Type 2 diabetes mellitus and colorectal cancer risk: is homocysteine the missing link?

Type 2 diabetes and the risk of colorectal polyps: A retrospective nationwide population-based study

The incidence rates of type 2 diabetes mellitus (T2DM) and colorectal polyps have been increasing over the last decades. However, direct associations between T2DM and colorectal polyps have not been extensively reported. We will explore the relationship between T2DM and colorectal polyps.In the retrospective study, we classified DM and NonDM groups (control) from 993,516 people in Taiwan nationwide population insurance database from the period of 2000 to 2013. We collected data on income and comorbidities through the international classification of diseases, ninth revision-clinical modification (ICD-9-CM) codes.The T2DM group had a higher incidence rate of colorectal polyps (31.97%, 95% confidence interval [CI] = 30.97-33.28) than the control group (25.9%, 95% CI = 25.1-26.72), and the crude incidence ratio was 1.235 (95% CI = 1.174-1.300). In 13 years of follow-up (2000-2013), T2DM was linked to a significantly higher cumulative probability of colorectal polyps (log-rank test: P = .0001).Patients with T2DM had a 1.23-fold higher risk of new colorectal polyps than control patients in 13 years of follow-up. We explain the T2DM increases incidence for colorectal polyps in long term follow-up.

Hyperhomocysteinemia as a potential contributor of colorectal cancer development in inflammatory bowel diseases: A review

Homocysteine is an amino acid generated metabolically by the S-adenosylmethionine-dependent transmethylation pathway. In addition to being a well-known independent risk factor for coronary heart disease, is also a risk factor for cancer. Patients suffering from inflammatory bowel diseases (IBD) including ulcerative colitis and Crohn’s disease are at increased risk of developing colorectal cancer in comparison to healthy individuals. Furthermore, the risk of hyperhomocysteinaemia is significantly higher in IBD patients when compared with controls. In the present article, we review the mechanisms in which hyperhomocysteinemia may contribute to increased risk of colorectal cancer in IBD patients.

Is diabetes a causal agent for colorectal cancer? Pathophysiological and molecular mechanisms

The possible relationship between diabetes mellitus (DM) and colorectal cancer (CRC), concerning pathophysiological and molecular mechanisms is highlighted in this review. The most recent and complete articles and developments in this particular field were thoroughly reviewed. Common risk factors, such as obesity, sedentary lifestyle, and Western diet between DM and CRC, led to the theory that DM might be a causal agent for CRC development. Various studies have connected type 2 DM and CRC, either proximal or distal, in both sexes. Additionally, chronic insulin treatment has been linked with increased colorectal tumor risk among type 2 diabetic patients. Interestingly, elevated hemoglobin A1c has been proven to be an independent predictor of aggressive clinical behavior in CRC patients. These mechanisms include the insulin-like growth factor-hyperinsulinemia theory and the participation of oncogenic intracellular signaling pathways. Furthermore, it has been proposed that Cox-2 inhibitors might have a role in decreasing the incidence of CRC. Finally, the use of statins to reduce the risk for colon cancer in patients with diabetes has remained controversial. Diabetic patients over 50 should receive counseling regarding their elevated risk for CRC, and screening colonoscopy should be recommended before initiating insulin therapy. However, there are no current guidelines, and this strategy is not yet applicable to some countries, as the corresponding risk would not allow screening colonoscopy to be adopted. There is strong evidence to indicate that DM is a causal agent for CRC development. This conclusion provides new impetus for re-evaluating CRC screening worldwide.