Moderate vitamin B6 deficiency and sulfur amino acid metabolism in male and female rats

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Hernandez Garcia, Frida
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Homocysteine, cysteine, and methionine are sulfur amino acids. Methionine converts to cysteine in the transsulfuration pathway, utilizing homocysteine as an intermediate. Research indicates that vitamin B6 deficiency may impair the regulation of cellular homocysteine concentrations and decrease cysteine synthesis. Previous studies on B6 deficiency focused solely on male rats overlooking sex-specific differences. This study aims to demonstrate that moderate vitamin B6 deficiency intake in rats affects methionine plasma levels, leading to reduced conversion into cysteine within the transsulfuration pathway compared to the adequate vitamin B6 group. Thus, moderately deficient rats are expected to exhibit decreased B6 plasma levels, with sex contributing to specific differences. Forty-six seven-week-old female and male Sprague-Dawley rats were randomly assigned to receive either a moderate (0.7 mg/day) or adequate (7.0 mg/day) B6 diet for five weeks. Plasma SAA, B6, estrogen, progesterone, and 1-carbon metabolites in plasma, and enzyme expression of CBS and CGL in the liver were determined. A significant diet effect was observed in 5-MTHF, GSH, choline, glycine, and cystine, with lower plasma levels in the moderate B6 diet group. Conversely, cystathionine and GSSG showed higher plasma levels in the same diet group. Furthermore, a sex effect was evident, with significantly higher plasma levels in male groups for 5-MTHF, methionine, DHFR, vitamin B12 and B2, acetylcholine, choline glutamic acid, SAM, glycine, serine, and GSSG. On the contrary, total cysteine, estrogen, and betaine were significantly higher in female groups. Finally, a sex-by-diet interaction was observed in CBS enzyme expression, with males exhibiting higher expression levels in the adequate diet group compared to the moderate deficiency group, while females showed higher expression levels in the moderate B6 deficient diet group. This study underscores the importance of including both sexes in nutrition research and emphasizes the importance of maintaining an adequate intake of B6 to support optimal functioning of the transsulfuration pathway and metabolism.
Sulfur amino acids, Vitamin B6 moderate deficiency, Metabolism