Associations of cortisol with neuroinflammation biomarkers in a memory clinic cohort

Abstract

AbstractBackgroundCortisol, one of the most important mediators of stress in humans, is often found increased in Alzheimer’s disease (AD) patients and correlates with disease severity. Stress response and inflammation are two systems that are tightly associated to one another. Several lines of evidence suggest that cortisol can promote inflammation. However, less is known on the interaction of cortisol with neuroinflammation in the context of AD, and to the best of our knowledge there are no human studies that have systematically explored the association of these two systems in AD patients so far. The aim of this study was to investigate levels of cerebrospinal fluid (CSF) biomarkers of neuroinflammation and their relationship to salivary cortisol in a memory clinic cohort.MethodA total of 108 memory clinic patients with subjective cognitive decline (SCI, n = 40), mild cognitive impairment (MCI, n = 39) and AD (n = 29), from the Karolinska University Hospital in Stockholm, Sweden, were included in this study. Salivary cortisol was collected at six timepoints during the day on two days, to quantify awakening cortisol, cortisol awakening response (CAR), bedtime cortisol and total cortisol. CSF levels of 37 neuroinflammation and cerebrovascular dysfunction biomarkers were determined by a multiplex immunoassay. Associations among cortisol and neuroinflammation markers were assessed by linear regression models adjusting for age and diagnosis. ANCOVA tests were used to compare biomarker levels between the diagnostic groups.ResultAwakening cortisol was significantly elevated in the AD group compared to the SCI and MCI participants. Higher IP‐10 and placental growth factor (PlGF) levels were associated with decreased CAR independent of age and diagnosis. Thymus and activation‐regulated chemokine (TARC), CRP, intracellular adhesion molecule 1 (ICAM‐1) and vascular cell adhesion molecule 1 (VCAM‐1) levels were upregulated in MCI participants compared to SCI and AD.ConclusionWe provide evidence that the HPA axis is altered in AD. Moreover, salivary cortisol is associated to neuroinflammation in an age and diagnosis independent manner. Finally, neuroinflammatory and vascular dysfunction regulators are increased in CSF during MCI stages followed by a drop in their levels in AD participants, presumably reflecting a more active role of neuroinflammation at an early state.