Submitted on September 13, 2005
Revised on November 10, 2005
Accepted on December 5, 2005
Participation of mammary gland in the synthesis of long chain polyunsaturated fatty acid in lactating rat: Role of ù5 and ù6 desaturases, SREBP-1, PPAR
, and PGC-1
Maricela Rodriguez-Cruz, Armando R. Tovar, Berenice Palacios-González, Martha del Prado, and Nimbe Torres
Physiology of Nutrition, Instituto Nacional de Ciencias Medicas y Nutricion SZ, Mexico, DF 14000
Corresponding Author: nimbet{at}quetzal.innsz.mx
Newborn requires polyunsaturated fatty acids (PUFAs) for normal growth and brain development. They are provided by maternal milk; however, it is not known whether the lactating mammary gland can synthesize long chain PUFAs (LC-PUFAs) through the action of the enzymes 5 and 6 desaturases. Therefore, the purpose of the present work was 1) to assess if mammary gland expresses 5 and 6 desaturases, 2) to study if they are regulated by the transcription factors SREBP-1 and PPARa, and the coactivator PGC-1ß, and 3) to evaluate if these desaturases are regulated by the lipid concentration in the diet. The results showed that on day 12 of lactation approximately 35% of the linoleic acid in the diet, which the precursor of LC-PUFAs is transferred to the mammary gland. In addition there was an expression of 5 and 6desaturases in mammary gland as well as in liver and adipose tissue. The presence of corn oil in the diet regulated the expression of 5 and 6 desaturases in mammary gland and liver but not in adipose tissue. The higher the corn oil content in the diet the lower the expression of both desaturases. Expression of 5 and 6D was associated positively with similar changes in SREBP-1 and PGC-1ß in mammary gland and liver. On the other hand, the expression of both desaturases was inversely associated with PPARa mRNA and PGC 1-a in the liver, however, in the mammary gland PPARa was barely detected and it was not affected by the corn oil content in the diet, whereas PGC-1a expression increased as the corn oil in the diet increased. These results indicate that the lactating mammary gland has the capacity to synthesize LC-PUFAs similar to liver, and can be regulated by the lipid content in the diet in both tissues.
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