Correspondence to: Celia Mary Ross, M.S., Research and Analytical Laboratories, 106 Short St., Kernersville, NC 27284.
Hu et al. (1) reported a correlation between non-insulin-dependent diabetes mellitus (NIDDM) and colorectal cancer in women. Their article includes a discussion of possible mechanisms by which NIDDM could lead to colorectal cancer. They point out that insulin can function as a growth factor for colonic cancer cells. In addition, they discuss other possible contributing factors, such as elevated levels of fecal bile acid and a longer bowel transit time. Another possible mechanism needs to be considered.
Hyperglycemia initiates a reactive oxygen species (ROS) chain reaction (2). This ROS chain reaction consumes antioxidants, resulting in lower than normal levels of antioxidant activity (3). Impaired antioxidant activity might allow free radicals produced from other sources to go unchecked. This increased oxidative load in NIDDM is associated with increased oxidative damage to DNA (4). Oxidative damage is associated with cancer (5). This process could work in synergy with hyperinsulinemia to increase the risk of cancer in NIDDM. This hypothesis needs further investigation.
REFERENCES
1
Hu FB, Manson JE, Liu S, Hunter D, Colditz GA, Michels KB, et
al. Prospective study of adult onset diabetes mellitus (type 2) and risk of colorectal cancer in
women. J Natl Cancer Inst 1999;91:542-7.
2 Delmas-Beauvieux MC, Peuchant E, Thomas MJ, Dobourg L, Pinto AP, Clerc M, et al. The place of electron spin resonance methods in the detection of oxidative stress in type 2 diabetes with poor glycemic control. Clin Biochem 1998;31:221-8.[Medline]
3 Maxwell SR, Thomason H, Sandler D, Leguen C, Baxter MA, Thorpe GH, et al. Antioxidant status in patients with uncomplicated insulin-dependent and non-insulin-dependent diabetes mellitus. Eur J Clin Invest 1997;27:484-90.[Medline]
4 Dandona P, Thusu K, Cook S, Snyder B, Makowski J, Armstrong D, et al. Oxidative damage to DNA in diabetes mellitus. Lancet 1996;347:444-5.[Medline]
5 Klaunig JE, Xu Y, Isenberg JS, Bachowski S, Kolaja KL, Jiang J, et al. The role of oxidative stress in chemical carcinogenesis. Environ Health Perspect 1998;106 (suppl 1):289S-95.
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