INS and diabetes mellitus: DM can be categorized into four types: Type 1 DM (T1DM) caused by autoimmune destruction of β-cells, Type 2 DM (T2DM) due to impaired insulin secretion and the insensitivity of target tissues to insulin, gestational diabetes mellitus (GDM), and a fourth category that includes less common types of DM (caused by genetic mutations and drug exposure) [5,6].