Department of Surgery, James A. Haley Veterans Affairs Medical Center, University of South Florida, Tampa, Florida, USA.
Surg Obes Relat Dis. 2012 Jan-Feb;8(1):73-81. doi: 10.1016/j.soard.2011.07.019. Epub 2011 Aug 27.
Obesity induces steatosis and increases oxidative stress, as well as chronic inflammation in the liver. The balance between lipogenesis and lipolysis is disrupted in obese animals. At a cellular level, the changes in metabolic sensors and energy regulators are poorly understood. We hypothesized that diet-induced steatosis increases oxidative stress, inflammation, and changes the metabolic regulators to promote energy storage in mice. The setting was a university-affiliated basic science research laboratory.
Four-week-old C57BL mice were fed a high-fat diet (n = 8) or regular chow (n = 8) for 7 weeks. The liver sections were stained for fat content and immunofluorescence. Liver homogenates were used for protein analysis by immunoblotting and mRNA analysis by reverse transcriptase-polymerase chain reaction. The gels were quantified using densitometry P ≤ .05 was considered significant.
The high-fat diet upregulated protein kinase-C atypical isoforms ζ and λ and decreased glucose tolerance and the interaction of insulin receptor substrate 2 with phosphoinositide kinase-3. The high-fat diet increased the transcriptional factors liver X receptor (4321 ± 98 versus 2981 ± 80) and carbohydrate response element-binding protein (5132 ± 135 versus 3076 ± 91), the lipogenesis genes fatty acid binding protein 5, stearoyl-co-enzyme A desaturase-1, and acetyl-co-enzyme A carboxylase protein, and fatty acid synthesis. The high-fat diet decreased 5'-adenosine monophosphate-activated protein kinase (2561 ± 78 versus 1765 ± 65), glucokinase-3β (2.214 ± 34 versus 3356 ± 86), and SIRT1 (2015 ± 76 versus 3567 ± 104) and increased tumor necrosis factor-α (3415 ± 112 versus 2042 ± 65), nuclear factor kappa B (5123 ± 201 versus 2562 ± 103), cyclooxygenase-2 (4230 ± 113 versus 2473 ± 98), nicotinamide-adenine dinucleotide phosphate oxidase (3501 ± 106 versus 1600 ± 69) and reactive oxygen species production (all P < .001, obese mice versus lean mice).
A high-fat diet impairs glucose tolerance and hepatic insulin signaling, upregulates transcriptional and translational activities that promote lipogenesis, cytokine production, proinflammatory signaling, and oxidative stress, and downregulates lipolysis. Understanding the complex cellular signals triggered by obesity might have profound clinical implications.
肥胖会导致肝脏脂肪变性和氧化应激增加以及慢性炎症。肥胖动物的脂肪生成和脂肪分解之间的平衡被打破。在细胞水平上，代谢传感器和能量调节剂的变化还不清楚。我们假设，饮食诱导的脂肪变性会增加氧化应激、炎症，并改变代谢调节剂，以促进小鼠的能量储存。该研究在一个附属的基础科学研究实验室进行。
4 周龄 C57BL 小鼠喂食高脂肪饮食（n = 8）或普通饲料（n = 8）7 周。用脂肪染色和免疫荧光法对肝组织切片进行染色。用免疫印迹法和逆转录聚合酶链反应分析肝匀浆的蛋白分析和 mRNA 分析。使用密度计对凝胶进行定量分析，P ≤.05 被认为具有统计学意义。
高脂肪饮食上调了蛋白激酶-C 非典型同工型 ζ 和 λ，并降低了葡萄糖耐量和胰岛素受体底物 2 与磷酸肌醇 3-激酶的相互作用。高脂肪饮食增加了转录因子肝 X 受体（4321 ± 98 与 2981 ± 80）和碳水化合物反应元件结合蛋白（5132 ± 135 与 3076 ± 91）、脂肪生成基因脂肪酸结合蛋白 5、硬脂酰辅酶 A 去饱和酶-1 和乙酰辅酶 A 羧化酶蛋白以及脂肪酸合成。高脂肪饮食降低了 5'-腺嘌呤单磷酸激活蛋白激酶（2561 ± 78 与 1765 ± 65）、葡糖激酶-3β（2.214 ± 34 与 3356 ± 86）和 SIRT1（2015 ± 76 与 3567 ± 104），并增加了肿瘤坏死因子-α（3415 ± 112 与 2042 ± 65）、核因子 kappa B（5123 ± 201 与 2562 ± 103）、环氧化酶-2（4230 ± 113 与 2473 ± 98）、烟酰胺腺嘌呤二核苷酸磷酸氧化酶（3501 ± 106 与 1600 ± 69）和活性氧（所有 P <.001，肥胖小鼠与瘦小鼠相比）的产生。
高脂肪饮食会损害葡萄糖耐量和肝胰岛素信号，上调促进脂肪生成、细胞因子产生、促炎信号和氧化应激的转录和翻译活性，并下调脂肪分解。了解肥胖引发的复杂细胞信号可能具有深远的临床意义。
