Imprinting: RNA expression for homocysteine recycling in the human oocyte
FERTILITY AND STERILITY
Authors: Benkhalifa, Moncef; Montjean, Debbie; Cohen-Bacrie, Paul; Menezo, Yves
Abstract
Objective: To investigate whether homocysteine, a well known inhibitor of methylation, which is produced after imprinting and other methylation processes, can be recycled to methionine in the oocyte, at least until the stage of maternal to zygotic transition (i.e., four- to eight-cell stage); before this stage, most of the biochemical processes are carried out with the use of maternal stores of protein and mRNA. Design: A first approach using microarrays and then reverse-transcription polymerase chain reaction (RT-PCR) for methionine synthase (5-methyltetrahydrofolate-homocysteine methyltransferase [MTR]), betaine-homocysteine methyltransferase (BHMT), and cystathionine-beta synthase (CBS). Setting: Two private hospitals. Patient(s): Patients involved in IVF/ICSI procedures. Intervention(s): Germinal vesicle oocytes collected at the time of oocyte retrieval. RNA extraction amplification, RT-PCR, microarrays. Main Outcome Measure(s): mRNA expression of all the enzymes involved in the chain of methylation and recycling of homocysteine to methionine. Result(s): All of the enzymes required for methylation are present in the oocyte. Homocysteine can be recycled with BHMT and MTR. Conclusion(s): The human oocyte is able to regulate its Hey level via remethylation using MTR and BHMT but not CBS. This aspect is important, because recent studies have shown that controlled ovarian hyperstimulation affects the homocysteine concentration in follicular fluid. This may regulate, at least in part, the risk of imprinting problems during. IVF procedures. (Fertil Steril (R) 2010;93:1585-90. (C)2010 by American Society for Reproductive Medicine.)
Suppression Effects of Betaine-Enriched Spinach on Hyperhomocysteinemia Induced by Guanidinoacetic Acid and Choline Deficiency in Rats
SCIENTIFIC WORLD JOURNAL
Authors: Liu, Yi-Qun; Jia, Zheng; Han, Feng; Inakuma, Takahiro; Miyashita, Tatsuya; Sugiyama, Kimio; Sun, Li-Cui; Xiang, Xue-Song; Huang, Zhen-Wu
Abstract
Betaine is an important natural component of rich food sources, especially spinach. Rats were fed diets with betaine or spinach powder at the same level of betaine for 10 days to investigate the dose-dependent effects of spinach powder supplementation on hyperhomocysteinemia induced by guanidinoacetic acid (GAA) addition and choline deprivation. The GAA-induced hyperhomocysteinemia in rats fed 25% casein diet (25C) was significantly suppressed by supplementation with betaine or spinach, and it was completely suppressed by taking 11.0% spinach supplementation. The choline deprivation-induced enhancement of plasma homocysteine concentration in rats fed 25% soybean protein diet (25S) was markedly suppressed by 3.82% spinach. Supplementation with betaine or spinach partially prevented the effects of GAA on hepatic concentrations of methionine metabolites. The decrease in activity of betaine-homocysteine S-methyltransferase (BHMT) and cystathionine beta-synthase (CBS) in GAA-induced hyperhomocysteinemia was recovered by supplementation with betaine or spinach. Supplementation with betaine or spinach did not affect BHMT activity, whereas it partially restored CBS activity in choline-deprived 25S. The results indicated that betaine or spinach could completely suppress the hyperhomocysteinemia induced by choline deficiency resulting from stimulating the homocysteine removal by both remethylation and cystathionine formation.