17 Sep 2003

Could biopsy of olfactory epithelium yield early warnings of Alzheimer's disease (AD)? This possibility was raised by George Perry and colleagues who report in the August 29 online issue of Acta Neuropathologica that oxidative damage to olfactory neurons could be a harbinger of impending AD.

Perry, at the Case Western Reserve University, Cleveland, examined biopsies taken from the upper nasal cavity of eight patients with probable AD and three elderly control patients (ages 65-75). Samples from four suspected AD sufferers over age 65 had significantly higher levels of heme oxygenase-1 (HO-1) and hydroxynonenal pyrrole (HNE), two markers reported to be elevated in AD. While the four younger (ages 59-64) cognitively impaired patients also had elevated levels of HO-1 and HNE, these were not significant, though the authors point out that this may be due to lack of age-matched controls.

Oxidative damage is thought to be a major factor in the neurodegeneration seen in AD and other diseases of the central nervous system (see related debate). In the present study, however, the authors failed to detect changes in olfactory levels of the protein oxidation product carboxymethyl lysine, the glycation end-product pentosidine, or the nucleic acid byproduct 8-hydroxyguanosine, all well-characterized oxidative markers of AD. Perry suggests that changes "seen in the olfactory epithelium are only a portion of the full range of characteristics seen in AD." More extensive studies should reveal if olfactory biopsies could be useful as a diagnostic tool.—Tom Fagan