Inulin Consumption Modulates Human Intestinal Microflora and Decreases Fecal Water Extract Toxicity in HT-29 and Caco-2 cells

The gastrointestinal tract of human is a complex ecosystem which contains beneficial bacteria such as bifidobacteria and lactobacilli and pathogenic bacteria such as C. perfringens. The balance between beneficial bacteria and harmful pathogenic bacteria plays a key role in normal gut function and human health. Many researches indicate that the administration of prebiotics can modulate the intestinal microflora. Inulin, a kind of prebiotics, can selectively stimulate the growth of bifidobacteria. The aim of this study is to evaluate the effects of inulin intake on the change of intestinal microflora, fecal water content and fecal pH value in human subjects and to investigate fecal cytotoxicity and genotoxcity towards HT-29 and Caco-2 cells. Results indicated that inulin intake significantly increased the fecal bifidobacteria of treatment group from 9.46 log CFU/g in period 1 to 10.39 log CFU/g in period 2 and 10.90 log CFU/g in period 3 (p < 0.01), and were both higher than control group in period 2 and 3 (p < 0.01). Fecal C. perfringens also decreased significantly in treatment group from 7.36 log CFU/g in period 1 to 6.93 log CFU/g in period 2 (p < 0.05) and 6.60 log CFU/g in period 3 (p < 0.01), and were both lower than control group in period 2 and 3 (p < 0.01). During the experiment, fecal water contents were 75.5~77.7 % in treatment group and 77.3~78.6 % in control group without significant difference (p > 0.05). Fecal pH value of control group was 6.40~6.62 without significant difference (p > 0.05). However, in treatment group, the pH value significantly decreased from 6.60 in period 1 to 6.14 and 5.96 in period 2 and 3 after inulin intake (p<0.01). No differences were found for the height, weight, BMI and serum biochemical values of 20 subjects before and after the experiment (p > 0.05). MTT assay showed that inulin intake significantly decreased the fecal water cytotoxicity of treatment group toward HT-29 and Caco-2 cells (p < 0.05), but not in control group. Results from comet assay revealed that after inulin consumption, the genotoxicity of fecal water in treatment group significantly decreased (p < 0.05). To conclude the above, this study confirmed that inulin intake could increase the beneficial bacteria bifidobacteria but decrease harmful bacterial C. perfringens in human intestinal tract, and could decrease the toxicity of fecal water and therefore improve human intestinal health.ey words: intestinal microflora, inulin, bifidobacteria, Clostridium perfringens, cytotoxicity, genotoxicity