Cholesterol

INS-1 cells were procured from the National Infrastructure of Cell Line Resource (Beijing, China) and cultured in RPMI-1640 (Invitrogen, Carlsbad, CA, United States) added with L-glutamine, FBS (10%; Invitrogen), HEPES (10 mmol/L; Sigma, St. Louis, MO, United States), sodium pyruvate (1 mmol/L; Invitrogen), and β-mercaptoethanol (50 μmol/L; Sigma-Aldrich, ıSt. Louis, MI, United States) at 37°C in 5% CO₂.
For high-fat induction, cholesterol (Santa Cruz Biotechnology; Dallas, TX, United States) was dissolved in chloroform and diluted to 1, 2.5, and 5 and 10 mmol/L with a culture medium for 24 h (Kong et al., 2017 ); For GLP-1 treatment, cells were treated with GLP-1 agonist at a concentration of 10 nM exendin-4 (Ex-4) for 24 h (Zhu et al., 2014 (link)); For AMPK activation or inhibition, according to the aforementioned procedure (Zhang et al., 2009 (link); Shang et al., 2016 (link)), cells were pre-treated with 0.5 mM Acadesine (AICAR, an AMPK agonist) or 10 μM Compound C (an AMPK antagonist) for 4 h and subsequently co-treated with 10 nM Ex-4 for 24 h, respectively. For PARP-1 inhibition, INS-1 cells were treated with 5 mM 3-aminobenzaminde (3-AB) (Sigma) for 24 h. For LXR receptor activation, INS-1 cells were treated with 5 μM T0901317 for 4 h (Shrestha et al., 2016 (link)).