A randomized clinical trial of the effects of supplemental calcium and vitamin D3 on markers of their metabolism in normal mucosa of colorectal adenoma patients

Abstract

In cancer cell lines and rodent models, calcium and vitamin D favorably modulate cell proliferation, differentiation, and apoptosis in colonic epithelia. These effects may be modulated by local expression of the calcium receptor (CaR), the vitamin D receptor (VDR), and the P450 cytochromes, CYP27B1 and CYP24A1; however, they have yet to be investigated in humans. To address this gap, we conducted a randomized, double-blinded, placebo-controlled 2×2 factorial clinical trial. Patients with at least one pathology-confirmed colorectal adenoma were treated with 2 g/d elemental calcium and/or 800 IU/d vitamin D3 versus placebo over 6 months (n=92; 23 per group). CaR, VDR, CYP27B1, and CYP24A1 expression and distribution in biopsies of normal appearing rectal mucosa were detected by standardized, automated immunohistochemistry and quantified by image analysis. In the calcium-supplemented group, CaR expression increased 27% (P=0.03) and CYP24A1 expression decreased 21% (P=0.79). In the vitamin D3-supplemented group, CaR expression increased 39% (P=0.01) and CYP27B1 expression increased 159% (P=0.06). In patients supplemented with both calcium and vitamin D3, VDR expression increased 19% (P=0.13) and CaR expression increased 24% (P=0.05). These results provide mechanistic support for further investigation of calcium and vitamin D3 as chemopreventive agents against colorectal neoplasms, and CaR, VDR, CYP27B1, and CYP24A1 as modifiable, preneoplastic risk biomarkers for colorectal neoplasms.

Figure 1. Biomarker immunohistochemical images of colon crypts (200×)

A. calcium receptor B. vitamin D receptor C. CYP27B D. CYP24A1

Figure 2. Quantitative image analysis

A. finding scorable crypts B. tracing the hemicrypt C. automated sectioning of the trace D. automated quantification of CYP24A1 labeling optical density

Figure 3. Representative examples of labeling expression distribution* of the (A) calcium receptor†, the (B) vitamin D receptor†, (C) CYP27B1‡, and (D) CYP24A1‡ along normal colorectal crypts by treatment group at baseline and 6-month follow-up

^* Distribution plots represent labeling optical density in colon crypts ^† Representative example from the calcium/vitamin D₃ treatment group ^‡ Representative example from the vitamin D₃ treatment group