Actinomycin D effect on amino acid absorption from rat jejunal loops.

The absorption of amino acids from jejunal loops was suppressed in anesthetized rats treated previously with 1.0 or 1.5 micrograms of actinomycin D per gram of body weight. The absorption of the acidic, neutral, and basic amino acids showed selective differences in response that were relative to the degree of inhibition and to the time interval required to demonstrate actinomycin sensitivity.

Evidence that histidine is an essential amino acid in normal and chronically uremic man.

The requirement for dietary histidine was investigated in four normal and three chronically uremic men. Subjects lived in a metabolic unit where they were fed three isonitrogenous diets in the following order: a 40-g protein diet (28 plus or minus SD 8 days), a semi-synthetic amino acid diet deficient in histidine (35 plus or minus 2 days), and an amino acid diet which contained histidine (31 plus or minus 5 days). With ingestion of the histidine-deficient diet, nitrogen balance gradually became negative, and serum albumin decreased in six subjects. Plasma histidine fell by 82 plus or minus 6 per cent; muscle histidine decreased by 62 plus or minus 19 per cent; the hematocrit fell by 25 plus or minus 9 per cent; and serum iron rose. Subjects felt unwell, and in five cases a skin lesion consisting of fine scales, dry skin, and mild erythema developed. After administration of the histidine-repletion diet, nitrogen balance became positive in six subjects; serum albumin increased in five cases; plasma and muscle histidine rose; serum iron fell abruptly; a reticulocytosis ensued; and the hematocrit rose. The clinical symptoms and skin lesions disappeared. These observations indicate that histidine is an essential amino acid in normal and chronically uremic man. The absence of dietary histidine is associated with failure of normal erythropoiesis.

Vitamins C, E and A and heme oxygenase in rats fed methyl/folate-deficient diets.

There is evidence that the development of hepatocarcinoma in rats fed a methyl-deficient diet is associated with oxidative stress. We investigated, therefore, whether the tissue concentrations of the antioxidant vitamins ascorbic acid (AA) and alpha- and gamma-tocopherol (T) are altered in methyl/folate deficiency. We also measured retinol concentrations in tissues and hepatic mRNA expression of heme oxygenase (HO1). A 6% gelatin, 6% casein diet, devoid of choline and folate (CFD) was selected based on the high rate of tumor development in rats fed this diet. Spectrophotometric measurement of AA and HPLC determination of tissue T and retinol showed decreased concentrations of AA in blood; alpha- and gamma-T in lung, heart and plasma, alpha-T and retinol in liver; retinol in lung; and increased expression of hepatic HO1 mRNA. Similar alterations in tissue vitamin concentrations were found when the CFD diet devoid of niacin (CFND) was fed. Reducing alpha-T in the CFND diet (CFNED) further decreased hepatic alpha-T concentrations. These results show that chronic methyl/folate deficiency is associated with a compromised antioxidant defense system.

Plasma beta-carotene response in humans after meals supplemented with dietary pectin.

The purpose of this study was to determine the effect of pectin on plasma response to beta-carotene in humans. Using a crossover design, we evaluated the effect on plasma beta-carotene in seven subjects when 12 g citrus pectin was added to a 2092 kJ (500 kcal) controlled meal with 25 mg beta-carotene. Plasma samples were collected at 0, 8, 30, 48, and 192 h after the meals. Plasma beta-carotene was quantified with the use of HPLC. The increase in plasma beta-carotene concentration was significantly reduced by pectin at 30 and 192 h (paired t test; P less than 0.005 and less than 0.05, respectively). Mean percent increase in plasma beta-carotene concentration at 30 h after the meal with beta-carotene was reduced by more than one-half when pectin was added to the meal. These results indicate that the inhibitory effect of pectin may provide one explanation for observations of reduced plasma beta-carotene response in humans after the ingestion of carotenoid-rich foods when compared with equivalent doses of beta-carotene supplements.

Amino acid and protein metabolism in renal failure.

There are many cAUSES OF ALTERED AMINO ACID AND PROTEIN METABOLISM IN UREMIA WHICH MAY Lead to impaired growth, wasting, malnutrition, and other aspects of the uremic syndrome. These causes have complex interrelationships that are not well understood. The factors include altered nutrition due to poor intake, losses of nutrients during dialysis, and abnormal metabolism of many nutrients. Uremic toxins, superimposed catabolic illnesses, elevated or reduced serum hormone levels, reduced capacity of the kidney to synthesize certain amino acids and to degrade other amino acids, peptides, and small proteins, and decreased excretion of certain amino acids and peptides may also contribute to altered amino acid and protein metabolism. The response of certain plasma amino acids to protein restriction appears to differ in uremic patients as compared to normal subjects. Increased plasma levels of many products of amino acids and proteins in renal failure are due primarily to decreased urinary clearance by the kidney. However, for some metabolites, increased synthesis or decreased degradation may also contribute to elevated levels. These latter compounds include guanidinosuccinic acid, methylguanidine, certain middle molecules, and in some patients, phenylpyruvic acid.

Vitamin cofactor saturation indices for riboflavin, thiamine, and pyridoxine in placental tissue of Kenyan women.

Vitamin cofactor saturations of placental enzymes were assayed in 54 Kenyan women. In addition, studies were conducted to determine whether placental vitamin deficiencies were associated with deficiencies in maternal or cord blood and to determine whether neonatal birthweights were influenced by vitamin nutriture. All samples were analyzed by vitamin cofactor saturation tests of glutathione reductase, transketolase, and glutamic-pyruvic transaminase. Standard indices were used to determine vitamin deficiencies. The activity of placental diamine oxidase, a pyridoxal phosphate-requiring enzyme was also measured and examined in relation to pyridoxine nutriture. No placental riboflavin deficiencies were found although 73% of maternal red blood cells (RBC) and 35% of cord RBC were deficient. Thiamine deficiencies were found in 15% of placentas, 59% of maternal RBC and 41% of cord RBC. Pyridoxine deficiencies occurred in 24% of placentas, 35% of maternal RBC, and 15% of cord RBC. Low birth weights were found to be associated with maternal riboflavin deficiencies. Maternal RBC riboflavin and thiamine deficiencies correlated with deficiencies in cord blood, and pyridoxine deficiencies in maternal RBC were associated with deficiencies in the placenta. A trend of lower placental diamine oxidase activity was noted in pyridoxine-deficient placentas and pyridoxine-deficient mothers.

14CO2 expiration after 14C-histidine administration in normal and uremic men ingesting two levels of histidine.

The rates of histidine degradation were investigated in six normal and three chronically uremic men who were not undergoing dialysis therapy. The nine men were studied in the postabsorptive state after they had ingested one or more of the following diets for the indicated periods of time: a 40 g protein diet providing about 1100 mg/day of histidine for 27 +/- 9 SD days (seven studies), an amino acid diet providing only 65 mg/day of histidine (histidine-deficient diet) for 33 +/- 3 days (eight studies), and an amino acid diet providing about 1125 mg/day of histidine (histidine-replete diet) for 32 +/- 7 days (six studies). Diets are listed in the order of administration; five men received all three diets. After fasting overnight, subjects received an intravenous injection of 25 microCi/70 kg body weight of L-[ring-2-14C]-histidine (eight men) or L-carboxyl-14C]-histidine (one man), and expiration of 14CO2 was measured continuously for 2 h. With both tracers, expiration of 14CO2 fell with ingestion of the histidine-deficient diet (p less than 0.005) and then increased with intake of the histidine-replete diet (p less than 0.05). Free histidine in plasma and muscle also decreased with the histidine-deficient diet and rose with the histidine-replete diet. If other tissue free histidine pools changed similarly and protein turnover was not very different with the three diets, then the 14CO2 expiration data and the estimated specific activity of 14C-histidine indicate that histidine degradation fell markedly with the histidine-deficient diet and then increased with the histidine-replete diet. In uremic patients as compared to normal subjects no differences in the magnitude of 14C-histidine degradation or in the pattern of 14CO2 expiration were observed.

Biochemical assessment of the nutritional status of low-income pregnant women of Mexican descent.

Biochemical parameters of nutritional status were investigated in 300 women of Mexican descent during the first and second trimesters of pregnancy. Blood samples were obtained from the women during clinic visits, and measurements were made of serum iron, hemoglobin, hematocrit, serum protein, and transferrin saturation. Additionally, the nutritional status of seven vitamins was determined either by direct assay of the vitamin levels in blood or by measurement of erythrocyte enzyme stimulation. Thiamin and riboflavin were also determined in causal urine samples. Very few women, 8% or less, were classified as being low or deficient in hemoglobin, serum protein, iron, transferrin saturation, vitamin C, carotene, vitamin A, or vitamin B12. Thirty-one percent had low or deficient hematocrit values according to the guidelines used. Folic acid was the most prevalent vitamin deficiency, with 69% of the women having low or deficient serum levels. Based on the erythrocyte enzyme stimulation tests, 22% of the women were low or deficient in thiamin, 29% were low or deficient in riboflavin, and 9% were deficient in pyridoxine. None of the women had a low urinary excretion of thiamin, but 8% had excretion values of riboflavin below the acceptable level. Fewer deficiencies of thiamin and serum folic acid were observed in women taking vitamin and mineral supplements than in those who were not.

Biochemical evidence of thiamin deficiency in young Ghanian children.

Detailed biochemical studies for nutritional status were carried out on 146 Ghanaian children ages 6 months to 6 years over a 2-year period. Study children comprised three main groups: severe protein-calorie malnutrition; mild to moderate protein-calorie malnutrition and apparently healthy children. Erythrocyte transketolase activity and the percentage of erythrocyte transketolase pyrophosphate effect were also determined. In the first year of the study elevated percentage of transketolase pyrophosphate effect indicative of thiamin deficiency was found in all three of the above-mentioned groups, with the most widespread deficiency in the normal groups. In year 2, repeat studies of the severely malnourished group after 2 weeks of nutritional therapy with the administration of vitamin capsules, which included thiamin, resulted in the normalization of transketolase pyrophosphate effect. Apoenzyme activity was comparable in all groups studied. There were no obvious clinical signs of thiamin deficiency, although sensory testing was not performed. A relatively large number of children with high percentage of transketolase pyrosphosphate effect also had serum folic acid deficiency. This evidence of widespread biochemical thiamin deficiency is indicative of an at-risk population among young children for clinical thiamin deficiency. Further studies are needed to identify whether the problem is inadequate thiamin intake, destruction of thiamin by thiaminases or food preparation methods, or malabsorption of thiamin.

Nitrogen economy during very low calorie reducing diets: quality and quantity of dietary protein.

Controversy exists whether protein quantity or quality affect "nitrogen sparing" or physical health while subsisting on very low calorie diets. Therefore, in 38 obese men, nitrogen economy was evaluated over 2 months periods using one of five regimens: 1) 400 kcal high quality protein: 2) 400 kcal low quality protein; 3) 500 kcal 55 g protein natural food; 4) total fasting with potassium; and 5) total fasting without potassium. Up to the 20- and 40-day intervals, mean cumulative nitrogen deficity for all three diet groups was the same but 60% lower than with total fasting. However, within groups, individual capability to conserve nitrogen varied over as much as 2.8-fold. All 10 subjects of diet groups 1 and 2 had negative nitrogen balances to day 21, and six of these subjects were still negative by day 40. The improvement in nitrogen conservation and the ability to attain nitrogen equilibrium was unrelated to the differences in protein quantity and quality. Intake of essential or branched-chain amino acids was also unrelated to the efficiency of nitrogen conservation, as were insulin, glucagon, and 3-hydroxybutyrate levels. The only indicator correlating positively with nitrogen deficit was a fall in complement C3 (r = 0.87). Despite the extent of overall nitrogen loss, no cardiac arrhythmias were observed with either the high or low quality protein diet.

Vitamin B-6 nutriture and plasma diamine oxidase activity in pregnant Hispanic teenagers.

Vitamin B-6 status was assessed by measuring erythrocyte glutamic-pyruvic transaminase (EGPT) indices in 122 pregnant Hispanic teenagers. Seventeen percent were vitamin B-6 deficient (EGPT indices greater than 1.25) at the initial interview (first or second trimester). A daily supplement of 5 mg vitamin B-6, beginning at initial interview, did not reduce prevalence of vitamin B-6 deficiency at final interview (third trimester). No association was found between EGPT indices greater than 1.25 and the outcome of pregnancy. The activity of diamine oxidase (DAO), a vitamin B-6-dependent enzyme produced by the placental decidua, was measured in maternal plasma. At initial and final interviews, plasma-DAO activity was increased by in vitro addition of pyridoxal-5'-phosphate. The activity in early pregnancy was positively associated with dietary vitamin B-6 intake and was lower in teenagers with EGPT indices greater than 1.25 at the final interview. Findings suggest that plasma-DAO activity is influenced by vitamin B-6 status.

Zinc and copper nutriture in obese men receiving very low calorie diets of soy or collagen protein.

Balance studies for Zn and Cu were conducted over 40 days in 10 obese men housed in a metabolic balance unit. Two weight reduction diets providing 400 kcal and 100 g protein daily were administered; to five subjects, a collagen diet which was severely deficient in both Zn and Cu, and to another five subjects, a soy diet which provided a marginal intake of Zn and an adequate intake of Cu. Zn and Cu content of diets, plasma, red blood cells, urine, and feces were determined during eight 5-day periods. Balances were corrected for lean tissue catabolism or deposition. Holter ECG monitoring and measurement of the QTc interval were done on days 0 and 40. Both diets resulted in elevated plasma and red blood cell concentrations of Zn and Cu and in high urinary and fecal losses of Zn. By day 40, 6 of 10 subjects were in negative Zn balance. Urinary Zn was inversely correlated with measures of lean tissue catabolism. During each period, Cu balance was markedly positive in the soy-diet group and negative in the collagen-diet group. Shortening of prolonged QTc intervals was related to the Cu but not Zn status of the individual.

Zinc, vitamin B-6, and other nutrients in pregnant women attending prenatal clinics in Mexico.

Biochemical measurements and 24-h dietary recalls were conducted early (18.9 +/- 5.9 wk) and late (35.1 +/- 2.0 wk) in pregnancy in women attending clinics in Montemorelos, Mexico. Mean weight gain per week (0.4 +/- 0.2 kg) and birth weight (3381 +/- 456 g) were normal. Intakes tended to decline during pregnancy and declined significantly for zinc (p less than 0.05) and vitamin B-6 (p less than 0.03). Mean Zn intake late in pregnancy was low (7.8 +/- 3.3 mg/d). Various supplements were taken but none contained Zn. During pregnancy mean plasma Zn levels fell (p less than 0.001) and late in pregnancy 57% of the women had values suggestive of poor Zn status (less than or equal to 8.1 mumol/L). These data indicate that Zn intakes of approximately 8 mg/d will not maintain plasma Zn levels in late pregnancy. Erythrocyte glutamic-pyruvic transaminase (EGPT) index and the index of diamine oxidase (DAO), a vitamin B-6-requiring enzyme of placental origin, were correlated suggesting that DAO index may be useful in evaluating vitamin B-6 status in pregnancy.

PIP: Biochemical measurements and 24 hour dietary recalls were conducted early (18.9 +0- 5.9 weeks) and late (35.1 +or- 2.0 weeks) in pregnancy in women attending clinics in Montemorelos, Mexico. Mean weight gain per week (0.4 +or- 0.2 kg) and birth weight (3381 +or- 456 grams) were normal. Intakes tended to decline during pregnancy and declined significantly for zinc (p 0.05) and vitamin B-6 (p 0.03). Mean zinc intake late in pregnancy was low (7.8 +or- 3.3 mg/d). Various supplements were taken but none contained zinc. During pregnancy mean plasma zinc levels fell (p 0.001) and late in pregnancy 57% of the women had values suggestive of poor zinc status (or= 8.1 micromoles/liter). These data indicate that zinc intakes of approximately 8 mg/d will not maintain plasma zinc levels in late pregnancy. Erythrocyte glutamic-pyruvic transaminase (EGPT) index and the index of diamine oxidase (DAO), a vitamin B-6-requiring enzyme of placental origin, were correlated suggesting that DAO index may be useful in evaluating vitamin B-6 status in pregnancy.

Methylated niacin derivatives in plasma and urine after an oral dose of nicotinamide given to subjects fed a low-methionine diet.

Five healthy males, age 25-32 y, were fed in sequence a diet of ordinary foods (10 d, PI), a low-methionine diet (285 mg/d, 14 d, PII), and an adequate-methionine diet (725 mg/d, 7 d, PIII). Diets contained 9 g nitrogen (N) per day with soy protein and synthetic L-amino acids as the N sources in PII and PIII. In PII, subjects were in negative N balance whereas, in PIII, four subjects were in positive N balance. On the last day of each period, fasting subjects ingested a dose of nicotinamide (NAM, 102 mumol/kg body wt). Plasma and urine samples were analyzed for methylated derivatives of NAM by high-performance liquid chromatography (HPLC) methods. Mean values of methylated metabolites in urine from the three diet periods (for four subjects in N balance during PIII) were not different (59.8, 56.7, and 59.9 mumol/(kg body wt X 24 h) for PI, PII, and PIII, respectively). Plasma values of these metabolites also were similar. Results suggest that during a 2-wk period of negative N balance due to a low-methionine intake hepatic methylation processes are not impaired. These processes appear to have a higher metabolic priority than maintenance of the net protein synthesis rate.

Zinc supplementation during pregnancy: effects on selected blood constituents and on progress and outcome of pregnancy in low-income women of Mexican descent.

The effects of zinc supplementation on levels of various blood constituents and the outcome of pregnancy in 213 Hispanic women attending a prenatal clinic in Los Angeles was assessed in this double-blind study. The women were randomized into either a control (C) or a zinc-supplemented (Z) group and received similar vitamin and mineral supplements except that 20 mg zinc was added to the Z group's capsules. At the final interview, women (C + Z) with low serum Zn levels (less than or equal to 53 micrograms/dl) had higher (p less than 0.01) mean ribonuclease activity and lower (p less than 0.01) mean delta-aminolevulinic acid dehydratase activity than women with acceptable serum zinc levels. The incidence of pregnancy-induced hypertension was higher (p less than 0.003) in the C than in the Z group, but pregnancy-induced hypertension was not associated with low serum zinc levels at either the initial or final interview. The expected increase in serum copper levels was greater (less than 0.001) in women with pregnancy-induced hypertension (C + Z) than in normotensives. Except for pregnancy-induced hypertension, there was a higher incidence of abnormal outcomes of pregnancy in the noncompliers than in the compliers (C + Z).

Zinc supplementation during pregnancy: zinc concentration of serum and hair from low-income women of Mexican descent.

The effect of zinc supplementation on concentrations of zinc in hair and serum of 213 pregnant Hispanic women attending a clinic in Los Angeles was assessed using a random, double-blind experiment. Both the treatment (T) and control (C) groups received similar vitamin and mineral supplements except that 20 mg zinc was added to the supplements for the treatment group. Nutrient intakes were calculated from 24-h recalls. The initial mean dietary zinc intake of both groups was about 50% of the Recommended Dietary Allowance (9 +/- 5 mg). Initially there were no significant differences between the two groups in mean zinc levels in serum (66 +/- 11 micrograms/dl, C, and 65 +/- 12 micrograms/dl, T) or in hair (184 +/- 41 micrograms/g, C, and 175 +/- 38 micrograms/g, T). Zinc supplementation did not alter mean zinc levels in serum or hair but significantly (p less than 0.05) reduced the number of low serum zinc values (less than or equal to 53.3 micrograms/dl) toward the end of pregnancy. Although serum zinc levels do decline in pregnancy, our results suggest that severely depressed levels (less than or equal to 50 to 55 micrograms/dl) indicate inadequate zinc status.

Immunocompetence and oxidant defense during ascorbate depletion of healthy men.

To determine nonscorbutic effects of moderate vitamin C deficiency we measured immune function and oxidative damage in eight healthy men (25-43 y) who consumed 5-250 mg/d of ascorbic acid over 92 d on a metabolic unit. During ascorbic acid intakes of 5, 10, or 20 mg/d, subjects attained a state of moderate ascorbic acid deficiency as ascorbic acid concentrations in plasma, leucocytes, semen, and buccal cells dropped to less than 50% of baseline with no scorbutic symptoms observed. No changes in cell proliferation, erythrocyte antioxidant enzymes, and DNA strand breaks were observed; however, blood levels of glutathione and NAD(P) decreased during ascorbic acid deficiency, as did delayed hypersensitivity responsiveness. Concentrations of the oxidatively modified DNA base, 8-hydroxydeoxyguanosine in sperm DNA and fecapentaenes, ubiquitous fecal mutagens, were increased during ascorbic acid depletion. Moderate vitamin C deficiency, in the absence of scurvy, results in alteration of antioxidant chemistries and may permit increased oxidative damage.

Zinc supplementation during pregnancy in low-income teenagers of Mexican descent: effects on selected blood constituents and on progress and outcome of pregnancy.

As a follow-up of our study of pregnant women, we report effects of zinc supplementation during pregnancy in another population of 138 Hispanic teenagers in Los Angeles. Teenagers were randomized (double-blind) to a control or zinc-supplemented group and received similar daily vitamin and mineral supplements except for 20 mg zinc added to the zinc-supplemented group's capsules. Initially, mean dietary zinc intakes of both groups were about 50% of the Recommended Dietary Allowance and their mean serum zinc levels did not differ significantly (69.8 +/- 11.2 micrograms/dl in control and 69.0 +/- 11.4 micrograms/dl in zinc-supplemented group). Zinc supplementation did not maintain mean serum zinc levels during pregnancy but, as in our earlier study, it reduced (p = 0.018) the number of low serum zinc values (less than or equal to 53 micrograms/dl) in late pregnancy. Zinc supplementation did not affect outcome of pregnancy but serum zinc levels were lower (p = 0.038) in teenagers with pregnancy-induced hypertension than in normotensives.

Red cell and plasma folate, folate consumption, and the risk of colorectal adenomatous polyps.

Epidemiological and experimental evidence suggests that dietary folate may protect against colorectal carcinogenesis. The epidemiological relationship between a biochemical measure of folate status and colorectal neoplasia in a sizeable and generally healthy population does not yet appear to have been reported. We conducted a case-control study of the relationships among red cell folate, plasma folate, folate intake, and adenomatous polyps, intermediate markers for colorectal cancer. During 1991-1993, fasting blood samples were assayed and dietary and nondietary risk factor questionnaires were administered to men and women ages 50-75 years who had a free sigmoidoscopy at a health maintenance organization. We analyzed data from 682 subjects (332 cases and 350 controls), controlling for potential confounding by sex, age, sigmoidoscopy date, and clinic. For red cell folate levels 160 ng/ml (363 nmol/liter) or more, compared to lower levels, the odds ratio was 0.76 [95% confidence interval (CI) = 0.53-1.08]. For men, the corresponding odds ratio was 0.53 (CI = 0.32-0.87); for women, it was 1.16 (CI = 0.67-2.00). Results were essentially unchanged when adjusted for levels of blood nutrients and other potential confounding variables. Plasma folate and folate intake results were similar to red cell folate results, but the associations with polyps were weaker. Results are consistent with a protective effect of red cell folate concentration against the development of colorectal polyps, at least in men. A folate effect may depend on sex-specific interactions with other nutritional or physiological factors.

Metabolism of 1-14C-ornithine and 1,4-14C-putrescine in chronically uremic and control rats.

The metabolism of ornithine and putrescine was studied in vivo in chronically uremic and control rats. Rats were injected intraperitoneally with 1,4-14C-ornithine or 1,4-14C-putrescine and expired 14CO2 was collected for 4 hr. After injection of 1-14C-ornithine. 14CO2 expiration was decreased in uremic rats as compared to controls. Conversely, after 1,4-14C-putrescine injection, expiration of 14CO2 was increased in uremic rats as compared to controls. Four hours after the injection of 1-14C-ornithine, there was more radioactivity in liver and muscle and less radioactivity in kidney of uremic rats as compared to the respective sources in control rats. In uremic rats, 4 hr after 1,4-14C-putrescine injection, the radioactivity retained in the muscle and plasma was greater than in corresponding sources in control rats; whereas the radioactivity retained in uremic liver and kidney was similar to that of control rats. The greater putrescine-derived radioactivity retained in uremic tissues reflects either the retention of injection racer compounds, or retention or decreased catabolism of putrescine metabolites. From 14CO2 expiration data obtained, it appears that ornithine catabolism is reduced while putrescine catabolism is increased in uremia.