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Review
. 2021 May 31;11(6):353.
doi: 10.3390/metabo11060353.

Gut Microbiome and Metabolites in Patients with NAFLD and after Bariatric Surgery: A Comprehensive Review

Jacqueline Hoozemans  1   2 , Maurits de Brauw  2 , Max Nieuwdorp  1 , Victor Gerdes  1   3
Affiliations
Review

Gut Microbiome and Metabolites in Patients with NAFLD and after Bariatric Surgery: A Comprehensive Review

Jacqueline Hoozemans et al. Metabolites. .

Abstract

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing, as are other manifestations of metabolic syndrome such as obesity and type 2 diabetes. NAFLD is currently the number one cause of chronic liver disease worldwide. The pathophysiology of NAFLD and disease progression is poorly understood. A potential contributing role for gut microbiome and metabolites in NAFLD is proposed. Currently, bariatric surgery is an effective therapy to prevent the progression of NAFLD and other manifestations of metabolic syndrome such as obesity and type 2 diabetes. This review provides an overview of gut microbiome composition and related metabolites in individuals with NAFLD and after bariatric surgery. Causality remains to be proven. Furthermore, the clinical effects of bariatric surgery on NAFLD are illustrated. Whether the gut microbiome and metabolites contribute to the metabolic improvement and improvement of NAFLD seen after bariatric surgery has not yet been proven. Future microbiome and metabolome research is necessary for elucidating the pathophysiology and underlying metabolic pathways and phenotypes and providing better methods for diagnostics, prognostics and surveillance to optimize clinical care.

Keywords: NAFLD; bariatric surgery; gut microbiome; metabolites.

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Conflict of interest statement

M.N. is on the Scientific Advisory Board of Caelus Health, the Netherlands, and Kaleido Biosciences, USA. None of these possible conflicts of interest bear direct relation to the content of this review. All other authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Overview of the gut microbiome and metabolites, and relationship with NAFLD and bariatric surgery. (A) A systematic overview of how gut microbiota contribute to producing metabolites such as LPS, bile acids, SCFAs and trimethylamine. The metabolites enter the portal circulation, where they are further metabolized and enter the systemic circulation. (B) The spectrum of non-alcoholic fatty liver disease. The black arrow indicates that the different stages of NAFLD are associated with a different composition of gut microbiome and plasma metabolites. The smaller grey arrow indicates the possible relationship of gut microbiome composition and plasma metabolites on non-alcoholic fatty liver disease; however, this causal role remains to be verified. (C) Three types of bariatric interventions are displayed: sleeve gastrectomy, Roux-en-Y gastric bypass, and vertical gastric banding. Bariatric surgery is associated with changes in gut microbiome composition and altered metabolite levels. Bariatric surgery is also associated with improvements of fatty liver disease. (D) Different gut microbiota compositions and relative changes in metabolites are observed in individuals with NAFLD and after bariatric surgery compared to (lean and/or pre-operative) controls. Evidence points toward a causal role for microbiome and metabolites in the pathophysiology of fatty liver disease and improvement after bariatric surgery; however, this remains to be verified. LPS, lipopolysaccharides; SCFAs, short-chain fatty acids; ATP, adenosine triphosphate; NAFLD, non-alcoholic fatty liver disease; NASH, non-alcoholic steatohepatitis.
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