Effects of growth hormone on cardiac remodeling and soleus muscle in rats with aortic stenosis-induced heart failure

Abstract

Background: Skeletal muscle wasting is often observed in heart failure (HF). The growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis is impaired in HF. In this study, we evaluated the effects of GH on soleus muscle and cardiac remodeling in rats with aortic stenosis (AS)-induced HF.

Methods: AS was created by placing a stainless-steel clip on the ascending aorta. After clinically detecting HF, GH (2 mg/kg/day) was subcutaneously injected for 14 days (AS-GH group). Results were compared with those from Sham and non-treated AS groups. Transthoracic echocardiogram was performed before and after treatment. Protein expression was evaluated by Western blot and satellite cells activation by immunofluorescence. Statistical analyzes: ANOVA and Tukey or Kruskal-Wallis and Student-Newman-Keuls.

Results: Before treatment both AS groups presented a similar degree of cardiac injury. GH prevented body weight loss and attenuated systolic dysfunction. Soleus cross-sectional fiber areas were lower in both AS groups than Sham (Sham 3,556±447; AS 2,882±422; AS-GH 2,868±591 μm²; p=0.016). GH increased IGF-1 serum concentration (Sham 938±83; AS 866±116; AS-GH 1167±166 ng/mL; p<0.0001) and IGF-1 muscle protein expression and activated PI3K protein. Neural cell adhesion molecule (NCAM) immunofluorescence was increased in both AS groups. Catabolism-related intracellular pathways did not differ between groups.

Conclusion: Short-term growth hormone attenuates left ventricular systolic dysfunction in rats with aortic stenosis-induced HF. Despite preserving body weight, increasing serum and muscular IGF-1 levels, and stimulating PI3K muscle expression, GH does not modulate soleus muscle trophism, satellite cells activation or intracellular pathways associated with muscle catabolism.

Keywords: growth hormone; heart failure; muscle trophicity; satellite cells; skeletal muscle.

Figure 1

Photomicrographs of soleus muscle cross-sections stained with haematoxylin-eosin (A). Soleus muscle cross-sectional area (B). AS: aortic stenosis; AS-GH: aortic stenosis treated with growth hormone; n: number of animals. Data are expressed as mean ± standard deviation. ANOVA and Tukey; * p<0.05 vs Sham.

Figure 2

Representative immunofluorescence of soleus muscle cross-sections stained with anti-neural cell adhesion molecule (NCAM) and 4’,6-diamidino-2-phenylindole (DAPI) showing cell nucleus in blue and neural cell adhesion molecule (NCAM) in green (A). Quantification of staining intensity of NCAM (B). AS: aortic stenosis; AS-GH: aortic stenosis treated with growth hormone; n: number of animals. Data are expressed as mean ± standard deviation; ANOVA and Tukey; * p<0.05 vs Sham.

Figure 3

Insulin-like growth factor (IGF)-1: serum levels (A) and soleus muscle protein expression (B). AS: aortic stenosis; AS-GH: aortic stenosis treated with growth hormone; n: number of animals. Data are expressed as mean ± standard deviation. ANOVA and Tukey; * p<0.05 vs Sham; # p<0.05 vs AS.

Figure 4. Phosphorylated phosphatidylinositol-3-kinase (PI3K) and total PI3K protein expression in soleus muscle assessed by Western blot

AS: aortic stenosis; AS-GH: aortic stenosis treated with growth hormone; n: number of animals. Data are expressed as median and percentiles; Kruskal-Wallis and Student-Newman-Keuls; * p<0.05 vs Sham.