Author:
Cheng Clara M.,Tseng Victor,Wang Jie,Wang Daniel,Matyakhina Ludmila,Bondy Carolyn A.
Abstract
IGF action has been implicated in the promotion of oxidative stress and aging in invertebrate and murine models. However, some in vitro models suggest that IGF-I specifically prevents neuronal oxidative damage. To investigate whether IGF-I promotes or retards brain aging, we evaluated signs of oxidative stress and neuropathological aging in brains from 400-d-old Igf1−/− and wild-type (WT) mice. Lipofuscin pigment accumulation reflects oxidative stress and aging, but we found no difference in lipofuscin deposition in Igf1−/− and WT brains. Likewise, there was no apparent difference in accumulation of nitrotyrosine residues in Igf1−/− and WT brains, except for layer IV/V of the cerebral cortex, where these proteins were about 20% higher in the Igf1−/− brain (P = 0.03). We found no difference in the levels of oxidative stress-related enzymes, neuronal nitric oxide synthase, inducible nitric oxide synthase, and superoxide dismutase in Igf1−/− and WT brains. Tau is a microtubule-associated protein that causes the formation of neurofibrillary tangles and senile plaques as it becomes hyperphosphorylated in the aging brain. Tau phosphorylation was dramatically increased on two specific residues, Ser-396 and Ser-202, both glycogen synthase kinases target sites implicated in neurodegeneration. These observations indicate that IGF-I has a major role in regulating tau phosphorylation in the aging brain, whereas its role in promoting or preventing oxidative stress remains uncertain.
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77 articles.
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