Eight Democratic Senators on Tuesday asked U.S. regulators to launch an investigation into billionaire Carl Icahn’s activities in the U.S. biofuels blending credit market, saying the activist investor may have violated securities trading laws since becoming an adviser to President Donald Trump. “We are writing to request that your agencies investigate whether Carl Icahn violated insider trading laws, anti-market manipulation laws, or any other relevant laws based on his recent actions in the market for renewable fuel credits,” the senators said in a letter to the heads of the Securities and Exchange Commission, the Commodity Futures Trading Commission, and the...