Benzotropolone moiety in theaflavins is responsible for inhibiting peptide-transport and activating AMP-activated protein kinase in Caco-2 cells

Authors

  • Ha-Young Park Department of Bioscience and Biotechnology, Division of Bioresources and Biosciences, Faculty of Agriculture, Graduate School of Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581
  • Yuri Kunitake Department of Bioscience and Biotechnology, Division of Bioresources and Biosciences, Faculty of Agriculture, Graduate School of Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581
  • Toshiro Matsui Department of Bioscience and Biotechnology, Division of Bioresources and Biosciences, Faculty of Agriculture, Graduate School of Kyushu University, 6-10-1 Hakozaki, Fukuoka, 812-8581

DOI:

https://doi.org/10.31989/ffhd.v3i5.60

Abstract

Objective: In the small intestine, peptide transporter 1 (PEPT1) plays a role in the transport of di- and tri-peptides. Recently, we found that theaflavins (TFs), dimeric catechins, inhibited the transport of di-peptides across Caco-2 monolayers by suppressing the expression of PEPT1 through AMP-activated protein kinase (AMPK) activation. In this study, we investigated the structural requirement of theaflavins for the effect, and the mechanism(s) underling theaflavin-induced AMPK activation.

Methods: Theaflavin-3’-O-gallate (TF3’G) was used for this study, since it possessed the most potent inhibition power for peptide-transport among theaflavins. Absorption ability was measured with Caco-2 cell monolayers treated with or without 20 μM sample (TF3’G or its related compounds) in an Ussing Chamber. The amount of Gly-Sar (a model of PEPT1-transporing peptide) transport at fixed time-points to 60 min was determined by fluorescent naphthalene-2,3-dicarboxaldehyde-derivatized assay (Ex/Em: 405 nm/460 nm). The apparent permeability coefficient (Papp) was used to evaluate the permeability. Expression of PEPT1 protein in Caco-2 cells treated with or without 20 μM TF3’G in the presence or absence of inhibitor (10 μM compound C as AMPK inhibitor or 25 μM STO-609 as CaMKK inhibitor) was evaluated by Western blot.

Results: The Papp value of Gly-Sar significantly (P < 0.05) decreased in 20 μM purprogallin-treated Caco-2 cells as well as in TF3’G-treated cells, together with the reduction of PEPT1 expression, while their monomeric catechins did not show any Papp reduction. In TF3'G-treated Caco-2 cells, the recovery of the reduced PEPT1 expression was found by 10 μM compound C, but not STO-609.

Conclusion: The study demonstrated that the benzotropolone moiety in theaflavins was a crucial structural requirement for exerting the inhibition of intestinal peptide-transport, and the suppression of PEPT1 expression by theaflavins would be caused by activating LKB1/AMPK pathway, but not CaMKK/AMPK pathway.

Keywords: Theaflavin-3’-Ο-gallate, Peptide transport, PEPT1, Benzotropolone, AMP-activated protein kinase, Calmodulin-dependent protein kinase kinase  

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Published

2013-05-24

Issue

Vol. 3 No. 5 (2013): May 2013

Section

Research Articles

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