EPIDEMIOLOGY OF COLORECTAL-CANCER REVISITED - ARE SERUM TRIGLYCERIDESAND OR PLASMA-GLUCOSE ASSOCIATED WITH RISK/

Several aspects of Western diets, alcohol use, and exercise patterns w hich are related to the risk of colorectal cancer have systemic effect s in common. Those which increase the risk of colorectal cancer are po sitively associated with serum triglycerides and plasma glucose; those which decrease risk are negatively associated with serum triglyceride s and plasma glucose. These observations suggest the hypothesis that s erum triglycerides and/or plasma glucose may themselves be associated with colorectal cancer risk. Evidence for associations between colorec tal neoplasia and triglycerides and glucose comes from two recent stud ies of adenomatous polyps, presumed precursors for colorectal cancer, and from previous studies of diabetes and cancer. In addition, three r andomized trials, one in humans and two in animal models, suggest that diets which would be expected to increase serum triglycerides and pla sma glucose increase the levels of cellular indicators of colorectal c ancer risk. Biological mechanisms explaining associations between colo rectal neoplasia and serum triglycerides and/or plasma glucose might i nvolve luminal or circulatory effects: (a) triglycerides and/or glucos e may be associated with fecal bile acids, acids which are positively associated with colorectal cancer risk ire epidemiological studies and which promote colorectal cancer in animal models; (b) serum triglycer ides and/or plasma glucose might influence circulating hormones, such as insulin, which might themselves be involved in cancer development; (c) serum triglycerides and/or plasma glucose might be indicators of e nergy available through the circulation for neoplastic cells. Future r esearch should examine the associations between the risk of colorectal neoplasia and serum triglycerides and plasma glucose, explore possibl e biological mechanisms, and develop an understanding of whether biolo gical processes involving triglycerides, glucose, and insulin may be c ommon to a number of sites of cancer.