Key Findings:
Abdominal subcutaneous adipose tissue samples were assessed from 203 cases with newly diagnosed colorectal cancers (CRC) and elective surgery and 223 control subjects with planned abdominal surgery for benign disease and no history of CRC or polyp resection. Enhanced levels of the fatty acids including 16:1n 9, 20:3n6, and 22:5n3 were significantly higher in CRC patients than controls. In contrast, levels of ALA were significantly lower in CRC patients. The ratio of LA to ALA was also elevated in CRC cases. Further research in CRC to determine characteristics of fat storage and enzymatic activities in adipose tissue is recommended.
ABSTRACT:
Background: Unlike experimental results, epidemiologic studies that used dietary questionnaires were not convincing as regards the relations between dietary fatty acids (FAs) and risk of colorectal cancer (CRC). The FA composition of adipose tissue, which is considered to be an indicator of dietary intake over 2 to 3 years because of the slow turnover rate, appears promising but has so far been rarely used to explore the relation between CRC and exogenous or endogenously produced FAs. Objective: In this case-control study, we aimed to investigate associations between risk of CRC and the FA composition of subcutaneous adipose tissue and product-to precursor ratios as indexes of enzymatic activities. Design: From 2008 to 2011, we recruited 203 cases with newly diagnosed CRC and elective surgery with a curative intent and 223 control subjects with planned abdominal surgery for benign disease and no history of CRC or polyp resection. During surgery, abdominal subcutaneous adipose tissue samples were optimally collected, stored, and analyzed by using high-performance gas chromatography. Multivariate logistic regression was used to estimate ORs for CRC in relation to individual FAs divided into tertiles according to the FA distribution in controls. Results: After adjustment, significant positive associations with CRC risk were observed in highest compared with lowest tertiles of 16:1n9, 20:3n6, 22:5n3, and the ratio of 18:2n6 to 18:3n3. Significant inverse associations were observed for 18:3n3. Several product-to-precursor ratios showed significant differences between cases and controls in particular ratios that reflected elongase 2/5 activity. Conclusions: CRC patients presented higher concentrations of some FAs but lower concentrations of a-linolenic acid in their subcutaneous adipose tissue than did controls. These results may reflect both dietary patterns and altered FA metabolism but require mechanistic explorations. (Authors Abstract)