Circulating mRNA and plasma levels of osteoprotegerin and receptor activator of NF‐κB ligand in nonalcoholic fatty liver disease

Pathogenesis of the beginning and progression of nonalcoholic fatty liver disease (NAFLD) has not been clarified exactly. The osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) axis seems to play an imperative function in the onset and progression of this disease. The goal of the present study was to investigate the peripheral blood mononuclear cell (PBMC) expression and plasma levels of RANKL and OPG cytokines in NAFLD patients and compare them with healthy group. Plasma levels of OPG and RANKL were determined with ELISA kits in 57 men with NAFLD and 25 healthy men as controls. Biochemical and anthropometric parameters tests were also evaluated in the study groups. RANKL and OPG mRNA contents were evaluated by quantitative RT-PCR. OPG contents were markedly decreased in NAFLD patients as compared with healthy patients [1.43 (1.05-5.45)] versus [2.94 (1.76-4.73)] ng/mL; P = 0.007). The levels of RANKL were significantly reduced in NAFLD patients [74.00 (56.26-203.52) ng/mL] than in healthy patients [119.37 (83.71-150.13) ng/mL]; (P = 0.03). Also, OPG and RANKL gene expression were significantly decreased in NAFLD patients in comparison with the control group (P < 0.05). Moreover, receiver operating characteristic curve indicated that OPG may have a good capability to discriminate between NAFLD patients and normal individuals. A positive correlation was observed between OPG and RANKL in plasma sample (r = 0.495) (P = 0.000). Decreased plasma levels and gene expression of RANKL and OPG cytokines in NAFLD patients indicate that there is a relationship between these cytokines and the pathology of NAFLD disease. Confirmation of this association as well as the mechanism and role of these cytokines in NAFLD require further studies.