According to Brian Windhorst of ESPN, the Denver Nuggets discussed trading for James Harden with the Houston Rockets. In the closing paragraph of his column about the Miami Heat no longer pursuing a Harden trade, Windhorst says
Houston has had trade discussions with the Brooklyn Nets, Philadelphia 76ers and Denver Nuggets, among others, around Harden, who has requested a trade.
While this is the first time the Nuggets have been linked by a source with the credibility of Windhorst, it should not be very surprising that Denver is being mentioned in trade discussions for a disgruntled superstar.