The serum levels of insulin (kt30476, MSKbio, Wuhan, China), TC (kt30156, MSKbio, Wuhan, China), TGs (kt50023, MSKbio, Wuhan, China), LDL-C (kt25323, MSKbio, Wuhan, China) and LPS (E-EL-R0589c, Elabscience, Wuhan, China) as well as tumour necrosis factor-alpha (TNF-α, ml002859, mlbio, Shanghai, China), interleukin 6 (IL-6, ml064292, mlbio, Shanghai, China) and IL-1β (PI303, Beyotime, Beijing, China) levels in liver tissue were detected by specific ELISA kits. Briefly, rat serum was added into the enzyme-labelled plates and incubated at 37 °C for 90 min. Then, the fluid in the plates was discarded, and 100 μL biotinylated antibody was added into the plates. After 60 min incubation at 37 °C, the plates were washed by the buffer solution thrice, added with the enzyme-conjugated working solution and incubated at 37 °C for 30 min. Subsequently, the plates were supplemented with the substrate Reagent and incubated at 37 °C for 15 min. Following these, H2SO4 (2 M, 50 μL) was added to each well to terminate the reaction. Ultimately, the optical density at 450 nm was recorded under a microplate reader (ELx808, BioTek, Winooski, VT).
Later, homeostasis model assessment-insulin resistance (HOMA-IR) was calculated according to this formula (Jia N et al. 2018 ):
Later, homeostasis model assessment-insulin resistance (HOMA-IR) was calculated according to this formula (Jia N et al. 2018 ):