A novel role for adiponectin in regulating the immune responses in chronic hepatitis C virus infection

Preliminary Report on the Influence of Acute Inflammation on Adiponectin Levels in Older Inpatients with Different Nutritional Status

Inflammation can be triggered by a variety of factors, including pathogens, damaged cells, and toxic compounds. It is a biological response of the immune system, which can be successfully assessed in clinical practice using some molecular substances. Because adiponectin, a hormone released by adipose tissue, influences the development of inflammation, its evaluation as a potential measure of inflammation in clinical practice is justified. In the present contribution, statistical comparison of adiponectin concentration and selected molecular substances recognized in clinical practice as measures of inflammation were utilized to demonstrate whether adipose tissue hormones, as exemplified by adiponectin, have the potential to act as a measure of rapidly changing inflammation when monitoring older hospitalized patients in the course of bacterial infection. The study showed no statistically significant differences in adiponectin levels depending on the rapidly changing inflammatory response in its early stage. Interestingly, the concentration of adiponectin is statistically significantly higher in malnourished patients than in people with normal nutritional levels, assessed based on the MNA. According to the results obtained, adiponectin is not an effective measure of acute inflammation in clinical practice. However, it may serve as a biomarker of malnutrition in senile individuals.

The Role of Adipokines in the Pathologies of the Central Nervous System

Adipokines are protein hormones secreted by adipose tissue in response to disruptions in physiological homeostasis within the body's systems. The regulatory functions of adipokines within the central nervous system (CNS) are multifaceted and intricate, and they have been identified in a number of pathologies. Therefore, specific adipokines have the potential to be used as biomarkers for screening purposes in neurological dysfunctions. The systematic review presented herein focuses on the analysis of the functions of various adipokines in the pathogenesis of CNS diseases. Thirteen proteins were selected for analysis through scientific databases. It was found that these proteins can be identified within the cerebrospinal fluid either by their ability to modify their molecular complex and cross the blood-brain barrier or by being endogenously produced within the CNS itself. As a result, this can correlate with their measurability during pathological processes, including Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis, depression, or brain tumors.

The Role of Adipokines in the Pathogenesis of Psoriasis

Psoriasis is a chronic and immune-mediated skin condition characterized by pro-inflammatory cytokines and keratinocyte hyperproliferation. Dendritic cells, T lymphocytes, and keratinocytes represent the main cell subtypes involved in the pathogenesis of psoriasis, while the interleukin-23 (IL-23)/IL-17 pathway enhances the disease progression. Human adipose tissue is an endocrine organ, which secretes multiple proteins, known as adipokines, such as adiponectin, leptin, visfatin, or resistin. Current evidence highlights the immunomodulatory roles of adipokines, which may contribute to the progression or suppression of psoriasis. A better understanding of the complexity of psoriasis pathophysiology linked with adipokines could result in developing novel diagnostic or therapeutic strategies. This review aims to present the pathogenesis of psoriasis and the roles of adipokines in this process.

Innate metabolic responses against viral infections

Metabolic adaptation to viral infections critically determines the course and manifestations of disease. At the systemic level, a significant feature of viral infection and inflammation that ensues is the metabolic shift from anabolic towards catabolic metabolism. Systemic metabolic sequelae such as insulin resistance and dyslipidaemia represent long-term health consequences of many infections such as human immunodeficiency virus, hepatitis C virus and severe acute respiratory syndrome coronavirus 2. The long-held presumption that peripheral and tissue-specific 'immune responses' are the chief line of defence and thus regulate viral control is incomplete. This Review focuses on the emerging paradigm shift proposing that metabolic engagements and metabolic reconfiguration of immune and non-immune cells following virus recognition modulate the natural course of viral infections. Early metabolic footprints are likely to influence longer-term disease manifestations of infection. A greater appreciation and understanding of how local biochemical adjustments in the periphery and tissues influence immunity will ultimately lead to interventions that curtail disease progression and identify new and improved prognostic biomarkers.

Proteomics of fibrin amyloid microclots in long COVID/post-acute sequelae of COVID-19 (PASC) shows many entrapped pro-inflammatory molecules that may also contribute to a failed fibrinolytic system

BACKGROUND

Post-acute sequelae of COVID-19 (PASC), also now known as long COVID, has become a major global health and economic burden. Previously, we provided evidence that there is a significant insoluble fibrin amyloid microclot load in the circulation of individuals with long COVID, and that these microclots entrap a substantial number of inflammatory molecules, including those that might prevent clot breakdown. Scientifically, the most challenging aspect of this debilitating condition is that traditional pathology tests such as a serum CRP (C-reactive protein) may not show any significant abnormal inflammatory markers, albeit these tests measure only the soluble inflammatory molecules. Elevated, or abnormal soluble biomarkers such as IL-6, D-Dimer or fibrinogen indicate an increased risk for thrombosis or a host immune response in COVID-19. The absence of biomarkers in standard pathology tests, result in a significant amount of confusion for patients and clinicians, as patients are extremely sick or even bed-ridden but with no regular identifiable reason for their disease. Biomarkers that are currently available cannot detect the molecules present in the microclots we identified and are therefore unable to confirm their presence or the mechanisms that drive their formation.

METHODS

Here we analysed the protein content of double-digested microclots of 99 long COVID patients and 29 healthy controls. The patients suffering from long COVID reported their symptoms through a questionnaire completed by themselves or their attending physician.

RESULTS

Our long COVID cohort's symptoms were found to be in line with global findings, where the most prevalent symptoms were constant fatigue (74%,) cognitive impairment (71%) and depression and anxiety (30%). Our most noteworthy findings were a reduced level of plasma Kallikrein compared to our controls, an increased level of platelet factor 4 (PF4) von Willebrand factor (VWF), and a marginally increased level of α-2 antiplasmin (α-2-AP). We also found a significant presence of antibodies entrapped inside these microclots.

CONCLUSION

Our results confirm the presence of pro-inflammatory molecules that may also contribute to a failed fibrinolysis phenomenon, which could possibly explain why individuals with long COVID suffer from chronic fatigue, dyspnoea, or cognitive impairment. In addition, significant platelet hyperactivation was noted. Hyperactivation will result in the granular content of platelets being shed into the circulation, including PF4. Overall, our results provide further evidence of both a failed fibrinolytic system in long COVID/PASC and the entrapment of many proteins whose presence might otherwise go unrecorded. These findings might have significant implications for individuals with pre-existing comorbidities, including cardiovascular disease and type 2 diabetes.

The potential molecular implications of adiponectin in the evolution of SARS-CoV-2: Inbuilt tendency

Adiponectin (APN) is an adipokine concerned in the regulation of glucose metabolism, insulin sensitivity and fatty acid oxidation. APN plays a critical role in viral infections by regulating the immune response through its anti-inflammatory/pro-inflammatory axis. Reduction of APN may augment the severity of viral infections because APN inhibits immune cells’ response via suppression of inflammatory signaling pathways and stimulation of adenosine monophosphate protein kinase (AMPK). Moreover, APN inhibits the stimulation of nuclear factor kappa B (NF-κB) and regulates the release of pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNF-α) and interleukins (IL-18, IL-6). In COVID-19, abnormalities of the fatty tissue due to oxidative stress (OS) and hyperinflammation may inhibit the production and release of APN. APN has lung-protective effect and can prevent SARS-CoV-2-induced acute lung injury (ALI) through the amelioration of endoplasmic reticulum (ER) stress, endothelial dysfunction (ED) and stimulation of peroxisome proliferator-activated receptor-alpha (PPAR-α). It has been established that there is a potential correlation between inflammatory signal transduction pathways and APN that contributes to the development of SARS-CoV-2 infections. Deregulation of these molecular pathways affects the expression of APN and vice versa. In addition, the reduction of APN effect in SARS-CoV-2 infection could be a potential cause of the exacerbation of pro-inflammatory effects which are associated with the disease severity. In this context, exploratory, developmental, and extensive prospective studies are necessary.

Exploiting the obesity-associated immune microenvironment for cancer therapeutics

Obesity causes chronic low-grade inflammation and leads to changes in the immune landscape of multiple organ systems. Given the link between chronic inflammatory conditions and cancer, it is not surprising that obesity is associated with increased risk and worse outcomes in many malignancies. Paradoxically, recent epidemiological studies have shown that high BMI is associated with increased efficacy of immune checkpoint inhibitors (ICI), and a causal relationship has been demonstrated in the preclinical setting. It has been proposed that obesity-associated immune dysregulation underlies this observation by inadvertently creating a favourable microenvironment for increased ICI efficacy. The recent success of ICIs in obese cancer patients raises the possibility that additional immune-targeted therapies may hold therapeutic value in this context. Here we review how obesity affects the immunological composition of the tumor microenvironment in ways that can be exploited for cancer immunotherapies. We discuss existing literature supporting a beneficial role for obesity during ICI therapy in cancer patients, potential opportunities for targeting the innate immune system to mitigate chronic inflammatory processes, and how to pinpoint obese patients who are most likely to benefit from immune interventions without relying solely on body mass index. Given that the incidence of obesity is expanding on an international scale, we propose that understanding obesity-associated inflammation is necessary to reduce cancer mortalities and capitalize on novel therapeutic opportunities in the era of cancer immunotherapy.

Adiponectin/AdipoR1 Axis Promotes IL-10 Release by Human Regulatory T Cells

Background

Adiponectin is an important immunomodulatory mediator in inflammatory conditions. While we previously showed that adiponectin receptor 1 (AdipoR1) is expressed in murine regulatory T cells (Tregs), its expression in human Tregs remain unknown. Here, we examined the expression of AdipoR1 in human Tregs and whether its ligand, globular adiponectin (gAd) affects the Treg ability to secrete IL-10 and the role of Type 2 (T2) inflammation in such process.

Methods

Human Tregs from peripheral blood were analyzed by flow cytometry for AdipoR1, Helios and IL-10 expression. CD4⁺ T cells enriched from peripheral blood mononuclear cells (PBMCs) were cultured in the presence or the absence of gAd or the chemical adiponectin receptor agonist, AdipoRon, or in a T2 cytokine milieu. Flow cytometry was then used to assess intracellular IL-10, IL-10 secreting cells, FOXP3 and Helios expression, and phosphorylated p38 MAP kinase (MAPK). IL-10 levels in CD4⁺ T cell supernatants were quantified by ELISA.

Results

We found that a subset of human Tregs expressed AdipoR1. Importantly, more Helios^- cells expressed AdipoR1 than Helios⁺ cells. Likewise, there was a higher frequency of IL-10⁺ cells within Helios^- AdipoR1⁺ Tregs compared to Helios⁺ AdipoR1⁺ Tregs. In contrast, the IL-10 mean fluorescence intensity (MFI) was higher in Helios⁺ AdipoR1⁺ Tregs compared to Helios^-AdipoR1⁺ Tregs. When human CD4⁺ T cells were treated with gAd or AdipoRon, a significant increase in IL-10 secretion, FOXP3 expression, and p38 MAPK phosphorylation was observed in Helios^- AdipoR1⁺ Tregs. Interestingly, gAd under T2 cytokine milieu significantly increased the intracellular levels of IL-10, mainly in Helios⁺ AdipoR1⁺ Tregs, and IL-10 levels in supernatants of CD4⁺ T cells.

Conclusions

Collectively, our findings suggest that adiponectin/AdipoR1 axis promotes IL-10 release by Tregs, mainly in Helios^- Tregs, and the effect was amplified by T2 inflammation in Helios⁺ Tregs.

Roles of Adipokines in Digestive Diseases: Markers of Inflammation, Metabolic Alteration and Disease Progression

Adipose tissue is a highly dynamic endocrine tissue and constitutes a central node in the interorgan crosstalk network through adipokines, which cause pleiotropic effects, including the modulation of angiogenesis, metabolism, and inflammation. Specifically, digestive cancers grow anatomically near adipose tissue. During their interaction with cancer cells, adipocytes are reprogrammed into cancer-associated adipocytes and secrete adipokines to affect tumor cells. Moreover, the liver is the central metabolic hub. Adipose tissue and the liver cooperatively regulate whole-body energy homeostasis via adipokines. Obesity, the excessive accumulation of adipose tissue due to hyperplasia and hypertrophy, is currently considered a global epidemic and is related to low-grade systemic inflammation characterized by altered adipokine regulation. Obesity-related digestive diseases, including gastroesophageal reflux disease, Barrett's esophagus, esophageal cancer, colon polyps and cancer, non-alcoholic fatty liver disease, viral hepatitis-related diseases, cholelithiasis, gallbladder cancer, cholangiocarcinoma, pancreatic cancer, and diabetes, might cause specific alterations in adipokine profiles. These patterns and associated bases potentially contribute to the identification of prognostic biomarkers and therapeutic approaches for the associated digestive diseases. This review highlights important findings about altered adipokine profiles relevant to digestive diseases, including hepatic, pancreatic, gastrointestinal, and biliary tract diseases, with a perspective on clinical implications and mechanistic explorations.

Systematic review: chronic viral hepatitis and metabolic derangement

BACKGROUND

The liver has a critical role in the metabolism of glucose and lipids. Chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infection leads to a spectrum of liver disease including chronic hepatitis, cirrhosis and hepatocellular carcinoma. Metabolic syndrome (MetS) has a rising incidence owing to an epidemic of type 2 diabetes mellitus (T2DM) and obesity. Non-alcoholic fatty liver disease is a liver manifestation of MetS and has become the most common cause of chronic liver disease worldwide.

AIM

To summarise the interplay among hepatitis viruses, MetS and its components.

METHODS

We searched the literature about HBV, HCV infection, MetS, fatty liver and its components from PubMed.

RESULTS

With respect to the viral replication cycle, lipids are important mediators between viral entry and hepatocyte in HCV infection, but not in HBV infection. Thus, HCV infection is inversely associated with hyperlipidaemia and lipid rebound occurs following sustained viral response induced by interferon-based therapy or direct antiviral agents. In addition, HCV infection is positively associated with insulin resistance, hepatic steatosis, MetS and the risk of T2DM and atherosclerosis. In contrast, HBV infection may protect infected subjects from the development of MetS and hepatic steatosis. Accumulating evidence suggests that HBV infection is inversely associated with lipid metabolism, and exhibits no conclusive association with insulin resistance or the risk of T2DM and arteriosclerosis.

CONCLUSIONS

In patients with viral hepatitis and concurrent metabolic diseases, a multidisciplinary approach should be given rather than simply antiviral treatment.

Obesity and Fat Metabolism in Human Immunodeficiency Virus-Infected Individuals: Immunopathogenic Mechanisms and Clinical Implications

Metabolic complications relating to complex effects of viral and immune-mediated mechanisms are now a focus of clinical care among persons living with human immunodeficiency virus (PLHIV), and obesity is emerging as a critical problem. To address knowledge gaps, the US National Institutes of Health sponsored a symposium in May 2018 entitled "Obesity and Fat Metabolism in HIV-infected Individuals." Mechanisms relating to adipose dysfunction and fibrosis, immune function, inflammation, and gastrointestinal integrity were highlighted as contributors to obesity among PLHIV. Fibrotic subcutaneous adipose tissue is metabolically dysfunctional and loses its capacity to expand, leading to fat redistribution, including visceral obesity and ectopic fat accumulation, promoting insulin resistance. Viral proteins, including viral protein R and negative regulatory factor, have effects on adipogenic pathways and cellular metabolism in resident macrophages and T cells. HIV also affects immune cell trafficking into the adipose compartments, with effects on adipogenesis, lipolysis, and ectopic fat accumulation. Key cellular metabolic functions are likely to be affected in PLHIV by gut-derived cytokines and altered microbiota. There are limited strategies to reduce obesity specifically in PLHIV. Enhancing our understanding of critical pathogenic mechanisms will enable the development of novel therapeutics that may normalize adipose tissue function and distribution, reduce inflammation, and improve insulin sensitivity in PLHIV.

A Bioelectronic System to Measure the Glycolytic Metabolism of Activated CD4+ T Cells

The evaluation of glucose metabolic activity in immune cells is becoming an increasingly standard task in immunological research. In this study, we described a sensitive, inexpensive, and non-radioactive assay for the direct and rapid measurement of the metabolic activity of CD4+ T cells in culture. A portable, custom-built Cell Culture Metabolite Biosensor device was designed to measure the levels of acidification (a proxy for glycolysis) in cell-free CD4+ T cell culture media. In this assay, ex vivo activated CD4+ T cells were incubated in culture medium and mini electrodes were placed inside the cell free culture filtrates in 96-well plates. Using this technique, the inhibitors of glycolysis were shown to suppress acidification of the cell culture media, a response similar to that observed using a gold standard lactate assay kit. Our findings show that this innovative biosensor technology has potential for applications in metabolic research, where acquisition of sufficient cellular material for ex vivo analyses presents a substantial challenge.

Polymorphism rs1385129 Within Glut1 Gene SLC2A1 Is Linked to Poor CD4+ T Cell Recovery in Antiretroviral-Treated HIV+ Individuals

Untreated HIV infection is associated with progressive CD4+ T cell depletion, which is generally recovered with combination antiretroviral therapy (cART). However, a significant proportion of cART-treated individuals have poor CD4+ T cell reconstitution. We investigated associations between HIV disease progression and CD4+ T cell glucose transporter-1 (Glut1) expression. We also investigated the association between these variables and specific single nucleotide polymorphisms (SNPs) within the Glut1 regulatory gene AKT (rs1130214, rs2494732, rs1130233, and rs3730358) and in the Glut1-expressing gene SLC2A1 (rs1385129 and rs841853) and antisense RNA 1 region SLC2A1-AS1 (rs710218). High CD4+Glut1+ T cell percentage is associated with rapid CD4+ T cell decline in HIV-positive treatment-naïve individuals and poor T cell recovery in HIV-positive individuals on cART. Evidence suggests that poor CD4+ T cell recovery in treated HIV-positive individuals is linked to the homozygous genotype (GG) associated with SLC2A1 SNP rs1385129 when compared to those with a recessive allele (GA/AA) (odds ratio = 4.67; P = 0.04). Furthermore, poor response to therapy is less likely among Australian participants when compared against American participants (odds ratio: 0.12; P = 0.01) despite there being no difference in prevalence of a specific genotype for any of the SNPs analyzed between nationalities. Finally, CD4+Glut1+ T cell percentage is elevated among those with a homozygous dominant genotype for SNPs rs1385129 (GG) and rs710218 (AA) when compared to those with a recessive allele (GA/AA and AT/TT respectively) (P < 0.04). The heterozygous genotype associated with AKT SNP 1130214 (GT) had a higher CD4+Glut1+ T cell percentage when compared to the dominant homozygous genotype (GG) (P = 0.0068). The frequency of circulating CD4+Glut1+ T cells and the rs1385129 SLC2A1 SNP may predict the rate of HIV disease progression and CD4+ T cell recovery in untreated and treated infection, respectively.

Adiponectin Signaling Pathways in Liver Diseases

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

Metabolically active CD4+ T cells expressing Glut1 and OX40 preferentially harbor HIV during in vitro infection

High glucose transporter 1 (Glut1) surface expression is associated with increased glycolytic activity in activated CD4+ T cells. Phosphatidylinositide 3‐kinases (PI3K) activation measured by p‐Akt and OX40 is elevated in CD4+Glut1+ T cells from HIV+ subjects. TCR engagement of CD4+Glut1+ T cells from HIV+ subjects demonstrates hyperresponsive PI3K‐mammalian target of rapamycin signaling. High basal Glut1 and OX40 on CD4+ T cells from combination antiretroviral therapy (cART)‐treated HIV+ patients represent a sufficiently metabolically active state permissive for HIV infection in vitro without external stimuli. The majority of CD4+OX40+ T cells express Glut1, thus OX40 rather than Glut1 itself may facilitate HIV infection. Furthermore, infection of CD4+ T cells is limited by p110γ PI3K inhibition. Modulating glucose metabolism may limit cellular activation and prevent residual HIV replication in ‘virologically suppressed’ cART‐treated HIV+ persons.

The evolving relationship between adiponectin and insulin sensitivity in hepatitis C patients during viral clearance

BACKGROUND

The evolution of the relationship between adiponectin and insulin sensitivity in hepatitis C virus (HCV) patients during viral clearance is unclear and warrants investigation.

METHODS

A prospective study including 747 consecutive chronic hepatitis C (CHC) patients, of whom 546 had completed a course of anti-HCV therapy and underwent pre-, peri- and post-therapy surveys for anthropomorphic, viral, metabolic and hepatic profiles and adiponectin levels, was conducted in a tertiary care center.

RESULTS

Multivariate analyses indicated associations of sex, triglyceride levels and hepatic steatosis with adiponectin levels and of triglyceride levels and interferon λ3 (IFNL3) genotype with homeostasis model assessment-estimated insulin resistance (HOMA-IR) levels before anti-HCV therapy. In patients with a sustained virological response (SVR; n = 455), at 24 weeks post-therapy, sex, BMI, aspartate aminotransferase to platelet ratio index (APRI), HOMA-IR and steatosis were associated with adiponectin levels, and IFNL3 genotype was associated with HOMA-IR levels. GEE analysis demonstrated that SVR affected longitudinal trends in adiponectin levels. Compared with pre-therapy levels, adiponectin and APRI levels decreased 24 weeks post-therapy in SVR patients, regardless of baseline insulin resistance (IR). However, HOMA-IR levels decreased in SVR patients with baseline IR but increased in those without baseline IR. Compared with controls, immunohistochemical studies showed that pre-therapy CHC patients had higher hepatic adiponectin expression associated with hepatic fibrosis.

CONCLUSIONS

During HCV infection, adiponectin may affect insulin sensitivity through triglycerides. After viral clearance, adiponectin levels were directly associated with insulin sensitivity and decreased upon improved hepatic fibrosis; with a link to the IFNL3 genotype, insulin sensitivity improved only in patients with baseline IR.

Assessment of metabolic and mitochondrial dynamics in CD4+ and CD8+ T cells in virologically suppressed HIV-positive individuals on combination antiretroviral therapy

Metabolism plays a fundamental role in supporting the growth, proliferation and effector functions of T cells. We investigated the impact of HIV infection on key processes that regulate glucose uptake and mitochondrial biogenesis in subpopulations of CD4+ and CD8+ T cells from 18 virologically-suppressed HIV-positive individuals on combination antiretroviral therapy (cART; median CD4+ cell count: 728 cells/μl) and 13 HIV seronegative controls. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) production were also analysed in total CD4+ and CD8+ T cells. Among HIV+/cART individuals, expression of glucose transporter (Glut1) and mitochondrial density were highest within central memory and naïve CD4+ T cells, and lowest among effector memory and transitional memory T cells, with similar trends in HIV-negative controls. Compared to HIV-negative controls, there was a trend towards higher percentage of circulating CD4+Glut1+ T cells in HIV+/cART participants. There were no significant differences in mitochondrial dynamics between subject groups. Glut1 expression was positively correlated with mitochondrial density and MMP in total CD4+ T cells, while MMP was also positively correlated with ROS production in both CD4+ and CD8+ T cells. Our study characterizes specific metabolic features of CD4+ and CD8+ T cells in HIV-negative and HIV+/cART individuals and will invite future studies to explore the immunometabolic consequences of HIV infection.

Sustained High Levels of Both Total and High Molecular Weight Adiponectin in Plasma during the Convalescent Phase of Haemorrhagic Fever with Renal Syndrome Are Associated with Disease Severity

Haemorrhagic fever with renal syndrome (HFRS) is characterised by an uncontrolled immune response that causes vascular leakage. Adiponectin (APN) is an adipocytokine involved in prorevascularisation and immunomodulation. To investigate the possible effects of APN in the pathogenesis of HFRS, total and high molecular weight (HMW) APN levels in the plasma of patients with HFRS were quantified using enzyme-linked immunosorbent assay (ELISA). Compared with those in healthy controls, the plasma total and HMW APN levels in patients were elevated to different degrees from the fever onset and remained high at the convalescent phase. Consistent with these results, western blot analysis additionally showed that low molecular weight (LMW), middle molecular weight (MMW), and HMW APN levels were all elevated and contributed to the elevation of the total APN level. Importantly, sustained high levels of total and HMW APN at the convalescent phase were significantly higher in patients with critical disease than those in patients with mild or moderate disease. Moreover, total and HMW APN levels negatively correlated with white blood cell count and positively correlated with platelet count and serum albumin level. These results may provide insights into understanding the roles of total and HMW APN in the pathogenesis of HFRS.

Adiponectin Suppresses T Helper 17 Cell Differentiation and Limits Autoimmune CNS Inflammation via the SIRT1/PPARγ/RORγt Pathway

T helper 17 (Th17) cells are vital components of the adaptive immune system involved in the pathogenesis of most autoimmune and inflammatory syndromes, and adiponectin(ADN) is correlated with inflammatory diseases such as multiple sclerosis (MS) and type II diabetes. However, the regulatory effects of adiponectin on pathogenic Th17 cell and Th17-mediated autoimmune central nervous system (CNS) inflammation are not fully understood. In this study, we demonstrated that ADN could inhibit Th1 and Th17 but not Th2 cells differentiation in vitro. In the in vivo study, we demonstrated that ADN deficiency promoted CNS inflammation and demyelination and exacerbated experimental autoimmune encephalomyelitis (EAE), an animal model of human MS. Furthermore, ADN deficiency increased the Th1 and Th17 cell cytokines of both the peripheral immune system and CNS in mice suffering from EAE. It is worth mentioning that ADN deficiency predominantly promoted the antigen-specific Th17 cells response in autoimmune encephalomyelitis. In addition, in vitro and in vivo, ADN upregulated sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor γ (PPARγ) and inhibited retinoid-related orphan receptor-γt (RORγt); the key transcription factor during Th17 cell differentiation. These results systematically uncovered the role and mechanism of adiponectin on pathogenic Th17 cells and suggested that adiponectin could inhibit Th17 cell-mediated autoimmune CNS inflammation.

Metabolic alterations and hepatitis C: From bench to bedside

In addition to causing cirrhosis and hepatocellular carcinoma, hepatitis C virus (HCV) is thought to cause hypolipidemia, hepatic steatosis, insulin resistance, metabolic syndrome, and diabetes. The viral life cycle of HCV depends on cholesterol metabolism in host cells. HCV core protein and nonstructural protein 5A perturb crucial lipid and glucose pathways, such as the sterol regulatory element-binding protein pathway and the protein kinase B/mammalian target of rapamycin/S6 kinase 1 pathway. Although several lines of transgenic mice expressing core or full HCV proteins exhibit hepatic steatosis and/or dyslipidemia, whether they completely reflect the metabolic alterations in humans with HCV infection remains unknown. Many cross-sectional studies have demonstrated increased prevalences of metabolic alterations and cardiovascular events in patients with chronic hepatitis C (CHC); however, conflicting results exist, primarily due to unavoidable individual variations. Utilizing anti-HCV therapy, most longitudinal cohort studies of CHC patients have demonstrated the favorable effects of viral clearance in attenuating metabolic alterations and cardiovascular risks. To determine the risks of HCV-associated metabolic alterations and associated complications in patients with CHC, it is necessary to adjust for crucial confounders, such as HCV genotype and host baseline glucose metabolism, for a long follow-up period after anti-HCV treatment. Adipose tissue is an important endocrine organ due to its release of adipocytokines, which regulate lipid and glucose metabolism. However, most data on HCV infection and adipocytokine alteration are inconclusive. A comprehensive overview of HCV-associated metabolic and adipocytokine alterations, from bench to bedside, is presented in this topic highlight.

A Follow-Up Study of 50 Chronic Hepatitis C Patients: Adiponectin as a Resilience Biomarker for Major Depression

OBJECTIVE

Major depression (MD) is a condition associated with both hepatitis C virus (HCV) infection and pegylated interferon (IFN)-α treatment. IFN induces a depressive syndrome that is associated with an inflammatory profile. We aimed to investigate whether there is any specific alteration in plasma biomarkers associated with MD.

METHODS

HCV-monoinfected patients, with and without IFN treatment, were followed up for 18 months and went through structured psychiatric evaluation. We assessed plasma levels of brain-derived neurotrophic factor, tumor necrosis factor (TNF) and its soluble type 1 and type 2 receptors (sTNFR1 and sTNFR2, respectively), and adipokines (adiponectin, leptin and resistin) using ELISA.

RESULTS

Among the 50 patients included in the study, 14 were treated with IFN during the follow-up. Being older, not married, presenting higher body mass index, higher liver inflammatory activity, lower baseline adiponectin levels and use of IFN were associated with MD development. Higher levels of sTNFR1 during IFN treatment were associated with sustained virological response. The lack of a control group without HCV infection did not allow any assumption of a biomarker change exclusively due to the infection itself.

CONCLUSION

Adiponectin may be a resilience biomarker for MD in HCV-infected patients.

Serum adiponectin in HIV-1 and hepatitis C virus mono- and co-infected Kenyan injection drug users

Adiponectin is an important marker of anthropometric profiles of adipose tissue. However, association of adiponectin and adiposity in HIV mono- and co-infected and hepatitis (HCV) injection drug users (IDUs) has not been elucidated. Therefore, the relationship of total adiponectin levels with anthropometric indices of adiposity was examined in HIV mono-infected (anti-retroviral treatment, ART-naive, n=16 and -experienced, n=34); HCV mono-infected, n=36; HIV and HCV co-infected (ART-naive, n=5 and -experienced, n=13); uninfected, n=19 IDUs; and healthy controls, n=16 from coastal Kenya. Anthropometric indices of adiposity were recorded and total circulating adiponectin levels were measured in serum samples using enzyme-linked immunosorbent assay. Adiponectin levels differed significantly amongst the study groups (P<0.0001). Post-hoc analyses revealed decreased levels in HIV mono-infected ART-naive IDUs in comparison to uninfected IDUs (P<0.05) and healthy controls (P<0.05). However, adiponectin levels were elevated in HCV mono-infected IDUs relative to HIV mono-infected ART-naive (P<0.001) and -experienced (P<0.001) as well as HIV and HCV co-infected ART-naive (P<0.05) IDUs. Furthermore, adiponectin correlated with weight (ρ=0.687; P=0.003) and BMI (ρ=0.598; P=0.014) in HIV mono-infected ART-naive IDUs; waist circumference (ρ=-0.626; P<0.0001), hip (ρ=-0.561; P=0.001) circumference, and bust-to-waist ratio (ρ=0.561; P=0.001) in HIV mono-infected ART-experienced IDUs; waist girth (ρ=0.375; P=0.024) in HCV mono-infected IDUs; and waist-to-hip ratio (ρ=-0.872; P=0.048) in HIV and HCV co-infected ART-naive IDUs. Altogether, these results suggest suppression of adiponectin production in treatment-naive HIV mono-infected IDUs and that circulating adiponectin is a useful surrogate marker of altered adiposity in treatment-naive and -experienced HIV and HCV mono- and co-infected IDUs.

Adiponectin regulates psoriasiform skin inflammation by suppressing IL-17 production from γδ-T cells

Accumulating epidemiologic evidence has revealed that metabolic syndrome is an independent risk factor for psoriasis development and is associated with more severe psoriasis. Adiponectin, primarily recognized as a metabolic mediator of insulin sensitivity, has been newly drawing attention as a mediator of immune responses. Here we demonstrate that adiponectin regulates skin inflammation, especially IL-17-related psoriasiform dermatitis. Mice with adiponectin deficiency show severe psoriasiform skin inflammation with enhanced infiltration of IL-17-producing dermal Vγ4+γδ-T cells. Adiponectin directly acts on murine dermal γδ-T cells to suppress IL-17 synthesis via AdipoR1. We furthermore demonstrate here that the adiponectin level of skin tissue as well as subcutaneous fat is decreased in psoriasis patients. IL-17 production from human CD4- or CD8-positive T cells is also suppressed by adiponectin. Our data provide a regulatory role of adiponectin in skin inflammation, which would imply a mechanism underlying the relationship between psoriasis and metabolic disorders.

Correlates of adiponectin in hepatitis C-infected children: the importance of body mass index

OBJECTIVES

Adiponectin is a regulator of cytokines that, in turn, play a vital role in inflammatory and immune responses. Adiponectin is therefore likely to have a contributory role in hepatitis C virus (HCV) infection. We sought to characterize adiponectin levels and examine correlates in a pediatric HCV-infected cohort.

METHODS

We performed a cross-sectional study in children (5-17 years of age, n = 86) in the Pediatric Study of Hepatitis C (PEDS-C) trial. Adiponectin levels were univariately correlated with patient demographics, anthropometrics, and viral and histological measures. Multivariate regression models were used to identify the unique (ie, nonconfounded) associations with adiponectin concentrations.

RESULTS

Body mass index (BMI) had the highest univariate inverse correlation with log(e) adiponectin (r = -0.5, P < 0.0001). In multivariate analysis, BMI remained inversely correlated with log(e) adiponectin after accounting for age and route of HCV transmission (r = -0.38, P = 0.0003). Steatosis and fibrosis were inversely related to log(e) adiponectin in univariate analysis, but these associations were not statistically significant after multivariate adjustments (P ≥ 0.1827).

CONCLUSIONS

High BMI among HCV-infected children is associated with lower adiponectin levels. Practitioners should be cognizant of the possible risks of low adiponectin when managing HCV-infected children who are overweight. Further studies are indicated to determine the impact of having low adiponectin on HCV infection in youth.

Adiponectin serum level in chronic hepatitis C infection and therapeutic profile

Hepatic steatosis is commonly seen in the patients with chronic hepatitis C virus (HCV) infection. HCV is closely associated with lipid metabolism, and viral steatosis is more common in genotype 3 infection owing to a direct cytopathic effect of HCV core protein. In non-genotype 3 infection, hepatic steatosis is considered largely to be the result of the alterations in host metabolism; metabolic steatosis is primarily linked with HCV genotype 1. Adipose tissue secretes different hormones involved in glucose and lipid metabolisms. It has been demonstrated that adipocytokines are involved in the pathogenesis of non-alcoholic fatty liver disease, as the decreased plasma adiponectin levels, a soluble matrix protein expressed by adipoctyes and hepatocyte, are associated with liver steatosis. Various studies have shown that steatosis is strongly correlated negatively with adiponectin in the patients with HCV infection. The role of adiponectin in hepatitis C virus induced steatosis is still not completely understood, but the relationship between adiponectin low levels and liver steatosis is probably due to the ability of adiponectin to protect hepatocytes from triglyceride accumulation by increasing β-oxidation of free fatty acid and thus decreasing de novo free fatty acid production.

Adiponectin protects against acetaminophen-induced mitochondrial dysfunction and acute liver injury by promoting autophagy in mice

BACKGROUND & AIMS

Acetaminophen (APAP) overdose causes hepatic necrosis and acute liver injury by inducing mitochondrial dysfunction and damage. Although the biochemical pathways that mediate APAP-induced hepatotoxicity have been well studied, the body's defense mechanism to attenuate this disease remains elusive. This study investigated the roles of adiponectin, an adipocyte-secreted adipokine with pleiotropic protective effects against obesity-related metabolic dysfunction, in the pathogenesis of APAP-induced liver injury in mice.

METHODS

Adiponectin knockout (ADN KO) and C57 wild type mice were treated with an overdose of APAP, followed by histological and biochemical evaluation of liver injury and activation of autophagy. The mechanism of adiponectin in APAP-induced hepatocytic toxicity was also explored in primary cultured hepatocytes.

RESULTS

APAP overdose triggers a marked accumulation of adiponectin in injured liver tissues. ADN KO mice exhibit severely exacerbated mitochondrial dysfunction and damage, oxidative stress and necrosis and much higher mortality in response to APAP overdose, whereas these changes are reversed by a single injection of adiponectin. Mechanistically, adiponectin induces autophagosome formation by AMP-activated protein kinase (AMPK)-dependent activation of the Unc-51-like kinase 1, consequently leading to the removal of damaged mitochondria from hepatocytes. The protective effects of adiponectin against APAP-induced mitochondrial damage, oxidative stress and necrosis are abrogated by blockage of AMPK or pharmacological inhibition of autophagy.

CONCLUSIONS

Our findings suggest that the APAP-induced accumulation of adiponectin in liver tissues serves as an adaptive mechanism to ameliorate hepatotoxicity by promoting autophagy-mediated clearance of damaged mitochondria. Adiponectin agonists may represent a promising therapy for the drug-induced acute liver failure.

Adiponectin: A multitasking player in the field of liver diseases

Adiponectin is the most abundant adipokine synthesized by adipose tissue and has been shown to be a key component in the relationship between adiposity, insulin resistance and inflammation. It circulates in plasma at physiological concentrations that represent 0.05% of all plasma proteins. Adiponectin has trimeric, hexameric and multimeric forms that bind to receptors AdipoR1, AdipoR2 and T-cadherin especially in liver, muscle and endothelial cells. Adiponectin is considered a potent modulator of lipid and glucose metabolism with antidiabetic, antiatherogenic and anti-inflammatory properties, and plays an important role in the pathogenesis of metabolic diseases. The hepatoprotective effects of adiponectin, especially in non-alcoholic fatty liver disease (NAFLD), have been widely investigated, and its antisteatotic, anti-inflammatory and antifibrogenic effects have already been described. Adiponectin levels are reduced in individuals with fatty liver disease independently of body mass index, insulin resistance and other adipokines, and are inversely related to the severity of steatosis and necroinflammation, suggesting an important role in the relationship between adipose tissue, the liver and insulin sensitivity. Adiponectin has also been found to be reduced in cases of hepatitis B and C infection, and in cholestatic and autoimmune diseases, but is increased in patients with cirrhosis of different aetiologies. In addition, an important role for the liver in the regulation of adiponectin secretion by adipocytes, mediated by bile acids, has recently been proposed. The present report describes the importance of adiponectin in hepatic diseases as well as some future perspectives of the role of adiponectin as a biomarker and therapeutic target in liver diseases.

Increased glucose metabolic activity is associated with CD4+ T-cell activation and depletion during chronic HIV infection

OBJECTIVES

Glucose metabolism plays a fundamental role in supporting the growth, proliferation and effector functions of T cells. We investigated the impact of HIV infection on key processes that regulate glucose uptake and metabolism in primary CD4 and CD8 T cells.

DESIGN AND METHODS

Thirty-eight HIV-infected treatment-naive, 35 HIV+/combination antiretroviral therapy, seven HIV+ long-term nonprogressors and 25 HIV control individuals were studied. Basal markers of glycolysis [e.g. glucose transporter-1 (Glut1) expression, glucose uptake, intracellular glucose-6-phosphate, and L-lactate] were measured in T cells. The cellular markers of immune activation, CD38 and HLA-DR, were measured by flow cytometry.

RESULTS

The surface expression of the Glut1 is up-regulated in CD4 T cells in HIV-infected patients compared with uninfected controls. The percentage of circulating CD4Glut1 T cells was significantly increased in HIV-infected patients and was not restored to normal levels following combination antiretroviral therapy. Basal markers of glycolysis were significantly higher in CD4Glut1 T cells compared to CD4Glut1 T cells. The proportion of CD4Glut1 T cells correlated positively with the expression of the cellular activation marker, HLA-DR, on total CD4 T cells, but inversely with the absolute CD4 T-cell count irrespective of HIV treatment status.

CONCLUSION

Our data suggest that Glut1 is a potentially novel and functional marker of CD4 T-cell activation during HIV infection. In addition, Glut1 expression on CD4 T cells may be exploited as a prognostic marker for CD4 T-cell loss during HIV disease progression.

Variations of serum levels of adiponectin and resistin in chronic viral hepatitis

BACKGROUND AND AIMS

Several studies investigated the possible role of adipokines during chronic viral hepatitis, not producing defined results neither clearly establishing their behavior in course of anti-viral treatment. Our study evaluated blood concentrations of adiponectin and resistin in patients with chronic hepatitis C (CHC), B (CHB), and D (CHD) receiving anti-viral treatment, at baseline and after therapy.

METHODS

We examined 122 subjects, divided into two groups: 64 patients with chronic hepatitis C virus (HCV) infection (38 males and 26 females, mean age 47.25 yr) and 58 patients including 39 ones with chronic hepatitis B virus (HBV) infection (26 males and 13 females, mean age 48.46 yr) and 19 ones with chronic HBV-hepatitis D virus (HDV) infection (15 males and 4 females, mean age 45.79 yr). Serum levels of adiponectin and resistin were assayed by enzyme-linked immunosorbent assay.

RESULTS

In the group of CHC patients we observed a significant decrease in resistin after therapy (p=0.006), while not a significant increase in adiponectin after treatment (p=0.32). Evaluation of changes in adiponectin and resistin levels after anti-viral treatment, both in responders and non-responders, revealed no significant variations. In the group of HBV+ and HBV-HDV+ patients, we found a decrease in resistin after therapy (p=0.0016) and a not significant reduction in adiponectin after treatment (p=0.13). Furthermore, we noticed a significant reduction of resistin (p=0.006) in the sub-group of responders.

CONCLUSIONS

Our data suggested the possible marker role of adiponectin and resistin in the inflammatory process in course of chronic viral hepatitis.

Adiponectin in inflammatory and immune-mediated diseases

Circulating levels of adiponectin (APN) are reduced in obesity and associated comorbidities, with inflammation playing an important role in downregulating APN production. In contrast to obesity and metabolic disease, elevated systemic and local levels of APN are present in patients with inflammatory and immune-mediated diseases, including autoimmune and pulmonary conditions, heart and kidney failure, viral hepatitis, organ transplantation and perhaps critical illness. A positive association between inflammation and APN is usually reported in inflammatory/immune pathologies, in contrast with the negative correlation typical of metabolic disease. This review discusses the role of APN in modulation of inflammation and immunity and the potential mechanisms leading to increased levels of APN in inflammatory/immune diseases, including modification of adipose tissue physiology; relative contribution of different tissues and adipose depots; hormonal, pharmacological, nutritional and life style factors; the potential contribution of the microbiota as well as the role of altered APN clearance and release from T-cadherin-associated tissue reservoirs. Potential reasons for some of the apparently contradictory findings on the role of APN as a modulator of immunity and inflammation are also discussed, including a comparison of types of recombinant APN used for in vitro studies and strain-dependent differences in the phenotype of APN KO mice.

Perihepatic lymph node enlargement is a negative predictor of liver cancer development in chronic hepatitis C patients

BACKGROUND

Perihepatic lymph node enlargement (PLNE) is a common ultrasound finding in chronic hepatitis C patients. Although PLNE is considered to reflect the inflammatory response to hepatitis C virus (HCV), its clinical significance remains unclear.

METHODS

Between December 2004 and June 2005, we enrolled 846 chronic hepatitis C patients in whom adequate ultrasound examinations had been performed. PLNE was defined as a perihepatic lymph node that was at least 1 cm in the longest axis by ultrasonography. We analyzed the clinical features of patients with PLNE and prospectively investigated the association between PLNE and hepatocellular carcinoma (HCC) development.

RESULTS

We detected PLNE in 169 (20.0%) patients. Female sex, lower body mass index (BMI), and HCV serotype 1 were independently associated with the presence of PLNE. However, there were no significant differences in liver function tests, liver stiffness, and hepatitis C viral loads between patients with and without PLNE. During the follow-up period (mean 4.8 years), HCC developed in 121 patients. Unexpectedly, patients with PLNE revealed a significantly lower risk of HCC development than those without PLNE (p = 0.019, log rank test). Multivariate analysis revealed that the presence of PLNE was an independent negative predictor of HCC development (hazard ratio 0.551, p = 0.042). In addition, the sustained viral response rate in patients who received interferon (IFN) therapy was significantly lower in patients with PLNE than in patients without PLNE.

CONCLUSIONS

Patients with PLNE had a lower risk of HCC development than those without PLNE. This study may provide new insights into daily clinical practice and the pathophysiology of HCV-induced hepatitis and hepatocarcinogenesis.

Association of visceral obesity with high viral load and histological findings in elderly patients with genotype 1 chronic hepatitis C

OBJECTIVE

Genotype 1 chronic hepatitis C (G1CHC) is generally accompanied by metabolic disturbances related to visceral obesity, such as insulin resistance, steatosis, or dyslipidemia. Because these abnormalities negatively influence the clinical course of G1CHC, we sought to clarify the effect of visceral obesity on the pathophysiology of G1CHC.

METHODS

We evaluated 180G1CHC patients for the presence of visceral obesity on the basis of computed tomography findings. Multivariate analysis was performed to estimate the relationship between visceral obesity and demographic, viral, and biochemical characteristics of patients. The associations of visceral obesity with histological findings and serum adipokine levels were also analyzed.

RESULTS

Multiple logistic regression analysis revealed that visceral obesity was independently associated with metabolic syndrome, platelet count, high-density lipoprotein level, and serum viral load in elderly patients (≥65 years). Multiple linear regression analysis confirmed the association between visceral obesity and high viral load. However, visceral obesity was not correlated with viral load in non-elderly patients (<65 years). Histological data (160 patients) demonstrated the significant association between visceral obesity and steatosis. Furthermore, patients with visceral obesity showed increase in the severity of fibrosis with advancing age. However, age-associated fibrosis progression was not evident in patients without visceral obesity. The serum adiponectin level was significantly low in patients with visceral obesity, whereas those of leptin, tumor necrosis factor-α, and interleukin-6 were not affected significantly.

CONCLUSION

Visceral obesity was associated with high viral load and histological damage in elderly patients with reduced adiponectin levels.

Adiponectin induces pro-inflammatory programs in human macrophages and CD4+ T cells

Abundant experimental and clinical data support a modulatory role for adiponectin in inflammation, dysmetabolism, and disease. Because the activation of cells involved in innate and adaptive immunity contributes to the pathogenesis of diseases such as atherosclerosis and obesity, this study investigated the role of adiponectin in human macrophage polarization and T cell differentiation. Examination of the adiponectin-induced transcriptome in primary human macrophages revealed that adiponectin promotes neither classical (M1) nor alternative (M2) macrophage activation but elicits a pro-inflammatory response that resembles M1 more closely than M2. Addition of adiponectin to polyclonally activated CD4(+) T lymphocytes did not affect cell proliferation but induced mRNA expression and protein secretion of interferon (IFN)-γ and interleukin (IL)-6. Adiponectin treatment of CD4(+) T cells increased phosphorylation of p38 mitogen-activated protein kinase (MAPK) and signal transducer and activation of transcription (STAT) 4 and augmented T-bet expression. Inhibition of p38 with SB203580 abrogated adiponectin-induced IFN-γ production, indicating that adiponectin enhances T(H)1 differentiation through the activation of the p38-STAT4-T-bet axis. Collectively, our results demonstrate that adiponectin can induce pro-inflammatory functions in isolated macrophages and T cells, concurring with previous observations that adiponectin induces a limited program of inflammatory activation that likely desensitizes these cells to further pro-inflammatory stimuli.

HCV core-induced nonobese hepatic steatosis is associated with hypoadiponectinemia and is ameliorated by adiponectin administration

Obesity-related hepatic steatosis is commonly associated with central fat accumulation and alterations in adipocytokine secretion; however, the connection between nonobese hepatic steatosis and adipocytokines remains unclear. We aim to investigate this connection using an animal model of conditional hepatitis C virus (HCV) core-transgenic mice. Double transgenic mice (DTM) with doxycycline (dox)-regulated hepatic overexpression of the HCV core protein were fed standard rodent chow ad libitum following 1 month of a dox-rich diet. The mice exhibited nonobese hepatic steatosis at 2 months of age. The levels of leptin and adiponectin were assessed in 2-month-old DTM (i.e., HCV core-tetracycline transactivator (tTA)) and single transgenic mice (STM; i.e., tTA). The total fat mass and the body fat distribution of the mice were evaluated using dual-energy X-ray absorptiometry (DEXA) and magnetic resonance imaging (MRI). Microarray analyses and quantitative real-time PCR were conducted using RNA obtained from the visceral fat of paired DTM and STM. Adiponectin was administered intraperitoneally to the 2-month-old DTM. No significant differences of the various fat components were noted between the DTM and STM. Leptin mRNA was downregulated in the visceral fat of DTM (P = 0.011), and serum adiponectin protein levels were reduced in the DTM compared with those in the STM (P = 0.035). Adiponectin treatment also significantly ameliorated hepatic steatosis in the DTM compared to the controls (P = 0.024). In conclusion, HCV core-induced nonobese hepatic steatosis is associated with downregulation of the leptin gene in visceral fat and concurrent hypoadiponectinemia; however, these effects may be ameliorated by adiponectin treatment.

The metabolic syndrome in critically ill patients

Metabolic support in intensive care is a rapidly evolving field with new information being gathered almost on a daily basis. In endocrine practice, over the last 20 years, researchers have focussed on a new entity, termed the "metabolic syndrome". This describes the constellation of abnormalities which include central adiposity, insulin resistance and inflammation. All of these predispose the individual to a greater risk of cardiovascular events. Of interest is the observation that some of the metabolic abnormalities in sepsis and multiple organ dysfunction syndrome of critical illness share several common features with that of the metabolic syndrome. In this chapter we describe the features of the metabolic syndrome as is understood in endocrine parlance, the metabolic abnormalities of critical illness and explore the common threads underlying the pathophysiology and the treatment of the two syndromes. The role of adiponectin in the metabolic abnormalities in both the metabolic syndrome and in sepsis are reviewed. The potential role of the pleiotropic effects of statins in the therapy of sepsis is also discussed.

Serum adiponectin upon admission to the intensive care unit may predict mortality in critically ill patients

PURPOSE

Adiponectin has been proposed as an important regulator of glucose metabolism influencing obesity and insulin resistance, which are important risk factors for the outcome of critically ill patients. Moreover, experimental models of inflammation suggest protective anti-inflammatory properties of adiponectin. We therefore investigated the potential pathogenic role and prognostic value of circulating adiponectin levels in critical illness.

MATERIALS AND METHODS

One hundred seventy critically ill patients (122 with sepsis and 48 without sepsis) were prospectively studied at admission to the medical intensive care unit (ICU) and compared with 60 healthy controls. Patients' survival was followed for approximately 3 years.

RESULTS

Adiponectin serum concentrations did not differ between healthy controls and critically ill patients, neither in patients with nor in patients without sepsis. However, patients with decompensated liver cirrhosis had significantly elevated serum adiponectin levels. Likewise to non-critically ill subjects, ICU patients with preexisting diabetes or obesity displayed significantly reduced circulating adiponectin. Inflammatory cytokines did not correlate with serum adiponectin. Interestingly, low adiponectin levels at ICU admission were an independent positive predictor of short-term and overall survival.

CONCLUSIONS

Although serum concentrations did not differ in critically ill patients from controls, low adiponectin levels at admission to ICU have been identified as an independent predictor of survival.

Fibrosis is associated with adiponectin resistance in chronic hepatitis C virus infection

BACKGROUND

Chronic hepatitis C virus (HCV) infection is frequently associated with insulin resistance which has been suggested to promote fibrotic progression. Adiponectin, an adipocyte-derived insulin-sensitizing hormone, might play a protective role against hepatic fibrosis.

MATERIALS AND METHODS

This observational case-control study investigated the adiponectin status in insulin resistant, nondiabetic, chronic HCV-infected patients (n=54; 13 women, 41 men) compared with age-, sex- and BMI-matched healthy controls. Liver biopsies from patients with chronic HCV hepatitis were analysed for the adiponectin and adiponectin receptors (ADIPOR) 1 and 2 mRNA and protein expressions.

RESULTS

Serum adiponectin levels were higher in patients with chronic HCV hepatitis than in healthy controls (12·1±4·7 vs. 9·5±4·4 mg L(-1) in men, P = 0·01; 18·2±4·4 vs. 13·6±5·3mgL(-1) in women, P=0·02). BMI, HDL cholesterol and triglycerides levels correlated with adiponectin levels both in patients and in controls, while no correlation with glucose, insulin and HOMA-IR values could be detected. Nonetheless, insulin resistance was predictive of steatosis and fibrosis in chronic HCV-infected patients. Interestingly, patients with none or mild fibrosis showed serum adiponectin levels similar to those in healthy controls, while hyperadiponectinemia was associated with moderate to severe stages of fibrosis. Hyperadiponectinemia was unlikely sustained by liver production as hepatocytes did not express the protein. ADIPOR1 mRNA, but not ADIPOR2 levels, was reduced in chronic HCV hepatitis. The reduced ADIPOR1 expression was confirmed by immunohistochemistry.

CONCLUSIONS

In patients with chronic HCV hepatitis, fibrosis was associated with hyperadiponectinemia. Chronic HCV-infected hepatocytes showed reduced ADIPOR1 expression, suggesting a pattern of adiponectin resistance.

Potential role of leptin, adiponectin and three novel adipokines--visfatin, chemerin and vaspin--in chronic hepatitis

Chronic hepatitis C (CHC) is generally a slowly progressive disease, but some factors associated with rapid progression have been identified. Steatosis, independently of its metabolic or viral origin, leads to liver injury and fibrosis. It is suggested that hepatitis C virus may contribute to a wide spectrum of metabolic disturbances-namely, steatosis, insulin resistance, increased prevalence of impaired glucose tolerance, type 2 diabetes mellitus and lipid metabolism abnormalities. Adipokines, which are produced mainly by adipose tissue, may influence the inflammatory response and insulin sensitivity and contribute to the development of metabolic abnormalities in CHC and also regulate fibrogenesis and angiogenesis. Visfatin was described as an adipokine with immunomodulating and proinflammatory properties that promotes B-cell maturation and enhances activation of leukocytes, synthesis of adhesion molecules and production of proinflammatory cytokines. Visfatin exerts insulin-mimetic effects, decreases plasma glucose levels and regulates cell energy balance. Chemerin stimulates chemotaxis of dendritic cells, macrophages and natural killer (NK) cells toward the site of inflammation. On the other hand, it inhibits synthesis of proinflammatory mediators and enhances adiponectin production, influences adipocyte differentiation and maturation and regulates glucose uptake in adipocytes. Vaspin expression in human adipose tissue seems to be a compensatory mechanism associated with obesity and insulin resistance. Vaspin suppresses leptin, tumor necrosis factor (TNF)-α and resistin expression. Leptin protects against liver steatosis but accelerates fibrosis progression and exacerbates the inflammatory process. In contrast, adiponectin exerts a hepatoprotective effect. In this report, data indicating a possible role of these adipokines in the pathogenesis of chronic hepatitis are summarized.

Adiponectin is a negative regulator of antigen-activated T cells

Adiponectin (APN), a cytokine constitutively produced in fat tissue, has been shown to exert anti-inflammatory effects in various disease models. While the influence of APN on monocytic cells has been extensively studied in vitro, little is known about its role in T cells. In this study, we show that while <10% of human peripheral blood T cells express adiponectin receptors (AdipoRs) on their surface, most T cells store AdipoRs in intracellular compartments. AdipoRs colocalized with immune regulatory molecules CTLA-4 and TIRC7 within clathrin-coated vesicles. After stimulation, the expression of adiponectin receptor 1 (AdipoR1) and AdipoR2 was upregulated on the surface of antigen-specific T cells, as determined by tetramer or CD137 staining, and AdipoR1 and AdipoR2 coexpressed with CTLA-4. Addition of APN resulted in a significant diminution of antigen-specific T-cell expansion. Mechanistically, APN enhanced apoptosis and inhibited proliferation of antigen-specific T-cell lines. Further, APN directly inhibited cytokine production in response to antigen stimulation. In line with the in vitro data, APN-deficient (knockout, KO) mice had higher frequencies of CD137(+) T cells upon Coxsackie B virus infection. Altogether, our data suggest that APN is a novel negative T-cell regulator. In contrast to the CTLA-4 ligand B7 only expressed on APCs, APN is abundant in human plasma.

Clinical review: adiponectin biology and its role in inflammation and critical illness

Adiponectin is an adipokine first described just over a decade ago. Produced almost exclusively by adipocytes, adiponectin circulates in high concentrations in human plasma. Research into this hormone has revealed it to have insulin-sensitizing, anti-inflammatory and cardioprotective roles. This review discusses the history, biology and physiological role of adiponectin and explores its role in disease, with specific focus on adiponectin in inflammation and sepsis. It appears that an inverse relationship exists between adiponectin and inflammatory cytokines. Low levels of adiponectin have been found in critically ill patients, although data are limited in human subjects at this stage. The role of adiponectin in systemic inflammation and critical illness is not well defined. Early data suggest that plasma levels of adiponectin are decreased in critical illness. Whether this is a result of the disease process itself or whether patients with lower levels of this hormone are more susceptible to developing a critical illness is not known. This observation of lower adiponectin levels then raises the possibility of therapeutic options to increase circulating adiponectin levels. The various options for modulation of serum adiponectin (recombinant adiponectin, thiazolidinediones) are discussed.

Molecular cloning and expression pattern analysis of two novel disulfide isomerases in shrimp

Protein disulfide isomerase (PDI) catalyzes formation and isomerization of disulfide bridges and has chaperone activity. Currently, increasing evidence suggests the significance of PDI in immune and stress responses. To clarify the role of PDIs in the innate immunity of shrimp, two PDI genes were isolated and identified from Fenneropenaeus chinensis (fleshy prawn). FcPDI1 is 1878bp in length and encodes a protein of 383 amino acids. It has 18-amino acid signal peptide, 3 thioredoxin domains with 3 active sites of CGHC, and KEDL retention signal at its C-end. FcPDI1 is an atypical PDI. The open reading frame of FcPDI2 encodes a 497-amino acid protein and shows the classical domain organization a-b-b'-a'. Phylogenic analysis and multiple alignments show that FcPDI1 is similar to PDI that contains 3 thioredoxin domains from other species including invertebrates and vertebrates. FcPDI2, LvPDI, and insect PDIs are grouped into one cluster and are similar to PDIs having a-b-b'-a' domain organization. Tissue distribution shows that FcPDI1 and FcPDI2 were expressed in all detected tissues at the mRNA level. Changes in FcPDI1 and FcPDI2 expression at the mRNA level in hemocytes, hepatopancreas, gills, and ovaries upon Vibrio or white spot syndrome virus challenge were also analyzed. The results suggest that FcPDI1 and FcPDI2 might have roles in the innate immunity of shrimp. FcPDI1 was also successfully expressed in Escherichia coli and the recombinant FcPDI1 showed insulin reductase activity. Results show that FcPDI might play an important role in the innate immunity of shrimp.

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.

Advances in viral hepatitis: 50 years of Australian gastroenterology

Viral hepatitis classification, treatments and pathogenesis has been increasingly defined over the past 50 years. Australian researchers have made significant contributions in the areas of viral hepatitis A vaccine development, treatment outcomes for chronic hepatitis B and C, the role of liver transplantation and the pathogenesis of injury and disease progression. This review outlines some of these contributions.

Serum levels of adipokines in patients with chronic HCV infection: relationship with steatosis and fibrosis

BACKGROUND AND AIMS

Hepatic steatosis and fibrosis are common histological findings in patients with chronic hepatitis C virus (HCV) infection. In this study we sought to determine whether serum levels of three adipokines (leptin, adiponectin and resistin) show any biochemical correlation with hepatic steatosis and fibrosis in patients with chronic HCV infection.

METHODS

We examined a total of 51 patients with chronic HCV infection (22 males and 29 females, mean BMI: 27.4+/-5kg/m(2)) and 24 healthy control subjects (10 males and 14 females, mean BMI: 23.2+/-3kg/m(2)). Liver steatosis and fibrosis were scored on biopsies. Serum levels of leptin, adiponectin and resistin were determined by ELISA.

RESULTS

HCV genotypes were 1b in 41 patients (80.4%), 3a in three patients (5.9%), 2a in two patients (3.9%), 1a in two patients (3.9%), 1c in one patient (2%), and 2b in one patient (2%). Serum levels of leptin, resistin, and the leptin-to-adiponectin ratio were significantly higher in patients with chronic HCV infection than in controls. Steatosis and fibrosis were detected in 33.3% and 70.5% of chronic HCV patients, respectively. No significant association with serum adipokine levels and degree of steatosis was evident. Low serum levels of resistin were associated with the presence of fibrosis independently of potential confounders.

CONCLUSIONS

Patients with chronic HCV infection display elevated levels of adipokines in their sera. Reduced concentrations of resistin may be a biochemical marker of fibrosis in this patient group.

Adipokines in liver diseases

Adipokines are polypeptides secreted in the adipose tissue in a regulated manner. While some of these molecules are expressed only by adipocytes, resident and infiltrating macrophages and components of the vascular stroma markedly contribute to expression of other adipokines. As a result, adipose tissue inflammation is associated with a modification in the pattern of adipokine secretion. Leptin, adiponectin, and resistin are the best-studied molecules in this class, but cytokines such as tumor necrosis factor or interleukin-6 are also secreted at high levels by the adipose tissue. Several other molecules have been recently identified and are actively investigated. Adipokines interfere with hepatic injury associated with fatty infiltration, differentially modulating steatosis, inflammation, and fibrosis. Several studies have investigated plasma levels of adiponectin in patients with nonalcoholic fatty liver disease, to establish correlations with the underlying state of insulin resistance and with the type and severity of hepatic damage. Hepatitis C is another disease where adipokines may represent a link between viral infection, steatosis, and metabolic disturbances. Identification of the mediators secreted by expanded adipose tissue and their pathogenic role is pivotal in consideration of the alarming increase in the prevalence of obesity and of the detrimental role that this condition exerts on the course of liver diseases.

Changes in serum adiponectin concentrations in critical illness: a preliminary investigation

INTRODUCTION

Adiponectin plays an important role in the regulation of tissue inflammation and insulin sensitivity. Perturbations in adiponectin concentration have been associated with obesity and the metabolic syndrome. Data on adiponectin pathophysiology in critical illness are limited.

METHODS

Twenty three critically ill patients (9 severe sepsis, 7 burns, 7 trauma). Adiponectin assays on Days 3 (D3) and 7 (D7). Simultaneous, cortisol, cortisone and CRP measurements. Data from 16 historical controls were used for comparison.

RESULTS

The mean plasma adiponectin concentration for the ICU cohort on D3 and D7 were not significantly different (4.1 +/- 1.8 and 5.0 +/- 3.3 mcg/ml respectively, P = 0.38). However, these were significantly lower than the mean plasma adiponectin in the control population (8.78 +/- 3.81 mcg/ml) at D3 (P < 0.0001) and D7 (P = 0.002). Plasma adiponectin showed a strong correlation with plasma cortisol in the ICU group on both D3 (R2 = 0.32, P < 0.01) and D7 (R2 = 0.64, 0.001). There was an inverse correlation between plasma adiponectin and CRP on D7, R = -0.35.

CONCLUSIONS

In this preliminary study, critical illness was associated with lower adiponectin concentrations as compared with controls. A significant relationship between plasma cortisol and adiponectin in critically ill patients was evident, both during the early and late phases. These data raise the possibility that adiponectin may play a part in the inflammatory response in patients with severe illness.