172 Adaptations énergétiques à un jeûne prolongé sévère chez l’homme sain

Job title:

172 Adaptations énergétiques à un jeûne prolongé sévère chez l’homme sain

Company:

Centre National d’Etudes Spatiales

Job description

25-172 Adaptations énergétiques à un jeûne prolongé sévère chez l’homme sainPostuler25-172 Adaptations énergétiques à un jeûne prolongé sévère chez l’homme sain

• Doctorat, 36 mois
• Temps plein
• Indifférent
• Maitrise, IEP, IUP, Bac+4
• Life Sciences in Space

PostulerMissionSignificance:With the foreseen exploration towards the Moon and Mars, space missions are going to last up to 3 years. This extensive time without contact with Earth increases the likeliness of major failures in the life-support system. One of the major consequences could be a sudden and drastic limited food access, thus inducing severe energy restriction. Yet, astronauts will need to remain physically and psychologically performant to rapidly fix the issue for their own survival. Our team conducted a unique study in healthy men showing that 10 days of drastic fasting (250 kcal/day) combined with a daily physical activity program were not detrimental to muscle health. However, further studies are required to investigate the impact of prolonged fasting on energy metabolism.The objective of this study is to determine the adaptation of energy and protein metabolism at the organ level, both in terms of mass and function, to a drastic energy deficit. This prolonged fasting study will have multiple medical, scientific, and operational repercussions. It will also assess physiological resilience to the metabolic stress induced by fasting, providing essential data for mission planning. The results of this study will contribute to developing optimized nutritional strategies to maintain astronauts’ health and performance during periods of limited food resources. Finally, fasting could mitigate some of the negative effects of weightlessness on the human body, such as muscle and bone mass loss. Understanding these mechanisms is important for protecting astronauts’ health.Overall approach:This protocol will be carried out as part of the prolonged fasting study planned at Medes in late 2025. The protocol will consist of a drastic 7-day fast (250 kcal/day), preceded by 3 days of baseline measurements and followed by 3 days of refeeding in healthy, physically active men (n=10). Follow-up at 1 month and 6 months will also be conducted.In free-living conditions (before participants’ arrival at Medes), sleep, physical activity, and usual diet will be evaluated using activity monitors (Garmin watches and Actigraph GT3X+) and food diaries filled out for 3 days. Before, during the intervention, and during the refeeding period, daily physical activity, sleep, heart rate and oxygen saturation will be measured using wearable devices. Hunger and satiety will be measured using analog scales, resting metabolism rate by indirect calorimetry and hormones known to influence energy metabolism by classical lab techniques.Before and after fasting, body composition, waist circumference, body surface area, and volume will be measured by isotopic dilution, bioimpedance and DXA. Muscle and liver glycogen will be estimated in the morning using non-invasive near-infrared spectroscopy (NIRS). Muscle mass will be measured by creatine-D3 dilution. Water turnover changes will be obtained by isotopic dilution, and nitrogen turnover changes and protein synthesis will be measured using the 15N-labeled glycine method. Organ mass will be measured by magnetic resonance imaging (MRI).Feasibility:Our team has more than 25 years of experience with studies on human energetics and space physiology. We have the expertise, material and methods necessary to lead the project., including a mass spectrometry platform specialized in the measurement of energy and nutrient metabolism in humans.Data and samples collection will be completed by Year 1. The following 1.5 year will be dedicated to data and samples analysis. The last 6 months of the PhD will be dedicated to data interpretation, preparation of the PhD thesis manuscripts, the PhD defense and the development of future post-doctoral research plans. A minimum of 3 original articles will be submitted to international peer-reviewed journals in the field of space physiology, nutrition, and metabolism. The PhD student will present her/his research to at least 2 national or international conferences (e.g. IAC, IAA, COSPAR, etc) and to the JCJC of the CNES. We have no doubt this thesis is feasible within 3-year.Expertise to be acquired:Conductance of human research studyHands-on training with indirect calorimetry, metabolic research tracer techniques, accelerometry, assessment of feeding behavior and appetite, NIRS.Knowledge in human nutrition, and energy and nutrient metabolism.Dissemination of research findings (articles, conferences, presentations to media/lay audience)Statistical skillsCritical and analytical thinkingFor more Information about the topics and the co-financial partner (found by the lab !);contact Directeur de thèse –Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online before March 14th, 2025 Midnight Paris time !ProfilMaster or equivalent in nutrition, exercise physiology, physiology, or physiopathology; Past experience in research; Good level in English; Excellent ability to write and present; Team-player, collegial and autonomous; Curious and enthusiastic. Hard-worker

Expected salary

Location

Strasbourg, Bas-Rhin

Job date

Wed, 05 Feb 2025 06:45:59 GMT

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