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Thirdhand smoke linked to type 2 diabetes

Thirdhand smoke (THS) results when exhaled smoke gets on surfaces – clothing, hair, homes and cars. THS has been shown, in mice, to damage the liver and lungs, complicate wound-healing and cause hyperactivity. Add to this list now type 2 diabetes, the most common form of the disease.

Research published yesterday in PLOS ONE by a team led by scientists at the University of California, Riverside shows, in mice, that THS exposure causes insulin resistance, a precursor to type 2 diabetes.

“If confirmed in humans, our study could greatly impact how people view exposure to environmental tobacco toxins,” said Manuela Martins-Green, a professor of cell biology and neuroscience at UC Riverside and the lead author of the study. “Children and the elderly are especially vulnerable to THS and its impact on health. Because infants frequently crawl on carpets and touch objects exposed to exhaled smoke, they are at high risk for THS exposure. The elderly are at high risk simply because older organs are more susceptible to disease.”

Martins-Green explained that THS consists of tobacco smoke toxins that linger on surfaces and in dust after tobacco has been smoked.

“This includes toxins that become increasingly toxic with age and are re-emitted into the air or react with other chemicals in the environment to produce new pollutants,” she said. “Some of these pollutants are carcinogenic.”

Her research team found that cellular oxidative stress (arising because of reactive oxygen species) increases in mice exposed to THS, damaging proteins, fats and DNA, and leading to hyperglycemia (excess glucose in the blood stream) and insulinemia (excess insulin in the blood) – a condition also called insulin resistance. When the THS-exposed mice in her lab were treated with antioxidants, the oxidative stress, the molecular damage and the insulin resistance reversed, confirming that THS exposure increased oxidative stress.

“Dr. Martins-Green has a unique animal model for human exposure to THS, especially in small children. This mechanistic study gives us more evidence about the connection between exposure to THS and human health,” said Anwer Mujeeb, a biomedical and environmental sciences program officer at the Tobacco-Related Disease Research Program (TRDRP), which funded the study.

The pancreas makes insulin in the body. This hormone lets cells turn sugar – or glucose – from the food we eat into energy. To use and store blood glucose, the pancreas releases more insulin with each meal we eat. In type 1 diabetes, the pancreas no longer makes insulin. Patients are therefore given insulin to boost levels in the body. In type 2 diabetes, the pancreas makes insulin, but cells are not able to respond to it.