The microbiome is dispensable for normal respiratory function and chemoreflexes in mice

Area of Science:

• Microbiome research
• Respiratory physiology
• Cardiorespiratory interactions

Background:

• Gut microbiome composition is linked to respiratory health and diseases like obstructive sleep apnea.
• Previous studies on microbiome's respiratory effects used antibiotic depletion, potentially confounding results.
• Germ-free models offer a method to study respiratory function without microbiome interference.

Purpose of the Study:

• To investigate respiratory and metabolic alterations in germ-free (GF) mice compared to specific-pathogen-free (SPF) mice.
• To assess the impact of the microbiome on cardiorespiratory responses during normoxia, hypercapnia, and hypoxia.
• To determine if fecal microbiota transplantation can rescue observed phenotypes in GF mice.

Main Methods:

• Whole-body plethysmography was used to measure respiratory parameters in conscious, unrestrained GF and SPF adult mice and neonates.
• Mice were exposed to normoxic, hypercapnic, and hypoxic conditions.
• Autoresuscitation assays were performed on neonates; fecal transplants were conducted on adults.
• Respiratory analysis software, Breathe Easy, was utilized for data analysis.

Main Results:

• GF and SPF neonates exhibited differences in baseline/recovery cardiorespiratory parameters and body weight, but not survival.
• Adult GF mice showed altered oxygen consumption, suggesting metabolic changes.
• No significant respiratory alterations were observed in adult GF mice compared to SPF mice at baseline or after fecal transplant.

Conclusions:

• Unlike studies using antibiotic depletion, this research found no major respiratory alterations in adult germ-free mice.
• The gut microbiome may not be as critical for respiratory homeostasis in adult mice as previously suggested, especially with less invasive elimination methods.
• Altered oxygen consumption in germ-free mice indicates a potential role for the microbiome in metabolic regulation.