Lipids were extracted by chloroform:methanol (2:1, v/v)40. Cholesterol was quantified by GC/MS41. Triglyceride was quantified by GPO reagent set (Pointe Scientific)42. Cell DNA content was quantified by PicoGreen43. RNA was isolated by TRIZOL® reagent (Invitrogen) and RNeasy Mini Kit (Qiagen). All reagents were purchased from Sigma unless otherwise specified.