Mitochondrial DNA-encoded Genes Research Articles

EZH2 epigenetic enzyme inhibition improves the lipid metabolic disturbances and preserves cardiac function in a mouse model of myocardial infarction

EZH2 is an epigenetic enzyme repressing a wide variety of gene expression by adding methyl groups on histone H3 lysine 27 residue. In myocardial infarction (MI), most of these targeted genes are related to metabolism. This study aims to assess the benefit of GSK-343 (EZH2 inhibitor) on cardiac function and lipid metabolism in heart failure with reduced ejection fraction (HFrEF) induced by MI. We hypothesize that EZH2 modulates fatty acid (FA) cardiac metabolism and its inhibition minimizes lipid metabolism disruptions and improves cardiac function. Female mice underwent MI by ligation of left anterior descending coronary artery and were treated daily with vehicle or GSK-343 (7 days). We evaluated cardiac function (echocardiography), cardiac gene expression profiling (RNA-seq, RT-qPCR) and the circulating lipidome was assessed (mass spectrometry-based untargeted lipidomics). MI induced a reduction of EF from 46% (sham) to 18% (MI) while GSK-343 prevents this dysfunction (EF∼38%). RNA-seq analysis revealed wide gene expression changes in MI, changes normalized with GSK-343 treatment. The latter changes include, among the 561 down-regulated genes (FC 0.5 and 2; P = 10-4), 16 mitochondrial DNA-encoded genes (e.g. mt-Nd1, Mt-Rnr1), 57 genes related to mitochondrial function (e.g. Ppargc1-alpha) and 15 to lipid metabolism (e.g. Ppar-alpha, Acadm). As expected, most of these metabolic gene expressions were validated using RT-qPCR and emphasized a rescue upon GSK-343 treatment. We observed a similar pattern for other metabolic genes such as Klf15, an Ezh2 putative direct target gene and a master metabolic gene regulator, Cpt2 encoding a FA transporter and Pnpla2 implicated in triglyceride (TG) metabolism. Because disruption in FA utilization affect the lipidome, we used an untargeted lipidomics approach to evaluate the global impact of MI ± GSK-343. In plasma, while MI enhanced 18 TG (1.24–2.43-fold; P < 0.05) and decreased 32 choline glycerophospholipids (PC; 0.55–0.81-fold, P < 0.05), GSK-343 normalized these perturbations. Finally, in MI, some of these lipids positively correlated with EF (e.g. PC40:6; R = 0.84, P = 0.004) or with cardiac hypertrophy (e.g. DG18:1_18:2; R = 0.81, P = 0.007) while GSK-343 treatment abolished most of these correlations. Our study suggests that inhibiting EZH2 is of therapeutic interest to normalize lipid metabolism perturbations and improve cardiac function in HFrEF induced by MI.

Identification of a weight loss-associated causal eQTL in MTIF3 and the effects of MTIF3 deficiency on human adipocyte function.

Genetic variation at the MTIF3 (Mitochondrial Translational Initiation Factor 3) locus has been robustly associated with obesity in humans, but the functional basis behind this association is not known. Here, we applied luciferase reporter assay to map potential functional variants in the haplotype block tagged by rs1885988 and used CRISPR-Cas9 to edit the potential functional variants to confirm the regulatory effects on MTIF3 expression. We further conducted functional studies on MTIF3-deficient differentiated human white adipocyte cell line (hWAs-iCas9), generated through inducible expression of CRISPR-Cas9 combined with delivery of synthetic MTIF3-targeting guide RNA. We demonstrate that rs67785913-centered DNA fragment (in LD with rs1885988, r2 > 0.8) enhances transcription in a luciferase reporter assay, and CRISPR-Cas9-edited rs67785913 CTCT cells show significantly higher MTIF3 expression than rs67785913 CT cells. Perturbed MTIF3 expression led to reduced mitochondrial respiration and endogenous fatty acid oxidation, as well as altered expression of mitochondrial DNA-encoded genes and proteins, and disturbed mitochondrial OXPHOS complex assembly. Furthermore, after glucose restriction, the MTIF3 knockout cells retained more triglycerides than control cells. This study demonstrates an adipocyte function-specific role of MTIF3, which originates in the maintenance of mitochondrial function, providing potential explanations for why MTIF3 genetic variation at rs67785913 is associated with body corpulence and response to weight loss interventions.

Mitochondrial ribosomal stress in lung diseases.

Mitochondria are involved in a variety of critical cellular functions, and their impairment drives cell injury. The mitochondrial ribosome (mitoribosome) is responsible for the protein synthesis of mitochondrial DNA-encoded genes. These proteins are involved in oxidative phosphorylation, respiration, and ATP production required in the cell. Mitoribosome components originate from both mitochondrial and nuclear genomes. Their dysfunction can be caused by impaired mitochondrial protein synthesis or mitoribosome misassembly, leading to a decline in mitochondrial translation. This decrease can trigger mitochondrial ribosomal stress and contribute to pulmonary cell injury, death, and diseases. This review focuses on the contribution of the impaired mitoribosome structural components and function to respiratory disease pathophysiology. We present recent findings in the fields of lung cancer, chronic obstructive pulmonary disease, interstitial lung disease, and asthma. We also include reports on the mitoribosome dysfunction in pulmonary hypertension, high-altitude pulmonary edema, and bacterial and viral infections. Studies of the mitoribosome alterations in respiratory diseases can lead to novel therapeutic targets.

STEM-21. INHIBITING ADENINE SYNTHESIS ATTENUATES GLIOBLASTOMA CELL STEMNESS AND TEMOZOLOMIDE RESISTANCE

Abstract Glioblastoma (GBM) is a lethal brain cancer that exhibits high levels of drug resistance, a feature partially imparted by tumor cell stemness. Recent work has shown that homozygous MTAP deletion, a frequent genetic alteration in GBM, promotes the stemness of GBM cells. Here, exploiting the MTAP loss-conferred deficiency in adenine salvage, we demonstrated that subtle levels of adenine blockade via treatment with Alanosine, an inhibitor of de novo adenine synthesis, attenuate the stemness of MTAP-null GBM cells. Transcriptomic profiling performed on Alanosine-treated GBM cells revealed a reduction of mitochondrial DNA-encoded gene expression. Furthermore, Seahorse XF analysis showed that Alanosine treatment led to a reduction in mitochondrial respiration and eliminated GBM cells’ spare respiratory capacity, an important metabolic measure of cell fitness that is representative of their ability to respond to oxidative stress. Importantly, long term adenine shortage via treatment with low doses of Alanosine resulted in similarly compromised mitochondria functionality and attenuated GBM cells’ stemness. In further supporting this adenine blockade – compromised mitochondria – reduced stemness cascade, treatment with a mitochondrial respiration inhibitor attenuated the stemness of GBM cells, suggesting the importance of mitochondrial function in maintaining GBM stemness. Finally, in agreement with the diminished stemness and compromised mitochondrial function, we showed that Alanosine sensitized GBM cells to temozolomide (TMZ) in both in vitro cultures and in an orthotopic GBM model. Collectively, these results identify critical roles of adenine supply in maintaining stemness and mitochondrial function in GBM cells, suggest a targeted method of abrogating stemness and chemoresistance in GBMs, and support targeting adenine synthesis as a complementary approach for treating the half of GBMs harboring MTAP deletions.

Bawei Chenxiang Wan Ameliorates Cardiac Hypertrophy by Activating AMPK/PPAR-α Signaling Pathway Improving Energy Metabolism.

Bawei Chenxiang Wan (BCW), a well-known traditional Chinese Tibetan medicine formula, is effective for the treatment of acute and chronic cardiovascular diseases. In the present study, we investigated the effect of BCW in cardiac hypertrophy and underlying mechanisms. The dose of 0.2, 0.4, and 0.8 g/kg BCW treated cardiac hypertrophy in SD rat model induced by isoprenaline (ISO). Our results showed that BCW (0.4 g/kg) could repress cardiac hypertrophy, indicated by macro morphology, heart weight to body weight ratio (HW/BW), left ventricle heart weight to body weight ratio (LVW/BW), hypertrophy markers, heart function, pathological structure, cross-sectional area (CSA) of myocardial cells, and the myocardial enzymes. Furthermore, we declared the mechanism of BCW anti-hypertrophy effect was associated with activating adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)/peroxisome proliferator–activated receptor-α (PPAR-α) signals, which regulate carnitine palmitoyltransferase1β (CPT-1β) and glucose transport-4 (GLUT-4) to ameliorate glycolipid metabolism. Moreover, BCW also elevated mitochondrial DNA-encoded genes of NADH dehydrogenase subunit 1(ND1), cytochrome b (Cytb), and mitochondrially encoded cytochrome coxidase I (mt-co1) expression, which was associated with mitochondria function and oxidative phosphorylation. Subsequently, knocking down AMPK by siRNA significantly can reverse the anti-hypertrophy effect of BCW indicated by hypertrophy markers and cell surface of cardiomyocytes. In conclusion, BCW prevents ISO-induced cardiomyocyte hypertrophy by activating AMPK/PPAR-α to alleviate the disturbance in energy metabolism. Therefore, BCW can be used as an alternative drug for the treatment of cardiac hypertrophy.

Application of Genome Sequencing from Blood to Diagnose Mitochondrial Diseases.

Mitochondrial diseases can be caused by pathogenic variants in nuclear or mitochondrial DNA-encoded genes that often lead to multisystemic symptoms and can have any mode of inheritance. Using a single test, Genome Sequencing (GS) can effectively identify variants in both genomes, but it has not yet been universally used as a first-line approach to diagnosing mitochondrial diseases due to related costs and challenges in data analysis. In this article, we report three patients with mitochondrial disease molecularly diagnosed through GS performed on DNA extracted from blood to demonstrate different diagnostic advantages of this technology, including the detection of a low-level heteroplasmic pathogenic variant, an intragenic nuclear DNA deletion, and a large mtDNA deletion. Current technical improvements and cost reductions are likely to lead to an expanded routine diagnostic usage of GS and of the complementary “Omic” technologies in mitochondrial diseases.

Exercise alters the mitochondrial proteostasis and induces the mitonuclear imbalance and UPRmt in the hypothalamus of mice

The maintenance of mitochondrial activity in hypothalamic neurons is determinant to the control of energy homeostasis in mammals. Disturbs in the mitochondrial proteostasis can trigger the mitonuclear imbalance and mitochondrial unfolded protein response (UPRmt) to guarantee the mitochondrial integrity and function. However, the role of mitonuclear imbalance and UPRmt in hypothalamic cells are unclear. Combining the transcriptomic analyses from BXD mice database and in vivo experiments, we demonstrated that physical training alters the mitochondrial proteostasis in the hypothalamus of C57BL/6J mice. This physical training elicited the mitonuclear protein imbalance, increasing the mtCO-1/Atp5a ratio, which was accompanied by high levels of UPRmt markers in the hypothalamus. Also, physical training increased the maximum mitochondrial respiratory capacity in the brain. Interestingly, the transcriptomic analysis across several strains of the isogenic BXD mice revealed that hypothalamic mitochondrial DNA-encoded genes were negatively correlated with body weight and several genes related to the orexigenic response. As expected, physical training reduced body weight and food intake. Interestingly, we found an abundance of mt-CO1, a mitochondrial DNA-encoded protein, in NPY-producing neurons in the lateral hypothalamus nucleus of exercised mice. Collectively, our data demonstrated that physical training altered the mitochondrial proteostasis and induced the mitonuclear protein imbalance and UPRmt in hypothalamic cells.

Duodenal mucosal mitochondrial gene expression is associated with delayed gastric emptying in diabetic gastroenteropathy.

Hindered by a limited understanding of the mechanisms responsible for diabetic gastroenteropathy (DGE), management is symptomatic. We investigated the duodenal mucosal expression of protein-coding genes and microRNAs (miRNA) in DGE and related them to clinical features. The diabetic phenotype, gastric emptying, mRNA, and miRNA expression and ultrastructure of duodenal mucosal biopsies were compared in 39 DGE patients and 21 controls. Among 3175 differentially expressed genes (FDR < 0.05), several mitochondrial DNA–encoded (mtDNA-encoded) genes (12 of 13 protein coding genes involved in oxidative phosphorylation [OXPHOS], both rRNAs and 9 of 22 transfer RNAs) were downregulated; conversely, nuclear DNA–encoded (nDNA-encoded) mitochondrial genes (OXPHOS) were upregulated in DGE. The promoters of differentially expressed genes were enriched in motifs for transcription factors (e.g., NRF1), which regulate mitochondrial biogenesis. Seventeen of 30 differentially expressed miRNAs targeted differentially expressed mitochondrial genes. Mitochondrial density was reduced and correlated with expression of 9 mtDNA OXPHOS genes. Uncovered by principal component (PC) analysis of 70 OXPHOS genes, PC1 was associated with neuropathy (P = 0.01) and delayed gastric emptying (P < 0.05). In DGE, mtDNA- and nDNA-encoded mitochondrial genes are reduced and increased — associated with reduced mitochondrial density, neuropathy, and delayed gastric emptying — and correlated with cognate miRNAs. These findings suggest that mitochondrial disturbances may contribute to delayed gastric emptying in DGE.

Activation of Hippo signaling pathway mediates mitochondria dysfunction and dilated cardiomyopathy in mice.

Rationale: Mitochondrial dysfunction facilitates heart failure development forming a therapeutic target, but the mechanism involved remains unclear. We studied whether the Hippo signaling pathway mediates mitochondrial abnormalities that results in onset of dilated cardiomyopathy (DCM).Methods: Mice with DCM due to overexpression of Hippo pathway kinase Mst1 were studied. DCM phenotype was evident in adult animals but contractile dysfunction was identified as an early sign of DCM at 3 weeks postnatal. Electron microscopy, multi-omics and biochemical assays were employed.Results: In 3-week and adult DCM mouse hearts, cardiomyocyte mitochondria exhibited overt structural abnormalities, smaller size and greater number. RNA sequencing revealed comprehensive suppression of nuclear-DNA (nDNA) encoded gene-sets involved in mitochondria turnover and all aspects of metabolism. Changes in cardiotranscriptome were confirmed by lower protein levels of multiple mitochondrial proteins in DCM heart of both ages. Mitochondrial DNA-encoded genes were also downregulated; due apparently to repression of nDNA-encoded transcriptional factors. Lipidomics identified remodeling in cardiolipin acyl-chains, increased acylcarnitine content but lower coenzyme Q10 level. Mitochondrial dysfunction was featured by lower ATP content and elevated levels of lactate, branched-chain amino acids and reactive oxidative species. Mechanistically, inhibitory YAP-phosphorylation was enhanced, which was associated with attenuated binding of transcription factor TEAD1. Numerous suppressed mitochondrial genes were identified as YAP-targets.Conclusion: Hippo signaling activation mediates mitochondrial damage by repressing mitochondrial genes, which causally promotes the development of DCM. The Hippo pathway therefore represents a therapeutic target against mitochondrial dysfunction in cardiomyopathy.

The Genetic Evidence of Burn-Induced Cardiac Mitochondrial Metabolism Dysfunction.

Burn-induced cardiac dysfunction is thought to involve mitochondrial dysfunction, although the mechanisms responsible are unclear. In this study, we used our established model of in vivo burn injury to understand the genetic evidence of burn-induced mitochondrial confusion dysfunction by describing cardiac mitochondrial metabolism-related gene expression after burn. Cardiac tissue was collected at 24 hours after burn injury. An O2K respirometer system was utilized to measure the cardiac mitochondrial function. Oxidative phosphorylation complex activities were determined using enzyme activity assays. RT Profiler PCR array was used to identify the differential regulation of genes involved in mitochondrial biogenesis and metabolism. The quantitative qPCR and Western blotting were applied to validate the differentially expressed genes. Burn-induced cardiac mitochondrial dysfunction was supported by the finding of decreased state 3 respiration, decreased mitochondrial electron transport chain activity in complex I, III, IV, and V, and decreased mitochondrial DNA-encoded gene expression as well as decreased levels of the corresponding proteins after burn injury. Eighty-four mitochondrial metabolism-related gene profiles were measured. The mitochondrial gene profile showed that 29 genes related to mitochondrial energy and metabolism was differentially expressed. Of these 29 genes, 16 were more than 2-fold upregulated and 13 were more than 2-fold downregulated. All genes were validated using qPCR and partial genes were correlated with their protein levels. This study provides preliminary evidence that a large percentage of mitochondrial metabolism-related genes in cardiomyocytes were significantly affected by burn injury.

Mitochondrial gene signature in the prefrontal cortex for differential susceptibility to chronic stress

Mitochondrial dysfunction was highlighted as a crucial vulnerability factor for the development of depression. However, systemic studies assessing stress-induced changes in mitochondria-associated genes in brain regions relevant to depression symptomatology remain scarce. Here, we performed a genome-wide transcriptomic study to examine mitochondrial gene expression in the prefrontal cortex (PFC) and nucleus accumbens (NAc) of mice exposed to multimodal chronic restraint stress. We identified mitochondria-associated gene pathways as most prominently affected in the PFC and with lesser significance in the NAc. A more detailed mitochondrial gene expression analysis revealed that in particular mitochondrial DNA-encoded subunits of the oxidative phosphorylation complexes were altered in the PFC. The comparison of our data with a reanalyzed transcriptome data set of chronic variable stress mice and major depression disorder subjects showed that the changes in mitochondrial DNA-encoded genes are a feature generalizing to other chronic stress-protocols as well and might have translational relevance. Finally, we provide evidence for changes in mitochondrial outputs in the PFC following chronic stress that are indicative of mitochondrial dysfunction. Collectively, our work reinforces the idea that changes in mitochondrial gene expression are key players in the prefrontal adaptations observed in individuals with high behavioral susceptibility and resilience to chronic stress.

Heat exposure impairs porcine oocyte quality with suppressed actin expression in cumulus cells and disrupted F-actin formation in transzonal projections

BackgroundTranszonal projections (TZPs) constitute a structural basis for the communication between the oocyte and its surrounding cumulus cells (CCs), which play critical roles in promoting the oocyte maturation. Previously we found that heat stress (HS) causes loss of TZPs in porcine cumulus-oocyte complexes (COCs) with decreased density of filamentous actin (F-actin). However, the time-course responses of F-actin and its monomeric actins (β-actin and γ-actin) during the in vitro maturation of oocytes remain unclear.ResultsIn this study, excised porcine ovaries were exposed to HS at 41.5 °C for 1 h before COCs were isolated and matured in vitro for 44 h. HS significantly reduced oocyte quality, characterized by impaired cumulus expansion, delayed meiotic resumption and lower survival rate and polar body extrusion rate, as well as decreased expression of mitochondrial DNA-encoded genes and elevated mitochondrial reactive oxygen species concentration. Expression of β-actin and γ-actin in CCs increased gradually with oocytes maturation, which was significantly reduced in HS group, especially at 24 h and/or 44 h of in vitro maturation. By contrast, the number of TZPs and the fluorescence intensity of F-actin in zona pellucida decreased gradually during oocytes maturation, which were significantly reduced by HS at 24 h of in vitro maturation. Moreover, colocalization analyses revealed both β-actin and γ-actin contribute to the F-actin formation in porcine TZPs, and the colocalization of F-actin with GJ protein connexin 45 was significantly reduced in heat-exposed COCs.ConclusionsThe results indicate that the suppression of actin expressions in CCs, which may lead to the F-actin unstabilization in TZPs, will subsequently contribute to the compromised quality of oocytes under HS.

Relaxed sequence constraints favor mutational freedom in idiosyncratic metazoan mitochondrial tRNAs

Metazoan complexity and life-style depend on the bioenergetic potential of mitochondria. However, higher aerobic activity and genetic drift impose strong mutation pressure and risk of irreversible fitness decline in mitochondrial (mt)DNA-encoded genes. Bilaterian mitochondria-encoded tRNA genes, key players in mitochondrial activity, have accumulated mutations at significantly higher rates than their cytoplasmic counterparts, resulting in foreshortened and fragile structures. Here we show that fragility of mt tRNAs coincided with the evolution of bilaterian animals. We demonstrate that bilaterians compensated for this reduced structural complexity in mt tRNAs by sequence-independent induced-fit adaption to the cognate mitochondrial aminoacyl-tRNA synthetase (aaRS). Structural readout by nuclear-encoded aaRS partners relaxed the sequence constraints on mt tRNAs and facilitated accommodation of functionally disruptive mutational insults by cis-acting epistatic compensations. Our results thus suggest that mutational freedom in mt tRNA genes is an adaptation to increased mutation pressure that was associated with the evolution of animal complexity.

A Brief History of Mitochondrial Pathologies.

The history of “mitochondrial pathologies”, namely genetic pathologies affecting mitochondrial metabolism because of mutations in nuclear DNA-encoded genes for proteins active inside mitochondria or mutations in mitochondrial DNA-encoded genes, began in 1988. In that year, two different groups of researchers discovered, respectively, large-scale single deletions of mitochondrial DNA (mtDNA) in muscle biopsies from patients with “mitochondrial myopathies” and a point mutation in the mtDNA gene for subunit 4 of NADH dehydrogenase (MTND4), associated with maternally inherited Leber’s hereditary optic neuropathy (LHON). Henceforth, a novel conceptual “mitochondrial genetics”, separate from mendelian genetics, arose, based on three features of mtDNA: (1) polyplasmy; (2) maternal inheritance; and (3) mitotic segregation. Diagnosis of mtDNA-related diseases became possible through genetic analysis and experimental approaches involving histochemical staining of muscle or brain sections, single-fiber polymerase chain reaction (PCR) of mtDNA, and the creation of patient-derived “cybrid” (cytoplasmic hybrid) immortal fibroblast cell lines. The availability of the above-mentioned techniques along with the novel sensitivity of clinicians to such disorders led to the characterization of a constantly growing number of pathologies. Here is traced a brief historical perspective on the discovery of autonomous pathogenic mtDNA mutations and on the related mendelian pathology altering mtDNA integrity.

Heat stress induces distinct responses in porcine cumulus cells and oocytes associated with disrupted gap junction and trans-zonal projection colocalization.

Cumulus cells (CCs), the granulosa cells surrounding the oocytes, play critical roles in oocytes maturation through intercellular communication by extending trans-zonal projections (TZPs) to contact oocytes via gap junctions (GJs). The adverse effect of heat stress (HS) on oocyte maturation has been well documented, whereas the HS responses of CCs and the oocytes in association with GJ/TZP colocalization remain unclear. In this study, porcine cumulus-oocyte complexes (COCs) were subjected to HS at 41.5°C for 24 hr during in vitro maturation. Cumulus expansion was impaired and oocyte quality was reduced with lower survival rate, polar body extrusion rate, and early embryo developmental potentials. CCs and oocytes isolated from COCs demonstrated distinct responses to HS. The messenger RNA abundance of heat shock protein-related genes and mitochondrial DNA-encoded genes, together with ATP content, were significantly increased in CCs, yet decreased in oocytes, despite activation of caspase 3 detected in both CCs and oocytes. Similar changes were observed when denuded oocytes and isolated CCs subjected to HS separately, except mitochondria reactive oxygen species (mROS). In heat-stressed COCs, mROS was significantly increased only in oocytes. However, when isolated CCs and denuded oocytes were heat-stressed separately, mROS was significantly increased only in CCs. Moreover, F-actin, a TZP marker, and its colocalization with a GJ protein connexin-45, were significantly reduced in heat-exposed COCs. These results indicate that HS induces distinct responses in porcine CCs and oocytes in association with disrupted GJ and TZP colocalization.

Exercise-induced mitochondrial biogenesis coincides with the expression of mitochondrial translation factors in murine skeletal muscle.

The process of mitochondrial translation, in which mitochondrial (mt)DNA‐encoded genes are translated into proteins, is crucial for mitochondrial function and biogenesis. In each phase, a series of mitochondrial translation factors is required for the synthesis of mtDNA‐encoded mitochondrial proteins. Two mitochondrial initiation factors (mtIF2 and mtIF3), three mitochondrial elongation factors (mtEFTu, mtEFTs, and mtEFG1), one mitochondrial release factor (mtRF1L), and two mitochondrial recycling factors (mtRRF1 and mtRRF2) are mitochondrial translation factors that coordinate each translational phase. Exercise increases both nuclear DNA‐ and mtDNA‐encoded mitochondrial proteins, resulting in mitochondrial biogenesis in skeletal muscles. Therefore, mitochondrial translation factors are likely regulated by exercise; however, it is unclear whether exercise affects mitochondrial translation factors in the skeletal muscles. We investigated whether exercise training comprehensively increases this series of mitochondrial translation factors, as well as mtDNA‐encoded proteins, in the skeletal muscle. Mice were randomly assigned to either the sedentary or exercise group and housed in standard cages with or without a running wheel for 1 and 8 weeks. The expression levels of mitochondrial translation factors in the plantaris and soleus muscles were then measured. Exercise training concomitantly upregulated mitochondrial translation factors and mitochondrial proteins in the plantaris muscle. However, in the soleus muscle, these comprehensive upregulations were not detected. These results indicate that exercise‐induced mitochondrial biogenesis coincides with the upregulation of mitochondrial translation factors.

Butyrate stimulates adipose lipolysis and mitochondrial oxidative phosphorylation through histone hyperacetylation-associated β3 -adrenergic receptor activation in high-fat diet-induced obese mice.

What is the central question of this study? Butyrate can prevent diet-induced obesity through increasing energy expenditure. However, it is unclear whether β3 -adrenergic receptors (ARβ3) mediate butyrate-induced adipose lipolysis. What is the main finding and its importance? Short-term oral administration of sodium butyrate is effective in alleviating diet-induced obesity through activation of ARβ3-mediated lipolysis in white adipose tissue. Butyrate can prevent diet-induced obesity through increasing energy expenditure. However, it is unclear whether ARβ3 mediates butyrate-induced adipose lipolysis. In this study, weaned mice were were fed control (Con) or high-fat (HF) diet for 8weeks to establish obesity. High-fat diet-induced obese mice maintained on the HF diet were divided into two subgroups; the HFB group was gavaged with 80mg sodium butyrate (SB) per mouse every other day for 10days, whereas the HF group received vehicle. Chromatin immunoprecipitation assay was performed to determine the status of histone H3 lysine 9 acetylation (H3K9Ac) on the promoter of the β3 -adrenergic receptor (ARβ3) gene in epididymal white adipose tissue. It was shown that five gavage doses of SB significantly alleviated HF diet-induced obesity and restored plasma leptin concentration to the control level. Protein contents of ARβ3 and PKA, as well as ATGL and p-HSL (Ser563), were significantly upregulated in the HFB group compared with the HF group. Mitochondrial oxidative phosphorylation was enhanced by SB treatment. Sodium butyrate significantly increased the expression of four out of 13 mitochondrial DNA-encoded genes and significantly upregulated the protein contents of peroxisome proliferator-activated receptor-γ coactivator 1α and COX4. Moreover, SB administration enhanced the expression of ARβ3 and its downstream signalling. The Gprotein-coupled receptor43 and p-CREB (Ser133) were significantly stimulated by SB. In addition, an active transcription marker, H3K9Ac, was significantly enriched on the promoter of the ARβ3 gene. Our results indicate that short-term oral administration of SB is effective in alleviating diet-induced obesity through activation of the ARβ3-mediated lipolysis in the epididymal white adipose tissue.

Supplementing the maternal diet of rats with butyrate enhances mitochondrial biogenesis in the skeletal muscles of weaned offspring.

The present study aimed to investigate the effects of maternal dietary butyrate supplementation on energy metabolism and mitochondrial biogenesis in offspring skeletal muscle and the possible mediating mechanisms. Virgin female rats were randomly assigned to either control or butyrate diets (1 % butyrate sodium) throughout gestation and lactation. At the end of lactation (21 d), the offspring were killed by exsanguination from the abdominal aorta under anaesthesia. The results showed that maternal butyrate supplementation throughout gestation and lactation did not affect offspring body weight. However, the protein expressions of G-protein-coupled receptors (GPR) 43 and 41 were significantly enhanced in offspring skeletal muscle of the maternal butyrate-supplemented group. The ATP content, most of mitochondrial DNA-encoded gene expressions, the cytochrome c oxidase subunit 1 and 4 protein contents and the mitochondrial DNA copy number were significantly higher in the butyrate group than in the control group. Meanwhile, the protein expressions of type 1 myosin heavy chain, mitochondrial transcription factor A, PPAR-coactivator-1α (PGC-1α) and uncoupling protein 3 were significantly increased in the gastrocnemius muscle of the treatment group compared with the control group. These results indicate for the first time that maternal butyrate supplementation during the gestation and lactation periods influenced energy metabolism and mitochondrial biogenesis through the GPR and PGC-1α pathways in offspring skeletal muscle at weaning.

Receptor-interacting Protein 140 represses Sirtuin 3 to facilitate hypertrophy, mitochondrial dysfunction and energy metabolic dysfunction in cardiomyocytes.

The transcriptional cofactor receptor-interacting protein 140 (RIP140) is known as a deleterious regulator of cardiac mitochondrial function and energy metabolic homeostasis. This study revealed that RIP140 repressed Sirtuin 3 (SIRT3), a mitochondrial deacetylase that plays an important role in regulating cardiac function. RIP140 was overexpressed by adenovirus infection or was knocked down by RNA interference in neonatal rat cardiomyocytes. RIP140 overexpression repressed, while RIP140 silencing elevated the expression and activity of SIRT3. Ad-RIP140 enhanced the expressions of the cardiac hypertrophic markers and increased cardiomyocyte surface area, whereas SIRT3 overexpression prevented the effect of Ad-RIP140. Additionally, SIRT3 overexpression reversed Ad-RIP140-induced mitochondrial dysfunction and energy metabolic dysfunction, such as increase in oxidative stress, decrease in mitochondrial membrane potential and ATP production, as well as downregulation of mitochondrial DNA-encoded genes and genes related to mitochondrial genome replication and transcription, mitochondrial oxidative phosphorylation and fatty acid oxidation. In contrast, SIRT3 silencing exacerbated RIP140-induced cardiomyocyte hypertrophy and mitochondrial dysfunction. Furthermore, the repression of SIRT3 by RIP140 was dependent on estrogen-related receptor-α (ERRα). The involvement of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) was ruled out of SIRT3 suppression by RIP140. RIP140 and PGC-1α might act as functional antagonists on the regulation of SIRT3. This study indicates that suppression of SIRT3 by RIP140 facilitates the development of cardiomyocyte hypertrophy, mitochondrial dysfunction and energy metabolic dysfunction. Strategies targeting inhibition of RIP140 and upregulation of SIRT3 might improve cardiac energy metabolism and suggest therapeutic potential for heart diseases.

Alpha-Lipoic Acid Alleviates Acute Inflammation and Promotes Lipid Mobilization During the Inflammatory Response in White Adipose Tissue of Mice.

Recently, white adipose tissue has been shown to exhibit immunological activity, and may play an important role in host defense and protection against bacterial infection. Αlpha-lipoic acid (α-LA) has been demonstrated to function as an anti-inflammatory and anti-oxidant agent. However, its influence on the inflammatory response and metabolic changes in white adipose tissue remains unknown. We used male C57BL/6 mice as models to study the effect of α-LA on the inflammatory response and metabolic changes in white adipose tissue after stimulation with lipopolysaccharide (LPS). The non-esterified fatty acid content was measured by an automatic biochemical analyzer. The expression of inflammation-, lipid- and energy metabolism-related genes and proteins was determined by quantitative real-time polymerase chain reaction and western blotting. The results indicated that α-LA significantly decreased the epididymis fat weight index and the non-esterified fatty acid content in plasma compared with the control group. LPS significantly increased the expression of inflammation genes and α-LA reduced their expression. The LPS-induced expression of nuclear factor-κB protein was decreased by α-LA. Regarding lipid metabolism, α-LA significantly counteracted the inhibitory effects of LPS on the expression of hormone-sensitive lipase gene and protein. α-LA evidently increased the gene expression of fatty acid transport protein 1 and cluster of differentiation 36. Regarding energy metabolism, α-LA significantly increased the expression of most of mitochondrial DNA-encoded genes compared with the control and LPS group. Accordingly, α-LA can alleviate acute inflammatory response and this action may be related with the promotion of lipid mobilization in white adipose tissue.