arsenic exposure

Arsenic exposure linked to early puberty, obesity

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Exposure to low levels of arsenic through drinking water in utero resulted in signs of early puberty and obesity as adults in female mice, according to recent findings.

“We unexpectedly found that exposure to arsenic before birth had a profound effect on onset of puberty and incidence of obesity later in life,” Humphrey Yao, PhD, a reproductive biologist at the National Institute of Environmental Health Sciences (NIEHS), said in the release. “Although these mice were exposed to arsenic only during fetal life, the impacts lingered through adulthood.”

Currently, the Environmental Protection Agency states that the maximum allowable amount for arsenic in drinking water is 10 parts per billion.

The researchers divided female mice into three groups: control (no exposure), standard exposure (current EPA guideline) or high level (42.5 parts per billion). Exposure occurred during gestation, between 10 days after fertilization and birth corresponding to the middle of the first trimester and birth in humans.

The researchers found that both the high and low doses resulted in weight gain as well as onset of puberty.

“It’s very important to study both high doses and low doses,” Linda Birnbaum, PhD, director of NIEHS and the National Toxicology program, said in the release. “Although the health effects from low doses were not as great as with extremely high doses, the low-dose effects may have been missed it only high doses were studied.”

Low-level arsenic exposure may impair insulin sensitivity

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Urinary total arsenic levels in a group of nondiabetic Amish adults are associated with insulin sensitivity, but are not linked to beta-cell function measures, according to study data published in Diabetes/Metabolism Research and Reviews.

Sung Kyun Park, ScD, MPH, of the University of Michigan School of Public Health, and colleagues analyzed data from 221 adults without diabetes and normal glucose tolerance (n = 164) or impaired glucose tolerance (n = 57) participating in the Amish Family Diabetes study, a genetic epidemiology study of type 2 diabetes in Old Order Amish living in Lancaster, Pennsylvania. Participants were recruited between 1995 and 1998 (mean age, 53 years; 115 women). All participants underwent a 75 g oral glucose tolerance test and fasting blood sample to measure insulin sensitivity and beta-cell function; researchers also measured urinary arsenic concentrations. All arsenic concentrations among the participants were above the limit of detection (0.1 µg/L). To account for correlations among sibling participants, researchers used generalized estimating equations with an exchangeable correlation structure.

Urinary total arsenic was significantly and inversely associated with two insulin sensitivity measures after adjusting for age, sex, urinary creatinine and adiposity (Stumvoll metabolic clearance rate = –0.23 mg/[kg x min]; 95% CI, –0.38 to –0.09; Stumvoll insulin sensitivity index = –0.0029 mol/[kg x min x pM]; 95% CI, –0.0047 to –0.0011).

Urinary total arsenic also was significantly associated with higher fasting glucose levels (0.57 mg/dL per interquartile range increase; 95% CI, 0.06-1.09).

Researchers did not find a significant association between urinary arsenic and beta-cell function measures.

“Notably, these associations were stronger and remained statistically significant following covariate adjustment compared to the widely used index of insulin resistance, HOMA-IR, which is based on fasting measures of insulin and glucose,” the researchers wrote. “Previous mixed results may be partly due to low sensitivity of HOMA-IR.”