Study on the modulation of kidney and liver function of rats with diabetic nephropathy by Huidouba through metabolomics

Abstract

Ethnopharmacological relevance: Huidouba (HDB), a traditional Tibetan medicine, has been used for centuries in the Emei Mountain region of Sichuan, China, to treat diabetes and its complications. Known for its efficacy in nourishing kidney-Yin (kidney water) and regulating glucose and lipid metabolism, it is considered a"wonder drug"of Mount Emei.The study of Huidouba holds great significance for elucidating the mechanisms of action by which traditional Chinese and ethnic medicines treat diseases.

Aim of the study: To investigate the therapeutic effects and underlying mechanisms of Huidouba on diabetic nephropathy (DN) using metabolomic and molecular approaches.

Materials and methods: DN rat model was established using high fat diet and streptozotocin (STZ 30 mg/kg) injection. The 65 rats included in the study were divided into normal group, metformin positive control model group, HDB high dose group and HDB low dose group with 13 rats in each group by using random number table method.The rats in HDB treatment group were given a high dose (7.2 g/kg) and a low dose (3.6 g/kg) respectively for 8 weeks. Serum biochemical indices of rats were detected and histopathological analyses of liver, kidney and pancreas were performed. Metabolomics analysis of plasma was performed using UPLC-MS/MS technique. Western blot was used to analyse the expression of key proteins in the bile acid metabolic pathway.

Results: HDB administration modulated aberrant metabolic pathways in DN rats, leading to ameliorated hepato-renal functions. Notably, renal dysfunction markers were markedly attenuated: blood urea nitrogen (BUN) declined from 16.27 ± 3.32 mmol/L to 8.95 ± 1.24 mmol/L (HDBL) and 11.80 ± 1.52 mmol/L (HDBH), while serum creatinine (SCr) reduced from 56.00 ± 15.96 μmol/L to 28.75 ± 2.33 μmol/L (HDBL) and 28.01 ± 2.93 μmol/L (HDBH). Albumin-to-creatinine ratio (ACR-8) dropped from 7.68 ± 2.44 mg/g (Model) to 4.39 ± 0.92 mg/g (HDBL) and 5.20 ± 1.80 mg/g (HDBH), indicating preserved glomerular filtration.Hepatoprotective effects were evident, with alanine aminotransferase (ALT) levels decreasing from 148.6 ± 63.73 μmol/L (Model) to 90.45 ± 20.35 μmol/L (HDBL) and 82.67 ± 19.55 μmol/L (HDBH). Aspartate aminotransferase (AST) levels also trended downward (Model: 253.6 ± 225.9 μmol/L vs. HDBH: 147.5 ± 42.18 μmol/L). Histologically, HDB treatment reduced inflammatory infiltration in the liver, kidney, and pancreatic islets, alongside ameliorated tissue degeneration, including a significant reduction in renal fibrosis (renal fibrotic area percentage in the Model group was approx. 13.32 %, which decreased to approx. 7.31 % and 8.68 % in the HDB low and high dose groups, respectively). Untargeted metabolomics revealed upregulated bile acid metabolism pathways (Cholesterol 7alpha-hydroxylase (CYP7A1) and Farnesoid X receptor (FXR/NR1H4)), correlating with improved glucose-lipid homeostasis and attenuated oxidative stress.

Conclusions: The results of the study showed that both high- and low-dose HDB treatments effectively influenced key parameters in DN rats. High-dose HDB demonstrated superior efficacy in reducing total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), and ALT levels, while significantly elevating high-density lipoprotein-cholesterol (HDL-C) and insulin (INS) levels compared to the low-dose group. In contrast, low-dose HDB showed a more pronounced reduction in BUN. These findings indicate complex dose-related protective effects. While low-dose HDB showed a more pronounced reduction in BUN and renal fibrosis, high-dose HDB exhibited stronger regulation of glucose-lipid metabolism and insulin secretion. This latter effect involving glucose-lipid homeostasis is likely mediated through its more pronounced modulation of bile acid pathways (e.g., CYP7A1 and NR1H4 upregulation by high-dose HDB). Both doses alleviated liver damage by reducing ALT and AST levels, though high-dose HDB achieved a more significant reduction in hepatic steatosis and inflammatory infiltration. HDB not only improved renal function in DN rats (e.g., BUN decreased from 16.27 mmol/L in the Model group to 8.95 mmol/L in the HDBL group and 11.80 mmol/L in the HDBH group), but also significantly improved renal tissue structure, with quantitative Masson staining analysis showing a reduction in renal fibrotic area from 13.32 % in the Model group to approximately 7.31 % in the HDBL group and 8.68 % in the HDBH group, respectively. HDB demonstrated potential in regulating glucolipid metabolism and protecting the liver. The dose-dependent efficacy observed, particularly concerning these aspects of glucolipid metabolism and certain liver parameters where the high dose showed greater improvements, appears consistent with the trend for high-dose HDB to more strongly modulate bile acid signaling markers (such as CYP7A1 and NR1H4), a key pathway in metabolic regulation, suggesting a potential association.Furthermore, HDB modulates altered metabolic states by modulating the abnormal bile acid metabolism pathway associated with Type 2 Diabetes Mellitus (T2DM). Therefore, we believe that HDB is a promising ethnopharmaceutical for the amelioration of T2DM.

Keywords: Bile acids; Diabetes mellitus; Diabetic nephropathy; Huidouba; Metabolomics; Tibetan medicine.