Effect of reproductive states on lipid mobilization and linoleic acid metabolism in mammary glands (original) (raw)
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Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2011
Fatty acid desaturase 1 Fatty acid desaturase 2 Elongase 5 Sterol-regulatory element binding factor Pregnancy Lactation Metabolic adaptations are triggered in the maternal organism to synthesize milk with an adequate concentration of long-chain polyunsaturated fatty acids (LC-PUFAs) required to the newborn. They may be a high uptake of dietary linoleic acid and its conversion to LC-PUFAs by desaturases of fatty acids (FADS) 1 and 2 in the mammary gland (MG). It is unknown if they also occur from onset of pregnancy. The aim of this study was to explore the participation of the MG as a mechanism involved in LC-PUFAs synthesis to support their demand during pregnancy and lactation in rats. The expression of desaturases in MG was significantly (P b 0.05) higher (12.3-fold for FADS1 and 41.2-fold for FADS2) during the late pregnancy and throughout lactation (31.7-fold for FADS1 and 67.1-fold higher for FADS2) than in nonpregnant rats. SREBF-1c showed a similar pattern of increase during pregnancy but remained higher only during the early lactation (11.7-fold, P b 0.005). Transcript of ELOVL6 and FASN increased throughout pregnancy and lactation, respectively. ELOVL5 mRNA increased in MG only during lactation (2.8 to 5.3-fold, P b 0.005). Accordingly, a higher content of LC-PUFAs was found in lactating MG than in nonpregnant rats. Results suggest that MG participates from late pregnancy and throughout lactation by expressing desaturases and elongases as a mechanism involved in LC-PUFAs synthesis, probably by SREBF-1c. Because desaturases and ELOVL5 were expressed in cultured lactocytes and such expression was downregulated by linoleic and arachidonic acid, these cells may be a useful model for understanding the regulatory mechanisms for LC-PUFAs synthesis in MG.
Trans Fatty Acids in Maternal Diet May Impair Lipid Biosynthesis in Mammary Gland of Lactating Rats
Annals of Nutrition and Metabolism, 2002
Although trans fatty acids are known to influence essential fatty acid (EFA) metabolism and serum levels of lipids and lipoproteins, little is known about their effects on the metabolism of mammary glands (MGs) during lactation. In this study, 5 groups of lactating Wistar rats were fed semisynthetic diets containing 7% soy oil (control); 7% partially hydrogenated vegetable oil (7% PHVO); 13% PHVO +7% soy oil (13% PHVO); 5% PHVO +2% soy oil (5% PHVO), and 3.5% PHVO +3.5% soy oil (3.5% PHVO). Dams were killed on the 12th day of lactation. Weight, lipid content (LC), in vivo lipogenesis rate (LR) and activity of the lipogenic (ATP-citrate lyase and malic) enzymes were evaluated in the MGs. Maternal food intake, weight gain, and total MG weight were not found to be significantly different between the groups. The groups with 13, 7 and 5% PHVO presented a lower (p < 0.05) LR in MGs when compared to controls, whereas MG LC was higher in the 7 and 13% groups than in controls. The observe...
Changes in mammary fat pad composition and lipolytic capacity throughout pregnancy
Cell and Tissue Research, 2006
Changes in rat mammary fat pad during pregnancy were assessed by studying differences in the morphology and composition of the pad and in the levels of proteins involved in the accumulation and mobilization of fat stores. During pregnancy, the mammary fat pad weight had increased 1.8-fold by day 20, as compared with control rats. DNA content had increased two-fold by day 13 and remained stable until day 20. Protein content showed a two-fold increase on day 20, compared with control rats. As pregnancy advanced, both the percentage of mammary gland cells with respect to the whole mammary fat pad and the size of the adipocytes increased. The specific content of the different elements of the lipolytic pathway, viz. α 2Aadrenergic receptor (AR), β 3 -AR, cAMP-dependent protein kinase and hormone-sensitive lipase (HSL), underwent a decrease as pregnancy progressed, although adenylate cyclase increased greatly. The lipoprotein lipase (LPL) content per gram of tissue increased with pregnancy and the HSL-to-LPL ratio reflected a continuous increase in triglyceride storage throughout pregnancy. Thus, the mam-mary fat pad undergoes extensive morphological, compositional and metabolic transformation during pregnancy, attributable to the development of the mammary gland. The various elements of the lipolytic pathway and LPL undergo major changes during the development of the mammary gland focused towards the increase of fat stores and allowing the accumulation of lipid droplets in the epithelial mammary cells and an increase in adipocyte size.
The Journal of Lipid Research, 2005
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. The results showed that on day 12 of lactation, z35% of the linoleic acid in the diet, which is the precursor of PUFAs, is transferred to the mammary gland. There was expression of D5D and D6D 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 D5D and D6D was associated positively with similar changes in SREBP-1 and PGC-1b. 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.
AJP: Endocrinology and Metabolism, 2013
Expression of genes for lipid biosynthetic enzymes during initiation of lactation in humans is unknown. Our goal was to study mRNA expression of lipid metabolic enzymes in human mammary epithelial cell (MEC) in conjunction with the measurement of milk fatty acid (FA) composition during secretory activation. Gene expression from mRNA isolated from milk fat globule (MFG) and milk FA composition were measured from 6 h to 42 days postpartum in seven normal women. Over the first 96 h postpartum, daily milk fat output increased severalfold and mirrored expression of genes for all aspects of lipid metabolism and milk FA production, including lipolysis at the MEC membrane, FA uptake from blood, intracellular FA transport, de novo FA synthesis, FA and glycerol activation, FA elongation, FA desaturation, triglyceride synthesis, cholesterol synthesis, and lipid droplet formation. Expression of the gene for a key lipid synthesis regulator, sterol regulatory element-binding transcription factor ...
The Journal of nutrition, 1999
Rats fed a diet with high fat concentration produce larger amounts of milk with a higher lipid concentration than rats fed a lower fat diet. This investigation was designed to study the relationship between dietary fat intake, mammary gland lipid uptake and lipogenesis in rat dams fed, during pregnancy and lactation, one of two purified diets, with equal energy density, containing 2.5 (LL) or 20 g fat/100 g diet (HL). Milk lipid concentration and fatty acid composition were determined at d 14 of lactation. Mammary gland lipogenesis, lipoprotein lipase (LPL) activity and the uptake of [1-(14)C]triolein by the mammary gland and its transfer to the pups was measured. The intestinal absorption of oral (14)C-lipid, (14)CO(2) production and the amount of (14)C-lipid transferred to the pups (milk clot + pups carcass) were significantly higher in the HL group than in the LL group (P < 0.05). Mammary gland lipogenesis was 75% lower and LPL activity was 30% higher in the HL group (P < 0...
Journal of lipid research, 2006
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 ch...