Muscle metabolite and enzyme level quantification. (A) Plasma lactate levels, (B) Skeletal muscle lactate, (C) Muscle Glucose-6-Phosphate levels under basal and insulin-stimulated conditions. (D) Skeletal muscle hexokinase II, (E) Skeletal muscle glycogen phosphorylase, (F) Skeletal muscle GLUT-4 mRNA, (G) Skeletal muscle GLUT-4 protein, (H) Glucose-6-Phosphate Isomerase levels under insulin-stimulated conditions after a 6 h fasting period from control and gys1-KO mice at 22 weeks of age. Data shown are mean ± SEM (*p < 0.05 **p < 0.01 vs. control mice, n = 4–7 per group).