Background White sweet potato (WSP; Ipomoea batatas L. Simon No. 1) has many potential
beneficial effects on metabolic control and diabetes-related insulin resistance. The
improvement of insulin resistance by WSP tuber extracts on glucose uptake were not
investigated in C2C12 myoblast cells. Results WSP tuberous ethanol extract (WSP-E)
was partitioned with ethyl-acetate and water to obtain ethyl-acetate layer (WSP-EA)
and water layer (WSP-EW). The WSP-EA shows the highest total phenolic contents and
highest antioxidant activity by Folin-Ciocalteu and (2,2-diphenyl-1-picryl-hydrazyl-hydrate,
DPPH) assay, respectively. After low concentration horse serum on differentiation
inducement of C2C12 myoblasts into mature myotubes, the cells were treated with TNF-alpha
to induce insulin resistance. WSP-EA and WSP-EW extracts increased the uptake of fluorescence
glucose analogue (2-[N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl) amino]-2-deoxy-d-glucose,
2-NBDG) in a dose-dependent manner as examined by flow cytometry. The WSP-EA enhanced
glucose uptake by activation of phosphorylation of IR (pIR), IRS-1 (pIRS-1) and Akt
(pAkt) involved in PI3K (phosphatidylinositol 3-kinase)/protein kinase B (Akt) pathway,
also upregulated glucose transporter 4 (GLUT4) expression in myotubes. Conclusions
WSP-EA enhanced the glucose uptake in C2C12 myotubes through upregulating the PI3K/Akt
pathway. The in vitro data reveal that WSP tuber extracts has potential applications
to improve insulin resistance in diabetes.
