Peyot Marie-Line, Guay Claudiane, Latour Martin G, Lamontagne Julien, Lussier Roxane, Pineda Marco, Ruderman Neil B, Haemmerle Guenter, Zechner Rudolf, Joly Érik, Madiraju S R Murthy, Poitout Vincent, Prentki Marc
From the Molecular Nutrition Unit and the Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H1W 4A4, Canada.
Departments of Medicine and Physiology and Biophysics, Boston University School of Medicine and Diabetes Unit, Section of Endocrinology, Boston University School of Medicine and Boston Medical Center, Boston, Massachusetts 02118.
J Biol Chem. 2009 Jun 19;284(25):16848-16859. doi: 10.1074/jbc.M109.006650. Epub 2009 Apr 22.
Reduced lipolysis in hormone-sensitive lipase-deficient mice is associated with impaired glucose-stimulated insulin secretion (GSIS), suggesting that endogenous beta-cell lipid stores provide signaling molecules for insulin release. Measurements of lipolysis and triglyceride (TG) lipase activity in islets from HSL(-/-) mice indicated the presence of other TG lipase(s) in the beta-cell. Using real time-quantitative PCR, adipose triglyceride lipase (ATGL) was found to be the most abundant TG lipase in rat islets and INS832/13 cells. To assess its role in insulin secretion, ATGL expression was decreased in INS832/13 cells (ATGL-knockdown (KD)) by small hairpin RNA. ATGL-KD increased the esterification of free fatty acid (FFA) into TG. ATGL-KD cells showed decreased glucose- or Gln + Leu-induced insulin release, as well as reduced response to KCl or palmitate at high, but not low, glucose. The K(ATP)-independent/amplification pathway of GSIS was considerably reduced in ATGL-KD cells. ATGL(-/-) mice were hypoinsulinemic and hypoglycemic and showed decreased plasma TG and FFAs. A hyperglycemic clamp revealed increased insulin sensitivity and decreased GSIS and arginine-induced insulin secretion in ATGL(-/-) mice. Accordingly, isolated islets from ATGL(-/-) mice showed reduced insulin secretion in response to glucose, glucose + palmitate, and KCl. Islet TG content and FFA esterification into TG were increased by 2-fold in ATGL(-/-) islets, but glucose usage and oxidation were unaltered. The results demonstrate the importance of ATGL and intracellular lipid signaling for fuel- and non-fuel-induced insulin secretion.
激素敏感性脂肪酶缺陷小鼠的脂肪分解减少与葡萄糖刺激的胰岛素分泌(GSIS)受损有关,这表明内源性β细胞脂质储存为胰岛素释放提供信号分子。对HSL(-/-)小鼠胰岛中的脂肪分解和甘油三酯(TG)脂肪酶活性的测量表明β细胞中存在其他TG脂肪酶。使用实时定量PCR,发现脂肪甘油三酯脂肪酶(ATGL)是大鼠胰岛和INS832/13细胞中最丰富的TG脂肪酶。为了评估其在胰岛素分泌中的作用,通过小发夹RNA降低了INS832/13细胞(ATGL基因敲低(KD))中的ATGL表达。ATGL-KD增加了游离脂肪酸(FFA)向TG的酯化。ATGL-KD细胞显示葡萄糖或谷氨酰胺+亮氨酸诱导的胰岛素释放减少,以及在高葡萄糖而非低葡萄糖条件下对氯化钾或棕榈酸的反应降低。ATGL-KD细胞中GSIS的不依赖于K(ATP)的/放大途径显著减少。ATGL(-/-)小鼠胰岛素血症和低血糖,血浆TG和FFA降低。高血糖钳夹显示ATGL(-/-)小鼠的胰岛素敏感性增加,GSIS和精氨酸诱导的胰岛素分泌减少。因此,来自ATGL(-/-)小鼠的分离胰岛对葡萄糖、葡萄糖+棕榈酸和氯化钾的反应显示胰岛素分泌减少。ATGL(-/-)胰岛中的胰岛TG含量和FFA酯化增加了2倍,但葡萄糖利用和氧化未改变。结果证明了ATGL和细胞内脂质信号传导对燃料和非燃料诱导的胰岛素分泌的重要性。