Nature: Intestinal flora has a new role to play! It may protect against the harm of smoking

Feeding cesarean section babies a small amount of their mother's feces will make them healthier; transplanting other people's feces into the body can help alcoholics successfully quit their addiction; even the feces of healthy people can help cancer immunotherapy.

All these amazing effects of poop are inseparable from the intestinal flora that have coexisted with humans for hundreds of millions of years. In addition, the occurrence and treatment of hypertension, obesity, and diabetes are all closely related to the intestinal flora.

Now, a new study finds that gut bacteria can also break down nicotine that enters the bodies of mice, protecting them from smoking-related fatty liver disease.

The related research paper, titled "Gut bacteria alleviate smoking-related NASH by degrading gut nicotine", has been published in the authoritative scientific journal Nature.

The findings address the pathological implications of intestinal nicotine accumulation and identify an endogenous nicotine-degrading gut bacterium with potential value for the prevention and treatment of nonalcoholic steatohepatitis (NASH) in smokers .

Nicotine, nonalcoholic fatty liver disease, intestinal flora

As one of the most common unhealthy behaviors among humans, smoking has been listed by the World Health Organization (WHO) as the leading cause of preventable death in the world.

Smoking is linked to many diseases, including non-alcoholic fatty liver disease (NAFLD), which can lead to liver scarring and cancer. Nicotine in tobacco is a risk factor for many heart, liver and lung diseases and many cancers.

However, for most smokers, "nicotine addiction" makes it difficult for them to suppress the desire to smoke, and they often smoke again during the smoking cessation stage in order to avoid "withdrawal symptoms."

Popular Science Time: Withdrawal symptoms refer to a group of special psychological and physiological symptoms that occur after stopping the use of drugs or reducing the dosage or using antagonists to occupy receptors. After forced smoking cessation, smokers may experience symptoms such as restlessness, insomnia, increased blood pressure and arrhythmia, but most of these reactions will gradually disappear as the physical condition of the smokers recovers.

Previous studies have confirmed that smoking behavior is significantly associated with the evolution of NAFLD, and metabolites produced in the intestine play a key role in the evolution of NAFLD through the gut-liver axis.

Therefore, establishing the relationship between intestinal nicotine accumulation, gut-derived metabolites, and the evolution of NAFLD could provide new insights into tobacco-related liver disease.

(Source: Pixabay)

In this work, the research team tested fecal and serum samples from 30 smokers and 30 non-smokers and found that high levels of nicotine accumulated in the intestines after nicotine exposure.

Similar results were observed in a mouse model of nicotine exposure, where this accumulation was found to be associated with an increased risk of nonalcoholic fatty liver disease.

Comparing germ-free mice (without any microbes) and those with pre-specialized gut microbiota, nicotine levels were higher in the germ-free mice , suggesting that specific gut microbiota may regulate nicotine levels.

Furthermore, after screening the mouse microbiota, it was found that Bacteroides xylanisolvens could reduce intestinal nicotine concentrations in mice exposed to nicotine and reduce the severity of non-alcoholic fatty liver disease in these mice.

Using a liquid chromatography-mass spectrometry-based approach, the team detected high levels of intestinal nicotine in smokers and three mouse models of nicotine exposure. Thus, the distribution of nicotine in the intestine is independent of the delivery route.

Interestingly, Bacteroides xylanisolvens can also be found naturally in the human intestine. Moreover, Bacteroides xylanisolvens has been shown to be safe for in vivo use, and the European Union has authorized heat-treated dairy products fermented with Bacteroides xylanisolvens (DSM 23964) to be listed as food.

However, the research team also said that further research is needed on the ability of gut microbiota to break down nicotine in humans and prevent smoking-related diseases .

Stay away from non-alcoholic fatty liver disease

Fatty liver is a condition in which excessive fat accumulates in the liver. It accumulates in the liver cells in the form of giant vacuoles containing triglycerides, causing fatty degeneration.

It is generally believed that fatty liver is a single disease that occurs in people with alcoholism (i.e. alcoholic fatty liver) and obesity (i.e. non-alcoholic fatty liver) worldwide.

Nonalcoholic fatty liver disease refers to a group of liver conditions that affect people who rarely or never drink alcohol . It is divided into nonalcoholic fatty liver disease (NAFL) and nonalcoholic steatohepatitis (NASH).

(Source: Pixabay)

In fact, both nonalcoholic fatty liver disease and nonalcoholic steatohepatitis are associated with :

overweight and obesity;

Insulin resistance, which is when insulin becomes less effective at promoting glucose uptake into cells;

High blood sugar (hyperglycemia), which may indicate prediabetes or type 2 diabetes;

High levels of fat in the blood, especially triglycerides. These factors may promote the accumulation of fat in the liver. For some people, excess fat in the liver can become a toxin that acts on liver cells, causing liver inflammation and non-alcoholic steatohepatitis, and in severe cases, even cirrhosis and hepatocellular carcinoma.

Therefore, in order to reduce the risk of non-alcoholic fatty liver disease, in addition to quitting smoking and drinking, we also need to maintain a healthy diet and get enough exercise.

For example, choose a healthy plant-based diet rich in fruits, vegetables, whole grains and healthy fats; control your daily calorie intake and increase physical activity, etc.

Reference Links:

https://www.nature.com/articles/s41586-022-05299-4

https://www.mayoclinic.org/zh-hans/diseases-conditions/nonalcoholic-fatty-liver-disease/symptoms-causes/syc-20354567