The top shareholder of Japan\'s Olympus Corp. said Thursday it sold a third of its stake in the scandal-tainted camera and medical equipment maker after it admitted covering up huge investment losses over two decades.Nippon Life and its subsidiaries have reduced their combined holdings in Olympus from 8.18 percent to 5.11 percent, according to a report the insurer submitted to financial regulators on Thursday.The life assurer was Olympus\' biggest shareholder with a 8.26 percent stake as of the end of March.\"We have sold a part of our stake due to the current uncertain situation from the viewpoint of protecting our customers\' profits,\" Nippon Life, Japan\'s top life insurer, said in a statement, without disclosing when it sold the shares.But the insurer remains the top shareholder in Olympus and pledged to continue supporting the troubled company. \"We believe the strength of Olympus\' core businesses and its advanced technology will be maintained,\" it said.Olympus admitted last week that it had used corporate purchases to hide huge losses from securities investments following the bursting of Japan\'s economic bubble since around the 1990s. Its shares have been volatile since the scandal was revealed.The Tokyo Stock Exchange has warned Olympus could be delisted if it fails to meet the Dec. 14 deadline to file its April-September earnings results.