Sequential, randomized trial of a low-fat, high-fiber diet and soy supplementation: effects on circulating IGF-I and its binding proteins in premenopausal women

Perspective: Observational Studies Involving Low-Soy Intake Populations Have Limited Ability for Providing Insight into the Health Effects of Soybean Isoflavones

Isoflavones are naturally occurring plant compounds found in uniquely high amounts in soybeans and foods made from this legume. These soybean constituents have been proposed to exert several health benefits and as such they have been the subject of an enormous amount of research. This research includes randomized controlled trials (RCTs) and epidemiologic investigations. Although statistically significant associations between isoflavone intake and a wide range of health outcomes have been identified in cohorts involving low-isoflavone intake populations, we suggest that these associations are unlikely to have a causal basis because exposure is too low for isoflavones to exert physiologic effects. In cohorts involving predominantly non-Asian, non-vegetarian populations, the highest isoflavone intake category is typically ≤3 mg/d, an amount of isoflavones provided by ∼30 mL (2 tablespoons) of soymilk made from whole soybeans. In comparison, mean isoflavone intake in the upper intake categories in observational studies involving high-isoflavone intake populations is typically ≥50 mg/d. In RCTs, intervention doses of isoflavones typically range between 40 and 100 mg/d. Health professionals advising patients and clients about soy food and isoflavone intake need to be aware of the limitations of epidemiologic research involving low-isoflavone intake populations. Intake recommendations are best based on the results of RCTs using clinically relevant doses of isoflavones and epidemiologic studies involving populations for whom soy foods are a habitual part of the diet.

Impact of 18-Month Soy Protein Supplementation on Steroid Hormones and Serum Biomarkers of Angiogenesis, Apoptosis, and the Growth Hormone/IGF-1 Axis: Results of a Randomized, Placebo-Controlled Trial in Males Following Prostatectomy

Many studies have addressed the effects of dietary supplementation with soy protein on cancer risk and mortality, but there are only few randomized studies with soy in males. We used serum samples from a two-year trial of soy protein isolate supplementation in middle-aged to older males at risk of recurrence of prostate cancer after radical prostatectomy to determine soy effects on steroid hormones involved in prostate cancer (testosterone, SHBG, and estradiol) and explore the effects on biomarkers of the growth hormone/IGF-1 axis, apoptosis, and angiogenesis. Compared with a casein-based placebo, 18 mo, of consumption of 19.2 g/day of whole soy protein isolate containing 24 mg genistein-reduced circulating testosterone and SHBG, but not free testosterone, and did not affect serum concentrations of estradiol, VEGF, IGF-1, IGFBP-3, IGF-1/IGFBP-3 ratio, soluble Fas, Fas-ligand, and sFas/Fas-ligand ratio. Thus, soy protein supplementation for 18 mo, affected the androgen axis, but the effects on other cancer biomarkers remain to be more definitively determined. The study was registered at clinicaltrials.gov (NCT00765479).

The effect of soy intervention on insulin-like growth factor 1 levels: A meta-analysis of clinical trials

A low insulin-like growth factor 1 (IGF-1) level is known to be associated with many disorders. Several studies have shown that soy consumption may influence IGF-1, but the findings remain inconclusive. In this work, we conducted a systematic review and meta-analysis to provide a more accurate estimation of the effect of soy consumption on plasma IGF-1. A comprehensive systematic search was performed in Scopus, Embase, Web of Science, and PubMed/MEDLINE databases from inception until October 2019. Eight studies fulfilled the eligibility criteria. The pooled weighted mean difference (WMD) of the eligible studies was calculated with random-effects approach. Overall, a significant increment in plasma IGF-1 was observed following soy intervention (WMD: 13.5 ng/ml, 95% CI: 5.2, 21.8, I2 = 97%). Subgroup analyses demonstrated a significantly greater increase in IGF-1, when soy was administered at a dosage of ≤40 g/day (WMD: 11.7 ng/ml, 95% CI: 10.9 to 12.6, I2 = 98%), and when the intervention duration was <12 weeks (WMD: 26.6 ng/ml, 95% CI: 9.1 to 44.1, I2 = 0.0%). In addition, soy intervention resulted in a greater increase in IGF-1 among non-healthy subjects (WMD: 36 ng/ml, 95% CI: 32.7 to 39.4, I2 = 84%) than healthy subjects (WMD: 9.8 ng/ml, 95% CI: 8.9 to 10.7, I2 = 90%). In conclusion, this study provided the first meta-analytical evidence that soy intake may increase IGF-1 levels, but the magnitude of the increase is dependent on the intervention dosage, duration, and health status of the participants.

Does soy protein affect circulating levels of unbound IGF-1?

INTRODUCTION

Despite the enormous amount of research that has been conducted on the role of soyfoods in the prevention and treatment of chronic disease, the mechanisms by which soy exerts its physiological effects are not fully understood. The clinical data show that neither soyfoods nor soy protein nor isoflavones affect circulating levels of reproductive hormones in men or women. However, some research suggests that soy protein, but not isoflavones, affects insulin-like growth factor I (IGF-1).

METHODS

Since IGF-1 may have wide-ranging physiological effects, we sought to determine the effect of soy protein on IGF-1 and its major binding protein insulin-like growth factor-binding protein (IGFBP-3). Six clinical studies were identified that compared soy protein with a control protein, albeit only two studies measured IGFBP-3 in addition to IGF-1.

RESULTS

Although the data are difficult to interpret because of the different experimental designs employed, there is some evidence that large amounts of soy protein (>25 g/day) modestly increase IGF-1 levels above levels observed with the control protein.

CONCLUSION

The clinical data suggest that a decision to incorporate soy into the diet should not be based on its possible effects on IGF-1.

Effects of High-Order Interactions among IGFBP-3 Genetic Polymorphisms, Body Mass Index and Soy Isoflavone Intake on Breast Cancer Susceptibility

Background

Polymorphisms of IGF-1 and IGFBP-3 and environmental factors may work together to influence insulin-like growth factor (IGF) levels and thus breast cancer (BC) risk. However, very few studies have investigated high-order interactions among these variables.

Methods

A total of 277 newly diagnosed BC cases and 277 controls were recruited between October 2010 and July 2012. We collected each participant's demographic characteristics, dietary intake, and blood sample. IGF-1 rs1520220 and IGFBP-3 rs2854744 were then genotyped. A multi-analytic strategy combining unconditional logistic regression (ULR), generalized multifactor dimensionality reduction (GMDR), and classification and regression tree (CART) approaches was applied to systematically identify the interactions of the two single nucleotide polymorphisms (SNPs), body mass index (BMI), and daily intake of soy isoflavone (DISI) on BC susceptibility.

Results

In GMDR analyses, high-order interactions among BMI, DISI, and SNP rs2854744 were identified among overall and postmenopausal women. We also found significant dosage effects on BC risk with an increasing number of exposure factors, namely carrying the rs2854744 AA genotype, DISI <9.85 mg/day, and BMI ≥24 kg/m² (P_trend<0.05). Similarly, in CART analyses, compared with individuals having BMI<24kg/m², DISI<9.85 mg/day, and the rs2854744 CC+CA genotype, BC risk increased significantly for those carrying the rs2854744 AA genotype, with BMI<24 kg/m² and DISI<9.85 mg/day (OR = 1.95, 95%CI: 1.03–3.69), and also for those with BMI≥24kg/m² and DISI<9.85 mg/day (OR = 2.13, 95%CI: 1.00–4.51). Similar interaction effects were observed among postmenopausal women.

Conclusions

This study suggests high-order interactions of the IGFBP-3 rs2854744 AA genotype, BMI≥24kg/m², and DISI<9.85 mg/day on increased BC risk, particularly among postmenopausal women.

Genetic polymorphisms of insulin-like growth factor 1 and insulin-like growth factor binding protein 3, xenoestrogen, phytoestrogen, and premenopausal breast cancer

BACKGROUND

Previous studies suggest a combined effect of insulin-like growth factor 1 (igf-1) and igf binding protein 3 (igfbp-3) gene polymorphisms, xenoestrogen, and phytoestrogen on the igf-1 signalling pathway and serum concentrations in the igf system, which are associated with premenopausal breast cancer (bca) risk.

METHODS

Between 2010 and 2012, our study recruited 140 premenopausal bca patients and 160 community-based premenopausal control subjects. Participants were surveyed about oral contraceptive (oc) use, dietary habits, and other bca risk factors. TaqMan assays were used to determine igf-1 rs1520220 and igfbp-3 rs2854744 genotypes. Daily intakes of energy-adjusted soy isoflavones (easis) were calculated by the residual method. Multivariate logistic regression was applied to estimate the adjusted odds ratios (ors) and 95% confidence intervals (cis) of the igf-1 rs1520220 and igfbp-3 rs2854744 genotypes, oc use, and intake of easis. Stratified analyses were performed to detect the gene-environment combined effect, and multivariate logistic regression was used to estimate interaction coefficients (iors) by the multiplicative model, with 95% cis. The delta method was used to calculate interaction coefficients by the additive model [relative excess risk of interaction (reri), attributable proportions of interaction (apis)] and 95% cis.

RESULTS

The igf-1 and igfbp-3 genotypes, oc use, and easis were not found to be associated with bca risk (p > 0.05). Stratified analysis showed that the risk of bca was markedly increased in women carrying the igfbp-3C allele and using ocs compared with women either carrying the igfbp-3C allele or using ocs (or: 3.02; 95% ci: 1.04 to 8.79). The interaction coefficients ior, reri, and api were 4.89 (95% ci: 1.09 to 21.90), 2.42 (95% ci: -0.76 to 5.61), and 0.80 (95% ci: 0.46 to 1.67) respectively.

CONCLUSIONS

The igfbp-3 rs2854744 polymorphism and oc use might synergistically increase premenopausal bca risk.

Metabolic responses to a traditional Mexican diet compared with a commonly consumed US diet in women of Mexican descent: a randomized crossover feeding trial

BACKGROUND

Mexican immigrants are disproportionally affected by diet-related risk of metabolic dysfunction. Whether adhering to a traditional Mexican diet or adopting a US diet contributes to metabolic changes associated with future risk of type 2 diabetes and other chronic diseases has not been investigated.

OBJECTIVE

The purpose of this study was to test in a randomized crossover feeding trial the metabolic responses to a Mexican diet compared with a commonly consumed US diet.

DESIGN

First- and second-generation healthy women of Mexican descent (n = 53) were randomly assigned in a crossover design to consume a Mexican or US diet for 24 d each, separated by a 28-d washout period. Diets were eucaloric and similar in macronutrient composition. The metabolic responses to diets were assessed by measuring fasting serum concentrations of glucose, insulin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein 3 (IGFBP-3), adiponectin, C-reactive protein (CRP), and interleukin 6 (IL-6), as well as the homeostasis model assessment of insulin resistance (HOMA-IR) at the beginning and end of each period. Linear mixed models tested the intervention effect on the biomarkers, while adjusting for diet sequence, feeding period, baseline and washout biomarker concentrations, age, acculturation, and BMI.

RESULTS

Compared with the US diet, the Mexican diet reduced insulin by 14% [geometric means (95% CIs): 9.3 (8.3, 10.3) compared with 8.0 (7.2, 8.9) μU/mL; P = 0.02], HOMA-IR by 15% [2.0 (1.8, 2.3) compared with 1.7 (1.6, 2.0); P = 0.02], and IGFBP-3 by 6% (mean ± SEM: 2420 ± 29 compared with 2299 ± 29 ng/mL; P < 0.01) and tended to reduce circulating concentrations of IGF-1 by 4% (149 ± 2.6 compared with 144 ± 2.5 ng/mL; P = 0.06). There was no significant intervention effect on serum concentrations of glucose, adiponectin, CRP, or IL-6 in the US compared with the Mexican diet.

CONCLUSION

Compared with the commonly consumed US diet, the traditional Mexican diet modestly improved insulin sensitivity under conditions of weight stability in healthy women of Mexican descent, while having no impact on biomarkers of inflammation. This trial was registered at clinicaltrials.gov as NCT01369173.

Genetic and dietary determinants of insulin-like growth factor (IGF)-1 and IGF binding protein (BP)-3 levels among Chinese women

Background

Higher insulin-like growth factor (IGF)-1 and lower IGF binding protein (BP)-3 levels have been associated with higher commoncancer risk, including breast cancer. Dietary factors, genetic polymorphisms, and the combination of both may influence circulating IGF-1 and IGFBP-3 serum concentrations.

Methods

From September 2011 to July 2012, we collected demographic, reproductive and dietary data on 143 women (≥40 years). We genotyped IGF-1 rs1520220 and IGFBP-3 rs2854744 and measured circulating IGF-1 and IGFBP-3 levels in serum. Covariance analyses were used to estimate the associations of serum levels of IGF-1 and IGFBP-3, and the molar ratio of IGF-1to IGFBP-3 with IGF-1 rs1520220 and IGFBP-3 rs2854744 genotypes. We subsequently assessed the combined influence of genetics and diet (daily intake of protein, fat and soy isoflavones) on IGF-1 and IGFBP-3 levels.

Results

Among women aged less than 50 years, circulating IGF-1 serum levels were significantly lower for those with CC genotype for IGF-1 rs1520220 than levels for those with the GC or GG genotypes (in recessive model: P = 0.007).In gene-diet analyses among these women, we found carrying CC genotype for IGF-1 rs1520220 and high soy isoflavone intake tend to be associated with lower circulating IGF-1 levels synthetically (P = 0.002). Women with GG or GC genotypes for IGF-1 rs1520220 and with low intake of soy isoflavones had the highest levels of circulating IGF-1 (geometric mean [95% CI]: 195 [37, 1021] µg/L). Comparatively, women with both the CC genotype and high soy intake had the lowest levels of circulating IGF-1 (geometric mean [95% CI]: 120 [38,378] µg/L).

Conclusions

IGF-1 serum levels are significantly lower among women with the CC genotype for IGF-1-rs1520220. High soy isoflavone intake may interact with carrying CC genotype for IGF-1-rs1520220 to lower women's serum IGF-1 levels more.

Epithelial membrane protein 2 is a prognostic indictor for patients with urothelial carcinoma of the upper urinary tract

Upper urinary tract urothelial carcinoma is a relatively uncommon disease and is diagnosed more frequently at advanced stages. The prognosis of these patients mainly has been related to tumor stage and grade. As a result, the definition of prognostic indicators enabling precise patient selection is mandatory for neoadjuvant or adjuvant therapies. The epithelial membrane protein (EMP2) was identified as one of the up-regulated genes by isoflavones. EMP2 overexpression suppressed foci formation, anchorage-independent growth in vitro, and tumorigenicity in severe combined immunodeficiency mice (all P < 0.05). In addition, a cross-talk between EMP2 and integrins αV and β3 was shown in the regulation of cell adhesion and migration. Higher EMP2 expression was associated with a better progression-free survival (P = 0.008) and cancer-related death (P < 0.001). EMP2 was identified as a tumor-suppressor gene in urinary tract urothelial carcinoma and may be an innovative co-targeting candidate for designing integrin-based cancer therapy.

Low-fat diet with omega-3 fatty acids increases plasma insulin-like growth factor concentration in healthy postmenopausal women

The insulin-like growth factor pathway plays a central role in the normal and abnormal growth of tissues; however, nutritional determinants of insulin-like growth factor I (IGF-I) and its binding proteins in healthy individuals are not well defined. Three test diets-high-fat diet (40% energy as fat), low-fat diet (LF; 20% energy as fat), and a diet with low fat and high omega-3 fatty acid (LFn3; 23% energy as fat)--were tested in a randomized crossover designed controlled feeding trial in healthy postmenopausal women. Plasma IGF-I, IGF binding protein-3 (IGFBP-3), insulin, glucose, and ratio of IGF-I/IGFBP-3 concentrations were measured in response to diets. Insulin sensitivity was calculated using the homeostatic model assessment of insulin resistance We hypothesized that IGF-I, insulin, and glucose concentrations would decrease and IGFBP-3 concentration would increase in response to the low-fat diets. Eight weeks of the LFn3 diet increased circulating IGF-I (P < .001) and IGFBP-3 (P = .01) and the LF diet increased IGFBP-3 (P = .04), resulting in trends toward an increased IGF-I/IGFBP-3 ratio with the LFn3 diet and a decreased IGF-I/IGFBP-3 ratio with the LF diet (P = .13 for both comparisons). No statistically significant differences were detected between treatments at baseline or 8 weeks for IGF-1, IGFBP-3, or the ratio of IGF-1/IGFBP-3. Insulin, glucose, and the homeostatic model assessment of insulin resistance were not altered by the interventions. Low-fat diet with high n-3 fatty acids may increase circulating IGF-I concentrations without adversely affecting insulin sensitivity in healthy individuals.

Glycemic load effect on fasting and post-prandial serum glucose, insulin, IGF-1 and IGFBP-3 in a randomized, controlled feeding study

BACKGROUND/OBJECTIVES

The effect of a low glycemic load (GL) diet on insulin-like growth factor-1 (IGF-1) concentration is still unknown but may contribute to lower chronic disease risk. We aimed to assess the impact of GL on concentrations of IGF-1 and IGF-binding protein-3 (IGFBP-3).

SUBJECTS/METHODS

We conducted a randomized, controlled crossover feeding trial in 84 overweight obese and normal weight healthy individuals using two 28-day weight-maintaining high- and low-GL diets. Measures were fasting and post-prandial concentrations of insulin, glucose, IGF-1 and IGFBP-3. In all 80 participants completed the study and 20 participants completed post-prandial testing by consuming a test breakfast at the end of each feeding period. We used paired t-tests for diet component and linear mixed models for biomarker analyses.

RESULTS

The 28-day low-GL diet led to 4% lower fasting concentrations of IGF-1 (10.6 ng/ml, P=0.04) and a 4% lower ratio of IGF-1/IGFBP-3 (0.24, P=0.01) compared with the high-GL diet. The low-GL test breakfast led to 43% and 27% lower mean post-prandial glucose and insulin responses, respectively; mean incremental areas under the curve for glucose and insulin, respectively, were 64.3±21.8 (mmol/l/240 min; P<0.01) and 2253±539 (μU/ml/240 min; P<0.01) lower following the low- compared with the high-GL test meal. There was no effect of GL on mean homeostasis model assessment for insulin resistance or on mean integrated post-prandial concentrations of glucose-adjusted insulin, IGF-1 or IGFBP-3. We did not observe modification of the dietary effect by adiposity.

CONCLUSIONS

Low-GL diets resulted in 43% and 27% lower post-prandial responses of glucose and insulin, respectively, and modestly lower fasting IGF-1 concentrations. Further intervention studies are needed to weigh the impact of dietary GL on risk for chronic disease.

Cissus quadrangularis augments IGF system components in human osteoblast like SaOS-2 cells

Osteoporosis is a public health problem which is associated with significant morbidity and mortality. Growth factors are produced locally in the bone and control cellular events such as induction of bone growth. Signaling through the Insulin-like growth factor (IGF)-I receptor (IGF-IR) by locally synthesized IGF - I or IGF-II in osteoblast is considered crucial for normal development and for bone remodeling. Traditional use of Cissus quadrangularis (C. quadrangularis) in the treatment of bone disorders have been documented, however its regulatory effects on IGF system components remain largely unknown. The present study is employed to delineate the effects of ethanolic extract of C. quadrangularis on the regulation of IGF system components in human osteoblast like SaOS-2 cells. RT-PCR analysis revealed an increase in the mRNA expression of IGF-I, IGF-II, IGF-IR in cells treated with C. quadrangularis when compared with control cells. The mRNA expression of IGF binding protein-3 (IGFBP-3) did not differ significantly between control and C. quadrangularis treated cells. Immunoradiometric analysis revealed increased levels of IGF-I, IGF-II and IGFBP-3 in the conditioned medium of C. quadrangularis treated cultures when compared with control. Western blotting analysis revealed increase in protein levels of IGF-IR in cells treated with C. quadrangularis. These results indicate positive regulation of C. quadrangularis on the IGF system components of human osteoblast like SaOS-2 cells.

Dietary fat, fiber, and carbohydrate intake and endogenous hormone levels in premenopausal women

The authors conducted a cross-sectional study to investigate the associations of fat, fiber, and carbohydrate intake with endogenous estrogen, androgen, and insulin-like growth factor (IGF) levels among 595 premenopausal women. Overall, no significant associations were found between dietary intake of these macronutrients and plasma sex steroid hormone levels. Dietary fat intake was inversely associated with IGF-I and IGF-binding protein 3 (IGFBP-3) levels. When substituting 5% of energy from total fat for the equivalent amount of energy from carbohydrate or protein intake, the plasma levels of IGF-I and IGFBP-3 were 2.8% (95% confidence interval [CI] 0.3, 5.3) and 1.6% (95% CI 0.4, 2.8) lower, respectively. Animal fat, saturated fat, and monounsaturated fat intakes also were inversely associated with IGFBP-3 levels (P<0.05). Carbohydrates were positively associated with plasma IGF-I level. When substituting 5% of energy from carbohydrates for the equivalent amount of energy from fat or protein intake, the plasma IGF-I level was 2.0% (95% CI 0.1, 3.9%) higher. No independent associations between fiber intake and hormone levels were observed. The results suggest that a low-fat/high-fiber or carbohydrate diet is not associated with endogenous levels of sex steroid hormones, but it may modestly increase IGF-I and IGFBP-3 levels among premenopausal women.

Phase II prospective randomized trial of a low-fat diet with fish oil supplementation in men undergoing radical prostatectomy

Preclinical studies suggest lowering dietary fat and decreasing the ratio of omega-6 to omega-3 polyunsaturated fatty acids decreases the risk of prostate cancer development and progression. We conducted a phase II randomized trial to test the effect of decreasing dietary fat combined with decreasing the dietary omega-6:omega-3 ratio on biomarkers related to prostate cancer development and progression. Patients undergoing radical prostatectomy were randomly assigned to receive a low-fat diet with 5 grams of fish oil daily (dietary omega-6:omega-3 ratio of 2:1) or a control Western diet (omega-6:omega-3 ratio of 15:1) for four to six weeks prior to surgery. The primary endpoint was change in serum insulin-like growth factor I (IGF-1) between arms. Secondary endpoints were serum IGFBP-1, prostate prostaglandin E2 levels, omega-6:omega-3 fatty acid ratios, COX-2, and markers of proliferation and apoptosis. Fifty-five patients were randomized and 48 completed the trial. There was no treatment difference in the primary outcome. Positive secondary outcomes in the low-fat fish oil versus Western group were reduced benign and malignant prostate tissue omega-6:omega-3 ratios, reduced proliferation (Ki-67 index), and reduced proliferation in an ex vivo bioassay when patient sera was applied to prostate cancer cells in vitro. In summary, four to six weeks of a low-fat diet and fish oil capsules to achieve an omega-6:omega-3 fatty acid ratio of 2:1 had no effect on serum IGF-1 levels, though in secondary analyses, the intervention resulted in decreased prostate cancer proliferation and decreased prostate tissue omega-6:omega-3 ratios. These results support further studies evaluating reduction of dietary fat with fish oil supplementation on modulating prostate cancer biology.

Risks and benefits of dietary isoflavones for cancer

A high intake of fruits and vegetables is associated with a lower risk of cancer. In this context, considerable attention is paid to Asian populations who consume high amounts of soy and soy-derived isoflavones, and have a lower risk for several cancer types such as breast and prostate cancers than populations in Western countries. Hence, interest focuses on soyfoods, soy products, and soy ingredients such as isoflavones with regard to their possible beneficial effects that were observed in numerous experiments and studies. The outcomes of the studies are not always conclusive, are often contradictory depending on the experimental conditions, and are, therefore, difficult to interpret. Isoflavone research revealed not only beneficial but also adverse effects, for instance, on the reproductive system. This is also the case with tumor-promoting effects on, for example, breast tissue. Isoflavone extracts and supplements are often used for the treatment of menopausal symptoms and for the prevention of age-associated conditions such as cardiovascular diseases and osteoporosis in postmenopausal women. In relation to this, questions about the effectiveness and safety of isoflavones have to be clarified. Moreover, there are concerns about the maternal consumption of isoflavones due to the development of leukemia in infants. In contrast, men may benefit from the intake of isoflavones with regard to reducing the risk of prostate cancer. Therefore, this review examines the risks but also the benefits of isoflavones with regard to various kinds of cancer, which can be derived from animal and human studies as well as from in vitro experiments.

Effects of tomato- and soy-rich diets on the IGF-I hormonal network: a crossover study of postmenopausal women at high risk for breast cancer

To determine whether dietary modifications with tomato products and/or a soy supplement affected circulating levels of insulin-like growth factor (IGF)-1 and other markers of cell signaling in postmenopausal women at risk for developing breast cancer. Eligible and consented postmenopausal women at high risk for developing breast cancer were enrolled in a 26-week, two-arm (tomato and soy, 10 weeks each) longitudinal dietary intervention study in which each woman served as her own control. Changes in biochemical endpoints including IGF-I, IGF-binding protein (IGFBP)-3, estradiol, sex hormone-binding globulin (SHBG), C-peptide, and insulin were measured for each intervention arm. Carotenoid and isoflavone levels were measured to assess adherence. Significant increases in carotenoid and isoflavone levels during the tomato and soy study arms, respectively, suggested that women were adherent to both arms of the intervention. The tomato-rich diet had little effect on cell-signaling biomarkers previously associated with breast cancer risk. However, results of the soy intervention showed that concentrations of IGF-I and IGFBP-3 increased by 21.6 and 154.7 μmol/L, respectively (P = 0.001 for both) and SHBG decreased by 5.4 μmol/L (P < 0.001) after consumption of the soy protein supplement. Increased soy protein intake may lead to small, but significant, increases in IGF-I and IGFBP-3. Soy consumption also led to a significant decrease in SHBG, which has been hypothesized to promote, rather than prevent, cancer growth. Previous epidemiologic studies, however, have confirmed protective effect of soy on breast cancer. Additional investigation about the effect of soy on breast cancer risk and its mechanism of action is warranted.

Diet, body composition, and physical fitness influences on IGF-I bioactivity in women

OBJECTIVE

Insulin-like growth factor I (IGF-I) is a metabolic-regulatory hormone that mediates a variety of physiologic functions. Body composition, fitness status and intake of certain micro- and macronutrients are associated with circulating concentrations of immunoreactive IGF-I. The influence of these factors on IGF-I bioactivity; however, is undetermined. We assessed the relationships between IGF-I bioactivity and lifestyle factors purportedly associated with IGF-I immunoreactivity.

DESIGN

In a cross sectional study, fasted blood samples were obtained from 44 lightly active, college-age (20+/-2 yrs) women. IGF-I bioactivity was estimated by an assay which determines the ability of serum IGFs to phosphorylate IGF-I receptors in cultured cells; free and total IGF-I were measured by immunoassay. Estradiol and progesterone were measured by immunoassay. Body mass index was calculated from measured height and weight, bone mineral density and body fat percentage measured by dual energy X-ray absorptiometry, and peak oxygen consumption (VO(2peak)) determined during a graded treadmill protocol. A food frequency questionnaire measured habitual and a 5-day food record assessed short-term micro- and macronutrient intakes. Associations between bioactive, free and total IGF-I with body composition, sex hormones, VO(2peak), and dietary intake were assessed using univariate and multiple linear regression analyses.

RESULTS

Associations between bioactive IGF-I with age (r=-0.36, P<0.05), body fat percentage (r=-0.32, P<0.05), estradiol (r=0.31, P<0.05) and progesterone (r=0.33, P<0.05) concentrations, habitual alcohol (r=-0.38, P<0.05) and selenium intakes (r=0.41, P<0.01), free IGF-I with age (r=-0.34, P<0.05), estradiol (r=0.48, P<0.01) and progesterone (r=0.52, P<0.001) concentrations, habitual alcohol (r=-0.33, P<0.05) and isoflavone intakes (r=0.30, P<0.05) and total IGF-I with age (r=-0.27, P<0.05) and habitual alcohol intake (r=-0.33, P<0.05) were observed. Habitual alcohol intake was a negative predictor of bioactive, free and total IGF-I in multivariate models.

CONCLUSION

Of the lifestyle factors measured, the most robust relationship observed was a negative association between habitual alcohol intake and all measures of IGF-I. This finding suggests that alcohol intake may blunt the physiologic actions of the IGF-I axis.

The association between diet and serum concentrations of IGF-I, IGFBP-1, IGFBP-2, and IGFBP-3 in the European Prospective Investigation into Cancer and Nutrition

Circulating concentrations of insulin-like growth factor I (IGF-I) and IGF binding proteins (IGFBP) have been associated with the risk of several types of cancer. Dietary correlates of IGF-I and IGFBPs are not yet well established. The objective of this study was to assess the association between dietary intake and serum concentrations of IGF-I, IGFBP-1, IGFBP-2, and IGFBP-3 in a cross-sectional analysis of 4,731 men and women taking part in the European Prospective Investigation into Cancer and Nutrition. Diet was assessed using country-specific validated dietary questionnaires. Serum concentrations of IGF-I, IGFBP-1, IGFBP-2 and IGFBP-3 were measured, and the associations between diet and IGF-I and IGFBPs were assessed using multiple linear regression adjusting for sex, age, body mass index, smoking status, and alcohol and energy intake. Each 1 SD increment increase in total and dairy protein and calcium intake was associated with an increase in IGF-I concentration of 2.5%, 2.4%, and 3.3%, respectively (P for trend <0.001 for all) and a decrease in IGFBP-2 of 3.5%, 3.5%, and 5.4% (P for trend <0.001 for all), respectively. There were no significant associations between the intake of protein or calcium from nondairy sources and IGF-I. The results from this large cross-sectional analysis show that either the intake of dairy protein or calcium is an important dietary determinant of IGF-I and IGFBP-2 concentrations; however, we suggest that it is more likely to be protein from dairy products.

Race/ethnic variation in serum levels of IGF-I and IGFBP-3 in US adults

OBJECTIVES

The IGF axis plays a significant role in normal growth and development and variation in IGFs is associated with health outcomes. Past studies report variation in IGF levels among race/ethnic groups known to differ in disease incidence. This paper reports on race/ethnic variation in serum levels of IGF-I and IGF-BP3 in a nationally representative and ethnically diverse sample of US adults.

DESIGN

Serum IGF-I and IGFBP-3 levels from the fasting subsample (n = 6061) of respondents to the US National Health and Nutrition Examination Survey III (NHANES III) were analyzed using an IGF-I ELISA (Diagnostic Systems Laboratory (DSL) 10-5600) and an IGFBP-3 IRMA (DSL 6600). The NHANES is a combined examination and interview survey of a nationally representative sample of US adults. Regression analyses were used to estimate cross-sectional associations between the IGF axis and demographic variables.

RESULTS

In unadjusted analyses, serum IGF-I levels were higher in males than in females, and IGFBP-3 levels were higher in females than in males. Both analytes were lower in older adults. Univariate analyses indicate that serum levels of IGF-I are lower in female Non-Hispanic Whites (NHW) (256 [4.9]) and Hispanics (249 [6.6]) than in Non-Hispanic Blacks (NHB) (281 [4.9]). However, in males, IGF levels in NHWs (287 [3.6]) and NHBs (284 [4.3]) are similar and levels in Mexican-Americans are only moderately reduced (265 [3.4]). Notably, NHB's have the highest molar ratio of IGF-I:IGFBP-3 at all ages. After adjustment for age and BMI, gender and race/ethnicity differences persist.

CONCLUSIONS

These cross-sectional data support exploration of the IGF axis as an explanation for some race/ethnic differences in cancer incidence.

Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis

BACKGROUND

Hormonal effects of soy and isoflavones have been investigated in numerous trials with equivocal findings. We aimed to systematically assess the effects of soy and isoflavones on circulating estrogen and other hormones in pre- and post-menopausal women.

METHODS

The Cochrane Library, MEDLINE and EMBASE (plus reviews and experts) were searched to December 2007. Inclusion of randomized or residential crossover trials of soy or isoflavones for 4 or more weeks on estrogens, SHBG, FSH, LH, progesterone and thyroid hormones in women was assessed independently in duplicate. Six percent of papers assessed were included. Data concerning participants, interventions, outcomes, potential effect modifiers and trial quality characteristics were extracted independently in duplicate.

RESULTS

Forty-seven studies (11 of pre-, 35 of post- and 1 of perimenopausal women) were included. In premenopausal women, meta-analysis suggested that soy or isoflavone consumption did not affect primary outcomes estradiol, estrone or SHBG concentrations, but significantly reduced secondary outcomes FSH and LH [by ∼20% using standardized mean difference (SMD), P = 0.01 and 0.05, respectively]. Menstrual cycle length was increased by 1.05 days (95% CI 0.13, 1.97, 10 studies). In post-menopausal women, there were no statistically significant effects on estradiol, estrone, SHBG, FSH or LH, although there was a small statistically non-significant increase in total estradiol with soy or isoflavones (∼14%, SMD, P = 0.07, 21 studies).

CONCLUSIONS

Isoflavone-rich soy products decrease FSH and LH in premenopausal women and may increase estradiol in post-menopausal women. The clinical implications of these modest hormonal changes remain to be determined.

Prostate cancer prevention by nutritional means to alleviate metabolic syndrome

In 1987 when Reaven introduced syndrome X (metabolic syndrome, or MS), we were studying skeletal muscle insulin resistance and found that when rodents were fed a high-fat, refined-sugar (HFS) diet, insulin resistance developed along with aspects of MS, including hyperinsulinemia, hypertension, hypertriglyceridemia, and obesity. MS was controlled in rodents by switching them to a low-fat, starch diet and was controlled in humans with a low-fat starch diet and daily exercise (Pritikin Program). Others reported inverse relations between serum insulin and sex hormone-binding globulin (SHBG). When subjects were placed on the Pritikin Program, insulin fell and SHBG rose and it was suggested that prostate cancer might also be an aspect of MS. A bioassay was developed with tumor cell lines grown in culture and stimulated with serum before and after a diet and exercise intervention. Diet and exercise altered serum factors that slowed the growth rate and induced apoptosis in androgen-dependent prostate cancer cells. Changes in serum with diet and exercise that might be important include reductions in insulin, estradiol, insulin-like growth factor-I (IGF-I), and free testosterone with increases in SHBG and IGF binding protein-1. Hyperinsulinemia stimulates liver production of IGF-I, plays a role in the promotion of prostate cancer, and thus is the cornerstone for both MS and prostate cancer. Adopting a low-fat starch diet with daily exercise controls MS and should reduce the risk of prostate cancer.

Dietary soy and tea combinations for prevention of breast and prostate cancers by targeting metabolic syndrome elements in mice

BACKGROUND

The prevalence of metabolic syndrome is high and is increasing in parallel with increasing incidences of breast and prostate cancers. The combination of soy with tea was shown to have synergistic effects on preventing breast and prostate tumors, but the effects of soy and tea combinations on metabolic syndrome-related elements have not been investigated.

OBJECTIVE

We aimed to determine the effects of soy and tea components, alone and in combination, on abdominal adipose mass and serum concentrations of adipokines, growth factors, and sex hormones in male and female mice.

DESIGN

Male and female FVB/N mice were treated with soy, tea components, or both. Food intake and body weight were monitored weekly. At the end of the experiment, abdominal white adipose tissue was weighed, and serum concentrations of biomarkers were measured.

RESULTS

Whole teas, but not the tea polyphenol extracts, significantly reduced abdominal white adipose tissue by 43-60% in female mice and by 65-70% in male mice. The combination of soy phytochemical concentrate and green tea reduced serum insulin-like growth factor-I concentrations in both male and female mice in a synergistic manner. The soy phytochemical concentrate and tea combinations reduced serum estrogen concentrations in female mice in a synergistic manner. Soy phytochemical concentrate and teas also significantly reduced serum leptin concentrations in both male and female mice and testosterone concentrations in male mice.

CONCLUSION

Further research is warranted to investigate whether soy and tea combinations may prevent breast or prostate cancer in a synergistic manner in part by alleviating metabolic disorders.

Relationship of Dietary Protein and Soy Isoflavones to Serum IGF-1 and IGF Binding Proteins in the Prostate Cancer Lifestyle Trial

High levels of insulin-like growth factor 1 (IGF-1) are associated with increased risk of prostate cancer, whereas increased levels of some of its binding proteins (IGFBPs) seem to be protective. High intakes of dietary protein, especially animal and soy protein, appear to increase IGF-1. However, soy isoflavones have demonstrated anti-proliferative and apoptotic effects both in vitro and in vivo. We evaluated dietary intakes of total protein and soy isoflavones in relation to the IGF axis in prostate cancer patients making comprehensive lifestyle changes including a very low-fat vegan diet supplemented with soy protein (58 g/day). After one year, intervention group patients reported significantly higher intakes of dietary protein and soy isoflavones compared to usual-care controls (P < 0.001). IGF-1 increased significantly in both groups, whereas IGFBP-1 rose in the experimental group only (P < 0.01). Increases in vegetable protein over one year were associated with increases in IGFBP-1 among intervention group patients (P < 0.05). These results suggest that dietary protein and soy isoflavones, in the context of comprehensive lifestyle changes, may not significantly alter IGF-1. However, given the recent literature indicating that high intake of protein rich in essential amino acids (animal or soy protein) may increase IGF-1, it may be prudent for men with early stage prostate cancer not to exceed dietary protein recommendations.

Effect of a tomato drink intervention on insulin-like growth factor (IGF)-1 serum levels in healthy subjects

There is concern that dietary factors can modulate the insulin-like growth factor (IGF) system. The aim of this work was to evaluate the effect of a tomato drink intervention providing small amounts of lycopene and other carotenoids on serum levels of IGF-1. Twenty healthy young subjects participated in a repeated measure double-blind, cross-over design. Subjects consumed 250 ml of a tomato drink or a placebo drink for 26 days separated by 26 days wash-out. The tomato drink intake increased plasma lycopene, phytoene, phytofluene, and beta-carotene concentrations by 0.22, 0.12, 0.13, and 0.18 micromol/L, respectively (P < 0.05). No significant effect of the tomato drink intake on IGF-1 levels was observed. However, changes in lycopene before and after each experimental period were inversely and significantly correlated with those of IGF-1 (r = -0.33, P < 0.05, N = 20). No correlation was found with the other carotenoids. A significant reduction of IGF-1 serum level (-5.7%) was observed in subjects (n = 11) with the highest plasma lycopene response but also IGF-1 levels following the tomato drink intake (P < 0.05). No effect was evident after the placebo treatment. The results suggest that further exploration of the role of tomato lycopene on IGF-1 modulation both on healthy and on subjects at risk is necessary.

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

Epidemiological studies show that increased insulin-like growth factor (IGF)-I concentrations are related to increased colorectal cancer risk. A reduced colorectal cancer risk has been associated with isoflavones, which might affect the IGF-system because of their weak estrogenic activity. We conducted a randomized, placebo-controlled, double-blind crossover study to investigate the effect of an 8-wk isolated isoflavone supplementation (84 mg/d) on serum concentrations of total IGF-I, free IGF-I, total IGF-II, IGF binding protein (BP)-1, IGFBP-2, and IGFBP-3. Additionally, we investigated whether IGF-system component differences were related to concentrations of the more potent estrogenic isoflavone metabolite, equol. Our study population consisted of 37 men with a family history of colorectal cancer or a personal history of colorectal adenomas. Isoflavone supplementation did not significantly affect serum total IGF-I concentrations (relative difference between serum total IGF-I concentrations after isoflavone supplementation and after placebo: -1.3%, 95% CI -8.6 to 6.0%). Neither free IGF-I, nor total IGF-II, IGFBP-1, IGFBP-2, or IGFBP-3 concentrations were significantly altered. Interestingly, the change in serum IGF-I concentrations after isoflavone supplementation was negatively associated with serum equol concentrations (r=-0.49, P=0.002). In conclusion, isolated isoflavones did not affect the circulating IGF-system in a male high-risk population for colorectal cancer. However, to our knowledge, this is the first study that suggests isoflavones might have an IGF-I lowering effect in equol producers only. This underlines the importance of taking into account equol status in future isoflavone intervention studies.

Serum Insulin-Like Growth Factor-I Levels Among Women in Hawaii and Japan With Different Levels of Tofu Intake

Insulin-like growth factor-I (IGF-I) has been proposed as the link between diet and breast cancer risk. Due to their estrogen-like structure, soy isoflavones may affect IGF-I levels in a similar way as exogenous estrogens. In a cross-sectional design, we compared IGF-I levels between women with high and low soy intake. The analysis included 611 pre- and postmenopausal women: Japanese in Japan and Japanese and Caucasians in Hawaii. The subjects had participated in a previous study, were never diagnosed with breast cancer, provided a screening mammogram and a blood sample, and completed validated food-frequency questionnaires. The same laboratory analyzed all serum samples for IGF-I and IGF binding protein (IGFBP)-3 by enzyme-linked immunosorbent assay. We estimated covariate-adjusted mean IGF-I and IGFBP-3 levels by tofu intake. The respective mean IGF-I levels were 213, 257, and 255 ng/ml for Japanese in Japan, Japanese in Hawaii, and Caucasians in Hawaii. Tofu intake was higher in Japan than among Japanese and Caucasians in Hawaii (11.0 vs. 9.4 and 4.9 g/1,000 kcal). Mean IGF-I levels were 11% lower among women in the highest tofu intake category compared with the lowest, but the difference in IGF-I levels between the highest and lowest tofu category was only significant among women in Japan. Inclusion of total energy, total protein, meat, and dairy intake did not materially alter the association between tofu consumption and IGF-I levels. These findings suggest that a diet rich in soy foods and low in meats may be related to lower IGF-I levels, but it is unclear whether soy or other characteristics of diet and lifestyle are responsible for this association.

Toward a core nutraceutical program for cancer management

As previously suggested, it may be feasible to impede tumorevoked angiogenesis with a nutraceutical program composed of glycine, fish oil, epigallocatechin-3-gallate, selenium, and silymarin, complemented by a low-fat vegan diet, exercise training, and, if feasible, a salicylate and the drug tetrathiomolybdate. It is now proposed that the scope of this program be expanded to address additional common needs of cancer patients: blocking the process of metastasis; boosting the cytotoxic capacity of innate immune defenses (natural killer [NK] cells); preventing cachexia, thromboembolism, and tumor-induced osteolysis; and maintaining optimal micronutrient status. Modified citrus pectin, a galectin-3 antagonist, has impressive antimetastatic potential. Mushroombeta-glucans and probiotic lactobacilli can amplify NK activity via stimulatory effects on macrophages. Selenium, beta-carotene, and glutamine can also increase the number and/or cytotoxic activity of NK cells. Cachectic loss of muscle mass can be opposed by fish oil, glutamine, and beta-hydroxy-beta-methylbutyrate. Fish oil, policosanol, and vitamin D may have potential for control of osteolysis. High-dose aspirin or salicylates, by preventing NF-B activation, can be expected to aid prevention of metastasis and cachexia while down-regulating osteolysis, but their impacts on innate immune defenses will not be entirely favorable. A nutritional insurance formula crafted for the special needs of cancer patients can be included in this regimen. To minimize patient inconvenience, this complex core nutraceutical program could be configured as an oil product, a powder, and a capsule product, with the nutritional insurance formula provided in tablets. It would be of interest to test this program in nude mouse xenograft models.

Are all dilemmas in gerontology being swept under the carpet of intra-individual variability?

It is considered that there are great differences among elderly individuals, because the intra-individual variability is great. The differences among specific individuals grow with their age, so when adults reach a very old age, it seems that there are great differences among them--some are able to do some work, the others are not so able-bodied, whereas among high school students there is usually little difference in their physical ability. The research that supports the above mentioned points, however, does not exist and this opinion came about as a result of deduction. The goal of this study is to examine the fluctuations in the elderly and prove that the genetic difference plays a bigger role than the variability, as the intra-individual (or the between-person) variability is present everywhere, not only in very old people.

IGF-1, IGFBP-3, and Nutritional Factors in Young Black and White Men: The CARDIA Male Hormone Study

Nutritional factors might play a role in regulating serum levels of insulin-like growth factors (IGFs), which are associated with some cancers. We examined the associations of nutritional factors with IGF-1 and IGF binding protein-3 (IGFBP-3). Serum IGF-1 and IGFBP-3 levels and dietary intake were measured in 459 black and 682 white male subjects of the Coronary Artery Risk Development in Young Adults study at the Year 7 (1992-1993) exam. Analysis of covariance and multivariable linear regression were used to assess associations of IGFs with dietary factors by race. IGF-1 was positively associated with magnesium in both black and white men (P = 0.008 and 0.05, respectively). Calcium was positively significantly related to IGF-1 in black men (P = 0.04) and marginally so in white men (P = 0.09). In black men, IGFBP-3 was positively associated with magnesium (P = 0.02), and one serving of milk per day was associated with an 8.23-ng/ml higher IGF-1 concentration (P = 0.05). Tests for interaction, however, revealed no differences between blacks and whites in the associations of nutrients with IGF-1 or IGFBP-3. In conclusion, the associations of dietary factors with serum IGF-1 and IGFBP-3 observed in our study corroborate those from other studies and generally do not differ between black and white men.