Moderate Vitamin B-6 Restriction Does Not Alter Postprandial Methionine Cycle Rates of Remethylation, Transmethylation, and Total Transsulfuration but Increases the Fractional Synthesis Rate of Cystathionine in Healthy Young Men and Women  

Oleh:

Lamers, Yvonne ; Coats, Bonnie ; Ralat, Maria ; Quinlivan, Eoin P. ; Stacpoole, Peter W. ; Gregory III, Jesse F.

Jenis: Article from Journal - ilmiah internasional
Dalam koleksi: JN: The Journal of Nutrition vol. 141 no. 05 (May 2011), page 835-842 .
Topik: NUTRITION; Nutrient Physiology; Metabolism; Nutrient Interactions

Ketersediaan

Perpustakaan FK Nomor Panggil: J42.K.2011.01 Non-tandon: 1 (dapat dipinjam: 0) Tandon: tidak ada

Lihat Detail Induk

Isi artikel

Methionine is the precursor for S-adenosylmethionine (SAM), the major 1-carbon donor involved in >100 transmethylation reactions. Homocysteine produced from SAM must be metabolized either by remethylation for recycling of methionine or transsulfuration to form cystathionine and then cysteine. Pyridoxal 5'-phosphate (PLP) serves as a coenzyme in enzymes involved in transsulfuration as well as for primary acquisition of 1-carbon units used for remethylation and other phases of 1-carbon metabolism. Because the intake of vitamin B-6 is frequently low in humans and metabolic consequences of inadequacy may be amplified in the postprandial state, we aimed to determine the effects of marginal vitamin B-6 deficiency on the postprandial rates of remethylation, transmethylation, overall transsulfuration, and cystathionine synthesis. Healthy, young adults (4 male, 5 female; 20–35 y) received a primed, constant infusion of [1-13C]methionine, [methyl-2H3]methionine, and [5,5,5-2H3]leucine to quantify in vivo kinetics at normal vitamin B-6 status and after a 28-d dietary vitamin B-6 restriction. Vitamin B-6 restriction lowered the plasma PLP concentration from 49 ± 4 nmol/L (mean ± SEM) to 19 ± 2 nmol/L (P < 0.0001). Mean remethylation, transsulfuration, and transmethylation rates did not change in response to vitamin B-6 restriction; however, the responses to vitamin B-6 restriction varied greatly among individuals. The plasma cystathionine concentration increased from 142 ± 8 to 236 ± 9 nmol/L (P < 0.001), whereas the fractional cystathionine synthesis rate increased by a mean of 12% in 8 of 9 participants. Interrelationships among plasma concentrations of glycine and cystathionine and kinetic results suggest that individual variability occurs in normal postprandial 1-carbon metabolism and in the response to vitamin B-6 restriction.

Opini Anda

Klik untuk menuliskan opini Anda tentang koleksi ini!

Kembali