EIF2AK2 and chronic kidney disease: Moreover, subjects with elevated levels of PKR or its representative target, C/EBP homologous protein (CHOP), tended to exhibit higher Gdf15 levels than those with low PKR or CHOP expression (Fig. 1f [AKI] and 1 g [CKD]), thereby indicating a positive association between PKR signaling and Gdf15 expression.