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Multiple pathways ensure retinoid delivery to milk: studies in genetically modified mice
Sheila M O'Byrne1, Yuko Kako, Richard J Deckelbaum
1Institute of Human Nutrition, Columbia University, New York, NY 10032, USA. so2017@columbia.edu
American Journal of Physiology. Endocrinology and Metabolism
|December 31, 2009
Summary
Lecithin:retinol acyltransferase (LRAT) is crucial for forming milk retinyl esters, as shown in modified mice. Compensatory pathways ensure retinoid delivery, but LRAT is key for milk ester formation.
Area of Science:
- Nutritional biochemistry
- Developmental biology
- Lactation physiology
Background:
- Retinoids are essential for postnatal growth and development.
- Milk retinoids are critical for infant nutrition.
- The specific mechanisms of retinoid transfer into milk are not fully understood.
Purpose of the Study:
- To investigate the role of lecithin:retinol acyltransferase (LRAT) in milk retinyl ester formation.
- To explore the function of retinol-binding protein (RBP) in retinoid delivery to milk.
- To identify compensatory pathways for retinoid transport into milk.
Main Methods:
- Utilized genetically modified mouse models, including Lrat(-/-) and Rbp(-/-) mice.
- Analyzed the composition of milk retinoids (retinyl esters and unesterified retinol).
- Examined the role of lipoprotein lipase (LPL) and CD36 in retinoid and fatty acid transport.
Main Results:
- Mice lacking LRAT showed significantly altered milk retinyl ester composition, with increased unesterified retinol.
- Rbp(-/-) mice maintained normal milk retinoid levels, suggesting alternative delivery pathways.
- Lipoprotein lipase (LPL) plays a role in retinoid delivery to milk, independent of RBP.
- CD36 facilitated long-chain fatty acid delivery but not retinoid incorporation into milk.
Conclusions:
- LRAT is the primary enzyme responsible for the majority of retinyl ester formation in milk.
- Compensatory mechanisms, including LPL-dependent pathways, ensure adequate retinoid delivery to milk.
- Understanding these pathways is vital for ensuring proper retinoid nutrition during lactation.
