I think the OP is trying to argue that if TiO2 causes T2DM (by modulating production of insulin in the beta cells), it does not account for peripheral insulin r

I think the OP is trying to argue that if TiO2 causes T2DM (by modulating production of insulin in the beta cells), it does not account for peripheral insulin resistance that is also present in T2DM. So, it could be that T2DM patients simply don't clear TiO2 from their pancreas as well as non T2DM patients (perhaps impaired kidney function). On another hand TiO2 is a "magnet" for other heavy metals. Researches are proposing using it in water filters to filter out other heavy metals because it attracts them so much. Consequently, having it accumulate in your tissue can't be good for long term health.