Traditional Chinese Medicine, Ziyin-Mingmu Decoction, Regulates Cholesterol Metabolism, Oxidative Stress, Inflammation and Gut Microbiota in Age-related Macular Degeneration Models.

Abstract

Background: Age-related macular degeneration (AMD) is the commonest cause of retinal disorders in the aged population. Ziyin-Mingmu decoction (ZD) has been widely used to treat AMD patients over thousands of years, however the underlying functional mechanisms of ZD are largely elusive. In this study, we aim to elucidate the therapeutic mechanisms of ZD in AMD models.

Methods: An in vivo AMD mouse model and an in vitro AMD model were established. Cholesterol level in mouse tissues was measured. Expression of antioxidant genes and proinflammatory cytokines in mouse tissues and in human retinal pigment epithelial (RPE) cells were detected using biochemical approaches. Gut microbiota community and functional pathways were analysed using bioinformatics approach. Compounds in ZD were identified using HPLC/MS.

Results: High fat diet (HFD)-fed mice had significantly higher levels of cholesterol in the retina, RPE, liver and serum, and markedly decreased expression of cholesterol metabolism-associated genes in those tissues, compared to mice fed with normal diet. Similarly, expression of antioxidant and inflammation genes was dysregulated in HFD-fed mouse tissues. ZD treatment reversed these HFD-induced pathological effects. HFD also altered the composition of cecum bacterial communities and associated metabolic pathways, which returned to control levels by ZD. In vitro assays showed that H₂O₂ significantly increased oxidative stress and enhanced expression of proinflammatory cytokines. Co-treatment with ZD significantly counteracted these changes. HPLC/MS identified 105 compound in water extracted ZD and most are polyphenols.

Conclusion: Our data suggests that protection of ZD against AMD is possibly through mitigating cholesterol level, oxidative stress and inflammation, and modulating gut microbiota by polyphenols.