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Molecular Aspects of Medicine Feb 2017The active form of vitamin B6, pyridoxal 5'-phosphate (PLP), serves as a co-factor in more than 150 enzymatic reactions. Plasma PLP has consistently been shown to be low... (Review)
Review
The active form of vitamin B6, pyridoxal 5'-phosphate (PLP), serves as a co-factor in more than 150 enzymatic reactions. Plasma PLP has consistently been shown to be low in inflammatory conditions; there is a parallel reduction in liver PLP, but minor changes in erythrocyte and muscle PLP and in functional vitamin B6 biomarkers. Plasma PLP also predicts the risk of chronic diseases like cardiovascular disease and some cancers, and is inversely associated with numerous inflammatory markers in clinical and population-based studies. Vitamin B6 intake and supplementation improve some immune functions in vitamin B6-deficient humans and experimental animals. A possible mechanism involved is mobilization of vitamin B6 to the sites of inflammation where it may serve as a co-factor in pathways producing metabolites with immunomodulating effects. Relevant vitamin B6-dependent inflammatory pathways include vitamin B6 catabolism, the kynurenine pathway, sphingosine 1-phosphate metabolism, the transsulfuration pathway, and serine and glycine metabolism.
Topics: Animals; Biomarkers; Humans; Immunity; Inflammation; Pyridoxal Phosphate; Signal Transduction; Vitamin B 6
PubMed: 27593095
DOI: 10.1016/j.mam.2016.08.001 -
Nutrients Dec 2018With over two-thirds (71.6%) of the US adult population either overweight or obese, many strategies have been suggested for weight loss. While many are successful, the... (Review)
Review
With over two-thirds (71.6%) of the US adult population either overweight or obese, many strategies have been suggested for weight loss. While many are successful, the weight loss is often accompanied by a loss in lean body mass. This loss in lean body mass has multiple negative health implications. Therefore, weight loss strategies that protect lean body mass are of value. It is challenging to consume a significant caloric deficit while maintaining lean body mass regardless of macronutrient distribution. Therefore, the efficacy of various dietary supplements on body weight and body composition have been a topic of research interest. Chromium picolinate has been shown to improve body composition by maintaining lean body mass. In this paper we review some common weight loss strategies and dietary supplements with a focus on their impact on body composition and compare them to the effect of chromium picolinate.
Topics: Body Composition; Diet, Reducing; Humans; Iron Chelating Agents; Picolinic Acids; Weight Loss
PubMed: 30513859
DOI: 10.3390/nu10121876 -
Advances in Nutrition (Bethesda, Md.) Oct 2021Vitamin B-6 in the form of pyridoxine (PN) is commonly used by the general population. The use of PN-containing supplements has gained lots of attention over the past... (Review)
Review
Vitamin B-6 in the form of pyridoxine (PN) is commonly used by the general population. The use of PN-containing supplements has gained lots of attention over the past years as they have been related to the development of peripheral neuropathy. In light of this, the number of reported cases of adverse health effects due to the use of vitamin B-6 have increased. Despite a long history of study, the pathogenic mechanisms associated with PN toxicity remain elusive. Therefore, the present review is focused on investigating the mechanistic link between PN supplementation and sensory peripheral neuropathy. Excessive PN intake induces neuropathy through the preferential injury of sensory neurons. Recent reports on hereditary neuropathy due to pyridoxal kinase (PDXK) mutations may provide some insight into the mechanism, as genetic deficiencies in PDXK lead to the development of axonal sensory neuropathy. High circulating concentrations of PN may lead to a similar condition via the inhibition of PDXK. The mechanism behind PDXK-induced neuropathy is unknown; however, there is reason to believe that it may be related to γ-aminobutyric acid (GABA) neurotransmission. Compounds that inhibit PDXK lead to convulsions and reductions in GABA biosynthesis. The absence of central nervous system-related symptoms in PDXK deficiency could be due to differences in the regulation of PDXK, where PDXK activity is preserved in the brain but not in peripheral tissues. As PN is relatively impermeable to the blood-brain barrier, PDXK inhibition would similarly be confined to the peripheries and, as a result, GABA signaling may be perturbed within peripheral tissues, such as sensory neurons. Perturbed GABA signaling within sensory neurons may lead to excitotoxicity, neurodegeneration, and ultimately, the development of peripheral neuropathy. For several reasons, we conclude that PDXK inhibition and consequently disrupted GABA neurotransmission is the most plausible mechanism of toxicity.
Topics: Humans; Peripheral Nervous System Diseases; Pyridoxal Kinase; Pyridoxine; Vitamin B 6; Vitamins
PubMed: 33912895
DOI: 10.1093/advances/nmab033 -
Nutrients Jun 2023Vitamin B6 is a water-soluble vitamin that is naturally present in many foods and is accessible in many dietary supplements. The three natural forms are pyridoxine,... (Review)
Review
INTRODUCTION
Vitamin B6 is a water-soluble vitamin that is naturally present in many foods and is accessible in many dietary supplements. The three natural forms are pyridoxine, pyridoxal, and pyridoxamine. Both vitamin B6 deficiency and high B6 intake have been described as risk factors for developing peripheral neuropathy (PN). The aim of this systematic review is to characterize and comprehensively describe B6-related PN.
METHOD
A systematic, computer-based search was conducted using the PubMed database. Twenty articles were included in this review.
RESULTS
Higher vitamin B6 levels, which usually occur following the taking of nutritional supplements, may lead to the development of a predominantly, if not exclusively, sensory neuropathy of the axonal type. After pyridoxine discontinuation, such patients subjectively report improved symptoms. However, although low vitamin B6 levels can be seen in patients suffering from peripheral neuropathy of various etiologies, there is no firm evidence that low B6 levels have a direct causal relationship with PN. Many studies suggest subjective improvement of neuropathy symptoms in patients suffering from PN of various etiologies after receiving B6 supplementation; however, no data about B6 administration as a monotherapy exist, only as part of a combination treatment, usually with other vitamins. Therefore, the potential therapeutic role of B6 cannot be confirmed to date. Supplementation with vitamin B6, even as part of a nutritional multivitamin supplement, has not been proven harmful at permitted daily doses in patients who already suffer from PN.
CONCLUSION
Current scientific evidence supports a neurotoxic role of B6 at high levels. Although some studies suggest that low B6 is also a potential risk factor, further studies in this area are needed.
Topics: Humans; Pyridoxine; Vitamin B 6; Pyridoxal; Pyridoxamine; Vitamins; Peripheral Nervous System Diseases
PubMed: 37447150
DOI: 10.3390/nu15132823 -
Gut Sep 2017To compare efficacy of pharmacotherapies for chronic idiopathic constipation (CIC) based on comparisons to placebo using Bayesian network meta-analysis. (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
To compare efficacy of pharmacotherapies for chronic idiopathic constipation (CIC) based on comparisons to placebo using Bayesian network meta-analysis.
DATA SOURCES
We conducted searches (inception to May 2015) of MEDLINE, EMBASE, Scopus and Cochrane Central, as well as original data from authors or drug companies for the medications used for CIC.
STUDY SELECTION
Phase IIB and phase III randomised, placebo-controlled trials (RCT) of ≥4 weeks' treatment for CIC in adults with Rome II or III criteria for functional constipation; trials included at least one of four end points.
DATA EXTRACTION AND SYNTHESIS
Two investigators independently evaluated all full-text articles that met inclusion criteria and extracted data for primary and secondary end points, risk of bias and quality of evidence.
OUTCOMES
Primary end points were ≥3 complete spontaneous bowel movements (CSBM)/week and increase over baseline by ≥1 CSBM/week. Secondary end points were change from baseline (Δ) in the number of SBM/week and Δ CSBM/week.
RESULTS
Twenty-one RCTs (9189 patients) met inclusion and end point criteria: 9 prucalopride, 3 lubiprostone, 3 linaclotide, 2 tegaserod, 1 each velusetrag, elobixibat, bisacodyl and sodium picosulphate (NaP). All prespecified end points were unavailable in four polyethylene glycol studies. Bisacodyl, NaP, prucalopride and velusetrag were superior to placebo for the ≥3 CSBM/week end point. No drug was superior at improving the primary end points on network meta-analysis. Bisacodyl appeared superior to the other drugs for the secondary end point, Δ in number of SBM/week.
CONCLUSIONS
Current drugs for CIC show similar efficacy. Bisacodyl may be superior to prescription medications for Δ in the number of SBM/week in CIC.
Topics: Azabicyclo Compounds; Benzofurans; Bisacodyl; Chronic Disease; Citrates; Constipation; Defecation; Drug Monitoring; Gastrointestinal Agents; Humans; Organometallic Compounds; Picolines; Randomized Controlled Trials as Topic; Treatment Outcome
PubMed: 27287486
DOI: 10.1136/gutjnl-2016-311835 -
Archives of Gynecology and Obstetrics Oct 2023Nausea and vomiting during pregnancy (NVP) are common symptoms in pregnancy. Although no definitive treatment option for NVP, pyridoxine (Vitamin B6) supplementation has... (Meta-Analysis)
Meta-Analysis Review
PURPOSE
Nausea and vomiting during pregnancy (NVP) are common symptoms in pregnancy. Although no definitive treatment option for NVP, pyridoxine (Vitamin B6) supplementation has been used widely. The present study aims to systematically evaluate the current evidence regarding pyridoxine for the treatment of NVP.
METHODS
Data were obtained using a stepwise search process using keywords in the following online medical databases; PubMed, Web of Science, and Scopus for studies published before 1st May 2021. Studies reporting intervention with pyridoxine supplementation alone and/or with other active substances were included. A meta-analysis was performed on the PUQE score and Rhode's score for nausea and vomiting.
FINDINGS
Initial database searching indicated 548 potentially eligible articles, of which 18 studies satisfying the inclusion criteria were selected. Eight studies showed beneficial effects with pyridoxine alone as the supplementation, while six others found that the supplementation of pyridoxine in combination with another active substance had favourable effects. Supplementation of pyridoxine alone as well as combined treatment of pyridoxine with an active ingredient as the intervention significantly improved the symptoms of nausea according to Rhode's score [0.78 [95% CI: 0.26, 1.31; p = 0.003; I2 = 57%, p = 0.10)] and PUQE score [0.75 (95% CI: 0.28, 1.22; p = 0.002; I2 = 0%, p = 0.51)], respectively.
CONCLUSION
Supplementation of pyridoxine alone as well as with an active ingredient demonstrated beneficial effects for women suffering from NVP.
Topics: Pregnancy; Female; Humans; Pyridoxine; Vitamin B 6; Vomiting; Nausea; Pregnancy Complications; Dietary Supplements; Antiemetics
PubMed: 36719452
DOI: 10.1007/s00404-023-06925-w -
Advances in Nutrition (Bethesda, Md.) Jan 2015
Topics: Diet; Humans; Recommended Dietary Allowances; Vitamin B 6; Vitamin B Complex; Vitamin B Deficiency
PubMed: 25593152
DOI: 10.3945/an.113.005207 -
Cellular & Molecular Immunology Jul 2023Interleukin-33 (IL-33) is a crucial nuclear cytokine that induces the type 2 immune response and maintains immune homeostasis. The fine-tuned regulation of IL-33 in...
Interleukin-33 (IL-33) is a crucial nuclear cytokine that induces the type 2 immune response and maintains immune homeostasis. The fine-tuned regulation of IL-33 in tissue cells is critical to control of the type 2 immune response in airway inflammation, but the mechanism is still unclear. Here, we found that healthy individuals had higher phosphate-pyridoxal (PLP, an active form of vitamin B6) concentrations in the serum than asthma patients. Lower serum PLP concentrations in asthma patients were strongly associated with worse lung function and inflammation. In a mouse model of lung inflammation, we revealed that PLP alleviated the type 2 immune response and that this inhibitory effect relied on the activity of IL-33. A mechanistic study showed that in vivo, pyridoxal (PL) needed to be converted into PLP, which inhibited the type 2 response by regulating IL-33 stability. In mice heterozygous for pyridoxal kinase (PDXK), the conversion of PL to PLP was limited, and IL-33 levels were increased in the lungs, aggravating type 2 inflammation. Furthermore, we found that the mouse double minute 2 homolog (MDM2) protein, an E3 ubiquitin-protein ligase, could ubiquitinate the N-terminus of IL-33 and sustain IL-33 stability in epithelial cells. PLP reduced MDM2-mediated IL-33 polyubiquitination and decreased the level of IL-33 through the proteasome pathway. In addition, inhalation of PLP alleviated asthma-related effects in mouse models. In summary, our data indicate that vitamin B6 regulates MDM2-mediated IL-33 stability to constrain the type 2 response, which might help develop a potential preventive and therapeutic agent for allergy-related diseases.
Topics: Mice; Animals; Vitamin B 6; Interleukin-33; Pyridoxal; Inflammation; Asthma; Disease Models, Animal; Homeostasis
PubMed: 37217797
DOI: 10.1038/s41423-023-01029-6 -
American Journal of TherapeuticsVitamin B6 is essential for life and plays a critical role in many biochemical and physiological processes in the human body. The term B6 collectively refers to 6...
BACKGROUND
Vitamin B6 is essential for life and plays a critical role in many biochemical and physiological processes in the human body. The term B6 collectively refers to 6 water-soluble vitamers, and only the pyridoxal 5'-phosphate (PLP) serves as the biologically active form. A plasma PLP concentration above 30 nmol/L (7.4 μg/L) is indicative of an adequate vitamin B6 status for all age and sex groups. The currently recommended daily allowance of B6 (1.5-2 mg/d) from dietary sources frequently results in inadequate B6 status (<20 nmol/L or 5 μg/L) in many elderly patients and patients with comorbid conditions. PLP-based supplements are preferred and should be administered weekly in low doses (50-100 mg) to maintain a stable serum PLP level between 30 and 60 nmol/L or 7.4 and 15 μg/L.
AREAS OF UNCERTAINTY
It is challenging for physicians to prescribe a safe dose of B6 supplements because of the narrow therapeutic index. The association between elevated levels of pyridoxine and neuropathy is not well established. PLP-based supplements are shown to be least neurotoxic, but further clinical trials are needed to establish the long-term safety in high doses.
DATA SOURCES
PubMed search of randomized control trials and meta-analyses.
THERAPEUTIC OPINION
Plasma B6 levels should be ordered as a part of workup of any unexplained anemia before labeling as "anemia of chronic disease." B6 supplementation is also crucial in the management of chronic Mg deficiency resistant to therapy. When B6 is administered daily in supraphysiologic doses, there is a potential for the development of neurotoxicity (typically at levels >100 nmol/L or 25 μg/L). PLP-based supplements are preferred over pyridoxine supplements because of minimal neurotoxicity observed in neuronal cell viability tests. Since B6 metabolites have a long half-life, weekly administration is preferred over daily use to prevent toxicity.
Topics: Humans; Aged; Pyridoxine; Vitamin B 6; Pyridoxal Phosphate; Dietary Supplements
PubMed: 36608063
DOI: 10.1097/MJT.0000000000001460 -
Methods in Enzymology 2023Aromatic aminotransferases (Aro ATs) are pyridoxal-5-phosphate (PLP)-dependent enzymes that catalyze the transamination reactions of an aromatic amino acid (AAA) or a...
Aromatic aminotransferases (Aro ATs) are pyridoxal-5-phosphate (PLP)-dependent enzymes that catalyze the transamination reactions of an aromatic amino acid (AAA) or a keto acid. Aro ATs are involved in biosynthesis or degradation of AAAs and play important functions in controlling the production of plant hormones and secondary metabolites, such as auxin, tocopherols, flavonoids, and lignin. Most Aro ATs show substrate promiscuity and can accept multiple aromatic and non-aromatic amino and keto acid substrates, which complicates and limits our understanding of their in planta functions. Considering the critical roles Aro ATs play in plant primary and secondary metabolism, it is important to accurately determine substrate specificity and kinetic properties of Aro ATs. This chapter describes various methodologies of protein expression, purification and enzymatic assays, which can be used for biochemical characterization of Aro ATs.
Topics: Transaminases; Pyridoxal Phosphate; Keto Acids; Amino Acids, Aromatic; Substrate Specificity
PubMed: 36710018
DOI: 10.1016/bs.mie.2022.07.034