<p>Cardiovascular diseases (CVD) and their risk factors remain the leading cause of
morbidity and mortality in North America. Food-derived
bioactive peptides (BAP) have been shown to play a role in regulating
physiological pathways of CVD risk factors including hypertension, diabetes,
and chronic inflammation. Common sources of BAP include dairy and plant
proteins. In addition to being an alternative protein
source, it is now accepted that edible insect proteins can also confer
health benefits beyond nutrition. However, as with any novel protein source,
allergenicity remains a major concern surrounding edible insect consumption. </p>
<p>This
dissertation aimed to: 1) Evaluate the bioactive potential of peptides from an
edible cricket species and; 2) determine the effects of BAP production methods
on immunoreactivity. First, peptide-rich extracts were generated from farmed
food-grade crickets via enzymatic hydrolysis techniques with the commercial
protease Alcalase™. To measure the <i>in
vitro</i> bioavailability, cricket peptides were also subject to simulated
gastrointestinal digestion (SGD). Peptides and their digests were tested for
relevant bioactivities and active groups were further fractionated by
chromatographic methods to identify the major peptides responsible for the
bioactivity. When tested for <i>in vitro</i>
antihypertensive and anti-glycemic properties, cricket peptides were found to
inhibit the activities of angiotensin converting enzyme, dipeptidyl
peptidase-4, α-amylase, and α-glucosidase. The anti-inflammatory potential was
expounded using RAW-264.7 macrophages and human umbilical vein endothelial
cells (HUVEC). Cricket peptides (after SGD) effectively lowered NF-κB, MCP-1,
and IL-6 production in cells without affecting their viability. Proteomic
analyses identified 18 sequences from the enriched cationic peptide fraction
that showed the highest activity. Three novel peptides were identified via
molecular docking, as potent ACE-inhibitors and binding was similar to that of
the commercial drug captopril. Key binding characteristics included interaction
with hydrophobic amino acids (Phe, Pro, Leu) near the C-terminal position and
coordination with Zn (II) ions near the ACE active site.</p>
<p>Immunological
reactivity was measured by IgE-binding from shrimp-allergenic patient sera to
antigens present within cricket peptides. Our studies demonstrate that
immunoreactivity was impacted by enzymatic hydrolysis, depending on the
conditions and heating source used. Tropomyosin (a major shrimp allergen) was
extracted from both untreated crickets and protein hydrolysates, and verified
as the major reactive protein. Tropomyosin reactivity decreased (under both
partial and extensive hydrolysis) or retained (under conditions which prevented
epitope cleavage). However, using microwave-assisted enzymatic hydrolysis was
effective at decreasing tropomyosin reactivity in all immunoassays tested (IgG
and IgE). Proteomic and immunoinformatic analyses revealed prominent allergen
binding regions of cricket tropomyosin available for cleavage during enzymatic
hydrolysis. Conserved antigen regions showed greater homology with other
crustacean species, but not with other well studied allergenic insect proteins
(i.e., cockroach). Lastly, LC-MS/MS and FT-Raman spectrometry suggests that
reactivity was affected due to distinct epitope cleavage within the protein
instead of decreased antigen extractability/solubility. </p>
<p>The
findings of this dissertation support that edible cricket proteins are a
potential source of bioactive peptides for functional food or nutraceutical
development. Additionally, using protein extraction methods such as
microwave-assisted hydrolysis seems a promising tool for minimizing the
immunoreactivity of the allergen present in this edible cricket species.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/13360142 |
| Date | 10 December 2020 |
| Creators | Felicia G Hall (9739430) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY-NC-SA 4.0 |
| Relation | https://figshare.com/articles/thesis/BIOACTIVE_AND_ALLERGENIC_PROPERTIES_OF_EDIBLE_CRICKET_GRYLLODES_SIGILLATUS_PEPTIDES/13360142 |
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