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[Hereditary changes of apolipoproteins B and E]
Insights
Patients with hyperlipoproteinemia and familial hypercholesterolemia experience accelerated atherosclerosis due to lipoprotein accumulation. Macrophages engulf these lipoproteins, becoming foam cells and driving atherogenesis.
Area of Science:
- Cardiovascular Science
- Metabolic Disorders
- Lipid Metabolism
Context:
- Accelerated atherosclerosis is observed in patients with type III hyperlipoproteinemia and familial hypercholesterolemia.
- Lipoprotein remnants, including chylomicron remnants and very-low-density lipoprotein (VLDL) remnants/intermediate-density lipoprotein (IDL), accumulate in type III hyperlipoproteinemia, correlating with coronary disease.
- Defective apolipoprotein E (Apo E) impairs normal receptor-mediated catabolism of these lipoproteins.
Purpose:
- To elucidate the mechanisms linking specific dyslipidemias to atherogenesis.
- To understand the role of macrophages in the development of atherosclerotic lesions.
- To identify the molecular interactions between lipoproteins and macrophage receptors.
Summary:
- Type III hyperlipoproteinemia involves accumulating intestinal and hepatic lipoprotein remnants, linked to coronary disease, due to defective Apo E.
- Familial hypercholesterolemia is characterized by elevated IDL from defective LDL receptors, and familial defective Apo B100 increases LDL due to impaired LDL receptor interaction.
- Macrophages, derived from monocytes, are central to atherogenesis, acting as progenitors of foam cells by expressing receptors for chylomicron remnants, VLDL remnants, and modified low-density lipoprotein (LDL).
Impact:
- Provides insight into the pathogenesis of atherosclerosis in specific genetic lipid disorders.
- Highlights the critical role of macrophages in foam cell formation and lesion development.
- Establishes a link between specific lipoprotein abnormalities and the cellular mechanisms driving cardiovascular disease.
Abstract:
Accelerated atherosclerosis occurs in patients with type III hyperlipoproteinemia and familial hypercholesterolemia. The accumulation of chylomicron remnants of intestinal origin and of VLDL remnants or IDL of hepatic origin observed in type III hyperlipoproteinemia appears to correlate with coronary disease. The presence of defective forms of Apo E prevents normal receptor-mediated catabolism of these lipoproteins. Patients with familial hypercholesterolemia have an elevation of plasma IDL secondary to defective LDL receptors that impair normal catabolism. Familial defective Apo B100 is secondary to an abnormality of Apo B100 that prevents the normal interaction of LDL with the LDL receptor and increases plasma LDL. Macrophages (which are derived from circulating monocytes) have emerged as a key component in atherogenesis because they appear to be progenitors of foam cells in arterial lesions. Macrophages express receptors that recognize chylomicron remnants and VLDL remnants and chemically modified LDL. Thus, in the presence of these specific lipoproteins, macrophages are converted to cells that resemble foam cells.