Taste plays an important role in the regulation of food and fluid intake in animals. Taste information on the tongue is transmitted to the brain, and we feel hedonic or aversive sensation from the taste of a food. Various studies have shown that opioids or the dopamigenic system is deeply related to the hedonic response in the brain. Few studies have been made, however, about the aversion to food, which is an important signal for animals to protect them from poison that usually has a bitter taste and causes an aversive sensation. We recently suggested that diazepam binding inhibitor (DBI) was released in the brain after stimulation by an aversive taste and might be involved in the aversive sensations of taste. In this review we describe the studies on aversive sensation after eating and propose a novel concept that food aversion may be divided into aversion and rejection. Furthermore, we suggest that DBI is involved in aversion.
To elucidate the interactions of catechins with the cellular antioxidative system, human hepatorna HepG2 cells were incubated in a serum-free medium with catechins, and the level of thiobarbituric acid-reactive substances (TBARS) as a marker of lipid peroxidation was determined, as well as the contents of α-tocopherol (α-Toc) and glutathione (GSH) and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). TBARS was promptly decreased by the incubation with epigallocatechin 3-O-gallate (EGCG), and 12 h later TBARS in the cells with 10μM EGCG was about 15% (p<0.05) of that in the controls (without catechins). Epigallocatechin, epicatechin 3-O-gallate, and epicatechin also had an antioxidative activity, but a higher concentration was required to induce the same effect as EGCG. In the cells incubated with EGCG, the consumption of α-Toc and the formation of the oxidized form of GSH were suppressed. Although EGCG showed no effects on the Cu/Zn-SOD activity, the Mn-SOD activity in the cells was enhanced (p<0.05) by the incubation with EGCG. Moreover, the GSH-Px activity was maintained at a higher level (p<0.05) in the cells with EGCG, compared with that in the controls. when the cells were preincubated with EGCG, the cytotoxicity of H2O2 was significantly reduced. Furthermore, the decrease of cellular α-Toc content induced by exposure to H2O2 was prevented by the pretreatment of EGCG. These results suggest that EGCG taken up into HepG2 cells is preferentially used as an antioxidant, rather than α-Toc and GSH, to suppress lipid neroxidation and to protect these cells from oxidative damages.
The effects of vitamin C and/or E deficiency on lipoprotein metabolism were investigated in the inherently scorbutic Osteogenic Disorder Shionogi (ODS) rat. In the vitamin C-deficient (C-def) group, marked increases in plasma VLDL and LDL cholesterol were observed (by comparison with the vitamins C- and E-sufficient control group). In rats kept deficient in both vitamin C and vitamin E (C, E-def ), LDL cholesterol was significantly higher than in the C-def group even though the levels of VLDL and HDL cholesterol were similar between the two groups. TBARS values for the LDL fraction in the C-def group were of the same magnitude as in the E-def group, and these values were significantly higher than those obtained for the control group. In the C, E-def group, the values were even higher than in the E-def and C-def groups. The nondenatured PAGE of the LDL fraction indicated the appearance of HDLc in the C-def and C, E-def groups. The SDS-PAGE of the LDL fraction showed increased apo B-48 in the C-def and C, E-def groups and increased apo E in the C, E-def group. Decreased plasma LCAT activity in the E-def, C-def, and C, E-def groups indicated an alteration in HDL metabolism as a result of oxidation. These results suggest that lipid peroxidation and some distinct features of lipoprotein metabolism resulting from vitamin C deficiency become more significant when vitamin E is also deficient along with vitamin C deficiency.
The awareness of phosphorus intake is important because hyperphosphatemia and hypophosphatemia both impair bone metabolism. Phosphorus consumption from food was obtained from values in the Food Balance Sheet (FBS) of Japan from 1960 to 1995. The amounts of phosphorus calculated from the FBS increased gradually from 1, 243mg/d in 1960 to 1, 332mg/d in 1975 and to 1, 421mg/d in 1995. This is explained by the increased consumption of cow's milk and milk products, meat, and chicken eggs. The main foods supplying phosphorus in 1995 were cereals, milk and milk products, fishes and shellfishes, and vegetables; their contributions were 24.4, 15.8, 14.2, and 10.9%, respectively. The phosphorus-to-calcium ratio calculated from the FBS was 3.51 in 1960, which decreased to 2.89 in 1975 and 2.44 in 1995. Therefore total phosphorus consumption in 1995 was presumably more than 1, 500mg/d when imported food containing phosphorus and the consumption of phosphorus-containing food additives in Japan are also considered. These findings suggest that the phosphorus consumption estimated from the FBS is increasing and that more attention should be paid to the maintenance of healthy bones in Japan, where the average amount of calcium intake is less than 600m/d.
Triacylglycerols containing medium-and long-chain fatty acids (TML) have medium-and long-chain fatty acids in the same molecule. The effects of dietary TML on serum lipid levels and body fat were studied in six young men belonging to a university rowing club. A double-blind crossover study was performed in which for 3 wk the subjects ingested a liquid diet containing 20 g/d of soybean oil or TML in addition to their regular diets. Throughout the study, they were asked to keep their usual lifestyle, including diet and physical activity. The body composition of the subjects was measured weekly. Mood samples were taken at 0, 2, and 3 wk of each treatment period. There was no significant difference in energy intake between the soybean oil diet period and the TML diet period. The rate of variation of serum triacylglycerol concentration was significantly lower after a consumption of the TML liquid diet for 3 wk compared with the soybean oil liquid diet. The rate of variation of body fat mass was also significantly lower after a consumption of the TML liquid diet for 3 wk compared with the soybean oil liquid diet. However, the serum cholesterol concentra-tion did not change significantly during either dietary treatment. These results suggest that TML, compared with soybean oil, may have the potential to prevent hypertriglyceridemia and obesity caused by consumption of a high-fat diet.
Under microgravity conditions similar to those in space, it is known that various nutritional and physiological changes in the body are induced. Especially in the aspect of nutrition, muscle atrophy is a characteristic phenomenon accompanying weightlessness. This study was conducted to investigate the ameliorated effect of muscle atrophy caused by suspension hypokinesia by using the soy protein isolate (SPI) as the protein source in comparison with casein. Male Wistar strain rats (8 wk old) were divided into two groups, each suspended with a suspension harness, and fed on a 20% SPI diet or a 20% casein diet for 10d. The body weights of the suspended rats fed casein or SPI decreased similarly. The weight of the gastrocnemius and soleus muscle were decreased by suspension hypokinesia; however, the degree of the decrease of the muscle weights, especially soleus muscles, of rats fed the SPI diet was smaller than that of rats fed the casein diet. Serum Nτ-methylhistidine concentration was significantly lower in rats fed the SPI diet than in rats fed the casein diet. Similarly, the activities of muscle protein-degrading enzymes such as calpain and proteasome were significantly lower in rats fed the SPI diet than in rats fed the casein diet. Cathepsin B+L activities were not affected by the SPI or the casein diet. Therefore it is suggested that SPI caused a reduction of the proteolysis of myofibrillar protein in skeletal muscles through a reduction of calpain and proteasome activities, in consequence to ameliorate the muscle atrophy.
Adipose tissue is a unique tissue because its mass is readily changed by altering nutritional conditions. Therefore the activity and content of enzyme in the adipose tissue is significantly differed according to the way of their presentation: per g tissue, per whole tissue, or per cell number. In the present study, the effects of the ways of expressing the hor-mone sensitive lipase (HSL) activity and content were studied in rat by decreasing or in-creasing adipose tissue. Fasting caused a progressive decline in body weight and in the weight of the epididymal fat pad. When the HSL content was expressed per g of adipose tissue, the lipase activity and immunoreactive HSL protein content in fasting rats were higher than those in fed rats. On the other hand, when they were expressed as per fat pad, the lipase activity and immunoreactive HSL protein in fasting rats were lower than those in fed rats. The opposite results were observed in obesity. When the HSL content was expressed per g of adipose tissue, the lipase activity and immunoreactive HSL protein in obese rats were lower than in control rats. However, when the HSL content was expressed per fat pad, the lipase activity and immunoreactive HSL protein in the obese rats were higher than in the control rats. Therefore we must pay careful attention to the way of presentation of adipose tissue enzyme contents.
(-)-Hydroxycitrate (HCA) is known to inhibit increasing malonyl CoA concentration during endurance exercise. Furthermore, a short-term administration of HCA enhances endurance exercise performance in mice. Therefore we investigated the shortterm administration of HCA on the exercise performance of athletes. Subjects were administered 250mg of HCA or placebo as a control (CON) for 5d, after each time performing cycle ergometer exercise at 60% VO2max for 60min followed by 80% VO2max until exhaustion. Blood was collected and expired gas samples analyzed at rest and every 15min. The respiratory exchange ratio was significantly lower in the HCA trial than in the CON trial (p<0.05). Fat oxidation was significantly increased by short-term administration of HCA, and carbohydrate oxidation was significantly decreased (p<0.05) during exercise, presumably resulting in increasing the cycle ergometer exercise time to exhaustion after 1h of 60% VO2max exercise (p<0.05). These results suggest that a short-term administration of HCA enhances endurance performance with increasing fat oxidation, which spares glycogen utilization during moderate intensity exercise in athletes.
We have shown that the orally administered cyanidin 3-O-β-D-glucoside (C3G) attenuates the hepatic ischemia-reperfusion (I/R) injury, which was used as a model for oxidative stress through a decrease in neutrophil chemoattractant production in rats. The rats were subjected to hepatic I/R at 30 min after the administration of C3G (0.9 mmol/kg body weight) or vehicle. I/R treatment resulted in the elevation of oxidative stress marker [liver thiobarbituric acid-reactive substance, Nε-(hexanonyl) lysine and dity-rosine] levels in the liver and of the serum activities of marker enzymes for liver injury. The administration of C3G significantly suppressed these elevations, which had been caused by hepatic I/R. Liver myeloperoxidase activity, a useful marker for neutrophil infiltration into tissues, and the plasma and liver concentration of cytokine-induced neutrophil chemoattractant-1(CINC-1), which has a potent chemotactic activity, were markedly elevated in the control group after hepatic I/R. However, these elevations were significantly suppressed in the C3G group. C3G and its metabolites in the plasma and liver were detected in the C3G group after hepatic I/R. These results suggest that the absorbed C3G and/or its metabolites can act as antioxidants in the blood and liver and scavenge the reactive oxygen species, and brought on a decrease in neutrophil infiltration into the liver through the suppression of CINC-1 production and the tissue damage caused by neutrophils after I/R is attenuated.
The influence of dietary tung oil, containing a high level of α-eleostearic acid (cis-9, trans-11, trans-13-octadecatrienoic acid, EA) on growth, egg production, and lipid and fatty acid compositions in tissues and egg yolks of laying hens was studied in White Leghorn hens. Forty-week-old hens were divided into three groups of eight birds each and fed diets containing 0, 0.5, or 1.0% tong oil for 6 wk. The average body weight, feed consumption, rate of egg production, and weights of eggs and yolks were not affected. The weight of adipose tissue was remarkably small in hens fed tung oil, whereas the yolk lipid content did not change. Triglyceride level in heart and adipose tissue decreased in hens fed tung oil, and the level of linolenic acid (C18:3) in all tissues was decreased. α-EA was not almost deposited in the tissues and egg yolk of hens fed Lung oil, but conjugated linoleic acid (CLA) was detected in all tissues and egg yolks. The level of CLA in the tissues was signifi-cantly higher with increased dietary tung oil. The order of CLA level in tissue lipids was adi-pose tissue>liver>heart>breast muscle. Especially, the level of CLA in the lipids of adipose tissue and egg yolks of hens fed l.0% tung oil was 2.0% of the total fatty acid. These results supposed that dietary tung oil affected the lipid metabolism of laying hens and could modify the lipid and fatty acid composition in tissues and eggs.
The extractability of hordeins from barley grains was investigated after wet and dry heating conditions. It was found that the amount of hordeins extractable with 55% 2-propanol decreased in a time-dependent manner after barley grains were steamed (wet heating), whereas hordeins showed no effect from heating in an oven at 100°C for up to 120min (dry heating). The result of SDS-PAGE analysis revealed that B-hordein decreased time-dependently in extractability with wet heating and had almost completely disappeared by 60 min, but C-hordein remained unchanged until 120min. With the use of the hordein fraction prepared from the nonheated barley grains, it was confirmed that B-hordein sus-pended in boiling water lost solubility in 55% 2-propanol. The insolubilized B-hordein was redissolved by the addition of 2-mercaptoethanol to 1%, which suggested that the intermo-lecular disulfide bonds would play a significant role in the loss of solubility. On the other hand, C-hordein did not lose solubility from being heated under the same conditions.
We investigated the relationship between the absorptive pathway and the immune responses of the lung, particularly the phagocytic function of alveolar macrophages (MO) after oral administration of D-limonene in rats. D-Limonene was orally administered in oily solution with a stomach tube in thoracic duct-cannulated rats, and the lymphatic out-put of D-limonene was measured. D-Limonene levels reached a maximum in thoracic duct lymph and lung 3 h after its oral administration. It also significantly increased in bronchoalveolar lavage fluid (BALF) and alveolar Mφ, in which there was frequently a focal exu-dation of lipid droplets containing D-limonene into the alveolar cavity through alveolar cap-illary walls. Second, D-limonene orally given to rats (250, 500, 1, 000mg/kg/d) for 8 con-secutive days resulted in a marked increase in both the number and the phagocytic activity of alveolar Mφ compared to the controls. BALF from rats dosed with D-limonene (1, 000mg/kg/d) enhanced the phagocytic activity of alveolar Mφ from control rats because the dose was prolonged. The activity of alveolar Mφ following in vitro incubation with D-limonene also increased in a dose-dependent manner. An oral administration of D-limonene enhanced the Con A-stimulated proliferation of splenocytes. These results suggest that D-limonene taken up from the thoracic duct lymph moves to the lung and directly activates the immune response of alveolar Mφ there, or indirectly activates it through activated lymphocytes.
To evaluate the effects of long-term voluntary resistance exercise (climbing) compared with aerobic exercise (swimming) on iron status in severely (4mg Fe/kg diet) and mildly (18-29 mg Fe/kg diet) iron-deficient rats, we trained male Wistar rats for 8 wk to climb a wire-mesh tower (∅20cm×200cm, CLIMB) and to swim in a plastic pool (∅50cm×50cm, SWIM). These rats were compared with sedentary (SED) rats. After the experimental period, blood hemoglobin level, plasma iron concentration, and transferrin saturation were significantly lower in the 4mg Fe/kg diet rats than in the 18, 29, and 40mg Fe/kg diet rats. In 4mg Fe/kg diet rats, the hemoglobin level was significantly higher in the CLIMB group than in the SED and SWIM groups. On the other hand, neither exercise affected iron status in mildly iron-deficient rats. Bone marrow δ-aminolevulinic acid dehydratase activity was significantly higher in the CLIMB group than in the SWIM and SED groups. These results suggest that long-term resistance exercise is more effective than aerobic exercise in improving blood hemoglobin concentration in severely iron-deficient rats, probably because of an increase in heme biosynthesis. Resistance exercise may be a useful therapy for iron-deficient anemia.
Effects of barley tea drinking on blood fluidity were evaluated by measuring the passage time of whole blood with a microchannel array flow analyzer (MC-FAN). The ingestion of barley tea in 250mL amounts decreased the passage time of whole blood, but this did not occur with the ingestion of the same volume of water. 2, 3, 5-Trimethyl pyrazine at the same level as in barley tea also caused a significantly decreased time of blood passage in vitro. This suggests that alkylpyrazines may serve as factors affecting the blood fluidity in barley tea drinking.