Figure 2.

The effects of bile acids (BAs) on mitochondria and autophagy. The effects of BAs on mitochondria: DCA, CDCA, and their taurine conjugates activate MFN2 by binding directly to MFN2, promoting mitochondria-to-mitochondria fusion and mitochondria-to-ER fusion. These BAs, at normal concentration, promote the fusion between mitochondria, leading to the generation of ATP. By contrast, these BAs, at high concentration, promote the fusion between the mitochondria and the ER, leading to Ca2⁺ influx from the ER to the mitochondria. The effects of BAs on autophagy: secondary BAs (DCA and UDCA) induce autophagy and primary bile acids (CA, CDCA, and TCA) inhibit autophagy by preventing the formation of autolysosomes. In addition, the activation of TGR5, a receptor for secondary bile acids, leads to the activation of autophagy. By contrast, the activation of FXR, a receptor for primary bile acids, leads to the inhibition of autophagy.