NEFA-induced ROS impaired insulin signalling through the JNK and p38MAPK pathways in non-alcoholic steatohepatitis

Diacylglycerol O-acyltransferase (DGAT) isoforms play a role in peridroplet mitochondrial fatty acid metabolism in bovine liver

Hepatocellular lipid accumulation characterizes fatty liver in dairy cows. Lipid droplets (LD), specialized organelles that store lipids and maintain cellular lipid homeostasis, are responsible for the ectopic storage of lipids associated with several metabolic disorders. In recent years, non-ruminant studies have reported that LD-mitochondria interactions play an important role in lipid metabolism. Due to the role of diacylglycerol acyltransferase isoforms (DGAT1 and DGAT2) in LD synthesis, we explored mechanisms of mitochondrial fatty acid transport in ketotic cows using liver biopsies and isolated primary hepatocytes. Compared with healthy cows, cows with fatty liver had massive accumulation of LD and high protein expression of the triglyceride (TAG) synthesis-related enzymes DGAT1 and DGAT2, LD synthesis-related proteins perilipin 2 (PLIN2) and perilipin 5 (PLIN5), and the mitochondrial fragmentation-related proteins dynamin-related protein 1 (DRP1) and fission 1 (FIS1). In contrast, factors associated with fatty acid oxidation, mitochondrial fusion and mitochondrial electron transport chain complex were lower compared with those in the healthy cows. In addition, transmission electron microscopy revealed significant contacts between LD-mitochondria in liver tissue from cows with fatty liver. Compared with isolated cytoplasmic mitochondria, expression of carnitine palmitoyl transferase 1A (CPT1A) and DRP1 was lower, but mitofusin 2 (MFN2) and mitochondrial electron transport chain complex was greater in isolated peridroplet mitochondria from hepatic tissue of cows with fatty liver. In vitro data indicated that exogenous free fatty acids (FFA) induced hepatocyte LD synthesis and mitochondrial dynamics consistent with in vivo results. Furthermore, DGAT2 inhibitor treatment attenuated the FFA-induced upregulation of PLIN2 and PLIN5 and rescued the impairment of mitochondrial dynamics. Inhibition of DGAT2 also restored mitochondrial membrane potential and reduced hepatocyte reactive oxygen species production. The present in vivo and in vitro results indicated there are functional differences among different types of mitochondria in the liver tissue of dairy cows with ketosis. Activity of DGAT2 may play a key role in maintaining liver mitochondrial function and lipid homeostasis in dairy cows during the transition period.

A Review on The Phytochemistry and Pharmacology of The Genus Sterculia

The Sterculia genus is comprised of approximately 300 species, which have been widely used as traditional medicines to treat inflammation, snake bites, gastrointestinal diseases, skin diseases, microbial infections and many other diseases. To gain a comprehensive understanding of the therapeutic potential of Sterculia plants, an extensive literature search was conducted in CNKI, Bing, Wanfang Database, Springer Database, Elsevier Database, Google Scholar, Baidu Scholar, PubMed, and other similar websites from January 1971 to March 2024. The research indicated that Sterculia species predominantly contain flavonoids, terpenoids, phenylpropanoids, fatty acids, alkaloids and other chemical components. A wide range of pharmacologic activities such as anti-inflammatory, antioxidant, antibacterial and other biological activities have been reported. Nevertheless, there isn't much scholarly research on the therapeutic material basis of the genus Sterculia. This review reports the ethnobotany, phytochemicals, and biological activities of the plants in the Sterculia genus as herbal remedies.

Inositol-requiring enzyme 1α and c-Jun N-terminal kinase axis activation contributes to intracellular lipid accumulation in calf hepatocytes

During the perinatal period, dairy cows undergo negative energy balance, resulting in elevated circulating levels of nonesterified fatty acids (NEFA). Although increased blood NEFA concentrations are a physiological adaptation of early lactation, excessive NEFA in dairy cows is a major cause of fatty liver. Aberrant lipid metabolism leads to hepatic lipid accumulation and subsequently the development of fatty liver. Both inositol-requiring enzyme 1α (IRE1α) and c-Jun N-terminal kinase (JNK) have been validated for their association with hepatic lipid accumulation, including their regulatory functions in calf hepatocyte insulin resistance, oxidative stress, and apoptosis. Meanwhile, both IRE1α and JNK are involved in lipid metabolism in nonruminants. Therefore, the aim of this study was to investigate how IRE1α and JNK regulate lipid metabolism in bovine hepatocytes. An experiment was conducted on randomly selected 10 healthy cows (hepatic triglyceride [TG] content <1%) and 10 cows with fatty liver (hepatic TG content >5%). Liver tissue and blood samples were collected from experimental cows. Serum concentrations of NEFA and β-hydroxybutyrate (BHB) were greater, whereas serum concentrations of glucose and milk production were lower in cows with fatty liver. The western blot results revealed that dairy cows with fatty liver had higher phosphorylation levels of JNK, c-Jun, and IRE1α in the liver tissue. Three in vitro experiments were conducted using primary calf hepatocytes isolated from 5 healthy calves (body weight: 30-40 kg; 1 d old). First, hepatocytes were treated with NEFA (1.2 mM) for 0.5, 1, 2, 3, 5, 7, 9, or 12 h, which showed that the phosphorylated levels of JNK, c-Jun, and IRE1α increased in both linear and quadratic effects. In the second experiment, hepatocytes were treated with high concentrations of NEFA (1.2 mM) for 12 h with or without SP600125, a canonical inhibitor of JNK. Western blot results showed that SP600125 treatment could decrease the expression of lipogenesis-associated proteins (PPARγ and SREBP-1c) and increase the expression of fatty acid oxidation (FAO)-associated proteins (CPT1A and PPARα) in NEFA-treated hepatocytes. The perturbed expression of lipogenesis-associated genes (FASN, ACACA, and CD36) and FAO-associated gene ACOX1 were also recovered by JNK inhibition, indicating that JNK reduced excessive NEFA-induced lipogenesis and FAO dysregulation in calf hepatocytes. Third, short hairpin RNA targeting IRE1α (sh-IRE1α) was transfected into calf hepatocytes to silence IRE1α, and KIRA6 was used to inhibit the kinase activity of IRE1α. The blockage of IRE1α could at least partially suppressed NEFA-induced JNK activation. Moreover, the blockage of IRE1α downregulated the expression of lipogenesis genes and upregulated the expression of FAO genes in NEFA-treated hepatocytes. In conclusion, these findings indicate that targeting the IRE1α-JNK axis can reduce NEFA-induced lipid accumulation in bovine hepatocytes by modulating lipogenesis and FAO. This may offer a prospective therapeutic target for fatty liver in dairy cows.

Microbiome Sex-Related Diversity in Non-Muscle-Invasive Urothelial Bladder Cancer

Sex-specific discrepancies in bladder cancer (BCa) are reported, and new studies imply that microbiome may partially explain the diversity. We aim to provide characterization of the bladder microbiome in both sexes diagnosed with non-muscle-invasive BCa with specific insight into cancer grade. In our study, 16S rRNA next-generation sequencing was performed on midstream urine, bladder tumor sample, and healthy-appearing bladder mucosa. Bacterial DNA was isolated using QIAamp Viral RNA Mini Kit. Metagenomic analysis was performed using hypervariable fragments of the 16S rRNA gene on Ion Torrent Personal Genome Machine platform. Of 41 sample triplets, 2153 taxa were discovered: 1739 in tumor samples, 1801 in healthy-appearing bladder mucosa and 1370 in midstream urine. Women were found to have smaller taxa richness in Chao1 index than men (p = 0.03). In comparison to low-grade tumors, patients with high-grade lesions had lower bacterial diversity and richness in urine. Significant differences between sexes in relative abundance of communities at family level were only observed in high-grade tumors.

Role of transcription factor FOXM1 in diabetes and its complications (Review)

Diabetes mellitus is a chronic metabolic disease commonly associated with complications such as cardiovascular disease, nephropathy and neuropathy, the incidence of which is increasing yearly. Transcription factor forkhead box M1 (FOXM1) serves an important role in development of diabetes and its complications. The present study aimed to review the association between FOXM1 with pathogenesis of diabetes and its complications. FOXM1 may be involved in development and progression of diabetes and its complications by regulating cell biological processes such as cell cycle, DNA damage repair, cell differentiation and epithelial‑mesenchymal transition. FOXM1 is involved in regulation of insulin secretion and insulin resistance, and FOXM1 affects insulin secretion by regulating expression of insulin‑related genes and signaling pathways; FOXM1 is involved in the inflammatory response in diabetes, and FOXM1 can regulate key genes associated with inflammatory response and immune cells, which in turn affects occurrence and development of the inflammatory response; finally, FOXM1 is involved in the regulation of diabetic complications such as cardiovascular disease, nephropathy and neuropathy. In summary, the transcription factor FOXM1 serves an important role in development of diabetes and its complications. Future studies should explore the mechanism of FOXM1 in diabetes and find new targets of FOXM1 as a potential treatment for diabetes and its complications.

Exploration of natural flavones' bioactivity and bioavailability in chronic inflammation induced-type-2 diabetes mellitus

Diabetes, being the most widespread illness, poses a serious threat to global public health. It seems that inflammation plays a critical role in the pathophysiology of diabetes. This review aims to demonstrate a probable link between type 2 diabetes mellitus (T2DM) and chronic inflammation during its development. Additionally, the current review examined the bioactivity of natural flavones and the possible molecular mechanisms by which they influence diabetes and inflammation. While natural flavones possess remarkable anti-diabetic and anti-inflammatory bioactivities, their therapeutic use is limited by the low oral bioavailability. Several factors contribute to the low bioavailability, including poor water solubility, food interaction, and unsatisfied metabolic behaviors, while the diseases (diabetes, inflammation, etc.) causing even less bioavailability. Throughout the years, different strategies have been developed to boost flavones' bioavailability, including structural alteration, biological transformation, and innovative drug delivery system design. This review addresses current advancements in improving the bioavailability of flavonoids in general, and flavones in particular. Clinical trials were also analyzed to provide insight into the potential application of flavonoids in diabetes and inflammatory therapies.

Mitochondrial dynamics in health and disease: mechanisms and potential targets

Mitochondria are organelles that are able to adjust and respond to different stressors and metabolic needs within a cell, showcasing their plasticity and dynamic nature. These abilities allow them to effectively coordinate various cellular functions. Mitochondrial dynamics refers to the changing process of fission, fusion, mitophagy and transport, which is crucial for optimal function in signal transduction and metabolism. An imbalance in mitochondrial dynamics can disrupt mitochondrial function, leading to abnormal cellular fate, and a range of diseases, including neurodegenerative disorders, metabolic diseases, cardiovascular diseases and cancers. Herein, we review the mechanism of mitochondrial dynamics, and its impacts on cellular function. We also delve into the changes that occur in mitochondrial dynamics during health and disease, and offer novel perspectives on how to target the modulation of mitochondrial dynamics.

Free Fatty Acids Induce Apoptosis of Mammary Epithelial Cells of Ketotic Dairy Cows via the Mito-ROS/NLRP3 Signaling Pathway

Early lactation increases metabolic stress in ketotic dairy cows, leading to mitochondrial damage, apoptosis, and inflammatory response in mammary epithelial cells. The pyrin domain 3 (NLRP3) pathway involving the mitochondrial reactive oxygen species (Mito-ROS)-induced nucleotide-binding oligomerization domain-like receptor has been recognized as a key mechanism in this inflammatory response and cell apoptosis. This study aimed to elucidate the underlying regulatory mechanism of Mito-ROS-NLRP3 pathway-mediated mammary epithelial cell apoptosis in dairy cows with ketosis. Mitochondrial damage and cellular apoptotic program and NLRP3 inflammasome activation were observed in the mammary gland of ketotic cows. Similar damage was detected in MAC-T cells treated with exogenous fatty acids (FFAs). However, NLRP3 inhibitor MCC950 pretreatment or Mito-ROS scavenging by MitoTEMPO attenuated apoptosis in FFA-induced MAC-T cells by inhibiting the NLRP3 inflammasome pathway. These findings reveal that the Mito-ROS-NLRP3 pathway activation is a potent mechanism underlying mammary epithelial cell apoptosis in response to metabolic stress in ketotic dairy cows, which further contributes to reduced milk yield.

Reactive Oxygen Species: A Crosslink between Plant and Human Eukaryotic Cell Systems

Reactive oxygen species (ROS) are important regulating factors that play a dual role in plant and human cells. As the first messenger response in organisms, ROS coordinate signals in growth, development, and metabolic activity pathways. They also can act as an alarm mechanism, triggering cellular responses to harmful stimuli. However, excess ROS cause oxidative stress-related damage and oxidize organic substances, leading to cellular malfunctions. This review summarizes the current research status and mechanisms of ROS in plant and human eukaryotic cells, highlighting the differences and similarities between the two and elucidating their interactions with other reactive substances and ROS. Based on the similar regulatory and metabolic ROS pathways in the two kingdoms, this review proposes future developments that can provide opportunities to develop novel strategies for treating human diseases or creating greater agricultural value.

Mitofusin-2 gene polymorphisms and metabolic dysfunction associated fatty liver disease: a case-control study in a Chinese population

OBJECTIVES

Mitofusion-2 (Mfn2) may have a role in mitochondrial oxidative stress and insulin resistance that can promote the development of metabolic dysfunction associated fatty liver disease (MAFLD). This retrospective and case control study aimed to explore the relationships between common Mfn2 single nucleotide polymorphisms (SNPs) and MAFLD in a northern Han Chinese population.

METHODS

Six Mfn2 SNPs (rs2336384, rs873458, rs873457, rs4846085, rs2878677, and rs2236057) were genotyped using the ligase detection reaction in 466 MAFLD patients and 423 healthy controls. Genotype and allele frequencies were calculated, along with haplotype analysis and pairwise linkage disequilibrium.

RESULTS

The genotype distribution of rs2336384, rs2878677, and rs2236057 among the MAFLD patients showed a significantly different pattern from that of healthy controls. The data showed that an increased risk of MAFLD was significantly correlated with patients carrying the GG genotype of rs2336384, CC genotype of rs873457, TT genotype of rs4846085, TT genotype of rs2878677, and the AA genotype of rs2236057. Moreover, The GGCTTA haplotype was found to be adversely linked with MAFLD by haplotype analysis.

CONCLUSION

The current findings suggest a strong link between certain Mfn2 gene polymorphisms and MAFLD.

Puerarin Alleviates H2O2-Induced Oxidative Stress and Blood-Milk Barrier Impairment in Dairy Cows

During the perinatal period, the bovine mammary epithelial cells of dairy cows exhibit vigorous metabolism and produce large amounts of reactive oxygen species (ROS). The resulting redox balance disruption leads to oxidative stress, one of the main causes of mastitis. Puerarin (PUE) is a natural flavonoid in the root of PUE that has attracted extensive attention as a potential antioxidant. This study first investigated whether PUE could reduce oxidative damage and mastitis induced by hydrogen peroxide (H₂O₂) in bovine mammary epithelial cells in vitro and elucidated the molecular mechanism. In vitro, BMECs (Bovine mammary epithelial cells) were divided into four treatment groups: Control group (no treatment), H₂O₂ group (H₂O₂ stimulation), PUE + H₂O₂ group (H₂O₂ stimulation before PUE rescue) and PUE group (positive control). The growth of BMECs in each group was observed, and oxidative stress-related indices were detected. Fluorescence quantitative PCR (qRT-PCR) was used to detect the expression of tightly linked genes, antioxidant genes, and inflammatory factors. The expression of p65 protein was detected by Western blot. In vivo, twenty cows with an average age of 5 years having given birth three times were divided into the normal dairy cow group, normal dairy cow group fed PUE, mastitis dairy cow group fed PUE, and mastitis dairy cow group fed PUE (n = 5). The contents of TNF-α, IL-6, and IL-1β in milk and serum were detected. In BMECs, the results showed that the PUE treatment increased the activities of glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC); ROS and malondialdehyde (MDA) levels were reduced. Thus, PUE alleviated H₂O₂-induced oxidative stress in vitro. In addition, the PUE treatment eliminated the inhibition of H₂O₂ on the expression of oxidation genes and tight junction genes, and the enrichment degree of NRF-2, HO-1, xCT, and tight junctions (claudin4, occludin, ZO-1 and symplekin) increased. The PUE treatment also inhibited the expression of NF-κB-associated inflammatory factors (IL-6 and IL-8) and the chemokine CCL5 in H₂O₂-induced BMECs. In vivo experiments also confirmed that feeding PUE can reduce the expression of inflammatory factors in the milk and serum of lactating dairy cows. In conclusion, PUE can effectively reduce the oxidative stress of bovine mammary epithelial cells, enhance the tight junctions between cells, and play an anti-inflammatory role. This study provides a theoretical basis for PUE prevention and treatment of mastitis and oxidative stress. The use of PUE should be considered as a feed additive in future dairy farming.

Olanzapine-induced nonalcoholic fatty liver disease: The effects of differential food pattern and the involvement of PGRMC1 signaling

Detrimental dietary habits with high-fat food are common in the psychiatric population, leading to higher obesity rate. Olanzapine (OLZ), as one of the mainstream antipsychotic drugs, shows superior efficacy in treating schizophrenia but limited by adverse effects such as obesity, dyslipidemia and liver injury, which are risk factors for the development of nonalcoholic fatty liver disease (NAFLD). Progesterone receptor component 1 (PGRMC1) is a key regulator associated with antipsychotic drug-induced metabolic disorders. Our study aims to investigate whether high-fat supplementation worsens OLZ-induced NAFLD and to validate the potential role of PGRMC1 pathway. In vivo, eight-week OLZ treatment successfully induced hepatic steatosis in female C57BL/6 mice fed with either a high-fat or normal diet, which is independent of body weight gain. Likewise, in vitro, OLZ markedly led to hepatocyte steatosis along with enhanced oxidative stress, which was aggravated by free fatty acids. Moreover, in vivo and in vitro, high-fat supplementation aggravated OLZ-induced hepatic lipid accumulation and oxidative stress via inhibition of hepatic PGRMC1-AMPK-mTORC1/Nrf2 pathways. Inspiringly, PGRMC1 overexpression effectively reversed OLZ-induced hepatocyte steatosis in vitro. Hence, hepatic PGRMC1 is attributable to OLZ-induced NAFLD especially with high-fat supplementation and potentially serves as a novel therapeutic target.

Novel studies on Drosophila melanogaster model reveal the roles of JNK-Jak/STAT axis and intestinal microbiota in insulin resistance

The JNK pathway play a critical role in insulin resistance induced by a long-term high-sugar diet. However, the roles of up- and downstream molecules of the JNK pathway in insulin resistance are less known in vertebrates and invertebrates. As a classical organism in biological research, Drosophila melanogaster (D. melanogaster) has been widely applied to the studies of mechanism of insulin resistance. Based on previous studies, we found a novel predictive mechanism of the formation of insulin resistance in D. melanogaster. We found that JNK activated by high-sugar diet and dysregulated intestinal microbiota could mediate inflammation, and then the activated JNK released Upd3, which in turn stimulated Jak/STAT pathway to release ImpL2. ImpL2 can compete with Drosophila insulin-like peptides (Dilps) for binding with the insulin receptor and inhibit the activation of insulin pathway. In this study, we reviewed novel studies on the insulin signalling pathway based on the D. melanogaster model. The findings support our hypothesis. We, therefore, described how a long-term high-sugar diet disrupts intestinal microbiota to induce inflammation and the disruption of JNK-Jak/STAT axis. This description may offer some new clues to the formation of insulin resistance.

Sirtuin 3 relieves inflammatory responses elicited by lipopolysaccharide via the PGC1α-NFκB pathway in bovine mammary epithelial cells

Excessive inflammation in bovine mammary endothelial cells (BMEC) due to mastitis leads to disease progression and eventual culling of cattle. Sirtuin 3 (SIRT3), a mitochondrial deacetylase, downregulates pro-inflammatory cytokines in BMEC exposed to high concentrations of nonesterified fatty acids by blunting nuclear factor-κB (NFκB) signaling. In nonruminants, SIRT3 is under the control of PGC1α, a transcriptional cofactor. Specific aims were to study (1) the effect of SIRT3 on inflammatory responses of lipopolysaccharide (LPS)-challenged bovine mammary epithelial cells (bovine mammary alveolar cells-T, MAC-T) models, and (2) the role of PGC1α in the attenuation of NFκB signaling via SIRT3. To address these objectives, first, MAC-T cells were incubated in triplicate with 0, 50, 100, 150, or 200 μg/mL LPS (derived from Escherichia coli O55:B5) for 12 h with or without a 2-h incubation of the NFκB inhibitor ammonium pyrrolidine dithiocarbamate (APDC, 10 μM). Second, SIRT3 was overexpressed using adenoviral expression (Ad-SIRT3) at different multiplicity of infection (MOI) for 6 h followed by a 12 h incubation with 150 μg/mL LPS. Third, cells were treated with the PGC1α agonist ZLN005 (10 μg/mL) for 24 h and then challenged with 150 μg/mL LPS for 12 h. Fourth, cells were initially treated with the PGC1α inhibitor SR-18292 (100 μM) for 6 h followed by a 6-h culture with or without 50 MOI Ad-SIRT3 and a challenge with 150 μg/mL LPS for 12 h. Data were analyzed using one-way ANOVA with subsequent Bonferroni correction. Linear and quadratic contrasts were used to determine dose-responses to LPS. There were linear and quadratic effects of LPS dosage on cell viability. Incubation with 150 and 200 μg/mL LPS for 12 h decreased cell viability to 78.6 and 34.9%, respectively. Compared with controls, expression of IL1B, IL6, and TNFA was upregulated by 5.2-, 5.9-, and 2.7-fold with 150 μg/mL LPS; concentrations of IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) in cell medium also increased. Compared with the LPS group, LPS+APDC increased cell viability and reversed the upregulation of IL1B, IL6, and TNFA expression. However, mRNA and protein abundance of SIRT3 decreased linearly with increasing LPS dose. Ad-SIRT3 infection (50 MOI) reduced IL1B, IL6, and TNFA expression and also their concentrations in cell medium, and decreased pNFκB P65/NFκB P65 ratio and nuclear abundance of NFκB P65. The PGC1α agonist increased SIRT3 expression, whereas it decreased cytokine expression, pNFκB P65/NFκB P65 ratio, and prevented NFκB P65 nuclear translocation. Contrary to the agonist, the PGC1α inhibitor had opposite effects, and elevated the concentrations of IL-1β, IL-6, and TNF-α in cell medium. Overall, data suggested that SIRT3 activity could attenuate LPS-induced inflammatory responses in mammary cells via alterations in the PGC1α-NFκB pathway. As such, there may be potential benefits for targeting SIRT3 in vivo to help prevent or alleviate negative effects of mastitis.

Nuciferine Ameliorates Nonesterified Fatty Acid-Induced Bovine Mammary Epithelial Cell Lipid Accumulation, Apoptosis, and Impaired Migration via Activating LKB1/AMPK Signaling Pathway

High blood concentrations of nonesterified fatty acids (NEFAs) provoke various metabolic disorders and are associated with mammary tissue injury and decreased milk production in dairy cows. Nuciferine, an alkaloid found in Nelumbo nucifera leaves, has great potential for correcting lipid metabolism derangements and lipotoxicity. In this study, we evaluated the lipotoxicity induced by excessive NEFA in bovine mammary epithelial cells (bMECs) and investigated whether nuciferine alleviates NEFA-induced lipotoxicity and the underlying molecular mechanisms. We found that excessive NEFA (1.2 and 2.4 mM) induced lipid accumulation, apoptosis, and migration ability impairment in bMECs, whereas nuciferine could ameliorate these disarrangements, as indicated by decreasing triglyceride content, protein abundance of SREBP-1c, cytoplasmic cytochrome c, and cleaved caspase-3 and increasing protein abundance of PPARα and migration ability. Moreover, nuciferine could reverse NEFA-induced LKB1/AMPK signaling inhibition, and the protective effect of nuciferine on lipotoxicity caused by NEFA was abrogated by AMPK inhibitor dorsomorphin. Furthermore, transfection with LKB1 siRNA (si-LKB1) largely abolished the activation effect of nuciferine on AMPK. Overall, nuciferine can protect bMECs from excessive NEFA-induced lipid accumulation, apoptosis, and impaired migration by activating LKB1/AMPK signaling pathway.

CSAD Ameliorates Lipid Accumulation in High-Fat Diet-Fed Mice

Non-alcoholic fatty liver disease (NAFLD) is a chronic metabolic disease manifested in hepatic steatosis, inflammation, fibrosis, etc., which affects over one-quarter of the population around the world. Since no effective therapeutic drugs are available to cope with this widespread epidemic, the functional research of genes with altered expression during NAFLD helps understand the pathogenesis of this disease and the development of new potential therapeutic targets for drugs. In the current work, we discovered via the analysis of the Gene Expression Omnibus (GEO) dataset that cysteine sulfinic acid decarboxylase (CSAD) decreased significantly in NAFLD patients, which was also confirmed in multiple NAFLD mouse models (HFD-fed C57BL/6J, db/db and HFHFrHC-fed C57BL/6J mice). Next, CSAD's function in the progression of NAFLD was explored using AAV-mediated liver-directed gene overexpression in an HFD-fed mouse model, where the overexpression of CSAD in the liver could alleviate NAFLD-associated pathologies, including body weight, liver/body weight ratio, hepatic triglyceride and total cholesterol, and the degree of steatosis. Mechanically, we found that the overexpression of CSAD could increase the expression of some genes related to fatty acid β-oxidation (Acad1, Ppara, and Acox1). Furthermore, we also detected that CSAD could improve mitochondrial injury in vitro and in vivo. Finally, we proposed that the effect of CSAD on lipid accumulation might be independent of the taurine pathway. In conclusion, we demonstrated that CSAD is involved in the development of NAFLD as a protective factor, which suggested that CSAD has the potential to become a new target for drug discovery in NAFLD.

Expression and localization of NRF2/Keap1 signalling pathway genes in mouse preimplantation embryos exposed to free fatty acids

Obese women experience greater incidence of infertility, with reproductive tracts exposing preimplantation embryos to elevated free fatty acids (FFA) such as palmitic acid (PA) and oleic acid (OA). PA treatment impairs mouse preimplantation development in vitro, while OA co-treatment rescues blastocyst development of PA treated embryos. In the present study, we investigated the effects of PA and OA treatment on NRF2/Keap1 localization, and relative antioxidant enzyme (Glutathione peroxidase; Gpx1, Catalase; Cat, Superoxide dismutase; Sod1 and γ-Glutamylcysteine ligase catalytic unit; Gclc) mRNA levels, during in vitro mouse preimplantation embryo development. Female mice were superovulated, mated, and embryos cultured in the presence of bovine Serum albumin (BSA) control or PA, or OA, alone (each at 100 μM) or PA + OA combined (each at 100 μM) treatment. NRF2 displayed nuclear localization at all developmental stages, whereas Keap1 primarily displayed cytoplasmic localization throughout control mouse preimplantation development in vitro. Relative transcript levels of Nrf2, Keap1, and downstream antioxidants significantly increased throughout control mouse preimplantation development in vitro. PA treatment significantly decreased blastocyst development and the levels of nuclear NRF2, while OA and PA + OA treatments did not. PA and OA treatments did not impact relative mRNA levels of Nrf2, Keap1, Gpx1, Cat, Sod1 or Gclc. Our outcomes demonstrate that cultured mouse embryos display nuclear NRF2, but that PA treatment reduces nuclear NRF2 and thus likely impacts NRF2/KEAP1 stress response mechanisms. Further studies should investigate whether free fatty acid effects on NRF2/KEAP1 contribute to the reduced fertility displayed by obese patients.

Effects of supplementation of sodium acetate on rumen fermentation and microbiota in postpartum dairy cows

The primary product of rumen fermentation is acetic acid, and its sodium salt is an excellent energy source for post-partum cows to manage negative energy balance (NEB). However, it is unknown how adding sodium acetate (NAc) may affect the rumen bacterial population of post-partum cows. Using the identical nutritional total mixed ration (TMR), this research sought to characterize the impact of NAc supplementation on rumen fermentation and the composition of bacterial communities in post-partum cows. After calving, 24 cows were randomly assigned to two groups of 12 cows each: a control group (CON) and a NAc group (ACE). All cows were fed the same basal TMR with 468 g/d NaCl added to the TMR for the CON group and 656 g/d NAc added to the TMR for the ACE group for 21 days after calving. Ruminal fluid was collected before morning feeding on the last day of the feeding period and analyzed for rumen bacterial community composition by 16S rRNA gene sequencing. Under the identical TMR diet conditions, NAc supplementation did not change rumen pH but increased ammonia nitrogen (NH3-N) levels and microbial crude protein (MCP) concentrations. The administration of NAc to the feed upregulated rumen concentrations of total volatile fatty acids (TVFA), acetic, propionic, isovaleric and isobutyric acids without affecting the molar ratio of VFAs. In the two experimental groups, the Bacteroidota, Firmicutes, Patescibacteria and Proteobacteria were the dominant rumen phylum, and Prevotella was the dominant rumen genus. The administration of NAc had no significant influence on the α-diversity of the rumen bacterial community but upregulated the relative abundance of Prevotella and downregulated the relative abundance of RF39 and Clostridia_UCG_014. In conclusion, the NAc supplementation in the post-peripartum period altered rumen flora structure and thus improved rumen fermentation in dairy cows. Our findings provide a reference for the addition of sodium acetate to alleviate NEB in cows during the late perinatal period.

Estradiol production of granulosa cells is unaffected by the physiological mix of non-esterified fatty acids in follicular fluid

Ovarian cycle is controlled by circulating levels of the steroid hormone 17-β-estradiol, which is predominantly synthesized by the granulosa cells (GCs) of ovarian follicles. Our earlier studies showed that unsaturated fatty acids (USFs) downregulate and saturated fatty acids (SFAs) upregulate estradiol production in GCs. However, it was unclear whether pituitary gonadotropins induce accumulation of free fatty acids (FFAs) in the follicular fluid since follicle-stimulating hormone induces and luteinizing hormone inhibits estradiol production in the mammalian ovary. Interestingly, we show here the gas chromatography analysis of follicular fluid revealed no differential accumulation of FFAs between pre- and post-luteinizing hormone surge follicles. We therefore wondered how estradiol production is regulated in the physiological context, as USFs and SFAs are mutually present in the follicular fluid. We thus performed in vitro primary GC cultures with palmitate, palmitoleate, stearate, oleate, linoleate, and alpha-linolenate, representing >80% of the FFA fraction in the follicular fluid, and analyzed 62 different cell culture conditions to understand the regulation of estradiol biosynthesis under diverse FFA combinations. Our analyses showed co-supplementation of SFAs with USFs rescued estradiol production by restoring gonadotropin receptors and aromatase, antagonizing the inhibitory effects of USFs. Furthermore, transcriptome data of oleic acid–treated GCs indicated USFs induce the ERK and Akt signaling pathways. We show SFAs inhibit USF-induced ERK1/2 and Akt activation, wherein ERK1/2 acts as a negative regulator of estradiol synthesis. We propose SFAs are vital components of the follicular fluid, without which gonadotropin signaling and the ovarian cycle would probably be shattered by USFs.

Targeting IRE1α and PERK in the endoplasmic reticulum stress pathway attenuates fatty acid-induced insulin resistance in bovine hepatocytes

Endoplasmic reticulum (ER) stress can be induced by various stimuli and triggers the unfolded protein response to activate intracellular signaling pathways that are mediated by 3 ER-resident sensors: inositol requiring protein-1α (IRE1α), PKR-like ER kinase (PERK), and activating transcription factor-6 (ATF6). In nonruminants, ER stress plays a critical role in hepatic insulin resistance. However, whether ER stress plays a role in nonesterified fatty acid (NEFA)-induced hepatic insulin resistance in dairy cows is still unknown. Experiments were conducted using primary bovine hepatocytes isolated from 5 healthy calves (body weight: 30-40 kg; 1 d old). First, hepatocytes were treated with NEFA (1.2 mM) for 0.5, 1, 2, 3, 5, 7, 9, or 12 h. Treatment with NEFA elevated abundance of phosphorylated IRE1α and PERK, and cleavage of ATF6, along with the ER stress-associated genes XBP1, ATF4, and DNAJC3, resulting in both linear and quadratic effects. Furthermore, ER Tracker red staining and transmission electron microscopy results indicated that ER was dilated and degranulated in response to NEFA treatment, suggesting that ER stress was induced by NEFA treatment in bovine hepatocytes. Second, to assess the effect of ER stress on NEFA-induced insulin resistance, hepatocytes were treated with different concentrations of NEFA (0, 0.6, 1.2, or 2.4 mM) for 5 h with or without tauroursodeoxycholic acid (TUDCA, a canonical inhibitor of ER stress). Here, NEFA induced insulin resistance by increasing the abundance of insulin receptor substrate-1 (IRS1) phosphorylation at the inhibitory residue Ser 307 (S307) and decreasing the abundance of phosphorylated protein kinase B (AKT) and glycogen synthase kinase-3β (GSK3β) in a dose-dependent manner. This was accompanied by upregulation of an abundance of gluconeogenic genes [phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6-Pase)]. These detrimental effects of NEFA on insulin signaling could be reversed with TUDCA treatment, indicating a mechanistic link between ER stress and NEFA-induced insulin resistance. In a third experiment, pGPU6/GFP/Neo vectors containing short hairpin RNA targeting IRE1α were used to silence IRE1α transcription, and GSK2656157 (PERK phosphorylation inhibitor) and 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF; an inhibitor of ATF6) were used to block PERK and ATF6 branches, respectively. Notably, the silencing of the IRE1α branch improved NEFA-induced insulin resistance by decreasing phosphorylation of IRS1 (S307) and increasing phosphorylation of AKT and GSK3β, and reducing PEPCK and G6-Pase mRNA abundance, which was likely dependent on IRE1α kinase activity. Similarly, blockage of the PERK branch increased phosphorylation of AKT and GSK3β, and reduced PEPCK and G6-Pase mRNA abundance, but had no effect on phosphorylation of IRS1 (S307). However, results showed that inhibition of the ATF6 branch had no effects on phosphorylation of IRS1, AKT, and GSK3β, and instead found increasing PEPCK and G6-Pase mRNA abundance. Taken together, data in the present study found that impeding IRE1α and PERK signaling might aid in relieving hepatic insulin resistance. However, the more detailed mechanisms of how IRE1α and PERK signaling contribute to hepatic insulin resistance in dairy cows remain to be determined.

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.

Deletion of serine racemase reverses neuronal insulin signaling inhibition by amyloid-β oligomers

Dysregulation of insulin signaling in the Alzheimer's (AD) brain has been extensively reported. Serine racemase(SR) modulates insulin secretion in pancreatic islets. Similarly, we wonder whether or not SR regulates insulin synthesis and secretion in neurons, thereby modulating insulin signaling in the AD brain. Srr-knockout (Srr^-/- ) mice generated with the CRISPR/Cas9 technique were used. Using immunofluorescence and fluorescence in situ hybridization, the levels of insulin protein and insulin(ins2) mRNA significantly increased in the hippocampal but not in the hypothalamic sections of Srr^-/- mice compared with WT mice. Using real-time quantitative PCR, ins2 mRNA from primary hippocampal neuronal cultures of Srr^-/- mice significantly increased compared with the cultured neurons from WT mice. Notably, the secretion of proinsulin C-peptide increased in Srr^-/- neurons relative to WT neurons. By examining the membrane fractional proteins with immunoblotting, Srr^-/- neurons retained ATP-dependent potassium channel on plasmalemma and correspondingly contained higher levels of p-AMPK. Under treatment by Aβ42, the phosphorylation levels of insulin receptor substrate at serine 616,636 (p-IRS1^ser616,636 ) were significantly lower whereas p-AKT³⁰⁸ and p-AKT⁴⁷³ were higher in Srr^-/- neurons, compared with WT neurons, respectively. The phosphorylated form of c-Jun N-terminal kinase decreased in the cultured Srr^-/- neurons relative to the WT neurons upon Aβ42 treatment. In contrast, the phosphorylated protein kinase R remained at the same levels. Further, reactive oxygen species reduced in the cultured Srr^-/- neurons under Aβ42 treatment relative to the WT neurons. Altogether, our study indicated that Srr deletion promoted insulin synthesis and secretion of proinsulin C-peptide, thereby reversing insulin resistance by Aβ42. This study suggests that targeting the neuronal SR may be utilized to enhance insulin signaling which is inhibited at the early stage of the AD brain.

Oxidative Stress and Redox Signaling in the Pathophysiology of Liver Diseases

The increased production of derivatives of molecular oxygen and nitrogen in the form of reactive oxygen species (ROS) and reactive nitrogen species (RNS) lead to molecular damage called oxidative stress. Under normal physiological conditions, the ROS generation is tightly regulated in different cells and cellular compartments. Any disturbance in the balance between the cellular generation of ROS and antioxidant balance leads to oxidative stress. In this article, we discuss the sources of ROS (endogenous and exogenous) and antioxidant mechanisms. We also focus on the pathophysiological significance of oxidative stress in various cell types of the liver. Oxidative stress is implicated in the development and progression of various liver diseases. We narrate the master regulators of ROS-mediated signaling and their contribution to liver diseases. Nonalcoholic fatty liver diseases (NAFLD) are influenced by a "multiple parallel-hit model" in which oxidative stress plays a central role. We highlight the recent findings on the role of oxidative stress in the spectrum of NAFLD, including fibrosis and liver cancer. Finally, we provide a brief overview of oxidative stress biomarkers and their therapeutic applications in various liver-related disorders. Overall, the article sheds light on the significance of oxidative stress in the pathophysiology of the liver. © 2022 American Physiological Society. Compr Physiol 12:3167-3192, 2022.

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.

Liraglutide Regulates Mitochondrial Quality Control System Through PGC-1α in a Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is a multifactorial disorder, and there is strong evidence that mitochondria play an essential role in the disorder. Factors that regulate the mechanism of the mitochondrial quality control system have been drawing more and more attention. PGC-1α (peroxisome proliferator-activated receptor-γ coactivator-1α) is a powerful transcription factor involved in regulation of mitochondrial function. Glucagon-like peptide 1 (GLP-1), a brain-gut peptide, can enter the central nervous system through the blood-brain barrier and play neuroprotective role. However, whether the GLP-1R agonist liraglutide regulates mitochondrial quality control system through PGC-1α is still unclear. We administered different doses of liraglutide to intervene MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced PD model, and then immunofluorescence, Western blot, and stereotactic injection of lentivirus to downregulate PGC-1α were used to explore the mechanisms underlying the protective effect of liraglutide in PD. The results showed that MPTP lead to decreased mitochondrial biogenesis, disrupted mitochondrial dynamics, inhibited mitochondrial autophagy, and promoted cell apoptosis. While liraglutide effectively attenuated the neurotoxicity of MPTP, including reversing the dyskinesia caused by MPTP and preserving the expression of GLP-1R, TH, and PGC-1α in the substantia nigra (SN), further experiments showed that downregulation of PGC-1α expression via stereotactic injection PGC-1α lentivirus into the SN reversed the liraglutide protective effects. By PGC-1α downregulation, we found that PGC-1α can not only regulate mitochondria biogenesis, mitochondria dynamics, and autophagy, but also regulate cell apoptosis. In summary, liraglutide has a neuroprotective effect in the PD model induced by MPTP. This protective effect is accomplished by activating PGC-1α, which regulates the mitochondrial quality control system.

Platelet-Activating Factor Promotes the Development of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a multifaceted clinicopathological syndrome characterised by excessive hepatic lipid accumulation that causes steatosis, excluding alcoholic factors. Platelet-activating factor (PAF), a biologically active lipid transmitter, induces platelet activation upon binding to the PAF receptor. Recent studies have found that PAF is associated with gamma-glutamyl transferase, which is an indicator of liver disease. Moreover, PAF can stimulate hepatic lipid synthesis and cause hypertriglyceridaemia. Furthermore, the knockdown of the PAF receptor gene in the animal models of NAFLD helped reduce the inflammatory response, improve glucose homeostasis and delay the development of NAFLD. These findings suggest that PAF is associated with NAFLD development. According to reports, patients with NAFLD or animal models have marked platelet activation abnormalities, mainly manifested as enhanced platelet adhesion and aggregation and altered blood rheology. Pharmacological interventions were accompanied by remission of abnormal platelet activation and significant improvement in liver function and lipids in the animal model of NAFLD. These confirm that platelet activation may accompany a critical importance in NAFLD development and progression. However, how PAFs are involved in the NAFLD signalling pathway needs further investigation. In this paper, we review the relevant literature in recent years and discuss the role played by PAF in NAFLD development. It is important to elucidate the pathogenesis of NAFLD and to find effective interventions for treatment.

The Role and Mechanism of Oxidative Stress and Nuclear Receptors in the Development of NAFLD

The overproduction of reactive oxygen species (ROS) and consequent oxidative stress contribute to the pathogenesis of acute and chronic liver diseases. It is now acknowledged that nonalcoholic fatty liver disease (NAFLD) is characterized as a redox-centered disease due to the role of ROS in hepatic metabolism. However, the underlying mechanisms accounting for these alternations are not completely understood. Several nuclear receptors (NRs) are dysregulated in NAFLD, and have a direct influence on the expression of a set of genes relating to the progress of hepatic lipid homeostasis and ROS generation. Meanwhile, the NRs act as redox sensors in response to metabolic stress. Therefore, targeting NRs may represent a promising strategy for improving oxidation damage and treating NAFLD. This review summarizes the link between impaired lipid metabolism and oxidative stress and highlights some NRs involved in regulating oxidant/antioxidant turnover in the context of NAFLD, shedding light on potential therapies based on NR-mediated modulation of ROS generation and lipid accumulation.

Circulating tumor necrosis factor-α levels in non-alcoholic fatty liver disease: A systematic review and a meta-analysis

BACKGROUND AND AIM

To synthesize data on circulating tumor necrosis factor (TNF)-α levels between patients with histologically confirmed non-alcoholic fatty liver disease (NAFLD) (simple steatosis or non-alcoholic fatty liver [NAFL] and/or non-alcoholic steatohepatitis [NASH]) and controls.

METHODS

We performed a systematic search in PubMed, Scopus, and Cochrane Library. Fifty-six studies, published between 2003 and 2019, were finally included, reporting data from 5848 individuals (1634 controls and 4214 NAFLD patients).

RESULTS

Higher circulating TNF-α levels were observed in NAFLD patients than controls (standardized mean difference [SMD] 0.84; 95% confidence interval [95% CI] 0.59-1.09), NAFL patients than controls (SMD 0.56; 95% CI 0.27-0.85), NASH patients than controls (SMD 0.93; 95% CI 0.64-1.22), and NASH than NAFL patients (SMD 0.31; 95% CI 0.16-0.46). There were only minimal changes in the comparisons between groups after excluding studies with morbidly obese populations (n = 11), or pediatric/adolescent populations (n = 6), or other than enzyme-linked immunosorbent assay method of TNF-α measurement (n = 8). There was high heterogeneity among studies in all comparisons, which was not essentially affected after sensitivity analyses. The meta-regression analysis revealed that the male ratio was positively associated with TNF-α SMD in the comparison between patients with NASH and NAFL (beta = 0.809; 95% CI 0.052-1.566) and accounted for 36% (P = 0.037) of the heterogeneity in this pair of comparison. TNF-α SMD was not associated with age, body mass index, and alanine aminotransferase in any pair of comparisons.

CONCLUSIONS

Circulating TNF-α levels were higher in patients with NAFLD compared with controls. Higher levels of circulating TNF-α were also associated with the severity of NAFLD.

Cocultured porcine granulosa cells respond to excess non-esterified fatty acids during in vitro maturation

Background

Non-esterified fatty acids (NEFAs) are one of the main lipid components of follicular fluid at concentrations that depend on circulating levels. Elevated levels of NEFAs impair oocyte quality, development potential, and may subsequently influence the metabolism and reproductive fitness of offspring. Granulosa cells (GCs) are the follicular cells that are closely communicating with the oocyte. However, the responses of GCs exposed to high levels of NEFAs when cocultured with cumulus-oocyte complexes (COCs), and how they attenuate the negative effects of NEFAs on oocytes, are unclear.

Results

To better understand this protective effect, monolayers of porcine GCs were cocultured with COCs during in vitro maturation (IVM) in the presence of elevated levels of NEFAs. Genomic expression analysis was conducted to explore the responses of the GCs to the elevated levels of NEFAs. After limma algorithm analysis, 1,013 genes were differentially expressed between GCs cultured with and without elevated NEFAs. Among them, 438 genes were upregulated and 575 were downregulated. The differentially expressed genes were enriched in pathways related to metabolism, inflammation, and epithelial-mesenchymal transition.

Conclusions

The pathways and upstream regulators suggested that the cocultured GCs responded to the elevated NEFAs with (1) inhibition of the transition from granulosa to luteal cell, (2) interactions of metabolism change, anti-inflammation, mitochondrial function, and cell transition, (3) intercommunication with cocultured COCs of anti-inflammatory factors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00904-y.

Saponins of Momordica charantia increase insulin secretion in INS-1 pancreatic β-cells via the PI3K/Akt/FoxO1 signaling pathway

Saponins are the main bioactive substances with anti-hyperglycemic activities of Momordica charantia. This study aimed to verify the effects of M. charantia saponins on insulin secretion and explore the potential underlying mechanisms in INS-1 pancreatic β-cells. We injured INS-1 cells with 33.3mM glucose and then treated them with saponins. Saponins improved cell morphology and viability as demonstrated by inverted microscopy and CCK8 detection and significantly increased insulin secretion in a concentration-dependent manner as shown by ELISA. Thus, we obtained the optimal concentration for the subsequent experiments. Potential mechanisms were explored by immunofluorescence, western blotting, and RT-qPCR techniques. First, saponins increased the mRNA and protein levels of IRS-2 but decreased the serine 731 phosphorylation level of IRS-2. Moreover, saponins increased the phosphorylation of Akt protein and decreased the protein level of FoxO1, which were both reversed by the PI3K inhibitor ly294002. Furthermore, saponins increased the protein level of the downstream molecule and insulin initiating factor PDX-1, which was also reversed by ly294002. Saponins also increased Akt and PDX-1 mRNA and decreased FoxO1 mRNA, which were both reversed by ly294002. Saponins increased glucose-stimulated insulin secretion (GSIS) and intracellular insulin content, which were reversed by ly294002, as determined by ELISA. The immunofluorescence results also confirmed this tendency. In conclusion, our findings improve our understanding of the function of saponins in INS-1 pancreatic β-cells and suggest that saponins may increase insulin secretion via the PI3K/Akt/FoxO1 signaling pathway.

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

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

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

Ketotic dairy cows exhibit a state of negative energy balance (NEB) characterized by elevated circulating levels of β-hydroxybutyrate (BHB) and fatty acids. Impaired hepatic insulin signaling in dairy cows occurs frequently during the transition into lactation, but its role on liver function during this period is not well known. In nonruminants, endoplasmic reticulum (ER) stress is a causal factor contributing to impaired insulin signaling in the liver. Thus, the aim of this study was to investigate the status of hepatic insulin and ER stress signaling and whether ER stress contributes to impaired insulin signaling in dairy cows with ketosis. Healthy (control cows, n = 10, BHB ≤0.6 mM) and ketotic (ketotic cows, n = 10, BHB ≥1.2 mM) cows at 3 to 10 d in milk were selected for liver biopsy and blood sampling before feeding. In vitro experiments were conducted with isolated hepatocytes from 5 healthy calves (1 d old, fasted female, 30-40 kg of body weight). Treatments included BHB (0, 0.9, 1.8, 3.6 mM), tauroursodeoxycholic acid (TUDCA, a canonical inhibitor of ER stress), and different incubation times (0.5, 1, 2, 3, 5, 7, 9, or 12 h). Ketotic cows had lower daily milk yield (median: 29.50 vs. 23.00 kg), higher plasma nonesterified fatty acid (NEFA) (median: 0.33 vs. 1.17 mM), BHB (median: 0.43 vs. 3.22 mM), aspartate aminotransferase (median: 70.58 vs. 155.70 U/L), alanine aminotransferase (median: 18.31 vs. 37.90 U/L), lower plasma glucose (median: 4.32 vs. 2.37 mg/dL), and revised quantitative insulin sensitivity check index (median: 0.39 vs. 0.37) compared with healthy cows. Increased abundance of phosphorylated insulin receptor substrate-1 (IRS1) and decreased abundance of phosphorylated protein kinase B (AKT) and glycogen synthase kinase-3β (GSK3β) in ketotic cows indicated a state of insulin resistance. In addition, abundance of phosphorylated protein kinase RNA-like ER kinase (PERK) and inositol requiring protein-1α (IRE1α), and cleavage of activating transcription factor-6 (ATF6) were greater in the liver of ketotic cows. In vitro, at the early stages of incubation, treatment with BHB upregulated abundance of phosphorylated of IRE1α, PERK, and the cleavage of ATF6, as well as several unfolded protein response genes [X-box-binding protein-1 (XBP1), 78 kDa glucose-regulated protein (GRP78), and C/EBP homologous protein (CHOP)]. Furthermore, in response to increasing doses of BHB, the phosphorylation level of PERK, IRE1α, and the cleavage of ATF6, and the abundance of XBP1, GRP78, and CHOP increased. In addition, BHB treatment increased phosphorylation of IRS1 and decreased phosphorylation of AKT and GSK3β, and upregulated abundance of gluconeogenic genes (phosphoenolpyruvate carboxykinase and glucose-6-phosphatase). Importantly, these changes were reversed by inhibiting ER stress with TUDCA treatment. Overall, the present study indicated that reversing ER stress during ketosis might help alleviate hepatic insulin resistance. Targeting ER stress may represent a potential therapeutic target for controlling the negative aspects of ketosis on liver function.

Oxidative status in dairy goats: periparturient variation and changes in subclinical hyperketonemia and hypocalcemia

BACKGROUND

A better comprehension of the redox status during the periparturient period may facilitate the development of management and nutritional solutions to prevent subclinical hyperketonemia (SCHK) and subclinical hypocalcemia (SCHC) in dairy goats. We aimed to evaluate the variation in the redox status of dairy goats with SCHK and SCHC during their periparturient periods. Guanzhong dairy goats (n = 30) were assigned to SCHK (n = 10), SCHC (n = 10), and healthy (HEAL, n = 10) groups based on their blood β-hydroxybutyrate (BHBA) and calcium (Ca) concentrations. Blood were withdrawn from goats every week from 3 weeks before the expected parturition date to 3 weeks post-kidding. On the same day, the body condition scores (BCS) were evaluated, and the milk yield was recorded for each goat. The metabolic profile parameters and the indicators of oxidative status were determined by using the standard biochemical techniques.

RESULTS

In comparison with the HEAL goats, SCHK and SCHC goats presented with a more dramatic decline of BCS post-kidding and a significant decrease in the milk yield at 2- and 3-weeks postpartum, ignoring the obvious increase at 1-week postpartum. The levels of non-esterified fatty acids (NEFA) peaked at parturition, exhibiting significantly higher levels from 1-week prepartum to the parturition day in the SCHK and SCHC groups. The malondialdehyde (MDA) concentration was increased in the SCHK goats from 1-week antepartum until 3-weeks postpartum, with its concentration being significantly higher in the SCHC goats at parturition. The hydrogen peroxide (H2O2) concentration was significantly lower in the SCHK and SCHC goats from 2-weeks antepartum to 1-week post-kidding. The total antioxidant capacity (T-AOC) and the superoxide dismutase (SOD) level were decreased at 1-week antepartum in the SCHK and SCHC goats, respectively. The glutathione peroxidase (GSH-Px) level was increased in the SCHK and SCHC goats during the early lactation period.

CONCLUSIONS

The SCHK and SCHC goats exerted more efforts to maintain their redox homeostasis and to ensure the production performance than the HEAL goats during their periparturient period, probably owing to more intense fat mobilization and lipid peroxidation in the former.

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

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

Invited Review: Ketosis Diagnosis and Monitoring in High-Producing Dairy Cows

This work reviews the current impact and manifestation of ketosis (hyperketonemia) in dairy cattle, emphasizing the practical use of laboratory methods, field tests, and milk data to monitoring this disease. Ketosis is a major issue in high-producing cows, easily reaching a prevalence of 20% during early postpartum when the negative energy balance is well established. Its economic losses, mainly related to decreasing milk yield, fertility, and treatment costs, have been estimated up to €250 per case of ketosis/year, which can double if associated diseases are considered. A deep relationship between subclinical or clinical ketosis and negative energy balance and related production diseases can be observed mainly in the first two months postpartum. Fourier transform infrared spectrometry methods gradually take place in laboratory routine to evaluates body ketones (e.g., beta-hydroxybutyrate) and probably will accurately substitute cowside blood and milk tests at a farm in avenir. Fat to protein ratio and urea in milk are largely evaluated each month in dairy farms indicating animals at risk of hyperketonemia. At preventive levels, other than periodical evaluation of body condition score and controlling modifiable or identifying non-modifiable risk factors, the ruminatory activity assessment during the peripartum seems to be a valuable tool at farms. We conclude that a technological advance progressively takes place to mitigate the effects of these metabolic diseases, which challenge the high-yielding cows.

Characterization of the liver proteome in dairy cows experiencing negative energy balance at early lactation

Negative energy balance (NEB) is associated with metabolic disorders in early lactation dairy cows. Therefore, our objective was to characterize the liver proteome in cows experiencing either NEB or positive energy balance (PEB). Forty-two multiparous Holstein dairy cows were milked either 2 or 3 times daily for the first 30 days in milk (DIM) to alter EB, and were classified retrospectively as NEB (n = 18) or PEB (n = 22). Liver biopsies were collected from 10 cows (n = 5 from each milking frequency) at 17 ± 3 DIM (NEB, n = 6; PEB, n = 4). The liver proteome was characterized using label-free quantitative shotgun proteomics and Ingenuity Pathway Analysis used to identify key affected canonical pathways. Overall, 2741 proteins were identified, and 68 of those were differentially abundant (P ≤ 0.05 and FC ± 1.5). ENO3 (FC = 10.3, P < 0.01) and FABP5 (FC = -12.5, P = 0.045) were the most dramatically upregulated and downregulated proteins, respectively, in NEB cows. Numerous mitochondrial proteins (NDUFA5, NDUFS3, NDUFA6, COX7A2L, COX6C, and COA5) were differentially abundant. Canonical pathways associated with NEB were LPS/IL-1 mediated inhibition of RXR function, oxidative phosphorylation, and mitochondrial dysfunction. Additionally, cows experiencing NEB had less hepatic IL10 transcript abundance than PEB. Together, NEB was associated with altered hepatic inflammatory status, likely due to oxidative stress from mitochondrial dysfunction. SIGNIFICANCE: Our manuscript describes the associations of negative energy balance with the liver proteome in early lactation dairy cows, when metabolic stress and the incidence of diseases is increased. Specifically, we found associations of negative energy balance with shifts in hepatic protein abundance involved in fatty acid uptake, impaired anti-inflammatory responses, and mitochondrial dysfunction. Moving forward, differentially abundant proteins found in this study may be useful as either biological markers for disease or therapeutic targets to improve metabolic adaptations to lactation in postpartum dairy cattle.

Milk Fat Globule Membrane Supplementation During Suckling Ameliorates Maternal High Fat Diet-Induced Hepatic Steatosis in Adult Male Offspring of Mice

BACKGROUND

Exposure to a maternal high-fat diet (HFD) predisposes offspring to nonalcoholic fatty liver disease.

OBJECTIVES

The aim of this study was to explore whether milk fat globule membrane (MFGM) supplementation during suckling exerts a long-term protective effect on hepatic lipid metabolism in adult offspring exposed to maternal HFD.

METHODS

We fed 5-week-old female C57BL/6J mice either a HFD (60% kcal fat) or control diet (CD; 16.7% kcal fat) for 3 weeks before mating, as well as throughout gestation and lactation. After delivery, male offspring from HFD dams were supplemented with 1 g/(kg body weight·day) MFGM (HFD + MFGM group) or the same volume of vehicle (HFD group) during suckling. Male offspring from CD dams were also supplemented with vehicle during suckling (CD group). All offspring were weaned onto CD for 8 weeks. Histopathology, metabolic parameters, lipogenic level, oxidative stress, and mitochondria function in the liver were analyzed. A 1-way ANOVA and a Kruskal-Wallis test were used for multi-group comparisons.

RESULTS

As compared to the CD group, the HFD group had more lipid droplets in livers, and exhibited ∼100% higher serum triglycerides, ∼38% higher hepatic triglycerides, ∼75% higher serum aspartate aminotransferase, and ∼130% higher fasting blood glucose (P < 0.05). The changes of these metabolic parameters were normalized in the HFD + MFGM group. Phosphorylated mammalian targets of rapamycin and AKT were downregulated, but phosphorylated adenosine monophosphate-activated protein kinase was upregulated in the HFD + MFGM group as compared to the HFD group (P < 0.05). As compared to the CD group, the HFD group showed an ∼80% higher malondialdehyde level, and ∼20% lower superoxide dismutase activity (P < 0.05), which were normalized in the HFD + MFGM group. Additionally, mitochondria function was also impaired in the HFD group and normalized in the HFD + MFGM group.

CONCLUSIONS

MFGM supplementation during suckling ameliorates maternal HFD-induced hepatic steatosis in mice via suppressing de novo lipogenesis, reinforcing antioxidant defenses and improving mitochondrial function.

Protective role of Sterculia tragacantha aqueous extract on pancreatic gene expression and oxidative stress parameters in streptozotocin-induced diabetic rats

OBJECTIVES

The current study evaluates the protective role of aqueous extract of Sterculia tragacantha leaf (AESTL) on pancreatic gene expressions (insulin, PCNA, PDX-1, KI-67 and GLP-1R) and oxidative stress parameters in streptozotocin-induced diabetic rats.

METHODS

Diabetes mellitus was induced into the experimental Wistar animals via intraperitoneal (IP) injection of streptozotocin (35 mg/kg body weight) and 5% glucose water was given to the rats for 24 h after induction. The animals were categorized into five groups of 10 rats each as follows normal control, diabetic control, diabetic rats administered AESTL (150 and 300 mg/kg body weight) and diabetic rats administered metformin (200 mg/kg) orally for two weeks. Thereafter, the animals were euthanized, blood sample collected, pancreas harvested and some pancreatic gene expressions (such as insulin, PCNA, PDX-1, KI-67, and GLP-1R)s as well as oxidative stress parameters were analyzed.

RESULTS

The results revealed that AESTL significantly (p<0.05) reduced fasting blood glucose level, food and water intake, and lipid peroxidation in diabetic rats. Diabetic rats administered different doses of AESTL showed a substantial upsurge in body weight, antioxidant enzyme activities, and pancreatic gene expressions (insulin, PCNA, PDX-1, KI-67, and GLP-1R).

CONCLUSIONS

It can therefore be concluded that AESTL has the ability to protect the pancreas during diabetes mellitus conditions.

Hepatoprotective effect of Qushihuayu formula on non-alcoholic steatohepatitis induced by MCD diet in rat

Background

Non-alcoholic steatohepatitis (NASH) is an advanced form of non-alcoholic fatty liver disease (NAFLD) for which there is yet any standard pharmacotherapy. Traditional Chinese medicine formula such as Qushihuayu (QSHY) composing of multiple bioactive compounds has been used to treat NAFLD and NASH and shows beneficial effects over single compound treatment. This study aimed to investigate the mechanism of hepatoprotective effect of QSHY formula using a rat model.

Methods

Six-weeks old male Wistar rats were given methionine/choline supplemented (MCS) diet for 8 weeks and used as the blank control. Another 7 rats, which received methionine/choline deficient (MCD) diet in the first 6 weeks and a MCS&MCD (1:1) mixture diet in the last 2 weeks, were used as the model group. The groups of QSHY pre-treatment, low dosage, medium dosage and high dosage were given the same diet as the model group. Except for pre-treatment group (1 week in advanced of other groups), all QSHY treatment groups received QSHY formula by gavage every day since the MCD diet started.

Results

In the MCD diet group, the QSHY formula decreased the serum ALT and AST levels, lipid droplets, inflammation foci, FAS and α-SMA protein expression than MCD diet group. MAPK pathways phospharylation were markedly depressed by the QSHY formula. Moreover, QSHY formula enhanced PPAR-γ and p-p65 translocating into nucleus. The administration of QSHY increased hepatic mRNA levels of Transcription Factor 1 alpha (HNF1A), Hepatocyte Nuclear Factor 4 alpha (HNF4A) and Forkhead box protein A3 (FOXA3) which play a pivotal role in Hepatic stellate cell (HSCs) reprogramming.

Conclusion

These findings suggest that QSHY formula exerts a hepatoprotective effect against steatosis and fibrosis presumably via depressed MAPK pathways phosphorylation, reinforcement of PPAR-γ and p-p65 translocating into nucleus and enhanced HSCs reprogramming.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-021-00434-1.

Enhanced mitochondrial dysfunction and oxidative stress in the mammary gland of cows with clinical ketosis

Ketosis is a common metabolic disorder in high-producing dairy cows during the peripartal period. Negative energy balance leads to increased circulating levels of nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHB), consequently increasing the risk of ketosis. It is well-known that NEFA and BHB can induce lipotoxicity and oxidative stress in bovine tissues/organs including the liver and adipose tissue. Although the mammary gland is one important site for NEFA and BHB metabolism, whether an overload in their concentrations within mammary cells causes oxidative stress during ketosis remains unclear. Thus, the present study compared oxidative stress status and mitochondrial function in mammary tissues harvested by biopsy from healthy (n = 15) and clinically ketotic (n = 15) dairy cows within 2 to 3 wk postpartum. Compared with healthy cows, ketotic cows had depressed daily milk yield (median: 28.92 vs. 21.56 kg) and dry matter intake (median: 22.36 vs. 19.92 kg/d), accompanied by elevated plasma NEFA (median: 0.32 vs. 1.26 mM), BHB (median: 0.52 vs. 3.69 mM), and lower plasma glucose (median: 4.55 vs. 2.13 mM). As detected by a commercial kit, a greater level of reactive oxygen species in mammary epithelial cells of ketotic cows, and greater oxidant indices including hydrogen peroxide and malondialdehyde coupled with lower antioxidant indices including glutathione peroxidase, catalase, and superoxide dismutase activities as detected by the respective biochemical kits in the homogenate of mammary tissue of ketotic cows indicated increased oxidative stress status. Lower citrate synthase activity and ATP production as detected by the respective commercial kits coupled with lower mRNA and protein abundance of mitochondrial respiratory chain oxidative phosphorylation complexes I-V (CO I-V) in ketotic cows suggested an impairment of mitochondrial function. This was supported by lower mRNA and protein abundance of nucleus-derived mitochondrial function regulators including peroxisome proliferator activated receptor gamma coactivator 1 α, mitofusin 2, nuclear respiratory factor 1, and mitochondrial transcription factor A. Lower mitochondrial membrane potential evaluated via the tetraethylbenzimidazolylcarbocyanine iodide (JC-1) labeling method and swollen mitochondria in mammary epithelial cells of ketotic cows suggested the existence of mitochondrial damage. Overall, the present study revealed extensive mitochondrial dysfunction and oxidative stress in the mammary gland of clinically ketotic cows. As such, data suggest that reduced milk yield in cows with ketosis is partly due to enhanced oxidative stress along with mitochondrial dysregulation in the mammary gland.

Saponins of Momordica charantia increase insulin secretion in INS-1 pancreatic β-cells via the PI3K/Akt/FoxO1 signaling pathway

Saponins are the main bioactive substances with anti-hyperglycemic activities of Momordica charantia. This study aimed to verify the effects of M. charantia saponins on insulin secretion and explore the potential underlying mechanisms in INS-1 pancreatic β-cells. We injured INS-1 cells with 33.3mM glucose and then treated them with saponins. Saponins improved cell morphology and viability as demonstrated by inverted microscopy and CCK8 detection and significantly increased insulin secretion in a concentration-dependent manner as shown by ELISA. Thus, we obtained the optimal concentration for the subsequent experiments. Potential mechanisms were explored by immunofluorescence, western blotting, and RT-qPCR techniques. First, saponins increased the mRNA and protein levels of IRS-2 but decreased the serine 731 phosphorylation level of IRS-2. Moreover, saponins increased the phosphorylation of Akt protein and decreased the protein level of FoxO1, which were both reversed by the PI3K inhibitor ly294002. Furthermore, saponins increased the protein level of the downstream molecule and insulin initiating factor PDX-1, which was also reversed by ly294002. Saponins also increased Akt and PDX-1 mRNA and decreased FoxO1 mRNA, which were both reversed by ly294002. Saponins increased glucose-stimulated insulin secretion (GSIS) and intracellular insulin content, which were reversed by ly294002, as determined by ELISA. The immunofluorescence results also confirmed this tendency. In conclusion, our findings improve our understanding of the function of saponins in INS-1 pancreatic β-cells and suggest that saponins may increase insulin secretion via the PI3K/Akt/FoxO1 signaling pathway.

Knockdown of phosphatase and tensin homolog (PTEN) inhibits fatty acid oxidation and reduces very low density lipoprotein assembly and secretion in calf hepatocytes

Dairy cows with fatty liver exhibit hepatic lipid accumulation and disturbances in fatty acid oxidation and lipid transport. Phosphatase and tensin homolog (PTEN), a lipid phosphatase, regulates intrahepatic fatty acid oxidation and lipid transport in mice. Whether PTEN play a role in fatty acid oxidation and very low density lipoprotein (VLDL) assembly in calf hepatocytes are unknown. Hepatocytes isolated from 3 healthy female Holstein calves (1 d old, 30-40 kg) were infected with empty adenovirus with green fluorescent protein for 48 h (Ad-GFP group) or infected with PTEN knockdown adenovirus for 48 h (Ad-shPTEN group), or cultured in RPMI-1640 without Ad-shPTEN or Ad-GFP (control group). Compared with the Ad-GFP group, PTEN knockdown decreased mRNA and protein abundance and the activity of fatty acid oxidation-related molecules, including acyl-coA synthetase long-chain 1, carnitine palmitoyltransferase 1, carnitine palmitoyltransferase 2, and 3-hydroxy acyl-coA dehydrogenase. Furthermore, PTEN knockdown decreased mRNA and protein abundance of VLDL assembly-related molecules, including apolipoprotein B100, apolipoprotein E, microsomal triglyceride transfer protein, and low density lipoprotein receptor. Importantly, PTEN knockdown promoted triglyceride accumulation in hepatocytes and reduced the VLDL content in culture medium. A subsequent study was conducted on the following 4 groups: cells infected with Ad-GFP for 48 h and then treated with 2% BSA for another 24 h (Ad-GFP + BSA); cells infected with Ad-GFP for 48 h and then treated with 1.2 mM free fatty acids (FFA) and 2% BSA for another 24 h (Ad-GFP + 1.2 mM FFA); cells infected with Ad-shPTEN for 48 h and then treated with 2% BSA for another 24 h (Ad-shPTEN + BSA); cells infected with Ad-shPTEN for 48 h and then treated with 1.2 mM FFA and 2% BSA for another 24 h (Ad-shPTEN + 1.2 mM FFA). Compared with Ad-GFP + BSA, the abundances of PTEN and of fatty acid oxidation- and VLDL assembly-related proteins were lower in the Ad-GFP + 1.2 mM FFA group. Importantly, PTEN knockdown heightened the increase in triglyceride accumulation of hepatocytes and the decrease in VLDL content in culture medium induced by FFA. Overall, these in vitro data indicate that FFA inhibits PTEN expression, leading to triglyceride accumulation and the inhibition of VLDL assembly in calf hepatocytes. These findings suggest that PTEN may be a potential therapeutic target for FFA-induced hepatic steatosis in dairy cows.

Ferroptosis mediated by the interaction between Mfn2 and IREα promotes arsenic-induced nonalcoholic steatohepatitis

Exposure to arsenic is a risk factor for nonalcoholic steatohepatitis (NASH). Ferroptosis is a form of regulated cell death defined by the accumulation of lipid peroxidation. In the current study, we observed the occurrence of ferroptosis in arsenic-induced NASH by assessing ferroptosis related hallmarks. In vitro, we found that ferrostatin-1 effectively attenuated the executing of ferroptosis and NASH. Simultaneously, the expression of ACSL4 (acyl-CoA synthetase long-chain family member 4) was upregulated in rat's liver and L-02 cells exposed to arsenic. While, suppression of ACSL4 with rosiglitazone or ACSL4 siRNA remarkably alleviated arsenic-induced NASH and ferroptosis through diminishing 5-hydroxyeicosatetraenoic acid (5-HETE) content. Additionally, Mitofusin 2 (Mfn2), a physical tether between endoplasmic reticulum and mitochondria, has rarely been explored in the ferroptosis. Using Mfn2 siRNA or inositol-requiring enzyme 1 alpha (IRE1α) inhibitor, we found NASH and ferroptosis were obviously mitigated through reducing 5-HETE content. Importantly, Co-IP assay indicated that Mfn2 could interact with IRE1α and promoted the production of 5-HETE, ultimately led to ferroptosis and NASH. Collectively, our data showed that ferroptosis is involved in arsenic-induced NASH. These data provide insightful viewpoints into the mechanism of arsenic-induced NASH.

Effects of dietary inulin during late gestation on sow physiology, farrowing duration and piglet performance

In this study there was evaluation of effects of dietary inulin during late gestation on sow physiology, farrowing duration and piglet performance. At day 80 of gestation sows were randomly assigned to four groups：basal diet (CON); or basal diet with 0.8 %; 1.6 %; or 2.4 % inulin. The feeding of the diet with 1.6 % inulin resulted in larger weights of the litter at birth a shorter duration of the farrowing period, lesser average birth interval between piglets, lesser number of piglets dead at birth, and fewer piglets/sow dead at birth (P < 0.05). When sows were fed 0.8 % and 1.6 % IN, there was a larger litter weight at weaning, sow average daily feed intake and piglet average daily gain during lactation compared with values for these variables in the CON group (P <  0.05). Additionally, there was an increase in serum concentration of free fatty acid, total cholesterol, and high-density lipoprotein cholesterol with increasing amounts of inulin in the diet (linear, P <  0.05). Sows fed 1.6 % IN had greater serum concentrations of glucose than those in the CON group (P <  0.05). Furthermore, there was a linear increase in serum activity of total antioxidant capacity, total superoxide dismutase and glutathione peroxidase with increasing amounts of inulin in the diet (P <  0.05). In conclusion, results of the present study indicated feeding inulin during late gestation improved reproductive performance of sows, thus, may be a novel additive for the pig industry in improving efficiency of pork production.

Targeting DUSP7 signaling alleviates hepatic steatosis, inflammation and oxidative stress in high fat diet (HFD)-fed mice via suppression of TAK1

The non-alcoholic fatty liver disease (NAFLD), as a critical liver disease, is still lack of effective treatments because the molecular mechanism revealing the NAFLD pathogenesis remains unclear. Dual specific phosphatase 6 (DUSP7) shows effects on inflammatory response and is a negative feedback mechanism of the mitogen-activated protein kinase (MAPK) superfamily, which are critical factors in regulating NAFLD progression. However, the effects of DUSP7 on hepatic steatosis are still not fully understood. Here, we found that DUSP7 functioned as a negative regulator of NAFLD and in various metabolic disorders. DUSP7 expression was markedly reduced in liver samples from patients with simple hepatic steatosis or non-alcoholic steatohepatitis (NASH), as well as in liver tissues from high fat diet (HFD)-challenged mice or genetically obese (ob/ob) mice. DUSP7 knockout markedly accelerated insulin resistance, glucose intolerance, liver dysfunction, fibrosis and hepatic steatosis in HFD-fed mice. In addition, inflammatory response was significantly exacerbated in HFD-challenged mice with DUSP7 deletion, which was associated with the elevated activation of nuclear factor-κB (NF-κB) and MAPKs signaling pathways. Moreover, oxidative stress was detected in liver of HFD-induced mice, and this phenomenon was aggravated in mice with DUSP7 knockout. Importantly, we demonstrated that DUSP7 physically interacted with transforming growth factor β (TGF-β)-activated kinase (TAK1). DUSP7 deletion considerably promoted the activation of TAK1 in mice after HFD feeding, contributing to the lipid deposition, inflammatory response and reactive oxygen species (ROS) production. Taken together, DUSP7 might function as a protective factor against NAFLD development and metabolic disorder through alleviating dyslipidemia, inflammation and oxidative stress by directly interacting with TAK1 in hepatocytes, which was involved in the suppression of fibrosis. Thus, we may provide an effective strategy for the treatment of hepatic steatosis via targeting DUSP7.

Analysis of piRNA expression spectra in a non-alcoholic fatty liver disease mouse model induced by a methionine- and choline-deficient diet

Non-alcoholic fatty liver disease (NAFLD) has become a common health issue worldwide, and P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) have been shown to be differentially expressed in a variety of diseases. The aim of the present study was to investigate the potential relationship between piRNA and NAFLD. A NAFLD mouse model was established using a methionine- and choline-deficient (MCD) diet and methionine- and choline-sufficient (MCS) diet. Following this, mouse liver tissues were removed and stained with hematoxylin and eosin, and the levels of alanine aminotransferase, aspartate aminotransferase, total cholesterol and triglyceride were measured. Moreover, the liver tissues of the control and model groups were selected for piRNA gene chip analysis to identify piRNAs with differential expression in NAFLD. In addition, the differentially expressed piRNAs screened from the microarray were assessed by reverse transcription-quantitative PCR (RT-qPCR). piRNAs with potential research value were also selected for further analysis of target genes, using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways. The present study identified a total of 1,285 piRNAs with differential expression levels. The results indicated that in the model group, 641 piRNAs were upregulated, while 644 piRNAs were downregulated. Furthermore, piRNAs were enriched in ‘cancer’, ‘Hippo signaling’, ‘Wnt signaling’ and ‘Mitogen-activated protein kinase signaling’ pathways. The RT-qPCR results demonstrated that piRNA DQ566704 and piRNA DQ723301 were significantly upregulated in the model group, which was largely consistent with the analysis results of the piRNA arrays. Therefore, the results of the piRNA arrays and the further analyses in the present study were considered reliable. Collectively, the present results suggest that differentially expressed piRNAs exist in NAFLD and may affect the development of NAFLD via related pathways.

Mitochondrial membrane protein mitofusin 2 as a potential therapeutic target for treating free fatty acid-induced hepatic inflammation in dairy cows during early lactation

Inflammation is critical in the progression from benign hepatic lipidosis to pathological hepatic steatosis. The objective of this study was to examine the potential role of the outer mitochondrial membrane protein mitofusin 2 (MFN2) in the etiology of hepatic steatosis in dairy cows during early lactation. Using a nested case-control design, we compared blood and liver samples from 10 healthy cows and 10 age-matched cows with moderate fatty liver. Cows with moderate fatty liver had high liver triacylglycerols, elevated plasma concentrations of free fatty acids (FFA) and β-hydroxybutyrate, and low concentrations of glucose. Cows with moderate fatty liver had overactivated inflammatory pathways in the liver, as indicated by increased abundance of phosphorylated nuclear factor κB (NF-κB) p65, NLR family pyrin domain containing 3 (NLRP3) and caspase-1 inflammasome protein, and elevated plasma concentrations and hepatic mRNA abundance of their molecular targets IL-1β, IL-6, and tumor necrosis factor α (TNF-α). In the cell culture model, we were able to replicate our findings in cows with moderate fatty liver: 1.2 mM exogenous FFA decreased the abundance of MFN2 and upregulated phosphorylation levels of the inhibitor of NF-κB (IκB) α and NF-κB p65, the IκB kinase β activity, and the abundance of NLRP3, caspase-1, IL-1β, IL-6, and TNF-α. Whereas MFN2 knockdown potentiated the FFA-induced activation of these inflammatory pathways, overexpression of MFN2 attenuated the detrimental effect of excess exogenous FFA by improving mitochondrial function and decreasing the release of reactive oxygen species, suggesting that MFN2 may be a potential therapeutic target for FFA-induced hepatic inflammation in dairy cows during early lactation.

Effect of Caesalpinia bonduc Polyphenol Extract on Alloxan-Induced Diabetic Rats in Attenuating Hyperglycemia by Upregulating Insulin Secretion and Inhibiting JNK Signaling Pathway

Caesalpinia bonduc has been used in herbal medicines for the treatment of a wide range of diseases from decades. The present study has explored the remedial potential and underlying mechanism of polyphenol extract of Caesalpinia bonduc in alloxanized diabetic rats. HPLC/MS analysis confirmed the presence of phenolics in considerable concentrations in Caesalpinia bonduc extract. Administration of different doses (250 and 500 mg/kg) of CPP extract to hyperglycemic rats for 8 weeks restored blood and serum glucose, insulin, glycosylated hemoglobin, leptin, amylin, and carbohydrate metabolizing enzymes level towards normal compared to alloxanized diabetic group. The effect of CPP extract on various genes such as Pdx-1, Ins-1, ngn-3, GLUT-4, and IRS-1 in insulin signaling pathway and Traf-4, Traf-6, and Mapk-8 in MAPK downstream JNK cascade was examined through qRT-PCR to access the core molecular mechanism involved in CPP-induced recovery of diabetes. Results have revealed that CPP extract reduced oxidative stress in pancreatic β cells by restoring free radical scavenging potential, reducing the mRNA expression of Mapk-8, Traf-4, and Traf-6, and increasing the Pdx-1, Ins-1, ngn-3, GLUT-4, and IRS-1 expression ensuing regeneration of β cells and subsequent insulin release from pancreas. The results obtained in this study recommend that CPP extract may be a promising therapeutic restorative agent in the treatment of diabetes mellitus.