Effect of Farxiga on Renal Function and Size in Type 2 Diabetic Patients With Hyperfiltration

Hyperfiltration is a characteristic feature in experimental models of diabetes and is causally related to an increase in intraglomerular pressure. In newly diagnosed diabetic patients, both type 1 and type 2, hyperfiltration and enlarged kidney size commonly are observed, and these hemodynamic/anatomic abnormalities are associated with an increased risk for the development of diabetic nephropathy.

In poorly controlled diabetic individuals, the filtered load of glucose is markedly increased and glucose - with sodium - reabsorption by the SGLT2 transporter in the proximal tubule is augmented. As a consequence sodium delivery to the macula densa is reduced, making the kidney think that it is under perfused and this results in afferent renal arteriolar vasodilation. The efferent arteriole of the hyperfiltrating diabetic kidney also is hypersensitive to angiotensin II despite the absence of systemic RAS activation. The net result of these hemodynamic changes is an increase in intraglomerular pressure and hyperfiltration. Further, angiotensin is a potent growth factor and contributes to the increase in size of individual glomeruli and total kidney size. Since the intraglomerular pressure is related to the radius (r3) by the Law of LaPlace, the increase in glomerular size also contributes to hyperfiltration.

Based upon the preceding sequence, it follows that a drug that blocks glucose, along with sodium, reabsorption in the proximal tubule would enhance sodium delivery to the macula densa, cause afferent renal arteriolar constriction, reduce intraglomerular pressure/hyperfiltration, and decrease kidney size. In hyperfiltering diabetic patients with microalbuminuria, the investigators also would expect the microalbuminuria to decrease. Consistent with this scenario, animal studies have documented that both acute and chronic inhibition of SGLT2 decreases hyperfiltration and prevents diabetic nephropathy. A recent study in hyperfiltering type 1 diabetic patients treated with empagliflozin has provided additional support for the tubular glomerular feedback hypothesis.

The investigators propose to treat newly diagnosed, hyperfiltering T2DM patients with or without microalbuminuria with dapagliflozin or metformin for 4 months. The metformin-treated group will serve as controls for improved glycemic control, since the investigators have shown that insulin therapy to normalize A1c reduces hyperfiltration and kidney size in T1DM patients