Jumpei Yajima

Synergistic effects of psychological and immune stressors on inflammatory cytokine and sickness responses in humans

Activation of the innate immune system is commonly accompanied by a set of behavioural, psychological and physiological changes known as ‘sickness behaviour’. In animals, infection-related sickness symptoms are significantly increased by exposure to psychosocial stress, suggesting that psychological and immune stressors may operate through similar pathways to induce sickness. We used a double-blind, randomised, placebo-controlled design to examine the effect of acute psychological stress on immune and subjective mood responses to typhoid vaccination in 59 men. Volunteers were assigned to one of four experimental conditions in which they were either injected with typhoid vaccine or saline placebo, and then either rested or completed two challenging behavioural tasks. Typhoid vaccine induced a significant rise in participants’ serum levels of interleukin-6 (IL-6) and this response was significantly larger in the stress versus rest conditions. Negative mood increased immediately post-tasks, an effect also more pronounced in the vaccine/stress condition. In the vaccine/stress group, participants with larger IL-6 responses had heightened systolic blood pressure responses to tasks and elevated post-stress salivary levels of the noradrenaline metabolite 3-methoxy-phenyl glycol (MHPG) and cortisol. Our findings suggest that, as seen in animals, psychological and immune stressors may act synergistically to promote inflammation and sickness behaviour in humans.

Short sleeping time and psychobiological responses to acute stress

The aim of this study was to examine the association between self-reported sleeping time and psychobiological stress responses [3-Methoxy-4-hydroxyphenylglycol (MHPG) and Secretory immunoglobulin A (IgA), perceived stress responses]. Thirty seven healthy men and women were recruited, and participants were divided according to the habitual number of hours of sleep as follows: adequate sleepers (AS) (6-8h sleep per night regularly) (N=22) and short sleepers (SS) (less than 5h sleep per night regularly) (N=15). Salivary MHPG, s-IgA and perceived stress were measured at baseline, immediately after task and recovery period. An increase in free-MHPG during the task period was observed in AS although free-MHPG increased only after the task period in SS. The level of s-IgA in both groups significantly increased during the task period, and quickly returned to a basal level during the recovery period. The results show that less than 5h of sleep was associated with different responsiveness to the Stroop color word conflict task compared to sufficient sleep, especially in the NA system.

Salivary 3‐methoxy‐4‐hydroxyphenylglycol increases after awakening in healthy young adults

Levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) may reflect central noradrenergic activity. In this study, we investigated salivary MHPG changes after awakening, and explored their relationships with cortisol and peripheral autonomic activity. The participants were 25 college students. Saliva samples were collected on awakening and 30 min after awakening to determine MHPG and cortisol. Ambulatory electrocardiograms were obtained to assess heart rate, cardiac sympathetic index (CSI), and cardiac vagal index (CVI) before and after awakening. MHPG levels increased significantly during the first 30 min after awakening. Similarly, cortisol, heart rate, and CSI increased during the 30 min after awakening, but changes in MHPG did not correlate with changes in cortisol, heart rate, CSI, and CVI during that period. This study demonstrated that salivary MHPG levels increase after awakening, in common with cortisol, heart rate, and cardiac sympathetic activity.

Effects of Soup Intake for Fourteen Days on the Mood and the Difference in Cortisol of Awakening and Evening in the Clerical Employees: An Effectiveness Study Trial

In this study, an investigation based on an effectiveness study trial without special limitations was carried out regarding how 14 days’ continuous soup intake would change the mood of the participants and their salivary cortisol levels between awakening and evening. The participants consisted of 16 healthy workers who agreed to participate in the experiment. The participants led their normal daily lives without consuming soup for the first 14 days (controlled condition), and then consumed their chosen soup once a day, at approximately 3 p.m., for the next 14 days (soup condition). Their salivary cortisol levels were measured when they woke up in the morning (awakening) and at 5 p.m. on the last day of each condition, while their mood was evaluated by questionnaire at 5 p.m. every day. The irritation-anger score of the soup condition was significantly lower than that of the controlled condition, and the difference in the salivary cortisol level between awakening and evening in the soup condition was significantly higher compared with the controlled condition. As a result, this study suggests that continuous soup intake under conditions of free choice in the afternoon at the workplace may be effective in relieving stress of worker’s body and mind.