GM soybean oil causes less obesity and insulin resistance but is harmful to liver function

October 02, 2017

RIVERSIDE, Calif. - Researchers at the University of California, Riverside have tested a genetically-modified (GM) soybean oil used in restaurants and found that while it induces less obesity and insulin resistance than conventional soybean oil, its effects on diabetes and fatty liver are similar to those of conventional soybean oil.

Soybean oil is the major vegetable cooking oil used in the United States, and its popularity is on the increase worldwide. Rich in unsaturated fats, especially linoleic acid, soybean oil induces obesity, diabetes, insulin resistance, and fatty liver in mice.

UC Riverside researchers tested Plenish®, a genetically-modified (GM) soybean oil released by DuPont in 2014. Plenish is engineered to have low linoleic acid, resulting in an oil similar in composition to olive oil, the basis of the Mediterranean diet and considered to be healthful.

The study, published today in Nature Scientific Reports, is the first to compare the long-term metabolic effects of conventional soybean oil to those of Plenish.

The study also compares both conventional soybean oil and Plenish to coconut oil, which is rich in saturated fatty acids and causes the least amount of weight gain among all the high-fat diets tested.

"We found all three oils raised the cholesterol levels in the liver and blood, dispelling the popular myth that soybean oil reduces cholesterol levels," said Frances Sladek, a professor of cell biology, who led the research project.

Next, the researchers compared Plenish to olive oil. Both oils have high oleic acid, a fatty acid believed to reduce blood pressure and help with weight loss.

"In our mouse experiments, olive oil produced essentially identical effects as Plenish - more obesity than coconut oil, although less than conventional soybean oil - and very fatty livers, which was surprising as olive oil is typically considered to be the healthiest of all the vegetable oils," said Poonamjot Deol, an assistant project scientist working in Sladek's lab and the co-first author of the research paper. "Plenish, which has a fatty acid composition similar to olive oil, induced hepatomegaly, or enlarged livers, and liver dysfunction, just like olive oil."

Sladek explained that some of the negative metabolic effects of animal fat that researchers often see in rodents could actually be due to high levels of linoleic acid, given that most U.S. farm animals are fed soybean meal.

"This could be why our experiments are showing that a high-fat diet enriched in conventional soybean oil has nearly identical effects to a diet based on lard," she said.

The researchers further speculate that the increased consumption of soybean oil in the U.S. since the 1970s could be a contributing factor to the obesity epidemic. According to the Centers for Disease Control and Prevention, 35 percent of adults are obese. In some ethnic groups, however, such as Hispanics and African-Americans, between 42 percent and 48 percent of the population is obese. Obesity, officially designated by the American Medical Association in 2013 as a disease, is linked to diabetes, heart disease, and cancer.

"Our findings do not necessarily relate to other soybean products like soy sauce, tofu, or soy milk - products that are largely from the water-soluble compartment of the soybean; oil, on the other hand, is from the fat-soluble compartment," Sladek said. "More research into the amounts of linoleic acid in these products and others is needed."

Linoleic acid is an essential fatty acid. All humans and animals must obtain it from their diet.

"But just because it is essential does not necessarily mean it is good to have more of it in your diet," Deol said. "Our bodies need just 1-to-2 percent linoleic acid from our diet, but Americans, on average, have 8-to-10 percent linoleic acid in their diets."

Deol and Sladek recommend avoiding conventional soybean oil as much as possible.

"This might be difficult as conventional soybean oil is used in most restaurant cooking and found in most processed foods," Deol said. "One advantage of Plenish is that it generates fewer transfats than conventional soybean oil."

"But with its effects on the liver, Plenish would still not be my first choice of an oil," Sladek said. "Indeed, I used to use exclusively olive oil in my home, but now I substitute some of it for coconut oil. Of all the oils we have tested thus far, coconut oil produces the fewest negative metabolic effects, even though it consists nearly entirely of saturated fats. Coconut oil does increase cholesterol levels, but no more than conventional soybean oil or Plenish."

The researchers have not examined the cardiovascular effects of coconut oil.

"As a result, we do not know if the elevated cholesterol coconut oil induces is detrimental," Sladek said. "The take-home message is that it is best not to depend on just one oil source. Different dietary oils have far reaching and complex effects on metabolism that require additional investigation."

The study builds on an earlier study by the researchers that compared soybean oil to a high fructose diet and found soybean oil causes more obesity and diabetes than coconut oil.

Next, the researchers, who found a positive correlation between oxylipins (oxidized fatty acids) in linoleic acid and obesity, plan to determine whether the oxylipins cause obesity, and, if so, by what mechanism. They will also study the effects of conventional and GM soybean oil on intestinal health.
-end-
Sladek and Deol were joined in the study by UCR's Jane R. Evan and Antonia Rizo; along with Johannes Fahrmann (co-first author), Jun Yang, Michelle Salemi, Kwanjeera Wanichthanarak, Oliver Fiehn, Brett Phinney, and Bruce D. Hammock at UC Davis; and Dmitri Grapov at Creative Data Solutions, Mo.

Sladek and Deol were supported by grants from the National Institutes of Health, the National Institute of Environmental Health Sciences, the Crohn's and Colitis Foundation of America Career Development Award, the U.S. Department of Agriculture, the United Soybean Board Soy Health Research Program, the West Coast Metabolomics Center at UC Davis, and UCR.

DuPont provided Plenish oil for the study. The company played no role in designing the experiments or preparing the manuscript, and had no knowledge of the results prior to publication.

The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment is now nearly 23,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion.

University of California - Riverside

Related Diabetes Articles from Brightsurf:

New diabetes medication reduced heart event risk in those with diabetes and kidney disease
Sotagliflozin - a type of medication known as an SGLT2 inhibitor primarily prescribed for Type 2 diabetes - reduces the risk of adverse cardiovascular events for patients with diabetes and kidney disease.

Diabetes drug boosts survival in patients with type 2 diabetes and COVID-19 pneumonia
Sitagliptin, a drug to lower blood sugar in type 2 diabetes, also improves survival in diabetic patients hospitalized with COVID-19, suggests a multicenter observational study in Italy.

Making sense of diabetes
Throughout her 38-year nursing career, Laurel Despins has progressed from a bedside nurse to a clinical nurse specialist and has worked in medical, surgical and cardiac intensive care units.

Helping teens with type 1 diabetes improve diabetes control with MyDiaText
Adolescence is a difficult period of development, made more complex for those with Type 1 diabetes mellitus (T1DM).

Diabetes-in-a-dish model uncovers new insights into the cause of type 2 diabetes
Researchers have developed a novel 'disease-in-a-dish' model to study the basic molecular factors that lead to the development of type 2 diabetes, uncovering the potential existence of major signaling defects both inside and outside of the classical insulin signaling cascade, and providing new perspectives on the mechanisms behind insulin resistance in type 2 diabetes and possibly opportunities for the development of novel therapeutics for the disease.

Tele-diabetes to manage new-onset diabetes during COVID-19 pandemic
Two new case studies highlight the use of tele-diabetes to manage new-onset type 1 diabetes in an adult and an infant during the COVID-19 pandemic.

Genetic profile may predict type 2 diabetes risk among women with gestational diabetes
Women who go on to develop type 2 diabetes after having gestational, or pregnancy-related, diabetes are more likely to have particular genetic profiles, suggests an analysis by researchers at the National Institutes of Health and other institutions.

Maternal gestational diabetes linked to diabetes in children
Children and youth of mothers who had gestational diabetes during pregnancy are at increased risk of diabetes themselves, according to new research published in CMAJ (Canadian Medical Association Journal).

Two diabetes medications don't slow progression of type 2 diabetes in youth
In youth with impaired glucose tolerance or recent-onset type 2 diabetes, neither initial treatment with long-acting insulin followed by the drug metformin, nor metformin alone preserved the body's ability to make insulin, according to results published online June 25 in Diabetes Care.

People with diabetes visit the dentist less frequently despite link between diabetes, oral health
Adults with diabetes are less likely to visit the dentist than people with prediabetes or without diabetes, finds a new study led by researchers at NYU Rory Meyers College of Nursing and East Carolina University's Brody School of Medicine.

Read More: Diabetes News and Diabetes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.