Abstract
Background and objectives: Adipose tissue and skeletal muscle secrete adiponectin, a hormone abundantly secreted by adipocytes, that through the adiponectin receptor, regulate glucose and lipid metabolism. Adiponectin appears to protect skeletal muscles from inflammatory damage induced by oxidative stress. It has been suggested that decreased adiponectin levels could be associated with pathologic conditions, including obesity and diabetes. Furthermore, some studies suggest that exercise could have a beneficial effect by increasing adiponectin levels, but this observation remains controversial. It is also unknown if physical exercise modifies adiponectin expression in skeletal muscles. The aim of this study was to investigate the effect of chronic exercise on serum adiponectin and adiponectin expression in slow-twitch (soleus) and fast-twitch (plantaris) muscles in healthy rats. Materials and methods: Two-month-old male Wistar rats were randomly divided into three groups with n = 6 in each group: control (C), moderate-intensity training (MIT), and high-intensity training (HIT). The rats were conditioned to run on a treadmill for the 8-week period. Forty-eight hours after the last session, blood samples were collected for adiponectin measurements and total RNA was isolated from plantaris and soleus muscles to measure by RT-qPCR adiponectin receptor 1 and adiponectin mRNA expression level. Results: MIT and HIT groups had reduced adiponectin protein levels in serum and the plantaris muscle, but not changes in adiponectin protein were observed in the soleus muscle. No significant differences in Adiponectin receptor 1 (AdipoR1) gene expression were observed following intense or moderate exercise in either muscle group studied. Conclusions: Our study shows that decreasing levels of circulating adiponectin is a result of physical exercise and should not be generalized as a predictive marker of disease.
Highlights
Adiponectin, known as Adipoq is an adipocyte-derived factor [1]
We found that in C group was 3.25 ± 0.44 μg/mL (CV = 27%), in the moderate-intensity training (MIT)
Statistical comparison between MIT and high-intensity training (HIT) groups with C reveals that the trained groups have a significantly lower serum adiponectin concentration, as was previously shown [19] (Figure 1B)
Summary
Adiponectin, known as Adipoq is an adipocyte-derived factor [1]. Through adiponectin receptor activation (Adipor and Adipor2), this adipokine regulates glucose and lipid metabolismMedicina 2019, 55, 291; doi:10.3390/medicina55060291 www.mdpi.com/journal/medicinaMedicina 2019, 55, 291 and has anti-inflammatory properties [2,3,4]. Through adiponectin receptor activation (Adipor and Adipor2), this adipokine regulates glucose and lipid metabolism. Adiponectin over-expression, using molecular engineering techniques, increases insulin sensitivity and improves muscle performance [8,9]. Adipose tissue and skeletal muscle secrete adiponectin, a hormone abundantly secreted by adipocytes, that through the adiponectin receptor, regulate glucose and lipid metabolism. Adiponectin appears to protect skeletal muscles from inflammatory damage induced by oxidative stress. It has been suggested that decreased adiponectin levels could be associated with pathologic conditions, including obesity and diabetes. Some studies suggest that exercise could have a beneficial effect by increasing adiponectin levels, but this observation remains controversial. It is unknown if physical exercise modifies adiponectin expression in skeletal muscles. The aim of this study was to investigate the effect of chronic exercise on serum adiponectin and adiponectin expression in slow-twitch (soleus) and fast-twitch (plantaris) muscles in healthy rats
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