The 1,25D3 -MARRS receptor/PDIA3/ERp57 and lifespan.

Using MRI on mice bearing a targeted knockout (KO) of the 1,25D3 -MARRS receptor/PDIA3/ERp57 we found that they had decreased body fat relative to their littermate (LM) controls, a condition associated with increased lifespan. Others have found that lower body fat is correlated with decreased lipid droplets in intestinal cells that may be mediated by a factor secreted by germ cells (possibly estradiol). In a reducing environment estradiol competed for binding to the 1,25D3-MARRS receptor/PDIA3/ERp57. A consequence of this was that estradiol stimulated calcium uptake in enterocytes isolated from LM mice. In time course studies, lipid droplets increased in response to 1 nM estradiol from 1-5 D of culture, relative to corresponding controls, while at 6 and 7 D this steroid decreased lipid droplets. Enterocytes from LM or KOs incubated with estradiol for 1-4 D showed the hormone increased lipid droplets. Using the 4 D culture period, 1 and 10 nM estradiol significantly increased the number of lipid droplets in cells from LM mice by 40-60%, compared to equivalent conditions in KO mice. In assessing signal transduction pathways, the hormone increased phospho-Akt levels, but no differences were observed in phospho-mTORC1, or phospho-S6K (although cells from chicks did exhibit a hormone-mediated difference). Finally, the remaining mice (which had stopped reproducing) were allowed to die naturally and lifespan recorded. LM mice lived 687 ± 77 D (without an outlying value) while KO mice lived 740 D ± 80 D. These data suggest the 25D3 -MARRS receptor/PDIA3/ERp57 may contribute to the length of lifespan in mammals.