ADRB1 and type 2 diabetes mellitus: As presented in Figure 8 and Figure 9, the mRNA expression of salivary secretion pathway signaling molecules, including PKA, IP3R, β1-AR, AQP5, CHRM3, and AMY1, was significantly lower in the PG and SMG of T2DM rats than in those of CON rats, and the mRNA expression of inflammatory factors, such as IL-6 and TNF-α, was significantly higher in the PG and SMG of T2DM rats than in those of CON rats.