Octaphlorethol A, a novel phenolic compound isolated from a brown alga, Ishige foliacea, increases glucose transporter 4-mediated glucose uptake in skeletal muscle cells

► OPA, a new phenolic compound isolated from I. foliacea, stimulates glucose uptake. ► OPA activates the PI3-K/Akt and AMPK signaling pathways in skeletal muscle cells. ► We can find a new possibility of OPA as an antidiabetic compound. Skeletal muscle is the major site of glucose disposal. Promoting glucose uptake into this tissue may attenuate the insulin resistance that precedes type 2 diabetes. However, the anti-diabetic effect of marine algae on glucose uptake and metabolism in skeletal muscle remains poorly understood. Here, we report the glucose uptake effects of octaphlorethol A (OPA), a novel phenolic compound isolated from Ishige foliacea, on skeletal muscle cells. OPA increased glucose uptake in differentiated L6 rat myoblast cells in a dose-dependent manner relative to the control. In addition, we found that OPA increased glucose transporter 4 (Glut4) translocation to the plasma membrane. Furthermore, we also demonstrated these OPA effects essentially depended on the protein kinase B (Akt) and AMP-activated protein kinase (AMPK) activation. In summary, PI3-K/Akt and AMPK activation were involved in mediating the effects of OPA on glucose transport activation and insulin sensitivity. OPA can be further developed as a potential anti-diabetic therapy.