Louis Caroline, Van den Daelen Carine, Tinant Gilles, Bourez Sophie, Thomé Jean-Pierre, Donnay Isabelle, Larondelle Yvan, Debier Cathy
Institut des Sciences de la Vie, UCLouvain, Croix du Sud 2/L7.05.08, 1348, Louvain-la-Neuve, Belgium,
In Vitro Cell Dev Biol Anim. 2014 Jun;50(6):507-18. doi: 10.1007/s11626-014-9733-6. Epub 2014 Jan 30.
The triglycerides (TGs) stored in the white adipose tissue are mobilized during periods of negative energy balance. To date, there is no in vitro model of adipocytes imitating a long period of negative energy balance in which triglycerides are highly mobilized. Such model would allow studying the mobilization of TGs and lipophilic compounds trapped within the adipose tissue (e.g., pollutants and vitamins). The present study aims at developing a performing long-term in vitro lipolysis in adipocytes, resulting in a significant decrease of TG stores. Lipolysis was induced on differentiated rat adipocytes by a lipolytic medium with or without isoproterenol for 12 h. The condition with isoproterenol was duplicated, once with medium renewal every 3 h and once without medium renewal. Adding isoproterenol efficiently triggered lipolysis in a short time (3 h). However, a single stimulation by isoproterenol, without medium renewal, was not sufficient to reduce the TG content during a longer term (12 h). A reesterification of fatty acids occurred after a few hours of lipolysis, resulting in a novel increase of cellular lipids. Regular medium renewal combined with repeated isoproterenol stimulations led to almost emptied cells after 12 h. However, medium renewal without isoproterenol stimulation for 12 h was as efficient in terms of lipid mobilization. Our study demonstrates that, over a short-term period, isoproterenol is required to exert a significant lipolytic effect on adipocytes. During a long-term period, the presence of isoproterenol is no longer essential. Instead, medium renewal becomes the main factor involved in cell emptying. The efficiency of this protocol was demonstrated by visual tracking of the cells and by monitoring the dynamics of release of a lipophilic compound, PCB-153, from adipocytes during lipolysis.
储存在白色脂肪组织中的甘油三酯（TGs）在能量负平衡期间会被动员起来。迄今为止，尚无模仿甘油三酯高度动员的长期能量负平衡的脂肪细胞体外模型。这样的模型将有助于研究甘油三酯以及被困在脂肪组织中的亲脂性化合物（如污染物和维生素）的动员情况。本研究旨在开发一种在脂肪细胞中进行长期体外脂解的方法，从而使甘油三酯储存量显著减少。用含或不含异丙肾上腺素的脂解培养基对分化的大鼠脂肪细胞进行12小时的脂解诱导。含异丙肾上腺素的条件重复进行两次，一次每3小时更换培养基，一次不更换培养基。添加异丙肾上腺素能在短时间内（3小时）有效引发脂解。然而，仅用异丙肾上腺素单次刺激且不更换培养基，在较长时间（12小时）内不足以降低甘油三酯含量。脂解数小时后发生脂肪酸再酯化，导致细胞脂质含量再次增加。定期更换培养基并结合重复的异丙肾上腺素刺激，12小时后细胞几乎排空。然而，在12小时内不使用异丙肾上腺素刺激而仅更换培养基，在脂质动员方面同样有效。我们的研究表明，在短期内，需要异丙肾上腺素对脂肪细胞发挥显著的脂解作用。在长期过程中，异丙肾上腺素的存在不再是必需的。相反，更换培养基成为细胞排空的主要因素。通过对细胞的视觉追踪以及监测脂解过程中亲脂性化合物多氯联苯-153从脂肪细胞中的释放动态，证明了该方案的有效性。
