The announcement came as chairman Sir Roy Gardner said that he stood down from his post on 6 June.
Non-executive directors Ian Much and Jim O'Neill have also both resigned.
Andy Anson has been re-appointed as club commercial director. He was one of the three directors that Glazer voted off the board last November, during his struggle for control.
Glazer now has almost complete control of the United shares as part of his £790million takeover of the club.
The 76-year-old billionare is expected to delist the club's shares by June 30, ending United's 14-year presence on the London Stock Exchange.
Joel Glazer was appointed executive vice president of the NFL franchise Tampa Bay Buccaneers, owned by his father, in 1995 and he still holds this position.
Like brother Joel, Bryan Glazer was also made an executive vice president of the Tampa Bay Buccaneers in 1995.
