Fig. 10.
Effect of leptin deficiency on hepatic elongase and desaturase expression. Male lean (C57BL/6J-Lepob/+) and obese (C57BL/6J-Lepob/ob) mice (B6.V-Lep ob/J, No. 000632; Jackson Laboratories) were maintained on a Harlan-Teklad laboratory chow (No. 8640) diet and water ad libitum. Livers from these mice were used for the isolation of nuclear and microsomal protein for immunoblotting (A) and RNA extraction for qRT-PCR (B). A: Effect of obesity on SREBP-1 (microsomal and nuclear) and nuclear ChREBP, MLX, and HNF-4α abundance. Protein levels were measured by immunoblot analysis (see Materials and Methods). Triplicate samples for each phenotype are shown. The effect of leptin deficiency on the abundance of these proteins was quantified and expressed as fold change (means; n = 4) induced by leptin deficiency. Statistical significance (P) was assessed by Student’s t-test. B: Effect of leptin deficiency on elongase and desaturase expression. RNA was extracted and used for qRT-PCR analysis of elongase and desaturase expression. Results are expressed as fold change (transcript/cyclophilin) (means ± SD; n = 4). * P < 0.001 versus lean by Student’s t-test. C: Effect of leptin deficiency on elongase activity. Hepatic microsomal preparations were used for fatty acid elongase assays (see Materials and Methods). Results are expressed as elongase activity (nmol [14C]malonyl-CoA assimilated into fatty acids/mg protein) (means ± SD; n = 4). * P ≤ 0.01 versus lean by Student’s t-test. D: Effect of leptin deficiency on hepatic lipid composition. Total lipids were extracted and saponified; fatty acid levels were quantified by reverse-phase HPLC (see Materials and Methods). Results are expressed as fatty acid mol% (means ± SD; n = 4/group). * P ≤ 0.01 versus lean animals by Student’s t-test.