A Meta-Analysis of the Effects of Dietary Betaine on Milk Production, Growth Performance, and Carcass Traits of Ruminants

Betaine improves growth performance and health in monogastric animals under both thermoneutral and heat stress conditions, but results in ruminants have been more equivocal. This meta-analysis investigated the effects of betaine supplementation on productive performance, milk production and composition, and carcass traits of ruminants due to betaine supplementation. A comprehensive search for published studies investigating the effect of betaine was performed using Google Scholar, ScienceDirect, PubMed, and Scopus databases. Effect size analysis, random effects models, I2 statistics, and meta-regression analysis were utilized to assess differences in production parameters. Dietary betaine supplementation increased milk yield (+1.0 kg/d (weighted mean differences presented in this abstract), p < 0.001), dry matter intake (+0.15 kg/d, p < 0.001), and milk lactose (+0.05%, p = 0.010) in dairy cows housed under thermoneutral conditions. In the few studies conducted on small ruminants, there was an increase in milk yield in response to dietary betaine (0.45 kg/d, p = 0.040). Under heat stress conditions or grazing pasture during summer, dietary betaine increased milk yield (+1.0 kg/d, p < 0.001) and dry matter intake (+0.21 kg/d, p = 0.020). Dietary betaine increased final liveweight (+2.33 kg, p = 0.050) and back fat thickness (+0.74 cm, p < 0.001) in beef cattle. Dietary betaine increased final liveweight (0.14 kg, p = 0.010), daily gain (+0.019 kg/d, p < 0.001), and carcass weight (+0.80 kg, p < 0.001) but not backfat in small ruminants. These meta-analyses showed that dietary betaine increases liveweight in small ruminants and beef cattle and increases feed intake and milk yield in dairy cattle.

Insect Peptide CopA3 Mitigates the Effects of Heat Stress on Porcine Muscle Satellite Cells

Heat stress inhibits cell proliferation as well as animal production. Here, we aimed to demonstrate that 9-mer disulfide dimer peptide (CopA3) supplementation stabilizes porcine muscle satellite cell (PMSC) proliferation and heat shock protein (HSP) expression at different temperatures. Therefore, we investigated the beneficial effects of CopA3 on PMSCs at three different temperatures (37, 39, and 41 °C). Based on temperature and CopA3 treatment, PMSCs were divided into six different groups including treatment and control groups for each temperature. Cell viability was highest with 10 µg/mL CopA3 and decreased as the concentration increased in a dose-dependent manner. CopA3 significantly increased the cell viability at all temperatures at 24 and 48 h. It significantly decreased apoptosis compared to that in the untreated groups. In addition, it decreased the apoptosis-related protein, Bcl-2-associated X (BAX), expression at 41 °C. Notably, temperature and CopA3 had no effects on the apoptosis-related protein, caspase 3. Expression levels of HSP40, HSP70, and HSP90 were significantly upregulated, whereas those of HSP47 and HSP60 were not affected by temperature changes. Except HSP90, CopA3 did not cause temperature-dependent changes in protein expression. Therefore, CopA3 promotes cell proliferation, inhibits apoptosis, and maintains stable HSP expression, thereby enhancing the heat-stress-tolerance capacity of PMSCs.

Hydroxycarboxylic acid receptor 2 (HCA2) agonists induce NET formation and MMP-9 release from bovine polymorphonuclear leukocytes

Periparturient cows are commonly fed diets supplemented with Niacin (nicotinic acid, NA) because of its anti-lipolytic properties. NA confers its anti-lipolytic effects by activating the hydroxycarboxylic acid 2 receptor (HCA2). HCA2 is also activated by the ketone body beta-hydroxybutyrate (BHB) and circulating BHB levels are elevated in postpartum dairy cows. The HCA2 receptor is highly expressed in bovine polymorphonuclear leukocytes (PMN) and could link metabolic and innate immune responses in cattle. We investigated how HCA2 agonists affected bovine PMN function in vitro. We studied different PMN responses, such as granule release, surface expression of CD11b and CD47, generation of neutrophil extracellular traps (NETs), and apoptosis. NA, BHB, and 4,4aR,5,5aR-tetrahydro-1H-cyclopropa [4,5] cyclopenta [1,2-c] pyrazole-3-carboxylic acid (MK-1903) treatment triggered the release of matrix metalloproteinase 9 (MMP-9), a component of the tertiary granule, from neutrophils. Additionally, all HCA2 agonists induced NETs formation but did not affect surface expression of CD11b and CD47. Finally, none of the HCA2 agonists triggered apoptosis in bovine PMN. This information will give new insights into the potential role of the HCA2 receptor in the bovine innate immune response.

Procyanidin B2 Alleviates Heat-Induced Oxidative Stress through the Nrf2 Pathway in Bovine Mammary Epithelial Cells

The objective of this study was to investigate the protective effects and potential molecular mechanisms of procyanidin B2 (PB2) in MAC-T (mammary alveolar cells-large T antigen) cells during heat stress (HS). The MAC-T cells were divided into three treatment groups: control (37 °C), HS (42 °C), and PB2 + HS (42 °C). Compared with MAC-T cells that were consistently cultured at 37 °C, acute HS treatment remarkably decreased cell viability, reduced activities of catalase (CAT), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC), and elevated intracellular levels of malondialdehyde (MDA) and reactive oxygen species (ROS). Additionally, nuclear factor erythroid 2-related factor 2 (Nrf2) was activated and translocated to the nucleus, in accompaniment with upregulation of Nrf2, heme oxygenase 1 (HO-1), thioredoxin reductase 1 (Txnrd1), and heat shock protein 70 (HSP70). In parallel, both mRNA transcript and actual protein secretion of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), were increased by heat stress. Pretreatment of MAC-T cells with 0~25 μM PB2 alleviated the decline of cell viability by HS in a dose-dependent fashion and protected cells against HS-induced oxidative stress, as evidenced by significantly improved CAT, SOD, and T-AOC activity, as well as with decreased MDA and ROS generation. Furthermore, PB2 further activated the Nrf2 signaling pathway and reversed the inflammatory response induced by HS. Silencing of Nrf2 by si-Nrf2 transfection not only exacerbated HS-induced cell death and provoked oxidative stress and the inflammatory response, but also greatly abolished the cytoprotective effects under HS of PB2. In summary, PB2 protected MAC-T cells against HS-induced cell death, oxidative stress, and inflammatory response, partially by operating at the Nrf2 signal pathway.

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.

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.

Mechanism of action and the uses betaine in pig production

Betaine, the trimethyl derivative of glycine, is a good methyl group donor, and an important component in pig production. However, betaine has not been extensively studied in this field. Therefore, in this study, we reviewed the effects of betaine in pig production performance, meat quality and reproductive performance, as well as its mechanisms, to provide a theoretical basis for the optimal use and development of this compound.

Heat stress induces oxidative stress and activates the KEAP1-NFE2L2-ARE pathway in bovine endometrial epithelial cells

Heat stress adversely affects the reproductive function in cows. Although a relationship between heat stress and oxidative stress has been suggested, it has not been sufficiently verified in bovine endometrial epithelial cells. Here, we investigated whether oxidative stress is induced by heat stress in bovine endometrial epithelial cells under high temperature. Luciferase reporter assays showed that the reporter activity of heat shock element (HSE) and antioxidant responsive element (ARE) was increased in endometrial epithelial cells cultured under high temperature compared to that in cells cultured under basal (thermoneutral) temperature. Also, nuclear factor, erythroid 2 like 2 (NFE2L2), a master regulator of cellular environmental stress response, stabilized and the expression levels of antioxidant enzyme genes increased under high temperature. Immunostaining confirmed the nuclear localization of NFE2L2 in endometrial epithelial cells cultured under high temperature. Quantitative polymerase chain reaction analysis showed that the expression levels of representative inflammatory cytokine genes, such as prostaglandin-endoperoxide synthase 2 (PTGS2) and interleukin 8, were significantly decreased in endometrial epithelial cells cultured under high temperature compared to those in cells cultured under basal temperature. Thus, our results suggest that heat stress induces oxidative stress, whereas NFE2L2 plays a protective role in bovine endometrial epithelial cells cultured under heat stress 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.

CDK5RAP3, a Novel Nucleoplasmic Shuttle, Deeply Regulates HSF1-Mediated Heat Stress Response and Protects Mammary Epithelial Cells from Heat Injury

CDK5RAP3 was regarded as the most significant regulator of cellular responses against heat stress, which is associated with dysfunctions of the immune system and animal susceptibility to disease. Despite this, little known about how CDK5RAP3 regulates heat stress response. In this study, CDK5RAP3 conditional Knockout (CKO) mice, CDK5RAP3-/- mouse embryo fibroblasts (MEFs) and bovine mammary epithelial cells (BMECs) were used as an in vitro and in vivo model, respectively to reveal the role of CDK5RAP3 in regulating the heat stress response. The deletion of CDK5RAP3 unexpectedly caused animal lethality after 1.5-h heat stimulations. Furthermore, BMECs were re-cultured for eight hours after heat stress and was found that the expression of CDK5RAP3 and HSPs showed a similar fluctuating pattern of increase (0-2, 4-6 h) and decrease (2-4, 6-8 h). In addition to the remarkably enhanced expression of heat shock protein, apoptosis rate and endoplasmic reticulum stress, the deletion of CDK5RAP3 also affected nucleoplasmic translocation and trimer formation of heat shock factor 1 (HSF1). These programs were further confirmed in the mammary gland of CDK5RAP3 CKO mice and CDK5RAP3-/- MEFs as well. Interestingly, genetic silencing of HSF1 downregulated CDK5RAP3 expression in BMECs. Immunostaining and immunoprecipitation studies suggested a physical interaction between CDK5RAP3 and HSF1 being co-localized in the cytoplasm and nucleus. Besides, CDK5RAP3 also interacted with HSP90, suggesting an operative machinery at both transcriptional level and protein functionality of HSP90 per se. Together, our findings suggested that CDK5RAP3 works like a novel nucleoplasmic shuttle or molecular chaperone, deeply participating in HSF1-mediated heat stress response and protecting cells from heat injury.

Betaine ameliorates impaired steroidogenesis and apoptosis in mice granulosa cells induced by high glucose concentration

Betaine is a bioactive peptide whose beneficial effects on diabetes complications have been considered, previously. The present study aimed to investigate the possible protective effects of betaine against hyperglycemia-induced steroidogenesis impairment and apoptosis in mice granulosa cells. Ovarian granulosa cells were isolated from C57/BL6 mice and cultured in steroidogenesis medium (SM) containing 30 ng/ml FSH and 0.5 µM testosterone. The cells were cultured in SM containing low (5 mM) or high (30 mM) glucose concentrations for 24 h in the presence or absence of betaine (5 mM). At the end of the experiment, estradiol and progesterone were measured by ELISA in the culture medium. Expression of apoptosis and steroidogenesis associated genes and caspase-3 activity were determined by qRT-PCR and colorimetric assays, respectively. Exposure of mice granulosa cells to high glucose concentration inhibited the steroidogenesis by decreasing estradiol and progesterone secretion and downregulation of steroidogenesis-related genes including 3βHSD, Cyp11a1, Cyp19a1, and StAR. Betaine treatment could ameliorate the steroidogenesis impairment at molecular and biochemical levels. High glucose concentration also enhanced apoptosis in mice granulosa cells that were characterized by elevation of caspase-3 activity, upregulation of bax gene and downregulation of bcl2 gene. Betaine treatment could attenuate the apoptotic-related changes induced by high glucose concentration in granulosa cells. According to the results of the present study, betaine could ameliorate the adverse effects of hyperglycemia on the physiological function of ovarian granulosa cells. The results highlight the potential role of betaine for the intervention of ovarian dysfunction in diabetic patients. Abbreviations: AABA: Betaine-α-aminobutyric acid; AGEs: Advanced glycation end products; bax: bcl2 Associated X; bcl2: B-cell lymphoma 2; AMPK: AMP-activated protein kinase; BHMT: Betaine homocysteine methyltransferase; C/EBP: CCAAT-enhancer-binding proteins; Cyp11a1: Cholesterol side-chain cleavage cytochrome P450; Cyp19a1: Cytochrome P450 aromatase; DM: Diabetes mellitus; E2: Estradiol; ERS: Endoplasmic reticulum stress; GCs: Granulosa cells; GLUT: Glucose transporter; FSH: Follicle-stimulating hormone; 3βHSD: 3β-hydroxysteroid dehydrogenase; IL-1β: interleukin-1ß; LH: Luteinizing hormone; MDCK: Madin-Darby Canine Kidney cell; MT: Methionine synthase, MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NLRP3: NLR Family Pyrin Domain Containing 3; NF-κB: Nuclear factor κB; P4: Progesterone; ROS: Reactive oxygen species; SGLT: Sodium dependent glucose transporter; SLC7A6: Solute Carrier Family 7 Member 6; StAR: Steroidogenic acute regulatory protein; STZ: Streptozotocin; Tumor necrosis factor α: TNF-α; TXNIP: Thioredoxin interacting protein.

Gasotransmitters in pregnancy: from conception to uterine involution

Gasotransmitters are endogenous small gaseous messengers exemplified by nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S or sulfide). Gasotransmitters are implicated in myriad physiologic functions including many aspects of reproduction. Our objective was to comprehensively review basic mechanisms and functions of gasotransmitters during pregnancy from conception to uterine involution and highlight future research opportunities. We searched PubMed and Web of Science databases using combinations of keywords nitric oxide, carbon monoxide, sulfide, placenta, uterus, labor, and pregnancy. We included English language publications on human and animal studies from any date through August 2018 and retained basic and translational articles with relevant original findings. All gasotransmitters activate cGMP signaling. NO and sulfide also covalently modify target protein cysteines. Protein kinases and ion channels transduce gasotransmitter signals, and co-expressed gasotransmitters can be synergistic or antagonistic depending on cell type. Gasotransmitters influence tubal transit, placentation, cervical remodeling, and myometrial contractility. NO, CO, and sulfide dilate resistance vessels, suppress inflammation, and relax myometrium to promote uterine quiescence and normal placentation. Cervical remodeling and rupture of fetal membranes coincide with enhanced oxidation and altered gasotransmitter metabolism. Mechanisms mediating cellular and organismal changes in pregnancy due to gasotransmitters are largely unknown. Altered gasotransmitter signaling has been reported for preeclampsia, intrauterine growth restriction, premature rupture of membranes, and preterm labor. However, in most cases specific molecular changes are not yet characterized. Nonclassical signaling pathways and the crosstalk among gasotransmitters are emerging investigation topics.

Butyrate alleviates oxidative stress by regulating NRF2 nuclear accumulation and H3K9/14 acetylation via GPR109A in bovine mammary epithelial cells and mammary glands

Oxidative stress consistently affects lactation length and quality in dairy cows. Oxidative stress in the mammary gland of high-yielding dairy cows is a serious problem. Therefore, we studied the role of butyrate in dairy cow oxidative stress and further elucidated the mechanism of the antioxidative action of mammary epithelial cells in dairy cows. Oxidative stress and activated GPR109A were present in high-yielding dairy cows. Then, bovine mammary epithelial cells (BMECs) were isolated, and oxidative stress-related protein expression was measured, confirming that sodium butyrate (NaB) exerted antioxidant effects through GPR109A, NRF2 and H3K9/14 acetylation. To further study the antioxidative mechanism of butyrate in dairy cows, we also confirmed that butyrate promoted NRF2 nuclear accumulation and H3K9/14 acetylation through the AMPK signaling pathway by western blotting. Additionally, we preliminarily clarified the interaction between NRF2 and H3K9/14 acetylation by Co-IP and ChIP. Butyrate activated the AMPK signaling pathway through GPR109A to promote NRF2 nuclear accumulation and H3K9/14 acetylation, subsequently exerting antioxidant effects through the synergistic functions of these two processes. Then, we studied the effect of butyrate on oxidative stress in dairy cows in vivo, and the results were consistent with those in vitro. Therefore, butyrate played an antioxidant and antiapoptotic role through the GPR109A/AMPK/NRF2 signaling pathway, while H3K9/14 acetylation could promote NRF2 transcription and enhance the antioxidant capacity of BMECs.

Niacin nutrition and rumen-protected niacin supplementation in dairy cows: an updated review

As the precursor to NAD+ and NADP+, niacin is important for catabolic and anabolic redox reactions. In addition, niacin is known for its anti-lipolytic action via a hydroxycarboxylic acid-2-receptor-dependent mechanism. The anti-lipolytic effects of traditional free niacin supplementation during transition periods had been studied extensively, but the reported effects are ambiguous. In the past decade, a series of studies were conducted to evaluate the effects of rumen-protected niacin (RPN) on production performance and metabolic status in early lactation and on heat stress in dairy cows. Feeding RPN seems more effective than free niacin regarding increasing circulating niacin concentration. The rebound of plasma NEFA was found after termination of niacin abomasal infusion. Feeding RPN or infusion of niacin via the abomasum could suppress lipolysis and reduce insulin resistance in early lactation. Additionally, RPN supplementation could possibly relieve heat stress through vasodilation during moderate to severe heat stress condition. However, these beneficial effects of niacin supplementation have not always been observed. The inconsistent results across studies may be related to dosages of niacin supplementation, rebound of plasma NEFA concentration, stage of lactation or severity of heat stress. Overall, the current review is to present updated information on niacin nutrition in dairy cows and the recommendations are given for future research.

Do arachidonic acid metabolites affect apoptosis in bovine endometrial cells with silenced PPAR genes?

Peroxisome proliferator-activated receptors (PPARs) are expressed in bovine uterus, and their agonists are arachidonic acid (AA) metabolites. We hypothesised that silencing of PPAR genes in bovine endometrial stromal cells (ESC) would change the intracellular signalling through PPAR and affect apoptosis after cell treatment with different AA metabolites. The study's aims are detection of apoptosis and examining the influence of prostaglandins and leukotrienes on apoptosis occurring in physiological ESC and cells with silenced PPAR (α, δ, and γ) genes. Silencing the PPARα and PPARδ genes in cells resulted in increased DNA fragmentation and mRNA and protein expression of caspase (CASP) -3 and -8 (P < 0.05). Neither DNA fragmentation nor the mRNA and protein expression of CASP3 and -8 in cells with silenced PPARγ gene were changed compared to physiological cells (P > 0.05). Among PPARs, PPARα and PPARδ appear to inhibit apoptosis, and AA metabolites, as PPAR agonists, modify this process in bovine ESC.

Betaine protects against heat exposure-induced oxidative stress and apoptosis in bovine mammary epithelial cells via regulation of ROS production

Heat stress is one of the wide varieties of factors which cause oxidative stress in vivo; elevated temperature can lead to oxidative stress of dairy cows that affects milk production. The aim of this study was to determine the capacity of the betaine to act as an antioxidant against oxidative stress induced by heat exposure and apoptosis in mammary epithelial cells (mammary alveolar cells, MAC-T). The MAC-T were divided into four treatment groups: control (37 °C), heat stress (HS, 42 °C), betaine (37 °C), and HS + betaine. MAC-T under heat stress (HS) showed increased ROS accumulation, malondialdehyde (MDA) content, superoxide dismutase (SOD) concentration, and catalase (CAT) activity. During heat stress, betaine decreased the mRNA expression level of HSP70 and HSP27 in MAC-T. Bax/Bcl-2 ratio and caspase-3, the markers of apoptosis, were also elevated in MAC-T under heat stress. The markers of oxidative stress Nrf-2/HO-1 genes were also elevated in MAC-T under heat stress. Pretreatment of betaine reversed the heat-induced depletion in total antioxidant status, ROS accumulation, and SOD and CAT contents in MAC-T. Bax/Bcl-2 ratio and Nrf-2/HO-1 expression of heat-exposed MAC-T were also reduced with betaine supplementation. In conclusion, betaine alleviated oxidative stress and apoptosis of MAC-T by inhibiting ROS accumulation.