Sex Dimorphism of Nonalcoholic Fatty Liver Disease (NAFLD) in Pparg-Null Mice

Sexual dimorphism of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver condition. MASLD is a sexually dimorphic condition, with its development and progression influenced by sex chromosomes and hormones. Estrogens typically protect against, whereas androgens promote, MASLD. Therapeutic approaches for a sex-specific personalized medicine include estrogen replacement, androgen blockers, and novel drugs targeting hormonal pathways. However, the interactions between hormonal factors and inherited genetic variation impacts MASLD risk, necessitating more tailored therapies. Understanding sex disparities and the role of estrogens could improve MASLD interventions and management, whereas clinical trials addressing sex differences are crucial for advancing personalized treatment. This review explores the underappreciated impact of sexual dimorphism in MASLD and discusses the potential therapeutic application of sex-related hormones.

A genetic mouse model of lean-NAFLD unveils sexual dimorphism in the liver-heart axis

Lean patients with NAFLD may develop cardiac complications independently of pre-existent metabolic disruptions and comorbidities. To address the underlying mechanisms independent of the development of obesity, we used a murine model of hepatic mitochondrial deficiency. The liver-heart axis was studied as these mice develop microvesicular steatosis without obesity. Our results unveil a sex-dependent phenotypic remodeling beyond liver damage. Males, more than females, show fasting hypoglycemia and increased insulin sensitivity. They exhibit diastolic dysfunction, remodeling of the circulating lipoproteins and cardiac lipidome. Conversely, females do not manifest cardiac dysfunction but exhibit cardiometabolic impairments supported by impaired mitochondrial integrity and β-oxidation, remodeling of circulating lipoproteins and intracardiac accumulation of deleterious triglycerides. This study underscores metabolic defects in the liver resulting in significant sex-dependent cardiac abnormalities independent of obesity. This experimental model may prove useful to better understand the sex-related variability, notably in the heart, involved in the progression of lean-NAFLD.

Associations of serum uric acid levels and anthropometric parameters with non-alcoholic fatty liver disease in healthy individuals: innovative insights from a cross-sectional study

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD is a spectrum of liver disease with a rising prevalence, ranging from simple steatosis to steatohepatitis and cirrhosis, where a significant minority face potential complications. Determining the predictive markers plays a crucial role. This study examined the relationship between serum uric acid (SUA) levels and NAFLD in healthy individuals and identified potential other predictors.

MATERIAL AND METHODS

A cohort of 2162 healthy participants attending routine check-up visits between February 2021 and May 2023 were included. Participants underwent abdominal ultrasound, uric acid measurements, and anthropometric assessments by TANITA. NAFLD was graded using a "hepatic steatosis score." Statistical analysis included nonparametric tests, chi-squared tests, Fisher's exact test, ROC curve analysis, and logistic regression.

RESULTS

The median age was 45 years (range:18-65). 1017 were male, and 1145 were female. Among the participants, 53.9%, 26.3%, 17.9%, and 1.9% exhibited Grade 0, 1, 2, and 3 hepatic steatosis, respectively. ROC analysis showed 80.0% sensitivity and 78.8% specificity for detecting grade 2 or higher hepatic steatosis with a cutoff value of 5.21 mg/dl of SUA (AUC = 0.82, p < 0.001, 95%CI 0.79-0.84). There were significant associations between elevated uric acid levels and NAFLD. Participants with higher body fat percentages, BMI values, and waist-to-hip ratios also demonstrated an increased prevalence of steatosis. Gender significantly influenced liver steatosis, with males exhibiting higher grades compared to females. Logistic regression analysis highlighted positive associations between NAFLD and body fat percentage, waist-to-hip ratio, and uric acid levels. Each unit increase in uric acid levels corresponded to a 2.5-fold increase in the odds of NAFLD (p < 0.001, 95% CI = 2.20-2.84).

CONCLUSION

Our findings suggest a significant relationship between serum uric acid levels and NAFLD in healthy individuals. Elevated uric acid levels, in conjunction with other anthropometric parameters, may serve as potential predictive markers for NAFLD.

Sex difference in liver diseases: How preclinical models help to dissect the sex-related mechanisms sustaining NAFLD and hepatocellular carcinoma

Only a few preclinical findings are confirmed in the clinic, posing a critical issue for clinical development. Therefore, identifying the best preclinical models can help to dissect molecular and mechanistic insights into liver disease pathogenesis while being clinically relevant. In this context, the sex relevance of most preclinical models has been only partially considered. This is particularly significant in NAFLD and HCC, which have a higher prevalence in men when compared to pre-menopause women but not to those in post-menopausal status, suggesting a role for sex hormones in the pathogenesis of the diseases. This review gathers the sex-relevant findings and the available preclinical models focusing on both in vitro and in vivo studies and discusses the potential implications and perspectives of introducing the sex effect in the selection of the best preclinical model. This is a critical aspect that would help to tailor personalized therapies based on sex.

FMO2 ameliorates nonalcoholic fatty liver disease by suppressing ER-to-Golgi transport of SREBP1

BACKGROUND AND AIMS

NAFLD comprises a spectrum of liver disorders with the initial abnormal accumulation of lipids in hepatocytes called NAFL, progressing to the more serious NASH in a subset of individuals. Our previous study revealed that global flavin-containing monooxygenase 2 (FMO2) knockout causes higher liver weight in rats. However, the role of FMO2 in NAFLD remains unclear. Herein, we aimed to determine the function and mechanism of FMO2 in liver steatosis and steatohepatitis.

APPROACH AND RESULTS

The expression of FMO2 was significantly downregulated in patients with NAFL/NASH and mouse models. Both global and hepatocyte-specific knockout of FMO2 resulted in increased lipogenesis and severe hepatic steatosis, inflammation, and fibrosis, whereas FMO2 overexpression in mice improved NAFL/NASH. RNA sequencing showed that hepatic FMO2 deficiency is associated with impaired lipogenesis in response to metabolic challenges. Mechanistically, FMO2 directly interacts with SREBP1 at amino acids 217-296 competitively with SREBP cleavage-activating protein (SCAP) and inhibits SREBP1 translocation from the endoplasmic reticulum (ER) to the Golgi apparatus and its subsequent activation, thus suppressing de novo lipogenesis (DNL) and improving NAFL/NASH.

CONCLUSIONS

In hepatocytes, FMO2 is a novel molecule that protects against the progression of NAFL/NASH independent of enzyme activity. FMO2 impairs lipogenesis in high-fat diet-induced or choline-deficient, methionine-deficient, amino acid-defined high-fat diet-induced steatosis, inflammation, and fibrosis by directly binding to SREBP1 and preventing its organelle translocation and subsequent activation. FMO2 thus is a promising molecule for targeting the activation of SREBP1 and for the treatment of NAFL/NASH.

A network pharmacology-based approach to explore the effect of dihydromyricetin on non-alcoholic fatty liver rats via regulating PPARG and CASP3

BACKGROUND

Non-alcohol fatty liver disease (NAFLD) is the most prevalent hepatopathy in China, with few effective cures currently. This work aimed to confirm the effect of DHM in vivo/vitro and explore the potential mechanism based on a network pharmacology-based approach.

METHODS

The rats were fed using a high-fat diet (HFD) to accumulate lipid. DHM at different concentrations was used to treat the HFD rats. The serum total cholesterol (TC), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were detected using ELISA kits. The target genes of DHM against NAFLD were screened by online databases. Then, the cytotoxicity of DHM in primary hepatocytes and HepG2 cells was determined by MTT reagent. qRT-PCR was used to quantify the expression level of PPAGR and CASP3 mRNA. Cell apoptosis and intracellular triglyceride (TG) were detected.

RESULTS

HFD diet increased rat liver weight/body weight ratio, serum TC, ALT, and AST. But DHM treatment can reduce these elevated indicators. DHM targeted 14 potential genes in NAFLD. PPARG and CASP3 were two hub genes for DHM against NAFLD, with score factor coefficients of -7.1 and -6.8 kcal/mol. DHM reduced the increased PPARG mRNA level and intracellular TG induced by palmitic acid. DHM can reduce the increased CASP3 mRNA level and cell apoptosis induced by palmitic acid.

CONCLUSION

This work demonstrates a mechanism of DHM that alleviates lipid metabolism disorder and cell apoptosis for the treatment of NAFLD, evidencing the potential application of DHM in NAFLD.

Altered Lipid Moieties and Carbonyls in a Wistar Rat Dietary Model of Subclinical Fatty Liver: Potential Sex-Specific Biomarkers of Early Fatty Liver Disease?

Non-alcoholic fatty liver disease (NAFLD) is a condition in which excess fat builds up in the liver. To date, there is a lack of knowledge about the subtype of lipid structures affected in the early stages of NAFLD. The aim of this study was to analyze serum and liver lipid moieties, specifically unsaturations and carbonyls, by nuclear magnetic resonance (NMR) in a subclinical Wistar rat model of NAFLD for detecting early alterations and potential sex dimorphisms. Twelve weeks of a high-fat diet (HFD) induced fat accumulation in the liver to a similar extent in male and female Wistar rats. In addition to total liver fat accumulation, Wistar rats showed a shift in lipid subtype composition. HFD rats displayed increased lipid carbonyls in both liver and serum, and decreased in unsaturated fatty acids (UFAs) and polyunsaturated fatty acids (PUFAs), with a much stronger effect in male than female animals. Our results revealed that the change in fat was not only quantitative but also qualitative, with dramatic shifts in relevant lipid structures. Finally, we compared the results found in Wistar rats with an analysis in a human patient cohort of extreme obesity. For the first time to our knowledge, lipid carbonyl levels and lipoproteins profiles were analyzed in the context of subclinical NAFLD. The association found between lipid carbonyls and alanine aminotransferase (ALT) in a human cohort of extremely obese individuals further supports the potential role of lipid moieties as biomarkers of early NAFLD.

Gender Dimorphism in Hepatic Carcinogenesis-Related Gene Expression Associated with Obesity as a Low-Grade Chronic Inflammatory Disease

Non-alcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC) show clear evidence of sexual dimorphism, with a significantly higher incidence in males. Among the determining factors that could explain this sex-based difference, the specific distribution of fat by sex has been suggested as a primary candidate, since obesity is a relevant risk factor. In this context, obesity, considered a low-grade chronic inflammatory pathology and responsible for the promotion of liver disease, could lead to sexual dimorphism in the expression profile of genes related to tumor development. When we compared the expression levels of genes associated with the early stages of carcinogenesis in the liver between male and female diet-induced obesity (DIO) rats, we observed that the expression pattern was similar in obese male and female animals. Interestingly, the SURVIVIN/BIRC5 oncogene showed a higher expression in male DIO rats than in female DIO and lean rats. This trend related to sexual dimorphism was observed in leukocytes from patients with obesity, although the difference was not statistically significant. In conclusion, this study evidenced a similar pattern in the expression of most carcinogenesis-related genes in the liver, except SUVIVIN/BIRC5, which could be a predictive biomarker of liver carcinogenesis predisposition in male patients with obesity.

Exploring the Protective Effects and Mechanism of Huaji Jianpi Decoction against Nonalcoholic Fatty Liver Disease by Network Pharmacology and Experimental Validation

This paper was designed to predict the mechanisms of the active components of Huaji Jianpi Decoction (HJJPD) against nonalcoholic fatty liver disease (NAFLD) based on network pharmacology-combined animal experiments. The candidate compounds of HJJPD and its relative targets were obtained from TCMSP and PharmMapper web server, and the intersection genes for NAFLD were discerned using OMIM, GeneCards, and DisGeNET. Then, the target protein-protein interaction (PPI) and component-target-pathway networks were constructed. Moreover, gene function annotation (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to study the potential signaling pathways associated with HJJPD’s effect on NAFLD. Molecular docking simulation was preformed to validate the binding affinity between potential core components and key targets. Eventually, the candidate targets, the possible pathway, and the mechanism of HJJPD were predicted by the network pharmacology-based strategy, followed by experimental validation in the NAFLD mice model treated with HJJPD. A total of 55 candidate compounds and 36 corresponding genes were identified from HJJPD that are associated with activity against NAFLD, and then the network of them was constructed. Inflammatory response and lipid metabolism-related signaling pathways were identified as the critical signaling pathways mediating the therapeutic effect of the active bioactive ingredients on NAFLD. Compared with the model group, the liver wet weight, liver/body ratio, the levels of total cholesterol (TC), triglyceride (TG), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and high-density lipoprotein (HDL) in serum in the HJJPD low-dose (17.52 g/kg·d), medium-dose (35.04 g/kg·d), and high-dose (70.07 g/kg·d) groups significantly decreased ( $P<0.05$ ). Light microscope observation shows that HJJPD could control the degree of lipid denaturation of the mouse liver tissue to a great extent. RT-qPCR results show that the mRNA expression levels of peroxisome proliferative activated receptor gamma (PPARG), tumor necrosis factor-α (TNF-α), antiserine/threonine protein kinase 1 (AKT1), and prostaglandin-endoperoxide synthase (PTGS2) in the liver tissues of the three HJJPD groups (17.52 g/kg·d, 35.04 g/kg·d, and 70.07 g/kg·d) were significantly lower than those in the model group ( $P<0.05$ ). HJJPD can exert its effect by inhibiting hepatic steatosis and related mRNA expression and decreasing the levels of other liver-related indexes. This study suggested that HJJPD exerted its effect on NAFLD by modulating multitargets with multicompounds through multipathways. It also demonstrated that the network pharmacology-based approach might provide insights for understanding the interrelationship between complex diseases and interventions of HJJPD.

Tff3 Deficiency Protects against Hepatic Fat Accumulation after Prolonged High-Fat Diet

Trefoil factor 3 (Tff3) protein is a small secretory protein expressed on various mucosal surfaces and is involved in proper mucosal function and recovery via various mechanisms, including immune response. However, Tff3 is also found in the bloodstream and in various other tissues, including the liver. Its complete attenuation was observed as the most prominent event in the early phase of diabetes in the polygenic Tally Ho mouse model of diabesity. Since then, its role in metabolic processes has emerged. To elucidate the complex role of Tff3, we used a new Tff3-deficient mouse model without additional metabolically relevant mutations (Tff3-/-/C57BL/6NCrl) and exposed it to a high-fat diet (HFD) for a prolonged period (8 months). The effect was observed in male and female mice compared to wild-type (WT) counter groups (n = 10 animals per group). We monitored the animals’ general metabolic parameters, liver morphology, ultrastructure and molecular genes in relevant lipid and inflammatory pathways. Tff3-deficient male mice had reduced body weight and better glucose utilization after 17 weeks of HFD, but longer HFD exposure (32 weeks) resulted in no such change. We found a strong reduction in lipid accumulation in male Tff3-/-/C57BL/6NCrl mice and a less prominent reduction in female mice. This was associated with downregulated peroxisome proliferator-activated receptor gamma (Pparγ) and upregulated interleukin-6 (Il-6) gene expression, although protein level difference did not reach statistical significance due to higher individual variations. Tff3-/-/C57Bl6N mice of both sex had reduced liver steatosis, without major fatty acid content perturbations. Our research shows that Tff3 protein is clearly involved in complex metabolic pathways. Tff3 deficiency in C57Bl6N genetic background caused reduced lipid accumulation in the liver; further research is needed to elucidate its precise role in metabolism-related events.

Rodents on a high-fat diet born to mothers with gestational diabetes exhibit sex-specific lipidomic changes in reproductive organs

Maternal gestatonal diabetes mellitus (GDM) and offspring high-fat diet (HFD) have been shown to have sex-specific detrimental effects on the health of the offspring. Maternal GDM combined with an offspring HFD alters the lipidomic profiles of offspring reproductive organs with sex hormones and increases insulin signaling, resulting in offspring obesity and diabetes. The pre-pregnancy maternal GDM mice model is established by feeding maternal C57BL/6 mice and their offspring are fed with either a HFD or a low-fat diet (LFD). Testis, ovary and liver are collected from offspring at 20 weeks of age. The lipidomic profiles of the testis and ovary are characterized using gas chromatography-mass spectrometry. Male offspring following a HFD have elevated body weight. In reproductive organs and hormones, male offspring from GDM mothers have decreased testes weights and testosterone levels, while female offspring from GDM mothers show increased ovary weights and estrogen levels. Maternal GDM aggravates the effects of an offspring HFD in male offspring on the AKT pathway, while increasing the risk of developing inflammation when expose to a HFD in female offspring liver. Testes are prone to the effect of maternal GDM, whereas ovarian metabolite profiles are upregulated in maternal GDM and downregulated in offspring following an HFD. Maternal GDM and an offspring HFD have different metabolic effects on offspring reproductive organs, and PUFAs may protect against detrimental outcomes in the offspring, such as obesity and diabetes.

PPARs as Key Mediators in the Regulation of Metabolism and Inflammation

Nuclear receptors (NRs) form a large family of ligand-dependent transcription factors that control the expression of a multitude of genes involved in diverse, vital biological processes[…]