Adiponectin attenuates liver fibrosis by inducing nitric oxide production of hepatic stellate cells

Targeting AMPK as a potential treatment for hepatic fibrosis in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease, and often progresses to hepatic fibrosis, cirrhosis, and liver failure. Despite its increasing prevalence, effective pharmacological treatments for MASLD-related fibrosis remain limited. Recent research has highlighted AMP-activated protein kinase (AMPK) as a key regulator of the processes that promote fibrogenesis, and AMPK activation shows potential in mitigating fibrosis. Advances in AMPK activators and deeper insights into their role in fibrotic pathways have recently revitalized interest in targeting AMPK for fibrosis treatment. This review discusses the molecular mechanisms linking AMPK to hepatic fibrosis and evaluates emerging AMPK-directed therapies. Furthermore, it addresses challenges in clinical translation. Importantly, we combine the latest mechanistic discoveries with recent therapeutic developments to provide a comprehensive perspective on AMPK as a target for hepatic fibrosis treatment.

Statin Use and Development and Progression of Nonalcoholic Fatty Liver Disease Based on Ultrasonography

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) has emerged as a public health issue, while no drugs have been specifically approved for treatment.

OBJECTIVE

This study aimed to examine the association between statin use and NAFLD occurrence, progression, and regression.

METHODS

A cohort study was designed based on the Kailuan Study and electronic medical records from the Kailuan General Hospital. Participants aged 18 years with statin indication, including statin and nonstatin users, were enrolled from 2010 to 2017. Propensity score (PS)-matched cohorts were also used.

RESULTS

In the entire cohort, 21 229 non-NAFLD and 22 419 NAFLD patients (including 12 818 mild NAFLD patients) were included in the final analysis. After a median follow-up of about 4 years, the incidence of NAFLD occurrence and progression for statin users was lower than those for nonstatin users (occurrence: 84.7 vs 106.5/1000 person-years; progression: 60.7 vs 75.5/1000 person-years). Compared with nonstatin users, the risk of NAFLD occurrence (hazard ratio [HR]: 0.78; 95% CI, 0.70-0.87) and regression (HR [95% CI]; 0.71 [0.60-0.84]) was decreased in statin users. The significantly negative association was observed only in those with cumulative statin duration of 2 years or more (HR [95% CI] for occurrence 0.56 [0.46-0.69] vs 0.52 [0.30-0.90] for progression) and those with low or moderate atherosclerosis cardiovascular disease (ASCVD) risk (HR [95% CI] for occurrence 0.74 [0.66-0.82] vs 0.68 [0.57-0.80] for progression). No statistically significant correlation was observed between statin use, statin use duration, and NAFLD regression. The PS-matched cohort had similar results.

CONCLUSION

Taking statin may decrease the risk of NAFLD occurrence and progression in the population with statin indication, suggesting the potential role of statin both in primary and secondary prevention strategies for NAFLD, especially among those with low or moderate ASCVD risk.

Ultrasound-Mediated Biomimetic Microbubbles Effectively Reverse LSECs Capillarization and Exert Antiplatelet Therapy in Liver Fibrosis

Liver fibrosis, characterized by excessive tissue remodeling as a response to chronic liver injury, is accompanied by capillarization of liver sinusoidal endothelial cells (LSECs) and activated hepatic stellate cells (HSCs). Simvastatin (Sim) can modulate endothelial function by increasing endothelial nitric oxide synthase (eNOS)-dependent nitric oxide (NO) release, thereby reversing capillarization and attenuating liver fibrosis. However, monotherapy often demonstrates limited therapeutic effectiveness given the complex pathophysiology of liver fibrosis. Herein, a type of multifunctional liposomal microbubbles (MBs) carrying both Sim and platelet membrane (PM) has been designed for drug delivery targeting the inflammatory LSECs, with ultrasound-targeted microbubble destruction (UTMD) to mediate efficient release of these therapeutic agents inside the liver sinusoidal. In rat liver fibrosis model, the multifunctional MBs reverses capillarization through the increase of eNOS-dependent NO production. Subsequently, the MBs adhering to the inflammatory LSECs block the adhesion and activation of inherent platelet (PLT), thereby decreasing platelet-derived growth factor β (PDGF-β) to inhibit the HSCs activation. This study demonstrates the strong therapeutic efficacy of the multifunctional MBs integrating Sim and PLT against liver fibrosis, which highlights a great potential for effectively managing this intractable chronic disease.

The adiponectin-PPARγ axis in hepatic stellate cells regulates liver fibrosis

Hepatic stellate cells (HSCs) are key drivers of local fibrosis. Adiponectin, conventionally thought of as an adipokine, is also expressed in quiescent HSCs. However, the impact of its local expression on the progression of liver fibrosis remains unclear. We recently generated a transgenic mouse line (Lrat-rtTA) that expresses the doxycycline-responsive transcriptional activator rtTA under the control of the HSC-specific lecithin retinol acyltransferase (Lrat) promoter, which enables us to specifically and inducibly overexpress or eliminate genes in these cells. The inducible elimination of HSCs protects mice from methionine/choline-deficient (MCD) diet-induced liver fibrosis, confirming their causal involvement in fibrosis development. We generated HSC-specific adiponectin overexpression and null models that demonstrate that HSC-specific adiponectin overexpression dramatically reduces liver fibrosis, whereas HSC-specific adiponectin elimination accelerates fibrosis progression. We identify a local adiponectin-peroxisome proliferator-activated receptor gamma (PPARγ) axis in HSCs that exerts a marked influence on the progression of local fibrosis, independent of circulating adiponectin derived from adipocytes.

Adiponectin deficiency prevents chronic colitis-associated colonic fibrosis via inhibiting CXCL13 production

INTRODUCTION

Colonic fibrosis is a long-term complication of inflammatory bowel disease (IBD), often leading to functional impairment, intestinal obstruction, and surgery. Adiponectin (APN) is an adipokine derived from adipocytes that plays a pleiotropic role in fibrosis regulation, depending on tissue and cell type specific or disease context, but its role in colonic fibrosis remains unclear.

OBJECTIVE

To explore the role and involved mechanism of APN in chronic colitis-associated colonic fibrosis.

METHODS

Studies were performed in GEO database, colonic tissues of UC patients, dextran sulfate sodium (DSS)-induced colonic fibrosis in male wild-type (WT) and APN-/- mice, mouse L929 and human CCD-18Co fibroblasts treated with recombinant CXCL13 protein, and colonic fibrosis in WT mice infected with shRNA of CXCL13.

RESULTS

APN was highly expressed in the colonic tissues of UC patients and positively correlated with the colonoscopy score and colonic fibrosis markers COL1A1 and COL3A1. APN deficiency significantly improved chronic colitis-induced colonic fibrosis in mice with down-regulating collagenase accumulation and expressions of TGF-β, α-SMA, COL1A1, COL3A1, and MMP-9 in colonic tissues. Transcriptomics showed that APN deficiency mainly affected cytokine-cytokine receptor interactions, especially CXCL13 signaling. Follow-up studies showed that APN deficiency significantly decreased the number of colonic F4/80+CD206+CXCL13+ macrophages by weakening Akt phosphorylation. Additional experiments confirmed that CXCL13 notably increased the expressions of α-SMA and COL1A1 in mouse and human fibroblasts by activating p-Akt, p-p38, p-ERK, and p-JNK. Moreover, inhibiting CXCL13 with shRNA significantly ameliorated colonic fibrosis in mice with DSS-induced chronic colitis. Immunohistochemistry analysis revealed high expression of CXCL13 in the colon tissues of patients with UC, showing a positive correlation with APN, COL1A1, and COL3A1.

CONCLUSION

APN contributes to the progression of colonic fibrosis and can exacerbate this condition by regulating the secretion of CXCL13 in the colon, offering potential new perspectives on the pathophysiology of colonic fibrosis.

PPARβ/δ attenuates hepatic fibrosis by reducing SMAD3 phosphorylation and p300 levels via AMPK in hepatic stellate cells

The role of peroxisome proliferator-activated receptor (PPAR)β/δ in hepatic fibrosis remains a subject of debate. Here, we examined the effects of a PPARβ/δ agonist on the pathogenesis of liver fibrosis and the activation of hepatic stellate cells (HSCs), the main effector cells in liver fibrosis, in response to the pro-fibrotic stimulus transforming growth factor-β (TGF-β). The PPARβ/δ agonist GW501516 completely prevented glucose intolerance and peripheral insulin resistance, blocked the accumulation of collagen in the liver, and attenuated the expression of inflammatory and fibrogenic genes in mice fed a choline-deficient high-fat diet (CD-HFD). The antifibrogenic effect of GW501516 observed in the livers CD-HFD-fed mice could occur through an action on HSCs since primary HSCs isolated from Ppard-/- mice showed increased mRNA levels of the profibrotic gene Col1a1. Moreover, PPARβ/δ activation abrogated TGF-β1-mediated cell migration (an indicator of cell activation) in LX-2 cells (immortalized activated human HSCs). Likewise, GW501516 attenuated the phosphorylation of the main downstream intracellular protein target of TGF-β1, suppressor of mothers against decapentaplegic (SMAD)3, as well as the levels of the SMAD3 co-activator p300 via the activation of AMP-activated protein kinase (AMPK) and the subsequent inhibition of extracellular signal-regulated kinase-1/2 (ERK1/2) in LX-2 cells. Overall, these findings uncover a new mechanism by which the activation of AMPK by a PPARβ/δ agonist reduces TGF-β1-mediated activation of HSCs and fibrosis via the reduction of both SMAD3 phosphorylation and p300 levels.

Redox Homeostasis and Non-Invasive Assessment of Significant Liver Fibrosis by Shear Wave Elastography

Hepatic fibrosis with various origins can be estimated non-invasively by using certain biomarkers and imaging-based measurements. The aim of our study was to examine redox homeostasis biomarkers and liver stiffness measurements for the assessment of significant liver fibrosis in different etiologies of chronic liver diseases. A cohort study consisting of 88 chronic liver disease patients of both sexes (age 49.1 ± 14.7 years) was performed. Cytokine profiles as well as redox homeostasis characteristics were determined. Liver fibrosis stages were assessed with shear wave elastography. The plasma levels of four cytokines showed no significant alteration between the four fibrotic stages; however, higher values were measured in the F2-4 stages. Free sulfhydryl group concentration, the marker of redox homeostasis, was lower in significant fibrosis (F0-F1: 0.36 ± 0.06 vs. F2-4: 0.29 ± 0.08 mmol/L, p < 0.05). Higher chemiluminescence values, as free radical-antioxidant parameters, were detected in advanced fibrosis stages in erythrocytes (F0-F1: 36.00 ± 37.13 vs. F2-4: 51.47 ± 44.34 RLU%). These data suggest that oxidative stress markers can predict significant fibrosis, with the aim of reducing the number of protocol liver biopsies in patients unlikely to have significant disease; however, their role in distinguishing between the certain fibrosis groups needs further studies.

Exogenous APN protects normal tissues from radiation-induced oxidative damage and fibrosis in mice and prostate cancer patients with higher levels of APN have less radiation-induced toxicities

Radiation causes damage to normal tissues that leads to increased oxidative stress, inflammation, and fibrosis, highlighting the need for the selective radioprotection of healthy tissues without hindering radiotherapy effectiveness in cancer. This study shows that adiponectin, an adipokine secreted by adipocytes, protects normal tissues from radiation damage invitro and invivo. Specifically, adiponectin (APN) reduces chronic oxidative stress and fibrosis in irradiated mice. Importantly, APN also conferred no protection from radiation to prostate cancer cells. Adipose tissue is the primary source of circulating endogenous adiponectin. However, this study shows that adipose tissue is sensitive to radiation exposure exhibiting morphological changes and persistent oxidative damage. In addition, radiation results in a significant and chronic reduction in blood APN levels from adipose tissue in mice and human prostate cancer patients exposed to pelvic irradiation. APN levels negatively correlated with bowel toxicity and overall toxicities associated with radiotherapy in prostate cancer patients. Thus, protecting, or modulating APN signaling may improve outcomes for prostate cancer patients undergoing radiotherapy.

The mysterious association between adiponectin and endometriosis

Adiponectin is a pleiotropic cytokine predominantly derived from adipose tissue. In addition to its role in regulating energy metabolism, adiponectin may also be related to estrogen-dependent diseases, and many studies have confirmed its involvement in mediating diverse biological processes, including apoptosis, autophagy, inflammation, angiogenesis, and fibrosis, all of which are related to the pathogenesis of endometriosis. Although many researchers have reported low levels of adiponectin in patients with endometriosis and suggested that it may serve as a protective factor against the development of the disease. Therefore, the purpose of this review was to provide an up-to-date summary of the roles of adiponectin and its downstream cytokines and signaling pathways in the aforementioned biological processes. Further systematic studies on the molecular and cellular mechanisms of action of adiponectin may provide novel insights into the pathophysiology of endometriosis as well as potential therapeutic targets.

The role of novel adipokines and adipose-derived extracellular vesicles (ADEVs): Connections and interactions in liver diseases

Adipose tissues (AT) are an important endocrine organ that secretes various functional adipokines, peptides, non-coding RNAs, and acts on AT themselves or other distant tissues or organs through autocrine, paracrine, or endocrine manners. An accumulating body of evidence has suggested that many adipokines play an important role in liver metabolism. Besides the traditional adipokines such as adiponectin and leptin, many novel adipokines have recently been identified to have regulatory effects on the liver. Additionally, AT can produce extracellular vesicles (EVs) that act on peripheral tissues. However, under pathological conditions, such as obesity and diabetes, dysregulation of adipokines is associated with functional changes in AT, which may cause liver diseases. In this review, we focus on the newly discovered adipokines and EVs secreted by AT and highlight their actions on the liver under the context of obesity, nonalcoholic fatty liver diseases (NAFLD), and some other liver diseases. Clarifying the action of adipokines and adipose tissue-derived EVs on the liver would help to identify novel therapeutic targets or biomarkers for metabolic diseases.

AMPK stimulation inhibits YAP/TAZ signaling to ameliorate hepatic fibrosis

Hepatic fibrosis is driven by the activation of hepatic stellate cells (HSCs). The Hippo pathway and its effectors, YAP and TAZ, are key regulators of HSC activation and fibrosis. However, there is a lack of mechanistic understanding of YAP/TAZ regulation in HSCs. Here we show that AMPK activation leads to YAP/TAZ inhibition and HSC inactivation in vitro, while the expression of a kinase-inactive mutant reversed these effects compared to wild type AMPKɑ1. Notably, the depletion of LATS1/2, an upstream kinase of YAP/TAZ signaling, rescues YAP/TAZ activation, suggesting that AMPK may be mediating YAP/TAZ inhibition via LATS1/2. In the carbon tetrachloride mouse model of fibrosis, pharmacologic activation of AMPK in HSCs inhibits YAP/TAZ signaling and reduces fibrosis. The findings implicate AMPK as a critical regulator of YAP/TAZ signaling and HSC inactivation and highlight AMPK activation as a therapeutic target for the treatment of hepatic fibrosis.

Cellular stress in the pathogenesis of nonalcoholic steatohepatitis and liver fibrosis

The burden of chronic liver disease is rising substantially worldwide. Fibrosis, characterized by excessive deposition of extracellular matrix proteins, is the common pathway leading to cirrhosis, and limited treatment options are available. There is increasing evidence suggesting the role of cellular stress responses contributing to fibrogenesis. This Review provides an overview of studies that analyse the role of cellular stress in different cell types involved in fibrogenesis, including hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells and macrophages.

Maximakinin reduced intracellular Ca2+ level in vascular smooth muscle cells through AMPK/ERK1/2 signaling pathways

We detect the antihypertensive effects of maximakinin (MK) on renal hypertensive rats (RHRs) and further research the influence of MK on vascular smooth muscle cells (VSMCs) to explore its hypotensive mechanism. The effects of MK on arterial blood pressure were observed in RHRs. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assays were performed to detect the effect of MK on VSMC viability. Western blot and flow cytometry were used to investigate the influence of MK on intracellular Ca2+ levels and protein expression changes in VSMCs. In addition, specific protein inhibitors were applied to confirm the involvement of Ca2+-related signaling pathways induced by MK in VSMCs. MK showed a more significant antihypertensive effect than bradykinin in RHRs. MK significantly decreased intracellular Ca2+ concentrations. Furthermore, MK significantly induced the phosphorylation of signaling molecules, including extracellular signal-regulated kinase 1/2 (ERK1/2), P38, AMP-activated protein kinase (AMPK) and Akt in VSMCs. Moreover, only ERK1/2 inhibitor U0126 and AMPK inhibitor Compound C completely restored the decreased intracellular Ca2+ level induced by MK, and further research demonstrated that AMPK functioned upstream of ERK1/2 following exposure to MK. Finally, HOE-140, an inhibitor of the bradykinin B2 receptors (B2Rs), was applied to investigate the potential targets of MK in VSMCs. HOE-140 significantly blocked the AMPK/ERK1/2 pathway induced by MK, suggesting that the B2Rs might play an important role in MK-induced AMPK and ERK1/2 activation. MK significantly reduces blood pressure in RHRs. MK exerts its antihypertensive effect by activating the B2Rs and downstream AMPK/ERK1/2 pathways, leading to significantly reduced Ca2+ levels in VSMCs.

Investigation of Immunostimulatory Effects of Heat-Treated Lactiplantibacillus plantarum LM1004 and Its Underlying Molecular Mechanism

Postbiotics are defined as probiotics inactivated by heat, ultraviolet radiation, sonication, and other physical or chemical stresses. Postbiotics are more stable than probiotics, and these properties are advantageous for food additives and pharmacological agents. This study investigated the immunostimulatory effects of heat-treated Lactiplantibacillus plantarum LM1004 (HT-LM1004). Cellular fatty acid composition of L. plantarum LM1004 isolated form kimchi was analyzed by gas chromatography-mass spectrometry detection system. The nitric oxide (NO) content was estimated using Griess reagent. Immunostimulatory cytokines were evaluated using enzyme-linked immunosorbent assay. Relative protein expressions were evaluated by western blotting. Phagocytosis was measured using enzyme-labelled Escherichia coli particles. L. plantarum LM1004 showed 7 kinds of cellular fatty acids including palmitic acid (C16:0). The HT-LM1004 induced release of NO and upregulated the inducible NO synthase in RAW 264.7 macrophage cells. Tumor necrosis factor-α and interleukin-6 levels were also increased compared to control (non-treated macrophages). Furthermore, HT-LM1004 modulated mitogen-activated protein kinase (MAPK) subfamilies including p38 MAPK, extracellular signal-regulated kinase 1/2, and c-Jun N-terminal kinase. Therefore, these immunostimulatory effects were attributed to the production of transcriptional factors, such as nuclear factor kappa B (NF-κB) and the activator protein 1 family (AP-1). However, HT-LM1004 did not showed significant phagocytosis of RAW 264.7 macrophage cells. Overall, HT-LM1004 stimulated MAPK/AP-1 and NF-κB expression, resulting in the release of NO and cytokines. These results will contribute to the development of diverse types of food and pharmacological products for immunostimulatory agents with postbiotics.

Association between lower plasma adiponectin levels and higher liver stiffness in type 2 diabetic individuals with nonalcoholic fatty liver disease: an observational cross-sectional study

PURPOSE

Little is known about the association between plasma adiponectin levels and nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM). We examined whether there is an association between lower plasma adiponectin levels and the presence/severity of NAFLD in people with T2DM.

METHODS

We cross-sectionally recruited 79 men with non-insulin-treated T2DM and no known liver diseases, who had consecutively attended our diabetes outpatient service over a 6-month period and who underwent both ultrasonography and Fibroscan-measured liver stiffness (LSM). Nine single nucleotide polymorphisms (PNPLA3 rs738409 and other genetic variants) associated with NAFLD were investigated.

RESULTS

Among the 79 participants included (mean age 67 ± 10 years, BMI 27.7 ± 4 kg/m²), 28 did not have NAFLD, 32 had steatosis alone, and 19 had NAFLD with coexisting significant fibrosis (LSM ≥ 7.0 kPa by Fibroscan®). Compared to those without NAFLD, patients with hepatic steatosis alone and those with hepatic steatosis and coexisting significant fibrosis had lower high-molecular-weight adiponectin levels (5.5 [IQR 2.3-7.6] vs. 2.4 [1.8-3.7] vs. 1.6 [1.0-2.9] µg/mL; p < 0.001). After adjustment for age, body mass index, insulin resistance, and the PNPLA3 rs738409 variant, lower plasma adiponectin levels were found to be associated with increased odds of both steatosis alone (adjusted-odds ratio [OR] 2.44, 95% CI 1.04-5.56, p = 0.042) and NAFLD with coexisting significant fibrosis (adjusted-OR 3.84, 95% CI 1.23-10.0, p = 0.020). Similar findings were observed after adjustment for the other eight genotyped NAFLD-related polymorphisms.

CONCLUSION

Lower plasma adiponectin levels are closely associated with the presence and severity of NAFLD in men with T2DM, pointing to a role of adiponectin in NAFLD development and progression.

Therapeutic role of nitroglycerin against copper-nitrilotriacetate induced hepatic and renal damage

Earlier we have shown that exposure to copper-nitrilotriacetate (Cu-NTA) manifests toxicity by generating oxidative stress and potent induction of proliferative reaction in the liver and kidney. In the study, we look at the impact of nitroglycerin (GTN) administration on Cu-NTA-induced oxidative stress and hyperproliferative response in the liver and kidney. GTN administration intraperitoneally to male Wistar rats after Cu-NTA administration intraperitoneally caused substantial protection against Cu-NTA-induced tissue injury, oxidative stress and hyperproliferative response. Cu-NTA administration at a dose of 4.5 mg/kg body weight produces significant ( p < .001) elevation in biochemical parameters including aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN) and creatinine (CREA) with a concomitant increase in microsomal lipid peroxidation. Along with these alterations, we discovered a substantial increment in [3H]thymidine incorporation into hepatic and renal DNA synthesis ( p < .001). Cu-NTA-induced tissue damage and lipid peroxidation in hepatic and renal tissues were inhibited by GTN treatment in a dose-dependent manner ( p < .05–0.001). Furthermore, GTN can suppress the hyperproliferative response elicited by Cu-NTA by down-regulating the rate of [3H]thymidine incorporation into hepatic and renal DNA ( p < .01–0.001). Protective effect of GTN against Cu-NTA was also confirmed by histopathological changes in liver and kidney. This result suggests that GTN may serve as a scavenger for reactive oxygen species (ROS) and reduces toxic metabolites of Cu-NTA, thereby avoiding tissue injury and oxidative stress. Further, administration of NO inhibitor, NG-Nitroarginine methyl ester (L-NAME), exacerbated Cu-NTA induced oxidative tissue damage and cell proliferation. Overall, GTN reduces Cu-NTA-induced tissue damage, oxidative stress, and proliferative response in the rat liver and kidney, according to these findings. On the basis of the above results, present study suggests that GTN may be a potential therapeutic agent for restoration of oxidative damage and proliferation to liver and kidney.

Vanillic Acid and Non-Alcoholic Fatty Liver Disease: A Focus on AMPK in Adipose and Liver Tissues

Non-alcoholic fatty liver disease (NAFLD), a growing health issue around the world, is defined as the presence of steatosis in the liver without any other detectable byproducts such as alcohol consumption which includes a wide spectrum of pathologies, such as steatohepatitis, cirrhosis, and hepatocellular carcinoma. A growing body of evidence indicates that the reduction in the 5' adenosine monophosphate-activated protein kinase (AMPK) activity, which could be activated by the consumption of the drugs, hormones, cytokines, and dietary restriction, is related to some metabolic disorders such as obesity, diabetes, PCOS, and NAFLD. Vanillic acid (VA), as an anti-inflammatory, anti-oxidative, anti-angiogenic and anti-metastatic factor, has protective effects on the liver as in two animal models of liver damage. It reduces serum levels of transaminases, inflammatory cytokines, and the accumulation of collagen in the liver and prevents liver fibrosis. Besides, it decreases body and adipose tissue weight in a mice model of obesity and, similar to the liver tissue, diminishes adipogenesis through the activation of AMPK. It has been reported that VA can target almost all of the metabolic abnormalities of NAFLD, such as hepatic steatosis, inflammation, and hepatic injury, at least partially through the activation of AMPK. Therefore, in this review, we will discuss the possible and hypothetical roles of VA in NAFLD, with a special focus on AMPK.

The Power of Plasticity-Metabolic Regulation of Hepatic Stellate Cells

Hepatic stellate cells (HSCs) are resident non-parenchymal liver pericytes whose plasticity enables them to regulate a remarkable range of physiologic and pathologic responses. To support their functions in health and disease, HSCs engage pathways regulating carbohydrate, mitochondrial, lipid, and retinoid homeostasis. In chronic liver injury, HSCs drive hepatic fibrosis and are implicated in inflammation and cancer. To do so, the cells activate, or transdifferentiate, from a quiescent state into proliferative, motile myofibroblasts that secrete extracellular matrix, which demands rapid adaptation to meet a heightened energy need. Adaptations include reprogramming of central carbon metabolism, enhanced mitochondrial number and activity, endoplasmic reticulum stress, and liberation of free fatty acids through autophagy-dependent hydrolysis of retinyl esters that are stored in cytoplasmic droplets. As an archetype for pericytes in other tissues, recognition of the HSC's metabolic drivers and vulnerabilities offer the potential to target these pathways therapeutically to enhance parenchymal growth and modulate repair.

Hepatocyte-specific expression of human carboxylesterase 2 attenuates nonalcoholic steatohepatitis in mice

Human carboxylesterase 2 (CES2) has triacylglycerol hydrolase (TGH) activities and plays an important role in lipolysis. In this study, we aim to determine the role of human CES2 in the progression or reversal of steatohepatitis in diet-induced or genetically obese mice. High-fat/high-cholesterol/high-fructose (HFCF) diet-fed C57BL/6 mice or db/db mice were intravenously injected with an adeno-associated virus expressing human CES2 under the control of an albumin promoter. Human CES2 protected against HFCF diet-induced nonalcoholic fatty liver disease (NAFLD) in C57BL/6J mice and reversed steatohepatitis in db/db mice. Human CES2 also improved glucose tolerance and insulin sensitivity. Mechanistically, human CES2 reduced hepatic triglyceride (T) and free fatty acid (FFA) levels by inducing lipolysis and fatty acid oxidation and inhibiting lipogenesis via suppression of sterol regulatory element-binding protein 1. Furthermore, human CES2 overexpression improved mitochondrial respiration and glycolytic function, and inhibited gluconeogenesis, lipid peroxidation, apoptosis, and inflammation. Our data suggest that hepatocyte-specific expression of human CES2 prevents and reverses steatohepatitis. Targeting hepatic CES2 may be an attractive strategy for treatment of NAFLD.NEW & NOTEWORTHY Human CES2 attenuates high-fat/cholesterol/fructose diet-induced steatohepatitis and reverses steatohepatitis in db/db mice. Mechanistically, human CES2 induces lipolysis, fatty acid and glucose oxidation, and inhibits hepatic glucose production, inflammation, lipid oxidation, and apoptosis. Our data suggest that human CES2 may be targeted for treatment of non-alcoholic steatohepatitis (NASH).

Adiponectin Inhibits NLRP3 Inflammasome Activation in Nonalcoholic Steatohepatitis via AMPK-JNK/ErK1/2-NFκB/ROS Signaling Pathways

Adiponectin, an adipose-derived adipokine, possesses a hepatoprotective role in various liver disorders. It has been reported that hypoadiponectinemia can affect with the progression of non-alcoholic fatty liver diseases (NAFLD). Inflammasome activation has been recognized to play a major role during the progression of NAFLD. This research aimed to explore the effect of adiponectin on palmitate (PA)-mediated NLRP3 inflammasome activation and its potential molecular mechanisms. Male adiponectin-knockout (adiponectin-KO) mice and C57BL/6 (wild-type) mice were fed a high-fat-diet (HFD) for 12 weeks as an in vivo model of non-alcoholic steatohepatitis (NASH). Serum biochemical markers, liver histology and inflammasome-related gene and protein expression were determined. In addition, the hepatocytes isolated from wide type mice were exposed to PA in the absence or presence of adiponectin and/or AMPK inhibitor. The activation of NLRP3 inflammasome was assessed by mRNA and protein expression. Furthermore, ROS production and related signaling pathways were also evaluated. In the in vivo experiments, excessive hepatic steatosis with increased NLRP3 inflammasome and its complex expression were found in adiponectin-KO mice compared to wild-type mice. Moreover, the expression levels of NLRP3 inflammasome pathway molecules (NFκB and ROS) were upregulated, while the phosphorylation levels of AMPK, JNK, and Erk1/2 were downregulated in adiponectin-KO mice compared with wild-type mice. In the in vitro study, PA increased lipid droplet deposition, NF-kB signaling and ROS production. Additionally, PA significantly promoted NLRP3 inflammasome activation and complex gene and protein expression in hepatocytes. Adiponectin could abolish PA-mediated inflammasome activation and decrease ROS production, which was reversed by AMPK inhibitor (compound C). Furthermore, the results showed that the inhibitory effect of adiponectin on PA-mediated inflammasome activation was regulated by AMPK-JNK/ErK1/2-NFκB/ROS signaling pathway. Adiponectin inhibited PA-mediated NLRP3 inflammasome activation in hepatocytes. Adiponectin analogs or AMPK agonists could serve as a potential novel agent for preventing or delaying the progression of NASH and NAFLD.

Role of adipokines in systemic sclerosis pathogenesis

Systemic sclerosis (SSc) is a chronic autoimmune connective tissue disease with manifestations in multiple organs, including the skin, lung, heart, joints, gastrointestinal tract, kidney, and liver. Its pathophysiology is characterized by inflammation, fibrosis, and vascular damage, with an increased expression of numerous cytokines, chemokines, and growth factors. However, besides these growth factors and cytokines, another group of molecules may be involved in the pathogenesis of SSc: the adipokines. Adipokines are proteins with metabolic and cytokine-like properties, which were originally found to be expressed by adipose tissue. However, their expression is not limited to this tissue, and they can also be found in other organs. Therefore, this review will describe the current knowledge regarding adipokines in the context of SSc and try to elucidate their potential role in the pathogenesis of SSc.

From overnutrition to liver injury: AMP-activated protein kinase in nonalcoholic fatty liver diseases

Nonalcoholic fatty liver diseases (NAFLDs), especially nonalcoholic steatohepatitis (NASH), have become a major cause of liver transplant and liver-associated death. However, the pathogenesis of NASH is still unclear. Currently, there is no FDA-approved medication to treat this devastating disease. AMP-activated protein kinase (AMPK) senses energy status and regulates metabolic processes to maintain homeostasis. The activity of AMPK is regulated by the availability of nutrients, such as carbohydrates, lipids, and amino acids. AMPK activity is increased by nutrient deprivation and inhibited by overnutrition, inflammation, and hypersecretion of certain anabolic hormones, such as insulin, during obesity. The repression of hepatic AMPK activity permits the transition from simple steatosis to hepatocellular death; thus, activation might ameliorate multiple aspects of NASH. Here we review the pathogenesis of NAFLD and the impact of AMPK activity state on hepatic steatosis, inflammation, liver injury, and fibrosis during the transition of NAFL to NASH and liver failure.

The Absence of Adiponectin Alters Niacin's Effects on Adipose Tissue Inflammation in Mice

Obesity is an immunometabolic disease associated with chronic inflammation and the dysregulation of pro- and anti-inflammatory cytokines. One hallmark of obesity is reduced concentrations of the anti-inflammatory adipokine, adiponectin. Pharmacologic doses of niacin produce multiple metabolic benefits, including attenuating high-fat diet (HFD)-induced adipose tissue inflammation and increasing adiponectin concentrations. To determine if adiponectin mediates the anti-inflammatory effects of niacin, male C57BL/6J (WT) and adiponectin null (Adipoq^-/-) mice were maintained on a low-fat diet (LFD) or HFD for 6 weeks, before being administered either vehicle or niacin (360 mg/kg/day) for 5 weeks. HFD-fed mice had increased expression of genes associated with macrophage recruitment (Ccl2) and number (Cd68), and increased crown-like structure (CLS) number in adipose tissue. While niacin attenuated Ccl2 expression, there were no effects on Cd68 or CLS number. The absence of adiponectin did not hinder the ability of niacin to reduce Ccl2 expression. HFD feeding increased gene expression of inflammatory markers in the adipose tissue of WT and Adipoq^-/- mice. While niacin tended to decrease the expression of inflammatory markers in WT mice, niacin increased their expression in HFD-fed Adipoq^-/- mice. Therefore, our results indicate that the absence of adiponectin alters the effects of niacin on markers of adipose tissue inflammation in HFD-fed mice, suggesting that the effects of niacin on tissue cytokines may involve adiponectin.

Adipocytes protect fibroblasts from radiation-induced damage by adiponectin secretion

Prostate and colon cancers are among the most common cancers diagnosed annually, and both often require treatment with radiation therapy. Advancement in radiation delivery techniques has led to highly accurate targeting of tumor and sparing of normal tissue; however, in the pelvic region it is anatomically difficult to avoid off-target radiation exposure to other organs. Chronically the effects of normal urogenital tissue exposure can lead to urinary frequency, urinary incontinence, proctitis, and erectile dysfunction. Most of these symptoms are caused by radiation-induced fibrosis and reduce the quality of life for cancer survivors. We have observed in animal models that the severity of radiation-induced fibrosis in normal tissue correlates to damaged fat reservoirs in the pelvic region. We hypothesize that adipocytes may secrete a factor that prevents the induction of radiation-associated fibrosis in normal tissues. In these studies we show that the adipokine, adiponectin, is secreted by primary mouse adipocytes and protects fibroblasts from radiation-induced cell death, myofibroblast formation, and senescence. Further, we demonstrated that adiponectin does not protect colorectal or prostate cancer cells from radiation-induced death. Thus, we propose that adiponectin, or its downstream pathway, would provide a novel target for adjuvant therapy when treating pelvic cancers with radiation therapy.

Evaluation of Changes in the Expression Profile of mRNA and Proteinencoding Adiponectin in Ishikawa Cell Line under the Influence of Cisplatin - Preliminary Report

Background

A reduced concentration of adiponectin is considered as an independent factor of the risk of inducing endometrial cancer. Cisplatin is a drug used in the therapy of this type of neoplasm. However, knowledge of the effects of cisplatin on the adiponectin level is still limited.

Objective

The purpose of this study was to assess the impact of cisplatin depending on the concentration and time of exposition of the cells to the drug on the adiponectin level in the endometrial cancer cell line.

Methods

Cells of endometrial cancer cell line Ishikawa were exposed for 12,24 and 48 hour periods to cisplatin with the following concentrations: 2.5µM, 5µM, 10µM. The changes in the expression profile of adiponectin were compared to the RtqPCR reaction and ELISA test. The STATISTICA 13.0 PL program was used for statistical analysis (p<0.05).

Results

In the culture without the drug, the concentration of adiponectin was statistically lower than in the cell culture incubated with the drug. Changes on the mRNA level seem to be more specific than on the protein level, although in both cases, the same trend in the expression changes was noted.

Discussion

The longer the time of exposition of the cells to the drug, the expression of mRNA, and the adiponectin protein increased. Changes in the expression profile were characterized statistically (p<0.05).

Conclusion

Cisplatin, in a noticeable way, changes the expression profile of adiponectin. Molecular analysis indicated that in the case of endometrial cancer therapy should be implemented with a concentration of no less than 5 µM.

Palmitic acid stimulates NLRP3 inflammasome activation through TLR4-NF-κB signal pathway in hepatic stellate cells

Background

The NLRP3 inflammasome activation plays an important role in the development of NASH and fibrogenesis. However, the mechanisms involved in NLRP3 activation in hepatic stellate cells (HSCs) have been unclear. The aim of this study was to investigate the mechanism of NLRP3 activation in HSCs and the role of NLPR3 inflammasome activation in HSCs on the development of nonalcoholic steatohepatitis (NASH) to fibrosis.

Methods

Primary HSCs isolated from SD rats were incubated with palmitic acid and/or LPS, respectively. For in vivo animal experiment, 4-week-old SD rats were fed with high fat diet (HF-diet) for 12 weeks, SD rats were sacrificed at 0, 4, 8 and 12 w. In another group of animal experiment, 4-week-old SD rats were fed with HF-diet and a NLRP3 inhibitor (intraperitoneal injection of NLRP3 inhibitor glybenclamide 5 mg/kg, injected every 3 days) for 12 weeks. Liver tissue and serum were harvested. RT-PCR, WB, ELISA, immunofluorescence and immunohistochemistry were performed to assess the NLRP3 inflammasome activation and signal molecules.

Results

Palmitic acid stimulated NLPR3 inflammasome activation and fibrotic phenotype change in primary HSCs, LPS sensitizes the response of HSCs to palmitic acid. TLR4-NF-κB signal pathway was involved in NLRP3 inflammasome activation in palmitic acid-exposed HSCs and HF diet-induced NASH. It is evident that administration of NLRP3 inhibitor reduced the development of NASH to liver fibrosis in the NASH rat model.

Conclusions

Palmitic acid stimulates NLRP3 inflammasome activation through the TLR4-NF-κB signal pathway in HSCs. NLRP3 inflammasome activation in HSCs exacerbates the development of NASH to liver fibrosis.

Antiliver Fibrosis Screening of Active Ingredients from Apium graveolens L. Seeds via GC-TOF-MS and UHPLC-MS/MS

Although several studies have been performed on Apium graveolens L.(celery) seeds, their antiliver fibrosis effects remain to be unexplored. Firstly, we detected the effects of celery seeds extracted with different concentrations of aqueous ethanol on the proliferation of HSC-LX2 cells. Then, we detected the effects of fractions of the optimal effect extract on the proliferation and apoptosis of HSC-LX2 cells. Finally, the compounds of petroleum ether (PP), ethyl acetate (PE), n-butyl alcohol (PB), and water fractions (PW) of the optimal effect extract were determined by GC-TOF-MS and UHPLC-MS/MS, to confirm the potentially antifibrotic compounds combined with pharmacodynamic experiment of monomer compounds in vitro. The results revealed that 60% ethanol extract of celery seeds (60-extract) exhibited remarkable inhibition effect on the proliferation of HSC-LX2 cells compared with 95% ethanol and aqueous extract. Besides, it validated that the inhibition rates of PP, PE, PB, and PW on the proliferation of HSC-LX2 cells were 75.14%, 73.52%, 54.09%, and 43.36%, and their percentage of apoptotic cells were 37.5%, 4.3%, 0.7%, and 0.1% at high doses, respectively. Additionally, it was manifested that apigenin, aesculetin, and butylphthalide have major contribution to the overall compounds of celery seeds, and the inhibition effects on the cell proliferation clearly elevated with increase in their contents. In essence, apigenin, aesculetin, and butylphthalide may hopefully become the natural products of antiliver fibrosis, which laid a foundation for the subsequent development of celery seeds as antiliver fibrosis drugs.

Clinical associations of serum leptin and leptin/adiponectin ratio in systemic sclerosis

INTRODUCTION

Leptin and adiponectin have recently received the attention of researchers as attractive biomarkers in systemic sclerosis (SSc) because of their role in the inflammatory process, vascular function and fibrosis. We hypothesized that leptin and adiponectin may be associated with disease activity and severity in patients with SSc.

AIM

To compare serum leptin, adiponectin and leptin/adiponectin levels in patients with SSc and healthy controls and to evaluate their possible relationship with frequently used laboratory markers and clinical findings.

MATERIAL AND METHODS

The study included 48 Caucasian female patients with SSc and 38 healthy controls. Serum concentrations of leptin and adiponectin were measured in patients and controls using commercially available ELISA Kits (Quantikine ELISA Kit R&D Systems, Minneapolis, MN, USA). The results were assessed by the Mann-Whitney U-test and Spearman's correlation test.

RESULTS

Leptin and adiponectin levels correlated with body mas index in SSc patients (r = 0.495, p = 0.000398 and r = -0.306; p = 0.0342) in contrast to healthy controls (p = 0.070 and p = 0.256, respectively), and, in SSc patients only, a strong negative correlation was observed between leptin and adiponectin serum levels (r = -0.314; p = 0.0312). Diffuse form of the disease (dcSSc) was associated with significantly lower serum adiponectin levels (8638.62 ±10382.62). Active disease was associated with significantly lower leptin concentration (13700.49 ±18293.32) and there was a significant negative correlation between leptin serum level and activity index score (r = -0.342; p = 0.0185).

CONCLUSIONS

The results of our study indicate that leptin levels might correlate with disease activity and subtype in SSc patients.

Salvianolic acid B protects against ANIT-induced cholestatic liver injury through regulating bile acid transporters and enzymes, and NF-κB/IκB and MAPK pathways

The purpose of this study was to investigate the pharmacological effects of salvianolic acid B (SA-B) on α-naphthylisothiocyanate (ANIT)-induced cholestatic liver injury with the focus on bile acid homeostasis and anti-inflammatory pathways. Rats were randomly assigned into four groups. The control group was given normal saline (i.p.) for 7 consecutive days and on the 5th day was given the vehicle (i.g.). Model group was treated with normal saline (i.p.) for 7 days and administrated with ANIT (75 mg/kg, i.g.) on the 5th day. The SA-B groups were treated with SA-B (15 mg/kg and 30 mg/kg, i.p.) for 7 consecutive days as well as ANIT (75 mg/kg, i.g.) on the 5th day. We found that the serum levels of ALT, γ-GT, TBA, and other liver function indexes were found to be lower in the SA-B treatment groups than in the model group. SA-B also upregulated the transporters and enzymes involved in bile acid homeostasis such as Bsep, Oatp2, and Cyp3a2 in rats and BSEP, CYP3A4, and OATP2 in human cell lines. Moreover, SA-B suppressed NF-κB translocation into the nucleus, inhibited phosphorylation of p38 and JNK, and inhibited inflammation markers including IL-1β, IL-6, TGF-β, TNF-α, and COX-2 to extenuate cholestatic liver injury both in vivo and vitro. Taken together, our findings suggest that anti-cholestatic effects of SA-B may be associated with its ability to regulate NF-κB/IκB and MAPK inflammatory signaling pathways to inhibit inflammation and regulate transporters and enzymes to maintain bile acid homeostasis.

Adipokine expression in systemic sclerosis lung and gastrointestinal organ involvement

OBJECTIVES

The immunomodulatory properties of adipokines have previously been reported in autoimmune disorders. Less is known about the role of adipokines in systemic sclerosis (SSc). Lung and gastrointestinal tract are frequently involved in SSc; therefore, these organs were analyzed for adipokine expression as well as pulmonary samples of patients suffering from idiopathic pulmonary fibrosis (IPF) as comparison.

METHODS

Gastric samples (antrum, corpus) of SSc were analyzed immunohistochemically for adiponectin, resistin and visfatin compared with non-SSc related gastritis. Inflammatory cells were quantified in gastric samples and correlated with adipokine expression. Lung samples of SSc, IPF and healthy controls were also analyzed. Protein levels of lung tissue lysates and bronchoalveolar lavages (BAL) in minor fibrotic stages were measured by ELISA.

RESULTS

Lung sections of donor parenchyma showed significantly stronger adiponectin signals as IPF and SSc (donor vs. IPF: p < 0.0001). In SSc and IPF, resistin and visfatin were increased within immune cell infiltrates, but overall no difference in expression for resistin or visfatin compared to controls was observed. In BAL and lung protein lysates of early stages of fibrosis, adiponectin and visfatin were not reduced in IPF and SSc compared to controls. In gastric samples collected by standard endoscopic gastric biopsy, adiponectin was also significantly reduced in SSc- compared to non-SSc gastritis (p = 0.049) while resistin and visfatin were comparable although deeper fibrotic layers were not included in the respective samples. Adiponectin-positive tissues showed higher amounts of CD4⁺ but not CD8⁺ T cells. Controls showed no correlation between CD4⁺ T cells and resistin, whereas SSc showed significantly more CD4⁺ T cells in resistin-negative tissues.

CONCLUSION

Adipokines are expressed in gastric and lung samples of patients with SSc and in lung samples affected by IPF. Prominently, adiponectin levels were reduced in fibrotic SSc gastritic tissue as well as in IPF and SSc lung tissue. Consequently, adiponectin expression seems to be associated with fibrotic progression in the context of SSc and IPF.

AdipoRs- a potential therapeutic target for fibrotic disorders

Introduction: Fibrotic disorders are a leading cause of morbidity and mortality; hence effective treatments are still vigorously sought. AdipoRs (AdipoR1 and Adipo2) are responsible for the antifibrotic effects of adiponectin (APN). APN exerts antifibrotic effects by binding to its receptors. APN concentration and AdipoR expression are closely associated with fibrotic disorders. Decreased AdipoR expression may reduce APN-AdipoR signaling, while the upregulation of AdipoR expression may restore the anti-fibrotic effects of APN. Loss of APN signaling exacerbates fibrosis in vivo and in vitro. Areas covered: We assess the relationship between APN and fibrotic disorders, the structure of receptors for APN and the pathways accounting for APN or its analogs blocking fibrotic disorders. This article also discusses designed APN products and their therapeutic prospects for fibrotic disorders. Expert opinion: AdipoRs have a critical role in blocking fibrosis. The development of small-molecule agonists toward this target represents a valid drug development pathway.

Antifibrotics in liver disease: are we getting closer to clinical use?

The process of wound healing in response to chronic liver injury leads to the development of liver fibrosis. Regardless of etiology, the profound impact of the degree of liver fibrosis on the prognosis of chronic liver diseases has been well demonstrated. While disease-specific therapy, such as treatments for viral hepatitis, has been shown to reverse liver fibrosis and cirrhosis in both clinical trials and real-life practice, subsets of patients do not demonstrate fibrosis regression. Moreover, where disease-specific therapies are not available, the need for antifibrotics exists. Increased understanding into the pathogenesis of liver fibrosis sets the stage to focus on antifibrotic therapies attempting to: (1) Minimize liver injury and inflammation; (2) Inhibit liver fibrogenesis by enhancing or inhibiting target receptor-ligand interactions or intracellular signaling pathways; and (3) Promote fibrosis resolution. While no antifibrotic therapies are currently available, a number are now being evaluated in clinical trials, and their use is becoming closer to reality for select subsets of patients.

Adiponectin Signaling Pathways in Liver Diseases

In the liver, adiponectin regulates both glucose and lipid metabolism and exerts an insulin-sensitizing effect. The binding of adiponectin with its specific receptors induces the activation of a proper signaling cascade that becomes altered in liver pathologies. This review describes the different signaling pathways in healthy and diseased hepatocytes, also highlighting the beneficial role of adiponectin in autophagy activation and hepatic regeneration.

Adiponectin levels and insulin resistance among patients with chronic hepatitis C

Chronic hepatitis C virus (HCV) infection is associated with insulin resistance (IR), rapid disease progression, and decreased virological response to antiviral treatment. In addition, obesity is a risk factor for chronic hepatitis C evolution and is associated with IR. As adiponectin is an adipokine that is associated with obesity and IR, this study aimed to investigate serum levels of adiponectin among patients with HCV infection and IR. Thirty-three patients with untreated HCV infection underwent testing of serum adiponectin levels (capture ELISA) and were compared to 30 healthy subjects with similar body mass indexes (BMI). Data were also obtained for several homeostatic model assessment (HOMA) indexes: HOMA-IR, HOMA-β, and HOMA-adiponectin. Patients with HCV infection had higher adiponectin levels, which predominantly were observed among women. Hyperadiponectinemia was not associated with high BMI. Patients with HCV infection had higher HOMA-IR and HOMA-β values, although no difference was observed for HOMA-adiponectin. Patients with HCV infection and overweight/obese status had higher HOMA-IR values, although no association was observed for adiponectin levels. Hyperadiponectinemia and IR were not influenced by HCV load or liver fibrosis. The predictors of IR were BMI, glycemia, and serum levels of insulin and non-high-density lipoprotein cholesterol, but not adiponectin levels. Thus, patients with chronic hepatitis C have significant metabolic alterations (hyperadiponectinemia and high HOMA-IR values) that are independent of HCV viremia and liver fibrosis. Among these patients, HOMA-IR but not HOMA-adiponectin was appropriate for diagnosing IR.

Globular Adiponectin Limits Microglia Pro-Inflammatory Phenotype through an AdipoR1/NF-κB Signaling Pathway

We recently reported that increased levels of Adiponectin (ApN) in the brain led to microglia phenotype and activation state regulation, thus reducing both global brain inflammation and depressive-like behaviors in mice. Apart from this, little is known on ApN molecular effects on microglia, although these cells are crucial in both physiological and pathological processes. Here we fill this gap by studying the effects and targets of ApN toward neuroinflammation. Our findings suggest that ApN deficiency in mice leads to a higher sensitivity of mice to neuroinflammation that is due to enhanced microglia responsiveness to a pro-inflammatory challenge. Moreover, we show that globular ApN (gApN) exerts direct in vivo anti-inflammatory actions on microglia by reducing IL-1β, IL-6, and TNFα synthesis. In vitro, gApN anti-inflammatory properties are confirmed in brain-sorted microglia, primary cultured and microglia cell line (BV2), but are not observed on astrocytes. Our results also show that gApN blocks LPS-induced nitrosative and oxidative stress in microglia. Finally, we demonstrate for the first time that these anti-inflammatory and anti-oxidant actions of gApN on microglia are mediated through an AdipoR1/NF-κB signaling pathway.

Hepatic stellate cells as key target in liver fibrosis

Progressive liver fibrosis, induced by chronic viral and metabolic disorders, leads to more than one million deaths annually via development of cirrhosis, although no antifibrotic therapy has been approved to date. Transdifferentiation (or "activation") of hepatic stellate cells is the major cellular source of matrix protein-secreting myofibroblasts, the major driver of liver fibrogenesis. Paracrine signals from injured epithelial cells, fibrotic tissue microenvironment, immune and systemic metabolic dysregulation, enteric dysbiosis, and hepatitis viral products can directly or indirectly induce stellate cell activation. Dysregulated intracellular signaling, epigenetic changes, and cellular stress response represent candidate targets to deactivate stellate cells by inducing reversion to inactivated state, cellular senescence, apoptosis, and/or clearance by immune cells. Cell type- and target-specific pharmacological intervention to therapeutically induce the deactivation will enable more effective and less toxic precision antifibrotic therapies.

AMPK: a novel target for treating hepatic fibrosis

Fibrosis is a common process of excessive extracellular matrix (ECM) accumulation following inflammatory injury. Fibrosis is involved in the pathogenesis of almost all liver diseases for which there is no effective treatment. 5'-AMP-activated protein kinase (AMPK) is a cellular energy sensor that can ameliorate the process of hepatic fibrogenesis. Given the existing evidence, we first introduce the basic background of AMPK and hepatic fibrosis and the actions of AMPK in hepatic fibrosis. Second, we discuss the three phases of hepatic fibrosis and potential drugs that target AMPK. Third, we analyze possible anti-fibrosis mechanisms and other benefits of AMPK on the liver. Finally, we summarize and briefly explain the current objections to targeting AMPK. This review may aid clinical and basic research on AMPK, which may be a novel drug candidate for hepatic fibrosis.

Lack of adiponectin and adiponectin receptor 1 contributes to benign prostatic hyperplasia

PURPOSE

The incidence of benign prostatic hyperplasia increases among obese individuals, but few studies have fully explained the underlying mechanisms. Adiponectin has drawn much attention in recent years due to its protective role in obesity-related diseases. Here we aimed to investigate the possible molecular mechanisms and clinical significance of adiponectin in relation to benign prostatic hyperplasia.

METHODS

We analyzed data from 98 Chinese men, including 48 BPH cases and 50 controls in a case-control study. Then, we utilized a tissue microarray analysis to examine expression of AdipoR1 and p-p90RSK in normal and hyperplastic prostate tissues. These studies were followed by various in vitro approaches to examine the anti-proliferation effect and signaling pathways of adiponectin involved in benign prostatic hyperplasia.

RESULTS

Lower serum adiponectin levels were independently associated with larger prostate volume and an increased risk of benign prostatic hyperplasia. Benign prostatic hyperplasia tissues had a decreased expression of AdipoR1 and increased expression of p-p90RSK compared with normal prostate tissues. in vitro, adiponectin inhibited the proliferation of prostatic epithelial and stromal cells and arrested cells in the G₀/G₁ phase by decreasing phosphorylation of the MEK-ERK-p90RSK axis.

CONCLUSIONS

Our results suggest a possible negative regulatory mechanism in which adiponectin signaling antagonizes ERK-mediated cell proliferation, and a deficiency in adiponectin could facilitate the proliferation of prostate cells and consequently contribute to benign prostatic hyperplasia.

Adipokines in Liver Cirrhosis

Liver fibrosis can progress to cirrhosis, which is considered a serious disease. The Child-Pugh score and the model of end-stage liver disease score have been established to assess residual liver function in patients with liver cirrhosis. The development of portal hypertension contributes to ascites, variceal bleeding and further complications in these patients. A transjugular intrahepatic portosystemic shunt (TIPS) is used to lower portal pressure, which represents a major improvement in the treatment of patients. Adipokines are proteins released from adipose tissue and modulate hepatic fibrogenesis. These proteins affect various biological processes that are involved in liver function, including angiogenesis, vasodilation, inflammation and deposition of extracellular matrix proteins. The best studied adipokines are adiponectin and leptin. Adiponectin protects against hepatic inflammation and fibrogenesis, and leptin functions as a profibrogenic factor. These and other adipokines are supposed to modulate disease severity in patients with liver cirrhosis. Consequently, circulating levels of these proteins have been analyzed to identify associations with parameters of hepatic function, portal hypertension and its associated complications in patients with liver cirrhosis. This review article briefly addresses the role of adipokines in hepatitis and liver fibrosis. Here, studies having analyzed these proteins in systemic blood in cirrhotic patients are listed to identify adipokines that are comparably changed in the different cohorts of patients with liver cirrhosis. Some studies measured these proteins in systemic, hepatic and portal vein blood or after TIPS to specify the tissues contributing to circulating levels of these proteins and the effect of portal hypertension, respectively.

Adiponectin deficiency contributes to the development and progression of benign prostatic hyperplasia in obesity

The incidence of benign prostatic hyperplasia (BPH) is increasing among obese individuals, but few studies have fully explained the underlying mechanisms. We aimed to elucidate the relationship between obesity and BPH. Herein, we show that in prostatic epithelial and stromal cells, adiponectin exerts multifunctional effects including anti-proliferation, blocking of G1/S-phase progression and the promotion of apoptosis via inhibiting the MEK-ERK-p90RSK axis. Furthermore, we found that a high-fat diet (HFD) led to adiponectin deficiency and microscopic BPH in a mouse model of obesity. And an adiponectin supplement protected the obese mice from microscopic BPH. The present study provides evidence that adiponectin is a protective regulator in the development and progression of BPH and that adiponectin deficiency causally links BPH with obesity.

Adiponectin regulates aquaglyceroporin expression in hepatic stellate cells altering their functional state

BACKGROUND AND AIM

Obesity is a major risk factor for liver fibrosis and tightly associated with low levels of adiponectin. Adiponectin has antifibrogenic activity protecting from liver fibrosis, which is mainly driven by activated hepatic stellate cells (HSC). Aquaporins are transmembrane proteins that allow the movement of water and, in case of aquaglyceroporins (AQPs), of glycerol that is needed in quiescent HSC for lipogenesis. Expression of various AQPs in liver is altered by obesity; however, the mechanisms through which obesity influences HSCs activation and AQPs expression remain unclear. This study aimed to identify obesity-associated factors that are related to HSC AQPs expression activation and lipid storage.

METHODS

Correlations between serum adipokine levels and hepatic AQPs gene expression were analyzed from a cohort of obese patients. AQP and fibrotic gene expression was determined in a HSC line (LX2) and in a hepatocyte cell line (HepG2) after stimulation with adiponectin using quantitative real-time polymerase chain reaction.

RESULTS

We found that serum adiponectin significantly correlated with liver AQP3, AQP7, AQP9 gene expressions. In vitro, adiponectin induced upregulation of AQP3 gene and AQP3 protein expression in human HSCs, but not in hepatocytes, while AQP7, AQP9 remained undetectable. Accordingly, HSC stimulated with adiponectin increased glycerol uptake, lipogenic gene expression, and lipid storage while downregulating activation/fibrosis markers.

CONCLUSIONS

These findings demonstrate that adiponectin is a potent inhibitor of HSC activation and induces AQPs expression. Thus, low serum levels of adiponectin could be a mechanism how obesity affects the functional state of HSC, thereby contributing to obesity-associated liver fibrosis.

Metabolic Adaptation in Obesity and Type II Diabetes: Myokines, Adipokines and Hepatokines

Obesity and type II diabetes are characterized by insulin resistance in peripheral tissues. A high caloric intake combined with a sedentary lifestyle is the leading cause of these conditions. Whole-body insulin resistance and its improvement are the result of the combined actions of each insulin-sensitive organ. Among the fundamental molecular mechanisms by which each organ is able to communicate and engage in cross-talk are cytokines or peptides which stem from secretory organs. Recently, it was reported that several cytokines or peptides are secreted from muscle (myokines), adipose tissue (adipokines) and liver (hepatokines) in response to certain nutrition and/or physical activity conditions. Cytokines exert autocrine, paracrine or endocrine effects for the maintenance of energy homeostasis. The present review is focused on the relationship and cross-talk amongst muscle, adipose tissue and the liver as secretory organs in metabolic diseases.

Serum adipokines levels in patients with systemic sclerosis: A meta-analysis

BACKGROUND

Systemic sclerosis is an chronic inflammatory autoimmune diseases. Adipokine has been reported to play an important role in modulating immune responses. Recent studies suggest that adipokine also plays some roles in the pathogenesis of systemic sclerosis (SSc). However, published data regarding the relationship between plasma/serum adipokine levels and SSc are contradictory. The aim of this study was at performing a meta-analysis to derive a more accurate estimation and further investigate the association of plasma/serum leptin and adiponectin levels with SSc patients.

METHODS

PubMed, and Web of Science databases (up to Feb 20, 2016) were used to obtain all relative published literatures. The study quality was assessed by the Newcastle-Ottawa scale. Pooled standard mean difference (SMD) with 95% confidence interval (CI) was calculated by random-effect model analysis.

RESULTS

A total of fourteen studies were finally included in this meta-analysis. Among them, six of which were studied for the serum adiponectin levels in SSc patients, six of which were studied for the serum leptin levels in SSc patients, and two of them were studied both for serum adiponectin levels and serum leptin levels in SSc patients. The meta-analysis results showed that the serum adiponectin levels in SSc patients were significantly lower than that in normal controls (SMD = -0.608 ng/ml, 95% CI = -1.029 to -0.186, p = 0.005). However, there were no significant differences in serum leptin levels between SSc patients and healthy controls (SMD = -0.990 ng/ml, 95% CI = -2.340 to 0.359, p = 0.150). The subgroup analysis showed that Asia SSc patients with age less than 50 years old had lower plasma/serum adiponectin levels when compared with controls.

CONCLUSION

The serum adiponectin levels, but not serum leptin levels, in SSc patients were significantly lower than that in normal controls.

Melatonin enhances mitophagy and mitochondrial biogenesis in rats with carbon tetrachloride-induced liver fibrosis

Liver fibrosis leads to liver cirrhosis and failure, and no effective treatment is currently available. Growing evidence supports a link between mitochondrial dysfunction and liver fibrogenesis and mitochondrial quality control-based therapy has emerged as a new therapeutic target. We investigated the protective mechanisms of melatonin against mitochondrial dysfunction-involved liver fibrosis, focusing on mitophagy and mitochondrial biogenesis. Rats were treated with carbon tetrachloride (CCl4) dissolved in olive oil (0.5 mL/kg, twice a week, i.p.) for 8 wk. Melatonin was administered orally at 2.5, 5, and 10 mg/kg once a day. Chronic CCl4 exposure induced collagen deposition, hepatocellular damage, and oxidative stress, and melatonin attenuated these increases. Increases in mRNA and protein expression levels of transforming growth factor β1 and α-smooth muscle actin in response to CCl4 were attenuated by melatonin. Melatonin attenuated hallmarks of mitochondrial dysfunction, such as mitochondrial swelling and glutamate dehydrogenase release. Chronic CCl4 exposure impaired mitophagy and mitochondrial biogenesis, and melatonin attenuated this impairment, as indicated by increases in mitochondrial DNA and in protein levels of PTEN-induced putative kinase 1 (PINK1); Parkin; peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α); nuclear respiratory factor 1 (NRF1); and transcription factor A, mitochondrial (TFAM). CCl4-mediated decreases in mitochondrial fission- and fusion-related proteins, such as dynamin-related protein 1 (DRP1) and mitofusin 2, were also attenuated by melatonin. Moreover, melatonin induced AMP-activated protein kinase (AMPK) phosphorylation. These results suggest that melatonin protects against liver fibrosis via upregulation of mitophagy and mitochondrial biogenesis, and may be useful as an anti-fibrotic treatment.

A Combination of Leucine, Metformin, and Sildenafil Treats Nonalcoholic Fatty Liver Disease and Steatohepatitis in Mice

Sirt1, AMPK, and eNOS modulate hepatic energy metabolism and inflammation and are key players in the development of NASH. L-leucine, an allosteric Sirt1 activator, synergizes with low doses of metformin or sildenafil on the AMPK-eNOS-Sirt1 pathway to reverse mild NAFLD in preclinical mouse models. Here we tested a possible multicomponent synergy to yield greater therapeutic efficacy in NAFLD/NASH. Liver cells and macrophages or an atherogenic diet induced NASH mouse model was treated with two-way and three-way combinations. The three-way combination Sild-Met-Leu increased hepatic fatty acid oxidation and reduced lipogenic gene expression and inflammatory marker in vitro. In mice, Sild-Met-Leu reduced the diet induced increases of ALT, TGFβ, PAI-1, IL1β, and TNFα, hepatic collagen expression, and nearly completely reversed hepatocyte ballooning and triglyceride accumulation, while all two-way combinations had only modest effects. Therefore, these data provide preclinical evidence for therapeutic efficacy of Sild-Met-Leu in the treatment of NAFLD and NASH.