Ensuring Milk Quality

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Science  10 Aug 2007:
Vol. 317, Issue 5839, pp. 723
DOI: 10.1126/science.317.5839.723b

In discussions of diet and health, fat generally gets a bad rap. One notable exception is the case of newborn babies, who require substantial quantities of milk lipids for normal growth and development. Indeed, to meet this need, the mammary glands of new mothers secrete nearly 6 kg of fat during a typical 6-month lactation period.

In a study of genetically manipulated mice, Wan et al. show that the quality of fat in milk is as important to neonatal health as the quantity, and they begin to dissect the mechanism by which quality control is achieved. The authors noticed that nursing pups of female mice that were genetically deficient in the transcription factor PPAR-γ (peroxisome proliferator-activated receptor-γ) exhibited growth delays and hair loss. These abnormalities were not related to the genotypes of the fathers or the pups, nor were they related to maternal parenting behaviors. Instead, they could be traced to a nutritional defect in the milk produced by the mutant mothers—namely, the presence of pro-inflammatory lipids, which were the products of aberrantly overexpressed lipid oxidation enzymes in the maternal mammary glands. One confirmatory piece of evidence that hair loss in the pup was a consequence of inflammatory responses was that treatment with aspirin effectively prevented the alopecia. Thus, maternal PPAR-γ appears to protect nursing newborns by suppressing the production of “toxic” fats in milk. Interestingly, the source of the PPAR-γ mediating this protective effect is not the mammary epithelium but appears to be hematopoietic or endothelial cells. — PAK

Genes Dev. 21, 10.1101/gad.1567207 (2007).

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