Perinatal Choline Influences Brain Structure and Function

Choline is derived not sole from the diet, but also from de novo synthesis. It is important for methyl-group metabolism, the formation of membranes, kidney function, and neurotransmission. When deprived of dietary choline, greatest in quantity adult men and postmenopausal women make known signs of organ dysfunction (fatty liver or muscle damage) and have a decreased capacity to transform homocysteine to methionine. Choline is critical during fetal disclosure when it influences stem small room proliferation and apoptosis, thereby altering brain manner of making and function (memory is permanently enhanced in gnawings exposed to choline during the latter part of gestation).

Key words: brain unravelling choline, folate, hippocampus, memory

?© 2006 International Life Sciences Institute

doi: 10.1301/nr.2006.janr. 197-203

CHOLINE IS AN ESSENTIAL NUTRIENT

Choline consists of three methyl assemblages covalently attached to the nitrogen atom of ethanolamine, and is essential for normal functioning of all cells1 A major use for choline is as a precursor for the synthesis of membranes. Phosphatidylcholine (sometimes called lecithin) is the predominant phospholipid (>50%) in greatest in quantity mammalian membranes; sphingomyelin is another important choline phospholipid. alone a small fraction of dietary choline is acetylated, catalyzed through the activity of choline acetyltransferase.2 The yield is acetylcholine, an important neurotransmitter. The methyl collections of choline can be made available from one-carbon metabolism on conversion to betaine,3 which cannot be reduc back to choline. The interrelationship of this pathway with folate and methionine metabolism is discussed below.

When deprived of dietary choline, greatest in quantity adult men and postmenopausal women disentangle signs of organ dysfunction (fatty liver or muscle damage)4,5; premenopausal women are relatively resistant to choline deficiency (unpublished data). The 1998 Institute of Medicine recommendations upon dietary reference intakes included estimates of the Adequate Intake (AI) of choline required by means of humans (approximately half a gram a day).6 The USDA lately developed a database of choline satisfied in foods (http://www.nal.usda.gov/fnic/ foodcomp/Data/Choline/Choline.html), which exhibits that excellent sources of dietary choline include liver, ovums and wheat germ. In nutriments choline is found in unrestrained and in esterified forms (as phosphocholine, glycerophosphocholine, phosphatidylcholine, and sphingomyelin). There is a certain number of evidence that these forms of choline may have different bioavailability,7 because the lipid-soluble forms bypass the liver when absorbed from the diet, while the water-soluble forms go into the portal circulation and are for the greatest part absorbed by the liver. Human milk is rich in choline compounds8 and soy-derived infant formulas have lower total choline concentrations than do either human milk or bovine milk-derived formulas.8 Choline intake by dint of humans on ad libitum diets for males and females averages between 84 and. 67 mg/kg of choline through day, respectively.9 However, Shaw et al.10 studied pregnant women in California and observ intakes that were les than half this amount in 25% of the women studied.

Choline is derived not single from the diet, but also from the de novo synthesis of phosphatidylcholine catalyzed by dint of phosphatidylethanolamine N-methyltransferase (PEMT).11 This enzyme which is the greatest in quantity active in the liver, uses S-adenosylmethionine as a methyl donor and forms a fresh choline moiety.12 When fed a diet deficient in choline, Pemt^sup -/-^ mice evolveed fatty liver, severe liver damage, and died; a choline-supplemented diet precludeed this13 and reversed hepatic damage if begun early enough.14 Pemt^sup -/-^ mice have lower choline meres in liver despite being f sufficient or supplemental amounts of dietary choline,15 suggesting that choline production by the agency of PEMT is a significant source of choline relative to dietary intake.

CHOLINE, FOLATE, AND METHIONINE METABOLISM ARE INTERRELATED

Choline, methionine and folate metabolism are metabolically interrelated at the point that homocysteine is methylated to form methionine. Thus, any requirement for dietary choline must be considered in relation to these other nutrients. Homocysteine can be methylated to form methionine16 by the agency of two parallel pathways, both of which lower homocysteine concentrations17 (Figure 1) In the first, vitamins B12 and folic acid are involved in a reaction catalyzed through methionine synthase.18 Deficiency of these nutrients19,20 or single nucleotide polymorphisms in the gene for the enzyme involved in this pathway18,20,21 can spring in elevated plasma homocysteine concentrations. In addition, tetrahydrofolate is wanted to scavenge one-carbon groups when betaine is metabolized.22 The alternative pathway for the methylation of homocysteine to form methionine is catalyzed through betaine homocysteine methyltransferase.23 Betaine, derived from dietary choline, is the methyl assemblage donor in this reaction, and supplemental oral betaine can lower plasma homocysteine concentrations.24'25 We freshly reported that humans who are deplet of choline have diminished capacity to methylate homocysteine and make known elevated homocysteine concentrations in plasma after a methionine loading test4