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A new study in mice suggests that consumption of chemical compounds found in maltreated cooking oil could cause genetic changes that promote the progression of advanced breast cancer.
Researchers at the University of Illinois have discovered that frying oil subjected to thermal abuse – cooking oil that has been repeatedly reheated at high temperatures – can constitute a toxicological trigger that promotes the proliferation of tumor cells, metastases and changes in lipid metabolism. They reported their findings in the journal Cancer Prevention Research.
After following a low-fat diet for one week, one group of mice was fed with unheated fresh soybean oil, while another group consumed heat-treated oil for 16 weeks. Soybean oil was used in the study because of its common use by the restaurant industry in frying.
Scientists at I.I University simulated advanced-stage breast cancer by injecting 4T1 breast cancer cells into the tibia of each mouse. According to the study, 4T1 cells are an aggressive form of the disease that can spontaneously metastasize in several distant sites of the body, including the lungs, liver and lymph nodes.
Twenty days after inoculation with the tumor cells, the primary shin tumors of the mice that consumed the thermally stressed oil exhibited metastatic growth four times that of the mice consumed. fresh soybean oil. And when the researchers examined the animals' lungs, they found more metastasis in those who consumed thermally abused oil.
"There were twice as many tumors in the lungs, and they were more aggressive and invasive," said William G. Helferich, professor of food science and human nutrition, who led the research.
Nicki J. Engeseth, Professor of Food Chemistry, Acting Director of the Department, co-authored the document. Ashley W. Oyirifi, a graduate student, and Anthony Cam, a graduate of University I, were the main authors.
"I just thought these nodules in the lungs were small clones, but they were not. They have transformed themselves to become more aggressive. The metastases in the group of fresh oils were present, but they were not as invasive or aggressive, and the proliferation was not so extensive, "said Helferich.
The researchers, from left to right, Nicki J. Engeseth, professor of food chemistry, William G. Helferich, professor of food science, and Ashley Oyirifi, postgraduate student. Photo by L. Brian Stauffer
By examining both groups of mice, scientists found that metastatic lung tumors from those who consumed heat-treated frying oil expressed much more of a key protein, the Ki-67 , which is strictly associated with cell proliferation.
The expression of genes in the liver of these animals has also been modified. When the researchers performed an RNA sequencing analysis, they found 455 genes in which expression was at least twice as large – or, conversely, twice as low – as in mice consuming fresh oil.
Modified genetic pathways were associated with oxidative stress and foreign substance metabolism, Oyirifi said.
When the oil is reused repeatedly, the triglycerides are dissociated, oxidizing the free fatty acids and releasing acrolein, a toxic chemical with carcinogenic properties.
Scientists have long known that thermally abused oil contains acrolein and studies have linked its lipid peroxides with various health problems, including atherosclerosis and heart disease.
As the oil deteriorates, the polymer molecules also accumulate, raising nutritional and toxicological concerns, Engeseth said.
Countries in Europe and other countries regulate the amount of polar materials contained in cooking oil, which are triglycerides and chemically modified fatty acids used as chemical markers for the decomposition of oils. In general, these standards allow restaurants to use oil containing between 24 and 27% polar matter.
In contrast, the thermally overexploited oil used in this study contained about 15% polar material, while the fresh oil contained 2 to 4% or less, Helferich said.
"Since there is no regulation in the United States, it is very difficult for us to evaluate what exists," Engeseth said. "But the important thing is that the fried foods in these oils suck up a lot of oil. Even though we do not consume oil directly, we also consume oil that has been introduced into foods during frying. "
Recurrence is the biggest fear of breast cancer survivors and the majority of them have dormant tumor cells circulating in the bloodstream, Helferich said.
"What everybody is waking up, we think, but I am convinced that their diet activates them and creates an environment in different tissues that is more fertile for their growth," he said.
"Many cancer biologists are trying to understand what is happening on metastatic sites to prepare them for tumor growth," Oyirifi said. "We try to add to this conversation and help people understand that it may not just be an inherent biological mechanism, but also a lifestyle factor. While diet offers the potential to reduce the risk of breast cancer survivors, it offers them better control over their own health. "
This article has been republished from documents provided by the University of Illinois. Note: Content may have changed for length and content. For more information, please contact the cited source.
Reference:
Cam et al. (2019). Thermally abused frying oil potentiates lung metastasis in a mouse model of advanced breast cancer. Cancer Prevention Research doi: 10.1158 / 1940-6207.CAPR-18-0220
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