Higher Vitamin D Binding Protein Research Articles

Associations between serum vitamin D biomarkers and tumor expression of Ki67, p53, and COX-2 in colorectal cancer cases from the Southern Community Cohort Study

Higher 25-hydroxyvitamin D is associated with lower colorectal cancer (CRC) risk, with limited data from African Americans (AAs), who have greater risk for CRC and 25-hydroxyvitamin D deficiency. In a predominantly AA sample of CRC cases from the Southern Community Cohort Study (SCCS), we report associations between vitamin D biomarkers and tumor expression of proteins implicated in vitamin D’s anti-tumorigenic pathways (e.g. proliferation and inflammation) and CRC prognosis. SCCS participants with incident CRC were identified via state cancer registries. Serum 25-hydroxyvitamin D and vitamin D binding protein (VDBP) were measured at enrollment. ‘Free’ 25-hydroxyvitamin D was calculated via standard equation. Cellular Ki67, p53, and COX-2 were measured from tumor samples and categorized using literature-defined cut-points related to survival. Generalized linear models were used to measure associations between vitamin D exposures, tumor biomarkers, and stage. In total, 104 cases (40–79 years) were analyzed. 25-hydroxyvitamin D was not associated with high Ki67 (odds ratio (OR) per 1-standard deviation (SD) increase [95% confidence interval] 1.35[0.86–2.11]), p53 (0.75[0.47–1.20]), or COX-2 expression (1.25[0.78–2.01]), or metastatic disease (1.04[0.59–1.81]). Mean biomarker expression was unrelated to 25-hydroxyvitamin D (p-trend ≥.09). Null associations were observed for VDBP and free 25-hydroxyvitamin D. In AAs (n = 70), higher VDBP was associated with lower odds of high Ki67 expression (0.53[0.28–0.98], p-trend =.04). In conclusion, we observed no associations between 25-hydroxyvitamin D and prognostic marker expression in CRC. An inverse association between VDBP and tumor Ki67 in AAs is consistent with reports showing relationships with reduced CRC mortality.

Abstract 725: Biomarkers of circulating vitamin D status and expression of tumor molecular markers Ki67, p53, and COX2 among colorectal cancer cases in the Southern Community Cohort Study

Abstract Introduction: Epidemiologic studies and controlled trials provide evidence that higher 25-hydroxyvitaminD is associated with improved survival in colorectal cancer (CRC), although there are limited data in African Americans (AAs), who are at greater risk for CRC mortality and vitamin D deficiency. Herein, we report associations between vitamin D serum biomarkers collected at cohort entry up to 15 years prior to CRC onset and CRC tumor subtypes defined by high expression of tumor markers (Ki67, p53, and COX2) that represent cellular processes (proliferation, apoptosis, and inflammation) affected by vitamin D. Importantly, higher expression of these markers reflects greater risk for metastasis and CRC-specific mortality. Methods: Data arise from the Southern Community Cohort Study, a cohort from the southeastern United States where the majority of participants are AA. Incident CRC cases with tumor sample were analyzed (n=104). Expression of cellular Ki67, p53, and COX2 (% positivity) were measured and categorized by literature-defined high vs. low cut-points (20%, 10%, and 20%, respectively). Logistic models adjusted for age, race, and sex were used to measure associations between vitamin D biomarkers: 25-hydroxyvitaminD, vitamin D binding protein (VDBP), and calculated free 25-hydroxyvitaminD (vitamin D not bound by VDBP) and the odds of a more aggressive tumor subtype, defined by higher cellular expression. Associations were assessed in the full sample and the subsample of AAs (n=70). Results: There were 52 tumors with high Ki67 expression, 37 with high p53, and 50 with high COX2. Fifteen tumors had high expression of all three markers. Cases were 55.8±0.4 (mean±SE) years at enrollment (range 40-79). The median 25-hydroxyvitaminD was lower in cases with high p53 expressing tumors compared to low expression (13.5 vs. 18.0 ng/mL, respectively, p = .03). Median values for other biomarkers were similar by tumor subtype (p &gt .05). 25-hydroxyvitaminD was not associated with having a tumor with high Ki67 expression (odds ratio (OR) per 1 SD increase [95% CI] = 1.29 [0.85-1.95], p-trend = .23), high p53 expression (0.80 [0.52-1.23], p-trend = .30), or high COX2 expression (1.29 [0.83-2.00], p = .25). We observed null associations for VDBP, and free 25-hydroxyvitaminD with all tumor subtypes. Results were similar in AAs, although higher VDBP was associated with lower odds of high Ki67 tumors (0.45 [0.21-0.97], p-trend = .04 per 1 SD increase). Conclusion: In this sample of predominantly AA CRC cases, we observed no association between vitamin D biomarkers in stored serum and subsequent more aggressive CRC molecular subtypes. More work is needed to characterize the relationship between vitamin D and expression of CRC tumor markers, which may help clarify the protective role of maintaining adequate vitamin D levels in association with CRC. Citation Format: Thomas Lawler, Timothy Su, Qiuyin Cai, Mark Steinwandel, Wei Zheng, William J. Blot, Shaneda Warren Andersen. Biomarkers of circulating vitamin D status and expression of tumor molecular markers Ki67, p53, and COX2 among colorectal cancer cases in the Southern Community Cohort Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 725.

Association of GC Variants with Bone Mineral Density and Serum VDBP Concentrations in Mexican Population.

Vitamin D-binding protein (VDBP) is encoded by the GC gene and is an active participant in the control of bone metabolism. However, the effect of its major variants on VDBP concentration and bone mineral density (BMD) remains unclear. Our aim was to analyze the effect of major GC variants on serum VDBP concentration and BMD. We recruited individuals from the Health Workers Cohort Study, which includes employees of the Mexican Institute of Social Security (IMSS). A total of 1853 adults were included. The single nucleotide polymorphisms (SNPs) rs7041 and rs4588 were genotyped to identify the three best characterized haplotypes of GC. Serum VBDP, 25(OH)D and BMD were also measured. Among women, the G allele of rs7041 was associated with higher VDBP and BMD compared to homozygous TT. The A allele of rs4588 was associated with lower VDBP and BMD compared to CC homozygous. In men, GC variants were only associated with VDBP levels. We did not observe an association between free/bioavailable 25(OH)D and BMD in men and women. Our results support an association of VDBP in bone health. The G and C alleles, from rs7041 and rs4588, respectively, are associated with high concentrations of VDBP and BMD in this sample of Mexican postmenopausal women.

The Vitamin D Metabolite Ratio Is Independent of Vitamin D Binding Protein Concentration.

25-Hydroxyvitamin D [25(OH)D] may be a poor marker of vitamin D status as it reflects differences in vitamin D binding protein (VDBP) between individuals. The vitamin D metabolite ratio [VMR, ratio of 24,25(OH)2D3 to 25(OH)D3] is a marker of vitamin D status that has been hypothesized to be independent of variability in VDBP. This hypothesis has not been directly evaluated. We measured 25(OH)D3, 24,25(OH)2D3, 1,25(OH)2D3, and VDBP in 377 community-dwelling older adults that participated in the Health Aging and Body Composition Study. 24,25(OH)2D3 and 25(OH)D3 were used to calculate the VMR. We used linear regression to assess the relationship between VDBP with the VMR, 24,25(OH)2D3, 25(OH)D3, and 1,25(OH)2D3. Participants had mean age 75 ± 3 years, 52% were female, 40% were black, and 24% had chronic kidney disease. VDBP concentrations were associated with sex, serum albumin, and VDBP phenotype in multivariable models. In fully adjusted models, each 1% higher VDBP was associated with a 0.92%[95% CI(0.37,1.49%)], 0.76% (0.39, 1.13%), and 0.57% (0.29, 0.85%), higher 24,25(OH)2D3, 25(OH)D3, and 1,25(OH)2D3. The VMR was independent of VDBP concentration, [0.16%(-0.11, 0.44) higher VMR per 1% higher VDBP, P = .25]. The VMR was independent of VDBP concentration, whereas VDBP was strongly directly associated with the individual vitamin D metabolite concentrations. Prior studies evaluating only 25(OH)D3 may have been confounded by absence of data on VDBP status. The VMR may serve as an important biomarker of vitamin D status and clinical outcomes that can be utilized in populations with a large spectrum of VDBP concentrations.

Free 25-hydroxyvitamin-D concentrations are lower in children with renal transplant compared with chronic kidney disease

BackgroundTotal serum 25-hydroxyvitamin D [25(OH)D] is considered the best marker of vitamin D status and used routinely in clinical practice. However, 25(OH)D is predominantly bound to vitamin D-binding protein (VDBP), and it has been reported that the free-25(OH)D and 25(OH)D loosely bound to albumin fraction correlates better with clinical outcomes.MethodsWe assessed total-25(OH)D, measured free-25(OH)D, and calculated free-25(OH)D and their relationship with VDBP and biomarkers of mineral metabolism in 61 children (22 CKD 2–3, 18 dialysis, and 21 post-transplant).ResultsTotal-25(OH)D concentrations were comparable across the three groups (p = 0.09), but free- and bioavailable-25(OH)D (free- and albumin-25(OH)D) were significantly lower in the transplant group (both: p = 0.01). Compared to CKD and dialysis patients, the transplant group had significantly higher VDBP concentrations (p = 0.03). In all three groups, total-25(OH)D concentrations were positively associated with measured free-, calculated free-, and bioavailable-25(OH)D. Multivariable regression analysis showed that total-25(OH)D was the only predictor of measured free-25(OH)D concentrations in the dialysis group (β = 0.9; R2 = 90%). In the transplant group, measured free-25(OH)D concentrations were predicted by both total-25(OH)D and VDBP concentrations (β = 0.6, − 0.6, respectively; R2 = 80%). Correlations between parathyroid hormone with total-25(OH)D and measured and calculated free-25(OH)D were only observed in the transplant group (all: p < 0.001).ConclusionsIn transplanted patients, VDBP concentrations were significantly higher compared to CKD and dialysis patients, and consequently, free-25(OH)D concentrations were lower, despite a comparable total-25(OH)D concentration. We suggest that free-25(OH)D measures may be required in children with CKD, dialysis, and transplant, with further research required to understand its association with markers of mineral metabolism.

Abstract 3297: Prediagnostic circulating concentrations of vitamin D binding protein and survival among colorectal cancer patients

Abstract Higher total 25-hydroxyvitamin D [25(OH)D] levels are associated with an improvement in survival among colorectal cancer (CRC) patients, but the relationships between plasma vitamin D binding protein (VDBP), bioavailable or free 25(OH)D, and CRC survival remain unknown. In two prospective cohort studies, the Health Professionals Follow-Up Study and the Nurses’ Health Study, we examined the association between prediagnostic plasma levels of VDBP, bioavailable 25(OH)D, and free 25(OH)D and survival among 604 participants diagnosed with CRC between 1991 and 2011. Plasma 25(OH)D and VDBP were directly measured, while bioavailable and free 25(OH)D were calculated using a validated formula based on total 25(OH)D, VDBP, and albumin levels. Cox proportional hazards models were used to estimate hazard ratios (HRs) for overall and CRC-specific mortality, adjusted for other prognostic markers and potential confounders. During the follow-up, there were 279 deaths, 177 of which were due to CRC (63%). Higher VDBP levels were associated with a significant improvement in overall and CRC-specific survival (Ptrend=0.005 and 0.02, respectively). Compared to patients in the lowest quartile, those in the highest quartile of VDBP had a multivariable-adjusted HR of 0.61 (95% confidence interval [CI], 0.42-0.89) for overall mortality and 0.56 (95% CI, 0.35-0.92) for CRC-specific mortality. The results remained similar after further adjustment for total 25(OH)D levels. In contrast, no association with overall or CRC-specific mortality was observed for bioavailable or free 25(OH)D levels. In conclusion, higher prediagnostic plasma VDBP levels were associated with improved survival among CRC patients. The clinical utility of VDBP as a prognostic marker warrants further exploration, as well as research into underlying mechanisms of action. Citation Format: Chen Yuan, Mingyang Song, Brian M. Wolpin, Jeffrey A. Meyerhardt, Shuji Ogino, Bruce W. Hollis, Andrew T. Chan, Charles S. Fuchs, Kana Wu, Molin Wang, Stephanie A. Smith-Warner, Edward L. Giovannucci, Kimmie Ng. Prediagnostic circulating concentrations of vitamin D binding protein and survival among colorectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3297.

The Vitamin D Analog 1α,25-Dihydroxy-2β-(3-Hydroxypropyloxy) Vitamin D3 (Eldecalcitol) is a Potent Regulator of Calcium and Phosphate Metabolism

The vitamin D analog 1α,25-dihydroxy-2β-(3-hydroxypropyloxy)vitamin D(3) (ED-71 or eldecalcitol) has been developed for treatment of osteoporosis, but its effects on mineral metabolism have not been investigated in detail. In the present study, we compared the effects of eldecalcitol and calcitriol on calcium (Ca) and phosphate (Pi) handling in rats. Oral administration of eldecalcitol (0, 7.5, 20, or 50pmol) q.o.d. for 2weeks dose-dependently increased ionized Ca, intestinal Ca absorption, and urinary Ca excretion, while these doses of calcitriol had no significant effects. The highest dose of eldecalcitol did not alter serum Pi but stimulated both intestinal Pi absorption and urinary Pi excretion; the latter was attributable, in part, to increased serum FGF-23. The effects of high-dose eldecalcitol on Ca and Pi absorption and urinary excretion and FGF-23 persisted for several days following cessation of treatment. The higher potency of eldecalcitol on Ca and Pi handling was also observed in parathyroidectomized rats infused with PTH, excluding a role for differential regulation of PTH. Direct measurement of duodenal Ca absorption by the in situ loop method confirmed the higher potency of eldecalcitol in this segment via induction of TRPV6. These studies indicated that with chronic administration eldecalcitol is more potent than calcitriol at stimulating intestinal absorption of Ca and Pi, as well as FGF-23. The mechanisms responsible for the higher potency of eldecalcitol are speculated to be its higher vitamin D-binding protein (DBP) affinity and resistance to metabolism.