Role of genetic variation at the apo AI-CIII-AIV gene cluster in determining plasma apo AI levels in boys and girls

[－75 G/A Polymorphism of Apolipoprotein A1 Gene Promoter Region in Normal Pregnant Women and Patients With Gestational Diabetes Mellitus]

Objective

To investigate the －75 G/A single-nucleotide polymorphism in the promoter region of apolipoprotein A1 gene (apoA1) and its association with gestational diabetes mellitus (GDM) in pregnant women and to provide references for the exploration in the molecular genetic basis of GDM.

Methods

A total of 626 GDM patients and 1022 normal pregnant women, ie, the controls, were included in the study. The genotyping of apoA1 －75 G/A polymorphism was performed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glucose (Glu) were measured by enzymatic methods. Plasma insulin (INS) was measured by chemiluminescence immunoassay. The protein levels of apoA1 and apoB were measured by the turbidimetric immunoassay.

Results

Allele frequencies of G and A were 0.718 and 0.282 in the GDM group and 0.713 and 0.287 in the control group, respectively. Distribution of the genotype frequencies was found to be in Hardy-Weinberg equilibrium in both the GDM and control groups. There was no significant difference in the frequencies of alleles G and A and the genotypes of apoA1 －75 G/A polymorphism between the GDM and the control group (P>0.05). In the GDM group, the carriers with the genotype AA were associated with significantly higher levels of TC, HDL-C, and apoA1 than those with genotypes GG and GA did (all P<0.05). After the GDM patients were divided into obese and non-obese subgroups, the genotype-related apoA1 variation was observed only in obese patients, while the genotype-related TC and HDL-C variations were evident in non-obese patients (P<0.05). In the control group, carriers of genotypes AA and GA had higher systolic blood pressure (SBP) and HDL-C than the carriers of genotype GG did (all P<0.05). Carriers of genotypes AA had significantly lower Glu levels than carriers of genotypes GG and GA did (P<0.05). The control subjects were further divided into subgroups according to their body mass index (BMI). Analysis of the subgroups showed that AA carriers were associated with higher SBP levels in the obese control women only, while lower Glu levels were evident in both obese and non-obese control women.

Conclusion

These results suggest that －75 G/A polymorphism in the apoA1 gene is not associated with GDM. However, the genetic variation is closed associated with the plasma apoA1, HDL-C, and TC levels in GDM patients and plasma HDL-C, Glu, and SBP levels in the control subjects. The apoA1 variant-associated lipids and SBP variation is BMI dependent in both groups.

Association of rs670 variant of APOA1 gene with lipid profile and insulin resistance after 9 months of a high protein/low carbohydrate vs a standard hypocaloric diet

BACKGROUND & AIMS

A common G-to-A transition (rs670) in the APOA1 gene has been related with metabolism. We evaluate the association of this SNP with changes in lipid profile and insulin resistance in response to two diets.

METHODS

268 obese patients were randomly allocated to a high protein/low carbohydrate -Diet HP- vs. a standard hypocaloric diet -Diet S- for 9 months. Anthropometric and biochemical status were evaluated at 3 and 9 months.

RESULTS

179 subjects (66.8%) had the genotype GG, 79 patients GA (29.4%) and 10 subjects AA (3,8%). With both diets: the decrease of BMI, weight, waist circumference, fat mass was higher in A allele carriers than non-carriers. Also on both diets A allele carriers showed greater improvements in total cholesterol (-19.0 ± 2.5 mg/dl (non-A allele carriers -12.1 ± 2.0 mg/dl:p = 0.02 after Diet HP) and -13.1 ± 2.1 mg/dl (non-A allele carriers -8.9 ± 1.1 mg/dl:p = 0.02 after Diet S)), LDL-cholesterol (-18.0 ± 2.1 mg/dl (non-A allele carriers -8.3 ± 2.2 mg/dl:p = 0.01 after Diet HP) and -12.0 ± 1.5 mg/dl (non-A allele carriers -6.3 ± 2.3 mg/dl:p = 0.01 after Diet S)), insulin (-2.5 ± 0.2 mUI/L (in non A allele -1.8 ± 0.2 mUI/L:p = 0.01 after Diet HP) and -2.1 ± 0.1 mUI/L (non A allele carriers -1.2 ± 0.3 mUI/L:p = 0.01 after Diet S)), HOMA-IR (-1.3 ± 0.3 units (non A allele group -0.8 ± 0.2:p = 0.03 after Diet HP) and -1.1 ± 0.1 units (non A allele carriers -0.3 ± 0.2 mg/dl:p = 0.01 after Diet S)) than non-A allele carriers.

CONCLUSIONS

A allele carriers of rs670 ApoA1 polymorphism showed a higher decrease of insulin resistance, LDL cholesterol and adiposity induced by two different hypocaloric diet than non 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.

Implication of the rs670 variant of APOA1 gene with lipid profile, serum adipokine levels and components of metabolic syndrome in adult obese subjects

BACKGROUND & AIMS

A G-to-A transition located 75 base pairs upstream (rs670) from transcription start site of the APOA1 gene is related with metabolic parameters. The aim of the present investigation was to describe the association of rs670 with metabolic syndrome and metabolic parameters.

METHODS

The study involved a population of 1000 obese subjects. Measurements of anthropometric parameters, arterial blood pressure, fasting blood glucose, C-reactive protein (CRP), insulin concentration, insulin resistance (HOMA-IR), lipid profile, adipokines levels and prevalence of MetS was recorded. Genotype of ApoA1 gene polymorphism (rs670) was evaluated.

RESULTS

A sample of 1000 obese subjects with a mean BMI of 36.5 ± 5.0 kg/m² was enrolled. In males, weight (delta: 3.3 ± 1.2 kg; p = 0.01), fat mass (delta: 2.7 ± 1.1 kg; p = 0.01), waist circumference (delta: 2.8 ± 1.1 cm; p = 0.02), fasting glucose (delta: 8.9 ± 2.2 mg/dl; p = 0.01), insulin levels (delta: 3.7 ± 1.2 UI/L; p = 0.04) and HOMA-IR (delta: 1.2 ± 1.1 units; p = 0.02) were higher in non-A allele carriers than A allele carriers. In males without A allele, an increased risk of hyperglycemia (OR = 1.40, 95% CI = 1.09-2.09, p = 0.04), percentage of central obesity (OR = 4.55, 95% CI = 1.36-15.39, p = 0.01), percentage of low HDL-C (OR = 2.02, 95% CI = 1.02-4.03, p = 0.03) and prevalence of diabetes mellitus (OR = 2.14, 95% CI = 1.03-5.04, p = 0.03) were reported.

CONCLUSIONS

rs670 of APOA1 gene has a gender specific influence on serum glucose, insulin, HOMA-IR, fat mass, weight and waist circumference. Males without A allele showed high rates of central obesity, low levels of HDL, hyperglycemia and diabetes mellitus.

Effect of apolipoprotein A1 genetic polymorphisms on lipid profiles and the risk of coronary artery disease

Background

The disorder of lipid metabolism and genetic predisposition are major risk factors for coronary artery disease (CAD). Variants in the apolipoprotein A1 (APOA1) gene play an important role in the regulation of lipids. The objective of the present study was to investigate the effect of two polymorphisms (-75 G/A and +83 C/T) of APOA1 on lipid profiles and the risk of CAD.

Methods

A total number of 300 subjects with CAD and 300 age and sex matched healthy controls were enrolled for the study. Genotyping of the APOA1 was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) combined with gel electrophoresis, and then confirmed by direct sequencing.

Results

The frequencies of APOA1 -75 AA genotype [odds ratio (OR) =0.50, 95 % confidence interval (CI) = 0.28, 0.88; P = 0.02] and APOA1 -75 A allele (OR =0.76, 95 % CI = 0.59, 0.98; P = 0.04) were significantly lower in CAD than in controls. The APOA1 -75 A allele was significantly associated with increasing serum concentrations of ApoA1 and high-density lipoprotein cholesterol (HDL-C) (P < 0.001).

Conclusions

The individuals with the APOA1 -75 A allele were likely to have a lower risk of CAD as a result of its effect on higher serum concentrations of ApoA1 and HDL-C.

Gender-specific associations of the APOA1 -75G>A polymorphism with several metabolic syndrome components in Turkish adults

BACKGROUND

Variations in the apolipoprotein A-1 (APOA1) gene, a determinant of plasma high-density lipoprotein cholesterol (HDL-C) and apoA-I levels, may contribute to cardiovascular diseases. We evaluated the effects of a promoter polymorphism (-75G>A) in the APOA1 gene on metabolic syndrome (MetS) components in a Turkish population sample.

METHODS

Randomly selected 1515 Turkish adults (age 49.9±11.8 years, 785 females) were genotyped for -75G>A polymorphism using hybridization probes in Real-Time PCR LC480 device. MetS and atherogenic dyslipidemia were defined using the criteria of ATP III.

RESULTS

The -75AA genotype prevailed in 3.9% of men and 2.4% of women, and was independently associated with significantly higher HDL-C concentrations. Independent associations with the -75GA genotype existed only in men: higher diastolic and systolic blood pressure (BP) levels (p<0.05) were observed in male -75GA heterozygotes. Logistic regression revealed that the GA genotype confers elevated risk for atherogenic dyslipidemia (OR=1.57, 95% Cl 1.06-2.3) after adjustment for associated risk factors. Independent associations with atherogenic dyslipidemia or elevated BP did not emerge in women.

CONCLUSION

APOA1 -75G>A polymorphism is independently related to HDL-C concentrations. Independent associations of the -75GA genotype with elevated BP and atherogenic dyslipidemia were confined to men. These gender-modulated associations suggest novel gene-gender-environmental interactions.

Interactions between the apolipoprotein a1/c3/a5 haplotypes and alcohol consumption on serum lipid levels

BACKGROUND

The interactions between apolipoprotein (Apo) A1/C3/A5 haplotypes and alcohol consumption on serum lipid profiles have not been previously explored. The present study was undertaken to detect the polymorphisms of ApoA1 -75 bp G>A (rs1799837), ApoC3 3238C>G (rs5128), ApoA5 -1131T>C (rs662799), ApoA5 c.553G>T (rs2075291), and ApoA5 c.457G>A (rs3135507) and the interactions between their haplotypes and alcohol consumption on serum lipid levels.

METHODS

Genotyping was performed in 1,030 unrelated subjects (516 nondrinkers and 514 drinkers) aged 15 to 89. The interactions between ApoA1/C3/A5 haplotypes and alcohol consumption on serum lipid levels were detected by factorial regression analysis after controlling for potential confounders.

RESULTS

The frequencies of ApoC3 3238 CG/GG genotypes and ApoA1 -75 bp A allele in nondrinkers were higher in females than in males (p < 0.05). The frequencies of ApoC3 3238 CG/GG genotypes and G allele in drinkers were higher in females than in males (p < 0.05). The frequencies of ApoA1 -75 bp GA/AA genotypes and A allele in males were higher, and those of ApoC3 3238 CG/GG genotypes were lower in drinkers than in nondrinkers (p < 0.05 to 0.01). The frequency of ApoC3 3238 GG genotype in male drinkers was also higher in ≥25 g/d than in <25 g/d subgroups (p < 0.05). There were 11 haplotypes with a frequency >1% in our study population. The haplotypes of G-G-T-C-G (in the order of c.553G>T, c.457G>A, -1131T>C, 3238C>G, and -75 bp G>A), G-G-T-C-A, and G-G-C-G-G were shown consistent interactions with alcohol consumption to increase serum total cholesterol, high-density lipoprotein cholesterol (HDL-C), and ApoA1 levels (p < 0.05 to 0.001). The interactions between G-G-T-G-G (HDL-C and ApoA1), G-G-C-C-A (ApoA1), G-A-T-C-G (triglyceride), G-G-T-C-G (ApoA1/ApoB ratio), and G-G-C-G-G (ApoB) haplotypes and alcohol consumption on serum lipid levels were also detected (p < 0.05 to 0.001); the levels of these serum lipid parameters were significantly higher in drinkers than in nondrinkers.

CONCLUSIONS

The differences in serum lipid parameters between drinkers and nondrinkers might partly result from different interactions between the ApoA1/C3/A5 haplotypes and alcohol consumption.

Apolipoprotein A1/C3/A5 haplotypes and serum lipid levels

Background

The association of single nucleotide polymorphisms (SNPs) in the apolipoprotein (Apo) A1/C3/A4/A5 gene cluster and serum lipid profiles is inconsistent. The present study was undertaken to detect the association between the ApoA1/C3/A5 gene polymorphisms and their haplotypes with serum lipid levels in the general Chinese population.

Methods

A total of 1030 unrelated subjects (492 males and 538 females) aged 15-89 were randomly selected from our previous stratified randomized cluster samples. Genotyping of the ApoA1 -75 bp G>A, ApoC3 3238C>G, ApoA5 -1131T>C, ApoA5 c.553G>T and ApoA5 c.457G>A was performed by polymerse chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing. Pair-wise linkage disequilibria and haplotype analysis among the five SNPs were estimated.

Results

The levels of high-density lipoprotein cholesterol (HDL-C) and ApoA1 were lower in males than in femailes (P < 0.05 for each). The allelic and genotypic frequencies of the SNPs were no significant difference between males and females except ApoC3 3238C>G. There were 11 haplotypes with a frequency >1% identified in the cluster in our population. At the global level, the haplotypes comprised of all five SNPs were significantly associated with all seven lipid traits. In particular, haplotype G-G-C-C-A (6%; in the order of ApoA5 c.553G>T, ApoA5 c.457G>A, ApoA5 -1131T>C, ApoC3 3238C>G, and ApoA1 -75bp G>A) and G-A-T-C-G (4%) showed consistent association with total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), ApoA1, ApoB, and the ApoA1/ApoB ratio. In addition, carriers of haplotype G-G-T-C-G (26%) had increased serum concentration of HDL-C and ApoA1, whereas carriers of G-G-C-G-G (15%) had high concentrations of TC, triglyceride (TG) and ApoB. We also found that haplotypes with five SNPs explain much more serum lipid variation than any single SNP alone, especially for TG (4.4% for haplotype vs. 2.4% for -1131T>C max based on R-square) and HDL-C (5.1% for haplotype vs. 0.9% for c.553G>T based on R-square). Serum lipid parameters were also correlated with genotypes and several environment factors.

Conclusions

Several common SNPs and their haplotypes in the ApoA1/C3/A5 gene cluster are closely associated with modifications of serum lipid parameters in the general Chinese population.

Can novel Apo A-I polymorphisms be responsible for low HDL in South Asian immigrants?

Coronary artery disease (CAD) is the leading cause of death in the world. Even though its rates have decreased worldwide over the past 30 years, event rates are still high in South Asians. South Asians are known to have low high-density lipoprotein (HDL) levels. The objective of this study was to identify Apolipoprotein A-I (Apo A-I) polymorphisms, the main protein component of HDL and explore its association with low HDL levels in South Asians. A pilot study on 30 South Asians was conducted and 12-h fasting samples for C-reactive protein, total cholesterol, HDL, low-density lipoprotein (LDL), triglycerides, Lipoprotein (a), Insulin, glucose levels, DNA extraction, and sequencing of Apo A-I gene were done. DNA sequencing revealed six novel Apo A-I single nucleotide polymorphisms (SNPs) in South Asians, one of which (rs 35293760, C938T) was significantly associated with low (<40 mg/dl) HDL levels (P = 0.004). The association was also seen with total cholesterol (P = 0.026) and LDL levels (P = 0.032). This pilot work has highlighted some of the gene-environment associations that could be responsible for low HDL and may be excess CAD in South Asians. Further larger studies are required to explore and uncover these associations that could be responsible for excess CAD risk in South Asians.

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.

Synergistic effect between apolipoprotein E and apolipoprotein A1 gene polymorphisms in the risk for coronary artery disease

Alterations in lipid metabolism and genetic predisposition are major risk factors for coronary artery disease (CAD). Variations in genes involved in lipid metabolism may act synergistically to confer risk or protection against CAD. The objective of the present study was to determine such interactions in variants of apolipoprotein E and apolipoprotein A1 genes. One hundred and forty subjects with clinically confirmed CAD and 100 unrelated normal subjects participated in the study. Multiple regression analysis was used to relate lipid and apolipoprotein profiles with genotypes. Odd ratios were calculated for various combinations of ApoE and ApoA1 genotypes. Prevalence of ApoE 'E4' and ApoA1 'A' and 'T' alleles was significantly higher in patients than controls. Serum apolipoprotein E and apolipoprotein A1 levels were significantly lower in CAD patients than controls. When lipid parameters were related to genotypes, the polymorphisms associated to various markers were in agreement with previous reports. ApoE 2/4 genotype in combination with either ApoA1 heterozygous GA or CT genotype conferred higher risk of CAD. E3 allele in homozygous or heterozygous state in combination with ApoA1+83 CC genotype conferred highest protection (P < 0.05). Thus, it appears that ApoE and ApoA1 gene variants may act synergistically to associate with risk and protection against CAD.

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).

Genetic interactions with diet influence the risk of cardiovascular disease

Single-nucleotide polymorphisms are an integral component of the evolutionary process that over millennia have resulted from the interaction between the environment and the human genome. Relatively recent changes in diet have upset this interaction with respect to the nutritional environment, but nutritional science is beginning to better understand the interaction between genes and diet, with the resulting potential to influence cardiovascular disease risk by dietary modification. Single-nucleotide polymorphisms in several genes have been linked to differential effects in terms of lipid metabolism; however, even a simple model of benefit and risk is difficult to interpret in terms of dietary advice to carriers of the various alleles because of conflicting interactions between different genes. The n-3 family of polyunsaturated fatty acids is underrepresented in our modern diet; much of the benefit of polyunsaturated fatty acids found in studies of various polymorphisms seems to be linked to increased n-3 polyunsaturated fatty acid intake. The nascent science of nutrigenomics faces many challenges; more and better research is needed to clarify the picture, rebut scepticism, and re-invigorate the discussion concerning genetic polymorphism and its interaction with diet.

Association of two apolipoprotein A-I gene MspI polymorphisms with lipid and blood pressure levels

INTRODUCTION

Two MspI polymorphisms in the ApoA-I gene (G-75A and C83T) have been shown to be associated with plasma HDL-cholesterol levels.

METHODS

We used a PCR-based RFLP method to determine the association of these polymorphisms with lipid parameters in 271 non-diabetic, normotriglyceridaemic Chinese subjects, of whom 104 were patients with hypertension, with 10.2% having hypercholesterolaemia and the remainder were controls.

RESULTS

As expected, the hypertensive group had higher blood pressure and indices of obesity, and a more adverse lipid profile. No differences in the ApoA-I G-75A genotype or allele frequency distributions between the controls and patients were identified. However, there was a significantly lower frequency of the CT genotype (p=0.012) and T allele (p=0.011) in the affected subjects with hypercholesterolaemia or hypertension. Similarly, blood pressure and triglyceride levels were significantly lower and HDL-cholesterol levels significantly higher in the subjects with the CT genotype compared to those with the CC genotype (p<0.05). However, the G-75A genotypes did not appear to influence the lipid or blood pressure levels. The -75A allele frequency was higher in our healthy controls than an equivalent Caucasian population (31.1% vs. 18.3%, p<0.001), whereas the 83T allele frequency was similar between the healthy Chinese and Caucasian groups.

CONCLUSION

The 83T allele may be associated with a better lipid profile and blood pressure levels in this group of Chinese subjects.

Contribution of polymorphisms in the apolipoprotein AI-CIII-AIV cluster to hyperlipidaemia in patients with gout

BACKGROUND

Studies have shown that hyperuricaemia is independently related to the insulin resistance syndrome and that polymorphisms of the apolipoprotein AI-CIII-AIV cluster are also related to insulin resistance.

OBJECTIVE

To study the prevalence of polymorphisms of the apolipoprotein AI-CIII-AIV cluster in persons with gout and to determine whether these polymorphisms contribute to the pathophysiology of gout or to altered lipid concentrations.

METHODS

Plasma cholesterol, triglycerides, uric acid, VLDL, LDL, IDL, and HDL triglycerides, cholesterol, and the renal excretion of uric acid were measured in 68 patients with gout with gout and 165 healthy subjects. Polymorphisms were studied by amplification and RFLP in all subjects, using XmnI and MspI in the apolipoprotein AI gene and SstI in the apolipoprotein CIII gene.

RESULTS

The A allele at position -75 bp in the apolipoprotein AI gene was more common in patients with gout than in controls (p = 0.01). Levels of cholesterol, triglycerides, uric acid, basal glycaemia, and HDL cholesterol were higher in the patients (p<0.001). In the patients there was also an interaction between mutations at the two polymorphic loci studied in the apolipoprotein AI gene (p = 0.04). An absence of the mutation at position -75 bp of the apolipoprotein AI gene resulted in increased plasma triglyceride levels.

CONCLUSIONS

Gouty patients have an altered allelic distribution in the apolipoprotein AI-CIII-AIV cluster, which could lead to changes in levels of lipoproteins. This is not caused by a single mutation but rather by a combination of different mutations.

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.

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 the human apolipoprotein A-I promoter G-A mutation on postprandial lipoprotein metabolism

BACKGROUND

There is considerable interindividual variability in the postprandial lipid response to a fat-rich meal, and genetic factors have been considered to account for some of these effects. We previously showed that the G-A mutation 5' to the apolipoprotein (apo) A-I gene was significantly associated with the LDL-cholesterol response to diet.

OBJECTIVE

We evaluated whether this effect is mediated by mechanisms involving postprandial lipoprotein metabolism.

DESIGN

Twenty-eight G/G and 23 G/A healthy male subjects, homozygotes for the apo E3 allele, were subjected to a vitamin A fat-loading test. Blood was drawn at time 0 and every hour for 11 h.

RESULTS

There was a significant postprandial decrease in plasma cholesterol, LDL cholesterol, and apo B in G/G subjects but not in G/A subjects. A greater postprandial response in large triacylglycerol-rich lipoproteins (TRLs) and a smaller postprandial response in large TRL apo A-IV was observed in G/A than in G/G subjects. Retinyl palmitate in large and small TRL concentrations was similar for both genotypes. No significant genotype effects were detected for triacylglycerol concentrations in plasma, small TRL fraction, and apo A-I and HDL-cholesterol concentrations.

CONCLUSION

Our data suggest that the G-A mutation affects the LDL-cholesterol response to diet by mechanisms involving postprandial lipoprotein cholesterol metabolism.

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.

Polymorphisms in the insulin response element of APOC-III gene promoter influence the correlation between insulin and triglycerides or triglyceride-rich lipoproteins in humans

OBJECTIVE

To assess whether the -455 and -482 mutations in APOC-III gene insulin response element affect the relationships between plasma insulin and triglyceride-rich lipoprotein levels.

DESIGN

Population-based studies.

SUBJECTS

The population sample was composed of 983 subjects (485 men and 498 women), aged between 35 and 65 y, randomly sampled from the electoral rolls in Northern France and stratified on gender and 10 y age groups.

MEASUREMENTS

Plasma triglyceride, apolipoprotein C-III, apoB, LpC-III:B and LpE:B lipoprotein particles and insulin levels were measured. Two polymorphisms in APOC-III gene insulin response element (T-->C at -455 and/or C-->T at -482) were determined.

RESULTS

Plasma insulin was positively correlated to triglyceride levels (P<0.0001), apo C-III (P<0.003), LpC-III:B (P<0.0001), apoB (P<0.0001) and LpE:B (P<0.0001). This association differed significantly according to APOC-III insulin response element polymorphisms. The relationship between insulin and LpC-III:B (P<0.02) or apoB (P<0.02) was greater in women bearing the C allele of -455 than the T allele. Similarly, the relationship between insulin and LpC-III:B (P<0.02) or LpE:B (P<0.05) was greater in women bearing the T allele of -482 than the C allele. There was no evidence for any effect in men.

CONCLUSION

These results suggest that the relationship between plasma insulin and triglyceride-rich lipoprotein levels is partly influenced by polymorphisms in APOC-III insulin response element.

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.

Genetic association of five apolipoprotein polymorphisms with serum lipoprotein-lipid levels in African blacks

Genetic studies carried out mainly in European and European-derived populations have shown that common polymorphisms in genes coding for apolipoproteins are significant determinants of serum lipoprotein-lipid levels variation. However, except for a few sporadic studies, the distribution of apolipoprotein polymorphisms and their association with serum lipoprotein-lipid levels have not been evaluated systematically in African or African-derived populations. In this investigation we have studied five apolipoprotein polymorphisms, including APOA1/MspI-75 bp, APOA1/MspI+83 bp, APOC3/PvuII, APOE, and APOH in 786 Africans (493 men, 293 women) from Nigeria. The sample is comprised of Nigerian civil servants consisting of 462 junior staff (less affluent) and 324 senior staff (more affluent) where staff status is a correlate of their socioeconomic status. We first examined genetic associations in the total sample stratified by gender to determine the role of apolipoprotein polymorphisms in affecting serum lipid profile in the general population, and then by staff status to evaluate possible gene-environment interactions. In the total sample, the APOC3/PvuII polymorphism showed significant effect on HDL-cholesterol (P = 0.029) and HDL3-cholesterol (P = 0.009) in women, and the APOE polymorphism was significantly associated with total cholesterol (P = 0.031) and LDL-cholesterol (P = 0.0006) in women. Multiple regression analyses showed that the APOC3/PvuII polymorphism accounts for about 2 and 3% of the variation in HDL-cholesterol and HDL3-cholesterol, respectively, in women; while the APOE polymorphism accounted for about 5 and 6% of the variation in total- and LDL-cholesterol, respectively, in women. Whereas the association of the APOE polymorphism was independent of the staff status, the significant affect of the APOC3/PvuII polymorphism on HDL- and HDL3-cholesterol was confined to senior staff women where it explained about 7% of their variation. We also observed an interaction between staff and the APOH polymorphism in affecting cholesterol levels. The APOH polymorphism showed significant association with total cholesterol (P = 0.010) and LDL-cholesterol (P = 0.016) in senior staff women and explained about 7 and 5% of their phenotypic variations, respectively. These data indicate that gene-environment interaction may play an important role in affecting serum lipid profile in African populations.

Variation at the lipoprotein lipase and apolipoprotein AI-CIII gene loci are associated with fasting lipid and lipoprotein traits in a population sample from Iceland: interaction between genotype, gender, and smoking status

The effects of polymorphisms in the lipoprotein lipase (LPL) gene (HindIII and S447X) and in the apolipoprotein (apo) AI-CIII gene cluster (G75A and C1100T) on levels of fasting plasma triglycerides, apoCIII, high density lipoprotein cholesterol (HDL-C), and apoAI were examined in 315 healthy men and women from Iceland. Non-smoking and smoking men and women were examined separately because of the strong effects of smoking status and gender on lipoproteins. For the LPL gene, there were no significant associations between plasma traits and genotypes of the S447X polymorphism, but the LPL-HindIII polymorphism was associated with significant effects on levels of all traits, with the effect of genotype on triglycerides and apoAI being modulated by smoking status, (genotype x smoking interaction, P < .02). The H- allele was generally associated with slightly lower levels of apoCIII, with a lowering effect on triglycerides only in smokers and with a raising effect on ApoAI in non-smoking and smoking men and in non-smoking women. For the apoCIII C1100T polymorphism, smoking and non-smoking men with one or more T alleles had levels of triglycerides roughly 10% higher than those with only the C allele; in contrast, the women with the T allele had lower levels of triglycerides (15.7% lower in non-smokers, P = .04; gender x genotype interaction, P = .02). In males and females and in smokers and non-smokers, the T allele was associated with levels of apoCIII that were 9-20% higher than those with only the C allele (P = .004 overall). In the non-smoking men, nonlinear additive effects were observed with combinations of genotypes at the LPL and apoAI-CIII loci, with the HDL-C and apoAI raising effect associated with the A75 allele and H- allele seen only in those men with both alleles, and the apoCIII raising effect associated with the H+ and T alleles seen only in those with both alleles. Thus, variations at both of the LPL and apoAI-apoCIII loci influence levels of triglycerides, apoCIII, HDL-C, and apoAI, but these effects are strongly modulated by smoking and are different between men and women. The mechanisms for these interactions between smoking or gender and genes are unknown, but future studies should take such interactions into account.

Reduced LDL particle size in children consuming a very-low-fat diet is related to parental LDL-subclass patterns

BACKGROUND

A genetically influenced atherogenic lipoprotein phenotype characterized by a predominance of small, dense LDL particles (subclass pattern B) can be induced by low-fat diets in healthy subjects with large LDL particles (pattern A).

OBJECTIVE

The aim of this study was to test whether genetic predisposition to subclass pattern B contributes to susceptibility to induction of this trait by a low-fat diet.

DESIGN

The prevalence of pattern B in children is relatively low compared with that in older individuals, but genetic susceptibility to this trait in offspring can be inferred by its presence in their parents. Plasma lipoproteins were analyzed 10 d after a change from a usual diet to a very-low-fat (10% fat), high-carbohydrate diet in offspring (mean age: 14 y; range: 7-28 y) of 22 families according to parental LDL-subclass patterns when consuming a low-fat diet: AxA mating (9 families with 19 children), AxB mating (5 families with 10 children), and BxB mating (8 families with 21 children).

RESULTS

The very-low-fat, high-carbohydrate diet produced significantly greater decreases in LDL particle size in offspring of BxB parents (f1.gif" BORDER="0"> +/- SE: -0.55 +/- 0.16 nm) and AxB parents (-0.48 +/- 0.19 nm) than in offspring of AxA parents (0.14 +/- 0.20 nm). The number of children expressing pattern B with the 10%-fat diet and the proportion of children converting from pattern A to pattern B was significantly greater in offspring of BxB parents than in those with 1 or 2 pattern A parents.

CONCLUSION

A very-low-fat, high-carbohydrate diet can induce expression of LDL-subclass pattern B in genetically predisposed children with low expression of the trait while consuming their usual diets.

Gender related association between genetic variations of APOC-III gene and lipid and lipoprotein variables in northern France

The goal of the present study was to assess the impact of variability at the APOC-III insulin response element (APOC-III IRE) genetic locus on lipid, lipoprotein and complex lipoprotein particle levels as well as on the risk of dyslipidemia, in the population of northern France. To this end, 590 men and 579 women were randomly selected in the urban community of Lille in the framework of the MONICA project. Three polymorphisms, -482, -455 in the APOC-III insulin response element (IRE) and SstI in the 3'-noncoding region of the APOC-III gene locus were assessed. Compared to the most common alleles, the rare alleles of -482 and -455 were associated with increased levels of apoB-containing particles (LDL-cholesterol, apoB) and of triglyceride-related markers (apoC-III and LpC-III:B) in women, but not in men, suggesting a gender-related impact of APOC-III polymorphisms on these variables. Similarly, triglycerides, LpC-III:B and apoB were higher in women bearing the rare allele of SstI than in those with the most common allele. There was no evidence for any significant association between any of the -482, -455, and SstI alleles and lipid disorders (mixed hyperlipidemia, hypertriglyceridemia and hypercholesterolemia) in this sample of randomly selected men and women from northern France. In contrast, the prevalence of the haplotype that combined the rare alleles of the -482 and -455 sites was increased only in women with hypertriglyceridemia. Therefore, although the individual risk of hypertriglyceridemia is increased in women with the haplotype T, C at -482, -455, it appears that the -482, -455 and SstI APOC-III gene polymorphisms are not major contributors to the risk of dyslipidemia in the population of northern France.

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).

Lack of association between genetic variations of apo A-I-C-III-A-IV gene cluster and myocardial infarction in a sample of European male: ECTIM study

The goal of the present study was to compare the allele frequency of four polymorphisms at the apo A-I C-III A-IV cluster gene locus-ApoA-I: XmnI and PstI; ApoC-III: SstI; ApoA-IV: XbaI-between male patients who had had a myocardial infarction (n= 614) and matched controls (n = 764). The association with a number of lipid lipoprotein, apolipoprotein and lipoprotein particle variables was also assessed. Patients and subjects were recruited in Belfast, Lille, Strasbourg and Toulouse in the framework of the ECTIM study. In the control group, the frequencies of the different polymorphic alleles were homogeneous among recruitment centres suggesting the absence of any European North to South gradient for these cluster polymorphisms. There was no evidence for a significant difference in allelic distribution between cases and controls suggesting that apo A-I, C-III, A-IV gene cluster polymorphisms do not explain MI survival in this sample of European men. There was no statistically significant association between apo A-I C-III A-IV cluster gene polymorphisms and lipid, lipoprotein, apolipoprotein, and lipoprotein particle levels. In conclusion, in the ECTIM study, the apo A-I, C-III, A-IV gene cluster polymorphism is associated with neither circulating plasma variables nor MI survival.

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.

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.

Evidence against alterations in Lecithin:cholesterol acyltransferase (LCAT) activity in familial combined hyperlipidemia

Elevated concentrations of plasma cholesterol and triglycerides are characteristic of familial combined hyperlipidemia (FCHL) which may also present with reduced high density lipoprotein (HDL) cholesterol concentrations. Lecithin:cholesterol acyltransferase (LCAT) plays a key role in reverse cholesterol transport by converting unesterified cholesterol to cholesterol ester in the process of maturation of HDL in the presence of its activator, apolipoprotein (apo) A-I. We hypothesised that alterations in LCAT activity or plasma concentrations or gene sequence of apo A-I could influence HDL metabolism in these patients. We studied cholesterol concentrations of high density lipoprotein subfractions and LCAT activity in 25 FCHL subjects and 48 controls. Total HDL (p=0.018) and HDL2 (p=0.008) were significantly decreased in the FCHL group compared with controls. After analyses with adjusted data only HDL2 remained significantly decreased in the FCHL group (p=0.050). The LDLc/HDLc and A-I/HDLc ratios were significantly elevated in the FCHL group (p <0.0001), the latter suggesting the existence of compositional differences in the HDL particles of the FCHL individuals. LCAT activity assessed in the FCHL (19.94+/-3.95 nmol/ml per h) and control (20.13+/-6.86 nmol/ml per h) groups showed no statistically significant differences. A significant positive correlation of LCAT activity with total HDL (r=0.42), HDL3 cholesterol (r=0.46) and apolipoprotein A-I (r=0.47) was observed in affected subjects but not in controls. An association between a Ga(-75)-A variation in the promoter region of the apo A-I gene and elevated concentrations of apo A-I (p=0.009) and apo C-III (p=0.041) was observed. This association was strongly influenced by the status of the subject providing further evidence for a regulatory role of this genetic region in the expression of FCHL. Our data suggests that LCAT activity is normal in FCHL and, therefore, does not account for the abnormalities observed in these patients essentially with regard to the HDL2 subfraction.

The apolipoprotein A-I/C-III/A-IV gene cluster: ApoC-III and ApoA-IV expression is regulated by two common enhancers

Genetic, epidemiological and clinical evidence have clearly demonstrated the importance of the human apolipoprotein (apo) A-I/C-III/A-IV gene cluster in lipid metabolism and heart attack. The transcriptional regulation of these genes determines the level of the encoded proteins and therefore influences the concentration of triglycerides and cholesterol. Here, we analyze the existence of transcription control elements in the 6.6 kb apoC-III/A-IV intergenic region and their influence on the expression of both genes. Two main positive common control elements were found to modulate apoC-III and apoA-IV expression in HepG2 and in Caco-2 cells: the previously described apoC-III enhancer, located 0.8 kb upstream from the cap site of the gene, and a newly detected activating region located in the center of the intergenic sequence. The activity of both elements is highly increased by the hepatic and intestinal transcription factor HNF-4. Analysis of a 641 bp fragment containing the central element showed that it has the properties of a tissue-specific enhancer. Liver nuclear proteins interact with seven DNA binding sites present in this enhancer and HNF-4 specifically interacts with one of these sites. A third positive element, situated immediately upstream from the apoA-IV minimal promoter, is also activated by HNF-4; however, this element is not involved in apoC-III expression. In addition, two negative regions were identified, one located near the apoA-IV gene and the other one between the apoC-III enhancer and the newly identified central enhancer. In conclusion, negative and positive control elements are located in the apoC-III/A-IV intergenic region, including two enhancers important for the expression of the two genes. These results add new evidence that common regulatory elements for the expression of the apoA-I, apoC-III and apoA-IV genes are interspersed throughout the cluster.

Response to dietary fat and cholesterol and genetic polymorphisms

1. We examined common polymorphisms in the genes encoding the LDL receptor, lipoprotein lipase, apoAI, apoB, apoAIV and cholesteryl ester transfer protein and related them to changes in LDL and HDL cholesterol after high fat/high cholesterol diets. 2. The only significant association was seen with the apoIV polymorphism, which leads to a structural change in the protein. The response to fat and cholesterol in subjects with at least one apoAIV 2 allele was only 30% of that seen in subjects with the common apoIV 1 allele (P < 0.01), accounting for 6-7% of the variance in response. This confirms the results of two previous studies in which dietary cholesterol intake was changed. 3. No association were seen with polymorphisms of the other five genes examined.

Haplotype analysis of two APOA1/MspI polymorphisms in relation to plasma levels of apo A-I and HDL-cholesterol

A common MspI polymorphism (G/A) in the promoter region of the APOA1 gene (-75 bp) has been shown to be associated with plasma apo A-I and HDL-C variation in several, but not all, studies. Recently another MspI polymorphic site (+/-) in the 5'region of APOA1 (+83 bp) has been identified which may also be relevant to HDL metabolism. This study was undertaken to elucidate the individual and combined effects of these two polymorphisms on plasma apo A-I and HDL-C levels in a cohort of 534 normoglycemic US Whites from the San Luis Valley, Colorado. Both polymorphisms were in strong linkage disequilibrium (P < 0.005); of the expected four haplotypes (G+, G-, A+, A-) the A- was not observed in this sample. Single site RFLP analysis revealed an independent and significant effect associated with each polymorphism on plasma apo A-I variation but not on HDL-C variation. Further analyses showed that the genotype effects of both polymorphisms were confined to non-smokers only. Haplotype analysis, combining both RFLPs, was more informative as this explained almost twice the amount of phenotypic variation in plasma apo A-I compared to single RFLP analysis in non-smokers. Compared to the most common haplotype (G+), the A+ and G- haplotypes were associated with increased plasma apo A-I levels by 6.7 mg/dl and 22.0 mg/dl, respectively in non-smoking men, and by 4.6 mg/dl and 15.1 mg/dl in non-smoking women, respectively. These data indicate that haplotype analysis in this region may be important to elucidate the functional significance of the APOA1 gene in HDL metabolism.

The genetic determinants of plasma cholesterol and response to diet

In general, risk factors for multifactorial disorders such as atherosclerosis and hyperlipidaemia show a continuous distribution in the population, and this is the result of both interaction between genetic variation at genetic loci, and genetic and environmental interaction. Therefore, the investigation of the genetics of intermediate phenotypes such as levels of plasma lipid traits is likely to be particularly informative. Once the genes involved in determining the levels of these phenotypes have been identified, it should be possible to use the information to obtain a better understanding of the way these genetic variations determine the clinical end points. In the population it will be possible to identify a number of polygenes that are having a small effect on determining the trait, but for a particular individual, or the relatives of that individual, only a subset of all these polygenes will determine the level of the trait and therefore the risk of developing the disorder. In general, mutations with a large effect on the trait are rare in the population, By contrast, polymorphisms with a small effect on the trait may be common, such as is found with the effect of the apoE alleles and variation at the apoB gene locus on lipid levels. In the field of hyperlipidaemia and atherosclerosis research, molecular techniques have already given a great deal of information on how specific sequence variations in some of the candidate genes are involved in determining levels of plasma apoproteins, lipoproteins and lipids. As more mutations and sequence variations are identified, this will not only aid our understanding of the underlying pathology, but should be useful for identifying individuals who are at risk of developing atherosclerosis because of their particular genotype or combination of genotypes.

The apolipoprotein AICIII-AIV gene cluster: sequence of the ApoCIII-ApoAIV intergenic region

The genes coding for human apolipoproteins AI, CIII and AIV are tandemly organised in a cluster on chromosome 11. The sequence of 4 kb of the 6.6-kb ApoCIII-ApoAIV intergenic region was unknown until now. Since different elements involved in the transcriptional regulation of the three genes of the cluster were previously identified in this region, we decided to sequence it. We present here the complete sequence of the region. Its availability will allow study of the transcriptional regulation of ApoCIII and ApoAIV at the molecular level. In addition, the use of PCR to study the polymorphic sites detected in the ApoCIII-ApoAIV intergenic region will now be possible. Some of these sites have been associated with lipid disorders and coronary heart disease.

Association between genetic variation at the APO AI-CIII-AIV gene cluster and familial combined hyperlipidaemia

By using chemical cleavage mismatch analysis and the single strand conformation polymorphism technique, DNA fragments of the apo CIII gene, including the 5' flanking region and all the exons, were screened for sequence changes underlying the observed association between familial combined hyperlipidaemia (FCHL) and the apo AI-CIII-AIV gene cluster in affected individuals from eight FCHL families. A C1100-T transition in the wobble position of codon 14 in exon 3 and a T3206-G transversion in the non-translated region of exon 4 were identified, occurring in four and all probands, respectively. Using these variants and the G-75-A transition in the apo AI promoter, co-segregation of the gene cluster with hyperlipidaemia could be excluded in all eight families (lod score - infinity at theta = 0). No support for co-segregation was obtained using the affected pedigree member method of linkage analysis (overall T = -0.77 for f(p) = 1 [symbol: see text] p). The frequencies of T1100 and G3206 in a group of 55 patients with combined hyperlipidaemia were 0.35 and 0.52, respectively, which were significantly higher compared to 360 controls (0.21, p < 0.01 and 0.35, p < 0.005 respectively). In patients homozygous for the T1100 allele, levels of plasma triglyceride were 2.5-fold higher (868 mg/dl) than those homozygous for the C1100 allele (337 mg/dl), while patients heterozygous for the polymorphism had intermediate values (443 mg/dl) (p < 0.01). A similar association was seen in controls (p < 0.04). The three polymorphisms studied were in strong linkage disequilibrium in both the group of CHL patients and the unrelated individuals. This study confirms the association between common variation in the gene cluster and differences in plasma lipid levels in the general population and in patients with combined hyperlipidaemia, but fails to confirm co-segregation with FCHL, suggesting the role of other genetic or environmental factors in the aetiology of FCHL.

Variation at the hepatic lipase and apolipoprotein AI/CIII/AIV loci is a major cause of genetically determined variation in plasma HDL cholesterol levels

Genetic factors have been shown to play an important role in determining interindividual variation in plasma HDL-C levels, but the specific genetic determinants of HDL cholesterol (HDL-C) levels have not been elucidated. In this study, the effects of variation in the genomic regions encoding hepatic lipase, apolipoprotein AI/CIII/AIV, and the cholesteryl ester transfer protein on plasma HDL-C levels were examined in 73 normotriglyceridemic, Caucasian nuclear families. Genetic factors accounted for 56.5 +/- 13% of the interindividual variation in plasma HDL-C levels. For each candidate gene, adjusted plasma HDL-C levels of sibling pairs who shared zero, one, or two parental alleles identical-by-descent were compared using sibling-pair linkage analysis. Allelic variation in the genes encoding hepatic lipase and apolipoprotein AI/CIII/AIV accounted for 25 and 22%, respectively, of the total interindividual variation in plasma HDL-C levels. In contrast, none of the variation in plasma HDL-C levels could be accounted for by allelic variation in the cholesteryl ester transfer protein. These findings indicate that a major fraction of the genetically determined variation in plasma HDL-C levels is conferred by allelic variation at the hepatic lipase and the apolipoprotein AI/CIII/AIV gene loci.

Guanidine to adenine (G/A) substitution in the promoter region of the apolipoprotein AI gene is associated with elevated serum apolipoprotein AI levels in Chinese non-smokers

The influence of the guanidine to adenine (G/A) substitution in the promoter region of the apolipoprotein (apo) AI gene (at -75 bp) on serum lipids and apolipoproteins was studied in 287 healthy Chinese of both sexes in Singapore. Women had significantly higher levels of high-density lipoprotein cholesterol (HDLC) and apo AI and lower low-density lipoprotein cholesterol (LDLC). The distribution of genotypes was at Hardy-Weinberg equilibrium. The frequency of the A allele in the Chinese was significantly higher [0.27; 95% confidence interval (CI) 0.24-0.31] than that reported in Caucasians (0.12; 95% CI 0.09-0.14). In men, the A allele was associated with 20% higher apo AI; this association was completely absent in women. Furthermore, in men this association was only observed in those who had never smoked, and was absent in smokers. The G/A substitution explained 9% (P < 0.02) of the sample variance of apo AI in non-smoking men. The modulating influence of smoking could not be examined in women because too few women smoke. Although the impact of this polymorphism is modulated by hormones and smoking, it is of importance in determining levels of apo AI in healthy Chinese individuals. No association of the G/A substitution of the apo AI gene was observed with any other lipid traits.

Polymorphism in the promoter region of the apolipoprotein AI gene associated with differences in apolipoprotein AI levels: the European Atherosclerosis Research Study

The effect associated with the substitution of adenine (A) for guanidine (G) in the promoter region of the apolipoprotein AI gene (-75 bp) with plasma apo AI and high-density lipoprotein (HDL) levels was investigated in the European Atherosclerosis Research Study (EARS). This is a study of healthy offspring (cases) of fathers who had suffered premature myocardial infarction (MI) before age 55 years (n = 565) and age- and sex-matched controls (n = 1,078) from 12 European countries, divided into 5 regions based on geography and language. The frequency of the polymorphism was not significantly different among the regions and the relative frequency of the rare A allele was similar in cases and controls (0.159 vs. 0.142) combining data from all regions. Individuals with one or more A allele had significantly higher plasma apo AI levels (P < 0.05) than individuals homozygous for the G allele. This effect was consistent in all regions. The data were analyzed separately in males and females. In females, those with one or more A allele had significantly higher apo AI levels (P = 0.05) than individuals homozygous for the G allele, and this raising effect of the A allele was greater in cases than controls for both apo AI (5.23% vs. 1.56%) and HDL (4.48% vs. 1.89%). In males, the A allele was associated with higher levels of apo AI and HDL, but the effect was much smaller and the differences did not reach statistical significance. In the females, where the effect of the A allele was strongest, the effect on apo AI associated with genotype was evident in non-smokers, and individuals with one or two A alleles had 3.6% higher apo AI and 3.14% higher HDL levels than individuals homozygous for the G allele. However, in the female smokers the raising effect of the A allele was greatly reduced (0.56%). Thus genetic variation in the promoter region of the apo AI gene is associated with differences in apo AI and HDL levels in healthy individuals throughout Europe, but the effect is modulated by gender, environmental factors such as smoking, and a family history of MI.