Papers of the Month
By Nancy Lamontagne
Seafood consumption and Alzheimer’s disease
An NIEHS grantee and colleagues report that people with a higher risk of developing Alzheimer’s disease, who also consumed more seafood, showed fewer brain changes tied to the disease, despite exhibiting higher levels of mercury in their brains. The protective effects of eating seafood were only observed among people with the apolipoprotein 4 (APOE4) allele, a gene variant linked with increased risk of Alzheimer’s disease.
Mercury is a known neurotoxin, so the researchers wanted to determine whether seafood consumption raised brain mercury levels in older adults, and also whether seafood consumption or brain mercury levels correlated with brain changes related to Alzheimer’s. They examined deceased participants in the Memory and Aging Project who had reported seafood consumption annually, prior to their death.
Among 286 autopsied brains, the researchers found that higher levels of mercury were linked with eating more meals containing seafood each week. After adjusting for age, sex, education, and total energy intake, eating seafood one or more times a week was significantly correlated with fewer brain changes related to Alzheimer’s, including amyloid plaques and neurofibrillary tangles, but only among APOE4 carriers. The researchers also examined fish oil supplementation, but did not find the same protective effect among the small group of participants using these supplements.
Morris MC, Brockman J, Schneider JA, Wang Y, Bennett DA, Tangney CC, van de Rest O 2016. Association of seafood consumption, brain mercury level, and APOE epsilon4 status with brain neuropathology in older adults. JAMA 315(5):489-497.
Maternal diabetes and obesity associated with higher autism risk
Children of women who are both obese and diabetic are more than four times as likely to be diagnosed with autism spectrum disorder than children of healthy weight mothers without diabetes, according to a new study funded in part by NIEHS.
Previous studies have suggested a link between maternal diabetes and autism, but this is one of the first studies to examine the independent and combined association of maternal obesity and diabetes with the risk of autism in a group of children followed since birth. The researchers analyzed 2,734 mother-child pairs who were part of the Boston Birth Cohort, recruited at the Boston Medical Center at birth. They identified 102 children diagnosed with autism spectrum disorder during the study.
When examined individually, maternal obesity prior to pregnancy and pregestational diabetes were each associated with autism risk. However, the association was stronger for women with both risk factors. The researchers reported a significantly increased risk of children with autism in mothers with obesity and pregestational diabetes (hazard ratio 3.91, 95 percent confidence interval 1.76-8.68) and mothers with obesity and gestational diabetes (hazard ratio 3.04, 95 percent confidence interval 1.21-7.63).
Li M, Fallin MD, Riley A, Landa R, Walker SO, Silverstein M, Caruso D, Pearson C, Kiang S, Dahm JL, Hong X, Wang G, Wang MC, Zuckerman B, Wang X. 2016. The association of maternal obesity and diabetes with autism and other developmental disabilities. Pediatrics 137(2):1-10.
Atrazine exposure causes multigenerational developmental effects
NIEHS grantees report that zebrafish embryos exposed to the agricultural herbicide atrazine, a suspected endocrine-disrupting chemical, later developed reproductive problems and had offspring with physical deformities. The study suggests atrazine is an endocrine-disrupting chemical that can cause reproductive problems in adults and affect the next generation.
Atrazine is predominately used in the Midwest to control weeds on field crops and it often contaminates drinking water supplies. Most previous studies of the herbicide have examined developmental, pubertal, or adult exposures. This study looked at how developmental exposure affects adults and their offspring. The researchers exposed zebrafish to 0, 0.3, 3, or 30 parts per billion (ppb) of atrazine during embryonic development, with no further chemical exposure later in life.
Zebrafish exposed to concentrations of 3 and 30 ppb showed significant increases in progesterone levels. The 30 ppb group also exhibited a decrease in spawning and a significant increase in the breakdown of the ovarian follicles. The researchers observed physical changes in offspring, including a decrease in the head length to body ratio in the 30 ppb group, and a significant increase in ratio of head width to body in the 0.3 ppb and 3 ppb groups. The researchers also found alterations in genes associated with endocrine system development and function, tissue development, and behavior.
Wirbisky SE, Weber GJ, Sepulveda MS, Lin TL, Jannasch AS, Freeman JL. 2016. An embryonic atrazine exposure results in reproductive dysfunction in adult zebrafish and morphological alterations in their offspring. Sci Rep 6:21337.
Device improves detection of pollutants in water and sediment
NIEHS-supported researchers have developed and tested a new device for detecting and analyzing pollution in water and sediment. The instrument provides information about the presence and relative risk of chemicals of concern, while offering better accuracy, cost, and versatility than existing methods.
Today’s methods of collecting, preparing, and analyzing environmental samples can underestimate or overestimate a contaminant’s bioavailability, or the actual amount of the substance that can be absorbed by animals or people and cause harm. The new device, called the in situ sampler for biphasic water monitoring (IS2B), directly determines pollutant bioavailability in samples collected over time periods ranging from days to weeks. It can analyze contaminants that are either fully dissolved or suspended as particulates in free-flowing surface water, and those in the stagnant water in sediment. Because it can be used in the field, IS2B also eliminates the need to transport water and sediment for analysis.
The researchers tested the device by deploying it in an engineered wetland to monitor the pesticide fipronil and its transformation products. They detected fipronil and its products at concentrations as low as 0.040 nanograms per liter. Their measurements of fipronil and its products were statistically indistinguishable from those determined by conventional, more laborious techniques.
Supowit SD, Roll IB, Dang VD, Kroll KJ, Denslow ND, Halden RU. 2016. Active sampling device for determining pollutants in surface and pore water — the in situ sampler for biphasic water monitoring. Sci Rep 6:21886.