Lijin Litson | ALES Graduate Seminar

Date(s) - 24/01/2023
1:15 pm - 2:15 pm

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Lijin Litson. This seminar is open to the general public to attend.

MSc with Dr Lingyun Chen.

Zoom Link:

Thesis Topic: Developing peptides from oat protein with potential hypocholesterolemic and satiety effects

Abstract: The prevalence of cardiovascular diseases is a significant concern globally, and a move towards prevention through healthy diet and lifestyle modifications is recommended. Obesity and high cholesterol concentration in the blood are common risk factors for developing cardiovascular diseases. Excess weight is mainly due to poor food choices and lack of physical activity, increasing cholesterol concentration. Therefore, making healthy food choices is essential to reducing the risk of cardiovascular diseases. Currently, oat consumption is associated with cholesterol reduction, mainly due to the presence of dietary fiber, especially β-glucan. Oat protein has recently gained prominence for its nutritional value and functional properties. However, research on peptides generated from oat protein and their bioactivities is still limited. Therefore, this study aims to explore the feasibility of generating peptides from oat that can eventually impact cholesterol concentration in the blood and promote satiety effect in the gut.
Oat protein concentrate was hydrolyzed through simulated gut digestion using pepsin and trypsin as digestive enzymes. The hydrolysates were then fractionated as F1, F2, F3 and F4 based on their hydrophobicity using a reverse phase HPLC. Dipeptidyl-peptidase 4 (DPP-IV) enzyme inhibition assay was carried out using Caco-2 cells. DPP-IV is an enzyme that cleaves and inactivates incretin hormones such as glucagon-like peptide 1 (GLP-1). Studies indicate DPP-IV drug inhibitors allows the release of GLP-1, delays gastric emptying, and suppresses appetite. In this study, oat peptides fractions especially F4 showed 50% of DPP4 inhibition at the concentration of 50 ug/ml. Therefore, inhibiting the DPP4 enzyme would eventually lead in increase in GLP-1 levels which further increases the insulin level and enhances satiation Similarly, hypocholesteremic properties of oat peptides was carried out by evaluating HMG-CoA reductase (HMGCR) inhibition and micellar solubility of cholesterol. HMGCR is considered as the rate-limiting enzyme towards cholesterol formation in the body. Fractions such as F3, F4 and HP (hydrolyzed peptide) inhibited HMGCR enzyme with 85%, 79% and 83% of inhibition at 200 ug/ml in vitro and F1 at 2 mg/ml showed 38% decreased solubilization of cholesterol micelles. Therefore, these results suggests that oat peptide could have an impact on cholesterol concentration in the blood.
These oat peptides were further identified using LC-MS/MS and sequences such as AFEPLR and LGLSQQAAQR were found derived from 11S and 12S oat globulins. New de novo sequences rich in proline, arginine, phenylalanine, leucine, and valine were identified. The data suggests that the presence of hydrophobic amino acids could have favored the DPP-IV inhibition. The presence of alanine and leucine in F3 and F4 with the constant presence of proline could provide structural flexibility to maximize the binding with the hydrophobic pockets on HMGCR. However, the presence of arginine, lysine and tyrosine which could possess an amphipathic nature could be the reason for higher binding capacity in F1 fraction with bile salts which are amphipathic in nature as well.
Currently, statin drugs, bile sequestrants are used as targets of cholesterol treatment. Therefore, the idea to generate peptides with hypocholesteremic and satiety improving properties from oat proteins provides a significant strategy to develop natural and healthy food products for hypercholesteremia and obesity prevention or management. In addition, this would further increase the acceptance of oats as part of a healthy diet and advance the revenue of oat production industries.