Ellagic Acid Alters Muscle Fiber-Type Composition and Promotes Mitochondrial Biogenesis through the AMPK Signaling Pathway in Healthy Pigs

Identification of key genes and metabolites involved in intramuscular fat deposition in Laiwu pigs through combined transcriptomic and lipidomic analyses

Pork quality is a key goal in commercial pig farming. Intramuscular fat (IMF) content in pigs serves as a critical determinant of meat quality, yet its regulatory mechanism remains unclear. In this study, two different pig breeds Chinese native breed Laiwu (fatty-type) and Yorkshire (lean-type), were selected as research subjects. The molecular regulatory mechanisms affecting IMF content were investigated through integrated transcriptomic and lipidomic analysis. We identified critical genes, including ACC1, FASN, ELOVL6, SCD, and DGAT2, and elucidated their synergistic interactions in promoting IMF deposition in Laiwu pigs. The findings reveal that the coordinated action of genes such as ACC1 and FASN promotes the increased production of palmitic acid, which was subsequently elongated and desaturated by ELOVL6 and SCD to form long-chain fatty acids necessary for TG synthesis. Additionally, DGAT2 facilitates the extensive synthesis of TG, which is stored in lipid droplets under the regulation of PLIN1. This increased triglyceride synthesis and storage capacities in Laiwu pigs, functioning as one of the key factors contributing to its high IMF content. The study highlights the importance of gene-lipid interactions in IMF deposition and offers novel insights into the genetic and molecular basis of IMF accumulation, particularly in fatty pig breeds like the Laiwu. Our research findings provide new directions for developing targeted genetic or nutritional interventions to enhance IMF content and improve meat quality.

Chlorogenic Acid Improves High-Fat Diet-Induced Skeletal Muscle Metabolic Disorders by Regulating Mitochondrial Function and Lactate Metabolism

Mitochondria are pivotal in sustaining skeletal muscle and the systemic metabolic balance. Chlorogenic acid (CA) is a common dietary antioxidant known for its ability to modulate metabolic homeostasis. This study aimed to investigate the impact of CA on high-fat diet (HFD)-induced mitochondrial dysfunction and metabolic disorder in skeletal muscle. C57BL/6J mice fed with a HFD were treated with CA for 12 weeks. The study assessed the overall glycolipid metabolic status, exercise performance, muscle fiber type, and antioxidant capacity of skeletal muscle in HFD-fed mice treated with CA. Results showed that CA reduced fat accumulation, improved exercise capacity, and enhanced mitochondrial performance in HFD-fed mice. Untargeted metabolomics analysis revealed that lactate metabolism and mitochondrial fatty acid oxidation (FAO) responded positively to CA intervention. Molecular mechanisms demonstrated that CA intervention improved mitochondrial biogenesis and function, promoting FAO and oxidative phosphorylation in mitochondria and ultimately reducing fat deposition in skeletal muscle induced by HFD feeding. Mechanistically, CA decreased HFD-induced lactate production and protein lactylation in skeletal muscle, highlighting the importance of the LDHA-lactate axis in mitochondrial function improvement by CA. Therefore, this study provides additional insights supporting the potential of CA as a natural dietary supplement for metabolic syndrome and associated disorders.

Lycium barbarum polysaccharide mitigates high-fat-diet-induced skeletal muscle atrophy by promoting AMPK/PINK1/Parkin-mediated mitophagy

Sarcopenic obesity (SO) defined as the coexistence of obesity and sarcopenia. While the anti-obesity effects of Lycium barbarum polysaccharide (LBP), the main component of L. barbarum extract, are known, its efficacy against SO remains unexplored. Consequently, we aimed to investigate the therapeutic effects of LBP on SO and the elucidate the underlying mechanisms. Our results revealed that LBP administration decreased obesity-related factors, and increased muscle-related factors in mice fed a high-fat diet (HFD). LBP administration ameliorated PA- and HFD-induced hyperglycaemia by modulating IRS-1 and GLUT-4 levels while also mitigating the ectopic fat deposition. Furthermore, our results demonstrated that LBP can mitigate mitochondrial structural abnormalities and dysfunction-characterized by increased mitochondrial membrane potential and ATP levels, reduced reactive oxygen species levels-through the activation of mitophagy. However, these beneficial effects of LBP on skeletal muscle were negated by AMPK inhibitor and siRNA knockdown of Parkin expression. Taken together, our findings indicate that LBP may effectively modulate glucose and lipid metabolism while ameliorating skeletal muscle atrophy via the activation of the AMPK/PINK1/Parkin-mediated mitophagy pathway, thereby repairing the mitochondrial structure and function. Consequently, LBP emerges as a promising therapeutic candidate for addressing obesity-related impacts on skeletal muscle.

Natural plant polyphenols contribute to the ecological and healthy swine production

The absence of trace amounts of natural bioactive compounds with important biological activities in traditional dietary models for global farm animals, coupled with an incomplete theoretical system for animal nutrition, has led to unbalanced and inadequate animal nutrition. This deficiency has adversely impacted animal health and the ecological environment, presenting formidable challenges to the advancement of the swine breeding industry in various countries around the world toward high-quality development. Recently, due to the ban of antibiotics for growth promotion in swine diets, botanical active compounds have been extensively investigated as feed additives. Polyphenols represent a broad group of plant secondary metabolites. They are natural, non-toxic, pollution-free, and highly reproducible compounds that have a wide range of physiological functions, such as antioxidant, anti-inflammatory, immunomodulatory, antiviral, antibacterial, and metabolic activities. Accordingly, polyphenols have been widely studied and used as feed additives in swine production. This review summarizes the structural characteristics, classification, current application situation, general properties of polyphenols, and the latest research advances on their use in swine production. Additionally, the research and application bottlenecks and future development of plant polyphenols in the animal feed industry are reviewed and prospected. This review aims to stimulate the in-depth study of natural plant polyphenols and the research and development of related products in order to promote the green, healthy, and high-quality development of swine production, while also providing ideas for the innovation and development in the theoretical system of animal nutrition.

Candidate circRNAs related to skeletal muscle development in Dazu black goats

Circular RNA (CircRNA), as a classical noncoding RNA, has been proven to regulate skeletal muscle development (SMD). However, the molecular genetic basis of circRNA regulation in muscle cells remains unclear. In this study, the expression patterns of circRNAs in the longissimus dorsi muscle at embryonic day 75 and postnatal day 1 in DBGs were investigated to identify the key circRNAs that play an important role in SMD in goats. A total of 140 significantly and differentially expressed circRNAs (DEcircRNAs) were identified among the groups at different developmental stages. Among the 116 host genes (HGs) of DEcircRNAs, 76 were significantly and differentially expressed, which was confirmed by previous RNA_seq data. Furthermore, the expression pattern of 10 DEcircRNAs with RT-qPCR was verified, which showed 80% concordance rate with that of RNA_seq datasets. Moreover, the authenticity of seven randomly selected DEcircRNAs was verified by PCR Sanger sequencing. Based on the functional annotation results, among the 76 significantly and differentially expressed HGs, 74 were enriched in 845 GO terms, whereas 35 were annotated to 85 KEGG pathways. The results of this study could provide a comprehensive understanding of the genetic basis of circRNAs involved in SMD and muscle growth.

Hesperetin but not ellagic acid increases myosin heavy chain expression and cell fusion in C2C12 myoblasts in the presence of oxidative stress

Introduction

Skeletal muscle regeneration is impaired in elderly. An oxidative stress-induced decrease in differentiation capacity of muscle satellite cells is a key factor in this process. The aim of this study is to investigate whether orange polyphenol hesperetin and pomegranate polyphenol ellagic acid enhance myoblast differentiation in the presence and absence of oxidative stress, and to explore underlying mechanisms.

Methods

C2C12 myoblasts were proliferated for 24 h and differentiated for 120 h while exposed to hesperetin (5, 20, 50 μM), ellagic acid (0.05, 0.1 μM) or a combination (20 μM hesperetin, 0.05 μM ellagic acid) with and without oxidative stress-inducing compound menadione (9 μM) during 24 h of proliferation and during the first 5 h of differentiation. The number of proliferating cells was assessed using fluorescent labeling of incorporated 5-ethynyl-2'-deoxyuridine. Myosin heavy chain expression was assessed by fluorescence microscopy and cell fusion index was calculated. Furthermore, protein expression of phosphorylated p38 and myomixer were assessed using Western blot.

Results

None of the compounds induced effects on cell proliferation. Without menadione, 50 μM hesperetin increased fusion index by 12.6% compared to control (p < 0.01), while ellagic acid did not affect measured parameters of differentiation. Menadione treatment did not change myosin heavy chain expression and fusion index. In combination with menadione, 20 μM hesperetin increased myosin heavy chain expression by 35% (p < 0.01) and fusion index by 7% (p = 0.04) compared to menadione. Furthermore, the combination of menadione with hesperetin and ellagic acid increased myosin heavy chain expression by 35% compared to menadione (p = 0.02). Hesperetin and ellagic acid did not change p38 phosphorylation and myomixer expression compared to control, while treatment with menadione increased p38 phosphorylation (p < 0.01) after 5 h and decreased myomixer expression (p = 0.04) after 72 h of differentiation.

Conclusion and discussion

Hesperetin increased myosin heavy chain expression in the presence of oxidative stress induced by menadione, and increased cell fusion both in the presence and absence of menadione. Ellagic acid did not affect the measured parameters of myoblast differentiation. Therefore, hesperetin should be considered as nutritional prevention or treatment strategy to maintain muscle function in age-related diseases such as sarcopenia. Future research should focus on underlying mechanisms and translation of these results to clinical practice.

Nanophytomedicine: A promising practical approach in phytotherapy

The long and rich history of herbal therapeutic nutrients is fascinating. It is incredible to think about how ancient civilizations used plants and herbs to treat various ailments and diseases. One group of bioactive phytochemicals that has gained significant attention recently is dietary polyphenols. These compounds are commonly found in a variety of fruits, vegetables, spices, nuts, drinks, legumes, and grains. Despite their incredible therapeutic properties, one challenge with polyphenols is their poor water solubility, stability, and bioavailability. This means that they are not easily absorbed by the body when consumed in essential diets. Because of structural complexity, polyphenols with high molecular weight cannot be absorbed in the small intestine and after arriving in the colon, they are metabolized by gut microbiota. However, researchers are constantly working on finding solutions to enhance the bioavailability and absorption of these compounds. This study aims to address this issue by applying nanotechnology approaches to overcome the challenges of the therapeutic application of dietary polyphenols. This combination of nanotechnology and phytochemicals could cause a completely new field called nanophytomedicine or herbal nanomedicine.

Vitamin A regulates mitochondrial biogenesis and function through p38 MAPK-PGC-1α signaling pathway and alters the muscle fiber composition of sheep

BACKGROUND

Vitamin A (VA) and its metabolite, retinoic acid (RA), are of great interest for their wide range of physiological functions. However, the regulatory contribution of VA to mitochondrial and muscle fiber composition in sheep has not been reported.

METHOD

Lambs were injected with 0 (control) or 7,500 IU VA palmitate into the biceps femoris muscle on d 2 after birth. At the age of 3 and 32 weeks, longissimus dorsi (LD) muscle samples were obtained to explore the effect of VA on myofiber type composition. In vitro, we investigated the effects of RA on myofiber type composition and intrinsic mechanisms.

RESULTS

The proportion of type I myofiber was greatly increased in VA-treated sheep in LD muscle at harvest. VA greatly promoted mitochondrial biogenesis and function in LD muscle of sheep. Further exploration revealed that VA elevated PGC-1α mRNA and protein contents, and enhanced the level of p38 MAPK phosphorylation in LD muscle of sheep. In addition, the number of type I myofibers with RA treatment was significantly increased, and type IIx myofibers was significantly decreased in primary myoblasts. Consistent with in vivo experiment, RA significantly improved mitochondrial biogenesis and function in primary myoblasts of sheep. We then used si-PGC-1α to inhibit PGC-1α expression and found that si-PGC-1α significantly abrogated RA-induced the formation of type I myofibers, mitochondrial biogenesis, MitoTracker staining intensity, UQCRC1 and ATP5A1 expression, SDH activity, and enhanced the level of type IIx muscle fibers. These data suggested that RA improved mitochondrial biogenesis and function by promoting PGC-1α expression, and increased type I myofibers. In order to prove that the effect of RA on the level of PGC-1α is caused by p38 MAPK signaling, we inhibited the p38 MAPK signaling using a p38 MAPK inhibitor, which significantly reduced RA-induced PGC-1α and MyHC I levels.

CONCLUSION

VA promoted PGC-1α expression through the p38 MAPK signaling pathway, improved mitochondrial biogenesis, and altered the composition of muscle fiber type.

Rapid and visual evaluation the internal corruption of meat tissue by a designed near-infrared fluorescence probe with a broad pH response range

Rapid and visual evaluation the internal corruption of meat tissue is closely related to public health. The pH change caused by glycolysis and amino acid decomposition is an important indicator of meat freshness. Herein, we designed a pH-responsive NIR fluorescent probe (Probe-OH) based on protonation/deprotonation for monitoring the internal corruption of meat tissue. Probe-OH was synthesized by a stable hemicyanine skeleton with phenolic hydroxyl group, which exhibited excellent performances such as high selectivity, high sensitivity, fast response time (60 s), a broad pH-responsive range of 4.0-10.0, and superior spatio-temporal sampling ability. In addition, we conducted a paper chip platform to measure pH value in different meat samples (pork and chicken), which is convenient to evaluate pH value of meat by observing the color changes of paper strips. Furthermore, in combination with the NIR advantages of fluorescence imaging, Probe-OH was successfully applied to assess the freshness of pork and chicken breasts, and the structural changes of muscle tissue can be clearly observed under confocal microscope. The results of Z-axis scanning showed that Probe-OH could penetrate into the interior to monitor the internal corruption of meat tissue, the fluorescence intensity changes with scanning height in the meat tissue section, and reaches its maximum at 50 μm. To the best of our knowledge, there have been no reports of fluorescence probe being used to image the inside of meat tissue section so far. It is expected that we can provide a new rapid, sensitive, near-infrared fluorescence method for assessment of the freshness in the internal organization of meat.

Effect of resveratrol on skeletal slow-twitch muscle fiber expression via AMPK/PGC-1α signaling pathway in bovine myotubes

The purpose of this study was to evaluate the impact of resveratrol on slow-twitch muscle fiber expression in bovine myotubes. The results revealed that resveratrol enhanced slow myosin heavy chain (MyHC) and suppressed fast MyHC protein expression, accompanied by increased MyHC I/IIa and decreased MyHC IIx/IIb mRNA levels in bovine myotubes (P < 0.05). Resveratrol also enhanced the activities of succinic dehydrogenase (SDH), malate dehydrogenase (MDH) and the mitochondrial DNA (mtDNA) content, but reduced lactate dehydrogenase (LDH) activity (P < 0.05). Meanwhile, the protein and gene expression of AMPK, SIRT1 and PGC-1α were upregulated by resveratrol (P < 0.05). Furthermore, PGC-1α inhibitor SR-18292 could attenuate resveratrol-induced muscle fiber conversion from fast-twitch to slow-twitch. These results suggest that resveratrol might promote muscle fiber type transition from fast-twitch to slow-twitch through the AMPK/PGC-1α signaling pathway and mitochondrial biogenesis in bovine myotubes.