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Abstract
Lipids are major biological molecules and serve as an essential form of energy storage in animals. Lipids can be categorized into three groups: simple lipids, complex lipids, and phospholipids. The most common form of lipids is triglycerides. The lactating mammary gland is one of the most active triglyceride-synthesizing organs in the body. Triglycerides are major constituents of the milk of most mammals, providing a significant portion of the calories required for neonatal growth and a source of essential fatty acids. Milk lipids are secreted as cytoplasmic assemblies of triglyceride droplets surrounded by a phospholipid monolayer and surface-associated proteins called cytoplasmic lipid droplets (CLDs). CLDs are generated at the endoplasmic reticulum through a mechanism that is not fully understood. Adipophilin, a lipid droplet-associated protein, promotes CLD accumulation by inhibiting triglyceride lipolysis. Adipophilin is abundantly found in the mammary gland, and its size is closely related to the accumulation of CLDs.
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References
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- Baldwin RL, Yang YT. Enzymatic metabolic changes in the development of lactation. In: Larson BL, Smith VR, editors. Lactation. Academic Press; NY, USA: 1974. p. 349–407
- Boxer RB, Stairs DB, Dugan KD, et al. Isoform-specific requirement for Akt1 in the developmental regulation of cellular metabolism during lactation. Cell Metab; 2006. p. 475–490.
- Berwick DC, Hers I, Heesom KJ, Moule SK, Tavare JM. The identification of ATP-citrate lyase as a protein kinase B (Akt) substrate in primary adipocytes. J Biol Chem; 2002. p. 277:33895–33900.
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- Larigauderie G, Cuaz-Perolin C, Younes AB, et al. Adipophilin increases triglyceride storage in human macrophages by stimulation of biosynthesis inhibition of β-oxidation. FEBS J. 2006. p. 273:3498–3510.
- Ogg SL, Weldon AK, Dobbie L, Smith AJ, Mather IH. Expression of butyrophilin (Btn1a1) in lactating mammary gland is essential for the regulated secretion of milk-lipid droplets. Proc Natl Acad Sci USA; 2004. p. 101:10084–10089.
References
Donald Voet and others, Fundimentals of biochemistry, ISBN o- 471 -21495 -7, Printed in USA. (2006). p.23-27 ,234-242 and 77-90
Esterle, L., et al. "Milk, rather than other foods, is associated with vertebral bone mass and circulating IGF-1 in female adolescents.". Osteoporosis international (2009). p. 20.4: 567.
Skoet, F.Food and Agricultural commodities production – Cow milk, whole, fresh, FAOSTAT, Food and Agricultural Organization of the United Nations. faostat.fao.org. 2012. p. 91-105
Gerosa, A. Milk availability – Trends in production and demand and medium-term outlook. FAO, United Nations. 2012.Pp.14-45,189
Oftedal OT. Use of maternal reserves as a lactation strategy in large mammals. Proc Nutr Soc. 2000. 59:99–106.
Koletzko B, Rodriguez-Palmero M. Polyunsaturated fatty acids in human milk and their role in early infant development. J Mammary Gland Biol Neoplasia. 1999. p. 269–284.
Allen JC, Keller RP, Archer PC, Neville MC. Studies in human lactation: 6. Milk composition and daily secretion rates of macronutrients in the first year of lactation. Am J Clin Nutr. 1991. p. 54:69–80.
Rudolph MC, Neville MC, Anderson SM. Lipid synthesis in lactation: diet and the fatty acid switch. J Mammary Gland Biol Neoplasia. 2007. p. 12:269–281.
Bargmann W, Knoop A. Morphology of lactation; light & electro-microscopic studies on the mammary glands of rats. Z Zellforsch Mikrosk Anat. 1959. p. 49:344–388.
Mather IH, Keenan TW. Origin and secretion of milk lipids. J Mammary Gland Biol Neoplasia; 1998. p. 3:259–273.
Neville MC, McFadden TB, Forsyth I. Hormonal regulation of mammary differentiation and milk secretion. J Mammary Gland Biol Neoplasia; 2002. p.7:49–66.
Brisken C. Hormonal control of alveolar development its implications for breast carcinogenesis. J Mammary Gland Biol Neoplasia; 2002. p. 39–48.
Hollmann KH. Cytology fine structure of the mammary gland. In: Larson BL, Smith VR, editors. Lactation. Vol. 1. Academic Press; NY, USA; 1974. p. 3–95.
Russell TD, Palmer CA, Orlicky DJ, et al. Cytoplasmic lipid droplet accumulation in developing mammary epithelial cells: roles of adipophilin lipid metabolism. J Lipid Res; 2007. p. 48:1463–1475.
Herrera E. Lipid metabolism in pregnancy its consequences in the fetus newborn. Endocrine; 2002. p. 19:43–55.
Suckling KE, Stange EF. Role of acyl-CoA: cholesterol acyltransferase in cellular cholesterol metabolism. J Lipid Res; 1985. p.647–671.
Neville MC, Picciano MF. Regulation of milk lipid synthesis composition. Annu Rev Nutr; 1997. p. 17:159–184.
Baldwin RL, Yang YT. Enzymatic metabolic changes in the development of lactation. In: Larson BL, Smith VR, editors. Lactation. Academic Press; NY, USA: 1974. p. 349–407
Boxer RB, Stairs DB, Dugan KD, et al. Isoform-specific requirement for Akt1 in the developmental regulation of cellular metabolism during lactation. Cell Metab; 2006. p. 475–490.
Berwick DC, Hers I, Heesom KJ, Moule SK, Tavare JM. The identification of ATP-citrate lyase as a protein kinase B (Akt) substrate in primary adipocytes. J Biol Chem; 2002. p. 277:33895–33900.
Wolins NE, Brasaemle DL, Bickel PE. A proposed model of fat packaging by exchangeable lipid droplet proteins. FEBS Lett; 2006. p. 580:5484–5491.
Larigauderie G, Cuaz-Perolin C, Younes AB, et al. Adipophilin increases triglyceride storage in human macrophages by stimulation of biosynthesis inhibition of β-oxidation. FEBS J. 2006. p. 273:3498–3510.
Ogg SL, Weldon AK, Dobbie L, Smith AJ, Mather IH. Expression of butyrophilin (Btn1a1) in lactating mammary gland is essential for the regulated secretion of milk-lipid droplets. Proc Natl Acad Sci USA; 2004. p. 101:10084–10089.