Aspects of diagnosis, prognosis and treatment of nonalcoholic fatty liver disease

Abstract

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease globally. NAFLD is caused by obesity, often in combination with type 2 diabetes mellitus (T2D). Lifestyle modifications that lead to weight loss, primarily diet change, is the only treatment proven to reverse steatosis and nonalcoholic steatohepatitis (NASH). The projects included in this thesis explore different aspects of epidemiology, pathophysiology, and treatment of NAFLD.

A significant number of NAFLD patients will develop cirrhosis, and NAFLD has become a leading cause for the need of a liver transplantation in several parts of the world. We first performed a population-based cohort study including 4609 patients from the Nordic Liver Transplant Registry who were listed for liver transplantation between 1994 to 2015. We observed that NAFLD is increasing as a cause of severe liver disease in the Nordic countries.

Common genetic variants have been linked to more advanced forms of NAFLD in cross- sectional studies. How these polymorphisms affect the long-term risk of progressive disease is less known. Study 2 was a cohort study on 546 patients with NAFLD and 5,234 reference individuals matched on age, sex, and municipality. DNA samples were collected from all subjects with NAFLD. Genetic variants previously associated with NAFLD, NASH, and fibrosis were determined from blood samples or stored biopsies. Long-term outcomes were collected from national patient registers during a median follow-up of 20 years. The main finding was an association of the G/G genotype of the patatin-like phospholipase domain containing 3 (PNPLA3 rs738409) gene with an increased prevalence of NASH at baseline and the risk of developing severe liver disease during follow-up.

More research is needed to establish the role of adipose tissue in the pathogenesis of NAFLD and NASH. In study 3 we collected subcutaneous adipose tissue (SAT) from 32 patients with NAFLD and 15 healthy controls matched on BMI. We studied the association between SAT morphology and NASH or fibrosis. We found that subjects with NAFLD have hypertrophic SAT adipocytes compared to controls. Using RNA-sequencing of SAT, we explored genes that were differently expressed in subjects with NASH and compared our results to those seen in previous studies on morbidly obese subjects.

The final study of this thesis was an open label randomized controlled trial on 74 patients with NAFLD. We compared the efficacy of a low-carb high-fat diet (the LCHF diet), intermittent calorie restriction (the 5:2 diet) and standard diet recommendations on reduction of hepatic steatosis. Liver fat content was measured with magnetic resonance spectroscopy at baseline and after 12 weeks of treatment. The main finding was that the LCHF and the 5:2 diets were equally effective in reducing steatosis. Both were superior to the standard treatment given to the control group. The results of this thesis have implications on several aspects of NAFLD epidemiology, pathogenesis, and treatment.