Low serum adiponectin levels are predictive of advanced hepatic fibrosis in patients with NAFLD

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.

Exerkines and cardiometabolic benefits of exercise: from bench to clinic

Regular exercise has both immediate and long-lasting benefits on cardiometabolic health, and has been recommended as a cornerstone of treatment in the management of diabetes and cardiovascular conditions. Exerkines, which are defined as humoral factors responsive to acute or chronic exercise, have emerged as important players conferring some of the multiple cardiometabolic benefits of exercise. Over the past decades, hundreds of exerkines released from skeletal muscle, heart, liver, adipose tissue, brain, and gut have been identified, and several exerkines (such as FGF21, IL-6, and adiponectin) have been exploited therapeutically as exercise mimetics for the treatment of various metabolic and cardiovascular diseases. Recent advances in metagenomics have led to the identification of gut microbiota, a so-called "hidden" metabolic organ, as an additional class of exerkines determining the efficacy of exercise in diabetes prevention, cardiac protection, and exercise performance. Furthermore, multiomics-based studies have shown the feasibility of using baseline exerkine signatures to predict individual responses to exercise with respect to metabolic and cardiorespiratory health. This review aims to explore the molecular pathways whereby exerkine networks mediate the cardiometabolic adaptations to exercise by fine-tuning inter-organ crosstalk, and discuss the roadmaps for translating exerkine-based discovery into the therapeutic application and personalized medicine in the management of the cardiometabolic disease.

Expression and Function of BMP and Activin Membrane-Bound Inhibitor (BAMBI) in Chronic Liver Diseases and Hepatocellular Carcinoma

BAMBI (bone morphogenetic protein and activin membrane-bound inhibitor) is a transmembrane pseudoreceptor structurally related to transforming growth factor (TGF)-β type 1 receptors (TGF-β1Rs). BAMBI lacks a kinase domain and functions as a TGF-β1R antagonist. Essential processes such as cell differentiation and proliferation are regulated by TGF-β1R signaling. TGF-β is the best-studied ligand of TGF-βRs and has an eminent role in inflammation and fibrogenesis. Liver fibrosis is the end stage of almost all chronic liver diseases, such as non-alcoholic fatty liver disease, and at the moment, there is no effective anti-fibrotic therapy available. Hepatic BAMBI is downregulated in rodent models of liver injury and in the fibrotic liver of patients, suggesting that low BAMBI has a role in liver fibrosis. Experimental evidence convincingly demonstrated that BAMBI overexpression is able to protect against liver fibrosis. Chronic liver diseases have a high risk of hepatocellular carcinoma (HCC), and BAMBI was shown to exert tumor-promoting as well as tumor-protective functions. This review article aims to summarize relevant studies on hepatic BAMBI expression and its role in chronic liver diseases and HCC.

An adipocentric perspective on the development and progression of non-alcoholic fatty liver disease

Alongside the liver, white adipose tissue (WAT) is critical in regulating systemic energy homeostasis. Although each organ has its specialised functions, they must work coordinately to regulate whole-body metabolism. Adipose tissues and the liver are relatively resilient and can adapt to an energy surplus by facilitating triglyceride (TG) storage up to a certain threshold level without significant metabolic disturbances. However, lipid storage in WAT beyond a "personalised" adiposity threshold becomes dysfunctional, leading to metabolic inflexibility, progressive inflammation, and aberrant adipokine secretion. Moreover, the failure of adipose tissue to store and mobilise lipids results in systemic knock-on lipid overload, particularly in the liver. Factors contributing to hepatic lipid overload include lipids released from WAT, dietary fat intake, and enhanced de novo lipogenesis. In contrast, extrahepatic mechanisms counteracting toxic hepatic lipid overload entail coordinated compensation through oxidation of surplus fatty acids in brown adipose tissue and storage of fatty acids as TGs in WAT. Failure of these integrated homeostatic mechanisms leads to quantitative increases and qualitative alterations to the lipidome of the liver. Initially, hepatocytes preferentially accumulate TG species leading to a relatively "benign" non-alcoholic fatty liver. However, with time, inflammatory responses ensue, progressing into more severe conditions such as non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma, in some individuals (often without an early prognostic clue). Herein, we highlight the pathogenic importance of obesity-induced "adipose tissue failure", resulting in decreased adipose tissue functionality (i.e. fat storage capacity and metabolic flexibility), in the development and progression of NAFL/NASH.

Interplay between metabolic dysfunction-associated fatty liver disease and chronic kidney disease: Epidemiology, pathophysiologic mechanisms, and treatment considerations

The recently proposed nomenclature change from non-alcoholic fatty liver disease to metabolic dysfunction-associated fatty liver disease (MAFLD) has resulted in the reappraisal of epidemiological trends and associations with other chronic diseases. In this context, MAFLD appears to be tightly linked to incident chronic kidney disease (CKD). This association may be attributed to multiple shared risk factors including type 2 diabetes mellitus, arterial hypertension, obesity, dyslipidemia, and insulin resistance. Moreover, similarities in their molecular pathophysiologic mechanisms can be detected, since inflammation, oxidative stress, fibrosis, and gut dysbiosis are highly prevalent in these pathologic states. At the same time, lines of evidence suggest a genetic predisposition to MAFLD due to gene polymorphisms, such as the PNPLA3 rs738409 G allele polymorphism, which may also propagate renal dysfunction. Concerning their management, available treatment considerations for obesity (bariatric surgery) and novel antidiabetic agents (glucagon-like peptide 1 receptor agonists, sodium-glucose co-transporter 2 inhibitors) appear beneficial in preclinical and clinical studies of MAFLD and CKD modeling. Moreover, alternative approaches such as melatonin supplementation, farnesoid X receptor agonists, and gut microbiota modulation may represent attractive options in the future. With a look to the future, additional adequately sized studies are required, focusing on preventing renal complications in patients with MAFLD and the appropriate management of individuals with concomitant MAFLD and CKD.

Non-alcoholic fatty liver disease and type 2 diabetes - An Update

The global prevalence of non‐alcoholic fatty liver disease (NAFLD) is rising, along with the epidemic of diabesity. NAFLD is present in >70% of individuals with type 2 diabetes. Although the mutually detrimental relationship between NAFLD and type 2 diabetes has been well established, a multitude of recent studies have further shown that type 2 diabetes is closely linked to the development of cirrhosis, hepatocellular carcinoma, liver‐related morbidity and mortality. In contrast, NAFLD also negatively impacts type 2 diabetes both in terms of its incidence and related adverse clinical outcomes, including cardiovascular and chronic kidney diseases. In response to these global health threats, clinical care pathways for NAFLD and guidelines for metabolic dysfunction‐associated fatty liver disease have been developed. Several antidiabetic agents have been evaluated for their potential hepatic benefits with promising results. Furthermore, type 2 diabetes patients are increasingly represented in clinical trials of novel therapeutics for NAFLD. However, despite the wealth of knowledge in NAFLD and type 2 diabetes, lack of awareness of the disease and the potential weight of this problem remains a major challenge, especially among clinicians who are outside the field of hepatology and gastroenterology. This review therefore aimed to provide all diabetes care providers with a summary of the latest evidence that supports NAFLD as an emerging diabetic complication of increasing importance, and to present the current recommendations, focusing on the assessment and therapeutic strategies, on the management of NAFLD among type 2 diabetes patients.

Targeting adipose tissue to tackle NASH: SPARCL1 as an emerging player

Nonalcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease, affecting 1.5%-6.5% of the world population. Currently, there are no FDA-approved drugs to treat this disease. Accumulating evidence suggests that metabolically hazardous visceral fat contributes to NASH progression by releasing fatty acids and proinflammatory mediators. Therefore, targeting adipose tissue to reduce adipose inflammation may provide an effective strategy to treat NASH. Another strategy is to target specific inflammatory mediators that are produced by adipose tissue and contribute to NASH progression. In this issue of the JCI, Liu, Xiang, et al. demonstrate that secreted protein acidic and rich in cysteine-like protein 1 (SPARCL1) was highly upregulated in adipose tissue and played a role in exacerbating NASH progression in a mouse model of NASH. Thus, inhibition of SPARCL1 may provide another attractive strategy to tackle NASH.

Tissue-specific role and associated downstream signaling pathways of adiponectin

According to the World Health Organization, metabolic syndrome (MetS) can be defined as a pathological condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. The incidence of MetS keeps rising, as at least 35% of the USA population suffers from MetS. One of the worst comorbidities of metabolic syndrome are cardiovascular diseases that significantly amplifies the mortality associated with this syndrome. There is an urgent need to understand the pathophysiology of MetS to find novel diagnosis, treatment and management to mitigate the MetS and associated complications. Altered circulatory adiponectin levels have been implicated in MetS. Adiponectin has numerous biologic functions including antioxidative, anti-nitrative, anti-inflammatory, and cardioprotective effects. Being a pleiotropic hormone of multiple tissues, tissue-specific key signaling pathways of adiponectin will help finding specific target/s to blunt the pathophysiology of metabolic syndrome and associated disorders. The purpose of this review is to elucidate tissue-specific signaling pathways of adiponectin and possibly identify potential therapeutic targets for MetS as well as to evaluate the potential of adiponectin as a biomarker/therapeutic option in MetS.

Assessment of Lifestyle Factors Helps to Identify Liver Fibrosis Due to Non-Alcoholic Fatty Liver Disease in Obesity

Only some individuals with obesity develop liver fibrosis due to non-alcoholic fatty liver disease (NAFLD-fibrosis). We determined whether detailed assessment of lifestyle factors in addition to physical, biochemical and genetic factors helps in identification of these patients. A total of 100 patients with obesity (mean BMI 40.0 ± 0.6 kg/m²) referred for bariatric surgery at the Helsinki University Hospital underwent a liver biopsy to evaluate liver histology. Physical activity was determined by accelerometer recordings and by the Modifiable Activity Questionnaire, diet by the FINRISK Food Frequency Questionnaire, and other lifestyle factors, such as sleep patterns and smoking, by face-to-face interviews. Physical and biochemical parameters and genetic risk score (GRS based on variants in PNPLA3, TM6SF2, MBOAT7 and HSD17B13) were measured. Of all participants 49% had NAFLD-fibrosis. Independent predictors of NAFLD-fibrosis were low moderate-to-vigorous physical activity, high red meat intake, low carbohydrate intake, smoking, HbA_1c, triglycerides and GRS. A model including these factors (areas under the receiver operating characteristics curve (AUROC) 0.90 (95% CI 0.84–0.96)) identified NAFLD-fibrosis significantly more accurately than a model including all but lifestyle factors (AUROC 0.82 (95% CI 0.73–0.91)) or models including lifestyle, physical and biochemical, or genetic factors alone. Assessment of lifestyle parameters in addition to physical, biochemical and genetic factors helps to identify obese patients with NAFLD-fibrosis.

Molecular Mechanisms of Nonalcoholic Fatty Liver Disease (NAFLD)/Nonalcoholic Steatohepatitis (NASH)

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide and has garnered increasing attention in recent decades. NAFLD is characterized by a wide range of liver changes, from simple steatosis to nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. The pathogenesis of NAFLD/NASH is very complicated and involves lipid accumulation, insulin resistance, inflammation, and fibrogenesis. In addition, NAFLD is closely associated with complications such as obesity, dyslipidemia, and type 2 diabetes. In particular, the clinical spectrum, pathophysiology, and therapeutic options of NAFLD share many things in common with diabetes. Insulin resistance is an underlying basis for the pathogenesis of diabetes and NAFLD. This chapter focuses on the molecular mechanism involved in the pathogenesis of insulin resistance, diabetes, and NASH/NAFLD including those that drive disease progression such as oxidative stress, genetic and epigenetic mechanisms, adiponectin, cytokines, and immune cells.

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.

Agrimonia pilosa Ledeb. Ameliorates Hyperglycemia and Hepatic Steatosis in Ovariectomized Rats Fed a High-Fat Diet

Estrogen deficiency is associated with obesity, dyslipidemia, and increased insulin resistance in postmenopausal women. An efficient therapeutic agent prevents or improves postmenopausal conditions induced by estrogen deficiency. Here, we investigated the effects of aqueous Agrimonia pilosa Ledeb. extract on glucose and lipid metabolism in ovariectomized rats fed a high-fat diet (HFD). Female Sprague-Dawley rats were sham-operated or ovariectomized, and 3 weeks later were assigned to the following groups: sham-operated + HFD (S); ovariectomized + HFD (OVX); and ovariectomized + HFD with 0.5% A. pilosa aqueous extract (OVX + 0.5A) groups. Ovariectomy significantly increased body weight and dietary intake relative to the S group. However, A. pilosa treatment did not significantly affect weight gain or dietary intake. Blood triacylglycerol, total cholesterol, and low-density lipoprotein cholesterol levels tended to decrease in the A. pilosa-supplemented group. Blood glucose levels were significantly lower in the OVX + 0.5A group than those in the OVX group. Blood adiponectin and insulin concentrations increased significantly after A. pilosa treatment in the ovariectomized group. A. pilosa supplementation tended to decrease liver weights and prevented lipid accumulation. These effects correlated with reduced hepatic expression of lipogenesis-related genes (fatty acid synthase, acetyl-coenzyme A carboxylase alpha, and 3-hydroxy-3-methylglutaryl-coenzyme A reductase). Therefore, A. pilosa may improve metabolic disorders in ovariectomized rats.

Adipose Tissue-Liver Cross Talk in the Control of Whole-Body Metabolism: Implications in Nonalcoholic Fatty Liver Disease

Adipose tissue and the liver play significant roles in the regulation of whole-body energy homeostasis, but they have not evolved to cope with the continuous, chronic, nutrient surplus seen in obesity. In this review, we detail how prolonged metabolic stress leads to adipose tissue dysfunction, inflammation, and adipokine release that results in increased lipid flux to the liver. Overall, the upshot of hepatic fat accumulation alongside an insulin-resistant state is that hepatic lipid enzymatic pathways are modulated and overwhelmed, resulting in the selective buildup of toxic lipid species, which worsens the pro-inflammatory and pro-fibrotic shift observed in nonalcoholic steatohepatitis.

Serum cytokines, adipokines and ferritin for non-invasive assessment of liver fibrosis in chronic liver disease: a systematic review

Chronic liver disease (CLD) is a major health problem worldwide. Non-alcoholic fatty liver disease (NAFLD), chronic hepatitis C (CHC), chronic hepatitis B (CHB), and alcoholic liver disease (ALD) are the most common etiologies of CLD. Liver biopsy is the gold standard for assessment of liver fibrosis, however, it is an invasive method. This review attempts to evaluate the usefulness of serum adiponectin, serum leptin, serum ferritin, serum transforming growth factor-β1 (TGF-β1), and serum platelet derived growth factor-BB (PDGF-BB) as non-invasive markers in the diagnosis of liver fibrosis/cirrhosis. A systematic search in MEDLINE, Web of Science, Scopus, and local databases was performed to identify articles published in English or Persian as of November 2017. Studies conducted among CLD patients, with biopsy proven fibrosis/cirrhosis, and providing sufficient details of patients' clinicopathological characteristics were included. In the 95 studies included, there were a total of 15,548 CLD patients. More than 83% of studies were carried out in Asia and Europe. The relationship between liver fibrosis/cirrhosis and serum levels of ferritin, adiponectin, leptin, TGF-β1, and PDGF-BB was assessed in 42, 33, 27, nine, and three studies, respectively. Serum levels of the markers, particularly ferritin, could successfully predict liver fibrosis/cirrhosis, however, these data might not be clinically replicated and further studies are needed.

Probiotic culture supernatant improves metabolic function through FGF21-adiponectin pathway in mice

High-fat/high-fructose diet plus intermittent hypoxia exposure (HFDIH) causes metabolic disorders such as insulin resistance, obesity, nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. The purpose of this study is to examine the effects and understand the mechanism of action of Lactobacillus rhamnosus GG culture supernatant (LGGs) on HFDIH-induced metabolic dysfunction. Mice were fed high-fat:high-fructose diet for 15 weeks. After 3 weeks of feeding, the mice were exposed to chronic intermittent hypoxia for the next 12 weeks (HFDIH), and LGGs was supplemented over the entire experiment. HFDIH exposure significantly led to metabolic disorders. LGGs treatment showed significant improvements in indices of metabolic disorders including fat mass, energy expenditure, glucose intolerance, insulin resistance, increased hepatic steatosis and liver injury. HFDIH mice markedly increased adipose inflammation and adipocyte size, and reduced circulating adiponectin, which was restored by LGGs treatment. LGGs treatment increased hepatic FGF21 mRNA expression and circulating FGF21 protein levels, which were associated with increased hepatic PPARα expression and fecal butyrate concentration. In addition, HFDIH-induced hepatic fat accumulation and apoptosis were significantly reduced by LGGs supplementation. In summary, LGGs treatment increased energy expenditure and insulin sensitivity and prevented metabolic abnormalities in HFDIH mice, and this is associated with the FGF21-adiponectin signaling pathway. LGGs may be a potential prevention/treatment strategy in subjects with the metabolic syndrome.

Association between Helicobacter pylori infection and nonalcoholic fatty liver disease: A systematic review and meta-analysis of observational studies

BACKGROUND

The association between Helicobacter pylori (H. pylori) infection and nonalcoholic fatty liver disease (NAFLD) has been shown in many observational studies, but these conclusions remain controversial. Hence, we performed a meta-analysis to elucidate the association.

METHODS

A comprehensive search was conducted on relevant studies published from inception to December 31, 2018, in PubMed, EMBASE, and Web of Science databases. Odds ratio (OR) with 95% confidence interval (95% CI) were pooled by random-effect model, generic inverse variance method. Subgroup and sensitivity analyses were also done. Publication bias was estimated by the funnel plot, Begg's test, and Egger's test.

RESULTS

Fifteen studies (eleven cross-sectional, two case-control, and two cohort studies) were included in this meta-analysis. The pooled OR of NAFLD in patients with H. pylori infection was 1.19 (95% CI: 1.11-1.29, P < 0.00001) when compared with the patients without H. pylori infection. Similar results were observed when the subgroup analyses were stratified by different geographical locations, study designs, and confounders adjustment. In subgroup analysis stratified by different H. pylori testing methods, the correlation still exists when using UBT, serology, RUT, or SAT, but there was no statistically significant difference when using multiple detection methods (OR = 2.96, 95% CI: 0.37-23.94, P = 0.31). Sensitivity analyses showed that our results were robust. No evidence of substantial publication bias was detected.

CONCLUSIONS

Current evidence indicated that a positive association between H. pylori infection and the risk of NAFLD. Further prospective studies are warranted to strengthen the association and to clarify whether there is a causative link between them.

Whole-body vibration for patients with nonalcoholic fatty liver disease: a 6-month prospective study

Physical exercise has demonstrated benefits for managing nonalcoholic fatty liver disease (NAFLD). However, in daily life maintaining exercise without help may be difficult. A whole-body vibration device (WBV) has been recently introduced as an exercise modality that may be suitable for patients who have difficulty engaging in exercise. We tested WBV in patients with NAFLD and estimated its effectiveness. We studied the effects of a 6-month WBV program on hepatic steatosis and its underlying pathophysiology in 25 patients with NAFLD. Seventeen patients with NAFLD were designated as a control group. After WBV exercise, body weight in the study group decreased by only 2.5% compared with the control group. However, we found significant increases in muscle area (+2.6%) and strength (+20.5%) and decreases in fat mass (-6.8%). The hepatic (-9.9%) and visceral (-6.2%) fat content also significantly decreased (P < 0.05). There was substantial lowering of hepatic stiffness (-15.7%), along with improvements in the levels of inflammatory markers; tumor necrosis factor alpha (-50.9%), adiponectin (+12.0%), ferritin (-33.2%), and high-sensitivity C-reactive protein (-43.0%) (P < 0.05). These results suggest that WBV is an exercise option for patients with NAFLD that is effective, efficient, and convenient.

Efficacy of liraglutide in treating type 2 diabetes mellitus complicated with non-alcoholic fatty liver disease

Type 2 diabetes mellitus (T2DM) complicated with non-alcoholic fatty liver disease (NAFLD) is difficult to treat. The present study explored the efficacy of (liraglutide) Lira in treating T2DM complicated with NAFLD. A total of 127 patients suffering from T2DM complicated with NAFLD were enrolled in the present study, and randomly assigned to a Lira group (liraglutide injection: 0.6–1.2 mg/day, 12 weeks, n=52) or a Metformin (Met) group (oral metformin: 1000–1500 mg/day, 12 weeks, n=75). During the treatment phase, the values for fasting plasma glucose (FPG), 2 h plasma glucose (2hPG), glycated hemoglobin (HbA1c), aspartate aminotransferase (AST)/alanine aminotransferase (ALT), and adiponectin (APN) decreased in both the Lira and Met groups, and the levels of Δ2hPG, ΔAST/ALT, and ΔAPN in the Lira group were significantly lower than those in the Met group. The values for total cholesterol (TC), triglycerides (TG), low-and high-density lipoproteins (LDL and HDL), ALT, AST, weight, body mass index (BMI), waist to hip ratio (WHR), and C-reactive protein were markedly increased in both groups, and levels of ΔAST, ΔALT, Δweight, ΔBMI, ΔWHR, and ΔCRP (C-reactive protein) in the Lira group were significantly higher than those in the Met group. An analysis of treatment efficacy showed that liraglutide was better than metformin in its ability to significantly decrease the ALT levels in patients with combined T2DM and NAFLD. Furthermore, liraglutide was more effective than metformin at ameliorating the severity of T2DM complicated with NAFLD, and produced its effects by alleviating liver inflammation and improving liver function.

Adiponectin as a novel biomarker for liver fibrosis

Adiponectin is known to play primary roles in the regulation of systemic glucose homeostasis and lipid metabolism. Interestingly, emerging evidence indicates beneficial effects of adiponectin on liver fibrosis; however, the exact mechanisms of this action remain unclear. Herein, we aimed to summarize the recent findings regarding the role of adiponectin in liver fibrogenesis and update the current comprehensive knowledge regarding usefulness of adiponectin-based treatments in liver fibrosis. Adiponectin has been demonstrated to have an anti-fibrotic action in the liver by blocking the activation of hepatic stellate cell-mediated adenosine monophosphate-activated protein kinase and peroxisome proliferator-activated receptor-alpha pathways, which in turn diminish the expression of pro-fibrotic genes. In addition, hyperadiponectinemia was noted in patients with various chronic liver diseases (CLDs)-related liver fibrosis. An increase in circulating adiponectin levels was also found to be associated with the development of liver fibrosis, indicating a role of adiponectin as a non-invasive biomarker for predicting the progression of liver fibrosis. It is therefore reasonable to speculate that adiponectin may be developed as a new therapeutic candidate for the treatment of liver fibrosis. Nonetheless, future observations are still necessary to fully elucidate the extent of the effects of adiponectin on liver fibrotic outcomes, in order to modify adiponectin as an anti-fibrotic therapy that would speed up fibrosis reversal in patients with CLD.

Non-alcoholic fatty liver disease is an independent risk factor for inflammation in obstructive sleep apnea syndrome in obese Asian Indians

INTRODUCTION

Obstructive sleep apnea (OSA) has been estimated to affect 4-11% of the population and causes systemic inflammation which leads to metabolic syndrome (MS). Non-alcoholic fatty liver disease (NAFLD) is also associated with MS whether NAFLD is an additional risk factor for the systemic inflammation that occurs in OSA is unclear.

OBJECTIVE

In this study, we aimed to analyze the association of OSA and NAFLD with MS and systemic inflammation in Asian Indians.

METHODS

Total 240 (132 males and 108 females) overweight/obese subjects [body mass index (BMI > 23 kg/m²)] were recruited; of these, 124 subjects had OSA with NAFLD, 47 had OSA without NAFLD, 44 did not have OSA but had NAFLD and 25 had neither OSA nor without NAFLD. Severity of NAFLD was based on abdomen ultrasound and of OSA on overnight polysomnography. Clinical examinations, anthropometry, body composition, metabolic parameters, and inflammatory biomarkers were recorded.

RESULTS

Serum levels of leptin, macrophage migration inhibitory factor (MIF), interleukin-6 (IL-6), high sensitive C-reactive protein (Hs-CRP), and tumor necrosis factor alpha (TNF-α) were significantly higher, and adiponectin levels were significantly lower in OSA with NAFLD subjects. Prevalence of MS was significantly increased in OSA and NAFLD subjects (p = 0.001). There was a strong association and correlation between leptin, IL-6, Hs-CRP, MIF, and TNF-α in OSA and NAFLD subjects. Multivariate logistic regression showed that OSA was positively associated with the NAFLD [odds ratio (OR), (95% confidence interval (CL) 3.12 (2.58-7.72), (P = 0.002)].

CONCLUSION

NAFLD is an additional risk factor in OSA subject which contributes to systemic inflammation in Asian Indians.

Non-alcoholic fatty liver disease: A sign of systemic disease

Non-alcoholic fatty liver disease (NAFLD) is the most common form of liver disease and leading cause of cirrhosis in the United States and developed countries. NAFLD is closely associated with obesity, insulin resistance and metabolic syndrome, significantly contributing to the exacerbation of the latter. Although NAFLD represents the hepatic component of metabolic syndrome, it can also be found in patients prior to their presentation with other manifestations of the syndrome. The pathogenesis of NAFLD is complex and closely intertwined with insulin resistance and obesity. Several mechanisms are undoubtedly involved in its pathogenesis and progression. In this review, we bring together the current understanding of the pathogenesis that makes NAFLD a systemic disease.

The Association Between Helicobacter pylori Infection and Nonalcoholic Fatty Liver Disease

PURPOSE OF REVIEW

Helicobacter pylori (HP) infection is known to be a significant risk factor in the development of certain gastric conditions, such as ulcers, gastritis, and malignancy. Recently, however, the systemic effect of HP infection on other organ systems has come to be appreciated. In this review, we will explore the association between HP infection and nonalcoholic fatty liver disease (NAFLD), the hepatic component of metabolic syndrome.

RECENT FINDINGS

The possible association between HP infection and NAFLD initially stemmed from the isolation of HP bacteria in the livers of patients with NAFLD. Although there have been conflicting results, several subsequent clinical trials have demonstrated a higher rate of fatty liver and NASH in HP-positive patients compared to HP-negative patients; in addition, small trials examining the effect of HP eradication have shown improvement in markers of NAFLD activity, further supporting a link between these two conditions. The pathophysiology behind the possible association between HP infection and NAFLD has yet to be fully elucidated; several possible mechanisms include induction of a pro-inflammatory state that shifts the body toward a more lipogenic profile, and a hormonal shift that favors progression toward insulin resistance and fibrosis. The association between HP infection and NAFLD has been demonstrated in several clinical trials, including small trials evaluating the effect of HP eradication on NAFLD. Future studies examining the pathophysiology behind this association are the next step in characterizing the relationship between these two conditions.

Micronutrient Antioxidants and Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most important chronic liver diseases worldwide and has garnered increasing attention in recent decades. NAFLD is characterized by a wide range of liver changes, from simple steatosis to nonalcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma. The blurred pathogenesis of NAFLD is very complicated and involves lipid accumulation, insulin resistance, inflammation, and fibrogenesis. NAFLD is closely associated with complications such as obesity, diabetes, steatohepatitis, and liver fibrosis. During the progression of NAFLD, reactive oxygen species (ROS) are activated and induce oxidative stress. Recent attempts at establishing effective NAFLD therapy have identified potential micronutrient antioxidants that may reduce the accumulation of ROS and finally ameliorate the disease. In this review, we present the molecular mechanisms involved in the pathogenesis of NAFLD and introduce some dietary antioxidants that may be used to prevent or cure NAFLD, such as vitamin D, E, and astaxanthin.

Adiponectin as an anti-fibrotic and anti-inflammatory adipokine in the liver

Hepatic fibrosis is a dynamic process resulting from excessive deposition of extracellular matrix in the liver; uncontrolled progression of fibrosis can eventually lead to liver cirrhosis and/or hepatocellular carcinoma. The fibrogenic process is complex and modulated by a number of both hepatic and extra-hepatic biological factors. Growing evidence indicates that adipokines, a group of cytokines produced by adipose tissue, impart dynamic functions in liver and are involved in modulation of hepatic fibrosis. In particular, two key adipokines, adiponectin and leptin, directly regulate many biological responses closely associated with development and progression of hepatic fibrosis. Leptin acts as a pro-fibrogenic cytokine, while adiponectin possesses anti-fibrogenic and anti-inflammatory properties. Adiponectin, acting via its cognate receptors, adiponectin receptors 1 and 2, potently suppresses fibrosis and inflammation in liver via multiple mechanisms. This review summarizes recent findings concerning the role of adiponectin in fibrogenic process in liver and addresses the underlying molecular mechanisms in modulation of fibrosis.

Combined Adiponectin Deficiency and Resistance in Obese Patients: Can It Solve Part of the Puzzle in Nonalcoholic Steatohepatitis

BACKGROUND:

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent cause of liver disease, nonalcoholic steatohepatitis (NASH) and fibrosis in obese patients identifies the risk group with increased incidence of liver-related deaths.

AIM:

To clarify the role of serum adiponectin and its receptor liver gene expression in the progression of liver damage in NAFLD.

METHODS:

Fifty four (54) obese patients with NAFLD preliminary diagnosed by liver ultra-sound were recruited. Full medical history, anthropometric measurement, biochemical studies, serum adiponectin level, liver biopsy for histological examination and NAS score to identify NASH patients, and assessment of adiponectin receptor gene expression by RT-PCR, were conducted for each patients. Fifteen ages matched average weight healthy adult had been chosen as a control for serum adiponectin level.

RESULTS:

According to NAS score, patients were divided into non- NASH (8 patients), and NASH (46 patients). Serum adiponectin level was significantly lower in NAFLD patients compared to normal participants (p < 0.004). Serum adiponectin level was lower in NASH patients (4.437 ± 2.569 ng/dl in NASH vs. 5.138 ± 2.841 ng/dl in non-NASH). Adiponectin receptor liver gene expression was lower in NASH patients (0.8459 ± 0.4671 vs. 1.0688 ± 0.3965 in non-NASH).

CONCLUSION:

Both adiponectin deficiency and resistance had a role in progression of simple liver steatosis to severe injury in obese patients.

Epicardial Fat in Nonalcoholic Fatty Liver Disease: Properties and Relationships With Metabolic Factors, Cardiac Structure, and Cardiac Function

Nonalcoholic fatty liver disease (NAFLD) is closely related to insulin resistance and the metabolic syndrome and might be an important cardiovascular (CV) risk factor. Epicardial adipose tissue (EAT) has been implicated in the pathogenesis of obesity-related CV disease. In an NAFLD population, we investigated EAT thickness and its possible relations to NAFLD and cardiac structure and function. This was an observational study of 57 patients with NAFLD and 48 age-matched controls. Patients with NAFLD had significantly higher body mass index (P < .0001), waist circumference (P < .0001), and high-sensitivity C-reactive protein (P = .005), whereas high-density lipoprotein cholesterol (P = .01) and adiponectin (P = .005) levels were significantly lower. The EAT was not thicker in NAFLD but was positively related to indices of impaired glucose tolerance and inflammation, with diabetes being an independent predictor of EAT thickness (b* = 0.29, P = .04). No relations were found between EAT and cardiac structure and function. In conclusion, this study confirms a pathologic phenotype of NAFLD. Epicardial fat was not significantly related to NAFLD per se, but diabetes, glucose metabolism, and inflammation were closely related to its thickness.

OSAS-related inflammatory mechanisms of liver injury in nonalcoholic fatty liver disease

Obstructive sleep apnoea syndrome (OSAS) is a common sleep disorder, affecting over 4% of the general population, and is associated with metabolic syndrome and cardiovascular disease, independent of obesity and traditional risk factors. OSAS has been recently connected to nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disease in the world, which can be found in 30% of the general adult population. Several studies suggest that the chronic intermittent hypoxia (CIH) of OSAS patients may per se trigger liver injury, inflammation, and fibrogenesis, promoting NAFLD development and the progression from steatosis to steatohepatitis, cirrhosis, and hepatocellular carcinoma. In NAFLD patients, liver disease may be caused by hypoxia both indirectly by promoting inflammation and insulin resistance and directly by enhancing proinflammatory cytokine production and metabolic dysregulation in liver cells. In this review, we focus on molecular mechanisms linking OSAS to NAFLD, including hypoxia inducible factor (HIF), nuclear factor kappa B (NF-κB), YKL-40, unfolded protein response, and hypoxic adipose tissue inflammation, which all could provide novel potential therapeutic approaches for the management of NAFLD patients with OSAS.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Role of adiponectin in the metabolic effects of cannabinoid type 1 receptor blockade in mice with diet-induced obesity

The adipocyte-derived hormone adiponectin promotes fatty acid oxidation and improves insulin sensitivity and thus plays a key role in the regulation of lipid and glucose metabolism and energy homeostasis. Chronic cannabinoid type 1 (CB1) receptor blockade also increases lipid oxidation and improves insulin sensitivity in obese individuals or animals, resulting in reduced cardiometabolic risk. Chronic CB1 blockade reverses the obesity-related decline in serum adiponectin levels, which has been proposed to account for the metabolic effects of CB1 antagonists. Here, we investigated the metabolic actions of the CB1 inverse agonist rimonabant in high-fat diet (HFD)-induced obese adiponectin knockout (Adipo(-/-)) mice and their wild-type littermate controls (Adipo(+/+)). HFD-induced obesity and its hormonal/metabolic consequences were indistinguishable in the two strains. Daily treatment of obese mice with rimonabant for 7 days resulted in significant and comparable reductions in body weight, serum leptin, free fatty acid, cholesterol, and triglyceride levels in the two strains. Rimonabant treatment improved glucose homeostasis and insulin sensitivity to the same extent in Adipo(+/+) and Adipo(-/-) mice, whereas it reversed the HFD-induced hepatic steatosis, fibrosis, and hepatocellular damage only in the former. The adiponectin-dependent, antisteatotic effect of rimonabant was mediated by reduced uptake and increased β-oxidation of fatty acids in the liver. We conclude that reversal of the HFD-induced hepatic steatosis and fibrosis by chronic CB1 blockade, but not the parallel reduction in adiposity and improved glycemic control, is mediated by adiponectin.

Impact of nutrition and obesity on chronic liver disease

Undernutrition and obesity are at opposite ends of a spectrum that has an enormous impact on all aspects of liver diseases. The myriad effects of the opposing ends of the nutrition spectrum have led to a wealth of research aimed at elucidating the exact mechanisms of how they cause liver damage. In this article, the role of the liver in nutrient and energy metabolism is discussed, as well as the known and possible effects of specific nutrient deficiencies and obesity.

Potential role of Helicobacter pylori infection in nonalcoholic fatty liver disease

Accumulating evidence has implicated Helicobacter pylori (H. pylori) infection in extragastrointestinal diseases, including obesity, type 2 diabetes mellitus, cardiovascular disease, and liver disease. Recently, there has been a special focus on H. pylori infection as a risk factor for the development of nonalcoholic fatty liver disease (NAFLD). NAFLD is currently considered to be the most common liver disorder in western countries, and is rapidly becoming a serious threat to public health. The mechanisms of pathogenesis underlying NAFLD remain unclear at present and therapeutic options are limited. The growing awareness of the role of H. pylori in NAFLD is thus important to aid the development of novel intervention and prevention strategies, because the eradication of H. pylori is easy and much less expensive than long-term treatment of the other risk factors. H. pylori infection is involved in the pathogenesis of insulin resistance (IR), which is closely linked with NAFLD. It provides a new insight into the pathogenesis of NAFLD. This review probes the possible relationship between H. pylori and NAFLD, from the perspective of the potential mechanism of how H. pylori infection brings about IR and other aspects concerning this correlation.

Hypoadiponectinaemia in nonalcoholic fatty liver disease obese women is associated with infrequent intake of dietary sucrose and fatty foods

BACKGROUND

The present study aimed to investigate the relationship between adiponectinaemia and food intake among obese women with nonalcoholic fatty liver disease (NAFLD).

METHODS

In total, 60 obese women were examined by abdominal ultrasound for liver steatosis and subcutaneous and visceral adiposity. A standard interview (including questions about alcohol intake, medical history and physical activity), a physical examination (including height, weight, body mass index, waist and hip circumferences, waist-to-hip ratio, and body composition) and biochemical and clinical parameters (including serum glucose and insulin, homeostatic model assessment insulin resistance, lipid profile, aminotransferases, C-reactive protein, adiponectin, leptin, resistin, tumour necrosis factor-α, interleukin-6 levels and blood pressure) were performed. Food intake was evaluated by a qualitative food frequency questionnaire.

RESULTS

Twenty-four NAFLD patients and thirty-six controls were analysed. The Mann-Whitney test showed lower adiponectin levels in the liver disease group compared to controls (P < 0.05). The Pearson correlation coefficient indicated that adiponectinaemia was negatively correlated with lipid profile and serum tumour necrosis factor-α (P = 0.05) and was positively associated with adiposity measures and serum leptin (P < 0.05). By simple linear regression, all of these variables predicted serum adiponectin levels. Chi-squared and Fisher's exact tests indicated that, in both groups, food intake showed no differences, although sucrose and fatty foods were associated with lower adiponectin levels in the liver disease group (P < 0.05 and P < 0.05, respectively), as well as in the control group (P = 0.05 and P < 0.05, respectively).

CONCLUSIONS

Hypoadiponectinaemia in NAFLD was associated with dietary sucrose and fatty food intake, emphasising the important role of diet in the occurrence of this disease.

Obesity as the common soil of non-alcoholic fatty liver disease and diabetes: Role of adipokines

Non‐alcoholic fatty liver disease (NAFLD) describes a spectrum of liver conditions from simple steatosis, steatohepatitis to end‐stage liver disease. The prevalence of NAFLD has been on the rise in many parts of the world, including Asia, and NAFLD is now the liver disease associated with the highest mortality, consequent to the increased risk of cardiovascular diseases and hepatocellular carcinoma. Whereas NAFLD is an independent risk factor for type 2 diabetes, increased hepatic and peripheral insulin resistance contribute to the pathogenesis of both NAFLD and diabetes, which are associated with enhanced cardiovascular risk. Studies in humans and animal models have suggested obesity as the common link of these two diseases, likely mediated by adipose tissue inflammation and dysregulated adipokine production in obesity. In the present review, we discuss recent advances in our understanding of the role of several novel adipokines (adiponectin, adipocyte fatty acid binding protein and fibroblast growth factor‐21) in the pathophysiology of NAFLD and diabetes, as well as their use as potential biomarkers and therapeutic targets for dysglycemia in NAFLD patients.

Serum biomarkers in type 2 diabetic patients with non-alcoholic steatohepatitis and advanced fibrosis

AIM

Advanced stages of non-alcoholic fatty liver disease (NAFLD) are highly prevalent in type 2 diabetes (T2DM), however, no diabetes-related or biochemical variable seems to be predictive of severity of NAFLD. The aim of this study was to investigate the association of several serum biomarkers with the more severe histopathological stages of NAFLD in T2DM.

METHODS

In a cross-sectional design, 84 T2DM patients with biopsy-proven NAFLD had adiponectin, tumor necrosis factor-α, transforming growth factor (TGF)-β1, interleukin (IL)-6, -8 and -10, and C-reactive protein measured. NAFLD severity was evaluated by two hepatopathologists according to the non-alcoholic steatohepatitis (NASH) Clinical Research Network scoring system. Independent associations of cytokines with NASH and advanced fibrosis were evaluated by multivariate logistic regressions.

RESULTS

Sixty-six patients (78.6%) had NASH, and 52 patients (61.9%) had advanced fibrosis considering the highest score between the two pathologists. Patients with NASH or with advanced fibrosis had equal cytokine levels to those without NASH or with absent/light fibrosis, except for a lower serum adiponectin (8.59 vs 12.77 μg/mL; P = 0.015) in patients with NASH and a lower TGF-β1 (170 vs 180 pg/mL; P = 0.026) in patients with advanced fibrosis. In multivariate analysis, lower adiponectin was independently associated with NASH (odds ratio = 7.7, 95% confidence interval = 1.5-39.9, P = 0.014, for the subgroup with adiponectin below the median value), whereas both lower adiponectin and lower TGF-β1 levels were associated with advanced fibrosis.

CONCLUSION

Low adiponectin and low TGF-β1 are associated with severest NAFLD stages in T2DM and may be a valuable tool to support liver biopsy indication in this setting.

Adipocytokines and hepatocellular carcinoma

Adipocytokines are primarily adipocyte-derived products, although certain members are also synthesized by other cell types. These adipocytokines, similarly to classical cytokines, are characterized by very pleiotropic functions affecting biological processes throughout the body. An increasing number of adipocytokines has recently been recognized, such as adiponectin, leptin, pre-B cell colony-enhancing factor/Nampt/visfatin, resistin, progranulin, and others. Adiponectin has emerged as the most abundant circulating adipocytokine, is produced almost exclusively by adipocytes, and has mainly anti-inflammatory and anti-diabetic functions. In contrast, leptin is produced by many cell types beyond adipocytes, regulates immunity and T cell functions, and acts in a more pro-inflammatory fashion. Adipocytokines play a fundamental role in adipose tissue homeostasis (i.e. health) and disease, especially in obesity-related disorders such as non-alcoholic fatty liver diseases (NAFLD) and their complications, including hepatocellular carcinoma (HCC). Lack of adiponectin as observed in NAFLD drives steatosis and inflammation in the liver, and evidence is increasing that this adipocytokine has many anti-tumor properties and might play a rather protective role in HCC. The role of leptin in NAFLD is still unclear and this adipocytokine seems to have opposite effects in HCC, acting more as a tumor promoter. Evidence is increasing that HCC tissue produces various adipocytokines, and adiponectin expression in HCC seems to be decreased whereas leptin expression is rather increased. In conclusion, adipocytokines are increasingly recognized as pleiotropic molecules involved in the pathophysiology of HCC, which might lead to therapeutic approaches targeting these mediators.

The association between adipocytokines and biomarkers for nonalcoholic fatty liver disease-induced liver injury: a study in the general population

BACKGROUND AND AIM

Leptin and adiponectin have been implicated in the development of nonalcoholic fatty liver disease (NAFLD). However, the usefulness of adipocytokines as a screening tool for nonalcoholic steatohepatitis (NASH) and fibrosis could not be evaluated in the general population due to the invasive nature of liver biopsy. The aim was to evaluate the association between adipocytokines and presumed liver injury in the general population using noninvasive biomarkers.

METHODS

A cross-sectional study of 375 individuals, sampled from the National Health Survey was conducted. The exclusion criterion was any known secondary etiology for liver disease. Anthropometrics, serum leptin, adiponectin, insulin, lipids, and FibroMax were measured.

RESULTS

Three hundred and thirty-eight individuals met the inclusion criteria and had valid FibroMax. Fibrosis diagnosed by the FibroTest was found in 25.7% of the patients, of whom 12.8% had significant fibrosis. Steatohepatitis was diagnosed by the NASH test in 0.9% and borderline NASH in 31.4% of the patients. Adiponectin was an independent negative correlate of borderline NASH [odds ratio (OR): 0.92; 95% confidence interval (CI): 0.86-0.98/1 µg/ml] together with high-density lipoprotein, and leptin was a positive correlate (OR: 1.03; CI: 1.01-1.06/1 ng/ml), together with abdominal obesity, serum triglycerides, and HbA1C. The OR for borderline NASH was 20.7 (CI: 7.5-57.5) when both high leptin (upper quartile) and suboptimal adiponectin were present, adjusting for age and sex. The FibroTest was not associated with leptin and adiponectin. The strongest predictors for fibrosis were age, sex, abdominal obesity, and insulin.

CONCLUSION

Low adiponectin and high leptin and the combination of both have a strong independent association with presumed early-stage NASH. However, early-stage fibrosis cannot be predicted by these adipocytokines.

Adiponectin inhibits leptin signalling via multiple mechanisms to exert protective effects against hepatic fibrosis

Adiponectin is protective against hepatic fibrosis, whereas leptin promotes fibrosis. In HSCs (hepatic stellate cells), leptin signals via a JAK2 (Janus kinase 2)/STAT3 (signal transducer and activator of transcription 3) pathway, producing effects that enhance ECM (extracellular matrix) deposition. SOCS-3 (suppressor of cytokine signalling-3) and PTP1B (protein tyrosine phosphatase 1B) are both negative regulators of JAK/STAT signalling, and recent studies have demonstrated a role for adiponectin in regulating SOCS-3 expression. In the present study we investigate mechanisms whereby adiponectin dampens leptin signalling and prevents excess ECM production. We treated culture-activated rat HSCs with recombinant adiponectin, leptin, both or neither, and also treated adiponectin knockout (Ad-/-) and wild-type mice with leptin and/or carbon tetrachloride (CCl4) or saline. We analyse JAK2 and Ob-Rb (long form of the leptin receptor) phosphorylation, and PTP1B expression and activity. We also explore potential mechanisms through which adiponectin regulates SOCS-3-Ob-Rb association. Adiponectin inhibits leptin-stimulated JAK2 activation and Ob-Rb phosphorylation in HSCs, whereas both were increased in Ad-/- mice. Adiponectin stimulates PTP1B expression and activity in vitro, whereas PTP1B expression was lower in Ad-/-mice than in wild-type mice. Adiponectin also promotes SOCS-3-Ob-R association and blocks leptin-stimulated formation of extracellular TIMP-1 (tissue inhibitor of metalloproteinases-1)-MMP-1 (matrix metalloproteinase-1) complexes in vitro. These results suggest two novel mechanisms whereby adiponectin inhibits hepatic fibrosis: (i) by promoting binding of SOCS-3 to Ob-Rb, and (ii) by stimulating PTP1B expression and activity, thus inhibiting JAK2/STAT3 signalling at multiple points.

The adiponectin receptor homologs in C. elegans promote energy utilization and homeostasis

Adiponectin is an adipokine with insulin-sensitising actions in vertebrates. Its receptors, AdipoR1 and AdipoR2, are PAQR-type proteins with 7-transmembrane domains and topologies reversed that of GPCR's, i.e. their C-termini are extracellular. We identified three adiponectin receptor homologs in the nematode C. elegans, named paqr-1, paqr-2 and paqr-3. These are differently expressed in the intestine (the main fat-storing tissue), hypodermis, muscles, neurons and secretory tissues, from which they could exert systemic effects. Analysis of mutants revealed that paqr-1 and -2 are novel metabolic regulators in C. elegans and that they act redundantly but independently from paqr-3. paqr-2 is the most important of the three paqr genes: mutants grow poorly, fail to adapt to growth at low temperature, and have a very high fat content with an abnormal enrichment in long (C20) poly-unsaturated fatty acids when combined with the paqr-1 mutation. paqr-2 mutants are also synthetic lethal with mutations in nhr-49, sbp-1 and fat-6, which are C. elegans homologs of nuclear hormone receptors, SREBP and FAT-6 (a Δ9 desaturase), respectively. Like paqr-2, paqr-1 is also synthetic lethal with sbp-1. Mutations in aak-2, the C. elegans homolog of AMPK, or nhr-80, another nuclear hormone receptor gene, suppress the growth phenotype of paqr-2 mutants, probably because they restore the balance between energy expenditure and storage. We conclude that paqr-1 and paqr-2 are receptors that regulate fatty acid metabolism and cold adaptation in C. elegans, that their main function is to promote energy utilization rather than storage, and that PAQR class proteins have regulated metabolism in metazoans for at least 700 million years.

Molecular evolution of adiponectin in Carnivora and its mRNA expression in relation to hepatic lipidosis

Adiponectin is a novel adipocyte-derived hormone with low circulating concentrations and/or mRNA expression in obesity and non-alcoholic fatty liver disease (NAFLD). The adiponectin mRNA of several Carnivora species was sequenced to enable further gene expression studies in this clade with potential experimental species to examine the connections of hypoadiponectinemia to hepatic lipidosis. In addition, adiponectin mRNA expression was studied in the retroperitoneal fat of the American mink (Neovison vison), as hepatic lipidosis with close similarities to NAFLD can be rapidly induced to the species by fasting. The mRNA expression was determined after overnight-7d of food deprivation and 28d of re-feeding and correlated to the liver fat %. The homologies between the determined carnivoran mRNA sequences and that of the domestic dog were 92.2-99.1%. As the mRNA expression was not affected by short-term fasting and did not correlate with the liver fat %, there seems to be no clear connection between adiponectin and the development of lipidosis in the American mink. In the future, the obtained sequences can be utilized in further studies of adiponectin expression in comparative endocrinology.

Obstructive sleep apnea syndrome and fatty liver: Association or causal link?

Obstructive sleep apnea (OSA) is a complex disorder that consists of upper airway obstruction, chronic intermittent hypoxia and sleep fragmentation. OSA is well known to be associated with hypoxia, insulin resistance and glucose intolerance, and these factors can occur in the presence or absence of obesity and metabolic syndrome. Although it is well established that insulin resistance, glucose intolerance and obesity occur frequently with non-alcoholic fatty liver disease (NAFLD), it is now becoming apparent that hypoxia might also be important in the development of NAFLD, and it is recognized that there is increased risk of NAFLD with OSA. This review discusses the association between OSA, NAFLD and cardiovascular disease, and describes the potential role of hypoxia in the development of NAFLD with OSA.

Significance of serum adiponectin levels in patients with chronic liver disease

Adiponectin, which plays a pivotal role in metabolic liver diseases, is reduced in concentration in patients with NASH (non-alcoholic steatohepatitis). The aim of the present study was to determine adiponectin concentrations in patients with different forms and stages of chronic liver diseases. Serum adiponectin concentrations were measured in 232 fasting patients with chronic liver disease: 64 with NAFLD (non-alcoholic fatty liver disease), 123 with other chronic liver disease (e.g. viral hepatitis, n=71; autoimmune disease, n=18; alcohol-induced liver disease, n=3; or elevated liver enzymes of unknown origin, n=31) and 45 with cirrhosis. Circulating adiponectin levels were significantly lower in patients with NAFLD in comparison with patients with other chronic liver disease (4.8±3.5 compared with 10.4±6.3 μg/ml respectively; P<0.0001). Circulating adiponectin levels were significantly higher in patients with cirrhosis in comparison with patients without cirrhosis (18.6±14.5 compared with 8.4±6.1 μg/ml respectively; P<0.0001). Adiponectin concentrations correlated negatively with body weight (P<0.001), serum triacylglycerols (triglycerides) (P<0.001) and, in women, with BMI (body mass index) (P<0.001). Adiponectin concentrations correlated positively with serum bile acids (P<0.001), serum hyaluronic acid (P<0.001) and elastography values (P<0.001). Adiponectin levels were decreased in patients with NAFLD. In conclusion, adiponectin levels correlate positively with surrogate markers of hepatic fibrosis (transient elastography, fasting serum bile acids and hyaluronate) and are significantly elevated in cases of cirrhosis.

Coronary flow reserve is impaired in patients with nonalcoholic fatty liver disease: association with liver fibrosis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of cardiovascular disease. Coronary flow reserve (CFR) is widely used to examine the integrity of coronary microvascular circulation. We evaluated the prevalence of impaired CFR in patients with biopsy-proven NAFLD. We also investigated the independent clinical, biochemical, and liver histology predictors of CFR in the setting of NAFLD.

METHODS

Fifty-nine consecutive patients with NAFLD and 77 age- and gender-matched controls were evaluated. CFR recordings were performed by transthoracic Doppler harmonic echocardiography. CFR>or=2.0 was considered normal.

RESULTS

CFR was significantly lower in patients with NAFLD than in controls (2.11+/-0.45 vs. 2.52+/-0.62, P<0.001). An impaired CFR (i.e. <2) was found in 25 NAFLD patients (42.4%) whereas all controls had normal CFR values (P<0.001). A stepwise linear regression analysis in NAFLD patients identified liver fibrosis scores as the only independent predictor of CFR values (beta=-0.60; t=-2.44, P=0.021).

CONCLUSION

Our findings indicate that in patients with biopsy-proven NAFLD: (a) an abnormal CFR is found in approximately 42.4% of cases, and (b) liver fibrosis scores are an independent predictor of depressed CFR.

Hypoadiponectinemia and its association with liver fibrosis in morbidly obese patients

BACKGROUND

Reduced serum levels of adiponectin have been associated with insulin resistance and non-alcoholic fatty liver disease (NAFLD). However, the relationship between serum adiponectin levels and hepatic histology in NAFLD is controversial. The aim of this study was to explore associations between plasma adiponectin concentrations and liver histology in morbidly obese patients.

METHODS

We conducted a case-control study including obese patients undergoing bariatric surgery and normal controls. Anthropometric, standard biochemical variables as well as plasma adiponectin and leptin levels were determined. Liver biopsy was performed in all patients at the time of surgery.

RESULTS

Seventy morbidly obese patients (mean BMI, 40.6 ± 5.6 kg/m(2)) met the inclusion criteria and were compared with 69 controls (mean BMI, 22.8 ± 1.6 kg/m(2), p = 0.0001). Thirty patients (43%) had NAFLD and 20 (28%) of them fulfilled the histological criteria for steatohepatitis. Obesity was associated with increased leptin and decreased adiponectin levels. NAFLD patients exhibited decreased levels of serum adiponectin compared with matched controls [median (Q1-Q3), 3.9 (3.2-4.3) vs. 8.6 (6.5-9.2) μg/mL, p < 0.0001]. In univariate analysis, age, gender, type 2 diabetes mellitus, BMI, HOMA-IR, aspartate aminotransferase (AST), alanine aminotransferase, serum glucose, and adiponectin levels were independently associated with hepatic fibrosis. In multivariate analysis, AST [OR = 1.082 (1.000-1.170)], age [OR = 1.119 (1.023-1.225)], and serum adiponectin levels [OR = 0.529 (0.299-0.936)] were significantly associated with the presence of liver fibrosis.

CONCLUSIONS

NAFLD patients have lower plasma adiponectin concentrations than control subjects. Low adiponectin levels are associated with more severe liver histology. Serum adiponectin may be useful to estimate the severity of liver damage in obese patients with NAFLD.