Comparative effects of Saccharina japonica and Undaria pinnatifida on glycemic control in normal and diabetic animal models

Saccharina japonica and Undaria pinnatifida are edible brown seaweeds enriched in diverse bioactive compounds. Although dietary fibers derived from brown seaweeds are recognized for their glycemic benefits, comparative data on their species-specific effects remain limited. In this study, the effects of water extracts of S. japonica (SJW) and U. pinnatifida (UPW) on postprandial and chronic hyperglycemia were investigated. In C57BL/6 mice, oral carbohydrate tolerance tests demonstrated that UPW exerted stronger postprandial hyperglycemia-lowering effects, particularly following sucrose loading. Long-term glycemic effects were evaluated in a type 2 diabetes mellitus (T2DM) rat model. Four weeks of oral supplementation with SJW or UPW reduced fasting glucose levels and enhanced PI3K/Akt insulin signaling. Notably, UPW exhibited greater efficacy than SJW in promoting muscle glucose transporter 4 (GLUT4) expression and enhancing hepatic glycogen metabolism. Collectively, these findings highlight the potential of SJW and UPW as dietary interventions for glycemic control, with UPW demonstrating greater effectiveness. • S. japonica and U. pinnatifida are rich in soluble fiber for glycemic control. • U . pinnatifida water extract reduced postprandial glucose levels. • S. japonica and U. pinnatifida improved hyperglycemia and insulin resistance. • U. pinnatifida promotes GLUT4 expression, enhancing glucose uptake.