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Developmental changes in alpha-tocopherol, especially during infantile period
Insights
Alpha-tocopherol transfer protein (alpha-TTP) expression in neonatal rat liver increases after birth, correlating with rising plasma alpha-tocopherol levels. This suggests alpha-TTP
Area of Science:
- Biochemistry
- Developmental Biology
- Nutritional Science
Background:
- Alpha-tocopherol transfer protein (alpha-TTP) plays a crucial role in vitamin E metabolism.
- Understanding the developmental regulation of alpha-TTP is essential for comprehending vitamin E homeostasis.
Purpose of the Study:
- To investigate the developmental changes in alpha-TTP expression in neonatal rats.
- To explore the relationship between alpha-TTP expression and plasma tocopherol levels.
- To examine factors influencing alpha-TTP expression in cultured hepatocytes.
Main Methods:
- Developmental expression analysis of alpha-TTP in rat liver post-birth.
- Measurement of plasma alpha-tocopherol and gamma-tocopherol levels.
- Primary culture of rat hepatocytes to study alpha-TTP expression.
- Western and Northern blot analysis in vitamin E-deficient and -enriched rats.
Main Results:
- Neonatal rat liver alpha-TTP expression increased post-birth, reaching adult levels by 4 weeks.
- Plasma alpha-tocopherol to gamma-tocopherol ratio increased linearly during suckling, correlating with alpha-TTP development.
- Hepatocyte culture showed low alpha-TTP expression, modulated by epidermal growth factor and dexamethasone.
- Vitamin E status influenced alpha-TTP mRNA levels, indicating regulation of its synthesis.
Conclusions:
- Hepatic alpha-TTP expression is developmentally regulated after birth.
- The developmental increase in alpha-TTP expression likely contributes to the rise in plasma alpha-tocopherol levels.
- Hepatic differentiation state and vitamin E availability may influence alpha-TTP expression.
Abstract:
Developmental changes in expression of alpha-TTP after birth were investigated using rats with respect to plasma changes of tocopherols. The expression of alpha-TTP in the neonatal rat liver, which was very low immediately after birth, increased steadily during the two weeks of life before weanling and reached the adult level at 4 weeks. During the suckling period, the plasma ratio of alpha-tocopherol to gamma-tocopherol linearly increased, because plasma alpha-tocopherol was low immediately after birth, increased rapidly during the period, while gamma-tocopherol remained unchanged. The increase in the ratio seemed to correlate with the developmental expression of alpha-TTP in the liver during this period. The ratio also reached the adult level after 4 weeks. The expression of alpha-TTP was investigated using primary cultured rat hepatocytes. The expression of alpha-TTP was found to be extremely low after 20 h of culture. The decrease in alpha-TTP expression was exacerbated by adding epidermal growth factor to the culture medium and was inhibited by adding dexamethasone. These observations suggest that expression of alpha-TTP may be affected by the state of hepatic differentiation. The Western and Northern blot analysis of alpha-TTP in vitamin E deficient and enriched rats were compared to control rats. The decrease of mRNA of alpha-TTP observed in alpha-Toc-enriched rat liver and the increase of mRNA observed in the vitamin E deficient rat liver indicate the synthesis of alpha-TTP, although alpha-TTP itself was not altered.