Editing Choline (section)

===Functions in the fetus===
Choline is in high demand during pregnancy as a substrate for building [[cellular membrane]]s (rapid fetal and mother tissue expansion), increased need for one-carbon [[Moiety (chemistry)|moieties]] (a substrate for methylation of DNA and other functions), raising choline stores in fetal and placental tissues, and for increased production of lipoproteins (proteins containing "fat" portions).<ref>{{cite book | title = Institute of Medicine, Food and Nutrition Board. Dietary reference intakes for Thiamine, Riboflavin, Niacin, Vitamin B<sub>6</sub>, Folate, Vitamin B<sub>12</sub>, Pantothenic Acid, Biotin and Choline. | location = Washington, DC | publisher = National Academies Press | date = 1998 }}</ref><ref>{{cite book | vauthors = Allen LH | chapter = Pregnancy and lactation | veditors = Bowman BA, Russle RM | title = Present Knowledge in Nutrition | location = Washington DC | publisher = ILSI Press | date = 2006 | pages = 529–543 }}</ref><ref>{{cite journal | vauthors = King JC | title = Physiology of pregnancy and nutrient metabolism | journal = The American Journal of Clinical Nutrition | volume = 71 | issue = 5 Suppl | pages = 1218S–25S | date = May 2000 | pmid = 10799394 | doi = 10.1093/ajcn/71.5.1218s | doi-access = free }}</ref> In particular, there is interest in the impact of choline consumption on the brain. This stems from choline's use as a material for making cellular membranes (particularly in making phosphatidylcholine). Human brain growth is most rapid during the [[third trimester]] of pregnancy and continues to be rapid to approximately five years of age.<ref>{{cite journal | vauthors = Morgane PJ, Mokler DJ, Galler JR | title = Effects of prenatal protein malnutrition on the hippocampal formation | journal = Neuroscience and Biobehavioral Reviews | volume = 26 | issue = 4 | pages = 471–83 | date = June 2002 | pmid = 12204193 | doi = 10.1016/s0149-7634(02)00012-x | s2cid = 7051841 }}</ref> During this time, the demand is high for sphingomyelin, which is made from phosphatidylcholine (and thus from choline), because this material is used to [[Myelinated nerve fibers|myelinate]] (insulate) [[nerve fiber]]s.<ref>{{cite journal | vauthors = Oshida K, Shimizu T, Takase M, Tamura Y, Shimizu T, Yamashiro Y | title = Effects of dietary sphingomyelin on central nervous system myelination in developing rats | journal = Pediatric Research | volume = 53 | issue = 4 | pages = 589–93 | date = April 2003 | pmid = 12612207 | doi = 10.1203/01.pdr.0000054654.73826.ac | doi-access = free }}</ref> Choline is also in demand for the production of the neurotransmitter acetylcholine, which can influence the structure and organization of brain regions, [[neurogenesis]], myelination, and [[synapse]] formation. Acetylcholine is even present in the placenta and may help control [[cell proliferation]] and [[Cell differentiation|differentiation]] (increases in cell number and changes of multiuse cells into dedicated cellular functions) and [[parturition]].<ref>{{cite journal | vauthors = Sastry BV | title = Human placental cholinergic system | journal = Biochemical Pharmacology | volume = 53 | issue = 11 | pages = 1577–86 | date = June 1997 | pmid = 9264309 | doi = 10.1016/s0006-2952(97)00017-8 }}</ref><ref>{{cite journal | vauthors = Sastry BV, Sadavongvivad C | title = Cholinergic systems in non-nervous tissues | journal = Pharmacological Reviews | volume = 30 | issue = 1 | pages = 65–132 | date = March 1978 | pmid = 377313 }}</ref>

Choline uptake into the brain is controlled by a low-affinity transporter located at the blood–brain barrier.<ref>{{cite journal | vauthors = Lockman PR, Allen DD | title = The transport of choline | journal = Drug Development and Industrial Pharmacy | volume = 28 | issue = 7 | pages = 749–71 | date = August 2002 | pmid = 12236062 | doi = 10.1081/DDC-120005622 | s2cid = 34402785 }}</ref> Transport occurs when arterial blood plasma choline concentrations increase above 14&nbsp;μmol/L, which can occur during a spike in choline concentration after consuming choline-rich foods. Neurons, conversely, acquire choline by both high- and low-affinity transporters. Choline is stored as membrane-bound phosphatidylcholine, which can then be used for acetylcholine neurotransmitter synthesis later. Acetylcholine is formed as needed, travels across the synapse, and transmits the signal to the following neuron. Afterwards, [[acetylcholinesterase]] degrades it, and the free choline is taken up by a high-affinity transporter into the neuron again.<ref>{{cite journal | vauthors = Caudill MA | title = Pre- and postnatal health: evidence of increased choline needs | journal = Journal of the American Dietetic Association | volume = 110 | issue = 8 | pages = 1198–206 | date = August 2010 | pmid = 20656095 | doi = 10.1016/j.jada.2010.05.009 }}</ref>