Apolipoprotein E isoform phenotyping methodology and population frequency with identification of apoE1 and apoE5 isoforms

Apolipoprotein E5 and E7 in apparently healthy Japanese males: frequencies and relation to plasma lipid levels

In order to determine the frequencies of apolipoproteins (apo) E5 and E7 and their relation to plasma lipid levels, apo E phenotypes were determined in 608 healthy Japanese male adults by two-dimensional gel electrophoresis. Apo E5 and E7 were observed in 2.8% of the subjects, in addition to the three common apo E isoforms, E2, E3, and E4. Apo E5 was divided into two subtypes based on the migration rate on SDS/PAGE, E5f is the type with faster migration and E5s slower migration. The gene frequencies were: the epsilon 3 allele, 0.841; the epsilon 4 allele, 0.095; the epsilon 2 allele, 0.049; the epsilon 7 allele, 0.009; the epsilon 5 allele encoding apo E5f (the epsilon 5f allele), 0.004; and the epsilon 5 allele encoding apo E5s (the epsilon 5s allele), 0.001. The five individuals with apo E5f and the eleven with apo E7 were heterozygotes and normocholesterolemic. Also plasma apo B and apo E levels were not increased in any subjects with apo E5f or apo E7. The data suggests that apo E5f and E7 are not rare in the Japanese population but that neither apo E5f nor E7 are associated with hypercholesterolemia in most of the heterozygotes.

Familial lipoprotein disorders and premature coronary artery disease

Significant risk factors for premature coronary heart disease include: (1) family history, (2) elevated low density lipoprotein (LDL) cholesterol level > or = 160 mg/dl, l, (3) decreased high density lipoprotein (HDL) cholesterol level < 35 mg/dl, l, (4) cigarette smoking, (5) high blood pressure and (6) diabetes mellitus. All of these risk factors are common in patients with premature heart disease. Common familial lipid disorders associated with premature heart disease include familial lipoprotein(a) excess, familial dyslipidemia (elevated triglycerides and decreased HDL cholesterol), familial combined hyperlipidemia (elevations of LDL cholesterol and triglycerides, and often decreased HDL cholesterol), familial hypoapobetalipoproteinemia (elevated apolipoprotein B levels), familial hypoalphalipoproteinemia (low HDL cholesterol levels), and familial hypercholesterolemia (elevated LDL cholesterol levels). All these disorders have been characterized using age and gender specific 90th and 10th percentile values from the normal population. The diagnosis and potential management of these disorders is reviewed.

Frequency of the apolipoprotein E epsilon 2 allele is diminished in sporadic Alzheimer disease

Recent data have demonstrated genetic disequilibrium between inheritance of the apolipoprotein E (apoE) epsilon 4 allele and increased risk of Alzheimer disease. We tested the idea that inheritance of other allelic variations of apoE might also increase or decrease the risk of developing Alzheimer disease. We studied apoE genotypes in a large clinic based population of Alzheimer disease patients and age-compatible, tested control individuals. We confirm the genetic disequilibrium between apoE epsilon 4 and Alzheimer disease and now report that inheritance of apoE epsilon 2, another common variant of the apolipoprotein E gene, is negatively associated with risk of developing Alzheimer disease.

Effects of gender and menopausal status on the association of apolipoprotein E phenotype with plasma lipoprotein levels. Results from the Framingham Offspring Study

Apolipoprotein (apo) E phenotype is an important genetic determinant of plasma low-density lipoprotein (LDL) cholesterol and apo B levels. We have determined apo E phenotype by isoelectric focusing and plasma lipid, lipoprotein cholesterol, apo A-I, apo B, and lipoprotein(a) levels, as well as LDL particle size, in 2258 men and women participating in the Framingham Offspring Study. Apo E phenotype (E2/2, E2/4, E3/2, E3/3, E3/4, and E4/4) was not associated with plasma lipoprotein(a) levels but was associated with plasma LDL cholesterol levels, apo B levels, and LDL size in men and with plasma total cholesterol, LDL cholesterol, and apo B levels in women. The average effect of the epsilon 2 allele was to lower plasma LDL cholesterol levels by 9.2 mg/dL in men and by 13.7 mg/dL in women, while the average effect of the epsilon 4 allele was to increase LDL cholesterol levels by 2.6 mg/dL in men and by 5.4 mg/dL in women. When men were divided into two groups according to their age (< 50 and > or = 50 years old), the average effect of the epsilon 2 allele was to lower plasma levels of LDL cholesterol by 10.2 mg/dL in younger men and by 7.5 mg/dL in older men. In premenopausal women, the average effect of the epsilon 2 allele was to lower LDL cholesterol by 8.2 mg/dL and, in postmenopausal women, by 20.4 mg/dL. An opposite effect of the epsilon 4 allele was observed: the epsilon 4 allele was associated with increases in plasma LDL cholesterol levels of 4.0 mg/dL in younger men and of 1.0 mg/dL in older men.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid intolerance does not account for susceptibility to alcoholic and gallstone pancreatitis

BACKGROUND/AIMS

Hypertriglyceridemia is an established cause of pancreatitis and has been suggested as a predisposing factor in alcohol and gallstone-induced pancreatitis. The aims of this study were to determine fasting and postprandial triglyceride levels of alcoholics with pancreatitis, alcoholics without pancreatitis, patients with previous gallstone pancreatitis, patients with choledocholithiasis, and healthy controls.

METHODS

Oral lipid tolerance studies were performed in the above groups.

RESULTS

No relationship was found between alcoholic pancreatitis and hypertriglyceridemia, regardless of whether subjects were studied in the fasting state, after ingestion of fat, or after ingestion of fat with ethanol. Plasma triglyceride levels of alcoholics with pancreatitis remained similar to those of alcoholics without pancreatitis, but levels in both groups varied in relation to recent alcohol intake. Plasma triglyceride levels from both groups of alcoholics were greater than those of nonalcoholic healthy subjects. In addition, the previously reported association between postprandial hypertriglyceridemia and gallstone pancreatitis was not observed.

CONCLUSIONS

Plasma triglyceride levels do not account for individual susceptibility to either alcoholic or gallstone pancreatitis.

Genetic heterogeneity of apolipoprotein E and its influence on plasma lipid and lipoprotein levels

Apolipoprotein E (apoE) is one of the major protein constituents of chylomicron and very-low-density lipoprotein (VLDL) remnants and plays a central role as a ligand in the receptor-mediated uptake of these particles by the liver. Including the most common variant, apoE3, 30 apoE variants have been characterized. At present, 14 apoE variants have been found to be associated with familial dysbetalipoproteinemia, a genetic lipid disorder characterized by elevated plasma cholesterol and triglyceride levels and an increased risk for atherosclerosis. Seven apoE variants were found to be associated with other forms of hyperlipoproteinemia. This report presents an overview of all currently known apoE variants and their effects on lipoprotein metabolism.

Familial lipoprotein disorders and premature coronary artery disease

Although there is consensus that lipid variables, especially lipoprotein(a), are heritable and that elevated LDL cholesterol levels should be treated, there are no clear definitions of the common familial lipid disorders associated with premature CHD (lipoprotein(a) excess, FCH, familial dyslipidemia, familial hypoalphalipoproteinemia, familial hypercholesterolemia), nor do we have clear guidelines for the treatment of most of these disorders. Implementation of therapy for elevated LDL cholesterol in familial lipid disorders often has not occurred even in the United States. Before recommendations can be made for subjects with lipoprotein(a) excess and HDL deficiency (who often have combined hyperlipidemia or hypertriglyceridemia), prospective studies documenting benefit of CHD risk reduction must be carried out in subjects with lipoprotein(a) excess and HDL deficiency. One such study is being carried out with gemfibrozil in CHD patients with HDL deficiency. Current data do justify treatment of CHD patients with lipoprotein(a) excess with niacin because niacin has been shown to lower lipoprotein(a) levels as well as lower CHD risk mortality in random CHD patients. With regard to CHD patients with or without HDL cholesterol levels less than 35 mg/dL (0.9 mmol/L), efforts should be made to optimize their lipid profile and reduce their LDL cholesterol levels to less than 100 mg/dL (2.6 mmol/L).

Genetic associations with human longevity at the APOE and ACE loci

In an effort to dissect the genetic components of longevity, we have undertaken case-control studies of populations of centenarians (n = 338) and adults aged 20-70 years at several polymorphic candidate gene loci. Here we report results on two genes, chosen for their impact on cardiovascular risk, encoding apolipoprotein E (ApoE), angiotensin-converting enzyme (ACE). We find that the epsilon 4 allele of APOE, which promotes premature atherosclerosis, is significantly less frequent in centenarians than in controls (p < 0.001), while the frequency of the epsilon 2 allele, associated previously with type III and IV hyperlipidemia, is significantly increased (p < 0.01). A variant of ACE which predisposes to coronary heart disease is surprisingly more frequent in centenarians, with a significant increase of the homozygous genotype (p < 0.01). These associations provide examples of genetic influences on differential survival and may point to pleiotropic age-dependent effects on longevity.

ApoE4 polymorphism increases the risk for exercise-induced silent myocardial ischemia in older men

The apolipoprotein (apo) E4 polymorphism is associated with increased risk for symptomatic coronary artery disease (CAD). This study examines whether the apo epsilon allele is associated with an increased risk for exercise-induced silent myocardial ischemia (SI) in healthy, older (62 +/- 7 years; mean +/- SD), normocholesterolemic, nonsmoking male volunteers. The apo epsilon 4 allele was present in 20 of 45 (44%) men with SI on graded exercise treadmill testing compared with 22 of 127 (17%) men of comparable age with normal exercise tests (P < .001), resulting in a crude relative risk of 2.57 (95% confidence limits, 1.57 to 4.23) for SI in men with the apo epsilon 4 allele compared with those without the epsilon 4 allele. Although the lipoprotein lipid levels did not differ between men with normal exercise tests and those with SI, the men with the apoE 4/3 phenotype had higher total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels than those with the apoE 2/3 and 3/3 phenotypes (P < .05). Men with SI and the apoE 4/3 phenotype were older (64 +/- 5 versus 57 +/- 8 years, P < .01) and leaner (P < .01) than the normal non-SI men with the apoE 4/3 phenotype. The older age of the men with SI and the apoE 4/3 phenotype is consistent with a progression of atherosclerosis over time. Men with SI and the apoE 3/3 phenotype were of comparable age and body composition to apoE 3/3 phenotype men with normal exercise tests. Thus, even in the presence of normal LDL-C levels, the apo epsilon 4 allele may predispose older men to SI.

The apolipoprotein E gene and the serum low-density lipoprotein cholesterol response to dietary fiber

Our goal was to determine whether differences in apolipoprotein E (apo E) influenced the response to dietary changes aimed at reducing serum cholesterol levels, especially increases in fiber. Apo E phenotype and genotype were determined in 43 men and 24 women who had previously taken part in parallel 2-week metabolic dietary studies involving either wheat bran or oat bran supplementation at a level of 6.8 g fiber/1,000 kcal. Fasting blood lipid measurements had been made at the beginning and end of the 2-week metabolic period. Reductions in low-density lipoprotein (LDL) cholesterol levels across both oat and wheat bran diets were significantly different depending on the E allele (P = .048). The LDL cholesterol level reduction for E2 carriers (0.60 +/- 0.14 mmol/L, n = 13) was greater than that for E3 homozygotes (0.21 +/- 0.07 mmol/L, n = 38; P = .014) and E4 carriers (0.28 +/- 0.12 mmol/L, n = 16; P = .09). Only the change in dietary fiber on the oat bran diet was related significantly to the decrease in LDL cholesterol levels (r = -.47, P = .007; n = 32). No such relationship was seen on the wheat bran diet (r = -.010, P = .59; n = 33). Carriers of the E2 allele appear to be more responsive than noncarriers to a dietary change involving increased fiber intake. The data also support a lipid-lowering advantage of oat bran over wheat bran. Current dietary recommendations to reduce serum lipid levels may vary in effectiveness depending on distribution of apo E alleles in the different populations studied.

Gender differences in a type 2 (non-insulin-dependent) diabetic population with respect to apolipoprotein E phenotype frequencies

Apolipoprotein E polymorphism was examined in an Italian population of Type 2 (non-insulin-dependent) diabetic patients. There were significant differences (p < 0.05) in allele frequencies between male and female patients due to an under-representation of the E4 allele in the female group. No differences in allele frequencies were noted when non-diabetic male and female control subjects were compared. Both control groups exhibited similar allele distributions to that of male diabetic patients, but were significantly different (p < 0.05) from female diabetic patients. A closer examination of the female diabetic population revealed that under-representation of the E4 allele was principally confined to patients aged 60 years or older. This subgroup showed a significantly different (p < 0.05) allele frequency profile from control subjects (both men and women) and diabetic men, whereas this was not observed in the younger diabetic women (< or = 59 years). The results are consistent with the suggestion that the E4 allele may be a particular risk factor for female diabetic patients.

Apolipoprotein E polymorphism and its association with serum lipoprotein concentrations in black versus white children: the Bogalusa Heart Study

The structural gene locus for apolipoprotein E (apo E) is polymorphic. The relative apo E allele frequencies and the influence of this polymorphism on serum lipoprotein concentrations were studied in 8- to 17-year-old black (n = 444) and white (n = 446) children from the community of Bogalusa, LA. The frequencies of the e2, e3, and e4 alleles for white males/females were 0.027/0.024, 0.849/0.823, and 0.124/0.153, respectively; corresponding values for black males/females were 0.087/0.074, 0.713/0.721, and 0.20/0.205, respectively. Apo E phenotype distributions and allele frequencies showed a significant race difference, but no sex difference. Significant differences among apo E phenotypes were noted for total cholesterol, low-density lipoprotein cholesterol (LDL-C), and apo B in both races; significant effects were noted for high-density lipoprotein cholesterol (HDL-C) and apo A-I in black children, but not in white children. Among white children, the average excess of the apo e2 allele showed lower LDL-C (-12.5 mg/dL) and apo B (-15.8 mg/dL) concentrations, while the average excess of the apo e4 allele showed higher LDL-C (7.0 mg/dL) and apo B (7.5 mg/dL) concentrations. Black children showed a similar trend for these variables, but to a lesser degree; in addition, the average excess of apo e2 allele showed higher HDL-C (12.8 mg/dL) and apo A-I (8.3 mg/dL) concentrations in this racial group. It is noteworthy that the association of apo E polymorphism with serum lipoprotein concentrations noted in adults can be seen already in children.

Impact of apolipoprotein E polymorphism in determining interindividual variation in total cholesterol and low density lipoprotein cholesterol in Hispanics and non-Hispanic whites

The extent of apolipoprotein E (apo E) polymorphism and its effect on eight quantitative risk factors for coronary heart disease (total cholesterol; low density lipoprotein (LDL) cholesterol; total high density lipoprotein and its subfractions, HDL2 and HDL3; triglycerides; fasting glucose and fasting insulin) has been determined in 238 randomly selected Hispanics (120 males and 118 females) and 201 non-Hispanic whites (NHWs) (105 males and 96 females) from the San Luis Valley, Colorado. The frequencies for the E * 2, E * 3 and E * 4 alleles were 0.048, 0.853 and 0.099, respectively, in Hispanics and 0.080, 0.783 and 0.137, respectively, in NHWs. Relatively low frequency of the E * 2 and E * 4 alleles in Hispanics compared with NHWs is consistent with the genetic and anthropologic data that Hispanics have substantial Amerindian admixture. The impact of apo E polymorphism on each quantitative trait was estimated after adjusting for concomitant variables including age, cigarette smoking and body mass index in both genders and pre- or post-menopause status in females. The distribution of eight quantitative traits was analyzed among three common apo E phenotypes, 3-2, 3-3 and 4-3. In Hispanics, significant variability among apo E phenotypes was observed for total cholesterol (P = 0.001) in females only and the apo E polymorphism accounts for 12.4% variation in total cholesterol and 15.2% variation in LDL-cholesterol. In NHWs, significant mean differences among apo E phenotypes were observed for total cholesterol in both males (P = 0.007) and females (P = 0.0004). In NHW males and females, the apo E polymorphism explained 9.2% and 12.4%, respectively, of the variation in total cholesterol, and 15.1% and 6.6%, respectively, of the variation in LDL-cholesterol. In NHWs, borderline significance levels were also noted for phenotype specific differences in HDL2-cholesterol in males (P = 0.04) and females (P = 0.05), for total HDL cholesterol in females (P = 0.02) and HDL3-cholesterol in females (P = 0.06). While the estimated effects of the apo E polymorphism on quantitative traits differ somewhat between Hispanics and non-Hispanic whites, this probably reflects the overall difference in frequencies of the less common alleles in the Hispanics rather than a biological difference in the effects of these alleles on lipid metabolism.

Relation of apolipoprotein E phenotype to myocardial infarction and mortality from coronary artery disease

The apolipoprotein E polymorphism is a genetic determinant of low-density lipoprotein (LDL) cholesterol. Its status as a risk factor for coronary artery disease (CAD), either through a causal relation with LDL cholesterol level or independently, is less clearly established. Data from the Multiple Risk Factor Intervention Trial were used to examine the influence of apolipoprotein E phenotype on risk of coronary events. Of the 12,866 randomized participants, 619 were studied in a nested case-control design. CAD deaths (93) and nonfatal myocardial infarctions (113) were matched to 412 controls. The allele frequencies of apolipoprotein E in the white subset (epsilon 2 = 0.06, epsilon 3 = 0.79, and epsilon 4 = 0.15) were very similar to other nonselected white American populations, and the relation of apolipoprotein E on total and LDL cholesterol was generally similar to that seen in other studies, with the epsilon 2 allele being associated with lower and the epsilon 4 allele with higher total and LDL cholesterol. Allele frequencies were not the same for patients and control subjects. The presence of epsilon 4 was associated with an increased risk of CAD that was most evident for fatal cases. There was no relation between changes in LDL cholesterol over time during the trial and apolipoprotein E phenotypes.

Apo E allele frequencies in younger (age 42-50) vs older (age 65-90) women

Allelic variation at the apolipoprotein E (Apo E) structural locus has been shown to influence concentrations of total cholesterol and low density lipoprotein cholesterol (LDL-C). Apo E has six phenotypes resulting from three common alleles at this locus. The epsilon 2 allele is associated with lower LDL-C and the epsilon 4 allele with higher LDL-C. In the current study, we compared the epsilon allele distribution in two cohorts of white women recruited from population based listing of southwestern Pennsylvania. The "younger" cohort consisted of 473 women, age 42-50; the "older" cohort, 870 women, age 65-90. A comparison of the overall distribution of allele frequencies in the two cohorts was significantly different. The allele frequency of epsilon 4 was lower in the older cohort (0.098 vs. 0.122, P = 0.08) and the epsilon 2 allele frequency was higher (0.084 vs. 0.059, P = 0.05) in the older cohort. These observations are consistent with the hypothesis that there may be a selection against individuals with the epsilon 4 allele. However, future research is needed to confirm this observation and to compare survival in individuals by their epsilon allele.

Lipoprotein profile of a Greenland Inuit population. Influence of anthropometric variables, Apo E and A4 polymorphism, and lifestyle

Previously it has been reported that Greenland Inuit (Eskimos) from the Uummannaq district display low levels of plasma cholesterol and triglycerides and relatively high levels of high density lipoprotein (HDL) when compared with healthy Danish control subjects (Lancet 1971;1:1143-1146). Here we present data obtained in 1989 that show the following. In a group of 133 healthy adult Greenland Inuit from Nanortalik, the levels of plasma cholesterol and low density lipoprotein (LDL) cholesterol (6.39 and 4.39 mmol/l, respectively) were slightly higher than "normal" values found in western societies, whereas the HDL cholesterol level was markedly higher (1.64 mmol/l). Compared with most Caucasian populations, the Inuit population we studied exhibits a high apolipoprotein (APO)E*4 allele frequency (0.229), whereas the APOE*2 allele frequency was extremely low (0.015). In contrast to Caucasian populations, in the Inuit population the apoE polymorphism showed only a minor influence on the plasma lipid and (apo)lipoprotein levels, as evaluated by multiple regression analysis, with the exception of apoE levels. This absence of an effect could be explained by the low very low density lipoprotein (VLDL) plus intermediate density lipoprotein (IDL) cholesterol levels. The contributions of eicosapentaenoic acid and linoleic acid to the total amount of fatty acids in plasma cholesterol esters differed markedly from those reported in 1971 for another Greenland Inuit population (3.2% versus 15.8% and 49.5% versus 20.4%, respectively), thereby resembling values now found in the average western population. Even in those Inuit who reported exclusive consumption of the traditional Inuit diet (13% of the population), the fatty acid composition of the plasma cholesterol esters closely resembled the values measured in western populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein E1 Lys-146----Glu with type III hyperlipoproteinemia

During the screening of samples obtained from 5 individuals with type III hyperlipidemia, we identified a variant of apolipoprotein (apo) E which exhibited a discrepancy in apo E phenotype showing the E3/E1 isoform on isoelectric focusing (IEF) analysis and E3/E3 on gene analysis. Sequence analysis of the DNA of the proband that was amplified by PCR and subcloned, revealed a single substitution of one lysine (AAG) for one glutamic acid (GAG) at position 146, thereby adding two negatively charged units to apo E3. This defect had been described only for apo E1 to date (Mann et al. (1989) Clin. Res. 37, 520A (abstract)). In this case, PCR-mediated site-directed mutagenesis was used to identify the structural alterations forming the abnormal E1 genotype in the proband's family. Purified apo E1 Lys-146----Glu showed less than 10% of binding activity to apo B, E receptor on human skin fibroblasts compared with apo E3. This substitution demonstrates that Lys-146 is essential for the binding of apo E to the receptor.

The role of apolipoprotein E genetic variants in lipoprotein disorders

Apolipoprotein E plays a central role in lipoprotein metabolism by serving as a ligand for the binding of lipoproteins to lipoprotein receptors. Both common and rare variants of apoE have been described. The common variants apoE2 and apoE4 have a significant impact on interindividual variation of lipid and lipoprotein levels in normal subjects. The common variant apoE2 and more than half a dozen rare variants are defective in binding to the low-density lipoprotein (LDL) receptor, and all are causally associated with the lipid disorder type III hyperlipoproteinaemia (HLP). The mode of inheritance of the disorder can be either dominant or recessive, depending on the particular mutation(s) in apoE, although the mechanisms involved are not fully understood. The common variant apoE4 and other rare variants have been reported to be associated with a variety of other lipoprotein disorders, but a causal link has not been established.

Apolipoprotein E polymorphism in a Danish population compared to findings in 45 other study populations around the world

Apolipoprotein E (apoE) phenotypes were determined in a random sample of 466 Danish men born in 1948. The frequencies of the common alleles of the apoE gene were (with 95% confidence intervals) epsilon 2 = 0.085 (0.068-0.105), epsilon 3 = 0.741 (0.712-0.769), and epsilon 4 = 0.174 (0.150-0.200). These frequencies were compared to findings in 45 other study populations around the world (n greater than 100). The Danish population was found to cluster with populations from Iceland, Norway, Iceland, Scotland, the Netherlands, Germany, France (Paris), and Caucasian populations in Canada and the USA. The compiled data further show that dissimilarities in apoE allele frequencies among Caucasian populations are comparable to dissimilarities between some Caucasian and Asian populations. Notably, the frequency of epsilon 4 appears to be higher in northern regions of Europe (the Nordic countries, Scotland, Germany, and the Netherlands) than in southern regions (Switzerland, Tyrol, France [Nancy], Italy, and Spain).

Determination of apolipoprotein E phenotypes from stored or postmortem serum samples

In order to assess the validity of Apo E phenotyping from stored specimens, phenotypes determined from fresh serum samples were compared with those from stored (8 years at -20 degrees C) samples from the same individuals (n = 42). The effect of early postmortem period on Apo E phenotype determinability was studied by taking four duplicate blood samples from eight cadavers 2, 6, 12, and 24 h after death. Apo E phenotyping was performed directly from serum by isoelectric focusing and immunoblotting. From the cadavers, the same Apo E phenotypes were obtained 2, 6, 12, and 24 h after death. After eight years' storage five out of ten Apo E4/4 phenotypes were falsely recorded as Apo E4/3 and one out of six Apo E4/3, one out of 12 Apo E4/2 were falsely interpreted as Apo E3/3. Phenotypes Apo E2/2 (n = 2), Apo E3/2 (n = 10), and Apo E3/3 (n = 2) were correctly assessed after 8 years of storage. In the total material, 17% (7/42) of Apo E phenotypes were incorrectly assessed after the storage.

Association of apolipoprotein E and B polymorphisms with serum lipids

Genetic polymorphism of apolipoprotein E (apoE) and the Xbal restriction-fragment-length polymorphisms (RFLP) of the gene for apolipoprotein B (apoB) have both been shown to be associated with plasma lipid concentration. We studied the combined effect of these gene polymorphisms on serum cholesterol concentrations in 300 subjects aged nine to 18 years. In three way ANOVA, there was a statistically significant interaction between the effects of apoE phenotype and gender on serum cholesterol (P = 0.009). Therefore, males and females were analysed separately by two way ANOVA: there was no interaction between the effects of apoE phenotype and apoB Xbal polymorphism in either gender. In females, there were independent effects of both the apoE phenotype (P = 0.020) and the apoB Xbal genotype (P = 0.037) on serum cholesterol, but in males these effects were not statistically significant. These data suggest that variations at the apolipoprotein B and E gene locus play a role in the determination of serum cholesterol concentration in young female Finns.

Effect of apolipoprotein E polymorphism and XbaI polymorphism of apolipoprotein B on response to lovastatin treatment in familial and non-familial hypercholesterolaemia

Despite the well-documented efficacy of lovastatin, a wide inter-individual variation in treatment responses has been observed. The aim of the present study was to investigate the possible roles of apolipoprotein E (apo E) phenotype and apolipoprotein B (apo B) XbaI genotype on this variation. The apo E phenotype was determined in 232 subjects (78 cases of familial hypercholesterolaemia [FH] and 154 cases of non-familial hypercholesterolaemia [non-FH]) and the apo B XbaI genotype was determined in 211 subjects (67 cases of FH, 144 cases of non-FH). Depending on their baseline total serum cholesterol levels, these patients used a starting dose of lovastatin of either 20 or 40 mg nightly. After 6 weeks of therapy, slightly but significantly smaller reductions in LDL-cholesterol were observed in patients with the E4/3 phenotype compared with those with the E3/3 phenotype in non-FH with lovastatin 20 mg (-20 vs. -28%; P = 0.043) and in total cholesterol in FH with lovastatin 40 mg (-23 vs. -27%; P = 0.023). No significant differences were found in non-FH patients starting with lovastatin, 40 mg. After doubling of the lovastatin doses, all treatment responses became similar among apo E phenotypes. Moreover, when all patients using lovastatin 40 mg either at 6 or 12 weeks were pooled (n = 224), no differences in treatment responses were observed between the E3/2, E3/3, E4/3 and E4/4 phenotypes. The apo B XbaI genotype did not affect the hypocholesterolaemic efficacy of lovastatin in any of the patient groups. Thus our results indicate that inter-individual variation in the treatment response to lovastatin in both familial and non-familial hypercholesterolaemia is mainly due to factors other than the apo E phenotype or apo B XbaI genotype.

The effect of fasting triacylglyceride concentration and apolipoprotein E polymorphism on postprandial lipemia

To determine if apolipoprotein (apo) E polymorphism influences postprandial lipemia and hence can help explain the wide range of lipemic responses to a standardized fat meal observed previously, blood samples were collected from 25 healthy men whose postprandial responses to a standardized fat meal had been measured. Venous blood samples had been obtained before the fat meal (0.73 g fat/kg containing vitamin A) and hourly thereafter for 8 hours, plasma and chylomicron triacylglyceride (TAG) concentrations had been determined, and retinyl esters (REs) in the chylomicron and nonchylomicron fractions had been measured. The original results were reanalyzed by apo E phenotype (six E2/3; 14 E3/3; four E3/4 and one E4/4, grouped as E4). Contrary to what is known about the epsilon 4 allele, the apo E4 group displayed a significantly greater response curve than did either the apo E2/3 or E3/3 groups for both plasma TAG and chylomicron RE concentrations (p less than 0.01), as reflected in a later chylomicron RE peak for the apo E4 group (p less than 0.05). The E4 group tended (p = 0.18) to have a 40% higher fasting TAG than did either of the other groups, which may reflect bias in the selection of subjects. As fasting TAG is an important determinant in postprandial lipemia, results were normalized for this variable. After adjustment, the E4 group had the lowest TAG response relative to the E3/3 group (p less than 0.01). Our findings suggest that controlling for apo E phenotype may help to reduce interindividual variation in the postprandial response to a standard fat meal.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomedical relevance of two-dimensional protein mapping

State-of-the-art and future perspectives are discussed for the application of two-dimensional protein maps to basic medical research and routine clinical chemistry problems. Despite the technical advances that allow effective processing of a large number of samples and the refinement of devices and procedures for image analysis, at present two-dimensional maps are mostly confined to research purposes, i.e. to the inventory of normal constituents of body fluids and tissues on the one hand, and to qualitative-quantitative alterations of some protein spots in a number of instances (genetic, degenerative, infectious or xenobiotic diseases) on the other. It is hoped that in some instances a single primarily affected component will be able to be identified and then specifically tested (for instance by immunological means) as a diagnostic marker, but complex pathological patterns would still require the analysis of a large number of peptides at the resolution level only afforded by two dimensions. Further simplification of the protocols, for example with ready-made gels, and data reduction systems might then allow the application of the technique to be extended to general clinical laboratories.

Effects of polymorphisms in apolipoproteins E, A-IV, and H on quantitative traits related to risk for cardiovascular disease

The impact of the common alleles at structural loci coding for apolipoprotein (apos) A-IV, E, and H on 12 quantitative risk factors for cardiovascular disease (apos A-I, A-II, B, C-II, C-III, and E; total cholesterol; triglycerides; high density lipoprotein cholesterol; systolic blood pressure; diastolic blood pressure; and red blood cell sodium-lithium countertransport) was estimated in 453 unrelated individuals (227 men and 226 women) aged 26-63 years from the Rochester Family Heart Study, who were not using medications affecting lipid levels or blood pressure. Each risk factor was adjusted for concomitants (assay date, age, age, squared, height, weight and smoking status) before the genotypic effects on mean levels and variances were estimated. Allele frequencies were the same in men and women and were similar to those observed in other studies of US Caucasians. There were very different gender-specific estimates of the relative contribution of concomitants, measured genetic effects, and residual unexplained effects to the interindividual variation of particular traits. Allelic variation in apo E had effects on the greatest number of traits, namely apo E, apo B, apo C-II, and total cholesterol. An effect on triglycerides was dependent on the inclusion of hypertriglyceridemic subjects. Allelic effects of apo A-IV and apo H were much less than those estimated for the apo E polymorphism. A possible role for apo H in high density lipoprotein metabolism is suggested. This study indicates that variation in many genes may influence variation in a particular trait and that a particular gene may have pleiotropic effects on several traits.

Influences of common variants of apolipoprotein E on measures of lipid metabolism in a sample selected for health

Five-hundred seventy-five white-collar workers (374 men; 99% Caucasians) aged 20-59 years were selected on the basis of their being healthy and clinically free from cardiovascular risk factors (except smoking and family history). We have observed a higher relative frequency of the epsilon 3 allele in this population, as is true of populations with a low prevalence of coronary heart disease. Each of the 11 plasma lipid and lipoprotein traits studied was adjusted for age, weight, height, body mass index, plasma glucose, and uric acid in men and women separately. The influence of each of the three common apo E alleles on each adjusted trait was evaluated by use of the average excess statistic. We established that in a population selected for health, the epsilon 2 allele is associated with lower plasma levels of total cholesterol, low density lipoprotein (LDL) cholesterol, and apolipoprotein B associated with LDL cholesterol in both men and women. Conversely, the epsilon 4 allele is associated with higher levels of these traits in women only. In contrast to the findings in populations not selected for health, the presence of the epsilon 2 allele in our subjects tended to be associated with lower and the epsilon 4 allele with higher plasma triglyceride levels. Finally and of particular note, the influence of the apolipoprotein E polymorphism on plasma measures of LDL metabolism is different in men and women. Specifically, the influence of the epsilon 4 allele is of greater magnitude in women. A part of this gender difference in allele effects on LDL metabolism in women is associated with the use of oral contraceptives and postmenopausal hormone replacement therapy.

Apolipoprotein E polymorphism association with lipoprotein profile in endogenous hypertriglyceridemia and familial hypercholesterolemia

Apolipoprotein (apo) E polymorphism was among the first-reported genetic polymorphisms that explained part of the normal variation in plasma cholesterol concentrations in humans. The aim of this study was to assess the influence of allelic variation at the apo E gene locus on the plasma lipoprotein profile in hyperlipidemia. The lipoprotein levels of hyperlipidemic subjects of the major apo E phenotypes (E3/2, E3/3, and E4/3) were compared. One hundred eighty-two subjects with endogenous hypertriglyceridemia and 98 subjects with familial hypercholesterolemia due to a 10-kb deletion in their low density lipoprotein (LDL) receptor genes were compared with 424 normolipidemic controls from the same environmental background. LDL concentrations were lower in the E3/2 subset than in the E3/3 or E4/3 subset in the control, hypertriglyceridemic, and familial hypercholesterolemic groups. In absolute values, the magnitude of the effect was greatest in the familial hypercholesterolemic group. However, the direction and percentage change were identical in the presence or absence of the LDL receptor defect, indicating that the apo E phenotype effect is independent of LDL receptor status. Triglyceride and very low density lipoprotein (VLDL) cholesterol concentrations were higher in E3/2 than in E3/3 or E4/3 hypertriglyceridemic subjects, but this difference was not found in the familial hypercholesterolemic or control group. Thus, there seems to be a specific interaction between apo E isoforms and VLDL metabolism in hypertriglyceridemia; allelic variation at the apo E gene locus seems to be associated with specific alterations in the plasma lipoprotein profile of subjects with well-defined types of hyperlipidemia.

Regional differences in apolipoprotein E polymorphism in Finland

Apolipoprotein E (apoE) polymorphism is a genetic determinant of plasma lipid levels and of coronary heart disease risk. We determined apoE phenotypes and plasma lipid levels in 1564 subjects aged three to 18 years, living in five geographical areas of Finland in 1980. ApoE phenotyping was performed directly from plasma by isoelectric focusing and immunoblotting. The serum concentrations of total cholesterol, low density lipoprotein cholesterol and apolipoprotein B varied with apoE phenotype, and there were increases in all three variables (all P less than 0.001) of the order of E2/2 less than E3/2 less than E4/2 less than E3/3 less than E4/3 less than E4/4. These differences were present in all five areas. The mean levels of high density lipoprotein cholesterol, apolipoprotein A-I and triglyceride in the subjects did not differ between the apoE phenotypes or between their areas of residence. The apoE phenotype dependency of serum total and LDL cholesterol remained significant in all five areas during the six year follow-up from 1980 to 1986, when the mean level of serum total cholesterol fell by 5.8% in east (P less than 0.05) and by 4.4% in west Finland (P less than 0.05); the fall was steeper (P less than 0.01) in the east than the west. In all subjects, particularly those in west Finland, the size of the falls of serum total and LDL cholesterol concentrations depended on the apoE phenotype in the order of E3/2 less than E3/3 less than E4/3, but this effect was not seen in the east.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic studies of human apolipoproteins. XVI. APOE polymorphism and cholesterol levels in the Mayans of the Yucatan Peninsula, Mexico

Structural variation at the APOE locus is a major determinant of interindividual differences in cholesterol levels in populations at large. We have determined APOE structural polymorphism and estimated its impact on total cholesterol in the Mayans of the Yucatan Peninsula from Mexico. A unique pattern of APOE allele frequency distribution was observed, with no example of the APOE*2 allele and a relatively low incidence (9%) of the APOE*4 allele, giving rise to the lowest average heterozygosity at the APOE locus observed to date. The reported elevating affect of the APOE*4 allele on cholesterol has been found to be absent in the Mayans; several possible explanations which may account for the absence of this affect are discussed. In addition to APOE the gene products of five other apolipoprotein loci were screened and low frequency variation, possibly due to European admixture, was observed in two systems (APOH and APOA-IV).

Frequency and role of apo E phenotype in familial hypercholesterolemia and non-familial hyperlipidemia in the Japanese

The frequencies of the major apolipoprotein E(apo E) phenotypes in 65 normal, 426 hyperlipidemics, and 92 familial hypercholesterolemic Japanese subjects (FH) were studied, and features of hyperlipidemia compared between non-FH hyperlipidemia and FH. The frequencies of apo E phenotypes 3/3, 4/3, 3/2, 4/4 were almost the same in normal, non-FH hyperlipidemic, and FH subjects. The incidence of apo E7 was about 0.5% of total subjects. In type IV and V hyperlipidemias, incidence of E4/3 was higher than in any other hyperlipidemia. Incidence of E3/2 was also high in types III and V. In type II non-FH hyperlipidemia, incidence of E3/2 in type IIb was higher than in type IIa. VLDL-triglyceride, VLDL-cholesterol, apo C-II, apo C-III, and apo E levels were higher in E3/2 than in E3/3. But, in type IIa FH and type IIb FH, the incidence of E3/2 was the same, and lipid and apolipoprotein levels between 3/2 and 3/3 in FH were the same. These results indicate that allele epsilon 2 may be involved in the retention of VLDL or IDL, but not in FH.

Postprandial plasma vitamin A metabolism in humans: a reassessment of the use of plasma retinyl esters as markers for intestinally derived chylomicrons and their remnants

We investigated postprandial vitamin A metabolism by measuring retinyl ester, triglyceride, and apolipoprotein (apo)B-48 in the plasma lipoproteins of human subjects before and after fat-feeding. Following a 14-hour fast, eight healthy subjects (two men, six women, 28 to 79 years) were given a fat-rich meal (1 g fat/kg body weight) containing vitamin A (40 retinol equivalents per kilogram body weight). Blood was collected every 3 hours for 12 hours and lipoproteins were isolated by sequential ultracentrifugation. Mean plasma retinyl ester concentration peaked 6 hours after the fat-rich meal, whereas mean plasma triglyceride peaked at 3 hours. Data obtained from hourly samples in 3 subjects showed that changes in the postprandial plasma concentration of retinyl ester occurred 1 to 2 hours after changes in the plasma triglyceride concentration. In triglyceride-rich lipoproteins (TRL) of d less than 1.006 g/mL, retinyl ester similarly peaked at 6 hours, whereas triglyceride as well as apoB-48 peaked at 3 hours. Although retinyl esters were found mainly in TRL in the initial postprandial period (84%, 3 hours; 83%, 6 hours), in fasting and postprandial plasma, particularly 9 or more hours after fat-feeding, a large percentage of plasma retinyl esters were in low-density lipoproteins (LDL) (44%, fasting; 9%, 3 hours; 9%, 6 hours; 19%, 9 hours; 32%, 12 hours). A small percentage of retinyl esters were also found in postprandial high-density lipoproteins (HDL) (2% to 7%). ApoB-48 was not detected in LDL of fasting or postprandial plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein E4 homozygosity predisposes to serum cholesterol elevation during high fat diet

The hypothesis that apolipoprotein E (apo E)-isoform-related differences in plasma and LDL cholesterol concentrations are due to differential responses to dietary lipids was explored in 110 North Karelian subjects who had previously participated in dietary intervention studies. This was accomplished by collecting fresh blood samples for apo E phenotyping and by re-analysis of the original plasma lipid data according to apo E phenotypes. During high fat, high cholesterol baseline (p = 0.003) and switchback diets (p = 0.002), plasma cholesterol correlated inversely with the sum of subscript numbers (e.g., apo E3/4 = 7). Thus, subjects with the apo E4/4 phenotype had the highest (7.63 +/- 1.32 mmol/l), and subjects with the apo E3/2 phenotype had the lowest baseline levels of plasma cholesterol (5.85 +/- 1.48 mmol/l). This association became weaker during a low fat, low cholesterol diet intervention (p = 0.069). Greater reductions in plasma cholesterol occurred in subjects homozygous for the apo epsilon 4 allele (-1.84 mmol/l) as compared to subjects with other genotypes (-1.13 mmol/l) (p = 0.0097). Moreover, these subjects responded to the switchback diet by greater increases in plasma cholesterol (1.52 mmol/l) than others (0.92 mmol/l, p = 0.0141). The results suggest that the effect of apo epsilon genotype on plasma cholesterol is modulated by dietary fat and cholesterol intake.

Comparative molecular properties of swine and human very low density lipoproteins-apoproteins E and C

1. By means of 2-dimensional gradient-gel electrophoresis, the very low density lipoproteins (VLDL) apoproteins E and C profiles from human and swine plasma were studied. 2. The molecular properties (isoelectric point and molecular weight) of the VLDL apoproteins and their isoforms were determined and showed many similarities between species. 3. It also appears evident that a previously unrecognized apoprotein (C-III) and several associated isoforms may exist in swine; however, it's mobility on 2-dimensional gradient gels is very similar to Apo C-II.