Funcionalidad de las poliaminas sobre el desarrollo del sistema inmune y la microbiota intestinal durante el periodo de lactancia. Influencia del procesado de las fórmulas infantiles en el contenido en poliaminas y en la liberación de péptidos durante la digestión. Ensayo de funcionalidad empleando como modelo ratones balb/colahsd lactantes

Résumé

Polyamine Functionality on Immune System Development and Intestinal Microbiota During Lactation. Influence of the Infant Formula Manufacturing on Polyamine Content and Bioactive Peptide Releasing During Digestion. Assay of Functionality in a Lactating BALB/cOlaHsd Mice Model ABSTRACT Introduction: As has been recommended by a large number of health or breastfeeding organisations, whenever feasible, infants should be fully breastfed for at least six months. If full breastfeeding is not possible, safe and suitable infant formula should be used. According to the early programming theory, environmental exposure, including nutritional exposure during the intrauterine stage and during the perinatal months of life, might make children more susceptible to some diseases later in life. Indeed, it has been demonstrated that infants who have been breastfed have a lower susceptibility to some diseases than infants who were fed with artificial manufactured formulas. The fact that these changes are extended into adult life suggests than early exposure to nutritional factors are associated with epigenetic changes. Polyamines are organic polycations that are present in all mammalian cells. They have significant interest due to their reported biological roles in eukaryotic cells, because they are essential to cell proliferation and differentiation. Their presence has been demonstrated in human milk as being the most abundant spermidine and spermine polyamines. Objectives: the main objective of the present thesis was to evaluate whether the addition of polyamines after processing could improve immune system development and the microbial colonization pattern in a similar way that breast feeding do. Methods: A total of 60 mice pups (14-days old) were randomly assigned to four-day intervention groups as follows: 1) breastfed unweaned pups; 2) early weaned pups fed with infant formula; and 3) three different groups of early weaned pups fed with infant formula supplemented with increasing levels of polyamines. After a four-day diet intervention, samples were obtained. Microbiota composition was analysed by fluorescent in situ hybridization (FISH) coupled with flow cytometry detection, and by quantitative PCR targeted at 14 bacteria genus and species. The lymphocyte populations in the blood, spleen and mesenteric lymph nodes were analysed by fluorescence activated cell sorting (FACS); moreover, the expression of genes encoding T-cell and B-cell activation, proliferation and differentiation, as well as Toll-like receptors (TLRs), in the small intestinal tissues was assessed using a 96-well RT-PCR arrays. Results and Conclusions: Regarding the microbiota composition, independently of the analysis methods, our results showed, for the first time to our knowledge, that supplementation of infant formula with polyamines modulates Bacteroides-Prevotella, Bifidobacterium spp., Lactobacillus spp. and Akkermansia-like bacteria groups, including A. muciniphila, to levels closely related to normal lactation group, in a dose-dependent manner and immune system parameters in infant formula feeding compared to mice with normal lactation. Similar to microbiota, the supplementation of manufactured infant formula in polyamines induces changes in lymphocyte populations and gene expression, increasing the percentage of B-cells in blood and CD4+, CD8+ and B-cells in the spleen in a dose-dependent manner, and it reduces differences in the expression of Cd1d1, Cd40, Hdac5, Hdac7, Clcf1 and Tlr4 genes compared with normal lactation. The results obtained from this study highlight the complex interplay between nutrition, the immune system and microbial colonization patterns during lactation. Such an effect requires further investigation in human infants because supplementation of an infant formula in polyamines might contribute to healthy gastrointestinal tract development in children fed with commercial formula.