Structural characterization and anti-hepatic fibrosis effects of a novel polysaccharide from Astragalus complanatus seeds.

Hepatic fibrosis (HF) arises from dysregulated wound healing during chronic liver injury, progressing to liver dysfunction and carcinogenesis. Polysaccharides have emerged as promising candidates for HF treatment. In this study, a homogeneous galactomannan (45.0 kDa) was isolated from the seeds of Astragalus complanatus R. Br. Structural analysis revealed that it was composed of T-galactose (Gal), 1,4-mannose (Man), and 1,4,6-Man in a molar ratio of 1.47:1.00:1.42, featuring a β-1,4-Manp backbone with terminal α-Galp branches at O-6 of Manp. Additionally, ACSP-I's triple-helical structure was confirmed by Congo red assay and circular dichroism spectrum, while scanning electron microscopy revealed a lamellar morphology with pores on a slightly rough surface. ACSP-I exerted potent anti-fibrotic effects, suppressing hepatic stellate cells (HSCs) activation in vitro and attenuating CCl4-induced liver injury in vivo. Mechanistically, ACSP-I suppressed HSCs activation through inhibition of pyruvate kinase M2 (PKM2)-mediated glycolysis, which suppressed the expression of proliferation-related genes (MYC and CCND1), and inhibited histone lactylation to downregulate fibrotic genes (ACTA2 and COL1A1). These results identify ACSP-I as a PKM2 inhibitor for HF treatment and reveal new mechanisms of polysaccharide-mediated hepatoprotection.