Systematic Reviews
Copyright ©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Hepatol. Mar 27, 2024; 16(3): 452-464
Published online Mar 27, 2024. doi: 10.4254/wjh.v16.i3.452
Update in lean metabolic dysfunction-associated steatotic liver disease
Karina Sato-Espinoza, Perapa Chotiprasidhi, Mariella R Huaman, Javier Díaz-Ferrer
Karina Sato-Espinoza, Perapa Chotiprasidhi, Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN 55902, United States
Mariella R Huaman, Obesity and Metabolic, Center for Obesity and Metabolic Health, Lima 02002, Lima, Peru
Javier Díaz-Ferrer, Hepatology Service, Department of Digestive Diseases, Hospital Nacional Edgardo Rebagliati Martins, Lima 02002, Lima, Peru
Javier Díaz-Ferrer, Medicine Faculty, Universidad San Martin de Porres, Lima 02002, Lima, Peru
Javier Díaz-Ferrer, Gastroenterology Service, Clinica Internacional, Lima 02002, Lima, Peru
Author contributions: Sato-Espinoza K, Huaman MR, Diaz-Ferrer J, Chotiprasidhi P performed the methodology, wrote, reviewed and edited the manuscript.
Conflict-of-interest statement: There is no conflict of interest for any of the authors in this manuscript.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 checklist, and the manuscript was prepared and revised according to the PRISMA 2009 checklist.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Karina Sato-Espinoza, MD, Research Fellow, Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, 200 First ST SW, Rochester, MN 55902, United States. sato.angela@mayo.edu
Received: December 26, 2023
Peer-review started: December 26, 2023
First decision: January 11, 2024
Revised: January 19, 2024
Accepted: February 28, 2024
Article in press: February 28, 2024
Published online: March 27, 2024
Abstract
BACKGROUND

A new nomenclature consensus has emerged for liver diseases that were previously known as non-alcoholic fatty liver disease (NAFLD) and metabolic dysfunction-associated fatty liver disease (MAFLD). They are now defined as metabolic dysfunction-associated steatotic liver disease (MASLD), which includes cardiometabolic criteria in adults. This condition, extensively studied in obese or overweight patients, constitutes around 30% of the population, with a steady increase worldwide. Lean patients account for approximately 10%-15% of the MASLD population. However, the pathogenesis is complex and is not well understood.

AIM

To systematically review the literature on the diagnosis, pathogenesis, characteristics, and prognosis in lean MASLD patients and provide an interpretation of these new criteria.

METHODS

We conducted a comprehensive database search on PubMed and Google Scholar between January 2012 and September 2023, specifically focusing on lean NAFLD, MAFLD, or MASLD patients. We include original articles with patients aged 18 years or older, with a lean body mass index categorized according to the World Health Organization criteria, using a cutoff of 25 kg/m2 for the general population and 23 kg/m2 for the Asian population.

RESULTS

We include 85 studies in our analysis. Our findings revealed that, for lean NAFLD patients, the prevalence rate varied widely, ranging from 3.8% to 34.1%. The precise pathogenesis mechanism remained elusive, with associations found in genetic variants, epigenetic modifications, and adaptative metabolic response. Common risk factors included metabolic syndrome, hypertension, and type 2 diabetes mellitus, but their prevalence varied based on the comparison group involving lean patients. Regarding non-invasive tools, Fibrosis-4 index outperformed the NAFLD fibrosis score in lean patients. Lifestyle modifications aided in reducing hepatic steatosis and improving cardiometabolic profiles, with some medications showing efficacy to a lesser extent. However, lean NAFLD patients exhibited a worse prognosis compared to the obese or overweight counterpart.

CONCLUSION

MASLD is a complex disease comprising epigenetic, genetic, and metabolic factors in its pathogenesis. Results vary across populations, gender, and age. Limited data exists on clinical practice guidelines for lean patients. Future studies employing this new nomenclature can contribute to standardizing and generalizing results among lean patients with steatotic liver disease.

Keywords: Lean, Non-obese, Non-alcoholic fatty liver disease, Metabolic dysfunction-associated fatty liver disease, Metabolic dysfunction-associated steatotic liver disease, Guidelines, Diagnosis, Management, Pathogenesis, Treatment

Core Tip: Steatotic liver disease, extensively studied in overweight/obese patients, poses a unique challenge in lean individuals due to limited data on its pathogenesis, diagnosis, management, and risk factors. The lack of consensus in nomenclature impedes the comprehension and application of findings. To address this gap, we conducted a systematic review focusing on lean individuals with steatotic liver disease. This review interprets the new approach, introducing the term metabolic dysfunction-associated steatotic liver disease in alignment with current literature. We aim to enhance the understanding of steatotic liver disease in lean populations, contributing to a precise approach in research and clinical settings.