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Anaplerosis via pyruvate carboxylase is required for the fuel-induced rise in the ATP:ADP ratio in rat pancreatic islets.

Krus, Ulrika LU ; Rosengren, Anders LU ; Schuit, F ; Renström, Erik LU and Mulder, Hindrik LU orcid (2006) In Diabetologia 49(7). p.1578-1586
Abstract
AIMS/HYPOTHESIS: The molecular mechanisms of insulin release are only partially known. Among putative factors for coupling glucose metabolism to insulin secretion, anaplerosis has lately received strong support. The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells, and anaplerosis influences insulin secretion in beta cells. By inhibiting pyruvate carboxylase in rat islets, we aimed to clarify the hitherto unknown metabolic events underlying anaplerotic regulation of insulin secretion. METHODS: Phenylacetic acid (5 mmol/l) was used to inhibit pyruvate carboxylase in isolated rat islets, which were then assessed for insulin secretion, fuel oxidation, ATP:ADP ratio, respiration, mitochondrial membrane potential,... (More)
AIMS/HYPOTHESIS: The molecular mechanisms of insulin release are only partially known. Among putative factors for coupling glucose metabolism to insulin secretion, anaplerosis has lately received strong support. The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells, and anaplerosis influences insulin secretion in beta cells. By inhibiting pyruvate carboxylase in rat islets, we aimed to clarify the hitherto unknown metabolic events underlying anaplerotic regulation of insulin secretion. METHODS: Phenylacetic acid (5 mmol/l) was used to inhibit pyruvate carboxylase in isolated rat islets, which were then assessed for insulin secretion, fuel oxidation, ATP:ADP ratio, respiration, mitochondrial membrane potential, exocytosis and ATP-sensitive K(+) channel (K(ATP)-channel) conductance. RESULTS: We found that the glucose-provoked rise in ATP:ADP ratio was suppressed by inhibition of pyruvate carboxylase. In contrast, fuel oxidation, respiration and mitochondrial membrane potential, as well as Ca(2+)-induced exocytosis and K(ATP)-channel conductance in single cells, were unaffected. Insulin secretion induced by alpha-ketoisocaproic acid was suppressed, whereas methyl-succinate-stimulated secretion remained unchanged. Perifusion of rat islets revealed that inhibition of anaplerosis decreased both the second phase of insulin secretion, during which K(ATP)-independent actions of fuel secretagogues are operational, as well as the first and K(ATP)-dependent phase. CONCLUSIONS/INTERPRETATION: Our results are consistent with the concept that anaplerosis via pyruvate carboxylase determines pyruvate cycling, which has previously been shown to correlate with glucose responsiveness in clonal beta cells. These processes, controlled by pyruvate carboxylase, seem crucial for generation of an appropriate ATP:ADP ratio, which may regulate both phases of fuel-induced insulin secretion. (Less)
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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Insulin secretion, Mitochondria, Type 2 diabetes
in
Diabetologia
volume
49
issue
7
pages
1578 - 1586
publisher
Springer
external identifiers
  • wos:000238026100016
  • scopus:33744931361
  • pmid:16752176
ISSN
1432-0428
DOI
10.1007/s00125-006-0263-y
language
English
LU publication?
yes
id
8f12a027-a3f5-4dc4-b142-007cb81d9f6a (old id 155736)
alternative location
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16639595&dopt=Abstract
date added to LUP
2016-04-01 11:53:06
date last changed
2021-02-17 04:22:20
@article{8f12a027-a3f5-4dc4-b142-007cb81d9f6a,
  abstract     = {AIMS/HYPOTHESIS: The molecular mechanisms of insulin release are only partially known. Among putative factors for coupling glucose metabolism to insulin secretion, anaplerosis has lately received strong support. The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells, and anaplerosis influences insulin secretion in beta cells. By inhibiting pyruvate carboxylase in rat islets, we aimed to clarify the hitherto unknown metabolic events underlying anaplerotic regulation of insulin secretion. METHODS: Phenylacetic acid (5 mmol/l) was used to inhibit pyruvate carboxylase in isolated rat islets, which were then assessed for insulin secretion, fuel oxidation, ATP:ADP ratio, respiration, mitochondrial membrane potential, exocytosis and ATP-sensitive K(+) channel (K(ATP)-channel) conductance. RESULTS: We found that the glucose-provoked rise in ATP:ADP ratio was suppressed by inhibition of pyruvate carboxylase. In contrast, fuel oxidation, respiration and mitochondrial membrane potential, as well as Ca(2+)-induced exocytosis and K(ATP)-channel conductance in single cells, were unaffected. Insulin secretion induced by alpha-ketoisocaproic acid was suppressed, whereas methyl-succinate-stimulated secretion remained unchanged. Perifusion of rat islets revealed that inhibition of anaplerosis decreased both the second phase of insulin secretion, during which K(ATP)-independent actions of fuel secretagogues are operational, as well as the first and K(ATP)-dependent phase. CONCLUSIONS/INTERPRETATION: Our results are consistent with the concept that anaplerosis via pyruvate carboxylase determines pyruvate cycling, which has previously been shown to correlate with glucose responsiveness in clonal beta cells. These processes, controlled by pyruvate carboxylase, seem crucial for generation of an appropriate ATP:ADP ratio, which may regulate both phases of fuel-induced insulin secretion.},
  author       = {Krus, Ulrika and Rosengren, Anders and Schuit, F and Renström, Erik and Mulder, Hindrik},
  issn         = {1432-0428},
  language     = {eng},
  number       = {7},
  pages        = {1578--1586},
  publisher    = {Springer},
  series       = {Diabetologia},
  title        = {Anaplerosis via pyruvate carboxylase is required for the fuel-induced rise in the ATP:ADP ratio in rat pancreatic islets.},
  url          = {https://lup.lub.lu.se/search/files/2686636/625423.pdf},
  doi          = {10.1007/s00125-006-0263-y},
  volume       = {49},
  year         = {2006},
}