Former Enron chief executive Jeffrey Skilling pleaded not guilty to 36 counts of fraud and insider trading relating to the collapse of the Houston energy giant and was released on bail of five million dollars. The former number two at Enron Corp. turned himself into the FBI early Thursday and was led to US district court in handcuffs to answer the charges handed down by a grand jury. Skilling made no comment outside court, but his lawyers vigorously denied allegations that their client misled investors and regulators over the true financial standing of the once high-flying energy trader prior to its spectacular collapse in December 2001.