We evaluated the effects of KB290 as a probiotic on IBS symptoms and intestinal microflora in IBS patient. As a result, we found that taking KB290 improved the QOL, significantly alleviated their abdominal pain and improved their fecal properties, and significantly changed the composition of their intestinal microflora.
Previous reports have suggested that some probiotics alleviate the symptoms of IBS patients and improve their QOL and the composition of their intestinal microflora [5
]. The genera Bifidobacterium
have been reported to display lower and higher frequencies, respectively, among the microflora of IBS patients than among those of healthy individuals [17
]. In the present study, we focused our analysis on the frequencies of the genera Bifidobacterium
, which have been suggested to be related to IBS symptoms. Previous studies have shown that in healthy individuals with a tendency for constipation the frequencies of the genera Bifidobacterium
increase and the frequency of the genus Enterobacter
decreases after the consumption of KB290. In this study, not only did the frequency of the genus Bifidobacterium
increase after KB290 intake, but that of the genus Clostridium
also decreased. However, no increase in the frequency of the genus Lactobacillus
or decrease in that of the genus Enterococcus
was detected, probably because of the large inter-individual variations in human intestinal microflora. Human intestinal microflora have been shown to change with age and diet [18
]. In this study, no dietary restrictions were imposed on the subjects, and this might have been related to the lack of change in the frequencies of these genera after the test capsule consumption.
It is very difficult to obtain a detailed overview of intestinal microflora. For example, studies of intestinal microflora composition almost exclusively rely on the quantitative culturing of microbes from fecal samples. However, recent nucleic acid studies have indicated that the majority of bacteria in a variety of ecosystems are different from those detected in culture [21
]. Therefore, only part of the intestinal microflora of IBS patients can be examined by conventional techniques, and abnormalities in intestinal microbes that cause IBS might have been overlooked. Recently, the utility of molecular biological techniques such as RT-PCR analysis, denaturing gradient gel electrophoresis (DGGE), FISH, T-RFLP, and pyrosequencing for analyzing the 98% of intestinal microflora that have so far escaped analysis was evaluated, but no intestinal bacterium that can directly cause IBS has been identified [16
]. In this study, the intestinal microflora were analyzed using the T-RFLP technique, a molecular biological method, but our analysis primarily focused on the genera Bifidobacterium
. In the future, as analytical methods for intestinal microflora are developed, yielding a larger number of reports, intestinal bacterial species that are closely involved in the initiation and exacerbation of IBS might be identified.
A recent study suggested that the intestinal microflora plays an important role in brain-gut interactions [26
].Another report indicated that intestinal microflora affect the central nervous system [27
], and changes in host behavior associated with changes in intestinal microflora have been observed in animal experiments [28
]. Thus, based on recent findings regarding the functions of microbiota, the “microbiota - gut - brain axis” has been suggested as a new concept that describes the functional relationship that exists among microbiota, the gut, and the brain [29
It was reported that intestinal inflammation is involved in the pathogenesis of IBS and that probiotics alleviate the symptoms of IBS by normalizing the balance of anti-inflammatory and proinflammatory cytokines. However, we could not determine whether KB290 affects cytokine expression in this study [30
In this study, KB290 was shown to alleviate IBS symptoms and affect the frequencies of the genera Bifidobacterium and Clostridium among the constituents of the intestinal microflora, but the mechanism responsible for this could not be clarified. In the future, it will be necessary to more closely analyze the alterations in biomarker levels associated with the changes in intestinal microflora composition and symptom alleviation induced by KB290 intake and to clarify the changes KB290 causes in the composition of the intestinal microflora in greater detail. However, in consideration of the recently clarified role of intestinal microflora in the mechanisms of IBS symptom alleviation and the etiology of the disease, the intake of KB290, a probiotic, is considered to be able to contribute to symptomatic improvement in such patients.