The metabolic syndrome and risk of incident colorectal cancer

Interactions between insulin, body fat, and insulin-like growth factor axis proteins

BACKGROUND

The etiology of hormonally related cancers, such as breast and colon, has been linked to hyperinsulinemia and insulin resistance, the insulin-like growth factor (IGF) axis, and obesity.

METHODS

Data from 57 women (ages 30-50 years) were used to observationally examine cross-sectional and longitudinal relations between body fat (from dual-energy X-ray absorptiometry), insulin, IGF-I, and IGF-binding proteins (IGFBP-1, IGFBP-2, and IGFBP-3).

RESULTS

At baseline, participants who had greater than median body fat and insulin levels, >39% and >4.5 microunits/mL, respectively, had 2.3- to 2.6-fold lower IGFBP-1 (P < 0.004) and 1.9- to 2.0-fold lower IGFBP-2 (P < 0.004) compared with other participants; IGF-I and IGFBP-3 levels did not differ by body fat or insulin levels. Over 39 weeks, a 1 microunit/mL reduction in fasting insulin was associated with a 17% increase in IGFBP-1 (P = 0.02) and a 24% increase in IGFBP-2 (P = 0.02) compared with participants who did not reduce insulin; 2.0% loss of body fat over time did not alter IGFBP-1 or IGFBP-2 levels after adjustment for insulin. IGF-I and IGFBP-3 did not change in participants who lost body fat percentage or insulin over time.

CONCLUSIONS

These observational associations are consistent with the hypothesis that elevated insulin and body fat are associated with decreased IGFBP-1 and IGFBP-2 levels cross-sectionally; they further imply that IGFBP-1 and IGFBP-2 levels may be altered through change in insulin over time. By contrast, no cross-sectional or longitudinal associations were noted between IGF-I and IGFBP-3 with insulin or body fat.

The role of obesity and related metabolic disturbances in cancers of the colon, prostate, and pancreas

Recent evidence indicates that obesity and related metabolic abnormalities are associated with increased incidence or mortality for a number of cancers, including those of the colon, prostate, and pancreas. Obesity, physical inactivity, visceral adiposity, hyperglycemia, and hyperinsulinemia are relatively consistent risk factors for colon cancer and adenoma. Also, patients with type 2 diabetes mellitus have a higher risk of colon cancer. For prostate cancer, the relationship to obesity appears more complex. Obesity seems to contribute to a greater risk of aggressive or fatal prostate cancer but perhaps to a lower risk of nonaggressive prostate cancer. Furthermore, men with type 2 diabetes mellitus are at lower risk of developing prostate cancer. Long-standing type 2 diabetes increases the risk of pancreatic cancer by approximately 50%. Furthermore, over the past 6 years, a large number of cohort studies have reported positive associations between obesity and pancreatic cancer. Together with data from prediagnostic blood specimens showing positive associations between glucose levels and pancreatic cancer up to 25 years later, sufficient evidence now supports a strong role for diabetes and obesity in pancreatic cancer etiology. The mechanisms for these associations, however, remain speculative and deserve further study. Hyperinsulinemia may be important, but the role of oxidative stress initiated by hyperglycemia also deserves further attention.

Insulinlike growth factor I receptor and estrogen receptor beta expressions are inversely correlated in colorectal neoplasms and affected by the insulin resistance syndrome

The present study aimed at evaluating the modulation of insulin-like growth factor I receptor (IGF-IR) and estrogen receptor beta (ER-beta) expression and their correlation during tumorigenesis of sporadic colorectal cancer, with particular interest in the insulin resistance syndrome. In a series of 100 individuals (54 men and 46 women; mean age, 67.3 +/- 9.4 years) with colorectal neoplasms, classified as early adenomas (n = 25), advanced adenomas (n = 44), and adenocarcinomas (n = 31), IGF-IR and ER-beta expression was quantified in formalin-fixed, paraffin-embedded biopsy specimens, using confocal laser scanning microscopy and a computer-based method for assessment of immunofluorescent staining. All individuals were evaluated for insulin resistance markers (hyperglycemia, dyslipidemia, central obesity, and arterial hypertension), and 50 (26 men and 24 women; mean age, 68.2 +/- 9.0 years) were diagnosed with the insulin resistance syndrome. For the sequence of early adenoma-advanced adenoma-adenocarcinoma, a gradual increase in IGF-IR expression and a gradual decrease in ER-beta expression were observed. The partial correlation coefficient between IGF-IR and ER-beta expression, controlled for age, sex, insulin resistance, type of lesion, and location of lesion was 0.295 (P = .004, 2-tailed significance). Analysis of variance demonstrated that the effect of the insulin resistance syndrome on IGF-IR and ER-beta expression was significant (P = .007 and P = .018, respectively). The results suggest the combined effect of IGF-I and estrogens in colorectal cancer, with a distinctive role in individuals with the insulin resistance syndrome.

Metabolic abnormalities and risk for colorectal cancer in the physicians' health study

BACKGROUND

Obesity and diabetes are established risk factors for colorectal cancer but have mainly been assessed independently. There are few data about whether the metabolic syndrome, which refers to a clustering of cardiovascular disease risk factors thought to be related to insulin resistance, including obesity, type 2 diabetes, hyperlipidemia, and hypertension, is associated with colorectal cancer risk.

METHODS

During and after the randomized trial of aspirin and beta-carotene, 22,071 healthy male physicians, initially ages 40 to 84 years, reported overweight (body mass index, >or=27 kg/m2), diabetes, elevated blood pressure (>or=130/85 mmHg or use of antihypertensive medication), hypercholesterolemia (>or=240 mg/dL or use of lipid-lowering medication), and occurrence of cancer on annual questionnaires. Adjusted relative risks (RR) and 95% confidence intervals (95% CI) for time-varying metabolic abnormalities and colorectal cancer were estimated using a multivariable proportional hazards model.

RESULTS

During 369,966 person-years of follow-up (median, 19 years), 494 physicians developed colorectal cancer. With aging of the cohort, the prevalence of having two or more abnormalities increased from 13% to 35%. Overweight (RR, 1.4; 95% CI, 1.1-1.7) and diabetes (RR, 1.5; 95% CI, 1.1-2.0) were associated with increased risk for colorectal cancer, whereas elevated blood pressure (RR, 1.1; 95% CI, 0.9-1.3) and hypercholesterolemia (RR, 0.9; 95% CI, 0.7-1.1) were not. This model assessing metabolic abnormalities independently was more predictive for colorectal cancer than a model based on the number of abnormalities (each additional abnormality RR, 1.16; 95% CI, 1.05-1.29).

CONCLUSIONS

Out of the markers of the metabolic syndrome assessed, overweight and diabetes are risk factors for colorectal cancer, whereas, in contrast to their role in cardiovascular disease, elevated blood pressure and hypercholesterolemia are not.

Metabolic syndrome and gastrointestinal diseases

Metabolic syndrome is a cluster of metabolic abnormalities consisting essentially of obesity, especially abdominal obesity. Metabolic syndrome has been highlighted as a risk factor for cardiovascular and other chronic diseases. Obesity has been implicated in various gastrointestinal diseases such as gastroesophageal reflux diseases and colorectal cancer. Recently, abdominal obesity has been shown to be more important than obesity as expressed by an elevated body mass index as a causative factor for the development of these diseases. In addition to the mechanical effects of obesity, such as an increase in intra-abdominal pressure from large amounts of adipose tissue, substances that adipose tissues secrete, such as tumor necrosis factor-alpha, interleukin-6, leptin, and insulin-like growth factor-1, have been proposed to be pathogenic links to these diseases. In this review, we discuss the association of metabolic syndrome or the individual components of metabolic syndrome, focusing on obesity and abdominal obesity, with gastrointestinal diseases.

Biological effects of the superoxide radical

Can the superoxide radical exert deleterious effects independent of participating with H2O2 in the production of the hydroxyl radical? Examination of the superoxide-related literature reveals data suggesting an affirmative answer to this question.