Macrophages are involved in all inflammatory processes from killing pathogens to repairing damaged tissue. In the obese state, macrophages infiltrate into enlarged adipose tissue and polarize into pro-inflammatory M1 macrophages, resulting in chronic low-grade inflammation due to the secretion of inflammatory mediators. Rice bran oil (RBO) is an edible oil containing tocopherols, tocotrienols, and γ-oryzanol. Previous research in normal diet-fed mice suggested that RBO mitigates inflammatory responses by modulating mitochondrial respiration of macrophages. Therefore, we investigated if RBO had an anti-inflammatory effect in diet-induced obese mice by assessing the expression of inflammatory markers in epididymal white adipose tissue (eWAT) and polarization of bone marrow-derived macrophages (BMDMs). Rice bran oil exerted a local anti-inflammatory effect in white adipose tissue by suppressing the production of inflammatory mediators and upregulating transcription of anti-inflammatory genes. Rice bran oil also promoted anti-inflammatory M2 macrophage polarization in BMDMs thereby affecting systemic inflammation. Overall, our in vivo and ex vivo results highlight the potential of RBO as a dietary mediator that can ameliorate obesity-induced chronic low-grade inflammation by mediating the expression of inflammation-related factors and macrophage polarization.
Keywords: anti-inflammatory; chronic inflammation; high-fat diet; macrophage polarization; obesity; rice bran oil.