Cloning of oligopeptide transport carrier PepT1 and comparative analysis of PepT1 messenger ribonucleic acid expression in response to dietary nitrogen levels in yak () and indigenous cattle () on the Qinghai-Tibetan plateau

Linkages between rumen microbiome, host, and environment in yaks, and their implications for understanding animal production and management

Livestock on the Qinghai-Tibetan Plateau is of great importance for the livelihood of the local inhabitants and the ecosystem of the plateau. The natural, harsh environment has shaped the adaptations of local livestock while providing them with requisite eco-services. Over time, unique genes and metabolic mechanisms (nitrogen and energy) have evolved which enabled the yaks to adapt morphologically and physiologically to the Qinghai-Tibetan Plateau. The rumen microbiota has also co-evolved with the host and contributed to the host's adaptation to the environment. Understanding the complex linkages between the rumen microbiota, the host, and the environment is essential to optimizing the rumen function to meet the growing demands for animal products while minimizing the environmental impact of ruminant production. However, little is known about the mechanisms of host-rumen microbiome-environment linkages and how they ultimately benefit the animal in adapting to the environment. In this review, we pieced together the yak's adaptation to the Qinghai-Tibetan Plateau ecosystem by summarizing the natural selection and nutritional features of yaks and integrating the key aspects of its rumen microbiome with the host metabolic efficiency and homeostasis. We found that this homeostasis results in higher feed digestibility, higher rumen microbial protein production, higher short-chain fatty acid (SCFA) concentrations, and lower methane emissions in yaks when compared with other low-altitude ruminants. The rumen microbiome forms a multi-synergistic relationship among the rumen microbiota services, their communities, genes, and enzymes. The rumen microbial proteins and SCFAs act as precursors that directly impact the milk composition or adipose accumulation, improving the milk or meat quality, resulting in a higher protein and fat content in yak milk and a higher percentage of protein and abundant fatty acids in yak meat when compared to dairy cow or cattle. The hierarchical interactions between the climate, forage, rumen microorganisms, and host genes have reshaped the animal's survival and performance. In this review, an integrating and interactive understanding of the host-rumen microbiome environment was established. The understanding of these concepts is valuable for agriculture and our environment. It also contributes to a better understanding of microbial ecology and evolution in anaerobic ecosystems and the host-environment linkages to improve animal production.

The uniqueness and superiority of energy utilization in yaks compared with cattle in the highlands: A review

Yaks living on the Qinghai-Tibetan Plateau for a long time have evolved a series of mechanisms to adapt to the unique geographical environment and climate characteristics of the plateau. Compared with other ruminants, yaks have higher energy utilization and metabolic efficiency. This paper presents possible mechanisms responsible for the efficient energy utilization, absorption and metabolism resulting from the unique evolutionary process of yaks. It is hoped that the information discussed in this review will give a better insight into the uniqueness and superiority of yaks in regards to energy metabolism and utilization compared with cattle and open new avenues for the targeted regulation of energy utilization pathways of other ruminants.

Integrated proteomic, phosphoproteomic, and N-glycoproteomic analyses of the longissimus thoracis of yaks

Yaks (Bos mutus) live in the Qinghai–Tibet plateau. The quality of yak meat is unique due to its genetic and physiological characteristics. Identification of the proteome of yak muscle could help to reveal its meat-quality properties. The common proteome, phosphoproteome, and N-glycoproteome of yak longissimus thoracis (YLT) were analyzed by liquid chromatography-tandem mass spectrometry-based shotgun analysis. A total of 1812 common proteins, 1303 phosphoproteins (3918 phosphorylation sites), and 204 N-glycoproteins (285 N-glycosylation sites) were identified in YLT. The common proteins in YLT were involved mainly in myofibril structure and energy metabolism; phosphoproteins were associated primarily with myofibril organization, regulation of energy metabolism, and signaling; N-glycoproteins were engaged mainly in extracellular-matrix organization, cellular immunity, and organismal homeostasis. We reported, for the first time, the “panorama” of the YLT proteome, specifically the N-glycoproteome of YLT. Our results provide essential information for understanding post mortem physiology (rigor mortis and aging) and the quality of yak meat.

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A total of 2650 proteins were identified in yak longissimus thoracis.

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Common proteins were involved mainly in myofibril structure and energy metabolism.

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Phosphoproteins were associated with myofibrils, energy metabolism, and signaling.

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N-glycoproteins were engaged mainly in ECM organization, immunity, and homeostasis.

Cloning of oligopeptide transport carrier PepT2 and comparative analysis of PepT2 expression in response to dietary nitrogen levels in yak and cattle

The objectives of this study were clone oligopeptide transport carrier PepT2 and compare its abundance in kidney tissues of yak and cattle in response to different dietary nitrogen levels. Four adult female yaks were enrolled as donor animals for profiling the molecular characteristics and expression specificity of yak PepT2 (yPepT2), and twenty-four castrated males of each of two genotypes, yak (Bos grunniens) and indigenous cattle (Bos taurus) were used to explore PepT2 mRNA expression in kidney tissue in different nitrogen (N) levels (10.3, 19.5, 28.5 or 37.6 g N/kg dry matter; DM). Our results showed that the yPepT2 coding sequence region contains 2190 bp, and encodes a putative protein of 729 amino acids (AA) residues. The yPepT2 AA sequence identified eight putative extracellular N-glycosylation sites (Asn7, Asn80, Asn373, Asn435, Asn472, Asn508, Asn528, Asn587) and eight intracellular putative protein kinase C sites (Ser34, Ser264, Ser274, Ser376, Ser442, Ser586, Ser640, Ser724). The yPepT2 AA sequence was 98 and 94% identical to PepT2 from zebu cattle (Bos indicus) and sheep (Ovis aries), respectively. The relative PepT2 expression in kidney tissue for yak was greater than of indigenous cattle in the10.3 and 28.5 N/kg DM diet, but it was lower for yaks in 37.6 N/kg DM diet. These implied that relative PepT2 mRNA expression was higher in yak kidney than that in indigenous cattle at lower dietary N supplies, but more research on PepT2 will be required to determine the renal regulatory mechanisms.

Comparative study of growth performance, nutrient digestibility, and ruminal and fecal bacterial community between yaks and cattle-yaks raised by stall-feeding

The experiment was conducted to compare the growth performance, rumen fermentation, nutrient digestibility, and ruminal and fecal bacterial community between yaks and cattle-yaks. Ten male yaks (36-month-old) were used as the yak (YAK) group and 10 male cattle-yaks with similar age were selected as the cattle-yak (CAY) group. All the animals were fed same ration and the experiment lasted for 60 days. The results showed that the average daily gain and dry matter intake of CAY group were higher (P < 0.05) than those of YAK group. The ruminal concentrations of total volatile fatty acids, acetate, and butyrate were higher (P < 0.05) in CAY group than those in YAK group. However, the neutral detergent fiber and acid detergent fiber digestibility exhibited an opposite between two groups. In the rumen, the relative abundances of Prevotella 1 and Prevotellaceae UCG-001 were higher (P < 0.05) and Succiniclasticum and Butyrivibrio 2 were lower (P < 0.05) in YAK group compared to CAY group. In the feces, the unclassified Lachnospiraceae, Lachnospiraceae NK4A136 group, and Lachnospiraceae AC2044 group were significantly enriched (P < 0.05) in YAK group, whereas the Ruminococcaceae UCG-010, Ruminococcaceae UCG-013, and Succiniclasticum were significantly enriched (P < 0.05) in CAY group. Overall, under the same diet, the yaks have higher fiber utilization and cattle-yaks have higher energy utilization.

Cloning, phylogenetic analysis, and postnatal expression of oligopeptide transporter PepT1 in gastrointestinal tract of kid goats receiving supplemental feed or pasture

This study aimed to clone the cDNA of PepT1, an H+-dependent oligopeptide transporter, from kid goats and examine effects of physiological development (suckling, weaning, and post-weaning) of the animal and feeding system (supplemental feeding vs. grazing) on peptide transport capability. A 2395 bp cDNA sequence of pept1 (GenBank: MH308024) was cloned and phylogenetic analysis revealed a high homology and structure similarity with PepT1 of sheep and cattle. The pept1 was expressed throughout the gastrointestinal tract of kid goats immediately after birth and during development. Relative abundance of pept1 decreased in all segments except the middle-jejunum during suckling, whereas its expression in most segments of small intestine increased with age after weaning and remained stable thereafter. Middle-jejunum was the predominant expression site and probably the main peptide absorption site. Supplemental feeding enhanced pept1 expression because it increased protein intake compared with grazing. No feeding system × age interaction was observed in most segments; the expression was age related during suckling and diet related during weaning and post-weaning, indicating that feeding system and age had independent effects on pept1 expression. These results indicate that PepT1 plays an important role for protein nutrition in neonatal goats, and its expression can be affected by feeding system.

Signature of high altitude adaptation in the gluteus proteome of the yak

Yak is the unique Bovidae species in the Qinghai-Tibetan Plateau. A previous proteomic study has compared the yak muscle tissue to one cattle strain using the isobaric tags for relative and absolute quantification approach. In this study, to further investigate the molecular mechanisms underlying yak adaptation, the proteomic profiles of gluteus were compared between yak and one moderate-altitude cattle strain (Tibetan cattle) and two low-altitude cattle strains (Holstein and Sanjiang cattle) using a label-free quantitative method. The comparisons identified 20, 364, 143 upregulated proteins and 4, 6, 37 downregulated proteins in yak, compared with Tibetan, Holstein, and Sanjiang cattle, respectively. Protein-protein interaction analysis indicated that these differentially expressed proteins were mainly related to "oxidative phosphorylation" and "electron transport chain." Further analysis revealed that NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 11, NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 4, cytochrome C oxidase subunit 6A2, mitochondrial and cytochrome c oxidase subunit NDUFA4 were all increased in the yak, suggesting that yak might increase mitochondrial capacity to sustain metabolic rates under high altitude conditions, which might be a long-term adaptive mechanism underlying adaptation to high altitude environments. Yak increased the level of thioredoxin reductase 2 to protect themselves from oxidative damages. Moreover, the increased expression levels of phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha isoform and caveolin-1 in yak suggested that yaks promoted glucose uptake for adaptation to high altitude. These results provided more information to better understand the molecular mechanisms underlying yak adaption.

Expression of the Tas1r3 and Pept1 genes in the digestive tract of wagyu cattle

Animals have precise recognition systems for amino acids and peptides that regulate their feeding behavior as well as metabolic responses. Because of their particular gastrointestinal structure, ruminants are expected to have unique mechanisms of amino acid regulation in the digestive tract. To better understand these mechanisms in the ruminant digestive tract, the expression of Tas1r3 and Pept1 was studied along the gastrointestinal tract of Japanese Black cattle through quantitative RT-PCR and immunohistochemistry. Tas1r3 mRNA was detected ubiquitously along the gastrointestinal tract, and the most predominant expression was observed in the reticulum. In addition, the presence of Tas1r3 receptor was confirmed in the rumen through immunohistochemistry. The expression level of Pept1 mRNA was higher in the forestomach (rumen, reticulum, and omasum) and small intestine (duodenum) than that in the tongue, and predominant expression was observed in the rumen. By contrast, a negligible amount of Pept1 mRNA was detected in the abomasum and large intestine. Further studies on the roles of Tas1r3 and Pept1 in the digestive tract, in particular, in the four components of the stomach, will help us to understand the mechanisms of amino acids regulation in ruminants and provide the basis for formulating cattle diets to improve the health and productivity of cattle.

Rumen parameters of yaks (Bos grunniens) and indigenous cattle (Bos taurus) grazing on the Qinghai-Tibetan Plateau

Yaks and indigenous Qaidam cattle and cattle-yak crosses (C × Y) graze on the Qinghai-Tibetan Plateau (QTP) throughout the year, but yaks are raised at higher elevations than cattle. Yaks do not receive supplementary feed whereas cattle require supplementary feed during harsh winter. We hypothesized that yaks would cope with the severe conditions of the QTP better than cattle and utilize the pasture more efficiently. We also hypothesized that differences between species would be pronounced in winter, when conditions are particularly harsh. To test these hypotheses, seasonal rumen fluid parameters of yaks, C × Y and cattle (n = 3 for each) were examined. Rumen fluid was collected in summer and winter from each genotype 2, 5 and 12 hr after a day of grazing. Concentrations of total volatile fatty acid (VFA), acetate, propionate, isobutyrate and isovalerate were greater in yaks than in cattle in summer (p < 0.05), while propionate concentration was lower in yaks than in cattle in winter (p < 0.05). Concentrations of ammonia and urea were greater (p < 0.001) in yaks than in cattle (p < 0.001) in summer, whereas, concentrations of free amino acids (AA) were greater in cattle than in yaks in summer and winter (p < 0.001). Concentrations of total VFA, acetate, propionate and butyrate decreased linearly (p < 0.05), whereas concentrations of isobutyrate and isovalerate increased linearly for yak and C × Y with sampling time (p < 0.05) in summer. In summer, concentrations of isobutyrate and isovalerate were greater in yaks than in cattle (p < 0.05). In conclusion, rumen fermentation characteristics of yaks showed that they coped better than cattle or C × Y in the harsh climate as we hypothesized. However, in contrast to our hypothesis, this emerged only in summer, when pasture was plentiful and not in winter, when pasture was scarce.

Chicoric Acid Improves Heart and Blood Responses to Hypobaric Hypoxia in Tibetan Yaks

Yak is a wild bovine species living on the Qinghai Tibet Plateau that demonstrates good adaptability to the hypoxic environment. Chicoric acid, a natural phenolic compound, is known as having anti-oxidant, antiviral, anti-inflammatory and analgesic properties. However, its effect on hypoxia adaptability of yak is still unclear. In this study 40 yaks were selected that were of similar age, parity and weight, and divided into the control group and experimental groups 1, 2, 3, randomly. Results showed that chicoric acid significantly improved RBC, HGB, and WBC. There are significantly beneficial effects to increasing total protein contents ([Formula: see text]): all treatments increased HDL-C contents, and supplementations 100[Formula: see text]mg/h significantly decreased the content of TG on the 60th day ([Formula: see text]). Contents of the serum related enzymes like ALP, GOP and GPT showed varying degrees of change, but no significant differences and the indexes of anti-oxidant capacity (T-AOC and GSH-Px) were significantly improved ([Formula: see text]), but MDA was decreased ([Formula: see text]) under the action of the chicoric acid. Hypoxia-inducible factor in serum such as HIF-2[Formula: see text], EPO, ROS, Fe[Formula: see text] and Tf are all significantly decreased ([Formula: see text]). The myocardial mitochondrial parameters mtDNA, UCP2, PGC1-[Formula: see text], NRF1 and mitochondrial complexes were altered remarkably. Some indicators of glucose metabolism presented variation trends. Taken together, chicoric acid has shown a positive effect on the adaptive ability of yak in high altitude, hypoxic environment in plateau areas. Our findings reported a new potential means to enhance immunity and inflammatory response and improve the anti-oxidant capacity.

Functional characterization of oligopeptide transporter 1 of dairy cows

Background

It is well known that peptides play a vital role in the nutrition and health of dairy cows. Bovine oligopeptide transporter 1 (bPepT1) is involved in the peptide transport process in the gastrointestinal tracts of dairy cows. However, little information is known in the characteristics of bPepT1. Therefore, the purpose of this study was to characterize bPepT1 functionally using a mammalian cell expression system. The uptake of radiolabeled dipeptide glycyl-sarcosine ([³H]-Gly-Sar) into the bPepT1-transfected Chinese hamster ovary cells was measured at various pH and substrate concentrations and with or without 15 other small peptides that contained Met or Lys.

Results

Western blot results showed that the abundance of bPepT1 protein in the jejunum and ileum are the highest in the gastrointestinal tract of dairy cows. The uptake of [³H]-Gly-Sar by bPepT1-Chinese hamster ovary cells was dependent on time, pH, and substrate concentration, with a low K_m value of 0.94 ± 0.06 mmol/L and a maximum velocity of 20.80 ± 1.74 nmol/(mg protein • 5 min). Most of the di- and tripeptides were the substrates of bPepT1, based on substrate-competitive studies. However, bPepT1 has a higher affinity to the peptides with shorter chains, greater hydrophobicity, and negative or neutral charges.

Conclusions

These results demonstrated for the first time the functional characteristics of bPepT1, and they provide a new insight and better understanding into its vital role in absorbing a wide range of peptides from the digestive tract of dairy cows.