Characterization of genetic markers in the 3' end of the apo B gene and their use in family and population studies

The 3' end of the apo B gene is highly polymorphic. Two point mutations in the coding sequence of the gene create EcoRI (E+, E-) and XbaI (X+, X-) RFLPs. The two loci are in random association and the frequency of the four haplotypes, E+X+, E+X-, E-X+ and E-X- in the normolipidaemic population are 0.68, 0.30, 0.02 and 0.00, respectively. Although the polymorphic nucleotide underlying the EcoRI RFLP creates an amino acid substitution in the apo B protein (Glu----Lys) in a region close to a putative LDL-receptor recognition site(s), we find no statistically significant difference in the frequency of the apo BGlu and apo BLys alleles in hyperlipidaemic patients (familial hypercholesterolaemia, type IIA with no tendon xanthomas, IIB and probably IV) and the normolipidaemic population. In contrast, we confirm previous findings, that the X+ allele is in linkage disequilibrium with a genetic locus that predisposes to the development of higher fasting plasma triglyceride levels than the X- allele. We have characterized a highly polymorphic region immediately 3' to the apo B gene. At least 5 alleles of this locus exist in the population and our family studies show it should be an extremely informative locus to use in studies where polymorphic or mutant apo B alleles are suspected to underly certain forms of familial hyperlipidaemia. DNA sequence analysis of this highly polymorphic locus shows that the variation is entirely attributable to the number of times the simple repeating sequence 5'-TTTATAATTAAAATATTTATAATTAAATAT-3' is present.     

DNA polymorphisms of the apolipoprotein B gene (XbaI, EcoRI, and MspI RFLPs) in Norwegians at risk of atherosclerosis and healthy controls.

OBJECTIVES: Apo B is the exclusive protein constituent of LDL and is ligand on LDL, recognized and bound by the LDL receptor. Several restriction fragment length polymorphisms (RFLPs) of the apo B gene have been shown to be associated with variation in serum lipid levels in different populations. In this study we sought to determine the frequency of XbaI, EcoRI, and MspI polymorphisms and the haplotypes generated by these three polymorphic sites of the apo B gene and their influence on lipid levels in a sample of Norwegian subjects at risk of atherosclerosis and healthy control subjects. METHODS AND RESULTS: 108 White Norwegians at risk of atherosclerosis (cases) and 64 healthy individuals (controls) were examined for possible association between the alleles at the XbaI (X), EcoRI (R), and MspI (M) polymorphic restriction sites of the apolipoprotein B gene and serum lipid levels. The frequency of the M allele (absence of restriction site) was significantly higher in cases with high total cholesterol (TC), high low-density lipoprotein cholesterol (LDLC), and high apolipoprotein B (apo B) than in controls with normal TC, LDLC, and apo B (P < 0.04, P < 0.02, and P < 0.01, respectively). The frequencies of apo B genotypes detected with XbaI, EcoRI, and MspI did not differ significantly between cases and control subjects. A significant association between MspI genotypes and TC (P < 0.02), LDLC (P = 0.03), and apo B (P = 0.001) was observed only in cases. However, cases with the genotype M+/M+ had the lowest and those with the genotype M+/M- had the highest levels of serum TC, LDLC, and apo B. We did not observe any significant association between the alleles or genotypes detected with XbaI or EcoRI and serum lipid levels. In cases, genotypes defined by EcoRI and MspI RFLP paired loci differed significantly for apo B (chi 2 = 19; P = 0.007) but not for other blood lipids. EcoRI and MspI RFLPs change glutamic acid (Glu) 4154 to lysine (Lys) and arginine (Arg) 3611 to glutamine (Gln), respectively, which lie near the low density lipoprotein receptor binding region of apo B. Haplotypes containing "Lys/Arg Lys/Arg" (all basic amino acids) in cases were associated with low serum TC, LDLC, and apo B. In individuals at risk of atherosclerosis the concentration of serum lipids tends to be inversely related to the number of lysine and arginine. CONCLUSION: We conclude that variations in the apo B gene, resulting in changes of charged amino acids, affect the circulating blood lipids and that these may contribute to the risk of atherosclerosis.     

DNA polymorphisms of the gene for apolipoprotein B in patients with peripheral arterial disease

We have determined the frequency of DNA polymorphisms of the gene for human apolipoprotein B, detected with XbaI and EcoRI, in 205 patients with documented peripheral arterial disease. Of the patients, 78 have no evidence of disease in the coronary and carotid arteries, 64 have coexisting coronary artery disease but no evidence of carotid artery disease, 26 patients have coexisting carotid artery disease but no evidence of coronary artery disease, and 37 have coexisting coronary and carotid artery disease. Levels of triglycerides, cholesterol and apolipoprotein B were measured for each patient, and RFLP frequency was determined in all the patients. Lipid, lipoprotein and apolipoprotein levels were not significantly different between the different patient groups. Compared with a sample from the clinically well London population, the frequency of the R2 allele of the polymorphism detected with EcoRI, and the frequency of the X1 allele of the XbaI polymorphism was significantly higher in the patient group. The frequency of these alleles was not significantly different in the different patient groups. In patients with only peripheral arterial disease, individuals with the XbaI genotype X1X1 have the lowest and those with the genotype X2X2 have the highest mean levels of serum cholesterol. However, in all other patient groups this trend was reversed (X1X1 highest and X2X2 lowest). Our observations suggest that variation at the apo B locus is one of the factors involved in predisposing an individual to develop arterial disease but does not determine where in the arterial system the disease develops.     

Restriction fragment length polymorphisms in the apo B gene in relation to coronary artery disease

We have determined the frequencies of the alleles at the EcoRI (E), XbaI (X) and PvuII (P) polymorphic restriction sites in the apo B gene in 124 white men with coronary artery disease (CAD) and in 146 white men free from CAD. The frequencies of the E- (restriction site absent) and X- alleles were both significantly higher in normocholesterolaemic men with CAD than in those without CAD, but the frequency of the P+ allele (restriction site present) was similar in the 2 groups. The frequency of the E- allele was significantly higher in CAD men with hypertriglyceridaemia than in normal men without hypertriglyceridaemia. In the normocholesterolaemic men without CAD, the mean serum cholesterol concentration was higher in those with genotype X++ than in those with genotype X--. Mean serum LDL-apo B and LDL-cholesterol concentrations did not differ significantly between men with different XbaI or EcoRI genotypes. Serum apo A-I levels differed significantly between normal men with different XbaI genotypes. Serum HDL-cholesterol levels differed significantly between CAD men with different XbaI genotypes. These results suggest that in white men the E- and X- alleles are in linkage disequilibrium with a nearby allele that is causally related to CAD. It is also possible that the amino acid substitution at position 4154 in apo B, brought about by the nucleotide change responsible for the EcoRI polymorphism, has a direct effect on the atherogenicity of LDL.     

XbaI and c/g polymorphisms of the apolipoprotein B gene locus are associated with serum cholesterol and LDL-cholesterol levels in Finland

Several restriction fragment length polymorphisms (RFLPs) have been identified within or adjacent to the gene locus for apolipoprotein B (apo B), the major protein component of serum low density lipoprotein (LDL). One of these, detected with the restriction enzyme XbaI, has been suggested to be involved in the determination of serum lipid levels in some but not all populations. We determined the XbaI genotypes and serum lipoprotein levels of 176 apparently healthy unrelated Finns. Subjects homozygous (genotype X2X2) or heterozygous (genotype X1X2) for the presence of the XbaI restriction site within the apolipoprotein B gene (n = 113) had, on the average, an 11% higher serum total cholesterol (P = 0.01) level than those homozygous for the absence of this site (genotype X1X1, n = 63). In addition, the X2 allele was significantly associated with apo B(c), another allele reportedly associated with elevated serum cholesterol levels. The combined genotype (both X2 and apo B(c) alleles present) resulted in a greater elevation of total cholesterol (P = 0.004, when compared to subjects with neither allele) and LDL-cholesterol (P = 0.02) than the presence of either allele alone. The results suggest that both the XbaI and apo B(c/g) sites are in linkage disequilibrium with a functionally important DNA alteration within or adjacent to the apo B gene but the XbaI locus may be in stronger linkage disequilibrium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic evidence from 7 families that the apolipoprotein B gene is not involved in familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL) is the most common genetic form of hyperlipidemia in which affected individuals manifest multiple lipoprotein phenotypes. Although the molecular defect is still unknown, several kinetic studies have demonstrated increased turnover rates of apolipoprotein B (apo B) in patients with FCHL, irrespective of their lipoprotein phenotype. Using 3 restriction fragment length polymorphisms (RFLPs) of the apo B gene (XbaI, MspI and EcoRI) we have investigated 33 families which fulfill the diagnostic criteria of FCHL. No significant difference in allele frequency was found between 33 unrelated individuals with FCHL and 107 normolipidemic controls. 3-RFLP haplotypes were constructed in each pedigree. A co-segregation analysis was performed in 7 informative families. In no family was co-segregation observed between the haplotype of the apo B gene and the phenotype of FCHL. These data are not compatible with the hypothesis that FCHL is caused by mutations of the apo B gene acting as a simple mendelian trait.     

Lack of correlation between the apolipoprotein B XbaI polymorphism and blood lipid levels in a Swedish population

The possible connections between the apolipoprotein B (apo B) XbaI polymorphism and the serum levels of total cholesterol, triglycerides, LDL, HDL and apo B have been investigated among 187 randomly selected subjects from Gothenburg, Sweden. The interferences of age and sex on the serum lipoproteins and apo B concentrations were considered. Using multiple regression analysis, we compared the different lipid levels and the levels of apo B with the genotypes X1X1, X1X2 and X2X2 (X1 = without the XbaI restriction site, X2 = with the site), with age and with sex and with those factors combined with each other. A significantly higher concentration of serum cholesterol and LDL among men than among women was found and total serum cholesterol, LDL and apo B were positively correlated with age. The allele frequency of the XbaI polymorphism in the sample was 0.45 for the allele without the XbaI restriction site. No correlation was found between the apo B genotypes and the levels of serum lipoproteins or apo B.     

A study of DNA polymorphism in the apolipoprotein B gene in a Japanese population

A Japanese group comprising 53 hyperlipidemic and 54 normolipidemic subjects was genotyped for DNA restriction fragment length polymorphisms (RFLPs) at the apo B gene locus. The polymorphisms with XbaI and PvuII were present at allelic frequencies of 0.04 (X1 allele) and 0.96 (X2 allele), 0.94 (P1 allele) and 0.06 (P2 allele), respectively. Unlike the previous reported association of the X1 allele with hypercholesterolemia found in Caucasians there was no difference in the frequency of the X1 allele between normolipidemic and hypercholesterolemic Japanese. Among the Japanese, two RFLPs appear to be in linkage equilibrium and can be used in conjunction as a haplotype. There is no strong population association in our patient group between any allele of the RFLPs studied and hyperlipidemia.     

Apolipoprotein E phenotypes in patients with gout: relation with hypertriglyceridaemia.

OBJECTIVE--To elucidate the relationship, if any, between lipid abnormalities and apolipoprotein E (apo E) polymorphism, by investigating apo E phenotype and allele frequency. METHODS--Fasting blood samples were taken for determination of apo E phenotype and serum lipids in 221 male patients with gout and 141 control male subjects. Apo E phenotype was determined by one dimensional flat gel isoelectric focusing. RESULTS--Frequencies of apo E phenotypes in gout were apo E3/3 67.9%, E4/3 18.1%, E4/4 2.3%, E4/2 1.8%, E3/2 9.5%, and E2/2 0.5%; those in control male subjects were 74.5%, 15.6%, 0%, 1.4%, 7.1%, and 1.4%, respectively. Frequencies of the e2, e3, and e4 alleles in gout were 0.061, 0.817 and 0.122, compared with the corresponding control frequencies of 0.057, 0.858 and 0.085. These differences in apo E phenotype and allele frequencies between gout and control subjects were not significant. The frequency of apo e4 allele in hyperlipidaemic gout subjects was significantly greater than that in normolipidaemic gout subjects; in contrast, its frequency was not different between hyperlipidaemic and normolipidaemic control subjects. Serum triglyceride, total cholesterol, apo B and E concentrations were significantly greater in gouty patients with the apo E4/3 phenotype than in those with gout having the apo E3/3 phenotype. CONCLUSIONS--These data suggest that gout subjects with hyperlipidaemia (hypertriglyceridaemia, hypercholesterolaemia or both) possess the apo e4 allele with higher frequency than those with normolipidaemia. They also suggest that apo e4 may induce some susceptibility to the development of hyperlipidaemia in gout in addition to that induced by obesity or excessive alcohol consumption, and may contribute to the high prevalence of atherosclerotic diseases in gout patients.     

The contribution of candidate genes to the response of plasma lipids and lipoproteins to dietary challenge

The possible role of four candidate genes in lipid and lipoprotein response to diet was examined in 214 members of two large kibbutz settlements in Israel. Four site polymorphisms (signal peptide insertion/deletion, XbaI, EcoRI and MspI) of the apo B gene, the common apo E genotypes, three common mutations (T-93G, S447stop and N291S) of the LPL gene and the CETP I405V RFLP were determined. The average reduction induced by diet in participants with the absence of the EcoRI restriction site (L4154) of the apo B gene compared with those found to be homozygotes for the restriction site (G/G4154) were: 16.2 and 8.0 mg/dl for total cholesterol (TC) (P=0. 01); and 15.6 and 6.2 mg/dl for LDL-C (P=0.007), respectively. TC and LDL-C baseline levels were significantly different among the apo-E genotypes, yet there were no significant effects on lipid and lipoprotein dietary response. Triglyceride baseline values were significantly lower (P=0.007) among subjects with the LPL S447stop mutation and HDL-C was significantly lower (P=0.008) among subjects found to be heterozygous for the LPL N291S mutation. A heterogeneous response for triglyceride was observed for individuals with the S291 allele as compared to those individuals who were found to be homozygous for the N291 allele. No differences in dietary responsiveness were observed among the apo E and CETP genotypes. In conclusion, our results suggest that sequence variation(s) in the coding region of the apo B gene linked to the EcoRI polymorphism are associated with total cholesterol and LDL-C responsiveness to dietary manipulation. In our study population, LPL mutations had a significant effect on TG and HDL-C baseline levels and on their response to diet.     

Hep-G2 glucose transporter gene polymorphism in Caucasian, black, Hispanic and Japanese patients with NIDDM

DNA from non-diabetic Caucasians (n = 16), Blacks (n = 22), Hispanics (n = 13) and Japanese (n = 21), as well as DNA from 34 Caucasian, 19 Black, 19 Hispanic and 20 Japanese non-insulin-dependent diabetes mellitus (NIDDM) patients were examined for restriction fragment length polymorphism (RFLP) after digestion with enzymes BglII and XbaI, and hybridization with the glucose transporter probe, hGT2-2. There were significant differences in the incidence of the RFLPs between Caucasians and Blacks, both controls and patients with NIDDM. Digestion with XbaI revealed a higher incidence of the homozygotic state for allele I in NIDDM Caucasians (12 vs. 0%) than in controls. In NIDDM Blacks and Hispanics, we found a high incidence of a combination of two traits: 42% of the Black and 47% of the Hispanic NIDDM patients were homozygous for the BglII allele I and heterozygous for XbaI. Only 23% of non-NIDDM Blacks or Hispanics had this combination (P less than 0.05). There was no association between RFLP frequency and NIDDM among Japanese subjects. These data support the influence of race on both BglII and XbaI RFLPs. The homozygotes for XbaI in Caucasians and the presence of two specific traits in Blacks and Hispanics appear with higher frequency in NIDDM.     

Restriction fragment length polymorphisms of the apolipoprotein A-I, C-III, A-IV gene locus. Relationships with lipids, apolipoproteins, and premature coronary artery disease.

Data from various laboratories have indicated associations of various alleles determined by RFLPs within or adjacent to several apolipoprotein genes with abnormalities in plasma lipids and/or premature coronary artery disease (CAD). In order to assess such relationships we have examined allele frequencies of 8 different RFLPs within or adjacent to the apo A-I, C-III and A-IV gene complex on the long arm of chromosome 11 (MspI, 5' to the apo A-I gene; MspI, within the apo A-I gene; PstI, 3' to the apo A-I gene; SstI, 3' to the apo C-III gene; PvuII, within the apo C-III gene; PvuII, 5' to the apo C-III gene; XbaI, within the apo A-IV gene; and XbaI, 3' to the apo A-IV gene) in 202 patients with CAD (50% narrowing of one or more coronary arteries) prior to age 60 and 145 normal controls. None of the allele frequencies of these RFLPs were significantly different in cases as compared to controls. With regard to associations with plasma lipids and apolipoprotein levels, the rare allele determined by the absence of the PstI site was associated with elevated triglyceride levels (P less than 0.05) in cases, but not in controls. In contrast, the rate MspI allele 5' to the apo A-I gene was associated with elevated triglyceride levels (P less than 0.05) in controls but not in cases. In both cases and controls, subjects with the uncommon SstI allele had triglyceride levels that were 9 and 38% higher than in those without this allele. These differences were significant (P less than 0.05) only in controls. Our data indicate that the rare allele determined by the SstI site within this gene complex deserves further study in order to understand its association with elevated triglycerides in Caucasian populations. However, at the present time all these DNA markers lack sufficient specificity to be clinically useful for CAD risk assessment.     

Apolipoprotein A-I gene polymorphisms: frequency in patients with coronary artery disease and healthy controls and association with serum apo A-I and HDL-cholesterol concentration

We have investigated the association between serum high density lipoprotein-cholesterol (HDL-C) and apo A-I concentration and the PstI and XmnI restriction fragment length polymorphisms of the apolipoprotein AI-CIII-AIV multigene complex. Two groups of subjects were examined. The first comprised 174 unrelated male patients under 60 years of age with angiographic evidence of coronary artery disease (CAD). Of this group 34 were non-North European. The second group consisted of 104 unrelated healthy male North European subjects aged under 60 and free from demonstrable CAD, who attended a health screening clinic in London. For the PstI polymorphism, the frequency of the rarer P2 allele was 0.12 in both the North European and non-North European patients and this was higher than in the control group (P2 frequency 0.06, P less than 0.05). Healthy individuals with the genotype P1P2 had higher levels of apo A-I but similar levels of HDL-C compared to those with the genotype P1P1. However, CAD patients with the genotype P1P2 had lower serum levels of apo A-I and significantly lower serum levels of HDL-C compared to those with the genotype P1P1 (0.85 mmol/l vs. 1.0 mmol/l, P less than 0.05). The allele frequencies of the XmnI polymorphisms were not significantly different in the control group and the group of North European patients, although within the sample of non-North European patients, the frequency of the X2 allele was significantly higher than that found in the North European controls (0.26 vs. 0.09). Patients with the genotype X1X2 had a higher mean serum concentration of HDL-C and apo A-I compared with patients with the genotype X1X1 (1.14 and 0.93 mmol/l for HDL-C, P less than 0.05; 147 and 123 mg/dl for apo A-I, P less than 0.05). Associations between HDL-C and apo A-I levels and PstI and XmnI genotype were similar in patients taking and not taking beta-blockers. The data show that genetic variation in the apo AI-CIII-AIV gene cluster is associated with coronary artery disease although only weakly, and suggest that the mechanism of this association may operate through an effect in determining the serum concentration of apo A-I and HDL-cholesterol.     

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.     

中国人Ⅱa型高脂蛋白血症载脂蛋白E基因多态性的研究

为探讨中国人Ⅱa型高脂蛋白血症患者载脂蛋白E基因多态性及其与血脂和载脂蛋白水平的关系,采用聚合酶链反应－限制片长多态性法,分别对87例Ⅱa型高脂蛋白血症患者及230例血脂正常者的载脂蛋白E基因型、空腹血脂及载脂蛋白AⅠ、AⅡ、B100、CⅡ、CⅢ和E进行了全面分析。结果发现,Ⅱa型高脂蛋白血症患者的血清甘油三酯、总胆固醇、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇、非高密度脂蛋白胆固醇,以及载脂蛋白B100、CⅡ、CⅢ和E水平较对照组显著升高（P＜0．01）;;血清载脂蛋白E／CⅢ比值显著降低（P＜0．05）;Ⅱa型高脂蛋白血症组与对照组载脂蛋白E基因型及等位基因频率分布均以E3／3和ε3最高,Ⅱa型高脂蛋白血症组的ε4等位基因有增高的趋势,而ε2等位基因有降低的趋势（P＞0．05）。携带ε2等位基因组血清载脂蛋白E水平较E3／3基因型组显著升高,而携带ε4等位基因组血清载脂蛋白E水平较E3／3基因型及携带ε2乘位降低基因组显著（P＜0．001）。此结果提示,ε2及ε4等位基因与Ⅱa型高脂蛋白血症患者的血清载脂蛋白E水平有关。     

Lipid and lipoprotein abnormalities in South African Indian men with myocardial infarction

The Indian (Asian) population in South Africa has a high rate of coronary artery disease. Fasting serum lipid and lipoprotein levels were measured in 620 consecutive male survivors of myocardial infarction and compared with those of 524 healthy male volunteer controls, and the presence of hypercholesterolaemia and hypertriglyceridaemia in the patient group was related to other non-lipid coronary risk factors. All survivors and controls were below age 61 years. Total cholesterol, triglyceride and low-density-lipoprotein cholesterol concentrations varied significantly with age both in patient and control groups, whereas high-density-lipoprotein (HDL) cholesterol did not vary with age in either group. Using the 90th-percentile age-adjusted values of controls for total cholesterol (7.1 mmol/l) and triglyceride (3.0 mmol/l) as cut-off points, 287 (46%) survivors were hyperlipidaemic. Hypercholesterolaemia with or without associated hypertriglyceridaemia was the commonest abnormality: 125 (20%) patients showed hypercholesterolaemia without associated hypertriglyceridaemia; 73 (12%) had both hypercholesterolaemia and hypertriglyceridaemia and 89 (14%) hypertriglyceridaemia without associated hypercholesterolaemia. The frequency of hyperlipidaemia did not vary with age. HDL cholesterol levels below 0.66 mmol/l (10th percentile) were observed in 131 (22%) survivors. Obesity was significantly more frequent among hypertriglyceridaemic survivors, whilst diabetes and hypertension were seen more frequently in survivors with combined hypercholesterolaemia and hypertriglyceridaemia. No significant difference was noted in the frequency of smoking and family history of coronary artery disease in hyperlipidaemia and normolipidaemic patients.     

Apolipoprotein B gene polymorphisms are associated with lipid levels in men of South Asian descent.

Three polymorphic sites of the apolipoprotein B gene - the insertion/deletion signal peptide, XbaI and EcoRI sites - were examined in a sample of 107 healthy men and in 46 men with evidence of coronary heart disease selected from a large population survey of South Asians aged 40-69 in London, U.K. There were no significant differences in allele frequencies between cases and controls. Frequencies of the ins (insertion) and X- (absence of XbaI cutting site) alleles were higher in South Asians than in Europeans studied previously (South Asians versus Europeans ins: 0.80 vs. 0.68, P less than 0.025; X-: 0.71 vs. 0.47-0.56, P less than 0.001). The del allele was associated with higher levels of total cholesterol (P less than 0.05) and the X+ allele with lower levels of HDL cholesterol (P less than 0.05), and thus both polymorphisms were associated with differences in the ratio of HDL cholesterol to total cholesterol (ins/del, P less than 0.01; XbaI, P less than 0.001). Mean waist-hip girth ratio was lower in the 10 men homozygous for the X+ allele than in the 42 men with X-/X+ and 55 men with X-/X- genotypes; the means (+/- SEM) were 0.92 +/- 0.02, 0.97 +/- 0.01 and 0.96 +/- 0.01 respectively (P = 0.03). These data suggest that genetic variation in linkage disequilibrium with the XbaI and ins/del polymorphisms of the apo B gene contributes to the determination of total cholesterol and HDL cholesterol levels and possibly to obesity in South Asians.     

Genetic variation in the apolipoprotein AI-CIII-AIV gene cluster and coronary heart disease

Six RFLPs in the apolipoprotein (apo) AI-CIII-AIV gene region detected with the restriction enzymes XmnI, MspI, PstI, SstI and PvuII were used to study the role of genetic variation at this locus in the development of coronary heart disease and in the regulation of serum levels of various lipid and lipoprotein parameters in the Austrian population. 106 male patients with coronary heart disease and 118 matched controls were investigated. None of the alleles defined by these RFLPs was associated with increased coronary risk. In the patients, but not in the control group individuals with the genotype P1P2 for the PstI polymorphism in the 3' flanking region of the apo AI gene had significantly lower serum levels of high density lipoprotein (HDL)-cholesterol and apo AI levels than those with the genotype P1P1. The S2 allele of the SstI polymorphism at the 3' end of the apo CIII gene was significantly associated with elevated serum levels of triglycerides in the patient, but not in the control group. Controls with the genotype V2V2 for the PvuII(A) polymorphism at the 5' end of the apo CIII gene had significantly higher serum levels of apo B than those with V1V1 or V1V2. This association did not exist among the patients. These findings suggest that variation associated with some of these RFLPs is contributing to the determination of lipid levels in patients and controls, but that the RFLPs themselves cannot be used as markers for increased coronary risk in the Austrian population.     

Angiotensin-converting enzyme and apolipoproteins genes polymorphism in coronary artery disease

BACKGROUND: Association between angiotensin-converting enzyme (ACE) as well as apolipoprotein (apo) AI, B, and E polymorphisms and dyslipidemia and coronary artery disease (CAD) is controversial. HYPOTHESIS: This study assessed the distribution of ACE insertion/deletion, apo AI A/G mutation, apo B signal peptide insertion/deletion, apo B XbaI restriction fragment length, and apo E polymorphisms in 388 nondiabetic patients. METHODS: The study population included 112 patients with stable CAD, 139 patients with acute myocardial infarction (AMI), and 137 age-matched control subjects. RESULTS: Univariate analysis showed higher prevalence of XbaI X+/X+ genotype in patients with CAD (p = 0.02). Angiotensin-converting enzyme and apo polymorphisms were not associated with lipid levels or severity of CAD. When all genotypes known to be related to CAD; such as ACE DD, apo AI GG, apo B del/del, and XbaI X+X+, and E4 allele of apo E, were pooled, again no significant differences among groups were seen. Multivariate regression analysis disclosed traditional risk factors and elevated levels of apo B for men and reduced levels of apo AI for women as independent variables for CAD. CONCLUSIONS: In addition to traditional coronary risk factors, apo B and AI could be considered predictors of CAD. No association between either form of CAD and polymorphisms was noted.     

Variation of apolipoprotein B gene is associated with myocardial infarction and lipoprotein levels in Danes.

Three DNA polymorphisms (XbaI, EcoRI, MspI) in the 3'-end of the apolipoprotein B gene were studied in relation to atherosclerosis, lipoprotein levels and age in three groups of atherosclerotic individuals and in nonatherosclerotic controls. The atherosclerotic groups comprised a postmyocardial infarction group with a mean age of 48 years, a group of individuals operated on for carotid stenosis with a mean age of 62 years, and a group of 85-year-olds with clinical coronary artery disease, peripheral arterial disease, or both. All 311 individuals were unrelated Caucasians of Danish ancestry. For the XbaI polymorphism, the X- allele was an independent predictor for myocardial infarction on multivariate analysis, but did not distinguish between patients and controls on univariate analysis. Additionally, this polymorphism was associated with variation in lipoprotein levels, but there was no clear evidence of a gene dosage effect. For the EcoRI polymorphism, the E- allele was associated with elevated levels of VLDL cholesterol, plasma triglycerides and VLDL triglycerides. Similar, but weaker associations were found for the MspI polymorphism. There were no significant differences in allele frequencies as a function of age for any of the DNA polymorphisms. In conclusion, while variation associated with the EcoRI polymorphism appears to be involved in the regulation of VLDL metabolism, variation associated with the XbaI polymorphism may determine susceptibility to coronary artery disease independent of other conventional risk factors, but it also appears to affect variation in lipoprotein levels.