Polymorphisms in the fat mass and obesity-associated gene (FTO) are associated with human obesity and obesity-prone behaviors, including increased food intake and a preference for energy-dense foods. FTO demethylates N 6 -methyladenosine, a potential regulatory RNA modification, but the mechanisms by which FTO predisposes humans to obesity remain unclear. In adiposity-matched, normal-weight humans, we showed that subjects homozygous for the FTO "obesity-risk" rs9939609 A allele have dysregulated circulating levels of the orexigenic hormone acyl-ghrelin and attenuated postprandial appetite reduction. Using functional MRI (fMRI) in normal-weight AA and TT humans, we found that the FTO genotype modulates the neural responses to food images in homeostatic and brain reward regions. Furthermore, AA and TT subjects exhibited divergent neural responsiveness to circulating acyl-ghrelin within brain regions that regulate appetite, reward processing, and incentive motivation. In cell models, FTO overexpression reduced ghrelin mRNA N 6 -methyladenosine methylation, concomitantly increasing ghrelin mRNA and peptide levels. Furthermore, peripheral blood cells from AA human subjects exhibited increased FTO mRNA, reduced ghrelin mRNA N 6 -methyladenosine methylation, and increased ghrelin mRNA abundance compared with TT subjects. Our findings show that FTO regulates ghrelin, a key mediator of ingestive behavior, and offer insight into how FTO obesity-risk alleles predispose to increased energy intake and obesity in humans.Introduction FTO is an AlkB-like 2-oxoglutarate-dependent nucleic acid demethylase of uncertain cellular function (1). Genome-wide association studies (GWAS) have reliably established that SNPs within the first intron of FTO are robustly associated with increased BMI and adiposity across different ages and populations (2-6). Subjects homozygous for the "obesity-risk" A allele of FTO rs9939609 have a 1.7-fold increased risk for obesity compared with subjects homozygous for the low-risk T allele (2). Evidence to date suggests that the association between SNPs in FTO and BMI is predominantly driven by increased energy intake. Subjects homozygous for the obesity-risk A allele of rs9939609 exhibit overall increased ad libitum food-intake (7-9), particularly fat consumption (7, 9-11), and impaired satiety (12, 13). Furthermore, preschool AA children (AA denotes homozygosity for the A obesity-risk allele in the rs9939609 FTO variant) exhibit obesity-prone eating behaviors, including increased food responsiveness and a tendency to eat in

OBJECTIVEBariatric surgery causes durable weight loss. Gut hormones are implicated in obesity pathogenesis, dietary failure, and mediating gastrointestinal bypass (GIBP) surgery weight loss. In mice, we determined the effects of diet-induced obesity (DIO), subsequent dieting, and GIBP surgery on ghrelin, peptide YY (PYY), and glucagon-like peptide-1 (GLP-1). To evaluate PYY’s role in mediating weight loss post-GIBP, we undertook GIBP surgery in PyyKO mice.RESEARCH DESIGN AND METHODSMale C57BL/6 mice randomized to a high-fat diet or control diet were killed at 4-week intervals. DIO mice underwent switch to ad libitum low-fat diet (DIO-switch) or caloric restriction (CR) for 4 weeks before being killed. PyyKO mice and their DIO wild-type (WT) littermates underwent GIBP or sham surgery and were culled 10 days postoperatively. Fasting acyl-ghrelin, total PYY, active GLP-1 concentrations, stomach ghrelin expression, and colonic Pyy and glucagon expression were determined. Fasting and postprandial PYY and GLP-1 concentrations were assessed 30 days postsurgery in GIBP and sham pair-fed (sham.PF) groups.RESULTSDIO progressively reduced circulating fasting acyl-ghrelin, PYY, and GLP-1 levels. CR and DIO-switch caused weight loss but failed to restore circulating PYY to weight-appropriate levels. After GIBP, WT mice lost weight and exhibited increased circulating fasting PYY and colonic Pyy and glucagon expression. In contrast, the acute effects of GIBP on body weight were lost in PyyKO mice. Fasting PYY and postprandial PYY and GLP-1 levels were increased in GIBP mice compared with sham.PF mice.CONCLUSIONSPYY plays a key role in mediating the early weight loss observed post-GIBP, whereas relative PYY deficiency during dieting may compromise weight-loss attempts.

SummaryThe lateral habenula has been widely studied for its contribution in generating reward-related behaviors [1, 2]. We have found that this nucleus plays an unexpected role in the sedative actions of the general anesthetic propofol. The lateral habenula is a glutamatergic, excitatory hub that projects to multiple targets throughout the brain, including GABAergic and aminergic nuclei that control arousal [3, 4, 5]. When glutamate release from the lateral habenula in mice was genetically blocked, the ability of propofol to induce sedation was greatly diminished. In addition to this reduced sensitivity to propofol, blocking output from the lateral habenula caused natural non-rapid eye movement (NREM) sleep to become highly fragmented, especially during the rest (“lights on”) period. This fragmentation was largely reversed by the dual orexinergic antagonist almorexant. We conclude that the glutamatergic output from the lateral habenula is permissive for the sedative actions of propofol and is also necessary for the consolidation of natural sleep.

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