LEPR and type 2 diabetes mellitus: T2DM mice models are monogenic obese models (leptin receptor-deficient diabetic and obese (Leprdb/db and Lepob/ob) mice), polygenic obese models (Tsumura Suzuki obese diabetes (TSOD); Nagoya-Shibata-Yasuda (NSY); M16; C57Bl/6J; TallyHo/Jng and New Zealand obese (NZO) mice; Kuo Kondo (KK) mice; NoncNZO10/LtJ mice), and genetically-induced models of β-cell dysfunction (human islet amyloid peptide (hIAPP); AKITA and muscle insulin-like growth factor-1 receptor (IGF-1R)-lysine-arginine (MKR) mice) [38,39,40,41,42,44,45].