I'm with the others. I've quilted fabrics with metallic in them with 50/2 Aurifil cotton thread in top & bobbin with a 70/10 Microtex needle (same as usual) and didn't ever have any issues.
I almost never use poly thread so I don't know if you can apply thread conditioner to it, but maybe that would help??? I'd go with a 90/14 Microtex/Sharp needle & thread conditioner. The other things I'd try is skipping that last hook right by the needle and changing the direction of the spool pin (one thing at a time, of course). Oh, and probably before all of that, I'd make sure to floss my thread run maybe 3x & give my bobbin case a good cleaning & oiling.
PS -- I re-read your post & now am not sure I answered right. I'm assuming that it's your poly thread on top that's fraying. If that's not the case, ignore everything I wrote.
