The influence of the apolipoprotein E gene promoter (-219G/ T) polymorphism on postprandial lipoprotein metabolism in young normolipemic males

Quantile-dependent expressivity of postprandial lipemia

Purpose

“Quantile-dependent expressivity” describes an effect of the genotype that depends upon the level of the phenotype (e.g., whether a subject’s triglycerides are high or low relative to its population distribution). Prior analyses suggest that the effect of a genetic risk score (GRS) on fasting plasma triglyceride levels increases with the percentile of the triglyceride distribution. Postprandial lipemia is well suited for testing quantile-dependent expressivity because it exposes each individual’s genotype to substantial increases in their plasma triglyceride concentrations. Ninety-seven published papers were identified that plotted mean triglyceride response vs. time and genotype, which were converted into quantitative data. Separately, for each published graph, standard least-squares regression analysis was used to compare the genotype differences at time t (dependent variable) to average triglyceride concentrations at time t (independent variable) to assess whether the genetic effect size increased in association with higher triglyceride concentrations and whether the phenomenon could explain purported genetic interactions with sex, diet, disease, BMI, and drugs.

Results

Consistent with the phenomenon, genetic effect sizes increased (P≤0.05) with increasing triglyceride concentrations for polymorphisms associated with ABCA1, ANGPTL4, APOA1, APOA2, APOA4, APOA5, APOB, APOC3, APOE, CETP, FABP2, FATP6, GALNT2, GCKR, HL, IL1b, LEPR, LOX-1, LPL, MC4R, MTTP, NPY, SORT1, SULF2, TNFA, TCF7L2, and TM6SF2. The effect size for these polymorphisms showed a progressively increasing dose-response, with intermediate effect sizes at intermediate triglyceride concentrations. Quantile-dependent expressivity provided an alternative interpretation to their interactions with sex, drugs, disease, diet, and age, which have been traditionally ascribed to gene-environment interactions and genetic predictors of drug efficacy (i.e., personalized medicine).

Conclusion

Quantile-dependent expressivity applies to the majority of genetic variants affecting postprandial triglycerides, which may arise because the impaired functionalities of these variants increase at higher triglyceride concentrations. Purported gene-drug interactions may be the manifestations of quantile-dependent expressivity, rather than genetic predictors of drug efficacy.

Apolipoprotein E genetic variants interact with Mediterranean diet to modulate postprandial hypertriglyceridemia in coronary heart disease patients: CORDIOPREV study

BACKGROUND

We try to explore whether long-term consumption of two healthy dietary patterns (low-fat [LF] diet or Mediterranean diet [MedDiet]) interacts with the apolipoprotein E (APOE) single-nucleotide polymorphisms (SNPs: rs439401, rs440446 and rs7412) modulating postprandial hypertriglyceridemia (ppHTG) in coronary heart disease (CHD) patients.

METHODS AND RESULTS

We selected patients from the CORDIOPREV study with genotyping and who underwent an oral fat load test (FLT) at baseline and after 3 years follow-up (n = 506). After 3 years of follow-up, we found a gene-diet interaction between the APOE rs439401 SNP and MedDiet. Specifically, T-allele carriers in the MedDiet group showed a more significant decrease in postprandial triglycerides (TG: P = 0.03) and large triacylglycerol-rich lipoproteins (TRLs) TG (large TRLs TG; P = 0.01) compared with CC subjects. Consistently, the area under the curve of TG (AUC-TG; P-interaction = 0.03) and AUC-large TRLs TG (P-interaction = 0.02) were significantly lower in T-allele carriers compared with CC subjects.

CONCLUSIONS

The long-term consumption of a MedDiet modulates ppHTG through APOE genetic variants in CHD patients. This gene-diet interaction may contribute to a more precise dietary advice in CHD patients.

Apolipoprotein E-C1-C4-C2 gene cluster region and inter-individual variation in plasma lipoprotein levels: a comprehensive genetic association study in two ethnic groups

The apolipoprotein E-C1-C4-C2 gene cluster at 19q13.32 encodes four amphipathic apolipoproteins. The influence of APOE common polymorphisms on plasma lipid/lipoprotein profile, especially on LDL-related traits, is well recognized; however, little is known about the role of other genes/variants in this gene cluster. In this study, we evaluated the role of common and uncommon/rare genetic variation in this gene region on inter-individual variation in plasma lipoprotein levels in non-Hispanic Whites (NHWs) and African blacks (ABs). In the variant discovery step, the APOE, APOC1, APOC4, APOC2 genes were sequenced along with their flanking and hepatic control regions (HCR1 and HCR2) in 190 subjects with extreme HDL-C/TG levels. The next step involved the genotyping of 623 NHWs and 788 ABs for the identified uncommon/rare variants and common tagSNPs along with additional relevant SNPs selected from public resources, followed by association analyses with lipid traits. A total of 230 sequence variants, including 15 indels were identified, of which 65 were novel. A total of 70 QC-passed variants in NHWs and 108 QC-passed variants in ABs were included in the final association analyses. Single-site association analysis of SNPs with MAF>1% revealed 20 variants in NHWs and 24 variants in ABs showing evidence of association with at least one lipid trait, including several variants exhibiting independent associations from the established APOE polymorphism even after multiple-testing correction. Overall, our study has confirmed known associations and also identified novel associations in this genomic region with various lipid traits. Our data also support the contribution of both common and uncommon/rare variation in this gene region in affecting plasma lipid profile in the general population.

Is there a significant interaction effect between apolipoprotein E rs405509 T/T and ε4 genotypes on cognitive impairment and gray matter volume?

BACKGROUND

Evidence demonstrates that the T allele of the single-nucleotide polymorphism rs405509 in the apolipoprotein E (APOE) promoter is a risk factor for Alzheimer's disease. However, it is unknown whether rs405509 T allele synergizes with the APOE ε4 allele in influencing cognition and brain structure.

METHODS

We analyzed the interaction effect of the rs405509 T allele and the APOE ε4 allele on cognitive ability and brain gray matter volume among elderly people. The subjects were grouped into four groups according to APOE and rs405509 genotypes.

RESULTS

Significant interaction effects were found between rs405509 and APOE on general mental status, memory and attention. Analysis of the whole brain gray matter showed a significantly positive interaction effect between rs405509and APOE on the right inferior temporal gyrus and right fusiform gyrus (alphasim correction P < 0.001). In addition, there was a significant relationship between cognitive ability and gray matter volume.

CONCLUSIONS

The data indicate that the APOE rs405509 T homozygote modulates the effect of APOE ε4 on both cognitive performance and brain gray matter structure.

Effect of finishing period length with α-tocopherol supplementation on the expression of vitamin E-related genes in the muscle and subcutaneous fat of light lambs

The aim of this study was to investigate how different finishing period lengths with α-tocopherol supplementation or alfalfa grazing affect mRNA expression levels of genes related to vitamin E metabolism in L. thoracis (LT) muscle and subcutaneous fat (SF) from lambs of the Rasa Aragonesa breed. Indoors, concentrate-fed light lambs (n=48) were supplemented with 500 dl-α-tocopheryl acetate/kg concentrate for an average finishing period length of 0 (C), 10.7 (VE10d), 21.2 (VE20d) and, 32.3 (VE30d) days before slaughtering. Simultaneously, 8 lambs with their dams were alfalfa-grazed. The α-tocopherol affected in a short-term the expression of genes in LT muscle (ABCA1, LPL, APOE, and SREBP1) and SF (ABCA1, SCARB1, LPL, and PPARG). On the contrary, PPARA gene expression showed a long-term α-tocopherol effect because the highest levels of PPARA mRNA were found in the VE30d.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

Nutritional status, genetic susceptibility, and insulin resistance--important precedents to atherosclerosis

Atherosclerosis is a progressive disease that starts early in life and is manifested clinically as coronary artery disease (CAD), cerebrovascular disease, or peripheral artery disease. CAD remains the leading cause of morbidity and mortality in Western society despite the great advances made in understanding its underlying pathophysiology. The key risk factors associated with CAD include hypercholesterolemia, hypertension, poor diet, obesity, age, male gender, smoking, and physical inactivity. Genetics also play an important role that may interact with environmental factors, including diet, nutritional status, and physiological parameters. Furthermore, certain chronic inflammatory conditions also predispose to the development of CAD. The spiraling increase in obesity rates worldwide has made it more pertinent than ever before to understand the metabolic perturbations that link over nutrition to enhanced cardiovascular risk. Great breakthroughs have been made at the pharmacological level to manage CAD; statins and aspirin have revolutionized treatment of CAD and prolonged lifespan. Nonetheless, lifestyle intervention prior to clinical presentation of CAD symptoms would negate/delay the need for chronic pharmacotherapy in at-risk individuals which in turn would relieve healthcare systems of a costly burden. Throughout this review, we debate the relative impact of nutrition versus genetics in driving CAD. We will investigate how overnutrition affects adipose tissue biology and drives IR and will discuss the subsequent implications for the cardiovascular system. Furthermore, we will discuss how lifestyle interventions including diet modification and weight loss can improve both IR and metabolic dyslipidemia that is associated with obesity. We will conclude by delving into the concept that nutritional status interacts with genetic susceptibility, such that perhaps a more personalized nutrition approach may be more effective in determining diet-related risk as well as response to nutritional interventions.

Diet, genetics, and disease: a focus on the middle East and north Africa region

The Middle East and North Africa (MENA) region suffers a drastic change from a traditional diet to an industrialized diet. This has led to an unparalleled increase in the prevalence of chronic diseases. This review discusses the role of nutritional genomics, or the dietary signature, in these dietary and disease changes in the MENA. The diet-genetics-disease relation is discussed in detail. Selected disease categories in the MENA are discussed starting with a review of their epidemiology in the different MENA countries, followed by an examination of the known genetic factors that have been reported in the disease discussed, whether inside or outside the MENA. Several diet-genetics-disease relationships in the MENA may be contributing to the increased prevalence of civilization disorders of metabolism and micronutrient deficiencies. Future research in the field of nutritional genomics in the MENA is needed to better define these relationships.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

Association of apolipoprotein E promoter polymorphisms with bone structural traits is modified by dietary saturated fat intake - the Cardiovascular Risk in Young Finns study

Association of apolipoprotein E (APOE) ε4 allele with peripheral quantitative computed tomography (pQCT) bone traits at the distal and shaft sites of the radius and tibia was evaluated in the Young Finns Cohort (n=1777). We also analyzed the interactions of the APOE promoter polymorphisms (-219G/T rs405509 and +113G/C rs440446) and bone traits within the APOE ε3/ε3 genotype (n=1025 and n=1013, respectively), and investigated the gene-environment interactions on bone traits with longitudinal saturated fatty acids (SAFA) intake. Differences between the ε4 allele carriers and noncarriers were modest and mostly nonsignificant. Within the APOE promoter -219G/T polymorphism, cortical strength index (CSI) and compressive bone strength index (BSI) at the distal radius (linear, P=0.003 and P=0.05, respectively) and tibia (linear, P=0.01 and P=0.03, respectively), and CSI at the tibial shaft (linear, P=0.04) decreased towards the -219T/T genotype in women. In men, total cross-sectional areas at the radial site and stress-strain index (SSI) at the radial shaft (linear, P=0.03 and P=0.04 and P=0.05, respectively) increased, and conversely cortical bone density and CSI at the radial shaft (linear, P=0.005 and P=0.05, respectively) and CSI at the tibial shaft (linear, P=0.03) decreased towards the -219T/T genotype. In the highest SAFA tertile, women with the -219T/T genotype had the smallest total area and SSI at the radial shaft (P=0.01 and P=0.02, respectively). Subjects with the APOE +113C/C genotype shared similar bone traits as subjects with the APOE -219T/T genotype. In conclusion, APOE genotypes -219T/T and +113C/C could be genetic markers for cortical bone strength. Furthermore, high longitudinal SAFA intake seems to be more detrimental to bone in women with the -219T/T and +133C/C genotypes than others.

The APOE -219G/T and +113G/C polymorphisms affect insulin resistance among Turks

The -219G/T (rs405509) and +113G/C (rs440446) polymorphisms within the regulatory region of the apolipoprotein E (APOE) gene have been related to the transcriptional activity of the gene. We examined the effect of the stated polymorphisms and their construct haplotypes with the APOE ɛ2/ɛ3/ɛ4 polymorphism on lipid levels and insulin resistance in the Turkish Adult Risk Factor Study. Randomly selected 1774 adults (mean age, 55.0 ± 11.7 years; 51.2% women) participating in the population-based Turkish Adult Risk Factor Study were cross-sectionally analyzed for the -219G/T, +113G/C, and ɛ2/ɛ3/ɛ4 polymorphisms as well as their haplotypes. Insulin resistance was defined as the 70th percentile in the sample (>2.51) of the homeostatic model assessment (HOMA). The frequencies of the -219T and +113C alleles were 0.477 and 0.423, respectively; and those of haplotype 1 (GGɛ3) and haplotype 2 (TCɛ3) were 44.1% and 41.9%, respectively. The -219G/T and +113G/C genotypes (both P < .04) and diplotypes of haplotype 2 (TCɛ3) (P < .014) were inversely related to serum fasting insulin and the HOMA index, even after controlling for 8 relevant covariates, but not to serum lipids. Within the APOE3 group, haplotype 2 (TC-/TC+) heterozygotes had an odds ratio of 0.66 (95% confidence interval, 0.42-0.99) for HOMA of insulin resistance after adjusting for 8 covariates. APOE promoter polymorphisms and their diplotypes are independently related with serum fasting insulin levels and HOMA index among Turks.

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

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

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

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

Effects of variations in the APOA1/C3/A4/A5 gene cluster on different parameters of postprandial lipid metabolism in healthy young men

The APOA1/C3/A4/A5 gene cluster encodes important regulators of fasting lipids, but the majority of lipid metabolism takes place in the postprandial state and knowledge about gene regulation in this state is scarce. With the aim of characterizing possible regulators of lipid metabolism, we studied the effects of nine single nucleotide polymorphisms (SNPs) during postprandial lipid metabolism. Eighty-eight healthy young men were genotyped for APOA1 -2630 (rs613808), APOA1 -2803 (rs2727784), APOA1 -3012 (rs11216158), APOC3 -640 (rs2542052), APOC3 -2886 (rs2542051), APOC3 G34G (rs4520), APOA4 N147S (rs5104), APOA4 T29T (rs5092), and A4A5_inter (rs1263177) and were fed a saturated fatty acid-rich meal (1g fat/kg of weight with 60% fat, 15% protein and 25% carbohydrate). Serial blood samples were extracted for 11 h after the meal. Total cholesterol and fractions [HDL-cholesterol, LDL-cholesterol, trifacylglycerols (TGs) in plasma, TG-rich lipoproteins (TRLs) (large TRLs and small TRLs), apolipoprotein A-I and apolipoprotein B] were determined. APOA1 -2803 homozygotes for the minor allele and A4A5_inter carriers showed a limited degree of postprandial lipemia. Carriers of the rare alleles of APOA4 N147S and APOA4 T29T had lower APOA1 plasma concentration during this state. APOC3 -640 was associated with altered TG kinetics but not its magnitude. We have identified new associations between SNPs in the APOA1/C3/A4/A5 gene cluster and altered postprandial lipid metabolism.

Parental history of Alzheimer disease associated with lower plasma apolipoprotein E levels

BACKGROUND

Variation in APOE genotype is a determinant of Alzheimer disease (AD), but the risk associated with variation in plasma apoE levels has yet to be determined. Here, we studied offspring with and without a parental history of AD to identify the effect of plasma apoE levels at middle age on the risk of late-onset AD.

METHODS

Some 203 offspring from 92 families with a parental history of AD were compared with 197 offspring from 97 families without a parental history of AD. APOE genotypes and plasma apoE levels were assessed in all offspring. Difference in plasma apoE level between subjects with and without a parental history of AD was calculated using robust linear regression, both stratified and adjusted for APOE genotype.

RESULTS

Offspring with a parental history of AD were more likely to be an APOE epsilon4 allele carrier (46% vs 21%, p < 0.001) than offspring without such a parental history. Mean plasma apoE levels strongly decreased from epsilon2 to epsilon3epsilon3 to epsilon4 carriers (p < 0.001). Offspring with a parental history of AD had lower plasma apoE levels than subjects without such a history, both in analyses adjusted for APOE genotype (difference: -0.21 mg/dL, p = 0.02) and when using standardized Z scores, when stratified for APOE genotype (difference: -0.22, p = 0.009).

CONCLUSIONS

Our findings suggest that lower plasma apoE levels in middle age could be a risk factor for Alzheimer disease in old age, independent of APOE genotype.

Genetic influences on blood lipids and cardiovascular disease risk: tools for primary prevention

Genetic polymorphism in human populations is part of the evolutionary process that results from the interaction between the environment and the human genome. Recent changes in diet have upset this equilibrium, potentially influencing the risk of most common morbidities such as cardiovascular diseases, obesity, diabetes, and cancer. Reduction of these conditions is a major public health concern, and such a reduction could be achieved by improving our ability to detect disease predisposition early in life and by providing more personalized behavioral recommendations for successful primary prevention. In terms of cardiovascular diseases, polymorphisms at multiple genes have been associated with differential effects in terms of lipid metabolism; however, the connection with cardiovascular disease has been more elusive, and considerable heterogeneity exists among studies regarding the predictive value of genetic markers. This may be because of experimental limitations, the intrinsic complexity of the phenotypes, and the aforementioned interactions with environmental factors. The integration of genetic and environmental complexity into current and future research will drive the field toward the implementation of clinical tools aimed at providing dietary advice optimized for the individual's genome. This may imply that dietary changes are implemented early in life to gain maximum benefit. However, it is important to highlight that most reported studies have focused on adult populations and to extrapolate these findings to children and adolescents may not be justified until proper studies have been carried out in these populations and until the ethical and legal issues associated with this new field are adequately addressed.

Influence of genetic factors in the modulation of postprandial lipemia

Postprandial lipemia is traditionally defined by the extent and duration of the increase in plasma triglycerides in response to a fat-enriched meal. The relationship between alimentary lipemia and coronary disease is of great interest in view of the epidemiological and experimental evidence that underlies it. The rate of synthesis of triglyceride-rich lipoproteins, lipoprotein lipase-mediated triglyceride hydrolysis, and the hepatic capture of chylomicron remnants via the interaction of the lipoprotein receptor with APOE and LPL, are the fundamental pillars of the metabolism and modification of these lipoproteins. The modulation of such phenomena is influenced by both genetic and environmental factors, thus explaining their extraordinary individual variance. This review presents the current evidence linking a number of candidate genes to the modulation of postprandial lipid metabolism.

Dietary, physiological, genetic and pathological influences on postprandial lipid metabolism

Most of diurnal time is spent in a postprandial state due to successive meal intakes during the day. As long as the meals contain enough fat, a transient increase in triacylglycerolaemia and a change in lipoprotein pattern occurs. The extent and kinetics of such postprandial changes are highly variable and are modulated by numerous factors. This review focuses on factors affecting postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and risk of CHD. Postprandial lipoprotein metabolism is modulated by background dietary pattern as well as meal composition (fat amount and type, carbohydrate, protein, fibre, alcohol) and several lifestyle conditions (physical activity, tobacco use), physiological factors (age, gender, menopausal status) and pathological conditions (obesity, insulin resistance, diabetes mellitus). The roles of many genes have been explored in order to establish the possible implications of their variability in lipid metabolism and CHD risk. The postprandial lipid response has been shown to be modified by polymorphisms within the genes for apo A-I, A-IV, A-V, E, B, C-I and C-III, lipoprotein lipase, hepatic lipase, fatty acid binding and transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. Overall, the variability in postprandial response is important and complex, and the interactions between nutrients or dietary or meal compositions and gene variants need further investigation. The extent of present knowledge and needs for future studies are discussed in light of ongoing developments in nutrigenetics.

An apolipoprotein A-II polymorphism (-265T/C, rs5082) regulates postprandial response to a saturated fat overload in healthy men

Apolipoprotein (Apo) A-II is an apolipoprotein with an unknown role in lipid metabolism. It has been suggested that the presence of the less frequent allele of a single nucleotide polymorphism (Apo A-II -265T/C, rs5082) reduces the transcription rate of Apo A-II and enhances VLDL postprandial clearance in middle-aged men. To further investigate the role of Apo A-II -265T/C on lipid metabolism, we studied 88 normolipidemic young men. The participants were given a fatty meal containing 1 g fat and 7 mg cholesterol/kg weight and capsules containing 60,000 IU vitamin A (retinyl palmitate, 15.15 mg RE) per square meter body surface area. Postprandial lipemia was assessed during the 11 h following the meal. Total cholesterol (Chol) and triacylglycerols (TG) in plasma and TG-rich lipoproteins (TRL) (large TRL and small TRL) were measured, as well as HDL, Apo A-I, Apo B, Apo B-48, and Apo B-100. Postprandial responses were higher in the TT group than in carriers of the minor allele (CC/TC) for total TG in plasma (21.37% of change of area under curve, P = 0.014), large TRL-TG (24.75% change, P = 0.017) and small TRL-Chol (26.63% change, P = 0.003). Our work shows that carriers of the minor allele for Apo A-II -265T/C (CC/TC) have a lower postprandial response compared with TT homozygotes. This finding may partially explain the role of Apo A-II in lipid metabolism and can identify a population with a decreased risk of cardiovascular disease, as corresponds to the lower level of postprandial hypertriglyceridemia.

Methodology for studying postprandial lipid metabolism

BACKGROUND

Postprandial lipid metabolism in humans has deserved much attention during the last two decades. Although fasting lipid and lipoprotein parameters reflect body homeostasis to some extent, the transient lipid and lipoprotein accumulation that occurs in the circulation after a fat-containing meal highlights the individual capacity to handle an acute fat input. An exacerbated postprandial accumulation of triglyceride-rich lipoproteins in the circulation has been associated with an increased cardiovascular risk.

METHODS

The important number of studies published in this field raises the question of the methodology used for such postprandial studies, as reviewed.

RESULTS

Based on our experiences, the present review reports and discuss the numerous methodological issues involved to serve as a basis for further works. These aspects include aims of the postprandial tests, size and nutrient composition of the test meals and background diets, pre-test conditions, characteristics of subjects involved, timing of sampling, suitable markers of postprandial lipid metabolism and calculations.

CONCLUSION

In conclusion, we stress the need for standardization of postprandial tests.

Regulation of postprandial lipemia: an update on current trends

People spend a large percentage of their waking hours in the postprandial state. Postprandial lipemia is associated with disruptions in lipoprotein metabolism and inflammatory factors, cardiovascular disease, MetS, and diabetes. Commonly, the dietary sources of fat exceed the actual needs and the tissues are faced with the excess, with accumulation of chylomicrons and remnant particles. This review will summarize recent findings in postprandial lipemia research with a focus on human studies. The effects of dietary factors and other meal components on postprandial lipemia leads to the following question: do we need a standardized oral lipid tolerance test (OLTT)? An overview of recent findings on FABP2, MTP, LPL, apoAV, and ASP and the effects of body habitus (sex influence and body size), as well as exercise and weight loss, on postprandial lipemia will be summarized.

Dietary fat, genes and insulin sensitivity

Both insulin resistance and dyslipidaemia are determined by genetic and environmental factors. Depending on their expression and their function, gene variants may influence either insulin action or dyslipidaemia. The purpose of this review was to give some examples from recent studies of gene variants that influence insulin signalling and the interaction between gene and diet to predispose insulin resistance. Recent findings indicate a major role for genetic susceptibility to the insulin resistance syndrome. Nutrition also plays an important role in the development and progression of the condition. Genetic background may interact with habitual dietary fat composition, affecting predisposition to the insulin resistance syndrome and individual responsiveness to changes in dietary fat intake. Due to the complex nature of gene-environment interactions, therefore, therapeutic dietary therapy may require a 'personalized' nutrition approach in the future. Although results have not always been consistent, gene variants that affect primary insulin action or dyslipidaemia, and particularly their interaction with the environment, are important modulators of glucose metabolism and insulin resistance syndrome.

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.

A single nucleotide polymorphism of the apolipoprotein A–V gene −1131T>C modulates postprandial lipoprotein metabolism

The Apolipoprotein A-V (apoA-V) gene promoter polymorphism -1131T>C modulates triacylglycerol (TG) concentrations. We evaluate whether this polymorphism could be involved in the interindividual variability observed during postprandial lipemia. Fifty-one healthy apo E3E3 male volunteers [12 with -1131CC/CT genotype, and 39 with -1131TT genotype] underwent a Vitamin A fat-load test consisting of 1g of fat/kg body weight and 60,000IU of Vitamin A. Blood samples were taken at time 0 and every hour until the 6th and every 2h and 30 min until the 11th. Cholesterol (Chol) and TG were determined in plasma and Chol, TG, ApoB-100, ApoB-48, and retinyl palmitate (RP) were determined in lipoprotein fractions. Data of postprandial lipemia revealed that subjects with the -1131CT/CC genotype had a higher postprandial response of total plasma TG (p=0.043), large triacylglycerol-rich lipoproteins-TG (TRL-TG) (p=0.002), large TRL-Chol (p=0.004), small TRL-Chol (p=0.004) and small TRL-RP (p=0.001) than subjects with the -1131TT genotype. The modifications observed in postprandial lipoprotein metabolism in subjects with the apoA-V -1131T>C polymorphism could be involved in the increased fasting plasma TG concentrations previously described in carriers of the C allele.

Influencia de los factores genéticos y ambientales en el metabolismo lipídico y riesgo cardiovascular asociado al gen apoE

The apolipoprotein E (ApoE) plays an important role in lipid metabolism. This apoprotein presents three major isoforms (apoE2, apoE3 and apoE4) that modulate lipid levels. Carriers of the apoE4 allele have higher total and LDL-cholesterol plasma concentration and a greater coronary risk, particularly for myocardial infarction. Nevertheless, not all the people with this allele develop the disease, which suggests that other genetic or environmental factors are necessary for its total expression. In this review, we will analyze the importance of several polymorphisms in the apoE gene promoter region, as well as various environmental factors, including diet, in the association of this gene with lipid metabolism and cardiovascular risk.

Postprandial lipoprotein metabolism, genes and risk of cardiovascular disease

PURPOSE OF REVIEW

Several lines of evidence suggest that postprandial lipemia increases the risk of atherogenesis, and in each of the systems involved in postprandial metabolism the roles of many genes have been explored in order to establish the possible implications of their variability in coronary heart disease risk.

RECENT FINDINGS

This report focuses on recent results pertaining to postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and coronary heart disease. The postprandial lipid response was modified by polymorphisms within the genes for apolipoprotein AI, apolipoprotein E, apolipoprotein B, apolipoprotein CI, apolipoprotein CIII, apolipoprotein AIV, apolipoprotein AV, lipoprotein lipase, hepatic lipase, fatty acid-binding protein-2, the fatty acid transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. We also discuss recent advances in the effects of gene regulation using knockdown animal models on postprandial lipoprotein metabolism.

SUMMARY

The review discusses several of these factors as well as the potential impact of gene polymorphism on the variability of postprandial lipoprotein metabolism as intermediate phenotypes for coronary heart disease. The variability in postprandial lipid response is highly complex. Future studies will need to be large if they are to assess the effects of multiple polymorphisms.

Linkage analysis of LDL cholesterol in American Indian populations: the Strong Heart Family Study

Previous studies have demonstrated that low density lipoprotein cholesterol (LDL-C) concentration is influenced by both genes and environment. Although rare genetic variants associated with Mendelian causes of increased LDL-C are known, only one common genetic variant has been identified, the apolipoprotein E gene (APOE). In an attempt to localize quantitative trait loci (QTLs) influencing LDL-C, we conducted a genome-wide linkage scan of LDL-C in participants of the Strong Heart Family Study (SHFS). Nine hundred eighty men and women, age 18 years or older, in 32 extended families at three centers (in Arizona, Oklahoma, and North and South Dakota) were phenotyped for LDL-C concentration and other risk factors. Using a variance component approach and the program SOLAR, and after accounting for the effects of covariates, we detected a QTL influencing LDL-C on chromosome 19, nearest marker D19S888 at 19q13.41 [logarithm of odds (LOD) = 4.3] in the sample from the Dakotas. This region on chromosome 19 includes many possible candidate genes, including the APOE/C1/C4/C2 gene cluster. In follow-up association analyses, no significant evidence for an association was detected with the APOE*2 and APOE*4 alleles (P = 0.76 and P = 0.53, respectively). Suggestive evidence of linkage to LDL-C was detected on chromosomes 3q, 4q, 7p, 9q, 10p, 14q, and 17q. These linkage signals overlap positive findings for lipid-related traits and harbor plausible candidate genes for LDL-C.

The apolipoprotein E gene promoter (-219G/T) polymorphism determines insulin sensitivity in response to dietary fat in healthy young adults

Insulin sensitivity (IS) is determined by genetic and environmental factors, including diet. The apoE gene promoter -219G/T polymorphism is associated with coronary heart disease and increased postprandial triacylglycerol-rich lipoprotein concentration, circumstances related to insulin resistance. Thus, our aim was to determine whether this polymorphism modified the IS response to dietary fat in healthy young adults. Volunteers (n = 43) with the apoE3/E3 genotype (8 GG, 25 GT and 10 TT) completed 3 dietary periods, each lasting 4 wk. They first consumed a SFA-rich diet [38% fat (% of energy in the total diet), 20% SFA (% of energy in the total diet)], and then, in a randomized, crossover design, a carbohydrate (CHO)-rich diet (30% fat, 55% CHO) or a monounsaturated fatty acid (MUFA)-rich diet (38% fat, 22% MUFA). After each diet period, we investigated peripheral IS using the insulin suppression test. The steady-state plasma glucose (SSPG) concentration was lower (P < 0.05) in GG subjects than in GT and TT individuals, regardless of the diet consumed. Significant diet x genotype interactions were found for SSPG and plasma nonesterified FFA (NEFA) concentrations. Thus, the shift from the SFA-rich diet to the MUFA- or CHO-rich diets decreased (P < 0.05) the SSPG and NEFA concentrations in GG and GT, but not in TT subjects. In conclusion, carriers of the -219T allele are less insulin sensitive than GG individuals. Furthermore, only carriers of the -219G allele have improved IS when MUFA- or CHO-rich diets are consumed instead of a SFA-rich diet.

SINGLE NUCLEOTIDE POLYMORPHISMS THAT INFLUENCE LIPID METABOLISM: Interaction with Dietary Factors

Cardiovascular disease (CVD) risk is the result of complex interactions between genetic and environmental factors. During the past few decades, much attention has focused on plasma lipoproteins as CVD risk factors. The current evidence supports the concept that gene-environment interactions modulate plasma lipid concentrations and potentially CVD risk. The findings from studies examining gene-diet interactions and lipid metabolism have been highly promising. Several loci (i.e., APOA1, APOA4, APOE, and LIPC) are providing proof-of-concept for the potential application of genetics in the context of personalized nutritional recommendations for CVD prevention. However, the incorporation of these findings to the clinical environment is not ready for prime time. There is a compelling need for replication using a higher level of scientific evidence. Moreover, we need to evolve from the simple scenarios examined nowadays (i.e., one single dietary component, single nucleotide polymorphism, and risk factor) to more realistic situations involving interactions between multiple genes, dietary components, and risk factors. In summary, there is need for both large population studies and well-standardized intervention studies.

The key role of apolipoprotein E in atherosclerosis

Apolipoprotein E is a multifunctional protein that is synthesized by the liver and several peripheral tissues and cell types, including macrophages. The protein is involved in the efficient hepatic uptake of lipoprotein particles, stimulation of cholesterol efflux from macrophage foam cells in the atherosclerotic lesion, and the regulation of immune and inflammatory responses. Apolipoprotein E deficiency in mice leads to the development of atherosclerosis and re-expression of the protein reduces the extent of the disease. This review presents evidence for the potent anti-atherogenic action of apolipoprotein E and describes our current understanding of its multiple functions and regulation by factors implicated in the pathogenesis of cardiovascular disease.

The association of the apolipoprotein E gene promoter polymorphisms and haplotypes with serum lipid and lipoprotein concentrations

BACKGROUND

Apolipoprotein E (ApoE) is known to modulate lipoprotein transport and metabolism. The common APOE epsilon2/epsilon3/epsilon4 polymorphism explains part of the variation in plasma cholesterol levels. Polymorphisms of the APOE gene regulatory region are suggested to be involved in explaining variation of lipoprotein levels within the APOE epsilon2/epsilon3/epsilon4 genotypes.

OBJECTIVES

To study the associations of the APOE gene promoter polymorphisms -219G/T and +113G/C and their haplotypes with serum lipid and lipoprotein concentrations, especially within the most common APOE epsilon3/epsilon3 genotype group.

SUBJECTS AND METHODS

From 219 middle-aged Finnish men, APOE genotypes were determined and haplotypes estimated. Plasma lipoproteins were isolated by ultracentrifugation and their lipids were measured.

RESULTS

The studied APOE promoter polymorphisms and haplotypes associated with certain lipid variables independently of the APOE epsilon2/epsilon3/epsilon4 genotype. Within the APOE epsilon3/epsilon3 group, both -219G/G and +113G/G genotypes associated statistically significantly with higher levels of very low-density lipoprotein (VLDL) cholesterol, apoB and triglycerides, and tended to associate with lower HDL-cholesterol concentrations than the other genotypes. Compared with the -219T/+113C/epsilon3 haplotype, the more common -219G/+113G/epsilon3 haplotype was found more frequently among the group having high (over median) VLDL-cholesterol and triglyceride concentrations (OR 2.6, p<0.001 and OR=2.1, p=0.009, respectively).

CONCLUSIONS

In addition to the APOE epsilon2/epsilon3/epsilon4 polymorphism, the promoter polymorphisms -219G/T and +113G/C as well as their haplotype modulate lipid and lipoprotein concentrations in middle-aged Finnish men.

Apolipoprotein E gene promoter -219G->T polymorphism increases LDL-cholesterol concentrations and susceptibility to oxidation in response to a diet rich in saturated fat

BACKGROUND

The apolipoprotein E (APOE) gene promoter polymorphism (-219G-->T) has been associated with increased risk of myocardial infarction, premature coronary artery disease, and decreased plasma apolipoprotein E concentrations.

OBJECTIVE

We aimed to determine in healthy subjects whether this polymorphism modifies the susceptibility of LDL to oxidation and the lipid response to the content and quality of dietary fat.

DESIGN

Fifty-five healthy men with the APOE3/E3 genotype (7 GG, 38 GT, and 10 TT) completed 3 dietary periods, each lasting 4 wk. The first was a saturated fatty acid (SFA)-rich diet [38% fat-20% SFA and 12% monounsaturated fatty acid (MUFA)-and 47% carbohydrates (CHO)], which was followed by a CHO-rich diet (30% fat-<10% SFA and 12% MUFA-and 55% CHO) or a MUFA-rich diet (38% fat-<10% SFA and 22% MUFA-and 47% CHO) in a randomized crossover design. At the end of each dietary period, LDL oxidation susceptibility, lipids, and lipoproteins were measured.

RESULTS

Compared with carriers of the G allele, TT subjects had a significantly (P < 0.05) shorter lag time after the SFA diet. The replacement of the SFA diet by the CHO or MUFA diet induced a greater increase (P < 0.05) in lag time in the TT subjects than in the GG or GT subjects. Carriers of the T allele had higher LDL-cholesterol (P < 0.05) and apolipoprotein B (P < 0.05) plasma concentrations after the SFA diet than did GG subjects. Compared with GG subjects, carriers of the T allele had a significantly (P < 0.05) greater decrease in LDL cholesterol and apolipoprotein B when they changed from the SFA to the CHO diet.

CONCLUSION

The -219G-->T polymorphism may partially explain differences in individual responses to diet.

Nutrigenomics and nutrigenetics

PURPOSE OF REVIEW

Nutritional genomics has tremendous potential to change the future of dietary guidelines and personal recommendations. Nutritional genomics covers nutrigenomics, which explores the effects of nutrients on the genome, proteome and metabolome, and nutrigenetics, the major goal of which is to elucidate the effect of genetic variation on the interaction between diet and disease. Nutrigenetics has been used for decades in certain rare monogenic diseases such as phenylketonuria, and it has the potential to provide a basis for personalized dietary recommendations based on the individual's genetic makeup in order to prevent common multifactorial disorders decades before their clinical manifestation.

RECENT FINDINGS

Preliminary results regarding gene-diet interactions in cardiovascular diseases are for the most part inconclusive because of the limitations of current experimental designs. Success in this area will require the integration of various disciplines, and will require investigators to work on large population studies that are designed to investigate gene-environment interactions.

SUMMARY

Based on the current knowledge, we anticipate that in the future we will be able to harness the information contained in our genomes to achieve successful aging using behavioral changes, with nutrition being the cornerstone of this endeavor.