Development Of Liver Steatosis Research Articles

Hepatocyte-Specific PEX16 Abrogation in Mice Leads to Hepatocyte Proliferation, Alteration of Hepatic Lipid Metabolism, and Resistance to High-Fat Diet (HFD)-Induced Hepatic Steatosis and Obesity.

Obesity results in hepatic fat accumulation, i.e., steatosis. In addition to fat overload, impaired fatty acid β-oxidation also promotes steatosis. Fatty acid β-oxidation takes place in the mitochondria and peroxisomes. Usually, very long-chain and branched-chain fatty acids are the first to be oxidized in peroxisomes, and the resultant short chain fatty acids are further oxidized in the mitochondria. Peroxisome biogenesis is regulated by peroxin 16 (PEX16). In liver-specific PEX16 knockout (Pex16Alb-Cre) mice, hepatocyte peroxisomes were absent, but hepatocytes proliferated, and liver mass was enlarged. These results suggest that normal liver peroxisomes restrain hepatocyte proliferation and liver sizes. After high-fat diet (HFD) feeding, body weights were increased in PEX16 floxed (Pex16fl/fl) mice and adipose-specific PEX16 knockout (Pex16AdipoQ-Cre) mice, but not in the Pex16Alb-Cre mice, suggesting that the development of obesity is regulated by liver PEX16 but not by adipose PEX16. HFD increased liver mass in the Pex16fl/fl mice but somehow reduced the already enlarged liver mass in the Pex16Alb-Cre mice. The basal levels of serum triglyceride, free fatty acids, and cholesterol were decreased, whereas serum bile acids were increased in the Pex16Alb-Cre mice, and HFD-induced steatosis was not observed in the Pex16Alb-Cre mice. These results suggest that normal liver peroxisomes contribute to the development of liver steatosis and obesity.

PNPLA3 fatty liver allele was fixed in Neanderthals and segregates neutrally in humans

ObjectiveFat deposition is modulated by environmental factors and genetic predisposition. Genome-wide association studies identified PNPLA3 p.I148M (rs738409) as a common variant that increases risk of developing liver steatosis. When and...

The role of KLF2 in regulating hepatic lipogenesis and blood cholesterol homeostasis via the SCAP/SREBP pathway

Liver steatosis is a common metabolic disorder resulting from imbalanced lipid metabolism, which involves various processes such as de novo lipogenesis, fatty acid uptake, fatty acid oxidation, and VLDL secretion. In this study, we discovered that KLF2, a transcription factor, plays a crucial role in regulating lipid metabolism in the liver. Overexpression of KLF2 in the liver of db/db mice, C57BL/6J mice, and Cd36-/- mice fed on a normal diet resulted in increased lipid content in the liver. Additionally, transgenic mice (ALB-Klf2) that overexpressed Klf2 in the liver developed liver steatosis after being fed a normal diet. We found that KLF2 promotes lipogenesis by increasing the expression of SCAP, a chaperone that facilitates the activation of SREBP, the master transcription factor for lipogenic gene expression. Our mechanism studies revealed that KLF2 enhances lipogenesis in the liver by binding to the promoter of SCAP and increasing the expression of genes involved in fatty acid synthesis. Reduction of KLF2 expression led to a decrease in SCAP expression and a reduction in the expression of SREBP1 target genes involved in lipogenesis. Overexpression of KLF2 also increased the activation of SREBP2 and the mRNA levels of its downstream target SOAT1. In C57BL/6J mice fed a high-fat diet, overexpression of Klf2 increased blood VLDL secretion, while reducing its expression decreased blood cholesterol levels. Our study emphasizes the novelty that hepatic KLF2 plays a critical role in regulating lipid metabolism through the KLF2/SCAP/SREBPs pathway, which is essential for hepatic lipogenesis and maintaining blood cholesterol homeostasis.

Dominant-negative HNF1α mutant promotes liver steatosis and inflammation by regulating hepatic complement factor D

Patients with HNF1A variants may develop liver steatosis, while the underlying mechanism is still unclear. Here, we established a mouse model carrying the dominant-negative HNF1α P291fsinsC mutation (hHNF1Amut/-) and found that the mutant mice developed liver steatosis spontaneously under the normal chow diet. Transcriptome analysis showed significant upregulation of Cfd and other genes related to innate immune response in the liver of hHNF1Amut/- mice. The changes in lipid metabolism and complement pathways were also confirmed by proteomics. We demonstrated that HNF1α inhibited CFD expression in hepatocytes, and the P291fsinsC mutant could reverse this inhibitory effect. Furthermore, the suppression of CFD with specific inhibitor or siRNAs reduced triglyceride levels in hepatocytes, suggesting that CFD regulated hepatocyte lipid deposition. Our results demonstrate that the HNF1α P291fsinsC mutant promotes hepatic steatosis and inflammation by upregulating CFD expression, and targeting CFD may delay the progression of nonalcoholic fatty liver disease.

Recent Insights into the Biomarkers, Molecular Targets and Mechanisms of Non-Alcoholic Steatohepatitis-Driven Hepatocarcinogenesis.

Non-alcoholic fatty liver disease (NAFLD) or metabolic dysfunction-associated steatotic liver disease (MASLD) and steatohepatitis (NASH) are chronic hepatic conditions leading to hepatocellular carcinoma (HCC) development. According to the recent "multiple-parallel-hits hypothesis", NASH could be caused by abnormal metabolism, accumulation of lipids, mitochondrial dysfunction, and oxidative and endoplasmic reticulum stresses and is found in obese and non-obese patients. Recent translational research studies have discovered new proteins and signaling pathways that are involved not only in the development of NAFLD but also in its progression to NASH, cirrhosis, and HCC. Nevertheless, the mechanisms of HCC developing from precancerous lesions have not yet been fully elucidated. Now, it is of particular importance to start research focusing on the discovery of novel molecular pathways that mediate alterations in glucose and lipid metabolism, which leads to the development of liver steatosis. The role of mTOR signaling in NASH progression to HCC has recently attracted attention. The goals of this review are (1) to highlight recent research on novel genetic and protein contributions to NAFLD/NASH; (2) to investigate how recent scientific findings might outline the process that causes NASH-associated HCC; and (3) to explore the reliable biomarkers/targets of NAFLD/NASH-associated hepatocarcinogenesis.

Cross-talk between gut microbiota and liver steatosis: Complications and therapeutic target.

Liver steatosis is the most widespread chronic liver condition. Its global incidence is rising swiftly and is currently estimated to be 24%. Liver steatosis is strongly related with numerous metabolic syndrome characteristics, like obesity, insulin resistance, hyperlipidemia, and hypertension. The gastrointestinal tract contains about 100 trillion commensal organisms and more than 7,000 distinct bacterial strains. Fat deposition in the liver without secondary causes is known as liver steatosis. Dysregulation of the gut flora is one of the factors connected to the onset of fatty liver disease. Dietary choices may alter constitution of the microbiome and cause gut microbiome dysbiosis, particularly due to the intake of food high in fructose sugars, animal products, and saturated fats. Various gut bacteria cause nutrient metabolism in multiple ways, setting off different inflammatory cascades that encourage liver disease and pathways that help fat build up in the liver. Due to their relatively stable nature, genetic factors may not be responsible for the constant increase in liver steatosis incidence. Genetic factors set the stage for liver steatosis pathogenesis. This review will offer an overview of our present knowledge of the roles played by gut microbiota in regulating the development of liver steatosis, potential side effects, and potential treatment targets.

NAFLD and AATD Are Two Diseases with Unbalanced Lipid Metabolism: Similarities and Differences.

Non-alcoholic fatty liver disease (NAFLD) is a type of steatosis commonly associated with obesity, dyslipidemia, hypertension, and diabetes. Other diseases such as inherited alpha-1 antitrypsin deficiency (AATD) have also been related to the development of liver steatosis. The primary reasons leading to hepatic lipid deposits can be genetic and epigenetic, and the outcomes range from benign steatosis to liver failure, as well as to extrahepatic diseases. Progressive hepatocellular damage and dysregulated systemic immune responses can affect extrahepatic organs, specifically the heart and lungs. In this review, we discuss the similarities and differences between the molecular pathways of NAFLD and AATD, and the putative value of hepatic organoids as novel models to investigate the physio pathological mechanisms of liver steatosis.

Feeding of Hermetia illucens Larvae Meal Attenuates Hepatic Lipid Synthesis and Fatty Liver Development in Obese Zucker Rats.

The present study tested the hypothesis that dietary insect meal from Hermetia illucens (HI) larvae attenuates the development of liver steatosis and hyperlipidemia in the obese Zucker rat. To test the hypothesis, a 4-week trial with male, obese Zucker rats (n = 30) and male, lean Zucker rats (n = 10) was performed. The obese rats were assigned to three obese groups (group O-C, group O-HI25, group O-HI50) of 10 rats each. The lean rats served as a lean control group (L-C). Group L-C and group O-C were fed a control diet with 20% casein as protein source, whereas 25% and 50% of the protein from casein was replaced with protein from HI larvae meal in the diets of group O-HI25 and O-HI50, respectively. The staining of liver sections with Oil red O revealed an excessive lipid accumulation in the liver of group O-C compared to group L-C, whereas liver lipid accumulation in group O-HI25 and O-HI50 was markedly reduced compared to group O-C. Hepatic concentrations of triglycerides, cholesterol, C14:0, C16:0, C16:1, C18:0, C18:1, the sum of total fatty acids and hepatic mRNA levels of several genes associated with lipid synthesis and plasma concentration of cholesterol were markedly higher in group O-C than in group L-C, but lower in group O-HI50 than in group O-C (p < 0.05). In conclusion, partial replacement of casein by HI larvae meal attenuates liver steatosis and dyslipidemia in obese Zucker rats. This suggests that HI larvae meal serves as a functional food protecting from obesity-induced metabolic disorders.

Rol kyshkovoi mikrobioty, endotoksemii ta systemnoho zapalennia u patohenezi nealkoholnoi zhyrovoi khvoroby pechinky

Introduction. Currently there are few and contradictory data concerning the influence of intestinal microbiota (IM) disturbances on the nature and severity of inflammatory processes in the liver tissue, the role of microbial metabolites in the activation of steatosis and fibrosis processes in patients with non-alcoholic fatty liver disease (NAFLD). The aim of the study. To clarify the role of intestinal microbiota, endotoxemia and systemic inflammation in the development and progression of nonalcoholic fatty liver disease. Materials and methods. 108 patients with NAFLD were examined, control group included 30 people. Detection of CRP and TNF-alpha levels, endotoxin in blood serum was carried out by the immunoenzymatic method. Determination of IM composition at the level of the main phylotypes was carried out by the method of quantitative polymerase chain reaction in real time. Results. A weak direct correlation between TNF-alpha, CRP and endotoxin with Firmicutes content (F), and an inverse correlation between CRP with Bacteroidetes content (B) was revealed. The dependence of the ratio of main intestinal phyla (F/B) on markers of systemic inflammation in NAFLD patients with different levels of endotoxin was evaluated. In patients with NAFLD, as endotoxin concentration increased, a deeper imbalance of IM was observed. In the group of patients with NAFLD with a high level of endotoxin, the maximum values of the F/B index were observed. Also, the increase in the intestinal permeability of the mucous barrier depended not only on changes in the IM, but also on systemic inflammation. The highest levels of endotoxemia were observed in patients with a high F/B index and increased activity of pro-inflammatory markers. In patients with NAFLD with varying degrees of fatty infiltration of the liver, an imbalance of IM was detected in comparison with the control group. As the degree of steatosis increased in NAFLD patients, an increase in Firmicutes content was observed. The maximum shift in the balance of the main phyla towards a decrease in the relative content of Bacteroidetes and an increase in Firmicutes was determined in patients with 3rd degree of steatosis (p-value less than 0.05). In the group of patients with a low and moderate degree of steatosis, a similar trend of IM disorders was observed, but these changes were insignificant. The relative number of Actinobacteria exposed no differences between the examined patients. The analysis of changes in IM in patients with NAFLD depending on the stage of liver fibrosis revealed no significant differences both from the control group and between groups with different degrees of fibrosis. The obtained data indicate that the imbalance of IM makes a significant contribution to the development of liver steatosis, while other important factors are involved in the formation of fibrosis processes, in particular, inflammation, the activity of intestinal metabolites and regulatory molecules. Conclusions.The imbalance of the intestinal microbiota towards an increase in Firmicutes leads to an increase in the production of intestinal metabolites with subsequent initiation of systemic inflammation, which stimulates the accumulation of fat in hepatocytes, affecting the progression of steatosis and the processes of fibrosis in the liver.

Factors Associated With Liver Steatosis in People With Human Immunodeficiency Virus on Contemporary Antiretroviral Therapy.

Given the impact of new antiretroviral drugs on weight and metabolic parameters, their potential contribution to the development of liver steatosis is of concern. We investigated the determinants of liver steatosis in patients on antiretroviral therapy (ART) in the Swiss HIV Cohort Study (SHCS). Between 2019 and 2021, we measured liver stiffness and controlled attenuation parameter (CAP) using transient elastography in consecutive SHCS participants at Bern University Hospital. Individuals with viral hepatitis coinfection and pregnant women were excluded. We used multivariable logistic regression to explore factors associated with steatosis. Of 416 participants, 113 (27.2%) were female, median age was 51 years (interquartile range [IQR], 43-59), 305 (73.3%) were of European origin, and 212 (51.0%) were overweight/obese (body mass index [BMI] ≥25 kg/m2). Liver steatosis (CAP ≥248 dB/m) was present in 212 (51.0%) participants, 11 (5.2%) of whom had significant fibrosis or cirrhosis. One hundred seventy-nine (43.0%) met the criteria for metabolic-associated fatty liver disease (MAFLD). Among 64 individuals with a BMI <25 kg/m2 and liver steatosis, 31 (48.4%) had MAFLD. In multivariable analyses, BMI ≥25 kg/m2 (adjusted odds ratio, 5.76; 95% confidence interval, 3.57-9.29), age ≥50 years (1.88, 1.14-3.09), European origin (3.16, 1.69-5.89), and current use of tenofovir alafenamide (1.70, 1.08-2.69) were associated with liver steatosis. Exposure to integrase inhibitors was not associated with liver steatosis (0.83, 0.51-1.37). Our findings suggest a high prevalence of liver steatosis among people with HIV (PWH) on ART in Switzerland. In addition to established risk factors, the use of tenofovir alafenamide was associated with hepatic steatosis.

Endocrine and Metabolic Impact of Oral Ingestion of a Carob-Pod-Derived Natural-Syrup-Containing D-Pinitol: Potential Use as a Novel Sweetener in Diabetes.

The widespread use of added sugars or non-nutritive sweeteners in processed foods is a challenge for addressing the therapeutics of obesity and diabetes. Both types of sweeteners generate health problems, and both are being blamed for multiple complications associated with these prevalent diseases. As an example, fructose is proven to contribute to obesity and liver steatosis, while non-nutritive sweeteners generate gut dysbiosis that complicates the metabolic control exerted by the liver. The present work explores an alternative approach for sweetening through the use of a simple carob-pod-derived syrup. This sweetener consists of a balanced mixture of fructose (47%) and glucose (45%), as sweetening sugars, and a functional natural ingredient (D-Pinitol) at a concentration (3%) capable of producing active metabolic effects. The administration of this syrup to healthy volunteers (50 g of total carbohydrates) resulted in less persistent glucose excursions, a lower insulin response to the hyperglycemia produced by its ingestion, and an enhanced glucagon/insulin ratio, compared to that observed after the ingestion of 50 g of glucose. Daily administration of the syrup to Wistar rats for 10 days lowered fat depots in the liver, reduced liver glycogen, promoted fat oxidation, and was devoid of toxic effects. In addition, this repeated administration of the syrup improved glucose handling after a glucose (2 g/kg) load. Overall, this alternative functional sweetener retains the natural palatability of a glucose/fructose syrup while displaying beneficial metabolic effects that might serve to protect against the progression towards complicated obesity, especially the development of liver steatosis.

Changes in the liver proteome in apoE knockout mice exposed to inhalation of silica nanoparticles indicate mitochondrial damage and impairment of ER stress responses associated with microvesicular steatosis

The adverse effects of air pollution on the cardiovascular system have been well documented. Nonalcoholic fatty liver disease (NAFLD) is an independent risk factor for cardiovascular events. However, the influence of exposure to airborne particles on the development of NAFLD is less recognised. The aim of this study was to investigate the impact of silica nanoparticles (SiNPs) on the development of liver steatosis. We used molecular and proteomic SWATH-MS methods to investigate the changes in the liver proteome of apolipoprotein E-knockout mice (apoE−/− mice) exposed to SiNPs for 4 months in a whole-body exposure chamber. Exposure to SiNPs evoked microvesicular liver steatosis in apoE−/− mice. Quantitative liver proteomics showed significant downregulation of ribosomal proteins and endoplasmic reticulum proteins. Gene expression analysis revealed a reduced level of proteins related to endoplasmic reticulum stress. Treatment with SiNPs decreased mitochondrial membrane potential and increased the production of reactive oxygen species in cultured HepG2 cells. This is the first report that inhalation exposure to SiNPs induces microvesicular steatosis and significant changes in the liver proteome in vivo. Our results highlight the important role of silica and point to the ER stress response and mitochondrial dysfunction as potential mechanisms responsible for the increase in fatty liver by SiNPs.

Fetuin-A in Activated Liver Macrophages Is a Key Feature of Non-Alcoholic Steatohepatitis.

Fetuin-A, a plasma multifunctional protein known to play a role in insulin resistance, is usually presented as a liver secreted protein. However, fetuin-A adipose tissue production has been also described. Here, we evaluated fetuin-A production by the liver and the adipose tissue during metabolic dysfunction-associated fatty liver disease (MAFLD)-non-alcoholic steatohepatitis (NASH) development. Fetuin-A was evaluated by enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), Western blot, and immunofluorescence in male foz−/− mice fed a normal diet (ND) or a high fat diet (HFD) at various timepoints and in MAFLD-NASH patients. Foz−/− mice fed a short-term HFD developed liver steatosis, insulin resistance, and increased circulating levels of fetuin-A compared to ND-fed mice. In mice and patients with NASH, fetuin-A was located not only in healthy or steatotic hepatocytes but also in some macrophages forming lipogranulomas. In both mice and humans, a significant amount of fetuin-A was present in the adipose tissue compared to the liver. However, messenger ribonucleic acid levels and cell culture experiments indicate that fetuin-A is produced by the liver but not by the adipose tissue. In conclusion, fetuin-A is produced by steatotic hepatocytes at early timepoints in MAFLD and correlates with insulin resistance both in mice and humans. In NASH, fetuin-A also co-localizes with activated liver macrophages and could be interpreted as a signal released by damaged hepatocytes.

Butyrate ameliorates maternal high-fat diet-induced fetal liver cellular apoptosis.

A maternal high-fat diet (HFD) can impact the offspring’s development of liver steatosis, with fetal development in utero being a crucial period. Therefore, this study investigated the mechanism and whether butyrate can rescue liver injury caused by maternal HFD in the fetus. Pregnant female Sprague Dawley rats were randomly divided into two groups, prenatal HFD (58% fat) exposure or normal control diet (4.5% fat). The HFD group was fed an HFD 7 weeks before mating and during gestation until sacrifice at gestation 21 days. After confirmation of mating, the other HFD group was supplemented with sodium butyrate (HFSB). The results showed that maternal liver histology showed lipid accumulation with steatosis and shortened ileum villi in HFD, which was ameliorated in the HFSB group (P<0.05). There was increased fetal liver and ileum TUNEL staining and IL-6 expression with increased fetal liver TNF-α and malondialdehyde expression in the HFD group (P<0.05), which decreased in the HFSB group (P<0.05). The fetal liver expression of phospho-AKT/AKT and GPX1 decreased in the HFD group but increased in the HFSB group (P<0.05). In conclusion that oxidative stress with inflammation and apoptosis plays a vital role after maternal HFD in the fetus liver that can be ameliorated with butyrate supplementation.

Mice lacking α4 nicotinic acetylcholine receptors are protected against alcohol-associated liver injury.

Chronic heavy alcohol consumption is a major risk factor for the development of liver steatosis, fibrosis, and cirrhosis, but the mechanisms by which alcohol causes liver damage remain incompletely elucidated. This group has reported that α4 nicotinic acetylcholine receptors (α4 nAChRs) act as sensors for alcohol in lung cells. This study tested the hypothesis that α4 nAChRs mediate the effects of alcohol in the liver. Expression of acetylcholine receptor subunits in mouse liver was determined by RNA sequencing (RNA-seq). α4 nAChR knockout (α4 KO) mice were generated in C57BL/6J mice by introducing a mutation encoding an early stop codon in exon 4 of Chrna4, the gene encoding the α4 subunit of the nAChR. The presence of the inactivating mutation was established by polymerase chain reaction and genomic sequencing, and the lack of α4 nAChR function was confirmed in primary fibroblasts isolated from the α4 KO mice. Wild-type (WT) and α4 KO mice were fed the Lieber-DeCarli diet (with 36% of calories from alcohol) or pair fed an isocaloric maltose-dextrin control diet for a 6-week period that included a ramping up phase of increasing dietary alcohol. Chrna4 was the most abundantly expressed nAChR subunit gene in mouse livers. After 6 weeks of alcohol exposure, WT mice had elevated serum transaminases and their livers showed increased fat accumulation, decreased Sirt1 protein levels, and accumulation of markers of oxidative stress and inflammation including Cyp2E1, Nos2, Sod1, Slc7a11, TNFα, and PAI1. All these responses to alcohol were either absent or significantly attenuated in α4 KO animals. Together, these observations support the conclusion that activation of α4 nAChRs by alcohol or one of its metabolites is one of the initial events promoting the accumulation of excess fat and expression of inflammatory mediators. Thus, α4 nAChRs may represent viable targets for intervention in chronic alcohol-related liver disease.

Oxidative stress in nonalcoholic fatty liver disease: a reappraisal of the role in supporting inflammatory mechanisms

In the last decade, non-alcoholic fatty liver disease (NAFLD) and particularly its evolution to nonalcoholic steatohepatitis (NASH) have become a leading cause of chronic liver disease and cirrhosis as well as an important risk factor for hepatocellular carcinoma. Oxidative stress is a common feature of NAFLD/NASH and plays a key role in the complex of metabolic and cellular derangements that are involved in the development of liver steatosis, as well as in the transition to steatohepatitis. This review deals with the contribution of oxidative stress in promoting hepatic inflammation which represents a key factor in NAFLD evolution to liver fibrosis/cirrhosis. We discuss in detail recent data involving oxidative stress products as triggers for hepatic innate immunity and as a source of antigens implicated in sustaining lymphocyte-mediated adaptive immune responses. Attention is also paid to emerging evidence linking oxidative stress and extra-hepatic complications of NAFLD/NASH.

The Human Milk Oligosaccharide 2'-Fucosyllactose Alleviates Liver Steatosis, ER Stress and Insulin Resistance by Reducing Hepatic Diacylglycerols and Improved Gut Permeability in Obese Ldlr-/-.Leiden Mice.

Non-alcoholic fatty liver disease (NAFLD) is a complex multifactorial disorder that is associated with gut dysbiosis, enhanced gut permeability, adiposity and insulin resistance. Prebiotics such as human milk oligosaccharide 2′-fucosyllactose are thought to primarily improve gut health and it is uncertain whether they would affect more distant organs. This study investigates whether 2′-fucosyllactose can alleviate NAFLD development in manifest obesity. Obese hyperinsulinemic Ldlr-/-.Leiden mice, after an 8 week run-in on a high-fat diet (HFD), were treated with 2′-fucosyllactose by oral gavage until week 28 and compared to HFD-vehicle controls. 2′-fucosyllactose did not affect food intake, body weight, total fat mass or plasma lipids. 2′-fucosyllactose altered the fecal microbiota composition which was paralleled by a suppression of HFD-induced gut permeability at t = 12 weeks. 2′-fucosyllactose significantly attenuated the development of NAFLD by reducing microvesicular steatosis. These hepatoprotective effects were supported by upstream regulator analyses showing that 2′-fucosyllactose activated ACOX1 (involved in lipid catabolism), while deactivating SREBF1 (involved in lipogenesis). Furthermore, 2′-fucosyllactose suppressed ATF4, ATF6, ERN1, and NUPR1 all of which participate in endoplasmic reticulum stress. 2′-fucosyllactose reduced fasting insulin concentrations and HOMA-IR, which was corroborated by decreased intrahepatic diacylglycerols. In conclusion, long-term supplementation with 2′-fucosyllactose can counteract the detrimental effects of HFD on gut dysbiosis and gut permeability and attenuates the development of liver steatosis. The observed reduction in intrahepatic diacylglycerols provides a mechanistic rationale for the improvement of hyperinsulinemia and supports the use of 2′-fucosyllactose to correct dysmetabolism and insulin resistance.

Abstract 1463: Impaired reciprocal regulation between SIRT6 and TGF-β signaling as a potential mechanism for development and progression of fatty liver

Abstract Background: Non-alcoholic fatty liver disease (NAFLD) is associated with an increased risk of fibrotic liver disease and hepatocellular carcinoma (HCC). Dysregulated TGF-β signaling and loss of SIRT6 activity are implicated in fatty liver disease. SIRT6 limits fibrosis by inhibiting SMAD3 activity and limits de novo lipogenesis by inhibiting SREBP1 and SREBP2 activity. We hypothesized that altered reciprocal regulation between TGF-β signaling and SIRT6 contributes to NAFLD and its progression. The goal of this study was to identify regulatory crosstalk between SIRT6 and SMAD3 and SPTBN1, a regulator of SMAD3 activity. Methods: We used bioinformatics and chromatin immunoprecipitation (ChIP) with HepG2 cells to examine the binding of SMAD3 or CTCF to the SIRT6 gene in the presence or absence of TGF-β. Using cultured cells, we examined the effect of altering SPTBN1 or SMAD3 on SIRT6 abundance, and of altering SIRT6 on SPTBN1 and SMAD3 abundance. We examined liver phenotypes of SPTBN1+/- mice fed either a normal chow diet or a high-fat diet (HFD) and monitored body weight and serum total cholesterol and triglyceride concentrations, as well as analyzed liver tissue for SIRT6 abundance. Results: We identified two consensus SMAD-binding elements and two consensus CTCF binding sites in the SIRT6 promoter and showed by ChIP that TGF-β stimulated SMAD3 and CTCF binding to the promoter region of SIRT6. We found that deficiency in SMAD3 or SPTBN1 reduced SIRT6 mRNA and protein abundance. Overexpression of SIRT6 reduced expression of selected TGF-β-induced genes. Knockdown of SIRT6 increased SPTBN1 but not SMAD3 abundance and overexpression of SIRT6 reduced only SPTBN1 abundance. We found that fatty liver and associated metabolic changes induced by HFD is worse in SPTBN1+/- mice than in control mice. Furthermore, this condition was associated with reduced SIRT6 protein abundance in the liver. Conclusions: We found a reciprocal regulatory mechanism involving SPTBN1 through which SIRT6 can influence TGF-β signaling and identified SIRT6 as a target of TGF-β-SMAD3 signaling. The development of liver steatosis with reduced SIRT6 in SPTBN1+/- mice suggested that impaired induction of SIRT6 contributes to the severe liver phenotype, which resembles nonalcoholic steatohepatitis (NASH). Future investigation may yield opportunities to intervene and prevent NAFLD from progressing to NASH and thus reduce the risk of HCC. Citation Format: Kazufumi Ohshiro, Xiyan Xiang, David Bernstein, James M. Crawford, Bibhuti Mishra, Patricia S. Latham, Nancy R. Gough, Shuyun Rao, Lopa Mishra. Impaired reciprocal regulation between SIRT6 and TGF-β signaling as a potential mechanism for development and progression of fatty liver [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1463.

Elevated risk of liver steatosis in first-episode psychosis patients: Results from a 3-year prospective study

BackgroundCardiometabolic disorders are largely responsible for excess mortality in schizophrenia. Non-alcoholic fatty liver disease (NAFLD) is increasingly relevant in the development of metabolic risk factors that have been associated with antipsychotic treatment.We aimed to assess the incidence of NAFLD and metabolic disturbances during the first 3 years of antipsychotic treatment in patients with first episode of psychosis (FEP), and compare it with the incidence in a control group. MethodsData were obtained from patients with psychosis (n = 160) and healthy controls (n = 66) included in the Cantabria's clinical and research program on FEP (PAFIP) from 2012 to 2018. Fatty Liver Index (FLI) was used to estimate the amount of fat in the liver. FLI has been validated for the diagnosis of NAFLD against different standards such as liver ultrasound and biopsy. FLI and metabolic parameters were registered at baseline, 3 months and then yearly for 3 years. ResultsAt the end of the follow-up (3-years), 21.9 % of patients with psychosis developed a FLI ≥ 60, suggestive of liver steatosis, compared to only a 3 % of subjects within the control group (X2 = 12.120; p < 0.001). In the FEP patients group, developing a FLI ≥ 60 was statistically associated with significant increments in metabolic parameters, and with Metabolic Syndrome (MetS) (X2 = 16.151; p < 0.001) and high blood pressure (X2 = 10.654; p = 0.001). ConclusionsHaving a first episode of non-affective psychosis was significantly associated with developing liver steatosis (FLI ≥ 60) in the first three years after initiating antipsychotic treatment. The results highlight the importance of early screening the emergence of NAFLD in schizophrenia patients.

The mammalian rhomboid protein RHBDL4 protects against endoplasmic reticulum stress by regulating the morphology and distribution of ER sheets

In metazoans, the architecture of the endoplasmic reticulum (ER) differs between cell types and undergoes major changes throughout the cell cycle and according to physiological needs. Although much is known about how the different ER morphologies are generated and maintained, especially ER tubules, how context-dependent changes in ER shape and distribution are regulated and the factors involved are less well characterized, as are the factors that contribute to the positioning of the ER within the cell. By overexpression and KO experiments, we show that the levels of RHBDL4, an ER-resident rhomboid protease, modulate the shape and distribution of the ER, especially during conditions that require rapid changes in the ER sheet distribution, such as ER stress. We demonstrate that RHBDL4 interacts with cytoskeleton-linking membrane protein 63 (CLIMP-63), a protein involved in ER sheet stabilization, as well as with the cytoskeleton. Furthermore, we found that mice lacking RHBDL4 are sensitive to ER stress and develop liver steatosis, a phenotype associated with unresolved ER stress. Taken together, these data suggest a new physiological role for RHBDL4 and also imply that this function does not require its enzymatic activity.