P0978THE EFFECTS OF CHRONIC DAPAGLIFLOZIN TREATMENT ON THE RENAL MICROVASCULATURE IN A RAT MODEL OF TYPE 2 DIABETES
Authors: Ow Connie , Sukumaran Vijayakumar , Ngo Jennifer , Du Cheng Kun , Fujiwara Akihiro , Tsuchimochi Hirotsugu , Hosoda Hiroshi , Evans Roger , Pearson James 
Published: June 2020

Abstract

Background and Aims
Chronic kidney disease (CKD) is an ever-growing concern and CKD associated with diabetes accounted for ∼ 35% of new cases of end-stage renal failure. Clinical trials with insulin-independent sodium-glucose co-transporter 2 (SGLT2) inhibitors not only showed significant improvements in hyperglycemia and thus renal damage, but also reduced the risk of adverse cardiovascular events. Microvessels supply local tissue oxygen demands and are important controllers of regional perfusion. Endothelial dysfunction has been posited to be an important factor driving the pathogenesis of diabetic nephropathy, largely through impaired eNOS activity and thus reduced nitric oxide bioavailability. Thus, we aim to determine the effects of SGLT2 inhibition on vasodilator function in the renal vasculature. We hypothesize that rats chronically treated with dapagliflozin, a SGLT2 inhibitor, improves renal endothelial function and the microvessels are better able to maintain perfusion in response to the inhibition of nitric oxide synthase and prostaglandin blockade.

Method
Male Zucker fatty diabetic rats (8 wk old), a model of type 2 diabetes, were given daily oral gavage of 1 mg/kg dapagliflozin or its vehicle for up to 22 wks of age (n=6/group). Renal excretory function, glomerular filtration rate (GFR) and indices of renal injury was assessed before treatment and after every 4 wks up until 22 wks of age. GFR was assessed via transcutaneous clearance of FITC-sinistrin. Vasodilator function of the renal microvasculature was assessed via X-ray microangiography. We conducted successive imaging of the microvessels before and during infusion of acetylcholine (ACh) and sodium nitroprusside (SNP) which facilitated the assessment of endothelium dependent and independent dilation respectively. After which, rats were given successive boluses of L-NAME and indomethacin to assess the vasodilatory function of the microvasculature independent of nitric oxide and prostaglandins respectively. These inhibitors were given under the conditions of SNP clamp which allowed for us to titrate the blood pressure to baseline levels. Lastly, we assessed the ability of endothelium hyperpolarizing factors (EDHFs) to maintain microvascular perfusion when SNP infusion ceased and an infusion of ACh commenced while still under the effects of L-NAME and indomethacin.

Results
As expected, dapagliflozin alleviated hyperglycemia across the treatment period. There was a tendency for dapagliflozin to ameliorate the decline of GFR, although this apparent effect was not statistically significant. Dapagliflozin did not appear to improve indices of renal injury. Treatment with dapagliflozin alleviated polyuria but did not appear to have an impact on urine osmolarity or sodium excretion. The responses (vessel diameter) of renal microvessels to ACh and SNP was greater in dapagliflozin than in vehicle fed rats. The microvessels of vehicle fed rats appeared to undergo relative constriction in response to L-NAME and indomethacin even under the effects of SNP clamp. In contrast, microvessels of dapagliflozin fed rats appeared to be relatively well-perfused after NOS and COX blockade. This suggests that dapagliflozin may improve endothelial dysfunction commonly associated with diabetic nephropathy. Following NOS and COX blockade, ACh was infused in rats to determine the status of vasodilatory function mediated by EDHFs. The microvessels in diabetic rats did not appear to be dilated after infusion of ACh, suggesting that vasodilatory effects of EDHFs on the vasculature is diminished in diabetic rats. Dapagliflozin appeared to improve this effect in that the renal microvessels were dilated even when NOS and COX production was blocked/inhibited.

Conclusion
Chronic treatment of dapagliflozin may improve endothelial dysfunction and thus retard the progression of diabetic nephropathy in a rat model of type 2 diabetes.