FGF21 and Insulin resistance: Lack of CerS1 or CerS5 has been associated with improvement of systemic glucose homeostasis via increase in Fgf21 from skeletal muscle (Turpin‐Nolan et al., 2019) and insulin resistance (Gosejacob et al., 2016), respectively, indicating that the negative effects of CerS1 and CerS5 on skeletal muscle fiber size and strength are not secondary to insulin resistance.