Musclin Is Related to Insulin Resistance and Body Composition, but Not to Body Mass Index or Cardiorespiratory Capacity in Adults

Abstract

Background: We studied whether musclin function in humans is related to glycemic control, body composition, and cardiorespiratory capacity. Methods: A cross-sectional study was performed in sedentary adults with or without metabolic syndrome (MS). Serum musclin was measured by enzyme-linked immunosorbent assay. Insulin resistance (IR) was evaluated by the homeostatic model assessment (HOMA-IR). Body composition was determined by dual-energy X-ray absorptiometry and muscle composition by measuring carnosine in the thigh, a surrogate of fiber types, through proton magnetic resonance spectroscopy. Cardiorespiratory capacity was assessed through direct ergospirometry. Results: The control (n=29) and MS (n=61) groups were comparable in age (51.5±6.5 years old vs. 50.7±6.1 years old), sex (72.4% vs. 70.5% women), total lean mass (58.5%±7.4% vs. 57.3%±6.8%), and peak oxygen consumption (VO2peak) (31.0±5.8 mL O2./kg.min vs. 29.2±6.3 mL O2/kg.min). Individuals with MS had higher body mass index (BMI) (30.6±4.0 kg/m 2 vs. 27.4± 3.6 kg/m 2 ), HOMA-IR (3.5 [95% confidence interval, CI, 2.9 to 4.6] vs. 1.7 [95% CI, 1.1 to 2.0]), and musclin (206.7 pg/mL [95% CI, 122.7 to 387.8] vs. 111.1 pg/mL [95% CI, 63.2 to 218.5]) values than controls (P˂0.05). Musclin showed a significant relationship with HOMA-IR (β=0.23; 95% CI, 0.12 to 0.33; P˂0.01), but not with VO2peak, in multiple linear regression models adjusted for age, sex, fat mass, lean mass, and physical activity. Musclin was significantly associated with insulin, glycemia, visceral fat, and regional muscle mass, but not with BMI, VCO2peak, maximum heart rate, maximum time of work, or carnosine. Conclusion:In humans, musclin positively correlates with insulinemia, IR, and a body composition profile with high visceral adiposity and lean mass, but low body fat percentage. Musclin is not related to BMI or cardiorespiratory capacity.

Serum Levels of Myonectin Are Lower in Adults with Metabolic Syndrome and Are Negatively Correlated with Android Fat Mass

“…Cardiorespiratory fitness was assessed through an incremental treadmill ergospirometry test with an open circuit spirometer Oxycon Delta by Jaeger ® (VIASYS Health care GmbH, Pullach, Germany), as previously described [ 45 ]. Waist circumference was measured with fiberglass anthropometric tape at the midpoint between the lower edge of the rib cage and the iliac crest, according to the World Health Organization recommendations [ 46 ], and IR was estimated with the HOMA-IR [ 5 ].…”

“…Spectra were acquired on a Magnetom Skyra magnet with a Flex large 4-channels, 3T receive only, 516 × 224 mm, coil interface and the SyngoMR D13 program (Siemens Healthcare, Erlangen, Germany) as previously reported [5,45,54]. The spectra were processed with jMRUI [55] v5.2 software (http://www.jmrui.eu, accessed on 1 February 2020).…”

“…Serum levels of myokines are affected by conditions such as exercise and diet, and likewise, their levels influence the state of health and disease [ 2 , 4 ]. The study of myokines is key to understanding the role of skeletal muscle in the pathophysiology of conditions such as metabolic syndrome (MS) [ 5 ].…”

Reactive Oxygen and Nitrogen Species (RONS) and Cytokines—Myokines Involved in Glucose Uptake and Insulin Resistance in Skeletal Muscle

“…Musclin is a factor secreted by skeletal muscle and is a potent regulator of glucose metabolism [ 148 ]. In humans, an increase in the circulating musclin level has been reported in diagnosed T2D patients [ 149 ] and those with metabolic syndrome [ 150 ]. In the latter, a positive correlation was found between both altered insulinemia and glycemia and a body composition profile with high visceral fat and lean mass [ 150 ].…”

“…In humans, an increase in the circulating musclin level has been reported in diagnosed T2D patients [ 149 ] and those with metabolic syndrome [ 150 ]. In the latter, a positive correlation was found between both altered insulinemia and glycemia and a body composition profile with high visceral fat and lean mass [ 150 ]. The musclin-induced impairment of insulin-stimulated glucose uptake in skeletal muscle is related to Akt inhibition and PPARγ/LXRα in mice [ 93 ] and causes endoplasmic reticulum stress in rats [ 94 ].…”