Casein protective effect

A greater effect is apparent in postmenopausal women compared with men. The protein component seems to play a crucial role in the cardio-protective effect of soy. When soy-extracted phytoestrogens are added to animal-derived protein (casein), no effects on lipids are observed (Greaves et al., 1999). It is therefore clear that both the proteins from soy and the phytoestrogens need to be present to have a beneficial effect on lipid. In the presence of soy protein, the lipid-lowering effect is dose dependent on the phytoestrogen present (Crouse et al., 1999). 

The bioactivity of immunopeptides has been characterized by different in vitro and in vivo test systems. Casein-derived immunopeptides including fragments of agi- and (3-casein (Table V) have been shown to stimulate phagocytosis by murine macrophages, and to exert a protective effect against... 

Narisawa et al. (2008) demonstrated that protein fractions of skimmed milk provided protection against injury and inactivation of E. coli by high hydrostatic pressure treatment. The protective effect was found to increase with an increase in the concentration of protein in skimmed milk. Ramaswamy et al. (2009) indicated that casein and lactose present in milk were the major contributors for pressure protection of E. coli in milk during high-pressure treatment. Fat content in milk (0%-5%) had no significant influence on the destruction, however (Figure 5.13). 

Immunomodulating peptides. Enzymatic digests of human caseins contain immunomodulating peptides which stimulate the phagocytic activity of human macrophages in vitro and exert a protective effect in vivo in mice against Klebsiella pneumoniae infection. Two of the peptides were characterized as H.Val.Glu.Pro.Ile.Pro.Tyr (/6-CN f54-59) and H.Gly.Leu.Phe (origin not identified). 

Reynolds and del Rio (1984) found that both casein and whey proteins significantly reduced the extent of caries, with the former exerting the greater effect. Further evidence for the protective effect of casein was provided in a study on rats fed casein-enriched chocolate (Reynolds and Black, 1987). However, the palatibility of this innovative product was considered unacceptable for humans Concentrates containing various levels of whey protein, calcium, and phosphorus, but negligible amounts of casein, significantly reduced the incidence of dental caries in rats (Harper et al, 1987). Thus, there is evidence that milk proteins, calcium, and phosphate all exert an anticariogenic effect. 

While more research is necessary to define the precise mechanism(s) involved in the cariostatic effects of cheese, there is ample evidence to support the consumption of cheese at the end of a meal as an anticaries measure (Herod, 1991). Gedalia et al (1992) consider the most plausible mechanism for the protective effect of cheese to be related to the mineralization potential of casein-calcium phosphate of cheese and to the stimulation of saliva flow induced by its texture and/or flavor. 

Experiments with chemically induced colon cancer in the rat have partially, but not consistently, supported the dietary fiber hypothesis (12). Thus, Bauer et al. (13,14) recently reported that both high- and low-methoxylated pectin (6.5 or 5% in a diet containing 20% casein, 20% fat and no other dietary fiber) given during induction of colon cancer with subcutaneous 1.2-dimethyl— hydrazine, enhanced the yield of tumors. Guar gum, 5%, also tended to increase the tumor yield, although not significantly compared with controls on a virtually fiber-free diet. Others(15) however reported a protective effect of 15% pectin. 

In addition to essential fatty acids and vitamin E, dietary protein levels have been shown to play an important role in the toxicity of oxidized fats/oils. Witting et al. (1957), for example, observed an almost total lack of growth in rats fed a diet containing laboratory prepared heated com oil and 10% casein. With 20% casein in the diet, severe growth depression was still seen, but at 30% or more protein in the diet, only a mild effect was observed. While the mechanism of the protective effects of high dietary protein is not yet clear, it may be linked to an enhanced detoxification capability. Long-term feeding of thermally oxidized fats, for example, has been shown to be associated with an induction of hepatic microsomal enzymes (Andia and Street, 1975). 

Casein is the most important protein body in milk. Besides its chief function as nitrogenous food it plays the important role of protective colloid for the fat particles and also for calcium phosphate with which it forms a colloidal combination. It keeps the fat particles in a fine state of emulsion and prevents them from uniting into clots, probably due to the formation of a fine membrane around the particle. Casein may be precipitated from milk by acids. It is insoluble in water and also in the solutions of neutral salts, except sodium fluoride and potassium oxalate. Casein has acid properties, drives carbon dioxide out of carbonates, and is soluble in alkalis. The ammoniacal solution possesses a high protective effect toward colloidal gold. The gold number 0.01 indicates that it belongs therefore to the protective colloids of the first class. The behavior toward bases has been care-... 

Coagulation of Fat Particles. — The casein and the albumin act as protective colloids for the fat particles, hence it is necessary to offset this protective effect before the fat or butter can be obtained free from the casein. It is generally believed that the casein forms an envelope around the fat particles, but other explanations of protective action have been offered, f... 

Arsenic uptake in rabbit intestine is inhibited by phosphate, casein, and various metal-chelating agents (USEPA 1980). Mice and rabbits are significantly protected against sodium arsenite intoxication by (V-(2,3-dimercaptopropyl)phthalamidic acid (Stine et al. 1984). Conversely, the toxic effects of arsenite are potentiated by excess dithiols, cadmium, and lead, as evidenced by reduced food efficiency and disrupted blood chemistry in rodents (Pershagen and Vahter 1979). 

Kreuter and Speiser [77] developed a dispersion polymerization producing adjuvant nanospheres of polymethylmethacrylate) (PMMA). The monomer is dissolved in phosphate buffered saline and initiated by gamma radiation in the presence and absence of influenza virions. These systems showed enhanced adjuvant effect over aluminum hydroxide and prolonged antibody response. PMMA particles could be distinguished by TEM studies and the particle size was reported elsewhere to be 130 nm by photon correlation spectroscopy [75], The particle size could be reduced, producing monodisperse particles by inclusion of protective colloids, such as proteins or casein [40], Poly(methylmethacrylate) nanoparticles are also prepared... 

Although these experiments showed growth was possible using casein hydrolysate, Rose also demonstrated that when the amino acid mixture was used rather than the intact protein, additional calories had to be provided as fat plus carbohydrate, if nitrogen balance was to be maintained. It was later shown that the carbohydrate was needed to protect the free amino acids from oxidation in the intestinal epithelium in the course of absorption. Further, amino acids are poorly tolerated by mouth, causing vomiting and/or diarrhea. After World War II attempts to feed very emaciated prisoners in concentration camps with protein hydrolysates were unsuccessful. It was then recognized that osmotic effects from the amino acids were responsible for the unpleasant consequences. 

Kermack and Wright Biochem. J. XVII. 635,1923) have shown that gelatine at a of 4 T exerts but little protective power on a negative gum benzoin sol, acid gelatine precipitates the colloid in small concentrations whilst alkaline gelatine protects it. Similar observations have been made by Zsigmondy on the effect of casein on gold, but its exact isoelectric point was not established. 

Our interest in the effect of nutrition, especially dietary protein, was originally sparked by the studies of Madhavan and Gopalan (4) who were the first to show that low-protein (5% casein) diets completely protected rats from the hepatocarcinogenicity of AFBi, whereas diets containing 20% casein resulted in rats demonstrating the expected susceptibility. Wells et.al (4) later found that an 8% casein diet protected rats from AFBj induced liver tumors and the severity of liver involvement increased as dietary protein levels were increased from 22 to 30%. 

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