Chronic stress causes neuroendocrine-immune disturbances without affecting renal vitamin D metabolism in rats

Vitamin D (VD) insufficiency has been repeatedly observed in the medical conditions associated with inflammation, such as cardiovascular disease, diabetes and depression. However, contrasting to the observational evidence, randomized trials of VD supplementation failed to demonstrate such link. Given the recent evidence that the inflammatory process can in turn alter VD metabolism, it has been hypothesized that the insufficient VD status could be the result rather than the cause of chronic inflammation involved in the onset of depression and other disease conditions.

Chronic mild stress (CMS) is a valid animal model of depression that accompanied with neuroendocrine-immune disturbances. In the present research, we assessed serum VD concentrations and renal expression of the cytochromes P450 enzymes involved in VD activation (CYP27B1) and catabolism (CYP24A1) of rats following 8-week exposure to CMS.

While CMS induced the rats to a depression-like state and increased serum levels of the proinflammatory cytokines and corticosterone, and the antidepressant, sertraline, mitigated depression-like behaviors and neuroendocrine-immune disturbances, neither the stress regimen nor sertraline significantly affected endocrine metabolism of VD.

Our data suggest that the stress-induced neuroendocrine-immune disturbances may account for the development of depression, but are not responsible for the insufficient VD status that frequently observed in depressed patients.