SELECT 
  * 
FROM 
  cscart_mailing_lists 
  LEFT JOIN cscart_common_descriptions ON cscart_common_descriptions.object_id = cscart_mailing_lists.list_id 
  AND cscart_common_descriptions.object_holder = 'mailing_lists' 
  AND cscart_common_descriptions.lang_code = 'en' 
  INNER JOIN cscart_ult_objects_sharing ON (
    cscart_ult_objects_sharing.share_object_id = cscart_mailing_lists.list_id 
    AND cscart_ult_objects_sharing.share_company_id = 1 
    AND cscart_ult_objects_sharing.share_object_type = 'mailing_lists'
  ) 
WHERE 
  1 
  AND cscart_mailing_lists.status = 'A'

Query time 0.00954

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_mailing_lists system PRIMARY 1
1 SIMPLE cscart_common_descriptions const PRIMARY PRIMARY 107 const,const,const 1
1 SIMPLE cscart_ult_objects_sharing const PRIMARY PRIMARY 159 const,const,const 1 Using index

Result

list_id timestamp from_email from_name reply_to show_on_checkout show_on_registration status register_autoresponder object_id object_type description lang_code object object_holder share_company_id share_object_id share_object_type
1 0 no-reply@example.com Acme no-reply@example.com 1 1 A 0 1 en Company news and unique discounts for subscribers mailing_lists 1 1 mailing_lists