Nutrigénomique appliquée aux gènes candidats modulant les profils lipidique, glycémique et inflammatoire suite à une supplémentation en acides gras polyinsaturés oméga-3

La littérature suggère qu’une supplémentation en acides gras polyinsaturés (AGPI) oméga-3 (n-3) pourrait s’avérer bénéfique pour réduire les facteurs de risque métabolique liés aux maladies cardiovasculaires (MCV). Or, les effets rapportés par la supplémentation en AGPI n-3, notamment la diminution des concentrations de triglycérides (TG), peuvent varier d’un individu à l’autre, notamment en raison de variations génétiques. Il existe une grande variabilité interindividuelle dans la population, ce qui se répercute par des réponses différentes aux traitements nutritionnels. Dans le cadre de ce projet de doctorat, 210 participants ont été recrutés afin d’étudier la variabilité interindividuelle observée dans la réponse à une supplémentation en huile de poisson (5 grammes/jour) d’une durée de 6 semaines. Il a été démontré que 28,8% de l’échantillon ne répondait pas de la façon attendue à une supplémentation en AGPI n-3 où une augmentation des niveaux plasmatiques de TG était observée. Des polymorphismes nucléotidiques simples (SNPs) présents sur des gènes reliés à la voie de synthèse des AGPI n-3 et oméga-6 (n-6) (FADS1-2-3 et ELOVL2-5) affectent seuls, ou en interaction avec la diète, la réponse des TG plasmatiques suite à la supplémentation en huile de poisson. Ces mêmes SNPs modulent les niveaux d’acides gras (AG) dans les phospholipides (PPLs) du plasma ainsi que l’insulinémie à jeun et l’indice HOMA de sensibilité à l’insuline (HOMA-IS). Outre l’effet sur les TG plasmatiques, il a été observé que la supplémentation en AGPI n-3 exerce un effet modeste sur l’expression des principaux gènes inflammatoires et abaisse les niveaux plasmatiques des principaux biomarqueurs de l’inflammation (CRP, TNFA et IL-6) sous l’influence de SNPs des gènes inflammatoires (CRP, TNF-LTA, IL-1B et IL-6). Cette thèse comprend aussi un volet d’application des connaissances où la perception de la nutrigénomique, le niveau d’intérêt envers cette science, la compréhension des principales limitations des tests de nutrigénétique, ainsi que l’acquisition de compétences ont été évalués par les diététistes membres de l’Ordre professionnel des diététistes du Québec (OPDQ). Globalement, ces résultats démontrent la présence d’une grande variabilité interindividuelle observée dans les niveaux plasmatiques de TG et que des SNPs présents sur des gènes impliqués dans le métabolisme des lipides et de l’inflammation modulent les réponses lipidique, glycémique et inflammatoire suite à une supplémentation en AGPI n-3.The literature suggests that an n-3 polyunsaturated fatty acid (PUFA) supplementation may be beneficial in reducing metabolic risk factors for cardiovascular diseases (CVD). However, the effects reported by an n-3 PUFA supplementation, including lower TG levels, vary from one individual to another due to genetic variations. There is a great interindividual variability in the population, which is reflected by different responses to a dietary intervention. As part of this PhD project, 210 participants were recruited. In order to study the interindividual variability observed in the response to a nutrient, a 6-week fish oil (5 g/day) supplementation was carried out in the participants. It was shown that 28.8% of the study participants did not respond as expected to an n-3 PUFA supplementation. Moreover, an increase in TG plasma levels was observed in these hypo-responders. SNPs on genes related to the biosynthetic pathway of n-3 and n-6 fatty acids (FADS1-2-3 and ELOVL2-5) were associated alone or in an interaction effect with the fish oil supplementation with the plasma TG response following the 6-week n-3 PUFA supplementation. These same SNPs modulate fatty acid levels in plasma phospholipids as well as fasting insulin levels and homeostasis model assessment of insulin sensitivity (HOMA-IS) index. In addition to the effect on plasma TG, n-3 PUFA supplementation has been shown to exert a modest effect on the expression of inflammatory genes and to lower plasma levels of inflammatory biomarkers (CRP, TNFA and IL-6) under the influence of SNPs from inflammatory genes (CRP, TNF-LTA, IL-1B and IL-6). This thesis also includes a knowledge translation component where the perception of nutrigenomics, the level of interest in this science, the understanding of the main limitations of nutrigenetic testing, as well as the best ways to acquire knowledge in nutrigenomics were assessed by registered dietitians from the province of Quebec (Canada). Overall, these results demonstrate the presence of a large interindividual variability observed in the TG plasma levels and that SNPs on genes involved in lipid metabolism and inflammation may modulate the lipid, glycemic and inflammatory responses following an n-3 PUFA supplementation

Yogurt consumption : influence of body mass index and dietary restraint - cross-sectional analysis of the INFOGENE study

Background: Factors such as dietary restraint and the avoidance for fattening foods could possibly guide consumer towards yogurts with a smaller milk fat percentage (% MF). However, a growing body of evidence has linked high-fat dairy food intakes with a lower prevalence of obesity thus showing divergences with the actual dietary guidelines. Aim: The objective of the present study was to determine whether dietary restraint and the avoidance for fattening foods moderated the relationship between body mass index (BMI) and the preference for fatfree, low-fat or high-fat yogurts. Methods: A 91-items food frequency questionnaire was administered to 664 subjects from the INFOGENE study. Yogurt consumption was evaluated based on their fat content. Restrained eating and the avoidance for fattening foods were valuated using the threefactor eating questionnaire. Results: An interaction was observed between BMI and the dietary restraint status (p = 0.02). Positive correlations were observed between the score of dietary restraint, the score of the avoidance for fattening foods and fat-free yogurt consumption, independently of the BMI status. When groups were stratified according to the median of the score for the avoidance for fattening foods, lean individuals with the highest scores consumed less fat-free yogurt than overweight/obese individuals with the highest scores and more high-fat yogurt. Moreover, when groups were stratified according to the dietary restraint score allowing the dichotomization of restrained and unrestrained eaters, unrestrained and lean individuals consumed significantly more high-fat yogurts (in daily servings) than restrained and lean individuals and overweight/ obese individuals. Conclusion: Preferences and consumption of a particular type of yogurt with different % MF may vary depending on behavioral factors such as dietary restraint and the avoidance for fattening foods

Effects of FADS and ELOVL polymorphisms on indexes of desaturase and elongase activities: results from a pre-post fish oil supplementation

Polymorphisms (SNPs) within the FADS gene cluster and the ELOVL gene family are believed to influence enzyme activities after an omega-3 (n-3) fatty acid (FA) supplementation. The objectives of the study are to test whether an n-3 supplementation is associated with indexes of desaturase and elongase activities in addition to verify whether SNPs in the FADS gene cluster and the ELOVL gene family modulate enzyme activities of desaturases and elongases. A total 208 subjects completed a 6-week supplementation period with 5 g/day of fish oil (1.9–2.2 g/day of EPA ? 1.1 g/day of DHA). FA profiles of plasma phospholipids were obtained by gas chromatography (n = 210). Desaturase and elongase indexes were estimated using product-to-precursor ratios. Twenty-eight SNPs from FADS1, FADS2, FADS3, ELOVL2 and ELOVL5 were genotyped using TaqMan technology. Desaturase indexes were significantly different after the 6-week n-3 supplementation. The index of d-5 desaturase activity increased by 25.7 ± 28.8 % (p\0.0001), whereas the index of d-6 desaturase activity decreased by 17.7 ± 18.2 % (p\0.0001) post-supplementation. Index of elongase activity decreased by 39.5 ± 27.9 % (p\0.0001). Some gene–diet interactions potentially modulating the enzyme activities of desaturases and elongases involved in the FA metabolism post-supplementation were found. SNPs within the FADS gene cluster and the ELOVL gene family may play an important role in the enzyme activity of desaturases and elongases, suggesting that an n-3 FAs supplementation may affect PUFA metabolism

Changes in plasma phospholipid fatty acid patterns and their impact on plasma triglyceride levels following fish oil supplementation

The objective of the present study was to test for associations between changes in fatty acids (FAs) and changes in plasma triglyceride (TG) levels after an n-3 FA supplementation and to test whether SNPs from the FADS gene cluster were associ-ated with plasma FA levels or with specific FA patterns. A total of 210 subjects completed a 2-wk run-in period followed by 6-wk supplementation with 5g/d of fish oil. FA profiles of plasma phospholipids (PPLs) were obtained and 19 SNPs from the FADS gene cluster were genotyped. Principal component analysis was conducted and scores were calculated. There was an increase in EPA, DPA and DHA levels in PPLs as well as a decrease in ALA and all n-6 FA levels after the supplementa-tion. Factor analysis suggested 4 post-n-3 FA supplementation patterns. Changes in AA, ALA, DGLA, as well as changes in total n-3 and omega-6 FAs in absolute quantities of FAs were all associated with a change in TG levels whereas the cor-relation remained significant only for AA and DGLA when FAs were expressed as percentage of total FAs. Several SNPs from the FADS gene cluster were associated with post-supplementation FA levels. These results suggest that FAs alone or regrouped in factors could play a role in modulating plasma TG levels after fish oil supplementation. SNPs from the FADSgene cluster interact with both FAs and/or factors to modulate TG levels

Current knowledge and interest of French Canadians regarding nutrigenetics

Objective: The purpose of this study was to draw a global portrait of the current knowledge and interest regarding nutrigenetics in a population of French Canadians from the province of Quebec (Canada). Methods: A total of 2238 residents from the province of Quebec, Canada, were recruited via social networks and from the Laval University employees/students lists to participate to a 37-question online survey on nutrigenetics. Results: Most participants were not familiar with the term “nutrigenetics” (82.7%). Participants with good genetic literacy (26.8%) were less interested in nutrigenetic testing (p<0.0001). The vast majority of participants (90.7%) reported to be willing to follow a personalized diet based on nutrigenetic testing, especially if they came to know themselves as carriers of a polymorphism increasing the risk of certain diseases. Participants had higher interest in testing related to metabolic response to macronutrients (types of sugars, fats and proteins) than to micronutrients or other nutrients related to food intolerance. Conclusions: The attitude of French Canadians about nutrigenetics are very consistent with results from other survey published in the literature. Although few individuals are familiar with nutrigenetics, public’s attitude towards nutrigenetics is globally favourable

Nutrigenetic testing for personalized nutrition : an evaluation of public perceptions, attitudes, and concerns in a population of French Canadians

Background/aims: This study aimed to evaluate attitudes, perceptions and concerns about nutrigenetic testing for personalized nutrition in the general population of the province of Quebec, in Canada. Methods: A total of 1425 individuals from the province of Quebec fully completed a 37 question online survey on nutrigenetics and were included in analyses. Chi-square tests were used to test for associations between categorical variables. Results: The majority of participants (93.3%) considered dietitians as the best professionals to give personalized dietary advice based on nutrigenetic testing. The main reported advantage for nutrigenetic testing was “health” (23.5%), followed by “disease prevention” (22.2%). Among disadvantages, “no disadvantage” (24.4%), followed by “diet restriction” (12.9%) were mostly reported. The two major concerns raised were the accessibility to genetic testing by telemarketing companies and spammers (51.8%), and solicitation by companies using the personal genetic data to sell products (48.6%). Conclusions: French Canadians generally have a positive attitude towards nutrigenetics and find many benefits to its use. They rose up possible confidentiality issues associated with the management or property of genetic test results. However education about confidentiality issues is still considerably needed. These findings overall suggest that the population is interested by a more extensive use of nutrigenetics in health management

Association between polymorphisms in phospholipase A2 genes and the plasma triglyceride response to an n-3 PUFA supplementation : a clinical trial

Background: Fish oil-derived long-chain omega-3 (n-3) polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), reduce plasma triglyceride (TG) levels. Genetic factors such as single-nucleotide polymorphisms (SNPs) found in genes involved in metabolic pathways of n-3 PUFA could be responsible for well-recognized heterogeneity in plasma TG response to n-3 PUFA supplementation. Previous studies have shown that genes in the glycerophospholipid metabolism such as phospholipase A2 (PLA2) group II, IV, and VI, demonstrate changes in their expression levels in peripheral blood mononuclear cells (PBMCs) after n-3 PUFA supplementation. Methods: A total of 208 subjects consumed 3 g/day of n-3 PUFA for 6 weeks. Plasma lipids were measured before and after the supplementation period. Five SNPs in PLA2G2A, six in PLA2G2C, eight in PLA2G2D, six in PLA2G2F, 22 in PLA2G4A, five in PLA2G6, and nine in PLA2G7 were genotyped. The MIXED Procedure for repeated measures adjusted for age, sex, BMI, and energy intake was used in order to test whether the genotype, supplementation or interaction (genotype by supplementation) were associated with plasma TG levels. Results: The n-3 PUFA supplementation had an independent effect on plasma TG levels. Genotype effects on plasma TG levels were observed for rs2301475 in PLA2G2C, rs818571 in PLA2G2F, and rs1569480 in PLA2G4A. Genotype x supplementation interaction effects on plasma TG levels were observed for rs1805018 in PLA2G7 as well as for rs10752979, rs10737277, rs7540602, and rs3820185 in PLA2G4A. Conclusion: These results suggest that, SNPs in PLA2 genes may influence plasma TG levels during a supplementation with n-3 PUFA. This trial was registered at clinicaltrials.gov as NCT01343342

Polymorphisms in FFAR4 (GPR120) gene modulate insulin levels and sensitivity after fish oil supplementation

The objective was to test whether FFAR4 single nucleotide polymorphisms (SNPs) are associated with glycemic control-related traits in humans following fish oil supplementation. A total of 210 participants were given 3 g/day of omega-3 (n-3) fatty acids (FA) (1.9–2.2 g of eicosapentaenoic acid (EPA) and 1.1 g of docosahexaenoic acid (DHA)) during six weeks. Biochemical parameters were taken before and after the supplementation. Using the HapMap database and the tagger procedure in Haploview, 12 tagging SNPs in FFAR4 were selected and then genotyped using TaqMan technology. Transcript expression levels were measured for 30 participants in peripheral mononuclear blood cells. DNA methylation levels were measured for 35 participants in leukocytes. In silico analyses were also performed. Four gene–diet interactions on fasting insulin levels and homeostatic model assessment of insulin resistance (HOMA-IR) index values were found. rs17108973 explained a significant proportion of the variance of insulin levels (3.0%) and HOMA-IR (2.03%) index values. Splice site prediction was different depending on the allele for rs11187527. rs17108973 and rs17484310 had different affinity for transcription factors depending on the allele. n-3 FAs effectively improve insulin-related traits for major allele homozygotes of four FFAR4 SNPs as opposed to carriers of the minor alleles

Novel genetic loci associated with the plasma triglyceride response to an omega-3 fatty acid supplementation

A recent genome-wide association study (GWAS) by our group identified 13 loci associated with the plasma triglyceride (TG) response to omega-3 (n-3) fatty acid (FA) supplementation. This study aimed to test whether single-nucleotide polymorphisms (SNPs) within the IQCJ, NXPH1, PHF17 and MYB genes are associated with the plasma TG response to an n-3 FA supplementation. Methods: A total of 208 subjects followed a 6-week n-3 FA supplementation of 5 g/day of fish oil (1.9-2.2 g of eicosapentaenoic acid and 1.1 g of docosahexaenoic acid). Measurements of plasma lipids were made before and after the supplementation. Sixty-seven tagged SNPs were selected to increase the density of markers near GWAS hits. Results: In a repeated model, independent effects of the genotype and the gene-supplementation interaction were associated with plasma TG. Genotype effects were observed with two SNPs of NXPH1, and gene-diet interactions were observed with ten SNPs of IQCJ, four SNPs of NXPH1 and three SNPs of MYB. Positive and negative responders showed different genotype frequencies with nine SNPs of IQCJ, two SNPs of NXPH1 and two SNPs of MYB. Conclusion: Fine mapping in GWAS-associated loci allowed the identification of SNPs partly explaining the large interindividual variability observed in plasma TG levels in response to an n-3 FA supplementation

Effects of age, sex, body mass index and APOE genotype on cardiovascular biomarker response to an n-3 polyunsaturated fatty acid supplementation

Objectives: To test whether age, sex, body mass index (BMI), and the apolipoprotein E (APOE) genotype are associated with the metabolic response to an n-3 polyunsaturated fatty acid (PUFA) supplementation. Methods: 210 subjects followed a 2-week run-in period based on Canada’s Food Guide and underwent a 6-week 5 g/day fish oil supplementation (1.9 g of eicosapentaenoic acid and 1.1 g of docosahexaenoic acid). Cardiovascular disease risk factors were measured. Results: n-3 PUFA supplementation was associated with a decrease of plasma triglyceride levels (p = 0.0002) as well as with an increase of fasting glucose (FG) levels (p = 0.02). Age was associated with post-intervention plasma total cholesterol (p = 0.01), low-density lipoprotein cholesterol (p = 0.007), apolipoprotein B (p = 0.04), and insulin (p = 0.002) levels. Sex was associated with post-intervention plasma high-density lipoprotein cholesterol levels (p = 0.02). BMI was associated with plasma FG (p = 0.02) and insulin levels (p < 0.0001) after the supplementation. APOE genotype was associated with FG (p = 0.001) and C-reactive protein levels (p = 0.03) after the supplementation. Conclusion: Results suggest that age, sex, BMI, and the APOE genotype contribute to the inter-individual variability observed in the metabolic response to an n-3 PUFA supplementation