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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 -
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 -
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 -
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 -
Journal of the American Chemical Society Jun 2023Coenzymes are involved in ≥30% of enzymatic reactions and likely predate enzymes, going back to prebiotic chemistry. However, they are considered poor organocatalysts,...
Coenzymes are involved in ≥30% of enzymatic reactions and likely predate enzymes, going back to prebiotic chemistry. However, they are considered poor organocatalysts, and thus their pre-enzymatic function remains unclear. Since metal ions are known to catalyze metabolic reactions in the absence of enzymes, here we explore the influence of metal ions on coenzyme catalysis under conditions relevant to the origin of life (20-75 °C, pH 5-7.5). Specifically, Fe or Al, the two most abundant metals in the Earth's crust, were found to exhibit substantial cooperative effects in transamination reactions catalyzed by pyridoxal (PL), a coenzyme scaffold used by roughly 4% of all enzymes. At 75 °C and 7.5 mol % loading of PL/metal ion, Fe-PL was found to be 90-fold faster at catalyzing transamination than PL alone and 174-fold faster than Fe alone, whereas Al-PL was 85-fold faster than PL alone and 38-fold faster than Al alone. Under milder conditions, reactions catalyzed by Al-PL were >1000 times faster than those catalyzed by PL alone. Pyridoxal phosphate (PLP) exhibited similar behavior to PL. Experimental and theoretical mechanistic studies indicate that the rate-determining step in the PL-metal-catalyzed transamination is different from metal-free and biological PL-based catalysis. Metal coordination to PL lowers the p of the PL-metal complex by several units and slows the hydrolysis of imine intermediates by up to 259-fold. Coenzymes, specifically pyridoxal derivatives, could have exhibited useful catalytic function even before enzymes.
Topics: Pyridoxal; Pyridoxal Phosphate; Metals; Coenzymes; Amination; Catalysis
PubMed: 37278531
DOI: 10.1021/jacs.3c03542 -
The FEBS Journal Apr 2020Pyridoxal 5'-phosphate (PLP) is an organic cofactor employed by ~ 4% of enzymes. The structure of the PLP cofactor allows for the stabilization of carbanions through... (Review)
Review
Pyridoxal 5'-phosphate (PLP) is an organic cofactor employed by ~ 4% of enzymes. The structure of the PLP cofactor allows for the stabilization of carbanions through resonance. A small number of PLP-dependent enzymes employ molecular oxygen as a cosubstrate. Here, we review the biological roles and possible mechanisms of these enzymes, and we observe that these enzymes are found in multiple protein families, suggesting that reaction with oxygen might have emerged de novo in several protein families and thus could be directed to emerge again through laboratory evolution experiments.
Topics: Humans; Molecular Structure; Oxygen; Pyridoxal Phosphate
PubMed: 32142210
DOI: 10.1111/febs.15277 -
Nature Communications Sep 2023Induction of hypothermia during hibernation/torpor enables certain mammals to survive under extreme environmental conditions. However, pharmacological induction of...
Induction of hypothermia during hibernation/torpor enables certain mammals to survive under extreme environmental conditions. However, pharmacological induction of hypothermia in most mammals remains a huge challenge. Here we show that a natural product P57 promptly induces hypothermia and decreases energy expenditure in mice. Mechanistically, P57 inhibits the kinase activity of pyridoxal kinase (PDXK), a key metabolic enzyme of vitamin B6 catalyzing phosphorylation of pyridoxal (PL), resulting in the accumulation of PL in hypothalamus to cause hypothermia. The hypothermia induced by P57 is significantly blunted in the mice with knockout of PDXK in the preoptic area (POA) of hypothalamus. We further found that P57 and PL have consistent effects on gene expression regulation in hypothalamus, and they may activate medial preoptic area (MPA) neurons in POA to induce hypothermia. Taken together, our findings demonstrate that P57 has a potential application in therapeutic hypothermia through regulation of vitamin B6 metabolism and PDXK serves as a previously unknown target of P57 in thermoregulation. In addition, P57 may serve as a chemical probe for exploring the neuron circuitry related to hypothermia state in mice.
Topics: Animals; Mice; Body Temperature Regulation; Hypothermia; Pyridoxal Kinase; Pyridoxine; Vitamin B 6; Biological Products
PubMed: 37752106
DOI: 10.1038/s41467-023-41435-y -
The Korean Journal of Gastroenterology... May 2014Bowel preparation is essential for successful colonoscopy examination, and the most important factor is the bowel preparation agent used. However, selection of a bowel... (Review)
Review
Bowel preparation is essential for successful colonoscopy examination, and the most important factor is the bowel preparation agent used. However, selection of a bowel preparation agent invariably involves compromise. Originally, bowel preparation was performed for radiologic and surgical purposes, when the process involved dietary limitations, cathartics, and enemas, which had many side effects. Development of polyethylene glycol (PEG) solution led to substantive advancement of bowel preparation; however, despite its effectiveness and safety, the large volume involved, and its salty taste and unpleasant odor reduce compliance. Accordingly, modified PEG solutions requiring consumption of lower volumes and sulfate-free solutions were developed. Aqueous sodium phosphate is more effective and better tolerated than PEG solutions; however, fatal complications have occurred due to water and electrolyte shifts. Therefore, aqueous sodium phosphate was withdrawn by the US Food and Drug Administration, and currently, only sodium phosphate tablets remain available. In addition, oral sulfate solution and sodium picosulfate/magnesium citrate are also available, and various studies have reported on adjunctive preparations, such as hyperosmolar or stimulant laxatives, antiemetics, and prokinetics, which are now in various stages of development.
Topics: Administration, Oral; Cathartics; Citrates; Citric Acid; Colonic Diseases; Colonoscopy; Humans; Organometallic Compounds; Phosphates; Picolines; Polyethylene Glycols
PubMed: 24870298
DOI: 10.4166/kjg.2014.63.5.268 -
EcoSal Plus Apr 2021Vitamin B is an ensemble of six interconvertible vitamers: pyridoxine (PN), pyridoxamine (PM), pyridoxal (PL), and their 5'-phosphate derivatives, PNP, PMP, and PLP.... (Review)
Review
Vitamin B is an ensemble of six interconvertible vitamers: pyridoxine (PN), pyridoxamine (PM), pyridoxal (PL), and their 5'-phosphate derivatives, PNP, PMP, and PLP. Pyridoxal 5'-phosphate is a coenzyme in a variety of enzyme reactions concerning transformations of amino and amino acid compounds. This review summarizes all known and putative PLP-binding proteins found in the MG1655 proteome. PLP can have toxic effects since it contains a very reactive aldehyde group at its 4' position that easily forms aldimines with primary and secondary amines and reacts with thiols. Most PLP is bound either to the enzymes that use it as a cofactor or to PLP carrier proteins, protected from the cellular environment but at the same time readily transferable to PLP-dependent apoenzymes. and its relatives synthesize PLP through the seven-step deoxyxylulose-5-phosphate (DXP)-dependent pathway. Other bacteria synthesize PLP in a single step, through a so-called DXP-independent pathway. Although the DXP-dependent pathway was the first to be revealed, the discovery of the widespread DXP-independent pathway determined a decline of interest in vitamin B metabolism. In , as in most organisms, PLP can also be obtained from PL, PN, and PM, imported from the environment or recycled from protein turnover, via a salvage pathway. Our review deals with all aspects of vitamin B metabolism in , from transcriptional to posttranslational regulation. A critical interpretation of results is presented, in particular, concerning the most obscure aspects of PLP homeostasis and delivery to PLP-dependent enzymes.
Topics: Escherichia coli; Pyridoxal Phosphate; Pyridoxine; Vitamin B 6; Vitamins
PubMed: 33787481
DOI: 10.1128/ecosalplus.ESP-0004-2021