C3 and obesity due to melanocortin 4 receptor deficiency: Plasma C3 levels are also higher in non-alcoholic fatty liver disease (NAFLD) [4], a common comorbidity associated with obesity and in type 2 diabetes, and possibly also in type 1 diabetes; in agreement with this observation, alanine aminotransferase—a marker of liver dysfunction—was also associated with plasma levels of C3 [5].