We searched Pubmed using the following queries: “c-peptide and nephropathy and type 1 diabetes”, “c-peptide and retinopathy and type 1 diabetes”, “c-peptide and neuropathy and type 1 diabetes”, “c-peptide and microvascular complications and type 1 diabetes”, “c-peptide and macrovascular complications and type 1 diabetes”, “c-peptide replacement therapy and type 1 diabetes”, “c-peptide and Na+ K+ ATPase”, “c-peptide and eNOS”, “c-peptide and ERK”, and “c-peptide and GPR146”. Here, NOS3 is linked to type 1 diabetes mellitus.