Dietary inorganic phosphorus regulates the intestinal peptide transporter PepT1.
BACKGROUND
Both organic and inorganic phosphorus (Pi) are present in regularly consumed foods, such as meats, eggs, and dairy products. Pi is often included in foods as an additive (as hidden phosphorus). The intestinal peptide transporter PepT1 mediates protein absorption, which is disturbed in renal insufficiency. Our aim was to determine the effects of dietary Pi content on the peptide transport activity and expression of PepT1.


METHODS
The following animal models were used: (1) 7-week-old male Wistar rats; and (2) rats that underwent 3/4 nephrectomy to induce chronic kidney disease (CKD). The rats were fed a normal-protein (20%) diet containing low (0.02%), normal (0.6%), or high (1.2%) Pi levels. They were also fed diets containing varying amounts of protein and either low or normal Pi levels as follows: (1) low Pi/normal protein, (2) low Pi/high (50%) protein, (3) normal Pi/normal protein, and (4) normal Pi/high protein.


RESULTS
Intestinal peptide transport activity and PepT1 expression levels were significantly higher in the CKD rats than in sham-operated control ones. Compared with the normal-protein diet, the high-protein diet increased PepT1 expression in the CKD rats. Intestinal dipeptide transport activity and PepT1 protein levels did not increase in the rats fed the low-Pi/high-protein diet. In contrast, intestinal dipeptide transport activity and PepT1 protein expression were markedly increased in the rats fed the normal-Pi/high-protein diet.


CONCLUSIONS
Dietary Pi levels regulate intestinal peptide transport activity through PepT1.
Department of Molecular Nutrition, Institution of Health Biosciences, University of Tokushima Graduate School, Tokushima, Japan.
Junya
J
Furutani
Hiroko
H
Segawa
Fumito
F
Aranami
Shoji
S
Kuwahara
Mikio
M
Sugano
Kenji
K
Bannai
Hideyuki
H
Yamato
Mikiko
M
Ito
Ken-ichi
K
Miyamoto
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002908:Chronic Disease; D004032:Diet; D005786:Gene Expression Regulation; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D007668:Kidney / Q000187:drug effects / Q000473:pathology; D008297:Male; D009392:Nephrectomy / Q000379:methods; D000074011:Peptide Transporter 1; D016226:Phosphorus, Dietary / Q000008:administration & dosage* / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D051437:Renal Insufficiency / Q000188:drug therapy / Q000473:pathology; D027981:Symporters / Q000235:genetics* / Q000378:metabolism
D000074011:Peptide Transporter 1; D016226:Phosphorus, Dietary; C489940:Slc15a1 protein, rat; D027981:Symporters