Digestion and Absorption of Milk Phospholipids in Newborns and Adults

Abstract

Milk polar lipids provide choline, ethanolamine, and polyunsaturated fatty acids, which are needed for the growth and plasticity of the tissues in a suckling child. They may also inhibit cholesterol absorption by interacting with cholesterol during micelle formation. They may also have beneficial luminal, mucosal, and metabolic effects in both the neonate and the adult. The milk fat globule membrane contains large proportions of sphingomyelin (SM), phosphatidylcholine (PC), and phosphatidylethanolamine (PE), and some phosphatidylserine (PS), phosphatidylinositol (PI), and glycosphingolipids. Large-scale technical procedures are available for the enrichment of milk fat globule membrane (MFGM) in milk replacement formulations and food additives. Pancreatic phospholipase A2 (PLA2) and mucosal phospholipase B digest glycero-phospholipids in the adult. In the neonate, where these enzymes may be poorly expressed, pancreatic lipase-related protein 2 probably has a more important role. Mucosal alkaline SM-ase and ceramidase catalyze the digestion of SM in both the neonate and the adult. In the mucosa, the sphingosine is converted into sphingosine-1-phosphate, which is both an intermediate in the conversion to palmitic acid and a signaling molecule. This reaction sequence also generates ethanolamine. Here, we summarize the pathways by which digestion and absorption may be linked to the biological effects of milk polar lipids. In addition to the inhibition of cholesterol absorption and the generation of lipid signals in the gut, the utilization of absorbed choline and ethanolamine for mucosal and hepatic phospholipid synthesis and the acylation of absorbed lyso-PC with polyunsaturated fatty acids to chylomicron and mucosal phospholipids are important.

Milk fat globule membrane plus milk fat increase docosahexaenoic acid availability in infant formulas

“…The MFGM consists of a bilayer of polar lipids, primarily phosphatidylcholine (PC), sphingomyelin (SM), cholesterol as well as cerebrosides, gangliosides, glycosylated proteins and polypeptides, filaments, mucins, lactadherin, butyrophilin, and others [1]. Polar lipids account for about 1% of milk fat [2]. In the last decade, the importance of milk phospholipids (PL) and of the MFGM in early life nutrition has been reported (e.g., for infant growth, brain and cognitive development, gut microbiome and maturation, and defense against infections) [3][4][5][6][7].…”

“…They occur predominantly in the triacylglycerol (TAG) form and to a lesser extent as part of milk MFGM (PL form). The MFGM provides physical properties to the milk fat globule that enhances TAG digestion [ 2 ]. The access of the gut to milk polar lipids and water-soluble choline and ethanolamine favors mucosal and hepatic PC and phosphatidyl-ethanolamine (PE) generation.…”

Transcriptome analysis of intestine from alk-SMase knockout mice reveals the effect of alk-SMase

“…Recently, some important biological effects of alk-SMase were reported [ 7 ]. Researchers purified the protein [ 8 , 9 ], cloned the gene [ 5 ] and found essential roles for the enzyme in phospholipid hydrolysis [ 4 , 10 ], anti-inflammation [ 11 ], anti-tumorigenesis [ 12 ], cell proliferation and cholesterol metabolism [ 13 ].…”

The nutritional functions of dietary sphingomyelin and its applications in food

“…The activity of BSSL depends on bile salts with the optimal pH 8.5. It is worth noting that there is almost no ceramide formation in the proximal intestine where BSSL is most active ( 101 , 102 ). All the digested products and bile acid (BA) can be assembled into micelles, which assist in crossing the unstirred water layer for entering the enterocytes.…”