Role of PKCzeta translocation in the development of type 2 diabetes in rats following continuous glucose infusion.
OBJECTIVE
We investigated the molecular mechanisms of hyperglycaemia-induced insulin resistance and type 2 diabetes in rats receiving a continuous glucose infusion (GI).


METHODS
Female Wistar rats were infused with either 2.8 mol/L glucose or saline (2 mL/h) for durations varying from 0 to 15 days. Blood samples were analysed daily to determine glucose and insulin dynamics. Subsets of animals were sacrificed and soleus muscles were extracted for determination of protein expression, subcellular location, and activities of insulin-signalling proteins.


RESULTS
Rats accommodated this systemic glucose oversupply and developed insulin resistance on day 5 (normoglycaemia/hyperinsulinaemia) and type 2 diabetes on day 15 (hyperglycaemia/normoinsulinaemia). The effect of GI on protein kinase Czeta (PKCzeta) activity was independent of changes in phosphatidylinositol 3-kinase activity, and occurred in parallel with an increase in PDK1 activity. Activated PKCzeta was mainly located in the cytosol after 5 days of GI that was coincident with the translocation of GLUT4 to the plasma membrane, and normoglycaemia. After 15 days of GI, PKCzeta translocated from the cytosol to the plasma membrane with a concomitant decrease in PDK1 activity. This caused an increase in the association between PKCzeta and PKB and a decrease in PDK1-PKB reactions at the plasma membrane, leading to reduced PKB activity. The activity of PKCzeta per se was also compromised. The PKCzeta and PKB activity reduction and the blunted insulin-stimulated GLUT4 translocation eventually led to hyperglycaemia and diabetes.


CONCLUSIONS
Translocation of PKCzeta may play a central role in the development of type 2 diabetes.
Zhang
Jing-fang
JF
Department of Pathophysiology, Medical College, Wuhan University, Wuhan, Hubei, China.
Yang
Jing-ping Ou
JP
Wang
Guang-hao
GH
Xia
Zhengyuan
Z
Duan
Sheng Zhong
SZ
Wu
Yong
Y
D000818:Animals; D003924:Diabetes Mellitus, Type 2 / Q000201:enzymology*; D005260:Female; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006614:Hindlimb; D007262:Infusions, Intravenous; D007333:Insulin Resistance / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051381:Rats; D017208:Rats, Wistar; D000099221:Protein Kinase C zeta
D005947:Glucose; D051275:Glucose Transporter Type 4; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D000099221:Protein Kinase C zeta; C000631434:Pdk1 protein, rat