R219K polymorphism of the ABCA1 gene and its modulation of the variations in serum high-density lipoprotein cholesterol and triglycerides related to age and adiposity in white versus black young adults. The Bogalusa heart study

Assessment of genetic polymorphism associated with ATP-binding cassette transporter A1 (ABCA1) gene and fluctuations in serum lipid profile levels in patients with coronary artery disease

Background

Coronary artery disease (CAD) is one of the common genetic and clinical risk factors associated with cardiovascular and multifactorial disorder. ATP-binding cassette transporter A1 (ABCA1) gene plays an important role in lipid metabolism and in multiple studies associated with CAD. However, more studies are needed to identify the exact role of single nucleotide polymorphisms which may cause CAD.

Objectives

The aim of this study is to investigate the genetic association of polymorphism g.1051G > A in the ABCA1 gene with CAD patients in the Saudi population.

Methods

We included 315 confirmed CAD cases, and 205 non-CAD or control subjects in this case-control study. DNA isolation was carried out for all registered participants and the polymorphism g.1051G > A was genotyped with Polymerase Chain Reaction followed by Restriction Fragment Length Polymorphism analysis with EcoNI restriction enzyme.

Results

Modifiable risk factors such as Body Mass Index, smoking and diabetes were strongly associated and non-modifiable risk factors such as hypertension (Systolic Blood Pressure and Diastolic Blood Pressure) and serum analysis such as Fasting Blood Glucose, Total cholesterol (TC), Triglyceride (TG) and LDL-c were significantly associated in CAD cases (p < 0.05). Allele (OR-1.73;95% CI:1.33–2.26; p = 0.0004), GA vs GG (OR-2.26; 95% CI: 1.53–3.35; p = 0.0003 and dominant inheritance pattern (OR-2.23; 95% CI:1.56–3.20; p = 0.00009 was strongly associated with CAD cases and control subjects. The frequency level of use of atorvastatin was significantly different among GG, GA and AA subjects. Additionally, TC and TG levels were influenced by the presence of g.1051G > A polymorphism.

Conclusion

The polymorphism g.1051G > A in the gene ABCA1 is closely associated with the existence of the CAD subjects. This polymorphism could also affect the serum levels of the lipid profile, suggesting a possible occurrence of CAD in the Saudi population.

Association between the ABCA1 (R219K) polymorphism and lipid profiles: a meta-analysis

Conflicting evidence was found about the relationship between lipid profiles and R219K polymorphism in adenosine triphosphate-binding cassette exporter A1 (ABCA1) gene. In this study, four meta-analyses were conducted to assess the effect of R219K on lipid levels, including high-density lipoprotein cholesterol (HDLC), low-density lipoprotein cholesterol, total cholesterol, and triglycerides (TG). A total of 125 samples of 87 studies (about 60,262 subjects) were included. The effect of each study was expressed using the standard mean difference (SMD) and 95% confidence interval (95% CI) and pooled by meta-analysis in the random-effects model. Subgroup and meta-regression analyses were conducted to explore potential heterogeneity sources. The overall pooled effect showed the following results. (1) The R219K was significantly associated with HDLC level (SMD = - 0.25 mmol/L, 95%CI - 0.32 to - 0.18, z = - 6.96, P < 0.01, recessive genetic model). People with different genotypes had significantly different HDLC levels under the recessive, codominant and dominant genetic models (all Ps < 0.01). (2) A weak and indeterminate relationship between R219K and TG level was observed (SMD = 0.18 mmol/L, 95%CI 0.06-0.30, z = 3.01, P < 0.01, recessive genetic model). These findings suggested that R219K was associated with HDLC and TG levels, which might implicate a promising clinical application for lipid-related disorders, though the influences of race, health status, BMI, and other heterogeneity sources should be considered when interpreting current findings. The protocol was registered at PROSPERO (registration number: CRD42021231178).

Exome sequence association study of levels and longitudinal change of cardiovascular risk factor phenotypes in European Americans and African Americans from the Atherosclerosis Risk in Communities Study

Cardiovascular disease (CVD) is responsible for 31% of all deaths worldwide. Among CVD risk factors are age, race, increased systolic blood pressure (BP), and dyslipidemia. Both BP and blood lipids levels change with age, with a dose-dependent relationship between the cumulative exposure to hyperlipidemia and the risk of CVD. We performed an exome sequence association study using longitudinal data with up to 7805 European Americans (EAs) and 3171 African Americans (AAs) from the Atherosclerosis Risk in Communities (ARIC) study. We assessed associations of common (minor allele frequency > 5%) nonsynonymous and splice-site variants and gene-based sets of rare variants with levels and with longitudinal change of seven CVD risk factor phenotypes (BP traits: systolic BP, diastolic BP, pulse pressure; lipids traits: triglycerides, total cholesterol, high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C]). Furthermore, we investigated the relationship of the identified variants and genes with select CVD endpoints. We identified two novel genes: DCLK3 associated with the change of HDL-C levels in AAs and RAB7L1 associated with the change of LDL-C levels in EAs. RAB7L1 is further associated with an increased risk of heart failure in ARIC EAs. Investigation of the contribution of genetic factors to the longitudinal change of CVD risk factor phenotypes promotes our understanding of the etiology of CVD outcomes, stressing the importance of incorporating the longitudinal structure of the cohort data in future analyses.

Effects of Replacing Inorganic with Organic Iron on Performance, Egg Quality, Serum and Egg Yolk Lipids, Antioxidant Status, and Iron Accumulation in Eggs of Laying Hens

This study compared the effects dietary organic (ferrous glycine [FG]) versus inorganic (ferrous sulfate [FS]) iron in laying hens on performance, egg quality, serum and egg yolk lipids, antioxidant status, and iron enrichment of eggs. A total of 378 Shaver White layers were allotted to 7 treatments with 6 replicates (9 birds each) from 30 to 42 weeks of age. A basal diet (19 mg iron/kg) served as control, while the other six diets were supplemented with either FS or FG to provide 30, 60, and 120 mg/kg of added iron. Dietary FG and FS treatments improved (P < 0.05) laying rate, egg weight, and egg quality of layers, relative to the control, albeit eggshell strength and eggshell calcium also deteriorated with the highest level of FS (P < 0.05). The iron treatment groups exhibited a lower serum and egg yolk levels of triglycerides, total cholesterol, and low-density lipoprotein cholesterol that accompanied by higher levels of high-density lipoprotein cholesterol and greater activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) as compared with the control (P < 0.05). The contents of malondialdehyde and protein carbonyl were conversely related to the activities SOD and GPx (P < 0.05). The serum and egg fractions (yolk, albumen, and shell) displayed gradually increases in iron contents as the level of iron increased in the diet (P < 0.05), while FG was superior to FS at all tested levels (P < 0.05). To summary, FS can be replaced by FG, with more favorable impacts on egg quality and iron enrichment.

Novel associations of SNPs MYLIP rs3757354 and ABCA1 2230806 gene with early-onset-preeclampsia: A case-control candidate genetic study

OBJECTIVE

To investigate the association between MYLIP rs3757354 and ABCA1 2230806 single nucleotide polymorphisms in women with preeclampsia in China.

STUDY DESIGN

The case-control study involved 205 patients with preeclampsia and 145 controls. All women with preeclampsia were divided into two groups: 78 patients with early-onset preeclampsia and 127 with late-onset preeclampsia.

MAIN OUTCOME MEASURE

MYLIP rs3757354 and ABCA1 rs2230806 SNPs were analyzed through multiplex PCR for targeted next-generation sequencing technology. A secondary outcome was lipid profile changes and liver function in women with PE.

RESULTS

Maternal age (OR: 1.073, 95% CI = 1.006-1.145), BMI (OR: 1.118, 95% CI = 1.040-1.201), TG/HDL-C (OR: 1.536, 95% CI = 1.080-2.183), and TT genotype of SNP rs3757354 (OR: 3.238, 95% CI = 1.313-7.990) were associated with EOPE risk. Our study found that patients with TT genotype of ABCA1 rs2230806 had more severe hepatic dysfunction and higher HDL levels in the EOPE group compared with CC/CT genotype. There was no association between rs2230806 and the risk of PE.

CONCLUSION

The polymorphisms of rs3757354 are associated with the risk of EOPE in Chinese pregnant women. The TT genotype in ABCA1 rs2230806 is a strong predictive risk for elevated aminotransferase levels in pregnant women with EOPE.

The R219K Polymorphism of the ATP Binding Cassette Subfamily a Member 1 Gene and Susceptibility to Ischemic Stroke in Chinese Population

Stroke is the major cause of death and disability worldwide. ABCA1 R219K has been suggested as a risk factor for ischemic stroke, but the results remain inconclusive in the Chinese population. This study aimed to assess the association between ABCA1 R219K and ischemic stroke using meta-analysis. A systematic literature search was conducted to select eligible studies and the pooled odds ratio (OR) with 95% confidence interval (CI) was used to evaluate the strength of association. Fourteen studies containing 2865 cases and 3227 controls were included in the meta-analysis and the results suggested that there is a strong association between ABCA1 R219K and the ischemic stroke risks (K vs. R: OR = 0.837, 95% CI: 0.735- 0.954, p=0.008; KK vs. RR: OR = 0.689, 95% CI: 0.520-0.912, p=0.009; KK+RK vs. RR: OR = 0.782, 95% CI: 0.691-0.885, p<0.001). Subgroup analysis revealed that significant association was found for the 4 genetic models (p<0.05) in the Southern population, while in the northern population significant association was only found under the dominant model (KK+RK vs. RR: OR = 0.744, 95% CI: 0.583- 0.949, p<0.017). This meta-analysis suggested that ABCA1 R219K polymorphism might be a protective factor against developing IS, indicating this SNP may contribute to the pathogenesis of ischemic stroke and might be potentially used as a biomarker to predict the susceptibility to ischemic stroke.

Common gene polymorphism in ATP-binding cassette transporter A1 and coronary artery disease: A genetic association study and a structural analysis

ATP-binding cassette transporter A1 (ABCA1) has a crucial role in removing intracellular cholesterol and plays a protective role against atherosclerosis. Therefore, genetic polymorphisms in this gene may alter the susceptibility to coronary artery disease (CAD). This study was aimed to examine the association of rs2230806 (c.1051 G > A; p.R219K) variation in the ABCA1 gene with CAD in a case-control design which was followed by a meta-analysis and in silico approach. In the case-control study, 300 subjects including 150 individuals with CAD and 150 healthy controls were recruited. The c.1051 G > A genotyping was done by polymerase chain reaction-restriction fragment length polymorphism method. In the meta-analysis, eligible studies were collected from PubMed, Google Scholar, and ScienceDirect databases and pooled odds ratio, heterogeneity, publication bias, and sensitivity analyses were carried. Finally, some bioinformatics tools were employed to assess the impacts of p.R219K variation on ABCA1 protein structure. Our case-control examination showed a statistically significant association between c.1051 G > A genetic polymorphism and CAD risk. In addition, the meta-analysis showed reliable significant associations between c.1051 G > A transition and risk of CAD in the Caucasian population. In silico analysis showed that the p.R219K substitution could alter the secondary structure, hydrophobicity pattern, and Ramachandran plot of ABCA1. These findings elucidate that the c.1051 G > A variation could be a genetic risk factor for CAD and it could be considered as a prognostic and predictive biomarker for susceptible individuals.

Associations of the ABCA1 gene polymorphisms with plasma lipid levels: A meta-analysis

BACKGROUND

Studies on the associations of the adenosine triphosphate-binding cassette transporter A1 gene (ABCA1) rs2230806, rs2230808, and rs2066714 polymorphisms with plasma lipid levels have reported apparently conflicting findings. This meta-analysis aimed to clarify the relationships between the 3 polymorphisms and fasting lipid levels.

METHODS

A comprehensive search of the literature was carried out by using the databases including Medline, Google Scholar, Web of Science, Embase, Cochrane Library, CNKI, Wanfang, and VIP. The studies that presented mean lipids and standard deviations or standard errors according to the rs2230806, rs2230808, and/or rs2066714 genotypes were examined and included. The random effects model was used. Standardized mean difference and 95% confidence interval were used to assess the differences in lipid levels between the genotypes. Heterogeneity among studies was tested by Cochran's χ-based Q-statistic, and Galbraith plots were used to detect the potential sources of heterogeneity. Publication bias was assessed by Begg's rank correlation test as well as funnel plots.

RESULTS

Sixty-two studies (48,452 subjects), 12 studies (9853 subjects) and 14 studies (10,727 subjects) were identified for the rs2230806, rs2230808, and rs2066714 polymorphisms, respectively. A dominant model was used for all the polymorphisms in this meta-analysis. The A allele carriers of the rs2230806 polymorphism had higher levels of high-density lipoprotein cholesterol (HDL-C) (P <.001), and lower levels of low-density lipoprotein cholesterol (LDL-C) (P =.03) and triglycerides (TG) (P <.01) than the non-carriers. The A allele carriers of the rs2230808 polymorphism had higher levels of total cholesterol (TC) (P <.001) than the non-carriers. The G allele carriers of the rs2066714 polymorphism had higher levels of TC (P <.01) and HDL-C (P = .02) than the non-carriers.

CONCLUSION

The ABCA1 rs2230806, rs2230808, and rs2066714 polymorphisms are significantly associated with plasma lipid levels in the present meta-analysis.

Linkage analysis incorporating gene-age interactions identifies seven novel lipid loci: the Family Blood Pressure Program

OBJECTIVE

To detect novel loci with age-dependent effects on fasting (≥ 8 h) levels of total cholesterol, high-density lipoprotein, low-density lipoprotein, and triglycerides using 3600 African Americans, 1283 Asians, 3218 European Americans, and 2026 Mexican Americans from the Family Blood Pressure Program (FBPP).

METHODS

Within each subgroup (defined by network, race, and sex), we employed stepwise linear regression (retention p ≤ 0.05) to adjust lipid levels for age, age-squared, age-cubed, body-mass-index, current smoking status, current drinking status, field center, estrogen therapy (females only), as well as antidiabetic, antihypertensive, and antilipidemic medication use. For each trait, we pooled the standardized male and female residuals within each network and race and fit a generalized variance components model that incorporated gene-age interactions. We conducted FBPP-wide and race-specific meta-analyses by combining the p-values of each linkage marker across subgroups using a modified Fisher's method.

RESULTS

We identified seven novel loci with age-dependent effects; four total cholesterol loci from the meta-analysis of Mexican Americans (on chromosomes 2q24.1, 4q21.21, 8q22.2, and 12p11.23) and three high-density lipoprotein loci from the meta-analysis of all FBPP subgroups (on chromosomes 1p12, 14q11.2, and 21q21.1). These loci lacked significant genome-wide linkage or association evidence in the literature and had logarithm of odds (LOD) score ≥ 3 in the meta-analysis with LOD ≥ 1 in at least two network and race subgroups (exclusively of non-European descent).

CONCLUSION

Incorporating gene-age interactions into the analysis of lipids using multi-ethnic cohorts can enhance gene discovery. These interaction loci can guide the selection of families for sequencing studies of lipid-associated variants.

Increased risk of premature coronary artery disease in Egyptians with ABCA1 (R219K), CETP (TaqIB), and LCAT (4886C/T) genes polymorphism

BACKGROUND

Epidemiological studies have shown a strong inverse relationship between high-density lipoprotein (HDL) cholesterol (HDLc) levels and coronary artery disease (CAD), and a low concentration of plasma HDLc is considered an independent risk factor for premature atherosclerosis. Mutations in ATP-binding cassette A1 transporter (ABCA1), cholesteryl ester transfer protein (CETP), and lecithin: cholesterol acyltransferase (LCAT) reduce HDLc in humans.

OBJECTIVE

To date, no study had tested the association between these polymorphisms and premature CAD (PCAD) in the Egyptian population. Here we searched for ABCA1 (rs2230806), CETP (rs708272), and LCAT (rs5923) mutations in the Egyptian population and investigated the possible association between these gene polymorphisms and PCAD. We aimed to investigate the association between ABCA1, CETP, and LCAT gene polymorphisms and PCAD in Egyptians.

METHODS

A total of 235 Egyptians-116 with documented PCAD (PCAD group) and 119 controls-were enrolled in the study.

RESULTS

Mutation carriers with low HDLc had an elevated risk of PCAD (odds ratio [OR] = 11.38 for ABCA1 mutation carriers, P = .000; OR = 5.41 for CETP mutation carriers, P = .000; OR = 5.92 for LCAT mutation carriers, P = .000). Moreover, mutations in ABCA1, CETP, and LCAT were significantly associated with hyperlipidemia in this study.

CONCLUSION

These observations show that the R allele of ABCA1, the B1 allele of CETP, and the T allele LCAT genes are associated with PCAD in Egyptians. They have more considerable effect on patients with low HDLc.

ATP-binding cassette transporter A1 R219K polymorphism and ischemic stroke risk in the Chinese population: a meta-analysis

Recently, many studies have been focused on the association between the ATP-binding cassette transporter A1 (ABCA1) gene R219K polymorphism and ischemic stroke (IS). However, the study results have been inconsistent, especially in the Chinese population. Therefore, we performed a meta-analysis to better clarify the association between the ABCA1 gene and IS. All of the relevant studies used in our meta-analysis were identified using PubMed, OVID, Cochrane Library, Chinese Wan Fang database, Chinese VIP database, China National Knowledge Infrastructure (CNKI), and China Biological Medicine Database (CBM) up to May 2013. Statistical analysis was conducted with STATA software version 11.0. Odds ratios with 95% confidence intervals were applied to evaluate the strength of the association between ABCA1 gene R219K polymorphism and IS. Heterogeneity was evaluated using the Q-test and I(2) statistic. The funnel plots, Begg's and Egger's regression tests were used to assess the publication bias. Our meta-analysis showed the dominant genetic model (OR=0.92, 95% CI: 0.88-0.96), the recessive genetic model (OR=0.73, 95% CI: 0.51-1.05), the homozygote genetic model (OR=0.64, 95% CI: 0.44-0.94), the heterozygote genetic model (OR=0.81, 95% CI: 0.69-0.95), and the allelic genetic model (OR=0.83, 95% CI: 0.69-0.99). For R219K in IS, there were significant associations with these genetic models, but not with the recessive genetic model. Our meta-analysis indicated that the ABCA1 gene R219K polymorphism might be associated with IS and the K allele might be a protective factor in the Chinese population.

Association of gender, ABCA1 gene polymorphisms and lipid profile in Greek young nurses

OBJECTIVE

One of the important proteins involved in lipid metabolism is the ATP-binding cassette transporter A1 (ABCA1) encoding by ABCA1 gene. In this study we evaluated the single nucleotide polymorphisms (SNPs) of ABCA1 gene. We analyzed SNPs in chromosome 9 such as rs2230806 (R219K) in the position 107620867, rs2230808 (R1587K) in the position 106602625 and rs4149313 (I883M) in the position 106626574 according to gender and lipid profile of Greek nurses.

METHODS

The study population consisted of 447 (87 men) unrelated nurses who were genotyped for ABCA1 gene polymorphisms. Additionally, lipid profile [total cholesterol, triglycerides, high density lipoprotein cholesterol, low density lipoprotein cholesterol (LDL-C) and apolipoprotein A1] was evaluated.

RESULTS

The distribution of all three studied ABCA1 gene polymorphisms did not differ according to gender. However, only R219K genotype distribution bared borderline statistical significance (p = 0.08) between the two studied groups. Moreover, allele frequencies of R219K, R1587K and I88M polymorphisms did not differ according to gender. In general, blood lipid levels did not seem to vary according to ABCA1 gene polymorphisms, when testing all subjects or when testing only men or only women. However, a significant difference of LDL-C distribution was detected in all subjects according to R1587K genotype, indicating lower LDL-C levels with KK polymorphism (p = 0.0025). The above difference was solely detected on female population (p = 0.0053).

CONCLUSIONS

The ABCA1 gene polymorphisms frequency, distribution and lipid profile did not differ according to gender. However, in the female population the KK genotype of R1587K gene indicated lower LDL-C levels. Further studies, involving a higher number of individuals, are required to clarify genes and gender contribution.

Waist circumference is a strong and independent determinant of the distribution of HDL subfractions in overweight patients with cardiovascular risk factors

PURPOSE

Our aim was to determine the influence of waist circumference on the repartition of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) subfractions in patients with increased waist perimeter and one or more cardiovascular risk factor.

METHODS

All 117 patients without lipid-lowering therapy underwent routine clinical, biological evaluation and isolation of the following lipid subfractions: HDL2b, HDL2a, HDL3a, HDL3b, HDL3c and LDL1, LDL2, LDL3, LDL4.

RESULTS

Mean waist circumference was 102.9 cm for women and 109.4 cm for men, and 92 patients presented with metabolic syndrome. In the highest waist circumference tertile, when compared with the lowest one, an increased HDL3c (7.7% vs. 5.7% p=0.02) and a non-significant decrease of HDL2b percentages were observed with no difference in other subfractions. In multivariate analysis, only plasma triglycerides and waist circumference remained independent predictors of HDL3c percentage.

CONCLUSION

In our population, waist circumference was a strong and independent determinant of a shift in the distribution of HDL toward denser particles.

The role of ATP-binding-cassette-transporter-A1 (ABCA1) gene polymorphism on coronary artery disease risk

ATP-binding cassette transporter A1 (ABCA1) plays a pivotal role in intracellular cholesterol removal and exerts a protective effect against atherosclerosis. The role of genetic factors in susceptibility to coronary artery disease (CAD) is not clear. The aim of this study was to evaluate for the first time the possible association between R219K gene polymorphism and coronary artery disease in an Iranian adult population. A total of 207 consecutive patients with CAD (group A) and 94 patients without CAD (group B) were studied. We determined the presence of the R219K variant in the ABCA1 gene by polymerase chain reaction (PCR) and restriction analysis in 301 patients with and without CAD. The distribution of genotypes among the 2 groups was significantly different (P=0.009). In univariate analysis (with genotype AA as reference), the GG genotype was associated with a significantly increased risk of CAD (P=0.002; odds ratio [OR]=2.761; 95% confidence interval [CI]=1.418-5.374), but the GA genotype did not show a significant association (P=0.234) (data not shown). A multivariate logistic regression analysis (using sex as clinically significant variable, and using age, diabetes mellitus, low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein [HDL], smoking, body mass index [BMI], and genotype as statistically significant variables) was used to determine independent associations and adjusted ORs. The GG genotype (compared with the AA genotype) was an independent predictor of CAD (OR=2.856, 95% CI=1.307-6.241; P=0.009), followed by BMI (P=0.034; OR=1.100; 95% CI=1.007-1.200). The GG genotype in the ABCA1 gene is independently associated with CAD in Iranian patients.

Genotypic variation in ATP-binding cassette transporter-1 (ABCA1) as contributors to the high and low high-density lipoprotein-cholesterol (HDL-C) phenotype

The ATP-binding cassette transporter-1 (ABCA1) mediates cholesterol efflux and genotypic variation in ABCA1 and may impact reverse cholesterol transport and influence cardiovascular disease (CVD) risk. However, although mutations in ABCA1 have generally been identified with low HDL-C, few have undertaken a comparative evaluation between high and low high-density lipoprotein-cholesterol (HDL-C). Therefore, to evaluate for potential gain-of-function polymorphisms/mutations in ABCA1, 56 consecutive subjects were screened presenting with high (60-99 mg/dL [1.6-2.6 mmol/L]) or very high HDL-C (>100 mg/dL [2.6 mmol/L]) and were compared with subjects with average or low HDL-C (n = 68). Carrier frequencies of common ABCA1 polymorphisms, R219K, V771M, V825I, I883M, E1172D, and R1587K were also assessed. All 50 exons and exon-intron boundaries of ABCA1 were screened using single-stranded conformation polymorphism (SSCP). DNA samples with SSCP-shifts or differing band patterns were sequenced. For the 6 common polymorphisms, genotyping was determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism. Overall, 5 novel nonsynonymous mutations were identified, all of which were associated with low HDL-C. Of the 6 common ABCA1 polymorphisms, very high HDL-C was associated with a higher genotype frequency for R219K (P(trend) = 0.04) and higher genotype and allelic frequency for E1172D (P(trend) = 0.0004, P(trend) = 0.0002, respectively) compared with lower HDL-C. These data reaffirm that rare mutations in ABCA1 are associated with low HDL-C. However, at least 1 ABCA1 polymorphism (eg, E1172D) may contribute to the high HDL-C phenotype.

Polymorphisms of cholesterol metabolism genes CYP46 and ABCA1 and the risk of sporadic Alzheimer's disease in Chinese

Recent studies have demonstrated that cholesterol metabolism might play an important role in Alzheimer's disease (AD). Cholesterol 24-hydroxylase (CYP46) and ATP-binding cassette transporter A1 (ABCA1) have both been proposed to be involved in cholesterol metabolism in the brain. The purpose of this case-control study was to determine whether single nucleotide polymorphisms (SNPs) A-->G in the intron 2 of CYP46 gene and G-->A (R219K) in the exon 7 of ABCA1 gene are associated with sporadic AD in the Chinese Han population. Genotypes were determined by PCR-restriction fragment length polymorphism (PCR-RFLP) in 168 sporadic AD patients and 215 controls. There was no significant difference in the genotype or allele frequencies for CYP46 gene between AD patients and controls. However, we found an obvious association between the polymorphism of ABCA1 gene and AD (chi(2)=8.230, P=0.016). The risk for AD was significantly decreased in K allele (RK+KK genotypes) (adjusted OR=0.57, 95% CI=0.36-0.91, P=0.019) or KK homozygote carriers (adjusted OR=0.40; 95% CI=0.21-0.77, P=0.006) compared with RR genotypes carriers. Our results do not support a genetic association between the intron 2 polymorphism of CYP46 gene and the risk of sporadic AD, but reveal that KK genotype or K allele of ABCA1 gene may have a protective effect for sporadic AD in Chinese.

Genetic and nutrient determinants of the metabolic syndrome

PURPOSE OF REVIEW

The metabolic syndrome is a very common condition that is associated with an increased risk of type 2 diabetes mellitus and cardiovascular disease. The diverse clinical characteristics illustrate the complexity of the disease, involving several dysregulated metabolic pathways and multiple genetic targets. The increasing prevalence of obesity heightens the requirement to reduce the risk of the metabolic syndrome. In order to understand the aetiology, it is critical to appreciate the nature of multiple gene-gene and gene-nutrient interactions relevant to the metabolic syndrome.

RECENT FINDINGS

Research indicates a major role for genetic susceptibility to the metabolic syndrome. Nutrition clearly plays an important role in the development and progression of the condition. Genetic background can interact with habitual dietary fat composition, thereby affecting predisposition to the metabolic syndrome, and may also determine an individual's responsiveness to altered dietary fat intake. These studies indicate that therapeutic dietary therapy may require a 'personalized nutrition' approach, wherein a particular genetic profile may determine responsiveness of patients to specific dietary fatty acid interventions.

SUMMARY

Understanding the biological impact of gene-nutrient interactions will provide a key insight into the pathogenesis and progression of diet-related polygenic disorders. This review explores the hypothesis that genetic components of the metabolic syndrome may be modified by dietary fatty acid composition.

Variations on a gene: rare and common variants in ABCA1 and their impact on HDL cholesterol levels and atherosclerosis

Cholesterol and its metabolites play a variety of essential roles in living systems. Virtually all animal cells require cholesterol, which they acquire through synthesis or uptake, but only the liver can degrade cholesterol. The ABCA1 gene product regulates the rate-controlling step in the removal of cellular cholesterol: the efflux of cellular cholesterol and phospholipids to an apolipoprotein acceptor. Mutations in ABCA1, as seen in Tangier disease, result in accumulation of cellular cholesterol, reduced plasma high-density lipoprotein cholesterol, and increased risk for coronary artery disease. To date, more than 100 coding variants have been identified in ABCA1, and these variants result in a broad spectrum of biochemical and clinical phenotypes. Here we review genetic variation in ABCA1 and its critical role in cholesterol metabolism and atherosclerosis in the general population.

Associations between two common polymorphisms in the ABCA1 gene and subclinical atherosclerosis: Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVE

ABCA1 controls the first step in reverse cholesterol transport. The potential associations between G1051A (R219K) and -565C/T genetic polymorphisms in the ABCA1 gene, high-density lipoprotein cholesterol (HDL-C) and subclinical cardiovascular disease in the general population remains unclear. We examined these associations in a sample of Multi-Ethnic Study of Atherosclerosis (MESA) participants.

METHODS

Nine hundred and sixty-nine MESA participants were genotyped and underwent CT examinations for coronary artery calcification (CAC) and carotid ultrasound examinations for intima media thickness. Genetic association analyses were performed.

RESULTS

The AA genotype was associated with a 2.4mg/dl higher HDL-C, adjusting for age, gender, race/ethnicity and clinic site (p=0.04). There was a 28% lower prevalence of CAC (p=0.002) in those with AA genotype that persisted after further adjustment for HDL-C. There were no significant associations between -565C/T genotype and HDL-C. There were trends towards a higher prevalence of CAC in those with CT (PR=1.13, p=0.08) and TT (PR=1.16, p=0.08) genotypes, compared with CC genotype. Neither G1051A nor -565C/T polymorphisms were associated with carotid intima media thickness.

CONCLUSION

The AA genotype of the G1051A polymorphism is associated with slightly higher HDL-C and lower prevalence of CAC and thus may protect against subclinical cardiovascular disease. The T allele of -565 C/T polymorphism may increase risk for subclinical cardiovascular disease.

Prescribing BiDil: is it black and white?

The approval of BiDil as an adjunct treatment in self-identified blacks with heart failure raises questions regarding the underlying etiology of drug response in this target population and the ability to accurately identify patients who are most likely to benefit. Preliminary data have indicated that differences in nitric oxide synthesis between groups may account for differences in response to BiDil and genetic studies have begun to elucidate the mechanism of these differences. Until more accurate selection criteria are developed to identify patients who are most likely to benefit, both clinicians and the general public will need to consider the unique issues raised by BiDil.

Decreased frequencies of ABCA1 polymorphisms R219K and V771M in Hungarian patients with cerebrovascular and cardiovascular diseases

BACKGROUND AND PURPOSE

Genetic polymorphisms in ABC transporter A1 (ABCA1) may alter the regulation of plasma high-density lipoprotein (HDL), promoting or protecting from vascular diseases.

METHODS

We investigated 244 unrelated, consecutively enrolled patients with ischemic stroke, 150 patients with coronary heart disease (CHD) and 193 blood donors for allele frequencies (AFs) of three common ABCA1 polymorphisms (R219K, V771M and I883M).

RESULTS

Compared to controls (30.8 +/- 4.7 and 4.9 +/- 2.2%, respectively), decreased AFs were found in both patient groups for R219K and V771M (28.7 +/- 4.1 and 3.1 +/- 1.6% in stroke, and 25.7 +/- 5.0%; 1.3 +/- 1.3% in CHD patients, respectively). In a subset of stroke patients younger than 50, both variants occurred in significantly lower frequencies (22.4 +/- 5.5 and 1.8 +/- 1.7%, respectively). Similarly, among CHD patients younger than 60, AFs of R219K and V771M (22.6 +/- 7.5 and 0 +/- 1.6%, respectively) were decreased. V771M was almost exclusively (35/36) found in individuals carrying the R219K allele.

CONCLUSIONS

Our data confirm earlier observations that ABCA1 R219K and V771M polymorphisms may be associated with a protective role against CHD and extend those to another important pathologic condition, namely stroke.

Quantitative trait loci in ABCA1 modify cerebrospinal fluid amyloid-β1-42 and plasma apolipoprotein levels

The ATP-binding cassette transporter A1 encoded by ABCA1 plays an integral role in the efflux of cellular cholesterol and phospholipids, but may also be a central mediator of beta-amyloid (Abeta) processing. Here, genetic association of the common R219K variant of ABCA1 is shown with cerebrospinal fluid (CSF) Abeta 1-42 levels, reinforcing emerging evidence of a connection between lipid and Abeta metabolism. In support of this finding we demonstrate for the first time that CSF cholesterol and Abeta 1-42 are correlated. To affirm the plausible impact of ABCA1 variation on cholesterol and related traits as well as to empower a survey of possible interactions (e.g. age, gender, and smoking), a large Swedish population consisting of over 2,700 individuals was enlisted and extensive measures of plasma lipid parameters carried out. These analyses revealed that R219K has a strong effect on apolipoprotein B (APOB) and LDL-cholesterol (LDL-C) among smokers (P = 0.000055 and P = 0.00059, respectively), but not among non-smokers. In contrast, no effect was evident with apolipoprotein A (APOA1) or HDL-cholesterol (HDL-C) levels. Plasma APOB and LDL-C, but not APOA1 and HDL-C, were shown to be markedly elevated in smokers versus non-smokers, affirming that smoking may selectively impact the former pathway. No other genetic markers in ABCA1 exhibit effects as large as R219K, although a modest independent effect of R1587K was observed. Our data illuminate a possible genetic link between Abeta and cholesterol metabolism, but also provide an intriguing example of an environmental exposure that may modify a genotype-phenotype relationship.

Functional mutations of the ABCA1 gene in subjects of French-Canadian descent with HDL deficiency

Mutations in the ABCA1 gene cause defective cellular lipid efflux and severe familial HDL deficiency. We examined the prevalence of mutations at the ABCA1 gene in 58 unrelated probands of French-Canadian descent with HDL deficiency (HDL-C<5th percentile). A defective cellular cholesterol or phospholipid efflux (<75% and <70% of normal controls, respectively) was identified in 14/58 (24%) of subjects. Using direct sequencing of the ABCA1 gene, we found mutations in 12/58 ( approximately 20%) of subjects. Four probands were previously identified with diverse ABCA1 gene defects. However, we identified a novel frameshift mutation (F1840L, L1869X); a proband was heteroallelic for the N1800H mutation, previously reported in a case of Tangier disease, and a novel missense mutation (Q2210H); a novel variant (G616V), predicted to impart a functional defect in the protein, was also found in another proband. Three probands had the S1731C mutation, while two others had the R1851X and K776N documented mutations, respectively. Taken together, these data suggest that approximately 20% of French-Canadian patients with severe HDL deficiency are associated with a defective ABCA1. Interestingly, in two families studied, mutations in the ABCA1 gene did not segregate with the lipid efflux defect, suggesting that other proteins are involved in the ABCA1-mediated cellular lipid efflux.

The metabolic syndrome: A crossroad for genotype-phenotype associations in atherosclerosis

The metabolic syndrome comprises a set of metabolic and physiologic risk factors associated with elevated cardiovascular disease risk. The expression of each one of its major factors (hypertriglyceridemia, low high-density lipoprotein cholesterol levels, hypertension, abdominal obesity, and insulin resistance) has been found to be the result of complex interactions between genetic and environmental factors. Moreover, obesity may play a major role in triggering the metabolic syndrome by interacting with genetic variants at candidate genes for dyslipidemia, hypertension, and insulin resistance. In support of this hypothesis, several studies at multiple candidate genes have already demonstrated the significance of these interactions; however, the data and their reliability are still very limited, and in many cases replication studies are still lacking in the literature. Therefore, more studies with better epidemiologic design and standardized adiposity measures are needed to estimate the contribution of body weight and fat distribution to the genetic predisposition to the metabolic syndrome, which is the most common cardiovascular disease risk factor in industrialized societies.