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The present study aimed to characterize the influence of hypoxia-inducible factor-1α on heat shock protein 27 and cytochrome c translocation, yak meat microstructure destruction, and endogenous enzymes activities, refining the understanding of the tenderization process after slaughter. Postmortem yak longissimus thoracis et lumborum muscles were incubated with 0.9% saline or hypoxia-inducible factor-1α stabilizer dimethyloxaloylglycine at 4 °C for 6, 12, 24, 72, and 120 h. Results showed that hypoxia-inducible factor-1α activation promoted heat shock protein 27 migration and cytochrome c release, facilitating (P < 0.05) caspase-3 activity by mediating the heat shock protein 27/caspase-3 interaction but did not exert (P > 0.05) significant effects on the calpain-1 activity. Additionally, hypoxia-inducible factor-1α activation contributed to the mitochondrial apoptosis cascade, leading to a higher (P < 0.01) apoptosis rate. Therefore, these observations indicate that hypoxia-inducible factor-1α affects caspase-3 activity and tenderness of postmortem muscle through distinct regulatory mechanisms, possibly, in part, with heat shock protein 27 and cytochrome c mediation. • Hypoxia-inducible factor-1α elevated caspase-3 activity via inhibiting heat shock protein 27-caspase-3 interactions level. • The calcium levels and calpain-1 activity were not significantly affected by hypoxia-inducible factor-1α stabilization. • Hypoxia-inducible factor-1α involvement in the intrinsic mitochondrial apoptosis pathway improves muscle tenderization. • Steaks following hypoxia-inducible factor-1α activation possessed enhanced postmortem tenderness. [ABSTRACT FROM AUTHOR]

Although exhaustive studies have established that oxidative stress is a key contributor to accelerated postmortem metabolism, the specific reasons remain fully undefined. We hypothesized that nuclear accumulation of hypoxia-inducible factor-1α (HIF-1α), a significant transcription factor for energy metabolism, regulates postmortem glycolysis under oxidative stress. Postmortem yak longissimus dorsi (LD) muscles were incubated with saline, hydrogen peroxide (H 2 O 2), H 2 O 2 plus MAPK/ERK inhibitor (U0126), or H 2 O 2 plus U0126 and HIF-1α activator, dimethyloxalylglycine (DMOG), respectively. Changes in HIF-1α, MAPK/ERK signaling pathway, and postmortem metabolism levels were measured in muscles collected from all time points. Oxidative stress significantly activated MAPK/ERK pathway and increased HIF-1α expression and nuclear translocation (P < 0.05) although its mRNA levels were hardly affected (P > 0.05). Additionally, oxidative stress enhanced early postmortem muscle metabolism (P < 0.05). These effects were substantially weakened by U0126 treatment, which prevented oxidative stress-induced HIF-1α accumulation and glycolysis. Interestingly, this attenuation could be bypassed by DMOG (P < 0.05). Altogether, MAPK/ERK-dependent maintenance and enhancement of HIF-1α nuclear accumulation promotes postmortem metabolism during early postmortem under oxidative stress. These findings provide valuable information on postmortem metabolism that HIF-1α regulates glycolysis under oxidative stress and suggest that HIF-1α can serve as a target for controlling postmortem glycolysis. A schematic diagram demonstrates the HIF-1α-dependent regulation of the accelerated glycogen metabolism under oxidative stress in postmortem muscle. Postmortem hypoxia triggers a continuous ROS production while antioxidant capacities constantly decrease in the slaughtered muscle, inevitably promoting oxidative stress. Oxidative stress induces HIF-1α stabilization and nuclear accumulation, which is mediated by MAPK/ERK signaling pathway phosphorylation and activation. In the nucleus, increased HIF-1α accumulation increases the binding of HIF-1a to the HRE site within energy metabolism-related genes promoter, in turn, thereby activating the transcription of energy metabolism target genes associated with GLUT1, HK, PFK, and LDH. Thus, HIF-1α-dependent expression of these glycolytic genes promotes glycogen metabolism under oxidative stress in postmortem muscle. [Display omitted] • Oxidative stress promoted hypoxia-inducible factor (HIF)-1α nuclear accumulation. • Oxidative stress facilitated HIF-1α activation via MAPK/ERK signaling pathway. • HIF-1α accelerated glycogen metabolism under oxidative stress early postmortem. [ABSTRACT FROM AUTHOR]

Simple Summary: Exosomes are multivesicular bodies produced and secreted by living cells as membranous vesicles with a diameter of about 30–150 nm, density of 1.13–1.19 g/mL, and a typical "cup dish" shape. Exosomes carry proteins, miRNA, lncRNA, circRNA, and mRNA and their degradation fragments are involved in intracellular signal transduction important for regulation of cellular activities. Of these, miRNAs play an important role in the regulation of gene expression in important biological processes such as cell division, tissue development, and immune response. In this study, milk quality was determined and exosome miRNAs from yak and Jeryak milk sampled in June and December were characterized by sequencing. Differentially expressed miRNAs (DEMs) and pathways related to lactation performance were identified. In summary, this study provides data that can be used to develop alternative strategies for improving the lactation performance of yaks and Jeryaks. The Jeryak is the hybrid offspring of yaks and Jersey cattle and exhibit improved milk and meat yields. Biomolecules carried within milk exosomes are important for cell growth, development, immune regulation, and various pathophysiological processes. Previous studies showed that miRNAs regulate mammary gland development, lactation, and milk quality. This study explored the relationship between milk exosomes miRNAs and lactation performance. A comparison of the milk content showed that yak milk was of a better quality compared to Jeryak milk (casein, fat, TS, SNF, lactose). Milk collected in December was superior to that collected in June for both yak and Jeryak, except for lactose concentrations. Exosomes were extracted by density gradient centrifugation and miRNA expression profiles in milk exosomes from three yaks and three Jeryaks collected in June and December were detected by small RNA sequencing. In all, 22, 120, 78, and 62 differentially expressed miRNAs (DEMs) were identified in Jun_ JY vs. Jun_ Y (P1: Jeryak in June vs. Yak in June), Jun_ JY vs. Dec_ JY (P2: Jeryak in June vs. Jeryak in December), Dec_ JY vs. Dec_ Y (P3: Jeryak in December vs. Yak in December), and Jun_ Y vs. Dec_ Y (P4: Yak in June vs. Yak in December) groups. These DEMs were enriched in functions and signaling pathways related to lactation performance. In conclusion, these findings are a reference tool to study the molecular basis of lactation performance. [ABSTRACT FROM AUTHOR]

Simple Summary: The aim of our study was to investigate the effects of dietary supplementation with different protein levels after grazing on growth performance as well as on the proteomics of the LL muscle of Jersey-yak. The results showed that a certain amount of crude protein supplementation to Jersey-yak at the end of grazing significantly improved growth performance and increased their economic efficiency. In addition, we analyzed the proteomic differences in the longest dorsal muscle of Jersey-yak. From our analyses, we identified differences in the abundance of 434 proteins involved in pathways related to muscle growth and development and energy metabolism, among others. Several of the proteins enriched in these pathways, such as MYH8, are associated with myoblast development and differentiation as well as muscle development. In conclusion, the results of this study provide proteomic insights into the different feeding patterns of yak crossbred progeny, suggesting that a greater economic income can be achieved by improving their feeding conditions. Jersey-yak is a hybrid offspring of Jersey cattle and yak (Bos grunniens). Changing the feeding system of Jersey-yak can significantly improve its growth performance. In this study, tandem mass tag (TMT) proteomics technology was used to determine the differentially expressed proteins (DEPs) of the longissimus lumborum (LL) muscle of Jersey-yak fed different protein levels of diet. The results showed that compared with the traditional grazing feeding, the growth performance of Jersey-yaks was significantly improved by crude protein supplementation after grazing. A total of 3368 proteins were detected in these muscle samples, of which 3365 were quantified. A total of 434 DEPs were identified. Through analyses, it was found that some pathways related to muscle growth and development were significantly enriched, such as Rap1 signaling pathway, mTOR signaling pathway, and TGF-beta signaling pathway. A number of DEPs enriched in these pathways are related to muscle cell development, differentiation, and muscle development, including integrin subunit alpha 7 (ITGA7), myosin heavy chain 8 (MYH8), and collagen type XII alpha 1 chain (COL12A1). In conclusion, the results of this study provide insights into the proteomics of different feeding patterns of Jersey-yak, providing a stronger basis for further understanding the biological mechanism of hybrid varieties. [ABSTRACT FROM AUTHOR]

Cattle-yak is a hybrid F1 generation of cattle and yak, which has a history of more than 3000 years and has shown better production performance and higher economic benefits than those of yaks. However, up to now, there has been no study on the transcriptome-wide m6A methylation profile of bovine skeletal muscle and its potential biological function during muscle development. Here, we observed significant changes in the expression levels of muscle-related marker genes and methylation-related enzymes during the development of cattle-yak, and the overall m6A content in the Longissimus dorsi muscle of 18-month-old cattle-yak decreased significantly. A total of 36,602 peaks, 11,223 genes and 8388 lncRNAs were identified in the two groups, including 2989 differential peaks (427 up-regulated peaks and 2562 down-regulated peaks), 1457 differentially expressed genes (833 up-regulated genes and 624 down-regulated genes) and 857 differentially expressed lncRNAs (293 up-regulated lncRNAs and 564 down-regulated lncRNAs). GO and KEGG analysis revealed that they were significantly enriched in some muscle-related pathways (Wnt signaling pathway and MAPK signaling pathway) and high-altitude adaptation-related pathway (HIF-1 signaling pathway). Moreover, m6A abundance was positively correlated with gene expression levels, while it was negatively correlated with lncRNA expression levels. This indicates that m6A modification played an important role in the Longissimus dorsi muscle development of cattle-yak; however, the regulation mechanism of m6A-modified mRNA and lncRNA may be different. This study was the first report of transcriptome-wide m6A-modified mRNAs and lncRNAs atlas in the Longissimus dorsi muscle development of cattle-yak, one which will provide new perspectives for genetic improvement in bovines. [ABSTRACT FROM AUTHOR]

Simple Summary: Yak (Bos grunniens) is the most economically and culturally important domestic bovine species adapted to the extreme ecological environment of the Qinghai–Tibetan Plateau (QTP), which provides milk, meat, transportation, fuel (yak dung), and wool for local nomads as well as major sources of income. Calves are an important part of the sustainable development of the yak industry on the QTP, and the quality of calf rearing directly determines the production performance of adult animals. Under the traditional grazing management, late weaning (>180 days) of yak calves seriously affects the improvement of their production performance. A comparative study of fecal microbiota dynamics of yak and cattle (Bos taurus) calves in different months after weaning will help to understand the changes in intestinal microbiota structure, and will aid in in improving growth rate and survivability of early weaned calves. Our research will contribute to the development of appropriate strategies to regulate the gut microbiome and thus improve the growth and health of the grazing ruminants on the QTP. Background: The gut microbiota plays an important role in the health and production of animals. However, little information is available on the dynamic variations and comparison of intestinal microbiota in post-weaning yak calves living on the QTP. Methods: We explored the fecal bacterial microbiota succession of yak calves at different months after early weaning (60 d) compared with cattle calves by 16S rRNA gene amplicon sequencing and functional composition prediction. Results: We found no significant difference in blood biochemical parameters related to glucose and lipid metabolism between yaks and calves in different months after weaning. The core fecal bacterial microbiota from both species of calves was dominated by Ruminococcaceae, Rikenellaceae, and Bacteroidaceae. The fecal microbial community has a great alteration within the time after weaning in both cattle and yak calves, but cattle showed a larger change. After five months, the microbiota achieves a stable and concentrated state. This is also similar to the functional profile. Conclusions: Based on the exploration of dynamic changes in the fecal microbiota at an early stage of life, our results illustrated that there were no negative effects of intestinal microbiota succession on yak calves when early weaning was employed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Glu, Leu and Val were identified as differential amino acids of fermented yak milk in three regions. • Identified 5 bacterial genera and 3 fungi genera as contributors to flavor production. • Environmental factors had a greater influence on the composition of bacterial communities. • Lactobacillus and Streptococcus were associated with 2,3-pentanedione through 8 KEGG pathways. Traditional fermented yak milk has immense cultural and nutritional significance for Tibetan herders. In this study, we investigated the microbial community structure and flavour compounds in traditional fermented yak milk from three distinct regions of Gannan to explore the relationship between microbial composition and flavour compounds. The findings revealed significant variations in flavour compounds and the bacterial microbiota among the samples from the three regions. The dominant species identified in fermented yak milk were Streptococcus salivarius subsp. Thermophilus , Lactobacillus helveticus , and Kluyveromyces marxianus. Bidirectional orthogonal partial least-squares (O2PLS) analysis highlighted five bacterial genera and three fungal genera as contributors to the production of flavour-related compounds. Furthermore, regression analysis revealed that the Lactobacillus and Streptococcus genera were associated with the production of 2,3-pentanedione as well as eight predicted KEGG pathways. These findings provide valuable insights into the intricate relationship between flavour compounds and microbiota in traditional fermented yak milk. [ABSTRACT FROM AUTHOR]

A cattle-yak, which is a hybrid between a yak (Bos grunniens) and cattle (Bos taurus), is an important livestock animal, but basic questions regarding its physiology and environmental adaptation remain unanswered. To address this issue, the present study examined the species composition and functional characteristics of rumen microorganisms in the cattle-yak of different ages (2 and 3 years old) by metagenomic analysis. We found that rumen microbial community composition was similar at the two ages. Firmicutes, Fibrobacteres, Euryarchaeota, Bacteroidetes, and Proteobacteria were the predominant phyla, with Firmicutes accounting for the highest percentage of bacteria in 2-year-old (48%) and 3-year-old (46%) animals. Bacterial species involved in lignocellulose degradation were detected in the rumen of adult cattle-yaks including Ruminococcus flavefaciens, Ruminococcus albus, Fibrobacter succinogenes, and Prevotella ruminicola, with F. succinogenes being the most abundant. A total of 145,489 genes were annotated according to the Carbohydrate-active Enzyme database, which identified glycoside hydrolases as the most highly represented enzyme family. Further functional annotation revealed specific microflora and genes in the adult rumen that are potentially related to plateau adaptability. These results could explain the heterosis of the cattle-yak and provide insight into mechanisms of physiologic adaptation in plateau animals. [ABSTRACT FROM AUTHOR]

A crude cheese, Qula, which is mainly made up of casein, is a common milk product with local characteristics in northwestern China, such as Gansu, Xinjiang and Tibet. It is made from yak milk with a traditional method: defatting, acidifying, and drying in air (at room temperature). Qula is the raw materials of yak milk casein and collected by factory for further processing. Yak milk casein has been widely used in various fields, such as glues, papermaking, leather, food additives and pharmaceutical applications. However, the traditional process, especially for drying under the sun, can cause severe browning, yellowing and poor quality in Qula. Therefore, hot-air drying method which is based on the evaluation of color quality is adopted in Qula processing. Qula samples were from Gannan city in Gansu Province (Experimental group, 60%-62% moisture was conducted; Control group, 10%-12% moisture was conducted). L*, a*, b* values of dried products were taken as target parameters, and the three factors were scored by the comprehensive evaluation using the data standardization method. According to the central composite experimental design, the response surface methodology (RSM) was adopted to discuss the influence caused by drying temperature, material thickness and wind velocity based on the single factor test of temperature (30, 35, 40, 45, 50 and 55°C), material thickness (6, 8, 10, 12, 14 and 16 mm) and wind velocity (20, 40, 60, 80 and 100 m/min). In addition, the quadratic polynomial regression model was established by SAS software to optimize the drying techniques. The peroxide value (POV), thiobarbituric acid reactive substances (TBARS) and 5-hydroxymethylfurfural (HMF) were measured which are the important indictors of fat oxidation and furanic compound forms as an intermediate product in Maillard reaction. The results showed that the order of significance among three factors were: temperature>wind velocity> material thickness. The optimal parameters of hot-air drying were obtained with a temperature of 41°C, material thickness of 10 mm and wind velocity of 60 m/min, then the largest comprehensive score of 0.9012 was obtained. L* value of Qula by hot-air drying increased by 7.18 (P<0.05), a* and b* values reduced by 1.41 and 10.29, respectively (P<0.01), and the POV, TBARS value and the content of 5-HMF reduced by 1.15 g/100 g, 0.84 mg/kg and 1.973 mg/L, respectively (P<0.01). All in all, the damages which were caused by far oxidation and Maillard reaction can be reduced by this method; meanwhile, the color quality of Qula can be improved dramatically. [ABSTRACT FROM AUTHOR]