Salivary alpha-amylase and noradrenaline responses to corticotropin-releasing hormone administration in humans

Measuring short-term changes in stress-associated salivary analytes in free-ranging Japanese macaques (Macaca fuscata)

Monitoring short-term changes of endocrine responses in non-human primates living in wild populations is a challenge. Saliva contains enzymes, steroids, and various analytes that can be broadly useful for helping us understand physiological responses to social and environmental sources of stress as well as other compromises to an individual's health homeostasis. Salivary alpha-amylase and salivary cortisol are known to respond rapidly to stress, which can allow us to use these analytes to monitor stress on a time scale of minutes. We developed a non-invasive methodology for the collection of saliva and verified its applicability by conducting short-term interval sampling of focal individuals under varying social conditions in a group of semi-provisioned free-ranging Japanese macaques (Macaca fuscata) living endemically on the island of Koshima, Miyazaki prefecture, Japan. Monkeys were habituated to sampling by using ingestive attractants applied to cotton ropes. Their receptivity to chewing on the saliva sampling material provided and chewing time was recorded ad libitum during the initial habituation period of the troop to the sampling procedure. Focal animal behavior observations were conducted in conjunction with saliva sampling. Salivary analytes associated with stress, alpha-amylase and cortisol, were measured via enzyme immunoassay. Short-term changes in salivary alpha-amylase and salivary cortisol were examined in relation to short-term changes in social behavior, in particular aggression or grooming. We tested flow-rate effects in both analytes and found strong correlations between original sample results and their respective flow-rate transformed equivalents. Additionally, temperature effects on samples were tested and both analytes showed nearly the same values when stored at - 20, 4, and 30 °C conditions for 6 h; important information expected to facilitate future sampling in field conditions where freezer storage is uncertain. Our study shows that saliva can be repeatedly sampled non-invasively to investigate short-term changes in stress-associated markers in free-ranging Japanese macaques.

Hyperreactivity of Salivary Alpha-Amylase to Acute Psychosocial Stress and Norepinephrine Infusion in Essential Hypertension

It is unknown whether the observed general physiological hyperreactivity to acute psychosocial stress in essential hypertension also extends to salivary alpha-amylase (sAA), a surrogate sympathetic nervous system marker. Here, we investigated sAA reactivity to acute psychosocial stress in essential hypertensive males (HT) as compared to normotensive controls (NT). To shed light on underlying mechanisms, we moreover tested for sAA reactivity following a standardized norepinephrine (NE) infusion. We hypothesized that both acute psychosocial stress and an NE infusion of similar duration would lead to greater sAA reactivity in HT than in NT. In the stress study, we examined sAA reactivity to 15 min of acute psychosocial stress induced by the Trier Social Stress Test (TSST) in 19 HT and 23 NT up to 40 min after stress. In the infusion study, 20 HT and 22 NT received a standardized NE infusion (5 μg/mL/min) over 15 min mimicking NE release in reaction to acute psychosocial stress. HT exhibited greater sAA reactivity to the TSST as compared to NT (p = 0.049, η_p² = 0.08, f = 0.29). In reaction to the standardized NE infusion, HT showed higher sAA reactivity as compared to NT (p = 0.033, η_p² = 1.00, f = 0.33). Our findings suggest stress-induced sAA hyperreactivity in essential hypertension that seems to be at least in part mediated by a higher reactivity to a standardized amount of NE in HT. With respect to clinical implications, sAA stress reactivity may serve as a noninvasive marker indicative of early cardiovascular risk.

Salivary stress markers in dogs: Potential markers of acute stress

Along with the growing awareness of psychological stress in companion animals, several treatments have become available to address fear- and anxiety-related behaviors in dogs. To detect vulnerable individuals and apply effective treatments, reliable evaluations that can quantify individual stress responses are in high demand. To develop measurable variables that have clinical applications, more investigations are needed to increase our knowledge. When stress responses are activated by the sympathetic-adrenal-medullary (SAM) and hypothalamic-pituitary-adrenal (HPA) axes, the immune system is also activated. Although the peripheral cortisol level is commonly used as a stress biomarker, it primarily reflects the HPA axis response and does not sufficiently reflect the complexity of the stress response. Thus, this review primarily focuses on the available salivary biomarkers that mainly reflect the acute stress response through the activity of the SAM axis and the immune system in dogs. We hope that this review will promote the validation of these biomarkers in dogs and aid in the development of future studies to evaluate stress responses in dogs.

A Review of Biophysiological and Biochemical Indicators of Stress for Connected and Preventive Healthcare

Stress is a known contributor to several life-threatening medical conditions and a risk factor for triggering acute cardiovascular events, as well as a root cause of several social problems. The burden of stress is increasing globally and, with that, is the interest in developing effective stress-monitoring solutions for preventive and connected health, particularly with the help of wearable sensing technologies. The recent development of miniaturized and flexible biosensors has enabled the development of connected wearable solutions to monitor stress and intervene in time to prevent the progression of stress-induced medical conditions. This paper presents a review of the literature on different physiological and chemical indicators of stress, which are commonly used for quantitative assessment of stress, and the associated sensing technologies.

Metabolomic Biomarkers in Anxiety Disorders

Anxiety disorders range among the most prevalent psychiatric disorders and belong to the leading disorders in the study of the total global burden of disease. Anxiety disorders are complex conditions, with not fully understood etiological mechanisms. Numerous factors, including psychological, genetic, biological, and chemical factors, are thought to be involved in their etiology. Although the diagnosis of anxiety disorders is constantly evolving, diagnostic manuals rely on symptom lists, not on objective biomarkers and treatment effects are small to moderate. The underlying biological factors that drive anxiety disorders may be better suited to serve as biomarkers for guiding personalized medicine, as they are objective and can be measured externally. Therefore, the incorporation of novel biomarkers into current clinical methods might help to generate a classification system for anxiety disorders that can be linked to the underlying dysfunctional pathways. The study of metabolites (metabolomics) in a large-scale manner shows potential for disease diagnosis, for stratification of patients in a heterogeneous patient population, for monitoring therapeutic efficacy and disease progression, and for defining therapeutic targets. All of these are important properties for anxiety disorders, which is a multifactorial condition not involving a single-gene mutation. This review summarizes recent investigations on metabolomics studies in anxiety disorders.

It feels real: physiological responses to a stressful virtual reality environment and its impact on working memory

BACKGROUND

Virtual reality (VR) is increasingly used to study and treat psychiatric disorders. Its fidelity depends in part on the extent to which the VR environment provides a convincing simulation, for example whether a putatively stressful VR situation actually produces a stress response.

METHODS

We studied the stress response in 28 healthy men exposed either to a stressor VR elevator (which simulated travelling up the outside of a tall building and culminated in the participant being asked to step off the elevator platform), or to a control elevator. We measured psychological and physiological (salivary cortisol and alpha-amylase, blood pressure, pulse, skin conductance) stress indices. We also measured subsequent performance on the N-back task because acute stress has been reported to impact on working memory.

RESULTS

Compared to participants in the control elevator, those in the external elevator had increases in skin conductance, pulse and subjective stress and anxiety ratings, altered heart rate variability, and a delayed rise in cortisol. N-back performance was unaffected.

CONCLUSIONS

A putatively stressful VR elevator produces a physiological as well as a psychological stress response, supporting its use in the investigation and treatment of stress-related disorders, and its potential value as an experimental laboratory stressor.

Salivary alpha-amylase enzyme is a non-invasive biomarker of acute stress in Japanese macaques (Macaca fuscata)

Salivary alpha-amylase (sAA) enzyme functions as a digestive enzyme in many species that consume starch in their diet. Human studies have also revealed that sAA enzyme activity levels are positively correlated with the release of the stress hormone norepinephrine, allowing sAA to act as a biomarker for sympathetic nervous system activity. Recent non-human primate studies have incorporated sAA as a physiological stress marker. However, no published reports have investigated the time course of sAA from a stressful event to return to baseline levels in non-human primates. Furthermore, no validation of sAA as a stress biomarker has been reported for Japanese macaques (Macaca fuscata). This study had two primary aims: (1) to develop a systematic method for non-invasive saliva collection and, (2) to investigate sAA as a biomarker of acute stress in M. fuscata in order to better understand its acute stress-related characteristics. We developed a non-invasive method for cooperative saliva collection using positive reinforcement training (PRT) and tracked individual progress over 595 trials in ten individually housed Japanese macaques. We detected sAA enzyme in M. fuscata via kinetic reaction assay, then performed 22 acute stress tests. Four tests met conditions for interpreting sAA in response to an acute stressor and these results show that on average sAA activity rapidly increased post-stressor (mean ± SD = 4.2 ± 0.9 min) and returned to baseline shortly thereafter (10.4 ± 0.6 min). Our report reveals for the first time the temporal dynamics of sAA when applying acute stress to Japanese macaques and could be a useful tool for assessing animal welfare.

Visual preconditioning reduces emergence delirium in children undergoing ophthalmic surgery: a randomised controlled trial

BACKGROUND

Emergence delirium is a common complication in children, especially in preschool children undergoing ophthalmic surgery. The aim of the study was to investigate the effects of visual preconditioning (application of an eyepatch over the eye to be operated for ≥3 h the day before surgery) on emergence delirium after ophthalmic surgery under sevoflurane anaesthesia.

METHODS

One hundred and seventy-nine children undergoing unilateral cataract surgery, aged 3-7 yr, were involved in this prospective, blinded, randomised study. Subjects were randomised to receive visual preconditioning (Group P, n=89) or to receive programmed explanation the day before surgery (Group C, n=90). The primary outcome was incidence of emergence delirium evaluated by the paediatric anaesthesia emergence delirium (PAED) scale. The secondary outcomes included emergence time and post-anaesthesia care unit (PACU) stay time.

RESULTS

Children in Group P had a significantly lower incidence of emergence delirium than those in Group C [16.9% vs 44.4%, odds ratio (OR) 4.0, 95% confidence interval (CI) 2.0 to 8.0]. The maximal PAED score was lower in Group P than in Group C [4 (0-20) vs 9 (0-20), median difference -3.0, 95% CI -5.0 to -1.0]. Visual preconditioning prolonged emergence time (P<0.001) and PACU stay time (P=0.002).

CONCLUSION

Visual disturbance contributes to emergence delirium in preschool children undergoing ophthalmic surgery with sevoflurane, and prophylactic eyepatch treatment can reduce emergence delirium.

CLINICAL TRIALS REGISTRATION

NCT02590744.

Salivary cortisol and alpha-amylase: Is there consistency between psychosocial stress test and burdensome work shifts?

This study examined the consistency of salivary cortisol and alpha-amylase (sAA) total daily secretion between laboratory and field circumstances. The 95 participants were shift working female health care professionals with high (n = 53) or low (n = 42) psychosocial stress (job strain) measured by the Job Content Questionnaire (JCQ). The Trier Social Stress Test including a 5-min free speech and a mental arithmetic task was conducted with four, and field measurements with three daily saliva samples of cortisol and sAA during circadian rhythm and inter-shift recovery controlled morning shift, night shift, and a day off. The associations of salivary cortisol and sAA area under the curve with respect to ground (AUCg) and area under the curve with respect to increase (AUCi) between laboratory and field were tested using OLS (Ordinary Least Squares) regression. The sAA AUCg output in the laboratory was correlated with the output during all field measurement days and similarly among high and low job strain groups (p < 0.001). SAA AUCi and salivary cortisol AUCg and AUCi were not correlated between laboratory and field measurement, neither in the whole sample nor among the low or high job strain group. In conclusion, a laboratory measure of sAA AUCg output is promising in predicting stress-related output during burdensome work shifts and leisure time, whereas sAA AUCi or salivary cortisol seem not to have this potential.