Fig. 1

Detection of changes in cognitive function and gut microbiota in aged mice treated with metformin. a The escape latency was significantly decreased in the metformin-treated group during the acquisition phase. b The latency to reaching the former platform location was significantly decreased in the metformin-treated group. c The number of times the former platform location was crossed and d the time of staying the previous platform quadrant were significantly increased in the metformin-treated group during the probe test. e The mean velocity was not different between the two groups. f In the novel object recognition test, the number of times that a new object was touched was significantly increased in the metformin-treated group. g IL-6 protein was significantly decreased in the metformin-treated group. h The α diversity according to the Simpson index was increased after metformin treatment. i Heatmaps indicate the gut microbiota at the species level in metformin-treated groups is in favour of a younger phenotype (4 M) but not the older phenotype (18 M). Colours on the heatmap indicate the relative abundance of gut microbiota. Red indicates upregulated bacteria, and blue indicates downregulated bacteria. Ctrl, control; Met, metformin. The overall significance between the two groups was determined by Student’s t-test. *p < 0.05, **p < 0.01, ***p < 0.001, ns, not significant