title: Visualized absorption of anti-atherosclerotic dipeptide, Trp-His, in Sprague-Dawley rats by LC-MS and MALDI-MS imaging analyses.
abstract: METHODS
  The basic dipeptide, Trp-His, was found to show an in vivo anti-atherosclerotic effect when orally administered to apo E-deficient mice. In addition, this dipeptide causes vasorelaxation in contracted rat aorta via suppression of intracellular Ca(2+) signaling cascades. In this study, we attempted to determine whether Trp-His can be absorbed after single oral administration in Sprague-Dawley (SD) rats.
  
  
  RESULTS
  Trp-His and His-Trp (10 or 50 mg/kg) was orally administered to 8-week-old male SD rats. Both peptides in plasma were assayed by LC-MS/MS in combination with 2,4,6-trinitrobenzene sulfonate derivatization technique. In vitro transport experiments using Caco-2 cell monolayers were performed to evaluate the apparent permeability (Papp ). A phytic acid-aided MALDI-MS imaging (MSI) was conducted to visualize the distribution of dipeptides in the rat intestinal membrane. Trp-His was absorbed intact into SD rat blood, showing a maximal level at 1 h after administration at 10 mg/kg dose (Cmax , 28.7 ± 8.9 pmol/mL-plasma; area under the curve, 71.3 ± 18.7 pmol·h/mL-plasma). In contrast, His-Trp was surprisingly not detected, although the Papp was compatible to that of Trp-His. MSI analysis provided crucial evidence that Trp-His was visualized in the overall intestinal membrane. The Trp-His peptide was not visualized in the presence of Gly-Sar, which is a model peptide that is transported via the intestinal proton-coupled peptide transporter 1 (PepT1) transporter. The His-Trp molecular ion was not observed at the intestinal membrane. The MSI analysis illustrated that there is no absorption of His-Trp due to its unexpected hydrolysis by brush border proteases.
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the first study demonstrating that the vasoactive Trp-His is preferably transported across the rat intestinal membrane by PepT1 and is absorbed intact into the circulation. However, no absorption of His-Trp, a reverse sequence of absorbable Trp-His, is observed owing to hydrolysis by intestinal proteases. This suggests that the bioavailability of peptides may be determined in part by their protease resistance in the intestinal membrane.
authors: Faculty of Agriculture, Graduate School of Kyushu University, Fukuoka, Japan.
authors: Mitsuru
authors: M
authors: Tanaka
authors: Faculty of Agriculture, Graduate School of Kyushu University, Fukuoka, Japan.
authors: Seong-Min
authors: SM
authors: Hong
authors: Faculty of Agriculture, Graduate School of Kyushu University, Fukuoka, Japan.
authors: Sayaka
authors: S
authors: Akiyama
authors: Faculty of Agriculture, Graduate School of Kyushu University, Fukuoka, Japan.
authors: Qing-Qiang
authors: QQ
authors: Hu
authors: Faculty of Agriculture, Graduate School of Kyushu University, Fukuoka, Japan.
authors: Toshiro
authors: T
authors: Matsui
mesh_terms: D053000:Analytic Sample Preparation Methods; D000818:Animals; D050197:Atherosclerosis / Q000517:prevention & control; D018938:Caco-2 Cells; D002463:Cell Membrane Permeability; D002851:Chromatography, High Pressure Liquid; D019587:Dietary Supplements; D004151:Dipeptides / Q000008:administration & dosage / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D008297:Male; D000074011:Peptide Transporter 1; D010833:Phytic Acid / Q000737:chemistry; D017207:Rats, Sprague-Dawley; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D027981:Symporters / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D014302:Trinitrobenzenesulfonic Acid / Q000737:chemistry; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000097:blood / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004151:Dipeptides; D007202:Indicators and Reagents; D000074011:Peptide Transporter 1; C489940:Slc15a1 protein, rat; D027981:Symporters; D014665:Vasodilator Agents; C509582:tryptophyl-histidine; D010833:Phytic Acid; D014302:Trinitrobenzenesulfonic Acid
keywords: Absorption; Dipeptide; LC-MS; MALDI imaging; PepT1