Structural features of galacturonic acid-rich polysaccharides from Ziziphus jujuba and their protective effects against insulin resistance and muscle atrophy.

Polysaccharides from jujube (Ziziphus jujuba Mill., JP) exhibit health-promoting potential; however, their structure and roles in insulin resistance and muscle atrophy remain incompletely understood. This study characterized the structure of JP and evaluated its effects on insulin resistance and muscle atrophy in C2C12 myotubes exposed to palmitate (PA). By integrating advanced spectroscopic and microscopic analyses, we present the first three-dimensional structural model of JP, revealing a helical lamellar conformation with distinct glycosidic linkages. Structural analysis was conducted using ion chromatography, GC-MS, GPC-RI-MALS, FT-IR, and NMR spectroscopy. Functional effects were evaluated via glucose uptake, mitochondrial content, and myogenic gene expression. JP consisted of galacturonic acid, galactose, and rhamnose, with a molecular mass of 3.76 × 105 g/mol. Structural analysis revealed a helical lamellar conformation rich in 1,4-GalpA backbone and 1,2,(4)-Rhap linkages. Functionally, JP enhanced glucose uptake by upregulating glucose transporter type 4 expression and restored mitochondrial content. It also attenuated PA-induced muscle atrophy by increasing the expression of Myhc1a and Myhc2x. To our knowledge, this is the first study to demonstrate the dual protective effects of JP against insulin resistance and muscle atrophy in skeletal muscle cells, positioning it as a promising functional food ingredient or therapeutic agent for metabolic disorders.