Breast Milk :: Regulator of lipid metabolism ensures high quality breast milk

Mouse mammary glands deficient in PPAR?, a nuclear receptor that regulates the storage of fat, produce toxic milk that causes inflammation and baldness in suckling pups, report scientists at the Salk Institute for Biological Studies.

?We were quite surprised by the unexpected quality control mechanism that ensures the quality of breast milk,? says Ronald M. Evans, Ph.D., professor in the Salk Institute?s Gene Expression Laboratory and a Howard Hughes Medical Investigator. ?Our finding explains why breast milk is always clean and healthful, even when there?s a lot of inflammation going on in the mother?s body,? he adds.

The Salk research team ? led by Evans? published their findings in the August issue of the journal Genes & Development. They hope that a better understanding of PPAR? could help explain the role lipids and inflammation play in hair loss and other skin disorders and facilitate the development of new treatments for these diseases.

PPAR? acts as a genetic switch, sensitizing the body to insulin and lowering levels of circulating glucose. In fact PPAR? drugs, including Actos and Avandia, belong to the newest generation of anti-diabetic medications. Naturally occurring mutations in PPAR? lead to obesity and insulin resistance associated with type 2 diabetes.

Unexpectedly, postdoctoral researcher and first author Yihong Wan, Ph.D., observed that mice lacking PPAR? in endothelial cells had trouble rearing their newborns. ?Although the mothers seemed perfectly normal, the nursing offspring soon stopped growing and lost their hair,? says Wan. ?It took us some time to figure out what was going on.?

If the pups were given anti-inflammatory drugs such as aspirin or ibuprofen, the symptoms reversed and their fur started to regrow. ?These observations suggested that the milk produced by the mutant mice may be the source of the troubles,? explained Wan. A closer inspection revealed that the milk of PPAR?-deficient mice contained high levels of toxic fatty acids that set off an inflammatory response in the skin of nursing pups. According to Evans ?by examining the action of PPAR? in vivo, our work revealed an unexpected link between diet, inflammation and the quality of breast milk.?

?Milk is considered a pure and nutritious nourishment. It forms the bond between mother and infant and is one of the true sustaining forces in life. Yihong?s work showed us that this does not simply happen but it is the product of an intricate genetic program that ensures its purity,? says Evans.

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