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Abstract
Objective: We aimed to investigate the relationship between plasma and CSF progranulin (PGRN) levels.
Methods: Plasma and CSF PGRN were measured in a cohort of 345 subjects from the Mayo Clinic Study of Aging by ELISA. Single nucleotide polymorphism genotyping was performed using TaqMan assays. Associations between PGRN and sex, age at sample collection, diagnosis, single nucleotide polymorphism genotypes (GRN, SORT1, and APOE), and Pittsburgh compound B score were explored separately in CSF and plasma using single variable linear regression models. Pearson partial correlation coefficient was used to estimate the correlation of PGRN in CSF and plasma.
Results: Plasma (p = 0.0031) and CSF (p = 0.0044) PGRN significantly increased with age, whereas plasma PGRN levels were 7% lower (p = 0.0025) and CSF PGRN levels 5% higher (p = 0.0024) in male compared with female participants. Correcting for age and sex, higher plasma PGRN was associated with higher CSF PGRN (partial r = 0.17, p = 0.004). In plasma, both rs5848 (GRN; p = 0.002) and rs646776 (SORT1; p = 3.56E-7) were associated with PGRN, while only rs5848 showed highly significant association in CSF (p = 5.59E-14). Age, sex, rs5848 genotype, and plasma PGRN together accounted for only 18% of the variability observed in CSF PGRN.
Conclusions: While some correlation exists between plasma and CSF PGRN, age, sex, and genetic factors differently affect PGRN levels. Therefore, caution should be taken when using plasma PGRN to predict PGRN changes in the brain. These findings further highlight that plasma PGRN levels may not accurately predict clinical features or response to future frontotemporal lobar degeneration therapies.
GLOSSARY
- Aβ=
- β-amyloid;
- AD=
- Alzheimer disease;
- DAT=
- dementia of the Alzheimer type;
- FTLD=
- frontotemporal lobar degeneration;
- MCI=
- mild cognitive impairment;
- MCSA=
- Mayo Clinic Study of Aging;
- mRNA=
- messenger RNA;
- PGRN=
- progranulin;
- PiB=
- Pittsburgh compound B;
- SNP=
- single nucleotide polymorphism;
- SORT1=
- sortilin 1;
- TDP=
- TAR DNA-binding protein
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received June 25, 2013.
- Accepted in final form February 20, 2014.
- © 2014 American Academy of Neurology
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- Low plasma PGRN levels due to neutralizing PGRN-antibodies in patients with autoimmune diseases might lead to misdiagnosis of FTLD
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