Long-Term Oral Administration of Salidroside Alleviates Diabetic Retinopathy in db/db Mice

Abstract

Diabetic retinopathy (DR), a microvascular complication of diabetes mellitus, is the leading cause of vision loss in the working-age population worldwide. Unfortunately, current clinical treatments cannot completely prevent the occurrence and development of DR. Salidroside (Sal) is a medicinal supplement that has antioxidative and cytoprotective properties. This study aimed to investigate the therapeutic effect of Sal on DR. Briefly, Sal treatment was applied to wide-type mice and db/db mice (a widely used diabetic mice) at 25 mg/kg by oral gavage once daily from 8 weeks to 20 weeks. Mice's bodyweight, blood glucose, total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein were recorded and analyzed. Retinal trypsin digestion and evans blue dye assay were used to detect retinal microvessel changes and function. Retinal glutathione and malondialdehyde content measurements were applied to assess retinal oxidative stress. Full-length transcriptome analysis was performed to explore the underlying mechanisms of Sal protection. Our results found that Sal treatment could successfully relieve blood glucose and blood lipid abnormalities, and reduce retinal oxidative stress level in diabetic mice. Also, Sal treatment repaired the abnormal transcriptome caused by diabetes, alleviated the microvascular lesion of the fundus in diabetic mice, and protected retinal normal barrier function. This study enriches the indications of Sal in the treatment of diabetic diseases, providing practical research ideas for the comprehensive preventions and treatments of DR.

Keywords: diabetes; oxidative stress; retinopathy; salidroside; transcriptome; vascular barrier.

Figure 1

Sal improved blood glucose and lipid profiles in db/db mice. (A) The bodyweight of WT and db/db mice after Sal intervention. (B) The blood glucose of WT and db/db mice after Sal intervention. (C-F) The blood levels of total cholesterol (TC), high density lipoprotein (HDL), triglyceride (TG) and low density lipoprotein (LDL) in WT and db/db mice after Sal intervention. Data are the mean ± SD; ^##p < 0.01 (db/db mice compared with WT mice), *p < 0.05, **p < 0.01 (db/db + Sal mice compared with db/db mice).

Figure 2

Sal alleviated retinal microvascular changes in db/db mice. (A) The representative photomicrographs of normal and diabetic microvessel stained by Schiff’s reagent and hematoxylin; The green arrows pointed is acellular capillaries, and the red arrows pointed is pericyte ghost. (B) The number of pericyte ghost in WT and db/db mice after Sal intervention. (C) The number of acellular capillaries in WT and db/db mice after Sal intervention. Data are the mean ± SD. Scale bar = 50 μm.

Figure 3

Sal protected retinal vascular barrier function in db/db mice. (A) The representative photomicrographs of retinal vessels stained by evans blue in WT mice and db/db mice with or without Sal intervention. (B) Retinal normalized evans blue contents in WT and db/db mice after Sal intervention. Data are the mean ± SD. Scale bar = 500 μm.

Figure 4

Sal relieved retinal oxidative stress in db/db mice. (A) Retinal GSH contents in WT and db/db mice after Sal intervention. (B) Retinal MDA contents in WT and db/db mice after Sal intervention. Data are the mean ± SD.

Figure 5

Sal ameliorates retinal transcriptome abnormalities in db/db mice. (A) The Venn diagram showing the differentially expressed genes (DEGs) among WT mice, db/db mice and Sal-treated db/db mice. (B) The heat map showing the Sal-restored DEGs (35 genes) and Sal-aggravated DEGs (1 gene) between WT and db/db mice.

Figure 6

The analysis of DEGs between db/db mice and Sal-treated db/db mice. (A) The DEGs between db/db mice and Sal-treated db/db mice were analysed by KEGG databases. (B) The DEGs between db/db mice and Sal-treated db/db mice were analysed by GO databases.