Non-Alcoholic Fatty Liver Disease: Cause or Effect of Metabolic Syndrome

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease throughout the world. Pathophysiological insights into this disease have recently illustrated that various factors such as insulin resistance, innate immunity, metabolic inflammation, and the microbiota are of relevance. NAFLD, metabolic syndrome (MS), and type 2 diabetes (T2D) share many pathophysiological aspects, and inflammatory processes in the adipose tissue, gut, and liver have evolved to be of exceptional importance. Most of NAFLD patients are obese and encounter a high risk of developing MS and T2D. NAFLD, however, is also highly common in subjects with MS and T2D. Furthermore, reflecting its nature of a multisystem disease, NAFLD is associated with a high prevalence and incidence of cardiovascular and chronic kidney disease. These facts require screening strategies for MS/T2D in NAFLD patients and vice versa. Thus, the question of cause or effect cannot be answered as MS and NAFLD share many pathomechanisms, and at the time of either diagnosis both frequently coexist. This is also reflected by a global prevalence rate of 25% for both NAFLD and MS. For this reason, it is crucial that physicians are aware of the 'unholy liaison' between MS, T2D, and NAFLD.