Effect of vitamin D2 and vitamin D3 on the serum concentrations of 1,25(OH)2D2, and 1,25(OH)2D3 in normal subjects

Serum concentrations of vitamin D2 and vitamin D3 metabolites were measured in 19 normal subjects before and during treatment with either vitamin D2 or vitamin D3, 4000 IU per day for 8 weeks. Vitamin D2 treatment increased the serum concentration of 1,25(OH)2D2, but a corresponding decrease in 1,25(OH)2D3 resulted in an unchanged serum concentration of total 1,25(OH)2D. During treatment with vitamin D3, the serum concentration of 1,25(OH)2D metabolites was unchanged. We conclude that the production of 1,25(OH)2D is tightly regulated and that 1 alpha-hydroxylase does not discriminate between D2 and D3 metabolites in normal subjects.     

Serum vitamin D2 and vitamin D3 metabolite concentrations and absorption of vitamin D2 in elderly subjects

The serum vitamin D2 and vitamin D3 metabolite concentrations and intestinal absorption of vitamin D2 were determined in healthy ambulatory and chronically institutionalized elderly subjects with normal renal function. The 25-hydroxyvitamin D (25OHD) concentrations were normal in all subjects (range, 8-43 ng/ml), although institutionalized subjects had a significantly lower mean value [19.2 +/- 2 (+/- SEM) ng/ml; P less than 0.01] compared with ambulatory subjects (25.3 +/- 2 ng/ml). All but one ambulatory subject had 25OHD3 as the major circulating form, whereas 25OHD2 was the major circulating metabolite in one third of the institutionalized subjects. The mean 1,25-dihydroxyvitamin D [1,25-(OH)2D] concentration in both groups was normal, but nine subjects had levels at or below the lower limit of normal despite normal 25OHD concentrations. Separate assay of 1,25-(OH)2D2 and 1,25(OH)2D3 revealed proportional distributions similar to those for 25OHD2 and 25OHD3. To study the effect of age on the intestinal absorption of vitamin D, we compared serum vitamin D2 concentrations after oral administration of 50,000 IU vitamin D2 in both healthy vitamin D-sufficient elderly subjects and young adults. We found no evidence of malabsorption of vitamin D in the elderly subjects. In summary, elderly subjects in New York, whether institutionalized or not, have normal serum 25OHD concentrations. However, while most elderly subjects have normal serum 1,25-(OH)2D levels, a significant proportion fail to produce normal concentrations of 1,25-(OH)2D, possibly due to age-related disturbances in renal synthesis of the hormone.     

The same annual dose of 292000 IU of vitamin D3 (cholecalciferol) on either daily or four monthly basis for elderly women: 1‐year comparative study of the effects on serum 25(OH)D3 concentrations and renal function

Objective Daily dosing of vitamin D supplements may be difficult among older people. Infrequent administration of ‘megadoses’ controlled by health care personnel may overcome adherence problem. We compared the efficacy and safety of two oral dosages (800 IU daily or 97333 IU four monthly) of vitamin D₃ resulting in the equal annual dose of 292000 IU. Design Randomized, double‐blind, double‐dummy parallel group comparison. Patients Forty women aged 69·3–78·8 years. Interventions Vitamin D₃ 400 IU twice daily (D group) or vitamin D₃ oil 97333 IU every 4 months (4 M group) for 1 year. All received 1 g of calcium daily. Measurements Serum 25‐hydroxyvitamin D₃ [25(OH)D₃] in relation to the target levels of 50–75 nmol/l, PTH, serum type I procollagen aminoterminal propeptide (PINP), serum and urine calcium, renal function. Results A quantity of 25OHD₃ increased more in D group than in 4 M group (P < 0·0001). All participants in D group and 67% in 4 M group had 25(OH)D₃ above 50 nmol/l at 12 months; the target level of 75 nmol/l was reached by 47% and 28% respectively. PTH did not show any seasonal perturbation in either group. PINP declined and urinary calcium rose similarly in the study groups over time (P < 0·0001). Renal function did not worsen in either group. Conclusions In terms of serum 25(OH)D₃ concentrations, 800 IU daily was more efficient than a 97333 IU every 4 months. However, to increase adherence, the latter is still worth developing. Both treatments increased urinary excretion of calcium, but did not worsen renal function.     

Effects of vitamin D3, 25(OH) vitamin D3, 24,25(OH)2 vitamin D3, and 1,25(OH)2 vitamin D3 on the in vitro intestinal calcium absorption in the marine teleost, Atlantic cod (Gadus morhua)

The role of vitamin D3, 25(OH) vitamin D3, 24,25(OH)2 vitamin D3, and 1,25(OH)2 vitamin D3, in the regulation of calcium absorption across the intestine in the marine teleost, Gadus morhua, was investigated. The intestine was perfused, in vitro, both vascularly and through the intestinal lumen, and the calcium influx was measured using 45Ca. Vitamin D3 and its metabolites were tested in perfusate concentrations of 10 ng.ml-1.25(OH)D3 increased the intestinal calcium uptake by 65%, while 24,25(OH)2D3 decreased it by 36%. Vitamin D3 and 1,25(OH)2D3, on the other hand, did not affect the calcium influx across the intestinal mucosa. This indicates that 25(OH)D3 and 24,25(OH)2D3 may be active regulators of calcium transport across the intestine of Atlantic cod.     

The unpredictability of seasonal variations in serum vitamin D levels in children with asthma and/or rhinitis

BackgroundSome studies have showed that seasonality is an important determinant of vitamin D (vitD) status.ObjectiveWe evaluated whether there are differences in individual trends of serum vitD level over one year in asthmatic and rhinitic children.Materials and methodsNinety-two asthmatic and rhinitic paediatric patients were followed up for one year and their serum vitD level was detected at three-month intervals, once in each season.ResultsWe observed higher vitD levels at the end of summer and lower at the end of winter. However, the individual seasonal trend was very variable and unpredictable. If it is true that in a given season the majority of patients followed one direction (increase or decrease of serum vitD levels), nevertheless a substantial percentage behaved differently and unpredictably. For example, at the end of spring, 70% of patients showed an increase in serum vitD levels, but 30% showed a decrease. In addition, five individuals had a value ≥50 ng/ml in September and showed serum vitD levels ≥30 ng/ml throughout the year; 16 patients presented vitD value ≥40 ng/ml in September and always had ≥20 ng/ml in the other months.ConclusionsThe wide and unpredictable variability of the individual trend of serum vitD levels should be taken into account before deciding whether or not a drug supplementation is appropriate.     

Effects of a large dose of retinol or retinoic acid on the thyroid hormones in the rat

The daily food intake of a large dose of retinol (as palmitate) or retinoic acid (as all-trans retinoic acid) modifies numerous parameters of the thyroidal status in the rat. There were decreases of the serum total thyroxine (TT4) and triiodothyronine (TT3), and of the biological half-life of T4, while there were increases of the dialyzable fractions of T4 and T3 and of the apparent distribution space of T3. The possible causes of these changes are discussed.     

老年患者血清25羟维生素D3与冠状动脉狭窄程度的相关性研究

目的探讨血清25羟维生素D3与老年患者冠状动脉狭窄程度相关性。方法对269例老年患者行冠状动脉造影术,分为狭窄组114例和正常组155例,应用Gensini积分判断冠状动脉狭窄程度。测定血清25羟维生素D3水平,按照25羟维生素D3四分位数分为:Q1组(<15.0nmol/L)60例,Q2组(15.0~22.1nmol/L)74例,Q3组(22.2~35.6nmol/L)68例,Q4组(>35.6nmol/L)67例。结果狭窄组与正常组25羟维生素D3比较,差异有统计学意义[(25.05±16.08)nmol/L vs(31.83±22.36)nmol/L,P=0.004];Q1组、Q2组、Q3组与Q4组Gensini积分比较,差异有统计学意义(P<0.05,P<0.01)。血清25羟维生素D3与C反应蛋白呈负相关(r=-0.548,P=0.000),与Gensini评分呈负相关(r=-0.183,P=0.003)。多元logistic回归分析显示,血清25羟维生素D3是老年患者冠状动脉狭窄独立保护因素(P<0.01)。结论低水平25羟维生素D3与老年患者冠状动脉狭窄程度相关,需进一步研究证实补充25羟维生素D3是否会减少老年冠心病的发病。     

The importance of vitamin C for hydroxylation of vitamin D3 to 1,25(OH)2D3 in man

Summary The effects of vitamin C on 1,25(OH)2D3 synthesis in humans were evaluated; the study included 20 females. They were divided into 2 groups. The first of the 10 subjects (age range 55–71) received ascorbic acid at a dose of 150 mg/die i.v. for 10 days; the second 10 subjects (age range 55–69) received a placebo i.v. for 10 days. In a later study (after a 30-day washout) the same two groups were tested for the second time with ascorbic acid at a dose of 1,000 mg/die i.v. for 10 days and placebo i.v. for 10 days. Serum calcium and phosphorus, serum Ca++, serum proteins, blood and urinary pH, serum 25(OH)D3 and 1,25(OH)2D3, serum PTH, urinary hydroxyprolin were tested before and after the treatments. In the first study a significant increase in serum 1,25(OH)2D3 was observed after ascorbic acid while no significant variation was observed for the other parameters. In the second study, a significant increase in serum Ca++ and a significant decrease in serum 1,25(OH)2D3 were observed after ascorbic acid while no significant variation was observed for the other parameters. The authors conclude that ascorbic acid promotes 1,25(OH)2D3 synthesis at a paraphysiologic dose (150 mg/die) in humans but this synthesis is inhibited at higher doses (1,000 mg/die). The latter effect by Ca++ or by an effect of ascorbate on 1 alpha-hydroxylase enzyme could be mediated.     

Evaluation of circulating irisin levels in healthy young individuals after a single 100,000 IU vitamin D dose

Irisin is a newly discovered hormone produced by the muscle. This hormone is involved in glucose metabolism, muscle strength and energy expenditure. As vitamin D is also known as a key player in that field, we aimed to see if a single dose of 100,000 IU of vitamin D would modify circulating levels of irisin in 29 young adults. Irisin was determined with the Phoenix Elisa assay at day 0, day 3, day 7 day 15 and day 28 after the loading dose. If we observed a significant increase in 25(OH)D levels (from 19.8 ± 8.4 ng/mL to 33.0 ± 8.5 ng/mL), irisin levels remained constant throughout the study (median 104.5 ng/mL, with values ranging from 69.9 to 390.9 ng/mL). Interestingly, one subject presented irisin values that were three times higher than all the others.     

Changes in serum 25-hydroxyvitamin D and cholecalciferol after one whole-body exposure in a commercial tanning bed: a randomized study

We wanted to evaluate the cutaneous synthesis of 25OHD and cholecalciferol after one whole-body exposure to ultraviolet radiation type B (UVB) in a randomized setup. Healthy volunteers were randomized to one whole-body exposure in a commercial tanning bed with UVB emission (UVB/UVA ratio 1.8-2.0%) or an identical placebo tanning bed without UVB. The output in the 280-320?nm range was 450?μW/cm(2). Blood samples were analyzed for 25OHD and cholecalciferol at baseline and during 7?days after treatment. We included 20 volunteers, 11 to UVB and 9 to placebo treatment. During the first 6?h, no significant differences in 25OHD between the groups were found. At the end of the study, we found a mean increase of 25OHD in the UVB group of 4.5?nmol/l (SD 7?nmol/l) compared to a decline of -1.2?nmol/l (SD 7?nmol/l) in the placebo group (p?=?0.1). A linear mixed model yielded an increase of 25OHD in the UVB group of 1.0?nmol/l per 24?h (p?相似文献   

老年2型糖尿病患者颈动脉粥样硬化与血清25-羟维生素D_3水平的关系

目的探讨血清25-羟维生素D3[25(OH)D3]与老年2型糖尿病患者颈动脉粥样硬化发生、发展的相关性。方法选择2型糖尿病患者174例,根据颈动脉内膜中层厚度(IMT)水平分为IMT正常组84例,IMT增厚组90例;又根据颈动脉有无狭窄分为颈动脉无狭窄组141例,颈动脉狭窄组33例。测量血压、身高、体重,计算体质量指数(BMI),并检测空腹血糖、血脂、糖化血红蛋白等指标,采用酶联免疫分析法测定血清25(OH)D3水平。超声检测及计算IMT及狭窄情况。结果 IMT增厚组血清25(OH)D3水平明显低于IMT正常组(P<0.05);颈动脉狭窄组血清25(OH)D3水平明显低于颈动脉无狭窄组,空腹血糖、尿酸水平明显高于颈动脉无狭窄组(P<0.05)。相关分析显示,颈动脉IMT最大值与老年2型糖尿病患者25(OH)D3呈负相关(P<0.05),与尿酸呈正相关(P<0.01)。logistic回归分析显示,颈动脉狭窄与25(OH)D3、尿酸独立相关。结论在老年2型糖尿病患者中,低水平血清25(OH)D3可能是颈动脉粥样硬化的独立危险因素。     

血清1,25-二羟维生素D3水平在老年胃癌患者中的临床意义

目的：检测老年胃癌患者血清中1,25-二羟维生素D3[1,25-（OH）2D3]浓度,探讨其浓度水平与胃癌临床病例特征及预后的关系。方法选取惠州市第三人民医院2009年9月至2012年9月65例老年胃癌患者,利用酶联免疫吸附测定（ELISA）血清1,25-（OH）2D3的浓度,并分析其浓度水平与临床病理特征和预后的相关性。结果在65例样本中测得,经病理诊断后未接受任何治疗之前的血清1,25-（OH）2D3起始浓度为（18.26±4.13）μg/L,经治疗评估,出现进展时的浓度为（9.26±3.21）μg/L,差异具有统计学意义（P＝0.028）。二者与肿瘤的临床分期及分化程度显著相关（P＜0.05）,而与肿瘤的部位、浸润程度、淋巴结转移及远处转移等不相关（P＞0.05）。较高浓度的1,25-（OH）2D3（＞20μg/L）明显改善老年胃癌患者的生存（P＜0.05）。结论血清1,25-（OH）2D3水平可能成为判别胃癌恶性程度的指标,与老年胃癌患者的预后密切相关。     

Effects of a short-term vitamin D(3) and calcium supplementation on blood pressure and parathyroid hormone levels in elderly women

Calcium supplementation is effective in reducing blood pressure in various states of hypertension, including pregnancy-induced hypertension and preeclampsia. In addition, calcitropic hormones are associated with blood pressure. The hypothesis is that short-term therapy with calcium and vitamin D(3) may improve blood pressure as well as secondary hyperparathyroidism more effectively than calcium monotherapy. The effects of 8 weeks of supplementation with vitamin D(3) (cholecalciferol) and calcium on blood pressure and biochemical measures of bone metabolism were studied. The sample consisted of 148 women (mean +/- SD age, 74 +/- 1 yr) with a 25-hydroxycholecalciferol (25OHD(3)) level below 50 nmol/L. They received either 1200 mg calcium plus 800 IU vitamin D(3) or 1200 mg calcium/day. We measured intact PTH, 25OHD(3), 1,25-dihydroxyvitamin D(3), blood pressure, and heart rate before and after treatment. Compared with calcium, supplementation with vitamin D(3) and calcium resulted in an increase in serum 25OHD(3) of 72% (P < 0.01), a decrease in serum PTH of 17% (P = 0.04), a decrease in systolic blood pressure (SBP) of 9.3% (P = 0.02), and a decrease in heart rate of 5.4% (P = 0.02). Sixty subjects (81%) in the vitamin D(3) and calcium group compared with 35 (47%) subjects in the calcium group showed a decrease in SBP of 5 mm Hg or more (P = 0.04). No statistically significant difference was observed in the diastolic blood pressures of the calcium-treated and calcium- plus vitamin D(3)-treated groups (P = 0.10). Pearson coefficients of correlation between the change in PTH and the change in SBP were 0.49 (P < 0.01) for the vitamin D(3) plus calcium group and 0.23 (P < 0.01) for the calcium group. A short-term supplementation with vitamin D(3) and calcium is more effective in reducing SBP than calcium alone. Inadequate vitamin D(3) and calcium intake could play a contributory role in the pathogenesis and progression of hypertension and cardiovascular disease in elderly women.     

Pathophysiology of the immune system in elderly subjects with or without diabetes and variations after recombinant interleukin-2

This study reports two groups of elderly diabetic patients and normal subjects, with or without hypercholesterolemia and hypertriglyceridemia, who presented a decrease of the T lymphocyte-mediated function, proliferative capacity, phagocytosis, cytotoxicity and surface markers. This fall was more evident in hypercholesterolemic and hypertriglyceridemic subjects. The humoral responses and other parameters studied did not reveal significant variations. The authors also observed that recombinant interleukin-2 (rIL-2) stimulation determined a satisfactory response in healthy and diabetic subjects, while it did not normalize values in patients with altered lipid balance.     

Comparative sequential changes in serum and biliary levels of bile acid components after a single dose of D-galactosamine or partial hepatectomy in the rat

In order to characterize changes in bile acid profile during liver cell damage and regeneration, levels of bile acids in serum and bile were determined by high performance liquid chromatography (HPLC) in F344 rats treated with a single dose of D-galactosamine (galactosamine, 300 mg/kg, i.p.) or subjected to two-thirds partial hepatectomy (PH). In the serum, galactosamine caused elevation of conjugated bile acids such as taurocholic acid (TCA) and tauro-beta-muricholic acid (T beta MCA) at the 24 and 48-h time points, whereas unconjugated bile acids including cholic acid (CA) at 24 h and hyodeoxycholic acid (HDCA) at 48 h were increased after PH. In the bile, elevation of TCA showed most remarkable elevation at the 24-h time point in the galactosamine-treated group. All components of biliary bile acids showed rapid decreases from 24 to 48 h. The results demonstrated that while liver tissue damaged by galactosamine is able to conjugate bile acids it allows leakage into the blood stream. In contrast, the results for rats subjected to PH indicated that liver cells during DNA synthesis are not capable of conjugating all free bile acids with taurine although a similar leakage occurs. It is concluded that obvious elevation of serum TCA or CA and biliary T beta MCA could be a useful indicator of hepatocellular proliferation.     

Effect of 24,25-dihydroxyvitamin D3 on 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] metabolism in vitamin D-deficient rats infused with 1,25-(OH)2D3

Previous studies revealed that administration of 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3] to calcium (Ca)-deficient rats causes a dose-dependent reduction in markedly elevated serum 1,25-(OH)2D3 level. Although the results suggested that the metabolism of 1,25-(OH)2D3 was accelerated by 24,25-(OH)2D3, those experiments could not define whether the enhanced metabolism of 1,25-(OH)2D3 played a role in the reduction in the serum 1,25-(OH)2D3 level. In the present study, in order to address this issue more specifically, serum 1,25-(OH)2D3 was maintained solely by exogenous administration through miniosmotic pumps of 1,25-(OH)2D3 into vitamin D-deficient rats. Thus, by measuring the serum 1,25-(OH)2D3 concentration, the effect of 24,25-(OH)2D3 on the MCR of 1,25-(OH)2D3 could be examined. Administration of 24,25-(OH)2D3 caused a dose-dependent enhancement in the MCR of 1,25-(OH)2D3, and 1 microgram/100 g rat.day 24,25-(OH)2D3, which elevated serum 24,25-(OH)2D3 to 8.6 +/- 1.3 ng/ml, significantly increased MCR and suppressed serum levels of 1,25-(OH)2D3. The effect of 24,25-(OH)2D3 on 1,25-(OH)2D3 metabolism developed with a rapid time course, and the recovery of iv injected [1 beta-3H]1,25-(OH)2D3 in blood was significantly reduced within 1 h. In addition, there was an increase in radioactivity in the water-soluble fraction of serum as well as in urine, suggesting that 1,25-(OH)2D3 is rapidly degraded to a water-soluble metabolite(s). Furthermore, the reduction in serum 1,25-(OH)2D3 was associated with a reduction in both serum and urinary Ca levels. Because the conversion of [3H]24,25-(OH)2D3 to [3H]1,24,25-(OH)2D3 or other metabolites was minimal in these rats, 24,25-(OH)2D3 appears to act without being converted into other metabolites. These results demonstrate that 24,25-(OH)2D3 rapidly stimulates the metabolism of 1,25-(OH)2D3 and reduces its serum level. It is suggested that 24,25-(OH)2D3 plays a role in modifying serum 1,25-(OH)2D3 concentrations by affecting the metabolism of 1,25-(OH)2D3 and may have a therapeutic values in the treatment of hypercalcemia or hypercalciuria caused by 1,25-(OH)2D3 excess.