Dietary soy protein is associated with reduced intestinal mucosal polyamine concentration in male Wistar rats

The Molecular and Physiological Effects of Protein-Derived Polyamines in the Intestine

Consumption of a high-protein diet increases protein entry into the colon. Colonic microbiota can ferment proteins, which results in the production of protein fermentation end-products, like polyamines. This review describes the effects of polyamines on biochemical, cellular and physiological processes, with a focus on the colon. Polyamines (mainly spermine, spermidine, putrescine and cadaverine) are involved in the regulation of protein translation and gene transcription. In this, the spermidine-derived hypusination modification of EIF5A plays an important role. In addition, polyamines regulate metabolic functions. Through hypusination of EIF5A, polyamines also regulate translation of mitochondrial proteins, thereby increasing their expression. They can also induce mitophagy through various pathways, which helps to remove damaged organelles and improves cell survival. In addition, polyamines increase mitochondrial substrate oxidation by increasing mitochondrial Ca2+-levels. Putrescine can even serve as an energy source for enterocytes in the small intestine. By regulating the formation of the mitochondrial permeability transition pore, polyamines help maintain mitochondrial membrane integrity. However, their catabolism may also reduce metabolic functions by depleting intracellular acetyl-CoA levels, or through production of toxic by-products. Lastly, polyamines support gut physiology, by supporting barrier function, inducing gut maturation and increasing longevity. Polyamines thus play many roles, and their impact is strongly tissue- and dose-dependent. However, whether diet-derived increases in colonic luminal polyamine levels also impact intestinal physiology has not been resolved yet.

Soy consumption and colorectal cancer risk in humans: a meta-analysis

The purpose of the present study was to determine the relationship between soy consumption and colorectal cancer risk in humans by conducting a meta-analysis of available epidemiologic studies. We systematically reviewed publications obtained through a Medline literature search and identified four cohort and seven case-control studies on soy and colorectal cancer risk that met the inclusion criteria. We extracted the risk estimate (hazard ratio, relative risk, or odds ratio) of the highest and the lowest reported categories of intake from each study and conducted this analysis using a random-effects model. Our analysis did not find that soy consumption was associated with colorectal cancer risk [combined risk estimate, 0.90; 95% confidence interval (95% CI), 0.79-1.03] nor did the separate analyses on colon cancer (combined risk estimate, 0.88; 95% CI, 0.74-1.06) and rectal cancer (combined risk estimate, 0.88; 95% CI, 0.67-1.14). However, when separately analyzed on the basis of gender, we found that soy was associated with an approximately 21% reduction in colorectal cancer risk in women (combined risk estimate, 0.79; 95% CI, 0.65-0.97; P = 0.026), but not in men (combined risk estimate, 1.10; 95% CI, 0.90-1.33). Thus, consumption of soy foods may be associated with a reduction in colorectal cancer risk in women, but not in men.

Transport of putrescine across duodenal, jejunal and ileal brush-border membrane of chicks (Gallus domesticus)

Luminal polyamines and their absorption are essential for proliferation of the enterocytes and, therefore, nutrition, health and development of the animal. The transport systems that facilitate the uptake of putrescine were characterized in chick duodenal, jejunal and ileal brush-border membrane vesicles prepared by MgCl2 precipitation from three-week-old chicks. An inwardly-directed Na+ gradient did not stimulate putrescine uptake and, therefore, putrescine transport in chick intestine. In the duodenum, jejunum and ileum, kinetics of putrescine transport fitted a model with a single affinity component plus a non-saturable component. The affinity (Kt) for [3H]putrescine transport across the brush-border membrane increased along the length of the small intestine. A model of intermediate affinity converged to the data obtained for [3H]putrescine transport with Kt approximating 1.07 and 1.05 mM or duodenum and jejunum, respectively; and high affinity with a Kt of 0.35 mM for the ileum. The polyamines cadaverine, putrescine, spermidine and spermine strongly inhibited the uptake of [3H]putrescine into chick brush-border membrane vesicles, more so for the jejunum and ileum than the duodenum. The kinetics of cadaverine, spermidine and spermine inhibition are suggestive of competitive inhibition of putrescine transport. These uptake data indicate that a single-affinity system facilitates the intestinal transport of putrescine in the chick; and the affinity of transporter for putrescine is higher in the ileum than in the proximal sections of the small intestine. In addition, this study shows that the ileum of chicks plays an important role in regulating cellular putrescine concentration.

Proliferation of intestinal crypt cells by gastrin-induced ornithine decarboxylase

AIM: To determine whether the gastrin stimulated intestinal crypt cell (IEC-6) proliferation by induction of ornithine decarboxylase (ODC).

METHODS: IEC-6 cells were grown in DMEM containing 50 mL·L^-1 dialyzed fetal bovine serum for 24 h and then were treated with gastrin. The proliferative capability of the cells was monitored subsequently on d 1, 2, 3, and 4 after treatment with MTT assay at aborbance 570 nm. The cellular ODC mRNA expression, ODC activity, and putrescine content were examined by RT-PCR method, radiometric technique and high-performance liquid chromatography(HPLC) analysis respectively after 12 h of treatment.

RESULTS: On d1 after exposure of IEC-6 cells to pentagastrin, the proliferation increased initially and reached a peak on d3 at 250 μg·L^-1 concentration. Pentagastrin 500 μg·L^-1 increased cell proliferation on day 1 and day 2, and then decreased. Compared with control group, pentagastrin 250 μg·L^-1 increased ODC mRNA level by 1.09-fold (P < 0.05), ODC activity by 1.71-fold(P < 0.01), and putrescine content 5.30-fold (P < 0.01), respectively. Similarly, pentagastrin of 500 μg·L^-1 also increased ODC mRNA level by 1.16-fold (P < 0.05), ODC activity 1.63-fold(P < 0.05), and putrescine content 4.41-fold (P < 0.01), respectively. But there was not significant difference between them.

CONCLUSION: Gastrin is an agent which promotes IEC-6 cell proliferation involved in regulating ODC activity mechanism.

Evidence that the antioxidant flavonoids in tea and cocoa are beneficial for cardiovascular health

Epidemiologic studies suggest an inverse association of tea consumption with cardiovascular disease. The antioxidant effects of flavonoids in tea (including preventing oxidative damage to LDL) are among the potential mechanisms that could underlie the protective effects. Other possible mechanisms include attenuating the inflammatory process in atherosclerosis, reducing thrombosis, promoting normal endothelial function, and blocking expression of cellular adhesion molecules. Cocoa and chocolate can also be rich sources of flavonoids. Flavanols and procyanidins isolated from cocoa exhibit strong antioxidant properties in-vitro. In acute feeding studies, flavanol-rich cocoa and chocolate increased plasma antioxidant capacity and reduced platelet reactivity. Based on limited data, approximately 150 mg of flavonoids is needed to trigger a rapid antioxidant effect and changes in prostacyclin. Some dose-response evidence demonstrates an antioxidant effect with approximately 500 mg flavonoids. Brewed tea typically contains approximately 172 mg total flavonoids per 235 ml (brewed for 2 min); hence, consumption of 1 and 3.5 cups of tea would be expected to elicit acute and chronic physiologic effects, respectively. Chocolate is more variable with some products containing essentially no flavonoids (0.09 mg procyanidin/g), whereas others are high in flavonoids (4 mg procyanidin/g). Thus, approximate estimates of flavonoid rich chocolate needed to exert acute and chronic effects are 38 and 125 g, respectively. Collectively, the antioxidant effects of flavonoid-rich foods may reduce cardiovascular disease risk.

Dietary agents in cancer prevention: flavonoids and isoflavonoids

Flavones and isoflavones may play a prominent role in cancer prevention since these compounds are found in numerous plants that are associated with reduced cancer rates. This article reviews recent epidemiological and animal data on isoflavones and flavones and their role in cancer prevention. It covers aspects of the bioavailability of these dietary constituents and explores their mechanism of action. Human epidemiology data comes primarily from studies in which foods rich in isoflavones or flavones are associated with cancer rates. This approach has been particularly useful with isoflavones because of their abundance in specific foods, including soy foods. The bioavailability of flavones and isoflavones has been shown to be influenced by their chemical form in foods (generally glycoside conjugates), their hydrophobicity, susceptibility to degradation, the microbial flora of the consumer, and the food matrix. Some information is available on how these factors influence isoflavone bioavailability, but the information on flavones is more limited. Many mechanisms of action have been identified for isoflavone/flavone prevention of cancer, including estrogenic/antiestrogenic activity, antiproliferation, induction of cell-cycle arrest and apoptosis, prevention of oxidation, induction of detoxification enzymes, regulation of the host immune system, and changes in cellular signaling. It is expected that some combination of these mechanisms will be found to be responsible for cancer prevention by these compounds. Compelling data suggest that flavones and isoflavones contribute to cancer prevention; however, further investigations will be required to clarify the nature of the impact and interactions between these bioactive constituents and other dietary components.