Electroencephalogram spectral characteristics after alcohol ingestion in Japanese men with aldehyde dehydrogenase-2 genetic variations: comparison with peripheral changes.

BACKGROUND: Electroencephalographic (EEG) activity induced by alcohol ingestion may be influenced by individual differences in alcohol metabolism. Specifically, an absence of the low Km isozyme of aldehyde dehydrogenase (ALDH), found in many Asians, may be related to alterations of EEGs. METHODS: EEG power spectral changes induced by 0.4 ml/kg of alcohol ingestion were compared in two groups of Japanese subjects: NN (ALDH2*1/1, n = 19) and ND (ALDH2*2/1, n = 12). Peripheral changes in heart rate and facial skin temperature were evaluated after the same treatment. Blood ethanol, acetaldehyde, and catecholamine levels were determined to evaluate mediation of the ethanol metabolite, acetaldehyde, and its indirect action on EEGs through the effects on peripheral systems. RESULTS: As expected, blood acetaldehyde was about 10-fold higher in the ND subjects compared with the NN subjects during the postingestion period. Ethanol produced characteristic EEG changes during and after ingestion. The ND subjects, however, displayed brief periods of decrease in slow alpha immediately after alcohol ingestion and showed no long-term EEG changes. The EEG changes were parallel to peripheral changes. CONCLUSIONS: The lack of increased EEG power in the ND subjects may be partly mediated by a direct action of the high concentration of acetaldehyde in the central nervous system that penetrates from the peripheral blood. In addition to this direct action of acetaldehyde, an indirect action, such as feedback from peripheral changes, might prevent the characteristic increase in alpha and beta power observed in the NN subjects.

Bitter taste in aging: compound-specific decline in sensitivity.

Threshold sensitivity to and the perceived intensity of two bitter compounds, quinine sulfate and urea, were assessed in 52 young adults and 60 elderly adults. Consistent with previous literature, age-related declines in sensitivity to the bitterness of quinine were observed at both threshold and suprathreshold levels. In contrast, the same young and elderly subjects showed comparable sensitivity to the bitterness of urea. These results provide further support for the existence of multiple bitter taste transduction sequences in humans, and indicate that they may be differentially affected by aging.

Nutritional studies of the roles of dietary protein levels and umami in the preference response to sodium chloride for experimental animals.

Previously we found that appetite or preference for sodium chloride depends not only on a genetic factor, but also on the nutritional status, i.e., dietary protein levels. To determine whether all kinds of protein had reducing effects on sodium chloride intake, the effect of dietary protein source on appetite or preference for sodium chloride was studied. It was found that the effect depended not only on protein levels, but also on the protein sources, i.e., amino acid patterns of diets. On the other hand, the turnover time of gustatory taste bud cells was measured by the pulse-labeled method using 3H-thymidine. It was found that the turnover time of gustatory cells in the taste buds of rats fed a low-protein diet was longer than in rats fed a high-protein diet. This suggested that some reduction of receptor functions may occur with low-protein diet. It was found that the dietary protein levels and umami also modified appetite or preference for alcohol solutions.

Salt consumption and nutritional state especially dietary protein level.

To examine the background of excessive salt intake by the people who live in the northeastern district of the mainland of Japan, statistical analysis was carried out on salt consumption with nutritional status with data from the National Nutrition Survey of Japan and prefectural reports. We found that the dietary protein level (using the index animal-protein calorie intake:total calorie intake) was inversely proportional to the salt intake. To clarify the relationship between taste preference and nutritional status, the effects of dietary protein levels on the preference for salt were studied in spontaneously hypertensive rats (SHR), Wistar-Slc rats, and Sprague-Dawley (SD) rats. We found that the appetite or preference for sodium chloride depends not only on a genetic factor but also on the nutritional status, ie, dietary protein levels. We also observed that the preference for the monosodium glutamate solution was not induced in animals fed a low-protein diet. From these observations we speculated that the threshold of taste sensation is increased in rats fed a low-protein diet. To determine the threshold of taste sensation for NaCl, we calculated the turnover time of taste buds, which was lengthened in rats fed a low-protein diet. The findings from statistical analysis and the results from animal experiments suggest that taste preference is influenced not only by genetic factors but also by the nutritional status. Our hypothesis is that dietary protein level is one of the important factors affecting the taste preference for sodium chloride.