胰岛素抵抗大鼠模型中脂肪肝导致的循环极低密度脂蛋白特征。

Circulating very-low-density lipoprotein characteristics resulting from fatty liver in an insulin resistance rat model.

机构信息

Laboratory of Lipids and Lipoproteins, Department of Clinical Biochemistry, Faculty of Pharmacy and Biochemistry, INFIBIOC, University of Buenos Aires, Buenos Aires, Argentina.

出版信息

Ann Nutr Metab. 2010;56(3):198-206. doi: 10.1159/000276596. Epub 2010 Mar 4.

Abstract

The close association between nonalcoholic fatty liver and insulin resistance is now widely recognized. While the former is characterized by excessive intrahepatic triglyceride accumulation, the latter induces overproduction of very-low-density lipoprotein (VLDL) particles. It has not been well elucidated whether these apparently opposite mechanisms impact on VLDL characteristics or not. The aim of the present study was to evaluate the VLDL secretion and features resulting from insulin resistance and fatty liver in rats fed a sucrose-rich diet (SRD, i.e. addition of sucrose to drinking water during 12 weeks). No differences in calorie intake were observed in comparison to controls. Both groups showed similar weight gains throughout the treatment period. However, SRD rats showed an increased proportion of body fat as assessed by X-ray absorptiometry, increased visceral obesity, liver weight and fat accumulation in the liver (p < 0.04). Histological study revealed moderate micro- and macrovesicular steatosis. Fasting insulin, triglyceride and free fatty acid (FFA) levels increased while VLDLs decreased in SRD rats (p < 0.05). The chemical composition of VLDLs of SRD rats showed a higher percentage of triglycerides, and the VLDL triglyceride/protein ratio, an estimator of lipoprotein size, suggests that VLDL particles of SRD rats are larger than those of controls (p < 0.0005). FFA levels correlated with VLDL triglycerides (r = 0.49, p = 0.03) and liver fat content correlated with plasma triglycerides (r = 0.65), VLDL triglycerides (r = 0.55) and triglyceride/protein ratio (r = 0.52, p < 0.02). The VLDL secretion rate assay showed an increase in SRD rats (p < 0.02), confirming an overproduction despite liver fat accumulation. Our findings are consistent with an insulin resistance development model in which hepatic lipid content would constitute an important determinant of a triglyceride-rich, large-particle VLDL secretion; both features would increase its atherogenic potential.

摘要

非酒精性脂肪肝与胰岛素抵抗之间的密切关系现在已得到广泛认可。前者的特征是肝内甘油三酯过度积累,而后者则导致极低密度脂蛋白(VLDL)颗粒的过度产生。目前尚不清楚这些明显相反的机制是否会影响 VLDL 的特征。本研究旨在评估胰岛素抵抗和脂肪肝大鼠在富含蔗糖饮食(SRD,即在 12 周期间向饮用水中添加蔗糖)喂养下 VLDL 的分泌和特征。与对照组相比,两组的热量摄入没有差异。在整个治疗期间,两组的体重增加相似。然而,SRD 大鼠通过 X 射线吸收测定法评估显示体脂肪比例增加,内脏肥胖、肝重和肝脂肪堆积增加(p<0.04)。组织学研究显示中度微泡和大泡性脂肪变性。SRD 大鼠空腹胰岛素、甘油三酯和游离脂肪酸(FFA)水平升高,而 VLDL 降低(p<0.05)。SRD 大鼠 VLDL 的化学成分显示甘油三酯的百分比更高,VLDL 甘油三酯/蛋白比,一种脂蛋白大小的估计值,表明 SRD 大鼠的 VLDL 颗粒比对照组大(p<0.0005)。FFA 水平与 VLDL 甘油三酯相关(r=0.49,p=0.03),肝脂肪含量与血浆甘油三酯(r=0.65)、VLDL 甘油三酯(r=0.55)和甘油三酯/蛋白比相关(r=0.52,p<0.02)。VLDL 分泌率测定显示 SRD 大鼠增加(p<0.02),证实尽管肝脂肪堆积,但仍存在过度产生。我们的发现与胰岛素抵抗发展模型一致,其中肝内脂质含量将成为富含甘油三酯、大颗粒 VLDL 分泌的重要决定因素;这两个特征都会增加其动脉粥样硬化的潜在风险。

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