Apolipoprotein B polymorphism and altered apolipoprotein B and low density lipoprotein cholesterol concentrations in Finnish children

APOC3, CETP, fibrinogen, and MTHFR are genetic determinants of carotid intima-media thickness in healthy men (the Stanislas Cohort)

The purpose of this study was to examine the relationship between carotid intima-media thickness (CIMT) inter-individual variability and 16 polymorphisms of 11 genes associated with cardiovascular risk factors (genes among lipid and homocysteine metabolisms, blood viscosity, platelet aggregation, leukocyte adhesion and renin-angiotensin system). CIMT was measured by high resolution B-mode ultrasonography in an healthy population of 77 men and 84 women, aged 35-54 years and selected from a French Cohort: the Stanislas Cohort. The polymorphisms studied were genotyped by a multilocus approach. Statistical analyses were carried out by ANOVA, after adjustment of CIMT for age, body mass index, and smoking, and by multiple regression analyses. No association was found with APOB Thr71Ile, APOC3 -482C/T, -455T/C, GpIIIa P1A, AT1R 1166A/C, AGT Met235Thr, CBS Ile278Thr, SELE 98G/T, and SELE Ser128Arg, polymorphisms neither in men nor in women. Although, in women we did not find any association for APOC3 3206T/G, 3175C/G, 1100C/T, CETP Ile405Val, MTHFR 677C/T and fibrinogen -455G/A polymorphisms; in men these polymorphisms were associated with CIMT variability (p< or =0.01; p< or =0.05). The most interesting finding was that altogether these genes in men were able to explain a considerable part, 20.6%, of CIMT variability. Therefore, our study gives a new opportunity to understand CIMT variability.

Candidate gene polymorphisms in cardiovascular disease: a comparative study of frequencies between a French and an Italian population

A multilocus assay was used to genotype up to 27 variable sites in 15 genes in French and Italian, presumed to be healthy populations (n=1480, n=162, respectively). These genes are involved in lipid metabolism (APOE, APOB, APOC3, CETP, LPL, PON), homocysteine metabolism (CBS, MTHFR), blood viscosity (Fibrinogen, FV), platelet aggregation (GpIIIa), leukocyte adhesion (SELE), and renin-angiotensin system (AT1R, ACE, AGT). Allele frequencies for all the markers were compared between the two populations. Five allele frequencies differed between the two European countries: APOB 71Ile (p < 0.001), SELE 98T (p < 0.001), SELE 128Arg (p < or = 0.01), APOE E4 (p < or = 0.01) and MTHFR 677T (p < or = 0.01), suggesting the existence of a north-south gradient in European allele frequencies. The other allele frequencies : APOC3 -482T, -455C, 1100T, 3175G, 3206G; LPL -93G, 9Asn, 291Ser; CETP 405Val; PON 192Arg; ACE Del; AGT 235Thr; AT1R 1166C; CBS 278Thr, GpIIIa P1A2; Fibrinogen -455A, FV 506Gln and SELE 554Phe, were similar between the two populations. They were also similar to those observed in other European countries.

A multilocus genotyping assay for candidate markers of cardiovascular disease risk

A number of chronic diseases, including cardiovascular disease, appear to have a multifactorial genetic risk component. Consequently, techniques are needed to facilitate evaluation of complex genetic risk factors in large cohorts. We have designed a prototype assay for genotyping a panel of 35 biallelic sites that represent variation within 15 genes from biochemical pathways implicated in the development and progression of cardiovascular disease. Each DNA sample is amplified using two multiplex polymerase chain reactions, and the alleles are genotyped simultaneously using an array of immobilized, sequence-specific oligonucleotide probes. This multilocus assay was applied to two types of cohorts. Population frequencies for the markers were estimated using 496 unrelated individuals from a family-based cohort, and the observed values were consistent with previous reports. Linkage disequilibrium between consecutive pairs of markers within the apoCIII, LPL, and ELAM genes was also estimated. A preliminary analysis of single and pairwise locus associations with severity of atherosclerosis was performed using a composite cohort of 142 individuals for whom quantitative angiography data were available; evaluation of the potentially interesting associations observed will require analysis of an independent and larger cohort. This assay format provides a research tool for studies of multilocus genetic risk factors in large cardiovascular disease cohorts, and for the subsequent development of diagnostic tests.

Genetic variation in the amino-terminal part of apolipoprotein B: studies in hyperlipidemic patients

Hypertriglyceridemia is a heterogeneous lipid disorder often running in families. Variation in the apolipoprotein B (apo B) gene has been associated with serum triglyceride levels. Recently, a role of the amino-terminal end of apo B in binding with lipoprotein lipase (LPL) has been suggested. We screened the 5' end of the apo B gene in 76 Finnish severely hypertriglyceridemic (> 6 mmol/l) patients, using a single-strand conformation polymorphism (SSCP) screening method. We detected a previously unreported polymorphic C2316-->A change, causing a Val703-->Ile substitution. The minor 703 Ile allele frequency was 0.04 in hypercholesterolemic and normolipidemic population samples. This allele was associated with lower serum triglyceride levels in a normolipidemic population sample. Analysis of two previously reported polymorphisms also located in the amino-terminal domain of apo B (Thr71-->Ile and Val591-->Ala) revealed elevating effects on serum apo B concentrations in hypertriglyceridemic individuals. The 591 Ala allele was associated with elevated apo B (P=0.011), and individuals with both minor alleles (apo B 591 Ala + and apo B 71 Ile +) had higher apo B levels compared to subjects homozygous for both common alleles (P=0.004). Although no DNA sequence change seemed to be the cause of hypertriglyceridemia in our patients, genetic variation in the 5' end of the apo B gene may contribute to changes in serum apo B levels in hypertriglyceridemic patients.

Screening of the 3' two-thirds of the coding area of the apo B gene in Finnish hypercholesterolemic patients report of six new genetic variants

Hypercholesterolemia clustering in families not explained by either low density lipoprotein (LDL)-receptor mutations producing familial hypercholesterolemia (FH), or the apolipoprotein B (apo B) Arg3500-->Gln mutation with familial defective apo B (FDB), is common in the Finnish population. In search of previously unknown apo B mutations, we screened exons 26 to 29 of the apo B gene in 68 Finnish severely hypercholesterolemic (> or = 8 mmol/l) non-FH, non-FDB patients, using a single-strand conformation polymorphism analysis based screening method. Four rare and two polymorphic previously unreported DNA variations were detected. The rare variants were a three-nucleotide deletion, with the deletion of Asp2186, an A11961-->G change leading to a Thr3918-->Ala change, a T12922-->G change causing a Val4238-->Ala substitution, and a neutral T12935-->C change leading to a new RsaI cutting site. The polymorphic G12937-->C and G13569-->A changes leading to Arg4243-->Thr and Ala4454-->Thr substitutions, respectively, had minor allele frequencies of 0.03 and 0.02. None of these variants seemed to explain the hyperlipidemia in these patients. A major Finnish mutation causing severe hypercholesterolemia is unlikely to exist in the 3' two-thirds of the coding area of the apo B gene.

Two new immunogenetic polymorphisms of the apoB gene and their effect on serum lipid levels and responses to changes in dietary fat intake

In previous studies, apoB polymorphisms have been shown to modify serum lipid responses to changes in dietary fat intake. The functionally important apoB DNA change or changes underlying these effects have, however, remained unknown. Using a single-strand conformation polymorphism analysis-based screening method, we identified two previously unreported apoB polymorphisms located close to each other in the 5' region of apoB gene exon 26. This DNA segment corresponds to the binding site of monoclonal anti-apoB antibody D7.2. The two A-->G changes at apoB cDNA nucleotides 5869 and 5896 produced an Asn-->Ser change at amino acid 1887 and a His-->Arg change at amino acid 1896. In the Finnish population, allele frequencies of the rare alleles of the apoB 1887 (Asn-->Ser) and apoB 1896 (His-->Arg) polymorphisms were .02 and .11, respectively. Both polymorphisms were shown to have an independent effect on the binding affinity of LDL with monoclonal antibody D7.2. The effect of these polymorphisms on serum lipid levels and responses to changes in dietary fat intake in 102 healthy free-living subjects was assessed. The apoB 1896 Arg allele was associated with a higher serum LDL cholesterol level during a low-fat, low-cholesterol diet in men.

Identification of apolipoprotein B100 polymorphisms that affect low-density lipoprotein metabolism: description of a new approach involving monoclonal antibodies and dynamic light scattering

Rare mutations in apolipoprotein B (apoB) can cause defective binding of low-density lipoproteins (LDLs) to the LDL receptor, leading to elevated plasma cholesterol levels and premature atherosclerosis. This communication describes a novel approach to study the effects of apoB mutations on LDL metabolism. Monoclonal antibody MB19 identifies a common polymorphism in apoB, an Ile/Thr substitution at residue 71, by binding with a 60-fold higher affinity to apoB(Ile71)-containing LDL. Because each LDL contains a single apoB, a maximum of two LDLs may be bound by the bivalent monoclonal antibody. Thus, at the appropriate concentration, an equivalent amount of MB19 will promote substantial dimer formation of LDL containing the strongly binding apoB(Ile71), but little dimer formation of LDL containing the weakly binding apoB(Thr71). For LDL isolated from heterozygous individuals, the amount of dimer formed, determined by dynamic light scattering, yields an estimate of the allelic ratio of the two forms of LDL. For such individuals, not only the effect of the polymorphism recognized by MB19 but also the effects of other polymorphisms on the LDL allelic ratio can be determined. Examination of six normolipemic MB19 heterozygotes gave percent allelic ratios between 48:52 and 51:49 tight:weak-binding LDL, not significantly different from a 50:50 ratio. These individuals were also heterozygous for six common apoB polymorphisms, allowing calculation of the odds that each of these polymorphisms caused significant alterations in lipid levels. In contrast, the rare mutation at residue 3500 causing defective binding to the LDL receptor and familial defective apoB100 (FDB) resulted in substantial changes (26:74 and 13:87) in LDL allelic ratio in both of two FDB individuals examined.

Nutritional and genetic contributions to serum cholesterol concentration in a children's follow-up study

In the Finnish multicentre study of cardiovascular risk in young Finns in 1980, 1983 and 1986, 2429, 2052 and 1841 9 to 18-year-old children and adolescents participated. In 1980, subjects of eastern origin living in the west had, despite their western diet, higher serum cholesterol concentrations than subjects both residing in and originating from the west. In males, eastern origin increased the east/west difference in serum cholesterol concentrations. Between 1980 and 1986 the mean serum total cholesterol of the study cohorts decreased by 5.5% and simultaneously the east/west differences in serum cholesterol concentrations disappeared in boys. The study suggests that genetic background is a separate factor determining serum total cholesterol level, but with declining serum cholesterol concentrations the effect of the genetic factor does not become manifest.

Health-based reference values of the Mini-Finland Health Survey: 2. Cholesterol in total serum and in different lipoprotein fractions

The reference values for cholesterol concentrations in the whole serum and in its VLDL, LDL and HDL fractions have been produced based on the data obtained in the Mini-Finland Health Survey. The lipoprotein fractions were separated with ultracentrifugation. The aim was to obtain reference values for the apparently healthy, ambulatory population. Two health-derived criteria were used to select subjects for reference populations: those based on the literature available and those based on the recommendations published by the Committee on Reference Values of the Scandinavian Society for Clinical Chemistry and Clinical Physiology, with slight modifications. The 95% inner reference intervals of total serum cholesterol in all the subjects and in the two selection groups were 4.2-9.0, 4.2-8.4, and 4.2-8.5 mmol l-1 for men, and 4.2-9.4, 4.1-8.6, and 4.2-9.0 mmol l-1 for women, respectively. The corresponding medians were 6.3, 6.2 and 6.2 mmol l-1 in men, and 6.4, 6.0 and 6.1 mmol l-1 in women, respectively. Frequency distribution curves showed clear skewness to the right in VLDL cholesterol and slight skewness in LDL and HDL cholesterol. In women there was a clear rise in total, VLDL and LDL cholesterol after the early middle age, whereas HDL cholesterol was lower in the older age groups. In men the age dependency was not as prominent; total cholesterol levels showed lower levels in older men. Of the background lifestyle factors alcohol consumption, smoking, obesity and physical exercise had negligible associations with total, VLDL, LDL and HDL cholesterol reference intervals.

Typing of the 3' hypervariable region of the apolipoprotein B gene: approaches, pitfalls, and applications

Apolipoprotein B-100 is the principal protein component of lipoproteins with very low, intermediate, and low density. The interaction of apoB-100 with low density lipoprotein (LDL) receptors is responsible for the uptake of LDL into cells. An AT-rich hypervariable region is located adjacent to the 3' end of the apoB gene. It consists of a variable number of tandemly repeated sequences (VNTR). Two approaches were used to analyze this polymorphism. In both, the region harboring the VNTR was amplified with the polymerase chain reaction (PCR). In the first method, fluorescently labeled primers were used in the PCR reactions and products were separated in agarose gels by means of an automated fluorescent fragment analyzer. In the second method, PCR products were analyzed in denaturing polyacrylamide gels and detected with silver staining. Even in the highly sophisticated automated system, agarose gel electrophoresis did not always enable unequivocal assignment of VNTR alleles. In contrast, denaturing polyacrylamide gel electrophoresis made it possible to distinguish the 15 bp differences between the VNTR alleles in a precise and simple manner. The VNTR polymorphism was typed in 234 individuals. Among these were 136 patients with coronary artery disease and 74 healthy controls. Thirteen alleles could be distinguished. The allele containing 49 repeats (VNTR-49) was found in 9.2% of the coronary artery disease patients and in 4.7% of the controls. Thus, the VNTR-49 allele increases relative coronary risk by about twofold. It is concluded that the apoB VNTR polymorphism is a potentially useful genetic marker. Since agarose gel electrophoresis may lead to ambiguous results, we prefer typing by denaturing polyacrylamide gel electrophoresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic variants of apolipoprotein B: relation to serum lipid levels and coronary artery disease among the Finns

The genetic variation of apolipoprotein B has been studied extensively in Finns with the aid of protein and DNA polymorphisms. Population association studies confirmed significant associations between the XbaI polymorphism of the apolipoprotein B gene and elevated serum cholesterol levels, and dietary studies suggested that the XbaI and ins/del polymorphisms might modify the serum lipid response to dietary fat intake. Studies comparing patients and controls, however, did not confirm previous studies suggesting that the multi-allelic variation at the 3'VNTR region of the apolipoprotein B gene was associated with coronary artery disease. The results suggest that the apolipoprotein B gene is involved in the regulation of serum lipid levels. A yet unknown mutation in linkage disequilibrium with the XbaI site may contribute to this regulation.

DNA polymorphism studies. Approaches to elucidating multifactorial ischaemic heart disease: the apo B gene as an example

It is well established that elevated plasma levels of low-density lipoprotein (LDL) particles are a risk factor for ischaemic heart disease with the distribution in LDL levels seen in the general population being the result of interaction between environmental factors, such as dietary fat intake, and genetic variation that is present in different individuals. One of the candidate genes where such variation is likely to occur, is the gene coding for apolipoprotein B (apo B). Many studies have reported an association between a common polymorphism of the apo B gene, detected using the restriction enzyme XbaI, and differences in plasma lipid levels, explaining 3-5% of the variance in LDL-cholesterol levels in samples representative of the healthy population. It has been proposed that the mechanism of this association is due to functional amino acid changes within the apo B protein, that affect LDL catabolism by altering binding affinity to the LDL-receptor. Several amino acid substitutions in the apo B gene have now been characterized, and these form the basis of the different epitopes that create the Ag marker system. Previous studies have reported that the Ag(x) epitope is associated with lower plasma lipid levels, and until recently the molecular basis for this association has been unclear. We have determined that the Ag(x) epitope is associated with both a Pro-Leu2712, and Asn-Ser4311 substitution, with the Leu-Ser allele being associated with significantly lower levels of plasma lipids in a sample of healthy individuals from Sweden.(ABSTRACT TRUNCATED AT 250 WORDS)

Pedigree and sib-pair linkage analysis suggest the apolipoprotein B gene is not the major gene influencing plasma apolipoprotein B levels

Previous studies suggest that plasma apolipoprotein B-100 (apoB) level is strongly influenced by genetic factors. Characterizing alleles that influence plasma apoB level would help define genetic risk factors for coronary artery disease. This study examined the role of variability in the apolipoprotein B gene (APOB) in determining plasma apoB level. Twenty-three informative families from the Johns Hopkins Coronary Artery Disease Family Study were studied. Linkage analysis between three polymorphisms in the APOB gene (XbaI at codon 2488, MspI at codon 3611, and EcoRI at codon 4154) and a putative major gene with a codominant allele for elevated apoB levels gave evidence against linkage (LOD score of -7.9 at a recombination fraction of .001). None of the families had a LOD score greater than 0.5, while five families had a LOD score less than -0.5. Sib-pair analysis also showed no relationship between the proportion of genes identical by descent at the APOB locus and either crude or adjusted plasma apoB levels. Thus, in 23 informative families, there was no evidence for the presence, in APOB, of common alleles that influence plasma apoB levels. These results suggest that APOB is not the major locus influencing plasma apoB levels.

Lack of association between the apolipoprotein B gene 3' hypervariable region alleles and coronary artery disease in Finnish patients with angiographically documented coronary artery disease

Previous studies have suggested that some apolipoprotein B (apoB) 3' variable number of tandem repeats (3'VNTR) locus alleles are associated with coronary artery disease (CAD). We examined the possible association between the apoB 3'VNTR alleles and CAD in 387 Finnish subjects. Using the polymerase chain reaction and polyacrylamide gel electrophoresis, the 3'VNTR genotype was determined in 187 individuals with severe CAD confirmed by coronary angiography (patients), in 121 individuals with normal coronary angiograms (controls), and in 79 apparently healthy subjects (normals). In contrast to previous reports from other populations, the larger apoB 3'VNTR alleles were not significantly more frequent among CAD patients than among controls or normals. In addition, there was no significant association between the 3'VNTR alleles and serum lipid levels in this Finnish population.

Apolipoprotein B polymorphism and altered apolipoprotein B concentrations in Congolese blacks

The immunoreactivity of apolipoprotein B (apo B) in plasma obtained from 238 unrelated black African male subjects from the People's Republic of Congo was analysed by non-competitive Enzyme Linked-Immunosorbent Assay (ELISA) with monoclonal BIP 45 anti-LDL antibody. The polymorphism detected by BIP 45 monoclonal antibody is identical to the Ag(c,g) polymorphism. Antibody BIP 45 distinguishes three apo B allotypes (immunophenotypes) encoded by the two allelic genes apo B Ag(c) and apo B Ag(g). Because of co-dominant transmission, genotypes may be inferred from allotypes, and it has been shown that BIP 45 binds strongly to the Ag(c) factor and only weakly to the allelic Ag(g) factor. Analysis of the Congolese plasma samples indicated that 67.65% of them bound BIP 45 with low affinity (Ag(c-,g+) genotype), 28.15% with intermediate affinity (Ag(c+,g+) genotype) and 4.20% with high affinity (Ag(c+,g-) genotype). According to the Hardy-Weinberg equilibrium, this corresponds to gene frequencies of 0.817 and 0.183 for the type Ag(g)/Ag(c) alleles, respectively. After adjustment for age and body-mass index, it was found that the Ag(c) allele decreases the apo B level by 9.62 mg/dl and that the Ag(g) allele increases apo B by 0.43 mg/dl. Therefore, as much as 4.30% of the genetic variance for apo B level could be accounted for by the Ag(c,g) gene locus.

Identification of the base substitution responsible for the Ag(x/y) polymorphism of apolipoprotein B-100

The identification of the base substitution responsible for Ag(x/y) completes the description of the antigen group polymorphisms associated with the apolipoprotein B polypeptide. Surprisingly, all five antigen group polymorphisms alter restriction endonuclease cleavage sites and have associated restriction fragment length polymorphisms, thereby providing a convenient alternative for antigen group phenotyping.

Rapid typing of apolipoprotein B DNA polymorphisms by DNA amplification. Association between Ag epitopes of human apolipoprotein B-100, a signal peptide insertion/deletion polymorphism, and a 3'flanking DNA variable number of tandem repeats polymorphism of the apolipoprotein B gene

We present here rapid and efficient methods for the analysis of multiple variable apolipoprotein (apo) B loci using polymerase chain reaction based techniques. For illustrative purposes, we have applied these methods to establish an association between these polymorphisms and the apo B Ag immunological epitopes. The 5 DNA polymorphisms include 3 restriction endonuclease sites (for XbaI, EcoRI and MspI), a variable number of tandem repeat (VNTR) locus at the 3' end of the apo B gene, and an insertion/deletion polymorphism involving the signal peptide region of apo B. The latter two newly described polymorphisms are directly detectable following amplification and may have physiological effects on apo B expression because of their critical locations. All of these sites were typed using flanking oligonucleotides and the newly developed polymerase chain reaction. Amplification products were typed either directly (3' VNTR and signal peptide insertion/deletion alleles), or following specific enzyme digestion (for the restriction sites), or by allele specific oligonucleotides. The detailed methods presented will prove generally useful for rapidly typing DNA variation in the apo B gene. Using these techniques, we found a significant linkage disequilibrium between the Ag(t/z) locus and the 3' VNTR, and the Ag(c/g) locus and the signal peptide length polymorphism. Future association studies using these DNA polymorphisms should take into consideration that observed effects may be related to its linkage disequilibrium with the Ag loci and vice versa.

Alterations in serum lipids and apolipoproteins in male type 1 (insulin-dependent) diabetic patients with microalbuminuria

The relationships between serum lipid, apolipoprotein levels and urinary albumin excretion were investigated in 20 male Type 1 (insulin-dependent) diabetic patients with microalbuminuria (overnight urinary albumin excretion between 10 and 200 micrograms/min), in 18 male Type 1 diabetic patients without microalbuminuria and in 18 male control subjects. In the microalbuminuric patients low density lipoprotein cholesterol was higher than in the control subjects (p less than 0.05); the high density lipoprotein/low density lipoprotein cholesterol ratio was lower than in the normalbuminuric diabetic patients (p less than 0.05), and in the control subjects (p less than 0.01); apolipo-protein B was higher than in the normalbuminuric patients (p less than 0.05); the apolipoprotein A1/B ratio was lower than in the normoalbuminuric diabetic patients (p less than 0.05). Serum triglyceride was higher in the microalbuminuric diabetic patients and in the control subjects than in the normalbuminuric diabetic patients (p less than 0.05, for both), but was not different between the microalbuminuric diabetic patients and the control subjects. No significant differnces between the 3 groups were present with respect to serum cholesterol, high density lipo-protein cholesterol and apolipoprotein A1. In the 2 combined Type 1 diabetic groups there were significant correlations between urinary albumin excretion and the high density lipoprotein/low density lipoprotein cholesterol ratio (R -0.40, p less than 0.02), apolipoprotein B (R 0.35, p less than 0.05) and the apolipoprotein A1/B ratio (R -0.44, p les than 0.01). These results indicate microalbuminuria related differences in lipid and apolipoprotein levels in male Type 1 diabetic patients, which may contribute to an increased risk of cardiovascular disease.

Apolipoprotein B amino acid 3611 substitution from arginine to glutamine creates the Ag (h/i) epitope: the polymorphism is not associated with differences in serum cholesterol and apolipoprotein B levels

A G- to A-DNA sequence change in exon 26 of the human apolipoprotein B (apo B) gene leads to a glutamine substitution for arginine at codon 3611 of the mature apolipo-protein B100 and causes a loss of an MspI site. In 106 Finnish individuals, a complete correspondence exists between this MspI polymorphic site and the Ag (h/i) immunochemical polymorphism. Linkage disequilibrium was found between this MspI polymorphic site and the apo B XbaI and EcoRI variable sites and the Ag (al/d) and (c/g) epitope pairs; there is apparent linkage equilibrium with the apo B PvuII variable site. Based on three population studies (samples from London. Finland and Italy), no significant association was found between this RFLP and serum cholesterol and apo B levels. These data suggest that the arginine 3611----glutamine 3611 substitution has no significant effect on apo B function.

Cardiovascular risk in young Finns, results from the second follow-up study

A comprehensive study of coronary heart disease (CHD) risk factors and their determinants in children and adolescents in Finland was initiated in the late 1970's. The main cross-sectional study was undertaken in 1980, with 3596 subjects aged from 3 to 18 years participating. The first follow-up study was carried out in 1983, and the second in 1986. The present report describes briefly some findings in 2746 children and young adults, aged 9, 12, 15, 18, 21 and 24 years, participating in 1986. Serum total cholesterol concentrations, mean (SD), ranged between 4.31 (0.73) and 4.91 (0.81) mmol/l in boys, and between 4.73 (0.85) and 5.09 (0.82) mmol/l in girls, respectively. Mean serum cholesterol values had fallen from 1980 to 1986 by 5.4% in such age cohorts, which had been included in all three studies. Fat content in the diet remained unchanged (38 E %), whereas the mean P/S ratio increased from 0.24 in 1980 to 0.31 in 1986. Young Finns from East Finland had a higher somatic risk index than those from West Finland (P greater than 0.001). The clustering of somatic risk factors was stable between 1980 and 1986. Further follow-up of the cohorts will, we hope, provide the tools for implementing primary prevention of CHD in Finland.

Bsp 12861 restriction fragment length polymorphism detects Ag(c/g) locus of human apolipoprotein B in all 17 persons studied

Southern blot analysis of the genomic DNA from 17 individuals showed perfect correspondence between a Bsp 12861 restriction fragment length polymorphism (RFLP) and the Ag(c/g) locus on human apolipoprotein (apo) B. The RFLP polymorphism is caused by a C--------T transition at nucleotide 421 on the cDNA, resulting in a threonine-to-isoleucine conversion. Thus, three of the five Ag sites have now been tentatively located on the 4536 residue apo B peptide at amino acyl residues 71: Ag(c/g), 591 (Ag(a1/d), and 4154 Ag(t/z).

Apolipoprotein B gene haplotypes. Association between Ag and DNA polymorphisms

Berg et al. (Clin Genet 1986;30:515-520) have reported that an Xba I DNA polymorphic site in exon 26 of the apolipoprotein (apo) B gene is associated both with the Ag(x/y) immunochemical polymorphism and with elevated serum lipoprotein levels. Ma et al. (Arteriosclerosis 1987;7:301-305) have reported that the same Xba I polymorphism is associated with a different immunochemical polymorphism, Ag(c/g). To extend and clarify these observations, we have determined the Ag and Xba I polymorphism for 106 individuals. We find that the Xba I restriction fragment length polymorphism is in linkage disequilibrium with both Ag(x/y) and Ag(c/g) loci; thus, all 31 Xba I(X1/X1) genotypes observed in this study are also Ag(y/y). All but one of 22 Xba I(X2/X2) genotypes are also Ag(g/g). For individuals homozygous at either two or three of these loci, it was possible to determine the haplotypes for 128 apo B alleles. Of the eight possible apo B haplotypes, only four were represented in this unambiguous subpopulation, although other minor haplotypes were present in the total population from which it was derived. The identification of major apo B haplotypes in human populations may simplify the search for significant correlations between certain apo B alleles and lipid levels and atherosclerosis.