n-(4-acetamidobenzoyl)-l-glutamic-acid and 4-aminobenzoylglutamic-acid

The major route of folate turnover is by catabolic cleavage of the C9-N10 bond producing p-aminobenzoylglutamate (pABG) and its primary excretory form, p-acetamidobenzoylglutamate (ApABG). We hypothesize that total pABG (ApABG + pABG) excretion parallels both the mass of body folate pools from which these catabolites originate and the folate-status indicators.. The objective was to determine whether urinary folate catabolite excretion reflects body pool size and parallels the static and functional measures of folate status.. Urinary folate catabolite excretion was measured in women (aged 60-85 y) consuming controlled amounts of folate for 14 wk. A low-folate diet (120 microg/d) was consumed (n = 33) for 7 wk, and then subjects were randomly assigned to consume either 200 (n = 14) or 400 (n = 16) microg folate/d. Urinary pABG and ApABG concentrations were measured by HPLC at 0, 7, and 14 wk.. Urinary excretion of total pABG was significantly lower (P = 0.001) after depletion (73.9 +/- 4.7 nmol/d) than at baseline (115 +/- 12.7 nmol/d). This rate of decline (approximately 0.7% per day) is consistent with the kinetically measured rate of turnover of total body folate at moderate folate intakes. The average percentage increase in total pABG in response to folate repletion with 400 microg/d (75%) was significant (P = 0.02). Folate catabolite excretion was significantly (P = 0.0001) associated with serum and red blood cell folate, plasma homocysteine, and DNA hypomethylation after depletion and with serum folate (P = 0.001) and plasma homocysteine (P = 0.0002) after repletion with 400 microg folate/d.. Total urinary pABG excretion reflects total body folate pool size and is a long-term indicator that parallels functional measures of folate status.

Topics: 4-Aminobenzoic Acid; Aged; Aged, 80 and over; Aging; Diet; DNA Methylation; Erythrocytes; Female; Folic Acid; Glutamates; Homocysteine; Humans; Kinetics; Middle Aged; Nutritional Status; para-Aminobenzoates

To investigate the effects of pregnancy on folate metabolism, we conducted an 84-d study in second-trimester (gestational wk 14-25) pregnant women (n = 6) and nonpregnant controls (n = 6) with stable-isotopic tracer methods. All subjects were fed a diet containing approximately 272 nmol/d (120 microg/d) folate from food, along with supplemental folic acid that contained 15% [3',5'-(2)H(2)] folic acid ([(2)H(2)]folic acid) during d 1--41 and that was unlabeled during d 42--84 to yield a constant total folate intake of 1.02 or 1.93 micromol/d (450 or 850 microg/d). Isotopic enrichment of plasma folate, urinary folate and the urinary folate catabolites para-aminobenzoylglutamate (pABG) and para-acetamidobenzoylglutamate (ApABG) was determined at intervals throughout the study. The labeling of pABG and ApABG reflected that of tissue folate pools from which the catabolites originate. After the intake of labeled folic acid was terminated on d 41, labeling of urinary folate exhibited a biphasic exponential decline with distinct fast and slow components. In contrast, during d 42--84, the enrichment of urinary pABG and ApABG exhibited primarily monophasic exponential decline, and plasma folate underwent little decline of labeling during this period. Pregnant women and controls did not differ in estimates of body folate pool size and most aspects of the excretion of labeled urinary folate and catabolites, rates of decline of excretion, and areas under the curves for folate and catabolite excretion. Pregnant women, however, tended to have a slower rate of decline of pABG than ApABG and higher enrichment at d 42 of ApABG and pABG. These data support and extend our previous findings indicating that pregnancy (gestational wk 14--26) causes subtle changes in folate metabolism but does not elicit substantial increases in the rate or extent of folate turnover at these moderately high folate intakes.

Topics: 4-Aminobenzoic Acid; Adolescent; Adult; Case-Control Studies; Diet; Female; Folic Acid; Gas Chromatography-Mass Spectrometry; Glutamates; Humans; Isotope Labeling; Kinetics; Metabolic Clearance Rate; Nutritional Status; para-Aminobenzoates; Pregnancy; Pregnancy Trimester, Second; Tissue Distribution

Dual-label stable isotope dilution assays for the simultaneous quantification of isotopologic folates in clinical samples offer the perspective for differentiating between unlabeled folates from endogenous body pools and administered [13C5]-labeled folates from a test dose when performing bioavailability trials. In contrast to intact folates, this methodology could hitherto not be applied to the quantification of the folate catabolites, p-aminobenzoyl glutamate and p-acetamidobenzoyl glutamate. In this study, [2H4]-p-aminobenzoyl glutamate, [2H4]-p-acetamidobenzoyl glutamate, and unlabeled p-acetamidobenzoyl glutamate were synthesized. The synthesis of the [2H4]-labeled compounds started at unlabeled p-aminobenzoic acid. For the formation of p-acetamidobenzoyl glutamate, p-aminobenzoyl glutamate was acetylated. The new substances were applied successfully in stable isotope dilution assays for the simultaneous quantification of the [13C5]-labeled and unlabeled folate catabolites, p-aminobenzoyl glutamate and p-acetamidobenzoyl glutamate, along with the predominant folate vitamers in urine. The assays were based on clean-up by strong anion exchange followed by liquid chromatography-tandem mass spectrometry detection. Assay sensitivity was sufficient to detect the folate catabolites in physiologic concentrations. The limit of detection was below 0.4 and 0.3 nmol/100 g for p-aminobenzoyl glutamate isotopologues and p-acetamidobenzoyl glutamate isotopologues in urine, respectively. The successful synthesis of [2H4]-p-aminobenzoyl glutamate, [2H4]-p-acetamidobenzoyl glutamate, and unlabeled p-acetamidobenzoyl glutamate and the implementation of these substances in stable isotope dilution assays allows dual-label designs that provide a more detailed insight into human folate metabolism.

Topics: Carbon Isotopes; Deuterium; Folic Acid; Glutamates; Humans; Isotope Labeling; Magnetic Resonance Spectroscopy; Mass Spectrometry; para-Aminobenzoates

To estimate the rate of folate catabolism in pregnant and nonpregnant women and to derive the recommended dietary allowance for folate.. Prospective, observational study.. Rotunda Hospital, Dublin. WOMEN: Twenty-four healthy gravid women were studied once during each trimester and postpartum. Twenty-five nonpregnant controls were assessed before and after folic acid supplementation.. Women provided 24-hour urine collections while adhering to a strict dietary regimen containing no exogenous folate catabolites.. Urinary levels of p-acetamidobenzoylglutamate and p-aminobenzoylglutamate were measured by high pressure liquid chromatography.. The 24-hour excretion of folate catabolites, expressed as mean [95% CI] folate equivalents in microg) progressively increased during pregnancy. A peak was reached in the third trimester (349.1 microg [308.1 to 390.1]) where the rate was more than twice the rate in the nonpregnant control group (136.4 microg [112.4 to 160.4]) (P < 0.001). Based on our results the recommended dietary allowance for folate in nonpregnant women should be 250 microg and this should rise during pregnancy to 430 microg in the second trimester and 540 microg in the third trimester.. The rate of folate catabolism progressively increases during pregnancy reaching a peak in the third trimester at the time of maximal fetal growth. The increased demand for folate during pregnancy appears to be due to the accelerated breakdown of the vitamin because of its participation in cellular biosynthesis. These results provide a quantitative basis for the current debate on the appropriate recommended dietary allowance for folate in both pregnant and nonpregnant women.

Topics: 4-Aminobenzoic Acid; Adolescent; Dietary Supplements; Female; Folic Acid; Glutamates; Hemoglobins; Humans; para-Aminobenzoates; Pilot Projects; Pregnancy; Prospective Studies

Topics: 4-Aminobenzoic Acid; Chromatography, High Pressure Liquid; Chromatography, Ion Exchange; Folic Acid; Glutamates; Humans; para-Aminobenzoates

During pregnancy there is an increased requirement for folate. We studied pregnant women to determine whether the increased requirement might be due to enhanced catabolism of the vitamin. Six normal pregnant women provided 24 h urine samples during each trimester and postpartum while taking a defined diet. The urines were assayed for the folate breakdown products p-amino-benzoylglutamate (pABGlu) and its acetylated derivative p-acetamidobenzoylglutamate (apBGlu) by high-pressure liquid chromatography. Mean concentration of excreted apABGlu rose significantly in the second trimester but returned to baseline postpartum. This increased rate of folate catabolism produces an extra demand for dietary folate of about 200-300 micrograms per day in pregnant women, a considerably greater value than recent recommendations.

Topics: 4-Aminobenzoic Acid; Female; Folic Acid; Glutamates; Humans; para-Aminobenzoates; Pregnancy

We describe a reversed-phase high-performance liquid chromatographic procedure for the analysis of rat urine for p-aminobenzoylglutamate (pABGlu) and its acetamido derivative (p-acetamidobenzoylglutamate, apABGlu). These two catabolites arise following the in vivo cleavage of the folate molecule at the C-9-N-10 bond. Known quantities of high-specific-activity tritiated forms of the catabolites are added as internal standards to aliquots of rat urine. Following preliminary sample clean-up on C18 Sep-Pak cartridges, including derivatisation in the case of pABGlu, the urinary extracts are quantitated by HPLC. The present assay makes possible for the first time the determination of endogenous folate breakdown in the rat.

Topics: 4-Aminobenzoic Acid; Animals; Chromatography, High Pressure Liquid; Folic Acid; Glutamates; Male; para-Aminobenzoates; Rats; Rats, Wistar; Spectrophotometry, Ultraviolet

1. Folate deficiency is commonly found in alcoholic subjects although the causative mechanism is uncertain. It has been suggested that microsomal enzyme induction resulting from chronic alcohol ingestion might accelerate the rate of folate catabolism thus causing deficiency. 2. By using an experimental animal model to determine the rate of catabolism of [3H]pteroylglutamate (folic acid) by the quantitative estimation of the two urinary catabolites p-[3H]aminobenzoylglutamate and [3H]acetamidobenzoylglumate, we have measured both the rate of folate catabolism and the extent of microsomal-enzyme induction in mice after acute and chronic alcohol ingestion. 3. Despite significant evidence of enzyme induction in the chronic alcohol group, there was no difference in the rate of folate catabolism after acute or chronic alcohol ingestion when compared with that of the controls.

Topics: 4-Aminobenzoic Acid; Alcoholic Intoxication; Alcoholism; Animals; Edetic Acid; Enzyme Induction; Female; Folic Acid; Folic Acid Deficiency; Glutamates; Humans; Liver; Male; Mice; Microsomes, Liver; para-Aminobenzoates