Prevention of colorectal cancer with vitamin D

Vitamin D and liver fibrosis: Molecular mechanisms and clinical studies

Vitamin D plays a primary role in regulation of bone metabolism and calcium homeostasis. Interestingly, emerging evidence suggests protective effects of vitamin D against liver fibrogenesis. However, the precise mechanisms of this action remain mysterious. Herein, this review aimed to summarize the role of vitamin D in liver fibrosis pathology and to update the current comprehensive knowledge regarding the clinical utility of vitamin D-based treatment in liver fibrosis. In regard to its effect on liver fibrosis, vitamin D possesses an anti-fibrotic effect on hepatic stellate cells via vitamin D receptor-mediated specific signal transduction pathways, which in turn inhibit expression of pro-fibrogenic genes. Furthermore, several studies demonstrated a significant association between low vitamin D levels and an increased risk of liver fibrosis. Additionally, high prevalence of vitamin D deficiency was noted in patients with liver fibrosis, suggesting the use of vitamin D status as a biochemical marker reflecting the progression of liver fibrosis. It is therefore reasonable to postulate that vitamin D supplementation being a cost effective and relative simple procedure may benefit to liver fibrosis. Nevertheless, further research is needed to fully elucidate its regulatory role in inhibiting liver fibrogenesis and to estimate the safety and efficiency of vitamin D supplementation as a relatively inexpensive treatment for liver fibrosis in patients with chronic liver diseases.

Dietary factors and polymorphisms in vitamin D metabolism genes: the risk and prognosis of colorectal cancer in northeast China

CYP24A1 and CYP27B1 are critical genes determining 1α,25(OH)₂D₃ concentration and impacting on carcinogenesis. A case–control study including 528 colorectal cancer (CRC) patients and 605 cancer-free controls and a follow-up study with 317 cases were conducted in northeast China. Genotypes were tested by TaqMan Genotyping Assays. Individuals carrying the GG genotype of CYP27B1 G > T (rs10877012) exhibited decreased CRC risk compared with those with the TT genotype (OR_adjusted (OR_adj) = 0.57, 95% Confidence Interval (CI) = 0.38–0.84). Compared with the TT genotype, a significant association between the CC genotype of CYP27B1 C > T (rs4646536) and a reduced risk of CRC was observed (OR_adj = 0.59, 95% CI = 0.40–0.88). We also observed significant combined effects of the two polymorphisms in CYP27B1 with dietary factors, including the intake of cereals, overnight meal, allium vegetables, pork, canned fruit, and braised fish, on CRC risk. These associations remained significant after Bonferroni correction for multiple comparisons. The Hazard Ration (HR) of patients with the AA genotype (CYP24A1 A > G, rs4809957) was 2.38 (95% CI = 1.30–4.37) when compared with the GG genotype. Thus, our findings suggested that two polymorphisms in CYP27B1 are associated with CRC susceptibility. CYP24A1 A > G (rs4809957) polymorphism may lead to a worse prognosis of CRC.

Vitamin D supplementation for prevention of cancer in adults

BACKGROUND

The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of vitamin D supplementation for prevention of cancer in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, LILACS, Science Citation Index Expanded, and the Conference Proceedings Citation Index-Science to February 2014. We scanned bibliographies of relevant publications and asked experts and pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included randomised trials that compared vitamin D at any dose, duration, and route of administration versus placebo or no intervention in adults who were healthy or were recruited among the general population, or diagnosed with a specific disease. Vitamin D could have been administered as supplemental vitamin D (vitamin D₃ (cholecalciferol) or vitamin D₂ (ergocalciferol)), or an active form of vitamin D (1α-hydroxyvitamin D (alfacalcidol), or 1,25-dihydroxyvitamin D (calcitriol)).

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently. We conducted random-effects and fixed-effect model meta-analyses. For dichotomous outcomes, we calculated the risk ratios (RRs). We considered risk of bias in order to assess the risk of systematic errors. We conducted trial sequential analyses to assess the risk of random errors.

MAIN RESULTS

Eighteen randomised trials with 50,623 participants provided data for the analyses. All trials came from high-income countries. Most of the trials had a high risk of bias, mainly for-profit bias. Most trials included elderly community-dwelling women (aged 47 to 97 years). Vitamin D was administered for a weighted mean of six years. Fourteen trials tested vitamin D₃, one trial tested vitamin D₂, and three trials tested calcitriol supplementation. Cancer occurrence was observed in 1927/25,275 (7.6%) recipients of vitamin D versus 1943/25,348 (7.7%) recipients of control interventions (RR 1.00 (95% confidence interval (CI) 0.94 to 1.06); P = 0.88; I² = 0%; 18 trials; 50,623 participants; moderate quality evidence according to the GRADE instrument). Trial sequential analysis (TSA) of the 18 vitamin D trials shows that the futility area is reached after the 10th trial, allowing us to conclude that a possible intervention effect, if any, is lower than a 5% relative risk reduction. We did not observe substantial differences in the effect of vitamin D on cancer in subgroup analyses of trials at low risk of bias compared to trials at high risk of bias; of trials with no risk of for-profit bias compared to trials with risk of for-profit bias; of trials assessing primary prevention compared to trials assessing secondary prevention; of trials including participants with vitamin D levels below 20 ng/mL at entry compared to trials including participants with vitamin D levels of 20 ng/mL or more at entry; or of trials using concomitant calcium supplementation compared to trials without calcium. Vitamin D decreased all-cause mortality (1854/24,846 (7.5%) versus 2007/25,020 (8.0%); RR 0.93 (95% CI 0.88 to 0.98); P = 0.009; I² = 0%; 15 trials; 49,866 participants; moderate quality evidence), but TSA indicates that this finding could be due to random errors. Cancer occurrence was observed in 1918/24,908 (7.7%) recipients of vitamin D₃ versus 1933/24,983 (7.7%) in recipients of control interventions (RR 1.00 (95% CI 0.94 to 1.06); P = 0.88; I² = 0%; 14 trials; 49,891 participants; moderate quality evidence). TSA of the vitamin D₃ trials shows that the futility area is reached after the 10th trial, allowing us to conclude that a possible intervention effect, if any, is lower than a 5% relative risk reduction. Vitamin D₃ decreased cancer mortality (558/22,286 (2.5%) versus 634/22,206 (2.8%); RR 0.88 (95% CI 0.78 to 0.98); P = 0.02; I² = 0%; 4 trials; 44,492 participants; low quality evidence), but TSA indicates that this finding could be due to random errors. Vitamin D₃ combined with calcium increased nephrolithiasis (RR 1.17 (95% CI 1.03 to 1.34); P = 0.02; I² = 0%; 3 trials; 42,753 participants; moderate quality evidence). TSA, however, indicates that this finding could be due to random errors. We did not find any data on health-related quality of life or health economics in the randomised trials included in this review.

AUTHORS' CONCLUSIONS

There is currently no firm evidence that vitamin D supplementation decreases or increases cancer occurrence in predominantly elderly community-dwelling women. Vitamin D₃ supplementation decreased cancer mortality and vitamin D supplementation decreased all-cause mortality, but these estimates are at risk of type I errors due to the fact that too few participants were examined, and to risks of attrition bias originating from substantial dropout of participants. Combined vitamin D₃ and calcium supplements increased nephrolithiasis, whereas it remains unclear from the included trials whether vitamin D₃, calcium, or both were responsible for this effect. We need more trials on vitamin D supplementation, assessing the benefits and harms among younger participants, men, and people with low vitamin D status, and assessing longer duration of treatments as well as higher dosages of vitamin D. Follow-up of all participants is necessary to reduce attrition bias.

CYP24A1 inhibition facilitates the anti-tumor effect of vitamin D3 on colorectal cancer cells

AIM: The effects of vitamin D3 have been investigated on various tumors, including colorectal cancer (CRC). 25-hydroxyvitamin-D3-24-hydroxylase (CYP24A1), the enzyme that inactivates the active vitamin D3 metabolite 1,25-dihydroxyvitamin D3 (1,25-D3), is considered to be the main enzyme determining the biological half-life of 1,25-D3. During colorectal carcinogenesis, the expression and concentration of CYP24A1 increases significantly, suggesting that this phenomenon could be responsible for the proposed efficacy of 1,25-D3 in the treatment of CRC. The aim of this study was to investigate the anti-tumor effects of vitamin D3 on the human CRC cell line Caco-2 after inhibition of the cytochrome P450 component of CYP24A1 activity.

METHODS: We examined the expression of CYP24A1 mRNA and the effects of 1,25-D3 on the cell line Caco-2 after inhibition of CYP24A1. Cell viability and proliferation were determined by means of sulforhodamine-B staining and bromodeoxyuridine incorporation, respectively, while cytotoxicity was estimated via the lactate dehydrogenase content of the cell culture supernatant. CYP24A1 expression was measured by real-time reverse transcription polymerase chain reaction. A number of tetralone compounds were synthesized to investigate their CP24A1 inhibitory activity.

RESULTS: In response to 1,25-D3, CYP24A1 mRNA expression was enhanced significantly, in a time- and dose-dependent manner. Caco-2 cell viability and proliferation were not influenced by the administration of 1,25-D3 alone, but were markedly reduced by co-administration of 1,25-D3 and KD-35, a CYP24A1-inhibiting tetralone. Our data suggest that the mechanism of action of co-administered KD-35 and 1,25-D3 does not involve a direct cytotoxic effect, but rather the inhibition of cell proliferation.

CONCLUSION: These findings demonstrate that the selective inhibition of CYP24A1 by compounds such as KD-35 may be a new approach for enhancement of the anti-tumor effect of 1,25-D3 on CRC.

Integrating dietary supplements into cancer care

Many studies confirm that a majority of patients undergoing cancer therapy use self-selected forms of complementary therapies, mainly dietary supplements. Unfortunately, patients often do not report their use of supplements to their providers. The failure of physicians to communicate effectively with patients on this use may result in a loss of trust within the therapeutic relationship and in the selection by patients of harmful, useless, or ineffective and costly nonconventional therapies when effective integrative interventions may exist. Poor communication may also lead to diminishment of patient autonomy and self-efficacy and thereby interfere with the healing response. To be open to the patient's perspective, and sensitive to his or her need for autonomy and empowerment, physicians may need a shift in their own perspectives. Perhaps the optimal approach is to discuss both the facts and the uncertainty with the patient, in order to reach a mutually informed decision. Today's informed patients truly value physicians who appreciate them as equal participants in making their own health care choices. To reach a mutually informed decision about the use of these supplements, the Clinical Practice Committee of The Society of Integrative Oncology undertook the challenge of providing basic information to physicians who wish to discuss these issues with their patients. A list of leading supplements that have the best suggestions of benefit was constructed by leading researchers and clinicians who have experience in using these supplements. This list includes curcumin, glutamine, vitamin D, Maitake mushrooms, fish oil, green tea, milk thistle, Astragalus, melatonin, and probiotics. The list includes basic information on each supplement, such as evidence on effectiveness and clinical trials, adverse effects, and interactions with medications. The information was constructed to provide an up-to-date base of knowledge, so that physicians and other health care providers would be aware of the supplements and be able to discuss realistic expectations and potential benefits and risks.

An effective oral vitamin D replacement therapy in persons with spinal cord injury

BACKGROUND/OBJECTIVE

Vitamin D deficiency is prevalent in chronic spinal cord injury (SCI). A 3-month course of oral vitamin D(3) to 'normalize' serum vitamin D levels was investigated.

DESIGN

Prospective drug-intervention study.

SETTING

VA Medical Center; private rehabilitation facility.

METHODS

Seven individuals with chronic SCI and vitamin D deficiency completed 3 months of oral vitamin D(3) (i.e. cholecalciferol) supplementation. At screening, baseline, and months 1 and 3, blood was collected for serum calcium, 25 hydroxyvitamin D [25(OH)D], intact parathyroid hormone (iPTH), and N-telopeptide (NTx); 24-hour urine for calcium, creatinine, and NTx was performed. Oral vitamin D(3) (2000 IU daily) and elemental calcium (1.3 g daily) were prescribed for 90 days. The results are expressed as mean ± standard deviation (SD). Analysis of variance with a Fisher's post-hoc analysis was performed to test for differences between study visits. Subjects were classified as deficient (<20 ng/ml), relatively deficient (20-30 ng/ml), or not deficient (>30 ng/ml) in 25(OH)D.

RESULTS

Serum 25(OH)D levels were greater at months 1 and 3 than at baseline (26 ± 6 and 48 ± 17 vs. 14 ± 2 ng/ml; P = 0.005). Six of seven subjects were no longer deficient [25(OH)D >30 ng/ml] by month 3. Serum iPTH levels were significantly decreased at month 1 and month 3; serum NTx levels were significantly lower at month 3 than at baseline. Serum and urinary calcium levels remained within the normal range.

CONCLUSION

A daily prescription of 2000 IU of oral vitamin D(3) for 3 months safely raised serum 25(OH)D levels into the normal range in persons with chronic SCI on calcium supplementation.

Association between CYP1A1 polymorphism and colorectal cancer risk: a meta-analysis

Colorectal cancer is one of the most common forms of cancer and is the third leading cause of cancer-related death worldwide. Published data on the association between CYP1A1 (MspI and Ile ( 462 ) Val) polymorphisms and colorectal cancer risk are inconclusive. To address these issues, we carried out a meta-analysis of available case-control study. Online electronic searches of PubMed were performed. We identified 17 studies (6,673 colorectal cancer patients and 8,102 control subjects) that examined the association between CYP1A1 (MspI and Ile ( 462 ) Val) polymorphisms and risk of colorectal cancer. For CYP1A1 MspI polymorphism, we performed a meta-analysis from 13 studies including 5,468 cases and 6,492 controls. Overall, there was no statistically significant association between CYP1A1 MspI polymorphism and colorectal cancer susceptibility. In the subgroup analyses based on ethnicities, no statistically significant associations were observed in all genetic models. With respect to CYP1A1 Ile ( 462 ) Val polymorphism, a total of 14 studies including 6,654 cases and 7,859 controls were involved in this meta-analysis. The CYP1A1 Ile ( 462 ) Val polymorphism was associated with risk of colorectal cancer. Ethnic subgroup analyses revealed that significant associations were found in Asians and Caucasians. In summary, this meta-analysis suggests that CYP1A1 Ile ( 462 ) Val polymorphism was a low-penetrance susceptibility gene in colorectal cancer development. On the contrary, CYP1A1 MspI polymorphism does not seem capable of modifying colorectal cancer risk.

Vitamin D, disease and therapeutic opportunities

The discovery of the vitamin D endocrine system and a receptor for the hormonal form, 1α,25-dihydroxyvitamin D(3), has brought a new understanding of the relationship between vitamin D and metabolic bone diseases, and has also established the functions of vitamin D beyond the skeleton. This has ushered in many investigations into the possible roles of vitamin D in autoimmune diseases, cardiovascular disorders, infectious diseases, cancers and granuloma-forming diseases. This article presents an evaluation of the possible roles of vitamin D in these diseases. The potential of vitamin D-based therapies in treating diseases for which the evidence is most compelling is also discussed.