Select or Award-Winning Individual Scholarship

Document Type

Article

Publication Date

Spring 5-2022

Abstract

We display the capabilities of our established liquid chromatography-ion mobility spectrometry-mass spectrometry (LC-IMS-MS) workflow in the investigations of islet chemistry at the sub-single-islet level. We begin by characterizing the structural differences of Ins1 and Ins2 to present novel insights as to why their behaviors diverge. We then examine the effects of the stress hormone corticosterone, the rodent equivalent of human cortisol that is often used as a therapeutic, on pancreatic peptide hormone secretion. We also uncover the molecular connection behind the inverse relationship between type 2 diabetes (T2D) risk and chronic migraine via the neuropeptides CGRP and PACAP. Lastly, we apply our technique to the detection of posttranslational modifications (PTMs).

Through our studies, we elucidate how corticosterone-induced beta-cell proliferation may lead to insulin resistance. Our results show that the level of amylin, a peptide co-secreted with insulin from the beta-cells, increased significantly compared to the control samples, correlating well with an increase in beta-cell population observed in immunoassays. Furthermore, while the corticosterone-treated mice might produce a high level of insulin due to the proliferation of insulin-positive cells, the hormones were quickly degraded. Because the truncated form of insulin may not be as effective as the intact form, our data help rationalize insulin resistance induced by corticosterone.

We show that alpha-CGRP remodels amylin fibrillization, a process implicated in T2D. CGRP and/or amylin monomers reduce the secretion of both mouse Ins1 and Ins2 proteins, however, CGRP oligomers have a reverse effect on Ins1. Beyond the mechanistic insights, our data suggest that CGRP regulates insulin secretion and lowers the risk of T2D, thus rationalizing how migraine might be protective against T2D.

We observe that PACAP-38 enhances Ins1 secretion under glucose stimulation yet has no significant effects on Ins2 in-vitro. We address the need for future studies with transgenic mice to determine if PACAP’s remodeling of islet morphology can serve therapeutic purposes in T2D patients.

We demonstrate that DTIMS can capture important PTMs that can serve as biomarkers—Asn deamination and IsoAsp formation. Finally, we use DTIMS analysis to show that spontaneous cis/trans proline isomerization can occur under a different mobility type.

Comments

This thesis was submitted in fulfillment of the Biological Sciences: Biochemistry, Cellular, and Molecular Biology Honors Concentration at UTK. This work was supervised by my mentors Dr. Thanh D. Do and Aleksandra Antevska.

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