Salivary osteocalcin: Reactivity to acute social stress and associations with concomitant stress biomarkers in healthy African Americans.

Animal studies suggest that osteocalcin (OCN) may play an important role in the early steps of parasympathetic nervous system withdrawal to initiate the autonomic nervous system (ANS) component of the fight-or-flight response to stress. However, the OCN response to stress has not yet been well-characterized in humans. This study examined reactivity of OCN, measured in saliva, in response to acute social stress in healthy African Americans, and considered associations of OCN reactivity with well-established biomarkers associated with stress-reactivity of the autonomic, endocrine, and immune systems. Participants were 60 healthy African Americans (20 men, 40 women; Mage = 27.33 years) who completed a modified Trier Social Stress Test (TSST). Saliva collected before, during, and after the TSST was assayed for OCN, cortisol, alpha-amylase (sAA), and interleukin-6 (IL-6). Salivary OCN (sOCN) exhibited strong reactivity, including a 19% increase for the full sample, and a 58% increase from pre- to post-stressor levels among men. We also observed muted recovery of sOCN in response to the TSST, but only among men. Among men, individual differences in sOCN stress reactivity and recovery were significantly predicted by sAA reactivity and recovery (ß = .51, p = .021; ß = .45, p = .026, respectively), but not with task-related change in cortisol or IL-6. Findings suggest OCN may be a specific early-phase and ANS-related component of the multisystem acute stress response in humans. Results further highlight possible sex differences and raise awareness that OCN dysregulation may be implicated in stress-related health disparities.