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dc.contributor.authorGravdal, Anny
dc.date.accessioned2023-03-07T08:32:47Z
dc.date.issued2023-03-21
dc.date.submitted2023-01-11T12:59:19.360Z
dc.identifiercontainer/95/dd/20/30/95dd2030-b496-4c31-a2bf-1d3952bae63a
dc.identifier.isbn9788230841815
dc.identifier.isbn9788230840764
dc.identifier.urihttps://hdl.handle.net/11250/3056230
dc.descriptionPostponed access: the file will be accessible after 2025-03-21en_US
dc.description.abstractKarboksylester-lipase (CEL) er et fordøyelsesenzym som hovedsakelig er uttrykt i bukspytt-kjertelen. Det siste eksonet i CEL-genet inneholder et variabelt antall tandem repetisjoner (VNTR), altså en region av repeterte DNA-sekvenser. To sykdomsfremkallende CEL-varianter, kjent som CEL-MODY og CEL-HYB1, har begge en endret VNTR-region sammenlignet med det normale genet. CEL-MODY inneholder en enkelt-base delesjon som gir et skift i leseramme, mens i CEL-HYB1 stammer VNTR-regionen fra pseudogenet CELP. CEL-MODY-varianten forårsaker den arvelige sykdommen MODY8, som gir både diabetes og eksokrin dysfunksjon i bukspyttkjertelen. CEL-HYB1-varianten er en risikofaktor for kronisk pankreatitt, og er fem ganger overrepresentert i europeiske kohorter med pankreatitt-pasienter. CEL-MODY og CEL-HYB1 virker mest sannsynlig gjennom den såkalte misfolding-avhengige mekanismen for pankreatitt. Det overordnete målet med denne avhandlingen var å få en bedre forståelse av hvordan patogene CEL-varianter forårsaker sykdom i bukspyttkjertelen. I Artikkel Ⅰ brukte vi HEK293 celler for teste om noen enkelt-base delesjoner i VNTR-regionen er mer patogene enn andre. Celler som uttrykte varianter som ligger fremst i regionen viste nedsatt sekresjon, økt protein-aggregering og endoplasmatisk retikulum stress, trolig på grunn av et økt antall cysteiner og samtidig redusert O-glykosylering i VNTR´en. I Artikkel Ⅱ laget vi en ny modell for kronisk pankreatitt ved å sette VNTR-regionen fra CEL-MODY inn i mus. Musene utviklet spontan kronisk pankreatitt, med kjennetegn som atrofi, inflammasjon, fibrose og fettvev i bukspyttkjertelen. Musene ble ikke diabetiske, selv når de ble gjort homozygote for CEL-MODY eller ble satt på høy-fett diett. I Artikkel Ⅲ laget vi transgene mus for risiko-allelet CEL-HYB1 etter samme strategi som for CEL-MODY. Også Cel-HYB1-musene utviklet spontan kronisk pankreatitt, men med en mildere fenotype enn Cel-MODY. I tillegg observerte vi nedsatt glukosetoleranse for 12-måneder gamle Cel-HYB1 mus. I Artikkel Ⅳ screenet vi en norsk kohort med kronisk pankreatitt-pasienter for å finne bærere av CEL-HYB1. To av 154 pasienter (1.3%) var positive, og vi beskrev disse pasientene klinisk og kartla familien deres. Vi fant at CEL-HYB1 mest sannsynlig forårsaker pankreatitt i kombinasjon med andre risikofaktorer som røyking og pankreas divisium. Oppsummert har vi gjennom studier på celler, mus og pasienter fått ny og bedre forståelse for sykdomsmekanismene bak CEL-MODY og CEL-HYB1. Vi har lykkes i å lage helt nye musemodeller for kronisk pankreatitt. Disse gjenspeiler den eksokrine fenotypen knyttet til de to sykdomsvariantene, men vi avdekket ikke den karakteristiske endokrine dysfunksjonen for MODY8.en_US
dc.description.abstractCarboxyl ester lipase (CEL) is a digestive enzyme mainly expressed in the pancreas. The last exon of the CEL gene includes a variable number of tandem repeats (VNTR), i.e., a region of repeated DNA sequences. Two pathogenic CEL variants, denoted CEL-MODY and CEL-HYB1, both have altered VNTR regions compared with the normal gene. CEL-MODY contains a single-base deletion that changes the reading frame of the VNTR sequence, while the VNTR of CEL-HYB1 stems from the pseudogene CELP. The CEL-MODY variant causes the inherited disease MODY8, which is characterised by both diabetes and exocrine pancreatic dysfunction. The CEL-HYB1 variant is a risk factor for chronic pancreatitis, with a 5-fold overrepresentation in European materials of pancreatitis patients. CEL-MODY and CEL-HYB1 are considered to work through the so-called misfolding-dependent pathway of pancreatitis. The overall aim of this thesis was to gain better knowledge about how pathogenic CEL variants cause pancreatic disease. In Paper Ⅰ, we used HEK293 cells to test if some single-base deletions of the VNTR are more pathogenic than others. Cells expressing the proximal variants of this region displayed reduced secretion, increased protein aggregation and endoplasmic reticulum stress, attributed to both an increased number of cysteine residues and decreased O-glycosylation within the VNTR domain. In Paper Ⅱ, we created a novel model for chronic pancreatitis by inserting the VNTR from CEL-MODY in mouse. The mice developed spontaneous chronic pancreatitis, with hallmarks like atrophy, inflammation, fibrosis and fatty replacement of exocrine tissue. The mice did not become diabetic, even when made homozygous for CEL-MODY or exposed to a high-fat diet. In Paper Ⅲ, we generated transgenic mice carrying the CEL-HYB1 risk allele, using the same strategy as for CEL-MODY. The Cel-HYB1 mice, too, developed spontaneous chronic pancreatitis, although with a somewhat milder phenotype. In addition, we noted impaired glucose tolerance in Cel-HYB1 mice aged 12 months. In Paper Ⅳ, we screened a Norwegian cohort of chronic pancreatitis patients to identify carriers of CEL-HYB1. Two of 154 screened cases (1.3%) were positive. We described these patients clinically and mapped their families. We found that CEL-HYB1 most likely causes pancreatitis when acting in combination with other risk factors, such as smoking and pancreas divisium. In summary, through cellular, animal, and clinical studies, we have gained important new insight into the disease mechanisms involving CEL-MODY and CEL-HYB1. We have successfully created two fundamentally new mouse models for chronic pancreatitis. They recapitulate the exocrine phenotype associated with the two variants, although we did not uncover the endocrine dysfunction which is characteristic of MODY8.en_US
dc.language.isoengen_US
dc.publisherThe University of Bergenen_US
dc.relation.haspartPaper Ⅰ: Gravdal A, Xiao X, Cnop M, El Jellas K, Johansson S, Njølstad P.R, Lowe M.E, Johansson B.B, Molven A, Fjeld K. The position of single-base deletions in the VNTR sequence of the carboxyl ester lipase (CEL) gene determines proteotoxicity. Journal of Biological Chemistry 2021; 296, 100661. The article is available at: <a href="https://hdl.handle.net/11250/2975919" target="blank">https://hdl.handle.net/11250/2975919</a>.en_US
dc.relation.haspartPaper Ⅱ: Gravdal A, Wilhelm S, Abbedissen I, Alam J, Brekke R, Steine S.J, Zino S, Njølstad P.R, Johansson B.B, Lowe M.E, Xiao X, Molven A, Fjeld K. The MODY8-causing mutation of the human CEL gene triggers chronic pancreatitis but not diabetes in mice. Article not available in BORA.en_US
dc.relation.haspartPaper Ⅲ: Fjeld K, Gravdal A, Brekke R.S, Alam J, Wilhelm S.J, El Jellas K, Pettersen H.N, Lin J, Solheim M.H, Steine S.J, Johansson B.B, Njølstad P.R, Verbeke C.S, Xiao X, Lowe M.E, Molven A. The genetic risk factor CEL-HYB1 causes proteotoxicity and chronic pancreatitis in mice. Pancreatology 2022; 22:8, 1099-1111. The article is available at: <a href="https://hdl.handle.net/11250/3038662" target="blank">https://hdl.handle.net/11250/3038662</a>.en_US
dc.relation.haspartPaper Ⅳ: Tjora E, Gravdal A, Engjom T, Cnop M, Johansson B.B, Dimcevski G.G, Molven A, Fjeld K. Protein misfolding in combination with other risk factors in CEL-HYB1-mediated chronic pancreatitis. European Journal of Gastroenterology & Hepatology 2020; 33:6, 839-843. Article not available in BORA due to publisher restrictions. The article is available at: <a href="https://doi.org/10.1097/MEG.0000000000001963" target="blank">https://doi.org/10.1097/MEG.0000000000001963</a>.en_US
dc.rightsIn copyright
dc.rights.urihttp://rightsstatements.org/page/InC/1.0/
dc.titleCarboxyl ester lipase in pancreatic disease : In vitro and in vivo studies of human pathogenic CEL mutationsen_US
dc.typeDoctoral thesisen_US
dc.date.updated2023-01-11T12:59:19.360Z
dc.rights.holderCopyright the Author. All rights reserveden_US
dc.contributor.orcid0000-0002-5275-0028
dc.description.degreeDoktorgradsavhandling
fs.unitcode13-24-0
dc.date.embargoenddate2025-03-21


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