Isolated isoflavones do not affect the circulating insulin-like growth factor system in men at increased colorectal cancer risk

Polyphenols in the Prevention and Treatment of Colorectal Cancer: A Systematic Review of Clinical Evidence

Polyphenols are plant metabolites with potential anti-inflammatory and anti-proliferative effects, which may be advantageous for disorders like colorectal cancer (CRC). Despite promising in vitro and in vivo evidence, human clinical trials have yielded mixed results. The present study aimed to evaluate the clinical evidence of polyphenols for CRC prevention or treatment. A systematic review was performed according to PRISMA. Based on a PROSPERO registered protocol (CRD42024560044), online databases (PubMed and COCHRANE) were utilized for the literature search. A total of 100 studies articles were initially identified. After reviewing, 12 studies with a low risk of bias were selected, examining the effect of a variety of compounds. Curcumin demonstrated promise in various trials, mainly decreasing inflammatory cytokines, though results varied, and it did not lower intestinal adenomas or improve outcomes after chemotherapy. Neither epigallocatechin gallate nor artepillin C reduced the incidence of adenomas. Finally, fisetin seemed to improve the inflammatory status of patients under chemotherapy (5-fluorouracil). In summary, although certain polyphenols appear to exert some effect, their role in the prevention or treatment of CRC is inconclusive, and more clinical studies under more controlled conditions are needed.

Effects of Dietary Phytoestrogens on Hormones throughout a Human Lifespan: A Review

Dietary phytoestrogens are bioactive compounds with estrogenic activity. With the growing popularity of plant-based diets, the intake of phytoestrogen-rich legumes (especially soy) and legume-derived foods has increased. Evidence from preclinical studies suggests these compounds may have an effect on hormones and health, although the results of human trials are unclear. The effects of dietary phytoestrogens depend on the exposure (phytoestrogen type, matrix, concentration, and bioavailability), ethnicity, hormone levels (related to age, sex, and physiological condition), and health status of the consumer. In this review, we have summarized the results of human studies on dietary phytoestrogens with the aim of assessing the possible hormone-dependent outcomes and health effects of their consumption throughout a lifespan, focusing on pregnancy, childhood, adulthood, and the premenopausal and postmenopausal stages. In pregnant women, an improvement of insulin metabolism has been reported in only one study. Sex hormone alterations have been found in the late stages of childhood, and goitrogenic effects in children with hypothyroidism. In premenopausal and postmenopausal women, the reported impacts on hormones are inconsistent, although beneficial goitrogenic effects and improved glycemic control and cardiovascular risk markers have been described in postmenopausal individuals. In adult men, different authors report goitrogenic effects and a reduction of insulin in non-alcoholic fatty liver patients. Further carefully designed studies are warranted to better elucidate the impact of phytoestrogen consumption on the endocrine system at different life stages.

A prospective evaluation of plasma polyphenol levels and colon cancer risk

Polyphenols have been shown to exert biological activity in experimental models of colon cancer; however, human data linking specific polyphenols to colon cancer is limited. We assessed the relationship between pre-diagnostic plasma polyphenols and colon cancer risk in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition study. Using high pressure liquid chromatography coupled to tandem mass spectrometry, we measured concentrations of 35 polyphenols in plasma from 809 incident colon cancer cases and 809 matched controls. We used multivariable adjusted conditional logistic regression models that included established colon cancer risk factors. The false discovery rate (qvalues ) was computed to control for multiple comparisons. All statistical tests were two-sided. After false discovery rate correction and in continuous log2 -transformed multivariable models, equol (odds ratio [OR] per log2 -value, 0.86, 95% confidence interval [95% CI] = 0.79-0.93; qvalue  = 0.01) and homovanillic acid (OR per log2 -value, 1.46, 95% CI = 1.16-1.84; qvalue  = 0.02) were associated with colon cancer risk. Comparing extreme fifths, equol concentrations were inversely associated with colon cancer risk (OR = 0.61, 95% CI = 0.41-0.91, ptrend  = 0.003), while homovanillic acid concentrations were positively associated with colon cancer development (OR = 1.72, 95% CI = 1.17-2.53, ptrend  < 0.0001). No heterogeneity for these associations was observed by sex and across other colon cancer risk factors. The remaining polyphenols were not associated with colon cancer risk. Higher equol concentrations were associated with lower risk, and higher homovanillic acid concentrations were associated with greater risk of colon cancer. These findings support a potential role for specific polyphenols in colon tumorigenesis.

Effects of the phytoestrogen genistein on the porcine anterior pituitary insulin-like growth factor system

Estrogens have profound effects on the serum and anterior pituitary (AP) insulin-like growth factor (IGF) system in pigs. In this study we determined whether administration of the phytoestrogen genistein increased serum and AP concentrations of IGF-I and relative amounts of serum and AP insulin-like growth factor-binding protein (IGFBP). Twenty barrows of similar age (190 d) and weight (110 kg) were stratified by litter into one of four treatments: controls (C), estradiol (E), 200 mg genistein (G200), and 400 mg genistein (G400). Estradiol-treated pigs were injected daily with 2 mg of estradiol-17β intramuscularly (i.m.), whereas the G200 and G400 groups were injected daily with either 200 or 400 mg of genistein i.m., respectively, beginning on d 0 and continuing through d 15. Blood was collected on d 0, 3, 6, 9, and 13. Blood and AP were collected at slaughter on d 16. Serum and AP concentrations of IGF-I and luteinizing hormone (LH) were determined by radioimmunoassay. Relative amounts of serum IGFBP were determined by Western ligand blot analysis. Relative expression of AP IGF-I, IGF-I receptor (IGF-IR), gonadotropin-releasing hormone receptor, and LHβ subunit was determined by real-time reverse transcriptase polymerase chain reaction. Anterior pituitary concentrations of IGF-I were greater (P > 0.05) in E and G400 pigs compared with controls, whereas AP concentrations of LH were greater (P < 0.05) in G400 pigs compared with C and G200 pigs. Relative expression of LHβ was greater in G200 pigs compared with C pigs but did not differ from that in G400 pigs. Relative expression of AP IGF-IR was greater (P < 0.05) in E pigs compared with all other treatments; however, relative expression of AP IGF-IR was greater (P < 0.05) in both G200 and G400 pigs vs C pigs. No differences were detected (P > 0.05) in serum concentrations of IGF-I or relative amounts of serum and AP IGFBP among treatments. These data provide evidence that genistein is capable of modulating components of the AP IGF system that could affect the synthesis and release of LH.

Daidzein and genistein are converted to equol and 5-hydroxy-equol by human intestinal Slackia isoflavoniconvertens in gnotobiotic rats

Intestinal conversion of the isoflavone daidzein to the bioactive equol is exclusively catalyzed by gut bacteria, but a direct role in equol formation under in vivo conditions has not yet been demonstrated. Slackia isoflavoniconvertens is one of the few equol-forming gut bacteria isolated from humans and, moreover, it also converts genistein to 5-hydroxy-equol. To demonstrate the isoflavone-converting ability of S. isoflavoniconvertens in vivo, the metabolization of dietary daidzein and genistein was investigated in male and female rats harboring a simplified human microbiota without (control) or with S. isoflavoniconvertens (SIA). Feces, urine, intestinal contents, and plasma of the rats were analyzed for daidzein, genistein, and their metabolites. Equol and 5-hydroxy-equol were found in intestinal contents, feces, and urine of SIA rats but not in the corresponding samples of the control rats. 5-Hydroxy-equol was present at much lower concentrations than equol and the main metabolite produced from genistein was the intermediate dihydrogenistein. The plasma of SIA rats contained equol but no 5-hydroxy-equol. Equol formation had no effect on plasma concentrations of the insulin-like growth factor I. The concentrations of daidzein and genistein were considerably lower in all samples of the SIA rats than in those of the control rats. Male SIA rats had higher intestinal and fecal concentrations of the isoflavones and their metabolites than female SIA rats. The observed activity in the rat model indicates that S. isoflavoniconvertens is capable of contributing in vivo to the bioactivation of daidzein and genistein by formation of equol and 5-hydroxy-equol.

Emerging research on equol and cancer

Mechanisms of action of equol described using in vitro studies suggest possible effects of this compound in relation to cancer risk. However, experimental data are lacking with regard to the effects of S-(-)-equol (a gut bacterial product of daidzein), racemic equol, or even daidzein on tumorigenesis in vivo. Rodent studies, using racemic equol or daidzein in equol-producing animals, suggest that equol exposure does not stimulate mammary tumor growth, but there is little evidence that it is protective either. Racemic equol has been shown to inhibit skin carcinogenesis in hairless mice. Epidemiologic studies of associations between urinary or plasma isoflavone concentrations and breast cancer risk in women have reported no association nor increased risk associated with higher equol measures in low-soy-consuming populations but have reported a trend toward decreased cancer risk with increased equol in Asian populations. These population-based differences have been reported for prostate cancer too. Several studies in Asian men report lower equol concentrations or a lower prevalence of equol-producers among men with prostate cancer compared with controls, whereas studies in European populations report no association. Studies using intermediate biomarkers of cancer risk and susceptibility in humans also have examined the effects the equol-producer phenotype in relation to soy intake with varying results. Overall, the role of equol in relation to cancer remains unclear. With the availability of R- and S-equol, animal studies of carcinogenesis and human intervention studies addressing effects of the equol enantiomers on intermediate biomarkers may help to ascertain the role of equol in cancer risk.

Serum levels of IGF-I, IGFBP-3 and colorectal cancer risk: results from the EPIC cohort, plus a meta-analysis of prospective studies

Several prospective studies have shown a moderate positive association between increasing circulating insulin-like growth factor-I (IGF-I) levels and colorectal cancer risk. However, the associations were often statistically nonsignificant, and the relationship of cancer risk with IGF-I's major binding protein, IGFBP-3, showed major discrepancies between studies. We investigated the association of colorectal cancer risk with serum IGF-I, total and intact IGFBP-3, in a case-control study nested within the EPIC cohort (1,121 cases of colorectal cancer and 1,121 matched controls). Conditional logistic regression was used to adjust for possible confounders. Our present study results were combined in a meta-analysis with those from 9 previous prospective studies to examine the overall evidence for a relationship of prediagnostic serum IGF-I with colorectal cancer risk. In the EPIC study, serum concentrations of IGF-I and IGFBP-3 showed no associations with risk of colorectal cancer overall. Only in subgroup analyses did our study show moderate positive associations of IGF-I levels with risk, either among younger participants only (and only for colon cancer) or among participants whose milk intakes were in the lowest tertile of the population distribution (RR for an increase of 100 ng/ml = 1.43 [95% CI = 1.13-1.93]). Nevertheless, in the meta-analysis a modest positive association remained between serum IGF-I and colorectal cancer risk overall (RR = 1.07 [1.01-1.14] for 1 standard deviation increase in IGF-I). Overall, data from our present study and previous prospective studies combined indicate a relatively modest association of colorectal cancer risk with serum IGF-I.

Is equol the key to the efficacy of soy foods?

Gut bacterial modification of soy isoflavones produces metabolites that differ in biological activity from the parent compounds. Hydrolysis of glycosides results in more active compounds. In contrast, further degradation and transformation of aglycones produce more or less active compounds, depending on the substrate metabolized and the product formed. Bacterial metabolism of soy isoflavones varies among individuals. The predominant daidzein metabolites produced by human intestinal bacteria are equol and O-desmethylangolensin. Among humans, 30-50% have the bacteria capable of producing equol and 80-90% harbor O-desmethylangolensin-producing bacteria. Factors that influence the capacity to produce equol and O-desmethylangolensin are not clearly established; however, gut physiology, host genetics, and diet are reported to contribute to interindividual differences in conversion of daidzein to equol. Effects of these phenotypes on human health are poorly characterized. Some studies in high soy-consuming populations reported an inverse association between urinary and serum equol concentrations and breast and prostate cancer risk. Furthermore, several studies of soy supplementation and bone density suggest that soy products may be more effective in maintaining bone density in equol-producing individuals. Factors that contribute to the phenotypes and the relation of these specific phenotypes to human health need to be further elucidated. The extent to which isoflavone metabolism is key to the efficacy of soy foods remains to be established.

Expression of insulin-like growth factor system components in colorectal tissue and its relation with serum IGF levels

CONTEXT

The insulin-like growth factor (IGF)-system has been implicated in colorectal tumor carcinogenesis. Although both tumor expression levels and serum concentrations of IGF-system components are related to colorectal cancer risk, it is unknown whether IGF levels in tissue and serum are correlated.

OBJECTIVE

The objective of this study was to determine expression levels of various IGF-system components in different locations of the colorectum, and to investigate whether normal tissue IGF expression levels are correlated with serum IGF-I and IGF-II concentrations.

DESIGN

Biopsies from macroscopically normal mucosa at four locations in the colorectum (ascending, transverse, sigmoid colon, and rectum) and a fasting serum sample were obtained from 48 asymptomatic patients at increased risk of colorectal cancer. Expression levels of IGF-I, IGF-II, IGF-IR, IGF-IIR, and IGFBP-3 messenger RNA (mRNA) in tissue were quantitatively evaluated using real-time RT-PCR. Expression of IGF-IR protein in the ascending colon and rectum tissue specimens was assessed semi-quantitatively by immunohistochemistry. Serum IGF-I and IGF-II concentrations were determined using immunometric assays.

RESULTS

With the exception of IGF-IIR, mRNA levels of all the IGF-system components investigated, as well as IGF-IR protein expression, were significantly higher in the rectum compared with the ascending colon (p<or=0.001). Serum IGF-I and IGF-II concentrations did not correlate with any of the parameters studied in colorectal tissues.

CONCLUSIONS

Our results indicate that in humans IGF-system components are differentially expressed in the colorectum. Moreover, our findings suggest that local and circulating components of the IGF-system are differentially regulated. However, due to large intra-individual variation in mRNA expression, we cannot formally exclude undetected but existing routes of co-regulation.

Effects of lycopene on the insulin-like growth factor (IGF) system in premenopausal breast cancer survivors and women at high familial breast cancer risk

Insulin-like growth factor-I (IGF-I) is an important growth factor associated with increased risk of premenopausal breast cancer. We conducted a randomized, placebo-controlled, double-blind, crossover trial to evaluate whether tomato-derived lycopene supplementation (30 mg/day for 2 mo) decreases serum levels of total IGF-I in premenopausal women with 1) a history of breast cancer (n=24) or 2) a high familial breast cancer risk (n=36). Also, IGF binding protein (IGFBP) increasing effects were evaluated. Lycopene supplementation did not significantly alter serum total IGF-I and other IGF system components in the 2 study populations combined. However, statistically significant discordant results were observed between the 2 study populations (i.e., P<0.05 for total IGF-I, free IGF-I, and IGFBP-3). Total IGF-I and IGFBP-3 were increased in the breast cancer survivor population [total IGF-I=7.0%, 95% confidence interval (CI)= -0.2 to 14.3%; IGFBP-3=3.3%, 95% CI=0.7-6.0%), and free IGF-I was decreased in the family history population (-7.6%, 95% CI= -14.6 to -0.6%). This randomized controlled trial shows that 2 mo of lycopene supplementation has no effect on serum total IGF-I in the overall study population. However, lycopene effects were discordant between the 2 study populations showing beneficial effects in high-risk healthy women but not in breast cancer survivors.

Equol status modifies the association of soy intake and mammographic density in a sample of postmenopausal women

Only 30% to 50% of people produce the daidzein-metabolite equol after eating soy. We conducted a cross-sectional study of the associations between equol status, intake of soy foods, and mammographic density in a sample of postmenopausal women recruited at a radiology clinic near Buffalo, New York. Participants were 48 to 82 years old, had no history of cancer or breast reduction/augmentation, and no recent use of antibiotics or hormones. Percent density was measured by computer-assisted analysis of digitized images of craniocaudal films. Equol status was assessed using a soy-challenge protocol and usual soy intake by questionnaire. General linear models were used to assess independent and joint effects of equol status and intake of soy on multivariate adjusted percent density (covariates included age, body mass index, parity, age at first birth, and ever use of combined hormone therapy). Of 325 enrolled, 232 (71%) participants completed study assessments and are included in the present analysis. Mean percent density was 34% (+/-18%). Seventy-five (30%) participants were producers of equol. Forty-three (19%) participants reported regularly eating >1 soy food or supplement/wk. There were no significant independent associations of equol status or soy intake with percent density, but the interaction between these factors was significant (P < 0.01). Among equol producers, those with weekly soy intake had lower percent density (30.7% in weekly consumers of soy versus 38.9% in others; P = 0.08); among nonproducers, weekly soy intake was associated with higher percent density (37.5% in weekly soy consumers versus 30.7% in others; P = 0.03). Results suggest that equol producers and nonproducers may experience different effects of dietary soy on breast tissue.

Lycopene supplementation elevates circulating insulin-like growth factor binding protein-1 and -2 concentrations in persons at greater risk of colorectal cancer

BACKGROUND

Higher circulating insulin-like growth factor I (IGF-I) concentrations have been related to a greater risk of cancer. Lycopene intake is inversely associated with cancer risk, and experimental studies have shown that it may affect the IGF system, possibly through an effect on IGF-binding proteins (IGFBPs).

OBJECTIVE

The objective of our study was to investigate the effect of an 8-wk supplementation with tomato-derived lycopene (30 mg/d) on serum concentrations of total IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3.

DESIGN

We conducted a randomized, placebo-controlled, double-blinded crossover study in 40 men and 31 postmenopausal women with a family history of colorectal cancer, a personal history of colorectal adenoma, or both.

RESULTS

Lycopene supplementation significantly (P = 0.01) increased serum IGFBP-1 concentrations in women (median relative difference between serum IGFBP-1 concentrations after lycopene supplementation and after placebo, 21.7%). Serum IGFBP-2 concentrations were higher in both men and women after lycopene supplementation than after placebo, but to a lesser extent (mean relative difference 8.2%; 95% CI: 0.7%, 15.6% in men and 7.8%; 95% CI: -5.0%, 20.6% in women). Total IGF-I, IGF-II, and IGFBP-3 concentrations were not significantly altered by lycopene supplementation.

CONCLUSIONS

This is the first study known to show that lycopene supplementation may increase circulating IGFBP-1 and IGFBP-2 concentrations. Because of high interindividual variations in IGFBP-1 and IGFBP-2 effects, these results should be confirmed in larger randomized intervention studies.