INS and Insulin resistance: On the other hand, our observations of significantly increased peaks indicative of triglycerides at 1.33 ppm in chico flies (Table I) suggest that Drosophila could be also a useful model for studying insulin signaling since these flies with mutation in insulin receptor substrate (IRS), a Drosophila homolog of vertebrate IRS1-4, indeed show substantial increase in triglycerides (32,78) due to a mutated insulin signaling pathway (27), which causes reduced signaling through this pathway and insulin resistance.