DHA alleviates diet-induced skeletal muscle fiber remodeling via FTO/m6A/DDIT4/PGC1α signaling

METTL14-mediated m6A modification of DDIT4 promotes its mRNA stability in aging-related idiopathic pulmonary fibrosis

Although N6-methyladenosine (m6A) may be related to the pathogenesis of fibrotic process, the mechanism of m6A modification in aging-related idiopathic pulmonary fibrosis (IPF) remains unclear. Three-milliliter venous blood was collected from IPF patients and healthy controls. MeRIP-seq and RNA-seq were utilized to investigate differential m6A modification. The expressions of identified m6A regulator and target gene were validated using MeRIP-qPCR and real-time PCR. Moreover, we established an animal model and a senescent model of A549 cells to explore the associated molecular mechanism. Our study provided a panorama of m6A methylation in IPF. Increased peaks (3756) and decreased peaks (4712) were observed in the IPF group. The association analysis showed that 749 DEGs were affected by m6A methylation in IPF. Among the m6A regulators, the expression of METTL14 decreased in IPF. The m6A level of our interested gene DDIT4 decreased significantly, but the mRNA level of DDIT4 was higher in IPF. This was further verified in bleomycin-induced pulmonary fibrosis. At the cellular level, it was further confirmed that METTL14 and DDIT4 might participate in the senescence of alveolar epithelial cells. The downregulation of METTL14 might inhibit the decay of DDIT4 mRNA by reducing the m6A modification level of DDIT4 mRNA, leading to high expression of DDIT4 mRNA and protein. Our study provided a panorama of m6A alterations in IPF and discovered METTL14 as a potential intervention target for epigenetic modification in IPF. These results pave the way for future investigations regarding m6A modifications in aging-related IPF.

ETV5-Mediated Transcriptional Repression of DDIT4 Blocks Macrophage Pro-Inflammatory Activation in Diabetic Atherosclerosis

Atherosclerosis risk is elevated in diabetic patients, but the underlying mechanism such as the involvement of macrophages remains unclear. Here, we investigated the underlying mechanism related to the pro-inflammatory activation of macrophages in the development of diabetic atherosclerosis. Bioinformatics tools were used to analyze the macrophage-related transcriptome differences in patients with atherosclerosis and diabetic mice. LDLR-/- mice with DDIT4 depletion were generated and fed a Western diet to induce atherosclerosis. DDIT4 expression was elevated in diabetic mice and patients with atherosclerosis. Macrophage proinflammatory factors F4/80, Il-6, and TNFα were reduced in DDIT4-/-LDLR-/- mice and necrotic areas were decreased in the aortic root. Atherosclerotic plaque stability was increased in DDIT4-/-LDLR-/- mice, as evidenced by increased collagen and smooth muscle cell content. DDIT4, regulated by ETV5, acted on macrophages, affecting lipid accumulation, migration capacity, and pro-inflammatory responses. Knockdown of ETV5 increased expression of DDIT4 and pro-inflammatory factors in macrophages, increased necrotic core area in the aortic root, and decreased stability of atherosclerotic plaques in mice, which was abated by DDIT4 knockdown. The findings provide new insight into how diabetes promotes atherosclerosis and support a model wherein loss of ETV5 sustains transcription of DDIT4 and the pro-inflammatory activation of macrophages.

Alginate oligosaccharides relieve estrogen-deprived osteosarcopenia by affecting intestinal Th17 differentiation and systemic inflammation through the manipulation of bile acid metabolism

Alginate oligosaccharides (AOS) have gained attention for their capacity to regulate human health as prebiotics. Osteosarcopenia is a progressive disease of the musculoskeletal system and result in heavy burden of patients. Studies suggest that gut microbiota is involved in the pathogenesis of osteosarcopenia, whether AOS can improve the symptoms of osteosarcopenia by modulating gut microbiota remains to be elucidated. In this study, we proved that 200 mg/kg body weight AOS (MW = 4.9 kDa, G/M = 1.88) treatment significantly increased bone mass, boosted muscle function, and promoted gut barrier integrity in ovariectomized (OVX) mice. After AOS treatment, a marked reduction in the proportion of intestinal Th17 subsets and in peripheral levels of relevant inflammatory cytokines was observed compared to the OVX group. 16S rRNA sequencing indicated that AOS treatment could restore the imbalance of gut microbiota caused by estrogen deficiency. Additionally, the impact of AOS on bile acid changes was revealed according to metabolomics. In particular, the Th17 differentiation inhibitor, such as isoLCA, were significantly upregulated after AOS treatment. In conclusion, AOS can alleviate the symptoms of osteoporosis by modulating the relative abundance of gut microbiota and bile acid metabolism, thereby reducing the proportion of intestinal Th17 cells and peripheral Inflammation.

Acute exercise promotes WAT browning by remodeling mRNA m6A methylation

AIMS

Regular exercise promotes the beiging and metabolic adaptations of white adipose tissue (WAT) through the cumulative transcriptional responses that occur after each exercise session. However, the effects of a single bout of acute exercise and the role of N6-methyladenosine (m6A) in these adaptations remain unclear. We aim to investigate this further.

MATERIALS AND METHODS

We constructed mouse models for chronic (8 weeks of running) and acute (single 1-hour run) exercise to study the effects on white adipose tissue (WAT) metabolism and beiging through metabolic phenotyping and transcriptome sequencing. Additionally, we explored the impact of acute exercise on WAT m6A modification and target genes, combining m6A regulators with cell models to elucidate the role of m6A in WAT exercise adaptation.

KEY FINDINGS

Here, we reveal that upregulated m6A modification after acute exercise induces the formation of glycolytic beige fat (g-beige fat) in WAT. Mechanistically, the metabolite β-hydroxybutyrate (BHBA) secreted after acute exercise upregulates m6A modification in WAT. This enhances m6A-dependent translation of the histone acetyltransferase CREBBP, promoting the transcription of key beiging genes by increasing chromatin accessibility. Pharmacologically elevating circulating BHBA mimics the metabolic response induced by acute exercise, upregulating m6A modification and its downstream signals. Additionally, BHBA exhibits long-term effects, improving metabolic homeostasis in obesity by promoting thermogenesis in WAT.

SIGNIFICANCE

Our results reveal the role of metabolites in WAT metabolic adaptation through m6A-mediated chromatin accessibility after acute exercise, providing a novel therapeutic target for regulating WAT metabolism from a nutritional epigenetics perspective.

The molecular regulated mechanism of METTL3 and FTO in lipid metabolism of Hu sheep

BACKGROUND

Balanced lipid metabolism can improve the growth performance and meat quality of livestock. The m6A methylation-related genes METTL3 and FTO play important roles in animal lipid metabolism; however, the mechanism through which they regulate lipid metabolism in sheep is unclear.

RESULTS

We established lipid deposition models of hepatocytes and preadipocytes in Hu sheep. In the hepatocyte lipid deposition model, the genes expression levels of FABP4, Accα, ATGL and METTL3, METTL14, and FTO-were significantly up-regulated after lipid deposition (P < 0.05). Transcriptomic and metabolomic analyses showed that lipid deposition had a significant effect on MAPK, steroid biosynthesis, and glycerophospholipid metabolism pathway in hepatocytes. The m6A methylation level decreased but the difference was not significant after METTL3 interference, and the expression levels of FABP4 and ATGL increased significantly (P < 0.05); the m6A methylation level significantly increased following METTL3 overexpression, and LPL and ATGL expression levels significantly decreased (P < 0.05), indicating that overexpression of METTL3 inhibited the expression of lipid deposition-related genes in a m6A-dependent manner. The m6A methylation level was significantly increased, ATGL expression was significantly decreased (P < 0.05), and LPL, FABP4, and Accα expression was not significantly changed following FTO interference (P > 0.05); the m6A methylation level was significantly decreased after FTO overexpression, and LPL, FABP4, and ATGL expression was significantly increased (P < 0.05), indicating that FTO overexpression increased the expression of lipid deposition-related genes in a m6A-dependent manner. Transcriptomic and metabolomic analyses showed that m6A methylation modification mainly regulated lipid metabolism through triglyceride metabolism, adipocytokine signaling, MAPK signaling, and fat digestion and absorption in hepatocytes. In the lipid deposition model of preadipocytes, the regulation of gene expression is the same as that in hepatocytes.

CONCLUSIONS

METTL3 significantly inhibited the expression of lipid deposition-related genes, whereas FTO overexpression promoted lipid deposition. Our study provides a theoretical basis and reference for accurately regulating animal lipid deposition by mastering METTL3 and FTO genes to promote high-quality animal husbandry.

Long-chain n-3 polyunsaturated fatty acid supplementation and neuromuscular function in older adults

PURPOSE OF REVIEW

This review aims to explore the latest research investigating the effects of marine-derived long-chain n -3 polyunsaturated fatty acid (LC n -3 PUFA) supplementation on neuromuscular function in older adults.

RECENT FINDINGS

Ageing results in a decline in skeletal muscle strength and mass. There is growing evidence that LC n -3 PUFA supplementation increases muscle strength and mass in healthy older adults, yet the mechanisms underlying these effects remain elusive. Recent studies investigating LC n -3 PUFA supplementation have demonstrated effects on neuromuscular function such as increases in the compound muscle action potential (M-wave) amplitude and surface electromyography alongside increases in muscular strength. Therefore, evidence suggests that LC n -3 PUFA may elicit a beneficial effect at the neuromuscular junction and possess neuroprotective properties in older adults.

SUMMARY

LC n -3 PUFA supplementation may increase or maintain neuromuscular function throughout the ageing process. Further research is warranted to investigate the long-term effects LC n -3 PUFA supplementation on neuromuscular outcomes such as single motor unit properties and cortical/supraspinal networks, utilizing state-of-the-art techniques in neuromuscular physiology.

Light-phase time-restricted feeding disrupts the muscle clock and insulin sensitivity yet potentially induces muscle fiber remodeling in mice

Skeletal muscle plays a critical role in regulating systemic metabolic homeostasis. It has been demonstrated that time-restricted feeding (TRF) during the rest phase can desynchronize the suprachiasmatic nucleus (SCN) and peripheral clocks, thereby increasing the risk of metabolic diseases. However, the impact of dietary timing on the muscle clock and health remains poorly understood. Here, through the analysis of cycling genes and differentially expressed genes in the skeletal muscle transcriptome, we identified disruptions in muscle diurnal rhythms by 2 weeks of light-phase TRF. Furthermore, compared with ad libitum (AL) feeding mice, 2 weeks of light-phase TRF was found to induce insulin resistance, muscle fiber type remodeling, and changes in the expression of muscle growth-related genes, while both light-phase and dark-phase TRF having a limited impact on bone quality relative to AL mice. In summary, our research reveals that the disruption of the skeletal muscle clock may contribute to the abnormal metabolic phenotype resulting from feeding restricted to the inactive period. Additionally, our study provides a comprehensive omics atlas of the diurnal rhythms in skeletal muscle regulated by dietary timing.

Insights into the epitranscriptomic role of N6-methyladenosine on aging skeletal muscle

The modification of RNA through the N6-methyladenosine (m6A) has emerged as a growing area of research due to its regulatory role in gene expression and various biological processes regulating the expression of genes. m6A RNA methylation is a post-transcriptional modification that is dynamic and reversible and found in mRNA, tRNA, rRNA, and other non-coding RNA of most eukaryotic cells. It is executed by special proteins known as "writers," which initiate methylation; "erasers," which remove methylation; and "readers," which recognize it and regulate the expression of the gene. Modification by m6A regulates gene expression by affecting the splicing, translation, stability, and localization of mRNA. Aging causes molecular and cellular damage, which forms the basis of most age-related diseases. The decline in skeletal muscle mass and functionality because of aging leads to metabolic disorders and morbidities. The inability of aged muscles to regenerate and repair after injury poses a great challenge to the geriatric populace. This review seeks to explore the m6A epigenetic regulation in the myogenesis and regeneration processes in skeletal muscle as well as the progress made on the m6A epigenetic regulation of aging skeletal muscles.

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.

Insights into the role of RNA m6A modification in the metabolic process and related diseases

According to the latest consensus, many traditional diseases are considered metabolic diseases, such as cancer, type 2 diabetes, obesity, and cardiovascular disease. Currently, metabolic diseases are increasingly prevalent because of the ever-improving living standards and have become the leading threat to human health. Multiple therapy methods have been applied to treat these diseases, which improves the quality of life of many patients, but the overall effect is still unsatisfactory. Therefore, intensive research on the metabolic process and the pathogenesis of metabolic diseases is imperative. N6-methyladenosine (m6A) is an important modification of eukaryotic RNAs. It is a critical regulator of gene expression that is involved in different cellular functions and physiological processes. Many studies have indicated that m6A modification regulates the development of many metabolic processes and metabolic diseases. In this review, we summarized recent studies on the role of m6A modification in different metabolic processes and metabolic diseases. Additionally, we highlighted the potential m6A-targeted therapy for metabolic diseases, expecting to facilitate m6A-targeted strategies in the treatment of metabolic diseases.

The ω-3 Polyunsaturated Fatty Acid Docosahexaenoic Acid Enhances NK-Cell Antitumor Effector Functions

ω-3 polyunsaturated fatty acids (PUFA) are known to directly repress tumor development and progression. In this study, we explored whether docosahexaenoic acid (DHA), a type of ω-3 PUFA, had an immunomodulatory role in inhibiting tumor growth in immunocompetent mice. The number of natural killer (NK) cells but not the number of T or B cells was decreased by DHA supplementation in various tissues under physiologic conditions. Although the frequency and number of NK cells were comparable, IFNγ production by NK cells in both the spleen and lung was increased in DHA-supplemented mice in the mouse B16F10 melanoma tumor model. Single-cell RNA sequencing revealed that DHA promoted effector function and oxidative phosphorylation in NK cells but had no obvious effects on other immune cells. Using Rag2-/- mice and NK-cell depletion by PK136 antibody injection, we demonstrated that the suppression of B16F10 melanoma tumor growth in the lung by DHA supplementation was dependent mainly on NK cells. In vitro experiments showed that DHA directly enhanced IFNγ production, CD107a expression, and mitochondrial oxidative phosphorylation (OXPHOS) activity and slightly increased proliferator-activated receptor gamma coactivator-1α (PGC-1α) protein expression in NK cells. The PGC-1α inhibitor SR-18292 in vitro and NK cell-specific knockout of PGC-1α in mice reversed the antitumor effects of DHA. In summary, our findings broaden the current knowledge on how DHA supplementation protects against cancer growth from the perspective of immunomodulation by upregulating PGC-1α signaling-mediated mitochondrial OXPHOS activity in NK cells.

Nutritional Strategies for Muscle Atrophy: Current Evidence and Underlying Mechanisms

Skeletal muscle can undergo detrimental changes in various diseases, leading to muscle dysfunction and atrophy, thus severely affecting people's lives. Along with exercise, there is a growing interest in the potential of nutritional support against muscle atrophy. This review provides a brief overview of the molecular mechanisms driving skeletal muscle atrophy and summarizes recent advances in nutritional interventions for preventing and treating muscle atrophy. The nutritional supplements include amino acids and their derivatives (such as leucine, β-hydroxy, β-methylbutyrate, and creatine), various antioxidant supplements (like Coenzyme Q10 and mitoquinone, resveratrol, curcumin, quercetin, Omega 3 fatty acids), minerals (such as magnesium and selenium), and vitamins (such as vitamin B, vitamin C, vitamin D, and vitamin E), as well as probiotics and prebiotics (like Lactobacillus, Bifidobacterium, and 1-kestose). Furthermore, the study discusses the impact of a combined approach involving nutritional support and physical therapy to prevent muscle atrophy, suggests appropriate multi-nutritional and multi-modal interventions based on individual conditions to optimize treatment outcomes, and enhances the recovery of muscle function for patients. By understanding the molecular mechanisms behind skeletal muscle atrophy and implementing appropriate interventions, it is possible to enhance the recovery of muscle function and improve patients' quality of life.

Romidepsin exhibits anti-esophageal squamous cell carcinoma activity through the DDIT4-mTORC1 pathway

Esophageal squamous cell carcinoma (ESCC) is one of the most common human malignancies worldwide and is associated with high morbidity and mortality. Current treatment options are limited, highlighting the need for development of novel effective agents. Here, a high-throughput drug screening (HTS) was performed using ESCC cell lines in both two- and three-dimensional culture systems to screen compounds that have anti-ESCC activity. Our screen identified romidepsin, a histone deactylase inhibitor, as a potential anti-ESCC agent. Romidepsin treatment decreased cell viability, induced apoptosis and cell cycle arrest in ESCC cell lines, and these findings were confirmed in ESCC cell line-derived xenografted (CDX) mouse models. Mechanically, romidepsin induced transcriptional upregulation of DNA damage-inducible transcript 4 (DDIT4) gene by histone hyperacetylation at its promoter region, leading to the inhibition of mammalian target of rapamycin complex 1 (mTORC1) pathway. Furthermore, romidepsin exhibited better efficacy and safety compared to the conventional therapeutic drugs in ESCC patient-derived xenografted (PDX) mouse models. These data indicate that romidepsin may be a novel option for anti-ESCC therapy.

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.

A review on the role of RNA methylation in aging-related diseases

Senescence is the underlying mechanism of organism aging and is robustly regulated at the post-transcriptional level. This regulation involves the chemical modifications, of which the RNA methylation is the most common. Recently, a rapidly growing number of studies have demonstrated that methylation is relevant to aging and aging-associated diseases. Owing to the rapid development of detection methods, the understanding on RNA methylation has gone deeper. In this review, we summarize the current understanding on the influence of RNA modification on cellular senescence, with a focus on mRNA methylation in aging-related diseases, and discuss the emerging potential of RNA modification in diagnosis and therapy.

Ythdf2-mediated STK11 mRNA decay supports myogenesis by inhibiting the AMPK/mTOR pathway

An emerging research focus is the role of m6A modifications in mediating the post-transcriptional regulation of mRNA during mammalian development. Recent evidence suggests that m6A methyltransferases and demethylases play critical roles in skeletal muscle development. Ythdf2 is a m6A "reader" protein that mediates mRNA degradation in an m6A-dependent manner. However, the specific function of Ythdf2 in skeletal muscle development and the underlying mechanisms remain unclear. Here, we observed that Ythdf2 expression was significantly upregulated during myogenic differentiation, whereas Ythdf2 knockdown markedly inhibited myoblast proliferation and differentiation. Combined analysis of high-throughput sequencing, Co-IP, and RIP assay revealed that Ythdf2 could bind to m6A sites in STK11 mRNA and form an Ago2 silencing complex to promote its degradation, thereby regulating its expression and consequently, the AMPK/mTOR pathway. Furthermore, STK11 downregulation partially rescued Ythdf2 knockdown-induced impairment of proliferation and myogenic differentiation by inhibiting the AMPK/mTOR pathway. Collectively, our results indicate that Ythdf2 mediates the decay of STK11 mRNA, an AMPK activator, in an Ago2 system-dependent manner, thereby driving skeletal myogenesis by suppressing the AMPK/mTOR pathway. These findings further enhance our understanding of the molecular mechanisms underlying RNA methylation in the regulation of myogenesis and provide valuable insights for conducting in-depth studies on myogenesis.

Comparison of muscle fiber characteristics and meat quality between newborn and adult Haimen goats

Goat meat is popular with consumers for its rich nutritional content. Muscle fiber characteristics have been shown to play a crucial role in determining the quantity and quality of meat. However, little is known about the temporal changes in muscle fiber characteristics and meat quality during growth in goats. In this study, muscle fiber type, fiber diameter, fiber cross-sectional area (CSA), glycolytic potential (GP), meat pH, and meat color were analyzed in the gastrocnemius (GAS), gluteus medius (GM), biceps brachii (BB), longissimus lumborum (LL) muscles from newborn (NHMG) and adult (AHMG) Haimen goats. The distribution of type I and type Π fiber in goats is not consistent across the four muscles and undergoes alterations with age. The diameter and CSA of the muscle fibers were similar among the four NHMG muscles. However, in AHMG, the LL muscle had the largest fiber in terms of both diameter and CSA, followed by BB, GM, and GAS muscles. Moreover, the CSA of type Π fibers was higher than that of type I fibers in both NHMG and AHMG. GP values ranged from 90 to 140 umol/g across the muscle and no significant differences were observed. AHMG had a higher pH level and a* value, but lower L* and b* values than NHMG. Overall, our findings enhance our understanding of the changes in muscle fiber type and meat quality during the growth in Haimen goats and provide a basis for future research on the development and transformation of muscle fibers in goats.

Altered m6A RNA methylation governs denervation-induced muscle atrophy by regulating ubiquitin proteasome pathway

BACKGROUND

Denervation-induced muscle atrophy is complex disease involving multiple biological processes with unknown mechanisms. N6-methyladenosine (m6A) participates in skeletal muscle physiology by regulating multiple levels of RNA metabolism, but its impact on denervation-induced muscle atrophy is still unclear. Here, we aimed to explore the changes, functions, and molecular mechanisms of m6A RNA methylation during denervation-induced muscle atrophy.

METHODS

During denervation-induced muscle atrophy, the m6A immunoprecipitation sequencing (MeRIP-seq) as well as enzyme-linked immunosorbent assay analysis were used to detect the changes of m6A modified RNAs and the involved biological processes. 3-deazidenosine (Daa) and R-2-hydroxyglutarate (R-2HG) were used to verify the roles of m6A RNA methylation. Through bioinformatics analysis combined with experimental verification, the regulatory roles and mechanisms of m6A RNA methylation had been explored.

RESULTS

There were many m6A modified RNAs with differences during denervation-induced muscle atrophy, and overall, they were mainly downregulated. After 72 h of denervation, the biological processes involved in the altered mRNA with m6A modification were mainly related to zinc ion binding, ubiquitin protein ligase activity, ATP binding and sequence-specific DNA binding and transcription coactivator activity. Daa reduced overall m6A levels in healthy skeletal muscles, which reduced skeletal muscle mass. On the contrary, the increase in m6A levels mediated by R-2HG alleviated denervation induced muscle atrophy. The m6A RNA methylation regulated skeletal muscle mass through ubiquitin-proteasome pathway.

CONCLUSION

This study indicated that decrease in m6A RNA methylation was a new symptom of denervation-induced muscle atrophy, and confirmed that targeting m6A alleviated denervation-induced muscle atrophy.

Pb inhibited C2C12 myoblast differentiation by regulating HDAC2

Myogenesis is a crucial process governing skeletal muscle development and homeostasis. Lead (Pb) exposure impaired the development and the health of bones, which slows the growth of children. However, it is far from clear what exactly the effects of Pb on skeletal muscle development are. In this study, C2C12 cells are commonly used as an in vitro model of muscle regeneration due to their ability to transition from a proliferative phase into differentiated myofibers. The dose of 1, 5, and 10 μM Pb were adopted to study the toxicity of Pb on C2C12 proliferation and differentiation. First, the effects of Pb on cell viability were detected and the results demonstrated that 5 μM and 10 μM Pb exposure decreased cell viability, while 1 μM Pb exposure has no obvious effects on cell viability. Then, 1-10 μM Pb exposure seriously reduced the C2C12 myoblasts differentiation, with the decrease of myogenic differentiation marker genes expression, including Muscle creatine kinase (MCK), Myosin Heavy Chain 4 (MYH4), Myogenin (MYOG), Myogenic Differentiation (MYOD). What's more, it was found that the epigenetic modifier histone deacetylase-2 (HDAC2) was upregulated after Pb exposure on C2C12 myoblasts. Further studies conclusively showed knockdown of HDAC2 ameliorated Pb-damaged C2C12 myoblasts differentiation, indicating HDAC2 plays a vital role in the Pb-induced C2C12 myoblasts differentiation deficits. In summary, these results demonstrated that Pb exposure inhibited C2C12 myoblasts differentiation by regulating HDAC2.

Advances in nutritional supplementation for sarcopenia management

Sarcopenia is a syndrome characterized by a decline in muscular mass, strength, and function with advancing age. The risk of falls, fragility, hospitalization, and death is considerably increased in the senior population due to sarcopenia. Although there is no conclusive evidence for drug treatment, resistance training has been unanimously recognized as a first-line treatment for managing sarcopenia, and numerous studies have also pointed to the combination of nutritional supplementation and resistance training as a more effective intervention to improve quality of life for people with sarcopenia. People with both malnutrition and sarcopenia have a higher mortality rate, so identifying people at risk of malnutrition and intervening early is extremely important to avoid sarcopenia and its associated problems. This article provides important information for dietary interventions in sarcopenia by summarizing the discoveries and developments of nutritional supplements such as protein, leucine, β-hydroxy-β-methylbutyric acid, vitamin D, vitamin C, vitamin E, omega-3 fatty acids, creatine, inorganic nitrate, probiotics, minerals, collagen peptides, and polyphenols in the management of sarcopenia.

Docosahexaenoic Acid Alters Lipid Metabolism Processes via H3K9ac Epigenetic Modification in Dairy Goat

Goat milk is increasingly recognized by consumers due to its high nutritional value, richness in short- and medium-chain fatty acids, and richness in polyunsaturated fatty acids (PUFA). Exogenous supplementation of docosahexaenoic acid (DHA) is an important approach to increasing the content of PUFA in goat milk. Several studies have reported benefits of dietary DHA in terms of human health, including potential against chronic diseases and tumors. However, the mechanisms whereby an increased supply of DHA regulates mammary cell function is unknown. In this study, we investigated the effect of DHA on lipid metabolism processes in goat mammary epithelial cells (GMEC) and the function of H3K9ac epigenetic modifications in this process. Supplementation of DHA promoted lipid droplet accumulation increased the DHA content and altered fatty acid composition in GMEC. Lipid metabolism processes were altered by DHA supplementation through transcriptional programs in GMEC. ChIP-seq analysis revealed that DHA induced genome-wide H3K9ac epigenetic changes in GMEC. Multiomics analyses (H3K9ac genome-wide screening and RNA-seq) revealed that DHA-induced expression of lipid metabolism genes (FASN, SCD1, FADS1, FADS2, LPIN1, DGAT1, MBOAT2), which were closely related with changes in lipid metabolism processes and fatty acid profiles, were regulated by modification of H3K9ac. In particular, DHA increased the enrichment of H3K9ac in the promoter region of PDK4 and promoted its transcription, while PDK4 inhibited lipid synthesis and activated AMPK signaling in GMEC. The activation of the expression of fatty acid metabolism-related genes FASN, FADS2, and SCD1 and their upstream transcription factor SREBP1 by the AMPK inhibitor was attenuated in PDK4-overexpressing GMEC. In conclusion, DHA alters lipid metabolism processes via H3K9ac modifications and the PDK4-AMPK-SREBP1 signaling axis in goat mammary epithelial cells, providing new insights into the mechanism through which DHA affects mammary cell function and regulates milk fat metabolism.

Docosahexaenoic Acid Attenuates Radiation-Induced Myocardial Fibrosis by Inhibiting the p38/ET-1 Pathway in Cardiomyocytes

PURPOSE

Radiation-induced myocardial fibrosis (RIMF) is a severe delayed complication of thoracic irradiation (IR). Endothelin-1 (ET-1) is critical in cardiac fibroblast activation, and docosahexaenoic acid (DHA) is protective against various cardiac diseases. This study aimed to explore the roles of ET-1 in RIMF and the potential of DHA in preventing RIMF.

METHODS AND MATERIALS

Hematoxylin and eosin, sirius red, and Masson trichrome staining were carried out to evaluate the histopathologic conditions in mouse models. Enzyme-linked immunosorbent assays were used to detect the concentration of ET-1 in serum and cell supernatants. Western blotting, immunofluorescence, and immunohistochemistry were used to assess the protein levels. The phenotypic alterations of cardiac fibroblasts were evaluated by cell proliferation/migration assays and α-smooth muscle actin (α-SMA) detection.

RESULTS

Radiation increased ET-1 expression and secretion by increasing p38 phosphorylation in cardiomyocytes, and ET-1 markedly promoted the activation of cardiac fibroblasts, which were characterized by enhanced fibroblast proliferation, migration, and α-SMA expression. Cardiomyocyte-derived ET-1 mediated radiation-induced fibroblast activation by targeting the PI3K-AKT and MEK-ERK pathways in fibroblasts. DHA suppressed ET-1 levels by blocking p38 signaling in cardiomyocytes and significantly attenuated the activation of cardiac fibroblasts induced by the IR/ET-1 axis. Importantly, DHA decreased collagen deposition and α-SMA expression, alleviating cardiac fibrosis caused by radiation in mouse models.

CONCLUSIONS

Our findings demonstrate that radiation facilitates cardiac fibroblast activation by enhancing p38/ET-1 signaling in cardiomyocytes, revealing the IR/p38/ET-1 regulatory axis in RIMF for the first time. DHA effectively inhibits fibroblast activation by targeting p38/ET-1 and can be recognized as a promising protective agent against RIMF.

Reduced energy metabolism contributing to aging of skeletal muscle by serum metabolomics and gut microbiota analysis

AIMS

Sarcopenia is an age-related syndrome characterized by a gradual loss of the muscle mass, strength, and function. It is associated with a high risk of adverse consequences such as poorer quality of life, falls, disability and mortality among the elderly. The aim in this study is to investigate the pathological mechanism of sarcopenia.

MAIN METHODS

The aging of skeletal muscle was investigated by the D-galactose induced accelerated aging model combining with constrained motion. After 10 weeks, muscle function and gastrocnemius muscle index, and morphology of muscle fibers were evaluated, and myostatin, IGF-1 and ATP in skeletal muscle were also determined. Then the mechanism of aging-related skeletal muscle dysfunctions was investigated based on untargeted serum metabolomics and 16S rRNA gene sequencing. Four key metabolites were validated by the D-galactose-induced C2C12 senescent cell model in vitro.

KEY FINDINGS

Results showed that gastrocnemius muscle mass was decreased significantly, morphology of muscle fibers was altered, and muscle function was damaged in the aged group. Furthermore, increased MSTN, and decreased IGF-1 and ATP were also observed in the aging skeletal muscle. Importantly, alteration of the key pathways including riboflavin biosynthesis and energy metabolism contributed to the aging of skeletal muscle. Four key metabolites, including riboflavin, α-ketoglutaric acid and two dicarboxylic acids, which were involved in these metabolic pathways, could promote the proliferation of C2C12 cells.

SIGNIFICANCE

These findings provide novel insights into pathological mechanism of sarcopenia, and will facilitate the development of therapeutic and preventive strategies for sarcopenia.

The emergent role of mitochondrial RNA modifications in metabolic alterations

Mitochondrial epitranscriptomics refers to the modifications occurring in all the different RNA types of mitochondria. Although the number of mitochondrial RNA modifications is less than those in cytoplasm, substantial evidence indicates that they play a critical role in accurate protein synthesis. Recent evidence supported those modifications in mitochondrial RNAs also have crucial implications in mitochondrial-related diseases. In the light of current knowledge about the involvement, the association between mitochondrial RNA modifications and diseases arises from studies focusing on mutations in both mitochondrial and nuclear DNA genes encoding enzymes involved in such modifications. Here, we review the current evidence available for mitochondrial RNA modifications and their role in metabolic disorders, and we also explore the possibility of using them as promising targets for prevention and early detection. Finally, we discuss future directions of mitochondrial epitranscriptomics in these metabolic alterations, and how these RNA modifications may offer a new diagnostic and theragnostic avenue for preventive purposes. This article is categorized under: RNA Processing > RNA Editing and Modification.

Research progress of m6A regulation during animal growth and development

Environmental factors, genetic factors, and epigenetics are involved in animal growth and development. Among them, methylation is one of the abundant modifications of epigenetics. N6-methyladenosine(m⁶A) is extensive in cellular RNA, of which mRNA is the most common internal modification. m⁶A modification regulates life activities dynamically and reversibly, including expressed genes, RNA metabolism, and protein translation. The m⁶A modifications are closely related to human diseases involving heart failure, tumors, and cancer. It is relatively in-depth in the medical field. However, there are few studies on its biochemical function in animals. We summarized the latest paper related to the chemical structure and role of the writers, the erasers, and the readers to study exerting dynamic regulation of m⁶A modification of animal growth and development. Furthermore, the key roles of m⁶A modification were reported in the process of RNA metabolism. Finally, the dynamic regulation of m⁶A modification in animal growth and development was reviewed, including brain development, fertility, fat deposition, and muscle production. It reveals the key roles of m⁶A modification and the regulation of gene expression, aiming to provide new ideas for m⁶A methylation in animal growth and development.

Transcriptome-wide study revealed m6A and miRNA regulation of embryonic breast muscle development in Wenchang chickens

N⁶-Methyladenosine (m6A) modification has been shown to play important role in skeletal muscle development. Wenchang chickens are commonly used as a high-quality animal model in researching meat quality. However, there have been no previous reports regarding the profile of m6A and its function in the embryonic breast muscle development of Wenchang chickens. In this paper, we identified different developmental stages of breast muscle in Wenchang chickens and performed m6A sequencing and miRNA sequencing in the breast muscle of embryos. Embryo breast muscles were weighed and stained with hematoxylin–eosin after hatching. We found that myofibers grew fast on the 10^th day after hatching (E10) and seldom proliferated beyond the 19^th day after hatching (E19). A total of 6,774 differentially methylated genes (DMGs) were identified between E10 and E19. For RNA-seq data, we found 5,586 differentially expressed genes (DEGs). After overlapping DEGs and DMGs, we recorded 651 shared genes (DEMGs). Subsequently, we performed miRNA-seq analysis and obtained 495 differentially expressed miRNAs (DEMs). Then, we overlapped DEMGs and the target genes of DEMs and obtained 72 overlapped genes (called miRNA-m6A-genes in this study). GO and KEGG results showed DEMGs enriched in many muscle development-related pathways. Furthermore, we chose WNT7B, a key regulator of skeletal muscle development, to perform IGV visualization analysis and found that the m6A levels on the WNT7B gene between E10 and E19 were significantly different. In conclusion, we found that miRNAs, in conjunction with m6A modification, played a key role in the embryonic breast muscle development of Wenchang chickens. The results of this paper offer a theoretical basis for the study of m6A function in muscle development and fat deposition of Wenchang chickens.

Soluble Epoxide Hydrolase as a Therapeutic Target for Neuropsychiatric Disorders

It has been found that soluble epoxide hydrolase (sEH; encoded by the EPHX2 gene) in the metabolism of polyunsaturated fatty acids (PUFAs) plays a key role in inflammation, which, in turn, plays a part in the pathogenesis of neuropsychiatric disorders. Meanwhile, epoxy fatty acids such as epoxyeicosatrienoic acids (EETs), epoxyeicosatetraenoic acids (EEQs), and epoxyeicosapentaenoic acids (EDPs) have been found to exert neuroprotective effects in animal models of neuropsychiatric disorders through potent anti-inflammatory actions. Soluble expoxide hydrolase, an enzyme present in all living organisms, metabolizes epoxy fatty acids into the corresponding dihydroxy fatty acids, which are less active than the precursors. In this regard, preclinical findings using sEH inhibitors or Ephx2 knock-out (KO) mice have indicated that the inhibition or deficiency of sEH can have beneficial effects in several models of neuropsychiatric disorders. Thus, this review discusses the current findings of the role of sEH in neuropsychiatric disorders, including depression, autism spectrum disorder (ASD), schizophrenia, Parkinson’s disease (PD), and stroke, as well as the potential mechanisms underlying the therapeutic effects of sEH inhibitors.