XBP1 and kidney disorder: Supporting a role of ER stress in regulating CPT2 expression in the kidney in the course of CKD, we observed in the cohort of 201 CKD patients and healthy donors cited above (31) that ER stress response genes (PDI, heat shock protein family A member 5 [HSPA5], and XBP1) (43), and biomarkers of ER stress–related kidney diseases (LNC2 and MANF) (39, 44), were highly expressed in the tubulointerstitial compartment of patients with low eGFR, and, importantly, CPT2 expression was reduced in kidneys expressing the ER stress signature (Figure 6A).