SAT-120 - Inverse association between Neurophysin-I, a surrogate biomarker of oxytocin, and cortisol responses during psychosocial stress

Background
Oxytocin (OXT) is a neuropeptide that is synthesised in the hypothalamic paraventricular and supraoptic nuclei and released into circulation from the posterior pituitary. Among others, OXT is involved in psychological and socio-behavioural processes. Beyond its known role in these processes, evidence from both animal and human studies suggests that OXT might also regulate neuroendocrine stress responses within the central nervous system. OXT is thought to suppress the stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis by exerting an inhibitory effect on cortisol secretion.

Design: This is a secondary analysis of a prospective observational study, which was conducted to investigate the relationship between copeptin concentration and psychological stress.

Methods: Twenty healthy adults (ten female) underwent the Trier Social Stress Test (TSST) which included a 30-minute waiting period, a 10-minute anticipation period, a 10-minute test period, and a 40-minute recovery period. For this analysis, plasma Neurophysin-I (NP-I), a surrogate biomarker of OXT, and plasma cortisol were measured at baseline (T0), 20 minutes (i.e. right after the stress, T1) and 40 minutes (i.e. 20 minutes into recovery, T2).

Results At T0, median [IQR] NP-I levels were 1237 pg/mL [693, 3143], decreasing to 1166 pg/mL [767, 3360] at T1. At T2, NP-I levels increased again to 1199 pg/mL [717, 3063]. Median cortisol levels were 435 nmol/L [385, 547] before psychological stress (T0) and peaked at 529 nmol/L [494, 701] at T1. At T2, cortisol levels decreased again to 507 nmol/L [438, 632].
Linear mixed-effects model analysis revealed that in healthy individuals, higher NP-I levels measured at both T1 (P = 0.004) and T2 (P < 0.001) were associated with lower plasma cortisol concentrations compared to T0.

Conclusion:
In healthy volunteers, higher NP-I levels were associated with a blunted cortisol response to psychological stress, suggesting a cortisol-buffering effect of NP-I mirroring OXT. These findings support the idea of an inverse relationship between NP-I concentrations and cortisol responses over time following stress exposure.

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