Wordpress - $wpdb->insert - MySQL NOW()

is there any possibility to use the MySQL NOW() in the $wpdb->insert call?

When I use the following code, NOW() is not working.

$data = array(
        'id' => NULL,
        'order' => serialize($_POST['data']['Order']),
        'created' => NOW(),
        'user_id' => $current_user->ID
    );

$wpdb->insert(ORDERS_TABLE, (array) $data );