Sitagliptin ameliorates ER stress in diabetic kidney disease through upregulation of SIRT1

Abstract Objectives Endoplasmic reticulum (ER) stress plays a significant role in the progression of diabetic kidney disease (DKD), and dipeptidyl peptidase-4 (DPP4) inhibitors are widely used antihyperglycemic agents, exerting renal beneficial effects in DKD. Here, we investigated the role of DPP4 inhibitor Sitagliptin (Sita) in ER homeostasis in the kidneys of diabetic DBA2/J (D2) mice and in albumin-stimulated HK-2 cells. Methods and Results ER stress was observed both in vivo and in vitro, as reflected by notably increased glucose-regulated protein of 78 kDa (GRP78), CHOP, high phosphorylation of PERK (p-PERK), and cleaved caspase3 (c-CASP3), whereas Sita effectively attenuated these disorders. Meanwhile, Sita increased the expression of SIRT1 both in vivo and in vitro. To further validate the potential effects of SIRT1 in regulating ER stress, we regulated SIRT1 by siRNA and overexpressed plasmids in albumin-overloaded HK-2 cells. Elevated SIRT1 alleviated albumin-induced ER stress, while decreased SIRT1 further aggravated ER stress in albumin-treated HK-2 cells. Conclusion The results suggest that a novel mechanism links the DPP4 enzyme to ER stress during tubular injury in DKD and highlight that SIRT1 may be a potential target for managing DKD.