Bacillus subtilis and Enterococcus faecium co-fermented feed alters antioxidant capacity, muscle fibre characteristics and lipid profiles of finishing pigs.

This study aimed to assess how Bacillus subtilis and Enterococcus faecium co-fermented feed (FF) affects the antioxidant capacity, muscle fibre types and muscle lipid profiles of finishing pigs. In this study, a total of 144 Duroc × Berkshire × Jiaxing Black finishing pigs were randomly assigned into three groups with four replicates (twelve pigs per replication). The three treatments were a basal diet (0 % FF), basal diet + 5 % FF and basal diet + 10 % FF, respectively. The experiment lasted 38 d after 4 d of acclimation. The study revealed that 10 % FF significantly increased the activity of superoxide dismutase (SOD) and catalase (CAT) compared with 0 % FF group, with mRNA levels of up-regulated antioxidant-related genes (GPX1, SOD1, SOD2 and CAT) in 10 % FF group. 10 % FF also significantly up-regulated the percentage of slow-twitch fibre and the mRNA expression of MyHC I, MyHC IIa and MyHC IIx, and slow MyHC protein expression while reducing MyHC IIb mRNA expression. Lipidomics analysis showed that 5 % FF and 10 % FF altered lipid profiles in longissimus thoracis. 10 % FF particularly led to an increase in the percentage of TAG. The Pearson correlation analysis indicated that certain molecular markers such as phosphatidic acid (PA) (49:4), Hex2Cer (d50:6), cardiolipin (CL) (72:8) and phosphatidylcholine (PC) (33:0e) could be used to indicate the characteristics of muscle fibres and were closely related to meat quality. Together, our findings suggest that 10 % FF improved antioxidant capacity, enhanced slow-twitch fibre percentage and altered muscle lipid profiles in finishing pigs.

Cold exposure alters lipid metabolism of skeletal muscle through HIF-1α-induced mitophagy.

BACKGROUND: In addition to its contractile properties and role in movement, skeletal muscle plays an important function in regulating whole-body glucose and lipid metabolism. A central component of such regulation is mitochondria, whose quality and function are essential in maintaining proper metabolic homeostasis, with defects in processes such as autophagy and mitophagy involved in mitochondria quality control impairing skeletal muscle mass and function, and potentially leading to a number of associated diseases. Cold exposure has been reported to markedly induce metabolic remodeling and enhance insulin sensitivity in the whole body by regulating mitochondrial biogenesis. However, changes in lipid metabolism and lipidomic profiles in skeletal muscle in response to cold exposure are unclear. Here, we generated lipidomic or transcriptome profiles of mouse skeletal muscle following cold induction, to dissect the molecular mechanisms regulating lipid metabolism upon acute cold treatment. RESULTS: Our results indicated that short-term cold exposure (3 days) can lead to a significant increase in intramuscular fat deposition. Lipidomic analyses revealed that a cold challenge altered the overall lipid composition by increasing the content of triglyceride (TG), lysophosphatidylcholine (LPC), and lysophosphatidylethanolamine (LPE), while decreasing sphingomyelin (SM), validating lipid remodeling during the cold environment. In addition, RNA-seq and qPCR analysis showed that cold exposure promoted the expression of genes related to lipolysis and fatty acid biosynthesis. These marked changes in metabolic effects were associated with mitophagy and muscle signaling pathways, which were accompanied by increased TG deposition and impaired fatty acid oxidation. Mechanistically, HIF-1α signaling was highly activated in response to the cold challenge, which may contribute to intramuscular fat deposition and enhanced mitophagy in a cold environment. CONCLUSIONS: Overall, our data revealed the adaptive changes of skeletal muscle associated with lipidomic and transcriptomic profiles upon cold exposure. We described the significant alterations in the composition of specific lipid species and expression of genes involved in glucose and fatty acid metabolism. Cold-mediated mitophagy may play a critical role in modulating lipid metabolism in skeletal muscle, which is precisely regulated by HIF-1α signaling.

GADD45A regulates subcutaneous fat deposition and lipid metabolism by interacting with Stat1.

BACKGROUND: Obesity, characterized by excessive white adipose tissue expansion, is associated with several metabolic complications. Identifying new adipogenesis regulators may lead to effective therapies for obesity-induced metabolic disorders. RESULTS: Here, we identified the growth arrest and DNA damage-inducible A (GADD45A), a stress-inducible histone-folding protein, as a novel regulator of subcutaneous adipose metabolism. We found that GADD45A expression was positively correlated with subcutaneous fat deposition and obesity in humans and fatty animals. In vitro, the gain or loss function of GADD45A promoted or inhibited subcutaneous adipogenic differentiation and lipid accumulation, respectively. Using a Gadd45a-/- mouse model, we showed that compared to wild-type (WT) mice, knockout (KO) mice exhibited subcutaneous fat browning and resistance to high-fat diet (HFD)-induced obesity. GADD45A deletion also upregulated the expression of mitochondria-related genes. Importantly, we further revealed that the interaction of GADD45A with Stat1 prevented phosphorylation of Stat1, resulting in the impaired expression of Lkb1, thereby regulating subcutaneous adipogenesis and lipid metabolism. CONCLUSIONS: Overall, our results reveal the critical regulatory roles of GADD45A in subcutaneous fat deposition and lipid metabolism. We demonstrate that GADD45A deficiency induces the inguinal white adipose tissue (iWAT) browning and protects mice against HFD-induced obesity. Our findings provide new potential targets for combating obesity-related metabolic diseases and improving human health.

Effect of a novel alkaline protease from Bacillus licheniformis on growth performance, carcass characteristics, meat quality, antioxidant capacity, and intestinal morphology of white feather broilers.

BACKGROUND: The present study was conducted to investigate the effects of dietary novel alkaline protease from Bacillus licheniformis on the growth performance, meat quality, antioxidant status and intestinal morphology of broilers. In total, 4000 broilers were randomly assigned into five groups and treated with normal control, normal control + 100 mg kg-1 protease, normal control + 200 mg kg-1 protease, normal control + 300 mg kg-1 protease and normal control + 400 mg kg-1 protease. RESULTS: Supplementing protease impacted final body weight (linear, P = 0.003; quadratic, P = 0.006) and decreased feed conversion rate (linear, P = 0.036) in broilers. Moreover, dietary protease significantly increased breast muscle rate (linear, P = 0.005; quadratic, P = 0.021) and decreased drip loss (linear, P < 0.001; quadratic, P < 0.001). In addition, dietary protease notably increased protein digestibility (linear, P = 0.001; quadratic, P = 0.006) and trypsin activity (linear, P = 0.002; quadratic, P = 0.009) in jejunum. Light microscopy revealed that the jejunum villi in the 300 mg kg-1 and 400 mg kg-1 groups exhibited greater height and a denser arrangement compared to those in the control group. The addition of protease decreased malondialdehyde content (linear, P < 0.001; quadratic, P < 0.001) and increased total antioxidant capacity (linear, P = 0.001; quadratic, P < 0.001) in pectoral muscles. CONCLUSION: The results of the present study suggest that dietary novel alkaline protease from B. licheniformis improved growth performance by affecting trypsin activity, protein digestibility, antioxidant capacity and intestinal health. © 2024 Society of Chemical Industry.

Global distribution, toxicity to humans and animals, biodegradation, and nutritional mitigation of deoxynivalenol: A review.

Deoxynivalenol (DON) is one of the main types of B trichothecenes, and it causes health-related issues in humans and animals and imposes considerable challenges to food and feed safety globally each year. This review investigates the global hazards of DON, describes the occurrence of DON in food and feed in different countries, and systematically uncovers the mechanisms of the various toxic effects of DON. For DON pollution, many treatments have been reported on the degradation of DON, and each of the treatments has different degradation efficacies and degrades DON by a distinct mechanism. These treatments include physical, chemical, and biological methods and mitigation strategies. Biodegradation methods include microorganisms, enzymes, and biological antifungal agents, which are of great research significance in food processing because of their high efficiency, low environmental hazards, and drug resistance. And we also reviewed the mechanisms of biodegradation methods of DON, the adsorption and antagonism effects of microorganisms, and the different chemical transformation mechanisms of enzymes. Moreover, nutritional mitigation including common nutrients (amino acids, fatty acids, vitamins, and microelements) and plant extracts was discussed in this review, and the mitigation mechanism of DON toxicity was elaborated from the biochemical point of view. These findings help explore various approaches to achieve the best efficiency and applicability, overcome DON pollution worldwide, ensure the sustainability and safety of food processing, and explore potential therapeutic options with the ability to reduce the deleterious effects of DON in humans and animals.

Potential key factors involved in regulating adipocyte dedifferentiation.

Adipocytes are the key constituents of adipose tissue, and their de-differentiation process has been widely observed in physiological and pathological conditions. For obese people, the promotion of adipocyte de-differentiation or maintenance of an undifferentiated state of adipocytes may help to improve their metabolic condition. Thus, understanding the regulatory mechanisms of adipocyte de-differentiation is necessary for treating metabolic diseases. Attractively, in addition to intracellular signals regulating adipocyte de-differentiation, external factors such as temperature and pressure also affect adipocyte de-differentiation. In this review, we summarize the recent progress in the field and discuss the regulatory roles and mechanisms of involved endogenous and exogenous factors during the process of de-differentiation.

The regulatory role of dietary factors in skeletal muscle development, regeneration and function.

Skeletal muscle plays a crucial role in motor function, respiration, and whole-body energy homeostasis. How to regulate the development and function of skeletal muscle has become a hot research topic for improving lifestyle and extending life span. Numerous transcription factors and nutritional factors have been clarified are closely associated with the regulation of skeletal muscle development, regeneration and function. In this article, the roles of different dietary factors including green tea, quercetin, curcumin (CUR), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and resveratrol (RES) in regulating skeletal muscle development, muscle mass, muscle function, and muscle recovery have been summarized and discussed. We also reviewed the potential regulatory molecular mechanism of these factors. Based on the current findings, dietary factors may be used as a potential therapeutic agent to treat skeletal muscle dysfunction as well as its related diseases.

Factors inducing transdifferentiation of myoblasts into adipocytes.

Fat infiltration in skeletal muscle is observed in several myopathies, is associated with muscular dysfunction, and is strongly correlated with insulin resistance, diabetes, obesity, and aging. In animal production, skeletal muscle fat (also known as intermuscular and intramuscular fat) is positively related to meat quality including tenderness, flavor, and juiciness. Thus, understanding the cell origin and regulation mechanism of skeletal muscle fat infiltration is important for developing therapies against human myopathies as well as for improving meat quality. Notably, age, sarcopenia, oxidative stress, injury, and regeneration can activate adipogenic differentiation potential in myoblasts and affect fat accumulation in skeletal muscle. In addition, several transcriptional and nutritional factors can directly induce transdifferentiation of myoblasts into adipocytes. In this review, we focused on the recent progress in understanding the muscle-to-adipocyte differentiation and summarized and discussed the genetic, nutritional, and physiological factors that can induce transdifferentiation of myoblasts into adipocytes. Moreover, the regulatory roles and mechanisms of these factors during the transdifferentiation process were also discussed.

Myokines mediate the cross talk between skeletal muscle and other organs.

Myokines are muscle-derived cytokines and chemokines that act extensively on organs and exert beneficial metabolic functions in the whole-body through specific signal networks. Myokines as mediators provide the conceptual basis for a whole new paradigm useful for understanding how skeletal muscle communicates with other organs. In this review, we summarize and discuss classes of myokines and their physiological functions in mediating the regulatory roles of skeletal muscle on other organs and the regulation of the whole-body energy metabolism. We review the mechanisms involved in the interaction between skeletal muscle and nonmuscle organs through myokines. Moreover, we clarify the connection between exercise, myokines and disease development, which may contribute to the understanding of a potential mechanism by which physical inactivity affects the process of metabolic diseases via myokines. Based on the current findings, myokines are important factors that mediate the effect of skeletal muscle on other organ functions and whole-body metabolism.

AMPK facilitates intestinal long-chain fatty acid uptake by manipulating CD36 expression and translocation.

Cellular long-chain fatty acids' (LCFAs) uptake is a crucial physiological process that regulates cellular energy homeostasis. AMPK has been shown to modulate LCFAs uptake in several kinds of cells, but whether it exerts an impact on intestinal LCFAs uptake is not quite clear. In the current study, we found that AMPK reinforced LCFAs uptake in intestinal epithelial cells (IECs). Moreover, intestinal epithelium-specific AMPK deletion impaired intestinal LCFAs absorption and protected mice from high-fat diet-induced obesity. Mechanistically, we discovered that AMPK deletion reduced the CD36 protein level by upregulating Parkin-mediated polyubiquitination of CD36 in IECs. Furthermore, our results revealed that AMPK affected PARK2 (gene name of Parkin) mRNA stability in a YTHDF2-dependent manner through FTO-dependent demethylation of N6 -methyladenosine (m6 A). Besides, AMPK promoted the translocation of CD36 to the plasma membrane in IECs, but the inhibition of AKT signaling suppressed this effect, which also halted the accelerated fatty acid uptake induced by AMPK. These results suggest that AMPK facilitates the intestinal LCFAs uptake by upregulating CD36 protein abundance and promoting its membrane translocation simultaneously. Such findings shed light on the role of AMPK in the regulation of intestinal LCFAs uptake.

The regulatory role of Myomaker and Myomixer-Myomerger-Minion in muscle development and regeneration.

Skeletal muscle plays essential roles in motor function, energy, and glucose metabolism. Skeletal muscle formation occurs through a process called myogenesis, in which a crucial step is the fusion of mononucleated myoblasts to form multinucleated myofibers. The myoblast/myocyte fusion is triggered and coordinated in a muscle-specific way that is essential for muscle development and post-natal muscle regeneration. Many molecules and proteins have been found and demonstrated to have the capacity to regulate the fusion of myoblast/myocytes. Interestingly, two newly discovered muscle-specific membrane proteins, Myomaker and Myomixer (also called Myomerger and Minion), have been identified as fusogenic regulators in vertebrates. Both Myomaker and Myomixer-Myomerger-Minion have the capacity to directly control the myogenic fusion process. Here, we review and discuss the latest studies related to these two proteins, including the discovery, structure, expression pattern, functions, and regulation of Myomaker and Myomixer-Myomerger-Minion. We also emphasize and discuss the interaction between Myomaker and Myomixer-Myomerger-Minion, as well as their cooperative regulatory roles in cell-cell fusion. Moreover, we highlight the areas for exploration of Myomaker and Myomixer-Myomerger-Minion in future studies and consider their potential application to control cell fusion for cell-therapy purposes.

Ascl2 inhibits myogenesis by antagonizing the transcriptional activity of myogenic regulatory factors.

Myogenic regulatory factors (MRFs), including Myf5, MyoD (Myod1) and Myog, are muscle-specific transcription factors that orchestrate myogenesis. Although MRFs are essential for myogenic commitment and differentiation, timely repression of their activity is necessary for the self-renewal and maintenance of muscle stem cells (satellite cells). Here, we define Ascl2 as a novel inhibitor of MRFs. During mouse development, Ascl2 is transiently detected in a subpopulation of Pax7+ MyoD+ progenitors (myoblasts) that become Pax7+ MyoD- satellite cells prior to birth, but is not detectable in postnatal satellite cells. Ascl2 knockout in embryonic myoblasts decreases both the number of Pax7+ cells and the proportion of Pax7+ MyoD- cells. Conversely, overexpression of Ascl2 inhibits the proliferation and differentiation of cultured myoblasts and impairs the regeneration of injured muscles. Ascl2 competes with MRFs for binding to E-boxes in the promoters of muscle genes, without activating gene transcription. Ascl2 also forms heterodimers with classical E-proteins to sequester their transcriptional activity on MRF genes. Accordingly, MyoD or Myog expression rescues myogenic differentiation despite Ascl2 overexpression. Ascl2 expression is regulated by Notch signaling, a key governor of satellite cell self-renewal. These data demonstrate that Ascl2 inhibits myogenic differentiation by targeting MRFs and facilitates the generation of postnatal satellite cells.

The regulatory role of melatonin in skeletal muscle.

Melatonin (N-acetyl-5-methoxy-tryptamine) is an effective antioxidant and free radical scavenger, that has important biological effects in multiple cell types and species. Melatonin research in muscle has recently gained attention, mainly focused on its role in cells or tissue repair and regeneration after injury, due to its powerful biological functions, including its antioxidant, anti-inflammation, anti-tumor and anti-cancer, circadian rhythm, and anti-apoptotic effects. However, the effect of melatonin in regulating muscle development has not been systematically summarized. In this review, we outline the latest research on the involvement of melatonin in the regulation of muscle development and regeneration in order to better understand its underlying molecular mechanisms and potential applications.

Myomaker, and Myomixer-Myomerger-Minion modulate the efficiency of skeletal muscle development with melatonin supplementation through Wnt/ß-catenin pathway.

Melatonin, a pleiotropic hormone secreted from the pineal gland, has been shown to exert beneficial effects in muscle regeneration and repair due to its functional diversity, including anti-inflammation, anti-apoptosis, and anti-oxidative activity. However, little is known about the negative role of melatonin in myogenesis. Here, using skeletal muscle cells, we found that melatonin promoted C2C12 cells proliferation and inhibits differentiation both in C2C12 cells and primary myoblasts in mice. Melatonin administration significantly down-regulated differentiation and fusion related genes and inhibited myotube formation both in C2C12 cells and primary myoblasts in mice. RNA-seq showed that melatonin down-regulated essential fusion pore components Myomaker and Myomixer-Myomerger-Minion. Moreover, melatonin suppressed Wnt/ß-catenin signaling. Inhibition of GSK3ß by LiCl rescued the influence of melatonin on differentiation efficiency, Myomaker, but not Myomxier in C2C12 cells. In conclusion, melatonin inhibits myogenic differentiation, Myomaker, and Myomixer through reducing Wnt/ß-catenin signaling. These data establish a link between melatonin and fusogenic membrane proteins Myomaker and Myomixer, and suggest the new perspective of melatonin in treatment or preventment of muscular diseases.

Cold-induced lipid dynamics and transcriptional programs in white adipose tissue.

BACKGROUND: In mammals, cold exposure induces browning of white adipose tissue (WAT) and alters WAT gene expression and lipid metabolism to boost adaptive thermogenesis and maintain body temperature. Understanding the lipidomic and transcriptomic profiles of WAT upon cold exposure provides insights into the adaptive changes associated with this process. RESULTS: Here, we applied mass spectrometry and RNA sequencing (RNA-seq) to provide a comprehensive resource for describing the lipidomic or transcriptome profiles in cold-induced inguinal WAT (iWAT). We showed that short-term (3-day) cold exposure induces browning of iWAT, increases energy expenditure, and results in loss of body weight and fat mass. Lipidomic analysis shows that short-term cold exposure leads to dramatic changes of the overall composition of lipid classes WAT. Notably, cold exposure induces significant changes in the acyl-chain composition of triacylglycerols (TAGs), as well as the levels of glycerophospholipids and sphingolipids in iWAT. RNA-seq and qPCR analysis suggests that short-term cold exposure alters the expression of genes and pathways involved in fatty acid elongation, and the synthesis of TAGs, sphingolipids, and glycerophospholipids. Furthermore, the cold-induced lipid dynamics and gene expression pathways in iWAT are contrary to those previously observed in metabolic syndrome, neurodegenerative disorders, and aging, suggesting beneficial effects of cold-induced WAT browning on health and lifespan. CONCLUSION: We described the significant alterations in the composition of glyphospholipids, glycerolipids, and sphingolipids and expression of genes involved in thermogenesis, fatty acid elongation, and fatty acid metabolism during the response of iWAT to short-term cold exposure. We also found that some changes in the levels of specific lipid species happening after cold treatment of iWAT are negatively correlated to metabolic diseases, including obesity and T2D.

Roles of phosphatase and tensin homolog in skeletal muscle.

The phosphatase and tensin homolog (PTEN), originally identified as a tumor suppressor, is an important regulator of the PI3K-Akt pathway. PTEN plays crucial roles in various cellular processes, including cell survival, cell growth, cell proliferation, cell differentiation, and cell metabolism. In metabolic tissues, PTEN expression affects insulin sensitivity and glucose homeostasis. In skeletal muscle, the deletion of PTEN regulates muscle development and protects the mutant mice from insulin resistance and diabetes. Notably, the regulatory role of PTEN in skeletal muscle stem cells has been recently reported. In this review, we mainly discuss the role of PTEN in regulating the development, glucose metabolism, stem cell fate decision, and regeneration of skeletal muscle.

Cold exposure induces nuclear translocation of CRTC3 in brown adipose tissue.

In mammals, cold stress activates the cAMP-protein kinase A (PKA) signaling pathway, increases brown adipose tissue (BAT) activity, and induces thermogenesis to maintain body temperature. The cAMP responsive element binding protein (CREB)-regulated transcription coactivator 3 (CRTC3) plays important role in adipose development and energy metabolism. However, the effect of cold exposure on the intracellular localization of CRTC3 in BAT is unclear. Here, we report that cold-treated mice have higher expression of uncoupling protein 1 (UCP1) in adipose tissues and lower body weights and fat masses. Notably, cold exposure results in the nuclear translocation of CRTC3 in BAT. Moreover, forskolin (FSK), the activator of PKA pathway, induces the nuclear translocation of CRTC3 in brown adipocytes. At the molecular level, cold exposure and FSK treatment decrease liver kinase B1 (Lkb1) expression in brown adipocytes, which is related to the nuclear localization of CRTC3. These results demonstrate that the localization of CRTC3 involves in regulating cold-induced upregulation of UCP1 in BAT and provide useful information for understanding the molecular regulation of BAT thermogenesis induced by a cold environment.

The role of satellite and other functional cell types in muscle repair and regeneration.

Skeletal muscles play essential roles in physiological processes, including motor function, energy hemostasis, and respiration. Skeletal muscles also have the capacity to regenerate after injury. Regeneration of skeletal muscle is an extremely complex biological process, which involves multiple cell types. Skeletal muscle stem cells (also known as satellite cells; SCs) are crucial for the development, growth, maintenance and repair of the skeletal muscle. Cell fates and function have been extensively studied in the context of skeletal muscle regeneration. In addition to SCs, other cell types, such as fibro-adipogenic precursors (FAPs), endothelial cells, fibroblasts, pericytes and certain immune cells, play important regulatory roles during skeletal muscle regeneration. In this review, we summarize and discuss the current research progress on the different cell types and their respective functions in skeletal muscle regeneration and repair.

Adipocyte-specific DKO of Lkb1 and mTOR protects mice against HFD-induced obesity, but results in insulin resistance.

Liver kinase B1 (Lkb1) and mammalian target of rapamycin (mTOR) are key regulators of energy metabolism and cell growth. We have previously reported that adipocyte-specific KO of Lkb1 or mTOR in mice results in distinct developmental and metabolic phenotypes. Here, we aimed to assess how genetic KO of both Lkb1 and mTOR affects adipose tissue development and function in energy homeostasis. We used Adiponectin-Cre to drive adipocyte-specific double KO (DKO) of Lkb1 and mTOR in mice. We performed indirect calorimetry, glucose and insulin tolerance tests, and gene expression assays on the DKO and WT mice. We found that DKO of Lkb1 and mTOR results in reductions of brown adipose tissue and inguinal white adipose tissue mass, but in increases of liver mass. Notably, the DKO mice developed fatty liver and insulin resistance, but displayed improved glucose tolerance after high-fat diet (HFD)-feeding. Interestingly, the DKO mice were protected from HFD-induced obesity due to their higher energy expenditure and lower expression levels of adipogenic genes (CCAAT/enhancer binding protein α and PPARγ) compared with WT mice. These results together indicate that, compared with Lkb1 or mTOR single KOs, Lkb1/mTOR DKO in adipocytes results in overlapping and distinct metabolic phenotypes, and mTOR KO largely overrides the effect of Lkb1 KO.

Regulation role of CRTC3 in skeletal muscle and adipose tissue.

The cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling pathway plays important role in regulating energy homeostasis. Many of the effects of the cAMP-PKA signaling is mediated through the cAMP responsive element binding protein (CREB) and its coactivator CREB-regulated transcription coactivators (CRTCs). CRTC3 is a member of CRTCs family proteins and plays important roles in glucose and energy metabolism. Previous studies show that global knockout of CRTC3 enhances oxygen consumption and energy expenditure and subsequently protects the knockout animal against obesity. In skeletal muscle, CRTC3 affects lipid and glycogen metabolism and mitochondrial biogenesis. In white adipocytes, CRTC3 regulates GLUT4 expression and glucose uptake. More recently, the localization and function of CRTC3 in brown fat have been reported. In this review, we mainly discuss the regulatory role of CRTC3 in skeletal muscle and adipose tissues.