Irisin/FNDC5 influences myogenic markers on skeletal muscle following high and moderate-intensity exercise training in STZ-diabetic rats

Abstract

In the present study, we investigated the effects of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on irisin and expression of myogenic markers (paired box 7 (Pax7), myogenic differentiation 1 (MyoD), myogenin) in skeletal muscle of diabetic rats. Eighty-four male Wistar rats (6 weeks of age) were randomly divided into seven groups (n = 12): basic control (Co Basic), 8 weeks control (Co 8w), diabetes mellitus (DM), HIIT, DM + HIIT, MICT, and DM + MICT groups. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ). The $\dot{V}{\text{o}}_{2max}$ protocol was characterized by running on a rodent treadmill with moderate intensity (60-70% $\dot{V}{\text{o}}_{2max}$ ), 60 min per session, 5 days/week, for 6 weeks. HIIT consisted of six 3-min runs at a high intensity (80-90% $\dot{V}{\text{o}}_{2max}$ ) alternated with 2-min running at low intensity (50% $\dot{V}{\text{o}}_{2max}$ ), 30 min per session, 5 days/week, for 6 weeks. Results showed that DM decreased myoblast markers compared to Co Basic and Co 8w groups. Fibronectin type III domain-containing protein 5 (FNDC5) mRNA decrease was correlated with myoblast markers (Pax7 r = 0.632, p = 0.027; MyoD r = 0.999, p = 0.001; myogenin r = 1.000, p = 0.001) in DM group. DM + MICT significantly increased gene expression of MyoD, myogenin, and FNDC5 compared to DM and DM + HIIT. The results also showed that the intensity and duration of exercise on the treadmill were effective in stimulating irisin and myogenic markers after DM.

Keywords: Diabetes; Exercise training; Irisin; Muscle cell; Pax7; Satellite cells.

Fig. 1

Blood glucose levels of rats in different groups. DM, DM + HIIT, and DM + MICT groups have higher blood glucose than healthy groups (with and without exercise). However, exercise and diabetes groups (DM + HIIT and DM + MICT) show a lower increase in blood glucose than DM. All values were expressed as a mean ± SD (n = 12/group). Co Basic Basic Control, Co 8w 8 weeks Control, DM diabetes mellitus, HIIT high-intensity interval training, DM + HIIT diabetes mellitus + high-intensity interval training, MICT moderate intensity continues training, DM + MICT diabetes mellitus + moderate intensity continues training

Fig. 2

The expression of a Pax7, b MyoD, c myogenin and d FNDC5 genes in soleus muscle. Exercise groups (with and without diabetes) showed higher mRNA levels of Pax7, MyoD, myogenin, and FNDC5 than DM group. HIIT exercise significantly increased FNDC5. All values were expressed as a mean ± SD (n = 12/group). Co Basic Basic Control, Co 8w 8 weeks Control, DM diabetes mellitus, HIIT high-intensity interval training, DM + HIIT diabetes mellitus + high-intensity interval training, MICT moderate intensity continues training, DM + MICT diabetes mellitus + moderate intensity continues training

Fig. 3

Change of irisin by ELISA methods. Exercise groups, especially HIIT, had a significant increase in irisin in the soleus muscle. Two exercise training methods in diabetic groups also increased irisin levels in the soleus muscle. All values were expressed as a mean ± SD (n = 12/group). Co Basic Basic Control, Co 8w 8 weeks Control, DM diabetes mellitus, HIIT high-intensity interval training, DM + HIIT diabetes mellitus + high-intensity interval training, MICT moderate intensity continues training, DM + MICT diabetes mellitus + moderate intensity continues training

Fig. 4

IHC of MyoD (a, b), Pax7 (c, d) and myogenin (e, f) proteins in soleus muscles of rats. Nuclei are stained with 49, 6-diamidino-2-phenylindole (DAPI, blue). Percentages of MyoD, Pax7 and myogenin positive nuclei are displayed in green. Protein levels of MyoD, Pax7 and myogenin in soleus muscle decreased with diabetes. However, exercise training, especially MICT, increased these myogenic proteins. All values were expressed as a mean ± SD (n = 5–7/group). Co Basic Basic Control, Co 8w 8 weeks Control, DM diabetes mellitus, HIIT high-intensity interval training, DM + HIIT diabetes mellitus + high-intensity interval training, MICT moderate intensity continues training, DM + MICT diabetes mellitus + moderate intensity continues training

Fig. 4

IHC of MyoD (a, b), Pax7 (c, d) and myogenin (e, f) proteins in soleus muscles of rats. Nuclei are stained with 49, 6-diamidino-2-phenylindole (DAPI, blue). Percentages of MyoD, Pax7 and myogenin positive nuclei are displayed in green. Protein levels of MyoD, Pax7 and myogenin in soleus muscle decreased with diabetes. However, exercise training, especially MICT, increased these myogenic proteins. All values were expressed as a mean ± SD (n = 5–7/group). Co Basic Basic Control, Co 8w 8 weeks Control, DM diabetes mellitus, HIIT high-intensity interval training, DM + HIIT diabetes mellitus + high-intensity interval training, MICT moderate intensity continues training, DM + MICT diabetes mellitus + moderate intensity continues training

Fig. 5

Western blot of MyoD, Pax7, and myogenin proteins (a–d). The protein expression of MyoD, Pax7 and myogenin by western blotting method also decreased in the diabetes group. However, both exercise training modalities (with and without diabetes) increased the expression of these proteins in the soleus muscles of Wistar rat. All values were expressed as a mean ± SD (n = 5–7/group). Co Basic Basic Control, Co 8w 8 weeks Control, DM diabetes mellitus, HIIT high-intensity interval training, DM + HIIT diabetes mellitus + high-intensity interval training, MICT moderate intensity continues training, DM + MICT diabetes mellitus + moderate intensity continues training