| Summary: | 碩士 === 中國醫藥大學 === 營養學系碩士班 === 101 === A novel approach for treatment of type 2 diabetes is the use of gut hormone glucagon-like peptide-1 (GLP-1), which possesses multi-functions such as the stimulation of insulin secretin and the blood glucose homeostasis. GLP-1 is a polypeptide that is rapidly inactivated by dipeptidyl peptidase IV (DPP-IV). DPP-IV is a postproline-cleaving enzyme with the specificity for removing X-proline or X-alanine dipeptides from the N-terminus of polypeptides. Therefore, the peptides with Pro or Ala as the penultimate amino acid residue of N-terminus would be efficient DPP-IV inhibitors to elongate the half life of endogenous GLP-1. It is well-known that gelatin is rich in Pro, Ala, Hyp, while that of warm-water fish skin has higher contents of the three amino acid residues than cold-water fish.
The objective of this study is to utilize commercial proteases flavourzyme to hydrolyze gelatin extracted from halibut, tilapia and milkfish skin, and to produce the DPP-IV inhibitory peptides and determine their antidiabetic activity in animal in vivo experiments. The results were shown as follows:
1. The contents of Pro, Ala, Hyp from halibut, tilapia, milkfish skin gelatin were 32.18, 37.6, 38.55 mole/100 mole amino acid residues. The warm-water fish (tilapia and milkfish) skin gelatin showed higher contents of the three amino acid residues than the cold-water fish (halibut).
2. Halibut, tilapia and milkfish skin gelatins were hydrolyzed with Fla at various enzyme/substrate (E/S) ratio (1, 3, 5%) for 4 h. The DHs and DPP-IV inhibitory activity of the gelatin hydrolysates obtained by Fla hydrolysis increased with the increment of E/S ratio. When the hydrolysis process was done with the E/S ratio of 5% for 6 and 8 h, the both warm-water fish skin gelatin hydrolysates showed the greater DPP-IV inhibition rates of 45-48% as compared to the cold-water fish. The hydrolysates from both warm-water fish skin gelatin with E/S of 5% and 6-h hydrolysis were used for ultrafiltration.
3. The peptides within <1 kDa fraction from tilapia skin gelatin hydrolysates had the greatest DPP-IV inhibition rate of 51.91% as compared to those within the other two high-molecular-weight fractions (1-2.5 kDa and >2.5 kDa). The <1 kDa fraction was then used to evaluate its in vivo antidiabetic effect by the animal experiment, and the peptides in this fraction were comprised of Pro and Ala of 11.22, 16.39 mole/100 mole amino acid residues, respectively.
4. The oral administration with medial dose (750 mg/kg BW) of tilapia fish skin gelatin hydrolysate could significantly (p<0.05) decrease the plasma DPP-IV activity for 31.74%, and slightly but insignificantly (p>0.05) increase plasma GLP-1 for 35.4% in diabetic (DM) rats. Also, the hydrolysate effectively increased the plasma insulin concentration for 121% (p<0.05) as compared to DM rats and improve the blood glucose control.
The tilapia fish skin gelatin hydrolysate is useful for the therapy or prevention of type 2 diabetes. Tilapia fish skin gelatin hydrolysate can be develop a new functional food and to increase the economic values of fish processing byproducts.
|
|---|
