Competitive Protein Binding Assay Research Articles

Assessing vitamin D metabolism- four decades of experience.

One hundred years ago, the role of vitamin D for bone mineralization and the prevention of rickets was discovered. Vitamin D comprises a group of over 50 metabolites with multiple functions that go far beyond calcium homeostasis and bone mineralization. Approximately 50years ago, first methods for the measurement of 25-hydroxyvitamin D (25(OH)D) in human blood were developed. Over the years, different analytical principals were employed including competitive protein binding assays, high-performance liquid chromatography, various immunoassay and mass spectrometric formats. Until the recent standardization of serum 25(OH)D measurement, agreement between methods was unsatisfactory. Since then, comparability has improved, but substantial variability between methods remains. With the advent of liquid chromatography tandem mass spectrometry (LC-MS/MS), the accurate determination of 25(OH)D and other metabolites, such as 24,25(OH)2D, becomes increasingly accessible for clinical laboratories. Easy access to 25(OH)D testing has triggered extensive clinical research showing that large parts of the population are vitamin D deficient. The variable response of vitamin D deficient individuals to supplementation indicates that assessing patients' vitamin D stores by measuring 25(OH)D provides limited insight into the metabolic situation. Meanwhile, first evidence has emerged suggesting that the simultaneous measurement of 25(OH)D, 24,25(OH)2D and other metabolites allows a dynamic evaluation of patients' vitamin D status on metabolic principals. This may help to identify patients with functional vitamin D deficiency from those without. It can be expected that research into the assessment vitamin D status will continue for another 50 years and that this will help rationalizing our approach in clinical practice.

Reduced serum vitamin D levels are associated with poor sleep quality in early stroke patients.

BackgroundPoor sleep quality and vitamin D deficiency are common in stroke patients. Our aim was to evaluate the possible association between vitamin D and sleep quality in acute ischemic stroke (AIS) patients.MethodsA total of 301 AIS patients were screened and completed 1-month follow-up. Serum 25-hydroxyvitamin D [25(OH)D] was used to assess the vitamin D status by a competitive protein-binding assay at baseline. All patients were divided into equal quartile according to the distribution of 25(OH)D. One month after stroke, sleep quality was evaluated by using Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) questionnaire; depression status was confirmed by 17-item Hamilton Depression Scale (HAMD).ResultsThere were 89 (29.6%) AIS patients with poor sleep quality 1-month post-event. Within 24 h after admission, serum 25(OH)D levels were significantly lower in patients with poor sleep quality after stroke (P < 0.001). In the results of multivariate-adjusted logistic regression analysis, the odds ratio (OR) of poor sleep quality was 6.199 (95% CI, 2.066–18.600) for the lowest quartile of 25(OH)D compared with the highest quartile. In patients without depression, reduced 25(OH)D were still significantly associated with poor sleep quality (OR = 8.174, 95% CI = 2.432–27.473). Furthermore, 25(OH)D and HAMD score were combined to enhance the diagnostic accuracy of poor sleep quality, with the area under the receiver operating characteristic curve of 0.775.ConclusionReduced serum levels of vitamin D at admission were independently and significantly associated with poor sleep quality at 1 month after stroke. Our findings suggested the combination of vitamin D and depression status could provide important predictive information for post-stroke sleep quality.

Conjugates of Aminopenicillins with Proteins: Synthesis, Immunogenic Properties, and Binding to the \u03b2-Lactam Receptor and Antibodies

A new approach to aminopenicillin modification and conjugation with proteins was developed using di-N-hydroxysuccinimide esters of dicarboxylic acids as crosslinkers. Acylation of ampicillin (Amp) and amoxicillin (Amox) with di-N-hydroxysuccinimide esters of adipic or terephthalic acids was carried out in an organic solvent. Subsequent conjugation of the resulting aminopenicillin derivatives with proteins was done in an aqueous medium at pH 8.3 to produce immunogenic and enzymatic conjugates of Amp and Amox. The β-lactam cycle of Amp was shown to remain intact after chemical modification and synthesis of linker conjugates. An immunogenic Amp–thyroglobulin conjugate containing an aromatic linker was used for long-term immunization of rabbits, and polyclonal antibodies thus obtained were found to bind Amp, Amox, and penicillin G with extremely high sensitivity. Amp and Amox conjugates with horseradish peroxidase (HRP) were synthesized and characterized in a competitive protein-binding (receptor) assay and a direct competitive enzyme-linked immunosorbent assay (ELISA). Of the model immunoassay systems tested, the best characteristics were observed for heterologous direct ELISA with polyclonal antibodies and the Amp–HRP conjugate that contained an adipic acid fragment as a linker: the Amp sensitivity was 0.03 ng/mL and IC50 = 0.20 ng/mL.

Vitamin D status and obesity in children from Chile

BackgroundVitamin D [25(OH)D] is essential for normal bone development and maintenance. Furthermore, its deficiency has been associated with obesity, cardiovascular diseases, insulin resistance, autoimmune diseases, and certain cancers.ObjectiveTo determine the incidence of serum 25(OH)D deficiency (<20 ng/ml) among apparently healthy Chilean children (4–14 years old) from three Chilean geographic areas during May–September 2018.Materials and methodsSerum 25(OH)D levels were measured by a competitive protein-binding ELISA assay in 1134 children, and correlations between serum 25(OH)D levels, BMI, and geographic area were calculated. Individuals were grouped according to their serum 25-hydroxyvitamin D levels (ng/ml): severe deficiency: <5; moderate deficiency: 5–10.9; mild deficiency: 11–20.9; insufficiency: 21–29.9 and sufficiency: 30–100.ResultsWe found 80.4% of children had serum 25(OH)D deficiency, with 1.7% severe, 24.6% moderate, and 54.1% mild. In the three cities, the percentage of serum 25(OH)D deficit was increased when comparing overweight or obesity with a healthy weight. Additionally, an interaction effect was observed between geographic area, nutritional status, and serum 25(OH)D levels using the factorial ANOVA test (p = 0.038). In Antofagasta, there were more overweight children and also a higher percentage of children with VitD deficiency (<30 ng/ml) compared to Santiago or Concepción.ConclusionThis study revealed a high prevalence of serum 25(OH)D deficiency in children between 4 and 14 years old in Chile (80.4%) during May–September 2018. Obese and overweight children had the highest prevalence of serum 25(OH)D deficiency.

Reference range for 24-h urine calcium, calcium/creatinine ratio, and correlations with calcium absorption and serum vitamin D metabolites in normal women.

Recommendations for a normal range for 24-h urine calcium vary from a low of 50 mg to a high of 400 mg; most "laboratory normal ranges" based on older literature are incorrect. The objective of this analysis is to define a normal range for young women age 25-45 years and older women age 55-90 years, white and black, for 24-h urine calcium and calcium/creatinine ratio, and to examine the relationship between 24-h urine calcium, calcium absorption, and vitamin D metabolites. Data from 3 studies was collected on 959 normal black and white women, ages 25-87 years, for 24-h urine calcium, creatinine, calcium intake, serum 25-hydroxyvitamin D (25OHD),1,25 dihydroxyvitamin D (1,25(OH)2D), and calcium absorption. Urine calcium and creatinine were measured on an auto-analyzer. Calcium absorption was measured by a single isotope method. Serum 25OHD and 1,25(OH)2D were measured by competitive protein binding assay or radioimmunoassay. Because 24-h urine calcium did not fit a normal distribution, non-parametric methods were used to determine the 95% reference interval (RI) and 90% non-parametric confidence intervals (CI) calculated for groups. The 95% reference intervals for 24-h urine calcium for women were as follows: black older 7-225 mg, black younger 8-285 mg; white older 37-275 mg, and white younger 23-287 mg. In older white women, 24-h urine calcium was significantly correlated with serum 1,25(OH)2 D, r = 0.23, p < 0.001, calcium intake r = 0.12, p = 0.001, and calcium absorption r = 0.18, p = 0.003, but not serum 25OHD r = 0.07, p = 0.06. The normal reference interval for 24-h urine calcium for black women is lower than white women. Twenty-four-hour urine calcium was correlated with serum 1,25(OH)2 D calcium intake and calcium absorption, but not serum 25OHD. This range will be useful clinically for defining hypercalciuria and for following patients on vitamin D and calcium treatment.

Efficient synthesis of 3-TBDMS-11α,25-dihydroxyvitamin D3 and D2 ethers

Vitamin D deficiency might cause a wide variety of human disorders. As a prerequisite for appropriate diagnosis and therapy, medicinally relevant vitamin D metabolites have to be assayed most accurately and with high specificity. It has been demonstrated, that vitamin D conjugates, linked via a hydroxyl group at C11, might be promising for the development of highly specific antibodies to be employed in competitive protein binding assays. The connective synthesis of 3-TBDMS-11α,25-dihydroxyvitamin D3 and D2 ethers in 500 mg scale, starting from vitamin D2, is described. For installation of a hydroxyl group at C11 a sequence of Pd(OAc)2 mediated oxidation of an enone, epoxidation and subsequent epoxide ring opening was applied to obtain a suitable CD-ring precursor, that was connected with an A-ring diphenylphosphine oxide by Wittig-Horner reaction. Finally, an appropriate side chain was installed, respectively.

Vitamin B12 concentrations in milk from Norwegian women during the six first months of lactation

BackgroundHuman milk vitamin B12 (B12) concentrations depend on maternal status and intake; only few data are available in high-income countries.ObjectiveWe assessed human milk B12 concentrations during the first 6 months postpartum in Norwegian women and its association with maternal dietary B12 intake and maternal urinary methylmalonic acid (MMA) concentration.MethodsIn this cross-sectional study, 175 mothers, exclusively (80%) or partially (20%) breastfeeding, were included. Milk B12 was measured by IMMULITE®/IMMULITE® 1000 B12 competitive protein binding assay and urinary MMA relative to creatinine (MMA/Cr) by liquid chromatography–tandem-mass spectrometry. Maternal habitual B12 intake and supplement use were estimated using a food frequency questionnaire.ResultsMean human milk B12 concentration was 327 pmol/L (range 140–1089), with 402 pmol/L at 1 month (n = 21), 333 pmol/L at four months (n = 32), and 299 pmol/L at 6 months (n = 21). Maternal B12 intake was 5 µg/d, 89% met the Estimated Average Requirement, and supplement use did not affect milk B12 concentrations. MMA/Cr was low in all women compared with published data. In exclusively breastfeeding women, MMA/Cr (beta (95% CI) −42.5 (−82.5, −2.5) and time since birth (−4.9 (−9.6, −0.3)) were significant predictors of human milk B12 concentrations. There was no association between total B12 intake and milk B12 concentration or between total B12 intake and MMA/Cr.ConclusionsMaternal B12 status and human milk B12 concentrations are likely sufficient, based on adequate maternal B12 dietary intake combined with low urinary MMA concentrations. Nevertheless, milk B12 concentration fell during 6 months postpartum while maternal B12 status did not change.

Association among Vitamin D Deficiency with some Inflammatory Marker in Iraqi Patients with Autoimmune Thyroiditis

Background: Hashimoto thyroiditis (HT) is a common chronic autoimmune disease of the thyroid gland, characterized by painless goiter and elevated thyroid antibodies. Hypovitaminosis D (vitamin D insufficiency and deficiency) is common among patients with HT.Method: : the study include (60) subjects compared with 30 apparently healthy control group were visiting nursing home hospital in Baghdad medical city, Levels of serum thyroid-stimulating hormone (TSH), free-triiodothyronine (FT3), free thyroxine (FT4), TgAbs, and TPOAbs were determined with automated immuno chemiluminescent assay (ICMA) kits (Abbott Laboratories, IL, USA). Levels of serum 25-hydroxyvitamin D 25(OH) D) were determined using a competitive protein-binding assay (Roche Diagnostics, Mannheim, Germany). The inter-assay variation coefficient for 25(OH)D measurement was 8.5%.Results: the level of the study parameters in autoimmune thyroiditis which show significant correlation in age ,BMI, vitamin D, anti TPO antibody,IL-17, TNF-? and thyroid function (p&lt;0.05) (p&lt;0.01) test but calcium shoe non significant correlation between patients and control group.Conclusion: The present work shows a significant association between circulating 25(OH)D and HT, also IL-17.

Competitive Protein Binding Assay of Naproxen by Human Serum Albumin Functionalized Silicon Dioxide Nanoparticles.

We have developed a new competitive protein binding assay (CPBA) based on human serum albumin functionalized silicon dioxide nanoparticles (nano-SiO2-HSA) that can be used for naproxen determination in urine. Compared with a conventional multi-well reaction plate, nano-SiO2 with a high surface-area-to-volume ratio could be introduced as a stationary phase, markedly improving the analytical performance. Nano-SiO2-HSA and horseradish peroxidase-labeled-naproxen (HRP-naproxen) were prepared for the present CPBA method. In this study, a direct competitive binding to nano-SiO2-HSAwas performed between the free naproxen in the sample and HRP-naproxen. Thus, the catalytic color reactions were investigated on an HRP/3,3′5,5′-tetramethylbenzidine (TMB)/H2O2 system by the HRP-naproxen/nano-SiO2-HSA composite for quantitative measurement via an ultraviolet spectrophotometer. A series of validation experiments indicated that our proposed methods can be applied satisfactorily to the determination of naproxen in urine samples. As a proof of principle, the newly developed nano-CPBA method for the quantification of naproxen in urine can be expected to have the advantages of low costs, fast speed, high accuracy, and relatively simple instrument requirements. Our method could be capable of expanding the analytical applications of nanomaterials and of determining other small-molecule compounds from various biological samples.

Fluorescence lateral flow competitive protein binding assay for the assessment of serum folate concentrations.

Folate is a micronutrient required for the production of new cells, making it a key factor in early fetal development and ensuring normal growth and maintenance of health. The increase in consumption of folate due to increased periconceptional supplementation and fortification of grains in many countries has led to a decrease in occurrence of folate deficiency and a class of birth defects called neural tube defects. However, an opportunity remains to further improve folate status of populations in areas with limited access to fortified foods and supplementation. Screening of women of reproductive age and other vulnerable populations for folate status would increase our understanding of the magnitude of the burden of folate deficiency and inform monitoring of public health programs. Current gold standard methods for folate assessment are time-intensive and require cold chain, sophisticated laboratory infrastructure, and highly-trained personnel. Our lateral flow assay is low-cost, easy to use, and allows a user to assess folate insufficiency at the point of care in less than 40 minutes. We evaluated the sensitivity and specificity of our assay in 24 human serum samples, including 8 samples with folate concentrations less than 10.0 nmol/L and 14 samples less than 13.4 nmol/L using the Immulite 2000 commercial assay as a reference standard. The sensitivity and specificity were found to be 93% (95% CI: 54.7–100.0) and 91% (95% CI: 80.0–100.0), respectively, when using our test to determine folate insufficiency based on a cutoff of 13.4 nmol/L. Our point-of-care diagnostic test for folate concentrations could inform screening and public health programs in at-risk populations.

Lower vitamin D levels are associated with depression in patients with gout.

BackgroundDepression is commonly observed among patients with gout. Low levels of vitamin D have been associated with depression in non-gout subjects. We examined the association of vitamin D levels with depression in patients with gout.MethodsWe conducted a cross-sectional study of 186 gout patients at the Endocrinology Department of First Affiliated Hospital of Jiaxing University. Levels of serum 25-hydroxyvi-tamin D (25(OH)D) were determined using a competitive protein-binding assay. The 17-item Hamilton Depression Scale was used for screening for depressive symptoms. Diagnosis of depression in gout patients was made in accordance with Diagnostic and Statistical Manual of Mental Disorders, fifth edition criteria for depression. Multivariate analysis was performed using logistic regression models.ResultsThirty-two gout patients (17.2%) were diagnosed as having depression. Patients with depression showed significantly lower 25(OH)D levels as compared to patients without depression (46.4±19.0 vs 57.0±17.3 nmol/L, P<0.001). Significant differences in 25(OH)D quartiles of gout patients were observed between the patients with depression and the patients without depression (P=0.003). In multivariate analyses, serum 25(OH)D levels (≤40.0 nmol/L) were independently associated with depression in patients with gout (OR 3.833, 95% CI 1.406–10.453, P=0.009).ConclusionOur study demonstrates an important association between serum vitamin D levels and depression in patients with gout.

Low vitamin D levels are associated with cognitive impairment in patients with Hashimoto thyroiditis

BackgroundCognitive impairment is commonly observed in patients with Hashimoto thyroiditis (HT). Low levels of vitamin D have been correlated with cognitive impairment in non-HT population. We examined the association of vitamin D levels with cognitive impairment in patients with HT.MethodsWe recruited 194 patients with HT and 200 healthy volunteers. Levels of serum 25-hydroxyvitamin D (25(OH)D) were measured using a competitive protein-binding assay. Cognitive funtion was assessed using Montreal Cognitive Assessment score (MoCA). Subjects with a MoCA scores < 26 are considered as having mild cognitive impairment (MCI). Multivariate analysis was performed using logistic regression models.ResultsFifty-five HT patients (28.4%) were diagnosed as having MCI. Patients with MCI had significantly lower 25(OH)D levels when compared with patients without MCI (33.9 ± 6.2 vs. 44.3 ± 9.6 nmol/L, P < 0.001). Significant differences in 25(OH)D quartiles of HT patients were observed between the patients with MCI and the patients without MCI (P < 0.001). In multivariate analyses, serum 25(OH)D levels (≤ 34.0 and ≥ 47.1 nmol/L) were significantly associated with cognitive impairment in patients with HT (OR 6.279, 95% CI 2.673–14.834, P < 0.001; OR 0.061, 95% CI 0.008–0.491, P = 0.009, respectively).ConclusionOur results demonstrate an important association between serum vitamin D levels and cognitive impairment in patients with HT.

Micronutrients in Human Milk: Analytical Methods

Exclusive breastfeeding is recommended by the WHO for the first 6 mo of life because human milk protects against gastrointestinal infections and supplies balanced and adequate nutrient contents to the infant. However, reliable data on micronutrient concentrations in human milk are sparse, especially because some micronutrients are affected by maternal diet. Microbiological and competitive protein-binding assays, nuclear magnetic resonance or inductively coupled plasma spectroscopy, and chromatographic analyses are among the methods that have been applied to human-milk micronutrient analysis. However, the validation or evaluation of analytical methods in terms of their suitability for the complex human-milk matrix has been commonly ignored in reports, even though the human-milk matrix differs vastly from blood, plasma, or urine matrixes. Thus, information on the validity, accuracy, and sensitivity of the methods is essential for the estimation of infant and maternal intake requirements to support and maintain adequate milk micronutrient concentrations for healthy infant growth and development. In this review, we summarize current knowledge on methods used for analyzing water- and fat-soluble vitamins as well as iron, copper, zinc, iodine, and selenium in human milk and their different forms in milk; the tools available for quality control and assurance; and guidance for preanalytical considerations. Finally, we recommend preferred methodologic approaches for analysis of specific milk micronutrients.

Low serum levels of vitamin D are associated with anxiety in children and adolescents with dialysis

Anxiety is a frequent and serious complication of children and adolescents receiving dialysis. Low serum vitamin D levels have been associated with anxiety in non-pediatric patients. This study sought to examine the possible association between serum vitamin D levels and the presence of anxiety in children and adolescents with dialysis in China. A total of 156 pediatric patients who were on hemodialysis or peritoneal dialysis and 100 healthy controls were included in the current study. Serum 25-hydroxyvitamin D [25(OH)D] levels were measured by using a competitive protein-binding assay. Anxiety was assessed by using the Chinese version of the Screen for Child Anxiety Related Emotional Disorders (SCARED, = 25 as cutoff). Among 156 patients, 110 had a current anxiety (70.5%) and 46 did not (29.5%). Serum levels of 25(OH)D were significantly lower in patients with anxiety than in normal controls (19.4 ± 10.3 vs. 38.6 ± 15.5 ng/ml, P < 0.001). Serum 25(OH)D levels (≤15.0 ng/ml) were independently associated with the existent of anxiety in children and adolescents receiving dialysis (OR 4.650, 95% CI 1.663–13.001, P = 0.003). Our research demonstrates that low serum levels of vitamin D are independently associated with anxiety among children and adolescents on dialysis, which needs to be confirmed in future experimental and clinical studies.

In Vitro and in Silico Competitive Binding of Brominated Polyphenyl Ether Contaminants with Human and Gull Thyroid Hormone Transport Proteins.

Tetradecabromo-1,4-diphenoxybenzene (TeDB-DiPhOBz) is a highly brominated additive flame retardant (FR). Debrominated photodegradates of TeDB-DiPhOBz are hydroxylated in vitro in liver microsomal assays based on herring gulls (Larus argentatus), including one metabolite identified as 4″-OH-2,2',2″,4-tetrabromo-DiPhOBz. Chemically related methoxylated tetra- to hexabromo-DiPhOBzs are known contaminants in herring gulls. Collectively, nothing is currently known about biological effects of these polybrominated (PB) DiPhOBz-based compounds. The present study investigated the potential thyroidogenicity of 2,2',2″,4-tetrabromo-(TB)-DiPhOBz along with its para-methoxy (MeO)- and hydroxy-(OH)-analogues, using an in vitro competitive protein binding assay with the human thyroid hormone (TH) transport proteins transthyretin (hTTR) and albumin (hALB). This model para-OH-TB-DiPhOBz was found to be capable of competing with thyroxine (T4) for the binding site on hTTR and hALB. In silico analyses were also conducted using a 3D homology model for gull TTR, to predict whether these TB-DiPhOBz-based compounds may also act as ligands for an avian TH transport protein despite evolutionary differences with hTTR. This analysis found all three TB-DiPhOBz analogues to be potential ligands for gull TTR and have similar binding efficacies to THs. Results indicate structure-related differences in binding affinities of these ligands and suggest there is potential for these contaminants to interact with both mammalian and avian thyroid function.

Organophosphate triesters and selected metabolites enhance binding of thyroxine to human transthyretin in vitro

The toxicological properties of organophosphate (OP) triesters that are used as flame retardants and plasticizers are currently not well understood, though increasing evidence suggests they can affect the thyroid system. Perturbation of thyroid hormone (TH) transport is one mechanism of action that may affect thyroid function. The present study applied an in vitro competitive protein binding assay with thyroxine (T4) and human transthyretin (hTTR) transport protein to determine the potential for the OP triesters, TDCIPP (tris(1,3-dichloro-2-propyl) phosphate), TBOEP (tris(butoxyethyl) phosphate), TEP (triethyl phosphate), TPHP (triphenyl phosphate), p-OH-TPHP (para-hydroxy triphenyl phosphate), and the OP diester DPHP (diphenyl phosphate), to competitively displace T4 from hTTR. Enhancement of T4 binding to hTTR, rather than the hypothesized competition, was observed for the six OP esters and in a concentration-dependent manner. For example, T4-hTTR binding was significantly increased at concentrations of TBOEP as low as 64 nM, and up to 184% of controls at 5000 nM. A plausible explanation of these results, which to our knowledge has not been previously reported, may be allosteric interactions of the OP esters with hTTR allowing T4 to access the second site of the TH binding pocket. These in vitro results suggest a novel mechanism of OP ester toxicity via T4 binding enhancement, and possible dysregulation of T4-hTTR interactions.

Low serum 25-hydroxyvitamin D concentrations in chronic insomnia patients and the association with poor treatment outcome at 2 months

BackgroundThe association between low 25-hydroxyvitamin D [25(OH)D] and sleep disorder has been reported. We investigated whether serum concentrations of 25(OH)D are altered in chronic insomnia patients. The relationship between serum concentrations of 25(OH)D and the treatment outcome in patients at 2months was also investigated. MethodsIn total, 181 chronic insomnia patients were consecutively recruited. All patients received pharmacotherapy for the treatment of chronic insomnia. Serum 25(OH)D concentrations were quantified by a competitive electrochemiluminescence protein binding assay. Treatment outcomes were defined as “response” versus “non-response”, according to the change of the Pittsburgh Sleep Quality Index (PSQI). We also recruited 100 healthy subjects as a control group. ResultsFifty-four out of 181 (29.8%) patients met the criteria for non-response. Chronic insomnia patients had significantly lower 25(OH)D concentrations compared with healthy controls (23.01±9.18 vs 27.17±6.41ng/ml, P<0.001). Non-response patients also had significantly lower 25(OH)D concentrations than those with response. Vitamin D deficiency(25(OH)D concentrations<20ng/ml) was independently associated with a higher probability of treatment non-response at 2months (odds ratio 11.636, 95% confidence interval 3.966–34.142, P<0.001). ConclusionsMeasurement of serum 25(OH)D concentrations are probably useful for judging treatment outcomes of pharmacotherapy in chronic insomnia patients.

Vitamin D status in relation to physical performance, falls and fractures in the Longitudinal Aging Study Amsterdam: A reanalysis of previous findings using standardized serum 25-hydroxyvitamin D values

The Longitudinal Aging Study Amsterdam (LASA) is an ongoing prospective cohort study in a representative sample of Dutch older persons. In previous LASA studies, lower serum 25-hydroxyvitamin D (25(OH)D) values, as assessed by a competitive protein binding assay or radioimmunoassay, have been associated with decreased physical functioning, falls and fractures. Recently, serum 25(OHD) values in LASA were standardized using the Vitamin D Standardization Program (VDSP) protocol as part of the European ODIN project. In the current manuscript, the influence of standardizing serum 25(OH)D values will be discussed using the associations with physical functioning, falls and fractures as examples.

Improvement of fatigue after vitamin D supplementation in kidney transplant recipients.

Low serum levels of vitamin D have been associated with fatigue in both healthy and clinical populations. Our aim was to evaluate the effect of vitamin D supplementation on fatigue in kidney transplant recipients (KTRs). In total, 137 patients after kidney transplant and 119 age- and sex-matched healthy volunteers were recruited. Serum levels of 25-hydroxyvitamin D (25(OH)D) were measured by competitive protein-binding assay. Fatigue was assessed using the subscale fatigue of the Checklist Individual Strength (CIS). Of all KTRs, 60 patients without initial vitamin D3 supplementation were started on vitamin D3 supplementation (cholecalciferol) 800 IU/d, with a follow-up examination after 3.0 to 9.0 months (mean, 6 months). Fatigue was found in 40.1% of KTRs. Serum 25(OH)D levels were inversely and independently associated with CIS scores in KTRs (P = .002). In the 60 patients who received vitamin D3 supplementation, 25(OH)D was overall increased at follow-up with 18.5% (P = .004) and CIS scores improved with 10.0% (P = .007). As vitamin D has beneficial effects on fatigue scores in KTRs, we suggest monitoring this parameter in KTRs and supplementation with vitamin D3 when vitamin D levels are low.

Association between Serum Vitamin D Levels and Sleep Disturbance in Hemodialysis Patients.

Sleep disturbance is a frequent and serious complication of hemodialysis (HD). Low serum vitamin D levels have been associated with sleep quality in non-HD subjects. Our aim was to examine the possible association between serum vitamin D levels and the presence of sleep disturbance in HD patients. We recruited 141 HD patients at the HD center of the First Affiliated Hospital of Jiaxing University during 2014–2015. Serum levels of 25-hydroxyvitamin D (25(OH)D) were determined by the competitive protein-binding assay. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI). Demographic, clinical and laboratory data were recorded. Meanwhile, 117 healthy control subjects were also recruited and underwent measurement of 25(OH)D. Eighty-eight patients (62.4%) had sleep disturbance (PSQI scores ≥ 5). Patients with sleep disturbance showed lower levels of 25(OH)D as compared to those without sleep disturbance (85.6 ± 37.4 vs. 39.1 ± 29.1 nmol/L, p < 0.001). In multivariate analyses, serum levels of 25(OH)D (≤48.0 nmol/L) were independently associated with sleep disturbance in HD patients (OR 9.897, 95% CI 3.356–29.187, p < 0.001) after adjustment for possible variables. Our study demonstrates that low serum levels of vitamin D are independently associated with sleep disturbance in HD patients, but the finding needs to be confirmed in future experimental and clinical studies.