1. Introduction
Non-alcoholic fatty liver disease (NAFLD) characterized by increased fatty lipid accumulation in the liver[1]. NAFLD affects all age group but especially in people in their 40s and 50s who are at high risk of heart disease because of such risk factors as obesity and type 2 diabetes[2]. The condition is also closely linked to metabolic syndrome, which is a cluster of abnormalities including increased abdominal fat, poor ability to use the hormone insulin, high blood pressure and high blood levels of triglycerides [3]. The prevalence of NAFLD has been reported about 24% in the world. Reports indicate that the prevalence of metabolic syndrome was significantly higher in NAFLD than healthy people (47% vs 23%)[4]. There is no effective treatment that completely reverses the effects of the NAFLD however healthy lifestyle such as dietary changes, regular physical activity and gradual weight loss lo that can improve the disease [5-7]. Increased prevalence of NAFLD is due to epidemiologic and pathophysiological communication with type 2 diabetes and obesity[8]. When glucose levels increase in diabetes or pre-diabetes, it provides more substrate for triglyceride production. In addition, deficit in the secretion of very low density lipoprotein (VLDL) is common in insulin resistance, and this process provides conditions for the accumulation of fat in the liver[9]. Insulin resistance is not just a factor in obesity, but it may also lead to NAFLD, even in thin individuals[9]. Adipose tissue is an active tissue that plays an important role in energy homeostasis, hormonal signaling, metabolic balance, and adipokines secretions. Evidence shows that the adipose tissue secretes more than 50 molecules signaling and hormones called adipokine [10]. Adipokines play a role in regulation of thermogenesis, appetite, glucose metabolism and insulin sensitivity[11]. Adiponectin is secreted from adipose tissue as a protein that has anti-inflammatory activity [12, 13]. It also plays a role in the metabolism of glucose and fats and plays an important role in reducing insulin resistance and the risk of cardiovascular disease[14]. Leptin is a hormone secreted from fat cells that helps to regulate body weight[15]. In human liver cells, leptin has some insulin-inducing activity that eventually causes insulin resistance. This insulin resistance, which is a common finding in patients with NAFLD, may be due to this role of leptin[16, 17].
Nigella sativa (NS) has been traditionally used in India, Arab countries, Europe and Iran to treat diseases such as asthma, hypertension, diabetes, inflammation, tumor, cough, bronchitis, headache, eczema, fever, dizziness, gastrointestinal disorders, impotence and Influenza[18] . NS has various chemicals including thymoquinone (TQ), unsaturated fatty acids and flavonoids[19, 20]. NS in medicine as anti-inflammatory and antioxidant used[21, 22]. TQ protects the liver from injury by several mechanisms such as inhibition of iron-dependent lipid peroxidation, elevation in glutathione level and total thiol content, radical scavenger, improving the activity of quinone reductase, catalase, superoxide dismutase and glutathione transferase, inhibition of NF-κB activity and inhibition of both lipoxygenase and cyclooxygenase also improves hepatic steatosis and prevents hepatic fibrosis[23]. Animal studies have shown that TQ diminishes thioacetamide-induced hepatic fibrosis and inflammation via activating LKB1-AMPK signaling pathway in mice[24, 25]. Since there is no study on the effects of NS oil on adiponectin, leptin levels and blood pressure in patients with NAFLD, we decided to perform this study.