By winning the 2013 National Championship, I think UofL became the first team to ever win national titles out of two different leagues. I haven't seen this written or talked about anywhere. But I believe it is another testament to the greatness of the basketball program that it has had the highest level of success in multiple leagues. It fits then that Pitino is our coach, being the only coach to win a championship at two different schools as well as take three different schools to the Final Four.
I think Kansas is the only other team that could make an argument, or UCLA, but they won their titles as members of regional conferences that evolved and added other teams. We won the title out of two completely different leagues, in name and membership. Just another fact to marvel at.