Yasushi Nakagami

Tryptophan Metabolism was Accelerated by Exercise in Rat

We have already reported that exercise activates kynurenine pathway. But, the mechanism for this activation by exercise is still unclear. Kynurenine is metabolized to NAD, which is an essential factor for energy metabolism. In this study, exercise on treadmill was loaded to rats until all-out and tryptophan metabolites and tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) activities were determined in the blood, livers, and macrophages, respectively, in the exercise-loaded rats. The mean values of serum tryptophan concentration decreased from 92.6 +/- 6.0 nmol/ml to 52.4 +/- 10.2 nmol/ml (p<0.05) just after treadmill load. The serum kynurenine concentration had increased from 2.06 +/- 0.25 nmol/ml to 3.08 +/- 0.62 nmol/ml (p<0.005). And whole blood NAD concentration increased from 68.8 +/- 14.6 nmol/ml to 77.9 +/- 19.1 nmol/ml (p<0.005). These results showed that exercise activated the kynurenine pathway of tryptophan metabolism and made NAD which will be concerned with energy metabolism in mitochondria. Tryptophan-NAD pathway was initiated by cleavage of indole ring of tryptophan by TDO in the liver and IDO in many organs. We had also found that the exercise increase IDO activity of macrophages, but not TDO activity.

Kynurenine Concentration of Serum Was Increased by Exercise

Kynurenine pathway of tryptophan makes a lot of physiological active substances, such as quinolinate, NAD and so on, suggesting that kynurenine itself may play a very important role physiologically. Therefore, we examined the influence of exercise on serum kynurenine concentration. At first, we assayed kynurenine concentration of students (n = 13) who took part in a rugby camp for three days. The mean value of kynurenine concentration of before and after training were 1.362 +/- 0.306 microM and 1.725 +/- 0.511 microM respectively. These data means that severe exercise rise the serum kynurenine concentration. Then we tried to examine the relationship between the level of exercise and serum kynurenine concentration. Serum kynurenine concentration had significantly increased immediately after the exercise from 1.869 +/- 0.285 microM to 2.138 +/- 0.248 microM of 24 hours later by loading of 65% heart rate max exercise for each subject. These results suggested that at least the severe exercise affect on the tryptophan metabolism. We will discuss the change of serum kynurenine concentration by another sports such as soccer game and 20 km run.

Relationships between Salivary Melatonin Levels, Quality of Sleep, and Stress in Young Japanese Females

A decrease in the quality of sleep is believed to cause anxiety and worsen depression. Comparisons of salivary melatonin levels with different factors including quality of sleep, state and trait anxieties, and depression, were conducted to examine whether there is a relationship between melatonin, presumably associated with sleep, and psychological stress. The saliva of healthy young females was collected during the daytime and before they went to bed at night (when they were awake and resting in a sitting position), and salivary melatonin levels were measured. The quality of sleep was scored using the Pittsburgh Sleep Quality Index (PSQI)–-a questionnaire method. State and trait anxieties, and depression were scored using other questionnaire methods: the State-Trait Anxiety Inventory (STAI) and Self-Rating Depression Scale (SDS), respectively. The following findings were obtained: (1) Salivary melatonin levels measured during the daytime and before going to bed were higher in females with a high depression score, compared to those with a low score, and there was a correlation between the depression scores and salivary melatonin levels measured at night; and (2) salivary melatonin levels measured before going to bed at night (in a sitting position) were higher in females with a high state anxiety score, suggesting a correlation between state anxiety scores and salivary melatonin levels during the night. Both depression and a sense of anxiety are forms of psychological stress. Therefore, it is assumed that, when a person is under psychological stress, the action of melatonin as a ligand on its receptor is reduced. Meaning psychological stress may induce oxidative stress in the body. On the other hand, no correlation was noted between the quality of sleep and salivary melatonin levels during the night, presumably because saliva was collected when the subjects were awake and sitting, rather than sleeping.