Phenotypic heterogeneity associated with defective apolipoprotein B-100 and occurrence of the familial hypercholesterolemia phenotype in the absence of an LDL-receptor defect within a Canadian kindred

Of 163 individuals with a diagnosis of heterozygous familial hypercholesterolemia (FH), only one subject was found to be positive for familial defective apo B-100 (FDB). The eight-member kindred ascertained through this subject who presented with both a clinical phenotype of FH and the FDB apo B-100 (Arg3500----Gln) mutation was studied. Plasma lipid and lipoprotein profiles, apo E phenotypes, apo B gene markers at the 3' hypervariable region and LDL-receptor haplotypes (ApaLI, PvuII, NcoI), were determined, together with LDL-receptor activity on freshly isolated blood lymphocytes. The FDB mutation, present in four relatives, was associated with three different phenotypes: FH and severe hypercholesterolemia, moderate hypercholesterolemia and normolipidemia. The FH phenotype occurred in the absence of any functional LDL-receptor defect. In homozygotes for the absence of the PvuII cutting site who had the apo B mutation, LDL-cholesterol levels were low in the presence of the apo E3/2 phenotype and high in the presence of the apo E4/4 phenotype. None of the major known environmental influences accounted for the wide range of variation in LDL-cholesterol among the affected members. Further observations in the spouse and offspring of the normolipidemic FDB subject confirmed the association of apo E4, the FDB mutation and the PvuII(-/-) genotype with high cholesterol levels. It is concluded that the phenotypic expression of the FDB mutation may vary widely as a function of the genetic environment within a family.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum lipoprotein profile in the Mediterranean variant of glucose-6-phosphate dehydrogenase deficiency

Sardinian males with erythrocyte glucose-6-phosphate dehydrogenase (G-6-PD) deficiency have lower serum levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and apolipoprotein B (ApoB), compared to normals. Since the enzyme deficiency is expressed also in nucleated cells, we studied cholesterol (C) and DNA synthesis and LDL-receptor expression in freshly isolated circulating mononuclear cells from normal and G-6-PD-deficient Sardinians. Synthesis of C (as 14C-acetate incorporation) and of DNA (as 3H-thymidine incorporation) was clearly reduced, both in basal state and after PHA stimulation, in G-6-PD-deficient cells compared to normal cells. On the other hand, no clear influence of G-6-PD deficiency on LDL-receptor expression could be demonstrated. The Mediterranean variant of G-6-PD deficiency is characterized, whatever the metabolic mechanism may be, by a serum lipoprotein pattern of reduced atherogenicity.

Reconstitution of the lipoprotein cholesteryl ester transfer process using isolated rat ovary plasma membranes

Steroidogenic cells are able to utilize lipoprotein-derived cholesteryl esters for steroidogenesis without internalizing intact lipoproteins. In the current report, we provide evidence that an early step in this process may be the selective extraction of cholesteryl esters at the cell (plasma membrane) surface. We have used a highly purified plasma membrane preparation from rat luteinized ovaries for incubation with rat- and human-derived high density (HDL) and low density (LDL) lipoproteins. The lipoproteins were modified with residualizing [125I]apoprotein or [3H]cholesteryl ester markers. Following trypsin treatment to remove intact surface-bound apoprotein particles, the membranes were analyzed for transferred radioactive labels. The results show that all the lipoproteins tested could serve as cholesteryl ester donors. Although far more [3H]cholesteryl ester than [125I]apoprotein radioactivity was transferred to plasma membranes in each case, and varied with the ligand used, the total (net) mass of cholesteryl ester transferred was comparable with the different lipoproteins. These data were confirmed using direct chemical methodology. Transfer was found to be specific for cholesteryl esters or ethers and did not involve other lipoprotein core lipids tested. Endomembranes from the same tissue could not substitute for plasma membranes as the primary cholesteryl ester acceptor. These results provide evidence that a reconstituted lipoprotein-plasma membrane system can simulate the cholesteryl ester extraction process described in situ and suggest uses for this methodology in future experiments designed to understand the transfer process.

DNA polymorphisms of the apolipoprotein B and A-I/C-III genes are associated with variations of serum low density lipoprotein cholesterol level in childhood

A number of restriction fragment length polymorphisms (RFLPs) of the apolipoprotein B (apoB) and apolipoprotein A-I/C-III(apoA-I/C-III) genes have been found to be associated with serum lipoprotein levels in many adult populations. In order to examine whether these genetic polymorphisms influence serum lipoprotein levels in childhood and adolescence, we determined the apoB XbaI and apoA-I/C-III SstI genotypes and serum lipoprotein concentrations in 307 healthy Finns aged 9 to 21 years. In the age groups of 9, 12, and 15 years, subjects homozygous for the X2 allele (the XbaI site present) of the apoB gene had mean serum low-density lipoprotein (LDL) cholesterol levels (3.69, 3.43, and 3.15 mmol/l, respectively) that were 12-20% higher than those in subjects homozygous for the absence of this allele (3.08, 3.02, and 2.80 mmol/l, respectively). This association was more significant in males than in females. At the age of 9 to 18 years, subjects carrying the S2 allele (SstI site present) of the apoA-I/C-III gene complex had an approximately 6-15% higher mean serum LDL-cholesterol level than those homozygous for its absence. The combined genotype X2+S2+ (the simultaneous presence of the X2 allele and the S2 allele) was associated with an even more marked elevation of serum LDL-cholesterol level than either allele alone. As an example, the serum LDL cholesterol concentration was 20% higher in 9-year-old subjects with at least one X2 and one S2 allele than in those without either allele (3.55 vs. 2.97 mmol/l, P less than 0.005). The S2 allele was found to be significantly more frequent in eastern than in western Finland, whereas no significant areal differences were seen in the occurrence of the X2 allele. In conclusion, genetic variations of the apoB and apoA-I/C-III gene loci influence serum lipoprotein concentrations already in childhood.

Genetic and environmental contributions to cholesterol and its subfractions in 11-year-old twins. The Medical College of Virginia Twin Study

We conducted a cross-sectional analysis of the genetic and environmental contributions to the variance of lipoprotein cholesterol and its subfractions in children during early adolescence. Univariate path analysis was used to determine the relative contributions of genes, individual environment, and family environment to these measures in 233 11-year-old Caucasian twin pairs. For high density lipoprotein, high density lipoprotein2, low density lipoprotein, very low density lipoprotein, and triglycerides, a model that incorporated genes and individual environmental variation but not common environment was sufficient to explain the variation. Different magnitudes of genetic effects were seen for total cholesterol in boys and girls. High density lipoprotein3 showed different magnitudes by sex for genetic and individual environmental effect. Intermediate density lipoprotein was the only cholesterol subfraction in which shared, or common, environment was found to make a statistically significant contribution to the variation.

Lipoprotein transport gene abnormalities underlying coronary heart disease susceptibility

There is a close association between lipoprotein abnormalities and coronary heart disease susceptibility. Since 1982, the genes for the lipoprotein transport proteins have been isolated and at least partially characterized. Mutations in these genes are now being defined that underlie the common abnormalities found in heart attack victims. This review presents our current state of knowledge on this subject.

Variation in Lp(a) levels and apo(a) isoform frequencies in five baboon subspecies

Elevated levels of lipoprotein (a) [Lp(a)] are positively correlated with risk of cardiovascular disease and are thought to be a function of allelic variation in apo(a), the unique protein component of Lp(a). In this article we examine subspecies variation in Lp(a) levels and apo(a) isoforms in the baboon. Breeding populations of the five subspecies (Papio hamadryas hamadryas, P.h. cynocephalus, P.h. ursinus, P.h. papio, and P.h. anubis) of common long-tailed baboons are maintained at the Southwest Foundation for Biomedical Research. Serum samples were obtained from at least 20 unrelated animals of each subspecies. Twelve different size isoforms (including the null) of apo(a) were identified across the five subspecies. These isoforms act as alleles; a maximum likelihood method was used to obtain the allele frequencies. Significant differences in apo(a) isoform frequencies were found between subspecies (chi 2(44) = 163.10, p less than 0.0001). Quantitative levels of Lp(a) also differed among subspecies. We evaluated the correlation between genetic distances calculated using the quantitative Lp(a) levels and the apo(a) isoform data. Observed genetic relationships among the subspecies are consistent with the present-day geographic distribution and information from other marker protein systems. The findings indicate that the marker apo(a) may have great utility in both evolutionary and biomedical studies.

Mixed model segregation analysis of LDL-C concentration with genotype-covariate interaction

Mixed model complex segregation analyses have in the past ignored the possibility of genotype-covariate interaction. Only in the nonmixed model with polygenic heritability equal to zero have segregation analyses been performed that allowed for genotype specific regression of the phenotype on covariates. We present an extension of Hasstedt's [1982] mixed model likelihood approximation which does allow for genotype-covariate interaction in the mixed model. Following description of this approximation, we validate the likelihood calculation by a Monte Carlo procedure based on the actual pedigree and missing data structure used in a complex segregation analysis of low density plus very low density lipoprotein cholesterol (LDL-C + VLDL-C) in baboons. The observed averages of the bootstrap parameter estimates adequately recover the generating values, which included parameters specifying genotype-covariate interaction. We then applied both a traditional complex segregation analysis and an analysis with genotype-covariate interaction to test for the presence of a major locus affecting LDL-C levels in baboons. The model including genotype-covariate interaction was significantly different from the model without interactions, and strongly supported the hypothesis that there is a segregating Mendelian locus as opposed to a random environmental factor. This major locus accounts for approximately 46% of the variance in LDL-C levels, as compared to 40% explained by a locus with no genotype-covariate interaction.

Familial aggregation of lipids and lipoproteins in families ascertained through random and nonrandom probands in the Iowa Lipid Research Clinics family study

The aggregation of lipids [total cholesterol (CH) and triglyceride (TG)] and lipoproteins [high-density lipoprotein cholesterol (HDL) and low-density lipoprotein cholesterol (LDL)] in families ascertained through random and nonrandom probands in the Iowa Lipid Research Clinics family study was examined. Nonrandom probands were selected because their lipid levels (at a prior screening visit) exceeded a certain pre-specified threshold. The statistical method conditions the likelihood function on the actual event that the proband's value is beyond the threshold. This method allows for estimation of the path model parameters in randomly and nonrandomly ascertained families jointly and separately, thus enabling tests of heterogeneity between the two types of samples. Marked heterogeneity between the random and the hyperlipidemic samples is detected in the multifactorial transmission for TG and HDL, and moderate heterogeneity is detected for CH and LDL, with a pattern of higher genetic heritability estimates in the random than nonrandom samples. The observed pattern of heterogeneity is compatible with a higher prevalence in the random sample of certain dyslipoproteinemias that are associated with nonelevated lipids. For the random samples, genetic heritabilities are higher for CH and HDL (about 60%) than for TG and LDL (about 50%). For the nonrandom samples those estimates are about 45, 40, 35 and 30% for HDL, CH, LDL and TG, respectively. Little to no cultural (familial environmental) heritability is evident for CH and LDL, although 10-20% of the phenotypic variance is due to cultural factors for TG and HDL. These results suggest that the etiologies for lipids and lipoproteins may be quite different in random versus hyperlipidemic samples.

A multivariate method for detecting genetic linkage, with application to a pedigree with an adverse lipoprotein phenotype

The robust or model-free method for detecting linkage developed by Haseman and Elston for data from sib pairs is extended to incorporate observations of multiple traits on each individual. A method is proposed that estimates the linear function that results in the strongest correlation between the squared pair differences in the trait measurements and identity by descent at a marker locus. The method is illustrated by the study of apolipoprotein and cholesterol levels in individuals from a large family that had many members diagnosed with coronary heart disease.

Lipid phenotypes, apolipoprotein genotypes and cardiovascular risk in nonagenarians

Despite great interest in the role of lipids in overall and disease-free survival, virtually no information is available on the lipids, lipoproteins and apolipoproteins of persons over 90 years of age. Furthermore, the genetic underpinnings of atherosclerosis and the particular genetic factors responsible for protection against coronary artery disease remain speculative. In Bloomfield, Nebraska, we studied 41 nonagenarians (10 males, 31 females), with a mean age of 92.7 years, in whom lipids, lipoproteins, apolipoproteins and restriction fragment length polymorphisms (RFLPs) of genes for apolipoprotein B (apo B), aop AI and apo CIII were assessed. Nearly complete historical, physical and laboratory data were obtained on 39 subjects. The mean diastolic and systolic blood pressures for this group were nonhypertensive, body mass indices (weight/height2) had a mean of 23.9 and triceps skinfold thickness measurements an overall mean of 14.8 mm. The mean total serum cholesterol was 5.42 mmol/l. HDL-cholesterol levels in females persisted to be higher when compared to males (P less than 0.013). The allele frequencies for apo AI (MspI and PstI), apo CIII (Sst) and apo B (XbaI) gene RFLPs were typical for larger population studies. In these preliminary studies, we did not identify a distinctive phenotype, genotype, or phenotype-genotype relationship. Diversity of cardiovascular risk was the hallmark of these nonagenarians.

Familial defective apolipoprotein B-100. Comparison with familial hypercholesterolemia in 18 cases detected in Munich

It has recently been suggested that a substitution of glutamine for arginine at residue 3500 of apolipoprotein (apo) B-100 causes familial defective apo B-100 (FDB), an autosomal, dominantly inherited disorder, which leads to increased serum cholesterol levels. From a sample of 243 patients from Munich with type IIa hyperlipoproteinemia (HL), we have identified eight individuals with the apo B-100 arginine(3500)----glutamine mutation. In a group of 57 subjects with defective low density lipoprotein receptor (LDLR), no mutant apo B alleles were detected. The frequency of FDB in patients with type IIa HL was estimated to be 3%. In the kindreds of three of the probands, 10 additional carriers of the apo B mutation were identified. Clinical and biochemical data reveal a striking similarity between patients with FDB and those with a defect in the LDLR gene. Our data support previous findings that FDB is a serious disorder causing premature atherosclerosis.

Genetic variance and heritability of serum cholesterol and triglycerides among Chinese twin neonates

In order to examine the genetic variance and heritability of serum total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides, a total of 349 pairs of same-sexed twin neonates born in four major general teaching hospitals in Taipei City were studied. Based on the placental pattern and 12 red blood cell antigens, 271 monozygotic (MZ) and 78 dizygotic (DZ) twin pairs were identified. There was a significant genetic variance for total cholesterol, HDL-C, LDL-C, and triglycerides both unadjusted and adjusted for sex, gestational age and placentation. The unadjusted heritability of total cholesterol, HDL-C, LDL-C, and triglycerides was 0.59, 0.30, 0.25 and 0.75, respectively; while the corresponding adjusted heritability was 0.74, 0.38, 0.31, and 0.49, respectively. Intrapair variance of serum lipids was not significantly different between monochorionic and dichorionic MZ twins.

Genetic and environmental determinants of serum lipids and lipoproteins in French Canadian families

The contribution of genetic and environmental factors in serum triglycerides (TG), total cholesterol (CHOL), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and HDL-C/CHOL ratio were studied in 1630 subjects from 375 families of French descent by using a path analysis procedure. Familial correlations were computed in several pairs of biological relatives and relatives by adoption after adjustment for age and gender effects and after further adjustment for physical fitness, level of habitual physical activity, total body fat and fat distribution, diet, smoking, and alcohol consumption. The model of path analysis allowed the separation of transmissible variance (t2) into genetic (h2) and cultural (b2) components of inheritance. Under the most parsimonious solution and after adjustment for age, gender, and concomitants, the transmissible variance was entirely accounted for by genetic factors (t2 = h2), with h2 estimates of 0.52, 0.55, 0.60, and 0.63 for TG, CHOL, LDL-C, HDL-C, and HDL-C/CHOL, respectively. These estimates were similar to those obtained after adjustment for age and gender effects only. The contribution of nontransmissible environmental factors ranged from 0.48 for TG to 0.37 for HDL-C/CHOL ratio. These results suggest that both genetic and environmental factors contribute to the variation in blood lipids and lipoproteins in this population and that nongenetic influences are not associated with cultural factors transmitted across generations.

Phenotypic effects of apolipoprotein structural variation on lipid profiles. IV. Apolipoprotein polymorphisms in a small group of black women from the healthy women study

Structural variation in apolipoprotein E has been shown to influence lipid and lipoprotein concentrations. The purpose of the present study was to investigate several apolipoproteins in a group of Black women from the Healthy Women Study (HWS). HWS is a community-based prospective study of 541 premenopausal women who are being followed through the menopause to determine the influence of biological, genetic, and psychosocial phenomenon on cardiovascular risk factors. Of the 541 subjects, 48 are Black. Serum from most of these 48 Black women was used to type seven apolipoproteins (APO A-I, APO A-II, APO A-IV, APO C-II, APO D, APO E, and APO H). Five of these apolipoproteins are polymorphic in Blacks (APO A-IV, APO C-II, APO D, APO E and APO H). Only two and three individuals, respectively, were heterozygous at the APO D and APO C-II loci. APO A-IV, E, and H exhibited more variation, however, only APO E phenotypes could be used for statistical analyses. Three common phenotypes, APO E 3-2, APO E 3-3, and APO E 4-3, were used in analysis of variance on four quantitative lipid variables. Despite small numbers, the effect of APO E phenotype was apparent. The APO E 3-2 phenotype showed reduced average levels of total cholesterol, apolipoprotein B (APO B) and low-density lipoprotein cholesterol (LDLc), and the APO E 4-3 phenotype showed increased levels (P less than or equal to .0497). The APO E3-3 homozygote was intermediate on all three. Because of small numbers in the cells of APO A-IV and APO H phenotypes, these were not analyzed with respect to quantitative lipids.

Further evidence for an association between the XbaI polymorphism at the apolipoprotein B locus and lipoprotein level

Subjects with non-familial hypercholesterolemia who were homozygous for absence of an XbaI restriction site in the apolipoprotein B gene (genotype X2X2) had significantly lower values of apolipoprotein B than those possessing the site. Our data are in agreement with those of Berg (1986) and Law et al. (1986) indicating that X2X2 homozygotes have lower levels of apolipoprotein B, total serum cholesterol, triglycerides and LDL cholesterol. The mechanism underlying this effect is unknown, but could reflect different LDL metabolism between subjects with different genotypes.

Heredity and changes in plasma lipids and lipoproteins after short-term exercise training in men

The aims of this controlled experiment were to investigate the effects of short-term aerobic exercise training on plasma lipid and lipoprotein concentrations and the role of heredity in determining the individual variation observed in the lipoprotein-lipid response. Six pairs of male monozygotic (MZ) twins were subjected to an exercise training program that induced a 22,000 kcal energy deficit after 22 consecutive days of training. This program significantly reduced body weight, percent body fat, and subcutaneous fat and significantly increased maximal oxygen consumption (VO2max) (p less than 0.005). The plasma insulin response to an oral glucose challenge was markedly reduced after training (p less than 0.001). Plasma triglyceride concentration decreased and the high density lipoprotein cholesterol (HDL-CHOL)/CHOL ratio increased with training (p less than 0.05). Subjects also displayed substantial individual variation in their response to exercise training, but the changes in plasma CHOL, apolipoprotein (apo) B low density lipoprotein cholesterol (LDL-CHOL), HDL-CHOL, and the HDL-CHOL/CHOL ratio tended to be similar within MZ twin pairs (0.67 less than or equal to ri less than or equal to 0.92; 0.05 greater than p less than 0.0001) thus indicating a significant effect of heredity on the sensitivity of plasma lipids and lipoproteins to exercise training.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of selective breeding on the cholesterolemic responses to dietary saturated fat and cholesterol in baboons

Positive assortative mating of baboons (Papio sp.) based on elevation of serum cholesterol concentrations in response to a cholesterol- and saturated fat-enriched diet produced 64 progeny (30 high line; 34 low line). When the animals were 3 to 4 years of age, we tested their lipoprotein cholesterol responses to dietary cholesterol and fat in a factorial experiment with two levels of dietary cholesterol (1.7 and less than 0.01 mg/kcal) and two types of fat, coconut oil (P/S 0.1) and corn oil (P/S 3.5), each providing 40% of total calories from fat; we also tested their responses to chow. The high line animals had significantly higher very low density plus low density lipoprotein (VLDL + LDL) and high density lipoprotein (HDL) cholesterol levels on all diets. The effects of dietary cholesterol on VLDL + LDL cholesterol concentrations were greater in high line animals than in low line animals, but dietary cholesterol's effects on HDL cholesterol were similar in both lines. The effects of saturated fat, compared to unsaturated fat, on both VLDL + LDL and HDL cholesterol levels were similar in both lines. Selective breeding produced lines diverging in lipoprotein cholesterol concentrations by acting on several different genetically mediated processes that control serum lipoprotein levels. At least one of these processes involves responsiveness of serum VLDL + LDL cholesterol concentration to dietary cholesterol.

Biological and cultural sources of familial resemblance in plasma lipids: a comparison between North America and Israel--the Lipid Research Clinics Program

Heterogeneity in determinants of familial resemblance of lipid and lipoprotein levels between populations in North America and Israel was investigated using path analysis. A common protocol, identical measurement techniques, and the same statistical procedures were used in the two samples. Both genetic (h2) and cultural (c2) determinants of inheritance were significant for all lipid variables in the two studies. Genetic and cultural heritability of total cholesterol (h2 = 0.61, c2 = 0.02), low-density lipoprotein cholesterol (h2 = 0.59, c2 = 0.02), and high-density lipoprotein cholesterol (h2 = 0.55, c2 = 0.06) did not differ significantly between North America and Israel, while there was a significant difference for triglyceride (h2 = 0.41, c2 = 0.07 in North America; h2 = 0.61, c2 = 0.05 in Israel). Secondary parameters of the path model describing intrafamilial environmental relationships differed between the two countries. In particular, there was a higher correlation between marital environments in Israel for all traits except triglyceride, and a larger effect of father's environment on offspring's environment in Israel for all traits. Within both populations, variation of plasma lipids and lipoproteins was mostly explained by genetic factors and random unmeasured environmental factors. The contribution of common family environment was found to be small, though statistically significant. This is probably due to homogeneity of the distribution of familial environmental determinants within both countries.

Detecting genetic effects on lipoprotein phenotypes in baboons: a review of methods and preliminary findings

Statistical methods for detecting the contribution of major genes to quantitative phenotypes have been widely applied in human family studies. Some of these methods are reviewed, and their application to analysis of an animal model for a human disease is described. Analysis of lipoprotein concentrations in pedigreed baboons provides evidence for genetic effects on specific lipoprotein components that have been associated with reduced susceptibility to atherosclerosis in humans.

Complex segregation analysis of plasma lipid and lipoprotein variables in a Jerusalem sample of nuclear families

Plasma lipid and lipoprotein concentrations from 3,074 nuclear families in the multiethnic Jerusalem Lipid Research Clinic study population were analyzed for possible involvement of major genes in determination of high levels of these traits. Complex segregation analysis under a mixed model including major gene and multifactorial transmissible components was performed on transformed-plasma lipids and lipoproteins after covariance adjustment for age, sex and environmental measures. Likelihood analysis provided evidence for recessive major genes influencing plasma triglyceride, and low-density lipoprotein cholesterol (LDL-C). The estimated gene frequencies for triglyceride and for hyperbetalipoproteinemia in our study population were about 0.1. Our positive results for total cholesterol and high-density lipoprotein cholesterol (HDL-C) were nonconclusive and the major effects could result from causes other than major genes. The mixed-model parameters were homogeneous across origin groups for LDL-C and HDL-C and heterogeneous for total plasma cholesterol and triglyceride. The multifactorial-transmission heritability index was similar in all origin groups for all the traits. The origin heterogeneity in the major gene parameters appeared to be mainly due to the North African group which favored a multifactorial transmission for all traits except for LDL-C.

Association between polymorphic blood markers and risk factors for cardiovascular disease in a large pedigree

A large pedigree with high prevalence of heart disease is investigated to analyse the association between polymorphic blood markers and quantitative risk factors for cardiovascular disease. The analysis incorporates a familial correlation structure among the individuals in the pedigree and a generalized power transformation to induce approximate residual normality of the risk factors. A total of 380 marker/risk factor combinations are analysed, and at the normal 1% significance level, positive associations are found between the A antigen of the ABO locus and both serum total cholesterol and low-density lipoprotein cholesterol, and negative associations are found between the B antigen of the ABO locus and serum total cholesterol, and between the B allele of acid phosphatase (AP) locus and systolic blood pressure.

Linkage and segregation analyses of apolipoproteins A1 and B, and lipoprotein cholesterol levels in a large pedigree with excess coronary heart disease: the Bogalusa Heart Study

Robust methods were employed, using data from a single large pedigree, to screen serum apolipoprotein A1 and B levels, serum lipoprotein cholesterol levels, and ratios of serum lipoprotein cholesterol fractions to apolipoprotein A1 and B levels for genetic linkage to 31 polymorphic markers. Segregation analyses were performed for each of the apolipoprotein and lipoprotein cholesterol fractions to obtain estimates for use in applying likelihood methods of linkage analysis. Trait-marker combinations for which linkages were suggested from the robust methods were then reexamined for linkage using the likelihood (lod score) method. Results from the segregation analyses were consistent with major gene determination of apo B and HDL-C levels, the HDL-C to apo A1 ratio, the LDL-C to apo B ratio, and a measure of relative content of cholesterol in HDL-C and LDL-C. Linkage between haptoglobin and the HDL-C/apo A1 ratio was suggested, with a lod score of 1.72 at theta = 0.05.

Genetic and cultural inheritance of serum lipids, low and high density lipoprotein cholesterol and serum apolipoproteins A-I, A-II and B

The genetic and cultural heritability of serum cholesterol and triglyceride concentrations, as well as of the concentrations of low and high density lipoprotein cholesterol and serum apolipoproteins A-I, A-II and B, were estimated by path analysis in families selected through probands with premature myocardial infarction and in families randomly selected from the general population. Genetic heritability was high for serum cholesterol (0.64) and low density lipoprotein cholesterol (0.67) concentrations, whereas it was lower for high density lipoprotein cholesterol level (0.42). Cultural inheritance was of less importance than genetic inheritance for all cholesterol variables. For serum triglyceride concentration genetic (0.33) and cultural (0.23) heritability was of similar significance. The results for serum apolipoproteins A-I and A-II parallelled those for HDL cholesterol. A marked intergenerational difference was found in the genetic heritability for apolipoprotein B concentration. The parental genetic heritability was 0.14, whereas the genetic heritability was 0.51 among siblings.

Heterogeneity in multifactorial inheritance of plasma lipids and lipoproteins in ethnically diverse families in Jerusalem

Genetic and cultural determinants of total cholesterol (TC), triglyceride (TG), low- and high-density lipoprotein cholesterol (LDL-C, HDL-C), and HDL-C/TC were estimated utilizing a path model in a random sample of nearly 4,000 families examined in the Jerusalem Lipid Research Clinic. The analyses were done separately in each of the ethnic groups categorized according to the parents' country of birth (Europe, Asia, North Africa, and Israel/mixed origin) in order to identify the nature and sources of any heterogeneity among the groups. Both genetic (h2) and cultural (c2) components of inheritance were significant for all lipid variables in each of the ethnic groups. Under the most parsimonious model, estimates of h2 in the ethnic groups were .40-.55, .40-.51, .45-.50, .41-.48, and .42-.78 for TC, LDL-C, HDL-C, HDL-C/TC, and TG, respectively. The c2 ranged from 3% to 5% for TC and LDL-C and from 4% to 10% for HDL-C, HDL-C/TC, and TG. The major parameters of the path model were generally homogeneous across the origin groups. The h2 appeared to be higher in the Asian and c2 was slightly greater in the European group. The stronger sibling environmental effect in the Asia group, the somewhat lower transmission of environment in the North African group, and the lower correlation between spouse environments in the North African group were the major sources of the origin heterogeneity. Within this population, genetic factors appear to be the major determinants of lipid variations, suggesting relative homogeneity of the distribution of environmental determinants of plasma lipids.