Exercise may directly protect against liver cancer, study suggests

Exercising regularly could prevent the development of the most common form of liver cancer, new research suggests.

Liver cancer is the fourth most common cause of cancer death worldwide and its prevalence is growing rapidly due to the worsening “diabesity pandemic” across the world.

Obesity and diabetes are common among those suffering from fatty liver disease – which can be a precursor to hepatocellular carcinoma.

More than 800,000 people worldwide are diagnosed with this cancer each year. It is also a leading cause of cancer deaths, accounting globally for more than 700,000 deaths each year.

“As yet there are very few effective therapies for liver cancer – the death rate approximates the incidence – so approaches to prevent liver cancer are greatly needed,” said Dr Geoffrey Farrell of the Australian National University Medical School, who led the study.

“Some population data suggest that persons who exercise regularly are less likely to develop liver cancer but, studies addressing whether this has a real biological basis, and, if so, identifying the molecular mechanism that produces such a protective effect, are few and the findings have been inconclusive.”

So in order to investigate the impact of regular exercise on those most at risk of developing liver cancer, the research team investigated how rates of exercise affected outcomes in obese/diabetic mice.

The research used a population of mice genetically driven to eat so they would become obese and develop type 2 diabetes as young adults.

The mice were also injected early in life with a low dose of a cancer-causing agent.

Then, half of the mice were allowed regular access to a running wheel. The other half were not given the opportunity to exercise and remained sedentary.

The mice with wheels ran up to 40 kilometres a day, the researchers found.

This slowed down the weight gain for just the first three months, but by the end of six months of experiments even the exercising mice were obese.

At six months, the researchers tested the two populations and found while most of the sedentary mice had developed liver cancer, none of the exercising mice had developed it.

The researchers said the experiment reveals exercise can stop development of liver cancer in mice that have fatty liver disease related to obesity and type 2 diabetes.

The exercising mice were completely protected against liver cancer development in the timeframe of these experiments. Weight gain did not mitigate the development of liver cancer.

Investigators also carried out studies which partly clarified how doing exercise can prevent liver cancer.

They found voluntary excercise impacted molecular pathways, including shutting down stress-activated proteins, and by activating a tumour suppressor gene known as the “guardian of the cell”.

“Exercise has already been shown to improve some outcomes for patients with cirrhosis. If the present studies in an animal model that closely resembles humans with fatty liver disease can be replicated in patients, it is likely that exercise could delay onset of liver cancer and mitigate its severity, if not completely prevent it – thereby greatly improving patient outcomes,” said Dr Farrell.

“Also, knowing the molecular pathways involved points to ways that drugs or pharmaconutrients (use of nutritional therapy) could be employed to harness the powerful protective effect of exercise to lower risk of liver cancer in overweight people with diabetes.”

The research is published in the Journal of Hepatology.