Differences in Adipokine and Hepatokine Levels among Non-diabetic Population Classified by Age and Sex

BACKGROUND Leptin, angiopoietin-related growth factor (AGF), adiponectin (ADP), and retinol-binding protein 4 (RBP4) are cytokines associated with the development of metabolic disorders, such as type 2 diabetes and cardio vascular disease. However, the levels of these cytokines have not extensively studied in non-diabetic subjects. Therefore, we analyzed the differences in these cytokine levels according to sex and age in non-diabetic Korean population. METHODS Blood samples were collected from 59 non-diabetic Korean adults (male, 32; female, 27). The anthropometric and biochemical data were measured at the health examination center. Serum adipokines and hepatokines were measured by enzyme linked immunosorbent assay (ELISA). The data were analyzed according to sex and age-based quartiles. RESULTS Serum leptin values were higher in females (8.60 ± 3 μg/ml) compared with males (2.99 ± 2.9 μg/ml). However, RBP4 was higher in males (84.05 ± 47.04 μg/ml) than in females (61.25 ± 45.42 μg/ml). The AGF and ADP values were not significantly different between males and females. RBP4 level was inversely correlated with age quartile in males, while leptin was significantly associated with body mass index and insulin resistance. CONCLUSION RBP4 and AGF levels showed age-associated change, and leptin was consistently higher in females. Therefore, a large-scale analysis to determine the normal range of adipokines and hepatokines concentration in healthy Korean population is necessary. When interpreting adipokine and hepatokine levels, the difference in age and sex needs to be taken into account.