Long-term intake of Lactobacillus paracasei KW3110 prevents age-related circadian locomotor activity and changes in gut metabolism in physiologically aged mice

Aging involves age-progressive loss of physiological functions in organs and tissues. We previously showed that Lactobacillus paracasei KW3110 suppressed age-related inflammation and prevented age-related retinal ganglion cell (RGC) loss. As RGCs mediate biological behaviors associated with responses to ambient light, we assessed whether L. paracasei KW3110 affects circadian locomotor activities in physiologically aged mice. The ratio of locomotor activity during the nighttime (active phase) to daytime (inactive phase) significantly decreased in physiologically aged mice compared with young mice: intake of L. paracaseiKW3110 prevented this decrease. We also performed metabolomics analysis of cecal contents using both capillary electrophoresis and liquid chromatography time-of-flight mass spectrometry to better understand the benefical effects for aging of L. paracasei KW3110 through a gut retina axis, since our previous study showed that L. paracasei KW3110 mitigated not only age-related expansions of intestinal inflammatory immune cells but age-related alternation of gut microbiome composition. Principal component analysis showed clear changes in metabolites between physiologically aged mice fed a diet containing L. paracasei KW3110 and age-matched control mice. Furthermore, we found that intake of L. paracasei KW3110 mitigated age-related changes in some fatty acids compared with age-matched control mice. Taken together, L. paracasei KW3110 might regulate age-related alternation of metabolites in cecal contents, potentially leading to suppression of age-related decline in physiological functions, including impairment of circadian locomotor activities.