|Topic:||Role of the Kidney in Blood Glucose Control .|
|Details:|| Although the liver is the major site of glucose homeostasis, the kidney plays a vital role in the overall process of regulating the level of blood glucose. The kidney carries out gluconeogenesis primarily using the carbon skeleton of glutamine and while so doing allows for the elimination of waste nitrogen and maintaining plasma pH balance. For the role of the kidneys in gluconeogenesis please visit that section of the Gluconeogenesis page. In addition to carrying out gluconeogenesis, the kidney regulates blood glucose levels via its ability to excrete glucose via glomerular filtration as well as to reabsorb the filtered glucose in the proximal convoluted tubules. In the average adult the kidneys will filter around 180gm of glucose per day. Of this amount less than 1% is excreted in the urine due to efficient reabsorption. This reabsorption process is critical for maintaining blood glucose homeostasis and for retaining important calories for energy production.
Transport of glucose from the tubule into the tubular glomerular epithelial cells is carried out by specialized transport proteins termed sodium-glucose co-transporters (SGLTs). The SGLTs represent a family of transporters that are involved in the transport of glucose, amino acids, vitamins, and ions and other osmolytes across the brush-border (apical) membranes of kidney tubule cells and intestinal epithelial cells. There are two SGLT transporters in the kidney involved in glucose reabsorption. SGLT1 is found primarily in the distal S3 segment of the proximal tubule and SGLT2 is expressed in the S1 and S2 segments (see the Figure below). The location of SGLT2 in the proximal tubule means that it is primarily responsible for glucose reabsorption. SGLT2 is a high-capacity low-affinity transporter that, due to its expression location, is responsible for approximately 90% of the glucose reabsorption activity of the kidney.
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