BACKGROUND:Human milk dynamically adapts its composition of immunoglobulins (Igs), cytokines, and other proteins as lactation progresses, influencing the infant's immune development and protection. Understanding how maternal factors, such as parity, influence the composition of human milk can provide strategies aimed at enhancing infant immune protection and reducing early-life infections. This study aims to investigate whether the immune composition of human milk differs based on parity, and if so, how these changes are related to infections in early life. METHODS:The study included 75 healthy mother-infant pairs from the MAMI cohort (Clinical Trial Registry NCT03552939), with milk samples collected from the same mothers at days 7 and 15 postpartum, during transitional lactation stage. Igs, cytokines, and adipokines were quantified using multiplex immunoassays and ELISA. A comparison was conducted between primiparous and multiparous mothers regarding both the overall and individual composition of immune components in human milk at each time point, as well as their evolution throughout the transitional phase. RESULTS:Infants from multiparous mothers recorded higher infection rates in early life than those of primiparous mothers. Some human milk immune components also differed by parity, with multiparous mothers exhibiting higher levels of IgA, total IgG, IgG1, IgG2, IgG3, IgE, and IL-23 at the beginning of the transitional phase (day 7), as well as higher IL-18 and IL-21 levels toward its end (day 15), compared to primiparous mothers. Additionally, the evolutionary pattern in levels of Igs, cytokines, and adipokines throughout the transitional milk stage also differed. Moreover, in multiparous mothers, higher levels of IgG, particularly IgG1 and IgG2 (day 7), as well as IL-18 and IL-22 (day 15), were associated with reduced infant infections, highlighting their potential protective role. CONCLUSIONS:Parity is a maternal factor that influences some immune components of human milk during the transitional stage and may be linked to the susceptibility of infants to infections during the first 6 months of life. Future studies aimed at analyzing the impact of the parity factor, among others, on the progression of immune components in human milk may contribute to a better understanding and improved strategies for newborn health.

Human milk represents a highly evolved bioactive system that promotes colonization by infant microbial pioneers, supports immune maturation, and fosters infant development. Beyond providing nutrition, human milk contains key bioactive components, such as microbes, metabolites, human milk oligosaccharides, immunoglobulins, lactoferrin, and antimicrobial peptides. These factors influence colonization of the infant gut microbiome and facilitate immune development and metabolic health, with implications for health outcomes and risk of non-communicable diseases. In this review, we highlight the impact of infant feeding, human milk constituents (especially bioactive compounds), and weaning on infant microbial trajectories. By understanding how early-life nutrition influences microbial colonization and nutrient sensing, i.e., "how we feed our microbes," we can develop targeted interventions and personalized diets to support proper gut maturation and disease prevention from infancy to adulthood, as well as explore the therapeutic potential of human milk bioactives beyond infancy, offering new strategies for disease prevention and treatment.

INTRODUCTION:Bifidobacteria typify the gut microbiota of healthy, breastfed infants. Altered gut microbiota composition in early infancy characterized by decreased Bifidobacterium abundance has been linked with a heightened risk of non-communicable diseases. Our goal was to assess factors impacting on the gut microbiota composition in infants throughout the allergy and obesity epidemics of the past decades. METHODS:We studied deliveries from a series of clinical studies, grouped by the year of birth into three time periods (1997-2001, 2005-2009, 2015-2022). Altogether, 48 full-term breastfed infants' having fecal samples available at the age of 1-3 months were studied for microbiota profiling by 16S rRNA gene amplicon sequencing. Perinatal factors including mode of birth and antibiotic exposure during pregnancy and at birth were taken into account. RESULTS:The richness and diversity of the infant gut microbiota decreased significantly over the three time periods. Reduced abundance of the phylum Actinobacteriota and its genus Bifidobacterium was detected in children born in 2015-2022 as compared to those born during the time periods 1997-2001 and 2005-2009. The time period of birth was the strongest determinant of the gut microbiota composition, followed by maternal pre-pregnancy body mass index, antibiotic exposure during pregnancy, and mode of birth. The relative abundance of members of the genus Bifidobacterium was significantly associated with elapsed time (1997-2022) and intrapartum antibiotic exposure. CONCLUSIONS:The depletion of gut microbiota richness and diversity and the selective reduction of relative abundance of the genus Bifidobacterium have occurred parallel to the increase in the prevalence of non-communicable diseases.

Diclofenac (DCF) exposure is of great concern due to the ecotoxicological risk linked with a decline of vulture populations in Southeast Asia, but also because it can affect the reproduction and neurotoxicity in mammals. Otherwise, selenium (Se) is an antioxidant essential element with key roles in health and with antagonistic action against pollutants, but in some cases with a synergistic effect. To investigate the potential intertwined mechanisms between DCF, Se, and gut microbiota, gut metabolomic and gut microbiota profiles were determined in mice after DCF exposure and Se supplementation. Speciation of selenoproteins in plasma was carried out by isotopic dilution analysis to quantify the levels of selenoproteins. Significant differences in the levels of 79% of the gut metabolites were determined after DCF exposure. The most significant altered pathway in DCF and DCF-Se groups is the primary bile biosynthesis, being the only pathway altered in mice exposed to DCF, while in DCF-Se, the metabolism of galactose and linoleic acid is also altered. Moreover, specific associations between specific gut microbiota and metabolites were determined in the studied mice groups suggesting intertwined mechanisms. Selenium supplementation modulated the gut metabolic and microbiota profiles affected by DCF.

Effects of different infant formula matrices and L. fermentum CECT5716 on epithelial barrier function and immune response.

Early-life colonization is a critical developmental process influencing infant biological programming, with bifidobacteria playing a key role. This systematic review examines the transmissibility of Bifidobacterium strains from mothers to infants. Adhering to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, 31 articles from 2009 to 2024 were selected from 2825 screened titles and abstracts. Using a narrative synthesis and meta-analysis, the review focuses on studies employing strain-level metagenomic approaches (Protocol registry CRD: CRD42023490507). Ten studies using shotgun metagenomic sequencing identified specific strains of B. adolescentis, B. angulatum, B. bifidum, B. breve, B. pseudocatenulatum, B. catenulatum, and B. longum shared between mothers and infants. A meta-analysis of 810 mother–infant pairs revealed an overall species transmissibility estimate of 30

BACKGROUND:Establishing optimal maternal nutritional habits during pregnancy, breastfeeding, and early life is crucial for the health and welfare of both the mother and the child. However, research is lacking to understand the associated mechanisms linking maternal diet to health outcomes. The objective of this study was to assess the potential influence of two distinct diets, consumed during gestation and lactation, on the microbiota composition, immunity and lipid metabolism of Lewis dams. METHODS:Diet 1 (D1, Mediterranean diet-like) was characterized by a high fibre content, vegetable protein, and fish oil; whereas Diet 2 (D2, slightly Western diet-like) was enriched with animal protein and lard. Fecal samples were collected weekly throughout the nutritional intervention. Blood, tissue samples (adipose tissue, intestine, mammary gland, spleen and liver) and cecal content were collected from the mother at the end of lactation (day 21) to examine the effects on the epithelial barrier, lipid metabolism, microbiota composition and metabolites, as well as the mucosal immunity. FINDINGS:According to our findings, consumption of the D1 diet had a beneficial impact on the mothers compared to the D2 diet. D1 increased the intestinal surface area and enhanced the mucosal immunity, as evidenced by a rise in fecal immunoglobulin (Ig) A and Ig-coated bacteria levels, along with an increase in total IgG in the mesenteric lymph nodes, as well as elevated levels of T helper (Th)1-associated IgG2c isotype. Furthermore, D1 influenced the adiposity and exerted an anti-obesogenic effect on brown adipose tissue by up-regulating the expression of the genes Ucp-1, Cidea, Prdm16 and Gpr43. D1 also influenced the cecal microbiota composition, impacting its functions such as the production of short-chain fatty acids in the caecum. D1 reduced microbiota diversity by increasing beneficial taxa, such as Ruminococcaceae family and Turicibacter genus, among others. These genera showed correlations with the analysed immune and lipid metabolism parameters suggesting that microbiome modulation serves as a link between the observed systemic effects and the dietary intervention. INTERPRETATION:The study highlights that a diet rich in fibre, vegetable protein, and fish oil, consumed during gestation and lactation, enhances maternal health by improving intestinal function, mucosal immunity, and exerting anti-obesogenic effects on lipid metabolism, likely mediated by modifications in the cecal microbiota composition and function. FUNDING:The study was supported by LaMarató-TV3 (DIM-2-ELI, ref. 2018-27/30-31).

BACKGROUND:Maternal nutritional status and dietary profile during pregnancy and lactation have short- and long-term impacts on offspring health. However, there is an incomplete understanding of the mechanisms behind these health effects. This study aims to assess the effect of maternal diet on the health of offspring by examining to unravel the impact of maternal diet on offspring health outcomes and evaluate the link between maternal nutrition, human milk immune components and neonatal colonisation as potential mechanisms that mediate the influence of maternal diet in the incidence of infant infections. METHODS:To assess this objective, we used two complementary approaches by which a clinical observational study based on the MAMI birth cohort guided a preclinical interventional analysis using a neonatal rat model of rotavirus-induced gastroenteritis. FINDINGS:The findings in both approaches demonstrated that a maternal diet rich in plant-based protein, fibre and polyunsaturated fatty acids, was linked to reduced incidence and severity of infections in offspring that would be mediated by beneficial modulation of the gut microbiota and immune system. Specifically, in the suckling rats, a predominant Th1 immune response and an enhanced virus-specific response were observed. Moreover, human milk IgA and rat milk IgG2c played a key protective role that complemented the effects of maternal diet. INTERPRETATION:These results strengthen the importance of maternal diet during pregnancy and lactation supporting infant health. FUNDING:The study was supported by LaMarató-TV3 (DIM-2-ELI, ref. 2018-27/30-31).

Enterococcus spp. some of which are pathogenic, are common gut microbiota members, including also infants. Infants may be more susceptible to Enterococcus due to their developing gut ecosystems. It is unclear whether antibiotic resistance genes (ARGs) and certain genomic traits in enterococci are restricted to the human subpopulation or more widespread. Furthermore, the correlation between these traits and geographic variation is poorly understood. Therefore, we sequenced 100 strains isolated from full-term healthy infants’ fecal samples from two geographically distant European cohorts (MAMI in Spain and LucKi from the Netherlands) to explore the diversity of Enterococcus spp. within the infant’s gut microbiome and assess cohort-specific traits such as ARGs. Most isolates were E. faecalis and E. gallinarum, with a total of 11 species identified. We found a rich reservoir of ARGs, plasmids, prophages and virulence factors in the infant strains, with minimal cohort-specific differences in resistome profiles. In addition, Epx, a pore-forming toxin associated with pathogenicity, was found in E. hirae strains. While metabolic profiles were similar across cohorts, E. faecalis strains harbored more virulence genes and prophages compared to other species. An analysis of public Enterococcus genomes revealed that multi-drug resistant (MDR) strains exist without any significant geographic or temporal pattern. Phenotypic resistance analysis indicated that 28% of MAMI strains were gentamicin resistant, compared to 5% of the strains from the LucKi cohort, though LucKi isolates were also resistant to other antibiotics. We also selected ten E. faecalis isolates with varying virulence gene repertoires for phenotypic virulence testing in Caenorhabditis elegans and found them killing at various rates, however no clear pattern emerged in correlation with any specific genetic determinant. Overall, our results suggest that Enterococcus spp. including ARGs, are highly mobile across Europe and beyond. Their adaptability likely facilitates long-distance dissemination, with strains being acquired early in life from community environments.

The role of the Maillard reaction and the accumulation of non-enzymatic glycation compounds in human milk have been scarcely considered. In this study, we investigated the proteins most susceptible to glycation, the identity of the corresponding modified residues and the quantitative relationship between protein-bound and free glycation compounds in raw human milk and, for comparison, in minimally processed infant formula and pasteurized bovine milk. In human milk, total protein-bound lysine modifications were up to 10% of the counterparts in infant formula, while Nε-carboxymethyllysine reached up to 27% of the concentration in the other two products. We demonstrated that the concentration of free pyrraline and methylglyoxal-hydroimidazolone were of the same order of magnitude in the three milk types. Our results delineate how the occurrence of some glycation compounds in human milk can be an unavoidable part of the breastfeeding and not an exclusive attribute of infant formulas and pasteurized bovine milk.

Most women who give birth will initiate lactation and breast/chestfeeding, with up to 40

A “postbiotic” is a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host. To encourage collaborative problem-solving to address the issues related to the characterization and quantification of postbiotics, a working group of academic and industry scientists involved in research or commercial production of postbiotics convened at the International Scientific Association for Probiotics and Prebiotics (ISAPP) 2024 meeting. This paper reports the outcomes of that discussion. Postbiotics are potentially compositionally complex mixtures, leading us to anticipate that full characterization and quantification of all components of a postbiotic product is not feasible. However, confirmation of the identity and quantity of the progenitor microorganism(s), quantification of some of its functional components, and a suitable description of the process of inactivation will be needed to assure the product can be sufficiently described and consistently reproduced. Measurement and quantification must be fit for purpose. Some useful methods include flow cytometry (FC), including innovations such as imaging FC, which has evolved into a mainstream technique suited to quantify inanimate cells, and quantitative polymerase chain reaction, which complements FC by enabling quantification and identity of microbes to the strain level. Other methods can be utilized depending on the complexity, type of microorganisms used (bacteria, yeasts, filamentous fungi), number of strains and cell integrity (intact vs. fragmented). Hence, no ‘gold standard’ methodology - analogous to colony-forming units for probiotics - is envisioned for postbiotics. This perspective focuses on the required microbial composition of postbiotics, not on the optional metabolite components, which can be measured using well-established methods. We propose a decision tree to aid deliberation among different quantification methods for postbiotics under development and being commercialized. We recognize that the evolution of technologies will likely result in future refinement of this decision tree, and we emphasize that our intent is not to prescribe a rigid framework, but rather to provide guiding principles on approaches to quantifying postbiotics.

The assembly of the gut resistome in early life is key to infant health. Specific perinatal factors such as cesarean section (C-section), antibiotic exposure and lack of breastfeeding practices are detrimental to proper microbial development and increase the antimicrobial resistance genes (ARGs). Using 265 gut longitudinal metagenomes from 66 mother-infant pairs, we investigated how perinatal factors influence the acquisition and dynamics of ARGs during the first year of life. Our findings reveal that Bifidobacterium plays a crucial role in modulating the infant resistome, with its high relative abundance being associated with a lower ARG load. Exclusive breastfeeding during the first month of life accelerates the reduction of ARGs and ensures a lower resistome burden at six months. Moreover, early breastfeeding cessation correlates with a higher ARG load, underscoring its long-term influence on microbial resilience. Importantly, we identify exclusive breastfeeding as a key strategy to mitigate the impact of C-section delivery on the infant gut resistome, counteracting the early-life antibiotic exposure associated with this procedure and the resulting resistance acquisition. By promoting a microbiome enriched in Bifidobacterium, breastfeeding may help suppress ARG-carrying taxa, reducing the risk of resistance dissemination. Our findings underscore the importance of breastfeeding as a natural intervention to shape the infant microbiome and resistome. Supporting breastfeeding through public health policies could help limit the spread of antimicrobial resistance in early life.

BACKGROUND:Early-life exposures might negatively affect fetal and infant development, predisposing children to obesity. This study aimed to systematically identify and evaluate risk factors for childhood obesity in preconception, pregnancy, and infancy, and assess their potential for future prediction and prevention strategies. METHODS:This systematic review (PROSPERO, CRD42022355152) included longitudinal studies from selected electronic databases published between inception and August 17th, 2022, identifying maternal, paternal, or infant risk factors from preconception until infancy for childhood obesity between 2 and 18 years. Screening and data extraction were conducted using standardized forms. We assessed risk factor quality on modifiability and predictive power using a piloted criteria template from ILSI-Europe-Marker-Validation-Initiative. FINDINGS:We identified 172 publications from observational and five publications from intervention studies involving n = 1,879,971 children from 37, predominantly high-income, countries. Average reported childhood obesity prevalence was 11.1%. Pregnancy and infancy risk factors were mostly studied. We identified 59 potential risk factors; 23 were consistently associated. Strongest risk factors were: higher maternal prepregnancy weight (n = 28/31 publications with positive associations), higher gestational weight gain (n = 18/21), maternal smoking during pregnancy (n = 23/29), higher birth weight (n = 20/28), large-size-for-gestational-age-at-birth (n = 17/18), no breastfeeding (n = 20/31), and higher infant weight gain (n = 12/12). Level of evidence was generally moderate due to unreliable exposure measurement, short follow-up/loss to follow-up, and risk of confounding. INTERPRETATION:We identified seven early-life risk factors, which were strongly associated with childhood obesity, and can contribute to future prediction and prevention strategies. These findings support the implementation of prevention strategies targeting these risk factors from a clinical and population perspective, where possible integrated with implementation studies.

Background: Despite the importance of gestation period for human health, studies addressing the impact of maternal microbiota on its progression and its modulation by maternal lifestyle are scarce. Although most of the evidence in the field comes from observational studies, we recently described how some lifestyle interventions during pregnancy reduced the small-for-gestational-age (SGA) incidence. We hypothesized the pregnant individual's microbiome modulation as potential mechanism by which lifestyle interventions could impact gestation progression. Objectives: The objectives of this study was to investigate the effect of pregnancy lifestyle interventions, based on a Mediterranean dietary pattern (MD) or Stress Reduction program (SR) that proved to be beneficial in reducing the SGA incidence, on the pregnant individuals' gut and vaginal microbiota as exploratory outcomes. Methods: In a random subsample (n = 351) from a trial including pregnancies randomly allocated into an MD intervention, an SR program, or nonintervention, maternal fecal/vaginal samples were collected at the end of the interventions, and in a subset (n = 85) also at recruitment. Microbiota was profiled by 16S rRNA gene sequencing. Multivariate models evaluated the associations of microbiota with the interventions. Results: Mothers included in the study presented a similar gut microbiota profile before the intervention; pregnancy MD intervention influenced the overall structure of gut microbiota, (R2 = 0.008, F = 1.885, P = 0.002), which resulted in enrichment in Firmicutes phylum (Coeff = 0.06, 95% confidence interval [CI]: 0.002, 0.118), related to the increment in health-associated taxa(Lachnospiraceae/Ruminococcaceae families) and other SCFA producers; and diminishment in Campylobacter genus (Coeff =-0.91, 95% CI: -1.361, -0.459). The link of the SR program with gut microbiota was more limited; however, some key components from these families were also affected. Microbial diversity of gut microbiota decreased as pregnancy progressed, with this effect more observable in the mothers that followed the interventions. The interventions have a negligible association with the vaginal microbiota. Conclusions: Pregnancy lifestyle interventions influence maternal gut microbiota. The trial was registered at clinicaltrials.gov Identifier as NCT03166332. Clinical Trial Information: Date of Institutional Review Board approval and registration: 16 December 2016; 19 April 2017; Date of initial participant enrollment and date of first outcome (i.e., delivery of the pregnant individual enrolled): 1 February 2017; 10 May 2017.

Immune system development during gestation and suckling is significantly modulated by maternal environmental and dietary factors. Breastfeeding is widely recognized as the optimal source of nutrition for infant growth and immune maturation, and its composition can be modulated by the maternal diet. In the present work, we investigated whether oral supplementation with Bifidobacterium breve M-16V and short-chain galacto-oligosaccharide (scGOS) and long-chain fructo-oligosaccharide (lcFOS) to rat dams during gestation and lactation has an impact on the immune system and microbiota composition of the offspring at day 21 of life. On that day, blood, adipose tissue, small intestine (SI), mesenteric lymph nodes (MLN), salivary gland (SG), cecum, and spleen were collected. Synbiotic supplementation did not affect the overall body or organ growth of the pups. The gene expression of Tlr9, Muc2, IgA, and Blimp1 were upregulated in the SI, and the increase in IgA gene expression was further confirmed at the protein level in the gut wash. Synbiotic supplementation also positively impacted the microbiota composition in both the small and large intestines, resulting in higher proportions of Bifidobacterium genus, among others. In addition, there was an increase in butanoic, isobutanoic, and acetic acid concentrations in the cecum but a reduction in the small intestine. At the systemic level, synbiotic supplementation resulted in higher levels of immunoglobulin IgG2c in plasma, SG, and MLN, but it did not modify the main lymphocyte subsets in the spleen and MLN. Overall, synbiotic maternal supplementation is able to positively influence the immune system development and microbiota of the suckling offspring, particularly at the gastrointestinal level.

The early gut microbiota composition is fundamentally important for piglet health, affecting long-term microbiome development and immunity. In this study, the gut microbiota of postparturient dams was compared with that of their offspring in three Finnish pig farms at three growth phases. The differences in fecal microbiota of three study development groups (Good, Poorly, and PrematureDeath) were analyzed at birth (initial exposure phase), weaning (transitional phase), and before slaughter (stable phase). Dam Lactobacillaceae abundance was lower than in piglets at birth. Limosilactobacillus reuteri and Lactobacillus amylovorus were dominantly expressed in dams and their offspring. Altogether 17 piglets (68%) were identified with Lactobacillaceae at the initial exposure phase, divided unevenly among the development groups: 85% of Good, 37.5% of Poorly, and 75% of PrematureDeath pigs. The development group Good was identified with the highest microbial diversity, whereas the development group PrematureDeath had the lowest diversity. After weaning, the abundance and versatility of Lactobacillaceae in piglets diminished, shifting towards the microbiome of the dam. In conclusion, the fecal microbiota of pigs tends to develop towards a similar alpha and beta diversity despite development group and rearing environment.