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¹ Exercise Biochemistry Laboratory, Department Of Kinesiology, College of Health and Human Development, California State University, Northridge, CA, USA

Several recent reports using cell lines have suggested that both Akt and atypical protein kinase C (aPKC) / are translocated to the plasma membrane (PM) in response to insulin. However, it has yet to be determined in skeletal muscle whether: (1) insulin increases PM-associated Akt2, aPKC and/or protein concentration, (2) the activity of these kinases is altered by insulin at the PM, and (3) high fat feeding alters the insulin-stimulated PM concentration and/or activity of Akt2 and aPKC /. Sprague-Dawley rats were randomly assigned to either normal (n = 16) or high fat (n = 16) dietary groups. Following a 12 week dietary period, animals were subjected to hind limb perfusions in the presence (n = 8 per group) or absence (n = 8 per group) of insulin. In normal skeletal muscle, total PI3-kinase, Akt2 and aPKC / activities were increased by insulin. PM-associated aPKC and , and aPKC / activity, but not Akt2 or Akt2 activity, were increased by insulin in normal muscle. High fat feeding did not alter total skeletal muscle Akt2, aPKC or aPKC protein concentration. Insulin-stimulated total PI3-kinase, Akt2 and aPKC / activities were reduced in the high fat fed animals. Insulin-stimulated PM aPKC , aPKC , aPKC / activity and GLUT4 protein concentration were also reduced in high fat fed animals. These findings suggest that in skeletal muscle, insulin stimulates translocation of aPKC and , but not Akt2, to the PM. In addition, high fat feeding impairs insulin-stimulated activation of total aPKC / and Akt2, as well as PM association and activation of aPKC and .

(Received 14 March 2005; accepted after revision 30 March 2005; first published online 31 March 2005)
Corresponding author B. B. Yaspelkis III: Department of Kinesiology, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330-8287, USA. Email: ben.yaspelkis{at}csun.edu

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