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. 2020 Nov 14;9(23):e018889. doi: 10.1161/JAHA.120.018889

Figure 2. Renal reabsorption of glucose.

Figure 2

A, Reabsorption of glucose in the proximal tubule. Sodium‐glucose cotransporter (SGLT) type 2 is expressed on the apical membrane of epithelial cells in the S1 segment of the proximal tubule, while glucose transporter 2 is expressed on the basolateral membrane. Epithelial cells of the S2/S3 segment express SGLT1 on the apical membrane and glucose transporter (GLUT) 1 on the basolateral membrane. The Na+‐K+‐ATPase pump is also located in the basolateral membrane of the proximal tubule and provides the energy for sodium‐glucose transport (through both SGLT2 and SGLT1). The pump drives Na+ exchange for K+ taking sodium out of the cytoplasm. As the intracellular Na+ concentration declines, sodium moves passively with glucose from the tubular lumen to the intracellular domain via the SGLT transporters. Once glucose is close to the proximal tubular cell, the concentration gradient passively translocates the molecule down into the interstitial space via the GLUTs. SGLT2 and GLUT2 together with SGLT1 and GLUT1 represent a coupled transport mechanism. In normal physiology, the SGLT2 in the S1 segment of the proximal tubule reuptakes 80% to 90% of the filtered glucose, while the remaining 10% to 20% is reabsorbed by SGLT1 in the S2/S3 segment. B, The normal glomerular filtration rate is ≈180 L/d. With an average daily‐long plasma glucose concentration of 100 mg/dL, the kidney filters ≈180 g of glucose every day, without glucose present in the urine.