I add custom field "currency_code" to table "catalog_product_entity".
And now I want save data for this field from model.
$product = Mage::getModel('catalog/product')->loadByAttribute('sku', '123456');
// it's work
echo $product->getData('currency_code');
echo $product->currency_code;
$product->setCurrencyCode('EUR');
$product->save();
// after that the field is not updated