The intestinal absorption of folates

Mode of action Criteria for selection of the critical effect and safe dose range for PFOA by the Alliance for risk assessment

In response to the current disparity in risk assessment values for PFOA from different agencies and countries, an international effort facilitated by the Alliance for Risk Assessment (ARA) was recently undertaken to characterize the range of scientifically supportable safe dose estimates. In this assessment (Burgoon et al., 2023), an evaluation of the evidence regarding the potential modes of action (MOA) for PFOA toxicity was performed first, so that it could be used to inform subsequent decisions regarding potential critical effects and studies. This review describes the evidence considered in the MOA evaluations that were performed as part of the ARA effort. The overall conclusions of this evaluation are that the available mechanistic data do not support any conclusion that reported epidemiological associations of blood concentrations of PFOA as low as 10 ng/mL with various health effects should be considered causal. It is more likely that the reported associations may instead reflect reverse causality/pharmacokinetic confounding. These conclusions are consistent with the opinions of the World Health Organization (WHO, 2022).

Late-life dietary folate restriction reduces biosynthesis without compromising healthspan in mice

Folate is a vitamin required for cell growth and is present in fortified foods in the form of folic acid to prevent congenital abnormalities. The impact of low-folate status on life-long health is poorly understood. We found that limiting folate levels with the folate antagonist methotrexate increased the lifespan of yeast and worms. We then restricted folate intake in aged mice and measured various health metrics, metabolites, and gene expression signatures. Limiting folate intake decreased anabolic biosynthetic processes in mice and enhanced metabolic plasticity. Despite reduced serum folate levels in mice with limited folic acid intake, these animals maintained their weight and adiposity late in life, and we did not observe adverse health outcomes. These results argue that the effectiveness of folate dietary interventions may vary depending on an individual's age and sex. A higher folate intake is advantageous during the early stages of life to support cell divisions needed for proper development. However, a lower folate intake later in life may result in healthier aging.

Relationship of dietary natural folate and synthetic folic acid co-exposure patterns with biological aging: findings from NHANES 2003-2018

Background: The mandatory folic acid fortification program in the United States has inevitably exposed most Americans to both natural folate and synthetic folic acid. We aim to examine the association of dietary folate co-exposure patterns with biological aging indicators. Methods: A total of 18 889 participants were enrolled from 2003 to 2018. Dietary intake of folate from diverse sources was evaluated by 24-hour dietary recall. Biological aging indicators were developed based on age-related clinical indicators, including the phenotypic age (PA), Klemera-Doubal method (KDM), homeostatic dysregulation (HD), and allostatic load (AL). The unsupervised K-means clustering method, logistic regression model, and restricted cubic spline (RCS) regression model were used to explore the relationship of natural folate and synthetic folic acid co-exposure with biological aging indicators. Results: The results indicated that higher intake of total folate, dietary folate, and food natural folate was associated with lower PA [OR = 0.75 (0.64, 0.88); OR = 0.79 (0.70, 0.90); OR = 0.65 (0.57, 0.75)], KDM [OR = 0.63 (0.53, 0.75); OR = 0.80 (0.65, 0.98); OR = 0.62 (0.49, 0.77)], HD [OR = 0.69 (0.56, 0.84); OR = 0.78 (0.67, 0.92); OR = 0.78 (0.68, 0.90)], and AL [OR = 0.69 (0.58, 0.82); OR = 0.73 (0.63, 0.85); OR = 0.74 (0.62, 0.90)], consistently. Four co-exposure patterns were generated based on the intake of folate from diverse sources, as follows: "low folate exposure group" to cluster 1, "dietary folate exposure group" to cluster 2, "mixed source high folate exposure group" to cluster 3, and "mixed source excessive folate exposure group" to cluster 4. Compared with cluster 1, participants in cluster 2 are associated with lower biological age indicators (ORPA = 0.82 [0.72, 0.93]; ORKDM = 0.58 [0.47, 0.70]; ORHD = 0.85 [0.75, 0.97]; ORAL = 0.87 [0.77, 0.98]), while participants in cluster 3 and cluster 4 are not. Conclusion: For individuals subjected to folic acid fortification programs, a higher intake of dietary folate, especially natural folate, coupled with a lower consumption of folic acid supplements, was found to be associated with lower biological age indicators.

Vitamin C-Dependent Uptake of Non-Heme Iron by Enterocytes, Its Impact on Erythropoiesis and Redox Capacity of Human Erythrocytes

In the small intestine, nutrients from ingested food are absorbed and broken down by enterocytes, which constitute over 95% of the intestinal epithelium. Enterocytes demonstrate diet- and segment-dependent metabolic flexibility, enabling them to take up large amounts of glutamine and glucose to meet their energy needs and transfer these nutrients into the bloodstream. During glycolysis, ATP, lactate, and H+ ions are produced within the enterocytes. Based on extensive but incomplete glutamine oxidation large amounts of alanine or lactate are produced. Lactate, in turn, promotes hypoxia-inducible factor-1α (Hif-1α) activation and Hif-1α-dependent transcription of various proton channels and exchangers, which extrude cytoplasmic H+-ions into the intestinal lumen. In parallel, the vitamin C-dependent and duodenal cytochrome b-mediated conversion of ferric iron into ferrous iron progresses. Finally, the generated electrochemical gradient is utilized by the divalent metal transporter 1 for H+-coupled uptake of non-heme Fe2+-ions. Iron efflux from enterocytes, subsequent binding to the plasma protein transferrin, and systemic distribution supply a wide range of cells with iron, including erythroid precursors essential for erythropoiesis. In this review, we discuss the impact of vitamin C on the redox capacity of human erythrocytes and connect enterocyte function with iron metabolism, highlighting its effects on erythropoiesis.

The functional roles of S-adenosyl-methionine and S-adenosyl-homocysteine and their involvement in trisomy 21

The one-carbon metabolism pathway is involved in critical human cellular functions such as cell proliferation, mitochondrial respiration, and epigenetic regulation. In the homocysteine-methionine cycle S-adenosyl-methionine (SAM) and S-adenosyl-homocysteine (SAH) are synthetized, and their levels are finely regulated to ensure proper functioning of key enzymes which control cellular growth and differentiation. Here we review the main biological mechanisms involving SAM and SAH and the known related human diseases. It was recently demonstrated that SAM and SAH levels are altered in plasma of subjects with trisomy 21 (T21) but how this metabolic dysregulation influences the clinical manifestation of T21 phenotype has not been previously described. This review aims at providing an overview of the biological mechanisms which are altered in response to changes in the levels of SAM and SAH observed in DS.

The Function of Probiotics and Prebiotics on Canine Intestinal Health and Their Evaluation Criteria

Maintaining homeostasis within the intestinal microbiota is imperative for assessing the health status of hosts, and dysbiosis within the intestinal microbiota is closely associated with canine intestinal diseases. In recent decades, the modulation of canine intestinal health through probiotics and prebiotics has emerged as a prominent area of investigation. Evidence indicates that probiotics and prebiotics play pivotal roles in regulating intestinal health by modulating the intestinal microbiota, fortifying the epithelial barrier, and enhancing intestinal immunity. This review consolidates literature on using probiotics and prebiotics for regulating microbiota homeostasis in canines, thereby furnishing references for prospective studies and formulating evaluation criteria.

Two maize homologs of mammalian proton-coupled folate transporter, ZmMFS_1-62 and ZmMFS_1-73, are essential to salt and drought tolerance

Folates are essential to the maintenance of normal life activities in almost all organisms. Proton-coupled folate transporter (PCFT), belonging to the major facilitator superfamily, is one of the three major folate transporter types widely studied in mammals. However, information about plant PCFTs is limited. Here, a genome-wide identification of maize PCFTs was performed, and two PCFTs, ZmMFS_1-62 and ZmMFS_1-73, were functionally investigated. Both proteins contained the typical 12 transmembrane helixes with N- and C-termini located in the cytoplasm, and were localized in the plasma membrane. Molecular docking analysis indicated their binding activity with folates via hydrogen bonding. Interference with ZmMFS_1-62 and ZmMFS_1-73 in maize seedlings through virus-induced gene silencing disrupted folate homeostasis, mainly in the roots, and reduced tolerance to drought and salt stresses. Moreover, a molecular chaperone protein, ZmHSP20, was found to interact with ZmMFS_1-62 and ZmMFS_1-73, and interference with ZmHSP20 in maize seedlings also led to folate disruption and increased sensitivity to drought and salt stresses. Overall, this is the first report of functional identification of maize PCFTs, which play essential roles in salt and drought stress tolerance, thereby linking folate metabolism with abiotic stress responses in maize.

Vitamin D promotes the folate transport and metabolism in zebrafish (Danio rerio)

Vitamin D (VD) is a fat-soluble sterol that possesses a wide range of physiological functions. The present study aimed to evaluate the effects of VD on folate metabolism in zebrafish and further investigated the underlying mechanism. Wild-type (WT) zebrafish were fed with a diet containing 0 IU/kg VD3 or 800 IU/kg VD3 for 3 wk. Meanwhile, cyp2r1 mutant zebrafish with impaired VD metabolism was used as another model of VD deficiency. Our results showed that VD deficiency in zebrafish suppressed the gene expression of folate transporters, including reduced folate carrier (RFC) and proton-coupled folate transporter (PCFT) in the intestine. Moreover, VD influenced the gene expression of several enzymes related to cellular folate metabolism in the intestine and liver of zebrafish. Importantly, VD-deficient zebrafish contained a remarkably lower level of folate content in the liver. Notably, VD was incapable of altering folate metabolism in zebrafish when gut microbiota was depleted by antibiotic treatment. Further studies proved that gut commensals from VD-deficient fish displayed a lower capacity to produce folate than those from WT fish. Our study revealed the potential correlation between VD and folate metabolism in zebrafish, and gut microbiota played a key role in VD-regulated folate metabolism in zebrafish.NEW & NOTEWORTHY Our study has identified that VD influences intestinal uptake and transport of folate in zebrafish while also altering hepatic folate metabolism and storage. Interestingly, the regulatory effects of VD on folate transport and metabolism diminished after the gut flora was interrupted by antibiotic treatment, suggesting that the regulatory effects of VD on folate metabolism in zebrafish are most likely dependent on the intestinal flora.

Folate receptor α deficiency - Myelin-sensitive MRI as a reliable biomarker to monitor the efficacy and long-term outcome of a new therapeutic approach

Cerebral folate transport deficiency, caused by a genetic defect in folate receptor α, is a devastating neurometabolic disorder that, if untreated, leads to epileptic encephalopathy, psychomotor decline and hypomyelination. Currently, there are limited data on effective dosage and duration of treatment, though early diagnosis and therapy with folinic acid appears critical. The aim of this long-term study was to identify new therapeutic approaches and novel biomarkers for assessing efficacy, focusing on myelin-sensitive MRI. Clinical, biochemical, structural and quantitative MRI parameters of seven patients with genetically confirmed folate receptor α deficiency were acquired over 13 years. Multimodal MRI approaches comprised MR-spectroscopy (MRS), magnetization transfer (MTI) and diffusion tensor imaging (DTI) sequences. Patients started oral treatment immediately following diagnosis or in an interval of up to 2.5 years. Escalation to intravenous and intrathecal administration was performed in the absence of effects. Five patients improved, one with a presymptomatic start of therapy remained symptom-free, and one with inconsistent treatment deteriorated. While CSF 5-methyltetrahydrofolate and MRS parameters normalized immediately after therapy initiation, myelin-sensitive MTI and DTI measures correlated with gradual clinical improvement and ongoing myelination under therapy. Early initiation of treatment at sufficient doses, considering early intrathecal applications, is critical for favorable outcome. The majority of patients showed clinical improvements that correlated best with MTI parameters, allowing individualized monitoring of myelination recovery. Presymptomatic therapy seems to ensure normal development and warrants newborn screening. Furthermore, the quantitative parameters of myelin-sensitive MRI for therapy assessments can now be used for hypomyelination disorders in general.

Low-dose daily folic acid (400 μg) supplementation does not affect regulation of folate transporters found present throughout the terminal ileum and colon of humans: a randomized clinical trial

BACKGROUND

Folic acid supplementation during the periconceptional period reduces the risk of neural tube defects in infants, but concern over chronic folic acid exposure remains. An improved understanding of folate absorption may clarify potential risks. Folate transporters have been characterized in the small intestine, but less so in the colon of healthy, free-living humans. The impact of folic acid fortification or supplementation on regulation of these transporters along the intestinal tract is unknown.

OBJECTIVE

The objective was to characterize expression of folate transporters/receptor (FT/R) and folate hydrolase, glutamate carboxypeptidase II (GCPII), from the terminal ileum and throughout the colon of adults and assess the impact of supplemental folic acid.

METHODS

In this 16-wk open-labeled randomized clinical trial, adults consumed a low folic acid-containing diet, a folate-free multivitamin, and either a 400 μg folic acid supplement or no folic acid supplement. Dietary intakes and blood were assessed at baseline, 8 wk, and 16 wk (time of colonoscopy). Messenger RNA (mRNA) expression and protein expression of FT/R and GCPII were assessed in the terminal ileum, cecum, and ascending and descending colon.

RESULTS

Among 24 randomly assigned subjects, no differences in dietary folate intake or blood folate were observed at baseline. Mean ± SD red blood cell folate at 16 wk was 1765 ± 426 and 911 ± 242 nmol/L in the 400 and 0 μg folic acid group, respectively (P < 0.0001). Reduced folate carrier, proton-coupled folate transporter, and folate-receptor alpha expression were detected in the terminal ileum and colon, as were efflux transporters of breast cancer resistance protein and multidrug resistance protein-3. Other than a higher mRNA expression of FR-alpha and GCPII in the 400 μg supplement group in the ascending colon, no treatment differences were observed (P < 0.02).

CONCLUSIONS

Folate transporters are present throughout the terminal ileum and colon; there is little evidence that a low dose of folic acid supplementation affects colonic absorption. This trial was registered at clinicaltrials.gov as NCT03421483.

B-Group Vitamins as Potential Prebiotic Candidates: Their Effects on the Human Gut Microbiome

In recent years, thousands of studies have demonstrated the importance of the gut microbiome for human health and its relationship with certain diseases. The search for new gut microbiome modulators has thus become an objective to beneficially alter the gut microbiome composition and/or metabolic activity, which may modify intestinal physiology. Growing evidence has shown that B-group vitamins might be considered as potential candidates as gut microbiome modulators. However, the relationship between the B-group vitamins and the gut microbiome remains largely unexplored. Studies have suggested that non-absorbed B-group vitamins administered orally can reach the distal intestine or even the colon where these vitamins may have potential health benefits for the host. Clinical trials supporting this effect are still limited. In this review, we discuss evidence regarding the modulatory effects of B-group vitamins on the gut microbiome with a focus on their potential role as prebiotic candidates.

Metabolomic Effects of Folic Acid Supplementation in Adults: Evidence from the FACT Trial

BACKGROUND

Folic acid (FA) is the oxidized form of folate found in supplements and FA-fortified foods. Most FA is reduced by dihydrofolate reductase to 5-methyltetrahydrofolate (5mTHF); the latter is the form of folate naturally found in foods. Ingestion of FA increases the plasma levels of both 5mTHF and unmetabolized FA (UMFA). Limited information is available on the downstream metabolic effects of FA supplementation, including potential effects associated with UMFA.

OBJECTIVE

We aimed to assess the metabolic effects of FA-supplementation, and the associations of plasma 5mTHF and UMFA with the metabolome in FA-naïve Bangladeshi adults.

METHODS

Sixty participants were selected from the Folic Acid and Creatine Trial; half received 800 μg FA/day for 12 weeks and half placebo. Plasma metabolome profiles were measured by high-resolution mass spectrometry, including 170 identified metabolites and 26,541 metabolic features. Penalized regression methods were used to assess the associations of targeted metabolites with FA-supplementation, plasma 5mTHF, and plasma UMFA. Pathway analyses were conducted using Mummichog.

RESULTS

In penalized models of identified metabolites, FA-supplementation was associated with higher choline. Changes in 5mTHF concentrations were positively associated with metabolites involved in amino acid metabolism (5-hydroxyindoleacetic acid, acetylmethionine, creatinine, guanidinoacetate, hydroxyproline/n-acetylalanine) and 2 fatty acids (docosahexaenoic acid and linoleic acid). Changes in 5mTHF concentrations were negatively associated with acetylglutamate, acetyllysine, carnitine, propionyl carnitine, cinnamic acid, homogentisate, arachidonic acid, and nicotine. UMFA concentrations were associated with lower levels of arachidonic acid. Together, metabolites selected across all models were related to lipids, aromatic amino acid metabolism, and the urea cycle. Analyses of nontargeted metabolic features identified additional pathways associated with FA supplementation.

CONCLUSION

In addition to the recapitulation of several expected metabolic changes associated with 5mTHF, we observed additional metabolites/pathways associated with FA-supplementation and UMFA. Further studies are needed to confirm these associations and assess their potential implications for human health.

TRIAL REGISTRATION NUMBER

This trial was registered at https://clinicaltrials.gov as NCT01050556.

Uncovering the essential roles of glutamate carboxypeptidase 2 orthologs in Caenorhabditis elegans

Human glutamate carboxypeptidase 2 (GCP2) from the M28B metalloprotease group is an important target for therapy in neurological disorders and an established tumor marker. However, its physiological functions remain unclear. To better understand general roles, we used the model organism Caenorhabditis elegans to genetically manipulate its three existing orthologous genes and evaluate the impact on worm physiology. The results of gene knockout studies showed that C. elegans GCP2 orthologs affect the pharyngeal physiology, reproduction, and structural integrity of the organism. Promoter-driven GFP expression revealed distinct localization for each of the three gene paralogs, with gcp-2.1 being most abundant in muscles, intestine, and pharyngeal interneurons, gcp-2.2 restricted to the phasmid neurons, and gcp-2.3 located in the excretory cell. The present study provides new insight into the unique phenotypic effects of GCP2 gene knockouts in C. elegans, and the specific tissue localizations. We believe that elucidation of particular roles in a non-mammalian organism can help to explain important questions linked to physiology of this protease group and in extension to human GCP2 involvement in pathophysiological processes.

Late-life dietary folate restriction reduces biosynthetic processes without compromising healthspan in mice

Folate is a vitamin required for cell growth and is present in fortified foods in the form of folic acid to prevent congenital abnormalities. The impact of low folate status on life-long health is poorly understood. We found that limiting folate levels with the folate antagonist methotrexate increased the lifespan of yeast and worms. We then restricted folate intake in aged mice and measured various health metrics, metabolites, and gene expression signatures. Limiting folate intake decreased anabolic biosynthetic processes in mice and enhanced metabolic plasticity. Despite reduced serum folate levels in mice with limited folic acid intake, these animals maintained their weight and adiposity late in life, and we did not observe adverse health outcomes. These results argue that the effectiveness of folate dietary interventions may vary depending on an individual's age and sex. A higher folate intake is advantageous during the early stages of life to support cell divisions needed for proper development. However, a lower folate intake later in life may result in healthier aging.

Spina Bifida Prevention: A Narrative Review of Folic Acid Supplements for Childbearing Age Women

Neural tube defects (NTDs) are malformations that occur during embryonic development, and they account for most central nervous system birth anomalies. Genetic and environmental factors have been shown to play a role in the etiology of NTDs. The different types of NTDs are classified according to anatomic location and severity of the defect, with most of the neural axis anomalies occurring in the caudal spinal or cranial areas. Spina bifida is a type of NTD that is characterized by an opening in the vertebral arch, and the level of severity is determined by the extent to which the neural tissue protrudes through the opened arch(es). Prevention of NTDs by administration of folic acid has been studied and described in the literature, yet there are approximately 300,000 cases of NTDs that occur annually, with 88,000 deaths occurring per year worldwide. A daily intake of at least 400 μg of folic acid is recommended especially for women of childbearing age. To provide the benefits of folic acid, prenatal vitamins are recommended in pregnancy, and many countries have been fortifying foods such as cereal grain products with folic acid; however, not all countries have instituted folic acid fortification programs. The present investigation includes a description of the pharmacology of folic acid, neural tube formation, defects such as spina bifida, and the relevance of folic acid to developing spina bifida. Women's knowledge and awareness of folic acid regarding its importance in the prevention of spina bifida is a major factor in reducing incidence worldwide.

Effect of dolutegravir on folate, vitamin B12 and mean corpuscular volume levels among children and adolescents with HIV: a sub-study of the ODYSSEY randomized controlled trial

INTRODUCTION

Dolutegravir-based antiretroviral therapy (ART) is the preferred antiretroviral treatment for children and adolescents living with HIV. A large surveillance study in Botswana previously raised concerns about an association between pre-conception dolutegravir and neural tube defects. Before these concerns were subsequently resolved, we set up a sub-study to look at the effect of dolutegravir on levels of folate and vitamin B12 in children and adolescents within the randomized ODYSSEY trial, as folate and vitamin B12 are known to play a crucial role in neural tube development.

METHODS

We conducted the sub-study among Ugandan ODYSSEY participants and compared folate and vitamin B12 between children randomized to dolutegravir-based ART (DTG) and non-dolutegravir-based standard-of-care treatment (SOC). Plasma folate was measured at enrolment and week 4 on stored samples; in addition, plasma and red blood cell (RBC) folate and vitamin B12 were assayed at week ≥96 in prospectively collected samples. RBC mean corpuscular volume (MCV) was measured 24-weekly in all ODYSSEY participants. Samples analysed in the sub-study were collected between September 2016 and October 2020.

RESULTS

A total of 229 children aged ≥6 years were included in the sub-study with median age at trial enrolment of 12.3 (interquartile range [IQR] 9.0, 14.7) years, and CD4 count of 501 (IQR 228, 695); 112 (49%) children were male. Most participants (225/229, 98%) had plasma folate results at enrolment and 214 (93%) children had results available for RBC folate, vitamin B12 and plasma folate at week ≥96. MCV results were analysed on 679 children aged ≥6 years enrolled in ODYSSEY. At week 4, mean plasma folate was significantly higher in the dolutegravir arm than in SOC (difference [DTG-SOC] 1.6 ng/ml, 95% CI 0.8, 2.3; p<0.001), and this difference persisted to week ≥96 (2.7 ng/ml, 95% CI 1.7, 3.7; p<0.001). Mean RBC folate at ≥96 weeks was also higher in the DTG arm (difference 73 ng/ml, 95% CI 3, 143; p = 0.041). There was no difference in the treatment arms for vitamin B12 levels at ≥96 weeks or change in MCV through trial follow-up.

CONCLUSIONS

Plasma and RBC folate levels were higher in children and adolescents receiving dolutegravir-based ART than on other ART regimens. Further studies are needed to clarify the mechanisms of these interactions and the clinical implications of increased blood folate levels.

Therapeutic strategies targeting folate receptor α for ovarian cancer

Epithelial ovarian cancer (EOC) is the deadliest gynecological cancer, and presents a major clinical challenge due to limited treatment options. Folate receptor alpha (FRα), encoded by the FOLR1 gene, is an attractive therapeutically target due to its prevalent and high expression in EOC cells. Recent basic and translational studies have explored several modalities, such as antibody-drug conjugate (ADC), monoclonal antibodies, small molecules, and folate-drug conjugate, to exploit FRα for EOC treatment. In this review, we summarize the function of FRα, and clinical efficacies of various FRα-based therapeutics. We highlight mirvetuximab soravtansine (MIRV), or Elahere (ImmunoGen), the first FRα-targeting ADC approved by the FDA to treat platinum-resistant ovarian cancer. We discuss potential mechanisms and management of ocular adverse events associated with MIRV administration.

Factors for the development of anemia in patients with newly introduced olaparib: A retrospective case-control study

Anemia is the most common dose-limiting toxicity of olaparib. However, few studies have analyzed the clinical features of olaparib-induced anemia. This study investigated the clinical features of olaparib-induced anemia. Additionally, the role of folate or vitamin B12 in olaparib-induced anemia was examined. This retrospective case-control study included patients who received olaparib at Mie University Hospital between January 2018 and December 2020. Data were collected between initiation of olaparib and discontinuation of olaparib or till December 2021. We investigated the development of grade ≥ 3 anemia during olaparib administration for at least 1 year. We examined patients with grade ≥ 3 anemia considering the mean corpuscular volume (MCV), its association with gastrointestinal events and cumulative dose of carboplatin. For the sub-study analysis, data on patients treated with olaparib for ovarian or endometrial cancer were collected to evaluate the Common Terminology Criteria for Adverse Events (CTCAE) or monthly changes in folate or vitamin B12 levels from baseline to 3 months after olaparib initiation. These data were collected between initiation of olaparib and discontinuation of olaparib or till November 2022. Patients with no data on folic acid or vitamin B12 levels were excluded from the sub-study. In the main study, 40 patients were included. Eighteen patients (45%) developed grade ≥ 3 anemia, and all patients discontinued treatment (94%) or reduced olaparib dose (67%) after developing anemia. Among the patients with grade ≥ 3 anemia, 9 (50%) exhibited macrocytic anemia and 15 (83%) had previously received carboplatin. The incidence of grade ≥ 2 dysgeusia was significantly higher in patients with grade ≥ 3 anemia (P = .034). Moreover, the cumulative dose of previously administered carboplatin was higher in patients who had 3 episodes of anemia (P = .102). In sub-study, 12 had data on folic acid and vitamin B12 levels. Sub-study analysis showed that none fulfilled the criteria for deficiency of folate or vitamin B12, while 3 developed grade 3 anemia. This study revealed that olaparib-induced anemia frequently occurs as macrocytic and normocytic erythroblastic anemia without folate or vitamin B12 deficiencies. A high cumulative dose of previously administered carboplatin and dysgeusia may be associated with olaparib-induced anemia.

Bacteria from the gut influence the host micronutrient status

Micronutrient deficiencies or "hidden hunger" remains a serious public health problem in most low- and middle-income countries, with severe consequences for child development. Traditional methods of treatment and prevention, such as supplementation and fortification, have not always proven to be effective and may have undesirable side-effects (i.e., digestive troubles with iron supplementation). Commensal bacteria in the gut may increase bioavailability of specific micronutrients (i.e., minerals), notably by removing anti-nutritional compounds, such as phytates and polyphenols, or by the synthesis of vitamins. Together with the gastrointestinal mucosa, gut microbiota is also the first line of protection against pathogens. It contributes to the reinforcement of the integrity of the intestinal epithelium and to a better absorption of micronutrients. However, its role in micronutrient malnutrition is still poorly understood. Moreover, the bacterial metabolism is also dependent of micronutrients acquired from the gut environment and resident bacteria may compete or collaborate to maintain micronutrient homeostasis. Gut microbiota composition can therefore be modulated by micronutrient availability. This review brings together current knowledge on this two-way relationship between micronutrients and gut microbiota bacteria, with a focus on iron, zinc, vitamin A and folate (vitamin B9), as these deficiencies are public health concerns in a global context.

Hyperhomocysteinemia in Cardiovascular Diseases: Revisiting Observational Studies and Clinical Trials

Thromboembolic manifestations are relatively frequent in patients with intermediate/severe hyperhomocysteinemia (>30 µmol/L) related to inherited disorders and deficiencies in vitamin B12 and folate. In contrast, moderate hyperhomocysteinemia (15-30 µmol/L) is a modest predictor of cardiovascular risk. The recognition of homocysteine as a cardiovascular risk factor has been challenged by some but not all randomized clinical trials. We reviewed the main data of this controversy and formulated conclusions to be translated in clinical practice.Homocysteine-lowering trials have been performed in cardiovascular subjects with moderate but not intermediate/severe hyperhomocysteinemia despite the dose-effect risk association. The first meta-analyses found no benefit and led cardiology societies not recommending homocysteine in the assessment of cardiovascular risk. This guideline challenged the need to diagnose and treat the nutritional and genetic causes of intermediate/major hyperhomocysteinemia and was not revised when larger meta-analyses concluded to a reduced risk of stroke. In a recent observational study, 84% of consecutive cardiovascular patients assessed for homocysteine had intermediate or major hyperhomocysteinemia, which was properly assessed in only half of the cases and related to B12 and/or folate deficiency and Addison/Biermer disease in 55% of these cases.In conclusion, revisiting observational studies and clinical trials suggests that cardiovascular patients should be screened for hyperhomocysteinemia, when no other risk factor is found. Patients with intermediate/major hyperhomocysteinemia should be properly assessed and treated for B vitamin deficiencies and inherited disorders according to current guidelines. Further trials are needed to assess the effect of lowering homocysteine according to hyperhomocysteinemia categories at baseline.

Brain Uptake of Folate Forms in the Presence of Folate Receptor Alpha Antibodies in Young Rats: Folate and Antibody Distribution

In a rat model, following exposure to rat folate receptor alpha antibodies (FRαAb) during gestation, FRαAb accumulates in the placenta and the fetus and blocks folate transport to the fetal brain and produces behavioral deficits in the offspring. These deficits could be prevented with folinic acid. Therefore, we sought to evaluate folate transport to the brain in young rat pups and determine what effect FRαAb has on this process, to better understand the folate receptor autoimmune disorder associated with cerebral folate deficiency (CFD) in autism spectrum disorders (ASD). When injected intraperitoneally (IP), FRαAb localizes to the choroid plexus and blood vessels including the capillaries throughout the brain parenchyma. Biotin-tagged folic acid shows distribution in the white matter tracts in the cerebrum and cerebellum. Since these antibodies can block folate transport to the brain, we orally administered various folate forms to identify the form that is better-absorbed and transported to the brain and is most effective in restoring cerebral folate status in the presence of FRαAb. The three forms of folate, namely folic acid, D,L-folinic acid and levofolinate, are converted to methylfolate while L-methylfolate is absorbed as such and all are efficiently distributed to the brain. However, significantly higher folate concentration is seen in the cerebrum and cerebellum with levofolinate in the presence or absence of FRαAb. Our results in the rat model support testing levofolinate to treat CFD in children with ASD.

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

E, K, B5, B6, and B9 vitamins and their specific immunological effects evaluated by flow cytometry

It has been proven that vitamins play an essential role in preventing certain diseases since ancient times. It is thus fruitless to approach the roles of vitamins without making reference to the techniques used in evaluating the effects of these micronutrients. Therefore, the aim of this paper was to summarize the immunological effects of E, K, B5, B6, and B9 vitamins evaluated by flow cytometry. Some of these significant effects were presented and discussed: (a) The role of vitamins E in the prevention and treatment of different types of cancer. (b) The properties of K vitamins in the development and maintenance of pheochromocytoma Cell Line 12 (PC12) cells in Parkinson's disease; (c) The improvement effect of vitamin B5 on the loss of bone mass in low estrogen conditions; (d) The anticancer role of vitamins B6. (e) The role of Vitamin B9 in the regulation of Treg cells. As such, the flow cytometry technique used to assess these properties is essential to evaluate the immunomodulatory effects of certain vitamins. The technique undergoes constant improvement which makes it possible to determine several parameters with a role in the modulation of the immune function and at the same time increase the accuracy of the methods that highlight them.

Folate in maternal rheumatoid arthritis-filial autism spectrum disorder continuum

Rheumatoid Arthritis (RA) is an inflammatory autoimmune disease that affects women three times more than men. Epidemiological studies found that the incidence of Autism Spectrum Disorder (ASD), a neurological and developmental disorder, in children born to mothers suffering from RA is higher compared with the control population. Considering that the pathogenesis of ASD could be traced back to pregnancy and in uterine conditions, and the evidence of reduced folate levels in the brain of ASD-affected children, we aimed to study the role of folate, as an important nutritional factor during pregnancy, in associating maternal RA to ASD development in the offspring. Folate balance during RA could be influenced twice, initially during the immune activation associated with disease onset, and later during the treatment with anti-folate drugs, with a potential consequence of folate deficiency. Maternal folate deficiency during pregnancy could increase homocysteine levels, oxidative stress, and global DNA hypomethylation, all known risk factors in ASD pathogenesis. These effects could be intensified by genetic polymorphisms in the folate system, which were also found as genetic risk factors for both RA and ASD. The available evidence suggests that folate level as an important factor during RA, pregnancy and ASD could have pathological and therapeutical significance and should be carefully monitored and investigated in the RA-pregnancy-ASD axis.

Intermediate role of gut microbiota in vitamin B nutrition and its influences on human health

Vitamin B consists of a group of water-soluble micronutrients that are mainly derived from the daily diet. They serve as cofactors, mediating multiple metabolic pathways in humans. As an integrated part of human health, gut microbiota could produce, consume, and even compete for vitamin B with the host. The interplay between gut microbiota and the host might be a crucial factor affecting the absorbing processes of vitamin B. On the other hand, vitamin B supplementation or deficiency might impact the growth of specific bacteria, resulting in changes in the composition and function of gut microbiota. Together, the interplay between vitamin B and gut microbiota might systemically contribute to human health. In this review, we summarized the interactions between vitamin B and gut microbiota and tried to reveal the underlying mechanism so that we can have a better understanding of its role in human health.

Novel localization of folate transport systems in the murine central nervous system

BACKGROUND

Folates are a family of B9 vitamins that serve as one-carbon donors critical to biosynthetic processes required for the development and function of the central nervous system (CNS) in mammals. Folate transport is mediated by three highly specific systems: (1) folate receptor alpha (FRα; FOLR1/Folr1), (2) the reduced folate-carrier (RFC; SLC19A1/Slc19a1) and (3) the proton-coupled folate transporter (PCFT; SLC46A1/Slc46a1). Folate transport into and out of the CNS occurs at the blood-cerebrospinal fluid barrier (BCSFB), mediated by FRα and PCFT. Impairment of folate transport at the BCSFB results in cerebral folate deficiency in infants characterized by severe neurological deficiencies and seizures. In contrast to the BCSFB, CNS folate transport at other brain barriers and brain parenchymal cells has not been extensively investigated. The aim of this study is to characterize folate transport systems in the murine CNS at several known barriers encompassing the BCSFB, arachnoid barrier (AB), blood-brain barrier (BBB) and parenchymal cells (astrocytes, microglia, neurons).

METHODS

Applying immunohistochemistry, localization of folate transport systems (RFC, PCFT, FRα) was examined at CNS barriers and parenchymal sites in wildtype (C57BL6/N) mice. Subcellular localization of the folate transport systems was further assessed in an in vitro model of the mouse AB. Gene and protein expression was analyzed in several in vitro models of brain barriers and parenchyma by qPCR and western blot analysis.

RESULTS

RFC, PCFT, and FRα expression was localized within the BCSFB and BBB consistent with previous reports. Only RFC and PCFT expression was detected at the AB. Varied levels of RFC and PCFT expression were detected in neuronal and glial cells.

CONCLUSIONS

Localization of RFC and PCFT within the AB, described here for the first time, suggest that AB may contribute to folate transport between the peripheral circulation and the CSF. RFC and PCFT expression observed in astrocytes and microglia is consistent with the role that one or both of these transporters may play in delivering folates into cells within brain parenchyma. These studies provide insights into mechanisms of folate transport in the CNS and may enhance our understanding of the critical role folates play in neurodevelopment and in the development of novel treatment strategies for disorders of brain folate deficiency due to impaired transporter function.

Exploring Intestinal Surface Receptors in Oral Nanoinsulin Delivery

Subcutaneous and inhaled insulins are associated with needle phobia, lipohypertrophy, lipodystrophy, and cough in diabetes treatment. Oral nanoinsulin has been developed, reaping the physiologic benefits of peroral administration. This review profiles intestinal receptors exploitable in targeted delivery of oral nanoinsulin. Intestinal receptor targeting improves oral insulin bioavailability and sustains blood glucose-lowering response. Nonetheless, these studies are conducted in small animal models with no optimization of insulin dose, targeting ligand type and content, and physicochemical and molecular biologic characteristics of nanoparticles against the in vivo/clinical diabetes responses as a function of the intestinal receptor population characteristics with diabetes progression. The interactive effects between nanoinsulin and antidiabetic drugs on intestinal receptors, including their up-/downregulation, are uncertain. Sweet taste receptors upregulate SGLT-1, and both have an undefined role as new intestinal targets of nanoinsulin. Receptor targeting of oral nanoinsulin represents a viable approach that is relatively green, requiring an in-depth development of the relationship between receptors and their pathophysiological profiles with physicochemical attributes of the oral nanoinsulin. SIGNIFICANCE STATEMENT: Intestinal receptor targeting of oral nanoinsulin improves its bioavailability with sustained blood glucose-lowering response. Exploring new intestinal receptor and tailoring the design of oral nanoinsulin to the pathophysiological state of diabetic patients is imperative to raise the insulin performance to a comparable level as the injection products.

Microfluidized Dextran Microgels Loaded with Cisplatin/SPION Lipid Nanotherapeutics for Local Colon Cancer Treatment via Oral Administration

Multifunctional sequential targeted delivery system is developed as an efficient therapeutic strategy against malignant tumors with selective accumulation and minimal systemic drug absorption. The therapeutic system is comprised of microfluidized dextran microgels encapsulating cisplatin/superparamagnetic iron oxide nanoparticles (SPIONs)-loaded trilaurin-based lipid nanoparticles (LNPs). The microgel system is imparted hierarchically dual targeting via dextran and folic acid (FA) residues, leading to increases both in retention of the microgels in colon and in cellular uptake of the therapeutic LNPs by colon cancer cells while being used for oral therapeutic delivery. Encapsulation of the therapeutic LNPs into dextran microgels attained by microfluidized crosslinking reaction reduces gastrointestinal adhesion and prevents the FA-modified LNPs from cellular transport by proton-coupled FA transporters in small intestine during their oral delivery to colon. Upon enzymatic degradation of the dextran microgels by dextranase present exclusively in colon, LNPs thus released become more recognizable and readily internalized by FA receptor-overexpressing colon cancer cells. The combined chemo/magnetothermal therapeutic effect of dual targeted lipid nanoparticle-loaded microgels from entrapped lipidized cisplatin and alternating magnetic field-treated SPIONs significantly inhibits tumor growth and suppresses metastatic peritoneal carcinomatosis in orthotopic colon cancer-bearing mice.

Biology and therapeutic applications of the proton-coupled folate transporter

INTRODUCTION

The proton-coupled folate transporter (PCFT; SLC46A1) was discovered in 2006 as the principal mechanism by which folates are absorbed in the intestine and the causal basis for hereditary folate malabsorption (HFM). In 2011, it was found that PCFT is highly expressed in many tumors. This stimulated interest in using PCFT for cytotoxic drug targeting, taking advantage of the substantial levels of PCFT transport and acidic pH conditions commonly associated with tumors.

AREAS COVERED

We summarize the literature from 2006 to 2022 that explores the role of PCFT in the intestinal absorption of dietary folates and its role in HFM and as a transporter of folates and antifolates such as pemetrexed (Alimta) in relation to cancer. We provide the rationale for the discovery of a new generation of targeted pyrrolo[2,3-d]pyrimidine antifolates with selective PCFT transport and inhibitory activity toward de novo purine biosynthesis in solid tumors. We summarize the benefits of this approach to cancer therapy and exciting new developments in the structural biology of PCFT and its potential to foster refinement of active structures of PCFT-targeted anti-cancer drugs.

EXPERT OPINION

We summarize the promising future and potential challenges of implementing PCFT-targeted therapeutics for HFM and a variety of cancers.

Folate Pathway Gene Single Nucleotide Polymorphisms and Neural Tube Defects: A Systematic Review and Meta-Analysis

Neural tube defects (NTDs) are congenital abnormalities in the central nervous system. The exact etiology of NTDs is still not determined, but several genetic and epigenetic factors have been studied. Folate supplementation during gestation is recommended to reduce the risk of NTDs. In this review we examine single nucleotide polymorphisms (SNPs) of the genes in the folate pathway associated with NTD. We reviewed the literature for all papers discussing both NTDs and SNPs in the folate pathway. Data were represented through five different genetic models. Quality assessment was performed using the Newcastle-Ottawa Scale (NOS) and Cohen's Kappa inter-rater coefficient assessed author agreement. Fifty-nine papers were included. SNPs in MTHFR, MTRR, RFC genes were found to be highly associated with NTD risk. NOS showed that high quality papers were selected, and Kappa Q-test was 0.86. Our combined results support the notion that SNPs significantly influence NTDs across the population, particularly in Asian ethnicity. Additional high-quality research from diverse ethnicities is needed and meta-regression analysis based on a range of criteria may provide a more complete understanding of the role of folate metabolism in NTDs.

Folic Acid and the Prevention of Birth Defects: 30 Years of Opportunity and Controversies

For three decades, the US Public Health Service has recommended that all persons capable of becoming pregnant consume 400 μg/day of folic acid (FA) to prevent neural tube defects (NTDs). The neural tube forms by 28 days after conception. Fortification can be an effective NTD prevention strategy in populations with limited access to folic acid foods and/or supplements. This review describes the status of mandatory FA fortification among countries that fortify (n = 71) and the research describing the impact of those programs on NTD rates (up to 78% reduction), blood folate concentrations [red blood cell folate concentrations increased ∼1.47-fold (95% CI, 1.27, 1.70) following fortification], and other health outcomes. Across settings, high-quality studies such as those with randomized exposures (e.g., randomized controlled trials, Mendelian randomization studies) are needed to elucidate interactions of FA with vitamin B12 as well as expanded biomarker testing.

Absorption and Tissue Distribution of Folate Forms in Rats: Indications for Specific Folate Form Supplementation during Pregnancy

Food fortification and folic acid supplementation during pregnancy have been implemented as strategies to prevent fetal malformations during pregnancy. However, with the emergence of conditions where folate metabolism and transport are disrupted, such as folate receptor alpha autoantibody (FRαAb)-induced folate deficiency, it is critical to find a folate form that is effective and safe for pharmacologic dosing for prolonged periods. Therefore, in this study, we explored the absorption and tissue distribution of folic acid (PGA), 5-methyl-tetrahydrofolate (MTHF), l-folinic acid (levofolinate), and d,l-folinic acid (Leucovorin) in adult rats. During absorption, all forms are converted to MTHF while some unconverted folate form is transported into the blood, especially PGA. The study confirms the rapid distribution of absorbed folate to the placenta and fetus. FRαAb administered, also accumulates rapidly in the placenta and blocks folate transport to the fetus and high folate concentrations are needed to circumvent or overcome the blocking of FRα. In the presence of FRαAb, both Leucovorin and levofolinate are absorbed and distributed to tissues better than the other forms. However, only 50% of the leucovorin is metabolically active whereas levofolinate is fully active and generates higher tetrahydrofolate (THF). Because levofolinate can readily incorporate into the folate cycle without needing methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MS) in the first pass and is relatively stable, it should be the folate form of choice during pregnancy, other disorders where large daily doses of folate are needed, and food fortification.

ESPEN micronutrient guideline

BACKGROUND

Trace elements and vitamins, named together micronutrients (MNs), are essential for human metabolism. Recent research has shown the importance of MNs in common pathologies, with significant deficiencies impacting the outcome.

OBJECTIVE

This guideline aims to provide information for daily clinical nutrition practice regarding assessment of MN status, monitoring, and prescription. It proposes a consensus terminology, since many words are used imprecisely, resulting in confusion. This is particularly true for the words "deficiency", "repletion", "complement", and "supplement".

METHODS

The expert group attempted to apply the 2015 standard operating procedures (SOP) for ESPEN which focuses on disease. However, this approach could not be applied due to the multiple diseases requiring clinical nutrition resulting in one text for each MN, rather than for diseases. An extensive search of the literature was conducted in the databases Medline, PubMed, Cochrane, Google Scholar, and CINAHL. The search focused on physiological data, historical evidence (published before PubMed release in 1996), and observational and/or randomized trials. For each MN, the main functions, optimal analytical methods, impact of inflammation, potential toxicity, and provision during enteral or parenteral nutrition were addressed. The SOP wording was applied for strength of recommendations.

RESULTS

There was a limited number of interventional trials, preventing meta-analysis and leading to a low level of evidence. The recommendations underwent a consensus process, which resulted in a percentage of agreement (%): strong consensus required of >90% of votes. Altogether the guideline proposes sets of recommendations for 26 MNs, resulting in 170 single recommendations. Critical MNs were identified with deficiencies being present in numerous acute and chronic diseases. Monitoring and management strategies are proposed.

CONCLUSION

This guideline should enable addressing suboptimal and deficient status of a bundle of MNs in at-risk diseases. In particular, it offers practical advice on MN provision and monitoring during nutritional support.

Gut microbiome: Linking together obesity, bariatric surgery and associated clinical outcomes under a single focus

Obesity is increasingly prevalent in the post-industrial era, with increased mortality rates. The gut microbiota has a central role in immunological, nutritional and metabolism mediated functions, and due to its multiplexity, it is considered an independent organ. Modern high-throughput sequencing techniques have allowed phylogenetic exploration and quantitative analyses of gut microbiome and improved our current understanding of the gut microbiota in health and disease. Its role in obesity and its changes following bariatric surgery have been highlighted in several studies. According to current literature, obesity is linked to a particular microbiota profile that grants the host an augmented potential for calorie release, while limited diversity of gut microbiome has also been observed. Moreover, bariatric surgery procedures represent effective interventions for sustained weight loss and restore a healthier microbiota, contributing to the observed fat mass reduction and lean mass increase. However, newer evidence has shown that gut microbiota is only partially recovered following bariatric surgery. Moreover, several targets including FGF15/19 (a gut-derived peptide), could be responsible for the favorable metabolic changes of bariatric surgery. More randomized controlled trials and larger prospective studies that include well-defined cohorts are required to better identify associations between gut microbiota, obesity, and bariatric surgery.

Transporters in drug development: International transporter consortium update on emerging transporters of clinical importance

During its 4^th transporter workshop in 2021, the International Transporter Consortium (ITC) provided updates on emerging clinically relevant transporters for drug development. Previously highlighted and new transporters were considered based on up-to-date clinical evidence of their importance in drug-drug interactions and potential for altered drug efficacy and safety, including drug-nutrient interactions leading to nutrient deficiencies. For the first time, folate transport pathways (PCFT, RFC, and FRα) were examined in-depth as a potential mechanism of drug-induced folate deficiency and related toxicities (e.g., neural tube defects, megaloblastic anemia). However, routine toxicology studies conducted in support of drug development appear sufficient to flag such folate deficiency toxicities, while prospective prediction from in vitro folate metabolism and transport inhibition is not well enough established to inform drug development. Previous suggestion of retrospective study of intestinal OATP2B1 inhibition to explain unexpected decreases in drug exposure were updated. Furthermore, when the absorption of a new molecular entity is more rapid and extensive than can be explained by passive permeability, evaluation of OATP2B1 transport may be considered. Emerging research on hepatic and renal OAT2 is summarized, but current understanding of the importance of OAT2 was deemed insufficient to justify specific consideration for drug development. Hepatic, renal, and intestinal MRPs (MRP2, MRP3, MRP4) were revisited. MRPs may be considered when they are suspected to be the major determinant of drug disposition (e.g., direct glucuronide conjugates); MRP2 inhibition as a mechanistic explanation for drug-induced hyperbilirubinemia remains justified. There were no major changes in recommendations from previous ITC whitepapers.

Structural basis for recognition and transport of folic acid in mammalian cells

Structural studies on mammalian vitamin transport lag behind other metabolites. Folates, also known as B9 vitamins, are essential cofactors in one-carbon transfer reactions in biology. Three different systems control folate uptake in the human body; folate receptors function to capture and internalise extracellular folates via endocytosis, whereas two major facilitator superfamily transporters, the reduced folate carrier (RFC; SLC19A1) and proton-coupled folate transporter (PCFT; SLC46A1) control the transport of folates across cellular membranes. Targeting specific folate transporters is being pursued as a route to developing new antifolates with improved pharmacology. Recent structures of the proton-coupled folate transporter, PCFT, revealed key insights into antifolate recognition and the mechanism of proton-coupled transport. Combined with previously determined structures of folate receptors and new predictions for the structure of the RFC, we are now able to develop a structure-based understanding of folate and antifolate recognition to accelerate efforts in antifolate drug development.

Reduced Kidney Function Is Associated with Increasing Red Blood Cell Folate Concentration and Changes in Folate Form Distributions (NHANES 2011-2018)

Background: Current studies examining the effects of high concentrations of red blood cell (RBC) or serum folates assume that high folate concentrations are an indicator of high folic acid intakes, often ignoring the contributions of other homeostatic and biological processes, such as kidney function. Objective: The current study examined the relative contributions of declining kidney function, as measured by the risk of chronic kidney disease (CKD), and usual total folic acid intake on the concentrations of RBC folate and serum folate (total as well as individual folate forms). Design: Cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) collected in 2-year cycles were combined from 2011 to 2018. A total of 18,127 participants aged ≥16 years with available folate measures, kidney biomarker data (operationalized as a categorical CKD risk variable describing the risk of progression), and reliable dietary recall data were analyzed. Results: RBC folate concentrations increased as CKD risk increased: low risk, 1089 (95% CI: 1069, 1110) nmol/L; moderate risk, 1189 (95% CI: 1158, 1220) nmol/L; high risk, 1488 (95% CI: 1419, 1561) nmol/L; and highest risk, 1443 (95% CI: 1302, 1598) nmol/L (p < 0.0001). Similarly, serum total folate concentrations increased as CKD risk increased: low risk: 37.1 (95% CI: 26.3, 38.0) nmol/L; moderate risk: 40.2 (95% CI: 38.8, 41.7) nmol/L; high risk: 48.0 (95% CI: 44.3, 52.1) nmol/L; the highest Risk: 42.8 (95% CI: 37.8, 48.4) nmol/L (p < 0.0001). The modeled usual intake of folic acid showed no difference among CKD risk groups, with a population median of 225 (interquartile range: 108−390) µg/day. Conclusion: Both RBC and serum folate concentrations increased with declining kidney function without increased folic acid intake. When analyzing associations between folate concentrations and disease outcomes, researchers may want to consider the confounding role of kidney function.

Functionalized LbL Film for Localized Delivery of STAT3 siRNA and Oxaliplatin Combination to Treat Colon Cancer

The aim of the study was to develop and evaluate the efficacy of a functionalized layer-by-layer (LbL) assembled film entrapped with oxaliplatin (OX) and signal transducer and activator of transcription 3 (STAT3) siRNA in the localized treatment of colon cancer. The LbL film was prepared by the sequential layering of chitosan (CS) and alginate to attain desired physical and mechanical properties. The film was functionalized by coating folic acid-conjugated CS on one side. On the other side, polycaprolactone was coated as a backing layer to provide directional drug release. OX was entrapped within the layers of the film, while STAT3 siRNA was complexed with CS to form nanoparticles before entrapment in the LbL film. The CS-siRNA nanoparticles were taken up by the colon carcinoma, Caco-2 cells within 3 h and provided concentration-dependent reduction in STAT3 protein expression. The functionalized LbL film (F-LbL film) selectively adhered to the colon cancer tissue in the mice model, whereas the nonfunctionalized film adhered to the normal colon tissue. The combination of OX and STAT3 siRNA provided significantly greater tumor regression, survival rate, and STAT3 protein suppression after localized delivery through oral administration compared with intravenous administration. Taken together, the F-LbL film can selectively bind to colon tumors for localized delivery of drugs to treat colon cancer.

Emerging roles for folate receptor FOLR1 in signaling and cancer

Folates are B vitamins that function in one-carbon metabolism. Folate receptors are one of three major types of folate transporters. The folate receptors FOLR1 and FOLR2 are overexpressed in multiple cancers. The overexpression of FOLR1 is often associated with increased cancer progression and poor patient prognosis. There is emerging evidence that FOLR1 is involved in signaling pathways that are independent of one-carbon metabolism. Recent publications implicate a direct role of FOLR1 in three signaling pathways: JAK-STAT3, ERK1/2, and as a transcription factor. Six other signaling pathways have been proposed to include FOLR1, but these currently lack sufficient data to infer a direct signaling role for FOLR1. We discuss the data that support noncanonical roles for FOLR1, and its limitations.

Differential toxicity to murine small and large intestinal epithelium induced by oncology drugs

Gastrointestinal toxicity is a major concern in the development of drugs. Here, we establish the ability to use murine small and large intestine-derived monolayers to screen drugs for toxicity. As a proof-of-concept, we applied this system to assess gastrointestinal toxicity of ~50 clinically used oncology drugs, encompassing diverse mechanisms of action. Nearly all tested drugs had a deleterious effect on the gut, with increased sensitivity in the small intestine. The identification of differential toxicity between the small and large intestine enabled us to pinpoint differences in drug uptake (antifolates), drug metabolism (cyclophosphamide) and cell signaling (EGFR inhibitors) across the gut. These results highlight an under-appreciated distinction between small and large intestine toxicity and suggest distinct tissue properties important for modulating drug-induced gastrointestinal toxicity. The ability to accurately predict where and how drugs affect the murine gut will accelerate preclinical drug development.

Visible-light and near-infrared fluorescence and surface-enhanced Raman scattering point-of-care sensing and bio-imaging: a review

This review article deals with the concepts, principles and applications of visible-light and near-infrared (NIR) fluorescence and surface-enhanced Raman scattering (SERS) in in vitro point-of-care testing (POCT) and in vivo bio-imaging. It has discussed how to utilize the biological transparency windows to improve the penetration depth and signal-to-noise ratio, and how to use surface plasmon resonance (SPR) to amplify fluorescence and SERS signals. This article has highlighted some plasmonic fluorescence and SERS probes. It has also reviewed the design strategies of fluorescent and SERS sensors in the detection of metal ions, small molecules, proteins and nucleic acids. Particularly, it has provided perspectives on the integration of fluorescent and SERS sensors into microfluidic chips as lab-on-chips to realize point-of-care testing. It has also discussed the design of active microfluidic devices and non-paper- or paper-based lateral flow assays for in vitro diagnostics. In addition, this article has discussed the strategies to design in vivo NIR fluorescence and SERS bio-imaging platforms for monitoring physiological processes and disease progression in live cells and tissues. Moreover, it has highlighted the applications of POCT and bio-imaging in testing toxins, heavy metals, illicit drugs, cancers, traumatic brain injuries, and infectious diseases such as COVID-19, influenza, HIV and sepsis.

Folate Metabolism in Hepatocellular Carcinoma. What Do We Know So Far?

Cancer cells are characterized by accelerated proliferation and an outstanding adaptation of their metabolic pathways to meet energy demands. The folate cycle, also known as folate metabolism or one-carbon metabolism, through enzymatic interconversions, provides metabolites necessary for nucleotide synthesis, methylation, and reduction power, helping to maintain the high rate of proliferation; therefore, the study of this metabolic pathway is of great importance in the study of cancer. Moreover, multiple enzymes involved in this cycle have been implicated in different types of cancer, corroborating the cell's adaptations under this pathology. During the last decade, nonalcoholic fatty liver disease has emerged as the leading etiology related to the rise in the incidence and deaths of hepatocellular carcinoma. Specifically, cholesterol accumulation has been a determinant promoter of tumor formation, with solid evidence that an enriched-cholesterol diet plays a crucial role in accelerating the development of an aggressive subtype of hepatocellular carcinoma compared to other models. In this review, we will discuss the most recent findings to understand the contribution of folate metabolism to cancer cells and tumor microenvironment while creating a link between the dynamics given by cholesterol and methylenetetrahydrofolate dehydrogenase 1-like, a key enzyme of the cycle located in the mitochondrial compartment.

Role of Vitamin B12 and Folate in Metabolic Syndrome

Metabolic syndrome (MS) is a collection of pathological metabolic conditions that includes insulin resistance, central or abdominal obesity, dyslipidemia, and hypertension. It affects large populations worldwide, and its prevalence is rising exponentially. There is no specific mechanism that leads to the development of MS. Proposed hypotheses range from visceral adiposity being a key factor to an increase in very-low-density lipoprotein and fatty acid synthesis as the primary cause of MS. Numerous pharmaceutical therapies are widely available in the market for the treatment of the individual components of MS. The relationship between MS and vitamin B complex supplementation, specifically folic acid and vitamin B12, has been a subject of investigation worldwide, with several trials reporting a positive impact with vitamin supplementation on MS.

In this study, an all-language literature search was conducted on Medline, Cochrane, Embase, and Google Scholar till September 2021. The following search strings and Medical Subject Headings (MeSH) terms were used: “Vitamin B12,” “Folate,” “Metabolic Syndrome,” and “Insulin Resistance.” We explored the literature on MS for its epidemiology, pathophysiology, newer treatment options, with a special focus on the effectiveness of supplementation with vitamins B9 and B12.

According to the literature, vitamin B12 and folate supplementation, along with a host of novel therapies, has a considerable positive impact on MS. These findings must be kept in mind while designing newer treatment protocols in the future.

Folic Acid Absorption Characteristics and Effect on Cecal Microbiota of Laying Hens

This experiment was conducted to investigate the characteristics of folic acid (FA) absorption in laying hens and the effect of FA supplementation on cecal microbiota. A total of 432 healthy hens (30-week-old) were randomly assigned to four diets supplemented with FA: 0, 1, 6, and 24 mg/kg of feed for 8 w. Blood, duodenum, jejunum, ileum, cecum, and cecal chyme samples (six samples per treatment) were collected from the hens at the end of the feeding trial. Expression profiles of folate transport and transformation genes in intestine and cecal microbiota were detected. Results showed that serum folate level significantly increased (P < 0.01) with an increase in dietary FA supplementation, reaching a plateau at 6 mg/kg FA supplementation. The expression of FA transport and transformation genes was not affected in the cecum (P > 0.05) by dietary FA supplementation; however, it was affected in the duodenum, jejunum, and ileum and mostly showed a downward trend in treatment groups (P < 0.05). The genes affected include duodenal folate receptor (Folr) and dihydrofolate reductase (Dhfr), jejunal proton-coupled folate transporter (Pcft) and reduced folate carrier (Rfc), and ileal ATP binding cassette subfamily C member (Abcc2), Abcc3, Rfc, Folr, and Dhfr. Furthermore, according to the operational taxonomic unit classification and taxonomic position identification, the cecal microbiota population of the hens was not affected by dietary FA supplementation at the phylum, class, order, family, genus, and species levels (P > 0.05). However, the relative abundance of some microbiota was affected by dietary FA supplementation (P < 0.05). In conclusion, FA transport from the intestinal lumen into enterocytes, and then into the bloodstream, is strictly regulated, which may be associated with the regulation of the expression profiles of genes involved in FA absorption. Pathogenic bacteria decreased in the cecum, especially at 24 mg/kg supplementation, but the beneficial bacteria (Bifidobacteriaceae) decreased at this level, too. Overall, FA supplementation at 6 mg/kg, which was selected for folate-enriched egg production, did not affect the health and metabolism of laying hens negatively.

Molecular Mechanisms of Alcohol-Induced Colorectal Carcinogenesis

The etiology of colorectal cancer (CRC) is complex. Approximately, 10% of individuals with CRC have predisposing germline mutations that lead to familial cancer syndromes, whereas most CRC patients have sporadic cancer resulting from a combination of environmental and genetic risk factors. It has become increasingly clear that chronic alcohol consumption is associated with the development of sporadic CRC; however, the exact mechanisms by which alcohol contributes to colorectal carcinogenesis are largely unknown. Several proposed mechanisms from studies in CRC models suggest that alcohol metabolites and/or enzymes associated with alcohol metabolism alter cellular redox balance, cause DNA damage, and epigenetic dysregulation. In addition, alcohol metabolites can cause a dysbiotic colorectal microbiome and intestinal permeability, resulting in bacterial translocation, inflammation, and immunosuppression. All of these effects can increase the risk of developing CRC. This review aims to outline some of the most significant and recent findings on the mechanisms of alcohol in colorectal carcinogenesis. We examine the effect of alcohol on the generation of reactive oxygen species, the development of genotoxic stress, modulation of one-carbon metabolism, disruption of the microbiome, and immunosuppression.

Structural basis of antifolate recognition and transport by PCFT

Folates (also known as vitamin B9) have a critical role in cellular metabolism as the starting point in the synthesis of nucleic acids, amino acids and the universal methylating agent S-adenylsmethionine1,2. Folate deficiency is associated with a number of developmental, immune and neurological disorders3-5. Mammals cannot synthesize folates de novo; several systems have therefore evolved to take up folates from the diet and distribute them within the body3,6. The proton-coupled folate transporter (PCFT) (also known as SLC46A1) mediates folate uptake across the intestinal brush border membrane and the choroid plexus4,7, and is an important route for the delivery of antifolate drugs in cancer chemotherapy8-10. How PCFT recognizes folates or antifolate agents is currently unclear. Here we present cryo-electron microscopy structures of PCFT in a substrate-free state and in complex with a new-generation antifolate drug (pemetrexed). Our results provide a structural basis for understanding antifolate recognition and provide insights into the pH-regulated mechanism of folate transport mediated by PCFT.

The toxic side of one-carbon metabolism and epigenetics

One-carbon metabolism is a central metabolic hub that provides one-carbon units for essential biosynthetic reactions and for writing epigenetics marks. The leading role in this hub is performed by the one-carbon carrier tetrahydrofolate (THF), which accepts formaldehyde usually from serine generating one-carbon THF intermediates in a set of reactions known as the folate or one-carbon cycle. THF derivatives can feed one-carbon units into purine and thymidine synthesis, and into the methionine cycle that produces the universal methyl-donor S-adenosylmethionine (AdoMet). AdoMet delivers methyl groups for epigenetic methylations and it is metabolized to homocysteine (Hcy), which can enter the transsulfuration pathway for the production of cysteine and lastly glutathione (GSH), the main cellular antioxidant. This vital role of THF comes to an expense. THF and other folate derivatives are susceptible to oxidative breakdown releasing formaldehyde, which can damage DNA -a consequence prevented by the Fanconi Anaemia DNA repair pathway. Epigenetic demethylations catalysed by lysine-specific demethylases (LSD) and Jumonji histone demethylases can also release formaldehyde, constituting a potential threat for genome integrity. In mammals, the toxicity of formaldehyde is limited by a metabolic route centred on the enzyme alcohol dehydrogenase 5 (ADH5/GSNOR), which oxidizes formaldehyde conjugated to GSH, lastly generating formate. Remarkably, this formate can be a significant source of one-carbon units, thus defining a formaldehyde cycle that likely restricts the toxicity of one-carbon metabolism and epigenetic demethylations. This work describes recent advances in one-carbon metabolism and epigenetics, focusing on the steps that involve formaldehyde flux and that might lead to cytotoxicity affecting human health.

Methotrexate impacts conserved pathways in diverse human gut bacteria leading to decreased host immune activation

Immunomodulatory drugs can inhibit bacterial growth, yet their mechanism of action, spectrum, and clinical relevance remain unknown. Methotrexate (MTX), a first-line rheumatoid arthritis (RA) treatment, inhibits mammalian dihydrofolate reductase (DHFR), but whether it directly impacts gut bacteria is unclear. We show that MTX broadly alters the human gut microbiota. Drug sensitivity varied across strains, but the mechanism of action against DHFR appears conserved between mammalian and bacterial cells. RA patient microbiotas were sensitive to MTX, and changes in gut bacterial taxa and gene family abundance were distinct between responders and non-responders. Transplantation of post-treatment samples into germ-free mice given an inflammatory trigger led to reduced immune activation relative to pre-treatment controls, enabling identification of MTX-modulated bacterial taxa associated with intestinal and splenic immune cells. Thus, conservation in cellular pathways across domains of life can result in broad off-target drug effects on the human gut microbiota with consequences for immune function.