ApoA-IV phenotype affects diet-induced plasma LDL cholesterol lowering

Adults with familial hypercholesterolaemia have healthier dietary and lifestyle habits compared with their non-affected relatives: the SAFEHEART study

Objective

Healthy lifestyle habits are the cornerstone in the management of familial hypercholesterolaemia (FH). Nevertheless, dietary studies on FH-affected populations are scarce. The present study analyses dietary habits, adherence to a Mediterranean diet pattern and physical activity in an adult population with FH and compares them with their non-affected relatives.

Design

Cross-sectional study.

Setting

Data came from SAFEHEART, a nationwide study in Spain.

Participants

Individuals (n 3714) aged ≥18 years with a genetic diagnosis of FH (n2736) and their non-affected relatives (n 978). Food consumption was evaluated using a validated FFQ.

Results

Total energy intake was lower in FH patients v. non-affected relatives (P<0·005). Percentage of energy from fats was also lower in the FH population (35 % in men, 36 % in women) v. those non-affected (38 % in both sexes, P<0·005), due to the lower consumption of saturated fats (12·1 % in FH patients, 13·2 % in non-affected, P<0·005). Consumption of sugars was lower in FH patients v. non-affected relatives (P<0·05). Consumption of vegetables, fish and skimmed milk was higher in the FH population (P<0·005). Patients with FH showed greater adherence to a Mediterranean diet pattern v. non-affected relatives (P<0·005). Active smoking was lower and moderate physical activity was higher in people with FH, especially women (P<0·005).

Conclusions

Adult patients with FH report healthier lifestyles than their non-affected family members. They eat a healthier diet, perform more physical activity and smoke less. However, this patient group’s consumption of saturated fats and sugars still exceeds guidelines.

Characterization of metabolic responses to healthy diets and association with blood pressure: application to the Optimal Macronutrient Intake Trial for Heart Health (OmniHeart), a randomized controlled study

Background

Interindividual variation in the response to diet is common, but the underlying mechanism for such variation is unclear.

Objective

The objective of this study was to use a metabolic profiling approach to identify a panel of urinary metabolites representing individuals demonstrating typical (homogeneous) metabolic responses to healthy diets, and subsequently to define the association of these metabolites with improvement of risk factors for cardiovascular diseases (CVDs).

Design

24-h urine samples from 158 participants with pre-hypertension and stage 1 hypertension, collected at baseline and following the consumption of a carbohydrate-rich, a protein-rich, and a monounsaturated fat-rich healthy diet (6 wk/diet) in a randomized, crossover study, were analyzed by proton (1H) nuclear magnetic resonance (NMR) spectroscopy. Urinary metabolite profiles were interrogated to identify typical and variable responses to each diet. We quantified the differences in absolute excretion of metabolites, distinguishing between dietary comparisons within the typical response groups, and established their associations with CVD risk factors using linear regression.

Results

Globally all 3 diets induced a similar pattern of change in the urinary metabolic profiles for the majority of participants (60.1%). Diet-dependent metabolic variation was not significantly associated with total cholesterol or low-density lipoprotein (LDL) cholesterol concentration. However, blood pressure (BP) was found to be significantly associated with 6 urinary metabolites reflecting dietary intake [proline-betaine (inverse), carnitine (direct)], gut microbial co-metabolites [hippurate (direct), 4-cresyl sulfate (inverse), phenylacetylglutamine (inverse)], and tryptophan metabolism [N-methyl-2-pyridone-5-carboxamide (inverse)]. A dampened clinical response was observed in some individuals with variable metabolic responses, which could be attributed to nonadherence to diet (≤25.3%), variation in gut microbiome activity (7.6%), or a combination of both (7.0%).

Conclusions

These data indicate interindividual variations in BP in response to dietary change and highlight the potential influence of the gut microbiome in mediating this relation. This approach provides a framework for stratification of individuals undergoing dietary management. The original OmniHeart intervention study and the metabolomics study were registered at www.clinicaltrials.gov as NCT00051350 and NCT03369535, respectively.

Evaluating the Causal Relation of ApoA-IV with Disease-Related Traits - A Bidirectional Two-sample Mendelian Randomization Study

Apolipoprotein A-IV (apoA-IV) has been observed to be associated with lipids, kidney function, adiposity- and diabetes-related parameters. To assess the causal relationship of apoA-IV with these phenotypes, we conducted bidirectional Mendelian randomization (MR) analyses using publicly available summary-level datasets from GWAS consortia on apoA-IV concentrations (n = 13,813), kidney function (estimated glomerular filtration rate (eGFR), n = 133,413), lipid traits (HDL cholesterol, LDL cholesterol, triglycerides, n = 188,577), adiposity-related traits (body-mass-index (n = 322,206), waist-hip-ratio (n = 210,088)) and fasting glucose (n = 133,010). Main analyses consisted in inverse-variance weighted and multivariable MR, whereas MR-Egger regression and weighted median estimation were used as sensitivity analyses. We found that eGFR is likely to be causal on apoA-IV concentrations (53 SNPs; causal effect estimate per 1-SD increase in eGFR = −0.39; 95% CI = [−0.54, −0.24]; p-value = 2.4e-07). Triglyceride concentrations were also causally associated with apoA-IV concentrations (40 SNPs; causal effect estimate per 1-SD increase in triglycerides = −0.06; 95% CI = [−0.08, −0.04]; p-value = 4.8e-07), independently of HDL-C and LDL-C concentrations (causal effect estimate from multivariable MR = −0.06; 95% CI = [−0.10, −0.02]; p-value = 0.0014). Evaluating the inverse direction of causality revealed a possible causal association of apoA-IV on HDL-cholesterol (2 SNPs; causal effect estimate per one percent increase in apoA-IV = −0.40; 95% CI = [−0.60, −0.21]; p-value = 5.5e-05).

Acyl chain length, saturation, and hydrophobicity modulate the efficiency of dietary fatty acid absorption in adult humans

Intestinal fat absorption is known to be, overall, a highly efficient process, but much less is known about the efficiency with which individual dietary fatty acids (FA) are absorbed by the adult small intestine. We therefore measured the absorption efficiency of the major dietary FA using sucrose polybehenate (SPB) as a nonabsorbable marker and analyzed how it is modulated by acyl chain physicochemical properties and polymorphisms of proteins involved in chylomicron assembly. Dietary FA absorption efficiency was measured in 44 healthy subjects fed a standard diet containing 35% fat and 5% SPB. FA and behenic acid (BA) were measured in homogenized diets and stool samples by gas chromatography-mass spectroscopy, and coefficients of absorption for each FA were calculated as 1 - [(FA/BA)feces/(FA/BA)diet]. Absorption coefficients for saturated FA decreased with increasing chain length and hydrophobicity (mean ± SE) and ranged from 0.95 ± 0.02 for myristate (14:0), 0.80 ± 0.03 for stearate (18:0), to 0.26 ± 0.02 for arachidate (20:0). Absorption coefficients for unsaturated FA increased with increasing desaturation from 0.79 ± 0.03 for elaidic acid (18:1t), 0.96 ± 0.01 for linoleate (18:2), to near complete absorption for eicosapentaenoic (20:5) and docosahexaenoic (22:6) acids. Of several common genetic polymorphisms in key proteins involved in the chylomicron assembly pathway, only the intestinal fatty acid-binding protein-2 A54T allele (rs1799883) had any impact on FA absorption. We conclude that acyl chain length, saturation, and hydrophobicity are the major determinants of the efficiency with which dietary FA are absorbed by the adult small intestine.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Role of cholesterol 7alpha-hydroxylase (CYP7A1) in nutrigenetics and pharmacogenetics of cholesterol lowering

The relationship between dietary composition/cholesterol-lowering therapy and final plasma lipid levels is to some extent genetically determined. It is clear that these responses are under polygenic control, with multiple variants in many genes participating in the total effect (and with each gene contributing a relatively small effect). Using different experimental approaches, several candidate genes have been analyzed to date.Interesting and consistent results have been published recently regarding the A-204C promoter variant in the cholesterol 7alpha-hydroxylase (CYP7A1) gene. CYP7A1 is a rate-limiting enzyme in bile acid synthesis and therefore plays an important role in maintaining cholesterol homeostasis. CYP7A1-204CC homozygotes have the greatest decrease in total cholesterol level in response to dietary changes in different types of dietary intervention studies. In contrast, one study has reported that the effect of statins in lowering low-density lipoprotein (LDL)-cholesterol levels was slightly greater in -204AA homozygotes. The CYP7A1 A-204C variant accounts for a significant proportion of the genetic predisposition of the response of plasma cholesterol levels.

Effects of chenodeoxycholic acid and deoxycholic acid on cholesterol absorption and metabolism in humans

Quantitative and qualitative differences in intralumenal bile acids may affect cholesterol absorption and metabolism. To test this hypothesis, 2 cross-over outpatient studies were conducted in adults with apo-A IV 1/1 or apo-E 3/3 genotypes. Study 1 included 11 subjects 24 to 37 years of age, taking 15 mg/kg/day chenodeoxycholic acid (CDCA) or no bile acid for 20 days while being fed a controlled diet. Study 2 included 9 adults 25 to 38 years of age, taking 15 mg/kg/day deoxycholic acid (DCA) or no bile acid, following the same experimental design and procedures as study 1. CDCA had no effect on plasma lipid concentrations, whereas DCA decreased (P < 0.05) plasma high-density lipoprotein (HDL)-cholesterol and tended to decrease (P = 0.15) low-density lipoprotein (LDL)-cholesterol. CDCA treatment enriched (P < 0.0001) bile with CDCA and increased cholesterol concentration in micelles, whereas meal-stimulated bile acid concentrations were decreased. DCA treatment enriched (P < 0.0001) bile with DCA and tended to increase intralumenal cholesterol solubilized in micelles (P = 0.06). No changes were found in cholesterol absorption, free cholesterol fractional synthetic rate (FSR), or 3-hydroxy-3 methylglutaryl (HMG) CoA reductase and LDL receptor messenger ribonucleic acid (mRNA) levels after CDCA treatment. DCA supplementation tended to decrease cholesterol absorption and reciprocally increase FSR and HMG CoA reductase and LDL receptor mRNA levels. Results of these 2 studies suggest that the solubilization of cholesterol in the intestinal micelles is not a rate-limiting step for its absorption.

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Association of apo A-IV 360 (Gln → His) polymorphism with plasma lipids and lipoproteins: the Framingham Offspring Study

The effect of a common apolipoprotein (apo) A-IV polymorphism (substitution of histidine for glutamine at position 360) on plasma lipid, lipoprotein cholesterol and lipoprotein(a) (Lp(a)) levels, and on low-density lipoprotein (LDL) particle size was examined by genotyping in 2322 Caucasian men and women (mean age: 48.9+/-10.1 years) participating in the Framingham Offspring Study (FOS). The relative frequencies of the apo A-IV-Gln (apo A-IV-1) and the apo A-IV-His (apo A-IV-2) alleles were 0.932 and 0.068, respectively, and were in Hardy-Weinberg equilibrium. No effect of the apo A-IV-2 genotype was observed on plasma triglyceride, total and lipoprotein cholesterol, and LDL particle size in either men or women after adjustment for age and body mass index. To avoid a possible interaction between the apo E genotype and the apo A-IV genotype, subgroup analyses were undertaken in 1,414 male and female subjects with the apo E3/3 genotype. Among women in this group there was a significant effect of the apo A-IV-2 allele on triglyceride levels (p=0.046). This effect was no longer significant after adjustment for age and BMI (p=0.074). No significant allele effect on other lipoprotein levels, including Lp(a), was noted in apo E3/3 men or women. We have also conducted a meta-analysis of our own data and of other studies found in the literature, indicating a significant lowering effect of apo A-IV-2 on plasma triglycerides, but no effects on other parameters. In conclusion, the apo A-IV-2 allele is associated with a modest reduction in plasma triglyceride levels in the general population.

Nutritional genomics

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

Dietary Treatment of Hypercholestrolemia: Can We Predict Long-Term Success?

OBJECTIVE

To look for associations between changes in LDL cholesterol and baseline characteristics of patients receiving dietary therapy for hypercholesterolemia.

METHODS

Ninety-six hypercholesterolemic individuals aged 30-65 from three primary care clinics and a worksite clinic received counseling by a physician and/or a dietitian for lifestyle and dietary modifications. Baseline nutritional intake was evaluated using three-day food diaries. Lipoprotein levels were evaluated at six weeks and thereafter every three months for one year. Partial (adjusted) correlations (beta) were calculated between baseline parameters (demographic, anthropometric, nutritional and laboratory) and changes of LDL cholesterol for the short and long term (three and 12 months).

RESULTS

The average LDL cholesterol level decreased by 6 +/- 10% (p < 0.001) at the end of 12 months. This reduction was positively correlated with baseline LDL cholesterol level (beta = +0.4, p = 0.001), and negatively correlated with the baseline BMI (beta = -0.2, p < 0.05) and saturated fat intake (beta = -0.3, p < 0.05). The differences between low and high subgroups of baseline LDL cholesterol, BMI and saturated fat intake became apparent only after six to twelve months of therapy and probably result from varying levels of adherence to the dietary regimen. A significant correlation was found between the change in LDL cholesterol after six weeks and the change in LDL cholesterol after 12 months (beta = 0.4, p < 0.001).

CONCLUSIONS

The probability of successfully reducing LDL cholesterol with dietary therapy can be predicted by baseline LDL cholesterol level, BMI and saturated fat intake, as well as by the response to dietary changes within six weeks of therapy.

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.

Effect of ursodeoxycholic acid on cholesterol absorption and metabolism in humans

Qualitative and quantitative changes in intraluminal bile acid composition may alter cholesterol absorption and synthesis and LDL receptor expression. In a randomized crossover design outpatient study, 12 adults aged 24-36 years took 15 mg/kg/day ursodeoxycholic acid (UDCA) or no bile acid supplement (control) for 20 days while being fed a controlled diet (AHA Step II). A liquid meal of defined composition was then given and luminal samples collected. Cholesterol absorption and cholesterol fractional synthetic rate (FSR) were assessed by stable isotopic methods. With UDCA treatment, bile was enriched significantly (P < 0.0001) to 40.6 +/- 2.6% (mean +/- SEM) compared with 2.2 +/- 2.6% for controls. Regardless, plasma total, HDL, and LDL cholesterol were unchanged with UDCA treatment. Intraluminal cholesterol solubilized in the aqueous phase during the entire collection was decreased (P = 0.012) in UDCA-treated subjects (101.0 +/- 7.2 mg/ml/120 min) compared with controls (132.5 +/- 7.2 mg/ml/120 min.). Percent micellar cholesterol was increased in UDCA-treated versus controls after meal ingestion. No changes were found in cholesterol absorption, FSR, or LDL receptor mRNA with UDCA treatment compared with controls. Thus, despite marked enrichment in luminal bile with UDCA and decreased cholesterol solubilization, no differences in cholesterol absorption or metabolism are found when diet and genetic differences in absorption are carefully controlled.

Cladistic analysis of human apolipoprotein a4 polymorphisms in relation to quantitative plasma lipid risk factors of coronary heart disease

Genetic variation in several genes involved in lipid metabolism is known to affect population variation in quantitative lipid risk factor profiles for coronary heart disease (CHD). The apolipoprotein A-IV gene (APOA4) is one such candidate gene. We genotyped five polymorphisms in the APOA4 gene (codon 127, codon 130, codon347, codon 360 and 3' VNTR) and investigated their impact on plasma lipid trait levels in three populations comprising 604 U.S. non-Hispanic Whites (NHWs), 408 U.S. Hispanics and 708 Nigerian Blacks. Cladistic analysis was carried out to identify 5-site haplotypes that were associated with significant phenotypic differences in each population. The distribution of APOA4 genotypes was significantly different between ethnic groups. The Africans were monomorphic for two of the five sites (codons 130 and 360), but possess a unique 12 bp insertion that was not observed in NHWs and Hispanics. Due to linkage disequilibrium between the sites, only 6 haplotypes were observed in NHWs and Hispanics, and 4 in Africans. Several gender-and ethnic-specific associations between genotypes and plasma lipid traits were observed when single sites were used. Several haplotypes were identified by cladistic analysis that may carry functional mutations that affect plasma lipid trait levels.

Apolipoprotein A-IV polymorphisms and diet-gene interactions

Apolipoprotein A-IV is a 46kDa glycoprotein that is synthesized by intestinal enterocytes and is incorporated into the surface of nascent chylomicrons. Considerable evidence suggests that apolipoprotein A-IV plays a role in intestinal lipid absorption and chylomicron assembly. We have proposed that polymorphisms that alter the interfacial behavior of apolipoprotein A-IV may modulate the physical properties and metabolic fate of plasma chylomicrons. Of the reported genetic polymorphisms of apolipoprotein A-IV, two, Q360H and T347S, are known to occur at high frequencies among the world populations. Biophysical studies have established that the Q360H isoprotein displays higher lipid affinity; conversely the T347S isoprotein is predicted to be less lipid avid. Recent studies have shown that the Q360H polymorphism is associated with increased postprandial hypertriglyceridemia, a reduced low-density lipoprotein response to dietary cholesterol in the setting of a moderate fat intake, an increased high-density lipoprotein response to changes in total dietary fat content, and lower body mass and adiposity; the T347S polymorphism appears to confer the opposite effects. Studies on the diet-gene interactions of other apolipoprotein A-IV alleles are needed, as are studies on the interactions between apolipoprotein A-IV alleles and other apolipoprotein polymorphisms.

Lipoproteins, nutrition, and heart disease

This article reviews the current status of our knowledge of lipoproteins, nutrition, and coronary heart disease (CHD). Special emphasis is placed on CHD risk assessment, dietary intervention studies, diet-gene interactions, and current dietary guidelines and the contributions of my laboratory to these areas. CHD remains a major cause of death and disability, and risk factors include age, sex, hypertension, smoking, diabetes, elevated serum LDL cholesterol, and low HDL cholesterol. Emerging independent risk factors include elevated serum concentrations of lipoprotein(a), remnant lipoproteins, and homocysteine. The cornerstone of CHD prevention is lifestyle modification. Dietary intervention studies support the concepts that restricting saturated fat and cholesterol and increasing the intake of essential fatty acids, especially n - 3 fatty acids, reduces CHD risk. The variability in LDL-cholesterol response to diet is large, related in part to APOE and APOA4 genotype. The use of antioxidants in intervention studies has not been shown to reduce CHD risk. Compliance with dietary recommendations remains a major problem, and directly altering the food supply may be the most effective way to ensure compliance. The available data indicate that the recommendation to use fats, oils, and sugars sparingly for CHD prevention should be modified to a recommendation to use animal, dairy, and hydrogenated fats; tropical oils; egg yolks; and sugars sparingly and to increase the use of vegetables, fruit, and whole grains.

Is there a genetic basis for resistance to atherosclerosis?

Atherosclerosis and its major clinical manifestation, coronary heart disease, is and will remain the main cause of mortality. Reviews on this subject dealt with factors that enhance development of atherosclerosis. This review deals with a new facet, that some individuals are less prone to develop atherosclerosis: (1) despite high cholesterol intake or (2) despite hypercholesterolemia with elevated low-density lipoprotein cholesterol (LDL-C) levels. The variability of response of plasma cholesterol to dietary intake was shown to be regulated by liver x receptor (LXR) that determines the rate of intestinal cholesterol absorption through the ATP-binding cassette (ABC) gene family. Other gene products, such as apolipoprotein-E (apo-E), scavenger receptor-B1 (SR-B1) and acyl coenzyme: cholesterol acyltransferase-2 (ACAT-2) affect cholesterol absorption also. The role of a genetic background for relative resistance to atherosclerosis is highlighted by subjects with familial hypercholesterolemia in whom high plasma cholesterol levels has not curtailed their expected life span. Studies in animals have shown that resistance to atherosclerosis in spite of hypercholesterolemia is affected by factors such as high-density lipoprotein (HDL) phospholipids that enhance reverse cholesterol transport, non-responsiveness to induction or lack of monocyte chemotactic protein-1 (MCP-1), C-C chemokine receptor 2 (CCR2), macrophage colony stimulating factor (MCSF), or vascular cell adhesion molecule-1 (VCAM-1). Since macrophages have been regarded as pro- or anti-atherogenic, evidence was collated that the high activity of scavenger receptors may contribute towards resistance to atherosclerosis if accompanied by adequate amounts of apo-E for cholesterol removal.

Genetic polymorphisms and lipid response to dietary changes in humans

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects on blood lipids of a blood pressure-lowering diet: the Dietary Approaches to Stop Hypertension (DASH) Trial

BACKGROUND

Effects of diet on blood lipids are best known in white men, and effects of type of carbohydrate on triacylglycerol concentrations are not well defined.

OBJECTIVE

Our goal was to determine the effects of diet on plasma lipids, focusing on subgroups by sex, race, and baseline lipid concentrations.

DESIGN

This was a randomized controlled outpatient feeding trial conducted in 4 field centers. The subjects were 436 participants of the Dietary Approaches to Stop Hypertension (DASH) Trial [mean age: 44.6 y; 60% African American; baseline total cholesterol: < or = 6.7 mmol/L (< or = 260 mg/dL)]. The intervention consisted of 8 wk of a control diet, a diet increased in fruit and vegetables, or a diet increased in fruit, vegetables, and low-fat dairy products and reduced in saturated fat, total fat, and cholesterol (DASH diet), during which time subjects remained weight stable. The main outcome measures were fasting total cholesterol, LDL cholesterol, HDL cholesterol, and triacylglycerol.

RESULTS

Relative to the control diet, the DASH diet resulted in lower total (-0.35 mmol/L, or -13.7 mg/dL), LDL- (-0.28 mmol/L, or -10.7 mg/dL), and HDL- (-0.09 mmol/L, or -3.7 mg/dL) cholesterol concentrations (all P < 0.0001), without significant effects on triacylglycerol. The net reductions in total and LDL cholesterol in men were greater than those in women by 0.27 mmol/L, or 10.3 mg/dL (P = 0.052), and by 0.29 mmol/L, or 11.2 mg/dL (P < 0.02), respectively. Changes in lipids did not differ significantly by race or baseline lipid concentrations, except for HDL, which decreased more in participants with higher baseline HDL-cholesterol concentrations than in those with lower baseline HDL-cholesterol concentrations. The fruit and vegetable diet produced few significant lipid changes.

CONCLUSIONS

The DASH diet is likely to reduce coronary heart disease risk. The possible opposing effect on coronary heart disease risk of HDL reduction needs further study.

Human apolipoprotein A-IV metabolism within triglyceride-rich lipoproteins and plasma

In order to investigate the metabolism of apo A-IV within TRL and plasma, we assessed TRL and plasma apo A-IV kinetics in 19 and 4 subjects, respectively, consuming an average US diet for a 6-week period. At the end of this diet study, each subject received a primed-constant infusion of deuterated leucine over a 15 h time period with hourly feeding, and blood samples were drawn at 10 time points. TRL was separated by ultracentrifugation. Apo A-IV was isolated by immunoprecipitation and/or SDS-PAGE. Apo A-IV concentrations were determined by immunoelectrophoresis. Stable isotope tracer/tracee ratios were measured by gas chromatography/mass spectrometry, and the data were analyzed by multicompartmental modeling. The mean concentrations of plasma and TRL apo A-IV during the isotope infusion period were 21.0+/-3.2 and 0.66+/-0.25 mg/dl, respectively, and these values were 11.5 and 30.5% higher than those of fasting samples. The mean TRL and plasma apo A-IV residence times (RT) were 1.97+/-0.57 and 2.71+/-0.65 days, and transport rates (TR) were 0.17+/-0.19 and 3.90+/-1.24 mg/kg per day, respectively. There were significant correlations between TRL apo A-IV concentrations and TR (r(2)=0.79, P<0.001), and between TRL apo A-IV pool size and TRL cholesterol levels (r(2)=0.29, P=0.02). Our data indicated that; (1) TRL apo A-IV has a RT of 1.97 days which is similar to that earlier reported for HDL apo A-IV; (2) Apo A-IV recirculates between TRL and other slowly turning over pools; (3) the primary determinant of TRL apo A-IV levels is its TR; and (4) there is no correlation between TRL apo A-IV and apo B48 fractional catabolism in TRL.

Gene-diet interaction and plasma lipid response to dietary intervention

Research in the field of gene-diet interactions as determinants of plasma lipid response to dietary interventions has accumulated a substantial body of evidence during the past decade. Several candidate genes have shown some promise as potential markers of individual dietary responsiveness. Among the best characterized are the APOE, APOA4, APOB, APOC3, and LPL loci. Other genes are being continuously incorporated to this most interesting search. However, in very few cases has consensus been achieved about the usefulness of genetic markers as clinically significant predictors of dietary response. The increased ability to generate genotypic information, in combination with the knowledge from the human genome project and more comprehensive experimental designs, will dramatically improve our capacity to answer many of our current questions. It will also help to prove that knowledge of an individual's genetic background will facilitate more precise dietary counseling and intervention, and more efficacious primary and secondary coronary heart disease prevention.

The apolipoprotein A-IV-360His polymorphism determines the dietary fat clearance in normal subjects

Apolipoprotein IV (apo A-IV) has been related to fat absorption and to the activation of some of the enzymes involved in lipid metabolism. Several polymorphic sites within the gene locus for apo A-IV have been detected. Previous studies have shown that the A-IV-2 isoform produces a different plasma lipid response after the consumption of diets with different fat and cholesterol content. The present study was designed to evaluate whether the apo A-IV 360His polymorphism could explain, at least in part, the interindividual variability observed during postprandial lipemia. Fifty-one healthy male volunteers (42 homozygous for the apo A-IV 360Gln allele (Gln/Gln) and nine carriers of the A-IV-360His allele), homozygous for the apo E3 allele, were subjected to a vitamin A-fat load test consisting of 1 g of fat/kg body weight and 60000 IU of vitamin A. Blood was drawn at time 0 and every hour for 11 h. Plasma cholesterol (C), triacylglycerol (TG), and C, TG, apo B-100, apo B-48, apo A-IV and retinyl palmitate (RP) were determined in lipoprotein fractions. Data of postprandial lipemia revealed that subjects with the apo A-IV 360His allele had significantly greater postprandial levels in small triacylglycerol rich lipoproteins (TRL)-C (P<0.02), small TRL-TG (P<0.01) and large TRL-TG (P<0.05) than apo A-IV 360Gln/Gln subjects. In conclusion, the modifications observed in postprandial lipoprotein metabolism in subjects with the A-IV 360His allele could be involved in the different low density lipoprotein (LDL)-C responses observed in these subjects following a diet rich in cholesterol and saturated fats.

Influence of genetic polymorphisms on responsiveness to dietary fat and cholesterol

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

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

BACKGROUND AND AIMS

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Common apolipoprotein A-IV variants are associated with differences in body mass index levels and percentage body fat

OBJECTIVE

To determine the relationship between two common apoA-IV variants (Thr347-->Ser; Gln360-->His), and body mass index (BMI) and percentage body fat.

DESIGN

Cross-sectional study.

SUBJECTS

Eight-hundred and forty-eight subjects screened for participation in ongoing clinical studies.

MEASUREMENTS

ApoA-IV genotype, body mass index, waist-to-hip ratio and percentage body fat by bioelectric impedance.

RESULTS

Participants had an average age of 41+/-12 y and an average BMI of 28.2+/-5.5 kg/m2. Individuals homozygous for the Ser347 allele had higher BMI (32.3+/-6.6 vs 28.6+/-5.3 kg/m2; P<0.01) and percentage body fat (36.9+/-7.8 vs 31.0+/-9.6%; P<0.05) compared with individuals homozygous for Thr347. In contrast, the presence of at least one copy of the His360 allele was associated with lower BMI (27.2+/-5.0 vs 28.4+/-5.6 kg/m2; P<0.05) and percentage body fat (28.6+/-8.2 vs 30.7+/-9.1%; P<0.05). The genotype effects persisted after normalization of the data for the potential confounding effects of gender, age and race. When grouped by BMI percentile, the frequency of the Ser347/Ser347 genotype increased while the frequency of the His360 allele decreased with increasing BMI.

CONCLUSIONS

These data suggest a role for apoA-IV in fat storage or mobilization and that genetic variations in the apoA-IV gene may play a role in the development of obesity.

360His polymorphism of the apolipoproteinA-IV gene and plasma lipid response to energy restricted diets in overweight subjects

Obesity is commonly associated with high rates of cardiovascular disease (CVD). Weight loss in obese subjects reduces risk factors for CVD but this response is not uniform. Genetic factors could be involved in this variability. The 360His polymorphism of apolipoproteinA-IV (apoA-IV) influences the lipid response to fat intake, but it is unclear whether this polymorphism could contribute to lipid variability during weight loss. Therefore, we assessed the effects of an energy restricted diet (6.3 MJ) for 12 weeks on weight loss and plasma lipids according to apoA-IV genotype in 186 overweight/obese subjects (BMI mean 33+/-4.3, range 25.0-48.0 kg/m(2)). The frequency of the 360His allele was 0.083. Energy restriction for 12 weeks resulted in an average weight loss of 8. 25+/-0.28 kg. HDL-C increased 5.4% in subjects with the apoA-IV-1/1 genotype with weight loss compared to a 2.6% decrease in apoA-IV-1/2 subjects (P=0.035). This was more apparent when only the subjects with type 2 diabetes (n=57) were analyzed (P=0.003). ApoA-IV genotype was not related to change in total cholesterol, LDL-C or triglyceride concentrations. Therefore, weight loss as a treatment to reduce CVD risk factors may be more effective in subjects with the apoA-IV-1/1 variant as compared to those with the apoA-IV-1/2 variant, especially in subjects with type 2 diabetes.

Genetic factors associated with response of LDL subfractions to change in the nature of dietary fat

A preponderance of dense low density lipoprotein (LDL) particles is associated with an increased risk of coronary heart disease. It has been shown that dense LDL levels can be modified by diet. We investigated the contribution of polymorphisms in the genes for apolipoprotein (apo) B, apo AIV, lipoprotein lipase (LPL) and cholesterol ester transfer protein (CETP) to variation in the changes in plasma concentrations of dense LDL between a high saturated and a high polyunsaturated fatty acid diet. A total of 46 freeliving individuals (19 men and 27 women) completed a crossover trial with two dietary interventions of 4 weeks each, a high saturated fat diet (providing 21% energy from saturated fat and 3% energy from polyunsaturated fat) and a high polyunsaturated fat diet (providing 11% energy as saturated fat and 10% energy as polyunsaturated fat). Overall, the change in dense LDL between the saturated and polyunsaturated fat period was 0.17+/-0.33 mmol/L and this change was similar in men and women. Of the polymorphisms studied only variation in the apo AIV gene causing the substitution of histidine for glutamine at position 360 (Q360H) was associated with significant differences in the change in dense LDL concentration. Apo AIV Q/H individuals (n=6) showed a three-fold greater change in dense LDL cholesterol unadjusted for Lp(a) levels than Q/Q individuals (0.46+/-0.27 versus 0.12+/-0.31 mmol/L, p=0.02). The greater decrease in dense LDL cholesterol with an increase in polyunsaturated fat seen in those with the apo AIV H360 variant, who represent roughly 10% of the general population, suggests that they may benefit most from a PUFA rich lipid lowering diet.

The genetic background modifies the effects of the obesity mutation, 'fatty', on apolipoprotein gene regulation in rat liver

BACKGROUND

Obesity is associated with disorders of plasma lipid transport in many, but not in all obese subjects. The effects of obesity on the regulation of genes involved in plasma lipid transport may depend on specific mutations causing or contributing to obesity and/or on interactions of a specific obesity mutation with the genetic background. The 'fatty' (Glu269Pro) leptin receptor mutation causes severe obesity associated with hypertriglyceridaemia and altered hepatic apolipoprotein gene regulation in Zucker fatty rats.

OBJECTIVE

To determine whether the effects of the obesity mutation 'fatty' on apolipoprotein gene regulation in rat liver depend on the genetic background.

METHODS

We studied hepatic apolipoprotein (apo) A-IV, A-I, and C-III gene expression in obese rats carrying the 'fatty' mutation on the background of the Zucker or Wistar strain.

RESULTS

Basal apoA-IV gene expression was increased in fatty rats of both strains, whereas apoA-I and apoC-III gene expression differed between Wistar and Zucker fatty rats: apoA-I gene transcription was reduced to half and apoC-III mRNA was increased two-fold in Wistar fatty, but not in Zucker fatty rats vs lean controls. A fish oil diet suppressed apoA-IV, but not apoA-I gene transcription in Wistar fatty rats, whereas in Zucker fatty rats apoA-IV transcription was unaffected, but apoA-I transcription was suppressed.

CONCLUSIONS

Interactions of the 'fatty' leptin receptor mutation with the genetic background significantly affect the basal and diet-induced regulation of the apoA-IV, C-III and A-I genes in rat liver. The genetic background may therefore be a major determinant of the consequences of a specific obesity mutation for plasma lipid transport.

Apolipoprotein E regulates dietary cholesterol absorption and biliary cholesterol excretion: studies in C57BL/6 apolipoprotein E knockout mice

The present study examined the role of apolipoprotein E (apoE) in the regulation of dietary cholesterol absorption and biliary cholesterol excretion. Increasing dietary cholesterol from 0.02% to 0.5% in C57BL/6 wild-type mice decreased the percentage of dietary cholesterol that is absorbed by 25%, and this decrease was associated with a 2-fold increase in gallbladder biliary cholesterol concentration. In contrast, increasing dietary cholesterol from 0. 02% to 0.5% in C57BL/6 apoE knockout mice produced no significant suppression of the percentage dietary cholesterol absorption and increased gallbladder biliary cholesterol concentration only 16%. Whereas in wild-type mice, the increase in dietary cholesterol increased the hepatic excretion of biliary cholesterol 4-fold, there was only a 2-fold increase in apoE knockout mice. On both the low- and the high-cholesterol diets, whole liver and isolated hepatocyte cholesterol content was higher in the apoE knockout mice. These results suggest that, in response to dietary cholesterol, apoE may play a critical role in decreasing the percentage absorption of dietary cholesterol and increasing biliary cholesterol excretion. These observations suggest a mechanism whereby the absence of apoE contributes to the propensity for tissue cholesterol deposition and accelerated atherogenesis in apoE knockout mice.

Apolipoprotein E regulates dietary cholesterol absorption and biliary cholesterol excretion: Studies in C57BL/6 apolipoprotein E knockout mice

The present study examined the role of apolipoprotein E (apoE) in the regulation of dietary cholesterol absorption and biliary cholesterol excretion. Increasing dietary cholesterol from 0.02% to 0.5% in C57BL/6 wild-type mice decreased the percentage of dietary cholesterol that is absorbed by 25%, and this decrease was associated with a 2-fold increase in gallbladder biliary cholesterol concentration. In contrast, increasing dietary cholesterol from 0. 02% to 0.5% in C57BL/6 apoE knockout mice produced no significant suppression of the percentage dietary cholesterol absorption and increased gallbladder biliary cholesterol concentration only 16%. Whereas in wild-type mice, the increase in dietary cholesterol increased the hepatic excretion of biliary cholesterol 4-fold, there was only a 2-fold increase in apoE knockout mice. On both the low- and the high-cholesterol diets, whole liver and isolated hepatocyte cholesterol content was higher in the apoE knockout mice. These results suggest that, in response to dietary cholesterol, apoE may play a critical role in decreasing the percentage absorption of dietary cholesterol and increasing biliary cholesterol excretion. These observations suggest a mechanism whereby the absence of apoE contributes to the propensity for tissue cholesterol deposition and accelerated atherogenesis in apoE knockout mice.

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).

Abnormal blood lipids: is it environment or is it genes?

Genetic and environmental factors contribute to the development and progression of atherosclerotic coronary heart disease processes. Major independent risk factors for coronary heart disease, including adverse levels of plasma lipids and lipoproteins, are also influenced by genetic and potentially modifiable environmental factors. Recent advances in molecular biology have resulted in the identification of specific genes associated with lipid disorders. The complex gene-environment interplay that contributes to interindividual variation in components of the lipid profile is also partially clarified. This article provides an overview of available data on the genetic and environmental influences on lipids and lipoproteins with emphasis on implications for clinical practice and future research.

Genetic predictors of plasma lipid response to diet intervention

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

Apolipoprotein A-IV-2 allele: association of its worldwide distribution with adult persistence of lactase and speculation on its function and origin

Apolipoprotein A-IV (apo A-IV) is a 46-Kd plasma glycoprotein that may play a major role in intestinal lipid absorption. A genetic polymorphism in the apo A-IV gene, apo A-IV-2, encodes a His-->Gln substitution at codon 360 that alters the biological function of this apolipoprotein. As the worldwide distribution of the apo A-IV-2 allele appeared similar to the frequency of a genetic polymorphism that determines the persistence of lactase into adulthood, we examined the relationship between the apo A-IV-2 and lactase persistence polymorphisms by compiling the prevalence of adult lactase persistence in all populations in which the frequency of the apo A-IV-2 allele has been determined. Across 29 groups, there was an extremely strong correlation (4 = 0.937, P < 0.000001) between apo A-IV-2 allele frequency and the prevalence of adult lactase persistence. Apo A-IV-2 allele frequency was highest in Iceland, an ancient Viking colony, and decreased across Europe in a north-to-south and west-to-east gradient, generally following hypothetical isoclines for the lactase persistence gene. There were no correlations between the population frequencies of the apo E2, E3, or E4 alleles and either the prevalence of lactase persistence or the frequency of the apo A-IV-2 allele. In light of the effects of the apo A-IV-2 polymorphism on lipid metabolism, we speculate that the apo A-IV-2 allele may have originated in ancient Scandinavia, spread by conferring a nutritional advantage in the setting of a lifelong high milkfat intake, and was later carried southwards by the Viking incursions into Europe.

Differences between men and women in the response of serum cholesterol to dietary changes

BACKGROUND

Hypercholesterolaemia is initially treated by diet. However, most studies of diet and cholesterol response have been carried out in men, and it is not known whether women react to diet to the same extent as men do. We therefore studied sex differences in the response of serum cholesterol and lipoproteins to diet.

MATERIALS AND METHODS

We measured the responses of serum cholesterol to a decrease in dietary saturated fat in seven trials involving 126 men and 147 women, to a decrease in dietary trans fat in two trials (48 men and 57 women) and to a decrease in dietary cholesterol in eight trials (74 men and 70 women). We also measured responses to the coffee diterpene cafestol, which occurs in unfiltered coffee, in nine trials (72 men and 61 women). All subjects were lean and healthy.

RESULTS

The response of total cholesterol (+/- standard deviation) to a decrease in the intake of saturated fat was greater in men (-0.62 +/- 0.39 mmol L-1) than in women (-0.48 +/- 0.39 mmol L-1; 95% confidence interval, 0.04-0.23 mmol L-1). The response of total cholesterol to a decrease in the intake of cafestol was also larger in men (-1.01 +/- 0.49 mmol L-1) than in women (-0.80 +/- 0.49 mmol L-1; 95% confidence interval, 0. 04-0.39 mmol L-1). Responses to trans fat and to dietary cholesterol did not differ between men and women.

CONCLUSION

Men have larger responses of total and low-density lipoprotein cholesterol to saturated fat and cafestol than women do.

Treatment of dyslipidemia: genetic interactions with diet and drug therapy

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

The genetics of serum lipid responsiveness to dietary interventions

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

Genes, variation of cholesterol and fat intake and serum lipids

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

Diet, lipoproteins, and coronary heart disease

Current dietary recommendations to decrease coronary heart disease (CHD) risk in the general population include reduction of total fat intake to less than or equal to 30% of energy, saturated fat to less than 10% of energy, and dietary cholesterol to less than 300 mg/day. Further restrictions in saturated fat to less than 7% of energy and in dietary cholesterol to less than 200 mg/day are indicated for those individuals with elevated low-density lipoprotein (LDL) cholesterol concentrations. Under controlled conditions, such diets reduce LDL cholesterol by 15% to 20%. However, in the out-patient setting, only 5% to 10% reductions in LDL cholesterol have been achieved, and large variability in dietary response is observed due to differences in compliance, as well as to genetic heterogeneity. This article reviews epidemiologic studies and dietary intervention trials that support a direct relationship between diet, lipoproteins, and CHD risk, with the ultimate goal of providing a framework for dietary management of the hyperlipidemic patient.

Functional food science and the cardiovascular system

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

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.