Abstract: Objective To explore the protective effect and underlying mechanism of Twenty-One-Ingredient Shenqi pills (SQW) against renal injury in diabetic kidney disease (DKD) rats based on the advanced glycation end products (AGEs)/receptor for advanced glycation end products (RAGE) signaling pathway. Methods A DKD rat model was established by feeding high-glucose and high-fat diet for 6 consecutive weeks combined with intraperitoneal injection of streptozotocin (STZ). Rats were randomly divided into a normal group, model group, SQW group, irbesartan (EBST) group, and SQW combined with EBST (SQW+EBST) group, with 8 rats in each group. Except the normal group and model group, all these groups were given intragastric perfusion of SQW (6.3 g·kg^-1·d^-1), irbesartan (15.75 mg·kg^-1·d^-1), and SQW (6.3 g·kg^-1·d^-1) combined with irbesartan (15.75 mg·kg^-1·d^-1), respectively. The normal group and model group were given an equal volume of distilled water by gavage once a day for 12 consecutive weeks. The general conditions of rats during the experiment were observed and recorded, fasting blood glucose (FBG) was detected, and urine was collected with metabolic cages to determine 24-hour urinary total protein (24h-UTP) levels. After anesthesia, blood was collected from the abdominal aorta to separate serum, and renal tissues were harvested and weighed to calculate renal indexes. The serum levels of blood urea nitrogen (BUN), serum creatinine (SCr), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were detected. The contents of malondialdehyde (MDA) and superoxide dismutase (SOD) in renal tissues were determined. HE staining and Masson staining were used to observe the pathomorphological changes of renal tissues in each group. The mRNA expression level of RAGE in renal tissues was detected by qRT-PCR, and the protein expression levels of AGEs and RAGE were determined by Western Blot. Results Compared with the normal group, rats in the model group presented with poor mental state, sluggish response, reduced activity, emaciation, withered and yellow hair, and significantly increased daily water intake, food intake and urine output. In the model group, the levels of FBG, renal indexes, BUN, SCr, 24h-UTP, MDA, IL-6, TNF-α, as well as the mRNA and protein expression of AGEs and RAGE in renal tissues were significantly increased to varying extents (P<0.01 or P<0.001), while body weight and SOD levels were significantly decreased (P<0.001). Pathologically, the glomerular volume was increased, basement membrane thickened, and mesangial proliferation and glomerular collagen hyperplasia occurred in the model group. Compared with the model group, the levels of FBG, renal indexes, BUN, SCr, 24h-UTP, MDA, IL-6, TNF-α, and the mRNA and protein expression levels of AGEs and RAGE in the SQW group, EBST group and SQW+EBST group were significantly decreased (P<0.05, P<0.01 or P<0.001), body weight and SOD levels were significantly increased (P<0.05, P<0.01 or P<0.001), and the renal pathological damage was alleviated correspondingly after 12 weeks of continuous intragastric administration. These improvements were the most pronounced in the SQW+EBST group, which was superior to SQW alone and EBST alone. Conclusion Twenty-One-Ingredient Shenqi pills can effectively protect the kidney and delay the progression of DKD by inhibiting the activation of the AGEs/RAGE signaling pathway, suppressing oxidative stress and inflammatory response, mitigating renal pathological damage and improving proteinuria. Moreover, the combined use of traditional Chinese medicine and Western medicine is superior to single drug use.

Key words: Twenty-One-Ingredients Shenqi Pill, Diabetic Kidney Disease (DKD), Advanced Glycation End Products (AGEs), Receptor for Advanced Glycation End Products (RAGE), AGEs/RAGE Signaling Pathway, Oxidative Stress, Inflammation, Rats