Concise synthesis of 7-dehydrocholesterol and 25-hydroxy-7-dehydrocholesterol.

Tissue content of vitamin D3 and 25-hydroxy vitamin D3 in minipigs after cutaneous synthesis, supplementation and deprivation of vitamin D3

Objective To investigate the serum 25-hydroxy vitamin D concentrations and related factors in early pregnancy. Methods Plasma was collected in the first trimester from 23 396 pregnant women to investigate the vitamin D level, and its distribution and differences in different age, body maxx index(BMI) and seasons between primipara and multipara. Preterm birth was used as an indicator of clinical outcomes. Vitamin D concentrations were measured using chemiluminescence microparticle immunoassay. Results 25-hydroxy vitamin D level was 42.0(17.6-76.6)nmol/L in totally 23 396 pregnant women with early pregnancy, and 5% and 95% percentile sites of vitamin D level were 20.2 nmol/L and 70.7 nmol/L respectively. There were 18 170(77.7%) primiparas and 5 226(22.3%) multiparas, with the mean age of 30.0(24.0-38.0) years and BMI of 20.7(16.5-27.6)kg/m2. The number of cases detected in spring (March, April and May), summer(June, July and August), autumn(September, October and November months) and winter(December, January and February) were 5 878, 5 554, 5 974, and 5 990, respectively, and the vitamin D levels were 40.0(29.3, 52.7)nmol/L, 46.2(35.6, 57.2)nmol/L, 43.8(33.1, 54.8)nmol/L and 37.2(26.9, 49.9)nmol/L respectively, with the difference in vitamin D levels statistically significant among the four seasons (P<0.001). According to BMI, all pregnant women were divided into four groups as BMI<18.5 kg/m2, 18.5 kg/m2≤BMI≤23.9 kg/m2, 24 kg/m2≤BMI≤27.9 kg/m2, BMI≥28 kg/m2, and the levels of 25-hydroxy vitamin D were 43.5(30.9, 56.9)nmol/L, 42.1(30.8, 53.8)nmol/L, 39.9(30.7, 50.4)nmol/L and 39.7(30.7, 49.4)nmol/L respectively with the difference statistically significant among the four groups. The levels of vitamin D detected in pregnant women with age<25 years, 25~29 years, 30~34 years, ≥35 years were 39.1(28.4, 52.3)nmol/L, 41.3(30.1, 52.9)nmol/L, 42.4(31.2, 54.1)nmol/L and 43.8(31.9, 55.7)nmol/L respectively and the difference was statistically significant (P<0.001). The levels of 25- hydroxy vitamin D in primary and multiparas were 41.6(30.2, 52.9)nmol/L and 43.5(32.5, 56.8) nmol/L with the difference statistically significant (P<0.001). Among women of different gestational age during childbirth, the differences in serum 25-hydroxy vitamin D in early pregnancy were not statistically significant(P=0.121). The severe deficiency of vitamin D in early pregnancy was defined as serum level of 25-hydroxy vitamin D less than 5th level. There were statistical differences in the probability of severe vitamin D deficiency of different ages, seasons and BMI between primiparas and multiparas. Conclusions Pregnant women of lower weight, lower age and primiparity have higher incidence of the severe vitamin D deficiency in early trimester of pregnancy. There is significant difference in 25-hydroxy vitamin D level among the different seasons (winter<spring <autumn <summer). Vitamin D level in early pregnancy is not associated with preterm birth. Key words: 25-hydroxy vitamin D; Vitamin D deficiency; Early pregnancy

Objective To investigate the relationship between serum vitamin D level and prognosis in patients with acute cerebral infarction. Methods One hundred patients with acute cerebral infarction within 48 h and 60 healthy subjects were selected. The serum 25-hydroxy-vitamin D level was measured. The patients with acute cerebral infarction were divided into vitamin D sufficient group, vitamin D insufficient group and vitamin D deficiency group according to the serum 25-hydroxy-vitamin D level. The National Institutes of Health stroke scale (NIHSS) before treatment and 14 d after treatment was evaluated, and this result reflected short-term prognosis; the long-term prognosis was evaluated by modified Rankin scale (mRS) 3 months after treatment. Results The serum 25-hydroxy-vitamin D level in patients with acute cerebral infarction was significantly lower than that in healthy subjects: (14.21 ± 0.98) μg/L vs. (22.43 ± 1.01) μg/L, and there was statistical difference (t = 3.95, P = 0.012). The patients with acute cerebral infarction were divided into 3 groups according to the serum 25-hydroxyvitamin D level: vitamin D sufficient group (19 cases), vitamin D insufficient group (28 cases) and vitamin D deficiency group (53 cases). The NIHSS before treatment and 14 d after treatment in vitamin D sufficient group was significantly lower than that in vitamin D insufficient group and vitamin D deficiency group: (7.03 ± 1.82) scores vs. (10.21 ± 2.03) and (14.35 ± 2.96) scores, (2.04 ± 1.86) scores vs. (5.21 ± 2.28) and (10.38 ± 2.34) scores, and that in vitamin D insufficient group was significantly lower than that in vitamin D deficiency group, and there were statistical differences (P <0.01). The Pearson correlation analysis result showed that the serum 25-hydroxy-vitamin D level was negatively correlated with NIHSS scores (r = -1.738, P = 0.031). The short-term total effective rate in vitamin D sufficient group was significantly higher than that in vitamin D insufficient group and vitamin D deficiency group: 17/19 vs. 67.9% (19/28) and 47.2% (25/53), and that in vitamin D insufficient group was significantly higher than that in vitamin D deficiency group, and there were statistical differences (P <0.05). The long-term good prognosis rate in vitamin D sufficient group was significantly higher than that in vitamin D insufficient group and vitamin D deficiency group: 18/19 vs. 75.0% (21/28) and 50.9% (27/53), and that in vitamin D insufficient group was significantly higher than that in vitamin D deficiency group, and there were statistical differences (P<0.05). Conclusions The serum vitamin D level is significantly decreased in patients with acute cerebral infarction. It is negatively correlated with NIHSS scores. And it is important to judge prognosis. Key words: Brain infarction; Vitamin D; Prognosis; National Institutes of Health stroke scale

Objective To explore the relationship between serum 25-hydroxy vitamin D, total IgE levels and the severity of asthma acute attack in children. Methods The serum of 98 asthmatic children and 30 healthy children were recruited from out-patient and emergency departments of pediatrics of our hospital from June 2014 to December 2015. Detected serum 25-(OH)D3 level with the electrochemical luminescence method, detected serum total IgE level with immune radiometric analysis. Results Compared to the control, serum 25-hydroxy vitamin D level decreased but serum total IgE level increased in asthma children with different degree of disease (P<0.05). As the process of the disease, serum 25-hydroxy vitamin D level reduced and serum total IgE level increased. The correlation analysis results showed that serum 25-hydroxy vitamin D and total IgE levels were not relevant in remission group and mild group (r=0.207, P=0.112; r=0.127, P=0.251), there was negative correlation between serum 25-hydroxy vitamin D and total IgE levels in moderate to severe children (r=﹣0.698, P<0.05). Conclusion Serum 25-hydroxy vitamin D, total IgE levels are closely correlated with the severity of asthma acute attack in children, which provides the basis for vitamin D in the prevention of asthma in children. Key words: Children; Asthma acute attack; 25-hydroxy vitamin D; Total IgE

Objective To evaluate the serum 25-hydroxy vitamin D 3 level in newly diagnosed type 2 diabe-tes,and its relationship with function of islet beta cell .Methods 60 newly diagnosed type 2 diabetes patients and 48 normal glucose tolerance healthy control cases were selected .The level of serum 25-hydroxy vitamin D3 of two groups were measured using the way of high performance liquid chromatograph .The difference was compared between two groups.Insulin resistance index（HOMA-IR） and islet beta cell secrete index（HOMA-β） was used to respectively es-timate insulin sensitivity and islet beta cell function in type 2 diabetes group .The correlation was analyzed between 25-hydroxy vitamin D 3 and fasting blood glucose ,HOMA-IR,HOMA-β.Results The level of serum 25-hydroxy vita-min D3 （28.68 ±1.61） ng/mL in type 2 diabetes group was significantly lower than that of control group （41.30 ± 1.12）ng/mL（t=3.47,P〈0.01）.There is negative correlation between 25-hydroxyl vitamin D3 and fasting glucose （r=0.48,P〈0.05）.There was positive correlation between 25-hydroxy vitamin D3 and HOMA-IR（r=0.52,P〈0.05）.There was no correlation between 25-hydroxy vitamin D3 and HOMA-β（r=-0.06,P〉0.05）.Conclusion The level of 25-hydroxy vitamin D 3 was significantly low in newly diagnosed type 2 diabetes patients .Low serum 25-hydroxyl vitamin D 3 level affects islet beta secretion cell function ,the supplementation of vitamin D 3 may be a simple and effective method to reduce the ocurrence of type 2 diabetes . Key words: diabetes,type 2 25-hydroxy vitamin D3 ; Insulin resistance index; islet beta cell secrete index

Many clinicians are confused about the benefits and risks of vitamin D and calcium supplementation for midlife and older women. We offer guidance on the appropriate use of these supplements. Vitamin D Long recognized as important for skeletal health, vitamin D has garnered recent interest for its possible nonskeletal benefits. This vitamin is synthesized in the skin in response to sunlight and can also be ingested as vitamin D3 (cholecalciferol) or vitamin D2 (ergocalciferol). Natural dietary sources of vitamin D are few and include fatty fish and egg yolks. Vitamin D is also commonly added to milk and some other dairy products, cereals, and orange juice. Vitamin D is hydroxylated in the liver to 25-hydroxyvitamin D [25(OH)D], the major circulating metabolite, and is then further converted to 1,25-dihydroxyvitamin D (calcitriol). A recent evidence-based Institute of Medicine (IOM) report1,2 provides guidelines about the amount of vitamin D that most North American women should consume. The IOM's review confirmed that vitamin D clearly confers bone benefits, but found that current data are insufficient to conclude that it lowers risk for nonskeletal diseases (e.g., cardiovascular disease [CVD], diabetes, cancer); thus, the IOM based its recommendations only on the amount required for bone health: Because the IOM …

Objective To investigate the levels of serum 25-hydroxy vitamin D in autumn and winter among children of Shenmu city, Shaanxi province, and to provide theoretical basis for prevention and treatment of rickets in this area. Methods From June 2016 to December 2016, a total of 277 children in the children′s health clinic were sleceted.The morning fasting blood was extracted and serum levels of 25-hydroxy vitamin D were measured by enzyme-linked immunosorbent assay(ELISA). Results Among the 277 cases, there were 181 males and 96 females, including 163 infants(58.8%), 75 toddlers(27.1%), 24 preschool children(8.7%) and 15 school-going children(5.4%). The median (interquartile range) of serum 25-hydroxyl vitamin D was 33.21(14.93)nmol/L.Among all children, 4.3% had severe vitamin D deficiency, 15.9% had moderate deficiency, 57.0% had mild deficiency, 7.9% had insufficient vitamin D levels, 11.9% had suitable vitamin D levels, while 2.9% had excess of vitamin D. There was no statistically significant difference in the level of 25-hydroxyl vitamin D between different age groups(H=10.133, P>0.05), and different gender groups(Z=0.712, 1.094, 0.476, 0.000, all P>0.05). The levels of serum 25-hydroxyl vitamin D in serum extracted in autumn were higher than those extracted in winter(75.96% vs.90.75%, χ2=11.27, P<0.05). Conclusion There is significant deficiency of serum 25-hydroxyl vitamin D in Shenmu children, which significantly increased in winter.The outdoor activities should be strengthened and the vitamin D should be timely supplemented to prevent the occurrence of rickets. Key words: Rickets; 25-Hydroxyvitamin D 2; Child; Autumn and winter

In food databases, the specific contents of vitamin D3 and 25-hydroxyvitamin D3 in food have been implemented in the last 10 years. No consensus has yet been established on the relative activity between the components. Therefore, the objective of the present study was to assess the relative activity of 25-hydroxyvitamin D3 compared to vitamin D3. The design was a parallel study in pigs (n 24), which from an age of 12 weeks until slaughter 11 weeks later were fed approximately 55 microg vitamin D/d, as vitamin D3, in a mixture of vitamin D3 and 25-hydroxyvitamin D3, or 25-hydroxyvitamin D3. The end-points measured were plasma 25-hydroxyvitamin D3, and in the liver and loin the content of vitamin D3 and 25-hydroxyvitamin D3. Vitamin D3 and 25-hydroxyvitamin D3 in the feed did not affect 25-hydroxyvitamin D3 in the plasma, liver or loin differently, while a significant effect was shown on vitamin D3 in the liver and loin (P < 0.001). 25-Hydroxyvitamin D3 in the plasma, liver and loin significantly correlates with the sum of vitamin D3 and 25-hydroxyvitamin D3 in the feed (P < 0.05). Therefore, 25-hydroxyvitamin D3 should be regarded as having the same activity as vitamin D3 in food databases. Sole use of 25-hydroxyvitamin D3 as a vitamin D source in pig feed will produce liver and meat with a negligible content of vitamin D3, while an increased content of vitamin D3 in the feed will produce liver and meat with increased content of both vitamin D3 and 25-hydroxyvitamin D3.

Objective To investigate the value of 25-hydroxy vitamin D levels in patients with type 2 diabetic nephropathy. Methods Six hundred type 2 diabetic patients were enrolled in the study. The height, weight and fasting venous blood lipids and 25 hydroxyvitamin D levels were measured, and the urinary albumin excretion rates in one day were calculated, the relationship between diabetic nephropathy and 25 hydroxyvitamin D levels was analyzed. Results There was no significant difference in the gender, age, LDL-C, TC, HbAlc, HDL-C levels, body mass index (BMI), smoking history between the two groups (P<0.05). The TG level, incidences of hypertension, obesity, serum creatinine levels, use of hypoglycemic drugs ratio were higher, the duration of diabetes was longer (P<0.05). The incidence of high blood lipid in macroalbuminuria group was higher than other groups (P<0.05). The vitamin deficiency rates in patients with diabetic nephropathy were significantly higher than those in patients without diabetic nephropathy (P<0.05). The urinary albumin excretion rate in vitamin D deficiency group was significantly higher than that of the other two groups (P<0.05). Women were more likely to have difficiency of vitamin D than men (P<0.05). The decreased HDL-C levels was correlated with lack of vitamin D, and smoking and hyperlipidemia abnormal proportion, HbAlc, duration of diabetes, hypertension were not correlated with vitamin D difficiency. There was a significant negative correlation between UAER and Vitamin D levels (r=-1.792, P<0.01), but the serum creatinine concentration with vitamin D levels was not correlated, and lack of vitamin D could significantly increase the incidence of diabetic nephropathy (P<0.05). Conclusions The patients with type 2 diabetes has low 25-vitamin D levels, and the risk of diabetic nephropathy in patients with type 2 diabetes mellitus increases with the decrease of the level of 25-hydroxy vitamin D. Key words: 25-hydroxy vitamin D; Diabetic nephropathy; Type 2 diabetes mellitus; Urinary albumin excretion rate; Detection value

Our previous work has shown that feeding 5 million international units (IU) of vitamin D3 to beef steers can produce tender strip loin and top round steaks. Our current experiment was designed to determine whether feeding two metabolites of vitamin D3, 25- hydroxyvitamin D3, and 1,25-dihysroxyvitamin D3, produces tender strip loin, top round, and top blade steaks more effectively than does supplemental vitamin D3 without leaving a substantial amount of residual vitamin D3 in muscle. Thirty-three continental crossbred steers were randomly allotted to one of four treatment groups. The first group was fed a placebo. The second group received 5 million IU of vitamin D3 each day for nine days and was slaughtered two days later. The third group received one dose of 125 mg of 25-hydroxyvitamin D3 four days before harvest, and the fourth group received one dose of 500 mg of 1,25- dihydroxyvitamin D3 three days before harvest. Blood samples were collected before treatment and at the time of slaughter for subsequent analysis of calcium, vitamin D3, 25-hydroxyvitamin D3, and 1,25-dihydroxyvitamin D3 concentrations in plasma. Steaks from the longissimus lumborum (strip loin) and semimembranous (top round) muscles were collected from each animal and aged for 8, 14, and 21 days, and steaks from the infraspinatus were collected and aged for 14 and 21 days. All steaks were analyzed for tenderness by Warner-Bratzler shear force determination. Concentrations of vitamin D3 in plasma were higher in vitamin D3- treated cattle (P < 0.0001). Concentrations of plasma 25-hydroxyvitamin D3 were increased in 25- hydroxyvitamin D3-treated cattle, but not as high as vitamin D3-treated cattle (P < 0.0001). 1,25- Dihydroxyvitamin D3 concentrations were higher in 1,25-dihydroxyvitamin D3-treated animals compared with all treatments (P < 0.0001). Supplementing steers with vitamin D3 increased the concentration of vitamin D3 and 25-hydroxyvitamin D3 in the meat of all muscles sampled (P < 0.0001). Supplementing steers with 25-hydroxyvitamin D3 increased the concentration of 25-hydroxyvitamin D3 in meat, but to an amount less than half that of cattle treated with vitamin D3. Warner-Bratzler shear force analysis showed that feeding 1,25- dihydroxyvitamin D3 did not significantly lower shear force values, but supplemental vitamin D3 and 25-hydroxyvitamin D3 produced longissimus lumborum and semimembranous steaks with lower shear force values (P < 0.06). Analysis of Western blots showed that longissimus lumborum and semimembranous steaks from cattle fed supplemental vitamin D3 and 25-hydroxyvitamin D3 (but not steaks from cattle fed 1,25- dihydroxyvitamin D3), had greater proteolysis of troponin T to a 30 kDa component.

Objective To analyze the serum level of 25-hydroxy vitamin D3 and the degree of vitamin D deficiency in the patients with type 2 diabetes mellitus,and the relationships between the degree of vitamin D deficiency,durations of diabetes and glycosylated hemoglobin A1c (HbA1c) levels were also investigated.Methods 140 patients with type 2 diabetes mellitus (60 male and 80 female) were selected from the Department of Endocrinology of The General Hospital of Tianjin Medical University,aged 21 to 89,with an average age of (58.25 ± 13.76) years old.Serum 25-hydroxy vitamin D3 levels between different age groups (＜50,≥ 50 and ＜70,≥70years old group) and tested season groups (winter and spring,summer and autumn group),different duration of diabetes groups (＜ 10,≥ 10 and ＜20,≥ 20 years group) and different HbA l c level groups (＜ 7％,≥7％ and＜ 10％,≥ 10％) were compared.Results (1)The serum 25(OH)D3 levels of these 140 patients were all below normal range,and the average levels was (40.07 ± 16.12) nmol/L.The prevalence of severe vitamin D deficiency,deficiency and sufficiency were 13.57％,67.86％ and 4.29％,respectively.But there was no significant difference between male and female both in the serum 25(OH)D3 levels and the degree of vitamin D deficiency(t =0.803,x2=0.189,both P ＞0.05).(2) The serum 25(OH)D3 levels of patients aged ≥ 50 and＜70 were lower than that of the subjects aged ＜50 in male (F =2.362,P ＜0.05).In female,the serum 25 (OH)D3 levels of patients aged ≥ 50 were lower than that of the subjects aged ＜50 (F =3.928,P ＜ 0.05),and the percentages of vitamin D deficiency were also greater than that in patients younger than 50 years (x2=10.036,P ＜0.01).(3)The serum 25(OH)D3 levels in winter and spring were lower than that in summer and autumn (t =-4.681,P ＜0.01),and the percentage of severe vitamin D deficiency and deficiency were increased as well (x2=18.202,P ＜ 0.01).(4)The serum 25(OH)D3 levels in patients whose durations of diabetes were more than 10 years were lower than that of patients with diabetic duration less than 10 years (F =5.489,P ＜0.05,P ＜0.01),and the percentage of severe vitamin D deficiency in patients whose durations were more than 20 years was higher than that of patients with diabetic duration less than 10 years (x2=7.284,P ＜0.05).(5)The serum 25 (OH)D3 levels in patients whose HbA l c were more than 7％ were lower than those with HbAlc lower than 7％(F =3.963,P ＜0.01),and the percentages of severe vitamin D deficiency and deficiency were higher than that of patients with HbAlc lower than 7％ as well (x2=6.712,P ＜0.05).Conclusion Vitamin D deficiency is common in patients with type 2 diabetes,especially in patient with long durations and continuously poor blood glucose control.The assessment and supplement of vitamin D should be strengthened in patients with diabetes especially in winter. Key words: 25-Hydroxy vitamin D3; Vitamin D deficiency; Vitamin D insufficiency; Diabetes mellitus

Vitamin D is taken up from food as D 2 and D 3 . Vitamin D 3 is also synthesized from 7-dehydrocholesterol in the skin by the exposure of ultraviolet B. The D 2 and D 3 , which are called native vitamin D, are hydroxylated at C25 in the liver by CYP2R1 and then at C1 in the kidney by CYP27B1, to be converted to an active vitamin D metabolite, 1,25-dihydroxyvitamin D[1,25(OH) 2 D]. CYP24A1 converts 25-hydroxyvitamin D(25OHD)and 1,25(OH) 2 D to 24,25-dihydroxyvitamin D[24,25(OH) 2 D]and 1,24,25-trihydroxyvitamin D[1,24,25(OH) 3 D], respectively, to decrease the level of 1,25(OH) 2 D. CYP27B1 and CYP24A1 are mainly expressed in the kidney but also detected in other tissues, and it is suggested that 1,25(OH) 2 D produced in the extra-renal tissues may exert its effects locally.

Vitamin D deficiency/insufficiency not only results in disorders of skeletal system, but may also be associated with other nonskeletal diseases. Therefore, measurement of 25-hydroxyvitamin D has received more and more attentions. Common methods for 25-hydroxyvitamin D testing include vitamin D binding protein-based competitive assays, immunoassays, high performance liquid chromatography (HPLC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Vitamin D binding protein-based assays and immunoassays can be performed on automated chemistry analyzers, permitting an easy and quick measurement with high throughput. However, significant variability exists among various assays. They cannot separate 25-hydroxyvitamin D3 and D2 either. HPLC method can separate D3 and D2, but the sensitivity and specificity are not as good as mass spectrometry. LC-MS/MS is more specific and sensitive and it can measure D3 and D2 individually. However, the methodology is more complicated and its throughput is relatively low. Also, it requires special instrument and operators who need additional training. In addition, most LC-MS/MS methods are developed and validated by individual laboratories, so the standardization of the method is an urgent problem to be solved. Although the specificity of LC-MS/MS method is high, some metabolites may still interfere with the assay. The reference interval of 25-hydroxyvitamin D is still controversial and how to establish gender- and age-specific reference intervals remains debatable. Besides 25-hydroxyvitamin D, whether its metabolites and free 25-hydroxyvitamin D should be measured is still questionable. Although 25-hydroxyvitamin D testing is primarily used for the diagnosis and treatment of skeletal diseases, epidemiological studies suggest that vitamin D deficiency/insufficiency may be related to the development and prognosis of nonskeletal diseases. However, more evidence is needed in order to determine the causal relationship between them and the mechanism. (Chin J Lab Med, 2017, 40: 744-747) Key words: Vitamin D; Chromatography, liquid; Tandem mass sectrometry

Objective To analyze the level of 25-hydroxy vitamin D [25-(OH)D]in serum from 0 to 5 years old children in Nanjing area so as to provide some guides on clinical application. Methods The serum 25-(OH)D level was detected by using enzyme-linked immunosorbent assay kit in children from 0 to 5 years old that took health examination in Nanjing Maternal and Child Health Hospital Affiliated to Nanjing Medical University from June 2013 to May 2014.The average vitamin D levels and deficiency rates were analyzed, and the factors such as age, sex and season which might induce vitamin D deficiency were analyzed. Results The average 25-(OH)D level in serum was (81.5±30.4) nmol/L, with a deficiency rate of 9.5%(271/23 944 cases). Among them, the 25-(OH)D level of boys was (81.9±31.6) nmol/L, while for girls it was (81.3±29.8) nmol/L.The main vitamin D deficiency ages of children were more than 4 to 5 years old.Vitamin D in male children [(64.9±21.2) nmol/L] was higher than female children [(60.8±21.2) nmol/L] (t=0.98, P<0.05) and vitamin D levels were influenced by seasonal variation.Vitamin D level of the third quarter [(108.1±11.6) nmol/L]was significantly higher than other quarters[(71.8±15.6) nmol/L, (95.5±21.2)nmol/L, (86.6±3.5) nmol/L] (F=4.53, P=0.03). Conclusions As a vital nutrient, the supplementation of vitamin D should be carried out in different development periods of the children and the supplement should also be based on local seasonal changes. Key words: 25-hydroxy vitamin D; 0-5 years old children; Changes of season

Simple SummarySubclinical hypocalcemia severely affects the lactation and health of dairy cows. Subclinical hypocalcemia is still a concern with cows after postpartum oral Ca; thus, the single treatment approach gradually has shifted to a multitreatment approach in terms of subclinical hypocalcemia. Supplementing 25-hydroxyvitamin D3 could solve the problem of insufficient vitamin D3 synthesis and blocked conversion in transition cows. The present study showed that feeding 25-hydroxyvitamin D3 combined with oral calcium not only improved serum 25-hydroxyvitamin D3 status and calcium homeostasis, but also had potential benefits on lactation performance and the health status during the transition period.Little information is available regarding the effect of supplementing 25-hydroxyvitamin D3 during the transition period combined with a postpartum oral calcium bolus on Ca homeostasis. The objectives of the current study were to evaluate the effects of 25-hydroxyvitamin D3 combined with postpartum oral calcium bolus on lactation performance, serum minerals and vitamin D3 metabolites, blood biochemistry, and antioxidant and immune function in multiparous dairy cows. To evaluate the effects of 25-hydroxyvitamin D3 combined with oral calcium, 48 multiparous Holstein cows were randomly assigned to one of four treatments: (1) supplementing 240 mg/day vitamin D3 without a postpartum oral Ca bolus (control), (2) supplementing 240 mg/day vitamin D3 with an oral Ca bolus containing 90 g of Ca immediately post-calving (Ca + VitD), (3) supplementing 6 g/day 25-hydroxyvitamin D3 without an oral Ca bolus (25D), and (4) supplementing 6 g/day 25-hydroxyvitamin D3 with an oral Ca bolus containing 90 g of Ca immediately post-calving (Ca + 25D). Lactation performance during the first 21 days was measured. Blood was collected at the initiation of calving and then 1, 2, 7, 14, and 21 days relative to the calving date. The yield of milk (0.05 < p < 0.10), energy-corrected milk (p < 0.05), 3.5% fat-corrected milk (p < 0.05), and milk protein (p < 0.05) were significantly higher in 25-hydroxyvitamin D3-treated groups within 3 weeks of lactation than in vitamin D3-treated cows. The iCa (p < 0.05) and tCa (p < 0.05) were higher in both Ca and 25D + Ca cows than in the control and 25D groups within 48 h. The concentrations of serum tCa (p < 0.05), tP (p < 0.05), and 25-hydroxyvitamin D3 (p < 0.05) in 25D and 25D + Ca cows were higher than those in control and Ca cows within 21 days postpartum. Feeding 25-hydroxyvitamin D3 also showed a lower concentration of malondialdehyde (p < 0.05), interleukin 6 (p < 0.05), and tumor necrosis factor-alpha (TNF-α) (p < 0.05), as well as a higher concentration of alkaline phosphatase (p < 0.05), total antioxidant capacity (p < 0.05), and immunoglobulin G (p < 0.05) than vitamin D3. Supplementing Ca bolus also showed lower concentrations of alanine transaminase (p < 0.05) and TNF-α (p < 0.05). In conclusion, supplementing 25-hydroxyvitamin D3 during the transition period combined with a postpartum oral calcium bolus improved lactation performance, Ca homeostasis, and antioxidant and immune function of medium-production dairy cows within 21 days postpartum.