GDF15 and Cachexia: One candidate that may drive the cachexia in this model is a recently described peptide hormone, GDF15, whose induction by cellular stress and the ISR has been well described and acts centrally in suppressing food intake.22,23 GDF15 can only mediate its effects centrally through increased levels in the circulation.24 Therefore, we examined plasma GDF15 from Ppp1r15aΔC/ΔC and Ppp1r15a+/+ mice, non-irradiated, and at different time points post-irradiation.