title: Differences in preterm and term milk fatty acid compositions may be caused by the different hormonal milieu of early parturition.
abstract: BACKGROUND
  The hormonal milieus of pregnancy and lactation are driving forces of nutrient fluxes supporting infant growth and development. The decrease of insulin sensitivity with compensatory hyperinsulinemia with advancing gestation, causes adipose tissue lipolysis and hepatic de novo lipogenesis (DNL).
  
  
  METHODS
  We compared fatty acid (FA) contents and FA-indices for enzyme activities between preterm (28-36 weeks) and term (37-42) milks, and between colostrum (2-5 days), transitional (6-15) and mature (16-56) milks. We interpreted FA differences between preterm and term milks, and their changes with lactation, in terms of the well known decrease of insulin sensitivity during gestation and its subsequent postpartum restoration, respectively.
  
  
  RESULTS
  Compared with term colostrum, preterm colostrum contained higher indices of DNL in the breast (DNL-breast) and medium chain saturated-FA (MCSAFA), and lower DNL-liver and monounsaturated-FA (MUFA). Preterm milk also had higher docosahexaenoic acid (DHA) in colostrum and transitional milk and higher arachidonic acid (AA) in mature milk. Most preterm-term differences vanished with advancing lactation. In both preterm and term milks, DNL-breast and MCSAFA increased with advancing lactation, while DNL-liver, MUFA, long chain SAFA and AA decreased. DHA decreased in term milk. MUFA was inversely related to MCSAFA in all samples, correlated inversely with PUFA in colostrum and transitional milks, but positively in mature milk. MCSAFA correlated inversely with PUFA in mature milk.
  
  
  CONCLUSIONS
  Higher maternal insulin sensitivity at preterm birth may be the cause of lower MUFA (a proxy for DNL-liver) and higher MCSAFA (a proxy for DNL-breast) in preterm colostrum, compared with term colostrum. Restoring insulin sensitivity after delivery may be an important driving force for milk FA-changes in early lactation.
authors: Laboratory Medicine, University Medical Center Groningen, The Netherlands. remkokuipers@hotmail.com
authors: Remko S
authors: RS
authors: Kuipers
authors: Martine F
authors: MF
authors: Luxwolda
authors: D A Janneke
authors: DA
authors: Dijck-Brouwer
authors: Frits A J
authors: FA
authors: Muskiet
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D003126:Colostrum / Q000378:metabolism; D003430:Cross-Sectional Studies; D004041:Dietary Fats / Q000378:metabolism; D004281:Docosahexaenoic Acids / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D005399:Fishes; D006728:Hormones / Q000378:metabolism*; D006801:Humans; D008460:Meat; D008895:Milk, Human / Q000378:metabolism*; D011247:Pregnancy; D047928:Premature Birth / Q000378:metabolism*; D013636:Tanzania
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D006728:Hormones; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid; D044943:Fatty Acid Desaturases