characterization-immune-cells-human-adipose-tissue-using-flow

Characterization of Immune Cells in Human Adipose Tissue by Using Flow Cytometry

Infiltration of immune cells in the subcutaneous and visceral adipose tissue (AT) deposits leads to a low-grade inflammation contributing to the ...

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Rupture-prone atherosclerotic plaques are characterized by inflammation and a large necrotic core. Inflammation is linked to high metabolic activity. Advanced glycation endproducts (AGEs) and their major precursor methylglyoxal are formed during high metabolic activity and can have detrimental effects on cellular function and may induce cell death. Therefore, we investigated whether plaque AGEs are increased in human carotid rupture-prone plaques and are associated with plaque inflammation and necrotic core formation.

Higher levels of advanced glycation endproducts in human carotid atherosclerotic plaques are associated with a rupture-prone phenotype.

Advanced glycation end-products (AGEs) and their precursors have been associated with the development of atherosclerosis. We recently discovered that glyoxalase 1 (GLO1), the major detoxifying enzyme for AGE precursors, is decreased in ruptured human plaques, and that levels of AGEs are higher in rupture-prone plaques. We here investigated whether overexpression of human GLO1 in ApoE(-/-) mice could reduce the development of atherosclerosis.

Glyoxalase 1 overexpression does not affect atherosclerotic lesion size and severity in ApoE-/- mice with or without diabetes.

Genome-wide association studies (GWASs) provide an unprecedented opportunity to examine, on a large scale, the association of common genetic variants with complex diseases like type 2 diabetes (T2D) and cardiovascular disease (CVD), thus allowing the identification of new potential disease loci. Using this approach, numerous studies have associated SNPs on chromosome 9p21.3 situated near the cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) locus with the risk for coronary artery disease (CAD) and T2D. However, identifying the function of the nearby gene products (CDKN2A/B and ANRIL) in the pathophysiology of these conditions requires functional genomic studies. We review the current knowledge, from studies using human and mouse models, describing the function of CDKN2A/B gene products, which may mechanistically link the 9p21.3 risk locus with CVD and diabetes.

Functional genomics of the CDKN2A/B locus in cardiovascular and metabolic disease: what have we learned from GWASs?

Normalization of hypercholesterolaemia, inflammation, hyperglycaemia, and obesity are main desired targets to prevent cardiovascular clinical events. Here we present a novel regulator of cholesterol metabolism, which simultaneously impacts on glucose intolerance and inflammation.

Deficiency of the oxygen sensor prolyl hydroxylase 1 attenuates hypercholesterolaemia, atherosclerosis, and hyperglycaemia.

Prolonged endurance-type exercise is associated with elevated cardiac troponin (cTn) levels in asymptomatic recreational athletes. It is unclear whether exercise-induced cTn release mirrors a physiological or pathological underlying process. The aim of this study was to provide a direct comparison of the release kinetics of high-sensitivity cTnI (hs-cTnI) and T (hs-cTnT) after endurance-type exercise. In addition, the effect of remote ischemic preconditioning (RIPC), a cardioprotective strategy that limits ischemia-reperfusion injury, was investigated in a randomized controlled crossover manner. Twenty-five healthy volunteers completed an outdoor 30-km running trial preceded by RIPC (4 × 5 min 220 mm Hg unilateral occlusion) or control intervention. hs-cTnT, hs-cTnI, and sensitive cTnI (s-cTnI) concentrations were examined before, immediately after, 2 and 5 hours after the trial. The completion of a 30-km run resulted in a significant increase in circulating cTn (time: all p <0.001), with maximum hs-cTnT, hs-cTnI, and s-cTnI levels of 47 ± 27, 69 ± 62, and 82 ± 64 ng/L (mean ± SD), respectively. Maximum hs-cTnT concentrations were measured in 60% of the participants at 2 hours after exercise, compared with maximum hs-cTnI and s-cTnI concentrations at 5 hours in 84% and 80% of the participants. Application of an RIPC stimulus did not reduce exercise-induced cTn release (time × trial: all p >0.5). In conclusion, in contrast to acute myocardial infarction, maximum hs-cTnT levels after exercise precede maximum hs-cTnI levels. Distinct release kinetics of hs-cTnT and hs-cTnI and the absence of an effect of RIPC favors the concept that exercise-induced cTn release may be mechanistically distinct from cTn release in acute myocardial infarction.

Cardiac Troponin T and I Release After a 30-km Run.

Immune cell accumulation in adipose tissue (AT) is associated with the development of AT inflammation, resulting in metabolic dysfunction. Circulating immune cell patterns may reflect immune cell accumulation in expanding AT. However, data linking human leukocytes in blood and AT is lacking. We investigated whether blood immune cell populations are associated with their counterparts in subcutaneous (scAT) or visceral AT (vAT). Flow cytometry was performed on blood, scAT and vAT from 16 lean and 29 obese men. Circulating natural killer (NK)-cells, classical monocytes and nonclassical monocytes were higher in obese individuals. vAT, but not scAT, of obese individuals contained more inflammatory CD11c"M1" macrophages and NK cells compared to lean individuals. Blood classical monocytes were associated with CD11cmacrophages in vAT but not scAT. This association was unrelated to expression of the adhesion molecules CD11b and CD11c or of the chemokine receptor CX3CR1 on these monocytes. Other AT immune cells were not associated with their respective counterparts in blood. Finally, CD11cmacrophages and CD4T-cells in vAT were associated with their counterparts in scAT. In conclusion, blood classical monocytes reflect CD11cmacrophages in vAT.

Circulating classical monocytes are associated with CD11cmacrophages in human visceral adipose tissue.

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS). The activation of inflammatory cells is crucial for the development of MS and is shown to induce intracellular glycolytic metabolism in pro-inflammatory microglia and macrophages, as well as CNS-resident astrocytes. Advanced glycation endproducts (AGEs) are stable endproducts formed by a reaction of the dicarbonyl compounds methylglyoxal (MGO) and glyoxal (GO) with amino acids in proteins, during glycolysis. This suggests that, in MS, MGO-derived AGEs are formed in glycolysis-driven cells. MGO and MGO-derived AGEs can further activate inflammatory cells by binding to the receptor for advanced glycation endproducts (RAGE). Recent studies have revealed that AGEs are increased in the plasma and brain of MS patients. Therefore, AGEs might contribute to the inflammatory status in MS. Moreover, the main detoxification system of dicarbonyl compounds, the glyoxalase system, seems to be affected in MS patients, which may contribute to high MGO-derived AGE levels. Altogether, evidence is emerging for a contributing role of AGEs in the pathology of MS. In this review, we provide an overview of the current knowledge on the involvement of AGEs in MS.

Methylglyoxal-Derived Advanced Glycation Endproducts in Multiple Sclerosis.

Myelin-containing macrophages and microglia are the most abundant immune cells in active multiple sclerosis (MS) lesions. Our recent transcriptomic analysis demonstrated that collectin placenta 1 (CL-P1) is one of the most potently induced genes in macrophages after uptake of myelin. CL-P1 is a type II transmembrane protein with both a collagen-like and carbohydrate recognition domain, which plays a key role in host defense. In this study we sought to determine the dynamics of CL-P1 expression on myelin-containing phagocytes and define the role that it plays in MS lesion development. We show that myelin uptake increases the cell surface expression of CL-P1 by mouse and human macrophages, but not by primary mouse microglia in vitro. In active demyelinating MS lesions, CL-P1 immunoreactivity was localized to perivascular and parenchymal myelin-laden phagocytes. Finally, we demonstrate that CL-P1 is involved in myelin internalization as knockdown of CL-P1 markedly reduced myelin uptake. Collectively, our data indicate that CL-P1 is a novel receptor involved in myelin uptake by phagocytes and likely plays a role in MS lesion development.

Scavenger receptor collectin placenta 1 is a novel receptor involved in the uptake of myelin by phagocytes.

The genomic CDKN2A/B locus, encoding p16among others, is linked to an increased risk for cardiovascular disease and type 2 diabetes. Obesity is a risk factor for both cardiovascular disease and type 2 diabetes. p16is a cell cycle regulator and tumour suppressor. Whether it plays a role in adipose tissue formation is unknown. p16knock-down in 3T3/L1 preadipocytes or p16deficiency in mouse embryonic fibroblasts enhanced adipogenesis, suggesting a role for p16in adipose tissue formation. p16-deficient mice developed more epicardial adipose tissue in response to the adipogenic peroxisome proliferator activated receptor gamma agonist rosiglitazone. Additionally, adipose tissue around the aorta from p16-deficient mice displayed enhanced rosiglitazone-induced gene expression of adipogenic markers and stem cell antigen, a marker of bone marrow-derived precursor cells. Mice transplanted with p16-deficient bone marrow had more epicardial adipose tissue compared to controls when fed a high-fat diet. In humans, p16gene expression was enriched in epicardial adipose tissue compared to other adipose tissue depots. Moreover, epicardial adipose tissue from obese humans displayed increased expression of stem cell antigen compared to lean controls, supporting a bone marrow origin of epicardial adipose tissue. These results show that p16modulates epicardial adipose tissue development, providing a potential mechanistic link between the genetic association of the CDKN2A/B locus and cardiovascular disease risk.

The tumour suppressor CDKN2A/p16regulates adipogenesis and bone marrow-dependent development of perivascular adipose tissue.

Obesity is a risk factor for non-alcoholic steatohepatitis (NASH). This risk has been attributed to visceral adipose tissue (vAT) expansion associated with increased proinflammatory mediators. Accumulation of CD11cproinflammatory adipose tissue macrophages (ATM) is an important driver of vAT inflammation. We investigated the role of ATMs in hepatic inflammation during NASH development.

Article	Year
Higher levels of advanced glycation endproducts in human carotid atherosclerotic plaques are associated with a rupture-prone phenotype. European heart journal\| PubMed ID: 24126878	2013
Glyoxalase 1 overexpression does not affect atherosclerotic lesion size and severity in ApoE-/- mice with or without diabetes. Cardiovascular research\| PubMed ID: 25139743	2014
Functional genomics of the CDKN2A/B locus in cardiovascular and metabolic disease: what have we learned from GWASs? Trends in endocrinology and metabolism: TEM\| PubMed ID: 25744911	2015
Deficiency of the oxygen sensor prolyl hydroxylase 1 attenuates hypercholesterolaemia, atherosclerosis, and hyperglycaemia. European heart journal\| PubMed ID: 27125949	2016
Cardiac Troponin T and I Release After a 30-km Run. The American journal of cardiology\| PubMed ID: 27282835	2016
Circulating classical monocytes are associated with CD11cmacrophages in human visceral adipose tissue. Scientific reports\| PubMed ID: 28198418	2017
Methylglyoxal-Derived Advanced Glycation Endproducts in Multiple Sclerosis. International journal of molecular sciences\| PubMed ID: 28212304	2017
Scavenger receptor collectin placenta 1 is a novel receptor involved in the uptake of myelin by phagocytes. Scientific reports\| PubMed ID: 28317919	2017
The tumour suppressor CDKN2A/p16regulates adipogenesis and bone marrow-dependent development of perivascular adipose tissue. Diabetes & vascular disease research\| PubMed ID: 28868898	2017
Adipose tissue macrophages induce hepatic neutrophil recruitment and macrophage accumulation in mice. Gut\| PubMed ID: 29074725	2017

Kristiaan Wouters

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