Influence of mutation in human apolipoprotein A-1 gene promoter on plasma LDL cholesterol response to dietary fat

[Influence of rs670 variant of APOA1 gene on serum HDL response to an enriched-polyunsaturated vs. an enriched-monounsaturated fat hypocaloric diet]

Introduction

Background and objectives: genetic variants of the APOA1 gene have been related to lipid profile in obese subjects. Our aim was to analyze the effects of the rs670 APOA1 gene polymorphism on metabolic changes secondary to an enriched-polyunsaturated fat vs. an enriched-monounsaturated fat hypocaloric diet. Methods: 360 Caucasian obese subjects were randomly allocated to two groups. One group received an enriched-polyunsaturated fat (diet P) and the other an enriched-monounsaturated fat hypocaloric diet (diet M) during 12 weeks. The effects on serum biomarkers related to lipid and carbohydrate metabolism were evaluated before and after the dietary intervention. Results: after both diets, body mass index, weight, fat mass, waist circumference, systolic blood pressure, plasma leptin concentration, and waist circumference decreased in all patients. After 12 weeks of intervention with diet P, plasma insulin levels and HOMA-IR decreased in A-allele carriers: delta: -7.3 ± 2.2 IU/L (p = 0.01), and delta: -2.8 ± 0.5 units (p = 0.02), respectively. The same changes in delta were observed after diet M in A-allele carriers: insulin delta: -5.9 ± 1.2 IU/L (p = 0.01), and HOMA-IR delta: -2.1 ± 0.8 units (p = 0.02). In A-allele carriers, LDL-cholesterol decreased and HDL-cholesterol increased after the dietary intervention with diet P: delta: -12.1 ± 4.3 mg/dL (p = 0.01), and delta: 2.6 ± 0.7 mg/dL (p = 0.01), respectively. No differences in lipid profile were observed after diet M. These improvements were not observed in non-A-allele carriers after both interventions. Conclusions: our study showed the association of the rs670 ApoA1 polymorphism with insulin resistance changes as induced by both diets. An enriched-polyunsaturated fat diet produced an additional improvement of HDL-cholesterol and LDL-cholesterol in A-allele carriers.

Role of rs670 variant of APOA1 gene on metabolic response after a high fat vs. a low fat hypocaloric diets in obese human subjects

BACKGROUND & AIMS

A common G-to-A transition located 75 base pairs upstream (rs670) from transcription start site of the APOA1 gene has been related with some metabolic parameters. Our aim was to analyze the effects of rs670 APOA1 gene polymorphism on lipid profile and metabolic changes after two different hypocaloric diets.

METHODS

282 obese subjects were randomly allocated during 12 weeks (Diet HF - high fat diet vs. Diet LF - low fat diet). Anthropometric and biochemical status were evaluated.

RESULTS

Body mass index, weight, fat mass, waist circumference, systolic blood pressure, leptin levels and waist circumference decreased in all patients in average after both diets. In A allele carriers after 12 weeks with both diets, insulin levels (Delta diet HF: -5.3 + 1.2 UI/L; P = 0.02 and Delta diet LF: -5.8 + 1.3 UI/L; P = 0.02) and HOMA-IR (Delta diet HF: -2.9 + 0.8 units; P = 0.01 and Delta diet LF: -2.2 + 0.9 units; P = 0.03) improved in a significant way. With the low fat diet, A allele carriers showed a statistical improvement in HDL-cholesterol levels (Delta: 4 + 1 mg/dl; P = 0.03).

CONCLUSIONS

Our study showed the association of rs670 ApoA1 polymorphism with a decrease of insulin resistance induced by both diets and provided additional evidence on HDL-cholesterol increase after a LF hypocaloric diet in A allele carriers.

Role of rs670 variant of APOA1 gene on lipid profile, insulin resistance and adipokine levels in obese subjects after weight loss with a dietary intervention

OBJECTIVE

The aim of this study was to analyze the effects of rs670 APOA1 gene polymorphism on obesity parameters, lipid profile, glucose metabolism markers, blood pressure and adipokine levels after a hypocaloric diet with Mediterranean pattern.

MATERIAL AND METHODS

A population of 82 obese patients was studied before and after 12 weeks on a hypocaloric diet (500 kcal per day) in an interventional study of one arm. GG and GA + AA subjects receiving the same diet. Anthropometric measures and biochemical parameters (lipid profile, glucose metabolism, blood pressure and adipokine levels) were measured. Genotype of ApoA1 gene polymorphism (rs670) was evaluated. The A allele is the risk allele.

RESULTS

After dietary intervention and in both genotype groups (GG vs. GA + AA), body mass index (BMI) (delta: -1.0 ± 0.8 kg/m² vs. -1.4 ± 1.0 kg/m²: p = 0.02), weight (delta: -2.6 ± 2.1 kg vs. -3.6 ± 2.2 kg: p = 0.03), fat mass (delta: -1.6 ± 1.1 kg vs. -3.2 ± 1.0 kg: p = 0.01) and waist circumference (delta: -1.8 ± 0.6 cm vs. -2.2 ± 1.1 cm: p = 0.02) decreased. The decrease of the anthropometric parameters was higher in A allele carriers than non-A allele carriers. In A allele carriers, total cholesterol (delta: -11.1 ± 7.1 mg/dl vs. -20.1 ± 9.0 mg/dl: p = 0.02), LDL cholesterol (delta: -10.7 ± 4.1 mg/dl vs. -21.2 ± 8.0 mg/dl: p = 0.01), insulin levels (delta: -0.6 ± 0.8 UI/L vs. 3.7 ± 1.1 UI/L; p = 0.002) and insulin resistance with HOMA-IR (delta: -0.2 ± 0.3 units vs. 0.8 ± 0.4 units; p = 0.01) decreased. The improvement of leptin was similar in both genotype groups. Resistin and adiponectin levels remained unchanged after dietary intervention.

CONCLUSION

In this study the APOA1 (rs670) gene showed important effects on body weight, adiposity, LDL-cholesterol levels and insulin resistance after 12 weeks of the dietary intervention.

Dietary patterns interact with APOA1/APOC3 polymorphisms to alter the risk of the metabolic syndrome: the Tehran Lipid and Glucose Study

The interaction of genetic and dietary factors, as an area of CVD research, has been explored poorly. The aim of the present study was to examine the interaction of dietary patterns and three genetic variants of APOA1 and APOC3, both independently and in combination, relative to the risk of the metabolic syndrome (MetS) in Tehranian adults. In the present matched, nested case–control study, 414 subjects with the MetS and 414 controls were selected from the participants of the Tehran Lipid and Glucose Study. Dietary patterns were determined by factor analysis. APOC3 (rs5128 3238C>G) and APOA1 (rs670, − 75G>A and rs5069,+83C>T) SNP were genotyped by the conventional PCR followed by the restriction fragment length polymorphism technique. Overall, three major dietary patterns were extracted: healthy dietary pattern (HDP); Western dietary pattern (WDP); fat–sweet dietary pattern (FSDP). The A and T allele carriers of the APOA1 SNP had a greater risk of developing the MetS in the highest quartile of WDP scores (OR 3·22, 95 % CI 1·21, 8·58, Pinteraction= 0·03). Compared with other genotype combinations, the combined effect of APOC3/APOA1 (CC/GA+AA/CT+TT) genotypes showed a further increase in the risk of the MetS in the highest quartile of WDP scores (OR 1, 2·49, 8·73, 6·32, Ptrend< 0·001, Pinteraction= 0·003). A significant interaction was found between the quartiles of FSDP scores and the APOA1 diplotype (GA+AA/CT+TT). OR for these genotype carriers were 1, 0·65, 0·57 and 0·22 (Ptrend= 0·006) in the lowest to the highest quartile of FSDP scores when compared with the other combined genotypes (Pinteraction= 0·03). Our findings suggest that the WDP and FSDP are associated with APOA1 and APOC3 SNP in relation to the risk of the MetS.

FTO T/A and peroxisome proliferator-activated receptor-γ Pro12Ala polymorphisms but not ApoA1 -75 are associated with better response to lifestyle intervention in Brazilians at high cardiometabolic risk

BACKGROUND

The role of obesity-related polymorphisms on weight loss and inflammatory responses to interventions is unclear. We investigated associations of certain polymorphisms with response to a lifestyle intervention.

METHODS

This 9-month intervention on diet and physical activity included 180 Brazilians at high cardiometabolic risk, genotyped for the fat mass and obesity-associated (FTO) T/A, peroxisome proliferator-activated receptor-γ (PPARγ) Pro12Ala, and ApoA1 -75G/A polymorphisms. Changes in metabolic and inflammatory variables were analyzed according to these polymorphisms.

RESULTS

The intervention resulted in lower energy intake and higher physical activity. Anthropometric measurements, 2-hr plasma glucose, insulin, high-density lipoprotein cholesterol (HDL-C), and apolipoprotein B (ApoB) improved significantly for the total sample, and these benefits were similar among genotypes. Only variant allele carriers of FTO T/A decreased fasting plasma glucose after intervention (99.9±1.3 to 95.6±1.4 mg/dL, P=0.021). Mean blood pressure reduced after intervention in variant allele carriers of the PPARγ Pro12Ala (109.4±2.1 to 101.3±2.1 mmHg, P<0.001). Improvement in lipid variables was not significant after adjustment for medication. Only the reference genotype of PPARγ Pro12Ala increased apolipoprotein A1 (ApoA1) after intervention (134.3±2.4 to 140.6±2.3 mg/dL, P<0.001). Only variant allele carriers of FTO reduced C-reactive protein (CRP) concentration (0.366±0.031 to 0.286±0.029 mg/dL, P=0.023).

CONCLUSION

In Brazilian individuals, the FTO T/A polymorphism induces a favorable impact on inflammatory status and glucose metabolism. The reference genotype of PPARγ Pro12Ala seems to favor a better lipid profile, while the variant allele decreases blood pressure. Our data did not support benefits of the variant allele of ApoA1 -75G/A polymorphism. Further studies are needed to direct lifestyle intervention to subsets of individuals at cardiometabolic risk.

Nutritional genomics for the characterization of the effect of bioactive molecules in lipid metabolism and related pathways

Cardiovascular disease and cancer are the main causes of morbidity and mortality worldwide. Thus, investigators have focused their efforts on gaining insight into understanding the mechanisms involved in the development and evolution of these diseases. In the past decade, and with the contribution of the -omics technologies, strong evidence has supported an essential role of gene-nutrient interactions in these processes, pointing at natural bioactive molecules as promising complementary agents that are useful in preventing or mitigating these diseases. In addition, alterations in lipid metabolism have recently gained strong interest since they have been described as a common event required for the progression of both diseases. In the present review, we give an overview of lipid metabolism, mainly focusing on lipoprotein metabolism and the mechanisms controlling lipid homeostasis. In addition, we review the modulation of lipid metabolism by bioactive molecules, highlighting their potential use as therapeutic agents in preventing, and treating chronic diseases such as cardiovascular disease and cancer. Finally, we report the usefulness of the -omics technologies in nutritional research, focusing on recent findings, within nutritional genomics, in the interaction of bioactive components from foods with several genes that are involved in the development and progression of these diseases.

Nutrigenetics of the lipoprotein metabolism

It is well known that lipid metabolism is a cornerstone in the development of the commonest important chronic diseases worldwide, such as obesity, cardiovascular disease, or metabolic syndrome. In this regard, the area of lipid and lipoprotein metabolism is one of the areas in which the understanding of the development and progression of those metabolic disorders has been studied in greater depth. Thus, growing evidence has demonstrated that while universal recommendations might be appropriate for the general population, in this area there is great variability among individuals, related to a combination of environmental and genetic factors. Moreover, the interaction between genetic and dietary components has helped in understanding this variability. Therefore, with further study into the interaction between the most important genetic markers or single-nucleotide polymorphisms (SNPs) and diet, it may be possible to understand the variability in lipid metabolism, which could lead to an increase in the use of personalized nutrition as the best support to combat metabolic disorders. This review discusses some of the evidence in which candidate SNPs can affect the key players of lipid metabolism and how their phenotypic manifestations can be modified by dietary intake.

Gene-nutrient interactions and gender may modulate the association between ApoA1 and ApoB gene polymorphisms and metabolic syndrome risk

OBJECTIVE

Dyslipidemia is a key feature of the metabolic syndrome (MetS), which is determined by both genetic and dietary factors.

METHODS

We determined the relationships between ApoA1 and ApoB polymorphisms and MetS risk, and whether dietary fat modulates this in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754).

RESULTS

ApoB rs512535 and ApoA1 rs670 major G allele homozygotes had increased MetS risk (OR 1.65 [CI 1.24, 2.20], P = 0.0006; OR 1.42 [CI 1.08, 1.87], P = 0.013), which may be, partly, explained by their increased abdominal obesity and impaired insulin sensitivity (P<0.05) but not dyslipidemia. Interestingly these associations derived primarily from the male GG homozygotes (ApoB rs512535 OR 1.92 [CI 1.31, 2.81], P = 0.0008; ApoA1 rs670 OR 1.50 [CI 1.05, 2.12], P = 0.024). MetS risk was exacerbated among the habitual high-fat consumers (>35% energy) (ApoB rs512535 OR 2.00 [CI 1.14, 3.51], P = 0.015; OR 1.58 [CI 1.11, 2.25], P = 0.012 for ApoA1 rs670). In addition a high monounsaturated fat (MUFA) intake (>14% energy) increased MetS risk (OR 1.89 [CI 1.08, 3.30], P = 0.026 and OR 1.57 [CI 1.10, 2.40], P = 0.014 for ApoB rs512535 and ApoA1 rs670, respectively). MetS risk was abolished among the habitual low-fat consumers (<35% energy). Saturated and polyunsaturated fat intake did not modulate MetS risk.

CONCLUSION

ApoB rs512535 and ApoA1 rs670 may influence MetS risk. Apparent modulation of these associations by gender and dietary fat composition suggests novel gene-gender-diet interactions.

The common apolipoprotein A-1 polymorphism -75A>G is associated with ethnic differences in recurrent coronary events after recovery from an acute myocardial infarction

Since data regarding the relationship between a common polymorphism (SNP) of the apoA1 gene with apoA1 levels and risk of coronary artery disease are inconsistent, we hypothesized that its association with recurrent coronary events differs for White and Black individuals with diagnosed coronary heart disease. The apoA1 -75G>A SNP was genotyped in a cohort of 834 Black (n=129) and White (n=705) post-myocardial infarction patients. Recurrent coronary events (coronary-related death, non-fatal myocardial infarction, or unstable angina) were documented during an average follow-up of 28 months. Thirty percent of White and 21% of Black patients carried the SNP. Cox proportional-hazards regression analysis, adjusting for clinical and laboratory covariates, demonstrated that the SNP was not associated with recurrent events in the total cohort (HR=1.37, 95% CI 0.95-1.97; p= 0.09) but was the only variable associated with an increased risk of recurrent cardiac events in Blacks (HR=2.40, 95% CI 1.07-5.40; p= 0.034). Conversely in Whites, the SNP was not associated with recurrent events (HR=1.12, 95% CI 0.75-1.67; p= 0.59) whereas apoB (HR=1.78, 95% CI 1.20 -2.65; p= 0.0042) and calcium channel blocker use (HR=2.53, 95% CI 1.72-3.72; p<0.001) were associated; p= 0.0024 for interaction between ethnicity and the SNP. A common apoA1 SNP is associated with a significantly increased risk of recurrent cardiac events among Black, but not White, postmyocardial infarction patients. Relationships with lipoproteins may help explain this finding.

Angiotensin-converting enzyme and apolipoproteins genes polymorphism in coronary artery disease

BACKGROUND

Association between angiotensin-converting enzyme (ACE) as well as apolipoprotein (apo) AI, B, and E polymorphisms and dyslipidemia and coronary artery disease (CAD) is controversial.

HYPOTHESIS

This study assessed the distribution of ACE insertion/deletion, apo AI A/G mutation, apo B signal peptide insertion/deletion, apo B XbaI restriction fragment length, and apo E polymorphisms in 388 nondiabetic patients.

METHODS

The study population included 112 patients with stable CAD, 139 patients with acute myocardial infarction (AMI), and 137 age-matched control subjects.

RESULTS

Univariate analysis showed higher prevalence of XbaI X+/X+ genotype in patients with CAD (p = 0.02). Angiotensin-converting enzyme and apo polymorphisms were not associated with lipid levels or severity of CAD. When all genotypes known to be related to CAD; such as ACE DD, apo AI GG, apo B del/del, and XbaI X+X+, and E4 allele of apo E, were pooled, again no significant differences among groups were seen. Multivariate regression analysis disclosed traditional risk factors and elevated levels of apo B for men and reduced levels of apo AI for women as independent variables for CAD.

CONCLUSIONS

In addition to traditional coronary risk factors, apo B and AI could be considered predictors of CAD. No association between either form of CAD and polymorphisms was noted.

ApolipoproteinA1-75 G/A (M1-) polymorphism and lipoprotein(a); anti- vs. pro-Atherogenic properties

BACKGROUND

ApolipoproteinA1 (apoA1) is the major apoprotein constituent of high-density-lipoprotein(HDL). The relationship of apoA1 -75 bp(M1-) allele polymorphism with lipoprotein phenotype and cardiovascular disease (CVD) remain unclear. Overnight fasting blood samples were collected from a cohort of high-risk Omani population, 90 non-diabetic subjects and 149 type 2 diabetes mellitus (T2DM) subjects for genotype and phenotype studies.

RESULTS

The M1+ and M1- alleles frequencies were 0.808 and 0.192 for M1+ and M1-, respectively, comparable to the frequency of apoA1 (M1+ and M1-) amongst a healthy Omani population, 0.788 and 0.212, respectively. The frequencies of the hetero- and homozygous subjects for the MspI polymorphism at -75 (M1-) of the apoA1 gene were in Hardy-Weinberg equilibrium. The mean Lp(a) concentration was significantly higher(P = 0.02) in subjects carrying M1- allele compared to M1+ allele of the APOA1 gene with an odd ratio of 2.3(95% CI, 1.13-14.3), irrespective of gender and the diabetic status.

CONCLUSION

ApolipoproteinA1-75 G/A (M1-) polymorphism is relatively common and is positively associated with Lp(a) and therefore, may confer a potential risk for cardiovascular disease (CVD).

Polymorphisms in the APOA1/C3/A4/A5 gene cluster and cholesterol responsiveness to dietary change

BACKGROUND

The relationship between dietary composition and plasma lipids is to some extent genetically determined. It has been found that variants of some genes (e.g., apolipoprotein E and cholesterol 7-alpha hydroxylase) play an important role in changes in plasma lipid levels in response to dietary intervention. We analyzed the effect of variation in the apolipoprotein (APO) APOA1/C3/A4/A5 gene cluster on decreases in plasma cholesterol levels over an 8-year follow-up study.

METHODS

Men (n=133) from the Czech population, for which dietary composition has markedly changed (red meat 80-->68 kg/person/year, animal fat 16-->9 kg/person/year, fruits and vegetables 133-->150 kg/person/year) were recruited. APOA1 (G-75>A and C83>T), APOC3 (C-482>T and C3238>G), APOA4 (Thr347>Ser and Gln360His) and APOA5 (T-1131>C, Ser19>Trp and Val153>Met) variants were analyzed by PCR and restriction analysis. Lipid levels were analyzed in 1988 and 1996. Dietary information was obtained from the Institute of Agricultural Economy.

RESULTS

In APOA5 Ser19Ser homozygotes (n=105), plasma cholesterol was relatively stable over the years (6.1+/-1.3 and 5.6+/-1.0 mmol/L in 1988 and 1996), but the decrease was much higher in Trp19 carriers (n=27; 6.5+/-1.6 vs. 5.1+/-1.1 mmol/L). This difference in change is significant at p<0.005. Similarly, a better response to dietary changes was detected in carriers of the common APOA4 haplotypes Thr-347Thr/Gln360Gln and Thr347Ser/Gln360Gln (n=102; 6.3+/-1.3 and 5.5+/-1.1 mmol/L in 1988 and 1996, p<0.001). Total cholesterol was relatively stable over time in carriers (n=18) of at least one His360 allele and/or two Ser347 alleles (5.7+/-1.1 and 5.5+/-0.9 mmol/L in 1988 and 1996, n.s.). Other variants analyzed did not influence the change in lipid measurements over time.

CONCLUSIONS

APOA4 and APOA5 variants may play an important role in the individual sensitivity of lipid parameters to dietary composition in men.

Variation in the cholesteryl ester transfer protein (CETP) gene does not influence individual plasma cholesterol response to changes in the nature of dietary fat

BACKGROUND AND AIMS

Some individuals respond to a greater extent than others to changes in dietary fat and cholesterol even when dietary intake is consistent. A prospective study has been undertaken in which two groups of individuals according to cholesteryl ester transfer protein (CETP) genotype were compared in terms of plasma lipid response to altering the nature of dietary fat in a free-living situation.

METHODS AND RESULTS

Following genotyping, 35 individuals with the CETP Taq1 B1B1 genotype were paired with age and sex-matched individuals with one or two CETP B2 alleles, to undertake a single crossover trial with a diet high in saturated fat and a diet high in polyunsaturated fat. There was no washout period between the two 4-week phases. Plasma lipoproteins were measured at the beginning and end of each phase. The difference (95% CI) in plasma LDL-cholesterol concentration at the end of the PUFA and SAFA diets was 0.95 (0.71, 1.19) mmol/l in the CETP B1B1 group and 0.80 (0.57, 1.04) mmol/l in the group with at least one CETP B2 allele. The dietary induced changes in the two genotype groups were not significantly different (p=0.38) from each other. Comparable results were observed for plasma total cholesterol. The high PUFA and SAFA diets did not significantly alter plasma HDL concentration in either of the CETP genotype groups. Response was also similar according to apolipoprotein E genotype (E3E3 vs E4+) and lipoprotein lipase genotype (S447X).

CONCLUSIONS

The results of this study do not support previous studies in which CETP genotype predicted plasma LDL-cholesterol response to diet. CETP genotype does not significantly affect the change in plasma total and LDL-cholesterol concentrations that occur when altering the nature of dietary fat. These data suggest that the influence of genetic factors on total and LDL-cholesterol may be relatively small in comparison with the effect of dietary manipulation.

APOA1 polymorphism influences risk for early-onset nonfamiliar AD

Alterations in cholesterol homeostasis influence the risk for Alzheimer's disease (AD). Apolipoprotein A1 is the major apolipoprotein of the high-density lipoprotein and is involved in reverse cholesterol transport. Variation in the apolipoprotein A1 gene (APOA1) might influence the function of the protein, and thus brain cholesterol metabolism, leading to an increased risk for AD. Two polymorphisms of APOA1, a G/A substitution at position -75bp and a C/T and G/A base substitution at position +83bp or +84bp, or both, in the APOA1 promoter, have been described. We investigated the effect of these polymorphisms on the risk for AD in 427 AD patients and 500 healthy control subjects of German and English descent. The A allele of the APOA1 -75bp G/A polymorphism was associated with an increased risk for AD in subjects with an age at onset of 66 years or younger. Further data analysis indicated that AD patients homozygous for the A allele at position -75bp presented with disease onset 8 years earlier than carriers of at least one G allele. No influence of the +83/84bp polymorphism on the risk for AD was observed. These results suggest that variants of APOA1 might influence the onset and the risk for AD.

Association between MspI polymorphism of the APO AI gene and Type 2 diabetes mellitus

AIMS

Genes of the Apo AI/CIII/AIV cluster on chromosome 11 have been related to plasma lipid patterns. The close relationship between carbohydrate metabolism and lipid metabolism warrants investigation of the association between this cluster and Type 2 diabetes mellitus. We therefore examined the possible association between polymorphisms of this cluster and Type 2 diabetes mellitus as part of a study of the prevalence of diabetes and the metabolic syndrome in southern Spain.

METHODS

A total of 1224 persons were selected randomly from the town of Pizarra in the province of Malaga, southern Spain. The sample errors for the prevalence of Type 2 diabetes mellitus and the three polymorphisms studied were all < or = 4%. All subjects underwent phenotyping after an oral glucose tolerance test (75 g) (WHO 1998 criteria) and the XmnI and MspI polymorphisms of Apo AI and the SstI polymorphism of Apo CIII were genotyped.

RESULTS

Those subjects with the mutated AA genotype of the MspI polymorphism (-75 G-->A) of Apo AI had a greater risk of impaired glucose tolerance [odds ratio (OR) = 1.95, CI = 1.02-3.8, P = 0.05], Type 2 diabetes mellitus, both known (OR = 7.38, CI = 1.3-39.7, P = 0.02) and unknown (OR = 3.7, CI = 1.4-9.9, P = 0.009). This risk was independent of age, sex, obesity, triglyceride level, HDL cholesterol and pattern of insulin resistance.

CONCLUSIONS

Pending confirmation in prospective studies, the AA genotype of the MspI polymorphism of the Apo AI gene, within the Apo A-I/C-III/A-IV cluster, seems to be a risk factor for Type 2 diabetes mellitus.

Nutritional genomics

Nutritional genomics has tremendous potential to change the future of dietary guidelines and personal recommendations. Nutrigenetics will provide the basis for personalized dietary recommendations based on the individual's genetic make up. This approach has been used for decades for certain monogenic diseases; however, the challenge is to implement a similar concept for common multifactorial disorders and to develop tools to detect genetic predisposition and to prevent common disorders decades before their manifestation. The preliminary results involving gene-diet interactions for cardiovascular diseases and cancer are promising, but mostly inconclusive. Success in this area will require the integration of different disciplines and investigators working on large population studies designed to adequately investigate gene-environment interactions. Despite the current difficulties, preliminary evidence strongly suggests that the concept should work and that we will be able to harness the information contained in our genomes to achieve successful aging using behavioral changes; nutrition will be the cornerstone of this endeavor.

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.

Obesity and alcohol modulate the effect of apolipoprotein E polymorphism on lipids and insulin

OBJECTIVE

To assess the interaction between apolipoprotein (apo) E polymorphism, alcohol consumption, and BMI on insulin, lipid, and lipoprotein levels in men.

RESEARCH METHODS AND PROCEDURES

Cross-sectional study of 266 healthy men without hypolipidemic or antidiabetic drug treatment. BMI, apo E polymorphisms, insulin, and lipid and lipoprotein levels were assessed. Alcohol consumption was assessed by questionnaire. epsilon2/epsilon4 carriers were excluded from the analysis.

RESULTS

On bivariate analysis, epsilon2 carriers had lower levels of total and low-density lipoprotein cholesterol and higher levels of apo E and lipoparticle B:E than epsilon3 carriers, the opposite being found for epsilon4 carriers compared with epsilon3 carriers; epsilon4 carriers also had significantly higher insulin levels. On multivariate analysis, significant interactions (p < 0.04) between apo E alleles and increased BMI were found for total and low-density lipoprotein cholesterol and insulin levels, the increase in those parameters with BMI being stronger among epsilon4 carriers than among epsilon3 or epsilon2 carriers. Significant interactions (p < 0.02) between apo E alleles and alcohol consumption were also found for apo B levels, which increased in epsilon2 carriers but remained relatively stable in epsilon3 and tended to decrease in epsilon4 carriers.

DISCUSSION

These data suggest that effects of apo E alleles on lipids and insulin levels are partly dependent on environmental variables such as BMI and alcohol intake. These findings highlight the importance of gene x environment interactions on the deleterious effect of obesity on cardiovascular risk factors.

Association of two apolipoprotein A-I gene MspI polymorphisms with high density lipoprotein (HDL)-cholesterol levels and indices of obesity in selected healthy Chinese subjects and in patients with early-onset type 2 diabetes

OBJECTIVE

Previous studies have reported associations between two apolipoprotein A-I (apoA-I) gene MspI polymorphisms (G-75A and C83T) and high density lipoprotein (HDL)-cholesterol and/or apoA-I levels, but have not investigated the relationship with obesity.

METHODS

We determined the distribution of these polymorphisms in 482 early-onset (< or = 40 years) Type 2 Chinese diabetics and 167 Chinese selected healthy controls.

RESULTS

The -75A and 83T allele frequencies were similar in the diabetic and healthy subjects. In the healthy control subjects, HDL-cholesterol levels were significantly higher in the AA homozygotes than in the GG/GA carriers (1.74 +/- 0.58 vs. 1.45 +/- 0.58 mmol/l, P<0.001). Furthermore, analyses showed a significant relationship between increasing HDL-cholesterol tertiles and the AA genotype frequency in the selected healthy subjects (3.6, 8.9 and 16.1%, P=0.026). For the C83T polymorphism, healthy male CT carriers had higher HDL-cholesterol levels than CC homozygotes (1.71 +/- 0.57 vs. 1.25 +/- 0.30 mmol/l, P=0.001), but this was not found in females. No relationship between these polymorphisms and lipid levels was found in the diabetics, who had a more adverse lipid profile than the selected controls. In the diabetics, but not the controls, in CT carriers compared to CC homozygotes there were lower levels of body mass index (BMI; 23.8 +/- 3.9 vs. 25.4 +/- 4.7 kg/m2, P=0.048) and waist-to-height ratio (0.49 +/- 0.06 vs. 0.52 +/- 0.07, P=0.023), and this relationship was supported by tertile analysis.

CONCLUSIONS

The -75AA genotype was associated with higher HDL-cholesterol levels in the selected healthy, but not diabetic, subjects. The 83T allele was associated with greater indices of obesity in the diabetic patients, and with higher HDL-cholesterol in heterozygous healthy male subjects.

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.

Polymorphism exon 1 variant at the locus of the scavenger receptor class B type I gene: influence on plasma LDL cholesterol in healthy subjects during the consumption of diets with different fat contents

BACKGROUND

The association between polymorphisms in the scavenger receptor class B type I (SRB-I) gene and variations in basal plasma concentrations of cholesterol in humans has recently been described.

OBJECTIVE

The objective of the study was to determine whether the exon 1 variant (G-->A) at the SRB-I gene is associated with the lipid response to the content and quality of dietary fat in healthy subjects.

DESIGN

We studied 97 healthy volunteers with exon 1 polymorphism [65 homozygous for allele 1 (1/1) and 32 heterozygous for allele 2 (1/2)]. Both groups consumed 3 diets lasting 4 wk each. The first was a saturated fatty acid (SFA)-rich 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) according to a randomized crossover design. At the end of each dietary period, plasma concentrations of triacylglycerol and of total, LDL, and HDL cholesterol were measured.

RESULTS

Carriers of the 1/2 genotype had a trend toward higher concentrations of LDL cholesterol (P < 0.11) after the SFA-rich diet than did those who were homozygous for 1/1. Carriers of the mutation showed a significantly greater (P = 0.007) decrease in LDL-cholesterol concentrations (-23%) in changing from an SFA-rich diet to a Cho-rich diet than did noncarriers of the mutation (-16%).

CONCLUSION

Carriers of the minority allele, 1/2, are more susceptible to the presence of SFA in the diet because of a greater increase in LDL cholesterol.

The apo A-I gene promoter region polymorphism determines the severity of hyperlipidemia after heart transplantation

BACKGROUND

To study whether the Apolipoprotein A-I (apo A-I) promoter region gene polymorphism produces changes in the lipid profile of heart transplant recipients.

METHODS

One hundred and three heart transplant recipients (93 men and 10 women, with a mean age of 47 +/- 13 yr) receiving triple immunosuppressive therapy were submitted to a genetic study of the apo A-I gene promoter region. Anthropometric and analytical data, including lipid profile, arterial blood pressure, were collected prior to transplantation and 3, 6, 12, and 24 months after transplantation.

RESULTS

Sixty-three subjects had the GG genotype and 40 the GA genotype. Carriers of the GA genotype had higher triglyceride levels at 6 months and 2 yr (2.50 +/- 1.20 versus 1.93 +/- 0.98 mmol/L and 2.46 +/- 1.58 versus 1.60 +/- 0.68 mmol/L, respectively, p < 0.001), and a greater rise in LDL-cholesterol at 1 yr than the GG subjects (4.57 +/- 1.16 versus 4.16 +/- 1.18 mmol/L, p < 0.05). Multiple regression analyses showed that genetic variants at the apo A-I promoter region are responsible for 11% of the variability in triglyceride levels at 6 months (p = 0.005).

CONCLUSIONS

The GA genotype of the apo A-I promoter region produces a greater rise in plasma triglyceride and LDL-cholesterol levels in heart transplant patients.

Effects of apolipoprotein A-I genetic variations on plasma apolipoprotein, serum lipoprotein and glucose levels

The present authors investigated the individual and combined associations of the apolipoprotein (apo) A-I -75 bp and +83 bp polymorphisms with plasma lipid, lipoprotein and apolipoprotein levels in 734 Caucasian men and women. The frequency of the A allele at position -75 bp (G-->A) was 0.14 in women and 0.17 in men. The frequencies for the rare M2 allele at position +83 bp and/or 84 bp (C-->T and G-->A, respectively) were 0.04 and 0.05 in women and men, respectively. In women, the A allele was associated with significantly higher levels of apo B (P = 0.016), total cholesterol (TC) (P = 0.005), low-density lipoprotein cholesterol (LDL-C) (P = 0.018) and TC:high-density lipoprotein (HDL) ratio (P = 0.026) compared to the G/G subjects. In men, no significant associations were detected between the -75 bp polymorphism and any lipid trait examined. The M2 allele for the +83 bp polymorphism was significantly associated in men with higher levels of apo A-I (P = 0.002) and TC (P = 0.046). In women, a significant effect was observed for TC (P = 0.036), with M2+/- subjects having lower levels than M2+/+ subjects. Significant linkage disequilibrium (P = 0.037) between the apo A-I -75 bp and +83 bp polymorphisms was detected. Women carrying both rare alleles (G/A M2+/-) had significantly higher TC:HDL ratios (P = 0.031) compared to the other haplotypes. In men, significant differences were observed for apo A-I (P = 0.021) and TC (P = 0.044), with carriers of the G/G M2+/- haplotype having the highest values compared to other genotype combinations. In conclusion, the -75 bp (G/A) polymorphism appears to have a significant effect on levels of apo B, plasma TC and LDL-C in women, while the +83 bp polymorphism seems to affect the apo A-I levels in men, and the plasma cholesterol levels in both genders.

Polyunsaturated fatty acids modulate the effects of the APOA1 G-A polymorphism on HDL-cholesterol concentrations in a sex-specific manner: the Framingham Study

BACKGROUND

A common G-to-A substitution in the promoter area (-75 base pairs) of the apolipoprotein A-I gene (APOA1) has been described. The A allele was shown to be associated with higher HDL-cholesterol concentrations in some studies but not in others.

OBJECTIVE

We examined whether dietary fat modulates the association between this polymorphism and HDL-cholesterol concentrations.

DESIGN

We studied a population-based sample of 755 men and 822 women from the Framingham Offspring Study.

RESULTS

The frequency of the A allele was 0.165. No significant differences were observed between G/G subjects and carriers of the A allele for any lipid variables. In multivariate linear regression models, HDL-cholesterol concentrations in women were associated with a significant interaction between polyunsaturated fatty acid (PUFA) intake as a continuous variable and APOA1 genotype (P = 0.005). By using 3 categories of PUFA intake, we found a significantly different effect of APOA1 genotype across PUFA categories in women. When PUFA intake was <4% of energy, G/G subjects had approximately 14% higher HDL-cholesterol concentrations than did carriers of the A allele (P < 0.05). Conversely, when PUFA intake was >8%, HDL-cholesterol concentrations in carriers of the A allele were 13% higher than those of G/G subjects (P < 0.05). No significant allelic difference was observed for subjects in the range of PUFA intake of 4-8% of energy. These interactions were not significant in men.

CONCLUSIONS

We found a significant gene-diet interaction associated with the APOA1 G-A polymorphism. In women carriers of the A allele, higher PUFA intakes were associated with higher HDL-cholesterol concentrations, whereas the opposite effect was observed in G/G women.

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.

Variations in the promoter region of the apolipoprotein A-1 gene influence plasma lipoprotein(a) levels in Asian Indian neonates from Singapore

We studied the influence of two DNA polymorphisms (-75 bp G/A and +83 bp C/T) in the promoter region of the apolipoprotein A-1 (apoA1) gene on cord plasma level of lipoprotein(a) [Lp(a)] in 1076 newborns of both genders from the three major ethnic groups in Singapore-Chinese, Malays, and Asian Indians. The frequency of the A: allele at -75 bp in the Indians was significantly lower than the Chinese and Malays. There was no linkage disequilibrium between the two sites studied. Both polymorphic sites were not significantly associated with any lipid factors except for Lp(a) levels in the Asian Indians. The AA and CC homozygotes were significantly associated with lower Lp(a) levels. These associations were specific only to the male Indian neonates. The genetic variations at the -75 and +83 bp explained 6.9% and 7.2%, respectively, of the total variability of plasma Lp(a) levels at birth in the Asian Indians. The Lp(a) levels were also significantly different between composite genotypes in the order GG/TT > GA/CT > GG/CT > GA/CC > GG/CC > AA/CC. The effects of the two polymorphisms seem to be additive as the composite genotypes were able to explain 14% of the Lp(a) variance, equivalent to the sum of the two constituent sites. Our results showed that there is significant ethnic- and gender-specific influence of the apoA1 gene on plasma Lp(a) levels at birth that is inherent and independent of known gene-environment interactions.

Influence of genetic polymorphisms on responsiveness to dietary fat and cholesterol

Genes influence quantitative variations in plasma lipoprotein concentrations. For example, intake of dietary saturated fat and cholesterol raises the average serum cholesterol concentration, leading to a higher risk of coronary artery disease in populations. However, not all individuals within the population are susceptible: genetic factors appear to render individuals either "dietary responsive" or "dietary nonresponsive." In this review, we focus on current knowledge about the influence of genetic polymorphisms in certain genes on the lipoprotein response to dietary fat and cholesterol. Our preliminary studies in the Dietary Intervention Study in Children suggest a significant dose-response relation between the decrease in LDL cholesterol from baseline to 36 mo of follow-up in both the intervention group (who consumed a low-fat, low-cholesterol diet) and the usual care group (who consumed a regular diet) and the presence of the APOA1*A allele at the M1 site and the + site at the M2 site of the gene encoding apolipoprotein (apo) A-I. The DNA polymorphisms on the genes encoding apo A-IV, apo B, apo C-III, apo E, lipoprotein lipase, cholesteryl ester transfer protein, lecithin:cholesterol acyltransferase (phosphatidylcholine-sterol O:-acyltransferase), and LDL receptor were found by others to be associated with the plasma lipoprotein response to dietary intervention. Possible mechanisms involved in these effects are discussed and certain discrepancies in the literature about some genetic effects on responsiveness are analyzed. An improved understanding of the influence of specific genes on lipoprotein responsiveness to dietary fat and cholesterol may allow us to identify and counsel certain individuals to avoid high-fat diets so that they may reduce their risk of developing hyperlipidemia and coronary artery disease.

The effect of apolipoprotein B xbaI polymorphism on plasma lipid response to dietary fat

BACKGROUND AND AIMS

Lipid response to dietary fat and cholesterol is, to a large extent, genetically controlled. Apolipoprotein B (apo B) plays a dominant role in cholesterol homeostasis. Several polymorphic sites within or adjacent to the gene locus for apo B have been detected. The X+ allele of the XbaI restriction fragment polymorphism of the apo B gene has been found to be associated with higher serum cholesterol and/or triglyceride levels. In order to study the influence of this mutation on the plasma lipid response in diets of varying fat content, 72 healthy male subjects were studied, 21 X- X- (X-) and 51 X+ (X+ X- or X+ X+).

METHODS AND RESULTS

These subjects followed three consecutive 28-day diet periods: one rich in saturated fats (SAT diet; 38% fat, 20% saturated); a National Cholesterol Education Program type I diet (NCEP-I diet) (28% fats, < 10% saturated); and a third monounsaturated (MUFA diet) (38% fats, 22% monounsaturated). The different genotypes can be observed to have significant effects on total and LDL cholesterol concentrations (P < 0.017). X+ individuals had higher levels of total and LDL cholesterol after the consumption of a SAT diet (P < 0.012; P < 0.006, respectively), NCEP diet (P < 0.060; P < 0.054, respectively) and MUFA diet (P < 0.022; P < 0.042, respectively) in comparison with X- individuals. A significant interaction between genotypes and dietary effects was observed for diet-induced changes in plasma triglycerides (P < 0.032). Significant decreases in the absolute values of triglyceride concentrations (-0.18 mmol L(-1), P < 0.024) were noted in the X- subjects after the high intake of a MUFA diet, while no significant differences were observed in the X+ individuals (0.006 mmol L(-1), P < 0.858).

CONCLUSIONS

Our results suggest that the total triglyceride response to diet is influenced by the apo B XbaI polymorphism.

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).

Use of hierarchical models for meta-analysis: experience in the metabolic ward studies of diet and blood cholesterol

Overviews that combine single effect estimates from published studies generally use a summary statistic approach where the effect of interest is first estimated within each study and then averaged across studies in an appropriately weighted manner. Combining multiple regression coefficients from publications is more problematic, particularly when there are differences in study design and inconsistent reporting of effect sizes and standard errors. This paper describes the use of a hierarchical model in such circumstances. Its use is illustrated in a meta-analysis of the metabolic ward studies that have investigated the effect of changes in intake of various dietary lipids on blood cholesterol. These studies all reported average blood cholesterol for groups of individuals who were studied on one or more diets. Thirty-one studies had randomized cross-over designs, 12 had matched parallel group designs, 12 had non-randomized Latin square designs and 16 had other uncontrolled designs. The hierarchical model allowed the different types of comparison (within-group between-diet, between matched group) that were made in the various studies to each contribute to the overall estimates in an appropriately weighted manner by distinguishing between-study variation, within-study between-matched-group variation and within-group between-diet variation. The hierarchical models do not require consistent specification of effect sizes and standard errors and hence have particular utility in combining results from published studies where the relationships between a dependent variable and two or more predictors have been investigated using heterogeneous methods of analysis.

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.

Polymorphism in apoprotein-CIII gene and coronary heart disease

BACKGROUND

The aim of this study was to look into the association, if any, of apoprotein-CIII variant allele with hypertriglyceridemia, hypercholesterolemia and coronary heart disease (CHD).

PATIENTS AND METHODS

The prevalence of a C to G substitution in the 3' untranslated region of apoprotein-CIII was studied in a sample of 92 angiographed Saudi subjects, consisting of 65 males and 27 females. The subjects were genotyped by amplification followed by digestion of the gene fragment containing the polymorphic site with Sac I restriction enzyme.

RESULTS

The variant allele of apoprotein-CIII was found to be associated neither with hypertriglyceridemia nor with hypercholesterolemia. However, a significant association of this allele (P<0.01) was found with coronary heart disease, independent of other risk factors such as smoking, diabetes and hypertension. An estimation of odds ratio using logistic regression with various risk factors in the model showed that the individuals with this rare allele were 3.4 times more at risk of developing coronary heart disease. This estimate of risk held even after analyzing a subset of individuals above 45 years of age.

CONCLUSION

While the association between apoprotein-CIII variant allele and dyslipidemia could not be established in this study, the relationship between this marker and CHD was highlighted in the studied subjects.

The genetics of serum lipid responsiveness to dietary interventions

CHD is a multifactorial disease that is associated with non-modifiable risk factors, such as age, gender and genetic background, and with modifiable risk factors, including elevated total cholesterol and LDL-cholesterol levels. Lifestyle modification should be the primary treatment for lowering cholesterol values. The modifications recommended include dietary changes, regular aerobic exercise, and normalization of body weight. The recommended dietary changes include restriction in the amount of total fat, saturated fat and cholesterol together with an increase in the consumption of complex carbohydrate and dietary fibre, especially water-soluble fibre. However, nutrition scientists continue to question the value of these universal concepts and the public health benefits of low-fat diets, and an intense debate has been conducted in the literature on whether to focus on reduction of total fat or to aim efforts primarily towards reducing the consumption of saturated and trans fats. Moreover, it is well known that there is a striking variability between subjects in the response of serum cholesterol to diet. Multiple studies have examined the gene-diet interactions in the response of plasma lipid concentrations to changes in dietary fat and/or cholesterol. These studies have focused on candidate genes known to play key roles in lipoprotein metabolism. Among the gene loci examined, APOE has been the most studied, and the current evidence suggests that this locus might be responsible for some of the inter-individual variability in dietary response. Other loci, including APOA4, APOA1, APOB, APOC3, LPL and CETP have also been found to account for some of the variability in the fasting and fed states.

Genes, variation of cholesterol and fat intake and serum lipids

Several studies have examined gene-diet interactions in the response of plasma lipid concentrations to changes in dietary fat and/or cholesterol. Among the gene loci examined, APOE has been the most studied, and the current evidence suggests that this locus might be responsible for some of the interindividual variability in dietary response. Other loci, including APOA4, APOA1 and APOB have also been found to account for some of the variability in the fasting and fed states.

The effect on transcription efficiency of the apolipoprotein AI gene of DNA variants at the 5' untranslated region

Elevated circulating levels of high-density lipoprotein and apolipoprotein AI are associated with reduced coronary artery disease risk. We have shown that a C to T substitution at +83 bp and a G to A substitution at -75 bp of the apolipoprotein AI gene are both related to increased high-density lipoprotein levels in a healthy population but not in a coronary population, among whom the same mutations are associated with increased disease severity. In the present study, we explored the effects of these base changes on transcriptional efficiency in vitro. We directionally cloned (using polymerase chain reaction) the 5' region of the apolipoprotein AI gene (-281 to +330 bp) with GC, GT, and AC haplotypes into a pGL3-luciferase reporter gene basic vector, and transfected the constructed vectors into HepG2 cells. The cells carrying the T allele at the +83 bp site (GT 112.3 +/- 12.4) had the same transcriptional efficiency as those bearing the C allele (GC 126.3 +/- 9.6). However, for cells with the A allele at -75 bp there was a twofold decrease in transcription (AC 63.1 +/- 9.3) accompanied by similar changes in Luc+ mRNA levels; this reduced transcription was only present if the apolipoprotein AI leader sequence was included in the insert. While the findings are inconsistent with the T or A allele being associated with higher high-density lipoprotein levels, they are consistent with the finding that the alleles are associated with an increased coronary artery disease risk, and demonstrate that the 5' leader region of the apolipoprotein AI gene participates in regulating apolipoprotein AI transcription. They also suggest that other regions of the apolipoprotein AI gene may have an active role in such regulation, and that environmental effects may influence allele-specific expression.

Functional food science and the cardiovascular system

Cardiovascular disease has a multifactorial aetiology, as is illustrated by the existence of numerous risk indicators, many of which can be influenced by dietary means. It should be recalled, however, that only after a cause-and-effect relationship has been established between the disease and a given risk indicator (called a risk factor in that case), can modifying this factor be expected to affect disease morbidity and mortality. In this paper, effects of diet on cardiovascular risk are reviewed, with special emphasis on modification of the plasma lipoprotein profile and of hypertension. In addition, dietary influences on arterial thrombotic processes, immunological interactions, insulin resistance and hyperhomocysteinaemia are discussed. Dietary lipids are able to affect lipoprotein metabolism in a significant way, thereby modifying the risk of cardiovascular disease. However, more research is required concerning the possible interactions between the various dietary fatty acids, and between fatty acids and dietary cholesterol. In addition, more studies are needed with respect to the possible importance of the postprandial state. Although in the aetiology of hypertension the genetic component is definitely stronger than environmental factors, some benefit in terms of the development and coronary complications of atherosclerosis in hypertensive patients can be expected from fatty acids such as alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. This particularly holds for those subjects where the hypertensive mechanism involves the formation of thromboxane A2 and/or alpha 1-adrenergic activities. However, large-scale trials are required to test this contention. Certain aspects of blood platelet function, blood coagulability, and fibrinolytic activity are associated with cardiovascular risk, but causality has been insufficiently proven. Nonetheless, well-designed intervention studies should be initiated to further evaluate such promising dietary components as the various n-3 and n-6 fatty acids and their combination, antioxidants, fibre, etc. for their effect on processes participating in arterial thrombus formation. Long-chain polyenes of the n-3 family and antioxidants can modify the activity of immunocompetent cells, but we are at an early stage of examining the role of immune function on the development of atherosclerotic plaques. Actually, there is little, if any, evidence that dietary modulation of immune system responses of cells participating in atherogenesis exerts beneficial effects. Although it seems feasible to modulate insulin sensitivity and subsequent cardiovascular risk factors by decreasing the total amount of dietary fat and increasing the proportion of polyunsaturated fatty acids, additional studies on the efficacy of specific fatty acids, dietary fibre, and low-energy diets, as well as on the mechanisms involved are required to understand the real function of these dietary components. Finally, dietary supplements containing folate and vitamins B6 and/or B12 should be tested for their potential to reduce cardiovascular risk by lowering the plasma level of homocysteine.

Plasma lipid response to hypolipidemic diets in young healthy non-obese men varies with body mass index

Lipid response to dietary fat is highly variable among individuals of a population. The aim of this study was to establish whether being overweight is one of the factors that determines this response. Forty-one non-obese healthy men were divided into two groups according to body mass index as follows: controls, <25 kg/m2; overweight, >25 kg/m2 but <30 kg/m2. After consuming a saturated fat-rich diet (SAT diet: 38% fat, 20% saturated) for 4 wk, subjects were switched to a low fat diet [National Cholesterol Education Program (NCEP)-I diet: 28% fat, 10% saturated] for 4 wk and then to a monounsaturated fat-rich diet (MUFA diet: 38% fat, 22% monounsaturated) for 4 wk. Data were analyzed by Student's t test and two-way ANOVA for repeated measures. After consuming the NCEP-I diet, the overweight subjects had a smaller decrease relative to the SAT diet period in plasma total cholesterol [-0.30 vs. -0.67 mmol/L (-7 vs. -16%), P < 0.02] and low density lipoprotein-cholesterol concentrations [-0.24 vs. -0.55 mmol/L (-9 vs. -21%), P < 0.04] than controls. However, in the overweight subjects, the MUFA diet produced a greater decrease in plasma triglycerides than in the controls relative to the SAT diet period [-0.36 vs. -0.03 mmol/L (-26 vs. -4%), P < 0.006] and to the NCEP-I diet period [-0.29 vs. 0. 01 mmol/L (-22 vs. 1%), P < 0.01). Plasma cholesterol concentrations changed to a lesser extent, and triglyceride concentration to a greater extent, in overweight but non-obese young men than in those of normal weight in response to changes in dietary fat composition. Our data suggest that in the diet treatment of obese hyperlipemic subjects, it is more important for them to lose weight than to change the fat composition of their diets.

Influence of genetic variation at the apo A-I gene locus on lipid levels and response to diet in familial hypercholesterolemia

We have examined the apo AI - 75 (G/A) and apo AI + 83(MspI +/-) polymorphisms at the APOA1 gene locus for associations with plasma lipid levels and response to an NCEP-I diet in 69 (44 women, 25 men) heterozygotes for familial hypercholesterolemia (FH). Subjects were studied at baseline (after consuming for one month a diet with 35%, fat, 10% saturated, and 300 mg/day cholesterol) and after 3 months of an NCEP-I diet. No gender-related differences for any of the lipid variables examined were found and the data were analyzed for men and women combined. For the apo AI - 75 (G/A) polymorphism, there were 51 G/G and 18 G/A subjects. At baseline, G/A subjects showed significantly lower total cholesterol (p = 0.0036), and LDL-C (p = 0.0023), and apo B (p = 0.0209), than G/G individuals, but no differences were found for HDL-C, triglycerides and VLDL-C values. Following the NCEP-I diet these genotype-related differences remained significant for total and LDL-C. The MspI (-) allele at the apo AI + 83 polymorphism was detected in the heterozygous state in five subjects and its presence was not associated with altered baseline lipids nor with dietary response to the NCEP-I diet. Our results suggest that FH subjects carrying the A allele at the apoAI - 75 (G/A) polymorphism have significantly lower total and LDL-C and apo B baseline levels but respond to a low-fat diet with similar reductions in total and LDL-C when compared with homozygotes for the G allele at this polymorphic site.

The A/G polymorphism in the -78 position of the apolipoprotein A-I promoter does not have a direct effect on transcriptional efficiency

A promoter polymorphism A/G at position 78 bp upstream of the transcription initiation site characterizes the human apolipoprotein A-I gene. Some studies correlated the higher Apo A-I levels or increased Apo A-I transcription efficiency with the A allele, while other studies did not confirm these results. We have investigated the in vitro effects of this transition on the transcriptional efficiency of ApoAI gene by creating two sets of identical constructs with the whole Apo A-I promoter, carrying the A or the G, linked to the complete ApoAI gene. The relative activity of the two promoter alleles was determined through a quantitative RT-PCR system after transient tranfections of human HepG2 cell line in basal state and after stimulation with retinoic acid or 17beta-estradiol. Our results exclude differences in promoter activity linked to the A or G promoter alleles either in basal or in stimulated conditions. The data suggest that the A/G polymorphism does not directly affect the transcriptional efficiency of ApoAI gene, although it may be in linkage disequilibrium with other regulatory sequences and the combination of these elements may explain the contradictory results of the ApoAI gene expression.

Human apolipoprotein A-I gene promoter mutation influences plasma low density lipoprotein cholesterol response to dietary fat saturation

Previous studies have shown that the A to G transition occurring at position -75 bp upstream of the transcriptional start site in the human apolipoprotein A-I gene may affect plasma high density lipoprotein cholesterol (HDL-C) levels and low density lipoprotein cholesterol (LDL-C) response to changes in amount of dietary fat. We have examined the response to dietary fat saturation as a function of this mutation in 50 men and women. Subjects were first fed a saturated (SAT) fat diet (35% fat, 17% SAT) for 28 days, followed by a diet rich in monounsaturated fatty (MUFA) acids (35% fat, 22% MUFA) for 35 days and a diet rich in polyunsaturated (PUFA) fat (35% fat, 13% PUFA) for 35 days. All meals were prepared and consumed at the study sites. Lipoproteins were measured at the end of each diet period. The allele frequency for the A allele was 0.13. Subjects carrying the A allele had higher plasma cholesterol, LDL-C and triglyceride levels than those homozygotes for the G allele. As compared to the SAT diet, a PUFA diet induced significantly greater plasma total (P = 0.003) and LDL-C decreases (P = 0.001) in G/A women (-1.62 and -1.32 mmol/l, respectively) than in G/G subjects (-0.87 and -0.74 mmol/l for plasma and LDL-C, respectively). Multiple regression analysis demonstrated that in women, the variability in LDL-C response from a diet rich in SAT fat to a diet rich in PUFA was primarily due to LDL-C levels (during the SAT phase), accounting for 55.1% of the variance, waist to hip ratio (W/H; 11.4%) and the G/A polymorphism (10%). Whereas in men the major determinant of this response was smoking (21.4%). In conclusion, the G/A polymorphism appears to have a small but significant effect on plasma LDL-C responsiveness to changes in dietary fat saturation specially in women.

Effect of response to a low-fat diet among adolescent males on their adult blood cholesterol levels

BACKGROUND

While primary prevention of adult cardiovascular diseases should begin early, there are problems in identifying children at increased risk of future disease.

METHODS

We did a follow-up study in 1991-1992 of 100 male former students at a boarding high school who had blood cholesterol measured in 1970-1971 both prior to and following a school-wide, reduced-fat dietary intervention. We compared adult cholesterol levels of the 50 subjects whose cholesterol decreased > or = 16.5% (the median decrease) following the 1970-1971 intervention (Diet-Sensitive) with the 50 whose response was < 16.5% (Non-Diet-Sensitive).

RESULTS

Blood cholesterol of adults who were Diet-Sensitive in 1970-1971 was 4.2 mg/dl lower than their baseline values in adolescence, while adults classified as Non-Diet-Sensitive as adolescents showed a 15.9 mg/ dl increase in cholesterol over 21 years. Adjusting for baseline adolescent values, Non-Diet-Sensitive subjects were 4.8 (95% CI 1.4, 15.9) times as likely as Diet-Sensitive subjects to have adult cholesterol > or = 200 mg/ dl. Also, Diet-Sensitive adults on a low-fat diet had adult blood cholesterol levels > 20 mg/dl lower than Non-Diet-Sensitive adults on a similar diet (180.1 vs 202.1 mg/dl, respectively).

CONCLUSIONS

Degree of response to a low-fat, low-cholesterol diet during adolescence may identify male subjects who will have differing patterns of cholesterol change over time.