Connexins, diabetes and the metabolic syndrome

Diabetes and the related metabolic syndrome are multi system disorders that result from improper interactions between various cell types. Even though the underlying mechanism remains to be fully understood, it is most likely that both the long and the short distance range cell interactions, which normally ensure the physiologic functioning of the pancreas, and its relationships with the insulin-targeted organs, are altered. This review focuses on the short-range type of interactions that depend on the contact between adjacent cells and, specifically, on the interactions that are dependent on connexins. The widespread distribution of these membrane proteins, their multiple modes of action, and their interactions with conditions/molecules associated to both the pathogenesis and the treatment of the 2 main forms of diabetes and the metabolic syndrome, make connexins an essential part of the chain of events that leads to metabolic diseases. Here, we review the present state of knowledge about the molecular and cell biology of the connexin genes and proteins, their general mechanisms of action, the roles specific connexin species play in the endocrine pancreas and the major insulin-targeted organs, under physiological and patho-physiological conditions.