Thèse Effets Protecteurs des Odeurs sur les Desordres Emotionnels et Cognitifs Lies a l'Alimentation H/F - Doctorat.Gouv.Fr

Établissement : Université de Bordeaux École doctorale : Sciences de la Vie et de la Santé Laboratoire de recherche : Nutrition et Neurobiologie Intégrée Direction de la thèse : David JARRIAULT ORCID 0000000240827083 Début de la thèse : 2026-10-01 Date limite de candidature : 2026-05-20T23:59:59 L'alimentation de type « occidentale », riche en graisse et en sucre est associée à un risque pour la santé mentale. Un régime alimentaire déséquilibré peut altérer les fonctions cognitives et entrainer de l'anxiété et des symptômes dépressifs. De nombreuses études ont montré le potentiel de molécules odorantes pour améliorer les performances cognitives ou diminuer l'anxiété. Ce projet propose d'évaluer l'efficacité de 3 composés odorants pour contrer les effets d'une alimentation riche en graisse et en sucres simples sur les capacités cognitives et les troubles de l'humeur. Des souris nourries avec un régime alimentaire gras et sucré seront testées pour leurs performances cognitives et leurs symptômes de type anxieux/dépressif après exposition à des odeurs. L'activité neuronale de 2 réseaux impliqués dans ces fonctions cérébrales (hippocampe et raphé) sera caractérisée par électrophysiologie. Le système oxytocinergique
pourrait jouer un rôle clé dans cette modulation et le troisième axe de ce projet de recherche évaluera son implication. Le système olfactif de par ses connexions avec de nombreux réseaux neuronaux représente une voie privilégiée pour la modulation des fonctions cognitives et émotionnelles. Preserving mental health is a major challenge for our societies. Impaired cognitive and mental capacities have a significant impact on patients' quality of life. Our diet can play a role in preserving brain function, but it can also be harmful depending on its composition. A diet high in fat and sugar is associated with reduced cognitive capacity and mood disorders. Odours have been shown to have anxiolytic properties and could offer alternative therapeutic benefits to existing treatments.
Numerous studies carried out on animal models, including those carried out by the NutriNeuro laboratory, have demonstrated the deleterious impact of a diet high in fat and sugar on animal mental health. The team's research has also shown an alteration in the functioning of neural networks involved in the control of emotions or cognition, such as the serotonin network originating from the dorsal nucleus of the raphe, following consumption of a diet rich in fat and sugar. Pharmaceutical treatments exist to improve mental health, but they are accompanied by adverse effects that can be severe. Studies in humans and animal models have demonstrated the anxiolytic properties of certain plant derived odorants (e.g. rose, citrus extracts). In addition, data from our team show that sage extracts improve cognitive abilities in the Morris pool test. These various studies carried out in healthy individuals suggest an olfactory modulation of the neural networks involved in cognitive and emotional functions.
Oxytocin is involved in mood and cognitive regulation namely in relation to the nutritional status. Among various stimuli, oxytocin neurons can be modulated by odours. Our hypothesis is that the beneficial effects of the odours presented above on mood and cognitive disorders could be mediated by oxytocin secreting neurons. We aim at testing the protective effect of olfactory stimulation on cognitive and mood disorders associated with dietary imbalances. Effectiveness of odour exposure in reducing these disorders in the context of an unbalanced diet will first be tested in mice made obese and diabetic after being fed a diet enriched with fat and sugar. Second, mechanisms underlying this modulatory effect on the neuronal networks involved in these disorders will be characterized: the hippocampal network for its role in cognitive functions and the serotonin network for its role in controlling emotions. Last, the involvement of the oxytocinergic system in this modulation will be examined. This thesis project will be performed with an integrated approach associating patch-clamp electrophysiology, fiber photometry and cognitive and emotional behaviour monitoring in original transgenic mouse models. These experiments will be conducted on animals fed with either standard or obesogenic diet (HFHS diet).
Part 1 : Odorant impact on high fat diet induced cognitive and emotional disorders
- Metabolic characterization of high fat and high sugar diet on mice
- Behavioural assessment of cognitive and emotional functions (cognition: Y-maze, Object recognition, Object location; emotions: open field test and elevated plus maze, test for suppression of food intake by novelty)
Part 2 : Olfactory modulation of cognition and emotion regulating neuronal networks
- Hippocampal synaptic plasticity in HFHS fed mice after chronic odour exposure (patch-clamp)
- Physiological characterization of 5HT neurons in matching conditions via patch-clamp recording in Pet1-cre/mCherry mice
- Quantification of markers of synaptic plasticity in the hippocampus and tissue serotonin levels measured by HPLC
Part 3 : Olfactory modulation of oxytocin secreting neurons in the hypothalamus
- Physiological characterization of oxytocin secreting neurons of the hypothalamus in STD and HFHS fed mice after chronic odour exposure (patch-clamp in OT-cre/mCherry mice)
- In vivo modulation of oxytocin secreting neurons by odours monitored via fiber photometry
- Behavioural assessment of cognitive and emotional functions in high fat mice with chemogenetic inhibition of oxytocin secreting neurons of the hypothalamus during odour exposure.

Connaissances de base en neurosciences et/ou nutrition, aisance avec la manipulation d'animaux.