The role of protein kinase C (PKCs) isoforms in the regulation of glucose metabolism by insulin is complex, partly due to the large PKC family consisting of three sub-groups: conventional, novel and atypical. Activation of some conventional and novel PKCs in response to increased levels of diacylglycerol (DAG) have been shown to counteract insulin signalling. However, roles of atypical PKCs (aPKCs) remain poorly understood. aPKCs act as molecular switches by promoting or suppressing signalling pathways, in response to insulin or ceramides respectively. Understanding how DAG- and ceramide-activated PKCs impair insulin signalling would help to develop treatments to fight insulin resistance.