A novel hepatokine, HFREP1, plays a crucial role in the development of insulin resistance and type 2 diabetes

Aims/hypothesis: Type 2 diabetes is highly correlated with nonalcoholic fatty liver disease (NAFLD). Hepatocyte-derived fibrinogen-related protein 1 (HFREP1) is a hepatokine that mediates NAFLD development; however, the role of HFREP1 in the development of insulin resistance and diabetes remains obscure. Methods: A total of 193 age- and sex-matched participants with normal glucose tolerance, impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and newly diagnosed diabetes (NDD) were recruited for a cross-sectional study. Plasma HFREP1 levels were measured and multivariate linear regression analysis was used to evaluate the relationship between HFREP1, IFG, IGT and NDD. The causal relationship between HFREP1 and insulin resistance was then investigated in animal and cell models. Glucose and insulin tolerance tests, and euglycaemic–hyperinsulinaemic clamp, were used to evaluate insulin sensitivity in animals with Hfrep1 overexpression or knockdown in liver by lentiviral vectors. HepG2 cells were used to clarify the possible mechanism of HFREP1-induced insulin resistance. Results: Plasma HFREP1 concentrations were significantly increased in participants with IFG, IGT and NDD. HFREP1 concentrations were independently associated with fasting plasma glucose levels, insulin resistance, IFG, IGT and NDD. Injection of recombinant HFREP1 or Hfrep1 overexpression induced insulin resistance in mice, and HFREP1 disrupted insulin signalling to induce insulin resistance through an extracellular signal-regulated kinase (ERK)1/2-dependent pathway. Moreover, hepatic knockdown of HFREP1 improved insulin resistance in both mice fed a high-fat diet and ob/ob mice. Conclusions/interpretation: These findings highlight the crucial role of HFREP1 in insulin resistance and diabetes, and provide a potential strategy and biomarker for developing therapeutic approaches to combat these diseases.