In patients with type 1 diabetes mellitus in the DK/DKA group (Table 3, Fig. 2), the plasma glucagon level was positively correlated with plasma glucose, serum osmolality, and serum creatinine, whereas a negative correlation was seen with serum CPR (ρ = − 0.47, P = 0.016) and serum CPR/plasma glucose ratio (ρ = − 0.67, P = 0.0002). This evidence concerns the gene GCG and diabetes mellitus.