Glycosylation of Acetylcholinesterase and Butyrylcholinesterase Changes as a Function of the Duration of Alzheimer’s Disease J. Sa ´ez-Valero, 1,2 L.R.Fodero, 1,6 M. Sjo ¨ gren, 3 N. Andreasen, 4 S. Amici, 5 V. Gallai, 5 H. Vanderstichele, 4 E. Vanmechelen, 4 L. Parnetti, 5 K. Blennow, 3 and D. H. Small 6 * 1 Department of Pathology, University of Melbourne, Victoria, Australia 2 Instituto de Neurociencias, Universidad Miguel Herna ´ndez-CSIC, San Juan de Alicante, Spain 3 Department of Clinical Neuroscience, Go ¨teborg University, Mo ¨lndal, Sweden 4 Innogenetics B.V., Industriepark Azijnaarde, Gent, Belgium 5 Department of Neuroscience, University of Perugia, Perugia, Italy 6 Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia The identification of biochemical markers of Alzheimer’s disease (AD) may help in the diagnosis of the disease. Previous studies have shown that A 1– 42 is decreased, and tau and phospho-tau are increased in AD cerebro- spinal fluid (CSF). Our own studies have identified glyco- sylated isoforms of acetylcholinesterase (Glyc-AChE) and butyrylcholinesterase (Glyc-BuChE) that are in- creased in AD CSF. Glyc-AChE is increased in APP (SW) Tg2576 transgenic mice prior to amyloid plaque deposi- tion, which suggests that Glyc-AChE may be an early marker of AD. The aim of this study was to determine whether Glyc-AChE or Glyc-BuChE is increased in CSF at early stages of AD and to compare the levels of these markers with those of A 1– 42 , tau and phospho-tau. Lumbar CSF was obtained ante mortem from 106 non-AD patients, including 15 patients with mild cogni- tive impairment (MCI), and 102 patients with probable AD. Glyc-AChE, tau and phospho-tau were significantly increased in the CSF of AD patients compared to non- neurological disease (NND) controls. A 1– 42 was lower in the AD patients than in NND controls. A positive corre- lation was found between the levels of Glyc-AChE or Glyc-BuChE and disease duration. However, there was no clear correlation between the levels of tau, phospho- tau or A 1– 42 and disease duration. The results suggest that Glyc-AChE and Glyc-BuChE are unlikely to be early markers of AD, although they may have value as markers of disease progression. © 2003 Wiley-Liss, Inc. Key words: Alzheimer’s; acetylcholinesterase; biomark- ers; cerebrospinal fluid The identification of a biomarker of Alzheimer’s disease (AD) would assist in diagnosis of the disease. Sev- eral candidate biomarkers of AD have been identified in cerebrospinal fluid (CSF; Small, 2002). A number of stud- ies have shown that total tau and phosphorylated isoforms of tau are increased in AD CSF, whereas the amyloid-  1– 42 polypeptide (A 1– 42 ) is decreased (Vandermeeren et al., 1993; Blennow et al., 1995; Kanai et al., 1998; Tapiola et al., 2000; Itoh et al., 2001; Maruyama et al., 2001; Mehta et al., 2001; Shoji et al., 2002). While none of these markers alone provides sufficient sensitivity or specificity for routine use in the diagnosis of AD, recent studies suggest that the combined measurement of CSF A 1– 42 and tau meets the requirements for clinical use in discrim- inating AD from normal aging and specific neurologic disorders (Shoji et al., 1998; Hulstaert et al., 1999). The levels of acetylcholinesterase (AChE; Atack et al., 1983, 1986; Fishman et al., 1986; Small et al., 1996) and butyrylcholinesterase (BuChE; Friede, 1965; Arendt et al., 1992; Moran et al., 1993; Geula and Mesulam, 1995) are altered in the AD brain. AChE, like BuChE, is increased around amyloid plaques and in tangle-bearing neurons in the cortex (Friede, 1965; Ulrich et al., 1990; Moran et al., 1993; Wright et al., 1993; Mesulam and Geula, 1994; Geula and Mesulam, 1995). Our previous studies have identified unusual glycoforms of both AChE (Glyc-AChE) and BuChE (Glyc-BuChE) that are in- creased in postmortem CSF of AD patients (Sa ´ez-Valero et al., 1997, 1999; Sa ´ez-Valero and Small, 2001). Glyc- AChE levels are also increased in lumbar CSF collected ante mortem from AD patients (Sa ´ez-Valero et al., 2000). Contract grant sponsor: National Health and Medical Research Council of Australia; Contract grant sponsor: Swedish Medical Research Council; Contract grant sponsor: Axonyx Inc. (New York); Contract grant sponsor: MCyT of Spain (Ramo ´n y Cajal Program). J. Sa ´ez-Valero and L. R. Fodero contributed equally to this paper. *Correspondence to: Dr. David H. Small, Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia. E-mail: dhs@mira.net Received 14 November 2002; Revised 27 January 2003; Accepted 28 January 2003 Journal of Neuroscience Research 72:520 –526 (2003) © 2003 Wiley-Liss, Inc.