ASP4000, a novel, selective, dipeptidyl peptidase 4 inhibitor with antihyperglycemic activity

Food protein hydrolysates as a source of dipeptidyl peptidase IV inhibitory peptides for the management of type 2 diabetes

The prevalence of type 2 diabetes mellitus (T2DM) is increasing and it is estimated that by 2030 approximately 366 million people will be diagnosed with this condition. The use of dipeptidyl peptidase IV (DPP-IV) inhibitors is an emerging strategy for the treatment of T2DM. DPP-IV is a ubiquitous aminodipeptidase that cleaves incretins such as glucagon like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), resulting in a loss in their insulinotropic activity. Synthetic DPP-IV drug inhibitors are being used to increase the half-life of the active GLP-1 and GIP. Dietary intervention is accepted as a key component in the prevention and management of T2DM. Therefore, identification of natural food protein-derived DPP-IV inhibitors is desirable. Peptides with DPP-IV inhibitory activity have been identified in a variety of food proteins. This review aims to provide an overview of food protein hydrolysates as a source of the DPP-IV inhibitory peptides with particular focus on milk proteins. In addition, the proposed modes of inhibition and structure-activity relationship of peptide inhibitors are discussed. Milk proteins and associated peptides also display insulinotropic activity and help regulate blood glucose in healthy and diabetic subjects. Therefore, milk protein derived peptide inhibitors may be a unique multifunctional peptide approach for the management of T2DM.

Effects of novel chalcone derivatives on α-glucosidase, dipeptidyl peptidase-4, and adipocyte differentiation in vitro

Chana series are new chalcone derivatives. To evaluate the possibility of Chana series as therapeutic agents of type 2 diabetes, the inhibitory effects of Chana series on the activities of α-glucosidase and DPP-4 were investigated using in vitro enzyme assays, and their effects on adipocyte differentiation were investigated in C3H10T1/2 cells. Chana 1 and Chana 7 among the Chana series showed significant inhibition of α-glucosidase activity. In DPP-4 enzyme assay, Chana 1 exhibited the highest inhibitory activity while Chana 7 did not. In MTT assay, Chana 1 did not show significant cytotoxicity up to a concentration of 250 μM, whereas cytotoxicity was observed with Chana 7 at a concentration of 300 μM. In addition, Chana 1 induced adipocyte differentiation. Therefore, Chana 1 showed inhibitory effects on α-glucosidase and DPP-4 as well as a stimulatory effect on adipocyte differentiation, suggesting that Chana 1 may be a potential beneficial agent for the treatment of type 2 diabetes.

The corn protein, zein hydrolysate, administered into the ileum attenuates hyperglycemia via its dual action on glucagon-like peptide-1 secretion and dipeptidyl peptidase-IV activity in rats

We previously showed that a hydrolysate prepared from corn zein [zein hydrolysate (ZeinH)] strongly stimulates glucagons-like peptide-1 (GLP-1) secretion from the murine GLP-1-producing enteroendocrine cell line and in the rat small intestine, especially in the ileum. Here, we investigated whether ZeinH administered into the ileum affects glucose tolerance via stimulating GLP-1 secretion. To observe the effect of luminal ZeinH itself on GLP-1 secretion and glycemia, ip glucose tolerance tests were performed in conscious rats with ileal and jugular catheters, and plasma glucose, insulin, and GLP-1 (total and active) were measured. In addition, plasma dipeptidyl peptidase-IV activities in the ileal vein were measured after the administration of ZeinH into the ileal-ligated loop in anesthetized rats. The ileal administration of ZeinH attenuated the glucose-induced hyperglycemia accompanied by the enhancement of insulin secretion, whereas meat hydrolysate (MHY) neither induced insulin secretion nor attenuated hyperglycemia. The antihyperglycemic effect was also demonstrated by the oral administration of ZeinH. From these results, it was predicted that the GLP-1-releasing potency of ZeinH was higher than that of MHY. However, both peptides induced a similar increase in total GLP-1 concentration after the ileal administration. In contrast, active GLP-1 concentration was increased only in ZeinH-treated rats. In anesthetized rats, ileal administration of ZeinH, but not MHY, decreased plasma dipeptidyl peptidase-IV activity in the ileal vein. These results indicate that the ileal administration of a dietary peptide, ZeinH, has the dual functions of inducing GLP-1 secretion and inhibiting GLP-1 degradation, resulting in the enhancement of insulin secretion and the prevention of hyperglycemia in rats.

ASP4000, a slow-binding dipeptidyl peptidase 4 inhibitor, has antihyperglycemic activity of long duration in Zucker fatty rats

ASP4000 ((2S)-1-{[(1R,3S,4S,6R)-6-hydroxy-2-azabicyclo[2.2.1]hept-3-yl]carbonyl}-2-pyrrolidinecarbonitrile hydrochloride) is a novel, potent and selective dipeptidyl peptidase 4 (DPP IV, EC 3.4.14.5) inhibitor (Keiko Tanaka-Amino et al. in Eur J pharmacol 59:444-449, 2008). The aim of the present study was to characterize the kinetic profile of and identify the long duration effect of the antihyperglycemic activity of ASP4000. ASP4000 was found to inhibit human recombinant DPP4 activity with a K(i) of 1.05 nM, a k(on) value of 22.3 x 10(5) M(-1) s(-1), and a k (off) of 2.35 x 10(-3) M(-1) s(-1), with higher affinity than that of vildagliptin. The kinetic studies indicate that both the formation and dissociation of ASP4000/DPP4 complex were faster than those of vildagliptin, and that ASP4000 slow-bindingly inhibits DPP4 with a different mode of inhibition than vildagliptin. In addition, ASP4000 augmented the insulin response and ameliorated the glucose excursion during the oral glucose tolerance test in Zucker fatty rats at 4 h post dosing. ASP4000 is expected to be a promising, long duration DPP4 inhibitor for type 2 diabetes.