Chapter 7 - Diseases of Renal Glucose Handling

Abstract

This chapter describes the normal mechanisms of renal glucose reabsorption and their genetic disturbances. The urine from normal healthy subjects contains a small amount of glucose, ranging from 0.3 to 1.1 moles (or 100-300 mg)/day/1.73 m2. This is a small fraction of the normal filtered glucose load, ~180 grams/day and, given the volume of urine produced in 24 hours, ~950 ml, the glucose concentration in urine is generally only ~8% of the plasma concentration. There are two genetic disorders where glucose excretion ranges up to a high of 250 grams/day/1.73 m2, i.e., in subjects with Fanconi-Bickel syndrome and with familial renal glucosuria. Fanconi-Bickel syndrome (FBS) subject presents with an array of other symptoms ranging from failure to grow to hepatomegaly. Glucose-galactose malabsorption (GGM) presents in newborn children as a massive life-threatening diarrhea and this is caused by variations in the sodium/glucose cotransporter (SGLT1) gene. In patients with GGM, glucose and galactose are not absorbed and diarrhea results from the osmotic load in the gut. The diarrhea resolves on eliminating lactose, glucose, and galactose from the diet, but promptly resumes on adding one or more of the sugars back. FFG is an autosomal recessive renal tubular disorder characterized by urinary glucose excretion in the presence of normal blood glucose levels and normal oral glucose tolerance. This is an isolated renal tubular disorder, where the glomerular filtration rate (GFR) and reabsorption of salt, water, and other nutrients is normal. The level of glucose excretion ranges from 1 up to 169 grams/day/1.73 m2.