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PubMed1966

Lipid transfer between human serum high density lipoproteins and egg yolk lipoproteins in incubation mixtures.

Ultracentrifugally isolated human serum high density lipoproteins of d 1.063-1.21 (HDL) were incubated with egg yolk lipoproteins of d < 1.006 for up to 24 hr at various concentrations. Transfer of HDL cholesterol esters to egg yolk lipoproteins occurred simultaneously with transfer of glycerides from egg yolk lipoproteins to HDL. These observations show that exchange of lipids can take place between lipoproteins in the absence of other serum proteins and enzymes. The mole ratios of HDL cholesterol esters to glycerides approached an integral value of 1 : 1 during the course of the incubation. These results suggest that lipid components form complexes within the HDL structure.

Adult↗
PubMed1984

Estradiol-induced alteration of very-low-density lipoprotein assembly. Possible competition among apoproteins for incorporation into nascent very-low-density lipoprotein.

The hypothesis that the apoprotein composition of nascent very-low-density lipoprotein (VLDL) secreted by the hepatocyte is determined by the relative rates of apoprotein synthesis and their affinities of binding to VLDL was tested using chick hepatocytes in monolayer culture. Chick cells were chosen for the study of lipoprotein assembly since estradiol treatment can be used to alter the composition of the apoprotein mixture synthesized by these cells. The secretion of apoprotein (apo) B by estradiol-treated hepatocytes was elevated 4.2-fold above the basal level measured in control cells. Furthermore, estradiol-treated cells secreted apo-II, a major VLDL apoprotein not synthesized prior to estradiol treatment, at a level equivalent to that of apo-B. However, no difference in the secretion of apo-A-I and other newly identified nascent VLDL apoproteins was detected. These changes in relative rates of apoprotein synthesis altered the composition of nascent VLDL secreted by control versus estradiol-induced cells from: apo-B, 22 to 40%; apo-II, 0 to 32%; apo-37 kDa, 14 to 6%; apo-A-I, 31 to 12%; apo-17 kDa, 10 to 4%; apo-9 kDa, 15 to less than 10%; and apo-6 kDa, 8 to less than 2%. To investigate the basis for the preferential incorporation of apo-B and apo-II into nascent VLDL, the relative affinities of the apoproteins for VLDL were compared by measuring their capacities to transfer from VLDL into other lipoprotein or nonlipoprotein density classes. Culture medium containing [3H]leucine-labeled VLDL was incubated with plasma deficient in lipoproteins of rho less than 1.006 g/ml. Within 30 min of incubation at 37 degrees C, 3H-labeled apo-A-I and apo-9 kDa exchanged between VLDL and high-density lipoprotein, whereas apo-37 kDa exchanged between VLDL and the rho greater than 1.21 g/ml fraction. Neither apo-B nor apo-II underwent transfer from nascent VLDL. These results suggest that the relative rates of input of apoproteins into the secretory pathway and their affinities of binding to the nascent VLDL particle determine their extent of incorporation into, and, thus, the apoprotein composition of secreted VLDL.

Animals↗
PubMed1984

Studies on the apoproteins of the major lipoprotein of the yolk of hen's eggs. V. Protein sulfhydryl groups: accessibility in the lipoprotein and the effect of temperature.

Sulfhydryl groups in the apoproteins of the major lipoprotein (density 0.95 g/ml) of hen's egg yolk have been studied by colorimetry, analysis for carboxymethylcysteine, and labelling with [14C]iodo-compounds and their distribution amongst the individual apoproteins (i.e. apovitellenins I-VI) has been determined. In the intact lipoprotein, reaction of sulfhydryl groups with aqueous reagents was slower than in the apoprotein mixture and there were large differences amongst different reagents in the extent of reaction. If the lipoprotein was heated for a short time in 1 mM EDTA above about 70 degrees C and then cooled, more sulfhydryl groups were accessible although the total number did not change. This increase in accessibility was accompanied by the disruption of the lipoprotein structure and an increase in the viscosity of its solutions. Furthermore, the isolated apoprotein mixture was less soluble in urea solutions and formed a gel, probably as a result of cross-linking by inter-protein disulfides. There was also a small change in the distribution of sulfhydryl groups so it is likely that sulfhydryl-disulfide interchanges occurred on heating. It is suggested that such interchanges help determine the physical properties of heated yolk and that in the intact lipoprotein sulfhydryl groups are concealed to prevent sulfhydryl-disulfide interchanges in the egg.

Animals↗
PubMed1983

Lipoproteins of the extravascular space: alterations in low density lipoproteins of interstitial inflammatory fluid.

Although extrahepatic degradation of low density lipoproteins (LDL) by peripheral cells is considered to be a significant component of daily cholesterol homeostasis, the nature of lipoproteins in the extravascular space has not been well described. Using a sponge implantation model in the rabbit, we examined lipoproteins prepared from interstitial inflammatory fluid. Inflammatory fluid cholesterol is correlated with plasma values, (r = 0.735, P less than 0.01), but triglyceride values are not. Examination of inflammatory fluid lipoproteins by agarose gel electrophoresis, column chromatography, and density gradient centrifugation revealed a marked reduction in LDL concentration as compared to plasma LDL. Inflammatory fluid low density lipoproteins prepared by sequential density flotation had a larger mean diameter, they were erratic in shape, and contained more triglyceride and less cholesterol and cholesteryl ester than plasma LDL. Total cholesterol to protein ratio was significantly reduced in inflammatory fluid LDL (0.73 vs. 1.10, P less than 0.05). Inflammatory fluid LDL migrated further than plasma LDL on agarose electrophoresis, despite similar apoprotein patterns. These data concur with findings of altered composition and electrophoretic mobility of plasma LDL modified in vitro by exposure to acetylating agents, malondialdehyde, or aortic cells in culture, and they may represent the actual form of LDL in the extravascular space.

Animals↗
PubMed1982

Rat plasma lipoproteins: re-evaluation of a lipoprotein system in an animal devoid of cholesteryl ester transfer activity.

Plasma lipoproteins from male rats were isolated by rate zonal centrifugation. Four lipoproteins were identified: VLDL, LDL, HDL1, and HDL2. LDL, HLD1, and some HDL2 distributed within the salt density interval of 1.006-1.085 g/ml, while HDL2 was found in the 1.063-1.21 g/ml interval. HDL3 was not identified in the rat. Rat VLDL is poor in cholesteryl esters (1.5-3.0% of total mass) and nearly lacks the smaller and denser particle subpopulation which is predominant in humans. Rat LDL, containing a relatively large amount of triglyceride (20.2% of total mass) and a small amount of cholesteryl ester (27.5%), could be isolated free of apoproteins other than apoB. HDL1 is a cholesteryl ester-rich lipoprotein that occupies a density interval overlapping both LDL and HDL2. ApoE is the major protein constituent of HDL1; apoA-I, A-IV, and C are also present. Apo-A-I-rich HDL2 is the only human-like HDL subpopulation found in rats. Lipoproteins from fasted and non-fasted rats were essentially similar. Arachidonic acid contributed 56.7% and 72.3% of total cholesteryl ester fatty acids in HDL1 and HDL2, respectively, but only 7.9% and 27.3% in VLDL and LDL, respectively. Palmitic, palmitoleic, and oleic acids were the major cholesteryl ester fatty acids in VLDL and LDL. In vitro incubation of biosynthetically labeled HDL2 cholesteryl ester with rat plasma demonstrated minimal transfer of the labeled cholesteryl ester to VLDL and LDL. These results indicate biological immiscibility of HDL cholesteryl esters with those of lower density lipoproteins. The finding of cholesteryl ester-poor VLDL and LDL and the presence of HDL as larger and less dense subpopulations is compatible with the absence of cholesteryl ester transfer activity in an animal with pronounced LCAT activity.

Animals↗
PubMed1994

Macrophage-mediated oxidation of extracellular low density lipoprotein requires an initial binding of the lipoprotein to its receptor.

Cells of the arterial wall including macrophages were shown to oxidize low density lipoprotein (LDL) in vitro. Upon incubation of LDL with J-774.A1 macrophage-like cell line for 18 h in the presence of 1 microM CuSO4, extensive macrophage-mediated oxidation of the LDL fatty acids and cholesterol moieties was demonstrated. Similar results were found with mouse peritoneal macrophages or human monocyte-derived macrophages. Several lines of evidence suggest that LDL binding to the LDL receptor on macrophages is required for the cell-mediated oxidation of LDL. 1) Incubation of the cells in the presence of monoclonal antibody to the LDL receptor (IgG-C7), substantially inhibited lipoprotein oxidation. 2) Pretreatment of LDL with monoclonal antibodies to the LDL receptor binding domains on the LDL apoB-100 (mAbs B1B6 and B1B3) inhibited cell-mediated oxidation of LDL by 52-95%. 3) Down-regulation of the macrophage LDL receptors (by preloading the cells with cholesterol) reduced LDL oxidation by 42%. 4) Up-regulation of the LDL receptor (by macrophage incubation in serum-free medium) was associated with 80% elevation in LDL oxidation. 5) Macrophage activation with lipopolysaccharide up-regulated the LDL receptors and was associated with up twofold increase LDL oxidation. 6) Human monocyte-derived macrophages from a patient with homozygous familial hypercholesterolemia, which lack the LDL receptor, failed to oxidize the LDL. 7) On using acetylated LDL or methylated LDL, which do not bind to the LDL receptor, macrophage-mediated oxidation of the lipoprotein did not occur. The binding of LDL to the macrophage LDL receptor under oxidative stress induced the oxidation of extracellular unbound LDL as demonstrated by cell-mediated lipid peroxidation of mAb B1B6-treated LDL by cells that were preincubated with native LDL. Furthermore, macrophage conditioned medium (MCM) that was obtained after 5 h of cells preincubation with native LDL under oxidative stress (1 microM CuSO4), followed by lipoprotein removal and a further 18 h of cell incubation (but not MCM that was similarly obtained without cell preincubation with LDL), was found to contain oxidized linoleic and arachidonic acids and was able to induce LDL lipids peroxidation. In conclusion, macrophage-mediated oxidation of LDL requires an initial binding of the lipoprotein to the LDL receptor on the cell surface under oxidative stress. This interaction leads to the formation and release of cellular oxidized polyunsaturated fatty acids that can oxidize the LDL molecule extracellularly.

Acetylation↗
PubMed1994

Oxidized low density lipoprotein leads to macrophage accumulation of unesterified cholesterol as a result of lysosomal trapping of the lipoprotein hydrolyzed cholesteryl ester.

The early atherosclerotic lesion is comprised of foam cell macrophages filled with cholesteryl ester (CE), unesterified cholesterol (UC), and cholesterol oxides. Upon incubation of macrophages with oxidized low density lipoprotein (Ox-LDL), they accumulate UC rather than CE, which was shown to accumulate after incubation of cells with acetylated LDL (Ac-LDL). Using lipoproteins that were doubly labeled in their CE as well as in their protein moieties, we have demonstrated that lysosomal hydrolysis of the Ox-LDL CE was similar to the hydrolysis of the CE in Ac-LDL or native LDL whereas, as shown previously, a markedly impaired degradation of the protein moiety of Ox-LDL was observed. Cell fractionation revealed that the UC was derived from the hydrolyzed CE in Ox-LDL and was trapped in the macrophage lysosomal fraction, whereas in cells incubated with Ac-LDL, the lipoprotein UC was rapidly transported to the microsomal and cytosolic compartments. Lysosomal accumulation of Ox-LDL-derived UC could be related to the effect of the oxysterols in Ox-LDL, as oxidation of Ac-LDL or incubation of macrophages with Ac-LDL in the presence of oxysterols, in comparison to cell incubation with Ac-LDL, resulted in lysosomal accumulation of unesterified cholesterol. As a consequence of lysosomal trapping of Ox-LDL-derived UC, its availability to esterification was markedly impaired (by 6-fold), in comparison to the cholesterol esterification rate of Ac-LDL-derived UC. However, when the cholesterol esterification was expressed per lysosomal released UC, cellular cholesterol esterification rate of Ox-LDL-derived UC was found to be similar to that of Ac-LDL-derived UC. High density lipoprotein (HDL)-mediated efflux of the Ox-LDL-derived cholesterol from macrophages was similar to that found for Ac-LDL-derived cholesterol after 24 h of cell incubation with HDL3. Major defects in the cellular metabolism of Ox-LDL-derived 7-ketocholesterol were also found and could be related to its lysosomal trapping (together with the UC), its limited capacity to be esterified, and a 40% reduction in its HDL-mediated efflux from macrophages, in comparison to the efflux of the Ox-LDL-derived UC. We conclude that upon incubation of macrophages with Ox-LDL, lysosomal hydrolysis of the lipoprotein CE is not impaired but cellular accumulation of the Ox-LDL-derived UC occurs as a result of trapping of the hydrolyzed CE in the macrophage lysosomal compartment which may be related to the effect of oxysterols in Ox-LDL.

Animals↗
PubMed1977

Improved assessment of plasma lipoprotein patterns. III. Direct measurement of lipoproteins after gel-electrophoresis.

Based on a previously described technique [Clin. Chem. 19, 737 (1973)] of precipitating plasma lipoproteins with polyanions after their electrophoretic separation in gels, a new method is presented for measuring normal plasma lipoproteins densitometrically. The method is fast and easy; the CV for beta-, pre-beta-, and alpha-lipoproteins was less than 5% in one series. Results are linearly related to concentration up to 10 g of total lipoprotein per liter. No unusual equipment is required. Standardization is done with the aid of a commercially available filter. Total plasma cholesterol and cholesterol calculated from quantified lipoprotein fractions were highly (r = 0.963) correlated.

Adult↗
PubMed1997

Alcohol feeding impedes early atherosclerosis in low-density lipoprotein receptor knockout mice: factors in addition to high-density lipoprotein-apolipoprotein A1 are involved.

The effect of alcohol feeding on the development of atherosclerosis was investigated in low-density lipoprotein receptor gene-knockout (LDLR-/-) mice. Eight-week-old male mice were pair-fed atherogenic liquid diets containing ethanol at different levels (w/v; group A, 5%; group B, 2.5%; and group C, 0%). Tissue sections of the heart were stained with Oil Red O to examine for fatty lesions in proximal aorta. Results showed that the lesion size of group A was 70% smaller than group C after 6 weeks. By contrast, the lesion size of group B was not significantly different from that of group C. Serum high-density lipoprotein-apolipoprotein A1 (apo A1) A1 in LDLR-/- mice was suppressed by feeding the atherogenic diet, but the decrease was negated by alcohol (both groups A and B). The effectiveness of 5% alcohol to protect against atherosclerosis waned with time, but was still noticeable at 12 weeks, even though serum apo A1 remained high. Serum apolipoprotein E was increased by the high fat diet, but not altered by alcohol in the diet. Our data, therefore, show that: (1) alcohol-feeding impedes early atherosclerosis in LDLR-/- mice (this effect of alcohol is dose-dependent); (2) the protective effect of alcohol is not entirely attributable to an elevated serum high-density lipoprotein-apo A1; and (3) severe impairment of lipoprotein metabolism due to a lack of low-density lipoprotein receptors can eventually overwhelm the protective effect of alcohol against atherosclerosis.

Alcohol Drinking↗
PubMed1998

Mild oxidation of lipoproteins increases their affinity for surfaces covered by heparan sulfate and lipoprotein lipase.

Lipoprotein lipase (LPL) is present in cells involved in development of atherosclerosis (endothelial cells, smooth muscle cells, and macrophages). A direct involvement of LPL in atherogenesis has been suggested. Previously we used the surface plasmon resonance technique to study the interaction of lipoproteins with surfaces covered by heparan sulfate proteoglycans (HSPG) and LPL [A. Lookene et al. (1997) Biochemistry 36, 5267-5275]. The binding was much increased by the presence of LPL. Here we demonstrate that mild oxidation of low-density-lipoprotein (LDL) and very-low-density lipoprotein (VLDL) in vitro increases their binding to surfaces covered by HSPG and LPL, while extensive oxidation decreases it. Similar results were obtained with a lipid emulsion (Intralipid), indicating that oxidation-induced changes of the lipid part could explain the effects. LPL increased binding and uptake of the mildly oxidized (compared to nonoxidized) LDL by THP-I monocyte-derived macrophages. Our studies indicate that LPL has the highest affinity for mildly oxidized LDL and support its involvement in development of atherosclerosis.

Animals↗
PubMed1987

Net lipid transfer between lipoproteins in fish-eye disease plasma supplemented with normal high density lipoproteins.

Native fish-eye disease plasma, which is deficient of both high density lipoproteins (HDL) and lecithin-cholesterol acyltransferase activity (alpha-LCAT), processing the free cholesterol of these lipoproteins, has been supplemented with normal isolated HDL2 or HDL3 and incubated in vitro at 37 C. After incubation for 0, 7.5 and 24 hr the very low density (VLDL) and low density (LDL) lipoproteins as well as HDL were isolated, and their contents of triglycerides, phospholipids and free, esterified and total cholesterol were quantified. The resulting net mass transfer of the different lipids revealed a functioning transfer of cholesteryl esters and all other analyzed lipids between the lipoproteins, although no de novo esterification of the HDL cholesterol by LCAT in this plasma occurred. In accordance with previous findings there was a functioning esterification process of the free cholesterol of the combined VLDL and LDL of fish-eye disease plasma. The present reports make it reasonable to conclude that the lack of HDL cholesterol esterification in this disease is not a result of a deficiency of cholesteryl ester transfer or lipid transfer activities.

Cholesterol↗
PubMed2000

Binding of human lipoproteins (low, very low, high density lipoproteins) to recombinant envelope proteins of hepatitis C virus.

Heterogeneities in the density of hepatitis C virus (HCV)-RNA-carrying material from human sera (1.03-1.20 g/ml) are partially due to the binding of lipoproteins [low density (LDL), very low density (VLDL), high density (HDL) lipoproteins] and immunoglobulins. In this study we demonstrate the binding of recombinant HCV envelope protein (El/E2) to human LDL, VLDL and HDL on a molecular basis. The binding of lipoproteins was restricted to the middle part of the El gene product (amino acids 222-336) and the C-terminal part of the E2 protein (amino acids 523-809). Lipoproteins did not bind to recombinant HCV core protein.

Animals↗
PubMed1987

Metabolic consequences of genetic heterogeneity of lipoprotein composition (lipoprotein heterogeneity).

Lipoprotein composition varies among different genetic forms of hyperlipidemia. An increase in hepatic triglyceride (TG) synthesis in subjects with familial hypertriglyceridemia (FHTG) is associated with secretion of large, TG-enriched, very low-density lipoproteins (VLDL), which have an increased affinity for lipoprotein lipase (LPL) in vivo as compared with VLDL from subjects with familial combined hyperlipidemia (FCHL) or from normal subjects. Elevated levels of plasma low-density lipoprotein (LDL) apoprotein B in FCHL are associated with high apoprotein B production rates. The LDL in FCHL is heterogeneous, with a preponderance of an LDL subfraction, which is denser, smaller, and lipid poor as compared with LDL from normal subjects. The more buoyant LDL subfraction in FCHL seems to be catabolized more rapidly than this dense LDL subfraction.

Apolipoproteins B↗
PubMed1990

Effects of intravenous infusions of commercial fat emulsions (Intralipid 10 or 20%) on rat plasma lipoproteins: phospholipids in excess are the main precursors of lipoprotein-X-like particles.

Like most commercial parenteral emulsions, Intralipid contains the same amount of phospholipids (12 mg/ml) to stabilize 100 or 200 mg of soybean oil (10 or 20% formula, respectively). By centrifugation, 10 or 20% Intralipid was separated into a supernatant, fat particles containing the bulk of triacylglycerols stabilized by a fraction of phospholipids and an infranatant--called mesophase--consisting mainly of phospholipids used in excess as emulsifier. We observed that the initial triacylglycerol/phospholipid ratio of the emulsion (100/12 and 200/12, respectively) determines the size of the triacylglycerol-rich particles (260 and 350 nm) as well as the phospholipid content of the mesophase (6.02 and 4.67 mg/ml). To understand the mechanism of the lipoprotein-X (LPX) accumulation generally reported after intravenous fat infusions, plasma lipid levels and lipoprotein profiles were first compared in the rats after infusion (at a constant rate of 0.5 or 1 ml/h for 43 h) of Intralipid 10 or 20%. For the same intravenous triacylglycerol load (100 mg/h), rats infused with Intralipid 10% at 1 ml/h displayed higher triacylglycerol levels than rats infused with the 20% emulsion at 0.5 ml/h, suggesting that the size of exogenous fat particles modulated the catabolic rate of their triacylglycerols. The plasma levels of LPX varied according to the infusion rate of phospholipids not associated with triacylglycerol-rich particles of the emulsion. Moreover, an apo E and apo B enrichment of plasma and an elevation of the apo B48/apo B100 ratio was always observed after Intralipid infusions. In order to confirm that phospholipids of the mesophase are the main LPX precursors, lipoprotein profiles were then compared in the rats after intravenous infusion, at a constant rate of 1 ml/h, of either the mesophase or a suspension of triacylglycerol-rich particles isolated from Intralipid 20%. As expected, significant LPX amounts were only detected in rats infused with the pure mesophase of the emulsion. It was concluded that products of the lipolysis of exogenous fat particles play only a minor role in the formation of LPX. In fact these abnormal lipoproteins are generated by phospholipids of the mesophase which, like infused liposomes, actively mobilize endogenous free cholesterol. Consequently, in order to be considered as true chylomicron models for safe fat delivery in parenteral nutrition and in order to prevent some detrimental effects on cholesterol metabolism, commercial emulsions should be cleared of phospholipid excess.

Animals↗
PubMed1991

The NHLBI Twin Study: heritability of apolipoprotein A-I, B, and low density lipoprotein subclasses and concordance for lipoprotein(a).

Heritability of plasma apolipoprotein (apo) A-I, apo B, and low density lipoprotein (LDL) subclasses and concordance for lipoprotein(a) excess were assessed in 109 monozygotic (MZ) and 113 dizygotic (DZ) twin pairs participating in the third examination of the National Heart, Lung, and Blood Institute Twin Study. The intraclass correlation coefficient for apo A-I was significantly greater in MZ twins (0.56) than in DZ twins (0.37, P less than 0.05); however, apo A-I showed an unequal distribution in the two groups, with significantly greater total variance in DZ twins. Therefore the among-component estimate of genetic variance was applied, and the results indicated no significant heritability for apo A-I (P = 0.59). MZ and DZ twins had equal apo B variance. The intraclass correlation coefficient for apo B in MZ twins (0.71) was significantly higher than in DZ twins (0.25) (P less than 0.0001), indicating significant heritability for apo B. Plasma apo A-I levels were significantly correlated with alcohol intake (P less than 0.0001), body mass index (BMI, P less than 0.0001), and physical activity, while apo B levels were significantly correlated only with BMI (P less than 0.05). After plasma apo A-I and apo B concentrations were adjusted for all of these variables and for cigarette smoking, the analysis of variance and intraclass correlation coefficients remained virtually unchanged. The LDL type intraclass correlation coefficient was higher in MZ twins (0.58) than in DZ twins (0.32, P less than 0.005); however, greater total variance for this parameter in DZ twins was observed and after applying the among component estimate of genetic variance, no significant heritability of LDL type was observed. After adjustment for covariate effects the conclusions were not changed. Only 8.4% of MZ twin pairs, as compared with 26.7% of DZ twin pairs, were discordant for elevated lipoprotein(a) on gradient gels (P less than 0.0001). Our data indicate that there is a strong heritability for plasma apo B and lipoprotein(a), with only weak evidence for heritability of LDL type or plasma apo A-I levels within this population sample.

Aged↗
PubMed1978

Lipoprotein lipase activity in adipose tissue and skeletal muscle of runners: relation to serum lipoproteins.

Physically well-trained people generally have lower VLDL-triglyceride and higher HDL-cholesterol levels than sedentary subjects. To examine the underlying mechanisms of this lipoprotein pattern, we measured the lipoprotein lipase (LPL) activity in needle biopsy specimens of adipose tissue and skeletal muscle of competitive runners and of body weight-matched, physically less-active controls. The active sportsmen were either sprinters, whose training program consisted mainly of athletics of short duration or long distance runners undergoing a strenuous endurance exercise program. In sprinters (all males) the serum lipid and lipoprotein concentrations did not differ significantly from those of controls and the mean LPL activities in muscle and adipose tissue were also similar in these two groups. The long distance runners (both sexes), on the other hand, had higher means levels of HDL-cholesterol than the respective controls. The LPL-activity of both adipose tissue (p less than 0.05) and skeletal muscle (p less than 0.01) was significantly higher in male long distance runners than in control males. Female runners had higher muscle LPL activity than controls (p less than 0.01) but in adipose tissue the difference in LPL activity was not significant. Rough estimates calculated for LPL activity present in whole body adipose tissue and skeletal muscle indicated that total LPL activity was 2.3 times higher in male long distance runners and 1.5 times higher in female long distance runners than in the respective controls. In combined groups of male runners and controls, there was a highly significant positive correlation between the serum HDL-cholesterol level and the LPL activity of adipose tissue expressed per tissue weight (r = +0.72, p less than 0.001) or per whole body fat (r = +0.62, p less than 0.001). The group means of HDL-cholesterol and adipose tissue LPL activity in the five cohorts studied (male sprinters, distance runners and controls and female distance runners and controls) were also positively correlated (r = +0.94). It is concluded that endurance training is associated with an adaptive increase of LPL activity not only in skeletal muscle but also in adipose tissue. These changes are not observed in sprinters who are trained by exercises of shorter duration. The high HDL-cholesterol levels of physically well-trained people are probably accounted for, at least partly, by the increased LPL activity and the concomitant rapid turnover or triglyceride-rich lipoproteins.

Adipose Tissue↗
PubMed1983

Plasma lipoproteins and lipolytic enzyme activities during endurance training in sedentary men: changes in high-density lipoprotein subfractions and composition.

Eighteen healthy sedentary males took part in supervised bicycle training for 50 minutes three to five times a week. Twelve subjects (group A) trained for 6 weeks at heavy intensity, and six subjects (group B) trained for 12 weeks at moderate intensity. Maximal oxygen uptake increased by about 20% (P less than 0.01). Body weight and composition as well as diet remained unchanged. After 6 weeks plasma high-density lipoprotein (HDL) cholesterol concentrations had increased by 7% (P less than 0.05) in all subjects. The increase was most marked in group B at 14% (P less than 0.05) compared to 3% in group A (ns). Apolipoprotein AI (apo AI) increased by about 7% in both groups (P less than 0.01). After 12 weeks HDL cholesterol and apo AI levels had almost returned to initial values. Measurements of HDL components showed increases of 6% to 12% in free cholesterol, cholesteryl ester (P less than 0.05), and phospholipid (P less than 0.01); whereas, the minor triglyceride fraction decreased by 20% (P less than 0.01). Zonal ultracentrifugation in four subjects revealed a preferential rise of about 35% in the HDL2 subfraction, increasing the HDL2/HDL3 ratio by about 20%. In parallel, the composition of the lipoprotein classes changed. The protein moiety of all classes, except low-density lipoprotein (LDL), expanded at the expense of the core components cholesteryl ester and triglyceride. Hepatic lipase (HL) activity decreased by 6% (P less than 0.05), and lipoprotein lipase (LPL) activity in adipose tissue increased by about 50% (P less than 0.05) during the first 6 weeks of training, while LPL activity in postheparin plasma and skeletal muscle did not change. The transient rise in HDL cholesterol levels was correlated (P less than 0.05) to the elevation of adipose tissue LPL activity. The alterations in HDL concentration were also related to changes in body composition and diet, especially to an increase in fat intake.

Adult↗
PubMed2004

Effects of atorvastatin on triglyceride-rich lipoproteins, low-density lipoprotein subclass, and C-reactive protein in hemodialysis patients.

Dyslipidemia is an important risk factor for cardiovascular disease in patients with chronic renal failure (CRF). We evaluated the safety and efficacy of atorvastatin in patients with dyslipidemia associated with CRF who were undergoing hemodialysis (HD). Thirty-five patients who were receiving HD were given atorvastatin (10 mg/d) for 3 months. Chylomicron (CM), light and dense very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and light and dense low-density lipoprotein (LDL) were separated by ultracentrifugation. Apolipoprotein (apo) B was measured by electroimmunoassay. Mean LDL particle diameter was measured by gradient gel electrophoresis. Atorvastatin therapy reduced LDL-cholesterol (C) by 36% and remnant-like particle (RLP)-C by 58%. Atorvastatin significantly reduced apo B, apo CIII, and apo E in VLDL by 40% to 46% and IDL-apo B by 66%. Atorvastatin also significantly reduced cholesterol in CM, light VLDL, and dense VLDL without consistently affecting triglyceride (TG) in these lipoproteins. Atorvastatin similarly reduced both light and dense LDL-apo B by 38%. LDL particle size in the HD patients significantly increased during atorvastatin treatment from 25.7 +/- 0.4 to 26.2 +/- 0.6 nm. High sensitive C-reactive protein (HS-CRP) was halved by atorvastatin decreasing from 0.08 +/- 0.05 to 0.04 +/- 0.03 mg/dL. Atorvastatin treatment did not affect the creatinine kinase level, and no classical adverse effects were observed during the study. These results suggest that atorvastatin is safe and effective for the management of dyslipidemia in patients with CFR who are receiving HD, which may help to suppress the development of atherosclerosis.

Alanine Transaminase↗