Genes, variation of cholesterol and fat intake and serum lipids

Association of APOE gene polymorphism with lipid profile and coronary artery disease in Afro-Caribbeans

OBJECTIVES

Apolipoprotein E gene (APOE) polymorphism is associated with the lipid profile and cardio-vascular disease. However, these relationships vary between ethnic groups. We evaluated, for the first time in an Afro-Caribbean population, the distribution of APOE polymorphisms and their associations with coronary artery disease (CAD), the lipid profile and other cardio-metabolic risk factors.

METHODS

We studied 712 Afro-Caribbean subjects including 220 with documented CAD and 492 healthy subjects. TaqMan assays were performed to genotype rs7412 and rs429358, the two variants that determine the APOE alleles ε2, ε3 and ε4. The association between APOE genotype and the lipid profile was analysed by comparing ε2 carriers, ε3 homozygotes and ε4 carriers.

RESULTS

The frequencies of ε2, ε3 and ε4 in the overall sample were 8%, 70% and 22%, respectively. CAD was not associated with APOE polymorphism. The total cholesterol level was higher in ε4 carriers compared with ε2 carriers: 5.07 vs 4.59 mmol/L (P = 0.016). The LDL-cholesterol level was lower in APOE ε2 carriers compared with ε3 homozygotes and ε4 carriers: 2.65 vs 3.03 and 3.17 mmol/L, respectively (p = 0.002). The total cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios were similar in the three allelic groups. APOE polymorphism was not associated with diabetes, hypertension, waist circumference or body mass index.

CONCLUSIONS

Our results indicate that APOE gene polymorphism is associated with the lipid profile but not with CAD in Afro-Caribbean people. This lack of association with CAD may be explained by the low atherogenic profile observed in ε4 carriers, which may warrant further investigation.

Age, APOE and sex: Triad of risk of Alzheimer's disease

Age, apolipoprotein E ε4 (APOE) and chromosomal sex are well-established risk factors for late-onset Alzheimer's disease (LOAD; AD). Over 60% of persons with AD harbor at least one APOE-ε4 allele. The sex-based prevalence of AD is well documented with over 60% of persons with AD being female. Evidence indicates that the APOE-ε4 risk for AD is greater in women than men, which is particularly evident in heterozygous women carrying one APOE-ε4 allele. Paradoxically, men homozygous for APOE-ε4 are reported to be at greater risk for mild cognitive impairment and AD. Herein, we discuss the complex interplay between the three greatest risk factors for Alzheimer's disease, age, APOE-ε4 genotype and chromosomal sex. We propose that the convergence of these three risk factors, and specifically the bioenergetic aging perimenopause to menopause transition unique to the female, creates a risk profile for AD unique to the female. Further, we discuss the specific risk of the APOE-ε4 positive male which appears to emerge early in the aging process. Evidence for impact of the triad of AD risk factors is most evident in the temporal trajectory of AD progression and burden of pathology in relation to APOE genotype, age and sex. Collectively, the data indicate complex interactions between age, APOE genotype and gender that belies a one size fits all approach and argues for a precision medicine approach that integrates across the three main risk factors for Alzheimer's disease.

Advances in the development of genetic markers for the diagnosis of disease and drug response

Genetic diversity, including single nucleotide polymorphisms, contributes to both disease susceptibility and variability in drug response. Since most genes contain multiple single nucleotide polymorphisms, identifying those that are most relevant with respect to disease or drug response is important and may uncover variants that are predictive of either disease susceptibility or therapeutic response to drugs, both with respect to efficacy and toxic side effects. The candidate gene approach has been widely used to search for the genetic basis of pharmacogenomic traits. Although a few successful examples have emerged from this approach, notably trastuzumab (Herceptin; Genentech), imatinib mesylate (Gleevec (USA), Glivec; Novartis) and certain drugs that demonstrate variable efficacy or adverse effects that are attributed to metabolizing enzymes, for most drugs, the genetic variations that determine their clinical response remain uncovered. Genome-wide linkage approach presents an alternative to the candidate gene approach. The powerful combination of linkage when coupled to ultra-high-throughput genotyping, gene array and proteomics technology, together with innovative bioinformatic resources, provides a focused integrative strategy for pinpointing disease-causing genes that may generate validated drug targets and genes that are responsible for differential drug response. Thus, it is anticipated that genetic research will soon generate new information that can be used to develop novel therapeutic strategies and diagnostic tests that will ultimately lead to safer and more efficacious drugs for all patients. This review addresses recent advances in the development of genetic markers that can be used to diagnose disease or drug response.

Ablation of the transcriptional regulator Id1 enhances energy expenditure, increases insulin sensitivity, and protects against age and diet induced insulin resistance, and hepatosteatosis

Obesity is a major health concern that contributes to the development of diabetes, hyperlipidemia, coronary artery disease, and cancer. Id proteins are helix-loop-helix transcription factors that regulate the proliferation and differentiation of cells from multiple tissues, including adipocytes. We screened mouse tissues for the expression of Id1 and found that Id1 protein is highly expressed in brown adipose tissue (BAT) and white adipose tissue (WAT), suggesting a role for Id1 in adipogenesis and cell metabolism. Id1(-/-) mice are viable but show a significant reduction in fat mass (P<0.005) over the life of the animal that was not due to decreased number of adipocytes. Analysis of Id1(-/-) mice revealed higher energy expenditure, increased lipolysis, and fatty acid oxidation, resulting in reduced triglyceride accumulation in WAT compared to Id1(+/+) mice. Serum levels of triglycerides (193.9±32.2 vs. 86.5±33.8, P<0.0005), cholesterol (189.4±33.8 vs. 110.6±8.23, P<0.0005) and leptin (1263±835 vs. 222±260, P<0.005) were significantly lower in aged Id1(-/-) mice compared to Id1(+/+) mice. Id1-deficient mice have higher resting (P<0.005) and total (P<0.05) O(2) consumption and lower respiratory exchange ratio (P<0.005), confirming that Id1(-/-) mice use a higher proportion of lipid as an energy source for the increased energy expenditure. The expression of PGC1α and UCP1 were 2- to 3-fold up-regulated in Id1(-/-) BAT, suggesting that loss of Id1 increases thermogenesis. As a consequence of higher energy expenditure and reduced fat mass, Id1(-/-) mice displayed enhanced insulin sensitivity. Id1 deficiency protected mice against age- and high-fat-diet-induced adiposity, insulin resistance, and hepatosteatosis. Our findings suggest that Id1 plays a critical role in the regulation of energy homeostasis and could be a potential target in the treatment of insulin resistance and fatty liver disease.

Dietary cholesterol: from physiology to cardiovascular risk

Dietary cholesterol comes exclusively from animal sources, thus it is naturally present in our diet and tissues. It is an important component of cell membranes and a precursor of bile acids, steroid hormones and vitamin D. Contrary to phytosterols (originated from plants), cholesterol is synthesised in the human body in order to maintain a stable pool when dietary intake is low. Given the necessity for cholesterol, very effective intestinal uptake mechanisms and enterohepatic bile acid and cholesterol reabsorption cycles exist; conversely, phytosterols are poorly absorbed and, indeed, rapidly excreted. Dietary cholesterol content does not significantly influence plasma cholesterol values, which are regulated by different genetic and nutritional factors that influence cholesterol absorption or synthesis. Some subjects are hyper-absorbers and others are hyper-responders, which implies new therapeutic issues. Epidemiological data do not support a link between dietary cholesterol and CVD. Recent biological data concerning the effect of dietary cholesterol on LDL receptor-related protein may explain the complexity of the effect of cholesterol on CVD risk.

Apolipoprotein E polymorphism, age and coronary heart disease

Plasma concentrations of lipids, lipoproteins, and apolipoproteins (apo) are established risk factors for coronary heart disease (CHD). The knowledge of lipid profile may predict the potential victims of cardiovascular disease before its initiation and progression and offer the opportunity for primary prevention. The most common apo E polymorphism has been found to influence blood lipid concentrations and its correlation with CHD has been extensively investigated in the last decade. At younger ages, death from CHD is influenced by genetic factors, while the genetic effect decreases at older ages where environmental factors may play a more prominent role. If apo E polymorphism is an important genetic factor in the pathogenesis of atherosclerosis, it could affect the age of CHD onset. This review analyses the influence of apo E polymorphism on blood lipids and CHD in respect to age.

The lipoprotein/lipid profile is modulated by a gene–diet interaction effect between polymorphisms in the liver X receptor-α and dietary cholesterol intake in French-Canadians

Genetic and nutritional factors interact together and modulate the plasma lipid profile. We identified variations in the gene encoding the liver X receptor α (LXRα) and investigated their effects on the plasma lipoprotein/lipid profile. We also examined whether the association between cholesterol intake and plasma lipid profile was modulated by LXRα variants. The LXRα gene was sequenced in thirty-five French-Canadian men with high plasma total cholesterol (>5·0 mmol/l) and LDL-cholesterol (>3·5 mmol/l) concentrations. Dietary cholesterol was obtained from a food-frequency questionnaire. The LXRα c.-115G>A, c.-840C>A and c.-1830T>C genotypes were determined by direct sequencing in 732 subjects. Molecular screening of the LXRα gene revealed sixteen variants. Genotypes c.-115G>A, c.-840C>A and c.-1830T>C (rare allele frequency of 14·3 %, 14·2 % and 11·0 %, respectively) were analysed further. Plasma total cholesterol concentrations were higher in carriers of the -115A, -840A and -1830C allele, compared with the -115G/G, -840C/C and -1830T/T homozygotes (P ≤ 0·05). In a model including the c.-115G>A polymorphism, cholesterol intake, the interaction term c.-115G>A × cholesterol intake (mg/d) and covariates, LXRα-115G>A explained 1·8 % and 2·1 % of the variance in total cholesterol and LDL-cholesterol concentrations (P = 0·02 andP = 0·01), whereas the interaction term explained 2·9 % (P = 0·002) and 2·8 % (P = 0·005), respectively. When subjects were divided into four groups according to the median of cholesterol (290·8 mg) and -115G>A genotypes, high cholesterol intake was associated with higher cholesterol levels in -115A carriers. Similar results were observed for c.-840C>A and c.-1830T>C. These results suggest that cholesterol intake interacts with LXRα variants to modulate the plasma lipid profile.

Effect of SstI polymorphism of the apolipoprotein CIII gene and environmental factors on risks of hypertriglyceridemia in Taiwan aborigines

BACKGROUND

Hypertriglyceridemia (HTG) is a heterogeneous metabolic disorder. The aim of this study was to examine associations among genetic polymorphisms, SstI polymorphism of apolipoprotein CIII (ApoCIII) and Hind III polymorphism of lipoprotein lipase (LPL), environmental factors and risks of HTG.

METHODS AND RESULTS

Two hundred and forty-nine southern Taiwanese aborigines were recruited for a cross-sectional study, which included 90 subjects with triglyceride (TG)>150 mg/dl (HTG) and 159 with TG<or=150 mg/dl (NTG). The frequencies of SstI major allele (S1) and minor allele (S2) of ApoCIII were 66.1% and 33.9% in HTG and 73.6% and 26.4% in NTG (p<0.1). In female subjects, the frequencies of the S2 allele was significantly higher in HTG (0.38) than NTG (0.27) (p<0.04). The frequencies of the LPL HindIII major allele (H+) and minor allele (H-) were similar between HTG (H+ 84.3%; H- 15.7%) and NTG (H+ 78.9%; H- 21.1%). In a multivariate adjusted logistic model, education<or=6 year (odds ratio (OR)=3.71, 95% confidence interval (CI): 1.24-8.13), Amis tribe (OR=3.08, 95% CI: 1.41-6.77), body mass index (BMI)>or=25 (OR=2.22, 95% CI: 1.18-4.16), starchy food consumption>or=3 times/week (OR=1.89, 95% CI: 1.00-3.59) and ApoCIII S2S2 genotype (OR=3.35, 95% CI: 1.10-10.19) were independently (p<0.05) associated with HTG risks. Among ApoCIII S1S1, S1S2 and S2S2 genotypes, ApoCIII and TG concentrations increased (p<0.01) in a dose-responsive manner.

CONCLUSIONS

The ApoCIII S2 variant and environmental factors, including education, tribal background, BMI and starchy food intake, modulate the risks of HTG in aboriginal Taiwanese. Interaction between genetic and environmental factors warrants further investigation.

Plasma triglyceride and HDL-cholesterol concentrations in Vietnamese girls are affected by lipoprotein lipase, but not apolipoprotein CIII polymorphism

Lipoprotein lipase (LPL) and apolipoprotein CIII (apoCIII) play an important role in HDL-cholesterol and triglyceride metabolism. This study examined the effects of LPL S447X and apoCIII SstI polymorphisms on the plasma lipid and lipoprotein concentrations in Vietnamese girls. Three hundred and fifty-one Vietnamese girls, from 7 to 9 y of age, were randomly selected from the urban and rural areas of Ho Chi Minh City, Vietnam. The presence of LPL S447X and apoCIII polymorphism was determined using the Invader assay, and the plasma lipid concentrations were measured by an enzymatic method. Dietary intakes and anthropometrics were assessed for each child. The frequencies of LPL 447X (11.9%) and apoCIII S2 (32.6%) polymorphisms in the Vietnamese were similar to those of other Asian populations. The frequency of LPL 447X was the same as that in Caucasians but the frequency of apoCIII S2 was approximately 3.8 times that in Caucasians. Overall, LPL 447X polymorphism was associated with a higher HDL-cholesterol concentration (7.4%, P = 0.007) and a lower triglyceride concentration (-13.6%, P = 0.04) than LPL 447S. The apoCIII S2 polymorphism was not associated with an increase in the plasma triglyceride concentration in Vietnamese girls with a low fat intake. However, due to the high frequency of the apoCIII SstI polymorphism and the increasingly westernized diet in Vietnam, attention should be paid to the interaction of genotype with the Vietnamese diet.

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.

The effect of dietary fat on LDL size is influenced by apolipoprotein E genotype in healthy subjects

LDL particle size is dependent on both genetic factors and environmental factors such as dietary fat composition. The apolipoprotein E (apoE) genotype is a major genetic determinant of LDL size. Thus, the aim of this work was to study whether the apoE genotype interacts with the quantity and quality of dietary fat, modifying LDL size in young healthy subjects. Healthy subjects (n = 84; 66 apoE 3/3, 8 apoE 4/3, 10 apoE 3/2) were subjected to 3 dietary periods, each lasting 4 wk. The first was an SFA-enriched diet (38% fat, 20% SFA), which was followed by a carbohydrate (CHO)-rich diet (30% fat, < 10% SFA, 55% carbohydrate) or a monounsaturated fatty acid (MUFA) olive oil-rich diet (38% fat, 22% MUFA) following a randomized crossover design. At the end of each diet period, LDL particle size and plasma levels of total cholesterol, LDL cholesterol (LDL-C), HDL-C, apoB, apoA-I, and triacylglycerols were determined. LDL particle size was significantly higher (P < 0.04) in subjects with the apoE 4/3 genotype compared with those with apoE 3/3 and apoE 3/2 in the basal state. LDL size was smaller (P < 0.02) after the CHO diet than after the MUFA or SFA diets. After the CHO diet, a significant increase in LDL particle size (P < 0.035) was noted with respect to the MUFA diet in apoE 4/3 subjects, whereas a significant decrease was observed in the apoE 3/3 individuals (P < 0.043). In conclusion, a Mediterranean diet, high in MUFA-fat increases LDL particle size compared with a CHO diet, and this effect is dependent of apoE genotypes.

Association of APOE genotype with carotid atherosclerosis in men and women

The aim of this study was to determine the association between APOE genotype and carotid atherosclerosis, defined as intimal-medial thickness (IMT) and stenosis, and to assess if other cardiovascular risk factors modify this association. A total of 1,315 men and 1,408 women from the Framingham Offspring Study underwent carotid ultrasound during examination cycle 6 and had complete data on APOE genotype. Three APOE genotype groups were defined: APOE2 (including E2/E2, E3/E2 genotypes), APOE3 (E3/E3), and APOE4 (including E4/E3, E4/E4 genotypes). Carotid IMT and the presence of carotid stenosis > 25% were determined by ultrasonography. In women, the APOE2 group was associated with lower carotid IMT (0.67 vs. 0.73 mm) and lower prevalence of stenosis (odds ratio = 0.49; 95% confidence interval = 0.30-0.81) compared with the APOE3 group. In men, APOE genotype was not associated with carotid IMT or stenosis in the whole group; however, diabetes modified the association between APOE genotype and carotid IMT (P for interaction = 0.044). Among men with diabetes, the APOE4 group was associated with a higher internal carotid artery IMT (1.22 mm) than the APOE3 group (0.90 mm) or the APOE2 group (0.84 mm). The E2 allele was associated with lower carotid atherosclerosis in women, and the E4 allele was associated with higher internal carotid IMT in diabetic men.

Effects of long-term overfeeding on plasma lipoprotein levels in identical twins

Twelve pairs of male monozygotic (MZ) twins (mean age +/- S.D.: 21 +/- 2 years) were subjected to an overfeeding protocol of 4.2 MJ (1000 kcal) above their pre-established individual daily energy needs, 6 days a week, over a period of 100 days. Body weight increased significantly (gain of 8.1 kg, P<0.001), as did fat mass (5.4 kg, P<0.001) after overfeeding. Plasma triacylglycerol (TG) levels significantly increased (P<0.05) without change in plasma cholesterol (CHOL). Plasma very-low-density-lipoprotein (VLDL)-TG, VLDL-Apoprotein (Apo) B, low-density-lipoprotein cholesterol (LDL-C) and LDL-Apo B (P</=0.05) rose, whereas high-density-lipoprotein cholesterol (HDL-C) levels fell (P<0.05) raising the CHOL/HDL-C ratio (20%) (P<0.001). Considerable individual differences occurred in plasma lipoprotein responses to overfeeding. However, these changes were not random; significant within-pair resemblance registered for the response of plasma CHOL, TG, VLDL-TG, VLDL-C, LDL-TG, HDL-C, HDL-Apo A-I, HDL2-C, HDL3-C to overfeeding (0.48</=ri</=0.85). Furthermore, a high within-pair resemblance was found for changes in ratios of CHOL/HDL-C (ri=0.86, P<0.0001) and HDL2-C/HDL3-C (ri=0.69, P<0.01). These results strongly suggest that the response of plasma lipoproteins to chronic energy surplus has a significant genetic component as does the detrimental effect of chronic caloric affluence on CHD risk.

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.

Diurnal triglyceridaemia and insulin resistance in mildly obese subjects with normal fasting plasma lipids

OBJECTIVE

A novel method has been developed to study diurnal triglyceride (TG) profiles using repeated capillary self-measurements in an 'out-of-hospital' situation. We assessed the diurnal capillary TG (TGc) profile in males with mild obesity and evaluated the use of plasma and capillary TG as markers of insulin resistance.

DESIGN

Cross-sectional study.

SETTING AND SUBJECTS

Fifty-four lean (body mass index, BMI < 25 kg m-2) and 27 mildly obese (25 < BMI < 30 kg m-2), normolipidaemic males measured capillary TG concentrations on six fixed time-points over a 3-day period in an 'out-of-hospital' situation.

MAIN OUTCOME MEASURES

The total area under the TGc curve (TGc-AUC) and incremental area under the TGc curve (TGc-IAUC) were used as estimation of diurnal triglyceridaemia. Fasting blood samples were obtained once. Food intake was recorded by all participants.

RESULTS

Obese and lean subjects had comparable fasting capillary TG concentrations (1.37 +/- 0.40 mmol L-1 and 1.32 +/- 0.53 mmol L-1, respectively). However, during the day, obese subjects showed a greater TG increase, resulting in significantly higher TGc-AUC (27.1 +/- 8.4 and 23.0 +/- 6.3 mmol h-1 l-1, respectively; P < 0.05) and TGc-IAUC (7.9 +/- 5.8 and 4.6 +/- 6.6 mmolh-1 L-1, respectively; P < 0.05). The total group of 81 males was divided into quartiles based on fasting plasma TG, fasting capillary TG, TGc-AUC and TGc-IAUC. Amongst these variables, TGc-AUC was the only significant discriminator of subjects with high homeostasis model assessment (HOMA) (insulin resistance) compared with low HOMA (insulin sensitive). Overall, BMI was the strongest determinant of HOMA.

CONCLUSIONS

Diurnal TG profiles can be used to investigate postprandial lipaemia in both lean and mildly obese subjects and may help to detect subjects with an underlying disposition for hypertriglyceridaemia related to insulin resistance, i.e. the metabolic syndrome.

Reproducibility of the serum lipid response to coffee oil in healthy volunteers

Background

Humans and animals show a certain consistency in the response of their serum lipids to fat-modified diets. This may indicate a genetic basis underlying this response. Coffee oil might be used as a model substance to investigate which genes determine differences in the serum lipid response. Before carrying out such studies our objective was to investigate to what extent the effect of coffee oil on serum lipid concentrations is reproducible within subjects.

Methods

The serum lipid response of 32 healthy volunteers was measured twice in separate five-week periods in which coffee oil was administered (69 mg cafestol / day).

Results

Total cholesterol levels increased by 24% in period 1 (range:0;52%) and 18% in period 2 (1;48%), LDL cholesterol by 29 % (-9;71%) and 20% (-12;57%), triglycerides by 66% (16;175%) and 58% (-13;202%), and HDL cholesterol did not change significantly: The range of the HDL response was -19;25% in period 1 and -20;33% in period 2.

The correlation between the two responses was 0.20 (95%CI -0.16, 0.51) for total cholesterol, 0.16 (95%CI -0.20, 0.48) for LDL, 0.67 (95%CI 0.42, 0.83) for HDL, and 0.77 (95%CI 0.56, 0.88) for triglycerides.

Conclusions

The responses of total and LDL cholesterol to coffee oil were poorly reproducible within subjects. The responses of HDL and triglycerides, however, appeared to be highly reproducible. Therefore, investigating the genetic sources of the variation in the serum-lipid response to coffee oil is more promising for HDL and triglycerides.

The combined effects of apolipoprotein E polymorphism and low-density lipoprotein cholesterol on cognitive performance in young adults

This study examined the relations of apolipoprotein E (ApoE) genotype and the low-density lipoprotein (LDL) cholesterol level to cognitive performance of 57 randomly selected healthy young adults. From the ongoing population-based study of Cardiovascular Risk in Young Finns, 25 men and 32 women were ApoE genotyped and participated in mental arithmetic and reaction time tasks. In contrast to findings obtained from studies with elderly subjects, ApoE4 polymorphism was associated with better cognitive performance. In addition, LDL cholesterol moderated this association. In the ApoE4 genotype group, low LDL cholesterol was associated with good performance in the mental arithmetic test, whereas for those without ApoE4 genotype, low LDL cholesterol was associated with poor performance. Performance in the reaction time task did not differ between the ApoE groups. In conclusion, assessment of the influence of ApoE on cognitive performance may require taking additional physiological factors, such as the level of cholesterol, into account.

Genetic variation and the lipid response to dietary intervention: a systematic review

There is wide interindividual variation in the lipid and lipoprotein responses to dietary change, and the existence of consistent hypo- and hyperresponders supports the hypothesis that responsiveness is related to genetic variation. Many studies have investigated the possibility that the heterogeneity in responsiveness to changes in dietary fat, cholesterol, and fiber intake is explained by variation in genes whose products affect lipoprotein metabolism, eg, apolipoproteins, enzymes, and receptors. A systematic review of the literature was carried out to investigate the effect of genetic variation on the lipid response to dietary intervention. A search strategy for the MEDLINE database retrieved 2540 articles from 1966 to February 2002. This strategy was adapted and performed on the EMBASE database, which retrieved 2473 articles from 1980 to week 9, 2002. Reference lists from relevant journal articles were also checked. This is the first systematic review of the literature, and it summarizes results available from 74 relevant articles. There is evidence to suggest that variation in the genes for apolipoprotein (apo) A-I, apo A-IV, apo B, and apo E contributes to the heterogeneity in the lipid response to dietary intervention. However, the effects of genetic variation are not consistently seen and are sometimes conflicting. Future studies need to have much larger sample sizes based on power calculations and carefully controlled dietary interventions and should investigate the effects of polymorphisms in multiple genes instead of the effects of polymorphisms in single genes.

Apolipoprotein E gene polymorphism alters lipids before pancreas transplantation

BACKGROUND

Pancreas transplantation (PTX) improves lipids in patients with type 1 diabetes mellitus. However, there are patients who have persistent abnormal lipids or develop new hyperlipidemia despite PTX. One factor that may influence the lipid profile is apolipoprotein E (Apo E) genotype. Apo E polymorphism, particularly E2 and E4 alleles, increases the risk of dyslipidemia. Apo E2 has also been found to increase risk of diabetic nephropathy and so may be more prevalent in PTX candidates.

METHODS

This study evaluated fasting-lipid profiles in type 1 diabetes patients who were pancreas transplant candidates to prospectively evaluate the impact of Apo E genotype on dyslipidemia before and after PTX.

RESULTS

Presence of one or more E4 alleles resulted in higher triglycerides ( =0.0446), lower HDL ( =0.0247), and a higher cholesterol-to-HDL (C/H) ratio ( =0.0405) before PTX when compared with those with E3/3 genotype. After PTX, lipids improved so there was no longer a difference in fasting lipids between patients with an E4 allele and E3/3 genotype. Presence of an E2 allele had no significant impact on fasting lipids before or after PTX.

CONCLUSIONS

Presence of an Apo E4 allele worsened HDL, triglycerides, and C/H ratio before PTX compared with those with E3/3 genotype, whereas the presence of an Apo E2 allele had no significant effect on lipids before or after PTX. Thus, Apo E4 has a larger impact than Apo E2 on fasting-lipid profile in PTX candidates, and Apo E gene polymorphism does not worsen lipid dyslipidemia after PTX, despite introduction of immunosuppressant medications known to cause dyslipidemia.

Locus controlling LDL cholesterol response to dietary cholesterol is on baboon homologue of human chromosome 6

OBJECTIVE

Cholesterolemic responses to dietary lipids are known to be heritable, but the genes that may affect this response have yet to be identified. Using segregation analysis, we previously detected a potential quantitative trait locus (QTL) in baboons that influenced low density lipoprotein cholesterol response to dietary cholesterol. We performed linkage analyses to locate this QTL by using data on the baboon genetic linkage map.

METHODS AND RESULTS

We obtained evidence for linkage of this potential QTL to the same locus (D6S311) on the baboon homologue of human chromosome 6 by using variance components and parametric linkage analysis methods (2-point lod scores 4.17 [genomic probability value 0.008] and 2.81 [genomic P=0.10], respectively). Linkage analyses of serum levels of apolipoprotein B dietary response, a correlated trait, also gave weak suggestive evidence of linkage to this chromosomal region (maximum 2-point lod score 1.91). Although the LPA locus is nearby, we found no evidence of linkage with LPA.

CONCLUSIONS

This report is the first to localize, in any primate species, a potential QTL that influences low density lipoprotein cholesterol response to dietary cholesterol.

Apolipoprotein E and diets: a case of gene-nutrient interaction?

Apolipoprotein E has key functions in lipoprotein metabolism, and polymorphisms in the apolipoprotein E gene are associated with distinct lipoprotein patterns. The possibility of gene-nutrient interactions for apolipoprotein E has been addressed in many studies. Although results have generally been mixed, the indications for such an interaction have been more common in studies employing a metabolic challenge. Studies directly designed to examine apolipoprotein E gene-nutrient interactions are needed.

Genetic polymorphisms and lipid response to dietary changes in humans

BACKGROUND

Previous studies on the effects of genetic polymorphisms on the serum cholesterol response to dietary treatments were often inconsistent and frequently involved small numbers of subjects.

MATERIALS AND METHODS

We studied the effect of 10 genetic polymorphisms on the responses of serum cholesterol to saturated and trans fat, cholesterol and the coffee diterpene, cafestol, as measured in 26 dietary trials performed over 20 years in 405 mostly normolipidaemic subjects.

RESULTS

Apoprotein A4 360-2 allele attenuated the response of low-density lipoprotein cholesterol to dietary cholesterol, but not in women. Subjects with the cholesteryl ester transfer protein TaqIb-1 allele had -0.02 to -0.05 mmol L-1 smaller responses of high-density lipoprotein cholesterol to diet than those with the 2/2 genotype. The effects of the other eight polymorphisms on cholesterol response were either inconsistent with results in previous studies or need to be replicated in other studies.

CONCLUSIONS

Apoprotein A4360 and cholesteryl ester transfer protein TaqIb polymorphisms may affect dietary responses. However, no one single genotype was a major determinant of a subject's lipid response to diet. Therefore, knowledge of these genotypes by themselves is of little use in the identification of subjects who may or may not benefit from dietary treatment.

Apolipoprotein E genotype affects plasma lipid response to atorvastatin in a gender specific manner

The response to therapy with hypolipidemic agents shows considerable individual variation. These differences may be due to the interaction of environmental and genetic factors that affect drug bioavailability, receptor function or ligand structure. Our objective was to assess the effect of apolipoprotein (apo) E genotype and gender on lipid-lowering response to the HMG CoA reductase inhibitor, atorvastatin. Genotyping was carried out on DNA from 328 male and female subjects who participated in a multicentric, double-blind clinical trial, and received 10 mg/day of atorvastatin. Our data demonstrate no significant gender differences for LDL cholesterol levels at baseline. Moreover, mean LDL-C lowering was similar in men (-36.2%, range -2.7 to -57.8%) and in women (-38.1%, range -9.5 to -58.5%) as compared to baseline. However, men carrying the epsilon2 allele had a significantly higher mean LDL-C response (-44%) than epsilon3 homozygotes (-37%) and epsilon4 carriers (-34%); P=0.01 for apoE group by treatment interaction. No such gene/treatment interactions were noted in women, with those carrying the epsilon2 allele showing a similar mean response (-34%) as epsilon3 homozygotes (-39%) and epsilon4 carriers (-34%). Mean plasma triglyceride lowering with atorvastatin was 17%. A significant apoE group by treatment interaction (P=0.010) was also observed in men, with epsilon2 carriers being more responsive (-27%) than epsilon3/3 (-13%) and epsilon4 (-22%). This interaction was not observed in women. In summary, atorvastatin treatment had similar effects on plasma lipid levels in both men and women; however, the apoE gene locus was a significant predictor of LDL-C and TG responses to atorvastatin therapy in men, but not in women.

Association of the Sst-I polymorphism at the APOC3 gene locus with variations in lipid levels, lipoprotein subclass profiles and coronary heart disease risk: the Framingham offspring study

Apolipoprotein (apo) CIII participates in the regulation of the metabolism of triglyceride-rich lipoproteins and it is a major component of chylomicrons and VLDL. The APOC3 gene is on chromosome 11q23 and is highly polymorphic. The less common allele (S2) of the SstI polymorphism on the 3' untranslated region of the APOC3 gene has been previously associated with increased triglycerides, total cholesterol (TC), and apoCIII levels and cardiovascular risk on several, but not all, studies. The aim of this study was to examine the association of this polymorphism with plasma lipid levels, lipoprotein subfractions and coronary heart disease (CHD) risk in a population-based study: The Framingham Offspring Study. The frequency of the S2 allele was 0.086, consistent with previous reports in Caucasian populations. In men, the S2 allele was associated with lower concentrations of high-density lipoprotein cholesterol (HDL-C; P<0.04) and HDL2-C (P<0.02) and a significant increase in apoCIII non-HDL (P<0.05). TG levels were higher in men carriers of the S2 allele, but this association did not reach statistical significance (P=0.30). Conversely, in women, the S2 allele was associated with increased TC (P<0.03), low-density lipoprotein cholesterol (LDL-C; P<0.03), and ApoB levels (P<0.04). Lipoproteins subfractions were also examined using nuclear magnetic resonance (NMR) spectroscopy. S2 male carriers had significantly lower concentrations of large LDL and a significant reduction in LDL particle size (P<0.04). In women, there was a significant increase in intermediate LDL particles (P<0.05) with no significant effect on lipoprotein diameters. We also examined the associations between the S2 allele and biochemical markers of glucose metabolism. In men, the S2 allele was associated with elevated fasting insulin concentrations (P<0.04), whereas no significant associations were observed in women. Despite the described associations with lipid and glucose metabolism related risk factors, we did not find any significant increase in CHD risk associated with the S2 allele in this population.

DIETARY ANDGENETICEFFECTS ONLOW-DENSITYLIPOPROTEINHETEROGENEITY

We have tested whether differences in distribution and dietary responsiveness of low-density lipoprotein (LDL) subclasses contribute to the variability in the magnitude of LDL-cholesterol reduction induced by diets low in total and saturated fat and high in carbohydrate. Our studies have focused on a common, genetically influenced metabolic profile, characterized by a predominance of small, dense LDL particles (subclass pattern B), that is associated with a two- to threefold increase in risk for coronary artery disease. We have found that healthy normolipidemic individuals with this trait show a greater reduction in LDL cholesterol and particle number in response to low-fat, high-carbohydrate diets than do unaffected individuals (subclass pattern A). Moreover, such diets result in reduced LDL particle size, with induction of pattern B in a substantial proportion of pattern A men. Recent studies have indicated that this response is under genetic influence. Future identification of the specific genes involved may lead to improved targeting of dietary therapies aimed at reducing cardiovascular disease risk.

Apolipoprotein E genotype and cardiovascular disease in the Framingham Heart Study

BACKGROUND

Apolipoprotein (apo) E is a constituent of lipoproteins with considerable variation due to cysteine-arginine exchanges. The apo E4 (Arg112-Cys) polymorphism has been associated with dementia and hypercholesterolemia. We investigated the relation of APOE genotype to cardiovascular disease (CVD) in the Framingham Offspring Study.

METHODS AND RESULTS

DNA was isolated from 3413 study participants and APOE genotypes were determined utilizing the polymerase chain reaction and restriction isotyping. In the entire group of subjects, 20.7% had apo E4/4 or E3/4 (Group E4); 14.1% had apo E2/2 or E2/3 (Group E2) and 63.9% had the apo E3/3 genotype (Group E3). Subjects with E2/4 (1.3%) were excluded. Period prevalence of CVD between examinations 1 and 5 (1971-1994) (366 events) was related to APOE genotype. Age adjusted period prevalence of CVD in men was 18.6% for Group E4, 18.2% for Group E2 and 12.7% for Group E3 (P=0.004); while in women these rates were 9.9, 4.9, and 6.6%, respectively (P=0.037). After adjustment for non-lipid risk factors the relative odds for CVD in Group E2 men was 1.79 (P=0.0098) and in Group E4 it was 1.63 (P=0.0086) compared with the Group E3; while in Group E4 women it was 1.56 (P=0.054). After adjustment for all CVD risk factors, the relative odds in Group E2 men was 1.94 (P=0.004) and in Group E4 men it was 1.51 (P=0.0262).

CONCLUSIONS

The presence of the apo E2 or apo E4 alleles in men is associated with significantly greater CVD risk. This genotypic information may help to identify individuals at increased risk for CVD events.

Gene-diet interactions and plasma lipoproteins: role of apolipoprotein E and habitual saturated fat intake

To test whether plasma lipoprotein levels and low density lipoprotein (LDL) particle size are modulated by an interaction between habitual saturated fat intake and apolipoprotein E (APOE) genotype, we studied 420 randomly selected free-living Costa Ricans. The APOE allele frequencies were 0.03 for APOE2, 0.91 for APOE3, and 0.06 for APOE4. The median saturated fat intake, 11% of energy, was used to divide the population into two groups, LOW-SAT (mean intake 8.6% energy) represents those below median intake, and HIGH-SAT (mean intake 13.5%) represents those above median intake. Significant interactions between APOE genotype and diet were found for VLDL (P = 0.03) and HDL cholesterol (P = 0.02). Higher saturated fat intake was associated with higher VLDL cholesterol (+29%) and lower HDL cholesterol (-22%) in APOE2 carriers, while the opposite association was observed in APOE4 carriers (-31% for VLDL cholesterol and +10% for HDL cholesterol). Higher saturated fat intake was associated with smaller LDL particles (-2%, P < 0.05) in APOE2 carriers, and larger LDL particles (+2%, P < 0.05) in APOE4 carriers, but the gene-diet interaction was not statistically significant (P = 0.09). Higher saturated fat intake was associated with higher LDL cholesterol in all genotypes (mean +/- SEM, LOW-SAT 2.61 +/- 0.05 vs. HIGH-SAT 2.84 +/- 0.05 mmol/L, P = 0.009). These data suggest that the APOE2 allele could modulate the effect of habitual saturated fat on VLDL cholesterol and HDL cholesterol in a population with an average habitual total fat intake of less than 30%.

Apolipoprotein E polymorphisms and concentration in chronic diseases and drug responses

Apolipoprotein (apo) E is an important circulating and tissue protein involved in cholesterol homeostasis and many other functions. The common polymorphism in the coding region of the gene, four polymorphisms in the promoter region, other additional single nucleotide polymorphisms, as well as several apo E variants have been identified. The common coding polymorphism strongly influences the lipid metabolism and the circulating concentration of apo E itself. This polymorphism is at the origin of the implication of apo E in cardiovascular and neurodegenerative diseases, but also of the relation of apo E with longevity. Probably due to its many metabolic and functional consequences, apo E polymorphism has been shown to influence the responses of patients to several drugs (fibrates, statins, hormone replacement therapy, anti-Alzheimer drugs) or environmental interventions (black tea, alcohol, diet). Apo E genotyping may be clinically helpful in defining the risk of patients and their responses to therapeutics. Finally, circulating apo E concentration appears to be altered in diseases and can be modulated by some of the drugs cited above. This parameter can thus also give interesting clinical information and could be a therapeutic target, providing it is validated. At the present time, we cannot exclude that apo E concentration may be the most prominent apo E parameter to be considered in health and disease, while apo E polymorphisms would represent only secondary parameters influencing apo E concentration.

[Apolipoprotein E gene polymorphism and risk of hypercholesterolemia: a case control study in a working population of Valencia]

BACKGROUND

The apolipoprotein E (apoE) gene is polymorphic with three common alleles (epsilon 2, epsilon 3, epsilon 4) whose allelic frequency and association with lipid levels varies from population to population. The aim of this study was to estimate the association between these genetic variants and the risk of hypercholesterolemia in a Mediterranean Spanish population.

PATIENTS AND METHODS

A case-control study in a working population from Valencia was carried out. A total of 330 cases (148 men and 182 women) with moderate hypercholesterolemia (total cholesterol > 200 mg/dl or with lipid lowering treatment) and age range 20 to 60 years, were identified. 330 normocholesterolemic controls matched by age and sex were selected. From all of them data of apoE genotype, body mass index, lipid and lipoprotein levels, socioeconomic and life-style variables were obtained.

RESULTS

The epsilon 2 allele frequency was statistically lower in cases (0.033) than in controls (0.086). The epsilon 4 allele frequency was higher in cases (0.115) than in controls (0.039). In the crude logistic regression analysis, the apoE polymorphism was related (p < 0.001) to the risk of hypercholesterolemia. After adjustment by age, body mass index, educational level, tobacco smoking, alcohol consumption and physical activity the epsilon 2 allele was associated with a lower risk of hypercholesterolemia (odds ratio [OR] = 0.36; 95% confidence interval (CI): 0.20-0.64), and the epsilon 4 allele was associated with a higher risk (OR = 3.04; 95% CI: 1.82-5.06).

CONCLUSIONS

The apoE genotype was significantly related to the risk of moderate hypercholesterolemia in the Mediterranean Spanish population.

Genetic determinants of plasma lipid response to dietary intervention: the role of the APOA1/C3/A4 gene cluster and the APOE gene

Polymorphisms at the APOA1/C3/A4 gene cluster and the APOE gene have been extensively studied in order to examine their potential association with plasma lipid levels, coronary heart disease risk and more recently with inter-individual variability in response to dietary therapies. Although the results have not been uniform across studies, the current research supports the concept that variation at these genes explains a significant, but still rather small, proportion of the variability in fasting and postprandial plasma lipid responses to dietary interventions. This information constitutes the initial frame to develop panels of genetic markers that could be used to predict individual responsiveness to dietary therapy for the prevention of coronary heart disease. Future progress in this complex area will come from experiments carried out using animal models, and from carefully controlled dietary protocols in humans that should include the assessment of several other candidate gene loci coding for products that play a relevant role in lipoprotein metabolism (i.e. APOB, CETP, LPL, FABP2, SRBI, ABC1 and CYP7).

Genetic predictors of plasma lipid response to diet intervention

There is a growing interest in determining the genetic predictors of plasma lipid response to diet intervention. Several candidate gene loci, namely, apolipoprotein (APO) A1, APOA4, APOC3, APOB, APOE, CETP, LPL, and FABP2, have been shown to explain a significant, but still rather small, proportion of the interindividual variability in dietary response. Other gene loci code for products that play a relevant role in lipoprotein metabolism and are prime candidates for future studies (ie, CYP7). Future progress in this complex area will come from experiments carried out using animal models and from carefully controlled dietary protocols in humans.

Treatment of dyslipidemia: genetic interactions with diet and drug therapy

Coronary heart disease (CHD) is multifactorial, and its manifestation is determined by multiple gene loci and their interaction with a cohort of environmental factors. Variation at several candidate gene loci has already been shown to have a significant effect over the spectrum of plasma lipid levels observed in the population. Moreover, some variants are known to influence the interindividual variability in response to dietary and pharmacologic interventions aimed to reduce atherogenic lipoproteins. The continuous progress in this area of research is getting us closer to the development of genetic screening panels that will allow a more precise assessment of individual CHD risk and response to therapeutic interventions.