Activation of STING pathway by mitochondrial fission negatively regulates adipogenic differentiation of 3 T3-L1 cells.

Abstract

Adipocyte hyperplasia refers to the increase in the number of adipocytes, whereas adipocyte hypertrophy pertains to the enlargement of individual adipocytes resulting from the accumulation of lipid droplets. In this study, we found that activation of the STING signalling pathway occurs during adipogenic differentiation of 3 T3-L1 preadipocytes. Interestingly, inhibiting the STING pathway by using STING antagonist H151 or siRNA targeting STING promotes adipocyte differentiation and increases adipocyte numbers, while activation of STING inhibits adipogenic differentiation. Silencing the STING canonical downstream IRF3, or inhibiting the proton channel activity of STING enhances adipogenic differentiation, confirming the negative modulation of adipogenic differentiation by STING. In vivo, intraperitoneal injection of H151 into mice with a high-fat diet further enhances the adipocyte hyperplasia, as shown by the increased volume of adipose tissues, but consistent sizes of adipocytes. During the adipogenic differentiation of 3 T3-L1 cells, DRP1-mediated mitochondrial fission is enhanced, and causes mitochondrial DNA leakage, which in turn activates the STING pathway. However, inhibition of mitochondrial fission represses adipogenic differentiation of 3 T3-L1 cells in spite of the down-regulation of STING pathway. Therefore, our results indicate that adipogenic differentiation is associated with DRP1-induced mitochondrial fission. However, the leakage of mitochondrial DNA caused by DRP1-induced mitochondrial fission activates the STING signalling pathway, which negatively regulates adipogenic differentiation. Tissue specific reduction of DRP1-associated mitochondrial fission or STING enhancement might be new strategies for the therapy of obesity-associated diseases.