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Neutral lipid transfer protein does not regulate alpha-tocopherol transfer between human plasma lipoproteins
E Granot1, I Tamir, R J Deckelbaum
1Department of Pediatrics, Hadassah University Hospital, Jerusalem, Israel.
Lipids
|January 1, 1988
Summary
Vitamin E is transported by lipoproteins, but its transfer between them is not mediated by the neutral lipid transfer protein. Instead, vitamin E distribution depends on lipoprotein mass ratios and acceptor-to-donor protein ratios.
Area of Science:
- Lipid metabolism
- Biochemistry
- Nutritional science
Background:
- Vitamin E, a fat-soluble vitamin, lacks a specific plasma carrier protein.
- It is transported via plasma lipoproteins, but its exact location within these particles and transfer mechanisms remain unclear.
- Hydrophobic molecules like vitamin E are hypothesized to associate with lipoprotein cores.
Purpose of the Study:
- To investigate whether the neutral lipid transfer protein (NLTP) mediates the transfer of vitamin E between human plasma lipoproteins.
- To determine the factors influencing vitamin E distribution among different lipoprotein fractions.
Main Methods:
- In vitro labeling of human plasma lipoprotein fractions with D-alpha(5-methyl-3H)tocopherol (a form of vitamin E).
- Incubation of labeled lipoproteins under conditions promoting varying degrees of neutral lipid exchange.
- Measurement of vitamin E transfer between very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL) in the presence and absence of NLTP or lipoprotein-poor plasma.
Main Results:
- Vitamin E transfer between VLDL, LDL, and HDL remained constant despite significant increases in neutral lipid transfer mediated by NLTP.
- Even high concentrations of NLTP, sufficient to saturate triglyceride transfer, did not enhance vitamin E transfer.
- Vitamin E distribution correlated with lipoprotein mass ratios, with higher transfer observed as the ratio of acceptor to donor lipoprotein protein increased.
Conclusions:
- The neutral lipid transfer protein does not mediate the transfer of vitamin E between plasma lipoproteins.
- Vitamin E's distribution is primarily governed by lipoprotein mass and protein ratios, suggesting a passive exchange mechanism rather than active protein-mediated transfer.