FSTL1 and obesity due to melanocortin 4 receptor deficiency: Although neither acute nor 7 days of mild intermittent hypoxia exposure induced changes in plasma concentrations of several myokines in people with obesity, we found that hypoxia exposure (1% O2) increased the secretion of SPARC, follistatin like 1 (FSTL1) and IL-6 in primary human myotubes [81].