Figure 1.
Changes in body weight and food intake during the experimental period.
(A) Body weight changes in each group. *p<0.05; significant with respect to untreated controls. (B) Food intake changes in each group during the experimental period. *p<0.05; significant with respect to the untreated controls.
Figure 2.
Serum glucose and insulin levels in the study groups.
(A) Serum glucose levels after sacrifice. #p<0.05; significant difference between the treatment group and the controls group. (B) Serum insulin levels in the study groups after sacrifice. #p<0.05; significant difference between the treatment group and the control group.
Table 1.
Body, gastrocnemius muscle, and soleus muscle weights of the experimental groups.
Figure 3.
Forelimb grip strengths and serum creatine kinase levels.
(A) Forelimb grip strengths in the study groups before sacrifice. Each dot represent the average of 5 tests per animal. #p<0.01; significant difference between the dexamethasone group and the control group. *p<0.05; significant difference between the dexamethasone treated group and 3 other groups. (B) Serum creatine kinase levels in the study groups. Serum creatine kinase levels were measured after sacrifice. #p<0.05; significant difference between the dexamethasone group and the control group. *p<0.05; significant difference between the dexamethasone group and the 3 other groups.
Figure 4.
Histological analysis of soleus muscle cross sections.
H&E stained sections of excised soleus muscle tissue in the control group (A), the dexamethasone treated group (B), the dexamethasone and leucine group (C), and the dexamethasone and HMB groups (D, E). Scale bar = 0.5 mm. (F) Protein concentration was measured in soleus muscles. #p<0.05; significant difference between the dexamethasone group and the control group. *p<0.05; significant differences between the dexamethasone group and the other 3 groups.
Figure 5.
Effects of HMB supplementation on dexamethasone-induced MyHC degradation.
(A) Representative western blot result of MyHC. Blots were quantified by densitometry and are expressed as relative to the control group. #p<0.05; significant difference between the dexamethasone group and the control group. *p<0.05; significant difference between the dexamethasone group and the other four groups. (B) MyHC mRNA levels in soleus muscles for the study groups. One representative blot of each protein from three experiments that yielded similar results, is shown. (C) Detection of ubiquitinated-MyHC by immunoprecipitation. Representative western blot result of ubiquitinated-MyHC and MyHC in each study group. Ratios of ubiquitinated-MyHC to MyHC were calculated by densitometry and are expressed relative to control group values. #p<0.05; significant difference between the dexamethasone group and the control group. *p<0.05; significant differences between the dexamethasone group and the other four groups.
Figure 6.
Effects of HMB supplementation on dexamethasone-induced MuRF1 and MyoD protein levels and on and in nuclear translocation of FOXO1.
(A) Representative western blot of MuRF1 in each study group. Blots were quantified by densitometry and values are expressed versus the control group. #p<0.05; significant difference between the dexamethasone group and the control group. *p<0.05; significant difference between the dexamethasone group and the other four groups. (B) Representative western blot result of nuclear FOXO1 in the study groups. The blots were quantified by densitometry and values are expressed relative to control group values. #p<0.05; significant difference between the dexamethasone group and the control group. *p<0.05; significant difference between the dexamethasone group and the other four groups. (C) Representative western blot result of nuclear MyoD in each study group. The blots were quantified by densitometry and values are expressed relative to control values. #p<0.05; significant difference between the dexamethasone group and the control group. *p<0.05; significant difference between the dexamethasone group and the other four groups.
Figure 7.
Proposed mechanism for the effect of HMB on dexamethasone-induced muscle atrophy.