In-vitro characterization of pancreatic functional units from Cel-MODY mice
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The digestive enzyme carboxyl-ester lipase (CEL) is secreted by pancreatic acinar cells into the duodenum where it hydrolyzes dietary fat, cholesteryl esters, and fat-soluble vitamins. To date, two single-base mutations in the variable number of tandem repeats (VNTR) in the last exon of CEL have been identified. These mutations lead to a frameshift and a truncated CEL protein and they cause monogenic diabetes, also known as Maturity-Onset Diabetes of the Young, type 8 (CEL-MODY). In addition to early-onset diabetes, the disease is characterized by the development of multiple cysts and lipomatosis in the pancreas, leading to pancreatic exocrine dysfunction and the progressive deterioration of the pancreas. To better understand the pathogenic mechanism of CEL-MODY disease, our group has developed a novel mice model. The main objective of this study was to investigate the function of primary acini and islets of Langerhans isolated from Cel-MODY mice. More specifically, we aimed to investigate the viability of primary isolated acini, their secretory capacity, and the intracellular distribution of CEL protein in freshly isolated acini. Furthermore, by testing different protocols for isolating islets of Langerhans from mice pancreas we aimed at characterizing their function by performing glucose-stimulated insulin secretion (GSIS) assays. Our results revealed no clear differences when performing morphological assessment of cell viability for acini isolated from the different mouse strains. However, measurements of intracellular ATP levels showed significantly lower metabolic rate in acini isolated from Cel-MODY mice compared to control mice. The cellular distribution of CEL-containing granules appeared slightly different for acini isolated from Cel-MODY mice. For this mouse strain, we also observed significant differences in basal secretion of amylase for acini. Isolated islets of Langerhans from MODY8 mice did secrete insulin according to different concentrations of glucose in a similar way as observed in the two control mice strains. At the histology level, fat infiltration was observed in some pancreatic lobes for 3-month old Cel-MODY mice. Moreover, isolation of acini and islets from this strain resulted in lower amount of cellular material, which possibly could reflect that only acini and isles from intact and healthy lobes of the pancreas survived the isolation procedure and became part of the experiments performed. Investigations of older Cel-MODY (>6 months), where a worse phenotype is expected due to the progressive nature of the pathogenic process, are needed in order to understand better how islet and acini function may be altered in this disease.
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