Immunoregulatory Effect of Acanthopanax trifoliatus (L.) Merr. Polysaccharide on T1DM Mice

Abstract

Background

Acanthopanax trifoliatus (L.) Merr. is a medicinal plant found in Southeast Asia, and its young leaves and shoots are consumed as a vegetable. The main bioactive components of this herb are polysaccharides that have significant anti-diabetic effects. The aim of this study was to evaluate the immunoregulatory effect of A. trifoliatus (L.) Merr. polysaccharide (ATMP) on a mouse model of type 1 diabetes mellitus (T1DM).

Methods

The monosaccharide composition and mean molecular mass of ATMP were determined by HPLC and HPGPC. T1DM was induced in mice using STZ, and 35, 70 and 140mg/kg ATMP was administered daily via the intragastric route for six weeks. Untreated and metformin-treated positive control groups were also included. The body weight of the mice, food and water intake and fasting glucose levels were monitored throughout the 6-week regimen. Histological changes in the pancreas and spleen were analyzed by H&E staining. Oral glucose tolerance was evaluated with the appropriate test. Peroxisome proliferator-activated receptor γ (PPARγ) mRNA and protein levels in the spleen were measured by quantitative real time PCR and Western blotting. IL-10, IFN-γ and insulin levels in the sera were determined by ELISA. The CD4⁺ and CD8⁺T cells in spleen tissues were detected by immunohistochemistry (IHC).

Results

ATMP and metformin significantly decreased fasting blood glucose, and the food and water intake after 6 weeks of treatment. In contrast, serum insulin levels, glucose tolerance and body weight improved considerably in the high and medium-dose ATMP and metformin groups. T1DM was associated with pancreatic and splenic tissue damage. The high dose (140mg/kg) of ATMP reduced infiltration of inflammatory cells into the pancreas and restored the structure of islet β-cells in the diabetic mice. Consistent with this, 35, 70 and 140mg/kg ATMP increased IL-10 levels and decreased that of IFN-γ, thereby restoring the CD4⁺/CD8⁺ and Th1/Th2 cytokine ratio. At the molecular level, high-dose ATMP up-regulated PPARγ in the splenic cells.

Conclusion

ATMP exerts a hypoglycemic effect in diabetic mice by restoring the immune balance in the spleen.

Keywords:

• Acanthopanax trifoliatus (L.) Merr
• type 1 diabetes mellitus
• PPARγ
• CD4⁺ T cells
• CD8⁺ T cells
• immunoregulation

Acknowledgments

This study was supported by grants from the Natural Science Foundation of Guangdong Province (2017A030313623), Science and Technology Planning Project of Guangdong Province, China (2016ZC0172), the projects of Guangzhou key laboratory of construction and application of new drug screening model systems (No.201805010006) and Key Laboratory of New Drug Discovery and Evaluation of ordinary universities of Guangdong province (No. 2017KSYS002).

Abbreviations

ATMP, Acanthopanax trifoliatus (L.) Merr. polysaccharide; T1DM, type 1 diabetes mellitus; HPLC, high performance liquid chromatography; HPGPC, high performance gel permeation chromatography; OGTT, oral glucose tolerance test; PPARγ, peroxisome proliferator-activated receptor gamma; H&E, hematoxylin and eosin; STZ, streptozotocin; IL-10, Interleukin-10; IFN-γ, Interferon-γ; INS, insulin; ELISA, enzyme-linked immunosorbent assay; TBST, tris-buffer saline with Tween-20; IHC, immunohistochemistry; DAB, diaminobenzidine; IOD, integrated optical density; PVDF, polyvinylidene fluoride; Normal, normal group; Diabetes, untreated diabetic group; Metformin, diabetic group treated with metformin; ATMP-H, diabetic group treated with high dose ATMP; ATMP-M, diabetic group treated with medium dose ATMP; ATMP-L, diabetic group treated with low dose ATMP.

Disclosure

The authors declare that they have no conflicts of interest in this work.