LEP and type 2 diabetes mellitus: Regarding the relationship between heavy metal toxicity and T2D, a longitudinal study reported the link between exposure to heavy metals (Pb, Hg, and Cd), renal dysfunction biomarkers (RBP, NAG, and KIM-1), and plasma indicators for T2D (AAAs, BCAAs, leptin, and adiponectin) (Valcke et al., 2019).