Mahmood Saleh, Birkaya Barbara, Rideout Todd C, Patel Mulchand S
Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, and.
Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York.
Am J Physiol Endocrinol Metab. 2016 Jul 1;311(1):E117-27. doi: 10.1152/ajpendo.00064.2016. Epub 2016 May 10.
During the absorptive state, the liver stores excess glucose as glycogen and synthesizes fatty acids for triglyceride synthesis for export as very low density lipoproteins. For de novo synthesis of fatty acids from glucose, the mitochondrial pyruvate dehydrogenase complex (PDC) is the gatekeeper for the generation of acetyl-CoA from glucose-derived pyruvate. Here, we tested the hypothesis that limiting the supply of PDC-generated acetyl-CoA from glucose would have an impact on expression of key genes in the lipogenic pathway. In the present study, although the postnatal growth of liver-specific PDC-deficient (L-PDCKO) male mice was largely unaltered, the mice developed hyperinsulinemia with lower blood glucose levels in the fed state. Serum and liver lipid triglyceride and cholesterol levels remained unaltered in L-PDCKO mice. Expression of several key genes (ACL, ACC1) in the lipogenic pathway and their upstream regulators (LXR, SREBP1, ChREBP) as well as several genes in glucose metabolism (Pklr, G6pd2, Pck1) and fatty acid oxidation (FAT, Cpt1a) was downregulated in livers from L-PDCKO mice. Interestingly, there was concomitant upregulation of lipogenic genes in adipose tissue from L-PDCKO mice. Although, the total hepatic acetyl-CoA content remained unaltered in L-PDCKO mice, modified acetylation profiles of proteins in the nuclear compartment suggested an important role for PDC-generated acetyl-CoA in gene expression in de novo fatty acid synthesis in the liver. This finding has important implications for the regulation of hepatic lipid synthesis in pathological states.
在吸收状态下,肝脏将多余的葡萄糖储存为糖原,并合成脂肪酸用于甘油三酯合成,以极低密度脂蛋白的形式输出。对于从葡萄糖从头合成脂肪酸而言,线粒体丙酮酸脱氢酶复合体(PDC)是由葡萄糖衍生的丙酮酸生成乙酰辅酶A的关键调控因子。在此,我们检验了以下假设:限制由葡萄糖生成的PDC衍生的乙酰辅酶A的供应会对脂肪生成途径中关键基因的表达产生影响。在本研究中,尽管肝脏特异性PDC缺陷(L-PDCKO)雄性小鼠的出生后生长基本未受影响,但这些小鼠在进食状态下出现了高胰岛素血症且血糖水平较低。L-PDCKO小鼠的血清和肝脏脂质甘油三酯及胆固醇水平保持不变。L-PDCKO小鼠肝脏中脂肪生成途径中的几个关键基因(ACL、ACC1)及其上游调节因子(LXR、SREBP1、ChREBP)以及葡萄糖代谢(Pklr、G6pd2、Pck1)和脂肪酸氧化(FAT、Cpt1a)中的几个基因的表达均下调。有趣的是,L-PDCKO小鼠脂肪组织中的脂肪生成基因同时上调。尽管L-PDCKO小鼠肝脏中的总乙酰辅酶A含量保持不变,但核区室中蛋白质的修饰乙酰化谱表明,PDC衍生的乙酰辅酶A在肝脏从头脂肪酸合成的基因表达中起重要作用。这一发现对病理状态下肝脏脂质合成的调节具有重要意义。