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• W2153042528 abstract "We examined whether postprandial (PP) chylomicrons (CMs) can serve as vehicles for transporting cholesterol from endogenous cholesterol-rich lipoprotein (LDL+HDL) fractions and cell membranes to the liver via lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) activities. During incubation of fresh fasting and PP plasma containing [3H]cholesteryl ester (CE)-labeled LDL+HDL, both CMs and VLDL served as acceptors of [3H]CE or cholesterol from LDL+HDL. The presence of CMs in PP plasma suppressed the ability of VLDL to accept [3H]CE from LDL+HDL. In reconstituted plasma containing an equivalent amount of triglycerides from isolated VLDL or CMs, a CM particle was about 40 times more potent than a VLDL particle in accepting [3H]CE or cholesterol from LDL+HDLs. When incubated with red blood cells (RBCs) as a source for cell membrane cholesterol, the cholesterol content of CMs, VLDL, LDL, and HDL in PP plasma increased by 485%, 74%, 13%, and 30%, respectively, via LCAT and CETP activities. The presence of CMs in plasma suppressed the ability of endogenous lipoproteins to accept cholesterol from RBCs.Our data suggest that PP CMs may play an important role in promoting reverse cholesterol transport in vivo by serving as the preferred ultimate vehicle for transporting cholesterol released from cell membranes to the liver via LCAT and CETP. We examined whether postprandial (PP) chylomicrons (CMs) can serve as vehicles for transporting cholesterol from endogenous cholesterol-rich lipoprotein (LDL+HDL) fractions and cell membranes to the liver via lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) activities. During incubation of fresh fasting and PP plasma containing [3H]cholesteryl ester (CE)-labeled LDL+HDL, both CMs and VLDL served as acceptors of [3H]CE or cholesterol from LDL+HDL. The presence of CMs in PP plasma suppressed the ability of VLDL to accept [3H]CE from LDL+HDL. In reconstituted plasma containing an equivalent amount of triglycerides from isolated VLDL or CMs, a CM particle was about 40 times more potent than a VLDL particle in accepting [3H]CE or cholesterol from LDL+HDLs. When incubated with red blood cells (RBCs) as a source for cell membrane cholesterol, the cholesterol content of CMs, VLDL, LDL, and HDL in PP plasma increased by 485%, 74%, 13%, and 30%, respectively, via LCAT and CETP activities. The presence of CMs in plasma suppressed the ability of endogenous lipoproteins to accept cholesterol from RBCs. Our data suggest that PP CMs may play an important role in promoting reverse cholesterol transport in vivo by serving as the preferred ultimate vehicle for transporting cholesterol released from cell membranes to the liver via LCAT and CETP. Reverse cholesterol transport (RCT), a process of transporting cholesterol from cell membranes to the liver for its excretion, occurs in the plasma compartment in vivo. Both lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer proteins (CETPs) may play an important role in regulating the rate of RCT by influencing the rate at which cholesterol released from cell membranes into plasma is trapped in the core of HDL via esterification and the rate at which the trapped HDL-cholesteryl ester (CE) is then transferred to apolipoprotein B (apoB)-containing lipoproteins for delivery to the liver (1Glomset J.A. Norum K.R. The metabolic role of lecithin:cholesterol acyltransferase: perspective from pathology.Adv. Lipid Res. 1973; 11: 1-65Google Scholar, 2Fielding C.J. Fielding P.E. Cholesterol transport between cells and body fluids.Med. Clin. North Am. 1982; 66: 368-373Google Scholar, 3Tall A.R. Plasma cholesteryl ester transfer protein.J. Lipid Res. 1993; 34: 1255-1274Google Scholar). CETP promotes the transfer of CE from HDL to various apoB-containing lipoproteins [LDL, VLDL, IDL, and chylomicrons (CMs)] in plasma (3Tall A.R. Plasma cholesteryl ester transfer protein.J. Lipid Res. 1993; 34: 1255-1274Google Scholar, 4Largost L. Regulation of cholesteryl ester transfer protein (CETP) activity: review of in vitro and in vivo studies.Biochim. Biophys. Acta. 1994; 12: 209-236Google Scholar, 5Barter P.J. Hopkins G.H. Calvert G.D. Pathways for incorporation of esterified cholesterol into very low and low density lipoproteins in plasma incubated in vitro.Biochim. Biophys. Acta. 1982; 713: 136-148Google Scholar, 6Marzetta C.A. Meyers T.J. Albers J.J. Lipid transfer protein-mediated distribution of HDL-derived choelsteryl esters among plasma apoB-containing lipoprotein subpopulations.Arterioscler. Thromb. 1993; 13: 834-841Google Scholar, 7Guerin M. Dolphin P.J. Chapman M.J. Preferential cholesteryl ester acceptors among LDL subspecies of subjects with familial hypercholesterolemia.Arterioscler. Thromb. 1994; 14: 679-685Google Scholar, 8Lassel T.S. Guerin M. Auboiron S. Chapman M.J. Guy-Grand B. Preferential cholesteryl ester acceptors among triglyceride-rich lipoproteins during alimenatary lipemia in normolipidemic subjects.Arterioscler. Thromb. Vasc. Biol. 1998; 18: 65-74Google Scholar, 9Lassel T.S. Guerin M. Auborion S. Guy-Grand B. Chapman M.J. Evidence for a cholesteryl ester donor activity of LDL particles during alimentary lipemia in normolipidemic subjects.Atherosclerosis. 1999; 147: 41-48Google Scholar), but the catabolic rate and fate of these various apoB-containing lipoproteins differ in vivo (10Gotto A.M. Pownall H.J. Havel R.J. Introduction to the plasma lipoproteins.Methods Enzymol. 1986; 128: 3-41Google Scholar). Thus, the rate of RCT promoted by LCAT and CETP might then depend on the rate and extent of transfer of HDL-CE to various apoB-containing lipoproteins in plasma in vivo. Although the extent of in vivo transfer of CE from HDL to various apoB-containing lipoproteins is known to be influenced by the levels of individual apoB-containing lipoproteins in plasma (11Lally J.I. Barter P.J. The in vivo metabolism of esterified cholesterol in plasma high density lipoproteins of rabbits.J. Lab. Clin. Med. 1979; 93: 570-582Google Scholar), the rate and potencies of the various apoB-containing lipoproteins to accept CE from HDL in vivo have not yet been fully elucidated. An earlier study (12Nestel P.J. Reardon M. Billington T. In vivo transfer of cholesteryl esters from high density lipoproteins to very low density lipoproteins in man.Biochim. Biophys. Acta. 1979; 573: 403-407Google Scholar) examining the fate of [3H]CE-labeled HDL injected into fasting humans showed that 3H-labeled CE on HDL appeared more rapidly on VLDL than on LDL. In rabbits, 3H-labeled CE on HDL injected intravenously appeared on VLDL and LDL, with peak activity seen between 30 and 60 min and between 60 and 120 min after injection, respectively (11Lally J.I. Barter P.J. The in vivo metabolism of esterified cholesterol in plasma high density lipoproteins of rabbits.J. Lab. Clin. Med. 1979; 93: 570-582Google Scholar). Goldberg, Beltz, and Pittman (13Goldberg D.I. Beltz W.P. Pittman R.C. Evaluation of pathways for the cellular uptake of high density lipoprotein cholesteryl esters in rabbits.J. Clin. Invest. 1991; 87: 331-346Google Scholar) reported that in rabbits, 30% of 3H-labeled CE on HDL was cleared from plasma after transfer to VLDL, with 36% cleared after transfer to LDL, although VLDL levels are much lower than those of LDL in rabbit plasma. In humans, a large amount of dietary fat (>80 g) fluxes daily into circulating blood as CMs during postprandial (PP) lipemic periods (14Hussain M.M. Kedees M.H. Singh K. Athar H. Jamail N.Z. Signposts in the assembly of chylomicrons.Front. Biosci. 2001; 6: 320-321Google Scholar). Although CMs may serve as acceptors of endogenous CEs from HDL and LDL as well as CEs derived from cell membranes via LCAT, the potential role of CMs in transporting these CEs to the liver has not yet been fully evaluated. In PP plasma obtained from normolipidemic subjects, 72%, 19%, 6%, and 2% of [3H]CE on HDL transferred to LDL, VLDL, CMs, and IDL, respectively (8Lassel T.S. Guerin M. Auboiron S. Chapman M.J. Guy-Grand B. Preferential cholesteryl ester acceptors among triglyceride-rich lipoproteins during alimenatary lipemia in normolipidemic subjects.Arterioscler. Thromb. Vasc. Biol. 1998; 18: 65-74Google Scholar). CETP in plasma promotes the transfer of CE from LDL to the triglyceride (TG)-rich lipoprotein (TRL) fractions (4Largost L. Regulation of cholesteryl ester transfer protein (CETP) activity: review of in vitro and in vivo studies.Biochim. Biophys. Acta. 1994; 12: 209-236Google Scholar). It has also been reported that CEs that were first transferred from HDL to LDL were then transferred secondarily to CMs during PP phases (9Lassel T.S. Guerin M. Auborion S. Guy-Grand B. Chapman M.J. Evidence for a cholesteryl ester donor activity of LDL particles during alimentary lipemia in normolipidemic subjects.Atherosclerosis. 1999; 147: 41-48Google Scholar). Induction of PP lipemia accompanies an increase in the plasma activities of both LCAT and CETP (15Rose H.G. Juliano J. Regulation of plasma lecithin:cholesterol acyltransferase in man. II. Activation during alimentary lipemia.J. Lab. Clin. Med. 1977; 89: 525-532Google Scholar, 16Castro G.R. Fielding C.J. Effect of postprandial lipemia on plasma cholesterol metabolism.J. Clin. Invest. 1985; 75: 874-882Google Scholar, 17Tall A. Sammett D. Granot E. Mechanism of enhanced choelsteryl ester transfer from high density lipoproteins to apoB-containing lipoproteins during alimentary lipemia.J. Clin. Invest. 1986; 77: 1163-1172Google Scholar) and a net decrease in CE levels on both LDL and HDL, as well as in plasma total CE levels (18Dubois C. Armand M. Azais-Braesco V. Portugal H. Pauli A-M. Bernard P-M. Latge L. Lafont H. Borel P. Lairon D. Effect of moderate amount of emulsified dietary fat on postprandial lipemia and lipoproteins in normolipidemic adults.Am. J. Clin. Nutr. 1994; 60: 374-382Google Scholar), and a shift in the distribution of CEs from endogenous lipoproteins to CMs (19Dullaart R.P.F. Groener J.E.M. Wijk H.V. Sluiter W.J. Erkelens D.W. Alimentary lipemia-induced redistribution of cholesteryl ester between lipoproteins. Studies in normolipidemic, combined hyperlipidemic, and hypercholesterolmic men.Arteriosclerosis. 1989; 9: 614-622Google Scholar). These observations suggest that CMs appearing in PP plasma may serve as acceptors of CEs from both LDL and HDL. Eisenberg (20Eisenberg S. Preferential enrichment of large-sized very low density lipoprotein populations with transferred cholesteryl esters.J. Lipid Res. 1985; 26: 487-494Google Scholar) reported that the potency of apoB-containing lipoproteins as acceptors of CEs from HDL increased with the increase in their particle sizes, surface areas, or TG-to-CE ratios. Because CM particles are larger and have a higher TG-to-CE ratio and surface area than any other apoB-containing lipoproteins in plasma, CMs may serve as the preferred acceptors of CEs from HDL via CETP. We observed recently that PP lipemia-mediated increases in plasma CETP activity were primarily due not to the change in the CETP protein mass but to the increased levels of CMs available to serve as acceptors of CEs (21Chung B.H. Doran S. Liang P. Osterlund L. Cho B.H.S. Oster R.A. Darnell B. Franklin F. Alcohol-mediated enhancement of postprandial lipemia: a contributing factor for an increase in plasma HDL and a decrease in risk of cardiovascular disease.Am. J. Clin. Nutr. 2003; 78: 391-399Google Scholar). Castro and Fielding (16Castro G.R. Fielding C.J. Effect of postprandial lipemia on plasma cholesterol metabolism.J. Clin. Invest. 1985; 75: 874-882Google Scholar) were first to report that human plasma containing PP lipoproteins was better able to promote cholesterol efflux from cultured cells by increasing the extent of LCAT and CETP reactions. We have reported previously that PP appearance of CMs in plasma increased the potencies of plasma TRL to accept cholesterol released from red blood cells (RBCs) (22Chung B.H. Franklin F. Cho B.H.S. Segrest J.P. Hart K. Darnell B. Potencies of lipoproteins in fasting and postprandial plasma to accept additional cholesterol molecules released from cell membranes.Arterioscler. Thromb. Vasc. Biol. 1998; 18: 1217-1230Google Scholar). Inasmuch as it is known that the clearance of PP CMs from circulating blood is mediated primarily by hepatic uptake (23Cooper A.D. Hepatic uptake of chylomicron remnants.J. Lipid Res. 1997; 38: 2173-2192Google Scholar), the LCAT- and CETP-mediated acceptance of cholesterol released from cell membranes by PP CMs could possibly lead to an increase in the rate of RCT in vivo. To examine the potential of CMs as vehicles for promoting RCT, we determined the effect of the PP appearance of CMs on 1) the alteration in the balance of cholesterol between TRL and endogenous cholesterol-rich LDL and HDL fractions in vivo, 2) the extent of the LCAT- and CETP-mediated transfer of cholesterol from endogenous cholesterol-rich lipoproteins (LDL+HDLs) to TRL in vitro, and 3) the potencies of endogenous lipoproteins as well as CMs to accept additional cholesterol released from RBC membranes via LCAT and CETP. Healthy normolipidemic adult men and postmenopausal women were recruited. Interested volunteers underwent a screening examination at the General Clinical Research Center (GCRC), University of Alabama at Birmingham Medical School. Examination included a documentation of a brief medical history, physical examination, and measurement of body weight, height, and fasting plasma lipid and lipoprotein cholesterol levels. Subjects with a fasting TG level above the 75th percentile, plasma cholesterol above the 90th percentile, or HDL-cholesterol below the 10th percentile for their respective age groups were excluded from the study. Eight men aged 33–49 years (35.3 ± 4.5) and eight postmenopausal women aged 45–62 years (51.9 ± 6.6) participated in this study. The mean body mass indexes of men and women were 25.3 ± 4.1 and 29.6 ± 4.5, respectively. Fasting and PP plasma samples used in this study were obtained from subjects after consumption for 16 days of a normal diet rich in polyunsaturated fatty acids, which provided 15%, 50%, and 35% of its calories from proteins, carbohydrates, and fat, respectively and contained 175 mg cholesterol/1,000 kcal. Saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids in the diet provided 7.5%, 12%, and 15.5% of total calories, respectively. All daily meals, prepared by the GCRC Research Kitchen, were provided to the study subjects. Briefly, on the evening before the fat-loading test, study subjects were admitted to the GCRC and were provided dinner. After fasting overnight at the GCRC, study subjects were given a challenge breakfast. To maximize the PP lipemic response, the challenge meal contained a slightly higher level of fat (40% calories from fat) than the background diet (35% calories from fat) but with the same fatty acid composition. The challenge meal was whole foods, providing 50% of the total daily caloric intake. Fasting and PP blood samples were collected from study subjects immediately prior to the meal (40 ml) and 4 h after the meal (80 ml). The research protocol for using human subjects was approved by the Institutional Review Board at the University of Alabama at Birmingham. Blood samples were collected in tubes containing ethylenediaminetetraacetic acid (0.1%) and immediately placed in an ice bath. After blood samples were spun at 1,000 rpm for 10 min in a precooled (4°C) centrifuge, about two-thirds of the plasma in the tube separated from RBCs, with the remaining one-third becoming trapped within the packed RBCs. After removal of the upper plasma fraction, plasma trapped within the packed RBCs and a small portion of separated plasma were placed in a 37°C water bath for 3–16 h to allow lipoproteins in the plasma to interact with endogenous LCAT, CETP, and/or RBCs. The remaining plasma was kept in an ice bath. After overnight incubation, plasma trapped within the packed RBCs was recovered by centrifuging blood at 3,500 rpm for 25 min. A portion of each plasma sample was stored in several aliquots at −70°C. The plasma lipoprotein cholesterol and TG profiles showing the level and distribution of cholesterol or TG among VLDL, LDL, and HDL density fractions in fresh and incubated fasting plasma and 4 h PP plasma were determined by the modified lipoprotein cholesterol autoprofiler method developed in this laboratory (24Chung B.H. Segrest J.P. Ray M.L. Brunzell J.D. Hokanson J.E. Krauss R.M. Beaudrie K. Cone J.T. Single vertical spin density gradient ultracentrifugation.Methods Enzymol. 1986; 128: 181-209Google Scholar). This method involves: 1) short (150 min), single-spin, density-gradient ultracentrifugal separation of the major lipoprotein fractions in plasma in a swing-out rotor (Beckman SW 50.1); 2) continuous-flow online mixing of effluents from density gradient tubes with enzymatic cholesterol and TG reagents; 3) online incubation of mixtures and online measurement of absorbance produced; and 4) calculation of lipoprotein cholesterol and TG levels by a computer program. To determine the levels of cholesterol associated with CMs in 4 h PP plasma, CM-free PP plasma was prepared by removing intact CMs in 4 h PP plasma after ultracentrifugation of PP plasma at 30,000 rpm for 30 min in a swing-out rotor (Beckman SW 50.1). After determination of lipoprotein cholesterol profiles of PP plasma and CM-free PP plasma, the levels of cholesterol associated with intact large CMs were then determined by subtracting cholesterol levels of the VLDL density fraction in CM-free PP plasma from those in PP plasma. Following quantitative separation of the VLDL density fraction (0.6 ml) from fasting, 4 h, and CM-free 4 h plasma (4 ml), PP changes in levels of TRL apoB-100 and apoB-48 were determined. TRL apoB-100 and apoB-48 levels were determined using a modified method of the SDS gel electrophoresis method described by Kotite, Bergeron, and Havel (25Kotite L. Bergeron N. Havel R.J. Quantification of apolipoproteins B-100, B-48, and E in human triglyceride-rich lipoproteins.J. Lipid Res. 1995; 36: 890-900Google Scholar). Briefly, isolated fasting VLDL solution containing 10 μg of TG and an equivalent volume of the VLDL density fraction separated from 4 h PP plasma and CM-free 4 h plasma were loaded onto a 4–20% SDS gradient gel. Molecular weight standards and apoB-100 standard, prepared from LDL, were also loaded onto the same SDS gel. After electrophoretic separation of apoB-100 and apoB-48 on TRL, gels were stained with gel code blue stain (Pierce Co., Rockford, IL), and then the protein mass of apoB-100 and apoB-48 bands in the gel were quantified based on the apoB-100 standard by using the UVP gel imaging system (Quest Scientific Co., Cumming, GA). PP increases in the number of VLDL, CMs, and CM remnant particles were determined following conversion of the TRL apoB-100 and apoB-48 masses (μg) into molar concentration using molecular weights (MWs) of 555,486 for apoB-100 and 260,416 for apoB-48. The CETP-mediated redistribution of [3H]CE on HDL and LDL as well as the cholesterol mass among lipoprotein fractions was determined following incubation of reconstituted PP plasma containing trace amounts of [3H]CE-labeled LDL and/or [3H]CE-labeled HDL at 37°C for 16 h. We radiolabeled LDL and HDL in TRL-free fasting or 4 h PP plasma with [3H]CE using the procedure described by Thomas and Rudel (26Thomas M.S. Rudel L.L. 3H-cholesteryl ester labeling and transfer among human and nonhuman primate plasma lipoproteins.Anal. Biochem. 1983; 130: 215-222Google Scholar). The distribution of [3H]CE between LDL and HDL in the TRL-free plasma was observed to be very similar to the distribution of their cholesterol mass. After isolating [3H]CE-labeled LDL and HDL in d>1.006 g/ml plasma fraction by density gradient ultracentrifugation (24Chung B.H. Segrest J.P. Ray M.L. Brunzell J.D. Hokanson J.E. Krauss R.M. Beaudrie K. Cone J.T. Single vertical spin density gradient ultracentrifugation.Methods Enzymol. 1986; 128: 181-209Google Scholar), a trace amount of each was added to reconstituted plasma containing isolated VLDL, CMs, TRL, or no TRL. After incubating the [3H]CE-labeled LDL and/or HDL alone or after their addition into reconstituted plasma at 37°C for 3–16 h, the distribution of [3H]CE radioactivity among VLDL, LDL, and HDL density fractions or transfer of [3H]CE from LDL+HDL to the VLDL density fraction was measured after separating VLDL, LDL, and HDL density fractions by density gradient ultracentrifugation (24Chung B.H. Segrest J.P. Ray M.L. Brunzell J.D. Hokanson J.E. Krauss R.M. Beaudrie K. Cone J.T. Single vertical spin density gradient ultracentrifugation.Methods Enzymol. 1986; 128: 181-209Google Scholar). Changes in the distribution of cholesterol mass among VLDL, LDL, and HDL density fractions of reconstituted plasma after their incubation at 37°C for 16 h were also measured by obtaining the plasma lipoprotein cholesterol profile using the procedure described above (24Chung B.H. Segrest J.P. Ray M.L. Brunzell J.D. Hokanson J.E. Krauss R.M. Beaudrie K. Cone J.T. Single vertical spin density gradient ultracentrifugation.Methods Enzymol. 1986; 128: 181-209Google Scholar). The potency of VLDL, isolated from fasting plasma, and CMs, isolated from 4 h PP plasma, to act as acceptors of [3H]CE or cholesterol mass from LDL+HDL was examined following incubation of reconstituted plasma containing isolated VLDL or CMs. The reconstituted plasma was prepared by adding equivalent amounts of TG from isolated VLDL or CMs to a common fresh TRL-free plasma containing a trace amount of [3H]CE-labeled LDL+HDL. During the incubation of the above reconstituted plasma at 37°C, the levels of [3H]CE radioactivity transferred from LDL+HDL into the VLDL density fraction and/or the increase in cholesterol content of the VLDL density fraction were measured by the procedures described above. To compare the relative potencies of particles of VLDL and CM for accepting CE from LDL+HDL, the number of TG molecules per particle of VLDL and CM was determined by quantifying apoB-100 or apoB-48 levels on isolated fasting VLDL or 4 h PP CMs by the SDS gradient gel method described above. Briefly, isolated VLDL containing 10 μg of TG and CMs containing 150 μg of TG were loaded onto a 4–20% SDS gradient gel, and apoB-100 and/or apoB-48 on VLDL and CMs were separated from other apolipoproteins. Then, masses of apoB-100 and/or apoB-48 associated with 10 μg of VLDL TG or 150 μg of CM TG were determined based on an apoB-100 standard on the gel. The number of TG molecules per particle of VLDL and CM was then determined by calculating the molar ratio of TG to VLDL apoB-100 or to CM apoB-48 based on the mass ratio. The potency per particle of CM and VLDL to accept CE or cholesterol mass from LDL+HDL was determined based on the potencies of VLDL and CMs containing equivalent TG to accept CE from LDL+HDL and on the number of TG molecules per particle of VLDL and CM. In other experiments, the rate and extent of transfer of 3H-labeled CE from LDL+HDL to VLDL and/or CMs in reconstituted plasma, fasting plasma, PP plasma and/or CM-free plasma were also determined by the procedures described above. To determine the effect of PP lipemia on the extent of esterification of unesterified cholesterol (UC) by endogenous LCAT in plasma and on the extent of partitioning of LCAT-produced CE into TRL, fasting and PP plasma were labeled with [3H]UC by the procedure previously described by Yen and Nishida (27Yen F.T. Nishida T. Rapid labeling of lipoproteins in plasma with radioactive cholesterol. Application for measurement of plasma cholesterol esterification.J. Lipid Res. 1990; 31: 349-353Google Scholar). After incubation of [3H]UC-labeled fasting and PP plasma for 16 h, VLDL, LDL, and HDL density fractions of incubated plasma were fractionated quantitatively by density-gradient ultracentrifugation at 4°C (24Chung B.H. Segrest J.P. Ray M.L. Brunzell J.D. Hokanson J.E. Krauss R.M. Beaudrie K. Cone J.T. Single vertical spin density gradient ultracentrifugation.Methods Enzymol. 1986; 128: 181-209Google Scholar). Following the measurement of the total [3H]radioactivity associated with VLDL, LDL, and HDL fractions, lipids were extracted from a portion of plasma and VLDL, LDL, and HDL fractions by using chloroform:methanol (2:1, v/v). UC and CE in the lipid extracts were separated on a silica gel thin-layer plate using chloroform:hexane (3:1, v/v) as a developing solvent. The ratio of [3H]CE to [3H]UC was determined by measuring the 3H radioactivity associated with the CE and UC bands. The distribution of 3H-labeled CE, formed in plasma by LCAT, among VLDL, LDL, and HDL density fractions was then calculated. The levels of total cholesterol, UC, and TG in plasma or in the lipoprotein fraction were measured by using enzymatic assay kits of cholesterol, UC, and TG purchased from Waco Diagnostic Co. (Richmond, VA). Quantitative variables were expressed as mean ± SD. Student t-tests were applied to compare the level of lipoproteins or lipids in fasting and PP plasma and control and LCAT- and CETP-reacted plasma. Lipoprotein TG profiles and cholesterol profiles of fasting and 4 h plasma from a subject with a brisk PP lipemic response, presented in Fig. 1A, B, show the PP lipemia-induced changes in level and distribution of TG and cholesterol among lipoproteins in fasting plasma. The PP lipemia-mediated changes in mean levels of lipids and lipoprotein cholesterol of fasting plasma from all study subjects are also shown (Fig. 1C). The PP lipemia caused a significant increase in plasma TG levels, owing primarily to an increase in the levels of TG associated with the VLDL density fraction (Fig. 1A, C). PP lipemia, although causing no significant change in plasma total cholesterol, did cause a significant increase in the cholesterol level in the VLDL density fraction and a concomitant small but significant decrease in cholesterol levels on both LDL and HDL (Fig. 1A, C). The above data indicate that PP lipemia may shift the distribution of cholesterol from LDL and HDL to PP TRL. Although the data were not included, we observed that decreased cholesterol levels on LDL and HDL in 4 h PP plasma returned to near fasting level at 7 h PP with almost complete clearance of PP TRL from plasma. Figure 2shows the SDS gel electrophoregrams of VLDL density fraction isolated from fasting plasma and 4 h PP plasma obtained from a subject with a brisk PP lipemic response (Fig. 2A) and PP change in TRL apoB-100 and apoB-48 of all study subjects (Fig. 2C). To determine the levels of apoB-48 associated with CMs and CM remnants in 4 h plasma, intact CMs were removed centrifugally from 4 h PP plasma, and the levels of apoB-48 and apoB-100 associated with TRL isolated CM-free 4 h PP plasma were also determined. In densitometric scans of gels (Fig. 2A, C), apoB-48 was detectable in fasting plasma VLDL. Determination of particle numbers based on the molar concentration of apoB-48 and apoB-100 in fasting VLDL obtained from all study subjects indicates that the number of apoB-48-containing CM remnant particles in fasting plasma was about 6.1% of apoB-100-containing VLDL particles (Fig. 2C). PP lipemia increased both apoB-100- and apoB-48-containing TRL particles in fasting plasma (Fig. 2). The extent of this increase was much greater for apoB-48-containing particles (170%) than for apoB-100-containing particles (44.8%). However, the total numbers of apoB-100-containing particles resulting from PP increase (Δ 44.8 particles of PP VLDL per 100 fasting VLDL particles) was much greater (4.2-fold) than that of apoB-48-containing particles (Δ 10.4 particles of PP CM per 100 particles of fasting VLDL) (Fig. 2C). Centrifugal removal of CMs from 4 h PP plasma only minimally lowered the TRL apoB-48 level or TRL apoB-48-to-apoB-100 ratio (Fig. 2A–C) despite ∼72% decrease of plasma TG level, which had increased in 4 h PP plasma (data not shown). The differences in mean molar concentrations of apoB-48 associated with TRL isolated from 4 h PP plasma and CM-free 4 h PP plasma (Fig. 2C) indicate that the numbers of intact CM particles were only ∼20% of total apoB-48-containing TRL particles in 4 h PP plasma or 31.7% of apoB-48-containing particles resulting from PP increase. The above data indicate that the major portion (80%) of apoB-48 in 4 h plasma was associated with CM remnants. The data shown in Fig. 2C further show that the number of intact CM particles was ∼2% of the total apoB-100- and apoB-48-containing TRL particles in 4 h PP plasma.Fig. 2PP changes in composition and levels of apoB associated with fasting VLDL. Sodium dodecyl sulfate gradient gels (A) and densitometric scans of the gel (B) showing the separation and levels of apoB-100 and apoB-48 in VLDL density fraction isolated quantitatively from fasting plasma, 4 h PP plasma, and chylomicron (CM)-free 4 h PP plasma (4 h −CM). The 4 h −CM plasma was obtained following centrifugal removal of intact CMs from 4 h PP plasma (30,000 rpm for 30 min in a Beckman SW 55 swing-out rotor). C: Mean levels ± SD (pmol) of apoB-100 on 4 h PP triglyceride-rich lipoprotein (TRL) and apoB-48 on the VLDL density fraction of fasting, 4 h PP, and CM-free 4 h PP TRL relative to that of 100 pmol of fasting VLDL apoB-100. Following determination of the masses of apoB-100 and apoB-48 in the same volume of VLDL density fraction separated quantitatively from 4 ml fasting, 4 h PP, and CM-free 4 h PP plasma by SDS gels, the levels of apoB-100 and apoB-48 in PP TRL or apoB-48 in fasting plasma relative to that of fasting VLDL apoB-100 were calculated. Molecular weights of 555,486 for apoB-100 and 260,416 for apoB-48 were used to convert their masses into molar concentration. The net PP increases in level" @default.
• W2153042528 created "2016-06-24" @default.
• W2153042528 creator A5004041257 @default.
• W2153042528 creator A5004632018 @default.
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• W2153042528 date "2004-07-01" @default.
• W2153042528 modified "2023-10-16" @default.
• W2153042528 title "Postprandial chylomicrons" @default.
• W2153042528 cites W13663154 @default.
• W2153042528 cites W1604097175 @default.
• W2153042528 cites W1819179971 @default.
• W2153042528 cites W1879152806 @default.
• W2153042528 cites W1879810571 @default.
• W2153042528 cites W1945310293 @default.
• W2153042528 cites W1947290316 @default.
• W2153042528 cites W1954105369 @default.
• W2153042528 cites W1954754525 @default.
• W2153042528 cites W1958191918 @default.
• W2153042528 cites W1969468438 @default.
• W2153042528 cites W1972352663 @default.
• W2153042528 cites W1975082311 @default.
• W2153042528 cites W1988448764 @default.
• W2153042528 cites W1989958072 @default.
• W2153042528 cites W1991272474 @default.
• W2153042528 cites W1994830791 @default.
• W2153042528 cites W1998091483 @default.
• W2153042528 cites W2012504949 @default.
• W2153042528 cites W2027904194 @default.
• W2153042528 cites W2029164903 @default.
• W2153042528 cites W2037581676 @default.
• W2153042528 cites W2048665959 @default.
• W2153042528 cites W2054827051 @default.
• W2153042528 cites W2061926945 @default.
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