Molecular mediators of hepatic steatosis and liver injury

Zebrafish: An emerging model system to study liver diseases and related drug discovery

The zebrafish has emerged as a powerful vertebrate model for studying liver-associated disorders. Liver damage is a crucial problem in the process of drug development and zebrafish have proven to be an important tool for the high-throughput screening of drugs for hepatotoxicity. Although the structure of the zebrafish liver differs to that of mammals, the fundamental physiologic processes, genetic mutations and manifestations of pathogenic responses to environmental insults exhibit much similarity. The larval transparency of the zebrafish is a great advantage for real-time imaging in hepatic studies. The zebrafish has a broad spectrum of cytochrome P450 enzymes, which enable the biotransformation of drugs via similar pathways as mammals, including oxidation, reduction and hydrolysis reactions. In the present review, we appraise the various drugs, chemicals and toxins used to study liver toxicity in zebrafish and their similarities to the rodent models for liver-related studies. Interestingly, the zebrafish has also been effectively used to study the pathophysiology of nonalcoholic and alcoholic fatty liver disease. The genetic models of liver disorders and their easy manipulation provide great opportunity in the area of drug development. The zebrafish has proven to be an influential model for the hepatic system due to its invertebrate-like advantages coupled with its vertebrate biology. The present review highlights the pivotal role of zebrafish in bridging the gap between cell-based and mammalian models.

Fatty Acid Synthase Inhibitor TVB-2640 Reduces Hepatic de Novo Lipogenesis in Males With Metabolic Abnormalities

BACKGROUND AND AIMS

Elevated hepatic de novo lipogenesis (DNL) is a key distinguishing characteristic of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis. In rodent models of NAFLD, treatment with a surrogate of TVB-2640, a pharmacological fatty acid synthase inhibitor, has been shown to reduce hepatic fat and other biomarkers of DNL. The purpose of this phase I clinical study was to test the effect of the TVB-2640 in obese men with certain metabolic abnormalities that put them at risk for NAFLD.

APPROACH AND RESULTS

Twelve subjects (mean ± SEM, 42 ± 2 years, body mass index 37.4 ± 1.2 kg/m² , glucose 103 ± 2 mg/dL, triacylglycerols 196 ± 27 mg/dL, and elevated liver enzymes) underwent 10 days of treatment with TVB-2640 at doses ranging from 50-150 mg/day. Food intake was controlled throughout the study. Hepatic DNL was measured before and after an oral fructose/glucose bolus using isotopic labeling with 1-¹³ C₁ -acetate intravenous infusion, followed by measurement of labeled very low-density lipoprotein palmitate via gas chromatography mass spectometry. Substrate oxidation was measured by indirect calorimetry. Across the range of doses, fasting DNL was reduced by up to 90% (P = 0.003). Increasing plasma concentrations of TVB-2640 were associated with progressive reductions in the percent of fructose-stimulated peak fractional DNL (R²  = -0.749, P = 0.0003) and absolute DNL area under the curve 6 hours following fructose/glucose bolus (R²  = -0.554, P = 0.005). For all subjects combined, alanine aminotransferase was reduced by 15.8 ± 8.4% (P = 0.05). Substrate oxidation was unchanged, and safety monitoring revealed that the drug was well tolerated, without an increase in plasma triglycerides. Alopecia occurred in 2 subjects (reversed after stopping the drug), but otherwise no changes were observed in fasting glucose, insulin, ketones, and renal function.

CONCLUSION

These data support the therapeutic potential of a fatty acid synthase inhibitor, TVB-2640 in particular, in patients with NAFLD and nonalcoholic steatohepatitis.

α-Linolenic Acid-Enriched Cold-Pressed Perilla Oil Suppress High-Fat Diet-Induced Hepatic Steatosis through Amelioration of the ER Stress-Mediated Autophagy

Perilla oil has been considered to have excellent potential for treating various diseases due to its contents of beneficial fatty acids, such as α-linolenic acid, oleic acid and linoleic acid. The therapeutic effects and molecular mechanism of an α-linolenic acid-enriched cold-pressed perilla oil (LEP) on hepatic steatosis of an obesity model were investigated by analyzing alterations in fat accumulation and endoplasmic reticulum (ER) stress-mediated autophagy, in high-fat diet (HFD)-induced obesity C57BL/6N mice treated with LEP for 16 weeks. Although no significant alterations were detected in body weight and most organ weights, the liver weight and accumulation of lipid droplets in the liver section were significantly lower in HFD + LEP treated group as compared to the HFD + Vehicle treated group. Reduced mRNA expression levels of adipogenesis and lipogenesis regulating factors, including the peroxisome proliferator-activated receptor (PPAR)_γ, CCAAT/enhancer-binding protein (C/EBP)α, fatty acid synthase (FAS), and adipocyte fatty acid-binding protein 2 (aP2) were observed after LEP treatment for 16 weeks, while the levels of lipolysis were remarkably increased in the same group. Moreover, the LEP-treated groups showed suppression of ER stress-regulating factors, such as the C/EBP homologous protein (CHOP), eukaryotic translation initiation factor 2α (eIF2α), inositol-requiring protein 1 (IRE1)α, and Jun-N-terminal kinase (JNK) during anti-hepatic steatosis effects. The expression level of the microtubule-associated protein 1A/1B-light chain 3 (LC3) protein and phosphatidylinositol-3-kinase (PI3K)/AKT/ mammalian target of rapamycin (mTOR) pathway for the autophagy response showed a significant decrease in the HFD+LEP-treated group. Furthermore, ER stress-mediated autophagy was accompanied with enhanced phosphorylation of extracellular signal-regulated kinase (ERK), JNK, and p38 protein in the mitogen-activated protein (MAP) kinase signaling pathway. Taken together, the results of the present study indicate that treatment with LEP inhibits hepatic steatosis in the HFD-induced obese model through regulation of adipogenesis and lipolysis. We believe our results are the first to show that the anti-hepatic steatosis activity of α-linolenic acid from cold-pressed perilla oil might be tightly correlated with the amelioration of ER stress-mediated autophagy.

The role of AMPKα2 in the HFD-induced nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is associated with hepatic steatosis, inflammation and liver fibrosis and has become one of the leading causes of hepatocellular carcinoma and liver failure. However, the underlying molecular mechanism of hepatic steatosis and the progression to nonalcoholic steatohepatitis (NASH) are not fully understood. Herein, we discovered that AMPKα2 catalytic subunit showed reduced expression in the liver following high fat diet (HFD) feeding to mice. Importantly, knockout of AMPKα2 in mice aggravated NAFLD, hepatic steatosis, inflammation and fibrosis. On the other hand, hepatocyte-targeted overexpression of AMPKα2 prevented or reversed NAFLD indications. In vivo mechanistic studies revealed that increased phosphorylation of IKKα/β and NF-κB in HFD-fed AMPKα2^-/- mice compared to WT mice, and treatment of these mouse cohorts with an inhibitor of NF-κB signaling for 4 weeks, effectively attenuated the progression of steatohepatitis and metabolic disorder features. In summary, AMPKα2 provides a protective role in the process of hepatic steatosis to NASH progression through suppression of liver NF-κB signaling.

CCL2/CCR2 signaling in cancer pathogenesis

Chemokines are a family of small cytokines, which guide a variety of immune/inflammatory cells to the site of tumor in tumorigenesis. A dysregulated expression of chemokines is implicated in different types of cancer including prostate cancer. The progression and metastasis of prostate cancer involve a complex network of chemokines that regulate the recruitment and trafficking of immune cells. The chemokine CCL2 and its main receptor CCR2 have been receiving particular interest on their roles in cancer pathogenesis. The up-regulation of CCL2/CCR2 and varied immune conditions in prostate cancer, are associated with cancer advancement, metastasis, and relapse. Here we reviewed recent findings, which link CCL2/CCR2 to the inflammation and cancer pathogenesis, and discussed the therapeutic potential of CCL2/CCR2 axis in cancer treatment based on results from our group and other investigators, with a major focus on prostate cancer. Video Abstract.

Sodium acetate-mediated inhibition of histone deacetylase alleviates hepatic lipid dysregulation and its accompanied injury in streptozotocin-nicotinamide-induced diabetic rats

OBJECTIVE

Hepatic lipid dysregulation with consequent lipotoxicity remains critical in the progression of non-alcoholic fatty liver disease, a rising prevalent complication of diabetes mellitus particularly type 2 diabetes. Diabetes-associated hepatic complications are among the leading causes of liver-related morbidity and mortality worldwide. Short chain fatty acids (SCFAs) have been demonstrated to regulate glycemic metabolism but its effect on diabetes-driven hepatic perturbation is unknown. This study is therefore designed to investigate the effect of SCFAs, acetate on diabetes-characterised hepatic lipotoxicity, and plausible involvement of histone deacetylase (HDAC) activity.

METHODS

Adult male Wistar rats (230-260 g) were allotted into groups (n = 6/group) namely: control (vehicle; p.o.), sodium acetate (SAT)-treated (200 mg/kg), diabetic with/without SAT groups. Diabetes was induced by intraperitoneal injection of streptozotocin 65 mg/kg after a dose of nicotinamide 110 mg/kg.

RESULTS

Data from diabetic animals showed increased fasting glycemia and insulinemia, decreased insulin sensitivity and body weight with increased relative hepatic mass. It also revealed increased hepatic lipid, serum/hepatic malondialdehyde, tissue necrosis factor-α, uric acid, aspartate transaminase, alanine aminotransferase and decreased glutathione content with elevated hepatic HDAC. Histologically, the hepatic tissue was characterised with disrupted architecture, inflammation of central vein and foci of periportal and sinusoidal cellular infiltration. However, these alterations were attenuated by sodium acetate.

CONCLUSION

The study demonstrates that diabetes mellitus drives hepatic lipotoxicity, characterised with lipid accumulation, excessive lipid peroxidation, pro-inflammation, depleted glutathione content and accompanied by increased HDAC activity. Besides, the study suggests that acetate ameliorates diabetes-associated hepatic lipotoxicity through HDAC suppression and enhancement of insulin sensitivity.

Exogenous Liposomal Ceramide-C6 Ameliorates Lipidomic Profile, Energy Homeostasis, and Anti-Oxidant Systems in NASH

In non-alcoholic steatohepatitis (NASH), many lines of investigation have reported a dysregulation in lipid homeostasis, leading to intrahepatic lipid accumulation. Recently, the role of dysfunctional sphingolipid metabolism has also been proposed. Human and animal models of NASH have been associated with elevated levels of long chain ceramides and pro-apoptotic sphingolipid metabolites, implicated in regulating fatty acid oxidation and inflammation. Importantly, inhibition of de novo ceramide biosynthesis or knock-down of ceramide synthases reverse some of the pathology of NASH. In contrast, cell permeable, short chain ceramides have shown anti-inflammatory actions in multiple models of inflammatory disease. Here, we investigated non-apoptotic doses of a liposome containing short chain C6-Ceramide (Lip-C6) administered to human hepatic stellate cells (hHSC), a key effector of hepatic fibrogenesis, and an animal model characterized by inflammation and elevated liver fat content. On the basis of the results from unbiased liver transcriptomic studies from non-alcoholic fatty liver disease patients, we chose to focus on adenosine monophosphate activated kinase (AMPK) and nuclear factor-erythroid 2-related factor (Nrf2) signaling pathways, which showed an abnormal profile. Lip-C6 administration inhibited hHSC proliferation while improving anti-oxidant protection and energy homeostasis, as indicated by upregulation of Nrf2, activation of AMPK and an increase in ATP. To confirm these in vitro data, we investigated the effect of a single tail-vein injection of Lip-C6 in the methionine-choline deficient (MCD) diet mouse model. Lip-C6, but not control liposomes, upregulated phospho-AMPK, without inducing liver toxicity, apoptosis, or exacerbating inflammatory signaling pathways. Alluding to mechanism, mass spectrometry lipidomics showed that Lip-C6-treatment reversed the imbalance in hepatic phosphatidylcholines and diacylglycerides species induced by the MCD-fed diet. These results reveal that short-term Lip-C6 administration reverses energy/metabolic depletion and increases protective anti-oxidant signaling pathways, possibly by restoring homeostatic lipid function in a model of liver inflammation with fat accumulation.

Beneficial Effects of Insect Extracts on Nonalcoholic Fatty Liver Disease

It is well known that nonalcoholic fatty liver disease (NAFLD) is a common disease worldwide because of unhealthy changes in dietary habits. In this study, we determined the effects of Tenebrio molitor Linnaeus, 1758 extract (TML) and Allomyrina dichotoma Linnaeus, 1771 larvae extract (ADL) in cellular and animal models. In vitro, TML and ADL treatments did not cause cytotoxicity, but attenuated the accumulation of lipid in HepG2 cells induced by free fatty acids. In vivo, mice were orally treated with TML and ADL for 10 weeks during high-fat diet feeding. TML and ADL administration significantly reduced the weight of body, liver tissue, and adipose tissue. Serum lipid profiles, hepatic functional parameters, and glucose levels were ameliorated by TML and ADL. Moreover, TML and ADL suppressed increased lipogenesis and inflammation-related makers, and improved antioxidant enzyme activity. In liver tissue, the decreased lipid accumulation by administration of TML and ADL was observed using Oil Red O and Hematoxylin and Eosin staining. Therefore, we suggest that TML and ADL may be having a therapeutic potential and is used to develop a therapeutic agent for NAFLD.

Liver-related long-term outcomes of thiazolidinedione use in persons with type 2 diabetes

BACKGROUND & AIMS

Studies have described prominent histologic improvement in patients with nonalcoholic steatohepatitis (NASH) using thiazolidinedione (TZD); however, these were all short term with moderate sample size, no liver-related long-term outcomes could be noted.

METHODS

This retrospective cohort study enrolled patients with newly diagnosed type 2 diabetes mellitus (T2DM) from Taiwan's National Health Insurance Research Database between 1 January 2000 and 31 December 2013. We matched TZD users and nonusers at a 1:1 ratio through propensity score matching. This study included 5095 paired TZD users and nonusers. Cox proportional hazard models were used to compare the risks of cirrhosis, hepatic decompensation, hepatic failure and all-cause mortality between TZD users and nonusers. The Kaplan-Meier method was used to compare the cumulative incidence of these main outcomes.

RESULTS

The incidence rates of cirrhosis, hepatic decompensation, hepatic failure and all-cause mortality during follow-up were 0.77 vs 1.95, 1.43 vs 1.75, 0.36 vs 0.70, and 4.89 vs 3.78 per 1000 person-years between TZD users and nonusers. The adjusted hazard ratios of cirrhosis, hepatic decompensation, hepatic failure and all-cause mortality were 0.39 (95% confidence interval [CI]: 0.21-0.72), 0.86 (95% CI: 0.52-1.44), 0.46 (95% CI: 0.18-1.17) and 1.18 (95% CI: 0.87-1.61) respectively.

CONCLUSIONS

Our study demonstrated that TZD use could significantly lower the risk of cirrhosis. In clinical settings, TZD use might be able to improve liver-related long-term outcomes.

Androgen aggravates liver fibrosis by activation of NLRP3 inflammasome in CCl4-induced liver injury mouse model

Studies have shown that there are differences between the sexes regarding to the occurrence and development of liver diseases, which may be associated with sex hormones. However, the mechanisms behind it are largely unknown. In this study, we first investigated the differences of liver injury between male and female mice, using the CCl₄-induced liver injury mouse model. It showed that the liver damage of male mice was much more severe than that of female mice. Both the acute injury and fibrosis of the liver were reduced when androgens were depleted by castration of male mice. The vulnerability of male liver was associated with testis endocrine and excessive activation of inflammatory response in the liver. Castrated male mice with testosterone supplementation showed aggravated liver inflammatory response and fibrosis. The activity of NOD-like receptor protein 3 (NLRP3) inflammasome was increased when testosterone supplementation was provided. However, the enhanced inflammatory response and fibrosis due to testosterone supplementation were negated by inhibiting the activation of NLRP3 using the specific small molecule inhibitor MCC950. It suggests that testosterone is a key factor that influences liver injury by regulating the NLRP3 inflammasome activation-mediated inflammatory response.

Glycemic Measures and Development and Resolution of Nonalcoholic Fatty Liver Disease in Nondiabetic Individuals

CONTEXT

Type 2 diabetes (T2D) is closely associated with nonalcoholic fatty liver disease (NAFLD); however, evidence regarding the link between blood glucose, especially below the threshold for T2D, and NAFLD is scarce.

OBJECTIVE

The objective of this work is to examine the associations of fasting glucose, oral glucose tolerance test (OGTT) 2-hour glucose, and hemoglobin A1c (HbA1c), and changes in these measures with development and resolution of NAFLD in nondiabetic individuals.

METHODS

This longitudinal cohort study comprised 4273 Chinese adults age 40 years or older and free of baseline T2D from 2010 to 2015. Blood sampling was performed during the OGTT test. NAFLD was ascertained by hepatic ultrasonography. Risk ratios (RRs) were calculated using modified Poisson regression models.

RESULTS

During a mean 4.4 years of follow-up, NAFLD occurred in 573 (17.9%) of the 3209 participants without baseline NAFLD and resolved in 304 (28.6%) of the 1064 participants with baseline NAFLD. OGTT 2-h glucose was positively associated with NAFLD incidence (RR per 1-SD increase: 1.16, 95% CI: 1.08-1.25), whereas fasting (RR: 0.86, 95% CI: 0.78-0.94) and 2-hour glucose (RR: 0.85, 95% CI: 0.77-0.93) were inversely associated with resolution of NAFLD. Glycemic deterioration conferred increased risk of developing NAFLD and decreased likelihood of resolution of NAFLD than maintaining normal glycemic regulation (NGR). The strongest associations were observed for individuals who developed T2D. Meanwhile, baseline or incident NAFLD significantly increased the risk of deterioration in glucose metabolism.

CONCLUSIONS

Increased glycemic levels within the nondiabetic range, as well as progression from NGR to T2D or prediabetes, were adversely associated with development and improvement of NAFLD.

L-Selectin/CD62L is a Key Driver of Non-Alcoholic Steatohepatitis in Mice and Men

CD62L (L-Selectin) dependent lymphocyte infiltration is known to induce inflammatory bowel disease (IBD), while its function in the liver, especially in non-alcoholic steatohepatitis (NASH), remains unclear. We here investigated the functional role of CD62L in NASH in humans as well as in two mouse models of steatohepatitis. Hepatic expression of a soluble form of CD62L (sCD62L) was measured in patients with steatosis and NASH. Furthermore, CD62L^−/− mice were fed with a methionine and choline deficient (MCD) diet for 4 weeks or with a high fat diet (HFD) for 24 weeks. Patients with NASH displayed increased serum levels of sCD62L. Hepatic CD62L expression was higher in patients with steatosis and increased dramatically in NASH patients. Interestingly, compared to wild type (WT) mice, MCD and HFD-treated CD62L^−/− mice were protected from diet-induced steatohepatitis. This was reflected by less fat accumulation in hepatocytes and a dampened manifestation of the metabolic syndrome with an improved insulin resistance and decreased cholesterol and triglyceride levels. Consistent with ameliorated disease, CD62L^−/− animals exhibited an enhanced hepatic infiltration of Treg cells and a strong activation of an anti-oxidative stress response. Those changes finally resulted in less fibrosis in CD62L^−/− mice. Additionally, this effect could be reproduced in a therapeutic setting by administrating an anti-CD62L blocking antibody. CD62L expression in humans and mice correlates with disease activity of steatohepatitis. CD62L knockout and anti-CD62L-treated mice are protected from diet-induced steatohepatitis suggesting that CD62L is a promising target for therapeutic interventions in NASH.

Higher fatty liver index is associated with increased risk of new onset heart failure in healthy adults: a nationwide population-based study in Korea

Background

Heart failure (HF) is relatively common cardiovascular disease with high mortality and morbidity. Although it is associated with many cardiovascular risk factors, the association between nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disease, and HF has not been evaluated in a large-scale cohort study. Thus, we evaluated the ability of the fatty liver Index (FLI), a surrogate marker of NAFLD, to predict the development of HF in healthy individuals.

Methods

We analyzed the association between the FLI and new-onset HF with multivariate Cox proportional-hazards models in 308,578 healthy persons without comorbidities who underwent the National Health check-ups in the republic of Korea from 2009 to 2014.

Results

A total of 2532 subjects (0.8%) were newly diagnosed with HF during the study period (a median of 5.4 years). We categorized our subjects into quartile groups according to FLI (Q1, 0–4.9; Q2, 5.0–12.5; Q3, 12.6–31.0; and Q4, > 31.0). The cumulative incidence of HF was significantly higher in the highest FLI group than in the lowest FLI group (Q1, 307 [0.4%] and Q4, 890 [1.2%]; P < 0.001). Adjusted hazard ratio (HRs) indicated that the highest FLI group was independently associated with an increased risk for HF (HR between Q4 and Q1, 2.709; 95% confidence interval = 2.380–3.085; P < 0.001). FLI was significantly associated with an increased risk of new-onset HF regardless of their baseline characteristics.

Conclusions

Higher FLI was independently associated with increased risk of HF in a healthy Korean population.

The Associations between Liver Enzymes and Cardiovascular Risk Factors in Adults with Mild Dyslipidemia

Hypertension and dyslipidemia often occur as comorbidities, with both being strong risk factors for developing cardiovascular diseases (CVD). Abnormal liver function test could reflect a potential CVD risk even in patients with mild dyslipidemia. The aim of this study was to assess the compounding relationship between liver enzymes and cardiovascular risk factors in subjects with mild dyslipidemia. The present analysis was performed among 438 participants who had enrolled in at least one of the nine clinical studies done at the Chonbuk National University Hospital between 2009 and 2019. Significant linear increasing trends were observed in blood pressure level and other cardiovascular risk factors across quartiles of serum γ-glutamyltransferase (GGT) or alanine aminotransferase (ALT), with the increment in hypertension prevalence occurring across the quartiles of GGT and ALT. On multivariate logistic regression analyses, the odds ratios for hypertension, adjusted for smoking, drinking and obesity, in the highest quartiles of GGT, ALT, aspartate aminotransferase, and alkaline phosphatase were 3.688, 1.617, 1.372, and 1.166, respectively. Our study indicates that GGT is a superior marker for predicting CVD risk among liver enzymes. Routine screening of plasma GGT levels in patients with mild dyslipidemia will allow for early detection of CVD.

Capsaicinoid nonivamide improves nonalcoholic fatty liver disease in rats fed a high-fat diet

Nonalcoholic fatty liver disease (NAFLD) is a chronic disease that causes morbidity associated with metabolic syndrome. NAFLD is a worldwide problem and represents a major cause of liver injury, which can lead to liver cell death. We investigated the effects of nonivamide (pelargonic acid vanillylamide, PAVA; 1 mg/kg) and rosuvastatin (RSV; 10 mg/kg) on hepatic steatosis induced by a high-fat diet (HFD). Male Sprague-Dawley rats were fed a HFD for 16 weeks then received PAVA or RSV for 4 additional weeks. We examined the metabolic parameters, function, fat content, histological alterations, reactive oxygen species production, and apoptotic cell death of the liver, in addition to the expression of the following important molecules: transient receptor potential cation channel subfamily V member 1 (TRPV1) phosphorylation of sterol regulatory element binding protein (pSREBP-1c/SREBP-1c), total and membrane glucose transporter 2 (GLUT2), 4-hydroxynonenal (4-HNE), and cleaved caspase-3. HFD-induced hepatic steatosis was associated with significantly increased morphological disorganization, injury markers, oxidative stress, lipid peroxidation, and apoptosis. However, metabolic dysfunction and hepatic injury were reduced by RSV and PAVA treatment. PAVA regulated lipid deposition, improved insulin resistance, and decreased oxidative stress and apoptotic cell death. Therefore, PAVA represents a promising therapeutic approach for treating metabolic disorders in patients with NAFLD.

The Endothelium as a Driver of Liver Fibrosis and Regeneration

Liver fibrosis is a common feature of sustained liver injury and represents a major public health problem worldwide. Fibrosis is an active research field and discoveries in the last years have contributed to the development of new antifibrotic drugs, although none of them have been approved yet. Liver sinusoidal endothelial cells (LSEC) are highly specialized endothelial cells localized at the interface between the blood and other liver cell types. They lack a basement membrane and display open channels (fenestrae), making them exceptionally permeable. LSEC are the first cells affected by any kind of liver injury orchestrating the liver response to damage. LSEC govern the regenerative process initiation, but aberrant LSEC activation in chronic liver injury induces fibrosis. LSEC are also main players in fibrosis resolution. They maintain liver homeostasis and keep hepatic stellate cell and Kupffer cell quiescence. After sustained hepatic injury, they lose their phenotype and protective properties, promoting angiogenesis and vasoconstriction and contributing to inflammation and fibrosis. Therefore, improving LSEC phenotype is a promising strategy to prevent liver injury progression and complications. This review focuses on changes occurring in LSEC after liver injury and their consequences on fibrosis progression, liver regeneration, and resolution. Finally, a synopsis of the available strategies for LSEC-specific targeting is provided.

The effects of metformin administration on liver enzymes and body composition in non-diabetic patients with non-alcoholic fatty liver disease and/or non-alcoholic steatohepatitis: An up-to date systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide. One treatment is the use of metformin but its efficacy remains to be established.

OBJECTIVE

The present systematic review and meta-analysis aimed to provide a more robust examination of the evidence for the effectiveness of metformin for treating non-diabetic NAFLD patients.

METHODS

An extensive literature search was undertaken using online databases (PubMed, Embase, Scopus, Web of Science and Cochrane Library) to detect randomized controlled trials (RCTs) investigating the effect of metformin administration on liver enzymes and body composition in non-diabetic NAFLD patients up to 10 December 2019. A random-effects or fixed-effect models were performed to pool weighted mean difference (WMD) and 95% confidence intervals (CI).

RESULTS

Six RCTs involving 307 individuals were included to the present meta-analysis. Compared to controls, metformin significantly reduced body mass index (BMI) (WMD: -0.77 kg/m², 95 % CI = [-1.46, -0.07], P = 0.03, I² = 0.0 %) and serum aspartate aminotransferase (AST) (WMD: -5.94 U/L, 95 % CI = [-11.51, -0.38], P = 0.03, I² = 67.6 %). Also, body weight (WMD: -2.70 kg, 95 % CI = [-5.49, 0.09], P = 0.05, I² = 33.7%) was marginally significant and serum alanine transaminase (ALT) (WMD: -5.04 U/L, 95 % CI = [-13.92, 3.84], P = 0.26, I² = 60.9 %) was not statistically significant affected by metformin administration. There was no evidence of publication bias.

CONCLUSION

In summary, the present study emphasizes the clinical importance of metformin administration for improving liver function and body composition in non-diabetic NAFLD patients. Moreover, the further large-scale and well-designed RCTs are required to confirm these findings.

Ginsenoside Rg2 Ameliorates High-Fat Diet-Induced Metabolic Disease through SIRT1

Ginsenoside Rg2 has been previously reported to reduce glucose production and adipogenesis in adipose tissue. However, the effects of ginsenosides Rg2 on hepatic lipid metabolism remain vacant. In this study, we found that ginsenoside Rg2 treatment significantly attenuated oleic acid and palmitic acid (OA&PA)-induced intracellular lipid deposition and oxidative stress in mouse primary hepatocytes. C57BL/6J mice that are fed with a high-fat diet (HFD) and treated with ginsenosides Rg2 displayed decreased body weight, reversed hepatic steatosis, and improved glucose tolerance and insulin sensitivity. Ginsenoside Rg2 administration significantly ameliorated HFD-induced hepatic oxidative stress and apoptosis. Moreover, Ginsenoside Rg2 had a good affinity with Sirtuin1 (SIRT1) and regulated its expression in vivo and in vitro. Deficiency of SIRT1 eliminated the therapeutic effect of ginsenoside Rg2 on lipid accumulation and overproduction of reactive oxygen species (ROS) in OA&PA-induced mice primary hepatocytes. Ginsenoside Rg2 treatment failed to alter the lipid and glucose disorder in hepatic SIRT1 deficient mice feeding on HFD. SIRT1 deficiency dissolves the therapeutic effect of ginsenoside Rg2 on oxidative stress and hepatocyte apoptosis induced by HFD. In summary, ginsenoside Rg2 plays a therapeutic role in HFD-induced hepatosteatosis of mice by decreasing the lipogenesis process and improving antioxidant capacity in an SIRT1-dependent manner.

Niacin Ameliorates Hepatic Steatosis by Inhibiting De Novo Lipogenesis Via a GPR109A-Mediated PKC-ERK1/2-AMPK Signaling Pathway in C57BL/6 Mice Fed a High-Fat Diet

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. Hepatic de novo lipogenesis (DNL) has been suggested to contribute to the pathogenesis of NAFLD. Recent studies have demonstrated that niacin (NA) modulates hepatic DNL through GPR109A. However, the underlying mechanism remains largely unknown.

OBJECTIVES

This study aims to elucidate the potential molecular mechanism by which GPR109A inhibits hepatic DNL.

METHODS

C57BL/6 wild-type (WT) and Gpr109a knockout (KO) mice (male, 5 wk old) were fed a high-fat diet (60% energy from fat) firstly for 6 wk to generate a diet-induced obese model. Subsequently, they were randomly divided into 4 groups for the next 8-9 wk: WT mice with oral water [WT + vehile (VE)], WT mice with oral NA (50 mM, dissolved in water) (WT + NA), KO mice with oral water (KO + VE), and KO mice with oral NA (50 mM) (KO + NA). Mechanisms were examined in HepG2 cells. Body composition, liver histology, biomarkers of hepatic function, lipid accumulation, and lipid synthesis signals in HepG2 cells were measured.

RESULTS

Upon activation, GPR109A apparently protected against obesity and hepatic steatosis (P < 0.05). The concentrations of hepatic Tnf-α in the WT + NA group were about 50% of those in the WT + VE group (P < 0.05). The activities of serum alanine transaminase and aspartate transaminase were 26.7% and 53.5% lower in the WT + NA group than in the WT + VE group, respectively (P < 0.05). In HepG2 cells, activation of GPR109A resulted in remarkable inhibition of oleic acid-induced lipid accumulation via a protein kinase C-extracellular signal-regulated kinase-1/2-AMP-activated protein kinase signaling pathway.

CONCLUSIONS

NA inhibits hepatic lipogenesis in C57BL/6 mice through a GPR109A-mediated signaling pathway, consistent with the mechanistic studies in HepG2 cells, suggesting its potential for treatment of NAFLD and other fatty liver diseases.

Chrysin ameliorates hepatic steatosis induced by a diet deficient in methionine and choline by inducing the secretion of hepatocyte nuclear factor 4α-dependent very low-density lipoprotein

We investigated the effects of chrysin (CHR) on nonalcoholic fatty liver disease (NAFLD) in mice. The NAFLD mouse model was established using a diet deficient in methionine and choline (MCD). CHR was shown to attenuate MCD-induced hepatic fat accumulation, increase very low-density lipoprotein (VLDL) secretion, and decrease hepatic oxidative stress in NAFLD mice. Inhibition of oxidative stress or direct suppression of protein kinase C (PKC) by CHR significantly reduced PKC activity in the liver, leading to a decrease in inhibitory phosphorylation of hepatocyte nuclear factor 4α (HNF4α). The resulting activation of HNF4α led to induced transcription of apolipoprotein B and VLDL secretion. Together, these results show that CHR effectively ameliorates MCD-induced fatty liver in NAFLD mice by targeting the hepatic oxidative stress/PKC/HNF4α signaling pathway.

Polystyrene microplastic exposure disturbs hepatic glycolipid metabolism at the physiological, biochemical, and transcriptomic levels in adult zebrafish

Microplastics (MPs), which are new types of environmental pollutants, have recently received widespread attention worldwide. MPs can accumulate in the bodies of animals and in plants, and they can also enter the human body through the food chain. However, knowledge of the effects of MPs on the health of animals is still limited. In this experiment, adult male zebrafish were exposed to 20 or 100 μg/L of 5 μm polystyrene MP for 21 days in an attempt to determine the hepatic effects related to glycolipid metabolism at the biochemical and transcriptomic levels. It was found that body weight and condition factor decreased significantly in zebrafish after exposure to 20 and 100 μg/L polystyrene MP for 21 days. The transcription levels of major genes related to glycolipid metabolism decreased significantly in the liver. Correspondingly, the levels of major biochemical parameters, including Glu, pyruvic acid, α-ketoglutaric acid and IDH, were also decreased in the livers of exposed zebrafish, especially those in the 100 μg/L polystyrene MP-treated group. Moreover, the data on the hepatic transcriptome also confirmed that some genes related to fatty acid metabolism, amino acid metabolism and carbon metabolism tended to be decreased in the livers of exposed zebrafish. Taken together, our data confirmed that polystyrene PS-MP can induce hepatic glycolipid metabolism disorder at the physiological, biochemical, and transcriptomic levels in adult zebrafish after 21 days of exposure.

A Close Relationship between Non-Alcoholic Fatty Liver Disease Marker and New-Onset Hypertension in Healthy Korean Adults

Background and Objectives

Nonalcoholic fatty liver disease (NAFLD) is an excessive accumulation of fat into the liver as a result of increased inflammation and insulin resistance. Although there can be common pathogenic mechanisms for NAFLD and hypertension associated with the development of cardiovascular diseases, little data are showing the association between NAFLD and hypertension in a large-scale cohort study. Thus, we evaluated the ability of the fatty liver index (FLI), a surrogate marker of NAFLD, to predict the development of hypertension in healthy individuals.

Methods

We included 334,280 healthy individuals without known comorbidities who underwent the National Health check-ups in South Korea from 2009 to 2014. The association between the FLI and hypertension was analyzed using multivariate Cox proportional-hazards models.

Results

During a median of 5.2 years' follow-up, 24,678 subjects (7.4%) had new-onset hypertension. We categorized total subjects into quartile groups according to FLI (range: Q1, 0–4.9; Q2, 5.0–12.5; Q3, 12.6–31.0; and Q4, >31.0). The incidence of hypertension was higher in subjects with the highest FLI than in those with the lowest FLI (Q4, 9,968 [11.9%] vs. Q1, 2,277 [2.7%]; p<0.001). There was a significant correlation between the highest FLI and an increased risk of new-onset hypertension (adjusted hazard ratio between Q4 and Q1, 2.330; 95% confidence interval, 2.218–2.448; p<0.001). FLI was significantly associated with an increased risk of new-onset hypertension regardless of baseline characteristics.

Conclusions

Higher FLI was independently associated with increased risk of hypertension in a healthy Korean population.

Protective Effect of a Mixture of Astragalus membranaceus and Lithospermum erythrorhizon Extract against Hepatic Steatosis in High Fat Diet-Induced Nonalcoholic Fatty Liver Disease Mice

The present study aimed to evaluate the potential synergistic and protective effects of ALM16, a mixture of Astragalus membranaceus (AM) and Lithospermum erythrorhizon (LE) extract in a ratio of 7 : 3, against hepatic steatosis in high fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) mice. Forty-eight mice were randomly divided into eight groups and orally administered daily for 6 weeks with a normal diet (ND) or high fat diet alone (HFD), HFD with AM (HFD + 100 mg/kg AM extract), HFD with LE (HFD + 100 mg/kg LE extract), HFD with ALM16 (HFD + 50, 100, and 200 mg/kg ALM16), or HFD with MT (HFD + 100 mg/kg Milk thistle extract) as a positive control. ALM16 significantly decreased the body and liver weight, serum and hepatic lipid profiles, including triglyceride (TG), total cholesterol (TC), high-density lipoprotein-cholesterol (HDL), and low-density lipoprotein-cholesterol (LDL), and serum glucose levels, compared to the HFD group. Moreover, ALM16 significantly ameliorated the HFD-induced increased hepatic injury markers, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and gamma-glutamyltransferase (GGT)-1. Furthermore, as compared to the mice fed HFD alone, ALM16 increased the levels of phosphorylated AMP-activated protein kinase (p-AMPK) and acetyl-CoA carboxylase (p-ACC), thereby upregulating the expression of carnitine palmitoyltransferase (CPT)-1 and downregulating the expression of sterol regulatory element-binding protein (SREBP)-1c and fatty acid synthase (FAS). These results demonstrated that ALM16 markedly inhibited HFD-induced hepatic steatosis in NAFLD mice by modulating AMPK and ACC signaling pathways, and may be more effective than the single extracts of AM or LE.

Hepatoprotective Effect of Cranberry Nutraceutical Extract in Non-alcoholic Fatty Liver Model in Rats: Impact on Insulin Resistance and Nrf-2 Expression

Background

Non-alcoholic fatty liver disease (NAFLD) is a pathological accumulation of triglycerides (TGs) in the hepatocyte in the absence of alcohol intake. Untreated NAFLD is expected to progress into liver fibrosis. Cranberry is rich in polyphenols with antioxidant and anti-inflammatory activities.

Hypothesis

The present study was performed to evaluate our hypothesis of the possible anti-fibrotic effect of cranberry nutraceuticals in a high fat cholesterol diet induced (HFCD)-NAFLD in rats, focusing on improving insulin sensitivity and modulating the expression of nuclear factor erythroid-2-related factor-2 (Nrf2) (a transcription factor responsible for regulating cellular redox balance).

Method

Male albino wistar rats (12 weeks) received HFCD and/or cranberry (50 and 100 mg/kg/day, three times/week) orally for 8 consecutive weeks.

Results

In comparison to the HFCD group, cranberry treated groups (50 and 100 mg/kg) showed marked hepatoprotection, where it significantly decreased liver enzymes (alanine transaminases by 49 and 64% and aspartate transaminases by 45 and 64%; respectively), TGs, and ameliorated the histopathological alterations (such as inflammatory cells infiltration and ballooning degeneration) induced by HFCD. Cranberry also alleviated oxidative stress (malondialdehyde, glutathione, catalase and superoxide dismutase) and inflammation (tumor necrosis factor- alpha, interleukine-6 and nuclear factor kappa-b) and significantly reduced the HOMA-IR and TyG index. On the other hand, cranberry treated groups (50 and 100 mg/kg) showed a marked increase in the expression of adiponectin, by 8 and 13-fold, insulin receptor substrate-2 by 21 and 79%, and Nrf2 by 13 and 61%, respectively. Notably, cranberry significantly reduced the fibrotic markers, TGF–β and α-SMA expression and collagen deposition.

Conclusion

The present study showed that cranberry significantly attenuated NAFLD, in a dose dependent manner, which could be partially recognized by its antioxidant, anti-inflammatory activities, and its ability to improve insulin sensitivity. Notably, our study proves for the first time that the anti-fibrotic activity of cranberry is promising.

Dairy Foods and Dairy Fats: New Perspectives on Pathways Implicated in Cardiometabolic Health

Low-fat and nonfat dairy products have been promoted as part of a healthy dietary pattern by both US dietary guidelines and professional organizations for several decades. The basis for this recommendation stems in part from the putative negative cardiometabolic effects associated with saturated fat consumption. However, as nutrition research has shifted from a single nutrient to a whole-food/dietary pattern approach, the role of dairy foods and dairy fat in the diet-disease relationship is being reexamined. Most observational and experimental evidence does not support a detrimental relationship between full-fat dairy intake and cardiometabolic health, including risks of cardiovascular disease and type 2 diabetes. Indeed, an expanded understanding of the dairy food matrix and the bioactive properties of dairy fats and other constituents suggests a neutral or potentially beneficial role in cardiometabolic health. To consider how consuming dairy foods, including full-fat dairy, is associated with cardiometabolic health, this review provides an innovative perspective on mechanisms that link dairy consumption to 3 main biological systems at the core of metabolic health, the gastrointestinal, hepatic, and vascular systems.

Extrahepatic Manifestations of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) represents a global public health burden. NAFLD, while strongly associated with the metabolic syndrome, can occur independently from existing metabolic diseases. In addition to liver-related disease burden and mortality, significant extrahepatic disease outcomes coexist with NAFLD, including cardiovascular diseases, chronic kidney disease, and type 2 diabetes. Management of these comorbidities contributes to the overall public health burden of NAFLD. These extrahepatic manifestations require healthcare interventions that are vigilant in monitoring for progression of liver disease while simultaneously managing overall morbidity and mortality from other organ systems.

Obstructive sleep apnea and dyslipidemia: from animal models to clinical evidence

Lipid metabolism deregulation constitutes the pathogenic basis for the development of atherosclerosis and justifies a high incidence of cardiovascular-related morbidity and mortality. Some data suggest that dyslipidemia may be associated with sleep-disordered breathing, mainly obstructive sleep apnea (OSA), due to alterations in fundamental biochemical processes, such as intermittent hypoxia (IH). The aim of this systematic review was to identify and critically evaluate the current evidence supporting the existence of a possible relationship between OSA and alterations in lipid metabolism. Much evidence shows that, during the fasting state, OSA and IH increase lipid delivery from the adipose tissue to the liver through an up-regulation of the sterol regulatory element-binding protein-1 and stearoyl-CoA desaturase-1, increasing the synthesis of cholesterol esters and triglycerides. In the postprandial state, lipoprotein clearance is delayed due to lower lipoprotein lipase activity, probably secondary to IH-up-regulation of angiopoietin-like protein 4 and decreased activity of the peroxisome proliferator-activated receptor alpha. Moreover, oxidative stress can generate dysfunctional oxidized lipids and reduce the capacity of high-density lipoproteins (HDL) to prevent low-density lipoprotein (LDL) oxidation. In the clinical field, several observational studies and a meta-regression analysis support the existence of a link between OSA and dyslipidemia. Although there is evidence of improved lipid profile after apnea-hypopnea suppression with continuous positive airway pressure (CPAP), the majority of the data come from observational studies. In contrast, randomized controlled trials evaluating the effects of CPAP on lipid metabolism present inconclusive results and two meta-analyses provide contradictory evidence.

Relationship Between Ginsenoside Rg3 and Metabolic Syndrome

Metabolic syndrome is an important public health issue and is associated with a more affluent lifestyle. Many studies of metabolic syndrome have been reported, but its pathogenesis remains unclear and there is no effective treatment. The ability of natural compounds to ameliorate metabolic syndrome is currently under investigation. Unlike synthetic chemicals, such natural products have proven utility in various fields. Recently, ginsenoside extracted from ginseng and ginseng root are representative examples. For example, ginseng is used in dietary supplements and cosmetics. In addition, various studies have reported the effects of ginsenoside on metabolic syndromes such as obesity, diabetes, and hypertension. In this review, we describe the potential of ginsenoside Rg3, a component of ginseng, in the treatment of metabolic syndrome.

Molecular Mechanisms: Connections between Nonalcoholic Fatty Liver Disease, Steatohepatitis and Hepatocellular Carcinoma

Nonalcoholic fatty liver disease (NAFLD), including nonalcoholic steatohepatitis (NASH), causes hepatic fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The patatin-like phospholipase-3 (PNPLA3) I148M sequence variant is one of the strongest genetic determinants of NAFLD/NASH. PNPLA3 is an independent risk factor for HCC among patients with NASH. The obesity epidemic is closely associated with the rising prevalence and severity of NAFLD/NASH. Furthermore, metabolic syndrome exacerbates the course of NAFLD/NASH. These factors are able to induce apoptosis and activate immune and inflammatory pathways, resulting in the development of hepatic fibrosis and NASH, leading to progression toward HCC. Small intestinal bacterial overgrowth (SIBO), destruction of the intestinal mucosa barrier function and a high-fat diet all seem to exacerbate the development of hepatic fibrosis and NASH, leading to HCC in patients with NAFLD/NASH. Thus, the intestinal microbiota may play a role in the development of NAFLD/NASH. In this review, we describe recent advances in our knowledge of the molecular mechanisms contributing to the development of hepatic fibrosis and HCC in patients with NAFLD/NASH.

Abomasally infused SFA with varying chain length differently affect milk production and composition and alter hepatic and mammary gene expression in lactating cows

The aim of the present study was to compare the effects of post-ruminally infused fat supplements, varying in fatty acid (FA) chain length, on animal performance, metabolism and milk FA. Eleven multiparous Holstein dairy cows were used in a replicated incomplete 3 × 3 Latin square design with 7-d periods, separated by 7-d washouts. Treatments were administered as abomasal infusions of enrichments providing 280 g/d of FA: (1) palmitic acid (98·4 % 16 : 0; PA), (2) caprylic and capric acids (56·2 % 8 : 0, 43·8 % 10 : 0; medium-chain TAG (MCT)) and (3) stearic acid (99·0 % 18 : 0; SA). Relative to PA, SA decreased the efficiency of fat-corrected milk production, which was associated with a tendency for higher DM intake and lower FA absorption with SA, whereas MCT was not different from PA for these variables. Milk fat concentration and yield were increased by PA relative to SA, but only fat yield tended to be greater relative to MCT. Relative to PA, MCT increased milk fat concentration of FA < 16 C, whereas SA increased FA > 16 C. Expression of mammary stearoyl-coA desaturase 1 was lower with SA than with PA. Relative to PA, liver expression of adenosine monophosphate-activated protein kinase-1 and pyruvate kinase was increased with MCT, whereas expression of these genes tended to be increased by SA. The mechanism of increased fat secretion with PA does not seem to be related to a modulation of the expression of lipogenesis-related genes, but rather to increased substrate availability as reflected by milk FA profile.

Physiological role of adiponectin in different tissues: a review

Adiponectin is the most important adipokine secreted by the adipose tissue. It carries out an important role in setting up the metabolism and improving the function of various organs. Adiponectin in the kidneys prevents degradation of the renal arteries, reduces protein excretion, and improves filtration. This role is accomplished by regulating anabolic pathways and reducing oxidative stress in the renal tissue. This hormone in the liver prevents the accumulation of fat and free radicals that cause damage to liver cells and tissue. This adipokine, by preventing inflammatory processes, oxidative stress, obesity and insulin resistance, improves vascular function and prevents the development of atherosclerosis. It seems that adiponectin can also be a therapeutic target for many metabolic diseases. This study aims to clarify the adipose tissue discharge. Here, the diverse physiological actions of adiponectin were reviewed to provide an overview of its therapeutic potential in different metabolic disorders.

Association between non-alcoholic fatty liver disease and risk of new-onset atrial fibrillation in healthy adults

BACKGROUND & AIMS

Previous studies demonstrated conflicting results regarding the association between non-alcoholic fatty liver disease (NAFLD) and atrial fibrillation (AF). The statistical power was not sufficient because of modest sample sizes of these studies. We analysed a large population-based cohort to evaluate the association between NAFLD and AF.

METHODS

We evaluated 334 280 healthy individuals without comorbidities who underwent National Health check-ups in South Korea from 2009 to 2014. NAFLD was defined by a surrogate marker, the fatty liver index (FLI). The association between FLI and AF incidence was analysed using multivariate Cox proportional hazards regression models.

RESULTS

During a median follow-up of 5.3 years, 1415 subjects (0.4%) were newly diagnosed with AF. Subjects were categorized into quartile groups according to FLI (range: Q1, 0-4.9; Q2, 5.0-12.5; Q3, 12.6-31.0; Q4, >31.0). The cumulative incidence of AF was significantly higher in subjects with higher FLIs than in those with lower FLIs (Q1, 167 [0.2%]; Q2, 281 [0.3%]; Q3, 470 [0.6%]; Q4, 497 [0.6%]; P < .001). Adjusted hazard ratios (HRs) indicated that a higher FLI was independently associated with an increased risk for AF (HR between Q4 and Q1, 1.35; 95% confidence interval [CI], 1.11-1.63; P = .002). After further adjustment for the interim events (diabetes, hypertension, heart failure and myocardial infarction), this association remained statistically significant (HR between Q4 and Q1, 1.55; 95% CI, 1.19-2.03; P = .001).

CONCLUSIONS

NAFLD, assessed by FLI, was independently associated with increased risk for AF in healthy Korean population. Moreover, NAFLD itself predisposes to AF independently of the interim events.

Acetyl-CoA carboxylase 1 and 2 inhibition ameliorates steatosis and hepatic fibrosis in a MC4R knockout murine model of nonalcoholic steatohepatitis

Acetyl-CoA carboxylase (ACC) catalyzes the rate-limiting step in de novo lipogenesis, which is increased in the livers of patients with nonalcoholic steatohepatitis. GS-0976 (firsocostat), an inhibitor of isoforms ACC1 and ACC2, reduced hepatic steatosis and serum fibrosis biomarkers such as tissue inhibitor of metalloproteinase 1 in patients with nonalcoholic steatohepatitis in a randomized controlled trial, although the impact of this improvement on fibrosis has not fully been evaluated in preclinical models. Here, we used Western diet-fed melanocortin 4 receptor-deficient mice that have similar phenotypes to nonalcoholic steatohepatitis patients including progressively developed hepatic steatosis as well as fibrosis. We evaluated the effects of ACC1/2 inhibition on hepatic fibrosis. After the confirmation of significant hepatic fibrosis with a 13-week pre-feeding, GS-0976 (4 and 16 mg/kg/day) treatment for 9 weeks lowered malonyl-CoA and triglyceride content in the liver and improved steatosis, histologically. Furthermore, GS-0976 reduced the histological area of hepatic fibrosis, hydroxyproline content, mRNA expression level of type I collagen in the liver, and plasma tissue metalloproteinase inhibitor 1, suggesting an improvement of hepatic fibrosis. The treatment with GS-0976 was also accompanied by reductions of plasma ALT and AST levels. These data demonstrate that improvement of hepatic lipid metabolism by ACC1/2 inhibition could be a new option to suppress fibrosis progression as well as to improve hepatic steatosis in nonalcoholic steatohepatitis.

Discovery of a role of the novel hepatokine, hepassocin, in obesity

Obesity is a public health problem that has raised concerns worldwide and is often associated with hepatic steatosis. Hepassocin is a novel hepatokine that causes hepatic steatosis and induces insulin resistance (IR). However, the role of hepassocin in obesity remains obscure. Thus, the aim of this study was to investigate the relationship between hepassocin levels and obesity. In total, 371 subjects who had a normal weight (NW), were overweight, or were obese were enrolled. We found that hepassocin levels in subjects who were overweight (6,705 ± 1,707 pg/ml) or obese (7,335 ± 2,077 pg/ml) were significantly higher than those of subjects with a NW (5,767 ± 1,500 pg/ml) (p < .001, test for trend). A multiple linear regression analysis showed that the body-mass index, waist circumference, nonalcoholic fatty liver disease, and homeostatic model assessment of IR were independently associated with hepassocin after adjusting for age, sex, high-sensitivity C-reactive protein, systolic blood pressure, high-density lipoprotein-cholesterol, log triglycerides, alanine transaminase, and the estimated glomerular filtration rate. This study provides evidence that subjects who were overweight or obese had significantly higher hepassocin levels than those with a NW. Hepassocin may be a useful biomarker in managing obesity and its related metabolic dysregulation.

Effect of Saxagliptin, a Dipeptidyl Peptidase 4 Inhibitor, on Non-Alcoholic Fatty Liver Disease

BACKGROUND AND AIM

Non-alcoholic fatty liver disease (NAFLD) represents a broad spectrum of chronic liver disease characterized by aberrant accumulation of triglycerides (TG) in hepatocytes without excessive alcohol consumption. Hepatic lipotoxicity derived from overaccumulation of free fatty acids is considered as one of the typical hallmarks of NAFLD. Insulin resistance (IR) and chronic inflammation are widely recognized as the key etiological factors associated with NAFLD. Dipeptidyl peptidase 4 inhibitor (DPP4i) is a novel pharmacological agent extensively applied in the treatment of Type 2 Diabetes Mellitus (T2DM) for decades which also have a liver protective effect.

METHODS

In order to invest the therapeutic efficiency and underlying mechanism of DPP4i saxagliptin, we used high-fat diet (HFD) and streptozotocin-induced NAFLD treated with saxagliptin. Biochemical, histomorphological, genetic and protein expression of related pathways were investigated.

RESULTS

Fasting blood glucose (FBG), TG, total cholesterol (TC), and low-density lipoprotein cholesterin significantly increased in NAFLD group, which also exhibited severe steatosis. Other remarkable findings were hyperinsulinemia, increased DPP4, PTP-1B and TNF-α level and decreased GLP-1, ACOX-1, CPT-1A expression, concomitant with liver DPP4 expression enhancement and serum DPP4 elevation. These undesirable consequences were alleviated by saxagliptin to a certain degree.

CONCLUSION

DPP4i saxagliptin improves NAFLD by ameliorating IR, inflammation, downregulation of hepatic DPP4 and sDPP4, as well as subsequent steatosis. The elevation of hepatic DPP4 and sDPP4 and succedent post-treatment decrease suggested that DPP4 may involve in the development of NAFLD. The anti-lipotoxic effect of DPP4i may involve the activation of CPT1A and ACOX1 related β-oxidation signaling pathway suppression of TNF-α mediated inflammatory and PTP-1B. The results covered in this article showed that saxagliptin affects many aspects of the pathological characteristics of NAFLD, suggesting that DPP4i saxagliptin may offer a novel therapeutic option for NAFLD.

Maternal conjugated linoleic acid alters hepatic lipid metabolism via the AMPK signaling pathway in chick embryos

The effects of maternal conjugated linoleic acid (CLA) on embryonic development and hepatic lipid metabolism were investigated in chick embryos. A total of 180 Arbor Acres female broiler breeders (36 wk old) were randomly divided into the following 3 dietary treatment groups: a basic diet (control), a basic diet containing 0.5% CLA (CLA1), and a basic diet containing 1.0% CLA (CLA2). The females were fed for 8 wk, and the eggs from each group were collected and hatched during the last 2 wk. The results showed that the addition of dietary CLA increased the broken egg rate and reduced the fertilization rate and the egg hatchability (P < 0.05). CLA enrichment decreased the polyunsaturated and monounsaturated fatty acids and increased the saturated fatty acids in the yolk sac (P < 0.05). The yolk sac weight, body weight, and body length had a linear decrease with CLA supplementation (P < 0.05). In the developing chick embryo (at E14) and newly hatched chick (D0), the serum triglyceride concentration decreased with maternal CLA supplementation and was accompanied by a reduction in subcutaneous adipose tissue deposition. In addition, maternal CLA supplementation mediated the hepatic lipid metabolism by decreasing the mRNA expression of sterol regulatory element-binding proteins-1c (SREBP-1c), fatty acid synthase and acetyl-CoA carboxylase, and increasing the mRNA expression of adenosine 5'-monophosphate-activated protein kinase α (AMPKα), peroxisome proliferator-activated receptors α (PPARα), liver fatty acid-binding protein, adipose triglyceride lipase and carnitine palmitoyltransferase in embryonic chick livers (P < 0.05). A drop in SREBP-1c protein expression and an increase in the protein expression of p-AMPKα and PPARα were also observed in the liver of chick embryo (P < 0.05). In conclusion, maternal CLA supplementation regulated the fatty acid composition in the yolk sac, and mediated embryonic chick development and hepatic lipometabolism, and these effects may be related to the AMPK pathway. These findings suggest the potential ability of maternal CLA supplementation to reduce fat deposition in chick embryos.

CGI-58: Versatile Regulator of Intracellular Lipid Droplet Homeostasis

Comparative gene identification-58 (CGI-58), also known as α/β-hydrolase domain-containing 5 (ABHD5), is a member of a large family of proteins containing an α/β-hydrolase-fold. CGI-58 is well-known as the co-activator of adipose triglyceride lipase (ATGL), which is a key enzyme initiating cytosolic lipid droplet lipolysis. Mutations in either the human CGI-58 or ATGL gene cause an autosomal recessive neutral lipid storage disease, characterized by the excessive accumulation of triglyceride (TAG)-rich lipid droplets in the cytoplasm of almost all cell types. CGI-58, however, has ATGL-independent functions. Distinct phenotypes associated with CGI-58 deficiency commonly include ichthyosis (scaly dry skin), nonalcoholic steatohepatitis, and hepatic fibrosis. Through regulated interactions with multiple protein families, CGI-58 controls many metabolic and signaling pathways, such as lipid and glucose metabolism, energy balance, insulin signaling, inflammatory responses, and thermogenesis. Recent studies have shown that CGI-58 regulates the pathogenesis of common metabolic diseases in a tissue-specific manner. Future studies are needed to molecularly define ATGL-independent functions of CGI-58, including the newly identified serine protease activity of CGI-58. Elucidation of these versatile functions of CGI-58 may uncover fundamental cellular processes governing lipid and energy homeostasis, which may help develop novel approaches that counter against obesity and its associated metabolic sequelae.

Momordica charantia mitigates hepatic injury following adjuvant treatment with antiretroviral drugs in diabetic animal models

Momordica charantia (M. charantia) is a medicinal plant, used in traditional practice for treating diseases like hypertension and diabetes mellitus. This study investigated the possible hepato-protective effect of M. charantia following treatment with highly active antiretroviral therapy (HAART) in diabetic rats. 48 adult male Sprague Dawley rats were divided into seven groups (A-G) of 7 animals per group and treated according to protocols. Diabetes was induced with streptozotocin (STZ) by intraperitoneal injection (45 mg/kg body weight). The animals were euthanized on the 10th week with liver removed for examination and blood obtained via cardiac puncture and centrifuged to collect the sera. Blood glucose levels (BGL) were consistently and significantly raised (p < 0.05) in all groups not receiving the adjuvant M. charantia. Treatment with M. charantia reverses the increase in BGL to near normal. Markers of liver injury assayed showed significant increase (p < 0.05) in AST, ALP and ALT levels in groups not receiving M. charantia. Adjuvant HAART and M. charantia caused significant declines in the liver enzymes (p < 0.05). Serum GGT was not markedly altered. Treatment with M. charantia significantly restored liver enzymes elevations to near normal comparable to control. Histopathological observations ranged from severe hepatocellular distortions, necrosis and massive fibrosis following treatment of HAART in diabetic groups not receiving M. charantia. Treatment with M. charantia did not show any sign of hepatotoxicity as judged from the histological and biochemical observations.

Saroglitazar Deactivates the Hepatic LPS/TLR4 Signaling Pathway and Ameliorates Adipocyte Dysfunction in Rats with High-Fat Emulsion/LPS Model-Induced Non-alcoholic Steatohepatitis

The most epidemic liver disorder non-alcoholic steatohepatitis (NASH) is characterized by hepatic steatosis and inflammation with hepatocellular damage. Recently, it is predictable to be the extensive cause for liver transplantation. The absence of an approved therapeutic agent for NASH is the reason for investigating saroglitazar (SAR) which showed promising effects as a dual PPAR-α/γ agonist in recent studies on NASH. Here, we aimed to investigate the effect of SAR on NASH induced in rats by the administration of high-fat emulsion (HFE) and small doses of lipopolysaccharides (LPS) for 5 weeks. Rats were divided into three groups: negative control group (saline and standard rodent chow), model group (HFE(10 ml/kg/day, oral gavage) + LPS(0.5 mg/kg/week, i.p)), and SAR-treated group (HFE(10 ml/kg/day, oral gavage) + LPS(0.5 mg/kg/week, i.p.) + SAR(4 mg/kg/day, oral gavage) starting at week 3.Treatment with SAR successfully ameliorated the damaging effects of HFE with LPS, by counteracting body weight gain and biochemically by normalization of liver function parameters activity, glucose, insulin, homeostasis model of assessment (HOMA-IR) score, lipid profile levels, and histopathological examination. Significant changes in adipokine levels were perceived, resulting in a significant decline in serum leptin and tumor necrosis factor-α (TNF-α) level concurrent with adiponectin normalization. The positive effects observed for SAR on NASH are due to the downregulation of the LPS/TLR4 pathway, as indicated by the suppression of hepatic Toll-like receptor 4 (TLR4), NF-κB, TNF-α, and transforming growth factor-β1 (TGF-β1) expression. In conclusion, this work verified that SAR ameliorates NASH through deactivation of the hepatic LPS/TLR4 pathway and inhibition of adipocyte dysfunction.

Sodium acetate protects against nicotine-induced excess hepatic lipid in male rats by suppressing xanthine oxidase activity

Fatty liver is the hepatic consequence of chronic insulin resistance (IR) and related syndromes. It is mostly accompanied by inflammatory and oxidative molecules. Increased activity of xanthine oxidase (XO) exerts both inflammatory and oxidative effects and has been implicated in metabolic derangements including non-alcoholic fatty liver disease. Short chain fatty acids (SCFAs) elicit beneficial metabolic alterations in IR and related syndromes. In the present study, we evaluated the preventive effects of a SCFA, acetate, on nicotine-induced dysmetabolism and fatty liver. Twenty-four male Wistar rats (n = 6/group): vehicle-treatment (p.o.), nicotine-treated (1.0 mg/kg; p.o.), sodium acetate-treated (200 mg/kg; p.o.) and nicotine + sodium acetate-treated groups. The treatments lasted for 8 weeks. IR was estimated by oral glucose tolerance test and homeostatic model assessment of IR. Plasma and hepatic free fatty acid, triglyceride (TG), glutathione peroxidase, adenosine deaminase (ADA), XO and uric acid (UA) were measured. Nicotine exposure resulted in reduced body weight, liver weight, visceral adiposity, glycogen content and glycogen synthase activity. Conversely, exposure to nicotine increased fasting plasma glucose, lactate, IR, plasma and hepatic TG, free fatty acid, TG/HDL-cholesterol ratio, lipid peroxidation, liver function enzymes, plasma and hepatic UA, XO and ADA activities. However, plasma and hepatic glucose-6-phosphate dehydrogenase-dependent antioxidant defense was not affected by nicotine. Concomitant treatment with acetate ameliorated nicotine-induced effects. Taken together, these results indicate that nicotine exposure leads to excess deposition of lipid in the liver by enhancing XO activity. The results also imply that acetate confers hepatoprotection and is accompanied by decreased XO activity.

Comparative effects of nanoemulsions loaded with duck oil and lard oil on palmitate-induced lipotoxicity

The effects of duck oil and lard oil on lipotoxicity induced by saturated long-chain fatty acids were evaluated in HepG2 cells. Lipotoxicity triggered by palmitate, a saturated fatty acid, was inhibited more by duck oil-loaded nanoemulsion (DO-NE) than by lard oil-loaded nanoemulsion (LO-NE) and control nanoemulsion (NE) in HepG2 cells. Accumulation of reactive oxygen species and lipid vacuoles in HepG2 cells induced by palmitate treatment was inhibited by DO-NE but not by LO-NE. Consistently, treatment of HepG2 cells with DO-NE, but not with NE or LO-NE, significantly reduced the expression levels of peroxisome proliferator-activated receptor-γ2 and sterol regulatory element-binding protein-1, which are key regulatory proteins in hepatic lipid accumulation. In addition, the cleavage of poly (ADP-ribose) polymerase and caspase-3 were reduced more by DO-NE than by LO-NE, indicating that DO-NE directly attenuates cellular damage induced by palmitate. Collectively, these results imply that the biological activity of duck oil against palmitate-induced cellular damage is more potent than that of lard oil. PRACTICAL APPLICATIONS: Accumulated lipids in nonadipose tissues, especially the liver, cause lipotoxicity, a pathologic feature of hepatic disorders, by inducing oxidative stress. A nanoemulsion loaded with duck oil, which is a functional food widely consumed by Korean people, inhibited lipotoxicity by suppressing lipid accumulation in HepG2 cells exposed to palmitate, which mimic nonalcoholic fatty liver disease. Thus, we propose that duck oil can be used as a functional food to improve lipid-induced hepatic disorders.

Effect of Curcumin on Growth Performance, Inflammation, Insulin level, and Lipid Metabolism in Weaned Piglets with IUGR

Simple Summary

Intrauterine growth retardation (IUGR) has adverse influences on the growth performance and body metabolism of animals. Curcumin, a naturally occurring phenolic compound, has been proven to improve the growth of pigs. However, the studies related to the role of curcumin in treating IUGR piglets are not clear. Therefore, the purpose of our study was to investigate the role of curcumin on the growth, secretion of serum cytokines and hepatic metabolism of IUGR piglets. We found that IUGR piglets are accompanied by impaired growth, inflammation, and insulin resistance, as well as increased hepatic lipid concentrations. Curcumin supplementation improved growth and reduced hepatic inflammatory levels, thereby attenuating insulin resistance and decreasing the hepatic lipid concentration of IUGR piglets.

Abstract

The possible causes of intrauterine growth retardation (IUGR) might stem from placental insufficiency, maternal malnutrition, inflammation in utero, and other causes. IUGR has had an adverse influence on human health and animal production. Forty weaned piglets with normal birth weights (NBWs) or IUGR were randomly divided into four treatments groups: NBW, NC (NBW with curcumin supplementation), IUGR, and IC (IUGR with curcumin supplementation) from 26 to 50 d. Levels of cytokines, glucose, and lipid metabolism were evaluated. IUGR piglets showed slow growth during the experiment. Piglets with IUGR showed higher levels of serum pro-inflammatory cytokines, insulin resistance, and hepatic lipid accumulation. Curcumin supplementation reduced the production of serum pro-inflammatory cytokines, attenuated insulin resistance and hepatic triglyceride, and enhanced the hepatic glycogen concentrations and lipase activities of IUGR piglets. The hepatic mRNA expressions of the insulin-signaling pathway and lipogenic pathway were influenced by IUGR and were positively attenuated by diets supplemented with curcumin. In conclusion, IUGR caused slow growth, insulin resistance, and increased hepatic lipid levels. Diets supplemented with curcumin improved growth, attenuated insulin resistance, and reduced lipid levels in the liver by regulating the hepatic gene expressions of the related signaling pathway in IUGR piglets.

Mammalian phospholipase D: Function, and therapeutics

Despite being discovered over 60 years ago, the precise role of phospholipase D (PLD) is still being elucidated. PLD enzymes catalyze the hydrolysis of the phosphodiester bond of glycerophospholipids producing phosphatidic acid and the free headgroup. PLD family members are found in organisms ranging from viruses, and bacteria to plants, and mammals. They display a range of substrate specificities, are regulated by a diverse range of molecules, and have been implicated in a broad range of cellular processes including receptor signaling, cytoskeletal regulation and membrane trafficking. Recent technological advances including: the development of PLD knockout mice, isoform-specific antibodies, and specific inhibitors are finally permitting a thorough analysis of the in vivo role of mammalian PLDs. These studies are facilitating increased recognition of PLD's role in disease states including cancers and Alzheimer's disease, offering potential as a target for therapeutic intervention.

Acupuncture on ST36, CV4 and KI1 Suppresses the Progression of Methionine- and Choline-Deficient Diet-Induced Nonalcoholic Fatty Liver Disease in Mice

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide, and its treatment remain a constant challenge. A number of clinical trials have shown that acupuncture treatment has beneficial effects for patients with NAFLD, but the molecular mechanisms underlying its action are still largely unknown. In this study, we established a mouse model of NAFLD by administering a methionine- and choline-deficient (MCD) diet and selected three acupoints (ST36, CV4, and KI1) or nonacupoints (sham) for needling. We then investigated the effects of acupuncture treatment on the progression of NAFLD and the underlying mechanisms. After two weeks of acupuncture treatment, the liver in the needling-nonapcupoint group (NG) mice appeared pale and yellowish in color, while that in the needling-acupoint group (AG) showed a bright red color. Histologically, fewer lipid droplets and inflammatory foci were observed in the AG liver than in the NG liver. Furthermore, the expression of proinflammatory signaling factors was significantly downregulated in the AG liver. A lipid analysis showed that the levels of triglyceride (TG) and free fatty acid (FFA) were lower in the AG liver than in the NG liver, with an altered expression of lipid metabolism-related factors as well. Moreover, the numbers of 8-hydroxy-2′-deoxyguanosine (8-OHdG)-positive hepatocytes and levels of hepatic thiobarbituric acid reactive substances (TBARS) were significantly lower in AG mice than in NG mice. In line with these results, a higher expressions of antioxidant factors was found in the AG liver than in the NG liver. Our results indicate that acupuncture repressed the progression of NAFLD by inhibiting inflammatory reactions, reducing oxidative stress, and promoting lipid metabolism of hepatocytes, suggesting that this approach might be an important complementary treatment for NAFLD.

Inter-organ cross-talk in metabolic syndrome

Maintenance of systemic homeostasis and the response to nutritional and environmental challenges require the coordination of multiple organs and tissues. To respond to various metabolic demands, higher organisms have developed a system of inter-organ communication through which one tissue can affect metabolic pathways in a distant tissue. Dysregulation of these lines of communication contributes to human pathologies, including obesity, diabetes, liver disease and atherosclerosis. In recent years, technical advances such as data-driven bioinformatics, proteomics and lipidomics have enabled efforts to understand the complexity of systemic metabolic cross-talk and its underlying mechanisms. Here, we provide an overview of inter-organ signals and their roles in metabolic control, and highlight recent discoveries in the field. We review peptide, small-molecule and lipid mediators secreted by metabolic tissues, as well as the role of the central nervous system in orchestrating peripheral metabolic functions. Finally, we discuss the contributions of inter-organ signalling networks to the features of metabolic syndrome.

Sex modifies the consequences of extended fructose consumption on liver health, motor function, and physiological damage in rats

Sex differences are evident in the presentation of metabolic symptoms. A shift of sex hormones that signal the onset of puberty combined with a poor diet consumed in adolescence is likely to have sex-specific, long-term impacts on adult physiology. Here, we expanded on existing literature to elucidate the sex-specific mechanisms driving physiological deficits following high fructose consumption. Male and female Wistar rats were fed a high-fructose (55%) diet beginning immediately postweaning for 10 wk. Female rats fed the high-fructose diet displayed elevated weight gain and extensive liver pathology consistent with markers of nonalcoholic fatty liver disease (NAFLD). Male rats fed the high-fructose diet exhibited increased circulating glucose along with moderate hepatic steatosis. Levels of cytokines and gene expression of inflammatory targets were not altered by fructose consumption in either sex. However, circulating levels of markers for liver health, including alanine transaminase and uric acid, and markers for epithelial cell death were altered by fructose consumption. From the alterations in these markers for liver health, along with elevated circulating triglycerides, it was evident that liver health had deteriorated significantly and that a number of factors were at play. Both adult fructose-fed male and female rats displayed motor deficits that correlated with aberrant structural changes at the neuromuscular junction; however, these deficits were exacerbated in males. These data indicate that consumption of a high-fructose diet beginning in adolescence leads to adult pathology that is modified by sex. Identification of these sex-specific changes has implications for treatment of clinical presentation of metabolic syndrome and related disorders.