Growth hormone enhances mitochondria biogenesis and endows mitochondrial thermogenesis in murine adipocytes

Abstract

Growth hormone (GH) can reduce the size of white adipocytes in vivo and in vitro. This catabolic effect was previously believed to be related to the breakdown of stored triglycerides into free fatty acids. However, little is known about its effects on mitochondria in adipose or adipocytes. We thus examined effects of GH on mitochondrial number change and metabolic changes in fat of diet induced obese mice as well as 3T3-L1 adipocytes. We first found in vitro GH increase the density of mitochondria in 3T3-L1 adipocytes. We figured out that GH enhanced the expression of mitochondria biogenesis related genes, such as peroxisome proliferative activated receptor gamma coactivator 1 alpha (Pgc1α), DNA polymerase gamma (Polg) and transcription factor A of mitochondria (Tfam) in vitro and in vivo. To explore the underlying mechanism, we further confirmed that the enhanced expression of these proteins was dependent on the three pathways of GH signaling transduction and that GH enhanced the promoter transactivation of Pgc1α or Polg. We also found that GH increased the cell death-inducing DNA fragmentation factor alpha subunit-like effector A (CIDEA) and uncoupling protein 1 (UCP1) expression by enhancing the promoter transactivation of Cidea. We further elucidated that GH induced UCP1 expression was dependent on CIDEA using CRISPR-Cas9 technique. We therefore conclude that GH has effects on reducing adipocyte size via promoting PGC1α and POLG mediated mitochondrial biogenesis, and also on increasing UCP1 expression via CIDEA. Making adipocytes browning by GH or its analogs may provide a therapeutic strategy for metabolic diseases.