An attempt has been made to assess the dipeptidyl peptidase‐IV (DPP‐IV) inhibitory potential of α‐lactalbumin separated from milk of Gir cow. α‐lactalbumin hydrolysates were prepared using three different enzymes at different enzyme‐to‐substrate (E:S) ratios (1:25, 1:50 and 1:100) treated for 2‐ to 12‐h durations. Pepsin‐treated hydrolysates showed maximum DPP‐IV inhibition of 87.81 ± 0.84% (IC50 = 0.78 mg/mL). The permeate of 3 kDa, which exhibited 84.47 ± 2.29% DPP‐IV inhibition, was fractionated through RP‐HPLC. All fractions were analysed for DPP‐IV inhibition activity. One novel peptide was identified through LC‐MS/MS, which showed adequate DPP‐IV inhibition (IC50 = 4.93 mM).

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An attempt has been made to encapsulate dipeptidyl peptidase‐IV (DPP‐IV) inhibitory peptides which were decrypted from hydrolysis of α‐lactalbumin of milk of Gir cows. The effect of salt, pectin, homogenising speed on emulsion stability and encapsulation efficiency was examined. The optimised double emulsion containing 5% DPP‐IV inhibitory peptides had 17.33 ± 0.97 μm mean diameter, −35.43 ± 1.85 mV zeta potential and 93.00 ± 0.90% encapsulation efficiency. The emulsion stored at 5 ± 1°C and 37 ± 1°C exhibited stability of 90 and 20 days respectively. Encapsulated peptides showed ~4 times better DPP‐IV inhibition activity than nonencapsulated after simulated digestion.

Dipeptidyl peptidase-IV (DPP-IV) is an exopeptidase mainly present in epithelial tissues of the liver, kidney, and intestine. It is involved in the cleavage of a variety of substrates including the incretin hormones like glucagon-like peptide-1 (GLP-1). GLP-1 binds to the GLP-1 receptors of pancreatic β-cells and leads to β-cell proliferation and increases insulin secretion through associated gene expression. In diabetes, a constant increase in the glucose level leads to glucotoxicity, which destroys pancreatic βcells, decreases the insulin level, and further increases the blood glucose level. Inhibition of DPP-IV is one of the strategies for the treatment of type 2 diabetes. In recent years, peptides derived from a variety of dietary proteins have been reported to exhibit inhibitory activity against the DPP-IV enzyme. Such peptides should also be protected from the action of digestive enzymes to keep their bioactivity intact. Therefore, the present investigation was aimed to evaluate the in vitro DPP-IV inhibition potential and in vivo antidiabetic potential of α-lactalbumin in non-encapsulated hydrolysate (NEH), freeze-dried encapsulated hydrolysate (FDEH), and emulsified encapsulated hydrolysate (EEH) forms. Percent DPP-IV inhibition by the NEH, FDEH, and EEH after simulated gastrointestinal digestion was 36 ± 2.28, 54 ± 2.02, and 64 ± 2.02, respectively. The oral administration of the NEH, FDEH, and EEH at a dose of 300 mg/kg body weight was evaluated in nicotinamide-streptozotocin-induced type 2 diabetic experimental rats in a study of 30 days. Rats in the diabetic control group showed an increase in the blood glucose level and liver function enzymes and a decrease in GLP-1, insulin, and antioxidative enzymes. Administration of hydrolysates reversed the parameters by lowering the blood glucose level and increasing GLP-1 and insulin levels in plasma. The blood lipid profile, liver enzyme (ALT, AST, and AP) levels, and catalase and superoxide dismutase activity were also found to be normalized and better managed in experimental diabetic rats.

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