Sanford Burnham Prebys scientists offer words of warning on risks of high fat to liver and heart health

Karen Ocorr uses fruit flies to look at genes that contribute to heart disease.
Karen Ocorr, an assistant professor at the Sanford Burnham Prebys Medical Discovery Institute in La Jolla, uses fruit flies to look at genes that contribute to heart disease.

It’s common knowledge that eating well and exercising are precursors to a healthy life — and seemingly the solution for many ailments. That’s why the No. 1 New Year’s resolution is to lose weight, eat better and/or exercise more.

Scientists at the Sanford Burnham Prebys Medical Discovery Institute in La Jolla have identified a few new specific health hazards that can come from a high-fat diet, including increased likelihood of liver cancer and heart toxicity.

Just in time for that New Year’s resolution, Karen Ocorr, Aaron Havas and Cynthia Lebeaupin delved into their specific fields of research and answered questions during a Jan. 14 webinar titled “How Your Diet Really Affects Your Body.” The event was part of SBP’s “Insights” lecture series.

Lebeaupin, a postdoctoral fellow in degenerative diseases at SBP’s Neuroscience and Aging Research Center, focuses her research on the progression from fatty liver disease to cancer.

Cynthia Lebeaupin
Cynthia Lebeaupin is a postdoctoral fellow in degenerative diseases at the Neuroscience and Aging Research Center at Sanford Burnham Prebys Medical Discovery Institute.

She said the most common cause of Americans being overweight or obese is related to behavior, such as an unhealthy diet or physical inactivity.

“Obesity can significantly affect all the major organ systems in our body,” she said. “It can increase health risks associated with the nervous system, the respiratory system, cardiovascular system, digestive and skeletal systems.”

However, it can hit the liver especially hard.

“Your liver is the metabolic gatekeeper,” Lebeaupin said. “It’s going to assure essential functions, either helping with digestion, detoxification, modulating your blood sugar levels and recycling excess building blocks like the macronutrients you eat to be distributed through the body.”

With obesity, the stress on the liver “is going to become chronic” and can lead to fatty liver disease, which can progress to cancer, she said.

In a similar field of study, Havas, a postdoctoral associate at Sanford Burnham Prebys, said liver cancer is considered one of the more deadly types, with a five-year survival rate of 18 percent.

“In the last 20 to 30 years, we’ve seen an increase in the instance of liver cancer being diagnosed. … That seems to be progressing continuously,” he said.

The biggest risk factors for liver disease that leads to cancer are obesity, age and a combination of the two, Havas said.

In a mouse study, he said, a high-fat diet (60 percent calories from fat) led to more gene expression of “immune modifying proteins” in older obese mice than young obese mice.

“These proteins prevent the immune system from becoming fully activated … and in some cases turn off the immune system and allow the cancer cells to populate and not be regulated by the immune system,” Havas said.

Aaron Havas is a postdoctoral associate at Sanford Burnham Prebys.

But this liver damage can be prevented and even reversed by — you guessed it — a healthy diet and exercise, Lebeaupin said.

Addressing several questions about the ketogenic, or “keto,” diet (a high-fat, low-carbohydrate diet that forces the body to burn fats rather than carbohydrates), she said it can be harmful to liver health due to its emphasis on high fat.

“It doesn’t discriminate against good and bad fat,” she said. “It’s not going to be a relatively good diet, because you are providing fat that the liver can store or distribute. Although there is hype around these diets, they haven’t been studied in the long term. So there are a lot of short-term effects when you eliminate food groups with the diet. ... If you don’t eat a wide variety of foods, you risk deficiency in vitamins and minerals.”

Unlike liver disease, heart disease cannot be reversed. And it can be caused by a surprisingly low amount of fat.

Ocorr, an assistant professor in the development, aging and regeneration program at SBP, uses fruit flies to look at genes that contribute to heart disease. Fly hearts have a similar structure to those of humans — a tube shape that closely resembles human prenatal hearts before their chambers develop.

A team of researchers at La Jolla’s Sanford Burnham Prebys Medical Discovery Institute co-authored a study published Nov. 25 that details changes observed in the hearts of fruit flies while in space over two missions — changes that may have implications for the treatment of human hearts both in and out of the atmosphere.

Ocorr said that in her study of fruit flies, when their diets were supplemented with about 30 percent fat (meaning 30 percent of daily calories came from fat), “after only five days, you can really see the effect on the heart. It’s a hugely lipotoxic effect.”

She noted that the U.S. Department of Agriculture’s dietary guidelines call for no more than 30 percent of one’s daily caloric intake to come from total fat and less than 10 percent from saturated fat.

Any high-fat diet, such as the keto diet, is “unsafe for the heart,” she said.

“The heart wasn’t designed to store fat,” Ocorr said. “So it has to bring in fat from the blood to fuel its very active beating patterns. If you have too much fat in your blood, the heart can pull it in, but it doesn’t have anywhere to be stored. It begins to cause problems with the cell membranes and in the arteries that feed the heart.”

Unlike the liver, the heart cannot regenerate, and damage from a high-fat diet cannot be reversed. “We haven’t gotten anywhere close yet,” she said.

The next lecture, “How to Fix a Broken Heart: Connecting Scientists and Clinicians to Advance Heart Health,” is scheduled for 1 p.m. Tuesday, Feb. 23, online. To register or view recordings of past lectures, visit