Lipolysis regulates major transcriptional programs in brown adipocytes [TC ETO exp]. Lipolysis regulates major transcriptional programs in brown adipocytes [TC ETO exp]

β-Adrenergic signaling is a core regulator of brown adipocyte function stimulating both lipolysis and transcription of thermogenic genes, thereby expanding the capacity for oxidative metabolism. Here we have used pharmacological inhibitors and a novel direct activator of lipolysis to acutely modulate the activity of lipases, thereby enabling us to uncover lipolysis-dependent signaling pathways downstream of β-adrenergic signaling in brown adipocytes. We show that induction of lipolysis leads to acute induction of several gene programs and is required for transcriptional regulation by β-adrenergic signals. Using machine-learning algorithms to infer causal transcription factors, we show that PPARs are key mediators of lipolysis-induced activation of genes involved in lipid metabolism and thermogenesis. Importantly, lipolysis also activates the unfolded protein response and regulates the core circadian transcriptional machinery independently of PPARs. Our results demonstrate that lipolysis generates important metabolic signals that exert profound pleiotropic effects on brown adipocyte transcription and function. Overall design: Immortalized mouse brown adipocytes (D7) pretreated for 1hr with etiher etomoxir (50uM) or triascin C (5uM) and subsequently stimulated +/- SR-3420 (10uM) for 3hrs.

β-肾上腺素能信号通路（β-Adrenergic signaling）是棕色脂肪细胞功能的核心调控因子，可同时激活脂解（lipolysis）过程与产热基因的转录，从而提升氧化代谢能力。本研究通过使用药理学抑制剂与一种新型脂解直接激活剂，对脂酶活性进行急性调控，借此揭示棕色脂肪细胞中β-肾上腺素能信号通路下游依赖于脂解的信号通路。研究结果显示，脂解的诱导可急性激活多种基因程序，且是β-肾上腺素能信号介导转录调控的必需环节。通过机器学习算法（machine-learning algorithms）推断因果转录因子，我们证实PPARs是脂解诱导激活脂质代谢与产热相关基因的关键介质。值得注意的是，脂解还可激活未折叠蛋白反应（unfolded protein response），并独立于PPARs调控核心昼夜节律转录机器（circadian transcriptional machinery）。本研究表明，脂解可产生重要的代谢信号，对棕色脂肪细胞的转录与功能产生显著的多效性影响。整体实验设计：将永生化小鼠棕色脂肪细胞（immortalized mouse brown adipocytes，D7）先用依托莫司（etomoxir，50μM）或三阿辛C（triascin C，5μM）预处理1小时，随后分别经SR-3420（10μM）处理或不添加该试剂，孵育3小时。