Regulatory Peptides最新文献

Background

The enteroendocrine hormone glucagon like peptide-2 (GLP-2) and its ligands are under development as therapeutic agents for a variety of intestinal pathologies. A number of these conditions occur in neonates and infants, and thus a detailed understanding of the effects of GLP-2 during the phase of rapid growth during infancy is required to guide the development of therapeutic applications. We studied the effects of GLP-2 in the neonatal pig to determine the potential effects of exogenous administration.

Methods

Two day old newborn domestic piglets were treated with GLP-2 (1–33) at 40 μg/kg/day or control drug vehicle (saline), by subcutaneous injection, given in two doses per day, (n = 6/group) for 42 days. Animals were weaned normally, over days 21–25. In the fifth week of life, they underwent neuro-developmental testing, and a pharmacokinetic study. On day 42, they were euthanized, and a complete necropsy performed, with histological assessment of tissues from all major organs.

Results

GLP-2 treatment was well tolerated, one control animal died from unrelated causes. There were no effects of GLP-2 on weight gain, feed intake, or behavior. In the treated animals, GLP-2 levels were significantly elevated at 2400 ± 600 pM while at necropsy, organ weights and histology were not affected except in the intestine, where the villus height in the small intestine and the crypt depth, throughout the small intestine and colon, were increased. Similarly, the rate of crypt cell proliferation (Ki-67 staining) was increased in the GLP-2 treated animals and the rate of apoptosis (Caspase-3) was decreased, the depth of the microvilli was increased and the expression of the mRNA for the GLP-2 receptor was decreased throughout the small and large intestine.

Conclusions

In these growing animals, exogenous GLP-2 at pharmacologic doses was well tolerated, with effects confined to the gastrointestinal tract.

Nesfatin-1 is an anorexigenic peptide that controls feeding behavior and glucose homeostasis. However, there is little data that exists regarding nesfatin-1 secretion in obese children and young adolescents. The aim of this study is to investigate serum nesfatin-1 in childhood and adolescent obesity and to study potential correlations with food intake, anthropometric indices, body composition and insulin resistance. Forty obese children and adolescents and 40 healthy control subjects were studied. Anthropometric measurements were assessed, dietary food intake was evaluated based on 3-days food record and body composition indices were evaluated using bioelectrical impedance analysis. Lipid profile, fasting blood sugar, fasting insulin and HOMA-IR were measured. Fasting serum nesfatin-1 was quantitatively assayed by ELISA. Serum nesfatin-1 was significantly higher in obese group (2.49 ± 1.96 ng/ml) than in control group (0.70 ± 0.81 ng/ml), P = 0.001. Positive correlations with serum insulin (P = 0.001), HOMA-IR (P = 0.000), BMI-SDS (P = 0.04), body fat % (P = 0.000), fat mass (P = 0.000), fat free mass (P = 0.03), CHO % (P = 0.000), and saturated fat % (P = 0.01) were found. While significant negative correlation with protein % (P = 0.000) was observed. In conclusion, our results denote that nesfatin-1 might have an important role in regulation of food intake and pathogenesis of insulin resistance in obese children and young adolescents.

Present experiments focused on measuring the effect of neuropeptide SF (NPSF) on the hypothalamus–pituitary–adrenal (HPA) axis and behavior. The peptide was administered in different doses (0.25, 0.5, 1, 2 μg) intracerebroventricularly to rats, and the behavior of which was then observed by telemetry and open-field test. Effect of NPSF on core temperature was also measured via telemetry. Plasma ACTH and corticosterone concentrations were measured to assess the influence of NPSF on the HPA activation. In addition, the changes in corticotrophin-releasing hormone (CRH) level in the hypothalamic paraventricular nucleus were continuously monitored by means of intracerebral microdialysis. Our results showed that NPSF augmented paraventricular CRH release and increased ACTH and corticosterone levels in the plasma. The release of corticosterone was successfully blocked by the pre-treatment of the CRH antagonist α-helical CRH_9–41. Spontaneous and exploratory locomotor activity was also stimulated according to the telemetric and open-field studies. However, NPSF only tended to alter stereotyped behavior in the open-field experiments. These results demonstrate that NPSF may play a physiologic role in the regulation of such circadian functions as the activity of motor centers and the HPA axis, through the release of CRH.

Background

C-type natriuretic peptide (CNP) is a member of the natriuretic peptide family. Cardiac ANP and BNP expressions are firmly established, whereas CNP expression in the mammalian heart remains controversial. In the present report, we used a porcine model of the neonatal period with high expressions of cardiac ANP and BNP in order to elucidate the cardiac CNP expression profile.

Methods

Plasma and cardiac tissue were obtained from newborn piglets during the first 72 h of life. The chamber-specific CNP mRNA contents were quantified by real-time PCR analysis. The proCNP concentrations in plasma and cardiac tissue extracts were quantified by a porcine-specific radioimmunoassay.

Results

Cardiac CNP mRNA contents (n = 24) were low compared to sites of known expression, where porcine seminal vesicle CNP mRNA contents were 200-fold higher. In addition, plasma proCNP concentrations in the newborn piglets (n = 44) were exceedingly low compared to proANP concentrations (5.3 pmol/L (3.2–8.6) vs. 3438 pmol/L (2790–5418), p < 0.0001). The proCNP concentrations in atrial tissue extracts were barely detectable (≤ 0.06 pmol/g) (n = 2) compared to ventricular proANP (130 pmol/g (101–159)) and atrial proANP (12,303 pmol/g (10,623–15,412)).

Conclusion

Our data show that the heart is not a major source of circulating proCNP in neonatal piglets.

This study was designed to investigate the alterations of substance P (SP) and its correlation with apoptosis of the retinal neurons in diabetic rats.

The study was carried out with diabetic rats induced by streptozotocin. Changes of SP and its mRNA were examined using enzyme-linked immunosorbent assay and reverse transcription polymerase chain reaction. The effect of restoration of SP level by capsaicin (20 mg/kg, s.c.) on the apoptosis of the retinal cells was studied. The apoptosis was evaluated by change of ratio of the apoptotic cells and caspase-3 activity in the retina.

It was found that increase in apoptosis of retinal cells, by 3.5 fold of control, was accompanied by reduction of SP, by 28% in protein and 32% in the mRNA in the retina at 10 weeks of induction of diabetes, compared to the controls. Capsaicin significantly elevated endogenous SP, by 29% in the mRNA and 17% in protein in the retina, with marked inhibition of the apoptosis and the activity of caspase-3 in the diabetic rats.

Induction of diabetes leads to the increase of cell apoptosis and the decrease of SP in the retina. The reduction of the endogenous SP and the increase of the cell apoptosis in the retina of the diabetic rats were reversed by pretreatment with capsaicin. Restoration of SP in the retina may be a novel option for prevention of the retinal injury during development of diabetes.

The hymenochirins are a family of cationic, amphipathic, α-helical host-defense peptides, first isolated from skin secretions of the Congo clawed frog Hymenochirus boettgeri (Pipidae). Of the four hymenochirins tested, hymenochirin-1B (IKLSPETKDNLKKVLKGAIKGAIVAKMV.NH₂) shows the greatest cytotoxic potency against non-small cell lung adenocarcinoma A549 cells (LC₅₀ = 2.5 ± 0.2 μM), breast adenocarcinoma MDA-MB-231 cells (LC₅₀ = 9.0 ± 0.3 μM), colorectal adenocarcinoma HT-29 cells (LC₅₀ = 9.7 ± 0.2 μM), and hepatocarcinoma HepG2 cells (LC₅₀ = 22.5 ± 1.4 μM) with appreciably less hemolytic activity against human erythrocytes (LC₅₀ = 213 ± 18 μM). Structure–activity relationships were investigated by synthesizing analogs of hymenochirin-1B in which Pro⁵, Glu⁶ and Asp⁹on the hydrophilic face of the helix were replaced by one or more L-lysine or D-lysine residues. The [D9K] analog displays the greatest increase in potency against all four cell lines (up to 6 fold) but hemolytic activity also increases (LC₅₀ = 174 ± 12 μM). The [D9k] and [E6k,D9k] analogs retain relatively high cytotoxic potency against the tumor cells (LC₅₀ in the range 2.1–21 μM) but show reduced hemolytic activity (LC₅₀ > 300 μM). The data suggest that hymenochirin-1B has therapeutic potential as a template to generate potent, non-toxic anti-cancer agents.

Mesotocin (MT) is a neurohypophysis hormone in non-mammalian vertebrates including chickens, and homologous of oxytocin (OT) in mammals. Oxytocin (OT) is a well known reproductive hormone in mammals, but the physiological roles of MT in chickens have not been clarified well. OT is thought to regulate feeding behavior because central and peripheral injections of OT inhibit feeding behavior in mammals. In avian, on the other hand, the effect of MT on feeding regulation has not yet been clarified. Therefore, the present study was carried out to examine whether MT is related to the regulation of feeding in chicks (Gallus gallus). Intracerebroventricular (ICV) injection of MT significantly decreased food intake in chicks while intraperitoneal injection had no effect. Behavioral observations revealed that ICV injection of MT significantly increased wing-flapping and preening, and tended to increase voluntary movement, implying that the anorexigenic effect of MT might be related to the stress response. However, neither plasma corticosterone concentration nor the mRNA expression of corticotrophin-releasing hormone (CRH) in the diencephalon was affected by ICV injection of MT. Moreover; ICV injection of CRH did not affect MT mRNA expression in the diencephalon. In sum, central injection of MT is associated with an anorexigenic response that does not appear CRH dependent in chicks.

Xenin-25 (Xen) is a 25-amino acid neurotensin-related peptide that activates neurotensin receptor-1 (NTSR1). We previously showed that Xen increases the effect of glucose-dependent insulinotropic polypeptide (GIP) on insulin release 1) in hyperglycemic mice via a cholinergic relay in the periphery independent from the central nervous system and 2) in humans with normal or impaired glucose tolerance, but not type 2 diabetes mellitus (T2DM). Since this blunted response to Xen defines a novel defect in T2DM, it is important to understand how Xen regulates islet physiology.

On separate visits, subjects received intravenous graded glucose infusions with vehicle, GIP, Xen, or GIP plus Xen. The pancreatic polypeptide response was used as an indirect measure of cholinergic input to islets. The graded glucose infusion itself had little effect on the pancreatic polypeptide response whereas administration of Xen equally increased the pancreatic polypeptide response in humans with normal glucose tolerance, impaired glucose tolerance, and T2DM. The pancreatic polypeptide response to Xen was similarly amplified by GIP in all 3 groups. Antibody staining of human pancreas showed that NTSR1 is not detectable on islet endocrine cells, sympathetic neurons, blood vessels, or endothelial cells but is expressed at high levels on PGP9.5-positive axons in the exocrine tissue and at low levels on ductal epithelial cells. PGP9.5 positive nerve fibers contacting beta cells in the islet periphery were also observed. Thus, a neural relay, potentially involving muscarinic acetylcholine receptors, indirectly increases the effects of Xen on pancreatic polypeptide release in humans.

The aim of this study was to analyze whether arginine vasopressin (AVP) may be considered a modulator of intestinal motility. In this view, we evaluated, in vitro, the effects induced by exogenous administration of AVP on the contractility of mouse distal colon, the subtype(s) of receptor(s) activated and the action mechanism. Isometric recordings were performed on longitudinal and circular muscle strips of mouse distal colon. AVP (0.001 nM–100 nM) caused concentration-dependent contractile effects only on the longitudinal muscle, antagonized by the V1 receptor antagonist, V-1880. AVP-induced effect was not modified by tetrodotoxin, atropine and indomethacin. Contractile response to AVP was reduced in Ca^2 +-free solution or in the presence of nifedipine, and it was abolished by depletion of calcium intracellular stores after repetitive addition of carbachol in calcium-free medium with addition of cyclopiazonic acid. U-73122, an inhibitor of the phospholipase C, effectively antagonized AVP effects, whilst it was not affected by an adenylyl cyclase inhibitor. Oxytocin induced an excitatory effect in the longitudinal muscle of distal colon at very high concentrations, effect antagonized by V-1880. The results of this study shown that AVP, via activation of V1 receptors, is able to modulate positively contractile activity of longitudinal muscle of mouse distal colon, independently by enteric nerve activation and prostaglandin synthesis. Contractile response is achieved by increase in cytoplasmatic Ca^2 + concentration via extracellular Ca^2 + influx from L-type Ca^2 + channels and via Ca^2 + release from intracellular stores through phospholipase C pathway. No modulation has been observed on the contractility of the circular muscle.