Study: link between arsenic exposure and type 2 diabetes

Study: link between arsenic exposure and type 2 diabetes

According to a study published in the August 20 issue of JAMA, an analysis using a representative sample of U.S. adults has found a relationship between higher levels of arsenic in the urine and an increased prevalence of type 2 diabetes.

It has been widely documented that arsenic from inorganic sources is highly toxic and causes cancer in humans. Drinking water that is contaminated with inorganic arsenic exposes millions of individuals worldwide to the toxin. Further, the public water supply of some 13 million Americans contains more than the 10 micrograms per liter of arsenic that is allowed by the U.S. Environmental Protection Agency. Research has shown that diabetes is associated with exposure to high concentrations of arsenic in drinking water and in the workplace, but little is known about the link between diabetes risk and lower levels of the element. Notably, there is an organic arsenic compound called arsenobetaine that is found in seafood and is considered non-toxic.

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

Baseline statistics showed that 7.7% of participants had type 2 diabetes. Statistically adjusting for additional diabetes risk factors and biomarkers indicating seafood consumption, the researchers found that those with type 2 diabetes had a 26% higher level of total arsenic in their urine compared to those without diabetes. The levels of arsenobetaine were no significantly different between the two groups.

The authors also found that:

  • Participants in the top one-fifth (20%) of total urine arsenic levels with 16.5 micrograms per liter had 3.6 times the odds of having type 2 diabetes as those in the lowest one-fifth with 3.0 micrograms per liter.
  • Participants in the top one-fifth of dimethylarsinate levels with 6.0 micrograms per liter had 1.5 times the odds as those in the lowest one-fifth with 2.0 micrograms per liter.
Before excretion, inorganic arsenic metabolizes to the compound dimethylarsinate.

"The potential role of arsenic in diabetes development is supported by experimental and mechanistic evidence," write the authors. The chemical response of insulin-sensitive cells that are exposed to insulin and sodium arsenite seems to include absorbing less glucose than cells exposed only to insulin. The researchers also propose that arsenic could influence genetic factors that interfere with insulin sensitivity, or it could contribute to oxygen-related cell damage, inflammation and cell death - all known to be 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," conclude the researchers. "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."

An accompanying editorial

"To date, this approach has focused on medication and lifestyle modification, but the role of environmental exposures must also be considered," they add. "While many questions remain about the role of arsenic in diabetogenesis, they can only be answered by additional research."

Kile and Christiani conclude: "In the meantime, arsenic exposure from drinking water is a widespread environmental pollutant that affects millions of individuals around the world. It is prudent to minimize arsenic exposure while its effect on metabolic diseases continues to be researched."

Arsenic Exposure and Prevalence of Type 2 Diabetes in US Adults

Ana Navas-Acien; Ellen K. Silbergeld; Roberto Pastor-Barriuso; Eliseo Guallar

JAMA. 300[7]: pp. 814-822.

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