A Role for Milk Proteins and their Peptides in Cancer Prevention

Abstract

A role for the amount and type of dietary protein in the etiology of cancer has not been studied extensively. Nevertheless, there is no compelling evidence from epidemiological studies to indicate that protein, at levels usually consumed, is a risk factor for cancer. On the other hand, animal studies suggest that certain peptides and amino acids derived from dietary proteins may influence carcinogenesis. The predominant protein in milk, casein, its peptides, but not liberated amino acids, have antimutagenic properties. Animal models, usually for colon and mammary tumorigenesis, nearly always show that whey protein is superior to other dietary proteins for suppression of tumour development. This benefit is attributed to its high content of cystine/cysteine and gamma-glutamylcyst(e)ine dipeptides, which are efficient substrates for the synthesis of glutathione. Glutathione is an ubiquitous cellular antioxidant that directly or through its associated enzymes destroys reactive oxygen species, detoxifies carcinogens, maintains proteins in a reduced state and ensures a competent immune system. Various experiments showed that tumour prevention by dietary whey protein was accompanied by increased glutathione levels in serum and tissues as well as enhanced splenic lymphocyte proliferation, phagocytosis and natural killer, T helper and cytotoxic T cell activity. Whey protein components, beta-lactoglobulin, alpha-lactalbumin and serum albumin were studied infrequently, but results suggest they have anticancer potential. The minor component lactoferrin has received the most attention; it inhibits intestinal tumours and perhaps tumours at other sites. Lactoferrin acts by induction of apoptosis, inhibition of angiogenesis, modulation of carcinogen metabolising enzymes and perhaps acting as an iron scavenger. Supplementing cows with selenium increases the content of selenoproteins in milk, which on isolation inhibited colon tumorigenesis in rats.

Effects of trace elements and calcium on diabetes and obesity, and their complications: Protective effect of dairy products – A mini-review

“…Proteins are the best candidates with these properties [17,28]; specifically, they prevent oxidant effects of Fe in gut mucosa and liver (Fig. 1).…”

Acute and sub-acute toxicity studies of Passiflora nepalensis in rats

“…MPN increased the GSH-Px activity in liver. GSH-Px is an enzyme which prevents the generation of hydrogen peroxide and alkyl hydroperoxides in association with GSH and GSH-reductase, as well as the generation of more harmful metabolites such as the hydroxyl radical (Therond et al, 2000;Parodi, 2007). It also elevated the level of other endogenous antioxidant enzymes such as SOD and CAT in liver, in all the cases 160 and 320 mg/kg of MPN were most active.…”

Milk proteins-derived bioactive peptides in dairy products: molecular, biological and methodological aspects

“…Whey proteins contain lactoferrin, β-lactoglobulin, α-lactalbumin and serum albumin, and they were found to inhibit the growth of tumors more effectively than other food proteins [Parodi 2007]. In an acidic environment, α-lactalbumin forms the HAMLET (human α-lactalbumin made lethal to tumor cells) complex with oleic acid which inhibits the proliferation of various tumors by an apoptosislike mechanism [Svanborg et al 2003].…”

“…The combination of bioinformatics and chemometrics tools speeds up the screening of various peptide sources with high levels of biological activity and optimises the process of isolating (selected substrates) and identifying peptides in food products. The process of identifying and isolating peptides in a laboratory and in industrial applications is overviewed in Table 2 [Carrasco-Castilla et al , Korhonen and Pihlanto 2006, 2007, Langevin et al 2012, Minkiewicz and Dziuba 2009.…”