Impaired hepatic autophagic activity in dairy cows with severe fatty liver is associated with inflammation and reduced liver function

Live yeast (Saccharomyces cerevisiae) improves growth performance and liver metabolic status of lactating Hu sheep

Yeast, a natural starter culture, is widely used to improve digestion function in ruminants. However, whether yeast affects the physiological state of the liver in ruminants is currently unknown. The aim of this study was to investigate the effects of yeast on liver metabolic status and physiological functions of Hu sheep during lactation. A total of 24 lactating Hu sheep were randomly divided into 4 groups with 6 sheep in each group: the control group (normal diet) and the low-, medium-, and high-dose groups, in which each sheep was fed an additional 0.5 g, 1 g, and 2 g yeast per morning, respectively. Blood, liver, small intestine samples were collected for subsequent analysis, and milk production and BW were recorded during the experimental period. The results showed that dietary yeast supplementation mitigated BW loss, enhanced liver function, and increased milk protein and lactose contents in Hu sheep during lactation. Compared with the normal diet, dietary yeast supplementation reduced the content of lipid droplets in the liver, significantly upregulated the expression of lipid β-oxidation-related enzymes (PPARA and CPT1A), and significantly decreased the expression of lipid synthesis-related enzymes (FASN, PPARγ, DGAT1, and DGAT2) in the liver without affecting the capacity of the small intestine to absorb foodborne lipids. In addition, dietary yeast supplementation significantly decreased blood nonesterified free fatty acid content and increased blood glucose and liver expression of key enzymes involved in gluconeogenesis (PCK1α, FBP, and G6PC). These results suggest that dietary yeast supplementation may alleviate weight loss and enhance milk quality in Hu sheep during lactation. Furthermore, it can improve liver metabolic adaptability and protect liver health by regulating lipid metabolism and metabolic glucose homeostasis in the liver. Notably, adding 1 g or 2 g of yeast to the daily diet yields superior effects.

The role of glutathione S-transferase mu 2 in mitigating fatty acid-induced hepatic inflammation in dairy cows

Fatty liver is a major metabolic disorder in perinatal dairy cows, characterized by elevated plasma concentrations of nonesterified fatty acids (NEFA) and hepatic inflammation. Glutathione S-transferase mu 2 (GSTM2), a phase II detoxification enzyme, regulates cellular antioxidant and detoxification processes in nonruminants. However, its involvement in NEFA-induced hepatic inflammation in dairy cows with fatty liver remains unclear. This study aimed to elucidate the role of GSTM2 in mediating hepatic inflammation caused by elevated NEFA levels in dairy cows with severe fatty liver. An in vivo study was conducted using 10 healthy cows (hepatic triacylglycerol [TG] content <1%) and 10 cows with severe fatty liver (hepatic TG content >10%), matched for the number of lactations (median = 3, range = 2-4) and DIM (median = 9 d, range = 3-15 d). Liver tissue and blood samples were collected before feeding. Compared with healthy cows, cows with severe fatty liver had higher plasma concentrations of NEFA, BHB, haptoglobin (HP), plasma amyloid A (SAA), and lower plasma concentration of glucose. These cows also showed significantly lower abundance of hepatic GSTM2 and overactivated hepatic inflammatory pathways, as indicated by increased abundance of phosphorylated inhibitor of κB (IκB)α and nuclear factor κB (NF-κB) p65, NLR family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing CARD (ASC), and caspase-1 (CASP1), as well as mRNA levels of tumor necrosis factor α (TNFA), IL6, and IL1B. In vitro, hepatocytes isolated from 5 healthy calves (1 d old, fasted female, 30-40 kg of BW) were used to determine the effects of GSTM2 on hepatic inflammation. First, hepatocytes were treated with NEFA (1.2 mM) for varying durations (0.5, 1, 3, 6, 9, 12, 15, or 18 h). The NEFA treatment significantly increased the phosphorylation of IκBα and NF-κB p65, protein abundance of NLRP3, ASC and CASP1, and mRNA levels of TNFA, IL6 and IL1B, peaking at 9 and 12 h. Second, hepatocytes were treated with different concentrations of NEFA (0, 0.6, 1.2, or 2.4 mM) for 9 h, which decreased GSTM2 protein and mRNA abundance. Meanwhile, GSTM2 was silenced using small interfering RNA or overexpressed using adenovirus for 48 h in hepatocytes, followed by NEFA treatment. Silencing GSTM2 augmented the NEFA-induced increase in phosphorylation of IκBα and NF-κB p65, as well as protein abundance of NLRP3, ASC and CASP1, and mRNA levels of TNFA, IL6 and IL1B. Conversely, overexpression of GSTM2 mitigated these inflammatory signals upon NEFA treatment. In summary, these findings indicate that GSTM2 plays a crucial role in modulating NEFA-induced hepatic inflammation. Targeting GSTM2 may offer new strategies to treat or prevent fatty liver disease in dairy cows.

Effects of probiotic and yeast extract supplement on liver functionality index and metabolic parameters in transition period of dairy cattle

This research sought to evaluate the potential effects of probiotics and yeast cell wall (YCW) supplements on the liver functionality index (LFI) and metabolic parameters of dairy cattle throughout the transitional period. A cohort of forty dry cows was randomly divided into four groups, namely the probiotic group (Pr) receiving a basal diet combined with a blend of Bacillus subtilis, Bacillus lechiniformis, Streptococcus Thermophilis, and Enterococcus faecium; the YCW group receiving a basal diet enriched with Saccharomyces cerevisiae; the probiotic and yeast cell wall extract group (P & Y) receiving a basal diet supplemented with a mixture of probiotic and yeast cell wall extract; and the control group adhering to the basal diet. The intervention was initiated 21 days before calving and persisted until 28 days post-calving, except for the control group. The study entailed the collection of blood samples at four sampling times, encompassing 21 days preceding calving, seven days before calving, seven days post-calving, and four weeks post-calving. Multiple biochemical parameters were assessed, including urea, blood urea nitrogen (BUN), Gamma-glutamyl transferase (GGT), total bilirubin (TB), albumin, total protein (TP), globulin, glucose, triglyceride, cholesterol, and liver functionality index. The results showed that the Pr group exhibited reduced average levels of GGT and glucose compared to the control group (P < 0.05). Similarly, the P & Y group demonstrated lower average BUN, TB, and cholesterol levels than the control (P < 0.05). Notably, the LFI exhibited a discernible trend towards elevation in the Pr group compared to the control group (P = 0.007) and the P & Y group (P = 0.007). In essence, supplementation of YCW and probiotics is associated with advantageous effects on metabolic parameters and liver function.

Elevated RBP4 in Subclinical Ketosis Cows Inhibits Follicular Granulosa Cell Proliferation and Steroid Hormone Synthesis

The mechanism by which subclinical ketosis (SCK) causes postpartum reproductive disorders in dairy cows remains unclear. In this study, cows within the day 14 to 21 postpartum period were categorized into the SCK group or the control group. Subsequently, they were monitored until 45 d to 60 d postpartum and divided into the SCK anestrus group (SCK-AE, n = 12) and the control estrus group (C-E, n = 12). In comparison to the C-E group, the RBP4 and p-AKT of the SCK-AE group exhibited increased levels in serum, liver, and ovaries. In the in vitro experimental cultivation of granulosa cells (GCs), after adding RBP4, cell proliferation, steroid hormone secretion and synthesis, and GLUT4 secretion were inhibited, and cell apoptosis was exacerbated. After silencing STRA6 (RBP4 receptor), cell proliferation and steroid hormone secretion and synthesis, as well as the inhibition of GLUT4, were alleviated, and the situation of cell apoptosis also improved. The SC79 activator could promote the phosphorylation of AKT, thus alleviating the increased cell proliferation, steroid hormone secretion and synthesis, GLUT4 inhibition, and apoptosis rate in cow GCs induced by RBP4 stimulation. Our research indicates that elevated RBP4 levels in SCK cows inhibit the proliferation, apoptosis, and steroid hormone synthesis of GCs through the STRA6 receptor and the PI3K/AKT pathway.

Dissecting loci that underpin the genetic correlations between production, fertility, and urea traits in Australian Holstein cattle

Unfavorable genetic correlations between milk production, fertility, and urea traits have been reported. However, knowledge of the genomic regions associated with these unfavorable correlations is limited. Here, we used the correlation scan method to identify and investigate the regions driving or antagonizing the genetic correlations between production vs. fertility, urea vs. fertility, and urea vs. production traits. Driving regions produce an estimate of correlation that is in the same direction as the global correlation. Antagonizing regions produce an estimate in the opposite direction of the global estimates. Our dataset comprised 6567, 4700, and 12,658 Holstein cattle with records of production traits (milk yield, fat yield, and protein yield), fertility (calving interval) and urea traits (milk urea nitrogen and blood urea nitrogen predicted using milk-mid-infrared spectroscopy), respectively. Several regions across the genome drive the correlations between production, fertility, and urea traits. Antagonizing regions were confined to certain parts of the genome and the genes within these regions were mostly involved in preventing metabolic dysregulation, liver reprogramming, metabolism remodeling, and lipid homeostasis. The driving regions were enriched for QTL related to puberty, milk, and health-related traits. Antagonizing regions were mostly related to muscle development, metabolic body weight, and milk traits. In conclusion, we have identified genomic regions of potential importance for dairy cattle breeding. Future studies could investigate the antagonizing regions as potential genomic regions to break the unfavorable correlations and improve milk production as well as fertility and urea traits.

Graduate Student Literature Review: Exploring choline's important roles as a nutrient for transition dairy cows

In late gestation and in the first weeks postpartum, lipid droplets accumulate in the hepatic tissue resulting in approximately 40% to 50% of the dairy cows developing hepatic lipidosis in the first weeks of lactation. Elevated concentrations of triacylglycerol in the hepatic tissue are associated with increased risk of peripartum diseases and impaired productive performance. Cows with hepatic lipidosis need to dispose the excess of hepatic triacylglycerol, but this is a slow process in the bovine liver and relies on primary mechanisms such as complete oxidation and ketogenesis because of the limited export of triacylglycerols as lipoproteins. Choline is a lipotropic compound because, among other functions, it facilitates the export of lipids from the liver. Supplementing choline as rumen-protected choline (RPC) to diets of feed-restricted dairy cows reduces the degree of triacylglycerol infiltration into the hepatic parenchyma in part by enhancing export of triacylglycerol as nascent lipoprotein. The reduced accumulation of triacylglycerol in hepatic tissue in feed-restricted cows fed RPC might affect secondary pathways involved in hepatic disposal of fatty acids such as increased cellular autophagy and lipophagy and minimize endoplasmic reticulum stress response and hepatocyte inflammation. Collectively, these effects on secondary pathways might further reduce the severity of hepatic lipidosis in cows. One of the benefits of supplementing RPC is improved fat digestibility, perhaps because choline, through phosphatidylcholines, facilitates lipid transport within the enterocyte by increasing the synthesis of chylomicrons. Finally, when supplemented during the transition period, RPC improves productive performance of cows, irrespective of their body condition, that extends well beyond the period of supplementation. This review summarizes the current understanding of hepatic lipidosis in early lactation, recapitulates the absorption, transport and metabolism of choline, and discusses its role on hepatic metabolism and gastrointestinal functions, which collectively results in improved performance in dairy cows.

Effects of dietary energy level on antioxidant capability, immune function and rectal microbiota in late gestation donkeys

Introduction

This study investigated the effects of dietary energy level on the antioxidant capability, immune function, and rectal microbiota in donkey jennets during the last 60 days of gestation.

Methods

Fifteen pregnant DeZhou donkeys with age of 6.0 ± 0.1 years, body weight of 292 ± 33 kg, parity of 2.7 ± 0.1 parities and similar expected date of confinement (74 ± 4 days) were randomly allocated to three groups and feed three diets: high energy (10.92 MJ/kg, H), medium energy (10.49 MJ/kg, M), and low energy (9.94 MJ/kg, L).

Results and Discussion

The serum activity of catalase (CAT), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) in group M was significantly higher, whereas the concentrations of malondialdehyde (MDA), interleukin 1 (IL-1), IL-2, and IL-6 were lower than those recorded for groups H and L (p ≤ 0.05). The dietary energy level significantly affected rectal microbial community structure in the jennet donkeys 35 days and 7 days before the parturition (p ≤ 0.05). The abundances of norank_f_norank_o_Coriobacteriales genus was significantly higher (p ≤ 0.05) in group H, and the abundances of norank_f_norank_o_Mollicutes_RF39 and the Candidatus_Saccharimonas were higher in group L (p ≤ 0.05). The abundance of Fibrobacter in group M was significantly increased (p ≤ 0.05). The abundance of norank_f_norank_o_Coriobacteriales was positively correlated with average daily gain (ADG) and tumor necrosis factor-α (TNF-α) concentrations (p ≤ 0.05). The abundance of norank_f_norank_o_Mollicutes_RF39 was positively correlated with IL-2 and IL-6 concentrations. The abundance of Candidatus_Saccharimonas was positively correlated with CAT, T-SOD and GSH-Px activities (p ≤ 0.05). The abundance of Fibrobacter was positively correlated with CAT and T-SOD activities (p ≤ 0.05), but negatively correlated with IL-2 concentration (p ≤ 0.05). In conclusion, an appropriate dietary with an energy content of 10.49 MJ/kg for jennet donkeys during late gestation increased the prenatal antioxidant capacity, reduced inflammatory cytokines, and promoted fetal growth, and these changes were related to diet-induced changes in rectal microbiota compositions.

Subclinical ketosis leads to lipid metabolism disorder by downregulating the expression of acetyl-coenzyme A acetyltransferase 2 in dairy cows

Ketosis is a metabolic disease that often occurs in dairy cows postpartum and is a result of disordered lipid metabolism. Acetyl-coenzyme A (CoA) acetyltransferase 2 (ACAT2) is important for balancing cholesterol and triglyceride (TG) metabolism; however, its role in subclinical ketotic dairy cows is unclear. This study aimed to explore the potential correlation between ACAT2 and lipid metabolism disorders in subclinical ketotic cows through in vitro and in vivo experiments. In the in vivo experiment, liver tissue and blood samples were collected from healthy cows (CON, n = 6, β-hydroxybutyric acid [BHBA] concentration <1.0 mM) and subclinical ketotic cows (subclinical ketosis [SCK], n = 6, BHBA concentration = 1.2-3.0 mM) to explore the effect of ACAT2 on lipid metabolism disorders in SCK cows. For the in vitro experiment, bovine hepatocytes (BHEC) were used as the model. The effects of BHBA on ACAT2 and lipid metabolism were investigated via BHBA concentration gradient experiments. Subsequently, the relation between ACAT2 and lipid metabolism disorder was explored by transfection with siRNA of ACAT2. Transcriptomics showed an upregulation of differentially expression genes during lipid metabolism and significantly lower ACAT2 mRNA levels in the SCK group. Compared with the CON group in vivo, the SCK group showed significantly higher expression levels of peroxisome proliferator-activated receptor γ (PPARγ) and sterol regulator element binding protein 1c (SREBP1c) and significantly lower expression levels of peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyl-transferase 1A (CPT1A), sterol regulatory element binding transcription factor 2 (SREBP2), and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR). Moreover, the SCK group had a significantly higher liver TG content and significantly lower plasma total cholesterol (TC) and free cholesterol content. These results were indicative of TG and cholesterol metabolism disorders in the liver of dairy cows with SCK. Additionally, the SCK group showed an increased expression of perilipin-2 (PLIN2), decreased expression of apolipoprotein B, and decreased plasma concentration of very low-density lipoproteins (VLDL) and low-density lipoproteins cholesterol (LDL-C) by downregulating ACAT2, which indicated an accumulation of TG in liver. In vitro experiments showed that BHBA induced an increase in the TG content of BHEC, decreased content TC, increased expression of PPARγ and SREBP1c, and decreased expression of PPARα, CPT1A, SREBP2, and HMGCR. Additionally, BHBA increased the expression of PLIN2 in BHEC, decreased the expression and fluorescence intensity of ACAT2, and decreased the VLDL and LDL-C contents. Furthermore, silencing ACAT2 expression increased the TG content; decreased the TC, VLDL, and LDL-C contents; decreased the expression of HMGCR and SREBP2; and increased the expression of SREBP1c; but had no effect on the expression of PLIN2. These results suggest that ACAT2 downregulation in BHEC promotes TG accumulation and inhibits cholesterol synthesis, leading to TG and cholesterol metabolic disorders. In conclusion, ACAT2 downregulation in the SCK group inhibited cholesterol synthesis, increased TG synthesis, and reduced the contents of VLDL and LDL-C, eventually leading to disordered TG and cholesterol metabolism.

Inflammatory tone in liver and adipose tissue in dairy cows experiencing a healthy transition from late pregnancy to early lactation

The transition from late pregnancy (LP) to early lactation (EL) in dairy cows is characterized by a major reorganization of the metabolic activities of liver and adipose tissue in support of milk synthesis. This reorganization has been attributed in large part to variation in the plasma concentration and actions of growth hormone, insulin, and other metabolic hormones. A role for the immune system has also been suggested by a near-universal rise in circulating levels of liver-derived acute-phase proteins (APP) in early lactating cows. However, less attention has been devoted to the possibility that resident macrophages of liver and adipose tissue adopt a proinflammatory state (referred herein as inflammatory tone) in parallel with the rise in plasma APP. We addressed this question by measuring the expression of genes expressed predominantly in the resident macrophage population of liver and adipose tissue and indicative of a proinflammatory (tumor necrosis factor α, IL-6, IL-12, resistin, and cluster of differentiation 80 [CD80]) or anti-inflammatory state (IL-10 and chitinase-3-like protein 1 [CHI3L1]). In a first group of cows, none of these inflammatory gene markers were regulated in liver between LP on d -29 (relative to parturition) and on d 8 of EL despite 1.7 to 5.6-fold upregulation in the expression of the APP (haptoglobin, serum amyloid α, and orosomucoid 1). In a second group of healthy cows, expression of the inflammatory gene markers did not differ between livers with low (<5.3%) or high (>11.5%) triglyceride content on d 7 of EL. In adipose tissue, a modest increase in inflammatory tone was suggested between LP and EL by increased CD80 expression and decreased CHI3L1 expression in EL. To assess the possibility that inflammatory tone would be more prominent if assayed in a cell compartment enriched with macrophages, adipose tissue was obtained in LP on d -28 and in EL on d +10 from cows experiencing a healthy transition period and fractionated into its adipocyte and stromal vascular cell (SVC) compartments. Expression of inflammatory gene markers was higher in SVC than adipocytes but remained unregulated in SVC between LP and EL. Overall, these results suggest little change in the inflammatory tone of resident macrophages in liver and adipose tissue of healthy transition dairy cows and do not support a role for the local immune system in the reorganization of metabolism in these tissues at the onset of lactation.

Vine tea extract ameliorated acute liver injury by inhibiting hepatic autophagy and reversing abnormal bile acid metabolism

Gut microbiota disturbance, autophagy dysregulation, and accumulation of hepatic bile acids (BAs) are essential features of liver injury. Therefore, regulating autophagy and BA metabolism are potential strategies for treating liver diseases. Vine tea has been seen beyond a pleasant tea in food science. Our previous study found that vine tea extract (VTE) intervention alleviated acute liver injury (ALI) by restoring gut microbiota dysbiosis. In this study, we aim to investigate the effect of VTE on carbon tetrachloride (CCl4)-induced hepatic autophagy and BA metabolism disorder in mice. The results showed that VTE effectively suppressed CCl4-induced liver fibrosis and hepatic autophagy. LC-MS/MS assay suggested that VTE affected fecal BA production by reducing the fecal BA levels and improving cholestasis in ALI mice. Besides, VTE inhibited BA synthesis, promoted BA transport in the liver, and enhanced BA reabsorption in the ileum through the farnesoid X receptor (FXR)-related signaling pathway. The hepatic expressions of Fxr and Abca1 were elevated by VTE. Finally, the depletion of gut microbiota in ALI mice had a negative impact on abnormal autophagy and BA metabolism. It was also noted that the administration of VTE did not provide any additional improvement in this regard. Overall, VTE ameliorated ALI by reversing hepatic autophagy and abnormal BA metabolism, and the beneficial effects of VTE on liver injury depended on the existence of gut microbiota.

AdipoRon alleviates fatty acid-induced lipid accumulation and mitochondrial dysfunction in bovine hepatocytes by promoting autophagy

During the transition period in dairy cows, high circulating concentrations of nonesterified fatty acids (NEFA) increase hepatic lipid deposits and are considered a major pathological factor for liver damage. We investigated whether AdipoRon, a synthetic small-molecule agonist of adiponectin receptors 1 and 2 shown to prevent liver lipid accumulation in nonruminants, could alleviate NEFA-induced lipid accumulation and mitochondrial dysfunction. Bovine hepatocytes were isolated from 5 healthy Holstein female newborn calves (1 d of age, 30-40 kg, fasting), and independently isolated hepatocytes from at least 3 different calves were used for each subsequent experiment. The composition and concentration of NEFA used in this study were selected according to hematological criteria of dairy cows with fatty liver or ketosis. First, hepatocytes were cultured with various concentrations of NEFA (0, 0.6, 1.2, or 2.4 mM) for 12 h. In a second experiment, hepatocytes were treated with AdipoRon at different concentrations (0, 5, 25, or 50 μM for 12 h) and times (25 μM for 0, 6, 12, or 24 h) with or without NEFA (1.2 mM) treatment. In the last experiment, hepatocytes were treated with AdipoRon (25 μM), NEFA (1.2 mM), or both for 12 h after treatment with or without the autophagy inhibitor chloroquine. Hepatocytes treated with NEFA had increased protein abundance of sterol regulatory element-binding protein 1c (SREBP-1c) and mRNA abundance of acetyl-CoA carboxylase 1 (ACACA), and decreased protein abundance of peroxisome proliferator-activated receptor α (PPARA), proliferator-activated receptor gamma coactivator-1 α (PGC-1α), mitofusin 2 (MFN2), cytochrome c oxidase subunit IV (COX IV), and mRNA abundance of carnitine palmitoyltransferase 1A (CPT1A), along with lower ATP concentrations. AdipoRon treatment reversed these effects, suggesting this compound had a positive effect on lipid metabolism and mitochondrial dysfunction during the NEFA challenge. In addition, upregulated expression of microtubule-associated protein 1 light chain 3-II (LC3-II, encoded by MAP1LC3) and downregulated expression of sequestosome-1 (SQSTM1, also called p62) indicated that AdipoRon enhanced autophagic activity in hepatocytes. The fact that chloroquine impeded the beneficial effects of AdipoRon on lipid accumulation and mitochondrial dysfunction suggested a direct role for autophagy during NEFA challenge. Our results suggest that autophagy is an important cellular mechanism to prevent NEFA-induced lipid accumulation and mitochondrial dysfunction in bovine hepatocytes, which is consistent with other studies. Overall, AdipoRon may represent a promising therapeutic agent to maintain hepatic lipid homeostasis and mitochondrial function in dairy cows during the transition period.

Effect of Myricetin on Lipid Metabolism in Primary Calf Hepatocytes Challenged with Long-Chain Fatty Acids

Triacylglycerol (TAG) accumulation and oxidative damage in hepatocytes induced by high circulating concentrations of fatty acids (FA) are common after calving. In order to clarify the role of myricetin on lipid metabolism in hepatocytes when FA metabolism increases markedly, we performed in vitro analyses using isolated primary calf hepatocytes from three healthy female calves (1 d old, 42 to 48 kg). Two hours prior to an FA challenge (1.2 mM mix), the hepatocytes were treated with 100 μM (M1), 50 μM (M2), or 25 μM (M3) of myricetin. Subsequently, hepatocytes from each donor were challenged with or without FA for 12 h in an attempt to induce metabolic stress. Data from calf hepatocyte treatment comparisons were assessed using two-way repeated-measures (RM) ANOVA with subsequent Bonferroni correction. The data revealed that hepatocytes challenged with FA had greater concentrations of TAG and nonesterified fatty acids (NEFA), oxidative stress-related MDA and H2O2, and mRNA and protein abundance of lipid synthesis-related SREBF1 and inflammatory-related NF-κB. In addition, the mRNA abundance of the lipid synthesis-related genes FASN, DGAT1, DGAT2, and ACC1; endoplasmic reticulum stress-related GRP79 and PERK; and inflammatory-related TNF-α also were upregulated. In contrast, the activity of antioxidant SOD (p < 0.01) and concentrations of GSH (p < 0.05), and the protein abundance of mitochondrial FA oxidation-related CPT1A, were markedly lower. Compared with FA challenge, 50 and 100 μM myricetin led to lower concentrations of TAG, NEFA, MDA, and H2O2, as well as mRNA and protein abundance of SREBF1, DGAT1, GRP78, and NF-κB. In contrast, the activity of SOD (p < 0.01) and mRNA and protein abundance of CPT1A were markedly greater. Overall, the results suggest that myricetin could enhance the antioxidant capacity and reduce lipotoxicity, endoplasmic reticulum stress, and inflammation. All of these effects can help reduce TAG accumulation in hepatocytes.

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 β-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 β-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 β-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.

Low abundance of mitophagy markers is associated with reactive oxygen species overproduction in cows with fatty liver and causes reactive oxygen species overproduction and lipid accumulation in calf hepatocytes

Mitochondria are the main site of fatty acid oxidation and reactive oxygen species (ROS) formation. Damaged or dysfunctional mitochondria induce oxidative stress and increase the risk of lipid accumulation. During the process of mitophagy, PTEN induced kinase 1 (PINK1) accumulates on damaged mitochondria and recruits cytoplasmic Parkin to mitochondria. As an autophagy receptor protein, sequestosome-1 (p62) binds Parkin-ubiquitinated outer mitochondrial membrane proteins and microtubule-associated protein 1 light chain 3 (LC3) to facilitate degradation of damaged mitochondria. In nonruminants, clearance of dysfunctional mitochondria through the PINK1/Parkin-mediated mitophagy pathway contributes to reducing ROS production and maintaining metabolic homeostasis. Whether PINK1/Parkin-mediated mitophagy plays a similar role in dairy cow liver is not well known. Thus, the objective of this study was to investigate mitophagy status in dairy cows with fatty liver and its role in free fatty acid (FFA)-induced oxidative stress and lipid accumulation. Liver and blood samples were collected from healthy dairy cows (n = 10) and cows with fatty liver (n = 10) that had a similar number of lactations (median = 3, range = 2 to 4) and days in milk (median = 6 d, range = 3 to 9 d). Calf hepatocytes were isolated from 5 healthy newborn female Holstein calves (1 d of age, 30-40 kg). Hepatocytes were transfected with small interfering RNA targeted against PRKN for 48 h or transfected with PRKN overexpression plasmid for 36 h, followed by treatment with FFA (0.3 or 1.2 mM) for 12 h. Mitochondria were isolated from fresh liver tissue or calf hepatocytes. Serum concentrations of β-hydroxybutyrate were higher in dairy cows with fatty liver. Hepatic malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) were greater in cows with fatty liver. The lower protein abundance of PINK1, Parkin, p62, and LC3-II in hepatic mitochondrial fraction of dairy cows with fatty liver indicated the mitophagy was impaired. In hepatocytes, knockdown of PRKN decreased protein abundance of p62 and LC3-II in the mitochondrial fraction, and increased contents of triacylglycerol (TG), MDA, and H₂O₂. In addition, protein abundances of PINK1, Parkin, p62, and LC3-II were lower in the mitochondrial fraction from hepatocytes treated with 1.2 mM FFA than the hepatocytes treated with 0.3 mM FFA, whereas the content of TG, MDA, and H₂O₂ increased. In 1.2 mM FFA-treated hepatocytes, PRKN overexpression increased protein abundance of p62 and LC3-II in the mitochondrial fraction and decreased contents of TG, MDA, and H₂O₂. Together, our data demonstrate that low abundance of mitophagy markers is associated with ROS overproduction in dairy cows with fatty liver and impaired mitophagy induced by a high concentration of FFA promotes ROS production and lipid accumulation in female calf hepatocytes.

Activation of Transcription Factor EB Is Associated With Adipose Tissue Lipolysis in Dairy Cows With Subclinical Ketosis

Excessive lipid mobilization for adipose tissue caused by severe negative energy balance is the pathological basis for subclinical ketosis (SCK) in dairy cows. In non-ruminants, transcription factor EB (TFEB) was reported to play a role in the regulation of lipid catabolism, but its role in the control of lipolysis in the bovine is unknown. The present study aimed to determine whether the enhanced TFEB transcriptional activity contributes to lipolysis of adipose tissue in SCK cows, and to explore the possibility of establishing a therapeutic strategy by using TFEB as a target to control lipolysis. Thirty cows with similar lactation number (median = 3, range = 2–4) and days in milk (median = 6 d, range = 3–9) were selected into a healthy control (n = 15) and SCK (n = 15) group, and used for subcutaneous adipose tissue biopsies and blood sampling. Adipocytes from healthy Holstein calves were used as a model for in vitro studies involving treatment with 10 μM isoproterenol (ISO) for 0, 1, 2 and 3 h, 250 nM of the TFEB activator Torin1 for 3 h, or used for transfection with TFEB small interfering RNA for 48 h followed by treatment with 10 μM ISO for 3 h. Compared with healthy cows, adipose tissue in SCK cows showed increased lipolysis accompanied by enhanced TFEB transcriptional activity. In vitro, ISO and Torin1 treatment increased lipolysis and enhanced TFEB transcriptional activity in calf adipocytes. However, knockdown of TFEB attenuated ISO-induced lipolysis in adipocytes. Overall, these findings indicated that enhanced transcriptional activity of TFEB may contribute to lipolysis of adipose tissue in dairy cows with SCK. The regulation of TFEB activity may be an effective therapeutic strategy for controlling overt lipolysis in ketotic cows.

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 β-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.

High-Fat Diet-Induced Fatty Liver Is Associated with Immunosuppressive Response during Sepsis in Mice

High-fat diet-induced fatty liver is an indolent and chronic disease accompanied by immune dysfunction and metabolic disturbances involving numerous biological pathways. This study investigated how this abnormal metabolic disorder influences sepsis in mice. Mice were fed with normal chow (NC) or high-fat diet (HFD), and palmitic acid (PA) was used to treat hepatocytes to mimic fat accumulation in vitro. Lipopolysaccharide (LPS) was used to induce sepsis and related immune responses. Mice fed on a high-fat diet displayed higher mortality and more severe liver damage but compromised immunoreaction. The supernatant from PA-treated primary hepatocytes markedly diminished the inflammatory cytokine expression of macrophages after LPS stimulation, which showed a state of immunosuppression. Metabolomics analysis indicated the level of many key metabolites with possible roles in immunoreaction was altered in the HFD and PA groups compared with corresponding controls; specifically, β-hydroxybutyric acid (BHB) showed an immunosuppressive effect on Raw264.7 cells during the LPS stimulation. Transcriptomic analysis suggested that several differential signaling pathways may be associated with the alteration of immune function between the NC and HFD groups, as well as in the in vitro model. Our study suggests that the consumption of HFD may alter the hepatic metabolic profile, and that certain metabolites may remold the immune system to immunosuppressive state in the context of sepsis.

Dietary fucoidan extracted from macroalgae Saccharina japonica alleviate the hepatic lipid accumulation of black seabream (Acanthopagrus schlegelii)

The use of an artificial diet often leads to the increase of risk factors for the development of liver diseases, such as hepatic lipid accumulation (HLA) in commercially cultured fish species. Our previous study showed that dietary Saccharina japonica could effectively alleviate HLA in black seabream (Acanthopagrus schlegelii), which may be linked predominantly to S. japonica fucoidan. Thus, a 56d nutritional trial was designed to investigate the effects of dietary fucoidan (CTRL, 0 g kg^-1; ASJ1, 0.75 g kg^-1; ASJ2, 3.00 g kg^-1) on growth performance, fillets nutritional values, and HLA of black seabream. Results showed that dietary fucoidan significantly improved the growth and the contents of n-3 polyunsaturated fatty acids (n-3PUFA) in fillets of black seabream. Moreover, dietary fucoidan improved HLA-related parameters, including reducing serum and liver lipid contents and the activity of aminotransferase. Meanwhile, histological analysis showed that dietary fucoidan reduced the area of hepatic lipid droplets in black seabream (P < 0.05). In addition, the transcriptomic analysis of differentially expressed gene (DEG) showed that all DEG in fatty acid metabolism, primary bile acid biosynthesis, and fatty acid biosynthesis were down-regulated, and all DEG in the regulation of autophagy were up-regulated in the ASJ1 group compared with CTRL group. Moreover, the metabolomic analysis of differentially expressed metabolite (DEM) found that lipid metabolism was the main type of KEGG pathway altered by fucoidan supplementation. Furthermore, the combined transcriptomic and metabolomic analysis found that dietary fucoidan mainly modified the lipid metabolic pathway of primary bile acid biosynthesis, glycerophospholipid metabolism, and arachidonic acid metabolism in the liver. In general, dietary fucoidan effectively alleviated HLA of black seabream, and the underlying mechanism may be ascribed to promoting the autophagy and inhibiting the synthesis of lipids and bile acids.

NEFA Promotes Autophagosome Formation through Modulating PERK Signaling Pathway in Bovine Hepatocytes

During the perinatal period, the abnormally high plasma non-esterified fatty acids (NEFA) concentration caused by the negative energy balance (NEB) can impose a significant metabolic stress on the liver of dairy cows. Endoplasmic reticulum (ER) stress is an important adaptive response that can serve to maintain cell homeostasis in the event of stress. The protein kinase R-like endoplasmic reticulum kinase (PERK) pathway is the most rapidly activated cascade when ER stress occurs in cells and has an important impact on the regulation of hepatic lipid metabolism and autophagy modulation. However, it is unknown whether NEFA can affect autophagy through modulating the PERK pathway, under NEB conditions. In this study, we provide evidence that NEFA treatment markedly increased lipid accumulation, the phosphorylation level of PERK and eukaryotic initiation factor 2α (eIF2α), and the expression of glucose-regulated protein 78 (Grp78), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP). More importantly, NEFA treatment can cause a substantial increase in the protein levels of autophagy-related gene 7 (ATG7), Beclin-1 (BECN1), sequestosome-1 (p62), and microtubule-associated protein 1 light chain 3 (LC3)-II, and in the number of autophagosomes in primary bovine hepatocytes. The addition of GSK2656157 (PERK phosphorylation inhibitor) can significantly inhibit the effect of NEFA on autophagy and can further increase lipid accumulation. Overall, our results indicate that NEFA could promote autophagy via the PERK pathway in bovine hepatocytes. These findings provide novel evidence about the potential role of the PERK signaling pathway in maintaining bovine hepatocyte homeostasis.

Factors associated with negative energy balance in periparturient dairy cows raised under tropical climate of Thailand-A mini-review

This review attempted to explain factors associated with negative energy balance (NEB) occurring during the periparturient period in dairy cows raised under tropical climatic conditions. The NEB has long been proven as an inevitable event in periparturient dairy cows. This condition had negative effects on the overall performances of dairy cows, including milk production, reproduction, and health condition. Therefore, periparturient management to overcome the NEB problem is vital for optimizing profit in dairy farming. In most tropical countries such as Thailand, dairy cows have been predominantly kept by small-holder farmers. Consequently, baseline milk yields, feed availability, feeding management, and general farming practices are different from typical commercial dairy farming. Heat stress also plays a crucial role in NEB conditions, and elevated temperature-humidity indexes above-normal conditions are recorded throughout the year. These factors influence the NEB in tropical dairy cows, which could result in different outcomes and consequences. Understanding the affecting components of NEB in dairy cows would help alleviate the severity of the NEB and its consequences, optimizing the dairy cow's performance.

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.

TLR4 Knockout Attenuates BDL-induced Liver Cholestatic Injury through Amino Acid and Choline Metabolic Pathways

The exact mechanism by which knockout of Toll-like receptor 4 (TLR4) attenuates the liver injury remains unclear. The present study aimed to examine the role of TLR4 in the pathogenesis of bile duct ligation (BDL)-induced liver cholestatic injury and the underlying mechanism. Wild type (WT) mice and TLR4 knockout (TLR4-KO) mice were used for the establishment of the BDL model. Metabolomics were applied to analyze the changes of small molecular metabolites in the serum and liver of the two groups. The serum biochemical indexes and the HE staining results of liver tissue showed that liver damage was significantly reduced in TLR4-KO mice after BDL when compared with that in WT mice. The metabolite analysis results showed that TLR4 KO could maintain the metabolisms of amino acids- and choline-related metabolites. After BDL, the amino acids- and choline-related metabolites, especially choline and 3-hydroxybutyrate, were significantly increased in WT mice (both in serum and liver), but these metabolites in the liver of TLR4-KO mice after BLD were not significant different from those before BLD. In conclusion, TLR4 KO could attenuate BDL-induced liver cholestatic injury through regulating amino acid and choline metabolic pathways.

Propionate alleviates palmitic acid-induced endoplasmic reticulum stress by enhancing autophagy in calf hepatic cells

Negative energy balance-induced high blood concentrations of free fatty acids during the early postpartum period in dairy cows is a major cause of liver injury. Cows in severe negative energy balance often have suboptimal intakes of feed, which contributes to shortfalls in production of ruminal propionate and circulating glucose. Although increasing propionate production by the rumen through feed additives such as propylene glycol is effective in helping cows alleviate the shortfall in dietary energy supply, mechanisms whereby propionate affects liver function beyond gluconeogenesis are unknown. Therefore, the objective of this study was to investigate whether propionate could protect calf hepatic cells from palmitic acid (PA)-induced lipotoxicity and the underlying mechanisms. Calf hepatic cells were isolated from 5 healthy calves (1 d old, female, 30-40 kg, fasting) and treated with various concentrations of PA (0, 100, 200, or 400 μM) and propionate (0, 1, 2, or 4 mM) after being administered with or without autophagic inhibitor. Propionate enhanced autophagic activity in calf hepatic cells, as indicated by elevated expression of autophagy markers LC3-II (microtubule-associated protein 1 light chain 3-II, encoded by MAP1LC3) and decreased expression of SQSTM1 (sequestosome-1, also called p62). Conversely, PA suppressed autophagic activity and decreased cell viability, which was improved by propionate in calf hepatic cells. In addition, propionate decreased the phosphorylation of proteins EIF2AK3 (kinase R/PKR like ER kinase) and ERN1 (inositol-requiring enzyme 1α) and cleaved ATF6 (activating transcription factor 6) in PA-treated calf hepatic cells, indicating the suppression effect of propionate on endoplasmic reticulum (ER) stress. However, inhibition of autophagic activity by chloroquine or bafilomycin A1 impede the beneficial effects of propionate on ER stress and cell viability. These results demonstrated that propionate alleviates ER stress and elevates cell viability in PA-treated calf hepatic cells by enhancing autophagy, which implies that autophagy may be a promising target in improving liver injury of dairy cows during transition period.

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 β-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.

Inhibition of cell death inducing DNA fragmentation factor-α-like effector c (CIDEC) by tumor necrosis factor-α induces lipolysis and inflammation in calf adipocytes

Dairy cows with ketosis exhibit signs of pronounced adipose tissue lipolysis and systemic inflammation, both of which exacerbate this metabolic disorder. In nonruminants, CIDEC plays a pivotal role in the formation of large unilocular lipid droplets. The present study aimed to ascertain the role of CIDEC in the lipolytic and inflammatory response of white adipose tissue (WAT) in vivo and in vitro. Subcutaneous adipose tissue and blood samples were collected from 15 healthy cows (blood β-hydroxybutyrate concentration < 1.2 mM) and 15 cows with clinical ketosis (blood β-hydroxybutyrate concentration > 3.0 mM) that had a similar number of lactations (median = 3, range = 2-4) and days in milk (median = 6 d, range = 3-9). Adipocytes isolated from 5 healthy Holstein calves (1 d old, female, 30-40 kg) were used for in vitro studies. Isolated adipocytes were treated with 0, 0.1, 1, or 10 ng/mL TNF-α for 3 h, transfected with CIDEC small interfering RNA for 48 h, or transfected with CIDEC overexpression adenovirus for 48 h followed by treatment with TNF-α (0.1 ng/mL) for 3 h. Serum concentrations of fatty acids were greater, and dry matter intake, milk yield, and serum glucose concentrations lower in cows with clinical ketosis. Protein and mRNA abundance of CIDEC were lesser in subcutaneous WAT of clinically ketotic versus healthy cows. Furthermore, the ratio of phosphorylated hormone sensitive lipase (p-LIPE) to LIPE, phosphorylated RELA (p-RELA) to RELA, and protein abundance of PNPLA2 and phosphorylated inhibitor of κBα (p-NFKBIA) were greater in dairy cows with clinical ketosis. The mRNA abundance of proinflammatory cytokines TNFA and IL1B were greater, and the anti-inflammatory cytokine IL10 was lower in WAT of dairy cows with clinical ketosis. In calf adipocytes, exogenous TNF-α (0.1, 1, or 10 ng/mL) decreased protein and mRNA abundance of CIDEC. In addition, exogenous TNF-α or knockdown of CIDEC reduced the secretion of the anti-inflammatory cytokine IL-10, but increased the ratio of p-LIPE to LIPE, p-RELA to RELA, protein abundance of PNPLA2 and p-NFKBIA, glycerol content, and the secretion of IL-1β in calf adipocytes. Overexpression of CIDEC in TNFα-treated adipocytes attenuated lipolysis and activation of the NF-κB signaling pathway. Overall, these data suggest that inhibition of lipid droplet-associated protein CIDEC by TNF-α contributes to the pronounced lipolysis and inflammation of calf adipocytes, and CIDEC is a relevant target in clinically ketotic cows.

Adenosine 5'-monophosphate-activated protein kinase ameliorates bovine adipocyte oxidative stress by inducing antioxidant responses and autophagy

Adipose tissue concentration of reactive oxygen species (ROS) increases in dairy cows with ketosis, suggesting that the tissue experiences oxidative stress. Autophagy, an adaptive response to cellular stress, has been shown to promote survival and plays a critical role in antioxidant responses. Dysregulation of adenosine 5'-monophosphate-activated protein kinase (AMPK) is closely related to antioxidant responses and autophagy of adipocytes in animal models of metabolic disorders, but its role in bovine adipose tissue during periods of stress is unknown. We hypothesized that AMPK may play important roles in the regulation of oxidative stress in adipose tissue of ketotic cows. Specific objectives were to evaluate autophagy status and AMPK activity in adipose tissue of ketotic cows, and their link with oxidative stress in isolated bovine adipocytes. Selection of 15 healthy and 15 clinically ketotic Holstein cows at 17 (±4) d postpartum was performed after a thorough veterinary evaluation for clinical symptoms and also based on serum β-hydroxybutyrate concentrations before collection of subcutaneous adipose tissue samples. Primary cultures of bovine adipocytes isolated from the harvested adipose tissue were stimulated with varying concentrations of H₂O₂ (0, 50, 100, 200, or 400 μM) for 2 h. In another experiment, adipocytes were cultured with the AMPK activator A769662 or adenovirus-containing small interfering RNA (ad-AMPKα-siRNA) for 3 or 48 h, respectively, followed by H₂O₂ exposure (200 μM) for 2 h. Compared with healthy cows, clinical ketosis led to increased abundance of AMPK and nuclear factor erythroid-derived 2-like 2 (NFE2L2), but lower abundance of Kelch-like ECH-associated protein 1 (KEAP1) in adipose tissue. Abundance of the key proautophagy proteins Beclin1, sequestosome 1 (SQSTM1), autophagy-related gene 7 (ATG7), ATG5, and ratio of microtubule-associated protein light chain 3 (LC3) II to LC3I were greater in adipose tissue of ketotic cows. In bovine adipocytes, treatment with H₂O₂ induced accumulation of ROS and malondialdehyde (MDA), whereas H₂O₂ stimulation inhibited activities of the antioxidant enzymes glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). Addition of AMPK activator A769662 increased antioxidant response via activating NFE2L2 and its downstream targets heme oxygenase 1 (HMOX1), superoxide dismutase 1 (SOD1), catalase (CAT), and glutathione-S-transferase (GST) to improve H₂O₂-induced oxidative stress in adipocytes. Simultaneously, activation of AMPK increased abundance of Beclin1, SQSTM1, ATG7, ATG5, and ratio of LC3II to LC3I. In contrast, inhibition of AMPK downregulated abundance of NFE2L2, HMOX1, SOD1, CAT, Beclin1, SQSTM1, ATG7, ATG5, and ratio of LC3II to LC3I, and further aggravated H₂O₂-induced oxidative stress. Overall, these data indicate that activation of AMPK, as an adaptive mechanism for acute metabolic regulation of adipose tissue homeostasis, can induce antioxidant responses and autophagy, and further reduce oxidative stress in bovine adipocytes.

Hepatic autophagy and mitophagy status in dairy cows with subclinical and clinical ketosis

Severe negative energy balance around parturition is an important contributor to ketosis, a metabolic disorder that occurs most frequently in the peripartal period. Autophagy and mitophagy are important processes responsible for breaking down useless or toxic cellular material, and in particular damaged mitochondria. However, the role of autophagy and mitophagy during the occurrence and development of ketosis is unclear. The objective of this study was to investigate autophagy and mitophagy in the livers of cows with subclinical ketosis (SCK) and clinical ketosis (CK). We assessed autophagy by measuring the protein abundance of microtubule-associated protein 1 light chain 3-II (LC3-II; encoded by MAP1LC3) and sequestosome-1 (p62, encoded by SQSTM1), as well as the mRNA abundance of autophagy-related genes 5 (ATG5), 7 (ATG7), and 12 (ATG12), beclin1 (BECN1), and phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3). Mitophagy was evaluated by measuring the protein abundance of the mitophagy upstream regulators PTEN-induced putative kinase 1 (PINK1) and Parkin. Liver and blood samples were collected from healthy cows [n = 15; blood β-hydroxybutyrate (BHB) concentration <1.2 mM], cows with SCK (n = 15; blood BHB concentration 1.2 to 3.0 mM) and cows with CK (n = 15; blood BHB concentration >3.0 mM with clinical signs) with similar lactation numbers (median = 3, range = 2 to 4) and days in milk (median = 6, range = 3 to 9). The serum activity of aspartate aminotransferase and alanine aminotransferase was greater in cows with CK than in healthy cows. Levels of oxidative stress biomarkers malondialdehyde and hydrogen peroxide were also higher in liver tissue from ketotic cows (SCK and CK) than from healthy cows. Compared with cows with CK and healthy cows, the hepatic mRNA abundance of MAP1LC3, SQSTM1, ATG5, ATG7, ATG12, and PIK3C3 was upregulated in cows with SCK. Compared with healthy cows, cows with SCK had a lower abundance of p62 and a greater abundance of LC3-II, but levels of both were higher in cows with CK. The mRNA abundance of ATG12 was lower in cows with CK than in healthy cows. Furthermore, the hepatic protein abundance of PINK1 and Parkin was greater in cows with SCK and slightly lower in cows with CK than in healthy cows. These data demonstrated differences in the hepatic activities of autophagy and mitophagy in cows with SCK compared with cows with CK. Although the precise mechanisms for these differences could not be discerned, autophagy and mitophagy seem to be involved in ketosis.

Mitochondrial dysfunction and endoplasmic reticulum stress in calf hepatocytes are associated with fatty acid-induced ORAI calcium release-activated calcium modulator 1 signaling

The store-operated Ca²⁺ entry (SOCE) moiety ORAI calcium release-activated calcium modulator 1 (ORAI1) located in the endoplasmic reticulum (ER) participates in key cellular functions such as protein folding, transport, and secretion, and lipid metabolism. We used an in vitro approach to test whether exogenous fatty acids alter ORAI1 signaling and to explore potential consequences on mitochondrial dysfunction and ER stress. First, hepatocytes isolated from 4 healthy female calves (1 d old, 40-50 kg) were challenged with a 1.2 mM mixture of oleic, linoleic, palmitic, stearic, and palmitoleic acids for 0.5, 1, 3, 6, 9, and 12 h to measure oxidative stress [intracellular reduced glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), and hydrogen peroxide] and ER stress (protein abundance of PERK, IRE, ATF6, and GRP78). Concentrations of GSH and SOD decreased at 0.5 h, and MDA and hydrogen peroxide increased at 1 h; ER stress proteins increased at 6 h. To determine whether ER stress was caused by oxidative stress, primary calf hepatocytes were treated with the same 1.2 mM fatty acid mix or the reactive oxygen species (ROS) inhibitor N-acetylcysteine (NAC) for 6 h. We found that NAC prevented an increase in ER stress protein abundance. Next, the role of ORAI1 on ER stress was measured by transfecting hepatocytes with small interfering (si)ORAI1 or the ORAI1 inhibitor BTP2, followed by a challenge with 1.2 mM fatty acids for 3 h. Without inhibiting ORAI1, exogenous fatty acids upregulated ORAI1 mRNA and protein abundance, oxidative stress, ER stress proteins, and protein abundance of marker indicators of an opened mitochondrial permeability transition pore (mPTP). Inhibition with BPT2 or silencing via siORAI1 abrogated oxidative stress, including increased GSH concentration and SOD activity, decreased MDA, hydrogen peroxide, and ROS concentration; ER stress protein abundance was downregulated, and mitochondrial function was restored. Last, changes in markers of mPTP opening were evaluated by culturing hepatocytes for 6 h with the sarcoendoplasmic Ca²⁺ ATPase inhibitor thapsigargin or the calcium ionophore ionomycin. We detected an increase in VDAC1, CLPP, and CypD protein abundance, all of which indicated opening of the mPTP. Overall, data from these in vitro studies suggest that ORAI1 mediates ER stress induced by high concentrations of fatty acids, in part through alleviating mitochondrial dysfunction caused by oxidative stress.

Metabolic Profiling of Plasma in Different Calving Body Condition Score Cows Using an Untargeted Liquid Chromatography-Mass Spectrometry Metabolomics Approach

This study was undertaken to identify metabolite differences in plasma of dairy cows with a normal or high calving body condition score (CBCS), using untargeted liquid chromatography-mass spectrometry (LC-MS) metabolomics. Sixteen multiparous dairy cows were assigned to one of two groups based on CBCS (0 to 5 scale): Normal group (NBCS, 3.25 ≤ BCS ≤ 3.5, n = 8), and high BCS group (HBCS, BCS ≥ 4, n = 8). Plasma samples were collected for metabolomics analysis and evaluation of biomarkers of lipid metabolism (nonesterified fatty acid (NEFA) and β-hydroxybutyrate (BHB)), and cytokines (leptin, adiponectin, tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6)). A total of 23 differential metabolites were identified, and functional analyses were performed using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Among these metabolites, the concentrations of six lysophosphatidylcholines and one phosphatidylethanolamine, were lower in the HBCS group than in the NBCS group (p < 0.01). Furthermore, these metabolites were involved in these four pathways, among others: glycerophospholipid metabolism, retrograde endocannabinoid signaling, autophagy, and glycosylphosphatidylinositol (GPI)-anchor biosynthesis (p < 0.05). In addition, plasma concentrations of leptin (p = 0.06) and TNF-α (p = 0.08) tended to be greater while adiponectin (p = 0.09) lower in HBCS cows than in NBCS cows. The concentrations of NEFA, BHB, or IL-6 did not differ between NBCS and HBCS groups. More importantly, based on the results of the Spearman's correlation analysis, the seven important metabolites were negatively correlated with indices of lipid metabolisms, proinflammatory cytokines, and leptin, but positively correlated with adiponectin. These results demonstrate that CBCS has a measurable impact on the plasma metabolic profile, even when NEFA and BHB are not different. In addition, the identified differential metabolites were significantly correlated to lipid metabolism and inflammation in the over-conditioned fresh cows, which are expected to render a metabolic basis for the diseases associated with over-conditioned dry cows.

Protein acetylation in mitochondria plays critical functions in the pathogenesis of fatty liver disease

BACKGROUND

Fatty liver is a high incidence of perinatal disease in dairy cows caused by negative energy balance, which seriously threatens the postpartum health and milk production. It has been reported that lysine acetylation plays an important role in substance and energy metabolism. Predictably, most metabolic processes in the liver, as a vital metabolic organ, are subjected to acetylation. Comparative acetylome study were used to quantify the hepatic tissues from the severe fatty liver group and normal group. Combined with bioinformatics analysis, this study provides new insights for the role of acetylation modification in fatty liver disease of dairy cows.

RESULTS

We identified 1841 differential acetylation sites on 665 proteins. Among of them, 1072 sites on 393 proteins were quantified. Functional enrichment analysis shows that higher acetylated proteins are significantly enriched in energy metabolic pathways, while lower acetylated proteins are significantly enriched in pathways related to immune response, such as drug metabolism and cancer. Among significantly acetylated proteins, many mitochondrial proteins were identified to be interacting with multiple proteins and involving in lipid metabolism. Furthermore, this study identified potential important proteins, such as HADHA, ACAT1, and EHHADH, which may be important regulatory factors through modification of acetylation in the development of fatty liver disease in dairy cows and possible therapeutic targets for NAFLD in human beings.

CONCLUSION

This study provided a comprehensive acetylome profile of fatty liver of dairy cows, and revealed important biological pathways associated with protein acetylation occurred in mitochondria, which were involved in the regulation of the pathogenesis of fatty liver disease. Furthermore, potential important proteins, such as HADHA, ACAT1, EHHADH, were predicted to be essential regulators during the pathogenesis of fatty liver disease. The work would contribute to the understanding the pathogenesis of NAFLD, and inspire in the development of new therapeutic strategies for NAFLD.

Effects of supplementation of green tea extract on the milk performance of peripartal dairy cows and the expression of stress response genes in the liver

Background

We hypothesised that supplementation of green tea extract (GTE) in dairy cows during the transition period can attenuate proinflammatory conditions and prevent endoplasmic reticulum (ER) stress in the liver of these cows. Thirty Holstein cows with an average parity of 3.06 (± 1.31, SD) were divided into a control group and a group that received a daily amount of 10 g of GTE from d 7 before the calving day and a daily amount of 20 g of GTE from the day of calving until d 7 of lactation.

Results

Cows supplemented with GTE did not show differences in energy intake or milk yield in weeks 2–7 of lactation. However, these cows had a lower milk fat concentration and a lower energy corrected milk yield than the control cows and showed a trend of improved energy balance. The relative mRNA concentrations of proinflammatory genes, genes involved in the acute phase reaction and antioxidant genes in the liver in weeks 1, 4 and 7 of lactation were not different between the two groups of cows. The concentrations of α-tocopherol and the Trolox equivalent antioxidant capacity in plasma were not different between the two groups. However, the group supplemented with GTE showed significant reductions of some genes of the unfolded protein response (UPR) in week 1 and a trend of lower liver triacylglycerol (TAG) concentrations in the liver compared to the control group.

Conclusions

This study shows that supplementation of GTE in dairy cows lowers the fat concentration in the milk but overall has no effect on the expression of inflammatory genes and the antioxidative status in dairy cows during early lactation. The finding of reduced mRNA levels of genes involved in the UPR at week 1, however, supports other results showing that supplementation of polyphenols could prevent the development of ER stress in the liver of cows during early lactation. The finding of a tendency towards a reduced TAG concentration in the liver of cows supplemented with GTE might be due to an improved energy balance in these cows.

Postpartum supplementation with fermented ammoniated condensed whey altered nutrient partitioning to support hepatic metabolism

Our previously published paper demonstrated that fermented ammoniated condensed whey (FACW) supplementation improved feed efficiency and metabolic profile in postpartum dairy cows. The objective of this study was to further explore the effects of FACW supplementation on liver triglyceride content, hepatic gene expression and protein abundance, and plasma biomarkers related to liver function, inflammation, and damage. Individually fed multiparous Holstein cows were blocked by calving date and randomly assigned to postpartum (1 to 45 d in milk, DIM) isonitrogenous treatments: control diet (n = 20) or diet supplemented with FACW (2.9% dry matter of diet as GlucoBoost; Fermented Nutrition, Luxemburg, WI, replacing soybean meal; n = 19). Liver biopsies were performed at 14 and 28 DIM for analysis of mRNA expression, protein abundance, and liver triglyceride content. There was marginal evidence for a reduction in liver triglyceride content at 14 DIM in FACW-supplemented cows compared with the control group. Cows supplemented with FACW had greater mRNA expression of glucose-6-phosphatase at 14 DIM relative to control. Supplementation with FACW increased mRNA expression of pyruvate carboxylase (PC), but did not alter cytosolic phosphoenolpyruvate carboxykinase (PCK1), resulting in a 2.4-fold greater PC:PCK1 ratio for FACW-supplemented cows compared with control. There was no evidence for a FACW effect on mRNA expression of propionyl-CoA carboxylase nor on mRNA expression or protein abundance of lactate dehydrogenase A or B. Cows supplemented with FACW had lower plasma urea nitrogen compared with control. Plasma l-lactate was greater for FACW-supplemented cows compared with control at 2 h before feeding time at 21 DIM. There was no evidence for altered expression of IL1B or IL10, or blood biomarkers related to liver function and damage. Greater glucose-6-phosphatase and PC gene expression, together with greater blood glucose and similar milk lactose output, suggests that FACW increased the supply of glucose precursors, resulting in greater gluconeogenesis between 3 and 14 DIM. Greater hepatic PC:PCK1 ratio, together with previously reported decreased plasma β-hydroxybutyrate and the marginal evidence for lower liver triglyceride content at 14 DIM, suggests greater hepatic capacity for complete oxidation of fatty acids in FACW-supplemented cows compared with control. Overall, improvements in metabolite profile and feed efficiency observed with postpartum supplementation of FACW may be attributed to increased gluconeogenic and anaplerotic precursors, most likely propionate, due to modulated rumen fermentation.

Sirtuin 3 improves fatty acid metabolism in response to high nonesterified fatty acids in calf hepatocytes by modulating gene expression

Sirtuin 3 (SIRT3), a mitochondrial deacetylase, is a key regulator of energy metabolism in the liver. In nonruminants, the hepatic abundance of SIRT3 is decreased in individuals with nonalcoholic fatty liver diseases, and recovery of SIRT3 alleviates hepatic triacylglycerol (TG) deposition. However, the level of SIRT3 expression and its effects on lipid metabolism in dairy cows have not been characterized. Here we studied the hepatic expression of SIRT3 in cows with fatty liver and the role of SIRT3 in fatty acid metabolism in bovine hepatocytes. This in vivo study involved 10 healthy cows and 10 cows with fatty liver, from which we collected samples of liver tissue and blood. Primary hepatocytes were isolated from Holstein calves and treated with 0, 0.5, or 1.0 mM nonesterified fatty acids (NEFA) for 24 h or transinfected with SIRT3 overexpression adenovirus (Ad-SIRT3)/SIRT3-short interfering (si)RNA for 48 h. Cows with fatty liver displayed lower serum glucose concentrations but higher serum NEFA and β-hydroxybutyrate concentrations relative to healthy cows. Cows with fatty liver also had significant lower mRNA and protein abundance of hepatic SIRT3. Incubation of primary hepatocytes with NEFA reduced SIRT3 abundance in primary hepatocytes in a dose-dependent manner. Fatty acid (1 mM) treatment also markedly increased the abundance of acetyl-CoA carboxylase 1 (ACC1) and fatty acid synthase (FAS) but significantly decreased the abundance of carnitine palmitoyltransferase I (CPT1A), carnitine palmitoyltransferase II (CPT2), and acyl-CoA oxidase (ACO). Knockdown of SIRT3 by SIRT3-siRNA downregulated the mRNA abundance of CPT1A, CPT2, and ACO. In contrast, overexpression of SIRT3 by Ad-SIRT3 upregulated the mRNA abundance of CPT1A, CPT2, and ACO; downregulated the mRNA abundance of ACC1 and FAS; and consequently, decreased intracellular TG concentrations. Overexpression of SIRT3 ameliorated exogenous NEFA-induced TG accumulation by downregulating the abundance of ACC1 and FAS and upregulating the abundance of CPT1A, CPT2, and ACO in calf hepatocytes. Our data demonstrated that cows with fatty liver had lower hepatic SIRT3 contents, and an increase in SIRT3 abundance by overexpression mitigated TG deposition by modulating the expression of lipid metabolism genes in bovine hepatocytes. These data suggest a possible role of SIRT3 as a therapeutic target for fatty liver disease prevention in periparturient dairy cattle.

Short communication: Enhanced autophagy activity in liver tissue of dairy cows with mild fatty liver

During the transition period, dairy cows are challenged by increased energy demands and decreased dry matter intake, which can induce a variety of metabolic disorders, especially fatty liver. Dairy cows suffering from mild or moderate fatty liver in this period show no distinct clinical symptoms, indicating the occurrence of adaptive processes. The process of autophagy (an adaptive response) leads to degradation of intracellular components to generate energy and maintains cellular homeostasis during negative nutrient status. Whether autophagy is involved in metabolic adaptations of the pathological course of mild fatty liver is unclear. Thus, the aim of this study was to determine hepatic autophagy status in dairy cows with mild fatty liver. Liver samples were collected from healthy cows (n = 15), defined as having hepatic triglyceride (TG) content <1% on a wet weight basis, and cows with mild fatty liver (n = 15), defined as having hepatic TG content between 1 and 5%. The abundance of the ubiquitinated proteins, microtubule-associated protein 1 light chain 3 (MAP1LC3, also called LC3-II) and sequestosome-1 (SQSTM1, also called p62) was lower, whereas the mRNA abundance of MAP1LC3 and SQSTM1 was greater in cows with mild fatty liver. The hepatic mRNA abundance of autophagy-related (ATG) genes ATG5 and ATG7 was greater in response to fatty liver. However, the protein abundance of ATG5 and ATG7 did not differ between healthy and mild fatty liver cows. Together, these data indicate that the formation and degradation of autophagosomes is enhanced in the liver of cows with mild fatty liver. Besides, these results are conducive to define the adaptation mechanisms of dairy cows during the transition period.