Aldose reductase and sorbitol dehydrogenase activities in diabetic brain: In vivo kinetic studies using ¹⁹F 3-FDG NMR in rats

The effects of diabetes mellitus on the kinetic constants of aldose reductase and sorbitol dehydrogenase in rat brain were investigated non-invasively in vivo using the 3-fluoro-3-deoxy-D-glucose (3-FDG) 19-fluorine (¹⁹F) nuclear magnetic resonance (NMR) method. While forward flux for both aldose reductase and sorbitol dehydrogen-ase (k₁ and k₂) were significantly increased, there was no corresponding increase in reverse flux (k₃ and k₄), and leakage of fructose (k₅) was negligible. These findings indicate that the enzymatic kinetics of aldose reductase sorbitol (ARS) in diabetic brain undergo alteration favoring intracellular sorbitol and fructose accumulation, the frequently implicated biochemical basis of diabetic complications.