The Taurine-Conjugated Bile Acid (TUDCA) Normalizes Insulin Secretion in Pancreatic β-Cells Exposed to Fatty Acids: The Role of Mitochondrial Metabolism.

Abstract

Bile acid tauroursodeoxycholic (TUDCA), formed from the association of ursodeoxycholic acid (UDCA) with taurine, has already been shown to increase mitochondrial biogenesis and cell survival, in addition to reduce reticulum stress markers in different cell types. However, its mechanism of action upon insulin secretion control in obesity is still unknown. In this sense, we seek to clarify whether taurine, associated with bile acid, could improve the function of the pancreatic β-cells exposed to fatty acids through the regulation of mitochondrial metabolism. To test this idea, insulin-producing cells (INS1-E) were exposed to a fatty acid mix containing 500μM of each palmitate and oleate for 48hours treated or not with 300μM of TUDCA. After that, glucose-stimulated insulin secretion and markers of mitochondrial metabolism were evaluated. Our results showed that the fatty acid mix was efficient in inducing hyperfunction of INS1-E cells as observed by the increase in insulin secretion, protein expression of citrate synthase, and mitochondrial density, without altering cell viability. The treatment with TUDCA normalized insulin secretion, reducing the protein expression of citrate synthase, mitochondrial mass, and the mitochondrial membrane potential. This effect was associated with a decrease in the generation of mitochondrial superoxide and c-Jun N-terminal kinase (JNK) protein content. The findings are also consistent with the hypothesis that TUDCA normalizes insulin secretion by improving mitochondrial metabolism and redox balance. Thus, it highlights likely mechanisms of the action of this bile acid on the glycemic homeostasis reestablishment in obesity.