The nutritional effects of pyridoxine-a-glucoside (PN-α-Glc), pyridoxine-5'β-glucoside (PN-5'β-Glc) and ε-N-(phosphopyridoxyl)-lysine (PNP-Lys) were examined by means of: 1) transport across the intestinal wall using everted rat intestine, 2) metabolic conversion by liver or kidney homogenate, and 3) oral administration of the compound to B₆-deficient rats and the subsequent analysis of B₆ derivatives found in plasma. Using everted sacs prepared from rat small intestine, PN-α-Glc was transported into the serosal side in its intact form. On the other hand, a part of PN-5'β-Glc was found as PN on the serosal side (PN-5'β-Glc: PN=2:1) . When PN-α-Glc, PN-5'β-Glc or PNP-Lys was incubated with liver or kidney homogenate for 3h at pH 6.0, PN-α-Glc was hydrolyzed to PN (6%), while there was no hydrolysis of PN-5'β-Glc. After 30min of administration of each B₆ derivative to B₆-deficient rats, blood was collected from the heart, and the B6-derivatives found in plasma were analyzed. It was ascertained that PN-α-Glc served as well as PN as a B₆ nutrient, while PN-5'β-Glc and PNP-Lys were not easily metabolized to the coenzyme form, pyridoxal 5'-phosphate.

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We recently reported that the concentration of supplemental ascorbate which inhibits cell growth is positively related to intracellular catalase activity. It is assumed that the cells with high catalase activity are resistant to high concentrations of ascorbate since catalase can decompose hydrogen peroxide (H₂O₂) induced by the auto-oxidation of ascorbate in cultured medium. In this study, we investigated whether intracellular catalase activity affects the uptake of ascorbate into animal tissue and cultured cells. Ascorbate concentrations in the tissues of guinea pigs and various cultured cells, with and without supplementation of ascorbate, were determined to evaluate the efficiency of ascorbate uptake. We found a positive correlation between the efficiency of ascorbate uptake and catalase activity in various tissues of guinea pigs (r=0.767, p<0.05). Furthermore, a positive correlation between the two was also found in various species of cultured cells. This study indicates that tissues and cells with higher efficiency of ascorbate uptake are required for higher catalase activity, presumably for the decomposition of H₂O₂ from ascorbate.

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A study has been carried out on the nutritional status of vitamin A and E in 93 institutionalized elderly people in Granada (Spain) by studying their vitamin intake and the serum values of retinol and a-tocopherol. The influence of lipid intake and lipids in plasma has been also discussed. The vitamin A intake is higher than the recommended amount and represent 209% DR in men and 217% DR in women. The vitamin E intake is deficient in 33% of the men and 27% of the women. The serum values of retinol indicate that 11 % of the women have a deficiency (<0.7μIM), and that 39% of the men and 32% of the women have low values (0.7-1.22<M). As for the serum values of α-tocopherol, 6% of the women have deficient values, and 82% of the men and 37% of the women have low values (11.6-23.2<M).

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It is widely known that hypomagnesemia is one of the symptoms observed in diabetic patients. This study was performed to assess the effect of chronic magnesium (Mg) deficiency on glucose metabolism in rats. Male Sprague-Dawley rats (at the age of four weeks) were given a Mg-deficient diet or a control diet for two to eight weeks. The rats were orally administered sucrose solution (2g/kg BW) every two weeks, and blood was drawn from a tail vein before and 15 min after sucrose loading to determine the concentrations of blood glucose and plasma insulin. At the same time, other rats in a non-fasted condition were sacrificed by decapitation (rats sacrificed at eight weeks were rats used for sucrose loading). The epididymal fat pads were immediately removed and adipocytes were isolated. The amount of glucose transporter 4 (GLUT4) in the plasma membranes and low-density microsomal membranes prepared from the adipocytes was measured by immunoblotting to estimate the influence of chronic Mg deficiency on glucose metabolism at the cellular level. In addition, plasma biochemical parameters and muscle mineral contents were also evaluated. The glucose concentration in fasted blood was significantly lower in Mg-deficient rats than in control rats throughout the experiment period. The feeding of a Mg-deficient diet also attenuated the response of blood glucose and plasma insulin: the glucose level in blood tended to be lower in Mg-deficient rats at 15 min after oral sucrose administration, and the difference was significant at two and eight weeks. The plasma insulin level in Mg-deficient rats was also lower, reaching a significant difference at two weeks. When animals were sacrificed in a non-fasted condition at 2-week intervals, the plasma glucose level was also significantly decreased in Mg-deficient rats as compared to control rats throughout the experiment period. The plasma insulin level in non-fasted Mg-deficient rats was also significantly decreased at two and six weeks. The Mg-deficient diet increased plasma triglyceride, but the difference was significant only at four weeks, and plasma cholesterol remained unchanged. The plasma Mg level was markedly lower in Mg-deficient rats throughout the experiment period. In Mg-deficient rats, the Mg content in muscle was significantly reduced at two and eight weeks, whereas the calcium and sodium contents were significantly increased throughout the experiment period. In Mg-deficient rats, the degree of translocation of GLUT4 to plasma membranes in the adipocytes stimulated by insulin was reduced only at eight weeks. In conclusion, since fasted and non-fasted blood glucose levels and the response of blood glucose to sucrose loading were decreased in Mg-deficient rats, it is suggested that Mg deficiency induces changes in the glucose metabolism via impaired glucose absorption in the intestine or an altered glucose uptake in the liver and/or peripheral tissues.

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We studied the effects of dietary lipids on platelet aggregation and lipid metabolism in rats by varying the n-3/n-6 ration while maintaining the polyunsaturated fatty acid/saturated fatty acid (P/S) ratio fixed, and vice versa. After two weeks, the platelet counts decreased as the dietary n-3/n-6 ratio rose, and platelet aggregation was sufficiently suppressed at the ratio of 0.2. Differences in the dietary P/S ratio, however, did not affect either the platelet counts nor platelet aggregation. As the dietary n-3/n-6 ratio rose, the proportion of arachidonic acid (AA) in the plasma and the phospholipids (PL) of the platelets and aorta decreased gradually, whereas the proportion of eicosapentaenoic acid (EPA) in each tissue increased gradually. The proportion of EPA was higher in the platelets than in the aorta, while that of docosahexaenoic acid (DHA) was higher in the latter. The production of platelet thromboxane A₂ (TXA₂) and aortic prostacyclin (PGI₂) showed sharp declines, from the values for the n-3/n-6 ratio of 0.02 (control) to those for 0.5. These results suggest that the n-3/n-6 ratio of dietary fats necessary to ensure the suppression of platelet aggregation in normal rats would be at least 0.2 and no more than 0.5.

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Changes of serum alkaline phosphatase (sALP) isoenzymes under fasting conditions were examined using polyacrylamide gel electrophoresis (PAGE), amino-acids (L-phenylalanine (L-Phe), L-homoarginine (L-HArg)) inhibition and wheat germ agglutinin (WGA) treatment. The sALP of non-fasted rats was separated into three bands (Sl, S2, S3) by PAGE. The molecular weight (M.W.) of S 1 corresponded to that of an isoenzyme found in the ileum. By the addition of L-Phe, the staining intensity of 51 was weakened, S2 and S3 remained unchanged and the total activity of the isoenzymes extracted from intestine decreased. On the other hand, the activity of isoenzymes extracted from kidney and bone decreased by the addition of L-HArg. Therefore, S 1 was judged to be derived from intestine. The activities of total sALP and S 1 decreased from 16 h of fasting. Total sALP activity and sALP activity of the supernatant prepared by WGA treatment decreased, whereas the ALP activity of the precipitate (difference between total sALP activity and supernatant sALP activity) did not change. The activity band of the precipitate corresponded to that of S3 by PAGE. Therefore, 53 was judged to be derived from bone. In conclusion, under fasting conditions, the activity of S1 decreased while the activities of S2 and S3 remained unchanged.

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The effects of body weight cycling on energy metabolism and body fat accumulation were examined in sedentary and exercised rats. Ten rats were sacrificed before the experiment to obtain basal data, and then 90 rats were divided into three groups; control (CN), food restricted (FR) and weight cycling (WC). Food intake in rats of the FR group was restricted constantly to 70% of the intake of the CN group. The rats of WC group were subjected to four bouts of weight cycling consisting of 7days food restriction followed by 7-days refeeding, but were fed the same total amount of dietary energy as that of the FR group throughout the experimental period. The rats of all groups were meal-fed twice a day. Half of the rats in each group were exercised by running on a treadmill (30min/day) throughout the experimental period. The body weight, abdominal adipose tissue weight, body fat, body protein and energy restoration for the study in both sedentary and exercised groups were greater in the WC group than in the FR group. The resting metabolic rate of the WC group after four bouts of weight cycling was lower than that of the FR group in the sedentary rats, but this difference was not observed in the exercised rats. Also, the thermic effect of food (TEF) in the sedentary rats for 6 h after a meal was significantly less in the WC group as compared to that of the FR group. However, the TEF for the exercised rats was not different between the two groups. The serum insulin level, activities of lipogenic enzymes and lipoprotein lipase in adipose tissue for the sedentary rats of the WC group were higher than those of the FR group, but did not differ in the exercised rats. These results suggest that weight cycling increases body fat deposition and energy efficiency by decreasing energy expenditure, particularly the TEF, and that exercise training can alleviate the effects of weight cycling on the energy metabolism.

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We recently reported that fatty liver and hypertriglyceridemia are easily induced by the administration of an inhibitor of fatty acid oxidation (emeriamine; (R)-3-amino-4-trimethylaminobutyric acid) to fasting rats, and that these conditions are not accompanied by the increased de novo synthesis of fatty acid [J. Nutr. Sci. Vitaminol., 42, 111120, (1996)]. To study whether emeriamine-induced fatty liver is affected by nutrients during recovery from fatty acid oxidation inhibition, we fed rats with either a high-carbohydrate (HCHO) diet or a high-fat (HFAT) diet. Rats fed an HCHO diet following the administration of emeriamine showed a marked decrease in serum and hepatic triglycerides, and a marked increase in hepatic glycogen. The lower levels of serum and hepatic triglycerides were accompanied by decreased activities of the NADPH-generating enzymes such as malic enzyme and glucose-6-phosphate dehydrogenase. By contrast, rats fed an HFAT diet showed less significant changes in hepatic triglyceride and glycogen levels. These results suggest a reciprocal relationship between the triglyceride level and glycogen accumulation caused by HCHO diet during recovery from emeriamine.

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The influence of non-purified and AIN purified diets on the development of hypertension was examined in deoxycorticosterone acetate (DOCA)-salt hypertensive rats and SHRs. For DOCA-salt hypertensive rats, the development of hypertension was slower in rats fed the AIN 76-purified diet than in those fed the non-purified diet throughout the experimental period of about five weeks. In an experiment using spontaneously hypertensive rats (SHRs), 4-week-old rats were fed either a nonpurified diet, a AIN76-purified diet or a AIN93G-purified diet for about nine weeks. In the first 1-2 weeks, the blood pressure was lower in the SHRs fed the AIN93G-purified diet than in those fed the non-purified diet. However, no significant difference in blood pressure was observed within the SHR group thereafter.

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A modified method for the determination of pyridinoline using high-performance liquid chromatography (HPLC) has been applied to analyze the urine of healthy adults and patients with rheumatoid arthritis. The concentrations of pyridinoline in the urine of healthy Japanese men and women (average age: 50.6 and 51.8 yr, respectively) during morning fasting were 28.8±2.8 (SEM) and 34.8±3.5 nmol/mmol creatinine, respectively. In the case of patients with rheumatoid arthritis, the urinary concentration of pyridinoline was 49.1±8.3 nmol/mmol creatinine (women, average age, 61.1 yr), which was significantly higher than that of healthy women of the same age (p<0.05). This study supports the application of HPLC for urinary pyridinoline analysis and as a screening test for patients with bone disease.

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The effects of calcitonin (CT) administration on calcium (Ca) concentrations in plasma and skeletal muscle as well as the calpain activity of skeletal muscle were examined in young growing male rats treated with corticosterone (CTC). The rats received subcutaneous injections of CTC (5mg/100g body weight/day), or both CTC and CT (100m unit/100g body weight/day) for four days. Control rats received placebos. The rats were sacrificed 24 h after the final injections, and blood was taken followed by dissections to remove gastrocnemius and extensor digitorum longus muscles. Plasma Ca concentration was increased and muscle Ca concentration and its calpain activity tended to be increased by CTC. The CTC-induced increases in muscle Ca concentration and its calpain activity were significantly minimized by the simultaneous injection of CT. However, CTC-induced hypercalcemia was not minimized by CT. The present observations indicate that CT decreases Ca concentration in skeletal muscle cell and its calpain activity, followed by a suppression of muscle proteolysis in rats treated with CTC.

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