Apolipoprotein A1 deficiency in mice primes bone marrow stem cells for T cell lymphopoiesis.

The bone marrow has emerged as a potentially important target in cardiovascular disease as it generates all leukocytes involved in atherogenesis. In the current study, we evaluated whether a change in bone marrow functionality underlies the increased atherosclerosis susceptibility associated with high-density lipoprotein (HDL) deficiency. We found that HDL deficiency in mice due to the genetic lack of hepatocyte-derived apolipoprotein A1 (APOA1) was associated with an increase in the Lin-Sca-1+Kit+ (LSK) bone marrow stem cell population and lymphoid-primed multipotent progenitor numbers, which translated into a higher production and systemic flux of T cell subsets. In accordance with APOA1 deficiency-associated priming of stem cells to increase T lymphocyte production, atherogenic diet-fed low-density lipoprotein receptor knockout mice transplanted with bone marrow from APOA1-knockout mice displayed marked lymphocytosis as compared to wild-type bone marrow recipients. However, atherosclerotic lesion sizes and collagen contents were similar in the two groups of bone marrow recipients. In conclusion, systemic lack of APOA1 primes bone marrow stem cells for T cell lymphopoiesis. Our data provide novel evidence for a regulatory role of HDL in bone marrow functioning in normolipidemic mice.

Links between macrophages in perivascular adipose tissue and arterial wall: a role in atherosclerosis initiation?

BACKGROUND: Inflammation of adipose tissue in relation to atherosclerosis is currently widely studied in patients with advanced disease. However, data regarding polarization of adipose tissue and arterial wall macrophages and their mutual link in the early stages of atherosclerosis are scarce. The main aim of this cross-sectional study was to characterize macrophage subpopulations in arterial wall and adjacent adipose tissue; and to determine links between different subpopulations in a relatively healthy population living kidney donors. METHODS: The presence of cardiovascular risk factors was established in 68 living kidney donors. Macrophage polarization was analyzed by flow cytometry and confirmed by RT-PCR in samples of visceral adipose tissue, renal artery and adjacent perivascular adipose tissue collected during hand-assisted retroperitoneoscopic nephrectomy. RESULTS: CD14+CD16+CD36high macrophages were found only in adipose tissues and were strongly positively associated with several cardiovascular risk factors. The CD14+CD16+CD36low subpopulation was positively associated with the presence of several cardiovascular risk factors to a lesser extent in all studied tissues. In contrast, the proportion of CD14+CD16-CD36low macrophages was negatively linked to several cardiovascular risk factors and increased in subjects on statin therapy. The proportion of CD14+CD16+CD36low macrophages in perivascular, not visceral adipose tissue was associated with that of both macrophage subtypes in the arterial wall, suggesting a direct link between perivascular adipose tissue and the arterial wall. CONCLUSIONS: We confirmed the association of three macrophage subtypes in adipose tissue and arterial wall to the studied cardiovascular risk factors. Macrophage polarization in perivascular, but not visceral adipose tissue was linked to macrophage polarization in the arterial wall.

Rapid Drop in Coronary Heart Disease Mortality in Czech Male Population-What Was Actually behind It?

The high mortality of coronary heart disease (CHD) among Czech men-one of the highest worldwide-began to decline in 1991 soon after the abolition of government subsidies to all foodstuffs rich in animal fat. As participants in the WHO MONICA Project, we were able to analyze the CHD risk factors just before and after this major economic change. We had previously documented that the originally subsidized prices decreased animal fat consumption and consequently non-HDL cholesterol concentrations in the population. By the early 1990s, no progress had been made in the treatment of acute myocardial infarction, statins were unavailable as was not the currently more effective antihypertensive therapy. Our recent research proved a close relationship between cholesterolemia and proinflammatory macrophages in adipose tissue and accelerated macrophage polarization with increased palmitate and palmitoleate contents in cell membrane phospholipids. By contrast, the proportion of proinflammatory macrophages decreases with increasing presence of n-3 fatty acids in the cell membrane. The combination of non-HDL cholesterol drop and a decreased proportion of proinflammatory macrophages due to replacement of alimentary fat decreased CHD mortality immediately.

Statins Directly Influence the Polarization of Adipose Tissue Macrophages: A Role in Chronic Inflammation.

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.

Polarization of Macrophages in Human Adipose Tissue is Related to the Fatty Acid Spectrum in Membrane Phospholipids.

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+CD36high 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.