Telomere length, antioxidant status and incidence of ischaemic heart disease in type 2 diabetes

Background

Type 2 diabetes (T2D) is associated with an increased risk of ischaemic heart disease (IHD). An accelerated process of vascular ageing induced by an increased oxidative stress exposure is suggested as potential pathway accounting for this association. However, no studies have explored the relationship between markers of vascular ageing, measures of oxidative stress and risk of IHD in T2D.

Objectives

To explore the association between plasma antioxidant status, marker of cellular ageing (leukocyte telomere length, LTL) and 10 years risk of IHD in patients with T2D.

Methods

Between 2001 and 2002, 489 Caucasians subjects with T2D were enrolled at the diabetic clinic, University College London Hospital. Plasma total anti-oxidant status (TAOS) and LTL were measured by photometric microassay and RT-PCR, respectively. The incidence of IHD over 10 years was determined through linkage with the national clinical audit of acute coronary syndrome in UK.

Results

At baseline, TAOS was associated with LTL (age adjusted: r = 0.106, p = 0.024). After 10 years, 61 patients developed IHD. Lower TAOS and shorter LTL at baseline predicted an increased IHD risk at follow-up (age adjusted: p = 0.033 and p = 0.040, respectively). These associations were independent of age, gender, cardiovascular risk factors, circulating levels of CRP and medication differences.

Conclusions

Reduced TAOS and short LTL are interrelated pathways which predict risk of IHD in patients with T2D. Our findings suggest that antioxidant defences are important to maintain telomere integrity, potentially reducing the progression of vascular ageing in patients with T2D.

Human apolipoprotein E isoforms differentially affect bone mass and turnover in vivo

The primary role of apolipoprotein E (apoE) is to mediate the cellular uptake of lipoproteins. However, a new role for apoE as a regulator of bone metabolism in mice has recently been established. In contrast to mice, the human APOE gene is characterized by three common isoforms APOE ε2, ε3, and ε4 that result in different metabolic properties of the apoE isoforms, but it remains controversial whether the APOE polymorphism influences bone traits in humans. To clarify this, we investigated bone phenotypes of apoE knock-in (k.i.) mice, which express one human isoform each (apoE2 k.i., apoE3 k.i., apoE4 k.i.) in place of the mouse apoE. Analysis of 12-week-old female k.i. mice revealed increased levels of biochemical bone formation and resorption markers in apoE2 k.i. animals as compared to apoE3 k.i. and apoE4 k.i., with a reduced osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) ratio in apoE2 k.i., indicating increased turnover with prevailing resorption in apoE2 k.i. Accordingly, histomorphometric and micro-computed tomography (µCT) analyses demonstrated significantly lower trabecular bone mass in apoE2 than in apoE3 and apoE4 k.i. animals, which was reflected by a significant reduction of lumbar vertebrae maximum force resistance. Unlike trabecular bone, femoral cortical thickness, and stability was not differentially affected by the apoE isoforms. To extend these observations to the human situation, plasma from middle-aged healthy men homozygous for ε2/ε2, ε3/ε3, and ε4/ε4 (n = 21, n = 80, n = 55, respectively) was analyzed with regard to bone turnover markers. In analogy to apoE2 k.i. mice, a lower OPG/RANKL ratio was observed in the serum of ε2/ε2 carriers as compared to ε3/ε3 and ε4/ε4 individuals (p = 0.02 for ε2/ε2 versus ε4/ε4). In conclusion, the current data strongly underline the general importance of apoE as a regulator of bone metabolism and identifies the APOE ε2 allele as a potential genetic risk factor for low trabecular bone mass and vertebral fractures in humans.

Lipoprotein Candidate Genes for Multivariate Factors of the Insulin Resistance Syndrome: A Sib-pair Linkage Analysis in Women Twins

The insulin resistance syndrome (IRS) is characterized by a combination of interrelated coronary heart disease risk factors, including low high-density lipoprotein cholesterol (HDLC) levels, obesity and increases in triglyceride (TG), systolic and diastolic blood pressure (BP), small low-density lipoprotein particles (LDL-size), and fasting and postload plasma insulin and glucose. Using factor analysis, we previously identified multivariate factors based on data from women participating in the Kaiser Permanente Women Twins Study: 1) Weight/Fat, 2) Insulin/Glucose, 3) Lipids, and 4) BP. The purpose of this study is to evaluate evidence for genetic linkage between the multivariate factors and candidate genes. Quantitative sib-pair analysis based on the factor scores with markers for 9 candidate genes was carried out based on data from 126 pairs of dizygotic (DZ) women twins from the second exam of the Kaiser Permanente Women Twins study. Suggestive evidence for linkage was found for the Weight/fat factor and the Apo E gene (p= 0.01), and stronger evidence for linkage with the Lipid factor and the cholesterol ester transfer protein (p= 0.002) gene. Therefore, the CETP gene appears to influence covariation in LDL size, TG, and HDL, and may account for a portion of the well-established statistical and metabolic associations observed between these risk factors.

The PPARGC1A gene Gly482Ser in Polish and Russian athletes

Peroxysome proliferator-activated receptor gamma coactivator-1-alpha (PGC-1α; encoded by the gene PPARGC1A in humans) is a crucial component in training-induced muscle adaptation because it is a co-activator of transcriptional factors that control gene expression in coordinated response to exercise. It has been suggested that a Gly482Ser substitution in PPARGC1A has functional relevance in the context of human disorders and athletic performance. To test this hypothesis, we examined the genotype distribution of PPARGC1A Gly482Ser in a group of Polish athletes and confirmed the results obtained in a replication study of Russian athletes. We found that the 482Ser allele was under-represented in the cohort of Polish and Russian athletes examined compared with unfit controls (P < 0.0001). A statistically significant low frequency of the 482Ser allele was observed among the endurance,strength-endurance, and sprint-strength groups of Polish athletes (P = 0.019, P = 0.022, and P < 0.0001, respectively). The replication study revealed that the 482Ser allele was also less prevalent in Russian endurance and strength-endurance athletes (P = 0.029 and P < 0.0001, respectively). Our results suggest that the PPARGC1A Gly482Ser polymorphism is associated with elite endurance athletic status. These findings support the hypothesis that the PPARGC1A 482Ser allele may impair aerobic capacity: thus, the Gly482 allele may be considered a beneficial factor for endurance performance.

MeltMADGE for mutation scanning of specific genes in population studies

MeltMADGE reconfigures the mutation scanning process of denaturing gradient gel electrophoresis so that the independent variable is time rather than space and the dependent (denaturing) variable is temperature rather than concentration of chemical denaturant. Use of a thermal ramp enables the use of a homogeneous gel and therefore of high-density arrays of wells such as those of microplate array diagonal gel electrophoresis (MADGE). In this configuration, electrophoresis of products on 10-12 96-well meltMADGE gels can be conducted in a 1- to 2-liter tank in a 1- to 2-h run, enabling the scanning of a target amplicon in over 1,000 subjects simultaneously. Gels are read by imaging the fluorescence of UV-excited ethidium bromide, giving a simple, economical system for identifying rarer sequence variants in target genes; it is suitable for large-scale case-control or population studies and other comparable applications. Different amplicons with similar melting characteristics can also be combined in the same run.

APOE/C1/C4/C2 gene cluster genotypes, haplotypes and lipid levels in prospective coronary heart disease risk among UK healthy men

The role of common APOE variants on plasma lipids, particularly low density lipoprotein (LDL) levels, and coronary heart disease (CHD) risk is well known; the influence of variation in the other nearby apolipoprotein genes APOC1, APOC4 and APOC2 is unclear. This study examines the association between APOE/C1/C4/C2 gene cluster variation using tagging SNPs and plasma lipid concentration along with risk of CHD in a prospective cohort. Genotypes for 11 common APOE/C1/C4/C2 SNPs were determined in 2,767 middle-aged (49 to 64 years) men from the Second Northwick Park Heart Study, with 275 CHD events over a 15-year follow-up period. Seven SNPs showed significant associations with one or more lipid trait in univariate analysis. Multivariate and haplotype analysis showed that the APOE genotypes are most strongly associated with effects on LDL-C and apoB concentration (explaining 3.4% of the LDL-C variance) while the other SNPs in this gene cluster explained an additional 1.2%. Haplotypes in APOC2 and APOC4 were associated with modest effects on HDL-C and apoAI (explaining respectively 1.4% and 1.2%). Carriers of the APOE ɛ2 SNP had a significantly lower risk of CHD hazard ratio (HR) of 0.63 (95% confidence interval [CI]: 0.42-0.95), as did carriers of the APOC2 SNP rs5127 (HR = 0.72, 95% CI: 0.56-0.93), while carriers of APOC1 SNP rs4803770 had higher risk of CHD (HR = 1.36, 95% CI: 1.04-1.78) compared with noncarriers. While the common APOE polymorphism explains the majority of the locus genetic determinants of plasma lipid levels, additional SNPs in the APOC1/C2 region may contribute to CHD risk, but these effects require confirmation.

Association of telomere length with type 2 diabetes, oxidative stress and UCP2 gene variation

OBJECTIVE

High oxidative stress potentially leads to accelerated telomere shortening and consequent premature cell senescence, implicated in type 2 diabetes (T2D) development. Therefore, we studied the association of leukocyte telomere length (LTL) with the presence of T2D, as well as the effect on the patients' LTL of plasma oxidative stress and of variation in UCP2, a gene involved in the mitochondrial production of reactive oxygen species.

METHODS

Mean LTL was determined in 569 Caucasian, 103 South Asian and 70 Afro-Caribbean T2D patients aged from 24 to 92 years, 81 healthy Caucasian male students aged from 18 to 28 years and 367 healthy Caucasian men aged from 40 to 61 years by real-time PCR. Plasma total antioxidant status (TAOS) was measured in the T2D patients by a photometric microassay. The patients were also genotyped for the UCP2 functional variants -866G>A and A55V.

RESULTS

Afro-Carribeans had 510bp longer mean length compared to Caucasians (p<0.0001) and 500bp longer than South Asians (p=0.004). T2D subjects displayed shorter age-adjusted LTL compared to controls [6.94(6.8-7.03) vs. 7.72(7.53-7.9), p<0.001] with subjects in the middle and the lowest tertile of LTL having significantly higher odds ratios for T2D compared to those in the highest tertile [1.50(1.08-2.07) and 5.04(3.63-6.99), respectively, p<0.0001]. In the patients, LTL was correlated negatively with age (r=-0.18, p<0.0001) and positively with TAOS measures (r=0.12, p=0.01) after adjusting for age, while carriers of the UCP2 -866A allele had shorter age-adjusted LTL than common homozygotes [6.86(6.76-6.96)kb vs. 7.03(6.91-7.15)kb, p=0.04].

CONCLUSION

The present data suggest that shorter LTL is associated with the presence of T2D and this could be partially attributed to the high oxidative stress in these patients. The association of the UCP2 functional promoter variant with the LTL implies a link between mitochondrial production of reactive oxygen species and shorter telomere length in T2D.

PPARG Gene polymorphism and locomotor activity in humans

The distribution of PPARG gene allele frequencies (Pro/Ala polymorphism) was studied in sportsmen specialized in speed and force athletics. A relationship between genotypes and human muscle transverse section area was evaluated. The PPARG Ala allele was significantly more incident in athletes than in controls, the incidence increasing with higher athletic qualification. A hypertrophic effect of PPARG Ala allele on muscle fibers was detected. Hence, the PPARG Pro12Ala polymorphism is associated with human motor activity.

Effect of HIF1A gene polymorphism on human muscle performance

Allele distribution of hypoxia-inducible factor gene (HIF1A; Pro582Ser polymorphism) was studied in power-oriented athletes and controls practicing no athletics; genotype relationships with muscle fiber composition were studied in speed skaters. Genotyping was carried out by PCR. The composition of muscle fibers was evaluated by the immunohistochemical analysis of m. vastus lateralis. The incidence of HIF1A Ser allele was significantly higher in weight-lifters than in controls (17.9 vs. 8.5%; p=0.001) and increased with athletic skill improvement. A relationship between HIF1A Ser allele and predominance of fast-twitch muscle fibers was shown (Pro/Ser 46.2 (13.8)%, Pro/Pro 31.4 (8.2)%; p=0.007). Hence, HIF1A Pro582Ser polymorphism is associated with muscle activity in humans.

The association of telomere length with paternal history of premature myocardial infarction in the European Atherosclerosis Research Study II

Inter-individual variability in telomere length is highly heritable and has been correlated with risk of coronary heart disease (CHD). Our aim was to determine the association of mean leukocyte telomere length with paternal history of premature myocardial infarction (MI). Mean leukocyte telomere length was measured with real-time polymerase chain reactions in 369 male students (18–28 years) with a paternal history of MI before the age of 55, recruited from 14 European universities, serving as cases and 396 age-matched controls with no paternal history of CHD. Overall, cases had borderline significantly shorter mean length (~550 bp), adjusted for age and geographical region, than controls (p = 0.05). A significant difference in telomere length across the geographical regions of Europe was observed (p < 0.0001), with shorter mean length in the Baltic and South and the longest in the Middle. The case–control difference (∼2.24 kb) in mean length was highly significant only in the Baltic region (p < 0.0001). There is suggestive evidence that, in young men, the biological expression of a paternal history of premature MI is at least in part mediated through inherited short telomeres. The association with paternal history of MI is strongly seen only in the Baltic compared to the rest of Europe, but this is not explained by shorter telomere length in this region.

Systemic markers of inflammation and cognitive decline in old age

OBJECTIVES

To investigate whether higher circulating levels of C-reactive protein (CRP), interleukin-6 (IL-6), and alpha1-antichymotrypsin (ACT) are associated with worse cognitive function and decline in old age.

DESIGN

Two independent population-based cohort studies.

SETTING

The Rotterdam Study (mean follow-up 4.6 years) and the Leiden 85-plus Study (maximal follow-up 5 years).

PARTICIPANTS

Three thousand eight hundred seventy-four individuals, mean age 72, from the Rotterdam Study, and 491 individuals, all aged 85, from the Leiden 85-plus Study.

MEASUREMENTS

Both studies assessed global cognition, executive function, and memory. Linear regression analyses were used in the current study to investigate the associations between inflammatory markers and cognitive function and decline.

RESULTS

In the Rotterdam Study, higher levels of CRP and IL-6 were cross-sectionally associated with worse global cognition and executive function (P<.05). ACT was not associated with cognitive function. In the Leiden 85-plus Study, estimates were similar for CRP, although not statistically significant. Higher IL-6 levels were related to a steeper annual decline in memory function in the longitudinal analysis in the Leiden 85-plus Study (P<.05). The effect of higher IL-6 levels on global and memory function decline was stronger in apolipoprotein E (APOE) epsilon4 carriers (P-interaction=.01) than in those who were not (P-interaction=.05). In the Rotterdam Study, higher IL-6 levels were related to a steeper annual decline in global cognition in APOE epsilon4 carriers only.

CONCLUSION

Systemic markers of inflammation are only moderately associated with cognitive function and decline and tend to be stronger in carriers of the APOE epsilon4 allele. Systemic markers of inflammation are not suitable for risk stratification.

Simple and effective determination of apolipoprotein E genotypes by positive/negative polymerase chain reaction products

Several protein and DNA-based methods have been previously described for the identification of apolipoprotein E isoforms or genotypes. However, all of them generate frequently false-positive results. The purpose of this study was to set up a new, simple, and effective method for the analysis of the apoE polymorphism. A total of 1,253 subjects previously examined for the apolipoprotein E polymorphism by restriction fragment length polymorphism were reanalyzed by our new method based on Taq DNA polymerase's inability to correctly initiate the replication in the presence of a mismatch at the 3' end of the primer. We conceived a combination of 4 specific primers in 3 different pairs sharing the same stringent polymerase chain reaction conditions to directly detect the presence/absence of polymerase chain reaction products, and thus reveal the 6 apolipoprotein E genotypes. We confirm our previous results in 1,171 subjects, whereas in 82 subjects out of 1,253 (about 6%), the results have been reinterpreted. The final analysis revealed a total of 12 homozygotic subjects for the e2 allele (1.0%), 874 homozygotes for the e3 allele (69.8 %), and 8 homozygotes for the e4 allele (0.6 %). The frequence of heterozygotes was 8.7% for the e2/e3 genotype (n=109), 1.4% for the e2/e4 genotype (n=17), and 0.6% for the e3/e4 genotype (n=8). Relative allele frequencies were e2=0.060, e3=0.834, and e4=0.106. We describe a new, simple, unequivocal, and nonexpensive method for the identification of the 6 apoE genotypes.

Variation in the cholesteryl ester transfer protein (CETP) gene does not influence individual plasma cholesterol response to changes in the nature of dietary fat

BACKGROUND AND AIMS

Some individuals respond to a greater extent than others to changes in dietary fat and cholesterol even when dietary intake is consistent. A prospective study has been undertaken in which two groups of individuals according to cholesteryl ester transfer protein (CETP) genotype were compared in terms of plasma lipid response to altering the nature of dietary fat in a free-living situation.

METHODS AND RESULTS

Following genotyping, 35 individuals with the CETP Taq1 B1B1 genotype were paired with age and sex-matched individuals with one or two CETP B2 alleles, to undertake a single crossover trial with a diet high in saturated fat and a diet high in polyunsaturated fat. There was no washout period between the two 4-week phases. Plasma lipoproteins were measured at the beginning and end of each phase. The difference (95% CI) in plasma LDL-cholesterol concentration at the end of the PUFA and SAFA diets was 0.95 (0.71, 1.19) mmol/l in the CETP B1B1 group and 0.80 (0.57, 1.04) mmol/l in the group with at least one CETP B2 allele. The dietary induced changes in the two genotype groups were not significantly different (p=0.38) from each other. Comparable results were observed for plasma total cholesterol. The high PUFA and SAFA diets did not significantly alter plasma HDL concentration in either of the CETP genotype groups. Response was also similar according to apolipoprotein E genotype (E3E3 vs E4+) and lipoprotein lipase genotype (S447X).

CONCLUSIONS

The results of this study do not support previous studies in which CETP genotype predicted plasma LDL-cholesterol response to diet. CETP genotype does not significantly affect the change in plasma total and LDL-cholesterol concentrations that occur when altering the nature of dietary fat. These data suggest that the influence of genetic factors on total and LDL-cholesterol may be relatively small in comparison with the effect of dietary manipulation.

Apo e4 allele is associated with endothelium-dependent arterial dilation in women with type 2 diabetes

OBJECTIVE

Previous studies have suggested that the e4 allele of apolipoprotein E (apo E) relates to the endothelium-dependent arterial dilation in men with type 2 diabetes. This study attempted to assess whether apo e4 allele is associated with endothelial dysfunction in women with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We selected 144 Chinese Han female type 2 diabetic patients without clinically detectable angiopathy. Polymerase chain reaction/ASO probes were used to determine their mouthwash DNA apo E genotypes, and high-resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperemia (with increased flow causing endothelium-dependent dilation) and after sublingual glyceryltrinitrate (GTN, an endothelium-independent dilator).

RESULTS

The flow-mediated arterial dilation among the subjects with e4/3 or e4/4 was 3.56+/-0.23%, which was significantly lower than that in subjects with e2/2 or e3/2 (3.97+/-0.36%) (p=0.000). The baseline vessel size, GTN-induced dilation and baseline blood flows were not significantly different among different apo E genotypes. On univariate analysis, reduced flow-mediated arterial dilation was significantly related to total cholesterol, LDL, Lp(a), high blood pressure, older age, family history of premature vascular disease, larger vessel size, duration of diabetes and e4 allele (p<0.05). By multiple stepwise regression analysis, reduced flow-mediated arterial dilation was associated with older age, large vessel size, duration of diabetes, positive family history, LDL, Lp(a) and e4 allele (p<0.01).

CONCLUSION

The apo e4 allele is associated with impairment of endothelium-dependent arterial dilation in the relatively early stage of female type 2 diabetes.

Integrated single-label liquid-phase assay of APOE codons 112 and 158 and a lipoprotein study in British women

BACKGROUND

Apolipoprotein E (APOE) is an important element of lipid metabolism and, hence, cardiovascular disorders. APOE has 3 main allelic variants: epsilon3, epsilon4, and epsilon2. Of these, epsilon3 is the most common, followed by epsilon4 and epsilon2. The associations of these isoforms with cardiovascular disorders and Alzheimer disease have been widely studied in different populations. Most of the genotyping in these studies has been performed with gel-based methods, which have important limitations, particularly for large epidemiologic studies. We therefore developed an integrated "one-tube" liquid-phase assay.

METHODS

To measure APOE isoforms, we developed an integrated single-label liquid-phase fluorescence assay containing 2 PCR primers, 2 probes, and 2 quencher oligonucleotides. We used a 384-well LightTyper, but the assay would be generically applicable for use with any fluorescence detector with thermal ramp control. We validated this method and applied it in the British Women's Heart and Health Study.

RESULTS

There were 4 melting peaks, at 41, 56, 61, and 69 degrees C, which generated 6 distinctive patterns representing genotypic combinations of epsilon3, epsilon4, and epsilon2. The magnitude and direction of the associations found with total cholesterol, HDL-cholesterol, triglycerides, and estimated LDL-cholesterol were consistent with previous reports.

CONCLUSION

The one-tube LightTyper assay presented here enables accurate, convenient, and economical genotyping of APOE and can be used for large epidemiologic studies.

PPARalpha gene variation and physical performance in Russian athletes

Peroxisome proliferator-activated receptor alpha (PPARalpha) regulates genes responsible for skeletal and heart muscle fatty acid oxidation. Previous studies have shown that the PPARalpha intron 7 G/C polymorphism was associated with left ventricular growth in response to exercise. We speculated that GG homozygotes should be more prevalent within a group of endurance-oriented athletes, have normal fatty acid metabolism, and increased percentages of slow-twitch fibers. We have tested this hypothesis in the study of a mixed cohort of 786 Russian athletes in 13 different sporting disciplines prospectively stratified by performance (endurance-oriented athletes, power-oriented athletes and athletes with mixed endurance/power activity). PPARalpha intron 7 genotype and allele frequencies were compared to 1,242 controls. We found an increasing linear trend of C allele with increasing anaerobic component of physical performance (P=0.029). GG genotype frequencies in endurance-oriented and power-oriented athletes were 80.3 and 50.6%, respectively, and were significantly (P<0.0001) different compared to controls (70.0%). To examine the association between PPARalpha gene variant and fiber type composition, muscle biopsies from m. vastus lateralis were obtained and analyzed in 40 young men. GG homozygotes (n=25) had significantly (P=0.003) higher percentages of slow-twitch fibers (55.5+/-2.0 vs 38.5+/-2.3%) than CC homozygotes (n=4). In conclusion, PPARalpha intron 7 G/C polymorphism was associated with physical performance in Russian athletes, and this may be explained, in part, by the association between PPARalpha genotype and muscle fiber type composition.

Apolipoprotein e4 allele and the risk of CAD death in type 2 diabetes mellitus with ischaemia electrocardiographic change

The presence of apolipoprotein (Apo) e4 allele is reported to be associated with the increased risk of coronary artery disease (CAD), as well as the impairment of endothelium-dependent arterial dilation in type 2 diabetes mellitus. Therefore, we hypothesized that Apo e4 allele increases the death risk from coronary artery disease in type 2 diabetes with ischaemia electrocardiographic change. From January 1993 to December 1999, 46 type 2 diabetic patients with e4/4 or e4/3, 96 with e3/3 and 45 with e2/2 or e3/2 genotypes were recruited. All subjects were unrelated elderly type 2 diabetic patients with ischaemia electrocardiographic change, aged 60-87 years, and their cardiac function were all the class I stage at their time of enrollment. A follow-up study of 3-10 years was undergone. The results are as follows: At baseline, serum total cholesterol and low-density lipoprotein (LDL) cholesterol concentrations were higher in subjects with e4/3 or e4/4 than in subjects with e2/2 or e3/2 (p<0.05). Lipoprotein(a) concentration was lower in subjects with e2/2 or e3/2 than in subjects with e3/3 and e4/3 or e4/4 (p < 0.05). During the 3-10 years follow-up period, a total of 55 patients who died from CAD were recorded in this sample. Compared with patients with e3/3 (p = 0.024) and patients with e2/2 or e2/3 genotypes (p = 0.002), the mortality rate of CAD in patients with e4/3 or e4/4 genotypes was the highest (47.8%). Stepwise discriminant analysis revealed that in the diabetic population studied Apo e4 allele was independently and significantly associated with CAD death (B = 0.65). However, the strength of the association decreased (B = 0.44) when total cholesterol, LDL-cholesterol and lipoprotein(a) were included in the model. Therefore, we concluded that Apo e4 allele increases the risk of CAD death in elderly type 2 diabetes mellitus with ischaemia electrocardiographic change.

Apolipoprotein e4 allele is predictor of coronary artery disease death in elderly patients with type 2 diabetes mellitus

The presence of the apolipoprotein (Apo) e4 allele is reported to be associated with the increased risk of coronary artery disease (CAD), as well as the impairment of endothelium-dependent dilation in type 2 diabetes mellitus. Therefore, we hypothesized that the Apo e4 allele increases the death risk from coronary artery disease in type 2 diabetes. From January 1993 to December 1999, 36 type 2 diabetic patients with e4/4 or e4/3, 62 with e3/3 and 33 with e2/2 or e3/2 genotypes were recruited. All subjects were unrelated, elderly, type 2 diabetic patients with coronary artery disease, aged 60-84 years, with cardiac function at the Class I stage at time of enrollment. A follow-up study of 3-10 years was undergone. The results are as follows: At baseline, serum total cholesterol and low density lipoprotein (LDL) cholesterol concentrations were higher in subjects with e4/3 or e4/4 than in subjects with e2/2 or e3/2 (P = 0.026). Lipoprotein(a) concentration was lower in subjects with e2/2 or e3/2 than in subjects with e3/3 (P = 0.044) and e4/3 or e4/4 (P = 0.038). During the 3-10 years follow-up period, a total of 39 patients who died from CAD was recorded in this sample. Compared with patients with e3/3 (P = 0.030) and patients with e2/2 or e3/2 genotypes (P = 0.001), the mortality rate of CAD in patients with e4/3 or e4/4 genotypes was the highest (50%). Stepwise discriminant analysis revealed that in the diabetic population studied the Apo e4 allele was independently and significantly associated with CAD death (B = 0.64). However, the strength of the association decreased (B = 0.48) when total cholesterol, LDL-cholesterol and lipoprotein(a) were included in the model. Therefore, we concluded that Apo e4 allele increases the risk of CAD death in elderly patients with type 2 diabetes mellitus.

Lipoprotein concentrations in newborns are associated with allelic variations in their mothers

BACKGROUND

Factors determining lipoprotein concentrations in the fetus are not yet fully understood. We postulated that an important factor is the genetic make-up of the mother. In the present study, we examined the associations between the cord blood concentrations of lipoproteins of 525 newborns and the polymorphisms present in their mothers on the genes of apolipoprotein E (APOE*E2, *E3, *E4), apolipoprotein C-III (APOC3*C3238G also called APOC3*S2) and lipoprotein lipase (LPL*S447X).

RESULTS

Newborns born of mothers with APOE*E2 allele had significantly lower cord blood LDL-C (P < 0.01) and apoB (P < 0.01) and significantly higher cord blood HDL-C and apoA1 (all P-values < 0.03) compared to those born of mothers with APOE*E3E3 genotype. These associations were independent of the presence of APOE*E2 allele in the newborns. Similarly, APOC3*S2 in mothers was associated with significantly lower (all P < 0.001) cord blood LDL-C, apoB, HDL-C and apoA1. In contrast, LPL*S447X in mothers lowered significantly cord blood LDL-C and apoB only when LPL*S447X was present in newborns. Most of the effects of these maternal polymorphisms on the newborns were independent of the changes of maternal lipoproteins generated by these polymorphisms.

CONCLUSIONS

This is the first evidence that maternal genetic variations influence fetal lipoprotein concentrations, independent of the genetic status of the fetus and of the variations of maternal lipoprotein concentrations generated by these genetic variants. It suggests that proteic components of maternal lipoproteins strongly control the metabolism of maternal lipoproteins carried out at the surface of the placenta to assure the cholesterol delivery to the fetus.

Lack of evidence for association of high altitude pulmonary edema and polymorphisms of the NO pathway

One essential factor in the development of high altitude pulmonary edema (HAPE) is elevated pulmonary artery pressure, possibly due to a lack of nitric oxide (NO) in pulmonary vessels. NOS3 gene polymorphisms (G894T, T-786C, and CA-repeats > or =38) might be linked to decreased NO synthesis and increased susceptibility to HAPE, while the C242T polymorphism of the CYBA gene [encoding for the NAD(P)H oxidase subunit p22phox] may increase NO availability and thus convey resistance to HAPE. To test this hypothesis, we genotyped 51 mountaineers susceptible and 52 mountaineers not susceptible to HAPE. Genotyping revealed similar genotype frequencies of the G894T and the T-786C NOS3 polymorphism in both groups (G894T: susceptibles, 39.2% GG, 47.1% GT, 13.7% TT; nonsusceptibles, 48.0% GG, 44.0% GT, 8.0% TT; p = 0.54. T-786C: susceptibles, 45.1% TT, 39.2% TC, 15.7% CC; nonsusceptibles, 53.8% TT, 40.4% TC, 5.8% CC; p = 0.28). Genotype frequencies of the C242T CYBA polymorphism were 43.1% CC, 47.1 % CT, and 9.8% TT in HAPE susceptibles and 38.0% CC, 52.0 % CT, and 10.0% TT (p = 0.92) in nonsusceptibles. There was also no difference between the two groups in the number of CA repeats (p = 0.57), and individuals with > or =38 CA repeats were not more likely to develop HAPE (p = 1.0). Haplotype analysis for the NOS3 polymorphisms also revealed no association with HAPE. The results of this study suggest that none of these genetic variants plays a substantial role in the pathogenesis of HAPE in Caucasians, but does not exclude epistatic effects that might still involve the genetic systems studied here.

A novel functional polymorphism in the PECAM-1 gene (53G>A) is associated with progression of atherosclerosis in the LOCAT and REGRESS studies

A 53G>A polymorphism identified in the 5' untranslated region (5'UTR) of the platelet endothelial cell adhesion molecule-1 (PECAM-1) gene alters a putative shear stress responsive element (SSRE). PECAM-1 was shown to be responsive to shear stress and transient transfection of human umbilical vein endothelial cell (HUVECs) with two luciferase reporter constructs driven by the PECAM-1 promoter and 5'UTR showed a response of the 53G allele, not the 53A allele, to shear stress. Association between the 53G>A, and the previously published L125V polymorphism, and coronary atherosclerosis was examined in two angiographic studies. The frequencies of the rare alleles of the 53G>A and L125V polymorphisms were 0.01 and 0.49, respectively, in the Lopid Coronary Angiography Trial (LOCAT) study and 0.02 and 0.49, respectively, in the Regression Growth Evaluation Statin Study (REGRESS) study. Compared with 53G homozygotes, carriers of the 53A allele showed less focal progression of disease in the LOCAT study and a similar trend in the diffuse progression of disease in the REGRESS study, whereas no association between L125V and coronary atherosclerosis was observed in either study. These data demonstrate that the PECAM-1 gene is responsive to shear stress in vitro and that decreased PECAM-1 gene expression in 53A carriers may influence reduced progression of vessel stenosis in patients with coronary artery disease.

Apolipoprotein e4 allele and endothelium-dependent arterial dilation in Type 2 diabetes mellitus without angiopathy

AIMS/HYPOTHESIS

Several studies have suggested a predisposing role of the e4 allele of apolipoprotein E (ApoE) in the development of atherosclerosis and cardiovascular disease in Type 2 diabetes. Therefore, we hypothesized that the e4 allele is also a risk factor for endothelial dysfunction. We attempted to assess whether Apo e4 allele is associated with endothelial dysfunction in the early stage of Type 2 diabetes.

METHODS

We selected 255 Chinese Han Type 2 diabtetic men without angiopathy. PCR or allele-specific oligonucleotide probes were used to analyse ApoE genotypes, and high resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperaemia and after sublingual glyceryltrinitrate.

RESULTS

The flow-mediated arterial dilation among the subjects with e4/3 or e4/4 was 3.14+/-0.32%, which was lower than that in subjects with e2/2 or e3/2 (4.04+/-0.30%) ( p=0.038). The baseline vessel size, glyceryltrinitrate-induced arterial dilation and baseline flow were not different among different ApoE genotypes. On univariate analysis, reduced flow-mediated arterial dilation was related to total cholesterol, LDL, lipoprotein(a) [Lp(a)], high blood pressure, older age, family history of premature vascular disease, larger vessel size, cigarette smoking, duration of diabetes and e4 allele ( p<0.05). By multiple stepwise regression analysis, reduced flow-mediated arterial dilation was associated with cigarette smoking, LDL, Lp(a), and e4 allele ( p<0.01).

CONCLUSION/INTERPRETATION

Apo e4 allele is associated with impairment of endothelium-dependent arterial dilation in the early stage of Type 2 diabetes.

No association between high-altitude tolerance and the ACE I/D gene polymorphism

PURPOSE

The absence (deletion allele [D]) of a 287 base-pair fragment in the ACE gene is associated with higher ACE tissue activity than its presence (insertion allele [I]) and, as such, may enhance vasoconstriction and fluid retention through increased levels of angiotensin II and aldosterone. Because fluid retention is found in acute mountain sickness (AMS) and exaggerated pulmonary hypertension is essential in the pathophysiology of high-altitude pulmonary edema (HAPE), we hypothesized that the DD genotype is associated with increased susceptibility to these illnesses.

METHODS

ACE genotype was thus determined in 83 mountaineers staying over night at 4559 m and related to AMS symptoms. Genotype was similarly determined in 76 mountaineers who had participated in previous studies at 4559 m; 38 of the latter group had a history of HAPE, and 25 had developed HAPE again during these studies.

RESULTS

The allele frequency was in Hardy-Weinberg equilibrium in both investigations. Neither the history nor the observed episodes of HAPE nor the prevalence of AMS defined as an AMS-C score >/= 0.70 (environmental symptom questionnaire) in the first study or in both studies taken together were significantly different between the genotypes DD, ID, and II.

CONCLUSION

We conclude that I/D-ACE gene polymorphism has no important effect on susceptibility to AMS or HAPE.

Insertion/deletion polymorphism of the angiotensin I-converting enzyme gene and arterial oxygen saturation at high altitude

There is a significant genetic influence on arterial oxygen saturation (Sa(O(2))) in high-altitude (HA) residents. It is not known whether this is true of lowlanders ascending to HA. The I allele of the angiotensin-converting enzyme (ACE) gene is associated with low ACE activity and elite endurance performance. An excess of the I allele has also been reported in South American natives living over 3,000 m and among elite HA mountaineers who demonstrate extreme endurance in a hypoxic environment, where maintenance of Sa(O(2)) is crucial to performance. We postulated that the I allele may confer an advantage at HA through genotype-dependent alterations in Sa(O(2)). Rapid ascent (n = 32) and slow ascent groups (n = 40), ascending to approximately 5,000 m over 12.0 and 18.5 days, respectively, had their Sa(O(2)) assessed throughout and compared with their ACE genotype. Resting Sa(O(2)) was independent of the ACE genotype and remained so for the slow ascent group, in whom the fall in Sa(O(2)) with ascent was genotype independent. However, Sa(O(2)) with ascent was significantly associated with the ACE genotype in the rapid ascent group (p = 0.01) with a relatively sustained Sa(O(2)) in the II subjects. These data are the first to report an association of the I allele with the maintenance of Sa(O(2)) at HA.

Rapid detection of polymorphisms of the nitric oxide cascade

NOS3 (endothelial nitric oxide (NO) synthase) and p22phox (subunit of NAD(P)H oxidase) are two genes whose products are involved in formation and degradation of NO, a ubiquitous signaling molecule largely responsible for the maintenance of normal endothelial function. The G894T polymorphism of NOS3 and the C242T polymorphism of p22phox are reportedly associated with numerous cardiovascular diseases. For each polymorphism we developed a rapid and reliable method with the hybridization probes format on the LightCycler and compared it with conventional PCR-restriction fragment length polymorphism (PCR-RFLP) analysis with regard to reliability, duration and cost. The new methods are more reliable, faster and less expensive than PCR-RFLP analysis and therefore represent a significant advantage in the detection of two candidate risk factors for cardiovascular diseases.

Association of APOE epsilon2/epsilon3/epsilon4 and promoter gene variants with dementia but not cardiovascular mortality in old age

The common apolipoprotein E (APOE) alleles epsilon2, epsilon3, and epsilon4 are associated with the risk of dementia and cardiovascular disease. Recently, two functional variants (- 219G/T and -491A/T) were identified in the promoter of the APOE gene that enable a further characterization of the role of the APOE locus in disease. We investigated the contribution of these APOE gene variants to dementia and cardiovascular mortality in old age using a population-based cohort of 648 subjects aged 85 years and over (Leiden 85-Plus Study). Genotypes containing an APOE epsilon4 allele were associated with a 4.1-fold (95% CI, 2.2-7.7) increased risk of dementia as compared to the epsilon3/epsilon3 genotype in old subjects. Moreover, homozygosity for the -219T allele was found to be associated with a 2.4-fold (95% CI, 1.0-5.8) increased risk independently of epsilon2 and epsilon4; the -491A/T variant was not associated with dementia. Over a 10-year follow-up period, the risk of cardiovascular mortality was not increased among epsilon4 carriers (RR, 0.6; 95% CI, 0.4-1.0) or -219T homozygous subjects (RR, 1.1; 95% CI, 0.7-1.7), nor did it decrease among -491T homozygous subjects (RR, 1.4; 95% CI, 0.6-3.1). In conclusion, both the APOE epsilon2/epsilon3/epsilon4 and the -219G/T variant were identified as risk factors for dementia but not cardiovascular mortality in old age. Our results support the hypothesis that both the isoform and the amount of APOE may influence the risk of dementia. Furthermore, they emphasize that variation at the APOE locus has a higher impact on the risk of dementia than on the risk of cardiovascular disease in old age.

The angiotensin converting enzyme I/D polymorphism in Russian athletes

The deletion (D) allele of the human ACE gene is associated with higher ACE activity than the insertion (I) allele. There is controversy as to whether the ACE genotype may be associated with elite athletic status; recent studies have identified no significant associations amongst those drawn from mixed sporting disciplines. However, such lack of association may reflect the mixed nature of such cohorts, given that an excess frequency of the I allele has been reported amongst elite endurance athletes, and an excess of the D allele amongst those engaged in more power-orientated sports. We examined this hypothesis by determining ACE I/D allele frequency amongst 217 Russian athletes (swimmers, skiers, triathletes and track-and-field participants) prospectively stratified by performance ('outstanding' or 'average'), and the duration of their event (SDA (<1 min), MDA (1 to 20 min), and LDA (>20 min): short, middle and long distance athletes respectively). ACE genotype and allele frequencies were compared to 449 controls. ACE genotype frequency amongst the whole cohort, or the outstanding athletes alone, was no different to that amongst sedentary controls. However, there was an excess of the D allele (frequency 0.72, P=0.001) amongst the outstanding SDA group, and an excess of the I allele (frequency 0.63, P=0.032) amongst the outstanding MDA group. These findings were replicated in the outstanding swimmers, with track and field SDA similarly demonstrating an excess of the D allele (P=0.01). There was no association found between the outstanding LDA and ACE genotype (P=0.27). These data not only confirm an excess of the D allele in elite SDA, and I allele in elite MDA, but also offer an explanation as to why any such association may be hard to detect amongst a heterogeneous cohort of mixed athletic ability and discipline.

Dementia and its associations in type 2 diabetes mellitus: the Fremantle Diabetes Study

BACKGROUND

recent studies indicate that diabetes is an important risk factor for dementia in older patients, but the cause remains unknown.

OBJECTIVES

to determine whether vascular or diabetes-related risk factors predict the development of dementia in older subjects with diabetes.

PATIENTS

63 patients with type 2 diabetes of mean age 75.3 years.

METHODS

Subjects were screened for cognitive impairment using the Mini-Mental State Examination (MMSE) and informants who knew the subjects answered the Informant Questionnaire for Cognitive Decline in the Elderly (IQCODE). Probable dementia was diagnosed using highly specific criteria based on the combination of both tests. Potential risk factors for dementia obtained at the time of the cognitive test and annually from a median of 3.2 years previously were examined using univariate methods and simple general linear modelling.

RESULTS

since there was a significant association between MMSE and English speaking ability, ten non-Anglo-Celt patients were excluded from the analysis. Probable dementia was diagnosed in six of the remaining 53 subjects (11%). Dementia was significantly and independently associated with higher diastolic and mean arterial blood pressure measurements over the 3 years before assessment. Blood pressure declined over this time in the patients with probable dementia and was similar to that in non-demented subjects at the time of cognitive assessment.

CONCLUSIONS

these preliminary data suggest that the high rate of dementia found in older people with diabetes may be explained by the high rate of hypertension in this population.

Apolipoprotein E4 and coronary heart disease in middle-aged men who smoke: a prospective study

BACKGROUND

The common isoforms of apolipoprotein E (apoE), E2, E3, and E4, are important determinants of plasma lipid concentrations, and the epsilon4 allele is associated with raised risk of coronary heart disease. We investigated whether the effect of smoking on coronary heart disease risk is affected by APOE genotype.

METHODS

We enrolled 3052 middle-aged men who were free of coronary heart disease for prospective cardiovascular surveillance in the second Northwick Park Heart Study (NPHSII). Smoking habit was ascertained at baseline and yearly by questionnaire. APOE genotype was identified by PCR and restriction enzyme digestion. Endpoints were fatal coronary heart disease, non-fatal myocardial infarction, and coronary artery surgery and silent myocardial infarction at follow-up.

FINDINGS

During 18836 person years of surveillance, 96 men had an acute myocardial infarction, 26 needed coronary artery surgery, and 14 had silent myocardial infarctions. Compared with never-smokers, risk of coronary heart disease in ex-smokers was 1.34 (95% CI 0.86-2.08) and in smokers it was 1.94 (1.25-3.01). This risk was independent of other classic risk factors. In never-smokers, risk was closely similar in men with different genotypes. Risk in men homozygous for the epsilon3 allele was 1.74 (1.10-2.77) in ex-smokers and 1.68 (1.01-2.83) in smokers, whereas in men carrying the epsilon4 allele risk was 0.84 (0.40-1.75) and 3.17 (1.82-5.50), respectively, with no significant differences in risk in the epsilon2 carriers. For the epsilon3 group, the genotype effect on risk was no longer significant after adjustment for classic risk factors (including plasma lipids). However, even after adjustment, smokers who were carriers of the epsilon4 allele, showed significantly raised risk of coronary heart disease compared with the non-smoking group (2.79, 1.59-4.91, epsilon4-smoking interaction p=0.007).

INTERPRETATION

Smoking increases the risk of coronary heart disease in men of all genotypes but particularly in men carrying the epsilon4 allele.

Polymorphisms in the thrombopoietin gene are associated with risk of myocardial infarction at a young age

Five polymorphisms in the thrombopoietin (TPO) gene were identified, one in the 5' untranslated region (UTR) (C1796T), two within intron 5 (C4830A and A4877C), and two in the 3' UTR (A5713G and A6160T). The allele frequencies were determined in a group of 450 healthy middle aged men from the UK and found to be 0.46 for 1796T, 0.38 for 4830A, 0.004 for 4877C, 0.47 for 5713G and 0.07 for 6160T. Genotypes for the three common polymorphisms were determined in a group of 176 young male Swedish survivors of a myocardial infarction (MI) and 186 age-matched controls and a group of 156 young Italian survivors of an MI and 147 age and sex matched controls. In both the Swedish and the Italian studies polymorphisms were found to be associated with increased risk of MI. In the Swedish sample the frequency of 4830A was significantly higher in controls (0.40) compared with patients (0.29) (P=0.003), with an odds ratio for AA homozygotes of 0.48 (0.25-0.92; P=0.03) compared with CC homozygotes. In the Italian sample the frequency of 5713G was significantly lower in controls (0.31) compared with cases (0.40) (P=0.03), with an odds ratio for GG homozygotes of 2.29 (1.08-4.89; P=0.03) compared with AA homozygotes. These risk associations are consistent since 4830A and 5713A show strong allelic association. After adjusting for other measured risk factors the effect on risk was still significant in the Italian sample 2.39 (1.02-5.58), but not in the Swedish sample 0.46 (0.16-1.32). The observation of frequency differences between cases and controls in two independent samples strongly suggests that the TPO gene is involved as a risk factor for developing MI at a young age, but the identified polymorphisms are probably acting as markers for an unidentified functional mutation elsewhere in the gene locus.

Variants in the cholesterol ester transfer protein and lipoprotein lipase genes are predictors of plasma cholesterol response to dietary change

There are no definitive explanations as to why individuals with hypercholesterolemia, a major cardiovascular risk factor, respond differently to dietary change. Fifty five free-living individuals completed a double crossover trial with two dietary regimens, a high saturated fat diet (providing 21% energy from saturated fat and 3% energy from polyunsaturated fat) and a high polyunsaturated fat diet (providing 11% energy as saturated fat and 10% energy as polyunsaturated fat), each phase continuing for 4 weeks. Extensive genotyping and several measures of dietary compliance have provided further insights regarding the determinants of extent of cholesterol response to changes in the nature of dietary fat. Individuals with the CETP B1B1 genotype and the LPL X447+ allele showed an average 0. 44 (95% CI: 0.22, 0.66) and 0.45 (95% CI: 0.18, 0.72) mmol/l greater change in total cholesterol, respectively, than those with one or more CETP B2 allele or homozygous for the LPL S447 allele when comparing diets high and low in saturated fat. Indices of dietary compliance including changes in reported saturated and polyunsaturated fat intake and change in triglyceride linoleate were not significantly different between the CETP genotypes. Change in reported saturated (r=0.36, P=0.04) and polyunsaturated (r=0.22, P=0. 05) fat intake and change in triglyceride linoleate (reflecting polyunsaturated fat intake) (r=0.21, P=0.07), also predicted total cholesterol response to dietary fat changes. In multivariate analyses, variation in the cholesterol ester transfer protein and lipoprotein lipase genes predicted response independent of measures of dietary compliance, suggesting that these two genes are important determinants of variation in cholesterol response to dietary change in free-living individuals.

Lack of association between lipaemia and central adiposity in subjects with an atherogenic lipoprotein phenotype (ALP)

OBJECTIVE

To investigate the associations between indices of adiposity and cardiovascular risk factors in individuals with an atherogenic lipoprotein phenotype (ALP).

SUBJECTS

Fifty-five men, aged 34-69 y, body mass index (BMI) 22-35 kg/m2, with an ALP lipid profile (triglycerides (TG) 1.5-4.0 mmol/l, HDL<1.1 mmol/l; %LDL-3>40% total LDL).

DESIGN

Each participant provided a fasting blood sample and underwent an 8 h postprandial assessment and had anthropometric measurements taken.

OUTCOME MEASURES

BMI, waist circumference (W), waist-to-hip ratio (W/H), sum of skinfolds (SSK), fasting and postprandial concentrations of glucose, insulin and plasma lipids, post-heparin lipase activity, and apoE genotype.

RESULTS

The expected positive associations between BMI, W and SSK and fasting and postprandial insulin were observed (r=0.42-0.65). Little association between glucose responses and any measures of adiposity was evident. Unexpectedly, there were no positive associations between measures of central adiposity (W and W/H) and fasting and postprandial TG responses, with a trend towards negative associations in this study group (TG AUC vs W, r=-0.23, P=0.097; TG IAUC vs W/H, r=-0.26, P=0.068). Subgroup analysis indicated that lack of a positive association between central adiposity and postprandial TG values was more evident in those with one E4 allele (r=-0.42, P=0.077) relative to non-E4 carriers (r=-0.16, P=0.430). The expected positive associations between insulin and TG responses were not observed (r=-0.03 to -0.36).

CONCLUSION

In this ALP group the expected positive association between TG responses and a centralized distribution of body fat was not observed, particularly in individuals with an apoE4 genotype. Our findings are not in line with the view that there is a clear causal relationship between insulin resistance and the lipid abnormalities associated with ALP.

Spectrum of LDL receptor gene mutations in heterozygous familial hypercholesterolemia

Familial hypercholesterolemia by usual definition reflects mutations of the LDL-receptor gene. Extensive molecular characterization of mutations ascertained mainly through homozygotes (the Dallas collection) has been presented by Hobbs et al. (Hum Mutat 1:445-446, 1992). This paper catalogues a spectrum of 134 mutations (27 novel mutations in 45 patients, 24 previously described mutations in 89 patients) ascertained through heterozygotes from the analysis of 791 patients with definite, probable, or possible FH, mainly from the UK, using high-throughput modifications of the single-strand conformation polymorphism technique. From a composite database of LDL receptor gene mutations complied from these two sets and from the literature, deductions are made about ascertainment bias, mutation rates, and molecular heterogeneity. Calculations suggest that there may be a large number of rare amino acid variants in the general population not causing classic FH. Approaches to, and feasibility of, molecular diagnostics are considered.

The effect of a gender difference in the apolipoprotein E gene DNA polymorphism on serum lipid levels in a Serbian healthy population

To date, no data have been available on relationship between apolipoprotein E polymorphism and lipid levels in Serbian populations. Blood samples were obtained from 591 healthy normal individuals (193 women and 398 men). A 244 bp sequence of the apolipoprotein E gene including the two polymorphic sites was amplified by polymerase chain reaction. After digestion with Hhal, DNA fragments were visualized by microplate array diagonal gel electrophoresis. In men, levels of both total and low-density lipoprotein cholesterol among the three apolipoprotein E genotype groups differed significantly (p <0.05). The epsilon2 allele was associated with lower concentrations of both total and low-density lipoprotein cholesterol, where the epsilon4 allele had the opposite effects. No significant effects of apolipoprotein E polymorphism on serum lipid levels were observed in women. The presented data could be taken into consideration in any future disease risk evaluation in this population.

Quantitative assessment of apolipoprotein E genotypes by image analysis of PCR-RFLP fragments

Apolipoprotein E (APOE) genotyping usually involves polymerase chain reaction (PCR) and assessment of restriction fragment length polymorphism (RFLP) by gel electrophoresis. We made determination of HhaI restriction endonuclease digestive patterns more objective and improved diagnostic accuracy with a quantitative approach using sensitive DNA stain (SYBR Green) and image analysis of gel patterns. For distinguishing true and partially-digested restriction fragments, band ratios were calculated for the staining intensity of gel patterns from 116 sample runs of 63 human blood specimens. Each of these specimens was independently genotyped for APOE by at least two (and most of them by three) different PCR-RFLP methods. Based on the distribution of band ratios, decision levels were established and used for developing a program for computer-aided interpretation of APOE genotypes (Microsoft Excel software). Appropriateness of the decision levels for band ratios was validated by APOE genotyping of additional 61 specimens. The approach described here is applicable to a variety of other molecular diagnostic techniques that are based on PCR-RFLP or sequence-specific signal amplifications.

Apolipoprotein E polymorphism: automated determination of apolipoprotein E2, E3, and E4 isoforms

Apolipoprotein E (apo E) plays an essential role in lipoprotein metabolism, where it is involved in the clearance of chylomicrons and very low density lipoproteins. Apart from some rare variants, apo E exists in three common isoforms (E2, E3, and E4). The different isoforms have not only been associated with different plasma lipid levels but have also been correlated with certain pathological conditions, such as lipid disorders (dysbetalipoproteinemia, hypercholesterolemia), cardiovascular diseases, and Alzheimer's disease. Here we describe a rapid, automated test for the determination of the most frequent polymorphisms (E2, E3, and E4). This polymerase chain reaction-based test allows the reliable discrimination of all six genotypes. The assay has been developed especially for the nonspecialized routine clinical laboratory by employing an analyzer and chemistry often present in this type of laboratory. Because of its low costs and easy handling, the assay can be performed on a daily basis.