Effects of subcutaneous leptin injections on hypothalamic gene profiles in lean and ob/ob mice

Objective: Leptin-deficient ob/ob mice are more sensitive to exogenous leptin than lean mice and leptin treatment normalizes many of the phenotypic characteristics of ob/ob mice. The primary objective of this experiment was to investigate whether this altered leptin sensitivity in ob/ob mice was reflected in the hypothalamic mRNA profile. Research Methods and Procedures: Fifteen-week-old feinale ob/ob and lean mice were treated with 14 days of subcutaneous (sc) infusion of phosphate-buffered saline (PBS) or leptin (10 mu g/d) using osmotic pumps. Real-time Taqman reverse transcription polymerase chain reaction (RT-PCR) (ABI Microfluidic cards) was used to quantitatively compare the mRNA levels of selected hypothalamic genes in these groups. Results: Hypothalamic mRNA levels for ob/ob control mice were higher for agouti-related protein (AGRP), neuropeptide Y (NPY), and arginine vasopressin (AVP), and lower for cocaine- and amphetamine-regulated transcript (CART), cAMP response element binding protein (CREB)-1 proopiomelanocortin (POMC)-1, and urocortin (UCN)-3 compared with lean controls. In leptin-treated ob/ob mice, hypothalamic mRNA levels were reduced for NPY, AGRP, AVP, and increased for suppressor of cytokine signaling 3 (SOCS3) compared with ob/ob controls. Leptin treatment dramatically up-regulated hypothalamic mRNA level of POMCI in both lean and ob/ob mice. Strong correlations were observed between hypothalamic Janus kinase 2 (JAK2) and CREB1, STAT3 and CREB 1, JAK2 and STAT3, NPY and AVP in all samples. Discussion: ob/ob and lean mice have different hypothalamic mRNA expression patterns (particularly those of feeding-related genes), and selected genes in ob/ob mice are more sensitive to exogenous leptin stimulation compared with lean mice.