Adiponectin downregulates CD163 whose cellular and soluble forms are elevated in obesity

PRRSV infection facilitates the shedding of soluble CD163 to induce inflammatory responses

Porcine reproductive and respiratory syndrome (PRRS), which poses substantial threats to the global pig industry, is primarily characterized by interstitial pneumonia. Cluster of differentiation 163 (CD163) is the essential receptor for PRRSV infection. Metalloproteinase-mediated cleavage of CD163 leads to the shedding of soluble CD163 (sCD163), thereby inhibiting PRRSV proliferation. However, the exact cleavage site in CD163 and the potential role of sCD163 in inflammatory responses during PRRSV infection remain unclear. Herein, we found that PRRSV infection increased sCD163 levels, as demonstrated in primary alveolar macrophages (PAMs), immortalized PAM (IPAM) cell lines, and sera from PRRSV-infected piglets. With LC-MS/MS, Arg-1041/Ser-1042 was identified as the cleavage site in porcine CD163, and an IPAM cell line with precise mutation at the cleavage site was constructed. Using the precisely mutated IPAM cells, we found that exogenous addition of sCD163 protein promoted inflammatory responses, while mutation at the CD163 cleavage site suppressed inflammatory responses. Consistently, inhibition of sCD163 using its neutralizing antibodies reduced PRRSV infection-triggered inflammatory responses. Importantly, sCD163 promoted cell polarization from M2 to M1 phenotype, which in turn facilitated inflammatory responses. Taken together, our findings identify sCD163 as a novel proinflammatory mediator and provide valuable insights into the mechanisms underlying the induction of inflammatory responses by PRRSV infection.

Cluster of differentiation molecules in the metabolic syndrome

Metabolic syndrome (MetS) represents a significant public health concern due to its association with an increased risk of cardiovascular disease, type 2 diabetes, and other serious health conditions. Despite extensive research, the underlying molecular mechanisms contributing to MetS pathogenesis remain elusive. This review aims to provide a comprehensive overview of the molecular mechanisms linking MetS and cluster of differentiation (CD) markers, which play critical roles in immune regulation and cellular signaling. Through an extensive literature review with a systematic approach, we examine the involvement of various CD markers in MetS development and progression, including their roles in adipose tissue inflammation, insulin resistance, dyslipidemia, and hypertension. Additionally, we discuss potential therapeutic strategies targeting CD markers for the management of MetS. By synthesizing current evidence, this review contributes to a deeper understanding of the complex interplay between immune dysregulation and metabolic dysfunction in MetS, paving the way for the development of novel therapeutic interventions.

Urinary soluble CD163 is a putative non-invasive biomarker for primary sclerosing cholangitis

Soluble CD163 (sCD163) is a selective marker of macrophages whose circulating levels have been found to be induced in patients with active inflammatory bowel disease (IBD). Urinary proteins are emerging as non-invasive diagnostic biomarkers, and here, sCD163 levels were measured in the urine of 18 controls and 63 patients with IBD by enzyme-linked immunosorbent assay. Urinary sCD163 levels did, however, not differentiate IBD patients from controls. Analysis of sCD163 in the serum of 51 of these patients did not show higher levels in IBD. Primary sclerosing cholangitis (PSC) is often associated with IBD, and sCD163 was higher in the urine of the 21 patients and in the serum of the 13 patients with PSC compared to patients with IBD. Of clinical relevance, urinary sCD163 levels were higher in PSC patients compared to those with other chronic liver diseases (n = 16), while serum sCD163 levels were comparable between the two groups. Serum sCD163 of IBD and PSC patients positively correlated with serum C-reactive protein. Serum creatinine and glomerular filtration rate, surrogate markers for renal function, did not significantly correlate with urinary or serum sCD163 levels in IBD or PSC patients. Moreover, urinary sCD163 was not related to fecal calprotectin levels whereas serum sCD163 of IBD patients showed a positive trend. PSC associated with IBD and PSC without underlying IBD had similar levels of urinary sCD163 while serum sCD163 tended to be higher in the latter group. In PSC patients, urinary sCD163 did not correlate with serum aminotransferase levels, gamma glutamyl transferase, alkaline phosphatase, bilirubin or the Model for End Stage Liver Disease score. Ursodeoxycholic acid was prescribed to our PSC patients and fecal levels of ursodeoxycholic acid and its conjugated forms were increased in PSC compared to IBD patients. Otherwise, fecal bile acid levels of IBD and PSC patients were almost identical, and were not correlated with urinary and serum sCD163 in PSC. In summary, our study identified urinary sCD163 as a potential biomarker for PSC.

CD163 as a Potential Biomarker-associated Immune Inflammation in Diabetes Mellitus: A Systematic Review and Bioinformatics Analysis

BACKGROUND

Several studies have identified CD163 as a potential mediator of diabetes mellitus through an immune-inflammation. Further study is necessary to identify its specific mechanism.

OBJECTIVES

In this study, we aimed to investigate CD163 as a potential biomarker associated with immune inflammation in diabetes mellitus through a systematic review and bioinformatics analysis.

METHODS

We searched PubMed, Web of Science, the Cochrane Library, and Embase databases with a time limit of September 2, 2022. Furthermore, we conducted a systematic search and review based on PRISMA guidelines. Additionally, diabetic gene expression microarray datasets GSE29221, GSE30528, GSE30529, and GSE20966 were downloaded from the GEO database (http://www.ncbi.nlm.nih.gov/geo) for bioinformatics analysis. The PROSPERO number for this study is CRD420222347160.

RESULTS

Following the inclusion and exclusion criteria, seven articles included 1607 patients, comprising 912 diabetic patients and 695 non-diabetic patients. This systematic review found significantly higher levels of CD163 in diabetic patients compared to non-diabetic patients. People with diabetes had higher levels of CRP expression compared to the control group. Similarly, two of the three papers that used TNF- α as an outcome indicator showed higher expression levels in diabetic patients. Furthermore, IL-6 expression levels were higher in diabetic patients than in the control group. A total of 62 samples were analyzed by bioinformatics (33 case controls and 29 experimental groups), and 85 differential genes were identified containing CD163. According to the immune cell correlation analysis, CD163 was associated with macrophage M2, γδ T lymphocytes, macrophage M1, and other immune cells. Furthermore, to evaluate the diagnostic performance of CD163, we validated it using the GSE20966 dataset. In the validation set, CD163 showed high diagnostic accuracy.

CONCLUSION

This study suggests CD163 participates in the inflammatory immune response associated with diabetes mellitus and its complications by involving several immune cells. Furthermore, the results suggest CD163 may be a potential biomarker reflecting immune inflammation in diabetic mellitus.

Macrophage-associated markers of metaflammation are linked to metabolic dysfunction in pediatric obesity

BACKGPOUND

Metabolically driven chronic low-grade adipose tissue inflammation, so-called metaflammation, is a central feature in obesity. This inflammatory tone is largely driven by adipose tissue macrophages (ATM), which express pro- and anti-inflammatory markers and cytokines such as, e.g., IL-1 receptor antagonist (IL-1RA), CD163 and osteopontin (OPN). Metaflammation ultimately leads to the development of cardiometabolic diseases. This study aimed to evaluate the association between selected adipose tissue macrophage-associated markers and metabolic comorbidities in pediatric obesity.

METHODS

From a pediatric cohort with obesity (n = 108), clinically thoroughly characterized including diverse routine blood parameters, oral glucose tolerance test and liver MRI, plasma IL-1RA, soluble (s)CD163 and OPN were measured by ELISA.

RESULTS

We observed significantly higher IL-1RA, sCD163, and OPN levels in the plasma of children with metabolic-dysfunction associated fatty liver disease (MAFLD) and metabolic syndrome. Moreover, IL-1RA and sCD163 correlated with hepatic disease and apoptosis markers alanine aminotransferase and CK-18. IL-1RA concentrations additionally correlated with insulin resistance, while children with disturbed glucose metabolism had significantly higher levels of sCD163.

CONCLUSION

MAFLD and other metabolic disorders in pediatric patients with obesity are associated with an elevation of adipose tissue macrophage-related inflammation markers.

Circulating soluble CD163 as a potential biomarker of diabetes complications

AIMS

To investigate whether soluble CD163 (sCD163) is altered in those with diabetes and various subtypes of complications and non-alcoholic fatty liver disease (NAFLD), and whether it can assess disease complications and severity in people with diabetes.

METHODS

Adults with diabetes (n = 101) were recruited and assessed for the presence of any complications (D^+Comps). Liver steatosis presence was determined by ultrasound and liver stiffness measurement (LSM) by transient elastography. Liver pathology other than non-alcoholic steatohepatitis (NASH) was excluded. Plasma sCD163 was measured by ELISA.

RESULTS

sCD163 was higher in D^+Comps (n = 59) compared to D^-comps (n = 42) in those with microvascular complications (n = 56; 1.3-fold), including a 1.4-fold increase in chronic kidney disease (CKD) (n = 42). sCD163 correlated positively with HbA_1c and urinary albumin-creatinine ratio and negatively with HDL-c in D^+Comps. sCD163 was increased 1.7-fold in those with advanced NASH fibrosis (LSM ≥ 10.3 kPa, n = 19) compared to those without (LSM < 10.3 kPa, n = 80). The AUC-ROC-curve was 0.64 for sCD163 to detect CKD and 0.74 to detect advanced NASH fibrosis.

CONCLUSIONS

In this study, the elevated circulating sCD163 occurred in people with diabetes who had microvascular complications or advanced NASH fibrosis, suggesting sCD163 may have clinical utility as a biomarker in certain diabetes complications and disease severity in NAFLD.

The clinical utility of CD163 in viral diseases

Macrophage activation and hypercytokinemia are notable presentations in certain viral infections leading to severe disease and poor prognosis. Viral infections can cause macrophage polarization into the pro-inflammatory M1 or anti-inflammatory M2 phenotype. Activated M1 macrophages usually restrict viral replication whereas activated M2 macrophages suppress inflammation and promote tissue repair. In response to inflammatory stimuli, macrophages polarize to the M2 phenotype expressing hemoglobin scavenger CD163 surface receptor. The CD163 receptor is shed as the soluble form, sCD163, into plasma or tissue fluids. sCD163 causes detoxification of pro-oxidative hemoglobin which produces anti-inflammatory metabolites that promote the resolution of inflammation. Hence, increased CD163 expression in tissues and elevated circulatory levels of sCD163 have been associated with acute and chronic inflammatory diseases. CD163 and other macrophage activation markers have been commonly included in the investigation of disease pathogenesis and progression. This review provides an overview of the involvement of CD163 in viral diseases. The clinical utility of CD163 in viral disease diagnosis, progression, prognosis and treatment evaluation is discussed.

Monocyte subtype expression patterns in septic patients with diabetes are distinct from patterns observed in obese patients

Background

Sepsis causes a high rate of mortality and long-term morbidity, associated with an imbalance of innate immunity against infections and inflammation. Obesity and diabetes increase the risk for disease severity. Monocyte dysfunction plays a major role and justify further investigations.

Objective

To investigate the distribution and inflammatory phenotypes in circulating monocyte subsets in patients manifesting with sepsis including septic shock with and without obesity and diabetes.

Methods

A total of 235 blood samples were tested from critically ill adult patients registered at the intensive care unit (ICU). The cohorts were divided into non-diabetic groups with or without obesity and diabetic groups with or without obesity, suffering from sepsis or septic shock. We determined frequencies of total monocytes and of monocyte subsets in the circulation and density expression levels of functional markers, including CD14, CD16, HLA-DR, CD33, CD163, CD206, and arginase-1 by flow cytometric analysis.

Results

When progressing to septic shock in non-diabetic and diabetic patients, the percentages of total monocytes among the leukocyte population and of CD33+ and CD14+ monocytes among the monocyte population were consistently down-regulated compared to non-sepsis in non-diabetic and diabetic patients, respectively. Non-diabetic sepsis patients further presented with decreased CD33 and up-regulated CD163 expression density, which was absent in diabetic patients. We subsequently addressed obesity-related changes of monocytes in non-diabetic and diabetic septic patients. Obese septic patients with diabetes were unique in displaying increased monocytic CD16 and CD163 expression. However, obese septic patients without diabetes solely presented with lower amounts of non-classical monocytes. Body mass index (BMI) dependent changes were restricted to diabetic septic patients, with a significantly higher diminution of the classical monocyte subset and concomitantly increased CD16 expression densities.

Conclusion

Distribution and phenotypes of monocyte subsets were differentially modulated in critically ill patients with and without metabolic disease when progressing to sepsis or septic shock. Only diabetic septic patients displayed decline of classical monocytes and increase of CD16 expression densities. Therefore, diabetes but not obesity appears to promote the inflammatory phenotype of circulating monocytes in critically ill patients.

Links between ectopic and abdominal fat and systemic inflammation: New insights from the SHIP-Trend study

BACKGROUND

Excessive fat accumulation in adipose tissue depots and organs such as the pancreas and the liver is associated with systemic low-grade chronic inflammation.

AIMS

To investigate the association between abdominal, hepatic, and pancreatic fat and the circulating level of inflammatory biomarkers.

METHODS

We used data from a subsample of the Study of Health in Pomerania (SHIP-Trend, n = 469). The plasma concentration of 37 inflammatory biomarkers was measured using the Bio-Plex-Pro™-Human-Inflammation-Panel-1. Subcutaneous and visceral adipose tissue (SAT and VAT), as well as hepatic and pancreatic fat, were determined by magnetic resonance imaging. We assessed the associations between fat content and inflammatory biomarkers using multiple linear regression.

RESULTS

Hepatic fat was associated with MMP-2 (β -0.11), PTX3 (β -0.14), and TNFSF12 (β -0.06). Pancreatic fat was associated with sTNFR1 (β 0.15), sTNFR2 (β 0.11), and sCD163 (β 0.13). VAT and SAT were associated with sCD163 (β^VAT 0.20, β^SAT 0.16), MMP-2 (β^VAT -0.12, β^SAT -0.10), OSTCN (β^VAT -0.16, β^SAT -0.10), sTNFR1 (β^VAT 0.13, β^SAT 0.13), sTNFR2 (β^VAT 0.13, β^SA 0.12), TNFSF12 (β^VAT -0.11, β^SAT -0.08), and TNFSF14 (β^VAT 0.21, β^SAT 0.20). VAT was additionally associated with TNFSF13B (β 0.08) and CHI3L1 (β 0.07).

CONCLUSIONS

Our findings provide new insights into the involvement of hepatic and pancreatic fat on systemic inflammation.

Alterations of CD163 expression in the complications of diabetes: A systematic review

AIMS

Diabetes mellitus is a state of chronic low-grade inflammation. Scavenger receptor CD163, expressed on monocyte/macrophage cells with anti-inflammatory functions, has been observed in diabetes complications. This review aimed to systematically survey human studies published until 31st January 2022 for CD163 expression, in particular diabetes complications and additionally to investigate whether CD163 may be implicated as a biomarker of, and mediator in, the progression of diabetes complications.

METHODS

A systematic literature search undertaken in Scopus, Embase and Medline established 79 papers of relevance. Data extraction and assessment followed the PRISMA workflow.

RESULTS

Based on specific criteria, 11 studies totalling 821 participants were included in this review. CD163 was quantified in various forms including soluble, cell surface, and mRNA measures. This review found that soluble CD163 was upregulated in diabetes complications in various local body fluids and systemically in plasma or serum and therefore implicated in the progression of those complications. CD163+ cells and mRNA were variably expressed across diabetes complications.

CONCLUSIONS

CD163 was altered in series of diabetes complications and the circulating sCD163 has potential utility as an inflammation biomarker. The variable expression of CD163 on cell surfaces and its mRNA across different diabetes complications warrants further systematic investigation.

The association of soluble CD163, a novel biomarker of macrophage activation, with type 2 diabetes mellitus and its underlying physiological disorders: A systematic review

This systematic review investigates the association of sCD163, a novel biomarker of macrophage activation, with type 2 diabetes mellitus (T2DM), insulin resistance, and beta-cell dysfunction. Sixteen studies (seven cross-sectional, two case-control, one nested case-control, three prospective cohort, and three experimental) were identified. Most studies demonstrated that elevated sCD163 concentrations were associated with increased insulin resistance. Cross-sectional, case-control, and nested case-control studies showed higher sCD163 in subjects with T2DM compared with healthy individuals. An 18-year follow-up prospective cohort study showed that elevated baseline sCD163 was a strong predictor of T2DM incidence. Prospective cohort studies demonstrated that baseline measures and longitudinal changes in sCD163 were positively associated with insulin resistance; however, associations with beta-cell function were inconsistent. Two experimental studies evaluated the relationship of sCD163 with T2DM and HOMA-IR after weight-reducing interventions. After very low-calorie diet treatments, sCD163 concentration declined significantly in patients with T2DM but was not associated with insulin resistance. Bariatric surgery did not significantly impact sCD163 levels. In a double-blind randomized controlled trial, resveratrol supplementation significantly reduced circulating sCD163 in T2DM patients. Current studies demonstrate the potential utility of sCD163 as an early biomarker of T2DM risk and highlight a potential mechanism linking obesity with T2DM onset.

Role of Macrophages and Related Cytokines in Kidney Disease

Inflammation is a key characteristic of kidney disease, but this immune response is two-faced. In the acute phase of kidney injury, there is an activation of the immune cells to fight against the insult, contributing to kidney repair and regeneration. However, in chronic kidney diseases (CKD), immune cells that infiltrate the kidney play a deleterious role, actively participating in disease progression, and contributing to nephron loss and fibrosis. Importantly, CKD is a chronic inflammatory disease. In early CKD stages, patients present sub-clinical inflammation, activation of immune circulating cells and therefore, anti-inflammatory strategies have been proposed as a common therapeutic target for renal diseases. Recent studies have highlighted the plasticity of immune cells and the complexity of their functions. Among immune cells, monocytes/macrophages play an important role in all steps of kidney injury. However, the phenotype characterization between human and mice immune cells showed different markers; therefore the extrapolation of experimental studies in mice could not reflect human renal diseases. Here we will review the current information about the characteristics of different macrophage phenotypes, mainly focused on macrophage-related cytokines, with special attention to the chemokine CCL18, and its murine functional homolog CCL8, and the macrophage marker CD163, and their role in kidney pathology.

Proteins linked to atherosclerosis and cell proliferation are associated with the shrunken pore syndrome in heart failure patients: Shrunken pore syndrome and proteomic associations

PURPOSE

The "Shrunken pore syndrome" (SPS) is characterized by a difference in renal filtration between cystatin C and creatinine, resulting in a low eGFR_cystatinC /eGFR_creatinine -ratio. Studies have demonstrated a high risk for cardiovascular morbidity and mortality for patients with SPS. In this discovery study, we explored associations between SPS and proteins implicated in cardiovascular disease and inflammation in patients with heart failure.

EXPERIMENTAL DESIGN

Plasma samples from 300 individuals in HARVEST-Malmö trial hospitalized for the diagnosis of heart failure (mean age 74.9 ± 11.5 years; 30.0% female), were analyzed with a proximity extension assay consisting of 92 proteins. A Bonferroni-corrected p-value of 0.05/92 = 5.4 × 10^-4 was considered significant in the initial age and sex-adjusted analyses. Presence of SPS was defined as eGFR_cystatinC ≤ 60% of eGFR_creatinine .

RESULTS

SPS presented with significant associations (p < 5.4 × 10^-4 ) in age and sex-adjusted logistic regressions with elevated levels of six proteins; scavenger receptor cysteine rich type 1 protein M130, tumor necrosis factor receptor 1, tumor necrosis factor receptor 2, osteoprotegerin, interleukin-2 receptor subunit alpha, and tyrosine-protein kinase receptor UFO. All proteins remained associated (p < 0.05) with SPS after multivariate adjustments.

CONCLUSIONS AND CLINICAL RELEVANCE

In heart failure patients, SPS was associated with proteins linked to atherosclerosis and cell proliferation.

Characterization of Macrophages and Myofibroblasts Appearing in Dibutyltin Dichloride-Induced Rat Pancreatic Fibrosis

Macrophages and myofibroblasts are important in fibrogenesis. The cellular characteristics in pancreatic fibrosis remain to be investigated. Pancreatic fibrosis was induced in F344 rats by a single intravenous injection of dibutyltin dichloride. Histopathologically, the induced pancreatic fibrosis was divided into 3 grades (1+, 2+, and 3+), based on collagen deposition. Immunohistochemically, CD68-expressing M1 macrophages increased with grade and CD163-expressing M2 macrophages also increased later than M1 macrophage appearance. Double immunofluorescence showed that there were macrophages coexpressing CD68 and CD163, suggesting a possible shift from M1 to M2 types; similarly, increased major histocompatibility complex class II- and CD204-expressing macrophages were polarized toward M1 and M2 types, respectively. These findings indicated the participation of M1- and M2-polarized macrophages. Mesenchymal cells staining positive for vimentin, desmin, and α-smooth muscle actin (α-SMA) increased with grade. There were mesenchymal cells coexpressing vimentin/α-SMA, desmin/α-SMA, and glial fibrillary acidic protein (GFAP)/α-SMA; Thy-1-expressing immature mesenchymal cells also increased in fibrotic lesions. Because α-SMA expression is a reliable marker for myofibroblasts, α-SMA-expressing pancreatic myofibroblasts might be originated from GFAP-expressing pancreatic stellate cells or Thy-1-expressing immature mesenchymal cells; the myofibroblasts could simultaneously express cytoskeletal proteins such as vimentin and desmin. The present findings would provide useful information for analyses based on features of macrophages and myofibroblasts in chemically induced pancreatic fibrosis.

Systemic, but not local, low-grade endotoxinemia increases plasma sCD163 independently of the cortisol response

Aims/hypothesis The macrophage-specific glycoprotein sCD163 has emerged as a biomarker of low-grade inflammation in the metabolic syndrome and related disorders. High sCD163 levels are seen in acute sepsis as a result of direct lipopolysaccharide-mediated shedding of the protein from macrophage surfaces including Kupffer cells. The aim of this study was to investigate if low-grade endotoxinemia in human subjects results in increasing levels of sCD163 in a cortisol-dependent manner. Methods We studied eight male hypopituitary patients and eight age- and gender-matched healthy controls during intravenous low-dose LPS or placebo infusion administered continuously over 360 min. Furthermore, we studied eight healthy volunteers with bilateral femoral vein and artery catheters during a 360-min infusion with saline and low-dose LPS in each leg respectively. Results: Systemic low-grade endotoxinemia resulted in a gradual increase in sCD163 from 1.65 ± 0.51 mg/L (placebo) to 1.92 ± 0.46 mg/L (LPS) at 220 min, P = 0.005 and from 1.66 ± 0.42 mg/L (placebo) to 2.19 ± 0.56 mg/L (LPS) at 340 min, P = 0.006. A very similar response was observed in hypopituitary patients: from 1.59 ± 0.53 mg/L (placebo) to 1.83 ± 0.45 mg/L (LPS) at 220 min, P = 0.021 and from 1.52 ± 0.53 mg/L (placebo) to 2.03 ± 0.44 mg/L (LPS) at 340 min, P < 0.001. As opposed to systemic treatment, continuous femoral artery infusion did not result in increased sCD163. Conclusion: Systemic low-grade endotoxinemia resulted in increased sCD163 to levels seen in the metabolic syndrome in both controls and hypopituitary patients. This suggests a direct and cortisol-independent effect of LPS on the shedding of sCD163. We observed no effect of local endotoxinemia on levels of serum sCD163.

Effect of Pericardial Fat Volume and Density on Markers of Insulin Resistance and Inflammation in Patients With Human Immunodeficiency Virus Infection

Treated human immunodeficiency virus (HIV) infection is characterized by ectopic fat deposition, a persistent inflammatory state, and increased cardiometabolic risk. In this secondary analysis of a placebo controlled trial of rosuvastatin among 147 HIV+ subjects (median age 46; 78% men) on stable antiretroviral therapy, we aimed to evaluate longitudinal associations between computed tomography (CT) measures of pericardial fat (PCF) volume and density, insulin resistance, and inflammation. We measured PCF volume and density (mean attenuation in Hounsfield units) by noncontrast gated CT at baseline and week 96. Homeostatic model of insulin resistance was calculated from fasting insulin and glucose at entry, 24, 48, and 96 weeks. At baseline, insulin resistance correlated positively with PCF volume and negatively with density. Similarly divergent correlations of volume and density were observed with waist:hip ratio, nadir CD4+ count, and duration of antiretroviral therapy. In a linear mixed model, PCF density was associated with insulin resistance independent of PCF volume, body mass index, metabolic syndrome, and biomarkers of immune activation and systemic inflammation; however, baseline PCF measures were not associated with longitudinal changes in insulin resistance. Soluble CD163, a marker of monocyte activation, positively correlated with PCF volume and was associated with insulin resistance in linear models. Statin treatment assignment did not affect PCF volume or density change (both p > 0.8). In conclusion, the quantity and quality (i.e., radiodensity) of PCF are differentially related to insulin resistance and inflammation in patients with treated HIV infection.

Activated macrophages control human adipocyte mitochondrial bioenergetics via secreted factors

OBJECTIVE

Obesity-associated WAT inflammation is characterized by the accumulation and local activation of macrophages (MΦs), and recent data from mouse studies suggest that macrophages are modifiers of adipocyte energy metabolism and mitochondrial function. As mitochondrial dysfunction has been associated with obesity and the metabolic syndrome in humans, herein we aimed to delineate how human macrophages may affect energy metabolism of white adipocytes.

METHODS

Human adipose tissue gene expression analysis for markers of macrophage activation and tissue inflammation (CD11c, CD40, CD163, CD206, CD80, MCP1, TNFα) in relationship to mitochondrial complex I (NDUFB8) and complex III (UQCRC2) was performed on subcutaneous WAT of 24 women (BMI 20-61 kg/m²). Guided by these results, the impact of secreted factors of LPS/IFNγ- and IL10/TGFβ-activated human macrophages (THP1, primary blood-derived) on mitochondrial function in human subcutaneous white adipocytes (SGBS, primary) was determined by extracellular flux analysis (Seahorse technology) and gene/protein expression.

RESULTS

Stepwise regression analysis of human WAT gene expression data revealed that a linear combination of CD40 and CD163 was the strongest predictor for mitochondrial complex I (NDUFB8) and complex III (UQCRC2) levels, independent of BMI. IL10/TGFβ-activated MΦs displayed high CD163 and low CD40 expression and secreted factors that decreased UQCRC2 gene/protein expression and ATP-linked respiration in human white adipocytes. In contrast, LPS/IFNγ-activated MΦs showed high CD40 and low CD163 expression and secreted factors that enhanced adipocyte mitochondrial activity resulting in a total difference of 37% in ATP-linked respiration of white adipocytes (p = 0.0024) when comparing the effect of LPS/IFNγ- vs IL10/TGFβ-activated MΦs.

CONCLUSION

Our data demonstrate that macrophages modulate human adipocyte energy metabolism via an activation-dependent paracrine mechanism.

Sitagliptin but not alpha glucosidase inhibitor reduced the serum soluble CD163, a marker for activated macrophage, in individuals with type 2 diabetes mellitus

AIMS

Dipeptidyl peptidase-4 inhibitor (DPP-4i) is commonly used worldwide for the treatment of type 2 diabetes mellitus. In addition to its hypoglycemic activity, DPP-4i might have anti-inflammatory effects. In this study we examined the effects of DPP-4i on the serum levels of soluble CD163 (sCD163), a marker for activated macrophages, in individuals with type 2 diabetes mellitus. We compared these anti-inflammatory effects with those of α glucosidase inhibitor (αGI).

METHODS

Japanese patients with type 2 diabetes mellitus who were stably maintained on ≤2mg/day glimepiride alone were recruited and randomly assigned to receive additional sitagliptin (n=37) or αGI (n=37). Levels of sCD163 were measured before the addition and after a 24-week treatment period.

RESULTS

Addition of sitagliptin significantly reduced the serum sCD163 (632 vs. 575ng/mL, p<0.05), while αGI did not display this effect (624 vs. 607ng/mL). The changes in levels of sCD163 were not related to changes in either HbA1c or body mass index (BMI).

CONCLUSIONS

Our results suggested that DPP-4i might exert anti-inflammatory effects in individuals with type 2 diabetes mellitus, which are independent of its effects on glycemia and BMI.

Adiposity influences airway wall thickness and the asthma phenotype of HIV-associated obstructive lung disease: a cross-sectional study

Background

Airflow obstruction, which encompasses several phenotypes, is common among HIV-infected individuals. Obesity and adipose-related inflammation are associated with both COPD (fixed airflow obstruction) and asthma (reversible airflow obstruction) in HIV-uninfected persons, but the relationship to airway inflammation and airflow obstruction in HIV-infected persons is unknown. The objective of this study was to determine if adiposity and adipose-associated inflammation are associated with airway obstruction phenotypes in HIV-infected persons.

Methods

We performed a cross-sectional analysis of 121 HIV-infected individuals assessed with pulmonary function testing, chest CT scans for measures of airway wall thickness (wall area percent [WA%]) and adipose tissue volumes (mediastinal and subcutaneous), as well as HIV- and adipose-related inflammatory markers. Participants were defined as COPD phenotype (post-bronchodilator FEV₁/FVC < lower limit of normal) or asthma phenotype (doctor-diagnosed asthma or bronchodilator response). Pearson correlation coefficients were calculated between adipose measurements, WA%, and pulmonary function. Multivariable logistic and linear regression models were used to determine associations of airflow obstruction and airway remodeling (WA%) with adipose measurements and participant characteristics.

Results

Twenty-three (19 %) participants were classified as the COPD phenotype and 33 (27 %) were classified as the asthma phenotype. Body mass index (BMI) was similar between those with and without COPD, but higher in those with asthma compared to those without (mean [SD] 30.7 kg/m² [8.1] vs. 26.5 kg/m² [5.3], p = 0.008). WA% correlated with greater BMI (r = 0.55, p < 0.001) and volume of adipose tissue (subcutaneous, r = 0.40; p < 0.001; mediastinal, r = 0.25; p = 0.005). Multivariable regression found the COPD phenotype associated with greater age and pack-years smoking; the asthma phenotype with younger age, female gender, smoking history, and lower adiponectin levels; and greater WA% with greater BMI, younger age, higher soluble CD163, and higher CD4 counts.

Conclusions

Adiposity and adipose-related inflammation are associated with an asthma phenotype, but not a COPD phenotype, of obstructive lung disease in HIV-infected persons. Airway wall thickness is associated with adiposity and inflammation. Adipose-related inflammation may play a role in HIV-associated asthma.

A novel atlas of gene expression in human skeletal muscle reveals molecular changes associated with aging

Background

Although high-throughput studies of gene expression have generated large amounts of data, most of which is freely available in public archives, the use of this valuable resource is limited by computational complications and non-homogenous annotation. To address these issues, we have performed a complete re-annotation of public microarray data from human skeletal muscle biopsies and constructed a muscle expression compendium consisting of nearly 3000 samples. The created muscle compendium is a publicly available resource including all curated annotation. Using this data set, we aimed to elucidate the molecular mechanism of muscle aging and to describe how physical exercise may alleviate negative physiological effects.

Results

We find 957 genes to be significantly associated with aging (p < 0.05, FDR = 5 %, n = 361). Aging was associated with perturbation of many central metabolic pathways like mitochondrial function including reduced expression of genes in the ATP synthase, NADH dehydrogenase, cytochrome C reductase and oxidase complexes, as well as in glucose and pyruvate processing. Among the genes with the strongest association with aging were H3 histone, family 3B (H3F3B, p = 3.4 × 10⁻¹³), AHNAK nucleoprotein, desmoyokin (AHNAK, p = 6.9 × 10⁻¹²), and histone deacetylase 4 (HDAC4, p = 4.0 × 10⁻⁹). We also discover genes previously not linked to muscle aging and metabolism, such as fasciculation and elongation protein zeta 2 (FEZ2, p = 2.8 × 10⁻⁸). Out of the 957 genes associated with aging, 21 (p < 0.001, false discovery rate = 5 %, n = 116) were also associated with maximal oxygen consumption (VO_2MAX). Strikingly, 20 out of those 21 genes are regulated in opposite direction when comparing increasing age with increasing VO_2MAX.

Conclusions

These results support that mitochondrial dysfunction is a major age-related factor and also highlight the beneficial effects of maintaining a high physical capacity for prevention of age-related sarcopenia.

Electronic supplementary material

The online version of this article (doi:10.1186/s13395-015-0059-1) contains supplementary material, which is available to authorized users.

Visceral obesity is associated with increased soluble CD163 concentration in men with type 2 diabetes mellitus

Monocyte/macrophage-specific soluble CD163 (sCD163) concentration is associated with insulin resistance and increases with deteriorating glycemic control independently of BMI. This led to the proposal of the hypothesis that obesity-associated white adipose tissue inflammation varies between individuals. The objective was to examine the effect of male overweight/obesity and type 2 diabetes mellitus (T2DM) on associations between adiposity parameters and sCD163. A total of 23 overweight/obese non-diabetic men, 16 overweight/obese men with T2DM, and a control group of 20 normal-weight healthy men were included. Body composition and regional body fat distribution were determined by whole-body dual X-ray absorptiometry scan and abdominal computed tomography (CT) scan. Serum sCD163 concentrations were determined by ELISA. Associations between adiposity parameters and sCD163 were investigated using multiple linear regression analysis. In the normal-weight healthy men, there was no significant association between adiposity parameters and sCD163, whereas in the overweight/obese non-diabetic men, measures of general and regional adiposity were positively associated with sCD163. In the overweight/obese men with T2DM, only visceral adipose tissue (VAT) and the ratio of VAT to abdominal subcutaneous adipose tissue (SAT), a measure of relative body fat distribution between VAT and SAT depots, were positively associated with sCD163. In a multivariate analysis, including VAT, upper-body SAT, and lower-body fat, adjusted for BMI and age, VAT remained a significant predictor of sCD163 in the overweight/obese T2DM men, but not in the overweight/obese non-diabetic men. Our results indicate that VAT inflammation is exaggerated in men with T2DM, and that propensity to store excess body fat viscerally is particularly detrimental in men with T2DM.

Iron homeostasis: a new job for macrophages in adipose tissue?

Elevated serum ferritin and increased cellular iron concentrations are risk factors for diabetes; however, the etiology of this association is unclear. Metabolic tissues such as pancreas, liver, and adipose tissue (AT), as well as the immune cells resident in these tissues, may be involved. Recent studies demonstrate that the polarization status of macrophages has important relevance to their iron-handling capabilities. Furthermore, a subset of macrophages in AT have elevated iron concentrations and a gene expression profile indicative of iron handling, a capacity diminished in obesity. Because iron overload in adipocytes increases systemic insulin resistance, iron handling by AT macrophages may have relevance not only to adipocyte iron stores but also to local and systemic insulin sensitivity.

Intrahepatic fat content correlates with soluble CD163 in relation to weight loss induced by Roux-en-Y gastric bypass

OBJECTIVE

Soluble CD163 (sCD163) is a new marker of obesity-related metabolic complications. sCD163 and CD163 mRNA were investigated in relation to the fat distribution at baseline and 12 months after Roux-en-Y gastric bypass (RYGB).

METHODS

Thirty-one obese subjects (BMI: 42.3 ± 4.7 kg/m(2)) were enrolled. Subcutaneous (SAT) and visceral adipose tissue (VAT) volume were determined by MRI, intrahepatic lipid content (IHL) by MR-spectroscopy, and body composition by DXA. Fasting blood samples and adipose tissue samples were obtained, and ELISA and RT-PCR were performed.

RESULTS

RYGB-induced weight loss (36 ± 11 kg) was accompanied by a significant reduction in sCD163 (2.1 ± 0.8 mg/l vs. 1.7 ± 0.7 mg/l), SAT, VAT, and IHL (all, P < 0.001). At baseline, sCD163 was associated with VAT (r = 0.40, P < 0.05) but not with SAT or IHL. Moreover, CD163 mRNA was significantly upregulated in VAT compared with SAT at baseline (P < 0.05) and significantly downregulated in SAT after RYGB (P < 0.001). ΔsCD163 was significantly associated with ΔIHL after RYGB compared with baseline (r = 0.40, P < 0.05).

CONCLUSIONS

RYGB-induced weight loss results in a reduction of sCD163 and CD163 mRNA. The association between ΔsCD163 and ΔIHL may reflect a reduction in sCD163-producing Kupffer cells in the liver. Moreover, sCD163 may be a marker of "unhealthy" fat distribution in obese subjects.

Reduced circulating levels of TWEAK are associated with gestational diabetes mellitus

BACKGROUND

To evaluate the inflammatory axis mediated by tumour necrosis factor-like weak inducer of apoptosis (TWEAK) and its scavenger receptor CD163 during pregnancy and their influence on insulin sensitivity in normal pregnancy and in gestational diabetes mellitus (GDM).

MATERIALS AND METHODS

One hundred and thirty seven women with one singleton pregnancy, 71 with normal glucose tolerance (NGT) and 66 with GDM were studied. Glucose metabolism was assessed by oral glucose tolerance test. Serum concentrations of soluble TWEAK (sTWEAK) and CD163 (sCD163) and insulin resistance (HOMA-IR index) were determined in maternal blood drawn at recruitment, in the early third trimester. Offspring weight and height were assessed at birth.

RESULTS

Women with GDM had lower circulating sTWEAK concentrations than control NGT group (237·8 (192·1-301·0) pg/mL vs. 277·2 (206·4-355·7) pg/mL; P = 0·013). sTWEAK was negatively associated with the presence of GDM (r = -0·212; P = 0·013), HOMA-IR index (r = -0·197; P = 0·021) and ponderal index of the newborn (r = -0·196; P = 0·025), but positively with HDL cholesterol (r = 0·283; P = 0·001). In multiple regression analysis, sTWEAK concentration emerged as one of the main predictors of insulin resistance, along with BMI, triglycerides and low concentrations of HDL cholesterol (R(2)  = 0·486; P < 0·001). No relationship was found between HOMA-IR index and sCD163 or sCD163/sTWEAK ratio.

CONCLUSIONS

sTWEAK concentrations are lower in patients with GDM compared with healthy pregnant women, and low concentrations of sTWEAK are associated with insulin resistance. These findings suggest that insulin resistance during pregnancy is closely linked to inflammatory imbalance and sTWEAK may represent a new candidate associated with GDM.

Regulation of CD163 mRNA and soluble CD163 protein in human adipose tissue in vitro

CD163-positive macrophages are highly expressed in the human adipose tissue (AT) particularly from obese individuals. However, little is known about the regulation of CD163 mRNA and the protein level of sCD163 in human AT. We aimed to examine the regulation of CD163 and sCD163 in AT. Human s.c. AT samples (n=5) were stimulated with dexamethasone (DEX; 200  nmol/l), lipopolysaccharide (LPS; 100  ng/ml), or DEX+LPS for various time periods up to 24  h. Gene expressions of CD163, ADAM17, IL10, and TNFA (TNF) were measured by RT-PCR. Protein levels of sCD163, IL10, and TNFα (TNF) were measured by ELISA. Furthermore, AT was separated into stromal and adipocyte fraction. We found that CD163 mRNA was strongly expressed in the stromal vascular fraction but hardly detectable in the isolated adipocytes. Incubating whole AT with DEX significantly up-regulated CD163 (P<0.001), whereas incubation with LPS had no effects on CD163 (P>0.05). By contrast, the protein level of sCD163 was not affected by DEX (P>0.05), but LPS significantly increased the level of sCD163 and TNFα (P<0.05). This might be due to the concomitant LPS stimulation of ADAM17, which is known to mediate shedding of the extracellular domains of sCD163 and TNFα. Finally, DEX significantly reduced the LPS-induced TNFα release to the incubation medium but had no effects on sCD163. We conclude that the expression of CD163 and the release of sCD163 are differentially regulated in human AT. Moreover, similar to studies on differentiated blood monocytes, TNFα and sCD163 are concomitantly released in human AT by LPS, which also up-regulate ADAM17.

Soluble CD163 is associated with CD163 mRNA expression in adipose tissue and with insulin sensitivity in steady-state condition but not in response to calorie restriction

CONTEXT

Soluble CD163 (sCD163) was suggested as a biomarker of insulin sensitivity and CD163 mRNA expression representing macrophage content in adipose tissue (AT).

OBJECTIVE

The aim of this study was to investigate, in cross-sectional and prospective design, the relationship between sCD163 circulating levels and CD163 mRNA expression in adipose tissue and insulin sensitivity assessed by euglycemic-hyperinsulinemic clamp.

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTIONS

Two cohorts of subjects were examined in the study. Cohort 1 included 42 women with a wide range of body mass index (17-48 kg/m(2)); cohort 2 included 27 obese women who followed a dietary intervention consisting of 1 month of a very low-calorie diet and 5 months of a weight-stabilization period.

MAIN OUTCOME MEASURES

Serum levels of CD163 and mRNA expression of CD163 and CD68 in sc and visceral (visc) AT were determined, and insulin sensitivity [expressed as glucose disposal rate (GDR)] was measured in cohort 1. In cohort 2, serum levels of CD163, mRNA expressions of CD163, CD68, and CD163-shedding factors [TNF-α-converting enzyme (TACE) and tissue inhibitor of metalloproteinase (TIMP3)] in sc AT were examined and GDR was measured before and during dietary intervention.

RESULTS

In cohort 1, circulating sCD163 correlated with CD163 mRNA levels in both sc and visc AT. sCD163 and CD163 mRNA expression in both fat depots correlated with GDR. In cohort 2, the diet-induced changes of sCD163 levels did not correlate with those of CD163, CD68, TACE, and TIMP3 mRNA levels. Although the pattern of the diet-induced change of sCD163 paralleled that of GDR, there was no correlation between the changes of these two variables.

CONCLUSION

sCD163 correlates with CD163 mRNA expression in sc and visc AT and with whole-body insulin sensitivity in the steady-state condition. These associations are not observed with respect to the diet-induced changes during a weight-reducing hypocaloric diet.

TWEAK: A New Player in Obesity and Diabetes

Obesity and type 2 diabetes (T2D) are associated with chronic low-grade inflammation. Mounting evidence suggests the involvement of an inflammatory switch in adipose tissue, both in mature adipocytes and immune-competent cells from the stromal vascular compartment, in the progression of obesity and insulin resistance. Several inflammatory cytokines secreted by obese adipose tissue, including TNFα and IL-6 have been described as hallmark molecules involved in this process, impairing insulin signaling in insulin-responsive organs. An increasing number of new molecules affecting the local and systemic inflammatory imbalance in obesity and T2D have been identified. In this complex condition, some molecules may exhibit opposing actions, depending on the cell type and on systemic or local influences. Tumor necrosis factor weak inducer of apoptosis (TWEAK), a cytokine of the tumor necrosis (TNF) superfamily, is gaining attention as an important player in chronic inflammatory diseases. TWEAK can exist as a full-length membrane-associated (mTWEAK) form and as a soluble (sTWEAK) form and, by acting through its cognate receptor Fn14, can control many cellular activities including proliferation, migration, differentiation, apoptosis, angiogenesis, and inflammation. Notably, sTWEAK has been proposed as a biomarker of cardiovascular diseases. Here, we will review the recent findings relating to TWEAK and its receptor within the context of obesity and the associated disorder T2D.

The macrophage-specific serum marker, soluble CD163, is increased in obesity and reduced after dietary-induced weight loss

OBJECTIVE

Soluble CD163 (sCD163) is a new macrophage-specific serum marker elevated in inflammatory conditions. sCD163 is elevated in obesity and found to be a strong predictor of the development of type 2 diabetes. We investigated whether dietary intervention and moderate exercise was related to changes in sCD163 and how sCD163 is associated to insulin resistance in obesity.

DESIGN AND METHODS

Ninety-six obese subjects were enrolled: 62 followed a very low energy diet (VLED) program for 8 weeks followed by 3-4 weeks of weight stabilization, 20 followed a moderate exercise program for 12 weeks, and 14 were included without any intervention. Fasting blood samples and anthropometric measures were taken at baseline and after intervention. Thirty-six lean subjects were included in a control group.

RESULTS

sCD163 was significantly higher in obese subjects (2.3 ± 1.0 mg/l) compared with lean (1.6 ± 0.4 mg/l, P < 0.001). Weight loss (11%) induced by VLED resulted in a reduction and partial normalization of sCD163 to 2.0 ± 0.9 mg/l (P < 0.001). Exercise for 12 weeks had no effect on sCD163. At baseline, sCD163 was significantly correlated with BMI (r = 0.46), waist circumference (r = 0.40), insulin resistance measured by the homeostasis model assessment (HOMA-IR; r = 0.41; all P < 0.001), and the leptin-to-adiponectin ratio (r = 0.28, P < 0.05). In a multivariate linear regression analysis with various inflammatory markers, sCD163 (β = 0.25), adiponectin (β = -0.24), and high sensitivity C-reactive protein (hs-CRP; β = 0.20) remained independently and significantly associated to HOMA-IR (all P < 0.05). After further adjustment for waist circumference, only sCD163 was associated with HOMA-IR (P < 0.05).

CONCLUSION

The macrophage-specific serum marker sCD163 is increased in obesity and partially normalized by dietary-induced weight loss but not by moderate exercise. Furthermore, we confirm that sCD163 is a good marker for obesity-related insulin resistance.

Perivascular fat, inflammation, and cardiovascular risk in HIV-infected patients on antiretroviral therapy

BACKGROUND

HIV-infection is characterized by chronic immune activation that persists despite effective antiretroviral therapy (ART) and is associated with elevated cardiovascular risk. Whether specific perivascular fat depots are associated with inflammation in HIV is unknown.

METHODS

In a cross-sectional study, epicardial (EAT) and thoracic periaortic (TAT) adipose tissue volumes were measured by computed tomography in 100 HIV-infected adults, on stable ART, with LDL-cholesterol ≤130 mg/dL and evidence of heightened T-cell activation (CD8+CD38+HLA-DR+ ≥19%) or increased inflammation (high sensitivity C-reactive protein ≥2 mg/L).

RESULTS

Overall, 77% were males and 70% African American. Mean (standard deviation) age and body mass index were 47 (10) years and 28 (6.4) kg/m(2), respectively. All subjects had HIV-1 RNA <1000 copies/mL with mean (standard deviation) CD4+ T cell count of 665 (280) cells/μL; 50% were on a protease inhibitor. EAT and TAT were correlated with each other (r = 0.766, p < 0.0001). Both were associated with metabolic syndrome, atherogenic lipid profile, insulin resistance, total and central body fat, serum biomarkers of inflammation, and soluble CD163, but not with cellular immune activation markers. In multivariable models that adjusted for age, sex, and other measures of adiposity, both perivascular fat depots were independently associated with the presence of coronary calcium.

CONCLUSIONS

Perivascular fat is associated with soluble CD163, biomarkers of inflammation, insulin resistance, and subclinical atherosclerosis in this population of virologically suppressed HIV-infected patients on ART. The association of perivascular fat with coronary artery calcification appears to be independent of other measures of adiposity.

CD163 and inflammation: biological, diagnostic, and therapeutic aspects

SIGNIFICANCE

The hemoglobin (Hb) scavenger receptor, CD163, is a macrophage-specific protein and the upregulated expression of this receptor is one of the major changes in the macrophage switch to alternative activated phenotypes in inflammation. Accordingly, a high CD163 expression in macrophages is a characteristic of tissues responding to inflammation. The scavenging of the oxidative and proinflammatory Hb leading to stimulation of the heme-oxygenase-1 and production of anti-inflammatory heme metabolites indicates that CD163 thereby indirectly contributes to the anti-inflammatory response.

RECENT ADVANCES

In addition to this biological role in inflammation, CD163 is a potential inflammation biomarker and a therapeutic target. The biomarker form of CD163 is the soluble plasma CD163 that arises from the increased shedding of CD163 mediated by the tumor necrosis factor-α (TNF-α) cleaving enzyme. This explains that a steadily increasing literature documents that the plasma level of soluble CD163 is increased in a large spectrum of acute and chronic inflammatory disorders. The nonshed membrane form of CD163 in macrophages constitutes a target for drugs to be directed to macrophages in inflammation. This approach has been used in an animal inflammation model to highly increase the apparent therapeutic index of anti-inflammatory glucocorticoid drug that was coupled to an anti-CD163 antibody. Furthermore, other recent animal data, which indirectly involve CD163 in macrophages, demonstrate that injections of haptoglobin attenuate Hb-induced damages after blood transfusion.

CRITICAL ISSUES AND FUTURE DIRECTIONS

The diagnostic and therapeutic properties of CD163 await further clinical studies and regulatory approval before implementation in the clinic.

The macrophage low-grade inflammation marker sCD163 is modulated by exogenous sex steroids

Soluble CD163 (sCD163) is a novel marker linked to states of low-grade inflammation such as diabetes, obesity, liver disease, and atherosclerosis, all prevalent in subjects with Turner syndrome (TS) and Klinefelter syndrome (KS). We aimed to assess the levels of sCD163 and the regulation of sCD163 in regards to treatment with sex hormone therapy in males with and without KS and females with and without TS. Males with KS (n=70) and age-matched controls (n=71) participating in a cross-sectional study and 12 healthy males from an experimental hypogonadism study. Females with TS (n=8) and healthy age-matched controls (n=8) participating in a randomized crossover trial. The intervention comprised of treatment with sex steroids. Males with KS had higher levels of sCD163 compared with controls (1.75 (0.47-6.90) and 1.36 (0.77-3.11) respectively, P<0.001) and the levels correlated to plasma testosterone (r=-0.31, P<0.01), BMI (r=0.42, P<0.001), and homeostasis model of assessment insulin resistance (r=0.46, P<0.001). Treatment with testosterone did not significantly lower sCD163. Females with TS not receiving hormone replacement therapy (HRT) had higher levels of sCD163 than those of their age-matched healthy controls (1.38±0.44 vs 0.91±0.40, P=0.04). HRT and oral contraceptive therapy decreased sCD163 in TS by 22% (1.07±0.30) and in controls by 39% (0.55±0.36), with significance in both groups (P=0.01 and P=0.04). We conclude that levels of sCD163 correlate with endogenous testosterone in KS and are higher in KS subjects compared with controls, but treatment did not significantly lower levels. Both endogenous and exogenous estradiol in TS was associated with lower levels of sCD163.

Soluble CD163 is associated with body mass index and blood pressure in hypertensive obese Saudi patients

BACKGROUND

The hallmark of vascular inflammation is the recruitment of circulating leucocytes, primarily monocytes, macrophages and T lymphocytes, into the vascular wall; however, the link between monocyte/macrophage activation and hypertension has not been established as yet. In this study, we determined how sCD163, a monocyte/macrophage soluble scavenger receptor and immunomodulator, relates to arterial blood pressure (BP) in hypertensive Saudi individuals.

MATERIALS AND METHODS

A total of 90 (30 non-hypertensive obese, 30 hypertensive obese and 30 lean normotensive controls) adult Saudi subjects, aged 40-60 years, participated in this cross-sectional study. Serum fasting blood glucose, triglycerides, total cholesterol, HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), leptin, adiponectin, resistin, insulin, tumour necrosis factor-alpha (TNF-α), PAI-1, angiotensin II, high-sensitivity C-reactive protein (hsCRP) and sCD163 were measured in all subjects studied.

RESULTS

sCD163 concentrations were significantly increased in obese hypertensive patients compared to controls (P=0.016). Positive correlations between sCD163 and body mass index (BMI) (r=0.27, P=0.01), systolic BP (r=0.25, P=0.01), diastolic BP (r=0.33, P=0.001), LDL-C (r=0.21, P=0.04), TNF-α (r=0.23, P=0.02) and hsCRP (r=0.33, P=0.008) were observed. Positive correlations between sCD163 and diastolic BP (r=0.23, P=0.04) and LDL-C (r=0.22, P=0.03) remained significant after controlling for BMI.

CONCLUSIONS

Taken together, these data demonstrate that the monocyte/macrophage activation-related sCD163 is positively associated with BMI and increased arterial BP with the elevation in diastolic BP being independent of the BMI.

Soluble CD163 is associated with body mass index and blood pressure in hypertensive obese Saudi patients

Eur J Clin Invest 2012; 42 (11): 1221–1226

Abstract

Background  The hallmark of vascular inflammation is the recruitment of circulating leucocytes, primarily monocytes, macrophages and T lymphocytes, into the vascular wall; however, the link between monocyte/macrophage activation and hypertension has not been established as yet. In this study, we determined how sCD163, a monocyte/macrophage soluble scavenger receptor and immunomodulator, relates to arterial blood pressure (BP) in hypertensive Saudi individuals.

Materials and methods  A total of 90 (30 non‐hypertensive obese, 30 hypertensive obese and 30 lean normotensive controls) adult Saudi subjects, aged 40–60 years, participated in this cross‐sectional study. Serum fasting blood glucose, triglycerides, total cholesterol, HDL‐cholesterol (HDL‐C), LDL‐cholesterol (LDL‐C), leptin, adiponectin, resistin, insulin, tumour necrosis factor‐alpha (TNF‐α), PAI‐1, angiotensin II, high‐sensitivity C‐reactive protein (hsCRP) and sCD163 were measured in all subjects studied.

Results  sCD163 concentrations were significantly increased in obese hypertensive patients compared to controls (P = 0·016). Positive correlations between sCD163 and body mass index (BMI) (r = 0·27, P = 0·01), systolic BP (r = 0·25, P = 0·01), diastolic BP (r = 0·33, P = 0·001), LDL‐C (r = 0·21, P = 0·04), TNF‐α (r = 0·23, P = 0·02) and hsCRP (r = 0·33, P = 0·008) were observed. Positive correlations between sCD163 and diastolic BP (r = 0·23, P = 0·04) and LDL‐C (r = 0·22, P = 0·03) remained significant after controlling for BMI.

Conclusions  Taken together, these data demonstrate that the monocyte/macrophage activation‐related sCD163 is positively associated with BMI and increased arterial BP with the elevation in diastolic BP being independent of the BMI.

Relationship between monocyte/macrophage activation marker soluble CD163 and insulin resistance in obese and normal-weight subjects

CONTEXT

The relationship of monocyte/macrophage activation to insulin resistance in obesity is unknown.

OBJECTIVE

To investigate a marker of macrophage activation, soluble CD163 (sCD163), in relationship to insulin resistance and metabolic parameters in obese and normal-weight subjects.

DESIGN AND PARTICIPANTS

Ninety-five healthy subjects (65 obese and 30 normal-weight) were studied. Plasma concentrations of sCD163 were assessed, as well as markers of glucose homeostasis, anthropometrics, cytokines and adipokines. The relationships between sCD163 and these parameters were investigated, and multiple regression modelling assessing the contribution of sCD163 to insulin resistance (HOMA-IR) was performed.

RESULTS

Soluble CD163 was significantly increased in obese subjects compared with normal-weight controls [974 (657, 1272) ng/ml vs 599 (423, 892) ng/ml, median (IQR); P < 0·0001]. sCD163 was strongly associated with HOMA-IR (Spearman's ρ = 0·37, P = 0·0003) and other metabolic parameters. In multiple regression modelling for log HOMA-IR, sCD163 remained significantly associated (P = 0·005) controlling for known mediators of insulin resistance including age, gender, visceral adiposity and inflammatory markers (model R(2) = 0·54, P < 0·0001). Additional nested multiple regression models for log HOMA-IR showed that sCD163 added more than other adipokines and inflammatory markers to the prediction of HOMA-IR.

CONCLUSIONS

Monocyte/macrophage activation, as reflected by sCD163 levels, is strongly associated with HOMA-IR in normal-weight and obese subjects after controlling for known mediators of insulin resistance. Moreover, sCD163 adds to standard risk markers for predicting insulin resistance. These data suggest that monocyte/macrophage activation may be an important determinant of insulin resistance in obesity.

Soluble CD163: a biomarker linking macrophages and insulin resistance

AIMS/HYPOTHESIS

Soluble CD163 (sCD163) was recently identified as a strong risk marker for developing type 2 diabetes. We hypothesised that sCD163 independently associates with insulin resistance.

METHODS

This cross-sectional study includes 234 participants: 96 with type 2 diabetes, 34 with impaired glucose tolerance (IGT) and 104 with normal glucose tolerance (NGT), matched for sex and BMI. Glucose-lowering medication was paused for 1 week before plasma samples were obtained for determination of sCD163 and other inflammatory and metabolic variables. Insulin resistance was estimated by homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Concentrations of sCD163 were 1.95 mg/l (0.63-6.97) in individuals with type 2 diabetes, 1.64 mg/l (0.58-4.19) in those with IGT, and 1.48 mg/l (0.48-4.11) (median [range]) in those with NGT (p < 0.0001). In univariate analyses, sCD163 correlated significantly with HOMA-IR (R = 0.44), insulin (R = 0.41), glucose (R = 0.30), triacylglycerol (R = 0.29) and HDL-cholesterol (R = -0.34) (all p < 0.0001). All but glucose remained significant when adjusting for age, sex, BMI and glycaemic group. In univariate regression analyses, HOMA-IR was associated with sCD163, C-reactive protein (CRP), TNF-α and IL-6 (all p ≤ 0.0001). An increase of 50% in sCD163 resulted in an estimated increase in HOMA-IR of 36% (95% CI 26, 48; p < 0.0001). In multiple linear regression analyses, sCD163 (p = 0.001) and CRP (p = 0.01) remained independent predictors of HOMA-IR, whereas TNF-α and IL-6 did not.

CONCLUSIONS/INTERPRETATION

Macrophage-specific sCD163 was strongly associated with insulin resistance independently of TNF-α and other predictors. Moreover, sCD163 was associated with well-known variables of the metabolic syndrome.

Coexpression network analysis in abdominal and gluteal adipose tissue reveals regulatory genetic loci for metabolic syndrome and related phenotypes

Metabolic Syndrome (MetS) is highly prevalent and has considerable public health impact, but its underlying genetic factors remain elusive. To identify gene networks involved in MetS, we conducted whole-genome expression and genotype profiling on abdominal (ABD) and gluteal (GLU) adipose tissue, and whole blood (WB), from 29 MetS cases and 44 controls. Co-expression network analysis for each tissue independently identified nine, six, and zero MetS–associated modules of coexpressed genes in ABD, GLU, and WB, respectively. Of 8,992 probesets expressed in ABD or GLU, 685 (7.6%) were expressed in ABD and 51 (0.6%) in GLU only. Differential eigengene network analysis of 8,256 shared probesets detected 22 shared modules with high preservation across adipose depots (D_ABD-GLU = 0.89), seven of which were associated with MetS (FDR P<0.01). The strongest associated module, significantly enriched for immune response–related processes, contained 94/620 (15%) genes with inter-depot differences. In an independent cohort of 145/141 twins with ABD and WB longitudinal expression data, median variability in ABD due to familiality was greater for MetS–associated versus un-associated modules (ABD: 0.48 versus 0.18, P = 0.08; GLU: 0.54 versus 0.20, P = 7.8×10⁻⁴). Cis-eQTL analysis of probesets associated with MetS (FDR P<0.01) and/or inter-depot differences (FDR P<0.01) provided evidence for 32 eQTLs. Corresponding eSNPs were tested for association with MetS–related phenotypes in two GWAS of >100,000 individuals; rs10282458, affecting expression of RARRES2 (encoding chemerin), was associated with body mass index (BMI) (P = 6.0×10⁻⁴); and rs2395185, affecting inter-depot differences of HLA-DRB1 expression, was associated with high-density lipoprotein (P = 8.7×10⁻⁴) and BMI–adjusted waist-to-hip ratio (P = 2.4×10⁻⁴). Since many genes and their interactions influence complex traits such as MetS, integrated analysis of genotypes and coexpression networks across multiple tissues relevant to clinical traits is an efficient strategy to identify novel associations.

Metabolic Syndrome (MetS) is a highly prevalent disorder with considerable public health concern, but its underlying genetic factors remain elusive. Given that most cellular components exert their functions through interactions with other cellular components, even the largest of genome-wide association (GWA) studies may often not detect their effects, nor necessarily provide insight into the complex molecular mechanisms of the disease. Rather than focusing on individual genes, the analysis of coexpression networks can be used for finding clusters (modules) of correlated expression levels across samples. In this study, we used a gene network–based approach for integrating clinical MetS, genotypic, and gene expression data from abdominal and gluteal adipose tissue and whole blood. We identified modules of genes related to MetS significantly enriched for immune response and oxidative phosphorylation pathways. We tested SNPs for association with MetS–associated expression (eSNPs), and tested prioritised eSNPs for association with MetS–related phenotypes in two large-scale GWA datasets. We identified two loci, neither of which had reached genome-wide significance levels in GWAs, associated with expression levels of RARRES2 and HLA-DRB1 and with MetS–related phenotypes, demonstrating that the integrated analysis of genotype and expression data from relevant multiple tissues can identify novel associations with complex traits such as MetS.

Systemic resistin is increased in type 2 diabetic patients treated with loop diuretics

Increased serum resistin was found in rodent models of obesity and insulin resistance, whereas contradictory results have been obtained in human studies. In humans, resistin is primarily released by monocytes/macrophages, suggesting that soluble levels may be associated with macrophage activation. Here, systemic and monocyte-released resistin levels were found to be similar in type 2 diabetic (T2D) patients, overweight controls and normal-weight controls. When adjusted for body mass index and age, serum resistin modestly correlated with gamma-glutamyltransferase levels, fasting glucose and interleukin-6. Systemic resistin was marginally increased in T2D patients treated with beta-blockers or urate-lowering drugs and was considerably higher in patients treated with loop diuretics. Monocyte-released resistin was even reduced by the loop diuretic furosemide, excluding the possibility that this drug may directly stimulate resistin synthesis. In summary, the current data indicate that changes accompanying renal dysfunction but not obesity or type 2 diabetes are associated with increased serum resistin.

Adiponectin stimulates release of CCL2, -3, -4 and -5 while the surface abundance of CCR2 and -5 is simultaneously reduced in primary human monocytes

The adipokine adiponectin is well known to affect the function of immune cells and upregulation of CCL2 by adiponectin in monocytes/macrophages has already been reported. In the current study the effect of adiponectin on CCL2, -3, -4, and -5 and their corresponding receptors CCR1, CCR2, and CCR5 has been analyzed. Adiponectin elevates mRNA and protein of the CC chemokines in primary human monocytes. Simultaneously the surface abundance of CCR2 and CCR5 is reduced while CCR1 is not affected. Downregulation of CCR2 by adiponectin is blocked by a CCR2 antagonist although expression of the CCL2 regulated genes CCR2 and TGF-beta 1 is not altered in the adiponectin-incubated monocytes. CCL2, -3, and -5 concentrations measured in supernatants of monocytes of normal-weight (NW), overweight (OW), and type 2 diabetic (T2D) patients positively correlate with BMI and are increased in obesity and T2D. In contrast CCL4 is similarly abundant in the supernatants of all of these monocytes. The degree of adiponectin-mediated induction of the chemokines CCL3, -4, and -5 negatively correlates with their basal levels and upregulation of CCL3 and CCL5 is significantly impaired in OW and T2D cells. Serum concentrations of these chemokines are almost equal in the three groups and do not correlate with the levels in monocyte supernatants. In conclusion these data demonstrate that adiponectin stimulates release of CCL2 to CCL5 in primary human monocytes, and induction in cells of overweight probands is partly impaired. Adiponectin also lowers surface abundance of CCR2 and CCR5 and downregulation of CCR2 seems to depend on autocrine/paracrine effects of CCL2.

In vitro and in vivo effects of metformin on human adipose tissue adiponectin

OBJECTIVE

The effects of metformin on adiponectin production are controversial and have never been investigated in human adipose tissue. We analysed whether metformin modulates, in vitro and in vivo, gene expression, protein content, and secretion of adiponectin.

METHODS

For the in vitro study, subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) samples from 5 non-diabetic obese patients were collected. For the in vivo investigation, 22 obese patients were randomly assigned to metformin+lifestyle (ML) or placebo+lifestyle (PL) intervention. SAT specimens and blood samples were collected before and after the intervention in both groups.

RESULTS

In in vitro experiments, treatment with metformin increased the expression and secretion of adiponectin in SAT, but not in VAT explants. In the in vivo study, a significant increase in adiponectin and a decreased expression of a macrophage activation marker (CD68) were observed only in SAT of the ML group.

CONCLUSION

These results demonstrate that metformin is able to up-regulate adiponectin gene expression, both in vivo and in vitro, and to stimulate adiponectin protein secretion from human SAT in vitro. It could be hypothesised that metformin-induced adiponectin increase within adipose tissue may have an unexpected role in the reduction of local inflammation.

Adiponectin primes human monocytes into alternative anti-inflammatory M2 macrophages

Altered macrophage kinetics is a pivotal mechanism of visceral obesity-induced inflammation and cardiometabolic risk. Because monocytes can differentiate into either proatherogenic M1 macrophages or anti-inflammatory M2 macrophages, approaches that limit M1 while promoting M2 differentiation represent a unique therapeutic strategy. We hypothesized that adiponectin may prime human monocytes toward the M2 phenotype. Adiponectin promoted the alternative activation of human monocytes into anti-inflammatory M2 macrophages as opposed to the classically activated M1 phenotype. Adiponectin-treated cells displayed increased M2 markers, including the mannose receptor (MR) and alternative macrophage activation-associated CC chemokine-1. Incubation of M1 macrophages with adiponectin-treated M2-derived culture supernatant resulted in a pronounced inhibition of tumor necrosis factor-alpha and monocyte chemotactic protein-1 secretion. Activation of human monocytes into M2 macrophages by adiponectin was mediated, in addition to AMP-activated protein kinase and peroxisome proliferator-activated receptor (PPAR)-gamma, via PPAR-alpha. Furthermore, macrophages isolated from adiponectin knockout mice demonstrated diminished levels of M2 markers such as MR, which were restored with adiponectin treatment. We report a novel immunoregulatory mechanism through which adiponectin primes human monocyte differentiation into anti-inflammatory M2 macrophages. Conditions associated with low adiponectin levels, such as visceral obesity and insulin resistance, may promote atherosclerosis, in part through aberrant macrophage kinetics.