Sterol Regulatory Element-binding Transcription Factor Research Articles

Anti-atherogenic role of green tea (Camellia sinensis) in South Indian smokers

Ethnopharmacological relevanceGreen tea (Camellia sinensis) is a popular beverage consumed all over the world due to its health benefits. Many of these beneficial effects of green tea are attributed to polyphenols, particularly catechins. Aim of the studyThe present study focuses on underlying anti-platelet aggregation, anti-thrombotic, and anti-lipidemic molecular mechanisms of green tea in South Indian smokers. Materials and methods: We selected 120 South Indian male volunteers for this study to collect the blood and categorised them into four groups; control group individuals (Controls), smokers, healthy control individuals consuming green tea, and smokers consuming green tea. Smokers group subjects have been smoking an average 16-18 cigarettes per day for the last 7 years or more. The subjects (green tea consumed groups) consumed 100 mL of green tea each time, thrice a day for a one-year period. ResultsLC-MS analysis revealed the presence of multiple phytocompounds along with catechins in green tea extract. Increased plasma lipid peroxidation (LPO), protein carbonyls, cholesterol, triglycerides, and LDL-cholesterol with decreased HDL-cholesterol levels were observed in smokers compared to the control group and the consumption of green tea showed beneficial effect. Furthermore, docking studies revealed that natural compounds of green tea had high binding energy with 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA) when compared to their positive controls, whereas (-) epigallocatechin-3-gallate (EGCG) and (-) epicatechin-gallate (ECG) had high binding energy with sterol regulatory element-binding transcription factor 1 (SREBP1c). Further, our ex vivo studies showed that green tea extract (GTE) significantly inhibited platelet aggregation and increased thrombolytic activity in a dose dependent manner. ConclusionIn conclusion, in smokers, catechins synergistically lower oxidative stress, platelet aggregation and modify an aberrant lipid profile. Furthermore, molecular docking studies supported green tea catechins' antihyperlipidemic efficacy through strong inhibitory activity on HMG-CoA reductase and SREBP1c. The mitigating effects on cardiovascular disease risk factors in smokers that have been reported can be attributed majorly to catechins or to their synergistic effects.

Effect of different levels of Lactobacillus added to diets on fat deposition and meat quality of Sunit lambs

In this study, we examined the impact of adding Lactobacillus to the diet on fat distribution and meat quality of Sunit lambs. For 90 days, twenty-four lambs (19.31 ± 0.47 kg) were fed diets that contained 0 (NP), 6 (P1), 12 (P2), or 24 (P3) g of Lactobacillus casei/d. The results suggested that dietary supplementation with Lactobacillus decreased serum triglyceride in Sunit lambs (P < 0.001). The loin muscle area displayed notable increases in the P1 group (P < 0.05). Meanwhile, tail and visceral fat deposition of lambs were reduced when Lactobacillus was added to the diet (P < 0.05). Compared with the NP group, the values of shear force and cooking loss of in the P1 group exhibited a significant reduction, and intramuscular fat content increased significantly (P < 0.05). Additionally, the P1 group showed an increase in polyunsaturated fatty acids and a decrease in saturated fatty acids in the longissimus thoracis and biceps femoris muscles (P < 0.05). The P1 group showed downregulation of protein kinase AMP-activated catalytic subunit alpha 2 (AMPKα2) and carnitine palmitoyltransferase 1B expression in the longissimus thoracis muscle (P < 0.05). However, there was an upregulation of acetyl-CoA carboxylase (ACC), sterol regulatory element binding transcription factor 1 (SREBF1), and fatty acid synthase (FASN) expression (P < 0.05). In conclusion, feeding Sunit lambs 6 g/d of Lactobacillus as a dietary supplement may be a valuable way to improve fat distribution and meat quality. The AMPK/ACC and AMPK/SREBF1/FASN signaling pathways may be involved in this outcome.

Adrenarche-accompanied rise of adrenal sex steroid precursors prevents NAFLD in Young Female rats by converting into active androgens and inactivating hepatic Srebf1 signaling

BackgroundNon-alcoholic fatty liver disease (NAFLD) has rapidly become the most common cause of chronic liver disease in children and adolescents, but its etiology remains largely unknown. Adrenarche is a critical phase for hormonal changes, and any disturbance during this period has been linked to metabolic disorders, including obesity and dyslipidemia. However, whether there is a causal linkage between adrenarche disturbance and the increasing prevalence of NAFLD in children remains unclear.ResultsUsing the young female rat as a model, we found that the liver undergoes a transient slowdown period of growth along with the rise of adrenal-derived sex steroid precursors during adrenarche. Specifically blocking androgen actions across adrenarche phase using androgen receptor antagonist flutamide largely increased liver weight by 47.97% and caused marked fat deposition in liver, thus leading to severe NAFLD in young female rats. Conversely, further administrating nonaromatic dihydrotestosterone (DHT) into young female rats across adrenarche phase could effectively reduce liver fat deposition. But, administration of the aromatase inhibitor, formestane across adrenarche had minimal effects on hepatic de novo fatty acid synthesis and liver fat deposition, suggesting adrenal-derived sex steroid precursors exert their anti-NAFLD effects in young females by converting into active androgens rather than into active estrogens. Mechanistically, transcriptomic profiling and integrated data analysis revealed that active androgens converted from the adrenal sex steroid precursors prevent NAFLD in young females primarily by inactivating hepatic sterol regulatory element-binding transcription factor 1 (Srebf1) signaling.ConclusionsWe firstly evidenced that adrenarche-accompanied rise of sex steroid precursors plays a predominant role in preventing the incidence of NAFLD in young females by converting into active androgens and inactivating hepatic Srebf1 signaling. Our novel finding provides new insights into the etiology of NAFLD and is crucial in developing effective prevention and management strategies for NAFLD in children.

Sodium butyrate alleviates free fatty acid-induced steatosis in primary chicken hepatocytes via the AMPK/PPARα pathway

Fatty liver hemorrhagic syndrome (FLHS) is a prevalent metabolic disorder observed in egg-laying hens, characterized by fatty deposits and cellular steatosis in the liver. Our preliminary investigations have revealed a marked decrease in the concentration of butyric acid in the FLHS strain of laying hens. It has been established that sodium butyrate (NaB) protects against metabolic disorders. However, the underlying mechanism by which butyrate modulates hepato-lipid metabolism to a great extent remains unexplored. In this study, we constructed an isolated in vitro model of chicken primary hepatocytes to induce hepatic steatosis by free fatty acids (FFA). Our results demonstrate that treatment with NaB effectively mitigated FFA-induced hepatic steatosis in chicken hepatocytes by inhibiting lipid accumulation, downregulating the mRNA expression of lipo-synthesis-related genes (sterol regulatory element binding transcription factor 1 (SREBF1), acetyl-CoA carboxylase 1(ACC1), fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), liver X receptor α (LXRα), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR)) (P < 0.05), and upregulating the mRNA and protein expression of AMP-activated protein kinase α1 (AMPKα1), peroxisome proliferator-activated receptor α (PPARα), and carnitine palmitoyl-transferase 1A (CPT1A) (P < 0.05). Moreover, AMPK and PPARα inhibitors (Compound C (Comp C) and GW6471, respectively) reversed the protective effects of NaB against FFA-induced hepatic steatosis by blocking the AMPK/PPARα pathway, leading to lipid droplet accumulation and triglyceride (TG) contents in chicken primary hepatocytes. With these findings, NaB can alleviate hepatocyte lipoatrophy injury by activating the AMPK/PPARα pathway, promoting fatty acid oxidation, and reducing lipid synthesis in chicken hepatocytes, potentially being able to provide new ideas for the treatment of FLHS.

PEDV inhibits HNRNPA3 expression by miR-218-5p to enhance cellular lipid accumulation and promote viral replication.

Porcine epidemic diarrhea virus (PEDV) requires complete dependence on the metabolic system of the host cell to complete its life cycle. There is a strong link between efficient viral replication and cellular lipid synthesis. However, the mechanism by which PEDV interacts with host cells to hijack cellular lipid metabolism to promote its replication remains unclear. In this study, PEDV infection significantly enhanced the expression of lipid synthesis-related genes and increased cellular lipid accumulation. Furthermore, using liquid chromatography-tandem mass spectrometry, we identified heterogeneous nuclear ribonucleoprotein A3 (HNRNPA3) as the interacting molecule of PEDV NSP9. We demonstrated that the expression of HNRNPA3 was downregulated by PEDV-induced miR-218-5p through targeting its 3' untranslated region. Interestingly, knocking down HNRNPA3 facilitated the PEDV replication by promoting cellular lipid synthesis. We next found that the knockdown of HNRNPA3 potentiated the transcriptional activity of sterol regulatory element-binding transcription factor 1 (SREBF1) through zinc finger protein 135 (ZNF135) as well as PI3K/AKT and JNK signaling pathways. In summary, we propose a model in which PEDV downregulates HNRNPA3 expression to promote the expression and activation of SREBF1 and increase cellular lipid accumulation, providing a novel mechanism by which PEDV interacts with the host to utilize cellular lipid metabolism to promote its replication.IMPORTANCEAs the major components and structural basis of the viral replication complexes of positive-stranded RNA viruses, lipids play an essential role in viral replication. However, how PEDV manipulates host cell lipid metabolism to promote viral replication by interacting with cell proteins remains poorly understood. Here, we found that SREBF1 promotes cellular lipid synthesis, which is essential for PEDV replication. Moreover, HNRNPA3 negatively regulates SREBF1 activation and specifically reduces lipid accumulation, ultimately inhibiting PEDV dsRNA synthesis. Our study provides new insight into the mechanisms by which PEDV hijacks cell lipid metabolism to benefit viral replication, which can offer a potential target for therapeutics against PEDV infection.

Nanoparticle Targeting in Chemo-Resistant Ovarian Cancer Reveals Dual Axis of Therapeutic Vulnerability Involving Cholesterol Uptake and Cell Redox Balance.

Platinum (Pt)-based chemotherapy is the main treatment for ovarian cancer (OC); however, most patients develop Pt resistance (Pt-R). This work shows that Pt-R OC cells increase intracellular cholesterol through uptake via the HDL receptor, scavenger receptor type B-1 (SR-B1). SR-B1 blockade using synthetic cholesterol-poor HDL-like nanoparticles (HDL NPs) diminished cholesterol uptake leading to cell death and inhibition of tumor growth. Reduced cholesterol accumulation in cancer cells induces lipid oxidative stress through the reduction of glutathione peroxidase 4 (GPx4) leading to ferroptosis. In turn, GPx4 depletion induces decreased cholesterol uptake through SR-B1 and re-sensitizes OC cells to Pt. Mechanistically, GPx4 knockdown causes lower expression of the histone acetyltransferase EP300, leading to reduced deposition of histone H3 lysine 27 acetylation (H3K27Ac) on the sterol regulatory element binding transcription factor 2 (SREBF2) promoter and suppressing expression of this key transcription factor involved in the regulation of cholesterol metabolism. SREBF2downregulation leads to decreased SR-B1 expression and diminished cholesterol uptake. Thus, chemoresistance and cancer cell survival under high ROS burden obligates high GPx4 and SR-B1 expression through SREBF2. Targeting SR-B1 to modulate cholesterol uptake inhibits this axis and causes ferroptosis in vitro and in vivo in Pt-R OC.

Betaine supplementation alleviates corticosterone-induced hepatic cholesterol accumulation through epigenetic modulation of HMGCR and CYP7A1 genes in laying hens

Excessive corticosterone (CORT) exposure could cause hepatic cholesterol accumulation in chickens and maternal betaine supplementation could decrease hepatic cholesterol deposition through epigenetic modifications in offspring chickens. Nevertheless, it remains uncertain whether providing betaine to laying hens could protect CORT-induced hepatic cholesterol accumulation via epigenetic mechanisms. This study aimed to examine the effects of dietary betaine on plasma and hepatic cholesterol contents, expression of cholesterol metabolic genes, as well as DNA methylation on their promoters in the liver of laying hens exposed to CORT. A total of 72 laying hens at 130 d of age were randomly divided into 3 groups: control (CON), CORT, and CORT+betaine (CORT+BET) groups. The experiment lasted for 35 d. Chickens in CON and CORT groups were fed a basal diet, whereas the CORT+BET group chickens were fed the basal diet supplemented with 0.1% betaine for 35 d. On d 28 of the experiment, chickens in CORT and CORT+BET groups received daily subcutaneous injections of CORT (4.0 mg/kg body weight), whereas the CON group chickens were injected with an equal volume of solvent for 7 d. The results showed that CORT administration led to a significant increase (P < 0.05) in the contents of cholesterol in plasma and liver, associated with activation (P < 0.05) of sterol regulatory element binding transcription factor 2 (SREBP2), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), lecithin-cholesterol acyltransferase (LCAT) and low-density lipoprotein receptor (LDLR) genes expression, and inhibition of cholesterol-7-alpha hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1) genes expression in the liver compared to the CON. In contrast, CORT-induced up-regulation of HMGCR mRNA and protein abundances and downregulation of CYP7A1 mRNA and protein abundances were completely normalized (P < 0.05) by betaine supplementation. Besides, CORT injection led to significant hypomethylation (P < 0.05) on HMGCR promoter and hypermethylation (P < 0.05) on CYP7A1 promoter. Moreover, dietary betaine rescued (P < 0.05) CORT-induced changes in methylation status of HMGCR and CYP7A1 genes promoters. These results indicate that dietary betaine addition protects laying hens from CORT-induced hepatic cholesterol accumulation via epigenetic modulation of HMGCR and CYP7A1 genes.

Lipid Metabolism Regulators Are the Possible Determinant for Characteristics of Myopic Human Scleral Stroma Fibroblasts (HSSFs).

The purpose of the current investigation was to elucidate what kinds of responsible mechanisms induce elongation of the sclera in myopic eyes. To do this, two-dimensional (2D) cultures of human scleral stromal fibroblasts (HSSFs) obtained from eyes with two different axial length (AL) groups, <26 mm (low AL group, n = 2) and >27 mm (high AL group, n = 3), were subjected to (1) measurements of Seahorse mitochondrial and glycolytic indices to evaluate biological aspects and (2) analysis by RNA sequencing. Extracellular flux analysis revealed that metabolic indices related to mitochondrial and glycolytic functions were higher in the low AL group than in the high AL group, suggesting that metabolic activities of HSSF cells are different depending the degree of AL. Based upon RNA sequencing of these low and high AL groups, the bioinformatic analyses using gene ontology (GO) enrichment analysis and ingenuity pathway analysis (IPA) of differentially expressed genes (DEGs) identified that sterol regulatory element-binding transcription factor 2 (SREBF2) is both a possible upstream regulator and a causal network regulator. Furthermore, SREBF1, insulin-induced gene 1 (INSIG1), and insulin-like growth factor 1 (IGF1) were detected as upstream regulators, and protein tyrosine phosphatase receptor type O (PTPRO) was detected as a causal network regulator. Since those possible regulators were all pivotally involved in lipid metabolisms including fatty acid (FA), triglyceride (TG) and cholesterol (Chol) biosynthesis, the findings reported here indicate that FA, TG and Chol biosynthesis regulation may be responsible mechanisms inducing AL elongation via HSSF.

Investigating the Diagnostic and Therapeutic Potential of SREBF2-Related Lipid Metabolism Genes in Colon Cancer.

Colon cancer is one of the leading causes of death worldwide, and screening of effective molecular markers for the diagnosis is prioritised for prevention and treatment. This study aimed to investigate the diagnostic and predictive potential of genes related to the lipid metabolism pathway, regulated by a protein called sterol-regulatory element-binding transcription Factor 2 (SREBF2), for colon cancer and patient outcomes. We used machine-learning algorithms to identify key genes associated with SREBF2 in colon cancer based on a public database. A nomogram was created to assess the diagnostic value of these genes and validated in the Cancer Genome Atlas. We also analysed the relationship between these genes and the immune microenvironment of colon tumours, as well as the correlation between gene expression and clinicopathological characteristics and prognosis in the China Medical University (CMU) clinical cohort. Three genes, 7-dehydrocholesterol reductase (DHCR7), hydroxysteroid 11-beta dehydrogenase 2 (HSD11B2), and Ral guanine nucleotide dissociation stimulator-like 1 (RGL1), were identified as hub genes related to SREBF2 and colon cancer. Using the TCGA dataset, receiver operating characteristic curve analysis showed the area under the curve values of 0.943, 0.976, and 0.868 for DHCR7, HSD11B2, and RGL1, respectively. In the CMU cohort, SREBF2 and DHCR7 expression levels were correlated with TNM stage and tumour invasion depth (P < 0.05), and high DHCR7 expression was related to poor prognosis of colon cancer (P < 0.05). Furthermore, DHCR7 gene expression was positively correlated with the abundance of M0 and M1 macrophages and inversely correlated with the abundance of M2 macrophages, suggesting that the immune microenvironment may play a role in colon cancer surveillance. There was a correlation between SREBF2 and DHCR7 expression across cancers in the TCGA database. This study highlights the potential of DHCR7 as a diagnostic marker and therapeutic target for colon cancer.

Acne Transcriptomics: Fundamentals of Acne Pathogenesis and Isotretinoin Treatment.

This review on acne transcriptomics allows for deeper insights into the pathogenesis of acne and isotretinoin's mode of action. Puberty-induced insulin-like growth factor 1 (IGF-1), insulin and androgen signaling activate the kinase AKT and mechanistic target of rapamycin complex 1 (mTORC1). A Western diet (hyperglycemic carbohydrates and milk/dairy products) also co-stimulates AKT/mTORC1 signaling. The AKT-mediated phosphorylation of nuclear FoxO1 and FoxO3 results in their extrusion into the cytoplasm, a critical switch which enhances the transactivation of lipogenic and proinflammatory transcription factors, including androgen receptor (AR), sterol regulatory element-binding transcription factor 1 (SREBF1), peroxisome proliferator-activated receptor γ (PPARγ) and signal transducer and activator of transcription 3 (STAT3), but reduces the FoxO1-dependent expression of GATA binding protein 6 (GATA6), the key transcription factor for infundibular keratinocyte homeostasis. The AKT-mediated phosphorylation of the p53-binding protein MDM2 promotes the degradation of p53. In contrast, isotretinoin enhances the expression of p53, FoxO1 and FoxO3 in the sebaceous glands of acne patients. The overexpression of these proapoptotic transcription factors explains isotretinoin's desirable sebum-suppressive effect via the induction of sebocyte apoptosis and the depletion of BLIMP1(+) sebocyte progenitor cells; it also explains its adverse effects, including teratogenicity (neural crest cell apoptosis), a reduced ovarian reserve (granulosa cell apoptosis), the risk of depression (the apoptosis of hypothalamic neurons), VLDL hyperlipidemia, intracranial hypertension and dry skin.

Morusinol Extracted from Morus alba Inhibits Cell Proliferation and Induces Autophagy via FOXO3a Nuclear Accumulation-Mediated Cholesterol Biosynthesis Obstruction in Colorectal Cancer.

The incidence rate of colorectal cancer (CRC) has been increasing significantly in recent years, and it is urgent to develop novel drugs that have more effects for its treatment. It has been reported that many molecules extracted from the root bark of Morus alba L. (also known as Cortex Mori) have antitumor activities. In our study, we identified morusinol as a promising anticancer agent by selecting from 30 molecules extracted from Morus alba L. We found that morusinol treatment suppressed cell proliferation and promoted apoptosis of CRC cells in vitro. Besides this, we observed that morusinol induced cytoprotective autophagy. The GO analysis of differentially expressed genes from RNA-seq data showed that morusinol affected cholesterol metabolism. Then we found that key enzyme genes in the cholesterol biosynthesis pathway as well as the sterol regulatory element binding transcription factor 2 (SREBF2) were significantly downregulated. Furthermore, additional cholesterol treatment reversed the anti-CRC effect of morusinol. Interestingly, we also found that morusinol treatment could promote forkhead box O3 (FOXO3a) nuclear accumulation, which subsequently suppressed SREBF2 transcription. Then SREBF2-controlled cholesterol biosynthesis was blocked, resulting in the suppression of cell proliferation, promotion of apoptosis, and production of autophagy. The experiments in animal models also showed that morusinol significantly impeded tumor growth in mice models. Our results suggested that morusinol may be used as a candidate anticancer drug for the treatment of CRC.

OR09-06 The Cholesterol Oxidation Product 7-Ketosterol Reduces Progesterone Production By Human Cytotrophoblast Cells In A Sex Dimorphic Manner

Abstract Disclosure: E. Ticiani: None. N. Pascuali: None. P. Danos: None. C. Murga-Zamalloa: None. I. Buhimschi: None. A. Veiga-Lopez: None. Many pregnancy complications including recurrent miscarriage and preterm birth are strongly associated with placental dysfunction and heightened inflammation. Diet-derived cholesterol, especially via consumption of fast foods that have undergone thermal processing or long-term storage, is highly susceptible to oxidation which results in cholesterol oxidation products, known as oxysterols. Oxysterols are known drivers of inflammation and have been implicated in chronic diseases, including atherosclerosis and neurodegeneration. We hypothesized that the prototype oxysterol 7-ketosterol (7-KT) induces reduced steroid synthesis and/or secretion in human placental cells associated with a pro-inflammatory response. To test this hypothesis, we isolated human primary cytotrophoblast cells (hCTB) from healthy term pregnancies with singleton female fetuses (n=4) and exposed them to 7-KT (2.5 µg/ml) or vehicle control (C; 0.1% DMSO) for 96h. Cells were subjected to RNA sequencing using Illumina TruSeq (p&amp;lt;0.05, FDR &amp;lt;0.05 and log2 fold change &amp;gt;1). Pathway analysis discovered that 10 of the most down-regulated genes (CYP51A1, MSMO1, IDI1, HMGCS1, HMGCR, ACAT2, DDX31, DHCR7, SREBF2, NLRP7) were associated with lipid metabolism. Among them, sterol regulatory element binding transcription factor 2 (SREBF2), is a known activator of cholesterol synthesis. Using female (n=4) and male hCTB (n=4), we further evaluated sex specific effects of 7-KT after 96h of exposure using RT-qPCR. We confirmed that 7-KT reduced the expression of SREBF2 in female and in male hCTB, as well as of genes responsible for cholesterol influx (LDLR) and synthesis (HMGCR and MVK), but not of the cholesterol efflux gene ABCA1. Similar gene expression patterns were observed in JEG-3 cells exposed to 7-KT, a choriocarcinoma cell line that retains the ability to synthetize progesterone. This was coupled with a ∼50% reduction in intracellular cholesterol in JEG-3 cells exposed to 7-KT. Considering that cholesterol is the precursor for progesterone, we assessed progesterone secretion in JEG-3 and in male and female-derived hCTBs cells by ELISA. 7-KT reduced progesterone secretion by JEG-3 and female hCTB by ∼40% while male hCTB were not affected. Additionally, a short exposure (24h) to 7-KT increased the expression of pro-inflammatory genes (IL1α, IL6 and TNFα) in female, but not male hCTB. Altogether, our results demonstrate that the oxysterol 7-KT induces early pro-inflammatory gene expression, followed by a reduction in cholesterol metabolism, lower intracellular cholesterol, and progesterone secretion. Future studies should further investigate the mechanism by which 7-KT drives sex-specific changes in placental cells, and the impact of excess oxysterols on pregnancy outcomes. Presentation: Friday, June 16, 2023

Genome-wide association meta-analysis identifies 17 loci associated with nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is common and partially heritable and has no effective treatments. We carried out a genome-wide association study (GWAS) meta-analysis of imaging (n = 66,814) and diagnostic code (3,584 cases versus 621,081 controls) measured NAFLD across diverse ancestries. We identified NAFLD-associated variants at torsin family 1 member B (TOR1B), fat mass and obesity associated (FTO), cordon-bleu WH2 repeat protein like 1 (COBLL1)/growth factor receptor-bound protein 14 (GRB14), insulin receptor (INSR), sterol regulatory element-binding transcription factor 1 (SREBF1) and patatin-like phospholipase domain-containing protein 2 (PNPLA2), as well as validated NAFLD-associated variants at patatin-like phospholipase domain-containing protein 3 (PNPLA3), transmembrane 6 superfamily 2 (TM6SF2), apolipoprotein E (APOE), glucokinase regulator (GCKR), tribbles homolog 1 (TRIB1), glycerol-3-phosphate acyltransferase (GPAM), mitochondrial amidoxime-reducing component 1 (MARC1), microsomal triglyceride transfer protein large subunit (MTTP), alcohol dehydrogenase 1B (ADH1B), transmembrane channel like 4 (TMC4)/membrane-bound O-acyltransferase domain containing 7 (MBOAT7) and receptor-type tyrosine-protein phosphatase δ (PTPRD). Implicated genes highlight mitochondrial, cholesterol and de novo lipogenesis as causally contributing to NAFLD predisposition. Phenome-wide association study (PheWAS) analyses suggest at least seven subtypes of NAFLD. Individuals in the top 10% and 1% of genetic risk have a 2.5-fold to 6-fold increased risk of NAFLD, cirrhosis and hepatocellular carcinoma. These genetic variants identify subtypes of NAFLD, improve estimates of disease risk and can guide the development of targeted therapeutics.

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

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

A high fat, high sugar diet induces hepatic Peroxisome proliferator-activated receptor gamma coactivator 1-alpha promoter hypermethylation in male Wistar rats

Previously we reported that a high fat, high sugar (HFHS) diet induced adiposity, hyperinsulinaemia, hyperleptinaemia, hypertriglyceridaemia and increased liver mass in male Wistar rats. In the present study, the mechanisms underlying the increased liver mass were further elucidated by assessing hepatic lipid accumulation and the expression and methylation status of key metabolic genes using histology, quantitative real-time PCR and pyrosequencing, respectively. The HFHS diet induced hepatic steatosis, increased hepatic triglycerides (1.8-fold, p < 0.001), and increased the expression of sterol regulatory element-binding transcription factor 1 (Srebf1) (2.0-fold, p < 0.001) and peroxisome proliferator-activated receptor gamma (Pparg) (1.7-fold, p = 0.017) in the liver. The expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (Pgc1a) was decreased (2.6-fold, p < 0.010), which was accompanied by hypermethylation (p = 0.018) of a conserved CpG site in the promoter of Pgc1a in HFHS fed rats compared to controls. In silico analysis identified putative binding sites for CCAAT/enhancer-binding protein beta (C/EBPß) and hepatocyte nuclear factor 1 (HNF1) within proximity to the hypermethylated CpG. As Pgc1a is a co-activator of several transcription factors regulating multiple metabolic pathways, hypermethylation of this conserved CpG site in the promoter of Pgc1a may be one possible mechanism contributing to the development of hepatic steatosis in response to a HFHS diet. However, further work is required to confirm the role of Pgc1a in steatosis.

CREB-Regulated Transcriptional Coactivator 2 Proteome Landscape is Modulated by SREBF1

cAMP response element-binding protein (CREB) regulated transcriptional coactivator 2 (CRTC2) is a critical transcription factor that maintains glucose homeostasis by activating CREB. Energy homeostasis is maintained through multiple pathways; therefore, CRTC2 may interact with other transcription factors, particularly under metabolic stress. CRTC2 liver-specific KO mice were created, and the global proteome, phosphoproteome, and acetylome from liver tissue under high-fat diet conditions were analyzed using liquid chromatography-tandem mass spectrometry and bioinformatics analysis. Differentially regulated proteins (DRPs) were enriched in metabolic pathways, which were subsequently corroborated through animal experiments. The consensus DRPs from these datasets were used as seed proteins to generate a protein-protein interaction network using STRING, and GeneMANIA identified fatty acid synthase as a mutually relevant protein. In an additional local-protein-protein interaction analysis of CRTC2 and fatty acid synthase with DRPs, sterol regulatory element binding transcription factor 1 (SREBF1) was the common mediator. CRTC2-CREB and SREBF1 are transcription factors, and DNA-binding motif analysis showed that multiple CRTC2-CREB–regulated genes possess SREBF1-binding motifs. This indicates the possible induction by the CRTC2–SREBF1 complex, which is validated through luciferase assay. Therefore, the CRTC2–SREBF1 complex potentially modulates the transcription of multiple proteins that fine-tune cellular metabolism under metabolic stress.

Effects of dietary standardized ileal digestible lysine to net energy ratio and wheat level on growth performance, meat quality, intestinal microbiota and body metabolism of finishing pigs

Lowing lysine (Lys): energy ratio based on corn-soybean diets could increase intramuscular fat (IMF) content, the effectiveness of it in enhancing IMF content when corn is partially substituted by wheat is unclear. This study aimed to determine the effects of dietary wheat levels and standardized ileal digestible (SID) Lys: net energy (NE) ratio on growth performance and meat quality, alteration in gut microbiota and body metabolism, as well as its correlation with meat quality are revealed via combined microbiome and metabolomic methods. A total of 72 pigs were randomly divided into four groups and fed with high SID Lys:NE ratio (HR) diets containing 25% wheat (W25HR), low SID Lys:NE ratio (LR) diets containing 25% wheat (W25LR), HR diets containing 55% wheat (W55HR) or LR diets containing 55% wheat (W55LR). Increasing dietary wheat level impaired feed utilization during 65–90 kg phase (P < 0.05) and enhanced meat color values (P < 0.05) of longissimus dorsi (LD) in finishing pigs. Enhancing dietary wheat level decreased relative abundance of Lactobacillus and Coprococcus (P < 0.05), and inhibited microbial carbohydrate metabolism capacity (P < 0.05) in colon of finishing pigs. Changes in microbial composition and carbohydrate metabolism capacity caused by wheat level led to alteration in meat color. LR diets improved feed utilization (P < 0.05), affected amino acid and lipid metabolism, and increased IMF content in LD (P < 0.05). Reducing SID Lys:NE ratio changed the concentrations of PA, delta-tocopherol, L-arginine, AzA, BA, and L-carnitine at the 25% wheat level and ARA, SDA, Glu, fructose-6-phosphate, and isorhamnetin at the 55% wheat level in the serum (P < 0.05, VIP > 1), which could serve as key biomarkers for predicting meat quality. LR diets upregulated mRNA expression levels of CCAAT/enhancer binding protein (C/EBP) α (P < 0.05), C/EBPβ (P < 0.01), sterol regulatory element-binding transcription factor 1c, fatty acid synthase (FAS) (P < 0.05), while downregulated mRNA abundance of adipose triglyceride lipase (ATGL) (P < 0.05) in liver at the 25% wheat level. The mRNA expression levels of C/EBPβ (P < 0.01), FAS, acetyl-coA carboxylase and fatty acid binding protein 1 (P < 0.05) were higher in the W55LR than W55HR groups, whereas mRNA abundance of ATGL was lower (P < 0.05). These results indicated that lowering SID Lys:NE ratio promoted lipogenesis, inhibited lipolysis and improved IMF deposition in LD via altering serum metabolism in different manner at two wheat level. LR diets containing 25% wheat was recommended to enhance the growth performance of finishing pigs, while concurrently achieving higher IMF content and improved meat color in the LD.

CircFOXN2 alleviates glucocorticoid- and tacrolimus-induced dyslipidemia by reducing FASN mRNA stability by binding to PTBP1 during liver transplantation.

We aimed to examine impacts and functional mechanism of circular RNA forkhead box N2 (FOXN2) in tacrolimus (TAC)- and dexamethasone (Dex)-induced lipid metabolism disorders. RNA level and protein contents in TAC, Dex, or combined TAC- plus Dex-treated patients and Huh-7 cells were measured utilizing quantitative real-time (qRT)-PCR and western blotting assays measured the formation of lipid droplet. Total cholesterol (TC) and triglyceride (TG) levels were determined using corresponding commercial kits and Oil red O staining. RNA immunoprecipitation and RNA pull-down verified the binding relationship among circFOXN2, polypyrimidine tract binding protein 1 (PTBP1) and fatty acid synthase (FASN). Male C57BL/6 mice were used to establish a dyslipidemia mouse model to validate the discoveries at the cellular level. Dex treatment significantly promoted TAC-mediated increase of TC and TG in serum samples and Huh-7 cells. Moreover, circFOXN2 was reduced but FASN was elevated in TAC-treated Huh-7 cells, and these expression trends were markedly enhanced by Dex cotreatment. Overexpression of circFOXN2 could reverse the accumulation of TC and TG and the upregulation of FASN and sterol regulatory element binding transcription factor 2 (SREBP2) mediated by Dex and TAC cotreatment. Mechanistically, circFOXN2 reduced FASN mRNA stability by recruiting PTBP1. The protective roles of circFOXN2 overexpression on lipid metabolism disorders were weakened by FASN overexpression. In vivo finding also disclosed that circFOXN2 greatly alleviated the dysregulation of lipid metabolism triggered by TAC plus Dex. CircFOXN2 alleviated the dysregulation of lipid metabolism induced by the combination of TAC and Dex by modulating the PTBP1/FASN axis.NEW & NOTEWORTHY Collectively, our experiments revealed for the first time that circFOXN2 alleviated the Dex- and TAC-induced dysregulation of lipid metabolism by regulating the PTBP1/FASN axis. These findings suggested that circFOXN2 and FASN might be candidate targets for the treatment of Dex- and TAC-induced metabolic disorders.

Regulation of cholesterol metabolism during high fatty acid–induced lipid deposition in calf hepatocytes

Cholesterol in the circulation is partly driven by changes in feed intake, but aspects of cholesterol metabolism during development of fatty liver are not well known. The objective of this study was to investigate mechanisms of cholesterol metabolism in calf hepatocytes challenged with high concentrations of fatty acids (FA). To address mechanistic insights regarding cholesterol metabolism, liver samples were collected from healthy control dairy cows (n = 6; 7-13 d in milk) and cows with fatty liver (n = 6; 7-11 d in milk). In vitro, hepatocytes isolated from 3 healthy female calves (1 d old) were challenged with or without a mix of 1.2 mM FA to induce metabolic stress. In addition, hepatocytes were processed with 10 µmol/L of the cholesterol synthesis inhibitor simvastatin or 6 µmol/L of the cholesterol intracellular transport inhibitor U18666A with or without the 1.2 mM FA mix. To evaluate the role of cholesterol addition, hepatocytes were treated with 0.147 mg/mL methyl-β-cyclodextrin (MβCD + FA) or 0.147 mg/mL MβCD with or without 10 and 100 µmol/L cholesterol before incubation with FA (CHO10 + FA and CHO100 + FA). In vivo data from liver biopsies were analyzed by 2-tailed unpaired Student's t-test. Data from in vitro calf hepatocytes were analyzed by one-way ANOVA. Compared with healthy cows, blood plasma total cholesterol and plasma low-density lipoprotein cholesterol content in cows with fatty liver was markedly lower, whereas the hepatic total cholesterol content did not differ. In contrast, compared with healthy controls, the triacylglycerol content in the liver and the content of FA, β-hydroxybutyrate, and aspartate aminotransferase in the plasma of cows with fatty liver were greater. The results revealed that both fatty liver in vivo and challenge of calf hepatocytes with 1.2 mM FA in vitro led to greater mRNA and protein abundance of sterol regulatory element binding transcription factor 1 (SREBF1) and fatty acid synthase (FASN). In contrast, mRNA and protein abundance of sterol regulatory element binding transcription factor 2 (SREBF2), acyl coenzyme A-cholesterol acyltransferase, and ATP-binding cassette subfamily A member 1 (ABCA1) were lower. Compared with the FA group, the cholesterol synthesis inhibitor simvastatin led to greater protein abundance of microsomal triglyceride transfer protein and mRNA abundance of SREBF2, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), ACAT2, and lower ABCA1 and FASN protein abundance. In contrast, compared with the FA group, the cholesterol intracellular transport inhibitor U18666A + FA led to greater total cholesterol concentration and greater protein and mRNA abundance of FASN. Compared with the MβCD + FA group, the addition of 10 µmol/L cholesterol led to greater concentration of cholesteryl ester and excretion of apolipoprotein B100, and greater protein and mRNA abundance of ABCA1 and microsomal triglyceride transfer protein, and lower concentration of malondialdehyde. Overall, a reduction in cholesterol synthesis promoted FA metabolism in hepatocytes likely to relieve the oxidative stress caused by the high FA load. The data suggest that maintenance of normal cholesterol synthesis promotes very low-density lipoprotein excretion and can reduce lipid accumulation and oxidative stress in dairy cows that experience fatty liver.

PRMT5 links lipid metabolism to contractile function of skeletal muscles.

Skeletal muscle plays a key role in systemic energy homeostasis besides its contractile function, but what links these functions is poorly defined. Protein Arginine Methyl Transferase 5 (PRMT5) is a well-known oncoprotein but also expressed in healthy tissues with unclear physiological functions. As adult muscles express high levels of Prmt5, we generated skeletal muscle-specific Prmt5 knockout (Prmt5MKO ) mice. We observe reduced muscle mass, oxidative capacity, force production, and exercise performance in Prmt5MKO mice. The motor deficiency is associated with scarce lipid droplets in myofibers due to defects in lipid biosynthesis and accelerated degradation. Specifically, PRMT5 deletion reduces dimethylation and stability of Sterol Regulatory Element-Binding Transcription Factor 1a (SREBP1a), a master regulator of de novo lipogenesis. Moreover, Prmt5MKO impairs the repressive H4R3 symmetric dimethylation at the Pnpla2 promoter, elevating the level of its encoded protein ATGL, the rate-limiting enzyme catalyzing lipolysis. Accordingly, skeletal muscle-specific double knockout of Pnpla2 and Prmt5 normalizes muscle mass and function. Together, our findings delineate a physiological function of PRMT5 in linking lipid metabolism to contractile function of myofibers.