Diverse roles for protein kinase C δ and protein kinase C ε in the generation of high-fat-diet-induced glucose intolerance in mice: regulation of lipogenesis by protein kinase C δ

This study aimed to determine whether protein kinase C (PKC) delta plays a role in the glucose intolerance caused by a high-fat diet, and whether it could compensate for loss of PKC epsilon in the generation of insulin resistance in skeletal muscle. Prkcd (-/-), Prkce (-/-) and wild-type mice were fed high-fat diets and subjected to glucose tolerance tests. Blood glucose levels and insulin responses were determined during the tests. Insulin signalling in liver and muscle was assessed after acute in vivo insulin stimulation by immunoblotting with phospho-specific antibodies. Activation of PKC isoforms in muscle from Prkce (-/-) mice was assessed by determining intracellular distribution. Tissues and plasma were assayed for triacylglycerol accumulation, and hepatic production of lipogenic enzymes was determined by immunoblotting. Both Prkcd (-/-) and Prkce (-/-) mice were protected against high-fat-diet-induced glucose intolerance. In Prkce (-/-) mice this was mediated through enhanced insulin availability, while in Prkcd (-/-) mice the reversal occurred in the absence of elevated insulin. Neither the high-fat diet nor Prkcd deletion affected maximal insulin signalling. The activation of PKC delta in muscle from fat-fed mice was enhanced by Prkce deletion. PKC delta-deficient mice exhibited reduced liver triacylglycerol accumulation and diminished production of lipogenic enzymes. Deletion of genes encoding isoforms of PKC can improve glucose intolerance, either by enhancing insulin availability in the case of Prkce, or by reducing lipid accumulation in the case of Prkcd. The absence of PKC epsilon in muscle may be compensated by increased activation of PKC delta in fat-fed mice, suggesting that an additional role for PKC epsilon in this tissue is masked.