VIP and diabetes mellitus: Wang et al. established a diabetic rat gastroenteropathy model with HS/HF combined with STZ, and after treatment with emodin (30, 60, and 90 mg/kg), the gastrointestinal transmission rate and serum substance P (SP) expression were increased, and serum vasoactive intestinal peptide (VIP) expression was decreased (Wang et al., 2023).