Buffett owned UnitedHealth shares before selling his stake in 2010, though his Berkshire Hathaway recently acquired shares.

The blue-chip Dow opened at a record high on Friday, as UnitedHealth's shares jumped after Berkshire Hathaway raised its stake in the health insurer, while expectations of an interest rate cut in September also lifted the mood.

The blue-chip Dow briefly hit a record high on Friday, as UnitedHealth's shares jumped after Berkshire Hathaway raised its stake in the health insurer, while investors assessed mixed data to gauge the Federal Reserve's monetary policy path this year.