Effects of 1α,25 Dihydroxyvitamin D3 on Pro-inflammatory Cytokines of Palmitic Acid Treated Thp-1 Cells.

The level of saturated fatty acids, such as palmitic acid (PA), correlates with chronic inflammation in obese and metabolic syndrome patients. However, low level of vitamin D3 is observed in those conditions. The aim of this study is to investigate effects of 1α,25(OH)2 D3 on PA-treated THP-1 cells. Using quantitative real-time polymerase chain reaction, we measure mRNA expression of pro-inflammatory cytokines: TNF-α, Interleukin (IL)-1β, IL-6, and chemokine IL-8 under PA and 1α,25(OH)2 D3 influence. PA, at all concentrations (25-100 μM), enhanced LPS stimulatory effect on those mRNA expression compared to LPS-treated and -untreated cells. Combination with 1α,25(OH)2 D3 increased cytokine expression at high (10-6 M) and high-normal (10-8 M) concentrations compared to PA + LPS and LPS alone, both for 2 and 24 h. However, low-normal (10-10 M) and low (10-12 M) levels of 1α,25(OH)2 D3 could not enhance PA effect, but mRNA expression of pro-inflammatory cytokine was higher than LPS-treated cells. Upstream pathway of 1α,25(OH)2 D3 , which is cholecalciferol, also gave the similar result. Further, inhibition of calcium pathway does not play a role in this mechanism. Thus, these findings support pro-inflammatory effect of PA and vitamin D3 on innate immune response, especially on fat-induced inflammation.

UNASSIGNED

The effect of vitamin D3 on chronic inflammation in obesity is uncertain. This study shows an in vitro possibility that vitamin D3 could exaggerate inflammation when combined with high SFAs. The idea of using vitamin D3 supplement to modulate inflammation in fat-related inflammation needs further refined experiments before its clinical application.