Mitochondrial Structural Abnormalities Research Articles

Implication of a novel truncating mutation in titin as a cause of autosomal dominant left ventricular noncompaction.

BACKGROUNDMutation in the titin gene (TTN) in left ventricular noncompaction (LVNC) has been reported with a highly heterogeneous prevalence, and the molecular mechanisms underlying the pathogenesis of TTN gene mutation are uncharacterized. In the present study, we identified a novel TTN mutation in a pedigree with LVNC and investigated the potential pathogenic mechanism by functional studies. METHODSThe whole-genome sequencing with linkage analysis was performed in a 3-generation family affected by autosomal dominant LVNC cardiomyopathy. The clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR/Cas9) technology was used to establish novel truncating mutation in TTN in a rat cardiomyoblast H9C2 cell line in vitro, in which functional studies were carried out and characterized in comparison to its wild-type counterpart. RESULTSA novel truncating mutation TTN p. R2021X was identified as the only plausible disease-causing variant that segregated with disease among the five surviving affected individuals, with an interrogation of the entire genome excluding other potential causes. Quantitative reverse transcription-polymerase chain reaction and cellular immunofluorescence supported a haploinsufficient disease mechanism in titin truncation mutation cardiomyocytes. Further functional studies suggested mitochondrial abnormities in the presence of mutation, including decreased oxygen consumption rate, reduced adenosine triphosphate production, impaired activity of electron translation chain, and abnormal mitochondrial structure on electron microscopy. Impaired autophagy under electron microscopy accompanied with activation of the Akt-mTORC1 signaling pathway was observed in TTN p. R2021X truncation mutation cardiomyocytes. CONCLUSIONSThe TTN p. R2021X mutation has a function in the cause of a highly penetrant familial LVNC. These findings expand the spectrum of titin’s roles in cardiomyopathies and provide novel insight into the molecular basis of titin-truncating variants-associated LVNC.

TMPRSS12 Functions in Meiosis and Spermiogenesis and Is Required for Male Fertility in Mice.

Serine proteases are involved in many physiological activities as initiators of proteolytic cascades, and some members have been reported to play roles in male reproduction. Transmembrane serine protease 12 (TMPRSS12) has been shown to regulate sperm motility and uterotubal junction migration in mice, but its role in the testis remains unknown. In this study, we verified that TMPRSS12 was expressed in the spermatocytes and spermatids of testis and the acrosome of sperm. Mice deficient in Tmprss12 exhibited male sterility. In meiosis, TMPRSS12 was demonstrated to regulate synapsis and double-strand break repair; spermatocytes of Tmprss12 −/− mice underwent impaired meiosis and subsequent apoptosis, resulting in reduced sperm counts. During spermiogenesis, TMPRSS12 was found to function in the development of mitochondria; abnormal mitochondrial structure in Tmprss12 −/− sperm led to reduced availability of ATP, impacting sperm motility. The differential protein expression profiles of testes in Tmprss12 −/− and wild-type mice and further molecule identification revealed potential targets of TMPRSS12 related to meiosis and mitochondrial function. Besides, TMPRSS12 was also found to be involved in a series of sperm functions, including capacitation, acrosome reaction and sperm-egg interaction. These data imply that TMPRSS12 plays a role in multiple aspects of male reproduction.

Survivin is essential for thermogenic program and metabolic homeostasis in mice

ObjectiveSurvivin is a member of the inhibitor of apoptosis family. Our previous study showed that survivin expression could be strongly induced by long-term, high-fat diet (HFD) exposure in vivo. It could also be induced by insulin through the PI3K/mTOR signaling pathway in vitro. Therefore, we hypothesized that under certain conditions, survivin expression might be required for adipocyte function. In the current study, we aim to further investigate the regulation of survivin expression in mature adipocytes upon various nutritional stimuli and the role of survivin using adipocyte-specific survivin knockout (SKO) mice. MethodsSKO mice were obtained by crossing survivinflox/flox mice with Adiponectin-Cre+/- mice. The overall metabolic phenotype was observed under chow diet (CD) and HFD feeding conditions. The thermogenic program of mice was detected upon cold exposure. The inguinal white adipose tissue (iWAT) and brown adipose tissue (BAT) stromal vascular fraction cells were isolated and differentiated into mature adipocytes, and the effects of survivin deletion on mature adipocyte function were detected in vitro. ResultsSurvivin expression in adipose tissue and adipocytes was regulated by short-term nutritional stress both in vivo and in vitro. The postnatal development of BAT was impaired in SKO mice, which resulted in drastically reduced BAT mass and decreased expression of the thermogenic protein Ucp1 in 24-week-old mice fed with CD. After HFD feeding, the iWAT and BAT mass of SKO mice were significantly decreased, causing ectopic lipid accumulation in the liver, which was associated with insulin resistance and glucose intolerance. Upon cold exposure, the expression of thermogenic genes and proteins was markedly reduced in BAT and iWAT of SKO mice, accompanied by abnormal mitochondrial structure and induced autophagy. Consistently, thermogenic program and mitochondrial oxidative phosphorylation were reduced in survivin-depleted brown and beige adipocytes in vitro. ConclusionsOur findings showed that survivin could be regulated by nutritional stress in adipocytes and revealed a new role of survivin in maintaining normal BAT mass and positively regulating the thermogenic program and mitochondrial oxidative phosphorylation.

Effects of vibration on the expression of mitochondrial fusion and fission genes and ultrastructure of skeletal muscle in rabbits

Objective: To study the effects of vibration on the expression of mitochondrial fusion and fission genes and ultrastructure of skeletal muscle in rabbits. Methods: Thirty-two 3.5-month-old New Zealand rabbits were randomly divided into low-intensity group, medium-intensity group, high-intensity group and control group, with 8 rabbits in each group. The rabbits in the experimental group were subjected to hind limb vibration load test for 45 days. The vibration intensity of the high intensity group was 12.26 m/s(2), the medium intensity group was 6.13 m/s(2), and the low intensity group was 3.02 m/s(2) according to the effective value of weighted acceleration[a(hw (4))] for 4 hours of equal energy frequency. The control group was exposed to noise only in the same experimental environment as the medium-intensity group. The noise levels of each group were measured during the vibration load experiment. After the test, the mRNA expression of mitochondrial fusion gene (Mfn1/Mfn2) and fission gene (Fis1, Drp1) by RT-PCR in the skeletal muscles were measured and the ultrastructure of the skeletal muscles were observed in high intensity group. Results: The mRNA expression of mitochondrial in the skeletal muscle tissues of control group, low intensity group, medium intensity group and high intensity group were Mfn1: 3.25±1.36, 3.85±1.90, 4.53±2.31 and 11.63±7.68; Mfn2: 0.68±0.25, 1.02±0.40, 0.94±0.33 and 1.40±0.45; Fis1: 1.05±0.62, 1.15±0.59, 1.53±1.06 and 2.46±1.51 and Drp1: 3.72±1.76, 2.91±1.63, 3.27±2.01 and 4.21±2.46, respectively. Compared with the control group, the expressions of Mfn1 mRNA, Mfn2 mRNA and Fis1 mRNA in the high-intensity group increased significantly (P<0.05) , and the expressions of Mfn2 mRNA in the medium-intensity group and the low-intensity group increased significantly (P<0.05) . Compared with the control group, the ultrastructure of skeletal muscle of high intensity group showed mitochondrial focal accumulation, cristae membrane damage, vacuole-like changes; Z-line irregularity of muscle fibers, and deficiency of sarcomere. Conclusion: Vibration must be lead to the abnormal mitochondrial morphology and structure and the disorder of energy metabolism due to the expression imbalance of mitochondrial fusion and fission genes in skeletal muscles of rabbits, which may be an important target of vibration-induced skeletal muscle injury.

Proteinopathies as Hallmarks of Impaired Gene Expression, Proteostasis and Mitochondrial Function in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal adult-onset neurodegenerative disease characterized by progressive degeneration of upper and lower motor neurons. As with the majority of neurodegenerative diseases, the pathological hallmarks of ALS involve proteinopathies which lead to the formation of various polyubiquitylated protein aggregates in neurons and glia. ALS is a highly heterogeneous disease, with both familial and sporadic forms arising from the convergence of multiple disease mechanisms, many of which remain elusive. There has been considerable research effort invested into exploring these disease mechanisms and in recent years dysregulation of RNA metabolism and mitochondrial function have emerged as of crucial importance to the onset and development of ALS proteinopathies. Widespread alterations of the RNA metabolism and post-translational processing of proteins lead to the disruption of multiple biological pathways. Abnormal mitochondrial structure, impaired ATP production, dysregulation of energy metabolism and calcium homeostasis as well as apoptosis have been implicated in the neurodegenerative process. Dysfunctional mitochondria further accumulate in ALS motor neurons and reflect a wider failure of cellular quality control systems, including mitophagy and other autophagic processes. Here, we review the evidence for RNA and mitochondrial dysfunction as some of the earliest critical pathophysiological events leading to the development of ALS proteinopathies, explore their relative pathological contributions and their points of convergence with other key disease mechanisms. This review will focus primarily on mutations in genes causing four major types of ALS (C9ORF72, SOD1, TARDBP/TDP-43, and FUS) and in protein homeostasis genes (SQSTM1, OPTN, VCP, and UBQLN2) as well as sporadic forms of the disease. Finally, we will look to the future of ALS research and how an improved understanding of central mechanisms underpinning proteinopathies might inform research directions and have implications for the development of novel therapeutic approaches.

Abnormal mitochondrial structure and function are retained in gingival tissues and human gingival fibroblasts from patients with chronic periodontitis.

The abnormal structure and function of mitochondria in cells is closely associated with inflammatory diseases. However, the physiology of mitochondria within gingival tissues and human gingival fibroblasts (HGFs) in patients with chronic periodontitis (CP) remains unclear. The objective of this study was to investigate the structure profile and function of mitochondria in gingival tissues and in HGFs derived from patients with or without CP. These features of mitochondria in HGFs were further analyzed when HGFs were induced by lipopolysaccharide (LPS) from Porphyromonas gingivalis (P.g). Gingival tissues and HGFs were collected from CP and healthy patients. Mitochondrial structure was assessed by transmission electron microscopy. Tissues or cells lysis was performed for mitochondrial DNA (mtDNA) quantification, and real-time polymerase chain reaction (RT-PCR) tests were used to determine mtDNA copy numbers. Western blot analysis was used to evaluate autophagy-related protein (ATG)-5, microtubule-associated protein light chain 3 (LC3), and mitochondrial matrix protein pyruvate dehydrogenase kinase isozyme 2 (PDK2) levels in tissues and HGFs from CP and healthy individuals. Tissues and HGFs from CP showed a significant greater mitochondrial structure destruction, lower mtDNA level, increased ATG5, LC3-II, and lower PDK2 protein levels than those of healthy individuals. In addition, LPS from P.g also triggered the same results in HGFs from healthy donors. Moreover, the challenge of HGFs from CP with LPS worsened these parameters. Mitochondrial structure and function within gingival tissues and HGFs from CP individuals were abnormal compared to those from healthy donors, and LPS could promote mitochondrial destruction.

Electroacupuncture Pretreatment Alleviates Cerebral Ischemia-Reperfusion Injury by Regulating Mitophagy via mTOR-ULK1/FUNDC1 Axis in Rats

Objective: Electroacupuncture (EA) pretreatment has been shown to alleviate cerebral ischemia-reperfusion (I/R) injury; however, the underlying mechanism remains unclear. To investigate the involvement of mTOR signaling in the protective role of EA in I/R-induced brain damage and mitochondrial injury. Methods: Sprague-Dawley male rats were pretreated with vehicle, EA (at Baihui and Shuigou acupoints), or rapamycin + EA for 30 min daily for 5 consecutive days, followed by the middle cerebral artery occlusion to induce I/R injury. The neurological functions of the rats were assessed using the Longa neurological deficit scores. The rats were sacrificed immediately after neurological function assessment. The brains were obtained for the measurements of cerebral infarct area. The mitochondrial structural alterations were observed under transmission electron microscopy. The mitochondrial membrane potential changes were detected by JC-1 staining. The alterations in autophagy-related protein expression were examined using Western blot analysis. Results: Compared with untreated I/R rats, EA-pretreated rats exhibited significantly decreased neurological deficit scores and cerebral infarct volumes. EA pretreatment also reversed I/R-induced mitochondrial structural abnormalities and loss of mitochondrial membrane potential. Furthermore, EA pretreatment downregulated the protein expression of LC3-II, p-ULK1, and FUNDC1 while upregulating the protein expression of p-mTORC1 and LC3-I. Rapamycin effectively blocked the above-mentioned effects of EA. Conclusion: EA pretreatment at Baihui and Shuigou alleviates cerebral I/R injury and mitochondrial impairment in rats through activating the mTORC1 signaling. The suppression of autophagy-related p-ULK1/FUNDC1 pathway is involved in the neuroprotective effects of EA.

Phenotype and pathology of the dilated cardiomyopathy with ataxia syndrome in children.

The dilated cardiomyopathy with ataxia syndrome (DCMA) is an autosomal recessive mitochondrial disease caused by mutations in the DnaJ heat shock protein family (Hsp40) member C19 (DNAJC19) gene. DCMA or 3-methylglutaconic aciduria type V is globally rare, but the largest number of patients in the world is found in the Hutterite population of southern Alberta in Canada. We provide an update on phenotypic findings, natural history, pathological findings, and our clinical experience. We analyzed all available records for 43 patients diagnosed with DCMA between 2005 and 2015 at the Alberta Children's Hospital. All patients studied were Hutterite and homozygous for the causative DNAJC19 variant (c.130-1G>C, IVS3-1G>C) and had elevated levels of 3-methyglutaconic acid. We calculated a birth prevalence of 1.54 cases per 1000 total births in the Hutterite community. Children were small for gestational age at birth and frequently required supplemental nutrition (63%) or surgical placement of a gastrostomy tube (35%). Early mortality in this cohort was high (40%) at a median age of 13 months (range 4-294 months). Congenital anomalies were common as was dilated cardiomyopathy (50%), QT interval prolongation (83%), and developmental delay (95%). Tissue pathology was analyzed in a limited number of patients and demonstrated subendocardial fibrosis in the heart, macrovesicular steatosis and fibrosis in the liver, and structural abnormalities in mitochondria. This report provides clinical details for a cohort of children with DCMA and the first presentation of tissue pathology for this disorder. Despite sharing common genetic etiology and environment, the disease is highly heterogeneous for reasons that are not understood. DCMA is a clinically heterogeneous systemic mitochondrial disease with significant morbidity and mortality that is common in the Hutterite population of southern Alberta.

Clinical Benefit and Improvement of Mitochondrial Function in Low Risk Myelodysplastic Syndrome Treated By Combination Ultra Coenzyme Q10 and L-Carnitine

Background: Structural mitochondrial abnormalities as well as alterations in gene expression of key mitochondrial proteins are well recognized in myelodysplastic syndrome (MDS), suggesting that mitochondrial dysfunction is important in the pathogenesis of this disease. Both Coenzyme Q10 and L- carnitine play an essential role in efficient cellular energy production. Clinical and cytogenetic response to high dose of Coenzyme Q10 in patients with MDS was demonstrated previously. The combination of L- carnitine and Coenzyme Q10 has shown a beneficial effect in other mitochondrial disorders. Aim: To assess the effect of combination of food supplements on the clinical course and mitochondrial function of peripheral blood cells obtained from patients with in low/intermediate- 1 risk MDS.Materials and Methods: Ultra-coenzyme Q10 (180 mg/day), L-carnitine (2000 mg/day) and a vitamin mineral complex were administered for 6 months; patients were allowed to continue treatment for an additional 6 months, if it was beneficial. Inclusion criteria were Hb<10.5g/dL or PLT<100x109/L or ANC<0.8X109/L. As of May 2017, 33 pts. have been enrolled in the study. Peripheral blood cells were assessed by the Seahorse XF analyzer which is a state- of- the- art tool for assessment of real time cellular respiration, by continuous measurement of Oxygen Consumption Rate (OCR) under different conditions in-vitro . Mitochondrial function assessment was performed at baseline and at six-month point. Results: The median age of the entire cohort was 75 years (range: 56-93), 20(61%) of pts. were male. Pts. were classified per IPSS-R: very low risk 7 (21%), low risk 21(64%),int. 5 (15%). Median Hb was 9.5 g/dL (6.4-12.2); 17 (52%) were transfusions dependent and 16(48%) failed treatment with erythropoietin stimulating agents (ESA). 28 patients completed treatment protocol. Six pts. (21.4%) showed a hematological Improvement according to IWG 2006 criteria (out of which 4 were transfusions dependent). Median time to the initial response was 9 weeks (5-24). At 3 months' time point 14 of 18 patients had an increased in their integral Quality of life (QOL) score per FACT questionnaire; mean improvement was 14.3 points per patient (p=0.011). The pre-treatment mitochondrial basal respiration and especially spare respiratory capacity tested on cells of 11 MDS cases were uniformly lower in comparison with healthy controls (p=0.04 and p=0.007,respectively). There was significant improvement of basal, as well as spare respiration in peripheral blood cells obtained from MDS patients after six months food supplements (p=0.0027 and p=0.02, respectively). Conclusions: We demonstrated for the first time that mitochondrial energy production in peripheral blood is impaired in patients with MDS. Furthermore, we showed that this is at least partially reversible with food supplementations known to augment mitochondrial function. Combination of Ultra coenzyme Q10 with L-carnitine and vitamin mineral complex leads to moderate clinical response in low/intermediate-1 risk MDS patients and improve QOL DisclosuresNo relevant conflicts of interest to declare.

Pyridostigmine Protects Against Diabetic Cardiomyopathy by Regulating Vagal Activity, Gut Microbiota, and Branched-Chain Amino Acid Catabolism in Diabetic Mice.

The disruption of gut microbes is associated with diabetic cardiomyopathy, but the mechanism by which gut microbes affect cardiac damage remains unclear. We explored gut microbes and branched-chain amino acid (BCAA) metabolite catabolism in diabetic cardiomyopathy mice and investigated the cardioprotective effect of pyridostigmine. The experiments were conducted using a model of diabetic cardiomyopathy induced by a high-fat diet + streptozotocin in C57BL/6 mice. The results of high-throughput sequencing showed that diabetic cardiomyopathy mice exhibited decreased gut microbial diversity, altered abundance of the diabetes-related microbes, and increased abundance of the BCAA-producing microbes Clostridiales and Lachnospiraceae. In addition, diabetes downregulated tight junction proteins (ZO-1, occludin, and claudin-1) and increased intestinal permeability to impair the intestinal barrier. These impairments were accompanied by reduction in vagal activity that manifested as increased acetylcholinesterase levels, decreased acetylcholine levels, and heart rate variability, which eventually led to cardiac damage. Pyridostigmine enhanced vagal activity, restored gut microbiota homeostasis, decreased BCAA-producing microbe abundance, and improved the intestinal barrier to reduce circulating BCAA levels. Pyridostigmine also upregulated BCAT2 and PP2Cm and downregulated p-BCKDHA/BCKDHA and BCKDK to improve cardiac BCAA catabolism. Moreover, pyridostigmine alleviated abnormal mitochondrial structure; increased ATP production; decreased reactive oxygen species and mitochondria-related apoptosis; and attenuated cardiac dysfunction, hypertrophy, and fibrosis in diabetic cardiomyopathy mice. In conclusion, the gut microbiota, BCAA catabolism, and vagal activity were impaired in diabetic cardiomyopathy mice but were improved by pyridostigmine. These results provide novel insights for the development of a therapeutic strategy for diabetes-induced cardiac damage that targets gut microbes and BCAA catabolism.

Metabolic Profiling in Human Fibroblasts Enables Subtype Clustering in Glycogen Storage Disease.

Glycogen storage disease subtypes I and III (GSD I and GSD III) are monogenic inherited disorders of metabolism that disrupt glycogen metabolism. Unavailability of glucose in GSD I and induction of gluconeogenesis in GSD III modify energy sources and possibly, mitochondrial function. Abnormal mitochondrial structure and function were described in mice with GSD Ia, yet significantly less research is available in human cells and ketotic forms of the disease. We hypothesized that impaired glycogen storage results in distinct metabolic phenotypes in the extra- and intracellular compartments that may contribute to pathogenesis. Herein, we examined mitochondrial organization in live cells by spinning-disk confocal microscopy and profiled extra- and intracellular metabolites by targeted LC-MS/MS in cultured fibroblasts from healthy controls and from patients with GSD Ia, GSD Ib, and GSD III. Results from live imaging revealed that mitochondrial content and network morphology of GSD cells are comparable to that of healthy controls. Likewise, healthy controls and GSD cells exhibited comparable basal oxygen consumption rates. Targeted metabolomics followed by principal component analysis (PCA) and hierarchical clustering (HC) uncovered metabolically distinct poises of healthy controls and GSD subtypes. Assessment of individual metabolites recapitulated dysfunctional energy production (glycolysis, Krebs cycle, succinate), reduced creatinine export in GSD Ia and GSD III, and reduced antioxidant defense of the cysteine and glutathione systems. Our study serves as proof-of-concept that extra- and intracellular metabolite profiles distinguish glycogen storage disease subtypes from healthy controls. We posit that metabolite profiles provide hints to disease mechanisms as well as to nutritional and pharmacological elements that may optimize current treatment strategies.

Extended regorafenib treatment can be linked with mitochondrial damage leading to cardiotoxicity

Regorafenib (RGF) has a great success in the treatment of colorectal cancer, gastrointestinal stromal tumours and hepatocellular carcinoma by inhibiting angiogenic, stromal and oncogenic kinases. However, RGF can induce life-threatening cardiotoxicity including hypertension and cardiac ischemia/infarction. The molecular mechanism of the adverse effects has not been elucidated. Mitochondrial dysfunction is one of the major causes of cardiac diseases since cardiac cells highly need ATP for their contractility. Therefore, we aimed to investigate molecular mechanisms of RGF-induced cardiac adverse effects using H9c2 cell model by focusing on mitochondria. Cells were treated with 0−20 μM RGF for 48 and 72 h. According to our results, RGF inhibited cell proliferation and decreased the ATP content of the cells depending on the exposure time and concentration. Loss of mitochondrial membrane potential was also observed at high dose. Mitochondrial fusion/fission genes and antioxidant SOD2 (superoxide dismutase) gene expression levels increased at high doses in both treatments. Mitochondrial DNA content decreased as exposure time and concentration increased. Also, protein expression levels of mitochondrial complex I and V have reduced and stress protein HSP70 level has increased following RGF treatment. Structural abnormalities in mitochondria was seen with transmission electron microscopy at the applied higher doses. Our findings suggest that RGF-induced cardiotoxicity may be associated with mitochondrial damage in cardiac cells.

Percutaneous transluminal renal angioplasty attenuates poststenotic kidney mitochondrial damage in pigs with renal artery stenosis and metabolic syndrome.

Percutaneous transluminal renal angioplasty (PTRA) has been used to treat renovascular disease (RVD), a chronic condition characterized by renal ischemia and metabolic abnormalities. Mitochondrial injury has been implicated as a central pathogenic mechanism in RVD, but whether it can be reversed by PTRA remains uncertain. We hypothesized that PTRA attenuates mitochondrial damage, renal injury, and dysfunction in pigs with coexisting renal artery stenosis (RAS) and metabolic syndrome (MetS). Four groups of pigs (n = 6 each) were studied after 16 weeks of diet-induced MetS and RAS (MetS + RAS), MetS + RAS treated 4 weeks earlier with PTRA, and Lean and MetS Sham controls. Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector computed tomography, and renal tubular mitochondrial structure and function and renal injury ex vivo. PTRA successfully restored renal artery patency, but mean arterial pressure remained unchanged. Stenotic kidney RBF and GFR, which fell in MetS + RAS compared to MetS, rose after PTRA. PTRA attenuated MetS + RAS-induced mitochondrial structural abnormalities in tubular cells and peritubular capillary endothelial cells, decreased mitochondrial H2 02 production, and increased renal cytochrome-c oxidase-IV activity and ATP production. PTRA also improved cortical microvascular and peritubular capillary density and ameliorated tubular injury and tubulointerstitial fibrosis in the poststenotic kidney. Importantly, renal mitochondrial damage correlated with poststenotic injury and dysfunction. Renal revascularization attenuated mitochondrial injury and improved renal hemodynamics and function in swine poststenotic kidneys. This study suggests a novel mechanism by which PTRA might be relatively effective in ameliorating mitochondrial damage and improving renal function in coexisting MetS and RAS.

Peripheral Blood Cell Mitochondrial Dysfunction in Myelodysplastic Syndrome Can Be Improved by a Combination of Coenzyme Q10 and Carnitine.

Structural mitochondrial abnormalities and genetic aberrations in mitochondrial proteins have been known in Myelodysplastic syndrome (MDS), yet there is currently little data regarding MDS's metabolic properties and energy production cells. In the current study, we used state-of-the-art methods to assess OXPHOS in peripheral blood cells obtained from MDS patients and healthy controls. We then assessed the effect of food supplements-Coenzyme Q10 and carnitine on mitochondrial function and hematological response. We show here for the first time that there is a significant impairment of mitochondrial respiration in peripheral blood cells in low-risk MDS, which can be improved with food supplements. We also show that these supplements may improve the cytopenia and quality of life.

Maternal nicotine exposure during pregnancy and lactation induces brown adipose tissue whitening in female offspring

Maternal nicotine exposure during pregnancy and lactation is associated with obesity in female offspring. Brown adipose tissue (BAT) is related to energy metabolism and obesity. In this study, we explored the mechanism of maternal nicotine exposure on BAT “whitening” in female offspring. Pregnant rats were randomly assigned to nicotine (1.0 mg/kg twice per day, subcutaneous administration) or control groups. The weight, structure, and microvascular density of interscapular BAT (iBAT) and the expression of PGC-1αUCP1 signals, mitochondrial biogenesis-related genes and angiogenesis-related genes were tested in 4- and 26-week-aged female offspring. In vitro, C3H10T1/2 cells were induced to differentiate into mature brown adipocytes, and 0–50 μM nicotine was treated on cells during the differentiation process. Nicotine-exposed females had higher iBAT weight, white-like adipocytes and abnormal mitochondrial structure in iBAT at 26 weeks rather than 4 weeks. The PGC-1αUCP1 signals and brown-like genes were down-regulated at 26 weeks, but the microvascular density and the expression of pro-angiogenic factors reduced more at 4 weeks in the nicotine group. In vitro, 50 μM nicotine significantly decreased the expression of PGC-1αUCP1 signals and angiogenesis-related genes. In conclusion, maternal nicotine exposure during pregnancy and lactation led to the “whitening” of BAT in adult female offspring: nicotine decreased BAT angiogenesis in the early development stage, and then, the impairment of blood vessels programed for the reduction of BAT phenotype through down-regulating the PGC-1αUCP1 signals in adulthood. This impairment of BAT may be a potential mechanism of nicotine-induced obesity in female offspring.

Mitochondrial dysfunction caused by novel ATAD3A mutations

Mitochondrial respiratory chain integrity depends on a number of proteins encoded by nuclear and mitochondrial genomes. Mutations of such factors can result in isolated or combined respiratory chain deficits, some of which can induce abnormal morphology of the mitochondrial network or accumulation of intermediary metabolites. Consequently, affected patients are clinically heterogeneous, presenting with central nervous system, muscular, or neurodegenerative disorders. ATAD3A is a nuclear-encoded ATPase protein of the AAA+ family and has been localized to the inner mitochondrial membrane. Recently reported mutations or large deletions in the ATDA3A gene in patients have been shown to induce altered mitochondrial structure and function and abnormal cholesterol metabolism in a recessive or dominant manner. Here, we report two siblings presenting axonal sensory-motor neuropathy associated with neonatal cataract. Genetic analyses identified two novel mutations in ATAD3A; a point mutation and an intronic 15bp deletion affecting splicing and leading to exon skipping. Biochemical analysis in patient cells and tissues showed abnormal function of the mitochondrial respiratory chain in muscle and abnormal mitochondrial cristae structure. These new cases underline the large spectrum of biochemical and clinical presentations of ATAD3A deficiency and the different modes of inheritance, making it an atypical mitochondrial disorder.

Frameshift mutation of Timm8a1 gene in mouse leads to an abnormal mitochondrial structure in the brain, correlating with hearing and memory impairment

BackgroundDeafness-dystonia-optic neuronopathy (DDON) syndrome is a progressive X-linked recessive disorder characterised by deafness, dystonia, ataxia and reduced visual acuity. The causative gene deafness/dystonia protein 1 (DDP1)/translocase of the inner membrane...

Age-specific effects of P2X7 receptors on olfactory function in mice.

This study aimed to explore the age-specific effects of P2X7 receptor (P2X7R) knockout on olfactory function in mice. In this study, we analyzed olfactory functions of 2-month-old, 10-month-old and 18-month-old female P2X7R KO mice and age-matched female C57BL/6 wildtype mice (WT mice) by buried food seeking test and olfactory avoidance test. The structure of mitochondria and synapses in olfactory bulb were observed by electron microscopy. The content of interleukin-1 (IL-1β) in olfactory bulb and transforming growth factor beta 1 (TGF-β1) in olfactory epithelium were analyzed by ELISA. The results indicated that middle and old-aged P2X7R KO mice showed better olfactory function than middle and old-aged WT mice. Mitochondrial structures were complete and more spine synapses were observed in middle and old-aged P2X7R KO mice. Compared with middle and old-aged WT mice, IL-1β content in olfactory bulb was decreased in middle and old-aged P2X7R KO mice, and there was no significant difference in TGF-β1 content in olfactory epithelium. However, worse olfactory function was observed in young-aged P2X7R KO mice compared with young-aged WT mice. Abnormal mitochondrial structure and less synapses in olfactory bulb were observed. TGF-β1 content in olfactory epithelium was significantly higher in P2X7R KO mice compared with young-aged WT mice. There was no significant difference in IL-1β content in olfactory bulb of young-aged mice. In conclusion, P2X7R knockout can improve the olfactory function of middle and old-aged mice, while it may cause damage to young-aged mice, suggesting that P2X7R plays age-specific role on olfactory functions in mice.

Novel ATAD3A recessive mutation associated to fatal cerebellar hypoplasia with multiorgan involvement and mitochondrial structural abnormalities

Lethal neonatal encephalopathies are heterogeneous congenital disorders that can be caused by mitochondrial dysfunction. Biallelic large deletions in the contiguous ATAD3B and ATAD3A genes, encoding mitochondrial inner membrane ATPases of unknown function, as well as compound heterozygous nonsense and missense mutations in the ATAD3A gene have been recently associated with fatal neonatal cerebellar hypoplasia. In this work, whole exome sequencing (WES) identified the novel homozygous variant c.1217 T > G in ATAD3A, predicting a p.(Leu406Arg) substitution, in four siblings from a consanguineous family presenting with fatal neonatal cerebellar hypoplasia, seizures, axial hypotonia, hypertrophic cardiomyopathy, hepatomegaly, congenital cataract, and dysmorphic facies. Biochemical phenotypes of the patients included hyperlactatemia and hypocholesterolemia. Healthy siblings and parents were heterozygous for this variant, which is predicted to introduce a polar chain within the catalytic domain of ATAD3A that shortens its beta-sheet structure, presumably affecting protein stability. Accordingly, patient's fibroblasts with the homozygous variant displayed a specific reduction in ATAD3A protein levels associated with profound ultrastructural alterations of mitochondrial cristae and morphology. Our findings exclude the causative role of ATAD3B on this severe phenotype, expand the phenotypical spectrum of ATAD3A pathogenic variants and emphasize the vital role of ATAD3A in mitochondrial biogenesis.

Protective effects of BACE1 inhibitory ligand molecules against amyloid beta-induced synaptic and mitochondrial toxicities in Alzheimer's disease.

Amyloid-β (Aβ) peptides are the major drivers of Alzheimer's disease (AD) pathogenesis, and are formed by successive cleavage of the amyloid precursor protein (APP) by the beta and gamma secretases. Mounting evidence suggests that Aβ and mitochondrial structural and functional abnormalities are critically involved in the loss of synapses and cognitive decline, in patients with AD. In AD brain, state the sequential proteolytic cleavage of APP by beta secretase 1 enzyme (BACE1) and γ-secretase leads to the production and release of Aβ40 and 42. BACE1 expression and activity increased in the brains of AD patients. Structurally, β-secretase has a very large binding site (1000Å) with fewer hydrophobic domains that makes a challenge to identify the specific targets/binding sites of BACE1. In the present study, we constructed a BACE1 pharmacophore with pepstatin and screened through molecular docking studies. We found one potential candidate (referred as ligand 1) that binds to the key catalytic residues of BACE1 and predicts to inhibit abnormal APP processing and reduce Aβ levels in AD neurons. Using biochemical, molecular, transmission electron microscopy, immunoblotting and immunofluorescence analyses, we studied the protective effects of ligand 1 against Aβ-induced synaptic and mitochondrial toxicities in mouse neuroblastoma (N2a) cells that express mutant APP. We found interaction between ligand 1 and BACE1 and this interaction decreased BACE1 activity, Aβ40 and 42 levels. We also found increased mitochondrial biogenesis, mitochondrial fusion and synaptic activity and reduced mitochondrial fission in ligand 1-treated mutant APP cells. Based on these results, we cautiously conclude that ligand 1 reduces Aβ-induced mitochondrial and synaptic toxicities, and maintains mitochondrial dynamics and neuronal function in AD.