Seric Musclin is not Increased in Patients with Metabolic Syndrome and Insulin Resistance

Abstract

Skeletal muscle has now been recognized as an endocrine tissue, through the production and secretion of myokines. Musclin is a myokine mainly secreted by fibers type II (FT-II) that induces insulin resistance (IR) in both cellular and murine models. We hypothesize that musclin could be involved in pathophysiology of metabolic syndrome (MS) in humans. PURPOSE: to evaluate the relationships among IR, seric musclin, area occupied by FT-II and muscle mass in adults with and without MS. METHODS: analytical study in adults with and without MS. Homeostatic model assessment (HOMA-IR) was used as indicator of IR, musclin was measured by ELISA, area of FT-II in right vastus lateralis muscle by proton magnetic resonance spectroscopy and both fat and lean mass of the body and the right thigh (absolute values in Kg, or indexes in Kg/m2 and Kg/Kg body mass) by dual X-ray absorptiometry. Data presented as mean±standard deviation. RESULTS: 23 subjects with and 10 without MS, comparable in age (51.6±5.7 with MS vs 53.5±6.3 without MS; P>0.05) and gender were included. Subjects with MS had higher values of insulin (18.3±7.4 vs 6.7±2.5 μU/ml; P<0.05) and HOMA-IR (4.6±2.2 vs 1.6±0.6; P<0.05). There were no differences between groups regarding glycaemia (99.1±8.8 vs 93.2±12.7), musclin (609.9±203.4 pg ml-1 vs 657.9±240.5 pg ml-1), area of FT-II (51.4±23.2% vs 49±26.7%) or absolute values or indexes of muscle mass. There were positive correlations between HOMA-IR and both body fat mass or thigh fat mass (r>0.46; P<0.05), between musclin and indexes of total lean mass (Kg m-2, r=0.51; P<0.05) and thigh lean mass (Kg m-2, r>0.54; P<0.05), also between area of FT-II and indexes of total lean mass (r>0.49; P<0.05). There was a negative trend between total lean mass and HOMA-IR (r=-0.34; P=0.07). We did not find correlation between HOMA- IR and musclin or area of FT-II. CONCLUSIONS: lean mass seems to determine seric musclin, however, this myokine was not associated to IR in our patients. These findings are in controversy with previous ones reported for cellular models. COLCIENCIAS 111562638757. CODI 2605. Interinstitucional 2016-1341. Colciencias doctoral scholarships 727-2015.