Adipokines and the immune system: an adipocentric view

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.

Cardiometabolic disease in Black African and Caribbean populations: an ethnic divergence in pathophysiology?

In the UK, populations of Black African and Caribbean (BAC) ethnicity suffer higher rates of cardiometabolic disease than White Europeans (WE). Obesity, leading to increased visceral adipose tissue (VAT) and intrahepatic lipid (IHL), has long been associated with cardiometabolic risk, driving insulin resistance and defective fatty acid/lipoprotein metabolism. These defects are compounded by a state of chronic low-grade inflammation, driven by dysfunctional adipose tissue. Emerging evidence has highlighted associations between central complement system components and adipose tissue, fatty acid metabolism and inflammation; it may therefore sit at the intersection of various cardiometabolic disease risk factors. However, increasing evidence suggests an ethnic divergence in pathophysiology, whereby current theories fail to explain the high rates of cardiometabolic disease in BAC populations. Lower fasting and postprandial TAG has been reported in BAC, alongside lower VAT and IHL deposition, which are paradoxical to the high rates of cardiometabolic disease exhibited by this ethnic group. Furthermore, BAC have been shown to exhibit a more anti-inflammatory profile, with lower TNF-α and greater IL-10. In contrast, recent evidence has revealed greater complement activation in BAC compared to WE, suggesting its dysregulation may play a greater role in the high rates of cardiometabolic disease experienced by this population. This review outlines the current theories of how obesity is proposed to drive cardiometabolic disease, before discussing evidence for ethnic differences in disease pathophysiology between BAC and WE populations.

Identification of Potential Biomarkers of Septic Shock Based on Pathway and Transcriptome Analyses of Immune-Related Genes

Immunoregulation is crucial to septic shock (SS) but has not been clearly explained. Our aim was to explore potential biomarkers for SS by pathway and transcriptional analyses of immune-related genes to improve early detection. GSE57065 and GSE95233 microarray data were used to screen differentially expressed genes (DEGs) in SS. Gene Ontology and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analyses of DEGs were performed, and correlations between immune cell and pathway enrichment scores were analyzed. The predictive value of candidate genes was evaluated by receiver operating characteristic (ROC) curves. GSE66099, GSE4607, and GSE13904 datasets were used for external validation. Blood samples from six patients and six controls were collected for validation by qRT-PCR and western blotting. In total, 550 DEGs in SS were identified; these genes were involved in the immune response, inflammation, and infection. Immune-related pathways and levels of infiltration of CD4 + TCM, CD8 + T cells, and preadipocytes differed between SS cases and controls. Seventeen genes were identified as potential biomarkers of SS (areas under ROC curves >0.9). The downregulation of CD8A, CD247, CD3G, LCK, and HLA-DRA in SS was experimentally confirmed. We identified several immune-related biomarkers in SS that may improve early identification of disease risk.

Beyond energy balance regulation: The underestimated role of adipose tissues in host defense against pathogens

Although the adipose tissue (AT) is a central metabolic organ in the regulation of whole-body energy homeostasis, it is also an important endocrine and immunological organ. As an endocrine organ, AT secretes a variety of bioactive peptides known as adipokines - some of which have inflammatory and immunoregulatory properties. As an immunological organ, AT contains a broad spectrum of innate and adaptive immune cells that have mostly been studied in the context of obesity. However, overwhelming evidence supports the notion that AT is a genuine immunological effector site, which contains all cell subsets required to induce and generate specific and effective immune responses against pathogens. Indeed, AT was reported to be an immune reservoir in the host's response to infection, and a site of parasitic, bacterial and viral infections. In addition, besides AT's immune cells, preadipocytes and adipocytes were shown to express innate immune receptors, and adipocytes were reported as antigen-presenting cells to regulate T-cell-mediated adaptive immunity. Here we review the current knowledge on the role of AT and AT's immune system in host defense against pathogens. First, we will summarize the main characteristics of AT: type, distribution, function, and extraordinary plasticity. Second, we will describe the intimate contact AT has with lymph nodes and vessels, and AT immune cell composition. Finally, we will present a comprehensive and up-to-date overview of the current research on the contribution of AT to host defense against pathogens, including the respiratory viruses influenza and SARS-CoV-2.

Adipokines as New Biomarkers of Immune Recovery: Apelin Receptor, RBP4 and ZAG Are Related to CD4+ T-Cell Reconstitution in PLHIV on Suppressive Antiretroviral Therapy

A significant proportion of people living with HIV (PLHIV) who successfully achieve virological suppression fail to recover CD4⁺ T-cell counts. Since adipose tissue has been discovered as a key immune organ, this study aimed to assess the role of adipokines in the HIV immunodiscordant response. This is a multicenter prospective study including 221 PLHIV starting the first antiretroviral therapy (ART) and classified according to baseline CD4⁺ T-cell counts/µL (controls > 200 cells/µL and cases ≤ 200 cells/µL). Immune failure recovery was considered when cases did not reach more than 250 CD4⁺ T cells/µL at 144 weeks (immunological nonresponders, INR). Circulating adipokine concentrations were longitudinally measured using enzyme-linked immunosorbent assays. At baseline, apelin receptor (APLNR) and zinc-alpha-2-glycoprotein (ZAG) concentrations were significantly lower in INRs than in immunological responders (p = 0.043 and p = 0.034), and they remained lower during all ART follow-up visits (p = 0.044 and p = 0.028 for APLNR, p = 0.038 and p = 0.010 for ZAG, at 48 and 144 weeks, respectively). ZAG levels positively correlated with retinol-binding protein 4 (RBP4) levels (p < 0.01), and low circulating RBP4 concentrations were related to a low CD4⁺ T-cell gain (p = 0.018 and p = 0.039 at 48 and 144 weeks, respectively). Multiple regression adjusted for clinical variables and adipokine concentrations confirmed both low APLNR and RBP4 as independent predictors for CD4⁺ T cells at 144 weeks (p < 0.001). In conclusion, low APLNR and RBP4 concentrations were associated with poor immune recovery in treated PLHIV and could be considered predictive biomarkers of a discordant immunological response.

Complements are involved in alcoholic fatty liver disease, hepatitis and fibrosis

The complement system is a key component of the body’s immune system. When abnormally activated, this system can induce inflammation and damage to normal tissues and participate in the development and progression of a variety of diseases. In the past, many scholars believed that alcoholic liver disease (ALD) is induced by the stress of ethanol on liver cells, including oxidative stress and dysfunction of mitochondria and protease bodies, causing hepatocyte injury and apoptosis. Recent studies have shown that complement activation is also involved in the genesis and development of ALD. This review focuses on the roles of complement activation in ALD and of therapeutic intervention in complement-activation pathways. We intend to provide new ideas on the diagnosis and treatment of ALD.

The role of complement system in adipose tissue-related inflammation

As the common factor linking adipose tissue to the metabolic context of obesity, insulin resistance and atherosclerosis are associated with a low-grade chronic inflammatory status, to which the complement system is an important contributor. Adipose tissue synthesizes complement proteins and is a target of complement activation. C3a-desArg/acylation-stimulating protein stimulates lipogenesis and affects lipid metabolism. The C3a receptor and C5aR are involved in the development of adipocytes' insulin resistance through macrophage infiltration and the activation of adipose tissue. The terminal complement pathway has been found to be instrumental in promoting hyperglycemia-associated tissue damage, which is characteristic of the major vascular complications of diabetes mellitus and diabetic ketoacidosis. As a mediator of the effects of the terminal complement complex C5b-9, RGC-32 has an impact on energy expenditure as well as lipid and glucose metabolic homeostasis. All of this evidence, taken together, indicates an important role for complement activation in metabolic diseases.

Protective Role of Complement C3 Against Cytokine-Mediated β-Cell Apoptosis

Type 1 diabetes is a chronic autoimmune disease characterized by pancreatic islet inflammation and β-cell destruction by proinflammatory cytokines and other mediators. Based on RNA sequencing and protein-protein interaction analyses of human islets exposed to proinflammatory cytokines, we identified complement C3 as a hub for some of the effects of cytokines. The proinflammatory cytokines interleukin-1β plus interferon-γ increase C3 expression in rodent and human pancreatic β-cells, and C3 is detected by histology in and around the islets of diabetic patients. Surprisingly, C3 silencing exacerbates apoptosis under both basal condition and following exposure to cytokines, and it increases chemokine expression upon cytokine treatment. C3 exerts its prosurvival effects via AKT activation and c-Jun N-terminal kinase inhibition. Exogenously added C3 also protects against cytokine-induced β-cell death and partially rescues the deleterious effects of inhibition of endogenous C3. These data suggest that locally produced C3 is an important prosurvival mechanism in pancreatic β-cells under a proinflammatory assault.

3D-templated, fully automated microfluidic input/output multiplexer for endocrine tissue culture and secretion sampling

A fully automated, 16-channel microfluidic input/output multiplexer (μMUX) has been developed for interfacing to primary cells and to improve understanding of the dynamics of endocrine tissue function. The device utilizes pressure driven push-up valves for precise manipulation of nutrient input and hormone output dynamics, allowing time resolved interrogation of the cells. The ability to alternate any of the 16 channels from input to output, and vice versa, provides for high experimental flexibility without the need to alter microchannel designs. 3D-printed interface templates were custom designed to sculpt the above-channel polydimethylsiloxane (PDMS) in microdevices, creating millimeter scale reservoirs and confinement chambers to interface primary murine islets and adipose tissue explants to the μMUX sampling channels. This μMUX device and control system was first programmed for dynamic studies of pancreatic islet function to collect ∼90 minute insulin secretion profiles from groups of ∼10 islets. The automated system was also operated in temporal stimulation and cell imaging mode. Adipose tissue explants were exposed to a temporal mimic of post-prandial insulin and glucose levels, while simultaneous switching between labeled and unlabeled free fatty acid permitted fluorescent imaging of fatty acid uptake dynamics in real time over a ∼2.5 hour period. Application with varying stimulation and sampling modes on multiple murine tissue types highlights the inherent flexibility of this novel, 3D-templated μMUX device. The tissue culture reservoirs and μMUX control components presented herein should be adaptable as individual modules in other microfluidic systems, such as organ-on-a-chip devices, and should be translatable to different tissues such as liver, heart, skeletal muscle, and others.

Characterization of In Vitro Engineered Human Adipose Tissues: Relevant Adipokine Secretion and Impact of TNF-α

Representative modelling of human adipose tissue functions is central to metabolic research. Tridimensional models able to recreate human adipogenesis in a physiological tissue-like context in vitro are still scarce. We describe the engineering of white adipose tissues reconstructed from their cultured adipose-derived stromal precursor cells. We hypothesize that these reconstructed tissues can recapitulate key functions of AT under basal and pro-inflammatory conditions. These tissues, featuring human adipocytes surrounded by stroma, were stable and metabolically active in long-term cultures (at least 11 weeks). Secretion of major adipokines and growth factors by the reconstructed tissues was determined and compared to media conditioned by human native fat explants. Interestingly, the secretory profiles of the reconstructed adipose tissues indicated an abundant production of leptin, PAI-1 and angiopoietin-1 proteins, while higher HGF levels were detected for the human fat explants. We next demonstrated the responsiveness of the tissues to the pro-inflammatory stimulus TNF-α, as reflected by modulation of MCP-1, NGF and HGF secretion, while VEGF and leptin protein expression did not vary. TNF-α exposure induced changes in gene expression for adipocyte metabolism-associated mRNAs such as SLC2A4, FASN and LIPE, as well as for genes implicated in NF-κB activation. Finally, this model was customized to feature adipocytes representative of progressive stages of differentiation, thereby allowing investigations using newly differentiated or more mature adipocytes. In conclusion, we produced tridimensional tissues engineered in vitro that are able to recapitulate key characteristics of subcutaneous white adipose tissue. These tissues are produced from human cells and their neo-synthesized matrix elements without exogenous or synthetic biomaterials. Therefore, they represent unique tools to investigate the effects of pharmacologically active products on human stromal cells, extracellular matrix and differentiated adipocytes, in addition to compounds modulating adipogenesis from precursor cells.

C57BL/6 and A/J Mice Have Different Inflammatory Response and Liver Lipid Profile in Experimental Alcoholic Liver Disease

Alcoholic liver disease (ALD) is an important worldwide public health issue characterized by liver steatosis, inflammation, necrosis, and apoptosis of hepatocytes with eventual development of fibrosis and cirrhosis. Comparison of murine models with different inflammatory responses for ALD is important for an evaluation of the importance of genetic background in the interpretation of ethanol-induced phenotypes. Here, we investigated the role of inflammation and genetic background for the establishment of ALD using two different mouse strains: C57BL/6 (B6) and A/J. B6 and A/J mice were treated with a high fat diet containing ethanol (HFDE) and compared to the controls for 10 weeks. Hepatomegaly and steatohepatitis were similar in B6 and A/J mice, but only A/J mice were resistant to weight gain. On the other hand, HFDE-fed B6 accumulated more triglycerides (TG) and cholesterol and presented more intense cellular infiltrate in the liver when compared to HFDM-fed mice. Liver inflammatory environment was distinct in these two mouse strains. While HFDE-fed B6 produced more liver IL-12, A/J mice increased the TNF-α production. We concluded that mouse genetic background could dictate the intensity of the HFDE-induced liver injury.

The cell biology of fat expansion

Adipose tissue is a complex, multicellular organ that profoundly influences the function of nearly all other organ systems through its diverse metabolite and adipokine secretome. Adipocytes are the primary cell type of adipose tissue and play a key role in maintaining energy homeostasis. The efficiency with which adipose tissue responds to whole-body energetic demands reflects the ability of adipocytes to adapt to an altered nutrient environment, and has profound systemic implications. Deciphering adipocyte cell biology is an important component of understanding how the aberrant physiology of expanding adipose tissue contributes to the metabolic dysregulation associated with obesity.

Tributyltin chloride leads to adiposity and impairs metabolic functions in the rat liver and pancreas

Tributyltin chloride (TBT) is an environmental contaminant used in antifouling paints of boats. Endocrine disruptor effects of TBT are well established in animal models. However, the adverse effects on metabolism are less well understood. The toxicity of TBT in the white adipose tissue (WAT), liver and pancreas of female rats were assessed. Animals were divided into control and TBT (0.1 μg/kg/day) groups. TBT induced an increase in the body weight of the rats by the 15th day of oral exposure. The weight gain was associated with high parametrial (PR) and retroperitoneal (RP) WAT weights. TBT-treatment increased the adiposity, inflammation and expression of ERα and PPARγ proteins in both RP and PR WAT. In 3T3-L1 cells, estrogen treatment reduced lipid droplets accumulation, however increased the ERα protein expression. In contrast, TBT-treatment increased the lipid accumulation and reduced the ERα expression. WAT metabolic changes led to hepatic inflammation, lipid accumulation, increase of PPARγ and reduction of ERα protein expression. Accordingly, there were increases in the glucose tolerance and insulin sensitivity tests with increases in the number of pancreatic islets and insulin levels. These findings suggest that TBT leads to adiposity in WAT specifically, impairing the metabolic functions of the liver and pancreas.

Levels of acylation stimulating protein and the complement component 3 precursor are associated with the occurrence and development of coronary heart disease

The aim of the present study was to investigate whether acylation stimulating protein (ASP) and complement component 3 (C3) are associated with the occurrence and development of coronary heart disease (CHD). The participants of the study were divided into three groups, including the healthy control (n=42), metabolic syndrome (MS, n=56) and CHD (n=62) groups. An enzyme-linked immunosorbent assay was used to measure the ASP concentrations, while an immunoturbidimetric assay was employed to determine the C3 concentrations. In addition, coronary angiography was performed to determine the severity of coronary artery disease in the CHD group. The CHD group was divided into three subgroups, according to the final Gensini score of coronary artery stenosis for each patient (mild, ≤20 points; moderate, 21–40 points; severe, >40 points). Western blotting and quantitative reverse transcription-polymerase chain reaction (RT-PCR) were performed to analyze the protein and mRNA expression levels of C3 in the CHD subgroups and the healthy control group. The concentrations of ASP and C3 in the CHD group were found to be significantly higher compared with the control and MS groups. In addition, the levels of ASP and C3 in the mild and moderate CHD subgroups were significantly higher compared with the healthy controls or mild CHD patients. Furthermore, the protein expression levels of C3 in the moderate and severe CHD patients were found to be significantly higher compared with the healthy individuals and the mild CHD patients. The quantitative RT-PCR results revealed that the mRNA expression levels of C3 in the moderate and severe CHD patients were significantly higher compared with the healthy control group and the mild CHD patients. Furthermore, the mean levels of C3 transcripts in the severe CHD patients were found to be higher compared with the moderate CHD subgroup (P<0.05). Therefore, ASP and C3 were found to be associated with the occurrence and development of CHD; thus, may be used as novel indexes for CHD.

Effect of cocoa butter and sunflower oil supplementation on performance, immunoglobulin, and antioxidant vitamin status of rats

This study investigated the effects of cocoa butter and sunflower oil alone and in combination on performance, some biochemical parameters, immunoglobulin, and antioxidant vitamin status in Wistar rats. Forty-eight male rats were assigned to four groups, consisting of 12 rats with 3 replicates. Control received balanced rat diet without oil, cocoa butter group received 3.5% cocoa butter, sunflower oil group received 3.5% sunflower oil, the last group received 1.75% sunflower oil + 1.75% cocoa butter supplementation in the rat diet for 8 weeks. The total feed consumption in sunflower oil group was statistically lower than in the other groups. The serum creatinine level was decreased in cocoa butter group compared to control. Triglyceride and VLDL cholesterol levels were decreased in only sunflower oil and only cocoa butter groups as compared to control. The level of Ig M was statistically lower in cocoa butter and cocoa butter + sunflower oil groups than in control and sunflower oil groups. There were no statistically important difference in vitamin concentrations among trial groups. It was concluded that the supplementation of cocoa butter in diet decreased Ig M level, while the supplementation of cocoa butter and sunflower oil alone decreased the triglyceride and VLDL cholesterol levels.

Structural and functional characterization of human and murine C5a anaphylatoxins

Complement is an ancient part of the innate immune system that plays a pivotal role in protection against invading pathogens and helps to clear apoptotic and necrotic cells. Upon complement activation, a cascade of proteolytic events generates the complement effectors, including the anaphylatoxins C3a and C5a. Signalling through their cognate G-protein coupled receptors, C3aR and C5aR, leads to a wide range of biological events promoting inflammation at the site of complement activation. The function of anaphylatoxins is regulated by circulating carboxypeptidases that remove their C-terminal arginine residue, yielding C3a-desArg and C5a-desArg. Whereas human C3a and C3a-desArg adopt a canonical four-helix bundle fold, the conformation of human C5a-desArg has recently been described as a three-helix bundle. Here, the crystal structures of an antagonist version of human C5a, A8(Δ71-73), and of murine C5a and C5a-desArg are reported. Whereas A8(Δ71-73) adopts a three-helix bundle conformation similar to human C5a-desArg, the two murine proteins form a four-helix bundle. A cell-based functional assay reveals that murine C5a-desArg, in contrast to its human counterpart, exerts the same level of activition as murine C5a on its cognate receptor. The role of the different C5a conformations is discussed in relation to the differential activation of C5a receptors across species.

Characterization of mouse mediastinal fat-associated lymphoid clusters

The association between adipose tissue and immunity has been established and fat-associated lymphoid clusters (FALCs) are considered as a source of immune cells. We discovered lymphoid clusters (LCs) in mouse mediastinal fat tissues (MFTs). In Th1-biased C57BL/6N (B6), Th2-biased DBA/2Cr (DBA) and autoimmune-prone MRL/MpJ (MRL) mice strains, LCs without a fibrous capsule and germinal center were observed in white-colored MFTs extending from the diaphragm to the heart. The number and size of the LCs were larger in 12-month-old mice than in 3-month-old mice in all of the examined strains. Moreover, B6 had an especially large number of LCs compared with DBA and MRL. The immune cells in the LCs consisted of mainly T-cells and some B-cells. The majority of T-cells were CD4+ helper T (Th) cells, rather than CD8+ cytotoxic T-cells and no obvious immune cell population difference was present among the strains. Furthermore, high endothelial venules and lymphatic vessels in the LCs were better developed in B6 mice than in the other strains. Interestingly, some CD133+ hematopoietic progenitor cells and some c-Kit+/CD127+ natural helper cells were detected in the LCs. BrdU+ proliferating cells were more abundant in the LCs of B6 mice than in the LCs of the other strains and the number of BrdU+ cells increased with age. This is the first report of LCs in mouse MFTs. We suggest that the mouse genetic background affects LC size and number. We term the LCs "mediastinal fat-associated lymphoid clusters". These clusters can be considered as niches for Th cell production.

Distinct associations of complement C3a and its precursor C3 with atherosclerosis and cardiovascular disease. The CODAM study

Complement C3 is a novel risk factor for cardiovascular disease (CVD), but the underlying mechanism is currently unknown. We determined the associations of the anaphylatoxin C3a, the activation product of C3, and of C3 itself with estimates of atherosclerosis and CVD. We studied associations of C3a and C3 with carotid intima-media thickness (cIMT), ankle-arm blood pressure index (AAIx) and CVD in cross-sectional analyses among 545 participants of the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) study (62% men, 59.4 ± 6.9 years) and examined effect modification by smoking. We conducted linear and logistic regression analyses with adjustments for age, sex, glucose metabolism status, lipids, adiposity, renal function, blood pressure, pack-years smoked, physical activity, use of medication and investigated mediation by inflammation. C3a was independently associated with cIMT (β=0.032 mm, [95% confidence interval: 0.004; 0.060]) and AAIx (β=-0.022, [-0.043; -0.001]), but C3 was not. Effect modification by smoking was only observed for CVD (P(smoking*C3a)=0.008, P(smoking*C3)=0.018), therefore these associations were stratified for smoking behaviour. Both C3a (odds ratio [OR] =2.96, [1.15; 7.62]) and C3 (OR =1.98, [1.21; 3.22]) were independently associated with CVD in heavy smokers. The association of C3 with CVD was independent of C3a. Low-grade inflammation did partially explain the association of C3a with AAIx, but not the other observed associations. This suggests that C3a and C3 have distinct roles in pathways leading to CVD. C3a may promote atherosclerosis and additionally advance CVD in heavy smokers. Conversely, C3 may be associated with CVD in heavy smokers via pathways other than atherosclerosis.

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.

Role of adipokines signaling in the modulation of T cells function

The field that links immunity and metabolism is rapidly expanding. Apparently non-immunological disorders such as obesity and type 2 diabetes have been linked to immune dysregulation, suggesting that metabolic alterations can be induced by or be consequence of an altered self-immune tolerance. In this context, adipose tissue produces and releases a variety of pro-inflammatory and anti-inflammatory factors, termed "adipokines," which can be considered as the bridge between obesity-related exogenous factors, such as nutrition and lifestyle, and the molecular events leading to metabolic syndrome, inflammatory, and/or autoimmune conditions. In obesity, increased production of most adipokines impacts on multiple functions such as appetite and energy balance, modulation of immune responses, insulin sensitivity, angiogenesis, blood pressure, lipid metabolism, and so on. This report aims to discuss some of the recent topics of adipocytokine research and their related signaling pathways, that may be of particular importance as could lead to effective therapeutic strategies for obesity-associated diseases.

Adipocytokine profile, cytokine levels and foxp3 expression in multiple sclerosis: a possible link to susceptibility and clinical course of disease

Background

Adipocytokines may be involved in multiple sclerosis (MS) as well as other autoimmune and inflammatory-related diseases. This study aims to compare levels of resistin, visfatin and leptin in three subgroups of MS patients with healthy subjects and also to study their relationship with Foxp3 expression and levels of several pro-inflammatory mediators such as interleukine-1 β(IL-1 β),tumor necrosis factor-α (TNF-α) and human sensitive C-reactive protein (hs-CRP).

Methods

A total of 391 subjects including 200 healthy controls and 191 MS patients were recruited for this case-control study. Circulating adipocytokines and inflammatory mediators were measured using immunoassay methods. Foxp3 gene expression in peripheral blood mononuclear cells (PBMC) was determined by quantitative real-time PCR. Fat tissue mass was evaluated by using dual energy X-ray absorptiometery (DEXA).

Results

A significant difference was observed in levels of inflammatory mediators, adipocytokines, Foxp3 gene expression and adipose tissue mass between MS patients and healthy controls. All adipocytokines were positively correlated with levels of inflammatory mediators and negatively correlated with Foxp3 expression in MS patients. In controls, there were positive correlations between circulating leptin and resistin with TNF-α and IL-1β in subgroup analysis, the highest levels of TNF-α, IL-1β, hs-CRP, resistin and leptin were observed in primary progressive-MS (PP-MS) patients. Also, expression of Foxp3 and levels of visfatin in relapsing remitting-MS(RR-MS) patients were higher compared with the other subgroups.

Conclusions

Our findings suggest the potential role of adipocytokines in pathogenesis and severity of MS. Notably, the relationship of adipocytokines levels with inflammatory cytokines as well as clinical features of MS could be considerable in translational medicine and biomarker studies.

A novel polymorphism (901G > a) of C5L2 gene is associated with coronary artery disease in Chinese Han and Uyghur population

BACKGROUND

C5L2, a G protein-coupled receptor (GPCR), has been demonstrated to be a ligand for acylation-stimulating protein (ASP). The aim of the present study is to evaluate the association of a novel variation (901A > G) of C5L2 gene with coronary artery disease (CAD).

METHODS

We identified a novel single nucleotide polymorphism (SNP), (901G > A), in exon 2 using a polymerase chain reaction direct-sequencing method. This nucleotide change causes the amino-acid order from Arginine to glutaminate at codon 300. We analyzed the relationship between this SNP and CAD in two independent case-control studies: one was in a Han population (492 CAD patients and 577 control subjects) and the other was in a Uygur population (319 CAD patients and 554 control subjects).

RESULTS

The frequency of AG genotype in CAD subjects was less than that in the control subjects not only in Han (1.8% vs 8.6%, P < 0.001, OR = 0.143, 95% CI: 0.068 ~ 0.302) but also in Uygur population (0.9% vs 5.2%, P = 0.001, OR = 0.246, 95% CI: 0.072 ~ 0.837). After adjustment for known CAD risk factors such as hypertension, diabetes, smoking, age and gender, the difference remained significant.

CONCLUSION

The 901G > A polymorphism of C5L2 may be a genetic maker of CAD in the Han and Uygur population in western China.

The complement anaphylatoxin C5a receptor contributes to obese adipose tissue inflammation and insulin resistance

Obese adipose tissue (AT) inflammation contributes critically to development of insulin resistance. The complement anaphylatoxin C5a receptor (C5aR) has been implicated in inflammatory processes and as regulator of macrophage activation and polarization. However, the role of C5aR in obesity and AT inflammation has not been addressed. We engaged the model of diet-induced obesity and found that expression of C5aR was significantly upregulated in the obese AT, compared with lean AT. In addition, C5a was present in obese AT in the proximity of macrophage-rich crownlike structures. C5aR-sufficient and -deficient mice were fed a high-fat diet (HFD) or a normal diet (ND). C5aR deficiency was associated with increased AT weight upon ND feeding in males, but not in females, and with increased adipocyte size upon ND and HFD conditions in males. However, obese C5aR(-/-) mice displayed improved systemic and AT insulin sensitivity. Improved AT insulin sensitivity in C5aR(-/-) mice was associated with reduced accumulation of total and proinflammatory M1 macrophages in the obese AT, increased expression of IL-10, and decreased AT fibrosis. In contrast, no difference in β cell mass was observed owing to C5aR deficiency under an HFD. These results suggest that C5aR contributes to macrophage accumulation and M1 polarization in the obese AT and thereby to AT dysfunction and development of AT insulin resistance.

Human skin mast cells express complement factors C3 and C5

We examine whether complement factor C3 or C5 is synthesized by human skin-derived mast cells and whether their synthesis is regulated by cytokines. C3 and C5 mRNAs were assessed by RT-PCR, and proteins by flow cytometry, confocal microscopy, Western blotting, and ELISA. C3 and C5 mRNAs were each expressed, and baseline protein levels/10(6) cultured mast cells were 0.9 and 0.8 ng, respectively, and located in the cytoplasm outside of secretory granules. C3 accumulated in mast cell culture medium over time and by 3 d reached a concentration of 9.4 ± 8.0 ng/ml, whereas C5 levels were not detectable (<0.15 ng/ml). Three-day incubations of mast cells with IL-1α, IL-1β, IL-17, IFN-γ, IL-6, or anti-FcεRI did not affect C3 protein levels in culture medium, whereas incubations with PMA, TNF-α, IL-13, or IL-4 enhanced levels of C3 1.7- to 3.3-fold. In contrast with C3, levels of C5 remained undetectable. Importantly, treatment with TNF-α together with either IL-4 or IL-13 synergistically enhanced C3 (but not C5) production in culture medium by 9.8- or 7.1-fold, respectively. This synergy was blocked by attenuating the TNF-α pathway with neutralizing anti-TNF-α Ab, soluble TNFR, or an inhibitor of NF-κB, or by attenuating the IL-4/13 pathway with Jak family or Erk antagonists. Inhibitors of PI3K, Jnk, and p38 MAPK did not affect this synergy. Thus, human mast cells can produce and secrete C3, whereas β-tryptase can act on C3 to generate C3a and C3b, raising the likelihood that mast cells engage complement to modulate immunity and inflammation in vivo.

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.

Morphological characteristics of the human skin over posterior aspect of heel in the context of pressure ulcer development

The posterior aspect of heel is known as a particularly vulnerable site for pressure ulcer development, however, it is not well understood why this is so. This study was undertaken to identify the morphological characteristics of the skin over posterior aspect of heel in the context of pressure ulcer development. Human skin tissues were obtained from four different sites of the body of 4 aged subjects postmortem: posterior aspect of heel, plantar aspect of heel, sacrum and centre of gluteus maximus. The skin samples were processed for the examination using light microscopy and scanning electron microscopy. The posterior aspect of heel was characterized by a thicker epidermis, denser distribution and larger diameter of capillaries in the papillary layer, 3-dimensional architecture of collagen fibre meshwork in the reticular layer and elliptic adipose tissues situated perpendicularly to the skin surface being surrounded by thick collagen and elastic fibre septa compared to the sacrum. Given our observations in the papillary layer of the posterior aspect of heel, we assume that the tissue of this area may be less tolerant to ischaemia since the tissue has high metabolic demand to provide oxygen and nutrients to the epidermis which protects underlying tissue from external force. In addition, elliptic configuration of adipose tissues in the posterior aspect of heel situated perpendicularly to the skin surface may result in deep lesion if the forces applied exceed the tolerable level since the forces will be concentrated within the elliptic compartments.

Complement system activation in cardiac and skeletal muscle pathology: friend or foe?

A major goal in current cardiology practice is to determine optimal strategies for minimizing myocardial necrosis and optimizing cardiac repair following an acute myocardial infarction. Temporally regulated activation and suppression of innate immunity may be critical for achieving this goal. Extensive experimental data in various animal models have indicated that inhibiting complement activation offers protection to cardiac tissue after ischemia/reperfusion. However, the results of clinical studies using complement inhibitors (mainly at the C5 level) in patients with acute myocardial infarction have largely been disappointing. In cases in which complement activation participates in the initial events of muscle cell destruction, as in autoimmune myocarditis or autoimmune muscle disorders, inhibition of complement activation is expected to prove a successful treatment. In other pathologic conditions in which complement is recruited by degenerating or dying muscle cells, as in ischemia, the ideal approach is probably to modulate rather than abruptly blunt complement activation. Beneficial effects of complement action with regard to waste disposal, recruitment of stem cells, regeneration, angiogenesis, and better utilization of energy sources under hypoxic conditions may also prove important for successful disease treatment. Patient outcome after myocardial infarction almost certainly depend upon the combined activation of several distinct but potentially interrelated signaling pathways, suggesting that a combination of treatments targeted to different pathways should be the therapy of choice, and modulation of complement could be one of them.

C5L2 and C5aR interaction in adipocytes and macrophages: insights into adipoimmunology

Obesity is associated with inflammation characterized by increased infiltration of macrophages into adipose tissue. C5aR-like receptor 2 (C5L2) has been identified as a receptor for acylation-stimulating protein (ASP) and the inflammatory factor C5a, which also binds C5aR. The present study examines the effects of ligands ASP and C5a on interactions between the receptors C5L2 and C5aR in 3T3-L1 adipocytes and J774 macrophages. BRET experiments indicate that C5L2 and C5aR form homo- and heterodimers in transfected HEK 293 cells, which were stable in the presence of ligand. Cell surface receptor levels of C5L2 and C5aR increased during 3T3-L1 adipocyte differentiation; both receptors are also highly expressed in J774 macrophages. Using confocal microscopy to evaluate endogenous receptors in adipocytes following stimulation with ASP or C5a, C5L2 is internalized with increasing perinuclear colocalization with C5aR. There is little C5a-dependent colocalization in macrophages. While adipocyte-conditioned medium (ACM) increased C5L2-C5aR colocalization in macrophages, this was blocked by C5a. ASP stimulation increased Akt (Ser(473)) phosphorylation in both cell types; C5a induced slight Akt phosphorylation in adipocytes with less effect in macrophages. ASP, but not C5a, increased fatty acid uptake/esterification in adipocytes. C5L2-C5aR homodimerization versus heterodimerization may thus contribute to differential responses obtained following ASP vs C5a stimulation of adipocytes and macrophages, providing new insights into the complex interaction between these two cell types within adipose tissue. Studying the mechanisms involved in the differential responses of C5L2-C5aR activation based on cell type will further our understanding of inflammatory processes in obesity.

Differential chemoattractant response in adipocytes and macrophages to the action of acylation stimulating protein

Obesity is characterized by chronic low-grade inflammation with increased adipose tissue pro-inflammatory cytokine production. Acylation stimulating protein (ASP) stimulates triglyceride synthesis and glucose transport via its receptor C5L2. Circulating ASP is increased in obesity, insulin resistance and metabolic syndrome. The present study examines the effects of normal (50 nM), high physiological (200 nM) and pathological (600 nM) levels of ASP on inflammatory changes in 3T3-L1 adipocytes and J774 macrophages and the underlying mechanisms involved. Treatment with ASP for 24h increased monocyte chemoattractant protein-1 (MCP1, 800%, P<0.001) and keratinocyte-derived chemokine (KC, >150%, P<0.01) secretion in adipocytes in a dose-dependent manner, with no effect on IL-6 or adiponectin. In macrophages, ASP had no effect on these cytokines. C5a, a ligand for C5L2 and C5aR receptors, differed from ASP. Macrophage-adipocyte coculture increased MCP-1 and adiponectin secretion, and ASP further enhanced secretion (P<0.001 and P<0.05, respectively) at doses of 50 nM and 200 nM. ASP increased Ser(468) and Ser(536) phosphorylation of p65 NFκB in a time- and concentration-dependent manner (P<0.05) as well as phosphorylation of Akt Ser(473) (p=0.02). ASP and insulin stimulations of Ser(536) p65 NFκB phosphorylation were comparable (both p<0.05) but not additive. Both inhibition of PI3kinase (with wortmannin) and NFκB (with BAY11-7085) prevented ASP stimulation of MCP-1 and KC secretion in adipocytes. These findings suggest that ASP, especially at high physiologic doses, may stimulate specific inflammatory cytokines in adipocytes through PI3kinase- and NFκB-dependant pathways, thus further promoting macrophage infiltration and local inflammation in obese adipose tissue.

Regulatory T cells, mTOR kinase, and metabolic activity

The field that links immunity and metabolism is rapidly expanding. Apparently, non-immunological disorders such as obesity and type 2 diabetes have been linked to immune dysregulation, suggesting that metabolic alterations can be induced by or be a consequence of an altered self-immune tolerance. In this context, a key role is played by signaling systems acting as metabolic "sensors" linking energy/nutritional status to regulatory T (Treg) cell functions. We propose that a dynamic/oscillatory activity of intracellular metabolism, through mTOR modulation, might represent a shift in understanding the molecular mechanisms governing Treg cell tolerance. In particular, the decision between Treg cell proliferation and hyporesponsiveness arises from their ability to probe the extracellular milieu and, modulating the metabolic intracellular signaling, to determine different qualitative and quantitative functional outcomes.

Influence of hypertension, obesity and nicotine abuse on quantitative and qualitative changes in acute-phase proteins in patients with essential hypertension

Background

Hypertension is a powerful risk factor for cardiovascular disease and frequently occurs in conjunction with obesity. Accumulative evidence suggests a link between inflammation and hypertension. The aim of study was to evaluate whether blood pressure, obesity and smoking may influence acute-phase response.

Material/Methods

Ninety-two patients with essential hypertension and 75 healthy volunteers as a control group were studied. In all subjects assessment of hsCRP, α1-acid glycoprotein (AGP), α1-antichymotrypsin, transferrin, α1-antitrypsin, and C3 and C4 complement were performed. Evaluation of glycosylation profile and reactivity coefficient (RC) for AGP was done by means of affinity immunoelectrophoresis with concanavalin A as a ligand.

Results

When compared to the controls, hypertensive subjects presented significantly higher hsCRP concentrations and lower transferrin level. Hypertensive patients had elevated AGP-AC. The intensification of the inflammatory reaction was greater in the subgroup of hypertensive patients smoking cigarettes. In obese hypertensives, elevated serum C3 complement level was found.

Conclusions

We conclude that arterial hypertension may evoke the acute-phase response in humans. Markers of acute-phase response are particularly strongly expressed in smokers. Serum C 3 complement, but not other APPs, is elevated in hypertension coexisting with obesity.

Leptin as a link between the immune system and kidney-related diseases: leading actor or just a coadjuvant?

Food intake and nutritional status modify the physiological responses of the immune system to illness and infection and regulate the development of chronic inflammatory processes, such as kidney disease. Adipose tissue secretes immune-related proteins called adipokines that have pleiotropic effects on both the immune and neuroendocrine systems, linking metabolism and immune physiology. Leptin, an adipose tissue-derived adipokine, displays a variety of immune and physiological functions, and participates in several immune responses. Here, we review the current literature on the role of leptin in kidney diseases, linking adipose tissue and the immune system with kidney-related disorders. The modulation of this adipose hormone may have a major impact on the treatment of several immune- and metabolic-related kidney diseases.

Intracellular metabolic pathways control immune tolerance

Disorders such as obesity and type 2 diabetes have been linked to immune dysfunction, raising the possibility that metabolic alterations can be induced by or be a consequence of alterations in immunological tolerance. Here, we describe how intracellular metabolic signalling pathways can 'sense' host energy/nutritional status, and in response, modulate regulatory T (Treg) cell function. In particular, we focus on mammalian target of rapamycin (mTOR) signalling, and how stimuli such as nutrients and leptin activate mTOR in an oscillatory manner to determine Treg cell proliferation status. We propose that metabolic changes such as nutritional deprivation or overload could dictate the characteristics of the Treg cell compartment and subsequent downstream immune reactions.

Thyroid hormone levels predict the change in body weight: a prospective study

BACKGROUND

Different studies, mostly cross-sectional, have found an association between low levels of thyroid hormones, even within the normal range, and a greater body mass index. The aim of this study was to determine the association between thyroid function and the risk for obesity.

MATERIALS AND METHODS

In this population-based prospective study, measurements were made of anthropometric parameters, thyroid hormone function and urinary iodine in a cohort of the Pizarra Study (n = 937), and repeated 6 years later (n = 784). At the second point, measurements were also made of leptin and adiponectin.

RESULTS

Among the persons who were not obese at the start of the study, the odds ratio (OR) of becoming obese for those in the fourth quartile (Q(4)) for free triiodothyronine (FT3) (versus those in Q(1)) was 2·94 (1·46-5·90) (P = 0·005). The OR of becoming obese in persons in Q(4) of FT4 (versus those in Q(1)) was 3·06 (1·23-7·43) (P = 0·01). Those persons in Q(4) of weight gain had a higher FT3 at the 6-year follow-up than those whose weight gain was in Q(1) (P < 0·001). Leptin correlated with thyrotropin (β = 0·58, P = 0·001) and the FT4 (β = -1·12, P = 0·005). Adiponectin correlated with FT3 (r = -0·24, P < 0·001). The urinary iodine correlated negatively with both the BMI (β = -0·08, P = 0·01) and the increase in weight (β = -0·08, P = 0·04).

CONCLUSIONS

The changes in the thyroid hormones could be the consequence, rather than the cause, of the increase in weight. The same pathophysiological mechanisms that induce obesity might also be modifying the thyroid hormone pattern.

Obesity and susceptibility to autoimmune diseases

For decades, obesity has been considered to be the result of the complex interaction between genes and the environment and its pathogenesis is still unresolved. The discovery of hormones and neural mediators responsible for the control of food intake and metabolism at the hypothalamic level has provided fundamental insights into the complicated pathways that control food intake. However, the molecular basis for the association between obesity and low-degree chronic inflammation is still unknown. More recently, the discovery of leptin, one of the most abundant adipocyte-derived hormones, has suggested that nutritional status, through leptin secretion, can control immune self-tolerance modulating Treg suppressive function and responsiveness. Furthermore, recent experimental evidence has shown the presence of an abundant adipose tissue-resident Treg population responsible for the control of metabolic parameters and glucose homeostasis. Better knowledge of the intricate network of interactions among leptin-related energy regulation, Treg activities and obesity could lead to valuable strategies for therapeutic intervention in obesity and obesity-associated insulin resistance.

CD55 deficiency protects against atherosclerosis in ApoE-deficient mice via C3a modulation of lipid metabolism

Atherosclerosis, the leading cause of death in the Western world, is driven by chronic inflammation within the artery wall. Elements of the complement cascade are implicated in the pathogenesis, because complement proteins and their activation products are found in the atherosclerotic plaque. We examined the role of CD55, a membrane inhibitor of the complement component 3 (C3) convertase, which converts C3 into C3a and C3b, in atherosclerosis. CD55-deficient (CD55^−/−) mice were crossed onto the atherosclerosis-prone apolipoprotein E (apoE)-deficient (apoE^−/−) background. High fat–fed male apoE^−/−/CD55^−/− mice were strongly protected from developing atherosclerosis compared with apoE^−/− controls. Lipid profiling showed significantly lower levels of triglycerides, nonesterified fatty acids, and cholesterol in apoE^−/−/CD55^−/− mice than that in controls after high-fat feeding, whereas body fat in apoE^−/−/CD55^−/− mice content was increased. Plasma levels of C3 fell, whereas concentrations of C3adesArg (alias acylation stimulating protein; ASP), produced by serum carboxypeptidase N–mediated desargination of C3a, increased in nonfasted high fat–fed apoE^−/−/CD55^−/− mice, indicating complement activation. Thus, complement dysregulation in the absence of CD55 provoked increased C3adesArg production that, in turn, caused altered lipid handling, resulting in atheroprotection and increased adiposity. Interventions that target complement activation in adipose tissue should be explored as lipid-decreasing strategies.

Hormones and the pilosebaceous unit

Hormones can exert their actions through endocrine, paracrine, juxtacrine, autocrine and intracrine pathways. The skin, especially the pilosebaceous unit, can be regarded as an endocrine organ meanwhile a target of hormones, because it synthesizes miscellaneous hormones and expresses diverse hormone receptors. Over the past decade, steroid hormones, phospholipid hormones, retinoids and nuclear receptor ligands as well as the so-called stress hormones have been demonstrated to play pivotal roles in controlling the development of pilosebaceous units, lipogenesis of sebaceous glands and hair cycling. Among them, androgen is most extensively studied and of highest clinical significance. Androgen-mediated dermatoses such as acne, androgenetic alopecia and seborrhea are among the most common skin disorders, with most patients exhibiting normal circulating androgen levels. The "cutaneous hyperandrogenism" is caused by in stiu overexpression of the androgenic enzymes and hyperresponsiveness of androgen receptors. Regulation of cutaneous steroidogenesis is analogous to that in gonads and adrenals. More work is needed to explain the regional difference within and between the androgn-mediated dermatoses. The pilosebaceous unit can act as an ideal model for studies in dermato-endocrinology.

The environmental chemical tributyltin chloride (TBT) shows both estrogenic and adipogenic activities in mice which might depend on the exposure dose

Exposure during early development to chemicals with hormonal action may be associated with weight gain during adulthood because of altered body homeostasis. It is known that organotins affect adipose mass when exposure occurs during fetal development, although no knowledge of effects are available for exposures after birth. Here we show that the environmental organotin tributyltin chloride (TBT) exerts adipogenic action when peripubertal and sexually mature mice are exposed to the chemical. The duration and extent of these effects depend on the sex and on the dose of the compound, and the effects are relevant at doses close to the estimated human intake (0.5μg/kg). At higher doses (50-500μg/kg), TBT also activated estrogen receptors (ERs) in adipose cells in vitro and in vivo, based on results from acute and longitudinal studies in ERE/luciferase reporter mice. In 3T3-L1 cells (which have no ERs), transiently transfected with the ERE-dependent reporter plus or minus ERα or ERβ, TBT (in a dose range of 1-100nM) directly targets each ER subtype in a receptor-specific manner through a direct mechanism mediated by ERα in undifferentiated preadipocytic cells and by ERβ in differentiating adipocytes. The ER antagonist ICI-182,780 inhibits this effect. In summary, the results of this work suggest that TBT is adipogenic at all ages and in both sexes and that it might be an ER activator in fat cells. These findings might help to resolve the apparent paradox of an adipogenic chemical being also an estrogen receptor activator by showing that the two apparently opposite actions are separated by the different doses to which the organism is exposed.

Cutting edge: the membrane attack complex of complement is required for the development of murine experimental cerebral malaria

Cerebral malaria is the most severe complication of Plasmodium falciparum infection and accounts for a large number of malaria fatalities worldwide. Recent studies demonstrated that C5(-/-) mice are resistant to experimental cerebral malaria (ECM) and suggested that protection was due to loss of C5a-induced inflammation. Surprisingly, we observed that C5aR(-/-) mice were fully susceptible to disease, indicating that C5a is not required for ECM. C3aR(-/-) and C3aR(-/-) × C5aR(-/-) mice were equally susceptible to ECM as were wild-type mice, indicating that neither complement anaphylatoxin receptor is critical for ECM development. In contrast, C9 deposition in the brains of mice with ECM suggested an important role for the terminal complement pathway. Treatment with anti-C9 Ab significantly increased survival time and reduced mortality in ECM. Our data indicate that protection from ECM in C5(-/-) mice is mediated through inhibition of membrane attack complex formation and not through C5a-induced inflammation.

Oleanolic acid reduces markers of differentiation in 3T3-L1 adipocytes

Oleanolic acid is a triterpenoid compound that is widely present in vegetables, medicinal herbs, and other plants and has potent antioxidant and antiinflammatory properties. However, the potential of oleanolic acid to offset obesity is not clear. This study tested the hypothesis that oleanolic acid suppresses the differentiation of 3T3-L1 adipocytes by downregulating cellular induction of peroxisome proliferators-activated receptor γ (PPARγ) and cytidine-cytidine-adenosine-adenosine-thymidine (CCAAT) enhancer binding protein α (C/EBPα). The 3T3-L1 adipocytes were cultured and differentiated in Dulbecco modified Eagle medium containing 10% fetal bovine serum for 6 to 8 days in the absence and presence of 1 to 25 μmol/L oleanolic acid according to differentiating protocols. Nontoxic oleanolic acid, at 25 μmol/L or less, dose-dependently attenuated lipid accumulation in differentiated adipocytes as evidenced by Oil Red O staining. Western blot analysis showed that the induction of PPARγ and C/EBPα was markedly attenuated in differentiated and oleanolic acid-treated adipocytes at their transcriptional messenger RNA levels. Furthermore, this study examined whether oleanolic acid dampened the induction of visfatin, a proinflammatory and visceral fat-specific adipokine expressed in adipocytes. Visfatin expression was inhibited in differentiated adipocytes exposed to a PPARγ inhibitor GW9662. In addition, the visfatin production was significantly repressed in 25 μmol/L oleanolic acid-treated adipocytes, possibly through blocking PPARγ activation. These results demonstrate that oleanolic acid may be a promising agent to disturb adipocyte differentiation and suppress obesity-associated inflammation.

Transplantation of adipose tissue protects BB/OK rats from type 1 diabetes development

B(io) B(reedding)/O(ttawa) K(alsburg) rats spontaneously develop insulin-dependent type 1 diabetes. Days before BB/OK rats become diabetic, their body seems to be flabby which may be attributed to loss of subcutaneous fat. However, the rats are normoglycemic and manifest 3-4 days later. This observation prompted us to search for possibilities to avoid the loss of adipose tissue. BB/OK rats were subcutaneously grafted with visceral adipose tissue. In total, 34 (71%) out of 48 male and 23 (49%) out of 47 female BB/OK rats grafted with adipose tissue developed type 1 diabetes so that significantly more females than males were protected from diabetes development (p=0.03). In the control group, 17 (85%) out of 20 male and 20 (95%) out of 21 female BB/OK rats were diabetic. Adipose tissue transplantation can protect BB/OK rats from type 1 diabetes development in a sex specific manner. One could conclude that the manipulations have influenced fat accumulation and/or fat metabolism which prevent type 1 diabetes development in about 50% of BB/OK rats. This idea is supported by the finding that a mutation in the leptin receptor of NOD mice suppresses type 1 diabetes progression.

The D299G/T399I Toll-like receptor 4 variant associates with body and liver fat: results from the TULIP and METSIM Studies

BACKGROUND

Toll-like-receptor 4 (TLR) is discussed to provide a molecular link between obesity, inflammation and insulin resistance. Genetic studies with replications in non-diabetic individuals in regard to their fat distribution or insulin resistance according to their carrier status of a common toll-like receptor 4 (TLR4) variant (TLR4(D299G/T399I)) are still lacking.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a cross-sectional analysis in individuals phenotyped for prediabetic traits as body fat composition (including magnetic resonance imaging), blood glucose levels and insulin resistance (oral glucose tolerance testing, euglycemic hyperinsulinemic clamp), according to TLR4 genotype determined by candidate SNP analyses (rs4986790). We analyzed N = 1482 non-diabetic individuals from the TÜF/TULIP cohort (South Germany, aged 39±13 y, BMI 28.5±7.9, mean±SD) and N = 5327 non-diabetic participants of the METSIM study (Finland, males aged 58±6 y, BMI 26.8±3.8) for replication purposes. German TLR4(D299G/T399I) carriers had a significantly increased body fat (XG in rs4986790: +6.98%, p = 0.03, dominant model, adjusted for age, gender) and decreased insulin sensitivity (XG: -15.3%, Matsuda model, p = 0.04; XG: -20.6%, p = 0.016, clamp; both dominant models adjusted for age, gender, body fat). In addition, both liver fat (AG: +49.7%; p = 0.002) and visceral adipose tissue (AG: +8.2%; p = 0.047, both adjusted for age, gender, body fat) were significantly increased in rs4986790 minor allele carriers, and the effect on liver fat remained significant also after additional adjustment for visceral fat (p = 0.014). The analysis in METSIM confirmed increased body fat content in association with the rare G allele in rs4986790 (AG: +1.26%, GG: +11.0%; p = 0.010, additive model, adjusted for age) and showed a non-significant trend towards decreased insulin sensitivity (AG: -0.99%, GG: -10.62%).

CONCLUSIONS/SIGNIFICANCE

TLR4(D299G/T399I) associates with increased total body fat, visceral fat, liver fat and decreased insulin sensitivity in non-diabetic Caucasians and may contribute to diabetes risk. This finding supports the role of TLR4 as a molecular link between obesity and insulin resistance.

Complement: a key system for immune surveillance and homeostasis

Nearly a century after the significance of the human complement system was recognized, we have come to realize that its functions extend far beyond the elimination of microbes. Complement acts as a rapid and efficient immune surveillance system that has distinct effects on healthy and altered host cells and foreign intruders. By eliminating cellular debris and infectious microbes, orchestrating immune responses and sending 'danger' signals, complement contributes substantially to homeostasis, but it can also take action against healthy cells if not properly controlled. This review describes our updated view of the function, structure and dynamics of the complement network, highlights its interconnection with immunity at large and with other endogenous pathways, and illustrates its multiple roles in homeostasis and disease.

Obesity-associated proinflammatory cytokines increase calcium sensing receptor (CaSR) protein expression in primary human adipocytes and LS14 human adipose cell line

Obesity-associated health complications are thought to be in part due to the low-grade proinflammatory state that characterizes this disease. The calcium sensing receptor (CaSR), which is expressed in human adipose cells, plays an important role in diseases involving inflammation. To assess the relevance of this protein in adipose pathophysiology, we evaluated its expression in adipocytes under obesity-related proinflammatory conditions. As in primary adipose cells, we established that LS14, a recently described human adipose cell line, expresses the CaSR. Differentiated LS14 and primary adipose cells were exposed overnight to cytokines typically involved in obesity-related inflammation (interleukin (IL)1beta, IL6 and tumor necrosis factor (TNF)alpha). The cytokines increased CaSR abundance in differentiated adipocytes. We incubated LS14 cells with medium previously conditioned (CM) by adipose tissue from subjects with a wide range of body mass index (BMI). Cells exposed to CM from subjects of higher BMI underwent a greater increase in CaSR protein, likely resulting from the greater proinflammatory cytokines secreted from obese tissue. Our observations that proinflammatory factors increase CaSR levels in adipocytes, and the reported ability of CaSR to elevate cytokine levels, open new aspects in the study of obesity inflammatory state pathophysiology, providing a potential novel therapeutic prevention and treatment target.

Regulatory T cells in obesity: the leptin connection

Studies to understand the pathogenesis of obesity have revealed mediators that are responsible for the control of food intake and metabolism at the hypothalamic level. However, molecular insight explaining the link between obesity and low-degree chronic inflammation remains elusive. The adipocyte-derived hormone leptin, and thereby the nutritional status, could control immune self-tolerance by affecting regulatory T (Treg) cell responsiveness and function. Furthermore, resident Treg cells, which are capable of modulating metabolism and glucose homeostasis, are abundant in adipose tissue. Here, we provide an update on recent findings relating Treg cells to obesity and discuss how the intricate network of interactions among leptin, Treg cells and adipose tissue might provide new strategies for therapeutic interventions.

Changes in adiponectin and leptin concentrations during glucocorticoid treatment: a pilot study in patients with polymyalgia rheumatica

This study is concerned with an evaluation of the effects of glucocorticoids (GC) on adiponectin and leptin concentrations in patients with polymyalgia rheumatica (PMR). Seven patients diagnosed with PMR were studied at baseline and after one and three months of prednisone treatment. Serum leptin and adiponectin, serum glucose and insulin, erythrocyte sedimentation rate, C-reactive protein, and IL-6 were all measured by commercial assays. The treatment with GC normalized inflammation markers and significantly increased adiponectin and leptin concentrations without any impairment of insulin sensitivity measured by HOMA-IR. Adiponectin significantly increased only between baseline and 1 month (P= 0.013). A significant correlation was found between adiponectin and leptin concentrations both at baseline and after 3 months of treatment (both rho = 0.89, P= 0.03). In addition, adiponectin correlated also with serum glucose at baseline (rho = 0.81, P= 0.047). According to our results, adiponectin concentrations seem to be driven by inflammation, whereas leptin seems to be increased directly by the use of steroids.