Low-dose prednisone therapy in rheumatoid arthritis: effect on vitamin D metabolism.
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24,25-Dihydroxyvitamin D 3↗
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Positive association between serum 25-hydroxyvitamin D level and bone density in osteoarthritis.
OBJECTIVE: To describe the association between serum 25-hydroxyvitamin D (25[OH]D) level and bone mineral density (BMD) in persons with primary knee osteoarthritis (OA). METHODS: We conducted a population-based survey of the Framingham Study. A total of 228 subjects with primary radiographic knee OA were identified. For vitamin D status, 25(OH)D levels < or =15 ng/ml were classified as vitamin D deficient, 25(OH)D levels 16-32 ng/ml were classified as hypovitaminosis D, and 25(OH)D levels >32 ng/ml were classified as vitamin D replete. We compared average BMD between categories of 25(OH)D levels in subjects with OA using a linear regression model while adjusting for sex, age, body mass index (BMI), knee pain, physical activity, cohort, and disease severity. RESULTS: Mean age was 74.4 years and 36% were men. Of 228 individuals, 15% were vitamin D deficient, 51% had hypovitaminosis D, and 34% were vitamin D replete. Compared with subjects with vitamin D deficiency, those with hypovitaminosis D had a 7.3% higher BMD (adjusted percent difference; P = 0.02) and vitamin D replete subjects had an 8.5% higher BMD (adjusted percent difference; P = 0.02; test for trend across categories: P = 0.04). CONCLUSION: We observed a significant positive association between serum 25(OH)D and BMD in individuals with primary knee OA, independent of sex, age, BMI, knee pain, physical activity, and disease severity. Given the high prevalence of low 25(OH)D status in persons with knee OA and the positive association between 25(OH)D and BMD, vitamin D supplementation may enhance BMD in individuals with OA.
Adult↗
Absorption of a pharmacological dose of vitamin D3 from two different lipid vehicles in man: comparison of peanut oil and a medium chain triglyceride.
The absorption of a pharmacological dose of vitamin D3 from two different lipid vehicles, peanut oil, containing long chain fatty acids, and a medium chain triglyceride was compared. Serial measurements of the serum concentration of vitamin D3 after dosage were made. The serum levels of 25-hydroxyvitamin D3, the major circulating vitamin D3 metabolite, were also determined. The analytical methods used were based on HPLC. In the fasting state, the serum levels of vitamin D3 were significantly higher after administration in peanut oil than after administration in the medium chain triglyceride. When the vitamin D3 dose was ingested together with food no difference between the two formulations was observed. Only small inter-formulation differences in serum 25-hydroxyvitamin D3 levels were detected. The results indicate that the presence of long chain fatty acids facilitates the absorption of vitamin D3.
Adult↗
Routine clinical determination of carotene, vitamin E, vitamin A, 25-hydroxy vitamin D3 and trans-vitamin K1 in human serum by straight phase HPLC.
A universal extraction procedure is described for fat-soluble vitamins in human serum. Methods are presented for routine quantitative analysis by isocratic straight phase HPLC with UV-detection of (alpha + beta)-carotene, vitamin E (alpha-tocopherol) and vitamin A (all-trans-retinol) in one single run, and of vitamin K1 (trans-phylloquinone) and 25-hydroxy vitamin D3 after sample clean-up using disposable reversed-phase cartridges. The limits of detection, precisions and selectivities of the developed assays are shown to be satisfactory after more than three years' experience. The routine clinical determination of fat-soluble vitamins can be performed in less than 5 mL of serum. Analyses of external quality control and randomly taken outpatient samples are shown to be of great value in assessing laboratory performance.
Calcifediol↗
Analysis of vitamin D and its metabolites using thermospray liquid chromatography/mass spectrometry.
A new method is described for the analysis of vitamin D and its metabolites utilizing thermospray (TSP) mass spectrometry as an on-line detector for high performance liquid chromatography. Ionization conditions were optimized for use with isocratic reversed phase chromatography. TSP mass spectrometry was employed in series with a UV absorbance detector to facilitate comparisons between the two methods of detection. Positive ion TSP mass spectra were recorded for vitamin D2, vitamin D3, 25-hydroxyvitamin D3 (25(OH)D3), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3). The spectra contained protonated molecular ions, ammonium adduct ions and fragment ions due to the loss of one or more molecules of water. A comparison of quantitative precision was made by determining UV absorbance and TSP standard curves for vitamin D3 using two different methods: (1) External standard method with post-column (post UV detector) addition of ammonium acetate. (2) As (1) but using the method of internal standards with a closely eluting internal standard (vitamin D2). In each case the quantitative precision (correlation coefficient) for UV absorbance detection was superior owing to intrinsic instability of the TSP ion beam. A stable isotopically labelled internal standard was employed in the development of an assay for 1,25(OH)2D3. The assay was used to quantify in vitro enzymic conversion of 25(OH)D3 to 1,25(OH)2D3 in guinea pig and sheep renal mitochondrial incubations. TSP LC/MS was also applied to analysis of an extract of human blood plasma in which D3 and each of its principal metabolites were identified in a single analysis.
24,25-Dihydroxyvitamin D 3↗
Quantitative determination of 25-hydroxyvitamin D3 3-sulphate in human plasma using high performance liquid chromatography.
The quantitative determination of 25-hydroxyvitamin D3 3-sulphate in human plasma was completed using reversed phase high performance liquid chromatography with UV detection (265 nm) and an internal standard method. The vitamin D sulphate fraction was obtained from a plasma specimen with the combined use of a Bond Elut C18 cartridge for solid-phase extraction and a piperidinohydroxypropyl Sephadex LH-20 column for lipophilic ion-exchange chromatography. Separation of the compounds was performed on a YMC-Pack ODS-AM column. The limit of quantitation was 5 ng/mL and the assay was linear from 5 to 50 ng/mL. The proposed method is satisfactory in its accuracy and precision.
Calcifediol↗
Quantification and kinetics of 25-hydroxyvitamin D3 by isotope dilution liquid chromatography/thermospray mass spectrometry.
A liquid chromatography/thermospray mass spectrometry method has been developed and used to measure the plasma levels and half-life of 25-hydroxyvitamin D3 in adults. The mean plasma levels of 25-hydroxyvitamin D3 averaged 40 ng ml-1 (n = 4) in summer and 30 ng ml-1 (n = 6) in winter. The method was also used to determine the half-life of serum 25-hydroxyvitamin D3 in subjects maintained on either high or low-fiber diets who had been given an intravenous infusion of (6,19,19-2H3)25-hydroxyvitamin D3 sufficient to label 5% of their estimated body pools. The half-life was determined to be 10.4 days (n = 4), which is approximately 50% of the currently accepted value of 19 days, determined using radiolabeled methods. This difference may be due to kinetic isotope effects arising as a result of the tritiated compounds being labeled at sites that undergo Cyt-P450-catalyzed oxidations.
Adult↗
Calciotropic hormones raise the chemically detectable [Pi] in UMR 106-06 osteoblast-like cells.
Uptake of orthophosphate (Pi) by osteoblast-like cells is known to be stimulated by parathyroid hormone (PTH), but effects on intracellular [Pi] have not been investigated. Here we show in rat osteoblast-like cells (UMR 106-06) that PTH (10(-11) to 10(-7) M) increases both 32Pi uptake and cellular [Pi] by up to 50 per cent. 1,25 Dihydroxyvitamin D3 (1,25D) (10(-12) to 10(-6) M) and salmon calcitonin (CT) (10(-12) to 10(-6) g ml-1) also increased cellular [Pi] (by up to 60 per cent), but the percentage increases in total cellular 32Pi uptake were smaller. The effects of 1,25D were transient (observable at 80 min and 6 h but not 24 h), and were also observed with 24,25 dihydroxy- and 25 hydroxyvitamin D3. Transient degradation of organic phosphorus pools to Pi might contribute to this increased [Pi]. These pools remain to be identified but were not shown to be phospholipids. Foetal bovine serum also affected cellular [Pi]. Care is therefore needed in distinguishing direct hormonal effects on cellular [Pi] from indirect effects arising from changes in the rate of cell growth.
24,25-Dihydroxyvitamin D 3↗
Comparison of Traditional Chinese Exercise and Equipment-Based Exercise on Glycaemic Control and Vitamin D Levels in Middle-Aged and Elderly Patients With Prediabetes: A Randomised Controlled Trial.
BACKGROUND: Prediabetes is a critical window for preventing progression to type 2 diabetes mellitus (T2DM). Both vitamin D deficiency and physical inactivity are associated with impaired glucose metabolism. This study compared the effects of Traditional Chinese Exercise (TCE) and Kuanle Equipment Exercise (KEE) on glycaemic measures, lipid profiles, body composition and serum 25-hydroxyvitamin D3 [25(OH)D3] in middle-aged and elderly adults with prediabetes. METHODS: We conducted a 12-week, single-centre, randomised controlled trial involving 62 participants with prediabetes (mean age 55.2 ± 8.4 years; 88.7% female). Participants were randomly assigned to control (usual care, n = 21), TCE (n = 20), or KEE (n = 21). Primary outcomes included fasting plasma glucose (FPG), 2-h OGTT glucose, glycated haemoglobin (HbA1c) and serum 25(OH)D3. Secondary outcomes comprised triglycerides, total cholesterol, LDL-C, HDL-C and body composition. RESULTS: At baseline, mean serum 25(OH)D3 was 21.53 ± 3.90 nmol/L. At 12 weeks, both TCE and KEE improved FPG, 2-h OGTT glucose, HbA1c and 25(OH)D3 versus control (all p ≤ 0.001). Relative changes in FPG were -9.4% (TCE) and -15.2% (KEE) versus -1.5% (control); corresponding changes were -14.6% and -21.2% for 2-h OGTT glucose, -6.7% and -12.9% for HbA1c, and +60.6% and +81.9% for 25(OH)D3. Direct TCE-KEE comparisons were not significant (all p > 0.05). In an exploratory analysis, change in 25(OH)D3 was inversely associated with change in 2-h OGTT glucose (partial r = -0.358, p = 0.006), but not with FPG, HbA1c, or triglycerides. CONCLUSIONS: Both TCE and KEE improved glycaemic outcomes and increased serum 25(OH)D3 compared with usual care in middle-aged and elderly adults with prediabetes. Although KEE produced numerically larger estimates, direct between-group comparisons were not significant, and the superiority of KEE over TCE was not established. These vitamin D findings require confirmation in trials that quantify sunlight exposure and dietary vitamin D intake.
Aged↗
Interaction of the vitamin D-binding protein (group-specific component) and its ligand 25-hydroxy-vitamin D3: binding differences of the various genetic types disclosed by isoelectric focusing.
The three common variants of the vitamin D binding protein, also known as group specific component (Gc), namely types 1S, 1F and 2, as well as some rare variants were studied by thin-layer polyacrylamide gel isoelectric focusing in a pH 4.5-5.4 carrier ampholyte generated pH gradient, additionally containing N-(2-acetamido)-2-aminoethanesulfonic acid (ACES). Prior to isoelectric focusing, whole serum or purified preparations of the vitamin D binding protein were incubated with 25-hydroxycholecalciferol at various ligand/protein ratios. Binding differences were found for the anodal and cathodal isoforms of Gc 1 variants and also for various allelic types. Isoforms with higher isoelectric points generally had a lower affinity for the ligand than the variants with lower isoelectric points.
Calcifediol↗
Severe cholestasis leads to vitamin D depletion without perturbing its C-25 hydroxylation in the dog.
The role of the liver as a contributory factor in the vitamin D deficiency of cholestatic liver disease has been studied in vivo in dogs with chronic bile duct ligation, whereas controls underwent diversion of the bile flow through the urinary bladder via a choledococystostomy anastomosis. The hepatic extraction of vitamin D3 was evaluated by the multiple indicator dilution technique, and the formation of 25-hydroxyvitamin D3 was assessed by directly sampling the hepatic effluent for up to 150 min after vitamin D3 administration. The serum and hemodynamic data indicate that dogs with chronic bile duct ligation had severe cholestasis and hepatocellular injury; histologically, macronodular cirrhosis was present. Dogs with choledococystostomy anastomosis had normal livers and normal liver function. The data indicate that the absence of normal bile flow into the intestinal lumen led to a progressive depletion of vitamin D reserve in both animals with choledococystostomy anastomosis and those with chronic bile duct ligation. However, neither the hepatic fractional extraction of vitamin D3, its hepatic clearance nor its transformation into 25-hydroxyvitamin D3 was significantly changed by chronic bile duct ligation. The results of the present studies indicate that the hepatic handling of vitamin D3 including its C-25 hydroxylation, is well preserved in the presence of severe cholestasis. They also suggest that the state of vitamin D depletion which often accompanies chronic cholestatic liver disease can largely be accounted for by factors such as secondary malabsorption of the vitamin due to the absence of adequate amounts of bile salts in the intestinal lumen, or by other factors which seem independent of the hepatic metabolism of vitamin D.
Animals↗
Bone disease in chronic childhood cholestasis. I. Vitamin D absorption and metabolism.
Metabolic bone disease is common in children and adults with chronic cholestasis. We evaluated baseline vitamin D (vitamin D2 and D3), 25-OH vitamin D2 and D3, 1,25(OH)2 vitamin D, vitamin D-binding protein, bone mineral content and dietary mineral content in six children (mean age: 12.1 years) with cholestasis since infancy. Absorption of 25-OH vitamin D3 and vitamin D2 was evaluated by measuring serial serum concentrations after a test dose. Bone mineral content was reduced by greater than 2 S.D. in five of six subjects compared to age-specific controls; none had radiographic evidence of rickets but all had osteopenia. Dietary Ca and P content in the subjects was comparable to the recommended daily allowance for age-specific children. Baseline serum vitamin D2 concentrations were undetectable in all but one cholestatic subject despite oral supplementation with 2,500 to 50,000 IU per day vitamin D2. Baseline serum 25-OH vitamin D was 33.2 +/- 6.0 ng per ml (mean +/- S.E.) and comparable to our laboratory norms (15 to 50 ng per ml). Serum 1,25(OH)2 vitamin D and "free" 1,25(OH)2 vitamin D were both significantly (p less than 0.05) reduced compared to controls. A significantly blunted rise and reduced area under the absorption curve (both p less than 0.001) after 1,000 IU per kg vitamin D2 was found in cholestatic children (0.8 ng +/- 0.5 ng per ml and 18.0 +/- 14.3 ng hr per ml, respectively) compared to controls (59.5 +/- 10.0 ng per ml and 1,780 +/- 253 ng hr per ml, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
25-Hydroxyvitamin D 2↗
In micronodular cirrhosis, hepatocytes retain a normal C-25 hydroxylation capacity toward vitamin D3: a study using the rat carbon tetrachloride-induced cirrhotic model.
To test further the competence of the cirrhotic liver to metabolize vitamin D3 at C-25, hepatocytes were isolated from controls and from CCl4-induced cirrhotic rat livers, as well as from partially hepatectomized rats. The transformation of D3 into 25-hydroxyvitamin D3 was studied in the presence of 10(7) hepatocytes at D3 concentrations of 20 nmol/L to 15.4 mumol/L. Histologically, micronodular cirrhosis was present in all CCl4-treated rats, whereas controls had normal livers; portal venous pressure (p less than 0.008) and intrahepatic collagen content (p less than 0.0001) were significantly increased in CCl4-treated rats, whereas no difference was found between the two groups in the total and ionized serum calcium, D3 metabolites, ALT, AST and alkaline phosphatase. Cytochrome P-450 was 0.27 +/- 0.02 and 0.25 +/- 0.02 nmol/10(6) hepatocytes in controls and cirrhotic rats (N.S.), and it significantly increased in both groups after phenobarbital or 3-methylcholanthrene administration (p less than 0.0001). 25-Hydroxyvitamin D3 formation was best described by power law equations and varied between 0.02 +/- 0.0004 and 29.57 +/- 2.8 in controls, and 0.024 +/- 0.0004 and 32.0 +/- 7.0 pmol.hr-1.10(6) hepatocytes-1 in cirrhotic rats. No statistically significant difference was found in the slopes of the 25-hydroxyvitamin D3 formation, but the y-axis intercept was found to be lower in cirrhotic rats under basal resting conditions (p less than 0.005). Inducers of the mixed function oxidases significantly increased 25-hydroxyvitamin D3 formation in controls as well as in cirrhotic rats (p less than 0.005). Moreover, both groups were found to respond similarly to the addition of modulators of the enzyme such as the calcium ionophore A23187 and parathyroid hormone. Partial hepatectomy was also without effect on the activation of D3. Furthermore, the cell sequestration of D3 was also found to be unperturbed in hepatocytes obtained from either cirrhotic or partially hepatectomized livers. The data indicate that in well-compensated micronodular cirrhosis, the C-25 hydroxylation of D3 is generally intrinsically normal at the cellular level and that it also remains fully responsive to in vivo and in vitro modulators of its activity.
Animals↗
Both high and low levels of blood vitamin D are associated with a higher prostate cancer risk: a longitudinal, nested case-control study in the Nordic countries.
Vitamin D inhibits the development and growth of prostate cancer cells. Epidemiologic results on serum vitamin D levels and prostate cancer risk have, however, been inconsistent. We conducted a longitudinal nested case-control study on Nordic men (Norway, Finland and Sweden) using serum banks of 200,000 samples. We studied serum 25(OH)-vitamin D levels of 622 prostate cancer cases and 1,451 matched controls and found that both low (</=19 nmol/l) and high (>/=80 nmol/l) 25(OH)-vitamin D serum concentrations are associated with higher prostate cancer risk. The normal average serum concentration of 25(OH)-vitamin D (40-60 nmol/l) comprises the lowest risk of prostate cancer. The U-shaped risk of prostate cancer might be due to similar 1,25-dihydroxyvitamin D(3) availability within the prostate: low vitamin D serum concentration apparently leads to a low tissue concentration and to weakened mitotic control of target cells, whereas a high vitamin D level might lead to vitamin D resistance through increased inactivation by enhanced expression of 24-hydroxylase. It is recommended that vitamin D deficiency be supplemented, but too high vitamin D serum level might also enhance cancer development.
Adult↗
Role of 24-hydroxylase in vitamin D3 growth response of OVCAR-3 ovarian cancer cells.
Vitamin D and its analogues are potent regulators of cell growth and differentiation both in vivo and in vitro. We studied the effects of 25-hydroxyvitamin D(3) [25(OH)D(3)], 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and vitamin D analogue, EB 1089, on the growth of a human ovarian cancer cell line, OVCAR-3. We also studied the expression of vitamin D metabolising enzymes 24-hydroxylase (24OHase) and 1alpha-hydroxylase (1alphaOHase). Our results showed that high concentrations (10 and 100 nM) of 1,25(OH)(2)D(3) inhibited a cell proliferation, whereas low concentration (0.1 nM) stimulated growth of the OVCAR-3 cells. In the concentration range of 10-500 nM a prohormone, 25(OH)D(3), stimulated growth. An amount of 1 nM EB 1089 and 100 nM 1,25(OH)(2)D(3) inhibited growth with an equal magnitude. The expression of 24OHase was strongly induced by 1,25(OH)(2)D(3) and EB 1089 in OVCAR-3 cells, and analysis of vitamin D metabolites showed the functionality of 24OHase. An inhibition of 24OHase activity with a novel 24OHase inhibitor enhanced growth-inhibiting effects of 1,25(OH)(2)D(3) and suppressed the growth stimulation of 100 nM 25(OH)D(3). We also report the expression of a vitamin D activating enzyme, 1alphaOHase, in 7 ovarian cancer cell lines. The production of 1,25(OH)(2)D(3) in OVCAR-3 cells was low, possibly due to an extensive activity of 24OHase or a low 1alphaOHase activity. These results suggest that in ovarian cancer cells vitamin D metabolizing enzymes might play a key role in modulating the growth response to vitamin D. The possible mitogenic effects of vitamin D should be considered when evaluating treatment of ovarian cancer with vitamin D.
25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
Enzyme kinetics hypothesis to explain the U-shaped risk curve for prostate cancer vs. 25-hydroxyvitamin D in nordic countries.
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Calcifediol↗
Rapid high-performance liquid chromatographic method for the estimation of toxicological levels of 25-hydroxycholecalciferol (25-OH D3) in human serum.
A reversed-phase HPLC method for determination of 25-hydroxycholecalciferol (25-OH D3) in serum samples is described. The method involves extraction of 25-OH D3 with hexane, followed by differential resolubilization in acetonitrile. The sample is then applied directly on the C18 bonded phase column of the liquid chromatograph, and developed in a acetonitrile-water solvent system. In the range 12.5-400 ng, a linear relationship was observed between detector response and the amount of 25-OH D3 placed on the column. Also, a very good correlation was observed between the amounts of 25-OH D3 added to serum samples, and the calculated amounts. The method can be used for screening for toxicological levels of 25-OH D3 in patients treated with high doses of vitamin D3.
Calcifediol↗
Characteristics of parathyroid hormone-specific cyclic changes of glucose-6-phosphate dehydrogenase activity in the distal convoluted tubule of the guinea pig.
The effect of parathyroid hormone (PTH) on the time course of glucose-6-phosphate dehydrogenase (G6PD) activity in the distal convoluted tubule of a vitamin D-depleted guinea pig was determined using quantitative cytochemistry. G6PD activity decreased to the stable basal level 5 hrs after the initiation of the kidney segment maintenance cultures. The exposure of the tissues to 1 pg/ml of bovine PTH-(1-84) induced a cyclic change of G6PD activity, whereas neither carboxyl-terminal PTH nor other hormones tested showed such activity. After a 16-min exposure to bovine PTH-(1-84), the peak height of each cycle began to decrease until it disappeared at 34 min. The second exposure to this hormone at 46 min reinduced a similar cyclic change with a similar peak, indicating full viability of the cells. When bovine PTH-(1-84) was incubated with an excess amount of anti-bovine PTH antibody, the PTH-induced G6PD activity was completely abolished. Throughout a 14-min exposure to either human PTH-(1-84), human PTH-(1-34) or bovine PTH-(1-84), similar cyclic changes were observed with the constant peak height regardless of the dose (10(-16)-10(-12) M), although the cycle length shortened progressively as the dose was increased. They were equipotent on a molar basis between the concentrations of 10(-16) and 10(-13) M at 6 min of hormone exposure. The present data demonstrate that the cytochemical bioassay of PTH in a vitamin D-depleted animal is based on a dose-dependent difference in the time course of G6PD activity.
Animals↗