Enhanced supply of methionine or arginine alters mechanistic target of rapamycin signaling proteins, messenger RNA, and microRNA abundance in heat-stressed bovine mammary epithelial cells in vitro

Nutritional Strategies to Alleviate Stress and Improve Welfare in Dairy Ruminants

Dairy ruminants provide a major part of the livestock and agriculture sectors. Due to the increase in world population and the subsequent increase in dairy product demands, the dairy sector has been intensified. Dairy farming intensification and the subsequent increase in animal nutritional demands and the increase in the average global temperature as well have subjected animals to various stress conditions that impact their health and welfare. Various management practices and nutritional strategies have been proposed and studied to alleviate these impacts, especially under heat stress, as well as during critical periods, like the transition period. Some of the nutritional interventions to cope with stress factors and ensure optimal health and production are the inclusion of functional fatty acids and amino acids and feed additives (minerals, prebiotics, probiotics, essential oils and herbs, phytobiotics, enzymes, etc.) that have been proven to regulate animals' metabolism and improve their antioxidant status and immune function. Thus, these nutritional strategies could be the key to ensuring optimum growth, milk production, and reproduction efficiency. This review summarizes and highlights key nutritional approaches to support the remarkable metabolic adaptations ruminants are facing during the transition period and to reduce heat stress effects and evaluate their beneficial effects on animal physiology, performance, health, as well as welfare.

Varying the ratio of Lys: Met through enhancing methionine supplementation improved milk secretion ability through regulating the mRNA expression in bovine mammary epithelial cells under heat stress

Introduction

The ratio of lysine (Lys) to methionine (Met) with 3.0: 1 is confirmed as the "ideal" profile for milk protein synthesis, but whether this ratio is suitable for milk protein synthesis under HS needs to be further studied.

Methods

To evaluate the molecular mechanism by which HS and Lys to Met ratios affect mammary cell functional capacity, an immortalized bovine mammary epithelial cell line (MAC-T) is incubated with 5 doses of Met while maintaining a constant concentration of Lys. The MAC-T cells was treated for 6 h as follow: Lys: Met 3.0: 1 (control 37°C and IPAA 42°C) or treatments under HS (42°C) with different ratios of Lys: Met at 2.0: 1 (LM20), 2.5: 1 (LM25), 3.5: 1 (LM35) and 4.0: 1 (LM40). RNA sequencing was used to assess transcriptome-wide alterations in mRNA abundance.

Results

The significant difference between control and other groups was observed base on PCA analysis. A total of 2048 differentially expressed genes (DEGs) were identified in the IPAA group relative to the control group. Similarly, 226, 306, 148, 157 DEGs were detected in the LM20, LM25, LM35 and LM40 groups, respectively, relative to the IPAA group. The relative mRNA abundance of HSPA1A was upregulated and anti-apoptotic genes (BCL2L1 and BCL2) was down-regulated in the IPAA group, compared to the control group (p < 0.05). Compared with the IPAA group, the relative mRNA abundance of anti-apoptotic genes and casein genes (CSN1S2 and CSN2) was up-regulated in the LM25 group (p < 0.05). The DEGs between LM25 and IPAA groups were associated with the negative regulation of transcription RNA polymerase II promoter in response to stress (GO: 0051085, DEGs of BAG3, DNAJB1, HSPA1A) as well as the mTOR signaling pathway (ko04150, DEGs of ATP6V1C2, WNT11, WNT3A, and WNT9A). Several DEGs involved in amino acids metabolism (AFMID, HYKK, NOS3, RIMKLB) and glycolysis/gluconeogenesis (AFMID and MGAT5B) were up-regulated while DEGs involved in lipolysis and beta-oxidation catabolic processes (ALOX12 and ALOX12B) were down-regulated.

Conclusion

These results suggested that increasing Met supply (Lys: Met at 2.5: 1) may help mammary gland cells resist HS-induced cell damage, while possibly maintaining lactation capacity through regulation of gene expression.

Effects of taurine on metabolomics of bovine mammary epithelial cells under high temperature conditions

High temperature induces heat stress, adversely affecting the growth and lactation performance of cows. Research has shown the protective effect of taurine against hepatotoxicity both in vivo and in vitro. This study aimed to investigate the effect of taurine on the metabolomics of mammary epithelial cells of dairy cows under high-temperature conditions. Mammary epithelial cells were exposed to 0 mmol/L (HS, control), 8 mmol/L (HT-8), and 32 mmol/L (HT-32) of taurine, then incubated at 42°C for 6 h. Metabolomics analysis was conducted using Liquid Chromatograph Mass Spectrometer (LC-MS). Compared with the HS group, 2,873 and 3,243 metabolites were detected in the HT-8 group in positive and negative ion modes. Among these, 108 and 97 metabolites were significantly upregulated in positive and negative ion modes, while 60 and 166 metabolites were downregulated. Notably, 15 different metabolites such as palmitic acid, adenine and hypoxanthine were screened out in the HT-8 group. Compared with the HS group, 2,873 and 3,243 metabolites were, respectively, detected in the HT-32 group in the positive and negative ion modes. Among those metabolites, 206 metabolites were significantly up-regulated, while 206 metabolites were significantly downregulated in the positive mode. On the other hand, 497 metabolites were significantly upregulated in the negative mode, while 517 metabolites were reported to be downregulated. Noteworthy, 30 distinct metabolites, such as palmitic acid, phytosphingosine, hypoxanthine, nonanoic acid, and octanoic acid, were screened out in the HT-32 group. KEGG enrichment analysis showed that these metabolites were mainly involved in lipid metabolism, purine metabolism and other biological processes. Overall, our study indicates that taurine supplementation alters the metabolites primarily associated with purine metabolism, lipid metabolism and other pathways to alleviate heat stress in bovine mammary epithelial cells.

L-arginine alleviates heat stress-induced mammary gland injury through modulating CASTOR1-mTORC1 axis mediated mitochondrial homeostasis

As global warming intensifies, extreme heat is becoming increasingly frequent. These extreme heatwaves have decreased the milk production of dairy animals such as cows and goats and have caused significant damage to the entire dairy industry. It is known that heat stress (HS) can induce the apoptosis and autophagy of mammary epithelial cells (MECs), leading to a decrease in lactating MECs. L-arginine can effectively attenuate HS-induced decreases in milk yield, but the exact mechanisms are not fully understood. In this study, we found that HS upregulated the arginine sensor CASTOR1 in mouse MECs. Arginine activated mTORC1 activity through CASTOR1 and promoted mitochondrial biogenesis through the mTORC1/PGC-1α/NRF1 pathway. Moreover, arginine inhibited mitophagy through the CASTOR1/PINK1/Parkin pathway. Mitochondrial homeostasis ensures ATP synthesis and a stable cellular redox state for MECs under HS, further alleviating HS-induced damage and improving the lactation performance of MECs. In conclusion, these findings reveal the molecular mechanisms by which L-arginine relieves HS-induced mammary gland injury, and suggest that the intake of arginine-based feeds or feed additives is a promising method to increase the milk yield of dairy animals in extreme heat conditions.

Enhancing bovine immune, antioxidant and anti-inflammatory responses with vitamins, rumen-protected amino acids, and trace minerals to prevent periparturient mastitis

Mastitis, the inflammatory condition of mammary glands, has been closely associated with immune suppression and imbalances between antioxidants and free radicals in cattle. During the periparturient period, dairy cows experience negative energy balance (NEB) due to metabolic stress, leading to elevated oxidative stress and compromised immunity. The resulting abnormal regulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), along with increased non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) are the key factors associated with suppressed immunity thereby increases susceptibility of dairy cattle to infections, including mastitis. Metabolic diseases such as ketosis and hypocalcemia indirectly contribute to mastitis vulnerability, exacerbated by compromised immune function and exposure to physical injuries. Oxidative stress, arising from disrupted balance between ROS generation and antioxidant availability during pregnancy and calving, further contributes to mastitis susceptibility. Metabolic stress, marked by excessive lipid mobilization, exacerbates immune depression and oxidative stress. These factors collectively compromise animal health, productive efficiency, and udder health during periparturient phases. Numerous studies have investigated nutrition-based strategies to counter these challenges. Specifically, amino acids, trace minerals, and vitamins have emerged as crucial contributors to udder health. This review comprehensively examines their roles in promoting udder health during the periparturient phase. Trace minerals like copper, selenium, and calcium, as well as vitamins; have demonstrated significant impacts on immune regulation and antioxidant defense. Vitamin B12 and vitamin E have shown promise in improving metabolic function and reducing oxidative stress followed by enhanced immunity. Additionally, amino acids play a pivotal role in maintaining cellular oxidative balance through their involvement in vital biosynthesis pathways. In conclusion, addressing periparturient mastitis requires a holistic understanding of the interplay between metabolic stress, immune regulation, and oxidative balance. The supplementation of essential amino acids, trace minerals, and vitamins emerges as a promising avenue to enhance udder health and overall productivity during this critical phase. This comprehensive review underscores the potential of nutritional interventions in mitigating periparturient bovine mastitis and lays the foundation for future research in this domain.

miR-196a Promotes Proliferation of Mammary Epithelial Cells by Targeting CDKN1B

Heat stress (HS) has become one of the key challenges faced by the dairy industry due to global warming. Studies have reported that miR-196a may exert a role in the organism's response to HS, enhancing cell proliferation and mitigating cellular stress. However, its specific role in bovine mammary epithelial cells (BMECs) remains to be elucidated. In this study, we aimed to investigate whether miR-196a could protect BMECs against proliferation arrest induced by HS and explore its potential underlying mechanism. In this research, we developed an HS model for BMECs and observed a significant suppression of cell proliferation as well as a significant decrease in miR-196a expression when BMECs were exposed to HS. Importantly, when miR-196a was overexpressed, it alleviated the inhibitory effect of HS on cell proliferation. We conducted RNA-seq and identified 105 differentially expressed genes (DEGs). Some of these DEGs were associated with pathways related to thermogenesis and proliferation. Through RT-qPCR, Western blotting, and dual-luciferase reporter assays, we identified CDKN1B as a target gene of miR-196a. In summary, our findings highlight that miR-196a may promote BMEC proliferation by inhibiting CDKN1B and suggest that the miR-196a/CDKN1B axis may be a potential pathway by which miR-196a alleviates heat-stress-induced proliferation arrest in BMECs.

Genetics, environmental stress, and amino acid supplementation affect lactational performance via mTOR signaling pathway in bovine mammary epithelial cells

Mammary glands are known for their ability to convert nutrients present in the blood into milk contents. In cows, milk synthesis and the proliferation of cow mammary epithelial cells (CMECs) are regulated by various factors, including nutrients such as amino acids and glucose, hormones, and environmental stress. Amino acids, in particular, play a crucial role in regulating cell proliferation and casein synthesis in mammalian epithelial cells, apart from being building blocks for protein synthesis. Studies have shown that environmental factors, particularly heat stress, can negatively impact milk production performance in dairy cattle. The mammalian target of rapamycin complex 1 (mTORC1) pathway is considered the primary signaling pathway involved in regulating cell proliferation and milk protein and fat synthesis in cow mammary epithelial cells in response to amino acids and heat stress. Given the significant role played by the mTORC signaling pathway in milk synthesis and cell proliferation, this article briefly discusses the main regulatory genes, the impact of amino acids and heat stress on milk production performance, and the regulation of mTORC signaling pathway in cow mammary epithelial cells.

Invited review: From heat stress to disease-Immune response and candidate genes involved in cattle thermotolerance

Heat stress implies unfavorable effects on primary and functional traits in dairy cattle and, in consequence, on the profitability of the whole production system. The increasing number of days with extreme hot temperatures suggests that it is imperative to detect the heat stress status of animals based on adequate measures. However, confirming the heat stress status of an individual is still challenging, and, in consequence, the identification of novel heat stress biomarkers, including molecular biomarkers, remains a very relevant issue. Currently, it is known that heat stress seems to have unfavorable effects on immune system mechanisms, but this information is of limited use in the context of heat stress phenotyping. In addition, there is a lack of knowledge addressing the molecular mechanisms linking the relevant genes to the observed phenotype. In this review, we explored the potential molecular mechanisms explaining how heat stress affects the immune system and, therefore, increases the occurrence of immune-related diseases in cattle. In this regard, 2 relatively opposite hypotheses are under focus: the immunosuppressive action of cortisol, and the proinflammatory effect of heat stress. In both hypotheses, the modulation of the immune response during heat stress is highlighted. Moreover, it is possible to link candidate genes to these potential mechanisms. In this context, immune markers are very valuable indicators for the detection of heat stress in dairy cattle, broadening the portfolio of potential biomarkers for heat stress.

Overview of the effect of rumen-protected limiting amino acids (methionine and lysine) and choline on the immunity, antioxidative, and inflammatory status of periparturient ruminants

Overproduction of reactive oxygen species (ROS) is a well-known phenomenon experienced by ruminants, especially during the transition from late gestation to successful lactation. This overproduction of ROS may lead to oxidative stress (OS), which compromises the immune and anti-inflammatory systems of animals, thus predisposing them to health issues. Besides, during the periparturient period, metabolic stress is developed due to a negative energy balance, which is followed by excessive fat mobilization and poor production performance. Excessive lipolysis causes immune suppression, abnormal regulation of inflammation, and enhanced oxidative stress. Indeed, OS plays a key role in regulating the metabolic activity of various organs and the productivity of farm animals. For example, rapid fetal growth and the production of large amounts of colostrum and milk, as well as an increase in both maternal and fetal metabolism, result in increased ROS production and an increased need for micronutrients, including antioxidants, during the last trimester of pregnancy and at the start of lactation. Oxidative stress is generally neutralized by the natural antioxidant system in the body. However, in some special phases, such as the periparturient period, the animal's natural antioxidant system is unable to cope with the situation. The effect of rumen-protected limiting amino acids and choline on the regulation of immunity, antioxidative, and anti-inflammatory status and milk production performance, has been widely studied in ruminants. Thus, in the current review, we gathered and interpreted the data on this topic, especially during the perinatal and lactational stages.

The Impact of Heat Stress on Immune Status of Dairy Cattle and Strategies to Ameliorate the Negative Effects

Heat stress (HS) is well known to influence animal health and livestock productivity negatively. Heat stress is a multi-billion-dollar global problem. It impairs animal performance during summer when animals are exposed to high ambient temperatures, direct and indirect solar radiations, and humidity. While significant developments have been achieved over the last few decades to mitigate the negative impact of HS, such as physical modification of the environment to protect the animals from direct heat, HS remains a significant challenge for the dairy industry compromising dairy cattle health and welfare. In such a scenario, it is essential to have a thorough understanding of how the immune system of dairy cattle responds to HS and identify the variable responses among the animals. This understanding could help to identify heat-resilient dairy animals for breeding and may lead to the development of climate resilient breeds in the future to support sustainable dairy cattle production. There are sufficient data demonstrating the impact of increased temperature and humidity on endocrine responses to HS in dairy cattle, especially changes in concentration of hormones like prolactin and cortisol, which also provide an indication of the likely im-pact on the immune system. In this paper, we review the recent research on the impact of HS on immunity of calves during early life to adult lactating and dry cows. Additionally, different strategies for amelioration of negative effects of HS have been presented.

Rumen-protected methionine during heat stress alters mTOR, insulin signaling, and 1-carbon metabolism protein abundance in liver, and whole-blood transsulfuration pathway genes in Holstein cows

We investigated effects of rumen-protected Met (RPM) during a heat stress (HS) challenge on (1) hepatic abundance of mTOR, insulin, and antioxidant signaling proteins, (2) enzymes in 1-carbon metabolism, and (3) innate immunity. Holstein cows (n = 32; mean ± standard deviation, 184 ± 59 d in milk) were randomly assigned to 1 of 2 environmental groups, and 1 of 2 diets [total mixed ration (TMR) with RPM (Smartamine M; 0.105% dry matter as top-dress) or TMR without (CON); n = 16/diet] in a split-plot crossover design. There were 2 periods with 2 phases. During phase 1 (9 d), all cows were in thermoneutral conditions (TN; temperature-humidity index = 60 ± 3) and fed ad libitum. During phase 2 (9 d), half the cows (n = 8/diet) were exposed to HS using electric heat blankets. The other half (n = 8/diet) remained in TN, but was pair-fed to HS counterparts. After a 14-d washout and 7-d adaptation period, the study was repeated (period 2) and environmental treatments were inverted relative to phase 2, but dietary treatments were the same. Blood was collected on d 6 of each phase 2 to measure immune function and isolate whole-blood RNA. Liver biopsies were performed at the end of each period for cystathione β-synthase (CBS) and methionine adenosyltransferase activity, glutathione concentration, and protein abundance. Data were analyzed using PROC MIXED in SAS. Abundance of CUL3, inhibitor of antioxidant responses, tended to be downregulated by HS suggesting increased oxidative stress. Heat-shock protein 70 abundance was upregulated by HS. Phosphorylated mTOR abundance was greater overall with RPM, suggesting an increase in pathway activity. An environment × diet (E × D) effect was observed for protein kinase B (AKT), whereas there was a tendency for an interaction for phosphorylated AKT. Abundance of AKT was upregulated in CON cows during HS versus TN, this was not observed in RPM cows. For phosphorylated AKT, tissue from HS cows fed CON had greater abundance compared with all other treatments. The same effect was observed for EIF2A (translation initiation) and SLC2A4 (insulin-induced glucose uptake). An E × D effect was observed for INSR due to upregulation in CON cows during HS versus TN cows fed CON or RPM. There was an E × D effect for CBS, with lower activity in RPM versus CON cows during HS. The CON cows tended to have greater CBS during HS versus TN. An E × D effect was observed for methionine adenosyltransferase, with lower activity in RPM versus CON during HS. Although activity increased in CON during HS versus TN, RPM cows tended to have greater activity during TN. Neutrophil and monocyte oxidative burst and monocyte phagocytosis decreased with HS. An (E × D) effect was observed for whole-blood mRNA abundance of CBS, SOD1 and CSAD; RPM led to upregulation during TN versus HS. Regardless of diet, CDO1, CTH, and SOD1 decreased with HS. Although HS increased hepatic HSP70 and seemed to alter antioxidant signaling, feeding RPM may help cows maintain homeostasis in mTOR, insulin signaling, and 1-carbon metabolism. Feeding RPM also may help maintain whole-blood antioxidant response during HS, which is an important aspect of innate immune function.

Downregulation of CASTOR1 Inhibits Heat-Stress-Induced Apoptosis and Promotes Casein and Lipid Synthesis in Mammary Epithelial Cells

Heat stress is one of the most important factors limiting the milk yields of dairy animals. This decline can be attributed to the heat-stress-induced apoptosis of mammary epithelial cells (MECs). The cytosolic arginine sensor for mTORC1 subunit 1 (CASTOR1) is a crucial upstream regulator of the mechanistic target of rapamycin complex 1 (mTORC1) signaling, which has close connections with apoptosis. However, the specific roles of CASTOR1 in regulating the apoptosis and lactation of MECs are still obscure. In the present study, we found that heat stress promotes apoptosis and CASTOR1's expression in HC11 cells. Downregulation of CASTOR1 inhibits heat-stress-induced apoptosis through a ROS-independent pathway. In addition, silencing of CASTOR1 promotes cell proliferation, cell cycle progression, and milk component synthesis, and overexpressing of CASTOR1 reverses these observations. Furthermore, we found that silencing of CASTOR1 contributes to the nuclear transport of SREBP1 and promotes lipid synthesis. This study demonstrates the pivotal roles of CASTOR1 in heat-stress-induced apoptosis and milk component synthesis in MECs.

RNA-Seq Reveals the Role of miR-29c in Regulating Inflammation and Oxidative Stress of Bovine Mammary Epithelial Cells

Healthy mammary gland is essential for milk performance in dairy cows. MicroRNAs (miRNAs) are the key molecules to regulate the steady state of mammary gland in dairy cows. This study investigated the potential role of miR-29c in bovine mammary epithelial cells (bMECs). RNA sequencing (RNA-seq) was used to measure the transcriptome profile of bovine mammary epithelial cells line (MAC-T) transfected with miR-29c inhibitor or negative control (NC) inhibitor, and then differentially expressed genes (DEGs) were screened. The results showed that a total of 42 up-regulated and 27 down-regulated genes were found in the miR-29c inhibitor group compared with the NC inhibitor group. The functional enrichment of the above DEGs indicates that miR-29c is a potential regulator of oxidative stress and inflammatory response in bMECs through multiple genes, such as forkhead box O1 (FOXO1), tumor necrosis factor-alpha (TNF-α), and major histocompatibility complex, class II, DQ alpha 5 (BoLA-DQA5) in the various biological process and signaling pathways of stress-activated mitogen-activated protein kinase (MAPK) cascade, Epstein-Barr virus infection, inflammatory bowel disease, etc. The results imply that miR-29c plays an important role in a steady state of bMECs or cow mammary gland and may be a potential therapeutic target for mastitis in dairy cows.

Effect of hyperthermia on cell viability, amino acid transfer, and milk protein synthesis in bovine mammary epithelial cells

The reduction of milk yield caused by heat stress in summer is the main condition restricting the economic benefits of dairy farms. To examine the impact of hyperthermia on bovine mammary epithelial (MAC-T) cells, we incubated the MAC-T cells at thermal-neutral (37°C, CON group) and hyperthermic (42°C, HS group) temperatures for 6 h. Subsequently, the cell viability and apoptotic rate of MAC-T cells, apoptosis-related genes expression, casein and amino acid transporter genes, and the expression of the apoptosis-related proteins were examined. Compared with the CON group, hyperthermia significantly decreased the cell viability (p < 0.05) and elevated the apoptotic rate (p < 0.05) of MAC-T cells. Moreover, the expression of heat shock protein (HSP)70, HSP90B1, Bcl-2-associated X protein (BAX), Caspase-9, and Caspase-3 genes was upregulated (p < 0.05). The expression of HSP70 and BAX (pro-apoptotic) proteins was upregulated (p < 0.05) while that of B-cell lymphoma (BCL)2 (antiapoptotic) protein was downregulated (p < 0.05) by hyperthermia. Decreased mRNA expression of mechanistic target of rapamycin (mTOR) signaling pathway-related genes, amino acid transporter genes (SLC7A5, SLC38A3, SLC38A2, and SLC38A9), and casein genes (CSNS1, CSN2, and CSN3) was found in the heat stress (HS) group (p < 0.05) in contrast with the CON group. These findings illustrated that hyperthermia promoted cell apoptosis and reduced the transport of amino acids into cells, which inhibited the milk proteins synthesis in MAC-T cells.

Immune and metabolic effects of rumen-protected methionine during a heat stress challenge in lactating Holstein cows

Multiparous, lactating Holstein cows (n = 32) were randomly assigned to one of two dietary treatments [TMR with rumen-protected Met (RPM) or TMR without RPM (CON)], and within each dietary treatment group cows were randomly assigned to one of two environmental treatment groups in a split-plot crossover design. In phase 1 (9 d), all cows were fed ad libitum and in thermoneutral conditions (TN). In phase 2 (9 d), group 1 (n = 16) was exposed to a heat stress (HS) challenge (HSC). Group 2 cows (n = 16) were pair-fed (PFTN) to HSC counterparts and remained in TN. After a 21-d washout period, the study was repeated (period 2) and the environmental treatments were inverted relative to treatments from phase 2 of period 1, while dietary treatments remained the same for each cow. During phase 1, cows in RPM had greater plasma Met concentration compared with cows in CON (59 and 30 µM, respectively; P < 0.001). Cows in PFTN had a greater decrease (P < 0.05) in plasma insulin than cows in HSC at 4 h (-2.7 µIU/mL vs. -0.7 µIU/mL) and 8 h (-7.7 µIU/mL vs. -0.4 µIU/mL) during phase 2. Compared with cows in PFTN, cows in HSC had an increase (P < 0.05) in plasma serum amyloid A (-59 µg/mL vs. +58 µg/mL), serum haptoglobin (-3 µg/mL vs. +33 µg/mL), plasma lipopolysaccharide binding protein (-0.27 and +0.11 µg/mL), and plasma interleukin-1β (-1.9 and +3.9 pg/mL) during phase 2. In conclusion, HSC elicited immunometabolic alterations; however, there were limited effects of RPM on cows in HSC.

Enhanced supply of methionine regulates protein synthesis in bovine mammary epithelial cells under hyperthermia condition

Recent evidence has shown that methionine (Met) supplementation can improve milk protein synthesis under hyperthermia (which reduces milk production). To explore the mechanism by which milk protein synthesis is affected by Met supplementation under hyperthermia, mammary alveolar (MAC-T) cells were incubated at a hyperthermic temperature of 42°C for 6 h in media with different concentrations of Met. While the control group (CON) contained a normal amino acid concentration profile (60 μg/mL of Met), the three treatment groups were supplemented with Met at concentrations of 10 μg/mL (MET70, 70 μg/mL of Met), 20 μg/mL (MET80, 80 μg/mL of Met), and 30 μg/mL (MET90,90 μg/mL of Met). Our results show that additional Met supplementation increases the mRNA and protein levels of BCL2 (B-cell lymphoma-2, an anti-apoptosis agent), and decreases the mRNA and protein levels of BAX (Bcl-2-associated X protein, a pro-apoptosis agent), especially at an additional supplementary concentration of 20 μg/mL (group Met80). Supplementation with higher concentrations of Met decreased the mRNA levels of Caspase-3 and Caspase-9, and increased protein levels of heat shock protein (HSP70). The total protein levels of the mechanistic target of rapamycin (mTOR) and the mTOR signalling pathway-related proteins, AKT, ribosomal protein S6 kinase B1 (RPS6KB1), and ribosomal protein S6 (RPS6), increased with increasing Met supplementation, and peaked at 80 μg/mL Met (group Met80). In addition, we also found that additional Met supplementation upregulated the gene expression of αS1-casein (CSN1S1), β-casein (CSN2), and the amino acid transporter genes SLC38A2, SLC38A3 which are known to be mTOR targets. Additional Met supplementation, however, had no effect on the gene expression of κ-casein (CSN3) and solute carrier family 34 member 2 (SLC34A2). Our results suggest that additional Met supplementation with 20 μg/mL may promote the synthesis of milk proteins in bovine mammary epithelial cells under hyperthermia by inhibiting apoptosis, activating the AKT-mTOR-RPS6KB1 signalling pathway, and regulating the entry of amino acids into these cells.

Effect of Heat Stress on Bovine Mammary Cellular Metabolites and Gene Transcription Related to Amino Acid Metabolism, Amino Acid Transportation and Mammalian Target of Rapamycin (mTOR) Signaling

Simple Summary

This study mainly employed metabolomics technology to determine changes of intracellular metabolite concentrations related to milk protein synthesis induced by heat stress (HS) in bovine mammary epithelial cells. HS was associated with significant differences in intracellular amino acid metabolism resulting in an increase in the intracellular amino acid concentrations. Moreover, HS promoted amino acid transportation and the activity of the mammalian target of rapamycin (mTOR) signaling pathway, which plays an important role as a central regulator of cell metabolism, growth, proliferation and survival. Greater expression of the alpha-S2-casein gene (CSN1S2) was also observed during HS. Overall, our study indicated that bovine mammary epithelial cells may have the ability to resist HS damage and continue milk protein synthesis partly through enhanced intracellular amino acid absorption and metabolism and by activating the mTOR signaling pathway during HS.

Abstract

Heat stress (HS) is one of the most serious factors to negatively affect the lactation performance of dairy cows. Bovine mammary epithelial cells are important for lactation. It was demonstrated that HS decreases the lactation performance of dairy cows, partly through altering gene expression within bovine mammary epithelial tissue. However, the cellular metabolism mechanisms under HS remains largely unknown. The objective of this study was to determine whether HS induced changes in intracellular metabolites and gene transcription related to amino acid metabolism, amino acid transportation and the mTOR signaling pathway. Immortalized bovine mammary epithelial cell lines (MAC-T cells, n = 5 replicates/treatment) were incubated for 12 h at 37 °C (Control group) and 42 °C (HS group). Relative to the control group, HS led to a greater mRNA expression of heat shock protein genes HSF1, HSPB8, HSPA5, HSP90AB1 and HSPA1A. Compared with the control group, metabolomics using liquid chromatography tandem–mass spectrometry identified 417 differential metabolites with p < 0.05 and a variable importance in projection (VIP) score >1.0 in the HS group. HS resulted in significant changes to the intracellular amino acid metabolism of glutathione, phenylalanine, tyrosine, tryptophan, valine, leucine, isoleucine, arginine, proline, cysteine, methionine, alanine, aspartate and glutamate. HS led to a greater mRNA expression of the amino acid transporter genes SLC43A1, SLC38A9, SLC36A1, and SLC3A2 but a lower mRNA expression of SLC7A5 and SLC38A2. Additionally, HS influenced the expression of genes associated with the mTOR signaling pathway and significantly upregulated the mRNA expression of mTOR, AKT, RHEB, eIF4E and eEF2K but decreased the mRNA expression of TSC1, TSC2 and eEF2 relative to the control group. Compared with the control group, HS also led to greater mRNA expression of the CSN1S2 gene. Overall, our study indicates that bovine mammary epithelial cells may have the ability to resist HS damage and continue milk protein synthesis partly through enhanced intracellular amino acid absorption and metabolism and by activating the mTOR signaling pathway during HS.

Lactiplantibacillus plantarum Reduced Renal Calcium Oxalate Stones by Regulating Arginine Metabolism in Gut Microbiota

Renal calcium oxalate (CaOx) stones are a common kidney disease. There are few methods for reducing the formation of these stones. However, the potential of probiotics for reducing renal stones has received increasing interest. We previously isolated a strain of Lactiplantibacillus plantarum N-1 from traditional cheese in China. This study aimed to investigate the effects of N-1 on renal CaOx crystal deposition. Thirty rats were randomly allocated to three groups: control group (ddH2O by gavage), model group [ddH2O by gavage and 1% ethylene glycol (EG) in drinking water], and Lactiplantibacillus group (N-1 by gavage and 1% EG in drinking water). After 4 weeks, compared with the model group, the group treated with N-1 exhibited significantly reduced renal crystals (P < 0.05). In the ileum and caecum, the relative abundances of Lactobacillus and Eubacterium ventriosum were higher in the control group, and those of Ruminococcaceae UCG 007 and Rikenellaceae RC9 were higher in the N-1-supplemented group. In contrast, the relative abundances of Staphylococcus, Corynebacterium 1, Jeotgalicoccus, Psychrobacter, and Aerococcus were higher in the model group. We also predicted that the arginase level would be higher in the ileal microbiota of the model group than in the N-1-supplemented group with PICRUSt2. The arginase activity was higher, while the level of arginine was lower in the ileal contents of the model group than in the N-1-supplemented group. The arginine level in the blood was also higher in the N-1-supplemented group than in the model group. In vitro studies showed that exposure to arginine could reduce CaOx crystal adhesion to renal epithelial HK-2 cells. Our findings highlighted the important role of N-1 in reducing renal CaOx crystals by regulating arginine metabolism in the gut microbiota. Probiotics containing L. plantarum N-1 may be potential therapies for preventing renal CaOx stones.

Dry Period Heat Stress Impacts Mammary Protein Metabolism in the Subsequent Lactation

Simple Summary

Heat stress during the dry period of dairy cows reduces milk yield in the following lactation. Factors such as altered mammary metabolism could impact yields and alter milk composition, including milk protein. We sought to determine if exposure to dry period heat stress would influence mammary milk protein metabolism during the subsequent lactation. Objectives were to first determine the impact of dry period heat stress on milk protein yields and secondly characterize the amino acid and protein profiles in the mammary tissue, milk, and blood to elucidate potential carry-over impact of dry period heat stress on systems that participate directly in milk protein metabolism (i.e., mTOR). We found that heat stress during the dry period reduces milk yield, protein content, and protein yield in the subsequent lactation. The plasma amino acid profile and mammary amino acid transporters are altered in dry period heat-stressed cows, and mammary mTOR signaling proteins are differentially expressed as well. It appears that dry period heat stress impacts mammary metabolism with consequences on milk yield and protein content. The continuous production of high-quality and -quantity milk is vital as a sustainable source of protein in the face of rising global temperatures.

Abstract

Dry period heat stress impairs subsequent milk production, but its impact on milk protein content and yield is inconsistent. We hypothesize that dairy cow exposure to dry period heat stress will reduce milk protein synthesis in the next lactation, potentially through modified amino acid (AA) transport and compromised mTOR signaling in the mammary gland. Cows were enrolled into heat-stressed (dry-HT, n = 12) or cooled (dry-CL, n = 12) treatments for a 46-day dry period then cooled after calving. Milk yield and composition and dry matter intake were recorded, and milk, blood, and mammary tissue samples were collected at 14, 42, and 84 days in milk (DIM) to determine free AA concentrations, milk protein fractions, and mammary AA transporter and mTOR pathway gene and protein expression. Dry matter intake did not significantly differ between treatments pre- or postpartum. Compared with dry-CL cows, milk yield was decreased (32.3 vs. 37.7 ± 1.6 kg/day) and milk protein yield and content were reduced in dry-HT cows by 0.18 kg/day and 0.1%. Further, dry-HT cows had higher plasma concentrations of glutamic acid, phenylalanine, and taurine. Gene expression of key AA transporters was upregulated at 14 and 42 DIM in dry-HT cows. Despite minor changes in mTOR pathway gene expression, the protein 4E-BP1 was upregulated in dry-HT cows at 42 DIM whereas Akt and p70 S6K1 were downregulated. These results indicate major mammary metabolic adaptations during lactation after prior exposure to dry period heat stress.

Effects of L-Histidine and Sodium Acetate on β-Casein Expression in Nutrient-Restricted Bovine Mammary Epithelial Cells

Simple Summary

Nutrient restriction is known to decrease the milk production and milk quality of dairy cows. However, providing cows with abundant nutrients also has a disadvantage because it will increase feed costs. Under such a situation, the use of feed additives can be a good strategy to reduce the feed cost. The objective of this study was to investigate the effects of histidine and sodium acetate on β-casein expression in nutrient-restricted bovine mammary epithelial cells. The results indicate that histidine has the potential to increase the β-casein levels in bovine mammary cells when the nutrient is restricted, suggesting that histidine is a potential feed additive for cows in a nutrient-insufficient environment.

Abstract

Nutrient restriction is a challenging condition for the mammary glands of dairy cows. In this condition, supplementing amino acids and energy sources might be a good strategy to improve the concentration of one of the most important caseins in bovine milk. Therefore, the objective of this study was to investigate the effects of L-histidine (His) and sodium acetate (Ace) in a nutrient-restricted (NR) immortalized bovine mammary epithelial cell line (MAC-T cells). The treatments for the MAC-T cells are as follows: experiment (1) 0–5% diluted basal medium; experiment (2) supplementation of 0–9.6 mM of His or Ace in NR or normal conditions; experiment (3) supplementation of 0–9.6 mM of Ace plus 0.15 mM of His in NR or normal conditions. The 1% diluted medium showed no significant effect on the cell viability with the basal medium; thus, it was selected as the NR condition. The relative expression of β-casein was significantly increased in the NR condition with the inclusion of 0.15 mM His alone or with Ace compared to that in control. The supplementation of Ace increased the β-casein level under normal conditions. However, it did not change the expression of β-casein under the NR condition. The results suggest that His has the potential to increase the β-casein expression under the NR condition.

Multifaceted role of one-carbon metabolism on immunometabolic control and growth during pregnancy, lactation and the neonatal period in dairy cattle

Dairy cattle undergo dramatic metabolic, endocrine, physiologic and immune changes during the peripartal period largely due to combined increases in energy requirements for fetal growth and development, milk production, and decreased dry matter intake. The negative nutrient balance that develops results in body fat mobilization, subsequently leading to triacylglycerol (TAG) accumulation in the liver along with reductions in liver function, immune dysfunction and a state of inflammation and oxidative stress. Mobilization of muscle and gluconeogenesis are also enhanced, while intake of vitamins and minerals is decreased, contributing to metabolic and immune dysfunction and oxidative stress. Enhancing post-ruminal supply of methyl donors is one approach that may improve immunometabolism and production synergistically in peripartal cows. At the cellular level, methyl donors (e.g. methionine, choline, betaine and folic acid) interact through one-carbon metabolism to modulate metabolism, immune responses and epigenetic events. By modulating those pathways, methyl donors may help increase the export of very low-density lipoproteins to reduce liver TAG and contribute to antioxidant synthesis to alleviate oxidative stress. Thus, altering one-carbon metabolism through methyl donor supplementation is a viable option to modulate immunometabolism during the peripartal period. This review explores available data on the regulation of one-carbon metabolism pathways in dairy cows in the context of enzyme regulation, cellular sensors and signaling mechanisms that might respond to increased dietary supply of specific methyl donors. Effects of methyl donors beyond the one-carbon metabolism pathways, including production performance, immune cell function, mechanistic target or rapamycin signaling, and fatty acid oxidation will also be highlighted. Furthermore, the effects of body condition and feeding system (total mixed ration vs. pasture) on one-carbon metabolism pathways are explored. Potential effects of methyl donor supply during the pepartum period on dairy calf growth and development also are discussed. Lastly, practical nutritional recommendations related to methyl donor metabolism during the peripartal period are presented. Nutritional management during the peripartal period is a fertile area of research, hence, underscoring the importance for developing a systems understanding of the potential immunometabolic role that dietary methyl donors play during this period to promote health and performance.

Effect of Soybean Oil Supplementation on Milk Production, Digestibility, and Metabolism in Dairy Goats under Thermoneutral and Heat Stress Conditions

Simple Summary

Heat stress (HS) not only reduces milk yield but also depresses its contents of fat and protein, which might negatively impact cheese making. Dietary supplementation with soybean oil (SBO) could increase milk fat and improve milk fatty acid (FA) profiles in dairy goats. In the present study dairy goats were exposed to thermoneutral (TN; 15 to 20 °C) or HS (12 h/d at 37 °C and 12 h/d at 30 °C) conditions. In each ambient temperature, goats were fed a control diet (CON) or the same diet supplemented with SBO. Goats in HS suffered depressed feed intake and milk production, but they had greater digestibility coefficients compared to TN goats. Regardless of the HS treatment, goats supplemented with SBO produced milk with greater contents of fat, monounsaturated FA, and conjugated linoleic acid, without any negative effects on milk protein content. In conclusion, dietary supplementation with soybean oil was a useful strategy to increase milk fat and improve its fatty acid profile. Both TN and HS goats responded to soybean oil supplementation similarly since the interaction between soybean oil supplementation and temperature treatment was not significant.

Abstract

In a previous work, we observed that heat-stressed goats suffer reductions in milk yield and its contents of fat and protein. Supplementation with soybean oil (SBO) may be a useful strategy to enhance milk quality. In total, eight multiparous Murciano–Granadina dairy goats (42.8 ± 1.3 kg body weight; 99 ± 1 days of lactation) were used in a replicated 4 × 4 Latin square design with four periods; 21 d each (14 d adaptation, 5 d for measurements and 2 d transition between periods). Goats were allocated to one of four treatments in a 2 × 2 factorial arrangement. Factors were no oil (CON) or 4% of soybean oil (SBO), and controlled thermal neutral (TN; 15 to 20 °C) or heat stress (HS; 12 h/d at 37 °C and 12 h/d at 30 °C) conditions. This resulted in four treatment combinations: TN-CON, TN-SBO, HS-CON, and HS-SBO. Compared to TN, HS goats experienced lower (p < 0.05) feed intake, body weight, N retention, milk yield, and milk protein and lactose contents. However, goats in HS conditions had greater (p < 0.05) digestibility coefficients (+5.1, +5.2, +4.6, +7.0, and +8.9 points for dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber, respectively) than TN goats. The response to SBO had the same magnitude in TN and HS conditions. Supplementation with SBO had no effects on feed intake, milk yield, or milk protein content. However, SBO supplementation increased (p < 0.05) blood non-esterified fatty acids by 50%, milk fat by 29%, and conjugated linoleic acid by 360%. In conclusion, feeding 4% SBO to dairy goats was a useful strategy to increase milk fat and conjugated linoleic acid without any negative effects on intake, milk yield, or milk protein content. These beneficial effects were obtained regardless goats were in TN or HS conditions.

Cytoprotective Effects of Taurine on Heat-Induced Bovine Mammary Epithelial Cells In Vitro

It is a widely known that heat stress induces a reduction in milk production in cows and impairs their overall health. Studies have shown that taurine protects tissues and organs under heat stress. However, there have yet to be studies showing the functions of taurine in mammary alveolar cells-large T antigen (MAC-T) (a bovine mammary epithelial cell line) cells under heat shock. Therefore, different concentrations of taurine (10 mM, 50 mM, and 100 mM) were tested to determine the effects on heat-induced MAC-T cells. The results showed that taurine protected the cells against heat-induced damage as shown by morphological observations in conjunction with suppressed the translocation and expression of heat shock factor 1 (HSF1). Moreover, taurine not only reversed the decline in antioxidase (superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX)) activities but also attenuated the accumulation of malondialdehyde (MDA). Meanwhile, mitochondrial damage (morphology and complex I activity) resulting from heat exposure was mitigated. Taurine also alleviated the rates of cell apoptosis and markedly depressed the mRNA expressions of BCL2 associated X, apoptosis regulator (BAX) and caspase3. Furthermore, compared with the heat stress (HS) group, the protein levels of caspase3 and cleaved caspase3 were decreased in all taurine groups. In summary, taurine improves the antioxidant and anti-apoptosis ability of MAC-T cells thereby alleviates damage of cells due to heat insults.

Potential role of specific microRNAs in the regulation of thermal stress response in livestock

Thermal stress is known to have harmful effects on livestock productivity and can cause livestock enterprises considerable financial loss. These effects may be aggravated by climate change. Stress responses to nonspecific systemic actions lead to perturbation of molecular pathways in the organism. The molecular response is regulated in a dynamic and synchronized manner that assurances robustness and flexibility for the restoration of functional and structural homeostasis in stressed cells and tissues. MicroRNAs (miRNAs) are micro molecules of small non-coding RNA that control gene expression at the post-transcriptional level. Recently, various studies have discovered precise types of miRNA that regulate cellular machinery and homeostasis under various types of stress, suggesting a significant role of miRNA in thermal stress responses in animals. The miRNAs revealed in this paper could serve as promising candidates and biomarkers for heat stress and could be used as potential pharmacological targets for mitigating the consequences of thermal stress. Stress miRNA pathways may be associated with thermal stress, which offers some potential approaches to combat the negative impacts of thermal stress in livestock. The review provides new data that can assist the elucidation of the miRNA mechanisms that mediate animals' responses to thermal stress.

Milk Production and Energetic Metabolism of Heat-Stressed Dairy Goats Supplemented with Propylene Glycol

Heat-stressed dairy animals increase their reliance on glucose. This elevated glucose demand is partially met by increasing the conversion of glucogenic amino acids (AA) in the liver. Propylene glycol (PG) is a glucogenic precursor and was not tested in dairy goats under thermoneutral (TN) and heat stress (HS) conditions simultaneously. We hypothesize that if HS-goats are fed with PG, they would get more glucose and consequently spare more glucogenic AA for milk protein synthesis rather than gluconeogenesis. Eight multiparous dairy goats (40.8 ± 1.1 kg body weight; 84 ± 1 days in milk) were used in a replicated 4 × 4 Latin square design of 4 periods; 21 d each (14 d adaptation, 5 d for measurements, and 2 d of transition). Goats were allocated to one of 4 treatments in a 2 × 2 factorial arrangement. Factors were control (CO) without PG or 5% of PG, and thermoneutral (TN; 15 to 20 °C) or heat stress (HS; 12 h/d at 37 °C and 12 h/d at 30 °C) conditions. Feed intake, rectal temperature, respiratory rate, milk yield, milk composition, and blood metabolites were measured. Compared to TN, HS goats had lower (p < 0.01) feed intake (-34%), fat-corrected milk (-15%), and milk fat (-15%). Heat-stressed goats also tended (p < 0.10) to produce milk with lower protein (-11%) and lactose (-4%) contents. Propylene glycol increased blood glucose (+7%; p < 0.05), blood insulin (+37%; p < 0.10), and body weight gain (+68%; p < 0.05), but decreased feed intake (-9%; p < 0.10) and milk fat content (-23%; p < 0.01). Furthermore, blood non-esterified fatty acids (-49%) and β-hydroxybutyrate (-32%) decreased (p < 0.05) by PG. In conclusion, supplementation of heat-stressed dairy goats with propylene glycol caused milk fat depression syndrome, but reduced body weight loss that is typically observed under HS conditions. Supplementation with lower doses of PG would avoid the reduced feed intake and milk fat depression, but this should be tested.

MicroRNAs as Biomarkers for Animal Health and Welfare in Livestock

MicroRNAs (miRNAs) are small and highly conserved non-coding RNA molecules that orchestrate a wide range of biological processes through the post-transcriptional regulation of gene expression. An intriguing aspect in identifying these molecules as biomarkers is derived from their role in cell-to-cell communication, their active secretion from cells into the extracellular environment, their high stability in body fluids, and their ease of collection. All these features confer on miRNAs the potential to become a non-invasive tool to score animal welfare. There is growing interest in the importance of miRNAs as biomarkers for assessing the welfare of livestock during metabolic, environmental, and management stress, particularly in ruminants, pigs, and poultry. This review provides an overview of the current knowledge regarding the potential use of tissue and/or circulating miRNAs as biomarkers for the assessment of the health and welfare status in these livestock species.

Effect of Heat Stress on Dairy Cow Performance and on Expression of Protein Metabolism Genes in Mammary Cells

Simple Summary

Environmental temperatures are increasing, and consequent global warming also has negative effects on dairy cattle farms, which may result in reduced production and poorer milk quality. The protein content of casein, in particular, is important in influencing the coagulation properties of milk and, therefore, the production and quality of cheese. The aim of this study was to assess the effect of heat stress on animal performance and on the expression of selected genes involved in milk protein metabolism. Eight dairy cows were kept under thermoneutral conditions for 8 days. The same animals were then maintained under mild heat stress conditions for an additional 8 days. The results of this study revealed that mild heat stress reduced the feed intake and performance of dairy cows in terms of milk and protein yield, but not the expression of the target genes involved in milk protein metabolism, such as those coding for caseins.

Abstract

The aim of this study was to assess the effect of heat stress on dairy cow performance and on the expression of selected genes involved in milk protein metabolism. Eight Italian Holstein Friesian cows were kept under thermoneutral conditions (temperature–humidity index (THI) < 72, CON) for 8 days and under mild heat stress conditions (72 < THI < 78, HS) for an additional 8 days. The rectal temperature, feed intake, and milk yield were recorded during the last 3 days of the CON and HS periods. During the same time period, milk samples were collected to assess the composition and expression of selected genes involved in milk protein metabolism. Gene expression analyses were performed on somatic cells from milk, which are representative of mammary tissue. In terms of dairy cow performance, HS resulted in lower milk and protein yields and feed intake but higher rectal temperature than for CON (p < 0.05). Under HS, there were greater abundances of HSPA1A (p < 0.05) and BCL2 (p < 0.05), compared to CON, but similar levels of CSN2 (p > 0.05), CSN3 (p > 0.05), HSPA8 (p > 0.05), and STAT5B (p > 0.05) mRNA. Mild heat stress reduced the performance of dairy cows without affecting the expression of genes coding for caseins.

Heat stress affects some physiological and productive variables and alters metabolism in dairy ewes

Heat stress (HS) has a significant economic impact on the global dairy industry. However, the mechanisms by which HS negatively affects metabolism and milk synthesis in dairy ewes are not well defined. This study evaluated the production and metabolic variables in dairy ewes under controlled HS conditions. Eight Lacaune ewes (75.5 ± 3.2 kg of body weight; 165 ± 4 d of lactation; 2.31 ± 0.04 kg of milk per day) were submitted to thermoneutral (TN) or HS conditions in a crossover design (2 periods, 21 d each, 6-d transition). Conditions (day-night, 12-12 h; relative humidity; temperature-humidity index, THI) were: TN (15-20°C; 50 ± 5%; THI = 59-65) and HS (28-35°C; 45 ± 5%; THI = 75-83). Ewes were fed ad libitum and milked twice daily. Rectal temperature, respiratory rate, feed intake, water consumption, and milk yield were recorded daily. Milk and blood samples were collected weekly. Additionally, TN and HS ewes were exposed to glucose tolerance test, insulin tolerance test, and epinephrine challenge. Heat stress reduced feed intake (-11%), and increased rectal temperature (+0.77°C), respiratory rate (+90 breaths/min), and water consumption (+28%). Despite the reduced feed intake, HS ewes produced similar milk to TN ewes, but their milk contained lower fat (-1.7 points) and protein (-0.86 points). Further, HS milk tended to contain more somatic cells (+0.23 log points). Blood creatinine was greater in HS compared with TN, but no differences in blood glucose, nonesterified fatty acids, or urea were detected. When glucose was infused, TN and HS had similar insulin response, but higher glucose response (+85%) was detected in HS ewes. Epinephrine infusion resulted in lower nonesterified fatty acids response (-215%) in HS than TN ewes. Overall, HS decreased feed intake, but milk production was not affected. Heat stress caused metabolic adaptations that included increased body muscle degradation and reduced adipose tissue mobilization. These adaptations allowed ewes to spare glucose and to avoid reductions in milk yield.

Methyl donor supply to heat stress-challenged polymorphonuclear leukocytes from lactating Holstein cows enhances 1-carbon metabolism, immune response, and cytoprotective gene network abundance

Mechanisms controlling immune function of dairy cows are dysregulated during heat stress (HS). Methyl donor supply-methionine (Met) and choline (Chol)-positively modulates innate immune function, particularly antioxidant systems of polymorphonuclear leukocytes (PMN). The objective of this study was to investigate the effect of Met and Chol supply in vitro on mRNA abundance of genes related to 1-carbon metabolism, inflammation, and immune function in short-term cultures of PMN isolated from mid-lactating Holstein cows in response to heat challenge. Blood PMN were isolated from 5 Holstein cows (153 ± 5 d postpartum, 34.63 ± 2.73 kg/d of milk production; mean ± SD). The PMN were incubated for 2 h at thermal-neutral (37°C; TN) or heat stress (42°C; HS) temperatures with 3 levels of Chol (0, 400, or 800 μg/mL) or 3 ratios of Lys:Met (Met; 3.6:1, 2.9:1, or 2.4:1). Supernatant concentrations of IL-1β, IL-6, and tumor necrosis factor-α were measured via bovine-specific ELISA. Fold-changes in mRNA abundance were calculated separately for Chol and Met treatments to obtain the fold-change response at 42°C (HS) relative to 37°C (TN). Data were subjected to ANOVA using PROC MIXED in SAS (SAS Institute Inc., Cary, NC). Orthogonal contrasts were used to determine the linear or quadratic effect of Met and Chol for mRNA fold-change and supernatant cytokine concentrations. Compared with PMN receiving 0 μg of Chol/mL, heat-stressed PMN supplemented with Chol at 400 or 800 μg/mL had greater fold-change in abundance of CBS, CSAD, GSS, GSR, and GPX1. Among genes associated with inflammation and immune function, fold-change in abundance of TLR2, TLR4, IRAK1, IL1B, and IL10 increased with 400 and 800 μg of Chol/mL compared with PMN receiving 0 μg of Chol/mL. Fold-change in abundance of SAHH decreased linearly at increasing levels of Met supply. A linear effect was detected for MPO, NFKB1, and SOD1 due to greater fold-change in abundance when Met was increased to reach Lys:Met ratios of 2.9:1 and 2.4:1. Although increasing Chol supply upregulated BAX, BCL2, and HSP70, increased Met supply only upregulated BAX. Under HS conditions, enhancing PMN supply of Chol to 400 μg/mL effectively increased fold-change in abundance of genes involved in antioxidant production (conferring cellular processes protection from free radicals and reactive oxygen species), inflammatory signaling, and innate immunity. Although similar outcomes were obtained with Met supply at Lys:Met ratios of 2.9:1 and 2.4:1, the response was less pronounced. Both Chol and Met supply enhanced the cytoprotective characteristics of PMN through upregulation of heat shock proteins. Overall, the modulatory effects detected in the present experiment highlight an opportunity to use Met and particularly Chol supplementation during thermal stress.

Effect of heat stress on udder health of dairy cows

This Research Reflection short review presents an overview of the effects of heat stress on dairy cattle udder health and discusses existing heat stress mitigation strategies for a better understanding and identification of appropriate abatement plans for future stress management. Due to high ambient temperatures with high relative humidity in summer, dairy cows respond by changes of physical, biochemical and biological pathways to neutralize heat stress resulting in decreased production performance and poorer immunity resulting in an increased incidence of intramammary infections (IMI) and a higher somatic cell count (SCC). In vitro studies on bovine polymorphonuclear cells (PMN) suggested that heat stress reduces the phagocytosis capacity and oxidative burst of PMN and alters the expression of apoptotic genes and miRNA which, together with having a negative effect on the immune system, may explain the increased susceptibility to IMI. Although there are limited data regarding the incidence rate of clinical mastitis in many countries or regions, knowledge of SCC at the cow or bulk tank level helps encourage farmers to improve herd health and to develop strategies for infection prevention and cure. Therefore, more research into bulk tank SCC and clinical mastitis rates is needed to explain the effect of heat stress on dairy cow udder health and functions that could be influenced by abatement plans.

The application of omics in ruminant production: a review in the tropical and sub-tropical animal production context

The demand for animal products (e.g. dairy and beef) in tropical regions is expected to increase in parallel with the public demand for sustainable practices, due to factors such as population growth and climate change. The necessity to increase animal production output must be achieved with better management and production technologies. For this to happen, novel research methodologies, animal selection and postgenomic tools play a pivotal role. Indeed, improving breeder selection programs, the quality of meat and dairy products as well as animal health will contribute to higher sustainability and productivity. This would surely benefit regions where resource quality and quantity are increasingly unstable, and research is still very incipient, which is the case of many regions in the tropics. The purpose of this review is to demonstrate how omics-based approaches play a major role in animal science, particularly concerning ruminant production systems and research associated to the tropics and developing countries. SIGNIFICANCE: Environmental conditions in the tropics make livestock production harder, compared to temperate regions. Due to global warming, the sustainability of livestock production will become increasingly problematic. The use of novel omics technologies could generate useful information to understand adaptation mechanisms of resilient breeds and/or species. The application of omics to tropical animal production is still residual in the currently available literature. With this review, we aim to summarize the most notable results in the field whilst encouraging further research to deal with the future challenges that animal production in the tropics will need to face.

Transcriptome Functional Analysis of Mammary Gland of Cows in Heat Stress and Thermoneutral Condition

Simple Summary

The current study employed RNA-seq technology to analyze the impact of heat stress on the whole transcript sequencing profile in the mammary glands of lactating Holstein dairy cows. In the findings of the current study, heat stress downregulated the expression of casein genes, which resulted in a decrease in milk production. Moreover, heat stress upregulated the gene expression of HSPA1A and HSP90B1, while it downregulated the expression of immune response-related genes that resulted in a reduction in milk yield. Furthermore, there was an increased synthesis of heat shock proteins and unfolded proteins that could reduce the availability of circulating amino acids for milk protein synthesis. The findings of the current experiment may help to explore the impact of heat stress on immune function, milk production, and milk protein synthesis in cows.

Abstract

Heat stress (HS) exerts significant effects on the production of dairy animals through impairing health and biological functions. However, the molecular mechanisms related to the effect of HS on dairy cow milk production are still largely unknown. The present study employed an RNA-sequencing approach to explore the molecular mechanisms associated with a decline in milk production by the functional analysis of differentially expressed genes (DEGs) in mammary glands of cows exposed to HS and non-heat-stressed cows. The results of the current study reveal that HS increases the rectal temperature and respiratory rate. Cows under HS result in decreased bodyweight, dry matter intake (DMI), and milk yield. In the current study, a total of 213 genes in experimental cow mammary glands was identified as being differentially expressed by DEGs analysis. Among identified genes, 89 were upregulated, and 124 were downregulated. Gene Ontology functional analysis found that biological processes, such as immune response, chaperone-dependent refolding of protein, and heat shock protein binding activity, were notably affected by HS. The Kyoto Encyclopedia of Genes and Genomes enrichment analysis found that almost all of the top-affected pathways were related to immune response. Under HS, the expression of heat shock protein 90 kDa beta I (HSP90B1) and heat shock 70 kDa protein 1A was upregulated, while the expression of bovine lymphocyte antigen (BoLA) and histocompatibility complex, class II, DRB3 (BoLA-DRB3) was downregulated. We further explored the effects of HS on lactation-related genes and pathways and found that HS significantly downregulated the casein genes. Furthermore, HS increased the expression of phosphorylation of mammalian target of rapamycin, cytosolic arginine sensor for mTORC1 subunit 2 (CASTOR2), and cytosolic arginine sensor for mTORC1 subunit 1 (CASTOR1), but decreased the phosphorylation of Janus kinase-2, a signal transducer and activator of transcription factor-5. Based on the findings of DMI, milk yield, casein gene expression, and the genes and pathways identified by functional annotation analysis, it is concluded that HS adversely affects the immune function of dairy cows. These results will be beneficial to understand the underlying mechanism of reduced milk yield in HS cows.

Amino acid transportation, sensing and signal transduction in the mammary gland: key molecular signalling pathways in the regulation of milk synthesis

The mammary gland, a unique exocrine organ, is responsible for milk synthesis in mammals. Neonatal growth and health are predominantly determined by quality and quantity of milk production. Amino acids are crucial maternal nutrients that are the building blocks for milk protein and are potential energy sources for neonates. Recent advances made regarding the mammary gland further demonstrate that some functional amino acids also regulate milk protein and fat synthesis through distinct intracellular and extracellular pathways. In the present study, we discuss recent advances in the role of amino acids (especially branched-chain amino acids, methionine, arginine and lysine) in the regulation of milk synthesis. The present review also addresses the crucial questions of how amino acids are transported, sensed and transduced in the mammary gland.

Supply of methionine and arginine alters phosphorylation of mechanistic target of rapamycin (mTOR), circadian clock proteins, and α-s1-casein abundance in bovine mammary epithelial cells

Methionine (Met) and arginine (Arg) regulate casein protein abundance through alterations in activity of the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway.

Methionine and arginine supplementation alter inflammatory and oxidative stress responses during lipopolysaccharide challenge in bovine mammary epithelial cells in vitro

Mastitis, inflammation of the udder, is one of the most common diseases hampering milk yield of dairy cows. Methionine (Met) and arginine (Arg) are key nutrients with potential to regulate inflammation and oxidative stress. The aim of this study was to evaluate the effect of increased supply of Met and Arg on mRNA and protein abundance associated with innate immune response and redox balance during lipopolysaccharide (LPS) stimulation in primary bovine mammary epithelial cells (BMEC). Primary BMEC (n = 4 replicates per treatment) were pre-incubated for 12 h in media with the following amino acid combinations: ideal profile of amino acids (control; Con), increased Met supply (incMet), increased Arg supply (incArg), and increased supply of Met and Arg (incMetArg). Subsequently, cells were challenged with or without LPS (1 µg/mL) and incubated for 6 h. Data were analyzed as a 2 × 2 × 2 factorial using the MIXED procedure of SAS 9.4 (SAS Institute Inc., Cary, NC). The downregulation of SLC36A1 and SLC7A1 mRNA abundance induced by LPS was attenuated in the incArg cultures. Although challenge with LPS led to lower abundance of proteins related to the antioxidant response (NFE2L2, NQO1, GPX1), lower levels of ATG7, and lower mRNA abundance of GPX3, we found little effect in cultures with incMet or incArg. Cultures with incMet, incArg, or incMetArg led to attenuation of the upregulation of SOD2 and NOS2 induced by LPS. Abundance of phosphorylated p65 (RELA) was greater after LPS stimulation, but the response was attenuated in cultures with incMet. The greater ratio of pRELA to total RELA in responses to LPS was also attenuated in cultures with incMetArg. The greater mRNA abundance of the proinflammatory cytokine IL1B induced by LPS was attenuated in cultures with incMet, and the same trend induced by LPS on CXCL2 was also alleviated in cultures with incArg. Overall, the data suggest that greater supply of Met and Arg alleviated the proinflammatory responses triggered by LPS through controlling the abundance of proinflammatory cytokines and chemokines and activity of NF-κB. Little benefit on oxidative stress induced by LPS challenge in BMEC was detected with greater supply of Met and Arg.

The mTORC1/4EBP1/PPARγ Axis Mediates Insulin-Induced Lipogenesis by Regulating Lipogenic Gene Expression in Bovine Mammary Epithelial Cells

4EBP1 is a chief downstream factor of mTORC1, and PPARγ is a key lipogenesis-related transcription factor. mTORC1 and PPARγ are associated with lipid metabolism. However, it is unknown which effector protein connects mTORC1 and PPARγ. This study investigated the interaction between 4EBP1 with PPARγ as part of the underlying mechanism by which insulin-induced lipid synthesis and secretion are regulated by mTORC1 in primary bovine mammary epithelial cells (pBMECs). Rapamycin, a specific inhibitor of mTORC1, downregulated 4EBP1 phosphorylation and the expression of PPARγ and the following lipogenic genes: lipin 1, DGAT1, ACC, and FAS. Rapamycin also decreased the levels of intracellular triacylglycerol (TAG); 10 types of fatty acid; and the accumulation of TAG, palmitic acid (PA), and stearic acid (SA) in the cell culture medium. Inactivation of mTORC1 by shRaptor or shRheb attenuated the synthesis and secretion of TAG and PA. In contrast, activation of mTORC1 by Rheb overexpression promoted 4EBP1 phosphorylation and PPARγ expression and upregulated the mRNA and protein levels of lipin 1, DGAT1, ACC, and FAS, whereas the levels of intracellular and extracellular TAG, PA, and SA also rose. Further, 4EBP1 interacted directly with PPARγ. Inactivation of mTORC1 by shRaptor prevented the nuclear location of PPARγ. These results demonstrate that mTORC1 regulates lipid synthesis and secretion by inducing the expression of lipin 1, DGAT1, ACC, and FAS, which is likely mediated by the 4EBP1/PPARγ axis. This finding constitutes a novel mechanism by which lipid synthesis and secretion are regulated in pBMECs.