Lipid Metabolism In Hepatocytes Research Articles

Recombinant leptins affect lipid metabolism in hepatocytes of Cynoglossus semilaevis

Leptin is a peptide hormone primarily produced by adipose tissue, which plays a crucial role in regulating energy balance by controlling appetite and energy expenditure. To better understand the intricate physiological functions of leptin in hepatocytes in tongue sole (Cynoglossus semilaevis), this study presents an integrated transcriptomic and metabolomic analysis of tongue sole hepatocytes following stimulation with lepA and lepB. Comparative analysis identified 2971 and 2900 upregulated differentially expressed genes (DEGs) and 1895 and 1821 downregulated DEGs in response to lepA and lepB stimulation, respectively. Notably, 5706 genes were commonly regulated by both stimulations, suggesting overlapping functional roles of these two leptin proteins. GO and KEGG enrichment analysis indicated significant enrichment in immune response (JAK-STAT signaling pathway, NF-κB signaling pathway, etc.) and lipid metabolism pathways, such as fatty acid synthesis, with similar findings for lepB. Metabolomic analysis demonstrated clear separation between treatment and control groups, with 34 medium- to long-chain fatty acids and numerous differentially expressed metabolites (DEMs) identified. KEGG analysis of the metabolome paralleled the transcriptomic findings, with shared pathways in lipid metabolism and immune function. Finally, joint analysis highlighted co-enrichment in linoleic acid metabolism and leishmaniasis pathways. Detailed mechanistic insights revealed the activation of JAK-STAT and NF-κB signaling pathways, modulation of arachidonic acid metabolism, and the influence on the MAPK signaling pathway. Additionally, lepA uniquely co-enriched in the fatty acid synthesis pathway, with specific gene regulation affecting the synthesis of various fatty acids. The study concluded that lepA and lepB exerted significant regulatory effects on lipid metabolism and immune responses in tongue sole hepatocytes through complex molecular networks. To our current knowledge, this represents the first direct evidence of leptin's role in immune function within teleost fish and offers valuable insights into the molecular mechanisms of lipid metabolism underlying the actions of lepA and lepB.

The deficiency of ALKBH5 contributes to hepatic lipid deposition by impairing VPS11-dependent autophagic flux.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Hepatic lipid deposition is a key factor in the development of NAFLD. N6-methyladenosine (m6A) modification, the most prevalent mRNA modification in eukaryotic cells, plays an important role in regulating hepatic lipid metabolism. However, its potential role in hepatic lipid deposition remains poorly understood. Histological and immunohistochemistry studies were used to investigate lipid deposition in free fatty acids (FFAs)-incubated LO2 cells, high-fat diet-fed mice models and clinical samples. Stable overexpression and knockdown of AlkB homolog 5 (ALKBH5) was manipulated to investigate the effects of ALKBH5 on m6A methylation and lipid metabolism in hepatocytes. RNA-sequencing transcriptome analysis and methylated RNA immunoprecipitation-quantitative-PCR analysis were used to reveal the potential downstream molecular targets of ALKBH5. ALKBH5 was down-regulated in fatty liver compared to normal liver in both humans and mice. Overexpression of ALKBH5 significantly improved FFA-induced lipid accumulation and promoted autophagosome-lysosome fusion in hepatocytes. Meanwhile, knockdown of ALKBH5 significantly increased the expression of microtubule-associated protein 1A/1B-light chain 3B and Sequestosome 1, leading to impaired autophagic flux and further lipid deposition in hepatocytes under FFA incubation. Overexpression of vacuolar protein sorting 11 (VPS11) reversed FFA-induced lipid accumulation in ALKBH5-silenced hepatocytes. Mechanistically, ALKBH5 alleviated hepatic lipid deposition and impaired autophagic flux by removing the m6A modification on VPS11 mRNA to promote its translation. Collectively, our findings revealed an epigenetic mechanism by which ALKBH5 alleviates hepatic lipid deposition by restoring VPS11-dependent autophagic flux, providing a potential target to counteract NAFLD.

Saccharomyces boulardii Mitigates Fructose-Induced Non-Alcoholic Fatty Liver in Rats.

Background and Objectives: Non-alcoholic fatty liver disease (NAFLD) is a growing global health concern closely linked to metabolic disorders, including obesity, insulin resistance, and dyslipidemia. Emerging evidence suggests that the gut-liver axis plays a critical role in the pathogenesis of NAFLD, with recent research highlighting the influence of gut microbiota, including fungal species such as Saccharomyces boulardii (S. boulardii). This study aimed to evaluate the effects of S. boulardii on lipid metabolism and oxidative stress in a rat model of fructose-induced NAFLD. Materials and Methods: Thirty Wistar rats were divided into three groups: a control group, a fatty liver group induced by 35% fructose supplementation, and a treatment group receiving S. boulardii (100 mg/kg/day) after fructose induction. Results: Biochemical analyses revealed that the treatment group exhibited significantly lower plasma levels of malondialdehyde (MDA), alanine aminotransferase (ALT), total triglycerides, and cholesterol compared to the untreated fatty liver group (p < 0.05). Furthermore, liver tissue analysis showed a marked reduction in lipid accumulation and fatty infiltration in the treatment group, with no visible lipid vacuoles in hepatocytes. The expression of aquaporin-8 (AQP8) and sirtuin-1 (SIRT1), key markers associated with hepatocyte function and lipid metabolism, was significantly higher in the S. boulardii group compared to the fatty liver group (p < 0.001). Conclusions: These findings indicate that S. boulardii supplementation mitigates the metabolic and oxidative stress-related alterations associated with fructose-induced NAFLD. In conclusion, our study suggests that S. boulardii exerts protective effects on the liver by reducing lipid accumulation and oxidative stress, highlighting its potential as a therapeutic intervention for NAFLD.

Coffee Bioactive N-Methylpyridinium: Unveiling Its Antilipogenic Effects by Targeting De Novo Lipogenesis in Human Hepatocytes.

Type 2 diabetes and nonalcoholic fatty liver diseases (NAFLDs) are promoted by insulin resistance (IR), which alters lipid homeostasis in the liver. This study aims to investigate the effect of N-methylpyridinium (NMP), a bioactive alkaloid of coffee brew, on lipid metabolism in hepatocytes. The effect of NMP in modulating lipid metabolism is evaluated at physiological concentrations in a diabetes cell model represented by HepG2 cells cultured in a high-glucose medium. Hyperglycemia triggers lipid droplet accumulation in cells and enhances the lipogenic gene expression, which is transactivated by sterol regulatory element binding protein-1 (SREBP-1). Lipid droplet accumulation alters the redox status and endoplasmic reticulum (ER) stress, leading to the activation of the unfolded protein response and antioxidative pathways by X-Box Binding Protein 1(XBP-1)/eukaryotic Initiation Factor 2 alpha (eIF2α) Protein Kinase RNA-Like ER Kinase and nuclear factor erythroid 2-related factor 2 (NRF2), respectively. NMP induces the phosphorylation of AMP-dependent protein kinase (AMPK) and acetyl-CoA carboxylase α (ACACA), and improves the redox status and ER homeostasis, essential steps to reduce lipogenesis and lipid droplet accumulation. These results suggest that NMP may be beneficial for the management of T2D and NAFLD by ameliorating the cell oxidative and ER homeostasis and lipid metabolism.

GCKIII kinases control hepatocellular lipid homeostasis via shared mode of action

Metabolic dysfunction–associated steatotic liver disease has emerged as a leading global cause of chronic liver disease. Our recent translational investigations have shown that the STE20-type kinases comprising the GCKIII subfamily—MST3, STK25, and MST4—associate with hepatic lipid droplets and regulate ectopic fat storage in the liver; however, the mode of action of these proteins remains to be resolved. By comparing different combinations of the silencing of MST3, STK25, and/or MST4 in immortalized human hepatocytes, we found that their single knockdown results in a similar reduction in hepatocellular lipid content and metabolic stress, without any additive or synergistic effects observed when all three kinases are simultaneously depleted. A genome-wide yeast two-hybrid screen of the human hepatocyte library identified several interaction partners contributing to the GCKIII-mediated regulation of liver lipid homeostasis, that is, PDCD10 that protects MST3, STK25, and MST4 from degradation, MAP4K4 that regulates their activity via phosphorylation, and HSD17B11 that controls their action via a conformational change. Finally, using in vitro kinase assays on microfluidic microarrays, we pinpointed various downstream targets that are phosphorylated by the GCKIII kinases, with known functions in lipogenesis, lipolysis, and lipid secretion, as well as glucose uptake, glycolysis, hexosamine synthesis, and ubiquitination. Together, this study demonstrates that the members of the GCKIII kinase subfamily regulate hepatocyte lipid metabolism via common pathways. The results shed new light on the role of MST3, STK25, and MST4, as well as their interactions with PDCD10, MAP4K4, and HSD17B11, in the control of liver lipid homeostasis and metabolic dysfunction–associated steatotic liver disease susceptibility.

Mulberry Twig Alkaloids Improved the Progression of Metabolic-Associated Fatty Liver Disease in High-Fat Diet-Induced Obese Mice by Regulating the PGC1α/PPARα and KEAP1/NRF2 Pathways.

Background/Objectives: Metabolic-associated fatty liver disease (MAFLD) is one of the most common liver disorders associated with obesity and metabolic syndrome, and poses a significant global health burden with limited effective treatments. The aim of this study was to assess the protective effects of mulberry twig alkaloids (SZ-A) on MAFLD and to further investigate the underlying mechanisms including the specific targets or pathways. Methods: Diet-induced obesity (DIO) and normal mouse models were established by feeding C57Bl/6J mice with a high-fat diet (HFD) or common diet for 12 weeks. SZ-A, dapagliflozin, and placebo were administered to corresponding mouse groups for 8 weeks. Data of fasting blood glucose, glucose tolerance, insulin tolerance, and the body weight of mice were collected at the baseline and termination of the experiment. Serum liver enzymes and lipids were measured by ELISA. Western blotting, qPCR, and pathological section staining were implemented to evaluate the degrees of liver steatosis, fibrosis, and oxidative stress in mice. Results: In DIO mouse models, high-dose SZ-A (800 mg/kg/d) treatment significantly inhibited HFD-induced weight gain, improved insulin tolerance, and reduced serum alanine aminotransferase, total cholesterol, and triglyceride levels compared with placebo. In DIO mice, SZ-A could alleviate the pathological changes of hepatic steatosis and fibrosis compared with placebo. Lipid catabolism and antioxidant stress-related proteins were significantly increased in the livers of the high-dose SZ-A group (p < 0.05). Inhibition of PGC1α could inhibit the function of SZ-A to enhance lipid metabolism in hepatocytes. PGC1α might interact with NRF2 to exert MAFLD-remedying effects. Conclusions: By regulating the expression of PGC1α and its interacting KEAP1/NRF2 pathway in mouse liver cells, SZ-A played important roles in regulating lipid metabolism, inhibiting oxidative stress, and postponing liver fibrosis in mice with MAFLD.

Plant miR6262 Modulates the Expression of Metabolic and Thermogenic Genes in Human Hepatocytes and Adipocytes.

Edible plants have been linked to the mitigation of metabolic disturbances in liver and adipose tissue, including the decrease of lipogenesis and the enhancement of lipolysis and adipocyte browning. In this context, plant microRNAs could be key bioactive molecules underlying the cross-kingdom beneficial effects of plants. This study sought to explore the impact of plant-derived microRNAs on the modulation of adipocyte and hepatocyte genes involved in metabolism and thermogenesis. Plant miR6262 was selected as a candidate from miRBase for the predicted effect on the regulation of human metabolic genes. Functional validation was conducted after transfection with plant miRNA mimics in HepG2 hepatocytes exposed to free fatty acids to mimic liver steatosis and hMADs cells differentiated into brown-like adipocytes. miR6262 decreases the expression of the predicted target RXRA in the fatty acids-treated hepatocytes and in brown-like adipocytes and affects the expression profile of critical genes involved in metabolism and thermogenesis, including PPARA, G6PC, SREBF1 (hepatocytes) and CIDEA, CPT1M and PLIN1 (adipocytes). Nevertheless, plant miR6262 mimic transfections did not decrease hepatocyte lipid accumulation or stimulate adipocyte browning. these findings suggest that plant miR6262 could have a cross-kingdom regulation relevance through the modulation of human genes involved in lipid and glucose metabolism and thermogenesis in adipocytes and hepatocytes.

Polyribonucleotide nucleotidyltransferase 1 participates in metabolic-associated fatty liver disease pathogenesis by affecting lipid metabolism and mitochondrial homeostasis

ObjectiveMetabolic-associated fatty liver disease (MAFLD) represents one of the most prevalent chronic liver conditions worldwide, but its precise pathogenesis remains unclear. This research endeavors to elucidate the involvement and molecular mechanisms of polyribonucleotide nucleotidyltransferase 1 (PNPT1) in the progression of MAFLD. MethodsThe study employed western blot and qRT-PCR to evaluate PNPT1 levels in liver specimens from individuals diagnosed with MAFLD and in mouse models subjected to a high-fat diet. Cellular studies investigated the effects of PNPT1 on lipid metabolism, apoptosis, and mitochondrial stability in hepatocytes. Immunofluorescence was utilized to track the subcellular movement of PNPT1 under high lipid conditions. RNA immunoprecipitation and functional assays were conducted to identify interactions between PNPT1 and Mcl-1 mRNA. The role of PPARα as an upstream transcriptional regulator of PNPT1 was investigated. Recombinant adenoviral vectors were utilized to modulate PNPT1 expression in vivo. ResultsPNPT1 was found to be markedly reduced in liver tissues from MAFLD patients and HFD mice. In vitro, PNPT1 directly regulated hepatic lipid metabolism, apoptosis, and mitochondrial stability. Under conditions of elevated lipids, PNPT1 relocated from mitochondria to cytoplasm, modifying its physiological functions. RNA immunoprecipitation revealed that the KH and S1 domains of PNPT1 bind to and degrade Mcl-1 mRNA, which in turn affects mitochondrial permeability. The transcriptional regulator PPARα was identified as a significant influencer of PNPT1, impacting both its expression and subsequent cellular functions. Alterations in PNPT1 expression were directly correlated with the progression of MAFLD in mice. ConclusionsThe study confirms the pivotal function of PNPT1 in the development of MAFLD through its interactions with Mcl-1 and its regulatory effects on lipid metabolism and mitochondrial stability. These insights highlight the intricate association between PNPT1 and MAFLD, shedding light on its molecular pathways and presenting a potential new therapeutic avenue for MAFLD management.

Radix Rehmanniae Praeparata extracts ameliorate hepatic ischemia-reperfusion injury by restoring lipid metabolism in hepatocytes

Ethnopharmacological relevanceHepatic ischemia/reperfusion injury (HIRI) is a common occurrence during or after liver surgery, representing a major cause for postoperative complications or increased morbidity and mortality in liver diseases. Rehmanniae Radix Praeparata (RRP) is a traditional Chinese medicine frequently used and has garnered extensive attention for its therapeutic potential treating cardiovascular and hepatic ailments. Recent studies have indicated the possibility of RRP in regulating lipid accumulation and apoptosis in hepatocytes. Aim of the studyThis study aimed to investigate the specific mechanisms by which RRP may impede the progression of HIRI through the regulation of lipid metabolism. Materials and methodsHigh-performance liquid chromatography (HPLC) was used to identify the major components of RRP water extract. C57BL/6J mice were orally given RRP at doses of 2.5 g/kg, 5 g/kg, and 10 g/kg for a duration of 7 days before undergoing HIRI surgery. Furthermore, we established a lipid-loaded in vitro model by exposing hepatocytes to oleic acid and palmitic acid (OAPA). The anti-HIRI effect of RRP was determined through transcriptomics and various molecular biology experiments. ResultsAfter identifying active ingredients in RRP, we observed that RRP exerted lipid-lowering and hepatoprotective effects on HIRI mice and OAPA-treated hepatocytes. RRP activated AMP-activated protein kinase (AMPK) and inhibited mammalian target of rapamycin (mTOR), which further on the one hand, inhibited the cleavage and activation of sterol regulatory element binding protein 2 (SREBP2) by limiting the movement of SREBPs cleavage-activating protein (SCAP)-SREBP2 complex with the help of endoplasmic reticulum lipid raft-associated protein 1 (ERLIN1) and insulin-induced gene 1 (INSIG1), and on the other hand, promoted liver X receptor α (LXRα) nuclear transportation and subsequent cholesterol efflux. Meanwhile, the anti-lipotoxic effect of RRP can be partly reversed by an LXRα inhibitor but largely blocked by the application of compound C, an AMPK inhibitor. ConclusionOur study elucidated that RRP served as a potential AMPK activator to alleviate HIRI by blocking SREBP2 activation and cholesterol synthesis, while also activating LXRα to facilitate cholesterol efflux. These findings shed new light on the potential therapeutic use of RRP for improving HIRI.

Ribosomal modification protein rimK-like family member A activates betaine-homocysteine S-methyltransferase 1 to ameliorate hepatic steatosis

Nonalcoholic fatty liver disease (NAFLD) is a serious threat to public health, but its underlying mechanism remains poorly understood. In screening important genes using Gene Importance Calculator (GIC) we developed previously, ribosomal modification protein rimK-like family member A (RIMKLA) was predicted as one essential gene but its functions remained largely unknown. The current study determined the roles of RIMKLA in regulating glucose and lipid metabolism. RIMKLA expression was reduced in livers of human and mouse with NAFLD. Hepatic RIMKLA overexpression ameliorated steatosis and hyperglycemia in obese mice. Hepatocyte-specific RIMKLA knockout aggravated high-fat diet (HFD)-induced dysregulated glucose/lipid metabolism in mice. Mechanistically, RIMKLA is a new protein kinase that phosphorylates betaine-homocysteine S-methyltransferase 1 (BHMT1) at threonine 45 (Thr45) site. Upon phosphorylation at Thr45 and activation, BHMT1 eliminated homocysteine (Hcy) to inhibit the activity of transcription factor activator protein 1 (AP1) and its induction on fatty acid synthase (FASn) and cluster of differentiation 36 (CD36) gene transcriptions, concurrently repressing lipid synthesis and uptake in hepatocytes. Thr45 to alanine (T45A) mutation inactivated BHMT1 to abolish RIMKLA’s repression on Hcy level, AP1 activity, FASn/CD36 expressions, and lipid deposition. BHMT1 overexpression rescued the dysregulated lipid metabolism in RIMKLA-deficient hepatocytes. In summary, RIMKLA is a novel protein kinase that phosphorylates BHMT1 at Thr45 to repress lipid synthesis and uptake. Under obese condition, inhibition of RIMKLA impairs BHMT1 activity to promote hepatic lipid deposition.

P-790 Engineering Vascularized Human Endometrial Organoids for In Vivo Tissue Regeneration and Repair Applications

Abstract Study question Is it possible to construct a vascularized endometrial organoid in vitro using endometrial epithelial organoids, endometrial stromal cells, and HUVECs? And its application value? Summary answer We have successfully engineered a vascularized endometrial organoid and demonstrated its remarkable ability to repair damaged endometrium. ScRNA-sequencing revealed intricate regulatory relationships among the cells. What is known already In vivo, endometrial epithelial organoids (EEOs) have been proven effective in repairing damaged endometrium. In vitro, when co-cultured with endometrial stromal cells (ESCs) in matrigel, EEOs self-assemble into endometrial assembloids that accurately replicate the native tissue’s characteristics. Endothelial cells play a critical regulatory role in various physiological processes across different tissues, such as lipid metabolism in hepatocytes, neurogenesis within the brain, and the menstrual cycle regulation in uterine endometrium. By leveraging organ-on-a-chip technology using HUVECs (commonly utilized endothelial cells), it is possible to construct functional and complex organoids with vascularization, including liver buds, brain organoids, and pancreatic islets. Study design, size, duration Different ratios of Fibrin and Matrigel were explored to optimize the hydrogel conditions. The composite medium was optimized with ExM and ECM. Cellular interactions were identified through cell-specific staining. Addition of reproductive hormones was performed to determine if the complexes exhibited hormone-responsive behavior. Transplantation of the organoid complexes into mice with endometrial injury was conducted to assess their repair capacity. Single-cell RNA sequencing was employed to identify cell clusters and analyze intercellular interactions. Participants/materials, setting, methods EEOs, ESCs, and HUVECs self-assemble into HEO complexes. EEOs and ESCs self-assemble into EO complexes as controls. Immunofluorescence and immunohistochemical analysis are conducted to detect cell-specific markers. PBS, Matrigel, EO and HEO complexes are transplanted into mice with endometrial injury. JC-1 staining and transmission electron microscopy are used to verify mitochondrial functionality. Electrical resistance measured by EVOM2, HUVEC tubule formation and sprouting assays are performed to investigate the formation of vascular networks within the complexes. Main results and the role of chance Under dynamic flow conditions of ExM and ECM at a ratio of 5:5, HEO complexes and EO complexes were self-assembled in a fibrin-matrigel hydrogel. The HEO complexes exhibited a capillary network-like structure, intricate cellular interactions, and a transcriptome profile similar to that of the in vivo endometrium. Moreover, HEO complexes responded to sex hormones, facilitating endometrial regeneration and improving the reproductive capacity of mice with endometrial injury. The subcutaneous transplantation of HEO complexes in mice revealed the perfusion of mouse blood within the human blood vessel network in the grafts, highlighting the participation of HUVECs in the vascular formation of the transplanted grafts. ScRNA sequencing analysis of HEO complexes demonstrated a notable rise in the proportion of proliferative subclusters of endometrial epithelial cells and stromal cells compared to EO complexes, especially under estrogen culture conditions. Additionally, HUVECs enhanced the mitochondrial functionality of endometrial cells and remodeled the extracellular matrix. Cell communication analysis revealed that endometrial epithelial and stromal cells enhance the formation of vascular networks in HUVECs within the HEO complexes through WNT7A and WNT5A signaling pathways. Limitations, reasons for caution Due to the time constraints of the study, we did not observe the birth rate of offspring mice following endometrial repair. ScRNA sequencing also uncovered that HUVECs promote ribosomal functionality in endometrial cells within HEO complexes, but further validation of this finding is necessary. Wider implications of the findings The implantation of HEO complexes derived from woman EEOs, ESCs, and HUVECs into the endometrium holds potential for “endometrial re-engineering” in the therapeutic management of Asherman’s syndrome or thin endometrium. Trial registration number not applicable

PFHpA alters lipid metabolism and increases the risk of metabolic dysfunction-associated steatotic liver disease in youth-a translational research framework.

To address the growing epidemic of liver disease, particularly in pediatric populations, it is crucial to identify modifiable risk factors for the development and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). Per- and polyfluoroalkyl substances (PFAS) are persistent ubiquitous chemicals and have emerged as potential risk factors for liver damage. However, their impact on the etiology and severity of MASLD remains largely unexplored in humans. This study aims to bridge the gap between human and in vitro studies to understand how exposure to perfluoroheptanoic acid (PFHpA), one of the emerging PFAS replacements which accumulates in high concentrations in the liver, contributes to MASLD risk and progression. First, we showed that PFHpA plasma concentrations were significantly associated with increased risk of MASLD in obese adolescents. Further, we examined the impact of PFHpA on hepatic metabolism using 3D human liver spheroids and single-cell transcriptomics to identify major hepatic pathways affected by PFHpA. Next, we integrated the in vivo and in vitro multi-omics datasets with a novel statistical approach which identified signatures of proteins and metabolites associated with MASLD development triggered by PFHpA exposure. In addition to characterizing the contribution of PFHpA to MASLD progression, our study provides a novel strategy to identify individuals at high risk of PFHpA-induced MASLD and develop early intervention strategies. Notably, our analysis revealed that the proteomic signature exhibited a stronger correlation between both PFHpA exposure and MASLD risk compared to the metabolomic signature. While establishing a clear connection between PFHpA exposure and MASLD progression in humans, our study delved into the molecular mechanisms through which PFHpA disrupts liver metabolism. Our in vitro findings revealed that PFHpA primarily impacts lipid metabolism, leading to a notable increase of lipid accumulation in human hepatocytes after PFHpA exposure. Among the pathways involved in lipid metabolism in hepatocytes, regulation of lipid metabolism by PPAR-a showed a remarkable activation. Moreover, the translational research framework we developed by integrating human and in vitro data provided us biomarkers to identify individuals at a high risk of MASLD due to PFHpA exposure. Our framework can inform policies on PFAS-induced liver disease and identify potential targets for prevention and treatment strategies.

Liver Fatty Acid-binding Protein Is a More Reliable Biomarker for Liver Injury in Nonalcoholic Steatohepatitis than Other Etiologies of Hepatitis.

Liver fatty acid-binding protein (LFABP) controls hepatocyte lipid metabolism and can be a biomarker in liver diseases. We compared the correlation of LFABP levels with liver histology in viral hepatitis and nonalcoholic fatty liver disease (NAFLD) and investigated the utility of serum LFABP as a biomarker for liver damage. We included 142 patients (60 chronic viral hepatitis B [CHB], 35 chronic viral hepatitis C [CHC], 47 NAFLD) and 40 healthy controls. LFABP levels were determined in all participants, and a liver biopsy was performed on patients. The nonalcoholic steatohepatitis (NASH) activity score (NAS), hepatosteatosis, liver inflammation, and fibrosis were evaluated for NAFLD patients. Ishak's histological scores were used for viral hepatitis. The correlation between LFABP levels and histologic scores was assessed in each group. Serum LFABP levels in CHB, CHC, NAFLD, and control groups were 2.2, 3.5, 7.6, and 2.1 ng/mL, respectively. LFABP levels were significantly higher in the NAFLD group compared to the control, CHC, and CHB groups. LFABP was significantly higher in the NASH group than in nonalcoholic steatohepatitis, 8 ng/mL and 5.4 ng/mL, respectively (P = .001). In the NAFLD group, LFABP levels showed a moderate positive correlation with NAS score (r = 0.58, P <.001), ballooning degeneration (r = 0.67, P <.001), and lobular inflammation (r = 0.62, P <.001). A logistic regression study showed that the level of LFABP was predictive of NASH independent of age, gender, homeostasis model of IR, body mass index, aspartate aminotransferase, and alanine aminotransferase (OR = 1.869, P = .01). LFABP specifically correlates with liver histology in NAFLD compared to viral hepatitis. Additionally, it can distinguish NASH from simple steatosis. LFABP may be a valuable biomarker for hepatocyte injury in NASH.

Effect of hydroxy-α-sanshool on lipid metabolism in liver and hepatocytes based on AMPK signaling pathway

BackgroundWith the increasing awareness of the safety of traditional Chinese medicine and food, as well as in-depth studies on the pharmacological activity and toxicity of Zanthoxylum armatum DC. (ZADC), it has been found that ZADC is hepatotoxic. However, the toxic substance basis and mechanism of action have not been fully elucidated. Hydroxy-α-sanshool (HAS) belongs to an amide compound in the fruits of ZADC, which may be hepatotoxic. However, the specific effects of HAS, including liver toxicity, are unclear. PurposeThe objectives of this research was to determine how HAS affects hepatic lipid metabolism, identify the mechanism underlying the accumulation of liver lipids by HAS, and offer assurances on the safe administration of HAS. MethodsAn in vivo experiment was performed by gavaging C57 BL/6 J mice with various dosages of HAS (5, 10, and 20 mg/kg). Biochemical indexes were measured, and histological analysis was performed to evaluate HAS hepatotoxicity. Hepatic lipid levels were determined using lipid indices and oil red O (ORO) staining. Intracellular lipid content were determined by biochemical analyses and ORO staining after treating HepG2 cells with different concentrations of HAS in vitro. Mitochondrial membrane potential, respiratory chain complex enzymes, and ATP levels were assessed by fluorescence labeling of mitochondria. The levels of proteins involved in lipogenesis and catabolism were determined using Western blotting. ResultsMice in the HAS group had elevated alanine and aspartate aminotransferase blood levels as well as increased liver index compared with the controls. The pathological findings showed hepatocellular necrosis. Serum and liver levels of triglycerides, total cholesterol, and low-density lipoprotein cholesterol levels were increased, whereas high-density lipoprotein cholesterol levels decreased. The ORO staining findings demonstrated elevated liver lipid levels. In vitro experiments demonstrated a notable elevation in triglyceride and total cholesterol levels in the HAS group. ATP, respiratory chain complex enzyme gene expression, mitochondrial membrane potential, and mitochondrial number were reduced in the HAS group. The levels of lipid synthesis-associated proteins (ACC, FASN, and SREBP-1c) were increased, and lipid catabolism-associated protein levels (PPARα and CPT1) and the p-AMPK/AMPK ratio were decreased in vivo and in vitro. ConclusionHAS has hepatotoxic effects, which can induce fatty acid synthesis and mitochondrial function damage by inhibiting the AMPK signaling pathway, resulting in aberrant lipid increases.

Effects of Deoxynivalenol and Its Acetylated Derivatives on Lipid Metabolism in Human Normal Hepatocytes.

Deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON) belong to type B trichothecenes that are widely detected in agricultural products as one of the most common classes of mycotoxins. In the present study, we aimed to characterize the alteration of lipid metabolism in normal human hepatocytes by poisoning with DON and its acetylated derivatives. After verifying the hepatotoxicity of the three toxins, DON, 15-ADON, and 3-ADON, the mRNA expression was determined by transcriptomics, and the results showed that DON and 15-ADON had a significant regulatory effect on the transcriptome, in which glycerophospholipid metabolism pathway and phospholipase D signaling pathways have not been reported in studies of DON and its acetylated derivatives. For further validation, we explored lipid metabolism in depth and found that PC (15:0/16:0), PC (16:1/18:3), PC (18:1/22:6), PC (16:0/16:0), PC (16:0/16:1), PC (16:1/18:1), PC (14:0/18:2), PE (14:0/16:0) and PE (18:1/18:3) were downregulated for all nine lipids. Combined with the transcriptome results, we found that hepatic steatosis induced by the three toxins, DON, 15-ADON and 3-ADON, was associated with altered expression of genes related to lipid oxidation, lipogenesis and lipolysis, and their effects on lipid metabolism in L-02 cells were mainly realized through the PC-PE cycle.

Polystyrene nanoplastics induce lipophagy via the AMPK/ULK1 pathway and block lipophagic flux leading to lipid accumulation in hepatocytes

Micro- and nanoplastic pollution has emerged as a significant global concern due to their extensive presence in the environment and potential adverse effects on human health. Nanoplastics can enter the human circulatory system and accumulate in the liver, disrupting hepatic metabolism and causing hepatotoxicity. However, the precise mechanism remains uncertain. Lipophagy is an alternative mechanism of lipid metabolism involving autophagy. This study aims to explore how polystyrene nanoplastics (PSNPs) influence lipid metabolism in hepatocytes via lipophagy. Initially, it was found that PSNPs were internalized by human hepatocytes, resulting in decreased cell viability. PSNPs were found to induce the accumulation of lipid droplets (LDs), with autophagy inhibition exacerbating this accumulation. Then, PSNPs were proved to activate lipophagy by recruiting LDs into autophagosomes and block the lipophagic flux by impairing lysosomal function, inhibiting LD degradation. Ultimately, PSNPs were shown to activate lipophagy through the AMPK/ULK1 pathway, and knocking down AMPK exacerbated lipid accumulation in hepatocytes. Overall, these results indicated that PSNPs triggered lipophagy via the AMPK/ULK1 pathway and blocked lipophagic flux, leading to lipid accumulation in hepatocytes. Thus, this study identifies a novel mechanism underlying nanoplastic-induced lipid accumulation, providing a foundation for the toxicity study and risk assessments of nanoplastics.

Resveratrol and (-)-Epigallocatechin-3-gallate Regulate Lipid Metabolism by Activating the AMPK Pathway in Hepatocytes.

The purpose of this study was to explore the effects of Res and EGCG on cell growth, cellular antioxidant levels, and cellular lipid metabolism in hepatocytes. In this experiment, leghorn male hepatoma (LMH) cells were used as hepatocytes. The results showed that 6.25-25 μM Res and EGCG had no adverse effects on cell viability and growth. Meanwhile, with the increasing dosage of Res and EGCG, the contents of total cholesterol (TC), total glyceride (TG), and malondialdehyde (MDA) in hepatocytes decreased significantly (p < 0.05), while the contents of glutathione peroxidase (GSH-Px), total superoxide dismutase (T-SOD), and catalase (CAT) increased significantly (p < 0.05). In addition, western blot results showed that Res and EGCG could significantly increase the expression of p-AMPK protein and reduce the expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) protein in hepatocytes (p < 0.05). Moreover, q-PCR results showed that with the increase in Res and EGCG, the expression of cholesterol- and fatty acid synthesis-related genes decreased significantly (p < 0.05). In conclusion, Res and EGCG can increase the antioxidant capacity of hepatocytes and reduce the synthesis of TC and TG in hepatocytes by activating AMPK, thereby regulating lipid metabolism in hepatocytes.

Temporal multiscale modeling of biochemical regulatory networks: Calcium-regulated hepatocyte lipid and glucose metabolism

Hepatocyte lipid and glucose metabolism is regulated not only by major hormones like insulin and glucagon but also by many other factors, including calcium ions. Recently, mitochondria-associated membrane (MAM) dysfunction combined with incorrect IP3-receptor regulation has been shown to result in abnormal calcium signaling in hepatocytes. This dysfunction could further lead to hepatic metabolism pathology. However, the exact contribution of MAM dysfunction, incorrect IP3-receptor regulation and insulin resistance to the calcium-insulin-glucagon interplay is not understood yet. In this work, we analyze the role of abnormal calcium signaling and insulin dysfunction in hepatocytes by proposing a model of hepatocyte metabolic regulatory network with a detailed focus on the model construction details besides the biological aspect. In this work, we analyze the role of abnormal calcium signaling and insulin dysfunction in hepatocytes by proposing a model of hepatocyte metabolic regulatory network. We focus on the model construction details, model validation, and predictions. We describe the dynamic regulation of signaling processes by sigmoid Hill function. In particular, we study the effect of both the Hill function slope and the distance between Hill function extremes on metabolic processes in hepatocytes as a model of nonspecific insulin dysfunction. We also address the significant time difference between characteristic time of glucose hepatic processing and a typical calcium oscillation period in hepatocytes. Our modeling results show that calcium signaling dysfunction results in an abnormal increase in postprandial glucose levels, an abnormal glucose decrease in fasting, and a decreased amount of stored glycogen. An insulin dysfunction of glucose phosphorylation, glucose dephosphorylation, and glycogen breakdown also cause a noticeable effect. We also get some insight into the so-called hepatic insulin resistance paradox, confirming the hypothesis regarding indirect insulin action on hepatocytes via dysfunctional adipocyte lipolysis.

Ablation of histone methyltransferase Suv39h2 in hepatocytes attenuates NASH in mice

AimsNon-alcoholic steatohepatitis (NASH) is characterized by aberrant lipid metabolism in hepatocytes. We investigated the involvement of a histone H3K9 methyltransferase Suv39h2 in the pathogenesis of NASH. Methods and materialsNASH is induced by feeding the mice with a high-fat high-carbohydrate (HFHC) diet or a high-fat choline-deficient amino acid defined (HFD-CDAA) diet. The Suv39h2f/f mice were crossbred with the Alb-Cre mice to specifically delete Suv39h2 in hepatocytes. Key findingsAblation of Suv39h2 in hepatocytes improved insulin sensitivity of the mice fed either the HFHC diet or the CDAA-HFD diet. Importantly, Suv39h2 deletion significantly ameliorated NAFLD as evidenced by reduced lipid accumulation, inflammation, and fibrosis in the liver. RNA-seq uncovered Vanin-1 (Vnn1) as a novel transcriptional target for Suv39h2. Mechanistically, Suv39h2 repressed Vnn1 transcription in hepatocytes exposed to free fatty acids. Consistently, Vanin-1 knockdown normalized lipid accumulation in Suv39h2-null hepatocytes. Importantly, a significant correlation between Suv39h2, Vanin-1, and hepatic triglyceride levels was identified in NASH patients. SignificanceOur study uncovers a novel mechanism whereby Suv39h2 may contribute to NASH pathogenesis and suggests that targeting the Suv39h2-Vanin-1 axis may yield novel therapeutic solutions against NASH.

Elevated expression of LCN13 through FXR activation ameliorates hepatocellular lipid accumulation and inflammation

BackgroundLipocalin 13 (LCN13) is a member of the lipocalin family that consists of numerous secretory proteins. LCN13 high-expression has been reported to possess anti-obesity and anti-diabetic effects. Although metabolic dysfunction-associated steatotic liver diseases (MASLD) including metabolic dysfunction-associated steatohepatitis (MASH) are frequently associated with obesity and insulin resistance, the functional role of endogenous LCN13 and the therapeutic effect of LCN13 in MASH and related metabolic deterioration have not been evaluated. MethodsWe employed a methionine-choline deficient diet model and MASH cell models to investigate the role of LCN13 in MASH development. We sought to explore the effects of LCN13 on lipid metabolism and inflammation in hepatocytes under PA/OA exposure using Western blotting, real-time RT-PCR, enzyme-linked immunosorbent assay, hematoxylin and eosin staining, oil red O staining. Using RNA sequencing, chromatin immunoprecipitation assay, and luciferase reporter assays to elucidate whether farnesoid X receptor (FXR) regulates human LCN13 transcription as a transcription factor. ResultsOur study found that LCN13 was down-regulated in MASH patients, MASH mouse and cell models. LCN13 overexpression in hepatocyte cells significantly inhibited lipid accumulation and inflammation in vitro. Conversely, LCN13 downregulation significantly exacerbated lipid accumulation and inflammatory responses in vivo and in vitro. Mechanistically, we provided the first evidence that LCN13 was transcriptionally activated by FXR, representing a novel direct target gene of FXR. And the key promoter region of LCN13 binds to FXR was also elucidated. We further revealed that LCN13 overexpression via FXR activation ameliorates hepatocellular lipid accumulation and inflammation in vivo and in vitro. Furthermore, LCN13-down-regulated mice exhibited aggravated MASH phenotypes, including increased hepatic lipid accumulation and inflammation. ConclusionOur findings provide new insight regarding the protective role of LCN13 in MASH development and suggest an innovative therapeutic strategy for treating MASH or related metabolic disorders.