Estructura y funcionalidad de la microbiota intestinal en niños nacidos de madres obesas y su efecto sobre el neurodesarrollo durante los primeros meses de vida

Resumen

Infancy is a critical period for organ maturation and growth. Observational studies have provided evidences about how influence of intrinsic and extrinsic factors in the early life can produce disturbances in the pathways that regulate energy expenditure, immune system and other systemic effects, promoting the development of certain diseases and altering the configuration and maturation of gut microbiota. A major challenge in microbial ecology is to identify its functional members and understand how their functional and phylogenetic dynamics ultimately influence human physiology and health. Critically important are the initial stages of microbiota colonization and maturation in the gut because early dysbiosis has been shown to affect human health later in life. Classical studies about the ethiology of obesity focused on dietary disorders and host genetic susceptibility. Recent studies have shown that mothers transmit distinct gut microbial communities to their offspring depending on maternal pre-pregnancy weight, which might favour to obesity development in infancy. Furthermore, studies in rodents provide evidence that the gut microbiota modulates brain development and synaptic related proteins showing that behaviour depends upon three psychoneuroimmune pathways, i.e., immune, hypothalamic pituitary adrenal axis and vagus nerve. Alterations of the gut microbiota impact exploratory and communicative behaviours and cognitive performance. Still, little is known about the association between gut microbiota and neurodevelopment in humans. The present study has been developed within the PREOBE Follow-up framework with the following objectives: Objective 1. To provide biological information on the relative importance of gut microbial taxa in ecosystem functioning, their collective functional pattern and the network topology in relation to host physiology during human early life. Objective 2. To analyse the effect of maternal obesity on the composition and functionality of the gut microbiota in their offspring. Objective 3. To test whether early gut microbioal ecosystem membership and metabolism associate with infant neurodevelopment Results and discussion Paper 1 Cerdó, T., Ruiz, A., Acuña, I., Jáuregui, R., Jehmlich, N., Haange, S. B., Martin von, B., Suárez, A. & Campoy, C. (2018). Gut microbial functional maturation and succession during human early life. Environmental microbiology. https://doi.org/10.1111/1462-2920.14235 The evolutional trajectory of gut microbial colonization from birth has been shown to prime for health later in life. Here, we combined cultivation‐independent 16S rRNA gene sequencing and metaproteomics to investigate the functional maturation of gut microbiota in faecal samples from full‐term healthy infants collected at 6 and 18 months of age. Phylogenetic analysis of the metaproteomes showed that Bifidobacterium provided the highest number of distinct protein groups. Considerable divergences between taxa abundance and protein phylogeny were observed at all taxonomic ranks. Age had a profound effect on early microbiota where compositional and functional diversity of less dissimilar communities increased with time. Comparisons of the relative abundances of proteins revealed the transition of taxon‐associated saccharolytic and fermentation strategies from milk and mucin‐derived monosaccharide catabolism feeding acetate/propanoate synthesis to complex food‐derived hexoses fuelling butanoate production. Furthermore, co‐occurrence network analysis uncovered two anti‐correlated modules of functional taxa. A low‐connected Bifidobacteriaceae‐centred guild of facultative anaerobes was succeeded by a rich club of obligate anaerobes densely interconnected around Lachnospiraceae, underpinning their pivotal roles in microbial ecosystem assemblies. Paper 2 Cerdó, T., Ruiz, A., Jáuregui, R., Azaryah, H., Torres-Espínola, F. J., García-Valdés, L., Segura, M.T., Suárez, A. & Campoy, C. (2018). Maternal obesity is associated with gut microbial metabolic potential in offspring during infancy. Journal of physiology and biochemistry, 74(1), 159-169. doi: 10.1007/s13105-017-0577-x Children born to obese mothers are at increased risk for obesity, but the mechanisms behind this association are not fully understood. Our study aimed to investigate differences in the functions encoded by the microbiome of infants at 18 months of age when the transition from early infant-feeding to solid family foods is established. To investigate the impact of maternal prepregnancy body mass index on infants’ gut microbiome, faecal samples from infants born to normoweight (n = 21) and obese mothers (n = 18) were analysed by 16S rRNA gene sequencing and a functional-inference-based microbiome analysis. Our results indicated that Firmicutes was significantly enriched in infants born to normoweight mothers whereas Bacteroidetes was significantly enriched in infants born to obese women. In both microbiomes, the greatest number of genes (>50%) that were assigned a function encoded for proteins involved in “metabolism” among tier 1 KEGG Orthology (KO) categories. At lower KO functional categories, the microbiome of infants born to normoweight mothers was characterized by a significant enrichment in the abundances of “pentose phosphate pathway” (p = 0.037), “lysine biosynthesis” (p = 0.043), “glycerolipid metabolism” (p = 0.042), and “C5-branched dibasic acid metabolism” (p = 0.045). Notably, the microbiome of infants born to obese mothers was significantly enriched in “streptomycin biosynthesis” (p = 0.047), “sulphur metabolism” (p = 0.041), “taurine and hypotaurine metabolism” (p = 0.036), and “lipopolysaccharide biosynthesis” (p = 0.043). Paper 3 Cerdó, T., García-Valdés, L., Altmäe, S., Ruíz, A., Suárez, A., & Campoy, C. (2016). Role of microbiota function during early life on child's neurodevelopment. Trends in food science & technology, 57, 273-288. https://doi.org/10.1016/j.tifs.2016.08.007 There are critical periods during pregnancy and early life when child's neurodevelopment can be altered, where different factors including hormones, stress, genetics, and diet have an important role. Novel studies are indicating that also gut microbiota and maternal obesity can influence child's neurodevelopment. This review summarises the current concepts related to microbiota-gut-brain axis, including microbiota modulation of the eating behaviour, child's cognitive function and brain structure, microbiota analysis techniques and neurodevelopment assessment in children. Further, we propose and present knowledge about potential mechanisms of action and ways to intervene for disease prevention and treatments, opening up an exciting area with important medical and industrial applications. This novel and fast developing research area is indicating that gut microbiota in association with body weight might have an important impact on foetal and child neurodevelopment. However, the exact mechanisms are not known and further research in the field is warranted. Within the MyNewGut Project we aim to analyse the impact of microbiota in association with body weight on cognitive and behaviour development in children. We will study the phylogeny and function of the gut microbial communities in overweight, obese and gestational diabetes pregnancies and in their progeny, in association with infants and children's cognitive and behavioural outcomes. As well, the impact of gut microbiome on brain structure and function during childhood will be evaluated. Results from this study will shed light on the impact of maternal and offspring gut microbiome and body weight on child's neurodevelopment, brain structure and function, and will suggest potential mechanisms for intervention. Paper 4 Cerdó, T., Ruíz, A., Suárez, A., & Campoy, C. (2017). Probiotic, Prebiotic, and Brain Development. Nutrients, 9(11), 1247. https://doi.org/10.3390/nu9111247 Recently, a number of studies have demonstrated the existence of a link between the emotional and cognitive centres of the brain and peripheral functions through the bi-directional interaction between the central nervous system and the enteric nervous system. Therefore, the use of bacteria as therapeutics has attracted much interest. Recent research has found that there are a variety of mechanisms by which bacteria can signal to the brain and influence several processes in relation to neurotransmission, neurogenesis, and behaviour. Data derived from both in vitro experiments and in vivo clinical trials have supported some of these new health implications. While recent molecular advancement has provided strong indications to support and justify the role of the gut microbiota on the gut–brain axis, it is still not clear whether manipulations through probiotics and prebiotics administration could be beneficial in the treatment of neurological problems. The understanding of the gut microbiota and its activities is essential for the generation of future personalized healthcare strategies. Here, we explore and summarize the potential beneficial effects of probiotics and prebiotics in the neurodevelopmental process and in the prevention and treatment of certain neurological human diseases, highlighting current and future perspectives in this topic. Draft Paper 5 Cerdó T., Ruiz, A., Acuña, I., Torres-Espínola, F.J., Jáuregui, R., Jehmlich, N., Haange, S. B., Martin von, B., Suárez, A. & Campoy, C. Intestinal bacteria are associated with the cognitive development of children at 6 months of age. Compelling evidence suggest that gut microorganisms influence neurodevelopment in mice. To test this hypothesis in humans, we conducted a longitudinal study in full-term healthy infants where cognitive function assessed with Bayley III was associated with gut microbial composition, structure and metabolism. Children were categorized according to their Bayley scores within each domain into two groups, above and below the median (50th percentile). Composite cognitive scale (CCS) was the only test in which both study groups, divided according to the mean, showed significant differences in gut microbial composition. Higher evenness (p<0.004), Shannon (p<0.011) and Simpson (p<0.021) diversity and reduced dominance (p<0.021) values in gut microbiota characterized the gut microbiota of infants with above median CCS. Principal coordinate analysis based on weighted UniFrac metrics of β-diversity showed that the gut microbiota of infants clustered by CCS (p<0.014), indicating significant phylogenetic dissimilarities in the microbial profile of highly abundant taxa. Taxa within Lactococcus and Lachnnospiraceae_Incertae_Sedis were significantly enriched in infants with below the median CCS. Conversely, taxa within Bacteroides showed a higher abundance in children with above the median CCS. Metaproteomic analyses suggested mechanisms that might underlie microbial effects on infant neurodevelopment. In main COG category, proteins involved in "Intracellular trafficking" were more abundant in children with below the median CCS while those involved in "Carbohydrate transport" were enriched in children with above the median CCS. In children with below the median CSS, there was increased abundance of "aspartate carbamoyl transferase" and "dihydroorotase". Interestingly, in children with above the median CSS "histidine ammonia lyase" was significantly enriched, an enzyme involved in histamine metabolism. Conclusions Conclusion 1. Our metaproteomics data revealed that the gut microbiota harbours a distinctive subset of biologically active microorganisms, indicating considerable discordance between microbial composition and phylogenetic origin of proteins at all taxonomic levels and suggesting that using bacterial taxa or even metagenomics as input information to build predictive theoretical models of microbial activity may be highly misleading. Conclusion 2. The detailed reconstruction of the gut microbial carbon metabolism by metaproteomic analysis, including the assignment of enzymes to microbial taxa, revealed alternate temporary microbial and metabolic configurations where community-wide metabolic relationships to harvest energy by fermentation of prevailing dietary and host-derived carbon substrates, mainly glycans, differentiated chronological states in infant early life. Conclusion 3. Our results show that the maturation of the gut microbiota during the first 18 months of life is a non-random process where two mutually exclusive modules of functional families, built around Bifidobacteriaceae (6 months) and Lachnospiraceae (18 months), which metabolically succeeded each other. Conclusion 4. Mothers imprinted different gut microbiotas in their children depending on their pre-pregnancy weight, enriched in taxa within Bacteroidetes in infants born to obese mothers and in Firmicutes in infants born to normoweight mothers, with different predicted metabolic outcomes that may influence infants’ development later in life. Conclusion 5. Our forecoming study will show an association between gut microbiota and infant cognitive performance where regulation of histidine metabolism by gut microbiota in early life may underlie this relationship.