TITLE:
The Mechanism of Decreased Serum Phosphorus Levels in Rats with Chronic Kidney Disease after Oral Administration of Bifidobacterium longum
AUTHORS:
Nobuo Nagano, Mayuko Futaya, Mamiko Kohno, Osami Nakano, Norihisa Nishida, Yoichi Matsuura, Mikiko Shimada, Kyoko Ito, Tetsuo Ando, Takaaki Tsutsui, Yoshitaka Ando, Kiyotsugu Omae, Kosaku Nitta, Hiroshi Sakura, Tetsuya Ogawa
KEYWORDS:
Bifidobacteria, CKD-MBD, Dysbiosis, Hyperphosphatemia, Intestinal pH, Short-Chain Fatty Acids
JOURNAL NAME:
Advances in Microbiology,
Vol.5 No.7,
July
22,
2015
ABSTRACT: Chronic
kidney disease (CKD) patients are prone to disturbances in the intestinal
microbiota, which contributes to CKD progression and complications. We
previously reported a reduction of serum phosphorus (P) levels in hemodialysis patients receiving
oral encapsulated bifidobacteria. The present study was conducted to clarify
the mechanisms of P-lowering effect of bifidobacteria on CKD rats. CKD was
induced in rats by 5/6 nephrectomy. Five weeks later, the rats were fed for 4
weeks on a powder diet containing encapsulated bifidobacteria. At the end of
the study, intestinal contents were sampled for analyses of pH, intestinal flora
and short-chain fatty acids (SCFAs). Oral administration of bifidobacteria
halted the onset and progression of hyperphosphatemia in CKD rats. The
increased number of bifidobacteria was confirmed in the cecum. In addition, the
increase in intestinal pH in CKD rats was decreased after bifidobacteria
treatment, along with increases in some SCFAs. Furthermore, positive
correlation between serum P levels and intestinal pH was observed. In
conclusion, the mechanism for the P-lowering effect of bifidobacteria was
supposed as follows: CKD conditions increase aerobic bacteria which hydrolyze
urea into ammonia. Elevated pH decreases ionization of intestinal calcium (Ca)
which leads to an increase in free phosphate ions through reduction of Ca
phosphate crystal precipitation. Administered bifidobacteria fermented
carbohydrates to produce SCFAs, resulting in acidification of the intestinal
lumen. The resulting low intestinal pH increases Ca ionization, which binds
with free phosphate ions as an intrinsic P binder, resulting in the reduction of
serum P levels.