The Effect of Korean Pine Nut Oil on the Factors Involved in Body Fat Accumulation in Obese Mice Fed High-fat Diet

Abstract

Korean pine nut oil (PNO) has been reported to suppress appetite by increasing satiety hormone release. However, the effects of PNO on the expression of satiety hormone receptors and neuropeptides have not been studied. Also, there is limited information on whether PNO has an influence on lipid metabolism. In this study, 5-wk-old C57BL/6 mice were fed control diets containing 10% kcal fat from PNO or soybean oil (SBO) (PC or SC) or high-fat diets containing 35% kcal fat from lard and 10% kcal fat from PNO or SBO (PHF or SHF) for 12 weeks. The mRNA expression levels of cholecystokinin related genes, ghrelin related genes, neuropeptides, and genes associated with lipid metabolism in the small intestine and white adipose tissue were quantified by real-time PCR. Overall, PNO-fed mice gained less weight (P = 0.01) and had less white adipose tissue (P < 0.01) despite no difference in daily food intake between SBO- and PNO-fed mice. PC and PHF groups had less amount of white adipose tissue compared with SC group (30% less, P = 0.05) and SHF group (18% less, P = 0.03), respectively. Altogether, PNO-fed mice had significantly higher mRNA expression of Growth hormone secretagogue receptor (Ghsr, P = 0.03) and Agouti-related peptide (Agrp, P = 0.02), and tended to have higher mRNA expression of Pro-opiomelanocortin (Pomc, P = 0.08) and Cocaine- and amphetamine-regulated transcript (Cart, P = 0.06) in hypothalamus. PC group had higher Ghsr mRNA expression than SC group (1.23-fold, P = 0.02). PHF group had higher Agrp mRNA expression than SHF group (2.16-fold, P = 0.02). Collectively, PNO-fed mice had lower mRNA expression of jejunal Cd36 (P = 0.03) and epididymal Lipoprotein lipase (Lpl, P = 0.02). PC group had lower Lpl mRNA expression than SC group (38% less, P = 0.04). Overall, PNO-fed mice tended to have lower jejunal Apolipoprotein A-IV mRNA expression (Apoa4, P = 0.07) and higher epididymal β3-adrenergic receptor mRNA expression (Adrb3, P = 0.08). Higher expression of Ghsr and Agrp mRNA in PNO-fed mice indicates that PNO-fed mice received stronger signal promoting energy consumption which might be due to less amount of white adipose tissue. The tendency of higher Pomc and Cart mRNA expression in PNO-fed mice suggests that mice in SHF group might have impaired POMC/CART pathway and failed to upregulate Pomc and Cart mRNA expression despite their higher body weight. The lower expression of Cd36 and Lpl mRNA, and the tendency of lower Apoa4 mRNA and higher Adrb3 mRNA expression in PNO-fed mice imply that PNO was less efficiently absorbed and stored in the body than SBO, which led to less fat accumulation in PNO-fed mice. In conclusion, PNO reduced weight gain and alleviated the possibility of POMC/CART pathway dysregulation in high-fat diet-fed mice. The lower weight gain of PNO-fed mice seemed to be due to the effect of PNO on lipid metabolism.