Affiliations: [a] Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| [b] Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden
Correspondence:
[*]
Correspondence to: Dr. Johan Svensson, Department of Internal Medicine, Gröna Stråket 8,
Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden. Tel.: +46317411712; Fax: +4631821524;
E-mail: johan.svensson@medic.gu.se.
Abstract: Background:Insulin-like growth factor-I (IGF-I) is important for amyloid-β (Aβ) metabolism, and also interacts with the brain vasculature. In previous IGF-I studies, it has not been evaluated whether Alzheimer’s disease (AD) patients had vascular comorbidities. Objective and Methods:A cross-sectional study of 40 consecutive non-diabetic AD patients and 36 healthy controls. We measured IGF-I in serum and cerebrospinal fluid (CSF) and also serum insulin. Mixed forms of AD and vascular dementia were excluded. Results:After adjustment for covariates including age, serum IGF-I level was higher in the AD group than in the controls, whereas CSF IGF-I and serum insulin were unchanged. Binary logistic regression confirmed that high serum IGF-I was associated with increased prevalence of AD [adjusted Odds Ratio (OR) = 1.83, 95% confidence interval (CI): 1.005–3.32 per standard deviation (SD) increase in serum IGF-I]. This association was more robust after exclusion of patients receiving treatment with acetylcholinesterase inhibitors or N-methyl D-aspartate (NMDA) receptor antagonists (OR = 2.23, 95 % CI: 1.10–4.48). In the total study population (n = 76) as well in the AD group (n = 40), serum IGF-I correlated negatively with CSF Aβ1-42, and CSF IGF-I correlated positively with CSF/serum albumin ratio, CSF total tau, and CSF phosphorylated tau. Conclusion:In AD patients without major brain vascular comorbidities, serum but not CSF levels of IGF-I were increased after correction for covariates. This association was strengthened by exclusion of patients receiving medical treatment. Overall, the results support the notion of IGF-I resistance in mild AD dementia.
