vitamin-d-2 and 7-dehydrocholesterol

CYP11A1, found only in vertebrates, catalyzes the first step of steroidogenesis where cholesterol is converted to pregnenolone. The purified enzyme, also converts desmosterol and plant sterols including campesterol and β-sitosterol, to pregnenolone. Studies, initially with purified enzyme, reveal that 7-dehydrocholesterol (7DHC), ergosterol, lumisterol 3, and vitamins D3 and D2 also serve as substrates for CYP11A1, with 7DHC being better and vitamins D3 and D2 being poorer substrates than cholesterol. Adrenal glands, placenta, and epidermal keratinocytes can also carry out these conversions and 7-dehydropregnenolone has been detected in the epidermis, adrenal glands, and serum, and 20-hydroxyvitamin D3 was detected in human serum and the epidermis. Thus, this metabolism does appear to occur in vivo, although its quantitative importance and physiological role remain to be established. CYP11A1 action on 7DHC in vivo is further supported by detection of Δ(7)steroids in Smith-Lemli-Opitz syndrome patients. The activity of CYP11A1 is affected by the structure of the substrate with sterols having steroidal or Δ(7)-steroidal structures undergoing side chain cleavage following hydroxylations at C22 and C20. In contrast, metabolism of vitamin D involves sequential hydroxylations that start at C20 but do not lead to cleavage. Molecular modeling using the crystal structure of CYP11A1 predicts that other intermediates of cholesterol synthesis could also serve as substrates for CYP11A1. Finally, CYP11A1-derived secosteroidal hydroxy-derivatives and Δ(7)steroids are biologically active when administered in vitro in a manner dependent on the structure of the compound and the lineage of the target cells, suggesting physiological roles for these metabolites. This article is part of a special issue entitled 'SI: Steroid/Sterol signaling'.

Topics: Animals; Cholecalciferol; Cholesterol Side-Chain Cleavage Enzyme; Dehydrocholesterols; Ergocalciferols; Humans; Sterols

Topics: 25-Hydroxyvitamin D 2; Adolescent; Aged; Animals; Calcitriol; Chemical Phenomena; Chemistry; Dehydrocholesterols; Ergocalciferols; Female; Humans; Infant; Osteomalacia; Pregnancy; Rats; Rickets; Ultraviolet Rays; Vitamin D

Topics: Adult; Aged; Animals; Calcifediol; Calcitriol; Child; Cholecalciferol; Dehydrocholesterols; Dihydroxycholecalciferols; Ergocalciferols; Female; Humans; Hydroxycholecalciferols; Infant, Newborn; Liver; Nutritional Requirements; Pregnancy; Skin; Species Specificity; Ultraviolet Rays; Vitamin D; Vitamin D Deficiency

To investigate seasonal variation of vitamin D levels in 148,821 serum samples during a 2year time period in a northern-latitude city in the United States.. Total vitamin D assay testing by chemiluminescence was performed on the DiaSorin Liaison. Vitamin D results were extracted from the laboratory information system without patient identification during 2011 and 2012 and separated by season and vitamin D results: less than 10ng/mL (deficient), 10-20.0ng/mL (insufficient), 20.1-30ng/mL (borderline), 30.1-40ng/mL (sufficient), 40.1-100ng/mL, and greater than 100ng/mL.. The seasonal winter period constituted the months of January through March; spring, April through June; summer, July through September; and fall, October through December. The data set analyzed included 36,643 samples during the winter, 38,299 in spring, 36,141 in summer, and 37,738 in fall and demonstrated an expected rise and fall in vitamin D levels.. This retrospective epidemiological study demonstrates seasonal variation of vitamin D levels at clinical decision points. Although not unexpected, this variation has an impact on studies relating low vitamin D levels to higher rates of cancer, cardiovascular disease, multiple sclerosis, diabetes, autoimmune disease, and a host of other health risk assessments.

Topics: Dehydrocholesterols; Ergocalciferols; Humans; Luminescence; Risk Assessment; Seasons; United States; Vitamin D; Vitamin D Deficiency

This study investigated the influence of alpine grazing on vitamin D (vitD) and bone metabolism in sheep and goats. Two groups of five adult lactating East Friesian milk sheep and Saanen dairy goats were kept on pastures at 2,000 to 2,600 m a.s.l. (SA: sheep alpine; GA: goats alpine) and 400 m a.s.l. (SL: sheep lowland; GL: goats lowland). The animals were milked twice daily and the milk yield was measured. Blood, milk, skin, and forage samples were collected and the left metatarsi were measured with peripheral quantitative computed tomography. The relative humidity and air temperature were recorded and the ultraviolet B (UVB) radiation was measured with a solar meter at both research stations. In addition, animals from the alpine group were equipped with a global positioning system receiver. The UVB radiation was higher at the alpine station (P<0.05) compared to the lowland station. In contrast, both the relative humidity and the air temperature were higher at the lowland station (P<0.04). The group GA produced more milk than GL (P<0.043). No differences in milk production between SA and SL were detected. Only minor differences between the alpine and lowland species groups were found in the total 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D serum concentration and in the 25(OH)D milk concentration. 25-hydroxyvitamin D2 concentration in serum was higher in sheep compared to goats and the 25(OH)D3 concentration in serum increased in all four groups but was higher in the alpine groups during the experiment. In addition, no differences in 7-dehydrocholesterol (7-DHC) concentrations in the skin at high altitude and lowland groups were detectable. However the 7-DHC concentrations in the skin of sheep were less than a tenth of the concentrations in the skin of goats and were nearly not detectable. In both groups SA and SL bone strength index increased during the trial (P=0.043). Bone strength index was lower in GA compared to GL at wk 12 (P=0.047). Mean serum Ca concentrations were higher and P concentrations were lower in the alpine groups than in the lowland groups (P=0.047). In both groups SA and GA the distance travelled increased during the trial. In conclusion, no effect of altitude on vitD status, vitD milk concentration and bone strength could be detected. Both sheep and goats are able to produce vitD in the skin, but sheep depend more on vitD intake with feedstuff, whereas goats rely more on cutaneous vitD production.

Topics: Altitude; Animal Feed; Animals; Bone and Bones; Calcium; Dairying; Dehydrocholesterols; Ergocalciferols; Female; Goats; Guanine; Lactation; Milk; Motor Activity; Phosphorus; Sheep; Vitamin D

Cytochrome P450scc (P450scc) catalyzes the cleavage of the side chain of both cholesterol and the vitamin D(3) precursor, 7-dehydrocholesterol. The aim of this study was to test the ability of human P450scc to metabolize ergosterol, the vitamin D(2) precursor, and define the structure of the major products. P450scc incorporated into the bilayer of phospholipid vesicles converted ergosterol to two major and four minor products with a k(cat) of 53 mol · min(-1) · mol P450scc(-1) and a K(m) of 0.18 mol ergosterol/mol phospholipid, similar to the values observed for cholesterol metabolism. The reaction of ergosterol with P450scc was scaled up to make enough of the two major products for structural analysis. From mass spectrometry, NMR, and comparison of the NMR data to that for similar molecules, we determined the structures of the two major products as 20-hydroxy-22,23-epoxy-22,23-dihydroergosterol and 22-keto-23-hydroxy-22,23-dihydroergosterol. Molecular modeling and nuclear Overhauser effect (or enhancement) spectroscopy spectra analysis helped to establish the configurations at C20, C22, and C23 and determine the final structures of major products as 22R,23S-epoxyergosta-5,7-diene-3β,20α-diol and 3β,23S-dihydroxyergosta-5,7-dien-22-one. It is likely that the formation of the second product is through a 22,23-epoxy (oxirane) intermediate followed by C22 hydroxylation with the formation of strained 22-hydroxy-22,23-epoxide (oxiranol), which is immediately transformed to the more stable α-hydroxyketone. Molecular modeling of ergosterol into the P450scc crystal structure positioned the ergosterol side chain consistent with formation of the above products. Thus, we have shown that P450scc efficiently catalyzes epoxide formation with ergosterol giving rise to novel epoxy, hydroxy, and keto derivatives, without causing cleavage of the side chain.

Topics: Cholesterol Side-Chain Cleavage Enzyme; Dehydrocholesterols; Epoxy Compounds; Ergocalciferols; Ergosterol; Ethylene Oxide; Humans; Hydroxylation; Kinetics; Magnetic Resonance Spectroscopy; Mass Spectrometry; Phospholipids

A comment on [W.J. Olds, A.R. McKinley, M.R. Moore, M.G. Kimlin, In vitro model of vitamin D(3) (cholecalciferol) synthesis by UV radiation: dose-response relationships, J. Photochem. Photobiol. B: Biol. 93 (2008) 88-93]. The article also discusses some related issues.

Topics: Cholecalciferol; Dehydrocholesterols; Dose-Response Relationship, Radiation; Ergocalciferols; Humans; Skin; Ultraviolet Rays

Provitamin D2, vitamin D2 and vitamin D3 were identified in the thallus of a lichen species, Cladina arbuscula (Wallr.) Hale and W.L. Culb. The identification of vitamin D3 was supported by: (1) co-chromatography in both reverse and straight phase HPLC (high performance liquid chromatography), (2) ultraviolet absorption spectrum, and (3) molecular ion peaks demonstrated by ESI (electrospray ionisation) mass spectrometry. The contents of vitamin D3 range from 0.67 to 2.04 μg g⁻¹ dry matter in the thalli of C. arbuscula specimens grown under different natural conditions, while provitamin D3 could not be detected. The ranges for provitamin D2 and vitamin D2 were 89-146 and 0.22-0.55 μg g⁻¹ dry matter, respectively, while the contents of provitamin D3 were below the detection limit (0.01 microg g(-1) dry matter). When C. arbuscula thalli collected at different latitudes from northern Finland to Greece were compared, a positive correlation of vitamin D2 and D3 contents with modelled UV-B radiation at the collection sites was found. A single sample of C. rangiferina from northern Finland gave much higher values for the vitamins. A possible reason could be the lower content of UV-B absorbing pigment in the latter species.

Topics: Ascomycota; Dehydrocholesterols; Ergocalciferols; Ultraviolet Rays

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Bone and Bones; Calcitriol; Calcium; Cholecalciferol; Dehydrocholesterols; Dihydroxycholecalciferols; Duodenum; Ergocalciferols; Kidney; Liver; Molecular Conformation; Parathyroid Hormone; Receptors, Calcitriol; Receptors, Steroid; S100 Calcium Binding Protein G; Secosteroids; Skin; Structure-Activity Relationship; Ultraviolet Rays; Vitamin D

Injection of about 1 ng/g body wt per day of either vitamin D3 or 1,25-(OH)2-vitamin D3 for 7 days induces hypercalcemia and hyperphosphatemia in fed American eels, Anguilla rostrata, but only hyperphosphatemia in unfed eels. These same analogs also stimulated the uptake of 45Ca from intestinal sacs in situ. The vitamin D3 appeared to be relatively more effective than the 1,25-(OH)2D3 metabolite and chlorpromazine inhibited the effect of vitamin D3 on intestinal calcium uptake. 7-Dehydrocholesterol, vitamin D2, and 24,25-(OH)2D3 did not stimulate hypercalcemia, hyperphosphatemia, or intestinal calcium uptake.

Topics: 24,25-Dihydroxyvitamin D 3; Animals; Calcitriol; Calcium; Chlorpromazine; Cholecalciferol; Dehydrocholesterols; Dihydroxycholecalciferols; Eels; Ergocalciferols; Fasting; Food; Intestinal Absorption; Phosphorus

The initial step in cholecalciferol (vitamin D3) metabolism is the photo-conversion of 7-dehydrocholesterol to previtamin D3. This reaction occurs in the epidermis and requires ultraviolet light. We measured the circulating concentration of vitamin D (ergocalciferol and cholecalciferol), 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D in 14 normal white, 9 normal black subjects, and in 9 white and 17 black hemodialysis patients. The mean plasma vitamin D in normal white subjects was greater than in normal black subjects, 4.01 +/- 1.02 ng/ml versus 0.96 +/- 0.30 ng/ml, respectively (P less than 0.05). Plasma 25-hydroxyvitamin D in normal blacks was also less than in normal whites, 17.7 +/- 1.5 ng/ml versus 31.3 +/- 3.0 ng/ml, respectively (P less than 0.01). In uremic white subjects, plasma vitamin D, 6.7 +/- 2.6 ng/ml, was similar to normal white subjects. However, vitamin D was not detectable in 12 of 17 uremic black subjects and was depressed in the remainder of the group. Following exposure to a single minimal erythema dose of ultraviolet-B irradiation, the maximal increase in plasma vitamin D was depressed in white dialysis patients as compared to healthy white subjects, 6.3 +/- 1.9 ng/ml versus 21.3 +/- 2.8 ng/ml, respectively (P less than 0.02). 7-Dehydrocholesterol content was similar in epidermis from site-matched skin of fresh cadavers and white hemodialysis patients, 131 +/- 23 ng/mg versus 124 +/- 14 ng/mg skin, respectively. It is concluded that chronic hemodialysis patients exhibit defective photoproduction of cholecalciferol, despite normal epidermal content of substrate, 7-dehydrocholesterol.

Topics: Adult; Cholecalciferol; Dehydrocholesterols; Epidermis; Ergocalciferols; Humans; Male; Renal Dialysis; Ultraviolet Rays; Uremia

To determine the role of the ring structure in the differential absorption of sterols, we have used rat jejunal brush border vesicles and erythrocytes to examine the uptake of cholesterol, campesterol, and sitosterol following successive chemical degradations of rings A and B. The cell and membrane preparations were incubated with the sterols and sterol analogues (about 30 micromolar each) dissolved in 7 mM sodium taurocholate and 0.6 mM egg phospholipid. The uptake of the analogues was analyzed by high performance liquid chromatography and capillary gas--liquid chromatography. In both membrane preparations, the uptake of the 7-dehydroanalogues of cholesterol, campesterol, and sitosterol was linear with time. 7-Dehydrocholesterol was absorbed 4-5 times faster than 7-dehydrositosterol by both preparations. The uptake of the campesterol analogue was intermediate between that of the analogues of cholesterol and sitosterol at all time points. Following conversion of the 7-dehydrosterols to their calciferol derivatives, the 27-carbon sterols were absorbed only 1.9 and 1.4 times faster than those of the 29-carbon sterols by the erythrocyte and brush border membranes, respectively. A similar degree of selectivity was expressed in the erythrocytes during the uptake of a steroid series possessing keto-4-ene ring system. Complete oxidation of the calciferol derivatives to the des-AB-8-ones resulted in a total loss of discrimination among the various side-chain homologues during absorption from micellar solutions. It is concluded that the selective absorption of animal and plant sterols depends upon the presence of a ring system having the bulk of the cholestane nucleus, although not necessarily a rigid or planar one containing a hydroxyl group.

Topics: Absorption; Animals; Cell Membrane; Cholesterol; Chromatography, High Pressure Liquid; Dehydrocholesterols; Ergocalciferols; Ergosterol; Erythrocytes; Gas Chromatography-Mass Spectrometry; Jejunum; Micelles; Microvilli; Phytosterols; Rats; Sitosterols; Structure-Activity Relationship

Topics: Animals; Biochemical Phenomena; Biochemistry; Biological Products; Blood; Cholecalciferol; Chromatography; Dehydrocholesterols; Ergocalciferols; Ergosterol; Horses; Liver; Neoplasms; Oxidation-Reduction; Research

Topics: Animals; Blood; Blood Proteins; Cattle; Cholecalciferol; Dehydrocholesterols; Enzyme Inhibitors; Enzyme Precursors; Ergocalciferols; Ergosterol; Horses; Lactones; Metabolism; Neoplasms; Oxidation-Reduction; Oxidoreductases; Pharmacology; Research; Thymus Gland; Thyroxine

Topics: Cholecalciferol; Cholesterol; Dehydrocholesterols; Ergocalciferols; Ergosterol; Humans; Radiation; Sterols; Vitamin D; Vitamins