Study on the mechanism of carambola root in preventing and treating diabetes nephropathy based on network pharmacology
Diabetes nephropathy (DKD) is one of the major complications of diabetes and the primary cause of end-stage renal disease (ESRD) in developed countries and regions. At present, there is a lack of specific therapeutic drugs for DKD. In clinical practice, the progression of diabetic kidney disease (DKD) is mainly delayed by controlling blood glucose, blood pressure, blood lipids, uric acid, as well as using renin-angiotensin system inhibitors and drugs to improve renal microcirculation.

Chinese herbal medicine has shown good effects in the prevention and treatment of complex diseases due to its advantages of multiple components, pathways, and targets. We conducted research on several traditional Chinese herbs and their active ingredients for anti DKD in the early stage, and found that the root of Averrhoa carambola L. (RAC), a plant in the Oxalis family, showed good advantages in preventing and treating DKD, but the mechanism of action is unclear. Network pharmacology is a research method based on holism and systematicity, which combines drug targets with biological information networks, similar to the holistic and dialectical views proposed by traditional Chinese medicine. Based on this, we will use network pharmacology methods to construct common targets between the main components of Populus euphratica root and DKD, and explore the potential mechanism of action of Populus euphratica root in preventing and treating DKD.

DKD has a high prevalence rate and a high risk of cardiovascular and cerebrovascular complications, which is an important risk factor for death of diabetes patients. However, due to the complex mechanism of DKD, there has been no breakthrough in the treatment of DKD at present. Our research group has conducted extensive studies on the treatment of DKD with walnut root in the early stage. It was found that the improvement of complications related to diabetes and renal damage by carambola root and its main components may be related to the regulation of glucose and lipid metabolism disorders, insulin resistance and oxidative stress. Further investigation revealed that its mechanism of occurrence may be related to multiple signaling pathways such as TLR4/NF – κ B and TGF β/Smad2/3. However, the specific mechanism of action still needs further clarification.

Traditional Chinese medicine has the characteristics of complex ingredients and wide pharmacological effects. The prevention and treatment of DKD by walnut root depends on which active ingredients and their corresponding targets, which is the focus of our attention. Our research group conducted extraction, separation, purification, and analysis of the effective components of walnut roots in the early stage, and obtained a total of 24 active compounds. Among these compounds, we found that compound 2 (walnut root cyclohexanedione) plays an important role in the prevention and treatment of DKD and is a potential major active ingredient. However, further research is needed to determine whether other components play an important role in the prevention and treatment of DKD. Through network pharmacology screening, we found that in addition to cyclohexanedione from starfruit roots, components such as bitter melon glycoside C, cherry extract, and carotenoids are also associated with multiple key targets of DKD. It reminds us that these components also play an important role in the prevention and treatment of DKD, and further verification is needed in the future.

In terms of key target screening, we identified 10 key targets, including matrix metalloproteinase 9 (MMP9), matrix metalloproteinase 2 (MMP2), epidermal growth factor receptor (EGFR), fibroblast growth factor 2 (FGF2), signal transducer and activator of transcription 3 (STAT3), mitogen activated protein kinase 1 (MAPK1), vascular endothelial growth factor A (VEGFA), caspase 3 (CASP3), oncogene Hras (HRAS), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Among these 10 key targets, MMP2 and MMP9 are important members of matrix metalloproteinases, with their main substrates being type IV collagen in the extracellular matrix (ECM). Their functions are closely related to the dynamic balance of degradation and remodeling of ECM. DKD patients exhibit early clinical manifestations of ECM accumulation in the glomerular basement membrane and mesangial area. MMP9, MMP2, and their tissue inhibitory factors (TIMPs) play a crucial role in ECM degradation. In addition, MMP9 binds to CD44 to release stored TGF – β 1, and MMP9 can also participate in angiogenesis by releasing vascular endothelial growth factor (VEGF).

KEGG enrichment analysis showed that key targets were mainly enriched in proteoglycan and tumor, bladder cancer, tumor related microRNA, EGFR tyrosine kinase inhibitor resistance, cancer pathway, AGE-RAGE signaling pathway in diabetes complications, relaxin (belonging to insulin family) signaling pathway, Kaposi’s sarcoma associated herpesvirus infection, endocrine resistance, hypoxia inducible factor related signaling pathway. Among these signaling pathways, AGE-RAGE signaling pathway, relaxin signaling pathway, endocrine resistance, hypoxia inducible factors are closely related to the occurrence and development of diabetes.

Advanced glycation end products (AGEs) – receptor for advanced glycation end products (RAGEs) signaling pathway is an important link in the occurrence and development of diabetes nephropathy. During the occurrence and development of DKD, AGE-RAGE mainly activates NF – κ B, causing the expression and release of a large number of adhesion molecules, growth factors, pro-inflammatory cytokines, etc., ultimately leading to chronic cell activation and tissue damage. Our previous research also found that DMDD, an extract of carambola root, can prevent and treat complications related to diabetes by inhibiting the activation of NF – κ B, thereby alleviating a series of inflammatory damage. AGE-RAGE can also stimulate the expression of VEGF, thereby increasing vascular permeability and leading to proteinuria. Additionally, AGE-RAGE can stimulate the production of TGF – β 1 and induce an increase in the expression of monocyte chemoattractant protein MCP-1, leading to the occurrence and development of DKD. We verified this signal pathway through animal experiments. The protein expression of TGF β 1 and NF – κ B was significantly up-regulated in the diabetes model group. After the intervention of carambola root extract, their expression levels were both down regulated and showed a dose-dependent trend, suggesting that AGE-RAGE signal pathway plays an important role in the prevention and treatment of DKD by carambola root extract.

In summary, this study used network pharmacology methods to screen out the main active ingredients that exert pharmacological effects in walnut roots, including cyclohexanedione, bitter melon glycoside C, cherry blossom extract, and carotenoids. These active ingredients mainly participate in the AGE-RAGE signaling pathway, Relaxin signaling pathway, insulin resistance signaling pathway, and hypoxia inducible factor signaling pathway to prevent and treat DKD through key targets such as MMP9, MMP2, EGFR, FGF2, STAT3, MAPK1, VEGFA, and CASP3. Through this study, the main pharmacological components, targets, and related pathways of Populus euphratica root in the prevention and treatment of DKD were preliminarily elucidated. These studies not only mutually validate our research group’s previous research, but also provide ideas and directions for more subsequent research.