Parkinson’s disease (PD) is a neurodegenerative disease characterized by motor impairment and the accumulation of alpha-synucleinopathy (α-syn), which can affect different levels of the brain-gut axis. There is a two-way communication between the gastrointestinal tract, and brain that includes the gut microbiota. This bidirectional communication between the gut microbiota and the brain includes many pathways, such as immune mechanisms, the vagus nerve, and microbial neurometabolite production. The common cause of constipation in PD is thought to be the accumulation of α-syn proteins in the enteric nervous system. Recent studies have focused on changes in microbial metabolites and gut microbiota dysbiosis. Microbiota dysbiosis is associated with increased intestinal permeability, intestinal inflammation, and neuroinflammation. Many factors, such as unbalanced nutrition, antibiotic use, age, and infection, result in alteration of microbial metabolites, triggering α-syn accumulation in the intestinal mucosa cells. Increased evidence indicates that the amount, type, and balance of dietary macronutrients (carbohydrates, proteins, and fats); high consumption of vegetables, fruits, and omega-3 fatty acids; and healthy diet patterns such as the Mediterranean diet may have a great protective impact on PD. This review focuses on the potential benefits of prebiotics, probiotics, and synbiotics to regulate microbiota dysbiosis along with the effect of diet on the gut microbiota in PD.

The prevalence of allergy has increased over the past decades, and this may be attributed in part to the intestinal microbiota dysfunction caused by antibiotics during early life. In this study, we evaluated how vancomycin could impair the intestinal microbiota during early life and then, consequently, alter susceptibilities to allergic diseases and related immunity in late adulthood. BALB/c (n=54) neonatal mice were used in this study. Mice in the vancomycin group were orally administered vancomycin for 21 days, while those in the allergy and control groups were perfused with the same volume of saline solution. Then, mice in the allergy and vancomycin groups were immunized with intraperitoneal ovalbumin with alum. At postnatal day 21, vancomycin significantly alter the fecal microbiota, with lower Bacteroidetes and Firmicutes counts and higher Proteobacteria counts. At postnatal day 56, the Bacteroidetes count was still significantly lower in vancomycin-treated mice. The serum IgE level in the control group was significantly lower than that in the vancomycin and allergy groups. The serum interleukin (IL)-6 level and the IL-4/interferon (IFN)-γ values were significantly higher in the vancomycin-treated mice, but the serum IL-17A level was lower than that in the control group. These results indicate that modifications of the intestinal microbiota composition during early life may be, at least in part, the key mechanism underlying the effect of vancomycin that influences the immune function of host animals in the adult stages.

Propolis possesses several immunological functions. We recently generated a conditional Ca²⁺ biosensor yellow cameleon (YC3.60) transgenic mouse line and established a five-dimensional (5D) (x, y, z, time, and Ca²⁺ signaling) system for intravital imaging of lymphoid tissues, including Peyer’s patches (PPs). To assess the effects of propolis on immune cells, we analyzed Ca²⁺ signaling in vitro and in vivo using CD11c-Cre/YC3.60^flox transgenic mice, in which CD11c⁺ dendritic cells (DCs) specifically express YC3.60. We found that propolis induced Ca²⁺ signaling in DCs in the PPs. Intravital imaging of PPs also showed that an intraperitoneal injection of propolis augmented Ca²⁺ signaling in CD11c⁺ cells, suggesting that propolis possesses immune-stimulating activity. Furthermore, CD11c⁺ cells in PPs in mice administrated propolis indicated an increase in Ca²⁺ signaling. Our results indicate that propolis induces immunogenicity under physiological conditions.

We conducted a randomized, double-blind, placebo-controlled parallel study to investigate the effects of a fermented milk on elderly nursing home residents. Eighty-eight participants each drank one bottle of fermented milk containing Lactobacillus casei strain Shirota, or a placebo, on a daily basis for 6 months in winter. Peripheral blood, saliva, fecal samples, and clinical data were analyzed to assess the milk’s efficacy. Fermented milk consumption was associated with a significant decrease in the number of days on which fever was detected and the mean duration of fever compared with these values in the placebo group. No significant differences were observed in other biological parameters. Continuous intake of this fermented milk could be beneficial for the elderly in terms of suppressing the number of days of detection of fever and the duration of fever, which usually increase in winter.

Microbial production of butyrate is impaired in patients with ulcerative colitis (UC); however, this inhibition is not well understood in Japanese UC patients. Therefore, we quantitatively analyzed genes encoding butyryl-CoA:acetate CoA-transferase (but) and butyrate kinase (buk) in the gut microbiota of Japanese patients with UC and healthy volunteers (HVs). But showed higher levels than buk. Moreover, patients with UC showed significantly decreased levels of but associated with Roseburia sp./Eubacterium rectale compared with HVs. But, which is associated with Faecalibacterium sp., was maintained in patients with UC, with an unchanged relative abundance of Faecalibacterium sp. microorganisms in patients with UC compared with HVs.