Boring AA hand?

[sweg]

Hello. This is my first post so go easy...
Can't stop thinking about this one and would like some opinions.

NL 5-10 6-handed. I am UTG and is dealt AsAh and make it 40. UTG+1 call, rest folds. UTG+1 is quite loose but a decent player. He has called raises with J9, QT etc. UTG+1 has about 1400 and I have him covered.

Flop is 6d7h8d. I lead for 100 and UTG+1 raises to 400.
I think and muck my aces.

Since he is loose preflop i really have trouble putting him on a hand.

Possible: set, Adxd, straight and/or flushdraw, 99-AA.
I played with him for a few hours and I have never seen him make a reraise this big.

Weak fold?

Sweg