Posted on Aug 11, 2017, 6 a.m.
Researchers have created an innovative stem cell testing system to gauge the health effects of everyday chemicals on human beings.
Scientists have found evidence that preservatives in food and other popular products disrupt human hormones and promote obesity. The findings originally stemmed from animal experiments. A recent study highlighted by Nature Communications confirms the findings in human beings.
The Widespread Use of Chemicals
Over 80,000 chemicals are registered for use in the United States in commonly used items like household cleaners, foods, lawn-care products and personal care products. Though few chemicals are believed to pose a major risk to human health, the National Toxicology Program's website states the organization is unsure of the effects of the chemicals on human health. Many of the chemicals aren't thoroughly tested due to barriers like cost, health risks of exposure and ethical matters.
Investigators from Cedars-Sinai created a unique protocol and platform to test the effects of chemicals on human beings. Tributyltin (TBT) is a compound commonly found in paint that seeps into water and accumulates in seafood. Butylhydroxytoluene (BHT) is an antioxidant regularly added to cereals and other foods. Its purpose is to safeguard nutrients and prevent fats from spoiling. Perfluoroctanoic acid (PFOA) is a polymer used in certain types of carpeting, cookware, and other commonly used products.
The investigators used tissues that produce hormones grown from actual human stem cells. Their aim was to demonstrate how regular exposure to such chemicals can interfere with signals transmitted from the digestive system to the brain to let individuals know when their stomach is full while eating. If this signaling system malfunctions, people tend to overeat and gain weight.
The investigators took blood samples from adults. They applied reprogramming genes to convert the cells to induced pluripotent stem cells. The team used these stem cells to grow human epithelium tissue that lines the gut. The brain's neuronal tissues were also used. They are located in the hypothalamus region of the brain that regulates metabolism and appetite. The investigators subjected the tissues to TBT, PFOA, and BHT separately and in combination. They observed what happened within the cells.
The investigators determined each chemical damages hormones that interact with the gut and the brain. When the three chemicals were tested together, the cumulative stress was quite powerful. BHT generated some of the most robust detrimental effects out of the three chemicals.
The investigators determined chemicals disturbed networks that prepare signaling hormones to keep their structure intact and be moved out of cells. This made them ineffective. The investigators also found the chemicals damaged mitochondria. These are cell structures that convert oxygen and food to energy to catalyze the body's metabolism. The chemical damage occurred in “young” cells at early stages of development so the findings show a defective hormone system might impact pregnant women and their offspring. Scientists have determined effects of endocrine disruptors can be transmitted to future generations in animals yet this has not been proved to be the case in humans.
Why the Study Matters
The study's new testing system might provide a safe, low-cost and much-needed method that can be used to assess the health ramifications of other chemicals. Other scientists have proven the compounds in question can disturb hormone systems in lab animals. Yet the study outlined above is the first to make use of human pluripotent stem tissues and cells to show how such compounds can disturb hormones that help signal between the brain and gut and prevent obesity. It is a landmark study as it dramatically boosts the understanding of how endocrine disruptors might damage the human body's hormonal systems. The finding also helps explain the rise of the obesity epidemic in the United States.
"This is a landmark study that substantially improves our understanding of how endocrine disruptors may damage human hormonal systems and contribute to the obesity epidemic in the U.S.," said Clive Svendsen, PhD, director of the institute and the Kerry and Simone Vickar Family Foundation Distinguished Chair in Regenerative Medicine. More than one-third of U.S. adults are considered to be obese, according to federal statistics.
Sareen was the principal investigator for the study, and research scientist Uthra Rajamani, PhD, was the first author.
Research reported in this publication was supported by the National Center for Advancing Translational Science of the National Institutes of Health under award number UL1TR000124.