Liver diseases, lipid hydroperoxides

Lithium compounds, bis(trimethylsilyl) peroxide reactions, 796-8, 799 Liver diseases, lipid hydroperoxides, 613 Liver microsomes, 4-hydroxynon-2-enal, 613-14... 

Contrary to LDL, high-density lipoproteins (HDL) prevent atherosclerosis, and therefore, their plasma levels inversely correlate with the risk of developing coronary artery disease. HDL antiatherogenic activity is apparently due to the removal of cholesterol from peripheral tissues and its transport to the liver for excretion. In addition, HDL acts as antioxidants, inhibiting copper- or endothelial cell-induced LDL oxidation [180], It was found that HDL lipids are oxidized easier than LDL lipids by peroxyl radicals [181]. HDL also protects LDL by the reduction of cholesteryl ester hydroperoxides to corresponding hydroperoxides. During this process, HDL specific methionine residues in apolipoproteins AI and All are oxidized [182]. 

Asai et al. (1999) determined that phospholipid hydroperoxides (PLOOH) are key products for oxidative injury in membranous phospholipid layers in the plasma, red blood cells (RBC), and liver of mice. The formation and accumulation of PLOOH have been confirmed in several cellular disorders, various diseases, and in aging. A lower PLOOH level was found in RBC of the spice-extract-fed mice (65 to 74% of the nonsupplemented control mice). The liver lipid peroxidizability induced with Fe2+/ascorbic acid was effectively suppressed in mice by dietary supplementation with the turmeric and capsicum extracts. Although no difference in the plasma lipids was observed, the liver triacylglycerol concentration of the turmeric-extract-fed mice was markedly reduced to half of the level in the control mice. These findings suggest that these spice extracts could act antioxidatively in vivo by food supplementation, and that the turmeric extract has the ability to prevent the deposition of triacylglycerols in the liver. 

Human serum paraoxonase (PON 1) is an esterase that is physically associated with high-density lipoprotein (HDL) and is also distributed in tissues such as liver, kidney, and intestine [38,39]. Activities of PON 1, which are routinely measured, include hydrolysis of organophosphates, such as paraoxon (the active metabolite of the insecticide parathion) hydrolysis of arylesters, such as phenyl acetate and lactonase activities. Human serum paraoxonase activity has been shown to be inversely related to the risk of cardiovascular disease [40,41], as shown in atherosclerotic, hypercholester-olemic, and diabetic patients [42-44]. In 1998 HDL-associated PON 1 was shown to protect LDL, as well as the HDL particle itself, against oxidation induced by either copper ions or free radical generators [45,46], and this effect could be related to the hydrolysis of the specific lipoproteins oxidized lipids such as cholesteryl linoleate hydroperoxides and oxidized phospholipids. Protection of HDL from oxidation by PON 1 was shown to preserve... 

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