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Role of Lingual and Gastric Lipases in Fat Digestion and Absorption
Published in Margit Hamosh, Lingual and Gastric Lipases: Their Role in Fat Digestion, 2020
The lactating mammary cells of several species contain two populations of fat droplets: relatively smaller ones (<1.5 μm) occurring throughout the cells and larger ones (>1.5 μm) found mainly in the apical (secretory) region of the cell. These larger droplets which account for almost all the fat in milk37, 45 appear to be in contact with the plasma membrane during the major part of their growth (3 to 4 h) (Table 3).40 The size and distribution of fat globules in human colostrum and milk indicate the presence of three subpopulations. The diameter of the globules increases from an average of 1.5 μm in colostrum to 4.0 μm in mature milk.46 The latter contain almost all the milk fat but amount to only 10 to 30% of total globules. In mature milk, globules less than 1 μm contain only a few percent of total fat but amount to 70 to 90% of the total number of globules (Table 4). The milk fat globule membrane comprises about 2% of the total weight of milk fat. Its thickness, which varies in different areas, is in the range of 5 to 50 nm.
Epithelial Membrane Antigen (EMA)
Published in Masahiko Mori, Histochemistry of the Salivary Glands, 2019
Epithelial membrane antigen (EMA) is a high molecular weight glycoprotein, low in protein and high in carbohydrate, with galactose and N-acetylgalactosamine residues as major sugars. It is isolated from human milk fat globule membrane.1 Polyclonal and monoclonal antibodies to EMA have been used in pathologic studies.2–8 Immunohistochemical deposition of EMA has been found at luminal surfaces of glandular structures, lateral borders of acinar cells, and in cytoplasms of squamous-cells of tumors. Reactivity of EMA is limited to human tissues. EMA does not cross-react to the other species. Immunohistochemical methods have detected EMA in normal human salivary glands, obstructive lesions, and many types of tumors.9,10 Two patterns appear in salivary gland lesions: surface-positive and whole cell-positive types.9 The former distribution is similar to carcinoembryonic antigen (CEA) when polyclonal CEA antibody is used, but is different when monoclonal CEA antibody is used. EMA immunohistochemistry may be used in diagnostic surgical pathology for epithelial, mesenchymal, and hematopoietic tumors in paraffin sections.11–14
The stomach and gastric function
Published in Paul Ong, Rachel Skittrall, Gastrointestinal Nursing, 2017
Fat digestion begins in the stomach. Gastric fat digestion is also much more significant in infants than it is in adults. The enzymes responsible for catalysing (breaking down) fats in the stomach originate from two sources: lingual lipase comes from the lingual serous glands in the mouth and gastric lipase from the gastric mucosa. Gastric lipase breaks down fats to free fatty acids and diglycerol and is important for releasing fatty acids from milk. Gastric lipase is active in the relatively low pH environment of the infants. By the age of 3 months the pH is even lower and this inactivates much of the gastric lipase. Fatty acids are essential for infant development, particularly brain, retinal and growth development. Triglyceride is the main energy source of the neonate. Other lipases such as pancreatic lipase and bile salt-dependent lipase are active in the small intestine and convert the triglyceride to monoglyceride which can then be absorbed. The activity of lingual and gastric lipase is essential because, unlike pancreatic and bile salt-dependent lipase, they are able to penetrate the phospholipid component of the milk fat globule membrane and hydrolyse triglycerides. Therefore the partial hydrolysis of fat in the stomach is a prerequisite for the completion of digestion and absorption of fatty acids and monoglycerol in the small intestine. Bile salts also contribute to the breaking down of the milk fat globule membrane.
Cohousing-mediated microbiota transfer from milk bioactive components-dosed mice ameliorate colitis by remodeling colonic mucus barrier and lamina propria macrophages
Published in Gut Microbes, 2021
Cong Liu, Shimeng Huang, Zhenhua Wu, Tiantian Li, Na Li, Bing Zhang, Dandan Han, Shilan Wang, Jiangchao Zhao, Junjun Wang
Human milk oligosaccharides (HMOs) and milk fat globule membrane (MFGM) are highly abundant in breast milk.24,25 HMOs resist gastrointestinal hydrolysis and digestion by pancreatic and brush-border enzymes, and are thus not absorbed in high amounts.26 Instead, they serve as prebiotic substrates for the gut microbes.27 Recent evidence has indicated that HMOs facilitate the gut microbiota establishment, promote intestinal development and stimulate immune maturation.27–29 Considering these beneficial effects and therapeutic potential of HMOs, mixtures of fructo-oligosaccharides (FOS), and galacto-oligosaccharides (GOS) have therefore been developed to resemble the molecular size distribution of the natural HMOs fraction found in human milk. Furthermore, they mimic the prebiotic from human milk, and are accessible to the gut microbiota.30 Therefore, the combination of FOS, and GOS could be used to examine the effects of HMOs on the gut microbial composition and intestinal epithelial barrier function.31 Also, MFGM has been shown to play an important role in modulating intestinal immune responses and the gut microbiota function.32–35 However, the roles of HMOs and MFGM in IBD remain unclear.
A complete proteomic profile of human and bovine milk exosomes by liquid chromatography mass spectrometry
Published in Expert Review of Proteomics, 2021
Kanchan Manohar Vaswani, Hassendrini Peiris, Yong Qin Koh, Rebecca J. Hill, Tracy Harb, Buddhika J. Arachchige, Jayden Logan, Sarah Reed, Peter S. W. Davies, Murray D. Mitchell
Four major proteins of interest lactadherin (MFG-E8), butyrophilin, perilipin-2, and xanthine oxidase were present in both the human and bovine milk exosomes used in this study. These proteins are commonly mentioned in the literature of the ‘total’ milk proteome [1]. Interestingly, these four proteins are major components of the milk fat globule membranes (MFGM) [20]. One function of MFGM is that it enables the fat to remain dispersed and ensures structural integrity of milk [21]. MFGM is a unique structure in milk that originates from both the apical plasma membrane of the lactocyte and the more internal cellular elements (reticulum membrane and cytosolic proteins) [22]. On the other hand, exosomes have an endocytic origin. Unlike exosomes, the MFGM protein group has been extensively characterized [18], and MGFM proteins can make up a significant proportion of the milk proteome (approx. 1–4%). Other proteins detected in this study, such as mucin-1, CD36, and fatty acid-binding protein (which were found common to exosomes from both species (Figure 1)) have also been found in MFGM and they help to stimulate intestinal epithelial health, promote gastric stability, and are involved in the antimicrobial (antiviral and antibacterial) activities in the infant gastrointestinal tract [23]. Although the MFGM may be similar in protein composition to an exosome, they have a unique complex triple membrane layer, while the exosomes have a double-membrane structure much like a cellular bilayer [24]. Due to these differences, the lipid compositions vary greatly between different types of vesicles [25]. While some are similar in size, the bulk of the MGFMs is larger than a typical exosome and the MGFM falls in the micrometer range (100x to 200X the size of an exosome). The lipid fraction of the MFGM accounts for half of its composition by weight [26]. MFGMs are found in the cream layer of milk [27], while the exosomes are obtained after removal of all the fat over several centrifugation steps.