Leptin

All solvents were of analytical grade from Merck. Biotechnolgy grade water (7732-18-5) and commercial oryzanol were obtained from Sigma-Aldrich. Rat adiponectin (Catalog No EZRADP-62 K) and insulin (Catalog No EZRMI-13 K) enzyme-linked immunosorbent assay (ELISA) kits were procured from Millipore Corporation. Rat retinol binding protein-4 dual ELISA kit (Catalog No AG-45A-0012YEK-K101) was obtained from Adipogen International, while 8-iso prostaglandin (Catlog No E-EL-R2488) and leptin (Catlog No E-EL-R0582) ELISA kits were purchased from Elabscience Biotechnology Co., Ltd. MethylFlash™ Methylated DNA Quantification Kit (Fluorometric) (Catalog No P-1035), Epiquick™ Total Histone Extraction Kit (Catalog No OP-0006), Epiquick™ Epiquick™ Total Histone H3 Acetylation Detection Fast Kit (Fluorometric) (Catalog No P-4031) and Epiquick™ Total Histone H4 Acetylation Detection Fast Kit (Fluorometric) (Catalog No P-4033) were obtained from EPIGENETIK.

Triglyceride, total cholesterol and high-density lipoprotein (HDL) cholesterol levels were measured in the serum samples using a clinical chemistry analyzer (Olympus AU480, Beckman Coulter, Brea, CA, USA). Serum samples were obtained by centrifugation (1000× g, 15 min) of blood samples taken from the jugular vein in plastic tubes with clot activator (BD Microtainer^® SST II).
The concentrations of insulin, leptin, adiponectin (Demeditec Diagnostics, Kiel, Germany) and glucagon (Elabscience, Wuhan, China) were determined in the plasma samples using a commercially available enzyme-linked immunosorbent assay (ELISA) with a sensitivity of 0.1 ng/mL (insulin), 0.081 ng/mL (adiponectin), <0.25 µg/mL (leptin) and 37.5 pg/mL (glucagon). Plasma samples were prepared by centrifugation (1500× g, 10 min) of blood samples taken from the jugular vein in plastic tubes containing EDTA salts (BD Vacutainer™ K2E), and were stored in aliquots at −80 °C until analyses were performed.
Glucose levels were determined in blood samples taken from an incision at the tip of the tail. Measurements were performed with a glucometer (iDIA, Hof, Germany) using the glucose oxidase method.
The Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) was calculated using the following formula: fasting plasma insulin (mIU/L) * fasting blood glucose (mmol/L)/22.5.

Leptin, F2-isoprostane, and insulin ELISA kits were purchased from Elabscience Biotechnology Co., Ltd (Wuhan, China), while adiponectin ELISA kit was from Millipore (Billerica, MA, USA). Lipid profile kits were purchased from Randox Laboratories Ltd (Crumlin, County Antrim, UK). GenomeLab GeXP Start Kit was from Beckman Coulter Inc (Miami, FL, USA), and RNA extraction kit was from RBC Bioscience Corp. (Taipei, Taiwan). Simvastatin was from Pfizer (New York, NY, USA) and RCL2 Solution from Alphelys (Toulouse, France). Analytical grade ethanol was purchased from Merck (Darmstadt, Germany). Cholesterol and cholic acid were purchased from Amresco (Solon, OH, USA) and Santa Cruz Biotechnology (Santa Cruz, CA, USA), respectively. Standard rat pellet was from Specialty feeds (Glen Forrest, WA, USA), while palm oil was supplied by Yee Lee Edible oils Sdn. Bhd. (Perak, Malaysia). EBN, of Aerodramus fuciphagus (white nest swiftlet) origin, supplied by Blossom View Sdn. Bhd (Terrengganu, Malaysia) was cleaned under tap water for 5 mins, dried at room temperature, and ground into powder manually using mortar and pestle before incorporating it into rat pellet.