Conversion of glutamate into proline by the leucine analog BCH enhances biphasic insulin secretion in pancreatic β-cells
(2025) In Journal of Biological Chemistry 301(5).- Abstract
Biphasic insulin secretion, which fails in type 2 diabetes, can be provoked by various nutrient stimuli, glucose being the superior physiological one. To identify pathways that may play a role in β-cell stimulus-secretion coupling, we compared β-cell and islet functional, secretory, and metabolic responses to glucose and 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), a leucine analog, that acts as an allosteric activator of glutamate dehydrogenase. We employed a range of techniques, including insulin secretion assays, mitochondrial activity measurements, ATP/ADP ratio assessments, and cytosolic Ca2+ level quantifications. Metabolomics was used to analyze cellular metabolite profiles in response to glucose and BCH.... (More)
Biphasic insulin secretion, which fails in type 2 diabetes, can be provoked by various nutrient stimuli, glucose being the superior physiological one. To identify pathways that may play a role in β-cell stimulus-secretion coupling, we compared β-cell and islet functional, secretory, and metabolic responses to glucose and 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), a leucine analog, that acts as an allosteric activator of glutamate dehydrogenase. We employed a range of techniques, including insulin secretion assays, mitochondrial activity measurements, ATP/ADP ratio assessments, and cytosolic Ca2+ level quantifications. Metabolomics was used to analyze cellular metabolite profiles in response to glucose and BCH. Additionally, we investigated the role of proline synthesis by silencing ALDH18A1, encoding proline 5-carboxylate synthase, in both clonal β-cells and human islets. BCH and glucose similarly induced a biphasic insulin response in INS-1 832/13 cells, paralleled by increased mitochondrial activity and raised ATP/ADP ratios, plasma membrane depolarization, and elevated cytosolic Ca2+ levels. Metabolomics revealed that proline levels increased significantly only in BCH-stimulated β-cells. Silencing ALDH18A1 disrupted insulin secretion in response to both glucose and BCH, accompanied by reduced cytosolic Ca2+ levels, ATP/ADP ratios, and mitochondrial activity. Our findings demonstrated that BCH-induced activation of glutamate dehydrogenase leads to the conversion of glutamate into proline, which apparently enhances β-cell stimulus-secretion coupling. This work identifies a previously unrecognized role of proline metabolism in β-cell function and provides novel insights into the complex regulation of insulin secretion.
(Less)
- author
- Gheibi, Sevda
LU
; Cataldo, Luis Rodrigo
LU
; Ardalani, Hamidreza LU ; Nocquet, Lisa LU ; Spégel, Peter LU ; Straub, Susanne G. ; Sharp, Geoffrey W.G. ; Fex, Malin LU and Mulder, Hindrik LU
- organization
- publishing date
- 2025-05
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- BCH, glutamate dehydrogenase, insulin secretion, proline, β-cells
- in
- Journal of Biological Chemistry
- volume
- 301
- issue
- 5
- article number
- 108449
- publisher
- American Society for Biochemistry and Molecular Biology
- external identifiers
-
- pmid:40154614
- scopus:105003373638
- ISSN
- 0021-9258
- DOI
- 10.1016/j.jbc.2025.108449
- language
- English
- LU publication?
- yes
- additional info
- Publisher Copyright: © 2025 The Authors
- id
- 87546a12-880d-42f7-b360-a12712c438af
- date added to LUP
- 2025-08-06 15:44:47
- date last changed
- 2025-10-01 20:54:57
@article{87546a12-880d-42f7-b360-a12712c438af, abstract = {{<p>Biphasic insulin secretion, which fails in type 2 diabetes, can be provoked by various nutrient stimuli, glucose being the superior physiological one. To identify pathways that may play a role in β-cell stimulus-secretion coupling, we compared β-cell and islet functional, secretory, and metabolic responses to glucose and 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), a leucine analog, that acts as an allosteric activator of glutamate dehydrogenase. We employed a range of techniques, including insulin secretion assays, mitochondrial activity measurements, ATP/ADP ratio assessments, and cytosolic Ca<sup>2+</sup> level quantifications. Metabolomics was used to analyze cellular metabolite profiles in response to glucose and BCH. Additionally, we investigated the role of proline synthesis by silencing ALDH18A1, encoding proline 5-carboxylate synthase, in both clonal β-cells and human islets. BCH and glucose similarly induced a biphasic insulin response in INS-1 832/13 cells, paralleled by increased mitochondrial activity and raised ATP/ADP ratios, plasma membrane depolarization, and elevated cytosolic Ca<sup>2+</sup> levels. Metabolomics revealed that proline levels increased significantly only in BCH-stimulated β-cells. Silencing ALDH18A1 disrupted insulin secretion in response to both glucose and BCH, accompanied by reduced cytosolic Ca<sup>2+</sup> levels, ATP/ADP ratios, and mitochondrial activity. Our findings demonstrated that BCH-induced activation of glutamate dehydrogenase leads to the conversion of glutamate into proline, which apparently enhances β-cell stimulus-secretion coupling. This work identifies a previously unrecognized role of proline metabolism in β-cell function and provides novel insights into the complex regulation of insulin secretion.</p>}}, author = {{Gheibi, Sevda and Cataldo, Luis Rodrigo and Ardalani, Hamidreza and Nocquet, Lisa and Spégel, Peter and Straub, Susanne G. and Sharp, Geoffrey W.G. and Fex, Malin and Mulder, Hindrik}}, issn = {{0021-9258}}, keywords = {{BCH; glutamate dehydrogenase; insulin secretion; proline; β-cells}}, language = {{eng}}, number = {{5}}, publisher = {{American Society for Biochemistry and Molecular Biology}}, series = {{Journal of Biological Chemistry}}, title = {{Conversion of glutamate into proline by the leucine analog BCH enhances biphasic insulin secretion in pancreatic β-cells}}, url = {{http://dx.doi.org/10.1016/j.jbc.2025.108449}}, doi = {{10.1016/j.jbc.2025.108449}}, volume = {{301}}, year = {{2025}}, }