Consumption of bonito extract suppresses the decrease in cerebral blood flow in stroke-prone spontaneously hypertensive rats.

The effect of consuming bonito extract (BE) on cerebral blood flow was evaluated in stroke-prone spontaneously hypertensive rats (SHRSP), a cerebrovascular disease model. BE dissolved in drinking water was given to 5-week-old male SHRSP for 7 weeks. Tap water was given to the control group. At the age of 12 weeks, blood flow and vascular diameter were measured in the middle cerebral artery. Both cerebral blood flow and cerebral vessel width were greater in the BE group than in the control group. Also, stroke occurred in 7 (with death in 2) of the 8 animals in the control group but in none of the 6 animals in the BE group. To clarify its mechanism, the expressions of nitrogen oxide synthase (NOS) and the superoxide dismutase activity (SOD) in the brain were evaluated. NOS mRNA expression and SOD activity in the cerebrum were higher in the BE group. These results suggest that the consumption of BE suppresses the decrease of cerebral blood flow and reduces the risk of stroke to maintain vasorelaxation through the production of nitrogen oxide and suppression of active oxygen generation.

Ingestion of bonito extract ameliorates peripheral blood flow in mice loaded from over crowding stress.

Bonito extract (BE) has been shown to improve various fatigue-related symptoms. The possibility that the improvement of blood flow contributes to the improvement of fatigue-related symptoms has been reported. However, even though BE has been found to increase peripheral blood flow in humans, an understanding of its mechanisms has remained elusive. The purpose of the present study is to construct an animal model system with which the blood flow-increasing effects of BE can be examined. Using mice loaded with crowding stress, an attempt was made to reproduce the increases in peripheral blood flow observed in humans after a single administration of BE. In this study, the crowded-condition mice (20 mice/cage) showed significantly increased catecholamine levels (noradrenaline, adrenaline, and dopamine) in their circulating blood and a decreased rate of skin blood perfusion in comparison with the normal-condition mice (6 mice/cage). The rate of skin blood perfusion was significantly increased by BE in the crowded-condition mice in comparison with the controls, but not influenced by BE in the normal-condition mice. This suggests that BE expands the vascular diameter by affecting the constriction of vessels induced by catecholamines.

The anti-fatigue effects of the low-molecular-weight fraction of bonito extract in mice.

Bonito extract (BE), a hot-water extract of bonito muscle, has traditionally been considered as a folk remedy for fatigue. In this study we investigated the effects of BE on physical fatigue. BE was divided into, high, mid, and low-molecular-weight fractions (LMF), to explore the effectiveness of BE compounds. The swimming times to exhaustion of mice administered 0.86 g/kg BE and those administered 0.86 g/kg LMF were significantly longer than those of the vehicle-treated mice in a forced swimming model, indicating that BE possesses an anti-fatigue effect and that the LMF contributes to this effect. The LMF was also confirmed to aid the recovery of locomotor activity after physical fatigue in a forced walking model. We also examined respiratory gas levels and found that oxygen consumption and lipid oxidation were significantly greater in the group administered LMF than in the vehicle group, indicating that LMF promotes the utilization of fatty acids as an energy source. To elucidate why the mice administered LMF showed an anti-fatigue effect, we evaluated metabolic variables during exercise. The concentrations of nonesterified fatty acids and ketone bodies were higher, whereas serum and muscle lactic acid levels were lower in the mice administered LMF than in those in the vehicle group after the start of swimming. When the results were taken as a group they indicated that the effect of BE administration on improving endurance capacity was mediated, at least partly, by an increased utilization of lipids as a source of energy during exercise.

Effect of dried-bonito broth intake on peripheral blood flow, mood, and oxidative stress marker in humans.

Dried-bonito broth (DBB) has been confirmed to improve various symptoms related to fatigue, but the reasons for this have remained unclear. Hypothesizing that DBB improves peripheral circulation together with mood states, we performed a randomized, double-blind, placebo-controlled crossover study in thirty-one healthy females. The subjects ingested DBB or a placebo for two weeks and changes in mood states after ingestion were investigated using the profile of mood states (POMS) questionnaire. The peripheral blood flow was also measured before and after ingestion of the test diet using a laser Doppler blood flow meter. The six mood factors and total mood disturbance score which reflect the mental states significantly improved, and a significant increase in peripheral blood flow was also found during DBB ingestion. As a result of correlation analysis between changes in each POMS score and changes in blood flow, it was suggested that a change in blood flow correlated with a change in some POMS factors and total mood disturbance. Based on these findings, we considered that blood flow may have increased in subjects whose mood states were markedly improved, suggesting that the improvement in mood states, including fatigue, was related to the increase in blood flow due to the improvement of peripheral circulation. To clarify whether DBB ingestion exhibits antioxidative activity, we investigated the urinary amounts of 8-hydroxy-2'-deoxyguanosine (8-OHdG) known as an oxidative stress marker and found that urinary excretion of the 8-OHdG for 24 h was significantly decreased during DBB ingestion. This study clarified that DBB ingestion improved mood states, increased peripheral blood flow, and decreased the oxidative stress marker.

Effect of dried-bonito broth on mental fatigue and mental task performance in subjects with a high fatigue score.

Dried-bonito broth is commonly employed as a soup and sauce base in Japanese cuisine and is considered to be a nutritional supplement that promotes recovery from fatigue. Previous human trials suggest that the ingestion of dried-bonito broth improves several mood states; however, its effect on fatigue has not yet been clarified. The aim of this study was to clarify the effects of daily ingestion of dried-bonito broth on fatigue and cognitive parameters by a placebo-controlled double blind crossover trial. Forty-eight subjects with fatigue symptoms ingested the dried-bonito broth or a placebo solution every day for 4 weeks. Mood states were evaluated by the Profile of Mood States (POMS), and mental task performance was evaluated by the Uchida-Kraepelin psychodiagnostic (UKP) test. Fatigue and total mood disturbance (TMD) scores on the POMS test decreased significantly during the dried-bonito broth ingestion (p<0.05), but did not change significantly during placebo ingestion. The change in vigor score during dried-bonito broth ingestion was significantly higher than that during placebo ingestion at 2 weeks (p<0.05). The results of the UKP test indicate that the numbers of both total answers and correct answers significantly increased during dried-bonito broth ingestion (p<0.05), while no significant changes were observed in the placebo ingestion. These results suggest that the daily ingestion of dried-bonito broth may improve the mood states, may reduce mental fatigue and may increase performance on a simple calculation task.