be up on (something)
To have the most current knowledge about a particular subject or issue; to be up to date on (something). Make sure you're up on this account before our meeting tomorrow morning. I'm not too up on the policy changes happening this year—is there a reference guide I can consult?
up on something, be
Be well informed or up-to-date about something, as in I'm not up on the latest models of cars. [Colloquial]
be up on
be well informed about a matter or subject.