Docosahexaenoic Acid Sources for the Developing Brain during Intrauterine Life

Abstract

Docosahexaenoic acid (DHA, 22: 6n-3) and arachidonic acid (AA, 20: 4n-6) provision to the developing fetus, with emphasis towards brain and vascular system growth, is a subject of increasing concern particularly under pathological conditions associated with premature birth or in utero growth restriction following obstruction of the maternal-fetal blood flow. Most of DHA, but also AA accretion under physiological conditions, is maternally dependent and requires adequate maternal nutrition and normally functioning placental-fetal circulation. It has been demonstrated that unlike other fatty acids (FA), DHA is preferentially transported across the placenta into the fetal circulation. The selective transplacental DHA transfer is probably mediated by specific carrier proteins. While some of the latter may be acting in fetal organs, the mechanism(s) for the selective accumulation of DHA in brain is still unknown. The fetal brain and also the fetal liver are capable of producing DHA from linolenic (LnA, 18:3 n-3) acid. How effective this local elongation-desaturation mechanism for DHA provision is and to what degree this route is activated in premature births is not clear. Transfer of DHA via the fetal gastrointestinal tract is an additional route to provide DHA to other fetal organs. As indicated by animal model studies, it holds the potential for DHA supply when the maternal pathway is compromised.

Plasma fatty acid profiles in 37 pairs of maternal and umbilical cord blood samples

“…Therefore, n-3 and n-6 fatty acids must cross the placenta to control the supply of fatty acids to the fetus during gestation. In recent decades, more attention has been focused not only on essential fatty acids such as linoleic acid (LN, 18:2n-6) and linolenic acid (LnN, 18:n-3) but also on their longer chains of polyunsaturated fatty acid (PUFA) such as arachidonic acid (AA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), for normal brain development and function (1)(2)(3)(4). Rapid brain growth occurs primarily during the third trimester in humans (5), and the brain at this period is known to be at highest risk to toxic pollutants.…”

Fetal brain development: The role of maternal nutrition, exposures and behaviors

“…AA and DHA are the major fatty acids of neural gray matter [37] and DHA is the major component of photoreceptor membranes in the retina [38]. Infants are unable to synthesize enough of these fatty acids; therefore, dietary supply is critical [39]. In rat studies, variations in maternal intake of these fatty acids alter fetal neuronal membrane composition and neurotransmitter levels involved in neurite extension, target finding and synaptogenesis [40].…”

Balancing the benefits of n-3 polyunsaturated fatty acids and the risks of methylmercury exposure from fish consumption

“…EPA and DHA are considered to be among the major beneficial nutrients obtained from fish consumption 129 . There are many recommendations for the inclusion of pre‐formed EPA and DHA in the human diet 130–132 .…”