Glycemic index, nutrient density, and promotion of aberrant crypt foci in rat colon

Dietary Approach of Patients with Hormone-Related Cancer Based on the Glycemic Index and Glycemic Load Estimates

Hormone-related cancers, namely breast, endometrial, cervical, prostate, testicular, and thyroid, constitute a specific group of cancers dependent on hormone levels that play an essential role in cancer growth. In addition to the traditional risk factors, diet seems to be an important environmental factor that partially explains the steadily increased prevalence of this group of cancer. The composition of food, the dietary patterns, the endocrine-disrupting chemicals, and the way of food processing and preparation related to dietary advanced glycation end-product formation are all related to cancer. However, it remains unclear which specific dietary components mediate this relationship. Carbohydrates seem to be a risk factor for cancer in general and hormone-related cancers, in particular, with a difference between simple and complex carbohydrates. Glycemic index and glycemic load estimates reflect the effect of dietary carbohydrates on postprandial glucose concentrations. Several studies have investigated the relationship between the dietary glycemic index and glycemic load estimates with the natural course of cancer and, more specifically, hormone-related cancers. High glycemic index and glycemic load diets are associated with cancer development and worse prognosis, partially explained by the adverse effects on insulin metabolism, causing hyperinsulinemia and insulin resistance, and also by inflammation and oxidative stress induction. Herein, we review the existing data on the effect of diets focusing on the glycemic index and glycemic load estimates on hormone-related cancers.

Monosodium glutamate-induced diabetic mice are susceptible to azoxymethane-induced colon tumorigenesis

Obese people and diabetic patients are known to be high risk of colorectal cancer (CRC), suggesting need of a new preclinical animal model, by which to extensively study the diverse mechanisms, therapy and prevention. The present study aimed to determine whether experimental obese and diabetic mice produced by monosodium glutamate (MSG) treatment are susceptible to azoxymethane (AOM)-induced colon tumorigenesis using early biomarkers, aberrant crypts foci (ACF) and β-catenin-accumulated crypts (BCACs), of colorectal carcinogenesis. Male Crj:CD-1 (ICR) newborns were daily given four subcutaneous injections of MSG (2 mg/g body wt) to induce diabetes and obesity. They were then given four intraperitoneal injections of AOM (15 mg/kg body wt) or saline (0.1 ml saline/10 g body wt). Ten weeks after the last injection of AOM, the MSG-AOM mice had a significant increase in the multiplicity of BCAC (13.83 ± 7.44, P < 0.002), but not ACF (78.00 ± 11.20), when compare to the Saline-AOM mice (5.45 ± 1.86 of BCAC and 69.27 ± 8.06 of ACF). Serum biochemical profile of the MSG-treated mice with or without AOM showed hyperinsulinemia, hypercholesteremia and hyperglycemia. The mRNA expression of insulin-like growth factor-1 receptor (IGF-1R, P<0.01) was increased in the MSG-AOM mice, when compared with the mice given AOM alone. IGF-1R was immunohistochemically expressed in the BCAC, but not ACF, in the AOM-treated mice. Our findings suggest that the MSG mice are highly susceptible to AOM-induced colorectal carcinogenesis, suggesting potential utility of our MSG-AOM mice for further investigation of the possible underlying events that affect the positive association between obese/diabetes and CRC.

Number of aberrant crypt foci associated with adiposity and IGF1 bioavailability

BACKGROUND

Dysregulation of the insulin-like growth factor (IGF) system, a common consequence of adiposity-induced insulin resistance, may be a key underlying mechanism linking excess body weight with colon cancer. Evidence has been derived from studies of cancer and polyps. Supporting data about aberrant crypt foci (ACF), putative pre-polyp changes, have been generated only from animal studies to date.

METHODS

We randomly selected 26 patients with sex-specific elevated waist-hip-ratio (WHR) and 26 with normal values from a series of 150 patients seeking routine colonoscopy at the University of Connecticut Health Center. Cross-sectional analyses were performed of ACF number (<5, > or = 5) in relation to total IGF1, IGF-binding protein-3 (IGFBP3), insulin, body mass index (BMI), WHR and waist circumference (WC). Visualized ACF in the 20 cm of the distal colon were counted using advanced endoscopic imaging.

RESULTS

Patients with > or = 5 ACF had higher BMI, WHR, and WC compared with patients with >5 ACF (p = 0.04, p = 0.03, and p = 0.01, respectively). IGFBP3 was reduced (p = 0.02) and IGF1:IGFBP3 molar ratio was greater (p = 0.03) in patients with > or = 5 ACF. We did not observe significant associations between ACF number and insulin or total IGF1.

CONCLUSIONS

Our study provides the first report in humans of a possible association of ACF prevalence and IGF1 bioavailability as characterized by IGF1:IGFBP3 molar ratio and IGFBP3 level. More research is needed to determine whether this relationship is varied by ACF features (e.g., size, dysplasia, molecular changes), synchronous cancer and polyps, and is modified by colon cancer risk factors.

Type 2 diabetes mellitus as risk factor for colorectal cancer

Colorectal cancer occurs more frequently in patients with type 2 diabetes mellitus. The hyperinsulinemia-hypothesis suggests that elevated levels of insulin and free IGF-1 promote proliferation of colon cells and lead to a survival benefit of transformed cells, ultimately resulting in colorectal cancer. In patients with type 2 diabetes mellitus, epidemiological studies show an increased risk for colorectal cancer and an even higher risk if patients are treated with sulphonylureas or insulin. Moreover, tumour progression at hyperinsulinemia is more rapid and tumour-associated mortality is increased. Colorectal cancer can be avoided by screening. Recommendations for colorectal cancer screening should employ the recent epidemiologic evidence. All patients with type 2 diabetes mellitus should be recommended to undergo colonoscopy before starting insulin therapy, and screening intervals should not exceed 5 years. For this concept, a review of the evidence is presented, and a screening algorithm for colorectal cancer in patients with type 2 diabetes mellitus is proposed.

Carbohydrate Digestibility Predicts Colon Carcinogenesis in Azoxymethane-Treated Rats

The purpose of this study was to compare the effect of carbohydrate structure and digestibility on azoxymethane (AOM)-induced colon carcinogenesis. Five groups of male Fischer 344 rats each comprising 30 animals were injected with AOM and fed a high-fat diet with 15% of various carbohydrates. The carbohydrate sources used were sucrose, cornstarch (a linear starch, reference group), potato starch (a branched starch), a short-chained oligofructose (Raftilose), and a long-chained inulin-type fructan (Raftiline). An interim sacrifice was performed after 9 wk to investigate markers of carbohydrate digestibility, including caecal fermentation (caecum weight and pH) and glucose and lipid metabolism [glucose, fructoseamine, HbA1c, triglycerides, and insulin-like growth factor (IGF) 1]. In addition potential early predictors of carcinogenicity [cell proliferation and aberrant crypt foci (ACF)] at 9 wk and their correlation to colon cancer risk after 32 wk were investigated. Tumor incidence was significantly reduced in animals fed oligofructose, and the number of tumors per animal was significantly reduced in animals fed inulin and oligofructose at 32 wk after AOM induction compared to the reference group fed sucrose. Increased caecum weight and decreased caecal pH were seen in groups fed oligofructose, inulin, and potato starch. Plasma triglyceride was decreased in rats fed oligofructose and inulin. Cell proliferation was increased in the proximal colon of rats fed sucrose, oligofructose, and inulin, and the number of cells per crypt decreased in rats fed oligofructose and inulin. The total number of ACF's was unaffected by treatment, and the size and multiplicity of ACF was unrelated to tumor development. It was concluded that less digestible carbohydrates with an early effect on caecum fermentation and plasma triglyceride decreased subsequent tumor incidence and multiplicity. This was unrelated to ACF, cell proliferation, and other markers of glucose and lipid metabolism.

Glycemic Index, Glycemic Load, and Carbohydrate Intake in Relation to Risk of Distal Colorectal Adenoma in Women

Case-control studies and a cohort study have shown inconsistent associations between a high glycemic index or a high glycemic load and risk of colorectal cancer. These dietary variables have not been examined in relation to risk of colorectal adenoma. We thus examined the associations between dietary glycemic index, glycemic load, and carbohydrate intake with risk of adenoma of the distal colon or rectum among 34,428 US women who were initially free of cancer or polyps, who completed a semi-quantitative food-frequency questionnaire in 1980, and who underwent endoscopy from 1980 through 1998. 1,715 adenoma cases (704 large adenomas, 894 small adenomas, 1,277 distal colon adenomas, and 504 rectal adenomas) were documented during 18 years of follow-up. Dietary glycemic index, glycemic load, and carbohydrate intake were not related to risk of total colorectal adenoma after adjustment for age and established risk factors [relative risk (RR) for extreme quintiles of glycemic index = 1.11, 95% confidence interval (CI) 0.94-1.32, P for trend = 0.66; RR for glycemic load = 0.92, 95% CI 0.76-1.11, P for trend = 0.63; RR for carbohydrate intake = 0.90, 95% CI 0.73-1.11, P for trend = 0.64]. In addition, no significant associations were found for large or small adenoma, distal colon or rectal adenoma, or across strata of body mass index. Our findings do not support the hypothesis that a high glycemic index diet, a high glycemic load diet, or high carbohydrate intake overall are associated with risk of colorectal adenoma.

Insulin and cancer

Obesity has recently been linked to mortality from the majority of cancers. The insulin/insulin-like growth factor (IGF) system may partly explain this effect. The metabolic syndrome, associated with hyperinsulinemia, may modulate this effect. Recent evidence supports the role of insulin and IGF-1 as important growth factors, acting through the tyrosine kinase growth factor cascade in enhancing tumor cell proliferation. In addition, the metabolic syndrome associated with a chronic inflammatory state and accompanying cytokine abnormalities may also contribute to tumor progression. Growing links between insulin and the etiology as well as prognosis in colon, prostate, pancreatic, and, particularly, breast cancer are reviewed. Of particular concern is the evidence that elevated IGF-1 may interfere with cancer therapy, adversely affecting prognosis. The role of insulin is of concern because of the increasing levels of obesity and the associated metabolic syndrome. Weight gain, through typical Western diet; limited levels of activity; and, more recently, stress-related changes in neuroendocrine function may lead to insulin resistance and hyperinsulinemia. The opportunity for a multidisciplinary approach involving nutrition, exercise, and stress reduction in an integrative setting may be crucial to limiting the insulin-resistant state and improving cancer outcomes.

Glycemic index in chronic disease: a review

AIM

The intent of this review is to critically analyze the scientific evidence on the role of the glycemic index in chronic Western disease and to discuss the utility of the glycemic index in the prevention and management of these disease states.

BACKGROUND

The glycemic index ranks foods based on their postprandial blood glucose response. Hyperinsulinemia and insulin resistance, as well as their determinants (eg high energy intake, obesity, lack of physical activity) have been implicated in the etiology of diabetes, coronary heart disease and cancer. Recently, among dietary factors, carbohydrates have attracted much attention as a significant culprit, however, different types of carbohydrate produce varying glycemic and insulinemic responses. Low glycemic index foods, characterized by slowly absorbed carbohydrates, have been shown in some studies to produce beneficial effects on glucose control, hyperinsulinemia, insulin resistance, blood lipids and satiety.

METHOD

Studies on the short and long-term metabolic effects of diets with different glycemic indices will be presented and discussed. The review will focus primarily on clinical and epidemiological data, and will briefly discuss in vitro and animal studies related to possible mechanisms by which the glycemic index may influence chronic disease.

Changing concepts of dietary fiber: implications for carcinogenesis

The dietary fiber (DF) hypothesis suggested that DF, as plant cell walls, protected against colorectal cancer. The implicit assumption in much historic literature was that the readily analyzed and quantified nonstarch polysaccharide (NSP) component was critical in cancer protection. However, the presence of polymeric phenolic components such as lignin or suberin has profound effects on the physicochemical properties of the cell walls and largely determines their physiological properties in humans. In certain groups of food plants, degradation of cell walls that contain neither lignin nor suberin releases ferulic acid and other hydroxycinnamic acids. These acids have antioxidant, antimutagenic, and other anticancer effects, including modulation of gene expression and immune response. Reexamination of literature on cancer protection suggests that plant cell walls containing significant amounts of phenolic components may be the most likely to protect against cancer. In the last 30 years, the definition of DF has been incrementally expanded to incorporate NSP extracted from plant cell walls and from sources other than plant cell walls, then resistant starch, and most recently nondigestible oligosaccharides. On the early definitions, increased consumption of DF could only be achieved by increasing the intake of whole grains, brans, or other food plant material that would increase the intake of plant cell walls containing significant amounts of phenolic components. However, the new definitions make it possible to increase "dietary fiber" without consuming any such materials. We suggest that this could have negative connotations for cancer risk in human populations.

Insulin, insulin-like growth factors and colon cancer: a review of the evidence

Insulin and insulin-like growth factor (IGF) axes are major determinants of proliferation and apoptosis and thus may influence carcinogenesis. In various animal models, modulation of insulin and IGF-1 levels through various means, including direct infusion, energy excess or restriction, genetically induced obesity, dietary quality including fatty acid and sucrose content, inhibition of normal insulin secretion and pharmacologic inhibition of IGF-1, influences colonic carcinogenesis. Human evidence also associates high levels of insulin and IGF-1 with increased risk of colon cancer. Clinical conditions associated with high levels of insulin (noninsulin-dependent diabetes mellitus and hypertriglyceridemia) and IGF-1 (acromegaly) are related to increased risk of colon cancer, and increased circulating concentrations of insulin and IGF-1 are related to a higher risk of colonic neoplasia. Determinants and markers of hyperinsulinemia (physical inactivity, high body mass index, central adiposity) and high IGF-1 levels (tall stature) are also related to higher risk. Many studies indicate that dietary patterns that stimulate insulin resistance or secretion, including high consumption of sucrose, various sources of starch, a high glycemic index and high saturated fatty acid intake, are associated with a higher risk of colon cancer. Although additional environmental and genetic factors affect colon cancer, the incidence of this malignancy was invariably low before the technological advances that rendered sedentary lifestyles and obesity common, and increased availability of highly processed carbohydrates and saturated fatty acids. Efforts to counter these patterns are likely to have the most potential to reduce colon cancer incidence, as well as cardiovascular disease and diabetes mellitus.

The influence of simple sugars and starch given during pre- or post-initiation on aberrant crypt foci in rat colon

The aim of the present study was to investigate the enhancing effect of dietary sugar on the development of aberrant crypt foci (ACF) in male F344 rats initiated with azoxymethane (AOM). The potential role of sugar as either a co-initiator or a promoter was investigated by giving diets high in sucrose and dextrin (61%) during either the pre-initiation, the initiation, and/or the post-initiation stage of the ACF development. The colonic cell proliferation, activity of colonic phase II enzymes, and a biomarker of lipid peroxidation were additionally examined in order to obtain information on the specific mechanisms involved in the suggested effect of sucrose and dextrin on ACF development. The number of large sized and the total number of ACF were significantly increased by feeding sucrose and dextrin in the post-initiation period. No positive association between colonic cell proliferation and ACF was seen. The level of oxidative stress in the cytosol from the proximal colon and colonic glutathione transferase and quinone reductase was not affected by the sugar treatments. The overall results from this study show that sucrose and dextrin enhance the number of preneoplastic lesions in AOM-initiated rats, and act primarily as promoters in the development of ACF.

The relation of type 2 diabetes and cancer

Increasing evidence indicates that individuals with type 2 diabetes (diabetes) are at elevated risk for several common human malignancies, including cancers of the colon, breast, endometrium, pancreas, and liver. In particular, the consistent positive results reported by prospective investigations make it unlikely that methodologic issues, occult tumors, or chance results could explain the findings. Since diabetes and impaired fasting glucose together affect >25% of Americans above age 50, even a moderate etiologic association (e.g., relative risk = 1.5) would explain >10% of involved malignancies. Laboratory studies have suggested biologically plausible mechanisms. Insulin, for example, is typically at high levels during the development and early stages of diabetes. Activation of the insulin receptor by its ligand, or cross-activation of the insulin-like growth factor-I receptor, has been shown to be mitogenic and promote tumorigenesis in various model systems. A "unifying concept," in fact, holds that hyperinsulinemia may underlie the cancer associations of several additional risk factors, including high waist circumference, visceral fat, waist-to-hip ratio, body mass index, sedentary lifestyle, and energy intake. In this review, we assess current evidence regarding the relation of type 2 diabetes with cancer, and evaluate the findings in terms of well-accepted criteria for establishing causality.

Nutrition in cancer prevention

Although variation in diet may account for approximately one third of the variation in cancer incidence worldwide, epidemiologic studies have proven to be a blunt instrument for identifying causal relationships between intakes of specific food constituents and cancer risk at specific sites. Diets rich in fruits and vegetables seem to be protective, but the adverse effects of beta carotene supplementation trials on lung cancer incidence in smokers caution against the attribution of benefit to single substances. Important diet-gene interactions may exist, as illustrated by differential responses to variation in folate status in those with methylenetetrahydrofolate reductase polymorphisms. Targeting initial intervention studies in those with explicit genetic predisposition to cancer may have both greater cost-effectiveness and fewer ethical difficulties than do similar studies in the general public.