TRPC6 Inactivation Does Not Protect Against Diabetic Kidney Disease in Streptozotocin (STZ)‐treated Sprague‐Dawley Rats

Abstract

Glomerular TRPC6 channels are up‐regulated in rodent models of diabetes mellitus, but the role of TRPC6 in driving progression of experimental diabetic nephropathy is controversial. We recently used CRISPR/Cas9 methods to generate Sprague‐Dawley rats with a deletion in exon 2 of the Trpc6 gene that renders the channels non‐functional [1]. In addition, we observed that animals lacking functional TRPC6 were protected in the chronic puromycin aminonucleoside (PAN) model of acquired FSGS [1]. In the present study, 300‐gram adult Trpc6del/del rats and their wild‐type Trpc6wt/wt littermates were examined in the STZ model of type‐1 diabetes using protocols approved by the University of Houston IACUC committee. In our experiments, diabetes was induced by a single intraperitoneal injection of STZ, while controls received vehicle. Animals were not treated with insulin. STZ‐treated rats with severe hyperglycemia (>450 mg/dl) by 5 days after treatment were used for analysis and were monitored for the next 10 weeks. At 4 and 10 weeks after STZ treatment, compared to vehicle‐treated controls, STZ‐treated rats had severe hyperglycemia (745 ± 144 mg/dl, mean ± SD at 10 weeks). They also had elevated plasma triglycerides and total cholesterol, and failed to gain weight. STZ‐treated rats also exhibited markedly increased urine albumin excretion, increased blood urea nitrogen (BUN), and increased plasma creatinine and decreased creatinine clearance, indicating marked declines in renal function in diabetic rats. Two‐way ANOVA analyses of these datasets revealed no differences between Trpc6wt/wt and Trpc6del/del rats in any of these parameters. There was no time in the course of the experiment where we obtained functional data suggesting a protective effect of TRPC6 inactivation on blood glucose, or kidney function in STZ diabetes. Histological analysis carried out 10 weeks after STZ treatment revealed marked glomerular and tubulointerstitial disease in STZ‐treated rats. Mesangial expansion was the prominent feature in glomeruli of STZ‐treated animals, and glomeruli were less disrupted than we previously observed in the chronic PAN model [1]. Blind semi‐quantitative analysis of glomerular histology revealed a significant effect of STZ but no protective effect of TRPC6 inactivation on glomerular pathology. In summary, TRPC6 inactivation does not prevent declines in renal function and appears to have no protective effect in the STZ model of type‐1 diabetes in Sprague‐Dawley rats. This is in marked contrast to our previous work in chronic PAN nephrosis, where TRPC6 inactivation preserves renal function and histology.Support or Funding InformationSupported by NIH grant R01‐DK104708.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.