Do tubular changes in the diabetic kidney affect the susceptibility to acute kidney injury?

Diabetes is the single largest contributor to the growing prevalence of chronic kidney disease (CKD), and episodes of acute kidney injury (AKI) increase the risk of advanced CKD in diabetic patients. Here we discuss whether the pathophysiological changes that occur in the tubular system of the diabetic kidney affect the intrinsic susceptibility to AKI. There is abundant data showing that drug-induced nephrotoxicity is attenuated in rodents with experimental diabetes mellitus, and some mechanistic explanations have been provided, in particular in response to aminoglycosides. Besides downregulation in proximal tubular megalin, which mediates the aminoglycoside uptake in proximal tubules, a role for hyperglycemia-induced activation of regenerative mechanisms has been proposed. The available clinical data, however, indicates that diabetes is a risk factor for AKI, including aminoglycoside nephrotoxicity. While much needs to be learned about this disconnect, the isolated induction of diabetes in otherwise healthy young adult rodents may simply not fully mimic the influence that diabetes exerts in the setting of a critically ill and often elderly patient. We speculate that diabetic tubular growth and the associated molecular signature (including upregulation of TGF-β, senescence, and inflammation) set up the development of diabetic nephropathy and renal failure in part by increasing the susceptibility to AKI, which further promotes hypoxia and apoptosis. Considering the strong association between AKI episodes and the cumulative risk of developing advanced CKD in diabetes, strategies that reduce AKI in these patients are expected to help reduce the growing burden of end-stage renal disease.