Kefir Supplementation Modifies Gut Microbiota Composition, Reduces Physical Fatigue, and Improves Exercise Performance in Mice

Abstract

The present study evaluated the potential beneficial effect of kefir (KF) against fatigue. Furthermore, the composition of the gut microbiota is related to health benefits in the host; therefore, the study also investigated the effect of KF on the gut microbiota composition. Male ICR mice from four groups (n = 8 per group) were orally administered KF once daily for four weeks at 0, 2.15, 4.31, and 10.76 g/kg/day and were designated as the vehicle, KF-1X, KF-2X, and KF-5X groups, respectively. The gut microbiota was analyzed using 16S rRNA gene sequencing. The results showed a significant clustering of cecum after treatment in the vehicle, KF-1X, KF-2X, and KF-5X groups. The KF-2X and KF-5X groups showed a decreased Firmicutes/Bacteroidetes ratio compared with the vehicle group. In addition, anti-fatigue activity and exercise performance were evaluated on the basis of exhaustive swimming time, forelimb grip strength, and levels of serum lactate, ammonia, glucose, blood urea nitrogen (BUN), and creatine kinase (CK) after a swimming exercise. The exhaustive swimming time for the KF-1X, KF-2X, and KF-5X groups was significantly longer than that for the vehicle group, and the forelimb grip strength of the KF-1X, KF-2X, and KF-5X groups was also significantly higher than that of the vehicle group. KF supplementation also decreased serum lactate, ammonia, BUN, and CK levels after the swimming test. However, tissue glycogen content, an important energy source for exercise, increased significantly with KF supplementation. Thus, KF supplementation can alter the gut microbiota composition, improve performance, and combat physical fatigue.

Keywords: antifatigue; exercise performance; gut microbiota; kefir.

Figure 1

Effects of kefir (KF) supplementation on the exhaustive swimming test. Data are presented as mean ± SD, n = 8. Bars with different letters (^a, ^b) indicate a significant difference at p < 0.05 determined using one-way ANOVA. Vehicle (glucose water), KF-1X (2.15 g/kg/day KF), KF-2X (4.31 g/kg/day KF), and KF-5X (10.76 g/kg/day KF).

Figure 2

Effects of kefir (KF) supplementation on the forelimb grip strength. Data are presented as mean ± SD, n = 8. Bars with different letters (^a, ^b) indicate a significant difference at p < 0.05 determined using one-way ANOVA. Vehicle (glucose water), KF-1X (2.15 g/kg/day KF), KF-2X (4.31 g/kg/day KF), and KF-5X (10.76 g/kg/day KF).

Figure 3

Effects of kefir (KF) supplementation on the serum levels of (a,b) lactate, (c,d) ammonia, and (e,f) glucose after a 10-min swimming test (a,c,e) and after a 20-min resting period (b,d,f). Data are presented as mean ± SD, n = 8. Bars with different letters (^a, ^b) indicate a significant difference at p < 0.05 determined using one-way ANOVA. Vehicle (glucose water), KF-1X (2.15 g/kg/day KF), KF-2X (4.31 g/kg/day KF), and KF-5X (10.76 g/kg/day KF).

Figure 4

Effects of kefir (KF) supplementation on the serum levels of (a) blood urea nitrogen (BUN) and (b) creatine kinase (CK) after a 90-min swimming test and a 60-min resting period. Data are presented as mean ± SD, n = 8. Bars with different letters (^a, ^b) indicate a significant difference at p < 0.05 determined using one-way ANOVA. Vehicle (glucose water), KF-1X (2.15 g/kg/day KF), KF-2X (4.31 g/kg/day KF), and KF-5X (10.76 g/kg/day KF).

Figure 5

Effects of kefir (KF) supplementation on (a) liver glycogen and (b) muscular glycogen. Data are presented as mean ± SD, n = 8. Bars with different letters (^a, ^b, ^c) indicate a significant difference at p < 0.05 determined using one-way ANOVA. Vehicle (glucose water), KF-1X (2.15 g/kg/day KF), KF-2X (4.31 g/kg/day KF), and KF-5X (10.76 g/kg/day KF).

Figure 6

Effects of kefir (KF) supplementation on (a) liver; (b) muscle; (c) heart; (d) kidney; (e) lungs; (f) epididymal fat pad (EFP); and (g) brown adipose tissue (BAT). Specimens were observed using a light microscopy. Hematoxylin and eosin stain, magnification: ×200 (a–e) and ×100 (f,g). Vehicle (glucose water), KF-1X (2.15 g/kg/day KF), KF-2X (4.31 g/kg/day KF), and KF-5X (10.76 g/kg/day KF).

Figure 7

(a) Effects of kefir (KF) supplementation on principal coordinate analysis (PCoA) of the gut microbiota composition in mice based on the Bray–Curtis distance measure of samples in the relative abundance profiles of an operational taxonomic unit; (b) Effects of KF supplementation on the phylum-level gut microbiota composition of mice. Only phyla with top 10 average abundances were included, with other phyla collapsed into “Others”; the effects of KF supplementation on the phylum-level gut microbiota composition of mice in the (c) KF-1X and vehicle groups; (d) KF-2X and vehicle groups, and (e) KF-5X and vehicle groups. The cladogram was generated from the linear discriminant analysis effect size (LEfSe) analysis, showing the most differentially abundant taxa enriched in the microbiota of mice in (c) the KF-1X (red) and vehicle (green) groups, (d) the KF-2X (red) and vehicle (green) groups, and (e) the KF-5X (red) and vehicle (green) groups. Significant differential abundances in LEfSe comparisons are sorted by p values in ascending order: vehicle (glucose water), KF-1X (2.15 g/kg/day KF), KF-2X (4.31 g/kg/day KF), and KF-5X (10.76 g/kg/day KF).