Ethnic Differences in Insulin Resistance as a Mediator of Cancer Disparities

Abstract

Ethnic differences in the incidence and prevalence of certain obesity-related cancers are well established. African Americans have increased risk of prostate, breast (premenopausal), and colorectal cancer and myeloma, compared to Caucasians with the lowest rates in Latinos, Asians, and Native Americans. Prior work in this area suggests that there are distinct ethnic differences in obesity-related metabolic risk factors for cancer, insulin resistance in particular, that are evident early in life, and may help explain ethnic differences in the incidence and prevalence of obesity-related cancers. The focus of this chapter is to review and discuss ethnic differences in insulin resistance and its link with other cancer-related metabolic risk factors including hyperinsulinemia, insulin-like growth factors, body fat distribution, adipose tissue biology, low-grade inflammation, non-esterified fatty acids, and oxidative stress. This chapter places a particular emphasis on ethnic differences between African Americans and Latinos for two reasons: (1) African Americans and Latinos are the two largest ethnic minority groups in the USA, and (2) these populations share a similar propensity for obesity and insulin resistance but markedly different profiles for obesity-related cancers, creating an informative comparative contrast. Although the literature is limited by an inconsistency in the terminology used for various ethnicities, in most cases we refer to Caucasian for any study using the terms Caucasian, White, or non-Hispanic White; Latino to describe people of Hispanic, Latino, or Mexican-American descent; African American to describe people of African, African American, or Black-Caribbean descent; Asian to describe people of Asian, South Asian, East Asian, and Southeast Asian descent or any other specific Asian ethnicity; and Native American to describe people of American Indian, Pima Indian, Aboriginal, First Nation, or Alaska Native ethnicity. We also recognize that there may be variation within these subgroups; however, comprehensive review of this literature is beyond the scope of this chapter.