Genetic basis of lipoprotein disorders

Sequencing of lipoprotein lipase gene in the Mediterranean river buffalo identified novel variants affecting gene expression

Lipoprotein lipase (LPL) is a key enzyme for lipid metabolism, playing a fundamental role in the composition of fat in adipose tissue and milk. The LPL gene has been seldom investigated in dairy ruminants and barely studied in river buffalo (Bubalus bubalis). The aim of this work was to explore the genetic diversity of LPL and its promoter and to identify functional mutations, using a combined approach based on sequencing, dual-color electrophoretic mobility shift assay, and quantitative PCR. Thirteen consensus sequences for transcription factors were found in the promoter. Eleven SNP were detected, and the attention was focused on the SNP with potential functional effects: g.-446A>G, because the presence of G created a consensus motif for the transcription factor Sp1, and g.107A>G, which was the only exonic SNP. We developed PCR-RFLP methods for genotyping the 2 SNP and calculated the allele frequencies. A strong linkage disequilibrium (D' = 1; r² = 0.903) was found between the 2 SNP. The dual-color electrophoretic mobility shift assay demonstrated that only genotype g.-446GG allowed the binding of the Sp1 transcription factor, resulting in overexpression of the gene (~2.5 fold), as confirmed by the quantitative PCR results. Haploinsufficiency is proposed as a regulation mechanism. This study adds further knowledge on the structure of the LPL gene and its expression in river buffalo, with potential effects on milk qualitative and quantitative production.

Sequence analysis and variant identification at the APOC3 gene locus indicates association of rs5218 with BMI in a sample of Kuwaiti's

Background

APOC3 is important in lipid transport and metabolism with limited studies reporting genetic sequence variations in specific ethnic groups. The present study aimed to analyze the full APOC3 sequence among Kuwaiti Arabs and test the association of selected variants with lipid levels and BMI.

Methods

Variants were identified by Sanger sequencing the entire APOC3 gene in 100 Kuwaiti Arabs. Variants and their genotypes were fully characterized and used to construct haplotype blocks. Four variants (rs5128, rs2854117, rs2070668, KUAPOC3N3 g.5196 A > G) were selected for testing association with serum lipid levels and BMI in a cohort (n = 733).

Results

APOC3 sequence (4.3 kb) of a Kuwaiti Arab was deposited in Genbank (accession number KJ437193). Forty-two variants including 3 novels were identified including an “A” insertion at genomic positions 116,700,599–116,700,600 (promoter region) and two substitutions in intron 1 at genomic positions 116,700,819 and 116,701,159. Only three variants, (rs5128, rs2854117, and rs2070668) were analyzed for association of which rs5128 showed a trend for association with increased BMI, TG and VLDL levels that was further investigated using multivariate analysis. A significant association of rs5128 with BMI (p <  0.05) was observed following a dominant genetic model with increased risk by an OR of 4.022 (CI: 1.13–14.30).

Conclusion

The present study is the first to report sequence analysis of APOC3 in an Arab ethnic group. This study supports the inclusion of rs5128 as a marker for assessing genetic risk to dyslipidemia and obesity and the inclusion of the novel variant g.5196 A > G for population stratification of Arabs.

Different Susceptibilities between Apoe- and Ldlr-Deficient Mice to Inflammation-Associated Colorectal Carcinogenesis

Hypercholesterolemia resulting in atherosclerosis is associated with an increased risk of ischemic heart disease and colorectal cancer (CRC). However, the roles of apoliprotein (Apo) E (Apoe) and low-density lipoprotein (Ldl) receptor (Ldlr) in colorectal carcinogenesis have not yet been investigated. In this study, we examined the susceptibility of Apoe-deficient and Ldlr-deficient mice, which are genetic animal models of atherosclerosis to azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colorectal carcinogenesis. In Experiment 1, male Apoe-deficient (n = 20) and wild type (WT) mice (C57BL/6J, n = 21) were treated with a single intraperitoneal (i.p.) injection of AOM (10 mg/kg body weight) and then given 1.5% DSS in drinking water for seven days. They were maintained up to week 20 and sacrificed for the histopathological examination of colorectal tumors. The mRNA expression of cyclooxygenase (Cox)-2, inducible nitric oxide synthase (Nos2), tumor necrosis factor (Tnf)-α interleukin (Il)-1β, and Il-6 was assayed in the colorectal mucosa. In Experiment 2, male Ldlr-deficient (n = 14) and WT mice (C57BL/6J, n = 10) were given a single i.p. injection of AOM (10 mg/kg body weight) and then given 2% DSS in drinking water for seven days. They were sacrificed at week 20 to evaluate their colorectum histopathologically. In Experiment 1, the multiplicity of CRCs was significantly higher in the Apoe-deficient mice (2.75 ± 1.48) than in the WT mice (0.62 ± 0.67). The serum lipoprotein levels in the Apoe-deficient mice were also significantly higher than in the WT mice. In Experiment 2, the incidence (29%) and multiplicity (0.50 ± 0.94) of CRCs in the Ldlr mice were significantly lower than in the WT mice (80% incidence and 3.10 ± 2.38 multiplicity). The mRNA expression of two inducible enzymes and certain pro-inflammatory cytokines in the colorectum of each genotype was greater than in the respective WT mice. The values in the Apoe-deficient mice were much greater than in the Ldlr mice. These findings suggest that Apoe-deficient mice showed increased susceptibility to inflammation-associated colorectal carcinogenesis due to their high reactivity to inflammatory stimuli.

Low density lipoprotein receptor gene Ava II polymorphism and serum lipid levels in the Guangxi Bai Ku Yao and Han populations

BACKGROUND

Several common genetic polymorphisms in the low density lipoprotein receptor (LDL-R) gene have associated with modifications of serum total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) levels, but the results are not consistent in different populations. Bai Ku Yao is a special subgroup of the Yao minority in China. The present study was undertaken to detect the association of LDL-R gene Ava Ⅱ polymorphism and serum lipid levels in the Guangxi Bai Ku Yao and Han populations.

METHODS

A total of 1024 subjects of Bai Ku Yao and 792 participants of Han Chinese were randomly selected from our previous stratified randomized cluster samples. Genotyping of the LDL-R gene Ava Ⅱ polymorphism was performed by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing.

RESULTS

The levels of serum TC, high density lipoprotein cholesterol (HDL-C), LDL-C, apolipoprotein (Apo) A1 and the ratio of ApoA1 to ApoB were lower in Bai Ku Yao than in Han (P < 0.01 for all). The frequency of A⁻ and A+ alleles was 65.5% and 34.5% in Bai Ku Yao, and 80.7% and 19.3% in Han (P < 0.001); respectively. The frequency of A⁻A⁻, A⁻A+ and A+A+ genotypes was 42.6%, 45.9% and 11.5% in Bai Ku Yao, and 64.9%, 31.6% and 3.5% in Han (P < 0.001); respectively. There was also significant difference in the genotypic frequencies between males and females in Bai Ku Yao (P <0.05), and in the genotypic and allelic frequencies between normal LDL-C (≤ 3.20 mmol/L) and high LDL-C (> 3.20 mmol/L) subgroups in Bai Ku Yao (P < 0.05 for each) and between males and females in Han (P < 0.05 for each). The levels of LDL-C in males and TC and HDL-C in females were different among the three genotypes (P < 0.05 for all) in Bai Ku Yao, whereas the levels of HDL-C in males and HDL-C and ApoA1 in females were different among the three genotypes (P < 0.05-0.001) in Han. The subjects with A+A+ genotype had higher serum LDL-C, TC, HDL-C or ApoA1 levels than the subjects with A-A+ and A⁻A⁻ genotypes. Spearman rank correlation analysis revealed that the levels of LDL-C in Bai Ku Yao and HDL-C in Han were correlated with genotypes (P < 0.05 and P < 0.01; respectively).

CONCLUSIONS

The association of LDL-R gene Ava Ⅱ polymorphism and serum lipid levels is different between the Bai Ku Yao and Han populations. The discrepancy might partly result from different LDL-R gene Ava Ⅱ polymorphism or LDL-R gene-environmental interactions.

Lactobacillus gasseri [corrected] CHO-220 and inulin reduced plasma total cholesterol and low-density lipoprotein cholesterol via alteration of lipid transporters

This randomized, double-blind, placebo-controlled, and parallel-designed study was conducted to investigate the effect of a synbiotic product containing Lactobacillus gasseri [corrected] CHO-220 and inulin on lipid profiles of hypercholesterolemic men and women. Thirty-two hypercholesterolemic men and women with initial mean plasma cholesterol levels of 5.7±0.32 mmol/L were recruited for the 12-wk study. The subjects were randomly allocated to 2 groups; namely the treatment group (synbiotic product) and the control group (placebo), and each received 4 capsules of synbiotic or placebo daily. Our results showed that the mean body weight, energy, and nutrient intake of the subjects did not differ between the 2 groups over the study period. The supplementation of synbiotic reduced plasma total cholesterol and low-density lipoprotein (LDL)-cholesterol by 7.84 and 9.27%, respectively, compared with the control over 12 wk. Lipoproteins were subsequently subfractionated and characterized. The synbiotic supplementation resulted in a lower concentration of triglycerides in the very low, intermediate, low, and high-density lipoprotein particles compared with the control over 12 wk. The concentration of triglycerides in lipoproteins is positively correlated with an increased risk of atherosclerosis. Our results showed that the synbiotic might exhibit an atheropreventive characteristic. Cholesteryl ester (CE) in the high-density lipoprotein particles of the synbiotic group was also higher compared with the control, indicating greater transport of cholesterol in the form of CE to the liver for hydrolysis. This may have led to the reduced plasma total cholesterol level of the synbiotic group. The supplementation of synbiotic also reduced the concentration of CE in the LDL particles compared with the control, leading to the formation of smaller and denser particles that are more easily removed from blood. This supported the reduced LDL-cholesterol level of the synbiotic group compared with the control. Our present study showed that the synbiotic product improved plasma total- and LDL-cholesterol levels by modifying the interconnected pathways of lipid transporters. In addition, although Lactobacillus gasseri [corrected] CHO-220 could deconjugate bile, our results showed a statistically insignificant difference in the levels of conjugated, deconjugated, primary, and secondary bile acids between the synbiotic and control groups over 12 wk, indicating safety from bile-related toxicity.

A polygenic basis for four classical Fredrickson hyperlipoproteinemia phenotypes that are characterized by hypertriglyceridemia

Numerous single nucleotide polymorphisms (SNPs) have been found in recent genome wide association studies (GWAS) to be associated with subtle plasma triglyceride (TG) variation in normolipidemic subjects. However, since these GWAS did not specifically evaluate patients with rare disorders of lipoprotein metabolism--'hyperlipoproteinemia' (HLP)--it remains largely unresolved whether any of these SNP determinants of modest physiological changes in TG are necessarily also determinants of most HLP phenotypes. To address this question, we evaluated 28 TG-associated SNPs from GWAS in 386 unrelated adult patients with one of five Fredrickson phenotypes (HLP types 2A, 2B, 3, 4 and 5) and 242 matched normolipidemic controls. We found that several SNPs associated with TG in normolipidemic samples, including APOA5 p.S19W and -1131T>C, TRIB1 rs17321515, TBL2 rs17145738, GCKR rs780094, GALNT2 rs4846914 and ANGPTL3 rs12130333, were significantly associated with HLP types 2B, 3, 4 and 5. The findings indicate that: (i) the TG-associated Fredrickson HLP types 2B, 3, 4 and 5 are polygenic traits; (ii) these Fredrickson HLP types share numerous genetic determinants among themselves; and (iii) genetic determinants of modest TG variation in normolipidemic population samples also underlie--to an apparently even greater degree--susceptibility to these rare HLP phenotypes. Thus, the TG-associated Fredrickson HLP types 2B, 3, 4 and 5, although historically considered to be distinct are actually complex traits sharing among them several common genetic determinants seen in GWAS of normolipidemic population samples.

Determinants of risk factors of atherosclerosis in the postinfarction period: The Tallinn MI Study

Environmental as well as genetic factors are involved in the pathogenesis of myocardial infarction. The disease is a frequent cause of mortality in the middle-aged male population of Estonia. The high prevalence of premature myocardial infarction (PMI) in this country is not fully understood. The association of atherogenic and thrombogenetic risk factors with lifestyle was evaluated in men who had suffered myocardial infarction at 55 years of age (n = 71) and in randomly selected corresponding controls (n = 85). Serum routine lipids, apolipoprotein (apo)A-I, apoB, apoE polymorphism, lipoprotein(a) and fibrinogen levels were determined. Behavioural risk factors, indices of obesity, blood pressure and pedigree data were registered. In 80.6 % of PMI subjects some type of hyperlipidaemia was observed (European Atherosclerosis Society Classification) and lipid-lowering drugs were taken by 13.9 % of patients. In PMI patients the most common positive determinants of atherogenic lipoprotein indices were waist-to-hip ratio and physical inactivity, and in controls, waist-to-hip ratio and apoE phenotype. The odds ratio (OR) of PMI was 8.9-fold greater in the highest tertile of apoB/apoA-I distribution compared with the lowest tertile. The OR of PMI in the highest tertile of fibrinogen distribution versus the lowest tertile was 6.2 (95 % CI 2.46-15.44), and OR of PMI in the highest Lp(a) tertile versus the lowest was 3.1 (95 % CI 1.31-7.40). Thus, atherogenic dyslipidaemia was the most serious cardiovascular risk factor among PMI patients. From two thrombogenesis-related markers, the levels of fibrinogen and Lp(a), the first one was more strongly associated with PMI status.

Genetic determinants of plasma lipoproteins

The search for common genetic determinants of plasma lipoproteins began in the early 1980s. Despite some exceptions, these efforts have not yet yielded a set of biological markers that can be used in clinical practice. By contrast, successes in defining the molecular basis of rare single-gene disorders, such as familial hypoalphalipoproteinemia, have shown the value of experimental designs that focus on genomic analysis of individuals within the tails of Gaussian distributions of quantitative lipoprotein traits. For example, this strategy showed that a small but relevant proportion of individuals within the <5% tail of plasma HDL-cholesterol distribution have mutations in genes that cause familial hypoalphalipoproteinemia. The value of clinical testing for genomic variants as an adjunct to a biochemical measurement of plasma lipoproteins, however, is at best questionable. A more direct impact of genetic studies is that definitions of 'common' and 'large genetic effects' have become more tempered, reflecting perhaps the biological reality that plasma lipoproteins are probably determined by the aggregate of numerous modest and occasional large genetic effects in addition to environmental factors. Here, we review recent progress on genomic variants and cholesterol metabolism, and discuss the impact these genetic studies will have on clinical cardiology.

Human pharmacogenomic variations and their implications for antifungal efficacy

Pharmacogenomics is defined as the study of the impacts of heritable traits on pharmacology and toxicology. Candidate genes with potential pharmacogenomic importance include drug transporters involved in absorption and excretion, phase I enzymes (e.g., cytochrome P450-dependent mixed-function oxidases) and phase II enzymes (e.g., glucuronosyltransferases) contributing to metabolism, and those molecules (e.g., albumin, A1-acid glycoprotein, and lipoproteins) involved in the distribution of antifungal compounds. By using the tools of population genetics to define interindividual differences in drug absorption, distribution, metabolism, and excretion, pharmacogenomic models for genetic variations in antifungal pharmacokinetics can be derived. Pharmacogenomic factors may become especially important in the treatment of immunocompromised patients or those with persistent or refractory mycoses that cannot be explained by elevated MICs and where rational dosage optimization of the antifungal agent may be particularly critical. Pharmacogenomics has the potential to shift the paradigm of therapy and to improve the selection of antifungal compounds and adjustment of dosage based upon individual variations in drug absorption, metabolism, and excretion.

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.

Plasma very-low-density lipoprotein, low-density lipoprotein, and high-density lipoprotein oxidative modification induces procoagulant profiles in endogenous hypertriglyceridemia

This study was to investigate whether oxidatively modified lipoproteins were associated with changes of pro- and anticoagulant profiles in hypertriglyceridemic subjects. Plasma VLDL, LDL, and HDL were isolated with the one-step density gradient ultracentrifugation method. The oxidation of the lipoproteins was identified. Prothrombin time (PT) and activated partial thrombplastin time (APTT), tissue plasminogen activator and plasminogen activator inhibitor-1, and platelet aggregation rate were determined with a reaction system consisting of mixed fresh normal plasma, in endogenous hypertriglyceridemic (HTG) patients, in in vitro modified lipoproteins from a normolipidemic donor, and in experimental rats. The results indicated that oxVLDL, oxLDL, and oxHDL occurred in the plasma of HTG patients. Compared with the control group, PT and APTT, incubated with plasma VLDL, LDL, or HDL from HTG patients, respectively, were significantly reduced, while platelet maximal aggregation rates were significantly higher (P < 0.05-0.01). Similar procoagulant profiles were observed in in vitro modified lipoprotein components and in rats with intrinsic hypertriglyceridemia as well. These results support our previous finding that LDL, VLDL, and HDL were all oxidatively modified in vivo in the subjects with HTG, and suggest that procoagulation state may result from the abnormal plasma lipoprotein oxidative modification in vivo.

Associations between plasma lipid parameters and APOC3 and APOA4 genotypes in a healthy population are independent of dietary cholesterol intake

To determine whether APOC3 and APOA4 genotypes influence plasma cholesterol fluctuations following a high cholesterol diet, a healthy population of 40 men and 51 women were studied. The crossover intervention randomly assigned participants to an EGG (640 mg/d cholesterol) or placebo (0 mg/d cholesterol) diet for 30 days, with a 3-week washout between periods. Allele-specific oligonucleotide hybridization was utilized to determine the presence or absence of APOC3 and APOA4 polymorphisms. Differences in plasma cholesterol between hyper- and hypo-responders were not influenced by genotype. However, an interaction (P < 0.0001) did exist between APOA4 allele, diet and gender with regard to triglycerides (TG). While female carriers of the APOA4(347) S allele had lower TG concentrations than those with the common T/T allele, males with the S allele had higher concentrations. The APOC3 SstI polymorphism analysis revealed that heterozygous carriers of the S2 allele had higher (P < 0.05) plasma apo C-III and TG concentrations, regardless of gender or dietary period. In addition, carriers of the S2 allele had smaller LDL peak particle diameter than those having the common APOC3 genotype. The presence of individual alleles in this population was associated with differences in plasma lipids and LDL size. However, these relationships were independent of dietary cholesterol.

Complex control of mouse apolipoprotein B gene expression revealed by targeted duplication

An elevated plasma level of apolipoprotein B-containing lipoproteins is a risk factor for atherosclerotic cardiovascular disease. Subtle genetic abnormalities in gene expression including an increased expression of the APOB gene may play an important role in determining overall risk. In an attempt to increase mouse Apob expression, we used gene targeting and duplicated approximately 65 kb of genomic DNA containing the Apob locus in its natural genomic position in mice. While we successfully generated mice carrying the Apob gene duplication, the amount of the total Apob mRNA was not increased in their liver. In the intestine, total Apob mRNA was reduced to half of the wild-type mice. Plasma lipids in the Apob duplication mice were not altered. Expression analyses showed that the proximal Apob gene in the duplicated locus was preferentially expressed in both tissues suggesting a limitation of tissue-specific enhancer function. The previously characterized distant intestinal control element was not duplicated, explaining the unequal ratio of intestinal Apob expression. While the existence of an additional liver-specific enhancer element is unknown, our findings suggest the presence of an additional enhancer outside the duplicated region, and that Apob gene expression is more complicated than previously thought.

Modest protective effects of isoflavones from a red clover-derived dietary supplement on cardiovascular disease risk factors in perimenopausal women, and evidence of an interaction with ApoE genotype in 49-65 year-old women

Data suggest that soy protein, a source of isoflavones, may have favorable effects on cardiovascular risk factors. Women (n = 205), ages 49-65 y, were randomized into this double blind, placebo-controlled trial of 43.5 mg red clover-derived isoflavones/d. A total of 177 women completed the trial. There were no differences between treatments for changes from baseline to 12 mo in total cholesterol, LDL cholesterol, triglycerides, HDL cholesterol, systolic and diastolic blood pressures, fibrinogen, and plasminogen activator inhibitor type 1 (PAI-1) (P >/= 0.1). Interactions between treatment and menopausal status were significant for changes in triglycerides and PAI-1 (P = 0.02 and P = 0.01), and changes were significant among perimenopausal women. In the isoflavone and placebo groups, changes in triglycerides were -0.2 +/- 0.6 and 0.4 +/- 0.6 mmol/L, P = 0.02, and changes in PAI-1 were -3.06 +/- 5.88 and 4.95 +/- 6.25 IU/L, P = 0.004, respectively. Interactions between apolipoprotein E (apoE) genotype and treatment tended to be significant for changes in total and LDL cholesterol (P = 0.06 and P = 0.05), and differences between treatments were significant in E2/E3 women. In the isoflavone and placebo groups, changes in total cholesterol were -0.61 +/- 0.79 and 0.18 +/- 0.79 mmol/L, P = 0.03, and changes in LDL cholesterol were -0.84 +/- 0.79 and -0.04 +/- 0.69 mmol/L, P = 0.02, respectively. Although there were potentially beneficial changes in triglycerides and PAI-1 among perimenopausal women consuming isoflavones, this study suggests that isoflavones alone are not responsible for the well-documented effects of soy protein on blood lipids. A larger study is required to confirm the effect modification by apoE genotype.

Novel QTLs for HDL levels identified in mice by controlling for Apoa2 allelic effects: confirmation of a chromosome 6 locus in a congenic strain

Atherosclerosis is a complex disease resulting from the interaction of multiple genes, including those causing dyslipidemia. Relatively few of the causative genes have been identified. Previously, we identified Apoa2 as a major determinant of high-density lipoprotein cholesterol (HDL-C) levels in the mouse model. To identify additional HDL-C level quantitative trait loci (QTLs), while controlling for the effect of the Apoa2 locus, we performed linkage analysis in 179 standard diet-fed F(2) mice derived from strains BALB/cJ and B6.C-H25(c) (a congenic strain carrying the BALB/c Apoa2 allele). Three significant QTLs and one suggestive locus were identified. A female-specific locus mapping to chromosome 6 (Chr 6) also exhibited effects on plasma non-HDL-C, apolipoprotein AII (apoAII), apoB, and apoE levels. A Chr 6 QTL was independently isolated in a related congenic strain (C57BL/6J vs. B6.NODc6: P = 0.003 and P = 0.0001 for HDL-C and non-HDL-C levels, respectively). These data are consistent with polygenic inheritance of HDL-C levels in the mouse model and provide candidate loci for HDL-C and non-HDL-C level determination in humans.

Marked reduction in serum high-density lipoprotein cholesterol concentrations in a woman with acute inflammation due to diabetic gangrene

BACKGROUND

C-reactive protein (CRP) is a well-established, sensitive marker of systemic inflammation and the risk of cardiovascular disease. High-density lipoprotein (HDL) is an anti-atherogenic lipoprotein known to be regulated by genetic and acquired factors.

METHODS

The patient was a 77-year-old Japanese woman, who was diagnosed with type 2 diabetes mellitus (DM), with a body height of 152 cm and a weight of 65 kg (body mass index 28.1 kg/m2). She suffered from diabetic foot gangrene in her right foot with high-grade fever when she visited our hospital. Her plasma glucose (PG) concentration and serum CRP were markedly elevated being 21.6 mmol/l and 370 mg/l, respectively, while her serum HDL-C concentrations were markedly low being 0.13 mmol/l. She was immediately admitted to our hospital and received intensive insulin treatment, along with intravenous-administration of antibiotics. Her general conditions were gradually improved and the high-grade fever disappeared, with concentrations of plasma PG and serum CRP being reduced, and concurrent reciprocal increase in her serum HDL-C concentrations.

RESULTS

To determine the potential causative factors responsible for the drastic change in serum HDL-C concentrations, we investigated the relationship of serum HDL-C to serum CRP, serum total protein (TP) and PG. Serum CRP and PG showed inverse relationships with serum HDL-C, while serum TP concentrations showed a positive association with HDL-C. After multivariate analyses with CRP, TP and PG as independent variables and serum HDL-C as dependent variable, CRP maintained its independent association with serum HDL-C. CRP also showed inverse correlations with lipoprotein lipase (LPL) mass and cholesteryl ester transfer protein mass.

CONCLUSIONS

In acute inflammation and poorly controlled diabetes, CRP is suggested to be inversely associated with serum HDL-C, independent of PG and TP.

Lipid-lowering effects of TAK-475, a squalene synthase inhibitor, in animal models of familial hypercholesterolemia

The lipid-lowering effects of 1-[2-[(3R,5S)-1-(3-acetoxy-2,2-dimethylpropyl)-7-chloro-1,2,3,5-tetrahydro-2-oxo-5-(2,3-dimethoxyphenyl)-4,1-benzoxazepine-3-yl] acetyl] piperidin-4-acetic acid (TAK-475), a novel squalene synthase inhibitor, were examined in two models of familial hypercholesterolemia, low-density lipoprotein (LDL) receptor knockout mice and Watanabe heritable hyperlipidemic (WHHL) rabbits. Two weeks of treatment with TAK-475 in a diet admixture (0.02% and 0.07%; approximately 30 and 110 mg/kg/day, respectively) significantly lowered plasma non-high-density lipoprotein (HDL) cholesterol levels by 19% and 41%, respectively, in homozygous LDL receptor knockout mice. The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, simvastatin and atorvastatin (in 0.02% and 0.07% admixtures), also reduced plasma levels of non-HDL cholesterol. In homozygous WHHL rabbits, 4 weeks of treatment with TAK-475 (0.27%; approximately 100 mg/kg/day) lowered plasma total cholesterol, triglyceride and phospholipid levels by 17%, 52% and 26%, respectively. In Triton WR-1339-treated rabbits, TAK-475 inhibited to the same extent the rate of secretion from the liver of the cholesterol, triglyceride and phospholipid components of very-low-density lipoprotein (VLDL). These results suggest that the lipid-lowering effects of TAK-475 in WHHL rabbits are based partially on the inhibition of secretion of VLDL from the liver. TAK-475 had no effect on plasma aspartate aminotransferase and alanine aminotransferase activities. Thus, the squalene synthase inhibitor TAK-475 revealed lipid-lowering effects in both LDL receptor knockout mice and WHHL rabbits.

A prospective study of the association between APOE genotype and the risk of myocardial infarction among apparently healthy men

BACKGROUND

Apolipoprotein E (apoE) plays an important role in lipid metabolism. Three common alleles in the APOE gene, E2/E3/E4, have been associated with lipoprotein disorders but their effects on myocardial infarction (MI) risk remain uncertain.

METHODS

In a prospective cohort of 14916 apparently healthy men enrolled in the Physicians' Health Study, APOE genotyping was conducted to determine three common alleles (E2/E3/E4) among 385 incident cases of first MI and among 373 age- and smoking-matched controls.

RESULTS

No significant differences in allele or genotype frequency for the APOE gene were detected between cases and controls. As expected, we observed significant positive associations between dyslipidemia (low HDL/high TG or high LDL) and MI risk (P<0.001) and between genotypes and levels of LDL (P<0.001), HDL (P=0.04) or TG (P=0.02). Compared with men homozygous for the E3 allele and after adjusting for multiple MI risk factors, men carrying the E4 allele (E4/4 or E4/3) had a relative risk of 0.93 (95% CI 0.63-1.37) and men carrying the E2 allele (E2/2 or E2/3) a relative risk of 1.03 (0.62-1.74). Moreover, no significant difference in MI risk was observed among different genotypes across different levels of lipids or smoking status.

CONCLUSIONS

These data from a prospective study of apparently healthy men do not support the simple view of E2 as a protective factor and E4 as a susceptibility factor in predicting future risk of MI independent of lipid parameters. Nor did we observe any interaction between smoking and apoE4 allele on MI risk.

O componente genético da determinação dos lipídeos séricos

Os níveis de lipídeos séricos são características multifatoriais determinadas por um grande número de fatores genéticos e ambientais. A identificação do componente genético dessas características tem sido intensamente investigada nos últimos anos. Esses estudos têm enfocado principalmente polimorfismos nos genes que codificam proteínas estruturais e enzimas relacionadas com o metabolismo de lipídeos. Estudos mais recentes mostraram que o efeito desses polimorfismos depende em parte das interações dos diferentes genótipos com os fatores de risco clássicos tais como tabagismo, sobrepeso ou sedentarismo. A variabilidade encontrada nesses genes parece também influir na resposta a fármacos comumente utilizados no tratamento das hiperlipidemias.

Low-density lipoprotein receptor gene mutation analysis and clinical correlation in Belgian hypercholesterolaemics

It is generally believed that patients with familial hypercholesterolaemia (FH) have a higher cardiovascular risk than hypercholesterolaemics without a defect in the low-density lipoprotein receptor (LDLR) gene. However, no conclusive evidence to support this view has yet been presented. We investigated this aspect in Belgian hyperlipidaemics as part of a comprehensive effort to determine the impact of FH in this population. DNA samples of 98 unrelated Belgian patients with a family history of autosomal dominant hypercholesterolaemia were screened for mutations in the LDLR gene, after exclusion of known mutations causing familial defective apolipoprotein B-100 (FDB). Eight of the 22 distinct LDLR gene mutations identified in 27 subjects have not previously been described in other populations. As expected, the mutation-positive patients had a significantly worse lipid profile than the mutation-negative subjects (p<0.05), but this did not correlate with clinical cardiovascular status. In conclusion, the presence of a mutation in the LDLR gene was not a reliable predictor of cardiovascular risk in the hyperlipidaemic subjects included in this study. However, it is possible that prolonged exposure to the high levels of LDL cholesterol in genetically proven FH patients will in future cause a higher incidence of coronary heart disease. Our data may reflect the genetic heterogeneity of inherited hypercholesterolaemia, recently shown to be caused by several major genes.

The apolipoprotein epsilon2 allele and the severity of coronary artery disease in Type 2 diabetic patients

AIMS

To examine the hypothesis that apolipoprotein E2 is associated with more severe coronary disease in Type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

In this retrospective cohort study, 491 patients with angiographically assessed coronary disease were recruited from those attending a university hospital cardiology department. Participants completed detailed questionnaires, from which the presence or absence of diabetes was determined. Fasting blood samples were obtained for apolipoprotein E genotype and measurement of blood lipid parameters.

RESULTS

The prevalence of triple vessel disease was significantly lower in non-diabetic, epsilon2 allele carriers (39.3% vs. 16.2%; odds ratio (OR) 0.30 (0.12-0.71), P < 0.03) compared with E3/3 carriers. In Type 2 diabetic patients, epsilon2 allele carriers had an excess of triple vessel disease compared with E3/3 genotypes (43.3 vs. 68.8%; OR 2.8 (1.07-7.30), P < 0.05). The differences were independent of other variables. The apo E4 subgroup showed no significant differences in the frequency of triple vessel disease.

CONCLUSIONS

Diabetic epsilon2 allele carriers had more severe coronary artery disease than diabetic patients with other apo E isoforms. In non-diabetic patients the epsilon2 allele appeared to protect against severe coronary disease. We hypothesize that interaction between the diabetic milieu and the epsilon2 allele accelerates plaque progression. It suggests that diabetic patients who are carriers of the epsilon2 allele, even in the heterozygous form, should be the focus of particular therapeutic attention. Diabet. Med. 18, 445-450 (2001)

The effect of amlodipine on endothelial function in young adults with a strong family history of premature coronary artery disease: a randomised double blind study

Endothelial dysfunction, an early event in atherogenesis, has been demonstrated in young asymptomatic subjects with a strong family history of premature coronary artery disease (CAD). In these subjects, preventive measures involving risk factor modification are not appropriate, and strategies employing novel antiatherogenic agents, such as the dihydropyridine calcium channel blocker, amlodipine, may be useful. Ninety-one subjects (mean age, 28.6 years; range, 18-40) with a strong family history of premature CAD and no other identified vascular risk factors were randomised to either 5 mg amlodipine (49 subjects) or placebo (42 subjects). Brachial artery flow mediated dilatation (FMD) (endothelium-dependent response) and response to glyceryltrinitrate (GTN) (direct smooth muscle dilator) were assessed non-invasively at baseline, and after 12 and 24 weeks using high-resolution vascular ultrasound. In those treated with amlodipine, mean FMD increased from 2.32+/-2.23% at baseline to 3.52+/-3.1% at 24 weeks (P<0.005). However, FMD also increased in the placebo group from 1.64+/-2.12 to 3.37+/-2.68% (P<0.002), and the difference between the FMD response in the amlodipine and placebo groups was not significant. Dilatation to GTN did not change in either group. Therefore, impaired endothelial function improved in family history subjects taking both amlodipine and placebo, but there is no difference between the groups.

Age-associated accumulation of the apolipoprotein C-III gene T-455C polymorphism C allele in a Russian population

Apolipoprotein C-III (apoC-III) is the major component of triglyceride-rich lipoproteins. One of six identified polymorphisms in the apoC-III 5'-untranslated region (T-455C) is located within a functional insulin-response element. In a group of 137 elderly individuals (70-106 years old), the allele distribution was analyzed using restriction fragment length polymorphisms. Statistical analysis of allele frequencies was performed on subgroups selected by age and in elderly patients with arterial hypertension or ischemic heart disease. A greater frequency of the apoC-III -455C allele was demonstrated with aging (p < .005). No statistically significant difference in allele distributions was detected between healthy subjects and groups of elderly patients of the same age with either ischemic heart disease or arterial hypertension. The increased incidence of the C allele with advanced age indicates that this variant promoter is associated with longevity. The greater incidence of this allele is detectable only in adults older than 80 years of age.

A new locus for autosomal recessive hypercholesterolemia maps to human chromosome 15q25-q26

High serum cholesterol is an established risk factor for cardiovascular disease and is the prime target for therapeutic intervention in large groups of patients. The development of modern treatments for this major risk factor was propelled by the early realization that forms of severe hypercholesterolemia could be caused by dominantly inherited defects in the LDL receptor or in the APOB gene. Further understanding of the mechanisms contributing to early atherosclerosis will allow for new targets for therapy. We therefore identified and investigated the genetics of families from Sardinia that have recessive inheritance of precocious hypercholesterolemia. We used five families in an analysis of linkage of the autosomal recessive hypercholesterolemia locus, termed "ARH1," to chromosome 15q25-q26. A genomewide search mapped the disease-causing gene with a LOD score of 3.3 and excluded major contributions to the phenotype of other genes. A candidate gene present in the mapped chromosome region-the ligand-activated liver-transcription-factor gene ARP1 (apolipoprotein regulatory-protein gene)-has been excluded after DNA sequencing. The close-bred nature of the Sardinian population offers unique opportunities for isolation of this hypercholesterolemia-causing gene.

[Clinical manifestations of heterozygote familial hypercholesterolemia in Spain. Study of 301 cases from the central and northern areas]

RATIONALE

To characterize clinical manifestations of familial hypercholesterolemia (FH) in Spain.

PATIENTS AND METHODS

A group of 301 cases of FH from central and north regions of Spain.

RESULTS

With a mean (SD) cholesterol level of 346 (58) mg/dl, only 7.6% of the patients have xanthomas and 20% ischaemic heart disease. 51% have a familial history of ischaemic heart disease.

CONCLUSIONS

Different from the results of literature, xanthomas are very infrequent in FH in Spain, so diagnosis should be suspected from other data. The high prevalence of familial history of ischaemic heart disease supports the usefulness of this feature as a marker for diagnosis and prevention.

Abnormal blood lipids: is it environment or is it genes?

Genetic and environmental factors contribute to the development and progression of atherosclerotic coronary heart disease processes. Major independent risk factors for coronary heart disease, including adverse levels of plasma lipids and lipoproteins, are also influenced by genetic and potentially modifiable environmental factors. Recent advances in molecular biology have resulted in the identification of specific genes associated with lipid disorders. The complex gene-environment interplay that contributes to interindividual variation in components of the lipid profile is also partially clarified. This article provides an overview of available data on the genetic and environmental influences on lipids and lipoproteins with emphasis on implications for clinical practice and future research.

Apolipoprotein E gene polymorphisms and serum cholesterol in healthy Irish adults: a proposed genetic marker for coronary artery disease risk

BACKGROUND

The apolipoprotein (Apo) E gene, and thus its gene product, plays a central and pervasive role in lipid metabolism by serving as a ligand for lipoprotein receptors. Polymorphisms of this gene have been associated with variation in lipid phenotypes in some Caucasian and Asian populations, but not in others. No such study has been carried out in a resident Irish population.

AIM

A study was designed to examine the relationship between serum cholesterols and Apo E genotype in a cohort of healthy Irish adults.

METHODS

One hundred healthy Irish adults, aged 19-65 years, were recruited from the Cork City area. Two fasting blood samples were collected from each subject. One was assayed for serum cholesterols--total and low-density lipoprotein (LDL), and high-density lipoprotein (HDL)--while the other sample was used for isolation of genomic DNA and determination of Apo E genotype.

RESULTS

While the E2 (12%) was the least prevalent, E3 was the most prevalent Apo E genotype (66%) in this group of healthy Irish adults. A significant Apo E gene-dosage effect was evident, whereby individuals with the Apo E2 genotype had a lower level of total cholesterol, E3 had intermediate levels, and E4 had a higher level. Moreover, those with the Apo E4 genotype had a significantly higher level of LDL cholesterol compared to E2 or E3 genotypes. There was no significant difference in mean serum adjusted HDL-cholesterol levels between the three Apo E genotypes.

CONCLUSION

These findings suggest that healthy Irish adults with the Apo E4 genotype have higher serum total and LDL-cholesterol levels than those with E2 or E3 Apo E genotypes and therefore may have a higher risk of atherosclerotic coronary artery disease and coronary heart disease in later life.

Prevention of coronary heart disease. Part II. Secondary prevention, detection of subclinical disease, and emerging risk factors

The prevention of CHD should be a major priority among primary care physicians and subspecialists who have any dealing with the cardiovascular system. There is ample evidence from epidemiologic studies for the impact of specific risk factors on CHD events. There is also ample evidence from observational studies and clinical trials that interventions of lifestyle and pharmacologic therapy can decrease morbidity and mortality from CHD before or after the first event. It behooves the physician who wishes to practice good medicine to understand the pathophysiologic roles of the risk factors and the evidence from epidemiologic studies and clinical trials for their association with cardiovascular disease. It is important to determine the efficacy of interventions, both lifestyle and pharmacologic, in modifying CHD risk. To be effective in doing so, the practicing physician has to have the motivation to determine target goals for risk factor modification in each patient, to understand the patient's own motivations in modifying risk factors, and to define clearly with the patient the expectations of such interventions. Although there are guidelines for risk factor modification in modification of cholesterol and in hypertension, the periodic renewal of these guidelines reflects the changing concepts of risk and its modification. A cardiovascular risk factor intervention categorization is presented in Table 12. The physician must be convinced that such intervention is beneficial to the patient, cost-effective, and thus fulfills the expectations of medical practice. The practice of medicine in the evaluation and treatment of coronary heart disease has always been challenging and stimulating. The prevention of CAD disease should ultimately provide the greatest accomplishment.

Genetic markers to predict polygenic disease

Many genetic markers that relate to common multifactorial disease in adults have been identified during the past 15 years. Their use as adjuncts for the diagnosis, prognosis, prediction of disease or targeting therapy for these disorders has commenced; good examples being the Factor V Leiden mutation for venous-thromboembolism, lipoprotein lipase mutations for hypertriglyceridemia and the apolipoprotein E4 variant for Alzheimer's dementia. However, extensive gene-gene interactions and gene-environment interactions make their use more complex than markers for the simpler monogenic disorders (eg, cystic fibrosis, or Duchennne's muscular dystrophy). Possible misapplications of the use of genetic markers for multifactorial disease are discussed.

Apolipoprotein E and methylenetetrahydrofolate reductase genetic polymorphisms in relation to other risk factors for cardiovascular disease in UK Caucasians and Black South Africans

Genetic polymorphisms for apolipoprotein E (apo E) and methylenetetrahydrofolate reductase (MTHFR) are believed to modulate risk of coronary heart disease (CHD) acting through regulation of lipid and homocysteine metabolism, respectively. The distributions of apo E and MTHFR alleles in Black South Africans, a population with a low CHD incidence, and UK Caucasians from the Cambridge area, with a higher CHD incidence, were therefore compared. Clinically healthy volunteers (207), including 107 UK Caucasians from the Cambridge area and 100 Black South Africans, participated in the study. Apo E and MTHFR genotypes were determined in all of them. Analyses for serum total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides and plasma fibrinogen were carried out in 65 UK Caucasians and 60 Black South Africans. The apo E epsilon4 allele, which is associated with elevated CHD risk, was present in 48% of Black South Africans compared to 20.8% of Caucasians (P < 0.0001); however, both total and LDL cholesterol levels in Black South Africans were 18-32% lower than in Caucasians with similar apo E genotypes. Hyperhomocysteinemia-causing MTHFR 677T variant was detected in only 20% of Black South Africans (no homozygotes) versus 56% of Caucasians with 12% homozygotes (P<0.0001). Our findings suggest that the potentially unfavourable pattern of apo E allele distribution in Black South Africans does not result in increased CHD incidence due to protection by dietary and/or other life style related factors. The exceptionally low frequency of MTHFR mutant homozygotes in this population suggests that this polymorphism should not be regarded as an important CHD risk factor among Black South Africans.

Genetic risk factors and ischaemic cerebrovascular disease: role of common variation of the genes encoding apolipoproteins and angiotensin-converting enzyme

DNA polymorphisms in genes encoding apolipoproteins (apo) A-I, C-III, B and E and angiotensin-converting enzyme (ACE) have been proposed to be associated with the risk of coronary artery disease (CAD). We studied whether the same genetic markers would also be associated with the occurrence and extent of atherosclerosis in cervical arteries. DNA samples from 234 survivors of stroke or a transient ischaemic attack aged 60 years or less were examined. The presence of atherosclerosis was assessed using aortic arch angiograms. The SstI polymorphism of apoA-I/C-III gene locus, the XbaI polymorphism of apoB gene, common apoE phenotypes and the insertion/deletion polymorphism of the ACE gene were analysed. The allele frequencies of the apoA-I/C-III, apoB, apoE or ACE gene did not differ between the groups with (n = 148) or without (n = 85) cervical atherosclerosis. However, when patients with at least one apoE4 allele and one X2 allele of apoB were combined and compared with those without either of them (E2E3 or E3E3 and X1X1), a significant association with the presence of cervical atherosclerosis was found (P = 0.03). The patients having the E2E3 phenotype had a significantly elevated serum triglyceride level compared with those with the E3E3 phenotype (P = 0.03). Serum high-density lipoprotein (HDL) cholesterol was lower in the patients with the E2E3 phenotype than in those with the E3E3 and E3E4 (P = 0.01 and P = 0.06, respectively). The apoB or ACE genotypes were not significantly associated with serum lipid or lipoprotein levels. There was no association between the ACE gene polymorphism and the occurrence of hypertension. In conclusion, the interaction of common apoB and apoE alleles may increase the risk of atherosclerosis in cervical arteries.

Elevated lipoprotein(a) levels and small apo(a) isoforms are compatible with longevity: evidence from a large population of French centenarians

Epidemiological studies have shown lipoprotein(a) (Lp(a)) to be an independent risk factor for cardiovascular disease. Lp(a) is a cholesterol-rich, low-density lipoprotein (LDL)-like particle to which a large glycoprotein, apolipoprotein(a) (apo(a)) is attached. Plasma Lp(a) levels are highly genetically determined and influenced to a minor degree by environmental factors. In an effort to determine whether Lp(a) might be associated with longevity, we have evaluated Lp(a) levels and apo(a) isoform sizes in a population of French centenarians (n = 109) compared to a control group (n = 227). The mean age of centenarians was 101.5 +/- 2.4 years while the control group was 39.4 +/- 7.2 years. Plasma levels of total cholesterol and triglyceride were within the normal range in both centenarian and control subjects. Lp(a) levels were higher in centenarians (both male and female) than in the normolipidemic control group (mean Lp(a) level = 0.33 +/- 0.42 and 0.22 +/- 0.27 mg/ml, respectively, P < 0.005). The distribution of apo(a) isoforms was significantly shifted towards small isoform size in the centenarian population as compared to the controls (54.4 and 41.4% of isoforms < or = 27 kringles (kr), respectively, P = 0.04). Nonetheless, the apo(a) size distribution in centenarians did not entirely explain the high Lp(a) levels observed in this population. Factors other than apo(a) size, and which may be either genetic or environmental in nature, appear to contribute to the elevated plasma Lp(a) levels of our centenarian population. We conclude therefore that high plasma Lp(a) levels are compatible with longevity.

Apolipoprotein E genotype modulates the effect of black tea drinking on blood lipids and blood coagulation factors: a pilot study

Apolipoprotein E (ApoE) genotype was determined in sixty-five subjects who had taken part in a 4-week randomized crossover trial to compare the effect of six mugs of black tea per day v. placebo on blood lipids and blood coagulation factors. Four ApoE genotype variants (seven E2/E3, forty-five E3/E3, twelve E3/E4 and one E4/E4) were found. ApoE allele frequency was within the range typical for Caucasian populations (ApoE-E2 5.4%; ApoE-E3 83.8%; ApoE-E4 10.8%). Individuals bearing at least one E4 allele had substantially higher levels of serum total cholesterol, LDL cholesterol and triacylglycerols. Mean plasminogen activator inhibitor (PAI-1) activity was higher in ApoE-E4 allele-bearing individuals (E3/E4 + E4/E4, 11.89 (SE 1.27) U/ml; E3/E3, 9.19 (SE 0.80) U/ml; E2/E3, 7.21 (SE 1.04) U/ml, P values of E4-group v. E3 and E2 being respectively 0.093 and 0.030). These unexpected findings imply that elevated PAI-1 activity may be a hitherto unrecognized additional factor involved in the increased cardiovascular disease risk associated with apoE-E4 allele. The interactions between tea drinking and genotype were also examined. In the E3/E3 homozygotes, HDL-cholesterol was significantly reduced in the tea period (mean placebo 1.54 mmol/l v. mean tea 1.50 mmol/l, P = 0.027). In the E2/E3 group, triacylglycerol concentration was significantly reduced (mean placebo 1.18 mmol/l v. mean tea 1.09 mmol/l, P = 0.039). Tea also caused a significant decrease of PAI-1 activity in the subjects with E2/E3 genotype (mean placebo 7.21 U/ml v. mean tea 5.88 U/ml, P = 0.007). In the other two genotype groups, there was no significant effect of tea. The results indicate that tea drinking has a beneficial effect on some cardiovascular disease risk-associated factors, especially in E2 allele-bearing individuals. Dietary intervention may be particularly effective in population groups with certain genetic characteristics.

Objectives, design and recruitment of a familial and longitudinal cohort for studying gene-environment interactions in the field of cardiovascular risk: the Stanislas cohort

The main objective of the Stanislas cohort is to study the role and the contribution of genetic and environmental factors to cardiovascular status. We plan: a) to describe the degree of association of a large number of cardiovascular risk indicators with cardiovascular endpoints, b) to evaluate the contribution of genetic and that of environmental factors to this association, c) to follow the evolution of these risk indicators during a period of at least ten years, d) to search for the determinants influencing this evolution. The principal variables studied are: a) blood pressure, cardiac mass, and wall thickness of carotid and femoral arteries, b) obesity and fat mass, c) indicators of lipid metabolism, d) genetic polymorphisms of several cardiovascular risk candidate genes, e) food, tobacco and alcohol consumption, f) consumption of drugs and anti-oxidant vitamins. Between September 1993 and August 1995, 1006 families consisting of the two biological parents with at least two children were recruited totalling 4295 individuals. This cohort will be followed up until 2004. There will be two health examinations five and ten years after the initial examination. A bank of blood samples (serum and plasma) in liquid nitrogen and DNA (-80 degrees C) has been established.

Progress in determining the genes for hypertension, insulin resistance, and dyslipidemia

For the first time, we have techniques available that may enable us to determine cause and effect in common cardiovascular diseases. The observations presented herein require cautious interpretation until replicated. There are currently several large programs under way that seek to establish substantial family resources for investigation of the genetic basis of hypertension. When interpreting the results of genome screens, it will be necessary to consider that we may link genetic loci for coexistent features such as dyslipidemia and insulin resistance to hypertension. Therefore, careful phenotypic data will be necessary to dissect out the causes of hypertension.

Calculation of LDL-cholesterol by using apolipoprotein B for classification of nonchylomicronemic dyslipemia

In this paper we propose a calculation of LDL-cholesterol (LDL-C) not affected by hypertriglyceridemia by using lipid quantities directly measured in total serum. We also propose an algorithm for the classification of nonchylomicronemic dyslipemias. Plasma apolipoproteins (apo) A-I, B, total cholesterol (TC), triglycerides (TG), and cholesterol of lipoproteins were measured in a group of 38 normolipemic and 120 dyslipemic patients (42 phenotype IIa, 38 IIb, and 40 IV) classified according to TG and LDL-C values. Discriminant analysis was applied to obtain the best classification with the lowest number of quantities directly measured from total serum (TC, TG, and apo B), and multiple regression analysis was performed to find an equation to calculate LDL-C from these quantities. Apo B seems to be a useful discriminator between normolipemic and phenotype IIa patients, by using a cutoff value of 1.35 g/L obtained by ROC curve analysis. The proposed algorithm, based on lipid quantities measured by easily automated methods, is shown to be a good alternative for the classification of nonhyperchylomicronemic dyslipemia. LDL-C calculated from TC, TG, and apo B proved a better estimate of true LDL-C than the estimate obtained with Friedewald’s formula.

Small genetic effects in complex diseases: a review of regulatory sequence variants in dyslipoproteinemia and atherosclerosis

OBJECTIVE

Most reported mutations that affect lipoprotein metabolism are found within the coding sequences of genes. Recently, a few mutations that occur within promoter sequences have been detected. These promoter sequence variants are the topic of the present review.

METHODS

Some of these variants are fairly common genomic variants in the promoter regions for candidate genes in lipoprotein metabolism, such as APOA1, APOC3, LPA, and LPL. It is possible that such regulatory sequence variants can result in chronic, modestly altered levels of expression of qualitatively normal gene products. This might have a cumulative effect on quantitative phenotypes, such as plasma lipoprotein concentrations, over the long term. Such an effect might not be detected by existing clinical, biochemical, and/or physiological assays.

RESULTS

At present, the most consistent evidence from several lines of experiments indicates that genomic variation in the APOC3 promoter creates slightly elevated plasma triglyceride concentrations within the physiologic range. This altered expression appears to predispose to hypertriglyceridemia in the presence of secondary factors. Genetic variants that produce small effects on promoter function might thus be one component of the predisposition to complex diseases.

CONCLUSION

The aggregate of many small effects may create or contribute to a background of susceptibility that, under appropriate conditions, leads to development of frank dyslipidemia and atherosclerosis.

A comparative study of the efficacy of simvastatin and gemfibrozil in combined hyperlipoproteinemia: prediction of response by baseline lipids, apo E genotype, lipoprotein(a) and insulin

Combined hyperlipoproteinemia (CHL) can be difficult to treat because of the heterogeneous nature of the lipoprotein abnormalities. We compared the relative efficacies of simvastatin and gemfibrozil and sought predictors of responsiveness in terms of the baseline lipids and other potential metabolic determinants (plasma insulin, Lp(a) and apo E genotype). Sixty-six subjects entered a cross-over, randomized trial involving 12 weeks on each drug. Efficacy was assessed after 6 and 12 weeks on each treatment. Simvastatin lowered total cholesterol 24%, triglycerides 12%, LDL cholesterol 33%, raised HDL cholesterol 13% and substantially reduced the cholesterol:triglyceride ratio in VLDL and IDL. Gemfibrozil lowered total cholesterol 5%, triglycerides 44%, raised HDL 26% and reduced VLDL and IDL lipids more than simvastatin did. LDL size increased with both treatments and HDL size increased with simvastatin. Responsiveness (25% fall in cholesterol or 40% fall in triglycerides) was shown by 31/61 subjects when taking simvastatin (cholesterol-lowering) and by 44/60 taking gemfibrozil (triglyceride-lowering). Responsiveness was greatest in those with apo E2 genotype with both drugs (P < 0.05). Unexpectedly, responders to simvastatin tended to have lower baseline total cholesterol but higher triglyceride levels than those whose cholesterol or triglyceride was lowered by gemfibrozil. Nevertheless, more hypercholesterolemic subjects responded to simvastatin and more hypertriglyceridemic subjects to gemfibrozil. Lp(a) (P = 0.04) and plasma insulin concentrations (P = 0.03) were negative predictors of percentage triglyceride-lowering with gemfibrozil. The difference between the two drugs in triglyceride-lowering lessened with rising insulin and falling HDL cholesterol. Thus, the responsiveness to the two major classes of lipid lowering drugs can be partly predicted from baseline lipids and related metabolic parameters.

The genetic basis of atherosclerosis

Atherogenesis is a complex process that involves the contributions of several pathophysiological sub-systems. The dissection of the genetic component of atherosclerosis has become possible using current molecular technologies and analytical methods. Genetic factors are considered to determine the limits under which atherosclerosis develops and environmental factors are considered to position an individual's risk within these limits. Atherosclerosis proceeds through a well-characterized series of pathological stages that involve key cell types and the expression of particular gene products. Reductionist experimental models have helped to produce a list of several hundred candidate genes for the study of the genetic component of atherosclerosis. Within certain families and isolated communities the effect of a single candidate gene upon atherosclerosis susceptibility may be profound, as in the case of mutations in the gene encoding the low-density lipoprotein receptor, which produce familial hypercholesterolemia and premature atherosclerosis. However, particular candidate genes have small effects on atherosclerosis or to one of its intermediate phenotypes, in whole populations. In addition, pleiotropy and epistasis can confound the identification of the genetic component of atherosclerosis. Despite these limitations, it might still be possible to use genetic information clinically in order to classify individuals who are susceptible to atherosclerosis, especially if as yet undiscovered candidate genes are found to be important determinants of disease. However, it will be impossible to predict the onset of a clinical manifestation of atherosclerosis in a particular person. This is due to the confounding influence of other forces, such as variations in interindividual environmental landscape, non-linear interactions between genes and environment, and even the possible influence of biological chaos.