Butter, ghee, and cream products play an important role in supplying various health-enhancing components to the human diet. These components are found mainly in MFGM, CLA, and SCFAs. They aid in the prevention of various diseases, such as osteoporosis, cancer, atherosclerosis, and other degenerative disorders in humans. Some components are endowed with nutrients, such as peptides, lipids, minerals, and vitamins, which have bioactive properties along with beneficial effects, and they extend the lifespan of humans. During the manufacture of sour cream and butter, lactic acid bacteria are added, which can generate various metabolites during the fermentation process. These probiotic microorganisms exert their beneficial properties through two mechanisms, indirectly through supplementing metabolites and directly by providing live cells. The sphingolipids and their metabolites have health-enhancing functions, including antimicrobial activity on certain pathogens like Listeria monocytogenes, inhibition of colon cancer, and regulation of the immune system. Dahi, a fat-enriched Indian sour cream product made from milk, has various health beneficial activities because of the rich supply of lactic acid bacteria and their metabolites produced during the fermentation (Vijayendra et al., 2008).
Milk fat globule membrane –
MFGM is a highly structured membrane that surrounds the milk fat globules and contains unique beneficial lipids and specific proteins. The primary lipids of MFGM are polar lipids and significant amounts of neutral lipids, such as cholesterol, triglycerides, diglycerides and monoglycerides (Wooding & Kemp, 1975). Isolation methods have identified the content of the MFGM neutral lipids, particularly triglycerides (Walstra, 1974, 1985; Kwak et al., 1989). Health attributes of MFGM mainly involve the polar lipids, such as sphingomyelin, phosphatidyl ethanolamine, phosphatidyl inositol, phosphatidyl choline, phosphatidyl serine, glucosylceramide, lactosylceramide, and gangliosides (Deeth, 1997; Danthine et al., 2000). In addition, some MFGM proteins are found to have health benefits, for example, fatty acid binding protein, xanthine dehydrogenase/ oxidase (XDH/XO), butyrophilin, BRCA2, and BRCA1.
Health benefits of MFGM polar lipids –
MFGM polar lipid fractions consist mainly of sphingolipids and glycerophospholipids. Sphingolipids are functional ingredients because of the presence of health beneficial components, such as sphingomyelin and its metabolites including sphingosine and ceramide (Schmelz et al., 2000). The metabolites of sphingolipids serve as second messengers that play a vital role in various cell activities, such as regulation, proliferation, and growth (Futerman & Hannun, 2004). Some metabolites have an opposite function in the cell: sphingosine and ceramide are antimitogenic and inhibit cell growth (Sweeney et al., 1998) while sphingosine 1-phosphate (S1P) is mitogenic. Defects in serine palmitoyl transferase suggest that exogenous feeding of sphingolipids is necessary for cell growth. Sphingomyelin is sequentially hydrolyzed by various intestinal enzymes and results in the synthesis of ceramide and sphingosine. These metabolites are easily absorbed by the intestine.
Small amounts of ingested metabolites are excreted in feces (Nilsson, 1969). Some studies report that feeding rats with sphingomyelin benefited neonatal gut maturation during suckling (Oshida et al., 2003).
Sphingolipids: anticholesterol effect and heart disease –
In the group of sphingolipids, sphingomyelin was found to minimize the intestinal uptake of cholesterol and other fats in rats (Noh & Koo, 2003). Pharmacological inhibition in the metabolism of sphingolipids can lead to obesity and cardiovascular diseases. The inhibitory effect was found to be greater with milk-derived sphingomyelin than egg-derived sphingomyelin by the direct inhibitory effect of the sphingomyelin long-chain fatty acyl group on lipolysis in the rumen (Noh & Koo, 2004; Spitsberg, 2005). An interaction was favored by saturation of the sphingomyelin long-chain fatty acyl chain (Eckhardt et al., 2002). Dietary uptake of sphingolipids also plays an important role in lowering plasma triacylglycerol and cholesterol (Duivenvoorden et al., 2006). It helps in preventing cardiovascular disease, deposition of fat in the liver, and other inflammatory diseases. Sphingolipid metabolites, such as ceramide and ganglioside GM3, are also assumed to play a major role in the process. However, over-uptake may also lead to the risk of certain metabolic disorders (Parillo & Riccardi, 2004). Lysosphingolipids present in high-density lipoprotein (HDL) are also found to be beneficial for the heart (Podrez, 2010). It protects the heart by releasing nitric oxide (Nofer et al., 2004). In a different study, a positive correlation was observed between neutral and acid sphingomyelinase activity and atherosclerosis (Pavoine & Pecker, 2009).
Sphingolipids and cancer –
Sphingolipid levels and the enzymes involved in metabolizing sphingolipids are found to be altered in cancer (Ryland et al., 2011). Dietary intake has positive effects on the progression of cancer; however, the mechanism is not clear. The rapid turnover of intestinal cells is delayed in cancer, and sphingomyelin showed benefits through ceramide and sphingosine by inducing cell differentiation and apoptosis (Merrill et al., 2001). Inhibitory levels of sphingolipids were found at both stages of colon tumorigenesis in mice, and also in the shift from malignant to benign in adenocarcinomas. A decrease in activity of sphingomyelinase may limit the production of certain metabolites that may have anticancer effects on colon cells. Even though sphingolipids have been found to have anticancer properties, human trials have not yet confirmed this. Some sphingomyelin metabolites, such as ceramide, were found to have antitumor effects, whereas sphingosine was found to be mutagenic through its metabolites (Zhang et al., 1990). However, some concentrations of sphingolipids had detectable effects in mice and humans (Vesper et al., 1999).
Sphingolipids: bactericidal effect –
Sphingolipids have been found to be protective against certain types of bacteria, viruses, and certain toxins through competitive inhibitory mechanisms. Among the sphingolipids, glycosphingolipids act as a membrane receptor that induces signaling and mediates infection via the membrane (Kaida & Kusunoki, 2010). Supplementing the diet with sphingolipids may prevent bacterial adhesion and shift the microbial load to the colon. Supplementation of certain sphingolipids in infant diets was found to increase the level of pathogenic bacteria in feces (Sprong et al., 2001). However, certain sphingolipid metabolized products, such as ceramide, were found not to be bactericidal, whereas lysosphingomyelin had greater bactericidal effects against L. monocytogenes (Sprong et al., 2001).
Sphingolipids: effects on diabetes mellitus and Alzheimer disease –
Sphingolipid metabolites serve as promoters and inhibitors for diabetes mellitus. Both types of diabetes mellitus occur because of reduced β-cell mass, which ultimately leads to decreased proliferation and increased apoptosis of liver cells (Hui et al., 2004). It also leads to insufficient amounts of insulin. The different metabolites of sphingolipids serve as regulators of β-cell survival, proliferation, and function. Oversupply of nutrients, in particular, fatty acids, may lead to metabolic disorders (Parillo & Riccardi, 2004). Metabolites, such as ceramide, produced due to excessive deposition of saturated fat, can inhibit the production of insulin by inducing β-cell apoptosis (Kelpe et al., 2003; Maedler et al., 2003). Some ceramide glycosylated derivatives, such as gangliosides, have been found to be antigens in certain autoimmune diseases (Misasi et al., 1997). Certain glycosphingolipid derivatives have a vital role in Alzheimer disease. The conformational change of amyloid β-protein from coiled to the more ordered β-sheet is facilitated by binding gangliosides. Age-related diseases are also associated with sphingolipids. In most tissues, changes in the content of sphingomyelin may lead to aging. Metabolized products, such as ceramide, act as senescence mediators in aging cell culture models (Vesper et al., 1999).
Sphingolipids and multiple sclerosis –
Multiple sclerosis affects more women than men and there are an estimated 400 000 patients in the USA (Compston & Coles, 2008). This chronic demyelinating disease is characterized by infiltrates in the central nervous system that leads to disability. Sphingolipids and their metabolites play an important role in the disease (Walter & Fassbender, 2010). They act as mediators of S1P, which binds to receptors of S1P1 and S1P4 on lymphocytes. The levels of expression on lymphocytes are varied: higher amounts are found in the lymph nodes and lower levels in the bloodstream (Lo et al., 2005).
Phospholipids are essential fatty acids and are essential for all living cell membranes, especially brain cells. They are bipolar in structure, which is essential for the biological functions of the cell membrane and provides stability. They comprise phosphatidylcholine (lecithin), phosphatidyl serine, phosphatidyl ethanolamine, and phosphatidylinositol. A few recent studies have reported the health benefits of MFGM phospholipids in lipid metabolism. Wat et al. (2009) reported that diets rich in phospholipids from dairy extracts reduced lipid levels in mice on a high-fat diet. A similar study reported that in mice the accumulation of cholesterol in hepatic cells was reduced after feeding them milk rich in phospholipids, with a significant increase in fecal cholesterol (Kamili et al., 2010). Health benefits vary with the concentration of phospholipids; phosphatidylserine had limited significance since the concentration is very low in dairy products (Rombaut & Dewettinck, 2006). Supplementation of phosphatidylserine in exercising humans altered endocrine function and well-being. Supplementation with 200mg/day of phosphatidylserine showed improvements in patients with Alzheimer disease (Heiss et al., 1994; Hashioka et al., 2004). Milk phospholipids play an important protective role in the duodenal mucosa of humans (Kivinen et al., 1992). Digested phospholipids, such as lysophosphatidylcholine, have a greater protective role against bacteria (van Rensburg et al., 1992). However, some lysophosphatidylcholine has a moderate sensitivity to Gram-positive bacteria and are not sensitive to Gram-negative bacteria (Sprong et al., 2001). Toxic and chemical attacks are prevented by phosphatidylcholine, which leads to less damage to the liver (Kidd, 2002). In infants, life-threatening toxic attacks on the gastrointestinal mucosa were prevented by phosphatidylcholine (Carlson et al., 1998). It also acts as a good source of choline, which helps in the synthesis and transport of neurotransmitters that aid in the development of the brain (Blusztajn, 1998). Furthermore, gastrointestinal digested phospholipid compounds also exhibit antimicrobial activity (van Hooijdonk et al., 2000).