Arsenic exposure may be associated with type 2 diabetes

In a study involving a representative sample of U.S. adults, higher levels of arsenic in the urine appear to be associated with increased prevalence of type 2 diabetes, according to a report in the August 20 issue of JAMA.

Arsenic from inorganic sources is highly toxic and causes cancer in humans, according to background information in the article. Millions of individuals worldwide are exposed to drinking water contaminated with inorganic arsenic, including 13 million Americans whose public water supply contains more than the U.S. Environmental Protection Agency standard of 10 micrograms per liter. Exposure to high concentrations of the element in drinking water and in the workplace has been shown to be associated with diabetes, but little is known about the effect of lower levels on diabetes risk. In contrast, arsenobetaine—an organic arsenic compound derived eating seafood—is considered non-toxic.

Ana Navas-Acien, M.D., Ph.D., of the Johns Hopkins Bloomberg School of Public Health, Baltimore, and colleagues studied 788 adults age 20 and older who had their urine tested for arsenic levels as part of the government-conducted 2003-2004 National Health and Nutrition Examination Survey (NHANES).

Overall, 7.7 percent of the participants had type 2 diabetes. After adjusting for diabetes risk factors and biomarkers of seafood intake, participants with type 2 diabetes had a 26 percent higher level of total arsenic in their urine than those without the disease. Levels of arsenobetaine were similar between the two groups.

After the same adjustment for related factors, the researchers found that participants in the top one-fifth of total urine arsenic levels (16.5 micrograms per liter) had 3.6 times the odds of having type 2 diabetes as those in the lowest one-fifth (3.0 micrograms per liter), and those in the top one-fifth of dimethylarsinate levels (6.0 micrograms per liter) had 1.5 times the odds as those in the lowest one-fifth (2.0 micrograms per liter). Dimethylarsinate is a compound into which inorganic arsenic is metabolized before excretion.

“The potential role of arsenic in diabetes development is supported by experimental and mechanistic evidence,” the authors note. Insulin-sensitive cells that are exposed to insulin and sodium arsenite appear to take in less glucose than cells exposed only to insulin. Arsenic could also influence genetic factors that interfere with insulin sensitivity and other processes, or could contribute to oxygen-related cell damage, inflammation and cell death (which have also been related to diabetes).

“From a public health perspective, confirmation of a role for arsenic in diabetes development would add to the concerns posed by the carcinogenic, cardiovascular, developmental and reproductive effects of inorganic arsenic in drinking water, and could substantially modify risk assessment and risk-benefit analyses estimating the consequences of arsenic exposure,” the authors conclude. “Given widespread exposure to inorganic arsenic from drinking water worldwide, elucidating the contribution of arsenic to the diabetes epidemic is a public health research priority with potential implications for the prevention and control of diabetes.”

(JAMA. 2008;300[7]:814-822. Available pre-embargo to the media at www.jamamedia.org.)

Editor’s Note: This work was supported by a grant from the National Institute of Environmental Health Sciences in Urban Environmental Health. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

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