Mechanical stretch activates glycometabolism‐related enzymes via estrogen in C₂C₁₂ myoblasts

Abstract

Moderate exercise improves glycometabolic disorder and type 2 diabetes mellitus in menopausal females. So far, the effect of exercise‐induced estrogen on muscular glycometabolism is not well defined. The current study was designed to explore the effect of mechanical stretch‐induced estrogen on glycometabolism in mouse C2C12 myoblasts. The mouse C2C12 myoblasts in vitro were assigned randomly to the control (C), stretch (S), and stretch plus aromatase inhibitor anastrozole (SA) groups. Cells in the S group were stretched by the Flexcell FX‐5000™ system (15% magnitude, 1 Hz frequency, and 6‐hr duration) whereas those in the SA group were treated with 400 μg/ml anastrozole before the same stretching. Glucose uptake, estradiol levels, PFK‐1 levels, and oxygen consumption rate were determined, and the expression of HK, PI3K, p‐AKT, AKT, and GLUT4 proteins were semiquantified with western blot analysis. Compared to the control, the estradiol level, oxygen consumption rate, expression of HK, PI3K, and PFK‐1 proteins, the ratio of p‐AKT to AKT, and the ratio of GLUT4 in the cell membrane to that in the whole cell were higher in the S group. On the other hand, the estradiol level, glucose uptake, expression of PFK‐1 and GLUT4 proteins, oxygen consumption rate, expression of HK protein, and the ratio of p‐AKT/AKT were lower in the myoblasts in the SA group than those in the S group. The level of estradiol was positively correlated with glucose uptake (p < .01, r = .818). Therefore, mechanical stretch‐induced estrogen increased the expression of glycometabolism‐related enzymes and proteins in the mouse C2C12 myoblasts.

TMF1 is upregulated by insulin and is required for a sustained glucose homeostasis

“…21,22 GLUT4 was shown to be expressed in myoblasts. 23 To examine the role of TMF1 in mediating the intracellular trafficking of GLUT4, we isolated from WT and TMF1 knockout (TMF1−/−) mice, skeletal myoblasts which serve as a target of insulin-directed glucose homeostasis. 22 The purity of the myoblasts was assayed by immunostaining of the cells for Pax7, and MyoD proteins, which are expressed in these cells (Figure S1).…”