Adipokine serum levels are related to liver histology in severely obese patients undergoing bariatric surgery. Obes Surg. 2009;19:1313-1323. [PMID: 19693638 DOI: 10.1007/s11695-009-9912-9]

Deciphering endocrine function of adipose tissue and its significant influences in obesity-related diseases caused by its dysfunction

Current research has found that adipose tissue is not only involved in energy metabolism, but also a highly active endocrine organ that secretes various adipokines, including adiponectin, leptin, resistin and apelin, which are involved in the regulation of physiology and pathology of tissues and organs throughout the body. With the yearly increasing incidence, obesity has become a risk factor for a variety of pathological changes, including inflammation and metabolic syndrome in various system (endocrine, circulatory, locomotor and central nervous system). Thus these symptoms lead to multi-organ dysfunctions, including the heart, liver, kidneys, brain and joints. An in-depth summary of the roles of adipokines in the regulation of other tissues and organs can help to provide more effective therapeutic strategies for obesity-related diseases and explore potential therapeutic targets. Therefore, this review has retrospected the endocrine function of adipose tissue under obesity and the role of dysregulated adipokine secretion in related diseases and the underlying mechanisms, in order to provide a theoretical basis for targeting adipokine-mediated systemic dysregulation.

Advances in Noninvasive Biomarkers for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) currently represents one of the most common liver diseases worldwide. Early diagnosis and disease staging is crucial, since it is mainly asymptomatic, but can progress to nonalcoholic steatohepatitis (NASH) or cirrhosis or even lead to the development of hepatocellular carcinoma. Over time, efforts have been put into developing noninvasive diagnostic and staging methods in order to replace the use of a liver biopsy. The noninvasive methods used include imaging techniques that measure liver stiffness and biological markers, with a focus on serum biomarkers. Due to the impressive complexity of the NAFLD's pathophysiology, biomarkers are able to assay different processes involved, such as apoptosis, fibrogenesis, and inflammation, or even address the genetic background and "omics" technologies. This article reviews not only the currently validated noninvasive methods to investigate NAFLD but also the promising results regarding recently discovered biomarkers, including biomarker panels and the combination of the currently validated evaluation methods and serum markers.

RESISTIN GENE POLYMORPHISM AND NONALCOHOLIC FATTY LIVER DISEASE RISK

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease and one of the main global health issues in which liver fat surpasses 5% of hepatocytes without the secondary causes of lipid accumulation or excessive alcohol consumption. Owing to the link between NAFLD and insulin resistance (IR) and obesity and the role of resistin in theses metabolic disorders, we explored the possible association between resistin gene (RETN) variant and NAFLD.

METHODS

A total of 308 unrelated subjects, including 152 patients with biopsy-proven NAFLD and 156 controls were enrolled and genotyped for the RETN gene rs3745367 variant using PCR-RFLP method.

RESULTS

NAFLD patients had higher liver enzymes, systolic blood pressure (SBP), and diastolic blood pressure (DBP) than the controls (P<0.001). However, we observed no significant difference in genotype and allele frequencies between the cases with NAFLD and the controls for the RETN rs3745367 polymorphism either before or after adjustment for confounding factors including age, BMI, sex, smoking status, SBP, and DBP.

CONCLUSION

To our knowledge, this study is the first one that investigated the association between RETN gene rs3745367 variant and biopsy-proven NAFLD. Our findings do not support a role for this gene polymorphism in NAFLD risk in Iranian population; nonetheless, they need to be further investigated in other populations.

Adipokines in Non-Alcoholic Fatty Liver Disease: Are We on the Road toward New Biomarkers and Therapeutic Targets?

Simple Summary

Non-alcoholic fatty liver disease (NAFLD) is an unmet medical need due to its increasingly high incidence, severe clinical consequences, and the absence of feasible diagnostic tools and effective drugs. This review summarizes the preclinical and clinical data on adipokines, cytokine-like hormones secreted by adipose tissue, and NAFLD. The aim is to establish the potential of adipokines as diagnostic and prognostic biomarkers, as well as their potential as therapeutic targets for NAFLD. The limitations of current research are also discussed, and future perspectives are outlined.

Abstract

Non-alcoholic fatty liver disease (NAFLD) has become the major cause of chronic hepatic illness and the leading indication for liver transplantation in the future decades. NAFLD is also commonly associated with other high-incident non-communicable diseases, such as cardiovascular complications, type 2 diabetes, and chronic kidney disease. Aggravating the socio-economic impact of this complex pathology, routinely feasible diagnostic methodologies and effective drugs for NAFLD management are unavailable. The pathophysiology of NAFLD, recently defined as metabolic associated fatty liver disease (MAFLD), is correlated with abnormal adipose tissue–liver axis communication because obesity-associated white adipose tissue (WAT) inflammation and metabolic dysfunction prompt hepatic insulin resistance (IR), lipid accumulation (steatosis), non-alcoholic steatohepatitis (NASH), and fibrosis. Accumulating evidence links adipokines, cytokine-like hormones secreted by adipose tissue that have immunometabolic activity, with NAFLD pathogenesis and progression; however, much uncertainty still exists. Here, the current knowledge on the roles of leptin, adiponectin, ghrelin, resistin, retinol-binding protein 4 (RBP4), visfatin, chemerin, and adipocyte fatty-acid-binding protein (AFABP) in NAFLD, taken from preclinical to clinical studies, is overviewed. The effect of therapeutic interventions on adipokines’ circulating levels are also covered. Finally, future directions to address the potential of adipokines as therapeutic targets and disease biomarkers for NAFLD are discussed.

Serum Resistin Levels in Adult Patients with Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

Previous studies reported that serum resistin levels were remarkably changed in patients with nonalcoholic fatty liver disease (NAFLD) but the conclusions were inconsistent. The aim of this study was to investigate accurate serum resistin levels in adult patients with NAFLD.

METHODS

A complete literature research was conducted in the PubMed, Embase, and Cochrane Library databases, and all the available studies up to 7 May 2020 were reviewed. The pooled standardized mean difference (SMD) values were calculated to investigate the serum resistin levels in patients with NAFLD and healthy controls.

RESULTS

A total of 28 studies were included to investigate the serum resistin levels in patients with NAFLD. Patients with NAFLD had higher serum resistin levels than controls (SMD=0.522, 95% confidence interval [CI]: 0.004-1.040, I ²=95.9%). Patients with nonalcoholic steatohepatitis (NASH) had lower serum resistin levels than the healthy controls (SMD=-0.44, 95% CI: -0.83-0.55, I ²=74.5%). In addition, no significant difference of serum resistin levels was observed between patients with NAFL and healthy controls (SMD=-0.34, 95% CI: -0.91-0.23, I ²=79.6%) and between patients with NAFL and NASH (SMD=0.15, 95% CI: -0.06-0.36, I ²=0.00%). Furthermore, subgroup and sensitivity analyses suggested that heterogeneity did not affect the results of meta-analysis.

CONCLUSIONS

This meta-analysis investigated the serum resistin levels in adult patients with NAFLD comprehensively. Patients with NAFLD had higher serum resistin levels and patients with NASH had lower serum resistin levels than healthy controls. Serum resistin could serve as a potential biomarker to predict the development risk of NAFLD.

Women Have a Lower Risk of Nonalcoholic Fatty Liver Disease but a Higher Risk of Progression vs Men: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

The risk of nonalcoholic fatty liver disease (NAFLD) and its progression may differ between men and women. We conducted a systematic review and meta-analysis to determine the relationship between sex and NAFLD, nonalcoholic steatohepatitis (NASH), and advanced NAFLD fibrosis.

METHODS

Studies reporting sex-stratified NAFLD prevalence among population-based samples and either NASH or advanced fibrosis among patients with biopsy-proven NAFLD were identified from MEDLINE, EMBASE, and Cochrane databases through December 2017. We calculated pooled relative risk ratios comparing women vs men for each outcome.

RESULTS

Our final analysis comprised 54 studies. Samples sizes were 62,239 for the NAFLD analysis, 5428 for the NASH analysis, and 6444 for the advanced fibrosis analysis. Women had a 19% lower risk of NAFLD than men in the general population (pooled risk ratio [RR], 0.81; 95% CI, 0.68-0.97; I² = 97.5%). Women had a similar risk of NASH (RR, 1.00; 95% CI, 0.88-1.14; I² = 85.1%), and a 37% higher risk of advanced fibrosis (RR, 1.37; 95% CI, 1.12-1.68; I² = 74.0%) than men. Age modified the effect of sex on NAFLD severity. Risks of NASH (RR, 1.17; 95% CI, 1.01-1.36) and advanced fibrosis (RR, 1.56; 95% CI, 1.36-1.80; I² = 0) were substantially higher in women in study populations with average ages of 50 years and older; sex differences in NASH and advanced fibrosis were attenuated in younger populations.

CONCLUSIONS

In a systematic review and meta-analysis, we found women to have a lower risk of NAFLD than men. However, once NAFLD is established, women have a higher risk of advanced fibrosis than men, especially after age 50 years.

Hepatic Lipidomics and Molecular Imaging in a Murine Non-Alcoholic Fatty Liver Disease Model: Insights into Molecular Mechanisms

An imbalance between hepatic fatty acid uptake and removal results in ectopic fat accumulation, which leads to non-alcoholic fatty liver disease (NAFLD). The amount and type of accumulated triglycerides seem to play roles in NAFLD progression; however, a complete understanding of how triglycerides contribute to NAFLD evolution is lacking. Our aim was to evaluate triglyceride accumulation in NAFLD in a murine model and its associations with molecular mechanisms involved in liver damage and adipose tissue-liver cross talk by employing lipidomic and molecular imaging techniques. C57BL/6J mice fed a high-fat diet (HFD) for 12 weeks were used as a NAFLD model. Standard-diet (STD)-fed animals were used as controls. Standard liver pathology was assessed using conventional techniques. The liver lipidome was analyzed by liquid chromatography–mass spectrometry (LC–MS) and laser desorption/ionization–mass spectrometry (LDI–MS) tissue imaging. Liver triglycerides were identified by MS/MS. The transcriptome of genes involved in intracellular lipid metabolism and inflammation was assessed by RT-PCR. Plasma leptin, resistin, adiponectin, and FABP4 levels were determined using commercial kits. HFD-fed mice displayed increased liver lipid content. LC–MS analyses identified 14 triglyceride types that were upregulated in livers from HFD-fed animals. Among these 14 types, 10 were identified in liver cross sections by LDI–MS tissue imaging. The accumulation of these triglycerides was associated with the upregulation of lipogenesis and inflammatory genes and the downregulation of β-oxidation genes. Interestingly, the levels of plasma FABP4, but not of other adipokines, were positively associated with 8 of these triglycerides in HFD-fed mice but not in STD-fed mice. Our findings suggest a putative role of FABP4 in the liver-adipose tissue cross talk in NAFLD.

Leptin/adiponectin ratio correlates with hepatic steatosis but not arterial stiffness in nonalcoholic fatty liver disease in Japanese population

BACKGROUND AND AIMS

Cardiovascular disease (CVD) is a leading cause of mortality in nonalcoholic fatty liver disease (NAFLD). The aim of this study was to investigate the relationship of leptin-to-adiponectin (L/A) ratio with hepatic steatosis and arterial stiffness in NAFLD.

METHODS

The subjects were 871 Japanese adults who participated in a health survey. Dietary intake, body composition, lipid profile, serum interleukin-6 (IL-6), leptin, and adiponectin were analyzed. NAFLD was defined as fatty liver on ultrasonography in the absence of other causes of steatosis. Arterial stiffness was evaluated by the brachial-ankle pulse wave velocity (baPWV).

RESULTS

The subjects with NAFLD had a greater body mass index (BMI) and body fat percentage (BFP); a higher intake of daily energy (kcal) and carbohydrates; and a higher prevalence of hypertension, diabetes, and hyperlipidemia. The subjects with NAFLD had higher serum leptin and lower serum adiponectin concentrations and a higher L/A ratio than subjects without NAFLD. The L/A ratio increased with increasing severity of steatosis. The L/A ratio showed positive correlations with BMI and BFP, and a negative correlation with age. Women had higher L/A ratio and BFP levels than men regardless of the presence or absence of NAFLD. There was a weak positive correlation between baPWV and severity of steatosis. BaPWV was strongly correlated with age, while no relation was found between baPWV and L/A ratio. IL-6 level was correlated with baPVW and age, while the correlation between Il and 6 level and L/A ratio was very weak. The L/A ratio was correlated with triglycerides and the ratio of total cholesterol to high-density lipoprotein-cholesterol.

CONCLUSION

L/A ratio and arterial stiffness were associated with the severity of steatosis, whereas there was no correlation between L/A ratio and arterial stiffness in NAFLD. These findings suggest that not only leptin and adiponectin but also other factors might be involved in the pathogenesis for atherosclerosis in NAFLD.

Adiponectin and the steatosis marker Chi3L1 decrease following switch to raltegravir compared to continued PI/NNRTI-based antiretroviral therapy

BACKGROUND

People with HIV are at for metabolic syndrome (MetS) and fatty liver disease, but the role of Antiretroviral therapy (ART) is poorly understood. MetS and fatty liver disease been associated with changes in adiponectin, soluble ST2 (sST2), chitinase 3-like 1 (Chi3L1), hyaluronic acid (HA), tissue inhibitor of metalloproteinase-1 (TIMP-1), lysyl oxidase-like-2 (LOXL2) and transforming growth factor β (TGF-β) concentrations in HIV-uninfected populations. Protease (PI) and non-nucleoside reverse transcriptase inhibitors (NNRTI) may contribute to these comorbidities, but the effects of switching from PI- or NNRTI to raltegravir (RAL) on these biomarkers is unknown.

METHODS

Cryopreserved plasma was obtained from a completed, prospective trial of HIV-infected women with central adiposity on NNRTI- or PI-based ART during which they were randomized to remain on their current ART or switch to a RAL based regimen. Biomarker concentrations were quantified using ELISA and Multiplex assays at baseline and 24 weeks after randomization. Wilcoxon-signed rank test evaluated within-group changes, Spearman and linear regression models evaluated correlations between biomarkers and clinical covariates.

RESULTS

Participants had a median age of 43 years, CD4+ T lymphocyte count 558 cells/mm3 and BMI 32 kg/m2; 35% met criteria for MetS. At baseline, higher adiponectin levels correlated with higher Chi3L1 levels (r = 0.42, p = 0.02), as did declines after 24 weeks (r = 0.40, p = 0.03). Changes in sST2 correlated with changes in Chi3L1 (r = 0.43, p = 0.02) and adiponectin (r = 0.40, p = 0.03). Adiponectin and Chi3L1 levels decreased significantly in women switched to RAL vs continue PI/NNRTI.

CONCLUSION

In women with HIV and central obesity, the hepatic steatosis/fibrosis marker Chi3L1 and adiponectin decrease in conjunction with sST2 decreases following switch to RAL. Whether switching from NNRTI/PI-based regimens to RAL can improve hepatic steatosis and dysmetabolism requires further study.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00656175.

Association of Adipokines with Development and Progression of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting 30% of the general population and 40% to 70% of obese individuals. Adipose tissue plays a crucial role in its pathogenesis, as it produces and secretes pro- and anti-inflammatory cytokines called adipokines. Adiponectin and leptin have well-determined actions in terms of NAFLD pathophysiology. Adiponectin deficiency is associated with a pro-inflammatory condition, as it is observed in obesity and other metabolic disorders. On the other hand, increased leptin levels, above the normal levels, act as a pro-inflammatory stimulus. Regarding other adipokines (resistin, visfatin, chemerin, retinol-binding protein 4, irisin), data about their contribution to NAFLD pathogenesis and progression are inconclusive. In addition, pharmacological agents like thiazolidinediones (pioglitazone and rosiglitazone), that are used in the management of NAFLD exert favourable effects on adipokine levels, which in turn may contribute to the improvement of liver function. This review summarizes the current knowledge and developments in the association between adipokines and NAFLD and discusses possible therapeutic implications targeting the modulation of adipokine levels as a potential tool for the treatment of NAFLD.

Adipokines and Non-Alcoholic Fatty Liver Disease: Multiple Interactions

Accumulating evidence links obesity with low-grade inflammation which may originate from adipose tissue that secretes a plethora of pro- and anti-inflammatory cytokines termed adipokines. Adiponectin and leptin have evolved as crucial signals in many obesity-related pathologies including non-alcoholic fatty liver disease (NAFLD). Whereas adiponectin deficiency might be critically involved in the pro-inflammatory state associated with obesity and related disorders, overproduction of leptin, a rather pro-inflammatory mediator, is considered of equal relevance. An imbalanced adipokine profile in obesity consecutively contributes to metabolic inflammation in NAFLD, which is associated with a substantial risk for developing hepatocellular carcinoma (HCC) also in the non-cirrhotic stage of disease. Both adiponectin and leptin have been related to liver tumorigenesis especially in preclinical models. This review covers recent advances in our understanding of some adipokines in NAFLD and associated HCC.

Adipokines in nonalcoholic fatty liver disease

Since the discovery of adipose tissue as a higly active endocrine tissue, adipokines, peptides produced by adipose tissue and exerting autocrine, paracrine and endocrine function, have gained increasing interest in various obesity-related diseases, including nonalcoholic fatty liver disease (NAFLD). Data regarding the association between NAFLD and circulating leptin and adiponectin levels are generally well documented: leptin levels increase, whereas adiponectin levels decrease, by increasing the severity of NAFLD. Data regarding other adipokines in histologically confirmed NAFLD populations are inconclusive (e.g., resistin, visfatin, retinol-binding protein-4, chemerin) or limited (e.g., adipsin, obestatin, omentin, vaspin etc.). This review summarizes evidence on the association between adipokines and NAFLD. The first part of the review provides general consideration on the interplay between adipokines and NAFLD, and the second part provides evidence on specific adipokines possibly involved in NAFLD pathogenesis. A thorough insight into the pathophysiologic mechanisms linking adipokines with NAFLD may result in the design of studies investigating the combined adipokine use as noninvasive diagnostic markers of NAFLD and new clinical trials targeting the treatment of NAFLD.

Effect of two polymorphisms of the resistin gene (rs10401670 and rs1862513) on resistin levels and biochemical parameters in morbidly obese patients 1 year after a biliopancreatic diversion surgery

BACKGROUND & AIMS

Two single nucleotide polymorphisms (SNPs) of the resistin gene RETN have been described: rs10401670 and rs1862513. The objective of this study was to investigate the effect of these SNPs on changes in serum resistin levels, biochemical parameters and weight after biliopancreatic diversion surgery in morbidly obese patients without diabetes mellitus.

METHODS

A sample of 155 patients with morbid obesity without diabetes mellitus was enrolled. Anthropometric and biochemical evaluations were realized at the basal visit and at 12 months. The percentage of subjects with hypertension and hyperlipidemia was also reported.

RESULTS

Initial percentage excess weight loss, body mass index, weight, waist circumference, fat mass, blood pressure, low-density lipoprotein cholesterol, total cholesterol, triglycerides levels, insulin and the homeostasis model assessment for insulin sensitivity (HOMA-IR) improve after 12 months. No differences in these improvements were detected between the two genotypes (wild vs mutant group) in each SNP analysis. Resistin levels only changed after surgery in wild genotypes of both SNPs (rs1862513 and rs10401670). The improvement in insulin levels was lower in the mutant group of rs1862513 (-3.4 ± 0.4 UI/dl vs -2.3 ± 0.2 UI/dl; P < 0.05) and rs1040167 (-3.3 ± 0.2 UI/dl vs -1.9 ± 0.3 UI/dl; P < 0.05). The decrease of HOMA-IR was lower in mutant group of rs1862513 (-1.4 ± 0.1 units vs -0.9 ± 0.3 units; P < 0.05) and rs10401670 (-1.2 ± 0.2 units vs -0.9 ± 0.3 units; P < 0.05).

CONCLUSIONS

The main result of this study was that the mutant genotype of two SNPs of the RETN gene (rs1862513 and rs10401670) was associated with a lack of change in resistin secondary to biliopancreatic diversion. The improvement in insulin levels and HOMA-IR was also lower in these patients.

Association of recently described adipokines with liver histology in biopsy-proven non-alcoholic fatty liver disease: a systematic review

The prevalence of non-alcoholic fatty liver disease (NAFLD) is rising, as is the prevalence of obesity and type 2 diabetes. It is increasingly recognized that an impaired pattern in adipokine secretion could play a pivotal role in the development of NAFLD. We performed a systematic review to evaluate the potential link between newly described adipokines and liver histology in biopsy-proven NAFLD patients. A computerized literature search was performed in PubMed, EMBASE and Web of Science electronic databases. Thirty-one cross-sectional studies were included, resulting in a total of seven different investigated adipokines. Studies included in this review mainly had a good methodological quality. Most adipokines were suggested to be involved in the inflammatory response that develops within the context of NAFLD, either at hepatic or systemic level, and/or hepatic insulin resistance. Based on literature, clinical studies suggest that chemerin, resistin and adipocyte-fatty-acid-binding protein potentially are involved in NAFLD pathogenesis and/or progression. However, major inconsistency still exists, and there is a high need for larger studies, together with the need of standardized assays to determine adipokine levels.

Circulating leptin in non-alcoholic fatty liver disease: a systematic review and meta-analysis

AIMS/HYPOTHESIS

Clinical data regarding circulating leptin levels in patients with non-alcoholic fatty liver disease (NAFLD) are conflicting. The purpose of this meta-analysis was to compare leptin levels between the following groups: patients with biopsy-proven NAFLD vs controls; simple steatosis (SS) patients vs controls; non-alcoholic steatohepatitis (NASH) patients vs controls and NASH patients vs SS patients.

METHODS

We performed a systematic search in PubMed, Scopus and the Cochrane Library. We analysed 33 studies, published between 1999 and 2014, including 2,612 individuals (775 controls and 1,837 NAFLD patients).

RESULTS

Higher circulating leptin levels were observed in NAFLD patients vs controls (standardised mean difference [SMD] 0.640; 95% CI 0.422, 0.858), SS patients vs controls (SMD 0.358; 95% CI 0.043, 0.673), NASH patients vs controls (SMD 0.617; 95% CI 0.403, 0.832) and NASH patients vs SS patients (SMD 0.209; 95% CI 0.023, 0.395). These results remained essentially unchanged after excluding studies involving paediatric or adolescent populations and/or individuals undergoing bariatric surgery. There was moderate-to-severe heterogeneity among studies in all comparisons, but no significant publication bias was detected. Meta-regression analysis demonstrated that BMI was inversely associated with leptin SMD and accounted for 26.5% (p = 0.014) and 32.7% (p = 0.021) of the between-study variance in the comparison between NASH patients and controls and NAFLD patients and controls, respectively. However, when bariatric studies were excluded, BMI did not significantly explain the between-study variance.

CONCLUSIONS/INTERPRETATION

Circulating leptin levels were higher in patients with NAFLD than in controls. Higher levels of circulating leptin were associated with increased severity of NAFLD, and the association remained significant after the exclusion of studies involving paediatric or adolescent populations and morbidly obese individuals subjected to bariatric surgery.

Novel therapeutic targets for steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the Western hemisphere and is growing as an indication for liver transplantation. There are currently no approved therapies for NAFLD, especially its aggressive phenotype non-alcoholic steatohepatitis (NASH). However, there has been an explosion of information related to NASH that provides detailed data on the molecular pathogenesis of NASH and its progression to cirrhosis. The current review summarizes the pathophysiological rationale for the selection of specific targets for the treatment of NASH and provides an overview of the current strategies being used for the treatment of NASH and the pathophysiological rationale for the use of these strategies. Specifically, those targets that are being studied in both alcoholic and non-alcoholic steatohepatitis are also mentioned.

A genetic risk score is associated with hepatic triglyceride content and non-alcoholic steatohepatitis in Mexicans with morbid obesity

BACKGROUND AND AIMS

Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) near/in PNPLA3, NCAN, LYPLAL1, PPP1R3B, and GCKR genes associated with non-alcoholic fatty liver disease (NAFLD) mainly in individuals of European ancestry. The aim of the study was to test whether these genetic variants and a genetic risk score (GRS) are associated with elevated liver fat content and non-alcoholic steatohepatitis (NASH) in Mexicans with morbid obesity.

METHODS

130 morbidly obese Mexican individuals were genotyped for six SNPs in/near PNPLA3, NCAN, LYPLAL1, PPP1R3B, and GCKR genes. Hepatic fat content [triglyceride (HTG) and total cholesterol (HTC)] was quantified directly in liver biopsies and NASH was diagnosed by histology. A GRS was tested for association with liver fat content and NASH using logistic regression models. In addition, 95 ancestry-informative markers were genotyped to estimate population admixture proportions.

RESULTS

After adjusting for age, sex and admixture, PNPLA3, LYPLAL1, GCKR and PPP1R3B polymorphisms were associated with higher HTG content (P < 0.05 for PNPLA3, LYPLAL1, GCKR polymorphisms and P = 0.086 for PPP1R3B). The GRS was significantly associated with higher HTG and HTC content (P = 1.0 × 10(-4) and 0.048, respectively), steatosis stage (P = 0.029), and higher ALT levels (P = 0.002). Subjects with GRS ≥ 6 showed a significantly increased risk of NASH (OR = 2.55, P = 0.045) compared to those with GRS ≤ 5. However, the GRS did not predict NASH status, as AUC of ROC curves was 0.56 (P = 0.219).

CONCLUSION

NAFLD associated loci in Europeans and a GRS based on these loci contribute to the accumulation of hepatic lipids and NASH in morbidly obese Mexican individuals.

Leptin in nonalcoholic fatty liver disease: a narrative review

Leptin, the first described adipokine, interplays with hepatic metabolism. The aim of this review was to summarize available data on the association between leptin and nonalcoholic fatty liver disease (NAFLD). Leptin has a potential dual action on NAFLD experimental models, exerting a possible anti-steatotic, but also a proinflammatory and profibrogenic action. Observational clinical studies have shown higher or similar leptin levels between simple steatosis and nonalcoholic steatohepatitis (NASH) compared with controls. Interventional studies showed that circulating leptin diminishes together with body mass index after successful weight loss following lifestyle modifications or bariatric surgery. Studies providing evidence for the effect of other medications on leptin levels in NAFLD populations are limited and of low power. Data from small studies claim that recombinant leptin administration had a possibly beneficial effect on steatosis, but not fibrosis, in NAFLD patients with hypoleptinemia. Although the aforementioned dual leptin action has not yet been validated in humans, leptin administration in NAFLD patients with normoleptinemia or hyperleptinemia is discouraged. Further well-controlled studies in cautiously selected populations are needed to elucidate whether leptin has any prognostic and therapeutic role in NAFLD patients.

Multiple hits, including oxidative stress, as pathogenesis and treatment target in non-alcoholic steatohepatitis (NASH)

Multiple parallel hits, including genetic differences, insulin resistance and intestinal microbiota, account for the progression of non-alcoholic steatohepatitis (NASH). Multiple hits induce adipokine secretion, endoplasmic reticulum (ER) and oxidative stress at the cellular level that subsequently induce hepatic steatosis, inflammation and fibrosis, among which oxidative stress is considered a key contributor to progression from simple fatty liver to NASH. Although several clinical trials have shown that anti-oxidative therapy can effectively control hepatitis activities in the short term, the long-term effect remains obscure. Several trials of long-term anti-oxidant protocols aimed at treating cerebrovascular diseases or cancer development have failed to produce a benefit. This might be explained by the non-selective anti-oxidative properties of these drugs. Molecular hydrogen is an effective antioxidant that reduces only cytotoxic reactive oxygen species (ROS) and several diseases associated with oxidative stress are sensitive to hydrogen. The progress of NASH to hepatocellular carcinoma can be controlled using hydrogen-rich water. Thus, targeting mitochondrial oxidative stress might be a good candidate for NASH treatment. Long term clinical intervention is needed to control this complex lifestyle-related disease.

The inhibitory effect of black soybean on hepatic cholesterol accumulation in high cholesterol and high fat diet-induced non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is defined as excess of fat in the liver. We investigated the effects of black soybean on the cholesterol metabolism and insulin resistance of mice fed high cholesterol/fat diets. Mice were randomly allocated into four groups that were fed different diets: the normal cholesterol/fat diet; high cholesterol/fat diets (HCD); and HCD with 1%, and 4% black soybean powder (1B-HCD, and 4B-HCD). Liver total cholesterol and triglyceride concentrations were significantly lower in the black soybean-supplemented groups than that in the HCD group. PCR revealed significantly lower hepatic SREBP2 and HMG-CoA reductase mRNA levels of black soybean-supplemented mice. Real-time PCR revealed significantly higher hepatic ABCA1 mRNA level of black soybean-supplemented mice, which may increase cholesterol efflux. Liver bile acids concentration was significantly high in the 4B-HCD group. Black soybean stimulated secretion of adiponectin, activation of pAMPK, and eliminated free fatty acids in the liver. Black soybean supplementation decreased MDA and nitrate level. The activities of SOD, catalase, and GPx were restored by black soybean supplementation. Our data strongly indicate that black soybean influences the balance between oxidative and antioxidative stress. We suggest that black soybean improves cholesterol metabolism, insulin resistance, and alleviates oxidative damage in NAFLD.

Leptin's role in lipodystrophic and nonlipodystrophic insulin-resistant and diabetic individuals

Leptin is an adipocyte-secreted hormone that has been proposed to regulate energy homeostasis as well as metabolic, reproductive, neuroendocrine, and immune functions. In the context of open-label uncontrolled studies, leptin administration has demonstrated insulin-sensitizing effects in patients with congenital lipodystrophy associated with relative leptin deficiency. Leptin administration has also been shown to decrease central fat mass and improve insulin sensitivity and fasting insulin and glucose levels in HIV-infected patients with highly active antiretroviral therapy (HAART)-induced lipodystrophy, insulin resistance, and leptin deficiency. On the contrary, the effects of leptin treatment in leptin-replete or hyperleptinemic obese individuals with glucose intolerance and diabetes mellitus have been minimal or null, presumably due to leptin tolerance or resistance that impairs leptin action. Similarly, experimental evidence suggests a null or a possibly adverse role of leptin treatment in nonlipodystrophic patients with nonalcoholic fatty liver disease. In this review, we present a description of leptin biology and signaling; we summarize leptin's contribution to glucose metabolism in animals and humans in vitro, ex vivo, and in vivo; and we provide insights into the emerging clinical applications and therapeutic uses of leptin in humans with lipodystrophy and/or diabetes.

Adiponectin negatively correlates with alcoholic and non-alcoholic liver dysfunction: Health check-up study of Japanese men

AIM

  Central obesity, insulin resistance and alcohol consumption are thought to be major risk factors for fatty liver formation. Adiponectin (APN) prevents fatty liver formation, and its serum levels are lower in subjects with central obesity and/or insulin resistance. The aim of this study was to explore the association among serum APN levels, central obesity, insulin resistance and liver dysfunction with or without fatty liver classified by alcohol consumption in healthy subjects.

METHODS

  A total of 5588 Japanese male subjects who underwent a health check-up were classified into three groups according to alcohol consumption: non- or light drinkers (15 g/day ≥ ethanol); mild drinkers (15 g/day < ethanol ≤ 30 g/day); and moderate- or heavy drinkers (30 g/day < ethanol). Central obesity and insulin resistance were assessed by waist circumference (WC) and Homeostasis Model of Assessment - Insulin Resistance (HOMA-IR), respectively.

RESULTS

  WC was significantly increased, while HOMA-IR was significantly decreased according to the extent of alcohol consumption. Serum alanine aminotransferase levels were significantly lower and serum APN levels were significantly higher in mild drinkers than in the other two groups. Multiple linear regression analysis showed that serum APN level served as the significant and independent determinant for liver dysfunction in the subjects with fatty liver, irrespective of alcohol consumption. However, WC became a non-significant determinant of liver dysfunction as alcohol consumption increased.

CONCLUSION

  Hypoadiponectinemia is a significant determinant for steatotic dysfunction for all levels of alcohol consumption, but central obesity was not a significant determinant for alcoholic fatty liver-induced liver dysfunction.

How adiponectin, leptin, and ghrelin orchestrate together and correlate with the severity of nonalcoholic fatty liver disease

BACKGROUND

Adipose tissue contributes to nonalcoholic fatty liver disease (NAFLD), being a source of fatty acids and cytokines such as leptin and adiponectin, and regulating ghrelin production. Their role in NAFLD pathogenesis remains controversial. We aimed to study the influence of those cytokines on the severity of NAFLD.

METHODS

Morbidly obese individuals with biopsy-proven NAFLD were recruited. The NAFLD activity score was applied to liver histology. Serum concentrations of adiponectin, leptin, and ghrelin were determined.

RESULTS

Eighty-two patients were included, 13% with nonalcoholic steatohepatitis (NASH). Hypertriglyceridemia (P=0.018) and metabolic syndrome (P=0.040) were independent factors associated with NASH. Leptin associated positively and ghrelin associated negatively with BMI; adiponectin associated negatively with the waist to hip ratio. Adiponectin associated negatively with insulin resistance, hypertension, and metabolic syndrome; ghrelin associated positively with diabetes mellitus. Adiponectin below 23 ng/ml associated with NASH (odds ratio 12.95, P<0.001). Leptin increased progressively (P=0.032) and adiponectin decreased (P=0.004) with increasing severity of steatosis. Also, leptin increased progressively with more severe fibrosis (P=0.053). A formula incorporating the three cytokines yielded an AUROC of 0.789 (P=0.002), a sensitivity of 81.8%, and a specificity of 76.1% for NASH.

CONCLUSION

An imbalance in adiponectin, leptin, and ghrelin seems to be associated with more severe NAFLD. A formula combining the three cytokines showed good accuracy for NASH.

Diagnosis and evaluation of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of elevated liver function tests results, after the commonly investigated causes have been excluded, and frequently coexists with type 2 diabetes mellitus (T2DM) because the conditions have common risk factors. As both T2DM and NAFLD are related to adverse outcomes of the other, diagnosis and valuation of fatty liver is an important part of the management of diabetes. Although noninvasive methods, such as biomarkers, panel markers, and imaging, may support a diagnostic evaluation of NAFLD patients, accurate histopathological findings cannot be achieved without a liver biopsy. As it is important to know whether steatohepatitis and liver fibrosis are present for the management of NAFLD, liver biopsy remains the gold standard for NAFLD diagnosis and evaluation. Therefore, new investigations of the pathogenesis of NAFLD are necessary to develop useful biomarkers that could provide a reliable noninvasive alternative to liver biopsy.

Serum total adiponectin in nonalcoholic fatty liver disease: a systematic review and meta-analysis

Hypoadiponectinemia might represent a risk factor for nonalcoholic fatty liver disease (NAFLD). We performed a systematic review and meta-analysis to evaluate the serum total adiponectin levels in patients with simple nonalcoholic fatty liver (NAFL), those with nonalcoholic steatohepatitis (NASH), and controls. Data were extracted from PubMed, EMBASE, and Cochrane Central Register of Controlled Trials electronic databases (up to December 2009). The main outcome was the weighted mean differences (WMDs) in adiponectin between comparison groups. Twenty-eight studies were included in the systematic review. A meta-analysis of 27 studies that reported data on 2243 subjects (698 controls and 1545 patients with NAFLD) was performed. Controls had higher serum adiponectin compared with NAFL patients (12 studies, random-effects WMD [95% confidence interval {CI}] = 3.00 [1.57-4.43], I² = 80.4%) or NASH patients (19 studies, random-effects WMD [95% CI] = 4.75 [3.71-5.78], I² = 84.1%). The NASH patients demonstrated lower adiponectin compared with NAFL patients (19 studies, random-effects WMD [95% CI] = 1.81 [1.09-2.53], I² = 71.7%). By performing a meta-regression analysis, body mass index, age, sex, and type 2 diabetes mellitus failed to account for heterogeneity. However, the performance of liver biopsy on controls had significant effect on the outcome and accounted for 76.7%, 85.5%, and 22.8% of the between-study variance for comparisons between controls vs NAFLD, NAFL, and NASH patients, respectively. Based on liver histology, serum adiponectin levels are similar in NAFL patients and controls, but hypoadiponectinemia may play an important pathophysiological role in the progression from NAFL to NASH.

Systematic review: the diagnosis and staging of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has become the most prevalent cause of liver disease in Western countries. The development of non-alcoholic steatohepatitis (NASH) and fibrosis identifies an at-risk group with increased risk of cardiovascular and liver-related deaths. The identification and management of this at-risk group remains a clinical challenge.

AIM

To perform a systematic review of the established and emerging strategies for the diagnosis and staging of NAFLD.

METHODS

Relevant research and review articles were identified by searching PubMed, MEDLINE and EMBASE.

RESULTS

There has been a substantial development of non-invasive risk scores, biomarker panels and radiological modalities to identify at-risk patients with NAFLD without recourse to liver biopsy on a routine basis. These modalities and algorithms have improved significantly in their diagnosis and staging of fibrosis and NASH in patients with NAFLD, and will likely impact on the number of patients undergoing liver biopsy.

CONCLUSIONS

Staging for NAFLD can now be performed by a combination of radiological and laboratory techniques, greatly reducing the requirement for invasive liver biopsy.

Non-invasive diagnosis of nonalcoholic fatty liver and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the USA and many other parts of the world. Its prevalence continues to rise; currently affecting about one in four adults and 10% of children in the USA. NAFLD represents a wide spectrum of conditions ranging from fatty liver, which in general follows a benign, no-progressive clinical course, to nonalcoholic steatohepatitis (NASH), a more serious form of NAFLD that may progress to cirrhosis and end-stage liver disease. Currently, the diagnosis of NASH requires an invasive liver biopsy with drawbacks of sampling and interpretation error. Clinical risk factors for NASH include diabetes and the metabolic syndrome; however, these are not sufficiently predictive of the condition by themselves. Routine liver enzyme levels are not reliable; however, novel plasma hepatocyte cell death markers either alone or in combination with clinical risk factors are potential non-invasive diagnostic tools for the future. This review provides a concise overview of the role non-invasive diagnostic tools for the differentiation of fatty liver from NASH as well as for the determination of presence and extent of fibrosis.

Increased soluble leptin receptor levels in morbidly obese patients with insulin resistance and nonalcoholic fatty liver disease

The adipocyte hormone, leptin has been demonstrated to have profibrogenic actions in vitro and in animal models. However, no correlation was found between plasma leptin levels and fibrosis stage in humans. Thus, our aim was to study whether soluble leptin receptor (SLR) or free leptin index (FLI; calculated as the ratio of leptin to SLR), may correlate better with the features of metabolic syndrome and with the histological grade and stage of nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH). We studied a population (n = 104) of morbidly obese patients undergoing bariatric surgery. Data including BMI, type 2 diabetes mellitus, hypertension, and hyperlipidemia were obtained. Plasma fasting leptin and SLR, fasting glucose and insulin were measured, and homeostasis model of assessment insulin resistance (HOMA(IR)) index and FLI were calculated. All patients had intraoperative liver biopsies. Leptin levels correlated with the BMI. The multiple regression analysis indicated that increasing HOMA and decreasing FLI were predictors of steatosis in the liver (P < 0.0003). SLR levels were positively correlated with the presence of diabetes mellitus and the stage of fibrosis. In conclusion, increased SLR levels in morbidly obese patients with diabetes are correlated with the stage of liver fibrosis, and may reflect progressive liver disease.

Nonalcoholic steatohepatitis: risk factors and diagnosis

Nonalcoholic steatohepatitis (NASH) represents the progressive form of nonalcoholic fatty liver disease with greater potential to lead to liver-related morbidity and mortality. Diagnosing NASH mandates more intensive clinical management and consideration for clinical trials. Currently, the diagnosis of NASH requires a liver biopsy, which is invasive, with drawbacks in sampling and interpretation error. Clinical risk factors for NASH include diabetes and the metabolic syndrome; however, these are not sufficiently predictive of the condition by themselves. Routine liver aminotransaminase levels are not reliable; however, novel plasma hepatocyte apoptosis markers, either alone or in combination with clinical risk factors, are potential noninvasive diagnostic tools for the future.

Advances in understanding the roles of leptin and adiponectin in the pathogenesis of chronic liver diseases

Leptin and adiponectin are adipokines that are abundantly expressed in adipose tissue and have multiple biological effects related to the development of human diseases. More and more studies have demonstrated that adipokines play important roles in the pathogenesis of steatosis, steatohepatitis and liver fibrosis, especially nonalcoholic fatty liver disease (NAFLD) and chronic hepatitis C (CHC). This paper reviews the recent advances in understanding the roles of leptin and adiponectin in the pathogenesis of liver diseases.

Chemerin correlates with markers for fatty liver in morbidly obese patients and strongly decreases after weight loss induced by bariatric surgery

CONTEXT

Chemerin is a new adipokine involved in in vitro adipogenesis and insulin resistance and associates with body mass index (BMI) in vivo.

OBJECTIVE

We investigated the role of chemerin in morbid obesity, associated metabolic diseases (insulin resistance, hepatic diseases), and postsurgery-induced weight loss.

SETTING

This was a prospective study performed at a university hospital.

SUBJECTS

Subjects included 60 obese female patients (BMI 50.0 +/- 1.0 kg/m(-2)) being candidates for gastric bypass.

STUDY DESIGN

Patients were examined before and 3, 6, and 12 months after surgery. In 27 patients, chemerin was measured after 2 yr.

MAIN OUTCOME

Outcomes included chemerin, anthropometric parameters, homeostasis model assessment for insulin resistance index (HOMA-IR), cholesterol, high-density lipoprotein, triglycerides, C-reactive protein, adipokines at all time points; and liver histology and macrophage content in fat at baseline.

RESULTS

Chemerin was substantially elevated in obese patients compared with nonobese persons (353.8 +/- 18.0 vs. 191 +/- 14 ng/ml, P < 0.001). Preoperatively, chemerin concentrations correlated positively with BMI, C-reactive protein, IL-6, HOMA-IR, and the amount of omental macrophages and negatively with high-density lipoprotein levels. Baseline chemerin was elevated in patients with a significant activity score for nonalcoholic fatty liver disease, portal inflammation, fibrosis, and fibroinflammation. After surgery, chemerin decreased significantly to 253.0 +/- 14.9 ng/ml after 1 yr and pursued its decrease in patients studied for 2 yr. After surgery, chemerin concentrations positively correlated with triglycerides. The strong decrease of chemerin in the 3 months after surgery was associated with the decrease in HOMA-IR and blood glucose.

CONCLUSIONS

Chemerin concentrations are elevated in morbidly obese patients and correlated with insulin resistance and markers of liver pathology. Chemerin plasma concentrations decreased after bariatric surgery. This study suggests that chemerin might mediate metabolic alterations in obesity, drastically improving after gastric bypass.

Leptin induces an inflammatory phenotype in lean Wistar rats

The present study addressed the hypothesis that leptin promotes leukocyte trafficking into adipose tissue. Accordingly, male Wistar rats were treated with saline or recombinant rat leptin (1 mg/kg) via the tail vein. Leukocyte trafficking in mesenteric venules was quantified by intravital microscopy. Treatment with leptin resulted in a 3- and 5-fold increases in rolling and firm adhesion, respectively. Compared to vehicle controls, leptin enhanced mRNA levels of IL-6 (8-fold) and MCP-1 (5-fold) in mesenteric adipose tissue (MAT). Similar increases in these markers were observed in mesenteric venules and in liver. Finally, the direct effect of leptin was assessed in C3A hepatocytes treated with leptin for 24 hours (7.8 ng/mL–125 ng/mL). Consistent with observations in vivo, production of ICAM-1, MCP-1, and IL-6 by hepatocytes was increased significantly. These findings support the hypothesis that leptin directly initiates inflammation in the local environment of mesenteric adipose tissue as well as systemically.