Serine and Glycine Metabolism in Hepatocytes from Mid Gestation Fetal Lambs

Narkewicz, Michael R.; Thureen, Patti J.; Sauls, S David; Tjoa, Susan; Nikolayevsky, N; Fennessey, Paul V.

doi:10.1203/00006450-199606000-00025

“…In liver, the non-phosphorylated pathway is presumed to operate mainly in the reverse direction for gluconeogenesis (4). Glycine also can be converted directly into L-serine by serine hydroxymethyltransferase, with N 5 ,N 10 -methylenetetrahydrofolate acting as a carbon donor (5). The relative contribution of these pathways to L-serine biosynthesis in vivo, however, remains to be determined.…”

mentioning

confidence: 99%

Targeted Disruption of the Mouse 3-Phosphoglycerate Dehydrogenase Gene Causes Severe Neurodevelopmental Defects and Results in Embryonic Lethality

Yoshida

¹

,

Furuya²,

Osuka³

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

D-3-Phosphoglyceratedehydrogenase (Phgdh; EC 1.1.1.95) is the first committed enzyme of L-serine biosynthesis in the phosphorylated pathway. To determine the physiological importance of Phgdh-dependent L-serine biosynthesis in vivo, we generated Phgdh-deficient mice using targeted gene disruption in embryonic stem cells. The absence of Phgdh led to a drastic reduction of Lserine metabolites such as phosphatidyl-L-serine and sphingolipids. Phgdh null embryos have small bodies with abnormalities in selected tissues and died after days post-coitum 13.5. Striking abnormalities were evident in the central nervous system in which the Phgdh null mutation culminated in hypoplasia of the telencephalon, diencephalon, and mesencephalon; in particular, the olfactory bulbs, ganglionic eminence, and cerebellum appeared as indistinct structures. These observations demonstrate that the Phgdh-dependent phosphorylated pathway is essential for normal embryonic development, especially for brain morphogenesis.

show abstract

“…glycine at approximately 10% enrichment for a further 24 h. Media was harvested at 0 and 24 h, cellular debris was removed by centrifugation, and the media was snap-frozen on dry ice and stored at Ϫ80°C until analysis. Serine and glycine 13 C media mole percent enrichment and concentration were determined at 0 and 24 h by GC/MS (11,12). Serine and glycine interconversion, production, and utilization rates were determined by stable isotope dilution as we have previously described (11,12).…”

Section: Methodsmentioning

confidence: 99%

“…It is now clear that fetal hepatic serine synthesis is not dependent on the ontogeny of the key enzymes of serine metabolism (Fig. 1) (13) or substrate availability (11,14).Serine and folate metabolism are directly linked. Studies in neuroblastoma cells that over-express MTHFS found a significant increase in serine production (15).…”

mentioning

confidence: 99%

Folate Cofactors Regulate Serine Metabolism in Fetal Ovine Hepatocytes

Narkewicz

¹

2002

Pediatric Research

0

View full text Add to dashboard Cite

The fetal liver is the primary site of fetal serine production. The regulation of this unique fetal hepatic serine production is unknown. We hypothesized that serine production would be responsive to folate cofactor supply or hormonal regulation. To test this hypothesis, we determined the effect of key folate cofactors and insulin and glucagon on serine and glycine metabolism in primary culture of fetal ovine hepatocytes. Hepatocytes were cultured in serum-free, low-folate media [5 nM 5-methyltetrahydrofolate (THF)] with or without 50 nM 5,10-methylene-THF (MTHF) or 5-formyl-THF (FTHF). Serine and glycine production (P) and utilization (U) were determined by stable isotope dilution with [1-13 C]serine and [1-13 C]glycine for 24 h. The effect of insulin (1 M) or glucagon (1 M) was determined in a similar manner. Under basal conditions, serine P (43.2 Ϯ 5.1 mol/mg DNA per 24 h) is greater than serine U (24.1 Ϯ 3.1 mol/mg DNA per 24 h), whereas glycine U (27.3 Ϯ 3.0 mol/mg DNA per 24 h) exceeds glycine P (16.7 Ϯ 1.9 mol/mg DNA per 24 h). MTHF results in a significant decrease in serine U (16.0 Ϯ 2.7 mol/mg DNA per 24 h; p ϭ 0.02 versus low folate), with no change in serine P. FTHF reduces serine P (36.2 Ϯ 4.9 mol/mg DNA per 24 h; p ϭ 0.01), but does not alter serine U. There were no effects on glycine metabolism with 50 nM MTHF or FTHF. Serine P and U were inversely correlated whereas glycine P and U were directly correlated with the media concentration of MTHF or FTHF. Glucagon treatment increased serine U by 260 Ϯ 65% versus low folate (p ϭ 0.0004) but did not change serine P. Insulin treatment led to parallel increases in both serine P and U. Both folate cofactor availability and hormone concentrations regulate serine metabolism in the fetal liver. We speculate that serine metabolism may be a marker of fetal hepatic folate cofactor supply. (Pediatr Res 52: 589-594, 2002) Abbreviations THF, tetrahydrofolate MTHF, methylene tetrahydrofolate FTHF, formyl tetrahydrofolate SHMT, serine hydroxymethyltransferase MTHFS, methenyl tetrahydrofolate synthase MEM, minimal essential medium BrdU, 5-bromo-2'-deoxyuridine GC/MS, gas chromatography-mass spectrometry Serine occupies a unique metabolic position in the fetus. Studies in the fetal sheep demonstrated that serine is one of only three amino acids to have a net production across the fetal liver (1, 2). However, serine is poorly transported across the placenta to the fetus (3, 4). Thus, the fetus must rely on endogenous production of serine to meet the majority of its serine requirements. Serine is an important amino acid for DNA and RNA synthesis and phospholipid synthesis (5, 6). In human fetuses, serine metabolism is similar to that of fetal sheep (7,8). Indeed, human fetuses that are small-forgestational age have selectively low levels of serine and glycine, suggesting an important role for serine in fetal growth (8 -10).Little is known about the regulation of fetal hepatic serine metabolism. Others and we have demonstrated that the majority of serine produced by the ...

show abstract

“…Others and we have demonstrated that the majority of serine produced by the fetal liver is derived from glycine (2,11,12). However, the regulation of fetal hepatic serine metabolism is unclear.…”

mentioning

confidence: 99%

“…It is now clear that fetal hepatic serine synthesis is not dependent on the ontogeny of the key enzymes of serine metabolism (Fig. 1) (13) or substrate availability (11,14).…”

mentioning

confidence: 99%

Folate Cofactors Regulate Serine Metabolism in Fetal Ovine Hepatocytes

Narkewicz

¹

,

Jones

²

,

Thompson

³

et al. 2002

Pediatr Res

Self Cite

6

0

View full text Add to dashboard Cite

The fetal liver is the primary site of fetal serine production. The regulation of this unique fetal hepatic serine production is unknown. We hypothesized that serine production would be responsive to folate cofactor supply or hormonal regulation. To test this hypothesis, we determined the effect of key folate cofactors and insulin and glucagon on serine and glycine metabolism in primary culture of fetal ovine hepatocytes. Hepatocytes were cultured in serum-free, low-folate media [5 nM 5-methyltetrahydrofolate (THF)] with or without 50 nM 5,10-methylene-THF (MTHF) or 5-formyl-THF (FTHF). Serine and glycine production (P) and utilization (U) were determined by stable isotope dilution with [1-13 C]serine and [1-13 C]glycine for 24 h. The effect of insulin (1 M) or glucagon (1 M) was determined in a similar manner. Under basal conditions, serine P (43.2 Ϯ 5.1 mol/mg DNA per 24 h) is greater than serine U (24.1 Ϯ 3.1 mol/mg DNA per 24 h), whereas glycine U (27.3 Ϯ 3.0 mol/mg DNA per 24 h) exceeds glycine P (16.7 Ϯ 1.9 mol/mg DNA per 24 h). MTHF results in a significant decrease in serine U (16.0 Ϯ 2.7 mol/mg DNA per 24 h; p ϭ 0.02 versus low folate), with no change in serine P. FTHF reduces serine P (36.2 Ϯ 4.9 mol/mg DNA per 24 h; p ϭ 0.01), but does not alter serine U. There were no effects on glycine metabolism with 50 nM MTHF or FTHF. Serine P and U were inversely correlated whereas glycine P and U were directly correlated with the media concentration of MTHF or FTHF. Glucagon treatment increased serine U by 260 Ϯ 65% versus low folate (p ϭ 0.0004) but did not change serine P. Insulin treatment led to parallel increases in both serine P and U. Both folate cofactor availability and hormone concentrations regulate serine metabolism in the fetal liver. We speculate that serine metabolism may be a marker of fetal hepatic folate cofactor supply. (Pediatr Res 52: 589-594, 2002) Abbreviations THF, tetrahydrofolate MTHF, methylene tetrahydrofolate FTHF, formyl tetrahydrofolate SHMT, serine hydroxymethyltransferase MTHFS, methenyl tetrahydrofolate synthase MEM, minimal essential medium BrdU, 5-bromo-2'-deoxyuridine GC/MS, gas chromatography-mass spectrometry Serine occupies a unique metabolic position in the fetus. Studies in the fetal sheep demonstrated that serine is one of only three amino acids to have a net production across the fetal liver (1, 2). However, serine is poorly transported across the placenta to the fetus (3, 4). Thus, the fetus must rely on endogenous production of serine to meet the majority of its serine requirements. Serine is an important amino acid for DNA and RNA synthesis and phospholipid synthesis (5, 6). In human fetuses, serine metabolism is similar to that of fetal sheep (7,8). Indeed, human fetuses that are small-forgestational age have selectively low levels of serine and glycine, suggesting an important role for serine in fetal growth (8 -10).Little is known about the regulation of fetal hepatic serine metabolism. Others and we have demonstrated that the majority of serine produced by the ...

show abstract

Serine and Glycine Metabolism in Hepatocytes from Mid Gestation Fetal Lambs

Cited by 23 publications

References 23 publications

Targeted Disruption of the Mouse 3-Phosphoglycerate Dehydrogenase Gene Causes Severe Neurodevelopmental Defects and Results in Embryonic Lethality

Targeted Disruption of the Mouse 3-Phosphoglycerate Dehydrogenase Gene Causes Severe Neurodevelopmental Defects and Results in Embryonic Lethality

Folate Cofactors Regulate Serine Metabolism in Fetal Ovine Hepatocytes

Folate Cofactors Regulate Serine Metabolism in Fetal Ovine Hepatocytes

Contact Info

Product

Resources

About