PGC-1α affects skeletal muscle and adipose tissue development by regulating mitochondrial biogenesis

Exercise induced irisin mitigates hepatitis in anabolic-androgenic steroids treated rats via modulation of PGC-1-α/PPARγ/Nrf2 and NRF2/NF-κB/TLR4 signaling

Irisin, a myokine released during exercise, has been shown to exert protective effects against metabolic and inflammatory disorders. Its role in mitigating hepatic damage induced by anabolic-androgenic steroids (AAS) remains largely unexplored. This study was conducted to examine the effects of exercise on irisin level and its capability to prevent hepatotoxicity caused by anabolic androgenic steroids (AAS) in rat model. The fifty-two male rats were divided into four groups: control, AAS treated (15 mg/kg/day S.C/8 W), exercised, and exercised- AAS treated. The following procedures were carried out: liver function tests, serum irisin, tissue inflammatory and oxidative stress markers, macro and micromorphological evaluation, and the examination of nuclear factor erythroid 2-related factor 2 (Nrf2), peroxisome proliferator-activated receptor-gamma (PPARγ) and its coactivator-1α (PGC1α) by immunohistochemistry. The liver tissue's expression of nuclear factor kappa B (NF-κB), Toll-like receptor-4 (TLR4), and Nrf2 mRNA was also assessed. After administering AAS to animals, aerobic exercise was found to significantly improve liver function tests, inflammation, and oxidative stress, reduce liver weight, improve morphological and histological changes, and improve the hepatic injury score. Furthermore, there was a notable rise in serum irisin, hepatic PPARγ, PGC1α, and Nrf2 immune-expressions and Nrf2 mRNA expression, while NF-κB and TLR4 mRNA expressions were significantly decreased. In conclusion, the irisin/PGC1α/PPARγ/Nrf2 and Nrf2/NF-κB/TLR4 signaling pathways may be modulated by aerobic exercise, which also reduces the liver's oxidative stress and inflammatory reactions to AAS treatment.

Aerobic Capacity Beyond Cardiorespiratory Fitness Linking Mitochondrial Function, Disease Resilience and Healthy Aging

Aerobic capacity is conventionally equated with cardiorespiratory fitness (CRF), but its physiological essence extends far beyond cardiopulmonary performance. Aerobic capacity is an integrative physiological indicator reflecting the entire process from oxygen uptake and transport to mitochondrial energy conversion, with mitochondrial function constituting its molecular core. Emerging evidence reveals robust associations between diminished aerobic capacity and increased risks of non-communicable chronic diseases and age-related functional decline. However, its potential as a valuable tool for early disease detection and intervention remains undervalued in clinical practice. By synthesizing recent clinical and experimental studies, we highlight the crucial role of aerobic capacity, particularly its mechanistic links to impaired mitochondrial function, which drives disease progression through impaired energy metabolism and chronic inflammation. Furthermore, exercise interventions designed to enhance aerobic capacity have shown promise in improving mitochondrial efficiency, promoting cardiometabolic adaptation, and boosting overall health, thus offering an effective strategy for chronic disease prevention. We advocate for inclusion of aerobic capacity assessments in routine health evaluations and emphasize the need to integrate aerobic capacity optimization into public health frameworks to advance preventive strategies against chronic diseases and promote healthy aging.

Cellular and Molecular Mechanisms of Phytochemicals Against Inflammation-Associated Diseases and Viral Infection

Inflammation-associated diseases have become widespread and pose a significant threat to human health, and the therapeutic methods for diverse diseases are inadequate due to the undesirable effects of synthetic ingredients. Recently, more and more evidence indicated that phytochemicals, plant secondary metabolites, have numerous therapeutic functions against human diseases via affecting a variety of mechanisms with their distinct advantages of high efficiency and low toxicity. Here, we highlight the mechanisms of phytochemicals to hinder inflammation-associated diseases (including Inflammatory diseases, cardiovascular diseases, metabolic syndrome, neurological disorders, skin diseases, respiratory diseases, kidney diseases, gastrointestinal diseases, retinal diseases, viral infections) by regulating the crosstalk among various signal cascades (including MicroRNAs, SIRT1, DNMTs, NF-κB, NLRP3, TGF-β, the Gasdermin-mediated pyroptosis pathway), which can be considered as a novel and potential therapeutic strategy. Furthermore, phytochemicals could prevent virus infection by disturbing different targets in the virus replication cycle. However, natural plants have shown limited bioavailability due to their low water solubility, the use of adjuvants such as liposomal phytochemicals, phytochemical nanoparticles and phytochemicals-phospholipid complex promote their bioavailability to exhibit beneficial effects against various diseases. The purpose of this review is to explore the molecular mechanisms and promising applications of phytochemicals in the fields of inflammation-associated diseases and virus infection to provide some direction.

APOE mediates the coupling of myogenesis and lipid metabolism in skeletal muscle: decoding intercellular crosstalk via a cell co-culture model

The growth and lipid accumulation of skeletal muscle directly affects the yield and meat quality characteristics of beef, which is the result of the interaction between skeletal muscle cells (SMCs) and intramuscular adipocytes (IMAs). Therefore, in this study, a co-culture system was used to simulate the in vivo cellular microenvironment, aiming to reveal the interaction patterns between bovine SMCs and IMAs during the proliferation and differentiation stages. The results showed that, compared with SMCs cultured alone, the presence of IMAs in the co-culture system inhibited the expression of proliferation markers such as PCNA, CDK1, CDK2, CCNA2, and CCNE2 in SMCs. This also affected the G1/S phase transition of SMCs, thereby inhibiting their proliferation rate. Meanwhile, the presence of IMAs also inhibited the expression of myogenesis markers such as MYHC, MYOD, MYOG, MYF5, and MYF6, thus hindering the myotube formation process of SMCs. Moreover, RNA-seq identified that the key genes APOE, APOD, SOX9, CAV3, SMPD3, and EDN2 that mediate the interaction between SMCs and IMAs in the co-culture system. Among that, APOE has a dual effect on myogenesis and lipid accumulation. Interfering with the expression of APOE inhibited the proliferation, differentiation and lipid accumulation of SMCs. Based on these findings, we determined that APOE is a key regulatory factor connecting muscle development and fat accumulation. As a potential intervention target, APOE has great potential and can open up new avenues for improving meat quality and production efficiency.

Mechanisms for Regulatory Effects of Exercise on Metabolic Diseases from the Lactate-Lactylation Perspective

Metabolic diseases, including cardiovascular diseases, type 2 diabetes mellitus (T2DM), osteoporosis, and non-alcoholic fatty liver disease (NAFLD), constitute a major global health burden associated with chronic morbidity and mortality. Lactate, once considered as a metabolic byproduct, has emerged as a key regulator of cellular reprogramming through lactylation, a novel post-translational modification (PTM) that dynamically couples metabolic flux to chromatin remodeling. Lactylation exerts dual regulatory roles as a signaling molecule via GPR81/GPR4-mediated pathways and as a substrate for the covalent modification of histones and metabolic enzymes. Pathologically, chronic hyperlactatemia suppresses mitochondrial biogenesis, driving metabolic cardiomyopathy through the epigenetic silencing of oxidative metabolism genes. Conversely, exercise-induced lactate surges transiently enhance insulin sensitivity via AMPK/PGC-1α/GLUT4 signaling, resolve inflammation through GPR81-mediated M2 macrophage polarization, and restore mitochondrial function via lactylation-dependent pathways. This review delineates lactylation as a spatiotemporal rheostat: chronic dysregulation perpetuates metabolic disorders, whereas acute exercise-mediated lactylation remodels transcriptional networks to restore metabolic homeostasis. Future research should integrate multiomics to clarify lactylation's spatiotemporal dynamics, tissue-specific thresholds, metabolism-immunity interactions, and metabolic-epigenetic crosstalk for the precision management of metabolic diseases.

Polyplex Nanomicelle-Mediated Pgc-1α4 mRNA Delivery Via Hydrodynamic Limb Vein Injection Enhances Damage Resistance in Duchenne Muscular Dystrophy Mice

Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene, leading to the absence of dystrophin and progressive muscle degeneration. Current therapeutic strategies, such as exon-skipping and gene therapy, face limitations including truncated dystrophin production and safety concerns. To address these issues, a novel mRNA-based therapy is explored using polyplex nanomicelles to deliver mRNA encoding peroxisome proliferator-activated receptor gamma coactivator 1 alpha isoform 4 (PGC-1α4) via hydrodynamic limb vein (HLV) administration. Using an in vivo muscle torque measurement technique, it is observed that nanomicelle-delivered Pgc-1α4 mRNA significantly improved muscle damage resistance and mitochondrial activity in mdx mice. Specifically, HLV administration of Pgc-1α4 mRNA in dystrophic muscles significantly relieved the torque reduction and myofiber injury induced by eccentric contraction (ECC), boosted metabolic gene expression, and enhanced muscle oxidative capacity. In comparison, lipid nanoparticles (LNPs), a widely used mRNA delivery system, does not achieve similar protective effects, likely due to their intrinsic immunogenicity. This foundational proof-of-concept study highlights the potential of mRNA-based therapeutics for the treatment of neuromuscular diseases such as DMD and demonstrates the capability of polyplex nanomicelles as a safe and efficient mRNA delivery system for therapeutic applications.

Dual Action of Pueraria montana var. lobata Extract on Myogenesis and Muscle Atrophy

Background/Objectives: Muscle atrophy, defined by diminished muscle mass and function, is a notable concern associated with aging, disease, and glucocorticoid treatment. Pueraria montana var. lobata extract (PMLE) demonstrates multiple bioactive properties, such as antioxidant, anti-inflammatory, and metabolic regulatory activities; however, its role in muscle atrophy has not been extensively investigated to date. This study examined how PMLE influences both muscle cell differentiation and dexamethasone (DEX)-induced muscle degeneration by focusing on the underlying molecular mechanisms. Methods: This study examined the effects of PMLE on myogenic differentiation and DEX-induced muscle atrophy. C2C12 myoblasts were treated with PMLE (10-100 ng/mL) and assessed for changes in the expression of myogenesis-related genes and activation of Akt/mTOR and AMPK/SIRT1/PGC-1α signaling cascades. In vivo, a DEX-induced muscle atrophy model was used to assess muscle mass, fiber morphology, and molecular changes. Results: PMLE PMLE promoted muscle cell development by increasing the expression of MyHC, MyoD, and myogenin while activating protein synthesis and mitochondrial biogenesis pathways. PMLE counteracted DEX-induced myotube atrophy, restoring myotube diameter and promoting cellular fusion in vitro. In vivo, PMLE mitigated muscle degradation in fast-twitch muscle groups and reversed DEX-induced suppression of key anabolic and mitochondrial pathways. Conclusions: These findings suggest that PMLE promotes myogenic differentiation and protects against muscle atrophy by regulating critical molecular pathways, indicating its promise as a treatment candidate for conditions involving muscle wasting. Further studies are required to assess its clinical application and long-term safety efficacy.

A Narrative Review on the Impact of Probiotic Supplementation on Muscle Development, Metabolic Regulation, and Fiber Traits Related to Meat Quality in Broiler Chickens

Public concern over drug resistance has led to governmental regulations banning the use of antibiotics as growth promoters, stimulating interest in developing complementary strategies to maintain animal production, mitigate infections, and enhance muscle characteristics and quality parameters, especially in meat-producing animals. Probiotics are recognized as a potential strategy for improving growth, primarily by promoting intestinal homeostasis. These microorganisms are suggested to modulate gut microbiota, preserving their ecosystem and influencing secondary metabolite production, which can directly or indirectly regulate skeletal muscle metabolism by influencing the expression of key muscle-related genes and the activity of various signaling factors. Several studies have documented the potential benefits of various strains of Bacillus, Enterococcus, and members of the Lactobacillaceae family on muscle characteristics. These studies have shown that probiotics not only modulated myogenic factors but also influenced proteins and enzymes involved in signaling pathways related to carbon metabolism, inflammatory response, mitochondrial dynamics, and antioxidant activity. These effects have been associated with improvements in meat quality parameters and enhanced growth performance. This manuscript seeks to present a brief overview of the impact of probiotic supplementation on muscle health and the quality of meat in broiler chickens.

Induction of UBQLN1-mediated PGC1α stability by isoliensinine overcame hypoxia-induced resistance in liver cancer cells

Hypoxia is a key reason for the failure of liver cancer therapy. Emerging evidences indicated that ROS played a crucial role in the sorafenib therapy, and overcoming the reduction in intracellular ROS levels was the first requirement for therapy resistance. Ubiquilin1 (UBQLN1) acted as an oncogene or suppressor gene involved in the protein degradation and abnormal protein aggregation. In this study, we proposed a novel strategy to reverse the hypoxia-induced resistance in liver cancer by isoliensinine (Iso), a significant bioactive compound derived from lotus seed. Based on preliminary screening, we found a significant elevation of UBQLN1 in liver cancer tissues obtained from the TCGA databases and in liver cancer cells under hypoxic model, which contributed to hypoxia-induced sorafenib resistance. Further data suggested that Iso significantly reversed the hypoxia-induced sorafenib resistance through directly targeting UBQLN1 and inducing ROS production. Notably, the ROS elevation induced by Iso could trigger IRP2-induced ferroptosis but remained below the threshold for mitochondrial damage in liver cancer cells. The related mechanism was that Iso reduced the binding between PGC1α and ubiquitin, promoting the stability of the PGC1α protein, which might accelerate mitochondrial energy metabolism. Taken together, our findings not only revealed that UBQLN1 played a critical role in ROS regulation, but also uncovered a previously unrecognized reversal mechanism of Iso in liver cancer, which promoted sensitization of sorafenib-induced ferroptosis by inhibition of UBQLN1/PGC1α pathway under hypoxia.

Managing Doxorubicin Cardiotoxicity: Insights Into Molecular Mechanisms and Protective Strategies

Cancer ranks as the second leading cause of death in the United States and poses a significant health challenge globally. Numerous therapeutic options exist for treating cancer, with chemotherapy being one of the most prominent. Chemotherapy involves the use of antineoplastic drugs, either alone or in combination with other medications, to target and kill cancer cells. However, these drugs can also adversely affect healthy cells, leading to various side effects. Among the most commonly used chemotherapy agents are anthracyclines, which include doxorubicin, daunorubicin, and epirubicin. Doxorubicin is particularly notable for its effectiveness but is also associated with significant cardiotoxicity, a common concern for patients undergoing chemotherapy. Unfortunately, there is currently no definitive treatment to prevent or reverse this cardiotoxicity. The cardiac effects of doxorubicin can manifest in several ways, including changes in electrocardiograms, arrhythmias, myocarditis, pericarditis, myocardial infarction, cardiomyopathy, heart failure, and congestive heart failure. These complications may arise during treatment, shortly after it concludes, or even weeks later. Various mechanisms have been proposed to explain doxorubicin-induced cardiotoxicity. Key factors include the inhibition of topoisomerase IIβ, mitochondrial damage, reactive oxygen species (ROS) production due to iron metabolism, increased oxidative stress, heightened inflammatory responses, and elevated rates of apoptosis and necrosis within cardiac tissue. This review article will provide a comprehensive overview of the current state of knowledge regarding doxorubicin-induced cardiomyopathy. We will explore the underlying molecular mechanisms contributing to this condition and discuss emerging therapeutic strategies aimed at mitigating its impact on cancer survivors.

Wu-Mei-Wan enhances brown adipose tissue function and white adipose browning in obese mice via upregulation of HSF1

BACKGROUND

This research aims to explore the anti-obesity potential of Wu-Mei-Wan (WMW), particularly its effects on adipose tissue regulation in obese mice induced by a high-fat diet (HFD). The study focuses on understanding the role of heat shock factor 1 (HSF1) in mediating these effects.

METHODS

HFD-induced obese mice were treated with WMW. Body weight, food intake, and histopathological analysis of adipose tissue were conducted. Brown adipose tissue (BAT) activity was evaluated using Positron Emission Tomography, and ultrastructural changes were examined via transmission electron microscopy. Proteomic analysis identified targets of WMW in obesity treatment. HSF1 expression was inhibited to confirm its role. Molecular docking studied interactions between WMW and HSF1. Short-chain fatty acids (SCFAs) in the intestines were measured to determine if WMW's effects on HSF1 are mediated through SCFAs. Protein expression was assessed using western blot, immunohistochemistry, immunofluorescence and RT-qPCR were employed to detect the mRNA levels. Statistical analyses included t-tests, ANOVA, and non-parametric tests like the Mann-Whitney U test or Kruskal-Wallis test.

RESULTS

WMW significantly mitigates the adverse effects of a HFD on body weight and glucose metabolism in obese mice. Both low-dose WMW and high-dose WMW treatments led to reduced weight gain and improved glucose tolerance, with low-dose WMW showing more pronounced effects. WMW also reversed structural damage in BAT, enhancing mitochondrial integrity and thermogenic function, particularly at the low dose. Additionally, WMW treatment promoted the browning of WAT, evidenced by increased expression of key thermogenic proteins such as UCP1 and PGC-1α. The increase in HSF1 expression in both BAT and WAT, observed with WMW treatment, was crucial for these beneficial effects, as inhibition of HSF1 negated the positive outcomes. Furthermore, WMW treatment led to elevated levels of short-chain fatty acids SCFAs in the intestines, which are associated with increased HSF1 expression.

CONCLUSIONS

WMW represents a potent therapeutic strategy for obesity, promoting metabolic health and beneficial modulation of adipose tissue through an HSF1-dependent pathway.

EGR1 mRNA expression levels and polymorphisms are associated with slaughter performance in chickens

With the implementation of the policy of "centralized slaughtering and chilled to market" and the development of the livestock processing industry, numerous researchers have begun to focus on the selection and breeding of broilers bred for slaughter. The selection of breeds with excellent slaughtering performance and high meat production performance has become one of the most important selective breeding goals. In our previous study, we conducted transcriptome sequencing on chicken breast tissues with high and low breast muscle rates and found higher early growth response protein 1 (EGR1) expression in breast tissues with a low breast muscle ratio, thus hypothesizing that the EGR1 gene is involved in the growth and development process of chicken muscle tissues. Therefore, we analyzed the gene functions and polymorphisms of EGR1 to investigate its association with slaughter traits. We used various experimental methods, including RT-qPCR, Cell Counting Kit 8, 5-ethynyl-2'-deoxyuridine, western blot, flow cytometry, and immunofluorescence, to validate EGR1's role in chicken primary myoblasts. The results of our functional validation experiments indicate that EGR1 is highly expressed in breast tissues with a low breast muscle content and plays a key role in regulating of muscle growth and development by promoting proliferation and inhibiting the differentiation of chicken primary myoblasts. In addition, we explored the relationship between the EGR1 gene polymorphisms and slaughter traits using mixed linear models for the first time. In a population of Jiangfeng M3 lineage partridge chickens, we identified 4 EGR1 single-nucleotide polymorphisms, 2 of which were significantly associated with slaughter traits, including live weight, slaughter weight, semi-eviscerated weight, eviscerated weight, leg weight, wing weight, and breast muscle rate. In summary, ectopic expression of EGR1 promotes the proliferation and differentiation of chicken primary myoblasts. In addition, polymorphisms in EGR1 were associated with slaughter performance, providing a potential basis for further utilization of EGR1 as a breeding marker.

Spotlight on the Mechanism of Action of Semaglutide

Initially intended to control blood glucose levels in patients with type 2 diabetes, semaglutide, a potent glucagon-like peptide 1 analogue, has been established as an effective weight loss treatment by controlling appetite. Integrating the latest clinical trials, semaglutide in patients with or without diabetes presents significant therapeutic efficacy in ameliorating cardiometabolic risk factors and physical functioning, independent of body weight reduction. Semaglutide may modulate adipose tissue browning, which enhances human metabolism and exhibits possible benefits in skeletal muscle degeneration, accelerated by obesity and ageing. This may be attributed to anti-inflammatory, mitochondrial biogenesis, antioxidant and autophagy-regulating effects. However, most of the supporting evidence on the mechanistic actions of semaglutide is preclinical, demonstrated in rodents and not actually confirmed in humans, therefore warranting caution in the interpretation. This article aims to explore potential innovative molecular mechanisms of semaglutide action in restoring the balance of several interlinking aspects of metabolism, pointing to distinct functions in inflammation and oxidative stress in insulin-sensitive musculoskeletal and adipose tissues. Moreover, possible applications in protection from infections and anti-aging properties are discussed. Semaglutide enhancement of the core molecular mechanisms involved in the progress of obesity and diabetes, although mostly preclinical, may provide a framework for future research applications in human diseases overall.

Effects of quercetin nanoemulsion on SIRT1 activation and mitochondrial biogenesis in the skeletal muscle of high-fat diet-fed mice

BACKGROUND/OBJECTIVES

Quercetin (QT) is a plant flavonoid that offers health benefits owing to its various bioactive properties; however, as a hydrophobic substance, it has considerably low bioavailability. We previously demonstrated that QT nanoemulsion (QT+NE) formulated via oil-in-water nanoemulsification exhibited more effective cholesterol-lowering activity than ordinary QT in high cholesterol-fed rats. In this study, we investigated the effects of QT+NE on the regulation of skeletal muscle mitochondrial function in high-fat diet (HD)-fed mice.

MATERIALS/METHODS

C57BL/6J mice were fed a normal chow diet (ND), HD (45% of calories from fat), or HD with 0.05% QT+NE or QT for 11 weeks. We analyzed sirtuin 1 (SIRT1) activation, mitochondrial changes, and the expression of genes involved in mitochondrial biogenesis in skeletal muscle.

RESULTS

Body weight and body weight gain decreased in the QT+NE group compared with that in the HD group (P < 0.05), but not in the QT group. Epididymal adipose tissue weight decreased in both the QT and QT+NE groups (P < 0.05). Plasma lipid levels also improved in both the QT and QT+NE groups (P < 0.05). QT+NE intake upregulated the messenger RNA levels of SIRT1, peroxisome proliferator-activated receptor-γ coactivator 1-α, nuclear respiratory factor 1, and mitochondrial transcription factor A in skeletal muscle compared with HD intake alone (P < 0.05), whereas QT did not. In particular, SIRT1 activity was significantly increased in the QT+NE group compared with that in the QT group (P < 0.05). HD intake reduced mitochondrial DNA content compared with ND intake; nevertheless, QT+NE intake retained it (P < 0.05).

CONCLUSION

Collectively, our findings suggest that QT+NE may be beneficial in enhancing mitochondrial biogenesis in skeletal muscle of HD-fed mice, which may be associated with SIRT1 activation.

Tanshinone I improves renal fibrosis by promoting gluconeogenesis through upregulation of peroxisome proliferator-activated receptor-γ coactivator 1α

BACKGROUND

Renal fibrosis, a hallmark of chronic kidney disease, is closely associated with dysregulated gluconeogenesis. Tanshinone I (Tan I), a bioactive compound derived from the traditional Chinese medicine Danshen, exhibits antifibrotic and anti-inflammatory properties. However, its effects on gluconeogenesis and the mechanisms through which it alleviates renal fibrosis remain unclear. This study aimed to investigate whether Tan I promotes gluconeogenesis and mitigates renal fibrosis.

METHODS

Both in vivo and in vitro experiments were conducted. A unilateral ureteral obstruction (UUO) mouse model was used. Masson's trichrome, HE, and immunofluorescence staining, along with Western blotting, were employed. Lactate concentrations and a pyruvate tolerance test were conducted to assess glucose metabolism. In vitro, HK2 cells and primary renal tubular cells were treated with transforming growth factor-β (TGFβ) to induce fibrosis, and the effects of Tan I on glucose and lactate levels were examined.

RESULTS

In the UUO model, Tan I reduced fibrosis, decreased lactate accumulation, and modulated fibrosis markers while upregulating gluconeogenesis markers. Tanshinone I restored impaired renal gluconeogenesis, as evidenced by increased pyruvate levels. In vitro, Tan I inhibited fibrosis, reduced lactate levels, and increased glucose levels in cell supernatants. It also restored gluconeogenesis protein expression and decreased fibrotic protein levels. Peroxisome proliferator-activated receptor-γ coactivator (PGC1α) expression was downregulated in UUO and TGFβ-stimulated models, and Tan I reversed this downregulation. Inhibition of PGC1α in TGFβ-stimulated cells counteracted the antifibrotic and gluconeogenesis-promoting effects of Tan I.

CONCLUSIONS

Tanshinone I ameliorated renal fibrosis by enhancing gluconeogenesis through upregulation of PGC1α.

Dietary Bacillus subtilis benefits meat quality by regulating the muscle fiber type and antioxidant capacity of broilers

The effects of dietary Bacillus subtilis (BS) on the meat quality of broilers were evaluated, with an emphasis on the regulation of muscle fiber types and antioxidant capabilities. One hundred and forty-four Arbor Acres male broilers were divided into 3 treatment groups (0, 300 mg/kg and 500 mg/kg dietary BS) and raised for 35 d. The results suggested that BS improved meat quality by improving the muscular pH, meat color, water holding capacity and shear force. Immunofluorescence staining revealed a positive impact of BS on the muscle fiber transformation in thigh muscles, and the gene/protein expression data from specific muscle fiber types confirmed this finding. BS activated AMP-activated protein kinase (AMPK), silent information regulator 1 and peroxisome proliferator-activated receptor gamma coactivator 1alpha. The postmortem analysis revealed that BS increased the activity of glutathione peroxidase and total antioxidant capacity while decreasing the malondialdehyde content. Additionally, BS increased the gene and protein expression of nuclear factor-like 2 (Nrf2) and activated the Nrf2 signaling pathway, including its downstream factors, such as heme oxygenase-1, catalase, superoxide dismutase and glutathione peroxidase. In conclusion, dietary BS improved meat quality by modifying muscle fiber types and enhancing the antioxidant capacity in broilers.

Energy metabolism: from physiological changes to targets in sepsis-induced cardiomyopathy

Sepsis is a systemic inflammatory response syndrome caused by a variety of dysregulated responses to host infection with life-threatening multi-organ dysfunction. Among the injuries or dysfunctions involved in the course of sepsis, cardiac injury and dysfunction often occur and are associated with the pathogenesis of hemodynamic disturbances, also defined as sepsis-induced cardiomyopathy (SIC). The process of myocardial metabolism is tightly regulated and adapts to various cardiac output demands. The heart is a metabolically flexible organ capable of utilizing all classes of energy substrates, including carbohydrates, lipids, amino acids, and ketone bodies, to produce ATP. The demand of cardiac cells for energy metabolism changes substantially in septic cardiomyopathy, with distinct etiological causes and different times. This review describes changes in cardiomyocyte energy metabolism under normal physiological conditions and some features of myocardial energy metabolism in septic cardiomyopathy and briefly outlines the role of the mitochondria as a center of energy metabolism in the septic myocardium, revealing that changes in energy metabolism can serve as a potential future therapy for infectious cardiomyopathy.

Hypomethylation in promoters of PGC-1α involved in exercise-driven skeletal muscular alterations in old age

Exercise training can significantly improve skeletal muscle mitochondrial function and has been proven to be highly relevant to alterations in skeletal muscle DNA methylation. However, it remains unclear whether late-in-life exercise has an effect on promoter methylation of PGC-1α, a key regulator of mitochondrial biogenesis. Here we employed two distinct exercise modalities, constant medium intensity exercise training (CMIT) and high-intensity interval exercise training (HIIT), to investigate their impacts on PGC-1α expression and methylation regulation in skeletal muscle of aged mice. The results revealed a notable decrease in PGC-1α expression in skeletal muscle of aged mice, accompanied by elevated methylation levels of the PGC-1α promoter, and increased DNA methyltransferase (DNMT) protein expressions. However, both forms of exercise training significantly corrected PGC-1α epigenetic changes, increased PGC-1α expression, and ameliorated skeletal muscle reduction. Furthermore, exercise training led to elevated expression of proteins related to mitochondrial biogenesis and energy metabolism in skeletal muscle, improving mitochondrial structure and function. In conclusion, late-in-life exercise improved skeletal muscle function, morphology, and mitochondria biogenesis, which may be associated with hypomethylation in promoters of PGC-1α and increased content of skeletal muscle PGC-1α. Notably, there was no clear difference between HIIT and CMIT in PGC-1α expression and skeletal muscle function.

Mitochondrial Adaptation in Skeletal Muscle: Impact of Obesity, Caloric Restriction, and Dietary Compounds

PURPOSE OF REVIEW: The global obesity epidemic has become a major public health concern, necessitating comprehensive research into its adverse effects on various tissues within the human body. Among these tissues, skeletal muscle has gained attention due to its susceptibility to obesity-related alterations. Mitochondria are primary source of energy production in the skeletal muscle. Healthy skeletal muscle maintains constant mitochondrial content through continuous cycle of synthesis and degradation. However, obesity has been shown to disrupt this intricate balance. This review summarizes recent findings on the impact of obesity on skeletal muscle mitochondria structure and function. In addition, we summarize the molecular mechanism of mitochondrial quality control systems and how obesity impacts these systems. RECENT FINDINGS: Recent findings show various interventions aimed at mitigating mitochondrial dysfunction in obese model, encompassing strategies including caloric restriction and various dietary compounds. Obesity has deleterious effect on skeletal muscle mitochondria by disrupting mitochondrial biogenesis and dynamics. Caloric restriction, omega-3 fatty acids, resveratrol, and other dietary compounds enhance mitochondrial function and present promising therapeutic opportunities.

Research progress on regulating factors of muscle fiber heterogeneity in poultry: a review

Control of meat quality traits is an important goal of any farm animal production, including poultry. A better understanding of the biochemical properties of muscle fiber properties that drive muscle development and ultimately meat quality constitutes one of the major challenging topics in animal production and meat science. In this paper, the existing classification methods of skeletal muscle fibers in poultry were reviewed and the relationship between contractile and metabolic characteristics of muscle fibers and poultry meat quality was described. Finally, a comprehensive review of multiple potential factors affecting muscle fiber distribution and conversion is presented, including breed, sex, hormones, growth performance, diet, muscle position, exercise, and ambient temperature. We emphasize that knowledge of muscle fiber typing is essential to better understand how to control muscle characteristics throughout the life cycle of animals to better manage the final quality of poultry meat.

Diet and physical exercise as key players to tackle MASLD through improvement of insulin resistance and metabolic flexibility

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) has emerged as a prevalent health concern, encompassing a wide spectrum of liver-related disorders. Insulin resistance, a key pathophysiological feature of MASLD, can be effectively ameliorated through dietary interventions. The Mediterranean diet, rich in whole grains, fruits, vegetables, legumes, and healthy fats, has shown promising results in improving insulin sensitivity. Several components of the Mediterranean diet, such as monounsaturated fats and polyphenols, exert anti-inflammatory and antioxidant effects, thereby reducing hepatic steatosis and inflammation. Furthermore, this dietary pattern has been associated with a higher likelihood of achieving MASLD remission. In addition to dietary modifications, physical exercise, particularly resistance exercise, plays a crucial role in enhancing metabolic flexibility. Resistance exercise training promotes the utilization of fatty acids as an energy source. It enhances muscle glucose uptake and glycogen storage, thus reducing the burden on the liver to uptake excess blood glucose. Furthermore, resistance exercise stimulates muscle protein synthesis, contributing to an improved muscle-to-fat ratio and overall metabolic health. When implemented synergistically, the Mediterranean diet and resistance exercise can elicit complementary effects in combating MASLD. Combined interventions have demonstrated additive benefits, including greater improvements in insulin resistance, increased metabolic flexibility, and enhanced potential for MASLD remission. This underscores the importance of adopting a multifaceted approach encompassing dietary modifications and regular physical exercise to effectively manage MASLD. This narrative review explores the biological mechanisms of diet and physical exercise in addressing MASLD by targeting insulin resistance and decreased metabolic flexibility.

Ling-gui-zhu-gan promotes adipocytes browning via targeting the miR-27b/PRDM16 pathway in 3T3-L1 cells

Introduction: Obesity, a global epidemic, is caused by an imbalance between energy intake and expenditure. The induction of white adipose browning to increase heat production has emerged as a potential effective strategy to address obesity. Ling-gui-zhu-gan (LGZG), a traditional Chinese medicine formula, has been proved to achieve promising results to combat obesity and related metabolic diseases, yet the mechanisms remain largely unexplored. This study aimed to elucidate the anti-obesity properties and the mechanisms of LGZG by investigating its browning effect on 3T3-L1 adipocytes. Methods: LGZG-containing serum obtained by oral administration of LGZG to animals was added to 3T3-L1 adipocytes to simulate in vivo conditions. Results: The results showed that 49 compounds were identified in LGZG-containing serum by UHPLC-Q-Orbitrap HRMS, including compounds such as atractylenolides and polyporenic acid C, etc. LGZG-containing serum alleviated the lipid accumulation and decreased both intracellular and extracellular triglyceride contents in a dose-dependent manner. This reduction is accompanied by enhanced mitochondrial respiratory and heat production function. Mechanistically, LGZG-containing serum led to a decrease in miR-27b expression and an increase in the mRNA and protein levels of browning-related markers, including UCP1, PRDM16, PGC-1α, PPARγ, CTBP1, and CTBP2. Further investigation using miR-27b mimic transfection confirmed that miR-27b/PRDM16 pathway might be a potential mechanism by which LGZG-containing serum promotes browning of 3T3-L1 adipocytes. Discussion: These results underscore the therapeutic potential of LGZG in addressing obesity and its associated metabolic disorders through the promotion of adipose browning.

SIRT1 signaling pathways in sarcopenia: Novel mechanisms and potential therapeutic targets

Sarcopenia is an aging-related skeletal disease characterized by decreased muscle mass, strength, and physical function, severely affecting the quality of life (QoL) of the elderly population. Sirtuin 1 (SIRT1), as a nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylases, has been reported to participate in various aging-related signaling pathways and exert protective effect on many human diseases. SIRT1 functioned as an important role in the occurrence and progression of sarcopenia through regulating key pathways related to protein homeostasis, apoptosis, mitochondrial dysfunction, insulin resistance and autophagy in skeletal muscle, including SIRT1/Forkhead Box O (FoxO), AMP-activated protein kinase (AMPK)/SIRT1/nuclear factor κB (NF-κB), SIRT1/p53, AMPK/SIRT1/peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), and SIRT1/live kinase B1 (LKB1)/AMPK pathways. However, the specific mechanisms of these processes have not been fully illuminated. Currently, several SIRT1-mediated interventions on sarcopenia have been preliminarily developed, such as SIRT1 activator polyphenolic compounds, exercising and calorie restriction. In this review, we summarized the predominant mechanisms of SIRT1 involved in sarcopenia and therapeutic modalities targeting the SIRT1 signaling pathways for the prevention and prognosis of sarcopenia.

Research Progress on the Regulating Factors of Muscle Fiber Heterogeneity in Livestock: A Review

The type of muscle fiber plays a crucial role in the growth, development, and dynamic plasticity of animals' skeletal muscle. Additionally, it is a primary determinant of the quality of both fresh and processed meat. Therefore, understanding the regulatory factors that contribute to muscle fibers' heterogeneity is of paramount importance. Recent advances in sequencing and omics technologies have enabled comprehensive cross-verification of research on the factors affecting the types of muscle fiber across multiple levels, including the genome, transcriptome, proteome, and metabolome. These advancements have facilitated deeper exploration into the related biological questions. This review focused on the impact of individual characteristics, feeding patterns, and genetic regulation on the proportion and interconversion of different muscle fibers. The findings indicated that individual characteristics and feeding patterns significantly influence the type of muscle fiber, which can effectively enhance the type and distribution of muscle fibers in livestock. Furthermore, non-coding RNA, genes and signaling pathways between complicated regulatory mechanisms and interactions have a certain degree of impact on muscle fibers' heterogeneity. This, in turn, changes muscle fiber profile in living animals through genetic selection or environmental factors, and has the potential to modulate the quality of fresh meat. Collectively, we briefly reviewed the structure of skeletal muscle tissue and then attempted to review the inevitable connection between the quality of fresh meat and the type of muscle fiber, with particular attention to potential events involved in regulating muscle fibers' heterogeneity.

Effects of moderate intensity training and lithium on spatial learning and memory in a rat model: The role of SIRT3 and PGC1-α expression levels and brain-derived neurotropic factor

In this study we investigated the potential synergistic effects of moderate interval training (MIT) and lithium on spatial learning and memory. Forty-two male Wistar males were classified into six groups including I: Control, II: 10 mg/kg/day IP lithium (Li10), III: MIT, IV: Li10 + MIT, V: 40 mg/kg/day IP lithium (Li40), and VI: Li40 + MIT. Then, the rats underwent Morris Water Maze (MWM) test to assess their spatial memory and learning ability. Brain-derived neurotrophic factor (BDNF) density was measured by enzyme-linked immunosorbent assay (ELISA), and the expression of PGC1 and SIRT3 were assessed via qRT-PCR. The results show that MIT improves both memory and spatial learning; but lithium alone, does not cause this. Additionally, those exposed to a combination of exercise and lithium also had improved spatial learning and memory. Finally, we observed a positive role of BDNF protein, and PGC1 gene on the effects of exercise and lithium.

Oral Administration of Nacre Extract from Pearl Oyster Shells Has Anti-Aging Effects on Skin and Muscle, and Extends the Lifespan in SAMP8 Mice

Pearl oysters have been extensively utilized in pearl production; however, most pearl oyster shells are discarded as industrial waste. In a previous study, we demonstrated that the intraperitoneal administration of pearl oyster shell-derived nacre extract (NE) prevented d-galactose-induced brain and skin aging. In this study, we examined the anti-aging effects of orally administered NE in senescence-accelerated mice (SAMP8). Feeding SAMP8 mice NE prevented the development of aging-related characteristics, such as coarse and dull hair, which are commonly observed in aged mice. Additionally, the NE mitigated muscle aging in SAMP8 mice, such as a decline in grip strength. Histological analysis of skeletal muscle revealed that the NE suppressed the expression of aging markers, cyclin-dependent kinase inhibitor 2A (p16) and cyclin-dependent kinase inhibitor 1 (p21), and increased the expression of sirtuin1 and peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1)- α, which are involved in muscle synthesis. These findings suggest that the oral administration of NE suppresses skeletal muscle aging. Moreover, NE administration suppressed skin aging, including a decline in water content. Interestingly, oral administration of NE significantly extended the lifespan of SAMP8 mice, suggesting that its effectiveness as an anti-aging agent of various tissues including skeletal muscle, skin, and adipose tissue.

Sexual dimorphism in thermogenic regulators and metrnl expression in adipose tissue of offspring mice exposed to maternal and postnatal overnutrition

Current study investigated the impact of maternal and postnatal overnutrition on phenotype of adipose, in relation to offspring thermogenesis and sex. Female C57BL/6 J mice were fed with CHOW or high fat diet (HFD) for 2 weeks before mating, throughout gestation and lactation. At weaning, pups were fed to 9 weeks old with CHOW or HFD, which resulted in four groups for each gender--male or female: CHOW-CHOW (CC), CHOW-HFD (CH), HFD-CHOW (HC), HFD-HFD (HH). Maternal and post-weaning HFD enhanced thermogenic factors such as Acox1, Dio2 and Cox8b in iBAT of male and female offspring, but increased SIRT1, PGC-1α and UCP1 only in female. However, Acox1, Dio2 and Cox8b mRNA expression and SIRT1, PGC-1α and UCP1 protein expression were only enhanced upon maternal and post-weaning HFD in sWAT and pWAT of female offspring. Increased metrnl expression in adipose were observed in sex- and depot-specific manner, while enhanced circulating metrnl level was only observed in male offspring undergoing maternal HFD. Palmitic acid changed metrnl expression during preadipocytes differentiation and siRNA-mediated knockdown of metrnl inhibited preadipocyte differentiation. Female offspring were more prone to resist adverse outcomes induced by maternal and post-weaning overnutrition, which probably related to metrnl expression and thermogenesis.

Aerobic training with moderate or high doses of vitamin D improve liver enzymes, LXRα and PGC-1α levels in rats with T2DM

Dysregulation of key transcription factors involved in hepatic energy metabolism, such as peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) and liver X receptor alpha (LXRα), has been observed in T2DM. The present study aims to investigate the effects of aerobic training and vitamin D supplementation on liver enzyme levels and the levels of PGC-1α and LXRα proteins in hepatocytes, in a rat model of T2DM. The study involved 56 male Wistar rats, divided into two groups: one was non-diabetic and acted as a control group (n = 8), and the other had induced diabetes (n = 48). The diabetic rats were then split into six subgroups: two groups received high or moderate doses of vitamin D and aerobic training (D + AT + HD and D + AT + MD); two groups received high or moderate doses of vitamin D alone (D + HD and D + MD); one group underwent aerobic training with vehicle (sesame oil; D + AT + oil), and one group was a diabetic control receiving only sesame oil (oil-receiving). The D + AT + HD and D + HD groups received 10,000 IU of vitamin D, while the D + AT + MD and D + MD groups received 5000 IU of vitamin D once a week by injection. The D + AT + oil group and the sham group received sesame oil. After eight weeks of treatment, body weight, BMI, food intake, serum insulin, glucose, 25-hydroxyvitamin D, ALT, AST, and visceral fat were measured. The levels of PGC-1α and LXRα proteins in the liver was assessed by western blotting. Statistical analysis was performed using the paired t-test, one-way analysis of variance (ANOVA), and the Tukey post hoc test at a significance level of P < 0.05. Body weight, food intake, and BMI decreased significantly in the D + AT + HD, D + AT + MD, D + AT + oil, D + HD, and D + MD groups with the highest reduction being observed in body weight and BMI in the D + AT + HD group. The D + AT + HD group exhibited the lowest levels of insulin, glucose, and HOMA-IR while the D + C group exhibited the highest levels among the diabetic groups. The D + AT + HD and D + AT + MD groups had lower levels of ALT and AST enzymes compared to the other groups with no significant difference between D + AT + HD and D + AT + MD. D + AT + HD (p = 0.001), D + AT + MD (p = 0.001), D + HD (p = 0.023), D + MD (p = 0.029), and D + AT + oil (p = 0.011) upregulated LXRα compared to D + C. Among these groups, D + AT + HD exhibited a more profound upregulation of LXRα than D + AT + MD, D + AT + oil, D + HD, and D + MD (p = 0.005; p = 0.002, p = 0.001, and p = 0.001, respectively). Similarly, D + AT + HD showed a more notable upregulation of PGC-1α compared to D + AT + oil, D + HD, and D + MD (p = 0.002; p = 0.001, and p = 0.001, respectively). Pearson correlation tests showed significant and negative correlations between serum 25-hydroxyvitamin levels and both visceral fat (r = - 0.365; p = 0.005) and HOMA-IR (r = - 0.118; p = 0.009); while positive and significant correlations between the liver-to-bodyweight ratio with both ALT and AST enzymes and also between QUICKI levels with LXRα (r = 0.578; p = 0.001) and PGC-1α (r = 0.628; p = 0.001). Combined administration of aerobic training and vitamin D supplementation potentially improves liver enzymes in type-2 diabetic rats that were simultaneous with upregulating the levels of PGC-1α and LXRα proteins in hepatocytes. These improvements were more significant when combining exercise with high-dose vitamin D supplementation. This study highlights the potential of this combination therapy as a new diabetes treatment strategy.

Role of hydrogen sulfide in the regulation of lipid metabolism: Implications on cardiovascular health

The World Health Organization (WHO) defines obesity as an urgency for health and a social emergency. Today around 39 % of people is overweight, of these over 13 % is obese. It is well-consolidated that the adipose cells are deputy to lipid storage under caloric excess; however, despite the classical idea that adipose tissue has exclusively a passive function, now it is known to be deeply involved in the regulation of systemic metabolism in physiological as well as under obesogenic conditions, with consequences on cardiovascular health. Beside two traditional types of adipose cells (white and brown), recently the beige one has been highlighted as the consequence of the healthy remodeling of white adipocytes, confirming their metabolic adaptability. In this direction, pharmacological, nutraceutical and nutrient-based approaches are addressed to positively influence inflammation and metabolism, thus contributing to reduce the obese-associated cardiovascular risk. In this scenario, hydrogen sulfide emerges as a new mediator that may regulate crucial targets involved in the regulation of metabolism. The current evidence demonstrates that hydrogen sulfide may induce peroxisome proliferator activated receptor γ (PPARγ), a crucial mediator of adipogenesis, inhibit the phosphorylation of perlipin-1 (plin-1), a protein implicated in the lipolysis, and finally promote browning process, through the release of irisin from skeletal muscle. The results summarized in this review suggest an important role of hydrogen sulfide in the regulation of metabolism and in the prevention/treatment of obese-associated cardiovascular diseases and propose new insight on the putative mechanisms underlying the release of hydrogen sulfide or its biosynthesis, delineating a further exciting field of application.

Exercise couples mitochondrial function with skeletal muscle fiber type via ROS-mediated epigenetic modification

Skeletal muscle is a heterogeneous tissue composed of different types of muscle fibers, demonstrating substantial plasticity. Physiological or pathological stimuli can induce transitions in muscle fiber types. However, the precise regulatory mechanisms behind these transitions remains unclear. This paper reviews the classification and characteristics of muscle fibers, along with the classical mechanisms of muscle fiber type transitions. Additionally, the role of exercise-induced muscle fiber type transitions in disease intervention is reviewed. Epigenetic pathways mediate cellular adaptations and thus represent potential targets for regulating muscle fiber type transitions. This paper focuses on the mechanisms by which epigenetic modifications couple mitochondrial function and contraction characteristics. Reactive Oxygen Species (ROS) are critical signaling regulators for the health-promoting effects of exercise. Finally, we discuss the role of exercise-induced ROS in regulating epigenetic modifications and the transition of muscle fiber types.

New Insights into Antioxidant Peptides: An Overview of Efficient Screening, Evaluation Models, Molecular Mechanisms, and Applications

Antioxidant peptides are currently a hotspot in food science, pharmaceuticals, and cosmetics. In different fields, the screening, activity evaluation, mechanisms, and applications of antioxidant peptides are the pivotal areas of research. Among these topics, the efficient screening of antioxidant peptides stands at the forefront of cutting-edge research. To this end, efficient screening with novel technologies has significantly accelerated the research process, gradually replacing the traditional approach. After the novel antioxidant peptides are screened and identified, a time-consuming activity evaluation is another indispensable procedure, especially in in vivo models. Cellular and rodent models have been widely used for activity evaluation, whilst non-rodent models provide an efficient solution, even with the potential for high-throughput screening. Meanwhile, further research of molecular mechanisms can elucidate the essence underlying the activity, which is related to several signaling pathways, including Keap1-Nrf2/ARE, mitochondria-dependent apoptosis, TGF-β/SMAD, AMPK/SIRT1/PGC-1α, PI3K/Akt/mTOR, and NF-κB. Last but not least, antioxidant peptides have broad applications in food manufacture, therapy, and the cosmetics industry, which requires a systematic review. This review introduces novel technologies for the efficient screening of antioxidant peptides, categorized with a new vision. A wide range of activity evaluation assays, encompassing cellular models, as well as rodent and non-rodent models, are provided in a comprehensive manner. In addition, recent advances in molecular mechanisms are analyzed with specific cases. Finally, the applications of antioxidant peptides in food production, therapy, and cosmetics are systematically reviewed.

Coenzyme Q10 Protects Against Hyperlipidemia-Induced Osteoporosis by Improving Mitochondrial Function via Modulating miR-130b-3p/PGC-1α Pathway

In hyperlipidemia-induced osteoporosis, bone marrow mesenchymal stem cells (BMSCs) differentiate into more adipocytes than osteoblasts, leading to decreased bone formation. It is vital to elucidate the effects of hyperlipidemia on bone metabolism and seek new agents that regulate adipocyte-osteoblast lineage allocation. CoQ10, a rate-limiting coenzyme of the mitochondrial respiratory chain, has been reported to decrease oxidative stress and lipid peroxidation by functioning as a mitochondrial antioxidant. However, its effect on hyperlipidemia-induced osteoporosis remains unknown. Here, we analyzed the therapeutic mechanisms of CoQ10 on hyperlipidemia-induced osteoporosis by using high-fat diet (HFD)-treated ApoE-/- mice or oxidized low-density lipoprotein (ox-LDL)-treated BMSCs. The serum lipid levels were elevated and bone formation-related markers were decreased in HFD-treated ApoE-/- mice and ox-LDL-treated BMSCs, which could be reversed by CoQ10. Additionally, PGC-1α protein expression was decreased in HFD-treated ApoE-/- mice and ox-LDL-treated BMSCs, accompanied by mitochondrial dysfunction, decreased ATP content and overgeneration of reactive oxygen species (ROS), which could also be antagonized by CoQ10. Furthermore, PGC-1α knockdown in vitro promoted ROS generation, BMSC apoptosis, and adipogenic differentiation while attenuating osteogenic differentiation in BMSCs. Mechanistically, it suggested that the expression of PGC1-α protein was increased with miR-130b-3p inhibitor treatment in osteoporosis under hyperlipidemia conditions to improve mitochondrial function. Collectively, CoQ10 alleviates hyperlipidemia-induced osteoporosis in ApoE-/- mice and regulates adipocyte-osteoblast lineage allocation. The possible underlying mechanism may involve the improvement of mitochondrial function by modulating the miR-130b-3p/PGC-1α pathway.

Long-term iron supplementation combined with vitamin B6 enhances maximal oxygen uptake and promotes skeletal muscle-specific mitochondrial biogenesis in rats

Introduction

Iron is an essential micronutrient that plays a crucial role in various biological processes. Previous studies have shown that iron supplementation is related to exercise performance and endurance capacity improvements. However, the underlying mechanisms responsible for these effects are not well understood. Recent studies have suggested the beneficial impact of iron supplementation on mitochondrial function and its ability to rescue mitochondrial function under adverse stress in vitro and rodents. Based on current knowledge, our study aimed to investigate whether the changes in exercise performance resulting from iron supplementation are associated with its effect on mitochondrial function.

Methods

In this study, we orally administered an iron-based supplement to rats for 30 consecutive days at a dosage of 0.66 mg iron/kg body weight and vitamin B6 at a dosage of 0.46 mg/kg.

Results

Our findings reveal that long-term iron supplementation, in combination with vitamin B6, led to less body weight gained and increased VO2 max in rats. Besides, the treatment substantially increased Complex I- and Complex II-driven ATP production in intact mitochondria isolated from gastrocnemius and cerebellum. However, the treatment did not change basal and succinate-induced ROS production in mitochondria from the cerebellum and skeletal muscle. Furthermore, the iron intervention significantly upregulated several skeletal muscle mitochondrial biogenesis and metabolism-related biomarkers, including PGC-1α, SIRT1, NRF-2, SDHA, HSL, MTOR, and LON-P. However, it did not affect the muscular protein expression of SIRT3, FNDC5, LDH, FIS1, MFN1, eNOS, and nNOS. Interestingly, the iron intervention did not exert similar effects on the hippocampus of rats.

Discussion

In conclusion, our study demonstrates that long-term iron supplementation, in combination with vitamin B6, increases VO2 max, possibly through its positive role in regulating skeletal muscle-specific mitochondrial biogenesis and energy production in rats.

Obesity-induced PARIS (ZNF746) accumulation in adipose progenitor cells leads to attenuated mitochondrial biogenesis and impaired adipogenesis

White adipose tissue (WAT) is critical for whole-body energy metabolism, and its dysfunction leads to various metabolic disorders. In recent years, many studies have suggested that impaired mitochondria may contribute to obesity-related decline in adipose tissue function, but the detailed mechanisms remain unclear. To investigate these mechanisms, we carried out a comprehensive analysis of WAT from mice with diet-induced obesity. We discovered the transcription factor Parkin interactive substrate (PARIS or ZNF746), which suppresses the expression of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), a key regulator of mitochondrial biogenesis, to be accumulated in adipose progenitor cells from obese mice. Furthermore, we demonstrated that 3T3-L1 preadipocytes with overexpression of PARIS protein exhibited decreased mitochondrial biogenesis and impaired adipogenesis. Our results suggest that the accumulation of PARIS protein may be a novel component in the pathogenesis of obesity-related dysfunction in WAT.

Restoring the infected powerhouse: Mitochondrial quality control in sepsis

Sepsis is a dysregulated host response to an infection, characterized by organ failure. The pathophysiology is complex and incompletely understood, but mitochondria appear to play a key role in the cascade of events that culminate in multiple organ failure and potentially death. In shaping immune responses, mitochondria fulfil dual roles: they not only supply energy and metabolic intermediates crucial for immune cell activation and function but also influence inflammatory and cell death pathways. Importantly, mitochondrial dysfunction has a dual impact, compromising both immune system efficiency and the metabolic stability of end organs. Dysfunctional mitochondria contribute to the development of a hyperinflammatory state and loss of cellular homeostasis, resulting in poor clinical outcomes. Already in early sepsis, signs of mitochondrial dysfunction are apparent and consequently, strategies to optimize mitochondrial function in sepsis should not only prevent the occurrence of mitochondrial dysfunction, but also cover the repair of the sustained mitochondrial damage. Here, we discuss mitochondrial quality control (mtQC) in the pathogenesis of sepsis and exemplify how mtQC could serve as therapeutic target to overcome mitochondrial dysfunction. Hence, replacing or repairing dysfunctional mitochondria may contribute to the recovery of organ function in sepsis. Mitochondrial biogenesis is a process that results in the formation of new mitochondria and is critical for maintaining a pool of healthy mitochondria. However, exacerbated biogenesis during early sepsis can result in accumulation of structurally aberrant mitochondria that fail to restore bioenergetics, produce excess reactive oxygen species (ROS) and exacerbate the disease course. Conversely, enhancing mitophagy can protect against organ damage by limiting the release of mitochondrial-derived damage-associated molecules (DAMPs). Furthermore, promoting mitophagy may facilitate the growth of healthy mitochondria by blocking the replication of damaged mitochondria and allow for post sepsis organ recovery through enabling mitophagy-coupled biogenesis. The remaining healthy mitochondria may provide an undamaged scaffold to reproduce functional mitochondria. However, the kinetics of mtQC in sepsis, specifically mitophagy, and the optimal timing for intervention remain poorly understood. This review emphasizes the importance of integrating mitophagy induction with mtQC mechanisms to prevent undesired effects associated with solely the induction of mitochondrial biogenesis.

Physical exercise ameliorates age-related deterioration of skeletal muscle and mortality by activating Pten-related pathways in Drosophila on a high-salt diet

The phosphatase and tensin congeners (Pten) gene affects cell growth, cell proliferation, and rearrangement of connections, and it is closely related to cellular senescence, but it remains unclear the role of muscle-Pten gene in exercise against age-related deterioration in skeletal muscle and mortality induced by a high-salt diet (HSD). In here, overexpression and knockdown of muscle Pten gene were constructed by building MhcGAL4 /PtenUAS-overexpression and MhcGAL4 /PtenUAS-RNAi system in flies, and flies were given exercise training and a HSD for 2 weeks. The results showed that muscle Pten knockdown significantly reduced the climbing speed, climbing endurance, GPX activity, and the expression of Pten, Sirt1, PGC-1α genes, and it significantly increased the expression of Akt and ROS level, and impaired myofibril and mitochondria of aged skeletal muscle. Pten knockdown prevented exercise from countering the HSD-induced age-related deterioration of skeletal muscle. Pten overexpression has the opposite effect on skeletal muscle aging when compared to it knockdown, and it promoted exercise against HSD-induced age-related deterioration of skeletal muscle. Pten overexpression significantly increased lifespan, but its knockdown significantly decreased lifespan of flies. Thus, current results confirmed that differential expression of muscle Pten gene played an important role in regulating skeletal muscle aging and lifespan, and it also affected the adaptability of aging skeletal muscle to physical exercise since it determined the activity of muscle Pten/Akt pathway and Pten/Sirt1/PGC-1α pathway.

Regulation of PGC-1α of the Mitochondrial Energy Metabolism Pathway in the Gills of Indian Medaka (Oryzias dancena) under Hypothermal Stress

Ectothermic fish exposure to hypothermal stress requires adjusting their metabolic molecular machinery, which was investigated using Indian medaka (Oryzias dancena; 10 weeks old, 2.5 ± 0.5 cm) cultured in fresh water (FW) and seawater (SW; 35‱) at room temperature (28 ± 1 °C). The fish were fed twice a day, once in the morning and once in the evening, and the photoperiod was 12 h:12 h light: dark. In this study, we applied two hypothermal treatments to reveal the mechanisms of energy metabolism via pgc-1α regulation in the gills of Indian medaka; cold-stress (18 °C) and cold-tolerance (extreme cold; 15 °C). The branchial ATP content was significantly higher in the cold-stress group, but not in the cold-tolerance group. In FW- and SW-acclimated medaka, the expression of genes related to mitochondrial energy metabolism, including pgc-1α, prc, Nrf2, tfam, and nd5, was analyzed to illustrate differential responses of mitochondrial energy metabolism to cold-stress and cold-tolerance environments. When exposed to cold-stress, the relative mRNA expression of pgc-1α, prc, and Nrf2 increased from 2 h, whereas that of tfam and nd5 increased significantly from 168 h. When exposed to a cold-tolerant environment, prc was significantly upregulated at 2 h post-cooling in the FW and SW groups, and pgc-1α was significantly upregulated at 2 and 12 h post-cooling in the FW group, while tfam and nd5 were downregulated in both FW and SW fish. Hierarchical clustering revealed gene interactions in the cold-stress group, which promoted diverse mitochondrial energy adaptations, causing an increase in ATP production. However, the cold-tolerant group demonstrated limitations in enhancing ATP levels through mitochondrial regulation via the PGC-1α energy metabolism pathway. These findings suggest that ectothermic fish may develop varying degrees of thermal tolerance over time in response to climate change. This study provides insights into the complex ways in which fish adjust their metabolism when exposed to cold stress, contributing to our knowledge of how they adapt.

Transcriptomics and metabolomics reveal improved performance of Hu sheep on hybridization with Southdown sheep

Consumers are increasingly demanding high-quality mutton. Cross breeding can improve meat quality and is widely used in sheep breeding. However, little is known about the molecular mechanism of cross breeding sheep meat quality. In this study, male Southdown and female Hu sheep were hybridized. The slaughter performance and longissimus dorsi quality of the 6-month-old hybrid offspring were measured, and the longissimus dorsi of the hybrid offspring was analyzed by transcriptomics and metabolomics to explore the effect of cross breeding on meat quality. The results showed that the production performance of Southdown × Hu F1 sheep was significantly improved, the carcass fat content was significantly decreased, and the eating quality of Southdown × Hu F1 sheep were better. Compared with the HS group (Hu × Hu), the NH group (Southdown × Hu) had 538 differentially expressed genes and 166 differentially expressed metabolites (P < 0.05), which were significantly enriched in amino acid metabolism and other related pathways. Up-regulated genes METTL21C, PPARGC1A and down-regulated gene WFIKKN2 are related to muscle growth and development. Among them, the METTL21C gene, which is related to muscle development, was highly correlated with carnosine, a metabolite related to meat quality (correlation > 0.6 and P < 0.05). Our results provide further understanding of the molecular mechanism of cross breeding for sheep muscle growth and meat quality optimization.

Cold-inducible PPA1 is critical for the adipocyte browning in mice

Promoting the thermogenic capacity of brown/beige adipocytes is becoming a promising strategy to counteract obesity and related metabolic diseases. Inorganic pyrophosphatase 1 (PPA1) is an enzyme that catalyzes the hydrolysis of PPi to Pi, and its presence is required for anabolism to take place in cells. Our previous study demonstrated the importance of PPA1 in maintaining adipose tissue function and whole-body metabolic homeostasis. In this study, we found that the expression of PPA1 was positively associated with the thermogenic capacity of brown/beige adipocytes. PPA1+/- mice exhibited less browning capacity in subcutaneous white adipose tissue compared to wild-type mice and also showed apparent cold intolerance. We found that decreased PPA1 abundance may lead to mitochondrial dysfunction and inhibited adipocyte browning both in vivo and in vitro. Furthermore, our study also revealed that PPA1 worked as a new target gene of nuclear respiratory factor 1 (NRF1), a major transcription regulator of mitochondrial biogenesis. Together, our findings indicated an essential role of PPA1 in mitochondrial function and browning in adipocytes and suggested PPA1 as a new therapeutic target for increasing thermogenesis to combat obesity and metabolic diseases.

Epicatechin promotes oocyte quality in mice during repeated superovulation

The negative impacts of repeated superovulation on mitochondrial function and oocyte quality remain unresolved. Epicatechin (EC), a polyphenolic compound found in the human diet with strong antioxidant activity, was investigated for its effects and underlying mechanism on embryonic development after repeated superovulation. The results showed that as the number of superovulation cycles increased, the number of 2-cell embryos decreased, the development of embryos in subsequent in vitro culture was delayed, the apoptosis rate of blastocyst cells increased and the number of blastocyst cells decreased. However, intraperitoneal injection of EC (10 mg/kg body-weight) for two consecutive days during repeated superovulation increased mitochondrial DNA copies in 2-cell embryos of mice. It also promoted the expression of antioxidant enzyme genes in ovaries, increased the content of glutathione (GSH) content and improved the antioxidant capacity of ovaries. Altogether, these results revealed that intraperitoneal injection of EC could increase the embryonic mitochondrial DNA copy number (mtDNA-CN) and enhance the ovary's antioxidant capacity and GSH content, ultimately promoting the quality of mouse embryos in the process of repeated superovulation.

Maternal and paternal obesity differentially reprogram the ovarian mitochondrial biogenesis of F1 female rats

Obesity has harmful consequences on reproductive outcomes and the rapid increase in obesity is assumed to be influenced by epigenetics and trans-generation effects. Our study aimed to explore the effect of maternal and/or paternal obesity on the ovarian tissues of the first-generation female offspring in rats. The study was conducted on 40 adult Wistar albino rats (20 males and 20 females). Obesity was induced by feeding them an obesogenic diet for 3 months. The pregnancy was induced in the females by mating with males in four combinations: healthy mother with healthy father (control parents, CP), healthy mother with obese fathers (OF), obese mothers with healthy father (OM), and obese mother with obese father (obese parents, OP). After delivery, the female offspring at two months were sacrificed, and the blood and ovarian tissues were collected to assess the studied parameters. Our result showed differential impacts of maternal and paternal obesity on the ovarian health of the female offspring. The female offspring of obese OM or OP showed early signs of obesity. These metabolic abnormalities were associated with signs of ovarian lesions, impaired folliculogenesis, and decreased oocyte quality and also showed significant alterations in mitochondrial biogenesis, redox status, inflammation, and microRNAs expression (miR-149 and miR-494). In conclusion, altered ovarian expression of microRNAs and associated impaired mitochondrial biogenesis pathways may be the root causes for the observed intergeneration transmission of the obesogenic phenotype.

Mitochondrial dysfunction and skeletal muscle atrophy: Causes, mechanisms, and treatment strategies

Skeletal muscle, which accounts for approximately 40% of total body weight, is one of the most dynamic and plastic tissues in the human body and plays a vital role in movement, posture and force production. More than just a component of the locomotor system, skeletal muscle functions as an endocrine organ capable of producing and secreting hundreds of bioactive molecules. Therefore, maintaining healthy skeletal muscles is crucial for supporting overall body health. Various pathological conditions, such as prolonged immobilization, cachexia, aging, drug-induced toxicity, and cardiovascular diseases (CVDs), can disrupt the balance between muscle protein synthesis and degradation, leading to skeletal muscle atrophy. Mitochondrial dysfunction is a major contributing mechanism to skeletal muscle atrophy, as it plays crucial roles in various biological processes, including energy production, metabolic flexibility, maintenance of redox homeostasis, and regulation of apoptosis. In this review, we critically examine recent knowledge regarding the causes of muscle atrophy (disuse, cachexia, aging, etc.) and its contribution to CVDs. Additionally, we highlight the mitochondrial signaling pathways involvement to skeletal muscle atrophy, such as the ubiquitin-proteasome system, autophagy and mitophagy, mitochondrial fission-fusion, and mitochondrial biogenesis. Furthermore, we discuss current strategies, including exercise, mitochondria-targeted antioxidants, in vivo transfection of PGC-1α, and the potential use of mitochondrial transplantation as a possible therapeutic approach.

Mitochondrial dysfunction in aging

Aging is a complex process that features a functional decline in many organelles. Although mitochondrial dysfunction is suggested as one of the determining factors of aging, the role of mitochondrial quality control (MQC) in aging is still poorly understood. A growing body of evidence points out that reactive oxygen species (ROS) stimulates mitochondrial dynamic changes and accelerates the accumulation of oxidized by-products through mitochondrial proteases and mitochondrial unfolded protein response (UPRmt). Mitochondrial-derived vesicles (MDVs) are the frontline of MQC to dispose of oxidized derivatives. Besides, mitophagy helps remove partially damaged mitochondria to ensure that mitochondria are healthy and functional. Although abundant interventions on MQC have been explored, over-activation or inhibition of any type of MQC may even accelerate abnormal energy metabolism and mitochondrial dysfunction-induced senescence. This review summarizes mechanisms essential for maintaining mitochondrial homeostasis and emphasizes that imbalanced MQC may accelerate cellular senescence and aging. Thus, appropriate interventions on MQC may delay the aging process and extend lifespan.

High-Fat Diet Promotes Adipogenesis in Offspring Female Rats Induced by Perinatal Exposure to 4-Nonylphenol

Background

Both high-fat diet (HFD) and 4-nonylphenol (4-NP) could affect fat formation in adipose tissue individually. We investigated whether HFD promote abnormal adipose tissue formation caused by early exposure to 4-NP in life and preliminarily explore the possible mechanisms involved.

Methods

The first-generation rats were treated with HFD on postnatal day after pregnant rats exposure to 5 ug/kg/day 4-NP. Then, the second generation rats started to only receive normal diet without 4-NP or HFD. We analyzed organ coefficient and histopathology of fat tissues, biochemical index, and gene level involved in lipid metabolism in female offspring rats.

Results

HFD and 4-NP interaction synergistically increased birth weight, body weight, and organ coefficients of adipose tissue in offspring female rats. HFD accelerately aggravated abnormal lipid metabolism and increased the adipocyte mean areas around the uterus of the offspring female rats induced by prenatal exposure to 4-NP. HFD also facilitate the regulation of gene expression involved lipid metabolism in offspring female rats induced by perinatal exposure to 4-NP, even passed on to the second generation of female rats. Moreover, HFD and 4-NP interaction synergistically declined the gene and protein expression of estrogen receptor (ER) in the adipose tissue of second-generation female rats.

Conclusion

HFD and 4-NP synergistically regulate the expression of lipid metabolism genes in adipose tissue of F2 female rats and promote adipose tissue generation, leading to obesity in offspring rats, which is closely related to low expression of ER. Therefore, ER genes and proteins may be involved in the synergistic effect of HFD and 4-NP.

MDFI regulates fast-to-slow muscle fiber type transformation via the calcium signaling pathway

Muscle fiber is the basic unit of skeletal muscle with strong self-adaptability, and its type is closely related to meat quality. Myod family inhibitor (Mdfi) has the function of regulating myogenic regulatory factors during cell differentiation, but how Mdfi regulates muscle fiber type transformation in myoblasts is still unclear. In the present study, we constructed overexpressing and interfering with Mdfi C2C12 cell models by lipofection. The immunofluorescence, quantitative real-time PCR (qPCR), and western blot results show that the elevated MDFI promoted mitochondrial biogenesis, aerobic metabolism and the calcium level by activating CaMKK2 and AMPK phosphorylation and then stimulated the conversion of C2C12 cells from fast glycolytic to slow oxidative type. In addition, after inhibiting IP3R and RYR channels, the higher MDFI reversed the blockage of calcium release from the endoplasmic reticulum by calcium channel receptor inhibitors and increased intracellular calcium levels. Therefore, we propose that the higher MDFI promotes muscle fiber types conversion through the calcium signaling pathway. These findings further broaden our understanding of the regulatory mechanism of MDFI in muscle fiber type transformation. Furthermore, our results suggest potential therapeutic targets for skeletal muscle and metabolic-related diseases.

Influence of Polyphenols on Adipose Tissue: Sirtuins as Pivotal Players in the Browning Process

Adipose tissue (AT) can be classified into two different types: (i) white adipose tissue (WAT), which represents the largest amount of total AT, and has the main function of storing fatty acids for energy needs and (ii) brown adipose tissue (BAT), rich in mitochondria and specialized in thermogenesis. Many exogenous stimuli, e.g., cold, exercise or pharmacological/nutraceutical tools, promote the phenotypic change of WAT to a beige phenotype (BeAT), with intermediate characteristics between BAT and WAT; this process is called "browning". The modulation of AT differentiation towards WAT or BAT, and the phenotypic switch to BeAT, seem to be crucial steps to limit weight gain. Polyphenols are emerging as compounds able to induce browning and thermogenesis processes, potentially via activation of sirtuins. SIRT1 (the most investigated sirtuin) activates a factor involved in mitochondrial biogenesis, peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), which, through peroxisome proliferator-activated receptor γ (PPAR-γ) modulation, induces typical genes of BAT and inhibits genes of WAT during the transdifferentiation process in white adipocytes. This review article aims to summarize the current evidence, from pre-clinical studies to clinical trials, on the ability of polyphenols to promote the browning process, with a specific focus on the potential role of sirtuins in the pharmacological/nutraceutical effects of natural compounds.

Revisiting Resveratrol as an Osteoprotective Agent: Molecular Evidence from In Vivo and In Vitro Studies

Resveratrol (RSV) (3,5,4'-trihydroxystilbene) is a stilbene found in abundance in berry fruits, peanuts, and some medicinal plants. It has a diverse range of pharmacological activities, underlining the significance of illness prevention and health promotion. The purpose of this review was to delve deeper into RSV's bone-protective properties as well as its molecular mechanisms. Several in vivo studies have found the bone-protective effects of RSV in postmenopausal, senile, and disuse osteoporosis rat models. RSV has been shown to inhibit NF-κB and RANKL-mediated osteoclastogenesis, oxidative stress, and inflammation while increasing osteogenesis and boosting differentiation of mesenchymal stem cells to osteoblasts. Wnt/β-catenin, MAPKs/JNK/ERK, PI3K/AKT, FoxOs, microRNAs, and BMP2 are among the possible kinases and proteins involved in the underlying mechanisms. RSV has also been shown to be the most potent SIRT1 activator to cause stimulatory effects on osteoblasts and inhibitory effects on osteoclasts. RSV may, thus, represent a novel therapeutic strategy for increasing bone growth and reducing bone loss in the elderly and postmenopausal population.

PGC-1α Is a Master Regulator of Mitochondrial Lifecycle and ROS Stress Response

Mitochondria play a major role in ROS production and defense during their life cycle. The transcriptional activator PGC-1α is a key player in the homeostasis of energy metabolism and is therefore closely linked to mitochondrial function. PGC-1α responds to environmental and intracellular conditions and is regulated by SIRT1/3, TFAM, and AMPK, which are also important regulators of mitochondrial biogenesis and function. In this review, we highlight the functions and regulatory mechanisms of PGC-1α within this framework, with a focus on its involvement in the mitochondrial lifecycle and ROS metabolism. As an example, we show the role of PGC-1α in ROS scavenging under inflammatory conditions. Interestingly, PGC-1α and the stress response factor NF-κB, which regulates the immune response, are reciprocally regulated. During inflammation, NF-κB reduces PGC-1α expression and activity. Low PGC-1α activity leads to the downregulation of antioxidant target genes resulting in oxidative stress. Additionally, low PGC-1α levels and concomitant oxidative stress promote NF-κB activity, which exacerbates the inflammatory response.

The Role of PGC-1α-Mediated Mitochondrial Biogenesis in Neurons

Neurons are highly dependent on mitochondrial ATP production and Ca²⁺ buffering. Neurons have unique compartmentalized anatomy and energy requirements, and each compartment requires continuously renewed mitochondria to maintain neuronal survival and activity. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key factor in the regulation of mitochondrial biogenesis. It is widely accepted that mitochondria are synthesized in the cell body and transported via axons to the distal end. However, axonal mitochondrial biogenesis is necessary to maintain axonal bioenergy supply and mitochondrial density due to limitations in mitochondrial axonal transport rate and mitochondrial protein lifespan. In addition, impaired mitochondrial biogenesis leading to inadequate energy supply and neuronal damage has been observed in neurological disorders. In this review, we focus on the sites where mitochondrial biogenesis occurs in neurons and the mechanisms by which it maintains axonal mitochondrial density. Finally, we summarize several neurological disorders in which mitochondrial biogenesis is affected.

Role of oxidative stress and inflammation-related signaling pathways in doxorubicin-induced cardiomyopathy

Doxorubicin (DOX) is a powerful and commonly used chemotherapeutic drug, used alone or in combination in a variety of cancers, while it has been found to cause serious cardiac side effects in clinical application. More and more researchers are trying to explore the molecular mechanisms of DOX-induced cardiomyopathy (DIC), in which oxidative stress and inflammation are considered to play a significant role. This review summarizes signaling pathways related to oxidative stress and inflammation in DIC and compounds that exert cardioprotective effects by acting on relevant signaling pathways, including the role of Nrf2/Keap1/ARE, Sirt1/p66Shc, Sirt1/PPAR/PGC-1α signaling pathways and NOS, NOX, Fe²⁺ signaling in oxidative stress, as well as the role of NLRP3/caspase-1/GSDMD, HMGB1/TLR4/MAPKs/NF-κB, mTOR/TFEB/NF-κB pathways in DOX-induced inflammation. Hence, we attempt to explain the mechanisms of DIC in terms of oxidative stress and inflammation, and to provide a theoretical basis or new idea for further drug research on reducing DIC. Video Abstract.