Disciplina de Fisiologia da Nutrição, Departamento de Fisiologia, Universidade Federal de São Paulo-UNIFESP, CEP 04023-062 São Paulo/SP, Brazil.
J Nutr Biochem. 2012 Jul;23(7):822-8. doi: 10.1016/j.jnutbio.2011.04.006. Epub 2011 Aug 17.
Hypothalamic insulin inhibits food intake, preventing obesity. High-fat feeding with polyunsaturated fats may be obesogenic, but their effect on insulin action has not been elucidated. The present study evaluated insulin hypophagia and hypothalamic signaling after central injection in rats fed either control diet (15% energy from fat) or high-fat diets (50% energy from fat) enriched with either soy or fish oil. Soy rats had increased fat pad weight and serum leptin with normal body weight, serum lipid profile and peripheral insulin sensitivity. Fish rats had decreased body and fat pad weight, low leptin and corticosterone levels, and improved serum lipid profile. A 20-mU dose of intracerebroventricular (ICV) insulin inhibited food intake in control and fish groups, but failed to do so in the soy group. Hypothalamic protein levels of IR, IRS-1, IRS-2, Akt, mTOR, p70S6K and AMPK were similar among groups. ICV insulin stimulated IR tyrosine phosphorylation in control (68%), soy (36%) and fish (34%) groups. Tyrosine phosphorylation of the pp185 band was significantly stimulated in control (78%) and soy (53%) rats, but not in fish rats. IRS-1 phosphorylation was stimulated only in control rats (94%). Akt serine phosphorylation was significantly stimulated only in control (90%) and fish (78%) rats. The results showed that, rather than the energy density, the fat type was a relevant aspect of high-fat feeding, since blockade of hypothalamic insulin signal transmission and insulin hypophagia was promoted only by the high-fat soy diet, while they were preserved in the rats fed with the high-fat fish diet.
下丘脑胰岛素抑制摄食，防止肥胖。富含多不饱和脂肪的高脂肪饮食可能会导致肥胖，但它们对胰岛素作用的影响尚未阐明。本研究评估了在给予对照饮食（脂肪供能 15%）或富含大豆或鱼油的高脂肪饮食（脂肪供能 50%）的大鼠中，中枢注射胰岛素后的摄食减少和下丘脑信号转导情况。大豆组大鼠脂肪垫重量增加，血清瘦素水平升高，但体重、血清脂质谱和外周胰岛素敏感性正常。鱼类组大鼠体重和脂肪垫重量降低，瘦素和皮质酮水平降低，血清脂质谱改善。20 mU 剂量的脑室注射（ICV）胰岛素抑制了对照组和鱼类组的摄食，但在大豆组却没有。各组下丘脑胰岛素受体（IR）、胰岛素受体底物 1（IRS-1）、胰岛素受体底物 2（IRS-2）、Akt、mTOR、p70S6K 和 AMPK 的蛋白水平相似。ICV 胰岛素刺激对照组（68%）、大豆组（36%）和鱼类组（34%）的 IR 酪氨酸磷酸化。对照组（78%）和大豆组（53%）大鼠的 pp185 带酪氨酸磷酸化明显受到刺激，但鱼类组大鼠没有。IRS-1 磷酸化仅在对照组大鼠中受到刺激（94%）。Akt 丝氨酸磷酸化仅在对照组（90%）和鱼类组（78%）大鼠中受到显著刺激。结果表明，与能量密度相比，脂肪类型是高脂肪饮食的一个相关方面，因为只有高脂肪大豆饮食促进了下丘脑胰岛素信号转导和胰岛素摄食减少，而高脂肪鱼类饮食则保留了这一作用。
