Role of hypothalamic leptin-LepRb signaling in NPY-CART-mediated appetite suppression in amphetamine-treated rats.

Leptin is an adipose tissue hormone which plays an important role in regulating energy homeostasis. Amphetamine (AMPH) is a drug of appetite suppressant, which exerts its effect by decreasing the expression of hypothalamic neuropeptide Y (NPY) and increasing that of cocaine- and amphetamine-regulated transcript (CART). This study investigated whether leptin, the leptin receptor (LepRb) and the signal transducer and activator of transcription-3 (STAT3) were involved in NPY/CART-mediated appetite suppression in AMPH-treated rats. Rats were given AMPH daily for four days, and changes in the levels of blood leptin and hypothalamic NPY, CART, LepRb, Janus kinases 2 (JAK2), and STAT3 were assessed and compared. During the AMPH treatment, blood leptin levels and hypothalamic NPY expression decreased, with the largest reduction observed on Day 2. By contrast, the expression of hypothalamic CART, LepRb, JAK2, and STAT3 increased, with the maximum response on Day 2. Furthermore, the binding activity of pSTAT3/DNA increased and was expressed in similar pattern to that of CART, LepRb, and JAK2. An intracerebroventricular infusion of NPY antisense 60min prior to AMPH treatment increased the levels of leptin, as well as the expression in LepRb, JAK2, and CART, whereas an infusion of STAT3 antisense decreased these levels and the expression of these parameters. The results suggest that blood leptin and hypothalamic LepRb-JAK2-STAT3 signaling involved in NPY-CART-regulated appetite suppression in AMPH-treated rats. The findings may aid understanding the role of leptin-LepRb during the treatment of anorectic drugs.

Participation of ghrelin signalling in the reciprocal regulation of hypothalamic NPY/POMC-mediated appetite control in amphetamine-treated rats.

Hypothalamic neuropeptide Y (NPY) and proopiomelanocortin (POMC) have been documented to participate in amphetamine (AMPH)-induced appetite suppression. This study investigated whether ghrelin signalling is associated with changes in NPY/POMC-mediated appetite control. Rats were given AMPH daily for four days, and changes in food intake, body weight, plasma ghrelin, hypothalamic NPY, melanocortin 3 receptor (MC3R), ghrelin O-acyltransferase (GOAT), acyl ghrelin (AG) and ghrelin receptor (GHSR1a) were examined and compared. Food intake, body weight and NPY expression decreased, while MC3R expression increased and expressed reciprocally to NPY expression during AMPH treatment. Plasma ghrelin and hypothalamic AG/GOAT/GHSR1a expression decreased on Day 1 and Day 2, which was associated with the positive energy metabolism, and returned to normal levels on Day 3 and Day 4, which was associated with the negative energy metabolism; this expression pattern was similar to that of NPY. Infusion with a GHSR1a antagonist or an NPY antisense into the brain enhanced the decrease in NPY and AG/GOAT/GHSR1a expression and the increase in MC3R expression compared to the AMPH-treated group. Peripheral ghrelin and the central ghrelin system participated in the regulation in AMPH-induced appetite control. These results shed light on the involvement of ghrelin signalling in reciprocal regulation of NPY/POMC-mediated appetite control and may prove useful for the development of anti-obesity drugs.

Growth Modulation of Diabetic Factors and Antidiabetic Drugs on Prostate Cancer Cell Lines.

Risk factors for prostate cancer (PCa) include age, hormones, race, family history and diet. Recently, epidemiologic evidence has indicated that history of diabetes mellitus (DM) is inversely associated with risk of PCa. However, epidemiological investigations have yielded inconsistent results. Hence, the exact mechanism of DM-induced reduction in the incidence of PCa has yet to be fully elucidated. The aim of this study was to investigate the effects of DM factors, including glucose, insulin and insulin-like growth factor-1 (IGF-1), on the proliferation of PCa cell lines in vitro. Cell proliferation and expression of hormone receptors was examined in MTT assay and Western blot analysis, respectively. The results showed that DM factors did not affect the viability of androgen receptor (AR)-expressing PCa cell lines. However, cell proliferation increased after treatment with DM factors in androgen-independent PCa cell lines. On PCa tissue arrays, intensities of total AR and nuclear IGF-1R were higher in malignant tissues than in normal prostate glands. In terms of hormonal receptors, androgen-dependent LNCaP cells treated with insulin and IGF-1 in a low-serum medium showed decreased expression of insulin receptor beta (IRß) and elevated expression of IGF-1 receptor beta (IGF-1Rß). Moreover, expression of AR was upregulated after insulin and IGF-1 treatment in LNCaP cells, but not in the other PCa cell lines. Most of the studied antidiabetic drugs promoted the viability of PCa cells. However, metformin decreased the viability of AR-expressing PCa cells. These results suggest that diabetic factors modify the expression of AR, IR and IGF-1R to increase cancer cell proliferation. Moreover, the growth suppressing effects of metformin on PCa may be via the regulation of the AR signaling pathway.

Both neuropeptide Y knockdown and Y1 receptor inhibition modulate CART-mediated appetite control.

Amphetamine (AMPH)-induced appetite suppression has been attributed to its inhibition of neuropeptide Y (NPY)-containing neurons in the hypothalamus. This study examined whether hypothalamic cocaine- and amphetamine-regulated transcript (CART)-containing neurons and NPY Y1 receptor (Y1R) were involved in the action of AMPH. Rats were treated daily with AMPH for four days, and changes in feeding behavior and expression levels of NPY, CART, and POMC were assessed and compared. The results showed that both feeding behavior and NPY expression decreased during AMPH treatment, with the biggest reduction occurring on Day 2. By contrast, the expression of CART and melanocortin 3 receptor (MC3R), a member of the POMC neurotransmission, increased with the maximum response on Day 2, directly opposite to the NPY expression results. The intracerebroventricular infusion of NPY antisense or Y1R inhibitor both modulated AMPH-induced anorexia and the expression levels of MC3R and CART. The results suggest that in the hypothalamus both POMC- and CART-containing neurons participate in regulating NPY-mediated appetite control during AMPH treatment. These results may advance the knowledge of molecular mechanism of anorectic drugs.

Targeting oxidative stress in the hypothalamus: the effect of transcription factor STAT3 knockdown on endogenous antioxidants-mediated appetite control.

It has been reported that the redox sensing system in the hypothalamus participates in fuel metabolism and that endogenous antioxidants contribute to the regulation of phenylpropanolamine (PPA), an anorectic drug-induced appetite suppression. We explored whether the signal transducer and activator of transcription-3 (STAT3) is involved in PPA's action. Rats were given PPA once a day for 4 days. Changes in endogenous antioxidants, Janus kinase-2 (JAK2), STAT3, neuropeptide Y (NPY), and proopiomelanocortin (POMC), levels during PPA treatment were assessed and compared. Feeding, body weight, and NPY decreased with the biggest reduction on Day 2 during PPA treatment. Antioxidants, JAK2, pSTAT3, POMC expression, and STAT3/DNA-binding activity increased and were expressed in a pattern opposite to NPY expression. Moreover, cerebral STAT3 knockdown modified PPA-induced anorexia and antioxidants, POMC, and NPY expression. superoxide dismutase immunoreactivity in the hypothalamus increased and the inhibition of hypothalamic reactive oxygen species (ROS) production reversed antioxidants, STAT3, POMC, and NPY expression. It is suggested that hypothalamic JAK2-STAT3 participates in regulating antioxidants-mediated appetite control. This result may further the understanding of ROS-involved appetite control.

Inhibiting neuropeptide Y Y1 receptor modulates melanocortin receptor- and NF-κB-mediated feeding behavior in phenylpropanolamine-treated rats.

Neuropeptide Y (NPY) and nuclear factor-kappa B (NF-κB) are involved in regulating anorexia elicited by phenylpropanolamine (PPA), a sympathomimetic drug. This study explored whether NPY Y1 receptor (Y1R) is involved in this process, and a potential role for the proopiomelanocortin system was identified. Rats were given PPA once a day for 4days. Changes in the hypothalamic expression of the NPY, Y1R, NF-κB, and melanocortin receptor 4 (MC4R) levels were assessed and compared. The results indicated that food intake and NPY expression decreased, with the largest reductions observed on Day 2 (approximately 50% and 45%, respectively), whereas NF-κB, MC4R, and Y1R increased, achieving maximums on Day 2 (160%, 200%, and 280%, respectively). To determine the role of Y1R, rats were pretreated with Y1R antisense or a Y1R antagonist via intracerebroventricular injection 1h before the daily PPA dose. Y1R knockdown and inhibition reduced PPA anorexia and partially restored the normal expression of NPY, MC4R, and NF-κB. The data suggest that hypothalamic Y1R participates in the appetite-suppression from PPA by regulating MC4R and NF-κB. The results of this study increase our understanding of the molecular mechanisms in PPA-induced anorexia.

Neuropeptide Y Y1 receptor knockdown can modify glutathione peroxidase and c-AMP response element-binding protein in phenylpropanolamine-treated rats.

It has been reported that antioxidative enzymes, neuropeptide Y (NPY), and c-AMP response element-binding protein (CREB) are involved in regulating phenylpropanolamine (PPA)-mediated appetite suppression. Here, we investigated whether Y1 receptor (Y1R) might be involved in this regulation. Rats were daily treated with PPA for 4 days. Changes in the contents of NPY, Y1R, glutathione peroxidase (GP), and CREB were assessed and compared. Results showed that Y1R, GP, and CREB increased, with a maximal increase about 100, 200, and 150 %, respectively, on Day 2. By contrast, NPY decreased with a biggest reduction about 48 % on Day 2 and the pattern of expression during PPA treatment was opposite to those of Y1R, GP, and CREB. Central knockdown (using antisense) or inhibition (using antagonist) of Y1R expression modulated the anorectic response of PPA and the reciprocal regulation between NPY and GP (or CREB), revealing an essential role of Y1R in regulating NPY, GP, and CREB. These results suggest that Y1R participates in the reciprocal regulation of NPY, GP, and CREB in the hypothalamus during PPA treatment in conscious rats. The present results may aid the therapeutic research of PPA and related antiobesity drugs.

Knocking down the transcript of NF-kappaB modulates the reciprocal regulation of endogenous antioxidants and feeding behavior in phenylpropanolamine-treated rats.

It has been reported that oxidative stress, antioxidants, and neuropeptide Y (NPY) are involved in regulating the feeding behavior of phenylpropanolamine (PPA), a sympathomimetic drug. This study explored whether transcription factor NF-κB is involved in this effect. Rats were treated daily with PPA for 4 days. Changes in hypothalamic NF-κB, NPY, superoxide dismutase (SOD), and glutathione peroxidase (GPx) levels during PPA treatment were assessed and compared. Results showed that NF-κB, SOD, and GPx increased, with a maximal response on Day 2, while the food intake and NPY decreased with the biggest reduction on Day 2 during PPA treatment. To further determine whether NF-κB was involved, intracerebroventricular infusion of antisense oligonucleotide was performed at 1 h before daily PPA in free-moving rats. Cerebral NF-κB knockdown could modify PPA anorexia and the expressions of NPY, SOD, and GPx. It is suggested that hypothalamic NF-κB participates in the reciprocal regulation of NPY and antioxidants, which mediated the appetite-suppressing effect of PPA. Results may further the understanding of the molecular mechanisms of PPA.

The effect of protein kinase C-delta knockdown on anti-free radical enzyme and neuropeptide Y gene expression in phenylpropanolamine-treated rats.

Hypothalamic neuropeptide Y (NPY) has been reported to involve in regulating behavioral response of phenylpropanolamine (PPA), a sympathomimetic agent. This study explored if protein kinase C (PKC)-delta signaling participated in this regulation. Moreover, possible roles of anti-free radical enzyme catalase (CAT) and nitrogen oxide synthase (NOS) were also examined. Rats were treated daily with PPA for 4 days. Changes in food intake and hypothalamic NPY, PKCdelta, CAT, and NOS contents were assessed and compared. Results showed that PKCdelta and CAT increased during PPA treatment, which were concomitant with decreases in NPY content and food intake, while the change of NOS was expressed differently. Moreover, PKCdelta knockdown could modify PPA anorexia as well as NPY and CAT expression, while NOS expression remained unchanged. Furthermore, pre-treatment with NOS inhibitor could modify both PPA anorexia and NPY content. It is suggested that PKCdelta participates in the anorectic response of PPA via the modulation of NPY and CAT, while NOS contribute to this modulation via a different mechanism during PPA treatment. Results provide molecular mechanism of NPY-mediated PPA anorexia and may aid the therapeutic research of PPA and other anti-obesity drugs.

Peonidin 3-glucoside inhibits lung cancer metastasis by downregulation of proteinases activities and MAPK pathway.

Anthocyanins, present in various vegetables and fruits as a nature colorant, have broad activities including anticarcinogenesis and antimutagenesis, which are generally attributed to their antioxidant activities. However, limited studies have been available concerning the inhibitory effect of peonidin 3-glucoside (P3G) for cancer metastasis. Here, we demonstrated that P3G could significantly inhibit the invasion (P < 0.001), motility (P < 0.05), secretion of matrix metalloproteinase (MMP)-2, MMP-9, and urokinase-type plasminogen activator (u-PA) of lung cancer cells. Meanwhile, P3G attenuated phosphorylation of extracellular signal-regulated kinase (ERK)1/2, a member of mitogen-activated protein kinase (MAPK) family involved in the upregulation of MMPs and u-PA, and also inhibited the activation of activating protein-1 (AP-1) as shown by Western blot and electrophoretic mobility shift assay. Thus, the inhibitory effects of P3G may be at least partly through inactivation of ERK 1/2 and AP-1 signaling pathways as confirmed by abolishment of P3G-inhibited H1299 cell invasion by overexpression of MAPK kinase 1 (MEK1). Finally, P3G was evidenced by its inhibition on the metastasis of Lewis lung carcinoma cells in vivo (P < 0.001). Taken together, these findings suggested that P3G could reduce the metastasis of lung cancer cells, thereby constituting an adjuvant treatment for metastasis control.

Roles of protein kinase Calpha isozyme in the regulation of oxidative stress and neuropeptide Y gene expression in phenylpropanolamine-mediated appetite suppression.

Hypothalamic neuropeptide Y (NPY) is an appetite stimulant in the brain. Although regulation of NPY expression has been reported to contribute to the appetite-suppressing effect of phenylpropanolamine (PPA), it is still unknown if protein kinase C (PKC) is involved in this effect. Rats were daily treated with PPA for 4 days. Changes in food intake, hypothalamic NPY, PKC, and proopiomelanocortin (POMC) mRNA levels were assessed and compared. Results showed that the NPY gene was down-regulated following PPA treatment, which was parallel with the decrease of feeding. Moreover, several isotypes of PKC mRNA level (alpha, betaI, betaII, gamma, delta, eta, lambda, epsilon, and zeta) were changed. Among these, alpha, delta, and lambda PKC were up-regulated along with POMC gene expression which coincided with down-regulation of the NPY gene. To further determine if PKCalpha was involved, infusions of antisense oligonucleotide into the cerebroventricle were performed at 1 h before daily PPA treatment in free-moving rats. Results showed that PKCalpha knock-down could modify both anorexia induced by PPA and the NPY mRNA levels. Moreover, PKCalpha knock-down could also modify superoxide dismutase (SOD) gene expression. It is suggested that PKCalpha participates in the regulation of PPA-mediated appetite suppression via the modulation of NPY and SOD gene expression.

Double immunofluorescent evidence that oxidative stress-associated activation of JNK/AP-1 signaling participates in neuropeptide-mediated appetite control.

Amphetamine (AMPH), an appetite suppressant, alters expression levels of neuropeptide Y (NPY) and cocaine- and amphetamine-regulated transcript (CART) in the hypothalamus. This study explored the potential role of cJun-N-terminal kinases (JNK) in appetite control, mediated by reactive oxygen species (ROS) and activator protein-1 (AP-1) in AMPH-treated rats. Rats were given AMPH daily for 4 days. Changes in feeding behavior and expression levels of hypothalamic NPY, CART, cFos, cJun, phosphorylated JNK (pJNK), as well as those of anti-oxidative enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GP) and glutathione S-transferase (GST), were examined and compared. Following AMPH treatment, food intake and NPY expression decreased, whereas the other proteins expression and AP-1/DNA binding activity increased. Both cerebral cJun inhibition and ROS inhibition attenuated AMPH anorexia and modified detected protein, revealing a crucial role for AP-1 and ROS in regulating AMPH-induced appetite control. Moreover, both pJNK/CART and SOD/CART activities detected by double immunofluorescent staining increased in hypothalamic arcuate nucleus in AMPH-treated rats. The results suggested that pJNK/AP-1 signaling and endogenous anti-oxidants participated in regulating NPY/CART-mediated appetite control in rats treated with AMPH. These findings advance understanding of the molecular mechanism underlying the role of pJNK/AP-1 and oxidative stress in NPY/CART-mediated appetite suppression in AMPH-treated rats.

Role of hypoxia-inducible factor-1α in regulating oxidative stress and hypothalamic neuropeptides-mediated appetite control.

Hypoxia-inducible factor 1 (HIF-1) is a transcriptional activator responding to hypoxia. Amphetamine (AMPH), however, can activate HIF-1 under normoxic conditions, which is associated with the co-activation of oxidative stress. Hypothalamic neuropeptides and anti-oxidative enzymes have been found to participate in amphetamine (AMPH)-mediated appetite control. The present study examined whether HIF-1 was involved in the oxidative stress and anorectic action of AMPH. Rats were daily treated with AMPH for 4 days, and expression levels of HIF-1α, superoxide dismutase (SOD), catalase, neuropeptide Y (NPY), proopiomelanocortin (POMC), phosphatidylinositol 3-kinase (PI3K), and nuclear factor-kappaB (NF-κB) were assessed and compared. Results revealed that feeding behavior and NPY decreased, whereas HIF-1α/DNA binding activity and SOD, POMC, PI3K, and NF-κB expression levels increased in AMPH-treated rats. Further experiment revealed that intracerebroventricular (i.c.v.) pretreatment with HIF-1α inhibitor modified feeding behavior and expression levels of hypothalamic protein assessed. Another experiment revealed that pretreatment (i.c.v.) with reactive oxygen species scavenger modulated HIF-1α, NPY, POMC, PI3K, and NF-κB expression levels in AMPH-treated rats. It is suggested that HIF-1α plays a functional role in the increase of oxidative stress and the modulation of NFκB/NPY/POMC-mediated appetite control in AMPH-treated rats. These findings advance the knowledge of HIF-1α in the regulation of central dopamine agonist-mediated appetite control.

Interrupting activator protein-1 signaling in conscious rats can modify neuropeptide Y gene expression and feeding behavior of phenylpropanolamine.

The mechanism for phenylpropanolamine (PPA)-induced anorexia has been attributed to its inhibitory action on hypothalamic neuropeptide Y (NPY), an orexigenic agent abundant in the brain. However, molecular mechanisms behind this effect are not well known. In this study, we investigated whether activator protein-1 (AP-1) signaling was involved. Rats were daily treated with PPA for 4 days. Changes in hypothalamic NPY, c-fos, c-jun, superoxide dismutase (SOD)-1, and SOD-2 mRNA contents were measured and compared. Results showed that c-fos and c-jun mRNA levels were increased following PPA treatment, which were relevant to a reduction in NPY mRNA level. To further determine if c-fos/c-jun genes were involved in PPA anorexia, infusions of antisense oligonucleotide into cerebroventricle were performed before daily PPA treatment in freely moving rats. Results showed that either c-fos or c-jun knock down could block PPA anorexia and restore NPY mRNA content to normal level. It is suggested that AP-1 signaling may participate in the central regulation of PPA-mediated appetite suppression via the modulation of NPY gene expression. Moreover, this modulation might be partly because of the neuroprotective effect of AP-1 since SOD gene was activated during PPA treatment.

Transcriptional interruption of cAMP response element binding protein modulates superoxide dismutase and neuropeptide Y-mediated feeding behavior in freely moving rats.

The appetite-suppressing effect of phenylpropanolamine (PPA) has been attributed to its inhibitory action on neuropeptide Y (NPY), an appetite stimulant. However, molecular mechanisms underlying this effect are not clear. This study aimed to investigate if cAMP response element binding protein (CREB) signaling was involved. Moreover, possible role of superoxide dismutase-2 (SOD-2) during PPA treatment was also examined. Rats were daily treated with PPA for 4 days. Changes in hypothalamic NPY, protein kinase A, CREB, and SOD-2 mRNA contents were measured and compared. Results showed that protein kinase A, CREB, and SOD-2 mRNA levels increased during PPA treatment, which is concomitant with decreases in NPY and feeding. Moreover, CREB DNA binding activity detected by electromobility shift assay increased during PPA treatment, revealing an involvement of CREB-dependent gene transcription. Furthermore, infusions of CREB antisense oligonucleotide (or missense control) into cerebroventricle were performed at 1 h before daily PPA treatment in free-moving rats, and results showed that CREB knockdown could block PPA-induced anorexia and modify NPY and SOD-2 mRNA content toward normal. It is suggested that CREB signaling may participate in the central regulation of PPA-mediated appetite suppression via the modulation of NPY gene expression and that an increase of SOD-2 may favor this modulation.

Knockdown of the transcript of ERK in the brain modulates hypothalamic neuropeptide-mediated appetite control in amphetamine-treated rats.

BACKGROUND AND PURPOSE: Amphetamine is a releaser of dopamine stored in synaptic terminals, which can suppress appetite by changing the expression levels of neuropeptide Y (NPY) and proopiomelanocortin (POMC) in the hypothalamus. This study explored whether ERKs are involved in appetite control mediated by cAMP response element binding protein (CREB), NPY and POMC in amphetamine-treated rats. EXPERIMENTAL APPROACH: Rats were given amphetamine for 4 days, and changes in feeding behaviour and expression levels of phosphorylated-ERK (pERK), pCREB, NPY and melanocortin MC3 receptors were examined and compared. KEY RESULTS: Following amphetamine treatment, food intake, body weight and NPY expression decreased, whereas the expression of pERK, pCREB, MC3 receptors and pCREB/DNA binding activity increased. In amphetamine-treated rats, both cerebral ERK knockdown and pretreatment with a peripheral dopamine receptor antagonist decreased NPY but increased pERK, pCREB and MC3 receptor expression. Moreover, the immunofluorescence of hypothalamic pERK increased following amphetamine treatment. CONCLUSIONS AND IMPLICATIONS: These results suggest that ERK/CREB signalling participates in the effects mediated by dopamine receptor/NPY/POMC on appetite control in rats treated with amphetamine. These findings advance the knowledge on the involvement of ERK/CREB signalling in the reciprocal regulation by NPY and POMC of appetite after amphetamine treatment.

Transcript of protein kinase A knock-down modulates feeding behavior and neuropeptide Y gene expression in phenylpropanolamine-treated rats.

Neuropeptide Y (NPY) is an appetite-controlling neuromodulator that contributes to the appetite-suppressing effect of phenylpropanolamine (PPA). Aims of this study were to investigate whether protein kinase A (PKA) signaling is involved in regulating NPY gene expression and PPA-induced anorexia. Rats were given daily with PPA for 5 days. Changes in daily food intake and hypothalamic NPY, PKA, cAMP response element binding protein (CREB), and pro-opiomelanocortin (POMC) gene expression were measured and compared. To further determine if PKA was involved, intracerebroventricular infusions of antisense oligodeoxynucleotide were performed at 60 min before daily PPA treatment in freely moving rats. Results showed that daily PKA, CREB, and POMC expression were increased following PPA treatment, which showed a closely reverse relationship with alterations of decreased feeding behaviors and NPY mRNA levels. Results also showed that PKA knock-down could block PPA-induced anorexia as well as restore NPY mRNA level, indicating the involvement of PKA signaling in the regulation of NPY gene expression. It is suggested that hypothalamic PKA signaling may participate in the central regulation of PPA-mediated appetite suppression via the modulation of hypothalamic NPY gene expression. The present findings reveal that manipulations at the molecular level of PKA or cAMP may allow the development of therapeutic agents to improve the undesirable properties of PPA or other amphetamine-like anorectic drugs.

Roles of central catecholamine and hypothalamic neuropeptide Y genome in the development of tolerance to phenylpropanolamine-mediated appetite suppression.

Phenylpropanolamine (PPA) is an appetite suppressant. Repeated treatment with PPA can decrease food intake on initial days, but on subsequent days, food intake gradually returns to normal (tolerant effect). In an attempt to investigate the underlying mechanisms of PPA tolerance, the authors examined the roles of catecholamine (CAT) and hypothalamic neuropeptide Y (NPY) genome. Results revealed that pretreatment with either bupropion, a CAT transporter inhibitor, or a-methylparatyrosine, a tyrosine hydroxylase inhibitor, modulated the effect of PPA tolerance. Moreover, results also revealed that the alteration in NPY messenger RNA level coincided with the change of feeding behavior during PPA treatment and that infusions of NPY antisense oligonucleotide into the cerebroventricle abolished the effect of PPA tolerance. These findings suggest that cerebral CAT and hypothalamic NPY genome are involved in the development of tolerance to PPA-induced appetite suppression.

Hypothalamic neuropeptide Y (NPY) and the attenuation of hyperphagia in streptozotocin diabetic rats treated with dopamine D1/D2 agonists.

1. Dopamine is an appetite suppressant, while neuropeptide Y (NPY), an appetite stimulant in the brain, is reported to be involved in anorectic action induced by a combined administration of D1/D2 agonists in normal rats. In diabetic rats, however, these factors have not been studied. 2. Rats (including normal, diabetic and insulin-treated diabetic rats) were given daily injections of saline or D1/D2 agonists for 6 days. Changes in food intake and hypothalamic NPY content of these rats were assessed and compared. 3. The D1/D2 agonist-induced anorectic responses were altered in diabetic rats compared to normal rats treated similarly. Both the anorectic response on the first day of dosing and the tolerant response on the subsequent days were attenuated. 4. This alteration was independent of the neuroendocrine disturbance on feeding behavior since the basic pattern of food intake during the time course of a 24-h day/night cycle was similar in normal and diabetic rats; the decrease of food intake following drug treatment was only shown at the initial interval of 0-6 h in both groups of rats. 5. However, this alteration coincided with changes in NPY content following D1/D2 coadministration. The replacement of insulin in diabetic rats could normalize both NPY content and D1/D2 agonist-induced anorexia. 6. It is demonstrated that the response of D1/D2 agonist-induced appetite suppression is attenuated in diabetic rats compared to normal rats and that elevated hypothalamic NPY content may contribute to this alteration.

Role of oxidative stress in disrupting the function of negative glucocorticoid response element in daily amphetamine-treated rats.

Amphetamine (AMPH)-induced appetite suppression is associated with changes in hypothalamic reactive oxygen species (ROS), antioxidants, neuropeptides, and plasma glucocorticoid. This study explored whether ROS and glucocorticoid response element (GRE), which is the promoter site of corticotropin-releasing hormone (CRH) gene, participated in neuropeptides-mediated appetite control. Rats were treated daily with AMPH for four days, and changes in food intake, plasma glucocorticoid and expression levels of hypothalamic neuropeptide Y (NPY), proopiomelanocortin (POMC), superoxide dismutase (SOD), CRH, and glucocorticoid receptor (GR) were examined and compared. Results showed that food intake decreased and NPY gene down-regulated, while POMC, SOD, and CRH gene up-regulated during AMPH treatment. GR and GRE-DNA bindings were disrupted on Day 1 and Day 2 when glucocorticoid levels were still high. Pretreatment with GR inhibitor or ROS scavenger modulated mRNA levels in NPY, POMC, SOD and CRH in AMPH-treated rats. We suggest that disruptions of negative GRE (nGRE) on Day 1 and Day 2 are associated with an increase in oxidative stress during the regulation of NPY/POMC-mediated appetite control in AMPH-treated rats. These results advance the understanding of molecular mechanism in regulating AMPH-mediated appetite suppression.