Colorectal cancer: another complication of diabetes mellitus?

A meta-analysis of the association of physical activity with reduced risk of colorectal cancer

BACKGROUND

Physical activity may be associated with reduced risk of colorectal cancer. The main aim of this paper is to review the available evidence for a link between exercise and large bowel cancer.

METHODS

A Cochrane-type methodology was performed. Data extracted included, type of study, type of physical activity measured and the numerical results. The risk ratios (RR) of the studies have been pooled according to the type of study, type of exercise, type of cancer and sex. Pooling was undertaken using fixed effect meta-analysis. A random effect meta-analysis was used where substantial heterogeneity existed.

RESULT

Data from 19 cohort studies showed a statistically significant reduction in the risk of colon cancer in physically active males, RR being 0.79 (95% CI 0.72-0.87) and 0.78 (95% CI 0.68-0.91) for occupational and recreational activities, respectively. In women only recreational activities are protective against colon cancer (RR = 0.71, 95%CI 0.57-0.88). Case-control studies showed significantly reduced risks of colon cancer in both sexes irrespective of the type of activity. No protection against rectal cancer is seen in either sex.

CONCLUSION

There is considerable evidence that physical activity is associated with reduced risk of colon cancer in both males and females.

From colonic polyps to colon cancer: pathophysiology, clinical presentation, and diagnosis

Epidemiologists, basic researchers, clinicians, and public health administrators unite! Develop and implement a simple, safe, and effective preventive and screening test for colon cancer. The public will willingly and enthusiastically accept such a test. Many thousands of lives are at stake every year.

Relationship between HbA(1)c and mortality in a Japanese population

AIM/HYPOTHESIS

HbA(1)c concentrations are known to be associated with all-cause excess mortality risk in Caucasians. However, the relationship has not been clarified well in the Japanese. In addition, studies of the relationship between HbA(1)c and mortality from malignant neoplasms are scarce.

METHODS

HbA(1)c was measured for 3,710 people of a cohort composed of A-bomb survivors and controls. At baseline they were divided into five groups: a normal HbA(1)c group of 1,143 individuals with HbA(1)c of <5.5%, a slightly high but normal HbA(1)c group of 1,341 individuals with HbA(1)c > or =5.5% to <6.0%, a slightly high HbA(1)c group of 589 individuals with HbA(1)c > or =6.0% to <6.5%, a high HbA(1)c group of 259 individuals with HbA(1)c > or =6.5%, and a group of 378 individuals known to have type 2 diabetes. Using a Cox proportional hazards model, hazard ratios based on comparisons with the normal HbA(1)c group were obtained.

RESULTS

During the observation period there were 754 deaths. For all-cause and cardiovascular disease mortality, a significant increase of the hazard ratio was observed for the slightly high HbA(1)c group. A similar increase in malignant neoplasm-related mortality was observed for both the high HbA(1)c group and the diabetes group.

CONCLUSIONS/INTERPRETATION

Our results suggest that individuals in the Japanese population with HbA(1)c levels of 6% or more might have increased mortality risk. The results indicate that HbA(1)c measurements should be sought even for people who have not been diagnosed with diabetes.

Dietary Glycemic Load, Carbohydrate, Sugar, and Colorectal Cancer Risk in Men and Women

Hyperinsulinemia may explain excess colorectal cancer among individuals who are overweight or inactive. Recent studies have observed elevated colorectal cancer risk among individuals with elevated insulin levels 2 hours after oral glucose challenge or with elevated plasma C-peptide levels. The effect of consuming a high glycemic diet on colorectal risk, however, remains uncertain. Two prospective cohort studies, the Nurses' Health Study and the Health Professionals Follow-up Study, contributed up to 20 years of follow-up. After exclusions, 1,809 incident colorectal cancers were available for analyses. Dietary glycemic load (GL) was calculated as a function of glycemic index (postprandial blood glucose response as compared with a reference food), carbohydrate content, and frequency of intake of individual foods reported on food frequency questionnaires. Multivariable Cox proportional hazards models were used to adjust for potential confounders. Intakes of dietary carbohydrate, GL, overall glycemic index, sucrose, and fructose were not associated with colorectal cancer risk in women. A small increase in risk was observed in men with high dietary GL (multivariate relative risk, 1.32; 95% confidence interval, 0.98-1.79; highest versus lowest quintile), sucrose or fructose (multivariate relative risk, 1.37; 95% confidence interval, 1.05-1.78; highest versus lowest quintile of fructose, P = 0.008). Associations were slightly stronger among men with elevated body mass index (≥25 kg/m2). Results among women were similar after stratifying by body mass index or physical activity. High intakes of GL, fructose, and sucrose were related to an elevated colorectal cancer risk among men. For women, however, these factors did not seem to increase the risk of colorectal cancer.

Diabetes Mellitus and Subsite-Specific Colorectal Cancer Risks in the Iowa Women's Health Study

Objective: Controversy remains regarding the association between type 2 diabetes mellitus (DM) and colorectal cancer (CRC) risk. To clarify and extend the existing data, we prospectively evaluated the association between self-reported type 2 DM (onset at &gt;30 years of age) and incident CRC, overall and by anatomic subsite, among postmenopausal women in the Iowa Women's Health Study (n = 35,230).

Methods: After 14 years of follow-up, a total of 870 incident CRC cases were identified through annual linkage to the Iowa Cancer Registry. DM was analyzed as reported at baseline and as a time-dependent variable using information obtained during follow-up. CRC risks were estimated using Cox proportional hazards regression models.

Results: After adjusting for age, body mass index and other potential confounding variables, the relative risk (RR) for women with DM versus women without DM was modestly increased at 1.4 [95% confidence interval (95% CI), 1.1-1.8]. By anatomic subsite, the RR for proximal colon cancer was statistically significantly increased (RR, 1.9; 95% CI, 1.3-2.6), whereas the RRs for distal colon (RR, 1.1; 95% CI, 0.6-1.8) and rectal cancer (RR, 0.8; 95% CI, 0.4-1.6) were not statistically different from unity. Analyses that included DM ascertained at baseline and follow-up yielded similar results.

Conclusion: In this large, prospective study of postmenopausal women, the association between DM and incident CRC was found to be subsite specific. If confirmed by others, this finding implies that CRC prevention strategies among type 2 DM patients should include examination of the proximal colon.

The pathophysiology, clinical presentation, and diagnosis of colon cancer and adenomatous polyps

A review of the pathophysiology, clinical presentation, and diagnosis of colon cancer and colonic polyps is important and timely. This field is rapidly changing because of breakthroughs in the molecular basis of carcinogenesis and in the technology for colon cancer detection and treatment. This article reviews colon cancer and colonic polyps, with a focus on recent dramatic advances, to help the pri-mary care physician and internist appropriately refer patients for screening colonoscopy and intelligently evaluate colonoscopic findings to reduce the mortality from this cancer.

Amount, Type, and Timing of Recreational Physical Activity in Relation to Colon and Rectal Cancer in Older Adults: the Cancer Prevention Study II Nutrition Cohort

Physical activity has consistently been associated with lower risk of colon cancer, but information is limited on the amount, type, and timing of activities. The relationship between physical activity and rectal cancer is unclear. We examined characteristics of recreational physical activity in relation to colon and rectal cancer in the Cancer Prevention Study II Nutrition Cohort of 70,403 men and 80,771 women (median age, 63 years); 940 colon and 390 rectal cancers were identified from enrollment in 1992 to 1993 through August 1999. The multivariate-adjusted rate ratios (95% confidence intervals) associated with any recreational physical activity compared with none were 0.87 (0.71-1.06) for colon cancer and 0.70 (0.53-0.93) for rectal cancer. Colon cancer risk decreased significantly with increasing total hours (P for trend without reference group = 0.007) and metabolic equivalent hours (P for trend = 0.006) per week of activities. No clear decrease in rectal cancer risk was seen with increasing hours per week of physical activity. Rate ratios (95% confidence intervals) were 0.72 (0.52-0.98) for &lt;2 hours, 0.68 (0.47-0.97) for 2 to 3 hours, 0.59 (0.41-0.83) for 4 to 6 hours, and 0.83 (0.59-1.16) for ≥7 hours per week of physical activity compared with none. Past exercise, as reported in 1982, was not associated with risk of either colon or rectal cancer. We conclude that increasing amounts of time spent at recreational physical activity are associated with substantially lower risk of colon cancer and that recreational physical activity is associated with lower risk of rectal cancer in older men and women.

Serum fructosamine and colorectal adenomas

The relationship of glucose in the blood with colorectal adenoma or cancer is not clear. Fructosamine, equivalent to total serum glycated proteins, is a marker of blood glucose levels in the previous 3 weeks. We evaluated in a case-control study the association between fructosamine and colorectal adenoma, a precursor of colorectal cancer. Cases were subjects with the first occurrence of one or more histologically confirmed colorectal adenomatous polyps removed after a complete colonoscopy (153 cases), and controls were subjects with normal colonoscopy performed in the same endoscopy units during the same period (84 controls). Serum fructosamine was measured by a colorimetric method. Unconditional multiple logistic regression was used for statistical analysis. We found that in non-diabetic subjects the risk of colorectal adenoma increased with the level of fructosamine, and the odds ratio of colorectal adenoma in subjects with fructosamine levels higher than the median (270 microg/100 ml), in comparison with subjects with fructosamine lower than the median, was 2.3 (95% CI: 1.1-4.8). The risk of colorectal adenoma increased also with increasing levels of serum triglycerides and cholesterol, and decreased with increasing levels of fasting serum insulin. The results of this study show that the risk of colorectal adenoma increases with the level of fructosamine, an indicator of the level of glucose in the blood more sensitive to foods with a high glycemic index.

DNA damage and repair in type 2 diabetes mellitus

DNA damage may be associated with type 2 diabetes mellitus (T2DM) and its complications mainly through oxidative stress. Little is known about DNA repair disturbances potentially contributing to the overall extent of DNA damage in T2DM, which, in turn, may be linked with genomic instability resulting in cancer. To assess whether DNA repair may be perturbed in 2DM we determined: (1) the level of endogenous basal DNA damage, this means damage recognized in the alkaline comet assay (DNA strand breaks and alkali labile sites) as well as endogenous oxidative and alkylative DNA damage (2) the sensitivity to DNA-damaging agents hydrogen peroxide and doxorubicin and the efficacy of removing of DNA damage induced by these agents in peripheral blood lymphocytes of T2DM patients and healthy individuals. The level of DNA damage and the kinetics of DNA repair was evaluated by the alkaline single cell gel electrophoresis (comet assay). Oxidative and alkylative DNA damage were assayed with the use of DNA repair enzymes endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (Fpg), recognizing oxidized DNA bases and 3-methyladenine-DNA glycosylase II (AlkA) recognizing alkylated bases. The levels of basal endogenous and oxidative DNA damage in diabetes patients were higher than in control subjects. There was no difference between the level of alkylative DNA in the patients and the controls. Diabetes patients displayed higher susceptibility to hydrogen peroxide and doxorubicin and decreased efficacy of repairing DNA damage induced by these agents than healthy controls. Our results suggest that type 2 diabetes mellitus may be associated not only with the elevated level of oxidative DNA damage but also with the increased susceptibility to mutagens and the decreased efficacy of DNA repair. These features may contribute to a link between diabetes and cancer and metrics of DNA damage and repair, measured by the comet assay, may be markers of risk of cancer in diabetes.

Insulin therapy and colorectal cancer risk among type 2 diabetes mellitus patients

BACKGROUND & AIMS

Endogenous hyperinsulinemia in the context of type 2 diabetes mellitus is potentially associated with an increased risk of colorectal cancer. We aimed to determine whether insulin therapy might increase the risk of colorectal cancer among type 2 diabetes mellitus patients.

METHODS

We conducted a retrospective cohort study among all patients with a diagnosis of type 2 diabetes mellitus in the General Practice Research Database from the United Kingdom. We excluded patients with <3 years of colorectal cancer-free database follow-up after the diabetes diagnosis as well as those insulin users who developed colorectal cancer after <1 year of insulin therapy. The remaining insulin users and the noninsulin-using type 2 diabetic patients were followed for the occurrence of colorectal cancer. Hazard ratios (HR) were determined in Cox proportional hazard analysis. A nested case-control study was conducted to perform multivariable analysis and to determine a duration-response effect.

RESULTS

The incidence of colorectal cancer in insulin users (n = 3160) was 197 per 100,000 person-years, compared with 124 per 100,000 person-years in type 2 diabetes mellitus patients not receiving insulin (n = 21,758). The age- and sex-adjusted HR of colorectal cancer associated with > or =1 year of insulin use was 2.1 (95% CI: 1.2-3.4, P = 0.005). The positive association strengthened after adjusting for potential confounders. The multivariable odds ratio associated with each incremental year of insulin therapy was 1.21 (95% CI: 1.03-1.42, P = 0.02).

CONCLUSIONS

Chronic insulin therapy significantly increases the risk of colorectal cancer among type 2 diabetes mellitus patients.

Insulin increase in colon cancerogenesis: a case-control study

BACKGROUND

Our aim was to establish whether individuals who develop colon cancer have elevated blood insulin concentrations.

METHODS

This was a case-control study in which 56 normoglycemic patients with colon cancer and a corresponding control group were investigated at the Clinical Hospital Split from April 1998 to April 1999. Data on age, weight, height, and sex of examinees were recorded and concentrations of glucose, insulin, and C-peptide were measured first in the morning before breakfast and again 90 min after breakfast.

RESULTS

In the male group of colon cancer patients, we found statistically significant higher blood insulin concentrations 90 min after breakfast (median 34.7 mIU/L, range 3.3-162.6 mIU/L) in comparison to male control group (median 20.7 mIU/L, range 3.1-122.1 mIU/L) (p=0.044). Concentration of C-peptide in blood 90 min after breakfast (median 3.28 nmol/L, range 0.38-6.1 nmol/L) was higher in the male group of colon cancer patients than in male control group (median 1.68 nmol/L, range 0.26-4.26 nmol/L) (p=0.001). No difference was found in concentrations of insulin, C-peptide, and glucose in blood measured in the morning before breakfast between the male group of colon cancer patients and male control group. Ratio of insulin 90 min after breakfast with respect to insulin in the morning before breakfast was higher in the male group of colon cancer patients (median 4.65, range 0.83-22.1) than in male control group (median 1.78, range 0.38-8.75) (p=0.005). Ratio of C-peptide 90 min after breakfast with respect to fasting C-peptide was higher in the male group of colon cancer patients (median 3.22, range 0.74-11.9) than in male control group (median 1.42, range 0.54-6.0) (p=0.001). Women with colon cancer also had statistically significant higher ratio of insulin and C-peptide with respect to female control group. In the female group of colon cancer patients, median for ratio of C-peptide was 2.42 (range 0.43-8.87), while in female control group it was 1.19 (range 0.62-15.4) (p=0.025). Median for ratio of insulin in the female group of colon cancer patients was 4.23 (range 0.25-8.54), while in female control group it was 1.17 (range 0.29-26.89) (p=0.007).

CONCLUSIONS

There was a higher increase of insulin 90 min after breakfast in the group of patients with colon cancer than in control group.

Preventing cancer, cardiovascular disease, and diabetes: a common agenda for the American Cancer Society, the American Diabetes Association, and the American Heart Association

Collectively, cardiovascular disease (including stroke), cancer, and diabetes account for approximately two-thirds of all deaths in the U.S. and about US dollars 700 billion in direct and indirect economic costs each year. Current approaches to health promotion and prevention of cardiovascular disease, cancer, and diabetes do not approach the potential of the existing state of knowledge. A concerted effort to increase application of public health and clinical interventions of known efficacy to reduce prevalence of tobacco use, poor diet, and insufficient physical activity-the major risk factors for these diseases-and to increase utilization of screening tests for their early detection could substantially reduce the human and economic cost of these diseases. In this article, the American Cancer Society, American Diabetes Association, and American Heart Association review strategies for the prevention and early detection of cancer, cardiovascular disease, and diabetes, as the beginning of a new collaboration among the three organizations. The goal of this joint venture is to stimulate substantial improvements in primary prevention and early detection through collaboration between key organizations, greater public awareness about healthy lifestyles, legislative action that results in more funding for and access to primary prevention programs and research, and reconsideration of the concept of the periodic medical checkup as an effective platform for prevention, early detection, and treatment.

Preventing Cancer, Cardiovascular Disease, and Diabetes

Collectively, cardiovascular disease (including stroke), cancer, and diabetes account for approximately two thirds of all deaths in the United States and about $700 billion in direct and indirect economic costs each year. Current approaches to health promotion and prevention of cardiovascular disease, cancer, and diabetes do not approach the potential of the existing state of knowledge. A concerted effort to increase application of public health and clinical interventions of known efficacy to reduce prevalence of tobacco use, poor diet, and insufficient physical activity—the major risk factors for these diseases—and to increase utilization of screening tests for their early detection could substantially reduce the human and economic cost of these diseases. In this article, the ACS, ADA, and AHA review strategies for the prevention and early detection of cancer, cardiovascular disease, and diabetes, as the beginning of a new collaboration among the three organizations. The goal of this joint venture is to stimulate substantial improvements in primary prevention and early detection through collaboration between key organizations, greater public awareness about healthy lifestyles, legislative action that results in more funding for and access to primary prevention programs and research, and reconsideration of the concept of the periodic medical checkup as an effective platform for prevention, early detection, and treatment.

Diabetes mellitus as a predictor of cancer mortality in a large cohort of US adults

Several studies have suggested that diabetes mellitus may alter the risk of developing a variety of cancers, and the associations are biologically plausible. To learn more about the relation between diabetes and cancer mortality, the authors examined associations with selected cancers in a large, prospective US cohort of 467,922 men and 588,321 women who had no reported history of cancer at enrollment in 1982. After 16 years of mortality follow-up, diabetes was significantly associated with fatal colon cancer in men (multivariate relative risk (RR) = 1.20, 95% confidence interval (CI): 1.06, 1.37) and women (RR = 1.24, 95% CI: 1.07, 1.43) and with pancreatic cancer in men (RR = 1.48, 95% CI: 1.27, 1.73) and women (RR = 1.44, 95% CI: 1.21, 1.72). For men, diabetes was significantly associated with liver cancer (RR = 2.19, 95% CI: 1.76, 2.72) and bladder cancer (RR = 1.43, 95% CI: 1.14, 1.80). In addition, diabetes was significantly associated with breast cancer in women (RR = 1.27, 95% CI: 1.11, 1.45). These associations were not explained by high body mass. Our findings suggest that diabetes is an independent predictor of mortality from cancer of the colon, pancreas, female breast, and, in men, of the liver and bladder.

Preliminary Communication: Glycated Hemoglobin, Diabetes, and Incident Colorectal Cancer in Men and Women: A Prospective Analysis from the European Prospective Investigation into Cancer–Norfolk Study

Background: Increasing evidence suggests that abnormal glucose metabolism may be associated with increased risk of colorectal cancer. Methods: We examined the relationship between known diabetes and glycated hemoglobin (HbA1c) concentrations measured in 1995 to 1997 and subsequent incident colorectal cancer after 6 years follow-up in 9,605 men and women ages 45 to 79 years in the European Prospective Investigation into Cancer–Norfolk Study. Results: Among individuals not known to have cancer at the baseline survey, there were 67 incident colorectal cancers. HbA1c concentration appeared continuously related to incident colorectal cancer risk, with lowest rates observed in those with HbA1c below 5%. Known diabetes was also associated with incident colorectal cancer, with relative risk (RR) 3.18 and 95% confidence interval (CI) 1.36-7.40 (P &lt; 0.01) adjusting for age and sex and RR 2.78 and 95% CI 1.10-7.00 (P = 0.03) adjusting for age, sex, body mass index, and smoking compared with those without known diabetes. The RR (95% CI) of incident colorectal cancer per 1% absolute increase in HbA1c was 1.34 (1.12-1.59; P &lt; 0.001). HbA1c concentrations appeared to explain the increased colorectal cancer risk associated with diabetes in multivariate models. Conclusions: Known diabetes was associated with ∼3-fold risk of colorectal cancer in this analysis; this increased risk was largely explained by HbA1c concentrations, which appears continuously related to colorectal cancer risk across the population distribution.

The metabolic syndrome or the insulin resistance syndrome? Different names, different concepts, and different goals

The goal of this article is to differentiate the insulin resistance syndrome from the metabolic syndrome. In the case of the insulin resistance syndrome, the abnormalities and clinical syndromes that are increased in prevalence in insulin-resistant individuals have been summarized, with a brief discussion of the causal relationship between insulin resistance, compensatory hyperinsulinemia, and associated consequences. Discussion of the metabolic syndrome has focused on the five criteria chosen by the adult treatment panel III to diagnose the syndrome, evaluating them in terms of their relationship to insulin resistance and their role as cardiovascular disease risk factors.

A Prospective Study of Plasma C-Peptide and Colorectal Cancer Risk in Men

BACKGROUND

Colorectal cancer and type 2 diabetes share many risk factors, and hyperinsulinemia appears to be associated with an increased risk of colorectal cancer. We used the concentration of plasma C-peptide (an indicator of insulin production) to determine whether insulin and insulin resistance are associated with the risk of developing colorectal cancer.

METHODS

We conducted a nested case-control study in the Physicians' Health Study. Plasma samples were collected from 14 916 cancer-free men from August 1982 through December 1984. Plasma C-peptide concentration, measured with an enzyme-linked immunosorbent assay, was available for 176 case patients who developed incident colorectal cancer through December 31, 1995, and 294 age- and smoking status-matched control subjects. Information on four other insulin resistance-related factors at baseline was obtained. We used conditional logistic regression models to investigate associations. All statistical tests were two-sided.

RESULTS

Plasma C-peptide concentration was positively associated with age, body mass index (BMI), and number of insulin resistance-related factors, and it was inversely associated with fasting time before the blood draw, alcohol consumption, and vigorous exercise. An increased concentration of plasma C-peptide was statistically significantly associated with an increased risk of colorectal cancer (relative risk [RR] for the highest versus lowest quintile of plasma C-peptide = 2.7, 95% confidence interval [CI] = 1.2 to 6.2; P(trend) =.047), after adjusting for age, smoking status, fasting, BMI, alcohol consumption, vigorous exercise, and aspirin assignment in the Physicians' Health Study. The association became even stronger when the analysis was further adjusted for factors related to insulin resistance other than insulin levels (RR for the highest versus lowest quintile = 3.4, 95% CI = 1.4 to 8.3; P(trend) =.02) or when data from case patients who were diagnosed during the first 5 years of follow-up were excluded (RR for the highest versus the lowest quintile = 3.4, 95% CI = 1.3 to 8.8; P(trend) =.03). Adjusting for plasma levels of insulin-like growth factor I (IGF-I) and its binding protein 3 (IGFBP-3) did not materially change the results. There was no apparent modification of risk by BMI, insulin resistance-related factors, or vigorous exercise.

CONCLUSION

Elevated insulin production, as reflected by elevated concentrations of plasma C-peptide, may predict the risk of developing colorectal cancer, independently of BMI, factors related to insulin resistance, or levels of IGF-I and IGFBP-3.

Relationship of visceral adipose tissue to recurrence of adenomatous polyps

OBJECTIVES

Insulin is a growth factor for colorectal cancer. Visceral adipose tissue (VAT) is strongly associated with insulin levels, and insulin and visceral obesity have been associated in cohort studies with colorectal cancer. The aim of this investigation was to determine whether VAT is associated with recurrence of adenomatous polyps, the precursor to colorectal cancer.

METHODS

As an ancillary study to the Polyp Prevention Trial, a randomized clinical trial that evaluated the effect of a low-fat, high-fiber, high vegetable and fruit diet on adenomatous polyp recurrence, subjects at one clinical center underwent measurement of VAT with a single-slice CT scan through the L4-L5 interspace. The scan was performed around the time of the subject's year 4 colonoscopy that determined adenoma recurrence.

RESULTS

Of 119 subjects, 44 of 84 men (52%) and 16 of 35 women (46%) had a recurrent adenoma (p= 0.51). Body mass index (BMI) and weight at baseline and at year 4 colonoscopy were unrelated to adenoma recurrence. In a multivariate model including visceral fat quartile, remote history of polyps, gender, age, and randomization group, only remote history of polyps was statistically significantly associated with recurrent adenoma with a relative risk of 4.6 (95% CI 1.7, 12.4, p= 0.001). There was no consistent monotonic trend of increased or decreased risk of recurrence as one ascended quartiles of adipose tissue for visceral, subcutaneous, or total abdominal fat.

CONCLUSION

In this study, no association between visceral adipose tissue and adenomatous polyp recurrence was observed. Further study and exploration of the role of VAT in adenoma progression is required.

Hyperinsulinaemia and hyperglycaemia: possible risk factors of colorectal cancer among diabetic patients

Hyperinsulinaemia and hyperglycaemia are two possible risk factors for colorectal cancer, which constitutes the third leading cause of cancer death in Western countries. Molecular evidence as well as animal models provide support for these associations: Insulin has been shown to be an important growth factor for colonic carcinoma cells, and both insulin and insulin-like growth factor-1 receptors have been detected in colon cancer tissue. The insulin-signal transduction pathway is involved in the regulation of gene expression and apoptosis. The role of hyperglycaemia in carcinogenesis could include pathways via luminal factors (related to fecal bile acid concentrations, stool bulk, and prolonged transit time) or circulatory factors (via glucose as the only energy source for neoplastic cells). This review summarizes the epidemiologic literature with respect to hyperinsulinaemia and hyperglycaemia as risk factors for colorectal cancer, and aims to integrate the biological and epidemiological evidence. Epidemiologic findings to date indicate a slightly increased risk of colorectal cancer for diabetic patients; however, there are some inconsistencies. Possible explanations for these inconsistencies include inadequate information about patients' diabetic disease and treatment states. We suggest that future studies should take medical history, staging and treatment for hyperinsulinaemia and hyperglycaemia into account to further our understanding of the role of hyperglycaemia and hyperinsulinaemia in colorectal carcinogenesis.

Insulin resistance and its contribution to colon carcinogenesis

The insulin resistance-colon cancer hypothesis, stating that insulin resistance may be associated with the development of colorectal cancer, represents a significant advance in colon cancer, as it emphasizes the potential for this cancer to become a modifiable disease. The fact that the incidence of insulin resistance has been increasing in the United States and much of the rest of the Western world where colon cancer remains the second leading cause of cancer death makes the exploration of the interrelationship of these conditions a subject of high priority. Here, we review the salient features of insulin resistance, defined as impaired biological response to the action of insulin. Recent epidemiological studies, evaluating potential associations between colon cancer risk and diabetes mellitus, dietary intake and metabolic factors, and IGF levels in several clinical settings, provide strong support of the insulin resistance-colon cancer hypothesis (without establishing causality). Mechanistically, insulin resistance has been associated with hyperinsulinemia, increased levels of growth factors including IGF-1, and alterations in NF-kappaB and peroxisome proliferator-activated receptor signaling, which may promote colon cancer through their effects on colonocyte kinetics. It is a reasonable expectation that in the not too distant future, critical interventions to the already mapped molecular sequence of events, which link two apparently disparate entities, combined with lifestyle changes could abrogate the development of colon cancer.

Diet, body weight, and colorectal cancer: a summary of the epidemiologic evidence

Colorectal cancer is the second leading cause of cancer death in the United States, and the number of new cases annually is approximately equal for men and women. Several nutritional factors are likely to have a major influence on risk of this cancer. Physical inactivity and excessive adiposity, especially if centrally distributed, clearly increase the risk of colon cancer. Hyperinsulinemia may be an important underlying risk factor. In conjunction with obesity and physical inactivity, which induce a state of insulin resistance, certain dietary patterns that stimulate insulin secretion, including high intakes of red and processed meats, saturated and trans-fats, and highly processed carbohydrates and sugars, may increase the risk of colon cancer. There is evidence suggesting that some component of red meat may independently increase the risk of colorectal cancer, and some micronutrients may be important as protective agents. Currently, the evidence is strongest for folate and calcium. Folate may be especially important in alcohol drinkers because alcohol appears to increase the risk, particularly when folate intake is low. This interaction may be related to the antifolate properties of alcohol. In contrast to earlier studies, more recent epidemiologic studies have generally not supported a strong influence of dietary fiber or fruits and vegetables, although these have other health benefits, and their consumption should be encouraged. The majority of colon cancers, as well as many other conditions, may be prevented by lifestyle alterations in the intake of these nutritional factors, in addition to other factors, such as smoking.

Impact of diabetes mellitus on outcomes in patients with colon cancer

PURPOSE

To determine the influence of diabetes mellitus on long-term outcomes and treatment-related toxicity among patients with curatively resected colon cancer.

PATIENTS AND METHODS

This study was a cohort study within a large, randomized adjuvant chemotherapy trial of 3,759 patients with high-risk stage II and stage III colon cancer treated between 1988 and 1992 throughout the United States. In the cohort, 287 patients were identified as having diabetes mellitus. With a median follow-up of 9.4 years, we analyzed differences in overall survival (OS) and colon cancer recurrence as well as treatment-related toxicity between patients with diabetes and those without diabetes.

RESULTS

At 5 years, patients with diabetes mellitus, compared with patients without diabetes, experienced a significantly worse disease-free survival (DFS; 48% diabetics v 59% nondiabetics; P <.0001), OS (57% v 66%; P <.0001), and recurrence-free survival (RFS; 56% v 64%, P =.012). Median survival was 6.0 years and 11.3 years for diabetics and nondiabetics, respectively. Compared with patients without a history of diabetes, those with diabetes had a 42% increased risk of death from any cause (P <.0001) and 21% increased risk for recurrence (P =.05) after adjustment for other predictors of colon cancer outcome. Treatment-related toxicities were similar between the two groups, although patients with diabetes experienced an increase in treatment-related diarrhea.

CONCLUSION

Patients with diabetes mellitus and high-risk stage II and stage III colon cancer experienced a significantly higher rate of overall mortality and cancer recurrence, even after adjustment for other predictors of colon cancer outcome. These results underscore the need for further research to understand the mechanism that underlies this relation.

Dairy products and colorectal cancer. A review of possible mechanisms and epidemiological evidence

OBJECTIVES

This review provides an overview of the principal hypotheses and epidemiological evidence of the possible links between colorectal cancer and intake of milk and/or dairy products.

METHODS

The first section outlines the main hypotheses about the possible effect of calcium, vitamin D, fats and other milk components. The possible role of acid lactic bacteria in fermented products is also discussed. The second section is a summary of the published epidemiological evidence. The results on milk, cheese and yoghurt are summarized using a meta-analytical approach. The results of studies on calcium and vitamin D are briefly described.

RESULTS

Case-control studies are heterogeneous and, on average, do not provide evidence of association between total intake of total dairy products, milk, cheese or yoghurt and colorectal cancer risk. The average result from cohort studies support the hypothesis of a protective effect of total dairy products (odds ratio (OR): 0.62; 95% confidence interval (CI): 0.52-0.74; P heterogeneity test: 0.93) and for milk (OR: 0.80; 95% CI: 0.68-0.95; P heterogeneity: 0.77). No association was found between cheese (OR: 1.10; 95% CI: 0.88-1.36; P heterogeneity: 0.55) or yoghurt (OR: 1.03; 95% CI: 0.83-1.28; P heterogeneity: 0.69) in cohort studies.

CONCLUSIONS

Cohort studies consistently found a protective effect of total dairy products and milk intake, but the evidence is not supported by case-control studies. No relationship was found with cheese or yoghurt intake. As the number of cohort studies is still limited, their results need to be confirmed by other prospective studies.

Physical activity and cancer prevention: etiologic evidence and biological mechanisms

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

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.

Epidemiology and prevention of colorectal cancer

CRC, the second-leading cause of cancer death in the United States, is a highly preventable disease. Ironically, available and effective screening technologies are not consistently applied, even as new ones are developed. This discordance between preventive opportunity and practice conveys a sobering message regarding nontechnologic issues that must be addressed if the promise of CRC prevention is to be realized. Our response to this message will determine the public health impact of cancer prevention. In the 1980s, cancer chemoprevention was regarded as scientific speculation. Within the last decade, however, cancer has been recognized as a late, nonobligate stage of carcinogenesis, a chronic process that provides time and targets for preventive intervention. Further advances are emerging out of rigorous clinical testing, which remains the limiting factor in transforming ingenious concepts into useful tools for the prevention of CRC. The challenges and rewards of participation in chemoprevention research--both as patients and health care providers-have never been greater.

Effect of diet on cancer development: is oxidative DNA damage a biomarker?

Free radicals and other reactive species are generated in vivo and many of them can cause oxidative damage to DNA. Although there are methodological uncertainties about accurate quantitation of oxidative DNA damage, the levels of such damage that escape immediate repair and persist in DNA appear to be in the range that could contribute significantly to mutation rates in vivo. The observation that diets rich in fruits and vegetables can decrease both oxidative DNA damage and cancer incidence is consistent with this. By contrast, agents increasing oxidative DNA damage usually increase risk of cancer development. Such agents include cigarette smoke, several other carcinogens, and chronic inflammation. Rheumatoid arthritis and diabetes are accompanied by increased oxidative DNA damage but the pattern of increased cancer risk seems unusual. Other uncertainties are the location of oxidative DNA damage within the genome and the variation in rate and level of oxidative damage between different body tissues. In well-nourished human volunteers, fruits and vegetables have been shown to decrease oxidative DNA damage in several studies, but data from short-term human intervention studies suggest that the protective agents are not vitamin C, vitamin E, beta-carotene, or flavonoids.

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.

Glucose intolerance, plasma insulin levels, and colon adenomas in Japanese men

Hyperinsulinemia may be related to colon carcinogenesis. Several studies have suggested that diabetes mellitus is related to increased risk of colon cancer. We examined cross-sectionally the relation of fasting plasma insulin levels and glucose tolerance status to colon adenomas. In a consecutive series of 951 men undergoing total colonoscopy for a health examination at the Japan Self Defense Forces Fukuoka Hospital from April 1998 to August 1999, we identified 233 cases of colon adenomas and 497 controls with normal colonoscopy. Glucose tolerance status was determined by a 75-g oral glucose tolerance test, and subjects were classified as normal, impaired glucose tolerance (IGT) or non-insulin dependent diabetes mellitus (NIDDM). Plasma insulin levels were measured after subjects had fasted overnight. Logistic regression analysis and analysis of covariance was used to control for age and obesity. While plasma insulin levels were unrelated to colon adenomas, NIDDM was associated with a significantly increased risk of colon adenomas. There was no association between IGT and colon adenomas. NIDDM was more strongly associated with proximal colon adenomas. The findings suggest that long-term hyperinsulinemic status associated with NIDDM may increase the risk of colon adenomas, and subsequently of colon cancer.

Physical activity and cancer risk: dose-response and cancer, all sites and site-specific

PURPOSE

The association between physical activity and overall and site-specific cancer risk is elaborated in relation to whether any observed dose-response association between physical activity and cancer can be interpreted in terms of how much physical activity (type, intensity, duration, frequency) is needed to influence site- and gender-specific cancer risk.

METHODS

Observational studies were reviewed that have examined the independent effect of the volume of occupational physical activity (OPA) and/or leisure time physical activity (LPA) on overall and site-specific cancer risk.

RESULTS

The evidence of cohort and case-control studies suggests that both leisure time and occupational physical activity protect against overall cancer risk, with a graded dose-response association suggested in both sexes. Confounding effects such as diet, body weight, and parity are often included as a covariate in the analyses, with little influence on the observed associations. A crude graded inverse dose-response association was observed between physical activity and colon cancer in 48 studies including 40,674 colon/colorectal cancer cases for both sexes. A dose-response effect of physical activity on colon cancer risk was especially observed, when participation in activities of at least moderate activity (>4.5 MET) and demonstrated by activities expressed as MET-hours per week. An observed inverse association with a dose-response relationship between physical activity and breast cancer was also identified in the majority of the 41 studies including 108,031 breast cancer cases. The dose-response relationship was in particular observed in case-control studies and supported by observations in cohort studies when participation in activities of at least moderate activity (>4.5 MET) and demonstrated by activities expressed by MET-hours per week. This association between physical activity and breast cancer risk is possibly dependent on age at exposure, age at diagnosis, menopausal status and other effect modifiers, e.g., body mass index. Furthermore, data concerning carcinoma of other cancers (prostate, lung, endometrium, ovary, and testicular cancers) are required.

CONCLUSION

A protective effect of physical activity on site-specific cancer risk with a dose-response association between physical activity and colon and pre- and postmenopausal breast cancer supported by identified biological mechanisms has been observed. The optimal permutation of type, intensity, duration, and frequency of physical activity across the lifespan is unclear, but it is gender, age, and site specific and supports moderate activity (>4.5 MET) more than light activities (<4.5 MET). The complicated nature of the physical activity variable, combined with lack of knowledge regarding possible biological mechanisms operating between physical activity and cancer, warrants further studies including controlled clinical randomized trials.

Type 2 diabetes and cognitive function in community-dwelling elderly women

OBJECTIVE

To examine the relationship of type 2 diabetes to cognitive function in community-dwelling women.

RESEARCH DESIGN AND METHODS

From 1995 to 1999, we administered four tests of cognitive function (Telephone Interview of Cognitive Status [TICS], immediate and delayed recall of the East Boston Memory Test, and verbal fluency) by telephone to 2,374 participants (70-78 years of age) of the Nurses' Health Study. Information on diabetes was collected biennially beginning in 1976; 82 women reported type 2 diabetes before their cognitive testing. We used linear and logistic regression models to calculate multivariate-adjusted mean differences in scores and relative risks of a low score (bottom 10% of the distribution) for diabetic women compared with nondiabetic women.

RESULTS

After multivariate adjustment, women with type 2 diabetes scored lower on all our cognitive tests than women without diabetes. On the general test of cognition (TICS), the mean difference in score between women with and without diabetes was -0.60 (95% CI -1.18 to -0.03, P = 0.04) and the relative risk of a low TICS score was 1.98 (95% CI 1.06 to 3.69). On a global score combining results of the four tests, the mean for diabetic women was lower than that among women without diabetes (adjusted difference in score -0.73, 95% CI -1.42 to -0.04, P = 0.04), and the relative risk of a low global score was 2.16 (95% CI 1.10 to 4.21). Relative to women without diabetes, longer duration of diabetes was associated with lower scores. Few diabetic women were pharmacologically treated (n = 31), but those taking medication had scores similar to those of women without diabetes.

CONCLUSIONS

In these women, diabetes was related to lower scores on several aspects of cognitive function. Longer duration of diabetes may be associated with poorer scores, but hypoglycemic therapy may ameliorate scores.

Hyperinsulinemia predicts fatal liver cancer but is inversely associated with fatal cancer at some other sites: the Paris Prospective Study

OBJECTIVE

To investigate whether insulin is a risk factor for death by site-specific cancers.

RESEARCH DESIGN AND METHODS

This was a prospective cohort study of 6,237 nondiabetic French working men between ages 44 and 55 years at baseline from the Paris Prospective Study cohort. Death by site-specific cancers was investigated in relation to baseline insulin concentrations during fasting and 2 h after a 75-g oral glucose tolerance test.

RESULTS

Of the original 6,237 men in the cohort, 1.739 died over the 23.8 years of follow-up. 778 (45%) from cancer. Baseline hyperinsulinemia, both fasting and 2-h, was significantly associated with fatal liver cancer, with age-adjusted standardized hazards ratios of 2.72 (95% CI 1.87-3.94) and 3.41 (2.23-5.21). In contrast, fasting hyperinsulinemia was inversely associated with fatal lip, oral cavity, and pharynx cancer and larynx cancer, with hazards ratios of 0.55 (0.41-0.75) and 0.63 (0.47-0.83), respectively; 2-h insulin concentrations were inversely associated with stomach and larynx cancers (hazards ratios 0.62 [0.43-0.90] and 0.66 [0.50-0.891, rcspectively). These relationships were stable after adjusting for other risk factors. Insulin concentrations remained negatively associated with deaths from these cancers in analyses restricted to men who smoked and in those who were not chronic alcohol consumers.

Colorectal cancer screening in North Carolina: associations with diabetes mellitus and demographic and health characteristics

BACKGROUND

Diabetes mellitus (DM) may increase the risk of colorectal cancer, a leading cause of cancer death in the United States. This report examines factors associated with colorectal cancer screening, including DM status.

METHODS

Data from the 1993/1995/1997 North Carolina (NC) Behavioral Risk Factor Surveillance System were analyzed to assess self-reported screening rates within guidelines for sigmoidoscopy/proctoscopy (sig/proct) and fecal occult blood test (FOBT).

RESULTS

Overall, 28.6, 27.2, and 19.7% received a sig/proct, FOBT, or either test within guidelines, respectively. Screening rates varied according to some demographic variables, but not by DM status. However, DM status changed some relationships between screening and some demographic/health characteristics.

CONCLUSIONS

Colorectal cancer screening in NC is similar to national rates, but certain subgroups are less likely to get screened. Persons with DM are as likely to get colorectal cancer screening, but some groups with DM (ethnic minorities, persons of low socioeconomic status) may be at high risk for not getting screened. Educational efforts to increase screening should target these groups.

Energy balance and cancer: the role of insulin and insulin-like growth factor-I

Recent theories propose that a Western lifestyle may increase cancer risk through alterations in the metabolism of insulin and insulin-like growth factors (IGF: McKeown-Eyssen, 1994; Giovannucci, 1995; Kaaks, 19%; Werner & LeRoith, 1996). Insulin regulates energy metabolism, and increases the bioactivity of IGF-I, by enhancing its synthesis. and by decreasing several of its binding proteins (IGFBP; IGFBP-1 and -2). Insulin and IGF-I both stimulate anabolic processes as a function of available energy and elementary substrates (e.g. amino acids). The anabolic signals by insulin or IGF-I can promote tumour development by inhibiting apoptosis, and by stimulating cell proliferation. Furthermore, both insulin and IGF-I stimulate the synthesis of sex steroids, and inhibit the synthesis of sex hormone-binding globulin (SFIBG), a binding protein that regulates the bioavailability of circulating sex steroids to tissues. The present paper reviews epidemiological findings relating the risk of cancers of the colo-rectum, pancreas, breast, endometrium and prostate to body size (obesity, height) and physical activity, and discusses the relationships between obesity and physical activity and plasma levels of insulin, IGF-I and IGFBP. Subsequent sections review epidemiological findings relating cancer risk to indices of chronic hyperinsulinaemia, and to plasma levels of IGF-I and IGFBP. Conclusions are that chronic hyperinsulinaemia may be a cause of cancers of the colon, pancreas and endometrium, and also possibly of the breast. On the other hand, elevated plasma IGF-I, as total concentrations or relative to levels of IGFBP-3, appears to be related to an increased risk of prostate cancer, breast cancer in young women, and possibly cob-rectal cancer. For cancers of the endometrium, breast and prostate, these findings are discussed in the context of relationships between insulin and IGF-I and levels of bioavailable sex steroids.

Prospective study of colorectal cancer risk and physical activity, diabetes, blood glucose and BMI: exploring the hyperinsulinaemia hypothesis

A sedentary lifestyle, obesity, and a Westernized diet have been implicated in the aetiology of both colorectal cancer and non-insulin dependent diabetes mellitus, leading to the hypothesis that hyperinsulinaemia may promote colorectal cancer. We prospectively examined the association between colorectal cancer risk and factors related to insulin resistance and hyperinsulinaemia, including BMI, physical activity, diabetes mellitus, and blood glucose, in a cohort of 75 219 Norwegian men and women. Information on incident cases of colorectal cancer was made available from the Norwegian Cancer Registry. Reported P values are two-sided. During 12 years of follow up, 730 cases of colorectal cancer were registered. In men, but not in women, we found a negative association with leisure-time physical activity (P for trend = 0.002), with an age-adjusted RR for the highest versus the lowest category of activity of 0.54 (95% CI = 0.37-0.79). Women, but not men, with a history of diabetes were at increased risk of colorectal cancer (age-adjusted RR = 1.55; 95% CI = 1.04-2.31), as were women with non-fasting blood glucose > or = 8.0 mmol l(-1)(age-adjusted RR = 1.98; 95% CI = 1.31-2.98) compared with glucose <8.0 mmol l(-1). Overall, we found no association between BMI and risk of colorectal cancer. Additional adjustment including each of the main variables, marital status, and educational attainment did not materially change the results. We conclude that the inverse association between leisure-time physical activity and colorectal cancer in men, and the positive association between diabetes, blood glucose, and colorectal cancer in women, at least in part, support the hypothesis that insulin may act as a tumour promoter in colorectal carcinogenesis.

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.

Diabetes mellitus and cancer

Although an association between diabetes and cancer was found over 100 years ago, the issue underwent different interpretations over the subsequent decades, and only modern, prospective, epidemiological cohort and case-control studies conducted in several countries have provided reliable evidence of an increased cancer risk in diabetic patients, mainly in those with type 2 diabetes. This risk varies according to the tumor site: it is the greatest for primary liver cancer, moderately elevated for pancreatic cancer, and relatively low for colorectal, endometrial, breast, and renal cancers. The cause of the association is not clear and remains the subject of different hypotheses. The most frequently cited reason is the potential effect of insulin. Found in high concentrations, due to insulin resistance in most patients with type 2 diabetes, this hormone is believed to express a mitogenic effect. This hypothesis needs to be confirmed in appropriately programmed prospective studies, but it may already be helpful in choosing an adequate treatment for type 2 diabetes to achieve optimal metabolic control with a simultaneous reduction in hyperinsulinemia, such as diet, physical exercise, metformin, and acarbose.

The prevalence and characteristics of colorectal neoplasia in acromegaly

An increased prevalence of colorectal neoplasia has been reported in acromegalic patients, and recommendations have been made for early colonoscopic screening and regular surveillance. This assumption, however, is frequently drawn from studies using selected control populations. To clarify colonoscopic management in these patients, we undertook a 2-center prospective screening colonoscopy study in 122 acromegalics (age range, 25-82 yr). In the absence of ideal age-matched controls, we calculated prevalence rates of occult adenocarcinomas and adenomas in the general population using cumulative data in the published literature from 8 autopsy studies (model 1, n = 3,559) and 4 screening colonoscopy studies (model 2, n= 810), applying linear regression models. Of the 115 patients with complete examinations, adenocarcinomas were discovered in 3 (2.6%), and at least 1 adenoma was found in 11, giving an overall prevalence of neoplasia of 12% (14 of 115). Prevalence rates for age bands 30-40, 40-49, 50-59, 60-69, and 70+ yr were 0%, 8%, 12%, 20%, and 21%, respectively. Compared with the 2 control models, the prevalence of occult colorectal cancer was not significantly increased (acromegalics vs. models 1 and 2, 2.6% vs. 2.3% and 0.9%), nor was there an increase in the prevalence of adenomas in any age band. Pathological characteristics showed some differences, in that adenomas in acromegalics tended to be right sided (68% vs. 57% and 56%), larger (for > or =10 mm, 27% vs. 13% and 9%), and of advanced histology (for tubulovillous, 27% vs. 4% and 22%). No associations were found between the presence of colonic neoplasia and the duration of disease, total GH exposure, cure status, and serum insulin-like growth factor I. This study has failed to demonstrate an increased prevalence of neoplasia in acromegalic patients compared with the expected prevalence in the general population and questions the need for an aggressive colonoscopic screening policy.

Physical activity in the prevention and treatment of other morbid conditions and impairments associated with obesity: current evidence and research issues

PURPOSE

To evaluate the current status of knowledge concerning the effects of physical activity in the treatment and prevention of obesity- related problems, including cancers of the colon, breast, uterus, and prostate; gallstones; osteoarthritis; back pain; sleep apnea; reproductive abnormalities; and impaired health-related quality of life.

DESIGN

A Medline literature search on the effects of physical activity in the above conditions was conducted. Only studies with some measure of weight and a description of the type of physical activity were included.

RESULTS

No controlled randomized trials of exercise in the treatment of any of the studied conditions in obese patients were identified. Most of the epidemiologic studies reviewed were beset with severe methodological weaknesses. Most of the 18 studies on physical activity and colon cancer risk showed a protective effect that in some studies appeared to be greater than expected by weight loss alone. Some but not all studies of hormone-dependent cancers and gallstones showed a protective effect for physical activity. There were insufficient data on the role of exercise for the other morbid conditions studied.

CONCLUSION

The scarce data available on the role of physical activity in the prevention of obesity-related chronic conditions listed above suggest a protective role that needs to be examined further in studies with improved methodologies. Well-designed intervention trials are needed to assess the role of physical activity in the treatment and long-term outcome of obese patients with these co-morbid conditions.

Increased blood glucose and insulin, body size, and incident colorectal cancer

BACKGROUND

Abdominal obesity--an elevated level of visceral adipose tissue--has been linked to colorectal cancer. Furthermore, elevated levels of visceral adipose tissue have been associated with hyperinsulinemia, and insulin is a growth factor in the colon. We assessed whether waist circumference, a surrogate measure of visceral adipose tissue, and metabolic parameters associated with visceral adipose tissue were related to colorectal cancer.

METHODS

In the Cardiovascular Health Study cohort, we examined the relationship of baseline measurements of body size, glucose, insulin, and lipoproteins to incident colorectal cancer. All P values are two-sided.

RESULTS

Among 5849 participants, 102 incident cases of colorectal cancer were identified. Individuals in the highest quartile of fasting glucose had a nearly twofold increased risk of colorectal cancer (relative risk [RR] = 1.8; 95% confidence interval [CI] = 1.0-3.1), and the linear trend RR (LT RR = 1.2; 95% CI = 1.0-1.5) for fasting glucose level was statistically significant (P =. 02). Glucose and insulin levels 2 hours after oral glucose challenge also exhibited statistically significant associations with colorectal cancer (2-hour glucose levels: RR = 2.4 [95% CI = 1.2-4. 7]/LT RR = 1.3 [95% CI = 1.0-1.6; P =.02]; 2-hour insulin levels: RR = 2.0 [95% CI = 1.0-3.8]/LT RR = 1.2 [95% CI = 1.0-1.5; P =.04]). Analysis of fasting insulin levels suggested a threshold effect, with values above the median associated with colorectal cancer (RR = 1.6; 95% CI = 1.1-2.4; P =.02). Higher levels of waist circumference were also statistically significantly associated with colorectal cancer (RR = 1.9; 95% CI = 1.1-3.3; P =.02).

CONCLUSIONS

These data provide, to our knowledge, the first direct evidence of an association between elevated visceral adipose tissue level, its associated metabolic effects, and colorectal cancer.

Increased oxidative damage to all DNA bases in patients with type II diabetes mellitus

Gas chromatography-mass spectrometry was used to measure the oxidative DNA damage in diabetic subjects and controls. Levels of multiple DNA base oxidation products, but not DNA base de-amination or chlorination products, were found to be elevated in white blood cell DNA from patients with type II diabetes as compared with age-matched controls. The chemical pattern of base damage is characteristic of that caused by an attack on DNA by hydroxyl radical. An increased formation of the highly reactive hydroxyl radical could account for many of the reports of oxidative stress in diabetic subjects. There was no evidence of an increased DNA damage by reactive nitrogen or chlorine species.

Prospective study of adult onset diabetes mellitus (type 2) and risk of colorectal cancer in women

BACKGROUND

The remarkable similarity of lifestyle and environmental risk factors for type 2 (non-insulin-dependent) diabetes mellitus and colon cancer has led to the hypothesis that diabetes may increase the risk of this cancer. We prospectively examined the relationship between diabetes and risk of colorectal cancer in a cohort of 118403 women aged 30 through 55 years who were without previously diagnosed cancer at baseline in 1976.

METHODS

The women, who were enrolled in the Nurses' Health Study, were assessed for history of diabetes at baseline and during follow-up by use of biennial questionnaires. Self-reported diabetes was validated by information obtained from a supplemental questionnaire on symptoms and treatment and was confirmed by medical record review in a sample of the participants. Incident cases of colorectal cancer were ascertained through medical record review. All reported P values are two-sided.

RESULTS

During 18 years of follow-up (201061 person-years), we documented 892 new cases of colorectal cancer. After adjustment for age, body mass index (weight in kg/height in m2), physical activity, and other covariates, relative risks (RRs) were 1.43 (95% confidence interval [CI] = 1.10-1.87; P = .009) for colorectal cancer, 1.49 (95% CI = 1.09-2.06; P = .01) for colon cancer, 1.11 (95% CI = 0.56-2.21; P = .76) for rectal cancer, 1.56 (95% CI = 1.07-2.28; P = .02) for advanced colorectal cancer, and 2.39 (95% CI = 1.46-3.92; P = .0005) for fatal colorectal cancer.

CONCLUSION

Our data provide support for the hypothesis that diabetes is associated with an increased risk of colorectal cancer in women.

Racial differences in symptoms and complications in adults with type 2 diabetes mellitus

OBJECTIVE

To compare the frequency of common symptoms and complications between African- and white American adults with type 2 diabetes mellitus in a primary care setting, and to examine associations of these conditions with glycemic control.

DESIGN

Three hundred and four adults with type 2 diabetes participated in this cross-sectional analysis; 142 of whom were African-Americans. Patients were recruited from a family practice ambulatory care unit and a community health center.

RESULTS

Both male and female African-Americans had higher mean diastolic blood pressure and poorer metabolic control than their white counterparts. After adjustment for diabetes duration, glycosylated hemoglobin and diastolic blood pressure, African-American females were significantly more likely to experience constipation and hypertension but less likely to experience chest pain, claudication, peripheral neuropathy or have peripheral vascular disease. Among male subjects, African-Americans were significantly more likely to experience blurred vision and hypertension but less likely to have peripheral atherosclerotic disease. Poor glycemic control was more strongly associated with the occurrence of common diabetic symptoms in African-American subjects.

CONCLUSIONS

Both African- and white Americans with type 2 diabetes are likely to experience a wide variety of symptoms and vascular complications. African-American subjects appear more likely than whites to experience symptoms related to glycemic control but less likely to have, or experience symptoms and complications of, cardiovascular disease. That nearly half of these subjects seen in a primary care setting had microalbuminuria suggests that vascular complications are likely to be present in the majority of adults with type 2 diabetes, even in these currently asymptomatic. These findings may have implications for screening and preventive strategies for the treatment of this disease.

Diet, lifestyle, and colorectal cancer: is hyperinsulinemia the missing link?

Several dietary and other lifestyle factors have been implicated in the development of colorectal cancer. However, the precise nature and actual magnitude of the relationship between individual nutrient intakes and other lifestyle factors and colorectal cancer risk are not clear. A unifying hypothesis has recently been proposed that explains why obesity, physical inactivity, alcohol, and consumption of a typical Western diet increase colorectal cancer risk. This hypothesis suggests that these dietary and other lifestyle factors are associated with insulin resistance and hyperinsulinemia and that hyperinsulinemia, in turn, may stimulate growth of colorectal tumors. Two recently published large prospective epidemiologic studies indicate a significant increase in colorectal cancer risk in subjects with diabetes mellitus, thereby supporting this hypothesis.