Oxytocin Absorption From Breast Milk By Newborns
등록일 2019년 01월 07일 목요일
수정일 2017년 11월 16일 목요일

Photo By goodluz via Shutterstock

The evidence has been undisputable over the decades, breast milk is the best nutrition that newborn can be fed on.It offers numerous advantages to both the mother and the infant.For the newborn, it provides all the energy and nutrients needed for the first few months of life (the World Health Organization recommends that an infant be breastfed immediately after birth and exclusively for 6 months).In, addition, it aids the newborn child's cognitive and sensory development, offers immunity against infectious and chronic illnesses and leads to faster recuperation in case of any illness.In fact, exclusive breastfeeding reduces infant mortality rates caused by common infant diseases such as diarrhea and pneumonia.Meanwhile, for the mother, it adds to their well-being and prosperity while also reducing the chances of ovarian cancer and breast cancer.

Among the nutrients present in breast milk is a hormone known as oxytocin.Oxytocin is the hormone that is also known as the mothering hormone, the anti-stress hormone, and the love hormone.In adults, it's produced by the pituitary gland in the brain, and its roles include relaxation, lowering stress, anxiety & blood pressure and causing muscle contractions.It's also the hormone involved in social relationships, bonding, trust, and love.

In mothers, the hormone's release is stimulated by breastfeeding which leads to a process known as the let-down reflex.In neonates, the absorption of oxytocin in the breast milk occurs in the digestive tract into their blood.However, whether this process can continue after the onset of gut closure remains unknown.A research team sought to figure this out by investigating oxytocin uptake from the gut of neonatal RAGE mice and wild mice.RAGE is an acronym for Receptors for Advanced Glycation End-Products and is a transmembrane receptor for Advanced Glycation End-Products (AGE).It's a multi-ligand receptor and a member of pattern-recognition receptors.AGE-RAGE binding can induce oxidative stress and inflammation which leads to tissue damages.  The research team was led by researchers of Kanazawa University and Hokkaido University from Japan, Krasnoyarusk State Medical University from Russia and the University of California San Francisco from USA.

The research results showed that there was a difference in the concentration of oxytocin in the blood of postnatal day 1 mice (both male and female) that stayed with their mother for 20 minutes compared to the mice that were fasted.The latter's was lower.There was also no clear difference in the oxytocin levels between the male and female pups.This suggested that oxytocin from breast milk is transmitted from the rat mothers to the neonates.

The plasma oxytocin concentration levels in the blood after oral delivery in suckling pups were significantly higher in newborn and two-day-old pups than in those that were administered oral saline.Also, the concentration remained at higher levels in 3-5 day old pups after they were administered oral oxytocin than in the saline controls.

Plasma oxytocin concentration in mice that were administered with the oxytocin injection in the intestines was found to decrease.However, the decrease was seen by researchers to be due to intestinal barriers and/or digestive development rather than a reflection of the decrease in the total amount of oxytocin absorption. 

On the other hand, mice whose RAGE gene was knocked out and later orally administered with oxytocin had an increase in oxytocin concentration in the blood on postnatal days 1-3.However, this decreased on postnatal day 4.In RAGE, knockout pups oxytocin concentration in the blood after oral administration was found to drop suddenly in postnatal day 4 and there were no subsequent differences in the oxytocin concentration afterward.

There was also a significant difference between the wild-type and RAGE knockout mice on postnatal days 4-6 suggesting that on postnatal days 1-3 gut closure had not been initiated and the oxytocin was freely permeable from the gut in both mice types.After the completion of gut closure, the wild-type mice expressing RAGE could ingest oxytocin.The researchers interpreted that on postnatal days 7-8  oxytocin was enzymatically cleaved but could not be absorbed in its intact form.

In addition, adult mice which were administered with a similar oral oxytocin dose as the neonates were found to have no increase in their plasma oxytocin concentrations.However, after a tenfold increase of the oral dosage, there was a significant increase in plasma oxytocin in the wild-type mice.The oxytocin was observed to increase linearly as a function of the dose applied directly to the intestine, while the RAGE knockout mice had significantly lower levels.

A mass spectrometry analysis by the researchers confirmed that oxytocin was transported into the blood in its intact form.A separate immunohistochemical study also established that RAGE molecules expressed themselves on the surface of intestinal epithelial cells.

This study has shown that some intestinal cells express RAGE which is responsible for absorption of oxytocin from the gut into the blood.Therefore, oxytocin is ingested by a specific molecular mechanism, and it can be orally administered as a medication and a nutrient.

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