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Abstract:
The central question to be addressed in this review can be stated as "How does hypoglycemia kill neurons?" Initial research on hypoglycemic brain damage in the 1930s was aimed at demonstrating the existence of any brain damage whatsoever due to insulin. Recent results indicate that uncomplicated hypoglycemia is capable of killing neurons in the brain. However, the mechanism does not appear to be simply glucose starvation of the neuron resulting in neuronal breakdown. Rather than such an "internal catabolic death" current evidence suggests that in hypoglycemia, neurons are killed from without, i.e. from the extracellular space. Around the time the EEG becomes isoelectric, an endogenous neurotoxin is produced, and is released by the brain into tissue and cerebrospinal fluid. The distribution of necrotic neurons is unlike that in ischemia, being related to white matter and cerebrospinal fluid pathways. The toxin acts by first disrupting dendritic trees, sparing intermediate axons, indicating it to be an excitotoxin. Exact mechanisms of excitotoxic neuronal necrosis are not yet clear, but neuronal death involves hyperexcitation, and culminates in cell membrane rupture. Endogenous excitotoxins produced during hypoglycemia may explain the tendency toward seizure activity often seen clinically. The recent research results on which these findings are based are reviewed, and clinical implications are discussed.
Insights
Hypoglycemia kills neurons not by glucose starvation but via an endogenous neurotoxin released into the extracellular space. This excitotoxin disrupts neuronal function, leading to cell death and potentially seizures.
Area of Science:
- Neuroscience
- Cell Biology
- Endocrinology
Background:
- Early research focused on confirming insulin-induced brain damage.
- Recent findings indicate uncomplicated hypoglycemia causes neuronal death.
Purpose of the Study:
- To investigate the mechanism by which hypoglycemia kills neurons.
- To differentiate between internal catabolic death and external factors.
Main Methods:
- Review of recent research on hypoglycemic brain damage.
- Analysis of neuronal death patterns and toxin distribution.
Main Results:
- Hypoglycemia-induced neuronal death involves an endogenous neurotoxin from the extracellular space.
- The toxin disrupts dendritic trees, acting as an excitotoxin.
- Necrotic neuron distribution correlates with white matter and cerebrospinal fluid pathways.
Conclusions:
- Neurons are killed by external factors, not just glucose starvation.
- Hypoglycemia-induced excitotoxins may cause seizure activity.
- Understanding this mechanism has clinical implications for managing hypoglycemia.