Brown rice and its component, [gamma]-oryzanol, attenuate the preference for dietary fat by decreasing hypothalamic endoplasmic reticulum stress in mice

C. Kozuka; K. Yabiku; S. Sunagawa; R. Ueda; S. Taira; T. Ikema; K. Yamakawa; M. Higa; M. Shimabukuro; H. Masuzaki

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Endocrine Abstracts (2012) 29 P1176

ICEECE2012 Poster Presentations Obesity (114 abstracts)

Brown rice and its component, γ-oryzanol, attenuate the preference for dietary fat by decreasing hypothalamic endoplasmic reticulum stress in mice

C. Kozuka ¹ , K. Yabiku ¹ , S. Sunagawa ¹ , R. Ueda ¹ , S. Taira ¹ , T. Ikema ¹ , K. Yamakawa ¹ , M. Higa ² , M. Shimabukuro ³ & H. Masuzaki ¹

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¹Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan; ²Tomishiro Central Hospital, Okinawa, Japan; ³University of Tokushima Graduate School of Health Biosciences, Tokushima, Japan.

It is known that brown rice (BR) prevents obesity and type 2 diabetes in humans. Previous studies have shown that exaggerated endoplasmic reticulum (ER) stress in the hypothalamus of obese mice is linked to hyperphagia. Here we tested the hypothesis that BR might decrease ER stress in hypothalamus, leading to the attenuation the preference for dietary fat.

Eight-week-old mice were randomly divided into three groups: the control, BR-containing diet, and the WR-containing diet groups. To explore the impact of BR on the preference for dietary fat, we performed the food choice tests between CD and HFD. The mice were allowed free access to both diets. The control group strongly preferred the HFD. On the contrary, BR group preferred CD (~12.5-fold vs control, ~3.7-fold vs WR), leading to the suppression of body weight gain. To assess the effect of BR on hypothalamic ER stress, the mRNA levels of ER stress-responsive genes were analyzed. BR significantly decreased the mRNA levels of these genes in the hypothalami of the mice fed HFD. In the food choice tests, the mice treated with 4-phenyl butyric acid (120 mg/kg per day i.p.), a well known ER stress eraser, significantly preferred CD. We investigated the effect of γ-oryzanol (Orz), a mixture of major bioactive components in BR, on the hypothalamic ER stress and the preference for dietary fat. Oral administration of Orz (20, 80, 320 mg/kg per day p.o.) decreased hypothalamic ER stress in the mice fed HFD. In the food choice tests, Orz-treated mice preferred CD (~2.1-fold vs vehicle).

Our study is the first demonstration that BR and its component, Orz, decrease hypothalamic ER stress and consequently attenuate the preference for dietary fat in mice. BR and Orz may be unique tools to ameliorate metablic syndrome through modulating feeding behavior.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.