In this study, we have utilised a model involving macrophage treatment with an SFA, a UFA or a combination of these and application of the CM generated to differentiated C2C12 myotubes in culture to determine whether and how increased local infiltration of macrophages into skeletal muscle during obesity ((Fink et al., 2013, Hevener et al., 2007, Nguyen et al., 2007); NAT, CWJ and MEC, unpublished data) might impact upon local insulin sensitivity and the differential effects of FA types in this context. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.