The adipsin-acylation stimulating protein system and regulation of intracellular triglyceride synthesis

Acylation stimulating protein/C3adesArg in the metabolic states: role of adipocyte dysfunction in obesity complications

Adipose tissue, as an endocrine organ, secretes several adipocyte-derived hormones named 'adipokines' that are implicated in regulating energy haemostasis. Substantial evidence shows that white adipose tissue-derived adipokines mediate the link between obesity-related exogenous factors (like diet and lifestyle) and various biological events (such as pre- and postmenopausal status) that have obesity consequences (cardiometabolic disorders). One of the critical aetiological factors for obesity-related diseases is the dysfunction of adipokine pathways. Acylation-stimulating protein (ASP) is an adipokine that stimulates triglyceride synthesis and storage in adipose tissue by enhancing glucose and fatty acid uptake. ASP acts via its receptor C5L2. The primary objective of this review is to address the existing gap in the literature regarding ASP by investigating its diverse responses and receptor interactions across multiple determinants of obesity. These determinants include diet composition, metabolic disorders, organ involvement, sex and sex hormone levels. Furthermore, this article explores the broader paradigm shift from solely focusing on adipose tissue mass, which contributes to obesity, to considering the broader implications of adipose tissue function. Additionally, we raise a critical question concerning the clinical relevance of the insights gained from this review, both in terms of potential therapeutic interventions targeting ASP and in the context of preventing obesity-related conditions, highlighting the potential of the ASP-C5L2 interaction as a pharmacological target. In conclusion, these findings validate that obesity is a low-grade inflammatory status with multiorgan involvement and sex differences, demonstrating dynamic interactions between immune and metabolic response determinants.

Complement component C3 is associated with body composition parameters and sarcopenia in community-dwelling older adults: a cross-sectional study in Japan

BACKGROUND

Chronic inflammation is a factor in the pathogenesis of sarcopenia, which is characterized by low muscle mass and reduced strength. Complement C3 is important in the management of the immune network system. This study seeks to determine the relationship between serum C3 levels and body composition and sarcopenia-related status in community-dwelling older adults.

METHODS

Study participants were 269 older adults living in rural Japan. A bioelectrical impedance analysis device was used to measure body composition parameters including body mass index (BMI), body fat percentage, waist-hip-ratio, and appendicular skeletal muscle mass index (SMI). Muscle function was measured by handgrip strength and 6-m walking speed. The correlation coefficients for C3 level and measurements were calculated using Pearson correlation analysis. Participants were categorized into normal, pre-sarcopenia, dynapenia, or sarcopenia groups. Sarcopenia was defined according to 2019 Asian Working Group for Sarcopenia definition, dynapenia was defined as low muscle function without low muscle mass, and pre-sarcopenia was defined as the presence of low muscle mass only. The C3 threshold score for sarcopenia status was evaluated by receiver operating characteristic curve (ROC) analysis.

RESULTS

Significant positive correlations were found between C3 and BMI, body fat percentage, and waist-hip ratio in both sexes, and further positive correlations with SMI were found in women. The relationship with body fat percentage was particularly strong. Body composition measurements (BMI, body fat percentage, and waist- hip ratio) and C3 levels were lowest in the sarcopenia group compared with the others. ROC analysis showed that the significant threshold of C3 for discriminating between the normal and sarcopenia groups was 105 mg/dL. Multiple logistic regression analysis showed that participants with C3 < 105 mg/dL had an odds ratio of 3.27 (95% confidence interval, 1.49-7.18) for sarcopenia adjusted by sex, age and body fat percentage.

CONCLUSION

C3 levels are suggested to be related to body composition and pathophysiological functions of sarcopenia. C3 is expected to become a useful biomarker for sarcopenia, for predicting the onset of the disease and for predicting the effectiveness of interventions.

Associations between Adipokines and Metabolic Dysfunction-Associated Fatty Liver Disease Using Three Different Diagnostic Criteria

Background: A panel of experts proposed a new definition of metabolic dysfunction-associated fatty liver disease (MAFLD) in 2020. To date, the associations between adipokines, such as adiponectin, adipsin, and visfatin and MAFLD remain unclear. Therefore, we aimed to evaluate the associations between each of these three adipokines and MAFLD using different diagnostic criteria. Methods: In total, 221 participants were included in our study based on medical examination. Detailed questionnaire information, physical examination, abdominal ultrasound, and blood-biochemical-test indexes were collected. The levels of adipokines were tested by using an enzyme immunoassay. Logistic regression models were used to assess the associations of the adipokines with MAFLD. Results: In total, 122 of the participants were diagnosed with MAFLD. Higher levels of adipsin and lower levels of adiponectin were found in the MAFLD group than in the non-MAFLD group (all p < 0.05). According to the logistic regression analysis, the ORs were 0.11 (95% CI: 0.05–0.23) for adiponectin, 4.46 (95% CI: 2.19–9.12) for adipsin, and 0.51 (95% CI: 0.27–0.99) for visfatin when comparing the highest tertile with the lowest tertile (all p-trend < 0.05). The inverse association between adiponectin and MAFLD was strongest when T2DM was used as the diagnostic criterion alone, and the positive association between adipsin and MAFLD was strongest when BMI was used as the diagnostic criterion alone. There was no significant association between visfatin and MAFLD, regardless of whether each of BMI, T2DM, or metabolic dysregulation (MD) was used as the diagnostic criterion for MAFLD alone. Conclusion: Adipsin levels were positively associated with MAFLD and adiponectin levels were inversely associated with MAFLD. The strength of these associations varied according to the different diagnostic criteria for MAFLD.

Increased Serum Adipsin Correlates with MAFLD and Metabolic Risk Abnormalities

PURPOSE

A panel of international experts proposed a new definition of fatty liver in 2020, namely metabolic dysfunction-associated fatty liver disease (MAFLD). As an adipokine, adipsin is closely related to metabolic-related diseases. In this study, we aimed to evaluate the relationship among MAFLD, serum adipsin, and metabolic risk abnormalities.

METHODS

Our study was a cross-sectional study based on the first follow-up of the Guangzhou Nutrition and Health Study (GNHS). A total of 908 patients with hepatic steatosis were involved in our study. Detailed data of patients were collected based upon questionnaire information, physical examination, and blood biochemical test.

RESULTS

Among the 908 patients, 789 patients were diagnosed with MAFLD. The levels of serum adipsin in the MAFLD group and non-MAFLD group were (3543.00 (3187.94-3972.50) ng/mL) and (3095.33 (2778.71-3354.77) ng/mL) (P < 0.001), respectively. After adjusting for potential confounders, adipsin levels were found to be associated with MAFLD. The OR was 3.46 (95% CI: 1.57-7.64) for adipsin when comparing subjects in the highest tertile with those in the lowest tertile. With the increase in the number of metabolic risk abnormalities, both the levels of serum adipsin and the proportion of moderate to severe fatty liver increased (all p-trend < 0.001).

CONCLUSION

Increased serum adipsin correlates with MAFLD. Both adipsin levels as well as fatty liver severity increase with higher numbers of metabolic risk abnormalities.

Adipsin – summing up large-scale results: A review

Adipsin is one of the first discovered adipokines hormones produced by adipose tissue. Adipsin performs the function of a regulator of carbohydrate and lipid metabolism and participates in the adaptation of metabolism to the real needs of the body, being a powerful stimulant of anabolic processes. A characteristic feature of adipsin is that it is also a complement factor D, which is necessary for the normal functioning of an alternative pathway of activation of the complement system. Due to this, adipsin is represented in the body as a link between the energy block of the endocrine system and the humoral block of the immune system. Adipsin is known as a regulator of the function of pancreatic beta cells, a stimulator of lipogenesis, a modulator of inflammation processes. Recently, there have been works indicating the effect of adipsin on the microbiota, as well as its role in non-alcoholic fatty liver disease. To date, there are a large number of publications describing the biochemical structure, functions of adipsin, mechanisms of regulation of its synthesis, as well as changes in the level of adipsin in various pathological conditions. Attempts are also described to pharmacologically influence adipsin in order to modulate its functions or use it as a biomarker for the diagnosis of diseases. However, there is currently no structured review that summarizes and systematizes all available information about this adipokine. This is exactly the task we set ourselves in this study. The paper contains the results of all available studies on adipsin. In some cases, they are contradictory in nature, which indicates the need for further research in detecting connections between the body's systems.

Tumor Suppressor Par-4 Regulates Complement Factor C3 and Obesity

Prostate apoptosis response-4 (Par-4) is a tumor suppressor that induces apoptosis in cancer cells. However, the physiological function of Par-4 remains unknown. Here we show that conventional Par-4 knockout (Par-4^-/-) mice and adipocyte-specific Par-4 knockout (AKO) mice, but not hepatocyte-specific Par-4 knockout mice, are obese with standard chow diet. Par-4^-/- and AKO mice exhibit increased absorption and storage of fat in adipocytes. Mechanistically, Par-4 loss is associated with mdm2 downregulation and activation of p53. We identified complement factor c3 as a p53-regulated gene linked to fat storage in adipocytes. Par-4 re-expression in adipocytes or c3 deletion reversed the obese mouse phenotype. Moreover, obese human subjects showed lower expression of Par-4 relative to lean subjects, and in longitudinal studies, low baseline Par-4 levels denoted an increased risk of developing obesity later in life. These findings indicate that Par-4 suppresses p53 and its target c3 to regulate obesity.

Complement in metabolic disease: metaflammation and a two-edged sword

We are currently experiencing an enduring global epidemic of obesity and diabetes. It is now understood that chronic low-grade tissue inflammation plays an important role in metabolic disease, brought upon by increased uptake of a so-called Western diet, and a more sedentary lifestyle. Many evolutionarily conserved links exist between metabolism and the immune system, and an imbalance in this system induced by chronic over-nutrition has been termed 'metaflammation'. The complement system is an important and evolutionarily ancient part of innate immunity, but recent work has revealed that complement not only is involved in the recognition of pathogens and induction of inflammation, but also plays important roles in cellular and tissue homeostasis. Complement can therefore contribute both positively and negatively to metabolic control, depending on the nature and anatomical site of its activity. This review will therefore focus on the interactions of complement with mechanisms and tissues relevant for metabolic control, obesity and diabetes.

Prevalence of metabolic syndrome in patients with rheumatoid arthritis in eastern China-A hospital based study

OBJECTIVE

The purpose of this hospital clinic based study was to evaluate the potential risk factors associated with the prevalence of MetS in RA population.

METHODS

From January 2015 to October 2018, 717 patients with RA and 717 healthy controls who were treated or performed physical examination in Tianjin First Central Hospital were enrolled in this study. The basic disease diagnoses were recorded. A questionnaire was performed on all participants to assess the demographic details of the RA cohort. Moreover, laboratory indicators related to glucose and lipid metabolism in patients with RA were also detected. The potential risk factors for MetS were also analyzed.

RESULTS

The prevalence of MetS were 31.2% and 34.2% in case and control groups, respectively (P = .22). There were lower levels of HDL-C, obesity, TG, LDL-C and TC in case group than control group (all P < .05). The hypertension levels in healthy controls was decreased in compared with patients with RA (P < .05). Nevertheless, in patients with RA, complement 3 (OR: 1.02; 95% CI: 1.01-1.03, P = .007) and less glucocorticoids use (OR: 0.63, 95% CI: 0.39-0.99, P = .046) were associated with MetS.

CONCLUSION

The prevalence of MetS was not associated with RA. Complement 3 may be associated with the higher prevalence of MetS in patients with RA. Glucocorticoids treatment may be associated with MetS.

The complex role of adipokines in obesity, inflammation, and autoimmunity

The global obesity epidemic is a major contributor to chronic disease and disability in the world today. Since the discovery of leptin in 1994, a multitude of studies have characterized the pathological changes that occur within adipose tissue in the obese state. One significant change is the dysregulation of adipokine production. Adipokines are an indispensable link between metabolism and optimal immune system function; however, their dysregulation in obesity contributes to chronic low-grade inflammation and disease pathology. Herein, I will highlight current knowledge on adipokine structure and physiological function, and focus on the known roles of these factors in the modulation of the immune response. I will also discuss adipokines in rheumatic and autoimmune diseases.

Complement activation in obesity, insulin resistance, and type 2 diabetes mellitus

Amplified inflammatory reaction has been observed to be involved in cardiometabolic diseases such as obesity, insulin resistance, diabetes, dyslipidemia, and atherosclerosis. The complement system was originally viewed as a supportive first line of defense against microbial invaders, and research over the past decade has come to appreciate that the functions of the complement system extend beyond the defense and elimination of microbes, involving in such diverse processes as clearance of the immune complexes, complementing T and B cell immune functions, tissue regeneration, and metabolism. The focus of this review is to summarize the role of the activation of complement system and the initiation and progression of metabolic disorders including obesity, insulin resistance and diabetes mellitus. In addition, we briefly describe the interaction of the activation of the complement system with diabetic complications such as diabetic retinopathy, nephropathy and neuropathy, highlighting that targeting complement system therapeutics could be one of possible routes to slow down those aforementioned diabetic complications.

Identification of neuropathic pain-associated genes and pathways via random walk with restart algorithm

BACKGROUND

Neuropathic pain (NP) develops from neuropathic lesions or diseases affecting the nervous system, and has become a serious public health issue due to its complex symptoms, high incidence and long duration. At present, the exact pathogenesis of NP is still unclear. In this study, we sought to identify the genes as well as the related molecular mechanisms associated with NP occurrence and development.

METHODS

We firstly identified the differentially expressed genes between NP spinal nerve ligation (SNL) rats and control sham rats and then projected them onto a STRING network for functional association analysis. Then, Random Walk with Restart (RWR) was conducted to find some new NP-related genes, with their potential functions sequentially analyzed by GO annotation and KEGG pathway analysis.

RESULTS

Some new NP-related genes, like Gng13, C3 and Cxcl2, were identified by RWR analysis. Meanwhile, some biological functions like inflammatory responses, chemotaxis and immune responses, as well as some signaling pathways, such as those involved in neuroactive ligand-receptor interactions, complement and blood coagulation cascade reactions, and cytokine-receptor interactions that the new NP- related genes were most activated were found to be associated with NP occurrence and development.

CONCLUSIONS

This study extends our knowledge of NP occurrence and development and provides new therapeutic targets for future NP treatment.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

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.

An overview of lipodystrophy and the role of the complement system

The complement system is a major component of innate immunity playing essential roles in the destruction of pathogens, the clearance of apoptotic cells and immune complexes, the enhancement of phagocytosis, inflammation, and the modulation of adaptive immune responses. During the last decades, numerous studies have shown that the complement system has key functions in the biology of certain tissues. For example, complement contributes to normal brain and embryonic development and to the homeostasis of lipid metabolism. However, the complement system is subjected to the effective balance between activation-inactivation to maintain complement homeostasis and to prevent self-injury to cells or tissues. When this control is disrupted, serious pathologies eventually develop, such as C3 glomerulopathy, autoimmune conditions and infections. Another heterogeneous group of ultra-rare diseases in which complement abnormalities have been described are the lipodystrophy syndromes. These diseases are characterized by the loss of adipose tissue throughout the entire body or partially. Complement over-activation has been reported in most of the patients with acquired partial lipodystrophy (also called Barraquer-Simons Syndrome) and in some cases of the generalized variety of the disease (Lawrence Syndrome). Even so, the mechanism through which the complement system induces adipose tissue abnormalities remains unclear. This review focuses on describing the link between the complement system and certain forms of lipodystrophy. In addition, we present an overview regarding the clinical presentation, differential diagnosis, classification, and management of patients with lipodystrophy associated with complement abnormalities.

Metabolic and oncogenic adaptations to pyruvate dehydrogenase inactivation in fibroblasts

Eukaryotic cell metabolism consists of processes that generate available energy, such as glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation (Oxphos), and those that consume it, including macromolecular synthesis, the maintenance of ionic gradients, and cellular detoxification. By converting pyruvate to acetyl-CoA (AcCoA), the pyruvate dehydrogenase (PDH) complex (PDC) links glycolysis and the TCA cycle. Surprisingly, disrupting the connection between glycolysis and the TCA cycle by inactivation of PDC has only minor effects on cell replication. However, the molecular basis for this metabolic re-equilibration is unclear. We report here that CRISPR/Cas9-generated PDH-knockout (PDH-KO) rat fibroblasts reprogrammed their metabolism and their response to short-term c-Myc (Myc) oncoprotein overexpression. PDH-KO cells replicated normally but produced surprisingly little lactate. They also exhibited higher rates of glycolysis and Oxphos. In addition, PDH-KO cells showed altered cytoplasmic and mitochondrial pH, redox states, and mitochondrial membrane potential (ΔΨM). Conditionally activated Myc expression affected some of these parameters in a PDH-dependent manner. PDH-KO cells had increased oxygen consumption rates in response to glutamate, but not to malate, and were depleted in all TCA cycle substrates between α-ketoglutarate and malate despite high rates of glutaminolysis, as determined by flux studies with isotopically labeled glutamine. Malate and pyruvate were diverted to produce aspartate, thereby potentially explaining the failure to accumulate lactate. We conclude that PDH-KO cells maintain proliferative capacity by utilizing glutamine to supply high rates of AcCoA-independent flux through the bottom portion of the TCA cycle while accumulating pyruvate and aspartate that rescue their redox defects.

Complement Components, C3 and C4, and the Metabolic Syndrome

INTRODUCTION

Increased systemic inflammation plays a significant role in the development of adult cardiometabolic diseases such as insulin resistance, dyslipidemia, atherosclerosis, and hypertension. The complement system is a part of the innate immune system and plays a key role in the regulation of inflammation. Of particular importance is the activation of complement components C3 and C4. C3 is produced primarily by the liver but is also produced in adipocytes, macrophages and endothelial cells, all of which are present in adipose tissues. Dietary fat and chylomicrons stimulate C3 production. Adipocytes in addition to producing C3 also have receptors for activated C3 and other complement components and thus also respond to as well as produce a target for complement. C3adesArg, also known as acylation stimulation factor, increases adipocyte triglyceride synthesis and release. These physiological effects play a significant role in the development of metabolic syndrome. Epidemiologically, obese adults and non-obese adults with cardiometabolic disease who are not obese have been shown to have increased complement levels. C4 levels also correlate with body mass index. Genetically, specific C3 polymorphisms have been shown to predict future cardiovascular events and. D decreased C4 long gene copy number is associated with increased longevity.

CONCLUSION

Future research is clearly needed to clarify the role of complement in the development of cardiovascular disease and mechanisms for its action. The complement system may provide a new area for intervention in the prevention of cardiometabolic diseases.

The complement system is dysfunctional in metabolic disease: Evidences in plasma and adipose tissue from obese and insulin resistant subjects

The relationship among chronic low-grade inflammation, insulin resistance and other obesity-associated metabolic disturbances is increasingly recognized. The possible mechanisms that trigger these immunologic alterations remain to be fully understood. The complement system is a crucial element of immune defense system, being important in the activation of innate and adaptative immune response, promoting the clearance of apoptotic and damaged endogenous cells and participating in processes of tissue development, degeneration, and regeneration. Circulating components of the complement system appear to be dysregulated in obesity-associated metabolic disturbances. The activation of the complement system is also evident in adipose tissue from obese subjects, in association with subclinical inflammation and alterations in glucose metabolism. The possible contribution of some components of the complement system in the development of insulin resistance and obesity-associated metabolic disturbances, and the possible role of complement system in adipose tissue physiology is reviewed here. The modulation of the complement system could constitute a potential target in the pathophysiology and therapy of obesity and associated metabolic disease.

Intermediate and low abundant protein analysis of vitamin D deficient obese and non-obese subjects by MALDI-profiling

Obesity is a pathological condition caused by genetic and environmental factors, including vitamin D deficiency, which increases the risk of developing cardiovascular disorders and diabetes. This case-control study was designed to verify whether serum profiles could be identified differentiating obese and non-obese Saudis characterized by vitamin D deficiency and pathological levels of triglycerides, high-density lipoprotein cholesterol and high total cholesterol levels. The serum protein profiles of 64 vitamin D deficient (serum 25(OH)D < 50nmol/L) individuals with metabolic syndrome and with (n = 31; BMI ≥ 30) or without (n = 33; BMI < 30) obesity were analyzed by a quantitative label-free mass spectrometry approach (MALDI-profiling), combined with different serum immunodepletion strategies (Human7 and Human14 immuno-chromatographies), to analyze the intermediate- and low-abundant protein components. The analysis of intermediate-abundant proteins (Human7) in obese vs. non-obese subjects identified 14 changed peaks (p < 0.05) in the m/z range 1500–35000. Furthermore, the Human14 depletion provided new profiles related to obesity (121 changed peaks). Among changed peaks, 11 were identified in the m/z range 1500–4000 Da by high-resolution tandem mass spectrometry, belonging to apolipoprotein CIII, apolipoprotein B100, alpha-1-antichymotrypsin and complement C3. Data herein show that distinct protein profiles identify specific peptides belonging to lipid metabolism and inflammation processes that are associated with obesity and vitamin D deficiency.

Non-traditional roles of complement in type 2 diabetes: Metabolism, insulin secretion and homeostasis

Type 2 Diabetes (T2D) is a disease of increasing importance and represents a growing burden on global healthcare and human health. In T2D, loss of effectiveness of insulin signaling in peripheral tissues cannot be compensated for by adequate insulin secretion, leading to hyperglycemia and resultant complications. In recent years, inflammation has been identified as a central component of T2D, both in inducing peripheral insulin resistance as well as in the pancreatic islet, where it contributes to loss of insulin secretion and death of insulin-secreting beta cells. In this review we will focus on non-traditional roles of complement proteins which have been identified in T2D-associated inflammation, beta cell secretory function, and in maintaining homeostasis of the pancreatic islet. Improved understanding of both traditional and novel roles of complement proteins in T2D may lead to new therapeutic approaches for this global disease.

Increased adipsin is associated with carotid intima media thickness and metabolic disturbances in polycystic ovary syndrome

CONTEXT

Adipsin, a protein secreted mainly from the adipose tissue, is a structural homologous of complement factor D, a rate-limiting enzyme of the alternative complement system. Growing evidence suggests that the alternative complement system plays a role both in the regulation of energy homoeostasis and in the atherosclerosis. Polycystic ovary syndrome (PCOS) is a reproductive and metabolic disease.

OBJECTIVE

To ascertain whether circulating adipsin levels are altered in women with PCOS, and whether there is an association between adipsin and metabolic parameters or carotid intima media thickness (CIMT).

PARTICIPANTS

A total of 144 women with PCOS and 144 age- and BMI-matched controls without PCOS were recruited for this cross-sectional study.

MAIN OUTCOME MEASURES

Circulating adipsin levels were measured using ELISA. Metabolic, hormonal parameters and CIMT were also determined.

RESULTS

Adipsin levels were significantly elevated in women with PCOS compared with controls (91·52 ± 14·11 vs 60·31 ± 9·71 ng/ml, P < 0·001). Adipsin positively correlated with BMI, homoeostasis model assessment of insulin resistance (HOMA-IR), free testosterone, high-sensitivity C-reactive protein (hs-CRP) and CIMT in both groups. Multivariate logistic regression analyses revealed that the odds ratio for PCOS was 3·25 for patients in the highest quartile of adipsin compared with those in the lowest quartile (OR=3·25, 95% CI=2·64-4·00, P = 0·016). Our findings further indicate that BMI, HOMA-IR, hs-CRP and free testosterone are independent factors influencing serum adipsin levels and that adipsin is an independent predictor for CIMT.

CONCLUSION

Circulating adipsin levels are significantly higher in women with PCOS, and the peptide is closely related to increased cardiovascular risk and metabolic disturbances.

Complement C3 Is the Strongest Predictor of Whole-Body Insulin Sensitivity in Psoriatic Arthritis

Objectives

To evaluate the correlation between inflammatory measures and whole-body insulin sensitivity in psoriatic arthritis (PsA) patients.

Methods

For the present study, 40 nondiabetic PsA patients were recruited. A standard oral glucose tolerance test (OGTT) was performed. The insulin sensitivity index (ISI), insulinogenic index (IGI) and oral disposition index (ODI) were calculated from dynamic values of glucose and insulin obtained during OGTT.

Results

In our study population, mean ISI was 3.5 ± 2.5, median IGI was 1.2 (0.7–1.8), mean ODI 4.5 ± 4.5. In univariate correlation analysis, ISI correlated inversely with systolic blood pressure (sBP) (R = -0.52, p = 0.001), diastolic blood pressure (dBP) (R = -0.45, p = 0.004) and complement C3 (R = -0.43, p = 0.006) and ODI correlated inversely with sBP (R = -0.38, p = 0.02), dBP (R = -0.35, p = 0.03) and complement C3 (R = -0.37, p = 0.02). No significant correlations were found between analyzed variables and IGI. In a stepwise multiple regression, only complement C3 entered in the regression equation and accounted for approximately 50% of the variance of ISI. Using a receiver operating characteristic (ROC) curve we identified the best cut-off for complement C3 of 1.32 g/L that yielded a sensitivity of 56% and a specificity of 96% for classification of insulin resistant patients.

Conclusions

In conclusion, our data suggest that serum complement C3 could represent a useful marker of whole-body insulin sensitivity in PsA patients.

Small Molecule-Induced Complement Factor D (Adipsin) Promotes Lipid Accumulation and Adipocyte Differentiation

Adipocytes are differentiated by various transcriptional cascades integrated on the master regulator, Pparγ. To discover new genes involved in adipocyte differentiation, preadipocytes were treated with three newly identified pro-adipogenic small molecules and GW7845 (a Pparγ agonist) for 24 hours and transcriptional profiling was analyzed. Four genes, Peroxisome proliferator-activated receptor γ (Pparγ), human complement factor D homolog (Cfd), Chemokine (C-C motif) ligand 9 (Ccl9), and GIPC PDZ Domain Containing Family Member 2 (Gipc2) were induced by at least two different small molecules but not by GW7845. Cfd and Ccl9 expressions were specific to adipocytes and they were altered in obese mice. Small hairpin RNA (shRNA) mediated knockdown of Cfd in preadipocytes inhibited lipid accumulation and expression of adipocyte markers during adipocyte differentiation. Overexpression of Cfd promoted adipocyte differentiation, increased C3a production, and led to induction of C3a receptor (C3aR) target gene expression. Similarly, treatments with C3a or C3aR agonist (C4494) also promoted adipogenesis. C3aR knockdown suppressed adipogenesis and impaired the pro-adipogenic effects of Cfd, further suggesting the necessity for C3aR signaling in Cfd-mediated pro-adipogenic axis. Together, these data show the action of Cfd in adipogenesis and underscore the application of small molecules to identify genes in adipocytes.

Bioactive peptides derived from natural proteins with respect to diversity of their receptors and physiological effects

We have found various bioactive peptides derived from animal and plant proteins, which interact with receptors for endogenous bioactive peptides such as opioids, neurotensin, complements C3a and C5a, oxytocin, and formyl peptides etc. Among them, rubiscolin, a δ opioid peptide derived from plant RuBisCO, showed memory-consolidating, anxiolytic-like, and food intake-modulating effects. Soymorphin, a μ opioid peptide derived from β-conglycinin showed anxiolytic-like, anorexigenic, hypoglycemic, and hypotriglyceridemic effects. β-Lactotensin derived from β-lactoglobulin, the first natural ligand for the NTS2 receptor, showed memory-consolidating, anxiolytic-like, and hypocholesterolemic effects. Weak agonist peptides for the complements C3a and C5a receptors were released from many proteins and exerted various central effects. Peptides showing anxiolytic-like antihypertensive and anti-alopecia effects via different types of receptors such as OT, FPR and AT2 were also obtained. Based on these study, new functions and post-receptor mechanisms of receptor commom to endogenous and exogenous bioactive peptides have been clarified.

Complement mediators: key regulators of airway tissue remodeling in asthma

The complement mediators are the major effectors of the immune balance, which operates at the interface between the innate and adaptive immunity, and is vital for many immunoregulatory functions. Activation of the complement cascade through the classical, alternative or lectin pathways thus generating opsonins like C3b and C5b, anaphylatoxins C3a and C5a, chemotaxin, and inflammatory mediators, which leads to cellular death. Complement mediators that accelerate the airway remodeling are not well defined; however, an uncontrolled Th2-driven adaptive immune response has been linked to the major pathophysiologic features of asthma, including bronchoconstriction, airway hyperresponsiveness, and airway inflammation. The mechanisms leading to complement mediated airway tissue remodeling, and the effect of therapy on preventing and/or reversing it are not clearly understood. This review highlights complement-mediated inflammation, and the mechanism through it triggers the airway tissue injury and remodeling in the airway epithelium that could serve as potential targets for developing a new drug to rescue the asthma patients.

Plasma complement C3 levels are associated with insulin secretion independently of adiposity measures in non-diabetic individuals

BACKGROUND AND AIMS

To evaluate if complement C3 is associated with insulin secretion, as suggested by recent in vitro studies, independently of confounders including adiposity measures.

METHODS AND RESULTS

1010 nondiabetic subjects were stratified into quartiles according to complement C3 values. Insulin secretion was assessed using indexes derived from oral glucose tolerance test (OGTT) in the whole study group and from intravenous glucose tolerance test (IVGTT) in a subgroup (n = 110). Significant differences between quartiles of C3 were observed in body mass index (BMI), waist, fat mass, blood pressure, total cholesterol, high density lipoprotein (HDL), triglycerides, fasting and 2-h post-load glucose, fasting insulin, C reactive protein (hsCRP), fibrinogen, aspartate aminotransferase (AST), alanine aminotransferase (ALT), complement C4, and insulin sensitivity with C3 quartiles exhibiting graded increases in cardio-metabolic risk factors. Differences in insulin secretion indexes between C3 quartiles remained significant after adjustment for age, gender, BMI, insulin sensitivity, blood pressure, total cholesterol, HDL, triglycerides, hsCRP, fibrinogen, and complement C4 levels (P < 0.0001). A multivariable regression analysis revealed that complement C3 is a contributor of insulin secretion, explaining 2.4% and 1.9% of variation of the Stumvoll index for first-phase and second-phase insulin secretion, respectively, and 2.1% of variation of the InsAUC30/GluAUC30 index, independently of gender, age, BMI, waist, fat mass, blood pressure, total cholesterol, HDL, triglycerides, hsCRP, fibrinogen, AST, ALT.

CONCLUSIONS

Complement C3 concentrations are associated with insulin secretion independently of important determinants of glucose homeostasis such as gender, age, adiposity, subclinical inflammation, and insulin sensitivity.

Adipose stem cells: biology, safety, regulation, and regenerative potential

This article discusses adipose-derived stem cell (ASC) biology, describes the current knowledge in the literature for the safety and regulation of ASCs, and provides a brief overview of the regenerative potential of ASCs. It is not an exhaustive listing of all available clinical studies or every study applying ASCs in tissue engineering and regenerative medicine, but is an objective commentary of these topics.

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.

Ethnic differences in acylation stimulating protein (ASP) in Xinjiang Uygur autonomous region, China

BACKGROUND

Acylation Stimulating Protein (ASP) stimulates adipocyte triglyceride synthesis and glucose transport. The aim was to examine ethnic difference in ASP and the relation to lipid profile and other parameters among Han, Uygur, and Kazak healthy populations matched for BMI, age and gender distribution.

METHODS

331 healthy persons were recruited in total (age 30-60 yr): 137 Han, 114 Uygur, and 80 Kazak. Anthropometric measurements including height, weight, waist circumference, hip circumference, blood pressure, ankle brachial index (ABI), and pulse wave velocity (PWV) were measured in all participants. Fasting concentrations of fasting glucose, uric acid, and lipids, including triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), ASP, complement C3, insulin, non-esterified fatty acid (NEFA) and C-reactive protein (CRP) were measured.

RESULTS

ASP in Uygurs was significantly lower than Han subjects (P=0.0003). The Uygurs demonstrated the highest C3 (P<0.001), CRP (P=0.001), and NEFA concentrations (P=0.008), the lowest %ASP/C3 (P<0.001) and TC levels (P=0.0008) vs those in Han and Kazak populations. In the Han group, glucose, the average ABI (an index of peripheral response) and diastolic blood pressure were significantly different from both Uygur and Kazak group (P=0.0007, P=0.0003, P=0.0001) while Kazaks show the lowest waist/hip circumference (WHR) (P=0.0003).

CONCLUSION

There are ethnic differences in ASP, C3, CRP and lipid profiles in healthy Han, Uygur, and Kazak populations. Overall, the Uygur populations presents with a disadvantageous metabolic profile as compared to Han and Kazak groups.

The pleiotropic role of HDL in autoimmune diseases

As is widely known, the classic function of HDL is reverse cholesterol transport (RCT), thus removing cholesterol from peripheral tissues. Early epidemiological studies, such as Framingham's, stated that increased HDL levels were associated with a significant decrease in relative risk for cardiovascular disease (CVD) mortality. However, those with heightened expectations in recent years for the development of therapeutic targets to increase HDL levels have been disappointed, because efforts have demonstrated the opposite effect on cardiovascular and global mortality. However, in contrast, studies have highlighted the complexity and the intriguing role of HDL in different pathological conditions, such as infections, neoplasms, and autoimmune diseases. In this review an attempt is made to summarize some biological pathways that link HDL function with the immune system, and its possible clinical repercussions in autoimmune diseases.

Comparative serum proteome expression of the steroid-induced femoral head osteonecrosis in adults

Steroid-induced osteonecrosis of the femoral head (SONFH) is a disabling, aseptic and ischemic disease that develops following steroid therapy. The pathogenesis of SONFH is unclear, so the early diagnosis and treatment for this disease is yet to be established. The purpose of the present study was to identify potential biomarkers for SONFH. The differential expression of serum proteins from patients with SONFH and healthy volunteers was analyzed by the proteomics method. The protein samples were labeled and subjected to isoelectric focusing and two-dimensional gel electrophoresis. The resultant protein spots were matched and quantified by an imaging analysis system. The differentially-expressed protein spots were subjected to in-gel trypsin digestion followed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Significantly lower levels of complement component 3 (C3), C4, inter-α-trypsin inhibitor heavy chain H4 and α-2-macroglobulin were found in the serum of patients with SONFH. These proteins are reported to be actively involved in intravascular coagulation, apoptosis and reactive oxygen species imbalance, indicating that multiple pathological reactions occur in SONFH and these proteins may serve as potential biomarkers for the diagnosis of SONFH.

Adipsin is an adipokine that improves β cell function in diabetes

A hallmark of type 2 diabetes mellitus (T2DM) is the development of pancreatic β cell failure, which results in insulinopenia and hyperglycemia. We show that the adipokine adipsin has a beneficial role in maintaining β cell function. Animals genetically lacking adipsin have glucose intolerance due to insulinopenia; isolated islets from these mice have reduced glucose-stimulated insulin secretion. Replenishment of adipsin to diabetic mice treated hyperglycemia by boosting insulin secretion. We identify C3a, a peptide generated by adipsin, as a potent insulin secretagogue and show that the C3a receptor is required for these beneficial effects of adipsin. C3a acts on islets by augmenting ATP levels, respiration, and cytosolic free Ca(2+). Finally, we demonstrate that T2DM patients with β cell failure are deficient in adipsin. These findings indicate that the adipsin/C3a pathway connects adipocyte function to β cell physiology, and manipulation of this molecular switch may serve as a therapy in T2DM.

LC-MS/MS quantitation of esophagus disease blood serum glycoproteins by enrichment with hydrazide chemistry and lectin affinity chromatography

Changes in glycosylation have been shown to have a profound correlation with development/malignancy in many cancer types. Currently, two major enrichment techniques have been widely applied in glycoproteomics, namely, lectin affinity chromatography (LAC)-based and hydrazide chemistry (HC)-based enrichments. Here we report the LC–MS/MS quantitative analyses of human blood serum glycoproteins and glycopeptides associated with esophageal diseases by LAC- and HC-based enrichment. The separate and complementary qualitative and quantitative data analyses of protein glycosylation were performed using both enrichment techniques. Chemometric and statistical evaluations, PCA plots, or ANOVA test, respectively, were employed to determine and confirm candidate cancer-associated glycoprotein/glycopeptide biomarkers. Out of 139, 59 common glycoproteins (42% overlap) were observed in both enrichment techniques. This overlap is very similar to previously published studies. The quantitation and evaluation of significantly changed glycoproteins/glycopeptides are complementary between LAC and HC enrichments. LC–ESI–MS/MS analyses indicated that 7 glycoproteins enriched by LAC and 11 glycoproteins enriched by HC showed significantly different abundances between disease-free and disease cohorts. Multiple reaction monitoring quantitation resulted in 13 glycopeptides by LAC enrichment and 10 glycosylation sites by HC enrichment to be statistically different among disease cohorts.

UVB-induced gene expression in the skin of Xiphophorus maculatus Jp 163 B

Xiphophorus fish and interspecies hybrids represent long-standing models to study the genetics underlying spontaneous and induced tumorigenesis. The recent release of the Xiphophorus maculatus genome sequence will allow global genetic regulation studies of genes involved in the inherited susceptibility to UVB-induced melanoma within select backcross hybrids. As a first step toward this goal, we report results of an RNA-Seq approach to identify genes and pathways showing modulated transcription within the skin of X. maculatus Jp 163 B upon UVB exposure. X. maculatus Jp 163 B were exposed to various doses of UVB followed by RNA-Seq analysis at each dose to investigate overall gene expression in each sample. A total of 357 genes with a minimum expression change of 4-fold (p-adj<0.05) were identified as responsive to UVB. The molecular genetic response of Xiphophorus skin to UVB exposure permitted assessment of; (1) the basal expression level of each transcript for each skin sample, (2) the changes in expression levels for each gene in the transcriptome upon exposure to increasing doses of UVB, and (3) clusters of genes that exhibit similar patterns of change in expression upon UVB exposure. These data provide a foundation for understanding the molecular genetic response of fish skin to UVB exposure.

C5aR and C5L2 act in concert to balance immunometabolism in adipose tissue

Recent studies suggested that the immunometabolic receptors; C5aR and C5L2, constitutively self-associate into homo-/heterodimers and that acylation stimulating protein (ASP/C3adesArg) or C5a treatment of adipocytes increased their colocalization. The present study evaluates the C5aR contribution in adipocytes to the metabolic and immune responses elicited by ligand stimulation. The effects of C5a, ASP, and insulin on cytokine production, triglyceride synthesis (TGS), and key signaling pathways were evaluated in isolated primary adipocytes and cultured 3T3-L1 differentiated adipocytes. In addition, mRNA expression of IRS1 and PGC1α was compared in adipose tissue samples from WT vs. C5aRKO mice. Both C5a and ASP directly increased MCP-1 (238±4%; P<0.001, and 377±2% vs. basal 100%; P<0.001, respectively) and KC (413±11%; P<0.001, and 529±16%; P<0.001 vs. basal 100%, respectively) secretion, TGS (131±1%; P<0.001, and 152±6%; P<0.001, vs. basal 100% respectively), and Akt/NFκB phosphorylation pathways in adipocytes. However, in C5aRKO adipocytes, C5a effects were disrupted, while stimulatory effects of ASP were mostly maintained. Addition of C5a completely blocked ASP signaling and activity in both C5aRKO and WT adipocytes as well as 3T3-L1 adipocytes. Furthermore, C5aRKO adipocytes revealed impaired insulin stimulation of cytokine production, with partial impairment of signaling and TGS stimulation, consistent with decreased IRS1 and PGC1α mRNA expression in adipose tissue. These observations indicate the importance of C5aR in adipose tissue metabolism and immunity, which may be regulated through heterodimerization with C5L2.

Dietary and flight energetic adaptations in a salivary gland transcriptome of an insectivorous bat

We hypothesized that evolution of salivary gland secretory proteome has been important in adaptation to insectivory, the most common dietary strategy among Chiroptera. A submandibular salivary gland (SMG) transcriptome was sequenced for the little brown bat, Myotis lucifugus. The likely secretory proteome of 23 genes included seven (RETNLB, PSAP, CLU, APOE, LCN2, C3, CEL) related to M. lucifugus insectivorous diet and metabolism. Six of the secretory proteins probably are endocrine, whereas one (CEL) most likely is exocrine. The encoded proteins are associated with lipid hydrolysis, regulation of lipid metabolism, lipid transport, and insulin resistance. They are capable of processing exogenous lipids for flight metabolism while foraging. Salivary carboxyl ester lipase (CEL) is thought to hydrolyze insect lipophorins, which probably are absorbed across the gastric mucosa during feeding. The other six proteins are predicted either to maintain these lipids at high blood concentrations or to facilitate transport and uptake by flight muscles. Expression of these seven genes and coordinated secretion from a single organ is novel to this insectivorous bat, and apparently has evolved through instances of gene duplication, gene recruitment, and nucleotide selection. Four of the recruited genes are single-copy in the Myotis genome, whereas three have undergone duplication(s) with two of these genes exhibiting evolutionary 'bursts' of duplication resulting in multiple paralogs. Evidence for episodic directional selection was found for six of seven genes, reinforcing the conclusion that the recruited genes have important roles in adaptation to insectivory and the metabolic demands of flight. Intragenic frequencies of mobile- element-like sequences differed from frequencies in the whole M. lucifugus genome. Differences among recruited genes imply separate evolutionary trajectories and that adaptation was not a single, coordinated event.

Elevated fetal adipsin/acylation-stimulating protein (ASP) in obese pregnancy: novel placental secretion via Hofbauer cells

CONTEXT AND OBJECTIVE

Obesity in pregnancy is associated with increased risks of obesity in the offspring. We investigated the relationship between obesity in pregnancy and circulating maternal and fetal levels of adipose tissue-derived factors adipsin and acylation stimulating protein (ASP) in lean and obese mothers.

DESIGN

Paired peripheral and cord blood samples were taken. Paired fat and placenta tissue were taken for explant culture. Media were assayed for secreted adipsin and ASP. Clinical parameters assayed included fasting insulin, glucose, and adipsin.

SETTING

The study was conducted at a university hospital maternity unit.

PATIENTS

Patients included 35 lean [body mass index (BMI) 19-25 kg/m(2), mean age 32 years and 39 obese (BMI) > 30 kg/m(2), mean age 32.49 years] pregnant Caucasian women, delivered by cesarean section at term.

MAIN OUTCOME MEASURE

Identification of placental macrophages [Hofbauer cells (HBCs)], as a source of adipsin and ASP was determined.

RESULTS

HBCs secreted both adipsin and ASP. Cord levels of adipsin (1663.78 ± 52.76 pg/mL) and ASP (354.48 ± 17.17 ng/mL) were significantly elevated in the offspring of obese mothers compared with their lean controls [1354.66 ± 33.87 pg/mL and 302.63 ± 14.98 ng/mL, respectively (P < .05 for both)]. Placentae from obese mothers released significantly more adipsin and ASP than placentae from lean mothers [546.0 ± 44 pg/mL · g vs 284.56 ± 43 pg/mL · g and 5485.75 ± 163.32 ng/mL · g vs 2399.16 ± 181.83 ng/mL · g, respectively (P < .05 for both)]. Circulating fetal adipsin and ASP positively correlated with maternal BMI (r = 0.611, P < .0001, and r = 0.391, P < .05, respectively). Fetal adipsin correlated positively with maternal (r = 0.482, P < .01) and fetal homeostasis model assessment of insulin resistance (r = 0.465, P < .01).

CONCLUSIONS

We demonstrate novel secretion of adipsin and ASP by placental HBCs.

International Union of Basic and Clinical Pharmacology. [corrected]. LXXXVII. Complement peptide C5a, C4a, and C3a receptors

The activation of the complement cascade, a cornerstone of the innate immune response, produces a number of small (74-77 amino acid) fragments, originally termed anaphylatoxins, that are potent chemoattractants and secretagogues that act on a wide variety of cell types. These fragments, C5a, C4a, and C3a, participate at all levels of the immune response and are also involved in other processes such as neural development and organ regeneration. Their primary function, however, is in inflammation, so they are important targets for the development of antiinflammatory therapies. Only three receptors for complement peptides have been found, but there are no satisfactory antagonists as yet, despite intensive investigation. In humans, there is a single receptor for C3a (C3a receptor), no known receptor for C4a, and two receptors for C5a (C5a₁ receptor and C5a₂ receptor). The most recently characterized receptor, the C5a₂ receptor (previously known as C5L2 or GPR77), has been regarded as a passive binding protein, but signaling activities are now ascribed to it, so we propose that it be formally identified as a receptor and be given a name to reflect this. Here, we describe the complex biology of the complement peptides, introduce a new suggested nomenclature, and review our current knowledge of receptor pharmacology.

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.

Hepatic nuclear factor 4α positively regulates complement C3 expression and does not interfere with TNFα-mediated stimulation of C3 expression in HepG2 cells

Complement C3 is involved in various protective and regulatory mechanisms of immune system. Recently it was established that C3 expression is regulated by nuclear receptors. Hepatic nuclear factor 4α (HNF4α) is a nuclear receptor critical for hepatic development and metabolism. We have shown that HNF4α is a positive regulator of C3 gene expression, realizing its effects through binding to two HNF4-response elements within the C3 promoter in HepG2 cells. TNFα is a well established positive regulator of C3 expression in hepatocytes during acute phase of inflammation. TNFα decreases the amount of HNF4α protein in HepG2 cells through NF-κB and MEK1/2 pathways thereby leading to a decrease in HNF4α bound to the C3 promoter. TNFα and HNF4α act in a synergetic way resulting in the potent activation of C3 transcription. These results suggest a novel mechanism of C3 regulation during acute phase response in HepG2 cells and display the mechanism of interaction of TNFα-induced pathways and HNF4α in transcriptional regulation of C3 gene.

Dyslipidemia in obesity: mechanisms and potential targets

Obesity has become a major worldwide health problem. In every single country in the world, the incidence of obesity is rising continuously and therefore, the associated morbidity, mortality and both medical and economical costs are expected to increase as well. The majority of these complications are related to co-morbid conditions that include coronary artery disease, hypertension, type 2 diabetes mellitus, respiratory disorders and dyslipidemia. Obesity increases cardiovascular risk through risk factors such as increased fasting plasma triglycerides, high LDL cholesterol, low HDL cholesterol, elevated blood glucose and insulin levels and high blood pressure. Novel lipid dependent, metabolic risk factors associated to obesity are the presence of the small dense LDL phenotype, postprandial hyperlipidemia with accumulation of atherogenic remnants and hepatic overproduction of apoB containing lipoproteins. All these lipid abnormalities are typical features of the metabolic syndrome and may be associated to a pro-inflammatory gradient which in part may originate in the adipose tissue itself and directly affect the endothelium. An important link between obesity, the metabolic syndrome and dyslipidemia, seems to be the development of insulin resistance in peripheral tissues leading to an enhanced hepatic flux of fatty acids from dietary sources, intravascular lipolysis and from adipose tissue resistant to the antilipolytic effects of insulin. The current review will focus on these aspects of lipid metabolism in obesity and potential interventions to treat the obesity related dyslipidemia.

Relationship of C5L2 receptor to skeletal muscle substrate utilization

Objective

To investigate the role of Acylation Stimulating Protein (ASP) receptor C5L2 in skeletal muscle fatty acid accumulation and metabolism as well as insulin sensitivity in both mice and human models of diet-induced insulin resistance.

Design and Methods

Male wildtype (WT) and C5L2 knockout (KO) mice were fed a low (LFD) or a high (HFD) fat diet for 10 weeks. Intramyocellular lipid (IMCL) accumulation (by oil red O staining) and beta-oxidation HADH enzyme activity were determined in skeletal muscle. Mitochondria were isolated from hindleg muscles for high-resolution respirometry. Muscle C5L2 protein content was also determined in obese type 2 diabetics and age- and BMI matched men.

Results

IMCL levels were increased by six-fold in C5L2KO-HFD compared to WT-HFD mice (p<0.05) and plasma insulin levels were markedly increased in C5L2KO-HFD mice (twofold, p<0.05). Muscle HADH activity was elevated in C5L2KO-LFD mice (+75%, p<0.001 vs. WT-LFD) and C5L2KO-HFD displayed increased mitochondrial fatty acid oxidative capacity compared to WT-HFD mice (+23%, p<0.05). In human subjects, C5L2 protein content was reduced (−48%, p<0.01) in type 2 diabetic patients when compared to obese controls. Further, exercise training increased C5L2 (+45%, p = 0.0019) and ASP (+80%, p<0.001) in obese insulin-resistant men.

Conclusion

The results suggest that insulin sensitivity may be permissive for coupling of C5L2 levels to lipid storage and utilization.

Up-regulation of the complement system in subcutaneous adipocytes from nonobese, hypertriglyceridemic subjects is associated with adipocyte insulin resistance

BACKGROUND

Dysfunctional adipose tissue plays an important role in the etiology of the metabolic syndrome, type 2 diabetes, and dyslipidemia. However, the molecular mechanisms underlying adipocyte dysfunction are incompletely understood.

AIM

The aim of the study was to identify differentially regulated pathways in sc adipocytes of dyslipidemic subjects.

METHODS

Whole-genome expression profiling was conducted on sc adipocytes from a discovery group of nine marginally overweight subjects with familial combined hyperlipidemia (FCHL) and nine controls of comparable body sizes as well as two independent confirmation groups. In this study, FCHL served as a model of familial insulin resistance and dyslipidemia, in the absence of frank obesity.

RESULTS

Functional analyses and gene set enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes or a custom pathway database identified the complement system and complement regulators as one of the top up-regulated pathways in FCHL [false discovery rate (FDR) < 1E-30]. Higher adipocyte complement expression in FCHL was confirmed in the appropriate confirmation group. Higher complement gene expression was associated with lower adipocyte insulin receptor substrate-1 expression as marker of adipocyte insulin resistance, independent of age, sex, or disease status, and this association was corroborated in the two confirmation groups. Additionally, complement gene expression was associated with triglycerides in the discovery set and with triglycerides and/or waist circumference in the confirmation groups. Complement pathway up-regulation did not appear to be driven by hypertriglyceridemia because a 40% pharmacological reduction in triglycerides did not affect complement expression.

CONCLUSIONS

These findings point to an up-regulation of a complement-related transcriptome in sc adipocytes under metabolically stressed conditions, even in the absence of overt obesity. Such up-regulation may subsequently influence downstream processes, including macrophage infiltration into adipose tissue and adipocyte insulin resistance.

Peroxisome proliferator-activated receptor α positively regulates complement C3 expression but inhibits tumor necrosis factor α-mediated activation of C3 gene in mammalian hepatic-derived cells

Complement C3 is a pivotal component of three cascades of complement activation. The liver is the main source of C3 in circulation and expression and secretion of C3 by hepatocytes is increased during acute inflammation. However, the mechanism of the regulation of the C3 gene in hepatocytes is not well elucidated. We showed that the C3 gene is the direct target for peroxisome proliferator-activated receptor α (PPARα) in human hepatoma HepG2 cells and mouse liver. Using PPARα siRNA and synthetic PPARα agonist WY-14643 and antagonist MK886 we showed that activation of PPARα results in up-regulation of C3 gene expression and protein secretion by HepG2 cells. The PPAR response element (PPRE), which is able to bind PPARα in vitro and in vivo, was found in the human C3 promoter. PPRE is conserved between human and mouse, and WY-14643 stimulates mouse C3 expression in the liver. TNFα increases C3 gene via NF-κB and, to a lesser extent, MEK1/2 signaling pathways, whereas TNFα-mediated stimulation of C3 protein secretion depends on activation of MEK1/2, p38, and JNK in HepG2 cells. Activation of PPARα abolishes TNFα-mediated up-regulation of C3 gene expression and protein secretion due to interference with NF-κB via PPRE-dependent mechanism in HepG2 cells. TNFα decreases PPARα protein content via NF-κB and MEK1/2 signaling pathways and inhibits PPARα binding with the human C3 promoter in HepG2 cells. These results suggest novel mechanism controlling C3 expression in hepatocytes during acute phase inflammation and demonstrate a crosstalk between PPARα and TNFα in the regulation of complement system.

Combined proteomic and metabolomic profiling of serum reveals association of the complement system with obesity and identifies novel markers of body fat mass changes

Obesity is associated with multiple adverse health effects and a high risk of developing metabolic and cardiovascular diseases. Therefore, there is a great need to identify circulating parameters that link changes in body fat mass with obesity. This study combines proteomic and metabolomic approaches to identify circulating molecules that discriminate healthy lean from healthy obese individuals in an exploratory study design. To correct for variations in physical activity, study participants performed a one hour exercise bout to exhaustion. Subsequently, circulating factors differing between lean and obese individuals, independent of physical activity, were identified. The DIGE approach yielded 126 differentially abundant spots representing 39 unique proteins. Differential abundance of proteins was confirmed by ELISA for antithrombin-III, clusterin, complement C3 and complement C3b, pigment epithelium-derived factor (PEDF), retinol binding protein 4 (RBP4), serum amyloid P (SAP), and vitamin-D binding protein (VDBP). Targeted serum metabolomics of 163 metabolites identified 12 metabolites significantly related to obesity. Among those, glycine (GLY), glutamine (GLN), and glycero-phosphatidylcholine 42:0 (PCaa 42:0) serum concentrations were higher, whereas PCaa 32:0, PCaa 32:1, and PCaa 40:5 were decreased in obese compared to lean individuals. The integrated bioinformatic evaluation of proteome and metabolome data yielded an improved group separation score of 2.65 in contrast to 2.02 and 2.16 for the single-type use of proteomic or metabolomics data, respectively. The identified circulating parameters were further investigated in an extended set of 30 volunteers and in the context of two intervention studies. Those included 14 obese patients who had undergone sleeve gastrectomy and 12 patients on a hypocaloric diet. For determining the long-term adaptation process the samples were taken six months after the treatment. In multivariate regression analyses, SAP, CLU, RBP4, PEDF, GLN, and C18:2 showed the strongest correlation to changes in body fat mass. The combined serum proteomic and metabolomic profiling reveals a link between the complement system and obesity and identifies both novel (C3b, CLU, VDBP, and all metabolites) and confirms previously discovered markers (PEDF, RBP4, C3, ATIII, and SAP) of body fat mass changes.

Acylation stimulating protein: a female lipogenic factor?

Acylation stimulating protein (ASP) is a potent lipogenic factor produced from adipocytes. Plasma ASP levels were shown to increase in obesity, diabetes mellitus type II and dyslipidemia, and decrease after weight loss and fasting. Growing evidence suggests that ASP may significantly contribute to subcutaneous fat storage in females. In vitro, ASP stimulated triglyceride synthesis to a larger extent in subcutaneous compared with omental adipocytes. The ASP receptor binding affinity to plasma membranes prepared from adipose tissue showed higher binding affinity to plasma membranes from female adipose tissue compared with male adipose tissue, and was more pronounced to subcutaneous compared with omental plasma membranes. Human studies demonstrated that postprandial triglyceride clearance predicted by ASP levels was more efficient in women than in men. In mice, postprandial triglyceride clearance, with intraperitoneal ASP administration, was faster in females compared with males. The ASP deficient mice were resistant to weight gain and had reduced fat mass that was more pronounced in females. Recent findings in humans and mice point to a significant association between progesterone and ASP variations in females. In this review, we highlight findings, to date, linking ASP to physiological and hormonal alterations that may contribute to subcutaneous fat distribution typical to females.

Complement C3 and cleavage products in cardiometabolic risk

This review summarizes available evidence on the role of serum complement component 3 (C3), produced by liver, adipocytes and activated macrophages at inflammation sites, and C3 cleavage products linking lipoproteins and metabolism to immunity. C3 and cleavage products are modified in several associated metabolic disorders including obesity, insulin resistance, type-2 diabetes, dyslipidemia, and cardiovascular diseases. Circulating C3 is independently and linearly associated with serum triglycerides, C-reactive protein (CRP), waist circumference and in some populations inversely with current smoking. The complement cascade is activated during myocardial ischemia and likely mediates immune and inflammatory responses in ischemic myocardium. Serum complement activation is elevated in unstable rather than stable angina pectoris suggesting added contribution to damage extension in acute coronary syndromes. In logistic regression models for incident metabolic syndrome (MetS), increasing C3 concentrations predicted MetS in women, after adjusting for continuous values of 3 major MetS components and other confounders, with a relative risk similar in magnitude to an established component suggesting elevated C3 likely constitutes part of the cluster of MetS in women. C3 interacts with MetS in men for independently conferring risk of incident type-2 diabetes and coronary heart disease (CHD). In women, though C3 is equally predictive of cardiometabolic risk, it is less so additively to MetS components or to CRP. Evidence suggests that circulating C3 might serve as a signal for an immune process that enhances - via mediation of increased apolipoprotein (apo) E levels - the development of dysfunctional apoA-I particles rendering them diabetogenic and atherogenic in populations prone to MetS or subsets of populations harboring impaired glucose tolerance. C3 activation also leads to production of chemoattractants C3a and C5a, and acylation stimulating protein (ASP, C3adesArg), a lipogenic hormone, which contribute additionally to the metabolic phenotypes generated. These observations have clinical and public health implications.