Hyperlipidemias: Kiss RS

Do R, Kiss RS, Gaudet D, Engert JC. · Department of Human Genetics, McGill University, Montreal, Quebec, Canada. · Clin Genet. · Pubmed #19054015 No free full text.

Abstract: High levels of plasma low-density lipoprotein cholesterol (LDL-C) are a significant risk factor for heart disease. Statins (3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors) have been extensively used to treat high-plasma LDL-C levels and are effective in preventing heart disease. However, statins can be associated with adverse side effects in some patients and do not work effectively in others. As an alternative to statins, the development of cholesterol-lowering agents that directly inhibit squalene synthase have shown promise. Clinical studies have shown that squalene synthase inhibitors are effective in lowering plasma levels of total cholesterol and LDL-C. Squalene synthase plays an important role in the cholesterol biosynthesis pathway as it is responsible for the flow of metabolites into either the sterol or the non-sterol branches of the pathway. In addition, variants of the squalene synthase gene appear to modulate plasma cholesterol levels in human populations and therefore may be linked to cardiovascular disease. In this review, we examine squalene synthase and the gene that codes for it (farnesyldiphosphate farnesyltransferase 1). In particular, we investigate their role in the regulation of cellular and plasma cholesterol levels, including data that suggest that squalene synthase may be involved in the etiology of hypercholesterolemia.

Kiss RS, Kavaslar N, Okuhira K, Freeman MW, Walter S, Milne RW, McPherson R, Marcel YL. · University of Ottawa Heart Institute, 40 Ruskin St, Ottawa, Ontario, K1Y 4W7, Canada. · Arterioscler Thromb Vasc Biol. · Pubmed #17303779 links to  free full text

Abstract: OBJECTIVE: We have used a multitiered approach to identify genetic and cellular contributors to high-density lipoprotein (HDL) deficiency in 124 human subjects. METHODS AND RESULTS: We resequenced 4 candidate genes for HDL regulation and identified several functional nonsynonymous mutations including 2 in apolipoprotein A-I (APOA1), 4 in lecithin:cholesterol acyltransferase (LCAT), 1 in phospholipid transfer protein (PLTP), and 7 in the ATP-binding cassette transporter ABCA1, leaving 88% (110/124) of HDL deficient subjects without a genetic diagnosis. Cholesterol efflux assays performed using cholesterol-loaded monocyte-derived macrophages from the 124 low HDL subjects and 48 control subjects revealed that 33% (41/124) of low HDL subjects had low efflux, despite the fact that the majority of these subjects (34/41) were not carriers of dysfunctional ABCA1 alleles. In contrast, only 2% of control subjects presented with low efflux (1/48). In 3 families without ABCA1 mutations, efflux defects were found to cosegregate with low HDL. CONCLUSIONS: Efflux defects are frequent in low HDL syndromes, but the majority of HDL deficient subjects with cellular cholesterol efflux defects do not harbor ABCA1 mutations, suggesting that novel pathways contribute to this phenotype.