Pre- and post-sexual maturity liver-specific ERa knockout does not impact hepatic mitochondrial function or steatosis but does alter gene expression
Compared to males, premenopausal women and female rodents are protected against hepatic steatosis and present with higher functioning mitochondria (greater hepatic mitochondrial respiration and reduced H2O2 emission). Despite evidence that estrogen action mediates female protection against steatosis, mechanisms remain unknown. Here we validated a mouse model with inducible reduction of liver ERa (LERKO) via AAV Cre. We phenotyped the liver health and mitochondrial function of LERKO mice (n=10-12 per group) on a short-term high-fat diet (HFD), and then tested if timing of LERKO induction at 2 timepoints (sexually immature: 4 wks old (n=11 per group) vs. sexually mature: 8-10 wks old (n=8 per group)) would impact HFD-induced outcomes. We opted for an inducible LERKO model due to known estrogen-mediated developmental programming, and report both receptor and tissue specificity with our model. Control mice were ERafl/fl receiving AAV with GFP only. Results show that there were no differences in body weight/composition or hepatic steatosis in LERKO mice with either short-term (4 wk) or chronic (8 wk) high-fat feeding. Similarly, LERKO genotype nor timing of LERKO induction (pre vs post sexual maturity) did not alter hepatic mitochondrial O2 and H2O2 flux, coupling, or OXPHOS protein. Transcriptomic analysis showed that hepatic gene expression in LERKO was significantly influenced by developmental stage. Together, these studies suggest that hepatic ERa is not required in female protection against HFD-induced hepatic steatosis nor does it mediate sexual dimorphism in liver mitochondria function. Overall design: RNA was extracted from liver tissue from individual mice in four groups (sexullay immature and mature, LERKO and flox mice, n = 4 per group)