Effects of Starvation on Lipid Metabolism and Gluconeogenesis in Yak

Protein Lactylation Profiles Provide Insights into Molecular Mechanisms Underlying Metabolism in Yak

Protein lysine lactylation, a recently discovered post-translational modification (PTM), is prevalent across tissues and cells of diverse species, serving as a regulator of glycolytic flux and biological metabolism. The yak (Bos grunniens), a species that has inhabited the Qinghai-Tibetan Plateau for millennia, has evolved intricate adaptive mechanisms to cope with the region's unique geographical and climatic conditions, exhibiting remarkable energy utilization and metabolic efficiency. Nonetheless, the specific landscape of lysine lactylation in yaks remains poorly understood. Herein, we present the first comprehensive lactylome profile of the yak, effectively identifying 421, 308, and 650 lactylated proteins in the heart, muscles, and liver, respectively. These lactylated proteins are involved in glycolysis/gluconeogenesis, the tricarboxylic acid cycle, oxidative phosphorylation, and metabolic process encompassing carbohydrates, lipids, and proteins during both anaerobic and aerobic glucose bio-oxidation, implying their crucial role in material and energy metabolism, as well as in maintaining homeostasis in yaks.

Starvation-induced autophagy modulates spermatogenesis and sperm quality in Nile tilapia

Spermatogenesis is a finely regulated process that involves the interaction of several cellular mechanisms to ensure the proper development and maturation of germ cells. This study assessed autophagy contribution and its relation to apoptosis in fish spermatogenesis during starvation. To that end, Nile tilapia males were subjected to 0 (control), 7, 14, 21, and 28 days of starvation to induce autophagy. Testes samples were obtained for analyses of spermatogenesis by histology, electron microscopy, immunohistochemistry, and western blotting. Sperm quality was assessed using a computer-assisted sperm analysis (CASA) system. Data indicated a significant reduction in gonadosomatic index, seminiferous tubule area, and spermatozoa proportion in fish subject to starvation compared to the control group. Immunoblotting revealed a reduction of Bcl2 and Beclin 1 associated with increased Bax and Caspase-3, mainly after 21 and 28 days of starvation. LC3 and P62 indicated reduced autophagic flux in these starvation times. Immunolabeling for autophagic and apoptotic proteins occurred in all development stages of the germ cells, but protein expression varied throughout starvation. Beclin 1 and Cathepsin D decreased while Bax and Caspase-3 increased in spermatocytes, spermatids, and spermatozoa after 21 and 28 days. Autophagic and lysosomal proteins colocalization indicated the fusion of autophagosomes with lysosomes and lysosomal degradation in spermatogenic cells. The CASA system indicated reduced sperm motility and velocity in animals subjected to 21 and 28 days of starvation. Altogether, the data support autophagy acting at different spermatogenesis stages in Nile tilapia, with decreased autophagy and increased apoptosis after 21 and 28 days of starvation, which results in a decrease in the spermatozoa number and sperm quality.

Transcriptomic analysis of mechanism underlying the effect of induced molting on semen quality and reproductive performance in aged Houdan roosters

The reproductive performance of breeder roosters has significant economic importance in the poultry industry. Breeder roosters have severely reduced semen quality with age and will be at risk of culling in the following years. In order to extend the use of breeder roosters, we drew on the induced molting model of hens and selected 35 Houdan roosters aged 50 wk for induced molting. By comparing the body weight, testicular weight, semen quality, and reproductive performance before and after induced molting, we found that induced molting could restore the body weight and testicular weight to the levels before molting (P > 0.05). At the same time, it significantly improved sperm motility (P < 0.05) and also improved reproductive performance such as fertilization rate and hatching rate. To further reveal the mechanism underlying the effects of induced molting on semen quality and reproductive performance in aged Houdan roosters, we collected testes from 3 periods: 1 d before fasting (F0), 15 d after fasting (F15), and 32 d after recovery feeding (R32) for transcriptome sequencing analysis. A total of 5,671 genes were detected in F0, F15, and R32, and trend analysis of the 5,671 differential genes showed 2 significant trends (profile 5 and profile 2). KEGG enrichment analysis of the genes in the 2 profiles, revealed significantly enriched pathway regulation of actin cytoskeleton. In the regulation of actin cytoskeleton pathway, we found a protein kinase gene (SRC) and a senescence gene (ROCK2). SRC was highly expressed at F15, leading to the phosphorylation of key substrates, which in turn disrupted the Sertoli cell spermatid connection and the spermiogenesis process, resulting in no mature spermatozoa produced from F15, SRC expression was inhibited at R32, the expression level was reduced, and mature spermatozoa reappeared. The senescence gene ROCK2 was highly expressed at F15 compared to F0 and R32, which may have been responsible for inducing senescence atrophy in the testes.

High energy level diet improves the growth performance and rumen fermentation of yaks in cold weather

To date, no research has been done on energy requirements for yaks in Tibetan cold weather. The findings of the current study provide proper energy requirements for yaks would facilitate scientific feeding of fattening yaks in cold weather. The metabolomics and 16s rRNA sequencing technologies were used to explore the underlying mechanism that affects the growth performance of yaks fed with different energy levels of diet in cold weather. Three groups of yaks (141.7 ± 3.34 kg) were fed with diets containing metabolizable energy 7.20, 7.89, and 8.58 MJ/kg DM (dry matter) and named the low-, medium-, and high-energy groups, respectively. The results showed that the average daily feed intake of the high-energy group was higher than that of the low-energy group (p  = 0.006). Plasma aspartate aminotransferase (p  = 0.004), alanine aminotransferase (p  < 0.001), and interferon-γ (p  < 0.001) in the high-energy group were lower than in the low-energy group. In contrast, superoxide dismutase (p  < 0.001), immunoglobulin G (p  < 0.001), and interleukin 2 (p  = 0.002) were higher than the low-energy group. The rumen microbial protein (p  = 0.025), total volatile fatty acids (p  = 0.029), and neutral detergent fiber digestibility (p  = 0.050) in the high-energy group were higher than in the low-energy group, whereas the acetate: propionate ratio (p  = 0.001) and ammonium nitrogen (p  = 0.001) were lower than in the low-energy group. The plasma metabolomics results displayed that yaks fed with a high-energy diet augmented the metabolism of arginine, proline, purine, taste transduction, pyrimidine, and glutathione pathways. The relative abundance of Methanobrevibacter in the high-energy group was lower (p  < 0.001), whereas the relative abundance of Methanosphaera (p  < 0.001) was higher than in the low-energy group. The results of the current study suggest that a high-energy diet in growing yaks during the cold season can improve growth performance, rumen microbial protein synthesis, antioxidants, and immunity.

Low Glucose plus β-Hydroxybutyrate Induces an Enhanced Inflammatory Response in Yak Alveolar Macrophages via Activating the GPR109A/NF-κB Signaling Pathway

Yaks are often subject to long-term starvation and a high prevalence of respiratory diseases and mortality in the withered season, yet the mechanisms that cause this remain unclear. Research has demonstrated that β-hydroxybutyrate (BHB) plays a significant role in regulating the immune system. Hence, we hypothesize that the low glucose and high BHB condition induced by severe starvation might have an effect on the pro-inflammatory response of the alveolar macrophages (AMs) in yaks. To validate our hypothesis, we isolated and identified primary AMs from freshly slaughtered yaks and cultured them in a medium with 5.5 mM of glucose or 2.8 mM of glucose plus 1-4 mM of BHB. Utilizing a real-time quantitative polymerase chain reaction (RT-qPCR), immunoblot assay, and enzyme-linked immunosorbent assay (ELISA), we evaluated the gene and protein expression levels of GPR109A (G-protein-coupled receptor 109A), NF-κB p65, p38, and PPARγ and the concentrations of pro-inflammatory cytokines interleukin (IL)-1β and IL-6 and tumor necrosis factor (TNF)-α in the supernatant. The results demonstrated that AMs exposed to low glucose plus BHB had significantly higher levels of IL-1β, IL-6, and TNF-α (p < 0.05) and higher activity of the GPR109A/NF-κB signaling pathway. A pretreatment of either pertussis toxin (PTX, inhibitor of GPR109A) or pyrrolidinedithiocarbamic (PDTC, inhibitor of NF-κB p65) was effective in preventing the elevated secretion of pro-inflammatory cytokines induced by low glucose plus BHB (p < 0.05). These results indicated that the low glucose plus BHB condition would induce an enhanced pro-inflammatory response through the activation of the GPR109A/NF-κB signaling pathway in primary yak AMs, which is probably the reason why yaks experience a higher rate of respiratory diseases and mortality. This study will offer new insight into the prevention and treatment of bovine respiratory diseases.

The Effects of Postpartum Yak Metabolism on Reproductive System Recovery

The goal of this study was to determine the metabolism of multiparous female yaks during the late perinatal period and identify its effects on reproductive recovery in order to explain the low reproduction rate of yaks. Eight multiparous female yaks were randomly selected as the sample, and serum was collected from the yaks every 7 days from the day of delivery until 28 days after the delivery (five time points). The presence of serum metabolic profiles and reproductive hormones was identified using ELISA. The key metabolites were identified using liquid chromatography-mass spectrometry, and a dynamic metabolic network representation was created using bioinformatics analysis. A total of 117 different metabolites were identified by calculating the fold change of the metabolite expression at each time point. The dynamic metabolic network was created to represent the activities of the key metabolites, metabolic indexes and reproductive hormones. The initial efficiency of the glucose metabolism in the late perinatal period was found to be low, but it increased during the final period. The initial efficiencies of the lipid and amino acid metabolisms were high but decreased during the final period. We inferred that there was a postpartum negative energy balance in female yaks and that the synthesis and secretion of estrogen were blocked due to an excessive fatty acid mobilization. As a result, the reproductive hormone synthesis and secretion were maintained at a low level in the late perinatal period, and this was the main reason for the delayed recovery of the reproductive function postpartum. However, the specific mechanism needs to be further verified.

Genome-wide identification of copy number variation and association with fat deposition in thin and fat-tailed sheep breeds

Copy number variants (CNVs) are a type of genetic polymorphism which contribute to phenotypic variation in several species, including livestock. In this study, we used genomic data of 192 animals from 3 Iranian sheep breeds including 96 Baluchi sheep and 47 Lori-Bakhtiari sheep as fat-tailed breeds and 47 Zel sheep as thin-tailed sheep breed genotyped with Illumina OvineSNP50K Beadchip arrays. Also, for association test, 70 samples of Valle del Belice sheep were added to the association test as thin-tailed sheep breed. PennCNV and CNVRuler software were, respectively, used to study the copy number variation and genomic association analyses. We detected 573 and 242 CNVs in the fat and thin tailed breeds, respectively. In terms of CNV regions (CNVRs), these represented 328 and 187 CNVRs that were within or overlapping with 790 known Ovine genes. The CNVRs covered approximately 73.85 Mb of the sheep genome with average length 146.88 kb, and corresponded to 2.6% of the autosomal genome sequence. Five CNVRs were randomly chosen for validation, of which 4 were experimentally confirmed using Real time qPCR. Functional enrichment analysis showed that genes harbouring CNVs in thin-tailed sheep were involved in the adaptive immune response, regulation of reactive oxygen species biosynthetic process and response to starvation. In fat-tailed breeds these genes were involved in cellular protein modification process, regulation of heart rate, intestinal absorption, olfactory receptor activity and ATP binding. Association test identified one copy gained CNVR on chromosomes 6 harbouring two protein-coding genes HGFAC and LRPAP1. Our findings provide information about genomic structural changes and their association to the interested traits including fat deposition and environmental compatibility in sheep.

Transcriptomic and Metabolomic Analyses Reveal Inhibition of Hepatic Adipogenesis and Fat Catabolism in Yak for Adaptation to Forage Shortage During Cold Season

Animals have adapted behavioral and physiological strategies to conserve energy during periods of adverse conditions. Hepatic glucose is one such adaptation used by grazing animals. While large vertebrates have been shown to have feed utilization and deposition of nutrients—fluctuations in metabolic rate—little is known about the regulating mechanism that controls hepatic metabolism in yaks under grazing conditions in the cold season. Hence, the objective of this research was to integrate transcriptomic and metabolomic data to better understand how the hepatic responds to chronic nutrient stress. Our analyses indicated that the blood parameters related to energy metabolism (glucose, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, lipoprotein lipase, insulin, and insulin-like growth factor 1) were significantly (p &lt; 0.05) lower in the cold season. The RNA-Seq results showed that malnutrition inhibited lipid synthesis (particularly fatty acid, cholesterol, and steroid synthesis), fatty acid oxidation, and lipid catabolism and promoted gluconeogenesis by inhibiting the peroxisome proliferator-activated receptor (PPAR) and PI3K-Akt signaling pathways. For metabolite profiles, 359 metabolites were significantly altered in two groups. Interestingly, the cold season group remarkably decreased glutathione and phosphatidylcholine (18:2 (2E, 4E)/0:0). Moreover, integrative analysis of the transcriptome and metabolome demonstrated that glycolysis or gluconeogenesis, PPAR signaling pathway, fatty acid biosynthesis, steroid biosynthesis, and glutathione metabolism play an important role in the potential relationship between differential expression genes and metabolites. The reduced lipid synthesis, fatty acid oxidation, and fat catabolism facilitated gluconeogenesis by inhibiting the PPAR and PI3K-Akt signaling pathways to maintain the energy homeostasis of the whole body in the yak, thereby coping with the shortage of forages and adapting to the extreme environment of the Qinghai-Tibetan Plateau (QTP).

Metabolic and blood acid-base responses to prepartum dietary cation-anion difference and calcium content in transition dairy cows

Dairy cows commonly undergo negative Ca balance accompanied by hypocalcemia after parturition. A negative dietary cation-anion difference (DCAD) strategy has been used prepartum to improve periparturient Ca homeostasis. Our objective was to determine the influence of a negative DCAD diet with different amounts of dietary Ca on the blood acid-base balance, blood gases, and metabolic adaptation to lactation. Multiparous Holstein cows (n = 81) were blocked into 1 of 3 dietary treatments from 252 d of gestation until parturition: (1) positive DCAD diet and low Ca (CON; containing +6.0 mEq/100 g DM, 0.4% DM Ca); (2) negative DCAD diet and low Ca (ND; -24.0 mEq/100 g DM, 0.4% DM Ca); or (3) negative DCAD diet plus high Ca supplementation (NDCA; -24.1 mEq/100 g DM, 2.0% DM Ca). There were 28, 27, and 26 cows for CON, ND, and NDCA, respectively. Whole blood was sampled at 0, 24, 48, and 96 h after calving for immediate determination of blood acid-base status and blood gases. Serum samples collected at -21, -14, -7, -4, -2, -1, at calving, 1, 2, 4, 7, 14, 21, and 28 d relative to parturition were analyzed for metabolic components. Results indicated that cows fed ND or NDCA had lower blood pH at calving but greater pH at 24 h after calving compared with CON. Blood bicarbonate, base excess, and total CO₂ (tCO₂) concentrations of cows in ND and NDCA groups were less than those of cows in CON at calving but became greater from 24 to 96 h postpartum. The NDCA cows had lower blood bicarbonate, base excess, and tCO₂ at 48 h and greater partial pressure of oxygen after calving compared with ND. Cows fed ND or NDCA diets had lower serum glucose concentrations than CON cows before calving but no differences were observed postpartum. Serum concentrations of total protein and albumin were greater prepartum for cows in ND and NDCA groups than for those in CON. Postpartum serum urea N and albumin concentrations tended to be higher for ND and NDCA cows. Cows fed ND or NDCA diets had elevated serum total cholesterol concentration prepartum. During the postpartum period, triglycerides and NEFA of cows fed ND or NDCA diets tended to be lower than those of CON. Cows fed the NDCA diet had greater postpartum total cholesterol in serum and lower NEFA concentration at calving than ND. In conclusion, feeding a prepartum negative DCAD diet altered blood acid-base balance and induced metabolic acidosis at calving, and improved protein and lipid metabolism. Supplementation of high Ca in the negative DCAD diet prepartum was more favorable to metabolic adaptation to lactation in dairy cows than the negative DCAD diet with low Ca.

Metagenomics Reveals That Intravenous Injection of Beta-Hydroxybutyric Acid (BHBA) Disturbs the Nasopharynx Microflora and Increases the Risk of Respiratory Diseases

It is widely accepted that maintenance of microbial diversity is essential for the health of the respiratory tract; however, there are limited reports on the correlation between starvation and respiratory tract microbial diversity. In the present study, saline/β-hydroxybutyric acid (BHBA) intravenous injection after dietary restriction was used to imitate different degrees of starvation. A total of 13 healthy male yaks were imposed to different dietary restrictions and intravenous injections, and their nasopharyngeal microbiota profiles were obtained by metagenomic shotgun sequencing. In healthy yaks, the main dominant phyla were Proteobacteria (33.0%), Firmicutes (22.6%), Bacteroidetes (17.2%), and Actinobacteria (13.2%); the most dominated species was Clostridium botulinum (10.8%). It was found that 9 days of dietary restriction and 2 days of BHBA injection (imitating severe starvation) significantly decreased the microbial diversity and disturbed its structure and functional composition, which increased the risk of respiratory diseases. This study also implied that oral bacteria played an important role in maintaining nasopharynx microbial homeostasis. In this study, the correlation between starvation and nasopharynx microbial diversity and its potential mechanism was investigated for the first time, providing new ideas for the prevention of respiratory diseases.

Effects of starvation and refeeding cycles on spermatogenesis and sex steroids in the Nile tilapia Oreochromis niloticus

Food restriction is part of the life cycle of many fish species; however, nutritional deficiency may negatively influence gametogenesis and gonadal maturation. The aim of this study was to evaluate the effects of food restriction on the spermatogenesis of Nile tilapia. For this, adult males were submitted to starvation and refeeding cycles (alternating periods of starvation and feeding) for 7, 14, 21, and 28 days. After 7 days of starvation, glycaemic and lipid levels were significantly reduced, followed by reduction of plasma testosterone (T) and 11-ketotestosterone (11-KT). In addition, reduced proliferation of spermatogonia and increased apoptosis of spermatocytes, spermatids, and spermatozoa was observed in starvation groups. In the refeeding groups, the sex steroids and the proportion of germ cells had no significant alterations compared to the control group, except for spermatozoa. In this sense, the present study suggests that starvation after 7 days progressively reduces T and 11-TK, resulting in damage to the production of spermatogenic cells, while refeeding may delay spermatogenesis but does not lead to testicular impairment.

Lipid Catabolism in Starved Yak Is Inhibited by Intravenous Infusion of β-Hydroxybutyrate

Simple Summary

Yak, which is the predominant and semi-domesticated livestock on the Qinghai-Tibet Plateau, suffers severe starvation and body weight reduction in the cold season because of the harsh highland environment. Lipids are important energy sources to starvation animals. β-hydroxybutyrate (BHBA) that is derived from lipid decomposition as the primary ketone body is with the function not only to provide energy for animals as energy materials, but also regulate lipid metabolism as signaling molecular. However, the effects of starvation and BHBA on lipid metabolism and its mechanism are still unclear for ruminant animals. Herein, we investigated the effects of starvation and intravenous infusion of BHBA solution on Yak growth, serum biochemistry, hormones, subcutaneous adipocyte morphology, fatty acid composition, activity of enzymes related to lipid metabolism, and signal pathway. The results showed that starvation promoted lipid catabolism and BHBA infusion up-regulated the mRNA expression of receptor GPR109A in subcutaneous adipose tissue, inhibited the Cyclic adenosine monophosphate(cAMP)/Protein kinase A (PKA)/cAMP-responsive element binding protein (CREB) signaling pathway, and inhibited lipolysis. Our study was beneficial for enriching the nutrition regulation theory of yaks and improving their growth potential.

Abstract

Lipid is the chief energy source for starved animals. β-hydroxybutyrate (BHBA) is the main ketone body produced by lipid decomposition. In Chinese hamster ovary (CHO) cell experiment, it was found that BHBA could be used not only as an energy substance, but also as a ligand of GPR109A for regulating lipid metabolism. However, whether BHBA can regulate lipid metabolism of yaks, and its effective concentration and signal pathway are not clear. This study investigated the effects and mechanism of starvation and BHBA on the lipid metabolism of yak. Eighteen male Jiulong yaks were selected and then randomly divided into three groups: normal feeding group (NG), starvation group (SG), and starvation with BHBA infusion group (SBG). The yaks in the NG group were freely fed during the trial, while the yaks in the SG and SBG groups fasted; from 7th to 9th days of the experiment, the NG and SG were infused continuous with 0.9% normal saline and SBG was infused 1.7 mmol/L BHBA solution respectively. The blood samples were collected on the 0th, 1st, 3rd, 5th, 7th, and 9th day of experiment. The subcutaneous adipose tissue of all the yaks in this study were taken from live bodies after infusion. Serum glucose, lipid metabolites, hormone concentrations, and mRNA and protein expressions of key factors of lipid metabolism and signaling pathway in subcutaneous adipose tissue were measured. The results showed that, as compared with NG, starvation significantly reduced the body weight of yak in SG, and significantly increased the concentration of BHBA in serum and the mRNA expression of PKA and CREB1 in subcutaneous adipose tissue, while the mRNA expression of MEK, PKC, ERK1/2, the area of adipocytes, and the proportion of saturated fatty acid were decreased. Whereas, further increase of BHBA concentration through infusion promoted the mRNA expression of GPR109A receptor in the subcutaneous adipose tissue of SBG, inhibited the mRNA expression of AC and PKA, and decreased the phosphorylation protein abundance of CREB1, and significantly increased the diameter and area of adipocytes. These findings suggest that starvation led to enhanced lipid catabolism in yaks. An increasing BHBA concentration could increase the mRNA expression of GPR109A receptor in subcutaneous adipose tissue and inhibit the cAMP/PKA/CREB signaling pathway and lipid decomposition.

Effects of Nutritional Deprivation and Re-Alimentation on the Feed Efficiency, Blood Biochemistry, and Rumen Microflora in Yaks (Bos grunniens)

Simple Summary

Yak, the predominant and semi-domesticated livestock on the Qinghai–Tibet Plateau, suffers severe starvation and body weight reduction in the cold season and recovers relatively rapid growth in the warm season every year, because of the harsh highland environment. Rumen microorganisms have critical nutritional and physiological functions for the growth of ruminant, but the strategy of rumen microorganism of yaks to cope with the starvation and re-alimentation challenges and the contributions of rumen microflora to compensatory growth remain unclear. Herein, we investigated the effects of starvation and refeeding on the growth, feed efficiency, blood biochemistry and rumen microbial community as well as functions of yaks. Our results indicated that the rumen microorganism, in part, contributed to yak adaption to starvation and compensatory growth during re-alimentation. Our study is helpful in the understanding and utilization of this natural character of yaks to explore and improve their growth potential.

Abstract

Yak suffers severe starvation and body weight reduction in the cold season and recovers relatively rapid growth in the warm season every year. Herein, we investigated the effects of starvation and refeeding on the growth, feed efficiency, blood biochemistry and rumen microbial community as well as functions of yaks. The results showed that starvation significantly reduced the body weight of yaks. Serum glucose and triglyceride concentrations significantly decreased, and β-hydroxybutyric acid and non-esterified fatty acid levels were significantly increased during the starvation period. Starvation also dramatically inhibited rumen microbial fermentations. Whereas, refeeding with the same diet significantly increased the feed efficiency, nutrient digestibility together with rumen acetate, propionate and microbial protein productions compared with those before starvation. The 16S rDNA sequencing results showed that starvation mainly decreased the ruminal protein-degrading bacteria Prevotella and propionate-producing bacteria Succiniclasticum populations and dramatically increased the denitrifying bacteria Thauera populations. Refeeding reduced the Euryarchaeota population and increased propionate-producing bacteria Succinivibrionaceae UCG-002 and starch-degrading bacteria Ruminobacter populations when compared with those before starvation. The predicted microbial metabolic pathways, related to amino acid and starch metabolisms, were also significantly altered during the starvation and refeeding. The results indicated that the rumen microorganisms and their metabolism pathways changed with feed supply, and these alterations in part contributed to yak adaption to starvation and re-alimentation. This study is helpful for enhancing the understanding and utilization of this natural character of yaks to explore and improve their growth potential.