lipolysis, reduction of hepatic steatosis, increase in hepatic glycogenesis, and decrease in gluconeogenesis. In addition, LCA restored energy homeostasis by promoting mitochondrial biogenesis, enhancing mitophagy, and reducing adenosine triphosphate production. Mechanistically, the metabolic benefits of LCA were associated with the downregulation of mammalian target of rapamycin complex 1 and activation of adenosine monophosphate-activated protein kinase, the two central regulators of metabolism. This study demonstrates that LCA can alleviate abnormal glucolipid metabolism and restore energy balance in diet-induced diabetic mice, highlighting its therapeutical potential for the treatment of diabetes.

Blood and liver telomere length, mitochondrial DNA copy number, and hepatic gene expression of mitochondrial dynamics in mid-lactation cows supplemented with l-carnitine under systemic inflammation

The current study was conducted to examine the effect of l-carnitine (LC) supplementation on telomere length and mitochondrial DNA copy number (mtDNAcn) per cell in mid-lactation cows challenged by lipopolysaccharide (LPS) in blood and liver. The mRNA abundance of 31 genes related to inflammation, oxidative stress, and the corresponding stress response mechanisms, the mitochondrial quality control and the protein import system, as well as the phosphatidylinositol 3-kinase/protein kinase B pathway, were assessed using microfluidics integrated fluidic circuit chips (96.96 dynamic arrays). In addition to comparing the responses in cows with or without LC, our objectives were to characterize the oxidative and inflammatory status by assessing the circulating concentration of lactoferrin (Lf), haptoglobin (Hp), fibrinogen, derivates of reactive oxygen metabolites (dROM), and arylesterase activity (AEA), and to extend the measurement of Lf and Hp to milk. Pluriparous Holstein cows were assigned to either a control group (CON, n = 26) or an LC-supplemented group (CAR; 25 g LC/cow per day; d 42 ante partum to d 126 postpartum (PP), n = 27). On d 111 PP, each cow was injected intravenously with LPS (Escherichia coli O111:B4, 0.5 µg/kg). The mRNA abundance was examined in liver biopsies of d -11 and +1 relative to LPS administration. Plasma and milk samples were frequently collected before and after the challenge. After LPS administration, circulating plasma fibrinogen and serum dROM concentrations increased, whereas AEA decreased. Moreover, serum P4 initially increased by 3 h after LPS administration and declined thereafter irrespective of grouping. The Lf concentrations increased in both groups after LPS administration, with the CAR group showing greater concentrations in serum and milk than the CON group. After LPS administration, telomere length in blood increased, whereas mtDNAcn per cell decreased; however, both remained unaffected in liver. For mitochondrial protein import genes, the hepatic mRNA abundance of the translocase of the mitochondrial inner membrane (TIM)-17B was increased in CAR cows. Moreover, TIM23 increased in both groups after LPS administration. Regarding the mRNA abundance of genes related to stress response mechanisms, 7 out of 14 genes showed group × time interactions, indicating a (local) protective effect due to the dietary LC supplementation against oxidative stress in mid-lactating dairy cows. For mtDNAcn and telomere length, the effects of the LPS-induced inflammation were more pronounced than the dietary supplementation of LC. Dietary LC supplementation affected the response to LPS primarily by altering mitochondrial dynamics. Regarding mRNA abundance of genes related to the mitochondrial protein import system, the inner mitochondrial membrane translocase (TIM complex) seemed to be more sensitive to dietary LC than the outer mitochondrial membrane translocase (TOM complex).

Mitochondrial DNA copy number in autism spectrum disorder and attention deficit hyperactivity disorder: a systematic review and meta-analysis

Background

Several reports suggest that altered mitochondrial DNA copy number (mtDNA-cn), a common biomarker for aberrant mitochondrial function, is implicated in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), but the results are still elusive.

Methods

A meta-analysis was performed to summarize the current indication and to provide a more precise assessment of the mtDNA-cn in ASD and ADHD. A search in the MEDLINE-PubMed, Scopus, and EMBASE databases was done to identify related studies up to the end of February 2023. The meta-analysis was conducted according to recommendations of the Cochrane Handbook of Systematic Reviews.

Results

Fourteen studies involving 666 cases with ASD and ADHD and 585 controls were collected and judged relevant for the systematic review and meta-analysis. The pooled results by a random effects meta-analysis was reported as a geometric mean of the estimated average response ratio and 95% confidence interval. Overall analysis of studies reported differences in mtDNA-cn in blood samples (k = 10) and non-blood samples (brain tissues and oral samples; k = 4) suggested significantly higher mtDNA-cn in patients compared to controls (p = 0.0275). Sub-analysis by stratifying studies based on tissue type, showed no significant increase in mtDNA-cn in blood samples among patients and controls (p = 0.284). Conversely, higher mtDNA-cn was observed in non-blood samples in patients than in controls (p = 0.0122). Further stratified analysis based on blood-cell compositions as potential confounds showed no significant difference in mtDNA-cn in peripheral blood samples of patients comparted to controls (p = 0.074). In addition, stratified analysis of aged-matched ASD and ADHD patients and controls revealed no significant difference in mtDNA-cn in blood samples between patients and controls (p = 0.214), whereas a significant increase in mtDNA-cn was observed in non-blood samples between patients and controls (p < 0.001). Finally, when the mtDNA-cn was analyzed in blood samples of aged-matched patients with ASD (peripheral blood, leukocytes, and PBMCs) or ADHD (peripheral blood), no significant difference in mtDNA-cn was observed between ASD patients and controls (p = 0.385), while a significant increase in mtDNA-cn was found between ADHD patients and controls (p = 0.033).

Conclusion

In this first meta-analysis of the evaluation of mtDNA-cn in ASD/ADHD, our results show elevated mtDNA-cn in ASD and ADHD, further emphasizing the implication of mitochondrial dysfunction in neurodevelopmental disorders. However, our results indicate that the mtDNA-cn in blood is not reflected in other tissues in ASD/ADHD, and the true relationship between blood-derived mtDNA-cn and ASD/ADHD remains to be defined in future studies. The importance of blood-cell compositions as confounders of blood-based mtDNA-cn measurement and the advantages of salivary mtDNA-cn should be considered in future studies. Moreover, the potential of mtDNA-cn as a biomarker for mitochondrial malfunction in neurodevelopmental disorders deserves further investigations.

Tissue heterogeneity of mitochondrial activity, biogenesis and mitochondrial protein gene expression in buffalo

BACKGROUND

Cellular metabolism is most invariant process, occurring in all living organisms, which involves mitochondrial proteins from both nuclear and mitochondrial genomes. The mitochondrial DNA (mtDNA) copy number, protein-coding genes (mtPCGs) expression, and activity vary between various tissues to fulfill specific energy demands across the tissues.

METHODS AND RESULTS

In present study, we investigated the OXPHOS complexes and citrate synthase activity in isolated mitochondria from various tissues of freshly slaughtered buffaloes (n = 3). Further, the evaluation of tissue-specific diversity based on the quantification of mtDNA copy numbers was performed and also comprised an expression study of 13 mtPCGs. We found that the functional activity of individual OXPHOS complex I was significantly higher in the liver compared to muscle and brain. Additionally, OXPHOS complex III and V activities was observed significantly higher levels in liver compared to heart, ovary, and brain. Similarly, CS-specific activity differs between tissues, with the ovary, kidney, and liver having significantly greater. Furthermore, we revealed the mtDNA copy number was strictly tissue-specific, with muscle and brain tissues exhibiting the highest levels. Among 13 PCGs expression analyses, mRNA abundances in all genes were differentially expressed among the different tissue.

CONCLUSIONS

Overall, our results indicate the existence of a tissue-specific variation in mitochondrial activity, bioenergetics, and mtPCGs expression among various types of buffalo tissues. This study serves as a critical first stage in gathering vital comparable data about the physiological function of mitochondria in energy metabolism in distinct tissues, laying the groundwork for future mitochondrial based diagnosis and research.

Insights regarding mitochondrial DNA copy number alterations in human cancer (Review)

Mitochondria are the critical organelles involved in various cellular functions. Mitochondrial biogenesis is activated by multiple cellular mechanisms which require a synchronous regulation between mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). The mitochondrial DNA copy number (mtDNA-CN) is a proxy indicator for mitochondrial activity, and its alteration reflects mitochondrial biogenesis and function. Despite the precise mechanisms that modulate the amount and composition of mtDNA, which have not been fully elucidated, mtDNA-CN is known to influence numerous cellular pathways that are associated with cancer and as well as multiple other diseases. In addition, the utility of current technology in measuring mtDNA-CN contributes to its extensive assessment of diverse traits and tumorigenesis. The present review provides an overview of mtDNA-CN variations across human cancers and an extensive summary of the existing knowledge on the regulation and machinery of mtDNA-CN. The current information on the advanced methods used for mtDNA-CN assessment is also presented.

Energetic metabolic reprogramming in Jurkat DFF40-deficient cancer cells

DNA fragmentation factor 40 (DFF40), or the caspase-activated DNase (CAD), is an endonuclease specific for double-stranded DNA. Alterations in its function and expression have been linked to apoptosis resistance, a mechanism likely used by cancer cells. However, how the DFF40-related apoptosis resistance pathway occurs remains unclear. Here, we sought to determine if DFF40 expression could be linked to cell metabolism through the regulation of mitochondrial integrity and function. We demonstrated that DFF40-deficient cells are more resistant to staurosporine and tributyltin (TBT)-induced apoptosis, and express higher levels of Mcl-1 at basal state. Treatment with TBT induces higher Bcl-2 and caspase-9 mRNA transcripts in DFF40 KO Jurkat cells, as well as enhanced Bcl-2 phosphorylation. A loss of DFF40 expression induces a higher mitochondrial mass, mtDNA copy number, mitochondrial membrane potential, and glycolysis rates in resting T cells. DFF40-deficient cells exhibit the Warburg effect phenotype, where they rely significantly more on glycolysis than oxidative phosphorylation and have a higher proliferative state, demonstrated by a higher Ki-67 transcription factor expression and AKT phosphorylation. Finally, we demonstrated with cell fractioning that DFF40 can translocate to the mitochondria following apoptosis induction. Our study reveals that DFF40 may act as a regulator of mitochondria during cell death and its loss could compromise mitochondrial integrity and cause an energetic reprogramming in pathologies such as cancer.

Effects of caloric overload before caloric restriction in the murine heart

The beneficial effects of caloric restriction (CR) against cardiac aging and for prevention of cardiovascular diseases are numerous. However, to our knowledge, there is no scientific evidence about how a high-calorie diet (HCD) background influences the mechanisms underlying CR in whole heart tissue (WHT) in experimental murine models. In the current study, CR-treated mice with different alimentary backgrounds were subjected to transthoracic echocardiographic measurements. WHT was then analyzed to determine cardiac energetics, telomerase activity, the expression of energy-sensing networks, tissue-specific adiponectin, and cardiac precursor/cardiac stem cell markers. Animals with a balanced diet consumption before CR presented marked cardiac remodeling with improved ejection fraction (EF) and fractional shortening (FS), enhanced OXPHOS complex I, III, and IV, and CKMT2 enzymatic activity. Mice fed an HCD before CR presented moderate changes in cardiac geometry with diminished EF and FS values, but improved OXPHOS complex IV and CKMT2 activity. Differences in cardiac remodeling, left ventricular systolic/diastolic performance, and mitochondrial energetics, found in the CR-treated mice with contrasting alimentary backgrounds, were corroborated by inconsistencies in the expression of mitochondrial-biogenesis-related markers and associated regulatory networks. In particular, disruption of eNOS and AMPK -PGC-1α-mTOR-related axes. The impact of a past habit of caloric overload on the effects of CR in the WHT is a scarcely explored subject that requires deeper study in combination with analyses of other tissues and organs at higher levels of organization within the organ system. Such research will eventually lead to the development of preventative and therapeutic strategies to promote health and longevity.

DNA Methylation of PGC-1α Is Associated With Elevated mtDNA Copy Number and Altered Urinary Metabolites in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex disorder that is underpinned by numerous dysregulated biological pathways, including pathways that affect mitochondrial function. Epigenetic mechanisms contribute to this dysregulation and DNA methylation is an important factor in the etiology of ASD. We measured DNA methylation of peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), as well as five genes involved in regulating mitochondrial homeostasis to examine mitochondrial dysfunction in an ASD cohort of South African children. Using targeted Next Generation bisulfite sequencing, we found differential methylation (p < 0.05) at six key genes converging on mitochondrial biogenesis, fission and fusion in ASD, namely PGC-1α, STOML2, MFN2, FIS1, OPA1, and GABPA. PGC-1α, the transcriptional regulator of biogenesis, was significantly hypermethylated at eight CpG sites in the gene promoter, one of which contained a putative binding site for CAMP response binding element 1 (CREB1) (p = 1 × 10^–6). Mitochondrial DNA (mtDNA) copy number, a marker of mitochondrial function, was elevated (p = 0.002) in ASD compared to controls and correlated significantly with DNA methylation at the PGC-1α promoter and there was a positive correlation between methylation at PGC-1α CpG#1 and mtDNA copy number (Spearman’s r = 0.2, n = 49, p = 0.04) in ASD. Furthermore, DNA methylation at PGC-1α CpG#1 and mtDNA copy number correlated significantly (p < 0.05) with levels of urinary organic acids associated with mitochondrial dysfunction, oxidative stress, and neuroendocrinology. Our data show differential methylation in ASD at six key genes converging on PGC-1α-dependent regulation of mitochondrial biogenesis and function. We demonstrate that methylation at the PGC-1α promoter is associated with elevated mtDNA copy number and metabolomic evidence of mitochondrial dysfunction in ASD. This highlights an unexplored role for DNA methylation in regulating specific pathways involved in mitochondrial biogenesis, fission and fusion contributing to mitochondrial dysfunction in ASD.

Mitochondrial DNA-Mediated Inflammation in Acute Kidney Injury and Chronic Kidney Disease

The integrity and function of mitochondria are essential for normal kidney physiology. Mitochondrial DNA (mtDNA) has been widely a concern in recent years because its abnormalities may result in disruption of aerobic respiration, cellular dysfunction, and even cell death. Particularly, aberrant mtDNA copy number (mtDNA-CN) is associated with the development of acute kidney injury and chronic kidney disease, and urinary mtDNA-CN shows the potential to be a promising indicator for clinical diagnosis and evaluation of kidney function. Several lines of evidence suggest that mtDNA may also trigger innate immunity, leading to kidney inflammation and fibrosis. In mechanism, mtDNA can be released into the cytoplasm under cell stress and recognized by multiple DNA-sensing mechanisms, including Toll-like receptor 9 (TLR9), cytosolic cGAS-stimulator of interferon genes (STING) signaling, and inflammasome activation, which then mediate downstream inflammatory cascades. In this review, we summarize the characteristics of these mtDNA-sensing pathways mediating inflammatory responses and their role in the pathogenesis of acute kidney injury, nondiabetic chronic kidney disease, and diabetic kidney disease. In addition, we highlight targeting of mtDNA-mediated inflammatory pathways as a novel therapeutic target for these kidney diseases.

The consequences of a high-calorie diet background before calorie restriction on skeletal muscles in a mouse model

The beneficial effects of calorie restriction (CR) are numerous. However, there is no scientific evidence about how a high-calorie diet (HCD) background influences the mechanisms underlying CR on skeletal muscles in an experimental mouse model. Herein we present empirical evidence showing significant interactions between HCD (4 months) and CR (3 months). Pectoralis major and quadriceps femoris vastus medialis, in the experimental and control groups, displayed metabolic and physiologic heterogeneity and remarkable plasticity, according to the dietary interventions. HCD-CR not only altered genetic activation patterns of satellite SC markers but also boosted the expression of myogenic regulatory factors and key activators of mitochondrial biogenesis, which in turn were also associated with metabolic fiber transition. Our data prompt us to theorize that the effects of CR may vary according to the physiologic, metabolic, and genetic peculiarities of the skeletal muscle described here and that INTM/IM lipid infiltration and tissue-specific fuel-energy status (demand/supply) both hold dependent-interacting roles with other key anti-aging mechanisms triggered by CR. Systematic integration of an HCD with CR appears to bring potential benefits for skeletal muscle function and energy metabolism. However, at this stage of our research, an optimal balance between the two dietary conditions, where anti-aging effects can be accomplished, is under intensive investigation in combination with other tissues and organs at different levels of organization within the organ system.

Do Autophagy Enhancers/ROS Scavengers Alleviate Consequences of Mild Mitochondrial Dysfunction Induced in Neuronal-Derived Cells?

Mitochondrial function is at the nexus of pathways regulating synaptic-plasticity and cellular resilience. The involvement of brain mitochondrial dysfunction along with increased reactive oxygen species (ROS) levels, accumulating mtDNA mutations, and attenuated autophagy is implicated in psychiatric and neurodegenerative diseases. We have previously modeled mild mitochondrial dysfunction assumed to occur in bipolar disorder (BPD) using exposure of human neuronal cells (SH-SY5Y) to rotenone (an inhibitor of mitochondrial-respiration complex-I) for 72 and 96 h, which exhibited up- and down-regulation of mitochondrial respiration, respectively. In this study, we aimed to find out whether autophagy enhancers (lithium, trehalose, rapamycin, and resveratrol) and/or ROS scavengers [resveratrol, N-acetylcysteine (NAC), and Mn-Tbap) can ameliorate neuronal mild mitochondrial dysfunction. Only lithium (added for the last 24/48 h of the exposure to rotenone for 72/96 h, respectively) counteracted the effect of rotenone on most of the mitochondrial respiration parameters (measured as oxygen consumption rate (OCR)). Rapamycin, resveratrol, NAC, and Mn-Tbap counteracted most of rotenone's effects on OCR parameters after 72 h, possibly via different mechanisms, which are not necessarily related to their ROS scavenging and/or autophagy enhancement effects. The effect of lithium reversing rotenone's effect on OCR parameters is compatible with lithium's known positive effects on mitochondrial function and is possibly mediated via its effect on autophagy. By-and-large it may be summarized that some autophagy enhancers/ROS scavengers alleviate some rotenone-induced mild mitochondrial changes in SH-SY5Y cells.

Diverse functional responses to high glucose by primary and permanent hybrid endothelial cells in vitro

Various types of human endothelial cells, including human umbilical vein endothelial cells (HUVECs) and the established hybrid EAhy926 cells, are used in experimental research. Here, we compared the biological properties of HUVECs and EAhy926 cells under normal (5 mM) and high glucose (30 mM; HG) conditions. The results showed that HG induced cellular senescence and a stronger DNA damage response in HUVECs than in EAhy926 cells. The magnitude of oxidative stress elicited in HUVECs by HG was also greater than that elicited in their established counterparts. Both endothelial cell types promoted the progression of breast (MCF7), ovarian (OVCAR-3), and lung (A549) cancer cells; however, the effects elicited by HG-treated HUVECs on adhesion (MCF7, OVCAR-3), proliferation (OVCAR-3), and migration (OVCAR-3) were more pronounced. Finally, HG stimulated the production of a higher number of proangiogenic agents in HUVECs than in EAhy926 cells. Collectively, our study shows that the functional properties of primary and established endothelial cells exposed to HG differ substantially, which seems to result from the higher sensitivity of the former to this stressor. The interchangeability of both types of endothelial cells in biomedical research should be considered with great care to avoid losing some biological effects due to the choice of cells with higher stress tolerance.

Effects of Curcumin on High Glucose-Induced Epithelial-to-Mesenchymal Transition in Renal Tubular Epithelial Cells Through the TLR4-NF-κB Signaling Pathway

OBJECTIVE

Diabetic kidney disease (DKD) is a microvascular complication in diabetes mellitus, while tubuloepithelial to mesenchymal transition (EMT) of mature tubular epithelial cells is a key point in the early development and progression of renal interstitial fibrosis. The present study aimed to investigate the protective effects of Curcumin on EMT and fibrosis in cultured normal rat kidney tubular epithelial cell line (NRK-52E).

METHODS

By using immunofluorescence staining and Western blot protocols, in vitro experiments were designed to analyze EMT markers, including collagen I and E-cadherin in high glucose (HG) exposed NRK-52E cells and to detect the expression levels of phosphorylated-NF-κB, TLR4 and reactive oxygen species (ROS) after Curcumin pre-treatment. With co-treatment with TAK242, these molecules in the TLR4-NF-κB signaling pathway were further evaluated.

RESULTS

Curcumin decreased the HG-induced EMT levels and ROS production in NRK-52E cells. Furthermore, Curcumin was found to inhibit the TLR4-NF-κB signaling activation in HG-induced EMT of NRK-52E cells.

CONCLUSION

The present study provides evidence suggesting a novel mechanism that Curcumin exerts the anti-fibrosis effects via inhibiting activation of the TLR4-NF-κB signal pathway and consequently protecting the HG-induced EMT in renal tubular epithelial cells. Thereby, TLR4-NF-κB may be a useful target for therapeutic intervention in DKD.

Hesperidin downregulates kinases lrrk2 and gsk3β in a 6-OHDA induced Parkinson's disease model

The depletion of dopamine in the striatum region and Lewy bodies are the hallmark characteristics of Parkinson's disease. The pathology also includes the upregulation of various Parkinson's disease (PARK) genes and kinases. Two such kinases, LRRK2 and GSK-3β have been directly implicated in the formation of tau and alpha-synuclein proteins, causing PD. Hesperidin (HES) is a flavanone glycoside that has multiple therapeutic benefits including neuroprotective effects. In this study, we examined the neuroprotective effects of HES against 6-hydroxydopamine (6-OHDA) induced-neurotoxicity in the in-vitro and in-vivo model. Hesperidin significantly protected the SH-SY5Y cells' stress against 6-OHDA induced toxicity by downregulating biomarkers of oxidative stress. Furthermore, HES downregulated the kinases lrrk2 and gsk3β along with casp3, casp9, and polg in the zebrafish model. The treatment with HES also improved the locomotor pattern of zebrafish that was affected by 6-OHDA. This study suggests that hesperidin could be a drug of choice in targeting kinases against a 6-OHDA model of PD.

Cilostazol ameliorates diabetic nephropathy by inhibiting highglucose- induced apoptosis

Diabetic nephropathy (DN) is a hyperglycemia-induced progressive development of renal insufficiency. Excessive glucose can increase mitochondrial reactive oxygen species (ROS) and induce cell damage, causing mitochondrial dysfunction. Our previous study indicated that cilostazol (CTZ) can reduce ROS levels and decelerate DN progression in streptozotocin (STZ)-induced type 1 diabetes. This study investigated the potential mechanisms of CTZ in rats with DN and in high glucose-treated mesangial cells. Male Sprague-Dawley rats were fed 5 mg/kg/day of CTZ after developing STZ-induced diabetes mellitus. Electron microscopy revealed that CTZ reduced the thickness of the glomerular basement membrane and improved mitochondrial morphology in mesangial cells of diabetic kidney. CTZ treatment reduced excessive kidney mitochondrial DNA copy numbers induced by hyperglycemia and interacted with the intrinsic pathway for regulating cell apoptosis as an antiapoptotic mechanism. In high-glucose-treated mesangial cells, CTZ reduced ROS production, altered the apoptotic status, and down-regulated transforming growth factor beta (TGF-β) and nuclear factor kappa light chain enhancer of activated B cells (NF-κB). Base on the results of our previous and current studies, CTZ deceleration of hyperglycemia-induced DN is attributable to ROS reduction and thereby maintenance of the mitochondrial function and reduction in TGF-β and NF-κB levels.

Accelerated hippocampal biological aging in bipolar disorder

OBJECTIVES

Evidence suggests accelerated aging mechanisms in bipolar disorder (BD), including DNA methylation (DNAm) aging in blood. However, it is unknown whether such mechanisms are also evident in the brain, in particular in association with other biological clocks. To investigate this, we interrogated genome-wide DNAm in postmortem hippocampus from 32 BD-I patients and 32 non-psychiatric controls group-matched for age and sex from the NIMH Human Brain Collection Core.

METHODS

DNAm age and epigenetic aging acceleration were estimated using the Horvath method. Telomere length (TL) and mitochondrial DNA (mtDNA) copy number were quantified by real-time PCR. Between-group differences were assessed by linear regression and univariate general linear models with age, sex, race, postmortem interval, tissue pH, smoking, and body mass index included as co-variates.

RESULTS

Groups did not differ for epigenetic aging acceleration when considering the entire sample. However, after splitting the sample by the median age, an epigenetic aging acceleration was detected in patients compared to controls among older subjects (P = .042). While TL did not differ between groups, a reduction in mtDNA copy number was observed in patients compared to controls (P = .047). In addition, significant correlations were observed between epigenetic aging acceleration and TL (r = -.337, P = .006), as well as between TL and mtDNA copy number (r = .274, P = .028).

CONCLUSIONS

Hippocampal aging may underlie neurocognitive dysfunctions observed in BD patients. Moreover, our results suggest a complex cross-talk between biological clocks in hippocampus that may underlie clinical manifestations of premature aging in BD.

Mitochondrial DNA Copy Number in Peripheral Blood as a Potential Non-invasive Biomarker for Multiple Sclerosis

The impaired mitochondrial function has been implicated in the pathogenicity of multiple sclerosis (MS), a chronic inflammatory, demyelinating, and neurodegenerative disease of the CNS. Circulating mtDNA copy number in body fluids has been proposed as an indicator for several neurodegenerative diseases, and the altered cerebrospinal fluid mtDNA has been shown as a promising marker for MS. The aim of this study was to determine changes and biomarker potential of circulating mtDNA in peripheral blood in MS. The mtDNA copy number was quantified by real-time PCR in blood samples from 60 patients with relapsing-remitting MS (RRMS) and 64 healthy controls. The RRMS patients had significantly lower circulating mtDNA copy number compared to controls. Subgroup analysis with stratification of RRMS patients based on disease duration under or over 10 years revealed that the mtDNA copy number was significantly lower in the group with longer disease duration. A negative correlation was observed between mtDNA copy number and disease duration. The ROC curve analysis indicated a significant ability of mtDNA copy number to separate RRMS patients from controls with an AUC of 0.859. This is the first study to measure peripheral blood mtDNA copy number in MS patients. Current data suggest that the reduction in peripheral blood mtDNA copy number may be an early event in MS and correlate with the disease progression. The findings of this study indicate that circulating blood-based mtDNA copy number may be a potential non-invasive candidate biomarker for mitochondria-mediated neurodegeneration and MS. This can put forward the clinical applicability over other invasive markers.

Superoxide dismutase down-regulation and the oxidative stress is required to initiate pupation in Bombyx mori

Perhaps, oxidative stress progresses pupation in some Lepidopteran insects; however, the reasons for this remain obscure. In our previous study, we clarified Bombyx mori SOD1 (BmSOD1) and B. mori SOD2 (BmSOD2) proteins respond in common to ultraviolet irradiation (UV) oxidative stress and metamorphosis. This result strongly suggested pupation initiates by oxidative stress and might mediate by down-regulation of expression of BmSOD1 and BmSOD2 proteins. Thus, we examined about these relationships in B. mori in this study. In the microarray data reanalysis, we found the Notch signaling pathways as the common pathways in pupation and UV oxidative stress in B. mori. Also, we showed a molting hormone, 20-hydroxyecdysone, leads not only generation of superoxide but also downregulation of the expression of BmSOD proteins during pupation in B. mori. Our findings can contribute to a deeper understanding of how biological defense systems work against environmental oxidative stress.

Urea Memory: Transient Cell Exposure to Urea Causes Persistent Mitochondrial ROS Production and Endothelial Dysfunction

Urea at post-dialysis levels induces increased ROS in a number of cell types. The aim of this study was to determine whether urea-induced production of ROS remains elevated after urea is no longer present, and, if it does, to characterize its origin and effects. Human arterial endothelial cells were incubated with 20 mM urea for two days, and then cells were incubated for an additional two days in medium alone. Maximal ROS levels induced by initial urea continued at the same level despite urea being absent. These effects were prevented by either MnSOD expression or by Nox1/4 inhibition with GKT13781. Sustained urea-induced ROS caused a persistent reduction in mtDNA copy number and electron transport chain transcripts, a reduction in transcription of mitochondrial fusion proteins, an increase in mitochondrial fission proteins, and persistent expression of endothelial inflammatory markers. The SOD-catalase mimetic MnTBAP reversed each of these. These results suggest that persistent increases in ROS after cells are no long exposed to urea may play a major role in continued kidney damage and functional decline despite reduction of urea levels after dialysis.

Increased mitochondrial common deletion in platelets from patients with type 2 diabetes is not associated with abnormal platelet activity or mitochondrial function

The present study examined the presence and frequency of the 4,977‑base pair mitochondrial (mt)DNA (mtDNA4977) deletion in blood platelets, and whether increased mtDNA4977 deletion was associated with abnormal mitochondrial and platelet function in type 2 diabetes mellitus. A total of 66 patients with type 2 diabetes mellitus and 23 healthy subjects were included in the present study. Patients were divided into three subgroups according to glycemic control, and the presence or absence of chronic diabetic complications: i) Good glycemic control [glycated hemoglobin (HbA1c) <7] without complications; ii) poor glycemic control (HbA1c ≥7) without complications; and iii) poor glycemic control (HbA1c ≥7) with complications. mtDNA4977 deletion, mtDNA copy number, adenine nucleotides, mitochondrial membrane potential and P‑selectin expression levels were analyzed in platelets. Although the frequency of mtDNA4977 deletion in platelets of the patient (96.9%) and control groups (95.6%) was extremely similar, the deletion level significantly increased in all the diabetic groups, compared with the healthy control group. However, the data from the present study revealed that an increased deletion frequency in platelets was not associated with disease severity, although there was clear interindividual variability. Furthermore, all other parameters were not significantly different among the groups, and there were no correlations between mtDNA4977 deletion frequency and all other studied parameters for any of the case groups. The results indicated that the mtDNA4977 deletion occurred in platelets, and increased deletion in patients with type 2 diabetes did not have a marked influence on mitochondrial and/or platelet dysfunction, when compared with the non‑diabetic subjects. Further research is required to elucidate the sources of inter‑individual variability observed in certain parameters.

A Mouse Model of Schnyder Corneal Dystrophy with the N100S Point Mutation

Schnyder corneal dystrophy (SCD) is a rare autosomal dominant disease in humans, characterized by abnormal deposition of cholesterol and phospholipids in cornea caused by mutations in the UbiA prenyltransferase domain containing 1 (UBIAD1) gene. In this study, we generated a mouse line carrying Ubiad1 N100S point mutation using the CRISPR/Cas9 technique to investigate the pathogenesis of SCD. In vivo confocal microscopy revealed hyper-reflective dot-like deposits in the anterior cornea in heterozygotes and homozygotes. No significant change was found in corneal epithelial barrier function or wound healing. Electron microscopy revealed abnormal mitochondrial morphology in corneal epithelial, stromal, and endothelial cells. Mitochondrial DNA copy number assay showed 1.27 ± 0.07 fold change in homozygotes versus 0.98 ± 0.05 variation in wild type mice (P < 0.05). Lipidomic analysis indicated abnormal metabolism of glycerophosphoglycerols, a lipid class found in mitochondria. Four (34:1, 34:2, 36:2, and 44:8) of the 11 glycerophosphoglycerols species identified by mass spectrometry showed a significant increase in homozygous corneas compared with heterozygous and wild-type mouse corneas. Unexpectedly, we did not find a difference in the corneal cholesterol level between different genotypes by filipin staining or lipidomic analysis. The Ubiad1N100S mouse provides a promising animal model of SCD revealing that mitochondrial dysfunction is a prominent component of the disease. The different phenotype in human and mouse may due to difference in cholesterol metabolism between species.

Peripheral blood mitochondrial DNA copy number as a novel potential biomarker for diabetic nephropathy in type 2 diabetes patients

The mitochondrial DNA copy number (mtDNA-CN) is a surrogate measure of mitochondrial function and altered mtDNA-CN reflects the oxidant-induced cell damage. A previous study by our group demonstrated that a reduction in the renal mtDNA-CN is implicated in the pathogenesis of diabetic nephropathy (DN), a leading cause of end-stage renal disease in diabetic patients. In the present study, it was investigated whether the mtDNA-CN in the peripheral blood may be utilized as a biomarker for DN in type 2 diabetes (T2D) patients. The study included 50 non-diabetic and 100 diabetic subjects. The diabetic subjects were sub-divided based on their albumin-to-creatinine ratio (ACR) into T2D patients with normoalbuminuria (n=50), DN patients with microalbuminuria (n=29) and DN patients with macroalbuminuria (n=21). The mtDNA-CN was measured in the peripheral blood by real-time polymerase chain reaction analysis. Patients with DN had a lower mtDNA-CN than patients with T2D and healthy controls (P<0.05). A sub-group analysis with stratification by the ACR indicated that a decreased mtDNA-CN was associated with the severity and the presence of DN, as it was lower in DN patients with macroalbuminuria than in DN patients with microalbuminuria and T2D patients with normoalbuminuria (P<0.01). The area under the receiver operating characteristic curve (AUC) for mtDNA-CN was 0.916 (sensitivity, 86% and specificity, 74%) and 0.961 (sensitivity, 96% and specificity, 88%) for differentiating DN patients from T2D patients without DN and from healthy controls, respectively. Furthermore, the AUC of mtDNA-CN for differentiating DN patients with microalbuminuria from those with macroalbuminuria was 0.895 (sensitivity, 83% and specificity, 85%). Multivariate analysis revealed that the mtDNA-CN was significantly associated with the occurrence and progression of DN, even after adjustment for age, mean blood pressure, glycated haemoglobin A1c and total cholesterol (P<0.05). In patients with DN, a decreased mtDNA-CN was negatively correlated with albuminuria and conventional risk factors for DN, and was positively correlated with the estimated glomerular filtration rate. The present results therefore suggest the utilization of circulating mtDNA-CN as a novel biomarker for the early diagnosis of DN and indicate the significance of decreased mtDNA-CN as another independent risk factor for DN.

Salidroside alleviates high glucose-induced oxidative stress and extracellular matrix accumulation in rat glomerular mesangial cells by the TXNIP-NLRP3 inflammasome pathway

Diabetic nephropathy (DN) is a metabolic disease characterized by mesangial cell proliferation and extracellular matrix (ECM) accumulation. Salidroside (SAL) is the major ingredient in Rhodiola rosea and possesses beneficial effects on DN. This study aimed to evaluate the effect of SAL on high glucose (HG)-induced oxidative stress and ECM accumulation and the underlying mechanism. Rat glomerular mesangial cells HBZY-1 were induced by high glucose (HG) in the presence or absence of SAL. Cell proliferation was measured by CCK-8 assay. The reactive oxygen species (ROS) level, malondialdehyde (MDA) level and superoxide dismutase (SOD) activity were detected to evaluate oxidative stress. The expression levels of ECM proteins including fibronectin (FN) and type IV collagen (Coll IV) were detected by qRT-PCR and western blot analysis. The expressions of thioredoxin-interacting protein (TXNIP), nod-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing CARD (ASC), and caspase-1 were assessed by western blot. Si-TXNIP or si-NC was transfected into HBZY-1 cells to inhibit TXNIP-NLRP3 inflammasome pathway. The results showed that SAL treatment alleviated HG-induced cell proliferation. SAL reduced the levels of ROS and MDA, and induced the SOD activity. Besides, the mRNA and protein expressions of FN and Coll IV were decreased by SAL. The expression levels of TXNIP, NLRP3, ASC, and caspase-1 were reduced in the SAL treated cells. In addition, TXNIP knockdown inhibited TXNIP-NLRP3 inflammasome activation and suppressed HG-induced cell proliferation, oxidative stress, and ECM accumulation. In conclusion, SAL alleviated HG-induced oxidative stress and ECM accumulation in rat glomerular mesangial cells by the TXNIP-NLRP3 inflammasome pathway.

Prostaglandin E1 protects coronary microvascular function via the glycogen synthase kinase 3β-mitochondrial permeability transition pore pathway in rat hearts subjected to sodium laurate-induced coronary microembolization

Prostaglandin E1 (PGE1) is used as a pretreatment for ischemia reperfusion injury in many biological systems. However, its value as a pretreatment for coronary microembolization (CME) is unknown. The goal of this study was to determine whether PGE1 would protect against CME. In a CME rat model, we observed microthrombi and early myocardial ischemia, with endothelium appearing exfoliated and mitochondria having irregular morphology and decreased internal complexity. The level of fibrinogen-like protein 2 prothrombinase was increased and superoxide dismutase and catalase levels were decreased. Moreover, mitochondria copy number and mitochondrial permeability transition pore (mPTP) opening were increased. Pretreatment with PGE1 (1 or 2 μg/kg) significantly improved these cardiological deficits, acting via the glycogen synthase kinase 3β (GSK-3β)-mPTP pathway. Unexpectedly, the phosphorylation of Akt at Ser473 decreased in the PGE1 at high dose. Overall, our findings suggested an important role for PGE1 in pretreatment of coronary microvascular dysfunction.

Mitochondrial Reactive Oxygen Species and Kidney Hypoxia in the Development of Diabetic Nephropathy

The underlying mechanisms in the development of diabetic nephropathy are currently unclear and likely consist of a series of dynamic events from the early to late stages of the disease. Diabetic nephropathy is currently without curative treatments and it is acknowledged that even the earliest clinical manifestation of nephropathy is preceded by an established morphological renal injury that is in turn preceded by functional and metabolic alterations. An early manifestation of the diabetic kidney is the development of kidney hypoxia that has been acknowledged as a common pathway to nephropathy. There have been reports of altered mitochondrial function in the diabetic kidney such as altered mitophagy, mitochondrial dynamics, uncoupling, and cellular signaling through hypoxia inducible factors and AMP-kinase. These factors are also likely to be intertwined in a complex manner. In this review, we discuss how these pathways are connected to mitochondrial production of reactive oxygen species (ROS) and how they may relate to the development of kidney hypoxia in diabetic nephropathy. From available literature, it is evident that early correction and/or prevention of mitochondrial dysfunction may be pivotal in the prevention and treatment of diabetic nephropathy.

Diabetic nephropathy in type 1 diabetes: a review of early natural history, pathogenesis, and diagnosis

Diabetic nephropathy constitutes a devastating complication in patients with type 1 diabetes mellitus, and its diagnosis is traditionally based on microalbuminuria. The aim of this review is to update through the medical literature the suggested early natural course of diabetic nephropathy, the theories behind the pathways of its pathogenesis, and its diagnosis. Poor glycemic control, dyslipidemia, smoking, advanced glycation end products, and environmental and genetic clues play an important role in the development of diabetic nephropathy. Microalbuminuria has been traditionally considered as a primary early marker of microvascular complication unraveling the risk for progress to the advanced stages of chronic kidney disease, but because of our inability to make an early diagnosis of diabetic nephropathy in young patients as well as nonalbuminuric diabetic nephropathy, recently, other additional markers of renal injury like serum and urinary neutrophil gelatinase-associated lipocalin, chitinase-3-like protein 1, cystatin C, and plasma growth differentiation factor 15 have been proposed to unmask early renal dysfunction, even before microalbuminuria supervenes. Copyright © 2016 John Wiley & Sons, Ltd.

Detecting signatures of selection within the Tibetan sheep mitochondrial genome

Tibetan sheep, a Chinese indigenous breed, are mainly distributed in plateau and mountain-valley areas at a terrestrial elevation between 2260 and 4100 m. The herd is genetically distinct from the other domestic sheep and undergoes acclimatization to adapt to the hypoxic environment. To date, whether the mitochondrial DNA modification of Tibetan sheep shares the same feature as the other domestic breed remains unknown. In this study, we compared the whole mitogenome sequences from 32 Tibetan sheep, 22 domestic sheep and 24 commercial sheep to identify the selection signatures of hypoxic-tolerant in Tibetan sheep. Nucleotide diversity analysis using the sliding window method showed that the highest level of nucleotide diversity was observed in the control region with a peak value of π = 0.05215, while the lowest π value was detected in the tRNAs region. qPCR results showed that the relative mtDNA copy number in Tibetan sheep was significantly lower than that in Suffolk sheep. None of the mutations in 12S rRNA were fixed in Tibetan sheep, which indicated that there has been less artificial selection in this herd than the other domestic and commercial breeds. Although one site (1277G) might undergo the purifying selection, it was not identified as the breed-specific allele in Tibetan sheep. We proposed that nature selection was the main drive during the domestication of Tibetan sheep and single mutation (or locus) could not reveal the signature of selection as for the high diversity in the mitogenome of Tibetan sheep.

Mitochondrial c-Fos May Increase the Vulnerability of Neuro2a Cells to Cellular Stressors

Although c-Fos expression in mitochondria is known to increase under excitatory injury via kainic acid or N-methyl-D-aspartate injection, the authentic function of c-Fos in mitochondria remains unknown. We found that c-Fos expression in the mitochondria of neuroblastoma Neuro2a cells was augmented by oxygen and glucose deprivation (OGD), which is a common in vitro model for brain ischemia. Then we demonstrated that Neuro2a cells stably expressing c-Fos exclusively in the mitochondria were more vulnerable to stressors such as OGD, rotenone (which is known to induce mitochondrial dysfunction) and hydrogen peroxide (a reactive oxygen species). Since mitochondrial dysfunction and the generation of reactive oxygen species are known to be caused by OGD, our findings indicate that mitochondrial c-Fos increases neuronal vulnerability to brain ischemia. This suggests that mitochondrial c-Fos play a potential role in inducing neuronal death on, and can therefore act as a potential drug target for brain ischemia.

Increased expression of mitochondrial DNA-encoded genes in human renal mesangial cells in response to high glucose-induced reactive oxygen species

Reactive oxygen species (ROS)-mediated disruption of mitochondrial respiratory function has been implicated in the complications of diabetes. The present study examined changes in the gene expression of mitochondrial DNA (mtDNA)-encoded subunits of electron transport chain complexes in response to high glucose-induced ROS overproduction in an in vitro model of diabetic nephropathy using human renal mesangial cells. Mitochondrial ROS generation was assessed by confocal microscopy and flow cytometry in the cells following culture in 5 and 25 mM glucose. The mRNA expression levels of nicotinamide adenine dinucleotide dehydrogenase 2 (ND2) of complex I, cytochrome b (CYTB) of complex III, cytochrome c oxidase (COI) of complex IV and ATPase 6 of complex V were analyzed by reverse transcription-quantitative polymerase chain reaction. The protein expression levels of ND2, CYTB, COI and ATPase 6 were analyzed by western blotting. A significant increase in mitochondrial ROS production was observed in the cells cultured in 25 mM glucose, compared with cells cultured in 5 mM glucose (P<0.05). The mRNA expression of ND2, CYTB, CO1 and ATPase 6 was significantly increased following culture in 25 mM glucose, compared with the cells cultured in 5 mM glucose (P<0.05). This increase in mRNA expression was accompanied by significant increases in protein expression following incubation in 25 mM glucose (P<0.05). The increase in mtDNA-encoded gene expression in the electron transport subunits following exposure to high glucose-induced ROS may be a compensatory response mechanism for the decline in mitochondrial function, which may be important in the development of diabetic nephropathy through enhanced ROS generation.

High glucose induces rat mesangial cells proliferation and MCP-1 expression via ROS-mediated activation of NF-κB pathway, which is inhibited by eleutheroside E

Glomerular hypertrophy and extracellular matrix accumulation are early features of diabetic nephropathy (DN). High glucose-induced oxidative stress is implicated in the etiology of DN. This study aims to investigate the effect of eleutheroside E (EE) on high glucose mediated rat mesangial cells (MCs) proliferation and monocyte chemoattractant protein-1 (MCP-1) expression and the underlying mechanism. MCs proliferation was assessed by MTT assay. Reactive oxygen species (ROS) level and MCP-1 expression were evaluated by ELISA kit. The protein expression of p47, NF-κB p65, p-NF-κB p65, IκBα, p-IκBα, IKKβ and p-IKKβ were determined by Western blot. The results showed that treatment with EE markedly attenuated high glucose induced MCs proliferation and in a dose-dependent manner. Intervention with EE also significantly blocked high glucose induced intracellular ROS production by decreasing NADPH oxidase activity. Meanwhile, EE administration could effectively alleviate the high glucose-stimulated activation of NF-κB, the degradation of IκBα and the expression of MCP-1. These results demonstrate that high glucose enhances MCs proliferation and MCP-1 expression by activating the ROS/NF-κB pathway and can be inhibited by EE. Our findings provide a new perspective for the clinical treatment of DN.

Mitochondrial DNA Copy Number in Sleep Duration Discordant Monozygotic Twins

STUDY OBJECTIVES

Mitochondrial DNA (mtDNA) copy number is an important component of mitochondrial function and varies with age, disease, and environmental factors. We aimed to determine whether mtDNA copy number varies with habitual differences in sleep duration within pairs of monozygotic twins.

SETTING

Academic clinical research center.

PARTICIPANTS

15 sleep duration discordant monozygotic twin pairs (30 twins, 80% female; mean age 42.1 years [SD 15.0]).

DESIGN

Sleep duration was phenotyped with wrist actigraphy. Each twin pair included a "normal" (7-9 h/24) and "short" (< 7 h/24) sleeping twin. Fasting peripheral blood leukocyte DNA was assessed for mtDNA copy number via the n-fold difference between qPCR measured mtDNA and nuclear DNA creating an mtDNA measure without absolute units. We used generalized estimating equation linear regression models accounting for the correlated data structure to assess within-pair effects of sleep duration on mtDNA copy number.

MEASUREMENTS AND RESULTS

Mean within-pair sleep duration difference per 24 hours was 94.3 minutes (SD 62.6 min). We found reduced sleep duration (β = 0.06; 95% CI 0.004, 0.12; P < 0.05) and sleep efficiency (β = 0.51; 95% CI 0.06, 0.95; P < 0.05) were significantly associated with reduced mtDNA copy number within twin pairs. Thus every 1-minute decrease in actigraphy-defined sleep duration was associated with a decrease in mtDNA copy number of 0.06. Likewise, a 1% decrease in actigraphy-defined sleep efficiency was associated with a decrease in mtDNA copy number of 0.51.

CONCLUSIONS

Reduced sleep duration and sleep efficiency were associated with reduced mitochondrial DNA copy number in sleep duration discordant monozygotic twins offering a potential mechanism whereby short sleep impairs health and longevity through mitochondrial stress.

Time-course effect of high-glucose-induced reactive oxygen species on mitochondrial biogenesis and function in human renal mesangial cells

The present study investigated the time-course effect of high-glucose-induced reactive oxygen species (ROS) on mitochondrial biogenesis and function in human renal mesangial cells and the effect of direct inhibition of ROS on mitochondria. The cells were cultured for 1, 4, and 7 days in normal glucose or high glucose in the presence and absence of Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP) or catalase. Mitochondrial ROS production was assessed by confocal microscope. mtDNA copy number and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), nuclear respiratory factors 1 (NRF-1), and mitochondrial transcription factor A (TFAM) transcripts were analyzed by real-time PCR. PGC-1α, NRF-1, and TFAM proteins were analyzed by Western blotting. Mitochondrial function was determined by assessing mitochondrial membrane potential and adenosine triphosphate (ATP) levels. High glucose induced significant increases in mitochondrial superoxide and hydrogen peroxide (H2 O2 ) at day 1, which remained significantly elevated at days 4 and 7. The copy number of mtDNA and expression of PGC-1α, NRF-1, and TFAM were significantly increased at 1 day in high glucose but were significantly decreased at 4 and 7 days. A progressive decrease in mitochondrial membrane potential was observed at 1, 4, and 7 days in high glucose, and this was associated with decreased ATP levels. Treatment of cells with MnTBAP or catalase during high-glucose incubation attenuated ROS production and reversed the alterations in mitochondrial biogenesis and function. Increased mitochondrial biogenesis in human renal mesangial cells may be an early adaptive response to high-glucose-induced ROS, and prolonged ROS production induced by chronic high glucose decreased mitochondrial biogenesis and impaired mitochondrial function. Protection of mitochondria from high-glucose-induced ROS may provide a potential approach to retard the development and progression of diabetic nephropathy.

Oxidative stress, mitochondrial perturbations and fetal programming of renal disease induced by maternal smoking

An adverse in-utero environment is increasingly recognized to predispose to chronic disease in adulthood. Maternal smoking remains the most common modifiable adverse in-utero exposure leading to low birth weight, which is strongly associated with chronic kidney disease (CKD) in later life. In order to investigate underlying mechanisms for such susceptibility, female Balb/c mice were sham or cigarette smoke-exposed (SE) for 6 weeks before mating, throughout gestation and lactation. Offspring kidneys were examined for oxidative stress, expression of mitochondrial proteins, mitochondrial structure as well as renal functional parameters on postnatal day 1, day 20 (weaning) and week 13 (adult age). From birth throughout adulthood, SE offspring had increased renal levels of mitochondrial-derived reactive oxygen species (ROS), which left a footprint on DNA with increased 8-hydroxydeoxyguanosin (8-OHdG) in kidney tubular cells. Mitochondrial structural abnormalities were seen in SE kidneys at day 1 and week 13 along with a reduction in oxidative phosphorylation (OXPHOS) proteins and activity of mitochondrial antioxidant Manganese superoxide dismutase (MnSOD). Smoke exposure also resulted in increased mitochondrial DNA copy number (day 1-week 13) and lysosome density (day 1 and week 13). The appearance of mitochondrial defects preceded the onset of albuminuria at week 13. Thus, mitochondrial damage caused by maternal smoking may play an important role in development of CKD at adult life.

Dormancy and quiescence of skeletal muscle stem cells

The skeletal muscle of vertebrates has a huge regenerative capacity. When destroyed after different types of injury, this organ can regenerate very quickly (less than 20 days following myotoxin injection in the mouse) ad integrum and repeatedly. The cell responsible for this regeneration is the so-called satellite cell, the muscle stem cell that lies on top of the muscle fibre, a giant, multinucleated cell that contains the contractile material. When injected in the muscle, satellite cells can efficiently differentiate into contractile muscle fibres. The satellite cell shows great therapeutic potential; and its regenerative capacity has triggered particular interest in the field of muscular degeneration. In this review we will focus on one particular property of the satellite cell: its quiescence and dormancy. Indeed adult satellite cells are quiescent; they lie between the basal lamina and the basement membrane of the muscle fibre, ready to proliferate, and fuse in order to regenerate myofibers upon injury. It has recently been shown that a subpopulation of satellite cells is able to enter dormancy in human and mice cadavers. Dormancy is defined by a low metabolic state, low mobility, and a long lag before division when plated in vitro, compared to quiescent cells. This definition is also based on current knowledge about long-term hematopoietic stem cells, a subpopulation of stem cells that are described as dormant based on the same criteria (rare division and low metabolism when compared to progeny which are dividing more often). In the first part of this review, we will provide a description of satellite cells which addresses their quiescent state. We will then focus on the uneven distribution of satellite cells in the muscle and describe evidence that suggests that their dormancy differs from one muscle to the next and that one should be cautious when making generalisations regarding this cellular state. In a second part, we will discuss the transition between active dividing cells in developing animals to quiescence. This mechanism could be used or amplified in the switch from quiescence to dormancy. In a third part, we will review the signals and dynamics that actively maintain the satellite cell quiescent. The in-depth understanding of these mechanisms is key to describing how dormancy relies on quiescent state of the cells. In a fourth part, we will deal with dormancy per se: how dormant satellite cells can be obtained, their characteristics, their metabolic profile, and their molecular signature as compared to quiescent cells. Here, we will highlight one of the most important recent findings: that quiescence is a prerequisite for the entry of the satellite cell into dormancy. Since dormancy is a newly discovered phenomenon, we will review the mechanisms responsible for quiescence and activation, as these two cellular states are better known and key to understanding satellite cell dormancy. This will allow us to describe dormancy and its prerequisites.

Grape seed procyanidin B2 ameliorates mitochondrial dysfunction and inhibits apoptosis via the AMP-activated protein kinase-silent mating type information regulation 2 homologue 1-PPARγ co-activator-1α axis in rat mesangial cells under high-dose glucosamine

Grape seed procyanidin B2 (GSPB2), an antioxidative and anti-inflammatory polyphenol in grape seed, has been found to have protective effects on diabetic nephropathy. Based on its favourable biological activities, in the present study, we aimed to investigate whether GSPB2 could inhibit apoptosis in rat mesangial cells treated with glucosamine (GlcN) under high-dose conditions. The results showed that the administration of GSPB2 (10 μg/ml) significantly increased the viability of mesangial cells treated with GlcN at a dose of 15 mM. We found that GSPB2 inhibited apoptosis in mesangial cells using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphates (dUTP) nick-end labelling staining and flow cytometry technique (P< 0·05 for both). GSPB2 treatment also suppressed oxidative stress by elevating the activity of glutathione peroxidase (P< 0·05) and superoxide dismutase (P< 0·01), as well as prevented cellular damage. GSPB2 enhanced the mRNA expression of nuclear respiratory factor 1, mitochondrial transcription factor A and mitochondrial DNA copy number in mesangial cells as determined by real-time PCR (P< 0·05 for each). Finally, GSPB2 treatment activated the protein expression of PPARγ co-activator-1α (PGC-1α), silent mating type information regulation 2 homologue 1 (SIRT1) and AMP-activated protein kinase (AMPK) in mesangial cells. These findings suggest that GSPB2 markedly ameliorates mitochondrial dysfunction and inhibits apoptosis in rat mesangial cells treated with high-dose GlcN. This protective effect could be, at least in part, due to the activation of the AMPK-SIRT1-PGC-1α axis.

Mn porphyrin-based SOD mimic, MnTnHex-2-PyP(5+), and non-SOD mimic, MnTBAP(3-), suppressed rat spinal cord ischemia/reperfusion injury via NF-κB pathways

Herein we have demonstrated that both superoxide dismutase (SOD) mimic, cationic Mn(III) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin (MnTnHex-2-PyP(5+)), and non-SOD mimic, anionic Mn(III) meso-tetrakis(4-carboxylatophenyl)porphyrin (MnTBAP(3-)), protect against oxidative stress caused by spinal cord ischemia/reperfusion via suppression of nuclear factor kappa B (NF-κB) pro-inflammatory pathways. Earlier reports showed that Mn(III) N-alkylpyridylporphyrins were able to prevent the DNA binding of NF-κB in an aqueous system, whereas MnTBAP(3-) was not. Here, for the first time, in a complex in vivo system-animal model of spinal cord injury-a similar impact of MnTBAP(3-), at a dose identical to that of MnTnHex-2-PyP(5+), was demonstrated in NF-κB downregulation. Rats were treated subcutaneously at 1.5 mg/kg starting at 30 min before ischemia/reperfusion, and then every 12 h afterward for either 48 h or 7 days. The anti-inflammatory effects of both Mn porphyrins (MnPs) were demonstrated in the spinal cord tissue at both 48 h and 7 days. The downregulation of NF-κB, a major pro-inflammatory signaling protein regulating astrocyte activation, was detected and found to correlate well with the suppression of astrogliosis (as glial fibrillary acidic protein) by both MnPs. The markers of oxidative stress, lipid peroxidation and protein carbonyl formation, were significantly reduced by MnPs. The favorable impact of both MnPs on motor neurons (Tarlov score and inclined plane test) was assessed. No major changes in glutathione peroxidase- and SOD-like activities were demonstrated, which implies that none of the MnPs acted as SOD mimic. Increasing amount of data on the reactivity of MnTBAP(3-) with reactive nitrogen species (RNS) (.NO/HNO/ONOO(-)) suggests that RNS/MnTBAP(3-)-driven modification of NF-κB protein cysteines may be involved in its therapeutic effects. This differs from the therapeutic efficacy of MnTnHex-2-PyP(5+) which presumably occurs via reactive oxygen species and relates to NF-κB thiol oxidation; the role of RNS cannot be excluded.

Keratoconus is associated with increased copy number of mitochondrial DNA

PURPOSE

To investigate the possible association of oxidative stress with keratoconus (KC), we estimated the changes in relative mitochondrial DNA (mtDNA) content.

METHODS

The study included 119 patients with KC and 208 controls matched for gender, ethnicity, and systemic disease status. We selected controls who were older than the patients since the mtDNA copy number tends to increase with age. The age mean (standard deviation) was 26.4(7.6) and 54.5(14.4) years for the patients and controls, respectively. The relative mtDNA copy number was estimated with the real-time quantitative PCR (qPCR) method using ND1 as the mtDNA gene and human globulin (HGB; also known as the cytoglobin gene, CYGB) as the reference single-copy nuclear gene.

RESULTS

The mean relative mtDNA content was significantly higher in patients with KC (1.20±0.45) than in the normal control subjects (1.04±0.36; p = 0.0004). Subjects with high mtDNA content (>1.259, i.e., greater than 75(th) percentile) were at an increased risk of the disease (odds ratio = 2.62, 95% confidence interval = 1.40 to 4.89; p =0.0025).

CONCLUSIONS

Increased mtDNA content in patients with KC may indicate mitochondrial respiratory chain defects and thus mitochondrial-abnormality involvement.