Guoji Yanke Zazhi (Jan 2023)
Protective effect of metformin on the retina of type 2 diabetic rats and its regulation on serum cystatin C
Abstract
AIM: To prepare the model of diabetic retinopathy(DR)on the basis of the model of type 2 diabetes mellitus(T2DM)in rats, observe the preventive and protective effect of metformin on DR in T2DM rats and the effect on serum Cystatin C(Cys C), and discuss its mechanism.METHODS: A total of 120 male SD rats were selected and 30 rats were randomly divided into blank control group A(10 rats), T2DM group(10 rats)and metformin intervention group A(10 rats). The remaining 90 rats were randomly divided into three groups: blank control group B(30 rats), DR group(30 rats)and metformin intervention group B(30 rats). Except for blank control groups A and B, T2DM models were constructed in all other groups. After modeling, rats in metformin intervention group A were given metformin by gavage, and rats in blank control group A and T2DM group were given normal saline by gavage. After 3mo of intervention, fasting blood glucose(FBG)and fasting serum insulin(FINS)indexes of the three groups were measured respectively, and the homeostasis model assessment of insulin resistance(HOMA-IR)was calculated and analyzed; The serum Cys C, tumor necrosis factor-α(TNF-α), the levels of Interleukin-8(IL-8), vascular endothelial growth factor(VEGF)and reactive oxygen species(ROS)were measured, and we observed the retinal tissue and vascular morphology of rats by FFA, HE staining and transmission electron microscopy; rats in metformin intervention group B began to give metformin by gavage 3mo after the course of T2DM, and other rats were given normal saline. According to the length of intervention, 10 rats were taken from each group and observed at 4, 5 and 6mo respectively. Serum levels of Cys C, TNF-α, IL-8, VEGF and ROS were measured in each group. We observed the retinal tissue and vascular morphology of rats by FFA, HE staining and transmission electron microscopy.RESULTS: The expressions of serum FBG, FINS, HOMA-IR, Cys C, TNF-α, IL-8, VEGF and ROS were statistically significant among the blank control group A, T2DM group and metformin intervention group A(P<0.05), which were the highest in T2DM group, and the metformin intervention group A were lower than T2DM group; The expression of Cys C, TNF-α, IL-8, VEGF and ROS of rat serum were statistically significant among the blank control group B, DR group and metformin intervention group B within the same age groups at 4, 5 and 6mo respectively(P<0.05), and were all the highest in DR group. The expressions of metformin intervention group B were lower than those of the DR group. With the prolongation of DR course, the expression of Cys C, TNF-α, IL-8, VEGF and ROS also increased further; FFA results showed that compared with the corresponding blank control group, the retinal blood vessels of each model group were tortuous, and microaneurysms and fluorescence leakage were visible with the prolongation of the disease course; HE staining results showed that compared with the corresponding blank control group, the retinal cells of each model group were arranged disorderly, and abnormal dilated blood vessels were visible with the prolongation of the disease course; Transmission electron microscopy results showed that compared with the corresponding blank control group, the retinal capillaries in each model group were seriously damaged; However, compared with the corresponding model group, the results of FFA, HE and transmission electron microscopy of rats in each metformin intervention group had different degrees of improvement.CONCLUSIONS: Metformin can improve retinal tissue lesions by down-regulating serum Cys C-mediated levels of inflammation and oxidative stress, thus playing a preventive and therapeutic role in the retinopathy in T2DM rats.
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