Markers Of Mitochondrial Biogenesis Research Articles

Resveratrol improves muscle regeneration in obese mice through enhancing mitochondrial biogenesis

Obesity is increasing rapidly worldwide and is accompanied by many complications, including impaired muscle regeneration. Obesity is known to inhibit AMP-activated protein kinase (AMPK) activity, which impedes mitochondrial biogenesis, myogenic differentiation and muscle regeneration. Resveratrol has an effective anti-obesity effect, but its effect on regeneration of muscle in obese mice remains to be tested. We hypothesized that resveratrol activates AMPK and mitochondrial biogenesis to improve muscle regeneration. Male C57BL/6J mice were fed a control diet or a 60% high-fat diet with or without resveratrol supplementation for 8 weeks and, then, the tibialis anterior muscle was subjected to cardiotoxin-induced muscle injury. Muscle tissue was collected at 3 and 7 d after injury. We found that resveratrol enhanced both proliferation and differentiation of satellite cells following injury in obese mice. Markers of mitochondrial biogenesis were upregulated in resveratrol-treated mice. In C2C12 myogenic cells, resveratrol activated AMPK and stimulated the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha, which were associated with enhanced myogenic differentiation. Such effects of resveratrol were abolished by AMPKα1 ablation, showing the mediatory roles of AMPK. In summary, dietary resveratrol activates AMPK/ proliferator-activated receptor gamma coactivator 1-alpha axis to facilitate mitochondrial biogenesis and muscle regeneration impaired due to obesity.

Formoterol PLGA-PEG Nanoparticles Induce Mitochondrial Biogenesis in Renal Proximal Tubules.

Formoterol is a long-acting β2 agonist (LABA). Agonism of the β2-adrenergic receptor by formoterol is known to stimulate mitochondrial biogenesis (MB) in renal proximal tubules and recover kidney function. However, formoterol has a number of cardiovascular side effects that limits its usage. The goal of this study was to design and develop an intravenous biodegradable and biocompatible polymeric nanoparticle delivery system that targets formoterol to the kidney. Poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) nanoparticles containing encapsulated formoterol were synthesized by a modified single-emulsion solvent evaporation technique resulting in nanoparticles with a median hydrodynamic diameter of 442 + 17 nm. Using primary cell cultures of rabbit renal proximal tubular cells (RPTCs), free formoterol, encapsulated formoterol polymeric nanoparticles, and drug-free polymeric nanoparticles were biocompatible and not cytotoxic over a wide concentration range. In healthy male mice, polymeric nanoparticles were shown to localize in tubules of the renal cortex and improved the renal localization of encapsulated formoterol compared to the free formoterol. At a lower total formoterol dose, the nanoparticle localization resulted in increased expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), the master regulator of MB, and increased electron transport chain proteins, markers of MB. This was confirmed by direct visual quantification of mitochondria and occurred with both free formoterol and the encapsulated formoterol polymeric nanoparticles. At the same time, localization of nanoparticles to the kidneys resulted in reduced induction of MB markers in the heart. These new nanoparticles effectively target formoterol to the kidney and successfully produce MB in the kidney.

Temporal characterization of mitochondrial impairment in the unilateral ureteral obstruction model in rats

Renal fibrosis is a well-known mechanism that favors chronic kidney disease (CKD) development in obstructive nephropathy, a significant pathology worldwide. Fibrosis induction involves several pathways, and although mitochondrial alterations have recently emerged as a critical factor that triggers renal damage in the obstructed kidney, the temporal mitochondrial alterations during the fibrotic induction remain unexplored. Therefore, in this work, we evaluated the time course of mitochondrial mass and bioenergetics alterations induced by a unilateral ureteral obstruction (UUO), a widely used model to study the mechanism involved in kidney fibrosis induction and progression. Our results show a marked reduction in mitochondrial oxidative phosphorylation (OXPHOS) in the obstructed kidney on days 7 to 28 of obstruction without significant mitochondrial coupling changes. Besides, we observed that mitochondrial mass was reduced, probably due to decreased biogenesis and mitophagy induction. OXPHOS impairment was associated with decreased mitochondrial biogenesis markers, the peroxisome proliferator-activated receptor γ co-activator-1alpha (PGC-1α), and nuclear respiratory factor 1 (NRF1); and also, with the induction of mitophagy in a PTEN-induced kinase 1 (PINK1) and Parkin independent way. It is concluded that the impairment of OXPHOS capacity may be explained by the reduction in mitochondrial biogenesis and the induction of mitophagy during fibrotic progression.

Mitochondrial Adaptation to Diet and Swimming Activity in Gilthead Seabream: Improved Nutritional Efficiency.

Sustained exercise promotes growth in different fish species, and in gilthead seabream we have demonstrated that it improves nutrient use efficiency. This study assesses for differences in growth rate, tissue composition and energy metabolism in gilthead seabream juveniles fed two diets: high-protein (HP; 54% protein, 15% lipid) or high energy (HE; 50% protein, 20% lipid), under voluntary swimming (VS) or moderate-to-low-intensity sustained swimming (SS) for 6 weeks. HE fed fish under VS conditions showed lower body weight and higher muscle lipid content than HP fed fish, but no differences between the two groups were observed under SS conditions. Irrespective of the swimming regime, the white muscle stable isotopes profile of the HE group revealed increased nitrogen and carbon turnovers. Nitrogen fractionation increased in the HP fed fish under SS, indicating enhanced dietary protein oxidation. Hepatic gene expression markers of energy metabolism and mitochondrial biogenesis showed clear differences between the two diets under VS: a significant shift in the COX/CS ratio, modifications in UCPs, and downregulation of PGC1a in the HE-fed fish. Swimming induced mitochondrial remodeling through upregulation of fusion and fission markers, and removing almost all the differences observed under VS. In the HE-fed fish, white skeletal muscle benefited from the increased energy demand, amending the oxidative uncoupling produced under the VS condition by an excess of lipids and the pro-fission state observed in mitochondria. Contrarily, red muscle revealed more tolerant to the energy content of the HE diet, even under VS conditions, with higher expression of oxidative enzymes (COX and CS) without any sign of mitochondrial stress or mitochondrial biogenesis induction. Furthermore, this tissue had enough plasticity to shift its metabolism under higher energy demand (SS), again equalizing the differences observed between diets under VS condition. Globally, the balance between dietary nutrients affects mitochondrial regulation due to their use as energy fuels, but exercise corrects imbalances allowing practical diets with lower protein and higher lipid content without detrimental effects.

Mechanisms of impaired mitochondrial homeostasis and NAD+ metabolism in a model of mitochondrial heart disease exhibiting redox active iron accumulation

Due to the high redox activity of the mitochondrion, this organelle can suffer oxidative stress. To manage energy demands while minimizing redox stress, mitochondrial homeostasis is maintained by the dynamic processes of mitochondrial biogenesis, mitochondrial network dynamics (fusion/fission), and mitochondrial clearance by mitophagy. Friedreich's ataxia (FA) is a mitochondrial disease resulting in a fatal hypertrophic cardiomyopathy due to the deficiency of the mitochondrial protein, frataxin. Our previous studies identified defective mitochondrial iron metabolism and oxidative stress potentiating cardiac pathology in FA. However, how these factors alter mitochondrial homeostasis remains uncharacterized in FA cardiomyopathy. This investigation examined the muscle creatine kinase conditional frataxin knockout mouse, which closely mimics FA cardiomyopathy, to dissect the mechanisms of dysfunctional mitochondrial homeostasis. Dysfunction of key mitochondrial homeostatic mechanisms were elucidated in the knockout hearts relative to wild-type littermates, namely: (1) mitochondrial proliferation with condensed cristae; (2) impaired NAD+ metabolism due to perturbations in Sirt1 activity and NAD+ salvage; (3) increased mitochondrial biogenesis, fusion and fission; and (4) mitochondrial accumulation of Pink1/Parkin with increased autophagic/mitophagic flux. Immunohistochemistry of FA patients' heart confirmed significantly enhanced expression of markers of mitochondrial biogenesis, fusion/fission and autophagy. These novel findings demonstrate cardiac frataxin-deficiency results in significant changes to metabolic mechanisms critical for mitochondrial homeostasis. This mechanistic dissection provides critical insight, offering the potential for maintaining mitochondrial homeostasis in FA and potentially other cardio-degenerative diseases by implementing innovative treatments targeting mitochondrial homeostasis and NAD+ metabolism.

SIRT5 Inhibition Induces Brown Fat-Like Phenotype in 3T3-L1 Preadipocytes.

Brown adipose tissue (BAT) activity plays a key role in regulating systemic energy. The activation of BAT results in increased energy expenditure, making this tissue an attractive pharmacological target for therapies against obesity and type 2 diabetes. Sirtuin 5 (SIRT5) affects BAT function by regulating adipogenic transcription factor expression and mitochondrial respiration. We analyzed the expression of SIRT5 in the different adipose depots of mice. We treated 3T3-L1 preadipocytes and mouse primary preadipocyte cultures with the SIRT5 inhibitor MC3482 and investigated the effects of this compound on adipose differentiation and function. The administration of MC3482 during the early stages of differentiation promoted the expression of brown adipocyte and mitochondrial biogenesis markers. Upon treatment with MC3482, 3T3-L1 adipocytes showed an increased activation of the AMP-activated protein kinase (AMPK), which is known to stimulate brown adipocyte differentiation. This effect was paralleled by an increase in autophagic/mitophagic flux and a reduction in lipid droplet size, mediated by a higher lipolytic rate. Of note, MC3482 increased the expression and the activity of adipose triglyceride lipase, without modulating hormone-sensitive lipase. Our findings reveal that SIRT5 inhibition stimulates brown adipogenesis in vitro, supporting this approach as a strategy to stimulate BAT and counteract obesity.

Neuropeptide Y and its receptors are expressed in chicken skeletal muscle and regulate mitochondrial function

Neuropeptide Y (NPY) is a highly conserved 36-amino acid neurotransmitter, which is primarily expressed in the mammalian arcuate nucleus of the hypothalamus. It is a potent orexigenic neuropeptide, stimulating appetite and inducing feed intake in a variety of species. Recent research has shown that NPY and its receptors can be expressed by peripheral tissues, but their role is not yet well defined. Specifically, this information is particularly sparse in avian species. Therefore, the aim of this study was to determine the expression of NPY and its receptors, and determine their regulation by environmental and nutritional stressors, in the skeletal muscle of avian species using in vivo and in vitro approaches. Here, we show that NPY and its receptors are expressed in chicken breast and leg muscle as well as in quail myoblast (QM7) cell line. Intraperitoneal injection of recombinant NPY increased feed intake in 9-d old chicks and upregulated the expression of NPY and NPY receptors in breast and leg muscle, suggesting autocrine and/or paracrine roles for NPY. Additionally, NPY is able to modulate the mitochondrial network. In breast muscle, a low dose of NPY upregulated (P < 0.05) the expression of genes involved in ATP production (uncoupling protein, UCP; nuclear factor erythroid 2 like 2, NFE2L2) and dynamics (mitofusin 1, MFN1), while a high dose decreased (P < 0.05) markers of mitochondrial dynamics (mitofusin 2, MFN2; OPA1 mitochondrial dynamin like GTPase, OPA1) and increased (P < 0.05) genes involved in mitochondrial biogenesis (D-loop, peroxisome proliferator activated receptor gamma, PPARG). In leg muscle, NPY decreased (P < 0.05) markers of mitochondrial biogenesis and ATP synthesis (D-loop; peroxisome proliferator activated receptor alpha, PCG1A; peroxisome proliferator-activated receptor gamma, coactivator 1 beta, PPARGC1B; PPARG; NFE2L2). In QM7 cells, genes associated with mitochondrial biogenesis, dynamics, and ATP synthesis were all upregulated (P < 0.05), even though basal respiration and ATP production were decreased (P < 0.05) with NPY treatment as measured by XF Flux analysis. Together, these data show that the NPY system is expressed in avian skeletal muscle and plays a role in mitochondrial function.

Evidence for a cardiometabolic sexual dimorphism in a non-obese mouse model of hepatic Lrpprc deficiency exhibiting microvesicular steatosis

A recent meta-analysis showed that 20% of the world's population suffers from non-alcoholic fatty liver disease (NAFLD) without obesity. The progression of NAFLD involves cardiac manifestations, but the underlying mechanisms are not well established. Our objective is to characterize the cardiometabolic manifestations of NAFLD and evaluate the presence of a sexual dimorphism. The cardiac phenotype was investigated in a mouse model of hepatic Lrpprc deficiency (H-Lrpprc −/− ), as these mice develop microvesicular steatosis in absence of obesity and a NAFLD lipidomic profile secondary to mitochondrial bioenergetic deficiency. The cardiac repercussions were studied using molecular (qPCR, immunoblots), lipidomic (mass spectrometry) and functional (oximetry on isolated mitochondria) approaches. Loss of Lrpprc was specific to the liver and residual expression was similar in both sexes. In female mice, Lrpprc deficiency in the liver was associated with a decreased cardiac expression of gene markers for mitochondrial biogenesis (Tfam) and fusion (Mfn1-2), as well as genes related to fatty acid (FA) metabolism, including transcriptional regulator Pparα, FA transporters (Cd36, Cpt1b, Cpt2), and ß-oxidation enzymes (Vlcad, Lcad, Mcad). FA-dependent mitochondrial respiration was also reduced while cardiac triglyceride levels were elevated. In contrast, these alterations were almost completely absent in male mice. Collectively these results indicate that metabolic defects in the liver consequent to mitochondrial dysfunction in absence of obesity result in significant abnormalities in mitochondrial and metabolic phenotype of the heart, particularly in females, thus highlighting the existence of a major sexual dimorphism. This experimental model may prove useful to better understand the mechanisms underlying the sex-related variability in the progression of NAFLD in humans.

Dietary Supplementation with NAD+ Precursors to Support Exercise: An Evaluation of the Clinical Evidence

Nicotinamide Adenine Dinucleotide (NAD+) is essential for the functionality of muscle cells. Multiple studies have demonstrated that NAD+ levels decline with age but are increased with aerobic exercise and resistance training. Preclinical studies have demonstrated that supplementation with NAD+ precursors, and specifically niacin and nicotinamide riboside, have positively impacted molecular indicators of muscle biogenesis. There have been suggestions that supplementation with NAD+ precursors may be beneficial to muscle health in sarcopenia and other physiological conditions of energy and muscle decline. The objective of this analysis is to evaluate if clinical dietary supplementation with NAD+ precursors influence exercise performance and indicators of muscle health in humans. Only peer-reviewed clinical studies that orally supplemented with NAD+ precursors as individual compounds and evaluated exercise and/or muscle biomarkers were included in the analysis. Of the over 50 published clinical studies that have evaluated various NAD+ precursors, only 9 studies met our criteria of having at least one study arm measuring an NAD+ precursor alone with an outcome related to exercise performance or muscle health. Of the precursors evaluated, one study evaluated extended release niacin, one evaluated the nicotinic acid derivative acipimox, four studies evaluated nicotinamide riboside, and three studies evaluated tryptophan. Five studies evaluated the benefit of NAD+ precursor supplementation in muscle biomarkers, eight studies included evaluation of physical performance before and after supplementation, but none of the studies included an exercise protocol for the study participants. Extended release niacin may have some benefits to muscle health following chronic supplementation as indicated by various molecular markers of mitochondrial biogenesis and muscle strength, though side effects related to flushing are concerning. Nicotinamide riboside supplementation was shown to increase muscle acetylcarnitine following exercise in one study; however, extended study duration and optimal dosing protocols may be necessary to show other benefits. Tryptophan was shown to benefit exercise performance. Future research studies would benefit from including an exercise protocol with or without NAD+ precursor supplementation, whole blood and muscle NAD+ and related metabolites analyses, along with multiple time points of evaluation throughout the study. Though there is some strong evidence that NAD+ precursors may benefit physical performance, each precursor appears to have different mechanisms and benefits. Therefore, additional research is recommended.

A single session of high‐intensity interval exercise in hypoxia did not change mitochondrial respiration or content in human skeletal muscle biopsies

Both high-intensity interval exercise (HIIE) and hypoxia have been suggested to affect mitochondria. However, it is not yet fully elucidated how a single session of HIIE in hypoxia affects mitochondrial respiration and content in human skeletal muscle. In this current study, we investigated the effects of a single session of HIIE combined with simulated hypoxia (3200 m, oxygen fraction of 14%) on mitochondrial respiration and content. We hypothesized that HIIE in hypoxia would induce substantial changes in mitochondrial respiration, but not in mitochondrial content. Ten healthy male participants (age, 28 ± 5 years; BMI, 26.0 ± 3.4) were recruited and completed three HIIE sessions (six 4-minute exercise bouts, separated by 2 minutes of resting) in a random order, separated by at least one week. Exercise sessions include an HIIE in hypoxia (88.4% of peak oxygen uptake (VO2peak) determined in hypoxia), an HIIE in normoxia matched for relative intensity (88.7% of VO2peak determined in normoxia), and an HIIE in normoxia matched for absolute intensity (74.1% of VO2peak determined in normoxia). Skeletal muscle samples were collected prior to, 3 hours, and 24 hours post-exercise to determine mitochondrial respiration and content. Hypoxia decreased VO2peak (by 20.2 ± 9.1%, p < 0.01), peak power output (PPO, by 9.4 ± 2.1%, p<0.01), and lactate threshold (LT, by 13.1 ± 3.0%, p<0.01). In the skeletal muscle biopsies, mitochondrial respiration, measured by Oroboros O2k with high-resolution respirometry, was similar among the three conditions prior to the HIIE interventions (p > 0.05) and remained unchanged both 3 and 24 hours after HIIE interventions performed in different conditions (p > 0.05). Citrate synthase activity, as a marker of mitochondrial content, did not differ prior to, or 3 and 24 hours after HIIE interventions among the three conditions (p > 0.05) . In conclusion, a single session of HIIE in hypoxia did not alter mitochondrial respiration and content. Gene expression and protein content of mitochondrial biogenesis markers are currently being analyzed.

Myostatin Inhibition-Induced Increase in Muscle Mass and Strength Was Amplified by Resistance Exercise Training, and Dietary Essential Amino Acids Improved Muscle Quality in Mice.

It has been frequently reported that myostatin inhibition increases muscle mass, but decreases muscle quality (i.e., strength/muscle mass). Resistance exercise training (RT) and essential amino acids (EAAs) are potent anabolic stimuli that synergistically increase muscle mass through changes in muscle protein turnover. In addition, EAAs are known to stimulate mitochondrial biogenesis. We have investigated if RT amplifies the anabolic potential of myostatin inhibition while EAAs enhance muscle quality through stimulations of mitochondrial biogenesis and/or muscle protein turnover. Mice were assigned into ACV (myostatin inhibitor), ACV+EAA, ACV+RT, ACV+EAA +RT, or control (CON) over 4 weeks. RT, but not EAA, increased muscle mass above ACV. Despite differences in muscle mass gain, myofibrillar protein synthesis was stimulated similarly in all vs. CON, suggesting a role for changes in protein breakdown in muscle mass gains. There were increases in MyoD expression but decreases in Atrogin-1/MAFbx expression in ACV+EAA, ACV+RT, and ACV+EAA+RT vs. CON. EAA increased muscle quality (e.g., grip strength and maximal carrying load) without corresponding changes in markers of mitochondrial biogenesis and neuromuscular junction stability. In conclusion, RT amplifies muscle mass and strength through changes in muscle protein turnover in conjunction with changes in implicated signaling, while EAAs enhance muscle quality through unknown mechanisms.

FDA-approved 5-HT1F receptor agonist lasmiditan induces mitochondrial biogenesis and enhances locomotor and blood-spinal cord barrier recovery after spinal cord injury

Vascular and mitochondrial dysfunction are well-established consequences of spinal cord injury (SCI). Evidence suggests mitigating these dysfunctions may be an effective approach in treating SCI. The goal of this study was to elucidate if mitochondrial biogenesis (MB) induction with a new, selective and FDA-approved 5-hydroxytryptamine receptor 1F (5-HT1F) receptor agonist, lasmiditan, can stimulate locomotor recovery and restoration of the blood-spinal cord barrier (BSCB) after SCI. Female C57BL/6 J mice were subjected to moderate SCI using a force-controlled impactor-induced contusion model followed by daily administration of lasmiditan (0.1 mg/kg, i.p.) beginning 1 h after injury. In the naïve spinal cord, electron microscopy revealed increased mitochondrial density and mitochondrial area, as well as enhanced mitochondrial DNA content. FCCP-uncoupled oxygen consumption rate (OCR), a functional marker of MB, was also increased in the naïve spinal cord following lasmiditan treatment. We observed disrupted mitochondrial DNA content, PGC-1α levels and FCCP-OCR in the injury site 3d after SCI. Lasmiditan treatment attenuated, and in some cases restored these deficits. Lasmiditan treatment also resulted in increased locomotor capability as early as 7d post-SCI, with treated mice reaching a Basso-Mouse Scale score of 3.3 by 21d, while vehicle-treated mice exhibited a score of 2.0. Integrity of the BSCB was assessed using Evans Blue dye extravasation. While SCI increased dye extravasation at 3d and 7d, dye accumulation in the spinal cord of lasmiditan-treated mice was attenuated 7d post-SCI, suggesting accelerated BSCB recovery. Finally, lasmiditan treatment resulted in decreased lesion volume and spared myelinated tissue 7d post-SCI. Collectively, these data reveal that 5-HT1F receptor agonist-induced MB using the FDA-approved drug lasmiditan may be an effective therapeutic strategy for the treatment of SCI.

Is the Mitochondrial Function of Keloid Fibroblasts Affected by Cytoglobin?

BackgroundA keloid is a benign skin tumour characterised by excessive proliferation of fibroblasts, a process that requires a sufficient amount of energy. The energy needs are associated with adequate oxygen (O2) flow and well-functioning mitochondria. It is known that cytoglobin (CYGB) has a function in O2 distribution. The aim of the present study was to explore whether the inhibition of CYGB expression caused impaired mitochondrial function of keloid fibroblasts.MethodsAn in vitro study was conducted on a keloid fibroblast derived from our previous study. The study was carried out in the laboratory of the Biochemistry & Molecular Biology Department, Faculty of Medicine, Universitas Indonesia (FMUI), from July to December 2018. CYGB expression was inhibited by small interfering ribonucleic acid (siRNA) and CYGB. Analysis of mitochondrial function was observed through peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), a mitochondrial biogenesis marker and the activity of the succinate dehydrogenase (SDH) enzyme in mitochondria.ResultsThe CYGB gene and protein were downregulated after treatment with CYGB siRNA. Inhibition of CYGB expression with siRNA also tended to decrease the levels of PGC-1α messenger ribonucleic acid (mRNA) and protein, as well as SDH enzyme activity.ConclusionInhibition of CYGB expression with siRNA tended to decrease mitochondrial biogenesis and function. This may be useful for understanding the excessive proliferation of fibroblasts in keloids and for development of treatment for keloids.

Deterioration of mitochondrial function in the human intercostal muscles differs among individuals with sarcopenia, obesity, and sarcopenic obesity

Sarcopenic obesity (SO) increases the risk of mortality more than sarcopenia or obesity alone. Sarcopenia weakens the peripheral and respiratory muscles, leading to respiratory complications. It also induces mitochondrial dysfunction in the peripheral muscle; however, whether mitochondrial dysfunction in respiratory muscles differs among individuals with obesity, sarcopenia, and SO remains unknown. We evaluated the deterioration of respiratory muscle strength and mitochondrial function among normal, sarcopenia, obesity, and SO subjects. Twenty-five patients who underwent lung resections were enrolled between April 2017 and January 2021, and their intercostal muscles were harvested. Based on their L3 muscle index and visceral fat area, the patients were divided into four groups (normal, obesity, sarcopenia, and SO). The clinical data, mRNA expression, and protein expressions associated with mitochondrial biogenesis/fusion/fission in the intercostal muscles were compared among the four groups. The respiratory muscle strength was evaluated using peak expiratory flow rate (PEFR). The PEFR values of the four groups were not significantly different. The levels of pAkt/Akt and mTOR (a marker of protein synthesis) were not significantly different among the four groups; however, those in the SO group were substantially lower than those in the sarcopenia or obesity groups. The levels of Atrogen-1 and MuRF1 (a marker of protein degradation) were not significantly different among the four groups; however, those in the SO group were substantially higher than those in the sarcopenia or obesity groups. Expression of PGC1-α (a marker of mitochondrial biogenesis) in the SO group was significantly lower than that in the normal group. MFN1 and MFN2 (marker of mitochondrial fusion) levels were significantly lower in the SO group than those in the normal group. DRP1 (a marker of mitochondrial fission) level in the SO group was substantially lower than that in the normal group. The expression of TNF-α (a pro-inflammatory cytokine) in the SO group was substantially lower than that in the normal group. Our results suggest that the deterioration of protein synthesis and degradation of mitochondrial function in the respiratory muscles was most prominent in the SO before the weakening of the respiratory muscles. The deterioration mechanism may differentially regulate obesity, sarcopenia, and SO.

Dietary cocoa ameliorates non-alcoholic fatty liver disease and increases markers of antioxidant response and mitochondrial biogenesis in high fat-fed mice

Cocoa powder, derived Theobroma cacao, is a popular food ingredient that is commonly consumed in chocolate. Epidemiological and human intervention studies have reported that chocolate consumption is associated with reduced risk of cardiometabolic diseases. Laboratory studies have reported the dietary supplementation with cocoa or cocoa polyphenols can improve obesity and obesity-related comorbidities in preclinical models. Non-alcoholic fatty liver disease (NAFLD), one such comorbidity, is a risk factor for cirrhosis and hepatocellular carcinoma. Limited studies have examined the effect of cocoa/chocolate on NAFLD and underlying hepatoprotective mechanisms. Here, we examined the hepatoprotective effects of dietary supplementation with 80 mg/g cocoa powder for 10 wks in high fat (HF)-fed obese male C57BL/6J mice. We found that cocoa-supplemented mice had lower rate of body weight gain (22%), hepatic triacylglycerols (28%), lipid peroxides (57%), and mitochondrial DNA damage (75%) than HF-fed controls. These changes were associated with higher hepatic superoxide dismutase and glutathione peroxidase enzyme activity and increased expression of markers of hepatic mitochondrial biogenesis. We also found that the hepatic protein expression of sirtuin 3 (SIRT3), and mRNA expression of peroxisome proliferator activated receptor g coactivator (PGC) 1a, nuclear respiratory factor 1, and forkhead box O3 were higher in cocoa-treated mice compared to HF-fed controls. These factors play a role in coordinating mitochondrial biogenesis and expression of mitochondrial antioxidant response factors. Our results indicate that cocoa supplementation can mitigate the severity of NAFLD in obese mice and that these effects are related to SIRT3/PGC1a-mediated increases in antioxidant response and mitochondrial biogenesis.

The ketogenic diet preserves skeletal muscle with aging in mice.

The causes of the decline in skeletal muscle mass and function with age, known as sarcopenia, are poorly understood. Nutrition (calorie restriction) interventions impact many cellular processes and increase lifespan and preserve muscle mass and function with age. As we previously observed an increase in life span and muscle function in aging mice on a ketogenic diet (KD), we aimed to investigate the effect of a KD on the maintenance of skeletal muscle mass with age and the potential molecular mechanisms of this action. Twelve‐month‐old mice were assigned to an isocaloric control or KD until 16 or 26 months of age, at which time skeletal muscle was collected for evaluating mass, morphology, and biochemical properties. Skeletal muscle mass was significantly greater at 26 months in the gastrocnemius of mice on the KD. This result in KD mice was associated with a shift in fiber type from type IIb to IIa fibers and a range of molecular parameters including increased markers of NMJ remodeling, mitochondrial biogenesis, oxidative metabolism, and antioxidant capacity, while decreasing endoplasmic reticulum (ER) stress, protein synthesis, and proteasome activity. Overall, this study shows the effectiveness of a long‐term KD in mitigating sarcopenia. The diet preferentially preserved oxidative muscle fibers and improved mitochondrial and antioxidant capacity. These adaptations may result in a healthier cellular environment, decreasing oxidative and ER stress resulting in less protein turnover. These shifts allow mice to better maintain muscle mass and function with age.

PGC-1\u03b1 regulates airway epithelial barrier dysfunction induced by house dust mite

BackgroundThe airway epithelial barrier function is disrupted in the airways of asthmatic patients. Abnormal mitochondrial biogenesis is reportedly involved in the pathogenesis of asthma. However, the role of mitochondrial biogenesis in the airway barrier dysfunction has not been elucidated yet. This study aimed to clarify whether the peroxisome proliferator-activated receptor γ coactivator-1alpha (PGC-1α), a central regulator of mitochondrial biogenesis, is involved in the disruption of the airway barrier function induced by aeroallergens.MethodsBEAS-2B cells were exposed to house dust mite (HDM) and the expressions of PGC-1α and E-cadherin, a junctional protein, were examined by immunoblotting. The effect of SRT1720, a PGC-1α activator, was investigated by immunoblotting, immunocytochemistry, and measuring the transepithelial electrical resistance (TEER) on the HDM-induced reduction in mitochondrial biogenesis markers and junctional proteins in airway bronchial epithelial cells. Furthermore,the effects of protease activated receptor 2 (PAR2) inhibitor, GB83, Toll-like receptor 4 (TLR4) inhibitor, lipopolysaccharide from Rhodobacter sphaeroides (LPS-RS), protease inhibitors including E64 and 4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) on the HDM-induced barrier dysfunction were investigated.ResultsThe amounts of PGC-1α and E-cadherin in the HDM-treated cells were significantly decreased compared to the vehicle-treated cells. SRT1720 restored the expressions of PGC-1α and E-cadherin reduced by HDM in BEAS-2B cells. Treatment with SRT1720 also significantly ameliorated the HDM-induced reduction in TEER. In addition, GB83, LPS-RS, E64 and AEBSF prevented the HDM-induced reduction in the expression of PGC1α and E-cadherin.ConclusionsThe current study demonstrated that HDM disrupted the airway barrier function through the PAR2/TLR4/PGC-1α-dependent pathway. The modulation of this pathway could be a new approach for the treatment of asthma.

Oral fucoidan improves muscle size and strength in mice.

Fucoidan is a sulfated polysaccharide found in a range of brown algae species. Growing evidence supports the long‐term supplementation of fucoidan as an ergogenic aid to improve skeletal muscle performance. The aim of this study was to investigate the effect of fucoidan on the skeletal muscle of mice. Male BL/6 mice (N = 8–10) were administered a novel fucoidan blend (FUC, 400 mg/kg/day) or vehicle (CON) for 4 weeks. Treatment and control experimental groups were further separated into exercise (CON+EX, FUC+EX) or no‐exercise (CON, FUC) groups, where exercised groups performed 30 min of treadmill training three times per week. At the completion of the 4‐week treatment period, there was a significant increase in cross‐sectional area (CSA) of muscle fibers in fucoidan‐treated extensor digitorum longus (EDL) and soleus fibers, which was accompanied by a significant increase in tibialis anterior (TA) muscle force production in fucoidan‐treated groups. There were no significant changes in grip strength or treadmill time to fatigue, nor was there an effect of fucoidan or exercise on mass of TA, EDL, or soleus muscles. In gastrocnemius muscles, there was no change in mRNA expression of mitochondrial biogenesis markers PGC‐1α and Nrf‐2 in any experimental groups; however, there was a significant effect of fucoidan supplementation on myosin heavy chain (MHC)‐2x, but not MHC‐2a, mRNA expression. Overall, fucoidan increased muscle size and strength after 4 weeks of supplementation in both exercised and no‐exercised mice suggesting an important influence of fucoidan on skeletal muscle physiology.

Caloric restriction reduces sympathetic activity similar to beta-blockers but conveys additional mitochondrio-protective effects in aged myocardium

Increased activation of sympathetic nervous system contributes to congestive heart failure (CHF) progression, and inhibition of sympathetic overactivation by beta-blockers is successful in CHF patients. Similarly, caloric restriction (CR) reduces sympathetic activity but mediates additional effects. Here, we compared the cardiac effects of CR (− 40% kcal, 3 months) with beta-blocker therapy (BB), diuretic medication (DF) or control diet in 18-months-old Wistar rats. We continuously recorded blood pressure, heart rate, body temperature and activity with telemetric devices and analysed cardiac function, activated signalling cascades and markers of apoptosis and mitochondrial biogenesis. During our study, left ventricular (LV) systolic function improved markedly (CR), mildly (BB) or even deteriorated (DF; control). Diastolic function was preserved by CR and BB but impaired by DF. CR reduced blood pressure identical to DF and BB and heart rate identical to BB. Plasma noradrenaline was decreased by CR and BB but increased by DF. Only CR reduced LV oxidative damage and apoptosis, induced AMPK and Akt phosphorylation and increased mitochondrial biogenesis. Thus, additive to the reduction of sympathetic activity, CR achieves protective effects on mitochondria and improves LV function and ROS damage in aged hearts. CR mechanisms may provide additional therapeutic targets compared to traditional CHF therapy.

Nanoparticle-encapsulated antioxidant improves placental mitochondrial function in a sexually dimorphic manner in a rat model of prenatal hypoxia.

Pregnancy complications associated with prenatal hypoxia lead to increased placental oxidative stress. Previous studies suggest that prenatal hypoxia can reduce mitochondrial respiratory capacity and mitochondrial fusion, which could lead to placental dysfunction and impaired fetal development. We developed a placenta-targeted treatment strategy using a mitochondrial antioxidant, MitoQ, encapsulated into nanoparticles (nMitoQ) to reduce placental oxidative stress and (indirectly) improve fetal outcomes. We hypothesized that, in a rat model of prenatal hypoxia, nMitoQ improves placental mitochondrial function and promotes mitochondrial fusion in both male and female placentae. Pregnant rats were treated with saline or nMitoQ on gestational day (GD) 15 and exposed to normoxia (21% O2 ) or hypoxia (11% O2 ) from GD15-21. On GD21, male and female placental labyrinth zones were collected for mitochondrial respirometry assessments, mitochondrial content, and markers of mitochondrial biogenesis, fusion and fission. Prenatal hypoxia reduced complex IV activity and fusion in male placentae, while nMitoQ improved complex IV activity in hypoxic male placentae. In female placentae, prenatal hypoxia decreased respiration through the S-pathway (complex II) and increased N-pathway (complex I) respiration, while nMitoQ increased fusion in hypoxic female placentae. No changes in mitochondrial content, biogenesis or fission were found. In conclusion, nMitoQ improved placental mitochondrial function in male and female placentae from fetuses exposed to prenatal hypoxia, which may contribute to improved placental function. However, the mechanisms (ie, changes in mitochondrial respiratory capacity and mitochondrial fusion) were distinct between the sexes. Treatment strategies targeted against placental oxidative stress could improve placental mitochondrial function in complicated pregnancies.