Department of Gastroenterology and Hepatology, Cleveland Clinic Lerner College of Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Dig Dis Sci. 2012 Oct;57(10):2497-503. doi: 10.1007/s10620-012-2198-0. Epub 2012 May 6.
African Americans have the highest incidence and mortality rates of colorectal cancer among all US racial and ethnic groups. Dietary factors, lifestyle factors, obesity, variability in screening rates, socioeconomic differences, barriers to screening, and differences in access to health care may be contributory factors to racial and ethnic disparities. African Americans are more likely to demonstrate microsatellite instability in their colorectal tumors leading to malignancy. However, these differences do not completely explain all the variances. Ample evidence implicates insulin resistance and its associated conditions, including elevated insulin and insulin-like growth factor-1 (IGF-1), in colorectal carcinogenesis. African Americans have a high risk for and a high prevalence of insulin resistance and subsequent overt type 2 diabetes. Recent clinical studies revealed that ethnic differences between whites and African Americans in early diabetes-related conditions including hyperinsulinemia already exist during childhood. African Americans have a much higher prevalence of vitamin D deficiency than whites throughout their life spans. Vitamin D deficiency has been associated with higher rates of diabetes and colorectal cancer, particularly in individuals with high serum insulin and IGF-1 levels. Moreover, African Americans have lower insulin sensitivity in tissues, independent of obesity, fat distribution, and inflammation. Further development of measures of biomarkers of tumor biology and host susceptibility may provide further insight on risk stratification in African Americans.
非裔美国人的结直肠癌发病率和死亡率在所有美国种族和族裔群体中最高。饮食因素、生活方式因素、肥胖、筛查率的差异、社会经济差异、筛查障碍以及获得医疗保健的差异可能是导致种族和族裔差异的因素。非裔美国人的结直肠肿瘤中更可能表现出微卫星不稳定性，从而导致恶性肿瘤。然而，这些差异并不能完全解释所有的差异。大量证据表明，胰岛素抵抗及其相关疾病，包括胰岛素和胰岛素样生长因子-1（IGF-1）升高，与结直肠癌的发生有关。非裔美国人患胰岛素抵抗和随后的 2 型糖尿病的风险高，患病率也高。最近的临床研究表明，白人和非裔美国人在儿童时期就已经存在与糖尿病相关的早期状况的种族差异，包括高胰岛素血症。非裔美国人在整个生命周期中的维生素 D 缺乏症的患病率远远高于白人。维生素 D 缺乏与糖尿病和结直肠癌的发生率较高有关，尤其是在血清胰岛素和 IGF-1 水平较高的人群中。此外，非裔美国人的组织胰岛素敏感性较低，与肥胖、脂肪分布和炎症无关。进一步开发肿瘤生物学和宿主易感性的生物标志物的措施可能会进一步深入了解非裔美国人的风险分层。
