Leptin supplementation of neonatal rats during the suckling period protects against being overweight in adulthood and ameliorates the control of food intake. This was associated with changes in the expression of hypothalamic genes involved in the central action of leptin: pro-opiomelanocortin (Pomc), leptin receptor (Lepr) and suppressor of cytokine signalling (Socs3). The purpose of the present study was to determine the methylation status within the promoter regions of these genes and to assess whether the observed changes in the expression levels of these genes could be explained by changes in their methylation status. Male rats were treated daily with an oral physiological dose of leptin or vehicle during the suckling period. After weaning, animals were fed with a normal-fat or a high-fat (HF) diet until aged 6 months. DNA was extracted from the hypothalamus and methylation within the promoter regions of the gene panel was measured by pyrosequencing. Pomc promoter methylation increased in control animals fed the HF diet but decreased in leptin-treated animals. In addition, there was a weak negative correlation between DNA methylation and POMC mRNA levels (P = 0·075). There were no changes in the methylation status of the CpG sites studied within the promoter regions of Lepr and Socs3 in response to leptin or HF treatments. This is the first demonstration that leptin treatment during lactation may programme methylation of an appetite-related gene in the hypothalamus of animals fed HF diets, with possible implications for gene expression and protection against the development of obesity.

Serotonin (5-hydroxytryptamine; 5-HT) 2C receptors and the downstream melanocortin pathway are suggested to mediate the appetite-suppressing effects of 5-HT drugs such as m-chlorophenylpiperazine (mCPP) and fenfluramine. Here, we report that fluvoxamine (3–30 mg/kg), a selective serotonin reuptake inhibitor (SSRI), in the presence of SB 242084 (1–2 mg/kg), a selective 5-HT2C receptor antagonist, exerts appetite-suppressing effects while fluvoxamine or SB 242084 alone has no effect. The appetite-suppressing effects were attenuated in the presence of SB 224289 (5 mg/kg), a selective 5-HT1B receptor antagonist. Moreover, CP 94253 (5–10 mg/kg), a selective 5-HT1B receptor agonist, exerted appetite-suppressing effects and significantly increased hypothalamic pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) gene expression and decreased hypothalamic orexin gene expression. These results suggest that fluvoxamine and inactivation of 5-HT2C receptors exert feeding suppression through activation of 5-HT1B receptors, and that 5-HT1B receptors up-regulate hypothalamic POMC and CART gene expression and down-regulate hypothalamic orexin gene expression in mice.