The loss of insulin receptor (IR) in white adipose tissue (WAT) is a feature of type 2 diabetes. Previously, we have demonstrated that feeding mice a preventive selenium rich HFD (SRHFD) , while not influencing obesity development, counteracted diet-induced downregulation of IR and insulin resistance. This was caused by selenite-induced Glutathione peroxidase 3 (GPx3) , which enhanced IR expression and concomitant whole-body insulin sensitivity. The positive correlation between GPX3 and IR levels was also present in humans. In the current study, we investigate A) which selenite (Se) transporter is responsible for the beneficial Se-induced metabolism of WAT using of 3T3-L1 cells, and B) the potential therapeutic effect of selenite supplementation in diet-induced obese mice. We find that LDL Receptor Related Protein (LRP) 8 is necessary for Se-induced upregulation of GPx3 and IR expression to modulate insulin action, as siRNA mediated LRP8 knockdown in 3T3-L1 cells abrogates Se-induced insulin-sensitizing effects with e.g. reduced GPx3 and IR expression. To assess the metabolic effect of selenite supplementation in diet-induced obese mice, C57BL/6N mice received a HFD for 6 weeks, which was followed by a SRHFD for further 12 weeks. Unexpectedly, feeding obese mice a SRHFD resulted in a 10% increase in body weight gain compared to the HFD-fed control group. Nevertheless, these mice exhibited signs of improved metabolism with a shift towards smaller adipocytes, as indicator of improved adipocyte metabolism, and decreased plasma insulin levels. Yet, this was accompanied by unaltered inflammation, GPx3 and IR expression.
In conclusion, our data suggest that LRP8 represents a novel Se-transporter in adipocytes controlling insulin sensitivity and that established obesity precludes the beneficial increase of Se-induced GPx3 and IR regulation in WAT, highlighting the potential importance of GPx3 as a mediator of adipose tissue insulin sensitivity.
R.Hauffe: None. M.Rath: None. A.Kleinridders: Other Relationship; Novozymes.
Deutsche Forschungsgemeinschaft (KL 2399/4-1) German Ministry of Education and Research BMBF (82DZD00302)