Novel Dipeptidyl Peptidase-4–Inhibiting Peptide Derived From β-Lactoglobulin

Abstract

In type 2 diabetic mellitus, glucose-dependent insulinotropic polypeptide (GIP) secretion is increased, but its insulinotropic effect is severely reduced, perhaps as a result of reduced GIP receptor expression or reduced β-cell sensitivity to GIP (1, 2). In addition, many studies demonstrated a progressive decline in postprandial glucagon-like peptide-1 (GLP-1) secretion, where individuals with type 2 diabetes demonstrate the greatest impairment in GLP-1 secretion (3,4). This difference has been called the incretin effect. Although GLP-1 has been used as a therapeutic drug, the clinical utility of native GLP-1 is limited by its short half-life (within 2 min) due to its rapid degradation to inactive metabolites by the enzyme dipeptidyl peptidase-4 (DPP-4) (5 -8). Therefore, DPP-4 inhibitor is also useful target for the therapy of type 2 diabetic mellitus. Sitagliptin, vildagliptin, saxagliptin, and alogliptin have been used in the clinic.On the other hand, α-lactoalbumin, β-lactoglobulin, and lactoferrin, which are major protein components of bovine milk whey, have been known to have many pharmacological functions such as anti-hypertensive, anti-inflammatory, analgesic, and insulinotropic properties (9). We also reported anti-inflammatory and analgesic activity of α-lactoalbumin (10). Milk products are powerful acute stimulants of insulin secretion (11,12) and have the ability to enhance the insulin response when supplied in a mixed meal (13). Frid et al. (14) reported that acute administration of whey protein-supplemented meals to individuals with type 2 diabetes was associated with significant increments in postprandial insulin responses and higher levels of GIP but not GLP-1. Recently, Tulipano et al. (15) reported that Ile-Pro-Ala, a DPP-4 inhibitor, was isolated from the hydrolysates of β-lactoglobulin, the major whey protein. After oral administration, milk protein is transferred to the duodenum from the stomach and digested by trypsin secreted from the pancreas. We already tested the effects of alpha-lactoalbumin and trypsin-treated alpha-lactoalbumin on DPP-4 activity and found that these proteins did not show any inhibitory effect on DPP-4. However, trypsin-treated β-lactoglobulin showed inhibitory effect on it. Then, we tested the hypoglycemic efficacy of trypsin-treated β-lactoglobulin in the oral glucose tolerance test using mice. Next we isolated the hypoglycemic peptide having DPP-4 inhibiting activity and identified the active amino acid sequence. Research and Development, Meiji Corporation, Ltd., 540 Naruda, Odawara, Kanagawa 250-0862, Japan Received May 12, 2011; Accepted June 29, 2011 Abstract. Trypsin-treated β-lactoglobulin significantly decreased the glucose level after an oral glucose tolerance test using mice. We performed the present study to identify the active peptide inhibiting dipeptidyl peptidase-4 from trypsin-treated β-lactoglobulin. Trypsin-treated β-lactoglobulin showed a concentration-dependent inhibition for dipeptidyl peptidase-4, with an IC 50 value of 210 μM, althoug...

Dipeptidyl peptidase IV inhibitory and antioxidative properties of milk protein-derived dipeptides and hydrolysates

“…This result was explained by the fact the N terminal residue of the peptide plays an important role in the inhibition of DPP-IV [11]. Different milk protein hydrolysates have been reported for their DPP-IV inhibitory potential including hydrolysates of-lactoglobulin [17,43].…”

“…Milk proteins, particularly, milk protein-derived peptides and amino acids have also been linked with the regulation of postprandial glycaemia and insulin secretion in normoglycaemic and type 2 diabetic subjects [6,8,23,24,26,32]. Peptides derived from -lactoglobulin have been shown to possess DDP-IV inhibitory activity in vitro [42,43].…”

“…Similarly, a DPP-IV inhibitory tryptic digest of -lactoglobulin induced a decrease in blood glucose level in mice following an oral glucose tolerance test when administered orally at 300 mg/kg body weight [43]. More recently, an in silico approach has been utilized to identify potential dietary protein precursors of DDP-IV inhibitory peptides [18].…”

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

“…Leu-Pro-Gln-Asn-Ile-Pro-Pro-Leu 46 (63) Leu-Pro-Gln-Asn-Ile-Pro-Pro 160 Pro-Gln-Asn-Ile-Pro-Pro-Leu 1500 Leu-Pro-Gln Val-Ala-Gly-Thr-Trp-Tyr 174 (64) β-lactoglobulin Ile-Pro-Ala 49 (65) β-lactoglobulin Ile-Pro-Ala-Val-Phe 45 (66) Ile-Pro-Ala-Val-Phe-Lys 143 Val-Leu-Val-Leu-Asp-Thr-Asp-Tyr-Lys 424 Thr-Pro-Glu-Val-Asp-Asp-Glu-Ala-Leu-Glu-Lys 320…”

“…Each individual WP has different physicochemical properties, which can be modified by enzymatic hydrolysis and hydrolysis of WP has been shown to release DPP-IV inhibitory peptides (13,(64)(65)(66) . Digestion of WP with pepsin and pancreatin generated peptides with DPP-IV inhibitory activity and peptic digestion produced the most potent hydrolysate with an IC 50 value of 0·075 mg/ml.…”