MTNR1B and type 2 diabetes mellitus: Rather, α-cell activation might play a prerequisite role in β-cell activation: (i) without the involvement of MT1, melatonin treatment would not yield significant effects on insulin release [37], and (ii) several single nucleotide polymorphisms in the MTNR1B gene, which encodes for MT2, are implicated in the pathogenesis of T2D [39].