Kinetics

Folates occur in the diet as PteGlun that must be hydrolyzed to the monoglutamate form (PteGlu) before absorption. The hydrolysis is catalyzed by gamma-glutamyl hydrolase (EC 3.4.19.9) found in the brush border of the intestinal mucosa. The PteGlu is primarily absorbed by active transport by reduced folate carrier (RFC) in the jejunum and upper duodenum.141,148 RFC is now known as solute carrier family 19, member 1 (SLC19A1) and is related to the thiamine transporters SLC10A2 and SLC19A3 that were discussed previously. This absorption is saturable and facilitated by the slightly acidic conditions found in these regions. Although the mucosa in these regions possesses dihydrofolate reduc-tase (DHFR, EC 1.5.1.3), most reduction to dihydrofolate (H2PteGlu, formerly called dihydrofolic acid or DHFA) and then to tetrahydrofolate (H4PteGlu, formerly called tetrahy-drofolic acid or THFA) and methylation occur in the liver. H4PteGlu is distributed to all tissues, where it is stored as polyglutamates, primarily pentaglutamates or heptagluta-mates (H4PteGlu5 or H4PteGlu7). The 5-methyl derivative (5-methyl-PteGlun) is the main transport and storage form in the body. The body stores 5 to 10 mg with approximately 50% in the liver. The major elimination pathway for the vitamin is biliary excretion as the 5-methyl derivative. Extensive enterohepatic cycling occurs. Only trace amounts are found in the urine. Large doses that exceed the tubular reabsorption limit, however, result in substantial amounts in the urine.

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Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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