The pathogenesis of folic acid deficiency in man

Folic acid and autism: updated evidences

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition that impairs communication, socialization, and behavior. The association of ASD with folic acid has been investigated due to the importance of this vitamin for neurological health. This study is an update of the publication 'Folic acid and autism: What do we know?' and aims to systematically review studies examining the relationship between folic acid and ASD. The search resulted in 2,389 studies on folic acid and ASD, which were selected by two reviewers based on their titles and abstracts. Studies meeting the inclusion criteria were fully read. The 52 included studies involved 10,429 individuals diagnosed with ASD and assessed the intake of vitamin B6, folic acid, and vitamin B12; serum levels of these vitamins, homocysteine, and methionine; therapeutic interventions using folic acid; and the association between maternal exposure to this vitamin and the risk of ASD. The evidence of insufficient folic acid intake in most individuals with ASD remains consistent in this update. No association was found between maternal exposure to folic acid and the risk of ASD in their children. Despite observed improvements in communication, socialization, and behavior in individuals with ASD following folic acid interventions, it is crucial to consider the individuality and complexity of ASD. Given the relevance of the topic, there remains a need for more high-quality research and clinical trials characterized by rigorous methodological designs.

Availability of monoglutamyl and polyglutamyl folates in normal subjects and in patients with coeliac sprue

Intestinal folate absorption was assessed in six normal subjects and in four patients with coeliac sprue who were studied before and after treatment by dietary gluten exclusion. Comparisons were made of the luminal disappearance from the perfused jejunum of 3H-pteroylmonoglutamate and pteroyl 14C-glutamylhexaglutamate, and of the 48-hour urinary recovery of each isotope after perfusion and a tissue saturating dose of folic acid. The labelled urinary folates consisted of folic acid, 10-formyltetrahydrofolate, and 5-methyltetrahydrofolate. In each group urinary recovery of 3H was significantly greater than that of 14C, confirming the evidence from jejunal perfusion that the availability of monoglutamyl folate is greater than that of polyglutamyl folate. According to the urinary recovery data, both folates were poorly absorbed in untreated coeliac sprue, but were normally absorbed after treatment. Assuming uniform displacement of the absorbed labelled folates by the parenteral flushing dose, the finding of greater urinary isotope recovery than of luminal folate disappearance from the perfused proximal jejunal segment suggests an adaptation of the distal small bowel for folate absorption in coeliac sprue.

Jejunal perfusion of simple and conjugated folates in celiac sprue

The intestinal absorption of [3H]-pteroylmonoglutamate (simple folic acid) and pteroyl-micron[14C]glutamyl-gamma-hexaglutamate ([14C]PG-7, conjugated folic acid) was assessed by the method of jejunal perfusion in five patients with proven celiac sprue who were studied after a gluten-containing or a gluten-free diet, and in nine normal subjects. The luminal disappearance of each folate was markedly impaired after exposure of the patients to dietary gluten and improved by gluten restriction, but not to within the range found in the normal subjects. The luminal disappearance of each folate was markedly impaired after exposure of the patients to dietary gluten and improved by gluten restriction, but not to within the range found in the normal subjects. In each experiment, column chromatography of the luminal aspirates revealed similar spectra of hydrolytic products of [14C]PG-7, whereas the fraction of the distal aspirate chromatogram appearing as pteroyl-micron[14C]glutamyl-gamma-monoglutamate ([14C]-PG-1) was similar in all three groups. By accounting for the variable effects of absorption on the luminal appearance of [14C]PG-1 and by correcting for mucosal hydrolysis which was not followed by release of [14C]PG-1 to the luminal contents, the calculated rate of in vivo hydrolysis of [14C]PG-7 to [14C]PG-1 was found impaired in both celiac sprue groups, with significant improvement on treatment. In mucosal biopsies from the sprue patients, the in vitro activity of folate conjugase in whole homogenates was higher and the activity of disaccharidase lower than in a group of 12 normal mucosal biopsies. These in vitro data suggest that the predominant cellular location of mucosal folate conjugase is different from that of disaccharidase, whereas comparison with the results of in vivo hydrolysis suggests that measurement of the enzyme in whole mucosal homogenates overestimates its significant digestive activity. The present studies indicate that (a) the mucosal lesion of celiac sprue significantly limits the intestinal absorption of both simple and conjugated folate, and (b) malabsorption of conjugated folate results from a combination of impaired hydrolysis and decreased mucosal uptake of hydrolytic product.

Coeliac disease during the teenage period: the value of serial serum folate estimations

A group of teenage coeliac patients has been followed at three monthly intervals in the Outpatient Department to assess their progress and also to monitor their ability to maintain a gluten-free diet. After a follow-up period of four to six years a detailed reassessment was carried out in hospital on 10 patients, only five of whom had persevered with a gluten-free diet. The jejunal mucosal histology of those patients who did not persist with a gluten-free diet remained ;flat' although these patients appeared to have remitted clinically. Those subjects who did persist with a gluten-free regime had a normal or near normal mucosal histology. It was difficult on the basis of clinical, haematological, or biochemical criteria to separate the two groups. The best single assessment of whether these patients were maintaining a gluten-free diet was serial serum folate estimations. It is often extremely difficult to say whether teenage coeliac patients are keeping to their diet unless repeated jejunal biopsies are obtained, and this study suggests that serial serum folate estimations can act as a reasonable criterion of whether subjects are maintaining a gluten-free regime.