Investigations of the anti-inflammatory effects of vitamin D in adipose tissue: results from an in vitro study and a randomized controlled trial.

Inflammation is a key feature of obesity and type 2 diabetes. The active vitamin D metabolite, 1,25-dihydroxyvitamin D [1,25(OH)₂D], modulates the inflammation in vitro. We studied whether inflammation in adipose tissue (AT) cultures could be reduced by incubation with 1,25(OH)₂D in vitro, or by oral treatment with vitamin D in vivo in obese subjects with low plasma levels of 25-hydroxyvitamin D. Samples of subcutaneous AT were stimulated with IL-1β to induce inflammation. In the in vitro study, samples were concomitantly incubated with or without 1,25(OH)₂D, and analyzed for mRNA and protein levels of inflammatory markers IL-6, IL-8, and MCP-1. In the in vivo study, samples of subcutaneous AT from obese subjects obtained before and after treatment with 7,000 IU of vitamin D daily or placebo in a randomized controlled trial were stimulated with IL-1β. The samples were analyzed for AT gene expression and compared with plasma markers of inflammation. In the in vitro study, concomitant incubation with 1,25(OH)₂D reduced mRNA levels of MCP-1 by 45% (p=0.01), of IL-6 by 32% (p=0.002), and of IL-8 by 34% (p=0.03), and reduced secretion of IL-8 protein by 18% (p=0.005). In vivo treatment with vitamin D did not reduce AT expression or circulating levels of MCP-1, IL-6, or IL-8. 1,25(OH)₂D has significant anti-inflammatory effects in AT in vitro. However, a similar reduction in AT and systemic inflammation cannot be obtained by oral treatment with vitamin D in obese subjects. © Georg Thieme Verlag KG Stuttgart · New York.

RCT Entities:   Population Interventions Outcomes