Sex-specific impact of asthma during pregnancy on infant gut microbiota

Microbial colonization programs are structured by breastfeeding and guide healthy respiratory development

Breastfeeding and microbial colonization during infancy occur within a critical time window for development, and both are thought to influence the risk of respiratory illness. However, the mechanisms underlying the protective effects of breastfeeding and the regulation of microbial colonization are poorly understood. Here, we profiled the nasal and gut microbiomes, breastfeeding characteristics, and maternal milk composition of 2,227 children from the CHILD Cohort Study. We identified robust colonization patterns that, together with milk components, predict preschool asthma and mediate the protective effects of breastfeeding. We found that early cessation of breastfeeding (before 3 months) leads to the premature acquisition of microbial species and functions, including Ruminococcus gnavus and tryptophan biosynthesis, which were previously linked to immune modulation and asthma. Conversely, longer exclusive breastfeeding supports a paced microbial development, protecting against asthma. These findings underscore the importance of extended breastfeeding for respiratory health and highlight potential microbial targets for intervention.

Maternal asthma in relation to infant size and body composition

Background

Asthma affects 10% of pregnancies and may influence offspring health, including infant size and body composition, through hypoxic and inflammatory pathways.

Objective

We sought to determine associations between maternal asthma and asthma phenotypes during pregnancy and infant size and body composition.

Methods

The B-WELL-Mom study (2015-19) is a prospective cohort of 418 pregnant persons with and without asthma recruited in the first trimester of pregnancy from 2 US obstetric clinics. Exposures were maternal self-reported active asthma (n = 311) or no asthma (n = 107), and asthma phenotypes were classified on the bases of atopy, onset, exercise induced, control, severity, symptomology, and exacerbations. Outcomes were infant weight, length, head circumference, and skinfold measurements at birth and postnatal follow-up, as well as fat and lean mass assessed by air displacement plethysmography at birth. Adjusted multivariable linear regression examined associations of maternal asthma and asthma phenotypes with infant outcomes.

Results

Offspring were born at a mean ± SD of 38 ± 2.3 weeks' gestation and were 18 ± 2.2 weeks of age at postnatal follow-up. Infants of participants with asthma had a mean ± SD fat mass of 11.0 ± 4.2%, birth weight of 3045.8 ± 604.3 g, and postnatal follow-up weight of 6696.4 ± 964.2 g, which were not different from infants of participants without asthma (respectively, β [95% confidence interval]: -0.1 [-1.4, 1.3], -26.7 [-156.9, 103.4], and 107.5 [-117.3, 332.3]). Few associations were observed between asthma or asthma phenotypes and infant size or body composition.

Conclusions

In a current obstetric cohort, maternal asthma during pregnancy was not associated with differential infant size or body composition.

The Footprint of Microbiome in Pediatric Asthma-A Complex Puzzle for a Balanced Development

Considered to be of greater complexity than the human genome itself, the microbiome, the structure of the body made up of trillions of bacteria, viruses, and fungi, has proven to play a crucial role in the context of the development of pathological processes in the body, starting from various infections, autoimmune diseases, atopies, and culminating in its involvement in the development of some forms of cancer, a diagnosis that is considered the most disabling for the patient from a psychological point of view. Therefore, being a cornerstone in the understanding and optimal treatment of a multitude of ailments, the body's microbiome has become an intensively studied subject in the scientific literature of the last decade. This review aims to bring the microbiome-asthma correlation up to date by classifying asthmatic patterns, emphasizing the development patterns of the microbiome starting from the perinatal period and the impact of pulmonary dysbiosis on asthmatic symptoms in children. Likewise, the effects of intestinal dysbiosis reflected at the level of homeostasis of the internal environment through the intestine-lung/vital organs axis, the circumstances in which it occurs, but also the main methods of studying bacterial variability used for diagnostic purposes and in research should not be omitted. In conclusion, we draw current and future therapeutic lines worthy of consideration both in obtaining and maintaining remission, as well as in delaying the development of primary acute episodes and preventing future relapses.

The impact of gender medicine on neonatology: the disadvantage of being male: a narrative review

This narrative non-systematic review addresses the sex-specific differences observed both in prenatal period and, subsequently, in early childhood. Indeed, gender influences the type of birth and related complications. The risk of preterm birth, perinatal diseases, and differences on efficacy for pharmacological and non-pharmacological therapies, as well as prevention programs, will be evaluated. Although male newborns get more disadvantages, the physiological changes during growth and factors like social, demographic, and behavioural reverse this prevalence for some diseases. Therefore, given the primary role of genetics in gender differences, further studies specifically targeted neonatal sex-differences will be needed to streamline medical care and improve prevention programs.

The rise to power of the microbiome: power and sample size calculation for microbiome studies

A priori power and sample size calculations are crucial to appropriately test null hypotheses and obtain valid conclusions from all clinical studies. Statistical tests to evaluate hypotheses in microbiome studies need to consider intrinsic features of microbiome datasets that do not apply to classic sample size calculation. In this review, we summarize statistical approaches to calculate sample sizes for typical microbiome study scenarios, including those that hypothesize microbiome features to be the outcome, the exposure or the mediator, and provide relevant R scripts to conduct some of these calculations. This review is intended to be a resource to facilitate the conduct of sample size calculations that are based on testable hypotheses across several dimensions of the microbiome. Implementation of these methods will improve the quality of human or animal microbiome studies, enabling reliable conclusions that will generalize beyond the study sample.

Nutritional Interventions and the Gut Microbiome in Children

The gut microbiome plays an integral role in health and disease, and diet is a major driver of its composition, diversity, and functional capacity. Given the dynamic development of the gut microbiome in infants and children, it is critical to address two major questions: (a) Can diet modify the composition, diversity, or function of the gut microbiome, and (b) will such modification affect functional/clinical outcomes including immune function, cognitive development, and overall health? We synthesize the evidence on the effect of nutritional interventions on the gut microbiome in infants and children across 26 studies. Findings indicate the need to study older children, assess the whole intestinal tract, and harmonize methods and interpretation of findings, which are critical for informing meaningful clinical and public health practice. These findings are relevant for precision health, may help identify windows of opportunity for intervention, and may inform the design and delivery of such interventions. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

How biological sex of the host shapes its gut microbiota

The gut microbiota is a complex system, consisting of a dynamic population of microorganisms, involved in the regulation of the host's homeostasis. A vast number of factors are driving the gut microbiota composition including diet, antibiotics, environment, and lifestyle. However, in the past decade, a growing number of studies also focused on the role of sex in relationship to changes in the gut microbiota composition in animal experiments as well as in human beings. Despite the progress in investigation techniques, still little is known about the mechanism behind the observed sex-related differences. In this review, we summarized current knowledge on the sex-dependent differences of the intestinal commensals and discuss the probable direct impact of sex hormones and more indirect effects such as dietary habits or antibiotics. While we have to conclude limited data on specific developmental stages, a clear role for sexual hormones and most probably for testosterone emerges.

Maternal exposures and the infant gut microbiome: a systematic review with meta-analysis

Early life, including the establishment of the intestinal microbiome, represents a critical window of growth and development. Postnatal factors affecting the microbiome, including mode of delivery, feeding type, and antibiotic exposure have been widely investigated, but questions remain regarding the influence of exposures in utero on infant gut microbiome assembly. This systematic review aimed to synthesize evidence on exposures before birth, which affect the early intestinal microbiome. Five databases were searched in August 2019 for studies exploring pre-pregnancy or pregnancy 'exposure' data in relation to the infant microbiome. Of 1,441 publications identified, 76 were included. Factors reported influencing microbiome composition and diversity included maternal antibiotic and probiotic uses, dietary intake, pre-pregnancy body mass index (BMI), gestational weight gain (GWG), diabetes, mood, and others. Eleven studies contributed to three meta-analyses quantifying associations between maternal intrapartum antibiotic exposure (IAP), BMI and GWG, and infant microbiome alpha diversity (Shannon Index). IAP, maternal overweight/obesity and excessive GWG were all associated with reduced diversity. Most studies were observational, few included early recruitment or longitudinal follow-up, and the timing, frequency, and methodologies related to stool sampling and analysis were variable. Standardization and collaboration are imperative to enhance understanding in this complex and rapidly evolving area.

Urine Microbe-Derived Extracellular Vesicles in Children With Asthma

PURPOSE

Several studies have found significant associations between asthma and microbiome. However, it is challenging to obtain-sputum and bronchoalveolar lavage samples from pediatric patients. Thus, we used voided urine to show that urine microbe-derived extracellular vesicles (EVs) in asthma are an available source for clinical research.

METHODS

Five urine samples were obtained at 2-3-month intervals from each patient with asthma (n = 20), and a single voided urine sample were obtained from each healthy child (n = 20). After isolating EVs, 16S rDNA pyrosequencing was performed. The Chao1 index and principal coordinate analysis (PCoA) were used to assess diversity. To predict microbiota functional capacities, Phylogenetic Investigation of Communities by Reconstruction of Unobserved States was used based on the Kyoto Encyclopedia of Genes and Genomes pathway database. Eight covariates were included in the EnvFit analysis to identify significant factors in the asthma group.

RESULTS

The asthma group showed lower Chao1 bacterial richness, and PCoA-based clustering differed significantly. Two phyla, and 13 families and genera were enriched or depleted. Functional profiling revealed significant differences between the asthma and control groups. EnvFit analysis of correlation to age, sex, body mass index, infection, season, asthma phenotype, severity, and symptoms was not significant except for infections associated with visit 1 and the season of visit 2.

CONCLUSIONS

This study showed that microbe-derived EVs were constantly altered in the urine of children with asthma, consistent with the findings of previous studies indicating microbiome changes in the lung and gut. The urine may reflect the specific pattern of microbiome EVs in children with asthma.

The Role of Short-Chain Fatty Acids in the Interplay between a Very Low-Calorie Ketogenic Diet and the Infant Gut Microbiota and Its Therapeutic Implications for Reducing Asthma

Gut microbiota is well known as playing a critical role in inflammation and asthma development. The very low-calorie ketogenic diet (VLCKD) is suggested to affect gut microbiota; however, the effects of VLCKD during pregnancy and lactation on the infant gut microbiota are unclear. The VLCKD appears to be more effective than caloric/energy restriction diets for the treatment of several diseases, such as obesity and diabetes. However, whether adherence to VLCKD affects the infant gut microbiota and the protective effects thereof on asthma remains uncertain. The exact mechanisms underlying this process, and in particular the potential role of short chain fatty acids (SCFAs), are still to be unravelled. Thus, the aim of this review is to identify the potential role of SCFAs that underlie the effects of VLCKD during pregnancy and lactation on the infant gut microbiota, and explore whether it incurs significant implications for reducing asthma.

Vitamin D supplementation in pregnancy and early infancy in relation to gut microbiota composition and C. difficile colonization: implications for viral respiratory infections

In Canada and the US, the infant diet is supplemented with vitamin D via supplement drops or formula. Pregnant and nursing mothers often take vitamin D supplements. Since little is known about the impact of this supplementation on infant gut microbiota, we undertook a study to determine the association between maternal and infant vitamin D supplementation, infant gut microbiota composition and Clostridioides difficile colonization in 1,157 mother-infant pairs of the CHILD (Canadian Healthy Infant Longitudinal Development) Cohort Study over 2009-2012. Logistic and MaAsLin regression were employed to assess associations between vitamin D supplementation, and C. difficile colonization, or other gut microbiota, respectively. Sixty-five percent of infants received a vitamin D supplement. Among all infants, infant vitamin D supplementation was associated with a lower abundance of genus Megamonas (q = 0.01) in gut microbiota. Among those exclusively breastfed, maternal prenatal supplementation was associated with lower abundance of Bilophila (q = 0.01) and of Lachnospiraceae (q = 0.02) but higher abundance of Haemophilus (q = 0.02). There were no differences in microbiota composition with vitamin D supplementation among partially and not breastfed infants. Neither infant nor maternal vitamin D supplementation were associated with C. difficile colonization, after adjusting for breastfeeding status and other factors. However, maternal consumption of vitamin-D fortified milk reduced the likelihood of C. difficile colonization in infants (adjustedOR: 0.40, 95% CI: 0.19-0.82). The impact of this compositional difference on later childhood health, especially defense against viral respiratory infection, may go beyond the expected effects of vitamin D supplements and remains to be ascertained.

Nutrition and the Gut Microbiota in 10- to 18-Month-Old Children Living in Urban Slums of Mumbai, India

In this cross-sectional study, we describe the composition and diversity of the gut microbiota among undernourished children living in urban slums of Mumbai, India, and determine how nutritional status, including anthropometric measurements, dietary intakes from complementary foods, feeding practices, and micronutrient concentrations, is associated with their gut microbiota. We collected rectal swabs from children aged 10 to 18 months living in urban slums of Mumbai participating in a randomized controlled feeding trial and conducted 16S rRNA sequencing to determine the composition of the gut microbiota. Across the study cohort, Proteobacteria dominated the gut microbiota at over 80% relative abundance, with Actinobacteria representation at <4%, suggesting immaturity of the gut. Increased microbial α-diversity was associated with current breastfeeding, greater head circumference, higher fat intake, and lower hemoglobin concentration and weight-for-length Z-score. In redundancy analyses, 47% of the variation in Faith's phylogenetic diversity (Faith's PD) could be accounted for by age and by iron and polyunsaturated fatty acid intakes. Differences in community structure (β-diversity) of the microbiota were observed among those consuming fats and oils the previous day compared to those not consuming fats and oils the previous day. Our findings suggest that growth, diet, and feeding practices are associated with gut microbiota metrics in undernourished children, whose gut microbiota were comprised mainly of Proteobacteria, a phylum containing many potentially pathogenic taxa.IMPORTANCE The impact of comprehensive nutritional status, defined as growth, nutritional blood biomarkers, dietary intakes, and feeding practices, on the gut microbiome in children living in low-resource settings has remained underreported in microbiome research. Among undernourished children living in urban slums of Mumbai, India, we observed a high relative abundance of Proteobacteria, a phylum including many potentially pathogenic species similar to the composition in preterm infants, suggesting immaturity of the gut, or potentially a high inflammatory burden. We found head circumference, fat and iron intake, and current breastfeeding were positively associated with microbial diversity, while hemoglobin and weight for length were associated with lower diversity. Findings suggest that examining comprehensive nutrition is critical to gain more understanding of how nutrition and the gut microbiota are linked, particularly in vulnerable populations such as children in urban slum settings.

Childhood allergy is preceded by an absence of gut lactobacilli species and higher levels of atopy-related plasma chemokines

Alterations in the composition and reduced diversity of the infant microbiome are associated with allergic disease in children. Further, an altered microbiota is linked to immune dysregulation, including skewing of different T helper (Th) subsets, which is also seen in atopic individuals. The aim of this study was, therefore, to investigate the associations between gut lactobacilli and Th‐related plasma factors in allergy development during childhood. A total of 194 children with known allergy status at 1 year of age were followed to 10 years of age. We used real‐time polymerase chain reaction (PCR) to investigate the presence of three lactobacilli species (Lactobacillus casei, L. paracasei, L. rhamnosus) in infant fecal samples (collected between 1 week and 2 months of age) from a subgroup of children. Plasma chemokines and cytokines were quantified at 6 months and at 1, 2, 5 and 10 years of age with Luminex or enzyme‐linked immunosorbent assay (ELISA). Fractional exhaled nitrogen oxide (FeNO) was measured and spirometry performed at 10 years of age. The data were analysed by non‐parametric testing and a logistic regression model adjusted for parental allergy. An absence of these lactobacilli and higher levels of the chemokines BCA‐1/CXCL13, CCL17/TARC, MIP‐3α/CCL20 and MDC/CCL22 in plasma at 6 months of age preceded allergy development. The presence of lactobacilli associated with lower levels of atopy‐related chemokines during infancy, together with higher levels of interferon (IFN)‐γ and lower FeNO during later childhood. The results indicate that the presence of certain lactobacilli species in the infant gut may influence allergy‐related parameters in the peripheral immune system, and thereby contribute to allergy protection.

The Infant Gut Microbiota and Risk of Asthma: The Effect of Maternal Nutrition during Pregnancy and Lactation

Research has amply demonstrated that early life dysbiosis of the gut microbiota influences the propensity to develop asthma. The influence of maternal nutrition on infant gut microbiota is therefore of growing interest. However, a handful of prospective studies have examined the role of maternal dietary patterns during pregnancy in influencing the infant gut microbiota but did not assess whether this resulted in an increased risk of asthma later in life. The mechanisms involved in the process are also, thus far, poorly documented. There have also been few studies examining the effect of maternal dietary nutrient intake during lactation on the milk microbiota, the effect on the infant gut microbiota and, furthermore, the consequences for asthma development remain largely unknown. Therefore, the specific aim of this mini review is summarizing the current knowledge regarding the effect of maternal nutrition during pregnancy and lactation on the infant gut microbiota composition, and whether it has implications for asthma development.

Perinatal factors and the risk of type 1 diabetes in childhood and adolescence-A register-based case-cohort study in Finland, years 1987 to 2009

OBJECTIVES

Our aim was to clarify previously reported associations and to explore new ones between various maternal background and perinatal factors and the risk of type 1 diabetes in childhood.

METHODS

We identified all children born 1 January 1987 to 31 December 2008 in Finland and diagnosed with type 1 diabetes by age 16 years or end of 2009 from the Special Reimbursement Register (n = 6862). A 10% random sample from each birth year cohort was selected as a reference cohort (n = 127 216). Information on perinatal factors was obtained from the Finnish Medical Birth Register.

RESULTS

Maternal diabetes (hazard ratios [HR] = 6.43; 95% confidence interval [CI] 5.35, 7.73), maternal asthma (HR = 1.23; 95% CI 1.06, 1.43), child's high birth length for gestational age (HR = 1.35; 95% CI 1.22, 1.51 highest vs lowest quintile) and premature or early term birth (HR = 1.21; 95% CI 1.05, 1.39 gestational weeks 33-36 and HR = 1.17; 95% CI 1.09, 1.26 gestational weeks 37-38 vs gestational weeks 39-40) was associated with an increased risk of type 1 diabetes when adjusted for several potential confounders. Maternal smoking during pregnancy (HR = 0.72; 95% CI 0.66, 0.77), high number of previous live births (HR = 0.65; 95% CI 0.55, 0.76 ≥ 4 vs 0 live births), and the child being born small for gestational age (HR = 0.80; 95% CI 0.67, 0.96) was associated with a decreased risk of type 1 diabetes.

CONCLUSIONS

Findings on maternal asthma and high birth length for gestational age increasing the risk of type 1 diabetes are novel and need to be confirmed. Our findings indicate that perinatal factors may play a role in the development of type 1 diabetes.

The role of gut microbiota in atopic asthma and allergy, implications in the understanding of disease pathogenesis

Asthma is a clinical syndrome characterized by chronic airway inflammation. There is mounting evidence on the role of microbiota in the development of asthma. This review focuses on the role of microbiota in maintaining the integrity of the epithelia and their role in regulating the immune response. The review compiles data from multiple studies on the role of microbiota in the innate immune response and the development and differentiation of CD4⁺ T cells, a major component of the adaptive arm of the immune response. As a result of dysbiosis, invariant natural killer T cells may induce T helper 2 cell differentiation and immunoglobulin E isotype switching through the release of interleukin-4 and interleukin-13. Furthermore, degradation of immunoglobulin A antibodies, increased circulating mast cells and basophils, and inflammation are among other mechanisms by which dysbiosis can induce or exacerbate asthma. After explaining the underlying mechanisms, the review derives conclusions from studies that investigate dysbiosis in infancy and the development of asthma later in life. The review also includes studies that investigate asthmatic mothers and the development of asthma in children and the role of dysbiosis in that regard. Finally, the review explains the statistical relationship between eczema and asthma through multiple studies that investigate the role of dysbiosis in both atopic states. This review provides insight into the role of dysbiosis in asthma, and an understanding that is required to establish clinical trials which aim to modulate the gut microbiota as a means of preventing and treating asthma.

The Sex-Gender Effects in the Road to Tailored Botanicals

Phenols are a wide family of phytochemicals that are characterized by large chemical diversity and are considered to bioactive molecules of foods, beverages, and botanicals. Although they have a multitude of biological actions, their beneficial effects are rarely evidenced in clinical research with high scientific rigor. This may occur due to the presence of numerous confounders, such as the modulation of phenol bioavailability, which can be regulated by microbiota, age, sex-gender. Sex-gender is an important determinant of health and well-being, and has an impact on environmental and occupational risks, access to health care, disease prevalence, and treatment outcomes. In addition, xenobiotic responses may be strongly influenced by sex-gender. This review describes how sex–gender differentially influences the activities of phenols also in some critical periods of women life such as pregnancy and lactation, considering also the sex of fetuses and infants. Thus, sex–gender is a variable that must be carefully considered and should be used to propose directions for future research on the road to tailored medicine and nutrition.

Sex Bias in Asthma Prevalence and Pathogenesis

Sex-related differences in asthma prevalence are well established and change through the reproductive phases of life. As children, boys have increased prevalence of asthma compared to girls. However, as adults, women have increased prevalence of asthma compared to men. Many factors, including genetics, environment, immunological responses, and sex hormones, affect the sex disparity associated with the development and control of asthma and other allergic diseases. Fluctuations of hormones during puberty, menstruation, pregnancy, and menopause, alter asthma symptoms and severity. In this article, we review clinical and epidemiological studies that examined the sex disparity in asthma and other allergic diseases as well as the role of sex hormones on asthma pathogenesis.

The association between early life antibiotic use and allergic disease in young children: recent insights and their implications

INTRODUCTION

Greater prescribing of antibiotics to infants has coincided with an epidemic of allergic disease. Through meta-analytic synthesis, accumulating evidence from prospective or database cohorts suggests a link between infant antibiotic treatment and the development of atopy. Stronger associations seen with multiple course and broad-spectrum antibiotic treatment add to biological plausibility. A major bias, confounding by indication, has been addressed in studies on antibiotic treatment of conditions which do not precede allergic disease. Areas covered: Our review provides an up-to-date synthesis of the current literature on associations between infant antibiotic exposure and future allergic disease. We discuss methods that assist in reducing study bias and look at new insights from studies of the infant gut microbiome. Expert commentary: Large-scale profiling of the gut microbiome provides a new tool for disentangling biases found in observational studies of infant antibiotic use. To date, microbial dysbiosis of the infant gut has been reported to predict allergic disease independent of antibiotic exposure up to 3 months after birth. However, these studies have not accounted for antibiotic treatment in later infancy. Continued study of the infant gut microbiome, mycobiome, or resistome will provide a closer link to antibiotic treatment or refute it as a cause of allergic disease.