Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lecithin:cholesterol acyltransferase (LCAT) and lysolecithin acyltransferase (LAT) are two activities carried out by the same plasma enzyme, but require different apoprotein activators. The LCAT reaction takes place primarily on high density lipoproteins (HDL) and is activated by serum albumin, whereas LAT takes place on low density lipoproteins (LDL) and is inhibited by albumin. In nephrotic syndrome (NS), the levels of serum albumin are reduced, whereas the LDL levels are increased, and therefore, the ratio of LAT/LCAT activities should be increased. To test this hypothesis, we estimated the lipid levels and the two enzyme activities in experimental NS induced in rats by the injection of anti-Fx1A antibody (passive Heymann nephritis). As found in other nephrotic conditions, the plasma lipid levels rose progressively as the proteinuria increased and the serum albumin concentration declined. In addition, the ratio of LAT/LCAT activities increased by about fourfold after nine days of induction of nephritis. The LCAT activity correlated positively and the LAT activity negatively with serum albumin levels. The esterified cholesterol correlated positively with LCAT activity in normal rats but negatively in nephrotic animals, indicating that most of the cholesteryl esters in NS may be non-LCAT derived. The free cholesterol/lecithin ratio, a known risk factor for atherosclerosis, increased significantly in nephrotic rats. Furthermore, since the increase in the LAT activity produces more disaturated lecithins, another putative risk factor, the cumulative risk of coronary heart disease may be increased in long-term NS.
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PMID:Plasma lipids and acyltransferase activities in experimental nephrotic syndrome. 277 94

The low-density lipoprotein (LDL) receptor (LDL-R) family consists of cell-surface receptors that recognize extracellular ligands and internalize them for degradation by lysosomes. The LDL-R is the prototype of this family, which also contains very-low-density lipoprotein receptors (VLDL-R), apolipoprotein E receptor 2, LRP, and megalin. The family members contain four major structural modules: the cysteine-rich complement-type repeats, epidermal growth factor precursor-like repeats, a transmembrane domain, and a cytoplasmic domain. Each structural module serves distinct and important functions. These receptors bind several structurally dissimilar ligands. It is proposed that instead of a primary sequence, positive electrostatic potential in different ligands constitutes a receptor binding domain. This family of receptors plays crucial roles in various physiologic functions. LDL-R plays an important role in cholesterol homeostasis. Mutations cause familial hypercholesterolemia and premature coronary artery disease. LDL-R-related protein plays an important role in the clearance of plasma-activated alpha 2-macroglobulin and apolipoprotein E-enriched lipoproteins. It is essential for fetal development and has been associated with Alzheimer's disease. Megalin is the major receptor in absorptive epithelial cells of the proximal tubules and an antigenic determinant for Heymann nephritis in rats. Mutations in a chicken homolog of VLDL-R cause female sterility and premature atherosclerosis. This receptor is not expressed in liver tissue; however, transgenic expression of VLDL-R in liver corrects hypercholesterolemia in experiment animals, which suggests that it can be a candidate for gene therapy for various hyperlipidemias. The functional importance of individual receptors may lie in their differential tissue expression. The regulation of expression of these receptors occurs at the transcriptional level. Expression of the LDL-R is regulated by intracellular sterol levels involving novel membrane-bound transcription factors. Other members of the family are not regulated by sterols. All the members are, however, regulated by hormones and growth factors, but the mechanisms of regulation by hormones have not been elucidated. Studies of these receptors have provided important insights into receptor structure-function and mechanisms of ligand removal and catabolism. It is anticipated that increased knowledge about the LDL-R family members will open new avenues for the treatment of many disorders.
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PMID:The mammalian low-density lipoprotein receptor family. 1044 20