Eicosapentaenoic acid-enriched phosphatidylcholine isolated from Cucumaria frondosa exhibits anti-hyperglycemic effects via activating phosphoinositide 3-kinase/protein kinase B signal pathway.

Eicosapentaenoic acid-enriched phosphatidylcholine was isolated from the sea cucumber Cucumaria frondosa ( Cucumaria -PC) and its effects on streptozotocin (STZ)-induced hyperglycemic rats were investigated. Male Sprague–Dawley rats were randomly divided into normal control, model control (STZ), low- and high-dose Cucumaria -PC groups (STZ + Cucumaria -PC at 25 and 75 mg/Kg·b·wt, intragastrically, respectively). Blood glucose, insulin, glycogen in liver and gastrocnemius were determined over 60 days. Insulin signaling in the rats' gastrocnemius was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. The results showed that Cucumaria -PC significantly decreased blood glucose level, increased insulin secretion and glycogen synthesis in diabetic rats. RT-PCR analysis revealed that Cucumaria -PC significantly promoted the expressions of glycometabolism-related genes of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), phosphoinositide 3-kinase (PI3K), protein kinase B (PKB), and glucose transporter 4 (GLUT4) in gastrocnemius. Western blotting assay demonstrated that Cucumaria -PC remarkably enhanced the proteins abundance of IR-β, PI3K, PKB, GLUT4, as well as phosphorylation of Tyr-IR-β, p85-PI3K, Ser473-PKB ( P P Cucumaria -PC exhibited significant anti-hyperglycemic activities through up-regulating PI3K/PKB signal pathway mediated by insulin. Nutritional supplementation with Cucumaria -PC, if validated for human studies, may offer an adjunctive therapy for diabetes mellitus.