Increased acylation stimulating protein concentrations in nonalcoholic fatty liver disease are associated with insulin resistance

From complement to complosome in non-alcoholic fatty liver disease: When location matters

Non-alcoholic fatty liver disease (NAFLD) is a growing public health threat and becoming the leading cause of liver transplantation. Nevertheless, no approved specific treatment is currently available for NAFLD. The pathogenesis of NAFLD is multifaceted and not yet fully understood. Accumulating evidence suggests a significant role of the complement system in the development and progression of NAFLD. Here, we provide an overview of the complement system, incorporating the novel concept of complosome, and summarise the up-to-date evidence elucidating the association between complement dysregulation and the pathogenesis of NAFLD. In this process, the extracellular complement system is activated through various pathways, thereby directly contributing to, or working together with other immune cells in the disease development and progression. We also introduce the complosome and assess the evidence that implicates its potential influence in NAFLD through its direct impact on hepatocytes or non-parenchymal liver cells. Additionally, we expound upon how complement system and the complosome may exert their effects in relation with hepatic zonation in NAFLD. Furthermore, we discuss the potential therapeutic implications of targeting the complement system, extracellularly and intracellularly, for NAFLD treatment. Finally, we present future perspectives towards a better understanding of the complement system's contribution to NAFLD.

Combined with multiplex and network analysis to reveal the key genes and mechanisms of nonalcoholic fatty liver disease

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) has become a significant cause of chronic liver disease in developed countries, as a result of the worldwide trend of obesity and associated metabolic syndrome. Obesity and high-fat diet (HFD) are very common in patients with NAFLD. However, how to screen out key differentially expressed genes (DEGs) is a challenging task. The purpose of this study is to study the screen of key genes and pathways of HFD on the formation process of non-alcoholic fatty liver through network pharmacological analysis.

METHODS

In this study, 173 genes associated with NAFLD were collected from the Gene Expression Omnibus (GEO) database. To find significant genes and pathways, combine network clustering analysis, topology analysis, and pathway analysis.

RESULTS

The results showed that there were four key signaling pathways related to HFD, including complement cascade, Atorvastatin ADME, Asthma and Aflatoxin activation and detoxification. In addition, we identified six representative key genes, including Ccl5, Tlr2, Cd274, Cxcl10, Cxcl9 and Cd74, and screened three intersecting genes in Mus musculus and Homo sapiens sample, including C3, F2 and C7.

CONCLUSIONS

In conclusion, our study constructed the NAFLD gene regulatory network of C57BL/6J mice for the first time and jointly analyzed the Mus musculus samples and Homo sapiens samples. It provides new insights for identifying potential biomarkers and valuable therapeutic clues, and puts forward a new method for web-based research. These findings may provide potential targets for early diagnosis, effective therapy and prognostic markers of NAFLD.

Association of complement components with the risk and severity of NAFLD: A systematic review and meta-analysis

Background

It is generally believed that complement system is strongly associated with the risk of nonalcoholic fatty liver disease (NAFLD). However, complement system contains a variety of complement components, and the relationship between complement components and the risk and severity of NAFLD is inconsistent. The aim of this meta-analysis was to evaluate the association of complement components with the risk and severity of NAFLD.

Methods

We searched PubMed, Embase, Cochrane Library, Google Scholar, Scopus, and ZhiWang Chinese databases from inception to May 2022 for observational studies reporting the risk of NAFLD with complement components. Random-effects meta-analysis was used to obtain pooled estimates of the effect due to heterogeneity.

Results

We identified 18 studies with a total of 18560 included subjects. According to recent studies, levels of complement component 3 (C3) (mean difference (MD): 0.43, 95% confidence interval (CI) 0.26-0.60), complement component 4 (C4) (MD: 0.04, 95% CI 0.02-0.07), complement component 5(C5) (MD: 34.03, 95% CI 30.80-37.27), complement factor B (CFB) (MD: 0.22, 95% CI 0.13-0.31) and acylation stimulating protein (ASP) (standard mean difference (SMD): 5.17, 95% CI 2.57-7.77) in patients with NAFLD were significantly higher than those in the control group. However, no statistical significance was obtained in complement factor D (CFD) levels between NAFLD and non-NAFLD (MD=156.51, 95% CI -59.38-372.40). Moreover, the levels of C3, C5, CFB, and ASP in patients with moderate and severe NAFLD were significantly higher than those in patients with mild NAFLD. Except for C4 and CFD, the included studies did not explore the changes in the severity of NAFLD according to the concentration of C4 and CFD.

Conclusions

This meta-analysis demonstrates that an increase in complement components including C3, C5, CFB, and ASP is associated with an increased risk and severity of NAFLD, indicating that they may be good biomarkers and targets for the diagnosis and treatment of NAFLD.

Systematic review registration

PROSPERO [https://www.crd.york.ac.uk/PROSPERO/], identifier CRD42022348650.

Machine learning models for predicting non-alcoholic fatty liver disease in the general United States population: NHANES database

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, affecting over 30% of the United States population. Early patient identification using a simple method is highly desirable.

AIM

To create machine learning models for predicting NAFLD in the general United States population.

METHODS

Using the NHANES 1988-1994. Thirty NAFLD-related factors were included. The dataset was divided into the training (70%) and testing (30%) datasets. Twenty-four machine learning algorithms were applied to the training dataset. The best-performing models and another interpretable model (i.e., coarse trees) were tested using the testing dataset.

RESULTS

There were 3235 participants (n = 3235) that met the inclusion criteria. In the training phase, the ensemble of random undersampling (RUS) boosted trees had the highest F1 (0.53). In the testing phase, we compared selective machine learning models and NAFLD indices. Based on F1, the ensemble of RUS boosted trees remained the top performer (accuracy 71.1% and F1 0.56) followed by the fatty liver index (accuracy 68.8% and F1 0.52). A simple model (coarse trees) had an accuracy of 74.9% and an F1 of 0.33.

CONCLUSION

Not every machine learning model is complex. Using a simpler model such as coarse trees, we can create an interpretable model for predicting NAFLD with only two predictors: fasting C-peptide and waist circumference. Although the simpler model does not have the best performance, its simplicity is useful in clinical practice.

Complement Component C3: A Novel Biomarker Participating in the Pathogenesis of Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is currently the most common cause of chronic liver disorder worldwide. The pathological spectrum of NAFLD ranges from simple steatosis to non-alcoholic steatohepatitis (NASH) that induces progressive liver cirrhosis and eventually hepatocellular carcinoma (HCC). However, the molecular mechanisms driving the transformation of NASH are obscure. There is a compelling need for understanding the pathogenic mechanisms of NASH, and thereby providing new insight into mechanism-based therapy. Currently, several studies reported that complement system, an innate immune system, played an important role in the pathogenesis of NAFLD, which was also proved by our recent study. Complement component 3 (C3), a protein of the innate immune system, plays a hub role in the complement system. Herein, we present a review on the role and molecular mechanism of C3 in NASH as well as its implication in NASH diagnosis and treatment.

Complement Properdin Regulates the Metabolo-Inflammatory Response to a High Fat Diet

Background and objectives: Overnutrition leads to a metabolic and inflammatory response that includes the activation of Complement. Properdin is the only amplifier of complement activation and increases the provision of complement activation products. Its absence has previously been shown to lead to increased obesity in mice on a high fat diet. The aim of this study was to determine ways in which properdin contributes to a less pronounced obese phenotype. Materials and Methods: Wild type (WT) and properdin deficient mice (KO) were fed a high-fat diet (HFD) for up to 12 weeks. Results: There was a significant increase in liver triglyceride content in the KO HFD group compared to WT on HFD. WT developed steatosis. KO had an additional inflammatory component (steatohepatitis). Analysis of AKT signalling by phosphorylation array supported a decrease in insulin sensitivity which was greater for KO than WT in liver and kidney. There was a significant decrease of C5L2 in the fat membranes of the KO HFD group compared to the WT HFD group. Circulating microparticles in KO HFD group showed lower presence of C5L2. Expression of the fatty acid transporter CD36 in adipose tissue was increased in KO on HFD and was also significantly increased in plasma of KO HFD mice compared to WT on HFD. CD36 was elevated on microparticles from KO on HFD. Ultrastructural changes consistent with obesity-associated glomerulopathy were observed for both HFD fed genotypes, but tubular strain was greater in KO. Conclusion: Our work demonstrates that complement properdin is a dominant factor in limiting the severity of obesity-associated conditions that impact on liver and kidney. The two receptors, C5L2 and CD36, are downstream of the activity exerted by properdin.

Lipotoxicity, neuroinflammation, glial cells and oestrogenic compounds

The high concentrations of free fatty acids as a consequence of obesity and being overweight have become risk factors for the development of different diseases, including neurodegenerative ailments. Free fatty acids are strongly related to inflammatory events, causing cellular and tissue alterations in the brain, including cell death, deficits in neurogenesis and gliogenesis, and cognitive decline. It has been reported that people with a high body mass index have a higher risk of suffering from Alzheimer's disease. Hormones such as oestradiol not only have beneficial effects on brain tissue, but also exert some adverse effects on peripheral tissues, including the ovary and breast. For this reason, some studies have evaluated the protective effect of oestrogen receptor (ER) agonists with more specific tissue activities, such as the neuroactive steroid tibolone. Activation of ERs positively affects the expression of pro-survival factors and cell signalling pathways, thus promoting cell survival. This review aims to discuss the relationship between lipotoxicity and the development of neurodegenerative diseases. We also elaborate on the cellular and molecular mechanisms involved in neuroprotection induced by oestrogens.

Role of Complement and Complement-Related Adipokines in Regulation of Energy Metabolism and Fat Storage

Adipose tissue releases many cytokines and inflammatory factors described as adipokines. In obesity, adipokines released from expanding adipose tissue are implicated in disease progression and metabolic dysfunction. However, mechanisms controlling the progression of adiposity and metabolic complications are not fully understood. It has been suggested that expanding fat mass and sustained release of inflammatory adipokines in adipose tissue lead to hypoxia, oxidative stress, apoptosis, and cellular damage. These changes trigger an immune response involving infiltration of adipose tissue with immune cells, complement activation and generation of factors involved in opsonization and clearance of damaged cells. Abundant evidence now indicates that adipose tissue is an active secretory source of complement and complement-related adipokines that, in addition to their inflammatory role, contribute to the regulation of metabolic function. This article highlights advances in knowledge regarding the role of these adipokines in energy regulation of adipose tissue through modulating lipogenic and lipolytic pathways. Several adipokines will be discussed including adipsin, Factor H, properdin, C3a, Acylation-Stimulating Protein, C1q/TNF-related proteins, and response gene to complement-32 (RGC-32). Interactions between these factors will be described considering their immune-metabolic roles in the adipose tissue microenvironment and their potential contribution to progression of adiposity and metabolic dysfunction. The differential expression and the role of complement factors in gender-related fat partitioning will also be addressed. Identifying lipogenic adipokines and their specific autocrine/paracrine roles may provide means for adipose-tissue-targeted therapeutic interventions that may disrupt the vicious circle of adiposity and disease progression. © 2019 American Physiological Society. Compr Physiol 9:1411-1429, 2019.

Short- and Long-Term Effects of Weight Loss on the Complement Component C3 After Laparoscopic Gastric Bypass in Obese Patients

BACKGROUND

The C3 complement component (C3c) is increasingly recognized as a cardiometabolic risk factor, but how it is affected after weight loss through gastric bypass is a question yet to be answered.

METHODS

A total of 66 obese patients underwent laparoscopic gastric bypass. Anthropometric parameters, total cholesterol (TC), triglycerides, high-density lipoprotein cholesterol (HDLc), low-density lipoprotein cholesterol (LDLc), glucose, insulin, HOMA-IR, liver enzymes, high-sensitivity C-reactive protein (hsCRP), and C3c levels were evaluated at baseline and at 1 and 5 years post-surgery.

RESULTS

All anthropometric and biochemical parameters improved significantly after surgery, although a deterioration was detected with respect to the percentage of excess of weight loss, insulin, TC, LDLc, and lactate dehydrogenase 5 years post-surgery. Despite this, a remission rate of 84 % was observed in the presence of metabolic syndrome after 5 years follow-up. hsCRP and C3c were reduced significantly after surgery and maintained throughout the experimental period. In addition, C3c was correlated with BMI and insulin at all time points. The multivariate regression model, in which C3c was a dependent variable, revealed that aspartate aminotransferase and BMI were independent variables at baseline, alkaline phosphatase and insulin were independent at 1 year post-surgery, and insulin, BMI, and TC were independent at 5 years post-surgery.

CONCLUSIONS

C3c may be a marker of the chronic inflammatory process underlying insulin resistance. Its association with BMI and liver enzymes supports a major role in metabolic activity, although future research is needed to clarify the nature of the molecular mechanisms involved and the physiological significance of these findings.

Relationships among acylation-stimulating protein, insulin resistance, lipometabolism, and fetal growth in gestational diabetes mellitus women

The aim of this study was to investigate the potential relationship between acylation-stimulating protein (ASP), insulin resistance, lipometabolism, the intrauterine metabolic environment and fetal growth in well-controlled gestational diabetes mellitus (GDM) women. A total of 55 well-controlled GDM women, 66 pregnant women with normal glucose tolerance (NGT) and their newborns, were included in this study. Fasting maternal and cord blood ASP, serum lipid profiles, glucose level, insulin level, HOMA-IR, in addition to neonatal anthropometry data, were measured. Maternal blood ASP in GDM is higher than that in NGT. In the GDM group, maternal blood ASP has a positive correlation with TG, FFA and HOMA-IR. Maternal and cord blood ASP levels of LGA fetuses correlate with elevated birth weight and SF4. Similarly, cord blood ASP levels of LGA fetuses also correlate with birth weight and SF4 in the NGT group. The maternal blood ASP level of GDM mothers is associated with lipometabolism, insulin resistance and LGA fetal growth. Nevertheless, the cord blood ASP level correlates with FFA of GDM mothers, LGA fetal growth of GDM and NGT mothers. ASP may be a biomarker for evaluating insulin resistance of GDM and LGA fetal growth.

Low acylation stimulating protein levels are associated with cardiometabolic disorders-secondary to autoimmune activation?

Objective:

We investigated the possible association of serum acylation stimulating protein (ASP) with cardiometabolic disorders and the evidence of autoimmune activation.

Methods:

Population-based randomly selected 1024 participants were cross-sectionally and prospectively analyzed. ASP concentrations were measured with a validated ELISA kit. Correlations were sought separately in subjects with no cardiometabolic disorders (n=427) designated as “healthy.”

Results:

ASP was positively correlated with total testosterone and inversely correlated with platelet activating factor (PAF), PAF-acetylhydrolase (AH), in each gender, and positively correlated in “healthy” men with lipoprotein [Lp](a) and apolipoprotein B. Correlations of ASP with PAF values ≥22 nmol/L were abolished, contrasted to a strongly inverse one in subjects with PAF <22 nmol/L. In linear regression analyses in the whole sample, ASP was inversely associated independently with PAF and PAF-AH and, in men, positively with Lp(a) and sex hormone-binding globulin. Prevalent and (at 2.0 years’ follow-up) incident metabolic syndrome (MetS, n=393), diabetes (n=154), and coronary heart disease (CHD, n=171) were analyzed by sex-, age-, and Lp(a)-adjusted logistic regression, using tertiles of ASP and PAF. The lower two (<42 nmol/L) ASP tertiles were a risk factor in combined sexes for MetS and diabetes. In women, incident CHD was predicted by either reduced or elevated ASP tertiles.

Conclusion:

Findings can be explained by the notion of operation of immune responses against both ASP and oxidized PAF-like lipids of Lp(a) to yield for “reduced” values and increased likelihood of cardiometabolic disorders.

Review: Non-alcoholic fatty liver disease: natural history, pathogenesis and treatment

Non-alcoholic fatty liver disease (NAFLD) is the term used to describe the alcohol-like liver injury that occurs in the absence of alcohol abuse. It embraces a range of histological abnormalities including simple steatosis or fatty liver, non-alcoholic steatohepatitis (NASH) and NAFLD induced cirrhosis. The predominant risk factor for NAFLD appears to be insulin resistance. Simple steatosis and NASH are generally asymptomatic and it is only the development of cirrhosis that has clinical consequence. At present, therapy in NAFLD concentrates on managing risk factors but in the future clinical trials may provide robust evidence for the use of insulin sensitising agents and other potential therapies.

Adipokines in nonalcoholic fatty liver disease

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

Serum complement C3 levels are associated with nonalcoholic fatty liver disease independently of metabolic features in Chinese population

Serum complement C3 levels are closely associated with obesity and related metabolic disorders. This study aimed to investigate the association between serum complement C3 levels with non-alcoholic fatty liver disease (NAFLD). A cross-sectional study was performed among adults who took their annual health examinations at Zhenhai Lianhua Hospital, Ningbo, China during 2014. We included 7540 participants (5069 men and 2471 women) in this study. NAFLD patients had higher serum complement C3 levels (P < 0.001), and these levels were positively associated with both NAFLD prevalence and severity (P < 0.001). The above association remains true among lean and metabolic syndrome-free participants. Multivariable regression analysis showed that serum complement C3 was independently associated with risk for NAFLD (OR = 5.231; 95% CI: 3.169–8.635). Serum complement C3 level is positively associated with prevalence and severity of NAFLD, and this association is independent of obesity and metabolic syndrome.

Association between complement C3 and prevalence of fatty liver disease in an adult population: a cross-sectional study from the Tianjin Chronic Low-Grade Systemic Inflammation and Health (TCLSIHealth) cohort study

Activation of the innate immune system plays a key role in the development of fatty liver disease (FLD). The complement system is a major humoral component of the innate immune response and complement C3 plays a central role, implying that C3 may be a powerful predictor or therapeutic target for FLD. However, few studies have assessed the association between C3 and FLD in a large population. Here we use a cross-sectional study to investigate the link between serum C3 levels and FLD. Participants were recruited from Tianjin Medical University's General Hospital-Health Management Centre. Serum C3 was measured using immunoturbidimetry method and FLD was diagnosed by liver ultrasonography. Multiple logistic regression analysis was used to examine the association between quartiles of C3 and FLD prevalence. The overall prevalence of nonalcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD) were 37.3% and 10.1%, respectively. After adjusting for covariates, the odds ratio of having NAFLD or AFLD (only in males) in the fourth quartile of C3 compared with the first quartile was 4.13 times greater (95% confidence interval, 2.97-5.77) (trend P values < 0.0001) and 2.09 times greater (95% confidence interval, 1.08-4.18) (trend P values = 0.02). This is the first study to demonstrate that serum C3 levels are independently associated with a higher prevalence of NAFLD and AFLD (only in males) in an adult population. Further studies are needed to establish a causal link and determine the precise role of C3 in FLD.

The role of complement factor C3 in lipid metabolism

Abundant reports have shown that there is a strong relationship between C3 and C3a-desArg levels, adipose tissue, and risk factors for cardiovascular disease, metabolic syndrome and diabetes. The data indicate that complement components, particularly C3, are involved in lipid metabolism. The C3 fragment, C3a-desArg, functions as a hormone that has insulin-like effects and facilitates triglyceride metabolism. Adipose tissue produces and regulates the levels of complement components, which promotes generation of inflammatory initiators such as the anaphylatoxins C3a and C5a. The anaphylatoxins trigger a cyto/chemokine response in proportion to the amount of adipose tissue present, and induce inflammation and mediate metabolic effects such as insulin resistance. These observations support the concept that complement is an important participant in lipid metabolism and in obesity, contributing to the metabolic syndrome and to the low-grade inflammation associated with obesity.

Complement alternative pathway activation in human nonalcoholic steatohepatitis

The innate immune system plays a major role in the pathogenesis of nonalcoholic steatohepatitis (NASH). Recently we reported complement activation in human NASH. However, it remained unclear whether the alternative pathway of complement, which amplifies C3 activation and which is frequently associated with pathological complement activation leading to disease, was involved. Here, alternative pathway components were investigated in liver biopsies of obese subjects with healthy livers (n = 10) or with NASH (n = 12) using quantitative PCR, Western blotting, and immunofluorescence staining. Properdin accumulated in areas where neutrophils surrounded steatotic hepatocytes, and colocalized with the C3 activation product C3c. C3 activation status as expressed by the C3c/native C3 ratio was 2.6-fold higher (p<0.01) in subjects with NASH despite reduced native C3 concentrations (0.94±0.12 vs. 0.57±0.09; p<0.01). Hepatic properdin levels positively correlated with levels of C3c (r_s = 0.69; p<0.05) and C3c/C3 activation ratio (r_s = 0.59; p<0.05). C3c, C3 activation status (C3c/C3 ratio) and properdin levels increased with higher lobular inflammation scores as determined according to the Kleiner classification (C3c: p<0.01, C3c/C3 ratio: p<0.05, properdin: p<0.05). Hepatic mRNA expression of factor B and factor D did not differ between subjects with healthy livers and subjects with NASH (factor B: 1.00±0.19 vs. 0.71±0.07, p = 0.26; factor D: 1.00±0.21 vs. 0.66±0.14, p = 0.29;). Hepatic mRNA and protein levels of Decay Accelerating Factor tended to be increased in subjects with NASH (mRNA: 1.00±0.14 vs. 2.37±0.72; p = 0.22; protein: 0.51±0.11 vs. 1.97±0.67; p = 0.28). In contrast, factor H mRNA was downregulated in patients with NASH (1.00±0.09 vs. 0.71±0.06; p<0.05) and a similar trend was observed with hepatic protein levels (1.12±0.16 vs. 0.78±0.07; p = 0.08). Collectively, these data suggest a role for alternative pathway activation in driving hepatic inflammation in NASH. Therefore, alternative pathway factors may be considered attractive targets for treating NASH by inhibiting complement activation.

The complement system in human cardiometabolic disease

The complement system has been implicated in obesity, fatty liver, diabetes and cardiovascular disease (CVD). Complement factors are produced in adipose tissue and appear to be involved in adipose tissue metabolism and local inflammation. Thereby complement links adipose tissue inflammation to systemic metabolic derangements, such as low-grade inflammation, insulin resistance and dyslipidaemia. Furthermore, complement has been implicated in pathophysiological mechanisms of diet- and alcohol induced liver damage, hyperglycaemia, endothelial dysfunction, atherosclerosis and fibrinolysis. In this review, we summarize current evidence on the role of the complement system in several processes of human cardiometabolic disease. C3 is the central component in complement activation, and has most widely been studied in humans. C3 concentrations are associated with insulin resistance, liver dysfunction, risk of the metabolic syndrome, type 2 diabetes and CVD. C3 can be activated by the classical, the lectin and the alternative pathway of complement activation; and downstream activation of C3 activates the terminal pathway. Complement may also be activated via extrinsic proteases of the coagulation, fibrinolysis and the kinin systems. Studies on the different complement activation pathways in human cardiometabolic disease are limited, but available evidence suggests that they may have distinct roles in processes underlying cardiometabolic disease. The lectin pathway appeared beneficial in some studies on type 2 diabetes and CVD, while factors of the classical and the alternative pathway were related to unfavourable cardiometabolic traits. The terminal complement pathway was also implicated in insulin resistance and liver disease, and appears to have a prominent role in acute and advanced CVD. The available human data suggest a complex and potentially causal role for the complement system in human cardiometabolic disease. Further, preferably longitudinal studies are needed to disentangle which aspects of the complement system and complement activation affect the different processes in human cardiometabolic disease.

Complement receptors C5aR and C5L2 are associated with metabolic profile, sex hormones, and liver enzymes in obese women pre- and postbariatric surgery

OBJECTIVE

Obesity is associated with metabolic dysfunction with sex differences and chronic, low-grade inflammation.We proposed that hepatic expression of immune complement C3 related receptors (C3aR, C5aR, and C5L2) would be associated with pre- or postmenopausal status and metabolic profile in severely obese women. We hypothesized that C5L2/C5aR ratio, potentially influencing the ASP/C5L2 metabolic versus C5a/C5aR immune response, would predict metabolic profiles after weight loss surgery.

MATERIALS AND METHODS

Fasting plasma (hormone, lipid, and enzyme analysis) and liver biopsies (RT-PCR gene expression) were obtained from 91 women during surgery.

RESULTS

Hepatic C5L2 mRNA expression was elevated in pre- versus postmenopausal women (P < 0.01) and correlated positively with circulating estradiol, estrone, ApoB, ApoA1, ApoA1/B, waist circumference, age, and LDL-C (all P < 0.05).While plasma ASP was lower in pre- versus postmenopausal women (P < 0.01), the hepatic C5L2/C5aR mRNA ratio was increased (P < 0.001) and correlated positively with estrone (P < 0.01) and estradiol (P < 0.001) and negatively with circulating ApoB and liver enzymes ALT, AST, and GGT (all P < 0.05). Over 12 months postoperatively, liver enzymes in low C5L2/C5aR mRNA ratio group remained higher (ALP and ALT, P < 0.05, AST and GGT, P < 0.001 2-way-ANOVA).

CONCLUSION

C5L2-C5aR association with other mediators including estrogens may contribute to hepatic metabolic and inflammatory function.

Plasma gamma-glutamyltransferase is strongly determined by acylation stimulating protein levels independent of insulin resistance in patients with acute coronary syndrome

Background. Steatosis is a manifestation of the metabolic syndrome often associated with release of liver enzymes and inflammatory adipocytokines linked to cardiovascular risk. Gamma-glutamyltransferase (GGT) is one sensitive liver marker recently identified as an independent cardiovascular risk factor. Mechanisms involved in enhanced hepatic lipogenesis causing steatosis are not yet identified and are usually linked to insulin resistance (IR). Acylation stimulating protein (ASP), a potent lipogenic factor, was recently shown to increase in patients with steatosis and was implicated in its pathogenesis. Aim. To investigate the association of plasma ASP levels with liver and metabolic risk markers in acute coronary syndrome (ACS) patients. Methods. 28 patients and 30 healthy controls were recruited. Their anthropometrics, lipid profile, liver markers, insulin, and ASP levels were measured. Results. In the patients, ASP, liver, and metabolic risk markers were markedly higher than in the controls. ASP strongly predicted GGT levels (B = 0.75, P < 0.0001), followed by triglycerides (B = 0.403, P = 0.017), together determining 57.6% variation in GGT levels. Insulin and IR correlated with metabolic risk components but not with liver enzymes. Conclusion. The strong association of ASP with GGT in ACS patients suggests that ASP, independent of IR, may contribute to a vicious cycle of hepatic lipogenic stimulation and GGT release promoting atherogenesis.

Increased acylation stimulating protein levels in young obese males is correlated with systemic markers of oxidative stress

OBJECTIVE

As little is known about relationship between acylation stimulating protein (ASP) and oxidative stress, whether there is any link between ASP and oxidative stress in young obese males were investigated.

DESIGN AND METHODS

Forty-five obese (median body mass index (BMI) = 36.99 (IQR = 3.65) kg m(-2)) male subjects (median age = 22 (IQR = 6) years) and 24 age-matched (median age = 22.5 (IQR = 4.8) years) healthy male volunteers (median body mass index (BMI) = 23.67 (IQR = 2.45) kg m(-2)) were recruited into the study. All obese subjects have BMI > 30 kg m(-2), while all controls have BMI < 25 kg m(-2).

RESULTS

Fasting plasma ASP, lipid hydroperoxide, high sensitivity C-reactive protein (hs-CRP), fasting insulin, triglyceride, LDL-cholesterol levels and HOMA-IR were higher, whereas the mean HDL-cholesterol levels and glutathione peroxidase (GPx) enzyme activity were significantly lower in obese subjects than controls. The linear regression analysis showed that lipid hydroperoxide was independently associated with only BMI, while ASP was independently associated with BMI and triglyceride.

CONCLUSIONS

The present data support the concept that obesity occurs under condition of compex interactions by adipokines, insulin, inflammation, and oxidative stress.

Activated complement factor 3 is associated with liver fat and liver enzymes: the CODAM study

BACKGROUND

The complement system may be involved in the pathogenesis of alcoholic and nonalcoholic liver disease, although studies in humans are scarce. For this reason, we investigated whether circulating levels of activated complement factor 3 (C3a) were associated with hepatic steatosis and hepatocellular damage.

MATERIALS AND METHODS

Plasma C3a, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT) were determined in 523 individuals (61% men, age 59 ± 7 years). Liver enzymes (LEs) were standardized and compiled into a LE score. Liver fat content was estimated using a predictive equation that has recently been validated with magnetic resonance spectrometry. Cross-sectional associations between C3a and liver fat or LE s were investigated with multiple linear regression analyses, stratified in no-to-moderate vs. heavy alcohol consumers (men: > 30 g/day; women: > 20 g/day).

RESULTS

C3a was associated with liver fat percentage both in the no-to-moderate (β = 0.223; 95%CI 0.036; 0.409) and in the heavy alcohol consumers (β = 0.632; 95%CI 0.259-1.004; P-interaction = 0.047). C3a was also associated with the LE score in heavy alcohol consumers (β = 0.917; 95%CI 0.443-1.392), but not in no-to-moderate alcohol consumers (β = 0.042; 95%CI -0.198 to 0.281; P-interaction = 0.001).

CONCLUSIONS

C3a levels, as a marker of complement activation, were associated with liver fat content and hepatocellular injury, at least in subjects who consume considerable amounts of alcohol daily.

The role of the complement system in metabolic organs and metabolic diseases

Emerging evidence points to a close crosstalk between metabolic organs and innate immunity in the course of metabolic disorders. In particular, cellular and humoral factors of innate immunity are thought to contribute to metabolic dysregulation of the adipose tissue or the liver, as well as to dysfunction of the pancreas; all these conditions are linked to the development of insulin resistance and diabetes mellitus. A central component of innate immunity is the complement system. Interestingly, the classical view of complement as a major system of host defense that copes with infections is changing to that of a multi-functional player in tissue homeostasis, degeneration, and regeneration. In the present review, we will discuss the link between complement and metabolic organs, focusing on the pancreas, adipose tissue, and liver and the diverse effects of complement system on metabolic disorders.

Advances in understanding the role of complement in the pathogenesis of fatty liver disease

Patients with fatty liver disease (FLD) exhibit various immunologic abnormalities in the adipose tissue and the liver. Complement plays an important role in the development of FLD. Innate immune dysfunction in the adipose tissue can lead to abnormal production of adipose-derived factors, some of which can activate complement. Complement can not only amplify the inflammatory response and lead to mitochondrial damage, but also inhibit hepatic fat disposal and promote lipid accumulation in hepatocytes. An exploration of the relationship between complement ant the liver can help us have a deep understanding of the mechanisms underlying the pathogenesis of FLD. The antagonists of the C5L2 receptor provide us potential new medicines for FLD. A further study of the role of complement in stress-induced liver remodeling can help clarify the role of complement in the development and progression of FLD.

Activation of the complement system in human nonalcoholic fatty liver disease

Activation of the innate immune system plays a major role in nonalcoholic fatty liver disease (NAFLD). The complement system is an important component of innate immunity that recognizes danger signals such as tissue injury. We aimed to determine whether activation of the complement system occurs in NAFLD, to identify initiating pathways, and to assess the relation between complement activation, NAFLD severity, apoptosis, and inflammatory parameters. Liver biopsies of 43 obese subjects with various degrees of NAFLD and of 10 healthy controls were analyzed for deposition of complement factors C1q, mannose-binding lectin (MBL), C4d, activated C3, and membrane attack complex (MAC)-associated C9. Furthermore, hepatic neutrophil infiltration, apoptosis, and pro-inflammatory cytokine expression were quantified. Whereas complement activation was undetectable in the liver of healthy subjects, 74% of the NAFLD patients showed hepatic deposition of activated C3 and C4d. C1q as well as MBL accumulation was found in most activated C3-positive patients. Strikingly, 50% of activated C3-positive patients also displayed MAC-associated C9 deposition. Deposition of complement factors was predominantly seen around hepatocytes with macrovesicular steatosis. Subjects showing accumulation of activated C3 displayed increased numbers of apoptotic cells. Importantly, hepatic neutrophil infiltration as well as interleukin (IL)-8 and IL-6 expression was significantly higher in patients showing activated C3 deposition, whereas patients with C9 deposition additionally had increased IL-1beta expression. Moreover, nonalcoholic steatohepatitis (NASH) was more prevalent in patients showing hepatic C9 or activated C3 deposition.

CONCLUSION

There is widespread activation of the complement system in NAFLD, which is associated with disease severity. This may have important implications for the pathogenesis and progression of NAFLD given the function of complement factors in clearance of apoptotic cells, hepatic fibrosis, and liver regeneration.

Change in plasma acylation stimulating protein during euglycaemic-hyperinsulinaemic clamp in overweight and obese postmenopausal women: a MONET study

OBJECTIVE

Acylation-stimulating protein (ASP) has been shown to positively stimulate fatty acid esterification and glucose uptake in adipocytes. In vitro studies demonstrate that insulin stimulates ASP secretion from adipocytes. Individuals with obesity and/or metabolic disturbances (insulin resistance and type 2 diabetes) have increased plasma ASP.

DESIGN

The present study was designed to evaluate whether ASP levels are influenced by the metabolic profiles of overweight and obese postmenopausal women during a euglycaemic/hyperinsulinaemic clamp (EHC). Patients The study population consisted of 76 overweight and obese sedentary postmenopausal women.

MEASUREMENTS

We evaluated insulin sensitivity, plasma ASP levels, body composition including visceral adipose tissue area, blood lipid profiles, liver enzymes, peak aerobic capacity, resting metabolic rate (RMR) and total energy expenditure (TEE).

RESULTS

We observed wide interindividual variations of ASP levels during the EHC. Therefore, subjects were divided into three groups based on ASP changes. Negative ASP Responders (NAR; n = 24) showed a -20% or greater decrease in ASP levels while Positive ASP Responders (PAR; n = 42) displayed ASP fluctuations superior to +20%. Ten subjects had little or no ASP change and were considered as Zero ASP responders (ZAR). PAR women displayed a worse metabolic profile than NAR women, including higher BMI, visceral adipose tissue, fasting insulin levels, lean body mass, and alanine aminotransferase (ALT), a marker of impaired liver function. After adjustment for BMI, only ALT remained significantly different, while lean body mass (P = 0.08) and visceral adipose tissue (P = 0.07) remained marginally higher. Correlation analysis of all subjects demonstrated that fasting ASP levels correlated positively with albumin and VO(2 peak) and this association remained significant after adjustments for the effect of BMI. In addition, the percentage maximal change in ASP levels during the EHC was positively associated with BMI, lean body mass, visceral adipose tissue, fasting insulin, HOMA, TEE, RMR, ALT and AST.

CONCLUSION

Overall these results suggest that an elevated ASP response during the EHC is associated with metabolic disturbances in overweight and obese postmenopausal women.

Effect of a hypocaloric diet in transaminases in nonalcoholic fatty liver disease and obese patients, relation with insulin resistance

OBJECTIVE

The aim of our study was to examine the changes in hypertransaminasemia after weight reduction in obese patients with and without nonalcoholic fatty liver disease (NAFLD) and the relation with insulin resistance.

RESEARCH METHODS

A population of 142 obesity nondiabetic was treated with a hypocaloric diet (1520 kcal) during 3 months. Patients were classified as group I (control, n=112) when serum (alanine aminotransferase) ALT activity was normal or group II (NAFLD, n=30) when serum ALT activity was greater than the upper limit of normal reference laboratory (>or=43 UI/L).

RESULTS

In control group, body mass index (BMI) (35.3+/-5.6 vs. 33.5+/-5.5: p<0.05), weight (89.6+/-17.2 kg vs. 85.6+/-16.5 kg: p<0.05) and insulin (15+/-7.9 mUI/L vs. 13.1+/-7.4 mUI/L: p<0.05) levels decreased. In NAFLD group, BMI (37.1+/-4.2 vs. 35.1+/-4.6: p<0.05), weight (101+/-22 kg vs. 96.4+/-11.6 kg: p<0.05), insulin (26.8+/-8.9 mUI/L vs. 12.7+/-8.4 mUI/L: p<0.05) and HOMA (3.1+/-1.6 vs. 1.9+/-1.7: p<0.05) decreased. Liver function improved in both groups (ALT; group I 19.9+/-4.6 UI/L vs. 18.3+/-3.9 UI/L: p<0.05 and group II 37.8+/-4.2 UI/L vs. 27.1+/-7.8 UI/L: p<0.05), (aspartate aminotransferase activity, AST) group I 22.1+/-8.2 UI/L vs. 19.9+/-7.1 UI/L: p<0.05 and group II 73.3+/-11.3 UI/L vs. 38.1+/-11.6UI/L: p<0.05).

CONCLUSION

We showed that weight reduction secondary to a hypocaloric diet were associated with improvement in hypertransaminasemia and insulin resistance in NAFLD patients.

Metformin decreases circulating acylation-stimulating protein levels in polycystic ovary syndrome

AIM

There are no studies that examine the circulating acylation-stimulating protein (ASP) levels in patients with polycystic ovary syndrome (PCOS). The present study was designed to determine the ASP levels in PCOS and to evaluate the effect of metformin on plasma fasting ASP concentrations.

METHODS

Twenty women with PCOS and 20 healthy controls matched for age and body mass index (BMI) were included in the study. We determined ASP and other biochemical parameters before and after treatment.

RESULTS

Baseline levels of plasma ASP, complement 3 (C3), waist-to-hip ratio (WHR), homeostasis model assessment-insulin resistance index (HOMA-IR), fasting insulin, triglycerides (TG) and very-low-density lipoprotein cholesterol (VLDL-C) were significantly higher in patients than in controls. After 3 months of metformin treatment, BMI, WHR, ASP, C3, fasting glucose, fasting insulin, HOMA-IR, total cholesterol, TG, VLDL-C and free testosterone decreased significantly, whereas apolipoprotein A-I and high-density lipoprotein cholesterol increased significantly.

CONCLUSIONS

The major novel information of the present study is that ASP and C3 values are markedly increased in non-obese patients with PCOS, with a decrease evidenced with metformin treatment.

Pharmacoeconomics and quality of life of current and emerging biologic therapies for inflammatory bowel disease

The development of biologic therapies for Crohn's disease and ulcerative colitis has profoundly affected the treatment of these diseases. The impact of these novel therapies has been tremendous in terms of their ability to cause clinical improvement in symptoms and endoscopic and histologic evidence of healing, as well as improvements in quality of life. However, the success of these new remedies comes with a significant price tag. In the current cost-containment environment of health care, it is essential to evaluate the impact of these novel and promising therapies on health care resource utilization, employment productivity, and quality of life. Despite the high cost of these new medications, they may result in a net cost savings through their ability to induce remission in the sickest of inflammatory bowel disease (IBD) patients, thereby averting the large expenditures associated with hospitalization and surgery. Likewise, by improving patients' physical symptoms, emotional well-being, and quality of life, biologic agents have the potential to reduce much of the unemployment, missed work, and disability through which IBD patients suffer. In a disease with an early age of onset and a chronic course with normal life expectancy, reducing morbidity and improving quality of life should be important measures of treatment success. Biologic therapies for IBD hold significant promise in this regard, allowing clinicians to achieve lasting remission in patients who are unresponsive to conventional therapies. Comparison of the costs and benefits of biologic therapies with conventional treatments for IBD is complicated by the need to assess the downstream effects of an intervention. For example, corticosteroids are inexpensive and very effective for induction of remission, but they come with significant long-term complications, such as osteoporosis, cataracts, impaired glucose tolerance, and poor wound healing, which must be taken into account when assessing their true cost as a maintenance medication. We do not yet have enough experience with biologic therapies to evaluate their potential to prevent or create future costs associated with adverse effects. However, as we move forward with our knowledge of biologic agents, an understanding of the economic and quality-of-life implications of these innovative therapies is crucial for patients, clinicians, and third-party payers alike.

Non-alcoholic fatty liver disease: further expression of the metabolic syndrome

Non-alcoholic fatty liver disease has been associated with metabolic disorders, including central obesity, dyslipidemia, hypertension and hyperglycemia. Metabolic syndrome, obesity, and insulin resistance are major risk factors in the pathogenesis of non-alcoholic fatty liver disease. Non-alcoholic fatty liver disease refers to a wide spectrum of liver damage, ranging from simple steatosis to non-alcoholic steatohepatitis, advanced fibrosis and cirrhosis.

The ASP receptor C5L2 is regulated by metabolic hormones associated with insulin resistance

Acylation-stimulating protein (ASP) and interaction with its receptor C5L2 influences adipocyte metabolism. We examined insulin resistance and differentiation-mediated regulation of C5L2 and the mechanistic impact on both C5L2 cell-surface protein and ligand binding to the receptor. C5L2 mRNA increased 8.7-fold with differentiation in 3T3-L1 cells (p < 0.0001) by day 9. In preadipocytes, insulin and dexamethasone increased C5L2 mRNA (1 μmol/L insulin resulted in a 2.6-fold increase, p < 0.01; 10 nmol/L dexamethasone resulted in a 17.9-fold increase, p < 0.01) and C5L2 cell-surface protein (100 nmol insulin resulted in a 2.7-fold increase, p < 0.001; 10 nmol/L dexamethasone resulted in a 2.8-fold increase, p < 0.001). In adipocytes, 100 nmol/L insulin increased C5L2 mRNA and ASP binding (respectively, 1.3-fold, p < 0.01; and 2.4-fold, p < 0.05). Dexamethasone decreased ligand binding (–60%, p < 0.02) without changing mRNA. Tumor necrosis factor alpha decreased C5L2 mRNA (–88% in preadipocytes and –38% in adipocytes, p < 0.001), C5L2 cell-surface protein (–53% in preadipocytes, p < 0.0001), and ASP binding (–60% and –49% in, respectively, preadipocytes and adipoctyes, p < 0.05). Conversely, 1 μmol/L and 10 nmol/L rosiglitazone increased, respectively, C5L2 mRNA (9.3-fold, p < 0.0001) and ASP binding (2.4-fold, p < 0.05). Thus, C5L2 mRNA increases with differentiation, insulin, and thiazolidinedione treatment, and decreases with tumor necrosis factor alpha, all of which results in functional changes in ASP–C5L2 response and may have implications for human metabolism.

Non-alcoholic steatohepatitis and metabolic syndrome

PURPOSE OF REVIEW

Non-alcoholic steatohepatitis is part of a disease spectrum, non-alcoholic fatty liver disease, ranging from simple steatosis to cirrhosis, which is the most frequent cause of abnormal liver tests. There is clinical and epidemiological evidence that non-alcoholic fatty liver disease is the hepatic manifestation of the metabolic syndrome, having in common insulin resistance.

RECENT FINDINGS

The interest in the metabolic syndrome concept has been questioned. Insulin resistance, oxidative stress, mitochondrial dysfunction, immune deregulation and adipokines seem to be crucial in the pathogenesis of non-alcoholic fatty liver disease. The main treatment continues to rely on lifestyle changes, including weight loss strategies. Bariatric surgery in morbidly obese patients and insulin-sensitizing agents seem to be beneficial.

SUMMARY

There is strong evidence of the association of non-alcoholic steatohepatitis with the features of the metabolic syndrome, with its increased cardiovascular risk. Population interventions in order to change lifestyles and diet patterns that constitute risk factors for both situations are urgently needed. There is, however, evidence that in the presence of other risk factors, insulin resistance may be less important. These secondary forms of non-alcoholic steatohepatitis must be recognized, as they are potentially treatable by withdrawing the steatogenic factor.