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Age-related changes of alpha-tocopherol transfer protein expression in rat liver
Insights
Alpha-tocopherol transfer protein (alpha-TTP) expression in neonatal rat liver increases after birth, correlating with rising plasma alpha-tocopherol levels. This suggests hepatic differentiation influences alpha-TTP expression and vitamin E regulation.
Area of Science:
- Biochemistry
- Developmental Biology
- Nutritional Science
Background:
- Alpha-tocopherol transfer protein (alpha-TTP) is crucial for vitamin E metabolism.
- Understanding alpha-TTP's developmental regulation is key to optimizing vitamin E status.
Purpose of the Study:
- To investigate the developmental changes in alpha-TTP expression in neonatal rats.
- To correlate these changes with plasma tocopherol levels and hepatic differentiation.
Main Methods:
- Studied alpha-TTP expression in rat liver post-birth.
- Analyzed plasma alpha-tocopherol and gamma-tocopherol concentrations.
- Utilized primary cultured rat hepatocytes to assess factors affecting alpha-TTP expression.
Main Results:
- Neonatal rat liver showed low alpha-TTP expression, increasing to adult levels by four weeks.
- Plasma alpha-tocopherol increased significantly during suckling, raising the alpha-tocopherol/gamma-tocopherol ratio.
- Epidermal growth factor decreased alpha-TTP expression in vitro, while dexamethasone inhibited this decrease.
Conclusions:
- Developmental expression of alpha-TTP in rat liver correlates with changes in plasma tocopherol ratios.
- Hepatic differentiation state appears to influence alpha-TTP expression, as shown by in vitro studies.
Abstract:
Developmental changes in expression of alpha-tocopherol transfer protein (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 four weeks. During the suckling period, the plasma ratio of alpha-tocopherol to gamma-tocopherol linearly increased, because plasma alpha-tocopherol which 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 four 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 20h 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.