Nishida Yuichiro, Nishijima Kazutoshi, Yamada Yosuke, Tanaka Hiroaki, Matsumoto Akiko, Fan Jianglin, Uda Yoichi, Tomatsu Hajime, Yamamoto Hiroyuki, Kami Kenjiro, Kitajima Shuji, Tanaka Keitaro
Department of Preventive Medicine, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan.
Center for Animal Resources and Collaborative Study, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.
Metabolomics. 2021 Feb 16;17(3):26. doi: 10.1007/s11306-021-01777-4.
INTRODUCTION: Overexpression of lipoprotein lipase (LPL) protects against high-fat-diet (HFD)-induced obesity and insulin resistance in transgenic rabbits; however, the molecular mechanisms remain unclear. Skeletal muscle is a major organ responsible for insulin-stimulated glucose uptake and energy expenditure. OBJECTIVES: The main purpose of the current study was to examine the effects of the overexpression of LPL on the skeletal muscle metabolomic profiles to test our hypothesis that the mitochondrial oxidative metabolism would be activated in the skeletal muscle of LPL transgenic rabbits and that the higher mitochondrial oxidative metabolism activity would confer better phenotypic metabolic outcomes. METHODS: Under a HFD, insulin resistance index was measured using the intravenous glucose tolerance test, and total energy expenditure (TEE) was measured by doubly-labeled water in control and LPL transgenic rabbits (n = 12, each group). Serum lipids, such as triglycerides and free fatty acid, were also measured. The skeletal muscle metabolite profile was analyzed using capillary electrophoresis time-of flight mass spectrometry in the two groups (n = 9, each group). A metabolite set enrichment analysis (MSEA) with muscle metabolites and a false discovery rate q < 0.2 was performed to identify significantly different metabolic pathways between the 2 groups. RESULTS: The triglycerides and free fatty acid levels and insulin resistance index were lower, whereas the TEE was higher in the LPL transgenic rabbits than in the control rabbits. Among 165 metabolites detected, the levels of 37 muscle metabolites were significantly different between the 2 groups after false discovery rate correction (q < 0.2). The MSEA revealed that the TCA cycle and proteinogenic amino acid metabolism pathways were significantly different between the 2 groups (P < 0.05). In the MSEA, all four selected metabolites for the TCA cycle (2-oxoglutaric acid, citric acid, malic acid, fumaric acid), as well as eight selected metabolites for proteinogenic amino acid metabolism (asparagine, proline, methionine, phenylalanine, histidine, arginine, leucine, isoleucine) were consistently increased in the transgenic rabbits compared with control rabbits, suggesting that these two metabolic pathways were activated in the transgenic rabbits. Some of the selected metabolites, such as citric acid and methionine, were significantly associated with serum lipids and insulin resistance (P < 0.05). CONCLUSION: The current results suggest that the overexpression of LPL may lead to increased activities of TCA cycle and proteinogenic amino acid metabolism pathways in the skeletal muscle, and these enhancements may play an important role in the biological mechanisms underlying the anti-obesity/anti-diabetes features of LPL overexpression.
引言:脂蛋白脂肪酶(LPL)的过表达可保护转基因兔免受高脂饮食(HFD)诱导的肥胖和胰岛素抵抗;然而,其分子机制仍不清楚。骨骼肌是负责胰岛素刺激的葡萄糖摄取和能量消耗的主要器官。 目的:本研究的主要目的是研究LPL过表达对骨骼肌代谢组学谱的影响,以验证我们的假设,即LPL转基因兔骨骼肌中的线粒体氧化代谢将被激活,且较高的线粒体氧化代谢活性将带来更好的表型代谢结果。 方法:在高脂饮食条件下,通过静脉葡萄糖耐量试验测量胰岛素抵抗指数,并通过双标记水法测量对照和LPL转基因兔(每组n = 12)的总能量消耗(TEE)。还测量了血清脂质,如甘油三酯和游离脂肪酸。使用毛细管电泳飞行时间质谱法分析两组(每组n = 9)的骨骼肌代谢物谱。对肌肉代谢物进行代谢物集富集分析(MSEA),错误发现率q < 0.2,以确定两组之间显著不同的代谢途径。 结果:与对照兔相比,LPL转基因兔的甘油三酯和游离脂肪酸水平以及胰岛素抵抗指数较低,而总能量消耗较高。在检测到的165种代谢物中,经错误发现率校正后(q < 0.2),两组之间有37种肌肉代谢物的水平存在显著差异。MSEA显示,两组之间三羧酸循环和生糖氨基酸代谢途径存在显著差异(P < 0.05)。在MSEA中,与对照兔相比,转基因兔中三羧酸循环选择的所有四种代谢物(2-氧代戊二酸、柠檬酸、苹果酸、富马酸)以及生糖氨基酸代谢选择的八种代谢物(天冬酰胺、脯氨酸、蛋氨酸、苯丙氨酸、组氨酸、精氨酸、亮氨酸、异亮氨酸)持续增加,表明这两种代谢途径在转基因兔中被激活。一些选择的代谢物,如柠檬酸和蛋氨酸,与血清脂质和胰岛素抵抗显著相关(P < 0.05)。 结论:目前的结果表明,LPL的过表达可能导致骨骼肌中三羧酸循环和生糖氨基酸代谢途径的活性增加,这些增强可能在LPL过表达的抗肥胖/抗糖尿病特征的生物学机制中起重要作用。
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