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MacLean EL, Carranza E, Gnanadesikan GE, King KM, Allen AM, Linde-Krieger LB, Feldman R, White-Traut RC, Hammock EAD, Carter CS, Leng G, Tecot SR, Bell AF. Neurophysin I is an analytically robust surrogate biomarker for oxytocin. Psychoneuroendocrinology 2024; 161:106951. [PMID: 38194845 PMCID: PMC10872509 DOI: 10.1016/j.psyneuen.2023.106951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 12/27/2023] [Accepted: 12/29/2023] [Indexed: 01/11/2024]
Abstract
Oxytocin is a pleiotropic neuropeptide that plays roles in biological processes ranging from birth, lactation, and social bonding to immune function, cardiovascular repair, and regulation of appetite. Although measurements of endogenous oxytocin concentrations have been performed for more than 50 years, the ability to measure oxytocin accurately poses notable challenges. One potential solution for overcoming these challenges involves measurement of oxytocin's carrier molecule - neurophysin I (NP-1) - as a surrogate biomarker. NP-1 is secreted in equimolar concentrations with oxytocin but has a longer half-life, circulates in higher concentrations, and can be measured using a sandwich immunoassay. We report experiments that 1) analytically validate a commercially available NP-1 sandwich immunoassay for use with human plasma and urine samples, 2) confirm the specificity of this assay, based on detection of NP-1 in plasma from wild-type but not oxytocin knockout mice, 3) demonstrate that NP-1 concentrations are markedly elevated in late pregnancy, consistent with studies showing substantial increases in plasma oxytocin throughout gestation, and 4) establish strong correlation between NP-1 and plasma oxytocin concentrations when oxytocin is measured in extracted (but not non-extracted) plasma. The NP-1 assay used in this study has strong analytical properties, does not require time-intensive extraction protocols, and the assay itself can be completed in < 2 h (compared to 16-24 h for a competitive oxytocin immunoassay). Our findings suggest that much like copeptin has become a useful surrogate biomarker in studies of vasopressin, measurements of NP-1 have similar potential to advance oxytocin research.
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Affiliation(s)
- Evan L MacLean
- College of Veterinary Medicine, University of Arizona, Tucson, AZ, USA; Department of Psychology, University of Arizona, Tucson, AZ, USA.
| | | | | | | | - Alicia M Allen
- Department of Family and Community Medicine, University of Arizona, Tucson, AZ, USA
| | | | - Ruth Feldman
- Center for Developmental Social Neuroscience, Reichman University, Israel; Yale Child Study Center, Yale University, New Haven, CT, USA
| | - Rosemary C White-Traut
- Children's Research Institute, Children's Wisconsin, Milwaukee, WI, USA; Department of Human Development Nursing Science, University of Illinois, Chicago, IL, USA
| | | | - C Sue Carter
- Kinsey Institute, Indiana University, Bloomington, IN, USA; Department of Psychology, University of Virginia, Charlottesville, VA, USA
| | - Gareth Leng
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
| | - Stacey R Tecot
- School of Anthropology, University of Arizona, Tucson, AZ, USA; Laboratory for the Evolutionary Endocrinology of Primates, University of Arizona, Tucson, AZ, USA
| | - Aleeca F Bell
- College of Nursing, University of Arizona, Tucson, AZ, USA
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