Beneficial Effects of Dietary Restriction on Cerebral Cortical Synaptic Terminals

Preservation of Glucose and Glutamate Transport and Mitochondrial Function After Exposure to Amyloid β-Peptide, Iron, and 3-Nitropropionic Acid

Authors

  • ZhiHong Guo,

  • Arzu Ersoz,

  • D. Allan Butterfield,

  • Mark P. Mattson


  • Abbreviations used : Aβ, amyloid β-peptide ; DHR, dihydrorhodamine ; DR, dietary restriction ; GRP, glucose-regulated protein ; HSP, heat-shock protein ; 3-NP, 3-nitropropionic acid.

Address correspondence and reprint requests to Dr. M. P. Mattson at Laboratory of Neurosciences, National Institute on Aging, GRC 4F01, 5600 Nathan Shock Drive, Baltimore, MD 21224, U.S.A. E-mail : mattsonm @ grc.nia.nih.gov

Abstract

Abstract : Recent studies have shown that rats and mice maintained on a dietary restriction (DR) regimen exhibit increased resistance of neurons to excitotoxic, oxidative, and metabolic insults in experimental models of Alzheimer's, Parkinson's, and Huntington's diseases and stroke. Because synaptic terminals are sites where the neurodegenerative process may begin in such neurodegenerative disorders, we determined the effects of DR on synaptic homeostasis and vulnerability to oxidative and metabolic insults. Basal levels of glucose uptake were similar in cerebral cortical synaptosomes from rats maintained on DR for 3 months compared with synaptosomes from rats fed ad libitum. Exposure of synaptosomes to oxidative insults (amyloid β-peptide and Fe2+) and a metabolic insult (the mitochondrial toxin 3-nitropropionic acid) resulted in decreased levels of glucose uptake. Impairment of glucose uptake following oxidative and metabolic insults was significantly attenuated in synaptosomes from rats maintained on DR. DR was also effective in protecting synaptosomes against oxidative and metabolic impairment of glutamate uptake. Loss of mitochondrial function caused by oxidative and metabolic insults, as indicated by increased levels of reactive oxygen species and decreased transmembrane potential, was significantly attenuated in synaptosomes from rats maintained on DR. Levels of the stress proteins HSP-70 and GRP-78 were increased in synaptosomes from DR rats, consistent with previous data suggesting that the neuroprotective mechanism of DR involves a “preconditioning” effect. Collectively, our data provide the first evidence that DR can alter synaptic homeostasis in a manner that enhances the ability of synapses to withstand adversity.

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