ヒト腸内シュウ酸分解菌に対する乳果オリゴ糖経口投与の効果

Abstract

シュウ酸分解菌を保有する健康成人男性12例に乳果オリゴ糖を1日10g、14日間、就寝前に服用させた。服用開始日・終了日に24時間尿中ショウ酸排泄量測定、糞便培養を行い、更に糞便中の総嫌気性菌数、総シュウ酸分解菌数を測定した。糞便培養検査では、12例中1例でシュウ酸加PYG寒天培地でのシュウ酸分解菌発育はみられたが、PYG寒天培地での菌発育はみられず、総嫌気性菌数は測定不可であった。糞便中の総嫌気性菌数はオリゴ糖投与後増加し、総シュウ酸分解菌数も投与後増加した。24時間尿中シュウ酸排泄量は投与前後で有意差はなかった。ショウ酸分離菌として分離同定された細菌は、細菌生化学的検査にてBifidobacterium adolescentisと判明した。そこで、Bifidobacterium adolescentisのtype strainの1つであるYIT 4011を用いてシュウ酸分解能の有無を調べた結果、YIT 4011にはシュウ酸分解能を認めず、全てのBifidobacterium adolescentisがシュウ酸分解能を有しているわけではないことが明らかとなった。

A variety of oxalate-degrading bacteria including Oxalobacter formigenes and some species of Bifidobacterium are known to colonize the human intestinal tract. Oral lactosucrose supplementation promotes the growth of Bifidobacterium in the human intestine. Therefore, we investigated the effect of oral lactosucrose supplementation on enteric oxalate-degrading bacteria in twelve healthy men (age ranging from 25 to 39 years). Lactosucrose was orally administered 10 g daily for 2 weeks without restriction of dietary intake. The total number of oxalate-degrading bacteria in feces and the 24-hour urinary excretion of oxalate were examined before and after lactosucrose supplementation. The total number of oxalate degrading-bacteria was significantly increased by lactosucrose supplementation (9.20 +/- 0.44 versus 9.77 +/- 0.46, p<0.05), although there was no significant change in the urinary oxalate excretion. The oxalate degrading-bacteria isolated from feces was biochemically identified as Bifidobacterium adolescentis. In conclusion, oral supplementation of 10 g lactosucrose daily for 2 weeks was effective in multiplying oxalate-degrading bacteria, but not in reducing urinary oxalate excretion under free non-restricted dietary intake. In addition, it was suggested that various species of Bifidobacterium were related to degradation of oxalate in the human intestine.