Serum Apelin Level and Insulin Resistance in Nonalcoholic Fatty Liver Disease and their Relationship to Histological Severity of Liver Disease

Background: Apelin is the endogenous ligand of APJ, which belongs to the family of G protein-coupled receptors. It is an adipokine plays a role in the regulation of glucose homeostasis and in obesity but the relationship of apelin levels in humans with nonalcoholic fatty liver disease (NAFLD) and its effect on the histological severity of NAFLD is lacking. Methods: Blood samples were collected from 125 consecutive patients with liver-biopsy-proven NAFLD and 30 subjects as controls. Serum apelin levels were measured. Body mass index (BMI) was calculated for all subjects, and serum insulin, C-peptide, and lipoprotein levels were also measured. Results: Mean serum apelin level and BMI in the NAFLD group were significantly higher than the controls (both p<0.001) . Both men and women in the NAFLD group had higher mean serum apelin levels than did the men and women in the control group (all p<0.001). Multivariate analysis showed that the percentage of hepatic steatosis, sex, BMI, and homeostasis model assessment of insulin resistance (HOMA IR) were related to serum apelin levels. Conclusion: These data suggest increased apelin level in NAFLD patients which is related to histological severity of the disease. These findings support the link between apelin, insulin resistance and BMI in these patients.