Exercise training alleviates MCT1 and MCT4 reductions in heart and skeletal muscles of STZ-induced diabetic rats

We compared the changes in monocarboxylate transporter 1 ( MCT1) and 4 (MCT4) proteins in heart and skeletal muscles in sedentary control and streptozotocin (STZ)-induced diabetic rats ( 3 wk) and in trained ( 3 wk) control and STZ-induced diabetic animals. In nondiabetic animals, training increased MCT1 in the plantaris (+51%; P < 0.01) but not in the soleus (+9%) or the heart (+14%). MCT4 was increased in the plantaris (+ 48%; P < 0.01) but not in the soleus muscles of trained nondiabetic animals. In sedentary diabetic animals, MCT1 was reduced in the heart ( - 30%), and in the plantaris ( - 31%; P < 0.01) and soleus ( - 26%) muscles. MCT4 content was also reduced in sedentary diabetic animals in the plantaris ( - 52%; P < 0.01) and soleus ( - 25%) muscles. In contrast, in trained diabetic animals, MCT1 and MCT4 in heart and/or muscle were similar to those of sedentary, nondiabetic animals ( P > 0.05) but were markedly greater than in the sedentary diabetic animals [ MCT1: plantaris +63%, soleus +51%, heart +51% ( P > 0.05); MCT4: plantaris +107%, soleus +17% ( P > 0.05)]. These studies have shown that 1) with STZ-induced diabetes, MCT1 and MCT4 are reduced in skeletal muscle and/or the heart and 2) exercise training alleviated these diabetes-induced reductions.