Intermediate metabolites and molecular correlates of one­carbon and nutrient metabolism differ in tissues from Holstein fetuses.

Methionine and folate cycles along with transsulfuration comprise the one­carbon metabolism (OCM) pathway. Amino acids and other nutrients feed into OCM, which is central to cellular function. mRNA abundance, proteins (Western blotting), and metabolites (GC-MC) associated with OCM were used to characterize these mechanisms in fetal tissues. Liver, whole intestine, and semitendinosus muscle were harvested from fetuses in 6 multiparous Holstein cows (37 kg milk/d, 100 d gestation). Data were analyzed using PROC MIXED (SAS 9.4). Protein abundance of BHMT was greatest (P < 0.01) in liver suggesting active remethylation of homocysteine to methionine. This idea was supported by the greater (P < 0.05) mRNA of CBS, BHMT, MTR, SHMT1, and MAT1A (encoding OCM enzymes) in liver. The antioxidant protein GPX3 had greatest (P < 0.05) abundance in liver, whereas the glutathione-transferase GSTM1 was 5-fold greater (P < 0.05) in intestine than liver and muscle. Greatest concentrations of glycine, serine, and taurine along with lower cysteine underscored the relevance of OCM in fetal liver. Phosphoethanolamine concentration was greatest (4-fold, P < 0.05) in intestine and along with the greatest (P < 0.05) mRNA of SLC44A1 (choline transporter), CHKA, and CEPT1 underscored the importance of the CDP-choline pathway. Greatest (P < 0.05) mRNA of PPARA, CPT1A, and HMGCS2 along with lower PCK1 in liver highlighted a potential reliance on fatty acid oxidation. In contrast, greater (P < 0.05) concentration of myo-inositol in muscle and intestine suggested both tissues rely on glucose as main source of energy. Future research should address how environmental inputs such as maternal nutrition alter these pathways in fetal tissues and their phenotypic outcomes.

Body condition prepartum and its association with term placentome nutrient transporters, one­carbon metabolism pathway activity, and intermediate metabolites in Holstein cows.

We investigated linkages among BCS prior to calving and placentome concentrations of metabolites, proteins in one­carbon metabolism (OCM) and protein synthesis, and nutrient transport. Multiparous Holstein cows retrospectively divided by prepartal BCS at -4 weeks relative to parturition into high BCS (HBCS = 3.58 ± 0.23; n = 9) or normal BCS (NBCS = 3.02 ± 0.17; n = 13) were used. BCS was assessed using a 5-point scale (1 = thin, 5 = fat). Four placentomes per cow were collected at delivery and frozen in liquid N. Western blotting was used for protein abundance. Cystathionine-ß-synthase (CBS) and betaine-homocysteine-S-methyltransferase (BHMT) activity were measured via 14C assays. Amino acids (AA) and metabolites in OCM were measured by liquid chromatography mass spectrometry (LC-MS). Compared with NBCS cows, the cellular stress sensor p-eIF2α was more than 2-fold greater (P = 0.04) in HBCS. Abundance of the AA-catabolism enzyme branched-chain α-ketoacid dehydrogenase complex was lower (P = 0.05) in HBCS cows. Although BHMT activity did not differ, greater concentration of betaine (P = 0.01) and lower (P = 0.05) concentration of dimethylglycine in HBCS cows suggested reduced flux through the methionine cycle. Despite a lack of difference in CBS activity, lower concentrations of cystathionine (P = 0.03) and hypotaurine (P = 0.04) along with lower cysteine and the tendency for lower total GSH (P = 0.10) in HBCS cows suggested a decrease in transsulfuration. Overall, associations between OCM in placentomes and BCS at calving exist. Identifying mechanisms responsible for these effects merits further research.

Abundance of proteins and genes associated with nutrient signaling, protein turnover, and transport of amino acids and glucose in fetuses from lactating Holstein cows.

Availability of nutrients in maternal circulation and abundance of nutrient transporters, metabolic enzymes, and nutrient-responsive proteins in fetal tissues coordinate growth. To begin characterizing these mechanisms, we evaluated the abundance of nutrient signaling genes and proteins in bovine fetal tissues. Liver, entire intestine, and semitendinosus muscle were harvested from fetuses (4 female, 2 male) collected at slaughter from 6 clinically-healthy multiparous Holstein dairy cows (167 ± 7 days in milk, 37 ± 6 kg milk/d, 100 ± 3 d gestation). Data were analyzed using PROC MIXED in SAS 9.4. Among proteins measured, abundance of the amino acid (AA) utilization and insulin signaling proteins p-AKT and p-mTOR was greater (P < 0.01) in liver and intestine. The abundance of p-EEF2 (translation elongation) and SLC2A4 (glucose uptake) was greater (P < 0.05) in liver relative to intestine and muscle suggesting this organ has a greater capacity for anabolic processes. In contrast, among mTOR signaling genes, the abundance of IRS1 was greatest (P < 0.01) in muscle and lowest in the intestine, whereas, abundance of AKT1 and mTOR was greater (P < 0.01) in intestine and muscle than liver. Abundance of the protein degradation-related genes UBA1, UBE2G1, and TRIM63 was greater (P < 0.01) in muscle than intestine and liver. Among nutrient transporters, abundance of glucose transporters SLC5A1 and SLC2A2 was greatest (P < 0.01) in the intestine than liver and muscle. Several AA transporters had greater (P < 0.01) abundance in the intestine or liver compared with muscle. Overall, these molecular analyses highlighted important biological differences on various aspects of metabolism in fetal tissues.

Feeding a Saccharomyces cerevisiae fermentation product before and during a feed restriction challenge on milk production, plasma biomarkers, and immune function in Holstein cows.

Periods of decreased feed intake may disrupt function of the intestinal barrier. Feeding NutriTek® (NTK; Diamond V, Cedar Rapids, IA), a postbiotic from S. cerevisiae fermentation (SCFP), improved health and supported anti-inflammatory functions. We investigated the effects of feeding NTK to cows before and during a period of feed restriction (FR) designed to model periods of intestinal barrier dysfunction. In total, 16 multiparous cows (97.1 ± 7.6 DIM; n = 8/group) were fed a control diet (CON) or CON plus 19 g/d NTK for 9 wk (Phase 1; P1) and then were subjected to an FR challenge for 5 d, during which they were fed 40% of their ad libitum intake from the 7 d prior to FR. Milk yield (MY) and DMI were collected daily. During FR, milk was collected daily for composition, blood daily to measure plasma biomarkers and to measure monocyte and neutrophil phagocytosis and oxidative burst on d 1, 3, and 5. Data were analyzed using a mixed model in SAS 9.4. All data were subjected to repeated measures ANOVA. Dietary treatment (TRT), Day, and their interaction (TRT × Day) were considered as fixed effects and cow as the random effect. For analysis of P1, data collected during a 7-d adaptation phase were used as a covariate. During P1, NTK cows tended to have greater DMI and had greater fat, ECM and FCM yields, and feed efficiency (ECM/DMI and FCM/DMI). Protein yield tended to be greater in NTK compared with CON cows. A tendency for greater monocyte phagocytosis was detected with NTK. However, during FR, feeding NTK led to lower MY and lactose yield and tended to lower solids percentage. While NTK cows tended to have reduced neutrophil oxidative burst than CON cows during FR (NTK: 26.20%, CON: 36.93%), there was no difference in phagocytosis (NTK: 7.92%, CON: 6.31%). Plasma biomarkers of energy metabolism, liver function, inflammation, and oxidative stress during the FR period did not differ. Overall, results suggested that feeding NTK increased the yield of FCM, ECM, feed efficiency and milk components prior to FR.

Postbiotic fermentation products have the potential to improve health and support anti-inflammatory functions when fed to lactating dairy cows. Since dairy cows experience disruptions of the intestinal barrier function at various stages of their life, for example, the transition into lactation, we sought to investigate potential beneficial effects of feeding a Saccharomyces cerevisiae fermentation (NTK) before and during a period of feed restriction to challenge gut function. Although feeding NTK increased yield of energy-corrected milk and feed efficiency prior to feed restriction (FR), it had no effect on production or plasma indices of metabolism, inflammation, and liver function during a period of abrupt FR to 40% of baseline feed intake.

Activated autophagy-lysosomal pathway in dairy cows with hyperketonemia is associated with lipolysis of adipose tissues.

Activated autophagy-lysosomal pathway (ALP) can degrade virtually all kinds of cellular components, including intracellular lipid droplets, especially during catabolic conditions. Sustained lipolysis and increased plasma fatty acids concentrations are characteristic of dairy cows with hyperketonemia. However, the status of ALP in adipose tissue during this physiological condition is not well known. The present study aimed to ascertain whether lipolysis is associated with activation of ALP in adipose tissues of dairy cows with hyperketonemia and in calf adipocytes. In vivo, blood and subcutaneous adipose tissue (SAT) biopsies were collected from nonhyperketonemic (nonHYK) cows [blood ß-hydroxybutyrate (BHB) concentration <1.2 mM, n = 10] and hyperketonemic (HYK) cows (blood BHB concentration 1.2-3.0 mM, n = 10) with similar days in milk (range: 3-9) and parity (range: 2-4). In vitro, calf adipocytes isolated from 5 healthy Holstein calves (1 d old, female, 30-40 kg) were differentiated and used for (1) treatment with lipolysis inducer isoproterenol (ISO, 10 µM, 3 h) or mammalian target of rapamycin inhibitor Torin1 (250 nM, 3 h), and (2) pretreatment with or without the ALP inhibitor leupeptin (10 µg/mL, 4 h) followed by ISO (10 µM, 3 h) treatment. Compared with nonHYK cows, serum concentration of free fatty acids was greater and serum glucose concentration, DMI, and milk yield were lower in HYK cows. In SAT of HYK cows, ratio of phosphorylated hormone-sensitive lipase to hormone-sensitive lipase, and protein abundance of adipose triacylglycerol lipase were greater, but protein abundance of perilipin 1 (PLIN1) and cell death-inducing DNA fragmentation factor-α-like effector c (CIDEC) was lower. In addition, mRNA abundance of autophagy-related 5 (ATG5), autophagy-related 7 (ATG7), and microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), protein abundance of lysosome-associated membrane protein 1, and cathepsin D, and activity of ß-N-acetylglucosaminidase were greater, whereas protein abundance of sequestosome-1 (p62) was lower in SAT of HYK cows. In calf adipocytes, treatment with ISO or Torin1 decreased protein abundance of PLIN1, and CIDEC, and triacylglycerol content in calf adipocytes, but increased glycerol content in the supernatant of calf adipocytes. Moreover, the mRNA abundance of ATG5, ATG7, and MAP1LC3B was upregulated, the protein abundance of lysosome-associated membrane protein 1, cathepsin D, and activity of ß-N-acetylglucosaminidase were increased, whereas the protein abundance of p62 was decreased in calf adipocytes treated with ISO or Torin1 compared with control group. Compared with treatment with ISO alone, the protein abundance of p62, PLIN1, and CIDEC, and triacylglycerol content in calf adipocytes were higher, but the glycerol content in the supernatant of calf adipocytes was lower in ISO and leupeptin co-treated group. Overall, these data indicated that activated ALP is associated with increased lipolysis in adipose tissues of dairy cows with hyperketonemia and in calf adipocytes.

Increased supply of methionine during a heat-stress challenge in lactating holstein cows alters mammary tissue mTOR signaling and its response to lipopolysaccharide.

The first objective was to investigate the effects of feeding rumen-protected methionine (RPM) during a heat stress (HS) challenge on abundance and phosphorylation of mechanistic target of rapamycin (mTOR)-related signaling proteins in mammary gland. The second objective was to investigate how HS and RPM may modulate the response of mammary gland explants to an inflammatory challenge using lipopolysaccharide (LPS). Thirty-two multiparous, lactating Holstein cows (184 ± 59 DIM) were randomly assigned to 1 of 2 environmental treatment groups, and 1 of 2 dietary treatments [TMR with RPM (Smartamine M; Adisseo Inc.; 0.105% DM as top dress) or TMR without RPM (CON)] in a crossover design. There were two periods with two phases per period. In phase 1 (9 d), all cows were in thermoneutral conditions (TN) and fed ad libitum. During phase 2 (9 d), group 1 (n = 16) cows were exposed to HS using electric heat blankets, whereas group 2 cows (n = 16) remained in TN but were pair-fed to HS counterparts to control for DMI decreases associated with HS. After a washout period (14 d), the study was repeated (period 2). Environmental treatments were inverted in period 2 (sequence), whereas dietary treatments remained the same. Mammary tissue was harvested via biopsy at the end of both periods. Tissue was used for protein abundance analysis and also for incubation with 0 or 3 µg/mL of LPS for 2 h and subsequently used for mRNA abundance. Data were analyzed using PROC MIXED in SAS. Analysis of protein abundance data included the effects of diet, environment and their interaction, and period and sequence to account for the crossover design. The explant data model also included the effect of LPS and its interaction with environment and diet. Abundance of phosphorylated mTOR and ratio of phosphorylated eukaryotic translation elongation factor 2 (p-EEF2) to total EEF2 in non-challenged tissue was greater with RPM supplementation (P = 0.04 for both) and in both cases tended to be greater with HS (P = 0.08 for both). Regardless of RPM supplementation, incubation with LPS upregulated mRNA abundance of IL8, IL6, IL1B, CXCL2, TNF, NFKB1, and TLR2 (P < 0.05). An environment × LPS interaction was observed for NFKB1 (P = 0.03); abundance was greater in LPS-treated explants from non-HS compared with HS cows. Abundance of CXCL2, NFKB1, NOS2, NOS1, and SOD2 was lower with HS (P < 0.05). Although LPS did not alter mRNA abundance of the antioxidant transcription factor NFE2L2 (P = 0.59), explants from HS cows had lower abundance of NFE2L2 (P < 0.001) and CUL3 (P = 0.04). Overall, RPM supplementation may alter mTOR activation in mammary tissue. Additionally, although HS reduced explant immune and antioxidant responses, RPM did not attenuate the inflammatory response induced by LPS in vitro.

Heat stress (HS) is an environmental issue worldwide and occurs when animals experience a heat load that exceeds their thermoregulatory capacity. Milk protein synthesis and overall production often decrease when cows are exposed to HS conditions, in part due to lower feed intake and a limit in the mammary supply of amino acids. Increasing post-ruminal supply of methionine to late-lactation cows upregulated abundance of p-mTOR in mammary tissue, providing a link with the greater milk protein production. Exposure of cows to a HS challenge also increased abundance of p-mTOR, but did not alter milk protein suggesting this response might have been associated with synthesis of other proteins. Further work at a translational level is needed to understand potential mechanisms whereby methionine may modulate mammary metabolism during periods of HS.

Increased adipose tissue lipolysis in dairy cows with fatty liver is associated with enhanced autophagy activity.

Lipolysis is increased in adipose tissue of cows with fatty liver during the transition period. Autophagy, a major cellular degradation process, plays a critical role in adipose tissue homeostasis. The objective of this study was to explore the relationship between lipolysis and autophagy in adipose tissue of cows with fatty liver. Using a nested case-control design, we compared blood and adipose tissue samples from 10 control cows [parity: median = 3, range = 2-4; days in milk: median = 8 d, range = 5-10 d; hepatic triacylglycerol content: median = 0.55% liver wt, range = 0.48-0.61% liver wt] and 10 lactation stage-matched cows with fatty liver (parity: median = 3, range = 2-4; days in milk: median = 9 d, range = 5-11 d; hepatic triacylglycerol content: median = 6.28% liver wt, range = 2.86-7.75% liver wt). Data were analyzed using paired t-tests. Serum concentrations of free fatty acids and ß-hydroxybutyrate were greater and glucose concentration was lower in cows with fatty liver, which we determined by using commercially-available kits. Furthermore, western blotting showed that increased protein abundance of ATGL (adipose triglyceride lipase), ATG5 (autophagy-related gene 5), and ATG7; ratio of phosphorylated (p)-HSL (hormone-sensitive lipase) to HSL and MAP1LC3 (microtubule-associated protein 1 light chain 3, also called LC3-II) to LC3-I along with decreased abundance of PLIN1 (perilipin 1), SQSTM1 (sequestosome-1, also called p62), and the ratio of p-mTOR (phosphorylated mechanistic target of rapamycin) to mTOR in cows with fatty liver. Quantitative reverse-transcription PCR revealed an increase in abundance of MAP1LC3 mRNA and a decrease in SQSTM1 mRNA in cows with fatty liver. These findings were replicated using an adipocyte model. Primary cultures of calf adipocytes isolated from the adipose tissue of the peritoneal omentum and mesentery were treated with 10 mM 3-methyladenine (3-MA), 5 nM rapamycin, 1 µM isoproterenol (ISO), and 1 µM ISO + 10 mM 3-MA. Comparisons among groups were analyzed using one-way ANOVA. Compared with the control, the 1 µM ISO treatment upregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it downregulated the abundance of PLIN1 and p62 in calf adipocytes. Compared with the 1 µM ISO treatment group, 1 µM ISO + 10 mM 3-MA downregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it upregulated the abundance of PLIN1 and p62. Compared with the control, the 5 nM rapamycin treatment upregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it downregulated the abundance of PLIN1 and p62 in calf adipocytes. Overall, these data indicated that increased lipolysis in adipose tissue of cows with fatty liver was associated with enhanced autophagy. However, the specific molecular mechanisms that link lipolysis and autophagy need to be further investigated.

Network Pharmacology-Based Analysis of Pogostemon cablin (Blanco) Benth Beneficial Effects to Alleviate Nonalcoholic Fatty Liver Disease in Mice.

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and is associated with high morbidity and mortality. Pogostemon cablin (Blanco) Benth/Huo Xiang (HX) is a perennial herb with unique anti-oxidant and anti-inflammatory properties, and thus, can positively affect liver function. In this study, we used network pharmacology to predict the potential mechanism of HX on NAFLD. Pharmacological experiments were used to verify the effect of HX on the functions of NAFLD. Network pharmacology identified nine components that interacted with 82 NAFLD-related targets, revealing four target genes: TNF, IL6, TP53, and AKT1. HX prevents the development and progression of NAFLD through different pathways and targets with quercetin-regulated lipid metabolism, anti-inflammatory, and anti-oxidant pathways playing an essential role in the treatment of NAFLD. Compared with feeding HFD, HX significantly attenuated lipid accumulation in vivo with mice and also in vitro with mouse liver cells. A high dose of HX decreased hepatocyte lipid accumulation and the abundance of SREBF1 and FASN. Validation experiments revealed that HX inhibited the activation of NF-κB/IκB signaling and decreased the release and levels of pro-inflammatory factors (TNF-α and IL-6). These data suggest that HX can attenuate abnormal lipid metabolic responses and enhance antioxidant mechanisms. Thus, the pharmacological effects from plants used in traditional Chinese medicine are achievde through a multi-level response.

Ruminal Microbes Exhibit a Robust Circadian Rhythm and Are Sensitive to Melatonin.

Gut hormones are not only able to regulate digestive, absorptive, and immune mechanisms of the intestine through biological rhythms, but impact the host through their interactions with intestinal microorganisms. Whether hormones in ruminal fluid have an association with the ruminal ecology is unknown. Objectives of the study were to examine relationships between the diurnal change in ruminal hormones and microbiota in lactating cows, and their associations in vivo and in vitro. For the in vivo study, six cows of similar weight (566.8 ± 19.6 kg), parity (3.0 ± 0.0), and milk performance (8,398.7 ± 1,392.9 kg/y) were used. They were adapted to natural light for 2 weeks before sampling and fed twice daily at 07:00 a.m. and 14:00 p.m. Serum, saliva, and ruminal fluid samples were collected at 02:00, 10:00, and 18:00 on the first day and 06:00, 14:00, and 22:00 on the second day of the experimental period. The concentrations of melatonin (MLT), growth hormone (GH), and prolactin (PRL) were measured via radioimmunoassay, whereas amplicon sequencing data were used to analyze relative abundance of microbiota in ruminal fluid. JTK_CYCLE analysis was performed to analyze circadian rhythms of hormone concentrations as well as the relative abundance of microbiota. For the in vitro study, exogenous MLT (9 ng) was added into ruminal fluid incubations to investigate the impacts of MLT on ruminal microbiota. The results not only showed that rumen fluid contains MLT, but the diurnal variation of MLT and the relative abundance of 9% of total rumen bacterial operational taxonomic units (OTUs) follow a circadian rhythm. Although GH and PRL were also detected in ruminal fluid, there was no obvious circadian rhythm in their concentrations. Ruminal MLT was closely associated with Muribaculaceae, Succinivibrionaceae, Veillonellaceae, and Prevotellaceae families in vivo. In vitro, these families were significantly influenced by melatonin treatment, as melatonin treatment increased the relative abundance of families Prevotellaceae, Muribaculaceae while it reduced the relative abundance of Succinivibrionaceae, Veillonellaceae. Collectively, ruminal microbes appear to maintain a circadian rhythm that is associated with the profiles of melatonin. As such, data suggest that secretion of melatonin into the rumen could play a role in host-microbe interactions in ruminants.

Nuclear factor erythroid 2-related factor 2 protects bovine mammary epithelial cells against free fatty acid-induced mitochondrial dysfunction in vitro.

Bovine mammary epithelial cells undergo an increase in metabolic rate, mitochondrial dysfunction, and oxidative stress after calving. Nuclear factor erythroid 2-related factor 2 (NFE2L2), a master regulator of cellular redox homeostasis, plays crucial roles in the regulation of mitochondrial function. The objective of this study was to investigate the role of NFE2L2 on mitochondrial function in bovine mammary epithelial cells under hyperlipidemic conditions. Three experiments were conducted as follows: (1) the immortalized bovine mammary epithelial cell line MAC-T was treated with various concentrations of free fatty acids (FFA; 0, 0.6, 1.2, or 2.4 mM) for 24 h to induce stress; (2) MAC-T cells were transfected with small interfering RNA targeting NFE2L2 (si-NFE2L2) and scrambled nontarget negative control (si-Control) for 48 h; and (3) MAC-T cells were pretreated with 10 µM sulforaphane (SFN), an activator of NFE2L2, for 24 h followed by treatment with 1.2 mM FFA for an additional 24 h. Results indicated that exogenous FFA challenge induced linear and quadratic increases in concentrations of mitochondrial reactive oxygen species (ROS). Compared with 0 mM FFA, mitochondrial membrane potential, mRNA abundance of oxidative phosphorylation complexes (CO I-V), protein abundance of nuclear respiratory factor 1 (NRF1), peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α), mitochondrial transcription factor A (TFAM), and NFE2L2 along with the contents of ATP, mitochondrial DNA (mtDNA), and total mitochondria were greater in the MAC-T challenged with 0.6 mM FFA group, but lower in the 1.2 and 2.4 mM FFA cultures. Knockdown of NFE2L2 via small interfering RNA led to greater mitochondrial ROS content and lower mitochondrial membrane potential along with contents of ATP, mtDNA, and total mitochondria. The SFN pretreatment upregulated protein abundance of NFE2L2 and attenuated the downregulation of NFE2L2 induced by FFA. Pretreatment with SFN attenuated the downregulation induced by FFA of PGC-1α, NRF1, and TFAM protein abundance along with contents of mtDNA and total mitochondria. Furthermore, SFN pretreatment attenuated the upregulation of mitochondrial ROS content, the downregulation of mitochondrial membrane potential, and the decreases in ATP, mtDNA, and mitochondrial content induced by FFA. Overall, data indicated that FFA inhibit NFE2L2, resulting in mitochondrial dysfunction and ROS production in bovine mammary epithelial cells. Thus, NFE2L2 may be a promising therapeutic target against metabolic challenge-driven mitochondrial dysfunction and oxidative stress in bovine mammary epithelial cells.

Reducing hepatic endoplasmic reticulum stress ameliorates the impairment in insulin signaling induced by high levels of ß-hydroxybutyrate in bovine hepatocytes.

Ketotic dairy cows exhibit a state of negative energy balance (NEB) characterized by elevated circulating levels of ß-hydroxybutyrate (BHB) and fatty acids. Impaired hepatic insulin signaling in dairy cows occurs frequently during the transition into lactation, but its role on liver function during this period is not well known. In nonruminants, endoplasmic reticulum (ER) stress is a causal factor contributing to impaired insulin signaling in the liver. Thus, the aim of this study was to investigate the status of hepatic insulin and ER stress signaling and whether ER stress contributes to impaired insulin signaling in dairy cows with ketosis. Healthy (control cows, n = 10, BHB ≤0.6 mM) and ketotic (ketotic cows, n = 10, BHB ≥1.2 mM) cows at 3 to 10 d in milk were selected for liver biopsy and blood sampling before feeding. In vitro experiments were conducted with isolated hepatocytes from 5 healthy calves (1 d old, fasted female, 30-40 kg of body weight). Treatments included BHB (0, 0.9, 1.8, 3.6 mM), tauroursodeoxycholic acid (TUDCA, a canonical inhibitor of ER stress), and different incubation times (0.5, 1, 2, 3, 5, 7, 9, or 12 h). Ketotic cows had lower daily milk yield (median: 29.50 vs. 23.00 kg), higher plasma nonesterified fatty acid (NEFA) (median: 0.33 vs. 1.17 mM), BHB (median: 0.43 vs. 3.22 mM), aspartate aminotransferase (median: 70.58 vs. 155.70 U/L), alanine aminotransferase (median: 18.31 vs. 37.90 U/L), lower plasma glucose (median: 4.32 vs. 2.37 mg/dL), and revised quantitative insulin sensitivity check index (median: 0.39 vs. 0.37) compared with healthy cows. Increased abundance of phosphorylated insulin receptor substrate-1 (IRS1) and decreased abundance of phosphorylated protein kinase B (AKT) and glycogen synthase kinase-3ß (GSK3ß) in ketotic cows indicated a state of insulin resistance. In addition, abundance of phosphorylated protein kinase RNA-like ER kinase (PERK) and inositol requiring protein-1α (IRE1α), and cleavage of activating transcription factor-6 (ATF6) were greater in the liver of ketotic cows. In vitro, at the early stages of incubation, treatment with BHB upregulated abundance of phosphorylated of IRE1α, PERK, and the cleavage of ATF6, as well as several unfolded protein response genes [X-box-binding protein-1 (XBP1), 78 kDa glucose-regulated protein (GRP78), and C/EBP homologous protein (CHOP)]. Furthermore, in response to increasing doses of BHB, the phosphorylation level of PERK, IRE1α, and the cleavage of ATF6, and the abundance of XBP1, GRP78, and CHOP increased. In addition, BHB treatment increased phosphorylation of IRS1 and decreased phosphorylation of AKT and GSK3ß, and upregulated abundance of gluconeogenic genes (phosphoenolpyruvate carboxykinase and glucose-6-phosphatase). Importantly, these changes were reversed by inhibiting ER stress with TUDCA treatment. Overall, the present study indicated that reversing ER stress during ketosis might help alleviate hepatic insulin resistance. Targeting ER stress may represent a potential therapeutic target for controlling the negative aspects of ketosis on liver function.

Sirtuin 3 inhibits nuclear factor-κB signaling activated by a fatty acid challenge in bovine mammary epithelial cells.

Susceptibility to mastitis is highest during the peripartal (transition) period and is often concomitant with other comorbidities such as ketosis. Although infection with pathogenic microorganisms and immune-dysfunction around calving clearly play key roles in mastitis development, other metabolic factors also contribute. Sirtuin 3 (SIRT3), a mitochondrial deacetylase regulating energy and redox homeostasis, antagonizes the lipotoxic effects of nonesterified fatty acids (NEFA). Thus, we hypothesized that increases in circulating NEFA concentrations, as observed in the transition period, provokes inflammatory responses that can be reversed via activation of SIRT3. Here we aimed to study (1) proinflammatory NF-κB signaling and SIRT3 abundance in mammary tissue of ketotic cows and healthy controls, and (2) the effect of SIRT3 on NF-κB activation in bovine mammary epithelial cells (BMEC) treated with high levels of NEFA. The mammary gland biopsy samples were from a previous study, which included 15 healthy cows and 15 ketotic cows. Primary BMEC were isolated from 3 healthy Holstein cows with collagenase III digestion. Purified BMEC were incubated with or without SIRT3 overexpression adenovirus for 48 h, then treated with 0, 0.6, 1.2, or 2.4 mM NEFA for 24 h. Mammary tissue of ketotic cows was associated with lower protein abundance of SIRT3 along with greater NF-κB P65 phosphorylation levels (p-NF-κB P65), p-NF-κB P65:NF-κB P65 ratio, and mRNA abundance of IL1B and IL6. In BMEC, exogenous NEFA dose-dependently reduced protein abundance of SIRT3, but increased p-NF-κB P65, p-NF-κB P65:NF-κB P65 ratio, and mRNA abundance of IL1B and IL6. Compared with green fluorescent protein adenovirus vector + NEFA, overexpression of SIRT3 in NEFA-treated BMEC downregulated p-NF-κB P65 and mRNA abundance of IL1B and IL6. Immunofluorescence indicated that overexpression of SIRT3 inhibited nuclear translocation of NF-κB P65. Overall, our data demonstrated that ketosis is associated with a reduction in SIRT3 abundance and activation of NF-κB signaling in the mammary gland. In vitro data provided evidence that high NEFA concentrations inhibit SIRT3, which contributes to enhanced NF-κB signaling including nuclear translocation and a pro-inflammatory response. The data suggest a promising role of SIRT3 as a target for helping alleviate localized inflammation of the mammary gland resulting from exposure to high concentrations of NEFA.

Free fatty acids impair autophagic activity and activate nuclear factor kappa B signaling and NLR family pyrin domain containing 3 inflammasome in calf hepatocytes.

Free fatty acids (FFA)-induced hepatic inflammation agravates liver injury and metabolic dysfunction in dairy cows with ketosis or fatty liver. Under stressful conditions, autophagy is generally considered as a cell protection mechanism, but whether the FFA-induced inflammatory and stress effect on hepatocytes involves an autophagy response is not well known. Thus, the objective of this study was to investigate the effects of FFA on autophagy and the role of autophagy in the activation of NF-κB (nuclear factor kappa B) signaling and NLRP3 (NLR family pyrin domain containing 3) inflammasome in calf hepatocytes. Calf hepatocytes were isolated from 3 healthy Holstein female new-born calves (1 d of age, 30-40 kg) and exposed to various concentrations of FFA (0, 0.3, 0.6, or 1.2 mM) after treatment with or without the autophagy inhibitor chloroquine (CQ) or the autophagy activator rapamycin. Expression of autophagy markers, LC3 (microtubule-associated protein 1 light chain 3) and p62 (sequestosome 1), NF-κB signaling, and NLRP3 inflammasome-related molecules were analyzed via western blot and quantitative real-time PCR. Results revealed that 0.6 and 1.2 mM FFA activated NF-κB signaling and NLRP3 inflammasome as indicated by an elevated ratio of p-NF-κB/NF-κB, protein abundance of NLRP3 and CASP1 (caspase 1), activity of CASP1, and mRNA abundance of IL1B and IL18. In addition, hepatocyte treated with 0.6 and 1.2 mM FFA or autophagy inhibitor CQ displayed increased protein abundance of p62 and LC3-II. Moreover, there was no difference in protein abundance of p62 and LC3-II between calf hepatocytes treated with 1.2 mM FFA and 1.2 mM FFA plus CQ, indicating that FFA inhibits autophagic activity in calf hepatocytes. Treatment with CQ led to overactivation of NF-κB signaling and NLRP3 inflammasome. Furthermore, CQ plus 1.2 mM FFA aggravated FFA-induced inflammation. In contrast, induction of autophagy by rapamycin ameliorated the FFA-activated NF-κB signaling and NLRP3 inflammasome as demonstrated by a lower ratio of p-NF-κB/NF-κB, protein abundance of NLRP3 and CASP1, activity of CASP1, and mRNA abundance of IL1B and IL18. Overall, inhibition of autophagy exacerbated, whereas induction of autophagy alleviated, FFA-induced inflammatory processes in calf hepatocytes, suggesting that impairment of autophagy might be partly responsible for hepatic inflammation and subsequent liver injury in dairy cows with ketosis or fatty liver. As such, regulation of autophagy may be an effective therapeutic strategy for controlling overt inflammatory responses in vivo.

Cadmium promotes apoptosis and inflammation via the circ08409/miR-133a/TGFB2 axis in bovine mammary epithelial cells and mouse mammary gland.

Cadmium is a common environmental heavy metal pollutant that can accumulate over long periods of time and cause disease. Thus, analysis of the molecular mechanisms affected by cadmium in the body could be of great significance for the prevention and treatment of cadmium-related diseases. In this study, flow cytometry, immunofluorescence, transmission electron microscopy, H&E (Hematoxylin Eosin) staining and TUNEL (TdT-mediated dUTP Nick-End Labeling) assays were used to verify that cadmium induced apoptosis and immune responses in bovine mammary epithelial cells (BMECs) and in mouse mammary gland. Isolated BMECs cultured with or without cadmium were collected to screen miRNA (microRNA) using high-throughput sequencing. There were 42 differentially-expressed miRNAs among which 27 were upregulated and 15 downregulated including bta-miR-133a, bta-miR-23b-5p, bta-miR-29e, bta-miR-365-5p, bta-miR-615, bta-miR-7, bta-miR-11975, bta-miR-127, and bta-miR-411a. Among those, miR-133a (which can specifically target TGFB2 (Recombinant Transforming Growth Factor Beta 2) was the most significantly downregulated with a fold-change of 5.27 in BMECs cultured with cadmium. Application of the double luciferase reporter system, western blotting, and qRT-PCR (Quantitative Real-time PCR) revealed that circ08409 can directly bind to miR-133a. Experiments demonstrated that circRNA-08409 could adsorb bta-miR-133a. Both circ08409 and TGFB2 significantly increased apoptosis and altered expression level of a series of inflammatory factors in BMECs. In contrast, miR-133a decreased significantly apoptosis and inflammation in the cells. Compared with cultures receiving only cadmium, the miR-133a+cadmium cultures exhibited significant reductions in the occurrence of late apoptosis. Overall, results indicated that circ08409 could relieve the inhibitory effect of miR-133a on TGFB2 expression by combining with miR-133a and subsequently modulating cell proliferation, apoptosis and inflammation. Overall, the data suggested that the circ08409/miR-133a/TGFB2 axis might play a role in mediating the effect of cadmium on BMECs. As such, data provide novel insights into controlling hazards that cadmium could induce in the mammary gland.

Abundance of solute carrier family 27 member 6 (SLC27A6) in the bovine mammary gland alters fatty acid metabolism.

Milk fatty acid (FA) composition is associated with the nutritional value of milk and is known to vary with the stage of lactation. Although biochemical aspects controlling FA metabolism in the bovine mammary gland are well-established, less is known about the underlying molecular mechanisms. Thus, to address some of these shortcomings, the present study sought to evaluate milk FA composition and mammary transcriptome profiles at different stages of lactation. Compared with 90 d of lactation, at 315 d of lactation, there was an increase in the concentrations of C18:2, polyunsaturated fatty acids (PUFA), and short-chain fatty acids (SCFA), and a decrease in C16:0 and long-chain fatty acids (LCFA) in milk. To further identify candidate genes and pathways responsible for these phenotypic differences, the transcriptome of bovine mammary tissue at 90 d (peak) and 315 d (late) of lactation was profiled using RNA-seq. A total of 827 differentially expressed genes were identified. Bioinformatic analysis revealed that the major differentially modulated lipid metabolic pathways were the PPAR signaling pathway, alpha-linolenic acid metabolism and linoleic acid metabolism. Compared with peak lactation, the mammary tissue at late lactation had lower abundance of genes related to FA transport and activation (CD36, SLC27A6, ACSM1, FABP3 and FABP4). Thus, to further explore the role of FA transport into mammary cells, we knocked down fatty acid transport protein 6 (solute carrier family 27 member 6, SLC27A6) in the bovine mammary epithelial cells (BMECs) using siRNA. The knockdown of SLC27A6 dramatically downregulated the mRNA abundance of genes associated with FA activation (ACSL4), oxidation (CPT1A) and transport (CD36), while the abundance of genes associated with transcription regulation (PPARG), diacylglycerol acyltransferase 1 (DGAT1), FA binding (FABP3), and desaturation (FADS2) was upregulated. In addition, SLC27A6 silenced the intracellular content of triglyceride (TG) and the percentage of C18:1cis9 and C20:4cis5,8,11,14 was greater, whereas that of C16:0 and C18:0 was lower. Overall, in vivo results indicated that LCFA transport into mammary cells during late lactation partly explains the difference in the FA profiles. In vitro analyses underscored how FA transport via SLC27A6 could dictate in part the intracellular utilization of FA for TG synthesis versus oxidation. The data provide strong support for a central role of SLC27A6 in the regulation of FA metabolism in BMECs.

Intracellular Ca2+ signaling and ORAI calcium release-activated calcium modulator 1 are associated with hepatic lipidosis in dairy cattle.

Fatty liver is a common metabolic disorder afflicting dairy cows during the periparturient period and is closely associated with endoplasmic reticulum (ER) stress. The onset of ER stress in humans and mice alters hepatic lipid metabolism, but it is unknown if such event contributes to fatty liver in dairy cows soon after parturition. ORAI calcium release-activated calcium modulator 1 (ORAI1) is a key component of the store-operated Ca2+ entry mechanism regulating cellular Ca2+ balance. The purpose of this study was to investigate the role of ORAI1 on hepatic lipidosis via ER stress in dairy cows. Liver tissue biopsies were collected from Holstein cows diagnosed as healthy (n = 6) or with hepatic lipidosis (n = 6). Protein and mRNA abundance of ER stress-related targets, lipogenic targets, or the transcription regulator SREBP1 and ORAI1 were greater in cows with lipidosis. In vitro, hepatocytes were isolated from four healthy female calves and used for culture with a 1.2 mM mixture of fatty acids (oleic, linoleic, palmitic, stearic, and palmitoleic acid) for various times (0, 3, 6, 9, or 12 h). As incubation time progressed, increases in concentration of Ca2+ and abundance of protein kinase RNA-like ER kinase (PERK), inositol-requiring protein 1α (IRE1α), and activating transcription factor-6 (ATF6) protein in response to exogenous fatty acids underscored a mechanistic link among Ca2+, fatty acids, and ER stress. In a subsequent study, hepatocytes were transfected with small interfering RNA (siORAI1) or the ORAI1 inhibitor BTP2 for 48 h or 2 h followed by a challenge with the 1.2 mM mixture of fatty acids for 6 h. Compared with control group, silencing or inhibition of ORAI1 led to decreased abundance of fatty acid synthesis (FASN, SREBP1, and ACACA) and ER stress-related proteins in bovine hepatocytes. Overall, data suggested that NEFA through ORAI1 regulate intracellular Ca2+ signaling, induce ER stress, and lead to lipidosis in isolated hepatocytes.

Disruption of endoplasmic reticulum homeostasis exacerbates liver injury in clinically ketotic cows.

Disruption of endoplasmic reticulum (ER) homeostasis, a condition termed "ER stress," contributes to the development of liver injury in nonruminants. Because liver injury is a prominent pathological feature associated with overproduction of ketone bodies in dairy cows with ketosis, understanding the ER stress state and its functional consequences on liver injury is of particular interest. Here, 30 multiparous cows (within 3 wk postpartum) classified based on blood ß-hydroxybutyrate (BHB) as healthy (n = 15, BHB <0.6 mM) or clinically ketotic (n = 15, BHB >3.0 mM) were used. Compared with healthy cows, ketotic cows had greater levels of serum fatty acids and activities of serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, γ-glutamyl transferase, and glutamate dehydrogenase but lower serum glucose. Furthermore, dairy cows with ketosis had greater protein abundance of ER stress markers in liver tissue, including protein kinase RNA-like ER kinase (PERK), inositol-requiring protein-1α (IRE1α), and cleaved activating transcription factor-6 (ATF6). Cows with ketosis also had higher mRNA levels of hepatic 78-kDa glucose-regulated protein (GRP78) and spliced X-box binding protein 1 (sXBP1). These data confirmed an enhanced ER stress state in clinically ketotic cows. To explore whether enhanced hepatic ER stress was induced by elevated ketone bodies and the possible contribution of ER stress to liver injury, in vitro experiments were then performed using isolated primary calf hepatocytes treated with incremental concentrations of BHB (0, 0.6, 1.2, 3.0, and 4.8 mM) for 12 h with or without overexpression of GRP78 (the master regulator of unfolded protein response). Phosphorylation levels of PERK and IRE1α proteins, level of cleaved ATF6 protein, and mRNA abundance of GRP78 and sXBP1 in hepatocytes increased after treatment with high (3.0 and 4.8 mM) BHB, indicating a mechanistic link between excessive BHB and enhanced hepatic ER stress. Furthermore, treatment with 3.0 and 4.8 mM BHB markedly elevated activities of aspartate aminotransferase and alanine aminotransferase in cell supernatant, indicating exacerbated hepatocyte damage after ER stress was enhanced. Overexpression of GRP78 attenuated both BHB-induced ER stress and the ensuing cellular damage, suggesting that hepatocyte damage caused by excessive BHB can be mediated via enhanced ER stress. Overall, the present study revealed that ER stress may exacerbate liver injury development in clinically ketotic cows, underscoring the biological relevance of this pathway in the context of liver injury.