Periconceptional dietary intake of choline and betaine and neural tube defects in offspring

An overview of evidence for a causal relationship between dietary availability of choline during development and cognitive function in offspring

This review is part of a series intended for non-specialists that will provide an overview of evidence for causal relationships between micronutrient deficiencies and brain function. Here, we review 34 studies in rodents linking the availability of choline during gestation and perinatal development to neurological function or performance of offspring in cognitive and behavioral tests. Experimental designs, major results, and statistical criteria are summarized in Tables 1-4. Based on our reading of the literature, the evidence suggests that choline supplementation during development results in improved performance of offspring in cognitive or behavioral tests, and in changes in a variety of neurological functional indicators: (1) enhanced performance was observed, particularly on more difficult tasks; (2) increases (choline supplementation) or decreases (choline deficiency) were observed in electrophysiological responsiveness and size of neurons in offspring; and (3) supplementation resulted in some protection against adverse effects of several neurotoxic agents (including alcohol) in offspring. Discussion topics include methodological issues, such as the importance of independent replication, causal criteria, and uncertainties in interpreting test results.

Genetic variation of folate-mediated one-carbon transfer pathway predicts susceptibility to choline deficiency in humans

Choline is a required nutrient, and some humans deplete quickly when fed a low-choline diet, whereas others do not. Endogenous choline synthesis can spare some of the dietary requirement and requires one-carbon groups derived from folate metabolism. We examined whether major genetic variants of folate metabolism modify susceptibility of humans to choline deficiency. Fifty-four adult men and women were fed diets containing adequate choline and folate, followed by a diet containing almost no choline, with or without added folate, until they were clinically judged to be choline-deficient, or for up to 42 days. Criteria for clinical choline deficiency were a more than five times increase in serum creatine kinase activity or a >28% increase of liver fat after consuming the low-choline diet that resolved when choline was returned to the diet. Choline deficiency was observed in more than half of the participants, usually within less than a month. Individuals who were carriers of the very common 5,10-methylenetetrahydrofolate dehydrogenase-1958A gene allele were more likely than noncarriers to develop signs of choline deficiency (odds ratio, 7.0; 95% confidence interval, 2.0-25; P < 0.01) on the low-choline diet unless they were also treated with a folic acid supplement. The effects of the C677T and A1298C polymorphisms of the 5,10-methylene tetrahydrofolate reductase gene and the A80C polymorphism of the reduced folate carrier 1 gene were not statistically significant. The most remarkable finding was the strong association in premenopausal women of the 5,10-methylenetetrahydrofolate dehydrogenase-1958A gene allele polymorphism with 15 times increased susceptibility to developing organ dysfunction on a low-choline diet.

Periconceptional dietary intake of myo-inositol and neural tube defects in offspring

BACKGROUND

Periconceptional intake of nutrients in addition to folic acid may contribute to neural tube defect (NTD) etiologies; a likely candidate is myo-inositol. We investigated whether maternal periconceptional dietary intake of myo-inositol influenced NTD risk.

METHODS

Data were derived from a case-control study of fetuses and infants with NTDs among 1989-1991 California births. Interviews were conducted with mothers of 454 NTD cases and with mothers of 462 nonmalformed controls. A standard 100-item food frequency questionnaire was used to assess nutrient intake.

RESULTS

We observed small increases in risk, with increases slightly more evident for anencephaly, associated with intakes of myo-inositol less than the highest intake quartile, e.g., risk of anencephaly was 1.3 (0.7-2.4) among fetuses whose mothers consumed lowest versus highest intakes of myo-inositol. These small increases, however, were imprecise, and also did not indicate increasing risk with decreasing level of myo-inositol intake. Adjusted risk estimates did not differ considerably from their unadjusted counterparts.

CONCLUSIONS

Our results do not indicate that myo-inositol intake, as measured in this study, is strongly associated with risk of human NTDs.

The impact of metabolism on DNA methylation

Methylation of genomic cytosines is one of the best characterized epigenetic mechanisms, and investigation of its relationship with other biochemical pathways represents a critical stage in the elucidation of biological information processing. The field also has immense potential for the development of medical treatments for any number of conditions ranging from aging to neurological disorders. The DNA methylation status of genes is responsible for many heritable traits and varies more or less independently of the genetic code. This variation is often a result of cellular environmental factors including metabolism. A key metabolite in this regard is homocysteine. Knowledge of homocysteine metabolism continues to be amassed, yet the part played by aberrant DNA methylation in homocysteine-related pathologies is often, at best, conjectural. In this analysis, we will review recent insights and attempt to speculate meaningfully concerning the dynamics of the methionine cycle in relation to DNA methylation and disease.

Plasma choline and betaine and their relation to plasma homocysteine in normal pregnancy

BACKGROUND

Plasma concentrations of total homocysteine (tHcy) decrease during pregnancy. This reduction has been investigated in relation to folate status, but no study has addressed the possible role of betaine and its precursor choline.

OBJECTIVE

We investigated the courses of plasma choline and betaine during normal human pregnancy and their relations to plasma tHcy.

DESIGN

Blood samples were obtained monthly; the initial samples were taken at gestational week (GW) 9, and the last samples were taken approximately 3 mo postpartum. The study population comprised 50 women of West African descent. Most of the subjects took folic acid irregularly.

RESULTS

Plasma choline (geometric x; 95% reference interval) increased continuously during pregnancy, from 6.6 (4.5, 9.7) micromol/L at GW 9 to 10.8 (7.4, 15.6) micromol/L at GW 36. Plasma betaine decreased in the first half of pregnancy, from 16.3 (8.6, 30.8) micromol/L at GW 9 to 10.3 (6.6, 16.2) micromol/L at GW 20 and remained constant thereafter. We confirmed a reduction in plasma tHcy, and the lowest concentration was found in the second trimester. From GW 16 onward, an inverse relation between plasma tHcy and betaine was observed. Multiple regression analysis showed that plasma betaine was a strong predictor of plasma tHcy from GW 20 onward.

CONCLUSIONS

The steady increase in choline throughout gestation may ensure choline availability for placental transfer with subsequent use by the growing fetus. Betaine becomes a strong predictor of tHcy during the course of pregnancy. Both of these findings emphasize the importance of choline and betaine status during normal human pregnancy.

Maternal diet alters exencephaly frequency in SELH/Bc strain mouse embryos

BACKGROUND

The SELH/Bc mouse inbred strain, with a high frequency of nonsyndromic, genetically-multifactorial exencephaly, is a model for human cranial neural tube defects (NTDs). Maternal diet affects risk of human NTDs.

METHODS

Exencephaly frequencies in SELH/Bc embryos were compared in 8 studies in which dams were fed alternative commercial Purina diets (5015 and 5001) or semisynthetic diets, and in several studies in which maternal diet was supplemented with a specific nutrient, either in drinking water or food before and during pregnancy, or by intraperitoneal injection on E7 and/or E8.

RESULTS

The exencephaly frequency in SELH/Bc embryos was 2- to 8-fold higher when the dams were fed Purina 5015 (averaging 23% exencephaly) or a semisynthetic diet modeled on Purina 5015 (averaging 28%) or NIH-31 standard diet (23%), compared with Purina 5001 (averaging 7%). The exencephaly frequency remained high (41%) on a semisynthetic diet modeled on Purina 5001. The exencephaly frequency was not reduced significantly by maternal supplementation with folic acid, nor with each of zinc, methionine, niacin, brewers' yeast, riboflavin, vitamin B12, or inositol. Nor was it reduced by maternal diets with supplemental methyl donors and cofactors or with reduced fat.

CONCLUSIONS

The frequency of exencephaly in SELH/Bc embryos is strongly influenced by a specific unidentified aspect of the commercial ration Purina 5001 that prevents 55-85% of exencephaly in SELH/Bc embryos, when directly compared with an alternative commercial ration Purina 5015 or its semisynthetic mimic. This strong maternal diet effect on NTD frequency may point to novel nutritional approaches to prevention of human NTDs.