Variations in vitamin D receptor transcription factor complexes associated with the osteocalcin gene vitamin D responsive element in osteoblasts and osteosarcoma cells

Long-Term Saccharin Consumption and Increased Risk of Obesity, Diabetes, Hepatic Dysfunction, and Renal Impairment in Rats

Background and objectives: This study evaluated the effect of chronic consumption of saccharin on important physiological and biochemical parameters in rats. Materials and Methods: Male Wistar rats were used in this study and were divided into four groups: A control group and three experimental groups (groups 1, 2, and 3) were treated with different doses of saccharin at 2.5, 5, and 10 mg/kg, respectively. Each experimental group received sodium saccharin once per day for 120 days while the control group was treated with distilled water only. In addition to the evaluation of body weight, blood samples [total protein, albumin, glucose, lipid profile, alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), creatinine, and uric acid] and urine (isoprostane) were collected in zero time, and after 60 and 120 days for biochemical evaluation. Liver (catalase activity) and brain (8-hydroxy-2’-deoxyguanosine, 8-OHdG) tissues were collected at time zero and after 120 days. Results: The data showed that saccharin at 5 mg/kg increased body weight of treated rats after 60 (59%) and 120 (67%) days of treatment. Increased concentration of serum glucose was observed after treatment with saccharin at 5 (75% and 62%) and 10 mg/kg (43% and 40%) following 60 and 120 days, respectively. The concentration of albumin decreased after treatment with saccharin at 2.5 (34% and 36%), 5 (39% and 34%), and 10 mg/kg (15% and 21%) after 60 and 120 days of treatment, respectively. The activity of LDH and uric acid increased proportionally with dosage levels and consumption period. There was an increased concentration of creatinine after treatment with saccharin at 2.5 (125% and 68%), 5 (114% and 45%), and 10 mg/kg (26% and 31%) following 60 and 120 days, respectively. Catalase activity and 8-OHdG increased by 51% and 49%, respectively, following 120 days of treatment with saccharin at 2.5 mg/kg. Elevation in the concentration of isoprostane was observed after treatment with saccharin at all doses. Conclusions: The administration of saccharin throughout the treatment period was correlated with impaired kidney and liver function. Both hyperglycemic and obesity-inducing side effects were observed. There was an increased oxidative status of the liver, as well as exposure to increased oxidative stress demonstrated through the increased levels of isoprostane, uric acid, 8-OHdG, and activity of catalase. Therefore, it is suggested that saccharin is unsafe to be included in the diet.

Generation and characterization of two immortalized human osteoblastic cell lines useful for epigenetic studies

Different model systems using osteoblastic cell lines have been developed to help understand the process of bone formation. Here, we report the establishment of two human osteoblastic cell lines obtained from primary cultures upon transduction of immortalizing genes. The resulting cell lines had no major differences to their parental lines in their gene expression profiles. Similar to primary osteoblastic cells, osteocalcin transcription increased following 1,25-dihydroxyvitamin D₃ treatment and the immortalized cells formed a mineralized matrix, as detected by Alizarin Red staining. Moreover, these human cell lines responded by upregulating ALPL gene expression after treatment with the demethylating agent 5-aza-2'-deoxycytidine (AzadC), as shown before for primary osteoblasts. We further demonstrate that these cell lines can differentiate in vivo, using a hydroxyapatite/tricalcium phosphate composite as a scaffold, to produce bone matrix. More importantly, we show that these cells respond to demethylating treatment, as shown by the increase in SOST mRNA levels, the gene encoding sclerostin, upon treatment of the recipient mice with AzadC. This also confirms, in vivo, the role of DNA methylation in the regulation of SOST expression previously shown in vitro. Altogether our results show that these immortalized cell lines constitute a particularly useful model system to obtain further insight into bone homeostasis, and particularly into the epigenetic mechanisms regulating sclerostin production.

Circulating 25-hydroxyvitamin D, VDR polymorphisms, and survival in advanced non-small-cell lung cancer

PURPOSE

We showed previously that in early-stage non-small-cell lung cancer (NSCLC), serum vitamin D levels and VDR polymorphisms were associated with survival. We hypothesized that vitamin D levels and VDR polymorphisms may also affect survival among patients with advanced NSCLC.

PATIENTS AND METHODS

We evaluated the relationship between circulating 25-hydroxyvitamin D levels; VDR polymorphisms, including Cdx-2 G>A (rs11568820), FokI C>T (rs10735810), and BsmI C>T (rs144410); and overall survival among patients with advanced NSCLC. Analyses of survival outcomes were performed using the log-rank test and Cox proportional hazards models, adjusting for sex, stage, and performance status.

RESULTS

There were 294 patients and 233 deaths, with median follow-up of 42 months. We found no difference in survival by circulating vitamin D level. The C/C genotype of the FokI polymorphism was associated with improved survival: median survival for C/C was 21.4 months, for C/T was 12.1 months, and for T/T was 15.6 months (log-rank P = .005). There were no significant effects on survival by the Cdx-2 or BsMI polymorphism. However, having increasing numbers of protective alleles was associated with improved survival (adjusted hazard ratio for two or more v zero to one protective alleles, 0.57; 95% CI, 0.41 to 0.79; P = .0008). On haplotype analysis, the G-T-C (Cdx-2-FokI-BsmI) haplotype was associated with worse survival compared with the most common haplotype of G-C-T (adjusted hazard ratio, 1.61; 95% CI, 1.21 to 2.14; P = .001).

CONCLUSION

There was no main effect of vitamin D level on overall survival in the advanced NSCLC population. The T allele of the VDR FokI>T polymorphism and the G-T-C (Cdx-2-FokI-BsmI) haplotype were associated with worse survival.

Polymorphisms of vitamin D receptor and survival in early-stage non-small cell lung cancer patients

Our previous analysis suggested that surgery season in the summer time and high vitamin D intake are associated with improved survival in early-stage non-small cell lung cancer (NSCLC) patients. Here, we investigated the associations of vitamin D receptor (VDR) polymorphisms of Cdx-2 G>A, FokI C>T, and BsmI C>T with overall survival (OS) and recurrence-free survival (RFS) in 373 early-stage NSCLC patients. The data were analyzed using log-rank test and Cox proportional hazards models. The median follow-up time was 71 months (range, 0.1-140 months), with 186 deaths and 127 recurrences. There was no association between VDR polymorphisms and survival, overall or among adenocarcinoma patients. Among squamous cell carcinoma (SCC) patients, the G/A+A/A genotype group of the Cdx-2 polymorphism was associated with better OS: the 5-year OS rates were 41% [95% confidence interval (95% CI), 28-53] for the G/G and 55% (95% CI, 39-71) for the G/A+A/A genotypes, respectively (P = 0.04, log-rank test), with the adjusted hazard ratio of 0.56 (95% CI, 0.33-0.95) for G/A+A/A versus G/G. For the joint effects of the three polymorphisms, subjects with two or more "protective" alleles have better OS among SCC patients, with the adjusted hazard ratios of 0.20 (95% CI, 0.09-0.48), 0.40 (95% CI, 0.19-0.87), and 0.43 (95% CI, 0.19-0.97), respectively, for subjects with two, three, and four or more "protective" alleles when compared with subjects with zero or one "protective" allele (P(trend) = 0.71). Similar associations were found in haplotype analysis and for RFS among SCC patients. In conclusion, VDR polymorphisms may be associated with improved survival among SCC patients of early-stage NSCLC.

Associations between vitamin D, vitamin D receptor gene and the androgen receptor gene with colon and rectal cancer

The transcriptional activity of the vitamin D receptor (VDR) gene is regulated, at least in part, by the androgen receptor (AR) gene. We evaluate how the number of polyglutamine (CAG) repeats of the AR gene influence colorectal cancer in conjunction with vitamin D, sunshine exposure and VDR. Studies of colon (1,580 cases and 1,968 controls) and rectal (797 cases and 1,016 controls) cancer were used. Vitamin D intake and average hours of sunshine exposure interacted with AR genotype in men. Men with low vitamin D intake or low levels of sunshine exposure who had 23+ CAG repeats of the AR gene had the greatest risk of colon cancer. ORs for men with 23 or more CAG repeats of the AR gene and in the lowest tertile of vitamin D intake or sunshine exposure were 1.71 (95% CI 1.14, 2.56) and 1.51 (95% CI 1.09, 2.09). Men with high levels of sunshine exposure were at reduced risk of developing rectal cancer if they had 23 or more CAG repeats (OR 0.62 95% CI 0.39, 0.97) than if they had fewer than 23 CAG repeats. The FF genotype of the Fok1 VDR gene was associated with reduced risk of colon cancer among women with any allele of 23+ CAG repeats (OR 0.62 95% CI 0.44, 0.88), whereas men with the LL/bb VDR genotypes were at reduced risk of rectal cancer if they also had 23+ CAG repeats (OR 0.71 95% CI 0.48, 1.05) relative to men with fewer than 23 CAG repeats of the AR gene. These data provide support for the role of vitamin D and sunshine exposure in the etiology of colorectal cancer and suggest that AR gene may modulate the association.

Associations between BMI, energy intake, energy expenditure, VDR genotype and colon and rectal cancers (United States)

Components of energy balance are important elements associated with colorectal cancer risk. In this study we examine the association between VDR genotypes, BMI, physical activity, and energy intake and risk of colorectal cancer. Data from a population-based case-control study of colon (1174 cases and 1174 controls) and rectal (785 cases and 1000 controls) cancer was used to evaluate the associations. The Bsm1, polyA, and Fok1 VDR polymorphisms were evaluated. For colon cancer, those who are obese were at greater risk of colon cancer if they had the SS or BB (OR = 3.50; 95% CI = 1.75-7.03; p interaction 0.03) or ff (OR = 2.62; 95% CI = 1.15-5.99; p interaction 0.12/) VDR genotypes. On the other hand, those who were least physically active were at greater risk of colon cancer if they had the ff VDR genotype (OR = 3.46; 95% CI = 1.58-7.58; p interaction 0.05). The association between energy intake and colon cancer appears to be driven more by energy intake than Bsm1 or polyA VDR genotypes, although there was a significant interaction between the Fok1 VDR polymorphism and energy intake and risk of both colon and rectal cancer (p interaction 0.01 for colon and 0.04 for rectal). These data suggest a relationship between VDR genotype and factors related to energy balance in modifying colorectal cancer risk.

The biological activities of 1alpha,25-dihydroxyvitamin D3 and its synthetic analog 1alpha,25-dihydroxy-16-ene-vitamin D3 in normal human osteoblastic cells and human osteosarcoma SaOS-2 cells are modulated by 17-beta estradiol and dependent on stage of differentiation

We compared the effects of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and its analog, 1alpha,25-dihydroxy-16-ene-vitamin D3 [1alpha,25(OH)2-16-ene-D3], as well as their interactions with 17-beta estradiol (E2) on osteoblastic function in our human normal (HOB) and osteosarcoma SaOS-2 cell models representing two different stages of differentiation, the more differentiated HOB+DEX cells and SaOS+DEX cells, and the corresponding less differentiated HOB-DEX and SaOS-DEX cells. The differential effects of 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-D3 and the modulation by E2 on ALP activity in HOB-DEX and HOB+DEX cells were small but significant. The most significant effects were seen in SaOS+DEX cells, in which 1alpha,25(OH)2-16-ene-D3 was 100-fold more potent than 1alpha,25(OH)2D3, the maximal enhancement being exerted at 0.1 nM and 10 nM, respectively. E2 enhanced the stimulatory effects of both compounds, with ALP being increased 2-fold at 0.1 nM (p<0.001). Osteocalcin (OC) production in HOB-DEX cells was stimulated 1.3 to 1.4-fold by 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-D3 at a concentration of 0.01 nM, with E2 inhibiting the effect of 1alpha,25(OH)2-16-ene-D3. In SaOS-DEX and SaOS+DEX cells, 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-D3 stimulated OC production 1.6-fold at 0.1 nM with E2 slightly enhancing the effect of 1alpha,25(OH)2D3. Western blot analysis of 1alpha,25(OH)2D3 receptor (VDR) levels showed that in SaOS+DEX cells, the effect of 1alpha,25(OH)2D3 was larger than that of 1alpha,25(OH)2-16-ene-D3. These results show that 1alpha,25(OH)2-16-ene-D3 is biologically active in human osteoblasts.

Chromatin hyperacetylation abrogates vitamin D-mediated transcriptional upregulation of the tissue-specific osteocalcin gene in vivo

Cells expressing the bone-specific osteocalcin (OC) gene exhibit two DNase I hypersensitive sites within the proximal (nt -170 to -70) and distal (nt -600 to -400) promoter. These sites overlap elements that independently or in combination contribute to basal and vitamin D-stimulated OC gene transcription. Here we address mechanisms that participate in control of chromatin remodelling at these sites. By applying nuclease digestion and indirect end-labeling or by combining intranuclear footprinting and ligation-mediated PCR, we investigated the effects of nuclear protein hyperacetylation on both chromatin organization and transcriptional activation of the OC gene in bone-derived cells. We report that chromatin hyperacetylation blocks vitamin D stimulation of OC transcription and prevents a key transition in the chromatin structure of the OC gene which is required for formation of the distal DNase I hypersensitive site. This transition involves interaction of sequence-specific nuclear factors and may be required for the ligand-dependent binding of the vitamin D receptor complex, which results in transcriptional enhancement.

In vivo occupancy of the vitamin D responsive element in the osteocalcin gene supports vitamin D-dependent transcriptional upregulation in intact cells

The steroid hormone vitamin D is a principal mediator of skeletal homeostasis. 1,25-Dihydroxyvitamin D3 treatment of ROS 17/2.8 osteoblast-like cells results in a ligand-dependent increase in transcription of the bone-specific osteocalcin gene. This transcriptional upregulation requires the positive cis-acting vitamin D responsive element (VDRE). We have used the ligation-mediated polymerase chain reaction to demonstrate that protein occupancy of the VDRE within the intact cell correlates with increased synthesis of osteocalcin transcripts. These protein-DNA contacts were not present in the absence of vitamin D or in osteosarcoma cells (ROS 24.1) lacking the vitamin D receptor. Our results establish in intact cells the requirement for both ligand- and receptor-dependent occupancy of the VDRE for vitamin D responsive enhancement of osteocalcin gene transcription.