Expression of neuromedin B in adipose tissue and its regulation by changes in energy balance

Abstract

Bombesin is one of the most powerful substances showing anorexic effects in the hypothalamus (Moody TW & Merali Z 2004 Bombesin-like peptides and associated receptors within the brain: distribution and behavioral implications. Peptides 25 511-520). In mammals, neuromedin B (NMB) is one member of a family of bombesin-like peptides, which have been shown to reduce food intake when administered systemically. Using Taqman real-time PCR with specific primers, we report the expression of NMB mRNA in both human and rodent adipose tissue. Expression of NMB in rodent epididymal adipose tissue was higher than in other tissues studied. Expression of NMB in adipose tissue appears to be regulated by changes in energy balance and leptin. It is decreased fourfold in the epididymal fat depot of ob/ob mice when compared with the same fat depot in lean mice. It is further decreased with the intra-peritoneally (i.p.) administration of leptin in both lean and obese ob/ob mice. This may relate to its function in food intake regulation or to changes in energy expenditure. We demonstrate that NMB expression in rodent adipose tissue is decreased in cold exposed animals. However, when we investigated the effects of NMB on resting metabolic rate by i.p. injection, there was no effect on oxygen consumption, RQ or physical activity when compared with saline-treated controls. In conclusion, NMB is expressed in both human and rodent adipose tissue and appears to be regulated by changes in energy balance. Given its anorexic effects centrally, it may form part of a new adipose tissue--hypothalamic axis regulating food intake.