The role of bariatric surgery in nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Bariatric Surgery and Metabolic Dysfunction-Associated Fatty Liver Disease: a 2022 Update

Non-alcoholic fatty liver disease (NAFLD) has been recently termed metabolic dysfunction-associated fatty liver disease (MAFLD) to address the strong association with the metabolic syndrome. The prevalence of MAFLD is significantly increased in obese individuals and treatment of obesity is currently the cornerstone of management of MAFLD. Bariatric and metabolic surgery nowadays emerges as a key therapeutic strategy for the treatment of the MAFLD. This review aims to provide an update on the novel studies reporting the outcomes of bariatric surgery on the spectrum of MAFLD, from hepatic steatosis to cirrhosis.

Accuracy of ultrasound diagnosis of nonalcoholic fatty liver disease in patients with classes II and III obesity: A pathological image study

Liver biopsy is the gold standard method to diagnose nonalcoholic fatty liver disease (NAFLD). However, ultrasound is widely recommended as the first-line imaging test for individuals with suspected NAFLD. This study aimed to estimate the accuracy of ultrasound as a screening test for NAFLD compared to liver biopsy in a cohort of patients with class II and III obesity undergoing bariatric surgery. This retrospective study included patients undergoing Roux-en-Y gastric bypass in southern Brazil between 2010 and 2019 who were screened for NAFLD with both ultrasound and liver biopsy. All samples were collected by a core biopsy needle and were analyzed by the same pathologist. Sensitivity, specificity, and positive and negative predictive values of ultrasound were estimated. The final database included 227 patients, mostly female (84%) and white (83.6%), with a mean age of 42.5 ± 10.2 years and a mean preoperative body mass index of 49.5 ± 8.4 kg/m². A total of 153 subjects (67.4%) were diagnosed with NAFLD through liver biopsies: 41 (18%) had fatty liver and 112 (49.3%) had nonalcoholic steatohepatitis. Ultrasound sensitivity was 88.9% and specificity was 44.6%. Positive and negative predictive values were 76.8% and 66.0%, respectively. Positive likelihood ratio was 1.6 (95% CI 1.30-1.98), and negative likelihood ratio was 0.25 (95% CI 0.15-0.42). Therefore, approximately three every four subjects with an ultrasound suggesting NAFLD were true positives. Ultrasound showed a good sensitivity in detecting NAFLD in patients with class II and III obesity.

Serum lipocalin-2 is a potential biomarker for the clinical diagnosis of nonalcoholic steatohepatitis

Background/Aims

Nonalcoholic steatohepatitis (NASH) is a progressive form of nonalcoholic fatty liver disease (NAFLD) characterized by hepatic steatosis, inflammation, hepatocellular injury, and fibrosis. We aimed to investigate the usefulness of a key biomarker, lipocalin-2 (LCN2), for the detection of NASH progression.

Methods

A mouse NASH model was established using a high-fat diet and a high-sugar drinking water. Gene expression profile of the NASH model was analyzed using RNA sequencing. Moreover, 360 NAFLD patients (steatosis, 83; NASH, 277), 40 healthy individuals, and 87 patients with alcoholic fatty liver disease were recruited.

Results

Inflammatory infiltration, focal necrosis in the leaflets, steatosis, and fibrosis were documented in the mouse liver. In total, 504 genes were differentially expressed in the livers of NASH mice, and showed significant functional enrichment in the inflammation-related category. Upregulated liver LCN2 was found to be significantly interactive with various interleukins and toll-like receptors. Serum LCN2 levels were significantly increased in NAFLD patients. Serum LCN2 levels were correlated with steatosis, intralobular inflammation, semiquantitative fibrosis score, and nonalcoholic fatty liver disease activity score. The area under the curve of serum LCN2 was 0.987 with a specificity of 100% and a sensitivity of 93.5% for NASH diagnosis, and 0.977 with almost the same specificity and sensitivity for steatosis.

Conclusions

LCN2 might be involved in the transition from NAFL to NASH by mediating inflammation. Serum LCN2 levels might be a novel biomarker for the diagnosis of NASH.

Characterization of the inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction: a hypothesis to explain influence of sex on the evolution and potential treatment of the disease

Accumulating evidence points to the existence of an inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction (HFpEF), which is characterized by biomarkers of inflammation, an expanded epicardial adipose tissue mass, microvascular endothelial dysfunction, normal-to-mildly increased left ventricular volumes and systolic blood pressures, and possibly, altered activity of adipocyte-associated inflammatory mediators. A broad range of adipogenic metabolic and systemic inflammatory disorders - e.g. obesity, diabetes and metabolic syndrome as well as rheumatoid arthritis and psoriasis - can cause this phenotype, independent of the presence of large vessel coronary artery disease. Interestingly, when compared with men, women are both at greater risk of and may suffer greater cardiac consequences from these systemic inflammatory and metabolic disorders. Women show disproportionate increases in left ventricular filling pressures following increases in central blood volume and have greater arterial stiffness than men. Additionally, they are particularly predisposed to epicardial and intramyocardial fat expansion and imbalances in adipocyte-associated proinflammatory mediators. The hormonal interrelationships seen in inflammatory-metabolic phenotype may explain why mineralocorticoid receptor antagonists and neprilysin inhibitors may be more effective in women than in men with HFpEF. Recognition of the inflammatory-metabolic phenotype may improve an understanding of the pathogenesis of HFpEF and enhance the ability to design clinical trials of interventions in this heterogeneous syndrome.

Clinical considerations in the management of non-alcoholic steatohepatitis cirrhosis pre- and post-transplant: A multi-system challenge

Non-alcoholic steatohepatitis (NASH) is the most common chronic liver disease worldwide, and the fastest growing indication for liver transplantation in the United States. NASH is now the leading etiology for liver transplantation in women, the second leading indication for men, and the most common cause amongst recipients aged 65 years and older. Patients with end-stage liver disease related to NASH represent a unique and challenging patient population due the high incidence of associated comorbid diseases, including obesity, type 2 diabetes (T2D), and hypertension. These challenges manifest in the pre-liver transplantation period with increased waitlist times and waitlist mortality. Furthermore, these patients carry considerable risk of morbidity and mortality both before after liver transplantation, with high rates of T2D, cardiovascular disease, chronic kidney disease, poor nutrition, and disease recurrence. Successful transplantation for these patients requires identification and management of their comorbidities in the face of liver failure. Multidisciplinary evaluations include a thorough pre-transplant workup with a complete cardiac evaluation, control of diabetes, nutritional support, and even, potentially, consultation with a bariatric surgeon. This article provides a comprehensive review of the conditions and challenges facing patients with NASH cirrhosis undergoing liver transplantation and provides recommendations for evaluation and management to optimize them before liver transplantation to produce successful outcomes.

Endocrine implications of bariatric surgery: a review on the intersection between incretins, bone, and sex hormones

Bariatric surgery is now the most widely used intervention for the treatment of human obesity. A large body of literature has demonstrated its efficacy in sustained weight loss and improvement in its associated comorbidities. Here, we review the effect of bariatric surgery in gut hormone physiology, bone remodeling and the reproductive axis. Rapid improvements in insulin release and sensitivity appear to be weight loss independent and occur immediately after surgery. These effects on pancreatic beta cells are mostly due to increased gut hormone secretion due to augmented nutrient delivery to the small intestine. Bone remodeling is also affected by gut hormones. Phenotypic skeletal changes observed in mice deficient in GLP‐1 or GIP suggest that increased incretins may improve bone density. However, these positive effects may be counterbalanced by the association between weight loss and a reduction in bone density. Finally, studies have shown a marked improvement following bariatric surgery in infertility and PCOS in women and hypogonadism in men. Thus, the net effect on endocrine systems after bariatric surgery will likely vary on an individual basis and depend on factors such as comorbidities, peri‐menopausal state, amount of weight loss, and likelihood to adhere to vitamin supplementation after surgery.

Probiotic Bifidobacterium lactis V9 attenuates hepatic steatosis and inflammation in rats with non-alcoholic fatty liver disease

Both steatosis and inflammation are key pathological events in the progression of non-alcoholic fatty liver disease (NAFLD). Probiotics are beneficial for the prevention and treatment of NAFLD. Bifidobacterium animalis subsp. lactis V9 (V9) is a newly isolated strain with favorable probiotic properties. The study aims to evaluate the effects and mechanisms of V9 on the hepatic steatosis and inflammatory responses in a rat model of NAFLD induced by high-fat diets (HFD). Our results showed that administration of V9 significantly attenuated the HFD-induced increases in alanine transaminase (ALT) and aspartate aminotransferase (AST) levels, resulting in alleviated hepatic steatosis. V9 supplementation reduced the accumulation of hepatic triglyceride and free fatty acid,while increasing the levels of glycogen. Serum levels of glucose were also decreased in HFD rats administrated with V9. Meanwhile, the transcription of SREBP-1c and FAS was reduced, and the hepatic expression of phosphorylated-AMPK and PPAR-α was restored after V9 administration. V9 suppressed the production of inflammatory cytokines (e.g. IL-6, IL-1β, and TNF-α) in HFD-fed rats. The anti-inflammatory effects of V9 was found to be associated with the inhibition of hepatic expression of TLR4, TLR9, NLRP3, and ASC mRNA. Furthermore, the activation of ERK, JNK, AKT and NF-κB were suppressed by V9 treatment. These results indicate that Bifidobacterium lactis V9 improves NAFLD by regulating de novo lipid synthesis and suppressing inflammation through AMPK and TLR-NF-κB pathways, respectively.

Randomised Double-Blind Placebo-Controlled Trial of Inulin with Metronidazole in Non-Alcoholic Fatty Liver Disease (NAFLD)

Background: Non-alcoholic fatty liver disease (NAFLD) can be ameliorated by weight loss although difficult to maintain. Emerging evidence indicates that prebiotics and antibiotics improve NAFLD. Aim: To determine whether inulin supplementation after brief metronidazole therapy is effective in reducing alanine aminotransferase (ALT) and maintaining weight loss achieved through a very-low-calorie diet (VLCD) among people with NAFLD. Methods: Sixty-two people with NAFLD commenced 4-week VLCD using Optifast meal replacements (600 kcal/day). Sixty were then randomised into a 12-week double-blind, placebo-controlled, parallel three-arm trial: (1) 400 mg metronidazole twice daily in Week 1 then inulin 4 g twice daily OR (2) placebo twice daily in week one then inulin OR (3) placebo-placebo. Main outcomes were ALT and body weight at 12 weeks. Fecal microbiota changes were also evaluated. Results: Mean body mass index (BMI) and ALT reduced after VLCD by 2.4 kg/m² and 11 U/L, respectively. ALT further decreased after metronidazole-inulin compared to after placebo-placebo (mean ALT change -19.6 vs. -0.2 U/L, respectively; p = 0.026); however, weight loss maintenance did not differ. VLCD treatment decreased the ratio of Firmicutes/Bacteroidetes (p = 0.002). Conclusion: Brief metronidazole followed by inulin supplementation can reduce ALT beyond that achieved after VLCD in patients with NAFLD.

Concurrent nonalcoholic fatty liver disease and type 2 diabetes: diagnostic and therapeutic considerations

Introduction: The relationship between nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) is complex and bidirectional. NAFLD increases the risk of incident diabetes and is very prevalent in T2DM patients and T2DM is an aggravating factor for NAFLD. Timely T2DM diagnosis and treatment in subjects with NAFLD and diagnosis, staging and treatment of NAFLD in those with T2DM are critical issues. Areas covered: PubMed/MEDLINE was searched for articles related to concomitant occurrence of NAFLD and T2DM between January 2013 and May 2019. Areas covered included epidemiological, diagnostic and therapeutic aspects. Expert opinion: there is a need for increased awareness on NAFLD adding liver disease as an end-organ complication of T2DM. Emphasis on use of simple non-invasive tools to triage patients with potentially severe liver disease should be made. Management of patients with NAFLD and T2DM relies on lifestyle optimization to achieve significant weight loss. Currently, there is no drug approved for treatment of NAFLD in patients with T2DM although Vitamin E and pioglitazone might be used in selected patients. Approved diabetic medications hold promise for NAFLD treatment and several liver-specific drugs are in evaluation clinical trials. A combination approach will likely represent the future of NAFLD therapeutics.

A Structured Literature Review of the Epidemiology and Disease Burden of Non-Alcoholic Steatohepatitis (NASH)

INTRODUCTION

Non-Alcoholic Steatohepatitis (NASH) is a chronic, progressive disease characterized by fatty liver and liver cell injury, advancing to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Diagnosis involves liver biopsy; however, as a result of its high cost and invasiveness, NASH remains underdiagnosed, and accurate burden of disease (BoD) data are lacking. Our aim was to understand the epidemiological and BoD landscape in NASH and identify knowledge gaps.

METHODS

The Ovid search engine was used to conduct a structured review, following quality systematic principles. It included publications that reported on epidemiology, quality of life (QoL) and BoD outcomes in NASH adults. Searches were limited to English language studies published between January 2007 and September 2017. Additional grey literature searches were conducted. A total of 53 references were selected; 38 were peer-reviewed and 15 were grey literature sources.

RESULTS

NASH is estimated to affect 3-5% of the global population, most suffering from several comorbidities. Advancing fibrosis drives clinical outcomes, with approximately 20% of patients developing cirrhosis and/or HCC, the latter being a leading cause of death in NASH. A recent model predicted the 15-year survival of advanced fibrosis patients at F3 and F4 as 51.0% and 28.4%, respectively. The limited data consistently show that NASH patients experience significantly poorer QoL and higher costs compared to non-NASH patients.

CONCLUSION

This first broad-ranging examination of NASH literature revealed a paucity of evidence, with poor-quality, small studies found. The overwhelming impact of NASH and its patient and healthcare burden is evident. Further evidence is needed to improve our understanding of NASH, especially as fibrosis stages advance.

FUNDING

Gilead Science Inc.

A structured literature review of interventions used in the management of nonalcoholic steatohepatitis (NASH)

Nonalcoholic steatohepatitis (NASH) is a chronic, progressive disease, that can advance to fibrosis, cirrhosis, and hepatocellular carcinoma. Despite being a leading cause of liver transplantation, there are no approved pharmacological treatments. Our aim was to identify literature on management options in NASH. Our structured review of interventions treating NASH patients from English language publications between 1 January 2007 and 25 September 2017 elicited 48 eligible references. Lifestyle management was identified as the mainstay of NASH therapy. Vitamin E and pioglitazone reported reductions in steatosis; however, although recommended for some, no therapies are indicated in NASH. Multiple investigational treatments reported efficacy in mild-to-moderate fibrosis in Phase II/III NASH trials. Lifestyle management, although the focus of clinical guidelines, is insufficient for patients progressing to advanced fibrosis. With no clear guidelines for patients requiring interventions beyond lifestyle modification, long-term outcomes data are needed, particularly in patients with moderate-to-severe fibrosis.

Changes in Bile Acid Metabolism, Transport, and Signaling as Central Drivers for Metabolic Improvements After Bariatric Surgery

PURPOSE OF REVIEW

We review current evidence regarding changes in bile acid (BA) metabolism, transport, and signaling after bariatric surgery and how these might bolster fat mass loss and energy expenditure to promote improvements in type 2 diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

The two most common bariatric techniques, Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), increase the size and alter the composition of the circulating BA pool that may then impact energy metabolism through altered activities of BA targets in the many tissues perfused by systemic blood. Recent reports in human patients indicate that gene expression of the major BA target, the farnesoid X receptor (FXR), is increased in the liver but decreased in the small intestine after RYGB. In contrast, intestinal expression of the transmembrane G protein-coupled BA receptor (TGR5) is upregulated after surgery. Despite these apparent conflicting changes in receptor transcription, changes in BAs after both RYGB and VSG are associated with elevated postprandial systemic levels of fibroblast growth factor 19 (from FXR activation) and glucagon-like peptide 1 (from TGR5 activation). These signaling activities are presumed to support fat mass loss and related metabolic benefits of bariatric surgery, and this supposition is in agreement with findings from rodent models of RYGB and VSG. However, inter-species differences in BA physiology limit direct translation and mechanistic understanding of how changes in individual BA species contribute to post-operative improvements of T2D and NAFLD in humans. Thus, details of all these changes and their influences on BAs' biological actions are still under scrutiny. Changes in BA physiology and receptor activities after RYGB and VSG likely support weight loss and promote sustained metabolic improvements.

A Review of Non-Alcoholic Fatty Liver Disease in HIV-Infected Patients: The Next Big Thing?

The burden of liver-related morbidity remains high among HIV-infected patients, despite advances in the treatment of HIV and viral hepatitis. Especially, the impact of non-alcoholic fatty liver disease (NAFLD) is significant with a prevalence of up to 50%. The pathogenesis of NAFLD and the reasons for progression to non-alcoholic steatohepatitis (NASH) are still not fully elucidated, but insulin resistance, mitochondrial dysfunction and dyslipidemia seem to be the main drivers. Both HIV-infection itself and combination antiretroviral therapy (cART) can contribute to the development of NAFLD/NASH in various ways. As ongoing HIV-related immune activation is associated with insulin resistance, early initiation of cART is needed to limit its duration. In addition, the use of early-generation nucleoside reverse transcriptase inhibitors and protease inhibitors is also associated with the development of NAFLD/NASH. Patients at risk should therefore receive antiretroviral drugs with a more favorable metabolic profile. Only weight reduction is considered to be an effective therapy for all patients with NAFLD/NASH, although certain drugs are available for specific subgroups. Since patients with NASH are at risk of developing liver cirrhosis and hepatocellular carcinoma, several non-antifibrotic and antifibrotic drugs are under investigation in clinical trials to broaden the therapeutic options. The epidemiology and etiology of NAFLD/NASH in HIV-positive patients is likely to change in the near future. Current guidelines recommend early initiation of cART that is less likely to induce insulin resistance, mitochondrial dysfunction and dyslipidemia. In contrast, as a result of increasing life expectancy in good health, this population will adopt the more traditional risk factors for NAFLD/NASH. HIV-treating physicians should be aware of the etiology, pathogenesis and treatment of NAFLD/NASH in order to identify and treat the patients at risk.

PNPLA3 rs738409 underlies treatment response in nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has now become the leading cause of chronic liver disease with its growing incidence worldwide. Patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 C > G reflects one of the critical genetic factors that confers high-risk to NAFLD. However, the role of PNPLA3 polymorphism in NAFLD treatment remains uncertain. Here, the present review reveals that NAFLD patients with G-allele at PNPLA3 rs738409 (PNPLA3 148M variant) are sensitive to therapies of lifestyle modification, dipeptidyl peptidase-4 inhibitors, and bariatric surgery. They exhibit much significant reduction of liver fat content, in concurrence with weigh loss and abolished insulin resistance, as compared to those of C-allele carriers. In contrast, patients bearing PNPLA3 rs738409 C-allele (PNPLA3 148I variant), instead of G-allele, demonstrate greater beneficial effects by omega-3 poly-unsaturated fatty acids and statin intervention. Improved adipose tissue-liver interaction and decrease in intrahepatic triglyceride efflux may contribute to the PNPLA3 rs738409 related diversities in therapeutic efficacy. Therefore, PNPLA3 rs738409 underlies the response to a variety of treatments, which warrants a personalized, precise medicine in NAFLD on the basis of genotype stratification.