Effects of vitamin D3 metabolites in ovariectomized rats

The effects of two vitamin D3 metabolites, 24R,25-dihydroxyvitamin D3 and 1 alpha,25-dihydroxyvitamin D3, were investigated in ovariectomized rats. The amount of ash in the femur on a defatted dry weight basis was significantly greater in rats treated with 1 microgram/kg 24R,25-dihydroxyvitamin D3, or 0.01 or 0.1 microgram/kg 1 alpha,25-dihydroxyvitamin D3 than in the controls. The concentration of bone gla protein in serum and amounts in the femur were significantly greater in rats treated with 1 or 10 micrograms/kg 24R,25-dihydroxyvitamin D3, but not those given 1 alpha,25-dihydroxyvitamin D3 compared with the controls. These results suggest that 24R,25-dihydroxyvitamin D3 increased bone mass probably through the stimulation of bone formation.     

Plasma vitamin D metabolites in a patient with sporadic hypophosphataemic osteomalacia (adult-onset type)

Sporadic hypophosphataemic osteomalacia (adult-onset type) was demonstrated in a 40-year-old man on the basis of severe osteomalacia, hypophosphataemia, hyperphosphaturia and glycinuria. Plasma immunoreactive parathyroid hormone (iPTH) concentration was 9.3 ng prot./ml (normal range: 4-8 ng prot./ml). Plasma 25-hydroxy-vitamin D and 24,25-dihydroxy-vitamin D concentrations were 11 and 2.4 ng/ml respectively. Basal 1 alpha,25-dihydroxy-vitamin D concentrations were slightly elevated (116 and 96 pg/ml) and increased to 240 pg/ml after 3 days on a low-phosphorus diet. The patient was put on oral treatment with 25-hydroxycholecalciferol (100 microgram per day) and phosphorus (1500 mg per day). On the 4th month on treatment, a clinical improvement was apparent. Plasma 25(OH)D was 44 ng/ml, plasma 1,25(OH)2D was 256 pg/ml. However, plasma phosphorus remained low (0.77 mmol/l). On the 9th month of treatment a radiological improvement was evident despite a persistent hypophosphataemia (0.68 mmol/l). These facts suggest in our patient the existence of a vitamin D-independent renal phosphorus leak.     

Effects of pravastatin and cholestyramine on circulating levels of parathyroid hormone and vitamin D metabolites

The subjects were 40 hypercholesterolemic patients (mean age, 58 years) receiving a low-fat diet and randomly assigned to treatment with placebo for eight weeks or 40 or 80 mg of pravastatin, 24 gm of cholestyramine, or 40 mg of pravastatin plus 24 gm of cholestyramine daily for 24 weeks. After eight weeks of active treatment, levels of total and low-density lipoprotein cholesterol were significantly reduced and the decline was maintained for the remaining 16 weeks. Parathyroid hormone levels and levels of the vitamin D metabolites 1,25(OH)2D3 and 25(OH)D3 did not change during treatment. The results indicate that 24 weeks of treatment with pravastatin and cholestyramine does not affect calcium metabolism.     

Purification of plasma vitamin D metabolites for radioimmunoassay

The ability of four solvent systems to extract tritiated 25-hydroxy vitamin D₃, 24,25-dihydroxy vitamin D₃, 25,26-dihydroxy vitamin D₃ and 1α,25-dihydroxy vitamin D₃ from plasma was compared. Diethyl ether gave the highest yield of metabolites and lowest yield of “lipid” materials, the dihydroxylated metabolites were more readily extracted than 25-hydroxy vitamin D₃. Following extraction with ether the vitamin D metabolites could be separated, without prior purification, on a 6.2 mm × 250 mm Zorbax-Sil high pressure liquid chromatography (HPLC) column, a simplification of previous methods. Plasma 1α,25-dihydroxy vitamin D levels measured after purification by this method were not significantly different from those obtained by an established, more complex method.     

Serum vitamin D metabolites in normal subjects after phototherapy

The serum concentrations of the major vitamin D metabolites (25-hydroxyvitamin D(2 + 3) (25-OH-D), 1,25-dihydroxyvitamin D(2 + 3) (1,25-(OH)2-D), and 24,25-dihydroxyvitamin D(2 + 3) (24,25-(OH)2-D) were studied in 22 healthy male volunteers before and after one or two treatments with whole body UVB or PUVA in conventional doses. The effect of UVB was investigated in the autumn and early spring, whereas the effect of PUVA was investigated only in the autumn. The pre-treatment values of two metabolites were significantly reduced in the spring compared to the autumn level (25-OH-D: 14.0 ng/ml versus 22.0 ng/ml, P less than 0.02; and 24,25-(OH)2-D: 1.23 ng/ml versus 2.74 ng/ml, P less than 0.01), whereas the serum concentration of 1,25-(OH)2-D was not significantly reduced in the spring. After UVB, a small, but not significant, rise in all metabolites was observed in the spring, whereas virtually no changes were measured after UVB or PUVA in the autumn. We conclude that UVB and PUVA do not lead to harmful concentrations of vitamin D metabolites in the blood of healthy subjects.     

Plasma leptin levels in rats with pancreatitis

Diagnosis of pancreatitis is based on the determination of serum amylase and lipase levels. However, recent identification of specific leptin receptors in the pancreas suggests that this peptide may also play some roles in the modulation of pancreatic function. The objective of the present study was to investigate the relationship between serum leptin levels and pancreatitis. Thirty male Wistar rats were divided into 3 groups: the control group, acute pancreatitis group and chronic pancreatitis group. Pancreatitis was induced by injection of ethyl alcohol into the common biliary duct. A sham laparotomy was performed in the control group. Control and acute pancreatitis groups were sacrificed 24 hours later, and chronic pancreatitis group was sacrificed on postoperative day 7. Blood was taken by cardiac puncture for the determination of plasma leptin levels, and the pancreatic tissue was excised for histopathologic confirmation of pancreatitis. Plasma leptin rose significantly from the median of 0.78 +/- 0.12 ng/ml in the control group to 1.92 +/- 0.10 ng/ml and 1.86 +/- 0.13 ng/ml in acute and chronic pancreatitis groups, respectively (p < 0.001, for both). There was no significant difference in the plasma leptin levels between the acute pancreatitis group and the chronic pancreatitis group (p > 0.05). These findings confirm that leptin has a role in pancreas inflammation, and the inflamed tissue can be the source of local production of leptin.     

The clinical significance of vitamin D levels and vitamin D receptor mRNA expression in colorectal neoplasms

Background/AimThis study aimed to investigate the clinical significance of changes in vitamin D [25(OH)D] levels and vitamin D receptor (VDR) mRNA expression in colorectal adenoma development.MethodsPlasma concentrations of 25(OH)D and mRNA expression of VDR in tissues were determined by enzyme‐linked immunosorbent assay (ELISA) and real‐time fluorescence quantitative polymerase chain reaction (RT‐qPCR), respectively. In addition, the concentration of plasma 25(OH)D and levels of VDR mRNA in tissues were compared among healthy individuals and adenoma and adenocarcinoma patients.ResultsVitamin D receptor expression in colorectal adenocarcinoma tissues was significantly lower than that in para‐cancerous tissues that were >5 cm away from malignant tumor sites (p < 0.01). The level of VDR expression in normal colorectal tissues from healthy individuals was significantly higher than that in colorectal adenomas (p < 0.01) and colorectal adenocarcinomas (p < 0.01); however, the VDR expression was not significantly different between colorectal adenomas and colorectal adenocarcinomas (p = 0.106). The concentration of 25(OH)D in healthy individuals was significantly higher than that in patients with colorectal adenomas (p < 0.01) and colorectal adenocarcinomas (p < 0.01); however, the concentration of 25(OH)D was not significantly different between colorectal adenomas and colorectal adenocarcinomas (p = 0.489). A low concentration of 25(OH)D was considered a risk factor for colorectal adenoma and colorectal adenocarcinoma, with odds ratios of 4.875 and 2.925, respectively.ConclusionsThe 25(OH)D levels and VDR mRNA expression might be associated with the development of colorectal adenoma and its progression to adenocarcinoma.     

The effect of the dihydroxylated metabolites of vitamin D and dietary phosphate restriction on bone disease in uraemic rats

Uraemic rats maintained on either a high or a low phosphate diet for 12 weeks were allocated to one of the following oral vitamin D treatment groups and received: 1,25-dihydroxycholecalciferol [1, 25-(OH)2D3], 24,25-dihydroxycholecalciferol [24,25-(OH)2D3], both 1,25-(OH)2D3 and 24,25-(OH)2D3, or no vitamin D supplements. Mean serum creatinine concentrations were elevated to a similar extent in all groups. Mean serum concentrations of calcium, phosphate and alkaline phosphatase were not significantly different from normal in any of the groups. In the group receiving the high phosphate diet and no vitamin D supplements, calcified bone area measured by quantitative computerized histomorphometry was significantly lower than in the group receiving the low phosphate diet and no vitamin D supplements (0.01 greater than P greater than 0.001), and in the groups receiving high phosphate diet and either 1,25-(OH)2D3 (0.01 greater than P greater than 0.001) or 24,25-(OH)2D3 (0.01 greater than P greater than 0.001). We conclude that uraemic rats maintained on a high phosphate diet for 12 weeks develop skeletal demineralization, this process does not occur in rats on a low phosphate diet, and a decrease in calcified bone area may be prevented by treatment with either 1,25-(OH)2D3 or 24,25-(OH)2D3.     

Plasma vitamin D-binding globulin in vitamin D deficiency, pregnancy and chronic liver disease.

Plasma concentrations of vitamin D-binding globulin were measured by radial immunodiffusion in healthy subjects, pregnancy, and during oestrogen therapy. Subjects with disorders of vitamin D metabolism (dietary deficiency, malabsorption, anticonvulsant therapy, chronic liver disease) were also studied. Neither sex nor age influenced the plasma vitamin D-binding globulin concentration in healthy subjects, but there was a significant increase in concentration during pregnancy and oestrogen therapy. Elevated levels were found in vitamin D deficient elderly but not younger subjects, while levels in subjects with chronic liver disease were significantly reduced. Normal levels of vitamin D-binding globulin were present in hypervitaminosis D and no vitamin D-binding globulin was detected in human milk. No correlation was observed between plasma 25-hydroxycholecalciferol levels and plasma vitamin D-binding globulin concentrations.     

Progress of liquid chromatography-mass spectrometry in measurement of vitamin D metabolites and analogues

Objective

Clinical testing for vitamin D nutritional status has experienced tremendous growth in the past several years, driven by research results linking various diseases with low serum 25-hydroxyvitamin D [25(OH)D] levels. Meanwhile, interest in the pathophysiological mechanism elucidation and pharmaceutical applications requires measurement of vitamin D metabolites and analogues. Liquid chromatography-mass spectrometry (LC-MS) has been increasingly utilized in these applications. In this work, our objective was to critically review the progress of LC-MS application in measuring vitamin D metabolites and analogues in biological fluids.

Methods

The LC-MS methods included were selected from those searchable in PubMed up to January 2010.

Results and Conclusion

LC-MS has unique advantages in measuring various vitamin D metabolites and analogues due to its flexibility, sensitivity, and specificity. Despite some controversies over serum 25(OH)D tests, LC-MS will be used for standardizing serum 25(OH)D assays using reference materials available from the National Institute of Standards and Technology.     

The effect of vitamin D and its metabolites on fracture repair in chicks

One-day-old chicks were depleted of vitamin D. At 3 weeks their right tibiae, and those of a control group given vitamin D3, were fractured and pinned. After fracture the controls were kept on vitamin D3. Another group was left vitamin D-deficient. The remaining depleted chicks, divided into four groups, were given vitamin D3, 24,25-dihydroxyvitamin D3 [24,25(OH)2D3], 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] or a combination of 24,25(OH)2D3 and 1,25(OH)2D3. The callus obtained after 9 and 14 days was subjected to torsional stress. The callus of chicks given vitamin D continuously showed the greatest resistance, whereas that of vitamin D-deficient chicks showed the smallest resistance. Repletion with either vitamin D3 or its metabolites increased the strength of the callus. Repletion with the combination of 24,25(OH)2D3 and 1,25(OH)2D3 produced the most marked results, in that the callus was even stronger than that of chicks replete with vitamin D3. It is concluded that 24,25(OH)2D3 is essential for bone formation in addition to the known active vitamin D metabolite 1,25(OH)2D3, and the possible clinical implications of these findings are discussed.