Apelin and Myostatin Levels in Adolescents With Type-1-Diabetes

Background: Myokines are secreted by skeletal muscle and play a role in their metabolic function and crosstalk with various tissues. Myokines appear to be involved in the pathogenesis of obesity and type 2 diabetes (T2D), yet little is known regarding their function in type 1 diabetes (T1D). Aim: To assess the levels and clinical correlates of a panel of five myokines, comparing adolescents with recent-onset T1D, prolonged disease, and healthy controls. Methods: Fifty-eight adolescents participated; 20 with recent-onset T1D, 20 with over 7 years of T1D, and 18 healthy controls were included. Clinical and laboratory data were collected, including levels of Apelin, Irisin, Interleukin-6 (IL-6), Fibroblast growth factor 21 (FGF21), and Myostatin. Results: Apelin levels were lower in patients with prolonged T1D compared with patients with recent-onset T1D and controls, (117.9 ± 94.3, 228.3 ± 181.6, and 224.4 ± 138.4 pg/ml, respectively; analysis of variance (ANOVA) p = 0.029). Other myokines did not differ significantly between groups. Apelin levels correlated with fasting C-peptide levels (r = 0.337, p = 0.010). In patients with prolonged T1D, myostatin positively correlated with insulin doses (total daily dose r = 0.590, p = 0.006 and basal daily dose r = 0.645, p = 0.002). Both apelin and myostatin levels negatively correlated with the diastolic blood pressure (BP) percentile (r = - 0.324, p = 0.013; r = - 0.302, p = 0.024, respectively). Conclusions: Our results demonstrate lower levels of apelin, a myokine related to the beneficial metabolic effects of skeletal muscle, in prolonged T1D. The correlations of apelin with C-peptide and myostatin with insulin doses may reflect a relationship with beta-cell function and insulin sensitivity.