An unusual form of diabetes may be caused by drinking arsenic-contaminated water

Like a careless criminal, even small amounts of toxic arsenic leave telltale fingerprints on victims’ bodies—although these fingerprints are different if the victim as Type 2 Diabetes, scientists report. And arsenic has many potential victims: more than 200 million people worldwide drink freshwater naturally contaminated with small amounts of arsenic. But for the first time, scientists have captured arsenic’s molecular fingerprint in the body fluids of people with and without diabetes from arsenic-contaminated Chihuahua, Mexico. By capturing these molecular fingerprints, the scientists have taken the first step towards reconstructing how arsenic may cause a little-understood form of Type 2 Diabetes.

While arsenic has many potential victims, Type 2 Diabetes has many confirmed ones. Roughly one out of fifteen adults—approximately 256 million people worldwide—has Type 2 Diabetes, and the excess glucose in their blood can damage their heart, kidneys, and nerves over time. But while people who drink arsenic-contaminated water are more likely to develop Type 2 Diabetes, scientists have observed that these arsenic-linked diabetics are different from most diabetics. Unlike most diabetics, their cells react normally to insulin, a hormone released by the pancreas that tells the cells to gobble up glucose from the blood. The problem—at least, the problem in arsenic-drinking lab rats which develop rat diabetes—is that the pancreas’s insulin-making cells seem to be poisoned by arsenic.

To figure out if this is true in humans, the scientists studied 176 people in Chihuaha, where the municipal water is contaminated with more than twice the WHO’s safety limit for arsenic. For each person with Type 2 Diabetes, the scientists matched them to another person the same gender, age, body-mass index, and the amount of arsenic in their tap water at home. The people with and without diabetes then donated their urine and blood plasma—body fluids which contain hundreds of known metabolites, the chemical residues of metabolism.

By examining the pattern of these metabolites, the scientists reconstructed how arsenic had changed people’s metabolism. When they looked at the metabolites unique to people who drank arsenic-contaminated water, they found that the people with diabetes had very different types of metabolites than people without diabetes. The diabetics’ different metabolites suggested that arsenic had changed how their bodies metabolize vitamins and amino acids, as well as how they get energy from food. Surprisingly, the metabolite pattern of the arsenic-linked diabetics was also very different from the metabolite patterns of most diabetics—providing the scientists with “a metabolic fingerprint” that hinted at molecular differences between these forms of diabetes.

 

Reference:
Martin, E., Gonzalez-Horta, C., Rager, J., Bailey, K., Sanchez-Ramirez, B., Ballinas-Casarrubias, L., Ishida, M., Gutierrez-Torres, D., Hernandez Ceron, R., Viniegra Morales, D., Baeza Terrazas, F., Jesse Saunders, R., Drobna, Z., Mendez, M., Buse, J., Loomis, D., Jia, W., Garcia-Vargas, G., Del Razo, L., Styblo, M., & Fry, R. (2015). Metabolomic Characteristics of Arsenic-Associated Diabetes in a Prospective Cohort in Chihuahua, Mexico Toxicological Sciences, 144 (2), 338-346 DOI: 10.1093/toxsci/kfu318