Dietary cystine essential in regulating mercaptalbumin levels
By dominguez // 2019-05-28
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In this study, researchers from the Kyoto Prefectural University in Japan examined the amino composition of dietary protein to determine if it modulates the oxidized/reduced state of plasma albumin in rats. Their study, which demonstrated the effects of protein quality, was published in the journal Nutrition Research.
  • The quantity of dietary protein influences the oxidized/reduced state of plasma albumin in rats.
  • However, the effects of protein quality on the oxidized/reduced state of plasma albumin are not well-understood.
  • The researchers hypothesized that the quality of dietary protein could modulate the oxidized/reduced state of plasma albumin.
  • To test their hypothesis, they used male Sprague-Dawley rats and fed them low-protein diets containing 5 percent casein (CA), 5 percent egg white (EW), or 6 percent wheat gluten (WG) for two weeks.
  • The researchers reported that plasma albumin concentration gradually decreased in rats fed each diet; however, they noticed no significant difference among the groups.
  • They reported that in rats fed the 5 percent CA diet, the percentage of mercaptalbumin within the total plasma albumin was significantly lower than in those fed the EW or WG diet.
  • Compared with EW or WG, CA contains lower amounts of glycine and cystine, so the researchers decided to supplement the diet with cystine and glycine.
  • In rats fed a 5 percent CA diet supplemented with cystine, the percentage of mercaptalbumin was significantly higher than that in rats fed a 5 percent CA diet supplemented with glycine.
  • The researchers also found that the expression of hepatic eukaryotic initiation factor 4E-binding protein 1 was significantly lower in rats fed the cystine-supplemented diet than in those fed the glycine-supplemented diet.
Based on their findings, the researchers concluded that dietary protein with a high cystine content maintains plasma mercaptalbumin levels in rats fed low-protein diets. Journal Reference: Kuwahata M, Kobayashi Y, Wada Y, Aoi W, Kido Y. DIETARY CYSTINE IS IMPORTANT TO MAINTAIN PLASMA MERCAPTALBUMIN LEVELS IN RATS FED LOW-PROTEIN DIETS. NUTRITION RESEARCH. August 2018;56:79–89. DOI: 10.1016/j.nutres.2018.04.019
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