Water soluble polysaccharides from the fruits of Lycium barbarum L. improve glucose and lipid metabolism and boost immune function in elderly mice fed a high-fat diet

Goji berry ( Lycium barbarum L.), a traditional Chinese herbal remedy and functional food, contains polysaccharides (LBP) as its main active constituents. LBP has been shown to improve blood glucose and immune function. However, its effects under ageing conditions, particularly with high-fat diet (HFD) consumption, remain unclear. Herein, we evaluated the effects of water-soluble LBP on glucose and lipid metabolism and on immune function in elderly mice fed a high-fat diet. 2-month-old and 17-month-old female C57BL/6 mice were used. The mice were assigned to 5 groups: young, ageing, ageing + 0.3% LBP, ageing + HFD, and ageing + HFD + 0.3% LBP. The results showed that 0.3% LBP extract treatment significantly reduced fasting blood glucose, insulin, total cholesterol, and low-density lipoprotein cholesterol levels and improved glucose tolerance in HFD-fed ageing mice. Histological and immunohistochemical analysis demonstrated that LBP extract ameliorated hepatic lipid accumulation and adipocyte hypertrophy and increased GLUT4 expression in adipocytes. Flow cytometry analysis demonstrated that in HFD-fed ageing mice, LBP extract intervention significantly decreased the proportion of peripheral MDSCs and increased the CD4 + /CD8 + ratio. Additionally, correlation analysis revealed significant associations among fasting blood glucose, MDSCs proportion, and CD4 + /CD8 + ratio. These findings highlight the preventive effect of LBP on aging-associated metabolic and immune dysfunction.