Expression of Protein Kinase C Isoforms in Pancreatic Islets and Liver of Male Goto- Kakizaki Rats, a Model of Type 2 Diabetes

Abstract

Protein kinase C (PKC) is a family of protein kinases controlling protein phosphorylation

and playing important roles in the regulation of metabolism. We have investigated expres- sion levels of PKC isoforms in pancreatic islets and liver of diabetic Goto-Kakizaki (GK) rats

with and without insulin treatment to evaluate their association with glucose homeostasis. mRNA and protein expression levels of PKC isoforms were assessed in pancreatic islets and liver of Wistar rats and GK rats with or without insulin treatment. PKCα and PKCζ mRNA expressions were down-regulated in islets of GK compared with Wistar rats. PKCα and phosphorylated PKCα (p-PKCα) protein expressions were decreased in islets of GK compared with insulin-treated GK and Wistar rats. PKCζ protein expression in islets was reduced in GK and insulin-treated GK compared with Wistar rats, but p-PKCζ was decreased only in GK rats. Islet PKCε mRNA and protein expressions were lower in GK

compared with insulin-treated GK and Wistar rats. In liver, PKCδ and PKCζ mRNA expres- sions were decreased in both GK and insulin-treated GK compared with Wistar rats. Hepatic

PKCζ protein expression was diminished in both GK rats with and without insulin treatment

compared with Wistar rats. Hepatic PKCε mRNA expression was down-regulated in insulin- treated GK compared with GK and Wistar rats. PKCα, PKCε, and p-PKCζ expressions were

secondary to hyperglycaemia in GK rat islets. Hepatic PKCδ and PKCζ mRNA expressions were primarily linked to hyperglycaemia. Additionally, hepatic PKCε mRNA expression could be under control of insulin.