Cholesterol efflux and macrophage polarization in human adipose tissue.

The pro-inflammatory status of adipose tissue (AT) has been found to be related to reverse cholesterol transport (RCT) from peritoneal macrophages. However, this finding was made in experimental models using induced peritonitis and isolated peritoneal macrophages of animals. This experimental relationship is in agreement with RCT changes in man in two extreme situations, sepsis or cardiovascular complications. Given the above, we sought to test RTC in relationship to macrophage polarization in the visceral AT (VAT) of living kidney donors (LKDs) and the effect of conditioned media obtained from their AT. The influence of ATCM on CE capacity was first assessed in an experiment where standard plasma was used as cholesterol acceptor from [14C] cholesterol labeled THP-1. Conditioned media as a product of LKDs' incubated AT showed no effect on CE. Likewise, we did not find any effect of individual plasma of LKDs on CE when individual plasma of LKDs were used as acceptors. On the other hand, we documented an effect of LKDs' adipose cell size on CE. Our results indicate that the pro-inflammatory status of human AT is not likely induced by disrupted RCT but might be influenced by the metabolic status of LKDs' adipose tissue.

Adipose tissue macrophages and atherogenesis - a synergy with cholesterolaemia.

Excessive LDL cholesterol concentration together with subclinical inflammation, in which macrophages play a central role, are linked pathologies. The process starts with the accumulation of macrophages in white adipose tissue and the switch of their polarization toward a pro-inflammatory phenotype. The proportion of pro-inflammatory macrophages in adipose tissue is related to the main risk predictors of cardiovascular disease. The cholesterol content of phospholipids of cell membranes seems to possess a crucial role in the regulation of membrane signal transduction and macrophage polarization. Also, different fatty acids of membrane phospholipids influence phenotypes of adipose tissue macrophages with saturated fatty acids stimulating pro-inflammatory whereas omega3 fatty acids anti-inflammatory changes. The inflammatory status of white adipose tissue, therefore, reflects not only adipose tissue volume but also adipose tissue macrophages feature. The beneficial dietary change leading to an atherogenic lipoprotein decrease may therefore synergically reduce adipose tissue driven inflammation.

Global DNA methylation in rats´ liver is not affected by hypercholesterolemic diet.

Increased plasma cholesterol levels are listed between the major atherosclerosis risk factors. The final plasma cholesterol levels result from the interplay between the genetic and environmental (diet, physical activity) factors. Little is known, how dietary factor influence epigenetics. We have analyzed, if an over-generation feeding of rat with cholesterol influences total liver-DNA methylation, and if total liver-DNA methylation differ between the different rat strains (Prague hereditary hypercholesterolemic rats, Prague hereditary hypertriglyceridemic rats and Wistar Kyoto rats). The animals were feed with high fat (additional 5 % over normal capacity) high cholesterol (2 %) diet for 14 days. DNA methylation in the liver tissue in different generations was analyzed using the liquid chromatography coupled with tandem mass spectrometry. We have not observed any significant changes in total liver-DNA methylation over the 9 generations of animals feed by fat/cholesterol enriched diet. Additionally, there were no differences in DNA methylation between different rat strains. In animal model, the dietary changes (hypercholesterolemic diet) not significantly influence the total DNA methylation status within the liver.

Adipose tissue collection from a living kidney donor; an experimental model for the research of atherosclerosis.

Thanks to an increased number of living-donor kidney transplants the IKEM transplant program offers the possibility of obtaining adipose tissue for scientific purposes from patients with varying degrees of atherosclerosis. Surgery mainly addresses vascular complications of this disease. On the other hand, surgery may also be the reason for the development and acceleration of atherosclerosis - for instance, acceleration of atherosclerosis in the living kidney donor, particularly if, although meeting internationally recognized donation criteria, the donor actually suffers from metabolic syndrome. The effort to refine the examinations of living kidney donors in terms of eliminating the risk of developing atherosclerosis is a long-term project. The aims are to determine the risk factors for living kidney donors and to prevent long-term complications after donation. The paper gives a detailed description of the technique of adipose tissue collection from a living kidney donor and of the experimental model for the research of atherosclerosis.The project has the potential to increase the safety of living kidney donation and to enhance our present knowledge of atherosclerosis development mechanisms.

Human genome evolution and development of cardiovascular risk factors through natural selection.

Impressive advances in molecular genetic techniques allow to analyze the effects of natural selection on the development of human genome. For example, the trend towards blonde hair and blue eyes was documented. The approach to analyze possible effects of natural selection on the evolution of recent phenotypes with high risk of cardiovascular disease has not been described yet. A possible effect on the evolution of two main risk factors - hypercholesterolemia and hypertension - is presented. The close relationship of non-HDL cholesterol blood concentration to the proportion of pro-inflammatory macrophages in human visceral adipose tissue might be a result of long-lasting natural selection. Individuals with higher proportion of this phenotype might also display a higher ability to fight infection, which was very common in human setting from prehistory until Middle Ages. Successful battle against infections increased the probability to survive till reproductive age. Similar hypothesis was proposed to explain frequent hypertension in African Americans. A long-lasting selection for higher ability to conserve sodium during long-term adaptation to low sodium intake and hot weather was followed by a short-term (but very hard) natural selection of individuals during transatlantic slave transport. Only those with very high capability to retain sodium were able to survive. Natural selection of phenotypes with high plasma cholesterol concentration and/or high blood pressure is recently potentiated by high-fat high-sodium diet and overnutrition. This hypothesis is also supported by the advantage of familial hypercholesterolemia in the 19th century (at the time of high infection disease mortality) in contrast to the disadvantage of familial hypercholesterolemia during the actual period of high cardiovascular disease mortality.

Experimental models of hyperlipoproteinemia and atherosclerosis.

The first experimental model of atherosclerosis (in rabbits) is more than hundred years old. Several animal species have been used to produce hyperlipoproteinemia and possible atherosclerosis. The gene manipulation produced the most used models recently. This review acknowledges the extensive study of atherosclerotic changes in experimental models of hyperlipoproteinemia and atherosclerosis to come to light thus far and the purpose here is not only to summarize the published data but also to try to add some details of our experience in using these models. In addition to rabbit (the old but also improved model by reno-vascular hypertension) dog, birds, pig, hamster, mice, rat and non-human primate's animal models are described. The gene manipulation produced the most used models two decades ago. Germline genetically engineered (without apoE or LDL receptor genes) animals have become the most used models producing atherosclerotic changes in the aorta. Recent new models also producing atherosclerotic changes but without germline genetic manipulation are also described.

Pro-inflammatory gene expression in adipose tissue of patients with atherosclerosis.

Inflammatory changes, both in the arterial wall and adipose tissue, play a crucial role in the development of atherosclerosis. We measured the gene expression of tumor necrosis factor-alpha (TNFalpha), monocyte chemoattractant protein-1 (MCP-1), and interleukin 6 (IL-6) in adipose tissue (AT) of living kidney donors (LKD) and patients with peripheral arterial disease (PAD). Quantitative polymerase chain reaction (qPCR) and flow cytometry analyses were performed in subcutaneous (SAT), visceral (VAT), and perivascular adipose tissue (PVAT). Data of PAD patients showed significantly higher expression in VAT in all three genes (TNFalpha 5-fold, p<0.05; MCP-1 3.6-fold, p<0.05; IL-6 18.8-fold, p<0.001). The differences in PVAT and SAT were less significant. Total body pro-inflammatory status was documented by higher TNFalpha concentration in patients (4.86+/-1.4 pg/ml) compared to LKDs (2.14+/-0.9 pg/ml; p<0.001), as was hsCRP (11.8+/-7.0 in PAD; 1.5+/-0.48 in LKDs; p=0.017). We found no age-dependent relationship between gene expression vs. TNFalpha and hsCRP concentrations in both compared groups. No effect of the atherosclerosis score on gene expression and circulating inflammatory markers within the PAD group was observed. Our results suggest that the AT of PAD patients infiltrated with macrophages produces more cytokines involved in the development of inflammation and atherosclerosis.

Human adipose tissue accumulation is associated with pro-inflammatory changes in subcutaneous rather than visceral adipose tissue.

The importance of the involvement of adipose tissue macrophage subpopulations in obesity-related disorders is well known from different animal models, but human data are scarcer. Subcutaneous (n=44) and visceral (n=52) adipose tissues of healthy living kidney donors were obtained during living donor nephrectomy. Stromal vascular fractions were isolated and analysed by flow cytometry using CD14, CD16, CD36 and CD163 antibodies. Total macrophage numbers in subcutaneous adipose tissue increased (P=0.02) with body mass index (BMI), with a similar increase seen in the proportion of phagocytic CD14+CD16+CD36high macrophages (P<0.01). On the other hand, there was an inverse correlation between anti-inflammatory CD14+CD16-CD163+ macrophages (P<0.05) and BMI. These correlations disappeared after excluding obese subjects (BMI ⩾30 kg m-2) from the analysis. Interestingly, none of these subpopulations were significantly related to BMI in visceral adipose tissue. Obesity per se is associated with distinct, highly phagocytic macrophage accumulation in human subcutaneous adipose tissue.

Association of intima-media thickness of carotid arteries with remnant lipoproteins in men and women.

The subclass of triglyceride-rich lipoproteins - remnant-like particles (RLP) seems to be strong and independent risk factor for cardiovascular disease. We evaluated the role of RLP and other risk factors (RF) with sonographically measured intima-media thickness of carotid arteries (IMT CCA) in a cohort of Czech population including women defined according to the time after menopause. We investigated relation of IMT CCA to age, weight, central obesity, plasma lipids including remnant-like particles cholesterol (RLP-C) and triglycerides (RLP-TG) in 136 men and 160 women. Using multiple linear regression analysis, significant association between IMT CCA and RLP-C was found in women 1-7 years after menopause. In the whole group of women, only age and fasting blood glucose were independently associated with IMT CCA. In men only age significantly correlated with IMT CCA. Significant decrease of all plasma lipids between 1988 and 1996 in men was detected, while in women significant increase in triglycerides and no change in non-HDL cholesterol was observed. RLP-C was the strongest independent RF for atherosclerosis in postmenopausal women but its association with IMT CCA was limited to several years after menopause. In conclusion, women changing reproductive status could be more sensitive to atherogenic impact of remnant lipoproteins.

Adipose tissue and atherosclerosis.

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.

The effect of ectopic fat on graft function after living kidney transplantation.

Renal transplantation is associated with a large number of risk factors that can have an influence on early renal graft function (ERGF). One of these factors could be the increasing number of obese kidney donors. The mechanisms of reduced ERGF in obese kidney donors are still poorly understood. To that end, we compared ERGF in recipients with body mass index (BMI), perivascular fat and plasma inflammation markers of live kidney donors. We hypothesized that the BMI of donors would negatively correlate with an average increase of glomerular filtration rate (GFR) and that it would also be associated with increased perivascular and plasma inflammation markers in the first seven days after transplantation. Between January 2013 and December 2014, some 58 living kidney transplantation pairs were included in the study. Donor and recipient demographic data, preoperative BMI, blood C-reactive protein (CRP) and adiponectin levels, perivascular adipose tissue (PAT) samples and recipient blood creatinine levels were analyzed. The median CRP of donors was 0.68 mg/l (max: 8.66 mg/l, min: 0.33 mg/l), the median of M1 macrophages (CD14+CD16+) in one gram of PAT was 5940 (max: 41 100, min: 248) and the median of adiponectin was 411 930 pg/ml (max: 14 217 000, min: 167 300) in plasma. We did not find any association between early renal graft function and the percentage of M1 macrophages in donor perirenal adipose tissue (p=0.83, r=0.03, n=58), adiponectin (p=0.65, r=0.06, n=58) or CRP (p=0.16, r=0.2, n=58) in plasma. The obesity level of donors, expressed as BMI, did not correlate with early renal graft function in the first seven days after transplantation. The associations between ERGF and plasma and perivascular fat inflammation markers were not significant. We confirmed a negative correlation between the BMI of recipients and an average increase of GFR in the first seven days after transplantation (p<0.02, r=-0.325, N=58). We confirmed a negative correlation of adiponectin plasma concentration to the BMI of donors.

Macrophage phenotypes in the adipose tissue of postmenopausal women.

Atherosclerosis pathology is the interplay between high intravascular LDL particle concentration and monocyte/macrophage presence within the sub-endothelial space of the artery. In this project, phenotypes of macrophages connected with subclinical inflammation in adipose tissue of living kidney donors were studied. Samples of subcutaneous adipose tissue of living kidney donors (n=36) were exposed to collagenase. Stromal vascular fraction (SVF) was eluted from the samples, then labeled with monoclonal antibodies (anti-CD14 and anti-calprotectin), conjugated with fluorochromes and analyzed by flow cytometry. The positive correlation between the number of total macrophages and calprotectin-positive macrophages with BMI in the subcutaneous adipose tissue of postmenopausal women was demonstrated (p<0.05; R=0.43 and p<0.01; R=0.60), whereas no positive correlation in premenopausal women and men was shown. In conclusion, we documented a significant effect of BMI increase on the presence of total macrophages in adipose tissue of postmenopausal women, in contrast to premenopausal women. This difference was much more pronounced when proinflammatory macrophages with membrane-bound calprotectin were analyzed.

Is the amount of coronary perivascular fat related to atherosclerosis?

Interesting and stimulating data about the effect of the perivascular adipose tissue size on atherogenesis are based mainly on CT findings. We studied this topic by directly analyzing perivascular adipose tissue in explanted hearts from patients undergoing transplantation. Ninety-six consecutive patients were included, including 58 with atherosclerotic coronary heart disease (CHD) and 38 with dilation cardiomyopathy (DCMP). The area of perivascular fat, area of the coronary artery wall, and ratio of CD68-positive macrophages within the perivascular fat and within the vascular wall were quantified by immunohistochemistry. There was no significant difference in the perivascular adipose tissue size between the two groups. Nevertheless, there was a significantly higher number of macrophages in the coronary arterial wall of CHD patients. In addition, we found a close relationship between the ratio of macrophages in the arterial wall and adjacent perivascular adipose tissue in the CHD group, but not in the DCMP group. According to our data interaction between macrophages in the arterial wall and macrophages in surrounding adipose tissue could be more important mechanism of atherogenesis than the size of this tissue itself.

Rs6922269 marker at the MTHFD1L gene predict cardiovascular mortality in males after acute coronary syndrome.

Myocardial infarction (MI) is the leading cause of death in industrialized countries. All the traditional risk factors for MI are responsible for approximately 50% of cases of MI cases. Attention therefore has recently focused on genetic variants that are not associated with conventional risk factors. One of them is the marker rs6922269, which has been suggested as a risk factor for development of MI in Western populations. We analyzed the relationship between rs6922269 variant on MTHFD1L gene and (i) risk of the acute coronary syndrome (ACS) in the Czech population and (ii) mortality in 7 years follow up. Rs6922269 (G>A) variant was analyzed (CR 99.3% for patients and 98.0% for controls) by PCR-RFLP in consecutively examined 1614 men and 503 women with ACS (age below 65 years) and in population-based controls--1191 men and 1368 women (aged up to 65 years). ANOVA and Chi square were used for statistical analysis. The genotype frequencies were almost identical (P=0.87) in the ACS patients and in controls and no differences were observed, if males (P=0.73) and females (P=0.93) were analysed separately. In addition, rs6922269 polymorphism was not associated with the classical risk factors (dyslipidemia, hypertension, obesity, smoking, diabetes) in control population. Cardiovascular mortality was significantly higher in males, carriers of the AA genotype (P<0.001, OR 2.52, 95% CI 1.40-4.55, for AA vs. +G). We conclude, that rs6922269 variant at MTHFD1L gene could be an important prognostic factor for cardiovascular mortality in patients after ACS.

Immunological aspects of atherosclerosis.

Atherosclerosis is a degenerative inflammatory disease of the vascular wall, which is characterized by the formation of atherosclerotic plaques that contain lipids, activated smooth muscle cells, immune cells, foam cells, a necrotic core and calcified sites. In atherosclerosis pathology, monocytes and macrophages play the most important role by accumulating redundant LDL particles in their oxidized form and producing proinflammatory cytokines. Atherosclerotic plaque macrophages reveal distinct phenotypes that are distinguished into M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages. Numerous environmental signals (cytokines, microbial cell molecules) that are received by macrophages drive their polarization, but it must be determined whether this classification reflects different macrophage subtypes or plasticity and phenotypic tissue changes, but the balance between subsets is crucial. M1 macrophages are dominant in symptomatic atherosclerotic plaques, while M2 macrophages are more frequent in asymptomatic plaques. Nevertheless, a positive correlation of both M1 and M2 macrophages with atherosclerotic lesion severity was also observed.

The response of hepatic transcriptome to dietary cholesterol in Prague hereditary hypercholesterolemic (PHHC) rat.

To understand the pathogenesis of hypercholesterolemia in Prague hereditary hypercholesterolemic (PHHC) rat, we analyzed the response of hepatic transcriptome to dietary cholesterol in PHHC and control Wistar rats. Male PHHC and Wistar rats were fed chow (C), 5 % fat (palm kernel oil) (CF) or 1 % cholesterol + 5 % fat (CHOL) diet for three weeks. Hepatic transcriptome was analyzed using Affymetrix GeneChip arrays. No differences were found in the effect of both control diets (C and CF) on lipid metabolism and gene expression of 6500 genes. Therefore, these data were pooled for further analysis. Dietary cholesterol induced accumulation of cholesterol and triacylglycerols in the liver in both strains and hypercholesterolemia in PHHC rats. However, there were no differences in response of hepatic transcriptome to CHOL diet. On the other hand, several genes were found to be differently expressed between both strains independently of the diet. Two of those genes, Apof and Aldh1a7, were studied in more detail, and their role in pathogenesis of hypercholesterolemia in PHHC rats could not been corroborated. In conclusion, the hypercholesterolemia in PHHC rats is due to physiological response of hepatic transcriptome to dietary cholesterol in different genetic background.

Reverse transport of cholesterol is the reason for resistance to development of atherosclerosis in Prague Hereditary Hypercholesterolemic (PHHC) rat.

The Prague Hereditary Hypercholesterolemic (PHHC) rat is a model of hypercholesterolemia. In previous experiments, it was found to be completely resistant to the development of atherosclerosis. It was assumed that the reverse transport of cholesterol (RCT) might be the reason for this resistance. In this study, RCT was measured in vivo by cholesterol efflux from macrophages to plasma, using previously established methods for RCT in mice (Rader 2003), optimized for measurements in rats. Primary cell culture of macrophages was labeled with (14)C-cholesterol and then injected intraperitoneally into rats. Plasma and feces were collected at 24 and 48 h. The plasma (14)C-cholesterol levels at both 24 and 48 h were significantly higher in male PHHC rats compared to control Wistar rats. The PHHC rats excreted less (14)C-cholesterol in feces in 24 and 48 h compared to Wistar rats. The largest pool of (14)C-cholesterol was found in the adipose tissue of PHHC rats and in contrast lower levels of (14)C-cholesterol were measured in the liver and muscle tissues of PHHC rats compared with Wistar rats. Increasing release of (14)C-cholesterol efflux from macrophages demonstrates accelerated RTC and leads to prevention of atherogenesis in PHHC rats.

Effect of different types of dietary fatty acids on subclinical inflammation in humans.

Replacing SAFAs (saturated fatty acids) for vegetable PUFAs (polyunsaturated fatty acids) has a well documented positive effect on the lipoprotein pattern while the direct effect of dietary fatty acids composition on systemic inflammation remains to be proven. In well controlled randomised cross-over study with 15 overweight/obese postmenopausal women, the effect of dietary switch on systemic inflammation was investigated. A two 3 weeks dietary period either with predominant animal fat (SAFA, 29 caloric % SAFA) or vegetable fat (PUFA 25 % caloric % PUFA) were interrupted by wash-out period. The expected increasing effect on SAFA diet to LDL-C (low density cholesterol) and opposite effect of PUFA diet was documented following changes in fatty acid spectrum in VLDL (very low density cholesterol) particles. The switch from SAFA diet to PUFA diet produced a significant change of CRP (C-reactive protein) concentration (p<0.01) whereas similar trend of IL-18 did not reach statistical significance. In this study, previous in vitro results of different SAFA and PUFA proinflammatory effects with well documented molecular mechanisms were first proven in a clinical study. It could be stated that the substantial change of dietary fatty acid composition might influence proinflammatory effect in addition to traditional cardiovascular risk factors.

A new atherogenic effect of saturated fatty acids.

There is increasing evidence that dietary saturated fatty acids (SAFA) have not only an indirect atherogenic effect due to increasing LDL-cholesterol concentration but also a direct effect by activating the inflammation process. This review summarizes several recent publications in this field. The effect of SAFA on the inflammation process mediated by Toll-like receptor 4/NF-kappaB pathway has been well documented in various in vitro culture studies of macrophages and adipocytes or in their co-culture. In contrast to these in vitro data, in vivo epidemiological studies or clinical experiments in men are less consistent. Well controlled cross-over studies in volunteers might enlighten the differences between saturated and unsaturated fatty acids dietary intake and proatherogenic inflammation effects.