Link between gut microbiota and diets investigated for non-alcoholic fatty liver disease

20 Mar 2023 --- Two recent studies, Spain-based and US-based, investigated the role of diets and eating patterns and the link between the gut microbiota, respectively, on developing or reducing non-alcoholic fatty liver disease (NAFLD). Besides being the leading cause of chronic liver disease, NAFLD is associated with harmful conditions such as metabolic syndrome, obesity, diabetes and dyslipidemia.

“Fatty liver disease is a global health epidemic,” says Kevin Staveley-O’Carroll, a professor in the department of surgery, one of the lead researchers of the study from Missouri.

“Not only is it becoming the leading cause of liver cancer and cirrhosis, but many patients I see with other cancers have fatty liver disease and don’t even know it. Often, this makes it impossible for them to undergo potentially curative surgery for their other cancers,” Staveley-O’Carroll continues.

Different dietary approaches
Published in Nutrients, the Spanish-based researchers from the University of Cordoba investigated the link between diets and developing NAFLD through a literature review of previously conducted studies.

While arguing that genetics and diet play a role in developing NAFLD, the study explains NAFLD’s relationship with cardiovascular disease. Due to the connection to obesity, NAFLD is forecasted to increase in the coming years, making it a public health concern. The World Obesity Federation recently predicted that by 2035, 51% of the world’s population will be overweight or obese if current patterns continue.

The study notes that to this day, no medical drug has shown indication as a potential treatment, although many drugs have been tested. Therefore, they push for lifestyle modifications by following a healthy diet and exercising regularly, as weight loss has shown potential improvements.

The US-based researchers say that unhealthy diets change the gut microbiota, producing pathogenic factors impacting the liver.It further concludes that socioeconomic status plays a role in how people eat, as high-income groups tend to eat healthier. Additionally, nutritional knowledge and education showed a higher awareness, leading to improved eating patterns. 

They also found that intermittent fasting positively affected participants with Type 2 diabetes, as NAFLD reduced. 

Gut-brain axis connection
The study from researchers at the University of Missouri-Columbia published in Nature, found a link between western diets and developing NAFLD, as the diet is high in fat and sugar due to a linkage between the gut-brain axis.

“We’re just beginning to understand how food and gut microbiota interact to produce metabolites that contribute to the development of liver disease,” says co-principal investigator Guangfu Li, associate professor in the department of surgery and department of molecular microbiology and immunology at the University of Missouri School of Medicine. 

“However, the specific bacteria, metabolites and underlying mechanisms were not well understood until now. This research is unlocking the how and why,” Li continues.

Further explaining that the liver and gut have a “close anatomical and functional connection via the portal vein,” the researchers say that unhealthy diets change the gut microbiota, producing pathogenic factors impacting the liver.

While conducting a study on mice, they found that when fed foods high in fat and sugar, the mice developed Blautia producta, a gut bacteria and a lipid causing inflammation and fibrosis in the liver.

The mice developed NAFLD with a resemblance to the human disease. When treated with antibiotics through drinking water, they found antibiotic-induced changes in the gut microbiota that might remove inflammatory responses.

Edited by Beatrice Wihlander