Soybean- and Lupin-Derived Peptides Inhibit DPP-IV Activity on In Situ Human Intestinal Caco-2 Cells and Ex Vivo Human Serum

Abstract

Recent investigations have focused on food-derived peptides as novel natural inhibitors of dipeptidyl peptidase IV (DPP-IV), a new target for diabetes. This study aimed to optimize fast, sensitive, and cost-effective DPP-IV assays in situ on human intestinal Caco-2 cells and ex vivo on human serum. Both assays were applied to investigate the inhibitory activity of soy and lupin peptides. The best conditions for in situ DPP-IV activity in Caco-2 cells were obtained using 2-day cells and 50 µM Gly-Pro-AMC. Sitagliptin, used as reference inhibitor, showed a dose-dependent response with a 50% inhibition concentration (IC50) of 0.6 µM. A lower IC50 (0.2 µM) was obtained for sitagliptin on human serum incubated with the substrate for 24 h. Both assays were applied to assess the activity of Lup1 (LTFPGSAED) and Soy1 (IAVPTGVA) on DPP-IV. Lup1 and Soy1 inhibited DPP-IV in situ, with IC50 values of of 207.5 and 223.2 µM, respectively, and maintained their inhibitory activity ex vivo on circulating DPP-IV with a slightly lower potency. These assays can be used to characterize the DPP-IV inhibitory activity of food-derived molecules more accurately than in vitro biochemical tests. This combined approach also considers their effects on the circulating form of DPP-IV, correlated to metabolic diseases.

Bioactive Peptides from Germinated Soybean with Anti-Diabetic Potential by Inhibition of Dipeptidyl Peptidase-IV, α-Amylase, and α-Glucosidase Enzymes

“…For instance, aromatic residues such as phenylalanine were found at the Ct end of peptides VVAEQAGEQGFE and HKNKNPF from F3. Proline was present at favorable positions of the N-terminal end of peptides VVNPDNNEN, EEPQQPQQ, QEPQESQQ, SQRPQDRHQ, and PETMQQQQQQ from F1 and SSPDIYNPQAGSVT from F3, although proline was not flanked by leucine, valine, phenylalanine, alanine, and glycine, in contrast with previous studies [ 35 , 36 ]. In addition, most of the peptides from F3 contained from four to six hydrophobic amino acid residues.…”

Phycobiliproteins from Arthrospira Platensis (Spirulina): A New Source of Peptides with Dipeptidyl Peptidase-IV Inhibitory Activity

“…This traditional approach doubtlessly represents a great limitation for a more realistic characterization of the hydrolysates with DPP-IV inhibitory activity. In light of these observations, a specific feature of our work was the employment of an intestinal cell-based assay for measuring the enzymatic activity, which represents a complementary and cost-effective strategy for a more efficient discovery of food-derived DPP-IV inhibitors [30]. In fact, the enterocyte luminal surface expresses a great quantity of DPP-IV: this means that, before absorption, any potential inhibitor deriving from food digestion is likely to interact with intestinal DPP-IV and other intestinal peptidases.…”

Antidiabetic Food-Derived Peptides for Functional Feeding: Production, Functionality and In Vivo Evidences

“…GLP-1 and GIP have half-lives of approximately 2 min and 5-7 min respectively, before they are degraded by DPP-IV [32,33]. DPP-IV is a cell surface (EC 3.4.14.5) that cleaves dipeptides from the N-terminus of polypeptides, in which proline is at the penultimate position [34]. DPP-IV can largely be found on the luminal surface of enterocytes; therefore, it can interact with any of the molecules from food intake before their absorption, that can be further metabolized before the molecules' interaction with soluble and vascular endothelial DPP-IV (the one affecting GIP and GLP-1 levels).…”

“…Protein intake can also elevate plasmatic GLP-1 levels [47]. This causes insulin secretion to be stimulated, in addition to inhibiting glucagon release [34], and the blood glucose level is adequately regulated. The first gliptin approved by the Food and Drug Administration (FDA) was sitagliptin, in 2006, and since then, more synthetic DPP-IV inhibitors have been approved, in spite of the adverse effects they may have.…”

“…The substrates usually employed for protein hydrolysis are of natural origin, usually with a high protein percentage. The most-studied protein substrates for obtaining antidiabetic peptides to date are milk [42,77,78] and soy proteins [34,79], due to their high biological value compared to other proteins. One such example is seen in Lacroix and Li-Chan [80], who described the formation of DPP-IV inhibitors from dairy proteins, using 11 enzymes and different substrates.…”