The effects of the apolipoprotein B signal peptide (ins/del) and XbaI polymorphisms on plasma lipid responses to dietary change

Dietary quality indices modify the effects of apolipoprotein B polymorphisms on biochemical and anthropometric factors in type 2 diabetes mellitus

We tried to identify the interaction between dietary quality indices and apolipoprotein B Ins/Del and EcoR1 polymorphisms on biochemical and anthropometric factors in patients with type 2 diabetes mellitus (T2DM). This cross-sectional study recruited 700 adults with T2DM in Tehran. The genotypes of Ins/Del and EcoR1 single nucleotide polymorphisms (SNP) were explored via polymerase chain reaction (PCR). Dietary quality index-international (DQI-I), healthy eating index-2015 (HEI-2015) and dietary phytochemical index (DPI) were calculated by semi-quantitative food frequency questionnaire (FFQ). In both crude and adjusted model for confounding factors, we observed significant interactions between DQI-I and Ins/Del SNP on leptin in and 8-iso-prostaglandin F2 α (8-iso-PGF2α), DPI and EcoR1 SNP on total cholesterol (TC) and between Ins/Del SNP and HEI-2015 on interleukin-18 (IL-18). Furthermore, in crude model there were close to meaningful interactions between EcoR1 SNP and DQI-I on total antioxidant capacity (TAC) and between EcoR1 SNP and HEI-2015 on serum leptin and superoxide dismutase (SOD) levels. Our finding indicated that the association between DQI-I, HEI-2015 and DPI with IL-18, TC, leptin and 8-iso-PGF2α in patients with T2DM might be dependent on Ins/Del and EcoR1 variants in ApoB gene.

Anti-obesity effects of galla rhois via genetic regulation of adipogenesis

In the present study, we investigated the effects of Galla Rhois (GR) on obesity and gene expression. We prepared a GR extract and various solvent fractions and evaluated the degree to which they inhibited adipocyte differentiation and adipogenesis in vitro. Among them, the GR ethyl acetate fraction (GE) had the lowest EC50 for adipocyte differentiation and adipogenesis and thus was selected for in vivo experiments. We induced obesity in C57BL/6 mice by providing them a high-fat diet (HFD). Then, GE (10-40 mg/kg) or orlistat (positive control, 4 mg/kg) was orally administered daily for six weeks. Mean body weights and weight gain were significantly lower in the GE40 group (40 mg/kg of GE) compared with the HFD group (p < 0.05). The most significant changes in serum glucose, total cholesterol, and triglyceride levels were confirmed in the GE40 group (p < 0.05). Epididymal fat was weighed and stained for body fat measurement, and significant differences were recorded from GE10 to GE40 (p < 0.05). Finally, 3T3-L1 pre-adipocytes were treated with GE, and cDNA from these cells was used for microarray analysis and qRT-PCR. Microarray analysis revealed 13 genes up-regulated and 21 genes down-regulated by GE. From the qRT-PCR analysis, we found that GE altered the mRNA expression of eosinophil peroxidase, glucose-dependent insulinotropic polypeptide receptor, and apolipoprotein B. Based on this study, we suggest that GR could be developed as an anti-obesity therapeutic agent.

Quantile-specific heritability of high-density lipoproteins with implications for precision medicine

BACKGROUND

We have previously shown that the effect of a high-density lipoprotein (HDL) genetic risk score depends on whether the phenotype (HDL cholesterol) is high or low relative to its distribution (quantile-dependent expressivity).

OBJECTIVE

Evidence for quantile-dependent expressivity was sought using a more inclusive genetic measure (quantile-specific heritability, h²) in a larger population (Framingham cohort).

METHODS

Quantile regression was used to test whether the offspring-parent (β_OP) and full-sib (β_FS) regression slopes increased with the percentiles of the offspring's HDL distribution in 10,650 parent-offspring pairs and 2130 sibships. Quantile-specific heritability was estimated by 2β_OP/(1 + r_spouse) and [(8β_FSr_spouse + 1)^0.5-1]/(2r_spouse), where r_spouse is the spouse correlation.

RESULTS

HDL cholesterol heritability estimated from β_OP increased significantly (P = 4.2 × 10^-5) from the 10^th (h² ± SE: 0.44 ± 0.03), 25^th (0.45 ± 0.03), 50^th (0.47 ± 0.03), and 75^th (0.56 ± 0.04) to the 90^th percentiles (0.65 ± 0.06) of the offspring's age- and sex-adjusted HDL cholesterol distribution. Heritability estimated from β_FS also increased significantly with the percentiles of the offspring's HDL cholesterol (P = .002), apo A1 (P = .006), HDL2 cholesterol (P = .003), and HDL3 cholesterol distribution (P = .02). Consistent with quantile-dependent expressivity, published pharmacologic and nutritional interventions that raised (eg, statin, fibrates, estrogen replacement therapy, efavirenz, and dietary fat) or lowered HDL cholesterol concentrations (tamoxifen, dietary carbohydrate) correspondingly increased and decreased genetic effects.

CONCLUSION

HDL cholesterol heritability increased with increasing percentile of the offspring's HDL distribution. Whereas precision medicine is based on the premise that genetic markers identify patients most likely to benefit from drugs and diet, quantile-dependent expressivity postulates that the strong signals from these genetic markers simply trace the heritability increase with increasing plasma HDL concentrations. Thus, quantile-dependent expressivity provides an alternative interpretation to these genotype-specific effects.

Associations of the APOB rs693 and rs17240441 polymorphisms with plasma APOB and lipid levels: a meta-analysis

BACKGROUND

The associations of the apolipoprotein B gene (APOB) rs693 and rs17240441 polymorphisms with plasma levels of APOB and lipids have been widely explored, but the results were inconclusive. This meta-analysis aimed to clarify the associations of the rs693 and rs17240441 polymorphisms with fasting APOB and lipid levels.

METHODS

Sixty-one studies (50,018 subjects) and 23 studies (8425 subjects) were respectively identified for the rs693 and rs17240441 polymorphisms by searching in PubMed, Google Scholar, Web of Science, Cochrane Library, Wanfang, VIP and CNKI databases. The following information was collected for each study: first author, age, gender, ethnicity, health condition, sample size, genotyping, lipid assay method, mean and standard deviation or standard error of APOB and lipid variables by genotypes. A dominant model was used for this meta-analysis.

RESULTS

The carriers of the rs693 variant allele (T) had higher levels of APOB [standardized mean difference (SMD) = 0.26, 95% confidence interval (CI) = 0.16-0.36, P < 0.01], triglycerides (TG) (SMD = 0.12, 95% CI = 0.05-0.20, P < 0.01), total cholesterol (TC) (SMD = 0.24, 95% CI = 0.17-0.30, P < 0.01) and low-density lipoprotein cholesterol (LDL-C) (SMD = 0.22, 95% CI = 0.14-0.30, P < 0.01), and lower levels of high-density lipoprotein cholesterol (HDL-C) (SMD = -0.06, 95% CI = -0.11-0.01, P = 0.01) than the non-carriers. The carriers of the rs17240441 deletion allele had higher levels of APOB (SMD = 0.13, 95% CI = 0.06-0.20, P < 0.01), TC (SMD = 0.17, 95% CI = 0.07-0.26, P < 0.01) and LDL-C (SMD = 0.15, 95% CI = 0.07-0.23, P < 0.01) than the non-carriers.

CONCLUSIONS

The rs693 polymorphism is significantly associated with higher levels of APOB, TG, TC and LDL-C, and lower levels of HDL-C. The rs17240441 polymorphism is significantly associated with higher levels of APOB, TC and LDL-C. Further studies are needed to elucidate the underlying mechanisms.

Genetic markers associated to dyslipidemia in HIV-infected individuals on HAART

This study evaluated the impact of 9 single nucleotide polymorphisms (SNPs) in 6 candidate genes (APOB, APOA5, APOE, APOC3, SCAP, and LDLR) over dyslipidemia in HIV-infected patients on stable antiretroviral therapy (ART) with undetectable viral loads. Blood samples were collected from 614 patients at reference services in the cities of Porto Alegre, Pelotas, and Rio Grande in Brazil. The SNPs were genotyped by conventional polymerase chain reaction (PCR) and real-time PCR. The prevalence of dyslipidemia was particularly high among the protease inhibitors-treated patients (79%). APOE (rs429358 and rs7412) genotypes and APOA5 −1131T>C (rs662799) were associated with plasma triglycerides (TG) and low-density-lipoprotein cholesterol levels (LDL-C). The APOA5 −1131T>C (rs662799) and SCAP 2386A>G (rs12487736) polymorphisms were significantly associated with high-density-lipoprotein cholesterol levels. The mean values of the total cholesterol and LDL-C levels were associated with both the APOB SP Ins/Del (rs17240441) and APOB XbaI (rs693) polymorphisms. In conclusion, our data support the importance of genetic factors in the determination of lipid levels in HIV-infected individuals. Due to the relatively high number of carriers of these risk variants, studies to verify treatment implications of genotyping before HAART initiation may be advisable to guide the selection of an appropriate antiretroviral therapy regimen.

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.

Haplotype analysis of signal peptide (insertion/deletion) and XbaI polymorphisms of the APOB gene in gallbladder cancer

PURPOSE

The incidence of gallbladder cancer (GBC) is usually paralleled by the prevalence of gallstone disease, and genes of cholesterol metabolism have been implicated in gallstone disease. The XbaI and insertion/deletion (ins/del) polymorphism of Apolipoprotein B (APOB) appears to influence cholesterol homoeostasis and possibly risk for gallstone disease. We examined the effect of these polymorphisms individually as well as their haplotypes on GBC and gallstone patients in North Indian population.

METHODS

The study comprises 123 consecutive cases of proven GBC, 172 cases of gallstone and 232 healthy subjects of similar age and sex. The genomic DNA was extracted from peripheral blood leucocytes and genotyping was performed using polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism.

RESULTS

In a case-control study, APOB XbaI and ins/del polymorphisms were not significantly associated with risk of GBC. Using the expectation maximization algorithm, four haplotypes were obtained, and haplotype X(+),D was found to be significantly higher in GBC patients without stone in comparison with healthy subjects [odds ratio (OR) 2.9, 95% confidence interval 1.2-6.6 P=0.012].

CONCLUSIONS

The X(+),D haplotype of APOB is associated with increased risk for development of GBC and the risk is not modified in the presence of gallstones.

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

Apolipoprotein B (apoB) is the sole protein component of low-density lipoprotein (LDL) and is thought to play an important role in atherogenesis. We performed a meta-analysis of the associations between the three most frequently investigated polymorphisms (XbaI, signal peptide insertion/deletion, EcoRI) in the apolipoprotein B (APOB) gene, lipid parameters, and the risk of ischemic heart disease (IHD). We restricted our analysis to Caucasians. Homozygotes for the XbaI X+ allele had significantly elevated levels of LDL cholesterol (LDL-C) and apoB, but a decreased risk (OR=0.80; 95%CI: 0.66-0.96) of IHD. Homozygosity for the signal peptide deletion allele was associated with similarly increased levels of LDL-C and apoB, and with an increased risk of IHD (OR=1.30; 95%CI: 1.08-1.58). Subjects homozygous for the rare EcoRI allele had significantly decreased levels of total and LDL cholesterol, but unaltered risk of IHD. We conclude that all three polymorphic apoB sites are associated with altered lipid levels, but not necessarily with a consistently altered risk of IHD. These data suggest that the relationship between apoB levels, hypercholesterolemia and IHD risk cannot have a simple molecular basis in the apoB gene.

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

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

Apolipoprotein E and apolipoprotein B genotypes and risk for spina bifida

BACKGROUND

Altered cholesterol metabolism and defects in cholesterol biosynthesis may influence abnormal central nervous system (CNS) development. During early stages of embryonic development, high levels of cholesterol are needed by rapidly proliferating cells that utilize cholesterol as a key cell membrane component. Alterations in cholesterol levels are influenced by variations in the apolipoprotein E (apoE) and apolipoprotein B (apoB) genes. The purpose of our study was to explore the possible association between infant genetic variations in the apoE and apoB genes and spina bifida (SB) risk.

METHODS

Genomic DNA was extracted from newborn screening blood spots obtained from 26 infants with SB and 73 non-malformed control infants. ApoE and apoB genotypes were determined by restriction enzyme digestion of PCR amplification products.

RESULTS

Genotype frequencies for the apoE and apoB polymorphisms were not statistically different between case and control infants. For each apoB polymorphism, however, the frequency of the wild-type allele was higher in SB infants as compared to controls. Additionally, the apoE genotype E2/E3 was observed more frequently in the controls than in SB infants [15% in controls compared to 4% in cases; OR = 0.2 (0-1.6)].

CONCLUSIONS

Results from this study suggest that genetic variations in the apoE and apoB genes, known to regulate cholesterol metabolism, do not substantially contribute to the risk of SB in infants.

Apolipoproteins AI, B, and E polymorphisms in severe aortic valve stenosis

Hypercholesterolemia has been related to aortic valve stenosis (AS). Polymorphisms of apolipoproteins (apo) AI, B, and E are associated with variable levels of plasma lipids, but the association between these polymorphisms and AS is unknown. In a case-control study of groups matched by age, sex, comparable body mass index, hypertension, triglycerides, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol, we analyzed the distribution of apo AI A/G mutation, apo B signal peptide insertion/deletion, apo B XbaI restriction fragment length. and apo E polymorphisms in 62 non-diabetic patients with severe aortic valve stenosis and 62 control subjects. All patients underwent echocardiographic analysis. Univariate analysis showed a higher prevalence of the XbaI X + /X + genotype (p = 0.007) of apo B and the apo E2 allele (p = 0.034) in patients with severe AS. Apo polymorphisms were not associated with lipid levels, left ventricular mass, or the aortic gradient.

Determinants of lipid level variability in French-Canadian children with familial hypercholesterolemia

The wide variability in the biochemical expression of familial hypercholesterolemia (FH) is only partly explained by mutational heterogeneity in the low density lipoprotein receptor (LDLR) gene. In the current study, we measured this biochemical variability in a group of children heterozygous for the >15-kb LDLR gene deletion (n=67) and examined the contribution of apolipoprotein (apo) E and B allelic variations to this phenotypic variability. Variances of total cholesterol (TC), LDL-C, and apoB concentrations and of the ratio of TC to high density lipoprotein cholesterol (HDL-C) were increased in FH subjects compared with controls. However, after taking the means into account, the coefficients of variation showed that the variability of LDL-C and apoB concentrations was smaller for FH than for controls and that the variability of TC and of the ratio TC to HDL-C was similar between both groups. The epsilon2/3 genotype was associated with lower mean TC, LDL-C, and apoB concentrations in FH. The magnitude of this effect was smaller in controls than in FH. Indeed, the percentages of total variance of TC, LDL-C, and apoB attributable to the apoE locus were 19.9%, 18.1%, and 11.8%, respectively, in FH cases and 5.9%, 7.4%, and 6.0%, respectively, in controls. We did not detect any effect of the apoB insertion/deletion polymorphism on lipid traits in FH children. However, in controls, we observed a strong interaction between apoE and apoB genotypes on apoB concentrations and on TC to HDL-C ratios. Our study reemphasizes the important role of apoE in lipid metabolism and illustrates that the effects of allelic variations on lipid traits are context dependent.

Genetic determination of plasma lipids and insulin in the Czech population

OBJECTIVES

To evaluate the association between plasma lipids and insulin and variation in the genes for apolipoproteins (APO) E (CfoI), B (insertion/deletion), C1 (HpaI), and C3 (C-482T, C3238G) in a population-based Czech Slavonic study.

DESIGN AND METHODS

In 131 men and 154 women, polymorphisms were investigated using PCR. In the same subjects plasma lipid levels and insulin were measured.

RESULTS

In the women, carriers of the e4 allele had higher apoB (p = 0.03) and triglyceride (p = 0.03) compared to e3 homozygotes, whereas in the men, the effect of the e4 allele was seen on total cholesterol (p = 0.02), LDL cholesterol (p = 0.003) and apoB (p = 0.001). Compared with SP27 (insertion) homozygotes of the APOB polymorphism, women SP24 (deletion) homozygotes had higher levels of total (p = 0.003) and LDL cholesterol (p = 0.007) and apoB (p = 0.05). No significant effect was seen in the men. Women homozygous for the APOC3 -482T allele had higher insulin levels than -482C homozygotes (p = 0.03). Men homozygous for APOC3 -482T allele have the highest plasma triglyceride level (p = 0.02). The APOC1 polymorphism exhibited no significant effect on any of the parameters studied.

CONCLUSIONS

In this sample, variation at the APOE, APOB and APOC3 genes play a role in determining plasma levels of insulin and lipids, and emphasize the importance of gender-associated effects in the genetic determinations.

Do polymorphisms of apoB, LPL or apoE affect the hypocholesterolemic response to weight loss?

To assess whether there is a differential hypocholesterolemic response to weight loss for subjects carrying polymorphisms of the apolipoprotein B and other genes. A before and after comparison of lipid parameters following a calorie controlled diet for an intervention period of 12 weeks. A lipid clinic based in a large teaching hospital. The difference in slope coefficients relating the percentage change in lipid parameters to the change in body weight (adjusted for age, gender and initial body mass index (BMI)), for genotype subgroups defined by polymorphisms of the 5'VNTR apoB gene, two mutations of the LPL gene and ApoE. One hundred and forty six subjects completed the intervention diet. While, on average, the intervention was successful (mean weight loss 3.9%), there was no statistically significant difference in the slope coefficients relating lipid change to weight loss for most of the genotypes tested. The slope difference for long versus short 5'VNTR alleles of the apoB gene was 0.445 (-1.307, 2.198) for apolipoprotein B and -0. 104 (-1.486, 1.278) for total cholesterol. However, subjects carrying at least one varepsilon4 allele were significantly hypo-responsive to weight loss, difference in slope coefficients -1.087 (-2.09, -0.084) and -1.320 (-2.589, 0.051) for total cholesterol and apoB, respectively. Although, this study is one of the largest of its kind, it has not replicated the findings of other smaller studies. These findings do not provide support for the use of genotype-targeted dietary advice in routine practice.

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.

Angiotensin-converting enzyme and apolipoprotein B polymorphisms in coronary artery disease

The association between angiotensin-converting enzyme (ACE) as well as apolipoprotein B polymorphisms and dyslipidemia and coronary artery disease (CAD) is controversial. We assessed the distribution of ACE insertion and/or deletion, apolipoprotein B signal peptide insertion and/or deletion, and apolipoprotein B XbaI restriction fragment length polymorphisms in 388 nondiabetic patients. We studied 112 patients with angiographically defined asymptomatic CAD or with stable functional classes I and II angina and 139 patients with acute myocardial infarction who were age matched to 137 control subjects. Univariate analysis showed higher prevalence of Xba50% reduction of lumen diameter. Overall, multivariable regression disclosed traditional risk factors and elevated levels of apolipoprotein B for men and reduced levels of apolipoprotein AI for women as independent variables for CAD. After adjustment for the most important subset of risk factors (age, hypertension, hypercholesterolemia, and smoking), apolipoprotein B XbaI polymorphism was disclosed as an independent variable for CAD. Apolipoprotein B XbaI was also selected as an independent variable for acute myocardial infarction after adjusting for age, hypertension, hypercholesterolemia, and smoking. Thus, in addition to traditional coronary risk factors, apolipoproteins B and AI, and apolipoprotein B XbaI polymorphism could be considered predictors of CAD.

Apolipoprotein B gene polymorphisms and serum lipids: meta-analysis of the role of genetic variation in responsiveness to diet

BACKGROUND

The genetic variance determining plasma lipid and lipoprotein concentrations may modify individual responsiveness to alterations in dietary fat and cholesterol content.

OBJECTIVE

The aim was to examine the role of apolipoprotein (apo) B DNA polymorphisms in responsiveness of plasma lipids and lipoproteins to diet.

DESIGN

A controlled dietary intervention study was conducted in 44 healthy, middle-aged subjects with a 3-mo baseline, a 1-mo fat-controlled, a 1-mo high-fat, and a 1-mo habitual diet period. We also conducted a meta-analysis of all published dietary trials, including our own.

RESULTS

In our own dietary study, the apo B XbaI restriction-site polymorphism affected the responsiveness to diet of the plasma LDL-cholesterol concentration (P < 0.05, repeated-measures analysis of variance). Especially during the high-fat diet, homozygous absence of the XbaI restriction site (X(-)/X(-)) was associated with a greater increase in LDL cholesterol (44 +/- 5%) than was X(+)/X(+) (27 +/- 7%) or X(+)/X(-) (40 +/- 5%). The high-fat diet also induced a larger increase in plasma LDL cholesterol in subjects with the R(-)/R(-) genotype (homozygous absence of the EcoRI restriction site) (59 +/- 10%) than in those with the R(+)/R(-) (39 +/- 6%) or R(+)/R(+) (36 +/- 4%) genotype. The M(+)/M(+) genotype (homozygous presence of the MspI restriction site) was also more responsive (41 +/- 3% increase in LDL cholesterol) than the M(+)/M(-) genotype (27 +/- 10% increase). The meta-analysis supported the finding of the significant role of the EcoRI and MspI polymorphisms, but not that of the XbaI polymorphism.

CONCLUSIONS

The present study indicated that the apo B EcoRI and MspI polymorphisms are associated with responsiveness to diet.

Single effects of apolipoprotein B, (a), and E polymorphisms and interaction between plasminogen activator inhibitor-1 and apolipoprotein(a) genotypes and the risk of coronary artery disease in Czech male caucasians

To evaluate whether polymorphisms in genes whose products are involved in lipid metabolism and fibrinolysis alter the risk of coronary artery disease (CAD), allele frequencies of four genetic polymorphisms were ascertained by PCR-based methods in 175 Czech male patients with coronary artery disease and in 222 Czech men with no symptoms of CAD. The following polymorphisms were studied: apolipoprotein B (apo B) signal peptide insertion/deletion polymorphism, 5' apolipoprotein(a) [apo(a)] TTTTA repeat polymorphism, apolipoprotein E (apo E) varepsilon2, varepsilon3, varepsilon4 polymorphism, and plasminogen activator inhibitor-1 (PAI-1) 4G/5G promoter polymorphism. Apo B and apo(a) allele frequencies differed significantly between the CAD and the control groups (P<0.01 each), with higher frequencies of apo B deletion and apo(a) shorter repeat alleles in the CAD group. We did not observe any differences in allele frequencies of either PAI-1 or apo E polymorphisms but the genotype frequencies of apo E were slightly different between the two groups (P<0.05). In addition, we observed a gene-gene interaction between the PAI-1 and apo(a) polymorphisms with respect to the risk of CAD. None of the polymorphisms studied were associated with the severity of CAD or a history of myocardial infarction. Our findings support the idea that several polymorphisms in apolipoprotein genes may by themselves and/or in interaction with other polymorphisms contribute to risk factors for CAD in men.

Optimal macronutrient balance

There is at present a justifiable debate as to the optimum level of total dietary fat which will reduce the risk of obesity without an elevation of plasma triacylglycerol or a depression of plasma HDL-cholesterol. Total plasma cholesterol and LDL-cholesterol levels are lowered and risk of fatal myocardial infarction is lowered when either saturated or trans-unsaturated fatty acids are replaced isoenergetically by either monounsaturated or polyunsaturated fatty acids. The triacylglycerol-raising and HDL-lowering effects of low-fat high-carbohydrate diets can be overcome with low intakes of n-3 polyunsaturated fatty acids and moderate exercise. Whilst a reduction in dietary fat is being attained in many countries, the reduction is uniform across all fatty acids, leaving dietary fat composition unchanged. The ability of low-fat diets to reduce cholesterol and cause a fall in body weight is not influenced by the carbohydrate ratio starch: sugars in the diet. However, weight-gain susceptibility to high intakes of dietary fat and the plasma cholesterol responsiveness to diet are considerably influenced by common genetic polymorphisms.

Direct association between the hepatic secretion of very-low-density lipoprotein apolipoprotein B-100 and plasma mevalonic acid and lathosterol concentrations in man

Apolipoprotein B-100 (apo B) is the principal structural and functional protein of the pro-atherogenic lipoproteins, but its homeostasis in man has not been clearly established. The hepatic availability of cholesterol substrate may be a determining factor. We examined whether there was a direct correlation between plasma concentrations of mevalonic acid (MVA) and lathosterol (indices of in vivo cholesterol synthesis) and hepatic secretion of very-low-density lipoprotein (VLDL) apo B in 13 normolipidaemic, healthy male subjects. The secretion of VLDL apo B was measured using a primed constant intravenous infusion of 1-[13C]-leucine (1 mg/kg per h) over 8 h. Gas-chromatography mass spectrometry (GCMS) was used to derive isotopic enrichment of apo B and fractional turnover rate was calculated using a monoexponential function. There was a highly significant positive correlation between the absolute secretion rate (ASR) of VLDL apo B and the plasma concentrations of mevalonic acid (r = 0.72, P = 0.005) and lathosterol (r = 0.81, P = 0.001) and the lathosterol:cholesterol ratio (r = 0.79, P = 0.001). In multiple regression analysis, these correlations remained significant after adjusting for waist circumference, age, apolipoprotein E genotype and dietary fat intake. The data further support the notion that the availability of cholesterol substrate regulates the hepatic secretion rate of apo B.

Determinants of the kinetics of very low-density lipoprotein apolipoprotein B-100 in non-obese men

1. Apolipoprotein B-100 (ApoB) is the principal structural and functional protein of the pro-atherogenic lipoproteins. Elevated plasma apoB is an independent risk factor for coronary artery disease. In the present study we aimed to assess the factors that determine the kinetics of apoB in the very low-density lipoprotein (VLDL) in healthy men. 2. We studied 17 non-obese men who were consuming an ad libitum diet and had the following characteristics: mean (+/-SD) age 45.5 +/- 9.7 years, body mass index (BMI) 25.1 +/- 1.4 kg/m2, waist:hip ratio 0.91 +/- 0.04, serum cholesterol 5.2 +/- 0.6 mmol/L, triglycerides 1.08 +/- 0.53 mmol/L and high-density lipoprotein-cholesterol 1.24 +/- 0.31 mmol/L. Daily dietary intake was as follows: total fat 76 +/- 26 g, carbohydrate 238 +/- 67 g, protein 103 +/- 33 g and alcohol 20 +/- 16 g. 3. The kinetics of VLDL ApoB were studied using a primed, constant infusion (1 mg/kg per h) of 1-[13C]-leucine over 8 h with measurement of isotopic enrichment of ApoB using gas chromatography/mass spectrometry. The fractional turnover rate of VLDL ApoB was estimated using a monoexponential function. The mean (+/-SD) absolute hepatic secretion rate (ASR) of ApoB was 8.5 +/- 4.6 mg/kg per day and the fractional catabolic rate (FCR) was 7.9 +/- 5.6 pools/day. The ASR was significantly correlated with the waist:hip ratio (r = 0.60; P = 0.04), but not with age, BMI, weight or nutrient intake. The FCR was significantly and inversely correlated with plasma triglycerides (r = -0.53; P = 0.03) and alcohol intake (r = -0.48; P = 0.05). 4. In conclusion, the hepatic secretion of VLDL ApoB in nonobese, healthy men is primarily determined by the waist:hip ratio, a measure of visceral fat. This is consistent with the hypothesis that the rate of lipid substrate supply in the liver regulates the output of ApoB. The fractional catabolism of VLDL ApoB may, however, be inversely related to alcohol intake and appears to determine the plasma concentration of triglycerides.

Study of apoB gene signal peptide insertion/deletion polymorphism in a healthy Serbian population: no association with serum lipid levels

The apolipoprotein B (apoB) signal peptide polymorphism was studied in unrelated healthy individuals. A total of 232 women and 222 men were analyzed separately. The relative frequencies of Del allele in women and men were 0.42 and 0.37, respectively. More heterozygous individuals were detected in comparison with other populations, using a modified silver staining method on polyacrylamide gel for visualization of Ins and Del alleles. There was no statistically significant difference in mean lipid levels adjusted for age, BMI, smoking habit and blood pressure between the three Ins/Del genotypes in both samples (ANOVA). Therefore, no differences were shown in the genotype frequency distribution throughout the lipid quartiles.