D3 Vitamin

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Fredrik H. Nystrom - One of the best experts on this subject based on the ideXlab platform.

Michael F Holick - One of the best experts on this subject based on the ideXlab platform.

  • disassociation of Vitamin d s calcemic activity and non calcemic genomic activity and individual responsiveness a randomized controlled double blind clinical trial
    Scientific Reports, 2019
    Co-Authors: Arash Shirvani, Tyler A Kalajian, Anjeli Song, Michael F Holick
    Abstract:

    The aims of this randomized controlled double-blind clinical trial were to assess the impact of Vitamin D supplementation on calcium metabolism and non-calcemic broad gene expression by relating them to the individual’s responsiveness to varying doses of Vitamin D3. Thirty healthy adults were randomized to receive 600, 4,000 or 10,000 IU/d of Vitamin D3 for 6 months. Circulating parathyroid hormone (PTH), 25(OH)D, calcium and peripheral white blood cells broad gene expression were evaluated. We observed a dose-dependent increase in 25(OH)D concentrations, decreased PTH and no change in serum calcium. A plateau in PTH levels was achieved at 16 weeks in the 4000 and 10,000 IU/d groups. There was a dose-dependent 25(OH)D alteration in broad gene expression with 162, 320 and 1289 genes up- or down-regulated in their white blood cells, respectively. Our results clearly indicated that there is an individual’s responsiveness on broad gene expression to varying doses of Vitamin D3. Vitamin D3 supplementation at 10,000 IU/d produced genomic alterations several fold higher than 4,000 IU/d even without further changes in PTH levels. Our findings may help explain why there are some inconsistency in the results of different Vitamin D’s clinical trials.

  • Environmental determinants of preVitamin D synthesis in the United Arab Emirates
    Dermato-endocrinology, 2017
    Co-Authors: Adam Buckley, Michael F Holick, Zara Hannoun, Nader Lessan, Maha T Barakat
    Abstract:

    ABSTRACTDespite abundant sunshine throughout the year, Vitamin D deficiency is endemic in the UAE. Solar radiation within the UVB range of the spectrum is required for the photosynthesis of preVitamin D3 in the skin. Atmospheric transmission of UVB is strongly influenced by atmospheric conditions and solar zenith angle. We investigated the effects of diurnal and seasonal variation on the availability of sufficient UVB radiation for adequate preVitamin D3 synthesis using an established in vitro model. Borosilicate ampoules of 7-dehydrocholesterol, the precursor of preVitamin D3, in ethanol (50 µg/mL) were exposed to direct sunlight in an urban area of Abu Dhabi, at one hourly intervals between 0800 and 1700, on one day of each month over a period of one year. Conversion to preVitamin D3, Vitamin D3 and metabolically inactive photoisomers was analyzed using high performance liquid chromatography. The efficiency of 7-dehydrocholesterol conversion to preVitamin D3 varied estimated UVB intensity. At the latitu...

  • CATALYZED THERMAL ISOMERIZATION BETWEEN PREVitamin D3 AND Vitamin D3 VIA BETA -CYCLODEXTRIN COMPLEXATION
    The Journal of biological chemistry, 1995
    Co-Authors: Xiao Q. Tian, Michael F Holick
    Abstract:

    To examine the effect of microenvironments on preVitamin D3 Vitamin D3 isomerization, we have conducted kinetic studies of the reaction in an aqueous solution of beta-cyclodextrin. Our results showed that at 5 degrees C, the forward (k1) and reverse (k2) rate constants for preVitamin D3 Vitamin D3 isomerization were increased by more than 40 and 600 times, respectively, compared with those in n-hexane (k1, 8.65 x 10(-6) versus 1.76 x 10(-7) s-1; k2, 8.48 x 10(-6) versus 1.40 x 10(-8) s-1), the fastest rate of this isomerization ever reported at this temperature. Thermodynamic studies revealed that the equilibrium constant of the reaction was significantly reduced by more than 12-fold when compared to that in n-hexane at 5 degrees C, and the percentage of Vitamin D3 at equilibrium was increased as the temperature was increased in beta-cyclodextrin. When complexed with beta-cyclodextrin, the preVitamin D3 Vitamin D3 isomerization became endothermic (delta H zero = 13.05 kJ mol-1) in contrast to being exothermic in other media. We propose that thermodynamically unfavorable cZc conformers of preVitamin D3 are stabilized by beta-cyclodextrin, and thus the rate of the isomerization is increased. This conformation-controlled process may play an important role in the modulation of preVitamin D3 Vitamin D3 endocrine system in vivo such as in the sea urchin.

Pär Jennersjö - One of the best experts on this subject based on the ideXlab platform.

Fang-xu Jiang - One of the best experts on this subject based on the ideXlab platform.

  • An overview of type 2 diabetes and importance of Vitamin D3-Vitamin D receptor interaction in pancreatic β-cells.
    Journal of diabetes and its complications, 2017
    Co-Authors: Abraham Neelankal John, Fang-xu Jiang
    Abstract:

    One significant health issue that plagues contemporary society is that of Type 2 diabetes (T2D). This disease is characterised by higher-than-average blood glucose levels as a result of a combination of insulin resistance and insufficient insulin secretions from the β-cells of pancreatic islets of Langerhans. Previous developmental research into the pancreas has identified how early precursor genes of pancreatic β-cells, such as Cpal, Ngn3, NeuroD, Ptf1a, and cMyc, play an essential role in the differentiation of these cells. Furthermore, β-cell molecular characterization has also revealed the specific role of β-cell-markers, such as Glut2, MafA, Ins1, Ins2, and Pdx1 in insulin expression. The expression of these genes appears to be suppressed in the T2D β-cells, along with the reappearance of the early endocrine marker genes. Glucose transporters transport glucose into β-cells, thereby controlling insulin release during hyperglycaemia. This stimulates glycolysis through rises in intracellular calcium (a process enhanced by Vitamin D) (Norman et al., 1980), activating 2 of 4 proteinases. The rise in calcium activates half of pancreatic β-cell proinsulinases, thus releasing free insulin from granules. The synthesis of ATP from glucose by glycolysis, Krebs cycle and oxidative phosphorylation plays a role in insulin release. Some studies have found that the β-cells contain high levels of the Vitamin D receptor; however, the role that this plays in maintaining the maturity of the β-cells remains unknown. Further research is required to develop a more in-depth understanding of the role VDR plays in β-cell function and the processes by which the beta cell function is preserved.

Maha T Barakat - One of the best experts on this subject based on the ideXlab platform.

  • Environmental determinants of preVitamin D synthesis in the United Arab Emirates
    Dermato-endocrinology, 2017
    Co-Authors: Adam Buckley, Michael F Holick, Zara Hannoun, Nader Lessan, Maha T Barakat
    Abstract:

    ABSTRACTDespite abundant sunshine throughout the year, Vitamin D deficiency is endemic in the UAE. Solar radiation within the UVB range of the spectrum is required for the photosynthesis of preVitamin D3 in the skin. Atmospheric transmission of UVB is strongly influenced by atmospheric conditions and solar zenith angle. We investigated the effects of diurnal and seasonal variation on the availability of sufficient UVB radiation for adequate preVitamin D3 synthesis using an established in vitro model. Borosilicate ampoules of 7-dehydrocholesterol, the precursor of preVitamin D3, in ethanol (50 µg/mL) were exposed to direct sunlight in an urban area of Abu Dhabi, at one hourly intervals between 0800 and 1700, on one day of each month over a period of one year. Conversion to preVitamin D3, Vitamin D3 and metabolically inactive photoisomers was analyzed using high performance liquid chromatography. The efficiency of 7-dehydrocholesterol conversion to preVitamin D3 varied estimated UVB intensity. At the latitu...