The effect of Gougunao tea polysaccharide on lipid metabolism in hyperlipidemia induced by a high-fat diet and its structural characteristics

In this study, the effect of Gougunao tea polysaccharide (GTP40) on lipid metabolism in high-fat diet (HFD)-induced hyperlipidemic mice and its core structure were investigated. GTP40 effectively reversed the increase in weights of the liver and adipose tissues induced by HFD. The oxidative stress of the liver was also significantly alleviated following GTP40 intervention. According to the results of Real-Time quantitative Polymerase Chain Reaction (RT-qPCR), the genes associated with lipolysis were upregulated after GTP40 treatment, while lipogenesis-related genes were downregulated. Additionally, a homogeneous polysaccharide (GTP40-5P, obtained by degrading GTP40 for 5 h) with a molecular weight of 27858 Da was fractionated from GTP40 by the partial acid hydrolysis method. GTP40-5P was mainly composed of 62.30 ± 0.70 % neutral sugar, 54.82 ± 0.51 % uronic acid and 2.52 ± 0.74 % protein. The results of methylation and nuclear magnetic resonance (NMR) analysis indicated that the backbone of GTP40-5P was consisted of →4)-<i>α</i>-D-Gal<i>p</i>A-(1 → 4)-<i>β</i>-D-Gal<i>p</i>-(1→ units, with the terminal residue <i>β</i>-D-Gal<i>p</i>-(1→ linked to →3,4)-<i>α</i>-D-Gal<i>p</i>A-(1→ at the <i>O</i>-3 site, suggesting that it should be classified as homogalacturonan (HG)-type pectin with partial methyl esterification. These findings indicate that GTP40 alleviates lipid metabolism disorders in hyperlipidemic mice primarily <i>via</i> the AMPK signaling pathway. Furthermore, the elucidation of the primary structure of Gougunao tea polysaccharide enhances the understanding of the structure-activity relationship.