Concentrations of vitamin B-12 and folate in maternal serum and fetal fluids, metabolite interrelationships, and hepatic transcript abundance of key folate and methionine cycle genes: the impacts of maternal nutrition during the first 50 d of gestation

Adequate maternal nutrition is key for proper fetal development and epigenetic programming. One-carbon metabolites (OCM), including vitamin B-12, folate, choline, and methionine, play a role in epigenetic mechanisms associated with developmental programming. This study investigated the presence of B-12 and folate in maternal serum, allantoic fluid (ALF), and amniotic fluid (AMF), as well as how those concentrations in all three fluids correlate to the concentrations of methionine-folate cycle intermediates in heifers receiving either a control (CON) or restricted (RES) diet for the first 50 d of gestation and fetal hepatic gene expression for methionine-folate cycle enzymes. Angus cross heifers (n=43) were estrus synchronized, bred via artificial insemination with semen from a single sire, and randomly assigned to one of two nutrition treatments (CON=20, RES=23). Heifers were ovariohysterectomized on either day 16 (n=14), 34 (n=15), or 50 of gestation (n=14), where samples of maternal serum (n=42), ALF (n=29), and AMF (n=11) were collected and analyzed for concentrations of folate and B-12. Concentrations of B-12 and folate in ALF were greater (P<0.05) in RES compared to CON. For ALF, folate concentrations were also greater (P<0.01) on day 34 compared to day 50. There was a significant (P=0.04) nutritionxfluid interaction for B-12 concentrations where concentrations were greatest in restricted ALF, intermediate in control ALF, and lowest in CON and RES serum and AMF. Folate concentrations were greatest (P<0.01) in ALF, intermediate in serum, and lowest in AMF. Additionally, positive correlations (P<0.05) were found between ALF and AMF folate concentrations and AMF concentrations of methionine, serine, and glycine. Negative correlations (P<0.05) between AMF folate and serum homocysteine were also observed. Both positive and negative correlations (P<0.05) depending on the fluid evaluated were found between B-12 and methionine, serine, and glycine concentrations. There was a downregulation (P=0.05) of dihydrofolate reductase and upregulation (P=0.03) of arginine methyltransferase 7 gene expression in RES fetal liver samples compared with CON fetal liver on day 50. Combined, these data show restricted maternal nutrition results in increased B-12 and folate concentrations present in fetal fluids, and increased expression of genes for enzymes within one-carbon metabolism. This study found a restricted maternal diet increased B-12 and folate concentrations in allantoic fluid, impacted correlations between B-12, folate, and other metabolites in the one-carbon metabolism pathway, and altered expression of the genes dihydrofolate reductase and arginine methyltransferase 7 in fetal liver at day 50 of gestation. These findings further our understanding on the impacts of restricted maternal nutrition on key factors in fetal programming and provide the next step in developing a strategic supplementation plan for times of limiting nutrition in beef cattle. Lay Summary When pregnant cattle have restricted access to feed or specific nutrients, calf development can be affected, and the degree of impairment depends, at least partially, on timing, duration, and severity of the limitations. A biochemical pathway present in cells that can be affected by limited nutrition is one-carbon metabolism. This pathway is related to epigenetics, which regulates gene expression or the turning on and off of genes. Two important vitamins in one-carbon metabolism are vitamins B-12 and folate. By understanding the amounts of those vitamins available to the developing calf, we can gain better insight into the regulation and potential avenues of improvement of calf growth and development. In this study, we found a nutrient restricted maternal diet increased the amount of B-12 and folate in calf allantoic and amniotic fluids. We also found that folate and B-12 were correlated to the presence of other nutrients in serum, allantoic fluid, and amniotic fluid. In addition, we found that a protein methylating gene in one-carbon metabolism had increased expression in calves from heifers receiving limited nutrition. This study is an important step in understanding how the nutrients available to a pregnant heifer during gestation affects nutrients available to the conceptus.

Automated summary

This study investigated the correlation between concentrations of B-12 and folate in maternal serum, allantoic fluid, and amniotic fluid, and concentrations of methionine-folate cycle intermediates in fetal fluids, as well as fetal hepatic gene expression. The study found that restricted maternal nutrition resulted in increased B-12 and folate concentrations in allantoic fluid, as well as altered gene expression in fetal liver. These findings contribute to our understanding of the effects of restricted maternal nutrition on fetal programming and can help in the development of strategic supplementation plans for beef cattle.