COLUMBUS: Ohio’s top utility regulator resigned on Friday, marking the fourth departure from the job since Gov. John Kasich was elected in 2010.Andre Porter, chairman of the Public Utilities Commission, said in his resignation letter that the decision to leave for the private sector was “very difficult.” His last day will be May 20.“The past five years have been filled with unforgettable life-changing experiences,” said Porter, who previously served as a utility commissioner and as Kasich’s director of commerce.