Glucose transfer, blood-brain

Recently, however, an unexpected complication has been associated with the use of human insulin. The transfer of patients from porcine insulin to human insulin has been suggested by some investigators to cause the death of diabetics due to a phenomenon named hypoglycemia unawareness , where there is a loss of sensation in the patient due to a drop in the blood glucose to dangerously low levels. This phenomenon is not associated with porcine insulin, probably due to its better penetration of the blood-brain barrier because of the difference in one amino acid. The experimental evidence is controversial at this time, but will lead to a reevaluation of the safety of human insulin (Wolff, 1992). 

The use of liposomes for the transfer of therapeutic enzymes through the "blood-brain" barrier, which permits to deliver these enzymes into cells of the central nervous system also seems very attractive. It has been already shown that horse raddish peroxidase, encapsulated into liposomes made of phosphatidylcholine, cholesterol and phosphatidic acid (7 2 1 molar ratio), acquires the ability to cross the hemato-encephalic barrier, whereas the native enzyme cannot. The presence of peroxidase in brain cells was proved by histochemical methods. The same authors have shown that after injection of the liposomal glucose oxidase into the rat s tail vein, up to 5% of the enzymatic activity can be discovered in brain tissues. ... 

Cunningham, V. Hargreaves, R. J., Pelling, D. and Moorhouse, S. R. (1986) Regional blood-brain glucose transfer in the rat a novel double-membrane kinetic analysis. ]. Cerebral Blood Flow Metah., 6, 305-314... 

Regional blood-to-brain transfer of glucose was not altered by chronic lead treatment. Table 2 shows mean values for regions of the cerebral hemisphere of control and lead-treated rats. Similar results were obtained in the hindbrain e.g. mean uptake (+ SE) in cerebellum was 0.85 + 0.05 and 0.82 + 0.04, and in the brainstem 1.03 + 0.05 and 1.00 + 0.05 jUmol/min/g wet tissue in control and lead-treated rats, respectively. 

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