Nutrigenetics: links between genetic background and response to Mediterranean-type diets

Fatty acid desaturase 2 (FADS 2) rs174575 (C/G) polymorphism, circulating lipid levels and susceptibility to type-2 diabetes mellitus

Several factors influence an individual's susceptibility in inter-individual lipid changes and its role in the onset of type-2 diabetes mellitus (T2DM). Considering the above fact, the present investigation focuses on determining the association between fatty acid desaturase 2 (FADS2) rs174575 (C/G) polymorphism, circulating lipid levels and susceptibility to type-2 diabetes mellitus. As per the inclusion and exclusion criteria a total of 429 subjects (non-diabetic-216; diabetic-213) were recruited for the study. Glycemic and lipid profile status were assessed using commercially available kits. Based on the previous reports SNP rs174575 of fatty acid desaturase gene (FADS2) was selected and identified using the dbSNP database. The amplified products were sequenced by means of Sanger sequencing method. Lipid profile status and apolipoprotein levels revealed statistically significant difference between the groups. Three models were assessed namely, recessive model (CC vs CG + GG), dominant model (CC + CG vs GG) and additive model (CC vs CG vs GG). The recessive model, displayed a statistically significant variations between the circulating lipid levels in T2DM. The multivariate model with genotype (G allele carriers), triglyceride (TG) and insulin served as a predictive model. The study results potentiate the functional link between FADS2 gene polymorphism, lipid levels and type-2 diabetes mellitus.

Plant sterol ester diet supplementation increases serum plant sterols and markers of cholesterol synthesis, but has no effect on total cholesterol levels

This double-blind, randomized, placebo-controlled, cross-over intervention-study was conducted in healthy volunteers to evaluate the effects of plant sterol ester supplemented margarine on cholesterol, non-cholesterol sterols and oxidative stress in serum and monocytes. Sixteen volunteers, average age 34 years, with no or mild hypercholesterolemia were subjected to a 4 week period of daily intake of 3g plant sterols per day supplied via a supplemented margarine on top of regular eating habits. After a wash-out period of one week, volunteers switched groups. Compared to placebo, a diet supplementation with plant sterols increased serum levels of plant sterols such as campesterol (+0.16±0.19mg/dL, p=0.005) and sitosterol (+0.27±0.18mg/dL, p<0.001) and increased markers of cholesterol synthesis such as desmosterol (+0.05±0.07mg/dL, p=0.006) as well as lathosterol (+0.11±0.16mg/dL, p=0.012). Cholesterol serum levels, however, were not changed significantly (+18.68±32.6mg/dL, p=0.052). These findings could not be verified in isolated circulating monocytes. Moreover, there was no effect on monocyte activation and no differences with regard to redox state after plant sterol supplemented diet. Therefore, in a population of healthy volunteers with no or mild hypercholesterolemia, consumption of plant sterol ester supplemented margarine results in increased concentrations of plant sterols and cholesterol synthesis markers without affecting total cholesterol in the serum, activation of circulating monocytes or redox state.

A randomised controlled trial of a Mediterranean Dietary Intervention for Adults with Non Alcoholic Fatty Liver Disease (MEDINA): study protocol

Background

Non-alcoholic fatty liver disease, the most prevalent liver disease in developed countries, remains difficult to manage with no proven safe and effective pharmacotherapy available. While weight reduction is the most commonly practiced treatment strategy, this is difficult to both achieve and/or maintain in the majority. Furthermore evidence-based dietary recommendations to guide the nutritional management of these patients are lacking. Using a randomised controlled trial design, this study compares the effectiveness of the Mediterranean diet to a standard low fat diet in terms of differences in insulin sensitivity, hepatic steatosis and metabolic outcomes in participants with non-alcoholic fatty liver disease.

Methods

Ninety four eligible patients who have non-alcoholic fatty liver disease and who are insulin resistant, will be randomised into either a Mediterranean or low fat diet group for a 3 month intervention period. Insulin sensitivity will be measured on peripheral blood using Homeostatic Model Assessment and liver fat content quantified using Magnetic Resonance Spectroscopy. Both arms will consist of three face to face and three telephone call follow up consultations delivered by an Accredited Practicing Dietitian. The intervention arm focuses on recommendations from the traditional Mediterranean diet which have been tailored for use in the Australian population The standard arm uses the Australian Guide to Healthy Eating and the Australian National Heart Foundation dietary guidelines. Study recruitment will take place at four major metropolitan hospitals in Melbourne, Australia. Data collection will occur at all face to face reviews including baseline, 6, and 12 weeks. A follow up assessment to measure sustainability will take place at 6 and 12 months. The primary end point is improved insulin sensitivity scores at the 12 week time point.

Discussion

This trial aims to demonstrate in a large cohort of participants with NALFD that a Mediterranean diet independent of weight loss can result in significant benefits in liver fat and insulin sensitivity and that these changes are sustained at 12 months. These metabolic changes would potentially lead to reductions in the risk of chronic liver disease, heart disease, type 2 diabetes and liver cancer.

Trial registration

Australia and New Zealand Clinical Trials Register ACTRN: ACTRN12615001010583.

Differences in Weight Loss Between Persons on Standard Balanced vs Nutrigenetic Diets in a Randomized Controlled Trial

BACKGROUND & AIMS

Many companies provide genetic tests for obesity-related polymorphisms (nutrigenetics) and make dietary recommendations for weight loss that are based on the results. We performed a randomized controlled trial to determine whether more participants who followed a nutrigenetic-guided diet lost ≥5% of their body weight than participants on a standard balanced diet for 8 and 24 weeks.

METHODS

We performed a prospective study of 51 obese or overweight U.S. veterans on an established weight management program at the Veterans Administration San Diego Healthcare System (the MOVE! program). Participants were randomly assigned to groups placed on a nutrigenetic-guided diet (balanced, low-carbohydrate, low-fat, or Mediterranean; n = 30) or a standard balanced diet (n = 21). Nutrigenetic diets were selected on the basis of results from the Pathway FIT test.

RESULTS

There was no significant difference in the percentage of participants on the balanced diet vs the nutrigenetic-guided diet who lost 5% of their body weight at 8 weeks (35.0% ± 20.9% vs 26.9% ± 17.1%, respectively; P = .28) or at 24 weeks. Both groups had difficulty adhering to the diets. However, adherence to the nutrigenetic-guided diet correlated with weight loss (r = 0.74; P = 4.0 × 10(-5)), but not adherence to standard therapy (r = 0.34; P = .23). Participants who had low-risk polymorphisms for obesity lost more weight than all other participants at 8 weeks (5.0% vs 2.9%, respectively; P = .02) and had significantly greater reductions in body mass index (6.4% vs 3.6%, respectively; P = .03) and waist circumference (6.5% vs 2.6%, respectively; P = .02) at 24 weeks.

CONCLUSIONS

In a prospective study, a nutrigenetic-based diet did not increase weight loss compared with a standard balanced diet. However, genetic features can identify individuals most likely to benefit from a balanced diet weight loss strategy; these findings require further investigation. ClinicalTrials.gov number: NCT01859403.

Strong and weak plasma response to dietary carotenoids identified by cluster analysis and linked to beta-carotene 15,15'-monooxygenase 1 single nucleotide polymorphisms

The mechanisms as well the genetics underlying the bioavailability and metabolism of carotenoids in humans remain unclear. To begin to address these questions, we used cluster analysis to examine individual temporal responses of plasma carotenoids from a controlled-diet study of subjects who consumed carotenoid-rich beverages. Treatments, given daily for 3 weeks, were watermelon juice at two levels (20-mg lycopene, 2.5-mg β-carotene, n=23 and 40-mg lycopene, 5-mg β-carotene, n=12) and tomato juice (18-mg lycopene, 0.6-mg β-carotene, n=10). Cluster analysis revealed distinct groups of subjects differing in the temporal response of plasma carotenoids and provided the basis for classifying subjects as strong responders or weak responders for β-carotene, lycopene, phytoene and phytofluene. Individuals who were strong or weak responders for one carotenoid were not necessarily strong or weak responders for another carotenoid. Furthermore, individual responsiveness was associated with genetic variants of the carotenoid metabolizing enzyme β-carotene 15,15'-monooxygenase 1. These results support the concept that individuals absorb or metabolize carotenoids differently across time and suggest that bioavailability of carotenoids may involve specific genetic variants of β-carotene 15,15'-monooxygenase 1.

Influence of SNPs in nutrient-sensitive candidate genes and gene–diet interactions on blood lipids: the DiOGenes study

Blood lipid response to a given dietary intervention could be determined by the effect of diet, gene variants or gene–diet interactions. The objective of the present study was to investigate whether variants in presumed nutrient-sensitive genes involved in lipid metabolism modified lipid profile after weight loss and in response to a given diet, among overweight European adults participating in the Diet Obesity and Genes study. By multiple linear regressions, 240 SNPs in twenty-four candidate genes were investigated for SNP main and SNP–diet interaction effects on total cholesterol, LDL-cholesterol, HDL-cholesterol and TAG after an 8-week low-energy diet (only main effect), and a 6-monthad libitumweight maintenance diet, with different contents of dietary protein or glycaemic index. After adjusting for multiple testing, a SNP–dietary protein interaction effect on TAG was identified for lipin 1 (LPIN1) rs4315495, with a decrease in TAG of − 0·26 mmol/l per A-allele/protein unit (95 % CI − 0·38, − 0·14,P= 0·000043). In conclusion, we investigated SNP–diet interactions for blood lipid profiles for 240 SNPs in twenty-four candidate genes, selected for their involvement in lipid metabolism pathways, and identified one significant interaction betweenLPIN1rs4315495 and dietary protein for TAG concentration.

Significant genotype by diet (G × D) interaction effects on cardiometabolic responses to a pedigree-wide, dietary challenge in vervet monkeys (Chlorocebus aethiops sabaeus)

Nutrient composition of a diet (D) has been shown to interact with genetic predispositions (G) to affect various lipid phenotypes. Our aim in this study was to confirm G × D interaction and determine whether the interaction extends to other cardiometabolic risk factors such as glycemic measures and body weight. Subjects were vervet monkeys (Chlorocebus aethiops sabaeus; n = 309) from a multigenerational pedigreed colony initially fed with a plant-based diet, standard primate diet (18% calories from protein, 13% from fat, and 69% from carbohydrates), and subsequently challenged for 8 weeks with a diet modeled on the typical American diet (18% calories from protein, 35% from fat, and 47% from carbohydrates). Our results showed that although exposure to the challenge diet did not result in significant changes in weight, most lipid and glycemic biomarkers moved in an adverse direction (P < 0.01). Quantitative genetic analyses showed that cardiometabolic phenotypes were significantly heritable under both dietary conditions (P < 0.05), and there was significant evidence of G × D interaction for these phenotypes. We observed significant differences in the additive genetic variances for most lipid phenotypes (P < 10(-4) ), indicating that the magnitude of genetic effects varies by diet. Furthermore, genetic correlations between diets differed significantly from 1 with respect to insulin, body weight, and some lipid phenotypes (P < 0.01). This implied that distinct genetic effects are involved in the regulation of these phenotypes under the two dietary conditions. These G × D effects confirm and extend previous observations in baboons (Papio sp.) and suggest that mimicking the typical human nutritional environment can reveal genetic influences that might not be observed in animals consuming standard, plant-based diets.

Diet, a new target to prevent depression?

BACKGROUND

Research on the role of diet in the prevention of depression is scarce. Some evidence suggests that depression shares common mechanisms with cardiovascular disease.

DISCUSSION

Before considering the role of diet in the prevention of depression, several points need to be considered. First, in general, evidence has been found for the effects of isolated nutrients or foods, and not for dietary patterns. Second, most previous studies have a cross-sectional design. Third, information is generally collected though questionnaires, increasing the risk of misclassification bias. Fourth, adequate control of confounding factors in observational studies is mandatory.

SUMMARY

Only a few cohort studies have analyzed the relationship between overall dietary patterns, such as the Mediterranean diet, and primary prevention of depression. They have found similar results to those obtained for the role of this dietary pattern in cardiovascular disease. To confirm the findings obtained in these initial cohort studies, we need further observational longitudinal studies with improved methodology, as well as large randomized primary prevention trials, with interventions based on changes in the overall food pattern, that include participants at high risk of mental disorders.

Gene-gene and gene-environment interactions defining lipid-related traits

PURPOSE OF REVIEW

Steps towards reducing chronic disease progression are continuously being taken through the form of genomic research. Studies over the last year have highlighted more and more polymorphisms, pathways and interactions responsible for metabolic disorders such as cardiovascular disease, obesity and dyslipidemia.

RECENT FINDINGS

Many of these chronic illnesses can be partially blamed by altered lipid metabolism, combined with individual genetic components. Critical evaluation and comparison of these recent studies is essential in order to comprehend the results, conclusions and future prospects in the field of genomics as a whole. Recent literature elucidates significant gene--diet and gene--environment interactions resulting in altered lipid metabolism, inflammation and other metabolic imbalances leading to cardiovascular disease and obesity.

SUMMARY

Epigenetic and epistatic interactions are now becoming more significantly associated with such disorders, as genomic research digs deeper into the complex nature of genetic individuality and heritability. The vast array of data collected from genome-wide association studies must now be empowered and explored through more complex interaction studies, using standardized methods and larger sample sizes. In doing so the etiology of chronic disease progression will be further understood.

Getting personal: considering variable interindividual responsiveness to dietary lipid-lowering therapies

PURPOSE OF REVIEW

There is substantial interindividual variation in the response of blood lipids to dietary therapies. The purpose of this review is to highlight recent developments in identifying patient-specific factors that contribute to the significant heterogeneity of responsiveness in lipids to dietary changes and consumption of dietary bioactive compounds.

RECENT FINDINGS

Recent findings suggest that a variety of patient-specific physiological, pathological, environmental, and genetic factors influence the effectiveness of dietary lipid-lowering therapies.

SUMMARY

Although genetic markers of responsiveness will revolutionize future personalized nutrition therapies, current research priorities should emphasize the identification of readily accessible metabolic biomarkers of responsiveness in patient subgroups.

Nutritional concerns, health and survival in old age

The ageing process is-apart from chance or good luck-not only influenced by factors intrinsic to the individual, but also by extrinsic factors that include environmental and lifestyle variables. This paper deals with the epidemiological evidence for the role of dietary patterns and key nutritional concerns in relation to survival and ageing related disorders that present themselves in later life. Dietary patterns, such as the Mediterranean diet, characterized by mainly plant foods including protective factors e.g. vegetables, nuts and monounsaturated fatty acids and excluding harmful factors e.g. trans-fatty acids and foods with a high glycemic factor, appear to be relevant even in old age. Specific nutritional concerns focus on general undernutrition, vitamin D and vitamin B(12). Prevalence of nutritional inadequacies, diagnostic criteria, causes and health consequences are described. The paper ends with recommendations for guidance on healthy diets for elderly people. An important challenge should be research to further expand the knowledge base, acknowledging the complexity of the ageing process and integrating different dimensions of research into human healthy ageing in properly designed studies. In the mean time reversing poor adherence to existing guidelines for a healthy diet remains a first challenge in public health nutritional practices.

Cellular proliferation, apoptosis and angiogenesis: molecular targets for nutritional preemption of cancer

Malignant cells are characterized by abnormal signaling pathways involving proliferation, apoptosis, and angiogenesis. These cancer centric pathways are known to be modified by several bioactive dietary components, although admittedly there are inconsistencies in the response. The response is dependent on the amount and duration of exposure to the dietary component and the cell type. While caution should be exercised when extrapolating in vitro data to in vivo conditions, such studies do provide valuable insights into plausible mechanisms. Significant gene-nutrient and nutrient-nutrient interactions may contribute to the uncertainty of the response to foods and/or their components. One of the challenges is the identification of which process(es), either singly or in combination, is/are most important in leading to a dietary-mediated phenotypic change. The dearth of controlled intervention studies that have investigated molecular targets for nutritional preemption in humans make firm dietary recommendations difficult. Until more definite information surfaces, a balanced but varied diet is most prudent.

Genetic variation in lipid desaturases and its impact on the development of human disease

Perturbations in lipid metabolism characterize many of the chronic diseases currently plaguing our society, such as obesity, diabetes, and cardiovascular disease. Thus interventions that target plasma lipid levels remain a primary goal to manage these diseases. The determinants of plasma lipid levels are multi-factorial, consisting of both genetic and lifestyle components. Recent evidence indicates that fatty acid desaturases have an important role in defining plasma and tissue lipid profiles. This review will highlight the current state-of-knowledge regarding three desaturases (Scd-1, Fads1 and Fads2) and their potential roles in disease onset and development. Although research in rodent models has provided invaluable insight into the regulation and functions of these desaturases, the extent to which murine research can be translated to humans remains unclear. Evidence emerging from human-based research demonstrates that genetic variation in human desaturase genes affects enzyme activity and, consequently, disease risk factors. Moreover, this genetic variation may have a trans-generational effect via breastfeeding. Therefore inter-individual variation in desaturase function is attributed to both genetic and lifestyle components. As such, population-based research regarding the role of desaturases on disease risk is challenged by this complex gene-lifestyle paradigm. Unravelling the contribution of each component is paramount for understanding the inter-individual variation that exists in plasma lipid profiles, and will provide crucial information to develop personalized strategies to improve health management.