Electrophoretic separation of plasma lipoproteins in agarose gel

Alcohol taken in moderation may prevent atherosclerosis, whereas heavy drinking has the opposite effect, in part by promoting oxidation of low density lipoproteins (LDL), a pathogenetic factor in atherogenesis. We assess here: 1 ) whether similar alterations can be reproduced in baboons fed 50% of energy as ethanol (the average intake of alcoholics) for 7-8 years, and 2 ) whether such alterations are affected by supplementation with polyenylphosphatidylcholine (PPC), a mixture of polyunsaturated phosphatidylcholines, shown to prevent alcoholic fatty liver, fibrosis, and cirrhosis. Ten animals were given the ethanolcontaining diet and ten were pair-fed isocaloric control diets. In half of the pairs, the diets were supplemented with 2.8 g of polyenylphosphatidylcholine/1000 kcal. Alcohol feeding increased LDL-lipoperoxides and made LDLproteins more negatively charged, changes that were attenuated or prevented by PPC. The oxidizability of LDL was determined in vitro by the formation of conjugated dienes after oxidation with copper. Alcohol shortened the lag time (which measures LDL antioxidant capacity); this effect was normalized by PPC supplementation. By contrast, PPC produced no changes in the controls. Thus polyenylphosphatidylcholine, by markedly attenuating the ethanol-induced increase in LDL oxidation, opposes one of the effects whereby alcohol promotes atherosclerosis. -Navder, K.

Section: Ldl Isolationmentioning

confidence: 99%

Oxidation of LDL in baboons is increased by alcohol and attenuated by polyenylphosphatidylcholine

Navder

Baraona

Leo

et al. 1999

“…The isolation was carried out without any EDTA and was completed in less than 3 h. The isolated LDL was dialyzed against phosphate buffered saline (PBS) at 4 Њ C for 4-6 h (38). The purity of the isolated LDL samples was established by agarose and acrylamide gel electrophoresis (38,39).…”

Section: Ldl Isolationmentioning

confidence: 99%

Estradiol as an antioxidant: incompatible with its physiological concentrations and function

Santanam

Shern-Brewer

Mcclatchey

et al. 1998

Estradiol has been documented to inhibit the oxidation of low density lipoprotein (LDL). We show that physiological concentrations of estradiol do not inhibit the oxidation of LDL by copper. LDL samples isolated from a ) premenopausal and postmenopausal women and from b ) women at different time periods during their menstrual cycle, who differ vastly in plasma estradiol levels, were also oxidized at the same rates by copper. In contrast, LDL samples isolated from c ) women who were hyperstimulated during in vitro fertilization (IVF), with estradiol concentrations above 2000 pg/ml, were resistant to oxidation by copper. However, these LDL samples were also oxidized at a higher rate by peroxidases. More importantly, subjects with high estradiol levels also showed an increase in myeloperoxidase (MPO) protein in the plasma. Based on these results, we conclude that at physiologic concentrations, it is unlikely that estradiol could act as an antioxidant. In fact, the ability of estradiol to induce MPO and become a prooxidant might instead suggest that MPO-mediated oxidative clearance of LDL from plasma by liver might favorably influence the outcome of atherosclerosis.-

“…In addition, the concentrations of apoA-I and total apoC were estimated based upon chromogenicity factors for human apoA-I and apoC-III (L. Kotite, R. Havel, unpublished data). The electrophoretic mobility of lipoprotein fractions was determined by staining with Sudan black B after separation by agarose gel electrophoresis (22). Non-denaturing 2-14% gradient gel electrophoresis of plasma, with lipid staining, and calculation of lipo-protein particle sizes from calibration curves was performed as described previously (23).…”

Section: Separation and Characterization Of Mouse Lipoproteinsmentioning

confidence: 99%

Metabolism of lipoproteins containing apolipoprotein B in hepatic lipase-deficient mice

Qiu

Bergeron

Kotite

et al. 1998

Mice lacking hepatic lipase have been reported to express mild hyperlipidemia characterized by increased concentrations of large high density lipoproteins, but normal concentrations of lipoproteins containing apolipoprotein B. Whereas hepatic lipase has been implicated in the clearance and processing of chylomicron remnants in rats, no such defect was found in these mice. We have further characterized the abnormal lipoprotein phenotype in young hepatic lipase-deficient mice and have found more pronounced elevations of high density lipoproteins associated in particular with a 5-fold increase in plasma concentrations of apolipoprotein E. In addition, there was a reduction in the concentration of low density lipoproteins containing apolipoprotein B-100 and B-48 relative to precursor lipoproteins of lower density and a pronounced deficiency of apolipoprotein B-containing low density lipoproteins with density exceeding 1.029 g/mL. Conversion of radiolabeled rabbit intermediate density lipoproteins to low density lipoproteins was reduced by 6-fold as compared with wild-type mice. Although clearance of cholesteryl ester-labeled chylomicrons from the blood was unimpaired in the deficient mice, that of chylomicron remnants was reduced. Furthermore, endocytosis of chylomicron cholesteryl esters into liver cells occurred more rapidly than in wild-type mice. The unimpaired hepatic clearance of injected chylomicron particles in hepatic lipase-deficient mice may be the result of greater acquisition of apoE from high density lipoproteins during remnant formation. These studies thus demonstrate a critical role for mouse hepatic lipase in the formation of small, dense low density lipoproteins, as well as participation in the normal clearance and processing of chylomicron remnants.