Search Results (26)

The focus on selecting broilers for rapid growth rates and enhanced breast muscle yield has resulted in a decline in meat quality. The differences in carcass characteristics and meat quality between Hubbard white broilers (HWs, a commercial breed) and Xueshan chickens (XSs, an indigenous breed) at market age were analyzed to determine the potential mechanisms responsible for these differences. The results show that HWs exhibited significantly better carcass performance than XSs, including the larger weight of the carcass, the breast muscle, and the thigh muscle (p < 0.01). In addition, based on HE staining analysis, HWs’ breast muscles had a considerably larger average myofiber area and diameter than those of XSs (p < 0.01). Furthermore, the physical characteristics of the meat revealed that XSs had higher redness and yellowness and also higher lightness. HW meat had a higher pH and thermal loss, but a lower shear force and drip loss than XS meat (p < 0.01). The content of saturated fatty acids (SFAs) and polyunsaturated fatty acids (PUFAs) was, remarkably, lower in the breast muscles of HWs than of XSs (p < 0.01). In contrast, HWs had a larger concentration of monounsaturated fatty acids (MUFAs) than XSs (p < 0.01). Finally, the breast muscles of XSs had lower levels of mRNA expression for genes linked to lipid metabolism, such as fatty acid binding protein 4 (Fabp4) and peroxisome proliferator-activated receptor alpha (Pparα), and had higher levels of the phosphofructokinase muscle type (Pfkm) compared to HWs (p < 0.01). These results indicate that a lower carcass yield was observed in XSs compared with HWs, but that XSs showed better performance in terms of meat quality than HW. Full article

Skeletal muscle diseases often exhibit fiber-type-specific characteristics and pose substantial clinical challenges, necessitating innovative therapies. The extracellular matrix (ECM) plays a pivotal role in muscle physiology and regeneration, influencing cell differentiation. However, its specific role and mechanisms influencing muscle fiber type specification remain insufficiently understood. In this study, C2C12^GFP myoblasts were differentiated into myofibers on plates coated with fibronectin, Collagen I, and Geltrex™. Differentiation occurred successfully across all ECM substrates, resulting in myofiber formation. Quantitative polymerase chain reaction (qPCR) analysis confirmed myogenic marker expression patterns, indicating decreased Pax7 and increased Myog levels by day 7. Protein analysis through Western blot and immunofluorescence assays along with transcriptomic profiling through RNA sequencing consistently indicated that Collagen I promoted slow-type fibers development, as evidenced by increased slow myofiber protein expression and the upregulation of slow fiber-associated genes, potentially mediated by pathways involving calcineurin/NFAT, MEF2, MYOD, AMPK, PI3K/AKT, and ERK1. In contrast, fibronectin and Geltrex™ led to fast-type fiber development, with elevated fast-type fiber protein levels and upregulation of fast fiber-associated genes, possibly through activation of HIF1A, FOXO1, NFKB, and ERK2. These findings elucidate ECM-mediated muscle fiber type differentiation mechanisms, informing future targeted therapies for muscle regeneration. Full article

Background: Ectopic fat deposition refers to lipid accumulation that affects metabolic function and tissue characteristics. Japanese Black cattle are distinguished by their high intramuscular fat content, which contributes to their distinctive character. However, the genetic mechanisms underlying these traits remain unclear. This study compared gene expression patterns in different muscle regions to identify genes associated with intramuscular fat accumulation. First, we conducted RNA sequencing to analyze differences in gene expression profiles among the sternocleidomastoid, pectoralis minor, and pectoralis major muscles. In addition, single-cell nuclear RNA sequencing was conducted to investigate the cellular composition of these muscle tissues. Results: Distinct gene expression patterns were observed among the different muscles. In the pectoralis, which contains a high proportion of intramuscular fat, adipocyte-related genes such as FABP4, SCD, and ADIPOQ were highly expressed. In addition, lipases such as PNPLA2, LPL, MGLL, and LIPE were predominantly expressed in intramuscular fat, whereas PLA2G12A, PLD3, and ALOX15 were specifically expressed in myofibers. Moreover, a subclass of fibro–adipogenic progenitor cells that differentiate into intramuscular adipocytes was found to express genes related to microenvironment formation, including ICAM1, TGFBRs, and members of the COL4A family. Conclusions: This study provides novel insight into the genetic regulation of intramuscular fat accumulation. It improves our understanding of the molecular mechanisms underlying their distinctive meat characteristics. Full article

Objectives: This study investigated the long-term effects of maternal undernutrition on overall muscle metabolism, growth performance, and muscle characteristics in postnatal offspring of Wagyu (Japanese Black) cattle. Methods: Wagyu cows were divided into nutrient-adequate (control, CNT; n = 4, 120% of requirements) and nutrient-restricted groups (NR; n = 4; 60% of requirements), and treated from day 35 of gestation until parturition. Diets were delivered on the basis of crude protein requirements, meeting 100% and 80% of dry matter requirements in CNT and NR groups, respectively. All offspring were provided with the same diet from birth to 300 days of age (d). Longissimus thoracis muscle (LM) samples were collected from the postnatal offspring. Results: The NR offspring had lower birth body weight, but their body weight caught up before weaning. These offspring showed enhanced efficiency in nutrient utilization during the post-weaning growth period. Comprehensive analyses of metabolites and transcripts revealed the accumulation of proteinogenic amino acid, asparagine, in NR offspring LM at 300 d, while the abundance of nicotinamide adenine dinucleotide (NADH) and succinate were reduced. These changes were accompanied by decreased gene expression of nicotinamide phosphoribosyltransferase (NAMPT), NADH: ubiquinone oxidoreductase subunit A12 (NDUFA12), and NADH dehydrogenase subunit 5 (ND5), which are essential for mitochondrial energy production. Additionally, NR offspring LM exhibited decreased abundance of neurotransmitter, along with a higher proportion of slow-oxidative myofibers and a lower proportion of fast-oxidative myofibers at 300 d. Conclusions: Offspring from nutrient-restricted cows might suppress muscle energy production, primarily in the mitochondria, and conserve energy expenditure for muscle protein synthesis. These findings suggest that maternal undernutrition programs a thrifty metabolism in offspring muscle, with long-term effects. Full article

Porcine latissimus dorsi muscle (LDM) is a crucial source of pork products. Meat quality indicators, such as the proportion of muscle fibers and intramuscular fat (IMF) deposition, vary during the growth and development of pigs. Numerous studies have highlighted the heterogeneous nature of skeletal muscle, with phenotypic differences reflecting variations in cellular composition and transcriptional profiles. This study investigates the cellular-level transcriptional characteristics of LDM in large white pigs at two growth stages (170 days vs. 245 days) using single-nucleus RNA sequencing (snRNA-seq). We identified 56,072 cells across 12 clusters, including myofibers, fibro/adipogenic progenitor (FAP) cells, muscle satellite cells (MUSCs), and other resident cell types. The same cell types were present in the LDM at both growth stages, but their proportions and states differed. A higher proportion of FAPs was observed in the skeletal muscle of 245-day-old pigs. Additionally, these cells exhibited more active communication with other cell types compared to 170-day-old pigs. For instance, more interactions were found between FAPs and pericytes or endothelial cells in 245-day-old pigs, including collagen and integrin family signaling. Three subclasses of FAPs was identified, comprising FAPs_COL3A1⁺, FAPs_PDE4D⁺, and FAPs_EBF1⁺, while adipocytes were categorized into Ad_PDE4D⁺ and Ad_DGAT2⁺ subclasses. The proportions of these subclasses differed between the two age groups. We also constructed differentiation trajectories for FAPs and adipocytes, revealing that FAPs in 245-day-old pigs differentiated more toward fibrosis, a characteristic reminiscent of the high prevalence of skeletal muscle fibrosis in aging humans. Furthermore, the Ad_PDE4D⁺ adipocyte subclass, predominant in 245-day-old pigs, originated from FAPs_PDE4D⁺ expressing the same gene, while the Ad_DGAT2⁺ subclass stemmed from FAPs_EBF1⁺. In conclusion, our study elucidates transcriptional differences in skeletal muscle between two growth stages of pigs and provides insights into mechanisms relevant to pork meat quality and skeletal muscle diseases. Full article

Skeletal muscle fiber characteristics are pivotal in assessing meat quality. However, there is currently a lack of research precisely quantifying the total number of myofibers (TNM) of skeletal muscles. This study used Arbor Acres (AA) broilers and Wenchang (WC) chickens to determine the TNM of several skeletal muscles and the meat quality of the pectoralis major muscle (PM). The results showed that the TNMs of the PM in AA males and females were 935,363.64 ± 92,529.28 and 873,983.72 ± 84,511.28, respectively, significantly higher than those in WC (511,468.97 ± 73,460.81 and 475,371.93 ± 70,187.83) at 7 days of age (p < 0.01). In terms of gastrocnemius medialis in AA males and females, we recorded values of 207,551.43 ± 31,639.97 and 177,203.23 ± 28,764.01, showing a significant difference compared to the values observed in WC (146,313.03 ± 29,633.21 and 124,238.9 ± 20,136.95) (p < 0.01). Similarly, the levels of gastrocnemius lateralis exhibited a significant difference between AA and WC (p < 0.01). Furthermore, the essential, umami, and sweet amino acids were found to be significantly higher in WC compared to AA (p < 0.01). These findings offer valuable data and insights for accurately quantifying the TNM in livestock and for the development of further genetic breeding strategies for meat quality. Full article

This study aimed to investigate the effects of dietary crude protein (CP) and lysine levels on growth performance, slaughter performance, meat quality, and myofiber characteristics of slow-growing chicken. A 3 × 3 factorial experiment was arranged, and the chickens were fed with 3 levels of dietary CP (16.0%, 17.0%, 18.0%) and 3 levels of dietary lysine (0.69%, 0.84%, 0.99%). A total of 540 8-week-old Beijing-You Chicken (BYC) female growing chickens were randomly allocated to 9 groups, 5 replicates per group, and 12 chickens per replicate. The birds were randomly allocated to one of the 9 experimental diets. Growth performance, slaughter performance, meat quality, and myofiber characteristics were determined at 16 weeks of age. The results showed that dietary CP level and the interaction of dietary CP and lysine levels affected average feed intake (AFI) (p < 0.05). The AFI in the 16.0% CP and 17.0% CP groups was higher than in the 18.0% CP group (p < 0.05). Dietary CP levels significantly affected body weight gain (BWG) (p < 0.05) at 9 to 16 weeks. The 18.0% CP group had the highest BWG (93.99 g). Dietary CP levels affected the percentage of leg muscle yield, and the percentage of leg muscle yield of the 16.0% CP group was significantly lower than that in the other two groups (p < 0.05). Dietary CP and lysine levels alone and their interactions did not affect pH_24h, drip loss, and cooking loss of breast muscle (p > 0.05). The shear force of the 18.0% CP group (29.55 N) was higher than that in the other two groups (p < 0.01). Dietary CP level affected myofiber characteristic (p < 0.01), with the lowest myofiber density (846.35 p·mm⁻²) and the largest myofiber diameter (30.92 μm) at 18.0% CP level. Dietary lysine level affected myofiber diameter, endomysium thickness, perimysium thickness (p < 0.01), with the largest myofiber diameter (29.29 μm) obtained at 0.84% lysine level, the largest endomysium thickness (4.58 μm) at 0.69% lysine level, and the largest perimysium thickness (9.26 μm) at 0.99% lysine level. Myofiber density was negatively correlated with myofiber diameter and endomysium thickness (R = −0.883, R = −0.523, p < 0.01); perimysium thickness had a significant negative correlation with shear force (R = −0.682, p < 0.05). Therefore, reducing dietary CP level and adding appropriate lysine can reduce myofiber diameter and increase perimysium thickness, reducing shear force and improving meat tenderness. A high lysine level (0.99%) in the low-CP (16.0%) diet can improve meat tenderness by regulating the myofiber characteristic without affecting production performance. Full article

Background and Objectives: Pelvic floor muscles (PFM) play a core role in defecation and micturition. Weakening of PFM underlies urogynecological disorders such as pelvic organ prolapse and stress urinary incontinence. Vaginal delivery damages PFM. Muscle trauma implies an inflammatory response mediated by myeloid cells, essential for subsequent recovery. Molecular signaling characterizing the pro-inflammatory phase shifts M1 macrophages to M2 macrophages, which modulate muscle repair. The present study aimed to evaluate histological characteristics and the presence of M1 and M2 macrophages in bulbospongiosus (Bsm) and pubococcygeus muscles (Pcm). Materials and Methods: Muscles from young nulliparous (N) and multiparous rabbits on postpartum days three (M3) and twenty (M20) were excised and histologically processed to measure the myofiber cross-sectional area (CSA) and count the centralized myonuclei in hematoxylin-eosinstained sections. Using immunohistochemistry, M1 and M2 macrophages were estimated in muscle sections. Kruskal–Wallis or one-way ANOVA testing, followed by post hoc tests, were conducted to identify significant differences (p < 0.05). Results: The myofiber CSA of both the Bsm and Pcm of the M3 group were more extensive than those of the N and M20 groups. Centralized myonuclei estimated in sections from both muscles of M20 rabbits were higher than those of N rabbits. Such histological outcomes matched significant increases in HLA-DR immunostaining in M3 rabbits with the CD206 immunostaining in muscle sections from M20 rabbits. Conclusions: A shift from the pro- to anti-inflammatory phase in the bulbospongiosus and pubococcygeus muscles of multiparous rabbits matches with centralized myonuclei, suggesting the ongoing regeneration of muscles. Full article

This study investigated the effects of dietary chitosan oligosaccharide (COS) supplementation on meat quality, antioxidant capacity, and muscle fiber characteristics in the thigh muscle of broilers. The results showed that dietary COS supplementation decreased shear force and increased crude protein content and nutritional value in the thigh muscle, while decreasing the content of C16:0, C18:0, and total saturated fatty acids. Dietary COS supplementation increased free radical scavenging activity, antioxidant enzyme activity, and antioxidant enzyme-related gene expression. Additionally, COS promoted MyHCI while decreasing MyHCIIb mRNA expression levels. The myofiber transformation was associated with upregulated gene expression of CaN, NFATc1, MyoD, and SIRT1. Together, the results of this study demonstrate that dietary COS supplementation improves meat quality, nutritional value, antioxidant capacity, and myofiber transformation to more oxidative muscle fibers in the thigh muscle of broilers when its supplemental level is 400 mg/kg. Full article

For fresh meat consumers, eating satisfaction is of utmost importance and tenderness is one of the most important characteristics in this regard. Our study examined beef of different animal biotypes of the autochthonous breed “Asturiana de los Valles” (AV) to determine if early postmortem oxidative and proteolytic processes may influence the final tenderness of the product. This meat-specialized breed shows different biotypes depending on the frequency of a myostatin mutation “mh” that induces double-muscling or muscular hypertrophy (mh/mh, mh/+, +/+). Samples from the longissimus dorsi muscles of yearling bulls were analyzed during the first 24 h postmortem. Changes in the redox balance of muscle cells were significant in the first hours after slaughter; total antioxidant activity was higher in the mh/mh biotype and it followed the shortening of the sarcomeres, a key parameter in understanding meat tenderness. The two proteolytic systems studied (proteasome and lysosome) followed distinct patterns. Proteasome activity was higher in the (mh/+) biotype, which correlated with higher protein damage. Lysosome proteolysis was increased in the more tender biotypes (mh genotypes). Autophagic activation showed significant differences between the biotypes, with (mh/mh) showing more intense basal autophagy at the beginning of the postmortem period that decreased gradually (p < 0.001), while in the normal biotype (+/+), it was slightly delayed and then increased progressively (p < 0.001). These results suggest that this type of catalytic process and antioxidant activity could contribute to the earlier disintegration of the myofibers, particularly in the mh/mh biotypes, and influence the conversion of muscle into meat. Full article

The aim of this study is to assess the differences in the meat quality, nutritional composition, carcass traits, and myofiber characteristics between Hy-Line grey chickens (HLG, commercial breed) and Guangyuan grey chickens (GYG, indigenous breed). A total of 20 55-week-old chickens were selected for slaughter. The HLG exhibited a larger carcass weight, breast muscle weight, and abdominal fat weight (p < 0.05). The GYG exhibited a higher crude protein content, lower shear force, and smaller fiber size in the thigh muscles, whereas the HLG presented higher pH values and lower inosine-5′-monophosphate content in the breast muscles (p < 0.05). Darker meat based on higher redness and yellowness values was observed in the GYG instead of the HLG (p < 0.05). The research results also revealed parameter differences between different muscle types. Simultaneously, a correlation analysis showed significant correlations between the meat quality traits and myofiber characteristics (p < 0.05). In conclusion, aged indigenous chickens perform better in terms of tenderness and nutritional value in the thigh muscles, and may exhibit a better flavor in the breast muscles, but have a smaller breast muscle weight. Therefore, the current investigation provides a theoretical basis for the different needs of consumers and the processing of meat from old laying hens. Full article

The Chuanzang black (CB) pig is a new crossbred between Chinese local breeds and modern breeds. Here, we investigated the growth performance, plasma indexes, carcass traits, and meat quality characteristics of conventional DLY (Duroc × Landrace × Yorkshire) crossbreed and CB pigs. The LC-MS/MS-based metabolomics of pork from DLY and CB pigs, as well as the relationship between the changes in the metabolic spectrum and meat quality, were analyzed. In this study, CB pigs presented lower final body weight, average daily gain, carcass weight, and eye muscle area than DLY pigs (p ˂ 0.05). Conversely, the ratio of feed to gain, marbling score, and meat color score of longissimus dorsi (LD) were higher in CB than DLY pigs (p ˂ 0.05). Moreover, psoas major (PM) showed a higher meat color score and a lower cooking loss in CB than DLY pigs (p ˂ 0.05). Interestingly, CB pigs showed lower myofiber diameter and area but higher myofiber density than DLY pigs (p ˂ 0.05). Furthermore, the mRNA expression levels of MyHC I, PPARδ, MEF2C, NFATC1, and AMPKα1 were higher in CB than DLY pigs (p ˂ 0.05). Importantly, a total of 753 metabolites were detected in the two tissues (e.g., psoas major and longissimus dorsi) of CB and DLY pigs, of which the difference in metabolite profiles in psoas major between crossbreeds was greater than that in longissimus dorsi. Specifically, palmitic acid, stearic acid, L-aspartic acid, corticosterone, and tetrahydrocorticosterone were the most relevant metabolites of psoas major meat quality, and tetrahydrocorticosterone, L-Palmitoylcarnitine, arachidic acid, erucic acid, and 13Z,16Z-docosadienoic acid in longissimus dorsi meat were positively correlated with meat quality. The most significantly enriched KEGG pathways in psoas major and longissimus dorsi pork were galactose metabolism and purine metabolism, respectively. These results not only indicated improved meat quality in CB pigs as compared to DLY pigs but may also assist in rational target selection for nutritional intervention or genetic breeding in the swine industry. Full article

Resveratrol is a natural polyphenol utilized in Chinese traditional medicine and thought to be one of the determinants of the “French Paradox”. More recently, some groups evidenced its properties as a calorie-restriction mimetic, suggesting that its action passes through the modulation of skeletal muscle metabolism. Accordingly, the number of studies reporting the beneficial effects of resveratrol on skeletal muscle form and function, in both experimental models and humans, is steadily increasing. Although studies on animal models confer to resveratrol a good potential to ameliorate skeletal muscle structure, function and performance, clinical trials still do not provide clear-cut information. Here, we first summarize the effects of resveratrol on the distinct components of the skeletal muscle, such as myofibers, the neuromuscular junction, tendons, connective sheaths and the capillary bed. Second, we review clinical trials focused on the analysis of skeletal muscle parameters. We suggest that the heterogeneity in the response to resveratrol in humans could depend on sample characteristics, treatment modalities and parameters analyzed; as well, this heterogeneity could possibly reside in the complexity of skeletal muscle physiology. A systematic programming of treatment protocols and analyses could be helpful to obtain consistent results in clinical trials involving resveratrol administration. Full article

The quail is an important research model, and the demand for quail meat has been increasing in recent years; therefore, it is worthwhile investigating the development of embryonic skeletal muscle and the expression patterns of regulatory genes. In this study, the expression of MyoD and Pax7 in the breast muscle (m. pectoralis major) and leg muscle (m. biceps femoris) of quail embryos on days 10 through 17 were determined using qRT-PCR. Paraffin sections of embryonic muscle were analyzed to characterize changes over time. Results showed that MyoD and Pax7 were expressed in both breast and leg muscles and played a significant role in embryonic muscle development. Compared to breast muscle, leg muscle grew faster and had greater weight and myofiber size. The findings suggested that embryonic day 12 (E12) may be a key point for muscle development. Correlation analysis showed that MyoD expression was significantly negatively correlated with muscle and embryo weight, whereas Pax7 gene expression had no significant correlation with these characteristics. These fundamental results provide a theoretical basis for understanding the characteristics and transition points of skeletal muscle development in quail embryos and an important reference for farmers raising quail from eggs. Full article

Disuse muscle atrophy is usually accompanied by changes in skeletal muscle structure, signaling, and contractile potential. Different models of muscle unloading can provide valuable information, but the protocols of experiments with complete immobilization are not physiologically representative of a sedentary lifestyle, which is highly prevalent among humans now. In the current study, we investigated the potential effects of restricted activity on the mechanical characteristics of rat postural (soleus) and locomotor (extensor digitorum longus, EDL) muscles. The restricted-activity rats were kept in small Plexiglas cages (17.0 × 9.6 × 13.0 cm) for 7 and 21 days. After this, soleus and EDL muscles were collected for ex vivo mechanical measurements and biochemical analysis. We demonstrated that while a 21-day movement restriction affected the weight of both muscles, in soleus muscle we observed a greater decrease. The maximum isometric force and passive tension in both muscles also significantly changed after 21 days of movement restriction, along with a decrease in the level of collagen 1 and 3 mRNA expression. Furthermore, the collagen content itself changed only in soleus after 7 and 21 days of movement restriction. With regard to cytoskeletal proteins, in our experiment we observed a significant decrease in telethonin in soleus, and a similar decrease in desmin and telethonin in EDL. We also observed a shift towards fast-type myosin heavy chain expression in soleus, but not in EDL. In summary, in this study we showed that movement restriction leads to profound specific changes in the mechanical properties of fast and slow skeletal muscles. Future studies may include evaluation of signaling mechanisms regulating the synthesis, degradation, and mRNA expression of the extracellular matrix and scaffold proteins of myofibers. Full article