Increased immune response in mice consuming rice bran oil

Summary

Background

Polyunsaturated fatty acids play a key role in a number of biological functions. Rice bran oil (RBO) is rich in linoleic acid, an essential n–6 fatty acid. n–6 fatty acids are said to have proinflammatory effects as a result of an increase in n–6 fatty acidderived eicosanoids. RBO is also rich in γ–oryzanol, a compound from the unsaponifiable fraction, with antioxidant properties.

Objective

The aim of this work is to examine the effect of RBO—and/or γ–oryzanol—enriched diets on the regulation of the immune response.

Methods

4 week–old Balb/C mice were fed diets enriched with either RBO or high oleic–sunflower oil (HOSO), for one month. Serum samples, bone marrow–derived macrophages and lymphocytes from the spleen were collected.

Results

Compared to HOSO, our results show that RBO modulates the immune system by enhancing B–lymphocyte proliferation (6842 ± 2959 vs 10073 ± 4186 cpm; HOSO vs RBO; n = 10 per group) and T_H1–type cytokines such as IL–2 (55.85 ± 18.2 vs 101.7 ± 21.6 pg/ml) or TNF–α (49.12 ± 18.6 vs 184.9 ± 46.2 pg/ml; HOSO vs RBO) in a significant way (n = 10 per group). Moreover, the reduction found in the T_H2 cytokine IL–4 (7.59 ± 2.3 vs 4.48 ± 1.6 pg/ml) and IgE (56.9 ± 39.2 vs 42.4 ± 35.2 ng/ ml; HOSO vs RBO, n = 10 per group) levels suggests RBO may have antiallergenic properties. To elucidate the role of γ–oryzanol, a similar study was also carried out including diets enriched with refined RBO or HOSO containing γ–oryzanol (2 %). Our results suggest that although γ–oryzanol may modulate the immune system, it is not responsible for the overall immunostimulation effect seen for RBO.

Conclusions

RBO–enriched diets could be useful in situations where a potentiation of the immune response was required. The fatty acids composition, more than the unsaponifiable fraction, might be responsible for this effect.