HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Milne, H. M. Articles by Persaud, S. J. Search for Related Content PubMed PubMed Citation Articles by Milne, H. M. Articles by Persaud, S. J. Social Bookmarking                What's this?

Uncoupling of Nutrient Metabolism From Insulin Secretion by Overexpression of Cytosolic Phospholipase A₂

¹ Beta Cell Development and Function Group, Division of Reproductive Health, Endocrinology and Development, King’s College London, London, U.K
² Biological Sciences, University of Warwick, Warwick, U.K
³ Metabolic Unit, Guy’s King’s and St. Thomas’ School of Medicine, King’s College London, London, U.K

We have generated MIN6 ß-cells that stably overexpress cytosolic phospholipase A₂ (cPLA₂) and show a ninefold increase in cPLA₂ activity. Overexpression of cPLA₂ did not affect the capacity of MIN6 cells to show elevations in intracellular Ca²⁺ concentration ([Ca²⁺]_i) in response to tolbutamide and KCl, and these depolarizing stimuli produced insulin secretion profiles in cPLA₂-overexpressing cells similar to those they produced in passage-matched nontransfected MIN6 cells. However, cPLA₂-overexpressing MIN6 cells did not respond to elevations in extracellular glucose with increases in ATP, [Ca²⁺]_i, or insulin secretion. Nontransfected MIN6 cells showed a rapid and sustained increase in NAD(P)H autofluorescence in response to 25 mmol/l glucose, and this was reduced by 95% in MIN6 cells overexpressing cPLA₂. This effect was mimicked in nontransfected MIN6 cells by p-(trifluoromethoxy) phenylylhydrazone, a mitochondrial uncoupler. Quantitative RT-PCR indicated that mRNA for uncoupling protein-2 (UCP-2) was increased in the cPLA₂-overexpressing MIN6 cells, and this could be prevented by exposure to 100 µmol/l methyl arachidonyl fluorophosphate, a cPLA₂ inhibitor. Glucose caused a decrease in rhodamine 123 fluorescence in control cells, but not in those overexpressing cPLA₂, consistent with the transfected cells being unable to maintain mitochondrial proton gradients as a consequence of UCP-2 upregulation. Our data indicate that overexpression of cPLA₂ results in severe impairment of the calcium and secretory responses of ß-cells to glucose through upregulation of UCP-2 and uncoupling of mitochondrial metabolism from ATP generation.

CiteULike    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				C. J. Nolan, M. S.R. Madiraju, V. Delghingaro-Augusto, M.-L. Peyot, and M. Prentki Fatty Acid Signaling in the {beta}-Cell and Insulin Secretion Diabetes, December 1, 2006; 55(Supplement_2): S16 - S23. [Abstract] [Full Text] [PDF]

				M. C Saleh, M. B Wheeler, and C. B Chan Endogenous islet uncoupling protein-2 expression and loss of glucose homeostasis in ob/ob mice. J. Endocrinol., September 1, 2006; 190(3): 659 - 667. [Abstract] [Full Text] [PDF]