Étude de la sélection sociale chez l'Hirondelle bicolore

Les interactions sociales sont omniprésentes dans la nature, et ce, dans une multitude de contextes sexuels ou non-sexuels, par exemple : les soins parentaux, le choix de partenaires et la compétition intraspécifique. Ces nombreuses interactions sociales ont d’ailleurs le potentiel d’influencer l’aptitude phénotypique d’un individu via un processus évolutif nommé la sélection sociale. Par exemple, dans un contexte de compétition intraspécifique, il est attendu qu’un trait avantageux pour un individu soit potentiellement défavorable pour ses compétiteurs. Toutefois, très peu d’études visent à quantifier la sélection sociale en milieu naturel. En ce sens, la quantité de recherches s’intéressant à ce processus évolutif est insuffisante et limite notre compréhension de la sélection totale agissant sur les traits. Dans cette optique, mon étude visait à quantifier la sélection sociale agissant sur quatre traits clefs (masse corporelle, longueur d’aile, date de ponte et taille de ponte) de la femelle Hirondelle bicolore (Tachycineta bicolor) dans un contexte de compétition intraspécifique via le calcul de gradients de sélection linéaires. Pour ce faire, le succès reproducteur a été utilisé en tant que proxy de l’aptitude phénotypique. Le succès reproducteur a été mesuré à divers stades de la saison de reproduction afin d’évaluer la sélection agissant au courant de ces différentes étapes. L’influence de l’environnement sur la direction et l’ampleur de la sélection sociale a également été évaluée en vérifiant l’effet de trois composantes liées à la qualité de l’habitat dans notre système d’étude : la densité de conspécifiques, la proportion de cultures extensives dans le paysage ainsi que la présence du Moineau domestique (Passer domesticus; un des principaux compétiteurs interspécifiques de l’Hirondelle). Globalement, les résultats n’indiquent pas de sélection sociale forte dans notre système d’étude. J’ai plutôt détecté des tendances marginales qui suggèreraient une influence positive de la masse corporelle et de la longueur d’aile des individus de l’environnement social agissant respectivement sur la taille de ponte et le nombre d’oisillons éclos de l’individu focal. Aussi, aucun effet de l’environnement sur la sélection sociale n’a été détecté. Toutefois, j’ai identifié certaines variables environnementales affectant l’aptitude phénotypique à différents stades de reproduction des femelles Hirondelle bicolore. Ainsi, mon étude contribue à documenter la sélection sociale en milieu naturel tout en soulignant l’importance d’intégrer les variables environnementales dans l’étude de la sélection

Comparaison de l'impact des acides gras trans laitiers et industriels sur l'homéostasie du cholestérol chez l'humain

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2010-2011Notre groupe de recherche a récemment démontré que des apports très élevés en acides gras trans naturels (AGTn) et industriels (AGTi) avaient des effets comparables sur les lipides et lipoprotéines plasmatiques. L'impact des différents AGT sur les processus impliqués dans l'homéostasie du cholestérol demeure toutefois inconnu et il nous est apparu important d'investiguer dans cette voie. Ce mémoire présente les résultats d'une étude dont l'objectif était de comparer l'impact des AGTi et des AGTn sur les marqueurs de la synthèse endogène et de l'absorption intestinale du cholestérol. Les résultats démontrent que le niveau d'absorption du cholestérol est modifié de façon plus importante suite à la consommation d'AGTn que d'AGTi, mais cette différence ne se reflète pas dans les concentrations de LDL-C entre les deux sources d'AGT. Il semble également que la consommation d'AGT n'affecte pas la synthèse endogène de cholestérol, peu importe leur origine

Alimentation et inflammation : considérations épidémiologiques, cliniques et métaboliques

Tableau d'honneur de la Faculté des études supérieures et postdorales, 2014-2015L’inflammation systémique et chronique dite « de faible intensité » est un élément clé du développement et de la progression de plusieurs désordres métaboliques tels que l’athérosclérose, le diabète de type 2 et les maladies cardiovasculaires. De plus en plus d’évidences suggèrent que l’alimentation jouerait un rôle de premier plan dans la modulation du profil inflammatoire, mais plusieurs questions demeurent non résolues à ce jour. Ainsi, l’objectif global du présent projet de doctorat était d’étudier l’impact de l’alimentation sur l’inflammation et ses mécanismes sous-jacents en utilisant trois approches expérimentales, soit 1) une approche épidémiologique, 2) une approche clinique et 3) une approche métabolique. L’alimentation a elle-même été étudiée sous différents angles incluant de simples nutriments (acides gras, dont les oméga-3), des aliments (produits laitiers) et des profils alimentaires reflétant l’alimentation dans sa globalité. En premier lieu, nous avons évalué les associations entre divers facteurs nutritionnels (oméga-3 et profils alimentaires) et le profil inflammatoire chez deux nations autochtones du Nord-du-Québec. Ces populations ont été choisies étant donné la forte et récente augmentation de la prévalence de plusieurs désordres métaboliques chez celles-ci parallèlement à un important phénomène de transition nutritionnelle. De façon globale, nos travaux démontrent que l’alimentation des Cris de la Baie-James et des Inuits du Nunavik semble exercer une influence non significative sur leur profil inflammatoire. En second lieu, nous avons réalisé une étude d’intervention nutritionnelle randomisée contrôlée portant sur l’impact de la consommation de produits laitiers sur l’inflammation ainsi qu’une revue systématique de la littérature sur le sujet. Il ressort de ces travaux que la consommation de produits laitiers dans le cadre d’une alimentation saine n’exerce aucun effet défavorable sur le profil inflammatoire. En troisième lieu, nous avons réalisé deux études d’intervention nutritionnelle randomisées contrôlées, conçues selon un devis en chassé-croisé, qui suggèrent que la consommation de divers acides gras, dont des acides gras oméga-3 d’origine marine, influence peu ou pas l’expression de gènes inflammatoires dans le sang de sujets avec obésité abdominale ou dans le duodénum d’hommes obèses et atteints du diabète de type 2. Bref, d’après l’ensemble des présents travaux, l’alimentation influencerait peu l’inflammation.Low-grade systemic inflammation is a key etiological factor in the development and progression of several multifactorial disorders including atherosclerosis, type 2 diabetes and cardiovascular diseases. Increasing evidence suggests that diet significantly modulates the inflammatory profile. However, several questions about this topic remain unanswered at this time. The major aim of the present PhD project was to study the impact of diet on inflammation and its underlying mechanisms by using three different experimental approaches, namely 1) an epidemiological approach, 2) a clinical approach and 3) a metabolic approach. Diet also has been studied from various angles including nutrients (dietary fatty acids, such as omega-3), foods (dairy products) and dietary patterns reflecting diet as a whole. First, we assessed the associations between different nutritional factors (omega-3 and dietary patterns) and circulating inflammatory biomarkers in two Aboriginal nations from Northern Quebec. These nations were selected based on the considerable and recent increase in the prevalence of several metabolic disorders in these populations in conjunction with an important nutrition transition. Overall, our work indicates that the diet of the James Bay Cree and Nunavik Inuit populations appears to exert only a trivial influence on their inflammatory profile. Second, we conducted a randomized crossover controlled nutrition intervention study assessing the impact of dairy product consumption on inflammation as well as a systematic review of the literature on this topic. Our work suggests that consumption of dairy products as part of a healthy diet has no adverse effect on the inflammatory profile. Third, we conducted two randomized crossover controlled nutrition intervention studies which showed that the consumption of different dietary fatty acids, including omega-3 fatty acids from marine sources, exerts little or no influence on the expression of inflammatory genes in whole blood cells of individuals with abdominal obesity or in duodenal cells of obese men with type 2 diabetes. Taken together, our various works presented here suggest that diet has a minor influence on inflammation

A health at every size intervention improves intuitive eating and diet quality in Canadian women

Background & aims: Health at Every Size® (HAES®) interventions focus on healthy lifestyle by promoting behavioral changes related to diet and physical activity while emphasizing self-acceptance and well-being through an empowerment and intuitive approach. The purpose of this study was to investigate the effects of a HAES® program on intuitive eating and diet quality in women. Methods: The HAES® intervention, offered by professionals from Health and Social Services Centers in Quebec (Canada), was composed of thirteen 3-h weekly meetings and a 6-h intensive day. For this study, 216 women (1.9% normal-weight, 21.1% overweight, 77.0% obese) who took part to the HAES program were compared to 110 women (3.9% normal-weight, 23.3% overweight, 72.8% obese) from a control group (waiting list). Intuitive eating was assessed using the Intuitive Eating Scale and diet quality was evaluated through the calculation of the Healthy Eating Index (HEI) from a validated web-based self-administrated food frequency questionnaire. Measurements were performed at baseline, post-intervention, and at one-year follow-up. Results: Women who participated in the HAES® program significantly increased their intuitive eating score compared to women in the control group at post-intervention and at follow-up (group by time interaction, p = 0.0002). A significant improvement in diet quality was also observed in the HAES® group in comparison with the control group at post-intervention (group by time interaction, p = 0.0139). The intuitive eating score and the HEI score were positively associated in the HAES® group at post-intervention (r = 0.20, p = 0.0237) and one-year follow-up (r = 0.22, p = 0.0359), but no such associations were noted in the control group (post-intervention, r = 0.04, p = 0.70; one-year follow-up, r = -0.15, p = 0.30). Conclusions: The HAES® program seems effective in improving intuitive eating and also favours improvements in diet quality. However, the association between intuitive eating and diet quality remains unclear, being positive and significant only after the HAES® intervention

Nutritional content of sliced bread available in Quebec, Canada : focus on sodium and fibre content

Bread is a highly consumed food and an important source of nutrients in the diet of Canadians, underlining the need to improve its nutritional quality. The Food Quality Observatory (Observatory) aimed to evaluate the nutritional value of the sliced bread products available in Quebec (Canada), according to their grain type and main flour. Analyses included comparing the bread’s sodium content to Health Canada’s daily values (DV) and sodium voluntary targets, comparing the bread’s fibre content thresholds with the source of fibre mentioned, and assessing whether the main flour was associated with the nutrient content. The nutritional values of 294 sliced breads available in Quebec were merged with sales data (from October 2016 to October 2017), with 262 products successfully cross-referenced. The results showed that 64% of the breads purchased were ‘low’ in fibre (i.e., below 2 g per two slices), while 47% were ‘high’ in sodium (i.e., above 15% DV per two slices). Attention should be paid to 100% refined grain bread and to bread with refined flour as the main flour, since they are great sellers, while showing a less favourable nutrient content. This study shows that there is room for improvement in the nutritional content of Quebec’s bread offer, particularly regarding sodium and fibre content

Understanding Gene-Lifestyle Interaction in Obesity: The Role of Mediation versus Moderation

BACKGROUND: Obesity results from complex interactions between genetic susceptibility to weight gain and poor eating and lifestyle behaviors. The approach that has been traditionally used in genetics to investigate gene-environment/lifestyle interaction in obesity is based on the concept of moderation or effect modification. Another approach called mediation analysis can be used to investigate gene-environment interaction in obesity. The objective of this review article is to explain the differences between the concepts of moderation and mediation and summarize the studies that have used mediation analysis to support the role of eating or lifestyle behaviors as putative mediators of genetic susceptibility to obesity. SUMMARY: Moderation is used to determine whether the effect of an exposure (genes associated with obesity) on an outcome (obesity phenotype) differs in magnitude and/or direction across the spectrum of environmental exposure. Mediation analysis is used to assess the extent to which the effect of the exposure on the outcome is explained by a given set of hypothesized mediators with the aim of understanding how the exposure could lead to the outcome. In comparison with moderation, relatively few studies used mediation analyses to investigate gene-environment interaction in obesity. Most studies found evidence that traits related to appetite or eating behaviors partly mediated genetic susceptibility to obesity in either children or adults. KEY MESSAGES: Moderation and mediation represent two complementary approaches to investigate gene-environment interaction in obesity and address different research questions pertaining to the cause-effect relationship between genetic susceptibility to obesity and various obesity outcomes. More studies relying on mediation are needed to better understand the role of eating and lifestyle habits in mediating genetic susceptibility to obesity

Assessing nutritional value of ready-to-eat breakfast cereals in the province of Quebec (Canada) : a study from the Food Quality Observatory

Objective: The Food Quality Observatory was created in the province of Quebec (Canada) in 2016. In this study, the Observatory aimed to generate a methodology to (1) test the use of sales data combined with nutrient values to characterise the nutritional composition of ready-to-eat (RTE) breakfast cereals offered and purchased in the province of Quebec (Canada) and (2) verify the extent to which a front-of-pack label based on the percentage of daily value (DV) for total sugar, as a strategy to improve the food supply, would be distributed in this food category. Design: Nutritional information were obtained by purchasing each RTE breakfast cereal available in the Greater Montreal area. Cereals were then classified according to their processing type. Setting: The nutritional values of 331 RTE breakfast cereals available in Quebec were merged with sales data covering the period between May 2016 and May 2017. A total of 306 products were successfully cross-referenced. Results: Granola and sweetened cereals were the most available (36·6 % and 19·6 %, respectively) and purchased (19·8 % and 40·9 % of sales, respectively). When compared with other types of cereals, granola cereals had a higher energy, fat, saturated fat, protein content and a lower Na content. A larger proportion of chocolate (65 %) and sweetened cereals (49 %) were above 15 % of the DV for sugar. Conclusions: This study showed that the methodology developed generates important data to monitor nutritional quality of the food supply and ultimately contribute to improve the nutritional quality of processed foods

Intakes of total, free, and naturally occurring sugars in the french-speaking adult population of the province of Québec, Canada : the PREDISE study

The objective of this study was to characterize the intakes of different types of sugars in an age- and sex-representative sample of French-speaking adults from five regions of the Province of Québec, Canada, enrolled in the cross-sectional PREDISE (PRÉDicteurs Individuels, Sociaux et Environnementaux) study (n = 1147, 18–65 years old; 50.2% women). Because only total sugar content of foods and beverages is available in the Canadian Nutrient File (CNF) 2015, the initial step of this study was thus to build a database of free and naturally occurring sugars content of each food item and recipe included in the R24W, which is an automated, self-administered, web-based, 24-h dietary recall validated to estimate nutrient intakes in French-speaking adults of the Province of Québec. Total sugars were manually differentiated into free and naturally occurring sugars using a systematic algorithm based on previously published systematic algorithms. The World Health Organization (WHO)’s free sugar definition was used to differentiate total sugars into free and naturally occurring sugars. Dietary intake estimates were assessed using three 24-h dietary recalls completed with the R24W. Mean total, free, and naturally occurring sugar intakes were 116.4 g (19.3% of daily energy intake (%E)), 72.5 g (11.7%E), and 44.0 g (7.5%E), respectively. Over half (57.3%) of the overall sample did not meet the WHO’s recommendation to consume less than 10%E from free sugars. Women had a higher %E from naturally occurring sugars than men and being younger was associated with a greater %E from free sugars. Sugar intakes among French-speaking adults from the Province of Québec were mainly in the form of free sugars, with the majority of the population exceeding the WHO recommendation regarding free sugar intake. This suggests that public health efforts towards reducing free sugar intake in this population are relevant and necessary, considering that overconsumption of free sugars negatively influences health outcomes