The influence of dietary proteins on colon cancer risk

Hemin, a major heme molecule, induced cellular and genetic alterations in normal colonic and colon cancer cells

Heme, a molecule abundant in red meat, is assumed to exert carcinogenic effects on normal colonic cells and tumour suppressive effects on cancer cells, though the hypothesis has not been explicitly proven yet. The present study aims to investigate hemin induced cytotoxic, genetic and biological alterations in both normal and cancerous colonic epithelial cells, which may imply its carcinogenic and anticarcinogenic properties. Normal colonic epithelial cells and colon carcinoma cells were treated with a 0-500 µM concentration of hemin for 1-4 days following which cytotoxicity and wound healing assays, western blot, rt-PCR and cell cycle analysis were performed. Interestingly, hemin was cytotoxic to normal colonic cells, but carcinoma cells were more resistant. Cell migration potential of both normal colonic cells and colon carcinoma cells was impeded by hemin. Hemin caused upregulation of both P53 and β-catenin gene and proteins expression in normal colonic cells with concomitant cell cycle arrest at G1(Gap 1) and G2/M (Gap 2/ Mitosis). G1 and G2 cell cycle arrests were also observed in colon carcinoma cells. In conclusion, the present study confirms that hemin, a main heme molecule present in red meat, facilitates behavioural, genetic and cell cycle kinetic alterations in both normal colonic epithelial and colon carcinoma cells.

Dual Effects of High Protein Diet on Mouse Skin and Colonic Inflammation

Chronic inflammation is a major etiology of cancer. Accumulating epidemiological and experimental evidences suggest that intake of high protein diet (HPD) is associated with colitis-associated colon cancer, however, most of the studies were confined in colon. Systemic influence of HPD on inflammation indices in different tissues of an organism has never been studied. We therefore investigated the effect of HPD on mouse skin and colonic inflammation using the well characterized inflammation induction protocol in both tissues (12-O-tetradecanoylphorbol-13-acetate [TPA] for skin and dextran sodium sulfate [DSS] for colon). ICR mice were grouped to normal diet (ND, 20% casein) or HPD (50% casein) groups. In each diet group, mice were treated with either vehicle (acetone or H₂O), TPA, TPA and DSS, or DSS. Experimental diet was fed for total 4 weeks. After 1 week of diet feeding, 6.5 nmol of TPA was topically applied twice a week for 2 weeks on the shaved mouse dorsal skin. Drinking water containing 2% DSS was administered for 7 days at the final week of experiment. The results showed that TPA-induced skin hyperplasia, epidermal cell proliferation, and cyclooxygenase-2 (COX-2) expression were reduced in HPD group compared to ND group. In contrast, HPD increased DSS-induced colon mucosal hyperplasia, colonocyte proliferation, COX-2 expression, and plasma nitric oxide compared to ND group. This suggests that HPD exerts differential effect on different tissue inflammation which implies efficacy of protein intervention to human also should be monitored more thoroughly.

Role of diets rich in omega-3 and omega-6 in the development of cancer

Over the past decade, some studies have addressed the therapeutic effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) and the opposite effects of omega-6 (ω-6) PUFAs on several diseases, including cardiovascular disorders, diabetes, neurodegenerative diseases, and cancer. Research demonstrates the safety of these naturally occurring ingredients. Of particular interest, several studies have shown that ω-3 PUFAs possess a therapeutic role against certain types of cancer. It is also known that ω-3 PUFAs can improve the efficacy and tolerability of chemotherapy. Previous reports have indicated that suppression of nuclear factor-κB, activation of AMPK/SIRT1, modulation of cyclooxygenase (COX) activity, and up-regulation of novel anti-inflammatory lipid mediators such as protectins, maresins, and resolvins, are the main mechanisms of the antineoplastic effect of ω-3 PUFAs. In contrast, several studies have demonstrated that ω-6 PUFAs induce progression in certain types of cancer. In this review, we discuss epidemiological and experimental studies addressing the relationship between the development of some types of cancer, including colon and colorectal carcinoma, breast cancer, prostate cancer, lung cancer and neuroblastoma, and the ingestion to ω-3 and ω-6 (PUFAs). We also discuss the clinical data, addressing the therapeutic role of omega-3 PUFA against different types of cancer.

Selective induction of apoptosis in human gastric cancer cells by Lactobacillus kefiri (PFT), a novel kefir product

The present study was undertaken to evaluate the effect of Lactobacillus kefiri (PFT), a novel kefir product, on apoptosis of gastric cancer cells (AGS), breast cancer cells (4T1), and human peripheral blood mononuclear cells (PBMCs). Cells were cultured with PFT and apoptosis was determined by flow cytometry using 7-AAD dye and cytospin preparation. Mitochondrial dysfunction and expression of Bcl2 were monitored by flow cytometry. Results showed that PFT induced apoptosis in AGS gastric cancer cells in a dose-dependent manner. Apoptosis was detected at a concentration of 0.3 mg/ml (20.8%), increased to 25.8% at 0.6 mg/ml, 37% at 1.2 mg/ml, 53.1% at 2.5 mg/ml, and peaked at 66.3% at 5.0 mg/ml. Apoptosis is associated with the decreased polarization of mitochondrial membrane potential (MMP) and decreased Bcl2 expression. PFT-treated AGS cells manifested membrane blebbing, nuclear condensation, and fragmentation as identified in cytospin cytocentrifuge Giemsa stained preparations. On the other hand, flow cytometry analysis showed that PFT did not induce apoptosis in 4T1 breast cancer cells nor in PBMCs. These results suggest that PFT is safe for white blood cells and selectively induces apoptotic effects in gastric cancer cells. Hence, it may have potential as a therapeutic agent for the treatment of gastric cancers.

Usage of whey protein may cause liver damage via inflammatory and apoptotic responses

The purpose of this study was to investigate the long- and short-term inflammatory and apoptotic effects of whey protein on the livers of non-exercising rats. Thirty rats were divided into three groups namely (1) control group, (2) short-term whey (WS) protein diet (252 g/kg for 5 days), and (3) long-term whey (WL) protein diet (252 g/kg for 4 weeks). Interleukin 1β (IL-1β), IL-6, tumor necrosis factor α (TNF-α), and cytokeratin 18 (CK-18-M30) were assessed using enzyme-linked immunosorbent assay and immunohistochemical methods. Apoptosis was evaluated using the terminal transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) method. Hepatotoxicity was evaluated by quantitation of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Based on the biochemical levels and immunohistochemical results, the highest level of IL-1β was identified in the WL group (p < 0.01). The IL-6 and TNF-α results were slightly lower in the WS group than in the control group and were highest in the WL group (p < 0.01). The CK-18-M30 and TUNEL results were highest in the WS group and exhibited medium intensity in the WL group (p < 0.01). AST results were statistically significant for all groups, while our ALT groups were particularly significant between the WL and control groups (p < 0.01). The results showed that when whey protein is used in an uninformed manner and without exercising, adverse effects on the liver may occur by increasing the apoptotic signal in the short term and increasing inflammatory markers and hepatotoxicity in the long term.

Partial chemical and functional characterization of milk whey products obtained by different processes

Whey protein samples (S-1 to S-5) were tested in vivo and in vitro for nutritional properties and selected bioactivities. Weanling male Wistar rats fed modified AIN-93G (12 g protein.100 g-1) diets for 21 days were used the in vivo studies. The nutritional parameters did not differ among the protein diets tested. Erythrocyte glutathione content was considered high and was higher for S-3, but liver glutathione was the same for all dietary groups. For S-3, cytokine secretion (IL-10 and TNF-α) by human peripheral blood mononuclear cells (in RPMI-1640 medium) was higher in the absence of antigen than in the presence of BCG antigen. Interleukin-4 secretion was repressed in all treatments. The IC50, whey protein concentration required to inhibit 50% of the melanoma cell proliferation, was 2.68 mg.mL-1 of culture medium for the S-3 sample and 3.66 mg.mL-1 for the S-2 sample. Based on these results, it was concluded that S-3 (whey protein concentrate enriched with TGF-β and lactoferrin) produced better nutritional and immunological responses than the other products tested.

Influência das proteínas do soro sobre enzimas hepáticas, perfil lipídico e formação óssea de ratos hipercolesterolêmicos

OBJETIVO: Avaliar o efeito do consumo das proteínas do soro do leite sobre parâmetros do metabolismo lipídico, hepático e renal, a formação óssea e as defesas antioxidantes de ratos submetidos à dieta hipercolesterolemiante. MÉTODOS: Trinta e dois ratos Fisher adultos foram divididos em 4 grupos, recebendo as seguintes dietas: grupo C, dieta padrão; grupo H, dieta hipercolesterolemiante; grupo PS, dieta padrão e proteínas do soro; grupo PSH dieta hipercolesterolemiante e proteínas do soro. A ingestão alimentar e o ganho de peso foram monitorados semanalmente. Após 8 semanas, o sangue dos animais foi coletado para dosagem bioquímica e os animais foram eutanasiados. Foram utilizados os testes estatísticos, análise de variância e o teste de Tukey. RESULTADOS: As proteínas do soro não reduziram o colesterol plasmático de forma significante, e promoveram um aumento na concentração plasmática de triacilgliceróis nos animais hipercolesterolêmicos. No entanto, reduziram a atividade da aspartato aminotransferase e da fosfatase alcalina, assim como a concentração plasmática de creatinina. Não se observou nenhum efeito sobre as defesas antioxidantes avaliadas. As dietas contendo as proteínas do soro geraram ossos mais pesados, com maior diâmetro e comprimento que as dietas contendo caseína. CONCLUSÃO: As proteínas do soro não apresentaram um efeito hipocolesterolemiante significante em ratos. No entanto, impediram de forma significante a ocorrência de alterações nos parâmetros indicadores das funções hepáticas e renais provocadas pela dieta hipercolesterolemiante. Os dados sugerem também que as proteínas do soro afetam positivamente a formação óssea, quando comparados com as dietas contendo caseína como fonte protéica.

Egg yolk proteins suppress azoxymethane-induced aberrant crypt foci formation and cell proliferation in the colon of rats

Dietary proteins can influence colonic carcinogenesis; some proteins have a promotional effect, whereas others exhibit a preventive effect. Dietary egg yolk proteins have been reported to suppress the expression of colon tumors in rats. In this study, we investigated the effect of consumption egg yolk proteins on cell proliferation in a rat model of azoxymethane (AOM)-induced colon cancer. We hypothesize, based on the literature of egg yolk protein actions, that they protect against colon tumor development. Therefore, male F344 rats were fed a purified AIN-93G diet containing either 20% casein (control) or 20% egg yolk proteins for 5 weeks. After 1 week on the experimental diet, the rats were administered weekly subcutaneous injections of saline or AOM for 2 weeks to induce aberrant crypt foci. Rats were administered an intraperitoneal injection of 5-bromo-2'-deoxyuridine 1 hour before being euthanized for examination of DNA synthesis in the colonic mucosa. The contents of the cecum were analyzed for the presence of short-chain fatty acids (SCFAs). In the AOM-injected rats, the yolk protein diet suppressed aberrant crypt foci formation and reduced the proliferative 5-bromo-2'-deoxyuridine-labeling index in the proximal colon when compared with the control diet. A significant increase in cecal SCFAs was observed in the rats that were fed egg yolk proteins. These results indicate that dietary egg yolk proteins have a preventive effect on AOM-induced large bowel carcinogenesis in rats; it exerts this effect by altering cell proliferation through SCFA production. This study suggests that the consumption of egg yolk proteins might be protective against colon carcinogenesis.

Differential effects of dietary whey, casein and soya on colonic DNA damage and large bowel SCFA in rats fed diets low and high in resistant starch

Feeding higher levels of dietary animal protein (as casein or red meat) increases colonic DNA damage and thins the colonic mucus barrier in rats. Feeding resistant starch (RS) reverses these changes and increases large bowel SCFA. The present study examined whether high dietary dairy (casein or whey) or plant (soya) proteins had similar adverse effects and whether dietary RS was protective. Adult male rats were fed diets containing 15 or 25 % casein, whey or soya protein with or without 48 % high amylose starch (as a source of RS) for 4 weeks. DNA damage was measured in isolated colonocytes using the comet assay. Higher dietary casein and soya (but not whey) increased colonocyte DNA damage. DNA damage was highest with soya when fed at 15 or 25 % protein without RS. Dietary RS attenuated protein-induced colonocyte DNA damage in all groups but it remained significantly higher in rats fed 25 % soya compared with those fed 15 % protein. Dietary protein level did not affect colonic mucus thickness overall but the barrier was thinner in rats fed high dietary casein. This effect was reversed by feeding RS. Caecal total SCFA and butyrate pools were higher in rats fed RS compared with digestible starch. Caecal and faecal SCFA were unrelated to genetic damage but correlated with mucus thickness. The present data confirm that higher dietary protein affected colonocyte DNA and colonic mucus thickness adversely but that proteins differ in their effects on these indices of colon health. The data show also that these changes were reversed by RS.

Effects of amino acid-derived luminal metabolites on the colonic epithelium and physiopathological consequences

Depending on the amount of alimentary proteins, between 6 and 18 g nitrogenous material per day enter the large intestine lumen through the ileocaecal junction. This material is used as substrates by the flora resulting eventually in the presence of a complex mixture of metabolites including ammonia, hydrogen sulfide, short and branched-chain fatty acids, amines; phenolic, indolic and N-nitroso compounds. The beneficial versus deleterious effects of these compounds on the colonic epithelium depend on parameters such as their luminal concentrations, the duration of the colonic stasis, the detoxication capacity of epithelial cells in response to increase of metabolite concentrations, the cellular metabolic utilization of these metabolites as well as their effects on colonocyte intermediary and oxidative metabolism. Furthermore, the effects of metabolites on electrolyte movements through the colonic epithelium must as well be taken into consideration for such an evaluation. The situation is further complicated by the fact that other non-nitrogenous compounds are believed to interfere with these various phenomenons. Finally, the pathological consequences of the presence of excessive concentrations of these compounds are related to the short- and, most important, long-term effects of these compounds on the rapid colonic epithelium renewing and homeostasis.

Dietary whey protein lowers serum C-peptide concentration and duodenal SREBP-1c mRNA abundance, and reduces occurrence of duodenal tumors and colon aberrant crypt foci in azoxymethane-treated male rats

We evaluated partially hydrolyzed whey protein (WPH) for inhibitory effects on the development of colon aberrant crypt foci (ACF) and intestinal tumors in azoxymethane (AOM)-treated rats. Pregnant Sprague-Dawley rats and their progeny were fed AIN-93G diets containing casein (CAS, control diet) or WPH as the sole protein source. Colons and small intestines from the male progeny were obtained at 6, 12, 20 and 23 weeks after AOM treatment. At 6 and 23 weeks, post-AOM, WPH-fed rats had fewer ACF than did CAS-fed rats. Intestinal tumors were most frequent at 23 weeks, post-AOM. At this time point, differences in colon tumor incidence with diet were not observed; however, WPH-fed rats had fewer tumors in the small intestine (7.6% vs. 26% incidence, P=.004). Partially hydrolized whey protein suppressed circulating C-peptide concentration (a stable indicator of steady-state insulin secretion) at all four time points relative to the corresponding CAS-fed animals. The relative mRNA abundance for the insulin-responsive, transcription factor gene, SREBP-1c, was reduced by WPH in the duodenum but not colon. Results indicate potential physiological linkages of dietary protein type with circulating C-peptide (and by inference insulin), local expression of SREBP-1c gene and propensity for small intestine tumorigenesis.

Functional Foods: A Survey of Health Claims, Pros and Cons, and Current Legislation

Functional foods stand for a new category of remarkably promising foods bearing properties (i.e., low cholesterol, antioxidant, anti-aging, anticancer, etc.) that have already rendered them quite appealing. There are many classes offunctionalfoods (pro- and pre-biotics, dietary fiber, low fat, etc.), and their definition is occasionally confused with that of nutraceuticals and novel foods. Consumers' main skepticism regarding functional foods resides in the veracity of health claims and in the low and often inadequate control of their claimed properties. Legislation concerning this matter is progressing at an extremely low pace and currently only Japan, the U.K., U.S.A., and Scandinavian countries have managed to make notable progress. Moreover, the labeling of functional foods is far from informative, providing scanty information about nutritional value, storage, and cooking recipes. It is anticipated that technological advances in the food industry, in conjunction with extensive clinical trials and governmental control, will eventually guarantee the credibility of health claims and ensure consumers' confidence in functional foods.

Meat as a component of a healthy diet - are there any risks or benefits if meat is avoided in the diet?

Meat is frequently associated with a "negative" health image due to its "high" fat content and in the case of red meat is seen as a cancer-promoting food. Therefore, a low meat intake, especially red meat is recommended to avoid the risk of cancer, obesity and metabolic syndrome. However, this discussion overlooks the fact, that meat is an important source for some of micronutrients such as iron, selenium, vitamins A, B12 and folic acid. These micronutrients are either not present in plant derived food or have poor bioavailability. In addition, meat as a protein rich and carbohydrate "low" product contributes to a low glycemic index which is assumed to be "beneficial" with respect to overweight, the development of diabetes and cancer (insulin resistance hypothesis). Taken together meat is an important nutrient for human health and development. As an essential part of a mixed diet, meat ensures adequate delivery of essential micronutrients and amino acids and is involved in regulatory processes of energy metabolism.

Propriedades fisiológicas-funcionais das proteínas do soro de leite

O presente artigo coloca em destaque as propriedades multifuncionais das proteínas presentes no soro de leite bovino, a começar pelo colostro que contém essas proteínas em concentrações muito elevadas e que tem por função garantir a proteção e a imunidade dos recém-nascidos. Essas mesmas proteínas continuam no leite, porém em concentrações bastante reduzidas. A utilização dessas proteínas nas formas de concentrados e isolados protéicos evidenciam propriedades muito favoráveis à saúde no sentido de diminuir o risco de doenças infecciosas e também as consideradas crônicas e/ou degenerativas. Enfatizou-se as propriedades das proteínas do soro de leite e de peptídios delas resultantes no estímulo ao sistema imunológico, na proteção contra microrganismos patogênicos e contra alguns tipos de vírus como o HIV e o vírus da hepatite C, na proteção contra vários tipos de câncer, particularmente de cólon, na proteção da mucosa gástrica contra agressão por agentes ulcerogênicos, evidenciou-se várias linhas de ação protetora das proteínas de soro contra agentes condicionadores de problemas cardiovasculares. Com base em várias propriedades funcionais das proteínas do soro de leite, discutiu-se a vantagem e os benefícios de seu uso como suplemento alimentar para atletas e esportistas em geral. Os possíveis benefícios de vários fatores de crescimento celular, presentes no soro de leite também foram discutidos.

Feeding of soy protein isolate to rats during pregnancy and lactation suppresses formation of aberrant crypt foci in their progeny's colons: interaction of diet with fetal alcohol exposure

Soy protein isolate (SPI) in the diet may inhibit colon tumorigenesis. We examined azoxymethane (AOM)-induced aberrant crypt foci (ACF) in male rats in relation to lifetime, pre-weaning, or post-weaning dietary exposure to SPI and also within the context of fetal alcohol exposure. Pregnant Sprague Dawley rats were fed AIN-93G diets containing casein (20%, the control diet) or SPI (20%) as the sole protein source starting on gestation day 4 (GD 4). Progeny were weaned on postnatal day (PND) 21 to the same diet as their dams and were fed this diet until termination of the experiment at PND 138. Rats received AOM on PND 89 and 96. Lifetime (GD 4 to PND 138) feeding of SPI led to reduced frequency of ACF with 4 or more crypts in the distal colon. Progeny of dams fed SPI only during pregnancy and lactation or progeny fed SPI only after weaning exhibited similarly reduced frequency of large ACF in distal colon. Number of epithelial cells, in the distal colon, undergoing apoptosis was unaffected by diet. SPI reduced weight gain and adiposity, but these were not correlated with fewer numbers of large ACF. Lifetime SPI exposure similarly inhibited development of large ACF in Sprague Dawley rats whose dams were exposed to ethanol during pregnancy. In summary, feeding of SPI to rat dams during pregnancy and lactation suppresses numbers of large ACF in their progeny, implying a long-term or permanent change elicited by the maternal diet. Moreover, results support the use of ACF as an intermediate endpoint for elucidating effects of SPI and its biochemical constituents in colon cancer prevention in rats.

Arachidonic acid and colorectal carcinogenesis

Colorectal carcinoma is a leading cause of cancer related death worldwide. This deadly disease advances through a series of clinical and histopathological stages, initiated by single crypt lesions to small benign tumors and finally to malignancy. Although some progress has been made in elucidating the formation of colorectal tumors at molecular/genetic levels, the possible mechanisms of dietary lipids in inducing and promoting colorectal tumorigenesis are poorly understood. Recent epidemiological studies, however, indicate that lipid-rich diet containing omega-6 fatty acids (i.e. linoleic acid, arachidonic acid, etc.) may somehow be related with the disease process. Rapid metabolism of arachidonic acid, increased activities of phospholipases (i.e. phospholipase-A2s), and the elevated levels of cyclooxygenase (COX) and lipoxygenase (LOX) in colonic cells were reported in various stages of the malignancy, suggesting a possible link between dietary lipids and the incidence of colorectal cancer. The major focus of this review is to delineate the recent findings on enhanced arachidonic acid metabolism and its conversion into eicosanoids during the initiation and progression of colorectal carcinogenesis. In addition, the identification and participation of various phospholipases are also discussed. It is speculated that many of these phospholipases can be used as targets for developing new drugs against colorectal as well as other adenocarcinomas.

Arachidonic acid and colorectal carcinogenesis

Colorectal carcinoma is a leading cause of cancer related death worldwide. This deadly disease advances through a series of clinical and histopathological stages, initiated by single crypt lesions to small benign tumors and finally to malignancy. Although some progress has been made in elucidating the formation of colorectal tumors at molecular/genetic levels, the possible mechanisms of dietary lipids in inducing and promoting colorectal tumorigenesis are poorly understood. Recent epidemiological studies, however, indicate that lipid-rich diet containing omega-6 fatty acids (i.e. linoleic acid, arachidonic acid, etc.) may somehow be related with the disease process. Rapid metabolism of arachidonic acid, increased activities of phospholipases (i.e. phospholipase-A2s), and the elevated levels of cyclooxygenase (COX) and lipoxygenase (LOX) in colonic cells were reported in various stages of the malignancy, suggesting a possible link between dietary lipids and the incidence of colorectal cancer. The major focus of this review is to delineate the recent findings on enhanced arachidonic acid metabolism and its conversion into eicosanoids during the initiation and progression of colorectal carcinogenesis. In addition, the identification and participation of various phospholipases are also discussed. It is speculated that many of these phospholipases can be used as targets for developing new drugs against colorectal as well as other adenocarcinomas.

A diet containing alpha-cellulose and fish oil reduces aberrant crypt foci formation and modulates other possible markers for colon cancer risk in azoxymethane-treated rats

There is a need for better understanding of the roles of dietary fats and fibers in colon cancer risk. We examined the effect of different dietary fiber and fat sources on an azoxymethane (AOM)-induced colon cancer in rats. In a 2 x 3 factorial design, rats were fed a semipurified diet containing soy-derived fiber (Fibrim), alpha-cellulose (Solkafloc) or resistant starch (RS; Hi-maize) at 10 g dietary fiber/100 g diet, combined with fish oil (FO) or sunflower seed oil (SSO) at 10 g/100 g diet, and lard added to all diets at 10 g/100 g, to provide a total of 20 g mixed fat/100 g diet. Sprague-Dawley rats (28 d of age) consumed diets for 4 wk and then two doses of AOM (15 mg/kg body) were administered 1 wk apart by subcutaneous injection. Rats were killed after 13 wk of consuming experimental diets. Colons were fixed in formalin and aberrant crypt foci (ACF) were quantified after staining. ACF counts were higher (+66%, P < 0.01) in rats fed SSO and RS, than in those fed alpha-cellulose and FO. Rats fed FO had 19% fewer ACF than those fed SSO (P < 0.05). alpha-Cellulose was associated with the highest cecal butyrate concentration (P < 0.001), the highest beta-glucuronidase specific activity (P < 0.001) and the lowest cecal water cytotoxicity (P < 0.001) relative to soy fiber- and RS-fed rats. There were inverse correlations between the number of ACF and cecal butyrate concentration (r = -0.33, P < 0.05) and between cecal water cytotoxicity and beta-glucuronidase activity (r = -0.70, P < 0.001). The greatest protection was associated with alpha-cellulose as the fiber source and FO as the fat source as measured by colon ACF numbers in rats.