title: Optogenetic control of insulin secretion in intact pancreatic islets with β-cell-specific expression of Channelrhodopsin-2.
abstract: Insulin is secreted from the pancreatic β-cells in response to elevated glucose. In intact islets the capacity for insulin release is determined by a complex interplay between different cell types. This has made it difficult to specifically assess the role of β-cell defects to the insulin secretory impairment in type 2 diabetes. Here we describe a new approach, based on optogenetics, that enables specific investigation of β-cells in intact islets. We used transgenic mice expressing the light-sensitive cation channel Channelrhodopsin-2 (ChR2) under control of the insulin promoter. Glucose tolerance in vivo was assessed using intraperitoneal glucose tolerance tests, and glucose-induced insulin release was measured from static batch incubations. ChR2 localization was determined by fluorescence confocal microscopy. The effect of ChR2 stimulation with blue LED light was assessed using Ca(2+) imaging and static islet incubations. Light stimulation of islets from transgenic ChR2 mice triggered prompt increases in intracellular Ca(2+). Moreover, light stimulation enhanced insulin secretion in batch-incubated islets at low and intermediate but not at high glucose concentrations. Glucagon release was not affected. Beta-cells from mice rendered diabetic on a high-fat diet exhibited a 3.5-fold increase in light-induced Ca(2+) influx compared with mice on a control diet. Furthermore, light enhanced insulin release also at high glucose in these mice, suggesting that high-fat feeding leads to a compensatory potentiation of the Ca(2+) response in β-cells. The results demonstrate the usefulness and versatility of optogenetics for studying mechanisms of perturbed hormone secretion in diabetes with high time-resolution and cell-specificity.
authors.affiliation: a Department of Clinical Sciences; Lund University Diabetes Centre; Malmö, Sweden.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Reinbothe
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Safi
authors.forename: Annika S
authors.initials: AS
authors.lastname: Axelsson
authors.forename: Inês G
authors.initials: IG
authors.lastname: Mollet
authors.forename: Anders H
authors.initials: AH
authors.lastname: Rosengren
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D058948:Cell Tracking / Q000379:methods; D002478:Cells, Cultured; D000075402:Channelrhodopsins; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D062308:Optogenetics; D009928:Organ Specificity / Q000235:genetics; D011401:Promoter Regions, Genetic; D019076:Transgenes
chemical_list: D001426:Bacterial Proteins; D000075402:Channelrhodopsins; D007328:Insulin; D008164:Luminescent Proteins; C054562:yellow fluorescent protein, Bacteria
keywords: Channelrhodopsin-2; beta-cells; diabetes; insulin secretion; islets; optogenetics