Fenugreek increases insulin-stimulated creatine content in l6C11 muscle myotubes

Purpose Creatine uptake by muscle cells is increased in the presence of insulin. Accordingly, compounds with insulin- like actions may also augment creatine uptake. The aim of this study was to investigate whether Trigonella foenumgraecum (fenugreek), an insulin mimetic, increases total intracellular creatine levels in vitro. Methods Total cellular creatine content was measured fluorometrically in L6C11 muscle myotubes treated for 1, 4, and 24 h with 0.5 mM creatine (CR), CR and 20 μg/mL fenugreek seed extract (CR + FEN), CR and 100 nM insulin (CR + INS), and CR + INS + FEN (n = 6 per treatment group). Alterations in the expression of the sodiumand chloride-dependent creatine transporter, SLC6A8, and key signaling proteins in the PI3-K/Akt pathway were determined. Results Compared to control (CON), CR + INS + FEN increased total creatine content after 4 h (P < 0.05), whereas all conditions increased SLC6A8 protein expression above CON at this time (P < 0.05). Changes in insulin signaling were demonstrated via increases in AktThr308 phosphorylation, with CR + INS > CON and CR at 1 h (P < 0.05) and with CR + INS + FEN > CON, CR, and CR + INS at 4 h (P < 0.05). In contrast, no changes in PKCζ/λ or GLUT4 phosphorylation were detected. Conclusion Fenugreek, when combined with insulin, modulates creatine content via a mechanism which is independent of the activity of SLC6A8, suggesting that an alternative mechanism is responsible for the regulation and facilitation of insulin-mediated creatine uptake in skeletal muscle cells.