Abstract
Functional foods containing peptides offer the possibility to modulate the absorption of sugars and insulin levels to prevent diabetes. This study investigates the potential of germinated soybean peptides to modulate postprandial glycaemic response through inhibition of dipeptidyl peptidase IV (DPP-IV), salivary α-amylase, and intestinal α-glucosidases. A protein isolate from soybean sprouts was digested by pepsin and pancreatin. Protein digest and peptide fractions obtained by ultrafiltration (<5, 5–10 and >10 kDa) and subsequent semipreparative reverse phase liquid chromatography (F1, F2, F3, and F4) were screened for in vitro inhibition of DPP-IV, α-amylase, maltase, and sucrase activities. Protein digest inhibited DPP-IV (IC50 = 1.49 mg/mL), α-amylase (IC50 = 1.70 mg/mL), maltase, and sucrase activities of α-glucosidases (IC50 = 3.73 and 2.90 mg/mL, respectively). Peptides of 5–10 and >10 kDa were more effective at inhibiting DPP-IV (IC50 = 0.91 and 1.18 mg/mL, respectively), while peptides of 5–10 and <5 kDa showed a higher potency to inhibit α-amylase and α-glucosidases. Peptides in F1, F2, and F3 were mainly fragments from β-conglycinin, glycinin, and P34 thiol protease. The analysis of structural features of peptides in F1–F3 allowed the tentative identification of potential antidiabetic peptides. Germinated soybean protein showed a promising potential to be used as a nutraceutical or functional ingredient for diabetes prevention.
Highlights
Diabetes mellitus (DM) is a metabolic disorder considered as one of the major health problems worldwide
This study investigates the potential of germinated soybean peptides to modulate postprandial glycaemic response through inhibition of dipeptidyl peptidase IV (DPP-IV), salivary α-amylase, and intestinal α-glucosidases
6GSPD showed moderate DPP-IV inhibitory activity with an IC50 value of 1.49 ± 0.14 mg/mL that was ~103 times less potent than Diprotin, in agreement with previous studies focused on protein derived hydrolysates; see Table 1 [7]
Summary
Diabetes mellitus (DM) is a metabolic disorder considered as one of the major health problems worldwide. Type 2 diabetes mellitus (T2DM) is characterized by dysregulation of carbohydrate, lipid, and protein metabolism, and results from impaired insulin secretion, insulin resistance, or a combination of both. Insulin secretion is stimulated resulting from the combined effects of Glucose-Dependent Insulinotropic Polypeptide (GIP) and Glucagon-Like Peptide-1 (GLP-1) on the pancreatic β-cells [3]. These incretins hormones exert their metabolic effects through activation of their receptors. The guideline of the American Diabetes Association and the European Association for the Study of Diabetes have recommended the use of these inhibitors as a potential first-line agent or in combination with other anti-hyperglycemic drugs [8]
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