Abstract
Intramuscular adipose is conducive to good pork quality, whereas subcutaneous adipose is considered as waste in pig production. So uncovering the regulation differences between these two adiposes is helpful to tissue-specific control of fat deposition. In this study, we found the sensitivity to glucocorticoids (GCs) was lower in intramuscular adipocytes (IMA) compared with subcutaneous adipocytes (SA). Comparison of glucocorticoid receptor (GR) revealed that IMA had lower GR level which contributed to its reduced GCs sensitivity. Higher methylation levels of GR promotor 1-C and 1-H were detected in IMA compared with SA. GR expression decrease was also found in adipocytes when treated with muscle conditioned medium (MCM) in vitro, which resulted in significant inhibition of adipocytes proliferation and differentiation. Since abundant myostatin (MSTN) was detected in MCM by ELISA assay, we further investigated the effect of this myokine on adipocytes. MSTN treatment suppressed adipocytes GR expression, cell proliferation and differentiation, which mimicked the effects of MCM. The methylation levels of GR promotor 1-C and 1-H were also elevated after MSTN treatment. Our study reveals the role of GR in muscle fiber inhibition on intramuscular adipocytes, and identifies myostatin as a muscle-derived modulator for adipose GR level.
Highlights
Adipose tissue is a large endocrine organ in the body, and functions in energy storage, hormone production, and immune function[1]
Cell viability assessment results showed that all three concentrations of DEX could promote the proliferation of subcutaneous adipocytes (SA) and intramuscular adipocytes (IMA) pre-adipocytes, of which 100 nM DEX treatment is of the highest efficiency
Distribution of body fat is an important predictor of metabolic abnormalities, because subcutaneous adipose is inversely associated with glucose and lipid concentrations, while increased intramuscular adipose is independently associated with insulin resistance and T2D29, 30
Summary
Adipose tissue is a large endocrine organ in the body, and functions in energy storage, hormone production, and immune function[1]. Subcutaneous adipose tissue (SAT), the major part of body fat, is supposed to be in the smallest amount possible in pig production. The reason might be that the regulation mechanisms for various fat tissues should be of similarities Even they are from different fat depots. This explains why IMAT and SAT are of moderate positive correlation[2]. Since the requirements for these two fat tissues are different, understanding the molecular regulation difference between IMAT and SAT is of great significance to pig breeding. (b) The differentiation of SA and IMA pre-adipocytes after induced with DEX. The molecular mechanism underlying differential GCs sensitivities of various adipose tissues still remains unknown
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