Serum adipokine and ghrelin levels in nonalcoholic steatohepatitis

Ghrelin regulating liver activity and its potential effects on liver fibrosis and Echinococcosis

Ghrelin widely exists in the central nervous system and peripheral organs, and has biological activities such as maintaining energy homeostasis, regulating lipid metabolism, cell proliferation, immune response, gastrointestinal physiological activities, cognition, memory, circadian rhythm and reward effects. In many benign liver diseases, it may play a hepatoprotective role against steatosis, chronic inflammation, oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress and apoptosis, and improve liver cell autophagy and immune response to improve disease progression. However, the role of Ghrelin in liver Echinococcosis is currently unclear. This review systematically summarizes the molecular mechanisms by which Ghrelin regulates liver growth metabolism, immune-inflammation, fibrogenesis, proliferation and apoptosis, as well as its protective effects in liver fibrosis diseases, and further proposes the role of Ghrelin in liver Echinococcosis infection. During the infectious process, it may promote the parasitism and survival of parasites on the host by improving the immune-inflammatory microenvironment and fibrosis state, thereby accelerating disease progression. However, there is currently a lack of targeted in vitro and in vivo experimental evidence for this viewpoint.

Role of the Ghrelin System in Colitis and Hepatitis as Risk Factors for Inflammatory-Related Cancers

It is not known exactly what leads to the development of colorectal cancer (CRC) and hepatocellular carcinoma (HCC), but there are specific risk factors that increase the probability of their occurrence. The unclear pathogenesis, too-late diagnosis, poor prognosis as a result of high recurrence and metastasis rates, and repeatedly ineffective therapy of both cancers continue to challenge both basic science and practical medicine. The ghrelin system, which is comprised of ghrelin and alternative peptides (e.g., obestatin), growth hormone secretagogue receptors (GHS-Rs), and ghrelin-O-acyl-transferase (GOAT), plays an important role in the physiology and pathology of the gastrointestinal (GI) tract. It promotes various physiological effects, including energy metabolism and amelioration of inflammation. The ghrelin system plays a role in the pathogenesis of inflammatory bowel diseases (IBDs), which are well known risk factors for the development of CRC, as well as inflammatory liver diseases which can trigger the development of HCC. Colitis-associated cancer serves as a prototype of inflammation-associated cancers. Little is known about the role of the ghrelin system in the mechanisms of transformation of chronic inflammation to low- and high-grade dysplasia, and, finally, to CRC. HCC is also associated with chronic inflammation and fibrosis arising from different etiologies, including alcoholic and nonalcoholic fatty liver diseases (NAFLD), and/or hepatitis B (HBV) and hepatitis C virus (HCV) infections. However, the exact role of ghrelin in the progression of the chronic inflammatory lesions into HCC is still unknown. The aim of this review is to summarize findings on the role of the ghrelin system in inflammatory bowel and liver diseases in order to better understand the impact of this system on the development of inflammatory-related cancers, namely CRC and HCC.

Circulating tumor necrosis factor-α levels in non-alcoholic fatty liver disease: A systematic review and a meta-analysis

BACKGROUND AND AIM

To synthesize data on circulating tumor necrosis factor (TNF)-α levels between patients with histologically confirmed non-alcoholic fatty liver disease (NAFLD) (simple steatosis or non-alcoholic fatty liver [NAFL] and/or non-alcoholic steatohepatitis [NASH]) and controls.

METHODS

We performed a systematic search in PubMed, Scopus, and Cochrane Library. Fifty-six studies, published between 2003 and 2019, were finally included, reporting data from 5848 individuals (1634 controls and 4214 NAFLD patients).

RESULTS

Higher circulating TNF-α levels were observed in NAFLD patients than controls (standardized mean difference [SMD] 0.84; 95% confidence interval [95% CI] 0.59-1.09), NAFL patients than controls (SMD 0.56; 95% CI 0.27-0.85), NASH patients than controls (SMD 0.93; 95% CI 0.64-1.22), and NASH than NAFL patients (SMD 0.31; 95% CI 0.16-0.46). There were only minimal changes in the comparisons between groups after excluding studies with morbidly obese populations (n = 11), or pediatric/adolescent populations (n = 6), or other than enzyme-linked immunosorbent assay method of TNF-α measurement (n = 8). There was high heterogeneity among studies in all comparisons, which was not essentially affected after sensitivity analyses. The meta-regression analysis revealed that the male ratio was positively associated with TNF-α SMD in the comparison between patients with NASH and NAFL (beta = 0.809; 95% CI 0.052-1.566) and accounted for 36% (P = 0.037) of the heterogeneity in this pair of comparison. TNF-α SMD was not associated with age, body mass index, and alanine aminotransferase in any pair of comparisons.

CONCLUSIONS

Circulating TNF-α levels were higher in patients with NAFLD compared with controls. Higher levels of circulating TNF-α were also associated with the severity of NAFLD.

Multidimensional Biomarker Analysis Including Mitochondrial Stress Indicators for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is accompanied by a complex and multifactorial pathogenesis with sequential progressions from inflammation to fibrosis and then to cancer. This heterogeneity interferes with the development of precise diagnostic and prognostic strategies for NAFLD. The current approach for the diagnosis of simple steatosis, steatohepatitis, and cirrhosis mainly consists of ultrasonography, magnetic resonance imaging, elastography, and various serological analyses. However, individual dry and wet biomarkers have limitations demanding an integrative approach for the assessment of disease progression. Here, we review diagnostic strategies for simple steatosis, steatohepatitis and hepatic fibrosis, followed by potential biomarkers associated with fat accumulation and mitochondrial stress. For mitochondrial stress indicators, we focused on fibroblast growth factor 21 (FGF21), growth differentiation factor 15 (GDF15), angiopoietin-related growth factor and mitochondrial-derived peptides. Each biomarker may not strongly indicate the severity of steatosis or steatohepatitis. Instead, multidimensional analysis of different groups of biomarkers based on pathogenic mechanisms may provide decisive diagnostic/prognostic information to develop a therapeutic plan for patients with NAFLD. For this purpose, mitochondrial stress indicators, such as FGF21 or GDF15, could be an important component in the multiplexed and contextual interpretation of NAFLD. Further validation of the integrative evaluation of mitochondrial stress indicators combined with other biomarkers is needed in the diagnosis/prognosis of NAFLD.

Pathophysiology of NAFLD and NASH in Experimental Models: The Role of Food Intake Regulating Peptides

Obesity, diabetes, insulin resistance, sedentary lifestyle, and Western diet are the key factors underlying non-alcoholic fatty liver disease (NAFLD), one of the most common liver diseases in developed countries. In many cases, NAFLD further progresses to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and to hepatocellular carcinoma. The hepatic lipotoxicity and non-liver factors, such as adipose tissue inflammation and gastrointestinal imbalances were linked to evolution of NAFLD. Nowadays, the degree of adipose tissue inflammation was shown to directly correlate with the severity of NAFLD. Consumption of higher caloric intake is increasingly emerging as a fuel of metabolic inflammation not only in obesity-related disorders but also NAFLD. However, multiple causes of NAFLD are the reason why the mechanisms of NAFLD progression to NASH are still not well understood. In this review, we explore the role of food intake regulating peptides in NAFLD and NASH mouse models. Leptin, an anorexigenic peptide, is involved in hepatic metabolism, and has an effect on NAFLD experimental models. Glucagon-like peptide-1 (GLP-1), another anorexigenic peptide, and GLP-1 receptor agonists (GLP-1R), represent potential therapeutic agents to prevent NAFLD progression to NASH. On the other hand, the deletion of ghrelin, an orexigenic peptide, prevents age-associated hepatic steatosis in mice. Because of the increasing incidence of NAFLD and NASH worldwide, the selection of appropriate animal models is important to clarify aspects of pathogenesis and progression in this field.

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.

Effect of Lactobacillus paracasei N1115 and fructooligosaccharides in nonalcoholic fatty liver disease

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is a growing health concern worldwide. Administration of probiotics and prebiotics has been proposed as a convenient and effective treatment. Our study aims to evaluate the therapeutic benefits of Lactobacillus paracasei N1115 (N1115) and fructooligosaccharides (FOS) by examining the histopathogenesis and underlying molecular events of NAFLD.

MATERIAL AND METHODS

An NAFLD mouse model was established by feeding C57BL/6 mice with a high-fat diet (HFD). N1115, FOS and synbiotics were administered for 16 weeks.

RESULTS

N1115, FOS and synbiotics alleviated HFD-induced hepatic steato-sis and release of tumor necrosis factor-α, and slowed the progression of cirrhosis. Compared to the HFD group, these dietary supplements reduced serum total triglyceride and cholesterol, and appeared to decrease the fasting blood glucose and insulin. Intraperitoneal glucose tolerance tests, homeostatic model assessment of insulin resistance and real-time PCR showed that the regimens could overcome insulin resistance. These findings were associated with the transcriptional repression of inflammatory factors such as lipopolysaccharides, Toll-like receptor 4 and nuclear factor-κB. Lastly, N1115, FOS, and synbiotics improved the intestinal barrier functions and histologic integrity. This was accompanied by the restoration of the p38 MAPK pathway and in-creased expression of the tight junction components occludin-1 and claudin-1.

CONCLUSIONS

N1115, FOS and synbiotics are effective in the prevention and treatment of NAFLD. Our data support the translation of these agents into clinical evaluation in human subjects with NAFLD and/or associated risk factors.

Nonalcoholic fatty liver disease: Diagnostic biomarkers

Nonalcoholic fatty liver disease is a common medical condition worldwide and its prevalence has increased notably in the past few years due to the increases in prevalence of obesity and metabolic syndrome. However, diagnosis of this disease is still a matter of debate because of disease variations and pathophysiologic alterations. Specific single markers have gained considerable attention recently, among them markers related to hepatic pathophysiology, inflammation, adipocytokines and so forth. But, it seems that no single marker is sufficient for diagnosis and staging of the disease, and applying a panel including different types of tests may be more useful.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

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.

The relationship between resistin and ghrelin levels with fibrosis in nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease. It is generally accepted that insulin resistance is a pathophysiological factor in the development of NAFLD. In the present study, the aim was to determine the relationship between resistin and ghrelin levels, which were found to be closely related to insulin resistance and fibrosis scores in NAFLD.

MATERIALS AND METHODS

A total of 40 (21 male, 19 female) NAFLD patients whose diagnosis was confirmed with biopsy and 40 (18 male, 22 female) healthy controls were included in the study.

RESULTS

In the comparison of resistin and ghrelin levels, only resistin values were found to be significantly higher in NAFLD group while there was no significant difference in ghrelin values (respectively P < 0.05; P = 0.078). In according to the fibrosis groups there was no difference about fasting plasma glucose, insulin values, Homeostatic Measurement Assessment-Insulin Resistance measurements and also resistin and ghrelin levels.

CONCLUSION

It has been understood that insulin resistance plays an important part in NAFLD. Larger studies are required that investigate the gene expression of hormones influencing insulin resistance, particularly resistin and ghrelin in order to determine their role in NAFLD.

Non-alcoholic fatty liver disease and type 2 diabetes mellitus: The liver disease of our age?

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease that might affect up to one-third of the adult population in industrialised countries. NAFLD incorporates histologically and clinically different non-alcoholic entities; fatty liver (NAFL, steatosis hepatis) and steatohepatitis (NASH-characterised by hepatocyte ballooning and lobular inflammation ± fibrosis) might progress to cirrhosis and rarely to hepatocellular cancer. NAFL increasingly affects children (paediatric prevalence is 4.2%-9.6%). Type 2 diabetes mellitus (T2DM), insulin resistance (IR), obesity, metabolic syndrome and NAFLD are particularly closely related. Increased hepatic lipid storage is an early abnormality in insulin resistant women with a history of gestational diabetes mellitus. The accumulation of triacylglycerols in hepatocytes is predominantly derived from the plasma nonesterified fatty acid pool supplied largely by the adipose tissue. A few NAFLD susceptibility gene variants are associated with progressive liver disease, IR, T2DM and a higher risk for hepatocellular carcinoma. Although not approved, pharmacological approaches might be considered in NASH patients.

Protective effects and mechanisms of total alkaloids of Rubus alceaefolius Poir on non‑alcoholic fatty liver disease in rats

The plant Rubus alceaefolius Poir is used as a hepatic protectant in Traditional Chinese Medicine. The aim of the present study was to confirm the protective effect of the total alkaloids of Rubus alceaefolius Poir (TARAP) on the liver and to evaluate the potential molecular mechanisms associated with adipocytokines underlying non-alcoholic fatty liver disease (NAFLD) in rats. To generate the NAFLD model, Sprague-Dawley rats were administered a high‑fat diet and following 12 weeks of model construction, rats were orally treated with a positive control drug and different doses of TARAP daily for 28 days. The rats were then sacrificed and the livers were collected to evaluate the liver index (LI) and observe histological changes by hematoxylin and eosin (H&E) staining. The secretion levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum were examined by ELISA. Finally, the expression levels of leptin (LEP), resistin and adiponectin (APN) in liver tissues were determined by immunohistochemistry (IHC). The results demonstrated that, in the group treated with methionine and choline bitartrate tablets and in the groups treated with different doses of TARAP, there was a significant reduction in the LI (P<0.05 or P<0.01), a downregulation of the secretion levels of ALT and AST, reduced levels of LEP and resistin and an increased expression of APN in the liver of NAFLD rats compared with the model group. Furthermore, the effect of TARAP treatment of NAFLD rats was dose dependent. In conclusion, TARAP is a potential agent for downregulating LEP and resistin and upregulating APN expression in rats with NAFLD. Furthermore, TARAP may be a potential candidate for improving treatment responses in patients with NAFLD.

Serum biomarkers in nonalcoholic steatohepatitis: value for assessing drug effects?

Nonalcoholic steatohepatitis (NASH) is a common chronic liver disease throughout the world. In the USA, approximately 3-5% of the population are affected, and the prevalence of this condition is increasing. NASH is associated with an increased risk of liver-related morbidity, such as cirrhosis and fibrosis, as well as cardiovascular disease, and in spite of several clinical studies investigating putative new drugs, no approved treatment is currently available. This is partly due to the nature of the disease. NASH is a complex, slowly progressing disease, and confirmatory clinical trials have long treatment durations and require invasive end points (a liver biopsy). Such invasive assessments are only accepted in confirmatory trials; clinical studies in the exploratory clinical development phase must rely on noninvasive biomarkers as the primary end point. Experimental and clinical research continues to achieve validation and qualification of biomarkers in NASH, which will hopefully assist the development of new treatments for NASH patients.

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.

Metabolic derangements mediate cognitive impairment and Alzheimer's disease: role of peripheral insulin-resistance diseases

Herein, we review evidence that systemic insulin-resistance diseases linked to obesity, type 2 diabetes, and non-alcoholic steatohepatitis promote neurodegeneration. Insulin-resistance dysregulates lipid metabolism, which promotes ceramide accumulation with attendant inflammation and endoplasmic reticulum (ER) stress. Mechanistically, we propose that toxic ceramides generated in extra-CNS tissues, e.g. liver, get released into peripheral blood, and subsequently transit across the blood-brain barrier into the brain where they induce brain insulin-resistance, inflammation, and cell death (extrinsic pathway). These abnormalities establish or help propagate a cascade of neurodegeneration associated with increased ER stress and ceramide generation, which exacerbate brain insulin-resistance, cell death, myelin degeneration, and neuro-inflammation. The data suggest that a mal-signaling network mediated by toxic ceramides, ER stress, and insulin-resistance should be targeted to disrupt positive feedback loops that drive the AD neurodegeneration cascade.

Plasma ghrelin levels in patients with familial Mediterranean fever

BACKGROUND

Familial Mediterranean fever (FMF) is an auto-inflammatory disorder characterized by febrile attacks. Increased acute-phase reactants are characteristic during febrile attacks. Ghrelin is a natural G-protein that decreases secretion of pro-inflammatory cytokines and acts as anti-inflammatory agent. The aim of this study was to investigate whether there is any change in ghrelin levels and whether increases in ghrelin levels can be used as a marker in these patients.

SUBJECTS AND METHODS

Thirty-seven male patients and 30 healthy men as a control group were included in the study. Blood samples were obtained for ghrelin measurements both before the attacks (pre-attack period; ghrelin 1 group) and during the attacks (ghrelin 2 group). Samples were kept at -80°C until the analysis was conducted and plasma ghrelin levels were measured using an immune-sorbent assay method.

RESULTS

Mean ghrelin levels measured during the attacks were significantly higher (11.01 ± 4.78 pg/ml) as compared to pre-attack levels (5.78 ± 2.17 pg/ml; p < 0.001). Similarly, mean ghrelin levels measured in FMF patients during an attack were significantly different from that of the control group (6.57 ± 4.13 pg/ml; p < 0.001).

CONCLUSIONS

In this study, high ghrelin levels were measured during attacks in FMF patients. This finding is in line with previous results regarding the fact that inflammatory response arising during an FMF attack is an acute inflammatory event. Our findings suggest that ghrelin levels measured during FMF attacks could be used as a biochemical indicator for the FMF attack in FMF patients and that it could be used for support of the diagnosis of the disease.

Triangulated mal-signaling in Alzheimer's disease: roles of neurotoxic ceramides, ER stress, and insulin resistance reviewed

Ceramides are lipid signaling molecules that cause cytotoxicity and cell death mediated by insulin resistance, inflammation, and endoplasmic reticulum (ER) stress. However, insulin resistance dysregulates lipid metabolism, which promotes ceramide accumulation with attendant inflammation and ER stress. Herein, we discuss two major pathways, extrinsic and intrinsic, that converge and often overlap in propagating AD-type neurodegeneration via a triangulated mal-signaling network. First, we review evidence that systemic insulin resistance diseases linked to obesity, type 2 diabetes, and non-alcoholic steatohepatitis promote neurodegeneration. Mechanistically, we propose that toxic ceramides generated in extra-CNS tissues (e.g., liver) get released into peripheral blood, and subsequently transit across the blood-brain barrier into the brain where they induce brain insulin resistance, inflammation, and cell death (extrinsic pathway). Then we discuss the role of the intrinsic pathway of neurodegeneration which is mediated by endogenous or primary brain insulin/IGF resistance, and impairs neuronal and oligodendrocyte survival, energy metabolism, membrane integrity, cytoskeletal function, and AβPP-Aβ secretion. The end result is increased ER stress and ceramide generation, which exacerbate brain insulin resistance, cell death, myelin degeneration, and neuroinflammation. Altogether, the data suggest that the triangulated mal-signaling network mediated by toxic ceramides, ER stress, and insulin resistance should be targeted to disrupt positive feedback loops that drive the AD neurodegeneration cascade.

Study of serum ghrelin changes and its correlation with malnutrition in liver cirrhosis in Egypt

Egypt has the highest prevalence of hepatitis C virus (HCV) all over the world, with an estimated 8-10 million among a population of 68 million having been exposed to the virus and 5-7 million active infections (Frank et al., 2000). It is considered the most common aetiology of chronic liver disease (CLD) in Egypt, where prevalence of antibodies to HCV (anti-HCV) is 10-fold greater than in the United States and Europe (Goldstone et al., 2002; Strickland et al., 2002). We have studied the role of plasma ghrelin, an orexigenic hormone that was found to correlate with malnourishment in CLD depending on Child classification. Sixty patients were divided in three groups according to Child classification and were compared to normal healthy controls (20 subjects). There was a highly significant correlation of plasma ghrelin and body mass index (BMI), mid arm circumference (MAC), waist circumference (WC) and tricuspid skin fold thickness (TSF). Also plasma ghrelin was specific and sensitive by the ROC curve analysis to BMI, which would indicate a new marker for malnourishment and possibility of a novel therapeutic approach.

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.

Ceramide-mediated insulin resistance and impairment of cognitive-motor functions

Obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic steatohepatitis (NASH) are associated with cognitive impairment, brain insulin resistance, and neurodegeneration. Recent studies linked these effects to increased pro-ceramide gene expression in liver and increased ceramide levels in serum. Since ceramides are neurotoxic and cause insulin resistance, we directly examined the role of ceramides as mediators of impaired signaling and central nervous system function using an in vivo model. Long Evans rat pups were administered C2Cer:N-acetylsphinganine or its inactive dihydroceramide analog (C2DCer) by i.p. injection. Rats were subjected to rotarod and Morris water maze tests of motor and cognitive function, and livers and brains were examined for histopathology and integrity of insulin/IGF signaling. C2Cer treatment caused hyperglycemia, hyperlipidemia, and mild steatohepatitis, reduced brain lipid content, and increased ceramide levels in liver, brain, and serum. Quantitative RT-PCR analysis revealed significant alterations in expression of several genes needed for insulin and IGF-I signaling, and multiplex ELISAs demonstrated inhibition of signaling through the insulin or IGF-1 receptors, IRS-1, and Akt in both liver and brain. Ultimately, the toxic ceramides generated in peripheral sources such as liver or adipose tissue caused sustained impairments in neuro-cognitive function and insulin/IGF signaling needed for neuronal survival, plasticity, and myelin maintenance in the brain. These findings support our hypothesis that a liver/peripheral tissue-brain axis of neurodegeneration, effectuated by increased toxic lipid/ceramide production and transport across the blood-brain barrier, could mediate cognitive impairment in T2DM and NASH.

The role of the gut microbiota in nonalcoholic fatty liver disease

Important metabolic functions have been identified for the gut microbiota in health and disease. Several lines of evidence suggest a role for the gut microbiota in both the etiology of nonalcoholic fatty liver disease (NAFLD) and progression to its more advanced state, nonalcoholic steatohepatitis (NASH). Both NAFLD and NASH are strongly linked to obesity, type 2 diabetes mellitus and the metabolic syndrome and, accordingly, have become common worldwide problems. Small intestinal bacterial overgrowth of Gram-negative organisms could promote insulin resistance, increase endogenous ethanol production and induce choline deficiency, all factors implicated in NAFLD. Among the potential mediators of this association, lipopolysaccharide (a component of Gram-negative bacterial cell walls) exerts relevant metabolic and proinflammatory effects. Although the best evidence to support a role for the gut microbiota in NAFLD and NASH comes largely from animal models, data from studies in humans (albeit at times contradictory) is accumulating and could lead to new therapeutic avenues for these highly prevalent conditions.

Cytokeratin-18 fragments and biomarkers of the metabolic syndrome in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) remains a leading cause of chronic liver disease. In the context of NAFLD, the presence of nonalcoholic steatohepatitis (NASH) portends an adverse prognosis with greater risk of liver fibrosis and cirrhosis. Although liver biopsy is the keystone of patient management in NAFLD, it is also increasingly clear that such evaluation has its limitations. The availability of biochemical markers of NAFLD and NASH has tremendous potential to radically alter management strategies for these conditions, as well as to monitor disease activity. Our article provides an overview of biomarker discovery and selection in the setting of NAFLD and highlights future directions in the field.

Adipokine serum levels are related to liver histology in severely obese patients undergoing bariatric surgery

BACKGROUND

Leptin, adiponectin, and resistin are adipokines linked to the development of insulin resistance, which plays a central role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). We aimed to define adipokine serum levels in severely obese patients undergoing bariatric surgery and to correlate these with anthropometric and metabolic variables, liver function tests, and histopathological parameters of NAFLD and nonalcoholic steatohepatitis (NASH).

METHODS

Surgical liver biopsies were obtained from 50 bariatric patients with no history of liver disease or significant alcohol consumption. Serum leptin, adiponectin, and resistin levels were measured, and histology was assessed using Brunt's and Kleiner's scoring systems.

RESULTS

Waist/hip ratio was significantly higher in men (p = 0.0001), and leptin (p = 0.036) and adiponectin (p = 0.0001) serum levels were higher in women. Forty-one of 50 patients (82%) had histological NAFLD, including 10 (20%) with NASH. Nine patients (18%) had normal liver histology (obese control subgroup). In NAFLD patients, serum adiponectin was negatively correlated with activity grade and fibrosis stage, resistin was negatively correlated with steatosis grade (p = 0.033), while leptin was not related to histology. Leptin/adiponectin ratio showed positive association with stage (p = 0.044). In the subgroup of NASH patients, adiponectin was negatively correlated only with stage (p = 0.01), while there was no correlation between leptin, resistin, or leptin/adiponectin and histology.

CONCLUSIONS

Serum adiponectin and resistin levels are related to liver histology in bariatric patients and may be indicative of the histological severity of NAFLD and the extent of hepatic steatosis, respectively. Serum leptin levels are not informative of underlying liver histology in severely obese patients.

Hepatic ceramide may mediate brain insulin resistance and neurodegeneration in type 2 diabetes and non-alcoholic steatohepatitis

Obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic steatohepatitis (NASH) can be complicated by cognitive impairment and neurodegeneration. Experimentally, high fat diet (HFD)-induced obesity with T2DM causes mild neurodegeneration with brain insulin resistance. Since ceramides are neurotoxic, cause insulin resistance, and are increased in T2DM, we investigated the potential role of ceramides as mediators of neurodegeneration in the HFD obesity/T2DM model. We pair-fed C57BL/6 mice with a HFD or control diet for 4-20 weeks and examined pro-ceramide gene expression in liver and brain and neurodegeneration in the temporal lobe. HFD feeding gradually increased body weight, but after 16 weeks, liver weight surged (P<0.001) due to lipid (triglyceride) accumulation (P<0.001), and brain weight declined (P<0.0001-Trend analysis). HFD feeding increased ceramide synthase, serine palmitoyl transferase, and sphingomyelinase expression in liver (P<0.05-P<0.001), but not brain. In HFD fed mice, temporal lobe levels of ubiquitin (P<0.001) and 4-hydroxynonenal (P<0.05 or P<0.01) increased, and tau, beta-actin, and choline acetyltransferase levels decreased (P<0.05-P<0.001) with development of NASH. In obesity, T2DM, or NASH, neurodegeneration with brain insulin resistance may be mediated by excess hepatic production of neurotoxic ceramides that readily cross the blood-brain barrier.

Mechanisms of ceramide-mediated neurodegeneration

Obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic steatohepatitis (NASH) can be associated with cognitive impairment or early neurodegeneration. Previously, we showed that diet-induced obesity with T2DM and NASH results in mild neurodegeneration with some features of AD, including brain insulin resistance. In a companion study, we correlated obesity/T2DM/NASH-associated central nervous system (CNS) abnormalities with increased pro-ceramide gene expression in liver. Since ceramides are neurotoxic and cause insulin resistance, we directly investigated the role of ceramides as mediators of neurodegeneration using an in vitro culture model. We treated PNET2 human CNS neuronal cells with D-erythro-Ceramide analogs (C2Cer:N-acetylsphinganine and C6Cer:N-hexanoylsphinganine), or the inactive dihydroceramide analog (C2DCer) for 48 h, and probed for changes in genes and proteins that are critical to insulin/IGF signaling, and associated with neurodegeneration. Exposure to C6Cer>C2Cer impaired energy metabolism, viability, and insulin and insulin-like growth factor signaling mechanisms, and resulted in increased levels of AbetaPP-Abeta and pTau, whereas C2D had no significant effect on these parameters. CNS exposure to neurotoxic ceramides from exogenous sources, including liver, can cause neurodegeneration with impairments in insulin and IGF signaling mechanisms, similar to the findings in experimental models of obesity/T2DM, and NASH.

Adiponectin prevents progression of steatohepatitis in mice by regulating oxidative stress and Kupffer cell phenotype polarization

AIM

We reported previously that hypoadiponectinemia enhances hepatic oxidative stress and accelerates progression of nonalcoholic steatohepatitis (NASH) in mice. However, the precise mechanism and preventive effects of adiponectin on NASH remain unclear. The aim of this study was to examine the effects of adiponectin on steatohepatitis using adiponectin-knockout (KO) mice and adenovirus-mediated adiponectin expression system.

METHODS

We used male KO mice and C57BL6/J (WT) mice fed methionine choline-deficient (MCD)-diet as a steatohepatitis model. Liver histology, hepatic oxidative stress markers, and hepatic gene expression levels were investigated. In addition, Hepa 1-6 cells, a mouse liver cell line, were cultured with or without recombinant adiponectin, and gene expressions were investigated by real-time RT-PCR.

RESULTS

After 2-week feeding of MCD diet, hepatic steatosis was enhanced and plasma alanine aminotransferase elevated in KO mice than in WT mice. In KO mice liver, thiobarbituric acid reactive substances increased, glutathione levels decreased, and mRNA expression levels of antioxidant enzymes (catalase, superoxide dismutase-1) downregulated. Adenovirus-mediated adiponectin expression prevented these changes in KO mice. Moreover, Kupffer cell infiltration was enhanced and mRNA levels of anti-inflammatory M2 macrophage markers (interleukin-10, arginase-1) were decreased in KO mice liver. In the in vitro study, adiponectin significantly increased catalase gene expression in Hepa 1-6 cells.

CONCLUSIONS

Lack of adiponectin enhanced, and adiponectin administration prevented steatohepatitis progression in mice. These changes were due to the anti-oxidative effects of adiponectin, and its effects on Kupffer cells recruitment and phenotype polarization. Augmentation of adiponectin effects could be a useful preventive approach for NASH progression.

Adipocytokines and liver disease

Adipose tissue is a massive source of bioactive substances known as adipocytokines, including tumor necrosis factor (TNF)-alpha, resistin, leptin, and adiponectin. Recent advances in medical research view obesity as a chronic low-grade inflammatory state. Hypertrophied adipocytes in obesity release chemokines that induce macrophage accumulation in adipose tissue. Accumulated macrophages in obese adipose tissue produce proinflammatory cytokines and nitric oxide, and these inflammatory changes induce adipocytokine dysregulation. The latter is characterized by a decrease in insulinsensitizing and anti-inflammatory adipocytokines, and an increase in proinflammatory adipocytokines. Adipocytokine dysregulation induces obesity-related metabolic disorders, the so-called metabolic syndrome. Metabolic syndrome is a cluster of metabolic abnormalities, including diabetes mellitus, hypertension, hyperlipidemia, and nonalcoholic steatohepatitis (NASH). Recent studies have revealed that obesity is an independent risk factor for chronic liver diseases, such as NASH, alcoholic liver disease, chronic hepatitis C, and hepatocellular carcinoma. A common mechanism underlying these hepatic clinical states is thought to be adipocytokine dysregulation. In this review, we discuss the association of adipocytokines, especially leptin, adiponectin, TNF-alpha, and resistin, with liver diseases.

A novel diagnostic biomarker panel for obesity-related nonalcoholic steatohepatitis (NASH)

BACKGROUND

Within the spectrum of nonalcoholic fatty liver disease (NAFLD), only patients with nonalcoholic steatohepatitis (NASH) show convincing evidence for progression. To date, liver biopsy remains the gold standard for the diagnosis of NASH; however, liver biopsy is expensive and associated with a small risk, emphasizing the urgent need for noninvasive diagnostic biomarkers. Recent findings suggest a role for apoptosis and adipocytokines in the pathogenesis of NASH. The aim of this study was to develop a noninvasive diagnostic biomarker for NASH.

METHODS

The study included 101 patients with liver biopsies who were tested with enzyme-linked immunosorbent assay (ELISA)-based assays. Of these, 69 were included in the biomarker development set and 32 were included in the biomarker validation set. Clinical data and serum samples were collected at the time of biopsy. Fasting serum samples were assayed for adiponectin, resistin, insulin, glucose, TNF-alpha, IL-6, IL-8, cytokeratin CK-18 (M65 antigen), and caspase-cleaved CK-18 (M30 antigen).

RESULTS

Data analysis revealed that the levels of M30 antigen (cleaved CK-18) predicted histological NASH with 70% sensitivity and 83.7% specificity and area under the curve (AUC) = 0.711, p < 10(-4), whereas the predictive value of the levels of intact CK-18 (M65) was higher (63.6% sensitivity and 89.4% specificity and AUC = 0.814, p < 10(-4)). Histological NASH could be predicted by a combination of Cleaved CK-18, a product of the subtraction of Cleaved CK-18 level from intact CK-18 level, serum adiponectin, and serum resistin with a sensitivity of 95.45% sensitivity, specificity of 70.21%, and AUC of 0.908 (p < 10(-4)). Blinded validation of this model confirmed its reliability for separating NASH from simple steatosis.

CONCLUSIONS

Four ELISA-based tests were combined to form a simple diagnostic biomarker for NASH.