The biosynthesis of biotin-vitamers from C18 fatty acids in the resting cell reaction system of yeasts was investigated. The formation of pimelic acid (a biotin precursor) and biotin-vitamers (a mixture of 7-keto-8-aminopelargonic acid and dethiobiotin) from linolenic, linoleic, and oleic acids was observed in certain yeasts belonging to the genera Cryptococcus, Candida, Rhodotorula, and Trichosporon. Metabolites from linolenic acid were analyzed by gas-liquid chromatography and mass spectrometry. Linoleic, oleic, stearic, heptadecanoic, palmitic, penta-decanoic, and pimelic acids were identified as metabolites of linolenic acid. The existence of a route to pimelic acid from linolenic acid in a strain of Rhodotorula rubra AKU 4836 was also indicated.
The effects of low protein intake on protein metabolism, including the size of pools and the protein synthesis rates, were studied by use of [15N] glycine in Papua New Guinea highlanders. Studies were made on 9 men between October and December in 1982. In experiment 1, two subjects were given a protein-free diet (PFD) containing 49.1 kcal/kg of energy. In experiment 2, subjects were given a sweet-potato diet (SPD) containing 45.4kcal/kg of energy and 0.507g/kg of protein for 8 days, and then were given a low-protein sweet-potato diet (LPSPD) containing 50.0 kcal/.kg of energy and 0.265g/kg of protein. During the SPD period, the sizes of the metabolic and active protein pools (mean±SD) were 270±134mgN/kg and 362±107mgN/kg, respectively, and the rates of active and inactive protein synthesis were 463±161 mgN/kg/day and 299±38mgN/kg/day, respectively. During the LPSPD period, the sizes of the metabolic pool and active protein pool were 131±64 mgN/kg and 378±106mgN/kg, respectively, and the rates of active and inactive protein synthesis were 490±206mgN/kg/day and 280±26mgN/kg/day, respectively. The protein metabolism in the LPSPD showed no significant difference from the SPD. The results suggest that, when the energy levels were approximately the same, protein metabolism in Papua New Guinea highlanders was maintained in spite of the decrease in protein intake.
Linoleic acid and its autoxidation products, hydroperoxides and their secondary products, were orally administered to rats (350mg each/rat). Hemorrhage was seen in the alimentary canal at 6 h after the dose of hydroperoxides. To examine their toxicities on intestinal mucoua, the activities of mucous enzymes (sucrase, maltase, and alkaline phosphatase) were measured. Hydroperoxides and their secondary products decreased the enzyme activities in jejunum at 6 h after the doses and increased them in both jejunum and ileum at 15 h, as compared to linoleic acid or saline solution. The decrease of enzyme activity was marked in the hydroperoxide group and the increase was marked in the secondary product group. Then, in in vitro experiments, the effects of autoxidation products on these enzymes were determined. Autoxidation products inactivated only alkaline phosphatase. Thus, the results in vivo disagreed with those in vitro. It was assumed that autoxidation products orally administered attacked a membrane of intestinal microvilli whereas in vitro they directly affected the enzymes.
Soy protein isolate (SPI) was enzymatically modified to produce oligopeptide mixtures having methionine at approximate levels of 1% and 3%. Each of them had an average molecular weight of slightly lower than 1, 000 daltons, They were compared with corresponding amino acid mixtures as well as with SPI for protein efficiency ratio (PER) and several other parameters. Normal and protein-malnourished rats were used as subjects for the comparison tests. When malnourished rats were subjected to a feeding test at a methionine level of 100 in nitrogen source, the oligopeptide mixture, OPM1, gave a significantly higher PER value than any of SPI and the amino acid mixtures. At a methionine level of 3%, both normal and malnourished rats utilized the oligopeptide mixture, OPM3, with higher efficiency than the amino acid mixture. These results suggest that the oligopeptide mixtures were utilized similarly to or more efficiently than SPI from which they were derived and the amino acid mixtures with exactly simulated amino acid composition.
A 26-day balance study was conducted to examine the effect of a high protein diet on calcium, magnesium, and phosphorus utilization in six healthy males (age 20-22 years, body weight 54.0-64.4 kg, body height 165-173cm). In addition, the effect of physical exercise on calcium, magnesium, and phosphorus balance was also examined. After a 2-day stabilization period, two levels of protein-control (1.0g/kg of body weight) and high (2.0g/kg of body weight) protein-diets were given for three 4-day periods at each protein level. During the last 4-day period of each protein level, subjects exercised on a bicycle ergometer for two 1-h periods daily at a load of 1.5kp., 50 cyc./min. The high protein diet increased urinary calcium and caused a significant negative calcium balance. Magnesium balance tended to be negative in the control diet. There were no significant changes in urinary calcium, magnesium, and phosphorus and also in the calcium, magnesium, and phosphorus balance during physical exercise.
A reduced metabolic rate in the etiology of obesity has been a subject of controversy. The prediction of the energy requirements for the obese using reference values may therefore be distorted. In order to examine this possibility, resting metabolic rate (RMR) while the subject was sitting comfortably in a chair was measured in a total of 134 moderately obese and normal-weight subjects (68 women aged 20 to 71 with a mean of 53.1 and 66 men aged 20 to 63 with a mean of 36.5). RMR per kg of body weight was significantly lower in the female obese subjects, but not in the male obese subjects. There was no evidence of difference in RMR between obese and normal-weight subjects in either sex when RMR was indexed with fat-free mass (FFM), indicating no substantial decrease in the metabolism due to obesity. Multiple regression analyses indicate that standardization of RMR by FFM eliminates the apparent difference in RMR between the sexes, and the diminution of RMR with age was not observed. While the best and logical prediction of RMR is to use FFM, regression analyses suggest an alternative way of predicting RMR by an incorporation of subscapular skinfold thickness to adjust the different body composition in lean and obese subjects. Prediction equations of postprandial RMR (kcal/24-h) while sitting are RMR=24.5 × FFM(kg)+303.7, and RMR=22.7× weight(kg)-13.6× SSF (subscapular skinfold: mm)+350.6. Problems in predicting RMR are discussed.
Male Sprague-Dawley rats were injected with 90mg/kg of streptozotocin at 2 days of age. After weaning, they were put on a fat-free diet supplemented with safflower oil (S), a combination of S and linseed oil (L) or a combination of evening primrose oil (E) and L for 8 weeks. Plasma glucose levels and glycosuria were significantly elevated in all 3 groups of diabetic rats in comparison with the corresponding control rats. The percentage of arachidonic acid (20:4n-6) in plasma phospholipids of the S+L and E+L groups was similar to that of the S group and did not differ between control and diabetic rats while adrenic acid (22:4n-6) and docosahexaenoic acid (22:6n-3) changed in proportion to dietary n-3 and n-6 fats content. Arachidonic acid in aorta phospholipids significantly reduced in all 3 groups of diabetic rats as compared to the corresponding control groups. Dhhomo-gamma-linolenic acid (20:3n-6) and arachidonic acid in aorta phospholipids increased by the E+L treatment. These results suggest that arachidonic acid in plasma phospholipids is kept constant regardless of the presence of diabetes of non-insulin-dependent type or dietary n-3 and n-6 fats supplementation. In aorta phospholipids, arachi-donic acid in diabetic animals reduced and this may be compensated by gamma-linolenic acid supplementation, which leads to increase of dihomo-gamma-linolenic acid and arachidonic acid levels.
Effects of dietary protein levels on the resistance against a bacterial infection and on the nutritional status were studied in mice to obtain basic data for the estimation of an optimal protein intake. Female DDY strain weanling mice were fed 5, 7, 10, 20, 30, or 40% casein diet. At 2 or 4 weeks on the diets, the mice were injected intraperitoneally with 5×103 or 5×104 group B streptococci/g body weight and their survival rates were observed for the following 10 days. Nutritional indices and cell numbers of thymus and spleen were also measured. The survival rate was higher in the order of 7, 10, 20, 30, 5, 40% casein diet group. Significant differences were observed between the 7% group and the 30, 5, or 40 group, and between the 10% group and the 5 or 40% group. The nutritional indices and cell numbers of the thymus and spleen were similar among the 20, 30, and 40% casein diet groups and decreased in the order of 10, 7, 500 casein diet groups. From the results, protein levels were categorized into 4 groups: severe protein deficiency with low resistance (5% casein diet), moderate protein deficiency with high resistance (7 and 1000 casein diets), normal protein intake with normal resistance (20% casein diet), and high protein intake with low resistance (30 and 40% casein diets). This grouping suggests that when the relation between immunocompetence and nutritional status is considered, both high and low protein intakes are undesirable and the optimal level of dietary pro-tein will be limited to a narrow range.