An important common characteristic of curcumin and vitamin D

Vitamin D, specifically 1,25-dihydroxycholecalciferol, has a wide range of effects in the human body.Although the role of vitamin D is mainly related to the muscular and skeletal system, numerous other effects have recently been proven, such as its benefits for the health of the immune, endocrine and neurological systems.

The mechanism of action of vitamin D in the body

The obligatory mediator of the action of vitamin D is a factor that enables gene transcription, and it is done by the vitamin D receptor (VDR). Binding of vitamin D to the receptor triggers a series of reactions. The 1,25D-VDR complex binds to VDRE = vitamin D responsive element and vitamin A receptor (RXR) with which it forms a heterodimer. Only then is a series of coactivators (DRIP complex) activated, which, once activated, initiates gene transcription mechanisms. By "rewriting" from mRNA to tRNA, the biosynthesis of the protein that is responsible for the biological effect of vitamin D in the target cell and tissue occurs.

VDR - more than the "ordinary" vitamin D receptor

In addition to the classic effect of the 1,25D-VDR complex on bone homeostasis, it was also discovered how this complex can affect cell growth and division.For example, vitamin D and its analogues show potential in preventing the development of cancer, especially of the colon and prostate. However, vitamin D is not the only key to anticarcinogenic activity. Namely, it was discovered that the VDR receptor itself plays an important role. Substances other than vitamin D can also bind to this receptor, such as the carcinogenic bile acid substance lithocholate (LCA). By binding to the VDR carcinogen receptor, bile acid ceases to be a carcinogen, moreover, it performs the same traditional functions in the body as vitamin D itself. This example indicates the possibility of the existence of other substances capable of binding to VDR.

Confirmed binding of curcumin to VDR

American scientists examined whether curcumin can bind to the VDR receptor, considering that curcumin and vitamin D coincide in their action.For example, it was discovered that both molecules suppress the activity of NF-kB, a signaling molecule known to stimulate the formation of cancer.

Research on colon cell culture has shown that curcumin really binds to VDR and triggers the same cascade of reactions as vitamin D and ultimately activates genes involved in cancer prevention (CYP3A4, CYP24, p21, TRPV6).

The synergistic effect of vitamin D and curcumin was confirmed on cells of malignant promyelocytic leukemia. Curcumin therapy in combination with vitamin D stimulated protective genes more strongly compared to vitamin D therapy alone. This finding is very interesting considering that VDRs have a stronger affinity for vitamin D binding, while the affinity for curcumin binding is very weak. So in an environment where there is an abundance of vitamin D, curcumin will not be able to bind to VDR in significant quantities.But again, the stimulation of "real" genes is stronger in the presence of curcumin thanks to another, independent mechanism of action, which is proof of multiple powerful effects of curcumin in cells.

Author: Prof. Dr.Sc. Darija Vranešić Bender, clinical nutritionist

Literature:

1. Bartik L, Whitfield GK, Kaczmarska M, Lowmiller CL, Moffet EW, Furmick JK, Hernandez Z, Haussler CA, Haussler MR, Jurutka PW. Curcumin: a novel nutritionally derived ligand of the vitamin D receptor with implications for colon cancer chemoprevention. J Nutr Biochem. 2010 Dec;21(12):1153-61.