Abstract
The purpose of this work was to study whether rat lactating mammary gland can synthesize PUFAs through the expression of Delta5 and Delta6 desaturases (Delta5D and Delta6D), whether these enzymes are regulated by the transcription factors sterol-regulatory element binding protein 1 (SREBP-1) and peroxisome proliferator-activated receptor alpha (PPARalpha) and the coactivator peroxisome proliferator-activated receptor gamma coactivator 1beta (PGC-1beta), and whether 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 is the precursor of PUFAs, is transferred to the mammary gland. There was expression of Delta5D and Delta6D in mammary gland, and it was regulated by the corn oil content in the diet. The higher the corn oil content in the diet, the lower the expression of both desaturases. Induction of Delta5D and Delta6D was associated positively with similar changes in SREBP-1 and PGC-1beta. Expression of PPARalpha was barely detected and was not affected by the corn oil content in the diet, whereas PGC-1beta expression increased as the corn oil in the diet increased. These results indicate that the lactating mammary gland has the capacity to synthesize PUFAs and can be regulated by the lipid content in the diet.
Highlights
The purpose of this work was to study whether rat lactating mammary gland can synthesize PUFAs through the expression of D5 and D6 desaturases (D5D and D6D), whether these enzymes are regulated by the transcription factors sterol-regulatory element binding protein 1 (SREBP-1) and peroxisome proliferator-activated receptor a (PPARa) and the coactivator peroxisome proliferator-activated receptor g coactivator 1b (PGC-1b), and whether these desaturases are regulated by the lipid concentration in the diet
Liver PPARa mRNA increased with the linoleic acid (LA) content in the diet, and there was little expression and no change of PPARa in mammary gland and adipose tissue. These results indicate that mammary gland participates in the synthesis of LC-PUFAs by increasing D6D and D5D expression when the LA content in the diet is low through reduction in the expression of SREBP-1, whereas in situations in which the presence of corn oil in the diet is high, there is an inhibition of D5D, D6D and SREBP-1 and an increase in the fatty acid oxidation through an increase in PPARa expression
Thereby, the lactating mammary gland has a large demand of nutrients for milk synthesis and to maintain the metabolic functions of lactocytes [19]
Summary
The purpose of this work was to study whether rat lactating mammary gland can synthesize PUFAs through the expression of D5 and D6 desaturases (D5D and D6D), whether these enzymes are regulated by the transcription factors sterol-regulatory element binding protein 1 (SREBP-1) and peroxisome proliferator-activated receptor a (PPARa) and the coactivator peroxisome proliferator-activated receptor g coactivator 1b (PGC-1b), and whether these desaturases are regulated by the lipid concentration in the diet. Expression of PPARa was barely detected and was not affected by the corn oil content in the diet, whereas PGC-1b expression increased as the corn oil in the diet increased These results indicate that the lactating mammary gland has the capacity to synthesize PUFAs and can be regulated by the lipid content in the diet.—Rodriguez-Cruz, M., A. Sterol-regulatory element binding protein 1c (SREBP-1c) and peroxisome proliferator-activated receptor a (PPARa), are transcription factors that play a key role in the regulation of desaturases by PUFAs in liver. Hypolipidemic compounds called peroxisome proliferators, such as fibrates, which are ligands of PPARa, induce the expression of enzymes involved in fatty acid oxidation as well as hepatic D5D and D6D [7]
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