Group-specific Component Research Articles

Genetic and environmental predictors of serum 25-hydroxyvitamin D concentrations among middle-aged and elderly Chinese in Singapore

Vitamin D is known for maintaining Ca homeostasis and bone structure, and may also decrease susceptibility to chronic and infectious diseases. However, data on vitamin D status and its predictors among Southeast Asian populations are limited. We evaluated the distribution and determinants (genetic and environmental) of serum 25-hydroxyvitamin D (25(OH)D) concentrations among 504 middle-aged and elderly participants (aged 45-74 years) in the Singapore Chinese Health Study. Data on dietary and other lifestyle factors were collected by trained interviewers. Serum 25(OH)D concentrations and genetic polymorphisms in vitamin D metabolism pathway enzymes (cytochrome P450 (CYP) 2R1, 3A4, 27B1, 24A1; vitamin D binding protein (also known as group-specific component, GC); and vitamin D receptor) were measured using stored biospecimens. Mean 25(OH)D concentration was 68·8 nmol/l. Serum 25(OH)D concentrations were positively associated with dietary vitamin D intake, and inversely associated with hours spent sitting at work. BMI was not associated with 25(OH)D concentrations. CYP2R1 rs10741657, rs12794714, rs1993116; CYP3A4 rs2242480; and GC rs4588, rs7041, rs16847015, rs2298849 were statistically significantly associated with 25(OH)D concentrations. Individuals with the Gc2-2 haplotype (rs4588AA/rs7041TT) had statistically significantly lower 25(OH)D concentrations compared to all other Gc haplotypes (P-trend < 0·001). The majority of participants (86 %) had 25(OH)D concentrations ≥ 50 nmol/l, which is consistent with the 2011 Institute of Medicine (US) recommendation for bone health, and 32 % had concentrations of ≥ 75 nmol/l that are thought to be required for broader health effects. Dietary vitamin D intake, hours spent indoors at work and genetic variation in CYP2R1, CYP3A4 and GC are significant predictors of 25(OH)D concentrations among Singapore Chinese.

Serum Gc-globulin levels are reduced in patients with severe acute pancreatitis

To investigate the role of group-specific component globulin (Gc-globulin) in the early process of severe acute pancreatitis (SAP). A total of 37 patients with SAP and 31 patients with mild acute pancreatitis (MAP) were enrolled in the study. Twenty healthy individuals served as controls. Blood samples were taken from SAP and MAP patients on the day of admission (day 1), day 7, and day 14. Serum total Gc-globulin levels were measured using an enzyme-linked immunosorbent assay. On admission, the total Gc-globulin levels of patients in the SAP group were 368 (270-455) mg/l (expressed as medians with interquartile range), which were significantly lower (P=0.007) compared with the control group [420 (299-585) mg/l]. In the SAP group, a significant decrease in serum total Gc-globulin was observed in patients who developed organ dysfunction [267 (242-306) mg/l] compared with patients who did not [414 (329-513) mg/l, P<0.001]. Patients with lower Gc-globulin levels were at a higher risk of developing organ dysfunction (P=0.005). Furthermore, serial measurements displayed increasing total Gc-globulin levels in survivors. Decreased total Gc-globulin was linked to poor outcomes of SAP. These data support our hypothesis that Gc-globulin may play an important role in the early process of acute pancreatitis. Gc-globulin might be a novel target for prognosis and therapy of SAP.

Allelic Determinants of Vitamin D Insufficiency, Bone Mineral Density, and Bone Fractures

Low 25-hydroxycholecalciferol [25(OH) vitamin D] status is known to play an important role in many diseases with focus on bone health. Based on recently reported genetic determinants of vitamin D insufficiency, we aimed to analyze genetic variants of group-specific component (GC), 7-dehydrocholesterol reductase (DHCR7), and cytochrome P450IIR-1 (CYP2R1) for association with vitamin D levels, bone mineral density (BMD), and bone fractures. We conducted a cross-sectional BMD and fracture study and a prospective cohort study. The cross-sectional study comprised participants of a BMD screening study, and the prospective cohort study comprised nursing home subjects. The cross-sectional study included 342 subjects (mean age, 55.3 ± 12.0 yr), and the prospective study included 1093 subjects (mean age, 84.0 ± 6.0 yr). Patients were stratified by GC, DHCR7, and CYP2R1 genotypes. For each gene, the allele associated with lower 25(OH) vitamin D levels was designated as "risk allele." The potential role of these risk alleles in fracture risk was analyzed by logistic regression analysis including age and sex as confounders. We measured BMD and fractures. GC genotypes were significantly associated with lower mean 25(OH) vitamin D levels in both cohorts (P = 0.001 and P = 0.048, respectively). There was no significant association of BMD with any of the genotypes. None of the alleles was associated with past fractures, whereas the DHCR7 G-allele was significantly associated with prospective fractures (odds ratio, 0.68; 95% confidence interval, 0.51-0.92; P = 0.011). The DHCR7 gene polymorphism may be a predictor for fracture risk.

Role of vitamin D on cancer immunotherapy

Dear Editor in Chief, With a great interest, we read a recently published paper in Frontier in Endocrinology journal by Vuolo et al., entitled “Vitamin D and Cancer” (Vuolo et al., 2012). They skillfully reviewed the role of vitamin D in all aspects of cancer such as cancer prevention, immune system and cancer, reverse effect of cancer on vitamin D, and vitamin D status in some important type of malignancy. This issue is a hot topic in oncology, but in this study there are some concerns which undermine the results to make a definite conclusion. Although they concluded that “The immune system seems to represent a relevant target for the antineoplastic effects of vitamin D,” (Vuolo et al., 2012) they did not consider anti-neoplastic role of activated form of vitamin D using for immunotherapy of cancer. It was recently shown that a group of vitamin D-binding protein (DBP) so called Gc protein is an important precursor for activating macrophage as one of the main innate immune cell for cancer immunotherapy (Nagasawa et al., 2005). Although the aim of the review by Vuolo et al. was the role of Vitamin D in cancer, it was confirmed that the level of vitamin D is related to Vitamin D binding proteins (Carpenter et al., 2012). In normal tissue, when a neoplastic tissue is arise, DBP is naturally activated by glycosylation and transform to DBP-derived macrophage-activating factor (Gc-MAF) by b-galactosidase and sialidase of B and T cells, respectively, which can activate macrophage to phagocyte the neoplastic cells. Group-specific component protein (Gc) as DBP preserve vitamin D in body fluids and put it available for tissues. But an enzyme (a-N-acetylgalactosaminidase) produced by neoplastic cells deactivate and denaturize this factor and provide neoplastic cells to spread (Yamamoto and Naraparaju, 1998; Ghanei et al., 2012). In some clinical studies, Gc-MAF has successfully been used for prostate, colorectal, and breast cancer (Yamamoto and Suyama, 2008; Yamamoto et al., 2008a,b). Therefore, vitamin D has a prominent role in natural tumorocidal activity of immune system as an initial precursor.

Erratum: Relationship between Group-Specific Component Protein and the Development of Asthma

Erratum: Relationship between Group-Specific Component Protein and the Development of Asthma

Genetic variants in vitamin D metabolism-related genes and body mass index: analysis of genome-wide scan data of approximately 7000 Chinese women

Vitamin D deficiency has been consistently associated with obesity. However, it is unclear whether vitamin D deficiency is the cause or consequence of obesity. We investigated this question by evaluating the association between genetic variants in vitamin D metabolism pathway genes and obesity-related traits. Using directly genotyped and imputed data from a genome-wide association study of 6922 women aged 25-70 years, we examined the association of 198 single-nucleotide polymorphisms (SNPs) in vitamin D pathway genes (CYP27A1, CYP27B1, CYP24A1, CYP2R1, group-specific component (GC) and vitamin D nuclear receptor (VDR)) with body mass index (BMI) and body weight. Per allele beta (β) estimates were calculated for this association using linear regression models, controlling for age, square of age, menopausal status and sample sets. Overall, only two SNPs (rs2248359 in CYP24A1 and rs10832313 in CYP2R1) had a nominally significant association with BMI and weight (P<0.05 for all), with no variation observed by menopausal status, physical activity or dietary energy intake. None of the SNPs examined in the VDR gene were associated with BMI or weight. Our findings suggest that common genetic variants in vitamin D pathway genes do not have a major role in obesity among Chinese women. This comprehensive evaluation of genetic polymorphisms in vitamin D metabolism-related genes and obesity-related traits did not provide strong evidence to support low vitamin D levels as a cause of obesity.

Association of Genetic Markers with Mental Retardation

Five red cell genetic markers namely, acid phosphatase locus 1 (ACP1), esterase D (ESD), glyoxalase locus 1 (GLO1), superoxide dismutase (SOD) and haemoglobin (HB) and five plasma proteins namely haptoglobin (HP), ceruloplasmin (CP), group specific component (GC), transferrin (TF) and albumin (ALB) were studied in mentally retarded individuals from Visakhapatnam area of north coastal Andhra Pradesh, South India. The results were compared with the data obtained from controls. Out of studied ten genetic markers, two namely ACP1 and HP showed significant differences between patients and controls. The risk estimates were also showing a significant association.

Association and expression quantitative trait loci (eQTL) analysis of porcine AMBP, GC and PPP1R3B genes with meat quality traits

The aim of this research was to screen polymorphism and to perform association study of porcine AMBP (alpha-1-microglobulin/bikunin precursor), GC (group-specific component protein) and PPP1R3B (protein phosphatase 1, regulatory (inhibitor) subunit 3B) genes with meat quality traits as well as to unravel the transcriptional regulation of these genes by expression QTL (eQTL) study. For this purpose, Duroc×Pietrain F2 resource population (DuPi; n=313) and a commercial breed Pietrain (Pi; n=110) were used for association and only DuPi for expression and eQTL study. A SNP was identified in the genes AMBP (g.22229C>T), GC (g.398C>T) and PPP1R3B (c.479A>G), respectively. In DuPi SNP of AMBP was associated (P<0.05) with meat colour, pH(1L), pH(24L), pH(24H) and conductivity(24L); SNP of GC showed tendency to association (P<0.10) with pH24H, conductivity(1L) and thawing loss, and SNP of PPP1R3B was associated (P<0.05) with meat colour, pH(1L), pH(24L), pH(24H) and shear force. In Pi SNPs of AMBP and GC was associated with pH(24H) and PPP1R3B SNP was associated with pH(24L). The mRNA levels in Longissimus dorsi muscle tissue of these three genes were evaluated by using qRT-PCR to identify association between gene expression and meat quality traits as well as to analyse eQTL. The mRNA expression of PPP1R3B associated with pH(24L) (P<0.05). Expression of these three genes was higher in animals with low pH of muscle. Linkage analysis using QTL Express revealed ten trans-regulated eQTL on seven porcine autosomes. Suggestive eQTL [P<0.05, CW (chromosome-wide)] were found for PPP1R3B on SSC3 and 13. These results revealed that genetic variation and gene expression of these genes are associated with the meat quality traits. These three genes could influence meat quality and could be potential positional, physiological and functional candidate gene for meat quality traits in pigs. However, the analysis of eQTL also suggested that we need to consider additional genes encoding for transcription factors (TF), via fine-mapping underlying the eQTL peaks, in order to understand interaction among these genes.

Proximal tubules and podocytes are toxicity targets of bucillamine in a mouse model of drug-induced kidney injury

Effective detection of potential nephrotoxicity is crucial for pre-clinical drug development. We evaluated a sensitive animal model for drug-induced kidney injury, which includes hemi-nephrectomy of mice. Although bucillamine and d-penicillamine are used for the treatment of rheumatoid arthritis in Japan, drug-related adverse effects on the kidney can limit their therapeutic utilities. When bucillamine (1000 or 2000 mg/kg/day) or d-penicillamine (2000 mg/kg/day) were orally administered to hemi-nephrectomised BALB/c mice, the urinary protein levels of bucillamine-treated mice, but not of those treated with d-penicillamine, the vehicle, or in bucillamine treated unnephrectomized mice, were significantly increased and remained high during the 4-week drug-loading period. Membranous glomerulonephropathy occasionally seen in bucillamine/d-penicillamine-treated arthritis patients was not reproduced in mice. Instead, our mouse model showed proximal tubular injury and podocyte foot process effacement in the bucillamine-treated kidneys. These two cell types are also the primary targets of the experimental Heymann membranous glomerulonephropathy. Gene expression profiling of the bucillamine-treated mice identified lipocalin 2 as a significantly up-regulated transcript together with cytochrome P450 CYP4a14, a group-specific component, and proprotein convertase subtilisin/kexin type 9. Moreover, large amounts of lipocalin 2 were detected in the urine of the bucillamine-treated mice, but not in the hemi-nephrectomised control mice. These results indicate that hemi-nephrectomy effectively promotes acute kidney injury by bucillamine, which is accompanied by up-regulation of the urinary biomarker lipocalin 2. Our mouse model with initial stage of kidney injury should be useful to analyse the pathogenesis of drug-induced glomerular and tubular injuries.

Relationship between Group-Specific Component Protein and the Development of Asthma

Airway inflammation and remodeling during asthma are attributed to the altered expression of biologically relevant proteins. To search for asthma-specific proteins in bronchoalveolar lavage fluid (BAL) from individuals with asthma and to validate the identified proteins in an experimental model of asthma. Liquid chromatography-tandem mass spectrometry was performed to identify proteins in BAL fluid found by two dimensional electrophoresis (2DE) to be differentially expressed in subjects with asthma versus control subjects. Group-specific component (Gc) and mRNA levels were measured using an ELISA, Western blots, and PCR. A neutralization study using an antibody against Gc protein was performed in an experimental asthma model. Based on 2DE, 15 proteins were significantly up-regulated or down-regulated in eight subjects with asthma compared with eight control subjects. The protein levels of Gc, hemopexin, and haptoglobin-b were increased, whereas the a1- antitrypsin and glutathione S-transferase levels were decreased in subjects with asthma. The Gc concentration in BAL fluid was significantly elevated in 67 subjects with asthma compared with that in 22 control subjects (P < 0.009). The Gc was significantly correlated with the neutrophil percentage in BAL fluid of subjects with asthma (P = 0.001). Gc mRNA and protein levels were higher in ovalbumin-sensitized/ challenged asthma mice than in sham-treated mice. Gc protein were expressed on alveolar macrophages and on epithelial cells. Treatment with an anti-Gc antibody dose-dependently reduced the ovalbumin sensitization/challenge-induced enhancement of airway hyperreactivity, airway inflammation, goblet cell hyperplasia,and levels of eotaxin, interleukin-4, -5, and -13, and interferon-g. Gc may be involved in the development of asthma, and the neutralization of Gc protein could be a therapeutic strategy for asthma.

Research on the correlation between platelet gelsolin and blood-stasis syndrome of coronary heart disease

To study the distribution of gelsolin in human platelet and plasma, and the association with blood-stasis syndrome (BSS) of coronary heart disease (CHD). Sixty patients with CHD (30 in BSS group and 30 in non-BSS group) and 30 healthy subjects (control group) were included in this study. The classification of the syndrome was based on clinical symptoms and signs. Gelsolin concentration in platelet rich plasma (PRP), platelet poor plasma (PPP), filamentous actin (F-actin) and group-specific component globulin (Gc-globulin) of PPP were determined by enzyme-linked immunosorbent assay (ELISA). The fluorescence intensity of CD62p and cytoplasmic calcium ([Ca(2+)](i)) in human platelets of patients and healthy persons was measured with flow cytometry. Compared with the control group, gelsolin in PRP of the BSS group increased significantly (P<0.01), while that in PPP of the BSS and non-BSS groups decreased markedly (P<0.05), the CD62p, [Ca(2+)](i) of platelet, F-actin, and Gc-globulin of the BSS and non-BSS groups increased significantly (P<0.01). Compared with the non-BSS group, the gelsolin concentration in PRP of BSS group increased significantly (P<0.01), the [Ca(2+)](i) of platelet of the BSS group increased markedly (P<0.01), while the F-actin and Gc-globulin of the BSS group had no statistical defference (P>0.05). Gelsolin concentration in PRP was increased and accompanied by the elevated [Ca(2+)](i) of platelet in CHD with BSS, while gelsolin in PPP were lowered markedly. We speculate that plasma gelsolin may clear F-actin from circulation, thus resulting in depletion of plasma gelsolin significantly. This, in addition to the increased calcium influx of platelets, may lead to the gelsolin abnormal expression on platelets during the process of BSS in CHD. Therefore, platelet gelsolin may serve as a new potential biomarker and a therapeutic target of BSS in CHD.

Effects of Cadmium and vitamin D binding protein-derived macrophage activating factor (DBP-MAF) in human breast cancer cells

We previously demonstrated that chronic exposure of the human breast cancer cell line MCF-7 to non-cytotoxic concentrations of Cadmium reduced viability and angiogenic potential of this cell line. In order to better understand these effects, cells, after Cadmium exposure, were treated with vitamin D binding protein-derived macrophage activating factor (DBP-MAF). DBP-MAF is a potent macrophage-activating factor derived from vitamin D binding protein, a polymorphic serum glycoprotein with multiple functions also known as a group specific component or Gc protein. Besides stimulating macrophages, DBP-MAF has anti-tumour properties. Our data demonstrate that the decrease of MCF-7 cell viability following Cadmium treatment was completely reversed when DBP-MAF was present in the cell medium. Following this observation, we further investigated the role of DBP-MAF in modulating angiogenesis, morphology and cytoskeleton structure of MCF-7 cell line. As shown by chorioallantoic membrane assay, DBP-MAF inhibited MCF-7 cancer cell-stimulated angiogenesis. Concerning cell morphology (studied by contrast phase light microscopy and after Papanicolaou staining), following DBP-MAF treatment, cell shape and growth pattern were significantly modified. Vimentin expression (studied by immunohistochemistry and Western blot analysis), considered a hallmark of human breast cancer progression, after DBP-MAF treatment, significantly varied. Intermediate filament status changes, consisting in a shift from a keratin-rich to a vimentin-rich network (epithelial-mesenchymal transition), were observed. In conclusion, we demonstrate that the anti-cancer effects of DBP-MAF can be attributed to multiple actions independent of macrophage stimulation such as reversal of Cadmium effects on cell viability, reversal of morphological malignant phenotype and inhibition of cancer cell-stimulated angiogenesis. For these reasons, DBP-MAF might represent an useful tool to control progression and differentiation of human breast cancer.

Effect modification of air pollution on Urinary 8-Hydroxy-2'-Deoxyguanosine by genotypes: an application of the multiple testing procedure to identify significant SNP interactions

BackgroundAir pollution is associated with adverse human health, but mechanisms through which pollution exerts effects remain to be clarified. One suggested pathway is that pollution causes oxidative stress. If so, oxidative stress-related genotypes may modify the oxidative response defenses to pollution exposure.MethodsWe explored the potential pathway by examining whether an array of oxidative stress-related genes (twenty single nucleotide polymorphisms, SNPs in nine genes) modified associations of pollutants (organic carbon (OC), ozone and sulfate) with urinary 8-hydroxy-2-deoxygunosine (8-OHdG), a biomarker of oxidative stress among the 320 aging men. We used a Multiple Testing Procedure in R modified by our team to identify the significance of the candidate genes adjusting for a priori covariates.ResultsWe found that glutathione S-tranferase P1 (GSTP1, rs1799811), M1 and catalase (rs2284367) and group-specific component (GC, rs2282679, rs1155563) significantly or marginally significantly modified effects of OC and/or sulfate with larger effects among those carrying the wild type of GSTP1, catalase, non-wild type of GC and the non-null of GSTM1.ConclusionsPolymorphisms of oxidative stress-related genes modified effects of OC and/or sulfate on 8-OHdG, suggesting that effects of OC or sulfate on 8-OHdG and other endpoints may be through the oxidative stress pathway.

Analysis of the Albumin/α-Fetoprotein/Afamin/Group specific component gene family in the context of zebrafish liver differentiation

Members of the Albumin/α-Fetoprotein/Afamin/Group specific component ( Alb/Afp/Afm/Gc) multi-gene family perform physiological functions essential for body homeostasis and are among the earliest genes to be expressed in the fetal liver in mammals. A comprehensive search of the zebrafish genome has led to the isolation of a single member of this gene family, exhibiting close homology to group specific component (gc; also described as vitamin D binding protein (dbp)). Our phylogenetic analyses did not uncover albumin in the genome, indicating its likely absence in zebrafish, whereas the absence of afp and afm is in agreement with previous findings that both genes arose at a later stage of vertebrate evolution. gc mRNA expression is initiated weakly around 55 hours post fertilisation (hpf) in the developing liver, and increases until it reaches a continuously high level from about 72 hpf onwards. Investigation of gc mRNA in hdac1 mutants revealed a severe delay of expression, indicating a defect in progression of hepatic differentiation. This provides further evidence for Hdac1 regulating the precise timely execution of hepatic gene expression programmes. Conversely, onset of gc expression was unaltered in cloche mutant embryos, which lack hepatic vasculature, suggesting that this particular step of hepatic differentiation occurs independently from endothelial cells. Our studies identify gc as the likely only member of the Alb/Afp/Afm/Gc gene family in zebrafish, providing important insights into the evolution of this multi-gene family in vertebrates. Furthermore, the identification of gc adds a valuable temporal marker for investigating progressive hepatic differentiation in zebrafish.

Vitamin D-Binding Protein Directs Monocyte Responses to 25-Hydroxy- and 1,25-Dihydroxyvitamin D

Serum 25-hydroxyvitamin D (25OHD) is a key factor in determining monocyte induction of the antimicrobial protein cathelicidin, which requires intracrine conversion of 25OHD to 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. Both vitamin D metabolites circulate bound to vitamin D-binding protein (DBP), but the effect of this on induction of monocyte cathelicidin remains unclear. Human monocytes were cultured in medium containing 1) serum from DBP knockout (DBP(-/-)) or DBP(+/-) mice, 2) serum-free defined supplement reconstituted with DBP or albumin (control), and 3) human serum with different DBP [group-specific component [Gc]] genotypes with varying affinities for vitamin D metabolites. In each case, response to added 1,25(OH)(2)D(3) or 25OHD(3) was determined by measuring expression of mRNA for cathelicidin and 24-hydroxylase. Monocyte internalization of DBP was assessed by fluorescent tagging followed by microscopic and flow cytometric analysis of tagged DBP. Monocytes cultured in DBP(-/-) serum showed more potent induction of cathelicidin by 25OHD(3) or 1,25(OH)(2)D(3) when compared with DBP(+/-) serum. Likewise, DBP added to serum-free medium attenuated 25OHD(3)/1,25(OH)(2)D(3) responses. Fluorescently tagged DBP showed low-level uptake by monocytes, but this did not appear to involve a megalin-mediated mechanism. Human serum containing low-affinity Gc2-1S or Gc2-2, respectively, supported 2.75-fold (P = 0.003) and 2.43-fold (P = 0.016) higher induction of cathelicidin by 25OHD relative to cells cultured with high affinity Gc1F-1F. These data indicate that DBP plays a pivotal role in regulating the bioavailablity of 25OHD to monocytes. Vitamin D-dependent antimicrobial responses are therefore likely to be strongly influenced by DBP polymorphisms.

Genome-wide association study of circulating vitamin D levels

The primary circulating form of vitamin D, 25-hydroxy-vitamin D [25(OH)D], is associated with multiple medical outcomes, including rickets, osteoporosis, multiple sclerosis and cancer. In a genome-wide association study (GWAS) of 4501 persons of European ancestry drawn from five cohorts, we identified single-nucleotide polymorphisms (SNPs) in the gene encoding group-specific component (vitamin D binding) protein, GC, on chromosome 4q12-13 that were associated with 25(OH)D concentrations: rs2282679 (P = 2.0 × 10−30), in linkage disequilibrium (LD) with rs7041, a non-synonymous SNP (D432E; P = 4.1 × 10−22) and rs1155563 (P = 3.8 × 10−25). Suggestive signals for association with 25(OH)D were also observed for SNPs in or near three other genes involved in vitamin D synthesis or activation: rs3829251 on chromosome 11q13.4 in NADSYN1 [encoding nicotinamide adenine dinucleotide (NAD) synthetase; P = 8.8 × 10−7], which was in high LD with rs1790349, located in DHCR7, the gene encoding 7-dehydrocholesterol reductase that synthesizes cholesterol from 7-dehydrocholesterol; rs6599638 in the region harboring the open-reading frame 88 (C10orf88) on chromosome 10q26.13 in the vicinity of ACADSB (acyl-Coenzyme A dehydrogenase), involved in cholesterol and vitamin D synthesis (P = 3.3 × 10−7); and rs2060793 on chromosome 11p15.2 in CYP2R1 (cytochrome P450, family 2, subfamily R, polypeptide 1, encoding a key C-25 hydroxylase that converts vitamin D3 to an active vitamin D receptor ligand; P = 1.4 × 10−5). We genotyped SNPs in these four regions in 2221 additional samples and confirmed strong genome-wide significant associations with 25(OH)D through meta-analysis with the GWAS data for GC (P = 1.8 × 10−49), NADSYN1/DHCR7 (P = 3.4 × 10−9) and CYP2R1 (P = 2.9 × 10−17), but not C10orf88 (P = 2.4 × 10−5).

Genetic Variation in the Vitamin D Receptor (VDR) and the Vitamin D–Binding Protein (GC) and Risk for Colorectal Cancer: Results from the Colon Cancer Family Registry

Epidemiologic evidence supports a role for vitamin D in colorectal cancer (CRC) risk. Variants in vitamin D-related genes might modify the association between vitamin D levels and CRC risk. In this analysis, we did a comprehensive evaluation of common variants in the vitamin D receptor (VDR) and the vitamin D-binding protein (GC; group-specific component) genes using a population-based case-unaffected sibling control design that included 1,750 sibships recruited into the Colon Cancer Family Registry. We also evaluated whether any associations differed by calcium supplement use, family history of CRC, or tumor characteristics. Heterogeneity by calcium and vitamin D intake was evaluated for a subset of 585 cases and 837 sibling controls who completed a detailed food frequency questionnaire. Age- and sex-adjusted associations were estimated using conditional logistic regression. Overall, we did not find evidence for an association between any single-nucleotide polymorphism (SNP) in VDR or GC and risk for CRC (range of unadjusted P values 0.01-0.98 for VDR and 0.07-0.95 for GC). None of these associations was significant after adjustment for multiple comparisons. We also found no evidence that calcium or vitamin D intake (food and supplement) from the food frequency questionnaire modified the association estimates between VDR and GC SNPs and CRC. We did observe associations between SNPs in GC and microsatellite unstable CRC, although these results should be confirmed in additional studies. Overall, our results do not provide evidence for a role of common genetic variants in VDR or GC in susceptibility to CRC.

Association between Gc genotype and susceptibility to TB is dependent on vitamin D status

Group-specific component (Gc) variants of vitamin D binding protein differ in their affinity for vitamin D metabolites that modulate antimycobacterial immunity. We conducted studies to determine whether Gc genotype associates with susceptibility to tuberculosis (TB). The following subjects were recruited into case-control studies: in the UK, 123 adult TB patients and 140 controls, all of Gujarati Asian ethnic origin; in Brazil, 130 adult TB patients and 78 controls; and in South Africa, 281 children with TB and 182 controls. Gc genotypes were determined and their frequency was compared between cases versus controls. Serum 25-hydroxyvitamin D (25(OH)D) concentrations were obtained retrospectively for 139 Gujarati Asians, and case-control analysis was stratified by vitamin D status. Interferon (IFN)-gamma release assays were also performed on 36 Gujarati Asian TB contacts. The Gc2/2 genotype was strongly associated with susceptibility to active TB in Gujarati Asians, compared with Gc1/1 genotype (OR 2.81, 95% CI 1.19-6.66; p = 0.009). This association was preserved if serum 25(OH)D was <20 nmol.L(-1) (p = 0.01) but not if serum 25(OH)D was > or =20 nmol.L(-1) (p = 0.36). Carriage of the Gc2 allele was associated with increased PPD of tuberculin-stimulated IFN-gamma release in Gujarati Asian TB contacts (p = 0.02). No association between Gc genotype and susceptibility to TB was observed in other ethnic groups studied.

Evaluation and Normalization of Cloud Obscuration Related BRDF Effects in Field Spectroscopy

The impact of target bidirectional reflectance in dual field of view spectroscopy was described and quantified using field measurements and ray-tracing simulations. A data-driven normalization method was developed to convert reflectance factors under cloud obscured conditions into clear sky reflectance by decomposing the target bidirectional reflectance into an isotropic target-specific component and a group-specific bidirectional component. An evaluation on tree, grass and gravel targets suggests a reduction in relative reflectance error obtained by normalization from 15% to less than 5% between 400 and 1800 nm. At higher wavelengths a decreased signal-to-noise ratio increases the errors.

Vitamin D Binding Protein Genotype and Osteoporosis

Osteoporosis is a bone disease leading to an increased fracture risk. It is considered a complex multifactorial genetic disorder with interaction of environmental and genetic factors. As a candidate gene for osteoporosis, we studied vitamin D binding protein (DBP, or group-specific component, Gc), which binds to and transports vitamin D to target tissues to maintain calcium homeostasis through the vitamin D endocrine system. DBP can also be converted to DBP-macrophage activating factor (DBP-MAF), which mediates bone resorption by directly activating osteoclasts. We summarized the genetic linkage structure of the DBP gene. We genotyped two single-nucleotide polymorphisms (SNPs, rs7041 = Glu416Asp and rs4588 = Thr420Lys) in 6,181 elderly Caucasians and investigated interactions of the DBP genotype with vitamin D receptor (VDR) genotype and dietary calcium intake in relation to fracture risk. Haplotypes of the DBP SNPs correspond to protein variations referred to as Gc1s (haplotype 1), Gc2 (haplotype 2), and Gc1f (haplotype3). In a subgroup of 1,312 subjects, DBP genotype was found to be associated with increased and decreased serum 25-(OH)D3 for haplotype 1 (P = 3 × 10−4) and haplotype 2 (P = 3 × 10−6), respectively. Similar associations were observed for 1,25-(OH)2D3. The DBP genotype was not significantly associated with fracture risk in the entire study population. Yet, we observed interaction between DBP and VDR haplotypes in determining fracture risk. In the DBP haplotype 1-carrier group, subjects of homozygous VDR block 5-haplotype 1 had 33% increased fracture risk compared to noncarriers (P = 0.005). In a subgroup with dietary calcium intake <1.09 g/day, the hazard ratio (95% confidence interval) for fracture risk of DBP hap1-homozygote versus noncarrier was 1.47 (1.06–2.05). All associations were independent of age and gender. Our study demonstrated that the genetic effect of the DBP gene on fracture risk appears only in combination with other genetic and environmental risk factors for bone metabolism.