Endocrine-disrupting chemicals may raise risk of cognitive disorders in future generations, animal study finds
Adverse cognitive effects linked to polychlorinated biphenyls (PCBs) exposure, a type of endocrine-disrupting chemical (EDC), have the potential to be passed down through generations, according to an animal study being presented Thursday at ENDO 2023, the Endocrine Society’s annual meeting in Chicago, Ill.
PCBs can mimic the effect of the hormone estrogen on the body, contributing to a variety of neuroendocrine, metabolic and reproductive problems.
“Endocrine-disrupting chemicals present in our food, air, water and personal products may cause cognitive-behavioral disorders like attention-deficit/hyperactivity disorder or overeating in future generations,” said Emily N. Hilz, Ph.D., a postdoctoral fellow at the University of Texas at Austin.
To explore this further, Hilz and colleagues administered a common PCB mixture called Aroclor 1221 to pregnant female rats. The adults (n=40), their offspring (n=80), and their future grandchildren (n=80) were all tested on behavioral tasks to assess pleasure-seeking, ability to pay attention, and cognitive flexibility.
“The grandchildren of rats exposed to EDCs while pregnant performed significantly worse on these tasks, showing impaired cognitive function and increased pleasure-seeking,” Hilz said. “This suggests EDCs program potential cognitive disorders or behavioral problems that only emerge in later generations.”
Grandchildren of rats that were exposed to the PCB mixture were more interested in eating for pleasure, according to the results of the sucrose preference test. While all of the tested animals preferred the sucrose solution to water, the grandchildren of mothers exposed to the PCB mixture consumed more of the sucrose solution.
The same rats had an impaired ability to switch between tasks or learn new rules. However, only the male grandchildren were more likely to become fixated with a visual cue, which is common in disorders such as ADHD.
The PCB mixture impaired different aspects of cognitive behavior between male and female rats, depending on the life stage when they were exposed. It’s not yet clear which biological systems might be driving this.
“Our findings suggest regulating EDCs in industrial and consumer products could reduce the prevalence of certain cognitive or behavioral disorders in the future,” Hilz said.
Hilz is scheduled to present at the Society’s ENDO 2023 endocrine-disrupting chemicals news conference at 10 AM Central on Saturday, June 17. Register to view the news conference livestream at endomediastream.com.
Exposure to dioxins can worsen thyroid function
CHICAGO—Exposure to dioxins can negatively impact thyroid function, according to a study presented Thursday at ENDO 2023, the Endocrine Society’s annual meeting in Chicago, Ill.
Dioxins are highly toxic compounds that are primarily produced by industrial processes, and their persistence in the environment makes them a significant public health concern. They are produced through a variety of incineration processes, including improper municipal waste incineration and burning of trash. They can be released into the air during natural processes, such as forest fires and volcanoes. Strict regulatory controls on major industrial sources of dioxin have greatly reduced emissions into the air.
Today people are exposed to dioxins primarily by eating food, in particular animal products, contaminated by these chemicals. Dioxins are absorbed and stored in fat tissue and, therefore, accumulate in the food chain. More than 90 percent of human exposure is through food, according to the National Institute of Environmental Health Sciences.
Recently, scientists have begun to study the potential impact of exposure to environmental chemicals, such as dioxins, on thyroid function. Thyroid dysfunction affects a significant portion of the population and can have a range of adverse health effects.
Previous studies of the relationship between dioxin exposure and thyroid function have produced inconsistent results, according to researcher Cheng Han, M.D., of the Boston University Chobanian & Avedisian School of Medicine in Boston, Mass.
In the new study, the researchers used three different statistical methods to investigate the combined effects of 20 environmental dioxins on thyroid function. They used data from the National Health and Nutritional Examination Survey (NHANES) from 2007 to 2010.
A total of 20 dioxins and levels of thyroid stimulating hormone (TSH) were measured in the blood of 2,818 adults. The researchers found that dioxins were significantly associated with high TSH. A high TSH level indicates that the thyroid gland is not making enough thyroid hormone.
“Although more research on how dioxins affect thyroid function is needed, efforts to reduce exposure to dioxins and other toxic chemicals could help to reduce the risk of thyroid dysfunction and improve public health outcomes,” Han said.
Prenatal exposure to phthalates may impact future fertility differently in males and females, animal study finds
Prenatal exposure to chemicals called phthalates, which are used in hundreds of products, may lead to hormonal changes in females that could affect their future fertility, suggests a study in mice being presented Thursday at ENDO 2023, the Endocrine Society’s annual meeting in Chicago, Ill.
The study found female mouse embryos exposed to phthalates during gestation had lower testosterone levels than those not exposed to the chemicals. Immediately after birth, female mice exposed to phthalates during gestation had lower levels of the hormone estradiol than those not exposed.
“These changes in hormone levels occurred during critical times in their development and could eventually lead to greater problems with fertility,” said lead researcher Mary Bunnell of the University of Illinois Urbana-Champaign in Urbana, Ill.
During the middle of gestation and during the period right after birth, the body develops and changes significantly. At these times, elevated sex hormones are crucial for proper reproductive development and function. In males, the primary sex hormone is testosterone, which is associated with penile and testicular growth and the masculinization of neurons. In females, the primary sex hormone is estradiol, which stimulates breast tissue and acts as a growth hormone for the reproductive organs. The rise in levels of these hormones allows for the maturation of the sexual organs and creates the basis for future fertility.
“The level of sex hormones during the fetal and neonatal periods are critical, and disruptions in the levels at these times can cause reproductive abnormalities that may not be evident until adulthood,” Bunnell said.
Endocrine-disrupting chemicals such as phthalates are ubiquitous in our environment, so it is extremely difficult to avoid exposure. According to the U.S. Food and Drug Administration, phthalates are used in the manufacture of toys, vinyl flooring and wall covering, detergents, lubricating oils, food packaging, pharmaceuticals, blood bags and tubing, and personal care products, such as nail polish, hair sprays, aftershave lotions, soaps, shampoos and perfumes. They can leach from packaging and into the food we consume.
Ongoing research has revealed many health concerns linked with phthalate exposure, particularly of the reproductive system and other endocrine systems. Prepubescent children are especially at risk. It has been shown that phthalates can cross the placenta, putting the developing fetus at risk of gestational exposure to these dangerous chemicals during a sensitive period of development, Bunnell said.
In the new study, researchers studied two groups of mice. In one group, the researchers mimicked human exposure to phthalates by orally dosing pregnant mice with a phthalate mixture formulated to reflect the levels of phthalates found in humans. In the second group, pregnant mice were not exposed to phthalates. They measured fetal and newborn hormones of the offspring in both groups.
During gestation, female embryos exposed to phthalates had lower testosterone levels than non-exposed females. Female newborns had lower estradiol than non-exposed females. However, they did not find such changes in males. The results show that prenatal phthalate exposure had sex-dependent effects on hormonal levels at critical times of development. Follow-up study indicates that those sex-dependent hormonal changes are not due to the impact on gonadal sex steroid production in males and females, but a sex-dependent impact on the liver’s metabolic capacity.
“This study initiates a new perspective on the reproductive toxicity of phthalates, placing the liver as the primary target,” Bunnell said. “It provides a unique approach to understanding sex-dependent effects of endocrine-disrupting chemicals, and it could pave the way for the development of clinical strategies to mitigate the effects of phthalate exposure.”
Bunnell is scheduled to present at the Society’s ENDO 2023 endocrine-disrupting chemicals news conference at 10 AM Central on Saturday, June 17. Register to view the news conference livestream at endomediastream.com.
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