Macrophages play important roles in adipose tissue inflammation and its consequences. Unfortunately, a detailed description of the macrophage phenotypes in different human adipose tissues is not available. Subcutaneous, visceral and perivascular adipose tissues were obtained from 52 living kidney donors during live donor nephrectomy. Stromal vascular fractions were isolated, and the macrophage phenotypes were analyzed by flow cytometry using surface markers (CD14, CD16, CD36, and CD163). In addition to CD16 positivity, pro-inflammatory macrophages also display high scavenger receptor CD36 expression. The great majority of CD16 negative macrophages express the anti-inflammatory CD163 marker. The presence of pro-inflammatory macrophages was almost twice as high in visceral (p < 0.0001) and perivascular (p < 0.0001) adipose tissues than in subcutaneous tissue. This difference was substantially more pronounced in the postmenopausal women subgroup, consequentlly, the total difference was driven by this subgroup. We obtained detailed information about M1 and M2 macrophage phenotypes in human adipose tissue. The visceral and perivascular adipose tissues had substantially higher pro-inflammatory characteristics than the subcutaneous tissue. The higher proportion of pro-inflammatory macrophages in the visceral adipose tissue of postmenopausal women might be related to an increased cardiovascular risk.

Rudolf Poledne, Ivana Kralova Lesna, Anna Kralova, Jiri Fronek, Sona Cejkova

Residential macrophages in adipose tissue play a pivotal role in the development of inflammation not only within this tissue, but also affect the proinflammatory status of the whole body. Data on human adipose tissue inflammation and the role of macrophages are rather scarce. We previously documented that the proportion of proinflammatory macrophages in human adipose tissue correlates closely with non-HDL cholesterol concentrations. We hypothesized that this is due to the identical influence of diet on both parameters and decided to analyze the fatty acid spectrum in cell membrane phospholipids of the same individuals as a parameter of the diet consumed. Proinflammatory and anti-inflammatory macrophages were isolated from human adipose tissue (n = 43) and determined by flow cytometry as CD14+CD16+CD36^high and CD14+CD16−CD163+, respectively. The spectrum of fatty acids in phospholipids in the cell membranes of specimens of the same adipose tissue was analyzed, and the proportion of proinflammatory macrophage increased with the proportions of palmitic and palmitoleic acids. Contrariwise, these macrophages decreased with increasing alpha-linolenic acid, total n-3 fatty acids, n-3/n-6 ratio, and eicosatetraenoic acid. A mirror picture was documented for the proportion of anti-inflammatory macrophages. The dietary score, obtained using a food frequency questionnaire, documented a positive relation to proinflammatory macrophages in individuals who consumed predominantly vegetable fat and fish, and individuals who consumed diets based on animal fat without fish and nut consumption. he present data support our hypothesis that macrophage polarization in human visceral adipose tissue is related to fatty acid metabolism, cell membrane composition, and diet consumed. It is suggested that fatty acid metabolism might participate also in inflammation and the risk of developing cardiovascular disease.

Background: The risk of cardiovascular disease is closely connected to adipose tissue inflammation. The links between cardiovascular risk predictors and pro and anti-inflammatory macrophages in human adipose tissue were analysed to gain an insight into the pathophysiology of cardiovascular disease. Design: Subcutaneous and visceral adipose tissues were obtained from 79 subjects, 52 living kidney donors (during nephrectomy) and 27 patients with peripheral artery disease (during arterial tree reconstruction). Methods: Macrophage subsets were isolated from adipose tissues and analysed by flow cytometry using CD14, CD16, CD36 and CD163 monoclonal antibodies. The mutually adjusted differences of phagocytic pro-inflammatory (CD14 + CD16 + CD36^high), anti-inflammatory (CD14 + CD16-CD163+) and transitional subsets of macrophages were analysed in relation to cardiovascular predictors (sex, age, body mass index, smoking, hypercholesterolaemia, hypertension and statin treatment). Results: Age, male sex and hypercholesterolaemia were closely positively associated with the phagocytic pro-inflammatory macrophage subset in visceral adipose tissues. Interestingly, the proportion of phagocytic pro-inflammatory macrophages was relevantly decreased by statin therapy. A strong positive association of body mass index to the phagocytic pro-inflammatory subset was found in subcutaneous adipose tissues only. A minor transitional subpopulation, CD14 + CD16 + CD36^lowCD163+, increased with age in both adipose tissues. This transitional subpopulation was also negatively associated with obesity and hypercholesterolaemia in visceral adipose tissues. Conclusion: An effect of cardiovascular risk predictors on adipose tissue macrophage subpopulations was revealed. Interestingly, while age, male sex and hypercholesterolaemia were connected with the pro-inflammatory macrophage subpopulation in visceral adipose tissues, body mass index had a prominent effect in subcutaneous adipose tissues only. A decreasing effect of statins on these pro-inflammatory macrophages was documented.

High-energy intake which exceeds energy expenditure leads to the accumulation of triglycerides in adipose tissue, predominantly in large-size adipocytes. This metabolic shift, which drives the liver to produce atherogenic dyslipidemia, is well documented. In addition, an increasing amount of monocytes/macrophages, predominantly the proinflammatory M1-type, cumulates in ectopic adipose tissue. The mechanism of this process, the turnover of macrophages in adipose tissue and their direct atherogenic effects all remain to be analyzed.

Statins represent one of the most widely used classes of drugs in current medicine. In addition to a substantial decrease in atherogenic low density lipoprotein (LDL) particle concentrations, several large trials have documented their potent anti-inflammatory activity. Based on our preliminary data, we showed that statins are able to decrease the proportion of pro-inflammatory macrophages (CD14+16+CD36high) in visceral adipose tissue in humans. In the present study including 118 healthy individuals (living kidney donors), a very close relationship between the pro-inflammatory macrophage proportion and LDL cholesterol levels was found. This was confirmed after adjustment for the most important risk factors. The effect of statins on the proportion of pro-inflammatory macrophages was also confirmed in an experimental model of the Prague hereditary hypercholesterolemia rat. A direct anti-inflammatory effect of fluvastatin on human macrophage polarization in vitro was documented. Based on modifying the LDL cholesterol concentrations, statins are suggested to decrease the cholesterol inflow through the lipid raft of macrophages in adipose tissue and hypercholesterolemia to enhance the pro-inflammatory macrophage phenotype polarization. On the contrary, due to their opposite effect, statins respond with anti-inflammatory activity, affecting the whole organism.