Loading a Taxonomy Term form for a user
If you want to pass variables to a form you can. See this similar post.

Just add $vars as second argument.

drupal_get_form('new_form', $vars);


and...

function new_form($form, &amp;$form_state, $vars) {


If you are trying to pass the user object to user_profile_form you can do it like so:

global $user;
$form_state = array();
$form_id = 'user_profile_form';
$args = array($user);
$form_state['build_info']['args'] = $args;
form_load_include($form_state, 'inc', 'user', 'user.pages');
print render(drupal_build_form($form_id, $form_state));


If you really want to load the user_profile_form inside another form (?) as suggested in your comment, you can do the snippet above but not render the form, just load it into an a variable and extract vars from it.

$loaded_profile_form_with_user = drupal_build_form($form_id, $form_state);