Introduction
Metabolic dysfunction-associated fatty liver disease (MAFLD), typically associated with obesity, is the leading cause of reversible insulin resistance, hepatic steatosis, and inflammation, which can be further progressed into unreversible fibrosis and finally liver failure when left without intervention. The necessity of timely intervention, especially changes in lifestyle, is well-recognized but is hampered by the lack of understanding of the molecular mechanisms involved.
A potential mediator of the beneficial effects of lifestyle change (less fat and carbohydrate intake, more physical exercise) is the gut microbiome1. Lower amounts of intestinal bacteria producing short-chain fatty acids, especially members of the Lachnospiraceae and Ruminococcaceae family, have been closely associated with MAFLD and fibrosis progression1-3, supporting the causality of the above associations.
Among the lifestyle changes suggested to counteract MAFLD, is intermittent fasting (IF)4,5. IF is a popular dietary regimen and is typically defined by repeated temporal abstinence of food intake for 12 to 24 hours6. The microbiome partly mediates the potential effects of IF on liver physiology, as shown in previous studies in which we showed that one month of 16 hours daily fasting (OMIF) increases the Lachnospiraceae and Ruminococcaceae families in non-obese human volunteers7 as well as in healthy mice8. Importantly, we observed that OMIF provokes weight loss and reduces GGT levels even in healthy volunteers7. We, therefore, hypothesized that OMIF has beneficial effects and can potentially reverse MAFLD through modulation of the microbiome composition.
Aims & Methods
The aim of the current study was to investigate the effects of OMIF on MAFLD phenotypes and especially how changes in the microbiome influence the results. Experimental OMIF in high-fat diet-induced iC57BL/6J mice was investigated, focusing on the change of insulin resistance, liver function biomarkers (AST [aspartate aminotransferase], ALT [alanine transaminase], GGT [gamma-glutamyl tansferase] and triglycerides) and histopathology, which were correlated to the gut microbiome determined by 16S rRNA-sequencing. The protective potential of OMIF against MALFD was prospectively studied in obese volunteers. Fecal microbiota transplantation was applied to pseudo-germ-free mice. Microbial metabolite effects were tested in human MAFLD liver-derived organoids.
Results
Experimental OMIF decreased insulin resistance (p<0.001), AST, ALT, and triglycerides levels (all p<0.05), and especially improved liver pathology by 63.0% (p<0.001), as indicated by steatosis and inflammation. The results correlated with Lachnospiraceae and butyrate-producing genera, both increased by 46.9% (p=0.003) and 63.0 % (p=0.001), respectively. In obese human volunteers, OMIF caused weight loss by 3.5% (p=0.003) and improved all liver function biomarkers (p<0.001). This again correlated with Lachnospiraceae and butyrate-producing genera, both increased by 53.6% (p=0.0005) and 28.4% (p=0.001), respectively. Transplantation of stool from either OMIF-treated mice or humans led to improved insulin sensitivity, liver function, and liver pathology (all p<0.05) in recipient mice. When exposed to butyrate, the MAFLD-mimicking liver organoids showed less microvesicular fatty accumulation (p<0.001).
Conclusion
Manipulation of the gut microbiome by OMIF can contract MAFLD. The Lachnospiraceae and butyrate-producing genera-enriched communities should be considered as new therapeutic targets in MAFLD.
References
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5. Albillos A, de Gottardi A, Rescigno M. The gut-liver axis in liver disease: Pathophysiological basis for therapy. J Hepatol 2020;72:558-577.
6. de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med 2019;381:2541-2551.
7. Su J, Wang Y, Zhang X, et al. Remodeling of the gut microbiome during Ramadan-associated intermittent fasting. Am J Clin Nutr 2021;113:1332-1342.
8. Su J, Li F, Wang Y, et al. Investigating Ramadan Like Fasting Effects on the Gut Microbiome in BALB/c Mice. Front Nutr 2022;9:832757.
