Liver Fibrosis/NASH

Metabolic dysfunction-associated steatotic liver disease (MASLD) (aka non-alcoholic fatty liver disease), commonly occurring in individuals with obesity and type 2 diabetes can lead to liver inflammation/ fibrosis. MASLD results from fat being disproportionately deposited in the liver. The goal of this mechanistic study is to investigate metabolic response in patients aged 20 to 80 years with non-alcoholic fatty liver disease, after niacin (vitamin B3) treatment. The main questions it aims to answer are: * Does Niacin lower the fat deposition in the liver? * Does Niacin raise White Adipose Tissue storage of dietary fatty acids? Researchers will compare Niacin to a placebo (a look-alike substance that contains no drug) to compare the metabolic response. Duration of study per participant: Up to 28 weeks

The goal of this clinical trial is to learn how physical exercise affects liver health in adults with metabolic dysfunction-associated steatotic liver disease (MASLD) or at-risk metabolic dysfunction-associated steatohepatitis (MASH); comparing responses between middle-aged adults (40-60 years old) and older adults (70 years and older) of any sex, as well as between participants with low-risk MASLD and high-risk MASH. The main question it aims to answer is: Could an exercise program reduce liver fat, inflammation and fibrosis, regardless of age and disease severity? Researchers will compare 4 different groups: A) older adults with at risk MASH who will exercise B) middle-aged people with at risk MASH who will exercise C) middle-aged people with low-risk MASLD who will exercise D) middle-aged people with low-risk MASLD who will not exercise, receiving usual care. Participants in the exercise groups will take part in a supervised 12-week exercise program that includes both strength and aerobic training, completed twice a week. All participants, including those receiving usual care, will have health asssessments before and after the 12-week period to measure changes in liver health.