It now seems clear that aPKC (atypical protein kinase C) isoforms are required for insulin-stimulated glucose transport in muscle and adipocytes. Moreover, there are marked defects in the activation of aPKCs under a variety of insulin-resistant conditions in humans, monkeys and rodents. In humans, defects in aPKC in muscle are seen in Type II diabetes and its precursors, obesity, the obesity-associated polycystic ovary syndrome and impaired glucose tolerance. These defects in muscle aPKC activation are due to both impaired activation of insulin receptor substrate-1-dependent PI3K (phosphoinositide 3-kinase) and the direct activation of aPKCs by the lipid product of PI3K, PI-3,4,5-(PO4)3. Although it is still uncertain which underlying defect comes first, the resultant defect in aPKC activation in muscle most certainly contributes significantly to the development of skeletal muscle insulin resistance. Of further note, unlike the seemingly ubiquitous presence of defective aPKC activation in skeletal muscle in insulin-resistant states, the activation of aPKC is normal or increased in livers of Type II diabetic and obese rodents. The maintenance of aPKC activation in the liver may explain how insulin-dependent lipid synthesis is maintained in these states, as aPKCs function mainly in the activation of enzymes important for lipid synthesis. Thus increased activation of liver aPKC in hyperinsulinaemic states may contribute significantly to the development of hyperlipidaemia in insulin-resistant states.
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Conference Article|
April 01 2005
Atypical protein kinase C in insulin action and insulin resistance
R.V. Farese;
R.V. Farese
1
1Research Service, James A. Haley Veterans Administration Medical Center, and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL 33612, U.S.A.
1To whom correspondence should be addressed, at James A. Haley Veterans Administration Hospital, 13000 Bruce B. Downs Blvd, Tampa, FL 33612, U.S.A. (email rfarese@hsc.usf.edu).
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M.P. Sajan;
M.P. Sajan
1Research Service, James A. Haley Veterans Administration Medical Center, and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL 33612, U.S.A.
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M.L. Standaert
M.L. Standaert
1Research Service, James A. Haley Veterans Administration Medical Center, and Department of Internal Medicine, University of South Florida College of Medicine, Tampa, FL 33612, U.S.A.
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Publisher: Portland Press Ltd
Received:
November 01 2004
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2005 The Biochemical Society
2005
Biochem Soc Trans (2005) 33 (2): 350–353.
Article history
Received:
November 01 2004
Citation
R.V. Farese, M.P. Sajan, M.L. Standaert; Atypical protein kinase C in insulin action and insulin resistance. Biochem Soc Trans 1 April 2005; 33 (2): 350–353. doi: https://doi.org/10.1042/BST0330350
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