Institute of Physiology - Project


ARRS N3-0170

Significance of exocrine-endocrine pancreatic interactions in health and disease

Pomen povezav med eksokrinim in endokrinim delom trebušne slinavke v zdravju in bolezni

Coordinating person: 
- assoc. prof. dr. Jurij Dolenšek (Faculty of Medicine University of Maribor)
- prof. dr. Viktoria Venglovecz (Department of Pharmacology and Pharmacotherapy University of Szeged, Hungary)

Grant period: 2021-2024

Summary:
Growing evidence supports the view that reciprocal interactions between the exocrine and the endocrine part of the pancreas play a significant role in nutrient homeostasis, both in health and disease. Influence of the exocrine tissue on the endocrine is evident in acute and chronic pancreatitis (AP and CP). Both diseases are associated primarily with extensive damage to the exocrine tissue, but are also commonly accompanied by secondary dysregulation of glucose homeostasis. This often leads to development of the so-called type 3c diabetes mellitus (T3cDM). It is hypothesized that the progressive inflammation and fibrosis, especially in CP, cause destruction of the islets and as a consequence, lead to decreased insulin secretion, one of the major etiopathogenic factors and clinical signs of T3cDM. The underlying mechanisms by which diabetes develops in these patients are not known. More specifically, the steps in the stimulus-secretion coupling cascade in beta cells that are targeted in pancreatitis have not been described yet. 

On the other hand, there are scant clinical data supporting the view that also the endocrine dysfunction influences exocrine function. More specifically, the presence of type 2 diabetes mellitus (T2DM) increases the risk of exocrine insuficiency, and the loss of insulin in type 1 diabetes mellitus (T1DM) leads to destruction of acinar tissue. It is not clear whether the exocrine damage is primary due to the same pathogenic process that led to the destruction of islets, or secondary and due to beta cell defects and destruction. 

The mouse model of AP and CP will be used to evaluate in vivo glucose homeostasis in mice and to assess the effect on the endocrine cells in situ using the acute pancreas tissue slice approach. Using multicellular functional imaging, electrophysiological characterization of the stimulus-secretion pathway, secretion assays, and both light and electron microscopy of endocrine cells, we will identify the molecular pathways linked to diabetes progression in the setting of AP and CP. A mouse model of T1DM will be utilized to functionally and morphologically evaluate exocrine pancreas dysfunction in T1DM, resolving underlying mechanisms leading to AP or CP. In contrast to previous studies, we will focus on both the acinar and ductal cells as two essential functional parts of the exocrine pancreas. The fully complementary expertise and already available hardware of the Slovenian and Hungarian partner will ensure completion of the project. 

A better understanding of the reciprocal interactions under physiological and pathophysiological conditions will identify novel signalling mechanisms and potential therapeutic targets. This shall contribute to our knowledge of the etiology of both pancreatitis and diabetes.


Figure 1. [Ca2+]i response in ductal cells after stimulation with 1mM chenodeoxycholic acid (CDCA). (A-B) Confocal fluorescence image of a ductal structure and surrounding acinar tissue with selected regions of interest (ROI) denoting nuclei of individual PDECs. (C) Concurrent transmitted light image. (B) Chenodeoxycholic acid (CDCA) induced [Ca2+]i responses of individual cells corresponding to numbered ROIs in panel B (1-6). (D) Dashed vertical line indicates the start of exposure to 1 mM CDCA. (E and F) Bee swarm plots with interquartile ranges and medians for delays of responses after stimulation with 1 mM CDCA (n=65 cells from 4 slices) (E) and durations of transient [Ca2+]i events (n=38 cells from 4 slices) (F).


Koordinator projekta:
- doc. dr. Jurij Dolenšek
- prof. dr. Viktoria Venglovecz (Oddelek za farmakologijo in farmakoterapijo, Univerza v Szeged, Madžarska)

Vsebina:
Čedalje več znanstvene podlage govori v prid pomembnosti vloge vzajemnega delovanja med eksokrinim in endokrinim delom trebušne slinavke pri uravnavi homeostaze hranil tako v zdravju kot tudi v bolezni. Vpliv eksokrinega tkiva na delovanje endokrinega dela trebušne slinavke je očiten v primeru akutnega in kroničnega pankreatitisa (AP in KP). Obe bolezni povzročata obsežne poškodbe eksokrinega tkiva, a pogosto povzročata sekundarno motnjo v uravnjavanju homeostaze glukoze. Le-ta pogosto vodi v razvoj t. i. sladkorne bolezni tipa 3C (SB3C). Domneva se, da progresivno vnetje in fibroza, kar še posebej velja za KP, povzročata uničenje Langerhansovih otočkov, kar posledično vodi v  zmanjšano izločanje inzulina, kar je eden izmed ključnih znakov SB3C. Mehanizmi nastanka sladkorne bolezni še pri teh bolnikih niso znani. Bolj natančno, ni še znano, kateri koraki v kaskadi sklopitve med celično stimulacijo in sekrecijo je prizadet pri pankreatitisu. 

Po drugi strani pa obstaja nekaj kliničnih podatkov, ki govorijo v prid temu, da tudi disfunkcija endokrinega tkiva vpliva na delovanje eksokrinega dela trebušne slinavke. Prisotnost sladkorne bolezni tipa 2 (SB2) poveča tveganje za razvoj AP in pomanjkanje inzulina v primeru sladkorne bolezni tipa 1 (SB1) povzroči poškodbo acinarnega tkiva. Ni znano, ali je vzrok poškodbe primaren, torej enak patogenim procesom, ki vodijo v uničenje Langerhansovih otočkov ali sekundaren, zaradi okvare in uničenja celic beta. 

Za in vivo oceno homeostaze glukoze pri miših in določevanje učinkov na endokrine celice in situ z uporabo tehnike akutne tkivne rezine trebušne slinavke bomo uporabili mišji model AP in CP. Z uporabo funkcionalnega snemanja več celic, elektrofiziološko karakterizacijo poti celične stimulacije in izločanja, testi izločanja, svetlobno in elektronsko mikroskopijo endokrinih celic bomo določili molekularne poti, ki so povezane z napredovanjem sladkorne bolezni v okviru AP in KP. Za funkcionalno in morfološko oceno okvare eksokrinega tkiva trebušne slinavke ob prisotnosti SB1 in s tem mehanizmov, ki vodijo v AP in KP, bomo uporabili mišji model SB1. Za razliko od predhodnih raziskav se bomo osredotočili tako na acinarne kot tudi duktalne celice kot dva najpomemnejša dela eksokrinega dela trebušne slinavke. 

Boljše razumevanje vzajemnega delovanja v fizioloških in patofizioloških pogojih bo razkrilo še neznane mehanizme signalizacije in potencialne terapevtske tarče. To bo prispevalo k našemu razumevanju etiologije tako pankreatitisa kakor tudi sladkorne bolezni.


Slika 1. [Ca2+]i odziv duktalnih celic po stimulaciji z 1 mM henodeoksiholno kislino (CDCA). (A) Konfokalna slika strukture dukta in acinarnih celic. (B) Na sliki iz A so označena jedra duktalnih celic, ki so bila osnova za izbiro polj interesa. Transmisijska slika A. (D) Stimulacija s CDCA je povzročila [Ca2+]i odziv posameznih duktalnih celic (številke pomenijo polja interesa na B). (E in F) Kvantifikacija zamikov in dolžin odzivov duktalnih celic po stimulaciji s CDCA.


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