Clinical Vitamin B6 Analysis: An Interlaboratory Comparison of Pyridoxal 5′-Phosphate Measurements in Serum

Overcoming the chromatographic challenges when performing LC-MS/MS measurements of pyridoxal-5'-phosphate

Pyridoxal-5'-phosphate (PLP), the active form of vitamin B6, is required for numerous enzymatic reactions. Vitamin B6 deficiency or exceptionally high levels of PLP have negative implications, making measurements of PLP imperative for diagnoses and monitoring in many clinical scenarios. Traditional assays are enzymatic, ELISA based, or employ HPLC with various detection modalities; all of these are prone to interferences and crossreactivity with other compounds. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been increasingly used to overcome these issues, but the high polarity of PLP raises chromatographic challenges. Using ion pairing reagents in the mobile phases is a possible solution, but these reagents often have deleterious effects on instrumentation. An alternative strategy is the addition of an ion pairing reagent after extraction, but prior to injection. To prove this, we used 1-octanesulfonic acid (OSA) without changing the LC method or column. With this technique, we observed a 2-4 fold increase in signal-to-noise ratio. Intraday and interday precision of replicate measurements also improved drastically compared to analyses without OSA, while also yielding a dramatic improvement in column life compared to our previous approach and to this point no deleterious effects on instrument hardware commonly associated with traditional ion pairing reagent techniques have been observed.

A one-step NIST traceable HPLC method for quantitation of vitamin B6 and 4-pyridoxic acid in human plasma

Objectives

Vitamin B6 deficiency is associated with a wide spectrum of clinical syndromes. While vitamin B6 status is primarily assessed by measuring the biologically active form of the vitamin, pyridoxal 5-phosphate (PLP), concurrent measurement of the final metabolite 4-pyridoxic acid (PA) can provide additional information regarding supplement intake and hypophosphatasia. The aim of this study is to develop a simple method traceable to the NIST standard reference material 3950 for simultaneous detection of PLP and PA.

Design & methods

A one-step reverse phase HPLC method with fluorescence detection was developed by evaluating different derivatization conditions, the use of an internal standard and different calibration strategies. The assay analytical performance was evaluated.

Results

Pre-column derivatization with semicarbazide showed the best overall performance in terms of signal to noise ratio, retention time and peak shape when compared to pre- or post-column derivatization with chlorite, pre-column or in-mobile phase derivatization using sodium bisulfite. The final method provided an analytical measurement range from 7.8 to 350 ​nmol/L for PLP and 3.3–339 ​nmol/L for PA, total imprecision <15% and <5% for PLP and PA respectively. Calibration against the NIST standard produced measured values within 3% of NIST assigned PLP values. The use of 4-deoxypyridoxine as internal standard did not improve precision or accuracy when compared to calibration using 5-level external standards.

Conclusions

This method combines derivatization and protein precipitation in one step and is traceable to NIST standard reference material 3950. It is simple and reliable for routine evaluation of vitamin B6 nutrition status.

DNA methylation and one-carbon metabolism related nutrients and polymorphisms: analysis after mandatory flour fortification with folic acid

There is a growing research interest in determining whether changes in the global status of DNA methylation are related to the environment, in particular, to one-carbon metabolism. So, our aim was to investigate the effect of dietary methyl-group donor intake (methionine, folate, choline, betaine, vitamins B2, B6 and B12), biomarkers (total folate, unmetabolised folic acid (FA), 5-methyltetrahydrofolate, homocysteine, vitamins B6 and B12 concentrations) and genetic variants (polymorphisms involved in one-carbon metabolism) on global DNA methylation in a population exposed to mandatory flour fortification with FA. A cross-sectional study of health and living conditions was conducted among a representative sample of residents in São Paulo, Brazil. The mean of global DNA methylation was lower in young people than in adults and the elderly (P = 0·049). No differences between genotypes of polymorphism and global DNA methylation mean were identified. We observed that the increase in betaine intake led to an absolute change in percentage of DNA methylation (β = 0·0005, P = 0·024) using multiple regression. Betaine intake alone was associated with an absolute change in percentage of global DNA methylation. The study did not find an association between global DNA methylation and folate status even in a population exposed to mandatory flour fortification with FA.

Chronophin regulates active vitamin B6 levels and transcriptomic features of glioblastoma cell lines cultured under non-adherent, serum-free conditions

BACKGROUND

The phosphatase chronophin (CIN/PDXP) has been shown to be an important regulator of glioma cell migration and invasion. It has two known substrates: p-Ser3-cofilin, the phosphorylated form of the actin binding protein cofilin, and pyridoxal 5'-phosphate, the active form of vitamin B6. Phosphoregulation of cofilin, among other functions, plays an important role in cell migration, whereas active vitamin B6 is a cofactor for more than one hundred enzymatic reactions. The role of CIN has yet only been examined in glioblastoma cell line models derived under serum culture conditions.

RESULTS

We found that CIN is highly expressed in cells cultured under non-adherent, serum-free conditions that are thought to better mimic the in vivo situation. Furthermore, the substrates of CIN, p-Ser3-cofilin and active vitamin B6, were significantly reduced as compared to cell lines cultured in serum-containing medium. To further examine its molecular role we stably knocked down the CIN protein with two different shRNA hairpins in the glioblastoma cell lines NCH421k and NCH644. Both cell lines did not show any significant alterations in proliferation but expression of differentiation markers (such as GFAP or TUBB3) was increased in the knockdown cell lines. In addition, colony formation was significantly impaired in NCH644. Of note, in both cell lines CIN knockdown increased active vitamin B6 levels with vitamin B6 being known to be important for S-adenosylmethionine biosynthesis. Nevertheless, global histone and DNA methylation remained unaltered as was chemoresistance towards temozolomide. To further elucidate the role of phosphocofilin in glioblastoma cells we applied inhibitors for ROCK1/2 and LIMK1/2 to our model. LIMK- and ROCK-inhibitor treatment alone was not toxic for glioblastoma cells. However, it had profound, but antagonistic effects in NCH421k and NCH644 under chemotherapy.

CONCLUSION

In non-adherent glioblastoma cell lines cultured in serum-free medium, chronophin knockdown induces phenotypic changes, e.g. in colony formation and transcription, but these are highly dependent on the cellular background. The same is true for phenotypes observed after treatment with inhibitors for kinases regulating cofilin phosphorylation (ROCKs and LIMKs). Targeting the cofilin phosphorylation pathway might therefore not be a straightforward therapeutic option in glioblastoma.

Circulating concentrations of biomarkers and metabolites related to vitamin status, one-carbon and the kynurenine pathways in US, Nordic, Asian, and Australian populations

Background: Circulating concentrations of biomarkers that are related to vitamin status vary by factors such as diet, fortification, and supplement use. Published biomarker concentrations have also been influenced by the variation across laboratories, which complicates a comparison of results from different studies.Objective: We robustly and comprehensively assessed differences in biomarkers that are related to vitamin status across geographic regions.Design: The trial was a cross-sectional study in which we investigated 38 biomarkers that are related to vitamin status and one-carbon and tryptophan metabolism in serum and plasma from 5314 healthy control subjects representing 20 cohorts recruited from the United States, Nordic countries, Asia, and Australia, participating in the Lung Cancer Cohort Consortium. All samples were analyzed in a centralized laboratory.Results: Circulating concentrations of riboflavin, pyridoxal 5'-phosphate, folate, vitamin B-12, all-trans retinol, 25-hydroxyvitamin D, and α-tocopherol as well as combined vitamin scores that were based on these nutrients showed that the general B-vitamin concentration was highest in the United States and that the B vitamins and lipid soluble vitamins were low in Asians. Conversely, circulating concentrations of metabolites that are inversely related to B vitamins involved in the one-carbon and kynurenine pathways were high in Asians. The high B-vitamin concentration in the United States appears to be driven mainly by multivitamin-supplement users.Conclusions: The observed differences likely reflect the variation in intake of vitamins and, in particular, the widespread multivitamin-supplement use in the United States. The results provide valuable information about the differences in biomarker concentrations in populations across continents.

Genetic Variants Involved in One-Carbon Metabolism: Polymorphism Frequencies and Differences in Homocysteine Concentrations in the Folic Acid Fortification Era

Folate and other B vitamins are essential co-factors of one-carbon metabolism, and genetic variants, such as polymorphisms, can alter the metabolism. Furthermore, the adoption of food fortification with folic acid showed a decrease of homocysteine concentration. The aim of this study was to investigate the frequencies of the polymorphisms of enzymes and carrier proteins involved in one-carbon metabolism, and to evaluate homocysteine concentrations in the presence of these genetic variants in a population exposed to mandatory food fortification with folic acid. Using data from a population-based cross-sectional study in São Paulo, Brazil, the study population comprised 750 participants above 12 years of age of both genders. A linear regression model was used to evaluate the homocysteine concentrations according to genetic variants and folate level. The results showed that the minor allelic frequencies were 0.33 for MTHFR (rs1801133), 0.24 for MTHFR (rs1801131), 0.19 for MTR (rs1805087), 0.42 for MTRR (rs1801394), 0.46 for RFC1 (rs1051266), and 0.47 for DHFR (19-bp deletion). The genetic variants of MTHFR 677C>T, MTRR 66A>G and RFC-1 80G>A were different according to race. The homocysteine concentrations increased in the CT and TT compared to CC genotypes of polymorphism MTHFR 677C>T in all populations, and differences between the homocysteine concentrations according to the genotypes of MTHFR 677C>T were observed regardless of folate level.

Suboptimal maternal and cord plasma pyridoxal 5' phosphate concentrations are uncommon in a cohort of Canadian pregnant women and newborn infants

Vitamin B₆ is important in fetal development, but little is known of the vitamin B₆ status of pregnant women and newborns in North America and potential modifying factors. This prospective study determined maternal and cord plasma concentrations of pyridoxal 5' phosphate (PLP; an indicator of vitamin B₆ status) in a convenience sample of 368 Canadian pregnant women and their newborns. The association of maternal intake of vitamin B₆ and fetal genetic variants with cord plasma PLP and homocysteine concentrations was also examined. Dietary and supplemental intakes of vitamin B₆ were assessed in early and mid to late pregnancy. PLP concentrations were measured in maternal plasma in early pregnancy and at delivery, and in cord plasma. Six fetal variants of the MTHFR and CβS genes were assessed for their association with cord plasma PLP and homocysteine concentrations. Geometric mean (95% CI) PLP concentrations were 107 (98, 116) nmol/L in early pregnancy and 58 (53, 62) nmol/L at delivery, respectively, and 296 (275, 319) nmol/L in cord blood (p < .0001). During early pregnancy and at delivery, 3.6% and 5.5% of women had plasma PLP concentrations <20 nmol/L, respectively. Ninety eight percent of the women with supplemental B₆ intake of at least the recommended dietary allowance had PLP concentrations >20 nmol/L. Fetal genetic variants were not associated with cord PLP and homocysteine concentrations. Vitamin B₆ deficiency is uncommon in a cohort of Canadian pregnant women due largely to prevalent vitamin B₆ supplement use.

A novel fully validated LC-MS/MS method for quantification of pyridoxal-5'-phosphate concentrations in samples of human whole blood

Quantification of pyridoxal-5'-phosphate (PLP) in biological samples is challenging due to the presence of endogenous PLP in matrices used for preparation of calibrators and quality control samples (QCs). Hence, we have developed an LC-MS/MS method for accurate and precise measurement of the concentrations of PLP in samples (20μL) of human whole blood that addresses this issue by using a surrogate matrix and minimizing the matrix effect. We used a surrogate matrix comprising 2% bovine serum albumin (BSA) in phosphate buffer saline (PBS) for making calibrators, QCs and the concentrations were adjusted to include the endogenous PLP concentrations in the surrogate matrix according to the method of standard addition. PLP was separated from the other components of the sample matrix using protein precipitation with trichloroacetic acid 10% w/v. After centrifugation, supernatant were injected directly into the LC-MS/MS system. Calibration curves were linear and recovery was >92%. QCs were accurate, precise, stable for four freeze-thaw cycles, and following storage at room temperature for 17h or at -80°C for 3 months. There was no significant matrix effect using 9 different individual human blood samples. Our novel LC-MS/MS method has satisfied all of the criteria specified in the 2012 EMEA guideline on bioanalytical method validation.

Simultaneous Determination of Underivatized Vitamin B1 and B6 in Whole Blood by Reversed Phase Ultra High Performance Liquid Chromatography Tandem Mass Spectrometry

Background

Vitamin B1 (thiamine-diphosphate) and B6 (pyridoxal-5’phosphate) are micronutrients. Analysis of these micronutrients is important to diagnose potential deficiency which often occurs in elderly people due to malnutrition, in severe alcoholism and in gastrointestinal compromise due to bypass surgery or disease. Existing High Performance Liquid Chromatography (HPLC) based methods include the need for derivatization and long analysis time. We developed an Ultra High Performance Liquid Chromatography Tandem Mass spectrometry (UHPLC-MS/MS) assay with internal standards for simultaneous measurement of underivatized thiamine-diphosphate and pyridoxal-5’phosphate without use of ion pairing reagent.

Methods

Whole blood, deproteinized with perchloric acid, containing deuterium labelled internal standards thiamine-diphosphate(thiazole-methyl-D₃) and pyridoxal-5’phosphate(methyl-D₃), was analyzed by UHPLC-MS/MS. The method was validated for imprecision, linearity, recovery and limit of quantification. Alternate (quantitative) method comparisons of the new versus currently used routine HPLC methods were established with Deming regression.

Results

Thiamine-diphosphate and pyridoxal-5’phosphate were measured within 2.5 minutes instrumental run time. Limits of detection were 2.8 nmol/L and 7.8 nmol/L for thiamine-diphosphate and pyridoxal-5’phosphate respectively. Limit of quantification was 9.4 nmol/L for thiamine-diphosphate and 25.9 nmol/L for pyridoxal-5’phosphate. The total imprecision ranged from 3.5–7.7% for thiamine-diphosphate (44–157 nmol/L) and 6.0–10.4% for pyridoxal-5’phosphate (30–130 nmol/L). Extraction recoveries were 101–102% ± 2.5% (thiamine-diphosphate) and 98–100% ± 5% (pyridoxal-5’phosphate). Deming regression yielded slopes of 0.926 and 0.990 in patient samples (n = 282) and national proficiency testing samples (n = 12) respectively, intercepts of +3.5 and +3 for thiamine-diphosphate (n = 282 and n = 12) and slopes of 1.04 and 0.84, intercepts of -2.9 and +20 for pyridoxal-5’phosphate (n = 376 and n = 12).

Conclusion

The described UHPLC-MS/MS method allows simultaneous determination of underivatized thiamine-diphosphate and pyridoxal-5’phosphate in whole blood without intensive sample preparation.

A quantile regression approach can reveal the effect of fruit and vegetable consumption on plasma homocysteine levels

INTRODUCTION

A reduction in homocysteine concentration due to the use of supplemental folic acid is well recognized, although evidence of the same effect for natural folate sources, such as fruits and vegetables (FV), is lacking. The traditional statistical analysis approaches do not provide further information. As an alternative, quantile regression allows for the exploration of the effects of covariates through percentiles of the conditional distribution of the dependent variable.

OBJECTIVE

To investigate how the associations of FV intake with plasma total homocysteine (tHcy) differ through percentiles in the distribution using quantile regression.

MATERIALS AND METHODS

A cross-sectional population-based survey was conducted among 499 residents of Sao Paulo City, Brazil. The participants provided food intake and fasting blood samples. Fruit and vegetable intake was predicted by adjusting for day-to-day variation using a proper measurement error model. We performed a quantile regression to verify the association between tHcy and the predicted FV intake. The predicted values of tHcy for each percentile model were calculated considering an increase of 200 g in the FV intake for each percentile.

RESULTS

The results showed that tHcy was inversely associated with FV intake when assessed by linear regression whereas, the association was different when using quantile regression. The relationship with FV consumption was inverse and significant for almost all percentiles of tHcy. The coefficients increased as the percentile of tHcy increased. A simulated increase of 200 g in the FV intake could decrease the tHcy levels in the overall percentiles, but the higher percentiles of tHcy benefited more.

CONCLUSIONS

This study confirms that the effect of FV intake on lowering the tHcy levels is dependent on the level of tHcy using an innovative statistical approach. From a public health point of view, encouraging people to increase FV intake would benefit people with high levels of tHcy.

Are plasma homocysteine concentrations in Brazilian adolescents influenced by the intake of the main food sources of natural folate?

BACKGROUND

Folate, a B vitamin, has been associated with a reduced concentration of plasma homocysteine (phcy), a marker of cardiovascular disease. The contribution of fruits and vegetables (FV) and other natural folate-rich foods to folate intake and folate status in Brazilian adolescents has hardly been determined.

OBJECTIVES

To investigate the intake of FV and beans and its association with the concentration of phcy in adolescents.

METHODS

This was a cross-sectional population-based study with a complex sample survey, with 198 adolescents who completed two 24-hour dietary recalls, a food frequency questionnaire, and a fasting blood draw. Usual dietary intake estimates were derived applying the Multiple Source Method. Three different generalized linear models with a gamma distribution were developed for each sex to evaluate the relationship between phcy and tertiles of FV intake as well as to evaluate the relationship between phcy and tertiles of FV and bean intake.

RESULTS

No association was found between phcy concentration and FV intake or between phcy and FV and beans. Serum folate and female sex were inversely related to phcy.

CONCLUSION

Phcy was not related to FV or FV and beans; this may be attributable to a low intake of these food groups.

A stable isotope dilution LC-ESI-MS/MS method for the quantification of pyridoxal-5'-phosphate in whole blood

Vitamin B6 is a cofactor in numerous biologic processes that include gluconeogenesis, neurotransmitter synthesis and amino acid metabolism. The aim of this study was to develop a method to measure the concentration of the biologically active form of vitamin B6 (pyridoxal-5'-phosphate, PLP) in whole blood with stable isotope dilution LC-ESI-MS/MS and compare this new procedure with an established HPLC method based on derivatization of pyridoxal-5'-phosphate. 50 μl of stable isotope (PLP-d3) was added to 250 μl of sample, followed by deproteinization with 10% trichloroacetic acid. After centrifugation, 20 μl of the supernatant was injected into the LC-ESI-MS/MS. Reversed phase chromatography was performed on a UPLC system, using a Waters™ Symmetry C18 column, with a gradient of 0.1% formic acid in methanol. PLP was measured on a tandem MS with a mass transition of 247.8>149.8 in the positive ion mode with a collision energy of 14 eV. The chromatographic run lasted 4 min. The method was linear from 4 to 8000 nmol/l. The intra-day and inter-day precision ranged between 1.7-2.8% and 3.0-4.1%, respectively. The mean absolute matrix-effect was 99.3% [97-102%]. The relative matrix-effect was 98.8%. The mean recovery was 98% [89-103%]. The lower limit of quantification was 4 nmol/l. The comparison of the LC-ESI-MS/MS method with our current HPLC method yielded the following equation: LC-ESI-MS/MS=1.11 [confidence interval, CI: 1.03-1.20] × HPLC+4.6 [CI: -1.3 to 11.0] (r²=0.94). This LC-ESI-MS/MS based method is characterized by simple sample processing and a short run time. The comparison with the current HPLC method is excellent although a significant proportional bias was detected. To conclude, the LC-ESI-MS/MS method is an appropriate method to determine PLP in whole blood.

Indicators and methods for folate, vitamin B-12, and vitamin B-6 status assessment in humans

PURPOSE OF REVIEW

Nutritional status assessment is a critical tool for the identification of nutrient deficiencies or excesses in individual healthcare and epidemiologic screening. Because low but 'normal' status of folate, vitamin B-12, and vitamin B-6 have been associated with an increased risk of chronic diseases, research has focused on defining sensitive indicators of B-vitamin status and on the development and validation of analytical methods for their quantification.

RECENT FINDINGS

With the increasing availability and more user-friendly configuration of liquid chromatograph-tandem mass spectrometers (LC-MS/MS), numerous analytical methods for determination of B-vitamin indicators by LC-MS/MS have been developed over the last years. These methods include folate assays for simultaneous determination of numerous folate forms at their specific reduction level. The functional indicators for vitamin B-12 status are plasma methylmalonic acid and total homocysteine and can be measured, either individually or in combination, by high-throughput analysis using LC-MS/MS. Methods for vitamin B-6 status assessment are multianalyte platforms that determine vitamin B-6 forms and functional indicators by the same assay.

SUMMARY

The high sensitivity, selectivity, and specificity of isotope-dilution LC-MS/MS [and gas chromatography-mass spectrometry (GC-MS)] techniques have allowed the development of reference methods and the creation of multianalyte platforms. The additional convenience of automated sample preparation enables high sample throughput and makes those sensitive methods prospective analytical candidates for larger settings including clinical laboratories.

Application of the high-performance liquid chromatography method with coulometric detection for determination of vitamin B(6) in human plasma and serum

A reversed-phase high-performance liquid chromatography method (HPLC) with coulometric electrochemical detection has been developed and validated for the simultaneous analysis of pyridoxamine-5'-phosphate (PMP), pyridoxamine (PM), pyridoxal 5'-phosphate (PLP), pyridoxal (PL), pyridoxine (PN) and 4-pyridoxic acid (4-PA) in human plasma and serum. The isocratic separation was achieved on C(18) column (250mmx4.6mm, I.D., 5microm) with a mobile phase consisted of 35mM sodium phosphate containing 2.5mM heptanesulfonic acid, adjusted to pH 3.2 with 85% orthophosphoric acid and 12% methanol (v/v). Within-run and between-run precisions expressed by the relative standard deviations were less than 2.7% and 7.7% for all the analysed vitamins and 4-PA, respectively. The limits of detection (LOD) and quantification (LOQ) were: 0.8 and 2.6nM, 1.1 and 3.8nM, 1.5 and 4.5nM, 1.3 and 4.2nM, 1.1 and 3.7nM, 2.1 and 6.3nM for PMP, PM, PLP, PL, PN and 4-PA, respectively. The recoveries ranged from 90.4% to 98.4%. Stability of vitamins was checked under a variety of storage conditions. The developed application demonstrated acceptable sensitivity, precision, accuracy, stability, and linearity over the physiological concentration range. The major advantage of the proposed method is its great simplicity.

Nonradioactive enzymatic assay for plasma and serum vitamin B(6)

Pyridoxal-5'-phosphate (PLP) is the biologically active form of vitamin B(6). Clinical studies suggest that low PLP concentrations are an independent risk factor for cardiovascular and other diseases. However, PLP concentrations are not routinely used for diagnosis because of the lack of a homogeneous, nonradioactive assay. We describe a homogeneous, nonradioactive, enzymatic PLP assay that uses the apo form of the recombinant PLP-dependent enzyme, homocysteine-alpha,gamma-lyase (rHCYase). The restoration of enzymatic activity by reconstitution of the holoenzyme is linearly dependant on the amount of PLP bound to the enzyme. Nanomolar concentrations of PLP can then be measured by the conversion (by reconstituted holo-rHCYase) of millimolar concentrations of homocysteine (HCY) to H(2)S. H(2)S combines with DBPDA (N,N-dibutylphenylenediamine) to form 3,7-Bis(dibutylamino)-phenothiazine-5'-ium chloride and the absorbance of this compound is read at 675 nm. The PLP enzymatic assay has a lower limit of detection of 14.8 nmol l(-1) and is linear to 300 nmol l(-1) and requires only 10 microl plasma or serum. This PLP assay is the first homogeneous, nonradioactive method for diagnosing vitamin B(6). The procedure takes approximately 2 h to complete.

Pyridoxal-5'-phosphate deficiency after intestinal and multivisceral transplantation

BACKGROUND

Successful intestinal transplantation is measured by the achievement of clinical nutritional autonomy (CNA). However, the ability of the graft to maintain normal micronutrient levels including vitamins has yet to be thoroughly evaluated.

OBJECTIVE

After an initial clinical observation of isolated cases of pyridoxal-5'-phosphate (PLP) deficiency, this prospective study was designed to address the incidence of, risk factors for, and management of PLP deficiency in adult intestinal transplant recipients.

DESIGN

Serum PLP and homocysteine concentrations were prospectively measured before and after transplantation at frequent intervals.

RESULTS

PLP deficiency occurred in 10% of candidates and in 96% of recipients within a median onset of 30 d (range: 4-118 d) after transplantation. Of this group, 41% were receiving parenteral nutrition (PN), 41% were receiving enteral feeding, and the remaining 18% had already achieved CNA. The overall cumulative risk was 24% at 15 d, 59% at 30 d, 79% at 45 d, and 90% at 90 d; none of the risk factors, including homocysteine concentrations, were significant. Nonetheless, the development of PLP deficiency during PN therapy was associated with a significant (P < 0.001) delay in the achievement of CNA. Despite development of severe deficiency in most cases, none of the subjects experienced clinical manifestations of PLP deficiency because of prompt replacement therapy.

CONCLUSIONS

Serial monitoring of serum PLP concentrations is recommended for PN-dependent patients with short-bowel syndrome before and after transplantation for early detection and prompt initiation of preemptive therapy. Long-term measurement at frequent intervals is also recommended, particularly for transplant recipients, to diagnose late deficiency despite achievement of CNA and to prevent toxicity from overdose.

Vitamin status in morbidly obese patients: a cross-sectional study

BACKGROUND

Morbid obesity is associated with low circulating concentrations of 25-hydroxyvitamin D. Few data on the concentrations of other vitamins in morbidly obese patients are available.

OBJECTIVE

The objective was to compare serum and blood vitamin concentrations in morbidly obese patients with those in healthy subjects.

DESIGN

In 2 public hospital departments (southeast Norway), we prospectively examined 110 consecutive patients (76 women) and 58 healthy controls (30 women) not taking multivitamin supplements. Patients and controls did not differ significantly in age or ethnicity. The mean (+/-SD) body mass index (in kg/m(2)) was 45 +/- 7 in the patients and was 24 +/- 3 in the controls. Patients with vitamin concentrations lower than 2 SD below the sex-specific mean in controls were considered to have inadequate vitamin status.

RESULTS

The morbidly obese women and men had significantly lower concentrations of vitamin B-6, vitamin C, 25-hydroxyvitamin D, and lipid-standardized vitamin E than did the healthy controls (P < 0.01 for each). The status of these vitamins was inadequate in a substantial proportion of the patients (11-38%). The status of vitamins A, B-1, B-2, and B-12 and of folic acid was adequate in most of the patients (95-100%). A moderately elevated C-reactive protein concentration was associated with lower vitamin A, B-6, and C concentrations. In a multiple regression analysis, concentrations of alkaline phosphatase (inverse relation) and vitamin C were the strongest determinants of serum vitamin B-6 concentrations.

CONCLUSIONS

Low concentrations of vitamin B-6, vitamin C, 25-hydroxyvitamin D, and vitamin E adjusted for lipids are prevalent in morbidly obese Norwegian patients seeking weight-loss treatment.