A new endogenous form of PYY isolated from canine ileum: Gly-extended PYY(1-36)

We purified and identified the peptide YY (PYY) forms present and determined their levels from a portion of the canine ileum directly adjacent to the cecum by a new extraction method designed to prevent and evaluate degradation of endogenous peptides. We used three reverse phase chromatography steps with radioimmunoassay of fractions for PYY-like-immunoreactivity (PYY-LI). The purified fractions underwent intact protein/peptide mass spectrometry identification and sequencing (i.e. "top-down" MS analysis). This analysis confirmed the identity of a new form of PYY, PYY(1-36)-Gly, which co-elutes with PYY(1-36)-NH(2) through all three of separation steps used. The PYY(1-36)-Gly form represents approximately 20% of the total PYY found in this region of the canine intestine. In addition, we also found that the PYY(3-36)-NH(2) form represents 6% of the total PYY in the canine ileo-cecal junction. The physiological implication of the Gly-extended form of PYY(1-36) warrants further investigation.     

Comparison of the inhibitory effects of PYY(3-36) and PYY(1-36) on gastric emptying in rats

We compared the effects of the two molecular forms of the brain-gut peptide YY (PYY), PYY(1-36) and PYY(3-36), on gastric emptying. Unanesthetized rats received 20-min intravenous infusions of rat PYY(1-36) (0, 1.7, 5, 17, 50, 100, 170 pmol x kg(-1) x min(-1)) and rat PYY(3-36) (0, 0.5, 1.7, 5, 17, 50, 100, 170 pmol x kg(-1) x min(-1)), either alone or combined, and gastric emptying of saline was measured during the last 10 min of infusion. For comparison, human PYY(3-36) was administered at 0, 17, and 50 pmol x kg(-1) x min(-1). Gastric emptying was decreased by 11, 24, 26 and 38% in response to 17, 50, 100, and 170 pmol x kg(-1) x min(-1) of rat PYY(1-36); by 10, 26, 41, 53, and 57% in response to 5, 17, 50, 100, and 170 pmol x kg(-1) x min(-1) of rat PYY(3-36); and by 35 and 53% in response to 17 and 50 pmol x kg(-1) x min(-1) of human PYY(3-36), respectively. Estimated ED50s were 470 and 37 pmol x kg(-1) x min(-1) for rat PYY(1-36) and PYY(3-36), respectively. In general, within an experiment, coadministration of PYY(1-36) and PYY(3-36) inhibited gastric emptying by an amount that was comparable to that produced when either peptide was given alone. We conclude that 1) intravenous infusion of PYY(1-36) and PYY(3-36) each produces a dose-dependent inhibition of gastric emptying in rats, 2) PYY(3-36) is an order of magnitude more potent than PYY(1-36) in inhibiting gastric emptying, 3) human PYY(3-36) and rat PYY(3-36) inhibit gastric emptying similarly, and 4) PYY(1-36) and PYY(3-36) do not appear to interact in an additive or synergistic manner to inhibit gastric emptying.     

Peripheral administration of PYY(3-36) produces conditioned taste aversion in mice

Peptide YY (PYY) is a postprandially released gut hormone. Peripheral administration of one form of the peptide PYY3-36 produces a short-term reduction in food intake in rodents. Initial reports suggested that effects of PYY3-36 on food intake are mediated by increasing the anorexigenic drive from melanocortin neurons in the hypothalamic arcuate nucleus. However, more recent data have demonstrated that the anorexigenic activity of PYY3-36 is not dependent on melanocortin ligands or their receptors in the CNS. We demonstrate here that the anorexigenic actions of PYY3-36 are also not dependent on the vagus nerve, a common pathway of satiety signaling. Peripherally administered PYY3-36 activates neurons in the area postrema and nucleus tractus solitarius, brainstem areas known to mediate effects of certain aversive stimuli. Furthermore, peripheral administration of PYY3-36 causes conditioned taste aversion in mice. Thus, inhibition of food intake by PYY3-36 may result in part from induction of an aversive response.     

A novel human Gal-3-O-sulfotransferase: molecular cloning, characterization, and its implications in biosynthesis of (SO(4)-3)Galbeta1-4(Fucalpha1-3)GlcNAc

Based on sequence homology with the previously cloned human cerebroside sulfotransferase (CST) cDNA, a novel sulfotransferase was cloned by screening a human fetal brain cDNA library. The novel sulfotransferase gene was present on human chromosome 11q13; the location was different from human CST and from that of the recently cloned human beta-Gal 3'-sulfotransferase (GP3ST). The isolated cDNA contained an open reading frame that encoded a predicted protein of 431 amino acid residues with type II transmembrane topology. The amino acid sequence showed 33% identity with that of human CST and 38% with that of human GP3ST. The recombinant enzyme expressed in Chinese hamster ovary cells catalyzed transfer of sulfate to position 3 of non-reducing beta-galactosyl residues in Galbeta1-4GlcNAc. Type 2 chains served as good acceptors, whereas type 1 chains served as poor acceptors, and intermediate activity was found toward Galbeta1-3GalNAc. Therefore, the substrate specificity was different from that of GP3ST. CST activity was not detected in the newly cloned enzyme. Northern blotting analysis showed that the sulfotransferase mRNA was strongly expressed in the thyroid and moderately expressed in the brain, heart, kidney, and spinal cord. Co-transfection of the enzyme cDNA and fucosyltransferase III into COS-7 cells resulted in expression of (SO(4)-3)Galbeta1-4(Fucalpha1-3)GlcNAc and a small amount of (SO(4)-3)Galbeta1-3(Fucalpha1-4)GlcNAc. These results indicated that the newly cloned enzyme is a novel Gal-3-O-sulfotransferase and is involved in biosynthesis of the (SO(4)-3)Galbeta1-4(Fucalpha1-3)GlcNAc structure.     

Primary structures of PYY, [Pro(34)]PYY, and PYY-(3-36) confer different conformations and receptor selectivity

We synthesized PYY-(1-36) (nonselective between Y(1) and Y(2) receptor subtype agonists), [Pro(34)]PYY (selective for Y(1)), and PYY-(3-36) (selective for Y(2)) to determine whether solution conformation plays a role in receptor subtype selectivity. The three peptides exhibited the expected specificities in displacing labeled PYY-(1-36) from cells transfected with Y(1) receptors (dissociation constants = 0.42, 0.21, and 1,050 nM, respectively) and from cells transfected with Y(2) receptors (dissociation constants = 0.03, 710, and 0.11 nM, respectively) for PYY-(1-36), [Pro(34)]PYY, and PYY-(3-36). Sedimentation equilibrium analyses revealed that the three PYY analogs were 80-90% monomer at the concentrations used for the subsequent circular dichroism (CD) and (1)H-nuclear magnetic resonance (NMR) studies. CD analysis measured helicities for PYY-(1-36), [Pro(34)]PYY, and PYY-(3-36) of 42%, 31%, and 24%, suggesting distinct differences in secondary structure. The backbone (1)H-NMR resonances of the three peptides further substantiated marked conformational differences. These patterns support the hypothesis that Y(1) and Y(2) receptor subtype binding affinities depend on the secondary and tertiary solution state structures of PYY and its analogs.     

Expression and purification of human PYY(3-36) in Escherichia coli using a His-tagged small ubiquitin-like modifier fusion

Human PYY(3-36) (hPYY3-36) is a 34 amino acid hormone that has received a great deal of attention due to its effects on appetite regulation. hPYY(3-36) was modified at the N-terminus with an octahistidine tag and factor Xa protease sequence along with the small ubiquitin-like modifier (SUMO) tag and expressed in Escherichia coli. The protein was purified from clarified E. coli lysate by immobilized metal affinity chromatography (IMAC) with a yield of 30±7mg/L of induced culture returned as an average over seven runs, and its identity was confirmed by Western blot and hPYY antibody recognition. The SUMO-tagged hPYY(3-36) was digested with two different proteases to return either His-tagged hPYY(3-36) or unmodified hPYY(3-36): (1) digestion with SUMO protease proceeded at about 50% efficiency yielding His-tagged hPYY(3-36); (2) digestion with factor Xa protease proceeded at greater than 90% efficiency yielding final hPYY(3-36). Products were purified from the digestion mixtures by reverse-phase high-performance liquid chromatography (C(18)) or IMAC, respectively, the identities were confirmed by mass spectrometry and hPYY antibody recognition, and the folded state of His-tagged hPYY(3-36) was investigated by circular dichroism spectroscopy.     

Effects of PYY1-36 and PYY3-36 on appetite, energy intake, energy expenditure, glucose and fat metabolism in obese and lean subjects

Nitric oxide (NO) and 5'-AMP-activated protein kinase (AMPK) are involved in glucose transport and mitochondrial biogenesis in skeletal muscle. Here, we examined whether NO regulates the expression of the major glucose transporter in muscle (GLUT4) and whether it influences AMPK-induced upregulation of GLUT4. At low levels, the NO donor S-nitroso-N-penicillamine (SNAP, 1 and 10 microM) significantly increased GLUT4 mRNA ( approximately 3-fold; P < 0.05) in L6 myotubes, and cotreatment with the AMPK inhibitor compound C ablated this effect. The cGMP analog 8-bromo-cGMP (8-Br-cGMP, 2 mM) increased GLUT4 mRNA by approximately 50% (P < 0.05). GLUT4 protein expression was elevated 40% by 2 days treatment with 8-Br-cGMP, whereas 6 days treatment with 10 microM SNAP increased GLUT4 expression by 65%. Cotreatment of cultures with the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one prevented the SNAP-induced increase in GLUT4 protein. SNAP (10 microM) also induced significant phosphorylation of alpha-AMPK and acetyl-CoA carboxylase and translocation of phosphorylated alpha-AMPK to the nucleus. Furthermore, L6 myotubes exposed to 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR) for 16 h presented an approximately ninefold increase in GLUT4 mRNA, whereas cotreatment with the non-isoform-specific NOS inhibitor N(G)-nitro-l-arginine methyl ester, prevented approximately 70% of this effect. In vivo, GLUT4 mRNA was increased 1.8-fold in the rat plantaris muscle 12 h after AICAR injection, and this induction was reduced by approximately 50% in animals cotreated with the neuronal and inducible nitric oxide synthases selective inhibitor 1-(2-trifluoromethyl-phenyl)-imidazole. We conclude that, in skeletal muscle, NO increases GLUT4 expression via a cGMP- and AMPK-dependent mechanism. The data are consistent with a role for NO in the regulation of AMPK, possibly via control of cellular activity of AMPK kinases and/or AMPK phosphatases.     

The PP-fold solution structure of human polypeptide YY and human PYY3-36 as determined by NMR

PYY3-36 is a biopharmaceutical antiobesity agent under development as well as an endogenous satiety hormone, which is generated by dipeptidyl peptidase-IV digestion of polypetide YY (PYY), and in contrast to the parent hormone, PYY is highly selective for the Y2 versus the Y1 receptor. NMR analysis revealed a highly ordered, back-folded structure for human PYY in aqueous solution similar to the classical PP-fold structure of pancreatic polypeptide. The NMR analysis of PYY3-36 also showed a folded structure resembling a PP-fold, which however was characterized by far fewer long distance NOEs than the PP-fold observed in the full-length peptide. This suggests that either a conformational change has occurred in the N-terminal segment of PYY3-36 or that this segments is characterized by larger dynamics. The study supports the notion that the PP-fold is crucial for establishing simultaneous interactions with two subsites in the receptor for binding of, respectively, the N- and C-terminal ends of PYY. The Y2 receptor only requires recognition of the C-terminal segment of the molecule as displayed by the Y2 selective PYY3-36.     

Enhancement of feeding suppression by PYY(3-36) in rats with area postrema ablations

We investigated suppression of food intake by intraperitoneal (IP) injections of peptide YY(3-36) (PYY(3-36)) (24, 60, or 150 microg/kg) in rats with ablations of the area postrema (APX) and in controls with sham ablations. In controls, PYY(3-36)-induced suppression was modest and short-lived, averaging 20% at most and persisting less than 6h. The highest dose tested (150 microg/kg) was even less effective than were the two lesser doses after 3h. APX did not diminish the potency of these effects of PYY(3-36). In fact, the magnitude of suppression produced by the greatest dose of PYY(3-36) in APX rats was significantly greater than in controls and PYY(3-36)-induced suppression was still present at 24h.     

Effect of subcutaneous injections of PYY1-36 and PYY3-36 on appetite, ad libitum energy intake, and plasma free fatty acid concentration in obese males

Intraveneous (i.v.) PYY(3-36) infusions have been reported to reduce energy intake (EI) in humans, whereas few studies exist on effects of PYY(1-36). The aim of the present study was to examine effects of subcutaneous (sc) injections of PYY(1-36) and PYY(3-36) on appetite, ad libitum EI, plasma concentrations of PYY and free fatty acids (FFA) in obese males. Twenty-four males (BMI 27-40 kg/m(2)) were randomly assigned to two groups receiving sc injections of either PYY(1-36) or PYY(3-36) in a blinded, placebo-controlled, dose-escalating, cross-over study. Subjects were studied 5 days in succession, with escalating doses of PYY(1-36) [saline, 50, 100, 150, and 200 pmol PYY(1-36)/kg lean body mass (LBM)], or PYY(3-36) (saline, 25, 50, 75, and 100 pmol PYY(3-36)/kg LBM), respectively. PYY injections resulted in dose-dependent increases in plasma PYY levels but no effect on EI in either the PYY(1-36) or the PYY(3-36) group. However, increasing doses of PYY(3-36), but not PYY(1-36), resulted in increased ratings of satiety and decreased ratings of hunger, thirst, and prospective food consumption. Although not dose dependently, significant elevation of plasma FFA was seen after injection of PYY(3-36), but not PYY(1-36). Although sc administration of PYY was well tolerated, it remains to be determined whether high-dose PYY(3-36) is sufficient in reducing EI in long-term trials, and if so, whether the reduction in EI occurs without nausea. PYY(1-36) is unlikely to be important in regulating energy intake. The PYY(3-36) administrations caused a non-dose-dependent mobilization of FFA, likely through a direct effect.     

Peptide YY containing enteroendocrine cells and peripheral tissue sensitivity to PYY and PYY(3-36) are maintained in diet-induced obese and diet-resistant rats

Peptide YY (PYY) is a gastrointestinal hormone, localized in enteroendocrine L-cells. Its hydrolyzed form PYY(3-36) is a satiety factor. The aim of this study was to identify if intestinal PYY enteroendocrine cells or content correlate with the diet-induced obese (DIO) or diet-resistant (DR) phenotypes. We also examined intestinal sensitivity to PYY and PYY(3-36) in DIO and DR rats. Animals were maintained on a medium-high fat diet and split into DIO and DR groups based on weight gain. PYY immunoreactive cells were unaltered in DIO intestine and stomach compared to DR rats. PYY content and circulating levels were also unchanged in DIO rats. Intestinal PYY and PYY(3-36) responses were enhanced in fasted rats, and equipotent in both DIO and DR jejunum. We conclude that PYY cell number, tissue content and peripheral sensitivity are maintained in DIO rats. Our data suggests that neither PYY nor PYY(3-36) contribute to the maintenance of either the DIO or DR phenotype, and that peripheral resistance to PYY and PYY(3-36) does not accompany DIO.     

Leptin extends the anorectic effects of chronic PYY(3-36) administration in ad libitum-fed rats

Acute administration of peptide YY(3-36) [PYY(3-36)] results in a reduction in food intake in several different vertebrates. However, long-term continuous administration of PYY(3-36) causes only a transient reduction in food intake, thus potentially limiting its therapeutic efficacy. We hypothesized that a fall in leptin levels associated with reduced food intake could contribute to the transient anorectic effects of continuous PYY(3-36) infusion and thus that leptin replacement might prolong the anorectic effects of PYY(3-36). Seven-day administration of 100 microg x kg body wt(-1) x day(-1) PYY(3-36) using osmotic minipumps caused a significant reduction in food intake of ad libitum-fed rats, but only for the first 2 days postimplantation. Circulating levels of leptin were reduced 1 day following continuous infusion of PYY(3-36), and combined leptin infusion at a dose of leptin that had no anorectic effects on its own (100 microg x kg body wt(-1) x day(-1)) prolonged the anorectic actions of PYY(3-36) in ad libitum-fed rats for up to 6 days postimplantation and yielded reduced weight gain compared with either peptide alone. The inhibitory effects of 100 microg x kg body wt(-1) x day(-1) PYY(3-36) on food intake were absent in rats refed after a 24-h fast and substantially reduced at a dose of 1,000 microg x kg body wt(-1) x day(-1) PYY(3-36). Leptin replacement was unable to recover the anorectic effects of PYY(3-36) in fasted rats. Our results suggest that an acute fall in leptin levels is not solely responsible for limiting duration of action of chronic PYY(3-36) infusion, yet chronic coadministration of a subanorectic dose of leptin can extend the anorectic effects of PYY(3-36).     

PYY(3-36) into the arcuate nucleus inhibits food deprivation-induced increases in food hoarding and intake

Central administration of neuropeptide Y (NPY) increases food intake in laboratory rats and mice, as well as food foraging and hoarding in Siberian hamsters. The NPY-Y1 and Y5 receptors (Rs) within the hypothalamus appear sufficient to account for these increases in ingestive behaviors. Stimulation of NPY-Y2Rs in the Arcuate nucleus (Arc) has an anorexigenic effect as shown by central or peripheral administration of its natural ligand peptide YY (3-36) and pharmacological NPY-Y2R antagonism by BIIE0246 increases food intake. Both effects on food intake by NPY-Y2R agonism and antagonism are relatively short-lived lasting ∼4 h. The role of NPY-Y2Rs in appetitive ingestive behaviors (food foraging/hoarding) is untested, however. Therefore, Siberians hamsters, a natural food hoarder, were housed in a semi-natural burrow/foraging system that had (a) foraging requirement (10 revolutions/pellet), no free food (true foraging group), (b) no running wheel access, free food (general malaise control) or (c) running wheel access, free food (exercise control). We microinjected BIIE0246 (antagonist) and PYY_(3-36) (agonist) into the Arc to test the role of NPY-Y2Rs there on ingestive behaviors. Food foraging, hoarding, and intake were not affected by Arc BIIE0246 microinjection in fed hamsters 1, 2, 4, and 24 h post injection. Stimulation of NPY-Y2Rs by PYY_(3-36) inhibited food intake at 0–1 and 1–2 h and food hoarding at 1–2 h without causing general malaise or affecting foraging. Collectively, these results implicate a sufficiency, but not necessity, of the Arc NPY-Y2R in the inhibition of food intake and food hoarding by Siberian hamsters.     

Synthesis and structural characterization of 1-(D-glycosyloxy)phthalazines

Coupling of the trimethylsilyl derivative of (2H)phthalazin-1-one with 1,2,3,4,6-penta-O-acetyl-alpha-D-glucopyranose and 1,2,3,4,6-penta-O-acetyl-alpha-D-galactopyranose in the presence of stannic chloride gave the respective glycosides, 2-(per-O-acetyl-D-glycosyloxy)phthalazines, which upon deacetylation gave the respective unprotected analogues. Under the same conditions 1,2,3,5-tetra-O-acetyl-beta-D-ribofuranose gave 1-(2,3,5-tri-O-acetyl-alpha-D-ribofuranosyloxy)phthalazine. Electrospray mass spectrometry aided the structural characterization of this series of 1-(D-glycosylyloxy)phthalazines. Low energy collisionally-induced dissociation tandem mass spectrometry of the protonated molecules confirmed the MS fragmentation routes and the structural identities of this novel series of glycosides.     

NMR structural characterization of cecropin A(1-8) - magainin 2(1-12) and cecropin A (1-8) - melittin (1-12) hybrid peptides.

In order to elucidate the structure-antibiotic activity relationships of the peptides, the three-dimensional structures of two hybrid peptides, CA(1-8) - MA(1-12) and CA(1-8) - ME(1-12) in trifluoroethanol-containing aqueous solution were investigated by NMR spectroscopy. Both CA(1-8) - MA(1-12) and CA(1-8) - ME(1-12) have strong antibacterial activity but only CA(1-8) - ME(1-12) has hemolytic activity against human erythrocytes. CA(1-8) - MA(1-12) has a hydrophobic 310-helix of only two turns combined with one short helix in the N-terminus with a flexible hinge section in between. CA(1-8) - MA(1-12) has a severely bent structure in the middle of the peptide. These structural features as well as the low hydrophobicity of CA(1-8) - MA(1-12) seem to be crucial for the selective lysis against the membrane of prokaryotic cells. CA(1-8) - ME(1-12) has an alpha-helical structure of about three turns in the melittin domain and a flexible structure with one turn in the cecropin domain connected with a flexible hinge section in between, and these might be the structural features required for membrane disruption against prokaryotic and eukaryotic cells. The central hinge region (Gly9-Ile10-Gly11) in an amphipathic antibacterial peptide is considered to play an important role in providing the conformational flexibility required for ion channel formation of the C-terminal hydrophobic alpha-helix on cell membrane.     

A new electrophoretically distinguishable variant of human diaphorase locus 3(DIA3): DIA3 6-1

Summary A new electrophoretic variant of the diaphorase locus 3 termed DIA3 6-1 has been detected in one Polish man during a population study.     

PYY (3-36) protects against high fat feeding induced changes of pancreatic islet and intestinal hormone content and morphometry

BackgroundProlonged high fat feeding negatively impacts pancreatic and intestinal morphology. In this regard, direct effects of PYY(3–36) on intestinal cell and pancreatic islet morphometry are yet to be fully explored in the setting of obesity.MethodsWe examined the influence of 21-days twice daily treatment with PYY(3–36) on these parameters in mice fed a high fat diet (HFD).ResultsPYY(3–36) treatment decreased food intake, body weight and circulating glucose in HFD mice. In terms of intestinal morphology, crypt depth was restored to control levels by PYY(3–36), with an additional enlargement of villi length. PYY(3–36) also reversed HFD-induced decreases of ileal PYY, and especially GLP-1, content. HFD increased numbers of PYY and GIP positive ileal cells, with PYY(3–36) fully reversing the effect on PYY cell detection. There were no obvious differences in the overall number of GLP-1 positive ileal cells in all mice, barring PYY(3–36) marginally decreasing GLP-1 villi cell immunoreactivity. Within pancreatic islets, PYY(3–36) significantly decreased alpha-cell area, whilst islet, beta-, PYY- and delta-cell areas remained unchanged. However, PYY(3–36) increased the percentage of beta-cells while also reducing percentage alpha-cell area. This was related to PYY(3-36)-induced reductions of beta-cell proliferation and apoptosis frequencies. Co-localisation of islet PYY with glucagon or somatostatin was elevated by PYY(3–36), with GLP-1/glucagon co-visualisation increased when compared to lean controls.ConclusionPYY(3–36) exerts protective effects on pancreatic and intestinal morphology in HFD mice linked to elevated ileal GLP-1 content.General significanceThese observations highlight mechanisms linked to the metabolic and weight reducing benefits of PYY(3–36).     

PYY(3-36) reduces food intake and body weight and improves insulin sensitivity in rodent models of diet-induced obesity

The gut hormone peptide YY (PYY) was recently proposed to comprise an endogenous satiety factor. We have studied acute anorectic functions of PYY(3-36) in mice and rats, as well as metabolic effects of chronic PYY(3-36) administration to diet-induced obese (DIO) mice and rats. A single intraperitoneal injection of PYY(3-36) inhibited food intake in mice, but not in rats. We next investigated the effects of increasing doses (100, 300, and 1,000 microg.kg-1.day-1) of PYY(3-36) administered subcutaneously via osmotic minipumps on food intake and body weight in DIO C57BL/6J mice. Whereas only the highest dose (1,000 microg.kg-1.day-1) of PYY(3-36) significantly reduced food intake over the first 3 days, body weight gain was dose dependently reduced, and on day 28 the group treated with 1,000 microg.kg-1.day-1 PYY(3-36) weighed approximately 10% less than the vehicle-treated group. Mesenteric, epididymal, retroperitoneal, and inguinal fat pad weight was dose dependently reduced. Subcutaneous administration of PYY(3-36) (250 and 1,000 microg.kg-1.day-1) for 28 days reduced body weight and improved glycemic control in glucose-intolerant DIO rats. Neither 250 nor 1,000 microg/kg PYY(3-36) elicited a conditioned taste aversion in male rats.     

The gut hormones PYY 3-36 and GLP-1 7-36 amide reduce food intake and modulate brain activity in appetite centers in humans

Obesity is a major public health issue worldwide. Understanding how the brain controls appetite offers promising inroads toward new therapies for obesity. Peptide YY (PYY) and glucagon-like peptide 1 (GLP-1) are coreleased postprandially and reduce appetite and inhibit food intake when administered to humans. However, the effects of GLP-1 and the ways in which PYY and GLP-1 act together to modulate brain activity in humans are unknown. Here, we have used functional MRI to determine these effects in healthy, normal-weight human subjects and compared them to those seen physiologically following a meal. We provide a demonstration that the combined administration of PYY(3-36) and GLP-1(7-36 amide) to fasted human subjects leads to similar reductions in subsequent energy intake and brain activity, as observed physiologically following feeding.