The Influence of Adiponectin on Transport of Low-Density Lipoproteins through Human Endothelial Cell Monolayer In Vitro.

The influence of adiponectin, a protein secreted by adipocytes, on the activation of transendothelial LDL transport, the initial event of atherogenesis, was studied. The addition of adiponectin to the cultured endothelial hybridoma EA.hy926 cells did not affect both basal and TNF-stimulated transendothelial transport of LDL. In addition, adiponectin affects neither expression levels of CAV1, SCARB1, and ACVRL1 genes encoding proteins involved in transendothelial LDL transport, nor the MMP secretion by the EA.hy926cells. At the same time, adiponectin suppressed the TNF-stimulated IL-8 production and expression of the adhesion molecule gene ICAM1 in these cells. Thus, adiponectin reduces proinflammatory activation of EA.hy926 cells, which is not accompanied by changes in the transendothelial LDL transport. We speculate that anti-inflammatory action of adiponectin is the base for the influence of this adipokine on atherogenesis.

[Adiponectin in normal and atherosclerotic intima of human aorta]. / Adiponektin v normal'noi i ateroskleroticheski izmenennoi intime aorty cheloveka.

BACKGROUND: Adiponectin (AN) is a protein synthesized by adipocytes that has regulatory effects on lipid and lipoprotein metabolism, increases tissue sensitivity to insulin, and modulates endothelial functions and inflammatory response. However, its involvement in the processes of atherogenesis remains poorly understood. OBJECTIVE: To determine the localization and sources of AN in atherosclerotic and normal human aortic intima. MATERIAL AND METHODS: Immunohistochemical study was performed on sections of atherosclerotic and normal human aorta obtained during autopsy. Reverse transcription real-time PCR was performed using biopsies of para-aortic and abdominal adipose tissue, intima-media of the thoracic aorta, atherosclerotic plaques of the human carotid and femoral arteries, as well as on endothelial cells isolated from the human thoracic aorta. Transendothelial transport of AN was evaluated in a two-chamber model using a monolayer of human endothelial cell hybridoma EA.Hy926. RESULTS: It has been established that AN is present in atherosclerotic but not in normal human aortic intima. At the same time, AN ADIPOQ mRNA was not detected either in the intima media of the human aorta, nor in isolated endothelial cells of the aorta, nor in cells of atherosclerotic plaques of the carotid and femoral arteries. AN slowly penetrated the endothelial monolayer in vitro, but this transport was significantly enhanced by the action of tumor necrosis factor-alpha (TNFa). CONCLUSION: Obtained data indicate that AN is present in atherosclerotic but not in normal aortic intima. We assume that AN is not synthesized by the cells of normal and atherosclerotic arterial walls, but permeates from the plasma. Transendothelial transport of AN, like many other plasma proteins, is activated during the development of atherosclerotic lesions, apparently under the action of pro-inflammatory cytokines, in particular, TNFα.

[The Influence of Adiponectin on Production of Apolipoproteins A-l and E by Human Macrophages].

Adiponectin is an adipose tissue hormone affecting energy and lipoprotein metabolism and modulating inflammatory responses. However, the role of this adipokine in atherogenesis remains poorly understood. The aim of this study was to investigate the effect of adiponectin on the production of apolipoproteins (apo) A-l and E by human macrophages (MP). The study was conducted on macrophage-like cells of the THP-1 cell line of two differentiation terms, 3 and 5 days (3d and 5d). Adiponectin (10 µg/mL) stimulated the expression of apoA-1 gene at the mRNA level in 5d MP, but not in 3d MP. The level of apoE mRNA in MP under the action of adiponectin was not affected. Adiponectin suppressed macrophage TNF gene expression, while it induced the expression of IL-10 gene in 5d MP. The secreted levels of apoA-1 and apoE proteins under the action of adiponectin in macrophages of both periods of differentiation remained unchanged, while the level of the surface apoA-1 protein in 5d MP was decreasing. Incubation of 5d MP with the PPARα nuclear receptor antagonist MK-886 or with the nuclear receptor LXR agonist TO-901317 resulted in cancellation of the stimulating effect of adiponectin on apoA-1 gene expression. These data indicate that adiponectin, in addition to its anti-inflammatory action, has a modulating effect on production of apoA-1 by macrophages. The latter is probably one of the mechanisms of the influence of this adipokine on atherogenesis.

[Role of adipokines and nonesterified fatty acids in the development of insulin resistance].

The purpose of the study was to reveal a possible role of adipokines, biologically active adipose tissue proteins (leptin and adiponectin) and nonesterified fatty acids in generating insulin resistance (IR). One hundred and fifty-seven patients (90 females and 67 males) aged 57.5±9.2 years were enrolled in the study. According to the HOMA index for IR, the patients were divided into 3 equal groups. The examinees with a high HOMA index were found to have elevated levels of fatty acids, leptin and decreased concentrations of adiponectin. At the same time according to the linear regression analysis, all these indices are its independent determinants. However, analysis of the data in the groups of patients with different body weight revealed that the increased concentrations of fatty acids and leptin may play a role in the development of IR in subjects with obesity while the higher level of fatty acids and lower adiponectin may be involved in patients without noticeable obesity. Thus, it may be assumed that leptin, adiponectin and nonesterified fatty acids may affect the development of IR; however, their contribution depends on the degree of adiposity.