Research conducted at the University of Campinas (UNICAMP) in São Paulo State, Brazil, shows that vigorous physical exercise such as strength and weight training can reduce accumulated liver fat and improve blood sugar control in obese and diabetic individuals in a short time span, even before significant weight loss occurs.
In experiments with mice, researchers at UNICAMP’s Molecular Biology of Exercise Laboratory (LaBMEx) found that two weeks of such exercise was sufficient to modify gene expression in liver tissue in ways that “burned” more stored lipids and contributed to the treatment of nonalcoholic fatty liver disease. Cellular insulin signaling in tissue improved, and hepatic synthesis of glucose decreased.
The results of the study, which was supported by São Paulo Research Foundation—FAPESP, are published in the Journal of Endocrinology.
“Everyone knows physical exercise helps control disease. Our research focuses on how and why this is so, on the mechanisms involved. If we can discover a key protein whose levels rise or fall with training, we’ll have taken a step toward the development of drugs that mimic some of the benefits of physical exercise,” said Leandro Pereira de Moura, a professor at UNICAMP’s School of Applied Sciences and the principal investigator of the study.
Moura explained that excess fat in the liver causes local inflammation, which makes liver cells less sensitive to the action of insulin. This condition can progress to cirrhosis and eventually to liver failure.
“In obese individuals at cardiometabolic risk, reducing liver fat is vital to help control diabetes,” Moura told. “The liver should produce glucose only under fasting conditions, but if insulin signaling in tissue is impaired, the liver releases glucose into the blood stream even after ingestion of carbohydrate, when insulin levels are high, and this raises the level of blood sugar.”
A moderate training protocol reduced liver fat and made the organ more sensitive to insulin, even before loss of body weight occurred. Credit: Guilherme Peruca
Strength training for mice
To investigate the effect of strength training on the liver, an experiment involving three groups of mice was performed. The control group, which was fed a standard diet (4 percent fat), remained lean and sedentary. The second and third groups were fed a hyperlipidemic diet (35 percent fat) for 14 weeks, long enough for the animals to become obese and diabetic. The second group remained sedentary, while the third group was submitted to a moderate strength training exercise protocol for 15 days after becoming obese and diabetic.
The exercise protocol consisted of climbing a staircase with a weight attached to the tail. Each day, the mice climbed the stairs 20 times at 90-second intervals. According to Moura, the protocol was designed to mimic strength training in humans.
“Before we began the experiment, we co