Inhibition of glucose stimulated insulin secretion by neuropeptide Y is mediated via the Y1 receptor and inhibition of adenylyl cyclase in RIN 5AH rat insulinoma cells.

Neuropeptide Y (NPY) has been shown to inhibit insulin secretion from the islets of Langerhans. We show that insulin secretion in the insulinoma cell line RIN 5AH is inhibited by NPY. 125I-Peptide YY (PYY) saturation and competition-binding studies using NPY fragments and analogues on membranes prepared from this cell line show the presence of a single class of NPY receptor with a Y1 receptor subtype-like profile. Inhibition of insulin secretion in this cell line by NPY fragments and analogues also shows a Y1 receptor-like profile. Both receptor binding and inhibition of insulin secretion showed the same orders of potency with NPY > [Pro34]-NPY > NPY 3-36 >> NPY 13-36. The Y1 receptor antagonist, BIBP 3226, blocks NPY inhibition of insulin secretion from, and inhibits 125I-PYY binding to, RIN 5AH cells. Northern blot analysis using a Y1-receptor specific probe shows that NPY Y1 receptors are expressed by RIN 5AH cells. Y5 receptors are not expressed in this cell line. Neuropeptide Y inhibition of insulin secretion is blocked by incubation with pertussis toxin, implying that the effect is via a G-protein (Gi or Go) coupled receptor. Neuropeptide Y inhibits the activation of adenylyl cyclase by isoprenaline in RIN 5AH cell lysates, and the stimulation of cAMP by glucagon-like peptide-1 (7-36) amide (GLP-1). It also blocks insulin secretion stimulated by GLP-1, but not by dibutyryl cyclic AMP. Hence, we suggest that NPY inhibits insulin secretion from RIN 5AH cells via a Y1 receptor linked through Gi to the inhibition of adenylyl cyclase.

Peptide analogue studies of the hypothalamic neuropeptide Y receptor mediating pituitary adrenocorticotrophic hormone release.

Hypothalamic neuropeptide Y (NPY) is thought to be important in the regulation of feeding and also in the release of Adrenocorticotrophic hormone (ACTH). Intracerebroventricular administration of NPY to male rats significantly increased plasma ACTH 10 min after injection and stimulated 2-h food intake. A series of analogues of NPY that have a greatly reduced affinity for the Y1 [human pancreatic polypeptide (human PP), NPY(3-36)], the Y2 ([Pro34]NPY, human PP), the Y3 (peptide YY), and the Y6 (human PP) receptor, all markedly stimulated ACTH release. Rat PP, which binds with high affinity to the Y4 receptor, was unable to stimulate ACTH release. A novel analogue fragment [Pro34]NPY(13-36) was synthesized as a ligand with low Y1 and Y2 receptor affinity. Interestingly, neither [Pro34]NPY(13-36) nor the selective Y5 receptor agonist [D-Trp32]NPY stimulated food intake, whereas both significantly increased plasma ACTH. Thus the hypothalamic NPY receptor mediating increases in plasma ACTH has a fragment activation profile unlike the Y1-Y4 or Y6 receptors and appears distinct from the NPY receptor controlling food intake.

Leptin rapidly suppresses insulin release from insulinoma cells, rat and human islets and, in vivo, in mice.

Obesity is associated with diabetes, and leptin is known to be elevated in obesity. To investigate whether leptin has a direct effect on insulin secretion, isolated rat and human islets and cultured insulinoma cells were studied. In all cases, mouse leptin inhibited insulin secretion at concentrations within the plasma range reported in humans. Insulin mRNA expression was also suppressed in the cultured cells and rat islets. The long form of the leptin receptor (OB-Rb) mRNA was present in the islets and insulinoma cell lines. To determine the significance of these findings in vivo, normal fed mice were injected with two doses of leptin. A significant decrease in plasma insulin and associated rise in glucose concentration were observed. Fasted normal and leptin receptor-deficient db/db mice showed no response to leptin. A dose of leptin, which mimicked that found in normal mice, was administered to leptin-deficient, hyperinsulinemic ob/ob mice. This caused a marked lowering of plasma insulin concentration and a doubling of plasma glucose. Thus, leptin has a powerful acute inhibitory effect on insulin secretion. These results suggest that the action of leptin may be one mechanism by which excess adipose tissue could acutely impair carbohydrate metabolism.

Glucagon-like peptide-1 (GLP-1) releases thyrotropin (TSH): characterization of binding sites for GLP-1 on alpha-TSH cells.

We have demonstrated specific binding sites for [125I]glucagon-like peptide 1 (GLP-1) on membranes from the rodent thyrotrope cell line, alpha-TSH. Specific [125I]GLP-1 binding was saturable and time dependent. Equilibrium saturation binding analysis was consistent with the presence of a single class of binding site (binding capacity, 85 +/- 7 fmol/mg protein) with a dissociation constant (Kd) of 28 +/- 13 pM. The specific GLP-1 receptor agonists, exendin-4 and exendin-3, and the antagonist, exendin-(9-39), bound to the receptor sites with high affinity (Ki = 190 +/- 70 pM; 130 +/- 50 and 1200 +/- 470 pM, respectively). Chemical cross-linking of [125I]GLP-1-receptor complexes revealed a single band of 64,300 +/- 100 Mr in alpha-TSH membranes. In addition, specific PCR studies demonstrated the presence of GLP-1 receptor messenger RNA. Binding of the peptide to alpha-TSH cell membranes resulted in increased intracellular cAMP concentrations (10 nM GLP-1, 1010 +/- 83 pmol/10(6) cells.h; control, 175 +/- 60 pmol/10(6) cells.h; P < 0.002), indicating that the receptor is linked to stimulation of adenylyl cyclase. GLP-1-mediated increases in cAMP were inhibited by exendin-(9-39) in a dose-dependent manner. Furthermore, GLP-1 stimulates basal TSH release from dispersed anterior pituitary cells in a concentration-dependent manner (100 nM GLP-1, 63 +/- 3 fmol/10(6) cells.h; control, 35 +/- 1 fmol/10(6) cells.h; P < 0.0005), but had no effect on basal PRL, GH, or LH release.

Cloning and molecular characterization of complementary deoxyribonucleic acid corresponding to a novel form of pituitary adenylate cyclase-activating polypeptide messenger ribonucleic acid in the rat testis.

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide that greatly stimulates adenylyl cyclase activity in cultured anterior pituitary cells, was isolated from ovine hypothalamus in 1989. Investigation of the distribution of PACAP messenger RNA (mRNA) in rat tissues by Northern blot analysis revealed an anomalous signal in the testis. In this study we have isolated and characterized this unusual mRNA, which is approximately 800 bases long (approximately 1.5 kilobases shorter than that reported in the rat hypothalamus). Cloning and sequencing of the complementary DNA corresponding to this message revealed that the sequences are identical except for 126 bases at the 5'-end of the 5'-untranslated region of the smaller transcript. This region has no homology to either the published hypothalamic sequence or any other known sequence. Northern blot analysis of total RNA from various species showed that a smaller form of PACAP mRNA is also present in human, murine, and bovine testis, although in these species the message is slightly smaller. In addition, Northern blot analysis of these tissues using a probe directed to the 126-base 5'-region, revealed conservation of this sequence between species. Although the structure of the rat PACAP gene is unknown, preliminary investigations into the origins of the two mRNA species by PCR of genomic DNA suggests that they are transcribed from separate genes and not the product of alternate splicing.

Personality traits associated with fear.

The extent to which personality characteristics are associated with fear was investigated. The amount of fear and the attributional style of 91 college students (74 women, 17 men) were measured using the Fear Questionnaire, the Fear Survey Schedule, and the Attributional Style Questionnaire. Analysis indicated that fear was significantly correlated with the responsibility for bad outcomes and with the tendency to generalize all outcomes to many situations. Findings are consistent with the view that significantly different attributional profiles emerge as fearfulness increases.

A relapse-prevention program: effects of electromyographic training on high and low levels of state and trait anxiety.

This study involved 40 college subjects and investigated the effects of EMG training on high and low state- and trait-anxiety scores. At pretreatment assessment subjects were administered the Spielberger State-Trait Anxiety Inventory (1970). Subjects were treated with EMG training with an established treatment criterion of 3 microvolts. All subjects achieved the treatment criterion within six 20-min. training sessions. Daily homework practice sessions were recorded on behavioral data cards. Two-way analysis of variance indicated significant mean differences on both state and trait anxiety at the conclusion of treatment. Interactions were significant, with EMG affecting subjects high in anxiety differently from subjects low in anxiety. Multiple t tests indicated high state-anxiety scores dropped significantly more than high trait-anxiety scores. A 6-mo. follow-up assessment, employing biweekly mailing of behavioral data cards along with a protective contingency instituted by informing subjects they would be contacted by phone if the data cards were not received, showed that state-anxiety scores remained significantly lower, while trait-anxiety scores returned to pretreatment levels.

Trimethobenzamide HCl in the treatment of nausea and vomiting associated with antineoplastic chemotherapy.

Fifty-five patients undergoing chemotherapy for various neoplastic processes were treated with trimethobenzamide or placebo to control nausea and vomiting. Trimethobenzamide was shown to be significantly better than placebo in relieving periodic and total nausea over the 48-hour study. Vomiting incidence was also reduced in the group receiving trimethobenzamide. Differences were noted in the degree of emetic stimulus associated with different chemotherapeutic regimens. No side effects attributable to trimethobenzamide were recorded.

Differential effects of hypnosis, biofeedback training, and trophotropic responses on anxiety, ego strength, and locus of control.

Pretested 60 college students on three scales: The IPAT Anxiety Scale, the Barron Ego-strength scale, and the Rotter I-E scale. The Ss then were assigned randomly to one of four treatment groups designated: Hypnotic treatment, biofeedback treatment, trophotropic treatment, and control. Three of these groups met separetely for 60 minutes once a week for 8 weeks. The control group did not meet during this time. During the sessions, each group was trained in a different technique for self-regulation. At the end of the 8-week period the scales were readministered to all groups. A series of covariance analyses indicated that hypnosis was a more effective self-regulatory technique for lowering anxiety levels when compared to biofeedback or trophotropic response procedures. With regard to increasing ego strength, both the hypnotic training group and the biofeedback training group proved to be significant. No significant difference was found between the experimental and control gorups on the I-E scores.