Aerobic exercise alleviates cognitive impairment in T2DM mice through gut microbiota

Abstract

The risk of cognitive impairment is markedly elevated in patients with type 2 diabetes mellitus (T2DM). While exercise has been shown to mitigate cognitive deficits associated with diabetes, the underlying mechanisms remain poorly understood. Recent studies suggest that exercise can modulate the composition of the gut microbiota, which, in turn, may influence the central nervous system via the microbiota-gut-brain axis. However, the specific role of gut microbiota in mediating exercise-induced improvements in cognitive function in T2DM remains unclear. In this study, we aimed to investigate whether exercise can alleviate cognitive impairment in T2DM mice by modulating the intestinal microbiota, and to elucidate the mechanisms underlying this effect. This study was conducted using male C57BL/6J mice. Mice fed a normal diet were assigned to the non-diabetic control group (NC), while those fed a high-fat diet were intraperitoneally injected with streptozotocin (STZ) and subsequently divided into the diabetic control group (DM), an exercise group (DM-EXE), and a fecal microbiota transplantation group (DM-FMT). The DM-EXE group underwent treadmill exercise for 8 weeks. During this period, the DM-FMT group received fecal microbiota transplants from the DM-EXE group for 2 consecutive days per week. Following the 8-week intervention, stool samples were collected for 16S rDNA high-throughput sequencing. The fear conditioning test was performed to assess cognitive function. Intestinal mucosa samples were collected to evaluate the expression of intestinal tight junction proteins. Additionally, the expression levels of synaptic proteins, glucose transporters, neurotrophic factors, and inflammatory markers were measured in the hippocampus. Our findings demonstrate that T2DM mice exhibit impaired cognitive function and significant alterations in their gut microbiota compared to non-diabetic controls. Exercise partially reversed these changes in the intestinal microbiota and alleviated cognitive impairment in T2DM mice. Additionally, transplantation of intestinal microbiota from exercised mice improved cognitive function in T2DM mice. Aerobic exercise may mitigate cognitive impairment in T2DM mice by modulating the gut microbiota. The underlying mechanisms appear to involve enhanced neural synaptic plasticity, reduced neuroinflammation, and improved neuronal glucose metabolism.

Keywords: Cognitive; Exercise; Microbiota; Type 2 diabetes mellitus.

Fig. 1

(a) Diagram of the experiment. Changes in body weight and random blood glucose in mice during the 8-week experiment. (b) Plot of body weight. (c) Plot of random blood glucose.

Fig. 2

Skeletal muscle fibers in T2DM were thickened after exercise. (a) Hematoxylin and eosin (H&E) staining of muscle tissues at the end of the 8-week experimental period. (b) Comparison of average normalized cross-sectional area of gastrocnemius muscle fibers. Normalization was based on the mean cross-sectional area of the NC group. ####P < 0.0001 versus DM group.

Fig. 3

Comparisons of fear conditioning test performance. (a) Schematic diagram of the fear conditioning test. (b) Comparison of the percentage of freezing duration (Freezing%). (c) Comparison of freezing time. **P < 0.005 versus NC group. ##P < 0.005, ####P < 0.0001 versus DM group.

Fig. 4

Analysis of gut microbiota. α diversity analysis was shown as the comparison of Chao1 index (a), Observed species (b), Simpson (c), and Shannon index (d). E-I PCoA plot established based on the weighted UniFrac distance was used to analyze βdiversity: (e) Comparison among four groups; (f) Comparison between NC group and DM group; (g) Comparison between DM group and DM-EXE group; (h) Comparison between DM group and DM-FMT group; (i) Comparison between DM-EXE group and DM-FMT group. (j–p) Comparison of intestinal flora abundance at different levels: (j–m) Phylum level; (n) Order level; (o) Family level; (p) genus level. *P < 0.05, **P < 0.005, ****P < 0.0001 versus NC group. #P < 0.05, ##P < 0.005 versus DM group.

Fig. 4

Analysis of gut microbiota. α diversity analysis was shown as the comparison of Chao1 index (a), Observed species (b), Simpson (c), and Shannon index (d). E-I PCoA plot established based on the weighted UniFrac distance was used to analyze βdiversity: (e) Comparison among four groups; (f) Comparison between NC group and DM group; (g) Comparison between DM group and DM-EXE group; (h) Comparison between DM group and DM-FMT group; (i) Comparison between DM-EXE group and DM-FMT group. (j–p) Comparison of intestinal flora abundance at different levels: (j–m) Phylum level; (n) Order level; (o) Family level; (p) genus level. *P < 0.05, **P < 0.005, ****P < 0.0001 versus NC group. #P < 0.05, ##P < 0.005 versus DM group.

Fig. 5

The exploration on the mechanism of exercise alleviating cognitive impairment in T2DM mice through microbiota. (a,b) Western blot analysis for tight junction proteins (Occludin and ZO1) and their quantification in the colonic mucosa. Proinflammatory factors IL-6 (c) and TNF-α (d) in the hippocampus detected by ELISA. (e,f) Western blot analysis for neurotrophic factors (BDNF and GDNF), synaptic proteins (SYN and PSD95), and (g,h) glucose transporter (GLUT1 and GLUT4) in the hippocampus. The membrane images were cropped from different membranes to remove irrelevant parts (Supplementary Fig. S1). *P < 0.05, **P < 0.005, ***P < 0.001, ****P < 0.0001 versus NC group. ^#P < 0.05, ^##P < 0.005, ^###P < 0.001, ^####P < 0.0001 versus DM group.

Fig. 6

Heatmap displays the Spearman’s correlation coefficients between microbiota and detected indicators. *P < 0.05, **P < 0.01.