Deficiencies in methyl donors, folate, and vitamin B12 are known to lead to brain function defects. Fetal development is the most studied but data are also available for such an impact in elderly rats. To compare the functional consequences of nutritional deficiency in young versus adult rats, we monitored behavioral outcomes of cerebellum and hippocampus circuits in the offspring of deficient mother rats and in adult rats fed a deficient diet from 2 to 8 months-of-age. We present data showing that the main deleterious consequences are found in young ages compared to adult ones, in terms of movement coordination and learning abilities. Moreover, we obtained sex and age differences in the deleterious effects on these functions and on neuronal layer integrity in growing young rats, while deficient adults presented only slight functional alterations without tissue damage. Actually, the cerebellum and the hippocampus develop and maturate according to different time lap windows and we demonstrate that a switch to a normal diet can only rescue circuits that present a long permissive window of time, such as the cerebellum, whereas the hippocampus does not. Thus, we argue, as others have, for supplements or fortifications given over a longer time than the developmental period.

Vitamin B9 (folate)/B12 (cobalamin) deficiency is known to induce brain structural and/or functional retardations. In many countries, folate supplementation, targeting the most severe outcomes such as neural tube defects, is discontinued after the first trimester. However, adverse effects may occur after birth because of some mild misregulations. Various hormonal receptors were shown to be deregulated in brain tissue under these conditions. The glucocorticoid receptor (GR) is particularly sensitive to epigenetic regulation and post-translational modifications. In a mother–offspring rat model of vitamin B9/B12 deficiency, we investigated whether a prolonged folate supplementation could restore the GR signaling in the hypothalamus. Our data showed that a deficiency of folate and vitamin B12 during the in-utero and early postnatal periods was associated with reduced GR expression in the hypothalamus. We also described for the first time a novel post-translational modification of GR that impaired ligand binding and GR activation, leading to decrease expression of one of the GR targets in the hypothalamus, AgRP. Moreover, this brain-impaired GR signaling pathway was associated with behavioral perturbations during offspring growth. Importantly, perinatal and postnatal supplementation with folic acid helped restore GR mRNA levels and activity in hypothalamus cells and improved behavioral deficits.

Background: The prevalence of neurodegenerative diseases like Alzheimer’s and mental disorders like depression or anxiety appears higher in patients with gastrointestinal tract diseases like inflammatory bowel disease (IBD). Conversely, depressed patients have higher rates of gastrointestinal disorders. These observations suggest bidirectional communication between the brain and the gastrointestinal tract, the so-called “gut–brain axis”. Moreover, an altered microbiota, called “dysbiosis”, has been reported in these diseases, highlighting the network between gut microbes and their host. The emergence of the microbiota as a key regulator of the gut–brain dialog has led to the establishment of the concept of the “microbiota–gut–brain axis”. Objectives: In this narrative review, we outline the main interaction channels between the gastrointestinal tract and the brain. Then, we summarize current knowledge of two major diets (i.e., Western and Mediterranean diets) and the principal dietary components that modulate the microbiota–gut–brain axis to discuss the mechanisms putatively involved in intestinal, psychiatric, and neurological disorders. Conclusions: Diet is a major factor influencing the gut microbiota, and consequently, also putatively systemic mechanisms through the microbiota–gut–brain axis. Indeed, the composition of the diet is crucial for health and disease. Despite the main role of diet, the physiological, cellular, or molecular mechanisms involved in the complex communication between the microbiome, gut, and brain are still poorly understood.

Notre approche biomimétique permet de régénérer une dent entière. Un protocole en deux étapes à partir de réassociations de cellules dentaires embryonnaires permet le développement de la couronne in vitro et, après implantation, la différenciation fonctionnelle des cellules, l’initiation du développement radiculaire et la vascularisation dentaire. Cependant, l’absence d’innervation a nécessité des expériences complémentaires :- La co-implantation de réassociations cellulaires avec un ganglion trigéminal permet la croissance d’axones autour de la dent formée, mais pas dans le mésenchyme dentaire.- Pour tenter de résoudre ce problème, la régénération axonale a été testée dans un contexte immunodéprimé en utilisant la cyclosporine A (CsA). Dans ces conditions, des fibres nerveuses entrent dans la pulpe dentaire, jusqu’aux odontoblastes. Cependant, la CsA a aussi un effet direct sur la croissance axonale.- Des co-implantations chez des souris immunodéprimées (Nude) montrent que l’immunomodulation seule suffit pour l’innervation de la dent.- Dans la dent, les axones assurent différentes fonctions en interagissant avec les cellules voisines. Les relations entre axones et autres cellules (odontoblastes, cellules endothéliales, péricytes et cellules gliales) ont été analysées dans les mésenchymes dentaire et péri-dentaire de réassociations implantées et comparées à ce que l’on observe pour une molaire physiologique à un stade similaire.Ce travail décrit les conditions permettant l’innervation des dents régénérées. Des expériences préliminaires encourageantes ont été réalisées avec des cellules souches pour remplacer la CsA.

Vitamin B9(folate)/B12 deficiency is known to induce brain structural and/or functional retardations. Besides neural tube defects in case of major consequences, several mild deregulations also lead to deleterious effect after birth, and folate supplementation recommended in some countries usually stop at the end of the first trimester. Various hormonal receptors were shown to be deregulated in brain tissue under this context. The glucocorticoid receptor (GR) is particularly sensitive to epigenetic regulation and post-traductional modifications. In a mother-offspring rat model of vitamin B9/B12 deficiency, we investigated whether a prolonged folate supplementation could restore the GR signalization in the hypothalamus. Our data showed that a deficiency in folate and vitamin B12 during the in-utero and the early postnatal periods was associated with reduced GR expression inn the hypothalamus. We also described for the first time a new post-traductional modification of GR that impaired ligand binding and GR activation, leading to decreased the expression of one of the GR targets in the hypothalamus, AgRP. Moreover, this brain-impaired GR pathway was associated with behavioral perturbations during offspring growth. Importantly, perinatal and postnatal supplementation with folic acid helped restore GR mRNA level and activity in hypothalamus cells and improved behavioral deficits.