Diabetes remains an insurmountable problem worldwide28. Chinese herbal medicine has been handed down in China for thousands of years and has a deep historical heritage. A large number of ancient texts on Chinese medicine have clearly documented the effects of herbs to improve diabetes, such as ginseng29, 30.
There is increasing evidence that ginsenosides have anti-diabetic and insulin-sensitizing properties. At the same time, ginsenosides not only have the effects of lowering blood sugar, improving insulin sensitivity, and regulating lipid metabolism but also can alleviate the occurrence of Diabetes Mellitus type 2 (T2DM) 31, 32.
Our group conducted some research on ginsenosides to improve diabetes. The ginsenoside 20(S)-Ginsenoside Rg3 had a protective effect on animal model diabetes by regulating the MAPK/NF-κB signaling pathway33. Rh1 ameliorates T2DM through AMPK/PI3K/Akt-mediated inflammatory and apoptosis signaling pathways12. The malonyl ginsenosides significantly reduced the fasting blood glucose, triglyceride, total cholesterol, low-density lipoprotein cholesterol levels, etc., and improved glucose tolerance and insulin resistance34, 35. The results showed that the hypoglycemic and insulin-sensitizing capabilities of Compound K (CK) on type 2 diabetes induced by HFD/STZ via down-regulation of PEPCK and G6Pase expression in the liver36. We found that CK could provide beneficial anti-diabetic effects in T2DM mice, and this protective effect may be mediated by preventing β-cell apoptosis by inhibiting the AMPK-JNK pathway37. The predicted results of the present work almost coincide with the findings of our group.
The results of KEGG signalling pathway enrichment analysis indicated that the above signalling pathway might be a significant signalling pathway for ginsenosides to improve diabetes. However, whether the unreported saponins in ginseng can improve diabetes mellitus and its mechanism of action are still unclear. Therefore, this study aimed to investigate the improving effects of ginsenosides on diabetes and their possible mechanisms of action based on network pharmacology and the molecular docking methodology.
As seen above, ginsenosides, as the main active ingredient, can be effective against diabetes. These previous reports provide sufficient support for our next step to explore the molecular mechanism of components obtained from ginseng to improve diabetes. In this work, the ginsenosides and their action targets were collected by data mining. In the Venn diagram of the intersection of components in ginseng and diabetes, 99 cross targets of protein-protein, and 9 core targets were screened by Cytoscape 3.7.0 software. VEGFA plays a major role in endothelial cell growth and angiogenesis and is an essential factor. There were considerable evidence that when diabetes occurs it often lead to overexpression of VEGFA, which can have a detrimental effect on the body38, 39. TNF is an important pro-inflammatory factor that can improve diabetes by reducing insulin signaling through phosphorylation of serine40. Moreover, TNF is closely associated with diabetic nephropathy and vascular dysfunction41.
The results of BP results showed that the ginsenosides were related to the process of positive regulation of protein STK activity, positive regulation of MAP kinase activity, regulation of lipid metabolic process, and positive regulation of reactive oxygen species metabolic process, etc. A lot of evidence has shown that oxidative stress damage leads to lipid peroxidation. Lipid peroxidation causes the rearrangement of peroxyl radicals which can lead to a large of pathological changes in the body. The occurrence of diabetes often leads to an abnormally high expression of reactive oxygen species (ROS). This can accelerate the onset of cardiovascular disease in diabetes. Many studies have confirmed that during the development of diabetes, a shift in glycolytic metabolism occurs, which lead to an overproduction of ROS in monocytes and macrophages. Furthermore, macrophages were produced in large numbers when diabetes occurs, releasing excessive amounts of pro-inflammatory factors and proteases that lead to inflammation. Because ROS were important mediators in the activation of pro-inflammatory signaling pathways, obesity- and hyperglycemia-induced ROS overproduction may favor the induction of M1-like pro-inflammatory macrophages during the onset and progression of diabetes42, 43. This will lead to further deterioration of the disease. These conditions increased the likelihood of cardiovascular disease in people with diabetes. When a patient suffers from concomitant cardiovascular disease, it was not conducive to the improvement of diabetes, forming a vicious circle.44. Fortunately, we found that ginsenosides may have a certain regulatory effect on the regulation of blood vessel diameter and vascular process in the circulatory system. When diabetes occurs, the body's skin healing ability is greatly reduced45. BP results show that ginsenosides have a regulatory effect on epithelial cell proliferation. This BP may improve diabetes-induced skin healing difficulties.
These BP were mainly closely related to the molecular functions of steroid binding, steroid hormone receptor activity, and adrenergic receptor activity. And that mainly occur in the mitochondrial outer membrane, an integral component of the presynaptic membrane, neuronal cell body, etc.
Ginsenosides might be involved in a wide range of BP in improving diabetes and its complications, and these BP are closely related to a variety of molecular functions and cellular components. Overall, our GO results clearly indicated that ginseng could be used to improve diabetes by modulating BP to ultimately improve it.
A lot of evidence shown that when diabetes occurs, it tends to cause a series of symptoms such as obesity, insufficient insulin secretion, inflammation, elevated cholesterol, and hardened blood vessels. Our KEGG enrichment analysis showed that insulin, AGE-RAGE, TNF, AMPK, VEGF, adipocyte factor, HIF-1, and PI3K-Akt signaling pathway might be the major signaling pathways12, 37. The HIF-1 pathway was a well-known regulator of cellular glucose46. When diabetics were exposed to a hypoxic environment, HIF was activated and this led to the release of large amounts of inflammatory factors from damaged organs47, 48. Diabetic patients often had a condition with elevated pro-inflammatory factors, such as TNF. TNF mediated inflammation, obesity, and insulin resistance were associated with diabetes49. It had been reported that the PI3K/AKT signalling pathway is activated when HKC cells were exposed to a high glucose environment. This promoted islet cell proliferation50. Ultimately it was beneficial for diabetes to improve. Overall, our results suggested that ginsenosides could act on multiple targets and in multiple pathways.
Our findings showed that ginsenosides might regulate the above signaling pathways by acting on Caspase 3, MTOR, VEGFA, MAPK1, JUN, TNF, STAT3, IL-1B, EGFR and other targets, thereby improving diabetes51, 52. When the binding energy of the receptor protein and the small molecule fraction is less than 0 kcal/mol, it indicates that the two can bind together, and when the binding energy is less than − 7.0kcal/mol, it indicates that the two can bind together more stably21. Our results show 224 molecular dockings with binding energies less than − 7.0 kmol/mol, which accounts for 89.2% of all docking results. This showed that the ginsenosides in ginseng could bind well to the nine core genes. Ginsenosides bind to core targets in a variety of ways, mainly hydrogen bonds, as we know that the binding energy of molecular docking is determined by both the receptor protein and the small molecule ligand. However, it is not clear which of the two has a greater impact on binding energy. In this part of the results, we found that receptor proteins had the greatest effect on the binding energy. The conformation and relative molecular mass of small molecules such as S- or R-type receptors had no significant effect on the binding energy. Although further investigation is needed to obtain more reliable conclusions, these results give us an important hint. Combined with the results of molecular docking implied that ginsenosides have some targeting to the receptor protein. To some extent, it can explain that ginsenosides can improve diabetes with certain targeting properties.
So far, more than 100 ginsenosides have been identified. Our prediction results indicated that 28 saponins had an anti-diabetic effect53. The predicted amount of saponins accounted for about 1/4 of the total. The remaining unpredicted ginsenosides may also have anti-diabetic effects. The reason for this could be the low OB and DL of other ginsenosides or their unclear target. However, compared with the existing reports, our predicted ginsenosides are relatively comprehensive and the mechanism of action is relatively systematic. Meanwhile, ginseng polysaccharide components have been shown to improve diabetes, but due to some limitations, these components could not be analyzed by network pharmacology54. This type of active ingredient still needs further research. Overall, the application of network pharmacology allowed the mechanisms of action of traditional Chinese medicine in the treatment of disease to be explored at the molecular level. It was more systematic to provide valid evidence and basis for the improvement of diabetes by ginseng. However, there were shortcomings, such as lesser reported herbs not being searchable, less comprehensive targets for some ingredients, and less software available to correspond to them.
In conclusion, our findings clearly indicated that the improved results of 28 ginsenosides in ginseng on diabetes were through a multi-component, multi-target, multi-pathway overall regulation. The process involved 99 relevant targets, 2238 GO terms and 169 signaling pathways. This result was consistent with traditional Chinese medicine theory. Among the 28 ginsenosides, PPT, Rh1, Rh2, Rh4, Ro, Rg1, and PPD interacted with more targets, BP, and signaling pathways. We speculated that these seven saponins might play a significant role in improving diabetes. A comparison with the literature and docking verification showed the authenticity and reliability of our results.