Gut Bacteria Reactivate Androgens to Control Nerve-Driven Intestinal Movement
New research reveals gut microbes reactivate excreted androgens via enzymes, directly regulating enteric neurons that control gut motility.
Summary
Scientists at Boston Children's Hospital have discovered a surprising partnership between gut bacteria and male sex hormones that controls how food moves through the intestines. The gut microbiome produces enzymes called beta-glucuronidases that reactivate androgens — like testosterone — that the body had already deactivated and excreted. These reactivated androgens then signal to specialized enteric neurons lining the gut, keeping intestinal movement running smoothly. When researchers wiped out gut bacteria with antibiotics in mice, androgen receptor expression in gut neurons dropped, testosterone levels fell, and gut motility became disordered. Replenishing androgen signaling or reintroducing the specific bacterial enzyme was enough to partially restore normal gut function. This discovery reveals a previously unknown axis linking the microbiome, hormones, and the enteric nervous system — with major implications for understanding conditions like irritable bowel syndrome and motility disorders.
Detailed Summary
The enteric nervous system — often called the 'second brain' — governs the complex muscle contractions that propel food through the gut. While diet, stress, and the microbiome are known to influence gut motility, the molecular mechanisms linking all three remain incompletely understood. This study from Harvard's Boston Children's Hospital illuminates a surprising new pathway that connects gut bacteria, steroid hormones, and specialized neurons.
Researchers found that androgen signaling — specifically through the androgen receptor — is essential for normal intestinal transit in mice. Two neuron populations were implicated: Nos1+ enteric neurons within the gut wall itself, and Scn10a+ spinal afferent neurons that relay gut sensations to the brain. Critically, this androgen signaling was entirely dependent on an intact gut microbiome.
When mice were treated with antibiotics to deplete gut bacteria, androgen receptor expression in enteric neurons collapsed, circulating testosterone levels dropped, and gut motility became dysregulated. The team traced this effect to bacterial beta-glucuronidase (GUS) enzymes, which reactivate androgens that the host body had conjugated — chemically inactivated — and excreted into the gut. Intracolonic administration of a specific GUS enzyme capable of metabolizing androgen glucuronides was sufficient to restore neuronal androgen signaling even in microbe-depleted mice, confirming the causal mechanism.
The pathway appears to be developmentally regulated: Nos1 neurons upregulate androgen receptor expression at puberty, coinciding with shifts in fecal GUS enzyme activity — observed in both mice and humans — suggesting this hormone-microbiome-neuron axis matures alongside the host.
The findings reframe the gut microbiome as an active hormonal regulator, not merely a metabolic bystander. For clinicians, this raises important questions about how antibiotic use, dysbiosis, and androgen deficiency may contribute to functional gastrointestinal disorders. Limitations include the animal-model focus and abstract-only access, warranting cautious extrapolation to human patients.
Key Findings
- Gut bacteria reactivate host-excreted androgens via beta-glucuronidase enzymes, enabling androgen receptor signaling in enteric neurons.
- Antibiotic-induced microbiome depletion abolished androgen receptor expression in gut neurons and caused intestinal dysmotility in mice.
- Restoring a single bacterial GUS enzyme was sufficient to rescue neuronal androgen signaling in antibiotic-treated mice.
- Nos1+ enteric neurons upregulate androgen receptors at puberty, paralleling developmental shifts in gut microbial enzyme activity.
- This microbiome-androgen-neuron axis operates in both mice and humans, suggesting broad translational relevance.
Methodology
The study used mouse models with antibiotic-induced microbiome depletion, hormone rescue experiments, and intracolonic enzyme administration to dissect the microbiome-androgen-enteric neuron axis. Neuronal androgen receptor expression and gut transit were key outcome measures. Human fecal GUS enzyme activity data were also included to support translational relevance.
Study Limitations
This summary is based on the abstract only, as the full paper is not open access, limiting assessment of methodology and statistical rigor. Findings are primarily from mouse models; direct human validation of the causal pathway has not yet been demonstrated. The interaction between biological sex and this androgen-motility axis in females warrants further investigation.
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