Hook for node preload
No there's no such hook I'm afraid (see the list of hooks for Drupal 7).

If you want caching that goes beyond the normal static page cache provided by node_load() then you might want to look at the Entity Cache module, which "puts core entities into Drupal's cache API.". Even if you don't end up using that module you can inspect the code to get some ideas for implementing your own caching system.