Protective Effect of a Highly Enriched Nacre-Derived Neutral Polysaccharide Fraction on D-Galactose-Induced Pancreatic Dysfunction.

Nacre, the iridescent inner layer of mollusk shells, has long been traditionally used in medicine. While we have previously demonstrated its anti-aging effects on muscle and skin, its impact on pancreatic dysfunction and glucose metabolism remains unclear. In this study, we aimed to isolate and identify an active component from nacre extract that improves glucose metabolism and to evaluate its potential to prevent or ameliorate pancreatic dysfunction and glucose metabolic abnormalities in a D-galactose-induced aging mouse model. A polysaccharide component was successfully isolated using a combination of reverse-phase and ion-exchange chromatography. Structural analyses revealed that it was primarily composed of glucose, mannose, and rhamnose, which together accounted for approximately 87% of the total monosaccharide content. Further characterization by FT-IR spectroscopy and MALDI-TOF-MS confirmed its identity as a neutral polysaccharide with glycosidic linkages and an estimated molecular weight of approximately 5000 Da. Intraperitoneal administration of this polysaccharide significantly improved glucose tolerance and prevented a decline in serum insulin levels in D-galactose-induced aging mice. Immunohistochemical analysis of pancreatic tissues revealed that the polysaccharide preserved insulin expression and suppressed the D-galactose-induced upregulation of cellular senescence and apoptosis markers. These findings suggest that this nacre-derived polysaccharide effectively mitigates pancreatic dysfunction and glucose metabolic dysfunction, indicating its potential as a natural therapeutic agent for age-related metabolic disorders.