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High-resolution Respirometry to Measure Mitochondrial Function of Intact Beta Cells in the Presence of Natural Compounds
Published on: January 23, 2018
Mitochondrial GTP regulates glucose-stimulated insulin secretion
Richard G Kibbey1, Rebecca L Pongratz, Anthony J Romanelli
1Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.
Cell Metabolism
|April 4, 2007
Summary
Mitochondrial GTP (mtGTP) from succinyl-CoA synthetase (SCS) is a key signal in pancreatic beta cells. Its production regulates glucose-stimulated insulin secretion (GSIS), impacting cellular metabolism and calcium signaling.
Area of Science:
- Metabolic regulation
- Cellular signaling
- Endocrinology
Background:
- Succinyl-CoA synthetase (SCS) exists in nucleotide-specific isoforms producing mitochondrial GTP (mtGTP) and ATP (mtATP).
- mtGTP production is tightly coupled to TCA cycle activity and may signal metabolic status.
- Pancreatic beta cells utilize glucose metabolism to stimulate insulin secretion (GSIS).
Purpose of the Study:
- To investigate the distinct roles of mtGTP and mtATP produced by SCS in regulating GSIS.
- To explore the signaling pathways linking mtGTP to insulin secretion.
Main Methods:
- Utilized siRNA to selectively suppress GTP- or ATP-producing SCS isoforms in INS-1 832/13 cells and rat islets.
- Measured glucose-stimulated insulin secretion (GSIS) in response to SCS isoform suppression.
- Assessed changes in cytosolic calcium, NAD(P)H, and ATP/ADP ratios.
Main Results:
- Suppression of the GTP-producing SCS pathway significantly reduced GSIS by 50%.
- Suppression of the ATP-producing SCS isoform doubled GSIS.
- Insulin secretion changes correlated with cytosolic calcium levels but not NAD(P)H or ATP/ADP ratios.
Conclusions:
- mtGTP, produced by SCS, plays a crucial role in controlling pancreatic beta cell GSIS.
- mtGTP may signal TCA cycle activity and modulate mitochondrial metabolism, potentially via mitochondrial calcium.
- mtGTP serves as a critical fuel signal regulating insulin secretion.
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