LDL: da síndrome metabólica à instabilização da placa aterosclerótica

Abstract

The dyslipidemia of the metabolic syndrome (MS) confers an elevated cardiovascular risk and is characterized by increased concentrations of triglycerides, decreased HDL-cholesterol and qualitative alterations in LDL which renders it more atherogenic, like the small dense LDL. Modified forms of LDL (mLDL) have been detected in vivo in the plasma and atherosclerotic plaques. A minor fraction of the total LDL has an electronegative charge and is represented by a heterogenic subpopulation of particles [LDL(-)], with higher potential to induce endothelial injury. It could be derived from oxidation, glication or other processes that alter its chemical composition and is increased in diabetic, hypercholesterolemic subjects, and in those with established coronary artery disease. mLDL are internalized by macrophages through scavenger receptors, originating foam cells and inducing an immune-inflammatory reaction. In the atherosclerotic process, the action of mLDL continues until plaque rupture and thrombogenesis, when it promotes apoptosis in endothelial and smooth muscle cells, and activates matrix metalloproteinases, weaken the fibrous cap, and further enhance the inflammatory process that ends in the thrombus formation. Development of new laboratory methods is necessary to enhance the clinical applicability of mLDL and the predictive power of the conventional lipid profile and other cardiovascular risk factors of the MS.

Perfil lipídico em escolares de Recife - PE

“…However, it is important to mention that there are subclasses of LDL, as one LDL is small and dense (LDL phenotype B) and another, which is larger. The LDL phenotype B, being smaller and denser, more easily cross the endothelial barrier and are more easily oxidable, which also makes them more atherogenic 27 . Thus, even in individuals with normal LDL-c levels, the lipid profile can be less favorable, given the proportion between the lipoprotein subclasses 28 .…”

Epidemiologia nutricional

“…A dislipidemia da SM caracteriza-se por hipertrigliceridemia, concentrações baixas de HDL (lipoproteína de alta densidade) e presença de partículas pequenas e densas de LDL (lipoproteína de baixa densidade) (Siqueira, Abdalla & Ferreira, 2006). O grande aporte de AGL ao fígado resulta na produção de VLDL, rica em triglicérides.…”

HDL: o yin-yang da doença cardiovascular

“…Essas células apresentam receptores denominados scavenger que reconhecem partículas de LDL modificadas por glicação, oxidação, carbamilação e associação com imunocomplexos. Quando colesterol entra na célula por meio desses receptores, não há ativação do mecanismo de contrarregulação da entrada de colesterol e ela passa a acumulá-lo, dando origem às chamadas células espumosas (19,20).…”