© 1996 American Heart Association, Inc.
Articles |
Dietary and Genetic Effects on LDL Size Measures in Baboons
the Department of Genetics, Southwest Foundation for Biomedical Research, San Antonio, Tex.
Correspondence to David L. Rainwater, PhD, Department of Genetics, Southwest Foundation for Biomedical Research, PO Box 760549, San Antonio, TX 78245-0549.
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Genetic and dietary effects on LDL phenotypes, including predominant LDL particle diameter, LDL size distribution, and non–HDL cholesterol and apoB concentrations, were investigated in 150 pedigreed baboons that are members of 19 sire groups. Baboons were fed a sequence of three defined diets differing in levels of fat and cholesterol. Increasing dietary fat had relatively little effect on two measures of LDL particle size. However, increasing the level of cholesterol in the diet resulted in larger increases of the predominant LDL particle diameters and in the proportion of stain on LDLs >28 nm. As expected, apoB and non–HDL cholesterol concentrations significantly increased when levels of dietary fat and cholesterol were increased. Correlations among the LDL phenotypes suggested that several different aspects of the LDL phenotype were captured by the four LDL measures across the three diets. Genetic effects indicated by sire group membership were significant both for expression of the LDL phenotypes and for response to changes in diet.
Key Words: LDL • diet • baboon • gradient gel electrophoresis
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
The characteristics of lipoprotein phenotypes are influenced by both dietary and genetic factors. A lipoprotein pattern that shows increased LDL-C is associated with increased risk for premature cardiovascular disease. Plasma LDLs are the principal transporters of cholesterol in the vascular compartment, and several subpopulations of LDL particles have been identified.1 2 Particles vary in size, hydrated density, and chemical composition.1 Austin et al3 have dichotomized this heterogeneity of human LDLs: type A LDLs are large and buoyant, with peak diameters >25.5 nm; type B particles are small and dense, with peak diameters <25.5 nm. The B phenotype appears to be associated with an increased risk of cardiovascular disease,3 4 5 probably because small LDLs are cleared from the circulation more slowly6 and are more susceptible to oxidation7 than the larger particles. In contrast, dietary induction of large cholesteryl ester–rich LDLs in African green monkeys results in atherogenic modifications in LDL particle composition.8 The increased atherogenicity of LDL particles is associated with the enrichment of these particles with cholesteryl esters.9 In humans, larger LDL particles are also associated with coronary artery disease in normolipidemic men.10 Together, these data suggest that LDL particles occurring at both extremes of LDL size may be more closely associated with cardiovascular disease than intermediate-sized particles.
Several epidemiological studies have implicated the effects of diet on atherogenic lipoprotein phenotypes.11 12 Cholesterol and the type of fat in diet are important factors that influence metabolic pathways and, ultimately, atherosclerosis.13 To clarify the connection between diet and atherogenesis, it is important to examine the role of different lipid components in the diet on lipoprotein characteristics. Because LDLs play a central role in the pathogenesis of atherosclerosis, there is a need to understand the dietary and genetic factors that influence their phenotypic variation. The objectives of the present study were to develop methods that would measure baboon LDL particle size properties, to determine how well the measures of LDL size correlated with measures of LDL concentrations, and to determine if genes influence LDL size phenotypes and responses to dietary changes.
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Animals and Blood Samples
One hundred fifty pedigreed baboons (79 females and 71 males) were subjected to a dietary challenge experiment. Animals were members of 19 sire groups, but none were full siblings. They were weaned onto LCLF monkey chow diet, and blood samples were obtained at 28 months (mean=28.0, SD=0.5) of age. A second blood sample was drawn after the baboons had been challenged with HCHF diet for 7 weeks. To wash out the effects of the HCHF diet, animals were fed the LCLF diet for 7 weeks before being fed LCHF diet for an additional 7 weeks before the third blood sample was drawn. Characteristics of the three diets are given in Table 1
.14
|
Baboons were fasted overnight and immobilized with ketamine 10 mg/kg before blood was drawn from the femoral vein. Serum was prepared by low-speed centrifugation after clotting and stored in aliquots15 at -80°C before use. Procedures were approved by the Institutional Animal Care and Use Committee of the Southwest Foundation for Biomedical Research.
At the beginning of the experiment, we tested for carryover effects of the HCHF diet into the LCHF diet by examining non–HDL-C concentrations. A blood sample was taken from 60 baboons at the end of the washout period (ie, LCLF-2), midway between the HCHF and LCHF diet blood samplings. The cholesterol concentrations (mean±SEM) for each of the diets were (in mmol/L) 1.25±0.06 for LCLF, 3.16±0.30 for HCHF, 1.27±0.07 for LCLF-2, and 1.62±0.10 for LCHF. Because paired t test analysis indicated there were no significant (P=.58, n=60) differences between the two LCLF diets and because the LCLF-2 diet sample occurred midway between the HCHF and LCHF diet samples, we concluded that there were no significant carryover effects.
Nondenaturing Gradient Gel Electrophoresis
We made nondenaturing 3% to 18% polyacrylamide gradient gels.16 17 Before loading the samples, the gels were prerun in TBE buffer ([in mmol/L] Tris 90, boric acid 81.5, and disodium EDTA 2.5, pH 8.35) at 120 V for 60 minutes in a Pharmacia GE-2/4 electrophoresis chamber. Samples were made dense with sucrose, and a volume containing 6 µL serum was loaded on the gels. Samples were subjected to electrophoresis for a total of 3000 v·h.18 After electrophoresis, the gels were stained17 18 with Sudan black B (Sigma), which several studies have shown19 20 21 predicts well the distributions of cholesterol among size-resolved lipoproteins. Gels were calibrated by using a Pharmacia high-molecular-weight standard that contains thyroglobulin (17 nm), carboxylated latex microspheres (38.0 nm; Duke Scientific), and a lyophilized plasma standard containing two bands of LDL with known diameters (27.5 and 26.6 nm).17 Proteins in the high-molecular-weight standard were stained with Coomassie brilliant blue R-250 (Sigma) by exposing the lower portion of the gel that contained these proteins to the stain; the gels were then destained in 50% methanol, 10% acetic acid, and 40% water.22 After destaining, the gels were soaked in TBE buffer to restore the size and shape of the gels before scanning.
Densitometry and Gel Calibration
The gels were scanned at 632.8 nm with an LKB-Ultroscan XL laser densitometer by using GelScan XL software (Pharmacia LKB, Biotechnology AB). Gels were calibrated for size by using the migration distance (Rf) of each standard relative to thyroglobulin; a quadratic equation in terms of relative migration distance was fit to the natural logarithms of the diameters of the standards, ie, ln(Diameter)=C0+C1Rf+C2Rf.17 On the basis of distributions of peak diameters, we identified the interval of 24 to 30 nm as the region containing baboon LDL. Particles >30 nm were likely to be lipoprotein(a)23 or IDLs or VLDLs, and we found that all baboon LDL particle diameters were 
25 nm. In fact, we seldom found cholesterol stained on LDL particles <24 nm. We developed a computer program that enabled us to calibrate gels, measure particle diameters, and determine the proportion of absorbance within specified size intervals as a fraction of total LDL absorbance (ie, size range 24 to 30 nm). For this study, we determined the fraction of stain occurring on LDL particles between 28 and 30 nm; this measure is termed "the proportion of larger LDLs." We have reported17 high repeatabilities for estimates of human LDLs: 0.927 for particle diameter (n=163) and 0.711 for a measure of absorbance in the proportion of larger LDLs (n=114). In this study, we determined repeatabilities for 27 baboon samples replicated on different gels: 0.902 for particle diameter and 0.922 for the proportion of larger LDLs estimate.
To generate average absorbance profiles for each diet (see Figure), we converted absorbance readings to fractional absorbance and transformed individual absorbance profiles from evenly spaced mobility distance coordinates to evenly spaced particle diameter coordinates.24 Fractional absorbances at each coordinate were averaged for the 150 baboons to produce the average absorbance profile. In comparisons of profiles from different diets, we tested for differences on a coordinate-by-coordinate basis; we assigned a significant difference if the mean±2 SEM of a coordinate from one profile did not enclose the mean±2 SEM of the corresponding coordinate in the other profile.
Chemical Assays
Cholesterol concentrations were measured by using enzymatic methods with a Gilford SBA-300 clinical chemistry analyzer. ApoB-containing lipoproteins were precipitated by using heparin-manganese,25 and HDL-C was measured from the supernatant. Non–HDL-C was calculated as the difference between total cholesterol and HDL-C concentrations. Plasma apoB concentrations were measured by using a competitive immunoassay developed in-house. Briefly, microplate wells were coated with 0.85 µg LDL protein (d=1.02 to 1.05 g/mL) followed by blocking with 0.5% albumin plus 0.05% Tween-20 (Sigma Chemical Co). Samples and the monoclonal mouse antibody MB4726 were incubated together in the wells at 37°C with orbital shaking at 120 rpm. Antibody bound to the plate was quantified by using a biotinylated secondary antibody coupled with an avidin-biotinylated alkaline phosphatase system (kit AK5002, Vector Laboratories). Bound alkaline phosphatase was assayed with p-nitrophenyl phosphate at A405nm by using a microplate reader. Interassay coefficients of variation for control products in these assays were 2.3% for serum cholesterol, 4.3% for HDL-C, and 7.1% for apoB.
Statistical Analyses
Analyses were performed by using a commercial package of statistical programs (StatGraphics, Manugistics). A paired t test was used to test for within-animal effects of diet on LDL measures. Multiple linear regression analysis was used to determine the correlations among the LDL measures, and ANOVA was used to determine the effects of sire on LDL measures and to evaluate the interactions of sire and diet. All traits were transformed by natural logarithms to reduce skewness. The Kolgomorov-Smirnov test revealed that only the estimate of the proportion of larger LDLs for the HCHF diet was not normally distributed after log transformation (P=.011).
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Effects of Diet on LDL Particle Diameters
We measured LDL particle diameters in serum samples from 150 baboons by using nondenaturing gradient gel electrophoresis. Mean particle diameters for baboons fed the LCLF, LCHF, and HCHF diets were 27.3, 27.4, and 28.0 nm, respectively. It appeared that increasing dietary fat content had relatively little effect on particle diameters, but increasing dietary cholesterol content in the high-fat diet caused a greater shift to larger particle diameters. However, when the effects of diet were considered within each animal by using paired t tests, we found significant effects of both fat (P=.0212) and cholesterol (P<.0001) on LDL particle diameters (Table 2
).
|
Effects of Diet on LDL Size Distributions
LDL size distributions were determined in the same gradient gels as those used to measure particle diameters. We defined larger LDLs by the proportion of LDL stain (ie, Sudan black B) occurring on LDL particles >28.0 nm. There were significant increases in the proportion of larger LDLs corresponding to increases in dietary fat (from 18% to 22%, P=.0002) and cholesterol (from 22% to 48%, P<.0001) (Table 2
). Again the larger responses were due to changes in dietary cholesterol. These observations are illustrated in the Figure, which presents the average absorbance profiles of LDL (Sudan black B) for animals fed the three diets. Indicated also are the LDL size ranges that were significantly different between the LCHF and HCHF diets (ie, cholesterol effect); there were no significant differences between the LCLF and LCHF diets (ie, the fat effect).
|
Effects of Diet on Concentrations of Non–HDL-C and ApoB
Increasing both fat and cholesterol in the diet caused significant increases of two additional measures of ß-lipoprotein phenotypes, ie, concentrations of apoB and non–HDL-C (Table 2). In response to dietary fat (LCLF versus LCHF), baboons averaged a 34% increase (0.46 mmol/L, P<.0001) in non–HDL-C and a 29% increase (10.9 mg/dL, P<.0001) in apoB concentrations. In response to dietary cholesterol (LCHF versus HCHF), baboons averaged a 93% increase (1.7 mmol/L, P<.0001) in non–HDL-C and a 55% increase (26.4 mg/dL, P<.0001) in apoB concentrations.
Effects of Diet on Correlations of LDL Phenotype Measures
Table 3 presents intercorrelations of the four LDL phenotype measures for each of the three diet samples. The sample correlations are the univariate phenotypic correlations for each pair of variables. The strongest correlations for each diet were between the two concentration variables and between the two size variables. Although in many cases they were significant, the pairwise correlations of size variable with concentration variable were considerably weaker, suggesting that the size measures contained information that was not present in the concentration measures. The patterns of correlation differed among the three diets. For the LCLF diet only the pairwise correlation of non–HDL-C with LDL size was significant, whereas for the LCHF diet both LDL size variables were significantly correlated with non–HDL-C; all correlations were significant for the HCHF diet sample measures. All the pairwise correlations were positive, indicating that the measures share common information about LDL phenotype. We also used a nonparametric approach (Spearman rank correlation) to test for significant correlations. The patterns of correlation were the same as those presented in the upper half of Table 3, except that two additional pairs (non–HDL-C and proportion of larger LDLs and apoB and LDL size on LCLF diet) were found to be significantly correlated by this test.
|
We also investigated the partial correlations between each pair of variables, ie, we estimated the correlations between each pair of variables after adjusting for the effects of the remaining two LDL measures (Table 3). As with the sample correlations, the pair of size variables and the pair of concentration variables were significantly correlated for each diet. When we examined the partial correlations for the four combinations of size and concentration variables, none were significant for the LCLF diet and only one (LDL size and non–HDL-C) was significant for the HCHF diet. In contrast, two of the correlations, proportion of larger LDLs and non–HDL-C and proportion of larger LDLs and apoB, were significant for the LCHF diet samples, and the latter pair was actually negatively related. These data suggest that after adjusting for the strong positive correlations of LDL size and non–HDL-C, proportion of larger LDLs was negatively correlated with apoB concentrations, but only for the LCHF diet.
Genetic Effects on Diet Response of LDL Phenotype Measures
The four measures of LDL phenotype for each baboon in the study were subjected to ANOVA, in which the main effects tested were sex, diet, and sire group membership and the interactions among these. There were significant effects of sire and diet on all measures, and effects of sex on the two measures of LDL size (Table 4). Variation among sire groups explained about 17% (range, 13% to 21%) of the total variation in each of the LDL measures. In addition, there were significant (P<.05) sirexdiet interactions for LDL diameters and apoB concentrations, indicating that members of different sire groups responded differently to various dietary compositions. Table 5 shows the sire group means of LDL diameter for each diet. When dietary fat content was increased (ie, LCLF to LCHF), we found that four sire groups showed decreases in LDL diameters, three showed essentially no change, and the remainder showed increases. Although there was variation in extent, all sire groups showed increases in LDL size when dietary cholesterol content was increased (ie, LCHF to HCHF).
|
|
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
We made four different measures of LDL phenotypes: non–HDL-C and apoB, which are LDL concentration variables, and LDL diameter and proportion of larger LDLs, which are measures of particle size. When the level of fat was increased in the diet, apoB and non–HDL-C increased by
30%, which is similar to other reports.27 Although there was a 20% increase of cholesterol stain in the larger LDL particles, there was only a slight (0.1 nm) though significant (P=.02) increase in average LDL diameter. Thus, it appears that the net effects of increasing dietary fat content are similar increases in both apoB and LDL-C and therefore little change in average particle diameter. Similar results have been reported in cynomolgus and African green monkeys.28 LDL-C increased when these animals were fed a saturated fat and low-cholesterol diet, but particle size changed only slightly. In their randomized crossover study of lipoprotein response to low- and high-fat diets, Dreon et al29 have shown that apoB levels are higher in pattern B subjects fed a high-fat as opposed to a low-fat diet, although pattern A subjects did not show any change in apoB levels. However, both groups demonstrated higher LDL-C levels with a high-fat diet. When cholesterol was added to the high-fat diet, apoB and non–HDL-C concentrations increased 55% and 93%, respectively. Similarly, apoB and LDL-C increased significantly in a study of human subjects fed high levels of cholesterol.30 In the present study, differences in apoB and non–HDL-C responses to dietary cholesterol resulted in a doubling of the proportion of larger LDLs and a highly significant increase in predominant particle diameter. In a diet study using cynomolgus and African green monkeys, there was a significant increase in the LDL particle size associated with higher amounts of dietary cholesterol.28 In African green monkeys,31 LDL particle size is significantly larger in groups fed saturated or monounsaturated fat than in groups fed polyunsaturated fat.
In addition to diet, there were significant effects of sex on the two measures of LDL size phenotype. However, the proportion of variance explained by sex was small (Table 4), perhaps due to the fact that 28-month-old baboons are not fully mature. We found that female baboons had larger LDLs, which has also been reported in studies of humans.2 32
The two measures of LDL concentrations are highly correlated, and our preliminary data suggest that there is a substantial overlap of phenotypic and genotypic information contained in the two measures of LDL concentration.26 We therefore asked, how well does one LDL measure predict any of the other three? Although it seems that the ratio of LDL-C to apoB should be a good predictor of LDL size, several studies report otherwise.33 34 Furthermore, in this study we found that only 25% of the variation in LDL diameter was predicted by the ratio of non–HDL-C to apoB (r=.498, n=402, data not shown). The results of this study as well as those from studies of human plasma lipoproteins17 35 36 suggest that measures of size and concentration represent independent aspects of lipoprotein phenotypes.
Another indication that there are several independent aspects of LDL phenotype contained in the four measures was demonstrated by the results of the multiple regression analyses. While pairwise correlations among the four measures were positive and most were significant, we found different patterns in multiple regression analyses. For example, only the other LDL size measure, LDL diameter, was significantly correlated with the proportion of larger LDLs for the animals fed the LCLF or HCHF diet. In contrast, both concentration variables were significantly correlated with the proportion of larger LDLs when baboons were fed the LCHF diet (Table 3). Furthermore, the correlation of the proportion of larger LDLs with apoB was actually negative after adjusting for the positive correlations of non–HDL-C and LDL diameter. Thus, the data support the hypothesis that a number of independent aspects of LDL phenotype are contained in the four measures (at least three independent factors for the LCHF diet samples). Furthermore, the measures show contrasting trends of correlation depending on the diet. It is likely that the independent aspects of LDL phenotypes revealed by the four measures across the three diets indicate the dominating influences of different metabolic pathways. For example, the LDL phenotype measures may reflect the feedback regulation of LDL levels by LDL receptors located in cell membrane37 and the promotion of lipoprotein secretion or apolipoprotein synthesis38 by dietary fats and cholesterol.
Major genes controlling substantial portions of variation in non–HDL-C and apoB concentrations have been reported in studies of humans39 40 41 42 and baboons,43 and there is a probability that a gene or genes exert pleiotropic effects on non–HDL-C and apoB.26 When considered as a dichotomous trait, human LDL sizes have been shown by segregation analyses to be under genetic control.44 However, the genetic control of LDL size is not as clear when size is considered as a continuous variable.45 Therefore, in this study we attempted to establish whether genes control variation in baboon LDL size phenotypes.
We employed environmental variation (ie, changes in diet composition) as a means to detect evidence for genetic control of LDL phenotypes. The 150 baboons in the study were the progeny of 19 sires (mean number of progeny per sire was 8; range, 3 to 16). Thus a significant sire effect represents a significant genetic effect. We found significant genetic (ie, sire group) effects on each of the LDL phenotypes measured in each of the dietary environments. In addition, we found significant genetic effects on patterns of response to different diets for both LDL diameter and apoB concentrations (ie, sirexdiet effects, Table 4).
In summary, the present study of baboons fed three different diets indicates that there are at least three different aspects of LDL phenotype contained in the four measures made for this study (LDL diameter, the proportion of larger LDLs, non–HDL-C, and apoB) and that genes influence LDL phenotypes and the patterns of LDL response to different diets. These observations imply that the four measures of baboon LDLs made on different diet samples reflect the underlying metabolic complexity that modulates LDL phenotypes and concomitant risk for cardiovascular disease.
|
Selected Abbreviations and Acronyms |
|---|
|
|
Acknowledgments |
|---|
We acknowledge the grant support from the Southwest Foundation Forum and the National Institutes of Health (HL28972). We thank the following individuals who provided excellent technical assistance: Janet N. Dryden, Constance L. Durocher, Thomas D. Dyer, Evelyn M. Jackson, Perry H. Moore, Jr, and Jane F. VandeBerg.
Received December 29, 1995;
revision received April 16, 1996;
|
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1. Krauss RM, Burke DJ. Identification of multiple subclasses of plasma low density lipoproteins in normal humans. J Lipid Res. 1982;23:97-104.[Abstract]
2.
McNamara JR, Campos H, Ordovas JM, Peterson J, Wilson PWF, Schaefer EJ. Effect of gender, age, and lipid status on low-density lipoprotein subfraction distribution: results from the Framingham Offspring Study. Arteriosclerosis. 1987;7:483-490.
3.
Austin MA, Breslow JL, Hennekens CH, Buring JE, Willett WC, Krauss RM. Low density lipoprotein subclass patterns and risk of myocardial infarction. JAMA. 1988;260:1917-1921.
4. Krauss RM. Low density lipoprotein subclasses and risk of coronary artery disease. Curr Opin Lipidol. 1991;2:248-252.
5.
Campos H, Genest JJ Jr, Blijlevens E, McNamara JR, Jenner JL, Ordovas JM, Wilson PWF, Schaefer EJ. Low-density lipoprotein particle size and coronary artery disease. Arterioscler Thromb. 1992;12:187-195.
6. Teng B, Sniderman AD, Soutar AK, Thompson GR. Metabolic basis of hyperapobetalipoproteinemia: turnover of apolipoprotein B in low density lipoprotein and its precursors and subfractions compared with normal and familial hypercholesterolemia. J Clin Invest. 1986;77:663-672.
7. Tribble DL, Holl LG, Wood PD, Krauss RM. Variations in oxidative susceptibility among six low density lipoprotein subfractions of differing density and particle size. Atherosclerosis. 1992;93:189-199.[Medline] [Order article via Infotrieve]
8. Rudel LL, Sawyer JK, Parks JS. Dietary fat, lipoprotein structure, and atherosclerosis in primates. Atheroscler Rev. 1991;23:41-50.
9. Rudel LL, Bond MG, Bullock BC. LDL heterogeneity and atherosclerosis in nonhuman primates. Ann N Y Acad Sci. 1985;454:248-253.[Medline] [Order article via Infotrieve]
10.
Campos H, Roederer GO, Lussier-Cacan S, Davignon J, Krauss RM. Predominance of large LDL and reduced HDL2 cholesterol in normolipidemic men with coronary artery disease. Arterioscler Thromb Vasc Biol. 1995;15:1043-1048.
11.
Grundy SM, Bilheimer DW, Blackburn H, Brown WV, Kwiterovich PO Jr, Mattson F, Schonfeld G, Weidman WH. Rationale of the Diet-Heart Statement of the American Heart Association: Report of the AHA Nutrition Committee. Arteriosclerosis. 1982;4:177-191.
12.
Heiss G, Tamir I, Davis CE, Tyroler HA, Rifkind BM, Schonfeld G, Jacobs D, Frantz ID. Lipoprotein cholesterol distributions in selected North American populations: the Lipid Research Clinics Program Prevalence Study. Circulation. 1980;61:302-315.
13.
Krauss RM. Genetic influences on lipoprotein response to dietary fat and cholesterol: overview. Am J Clin Nutr. 1995;62:457S. Editorial.
14. Mott GE, Lewis DS, McMahan CA. Infant diet affects serum lipoprotein concentrations and cholesterol esterifying enzymes in baboons. J Nutr. 1993;123:155-163.
15. Cheng M-L, Woodford SC, Hilburn JL, VandeBerg JL. A novel system for storage of sera frozen in small aliquots. J Biochem Biophys Methods. 1986;13:47-51.[Medline] [Order article via Infotrieve]
16. Rainwater DL, Andres DW, Ford AL, Lowe WF, Blanche PJ, Krauss RM. Production of polyacrylamide gradient gels for the electrophoretic resolution of lipoproteins. J Lipid Res. 1992;33:1876-1881.[Abstract]
17.
Singh ATK, Rainwater DL, Haffner SM, VandeBerg JL, Shelledy WR, Moore PH Jr, Dyer TD. Effect of diabetes on lipoprotein size. Arterioscler Thromb Vasc Biol. 1995;15:1805-1811.
18. McNamara JR, Campos H, Ordovas JM, Wilson PWF, Schaefer EJ. Gradient gel electrophoretic analysis of low density lipoproteins. Am Biotech Lab. 1988;6:28-33.
19.
Callais F, Roche D, Andreux JP. Value of polyacrylamide gradient gel electrophoresis of lipoproteins for determining HDL cholesterol. Clin Chem. 1987;33:1266. Technical brief.
20. Cheng M-L, Kammerer CM, Lowe WF, Dyke B, VandeBerg JL. Method for quantitating cholesterol in subfractions of serum lipoproteins separated by gradient gel electrophoresis. Biochem Genet. 1988;26:657-681.[Medline] [Order article via Infotrieve]
21. Gambert P, Farnier M, Bouzerand C, Athias A, Lallemant C. Direct quantitation of serum high density lipoprotein subfractions separated by gradient gel electrophoresis. Clin Chim Acta. 1988;172:183-190.[Medline] [Order article via Infotrieve]
22. Nichols AV, Krauss RM, Musliner TA. Nondenaturing polyacrylamide gradient gel electrophoresis. In: Segrest JP, Albers JJ, eds. Methods in Enzymology: Plasma Lipoproteins. New York, NY: Academic Press; 1986:417-431.
23. Rainwater DL, Manis GS, Kushwaha RS. Characterization of an unusual lipoprotein similar to human lipoprotein a isolated from the baboon, Papio sp. Biochim Biophys Acta. 1986;877:75-78.[Medline] [Order article via Infotrieve]
24. Williams PT, Krauss RM, Nichols AV, Vranizan KM, Wood PDS. Identifying the predominant peak diameter of high-density and low-density lipoproteins by electrophoresis. J Lipid Res. 1990;31:1131-1139.[Abstract]
25. Lipid Research Clinics Program. Manual of Laboratory Operations, I: Lipid and Lipoprotein Analysis. Washington, DC: US Government Printing Office; 1974. US Dept of Health, Education, and Welfare publication NIH 75-628.
26.
Young SG, Smith RS, Hogle DM, Curtiss LK, Witztum JL. Two new monoclonal antibody-based enzyme-linked assays of apolipoprotein B. Clin Chem. 1986;32:1484-1490.
27.
Krauss RM, Dreon DM. Low density lipoprotein subclasses and response to a low-fat diet in healthy men. Am J Clin Nutr. 1995;62:478S-487S.
28.
Rudel LL, Johnson FL, Sawyer JK, Wilson MS, Parks JS. Dietary polyunsaturated fat modifies low density lipoproteins and reduces atherosclerosis of nonhuman primates with high and low diet responsiveness. Am J Clin Nutr. 1995;62:463S-470S.
29. Dreon DM, Fernstrom HA, Miller B, Krauss RM. Low density lipoprotein subclass patterns and lipoprotein response to a reduced-fat diet in men. FASEB J. 1994;8:121-126.[Abstract]
30.
Ginsberg HN, Karmally W, Siddiqui M, Holleran S, Tall AR, Blaner WS, Ramakrishnan R. Increases in dietary cholesterol are associated with modest increases in both LDL and HDL cholesterol in healthy young women. Arterioscler Thromb Vasc Biol. 1995;15:169-178.
31.
Rudel LL, Parks JS, Sawyer JK. Compared with dietary monounsaturated and saturated fat, polyunsaturated fat protects African green monkeys from coronary artery atherosclerosis. Arterioscler Thromb Vasc Biol. 1995;15:2101-2110.
32.
Campos H, Blijlevens E, McNamara JR, Ordovas JM, Posner BM, Wilson PWF, Castelli WP, Schaefer EJ. LDL particle size distribution: results from the Framingham Offspring Study. Arterioscler Thromb. 1992;12:1410-1419.
33. Abate N, Vega GL, Grundy SM. Variability in cholesterol content and physical properties of lipoproteins containing apolipoprotein B-100. Atherosclerosis. 1993;104:159-171.[Medline] [Order article via Infotrieve]
34. Tallis GA, Shephard MDS, Sobecki S, Whiting MJ. The total apolipoprotein B/LDL-cholesterol ratio does not predict LDL size. Clin Chim Acta. 1995;240:63-73.[Medline] [Order article via Infotrieve]
35. Rainwater DL, Blangero J, Moore PH Jr, Shelledy WR, Dyer TD. Genetic control of apolipoprotein AI distribution among HDL subclasses. Atherosclerosis. 1995;118:307-317.[Medline] [Order article via Infotrieve]
36.
Rainwater DL, Ludwig MJ, Haffner SM, VandeBerg JL. Lipid and lipoprotein factors associated with variation in Lp(a) density. Arterioscler Thromb Vasc Biol. 1995;15:313-319.
37. Goldstein JL, Brown MS. The low density lipoprotein pathway and its relation to atherosclerosis. Annu Rev Biochem. 1977;46:897-930.[Medline] [Order article via Infotrieve]
38.
Craig WY, Nutik R, Cooper AD. Regulation of apoprotein synthesis and secretion in the human hepatoma HepG2: the effect of exogenous lipoprotein. J Biol Chem. 1988;263:13880-13890.
39. Kammerer CM, Atwood LD, Hixson JE, Hackleman SM, Mitchell BD, VandeBerg JL, Haffner SM, Stern MP, MacCluer JW. Major genes affect serum levels of low-density lipoprotein cholesterol and apolipoprotein B in Mexican Americans. Circulation. 1994;90(suppl I):I-509. Abstract.
40. Morton NE, Gulbrandsen CL, Rhoads GG, Kagan A, Lew R. Major loci for lipoprotein concentrations. Am J Hum Genet. 1978;30:583-589.[Medline] [Order article via Infotrieve]
41. Green P, Owen ARG, Namboodiri K, Hewitt D, Williams LR, Elston RC. The Collaborative Lipid Research Clinics Program Family Study: detection of major genes influencing lipid levels by examination of heterogeneity of familial variances. Genet Epidemiol. 1984;1:123-141.[Medline] [Order article via Infotrieve]
42. Pairitz G, Davignon J, Mailloux H, Sing CF. Sources of interindividual variation in the quantitative levels of apolipoprotein B in pedigrees ascertained through a lipid clinic. Am J Hum Genet. 1988;43:311-321.[Medline] [Order article via Infotrieve]
43. Konigsberg LW, Blangero J, Kammerer CM, Mott GE. Mixed model segregation analysis of LDL-C concentration with genotype-covariate interaction. Genet Epidemiol. 1991;8:69-80.[Medline] [Order article via Infotrieve]
44. Austin MA, Krauss RM. Genetic control of low density lipoprotein subclasses. Lancet. 1986;2:592-595.[Medline] [Order article via Infotrieve]
45. Austin MA, Jarvik GP, Hokanson JE, Edwards K. Complex segregation analysis of LDL peak particle diameter. Genet Epidemiol. 1993;10:599-604.[Medline] [Order article via Infotrieve]
This article has been cited by other articles:
 |
|
 |
|
  D. L. Rainwater, L. A. Cox, J. Rogers, J. L. VandeBerg, and M. C. Mahaney Localization of multiple pleiotropic genes for lipoprotein metabolism in baboons J. Lipid Res., July 1, 2009; 50(7): 1420 - 1428. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. L Rainwater, M. C Mahaney, J. L VandeBerg, and X. L. Wang Vitamin E dietary supplementation significantly affects multiple risk factors for cardiovascular disease in baboons Am. J. Clinical Nutrition, September 1, 2007; 86(3): 597 - 603. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Rainwater, M. C. Mahaney, X. L. Wang, J. Rogers, L. A. Cox, and J. L. VandeBerg Determinants of variation in serum paraoxonase enzyme activity in baboons J. Lipid Res., July 1, 2005; 46(7): 1450 - 1456. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X. L. Wang, D. L Rainwater, M. C Mahaney, and R. Stocker Cosupplementation with vitamin E and coenzyme Q10 reduces circulating markers of inflammation in baboons Am. J. Clinical Nutrition, September 1, 2004; 80(3): 649 - 655. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Bosse, L. Perusse, and M.-C. Vohl Genetics of LDL particle heterogeneity: from genetic epidemiology to DNA-based variations J. Lipid Res., June 1, 2004; 45(6): 1008 - 1026. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. K. Berneis and R. M. Krauss Metabolic origins and clinical significance of LDL heterogeneity J. Lipid Res., September 1, 2002; 43(9): 1363 - 1379. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. C. Mahaney, J. Blangero, D. L. Rainwater, G. E. Mott, A. G. Comuzzie, J. W. MacCluer, and J. L. VandeBerg Pleiotropy and Genotype by Diet Interaction in a Baboon Model for Atherosclerosis : A Multivariate Quantitative Genetic Analysis of HDL Subfractions in Two Dietary Environments Arterioscler Thromb Vasc Biol, April 1, 1999; 19(4): 1134 - 1141. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Rainwater, C. M. Kammerer, J. E. Hixson, K. D. Carey, K. S. Rice, B. Dyke, J. F. VandeBerg, S. H. Slifer, L. D. Atwood, H. C. McGill Jr, et al. Two Major Loci Control Variation in ß-Lipoprotein Cholesterol and Response to Dietary Fat and Cholesterol in Baboons Arterioscler Thromb Vasc Biol, July 1, 1998; 18(7): 1061 - 1068. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||