Critical review of acylation-stimulating protein physiology in humans and rodents

High-Intensity Interval Versus Moderate-Intensity Continuous Exercise Training on Glycemic Control, Beta Cell Function, and Aerobic Fitness in Women with Type 2 Diabetes

Objective: This study aimed to compare the effects of High-Intensity Interval Training (HIIT) and Moderate-Intensity Continuous Training (MICT) on glycemic control, beta-cell function, and aerobic fitness in women with Type 2 Diabetes Mellitus (T2DM). Methods: Thirty-six women with T2DM were assigned equally to HIIT, MICT, and control (CON) groups. Participants in the exercise cohorts underwent a 12-week training regimen (three sessions per week), while the CON group maintained an inactive lifestyle. Glycaemia variables, beta-cell function, maximal oxygen uptake (VO2max), lipid profiles, and body composition were assessed at baseline and post-intervention. Results: Both HIIT and MICT interventions led to significant improvements in glucose, insulin, HbA1c, and insulin resistance index. Moreover, visceral adiposity index (VAI), lipid accumulation product (LAP), total cholesterol (TC), and low-density lipoprotein (LDL) levels significantly decreased in the HIIT and MICT groups after 12 weeks. Triglyceride (TG) levels decreased only after MICT, while high-density lipoprotein (HDL) levels increased after both interventions. Maximal oxygen uptake (VO2max), body mass, body mass index (BMI), and waist circumference (WC) significantly improved in all exercise groups. Notably, the HIIT group showed greater reductions in body mass compared to MICT. Nevertheless, beta-cell function remained unaltered after these two exercise regimens. Conclusion: Both HIIT and MICT interventions effectively managed T2DM in women, regardless of exercise intensity. The HIIT regimen can be considered for time-efficient lifestyle interventions in people with T2DM.

Association between PM2.5 constituents and cardiometabolic risk factors: Exploring individual and combined effects, and mediating inflammation

BACKGROUND

The individual and combined effects of PM2.5 constituents on cardiometabolic risk factors are sparsely investigated. Besides, the key cardiometabolic risk factor that PM2.5 constituents targeted and the biological mechanisms remain unclear.

METHOD

A multistage, stratified cluster sampling survey was conducted in two typically air-polluted Chinese cities. The PM2.5 and its constituents including sulfate, nitrate, ammonium, organic matter, and black carbon were predicted using a machine learning model. Twenty biomarkers in three category were simultaneously adopted as cardiometabolic risk factors. We explored the individual and mixture association of long-term PM2.5 constituents with these markers using generalized additive model and quantile-based g-computation, respectively. To minimize potential confounding effects, we accounted for covariates including demographic, lifestyle, meteorological, temporal trends, and disease-related information. We further used ROC curve and mediation analysis to identify the key subclinical indicators and explore whether inflammatory mediators mediate such association, respectively.

RESULT

PM2.5 constituents was positively correlated with HOMA-B, TC, TG, LDL-C and LCI, and negatively correlated with PP and RC. Further, PM2.5 constituent mixture was positive associated with DBP, MAP, HbA1c, HOMA-B, AC, CRI-1 and CRI-2, and negative associated with PP and HDL-C. The ROC analysis further reveals that multiple cardiometabolic risk factors can collectively discriminate exposure to PM2.5 constituents (AUC>0.9), among which PP and CRI-2 as individual indicators exhibit better identifiable performance for nitrate and ammonium (AUC>0.75). We also found that multiple blood lipid indicators may be affected by PM2.5 and its constituents, possibly mediated through complement C3 or hsCRP.

CONCLUSION

Our study suggested associations of individual and combined PM2.5 constituents exposure with cardiometabolic risk factors. PP and CRI-2 were the targeted markers of long-term exposure to nitrate and ammonium. Inflammation may serve as a mediating factor between PM2.5 constituents and dyslipidemia, which enhance current understanding of potential pathways for PM2.5-induced preclinical cardiovascular responses.

New insights of acylation stimulating protein in modulating the pathological progression of metabolic syndromes

Obesity is associated with insulin resistance, hypertension, and coronary artery diseases which are grouped as metabolic syndrome. Rather than being a storage for energy, the adipocytes could synthesis and secret diverse hormones and molecules, named as adipokines. Under obese status, the adipocytes are dysfunctional with excessively producing the inflammatory related cytokines, such as interleukin 1 (IL-1), IL-6, and tumor necrosis factor α (TNF-α). Concerning on the vital role of adipokines, it is proposed that one of the critical pathological factors of obesity is the dysfunctional adipocytic pathways. Among these adipokines, acylation stimulating protein, as an adipokine synthesized by adipocytes during the process of cell differentiation, is shown to activate the metabolism of triglyceride (TG) by regulating the catabolism of glucose and free fatty acid (FFA). Recent attention has paid to explore the underlying mechanism whereby acylation stimulating protein influences the biological function of adipocyte and the pathological development of obesity. In the present review, we summarized the progression of acylation stimulating protein in modulating the physiological and hormonal catabolism which affects fat distribution. Furthermore, the potential mechanisms which acylation stimulating protein regulates the metabolism of adipose tissue and the process of metabolic syndrome were also summarized.

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.

Exploring the underlying mechanisms of obesity and diabetes and the potential of Traditional Chinese Medicine: an overview of the literature

Obesity and diabetes are closely related metabolic disorders that have become major public health concerns worldwide. Over the past few decades, numerous studies have explored the underlying mechanisms of these disorders and identified various risk factors, including genetics, lifestyle, and dietary habits. Traditional Chinese Medicine (TCM) has been increasingly recognized for its potential to manage obesity and diabetes. Weight loss is difficult to sustain, and several diabetic therapies, such as sulfonylureas, thiazolidinediones, and insulin, might make it harder to lose weight. While lifestyle changes should be the primary approach for people interested in lowering weight, drugs are also worth investigating. Since some of the newer glucose-lowering medications that cause weight loss, such as glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and sodium-glucose cotransporter 2 inhibitors (SGLT2i), are additionally utilized or are under consideration for use as anti-obesity drugs, the frontier between glucose-lowering medication and weight loss drugs appears to be shifting. This review provides an overview of the literature on the underlying mechanisms of obesity and diabetes and the prospect of TCM in their management. We discuss the various TCM interventions, including acupuncture, herbal medicine, and dietary therapy, and their effects on metabolic health. We also highlight the potential of TCM in regulating gut microbiota, reducing inflammation, and improving insulin sensitivity. The findings suggest that TCM may provide a promising approach to preventing and managing obesity and diabetes. However, further well-designed studies are needed to confirm the efficacy and safety of TCM interventions and to elucidate their underlying mechanisms of action.

Influence of Adipose Tissue on Early Metabolic Programming: Conditioning Factors and Early Screening

BACKGROUND

Obesity and being overweight have become one of the world's most severe health issues, not only because of the pathology but also because of the development of related comorbidities. Even when children reach adulthood, the mother's environment during pregnancy has been found to have a significant impact on obesity prevention in children. Thus, both maternal dietary habits and other factors such as gestational diabetes mellitus, excessive weight gain during pregnancy, smoking, or endocrine factors, among others, could influence newborn growth, adiposity, and body composition at birth, in childhood and adolescence, hence programming health in adulthood.

METHODS

The aim of this review is to analyze the most recent human studies on the programming of fetal adipose tissue to determine which modifiable factors may influence adiposity and thus prevent specific disorders later in life by means of a bibliographic review of articles related to the subject over the last ten years.

CONCLUSIONS

The importance of a healthy diet and lifestyle not only during pregnancy and the first months of life but also throughout childhood, especially during the first two years of life as this is a period of great plasticity, where the foundations for optimal health in later life will be laid, preventing the emergence of noncommunicable diseases including obesity, diabetes mellitus type 2, hypertension, being overweight, and any other pathology linked to metabolic syndrome, which is so prevalent today, through health programs beginning at a young age.

Acylation-stimulating protein and heart failure progression in arrhythmogenic right ventricular cardiomyopathy

AIMS

Our previous studies suggested that the complement system was critical in the prognosis of arrhythmogenic right ventricular cardiomyopathy (ARVC). The acylation-stimulating protein (ASP), generated through the alternate complement pathway, was reported to regulate lipogenesis and triglyceride storage. This study aimed to investigate the role of ASP in predicting adverse cardiac events in an ARVC cohort.

METHODS AND RESULTS

We enrolled 111 ARVC patients and 106 healthy volunteers, and measured their plasma ASP levels using enzyme-linked immunosorbent assays. Plasma ASP levels were significantly higher in the ARVC patients than in the healthy controls (2325.22 ± 20.08 vs. 2189.75 ± 15.55, P < 0.001), with a similar trend observed in the myocardial explant assay. Spearman correlation analysis indicated plasma ASP level associated with cardiac structural (right ventricular internal dimension, P = 0.006) and functional remodelling (left ventricular ejection fraction, P = 0.002) in ARVC patients. The ARVC patients were followed up for an average of 17.79 ± 1.09 months. Heart failure-associated events (HFAEs) were defined as heart transplantation, on a cardiac transplant list, or death due to end-stage heart failure. Plasma ASP levels in patients with HFAEs were significantly higher than in those without clinical events (2486.03 ± 26.70 vs. 2268.83 ± 23.51, P < 0.001) or those with malignant arrhythmic events (2486.03 ± 26.70 vs. 2297.80 ± 60.46, P = 0.008). LASSO (least absolute shrinkage and selection operator) and multivariable Cox regression analyses showed the ASP level (HR = 1.004, 95% CI [1.002,1.006], P = 0.002) was an independent predictor for adverse HFAEs in ARVC patients. The spline-fitting procedure was applied to illustrate the HFAE-free probabilities at different time points.

CONCLUSIONS

Our results suggest that plasma ASP may be a useful biomarker in prediction of adverse HF-associated events in ARVC patients.

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.

Cross-Sectional Associations between HDL Structure or Function, Cell Membrane Fatty Acid Composition, and Inflammation in Elderly Adults

BACKGROUND

Cell membrane fatty acid composition has been related to inflammation and cardiovascular disease (CVD) risk. Dysregulation of HDL function is also considered a CVD risk factor.

OBJECTIVES

We aimed to investigate whether the content of cell membrane fatty acids and HDL functionality are linked to each other as well as to inflammation.

METHODS

This cross-sectional analysis involved 259 participants (mean age: 67.9 y) with overweight/obesity (mean BMI: 29.5 kg/m2) from a coronary artery disease case-control study nested within the PREDIMED (PREvención con DIeta MEDiterránea) trial for which HDL functional parameters [apoA-I, apoA-IV, and apoC-III; cholesterol efflux capacity (CEC); HDL oxidative inflammatory index (HOII); sphingosine-1-phosphate (S1P); serum amyloid A (SAA); and complement-3 (C3) protein] were quantified. We also assessed 22 fatty acids in blood cell membranes using GC and inflammatory markers (IFN-γ and IL-1b, IL-6, IL-8, and IL-10) in serum. Associations of HDL-related variables with cell membrane fatty acids and with inflammatory markers were assessed using multivariable linear regression analyses with elastic net penalty.

RESULTS

ApoA-I, apoC-III, CEC, HOII, S1P, and SAA, but not apoA-IV and C3 protein, were associated with membrane fatty acids. S1P and SAA were directly associated with IL-6, whereas apoA-I and C3 protein showed inverse associations with IL-6. Specific fatty acids including myristic acid (14:0) and long-chain n-6 fatty acids being negatively and positively associated with IL-8, respectively, were also found to be positively associated with SAA.

CONCLUSIONS

This study suggests interrelations between indicators of inflammation and both blood cell membrane fatty acid composition and HDL structure/functional parameters in a Mediterranean population at high CVD risk.This trial was registered at www.isrctn.com as ISRCTN35739639.

Contrasting effects of <i>Ksr2</i>, an obesity gene, on trabecular bone volume and bone marrow adiposity

Pathological obesity and its complications are associated with an increased propensity for bone fractures. Humans with certain genetic polymorphisms at the kinase suppressor of ras2 (KSR2) locus develop severe early-onset obesity and type 2 diabetes. Both conditions are phenocopied in mice with <i>Ksr2</i> deleted, but whether this affects bone health remains unknown. Here we studied the bones of global <i>Ksr2</i> null mice and found that <i>Ksr2</i> negatively regulates femoral, but not vertebral, bone mass in two genetic backgrounds, while the paralogous gene, <i>Ksr1</i>, was dispensable for bone homeostasis. Mechanistically, KSR2 regulates bone formation by influencing adipocyte differentiation at the expense of osteoblasts in the bone marrow. Compared with <i>Ksr2</i>'s known role as a regulator of feeding by its function in the hypothalamus, pair-feeding and osteoblast-specific conditional deletion of <i>Ksr2</i> reveals that <i>Ksr2</i> can regulate bone formation autonomously. Despite the gains in appendicular bone mass observed in the absence of <i>Ksr2</i>, bone strength, as well as fracture healing response, remains compromised in these mice. This study highlights the interrelationship between adiposity and bone health and provides mechanistic insights into how <i>Ksr2</i>, an adiposity and diabetic gene, regulates bone metabolism.

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 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.

The function of adipsin and C9 protein in the complement system in HIV-associated preeclampsia

OBJECTIVE

In preeclampsia, there are excessive complement components expressed due to increased complement activation; therefore, this study investigated the concentration of adipsin and C9 in HIV-associated preeclampsia.

METHOD

The study population (n = 76) was stratified by pregnancy type (normotensive pregnant and preeclampsia) and by HIV status. Serum was assayed for the concentration of adipsin and C9 using a Bioplex immunoassay procedure.

RESULTS

Maternal weight did not differ (p = 0.1196) across the study groups. The concentration of adipsin was statistically different between the PE vs normotensive pregnant groups, irrespective of HIV status (p = 0.0439). There was no significant difference in adipsin concentration between HIV-negative vs HIV-positive groups, irrespective of pregnancy type (p = 0.6290). Additionally, there was a significant difference in adipsin concentration between HIV-negative normotensive vs HIV-negative preeclampsia (p < 0.05), as well as a difference between HIV-negative preeclampsia vs HIV-positive preeclampsia (p < 0.05). C9 protein expression was not statistically different between the normotensive and PE groups, regardless of HIV status (p = 0.5365). No statistical significance in C9 expression was found between HIV-positive vs HIV-negative groups, regardless of pregnancy type (p = 0.3166). Similarly, no statistical significance was noted across all study groups (p = 0.0774).

CONCLUSION

This study demonstrates that there is a strong correlation between the up-regulation of adipsin and PE and that adipsin is a promising biomarker to use as a diagnostic tool for PE.

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 polycystic ovary syndrome occurs in the postprandial and fasted state and is influenced by obesity and insulin sensitivity

OBJECTIVE

Polycystic ovary syndrome (PCOS) is associated with metabolic risk. Complement proteins regulate inflammation and lipid clearance but their role in PCOS-associated metabolic risk is unclear. We sought to establish whether the complement system is activated in PCOS in the fasting and postprandial state.

DESIGN

Case-control study.

PATIENTS

Fasting complement levels were measured in 84 women with PCOS and 95 healthy controls. Complement activation post-oral fat tolerance test (OFTT) was compared in 40 additional subjects (20 PCOS, 20 controls).

MEASUREMENTS

Activation pathway (C3, C4, C3a(desArg), factor B, factor H, properdin, Factor D) and terminal pathway (C5, C5a, terminal complement complex [TCC]) proteins were measured by commercial or in-house assays.

RESULTS

Fasting C3, C3a(desArg) and TCC concentrations were increased in insulin-resistant (adjusted differences: C3 0.13 g/L [95%CI 0-0.25]; C3a(desArg) 319.2 ng/mL [19.5-619]; TCC 0.66 μg/mL [0.04-1.28]) but not in insulin-sensitive women with PCOS. C3 and factor H levels increased with obesity. Post-OFTT, C3 and C4 levels increased to a similar extent in PCOS subjects and controls, whist factor H levels increased more in women with PCOS compared to controls (adjusted differences (area under the curve): 12 167 μg min/mL [4942-19 392]), particularly in the presence of concomitant obesity.

CONCLUSIONS

Activation and terminal complement pathway components are elevated in patients with PCOS, especially in the presence of insulin resistance and obesity.

Abdominal Obesity, Adipokines and Non-communicable Diseases

Abdominal obesity may be defined as excess deposits of fat in the abdominal region. It is a common health condition seen in South Asians and is positively related to non-communicable diseases (NCDs). It is independent of body mass index and measured by raised waist circumference for men≥90 cm and women≥80 cm. The reason for its prevalence being common in Indians finds its root from pregnancy, during fetal period and has emerged as a concept of 'Thin Fat Indian'. Malnutrition in such a critical period of growth has consequences in the form of reduced basal metabolic rate (BMR), reduced blood flow to growing tissues, reduced functional ability of vital organs, endocrine changes and reduced capacity of primary adipose tissue. However, excess of visceral fat facilitates high dosage of adipokines in the portal vein to liver and other body tissues having serious implications seen in the form NCDs like diabetes, hypertension, heart diseases, non-alcoholic fatty liver diseases, kidney disorders, cancer and other health problems. Abdominal obesity should be addressed before it has progressed further to defined health issues by exercise and diet, so that people can live a quality life.

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.

Integrins meet complement: The evolutionary tip of an iceberg orchestrating metabolism and immunity

Immunologists have recently realized that there is more to the classic innate immune sensor systems than just mere protection against invading pathogens. It is becoming increasingly clear that such sensors, including the inflammasomes, toll-like receptors, and the complement system, are heavily involved in the regulation of basic cell physiological processes and particularly those of metabolic nature. In fact, their "non-canonical" activities make sense as no system directing immune cell activity can perform such task without the need for energy. Further, many of these ancient immune sensors appeared early and concurrently during evolution, particularly during the developmental leap from the single-cell organisms to multicellularity, and therefore crosstalk heavily with each other. Here, we will review the current knowledge about the emerging cooperation between the major inter-cell communicators, integrins, and the cell-autonomous intracellularly and autocrine-active complement, the complosome, during the regulation of single-cell metabolism. LINKED ARTICLES: This article is part of a themed issue on Canonical and non-canonical functions of the complement system in health and disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.14/issuetoc.

Complement and human T cell metabolism: Location, location, location

The complement system represents one of the evolutionary oldest arms of our immune system and is commonly recognized as a liver-derived and serum-active system critical for providing protection against invading pathogens. Recent unexpected findings, however, have defined novel and rather "uncommon" locations and activities of complement. Specifically, the discovery of an intracellularly active complement system-the complosome-and its key role in the regulation of cell metabolic pathways that underly normal human T cell responses have taught us that there is still much to be discovered about this system. Here, we summarize the current knowledge about the emerging functions of the complosome in T cell metabolism. We further place complosome activities among the non-canonical roles of other intracellular innate danger sensing systems and argue that a "location-centric" view of complement evolution could logically justify its close connection with the regulation of basic cell physiology.

The Complement Receptor C5aR2: A Powerful Modulator of Innate and Adaptive Immunity

Complement activation generates the core effector protein C5a, a potent immune molecule that is linked to multiple inflammatory diseases. Two C5a receptors, C5aR1 (C5aR, CD88) and C5aR2 (C5L2, GPR77), mediate the biological activities of C5a. Although C5aR1 has broadly acknowledged proinflammatory roles, C5aR2 remains at the center of controversy, with existing findings supporting both immune-activating and immune-dampening functions. Recent progress has been made toward resolving these issues. Instead of being a pure recycler and sequester of C5a, C5aR2 is capable of mediating its own set of signaling events and through these events exerting significant immunomodulatory effects not only toward C5aR1 but also other pattern recognition receptors and innate immune systems, such as NLRP3 inflammasomes. This review highlights the existing knowns and unknowns concerning C5aR2 and provides a timely update on recent breakthroughs which are expected to have a substantial impact on future fundamental and translational C5aR2 research.

Acylation-stimulating protein is a surrogate biomarker for acute myocardial infarction: Role of statins

BACKGROUND:

Acylation-stimulating protein (ASP) is an adipokine synthesized within adipocytes environment due to adipocyte differentiation.

AIM:

The aim of this study was to assess changes in ASP levels in patients with acute myocardial infarction (MI) and to correlate these variations with disease variables.

SUBJECTS AND METHODS:

A total number of 111 patients previously and currently treated with rosuvastatin or atorvastatin presented with acute MI in a Coronary Care Unit, were divided into three groups, Group A: Thirty-nine patients treated with atorvastatin, Group B: Thirty patients treated with rosuvastatin, compared to 42 patients presented with MI not previously treated with statins were enrolled in this study. ASP and troponin-I levels and lipid profile were estimated in each group.

RESULTS:

The effects of atorvastatin and rosuvastatin compared to nonstatins-treated group on the anthropometric and biochemical variables in patients with acute MI showed significant difference in all biochemical and anthropometric parameters P < 0.05. Serum ASP (nmol/l) levels were higher in control patients 57.25 ± 9.15 compared to atorvastatin-treated patients 48.43 ± 7.42 and rosuvastatin-treated patients 49.33 ± 6.52 P = 0.0124.

CONCLUSION:

ASP levels are elevated in patients with acute MI and regarded as surrogate biomarker for acute MI also; therapy with statins leads to significant reduction in ASP levels compared to nonstatins-treated patients that presented with acute MI.

Endogenous Roles of Mammalian Flavin-Containing Monooxygenases

Flavin-containing monooxygenases (FMOs) catalyze the oxygenation of numerous foreign chemicals. This review considers the roles of FMOs in the metabolism of endogenous substrates and in physiological processes, and focuses on FMOs of human and mouse. Tyramine, phenethylamine, trimethylamine, cysteamine, methionine, lipoic acid and lipoamide have been identified as endogenous or dietary-derived substrates of FMOs in vitro. However, with the exception of trimethylamine, the role of FMOs in the metabolism of these compounds in vivo is unclear. The use, as experimental models, of knockout-mouse lines deficient in various Fmo genes has revealed previously unsuspected roles for FMOs in endogenous metabolic processes. FMO1 has been identified as a novel regulator of energy balance that acts to promote metabolic efficiency, and also as being involved in the biosynthesis of taurine, by catalyzing the S-oxygenation of hypotaurine. FMO5 has been identified as a regulator of metabolic ageing and glucose homeostasis that apparently acts by sensing or responding to gut bacteria. Thus, FMOs do not function only as xenobiotic-metabolizing enzymes and there is a risk that exposure to drugs and environmental chemicals that are substrates or inducers of FMOs would perturb the endogenous functions of these enzymes.

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.

Association of acylation stimulating protein and adiponectin with metabolic risk marker in North Indian obese women

BACKGROUND

Plasma concentrations of Acylation stimulating protein (ASP) and adiponectin are associated with body weight and energy homeostasis. The purpose of this study is to describe the potential role of acylation stimulating protein and adiponectin with metabolic risk marker in North Indian obese women.

METHODS

This is a case control study. Total 520 women were recruited for the study n = 260 women with obesity (BMI>30) study group and n = 260 women without obesity (BMI<25) control group. Serum ASP and adiponectin level were determined by enzyme linked immunosorbent assay.

RESULTS

Result indicated that WC, BP, lipid profile, FPG, FPI, IR (HOMA-IR), ASP were significantly higher but adiponectin and HDL were significantly lower in women with obesity than in women without obesity. Furthermore ASP was significantly positive correlated with WC, FPG, TG, VLDL, FPI and IR, whereas the correlation of adiponectin was significantly negative correlated with WC, FPG, TG, IR, ASP and significantly positive correlated with HDL in women with obesity.

CONCLUSION

The study shows that high level of ASP and low level of Adiponectin could be a potential marker of women with obesity among metabolic syndrome.

Glucose Restriction Plus Refeeding in Vitro Induce Changes of the Human Adipocyte Secretome with an Impact on Complement Factors and Cathepsins

Adipose tissue is a major endocrine organ capable of secreting adipokines with a role in whole-body metabolism. Changes in the secretome profile during the development of obesity is suspected to contribute to the risk of health complications such as those associated with weight regain after weight loss. However, the number of studies on weight regain is limited and secretome changes during weight regain have hardly been investigated. In an attempt to generate leads for in vivo studies, we have subjected human Simpson Golabi Behmel Syndrome adipocytes to glucose restriction (GR) followed by refeeding (RF) as an in vitro surrogate for weight regain after weight loss. Using LC-MS/MS, we compared the secreted protein profile after GR plus RF with that of normal feeding (NF) to assess the consequences of GR plus RF. We identified 338 secreted proteins of which 49 were described for the first time as being secreted by adipocytes. In addition, comparison between NF and GR plus RF showed 39 differentially secreted proteins. Functional classification revealed GR plus RF-induced changes of enzymes for extracellular matrix modification, complement system factors, cathepsins, and several proteins related to Alzheimer’s disease. These observations can be used as clues to investigate metabolic consequences of weight regain, weight cycling or intermittent fasting.

Adipose Tissue-Derived Signatures for Obesity and Type 2 Diabetes: Adipokines, Batokines and MicroRNAs

: Obesity is one of the main risk factors for type 2 diabetes mellitus (T2DM). It is closely related to metabolic disturbances in the adipose tissue that primarily functions as a fat reservoir. For this reason, adipose tissue is considered as the primary site for initiation and aggravation of obesity and T2DM. As a key endocrine organ, the adipose tissue communicates with other organs, such as the brain, liver, muscle, and pancreas, for the maintenance of energy homeostasis. Two different types of adipose tissues-the white adipose tissue (WAT) and brown adipose tissue (BAT)-secrete bioactive peptides and proteins, known as "adipokines" and "batokines," respectively. Some of them have beneficial anti-inflammatory effects, while others have harmful inflammatory effects. Recently, "exosomal microRNAs (miRNAs)" were identified as novel adipokines, as adipose tissue-derived exosomal miRNAs can affect other organs. In the present review, we discuss the role of adipose-derived secretory factors-adipokines, batokines, and exosomal miRNA-in obesity and T2DM. It will provide new insights into the pathophysiological mechanisms involved in disturbances of adipose-derived factors and will support the development of adipose-derived factors as potential therapeutic targets for obesity and T2DM.

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.

Hyperlipidemias and Obesity

The organs require oxygen and other types of nutrients (amino acids, sugars, and lipids) to function, the heart consuming large amounts of fatty acids for oxidation and adenosine triphosphate (ATP) generation.

The Effect of Atorvastatin (and Subsequent Metformin) on Adipose Tissue Acylation-Stimulatory-Protein Concentration and Inflammatory Biomarkers in Overweight/Obese Women With Polycystic Ovary Syndrome

Background: Atorvastatin has been shown to improve cardiovascular risk (CVR) indices in women with polycystic ovary syndrome (PCOS). Low-grade chronic inflammation of adipose tissue may link PCOS and adverse CVR. In pro-inflammatory states such as PCOS, spontaneous activation of the alternative pathway of complement results in increased generation of acylation stimulating protein (ASP) from adipocytes irrespective of body mass index. Methods: The objective of this study was to determine the effect of atorvastatin on markers of adipose tissue dysfunction and inflammation; acylation-stimulating-protein (ASP), interleukin-6 (IL-6), and monocyte-chemoattractant-protein-1 (MCP-1) in PCOS. This was a randomized, double-blind, placebo-controlled study where 40 medication-naive women with PCOS and biochemical hyperandrogenaemia were randomized to either atorvastatin 20 mg daily or placebo for 12 weeks. Following the 12 week randomization; both group of women with PCOS were subsequently started on metformin 1,500 mg daily for further 12 weeks to assess whether pre-treatment with atorvastatin potentiates the effects of metformin on markers of adipose tissue function We conducted a post-hoc review to detect plasma ASP and the pro-inflammatory cytokines IL6 and MCP-1 before and after 12 and 24 weeks of treatment. Results: There was significant reduction in ASP (156.7 ± 16.2 vs. 124.4 ± 14.8 ng/ml p <0.01), IL-6 (1.48 ± 0.29 vs.0.73 ± 0.34 pg/ml p = 0.01) and MCP-1 (30.4 ± 4.2 vs. 23.0 ± 4.5 pg/ml p = 0.02) after 12 weeks of atorvastatin that was maintained subsequently with 12 weeks treatment with metformin. There was a significant positive correlation between ASP levels with CRP (p < 0.01), testosterone (p < 0.01) and HOMA-IR (p < 0.01); IL-6 levels with CRP (p <0.01) and testosterone (p < 0.01) and MCP-1 with CRP (p < 0.01); testosterone (p < 0.01) and HOMA-IR (p < 0.02). Conclusions: This post-hoc analysis revealed that 12 weeks of atorvastatin treatment significantly decreased the markers of adipose tissue dysfunction and inflammation, namely ASP, IL-6 and MCP-1 in obese women with PCOS. Changes in adipose tissue markers were significantly associative with substantial improvements in HOMA-IR, testosterone and hs-CRP levels. ISRCTN Number: ISRCTN24474824.

Clearance kinetics of the VGF-derived neuropeptide TLQP-21

TLQP-21 is a multifunctional neuropeptide and a promising new medicinal target for cardiometabolic and neurological diseases. However, to date its clearance kinetics and plasma stability have not been studied. The presence of four arginine residues led us to hypothesize that its half-life is relatively short. Conversely, its biological activities led us to hypothesize that the peptide is still taken up by adipose tissues effectively. [¹²⁵I]TLQP-21 was i.v. administered in rats followed by chasing the plasma radioactivity and assessing tissue uptake. Plasma stability was measured using LC-MS. In vivo lipolysis was assessed by the palmitate rate of appearance.

RESULTS

A small single i.v. dose of [¹²⁵I]TLQP-21 had a terminal half-life of 110 min with a terminal clearance rate constant, k_t, of 0.0063/min, and an initial half-life of 0.97 min with an initial clearance rate constant, k_i, of 0.71/min. The total net uptake by adipose tissue accounts for 4.4% of the entire dose equivalent while the liver, pancreas and adrenal gland showed higher uptake. Uptake by the brain was negligible, suggesting that i.v.-injected peptide does not cross the blood-brain-barrier. TLQP-21 sustained isoproterenol-stimulated lipolysis in vivo. Finally, TLQP-21 was rapidly degraded producing several N-terminal and central sequence fragments after 10 and 60 min in plasma in vitro. This study investigated the clearance and stability of TLQP-21 peptide for the first time. While its pro-lipolytic effect supports and extends previous findings, its short half-life and sequential cleavage in the plasma suggest strategies for chemical modifications in order to enhance its stability and therapeutic efficacy.

Type 2 diabetes - An autoinflammatory disease driven by metabolic stress

Type 2 diabetes has traditionally been viewed as a metabolic disorder characterised by chronic high glucose levels, insulin resistance, and declining insulin secretion from the pancreas. Modern lifestyle, with abundant nutrient supply and reduced physical activity, has resulted in dramatic increases in the rates of obesity-associated disease conditions, including diabetes. The associated excess of nutrients induces a state of systemic low-grade chronic inflammation that results from production and secretion of inflammatory mediators from the expanded pool of activated adipocytes. Here, we review the mechanisms by which obesity induces adipose tissue dysregulation, detailing the roles of adipose tissue secreted factors and their action upon other cells and tissues central to glucose homeostasis and type 2 diabetes. Furthermore, given the emerging importance of adipokines, cytokines and chemokines in disease progression, we suggest that type 2 diabetes should now be viewed as an autoinflammatory disease, albeit one that is driven by metabolic dysregulation.

Complement C3 and Risk of Diabetic Microvascular Disease: A Cohort Study of 95202 Individuals from the General Population

BACKGROUND

Whether the complement system is involved in the development of diabetic microvascular disease is unknown. We tested the hypothesis that high concentrations of complement C3 are associated with increased risk of diabetic retinopathy, nephropathy, and neuropathy in individuals from the general population.

METHODS

We studied 95202 individuals from the general population with baseline measurements of complement C3, genotyped for rs1065489, rs429608, and rs448260 determining concentrations of complement C3, and enrolled in the Copenhagen General Population Study from 2003 through 2013, following them until April 10, 2013. Rs1065489, rs429608, and rs448260 were identified with genome-wide association scans in 3752 individuals from the Copenhagen City Heart Study.

RESULTS

The cumulative incidence was increased from the lowest tertile to the highest tertile of complement C3 for diabetic retinopathy (log-rank trend, P = 1 × 10^-20), nephropathy (P = 7 × 10^-15), and neuropathy (P = 5 × 10^-10). Multifactorially adjusted hazard ratios for a 1 SD higher concentration of complement C3 were 1.87 (95% CI, 1.61-2.18) for diabetic retinopathy, 1.90 (1.62-2.23) for diabetic nephropathy, and 1.56 (1.29-1.89) for diabetic neuropathy. The multifactorially adjusted hazard ratio for individuals with the highest vs lowest tertile of complement C3 was 3.29 (1.78-6.07) for retinopathy, 2.71 (1.42-5.16) for nephropathy, and 2.40 (1.26-4.54) for neuropathy.

CONCLUSIONS

High baseline concentrations of complement C3 were associated with increased risk of diabetic retinopathy, nephropathy, and neuropathy in individuals from the general population. These epidemiological findings were substantiated by a Mendelian randomization approach, potentially indicating causality.

Adipocytes affect castration-resistant prostate cancer cells to develop the resistance to cytotoxic action of NK cells with alterations of PD-L1/NKG2D ligand levels in tumor cells

BACKGROUND

Obesity affects prostate cancer (PCa) progression, and the periprostatic adipose tissue adjacent to the prostate is considered a driving force of disease progression. Adipocytes are the main cell population in adipose tissues and their paracrine role contributes to PCa progression, however its implication in modulating immune reactions remains largely unknown. We investigated the adipocyte role in controlling the susceptibility of castration-resistant PCa (CRPC) cells to the cytotoxic action of natural killer (NK) cells.

METHODS

Using primary NK cells as the NK cell source, NK cell cytotoxicities to CRPC cells, either control media treated or adipocyte-conditioned media (CM) treated, were tested in lactate dehydrogenase (LDH) release-based assays. The levels of programmed death receptor ligand (PD-L1) and NK group 2D (NKG2D) ligands in adipocyte CM-treated CRPC cells were analyzed in qPCR analyses. Effects of blocking adipocyte action on altering PD-L1/NKG2D ligand levels and the susceptibility of CRPC cells to NK cell cytotoxicity were investigated.

RESULTS

We found NK cell cytotoxicity to CRPC cells decreases when tumor cells are treated with adipocyte CM associated with PD-L1 and NKG2D ligand level alterations. Further, we discovered that the JAK/Stat3 signaling pathway was responsible for the adipocyte CM effect. Two adipokine molecules, IL-6 and leptin, were shown to be important in activation of the JAK/Stat3 signaling in CRPC cells to modulate the PD-L1/NKG2D ligand level alteration. Adding the inhibitors of JAK/Stat3 signaling or neutralizing antibodies of IL-6 or leptin increased the susceptibility of CRPC cells to NK cell action.

CONCLUSIONS

Blocking the adipocyte effect by inhibiting the IL-6/leptin-JAK/Stat3 signaling axis may enhance NK cell mediated immunity to CRPC cells and this strategy may help to develop future therapeutics to treat obese PCa patients.

Association of C5L2 genetic polymorphisms with coronary artery disease in a Han population in Xinjiang, China

Background

C5aR-like receptor 2 (C5L2) has been identified as a receptor for the inflammatory factor Complement 5a (C5a) and acylation-stimulating protein (ASP). ASP binding to C5L2 leading to a net accumulation of TG stores and glucose transporter. The aim of the present study is to evaluate the association of the SNPs of C5L2 gene with coronary artery disease (CAD) in a Chinese population.

Methods

We examined the role of the tagging single nucleotide polymorphisms (SNPs) of C5L2 gene for CAD using a case-control design. We determined the prevalence of C5L2 genotypes in 505 CAD patients and 469 age and sex-matched healthy control subjects of Han population.

Results

There was significant difference in genotype distributions of rs2972607 and rs8112962 between CAD patients and control subjects. The rs2972607 was found to be associated with CAD in a dominant model (AA vs. AG + GG, P<0.001). Similarly, the rs8112962 was found to be associated with CAD in a dominant model (TT vs CT + CC, P=0.016). The difference remained statistically significant after multivariate adjustment (OR =1.401, 95% confidence interval [CI]:1.026~1.914, P=0.034; OR = 1.541, 95%CI:1.093~ 2.172, P=0.014; respectively).

Conclusion

The results of this study indicate that both rs2972607 and rs8112962 of C5L2 gene are associated with CAD in a Han population of China.

An increase level of acylation stimulating protein is correlated with metabolic risk markers in North Indian obese women

BACKGROUND AND AIMS

The present study was to investigate the association between serum acylation stimulating protein (ASP) level with metabolic risk factors in North Indian obese women.

METHODS

This is a case control study, total n=322 women aged between 20 and 45 years (n=162 with metabolic syndrome & n=160 without metabolic syndrome) were recruited for the study according to National Cholesterol Education Program Treatment Panel (NCEPATP) guidelines. Serum ASP level were determined by enzyme linked immunosorbent assay.

RESULTS

Results indicated that circulating ASP and other metabolic risk factors (waist circumference, triglycerides, fasting plasma glucose etc) were significantly higher in women with metabolic syndrome (WmetS) than in women without syndrome (WometS) (p<0.001). Furthermore circulating ASP was significantly higher possitively correlated with waist circumference (r=0.51, p<0.001), triglyceride (r=0.56, p<0.001), glucose (r=0.70, p<0.001), and negatively correlated with high density lipoprotein(r=-0.56, p<0.001) in women with metabolic syndrome.

CONCLUSIONS

Conclusively circulating ASP was found to be significantly associated with hyperlipidemia, obesity and obesity related disorders in North Indian obese women.

Complement 3 serum levels as a pro-inflammatory biomarker for insulin resistance in obesity

INTRODUCTION

Obesity is frequently characterized by chronic inflammation and insulin resistance (IR). Obesity-associated inflammation is responsible for the complement system activation of which the third component (C3) plays the central role.

OBJECTIVE

to discuss several aspects of the central component of the complement system in relation to obesity and obesity-associated IR.

METHODS

A critical review of the relevant published English articles from 2003- 2014 was carried out using several search engines including PubMed, Google Scholar, and ScienceDirect. Keywords were used, including complement system, C3, obesity-induced inflammation, IR, ASP, and adipose tissue.

CONCLUSION

The defect in the adipose tissue secretory function during obesity may result in different metabolic disorders including IR. The C3 role during obesity-associated inflammation in IR is emerging. More longitudinal studies are warranted to evaluate the role of C3 among other pro-inflammatory biomarkers for IR.

Innovative approach to safely induce controlled lipolysis by superparamagnetic iron oxide nanoparticles-mediated hyperthermic treatment

During last years, evidence has been provided on the involvement of overweight and obesity in the pathogenesis and aggravation of several life-threatening diseases. Here, we demonstrate that, under appropriate administration conditions, polyhedral iron oxide nanoparticles are efficiently and safely taken up by 3T3 cell line-derived adipocytes (3T3 adipocytes) in vitro. Since these nanoparticles proved to effectively produce heat when subjected to alternating magnetic field, 3T3 adipocytes were submitted to superparamagnetic iron oxide nanoparticles-mediated hyperthermia treatment (SMHT), with the aim of modulating their lipid content. Notably, the treatment resulted in a significant delipidation persisting for at least 24h, and in the absence of cell death, damage or dedifferentiation. Interestingly, transcript expression of adipose triglyceride lipase (ATGL), a key gene involved in canonical lipolysis, was not modulated upon SMHT, suggesting the involvement of a novel/alternative mechanism in the effective lipolysis observed. By applying the same experimental conditions successfully used for 3T3 adipocytes, SMHT was able to induce delipidation also in primary cultures of human adipose-derived adult stem cells. The success of this pioneering approach in vitro opens promising perspectives for the application of SMHT in vivo as an innovative safe and physiologically mild strategy against obesity, potentially useful in association with balanced diet and healthy lifestyle.

IgG is elevated in obese white adipose tissue but does not induce glucose intolerance via Fcγ-receptor or complement

BACKGROUND/OBJECTIVES

In obesity, B cells accumulate in white adipose tissue (WAT) and produce IgG, which may contribute to the development of glucose intolerance. IgG signals by binding to Fcγ receptors (FcγR) and by activating the complement system. The aim of our study was to investigate whether activation of FcγR and/or complement C3 mediates the development of high-fat diet-induced glucose intolerance.

METHODS

We studied mice lacking all four FcγRs (FcγRI/II/III/IV^-/-), only the inhibitory FcγRIIb (FcγRIIb^-/-), only the central component of the complement system C3 (C3^-/-), and mice lacking both FcγRs and C3 (FcγRI/II/III/IV/C3^-/-). All mouse models and wild-type controls were fed a high-fat diet (HFD) for 15 weeks to induce obesity. Glucose metabolism was assessed and adipose tissue was characterized for inflammation and adipocyte functionality.

RESULTS

In obese WAT of wild-type mice, B cells (+142%, P<0.01) and IgG (+128% P<0.01) were increased compared to lean WAT. Macrophages of FcγRI/II/III/IV^-/-mice released lower levels of cytokines compared to wild-type mice upon IgG stimulation. Only C3^-/- mice showed reduced HFD-induced weight gain as compared to controls (-18%, P<0.01). Surprisingly, FcγRI/II/III/IV^-/- mice had deteriorated glucose tolerance (AUC +125%, P<0.001) despite reduced leukocyte number (-30%, P<0.05) in gonadal WAT (gWAT), whereas glucose tolerance and leukocytes within gWAT in the other models were unaffected compared to controls. Although IgG in gWAT was increased (+44 to +174%, P<0.05) in all mouse models lacking FcγRIIb, only FcγRI/II/III/IV/C3^-/- mice exhibited appreciable alterations in immune cells in gWAT, for example, increased macrophages (+36%, P<0.001).

CONCLUSIONS

Lack of FcγRs reduces the activity of macrophages upon IgG stimulation, but neither FcγR nor C3 deficiency protects against HFD-induced glucose intolerance or reduces adipose tissue inflammation. This indicates that if obesity-induced IgG contributes to the development of glucose intolerance, this is not mediated by FcγR or complement activation.

Identification of Flavin-Containing Monooxygenase 5 (FMO5) as a Regulator of Glucose Homeostasis and a Potential Sensor of Gut Bacteria

We have previously identified flavin-containing monooxygenase 5 (FMO5) as a regulator of metabolic aging. The aim of the present study was to investigate the role of FMO5 in glucose homeostasis and the impact of diet and gut flora on the phenotype of mice in which the Fmo5 gene has been disrupted (Fmo5^−/− mice). In comparison with wild-type (WT) counterparts, Fmo5^−/− mice are resistant to age-related changes in glucose homeostasis and maintain the higher glucose tolerance and insulin sensitivity characteristic of young animals. When fed a high-fat diet, they are protected against weight gain and reduction of insulin sensitivity. The phenotype of Fmo5^−/− mice is independent of diet and the gut microbiome and is determined solely by the host genotype. Fmo5^−/− mice have metabolic characteristics similar to those of germ-free mice, indicating that FMO5 plays a role in sensing or responding to gut bacteria. In WT mice, FMO5 is present in the mucosal epithelium of the gastrointestinal tract where it is induced in response to a high-fat diet. In comparison with WT mice, Fmo5^−/− mice have fewer colonic goblet cells, and they differ in the production of the colonic hormone resistin-like molecule β. Fmo5^−/− mice have lower concentrations of tumor necrosis factor α in plasma and of complement component 3 in epididymal white adipose tissue, indicative of improved inflammatory tone. Our results implicate FMO5 as a regulator of body weight and of glucose disposal and insulin sensitivity and, thus, identify FMO5 as a potential novel therapeutic target for obesity and insulin resistance.

Keeping It All Going-Complement Meets Metabolism

The complement system is an evolutionary old and crucial component of innate immunity, which is key to the detection and removal of invading pathogens. It was initially discovered as a liver-derived sentinel system circulating in serum, the lymph, and interstitial fluids that mediate the opsonization and lytic killing of bacteria, fungi, and viruses and the initiation of the general inflammatory responses. Although work performed specifically in the last five decades identified complement also as a critical instructor of adaptive immunity—indicating that complement’s function is likely broader than initially anticipated—the dominant opinion among researchers and clinicians was that the key complement functions were in principle defined. However, there is now a growing realization that complement activity goes well beyond “classic” immune functions and that this system is also required for normal (neuronal) development and activity and general cell and tissue integrity and homeostasis. Furthermore, the recent discovery that complement activation is not confined to the extracellular space but occurs within cells led to the surprising understanding that complement is involved in the regulation of basic processes of the cell, particularly those of metabolic nature—mostly via novel crosstalks between complement and intracellular sensor, and effector, pathways that had been overlooked because of their spatial separation. These paradigm shifts in the field led to a renaissance in complement research and provide new platforms to now better understand the molecular pathways underlying the wide-reaching effects of complement functions in immunity and beyond. In this review, we will cover the current knowledge about complement’s emerging relationship with the cellular metabolism machinery with a focus on the functional differences between serum-circulating versus intracellularly active complement during normal cell survival and induction of effector functions. We will also discuss how taking a closer look into the evolution of key complement components not only made the functional connection between complement and metabolism rather “predictable” but how it may also give clues for the discovery of additional roles for complement in basic cellular processes.

The neuropeptide TLQP-21 opposes obesity via C3aR1-mediated enhancement of adrenergic-induced lipolysis

OBJECTIVES

Obesity is characterized by excessive fat mass and is associated with serious diseases such as type 2 diabetes. Targeting excess fat mass by sustained lipolysis has been a major challenge for anti-obesity therapies due to unwanted side effects. TLQP-21, a neuropeptide encoded by the pro-peptide VGF (non-acronymic), that binds the complement 3a receptor 1 (C3aR1) on the adipocyte membrane, is emerging as a novel modulator of adipocyte functions and a potential target for obesity-associated diseases. The molecular mechanism is still largely uncharacterized.

METHODS

We used a combination of pharmacological and genetic gain and loss of function approaches. 3T3-L1 and mature murine adipocytes were used for in vitro experiments. Chronic in vivo experiments were conducted on diet-induced obese wild type, β1, β2, β3-adrenergic receptor (AR) deficient and C3aR1 knockout mice. Acute in vivo lipolysis experiments were conducted on Sprague Dawley rats.

RESULTS

We demonstrated that TLQP-21 does not possess lipolytic properties per se. Rather, it enhances β-AR activation-induced lipolysis by a mechanism requiring Ca2+ mobilization and ERK activation of Hormone Sensitive Lipase (HSL). TLQP-21 acutely potentiated isoproterenol-induced lipolysis in vivo. Finally, chronic peripheral TLQP-21 treatment decreases body weight and fat mass in diet induced obese mice by a mechanism involving β-adrenergic and C3a receptor activation without associated adverse metabolic effects.

CONCLUSIONS

In conclusion, our data identify an alternative pathway modulating lipolysis that could be targeted to diminish fat mass in obesity without the side effects typically observed when using potent pro-lipolytic molecules.

Serum biomarkers and changes in clinical/MRI evidence of golimumab-treated patients with ankylosing spondylitis: results of the randomized, placebo-controlled GO-RAISE study

Background

In the present study, we evaluated relationships between serum biomarkers and clinical/magnetic resonance imaging (MRI) findings in golimumab-treated patients with ankylosing spondylitis.

Methods

In the GO-RAISE study, 356 patients with ankylosing spondylitis randomly received either placebo (n = 78) or golimumab 50 mg or 100 mg (n = 278) injections every 4 weeks through week 24 (placebo-controlled); patients continuing GO-RAISE received golimumab through week 252. Up to 139/125 patients had sera collected for biomarkers/serial spine MRI scans (sagittal plane, 1.5-T scanner). Two blinded readers employed modified ankylosing spondylitis spine magnetic resonance imaging score for activity (ASspiMRI-a) and ankylosing spondylitis spine magnetic resonance imaging score for chronicity. Spearman correlations (r_s) were assessed between serum biomarkers (n = 73) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), C-reactive-protein (CRP)-based Ankylosing Spondylitis Disease Activity Score (ASDAS), modified Stokes Ankylosing Spondylitis Spine Score (mSASSS), and ASspiMRI scores. Serum biomarkers predicting postbaseline spinal fatty lesion development and inflammation were analyzed by logistic regression.

Results

Significant, moderately strong correlations were observed between baseline inflammatory markers interleukin (IL)-6, intracellular adhesion molecule-1, complement component 3 (C3), CRP, haptoglobin, and serum amyloid-P and baseline ASDAS (r_s = 0.39–0.66, p ≤ 0.01). Only baseline leptin significantly correlated with ASDAS improvement at week 104 (r_s = 0.55, p = 0.040), and only baseline IL-6 significantly predicted mSASSS week 104 change (β = 0.236, SE = 0.073, p = 0.002, model R² = 0.093). By logistic regression, baseline leptin, C3, and tissue inhibitor of metalloproteinase (TIMP)-1 correlated with new fatty lesions per spinal MRI at week 14 and week 104 (both p < 0.01). Changes in serum C3 levels at week 4 (r_s = 0.55, p = 0.001) and week 14 (r_s = 0.49, p = 0.040) significantly correlated with BASDAI improvement at week 14. Baseline IL-6 and TIMP-1 (r_s = −0.63, −0.67; p < 0.05) and reductions at week 4 in IL-6 (r_s = 0.61, p < 0.05) and C3 (r_s = 0.72; p < 0.05) significantly correlated with week 14 ASspiMRI-a improvement.

Conclusions

Extensive serum biomarker multiparametric analyses in golimumab-treated patients with ankylosing spondylitis demonstrated few correlations with disease activity or MRI changes; IL-6 weakly correlated with radiographic progression.

Trial registration

ClinicalTrials.gov identifier: NCT00265083. Registered on 12 December 2005.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1200-1) contains supplementary material, which is available to authorized users.

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.

Liver ubiquitome uncovers nutrient-stress-mediated trafficking and secretion of complement C3

Adaptation to changes in nutrient availability is crucial for cells and organisms. Posttranslational modifications of signaling proteins are very dynamic and are therefore key to promptly respond to nutrient deprivation or overload. Herein we screened for ubiquitylation of proteins in the livers of fasted and refed mice using a comprehensive systemic proteomic approach. Among 1641 identified proteins, 117 were differentially ubiquitylated upon fasting or refeeding. Endoplasmic reticulum (ER) and secretory proteins were enriched in the livers of refed mice in part owing to an ER-stress-mediated response engaging retro-translocation and ubiquitylation of proteins from the ER. Complement C3, an innate immune factor, emerged as the most prominent ER-related hit of our screen. Accordingly, we found that secretion of C3 from the liver and primary hepatocytes as well as its dynamic trafficking are nutrient dependent. Finally, obese mice with a chronic nutrient overload show constitutive trafficking of C3 in the livers despite acute changes in nutrition, which goes in line with increased C3 levels and low-grade inflammation reported for obese patients. Our study thus suggests that nutrient sensing in the liver is coupled to release of C3 and potentially its metabolic and inflammatory functions.