Body Composition and Biomarkers of Colorectal Cancer Risk in African Americans and Non-Hispanic Whites
thesisposted on 18.02.2018 by Sandra L. Gomez-Perez
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Introduction: Excess visceral adipose tissue (VAT) associates with inflammation, insulin resistance(IR) and colorectal cancer (CRC) risk. Compared to Non-Hispanic Whites (NHW), healthy African Americans (AA) have less VAT but increased risk for IR and CRC. The association between VAT, CRC and race/ethnicity is unclear. Methods: A case-control study (N=256; 128 cases, 128 controls) of AA and NHW patients with and without incident CRC characterized the relationship between abdominal adipose tissues (AAT), CRC and race/ethnicity. Cross-sectional computed tomography(CT) images were quantified for abdominal circumference (WC), VAT and other AAT. A cross-sectional analysis of serum samples from cases were used to assess the association between AAT, race/ethnicity and CRC. Also, a cross-sectional analysis was also used to explore the existence of hepatic steatosis by measuring hepatic fat content(HFC) in both groups. Results: Median and interquartile for age, body mass index (BMI), and WC were 62(10)years, 27(7)kg/m2 and 104(17)cm, respectively; sample was 79%(176/256) AA, 63%(158/256). Also, 28%(35/128) of cases and 31%(39/128) were obese (BMI≥30). No significant differences were found for VAT between cases and controls (p=0.9316) however, superficial subcutaneous adipose tissue (SSAT) was significantly higher in cases (p=0.0005). AA cases and controls had significantly lower VAT compared to NHW counterparts. Conditional logistic regression revealed that SSAT reduced the odds of CRC for AA only (OR: 0.24, 95%CI 0.07-0.85). Adiponectin and insulin-growth factor binding protein-3 were significantly lower in AA males compared to NHW males. The non-contrast technique of CT images showed lower prevalence of HFC for overall sample. Conclusions: No VAT-related CRC phenotype was found between cases and controls. Differences in VAT between AA and NHW cases versus controls resembles the body composition phenotype of healthy populations. The role of SSAT as protective against CRC requires further investigation especially in light of its accessibility for biopsy studies and the availability of new inexpensive and risk - free techniques for measuring SSAT using an ultrasound. The role of VAT and other AAT in the CRC pathway remains to be determined.