It is well known that adipocytes are heterogeneous, and research about how best to identify and categorize adipocyte subclasses is ongoing. Thermogenic adipocytes are generally identified by the presence of UCP1; the futile creatine cycle is also an important thermogenic process in these cells. However, a lack of suitable models — particularly for beige adipose tissue — has stalled research into the relative contributions of UCP1 and the futile creatine cycle to thermogenesis, and into determining how the two systems co-exist. Now, two papers published in Cell Metabolism have begun to fill these research gaps.

The researchers found that the SV40-Prdm16 cells had increased levels of UCP1 and TNAP (a marker of the futile creatine cycle), which led them to run a series of experiments to assess the functionality of the futile creatine cycle in these cells. For instance, mitochondria from these cells were shown to have increased respiration in the presence of creatine and conditions limiting ADP concentrations, which indicates that the cells have an active futile creatine cycle.

众所周知，脂肪细胞是异质的，关于如何最好地识别和分类脂肪细胞亚类的研究正在进行中。产热脂肪细胞通常通过 UCP1 的存在来识别；无用的肌酸循环也是这些细胞中重要的生热过程。然而，由于缺乏合适的模型（尤其是米色脂肪组织的模型），导致对 UCP1 和无效肌酸循环对生热作用的相对贡献以及确定这两个系统如何共存的研究陷入停滞。现在，发表在《细胞代谢》上的两篇论文已经开始填补这些研究空白。

研究人员发现 SV40-Prdm16 细胞的 UCP1 和 TNAP（无效肌酸循环的标记）水平升高，这促使他们进行了一系列实验来评估这些细胞中无效肌酸循环的功能。例如，在肌酸存在和限制 ADP 浓度的条件下，这些细胞的线粒体显示出呼吸作用增加，这表明细胞具有活跃的无效肌酸循环。