Molecular variation at the apolipoprotein B gene locus in relation to lipids and cardiovascular disease: a systematic meta-analysis

Apolipoprotein B: Bridging the Gap Between Evidence and Clinical Practice

Despite data suggesting that apolipoprotein B (apoB) measurement outperforms low-density lipoprotein cholesterol level measurement in predicting atherosclerotic cardiovascular disease risk, apoB measurement has not become widely adopted into routine clinical practice. One barrier for use of apoB measurement is lack of consistent guidance for clinicians on how to interpret and apply apoB results in clinical context. Whereas guidelines have often provided clear low-density lipoprotein cholesterol targets or triggers to initiate treatment change, consistent targets for apoB are lacking. In this review, we synthesize existing data regarding the epidemiology of apoB by comparing guideline recommendations regarding use of apoB measurement, describing population percentiles of apoB relative to low-density lipoprotein cholesterol levels, summarizing studies of discordance between low-density lipoprotein cholesterol and apoB levels, and evaluating apoB levels in clinical trials of lipid-lowering therapy to guide potential treatment targets. We propose evidence-guided apoB thresholds for use in cholesterol management and clinical care.

Apolipoprotein B and angiotensin-converting enzyme polymorphisms and aerobic interval training: randomized controlled trial in coronary artery disease patients

Physical training has been strongly recommended as a non-pharmacological treatment for coronary artery disease (CAD). Genetic polymorphisms have been studied to understand the biological variability in response to exercise among individuals. This study aimed to verify the possible influence of apolipoprotein B (ApoB: rs1042031 and rs693) and angiotensin-converting enzyme (ACE-ID: rs1799752) genotypes on the lipid profile and functional aerobic capacity, respectively, after an aerobic interval training (AIT) program in patients with CAD and/or cardiovascular risk factors. Sixty-six men were randomized and assigned to trained group (n=32) or control group (n=34). Cardiopulmonary exercise test was performed to determine the ventilatory anaerobic threshold (VAT) from cardiorespiratory variables. The AIT program, at an intensity equivalent to %VAT (70-110%), was conducted three times a week for 16 weeks. ApoB gene polymorphisms (-12669C>T (rs1042031) and -7673G>A (rs693)) were identified by real-time polymerase chain reaction (PCR). I/D polymorphism in the ACE gene (rs1799752) was identified through PCR and fragment size analysis. After 16 weeks, low-density lipoprotein (LDL) levels increased in the trained and control groups with the GA+AA genotype (-7673G>A) of the ApoB gene. Trained groups with ACE-II and ACE-ID genotypes presented an increase in oxygen consumption (VO2VAT) and power output after the AIT program. The presence of the ACE I-allele was associated with increased aerobic functional capacity after the AIT program. Increased LDL levels were observed over time in patients with the -7673G>A polymorphism of the ApoB gene. Trial Registration Information: ClinicalTrials.gov: NCT02313831.

Variants in the APOB gene was associated with Ischemic Stroke susceptibility in Chinese Han male population

Background

Stroke is an extremely complicated disease caused by multiple factors. Epidemiological studies have shown that genetic factors contribute to the pathogenesis of stroke. There is still little research on the effect of ApoB gene on stroke in Chinese Han population. The purpose of our research was to explore the effect of ApoB gene polymorphism on the genetic susceptibility to Ischemic Stroke in Chinese Han male population.

Materials and methods

7 polymorphisms in ApoB gene were selected and genotyped using Sequenom MassARRAY in 325 ischemic stroke male patients and 399 healthy male controls in Chinese Han population. The association between ApoB gene and genetic susceptibility to Ischemic Stroke was performed by the χ² test, genetic model analysis and haplotype analysis.

Results

In the allele model, ApoB rs1042034 “T” allele and rs673548 “G” allele increased the risk of the Ischemic Stroke (rs1042034: OR=1.29, 95%CI: 1.02-1.63, p=0.030; rs673548: OR=1.28, 95%CI: 1.02-1.62, p=0.034). Logistic regression analysis found that ApoB rs1042034 and rs673548 increased the risk of Ischemic Stroke in the log-additive model, the odds of having Ischemic Stroke would be 1.28-fold and 1.27-fold with the variant allele, respectively. We also found that the risk of individuals carrying the ApoB rs693 “AA-AG” genotype had Ischemic Stroke risk of 1.52-fold of carrying “GG” genotype in the dominant model. The haplotype analysis shown that “TAG” haplotype raised the risk of Ischemic Stroke (OR=1.52, 95%CI: 1.02-2.27, p=0.0042).

Conclusion

The polymorphisms of the ApoB gene may affect Ischemic Stroke occurrence.

Effect of SORT1, APOB and APOE polymorphisms on LDL-C and coronary heart disease in Pakistani subjects and their comparison with Northwick Park Heart Study II

Background

Many SNPs have been identified in genes regulating LDL-C metabolism, but whether their influence is similar in subjects from different ethnicities is unclear. Effect of 4 such SNPs on LDL-C and coronary heart disease (CHD) was examined in Pakistani subjects and was compared with middle aged UK men from Northwick Park Heart Study II (NPHSII).

Methods

One thousand nine hundred sixty-five (1770 non CHD, 195 CHD) UK and 623 (219 non CHD, 404 CHD) Pakistani subjects were enrolled in the study. The SNPs SORT1 rs646776, APOB rs1042031 and APOE rs429358, rs7412 were genotyped by TaqMan/KASPar technique and their gene score was calculated. LDL-C was calculated by Friedewald equation, results were analyzed using SPSS.

Results

Allele frequencies were significantly different (p = <0.05) between UK and Pakistani subjects. However, the SNPs were associated with LDL-C in both groups. In UK non CHD, UK CHD, Pakistani non CHD and Pakistani CHD respectively, for rs646776, per risk allele increase in LDL-C(mmol/l) was 0.18(0.04), 0.06(0.11), 0.15(0.04) and 0.27(0.06) respectively. For rs1042031, per risk allele increase in LDL-C in four groups was 0.11(0.04), 0.04(0.14), 0.15(0.06) and 0.25(0.09) respectively. For APOE genotypes, compared to Ɛ3, each Ɛ2 decreased LDL-C by 0.11(0.06), 0.07(0.15), 0.20(0.08) and 0.38(0.09), while each Ɛ4 increased LDL-C by 0.43(0.06), 0.39(0.21), 0.19(0.11) and 0.39(0.14) respectively. Overall gene score explained a considerable proportion of sample variance in four groups (3.8 %, 1.26 % 13.7 % and 12.3 %). Gene score in both non-CHD groups was significantly lower than CHD subjects.

Conclusions

The SNPs show a dose response association with LDL-C levels and risk of CHD in both populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0253-0) contains supplementary material, which is available to authorized users.

Association between apolipoprotein B gene polymorphisms and the risk of coronary heart disease (CHD): an update meta-analysis

OBJECTIVE

Polymorphisms in the apolipoprotein B (apoB) gene have been reported to be associated with coronary heart disease (CHD). However, the results on this topic are conflicting. The present study aims to derive a more precise estimation of the relationship between CHD and apoB genetic polymorphisms by meta-analysis.

METHODS

We identified a total of 54 studies involving 7236, 10,912, and 14,102 individuals, respectively, for EcoRI, XbaI, and SpIns/Del polymorphisms by searching in PubMed, Web of Science, Google Scholar, the Cochrane Library, Wanfang Data, SinoMed, and CNKI. We utilized RevMan 5.0 software to perform the meta-analyses.

RESULTS

A significant statistical association between apoB EcoRI polymorphism and CHD was observed under an allelic (p = 0.001, odds ratio (OR) = 1.33, 95% confidence interval (CI) = 1.12-1.57), dominant (p = 0.005, OR = 1.22, 95% CI = 1.06-1.40), and recessive (p = 0.04, OR = 1.33, 95% CI = 1.01-1.74) model. We also found similar association of apoB SpIns/Del polymorphism with CHD. However, we did not find association between apoB XbaI polymorphism and CHD.

CONCLUSION

The current meta-analysis found an association of EcoRI polymorphism and SpIns/Del polymorphism with an increased risk of CHD. No significant association between apoB XbaI polymorphism and CHD we observed in the present study.

Parent-of-Origin Effects of the APOB Gene on Adiposity in Young Adults

Loci identified in genome-wide association studies (GWAS) of cardio-metabolic traits account for a small proportion of the traits' heritability. To date, most association studies have not considered parent-of-origin effects (POEs). Here we report investigation of POEs on adiposity and glycemic traits in young adults. The Jerusalem Perinatal Family Follow-Up Study (JPS), comprising 1250 young adults and their mothers was used for discovery. Focusing on 18 genes identified by previous GWAS as associated with cardio-metabolic traits, we used linear regression to examine the associations of maternally- and paternally-derived offspring minor alleles with body mass index (BMI), waist circumference (WC), fasting glucose and insulin. We replicated and meta-analyzed JPS findings in individuals of European ancestry aged ≤50 belonging to pedigrees from the Framingham Heart Study, Family Heart Study and Erasmus Rucphen Family study (total N≅4800). We considered p<2.7x10^-4 statistically significant to account for multiple testing. We identified a common coding variant in the 4^th exon of APOB (rs1367117) with a significant maternally-derived effect on BMI (β = 0.8; 95%CI:0.4,1.1; p = 3.1x10^-5) and WC (β = 2.7; 95%CI:1.7,3.7; p = 2.1x10^-7). The corresponding paternally-derived effects were non-significant (p>0.6). Suggestive maternally-derived associations of rs1367117 were observed with fasting glucose (β = 0.9; 95%CI:0.3,1.5; p = 4.0x10^-3) and insulin (ln-transformed, β = 0.06; 95%CI:0.03,0.1; p = 7.4x10^-4). Bioinformatic annotation for rs1367117 revealed a variety of regulatory functions in this region in liver and adipose tissues and a 50% methylation pattern in liver only, consistent with allelic-specific methylation, which may indicate tissue-specific POE. Our findings demonstrate a maternal-specific association between a common APOB variant and adiposity, an association that was not previously detected in GWAS. These results provide evidence for the role of regulatory mechanisms, POEs specifically, in adiposity. In addition this study highlights the benefit of utilizing family studies for deciphering the genetic architecture of complex traits.

To date, genetic variants identified in large-scale genetic studies using recent technical and methodological advances explain only a small proportion of the genetic basis of obesity, diabetes and other cardiovascular risk factors. These studies were typically conducted in samples of unrelated individuals. Here we utilize a family-based approach to identify genetic variants associated with obesity-related traits. Specifically, we examined the separate contribution of maternally- vs. paternally-inherited common genetic variants to these traits. By examining 1250 young adults and their mothers from Jerusalem, we show that a specific genetic variant, rs1367117, located in the APOB gene on chromosome 2 is related to body mass index and waist circumference when inherited from mother and not from father. This maternal effect is not restricted to Jerusalemites, but is also seen in a large sample of individuals of European descent from independent family studies worldwide. Our findings provide support of the role of complex genetic mechanisms in obesity, and highlight the benefit of utilizing family studies for uncovering genetic pathways underlying common risk factors and diseases.

Association between the APOB XbaI and EcoRI polymorphisms and lipids in Chinese: a meta-analysis

Background

No previous meta-analysis was to report the association between the apolipoprotein B (APOB) XbaI and EcoRI polymorphisms and serum lipids in Chinese. We performed the study to investigate their potentially association.

Methods and Results

Studies in English and Chinese were found via a systematic search of Pubmed, Embase, CNKI and Wanfang databases. The dominant genetic model and random-effects model were used to pool data from individual studies. As a result, a total of 30 articles with 5611 subjects for XbaI and 2653 subjects for EcoRI were included in the current study. For the XbaI polymorphism, overall, subjects carrying X+ allele were significantly associated with higher TC,TG and LDL compared with X-X- genotype (Pvalue =0.0006, OR (95 %) = -0.55 (-0.86,-0.23); Pvalue = 0.0004, OR (95 %) = -0.30 (-0.47,-0.14); (Pvalue = 0.05, OR (95 %) = -0.23(-0.46,-0.00), respectively). Similar results were observed in the subgroups of Han, healthy individuals (HT), coronary heart disease (CHD), cerebral infarction (CI), and cholelithiasis. For HDL, positive association between X+ allele with Lower lipid value was found in CHD and CI subgroups. For EcoRI polymorphism, overall, the E- allele carriers were found to be obviously linked with elevated LDL and lower HDL compared with E + E+ genotype (Pvalue = 0.02,OR (95 %) = -0.27 (-0.49,-0.05); Pvalue = 0.01, OR (95 %) = 0.17 (0.03, 0.30), respectively). TC was significantly high in subjects carrying E- allele in the subgroup of hyperlipidemia. No evidence of publication bias was observed.

Conclusions

The two genetic variants of APOB may be associated with serum lipids in Chinese.

The APOB insertion/deletion polymorphism (rs17240441) influences postprandial lipaemia in healthy adults

Background

Apolipoprotein (apo)B is the structural apoprotein of intestinally- and liver- derived lipoproteins and plays an important role in the transport of triacylglycerol (TAG) and cholesterol. Previous studies have examined the association between the APOB insertion/deletion (ins/del) polymorphism (rs17240441) and postprandial lipaemia in response to a single meal; however the findings have been inconsistent with studies often underpowered to detect genotype-lipaemia associations, focused mainly on men, or with limited postprandial characterisation of participants. In the present study, using a novel sequential test meal protocol which more closely mimics habitual eating patterns, we investigated the impact of APOB ins/del polymorphism on postprandial TAG, non-esterified fatty acids, glucose and insulin levels in healthy adults.

Findings

Healthy participants (n = 147) consumed a standard test breakfast (0 min; 49 g fat) and lunch (330 min; 29 g fat), with blood samples collected before (fasting) and on 11 subsequent occasions until 480 min after the test breakfast. The ins/ins homozygotes had higher fasting total cholesterol, LDL-cholesterol, TAG, insulin and HOMA-IR and lower HDL-cholesterol than del/del homozygotes (P < 0.017). A higher area under the time response curve (AUC) was evident for the postprandial TAG (P < 0.001) and insulin (P = 0.032) responses in the ins/ins homozygotes relative to the del/del homozygotes, where the genotype explained 35% and 7% of the variation in the TAG and insulin AUCs, respectively.

Conclusions

In summary, our findings indicate that the APOB ins/del polymorphism is likely to be an important genetic determinant of the large inter-individual variability in the postprandial TAG and insulin responses to dietary fat intake.

Insights from human congenital disorders of intestinal lipid metabolism

The intestine must challenge the profuse daily flux of dietary fat that serves as a vital source of energy and as an essential component of cell membranes. The fat absorption process takes place in a series of orderly and interrelated steps, including the uptake and translocation of lipolytic products from the brush border membrane to the endoplasmic reticulum, lipid esterification, Apo synthesis, and ultimately the packaging of lipid and Apo components into chylomicrons (CMs). Deciphering inherited disorders of intracellular CM elaboration afforded new insight into the key functions of crucial intracellular proteins, such as Apo B, microsomal TG transfer protein, and Sar1b GTPase, the defects of which lead to hypobetalipoproteinemia, abetalipoproteinemia, and CM retention disease, respectively. These "experiments of nature" are characterized by fat malabsorption, steatorrhea, failure to thrive, low plasma levels of TGs and cholesterol, and deficiency of liposoluble vitamins and essential FAs. After summarizing and discussing the functions and regulation of these proteins for reader's comprehension, the current review focuses on their specific roles in malabsorptions and dyslipidemia-related intestinal fat hyperabsorption while dissecting the spectrum of clinical manifestations and managements. The influence of newly discovered proteins (proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 protein) on fat absorption has also been provided. Finally, it is stressed how the overexpression or polymorphism status of the critical intracellular proteins promotes dyslipidemia and cardiometabolic disorders.

Association between health-service use and multiplex genetic testing

PURPOSE

The objective of this work was to examine whether offers of multiplex genetic testing increase health-care utilization among healthy patients aged 25-40 years. The identification of genetic variants associated with common disease is accelerating rapidly. "Multiplex tests" that give individuals feedback on large panels of genetic variants have proliferated. Availability of these test results may prompt consumers to use more health-care services.

METHODS

A total of 1,599 continuously insured adults aged 25-40 years were surveyed and offered a multiplex genetic susceptibility test for eight common health conditions. Health-care utilization from automated records was compared in 12-month pre- and posttest periods among persons who completed a baseline survey only (68.7%), those who visited a study website but opted not to test (17.8%), and those who chose the multiplex genetic susceptibility test (13.6%).

RESULTS

In the pretest period, persons choosing genetic testing used an average of 1.02 physician visits per quarter as compared with 0.93 and 0.82 for the baseline-only and Web-only groups, respectively (P < 0.05). There were no statistically significant differences by group in the pretest use of any common medical tests or procedures associated with four common health conditions. When changes in physician and medical test/procedure use in the posttest period were compared among the groups, no statistically significant differences were observed for any utilization category.

CONCLUSIONS

Persons offered and completing multiplex genetic susceptibility testing used more physician visits before testing, but testing was not associated with subsequent changes in use. This study supports the supposition that multiplex genetic testing offers can be provided directly to the patients in such a way that use of health services is not inappropriately increased.

Polymorphism of the apolipoprotein B gene and association with plasma lipid and lipoprotein levels in the Mongolian Buryat

Allele frequencies at six RFLP sites (Ins/Del, ApaLI, AluI, XbaI, MspI, and EcoRI) of the apolipoprotein B gene (APOB) and the relationship of genotypes with plasma lipid and lipoprotein levels in the Mongolian Buryat were investigated. Common alleles at these sites in 110 Buryat subjects were I, G, A-, X-, M+, and E+; the frequencies of 0.809-0.991 differed strikingly from those of a few Asians and most Europeans. Five unambiguous haplotypes of all sites were revealed at 74%; haplotype IGA-X-M+E+ (000000) was the most frequent (67%), followed by IGA+X-M+E+ (001000) (19%). The frequency constitution differed significantly from the Chinese, Malaysians, and Caucasians but resembled the Indians. No APOB polymorphisms were associated with cholesterol levels (total, HDL and LDL). Significant associations of genotypes were shown with the triglyceride level only at the AluI and XbaI sites. The lipid level of A-A+ females or X-X+ males was higher than that of A-A- females or X-X- males, respectively.

Genomics of heart failure

Cardiovascular disease is the leading cause of death in men and women, and heart failure (HF) is associated with high rates of morbidity and mortality. Most common forms of HF are non-mendelian and the evidence for heritability is modest. Study of the genetic susceptibility to HF has been limited to patients with rare familial forms of HF and candidate gene association studies in patients with distinct subtypes of HF. However, with the completion of the human genome project and the development of the HapMap template, new large-scale genome-wide association studies are possible. This article reviews the status of these and other important developments in genomics, in particular genome-wide sequencing, and other "omics".

Genetic variants involved in gallstone formation and capsaicin metabolism, and the risk of gallbladder cancer in Chilean women

AIM: To determine the effects of genetic variants associated with gallstone formation and capsaicin (a pungent component of chili pepper) metabolism on the risk of gallbladder cancer (GBC).

METHODS: A total of 57 patients with GBC, 119 patients with gallstones, and 70 controls were enrolled in this study. DNA was extracted from their blood or paraffin block sample using standard commercial kits. The statuses of the genetic variants were assayed using Taqman^® SNP Genotyping Assays or Custom Taqman^® SNP Genotyping Assays.

RESULTS: The non-ancestral T/T genotype of apolipoprotein B rs693 polymorphism was associated with a decreased risk of GBC (OR: 0.14, 95% CI: 0.03-0.63). The T/T genotype of cholesteryl ester transfer protein (CETP) rs708272 polymorphism was associated with an increased risk of GBC (OR: 5.04, 95% CI: 1.43-17.8).

CONCLUSION: Genetic variants involved in gallstone formation such as the apolipoprotein B rs693 and CETP rs708272 polymorphisms may be related to the risk of developing GBC in Chilean women.

Genetic determinants of serum lipid levels in Chinese subjects: a population-based study in Shanghai, China

We examined the associations between 21 single nucleotide polymorphisms (SNPs) of eight lipid metabolism genes and lipid levels in a Chinese population. This study was conducted as part of a population-based study in China with 799 randomly selected healthy residents who provided fasting blood and an in-person interview. Associations between variants and mean lipid levels were examined using a test of trend and least squares mean test in a general linear model. Four SNPs were associated with lipid levels: LDLR rs1003723 was associated with total cholesterol (P-trend = 0.002) and LDL (P-trend = 0.01), LDLR rs6413503 was associated with total cholesterol (P-trend = 0.05), APOB rs1367117 was associated with apoB (P-trend = 0.02), and ABCB11 rs49550 was associated with total cholesterol (P-trend = 0.01), triglycerides (P-trend = 0.01), and apoA (P-trend = 0.01). We found statistically significant effects on lipid levels for LDLR rs6413503 among those with high dairy intake, LPL rs263 among those with high allium vegetable intake, and APOE rs440446 among those with high red meat intake. We identified new associations between SNPs and lipid levels in Chinese previously found in Caucasians. These findings provide insight into the role of lipid metabolism genes, as well as the mechanisms by which these genes may be linked with disease.

Apolipoprotein B and Cardiovascular Disease Risk: Position Statement from the AACC Lipoproteins and Vascular Diseases Division Working Group on Best Practices

Background: Low-density lipoprotein cholesterol (LDL-C) has been the cornerstone measurement for assessing cardiovascular risk for nearly 20 years.

Content: Recent data demonstrate that apolipoprotein B (apo B) is a better measure of circulating LDL particle number (LDL-P) concentration and is a more reliable indicator of risk than LDL-C, and there is growing support for the idea that addition of apo B measurement to the routine lipid panel for assessing and monitoring patients at risk for cardiovascular disease (CVD) would enhance patient management. In this report, we review the studies of apo B and LDL-P reported to date, discuss potential advantages of their measurement over that of LDL-C, and present information related to standardization.

Conclusions: In line with recently adopted Canadian guidelines, the addition of apo B represents a logical next step to National Cholesterol Education Program Adult Treatment Panel III (NCEP ATPIII) and other guidelines in the US. Considering that it has taken years to educate physicians and patients regarding the use of LDL-C, changing perceptions and practices will not be easy. Thus, it appears prudent to consider using apo B along with LDL-C to assess LDL-related risk for an interim period until the superiority of apo B is generally recognized.

Apolipoprotein B levels, APOB alleles, and risk of ischemic cardiovascular disease in the general population, a review

Apolipoprotein B is a key component in lipid metabolism. Subendothelial retention of apolipoprotein B containing lipoproteins is a necessary initiating event in atherogenesis, and high plasma levels of apolipoprotein B is a risk factor for atherosclerosis, whereas low levels may provide protection. The present review examines, with focus on general population studies, apolipoprotein B levels as a predictor of ischemic cardiovascular disease, as well as the association of mutations and polymorphisms in APOB with plasma apolipoprotein B levels, and risk of ischemic cardiovascular disease. The studies can be summarized as follows: (1) apolipoprotein B predicts ischemic cardiovascular events in both genders, and is better than LDL cholesterol in this respect; (2) linkage disequilibrium structure in APOB is more complex than expected from HapMap data, because a minimal set of tag single nucleotide polymorphisms capturing the entire variation in APOB cannot be identified, and thus most polymorphisms must be evaluated separately in association studies; (3) APOB mutations and polymorphisms are associated with a range of apolipoprotein B and LDL cholesterol levels, although the magnitude of effect sizes of common polymorphisms are modest; (4) both mutations and polymorphisms are associated with LDL metabolism in vivo; (5) association of APOB mutations and polymorphisms with lipid and disease phenotype cannot be predicted in silico using evolutionary conservation or existing prediction programs; and finally, (6) except for the E4154K polymorphism that possibly predicts a reduction in risk of ischemic cerebrovascular disease and ischemic stroke, common APOB polymorphisms with modest effect sizes on lipid levels do not predict risk of ischemic heart disease, myocardial infarction, ischemic cerebrovascular disease, or ischemic stroke in the general population.

Personalized Medicine in Coronary Artery Disease: Insights From Genomic Research

Prior clinical studies have demonstrated that a family history of coronary artery disease (CAD) is associated with future cardiovascular events. Although there are several Mendelian disorders that are associated with CAD, most common forms of CAD are believed to be multifactorial and the result of many genes with small individual effects. The identification of these genes and their variation would be very helpful for the prediction, prevention, and management of CAD; linkage analysis or candidate gene case-control studies have been largely unsuccessful. On the contrary, recent advances in genomic techniques have generated a large amount of deoxyribonucleic acid (DNA)-based information. The link between CAD and inflammation and biological pathways has been highlighted. In particular, several genome-wide association studies have replicated a novel gene marker on chromosome 9p21. The information gained from genomic studies, in combination with clinical data, is expected to refine personalized approaches to assess risk and guide management for CAD. Genetic risk scores derived from several functional single nucleotide polymorphisms (SNPs) or haplotypes in multiple genes may improve the prediction of CAD. Despite the complexity of CAD genetics, steady progress is expected.

New technologies for delineating and characterizing the lipid exome: prospects for understanding familial combined hyperlipidemia

This review summarizes the progress made in cutting through the biological and genetic complexity of the Gordian knot that is familial combined hyperlipidemia. We particularly focus on how the application of new genomic technologies, especially massively parallel sequencing and high-throughput genotyping platforms, promise to accelerate the gene discovery process in this common, highly atherogenic disorder, with important diagnostic and therapeutic implications.

Monogenic Hypocholesterolaemic Lipid Disorders and Apolipoprotein B Metabolism

The study of apolipoprotein (apo) B metabolism is central to our understanding of human lipoprotein metabolism. Moreover, the assembly and secretion of apoB-containing lipoproteins is a complex process. Increased plasma concentrations of apoB-containing lipoproteins are an important risk factor for the development of atherosclerotic coronary heart disease. In contrast, decreased levels of, but not the absence of, these apoB-containing lipoproteins is associated with resistance to atherosclerosis and potential long life. The study of inherited monogenic dyslipidaemias has been an effective means to elucidate key metabolic steps and biologically relevant mechanisms. Naturally occurring gene mutations in affected families have been useful in identifying important domains of apoB and microsomal triglyceride transfer protein (MTP) governing the metabolism of apoB-containing lipoproteins. Truncation-causing mutations in the APOB gene cause familial hypobetalipoproteinaemia, whereas mutations in MTP result in abetalipoproteinaemia; both rare conditions are characterised by marked hypocholesterolaemia. The purpose of this review is to examine the role of apoB in lipoprotein metabolism and to explore the key biochemical, clinical, metabolic and genetic features of the monogenic hypocholesterolaemic lipid disorders affecting apoB metabolism.

5' ins/del and 3' VNTR polymorphisms in the apolipoprotein B gene in relation to lipids and coronary artery disease

BACKGROUND

Studies that considered apolipoprotein B (APOB) gene polymorphisms as risk factors for coronary artery disease (CAD) have reported conflicting results. We sought to analyze the association between 5' ins/del and 3' VNTR polymorphisms of APOB, lipid parameters and CAD risk.

METHODS

We recruited 251 patients with CAD, documented by coronary angiography, and 94 controls. Genotyping was performed by PCR. Lipids and apolipoproteins were measured.

RESULTS

5' ins/del (ins/ins, ins/del, del/del) and 3' VNTR (LL, SS, LS) polymorphism frequencies were significantly (p<0.05) different between controls and CAD patients. LL and del/del were significantly associated with higher levels of apolipoprotein B (apoB), total cholesterol/high-density lipoprotein cholesterol ratio and apoB/apoA-I ratio (p<0.05) and with increased risk of CAD. The odds ratio for significant coronary stenosis associated with del/del was 3.2 (95% CI 1.6-36.42) (p=0.032) and with LL was 2.2 (95% CI 1.1-5.1) (p=0.042).

CONCLUSIONS

The two polymorphisms exert an impact on lipid levels and contribute to the susceptibility to the development of CAD.

Apolipoprotein polymorphisms and familial hypercholesterolemia

The majority of apolipoproteins known to play a major role in lipid metabolism were identified over 20 years ago, and nine of them (APOA1, -A2, -A4, -B48, -B100, -C1, -C2, -C3 and -E) have long been known to be most relevant to the regulation of lipoproteins. Polymorphisms of genes encoding apolipoproteins influence plasma levels of high-density lipoproteins (HDL), very-low-density lipoprotein (VLDL), low-density lipoprotein (LDL) chylomicrons or triglycerides. Familial hypercholesterolemia (FH), an autosomal dominant disorder, is caused by mutations mainly located in the low-density lipoprotein receptor (LDLR) gene, or more rarely within the apolipoprotein B-100 gene or the gene encoding a secreted proteinase PSCK9. FH is characterized by elevated concentrations of LDL, deposition of LDL-derived cholesterol in tendons, skin xanthomas, and premature coronary artery disease. The frequency of heterozygotes is approximately one in 500 persons, placing FH among the most common inborn errors of metabolism. The risk of cardiovascular disease in these patients is influenced not only by the type of the mutations they carry, but also by the haplotype of lipid modifier genes, as is the case of apolipoproteins. In this review, we present current information that demonstrates the impact of apolipoprotein polymorphisms on the FH phenotype.

Common and rare alleles in apolipoprotein B contribute to plasma levels of low-density lipoprotein cholesterol in the general population

CONTEXT

We have previously shown that rare mutations in the apolipoprotein B gene (APOB) may result in not only severe hypercholesterolemia and ischemic heart disease but also hypocholesterolemia. Despite this, common single-nucleotide polymorphisms (SNPs) in APOB have not convincingly been demonstrated to affect low-density lipoprotein (LDL) cholesterol levels.

OBJECTIVE

We tested the hypothesis that nonsynonymous SNPs in three important functional domains of APOB and APOB tag SNPs predict levels of LDL cholesterol and apolipoprotein B and risk of ischemic heart disease.

DESIGN

This was a prospective study with 25 yr 100% follow up, The Copenhagen City Heart Study.

SETTING

The study was conducted in the Danish general population.

PARTICIPANTS

Participants included 9185 women and men aged 20-80+ yr.

MAIN OUTCOME MEASURES

Levels of LDL cholesterol and apolipoprotein B and risk of ischemic heart disease and myocardial infarction were measured. The hypothesis was formulated before genotyping.

RESULTS

We genotyped 9185 individuals for APOB T71I (minor allele frequency: 0.33), Ivs4+171c>a (0.14), A591V (0.47), Ivs18+379a>c (0.30), Ivs18+1708g>t (0.45), T2488Tc>t (0.48), P2712L (0.21), R3611Q (0.09), E4154K (0.17), and N4311S (0.21). SNPs were associated with increases (T71I, Ivs181708g>t, T2488Tc>t, R3611) or decreases (Ivs4+171c>a, A591V, Ivs18+379a>c, P2712L, E4154, N4311S) in LDL cholesterol from -4.7 to +8.2% (-0.28 to 0.30 mmol/liter; P<or=0.002), and corresponding effects on cholesterol and apolipoprotein B levels. However, as predicted from the magnitude of the observed LDL cholesterol effects, none of these SNPs predicted risk of ischemic heart disease prospectively in the general population, in a case-control study, or as haplotypes.

CONCLUSIONS

Multiple common and rare alleles in APOB contribute to plasma levels of LDL cholesterol in the general population, although the effects of common alleles and haplotypes are modest.

Genetic variation and atherosclerosis

A family history of atherosclerosis is independently associated with an increased incidence of cardiovascular events. The genetic factors underlying the importance of inheritance in atherosclerosis are starting to be understood. Genetic variation, such as mutations or common polymorphisms has been shown to be involved in modulation of a range of risk factors, such as plasma lipoprotein levels, inflammation and vascular calcification. This review presents examples of present studies of the role of genetic polymorphism in atherosclerosis.

Multiple genetic determinants of plasma lipid levels in Caribbean Hispanics

OBJECTIVES

To identify candidate genes in relation to plasma lipid levels in Caribbean Hispanics.

DESIGN AND METHODS

A total of 114 single nucleotide polymorphisms (SNPs) at 17 lipid-related genes were genotyped in 477 Caribbean Hispanics from the Northern Manhattan Study (NOMAS). Analyses for each SNP and haplotype were performed to evaluate the associations with four lipid traits: high- and low-density lipoprotein cholesterol (HDL-C, LDL-C), triglyceride (TG) and total cholesterol (TC).

RESULTS

We identified 19 SNPs at 10 genes that were significantly related to lipids (p<0.01), including nine involved in the reverse cholesterol transport pathway, and one involved in bile acid synthesis. Three genes, namely the apolipoprotein A5, apolipoprotein B and cytochrome p450 polypeptide 7A1 genes, accounted for the largest proportion of variation in HDL-C/TG, TC and LDL-C respectively.

CONCLUSIONS

The cumulative effects of multiple genetic variants led to a substantially better prediction of inter-individual variations in lipid levels.

Relevance of Genetics and Genomics for Prevention and Treatment of Cardiovascular Disease

Atherosclerotic cardiovascular disease (CVD) is a major health problem in the United States and around the world. Evidence accumulated over decades convincingly demonstrates that family history in a parent or a sibling is associated with atherosclerotic CVD, manifested as coronary heart disease, stroke, and/or peripheral arterial disease. Although there are several mendelian disorders that contribute to CVD, most common forms of CVD are believed to be multifactorial and to result from many genes, each with a relatively small effect working alone or in combination with modifier genes and/or environmental factors. The identification and the characterization of these genes and their modifiers would enhance prediction of CVD risk and improve prevention, treatment, and quality of care. This scientific statement describes the approaches researchers are using to advance understanding of the genetic basis of CVD and details the current state of knowledge regarding the genetics of myocardial infarction, atherosclerotic CVD, hypercholesterolemia, and hypertension. Current areas of interest and investigation--including gene-environment interaction, pharmacogenetics, and genetic counseling--are also discussed. The statement concludes with a list of specific recommendations intended to help incorporate usable knowledge into current clinical and public health practice, foster and guide future research, and prepare both researchers and practitioners for the changes likely to occur as molecular genetics moves from the laboratory to clinic.

The APOB -516C/T polymorphism is associated with differences in insulin sensitivity in healthy males during the consumption of diets with different fat content

Several apo B polymorphic sites have been studied for their potential use as markers for CHD in the population and for potential gene-diet interactions. Our aim was to determine whether the presence of the -516C/T polymorphism in the APOB gene promoter modifies insulin sensitivity to dietary fat. We studied fifty-nine healthy volunteers (thirty men and twenty-nine women, thirty-six homozygotes for the -516C allele (C/C) (nineteen males and seventeen females) and twenty-three heterozygotes for the -516T allele (C/T) (eleven males and twelve females)). Subjects consumed three diets during the feeding study, 4 weeks each: an SFA-rich diet (38 % fat, 20 % SFA), followed by a carbohydrate (CHO)-rich diet (30 % fat, 55 % CHO) or a MUFA-rich diet (38 % fat, 22 % MUFA) following a randomised cross-over design. For each diet, we investigated peripheral insulin sensitivity with the insulin suppression test. Male carriers of the -516T allele showed a significantly greater decrease in steady-state plasma glucose concentrations when changing from the SFA-rich diet (9.18 (sd 1.35) mmol/l) to the MUFA (6.55 (sd 0.74) mmol/l) or the CHO (6.31 (sd 0.93) mmol/l) diets than did those who were homozygous for the C allele (P = 0.040). Furthermore, C/T subjects presented higher plasma NEFA values after consumption of the SFA diet compared with the MUFA and CHO diets (P = 0.001). This effect was not observed in females (P = 0.908). Our findings show that male carriers of the -516T allele, C/T, have a significant increase in insulin resistance after consumption of all diets, but the difference is more exaggerated after the SFA diet compared with the MUFA- and CHO-rich diets.

ApoB C7623T polymorphism predicts risk for steroid-induced osteonecrosis of the femoral head after renal transplantation

BACKGROUND

Nontraumatic osteonecrosis of the femoral head (ONFH) is caused by disruption of blood flow. This disease often occurs in association with steroid treatment. The pathology of steroid-induced ONFH remains unclear, although abnormalities in lipid metabolism have been reported to be involved. In this study, we examined the differences of gene polymorphism frequencies of apolipoprotein B (ApoB) and apolipoprotein A1 (ApoA1), which are important proteins for lipid transport, as well as of lipid parameters, between ONFH cases and referent patients among those who were subjected to renal transplantation.

METHODS

Subjects were 158 cases who had undergone renal transplant, including 34 cases that were diagnosed as ONFH after renal transplantation and 124 cases that were not. Four single nucleotide polymorphisms including C7623T and G12619A for the ApoB gene and G75A and C83T for the ApoA1 gene were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and Taqman real-time PCR chemistry. Also, serum levels of low-density lipoprotein (LDL), high-density lipoprotein (HDL), ApoB, and ApoA1 were measured. Their relationship to ONFH was statistically evaluated.

RESULTS

A higher frequency of 7623TT or CT of the ApoB gene was observed in ONFH cases than in referent patients (P = 0.033), resulting in an elevated odds ratio that was statistically significant (adjusted odds ratio = 6.37, 95% CI = 1.53-26.5, P = 0.011). No significant relationship was observed between other genes and ONFH. Regarding lipid parameters, a higher value of ApoB/ApoA1 ratio was observed in cases (P = 0.045).

CONCLUSION

For the prediction of ONFH, it is useful to analyze ApoB C7623T and plasma ApoB/ApoA1 ratio before the administration of steroids.

The APOB -516C/T polymorphism has no effect on lipid and apolipoprotein response following changes in dietary fat intake in a healthy population

Our goal was to determine whether the presence of the -516C/T polymorphism in the APOB gene promoter modifies the lipid response to changes in the amount and quality of dietary fat. We studied 97 young healthy volunteers (70 males and 27 females), 62 homozygotes for the -516C allele (C/C) (47 males and 15 females), 34 heterozygotes for the -516T allele (C/T) (22 males and 12 females) and one male homozygote for the -516T allele (T/T). Subjects consumed three different diets in successive 4-week dietary periods. During the first 28 days, all subjects consumed a saturated fatty acid (SFA)-rich diet (38% fat and 20% SFA). Then, using a randomized crossover design, subjects were assigned a carbohydrate (CHO)-rich diet (30% fat and 55% carbohydrate) or a monounsaturated fatty acid (MUFA)-rich diet (38% fat and 22% MUFA). At the end of each dietary period, plasma concentrations of triacylglycerols and of total, LDL, and HDL cholesterol were measured. No differences in plasma lipid and apolipoprotein response were found after changes in dietary fat intake in relation to the -516C/T polymorphism in our study population. In conclusion, our data suggest that the APOB -516C/T polymorphism has no effect on the lipid profile after changes in dietary fat intake in a healthy population.

Effect of apolipoprotein B polymorphism in kidney transplantation

INTRODUCTION

In kidney transplant recipients, dyslipidemia is a cardiovascular risk factor that also contributes to the development and progression of chronic allograft nephropathy. Apolipoprotein B (ApoB), present in low-density lipoproteins (LDL), is an important protein component of chylomicrons and very-low-density lipoproteins (VLDL). The del allele of the ApoB signal peptide polymorphism has been associated with elevated levels of total and LDL cholesterol and greater risk of coronary disease.

OBJECTIVE

The objective of this study was to assess the influence of ApoB polymorphism on allograft and patient survival among kidney transplant recipients.

METHODS

In this study, we analyzed 516 renal transplant recipients (38% were women, 62% were men), aged 46 +/- 15 years, with a minimum follow-up of 12 months (mean, 1854 +/- 806 days). The ApoB signal peptide was analyzed (insertion/deletion) using polymerase chain reaction (PCR) using genomic DNA. Clinical donor-recipient variables were assessed using a Cox multivariate model.

RESULTS

Polymorphism distribution was as follows: insertion/insertion (ins/ins) 51%, insertion/deletion (ins/del) 39%, and deletion/deletion (del/del) 9%, with no differences between the genders. Cholesterol levels at 12 months showed no differences between the ins/ins (217 +/- 46), ins/del (228 +/- 50), and del/del (227 +/- 54) groups. Presence of the ApoB signal peptide del/del or ins/del genotype was independently associated with lower patient survival in the group of men younger than 60 years (P < .05). Among the total deaths, cardiovascular causes predominated in the ins/del and del/del groups (50%) as compared with the ins/ins group (33%) (P < .01).

CONCLUSIONS

ApoB genetic polymorphism (del allele) seems to have an adverse effect on the long-term survival of kidney transplant recipients.

Genetic variations of the apolipoprotein B gene in Turkish patients with coronary artery disease

BACKGROUND

The results of studies that clarify the association of genetic markers at the apolipoprotein B (apo B) gene (EcoRI and XbaI polymorphisms) with coronary artery disease (CAD) are not consistent and suggest that the effect is context dependent (dependent on ethnicity and sex). The present study represents the first investigation of the apo B gene polymorphisms in Turkish patients with CAD and their influence on lipid levels.

AIM

The study investigated the association of apo B gene EcoRI and XbaI polymorphisms with CAD and with variation in lipid levels (total cholesterol (T-Chol), high-density lipoprotein cholesterol (HDL-Chol), low-density lipoprotein cholesterol (LDL-Chol), and triacylglycerol (TAG)).

SUBJECTS AND METHODS

The study group was composed of 150 individuals with angiographically documented CAD and 100 angiographically proven to be healthy controls. PCR-RFLP was used to determine the DNA polymorphisms of the apo B gene.

RESULTS

The frequencies of apo B genotypes detected with EcoRI (AA, AG, GG) and XbaI (CC, CT, TT) did not differ significantly between case and control subjects. A significant association between EcoRI genotypes and T-Chol (p < or = 0.05), and LDL-Chol (p < or = 0.001) was observed only in CAD patients. Patients with the AA genotype had higher levels of serum T-Chol and LDL-Chol compared with AG. With logistic regression analysis the XbaI TT genotype was found to be associated with CAD prevention. However, no significant differences in lipid variables were determined for the XbaI polymorphisms in the patients with CAD.

CONCLUSIONS

Apo B EcoRI genotypes were not found as risk factors for CAD, whereas XbaI TT genotype was detected to prevent against CAD in our study group.

Five polymorphisms in gene candidates for cardiovascular disease in Afro-Brazilian individuals

Associations of polymorphisms in the angiotensin I-converting enzyme (ACE), apolipoprotein B (APOB) and apolipoprotein E (APOE) genes with hypertension and variations in lipid serum levels were evaluated in 184 Afro-Brazilians with a familial history of coronary artery disease (CAD). ACE (Ins/Del) and APOB (Ins/Del, XbaI, and EcoRI) and APOE (HhaI) polymorphisms were determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analyses on agarose, and polyacrylamide gel electrophoresis. Serum lipids were measured by means of routine enzymatic assays. The results showed a high frequency of hypertension (44%) in Afro-Brazilians that was increased in subjects >40 years old and those with a blood mass index (BMI) higher than 25 kg/m(2) (P<0.001). The ACE Del allele was associated with hypertension in men >40 years old (P<0.05). APOE (HhaI) and APOB (XbaI and Ins/Del) polymorphisms were not associated with hypertension or variations in serum concentrations of lipids, while subjects with the APOB E- allele had higher low-density lipoprotein cholesterol (LDL-C) levels than E+ carriers (P<0.05). These results suggest that ACE Ins/Del polymorphism is associated with hypertension, and APOB EcoRI polymorphism is associated with LDL-C variation in Afro-Brazilians.

The effect of genetic variation on the lipid response to dietary change: recent findings

PURPOSE OF REVIEW

Dyslipidaemia is an important risk factor for cardiovascular disease, and can be modified by diet. However, the lipid response to dietary change may be influenced by genetic variation. This review examines recent research (published since August 2003) on the effect of genetic variation on the lipid response to dietary change.

RECENT FINDINGS

In 10 reports describing intervention studies and seven reports describing observational studies, the lipid response to diet was modified by polymorphisms within the genes for apoE, apoB, apoCIII, lipoprotein lipase, hepatic lipase, endothelial lipase, the liver fatty acid-binding protein, the beta3-adrenergic receptor, adipsin and the peroxisome proliferator-activated receptor gamma. The studies varied widely in terms of the number and type of study participants, the composition and duration of the dietary interventions, the nutrients studied and dietary assessment methods used in the observational studies, and the polymorphisms analysed--some of which had not been studied before with regard to the lipid response to diet.

SUMMARY

The lipid response to dietary change is highly complex. Future studies will have to be large in order to assess the effects of multiple polymorphisms, and will have to control for many factors other than diet. At present, it is premature to recommend the use of genotyping in the design of therapeutic diets. However, such studies may be useful in identifying the mechanisms by which dietary components influence lipid levels.

Apolipoprotein B signal peptide polymorphism and plasma LDL-cholesterol response to low-calorie diet

OBJECTIVE

To assess the effect of the apolipoprotein B Ins/Del signal peptide. Polymorphism on plasma lipid levels in overweight subjects before and after a low-calorie diet.

DESIGN

Diet intervention study (25% reduction in energy intake during 2.5 months) in relation to genetic factors.

SUBJECTS

A total of 231 unrelated patients (146 women/85 men) recruited on the basis of body mass index (BMI)> or =25 kg/m(2).

MEASUREMENTS

BMI, waist to hip ratio, blood lipids and lipoproteins, at entry and after 2.5 months, determination of apo B Ins/Del genotypes.

RESULTS

On spontaneous diet, subjects carrying the Del allele had higher LDL-cholesterol (Del/Del: 3.97+/-0.62 mmol/l; Ins/Del: 3.87+/-1.01 mmol/l; Ins/Ins: 3.61+/-0.88 mmol/l) (P=0.038). When submitted to low-calorie diet, subjects with Del/Del genotypes reduced their LDL-cholesterol (-16.8%) more than subjects with Ins/Del or Ins/Ins (-4.7% and +0.9%, respectively) (P=0.001).

CONCLUSION

In overweight or obese people, the response of plasma LDL-cholesterol levels to low-calorie diet is modulated by genetic variation at the apo B locus. Overweight subjects with the Del allele of the apo B signal peptide polymorphism are predisposed to high LDL cholesterol levels but their LDL cholesterol responds well to diet. These results demonstrate the importance of the interaction between genes and nutritional environment in the determination of the lipid levels.

Relation between XbA1 apolipoprotein B gene polymorphism and cardiovascular risk in a type 2 diabetic cohort

AIM

To evaluate in a prospective study the association of XbA1 apolipoprotein B (apoB) gene polymorphism with lipid parameters and cardiovascular (CV) events in a type 2 diabetic cohort.

METHODS AND RESULTS

A cohort of 212 type 2 diabetic patients, free of any cardiovascular complication, was studied. Cardiovascular events were registered for all the patients for 5 years. XbA1 apolipoprotein B gene polymorphism was analysed by PCR-RFLP method. A mild increase in HbA1c was found in X+X+ carriers (P = 0.014). Despite this lower glycemic control, there were no differences between genotype subgroups for lipid parameters except for apoB, significantly higher in X+X+ than in X-X- subjects. In univariate analysis, the cardiovascular events rate was higher in X-X- but did not reach statistical significance (P =0.07). In stepwise multivariate regression analysis, cardiovascular events risk was significantly higher in X- carriers (P = 0.014) and also in smokers, microalbuminuric and older patients.

CONCLUSIONS

We report for the first time in a prospective study the association of XbA1 apolipoprotein B gene polymorphism and cardiovascular events in a diabetic population. The mechanism underlying the excess of cardiovascular risk in X- carriers, despite a better metabolic profile, is likely to involve a linkage disequilibrium between apolipoprotein B gene locus and another gene locus related to cardiovascular risk.