In human subjects, aberrant crypt foci (ACF) can be classified as dysplastic or non-dysplastic using magnifying colonoscopy. Dysplastic ACF are thought to be a biomarker for the risk of colorectal cancer (CRC). Hyperinsulinemia and insulin-like growth factor-1 (IGF-1) have also been reported to be associated with an increased risk of CRC. To clarify this association, we investigated the relationship between diabetes risk, IGF-1 and the number of dysplastic ACF. Assessment of the number of dysplastic ACF in the entire colorectum is technically difficult, and we imaged the lower rectum only. Blood collections were taken in the morning on the day of colonoscopy. A total of 512 ACF were counted in 84 male participants, and a correlation was demonstrated to exist between age, body mass index (BMI), fasting blood sugar (FBS), insulin, homeostasis model assessment-insulin resistance (HOMA-IR), plasma leptin levels, plasma IGF-1 levels and the number of dysplastic ACF. A significant association between plasma IGF-1 levels and the number of dysplastic ACF was still demonstrable after adjustment for age, BMI, FBS, insulin, HOMA-IR and plasma leptin levels. Our findings suggest that increased plasma leptin and IGF-1 levels, hyper-insulinemia and insulin resistance may promote the growth of dysplastic ACF. The results of multiple regression analysis revealed that increased plasma IGF-1 levels are associated with the number of dysplastic ACF present, and may be an independent risk factor for CRC. In conclusion, elevated plasma IGF-1 may promote the growth of dysplastic ACF and play a key role in colon carcinogenesis in male individuals.

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