Loading metakeys with AJAX

Hi,

at the moment my theme I load posts with AJAX. But how can I can get also post meta keys via AJAX?

At the moment functions PHP is like this:

add_action('wp_ajax_nopriv_ajax_action', 'ajax_loading');
add_action('wp_ajax_ajax_action', 'ajax_loading');

function ajax_loading() {
	switch($_REQUEST['fn']) {
		case 'get_latest_posts':
		$output = ajax_get_latest_posts($_REQUEST['count']);
		break;
		default:
		$output = 'Error. No function specified.';
		break;
	}
	$output = json_encode($output);
	if (is_array($output)) {
		print_r($output);
	}
	else {
		echo $output;
	}
	die;
}

function ajax_get_latest_posts($count) {
     $posts = get_posts('numberposts='.$count.'&post_status=publish');

     return $posts;
}

And jQuery:

$.ajax({
		url: 'https://domain.com/wp-admin/admin-ajax.php',
		type: 'POST',
		data: {
			'action': 'ajax_action',
			'fn': 'get_latest_posts',
			'count': 15
		},
		dataType: 'JSON',
		success:function(data){
			//print stuff here
		},
		error: function(errorThrown){
			//error stuff here
		}
	});