Plant polysaccharides (PPS) composed of more than 10 monosaccharides show high safety and various pharmacological activities, including immunoregulatory, antitumor, antioxidative, antiaging, and other effects. In recent years, emerging evidence has indicated that many PPS are beneficial for metabolic diseases, such as cardiovascular disease (CVD), diabetes, obesity, and neurological diseases, which are usually caused by the metabolic disorder of fat, sugar, and protein. In this review, we introduce the common characteristics and functional activity of many representative PPS, emphasize the common risks and molecular mechanism of metabolic diseases, and discuss the pharmacological activity and mechanism of action of representative PPS obtained from plants including Aloe vera, Angelica sinensis, pumpkin, Lycium barbarum, Ginseng, Schisandra chinensis, Dioscorea pposite, Poria cocos, and tea in metabolic diseases. Finally, this review will provide directions and a reference for future research and for the development of PPS into potential drugs for the treatment of metabolic diseases.

Blood retinal barrier (BRB) damage is an important pathogenesis of diabetic retinopathy, and alleviating BRB damage has become a key target for DR treatment. We previously found that Lycopene seed polyphenols (LSP) maintained BRB integrity by inhibiting NLRP3 inflammasome-mediated inflammation. However, it is still unknown whether LSP inhibits retinal neovascularization with abnormal capillaries and its mechanism of action. Here, we employed db/db mice and hRECs to find that LSP increases the level of glycolipid metabolism, maintains the morphology of retinal endothelial cells and inhibits acellular capillary neogenesis. Mechanistic studies revealed that LSP inhibits the NLRP3 inflammasome, reduces cell apoptosis in retinal tissue, increases tight junction protein (TJ) expression, and reduces vascular endothelial growth factor (VEGF) and Ve-Cadherin in vivo and in vitro. Collectively, this study finds that LSP inhibits inflammation and angiogenesis to improve BRB function to ameliorate DR.