Dapagliflozin Binds Specifically to Sodium-Glucose Cotransporter 2 in the Proximal Renal Tubule

Abstract

Kidneys contribute to glucose homeostasis by reabsorbing filtered glucose in the proximal tubules via sodium-glucose cotransporters (SGLTs). Reabsorption is primarily handled by SGLT2, and SGLT2-specific inhibitors, including dapagliflozin, canagliflozin, and empagliflozin, increase glucose excretion and lower blood glucose levels. To resolve unanswered questions about these inhibitors, we developed a novel approach to map the distribution of functional SGLT2 proteins in rodents using positron emission tomography with 4-[ 18 F]fluoro-dapagliflozin (F-Dapa). We detected prominent binding of intravenously injected F-Dapa in the kidney cortexes of rats and wild-type and Sglt1-knockout mice but not Sglt2-knockout mice, and injection of SGLT2 inhibitors prevented this binding. Furthermore, imaging revealed only low levels of F-Dapa in the urinary bladder, even after displacement of kidney binding with dapagliflozin. Microscopic ex vitro autoradiography of kidney showed F-Dapa binding to the apical surface of early proximal tubules. Notably, in vivo imaging did not show measureable specific binding of F-Dapa in heart, muscle, salivary glands, liver, or brain. We propose that F-Dapa is freely filtered by the kidney, binds to SGLT2 in the apical membranes of the early proximal tubule, and is subsequently reabsorbed into blood. The high density of functional SGLT2 transporters detected in the apical membrane of the proximal tubule but not detected in other organs likely accounts for the high kidney specificity of SGLT2 inhibitors. Overall, these data are consistent with data from clinical studies on SGLT2 inhibitors and provide a rationale for the mode of action of these drugs.

Diabetes pharmacotherapy and effects on the musculoskeletal system

“…357 Studies using radio-fluorinated labeling of dapagliflozin have also examined organ specific SGLT2inhibitor binding in rat tissues, and while skeletal binding was not assessed, no specific binding to skeletal muscle was observed. 358 Similarly, mRNA expression of SGLT1 in muscle tissue of control and diabetic rats was found to be negligible. 359 Taken together, these studies indicate that SGLT2-inhibitor drugs are unlikely to have a specific direct effect on musculoskeletal tissues at the cellular level.…”

“…SGLT2 expression was not detected in cells of either the osteoblast or osteoclast lineages; SGLT1 was detected in MC3T3‐E1 differentiating osteoblasts, albeit at levels <1% of that observed in the kidney, but not in any cells of osteoclast lineage . Studies using radio‐fluorinated labeling of dapagliflozin have also examined organ specific SGLT2‐inhibitor binding in rat tissues, and while skeletal binding was not assessed, no specific binding to skeletal muscle was observed . Similarly, mRNA expression of SGLT1 in muscle tissue of control and diabetic rats was found to be negligible .…”

Physiology of renal glucose handling via SGLT1, SGLT2 and GLUT2

“…For example, using microPET to monitor Me-4FDG excretion into the urinary bladder, we have shown that intravenous injection of phlorizin or the specific SGLT2 inhibitor dapagliflozin rapidly increases excretion of Me-4FDG into the urinary bladder (Fig. 5 a) [ 32 ]. Dapagliflozin acts specifically on the kidneys, as shown by microPET imaging of mice injected with 4-[ 18 F]fluoro-dapagliflozin (F-Dapa) [ 32 ].…”

Interaction Between the Sodium‐Glucose–Linked Transporter 2 Inhibitor Dapagliflozin and the Loop Diuretic Bumetanide in Normal Human Subjects

“…D apagliflozin is a selective and competitive inhibitor of the renal proximal tubule sodium-glucose-linked transporter 2 (SGLT2). [1][2][3][4] It is approved for the treatment of type 2 diabetes mellitus (T2DM), where it promotes glycosuria. 1,5 T2DM increases the incidence of congestive heart failure (CHF).…”