Superconductive materials like Niob, which are rotating at high speed deform the gravitational field. You can name it Podkletnow-Effect. Do non-superconductive materials also show a small effect, if they are rotating at very high speed?
This is article about Podkletnow effect: http://www.ptep-online.com/index_files/2007/PP-10-13.PDF. Superconductivity does not have any relationship to the effect. While the effect has no unequivocal confirmation