Abstract
The oral administration of living Limosilactobacillus reuteri (formerly Lactobacillus reuteri) ATCC PTA 6475 cells has been shown preliminarily to prevent obesity in diet-derived obese mice and to act to ameliorate the decline in serum testosterone in old male mice. Through a clinical trial comprising a single-arm open-label pilot study in which all subjects received the same intervention, the present study aimed to evaluate whether L. reuteri ATCC PTA 6475 cells can also ameliorate the decline in serum testosterone levels in senior citizens and explore how the strain changes the intestinal microbiota. The trial was conducted with 10 eligible subjects (aged 50-69) at Hiroshima University from January to April 2024. They were instructed to take two capsules that contained a total of 1.0 × 10(10) living lyophilized cells of ATCC PTA 6475 strain every day. After the 12 weeks, although remarkable changes in sex hormones were not observed, significant decreases were observed in body fat percentage, blood pressure, and some inflammation-related parameters. In addition, analysis of the fecal microbiota indicated that intake of ATCC PTA 6475 cells significantly increased the relative abundance of the genera Butyricimonas, Holdemania, and Odoribacter, which have been reported to contribute to the amelioration of obesity phenotypes. In conclusion, although the present study was carried out as a pilot study with only 10 subjects, making a placebo-controlled study necessary in the future, it demonstrates the probiotic potential of the ATCC PTA 6475 strain.