Nutrition | EPFL Graph Search

La nutrition (du latin nutrire : nourrir) est l'ensemble des actions et processus par lesquels un être vivant récupère et transforme des substances (atomes, ions, molécules, contenues ou non dans des aliments) pour assurer son fonctionnement. La nutrition est également une science pluridisciplinaire, comportant deux grands axes. D'une part, la physiologie de la nutrition traite de la façon dont l'organisme opère la transformation des aliments, c'est-à-dire des processus métaboliques. Ceci comporte l'étude du rôle des macronutriments et des micronutriments au niveau des mécanismes biochimiques cellulaires, et les conséquences sur les tissus d'un déséquilibre entre l'énergie absorbée et l’énergie dépensée par l'organisme. D'autre part, la psychologie de la nutrition analyse le comportement alimentaire de l'individu ou du groupe. Elle met l'accent sur des questions telles que « pourquoi mangeons-nous ? » ou « comment choisissons-nous nos aliments ? ». Chez l'être humain, ces questions so

Redefining the metabolic landscape through TGF-beta/Activin signaling in Drosophila melanogaster

Wen Bin Chng

Multicellular organisms assess their nutritional state and adapt their metabolic landscape to match their energy demands. In this thesis, we address a longstanding conundrum of how an organism coordinates digestive enzyme expression in response to its nutritional status. Hydrolysis of food materials by endogenous or microbial-derived digestive enzymes precedes absorption through the gut lumen. Thus, modulation of endogenous digestive mechanism represents a pragmatic step to limit the uptake of nutrients when nutrients are in abundance. In Drosophila melanogaster, it is known that dietary glucose represses amylase transcript and enzymatic activity, in a process known as glucose repression. Here, we show that glucose reduces the expression of many carbohydrases, lipases, and glucose transporters, presumably to prevent nutritional overload after feeding. We found that the repression of carbohydrases is effected by nutritious sugars through the induction of the TGF-beta ligand, Dawdle. Interestingly, glucose repression of digestive enzymes is dependent upon the induction of Dawdle in the fat body, a tissue functionally analogous to the mammalian liver and adipose tissue. Dawdle is then transported via the circulation to activate TGFÎ²/Activin signaling in the midgut, leading to the repression of digestive enzymes expression. We later discovered that Dawdle expression in the fat body is regulated by the evolutionarily conserved Mio-bigmax transcription factor complex. In addition, expression of Dawdle must be tightly coordinated to reflect the nutritional state of adult flies, as flies overexpressing Dawdle are sensitive to starvation and have their TAG and glycogen stores rapidly depleted upon nutrient limitation. Thus, our results are consistent with a model whereby fat body derived Daw functions as a nutritional cue for carbohydrates to modulate metabolic responses in distal tissues. Its induction provides the nutritional signal to repress carbohydrate digestive capacity and stimulate peripheral insulin signaling. In conclusion, our study identifies the TGFÎ²/Activin signaling as a critical mechanism for carbohydrate homeostasis. Our results indicate that the fat body functions as a carbohydrate sensing tissue, which through the secretion of the TGFÎ² ligand, Daw, regulates organism-wide carbohydrate metabolism. Our work in Drosophila is likely to have a broader scientific impact by placing a pathway known for its role in development, immunity, and cancer, as an integral component for sugar sensing and metabolism.

EPFL2015

Computational Approaches for Studying Dietary Behaviors with Digital Traces

Kristina Gligoric

Human nutrition and dietary habits shape our health, daily life, societies, the environment, and life on earth in general. However, it remains challenging to understand and attempt to change dietary behaviors using traditional methods due to measurement and causal identification challenges.In this thesis, we contribute computational and causal approaches leveraging large-scale passively sensed digital traces to shed new light on our dietary behaviors and derive novel scientific insights. We study dietary behaviors in two types of contexts: campus-wide and worldwide. Based on digital traces capturing behaviors of tens of thousands of people on campus and millions of internet users, we develop observational study designs that enable the isolation of causal effects of implicit behavioral interventions, including forming social ties, being exposed to the food choice of others, and stay-at-home interventions. The thesis is organized into three parts.The first part presents studies based on situated on-campus food purchase logs. In the first study, we show how, when a person acquires a new eating partner on campus, the healthiness of their food choice shifts significantly in the direction of their new eating partner's dietary patterns. In the second study, we identify purchasing mimicry, i.e., copying the food choices of others in the purchasing queue, as a specific behavioral mechanism for how similarities in dietary behaviors between individuals occur on campus. The second part of the thesis leverages online information-seeking traces (Google search query logs). Studying worldwide dietary behaviors, we identify and describe global shifts in dietary interests during the first wave of the COVID-19 pandemic, larger and longer-lasting than the typical changes during the end-of-year holidays in Western countries.In the third part, we critically investigate the limits to how much computational approaches can reveal about dietary behaviors in the general population. We contribute a framework for reasoning about biases of digital traces and present a case study of food consumption in Switzerland. The bias estimates derived in the case study imply that researchers should aim to establish evidence of validity before relying on social media and tracking apps---two frequently used digital traces---as proxies for true food consumption in the general population.The novel scientific findings and methodological advances presented here contribute to the existing knowledge about human dietary behaviors and inform the design of future food systems, policies, and behavioral interventions.

EPFL2022

Nutrient Availability Does Not Affect Community Assembly in Root-Associated Fungi but Determines Fungal Effects on Plant Growth

Bing Bai, Florian Frédéric Vincent Breider

Nonmycorrhizal root-colonizing fungi are key determinants of plant growth, driving processes ranging from pathogenesis to stress alleviation. Evidence suggests that they might also facilitate host access to soil nutrients in a mycorrhiza-like manner, but the extent of their direct contribution to plant nutrition is unknown. To study how widespread such capacity is across root-colonizing fungi, we surveyed soils in nutrient-limiting habitats using plant baits to look for fungal community changes in response to nutrient conditions. We established a fungal culture collection and used Arabidopsis thaliana inoculation bioassays to assess the ability of fungi to facilitate host’s growth in the presence of organic nutrients unavailable to plants. Plant baits captured a representation of fungal communities extant in natural habitats and showed that nutrient limitation has little influence on community assembly. Arabidopsis thaliana inoculated with 31 phylogenetically diverse fungi exhibited a consistent fungus-driven growth promotion when supplied with organic nutrients compared to untreated plants. However, direct phosphorus measurement and RNA-seq data did not support enhanced nutrient uptake but rather that growth effects may result from changes in the plant’s immune response to colonization. The widespread and consistent host responses to fungal colonization suggest that distinct, locally adapted nonmycorrhizal fungi affect plant performance across habitats.