Bariatric surgery and nonalcoholic fatty liver disease

Abstract

The rising prevalence of nonalcoholic fatty liver disease (NAFLD) is associated with the increasing global pandemic of obesity. These conditions cluster with type II diabetes mellitus and the metabolic syndrome to result in obesity-associated liver disease. The benefits of bariatric procedures on diabetes and the metabolic syndrome have been recognized for some time, and there is now mounting evidence to suggest that bariatric procedures improve liver histology and contribute to the beneficial resolution of NAFLD in obese patients. These beneficial effects derive from a number of weight-dependent and weight-independent mechanisms including surgical BRAVE actions (bile flow changes, restriction of stomach size, anatomical gastrointestinal rearrangement, vagal manipulation, enteric hormonal modulation) and subsequent effects such as reduced lipid intake, adipocytokine secretion, modulation of gut flora, improvements in insulin resistance and reduced inflammation. Here, we review the clinical investigations on bariatric procedures for NAFLD, in addition to the mounting mechanistic data supporting these findings. Elucidating the mechanisms by which bariatric procedures may resolve NAFLD can help enhance surgical approaches for metabolic hepatic dysfunction and also contribute toward developing the next generation of therapies aimed at reducing the burden of obesity-associated liver disease.

Bile acids and nonalcoholic fatty liver disease

“…In fact, emerging evidence from mouse and human studies suggests that modulation of FXR (either in the liver or the intestine) and/or TGR5 may be useful in NAFLD treatment by enhancing insulin secretion and sensitivity, inhibiting lipogenesis, and stimulating oxidation of FAs. Moreover, studies showing that circulating BA levels increase along with the metabolic benefits after bariatric surgery, and that BAs might be involved in NAFLD/NASH reversion in this setting support the concept that variations in serum BA levels and/or composition have relevant metabolic effects. Of note, changes in circulating BAs with potential benefit for NAFLD/NASH can be achieved through modulation of BA transporters or manipulation of GM .…”

Correlation Between Nonalcoholic Fatty Liver Disease Features and Levels of Adipokines and Inflammatory Cytokines Among Morbidly Obese Individuals

“…The relationship between adiponectin and hepatoprotection has been previously observed in the literature (18)(19)(20)(21) . Since bariatric surgery leads to increases in the levels of adiponectin (22)(23)(24)(25) , it is reasonable to suppose that this mechanism is involved to some degree in the significant improvement of NAFLD reported after surgery (26)(27)(28)(29) .…”

Nonalcoholic fatty liver disease and bariatric surgery: a comprehensive review

“…Another meta-analysis, conducted by Bower et al, 156 revealed that bariatric surgery was associated with a significant reduction in the weighted incidence of a number of histological features of NAFLD, including steatosis (50.2%), fibrosis (11.9%), hepatocyte ballooning (67.7%) and lobular inflammation (50.7%); surgery was also associated with a reduction in liver enzyme levels. These authors emphasized that there was high heterogeneity among the methodologies and results, a factor that may have limited their analysis of these findings.…”