doktorska disertacija
Eva Paradiž (Author), Andraž Stožer (Mentor), Jurij Dolenšek (Co-mentor)

Abstract

Natančno uravnavanje sklopitve stimulacije in izločanja v celicah beta je ključnega pomena za vzdrževanje normoglikemije. Čeprav glukoza v tem procesu predstavlja primarni dražljaj, inkretini ključno prispevajo k povečanemu izločanju inzulina, delno tudi preko ojačitve znotrajcelične dinamike [Ca2+] ([Ca2+]IC). Podrobnosti o tem, kako inkretini vplivajo na rekrutacijo celic beta v fazi aktivacije, na aktivni čas in funkcionalno povezanost v fazi platoja in kako na njihovo deaktivacijo, še niso pojasnjene. S pomočjo konfokalne mikroskopije smo v svežih tkivnih rezinah trebušne slinavke z visoko resolucijo istočasno zajemali [Ca2+]IC signale v številnih celicah in tako sistematično proučili vpliv agonistov receptorjev GLP-1 (GLP-1RA), eksendina-4 (Ex-4) in GLP-1, na aktivnost sklopljenih celic beta. V nestimulativni koncentraciji glukoze (6 mM) je Ex-4 aktiviral približno četrtino celic beta v otočku. Kostimulacija z Ex-4 in glukozo (10 mM) je skrajšala zamik do aktivacije celic beta in pospešila dinamiko njihove aktivacije. Tako se je čas, ki je bil potreben, da so celice dosegle polovično vrednost maksimalnega aktivnega časa, v prisotnosti Ex-4 prepolovil. Aktivni čas in regularnost oscilacij [Ca2+]IC sta se povečala, zlasti v začetnem delu odziva celic beta. Kasnejše dodajanje Ex-4, ko so bile celice že aktivne, ni privedel do tako izrazitega porasta aktivnosti. Mrežne analize so potrdile povečano povezanost celic med fazo aktivacije in fazo platoja, pri čemer je vloga centralnih celic ostala stabilna tako v kontrolnih poskusih kot ob stimulaciji z Ex-4. Zanimivo je, da smo pri Ex-4 opazili dvojen učinek na deaktivacijo celic beta, tako da se je celična aktivnost pri nizkih koncentracijah podaljšala, pri visokih pa skrajšala. Naši poskusi so dosledno pokazali, da je GLP-1 šibkejši agonist. Kostimulacija z GLP-1RA in glukozo tako povzroči porast [Ca2+]IC med aktivacijo in aktivnostjo celic beta, kar kaže, da je učinek inkretinov v veliki meri mogoče pojasniti z ojačano dinamiko [Ca2+]IC. Predhodna stimulacija z inkretini ne privede do kritičnega podaljšanja aktivnosti celic beta, kar potrjuje njihovo nizko tveganje za razvoj hipoglikemije.

Keywords

beta cell;tissue slice;GLP-1 receptor agonists;confocal microscopy;calcium oscillations;

Data

Language: English
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UM MF - Faculty of Medicine
Publisher: [E. Paradiž Leitgeb]
UDC: 612.345/.346+611.018.72:616-074+577.175.72/.73(043.3)
COBISS: 190302723 Link will open in a new window
Views: 17
Downloads: 0
Average score: 0 (0 votes)
Metadata: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Other data

Secondary language: Slovenian
Secondary title: Effect of incretins and their analogues on calcium dynamics in beta cells in acute pancreas tissue slices
Secondary abstract: Precise control of beta cell stimulus-secretion coupling is crucial for maintaining normoglycemia. While glucose serves as a primary regulator of this process, incretins substantially augment beta cell insulin secretion, partly by enhancing intracellular Ca2+ ([Ca2+]IC) dynamics. However, the details of how precisely they affect beta cell recruitment during activation, their active time, and functional connectivity during plateau activity, and how they influence beta cell deactivation remain to be described. Performing functional confocal Ca2+ imaging in acute mouse pancreas tissue slices enabled us to systematically assess the effects of the GLP-1 receptor agonists, exendin-4 (Ex-4) and GLP-1, simultaneously in many coupled beta cells with high resolution. In otherwise substimulatory glucose (6 mM), Ex-4 was able to recruit approximately a quarter of beta cells into an active state. Costimulation with Ex-4 and stimulatory glucose (10 mM) shortened the activation delays and accelerated beta cell activation dynamics, so that the time required to reach half-maximal activation was effectively halved in the presence of Ex-4. Moreover, the active time and regularity of [Ca2+]IC oscillations increased, especially during the first part of beta cell response. Subsequent addition of Ex-4 to already active cells less effective in enhancing cellular activity. Network analyses further confirmed increased connectivity during activation and activity in the presence of Ex-4, with hub cell roles remaining rather stable in both control experiments and experiments with Ex-4. Interestingly, Ex-4 demonstrated an inconsistent effect on deactivation, slightly prolonging beta cell activity at low concentrations and shortening deactivation delays at high concentrations. Our experiments consistently verified that GLP-1 is a less potent agonist. In sum, costimulation by a GLP-1 receptor agonists and glucose increases [Ca2+]IC during beta cell activation and activity, indicating that the effect of incretins may, to an important extent, be explained by enhanced [Ca2+]IC dynamics. During deactivation, previous incretin stimulation does not critically prolong cellular activity, which corroborates their low risk of hypoglycemia.
Secondary keywords: celice beta;tkivna rezina;agonisti receptorjev GLP-1;konfokalna mikroskopija;kalcijeve oscilacije;
Type (COBISS): Dissertation
Thesis comment: Univ. v Mariboru, Medicinska fak.
Pages: VIII, 99 str.
ID: 21344155