On the basis of epidemiological data indicating that Americans and Europeans have a higher fat intake and show lower HDL-cholesterol levels than Japanese, we examined the hypothesis that a high fat intake is associated with low HDL-cholesterol levels. To examine the relationship between diet and the serum HDL-cholesterol level, 24-h dietary recall and examination of serum lipids were conducted on middle-aged healthy women in two rural communities. Mean values of cardiovascular risk characteristics and intake of nutrients and foods were compared among three HDL-cholesterol groups, stratified according to menopausal status. In both communities, regardless of menopausal status, mean values of relative body weight index and serum triglyceride were lower, and that of serum total cholesterol was higher in women with higher, than in those with lower HDL-cholesterol levels. Intake of total fat, animal fat, polyunsaturated fatty acids, saturated fatty acids, and percentage energy of total fat were positively associated with HDL-cholesterol levels, whereas percentage energy of carbohydrate was inversely associated. Although there was no significant association between intake of a single food and HDL-cholesterol, there was a weak positive association between meat or vegetable intake and HDL-cholesterol. Thus in contrast to our prior hypothesis, fat intake was found to be positively associated with high HDL-cholesterol levels in middle-aged rural Japanese women.

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A study was conducted to examine the effects of simultaneous ingestion of protein and carbohydrate on plasma levels of glucose, insulin and free amino acids in 11 healthy women. The levels of plasma glucose, insulin and free amino acids were assayed at 30 and 150min after ingestion of rice, eggs and rice+eggs, respectively. The quantity of rice and eggs corresponded to an energy value of 50g of carbohydrate. 1) Plasma glucose and insulin levels at 30min after ingestion: The increase in the level of plasma glucose after ingestion of rice alone was suppressed significantly (p<0.01) by simultaneous ingestion of eggs. However, the increase in the level of insulin induced by rice was not affected by simultaneous ingestion of eggs. 2) Plasma free amino acid levels at 150min after ingestion: Upon ingestion of rice+eggs, the plasma levels of most amino acids increased significantly, as was the case for eggs alone. Consequently, we examined whether the difference in the increase of each amino acid between eggs alone and rice+eggs was significant. The increase induced by rice+eggs was significantly less marked than that induced by eggs alone for V, L and I (p<0.05 for V, p<0.01 for L and I). Therefore, we conclude that the increase of plasma branched chain amino acids induced by ingestion of protein is suppressed by simultaneous ingestion of carbohydrate.

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A metabolic study was conducted to elucidate the effect of a diet enriched with various fatty acids in the form of triglycerides on serum lipids and lipoproteins in young women. The study was divided into two feeding periods of 5 days each, separated by a 7-day free diet period. Twelve healthy young women were divided into two groups, A (n=6) and B (n=6). The subjects in group A were fed a high-fat diet cooked with 60g/d triolein during the first period, and with 30 g/d tristearin during the second period. The subjects in group B were fed 60g/d trilinolein during the first period, and 30g/d tripalmitin during the second period. As well as the test fat, 10g/d beef tallow was added to the diet of both study groups during the second period to increase the test fatty acids and palatability of the test diet. The results obtained were as follows: 1) Significant decreases in mean serum total cholesterol, apo AI, AII and B, and LDL-cholesterol, -triglyceride and -phospholipids were observed after intake of the triolein or trilinolein diet. The serum HDL-cholesterol level was not affected by either diet. 2) The tristearin diet produced significant decreases in serum total cholesterol, LDL- and HDL-cholesterol, and apo AI and apo B. 3) The serum total and LDL-cholesterol levels were not affected by the tripalmitin diet, but the levels of HDL-cholesterol and apo AI were decreased significantly. The results of our short-term metabolic study suggest that the tested fatty acids do not increase the level of serum lipid when supplied in the form of triglyceride.

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The digestibility of whey protein-hydrolyzed peptide (WPP) prepared by hydrolysis of whey protein concentrate (WPC) with trypsin and papain was compared with that of WPC using an in vitro digestion test. WPP and WPC were rapidly digested by treatment with pepsin followed by pancreatin. WPP was easily digested with both enzymes. However, WPC was not digested completely by a single enzyme, and highmolecular-weight protein such as β-lactaglobulin and α-lactalbumin remained. In addition, nitrogen absorption in the rat intestine was evaluated in terms of changes in the amount of stomach contents and free amino acid concentration in plasma of rats administered WPP or WPC. At 7min after administration of WPP, the stomach contents decreased and the plasma free amino acid concentration reached maximum. The highest concentration of plasma free amino acid in rats administered WPC was observed after 30min. These findings demonstrate that WPP is a better-digestible and absorbable nitrogen source than WPC.

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The nutritive value of whey protein-hydrolyzed peptide (WPP) prepared by hydrolysis of whey protein concentrate (WPC) with trypsin and papain was compared with that of WPC and casein in rats. The weight gains of rats fed WPP and WPC were greater than that of rats fed casein. In terms of protein efficiency ratio (PER), biological value (BV) and net protein utilization (NPU), WPP and WPC were significantly superior to casein. The PER and BV of rats fed WPP were higher than those of rats fed WPC, whereas no difference in NPU was observed. The present findings suggest there is no adverse effect of hydrolysis of whey protein on nitrogen utilization, and that WPP is equal or superior to WPC in nutritive value.

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The effects of acid treatment and extrusion cooking of wheat bran on the availability of minerals (P, Ca, Mg, Zn) and the digestibility of dietary fiber were investigated in growing rats fed a diet rich in dietary fiber. Male Fischer rats were fed diets containing the following brans for 4 weeks: acid-treated bran, bran extruded after acid treatment, untreated bran and extruded bran. All the brans were added to the diet at 15% of total dietary fiber content. 1) Acid treatment or extrusion cooking of bran increased significantly the apparent absorption and retention of Ca, and extrusion cooking of the untreated bran had a similar effect on P and Mg, although there was no effect on Zn availability. 2) The weight of the right femur was increased by feeding on the acid-treated brans (acid-treated bran and bran extruded after acid treatment), and the content of Mg and Zn in the bone were significantly lower when rats were fed the extruded bran. 3) The apparent digestibility of dietary fiber in the diet was decrea ed by acid treatment of the bran.

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The effects of dried yeast (DY) on body weight, serum cholesterol levels, and perirenal and periepididymal adipose tissue cells were studied in young and old rats. The rats were fed with 0% (control), 12.5% and 25% DY diets. In the 25% DY group, the body weights of young rats were lower than in the control group. A DY dose-dependent decrease in body weight was observed. No correlation was observed between change in body weight and food or water intake, and DY did not affect the body weight of old rats. The effects of DY on serum total cholesterol and HDL-cholesterol levels in young rats were less marked than those in old rats. However, serum total cholesterol and HDL-cholesterol levels in DY-fed old rats were significantly lower than those in the control rats, and this lowering effect was dependent on DY dose. The radius and volume of cells in periepididymal adipose tissue of DY-fed old rats were significantly higher than those in the control rats. The numbers of cells in periepididymal and perirenal adipose tissues in 25% DY-fed rats were lower than those in the control rats. It is concluded that dried yeast reduces body weight gain in young rats, and changes the serum cholesterol level and the radius, volume and number of cells in the periepididymal adipose tissue of old rats.

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In order to examine the nutritional and physiological effects of dietary agar, 10% and 20% agar diets and a 20% cellulose diet were fed to rats ad libitum for 3 months. Rat fed the 10% and 20% agar diets showed increases in food intake and fecal excretion and decreases in food utilization efficiency, energy digestibility and cecal ammonia concentration (p<0.05 for 10% agar diet, p<0.01 for 20% agar diet). In addition, rats fed the 20% agar diet showed an increase of water intake (p<0.01), decreases in blood glucose and urea nitrogen levels (p<0.05), and tendencies for body weight gain and the level of blood triglyceride to be decreased. These effects of the agar diets were also found in rats fed the 20% cellulose diet, although the levels of blood urea nitrogen and cecal ammonia were unaffected. Dietary agar and cellulose did not have any significant effects on bacterial flora, bacterial counts, pH or concentrations of volatile fatty acids in the cecum, or on hematological and histopathological parameters.

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The effect of a low-sulfur-containing medium on lysosomal arylsulfatase activities (total combined activities of A and B) was studied using primary cultured hepatocytes from rats. Liver parenchymal cells isolated from rats fed on a 10% soybean protein isalate (SPI) diet for 3 or 5 weeks showed about a 2.0-fold increase of enzyme activity in comparison with rats fed on a laboratory chow diet or a 10% casein diet. The enzyme activities were measured in cells incubated for 48 h in MEM complete medium, serum-free MEM containing 1/10 the normal level of methionine and cysteine, or serum-free MEM lacking methionine, cystine and cysteine. No increase of enzyme activity was observed in any medium containing two sets of cells prepared from rats fed on the laboratory chow, or on the casein diet, corresponding to results obtaind in vivo. The enzyme activity in cells prepared from rats fed on the SPI diet remained higher for 48 h in serumfree MEM containing 1/10 the normal level of methionine and cysteine, or in serum-free MEM lacking both amino acids, whereas a rapid decrease of enzyme activity was observed in complete MEM medium. Thus, enzyme activities in hepatocytes might change in response to the concentration of sulfur-containing amino acids in the medium.

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The liver lipid components, plasma lipid levels, and platelet aggregation were determined, in rats fed experimental diets for 4 weeks. Fiftythree percent of the dietary fat in the linoleic acid (LA) group was 18: 2n-6, which was partially replaced by 18: 3n-6, 18: 3n-3, and n-3 polyunsaturated fatty acid (PUFA) in the γ-linolenic acid (GLN), α-linalenie acid (ALN) and fish oil (Fish) groups, respectively. The liver cholesterol level in the Fish group was significantly higher than the levels in the other groups, whereas the liver phospholipid level in the GLN group was significantly higher than the levels in the other groups. These results suggest that the effect of 18: 3n-6 on hepatic cholesterol metabolism may differ from that of n-3 PUFA. However, neither the plasma cholesterol level nor platelet aggregation induced by collagen was affected by dietary fat.

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