It is very well known that brown adipose tissue (BAT) is involved in thermogenesis, particularly in rodents. However, whether and how BAT affects the metabolic health of adult humans has been unclear. A new study addresses this issue.

In this study, the researchers generated mice with BAT-specific knockout of the mitochondrial BCAA carrier (MBC, encoded by Slc25a44), which meant that mitochondrial BCAA catabolism was blocked. They also used comprehensive isotope-labelled BCAA tracing, which enabled them to study the flux in cells and in mice. “In contrast to the idea of BCAA as fuel for thermogenesis, we found that BCAA are a major nitrogen source for the synthesis of many amino acids and glutathione, many of which are secreted outside BAT,” says Kajimura.

众所周知，棕色脂肪组织（BAT）参与生热作用，特别是在啮齿动物中。然而，BAT 是否以及如何影响成年人的代谢健康尚不清楚。一项新的研究解决了这个问题。

在这项研究中，研究人员培育了 BAT 特异性敲除线粒体 BCAA 载体（MBC，由Slc25a44编码）的小鼠，这意味着线粒体 BCAA 分解代谢被阻断。他们还使用了全面的同位素标记支链氨基酸示踪技术，这使他们能够研究细胞和小鼠中的通量。 “与支链氨基酸作为产热燃料的想法相反，我们发现支链氨基酸是合成许多氨基酸和谷胱甘肽的主要氮源，其中许多氨基酸和谷胱甘肽是在 BAT 之外分泌的，”Kajimura 说。