PubMed Health⌕ Search

Biomedical subjects

J E Leklem

Publications and source records attributed to J E Leklem.

At least 19 recordsLinked to original sources
PubMed1997

Changes in vitamin B-6 status indicators of women fed a constant protein diet with varying levels of vitamin B-6.

Changes in vitamin B-6 status indicators were evaluated in vitamin B-6-replete subjects. Ten young women consumed diets providing 85 g protein/d and 1.03, 1.33, 1.73, and 2.39 mg vitamin B-6/d for 12 or 15 d during four successive diet periods; in a second study, six women were fed diets providing 85 g protein/d and 0.84, 1.14, and 2.34 mg vitamin B-6/d for 10 or 12 d during three successive diet periods. Vitamin B-6 status indicators showing significant differences among intakes included urinary excretion of 4-pyridoxic acid and total vitamin B-6, pyridoxal 5'-phosphate and total vitamin B-6 in plasma, and xanthurenic acid excretion after a 2-g L-tryptophan load. Significant correlations were found between vitamin B-6 intake and 4-pyridoxic acid, total vitamin B-6, plasma pyridoxal 5'-phosphate, plasma total vitamin B-6, erythrocyte alanine aminotransferase percentage stimulation and postload excretion of xanthurenic acid and volatile amines (kynurenine plus acetylkynurenine). Depending on the indicator, between 20% and 70% of the subjects had inadequate values for 4-pyridoxic acid, total vitamin B-6, plasma pyridoxal 5'-phosphate, and erythrocyte alanine aminotransferase percentage stimulation at a vitamin B-6 intake of 1.33 mg/d (0.016 mg vitamin B-6/g protein). A ratio of dietary vitamin B-6 to protein > 0.016 mg/g is required for adequate vitamin B-6 status in women.

Adult↗
PubMed1997

Vitamin B6, vitamin C, and carpal tunnel syndrome. A cross-sectional study of 441 adults.

As part of an ongoing study of carpal tunnel syndrome (CTS) in industry, we measured plasma concentrations of pyridoxal 5'-phosphate (PLP, a measure of vitamin B6 status) and total ascorbate (ASC, a measure of vitamin C status) in 441 adult volunteers from six industries and a university exercise study. In the entire study group and in non-vitamin users (n = 218), there were no significant differences in mean plasma PLP or ASC concentrations between controls (neither symptoms nor slowing), subjects with symptoms only, subjects with median nerve slowing only, or subjects with CTS (symptoms + slowing). In male non-vitamin users (n = 137), there were significant inverse univariate associations between plasma PLP concentration and the prevalence of pain, the frequency of tingling and nocturnal awakening, and the Phalen test result. In this same subgroup, the ASC/PLP ratio was directly associated with the prevalence of pain and nocturnal awakening, and with the frequency of pain, tingling, and nocturnal awakening. In multivariate analyses, plasma ASC concentration predicted more median nerve slowing and confirmed CTS, and vitamin or vitamin interaction variables were independent predictors of 20 CTS-related outcomes. These multivariate relationships often occurred only after adjustment for age, gender, body mass index, serum alkaline phosphatase activity, or tobacco use. We conclude that there are significant relationships between plasma vitamin levels and both components of CTS (specific symptoms and median nerve slowing). The interaction between plasma PLP and ASC appears to be particularly important with respect to symptoms.

Adult↗
PubMed1996

Vitamin B-6 status indicators decrease in women consuming a diet high in pyridoxine glucoside.

Previous research has shown that the pyridoxine glucoside (PNG) form of vitamin B-6 has a reduced bioavailability compared with pyridoxine, but its effect on vitamin B-6 status has not been assessed. Following an 8-d adjustment period, nine women consumed diets containing a high or low amount of PNG for 18 d each, in a crossover design. The high and low PNG diets provided 1.52 mg/d (8.98 micromol/d) and 1.44 mg/d (8.57 micromol/d) of vitamin B-6, of which 27% and 9% was PNG, respectively. The dietary vitamin B-6 to protein ratio of both diets was 0.017 mg/g. Urinary excretions of 4-pyridoxic acid and total vitamin B-6 were significantly lower (P < 0.05) during the high PNG diet period than when the low PNG diet was consumed. Urinary PNG excretion was equal to about 9% of the total PNG intake during both periods. Plasma total vitamin B-6 (P < 0.01) and red blood cell pyridoxal 5'-phosphate (PLP) (P < 0.05) were significantly lower when the high PNG diet was consumed than during the low PNG diet period. Fecal total vitamin B-6 excretion was significantly higher (P < 0.001) when the high PNG diet was consumed. Women consuming a diet containing a higher percentage of the total vitamin B-6 intake as PNG exhibited a decrease in vitamin B-6 status indicators, consistent with the reduced bioavailability of PNG demonstrated in other studies, equal to a loss of 15-18% of the total vitamin B-6 intake. During the determination of Recommended Dietary Allowances, the reduced bioavailability of PNG and its presence in higher amounts in some diets should be considered.

Adult↗
PubMed1996

Vitamin B-6 status of women with a constant intake of vitamin B-6 changes with three levels of dietary protein.

To determine the effect of varying levels of dietary protein with a constant intake of vitamin B-6 (B-6) on B-6 status, nine women were fed diets providing daily intakes of 1.25 mg B-6 and 0.5, 1.0 and 2.0 g protein/kg body weight. After an 8-d adjustment period, the women consumed each level of dietary protein for 14 d in a Latin-square design. Several direct and indirect B-6 status indicators were measured in blood and urine. Significant differences among protein levels were found for urinary 4-pyridoxic acid (4-PA) excretion (P < 0.01), plasma pyridoxal 5'-phosphate (PLP) concentration (P < 0.05), and urinary excretion of volatile amines (VA, kynurenine plus acetylkynurenine) after a 2-g L-tryptophan load (P < 0.05). Nitrogen intake was significantly negatively correlated with urinary 4-PA excretion (r = -0.619, P < 0.001) and plasma PLP concentration (r = -0.549, P < 0.01), and positively correlated with erythrocyte alanine aminotransferase percentage stimulation (r = 0.418, P < 0.05) and urinary post-tryptophan load excretion of xanthurenic acid (r = 0.535, P < 0.05), kynurenic acid (r = 0.563, P < 0.05) and VA (r = 0.626, P < 0.01). Compared with men consuming diets with similar B-6 to protein ratios In a previous study, the women excreted a greater percentage of the B-6 intake as 4-PA, had lower plasma PLP concentrations and excreted greater amounts of postload urinary tryptophan metabolites at all three protein levels. If the Recommended Dietary Allowance (RDA) of vitamin B-6 is to be based on the dietary B-6 to protein ratio, gender differences in response to varying protein intakes should be considered. For the levels of protein intake used in this study and a B-6 intake of 1.25 mg/d, a B-6 to protein ratio of greater than 0.020 mg/g is required for adequate vitamin B-6 status in women.

Adult↗
PubMed1994

Vitamin B-6 status of school-aged patients with phenylketonuria.

A triad of measures of vitamin B-6 (B6) status (diet, plasma, and urine) was evaluated in 15 patients with phenylketonuria (PKU) and six control subjects (6-17 y): 1) 4-d reported dietary intakes of protein and B6; 2) fasting plasma concentrations of pyridoxal 5'-phosphate (PLP), total B6 (TB6), and alkaline phosphatase (AP) activity; and 3) 24-h urinary excretions of TB6 and 4-pyridoxic acid (4-PA). Compared with control subjects, patients had a significantly reduced mean protein intake (P < 0.001) and increased mean B6 intake (P < 0.05). Mean dietary B6:protein in patients, 0.043 mg/g protein, was over twice that of control subjects, 0.018 mg/g protein (P < 0.001). Mean plasma PLP and PLP/TB6 in patients were significantly increased compared with control subjects (P < or = 0.05). As a percent of B6 intake, mean urine TB6 was similar between the groups (6.8% patients vs 6.5% control subjects). These findings, along with a lower mean plasma AP activity in patients, support the possibility of a reduced turnover of the vitamin in PKU.

Adolescent↗
PubMed1991

Energy need in childhood and adult-onset obese women before and after a nine-month nutrition education and walking program.

The effect of a 9-month nutrition education and walking program on total calorie need, resting metabolic rate (RMR), thermic effect of food (TEF), body composition, and activity level was determined in seven women (28-41 years of age) with childhood-onset obesity (CO) and eight women (29-42 years of age) with adult-onset obesity (AO). A 3-week testing period was conducted before and after the 9-month program during which all subjects were fed a controlled, weight-maintaining metabolic diet which was used to determine daily calorie need. Body composition, RMR, and TEF were measured during the second and third weeks of both 3-week testing periods. Body weight decreased significantly for CO (mean -5.7 +/- 9.3 kg) and AO (mean -3.3 +/- 6.2 kg), but fat-free mass (FFM) was unchanged. When comparing pre to post data, mean total calorie need increased by 2.9 percent for CO and 3.1 percent for AO (P greater than 0.05), RMR decreased 3.6 percent for CO and 2.8 percent for AO (P less than 0.05), and TEF increased 11 percent for CO and 50 percent for AO (P less than 0.05). Time spent in light and moderate level activity increased significantly from pre to post. The increase in activity and TEF more than compensated for the slight decrease in RMR (mean -55 kcal/day), contributing to an overall increase in daily energy need (mean = 74 kcal/day) at the end of the program, even for the six women who lost greater than 5 kg body weight.

Adult↗
PubMed1990

Acute ingestion of glucose decreases plasma pyridoxal 5'-phosphate and total vitamin B-6 concentration.

The effect of the acute ingestion of glucose on the concentration of pyridoxal 5'-phosphate (PLP) and total vitamin B-6 (TB6) in plasma was studied. Five males and four females were given 1 g D-glucose/kg body wt. A blood sample was collected at 0-10 min and 0, 0.5, 1, 2, 3, 4, and 5 h and the plasma was analyzed for PLP and TB6. There was a significant decrease in both plasma PLP and TB6 (p less than 0.05) at 2 h. All nine subjects exhibited a decrease, and by 5 h the mean change from fasting was 8-10 nmol/L for PLP and 8-12 nmol/L for TB6 (an 18-21% decrease from that when fasting). Ingestion of 300 mL water in four subjects resulted in a mean decrease of 3.4 nmol PLP/L plasma and indicated that some but not all of the decrease may have been due to fluid ingestion per se. Ingestion of glucose is associated with a decrease in both circulating plasma PLP and TB6; therefore, carbohydrate ingestion should be considered when plasma PLP and TB6 concentrations are used to evaluate vitamin B-6 status. In addition, fasting blood samples should be used when evaluating vitamin B-6 status.

Administration, Oral↗
PubMed1990

In vivo evidence for a vitamin B-6 requirement in carnitine synthesis.

The purpose of this study was to determine whether there is a requirement for vitamin B-6 (B6) in carnitine synthesis. Rats were fed a B6-deficient (-B6) (0.04 mg pyridoxine [PN]/kg) diet (ad libitum or meal-fed) or a control (+B6) (5.7 mg PN/kg) diet (ad libitum or pair-fed). These diets were fed for 6 wk, then some of the rats were repleted with the +B6 diet for 2 wk. Total acid-soluble carnitine (TCN) and free carnitine (FCN) levels were compared in the plasma, liver, skeletal muscle, heart muscle and urine and rats fed +B6 or -B6 diets. In -B6 rats vs. +B6 rats, TCN levels were significantly lower (P less than 0.05) in the plasma, skeletal muscle, heart muscle and urine, but not in the liver. However, if rats were fasted for 3 d, liver TCN concentration of -B6 rats was significantly lower than that of +B6 rats. After B6-deficient rats were repleted with the +B6 diet, the TCN level in the plasma, liver, skeletal muscle, heart muscle and urine returned to the levels of control rats. Thus, the decrease in TCN and FCN levels with a B6-deficient diet and the increase of these levels after B6 repletion provides evidence for the B6 requirement in the biosynthesis of carnitine.

Analysis of Variance↗
PubMed1990

Vitamin B-6: a status report.

Over the past 50 yr there has been an increased awareness of the importance of vitamin B-6 in human nutrition. The knowledge base for evaluation of vitamin B-6 status has also increased. Indices for vitamin B-6 status can be separated into direct and indirect measures. Among the direct measures, plasma pyridoxal 5'-phosphate (PLP) is considered the most relevant. However, measurement of plasma pyridoxal or total vitamin B-6 and urinary 4-pyridoxic acid are also recommended. Indirect measures of vitamin B-6 include the assessment of urinary excretion of xanthurenic acid following a tryptophan load. This is a valid functional index for otherwise healthy persons. Evaluation of erythrocyte transaminase activity and stimulation with PLP provide an estimate of vitamin B-6 intake over an extended period of time. In addition to biochemical measures, determination of vitamin B-6 and protein intake are necessary. Present evidence suggests plasma PLP, urinary 4-pyridoxic acid, at least one indirect measure, and the intake of vitamin B-6 and protein are needed to properly assess vitamin B-6 status. The levels of plasma pyridoxal and erythrocyte PLP are newer measures of status and, with further refinement of methodology, may provide additional insight into vitamin B-6 status.

Erythrocytes↗
PubMed1989

Plasma pyridoxal 5'-phosphate concentration and dietary vitamin B-6 intake in free-living, low-income elderly people.

Free-living, elderly persons (aged greater than or equal to 60 y, n = 198) were recruited to determine the effects of age, sex, health status, dietary vitamin B-6 intakes, and B-6 supplement use on plasma pyridoxal 5'-phosphate (PLP). Vitamin B-6 intakes were determined from 3-d diet records; supplementation was based on self-reported brand and frequency data. Fasting blood samples were analyzed for PLP. Subjects were primarily low-income Caucasians. There was no linear relationship between dietary vitamin B-6 intake, age, sex or health status, and PLP while accounting for supplemental vitamin B-6 use. PLP, however, was negatively correlated with age (p less than 0.001) in individuals with PLP values between 32 and 90 nmol/L. Vitamin B-6 status was low (PLP less than 32 nmol/L) in 32% of this elderly population (n = 198) and could be attributed to low dietary vitamin B-6 intakes and/or the presence of health problems reported to alter vitamin B-6 status. This research suggests that low vitamin B-6 status is prevalent in low-income, elderly persons, especially those with multiple health problems.

Aged↗
PubMed1988

Effect of carbohydrate and vitamin B6 on fuel substrates during exercise in women.

Pyridoxal 5'-phosphate is an essential co-factor for glycogen phosphorylase and certain enzymes in the alanine-glucose cycle. Glycogen phosphorylase is also proposed as a storage reservoir for vitamin B6. To examine the effect of vitamin B6 and carbohydrate on fuel substrates during exercise, 5 young/trained, 5 young/un-trained, and 5 post-menopausal/un-trained women were alternately fed four diets (varying carbohydrate and B6 level) over a 7-wk period. Subjects were exercised at the end of each dietary period at 80% VO2max for 20 min on a cycle ergometer. Blood was drawn pre-, post-, post-30, and post-60 min of exercise and analyzed for plasma pyridoxal 5'-phosphate, glucose, free fatty acid, and lactate. ANOVA showed no difference among groups or diets for lactate, although lactate was significantly different over time (P less than 0.0001) on all diets. ANOVA showed significant time x group x diet inter-actions for free fatty acid (P less than 0.05) and significant diet x time (P less than 0.04) and time x group (P less than 0.03) inter-actions for glucose. Supplementation and/or increased carbohydrate resulted in lower free fatty acid during exercise in all groups. ANOVA showed no difference in pyridoxal 5'-phosphate for groups with respect to diet or time, but did show a significant increase from pre- to post-exercise and a significant decrease from post- to post-60 min of exercise. These results indicate that a high-carbohydrate diet and/or supplemental vitamin B6 can alter plasma fuel substrates during exercise in women; however, the effect depends on age and level of training.

Age Factors↗
PubMed1987

Vitamin B-6 status and bioavailability in vegetarian women.

It has been hypothesized that the vitamin B-6 status of vegetarians and nonvegetarians may differ in relation to bioavailability of vitamin B-6. Fasting blood samples and 24-h urine collections were obtained from 13 Seventh-day Adventist (SDA) vegetarian and 16 non-SDA nonvegetarian women aged 50-83 y. The two groups were further subdivided into vitamin users and nonusers. Dietary intake was estimated from a 3-d diet record. Plasma pyridoxal 5'-phosphate (PLP) was measured by an enzymatic method. Vitamin B-6 intakes were similar and provided 85% of the RDA for both groups. The vegetarians consumed significantly more crude fiber than the nonvegetarians. No significant differences were found between the two groups for plasma PLP, urinary 4-pyridoxic acid, and urinary vitamin B-6 among vitamin nonusers or for age categories within groups. There appeared to be no adverse effect of fiber on the availability or metabolism of vitamin B-6 between these free-living groups.

Aged↗
PubMed1987

Vitamin B-6 metabolism as affected by exercise in trained and untrained women fed diets differing in carbohydrate and vitamin B-6 content.

To assess the effect of exercise on vitamin B-6 metabolism in women, five young-trained, five young-untrained, and five postmenopausal-untrained women were alternately fed four diets and then exercised (80% VO2 max; 20 min) after each diet. The following diets were fed: 2 wk moderate carbohydrate (CHO) (49%) (2.3 mg B-6); 1 wk high CHO (64%) (2.4 mg B-6); 2 wk moderate CHO + B-6 (10.3 mg B-6); 1 wk high CHO + B-6); 1 wk high CHO + B-6 (10.4 mg B-6). Blood was drawn pre- and postexercise and post-30 min and post-60 min of exercise and analyzed for plasma pyridoxal 5'-phosphate (PLP) and total B-6. Twenty-four-hour urines were analyzed for 4-pyridoxic acid and urinary B-6. PLP and total B-6 increased significantly with exercise and decreased significantly from post- to post-60 min for all diets. Four-pyridoxic acid increased significantly from the preexercise day to the day of exercise for all diets. Although there was a significant change in B-6 metabolism with exercise, neither training, increased CHO, nor age had an effect on this change.

Adult↗
PubMed1985

The effects of a high-carbohydrate low-fat cholesterol-restricted diet on plasma lipid, lipoprotein, and apoprotein concentrations in insulin-dependent (type I) diabetes mellitus.

Six women with well-defined insulin-dependent diabetes mellitus (IDDM) were studied for 4 weeks during a control diet containing 45% of the calories as carbohydrate, 40% fat (P/S ratio 0.14), 15% protein, and 580 mg of cholesterol, and for 6 weeks during a high-carbohydrate low-fat cholesterol-restricted diet with 65% carbohydrate, 20% fat (P/S ratio 1.40), 15% protein, and 62 mg cholesterol. All subjects completed both dietary periods in a crossover experimental design. Individual menus were subject-selected from a calculated exchange list containing conventional food items consistent with current American dietary patterns. The diets were well-tolerated by all subjects. Total plasma cholesterol decreased from 201 to 156 mg/100 mL (P less than 0.05) during the cholesterol-restricted diet, while total plasma triglyceride (TG) increased from 96 to 115 mg/100 mL (P less than 0.01). During this same period, very low-density lipoprotein cholesterol (VLDL-C) and VLDL-TG increased from 17 to 21 mg/100 mL (P less than 0.05) and from 59 to 76 mg/100 mL (P less than 0.001), respectively, while low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) decreased from 126 to 90 mg/100 mL (P less than 0.05) and from 50 to 39 mg/100 mL (P less than 0.05), respectively. LDL-C/HDL-C and total-C/HDL-C ratios were lower but not significantly different, and LDL-TG and HDL-TG were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗