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Regulation of lipid droplet size in mammary epithelial cells by remodeling of membrane lipid composition-a potential mechanism.

Cohen BC, Shamay A, Argov-Argaman N - PLoS ONE (2015)

Bottom Line: Mitochondrial quantity and expression levels of genes associated with mitochondrial biogenesis and polar lipid composition were determined.When cultured with oleic acid, 22% of the cells contained large lipid droplets (>3 μm) and phosphatidylethanolamine concentration was higher by 23 and 63% compared with that in the control and palmitic acid treatments, respectively (P < 0.0001).Triglyceride secretion in the oleic acid treatment was 2- and 12-fold higher compared with that in the palmitic acid and control treatments, respectively.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Jerusalem, Israel.

ABSTRACT
Milk fat globule size is determined by the size of its precursors-intracellular lipid droplets-and is tightly associated with its composition. We examined the relationship between phospholipid composition of mammary epithelial cells and the size of both intracellular and secreted milk fat globules. Primary culture of mammary epithelial cells was cultured in medium without free fatty acids (control) or with 0.1 mM free capric, palmitic or oleic acid for 24 h. The amount and composition of the cellular lipids and the size of the lipid droplets were determined in the cells and medium. Mitochondrial quantity and expression levels of genes associated with mitochondrial biogenesis and polar lipid composition were determined. Cells cultured with oleic and palmitic acids contained similar quantities of triglycerides, 3.1- and 3.8-fold higher than in controls, respectively (P < 0.0001). When cultured with oleic acid, 22% of the cells contained large lipid droplets (>3 μm) and phosphatidylethanolamine concentration was higher by 23 and 63% compared with that in the control and palmitic acid treatments, respectively (P < 0.0001). In the presence of palmitic acid, only 4% of the cells contained large lipid droplets and the membrane phosphatidylcholine concentration was 22% and 16% higher than that in the control and oleic acid treatments, respectively (P < 0.0001). In the oleic acid treatment, approximately 40% of the lipid droplets were larger than 5 μm whereas in that of the palmitic acid treatment, only 16% of the droplets were in this size range. Triglyceride secretion in the oleic acid treatment was 2- and 12-fold higher compared with that in the palmitic acid and control treatments, respectively. Results imply that membrane composition of bovine mammary epithelial cells plays a role in controlling intracellular and secreted lipid droplets size, and that this process is not associated with cellular triglyceride content.

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Transcription levels of activity markers of mitochondria and phospholipid converting enzyme are modulated by free fatty acids (FFAs).Mammary epithelial cells were treated with 100 μM FFA (capric, palmitic or oleic acid) or with FFA-free medium (control) for 2 h; RNA was extracted and gene-expression levels of (A) PGC-1α, (B) PGC-1β, (C) NDUFAF3 and (D) PEMT were analyzed by real-time PCR. All data are presented as mean ± SEM of the expression level of the assayed gene normalized to the geometric mean of two housekeeping genes. Different letters indicate significant differences between treatment groups (P < 0.05).
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pone.0121645.g003: Transcription levels of activity markers of mitochondria and phospholipid converting enzyme are modulated by free fatty acids (FFAs).Mammary epithelial cells were treated with 100 μM FFA (capric, palmitic or oleic acid) or with FFA-free medium (control) for 2 h; RNA was extracted and gene-expression levels of (A) PGC-1α, (B) PGC-1β, (C) NDUFAF3 and (D) PEMT were analyzed by real-time PCR. All data are presented as mean ± SEM of the expression level of the assayed gene normalized to the geometric mean of two housekeeping genes. Different letters indicate significant differences between treatment groups (P < 0.05).

Mentions: PGC-1 coactivators have been shown to regulate mitochondrial biogenesis [34,35]. Therefore, in the present study, their gene-expression levels were determined as an indicator of mitochondrial quantity (Fig. 3). PGC-1α transcription levels were approximately 50% lower in the oleic acid treatment than in the palmitic and capric acid treatments (P = 0.001, Fig. 3A). PGC-1ß was elevated by both palmitic and oleic acid treatments, by 91 and 116%, respectively (P = 0.0001, Fig. 3B) compared to the control. Capric acid did not change PGC-1α or ß transcription levels compared to the control.


Regulation of lipid droplet size in mammary epithelial cells by remodeling of membrane lipid composition-a potential mechanism.

Cohen BC, Shamay A, Argov-Argaman N - PLoS ONE (2015)

Transcription levels of activity markers of mitochondria and phospholipid converting enzyme are modulated by free fatty acids (FFAs).Mammary epithelial cells were treated with 100 μM FFA (capric, palmitic or oleic acid) or with FFA-free medium (control) for 2 h; RNA was extracted and gene-expression levels of (A) PGC-1α, (B) PGC-1β, (C) NDUFAF3 and (D) PEMT were analyzed by real-time PCR. All data are presented as mean ± SEM of the expression level of the assayed gene normalized to the geometric mean of two housekeeping genes. Different letters indicate significant differences between treatment groups (P < 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4355593&req=5

pone.0121645.g003: Transcription levels of activity markers of mitochondria and phospholipid converting enzyme are modulated by free fatty acids (FFAs).Mammary epithelial cells were treated with 100 μM FFA (capric, palmitic or oleic acid) or with FFA-free medium (control) for 2 h; RNA was extracted and gene-expression levels of (A) PGC-1α, (B) PGC-1β, (C) NDUFAF3 and (D) PEMT were analyzed by real-time PCR. All data are presented as mean ± SEM of the expression level of the assayed gene normalized to the geometric mean of two housekeeping genes. Different letters indicate significant differences between treatment groups (P < 0.05).
Mentions: PGC-1 coactivators have been shown to regulate mitochondrial biogenesis [34,35]. Therefore, in the present study, their gene-expression levels were determined as an indicator of mitochondrial quantity (Fig. 3). PGC-1α transcription levels were approximately 50% lower in the oleic acid treatment than in the palmitic and capric acid treatments (P = 0.001, Fig. 3A). PGC-1ß was elevated by both palmitic and oleic acid treatments, by 91 and 116%, respectively (P = 0.0001, Fig. 3B) compared to the control. Capric acid did not change PGC-1α or ß transcription levels compared to the control.

Bottom Line: Mitochondrial quantity and expression levels of genes associated with mitochondrial biogenesis and polar lipid composition were determined.When cultured with oleic acid, 22% of the cells contained large lipid droplets (>3 μm) and phosphatidylethanolamine concentration was higher by 23 and 63% compared with that in the control and palmitic acid treatments, respectively (P < 0.0001).Triglyceride secretion in the oleic acid treatment was 2- and 12-fold higher compared with that in the palmitic acid and control treatments, respectively.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Jerusalem, Israel.

ABSTRACT
Milk fat globule size is determined by the size of its precursors-intracellular lipid droplets-and is tightly associated with its composition. We examined the relationship between phospholipid composition of mammary epithelial cells and the size of both intracellular and secreted milk fat globules. Primary culture of mammary epithelial cells was cultured in medium without free fatty acids (control) or with 0.1 mM free capric, palmitic or oleic acid for 24 h. The amount and composition of the cellular lipids and the size of the lipid droplets were determined in the cells and medium. Mitochondrial quantity and expression levels of genes associated with mitochondrial biogenesis and polar lipid composition were determined. Cells cultured with oleic and palmitic acids contained similar quantities of triglycerides, 3.1- and 3.8-fold higher than in controls, respectively (P < 0.0001). When cultured with oleic acid, 22% of the cells contained large lipid droplets (>3 μm) and phosphatidylethanolamine concentration was higher by 23 and 63% compared with that in the control and palmitic acid treatments, respectively (P < 0.0001). In the presence of palmitic acid, only 4% of the cells contained large lipid droplets and the membrane phosphatidylcholine concentration was 22% and 16% higher than that in the control and oleic acid treatments, respectively (P < 0.0001). In the oleic acid treatment, approximately 40% of the lipid droplets were larger than 5 μm whereas in that of the palmitic acid treatment, only 16% of the droplets were in this size range. Triglyceride secretion in the oleic acid treatment was 2- and 12-fold higher compared with that in the palmitic acid and control treatments, respectively. Results imply that membrane composition of bovine mammary epithelial cells plays a role in controlling intracellular and secreted lipid droplets size, and that this process is not associated with cellular triglyceride content.

Show MeSH
Related in: MedlinePlus