biology Review Emerging Roles of Metallothioneins in Beta Cell Pathophysiology: Beyond and above Metal Homeostasis and Antioxidant Response Mohammed Bensellam 1,* , D. Ross Laybutt 2,3 and Jean-Christophe Jonas 1 1 Pôle D’endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, B-1200 Brussels, Belgium;
[email protected] 2 Garvan Institute of Medical Research, Sydney, NSW 2010, Australia;
[email protected] 3 St Vincent’s Clinical School, UNSW Sydney, Sydney, NSW 2010, Australia * Correspondence:
[email protected]; Tel.: +32-2764-9586 Simple Summary: Defective insulin secretion by pancreatic beta cells is key for the development of type 2 diabetes but the precise mechanisms involved are poorly understood. Metallothioneins are metal binding proteins whose precise biological roles have not been fully characterized. Available evidence indicated that Metallothioneins are protective cellular effectors involved in heavy metal detoxification, metal ion homeostasis and antioxidant defense. This concept has however been challenged by emerging evidence in different medical research fields revealing novel negative roles of Metallothioneins, including in the context of diabetes. In this review, we gather and analyze the available knowledge regarding the complex roles of Metallothioneins in pancreatic beta cell biology and insulin secretion. We comprehensively analyze the evidence showing positive effects Citation: Bensellam, M.; Laybutt, of Metallothioneins on beta cell function and survival as well as the emerging evidence revealing D.R.; Jonas, J.-C. Emerging Roles of negative effects and discuss the possible underlying mechanisms. We expose in parallel findings Metallothioneins in Beta Cell from other medical research fields and underscore unsettled questions.