The circadian rhythm regulates biological processes that occur within 24 h in living organisms. It plays a fundamental role in maintaining biological functions and responds to several inputs, including food intake, light/dark cycle, sleep/wake cycle, and physical activity. The circadian timing system comprises a central clock located in the suprachiasmatic nucleus (SCN) and tissue-specific clocks in peripheral tissues. Several studies show that the desynchronization of central and peripheral clocks is associated with an increased incidence of insulin resistance (IR) and related diseases. In this review, we discuss the current knowledge of molecular and cellular mechanisms underlying the impact of circadian clock dysregulation on insulin action. We focus our attention on two possible mediators of this interaction: the phosphatases belonging to the pleckstrin homology leucine-rich repeat protein phosphatase family (PHLPP) family and the deacetylase Sirtuin1. We believe that literature data, herein summarized, suggest that a thorough change of life habits, with the return to synchronized food intake, physical activity, and rest, would doubtless halt the vicious cycle linking IR to dysregulated circadian rhythms. However, since such a comprehensive change may be incompatible with the demand of modern society, clarifying the pathways involved may, nonetheless, contribute to the identification of therapeutic targets that may be exploited to cure or prevent IR-related diseases.
Keywords: circadian clock; insulin sensitivity; insulin signaling; peripheral tissues.