Division of Diabetes and Endocrinology, Kobe University Graduate School of Medicine, Kobe, Japan.
Division of Development of Advanced Therapy for Metabolic Disease, Kobe University Graduate School of Medicine, Kobe, Japan.
J Diabetes Investig. 2021 Jul;12(7):1144-1151. doi: 10.1111/jdi.13511. Epub 2021 Feb 15.
AIMS/INTRODUCTION: Brown adipose tissue (BAT) utilizes large amounts of fuel for thermogenesis, but the mechanism by which fuel substrates are switched in response to changes in energy status is poorly understood. We have now investigated the role of Kruppel-like factor 15 (KLF15), a transcription factor expressed at a high level in adipose tissue, in the regulation of fuel utilization in BAT.
Depletion or overexpression of KLF15 in HB2 differentiated brown adipocytes was achieved by adenoviral infection. Glucose and fatty acid oxidation were measured with radioactive substrates, pyruvate dehydrogenase complex activity was determined with a colorimetric assay, and gene expression was examined by reverse transcription and real-time polymerase chain reaction analysis.
Knockdown of KLF15 in HB2 cells attenuated fatty acid oxidation in association with downregulation of the expression of genes related to this process including Acox1 and Fatp1, whereas it increased glucose oxidation. Expression of the gene for pyruvate dehydrogenase kinase 4 (PDK4), a negative regulator of pyruvate dehydrogenase complex, was increased or decreased by KLF15 overexpression or knockdown, respectively, in HB2 cells, with these changes being accompanied by a respective decrease or increase in pyruvate dehydrogenase complex activity. Chromatin immunoprecipitation showed that Pdk4 is a direct target of KLF15 in HB2 cells. Finally, fasting increased expression of KLf15, Pdk4 and genes involved in fatty acid utilization in BAT of mice, whereas refeeding suppressed Klf15 and Pdk4 expression.
Our results implicate KLF15 in the regulation of fuel switching between glucose and fatty acids in response to changes in energy status in BAT.
目的/引言：棕色脂肪组织（BAT）利用大量燃料进行产热，但对于燃料底物如何根据能量状态的变化进行切换的机制还知之甚少。我们现在研究了转录因子 Krüppel 样因子 15（KLF15）在调节 BAT 中燃料利用中的作用，该转录因子在脂肪组织中高水平表达。
通过腺病毒感染实现 HB2 分化的棕色脂肪细胞中 KLF15 的耗竭或过表达。用放射性底物测量葡萄糖和脂肪酸氧化，用比色法测定丙酮酸脱氢酶复合物活性，并用逆转录和实时聚合酶链反应分析检查基因表达。
HB2 细胞中 KLF15 的敲低减弱了脂肪酸氧化，同时下调与该过程相关的基因表达，包括 Acox1 和 Fatp1，而增加了葡萄糖氧化。HB2 细胞中丙酮酸脱氢酶激酶 4（PDK4）的基因表达，PDK4 是丙酮酸脱氢酶复合物的负调节因子，分别通过 KLF15 的过表达或敲低而增加或减少，这些变化伴随着丙酮酸脱氢酶复合物活性的相应降低或增加。染色质免疫沉淀显示 Pdk4 是 HB2 细胞中 KLF15 的直接靶标。最后，禁食增加了 BAT 中 KLF15、Pdk4 和参与脂肪酸利用的基因的表达，而重新喂养则抑制了 Klf15 和 Pdk4 的表达。
我们的结果表明，KLF15 参与了 BAT 中葡萄糖和脂肪酸之间燃料转换的调节，以响应能量状态的变化。
