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A mathematical model of the mitochondrial NADH shuttles and anaplerosis in the pancreatic beta-cell
KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA. KTH, School of Computer Science and Communication (CSC), Computational Biology, CB.
KTH, School of Computer Science and Communication (CSC), Computational Biology, CB.ORCID iD: 0000-0002-0550-0739
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2007 (English)In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 292, no 2, E373-E393 p.Article in journal (Refereed) Published
Abstract [en]

The pancreatic beta-cells respond to an increased glycolytic flux by secreting insulin. The signal propagation goes via mitochondrial metabolism, which relays the signal to different routes. One route is an increased ATP production that, via ATP-sensitive K+ (K-ATP) channels, modulates the cell membrane potential to allow calcium influx, which triggers insulin secretion. There is also at least one other "amplifying" route whose nature is debated; possible candidates are cytosolic NADPH production or malonyl-CoA production. We have used mathematical modeling to analyze this relay system. The model comprises the mitochondrial NADH shuttles and the mitochondrial metabolism. We found robust signaling toward ATP, malonyl-CoA, and NADPH production. The signal toward NADPH production was particularly strong. Furthermore, the model reproduced the experimental findings that blocking the NADH shuttles attenuates the signaling to ATP production while retaining the rate of glucose oxidation (Eto K, Tsubamoto Y, Terauchi Y, Sugiyama T, Kishimoto T, Takahashi N, Yamauchi N, Kubota N, Murayama S, Aizawa T, Akanuma Y, Aizawa S, Kasai H, Yazaki Y, Kadowaki T. Science 283: 981 - 985, 1999) and provides an explanation for this apparent paradox. The model also predicts that the mitochondrial malate dehydrogenase reaction may proceed backward, toward malate production, if the activity of malic enzyme is sufficiently high. An increased fatty acid oxidation rate was found to attenuate the signaling strengths. This theoretical study has implications for our understanding of both the healthy and the diabetic beta-cell.

Place, publisher, year, edition, pages
2007. Vol. 292, no 2, E373-E393 p.
Keyword [en]
systems biology, potassium-dependent adenosine triphosphate channel-independent, pathway of insulin secretion, reduced nicotinamide adenine dinucleotide, diabetes, fatty acid oxidation
National Category
Computer and Information Science
URN: urn:nbn:se:kth:diva-6059DOI: 10.1152/ajpendo.00589.2005ISI: 000243997100002PubMedID: 16849626ScopusID: 2-s2.0-33846882164OAI: diva2:10653
QC 20100823 Uppdaterad från manuskript till artikel (20100823)Available from: 2005-09-07 Created: 2005-09-07 Last updated: 2012-01-08Bibliographically approved
In thesis
1. Models of the metabolism of the pancreatic beta-cell
Open this publication in new window or tab >>Models of the metabolism of the pancreatic beta-cell
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The pancreatic β-cell secretes insulin in response to a raised blood glucose level. Deficiencies in this control system are an important part of the etiology of diabetes. The biochemical basis of glucose-stimulated insulin secretion is incompletely understood, and a more complete understanding is an important component in the quest for better therapies against diabetes.

In this thesis, mathematical modeling has been employed in order to increase our understanding of the biochemical principles that underlie glucosestimulated insulin secretion of the pancreatic β-cell. The modeling efforts include the glycolysis in theβ-cell with particular emphasis on glycolytic oscillations. The latter have earlier been hypothesized to be the cause of normal pulsatile insulin secretion. This model puts this hypothesis into quantitative form and predicts that the enzymes glucokinase and aldolase play important roles in setting the glucose concentration threshold governing oscillations. Also presented is a model of the mitochondrial metabolism in the β-cell, and of the mitochondrial shuttles that connect the mitochondrial metabolism to the glycolysis. This model gives sound explanations to what was earlier thought to be paradoxical behavior of the mitochondrial shuttles during certain conditions. Moreover, it predicts a strong signal from glucose towards cytosolic NADPH formation, a putative stimulant of insulin secretion. The model also identifies problems with earlier interpretations of experimental results regarding the β- cell mitochondrial metabolism. As an aside, an earlier proposed conceptual model of the generation of oscillations in the TCA cycle is critically analyzed.

Further, metabolic control analysis has been employed in order to obtain mathematical expressions that describe the control by pyruvate dehydrogenase and fatty acid oxidation over different aspects of the mitochondrial metabolism and the mitochondrial shuttles. The theories developed explain recently observed behavior of these systems and provide readily testable predictions.

The methodological aspects of the work presented in the thesis include the development of a new generic enzyme rate equation, the generalized reversible Hill equation, as well as a reversible version of the classical general modifier mechanism of enzyme action.

Trita-NA, ISSN 0348-2952 ; 0527
Computer science
National Category
Computer Science
urn:nbn:se:kth:diva-408 (URN)91-7178-140-0 (ISBN)
Public defence
2005-09-23, D2, KTH huvudbyggnad, Lindstedtsv. 5, Stockholm, 12:15
Available from: 2005-09-07 Created: 2005-09-07 Last updated: 2012-03-22

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