Hedgehog interacting protein activates sodium–glucose cotransporter 2 expression and promotes renal tubular epithelial cell senescence in a mouse model of type 1 diabetes

Aims/hypothesis Senescent renal tubular cells may be linked to diabetic kidney disease (DKD)-related tubulopathy. We studied mice with or without diabetes in which hedgehog interacting protein (HHIP) was present or specifically knocked out in renal tubules ( Hhip RT -KO), hypothesising that local deficiency of HHIP in the renal tubules would attenuate tubular cell senescence, thereby preventing DKD tubulopathy. Methods Low-dose streptozotocin was employed to induce diabetes in both Hhip RT -KO and control ( Hhip fl/fl ) mice. Transgenic mice overexpressing Hhip in renal proximal tubular cells (RPTC) ( Hhip RPTC -Tg) were used for validation, and primary RPTCs and human RPTCs (HK2) were used for in vitro studies. Kidney morphology/function, tubular senescence and the relevant molecular measurements were assessed. Results Compared with Hhip fl/fl mice with diabetes, Hhip RT -KO mice with diabetes displayed lower blood glucose levels, normalised GFR, ameliorated urinary albumin/creatinine ratio and less severe DKD, including tubulopathy. Sodium–glucose cotransporter 2 (SGLT2) expression was attenuated in RPTCs of Hhip RT -KO mice with diabetes compared with Hhip fl/fl mice with diabetes. In parallel, an increased tubular senescence-associated secretory phenotype involving release of inflammatory cytokines (IL-1β, IL-6 and monocyte chemoattractant protein-1) and activation of senescence markers (p16, p21, p53) in Hhip fl/fl mice with diabetes was attenuated in Hhip RT -KO mice with diabetes. In contrast, Hhip RPTC -Tg mice had increased tubular senescence, which was inhibited by canagliflozin in primary RPTCs. In HK2 cells, HHIP overexpression or recombinant HHIP increased SGLT2 protein expression and promoted cellular senescence by targeting both ataxia-telangiectasia mutated and ataxia-telangiectasia and Rad3-related-mediated cell arrest. Conclusions/interpretation Tubular HHIP deficiency prevented DKD-related tubulopathy, possibly via the inhibition of SGLT2 expression and cellular senescence. Graphical abstract