STAT3 and keratoconus: PPARδ hyperactivation by the GW diet or the HFD significantly increased expression levels of p-Stat3 (Tyr705) (Fig. 4d–i) and KRASmu activity (p-Erk1/2) (Fig. 4h–m) measured by IHC and Western blot in KC mice and, to a greater extent in KC/Pd mice.