The impact of tariffs and global trade disputes may be starting to filter down to corporate bottom lines. Automakers General Motors Co (GM) and Fiat Chrysler Automobiles NV(FCA) on Wednesday reduced future profit forecasts, citing in part the effect of tariffs. The warnings from the corporate heads come amid growing concern over tariffs and a possible global trade war. GM pointed to higher steel and aluminum costs for its 2018 profit forecast reduction due to tariffs imposed by US President Donald Trump's administration. Trump has also imposed tariffs on Canada, Mexico and China.