Increase in Aerobic Exercise May Slow Progression of Non-Alcoholic Fatty Liver Disease
Non-alcoholic fatty liver disease (NAFLD) affects as many as one in five Americans, according to the American Liver Association. For those with diabetes, the rate may be as high as four in five. Increasing exercise to one hour a day may slow the progression of fatty liver disease in obese people with prediabetes (formerly called borderline diabetes) by jumpstarting metabolism and slowing oxidative damage.
Exercise Improved Insulin Sensitivity and Markers of Liver Health
Excess fat in the liver can progress to a more serious form of liver disease known as non-alcoholic steatohepatitis or NASH. This occurs in about 20 to 30% of people with NAFLD and causes the liver to be inflamed and scarred. Advanced scarring, or cirrhosis, increases the risk for liver cancer and liver failure.
The link between diabetes and liver problems has long been overlooked, says physician-researcher Kenneth Cusi MD. His previous research conducted at the San Antonio VA Medical Center and the University of Texas Health Science Center found that mice fed a “junk food diet” – high fat and high sugar foods - for 16 weeks had sooner-than-expected symptoms of both diabetes and fatty liver disease.
Researchers at the Cleveland Clinic, led by Jacob M. Haus PhD, a research fellow in the Department of Pathobiology, studied 15 obese people with NAFLD. Each walked on a treadmill at 85% of their maximum heart rate for one hour per day for 7 consecutive days. Body composition, respiration, plasma glucose, and the liver’s polyunsaturated liver index (PUI) were measured. PUI is thought to be a marker of liver health.
The researchers also measured a hormone known as adiponectin, which is linked to fat-burning and improved insulin sensitivity. High blood levels are linked to a reduced risk of heart attack, and obese people often have lower levels of the protein hormone. Adiponectin also has anti-inflammatory effects on the cells lining the walls of the blood vessels.
At the end of the study, the participants’ PUI had increased an average of 84%. They also experienced increased insulin sensitivity, increased adiponectin levels, and a decrease in the production of reactive oxygen species (ROS) which can result in oxidative damage to tissues.
"We were able to correlate changes in adiponectin with PUI and the body’s resting energy metabolism," says Dr. Haus. "The latter gives us an indication of whether carbohydrate or fat is being metabolized. After exercise, the participants were burning more fat." Burning fat is a positive reaction to exercise, one that can defend against oxidative damage and therefore the damage of fatty liver disease.
"Exercise appears to affect the cumulative metabolic risk factors for the progression of nonalcoholic fatty liver disease," says Dr. Haus. "We like to think of exercise as medicine."
Dr. Haus presented his findings at the Experimental Biology 2011 meeting (EB 2011), held in April in Washington, DC.