Insulin" stimulated plasma membrane association and activation of Akt2, aPKC ζ and aPKC λ in high fat fed rodent skeletal muscle
Several recent reports using cell lines have suggested that both Akt and atypical protein kinase C (aPKC) ζ/λ 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 ζ and/or λ 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 ζ/λ. 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 ζ/λ activities were increased by insulin. PM‐associated aPKC ζ and λ, and aPKC ζ/λ 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 ζ or aPKC λ protein concentration. Insulin‐stimulated total PI3‐kinase, Akt2 and aPKC ζ/λ activities were reduced in the high fat fed animals. Insulin‐stimulated PM aPKC ζ, aPKC λ, aPKC ζ/λ 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 ζ and λ, but not Akt2, to the PM. In addition, high fat feeding impairs insulin‐stimulated activation of total aPKC ζ/λ and Akt2, as well as PM association and activation of aPKC ζ and λ.