| [ Summary ] |
An association between type 2 diabetes and colorectal cancer has long been discussed, but details concerning the interrelation of these two diseases remain largely unclarified. To address this issue, this review summarized relationships between the two diseases in the resident Japanese population(J-Japanese). In the J-Japanese population, prevalence rates for type 2 diabetes and age-standardized incidence rates of colorectal cancer have increased in relation to the adoption of western dietary habits. A positive correlation was observed between increased rates of these two diseases in J-Japanese populations and Japanese in the United States(US-Japanese). The highest incidence rates were US-Japanese. Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma(PPARγ)gene plays important roles in energy homeostasis. Compared with American-European populations, the frequency of the Ala allele related to lower risk of type 2 diabetes was much lower in the J-Japanese group. In our studies, an increased risk of colorectal cancer was seen in subjects with the Pro/Pro genotype and a high consumption of meat. Moreover, these factors were seen in men with a past or present history of diabetes and in women with both a past or present history of this disease and a family history of diabetes. In conclusion, our findings have provided support for the hypothesis that type 2 diabetes can increase the risk of colorectal cancer. |