| 1. |
- Adam, J., et al.
(författare)
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Fumarate Hydratase Deletion in Pancreatic beta Cells Leads to Progressive Diabetes
- 2017
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 20:13, s. 3135-3148
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Tidskriftsartikel (refereegranskat)abstract
- We explored the role of the Krebs cycle enzyme fumarate hydratase (FH) in glucose-stimulated insulin secretion (GSIS). Mice lacking Fh1 in pancreatic beta cells (Fh1 beta KO mice) appear normal for 6-8 weeks but then develop progressive glucose intolerance and diabetes. Glucose tolerance is rescued by expression of mitochondrial or cytosolic FH but not by deletion of Hif1 alpha or Nrf2. Progressive hyperglycemia in Fh1bKO mice led to dysregulated metabolism in b cells, a decrease in glucose-induced ATP production, electrical activity, cytoplasmic [Ca2+](i) elevation, and GSIS. Fh1 loss resulted in elevated intracellular fumarate, promoting succination of critical cysteines in GAPDH, GMPR, and PARK 7/DJ-1 and cytoplasmic acidification. Intracellular fumarate levels were increased in islets exposed to high glucose and in islets from human donors with type 2 diabetes (T2D). The impaired GSIS in islets from diabetic Fh1bKO mice was ameliorated after culture under normoglycemic conditions. These studies highlight the role of FH and dysregulated mitochondrial metabolism in T2D.
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| 2. |
- Tarasov, A. I., et al.
(författare)
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Monitoring real-time hormone release kinetics: Via high-content 3-D imaging of compensatory endocytosis
- 2018
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 18:18, s. 2838-2848
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Tidskriftsartikel (refereegranskat)abstract
- High-content real-time imaging of hormone secretion in tissues or cell populations is a challenging task, which is unlikely to be resolved directly, despite immense translational value. We approach this problem indirectly, using compensatory endocytosis, a process that closely follows exocytosis in the cell, as a surrogate read-out for secretion. The tissue is immobilized in an open-air perifusion chamber and imaged using a two-photon microscope. A fluorescent polar tracer, perifused through the experimental circuit, gets trapped into the cells via endocytosis, and is quantified using a feature-detection algorithm. The signal of the tracer that accumulates into the endocytotic system reliably reflects stimulated exocytosis, which is demonstrated via co-imaging of the latter using existing reporters. A high signal-to-noise ratio and compatibility with multisensor imaging affords the real-time quantification of the secretion at the tissue/population level, whereas the cumulative nature of the signal allows imprinting of the “secretory history” within each cell. The technology works for several cell types, reflects disease progression and can be used for human tissue.
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| 3. |
- Hamilton, A., et al.
(författare)
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Adrenaline stimulates glucagon secretion by Tpc2-Dependent ca2+ mobilization from acidic stores in pancreatic a-Cells
- 2018
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 67:6, s. 1128-1139
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Tidskriftsartikel (refereegranskat)abstract
- Adrenaline is a powerful stimulus of glucagon secretion. It acts by activation of b-adrenergic receptors, but the downstream mechanisms have only been partially elucidated. Here, we have examined the effects of adrenaline in mouse and human a-cells by a combination of electrophysiology, imaging of Ca2+ and PKA activity, and hormone release measurements. We found that stimulation of glucagon secretion correlated with a PKA- and EPAC2-dependent (inhibited by PKI and ESI-05, respectively) elevation of [Ca2+]i in a-cells, which occurred without stimulation of electrical activity and persisted in the absence of extracellular Ca2+ but was sensitive to ryanodine, bafilomycin, and thapsigargin. Adrenaline also increased [Ca2+]i in a-cells in human islets. Genetic or pharmacological inhibition of the Tpc2 channel (that mediates Ca2+ release from acidic intracellular stores) abolished the stimulatory effect of adrenaline on glucagon secretion and reduced the elevation of [Ca2+]i. Furthermore, in Tpc2-deficient islets, ryanodine exerted no additive inhibitory effect. These data suggest that b-adrenergic stimulation of glucagon secretion is controlled by a hierarchy of [Ca2+]i signaling in the a-cell that is initiated by cAMP-induced Tpc2-dependent Ca2+ release from the acidic stores and further amplified by Ca2+-induced Ca2+ release from the sarco/endoplasmic reticulum. © 2018 by the American Diabetes Association.
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