Effect of apolipoprotein E polymorphism on serum lipoprotein response to saturated fatty acids

Medium-Chain Triglyceride Oil and Blood Lipids: A Systematic Review and Meta-Analysis of Randomized Trials

BACKGROUND

Dietary saturated fat raises total cholesterol and LDL cholesterol levels. It is unclear whether these effects differ by the fatty acid chain lengths of saturated fats; particularly, it is unclear whether medium-chain fatty acids increase lipid levels.

OBJECTIVES

We conducted a systematic review to determine the effects of medium-chain triglyceride (MCT) oil, consisting almost exclusively of medium-chain fatty acids (6:0-10:0), on blood lipids.

METHODS

We searched Medline and Embase through March 2020 for randomized trials with a minimum 2-week intervention period that compared MCT oil with another fat or oil. Outcomes were total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride levels. Included studies were restricted to adults above 18 years of age. Studies conducted in populations receiving enteral or parenteral nutrition were excluded. Data were pooled using a random-effects meta-analysis.

RESULTS

Seven articles were included in the meta-analysis; LDL cholesterol and HDL cholesterol were reported in 6 studies. MCT oil intake did not affect total cholesterol (0.04 mmol/L; 95% CI, -0.11 to 0.20; I2 = 33.6%), LDL cholesterol (0.02 mmol/L; 95% CI, -0.13 to 0.17; I2 = 28.7%), or HDL cholesterol (-0.01 mmol/L; 95% CI, -0.10 to 0.09; I2 = 74.1%) levels, but did increase triglycerides (0.14 mmol/L; 95% CI, 0.01-0.27; I2 = 42.8%). Subgroup analyses showed that the effects of MCT oil on total cholesterol and LDL cholesterol differed based on the fatty acid profile of the control oil (Pinteraction = 0.003 and 0.008, respectively), with MCT oil increasing total cholesterol and LDL cholesterol when compared to a comparator consisting predominantly of unsaturated fatty acids, and with some evidence for reductions when compared to longer-chain SFAs.

CONCLUSIONS

MCT oil does not affect total cholesterol, LDL cholesterol, or HDL cholesterol levels, but does cause a small increase in triglycerides.

Saturated fat intake and alcohol consumption modulate the association between the APOE polymorphism and risk of future coronary heart disease: a nested case-control study in the Spanish EPIC cohort

The association is still not clear between the common APOE polymorphism and coronary heart disease (CHD) risk, nor its modulation by diet. Thus, our aim was to study the association between the APOE genotypes and incident CHD and how dietary fat and alcohol consumption modify these effects. We performed a nested case-control study in the Spanish European Prospective Investigation into Cancer and Nutrition cohort. Healthy men and women (41,440, 30-69 years) were followed up over a 10-year period, with the incident CHD cases being identified. We analyzed 534 incident CHD cases and 1123 controls. APOE, dietary intake and plasma lipids were determined at baseline. The APOE polymorphism was significantly associated with low-density lipoprotein cholesterol (LDL-C), and gene-alcohol interactions in determining LDL-C were detected. In the whole population, the E2 allele was significantly associated with a lower CHD risk than E3/E3 subjects [odds ratio (OR), 0.58; 95% confidence interval (CI), 0.38-0.89]. The E4 allele did not reach statistical significance vs. E3/E3 (OR, 1.17; 95% CI, 0.88-1.58). However, saturated fat intake modified the effect of the APOE polymorphism in determining CHD risk. When saturated fat intake was low (<10% of energy), no statistically significant association between the APOE polymorphism and CHD risk was observed (P=.682). However, with higher intake (≥10%), the polymorphism was significant (P=.005), and the differences between E2 and E4 carriers were magnified (OR for E4 vs. E2, 3.33; 95% CI, 1.61-6.90). Alcohol consumption also modified the effect of the APOE on CHD risk. In conclusion, in this Mediterranean population, the E2 allele is associated with lower CHD risk, and this association is modulated by saturated fat and alcohol consumption.

Personalized nutrition for the prevention of cardiovascular disease: a future perspective

Cardiovascular disease (CVD) is responsible for significant morbidity and mortality in the Western and developing world. This multi-factorial disease is influenced by many environmental and genetic factors. At present, public health advice involves prescribed population-based recommendations, which have been largely unsuccessful in reducing CVD risk. This is, in part, due to individual variability in response to dietary manipulations, that arises from nutrient-gene interactions (defined by the term 'nutrigenetics'). The shift towards personalized nutritional advice is a very attractive proposition, where, in principle, an individual can be given dietary advice specifically tailored to their genotype. However, the evidence-base for the impact of interactions between nutrients and fixed genetic variants on biomarkers of CVD risk is still very limited. This paper reviews the evidence for interactions between dietary fat and two common polymorphisms in the apolipoprotein E and peroxisome proliferator-activated receptor-gamma genes. Although an increased understanding of how these and other genes influence response to nutrients should facilitate the progression of personalized nutrition, the ethical issues surrounding its routine use need careful consideration.

Nutrigenetics and CVD: what does the future hold?

CVD is a common killer in both the Western world and the developing world. It is a multifactorial disease that is influenced by many environmental and genetic factors. Although public health advice to date has been principally in the form of prescribed population-based recommendations, this approach has been surprisingly unsuccessful in reducing CVD risk. This outcome may be explained, in part, by the extreme variability in response to dietary manipulations between individuals and interactions between diet and an individual's genetic background, which are defined by the term ‘nutrigenetics’. The shift towards personalised nutritional advice is a very attractive proposition. In principle an individual could be genotyped and given dietary advice specifically tailored to their genetic make-up. Evidence-based research into interactions between fixed genetic variants, nutrient intake and biomarkers of CVD risk is increasing, but still limited. The present paper will review the evidence for interactions between dietary fat and three common polymorphisms in theapoE,apoAIandPPARγgenes. Increased knowledge of how these and other genes influence dietary response should increase the understanding of personalised nutrition. While targeted dietary advice may have considerable potential for reducing CVD risk, the ethical issues associated with its routine use need careful consideration.

Biochemical Indicators of Nutritional Status and Dietary Intake in Costa Rican Cabécar Indian Adolescents

The purpose of this study was to determine the blood levels of selected nutritional status indicators and the dietary intake of Costa Rican Cabécar Indians aged 10 to 16 years. The results showed that 65% of the adolescents had an adequate body mass index (BMI) for their age, and 32% had a BMI < 5th percentile. Likewise, the study revealed a high prevalence of anemia (57%), deficient serum folate levels (54%), deficient vitamin B12 levels (31%), and subclinical vitamin A deficiency (10%). Additionally, the youngsters had elevated prevalences of high triglyceride levels (77%), borderline high-density lipoprotein (HDL) cholesterol levels (46%), homocysteine levels > 10 μmol/L (29%), and homozygous mutation of methylenetetrahydrofolate reductase (MTHFR) (49%). The diet was poor, being high in saturated fat and low in polyunsaturated fat, fiber, and several micronutrients. The dietary intakes of more than 55% of the adolescents did not meet 50% of the estimated average requirements (EAR) for zinc, vitamin A, vitamin C, vitamin B12, vitamin B2, and folate. Furthermore, a high prevalence of parasitosis was found (68%). Our results show an adolescent Cabécar population with a mosaic of nutritional deficiencies and cardiovascular risk factors.

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 polymorphism and serum lipid response to plant sterols in humans

BACKGROUND

The apolipoprotein E polymorphism may influence the absorption of cholesterol from the intestine and thus the response of serum cholesterol to diet. We decided to use plant sterols to investigate this and studied whether the cholesterol-lowering effect of plant sterols differed between subjects with different apolipoprotein E genotyes.

DESIGN

Thirty-one healthy subjects with the E3/4 or E4/4 genotype and 57 with the E3/3 genotype were fed sterol-enriched margarine or control margarine for 3 weeks each in a blind randomised cross-over design. The sterol margarine provided 3.2 g of plant sterols daily, was low-fat, and had the same fatty acid composition as the control margarine. Subjects used the margarines as part of their usual diet, which was fairly low in cholesterol (mean, 175 mg per day). The mean (+/- standard deviation) age of the subjects was 25 (+/- 11) years.

RESULTS

The apolipoprotein E polymorphism did not significantly affect the responses of total and LDL cholesterol. The decrease in total cholesterol was 0.36 mmol L-1 (7.4%) in the E3/3 subjects and 0.31 mmol L-1 (5.7%) in the epsilon 4 subjects (P = 0.50) and that in LDL cholesterol was 0.34 mmol L-1 (12.2%) in the E3/3 subjects and 0.32 mmol L-1 (9.8%) in the epsilon 4 subjects (P = 0.68).

CONCLUSION

The serum cholesterol response to plant sterols is not affected by the apolipoprotein E polymorphism in healthy subjects who consume a low-cholesterol diet.

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

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

Apoprotein E genotype and the response of serum cholesterol to dietary fat, cholesterol and cafestol

Previous studies on the effect of apoprotein E (APOE) polymorphism on the response of serum lipids to diet showed inconsistent results. We therefore studied the effect of apoprotein E polymorphism on responses of serum cholesterol and lipoproteins to various dietary treatments. We combined data on responses of serum cholesterol and lipoproteins to saturated fat, to trans-fat, to dietary cholesterol, and to the coffee diterpene cafestol with newly obtained data on the apoprotein E polymorphism in 395 mostly normolipidemic subjects. The responses of low-density lipoprotein (LDL-) cholesterol to saturated fat were 0.08 mmol/l larger in subjects with the APOE3/4 or E4/4 genotype than in those with the APOE3/3 genotype (95% confidence interval: -0.01-0.18 mmol/l). In contrast, responses of LDL-cholesterol to cafestol were 0.11 mmol/l smaller in subjects with the APOE3/4 or E4/4 genotype than in those with the APOE3/3 genotype (95% confidence interval: -0.29-0.07 mmol/l). Responses to dietary cholesterol and trans-fat did not differ between subjects with the various APOE genotypes. In conclusion, the APOE genotype may affect the response of serum cholesterol to dietary saturated fat and cafestol in opposite directions. However, the effects are small. Therefore, knowledge of the APOE genotype by itself may be of little use in the identification of subjects who respond to diet.

The effect of medium-chain triacylglycerols on the blood lipid profile of male endurance runners

Medium-chain triacylglycerol (MCT) oil is currently marketed for athletes as an ergogenic aid for optimal performance. Research assessing the blood lipid response of humans to MCT consumption is very limited and inconclusive. In this randomized cross-over study, male endurance runners (aged 30.5 +/- 5.5 years) were instructed to consume a low-fat diet (approximately 15% of energy) and consume either supplemental MCT oil (30 g twice each day) or long-chain triacylglycerol (LCT) oil (28 g corn oil twice each day) for 14 days. Each dietary trial was separated by at least 3 weeks. At the end of each trial, fasting blood samples were collected and analyzed for serum concentrations of total cholesterol (TC), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), and triacylglycerol (TG). Concentrations of TC (3.83 +/- 0.12 vs. 3.41 +/- 0.15 mmol/L, P = 0.004), LDL-C (1.76 +/- 0.12 vs. 1.51 +/- 0.14 mmol/L, P = 0.033), and TG (1.26 +/- 0.14 vs. 0.98 +/- 0.12 mmol/L, P = 0.006) were higher following the MCT trial than following the LCT trial, respectively. HDL-C concentration did not differ significantly between trials (MCT 1.48 +/- 0.05 mmol/L vs. LCT 1.45 +/- 0.04 mmol/L, P = 0.465). Although blood lipids remained within desirable ranges established by the National Cholesterol Education Program, these results suggest that consumption of MCT oil for 2 weeks negatively alters the blood lipid profile of athletes. Future studies should determine the effects of longer periods of MCT supplementation on serum lipids of exercisers and other groups of individuals. With little data suggesting that MCT are ergogenic, the adverse effects of MCT on blood lipid concentrations may outweigh any proposed benefits for athletes.

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).

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.