BuZhong YiQi Formula Alleviates Diabetes-Caused Hyposalivation by Activating Salivary Secretion Pathway in the Parotid and Submandibular Glands of Rats.

Background/Objectives: BuZhong Yiqi Formula (BZYQF) has significant ameliorative effects on type 2 diabetes mellitus (T2DM). However, its efficacy in alleviating the hyposalivation caused by T2DM needs to be confirmed, and its mechanism is unclear. Methods: Network pharmacology and molecular docking were combined to analyze the molecular mechanism by which BZYQF alleviates T2DM-caused hyposalivation. A T2DM rat model was induced to evaluate the efficacy of BZYQF. The total saliva before and after acid stimulation was collected to determine the salivary flow rate and salivary alpha-amylase (sAA) activity. The parotid (PG) and submandibular glands (SMG) of experimental rats were removed to perform histopathology observation, biochemical indicator determination, and expression detection of signaling molecules in the salivary secretion pathway. Results: The present study screened out 1014 potential targets of BZYQF regarding the treatment of T2DM. These targets were mainly involved in the formation of the receptor complex, exercising the neurotransmitter receptor activity and regulating secretion. They were significantly enriched in the salivary secretion pathway of β1-AR/PKA/AMY1 and CHRM3/IP3R/AQP5. Furthermore, in BZYQF, nine validated compounds were able to dock into the active site of β1-AR, and three validated compounds were able to dock into the active site of CHRM3. Animal experiments confirmed that BZYQF significantly reduces fasting blood glucose, total cholesterol and triglyceride levels; enhances insulin level and HOMA-IS (p < 0.05); and increases salivary flow rate (Basal: increase from 21.04 ± 14.31 to 42.65 ± 8.84 μL/min, effect size of Cohen's d = 6.80, p = 0.0078; Stimulated: increase from 36.88 ± 17.48 to 72.63 ± 17.67 μL/min, effect size of Cohen's d = 7.61, p = 0.0025) and sAA activity (Basal: increase from 0.68 ± 0.32 to 2.17 ± 0.77 U/mL, effect size of Cohen's d = 9.49, p = 0.0027; Stimulated: increase from 1.15 ± 0.77 to 4.80 ± 1.26 U/mL, effect size of Cohen's d = 13.10, p = 0.0001) in basal and stimulated saliva in T2DM rats. Further mechanistic studies revealed that BZYQF reduces glucose and lipid accumulation, enhances acetylcholine content, improves pathological lesions and inflammation, and significantly increases the expression of salivary secretion pathway signaling molecules, including PKA, IP3R, β1-AR, AQP5, CHRM3, and AMY1 in the PG and SMG of T2DM rats (p < 0.05). Conclusions: The present study demonstrated that BZYQF is able to alleviate T2DM-caused hyposalivation by improving glucose metabolism and activating the salivary secretion pathway in the PG and SMG of T2DM rats. This study might provide a novel rationale and treatment strategy for BZYQF in diabetes-induced hyposalivation in a clinical setting.