Hepatic Cholesterol Accumulation Research Articles

Steatotic liver disease induced by TCPOBOP-activated hepatic constitutive androstane receptor: primary and secondary gene responses with links to disease progression.

Constitutive Androstane Receptor (CAR, Nr1i3), a liver nuclear receptor and xenobiotic sensor, induces drug, steroid and lipid metabolizing enzymes, stimulates liver hypertrophy and hyperplasia, and ultimately, hepatocellular carcinogenesis. The mechanisms linking early CAR responses to later disease development are poorly understood. Here we show that exposure of CD-1 mice to TCPOBOP, a halogenated xenochemical and selective CAR agonist ligand, induces pericentral steatosis marked by hepatic accumulation of cholesterol and neutral lipid, and elevated circulating alanine aminotransferase, indicating hepatocyte damage. TCPOBOP-induced steatosis was weaker in the pericentral region but stronger in the periportal region in females compared to males. Early (1-day) TCPOBOP transcriptional responses were enriched for CAR-bound primary response genes, and for lipogenesis and xenobiotic metabolism and oxidative stress protection pathways; late (2-wk) TCPOBOP responses included many CAR binding-independent secondary response genes, with enrichment for macrophage activation, immune response and cytokine and reactive oxygen species production. Late upstream regulators specific to TCPOBOP-exposed male liver were linked to pro-inflammatory responses and hepatocellular carcinoma progression. TCPOBOP administered weekly to male mice using a high corn oil vehicle activated carbohydrate-responsive transcription factor (MLXIPL)-regulated target genes, dysregulated mitochondrial respiratory and translation regulatory pathways, and induced more advanced liver pathology. Overall, TCPOBOP exposure recapitulates histological and gene expression changes characteristic of emerging steatotic liver disease, including secondary gene responses in liver non-parenchymal cells indicative of transition to a more advanced disease state. Upstream regulators of both the early and late TCPOBOP response genes include novel biomarkers for foreign chemical-induced metabolic dysfunction-associated steatotic liver disease.

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.

Distinct bile acid alterations in response to a single administration of PFOA and PFDA in mice

Per- and polyfluoroalkyl substances (PFASs), a group of synthetic chemicals that were once widely used for industrial purposes and in consumer products, are widely found in the environment and in human blood due to their extraordinary resistance to degradation. Once inside the body, PFASs can activate nuclear receptors such as PPARα and CAR. The present study aimed to investigate the impact of perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) on liver structure and functions, as well as bile acid homeostasis in mice. A single administration of 0.1 mmole/kg of PFDA, not PFOA, elevated serum ALT and bilirubin levels and caused cholestasis in WT mice. PFDA increased total and various bile acid species in serum but decreased them in the liver. Furthermore, in mouse livers, PFDA, not PFOA, down-regulated mRNA expression of uptake transporters (Ntcp, Oatp1a1, 1a4, 1b2, and 2b1) but induced efflux transporters (Bcrp, Mdr2, and Mrp2–4). In addition, PFDA, not PFOA, decreased Cyp7a1, 7b1, 8b1, and 27a1 mRNA expression in mouse livers with concomitant hepatic accumulation of cholesterol. In contrast, in PPARα-null mice, PFDA did not increase serum ALT, bilirubin, or total bile acids, but produced prominent hepatosteatosis; and the observed PFDA-induced expression changes of transporters and Cyps in WT mice were largely attenuated or abolished. In CAR-null mice, the observed PFDA-induced bile acid alterations in WT mice were mostly sustained. These results indicate that, at the dose employed, PFDA has more negative effects than PFOA on liver function. PPARα appears to play a major role in mediating most of PFDA-induced effects, which were absent or attenuated in PPARα-null mice. Lack of PPARα, however, exacerbated hepatic steatosis. Our findings indicate separated roles of PPARα in mediating the adaptive responses to PFDA: protective against hepatosteatosis but exacerbating cholestasis.

The role of STAT3/VAV3 in glucolipid metabolism during the development of HFD-induced MAFLD.

Metabolic-associated fatty liver disease (MAFLD) is a globally prevalent chronic hepatic disease. Previous studies have indicated that the activation of the signal transducer and activator of transcription3 (STAT3) plays a vital role in MAFLD progression at the very beginning. However, the specific association between STAT3 and abnormal hepatic metabolism remains unclear. In this study, activated inflammation was observed to induce abnormal glucolipid metabolic disorders in the hepatic tissues of high-fat diet (HFD)-fed ApoE-/- mice. Furthermore, we found that the activation of STAT3 induced by HFD might function as a transcriptional factor to suppress the expression of VAV3, which might participate in intracellular glucolipid metabolism and the regulation of glucose transporter 4 (GLUT4) storage vesicle traffic in the development of MAFLD both in vitro and in vivo. We verified that VAV3 deficiency could retard the GLUT4 membrane translocation and impair the glucose homeostasis. Additionally, VAV3 participates in cholesterol metabolism in hepatocytes, eventually resulting in the accumulation of intracellular cholesterol. Moreover, rAAV8-TBG-VAV3 was conducted to restore the expression of VAV3 in HFD-fed ApoE-/- mice. VAV3 overexpression was observed to improve glucose homeostasis as well as attenuate hepatic cholesterol accumulation in vivo. In conclusion, the STAT3/VAV3 signaling pathway might play a significant role in MAFLD by regulating glucose and cholesterol metabolism, and VAV3 might be a potential therapeutic strategy which could consequently ameliorate MAFLD.

High Plant Protein Diet Ameliorated Hepatic Lipid Accumulation Through the Modulation of Gut Microbiota.

Substituting plant protein for animal protein has emerged as a promising strategy for managing atherogenic lipids. However, the impact of long-term intake of a high plant protein diet (HPD) on hepatic lipid disorder remains unclear. Eight-week-old apolipoprotein E deficient (apoE-/- ) mice are fed with either a normal protein diet (NCD) or HPD for 12 weeks. HPD intervention results in decreased body weight accompanied by increased energy expenditure, with no significant effect on glycemic control. Long-term intake of HPD improves the serum and hepatic lipid and cholesterol accumulation by suppressing hepatic squalene epoxidase (SQLE) expression, a key enzyme in cholesterol biosynthesis. Integrated analysis of 16S rDNA sequencing and metabolomics profiling reveals that HPD intervention increases the abundance of the Lachnospiraece family and serum levels of 12,13-DiHOME. Furthermore, in vivo studies demonstrate that 12,13-DiHOME significantly inhibits lipid accumulation, as well as SQLE expression induced by oleic acid in HepG2 cells. Diet rich in plant protein diet alleviates hyperlipidemia via increased microbial production of 12,13-DiHOME.

Saikosaponin a ameliorates diet-induced fatty liver via regulating intestinal microbiota and bile acid profile in laying hens

Fatty liver hemorrhagic syndrome is a widespread metabolic disease in laying hens that decreases egg production and even causes death in severe cases. Many traditional Chinese medicine ingredients, such as saikosaponin a (SSa), have been shown to alleviate fatty liver, but the underlying mechanisms remain unclear. In this study, we aimed to explore the alleviation of dietary SSa on excessive hepatic lipid deposition and the interactions between intestinal microbiota and bile acid (BA) in laying hens. Fifty-four 35-wk-old laying hens were randomly allocated into 3 treatment groups with 6 replicates (3 birds per replicate) and fed with a basal diet (CON), high-energy and low-protein diet (HELP), and HELP diet with 30 mg/kg SSa (HELP+SSa). SSa reversed diet-induced egg production rate decrease (P < 0.05). SSa could potently ameliorate HELP-induced accumulation of hepatic cholesterol and liver injury via the increase (P < 0.05) of mRNA expression of BA synthesis gene, such as cholesterol 7 alpha-hydroxylase 1. SSa treatment alleviated gut dysbiosis, especially reducing (P < 0.05) the relative abundance of bile salt hydrolase (BSH)-producing bacteria such as Lactobacillus, Bifidobacterium, and Turicibacter. Ileal BA metabolomic analysis revealed that SSa increased (P < 0.05) the content of tauro-conjugated BAs, mainly taurochenodeoxycholic acid and tauro-α-muricholic acid. The mRNA expression of farnesoid X receptor (FXR) and fibroblast growth factor 19 were decreased (P < 0.05) in intestine, which was associated with increased gene expression of enzymes in the BA synthesis that reduced the levels of cholesterol. Moreover, SSa treatment inhibited intestinal BA reabsorption via decreasing (P < 0.05) the mRNA expression of apical sodium-dependent bile acid transporter. Our findings indicated that SSa reduced liver cholesterol accumulation and alleviated fatty liver in laying hens through microbiota-BA-intestinal FXR crosstalk.

B-003 Decrease in Serum apoE-rich HDL-cholesterol May Be Associated With Cholesterol Accumulation in the Liver of Rats Fed A High-cholesterol Diet

Abstract Background Free cholesterol accumulation in the liver has been suggested to be one of risk factors for the progression of non-alcoholic fatty liver to non-alcoholic steatohepatitis. Therefore, a non-invasive approach to assess hepatic cholesterol accumulation in the early stage without elevation of liver enzymes (AST and ALT) may be useful in clinical setting. In this study, we show that serum apoE-rich HDL-cholesterol level is a possible indicator for predicting hepatic cholesterol accumulation in rats with diet-induced simple liver steatosis. Methods Male Sprague-Dawley rats (8 weeks) were purchased from Charles River Laboratories. Four different diets were obtained from Oriental Yeast; control diet (MF), high-fat diet (HF; 68% MF, 30% palm oil, and 2% cholic acid), high-cholesterol diet (HC; 95.5% MF, 2.5% cholesterol, and 2% cholic acid), and high-fat/high-cholesterol diet (HFC; 81.75% MF, 15% palm oil, 1.25% cholesterol, and 2% cholic acid). The rats were randomly divided into 4 groups and fed as follows. The control and HFC groups received the MF and HFC diets for 8 weeks, respectively. The HF/HC group received the HF diet for the first 4 weeks and the HC diet for the next 4 weeks. The HC/HF group received the HC diet first, then the HF diet. Blood and liver tissue specimens were collected under anesthesia. Total HDL fractions were isolated from whole sera by the polyethylene glycol precipitation method, and applied into a cation-exchange column (HiTrap SPHP, GE healthcare) for determining apoE-rich HDL-cholesterol levels. Correlations between variables were assessed with Spearman’s correlation coefficient (rs). Results Total cholesterol content of the liver was significantly higher in the HFC (11.1-fold, P &amp;lt; 0.001), HF/HC (9.1-fold, P &amp;lt; 0.001), and HC/HF (5.8-fold, P &amp;lt; 0.001) groups than the control group. Hepatic free cholesterol was also higher in the HFC (5.5-fold, P &amp;lt; 0.001), HF/HC (3.9-fold, P &amp;lt; 0.001), and HC/HF (3.3-fold, P &amp;lt; 0.001) groups. Hepatic triglycerides were slightly increased in the HC/HF (1.6-fold, P &amp;lt; 0.01) and HFC (1.5-fold, P &amp;lt; 0.05) groups. Serum apoE-rich HDL-cholesterol was significantly decreased in the HF/HC (0.21-fold, P &amp;lt; 0.001), HC/HF (0.25-fold, P &amp;lt; 0.001) and HFC (0.42-fold, P &amp;lt; 0.01) groups. The HFC group had significantly higher serum ALT (3.0-fold, P &amp;lt; 0.05) and AST (2.3-fold, P &amp;lt; 0.01) levels, compared with the control groups. There was a significant increase in hepatic mRNA expression of TNF-α (24.8-fold, P &amp;lt; 0.01) and TGF-β (3.8-fold, P &amp;lt; 0.001) only in the HFC group, indicating liver inflammation and stellate cell activation. To exclude the effects of hepatocyte injury on apoE-rich HDL metabolism, rats with ALT less than 100 U/mL (n = 16) were included in the following analysis. ApoE-rich HDL-cholesterol levels were significantly and inversely correlated with hepatic total cholesterol (rs = −0.535, P &amp;lt; 0.05) and free cholesterol (rs = −0.532, P &amp;lt; 0.05) levels but not with hepatic triglycerides. Furthermore, the ratio of ALT to apoE-rich HDL-cholesterol was more highly correlated with hepatic total cholesterol (rs = 0.626, P &amp;lt; 0.01) and free cholesterol (rs = 0.632, P &amp;lt; 0.01). There was no such correlation for apoE-poor HDL-cholesterol. Conclusion: The present observations suggest that serum apoE-rich HDL-cholesterol levels may be a useful indicator for cholesterol accumulation in the liver of cholesterol-fed rats.

A positive feedback between cholesterol synthesis and the pentose phosphate pathway rather than glycolysis promotes hepatocellular carcinoma.

Hepatic cholesterol accumulation and hypercholesterolemia are implicated in hepatocellular carcinoma (HCC). However, the therapeutic effects of cholesterol-lowering drugs on HCC are controversial, indicating that the relationship between cholesterol metabolism and HCC is more complex than anticipated. A positive feedback between cholesterol synthesis and the pentose phosphate pathway (PPP) rather than glycolysis was formed in tumors of c-Myc mice. Blocking the PPP prevented cholesterol synthesis and thereby HCC in c-Myc mice, while ablating glycolysis did not affect cholesterol synthesis and failed to prevent c-Myc-induced HCC. Unexpectedly, HMGCR (3-hydroxy-3-methylglutaryl-CoA reductase) and G6PD (glucose-6-phosphate dehydrogenase), the rate-limiting enzymes of cholesterol synthesis and the PPP, were identified as direct targets of microRNA-206. By targeting Hmgcr and G6pd, microRNA-206 disrupted the positive feedback and fully prevented HCC in c-Myc mice, while 100% of control mice died of HCC. Disrupting the interaction of microRNA-206 with Hmgcr and G6pd restored cholesterol synthesis, the PPP and HCC growth that was inhibited by miR-206. This study identified a previously undescribed positive feedback loop between cholesterol synthesis and the PPP, which drives HCC, while microRNA-206 prevents HCC by disrupting this loop. Cholesterol synthesis as a process rather than cholesterol itself is the major contributor of HCC.

Inhibition of microRNA-33b in humanized mice ameliorates nonalcoholic steatohepatitis.

Nonalcoholic steatohepatitis (NASH) can lead to cirrhosis and hepatocellular carcinoma in their advanced stages; however, there are currently no approved therapies. Here, we show that microRNA (miR)-33b in hepatocytes is critical for the development of NASH. miR-33b is located in the intron of sterol regulatory element-binding transcription factor 1 and is abundantly expressed in humans, but absent in rodents. miR-33b knock-in (KI) mice, which have a miR-33b sequence in the same intron of sterol regulatory element-binding transcription factor 1 as humans and express miR-33b similar to humans, exhibit NASH under high-fat diet feeding. This condition is ameliorated by hepatocyte-specific miR-33b deficiency but unaffected by macrophage-specific miR-33b deficiency. Anti-miR-33b oligonucleotide improves the phenotype of NASH in miR-33b KI mice fed a Gubra Amylin NASH diet, which induces miR-33b and worsens NASH more than a high-fat diet. Anti-miR-33b treatment reduces hepatic free cholesterol and triglyceride accumulation through up-regulation of the lipid metabolism-related target genes. Furthermore, it decreases the expression of fibrosis marker genes in cultured hepatic stellate cells. Thus, inhibition of miR-33b using nucleic acid medicine is a promising treatment for NASH.

Stigmasterol Protects Against Steatohepatitis Induced by High-Fat and High-Cholesterol Diet in Mice by Enhancing the Alternative Bile Acid Synthesis Pathway

BackgroundHepatic cholesterol accumulation is a significant risk factor in the progression of nonalcoholic fatty liver disease (NAFLD) to steatohepatitis. However, the precise mechanism by which stigmasterol (STG) mitigates this process remains unclear. ObjectivesThis study aimed to investigate the potential mechanism underlying the protective effect of STG in mice with NAFLD progressing to steatohepatitis while being fed a high-fat and high-cholesterol (HFHC) diet. MethodsMale C57BL/6 mice were fed an HFHC diet for 16 wk to establish the NAFLD model. Subsequently, the mice received STG or a vehicle via oral gavage while continuing the HFHC diet for an additional 10 wk. The study evaluated hepatic lipid deposition and inflammation as well as the expression of key rate-limiting enzymes involved in the bile acid (BA) synthesis pathways. BAs in the colonic contents were quantified using ultra-performance liquid chromatography-tandem mass spectrometry. ResultsCompared with the vehicle control group, STG significantly reduced hepatic cholesterol accumulation (P < 0.01) and suppressed the gene expression of NLRP3 inflammasome and interleukin-18 (P < 0.05) in the livers of HFHC diet-fed mice. The total fecal BA content in the STG group was nearly double that of the vehicle control group. Additionally, the administration of STG increased the concentrations of representative hydrophilic BAs in the colonic contents (P < 0.05) along with the upregulation of gene and protein expression of CYP7B1 (P < 0.01). Furthermore, STG enhanced the α-diversity of the gut microbiota and partially reversed the alterations in the relative abundance of the gut microbiota induced by the HFHC diet. ConclusionsSTG mitigates steatohepatitis by enhancing the alternative pathway for BA synthesis.

345 The Role of TCF7L2 in Hepatic Metabolic Zonation

OBJECTIVES/GOALS: Single nucleotide polymorphisms in the transcription factor 7-like 2 (TCF7L2) gene are associated with Type 2 Diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD). The metabolic function of TCF7L2 in the liver remains to be fully elucidated, but we hypothesized that TCF7L2 contributes to NAFLD through regulation of zonal metabolic pathways. METHODS/STUDY POPULATION: Using single nuclei RNA sequencing, we examined Tcf7l2 expression in periportal (PP) hepatocytes around the portal triad and pericentral (PC) hepatocytes surrounding the central vein of the liver. To visualize TCF7L2 transcriptional activity we used a TCF reporter mice, which expresses an H2B-eGFP fusion protein downstream of the conserved TCF DNA binding site. We disrupted Tcf7l2 transcriptional activity in mouse liver by breeding mice with a floxed Tcf7l2 exon 11, which encodes part of the DNA binding domain (DBD), to albumin-Cre mice (Hep-TCF7L2ΔDBD). Eight-week-old mice were fed a choline-deficient amino acid-defined high fat (CDAHFD) diet for 8 weeks. In liver samples harvested from these mice, we examined disruption to several key zonated metabolic pathways, and quantified the development of fibrosis. RESULTS/ANTICIPATED RESULTS: Single nuclei analysis revealed that Tcf7l2 mRNA was expressed primarily in parenchymal cells of the liver but was ubiquitous across the liver lobule. However, in immunofluorescence analysis of TCF reporter mice, the transcriptional activity of TCF7L2 was highly restricted to PC hepatocytes. Classic PC hepatocyte markers, including glutamine synthetase (Glul), were absent in Hep-TCF7L2ΔDBD mice. Following the CDAHFD, Hep-TCF7L2ΔDBD mice developed more severe fibrosis in histological analysis, and expressed elevated levels of genes involved in fibrogenesis, collagen synthesis and TGFβsignaling. Hep-TCF7L2ΔDBD mice also displayed hepatic cholesterol accumulation following the CDAHFD, which was likely the result of impaired pericentral bile acid synthesis. DISCUSSION/SIGNIFICANCE: Our results suggest that TCF7L2 plays an important role in the regulation of zonated metabolic pathways, which may contribute to the development of fibrosis. Ongoing analyses are exploring the mechanisms regulating the zonal transcriptional activity of TCF7L2.

Development of the novel ACLY inhibitor 326E as a promising treatment for hypercholesterolemia.

Hepatic cholesterol accumulation is an important contributor to hypercholesterolemia, which results in atherosclerosis and cardiovascular disease (CVD). ATP-citrate lyase (ACLY) is a key lipogenic enzyme that converts cytosolic citrate derived from tricarboxylic acid cycle (TCA cycle) to acetyl-CoA in the cytoplasm. Therefore, ACLY represents a link between mitochondria oxidative phosphorylation and cytosolic de novo lipogenesis. In this study, we developed the small molecule 326E with an enedioic acid structural moiety as a novel ACLY inhibitor, and its CoA-conjugated form 326E-CoA inhibited ACLY activity with an IC50=5.31±1.2μmol/L invitro. 326E treatment reduced de novo lipogenesis, and increased cholesterol efflux invitro and invivo. 326E was rapidly absorbed after oral administration, exhibited a higher blood exposure than that of the approved ACLY inhibitor bempedoic acid (BA) used for hypercholesterolemia. Chronic 326E treatment in hamsters and rhesus monkeys resulted in remarkable improvement of hyperlipidemia. Once daily oral administration of 326E for 24 weeks prevented the occurrence of atherosclerosis in ApoE-/- mice to a greater extent than that of BA treatment. Taken together, our data suggest that inhibition of ACLY by 326E represents a promising strategy for the treatment of hypercholesterolemia.

An Egg White-Derived Peptide Enhances Systemic Insulin Sensitivity and Modulates Markers of Non-Alcoholic Fatty Liver Disease in Obese, Insulin Resistant Mice

Non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of the metabolic syndrome, is a global health problem. Currently, no pharmacological treatment is approved for NAFLD. Natural health products, including bioactive peptides, are potential candidates to aid in the management of metabolic syndrome-related conditions, including insulin resistance and obesity. In this study, we hypothesized that an egg-white-derived bioactive peptide QAMPFRVTEQE (Peptide 2) would improve systemic and local white adipose tissue insulin sensitivity, thereby preventing high-fat diet-induced exacerbation of pathological features associated with NAFLD, such as lipid droplet size and number, inflammation, and hepatocyte hypertrophy in high-fat diet-fed mice. Similar to rosiglitazone, Peptide 2 supplementation improved systemic insulin resistance during the hyperinsulinemic-euglycemic clamp and enhanced insulin signalling in white adipose tissue, modulating ex vivo lipolysis. In the liver, compared with high-fat diet fed animals, Peptide 2 supplemented animals presented decreased hepatic cholesterol accumulation (p < 0.05) and area of individual hepatic lipid droplet by around 50% (p = 0.09) and reduced hepatic inflammatory infiltration (p < 0.05) whereas rosiglitazone exacerbated steatosis. In conclusion, Peptide 2 supplementation improved insulin sensitivity and decreased hepatic steatosis, unlike the insulin-sensitizing drug rosiglitazone.

Investigating microRNAs to Explain the Link between Cholesterol Metabolism and NAFLD in Humans: A Systematic Review.

Non-Alcoholic Fatty Liver Disease (NAFLD) is characterized by hepatic free cholesterol accumulation. In addition, microRNAs (miRNAs) might be involved in NAFLD development. Therefore, we systematically reviewed the literature to examine the link between miRNAs and cholesterol metabolism in NAFLD. Nineteen studies were retrieved by a systematic search in September 2022. From these papers, we evaluated associations between 13 miRNAs with NAFLD and cholesterol metabolism. Additionally, their diagnostic potential was examined. Four miRNAs (miR122, 34a, 132 and 21) were associated with cholesterol metabolism and markers for NAFLD. MiR122 was upregulated in serum of NAFLD patients, increased with disease severity and correlated with HDL-C, TAG, VLDL-C, AST, ALT, ALP, lobular inflammation, hepatocellular ballooning and NAFLD score. Serum and hepatic levels also correlated. Serum and hepatic miR34a levels were increased in NAFLD, and correlated with VLDL-C and TAG. Serum miR379 was also higher in NAFLD, especially in early stages, while miR21 gave ambiguous results. The diagnostic properties of these miRNAs were comparable to those of existing biomarkers. However, serum miR122 levels appeared to be elevated before increases in ALT and AST were evident. In conclusion, miR122, miR34a, miR21 and miR132 may play a role in the development of NAFLD via effects on cholesterol metabolism. Furthermore, it needs to be explored if miRNAs 122, 34a and 379 could be used as part of a panel in addition to established biomarkers in early detection of NAFLD.

Excessive sucrose exacerbates high fat diet-induced hepatic inflammation and fibrosis promoting osteoarthritis in mice model

Osteoarthritis (OA) is marked by chronic low-grade systemic inflammation and cartilage destruction. High fat diet causes obesity and increases the risk of knee OA-development. However, the impact of high dietary sugar intake on OA pathogenesis has not been elucidated yet. Therefore, we investigated the effects of a high-fat and high-sucrose (HF+HS) diet in experimental OA mouse models. Eight-week-old male C57BL/6J mice were fed a standard chow (n=6), high-fat (HF) (n=5), or HF+HS (n=7) diets for 12 weeks; thereafter, the mice underwent surgical destabilization of the medial meniscus (DMM) and received the same experimental diets for an additional 8 weeks. The pathogenesis of knee OA, obesogenic parameters, and inflammation levels in the liver and adipose tissue were investigated. HF+HS diet induced severe cartilage erosion with osteophyte development and subchondral bone plate thickening, indicating that HF+HS diet exacerbated OA. Despite marginal differences in metabolic parameters, hepatic free cholesterol accumulation increased in mice with DMM-induced OA fed on HF+HS diet than in those fed HF diet. Notably, the levels of inflammatory cytokines and fibrosis markers were greater in the livers of mice with DMM-induced OA, fed on HF+HS diet than those in the control group. However, adipose tissue remodeling was not affected by the HF+HS diet. These findings indicate that excess sucrose intake along with a HF diet triggers hepatic inflammation and fibrosis, thereby, contributing to OA pathogenesis.

Discussing the role of circular RNA in the pathogenesis of non-alcoholic fatty liver disease and its complications.

Circular RNAs (circRNAs) are class of non-coding RNA, which are characterized by a covalently closed loop structure. Functionally they can act on cellular physiology, notably by sponging microRNAs (miR), regulating gene expression or interacting with binding protein. To date, circRNAs might represent an interesting, underexploited avenue for new target discovery for therapeutic applications, especially in the liver. The first characteristic of non-alcoholic fatty liver disease (NAFLD) is hepatic cholesterol accumulation, followed by its advanced form of the affection, nonalcoholic steatohepatitis (NASH), due to the occurrence of lobular inflammation, irreversible fibrosis, and in some cases hepatocellular carcinoma (HCC). Therefore, studies have investigated the importance of the dysregulation of circRNAs in the onset of metabolic disorders. In this review, we summarize the potential role of circRNAs in the development of metabolic diseases associated with the liver such as NAFLD or NASH, and their potential to become therapeutic strategies for these pathologies.

Dietary choline prevents high fat-induced disorder of hepatic cholesterol metabolism through SREBP-2/HNF-4α/CYP7A1 pathway in a freshwater teleost yellow catfish Pelteobagrus fulvidraco

Lipid overload-induced hepatic cholesterol accumulation is a major public health problem worldwide, and choline has been reported to ameliorate cholesterol accumulation, but its mechanism remains unclear. Our study found that choline prevented high-fat diet (HFD)-induced cholesterol metabolism disorder and enhanced choline uptake and phosphatidylcholine synthesis in the liver tissues; choline incubation prevented fatty acid (FA)-induced cholesterol accumulation and FA-induced inhibition of bile acid synthesis. Moreover, compared to single FA incubation, choline incubation or FA + choline co-incubation increased the mRNA abundances and protein levels of HNF4α and up-regulated the degradation of cholesterol into bile acids. Mechanistically, choline prevented the FA-induced accumulation of SREBP2 protein and the interaction between SREBP2 and HNF4α, thereby enhancing the DNA binding capacity of the HNF4α to the CYP7A1 promoter, and promoting the degradation of cholesterol into bile acids. Our study elucidated the novel regulatory mechanisms of choline preventing HFD-induced cholesterol accumulation and increasing bile acid synthesis by SREBP-2/HNF-4α/CYP7A1 pathway.

Fatostatin inhibits SREBP2-mediated cholesterol uptake via LDLR against selective estrogen receptor α modulator-induced hepatic lipid accumulation

Estrogen receptor α (ERα) plays a key role in the adaptive response of liver metabolism to energy demands, especially in controlling lipid metabolism. Tamoxifen (TMX), a main drug for the treatment of ER-positive breast cancer in clinical, is a selective ER modulator (SERM). However, accordingly, the long-term use of TMX would lead to nonalcoholic fatty liver (NAFLD) in clinical, which had no definite treatment up to now. Fatostatin (Fato), an inhibitor of sterol-regulatory element binding protein 2 (SREBP2), was reported as a synergistic inhibitor of ER-positive breast cancer with TMX, but the hepatic lipid regulation of this combination is still unknown. Herein, we aimed to explore the effect and mechanism of Fato against TMX-induced NAFLD. The results identified that hepatic cholesterol content increase was the main reason for TMX-induced NAFLD. It was caused by the upregulation of circulating cholesterol uptake mediated by low density lipoprotein receptor (LDLR) in liver, which resulted from the activation of SREBP2. Meanwhile, Fato could inhibit activation of SREBP2-LDLR pathway, alleviating TMX-induced hepatic cholesterol accumulation. In summary, these results provided a new insight into the mechanism of TMX-induced NAFLD. Moreover, it supported the combination of Fato and TMX for the treatment of ER-positive breast cancer to reduce the adverse effect of TMX in clinical.

Abstract P3073: Altered Mitochondrial Mg 2+ Homeostasis In Liver Links Lipid Metabolism, Inflammation And Atherogenesis

Although evidences show the role of Mg 2+ in lipid metabolism and atherosclerosis, the molecular mechanism by which loss of Mg 2+ homeostasis promotes cardiovascular disease (CVD) is not known. Mg 2+ homeostasis is regulated by mitochondria and Mrs2 is the only known molecular machinery associated with mitochondrial Mg 2+ influx. To begin elucidating the importance of Mg 2+ homeostasis in lipid metabolism and CVD we made liver-specific Mrs2 KO mouse (Mrs2 Δhep ). Liver being the central hub of lipid metabolism, we asked whether loss of Mrs2 alters lipid metabolism and lipoprotein profile. Our results show increased accumulation of hepatic triacylglycerol (TG) and cholesterol in Mrs2 Δhep . Consistent with increased TG/cholesterol, plasma cholesterol and oxidized low density lipoprotein (ox-LDL) levels significantly differed between control and KO. Because ox-LDL contribute to atherosclerosis, we hypothesized altered hepatic lipid metabolism to induce inflammation, immune imbalance and accelerate lesions through modified atherogenic lipoprotein and cytokine profile. Quantification of plasma cytokines and chemokines were performed using the proteome profiler. Because T cells are critical drivers and modifiers of atherosclerosis, we quantified the lymphocyte and monocyte subsets by flow cytometry. Because T regulatory cells have anti-antherogenic roles, we studied the effect of ox-LDL on Tregs. Our results show increased and decreased levels of inflammatory and anti-inflammatory cytokines respectively in Mrs2 Δhep . In Mrs2 Δhep stimulation with ox-LDL showed an increased antigen specific proliferation of T-cells. We also observed increased and decreased population of Th17 and Tregs respectively. The decrease in Tregs population was attributed to increased apoptosis. In conclusion our observation suggests that high levels of ox-LDL in Mrs2 Δhep to induce inflammation and inflammatory cell expansion accompanied by apoptosis in Tregs. Our results conclude dysregulated Mg 2+ homeostasis to alter lipid metabolism and atherogenesis by inducing inflammation and compromised Tregs population. Our study will be the first of its kind to establish a triangular molecular link between Mg 2+ homeostasis, lipid metabolism, and atherogenesis.

Trehalose alleviated hepatic cholesterol accumulation via inhibiting transformation from glucose-derived acyl-CoA to cholesterol synthesis in Nile tilapia

Trehalose has been identified as an autophagy enhancer with atheroprotective properties in mammals that reduces cholesterol accumulation in the body. However, such effects have been rarely explored in aquatic animals. This study examined the effects of trehalose supplementation in a high-cholesterol diet on liver cholesterol accumulation and the related mechanisms in Nile tilapia (Oreochromis niloticus). The fish were fed high cholesterol (1.6%) diets supplemented with different levels (0, 1.5, 3 and 4.5%) of trehalose for eight weeks. The results showed that inclusion of 3% trehalose in high-cholesterol diet led to the significant reduction of viscerosomatic index (VSI), hepatosomatic index (HSI) and total and free cholesterol (TC and FC) accumulation in the serum and liver of fish. Moreover, 3% trehalose supplementation decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, indicating the alleviation of high-cholesterol diet-induced liver impairment. Surprisingly, such beneficial effects did not correlate with autophagy activity since dietary inclusion of 3% trehalose inhibited the expression of autophagy-related genes and proteins (atg5/12, autophagy related gene 5/12; Lc3, microtubule-associated protein 1 light chain 3 and Beclin protein). Also, the same group inhibited the expression of genes related to hepatic cholesterol synthesis, glycogen metabolism, glycolysis, and glucose oxidative phosphorylation. These results indicated that trehalose treatment reduced the capability of glucose catabolism in the liver of high-cholesterol diet-fed fish. In the primary hepatocytes of Nile tilapia, which were cultured in a medium containing high cholesterol concentration, the [1-14C]-glucose tracking test showed that trehalose treatment resulted in decreased cellular retention of 14C-glucose and unaltered release of 14CO2. Likewise, the trehalose treatment inhibited the expression of genes associated with glucose uptake and catabolism, cholesterol synthesis. Also, the inhibited autophagy activities were found in the primary hepatocytes treated with trehalose. Overall, trehalose treatment alleviated high-cholesterol diet-induced hepatic and serum cholesterol accumulation in Nile tilapia, but such effect was not associated with the autophagy activities. Alternatively, our results suggested that trehalose exerted a cholesterol-lowering effect via inhibiting the transformation from glucose-mediated acyl-CoA to cholesterol synthesis in the liver of fish. This is the first study revealing the cholesterol-lowering function of trehalose in fish and could contribute to developing new strategies for maintaining liver health in fish.