Biogenesis Signaling Research Articles

SGLT2 inhibitor downregulated oxidative stress via activating AMPK pathway for cardiorenal (CR) protection in CR syndrome rodent fed with high protein diet

This study tested the hypothesis that empagliflozin (EMPA) therapy effectively protected renal and heart functions via downregulating reactive oxygen species (ROS) and activating AMPK signaling in cardiorenal syndrome (CRS) (induced by doxorubicin-5/6 nephrectomy) rats. In vitro result showed that underwent p-Cresol treatment, the H9C2/NRK-52E cell viabilities, were significantly suppressed, whereas cellular levels of ROS and early/late apoptosis of these cells were significantly increased that were significantly reversed by EMPA treatment (all p < 0.001). The protein levels of the cell-stress/oxidative signaling (p-PI3K/p-Akt/p-mTOR/NOXs/p-DRP1) were significantly activated, whereas the mitochondrial biogenesis signaling (p-AMPK/SIRT-1/TFAM/PGC-1α) was significantly repressed in these two cell lines treated by p-Cresol and all of these were significantly reversed by EMPA treatment (all p < 0.001). Male-adult-SD rats were categorized into groups 1 [sham-operated control (SC)]/2 [SC + high protein diet (HPD) since day 1 after CKD induction]/3 (CRS + HPD)/4 (CRS + HPD+EMPA/20 mg/kg/day) and heart/kidney were harvested by day 60. By day 63, the renal function parameters (creatinine/BUN/proteinuria)/renal artery restrictive index/cellular levels of ROS/inflammation were significantly increased in group 3 than in groups 1/2, whereas heart function exhibited an opposite pattern of ROS among the groups, and all of these parameters were significantly reversed by EMPA treatment (all p < 0.0001). The protein levels of inflammation/ oxidative-stress/cell-stress signalings were highest in group 2, lowest in group 1 and significantly lower in group 4 than in group 2, whereas the AMPK-mitochondrial biogenesis displayed an opposite manner of oxidative-stress among the groups (all p < 0.0001). EMPA treatment effectively protected the heart/kidney against CRS damage via suppressing ROS signaling and upregulating AMPK-mediated mitochondrial biogenesis.

VEGFR2 blockade inhibits glioblastoma cell proliferation by enhancing mitochondrial biogenesis

BackgroundGlioblastoma is an aggressive brain tumor linked to significant angiogenesis and poor prognosis. Anti-angiogenic therapies with vascular endothelial growth factor receptor 2 (VEGFR2) inhibition have been investigated as an alternative glioblastoma treatment. However, little is known about the effect of VEGFR2 blockade on glioblastoma cells per se.MethodsVEGFR2 expression data in glioma patients were retrieved from the public database TCGA. VEGFR2 intervention was implemented by using its selective inhibitor Ki8751 or shRNA. Mitochondrial biogenesis of glioblastoma cells was assessed by immunofluorescence imaging, mass spectrometry, and western blot analysis.ResultsVEGFR2 expression was higher in glioma patients with higher malignancy (grade III and IV). VEGFR2 inhibition hampered glioblastoma cell proliferation and induced cell apoptosis. Mass spectrometry and immunofluorescence imaging showed that the anti-glioblastoma effects of VEGFR2 blockade involved mitochondrial biogenesis, as evidenced by the increases of mitochondrial protein expression, mitochondria mass, mitochondrial oxidative phosphorylation (OXPHOS), and reactive oxygen species (ROS) production, all of which play important roles in tumor cell apoptosis, growth inhibition, cell cycle arrest and cell senescence. Furthermore, VEGFR2 inhibition exaggerated mitochondrial biogenesis by decreased phosphorylation of AKT and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), which mobilized PGC1α into the nucleus, increased mitochondrial transcription factor A (TFAM) expression, and subsequently enhanced mitochondrial biogenesis.ConclusionsVEGFR2 blockade inhibits glioblastoma progression via AKT-PGC1α-TFAM-mitochondria biogenesis signaling cascade, suggesting that VEGFR2 intervention might bring additive therapeutic values to anti-glioblastoma therapy.

Effects of Exercise Intensity during the Detraining Period on Changed Muscle Hypertrophy- and Mitochondrial Biogenesis-Related Proteins after High-Intensity Interval Training

This study investigated whether different exercise intensities during detraining could maintain muscle hypertrophy and mitochondrial biogenesis signaling pathways activated high-intensity interval training (HIIT) in the flexor pollicis longus and soleus muscles of Sprague-Dawley rats. Fiver groups were studied: non-exercise ([NEG], n=6), HIIT only ([CTG], n=6), resting control ([CD], n=6), low-intensity exercise (LID, n=6), moderate-intensity exercise ([MID], n=6). The HIIT program consisted of 30-minute sessions of 24 m/min for eight weeks. During detraining (two weeks), LID and MID groups exercise three times per week at 8 m/min and 16 m/min, respectively. Muscle hypertrophy and mitochondrial biogenesis-related protein expression in the flexor pollicis longus and soleus muscles were analyzed using Western blotting. Compared to NEG, PI3K was higher in the CTG and LID in the flexor pollicis longus, while Akt and p-mTOR signaling pathways were significantly activated in MID and CTG. In the soleus muscle, p-AMPK expression was higher in CD and MID than in NEG, and FNDC5 was upregulated in LID compared to CTG and CD. These findings suggest that moderate-intensity exercise during detraining may help maintain HIIT-induced muscle hypertrophy signaling, while low-intensity exercise may contribute to sustaining HIIT-activated aerobic metabolism in skeletal muscle.

Effects and mechanism of perinatal nonylphenol exposure on cardiac function and myocardial mitochondria in neonatal rats

BackgroundNonylphenol (NP) is a common environmental endocrine disruptor that is associated with the development of cardiovascular disease. However, the toxic effect of NP on mitochondria in the heart of offspring to exposed individuals remains exclusive. ObjectiveTo investigate whether perinatal NP exposure causes mitochondrial damage in the hearts of offspring of exposed individuals and determine its mechanism of action through both animal and cell experiments. Methods and resultsFor the in vivo experiment, pregnant rats were randomly divided into four groups: the control group (corn oil, C), low dose group (2.5 mg/kg/day, L-NP group), medium dose group (50 mg/kg/day, M-NP group), and high dose group (100 mg/kg/day, H-NP group), with 12 rats in each group. The NP concentration in the hearts of offspring at PND21 and PND90 increased with the increase of the NP dose. Perinatal NP exposure induced a gradual increase in systolic blood pressure in offspring at PND90. In the H-NP group, there was a high degree of inflammatory cell infiltration, myofibril breaks, inconspicuous or absent nuclei, and pink collagen deposition. At PND90, the membrane integrity of mitochondria in the H-NP group was disrupted, the cristae disorder was aggravated, and there was internal lysis with vacuolation. Compared to the control group, the mitochondrial membrane potential of offspring at PND21 and PND90 was decreased in each of the NP exposure groups. NP exposure decreased the activity of mitochondrial respiratory enzyme complex I (CI) and increased the activity of mitochondrial respiratory enzyme complex IV (CIV) in the offspring. At PND21 and PND90, the mRNA and protein expression levels of cardiac mitochondrial PGC-1α, NRF-1, and TFAM decreased with increasing NP dose in a dose-dependent manner. In the in vitro experiment, H9C2 cells were divided into the following four groups: the blank group, RSV group (15 μg/ml), RSV + NP group (15 μg/ml RSV + 120 mmol/L NP), and NP group (120 mmol/L). With increasing NP concentration, the cell survival rate gradually decreased. Compared to the control, the membrane potential was significantly decreased in the NP group; the protein expression levels of SIRT1, PGC-1α, NRF-1, and TFAM in the NP group were significantly lower. ConclusionPerinatal NP exposure caused mitochondrial damage and dysfunction in the offspring of exposed individuals in a dose-dependent manner. This toxic effect may be related to NP-induced mitochondrial pathology in the offspring and the inhibition of both gene and protein expression involved in the PGC-1α/NRF-1/TFAM mitochondrial biogenesis signaling pathway following NP exposure.

Guilu Erxian Jiao enhances protein synthesis, glucose homeostasis, mitochondrial biogenesis and slow-twitch fibers in the skeletal muscle.

Guilu Erxian Jiao (GEJ) is a commonly used nutritional supplement due to its rich content of amino acids. It is also a traditional herbal medicine for improving degenerative joint. This study aimed to investigate the effect and mechanism of GEJ water extract (GEJ-WE) on skeletal muscle in C2C12 myotubes and C57BL/6J mice. Analysis of GEJ-WE were performed by high-performance liquid chromatography fingerprinting with chemical standards. Protein expression, mRNA level, glycogen content, mitochondria activity and ATP level were evaluated by western blots, real-time PCR, PAS staining, MTT and ATP bioluminescence assay, respectively. Skeletal muscle strength was evaluated by grip strength. Skeletal muscle volume, mass and fiber types were evaluated by micro computed tomography, histological analysis and immunofluorescence staining, respectively. Motor function was evaluated by rotarod performance and locomotor activity. In C2C12 myotubes, GEJ-WE significantly enhanced myogenic differentiation and myotube growth, protein synthesis signaling IGF-1/IGF-1R/IRS-1/Akt, Glut4 translocation, glycogen content, mitochondrial biogenesis signaling PGC-1α/NRF1/TFAM, mitochondrial activity and ATP production. However, IGF-1R antagonist AG1024 and PI3K inhibitor wortmannin reduced GEJ-WE-induced protein expression of MyHC, p-Akt, p-mTOR and p-GSK-3β, Glut4 translocation and glycogen content. In C57BL/6J mice, GEJ-WE not only upregulated protein synthesis and mitochondrial biogenesis signaling, but it also increased muscle volume, relative muscle weight, cross-sectional area of myofibers, glycogen content and transition of fast-to-slow type fibers of skeletal muscles. Moreover, GEJ-WE enhanced grip strength and motor activity of mice. In conclusion, the upregulation of protein synthesis, myogenic differentiation, glucose homeostasis, mitochondrial biogenesis and slow-twitch fibers contributes to the mechanisms of GEJ-WE on the enhancement of skeletal muscle mass and motor function.

Gestational Exercise Antagonises the Impact of Maternal High-Fat High-Sucrose Diet on Liver Mitochondrial Alterations and Quality Control Signalling in Male Offspring.

Maternal high-caloric nutrition and related gestational diabetes mellitus (GDM) are relevant modulators of the intrauterine environment, increasing the risk of liver metabolic alterations in mothers and offspring. In contrast, as a non-pharmacological approach against metabolic disorders, exercise is highly recommended in GDM treatment. We analysed whether gestational exercise (GE) protects mothers from diet-induced GDM metabolic consequences and mitigates liver mitochondrial deleterious alterations in their 6-week-old male offspring. Female Sprague Dawley rats were fed with control or high-fat high-sucrose (HFHS) diet and kept sedentary or submitted to GE. Male offspring were sedentary and fed with control diet. Sedentary HFHS mothers and their offspring showed impaired hepatic mitochondrial biogenesis and morphological evidence of mitochondrial remodelling. In contrast, GE-related beneficial effects were demonstrated by upregulation of mitochondrial biogenesis signalling markers and mitochondrial fusion proteins and downregulation of mitochondrial fission protein. Alterations in miR-34a, miR-130b, and miR-494, associated with epigenetic regulation of mitochondrial biogenesis, suggested that GE is a more critical modulator of intergenerational changes in miRs expression than the maternal diet. Our data showed that GE positively modulated the altered hepatic mitochondrial biogenesis and dynamics markers and quality control signalling associated with maternal HFHS-diet-related GDM in mothers and offspring.

Energetic and myocellular pathways in cardiac and skeletal muscle following anthracycline chemotherapy

Abstract Background Anthracycline-related cardiac dysfunction is a recognised consequence of cancer therapies. Here we assess resting cardiac and skeletal muscle energic status as an early mechanistic pathway of myocyte derangement and explore molecular targets of skeletal myocyte metabolism, protein synthesis/degradation and mitochondrial biogenesis signalling. Methods We conducted a prospective, mechanistic, observational, longitudinal study of chemotherapy-naive breast cancer patients undergoing anthracycline-based chemotherapy, compared to a healthy control group. 31P-Magnetic Resonance spectroscopy in cardiac and skeletal muscle (phosphocreatine/gamma adenosine triphosphate (PCr/yATP) and inorganic phosphate/phosphocreatine (Pi/PCr) ratios respectively), cardiac magnetic resonance (CMR) imaging inclusive of T1 and T2 mapping, echocardiography-derived global longitudinal strain function, serum NT-pro-BNP and skeletal muscle biopsies from the right vastus lateralis were assessed before and after 3 cycles of Flurouracil, Epirubicin and Cyclophosphamide followed by 3 cycles of Docetaxel. Statistical significance was set at p&amp;lt;0.05. Results Twenty-five female breast cancer patients (median age 53 years, range 32–74 years) receiving a mean epirubicin dose 307 mg/m2) and twenty-eight controls (median age 44 years, range 23–65) were recruited. All study assessments in breast cancer patients at pre-chemotherapy stage were comparable to the matched healthy controls. However, following chemotherapy, breast cancer patients demonstrated a small but significant reduction in cardiac function (global longitudinal strain −22.9±3.9 vs −19.1±3.3%, p=0.01 and CMR-derived ejection fraction 65±5 vs 62±4%, p=0.047), a mild increase in CMR-derived indexed left ventricular volumes (end diastolic 65±10 vs 74±11 ml/m2, p=0.014 and end systolic 23±5 vs 28±5 ml/m2, p=0.01) as well as an increase in left ventricular T1 and T2-mapping (1289±29 vs 1321±31 ms, p=0.004 and 50±4 vs 55±7 ms, p=0.027, respectively) and serum NT-Pro-BNP (49±25 vs 108±84 pg/m, p=0.008). After epirubicin, there was significant reduction in cardiac PCr/yATP ratio (2.0±0.7 vs 1.2±0.6, p=0.007) and a significant increase in skeletal muscle Pi/PCr ratio (0.13±0.04 vs 0.22±0.2, p=0.008) – Figure 1. Following chemotherapy, there was significant upregulation of skeletal myocyte protein synthesis (mammalian target of rapamycin, 0.44±0.4 vs 0.53±0.2, p&amp;lt;0.001) and degradation (Calcium/calmodulin dependent protein kinase II, 1.4±0.7 vs 2.7±1.1, p&amp;lt;0.001), metabolism (peroxisome proliferator-activated receptor gamma, 0.35±0.2 vs 0.60±0.1, p&amp;lt;0.001) and muscle mass regulator myostatin-2 (0.16±0.1 vs 0.24±0.1, p&amp;lt;0.001). Conclusion Contemporary doses of epirubicin for breast cancer result in significant reduction of cardiac and skeletal muscle high energy 31P-metabolism alongside skeletal myocellular alterations of protein synthesis and metabolic regulation pathways. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Tenovus ScotlandNHS Grampian Endowment fund

Gene Expression Changes Associated with Acute Mountain Sickness After Rapid Altitude Exposure at The South Pole

Many individuals travel to high altitude each year. Acclimatization to altitude occurs over the course of several days as the body adequately adapts to function in an environment with reduced partial pressure of oxygen. However, with a faster accent to attitude, comes an increased potential for maladaptations to occur, leading to the development of acute mountain sickness (AMS). Each year scientists and support workers are transported by plane from McMurdo Station in Antarctica (sea level) to the Amundsen‐Scott South Pole Station (2835m). This uniform and rapid deployment to altitude provides a unique opportunity to study the effects of hypobaric hypoxia on gene expression, which may help to illustrate the body’s ability to acclimatize to these environmental conditions.PurposeTo detect pathway specific gene expression changes associated with the development of AMS and help identify potential targets that may aid in the prediction of risk in the development of AMS symptoms due to rapid exposure to high altitude.MethodsVenous blood samples were collected from 53 (height 176.65±8.91cm, weight: 80.49±14.36kg) healthy subjects (38 (27 males; 11 females) that did not develop AMS and 15 (10 males; 5 females) that did develop AMS, as defined by the Lake Louis symptom questionnaire, collected at 2 different time points, with the first being at sea level and the second being after 48hr of altitude exposure). Microarray analysis was performed on the peripheral blood mononuclear cells (PBMCs) from the collected samples, and a logistic regression was performed to determine probe set association with AMS.ResultsThere was a total of 178 significant (p&lt;0.05) probe sets, with 156 of the probe sets being associated with AMS and 22 of the probe sets being associated with no AMS. The probe sets were entered into the Reactome Pathway Database (reactome.org). Pathways identified in association with AMS involved immune system pathways (interleukin signaling) and cellular responses to stimuli pathways (oxidative stress induced senescence signaling), and gene transcription pathways (mitochondrial biogenesis signaling, differentiation of hematopoietic stem cells). Interestingly, pathways identified in association with no development of AMS involved cell cycling pathways (mitotic signaling), chromatin organization pathways (chromatin modifying enzymes), metabolism pathways (utilization of ketone bodies) and the circadian clock pathway (circadian gene expression signaling).ConclusionThese findings indicate potential maladaptive responses within the immune system and mitochondrial function, may play a key role in why some individuals develop AMS symptoms. An individual’s ability to sufficiently utilize different metabolic fuel sources and adapt their circadian rhythm may also prevent the development of AMS symptoms.

RNAi-Mediated Knockdown of Calreticulin3a Impairs Pollen Tube Growth in Petunia.

Pollen tube growth depends on several complex processes, including exo/endocytosis, cell wall biogenesis, intracellular transport, and cell signaling. Our previous results provided evidence that calreticulin (CRT)—a prominent calcium (Ca2+)-buffering molecular chaperone in the endoplasmic reticulum (ER) lumen—is involved in pollen tube formation and function. We previously cloned and characterized the CRT gene belonging to the CRT1/2 subgroup from Petunia hybrida (PhCRT1/2), and found that post-transcriptional silencing of PhCRT1/2 expression strongly impaired pollen tube growth in vitro. Here, we report cloning of a new PhCRT3a homolog; we identified the full-length cDNA sequence and described its molecular characteristics and phylogenetic relationships to other plant CRT3 genes. Using an RNA interference (RNAi) strategy, we found that knockdown of PhCRT3a gene expression caused numerous defects in the morphology and ultrastructure of cultivated pollen tubes, including disorganization of the actin cytoskeleton and loss of cytoplasmic zonation. Elongation of siPhCRT3a pollen tubes was disrupted, and some of them ruptured. Our present data provide the first evidence that PhCRT3a expression is required for normal pollen tube growth. Thus, we discuss relationships between diverse CRT isoforms in several interdependent processes driving the apical growth of the pollen tube, including actomyosin-dependent cytoplasmic streaming, organelle positioning, vesicle trafficking, and cell wall biogenesis.

Hyperbaric Oxygen Therapy Improves Parkinson's Disease by Promoting Mitochondrial Biogenesis via the SIRT-1/PGC-1α Pathway.

Hyperbaric oxygen therapy (HBOT) has been suggested as a potential adjunctive therapy for Parkinson’s disease (PD). PD is a neurodegenerative disease characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The aim of this study was to investigate the protective mechanisms of HBOT on neurons and motor function in a 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD and 1-methyl-4-phenylpyridinium (MPP+)-mediated neurotoxicity in SH-SY5Y cells on the potential protective capability. In vivo: male C57BL/6 mice were randomly divided into three groups: control, MPTP group and MPTP+HBOT group. The MPTP-treated mice were intraperitoneally received MPTP (20 mg/kg) four times at 2 h intervals within a day. The day after MPTP treatment, MPTP+HBOT mice were exposed to hyperbaric oxygen at 2.5 atmosphere absolute (ATA) with 100% oxygen for 1 h once daily for 7 consecutive days. In vitro: retinoic acid (RA)-differentiated SH-SY5Y cells were treated with MPP+ for 1 h followed by hyperbaric oxygen at 2.5 ATA with 100% oxygen for 1 h. The results showed that MPTP induced a significant loss in tyrosine hydroxylase (TH)-positive neurons in the SNpc of mice. HBOT treatment significantly increased the number of TH-positive neurons, with enhanced neurotrophic factor BDNF, decreased apoptotic signaling and attenuated inflammatory mediators in the midbrain of MPTP-treated mice. In addition, MPTP treatment decreased the locomotor activity and grip strength of mice, and these effects were shown to improve after HBOT treatment. Furthermore, MPTP decreased mitochondrial biogenesis signaling (SIRT-1, PGC-1α and TFAM), as well as mitochondrial marker VDAC expression, while HBOT treatment was shown to upregulate protein expression. In cell experiments, MPP+ reduced neurite length, while HBOT treatment attenuated neurite retraction. Conclusions: the effects of HBOT in MPTP-treated mice might come from promoting mitochondrial biogenesis, decreasing apoptotic signaling and attenuating inflammatory mediators in the midbrain, suggesting its potential benefits in PD treatment.

Protein corona mitigated the cytotoxicity of CdTe QDs to macrophages by targeting mitochondria

Despite the potential of cadmium telluride quantum dots (CdTe QDs) in bioimaging and drug delivery, their toxic effects have been documented. It is known that the immunotoxicity of CdTe QDs targeting macrophages is one of their adverse effects, and the protein corona (PC) will affect the biological effects of QDs. In order to prove whether the PC-CdTe QDs complexes could alleviate the toxicity of CdTe QDs without weakening their luminescence, we investigated the impact of protein corona formed in fetal bovine serum (FBS) on the cytotoxicity of CdTe QDs to mitochondria. RAW264.7 cells were used as the model to compare the effects of CdTe QDs and PC-CdTe QDs complexes on the structure, function, quantity, morphology, and mitochondrial quality control of mitochondria. As result, the protein corona form in FBS alleviated the inhibition of CdTe QDs on mitochondrial activity, the damage to mitochondrial membrane, the increase of ROS, and the reduction of ATP content. Also, CdTe QDs increased the number of mitochondria in macrophages, while the complexes did not. In line with this, the morphology of mitochondrial network in macrophages which were exposed to CdTe QDs and PC-CdTe QDs complexes was different. CdTe QDs transformed the network into fragments, punctuations, and short rods, while PC-CdTe QDs complexes made the mitochondrial network highly branched, which was related to the imbalance of mitochondrial fission and fusion. Mechanically, CdTe QDs facilitated mitochondrial fission and inhibited mitochondrial fusion, while protein corona reversed the phenomenon caused by QDs. Besides mitochondrial dynamics, mitochondrial biogenesis and mitophagy were also affected. CdTe QDs increased the expression of mitochondrial biogenesis signaling molecules including PGC-1α, NRF-1 and TFAM, while PC-CdTe QDs complexes played the opposite role. With regard to mitophagy, they both showed promoting effect. In conclusion, the formation of protein corona alleviated the toxic effects of CdTe QDs on the mitochondria in macrophages and affected mitochondrial quality control. Under the premise of ensuring the fluorescence properties of CdTe QDs, these findings provided useful insight into reducing the toxicity of CdTe QDs from two perspectives: protein corona and mitochondria, and shared valuable information for the safe use of QDs.

MiR 208a Regulates Mitochondrial Biogenesis in Metabolically Challenged Cardiomyocytes.

Metabolic syndrome increases the risk for cardiovascular disease including metabolic cardiomyopathy that may progress to heart failure. The decline in mitochondrial metabolism is considered a critical pathogenic mechanism that drives this progression. Considering its cardiac specificity, we hypothesized that miR 208a regulates the bioenergetic metabolism in human cardiomyocytes exposed to metabolic challenges. We screened in silico for potential miR 208a targets focusing on mitochondrial outcomes, and we found that mRNA species for mediator complex subunit 7, mitochondrial ribosomal protein 28, stanniocalcin 1, and Sortin nexin 10 are rescued by the CRISPR deletion of miR 208a in human SV40 cardiomyocytes exposed to metabolic challenges (high glucose and high albumin-bound palmitate). These mRNAs translate into proteins that are involved in nuclear transcription, mitochondrial translation, mitochondrial integrity, and protein trafficking. MiR 208a suppression prevented the decrease in myosin heavy chain α isoform induced by the metabolic stress suggesting protection against a decrease in cardiac contractility. MiR 208a deficiency opposed the decrease in the mitochondrial biogenesis signaling pathway, mtDNA, mitochondrial markers, and respiratory properties induced by metabolic challenges. The benefit of miR 208a suppression on mitochondrial function was canceled by the reinsertion of miR 208a. In summary, miR 208a regulates mitochondrial biogenesis and function in cardiomyocytes exposed to diabetic conditions. MiR 208a may be a therapeutic target to promote mitochondrial biogenesis in chronic diseases associated with mitochondrial defects.

Effect of Aerobic Exercise on the Expression of Ppargc-1α and SIRT1 in Cardiac Muscle of Diabetic Male Wistar Rats

Background: Type 2 diabetic patients have an abnormally high rate of mortality due to cardiovascular diseases. Given the adverse impact of diabetes on mitochondrial biogenesis in heart cells and the role of exercise on mitochondrial biogenesis signaling, this study investigated the effect of eight weeks of aerobic exercise on PGC-1a and SIRT1 gene expression in the myocardium of diabetic male Wistar rats. Materials and Methods: This experimental study was conducted on 24 adult male Wistar rats (eight weeks old and weighing 278.26±18.06g), which were randomly assigned to three groups of healthy control (n=8), diabetic control (n=8), and diabetes+aerobic exercise (n=8). The exercise protocol consisted of eight weeks of exercise, three sessions a week, starting with 10 minutes of running at a speed of 10m/s in the first week and ultimately reaching 40 minutes of running at a speed of 18m/s in the eighth week. The changes were analyzed using the one-way analysis of variance and Tukey’s post hoc test. Results: Significant differences were observed between the groups in terms of body mass (P=0.0001), fasting glucose (P=0.004), serum insulin (P=0.023), and myocardial Ppargc- 1α expression (P=0.031). The post hoc test represented a notable weight decrease in the diabetic control group (P=0.001) and the diabetic exercise group (P=0.001) compared to the healthy control group. The results also showed a significant increase in the glucose level of the diabetic control group compared to the healthy control group (P=0.008) and a notable decrease in the diabetic exercise group’s glucose level in comparison with the diabetic control group (P=0.001). A significant decrease was also observed in the insulin level of the diabetic exercise group compared to the diabetic control group (P=0.034). The results of the post hoc test for Ppargc-1α expression changes showed significantly increased myocardial Ppargc-1α expression in the diabetic exercise group compared to the diabetic control group (P=0.009). No significant change was detected in the expression of SIRT1 (P=0.075). Conclusion: The findings suggest that exercise positively affects insulin resistance and weight changes by regulating genes related to mitochondrial biogenesis.

A Comparison of the Antioxidant Effects Between Hydrogen Gas Inhalation and Vitamin C Supplementation in Response to a 60-Min Treadmill Exercise in Rat Gastrocnemius Muscle.

The reactive oxygen species (ROS) produced during exercise act as a double-edged sword because they may cause oxidative damage but also play a role in the signaling pathways. A supplementation of exogenous antioxidants can reduce the total amount of ROS during exercise while it may also affect the ROS’ role in the signaling pathways of mitochondrial biogenesis. It has been suggested that hydrogen gas, as an antioxidant, can selectively scavenge hydroxyl radicals but does not affect superoxide anion’s signal transduction. The aim of this study was to compare the effects of 1-h hydrogen gas inhalation 30min prior to a treadmill exercise on the key biomarkers of mitochondrial biogenesis and related signaling pathways, and the activities of endogenous antioxidant enzymes, with those of vitamin C, in the rat skeletal muscle. Eighty-one 8-week-old male Sprague–Dawley (SD) rats were randomly assigned to three interventions (exercise-only, exercise+4%H2, and exercise+vitamin C at 500mg/kg weight, with 27 rats under each intervention), and sampled at pre-, immediately post and 4h post a 60-min treadmill exercise at speed of 27m/min and flat inclination, with nine rats in each sub-group. Expression of mitochondrial biogenetic markers and related signaling molecules in gastrocnemius muscle, and concentrations of oxidative stress markers in serum were measured. Two-way ANOVA or Kruskal–Wallis analyses showed that both hydrogen inhalation and vitamin C supplementation significantly reduced serum levels of MDA immediately after exercise and AGEs 4h after exercise. The pre-exercise supplement of vitamin C significantly reduced mitochondrial complex IV concentrations and PGC-1α, NRF-1, TFAM gene expression levels compared to the pre-exercise group, but the hydrogen gas intervention did not result in a reduction in these measurements. Unlike vitamin C, hydrogen inhalation did not blunt post-exercise mitochondrial biogenetic signals, but resulted in an increase in complex IV concentration, activation of PGC-1α, and TFAM and NRF-2 gene transcription, and up-regulation of PGC-1α protein expression. The findings indicated that hydrogen gas inhalation could play the role as an effective antioxidant in response to the exercise, whilst it did not significantly affect mitochondrial biogenesis. The dose–response relationship and antioxidant effects in different types of exercise for hydrogen inhalation require further investigation.

The mitochondrial biogenesis signaling pathway is a potential therapeutic target for myasthenia gravis via energy metabolism (Review).

Myasthenia gravis (MG) is an autoantibody-mediated autoimmune disease that is characterized by muscle weakness and fatigue. Traditional treatments for MG target the neuromuscular junction (NMJ) or the immune system. However, the efficacy of such treatments is limited, and novel therapeutic options for MG are urgently required. In the current review, a new therapeutic strategy is proposed based on the mitochondrial biogenesis and energy metabolism pathway, as stimulating mitochondrial biogenesis and the energy metabolism might alleviate myasthenia gravis. A number of cellular sensors of the energy metabolism were investigated, including AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1). AMPK and SIRT1 are sensors that regulate cellular energy homeostasis and maintain energy metabolism by balancing anabolism and catabolism. Peroxisome proliferator-activated receptor γ coactivator 1α and its downstream transcription factors nuclear respiratory factors 1, nuclear respiratory factors 2, and transcription factor A are key sensors of mitochondrial biogenesis, which can restore mitochondrial DNA and produce new mitochondria. These processes help to control muscle contraction and relieve the symptoms of MG, including muscle weakness caused by dysfunctional NMJ transmission. Therefore, the present review provides evidence for the therapeutic potential of targeting mitochondrial biogenesis for the treatment of MG.

Hypothermia Advocates Functional Mitochondria and Alleviates Oxidative Stress to Combat Acetaminophen-Induced Hepatotoxicity.

For years, moderate hypothermia (32 °C) has been proposed as an unorthodox therapy for liver injuries, with proven hepatoprotective potential. Yet, limited mechanistic understanding has largely denied its acceptance over conventional pharmaceuticals for hepatoprotection. Today, facing a high prevalence of acetaminophen-induced liver injury (AILI) which accounts for the highest incidence of acute liver failure, hypothermia was evaluated as a potential therapy to combat AILI. For which, transforming growth factor-α transgenic mouse hepatocytes (TAMH) were subjected to concomitant 5 mM acetaminophen toxicity and moderate hypothermic conditioning for 24 h. Thereafter, its impact on mitophagy, mitochondrial biogenesis, glutathione homeostasis and c-Jun N-terminal kinase (JNK) signaling pathways were investigated. In the presence of AILI, hypothermia displayed simultaneous mitophagy and mitochondrial biogenesis to conserve functional mitochondria. Furthermore, antioxidant response was apparent with higher glutathione recycling and repressed JNK activation. These effects were, however, unremarkable with hypothermia alone without liver injury. This may suggest an adaptive response of hypothermia only to the injured sites, rendering it favorable as a potential targeted therapy. In fact, its cytoprotective effects were displayed in other DILI of similar pathology as acetaminophen i.e., valproate- and diclofenac-induced liver injury and this further corroborates the mechanistic findings of hypothermic actions on AILI.

Maternal High Fat Diet and Diabetes Disrupts Transcriptomic Pathways That Regulate Cardiac Metabolism and Cell Fate in Newborn Rat Hearts.

Background: Children born to diabetic or obese mothers have a higher risk of heart disease at birth and later in life. Using chromatin immunoprecipitation sequencing, we previously demonstrated that late-gestation diabetes, maternal high fat (HF) diet, and the combination causes distinct fuel-mediated epigenetic reprogramming of rat cardiac tissue during fetal cardiogenesis. The objective of the present study was to investigate the overall transcriptional signature of newborn offspring exposed to maternal diabetes and maternal H diet.Methods: Microarray gene expression profiling of hearts from diabetes exposed, HF diet exposed, and combination exposed newborn rats was compared to controls. Functional annotation, pathway and network analysis of differentially expressed genes were performed in combination exposed and control newborn rat hearts. Further downstream metabolic assessments included measurement of total and phosphorylated AKT2 and GSK3β, as well as quantification of glycolytic capacity by extracellular flux analysis and glycogen staining.Results: Transcriptional analysis identified significant fuel-mediated changes in offspring cardiac gene expression. Specifically, functional pathways analysis identified two key signaling cascades that were functionally prioritized in combination exposed offspring hearts: (1) downregulation of fibroblast growth factor (FGF) activated PI3K/AKT pathway and (2) upregulation of peroxisome proliferator-activated receptor gamma coactivator alpha (PGC1α) mitochondrial biogenesis signaling. Functional metabolic and histochemical assays supported these transcriptome changes, corroborating diabetes- and diet-induced cardiac transcriptome remodeling and cardiac metabolism in offspring.Conclusion: This study provides the first data accounting for the compounding effects of maternal hyperglycemia and hyperlipidemia on the developmental cardiac transcriptome, and elucidates nuanced and novel features of maternal diabetes and diet on regulation of heart health.

The Involvement of Mitochondrial Biogenesis in Selenium Reduced Hyperglycemia-Aggravated Cerebral Ischemia Injury.

Selenium has been shown to possess antioxidant and neuroprotective effects by modulating mitochondrial function and activating mitochondrial biogenesis. Our previous study has also suggested that selenium protected neurons against glutamate toxicity and hyperglycemia-induced damage by regulating mitochondrial fission and fusion. However, it is still not known whether the mitochondrial biogenesis is involved in selenium alleviating hyperglycemia-aggravated cerebral ischemia reperfusion (I/R) injury. The object of this study is to define whether selenium protects neurons against hyperglycemia-aggravated cerebral I/R injury by promoting mitochondrial biogenesis. In vitro oxygen deprivation plus high glucose model decreased cell viability, enhanced reactive oxygen species production, and meanwhile stimulated mitochondrial biogenesis signaling. Pretreated with selenium significantly decreased cell death and further activated the mitochondrial biogenesis signaling. In vivo 30min of middle cerebral artery occlusion in the rats under hyperglycemic condition enhanced neurological deficits, enlarged infarct volume, exacerbated neuronal damage and oxidative stress compared with normoglycemic ischemic rats after 24h reperfusion. Consistent to the in vitro results, selenium treatment alleviated ischemic damage in hyperglycemic ischemic animals. Furthermore, selenium reduced the structural changes of mitochondria caused by hyperglycemic ischemia and further promoted the mitochondrial biogenesis signaling. Selenium activates mitochondrial biogenesis signaling, protects mitochondrial structure integrity and ameliorates cerebral I/R injury in hyperglycemic rats.

Is ATF4 Required for Skeletal Muscle Mitochondrial Biogenesis and Remodeling?

Skeletal muscle is an important tissue for the maintenance of whole‐body health and vitality. Regarded for its role in supporting posture and locomotion, the metabolic profile of muscle has further ramifications for mobility, risk of falls/injury, and the development of diseases. As mitochondria are responsible for the maintenance of metabolic health in muscle, they also contribute to muscle dysfunction and disease. The intricate regulation of mitochondrial content and function within muscle is essential to match the internal metabolic capability to the external demands being placed on the tissue. PGC‐1α is the master regulator of mitochondrial biogenesis, which refers to the synthesis of mitochondrial proteins transcribed by both nDNA and mtDNA. The synchronous expression of mitochondrial proteins from either genome is important in preserving proteostasis, as an imbalance in their expression can promote dysfunction within the organelle and trigger the mitochondrial unfolded protein response (UPRmt). ATF4, identified as a primary regulator of the UPRmt, upregulates the expression of mitochondrial chaperones and proteostasis to augment the protein handling ability of the organelle, and to re‐establish homeostasis. As ATF4 responds to acute cellular stresses, it has been implicated in regulating skeletal muscle health by mediating aging‐related, and disuse‐induced muscle atrophy and decline. However, while it is understood that ATF4 is involved in mediating the mitochondrial stress response, it has yet to be determined whether ATF4 is necessary for mitochondrial biogenesis in skeletal muscle. We measured ATF4 expression in C2C12 cells prior to, and following 4‐days of differentiation, and found ATF4 protein levels to be elevated over 3‐fold in differentiated myotubes. This induction of ATF4 coincided with 3–5‐fold increases in protein expression of mitochondrial content markers COX I and IV, despite modest decreases in UPRmt factors, mtHSP70, HSP60, and CPN10. Moreover, overexpression and knockdown of ATF4 in cultured myoblasts affected their ability to form multinucleated myotubes, indicating that the expression of ATF4 must be regulated to facilitate myotube formation. We examined the induction of ATF4 following contractile activity (CA), both in C2C12 myotubes, and rat TA muscle. CA was sufficient to induce 50–80% increases in ATF4 mRNA and protein in tissue and cultured cells, respectively, which preceded 1.5–2.5‐fold increases in mitochondrial content. Additionally, we observed a 2‐fold increase in ATF4 protein expression in hindlimbs of mice subjected to unilateral sciatic denervation, which corresponded with a 15–20% decrease in mitochondrial content. Taken together, these data suggest a possible regulatory role for ATF4 in determining mitochondrial adaptation within muscle during development, exercise and chronic disuse. Subsequent work investigating the impact of ATF4 ablation and exogenous expression on mitochondrial biogenesis signaling, as well as on mitochondrial function following contractile activity will further illustrate whether ATF4 is necessary and sufficient to promote improvements in mitochondrial content and function.Support or Funding InformationWork supported by NSERC, Canada.

MiR 208a Deficiency Promotes Mitochondrial Biogenesis in the metabolic heart

A high caloric regimen causes metabolic syndrome, which is a pre‐requisite for type 2 diabetes mellitus, and increases the risk for cardiovascular disease. Both metabolic syndrome and diabetes induce a common cardiac phenotype known as metabolic cardiomyopathy with an early onset as diastolic dysfunction that may progress to systolic dysfunction and congestive heart failure.While the normal heart is able to freely switch between glucose and fatty acid (FA) oxidation, the metabolic heart becomes almost completely reliant on FA oxidation for ATP production. This energetic dysregulation is supported by increased mitochondrial metabolism, which includes an increased mitochondrial mass and function. Based on the reported cardiac specificity of the microRNA (miR) 208a, we investigated its role in bioenergetic metabolism in the metabolic heart. Lewis rats exposed to a high fat diet (HFD) exhibit obesity, systemic insulin resistance, hyperglycemia, hyperlipidemia, cardiac diastolic dysfunction, and cardiac fibrosis. Microarray studies highlighted an altered miRNA expression profile in the heart upon HFD, including a decrease in miR 208a. CRISPR deletion of the miR 208a in cultured human SV40 cardiomyocytes exposed to diabetogenic conditions (high glucose, high albumin‐bound palmitate) led to a bioenergetics profile that favors mitochondrial FA metabolism including an increase in mitochondrial biogenesis signaling, electron transport chain complexes and critical enzymes for FA beta‐oxidation. In addition, miR 208‐a deficiency prevented the switch in the myosin heavy chain isoforms by increasing myosin heavy chain alpha, thus preserving cardiac contractility. We analyzed in silico for putative miR 208a targets focusing on mitochondrial outcomes using the TargetScanHuman database ( http://www.targetscan.org/cgi‐bin/targetscan/vert_71/targetscan.cgi). We found that mitochondrial ribosomal protein 28 (involved in mitochondrial translation and generation of mitochondrial DNA‐encoded electron transport chain subunits), MINOS1 (a conserved component of mitofilin complexes required for mitochondrial function and cristae organization), and MED7 (component of the Mediator Complex that regulates the transcription by facilitating the interaction between nuclear receptors, transcriptional co‐activator and co‐repressors, and chromatic modification factors with RNA Pol II) are rescued by miR 208a deficiency in cardiomyocytes exposed to diabetogenic conditions. In summary, miR 208a regulates nuclear and mitochondrial transcription, mitochondrial cristae organization and integrity in the diabetic heart, and supports the metabolic remodeling towards increased FA oxidation. Our data suggest that miR 208a may be a therapeutic target to promote mitochondrial biogenesis in chronic diseases associated with mitochondrial defects.Support or Funding InformationCentral Michigan University Early Career Grant, AIREA American Heart Association