An ethically guided preclinical device for phenotyping H₂ production in laboratory rodents

Dihydrogen (H₂) is produced endogenously by the intestinal microbiota through the fermentation of diet carbohydrates. Over the past few years, numerous studies have demonstrated the significant therapeutic potential of H₂ in various pathophysiological contexts, making the characterization of its production in laboratory species of major preclinical importance.

This study proposes an innovative solution to accurately monitor H₂ production in free-moving rodents while respecting animal welfare standards. The developed device consisted of a wire rodent cage placed inside an airtight chamber in which the air quality was maintained, and the H₂ concentration was continuously analyzed. After the airtightness and efficiency of the systems used to control and maintain air quality in the chamber were checked, tests were carried out on rats and mice with different metabolic phenotypes, over 12 min to 1-h experiments and repeatedly. H₂ production rates (HPR) were obtained using an easy calculation algorithm based on a first-order moving average.

HPR in hyperphagic Zucker rats was found to be twice as high as in control Wistar rats, respectively, 2.64 and 1.27 nmol.s^-1 per animal. In addition, the ingestion of inulin, a dietary fiber, stimulated H₂ production in mice. HPRs were 0.46 nmol.s^-1 for animals under control diet and 1.99 nmol.s^-1 for animals under inulin diet.

The proposed device coupled with our algorithm enables fine analysis of the metabolic phenotype of laboratory rats or mice with regard to their endogenous H₂ production.