GCG and type 2 diabetes mellitus: In this regard, hormones such as insulin and glucagon [42,43], adipokines/lipokines (adiponectin [44], leptin [45], and adipsin [46]), metabolites (amino acids [42,47], such as alanine [48,49]), lipids, free fatty acids [49,50,51], and glucagon-like peptide-1 are known metabolic regulators that disturb metabolism by signaling to various nerves and are crucial for T2D [52].