Polysaccharides from Cinnamon Processing Byproducts (Twig–Leaf) and Bark Alleviate Type 2 Diabetes via Modulating Gut Microbiota and the SCFA-GPR41/43-GLP-1/PYY Axis

Abstract Type 2 diabetes mellitus (T2DM) is a major global health challenge. This study provides the first comparative analysis of polysaccharides from cinnamon bark (CBP) and its deoiled twig–leaf byproduct (CTLP). Structural characterization revealed that CBP-P is a high-molecular-weight (368.069 kDa) arabinogalactan rich in Ara/Gal, whereas CTLP-P is a low-molecular-weight (12.343 kDa) galacturonan-rich pectic polysaccharide rich in GalA. In HFD/STZ-induced T2DM mice, both CBP and CTLP significantly ameliorated hyperglycemia, insulin resistance, and dyslipidemia. Mechanistically, they remodeled gut microbiota (enriching Muribaculaceae and Lactobacillaceae), increased cecal SCFAs, upregulated colonic GPR41/43, and elevated serum GLP-1/PYY. Correlation analysis supported this gut microbiota–SCFA–receptor–hormone axis. Our findings demonstrate that polysaccharides from both cinnamon bark and its cost-effective byproduct alleviate T2DM via a shared gut-microbiota-dependent pathway, providing a scientific foundation for developing sustainable, value-added functional ingredients from an underutilized cinnamon processing residue for metabolic health applications.