An updated method for the isolation and culture of primary calf hepatocytes

Strontium regulating lipid metabolism of bovine hepatocytes via SIRT1/SREBPs pathway

Periparturient dairy cows are susceptible to negative energy balance (NEB), which triggers excessive adipose mobilization, leading to elevated plasma non-esterified fatty acids (NEFA) and hepatic lipid accumulation. While strontium (Sr) has shown metabolic regulatory potential, its role in hepatic lipid homeostasis remains unclear. Using an NEFA-induced lipid accumulation model in bovine hepatocytes, we demonstrated that Sr (5-20 μM) significantly reduced intracellular triglyceride (TG) and total cholesterol (TC) levels. Further mechanistic studies revealed that Sr enhances SIRT1 expression and suppresses the expression and nuclear translocation of SREBP-1C/SREBP2, thereby downregulating downstream lipogenic enzymes including ACC, FASN, SCD1, and HMGCR. Molecular docking indicated that Sr²⁺ binds with high affinity to Asp-481/483 of SIRT1, while SIRT1 inhibition with EX-527 abolished Sr-mediated lipid-lowering effects. Additionally, Sr promoted PPARα nuclear translocation to enhance β-oxidation and upregulated LDLR expression to facilitate lipid efflux. This study elucidated the multi-target molecular mechanism of Sr alleviating lipid metabolism disorders in bovine hepatocytes through the SIRT1/SREBPs pathway, providing a theoretical foundation for the application of Sr in preventing metabolic diseases in dairy cows.

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.

Peroxisome Proliferator-Activated Receptor Activation in Precision-Cut Bovine Liver Slices Reveals Novel Putative PPAR Targets in Periparturient Dairy Cows

Metabolic challenges experienced by dairy cows during the transition between pregnancy and lactation (also known as peripartum), are of considerable interest from a nutrigenomic perspective. The mobilization of large amounts of non-esterified fatty acids (NEFA) leads to an increase in NEFA uptake in the liver, the excess of which can cause hepatic accumulation of lipids and ultimately fatty liver. Interestingly, peripartum NEFA activate the Peroxisome Proliferator-activated Receptor (PPAR), a transcriptional regulator with known nutrigenomic properties. The study of PPAR activation in the liver of periparturient dairy cows is thus crucial; however, current in vitro models of the bovine liver are inadequate, and the isolation of primary hepatocytes is time consuming, resource intensive, and prone to errors, with the resulting cells losing characteristic phenotypical traits within hours. The objective of the current study was to evaluate the use of precision-cut liver slices (PCLS) from liver biopsies as a model for PPAR activation in periparturient dairy cows. Three primiparous Jersey cows were enrolled in the experiment, and PCLS from each were prepared prepartum (−8.0 ± 3.6 DIM) and postpartum (+7.7± 1.2 DIM) and treated independently with a variety of PPAR agonists and antagonists: the PPARα agonist WY-14643 and antagonist GW-6471; the PPARδ agonist GW-50156 and antagonist GSK-3787; and the PPARγ agonist rosiglitazone and antagonist GW-9662. Gene expression was assayed through RT-qPCR and RNAseq, and intracellular triacylglycerol (TAG) concentration was measured. PCLS obtained from postpartum cows and treated with a PPARγ agonist displayed upregulation of ACADVL and LIPC while those treated with PPARδ agonist had increased expression of LIPC, PPARD, and PDK4. In PCLS from prepartum cows, transcription of LIPC was increased by all PPAR agonists and NEFA. TAG concentration tended to be larger in tissue slices treated with PPARδ agonist compared to CTR. Use of PPAR isotype-specific antagonists in PCLS cultivated in autologous blood serum failed to decrease expression of PPAR targets, except for PDK4, which was confirmed to be a PPARδ target. Transcriptome sequencing revealed considerable differences in response to PPAR agonists at a false discovery rate-adjusted p-value of 0.2, with the most notable effects exerted by the PPARδ and PPARγ agonists. Differentially expressed genes were mainly related to pathways involved with lipid metabolism and the immune response. Among differentially expressed genes, a subset of 91 genes were identified as novel putative PPAR targets in the bovine liver, by cross-referencing our results with a publicly available dataset of predicted PPAR target genes, and supplementing our findings with prior literature. Our results provide important insights on the use of PCLS as a model for assaying PPAR activation in the periparturient dairy cow.

An evaluation of maternal serum dynamic thiol-disulfide homeostasis and ischemia modified albumin changes in pregnant women with COVID-19

Objective:

It is thought that oxidative stress, free radicals, reactive oxygen species and reactive nitrogen species affect the pathophysiology of coronavirus disease-2019 (COVID-19). This study aimed to evaluate the oxidative status in pregnant patients with COVID-19 infection according to the changes seen in the levels of maternal serum thiol-disulfide and ischemia-modified albumin (IMA).

Materials and Methods:

A study group was formed of 40 pregnant women with confirmed COVID-19 infection (study group) and a control group of 40 healthy pregnant women with no risk factors determined. In this prospective, case-controlled study, analyses were made of the maternal serum native thiol, total thiol, disulfide, IMA, and disulfide/native thiol concentrations.

Results:

The maternal serum native thiol and total thiol concentrations in the study group were determined to be statistically significantly lower (p=0.007 and p=0.006, respectively), and the disulfide/native thiol ratio was higher but not to a level of statistical significance (p=0.473). There was no difference between the two groups regarding IMA levels (p=0.731).

Conclusion:

The thiol-disulfide balance was seen to shift in the oxidant direction in pregnancies with COVID-19, which might support the view that ischemic processes play a role in the etiopathogenesis of this novel disease.

Propionate alleviates fatty acid-induced mitochondrial dysfunction, oxidative stress, and apoptosis by upregulating PPARG coactivator 1 alpha in hepatocytes

Reduced feed intake during the transition period renders cows unable to meet their energy needs for maintenance and lactation, leading to a state of negative energy balance. Severe negative energy balance initiates fat mobilization and increases circulating levels of free fatty acids (FFA), which could induce hepatic mitochondrial dysfunction, oxidative stress, and apoptosis. Enhancing the hepatic supply of propionate (major gluconeogenic substrate) is a feasible preventive and therapeutic strategy to alleviate hepatic metabolic disorders during the transition period. Whether propionate supply affects pathways beyond gluconeogenesis during high FFA loads is not well known. Thus, the objective of this study was to investigate whether propionate supply could protect calf hepatocytes from FFA-induced mitochondrial dysfunction, oxidative stress, and apoptosis. Hepatocytes were isolated from 5 healthy calves (1 d old, female, 30-40 kg, fasting) and treated with various concentrations of propionate (0, 1, 2, and 4 mM propionate for 12 h) or for different times (2 mM propionate for 0, 3, 6, 12 and 24 h). Furthermore, hepatocytes were treated with propionate (2 mM), fatty acids (1.2 mM), or both for 12 h with or without 50 nM PGC-1α (peroxisome proliferator-activated receptor-gamma coactivator-1 alpha) small interfering RNA. Compared with the control group, protein abundance of PGC-1α was greater with 2 and 4 mM propionate treatment groups. Furthermore, protein abundance of TFAM (mitochondrial function marker mitochondrial transcription factor A) and VDAC1 (voltage-dependent anion channel 1) was greater with 1, 2, and 4 mM propionate, and COX4 (cyclooxygenase 4) was greater with 2 and 4 mM propionate groups. In addition, propionate supply led to an increase in protein abundance of PGC-1α, TFAM, VDAC1, and COX4 over time. Flow cytometry revealed that propionate treatment increased the number of mitochondria in hepatocytes compared with control group, but inhibition of PGC-1α abolished these beneficial effects. The lower protein abundance of PGC-1α, TFAM, COX4, and VDAC1 and activities of superoxide dismutase and glutathione peroxidase, along with greater production of reactive oxygen species, malondialdehyde, and apoptosis rate in response to treatment with high concentrations of FFA suggested an impairment of mitochondrial function and induction of oxidative stress and apoptosis. In contrast, propionate treatment hastened these negative effects. Knockdown of PGC-1α by small interfering RNA impeded the beneficial role of propionate on FFA-induced mitochondrial dysfunction, oxidative stress, and apoptosis. Overall, results demonstrated that propionate supply alleviates mitochondrial dysfunction, oxidative stress, and apoptosis in FFA-treated calf hepatocytes by upregulating PGC-1α. Together, the data suggest that PGC-1α may be a promising target for preventing or improving hepatic function during periods such as the transition into lactation where the FFA load on the liver increases.

NEFAs Influence the Inflammatory and Insulin Signaling Pathways Through TLR4 in Primary Calf Hepatocytes in vitro

Transition dairy cows are often in a state of negative energy balance because of decreased dry matter intake and increased energy requirements, initiating lipid mobilization and leading to high serum β-hydroxybutyrate (BHBA) and non-esterified fatty acid (NEFAs) levels, which can induce ketosis and fatty liver in dairy cows. Inflammation and insulin resistance are also common diseases in the perinatal period of dairy cows. What is the relationship between negative energy balance, insulin resistance and inflammation in dairy cows? To study the role of non-esterified fatty acids in the nuclear factor kappa beta (NF-κB) inflammatory and insulin signaling pathways through Toll-like receptor 4 (TLR4), we cultured primary calf hepatocytes and added different concentrations of NEFAs to assess the mRNA and protein levels of inflammatory and insulin signaling pathways. Our experiments indicated that NEFAs could activate the NF-κB inflammatory signaling pathway and influence insulin resistance through TLR4. However, an inhibitor of TLR4 alleviated the inhibitory effects of NEFAs on the insulin pathway. In conclusion, all of these results indicate that high-dose NEFAs (2.4 mM) can activate the TLR4/NF-κB inflammatory signaling pathway and reduce the sensitivity of the insulin pathway through the TLR4/PI3K/AKT metabolic axis.

Sirtuin 1 is involved in oleic acid-induced calf hepatocyte steatosis via alterations in lipid metabolism-related proteins

Sirtuin 1 (SIRT1), an NAD-dependent protein deacetylase, plays a central role in the control of lipid metabolism in nonruminants. However, the role of SIRT1 in hepatic lipid metabolism in dairy cows with fatty liver is not well known. Thus, we used isolated primary bovine hepatocytes to determine the role of SIRT1 in protecting cells against oleic acid (OA)-induced steatosis. Recombinant adenoviruses to overexpress (AD-GFP-SIRT1-E) or knockdown (AD-GFP-SIRT1-N) SIRT1 were used for transduction of hepatocytes. Calf hepatocytes isolated from five female calves (1 d old, 30 to 40 kg) were used to determine both time required and the lowest dose of OA that could induce triacylglycerol (TAG) accumulation. Analyses indicated that 0.25 mM OA for 24 h was suitable to induce TAG accumulation. In addition, OA not only led to an increase in TAG, but also upregulated mRNA and protein abundance of sterol regulatory element-binding transcription factor 1 (SREBF1) and downregulated SIRT1 and peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PPARGC1A). Thus, these in vitro conditions were deemed optimal for subsequent experiments. Calf hepatocytes were cultured and incubated with OA (0.25 mM) for 24 h, followed by adenoviral AD-GFP-SIRT1-E or AD-GFP-SIRT1-N transduction for 48 h. Overexpression of SIRT1 led to greater protein and mRNA abundance of SIRT1 along with fatty acid oxidation-related genes including PPARGC1A, peroxisome proliferator-activated receptor alpha (PPARA), retinoid X receptor α (RXRA), and ratio of phospho-acetyl-CoA carboxylase alpha (p-ACACA)/total acetyl-CoA carboxylase alpha (ACACA). In contrast, it resulted in lower protein and mRNA abundance of genes related to lipid synthesis including SREBF1, fatty acid synthase (FASN), apolipoprotein E (APOE), and low-density lipoprotein receptor (LDLR). The concentration of TAG decreased due to SIRT1 overexpression. In contrast, silencing SIRT1 led to lower protein and mRNA abundance of SIRT1, PPARGC1A, PPARA, RXRA, and greater protein and mRNA abundance of SREBF1, FASN, APOE, and LDLR. Further, those responses were accompanied by greater content of cellular TAG and total cholesterol (TC). Overall, data from these in vitro studies indicated that SIRT1 is involved in the regulation of lipid metabolism in calf hepatocytes subjected to an increase in the supply of OA. Thus, it is possible that alterations in SIRT1 abundance and activity in vivo contribute to development of fatty liver in dairy cows.

Angiopoietin-like protein 4 promotes very-low-density lipoprotein assembly and secretion in bovine hepatocytes in vitro

In dairy cows, fatty liver is one of the most common metabolic diseases that occurs during the periparturient period. Angiopoietin-like protein 4 (ANGPTL4) is a well-known downstream target of peroxisome proliferator-activated receptors (PPARs), which regulate the glucose and fatty acid metabolisms. The inhibition of lipoprotein lipase (LPL) activity interferes with the storage of triglycerides (TG) in adipocytes, which plays an essential role in lipid metabolism in rodents. However, it remains unclear whether ANGPTL4 is involved in the pathological process of fatty liver in dairy cows as a result of the regulation of the hepatocellular lipid transport system. This study intended to investigate the effect of ANGPTL4 on the very-low-density lipoprotein (VLDL) assembly and secretion in bovine hepatocytes. Bovine hepatocytes were isolated using a modified two-step perfusion and collagenase digestion process, and treated with different concentrations of ANGPTL4 (0, 4, 12, and 24 ng/ml) for 24 hr. The results showed that a high concentration of ANGPTL4 could significantly increase the extracellular concentration of VLDL while reducing the intracellular content of TG. Thus, it was confirmed that ANGPTL4 could promote the transport of TG in the form of VLDL by partially regulating the expression of related proteins in hepatocytes, thereby contributing to the partial adaptive regulation of lipid transport in dairy cows.

Undernutrition-induced lipid metabolism disorder triggers oxidative stress in maternal and fetal livers using a model of pregnant sheep

This study aimed to evaluate the oxidative status and antioxidant capacity in maternal and fetal livers upon undernutrition as well as the connection between oxidative stress and lipid metabolism disorder. Ten ewes, who were pregnant for 115 days, were restricted to a 30% level of ad libitum feed intake to develop an undernourished model, while another 10 pregnant ewes were fed normally as controls. Undernutrition induced severe lipid metabolism disorder and oxidative stress in blood, maternal liver, and fetal liver. RNA-sequencing data displayed that antioxidant capacity was changed and antioxidant genes were downregulated in maternal and fetal livers of the undernourished model. Non-esterified fatty acids (NEFAs) and beta-hydroxybutyrate (BHBA) levels showed a positive correlation with oxidative indices and negative correlation with the expression of antioxidant genes both in maternal and fetal livers. Primary hepatocytes experiments confirmed that both high levels of NEFAs and BHBA could elicit oxidative stress and decrease antioxidant capacity, and the peroxisome proliferator-activated receptor alpha (PPARA)/retinoid X receptor alpha (RXRA) signaling pathway played a vital role in enhancing antioxidant capacity and relieving oxidative stress. In conclusion, maternal undernutrition induced lipid metabolism disorder, which downregulated antioxidant genes, decreased antioxidant activity, and further triggered oxidative stress both in maternal and fetal livers. Activation of PPARA/RXRA signaling could enhance antioxidant capacity and mitigate oxidative stress. Our findings contribute to protecting the pregnant mother and her fetus from oxidative stress.

Identification of differentially expressed miRNAs on normal cell, fatty liver cell and processed cell by monoammonium glycyrrhizinate from cattle (Bos indicus) by deep sequencing approach

Cattle fatty liver has caused mass damage in milk production during the past few years. In our study, to identify different miRNAs involved in cell physiological regulation in fatty liver, we performed miRNA deep sequencing on a normal liver cell (S01), fatty liver cell (S02) and processed cell by monoammonium glycyrrhizinate (S03). As a result, a total of 15,277,462, 14,190,360 and 13,771,060 raw reads representing 13,904,074, 12,784,128 and 11,017,604 clean reads per library were obtained separately. Through bioinformatics analysis, a total of 511 known miRNAs were identified when they were aligned with the known animal miRNAs, and 197 novel miRNAs were predicted using mirDeep2 software. A total of 511 miRNAs including 101 known and 51 novel miRNAs were expressed significantly different. Additionally, expression levels of eight randomly selected miRNAs were confirmed using the stem-loop qPCR, and their expression profiles were consistent with the deep sequencing results. For better understanding the functions of miRNAs, a total of 14,231 targets were predicted. These predicted target genes were further analyzed by function annotation and enrichment pathways, the results showed that these targets of the identified miRNAs are involved in a broad range of physiological functions.

PPARA/RXRA signalling regulates the fate of hepatic non-esterified fatty acids in a sheep model of maternal undernutrition

Maternal undernutrition during late gestation accelerates body fat mobilization to provide more energy for foetal growth and development, which unbalances metabolic homeostasis and results in serious lipid metabolism disorder. However, detailed regulatory mechanisms are poorly understood. Here, a sheep model was used to explore the regulatory role of PPARA/RXRA signalling in hepatic lipid metabolism in undernutrition based on RNA sequencing and cell experiments. KOG function classification showed that lipid transport and metabolism was markedly altered in an undernourished model. In detail, when compared with the controls, fatty acid transport and oxidation and triglyceride metabolism were up-regulated in an undernourished model, while fatty acid synthesis, steroid synthesis, and phospholipid metabolism were down-regulated. Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis demonstrated that PPARA/RXRA signalling pathway was altered. Moreover, PPARA signalling associated genes were positively correlated with hepatic non-esterified fatty acid (NEFA) levels, while retinol metabolism associated genes were negatively correlated with blood beta-hydroxybutyric acid (BHBA) levels. Results of primary hepatocytes showed that NEFAs could activate PPARA signalling and facilitate fatty acid oxidation (FAO) and ketogenesis, while BHBA could inhibit RXRA signalling and repress FAO and ketogenesis. Excessively accumulated NEFAs in hepatocytes promoted triglyceride synthesis. Furthermore, activation of PPARA/RXRA signalling by WY14643 and 9-cis-retinoic acid could enhance FAO and ketogenesis and reduce NEFAs accumulation and esterification. Our findings elucidate the regulatory mechanisms of NEFAs and BHBA on lipid metabolism as well as the potential role of the PPARA/RXRA signalling pathway in hepatic lipid metabolism, which may contribute to exploring new strategies to maintain lipid metabolic homeostasis in human beings.

PTEN influences insulin and lipid metabolism in bovine hepatocytes in vitro

Dairy cows with fatty liver or ketosis display decreased insulin sensitivity and defects in the insulin receptor substrate (IRS)/PI3K/AKT signaling pathway. Phosphatase and tensin homolog (PTEN) is a well-known tumor suppressor and also a negative regulator of insulin signaling and peripheral insulin sensitivity. We investigated the hypothesis that PTEN may affect the insulin pathway-mediated hepatic glucose and lipid metabolism in dairy cows. Adenovirus vectors that over-express and silence PTEN were constructed, and then transfected into hepatocytes isolated from calves to investigate the effect of PTEN on PI3K/AKT signaling pathway. PTEN silencing increased the phosphorylation of AKT and the expression of PI3K but decreased the phosphorylation of IRS1, which increased the phosphorylation levels of glycogen synthase kinase-3β (GSK-3β) and expression of sterol regulatory element-binding protein-1c (SREBP-1c). Increased GSK-3β phosphorylation further up-regulated expression of the key enzymes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6-Pase) involved in gluconeogenesis. Furthermore, the expression of SREBP-1c target gene fatty acid synthase (FAS) also increased significantly. We further showed that PTEN over-expression could reverse the above results. PTEN negatively regulates the enzymes involved in hepatic gluconeogenesis and lipid synthesis, which suggests that PTEN may be a therapeutic target for ketosis and fatty liver in dairy cows.

High non-esterified fatty acid concentrations promote expression and secretion of fibroblast growth factor 21 in calf hepatocytes cultured in vitro

Negative energy balance is considered as the pathological basis of energy metabolic disorders in periparturient dairy cows. Serum non-esterified fatty acids (NEFA) are one of the most important indicators of energy balance status. Fibroblast growth factor 21 (FGF21) has been identified as a hepatokine involved in regulation of metabolic adaptations, such as promoting hepatic lipid oxidation and ketogenesis, during energy deprivation. However, the direct effects of NEFA on FGF21 expression and secretion in bovine hepatocytes are not entirely clear. The objective of this study was to investigate the effects of different NEFA concentrations on FGF21 expression and secretion in calf hepatocytes cultured in vitro. NEFA were added to the culture solution at final concentrations of 0.6, 1.2, 1.8 and 2.4 mmol/L. After 24 hr of continuous culture, FGF21 mRNA and protein expression levels in the hepatocytes were determined by real-time PCR and Western blot respectively. FGF21 secretion in the supernatant was determined by enzyme-linked immunosorbent assay (ELISA). The results showed that expression and secretion of FGF21 at 0.6 mmol/L NEFA-treated hepatocytes was higher than that of the control group (p < .05). The FGF21 expression and secretion were similar at 1.2, 1.8 and 2.4 mmol/L NEFA-treated hepatocytes and significantly higher than those observed for controls (p < .01). These data suggest that high concentrations of NEFA significantly promote FGF21 expression and secretion in bovine hepatocytes. In particular, this promotion occurs in a dose-dependent manner and may be involved in the pathological processes of energy metabolism disorders of dairy cows in the peripartum period.

High levels of acetoacetate and glucose increase expression of cytokines in bovine hepatocytes, through activation of the NF-κB signalling pathway

Elevated levels of blood interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumour necrosis factor–α (TNF–α) increase insulin resistance and result in inflammation. It is not clear whether elevated blood level of acetoacetate (ACAC) and decreased blood level of glucose, which are the predominant characteristics of clinical biochemistry in ketotic dairy cows, increase proinflammatory cytokines and subsequent inflammation. The objective of this study was to test the hypothesis that ACAC and glucose activate the NF-κB signalling pathway to regulate cytokines expression in bovine hepatocytes. Bovine hepatocytes were cultured with ACAC (0–4·8 mm) and glucose (0–5·55 mm) with or without NF-κB inhibitor PDTC for 24 h. The secretion and mRNA levels of cytokines were determined by enzyme-linked immunosorbent assay (ELISA) and real-time fluorescence quantitative polymerase chain reaction (qRT-PCR). The NF-κB signalling pathway activation was evaluated by western blotting. Results showed that the secretion and expression of IL-1β, IL-6 and TNF-α increased in an ACAC dose-dependent manner. Additionally, there was an increase in the secretion and mRNA expression of these three cytokines in glucose treatment group, which increased significantly when the glucose concentrations exceed 3·33 mm. Furthermore, both ACAC and glucose upregulated NF-κB p65 protein expression and IκBα phosphorylation levels. However, these effects were reduced by PDTC. These results demonstrate that elevated levels of ACAC and glucose increase the synthesis and expression of proinflammatory factors by activating NF-κB signalling pathway in hepatocytes, which may contribute to inflammation injury in ketotic dairy cows.

BHBA influences bovine hepatic lipid metabolism via AMPK signaling pathway

β-hydroxybutyric acid (BHBA), an important metabolite in β-oxidation, is involved in the development of ketosis in dairy cows. It is known that AMP-activated protein kinase (AMPK) signaling pathway plays an important role in the regulation of lipid metabolism in hepatocytes. In the present study, bovine hepatocytes were treated with BHBA at variable concontrations and Compound C (Cpd C, an AMPK inhibitor) to investigate the effects of BHBA on the AMPK signaling pathway. The results showed that when the concentration of BHBA reached 1.2 mM, the AMPK signaling pathway was activated and the expression of sterol regulatory element binding protein-1c (SREBP-1c) as well as its target genes were significantly decreased. And these decreases were blocked by Cpd C. The binding activity and nucleus translocation of SREBP-1c showed a similar trend. The expression of peroxisome proliferator activated receptor-α (PPARα), carbohydrates response element binding protein (ChREBP) and their target genes were significantly increased while they were negatively suppressed by the Cpd C. The content of triglyceride (TG) had no obviously change in the BHBA and Cpd C-treated groups. These results indicate that BHBA can activate AMPK signaling pathway and regulate lipid synthesis and lipid oxidation genes of AMPK but showed no effect on TG in bovine hepatocytes.

Effects of insulin-like growth factor-1 on the assembly and secretion of very low-density lipoproteins in cow hepatocytes in vitro

Fatty liver is a major metabolic disorder of dairy cows. One important reason is that hepatic very low-density lipoproteins (VLDL) assembly was significant decreased in dairy cows with fatty liver. In addition, the impairment of insulin-like growth factor (IGF)-1 synthesis was involved in the development of fatty liver. Therefore, the objective of this study was to investigate the effects of IGF-1 on the VLDL assembly in cow hepatocytes. In this study, cow hepatocytes were cultured and then transfected with Ad-GFP-IGF-1 (inhibited the IGF-1 expression) and Ad-GFP (negative control), and treated with different concentrations of IGF-1, respectively. The results showed that IGF-1 increased the mRNA abundance of apolipoprotein B100 (ApoB100), apolipoprotein E (ApoE), microsomal triglyceride transfer protein (MTTP), and low-density lipoprotein receptor (LDLR) and then increased the VLDL assembly in cow hepatocytes. Nevertheless, impairment of IGF-1 expression by Ad-GFP-IGF-1 could inhibit above genes expression and VLDL assembly in hepatocytes. Taken together, these results indicate that IGF-1 increases the VLDL assembly and impairment of IGF-1 expression decreases the VLDL assembly in cow hepatocytes.

NEFAs activate the oxidative stress-mediated NF-κB signaling pathway to induce inflammatory response in calf hepatocytes

Non-esterified fatty acids (NEFAs) are important induction factors of inflammatory responses in some metabolic diseases. High plasma levels of NEFAs and oxidative stress exist in the dairy cows with ketosis. The aim of this study was to investigate whether high levels of NEFAs can induce inflammatory response and the specific molecular mechanism in the hepatocytes of dairy cow. In vitro, primary cultured bovine hepatocytes were treated with different concentrations of NEFAs, PDTC (an NF-κB inhibitor) and NAC (an antioxidant). NEFAs significantly activated NF-κB pathway. Activated NF-κB upregulated the release of pro-inflammatory cytokines, thereby inducing inflammatory response in bovine hepatocytes. When PDTC was added, activation of NF-κB-mediated inflammatory response induced by NEFAs was inhibited. NEFAs treatment results in the overproduction of the markers of oxidative stress, reactive oxygen species (ROS) and malondialdehyde (MDA), which were ameliorated by NAC treatment. These increased ROS and MDA were caused by decreasing activity of antioxidant system, including glutathione peroxidase, superoxide dismutase and catalase, in bovine hepatocytes treated with NEFAs. NAC also ameliorated NEFAs-mediated NF-κB activation and the release of pro-inflammatory cytokines. These results indicate that high concentrations of NEFAs can induce cattle hepatocytes inflammatory response through activating the oxidative stress-mediated NF-κB signaling pathway.

Non-esterified fatty acids activate the AMP-activated protein kinase signaling pathway to regulate lipid metabolism in bovine hepatocytes

Non-esterified fatty acids (NEFAs) act as signaling molecules involved in regulating genes expression to modulate lipid metabolism. However, the regulation mechanism of NEFAs on lipid metabolism in dairy cows is unclear. The AMP-activated protein kinase (AMPK) signaling pathway plays a key role in regulating hepatic lipid metabolism. In vitro, bovine hepatocytes were cultured and treated with different concentrations of NEFAs and AMPKα inhibitors (BML-275). NEFAs increased AMPKα phosphorylation through up-regulating the protein levels of liver kinase B1. Activated AMPKα increased the expression and transcriptional activity of peroxisome proliferator-activated receptor α (PPARα). NEFAs also directly activate the PPARα independent of AMPKα. Activated PPARα increased the lipolytic genes expression to increase lipid oxidation. Furthermore, activated AMPKα inhibited the expression and transcriptional activity of the sterol regulatory element-binding protein 1c and carbohydrate responsive element-binding protein, which reduced the expression of lipogenic genes, thereby decreasing lipid synthesis. Activated AMPKα phosphorylated and inhibited acetyl-CoA carboxylase and increased carnitine palmitoyltransferase-1 activity, which increased lipid oxidation. Consequently, the triglyceride content in the NEFAs-treated hepatocytes was significantly decreased. These results indicate that NEFAs activate the AMPKα signaling pathway to increase lipid oxidation and decrease lipid synthesis in hepatocytes, which in turn, generates more ATP to relieve the negative energy balance in transition dairy cows.

Non-esterified fatty acids activate the ROS-p38-p53/Nrf2 signaling pathway to induce bovine hepatocyte apoptosis in vitro

A high plasma concentration of non-esterified fatty acids (NEFAs) is an important pathogenic factor that leads to ketosis and fatty liver in dairy cows. NEFAs may be associated with oxidative stress in dairy cows with ketosis or fatty liver and the subsequent induction of hepatocyte damage. However, the molecular mechanism of NEFAs-induced oxidative stress and whether NEFAs cause apoptosis of hepatocytes are unclear. Therefore, the aim of this study was to investigate the molecular mechanism of NEFAs-induced oxidative liver damage in bovine hepatocytes. The results showed that NEFAs increased oxidative stress, resulting in p38 phosphorylation. High activated p38 increased the expression, nuclear localization and transcriptional activity of p53 and decreased the nuclear localization and transcriptional activity of Nrf2 in bovine hepatocytes treated with high concentrations of NEFAs. High concentrations of NEFAs also promoted the apoptosis of bovine hepatocytes. Both N-acetyl-L-cysteine (NAC) and glucose (GLU) could attenuate the NEFA-induced apoptotic damage. These results indicate that NEFAs activate the ROS-p38-p53/Nrf2 signaling pathway to induce apoptotic damage in bovine hepatocytes.

Adiponectin activates the AMPK signaling pathway to regulate lipid metabolism in bovine hepatocytes

Adiponectin (Ad) plays a crucial role in hepatic lipid metabolism. However, the regulating mechanism of hepatic lipid metabolism by Ad in dairy cows is unclear. Hepatocytes from a newborn female calf were cultured in vitro and treated with different concentrations of Ad and BML-275 (an AMPKα inhibitor). The results showed that Ad significantly increased the expression of two Ad receptors. Furthermore, the phosphorylation and activity of AMPKα, as well as the expression levels and transcriptional activity of peroxisome proliferator activated receptor-α (PPARα) and its target genes involved in lipid oxidation, showed a corresponding trend of upregulation. However, the expression levels and transcriptional activity of sterol regulatory element binding protein 1c (SREBP-1c) and carbohydrate-responsive element-binding protein (ChREBP) decreased in a similar manner. When BML-275 was added, the p-AMPKα level as well as the expression and activity of PPARα and its target genes were significantly decreased. However, the expression levels of SREBP-1c, ChREBP and their target genes showed a trend of upregulation. Furthermore, the triglyceride (TG) content was significantly decreased in the Ad-treated groups. These results indicate that Ad activates the AMPK signaling pathway and mediates lipid metabolism in bovine hepatocytes cultured in vitro by promoting lipid oxidation, suppressing lipid synthesis and reducing hepatic lipid accumulation.

1,1-Bis (3'-indolyl)-1-(p-substitutedphenyl)methane compounds inhibit lung cancer cell and tumor growth in a metastasis model

1,1-Bis(3-indolyl)-1-(p-substitutedphenyl)methane (C-DIM) compounds exhibit remarkable antitumor activity with low toxicity in various cancer cells including lung tumors. Two C-DIM analogs, DIM-C-pPhOCH3 (C-DIM-5) and DIM-C-pPhOH (C-DIM-8) while acting differentially on the orphan nuclear receptor, TR3/Nur77 inhibited cell cycle progression from G0/G1 to S-phase and induced apoptosis in A549 cells. Combinations of docetaxel (doc) with C-DIM-5 or C-DIM-8 showed synergistic anticancer activity in vitro and these results were consistent with their enhanced antitumor activities invivo. Respirable aqueous formulations of C-DIM-5 (mass median aerodynamic diameter of 1.92±0.22μm and geometric standard deviation of 2.31±0.12) and C-DIM-8 (mass median aerodynamic diameter of 1.84±0.31μm and geometric standard deviation of 2.11±0.15) were successfully delivered by inhalation to athymic nude mice bearing A549 cells as metastatic tumors. This resulted in significant (p<0.05) lung tumor regression and an overall reduction in tumor burden. Analysis of lung tumors from mice treated with inhalational formulations of C-DIM-5 and C-DIM-8 showed decreased mRNA and protein expression of mediators of tumor initiation, metastasis, and angiogenesis including MMP2, MMP9, c-Myc, β-catenin, c-Met, c-Myc, and EGFR. Microvessel density assessment of lung tissue sections showed significant reduction (p<0.05) in angiogenesis and metastasis as evidenced by decreased distribution of immunohistochemical staining of VEGF, and CD31. Our studies demonstrate both C-DIM-5 and C-DIM-8 have similar anticancer profiles in treating metastatic lung cancer and possibly work as TR3 inactivators.

Effect of leptin on the gluconeogenesis in calf hepatocytes cultured in vitro

We have investigated the effect of leptin on gluconeogenesis in the liver. Hepatocytes were cultured and treated with 0, 2.5, 5, 10, 50, 100 ng/mL of leptin in groups I, II, III, IV, V, and VI, respectively. mRNA expression and enzyme activity of pyruvate carboxylase and phosphoenolpyruvate carboxykinase were determined by real-time fluorescence quantitative RT-PCR and biochemical kits, respectively. Compared with group I, mRNA expression of pyruvate carboxylase and phosphoenolpyruvate carboxykinase in groups III, IV, V, and VI were significantly lower (P < 0.01). Pyruvate carboxylase and phosphoenolpyruvate carboxykinase enzyme activity decreased significantly (P < 0.05) when leptin concentration exceeded 5 and 10 ng/mL, respectively. These results indicate that leptin markedly downregulated mRNA expression and enzyme activity of pyruvate carboxylase and phosphoenolpyruvate carboxykinase in hepatocytes, which suggests that high concentrations of LP inhibit hepatocyte gluconeogenesis, thus making negative energy balance more serious.

Acetic acid activates the AMP-activated protein kinase signaling pathway to regulate lipid metabolism in bovine hepatocytes

The effect of acetic acid on hepatic lipid metabolism in ruminants differs significantly from that in monogastric animals. Therefore, the aim of this study was to investigate the regulation mechanism of acetic acid on the hepatic lipid metabolism in dairy cows. The AMP-activated protein kinase (AMPK) signaling pathway plays a key role in regulating hepatic lipid metabolism. In vitro, bovine hepatocytes were cultured and treated with different concentrations of sodium acetate (neutralized acetic acid) and BML-275 (an AMPKα inhibitor). Acetic acid consumed a large amount of ATP, resulting in an increase in AMPKα phosphorylation. The increase in AMPKα phosphorylation increased the expression and transcriptional activity of peroxisome proliferator-activated receptor α, which upregulated the expression of lipid oxidation genes, thereby increasing lipid oxidation in bovine hepatocytes. Furthermore, elevated AMPKα phosphorylation reduced the expression and transcriptional activity of the sterol regulatory element-binding protein 1c and the carbohydrate responsive element-binding protein, which reduced the expression of lipogenic genes, thereby decreasing lipid biosynthesis in bovine hepatocytes. In addition, activated AMPKα inhibited the activity of acetyl-CoA carboxylase. Consequently, the triglyceride content in the acetate-treated hepatocytes was significantly decreased. These results indicate that acetic acid activates the AMPKα signaling pathway to increase lipid oxidation and decrease lipid synthesis in bovine hepatocytes, thereby reducing liver fat accumulation in dairy cows.

Neonatal livers: a source for the isolation of good-performing hepatocytes for cell transplantation

Hepatocyte transplantation is an alternative therapy to orthotopic liver transplantation for the treatment of liver diseases. However, the supply of hepatocytes is limited given the shortage of organs available to isolate good-functioning quality cells. Neonatal livers may be a potential source alternative to adult livers to obtain good-performing hepatic cells for hepatocyte transplantation, which has not yet been explored profoundly. High-yield preparations of viable hepatocytes were isolated from 1- to 23-day-old liver donors, cryopreserved, and banked. Cell integrity and functional quality assessment were performed after thawing. Neonatal hepatocytes showed better postthawing recovery compared with adult hepatocytes, as shown by the viability values that did not differ significantly from freshly isolated cells, a higher expression of adhesion molecules (β1-integrin, β-catenin, and E-cadherin), better attachment efficiency, cell survival, and a lower number of apoptotic cells. The metabolic performance of thawed hepatocytes has been assessed by ureogenesis and drug-metabolizing capability (cytochrome P450 and UDP-glucuronosyltransferase enzymes). CYP2A6, CYP2C9, CYP2E1, and CYP3A4 activities were found in all cell preparations, while CYP1A2, CYP2B6, CYP2C19, and CYP2D6 activities were detected only in hepatocytes from a few neonatal donors. The expression of UGT1A1 and UGT1A9 (transcripts and protein) was detected in all hepatocyte preparations, while activity was measured only in some preparations, probably due to lack of maturity of the enzymes. However, isoforms UGT1A6 and UGT2B7 showed considerable activity in all preparations. Compared to adult liver, the hepatocyte isolation procedure in neonatal livers also provides thawed cell suspensions with a higher proportion of hepatic progenitor cells (EpCAM(+) staining), which could also participate in regeneration of liver parenchyma after transplantation. These results could imply important advantages of neonatal hepatocytes as a source of high-quality cells to improve human hepatocyte transplantation applicability.

Effect of insulin-like growth factor-1 (IGF-1) on the gluconeogenesis in calf hepatocytes cultured in vitro

The major role of insulin-like growth factor-1 (IGF-1) in the liver is to mediate glucose uptake in hepatocytes to synthesize glycogen and maintain blood glucose homeostasis. In this study, to evaluate the role of IGF-1 on gluconeogenesis and nutrient metabolism in dairy cattle, pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PEPCK) expression and enzyme activity were evaluated in primary cultures of bovine hepatocytes treated with different concentrations of IGF-1 by quantitative polymerase chain reaction and spectrophotometry, respectively. The results showed that expression of PC and PEPCK were significantly lower in bovine hepatocytes by IGF-1 treatment in test group compare to the control group (P < 0.01). As IGF-1 concentration increased, PC and PEPCK enzyme activity in bovine hepatocytes decreased. Evaluating PC and PEPCK mRNA levels and enzyme activity may thus be useful to monitor subclinical ketosis in dairy cows.