• Infant gut microbiota and childhood BMI z-score
• Association of maternal gut microbiota taxa with maternal Ow/Ob and excessive GWG
• BMI-associated infant gut microbiota and the association with maternal characteristics of pre-pregnancy Ow/Ob and excessive GWG
What is already known on this topic
The prevalence of childhood obesity has been increasing in most countries across the globe in recent decades. The idea that the gut microbiota may play a vital and potentially etiological role in the development of obesity has gained traction. Differences in the gut microbiota have been associated with overweight/obesity in both adults and children and there is growing evidence of possible causal mechanisms.
What this research adds
Researchers studied the early-life gut microbiota at days 4, 10, 30, 120, 365, 730 and its association with body mass index (BMI) z-scores at the age of 12 years in a Norwegian prospective cohort. Researchers further evaluated how these BMI-associated taxa relate to maternal overweight/obesity (Ow/Ob) and excessive gestational weight gain (GWG).
In this cohort, the gut microbiota taxa at 2 years of age explained over 50% of the variation in childhood BMI. The subset of the early-life taxa within the gut microbiota predicted later childhood BMI. The preliminary results demonstrated that the infant gut microbiota, especially at the age of 2, may have the potential to help identify children at risk of developing obesity.
The infant gut microbiota is associated with later BMI and, particularly at 2 years of age, may have the potential to help identify children at risk for obesity. These are the conclusions of a study by M.A. Stanislawski and colleagues at the School of Public Health in Colorado, United States, published in the journal mBio.
Researchers examined the early-life gut microbiota at days 4, 10, 30, 120, 365, and 730 and the association with body mass index (BMI) z-scores at age 12 in a Norwegian prospective cohort (n=165), and evaluated how these BMI-associated taxa relate to maternal overweight/obesity (Ow/Ob) and excessive gestational weight gain (GWG) by performing 16S rRNA gene sequencing on the gut microbiota samples.
Infant gut microbiota and childhood BMI z-score
The overall infant gut microbiota taxonomic phylogeny at days 10 and 730 were significantly associated with sex and age-specific BMI z-scores at the age of 12 years. A specific subset of the taxa could be predictive of childhood BMI even though the overall composition is not considerably associated. Researchers further studied whether the gut microbiota taxa at each sampling time during the first 2 years of life can predict the later BMI.
The gut microbiota of infants during the first 4 months explained a considerable portion of the variation in BMI z-score. This association strengthened with age, and more than half of the variability in BMI z-scores at the age of 12 years was explained by the gut microbiota composition at 2 years of age.
This is substantially more than other predictors of child BMI. For example, taken together child BMI predictors like delivery mode, exclusive breast-feeding duration, antibiotic exposure, twin status, gestational age at birth, and maternal factors (including pre-pregnancy BMI and smoking during pregnancy) explained 15.2% of the variation in child BMI z-score.
The confounding variables of delivery mode, exclusive breastfeeding duration, antibiotic exposure, twin pregnancy, and gestational age included in the random forests were not among the most important predictors of later BMI; researchers estimated R2 values of the random forests both with and without these confounding factors and the values were comparable.
Association of maternal gut microbiota taxa with maternal Ow/Ob and excessive GWG
Maternal gut microbiota taxa associated with maternal Ow/Ob and excessive GWG showed substantial overlap at the species level with BMI-associated taxa in the infant.
In prior research work, researchers evaluated the association of maternal Ow/Ob and excessive GWG with maternal gut microbiota at the time of child birth in this cohort.
It was reported that maternal Ow/Ob was associated with alpha diversity and taxonomic differences in composition, while excessive GWG was associated only with taxonomic differences.
BMI-associated infant gut microbiota and the association with maternal characteristics of pre-pregnancy Ow/Ob and excessive GWG
Researchers studied the relationship between both excessive GWG and maternal pre-pregnancy Ow/Ob and the groups of infant gut microbiota taxa selected as most predictive of childhood BMI with permutational ANOVA. Maternal Ow/Ob was associated with the qualitative differences in the selected infant gut microbiota taxa at day 30; excessive GWG was associated with quantitative differences at day 730.
The gut microbiota, especially at 2 years of age, was strongly associated with later childhood BMI. Also, BMI z-scores at the age of 2 years were not considerably higher in the child population, who later became Ow/Ob, so the development of the gut microbiota composition that predicted later BMI preceded any measurable excess weight in children.
One avenue for the prevention of obesity would be through early detection of individuals/children at high risk for the development of obesity. The findings of this study suggest that fecal microbiota during early childhood may have the potential to be part of an obesity risk prediction algorithm, which could be especially advantageous given the ease of recovering samples from diapers. Dietary or other interventions could be considered for these individuals before they start gaining weight.
Both in this cohort and in many other studies, it was reported that maternal Ow/Ob and excessive GWG are the predictors of obesity in childhood. The maternal gut microbiota may contribute toward offspring risk of developing obesity through vertical transfer, as well as through in utero effects. There is strong evidence that many early infant gut taxa are transferred from mother to child. This is particularly true for certain taxa, including Bifidobacterium. Strain level similarity between mothers and infants decreases over the period, but species-level composition converges.
Overall, the findings of this study reveal a strong relationship between the infant gut microbiota at the age of 2 and the BMI at the age of 12. It also shows that the gut microbiota, a characteristic predictive of later BMI, precedes excessive weight gain. It suggests that the gut microbiota could have a potential role to help identify children at risk of developing obesity.
Researchers also found some support for the hypothesis that maternal Ow/Ob may influence some of the infant gut microbiota taxa that are associated with later BMI.
Further research studies especially focusing on the specific group of bacteria may also lead to greater explanation and clear understanding of the etiology of obesity. Additional research work would be required to extend these findings to other populations and to explore how the patterns may vary with early-life exposures.