Vitamin D Metabolism and Guidelines for Vitamin D Supplementation

Vitamin D is essential for bone health and is known to be involved in immunomodulation and cell proliferation. Vitamin D status remains a significant health issue worldwide. However, there has been no clear consensus on vitamin D deficiency and its measurement in serum, and clinical practice of vitamin D deficiency treatment remains inconsistent. The major circulating metabolite of vitamin D, 25-hydroxyvitamin D (25(OH)D), is widely used as a biomarker of vitamin D status. Other metabolic pathways are recognised as important to vitamin D function and measurement of other metabolites may become important in the future. The utility of free 25(OH)D rather than total 25(OH)D needs further assessment. Data used to estimate the vitamin D intake required to achieve a serum 25(OH)D concentration were drawn from individual studies which reported dose-response data. The studies differ in their choice of subjects, dose of vitamin D, frequency of dosing regimen and methods used for the measurement of 25(OH)D concentration. Baseline 25(OH)D, body mass index, ethnicity, type of vitamin D (D₂ or D₃) and genetics affect the response of serum 25(OH)D to vitamin D supplementation. The diversity of opinions that exist on this topic are reflected in the guidelines. Government and scientific societies have published their recommendations for vitamin D intake which vary from 400–1000 IU/d (10–25 μg/d) for an average adult. It was not possible to establish a range of serum 25(OH)D concentrations associated with selected non-musculoskeletal health outcomes. To recommend treatment targets, future studies need to be on infants, children, pregnant and lactating women.     

Prostaglandin profile and synthetic capacity of the colon: comparison of tissue sources and subcellular fractions.

Although there has been intense interest in the physiology and pathophysiology of prostaglandins (PGs) synthesized in the colon, little is known about the PG profile and synthetic capacity of different tissue sources and subcellular fractions as enzyme sources. Subcellular fractions prepared from the mucosa and muscle layer of rat colon were incubated with or without exogenous arachidonic acid ([3H]20:4n-6) for 30 min. In experiments with exogenous [3H]20:4n-6, the prostaglandin synthetic capacity of the colonic muscle layer was significantly higher than that of the mucosa. Among the subcellular fractions, microsomes had the highest PG synthetic capacity in both mucosa and muscle. The major PG product was PGI2 and PGD2 in the mucosal microsomes and PGI2 and PGE2 in the muscularis microsomes. However, production of PGI2 in the mucosa and PGE2 in the muscle was significantly reduced in the fractions containing both cytosol and microsome, resulting in an alteration of the PG profile. Substrate availability (exogenous vs endogenous supply) appears to influence the PG profile of the colon. In the colonic mucosa with exogenous [3H]20:4n-6, the production of PGI2 was 5 times higher than that of PGE2, whereas the production of PGE2 was twice higher than that of PGI2 in experiments with endogenous 20:4n-6. These observations indicate: 1) different PG profile and synthetic capacity of tissue sources and subcellular fractions; 2) alteration of PG profile due to the variation of 20:4n-6 availability. Thus, the outcome of experiments on the physiological role of PG in the colon may be determined, in part, by the tissue source and subcellular fraction selected for analysis. The present study also suggests that the variation of substrate availability in physiological and pathophysiological processes may affect the PG profile of the colon.     

Vitamin D and the kidney

The kidney is essential for the maintenance of normal calcium and phosphorus homeostasis. Calcium and inorganic phosphorus are filtered at the glomerulus, and are reabsorbed from tubular segments by transporters and channels which are regulated by 1α,25-dihydroxyvitamin (1α,25(OH)(2)D) and parathyroid hormone (PTH). The kidney is the major site of the synthesis of 1α,25(OH)(2)D under physiologic conditions, and is one of the sites of 24,25-dihydroxyvitamin D (24,25(OH)(2)D) synthesis. The activity of the 25(OH)D-1α-hydroxylase, the mixed function oxidase responsible for the synthesis of 1α,25(OH)(2)D, is regulated by PTH, 1α,25(OH)(2)D, fibroblast growth factor 23 (FGF23), inorganic phosphorus and other growth factors. Additionally, the vitamin D receptor which binds to, and mediates the activity of 1α,25(OH)(2)D, is widely distributed in the kidney. Thus, the kidney, by regulating multiple transport and synthetic processes is indispensible in the maintenance of mineral homeostasis in physiological states.     

Two methods for rapid assembly and oligomerization of synthetic genes: construction of human calcitonin-encoding sequences

Two fast, simple and reliable methods for construction of synthetic genes are described. The first represents a one-vial method for assembly and cloning of monomeric genes, and the second allows a simultaneous assembly, oligomerization and cloning of synthetic genes. Both methods consist of ligation of the synthetic oligodeoxyribonucleotides (oligos) building up the gene directly into the cloning vector, followed by screening of the recombinant clones for the presence of specific gene constructs. The average length of the oligomeric genes thus constructed is directly proportional to the molar ratio between the vector DNA and the synthetic oligos used. Both methods are illustrated by the construction of a series of human calcitonin-encoding genes.     

The effect of sunlight and UV lamps on EPR signal in nails

Radiation and Environmental Biophysics - The effects of illumination of nail clippings by direct sunlight, UV lamps and fluorescent bulbs on native and radiation-induced electron paramagnetic...     

Coarse root biomass for eucalypt plantations in Tasmania,Australia: sources of variation and methods for assessment

This study develops a feasible method for evaluating coarse root biomass (roots >2 mm diameter) of well established plantations of eucalypts and then examines coarse root biomass variability across tree age and size, fertilization treatment, species and site for Eucalyptus globulus and E. nitens in Tasmania, Australia. The most efficient sampling protocol consisted of rootball excavation and soil coring for bulk coarse roots, which when compared with total tree excavation estimated total coarse root biomass contained inside the sampled area to within 10%. Across all treatments, an average of 76% of the coarse root biomass was located within the rootball. The majority (>65%) of the coarse roots outside the rootball were located in the surface 20 cm of soil. When size class distribution was examined, 75% of coarse root biomass was found to occur in the larger (20+ mm) diameter size class, a size class that displayed considerable spatial heterogeneity. At the stand level, coarse root biomass ranged from 2.18 to 7.38 kg m ^-2 depending primarily on tree size but also on fertilization treatment, species and site. It is estimated that allocation to coarse root biomass production was around 0.2 kg m ^-2 year ^-1 (around 6% of estimated NPP) for the E. nitens stands examined in this study and around 1 kg m ^-2 year ^-1 (around 20% of estimated NPP) for the E. globulus stand examined. Robust relationships using above-ground parameters could be used to predict coarse root biomass regardless of fertilization or site, but species changed the relationship.     

Vitamin D and the immune system

The investigation of the potential influence of 1,25-(OH)2D3 on immune cells has expanded our understanding of hormone-cytokine interactions. 1,25-(OH)2D3 stimulates phenotypic and function changes in immature monocytes, alters protein synthesis, increases adherence, and augments interleukin-1 secretion. T lymphocyte proliferation and B cell immunoglobulin production are inhibited by the hormone. 1,25-(OH)2D3 decreases IL 2 and IFN-gamma synthesis by activated T lymphocytes in association with decreases in mRNA for these proteins. The step from the investigation of in vitro interactions to an understanding of in vivo effects of 1,25-(OH)2D3 on immune cells requires further study. On the basis of information at hand, such as the potential for macrophage conversion of 25-OH-D3 to 1,25-(OH)2D3, decreased or increased macrophage function in association with vitamin D3 status in vitro and in vivo, as well as altered T cell subset ratios and proliferative responses with administration of the hormone, it is tempting to speculate that 1,25-(OH)2D3 exerts an influence on immune cell function in concert with other recognized soluble mediators of monocyte and lymphocyte origin. The primary influence of 1,25-(OH)2D3 may vary with the tissue site. Systemic levels of hormone may aid in maintaining tonic immunosuppression and thus prevent trivial antigenic stimuli from initiating an immune response. Upon initiation of an immune response to a significant antigenic challenge 1,25-(OH)2D3 may, in concert with other suppressor mechanisms, limit the extent of the host response by inhibition of IL 2 and IFN-gamma production. At local sites of chronic inflammation concentrations of 1,25-(OH)2D3 may be elevated and may act in an autocrine or paracrine fashion to alter the immune response, for example, by increasing IL 1 production and antigen presentation by tissue monocyte/macrophages. The activation of T cells is associated with the synthesis of 1,25-(OH)2D3 receptors, thus potentially limiting T cell proliferation in the presence of the hormone. Other biological actions of IL 1, however, including effects on cells in bone, joint, and brain may be augmented. Thus, the end result of the opposing effects of 1,25-(OH)2D3 on immune cells and their secretory products may vary with the specific cells involved, their state of maturation and activation, and the local concentrations of the hormone. Studies to date support the concept of an expanded role for 1,25-(OH)2D3 in immune cell biology.     

Intercalibration of assessment methods for macrophytes in lowland streams: direct comparison and analysis of common metrics

The results of four macrophyte assessment methods (French Indice Biologique Macrophytique en Rivière, German Reference Index, British Mean Trophic Rank and Dutch Macrophyte Score) were compared, based on plant survey data of medium-sized lowland streams in Central Europe. To intercalibrate the good quality class boundaries two alternative methods were applied: direct comparison and the use of “common metrics”. While the French and British methods were highly related (R²>0.75), the German RI showed less (0.20<R²<0.55) and the Dutch DMS least correlation (R²<0.10) with other methods. Of 70 macrophyte metrics tested only Ellenberg_N was considerably related to three of the national assessment methods, thus representing a potential common metric for intercalibration. Comparison of quality class boundaries via regression analysis using both intercalibration approaches revealed major differences between classifications of the French, German and British methods, which are, in addition, related in a nonlinear way.     

Comparative assessment of soil microbial biomass determined by the methods of direct microscopy and substrate-induced respiration

The content of microbial biomass (MB) was determined in samples of gray forest, chestnut, and tundra soils with different physicochemical properties (0.4–22.7% C_org; 8.4–26.8% silt particles; pH 4.3–8.4) by the methods of substrate-induced respiration (MB_SIR) and direct microscopy (MB_M). The samples of two upper soil layers, 0–5 and 5–10 cm (without plant litter), from different ecosystems (forest, forest shelter belt, meadow, fallow, and arable) and elements of relief of interfluvial tundra (block/upper land plateau, depression between blocks) have been analyzed. The content of microbial biomass in the 0–5-cm soil layer was 216–8134 and 348–7513 μg C/g soil as measured by the methods of substrate-induced respiration and direct microscopy, respectively. The MB_SIR and MB_M values closely correlated with each other: r = 0.90 and 0.74 for 0–5 and 5–10 cm, respectively. The average MB_SIR/MB_M ratio was 90 and 60% for 0–5 and 5–10 cm, respectively. The portion of microbial carbon in total organic soil carbon was, on average, 4 and 3% (SIR) and 5 and 7% (direct microscopy) for 0–5 and 5–10 cm, respectively. Possible reasons for the differences between MB_SIR and MB_M values in the soils under study are discussed.     

Mechanisms for the selective action of Vitamin D analogs

The non-classical effects of 1,25(OH)(2)D(3) create possible therapeutic applications for immune modulation (e.g. auto-immune diseases and graft rejection), inhibition of cell proliferation (e.g. psoriasis, cancer) and induction of cell differentiation (e.g. cancer). The major drawback related to the use of 1,25(OH)(2)D(3) is its calcemic effect, which prevents the application of pharmacological concentrations. Several analogs are now available that show modest to good selectivity with regard to specific effects (e.g. anticancer or immune effects or bone anabolism versus hypercalcemia) when tested in appropriate in vivo models. The molecular basis for this selectivity is only partially understood and probably a variable mixture of mechanisms.     

Estimating direct and spill-over impacts of political elections on COVID-19 transmission using synthetic control methods

Mass gathering events have been identified as high-risk environments for community transmission of coronavirus disease 2019 (COVID-19). Empirical estimates of their direct and spill-over effects however remain challenging to identify. In this study, we propose the use of a novel synthetic control framework to obtain causal estimates for direct and spill-over impacts of these events. The Sabah state elections in Malaysia were used as an example for our proposed methodology and we investigate the event’s spatial and temporal impacts on COVID-19 transmission. Results indicate an estimated (i) 70.0% of COVID-19 case counts within Sabah post-state election were attributable to the election’s direct effect; (ii) 64.4% of COVID-19 cases in the rest of Malaysia post-state election were attributable to the election’s spill-over effects. Sensitivity analysis was further conducted by examining epidemiological pre-trends, surveillance efforts, varying synthetic control matching characteristics and spill-over specifications. We demonstrate that our estimates are not due to pre-existing epidemiological trends, surveillance efforts, and/or preventive policies. These estimates highlight the potential of mass gatherings in one region to spill-over into an outbreak of national scale. Relaxations of mass gathering restrictions must therefore be carefully considered, even in the context of low community transmission and enforcement of safe distancing guidelines.     

Metabolomics methods for the synthetic biology of secondary metabolism

Many microbial secondary metabolites are of high biotechnological value for medicine, agriculture, and the food industry. Bacterial genome mining has revealed numerous novel secondary metabolite biosynthetic gene clusters, which encode the potential to synthesize a large diversity of compounds that have never been observed before. The stimulation or "awakening" of this cryptic microbial secondary metabolism has naturally attracted the attention of synthetic microbiologists, who exploit recent advances in DNA sequencing and synthesis to achieve unprecedented control over metabolic pathways. One of the indispensable tools in the synthetic biology toolbox is metabolomics, the global quantification of small biomolecules. This review illustrates the pivotal role of metabolomics for the synthetic microbiology of secondary metabolism, including its crucial role in novel compound discovery in microbes, the examination of side products of engineered metabolic pathways, as well as the identification of major bottlenecks for the overproduction of compounds of interest, especially in combination with metabolic modeling. We conclude by highlighting remaining challenges and recent technological advances that will drive metabolomics towards fulfilling its potential as a cornerstone technology of synthetic microbiology.     

Vitamin D and fractures in the elderly

Osteoporosis and the subsequent fractures caused by this are a source of morbidity and mortality in the elderly population. It is also often the start of the cascade that culminates in frailty and dependence. Vitamin D has a direct relationship with the appearance of osteoporosis and with the risk of fractures. Receptors of this vitamin have also recently been described in other organs and systems of the body that are associated with muscle strength, cancer and overall mortality. Deficiency of this vitamin in the elderly population in Spain is very prevalent, both in the community and the hospitalised elderly. The diagnosis and treatment are straightforward and cheap. Its efficacy in the prevention of osteoporosis and in the appearance of fractures is perfectly demonstrated. In this review, we will look at the physiology and actions of this vitamin, as well as the principal studies that have demonstrated its effectiveness in the elderly population.     

Serum Vitamin D,Vitamin D Binding Protein,and Risk of Colorectal Cancer

Background

We previously reported a positive association between serum 25-hydroxyvitamin D (25(OH)D) and colorectal cancer risk. To further elucidate this association, we examined the molar ratio of 25(OH)D to vitamin D binding protein (DBP), the primary 25(OH)D transport protein, and whether DBP modified the association between 25(OH)D and colorectal cancer risk.

Methods

In a nested case-control study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, controls were 1∶1 matched to 416 colorectal cancer cases based on age and date of blood collection. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) for quartiles of 25(OH)D, DBP, and the molar ratio of 25(OH)D:DBP, a proxy for free, unbound circulating 25(OH)D.

Results

Comparing highest to lowest quartiles, DBP was not associated with colorectal cancer risk (OR = 0.91; 95% CI: 0.58, 1.42, p for trend  = 0.58); however, a positive risk association was observed for the molar ratio of 25(OH)D:DBP (OR = 1.44; 95% CI: 0.92, 2.26, p for trend  = 0.04). In stratified analyses, the positive association between 25(OH)D and colorectal cancer was stronger among men with DBP levels above the median (OR = 1.89; 95% CI: 1.07, 3.36, p for trend  = 0.01) than below the median (OR = 1.20; 95% CI: 0.68, 2.12, p for trend  = 0.87), although the interaction was not statistically significant (p for interaction  = 0.24).

Conclusion

Circulating DBP may influence the association between 25(OH)D and colorectal cancer in male smokers, with the suggestion of a stronger positive association in men with higher DBP concentrations. This finding should be examined in other populations, especially those that include women and non-smokers.