Renin inhibition improved muscular function by alleviating insulin resistance and AGEs/RAGE signaling in skeletal muscle associated with high glucose: Exploration of renin inhibitor tanshinone IIA

Diabeticsarcopenia (DS) is a key complication in skeletal muscle associated with hyperglycemia. This study aimed to clarify the role of tissue renin-angiotensin system (Ras) in DS and to explore novel Renin Inhibitor to preserve muscle associated with diabetes. A case-control study was performed to assess angiotensin II (Ang II) level in diabetes participants with/without sarcopenia. The docking analysis, the molecular dynamics simulation, and the surface plasmon resonance as well as the human renin-transfected HEK-293 cells and the mouse myoblasts C2C12 were employed to evaluate the binding of tanshinone IIA (Tan IIA) with Renin protein and the subsequent bioactivity. The db/db mice were orally administered with Tan IIA sulfonate for 8 weeks and the C2C12 cells culturing with high glucose (HG, 30 mM) were treated with Tan IIA. The DS participants displayed significant elevation in serum Ang II level. Consistently, high glucose induced up-regulation in protein expression of Renin and its downstream active peptide Ang II in C2C12 myoblasts. Tan IIA exhibited direct binding affinity with Renin protein, showed the comparable IC₅₀ value as aliskiren on Renin inhibitory activity, and inhibited Ang II content and expression of HEK-293 cells. The treatment of db/db mice with Tan IIA increased muscle index and strength, cross-sectional area of myofibers, protein expression of MHC, and mRNA expression of MRFs (MEF2C, MyoD, Myf5), and reduced expression and content of Ang II in skeletal muscle. Accordingly, Tan IIA promoted fusion index, wound healing and differentiation of the myoblasts, and enhanced protein expression of MyoD, MyoG and MHC of HG-treated myotubes. Furthermore, Tan IIA lowered the levels of fasting blood glucose and glycated serum protein, improved OGTT, and stimulated glycogen accumulation in liver and muscle, followed by increasing glucose uptake via 2-NBDG assay, up-regulating GLUT4 expression, and repressing phosphorylation of IRS1_Ser307 in differentiated myotubes upon to HG. Finally, the type 2 diabetic mice study showed the attenuation of Tan IIA on AGEs accumulation and on RAGE protein expression in muscle, and the in vitro study demonstrated the suppression of Tan IIA on RAGE expression and p38 phosphorylation. The present study indicated that the hyperactivity of Ras in skeletal muscle contributed to the development of diabetes sarcopenia, and that tanshinone IIA possessed the ability in direct inhibition on Renin activity, followed by its beneficial effects on skeletal muscle performance and glucose disposal, and its preservation against Insulin resistance and AGEs/RAGE signaling in muscle.

Diabetic sarcopenia; Glucose; Renin; Skeletal muscle; Tanshinone IIA.