Osteoblast Specific Overexpression of Mitoneet Leads to Decreased Bone Mass

Presentation Number: SAT 350
Date of Presentation: April 1st, 2017

Anyonya R Guntur*1 and Clifford J Rosen2
1Maine Medical Center, Scarborough, ME, 2Maine Medical Center Research Institute, Scarborough, ME

Abstract

MitoNEET is an outer mitochondrial membrane protein that regulates mitochondrial metabolism. Overexpression of MitoNEET in adipocytes specifically leads to inhibition of β-oxidation and decreased oxidative phosphorylation. To study the role of oxidative phosphorylation in osteoblasts we utilized a Doxycycline (Dox) inducible (Tet-ON) mouse model to overexpress MitoNEET in vivo. In this overexpression model, mice containing the tetracycline responsive element (TRE) fused to the MitoNEET open reading frame were crossed to Runx2 reverse-tetracycline trans-activator (rtTA) to generate osteoblast specific overexpression. Two groups of 4 week old male mice were generated and Dox+Saccharin, and Saccharin were introduced through drinking water for 12 weeks. To confirm overexpression, tibiae from mice positive and negative for TRE MitoNEET on Dox+Saccharin were isolated and rtQPCR analysis performed showing a significant increase in MitoNEET expression in bone. Skeletal phenotyping using DEXA at 8 and 12 weeks of age revealed that osteoblast specific MitoNEET overexpression led to a significant decrease in femoral BMD (n=6). Next, we performed indirect calorimetry to obtain energy expenditure (EE) and respiratory quotient (RQ) data. We found no significant difference in 24 hour energy expenditure even though body weight in the Dox+Saccharin group animals was significantly higher compared to Saccharin controls. Interestingly, 24 hour RQ was significantly lower in the MitoNEET overexpressing animals suggesting oxidation of fat (n=8-10, p=0.03). There was no difference in food consumption, but the group on Dox+Saccharindrank significantly less amount of water (n=8-10, p=0.009). Furthermore, MitoNEET overexpressing mice also had significantly lower sleep hours (n=8, p=0.017). In sum, manipulating MitoNEET expression specifically in the osteoblast impairs bone mass and leads to decreased respiratory quotient, further studies are underway to analyze potential mechanisms.

 

Nothing to Disclose: ARG, CJR