Jouy En Josas

The human gut microbiota is a complex and adaptable ecosystem closely linked to its host, influenced by factors such as diet, lifestyle, and age. It plays key roles in nutrition, immunity, and pathogen protection by breaking down otherwise indigestible fibers into short-chain fatty acids, which are essential for energy production, metabolism, and immune balance. Butyrate, the best-studied short-chain fatty acids, provides most of the energy for colonic cells, strengthens the intestinal barrier, reduces inflammation, and regulates gene expression related to cell growth, apoptosis, and autophagy. A decrease in butyrate-producing bacteria has been associated with intestinal, metabolic, neurological, and other diseases, including rheumatoid arthritis and fatty liver disease. Maintaining a healthy microbiota-particularly through a fiber-rich diet that supports butyrate producers-is essential for digestion, nutrient absorption, immune regulation, and overall health, highlighting the strategic role of butyrate in disease prevention and well-being. This project hypothesizes that increasing microbiota-derived butyrate could improve gut health. Its aim is to isolate and characterize probiotic strains capable of boosting butyrate production, in order to develop scientifically grounded, high-functionality probiotic products. The study will also assess whether butyrate production correlates with beneficial in vitro effects and further clarify how butyrate producers interact with both the microbiota and the host.

The gut microbiota plays a crucial role in health through its involvement in pathogen defense, immune regulation, and nutrient digestion. Microbiota diversity is essential to maintain these functions, and disturbances caused by antibiotic intake or extreme diets can lead to an imbalance (dysbiosis), which is often described as being implicated in numerous diseases as well as in the proliferation of antibiotic-resistant pathogens. The microbiota is defined as the community of microorganisms inhabiting the intestine, including bacteria, viruses, and bacteriophages (phages). These phages, through their ability to destroy the bacteria they infect, play an important role in regulating bacterial populations and could therefore be essential for restoring balance and diversity in the gut. Probiotics, foods that support the microbiota such as dairy products, are of particular interest because the specific interactions between phages and bacteria within these food microbiomes could stimulate microbiota restoration. This study aims to evaluate the effectiveness of phage-based functional foods in restoring intestinal homeostasis and, by extension, improving human health. It will serve as a model to examine how phages present in foods, particularly dairy products, influence gut microbial diversity and to determine whether these phages promote recovery after antibiotic-induced disturbances.

The perinatal period represents a critical window during which the establishment of the infant gut microbiota plays a central role in host physiology and immune system development. Cesarean delivery is associated with altered vertical transmission of maternal microbiota, leading to dysregulated host-microbiota interactions and impaired homeostasis. Epidemiological evidence indicates that disturbances in early-life colonization are linked to an increased risk of developing various non-communicable diseases later in life. Modern obstetric practices, while highly effective in reducing birth complications, have resulted in a high prevalence of cesarean deliveries. Several strategies have been explored to restore the microbiota of cesarean-born infants, including maternal vaginal or fecal microbiota transfer, but these approaches raise significant safety concerns. Breastfeeding has been shown to partially restore the gut microbiota of cesarean-born infants; however, breastfeeding rates are lower after cesarean section than after vaginal delivery, largely due to postnatal complications that interfere with breastfeeding initiation. Although specific infant formulas already exist for certain populations, none are currently designed to address the impaired primary colonization observed in cesarean-born infants. The SPECIFI-C project has been designed to fill this gap by developing an innovative infant formula tailored to the specific needs of this population. The strategy focuses on two main components: (i) optimization of the microbiological fraction through supplementation with beneficial microorganisms isolated from human breast milk and infant feces, and (ii) optimization of the lipid fraction by incorporating bioactive lipids such as docosahexaenoic acid (DHA) and alkylglycerols, which are naturally present in breast milk but absent from current formulas. The ultimate objective is to provide a safe and effective nutritional intervention that promotes healthy gut colonization and supports immune and physiological development in cesarean-born infants. By targeting a population that represents approximately 20% of births in France, the project aims to contribute to more precise and personalized nutrition strategies, with the potential to reduce both short- and long-term health risks associated with cesarean delivery.