Bile acids regulate nutrient absorption and mitochondrial function, they establish and maintain gut microbial community composition and mediate inflammation, and they serve as signalling molecules that regulate appetite and energy homeostasis. The observation that there are hundreds of bile acids, especially many amidated bile acids, necessitates a revision of many of the classical descriptions of bile acids and bile acid enzyme functions. For example, bile salt hydrolases also have transferase activity. There are now hundreds of known modifications to bile acids and thousands of bile acid-associated genes, especially when including the microbiome, distributed throughout the human body (for example, there are >2,400 bile salt hydrolases alone). The fact that so much of our genetic and small-molecule repertoire, in both amount and diversity, is dedicated to bile acid function highlights the centrality of bile acids as key regulators of metabolism and immune homeostasis, which is, in large part, communicated via the gut microbiome.

胆汁酸调节营养吸收和线粒体功能，它们建立和维持肠道微生物群落组成并介导炎症，并且它们充当调节食欲和能量稳态的信号分子。胆汁酸有数百种，尤其是许多酰胺化胆汁酸，这一观察结果需要对胆汁酸和胆汁酸酶功能的许多经典描述进行修订。例如，胆盐水解酶也具有转移酶活性。现在有数百种已知的胆汁酸修饰和数千种胆汁酸相关基因，特别是当包括分布在人体各处的微生物组时（例如，仅胆汁盐水解酶就有 >2,400）。事实上，我们的遗传和小分子库（无论是数量还是多样性）都致力于胆汁酸功能，这一事实凸显了胆汁酸作为代谢和免疫稳态关键调节剂的中心地位，这在很大程度上是通过肠道微生物组。