The effect of eight weeks resistance and aerobic training on myostatin and follistatin expression in cardiac muscle of rats

The Effect of Eight Weeks of High-Intensity Interval Training on Follistatin Gene Expression in the Fast and Slow Twitch Muscles of Rats with Myocardial Infarction

Background

Myocardial infarction causes mitochondrial atrophy and loss of function by reducing mitochondrial volume. Therefore, researchers are interested in finding a way to reduce the injuries and treat them. The study aims to evaluate the effect of 8 weeks of high-intensity interval training on follistatin (FST) gene expression in the fast and slow twitch muscles of rats with myocardial infarction.

Methods

The study was conducted in 2020 at the Cardiac Research Center, Shahid Rajaei University of Medical Sciences (Tehran, Iran). For this purpose, 12 male Wistar rats with myocardial infarction were assigned to the experimental group high-intensity interval training (3 days a week for 30 min, each interval consisting of 4 min of running with 85-90% VO2max intensity and 2 min of active recovery with intensity of 50-60% VO2max for 8 weeks) and a control group. Then, the expression of follistatin in fast and slow twitch muscle contraction genes was investigated as triggers and inhibitors of muscle atrophy. Statistical data were analyzed with SPSS18 (α≥0.05). To determine the normality of the data, the Kolmogorov-Smirnov test was used, and in the case of normality of the data distribution, the independent samples t test was used.

Results

Independent t test results showed that FST gene expression in the slow twitch (ST) muscle contraction group was significantly decreased compared with the control group (P<0.001). Moreover, the expression of the FST gene in fast twitch muscles was significantly increased in the severe exercise group compared with the control group (P<0.001).

Conclusion

Overall, 8 weeks of intense intermittent exercise decreased FST gene expression in slow and fast twitch muscles in rats with myocardial infarction.

Myostatin and the Heart

Myostatin (growth differentiation factor 8) is a member of the transforming growth factor-β superfamily. It is secreted mostly by skeletal muscles, although small amounts of myostatin are produced by the myocardium and the adipose tissue as well. Myostatin binds to activin IIB membrane receptors to activate the downstream intracellular canonical Smad2/Smad3 pathway, and additionally acts on non-Smad (non-canonical) pathways. Studies on transgenic animals have shown that overexpression of myostatin reduces the heart mass, whereas removal of myostatin has an opposite effect. In this review, we summarize the potential diagnostic and prognostic value of this protein in heart-related conditions. First, in myostatin-null mice the left ventricular internal diameters along with the diastolic and systolic volumes are larger than the respective values in wild-type mice. Myostatin is potentially secreted as part of a negative feedback loop that reduces the effects of the release of growth-promoting factors and energy reprogramming in response to hypertrophic stimuli. On the other hand, both human and animal data indicate that myostatin is involved in the development of the cardiac cachexia and heart fibrosis in the course of chronic heart failure. The understanding of the role of myostatin in such conditions might initiate a development of targeted therapies based on myostatin signaling inhibition.

Mountain ginseng inhibits skeletal muscle atrophy by decreasing muscle RING finger protein-1 and atrogin1 through forkhead box O3 in L6 myotubes

ETHNOPHARMACOLOGICAL RELEVANCE

Mountain ginseng (Panax ginseng C.A. Meyer) is a medicinal herb with immune effects, muscle damage protection and energy metabolism effects. However, the pharmacological role of mountain ginseng in dexamethasone (DEXA)-induced muscle atrophy through the forkhead box O (FOXO) family is not understood. Therefore, we hypothesized that mountain ginseng inhibits skeletal muscle atrophy by decreasing muscle RING finger protein-1 (MuRF1) and atrogin1 through FOXO3 in L6 myotubes.

METHODS

Rat myoblast (L6) cells or Sprague-Dawley (SD) rats were exposed to DEXA and mountain ginseng. The expressions of muscle atrophy targets such as MuRF1, atrogin1, MyHC (myosin heavy chain), HSP90, p-Akt, Akt, p-ERK1/2, ERK, FOXO3a, FOXO1, myostatin, and follistatin were analyzed by using Western blot analysis or real-time PCR. The diameter of myotubes was measured. Recruitment of glucocorticoid receptor (GR) or FOXO3a was analyzed by performing a chromatin immunoprecipitation (ChIP) assay.

RESULTS

Mountain ginseng treatment reduced muscle weight loss and collagen deposition in DEXA-induced rats. Mountain ginseng treatment led to decreases in MuRF1, atrogin1, p-ERK1/2, FOXO3a, FOXO1, and myostatin. Also, mountain ginseng treatment led to increases in the diameter of myotubes, MyHC, HSP90, p-Akt, and follistatin. Treatment with mountain ginseng reduced enrichment of GR, FOXO3a, and RNA polymerase II on the promoters.

CONCLUSIONS

These results suggest that mountain ginseng inhibits skeletal muscle atrophy by decreasing MuRF1 and atrogin1 through FOXO3a in L6 myotubes.

Hepatokines as a Molecular Transducer of Exercise

Exercise has health benefits and prevents a range of chronic diseases caused by physiological and biological changes in the whole body. Generally, the metabolic regulation of skeletal muscle through exercise is known to have a protective effect on the pathogenesis of metabolic syndrome, non-alcoholic fatty liver disease (NAFLD), type 2 diabetes (T2D), and cardiovascular disease (CVD). Besides this, the importance of the liver as an endocrine organ is a hot research topic. Hepatocytes also secrete many hepatokines in response to nutritional conditions and/or physical activity. In particular, certain hepatokines play a major role in the regulation of whole-body metabolic homeostasis. In this review, we summarize the recent research findings on the exercise-mediated regulation of hepatokines, including fibroblast growth factor 21, fetuin-A, angiopoietin-like protein 4, and follistatin. These hepatokines serve as molecular transducers of the metabolic benefits of physical activity in chronic metabolic diseases, including NAFLD, T2D, and CVDs, in various tissues.