Hi there,
First let's consider UTG opening range, if he's opening with 77+,A2s+,KTs+,QTs+,JTs,AJo+,KQo wich is 12% of the time, than with AKo you're about 60% favorite, and when you have that
equity you want to put more money in the pot by a reraising. It's +EV, and you can win the pot right away if he just fold.
If UTG 4-bet you with the top of his range, JJ+,AKs,AKo than he will be 60% favorite against AKo and 58% against AKs, here you can just call and see the flop if it bring some A, K, flush or straght draw.
Finally you have to track your results to see if you have to make some adjustment/balancing when playing on the limits you're in. for example if you know that your opponent is holding a weaker A on a board like A59 you just keep it in the pot by calling down preflop to the river.