Dietary supplementation with 1-kestose induces altered locomotor activity and increased striatal dopamine levels with a change in gut microbiota in male mice.

1-Kestose (KES), a dietary fiber and prebiotic carbohydrate, benefits various physiological functions. This study aimed to examine whether diets supplemented with KES over three consecutive generations could significantly affect some host physiological aspects, including behavioral phenotypes and gut microbial ecology. Mice that received KES-supplemented diets for three generations demonstrated increased activity compared with those fed diets lacking KES. Furthermore, the KES group showed increased striatal dopamine (DA) and serotonin (5-HT) levels. The observed increase in DA levels within the striatum was positively correlated with locomotor activity in the KES group but not in the control (CON) group. The α-diversities were significantly lower in the KES group compared to the CON group. The three-dimensional principal coordinate analysis revealed a substantial distinction between the KES and CON groups across each generation. At the genus level, most gut microbiota genera exhibited lower abundances in the KES group than in the CON group, except for Bifidobacteria and Akkermansia. Spearman's rank-order analysis indicated significant negative correlations between the striatal DA levels and α-diversity values. These findings suggest that prolonged supplementation with KES may stimulate increased locomotor activity along with elevated striatal DA levels, which are potentially associated with KES-induced alterations in the gut microbiota.

Dietary tryptophan, tyrosine, and phenylalanine depletion induce reduced food intake and behavioral alterations in mice.

Important precursors of monoaminergic neurotransmitters, dietary tryptophan (TRP), tyrosine, and phenylalanine (all referred to as TTP), play crucial roles in a wide range of behavioral and emotional functions. In the current study, we investigated whether diets devoid of TTP or diets deficient in TRP alone can affect body weight, behavioral characteristics, and gut microbiota, by comparing mice fed on these amino acids-depleted diets to mice fed on diets containing regular levels of amino acids. Both dietary TTP- and TRP-deprived animals showed a reduction in food intake and body weight. In behavioral analyses, the mice fed TTP-deprived diets were more active than mice fed diets containing regular levels of amino acids. The TRP-deprived group exhibited a reduction in serum TRP levels, concomitant with a decrease in serotonin and 5-hydroxyindoleacetic acid levels in some regions of the brain. The TTP-deprived group showed a reduction in TTP levels in the serum, concomitant with decreases in both phenylalanine and tyrosine levels in the hippocampus, as well as serotonin, norepinephrine, and dopamine concentrations in some regions of the brain. Regarding the effects of TRP or TTP deprivation on gut microbial ecology, the relative abundance of genus Roseburia was significantly reduced in the TTP-deprived group than in the dietary restriction control group. Interestingly, TTP was found even in the feces of mice fed TTP- and TRP-deficient diets, suggesting that TTP is produced by microbial or enzymatic digestion of the host-derived proteins. However, microbe generated TTP did not compensate for the systemic TTP deficiency induced by the lack of dietary TTP intake. Collectively, these results indicate that chronic dietary TTP deprivation induces decreased monoamines and their metabolites in a brain region-specific manner. The altered activities of the monoaminergic systems may contribute to increased locomotor activity.

Dietary delivery of acetate to the colon using acylated starches as a carrier exerts anxiolytic effects in mice.

Recently, short-chain fatty acids (SCFA) have been shown to play an important role in mediating the gut-brain interaction and thereby participate in the patho-physiological process of stress-related disorders. In the current study, we examined whether SCFA generated in the lower gut affects host metabolic and behavioral characteristics. To determine this, we used special diets containing acylated starches that can reach the colon without being absorbed in the upper gastrointestinal tract of male mice. The delivery of SCFA to the colon using this method induced a substantial increase in acetate, butyrate, and propionate in the cecum. Moreover, the diets containing acylated starches also decreased microbial diversity in the cecum, concomitant with a significant impact on microbial composition. In marble-burying (MB) tests, the mice that consumed diets containing acetylated starches showed a decrease in anxiety-like behavior compared with the mice that consumed diets containing either butyrylated or propionylated starches. Cecal acetate contents were significantly associated with anxiety-like behaviors when evaluated by elevated plus-maze and MB tests. Collectively, these results indicate that gut acetate elevation of a dietary origin may exert anxiolytic effects on behavioral phenotypes of the host.