Regulation of PepT1 peptide transporter expression in the rat small intestine under malnourished conditions.
OBJECTIVE
Many investigations suggested that peptide nutrition had a clinical advantage for nitrogen absorption. Recently, the cDNA encoding the H(+)/peptide cotransporter PepT1 was cloned. However, the regulatory mechanism of PepT1 expression under malnourished conditions has not been elucidated. The aim of this study was to clarify regulatory mechanisms of PepT1 expression.


METHODS
Sprague-Dawley rats were starved for 4 days, semistarved (50% amount of control) for 10 days, or given total parenteral nutrition (TPN) for 10 days. Rats with free feeding were used as control. Among those groups, the changes of PepT1 mRNA level in the jejunal mucosa and PepT1 protein density at the brush-border membranes were examined by Northern blot and by Western blot analysis, respectively.


RESULTS
Both starvation and TPN treatment caused a significant decrease in mucosal weight by 41 and 50% respectively. PepT1 mRNA level increased to 179% in the starved group and also to 161 and 164% in the TPN and semistarved groups, respectively. In contrast, sodium-dependent glucose transporter 1 mRNA expression showed no significant change. PepT1 protein density showed similar changes with the mRNA.


CONCLUSIONS
PepT1 gene expression was significantly enhanced under the malnourished conditions in spite of atrophic changes of intestinal mucosa.
Ihara
T
T
Second Department of Internal Medicine, Shiga University of Medical Science, Seta, Otsu, Japan.
Tsujikawa
T
T
Fujiyama
Y
Y
Bamba
T
T
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001835:Body Weight; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D004151:Dipeptides / Q000096:biosynthesis / Q000235:genetics*; D005786:Gene Expression Regulation; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D010289:Parenteral Nutrition, Total; D000074011:Peptide Transporter 1; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1; D013217:Starvation / Q000378:metabolism* / Q000628:therapy; D027981:Symporters
D002352:Carrier Proteins; D004151:Dipeptides; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D000074011:Peptide Transporter 1; D012333:RNA, Messenger; C489940:Slc15a1 protein, rat; C495676:Slc5a1 protein, rat; D051269:Sodium-Glucose Transporter 1; D027981:Symporters; D012964:Sodium