BACKGROUND: Although the role of vitamin D deficiency in causing osteomalacia is well recognised, there is limited evidence to suggest that vitamin D deficiency is associated with osteoporosis. One ...community based study has suggested a reduction in bone density in females with low vitamin D levels, while another has shown no effect of isolated vitamin D deficiency on population fracture rates. We aimed to assess bone density in a cohort of women with low vitamin D levels but no other identified risk factors for osteoporosis. We wished to see if there was any relationship between the two, in order to clarify whether measurement of vitamin D was justified in aiding selection of patients for DXA, and whether DXA was justified in patients found to have isolated vitamin D deficiency. METHODS: We identified 70 women referred to an open access DXA scanning service by their GP with low vitamin D levels (under 48 nmol/l) as their only risk factor. We performed DXA of hip and spine and recorded the absolute bone density and Z scores for each patient, together with their vitamin D levels. We calculated the mean (SD) values for Z score at hip and spine, and compared these to a control group of women referred for baseline DXA prior to commencing aromatase inhibitors for breast cancer. We also compared the results with those obtained from the rest of the GP database for women referred up with a 10 year risk of osteoporotic fractures calculated at over 10% using FRAX. These statistical comparisons were made using unpaired Students t test. Mean values for Z scores at hip and spine were calculated and compared within the index group for those with vitamin D levels above and below 20 nmol/l using Students t test. Correlation coefficients between vitamin D levels and Z scores at hip and spine were also calculated for the index group. RESULTS: Mean (SD) values for Z scores in the hip and spine for patients with isolated vitamin D deficiency were +0.30 (0.87) and +0.46 (0.92) respectively. These were not significantly different from controls whose corresponding values were +0.17 (0.34) and +0.49 (0.45). By contrast, patients with a 10 year risk of fracture of over 10% had lower values at hip -0.01 (0.07) and spine -0.13 (0.09) p = 0.01. Mean Z scores for those with very low vitamin D levels (under 20 nmol/l) were not significantly different at either site when compared to those with less severe deficiency (20-48 nmol/l) p = 0.26. There was no correlation between vitamin D levels and Z scores at hip or spine r = 0.01 CONCLUSIONS: There was no overall decrease in bone density associated with low vitamin D levels in women in our study. There is no evidence to support the routine measurement of vitamin D to select patients for DXA scanning. There is no reason to perform DXA scans in those patients who have an isolated vitamin D deficiency in the absence of defined risk factors for osteoporosis. Disclosure statement: The authors have declared no conflicts of interest.
We describe studies to assess the influence of polymorphism in the human glutathione S-transferase GSTM3 gene on susceptibility to high grade astrocytoma. Immunohisto-chemical studies using a ...GSTM3-specific antiserum identified expression of the GSTM3 subunit in astrocytes. The relative levels of expression of GSTM1 and GSTM3 in brain cytosols were determined after resolution of these enzymes using chromatofocusing. We found no differences in the level of GSTM3 activity in individuals with GSTM1 null and those with GSTMl-positive genotypes (GSTM1 A, GSTM1 B and GSTM1 A/B). A case-control study was performed to determine if GSTM3 alone or in combination with GSTM1 or GSTT1 influenced susceptibility to high grade astrocytoma. After correction for differences in age and gender, GSTM3 AA was not significantly different in cases compared with controls. No significant interactions between GSTM3 AA and GSTM1 null were identified. The significant interaction between GSTM3 AA and GSTT1 null appeared to result from the strength of the main effect (GSTT1 null). The data show that while GSTM3 is expressed in astrocytes and contributes significantly to total GST activity in human brain, it does not appear to influence susceptibility to high grade astrocytoma. Further, unlike lung, there appears to be no relationship between the level of GSTM3 activity in brain and GSTM1 genotype.
What is the relevance of major mergers and interactions as triggering mechanisms for active galactic nuclei (AGN) activity? To answer this longstanding question, we analyze 140 XMM-selected AGN host ...galaxies and a matched control sample of 1264 inactive galaxies over z~0.3-1.0 and log(M_*/M_sun)<11.7 with high-resolution HST/ACS imaging from the COSMOS field. The visual analysis of their morphologies by 10 independent human classifiers yields a measure of the fraction of distorted morphologies in the AGN and control samples, i.e. quantifying the signature of recent mergers which might potentially be responsible for fueling/triggering the AGN. We find that (1) the vast majority (>85%) of the AGN host galaxies do not show strong distortions, and (2) there is no significant difference in the distortion fractions between active and inactive galaxies. Our findings provide the best direct evidence that, since z~1, the bulk of black hole accretion has not been triggered by major galaxy mergers, therefore arguing that the alternative mechanisms, i.e., secular processes and minor interactions, are the leading triggers for the episodes of major black hole growth. We also exclude an alternative interpretation of our results: a significant time lag between merging and the observability of the AGN phase could wash out the most significant merging signatures, explaining the lack of enhancement of strong distortions on the AGN hosts. We show that this alternative scenario is unlikely due to: (1) recent major mergers being ruled out for the majority of sources due to the high fraction of disk-hosted AGN, (2) the lack of a significant X-ray signal in merging inactive galaxies as a signature of a potential buried AGN, and (3) the low levels of soft X-ray obscuration for AGN hosted by interacting galaxies, in contrast to model predictions.
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