Eloquent retrive update_at after update

I'm new with Laravel/Lumen and ORM. I've got this operation on the database:

$items = Item::where('id', $this->id)
    ->where('is_shown', 1);       
    ->update([
            'is_shown' => 0,
        ]);

How I can retrieve update_at column value after update operation without additional query?

via Chebli Mohamed