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Hyperglycemia not hypoglycemia alters neuronal dendrites and impairs spatial memory
John I Malone1, Suzan Hanna, Samuel Saporta
1Department of Pediatrics, University of South Florida College of Medicine, Tampa, FL, USA. jmalone@hsc.usf.edu
Pediatric Diabetes
|December 11, 2008
Summary
Chronic hyperglycemia, not hypoglycemia, impairs learning and memory by altering neuronal structure and brain polyol pathway activity. This suggests high blood sugar negatively impacts brain function more than low blood sugar.
Area of Science:
- Neuroscience
- Endocrinology
- Metabolic Disorders
Background:
- Previous research linked chronic hyperglycemia, but not hypoglycemia, to reduced neuronal size.
- Hyperglycemia-induced neuronal changes may negatively impact cognitive functions like learning and memory.
Purpose of the Study:
- To assess the effects of hyperglycemia and hypoglycemia on neuronal dendritic structure.
- To evaluate the impact of hyperglycemia and hypoglycemia on cognitive functioning in young rats.
Main Methods:
- Male Wistar rats (4 weeks old) underwent 8-week experimental manipulations.
- Groups included untreated controls, streptozotocin-induced diabetic (STZ-D) rats, and intermittent hypoglycemic rats.
- Cognitive function was assessed using the radial-arm water maze; brains were examined histologically and biochemically.
Main Results:
- Hyperglycemia increased brain sorbitol and inositol, and decreased taurine.
- STZ-D rats showed reduced neuronal dendritic branching and spine density.
- STZ-D rats exhibited impaired performance in the spatial memory water maze task.
Conclusions:
- Hyperglycemia, unlike hypoglycemia, adversely affected brain polyol pathway activity and neuronal structure.
- Hyperglycemia was associated with impaired long-term spatial memory.
- The hyperglycemic component of diabetes mellitus appears to have a greater adverse effect on brain function than intermittent hypoglycemia.
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