Opposite effects of 17-β estradiol and testosterone on mitochondrial biogenesis and adiponectin synthesis in white adipocytes.

Sexual dimorphism has been found in both mitochondrial functionality and adiponectin expression in white adipose tissue, with female rats presenting more functional mitochondria than males and greater adiponectin expression. However, little is known about the role of sex hormones in this dimorphism. The aim was to elucidate the role of sex hormones in mitochondrial biogenesis and dynamics and in adiponectin synthesis in white adipocytes, and also to provide new evidence of the link between these processes. 3T3-L1 preadipocytes were differentiated and treated either with 17-β estradiol (E₂; 10  nM), progesterone (Pg), testosterone (1  μM both), or a combination of Pg or testosterone with flutamide (FLT; 10  μM) or E₂ (1  μM). The markers of mitochondrial biogenesis and dynamics and adiponectin expression were analyzed. E₂ induced mitochondrial proliferation and differentiation in 3T3-L1, although testosterone showed opposite effects. Pg treatment stimulated proliferation but impaired differentiation. In concerns mitochondrial dynamics, these hormones promoted fusion over fission. FLT treatment indicated that Pg elicits its effects on mitochondrial dynamics through the androgen receptor. E₂ coadministration with testosterone or Pg reversed its effects. In conclusion, our results show that E₂ induces stimulation of mitochondrial biogenesis in white adipocytes in vitro, especially in situations that imply an impairment of mitochondrial function, whereas testosterone would have opposite effects. Moreover, testosterone and Pg alter mitochondrial dynamics by promoting fusion over fission, while E₂ stimulates both processes. All these alterations run in parallel with changes in adiponectin expression, thus suggesting the existence of a link between mitochondrial biogenesis and dynamics and adiponectin synthesis in white adipocytes.