Insulin-like growth factor binding protein-2 in at-risk adults and autopsy-confirmed Alzheimer brains
Marc James Quesnel, Anne Labonté, Cynthia Picard, Henrik Zetterberg, Kaj Blennow, Ann Brinkmalm, Sylvia Villeneuve, Judes Poirier, for the Alzheimer’s Disease Neuroimaging Initiative, Michael W Weiner, Paul Aisen, Ronald C. Petersen, Michael W Weiner, Paul Aisen, Ronald Petersen, Clifford R. Jack, William J. Jagust, John Q Trojanowki, Arthur W Toga, Laurel Beckett, Robert C Green, Andrew J. Saykin, John C Morris, Richard J. Perrin, Leslie M Shaw, Zaven S. Khachaturian, Maria Carrillo, William Z. Potter, Lisa L. Barnes, Marie Bernard, Héctor Alfredo Baptista González, Carole Ho, John Hsiao, Jonathan Jackson, Eliezer Masliah, Donna Masterman, Ozioma C. Okonkwo, Richard J. Perrin, Laurie Ryan, Nina Silverberg, Adam Fleisher, Michael W Weiner, Diana Truran Sacrey, Juliet Fockler, Cat Conti, Dallas P. Veitch, John Neuhaus, Chengshi Jin, Rachel L. Nosheny, Miriam T. Ashford, Derek Flenniken, Adrienne Kormos, Robert C Green, Tom Montine, Cat Conti, Ronald Petersen, Paul Aisen, Michael S. Rafii, Rema Raman, Gustavo Jiménez, Michael Donohue, Devon Gessert, Jennifer Salazar, Caileigh Zimmerman, Yuliana Cabrera, Sarah Walter, Garrett Miller, Godfrey Coker, Taylor Clanton, Lindsey Hergesheimer, Stephanie Smith, Olusegun Adegoke, Payam Mahboubi, Shelley Moore, Jeremy Pizzola, Elizabeth Shaffer, Brittany Sloan, Laurel Beckett, Danielle Harvey, Michael Donohue, Clifford R. Jack, Arvin Forghanian-Arani, Bret Borowski, Chad Ward, Christopher G. Schwarz, David Jones, Jeff Gunter, Kejal Kantarci, Matthew L. Senjem, Prashanthi Vemuri, Robert I. Reid, Nick C. Fox, Ian B. Malone, Paul M. Thompson, Sophia I. Thomopoulos, Talia M. Nir, Neda Jahanshad, Charles DeCarli, Alexander Knaack, Evan Fletcher
Abstract
Insulin, insulin-like growth factors (IGF) and their receptors are highly expressed in the adult hippocampus. Thus, disturbances in the insulin-IGF signalling pathway may account for the selective vulnerability of the hippocampus to nascent Alzheimer's disease (AD) pathology. In the present study, we examined the predominant IGF-binding protein in the CSF, IGFBP2. CSF was collected from 109 asymptomatic members of the parental history-positive PREVENT-AD cohort. CSF levels of IGFBP2, core AD and synaptic biomarkers were measured using proximity extension assay, ELISA and mass spectrometry. Cortical amyloid-beta (Aβ) and tau deposition were examined using 18F-NAV4694 and flortaucipir. Cognitive assessments were performed during up to 8 years of follow-up, using the Repeatable Battery for the Assessment of Neuropsychological Status. T1-weighted structural MRI scans were acquired, and neuroimaging analyses were performed on pre-specified temporal and parietal brain regions. Next, in an independent cohort, we allocated 241 dementia-free ADNI-1 participants into four stages of AD progression based on the biomarkers CSF Aβ42 and total-tau (t-tau). In this analysis, differences in CSF and plasma IGFBP2 levels were examined across the pathological stages. Finally, IGFBP2 mRNA and protein levels were examined in the frontal cortex of 55 autopsy-confirmed AD and 31 control brains from the Quebec Founder Population (QFP) cohort, a unique population isolated from Eastern Canada. CSF IGFBP2 progressively increased over 5 years in asymptomatic PREVENT-AD participants. Baseline CSF IGFBP2 was positively correlated with CSF AD biomarkers and synaptic biomarkers, and negatively correlated with longitudinal changes in delayed memory (P = 0.024) and visuospatial abilities (P = 0.019). CSF IGFBP2 was negatively correlated at a trend-level with entorhinal cortex volume (P = 0.082) and cortical thickness in the piriform (P = 0.039), inferior temporal (P = 0.008), middle temporal (P = 0.014) and precuneus (P = 0.033) regions. In ADNI-1, CSF (P = 0.009) and plasma (P = 0.001) IGFBP2 were significantly elevated in Stage 2 [CSF Aβ(+)/t-tau(+)]. In survival analyses in ADNI-1, elevated plasma IGFBP2 was associated with a greater rate of AD conversion (hazard ratio = 1.62, P = 0.021). In the QFP cohort, IGFBP2 mRNA was reduced (P = 0.049); however, IGFBP2 protein levels did not differ in the frontal cortex of autopsy-confirmed AD brains (P = 0.462). Nascent AD pathology may induce an upregulation in IGFBP2 in asymptomatic individuals. CSF and plasma IGFBP2 may be valuable markers for identifying CSF Aβ(+)/t-tau(+) individuals and those with a greater risk of AD conversion.