During puberty, the gut microbiota becomes more adult-like — but only in girls

Some gut microbes can affect the timing of puberty by regulating the levels of sex hormones in a sex-dependent manner. A new study published in Scientific Reports claims.
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What is already known on this topic
Gut microbes are thought to affect reproductive health by regulating the levels of sex hormones in the host. However, little is known about how the gut microbiota develops in people during puberty.

What this research adds
Researchers collected fecal samples and information on gastrointestinal symptoms and growth from 148 Finnish 13-year-olds. These data were then compared with those on adult microbiota from a group of 840 Finnish adults. The researchers found that the gut microbiota of girls became more similar to that of adults as puberty progressed, but no such development was seen in boys. As puberty advanced, girls had decreasing levels of Bacteroidia and increasing abundance of Clostridia. In girls, the timing of puberty was associated with exposure to a class of antibiotics called cephalosporins before they turned 10, as well as with high levels of Clostridiales and Ruminococcaceae.

Conclusions
The findings suggest that some gut microbes can affect the timing of puberty by regulating the levels of sex hormones in a sex-dependent manner.

The age at which puberty begins varies between individuals, and its onset is generally affected by genetic and environmental factors. New research shows that the gut microbiota of girls becomes more similar to that of adults as puberty progressed, but no such development is seen in boys.

The findings, published in Scientific Reports, suggest that some gut microbes can affect the timing of puberty by regulating the levels of sex hormones in a sex-dependent manner.

Scientists have known that gut microbes may affect reproductive health by regulating the sex-hormone levels in the host. However, little is known about how the gut microbiota develops in people during puberty.

To address this question, researchers led by Katri Korpela and Sampo Kallio at the University of Helsinki and Helsinki University Hospital collected fecal samples and information on gastrointestinal symptoms and growth from dozens of Finnish 13-year-olds. These data were then compared with those on adult microbiota from a group of Finnish adults.

Large-scale study

The study participants were part of an allergy-prevention clinical trial that included more than 1,000 pairs of mothers and children. At the age of 13 years, 960 participants were invited for a follow-up visit, during which they provided a fecal sample and filled in questionnaires about gastrointestinal symptoms. The researchers obtained growth data on about 300 children from school health-service records, and data on antibiotic use from the drug-purchase register of the Finnish National Health Insurance.

Both growth data and fecal samples were available for 148 kids, 65 boys and 83 girls. The researchers also obtained fecal samples from 840 healthy adults participating in the Finnish Health and Early Life Microbiota study.

As expected, at 13 years of age, boys were less mature than girls in terms of pubertal development. The composition of the microbiota of 13-year-olds differed depending on whether they started their growth take-off or were past their peak growth. Their gut microbiota became more similar to that of adults as puberty progressed, especially in girls. The more progressed girls were, the more adult-like their microbiota, the researchers found. However, no such changes were seen in boys.

Puberty timing

The team found that changes in the abundance of two abundant classes of gut bacteria, Clostridiales and Bacteroidales, drove the maturation of the microbiota in girls. During puberty, the abundance of Clostridiales increased and that of Bacteroidales decreased towards adult-like levels. The abundance of Firmicutes bacteria also increased with puberty progression, whereas the abundance of Bacteroidetes decreased.

The puberty-associated changes in the microbiota of girls appeared to lead to an increase in Ruminococcaceae and Lachnospiraceae and a decrease in Bacteroidales. Similar patterns were seen in boys. 

In girls, the timing of puberty was linked to exposure to a class of antibiotics called cephalosporins before they turned 10 as well as to high levels of Clostridiales and Ruminococcaceae. In boys, the timing of puberty was instead associated with low levels of Lactobacillaceae and Pasteurellaceae and high levels of Neisseriaceae.

The findings indicate that gut microbes, especially Ruminococcaceae bacteria, could affect pubertal timing by regulating host sex-hormone levels, the researchers say.