The role of the gut microbiome and exercise in non-alcoholic fatty liver disease

Abstract

In recent years, the human gut microbiome has been found to influence a multitude of non-communicable diseases such as cardiovascular disease and metabolic syndrome, with its components type 2 diabetes mellitus and obesity. It is recognized to be mainly influenced by environmental factors, such as lifestyle, but also genetics may play a role. The interaction of gut microbiota and obesity has been widely studied, but in regard to non-alcoholic fatty liver disease (NAFLD) as a manifestation of obesity and insulin resistance, the causal role of the gut microbiome has not been fully established. The mechanisms by which the gut microbiome influences lipid accumulation, inflammatory responses, and occurrence of fibrosis in the liver are a topic of active research. In addition, the influence of exercise on gut microbiome composition is also being investigated. In clinical trials, exercise reduced hepatic steatosis independently of weight reduction. Other studies indicate that exercise may modulate the gut microbiome. This puts forward the question whether exercise could mediate its beneficial effects on NAFLD via changes in gut microbiome. Yet, the specific mechanisms underlying this potential connection are largely unknown. Thus, associative evidence from clinical trials, as well as mechanistic studies in vivo are called for to elucidate the relationship between exercise and the gut microbiome in NAFLD. Here, we review the current literature on exercise and the gut microbiome in NAFLD.

Insights into the Impact of Microbiota in the Treatment of NAFLD/NASH and Its Potential as a Biomarker for Prognosis and Diagnosis

“…The microbiome and metabolites of the gut can directly reach the liver, being modulated by the gut barrier permeability, which is profoundly affected in these patients, as we discussed in our previous study [ 28 ]. The effects of physical exercise on endotoxemia and metabolites related to the gut are also potential mechanisms related to improvements in NAFLD/NASH [ 112 , 113 ]. For example, physical exercise increased the abundance of SCFAs, butyrate, and other SCFAs [ 109 ].…”

“…For example, physical exercise increased the abundance of SCFAs, butyrate, and other SCFAs [ 109 ]. Furthermore, exercise exerts an effect on other gut-derived metabolites related to hepatic metabolism such as bile acid, choline, and ethanol [ 113 ]. On the other hand, exercise restores these genetic capacities to the level of control mice, possibly contributing to improved metabolic alterations, including NAFLD [ 114 ].…”

“…However, the direct influence of physical exercise on changes in the microbiome has not been studied extensively in NAFLD/NASH patients. A recent study extensively discussed the effect of physical exercise on the microbiome in NAFLD/NASH [ 113 ]. Nonetheless it has not been defined what type of training generates a greater effect, possibly due to the fact that moderately intense physical activity may quickly lead to a reduction in intrahepatic lipid contents [ 115 ].…”

“…Thus, the principal recommendation is achieving the recent physical activity recommendation, which consists of 150–300 min of moderate–intensive physical activity per week, with the inclusion of both aerobic and muscle-strengthening activities. In addition, individuals should start with small amounts of physical activity, and some physical activity is better than none, especially for those not currently meeting these recommendations; further, reducing sedentary behaviors are recommend [ 113 , 117 , 118 ].…”

Effects of Cornus mas extract combined with aerobic and resistance exercise on blood metabolic parameters and liver enzymes of obese rats

“…Furthermore, visceral fat represents a source of free fatty acids that can be preferentially oxidized to glucose. Reducing visceral fat by decreasing abdominal obesity may be another important benefit of exercise leading to significant improvement in metabolic indicators (Albright et al, 2000;Houttu et al, 2020). Due to all these aforementioned factors, we can state that physical exercise has a positive impact on the treatment of fatty liver and metabolic diseases.…”