Effects of exogenous ghrelin on the tissue structure and somato-statin secretion in the pancreas of African ostrich chicks / Efectos de la grelina exógena en la estructura del tejido y la secreción de somato-estatinas en el páncreas de los polluelos de avestruz africanos

SUMMARY: This study aimed to investigate the effect of exogenous ghrelin on pancreatic growth and development in African ostrich chicks. Sixteen 40-day-old African ostrich chicks (male or female) were randomly divided into four groups and injected intravenously metatarsal vein with saline (control) or ghrelin (10, 50, and 100 μg/kg) for 6 days. Body and pancreas weight were determined, structural characteristics were observed using HE staining, somatostatin-immunopositive cells were detected using immunohistochemistry. The results were as follows: 1. The 50 and 100 μg/kg groups showed lower relative pancreas weight than the control group (P 0.05. Moreover, compared with the control, the islet cells in treatment groups were loosely arranged and showed reduced cytoplasm. In the exocrine pancreas, the volume of acinar cells in the 10, 50, and 100 μg/kg groups all decreased to varying degrees. 3. Somatostatin immunopositive cells were mainly located around the periphery of the islets and sporadically distributed in the center. The density of the somatostatin immunopositive cells in the 10, 50, and 100 μg/kg groups was higher than that in the control (P < 0.05). These findings suggest that exogenous ghrelin increases the area and number of islets and number of somatostatin immunopositive cells but reduces relative pancreas weight and effects the morphological and structural development of the pancreas, which may inhibit the pancreatic growth and development in African ostrich chicks.

RESUMEN: Este estudio tuvo como objetivo investigar el efecto de la grelina exógena sobre el crecimiento y desarrollo del páncreas en polluelos de avestruz africana. Dieciséis pollos de avestruz africana de 40 días (machos o hembras) se dividieron al azar en cuatro grupos y se inyectaron por vía intravenosa con solución salina (control) o grelina (10, 50 y 100 μg / kg) durante 6 días. determinadas, se observaron las características estructurales mediante tinción Hematoxilina-Eosina, se detectaron células inmunopositivas a somatostatina mediante inmunohistoquímica. Los resultados fueron los siguientes: ¨Los grupos de 50 y 100 μg / kg mostraron un menor peso relativo del páncreas que el grupo de control (P <0,05). El área de islotes por unidad de área del páncreas fue mayor en los grupos de 10, 50 y 100 μg / kg grupos que en el grupo de control (P <0,05). El número de islotes por unidad de área del páncreas fue menor en el grupo de 10 μg / kg que en el control (P <0,05). Además, en comparación con el control, las células de los islotes en los grupos de tratamiento estaban dispuestas de forma holgada y mostraban un citoplasma reducido. En el páncreas exocrino, el volumen de células acinares en los grupos de 10, 50 y 100 μg / kg disminuyó en diversos grados. Las células inmunopositivas de somatostatina se ubicaron principalmente alrededor de la periferia de los islotes y se distribuyeron esporádicamente en el centro. La densidad de las células inmunopositivas a la somatostatina en los grupos de 10, 50 y 100 μg / kg fue mayor que la del control (P <0,05). Estos hallazgos sugieren que la grelina exógena aumenta el área y el número de islotes y el número de células inmunopositivas a la somatostatina, pero reduce el peso relativo del páncreas, lo que puede inhibir el crecimiento y desarrollo pancreático en los polluelos de avestruz africana.

Somatostatin receptor 5-mediated modulation of outward K+ currents in rat retinal ganglion cells.

Somatostatin participants in multiple physiological functions by activating the five distinct G-protein-coupled receptors (sst1-sst5). In this study, we investigated the effect of sst5 activation on outward K currents in acutely isolated rat retinal ganglion cells using whole-cell patch-clamp techniques. Extracellular application of L-817,818, a specific sst5 agonist, significantly reduced outward K currents which was mainly the 4-aminopyridine and glybenclamide sensitive current components, but not the tetraethylammonium-sensitive one. The L-817,818 effect was mediated by sst5 since the suppression was eliminated when intracellular dialysis of the G-protein inhibitor GDP-ß-S or extracellular application of the sst5 antagonist BIM-23056. Intracellular phospholipase C/protein kinase C signaling pathway was involved in the L-817,818 effect because the L-817,818 effect on K currents was inhibited when rat retinal ganglion cells were pretreated with U73122 or chelerythrine chloride. However, L-817,818 persisted to reduce the K currents when cAMP/protein kinase A, calcium/calmodulin-dependent protein kinase II and mitogen-activated protein kinase/extracellular signal-regulated kinase signaling pathways were blocked respectively. These results suggest that sst5 activation suppresses 4-aminopyridine and glybenclamide-sensitive K currents in rat retinal ganglion cells by stimulating intracellular phospholipase C/protein kinase C signaling pathway, thereby regulating the rat retinal ganglion cell excitability.

A nitric oxide synthase inhibitor, L-NAME, prevents L-arginine-induced downregulation of the rat cortical somatostatinergic system.

Activation of NMDA receptors leads to nitric oxide (NO) synthesis by NO synthase (NOS) from L-arginine. Neuronal NOS colocalizes with somatostatinergic (SRIF) neurons and there is growing evidence of an interaction between NO and the cerebral SRIFergic system in several neurological diseases. Our aim was to study the effect of L-arginine on the regulation of the SRIFergic system in the frontoparietal cortex of male Sprague-Dawley rats. Intraperitoneal administration of L-arginine (150 mg/Kg), twice-daily during eight days, induced a decrease in SRIF receptor density, which was accompanied by a reduction in the capacity of SRIF to stimulate inositol-1,4,5-triphosphate (IP3) accumulation and SRIF-like immunoreactivity (SRIF-LI) levels. To determine if these changes were related to L-arginine-derived NO synthesis, a NOS inhibitor, Nω-nitro-L-arginine methyl ester was coadministered with L-arginine. Its coadministration prevented the reduction in the SRIF receptor density, accumulation of IP3 and SRIF-LI content. These findings indicate that L-arginine induces a deleterious effect on the cortical somatostatinergic system and that the inhibition of NOS could be helpful in some neurological disorders where this neurotransmitter system is affected.

The GLP1R Agonist Liraglutide Reduces Hyperglucagonemia Induced by the SGLT2 Inhibitor Dapagliflozin via Somatostatin Release.

The newest classes of anti-diabetic agents include sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 receptor (GLP1R) agonists. The SGLT2 inhibitor dapagliflozin reduces glucotoxicity by glycosuria but elevates glucagon secretion. The GLP1R agonist liraglutide inhibits glucagon; therefore, we hypothesize that the cotreatment of dapagliflozin with liraglutide could reduce hyperglucagonemia and hyperglycemia. Here we use five complementary models: human islet cultures, healthy mice, db/db mice, diet-induced obese (DIO) mice, and somatostatin receptor-2 (SSTR2) KO mice. A single administration of liraglutide and dapagliflozin in combination improves glycemia and reduces dapagliflozin-induced glucagon secretion in diabetic mice. Chronic treatment with liraglutide and dapagliflozin produces a sustainable reduction of glycemia compared with each drug alone. Moreover, liraglutide reduces dapagliflozin-induced glucagon secretion by enhancing somatostatin release, as demonstrated by SSTR2 inhibition in human islets and in mice. Collectively, these data provide mechanistic insights into how intra-islet GLP1R activation is critical for the regulation of glucose homeostasis.

Proposed mechanisms for oligonucleotide IMT504 induced diabetes reversion in a mouse model of immunodependent diabetes.

Type 1 diabetes (T1D) originates from autoimmune ß-cell destruction. IMT504 is an immunomodulatory oligonucleotide that increases mesenchymal stem cell cloning capacity and reverts toxic diabetes in rats. Here, we evaluated long-term (20 doses) and short-term (2-6 doses) effects of IMT504 (20 mg·kg(-1)·day(-1) sc) in an immunodependent diabetes model: multiple low-dose streptozotocin-injected BALB/c mice (40 mg·kg(-1)·day(-1) ip for 5 consecutive days). We determined blood glucose, glucose tolerance, serum insulin, islet morphology, islet infiltration, serum cytokines, progenitor cell markers, immunomodulatory proteins, proliferation, apoptosis, and islet gene expression. IMT504 reduced glycemia, induced ß-cell recovery, and impaired islet infiltration. IMT504 induced early blood glucose decrease and infiltration inhibition, increased ß-cell proliferation and decreased apoptosis, increased islet indoleamine 2,3-dioxygenase (IDO) expression, and increased serum tumor necrosis factor and interleukin-6 (IL-6). IMT504 affected islet gene expression; preproinsulin-2, proglucagon, somatostatin, nestin, regenerating gene-1, and C-X-C motif ligand-1 cytokine (Cxcl1) increased in islets from diabetic mice and were decreased by IMT504. IMT504 downregulated platelet endothelial cell adhesion molecule-1 (Pecam1) in islets from control and diabetic mice, whereas it increased regenerating gene-2 (Reg2) in islets of diabetic mice. The IMT504-induced increase in IL-6 and islet IDO expression and decreased islet Pecam1 and Cxcl1 mRNA expression could participate in keeping leukocyte infiltration at bay, whereas upregulation of Reg2 may mediate ß-cell regeneration. We conclude that IMT504 effectively reversed immunodependent diabetes in mice. Corroboration of these effects in a model of autoimmune diabetes more similar to human T1D could provide promising results for the treatment of this disease.

VEGF secretion by neuroendocrine tumor cells is inhibited by octreotide and by inhibitors of the PI3K/AKT/mTOR pathway.

Gastroenteropancreatic (GEP) endocrine tumors are hypervascular tumors able to synthesize and secrete high amounts of VEGF. We aimed to study the regulation of VEGF production in GEP endocrine tumors and to test whether some of the drugs currently used in their treatment, such as somatostatin analogues and mTOR inhibitors, may interfere with VEGF secretion. We therefore analyzed the effects of the somatostatin analogue octreotide, the mTOR inhibitor rapamycin, the PI3K inhibitor LY294002, the MEK1 inhibitor PD98059 and the p38 inhibitor SB203850 on VEGF secretion, assessed by ELISA and Western blotting, in three murine endocrine cell lines, STC-1, INS-r3 and INS-r9. Octreotide and rapamycin induced a significant decrease in VEGF production by all three cell lines; LY294002 significantly inhibited VEGF production by STC-1 and INS-r3 only. We detected no effect of PD98059 whereas SB203850 significantly inhibited VEGF secretion in INS-r3 and INS-r9 cells only. By Western blotting analysis, we observed decreased intracellular levels of VEGF and HIF-1alpha under octreotide, rapamycin and LY294002. For rapamycin and LY294002, this effect was likely mediated by the inhibition of the mTOR/HIF-1/VEGF pathway. In addition to its well-known anti-secretory effects, octreotide may also act through the inhibition of the PI3K/Akt pathway, as suggested by the decrease in Akt phosphorylation detected in all three cell lines. In conclusion, our study points out to the complex regulation of VEGF synthesis and secretion in neoplastic GEP endocrine cells and suggests that the inhibition of VEGF production by octreotide and rapamycin may contribute to their therapeutic effects.

Mice knock out for the histone acetyltransferase p300/CREB binding protein-associated factor develop a resistance to amyloid toxicity.

p300/CREB binding protein-associated factor (PCAF) regulates gene expression by acting through histone acetylation and as a transcription coactivator. Although histone acetyltransferases were involved in the toxicity induced by amyloid-beta (Abeta) peptides, nothing is known about PCAF. We here analyzed the sensitivity of PCAF knockout (KO) mice to the toxic effects induced by i.c.v. injection of Abeta(25-35) peptide, a nontransgenic model of Alzheimer's disease. PCAF wild-type (WT) and KO mice received Abeta(25-35) (1, 3 or 9 nmol) or scrambled Abeta(25-35) (9 nmol) as control. After 7 days, Abeta(25-35) toxicity was measured in the hippocampus of WT mice by a decrease in CA1 pyramidal cells and increases in oxidative stress, endoplasmic reticulum stress and induction of apoptosis. Memory deficits were observed using spontaneous alternation, water-maze learning and passive avoidance. Non-treated PCAF KO mice showed a decrease in CA1 cells and learning alterations. However, Abeta(25-35) injection failed to induce toxicity or worsen the deficits. This resistance to Abeta(25-35) toxicity did not involve changes in glutamate or acetylcholine systems. Examination of enzymes involved in Abeta generation or degradation revealed changes in transcription of presenilins, activity of neprilysin (NEP) and an absence of Abeta(25-35)-induced regulation of NEP activity in PCAF KO mice, partly due to an altered expression of somatostatin (SRIH). We conclude that PCAF regulates the expression of proteins involved in Abeta generation and degradation, thus rendering PCAF KO insensitive to amyloid toxicity. Modulating acetyltransferase activity may offer a new way to develop anti-amyloid therapies.

Hippocampal sst(1) receptors are autoreceptors and do not affect seizures in rats.

Somatostatin-14 (SRIF-14) exerts anticonvulsive effects in several rat seizure models, generally attributed to sst(2) receptor activation. Whereas sst(1) immunoreactivity has been localized to both polymorphic interneurons and principal cells in the rat hippocampus, its potential role as an inhibitory autoreceptor or as a receptor involved in mediating anticonvulsive actions remains unknown. We showed that intrahippocampal administration of the sst(1) antagonist SRA880 (1 microM) induced a robust increase in hippocampal SST-14 levels without affecting gamma-aminobutyric acid levels in conscious rats, indicating that the sst(1) receptor acts as an inhibitory autoreceptor. SRA880 did not affect seizure severity and did not reverse the anticonvulsive action of SRIF-14 (1 microM) against pilocarpine-induced seizures, suggesting that hippocampal sst(1) receptors are not involved in the anticonvulsive effects of SRIF-14.

Effects of memantine on soluble Alphabeta(25-35)-induced changes in peptidergic and glial cells in Alzheimer's disease model rat brain regions.

Soluble forms of amyloid-beta (Abeta) have been considered responsible for cognitive dysfunction prior to senile plaque formation in Alzheimer's disease (AD). As its mechanism is not well understood, we examined the effects of repeated i.c.v. infusion of soluble Alphabeta(25-35) on peptidergic system and glial cells in the pathogenesis of AD. The present study aims to investigate the protective effects of memantine on Abeta(25-35)-induced changes in peptidergic and glial systems. Infusion of Alphabeta(25-35) decreased the level of immunoreactive somatostatin (SS) and substance P (SP) in the hippocampus prior to neuronal loss or caspase activation, which is correlated with the loss of spine density and activation of inducible nitric-oxide synthase (iNOS). Biochemical experiment with peptide-degrading enzymes, prolyl oligopeptidase (POP) and endopeptidase 24.15 (EP 24.15) activities demonstrated a concomitant increase with the activation of glial marker proteins, glial fibrillary acidic protein (GFAP) and CD11b in the Abeta-treated hippocampus. Double immunostaining experiments of EP 24.15 and GFAP/CD11b antibodies clearly demonstrated the co-localization of neuro peptidases with astrocytes and microglia. Treatment with memantine, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist significantly attenuated Abeta(25-35)-induced changes of neuropeptides, their metabolizing enzymes, glial marker proteins, and activation of iNOS. Taken together, the data implies that memantine exerts its protective effects by modulating the neuropeptide system as a consequence of suppressing the glial cells and oxidative stress in AD model rat brain regions.

Effects of insulin and octreotide on memory and growth hormone in Alzheimer's disease.

Both insulin alone and the somatostatin analogue octreotide alone facilitate memory in patients with Alzheimer's disease (AD). Since octreotide inhibits endogenous insulin secretion, the cognitive effects of insulin and octreotide may not be independent. This study tested the individual and interactive effects of insulin and octreotide on memory and plasma growth hormone (GH) levels in older adults. Participants were 16 memory-impaired (AD = 7, amnestic mild cognitive impairment = 9; apolipoprotein E [APOE] epsilon4- [no epsilon4 alleles] = 9, epsilon4+ [1-2 epsilon4 alleles] = 7), and 19 cognitively-intact older adults (APOE epsilon4- = 17, epsilon4+ = 1). On separate days, fasting participants received counterbalanced infusions of: 1) insulin (1 mU.kg(-1).min(-1)) and dextrose to maintain euglycemia; 2) octreotide (150 microg/h); 3) insulin, dextrose, and octreotide; or 4) saline. Story recall was the principal endpoint. Insulin alone facilitated delayed recall for epsilon4- patients, relative to epsilon4+ patients (P = 0.0012). Furthermore, epsilon4- patients with higher Mattis Dementia Rating Scale (DRS) scores had greater octreotide-induced memory facilitation (P = 0.0298). For healthy adults, octreotide facilitated memory (P = 0.0122). Unexpectedly, hyperinsulinemia with euglycemia increased GH levels in healthy controls (P = 0.0299). Thus, insulin and octreotide appear to regulate memory in older adults. APOE epsilon4 genotype modulates responses to insulin and octreotide. Finally, insulin may regulate GH levels during euglycemia.

Hippocampal levels of phosphorylated protein kinase A (phosphor-S96) are linked to spatial memory enhancement by SGS742.

Cognitive enhancement by the GABA (B) receptor antagonist SGS742 has been well-documented, but mechanisms of action are not fully elucidated. Previous work has proposed involvement of somatostatin-14 and protein kinase C in cognitive enhancement; phospho-protein kinase A (p-PKA), fyn, and phospho-fyn are known signaling systems for spatial memory. It was the aim of the study to determine hippocampal levels of these proteins following SGS742-treatment and to correlate them with the outcome from the Morris water maze (MWM), represented by the parameter "time spent in the target quadrant" during the probe trial. OF1 mice were used for the experiments and divided into four groups: intraperitoneal SGS742 and saline solution treatment, both, tested in the MWM, and two yoked controls. Six hours following the probe trial, hippocampal protein levels were determined by immunoblotting. In the MWM, time spent in the target quadrant was significantly enhanced by SGS742 treatment. p-PKA levels were significantly increased only in the SGS742-treated group tested in the MWM as compared to saline treatment. In yoked controls, no significant differences in p-PKA levels between SGS742 and saline treatment were observed. Somatostatin-14 levels were significantly increased in both SGS742-treated groups. No statistically significant changes of other protein levels were observed. We propose that GABA (B) antagonism represented by SGS742 treatment led to cognitive enhancement involving p-PKA, because yoked controls treated with SGS742 were comparable to yoked saline-treated controls. The finding that somatostatin-14 was also induced in the SGS742-treated yoked controls points to a drug side effect, and therefore the role of somatostatin-14 for cognitive enhancement remains open.

Minocycline provides protection against beta-amyloid(25-35)-induced alterations of the somatostatin signaling pathway in the rat temporal cortex.

Minocycline is a semi-synthetic second-generation tetracycline known to improve cognition in amyloid precursor protein transgenic mice. Whether it can protect the somatostatin (SRIF) receptor-effector system, also involved in learning and memory, from alterations induced by chronic i.c.v. infusion of beta-amyloid peptide (Abeta)(25-35) is presently unknown. Hence, in the present study, we tested the effects of minocycline on the SRIF signaling pathway in the rat temporal cortex. To this end, male Wistar rats were injected with minocycline (45 mg/kg body weight) i.p. twice on the first day of treatment. On the following day and during 14 days, Abeta(25-35) was administered i.c.v. via an osmotic minipump connected to a cannula implanted in the left lateral ventricle (300 pmol/day). Minocycline (22.5 mg/kg, i.p.) was injected once again the last 2 days of the Abeta(25-35) infusion. The animals were killed by decapitation 24 h after the last drug injection. Our results show that minocycline prevents the decrease in SRIF receptor density and somatostatin receptor (sst) 2 expression and the attenuated capacity of SRIF to inhibit adenylyl cyclase (AC) activity, alterations present in the temporal cortex of Abeta(25-35)-treated rats. Furthermore, minocycline blocks the Abeta(25-35)-induced decrease in phosphorylated cyclic AMP (cAMP) response element binding protein (p-CREB) content and G-protein-coupled receptor kinase 2 (GRK) protein expression in this brain area. Altogether, the present data demonstrate that minocycline in vivo provides protection against Abeta-induced impairment of the SRIF signal transduction pathway in the rat temporal cortex and suggest that it may have a potential as a therapeutic agent in human Alzheimer's disease, although further studies are warranted.

A short acute octreotide test for response prediction of long-term treatment with somatostatin analogues in acromegalic patients.

The usefulness of the acute octreotide test in the selection of acromegalic patients for chronic somatostatin depot analogues treatment is controversial. The aim of the present study was to determine its accuracy for chronic response prediction, and the reliability of a short version of the classic 6-hour test. The data from 26 acromegalics (19 women, 7 men, mean age 52.6+/-13.1 years) studied with an acute octreotide test (6 hours sampling for GH measurement after octreotide 100 microg s. c.) were retrospectively analyzed. Eighteen of them followed chronic somatostatin depot analogues treatment for 12 months. GH nadir was always detected at 2 hours (mean decrease 75.9+/-24%). GH levels at 2 hours positively correlated with the other time-points (r(s) 0.97, 0.98, 0.97, 0.96 at 3, 4, 5 and 6 h, respectively; p<0.0001). During chronic treatment with maximal effective dose for 12 months, 61% of the patients achieved IGF1 <3 SD and 22% reached IGF1 <2 SD. GH nadir correlated with IGF1 decrease at 12 months (r(s) 0.76, p<0001). GH nadir of 9.2 ng/ml predicts IGF1 <3 SD with 82% sensitivity and 58% specificity (75% PPV, 67% NPV); for IGF1<2 SD, 75% sensitivity and 58% specificity are obtained for GH nadir 3.6 ng/ml, with 33% PPV and 89% NPV. Acute octreotide test reliably predicts response to long-term treatment; the short, 2-hour version is fully informative for therapeutic decisions in acromegalic patients.

Sulfonylurea compounds uncouple the glucose dependence of the insulinotropic effect of glucagon-like peptide 1.

Glucagon-like peptide (GLP)-1 mimetics have been reported to cause hypoglycemia when combined with sulfonylureas. This study investigated the impact of tolbutamide on the glucose dependence of the GLP-1-mediated effects on insulin, glucagon, and somatostatin secretion in the in situ perfused rat pancreas. At 3 mmol/l glucose, GLP-1 alone did not augment insulin secretion, whereas tolbutamide alone caused a rapid increase in insulin secretion. However, when GLP-1 and tolbutamide were administered simultaneously, insulin secretion increased significantly to 43.7 +/- 6.2 pmol/min (means +/- SE), exceeding the sum of the responses to GLP-1 (2.0 +/- 0.6 pmol/min; P = 0.019) and tolbutamide (11.3 +/- 3.8; P = 0.005) alone by a factor of 3.3. At 11 mmol/l glucose, co-infusion of GLP-1 and tolbutamide augmented insulin secretion to 141.7 +/- 10.3 vs. 115.36 +/- 14.1 (GLP-1) and 42.5 +/- 7.3 pmol/min (tolbutamide). Interestingly, increases in somatostatin secretion, both by glucose and GLP-1, were consistently paralleled by suppression of glucagon release. In conclusion, we demonstrate uncoupling of GLP-1 from its glucose dependence by tolbutamide. This uncoupling probably explains the tendency of GLP-1 to provoke hypoglycemia in combination with sulfonylureas. The results suggest that closure of ATP-sensitive K(+) channels by glucose might be involved in the glucose dependence of GLP-1's insulinotropic effect and that somatostatin acts as a paracrine regulator of glucagon release.

Chronic but not acute intracerebroventricular administration of amyloid beta-peptide(25-35) decreases somatostatin content, adenylate cyclase activity, somatostatin-induced inhibition of adenylate cyclase activity, and adenylate cyclase I levels in the rat hippocampus.

Although alterations in adenylate cyclase (AC) activity and somatostatin (SRIF) receptor density have been reported in Alzheimer's disease, the effects of amyloid beta-peptide (Abeta) on these parameters in the hippocampus are unknown. Our aim was to investigate whether the peptide fragment Abeta(25-35) can affect the somatostatinergic system in the rat hippocampus. Hence, Abeta(25-35) was injected intracerebroventricularly (i.c.v.) to Wistar rats in a single dose or infused via an osmotic minipump connected to a cannula implanted in the right lateral ventricle during 14 days. The animals were decapitated 7 or 14 days after the single injection and 14 days after chronic infusion of the peptide. Chronic i.c.v. infusion of Abeta(25-35) decreased SRIF-like immunoreactive content without modifying the SRIF receptor density, SRIF receptor expression, or the Gialpha(1), Gialpha(2), and Gialpha(3) protein levels in the hippocampus. This treatment, however, caused a decrease in basal and forskolin-stimulated AC activity as well as in the capacity of SRIF to inhibit AC activity. Furthermore, the protein levels of the neural-specific AC type I were significantly decreased in the hippocampus of the treated rats, whereas an increase in the levels of AC V/VI was found, with no alterations in type VIII AC. A single i.c.v. dose of Abeta(25-35) exerted no effect on SRIF content or SRIF receptors but induced a slight decrease in forskolin-stimulated AC activity and its inhibition by SRIF. Because chronic Abeta(25-35) infusion impairs learning and memory whereas SRIF facilitates these functions, the alterations described here might be physiologically important given the decreased cognitive behavior previously reported in Abeta-treated rats.

The influence of growth hormone status on physical impairments, functional limitations, and health-related quality of life in adults.

The availability of recombinant human GH and somatostatin analogs has resulted in widespread treatment for adults with GH deficiency (GHD) and those with GH excess (acromegaly). Despite being at opposite ends of the spectrum in terms of their GH/IGF-I axis, both of these populations experience overlapping somatic impairments. Adults with untreated GHD have low circulating levels of IGF-I that manifest as altered body composition with increased fat and reduced lean body and skeletal muscle mass. At the other end of the spectrum, adults with GH excess, who have elevated levels of IGF-I, also have altered body composition. Impairments that result from disorders of either GHD or GH excess are both associated with increased functional limitations, such as reduced ability to walk quickly for prolonged periods, and poorer health-related quality of life (HR-QoL). Adults with untreated GHD and GH excess both commonly complain of excessive fatigue that seems to be associated more with impaired aerobic than muscular performance. Several studies have documented that administration of GH or somatostatin analogs to adults with GHD or GH excess, respectively, ameliorates abnormal biochemical profile and the associated somatic impairments. However, whether these improvements translate into improved physical function in adults with GHD or GH excess remains largely unknown, and their impact on HR-QoL controversial. Review of placebo-controlled trials to date suggests that GH and somatostatin analogs have greater effects on gas exchange and aerobic performance than as anabolic agents on skeletal muscle mass and function. Future investigations should include dose-response studies to establish the optimal combination of pharmacological agents plus exercise required to improve not only biochemical markers but also physical function and HR-QoL in adults with GHD or GH excess.

Effect of probiotics and triple eradication therapy on the cyclooxygenase (COX)-2 expression, apoptosis, and functional gastric mucosal impairment in Helicobacter pylori-infected Mongolian gerbils.

BACKGROUND: Helicobacter pylori infection in Mongolian gerbils is an established experimental model of gastric carcinogenesis that mimics H. pylori-positive patients developing gastric ulcer and gastric cancer, but the effect of probiotic therapy on functional aspects of this infection remains unknown. METHODS: We compared the effects of intragastric inoculation of gerbils with H. pylori strain (cagA+ vacA+, 5 x 10(6) colony forming units/ml) with or without triple therapy including omeprazole, amoxicillin, and tinidazol or probiotic bacteria Lacidofil. Histology of glandular mucosa, the viable H. pylori, and density of H. pylori colonization were evaluated. The gastric blood flow was measured by H2-gas clearance method; the plasma gastrin and gastric luminal somatostatin were determined by RIA and expression of cyclooxygenase (COX)-2 and apoptotic Bax and Bcl-2 proteins were evaluated by Western blot. RESULTS: The gastric H. pylori infection was detected in all animals by histology and H. pylori culture. Basal gastric acid was significantly reduced in H. pylori-infected animals but not in those with triple therapy or Lacidofil. Early lesions were seen already 4 weeks upon H. pylori inoculation and consisted of chronic gastritis and glandular atypia associated with typical regenerative hyperplasia and increased mitotic activity and formation of apoptotic bodies. The H. pylori infection was accompanied by the fall in gastric blood flow, the marked increase in plasma gastrin, the significant fall in gastric somatostatin levels and Bcl-2 protein expression, and the rise in expression of COX-2 and Bax proteins. These mucosal changes were counteracted by the triple therapy and Lacidofil. CONCLUSIONS: H. pylori infection in gerbils, associated with regenerative hyperplasia of glandular structure, results in the suppression of gastric secretion, overexpression of COX-2, and enhancement in apoptosis and impairment of both, gastric blood flow and gastrin-somatostatin link that were reversed by anti-H. pylori triple therapy and attenuated by probiotics.

Intermittent hypoxia causes a suppressed pituitary growth hormone through somatostatin.

OBJECTIVES: The aim of this study was to investigate the response of the growth hormone (GH) in rat anterior pituitary to intermittent hypoxia (IH) and its modulation by hypothalamic somatostatin (SS). SETTING AND DESIGN: To observe the hypoxic response, rats were exposed to simulated altitude hypoxia (2 km or 5 km) in a hypobaric chamber for various days (4 h/d); to clarify SS-involvement, rats were pretreated with SS antagonist (cysteamine, CSH, 200 mg/kg/d, s.c.) then exposed to IH (5 km) for 2d. The GH mRNA and immunostaining GH in pituitary as well as immunostaining SS in median eminence (ME) of hypothalamus were assayed by RT-PCR and immuno-histochemistry, respectively. RESULTS: IH of 5 km altitude (IH5) markedly suppressed the body weight gain (BWG) of rats from 1d to 10d, and it was returned to control level henceforth, while no significant influence was showed in the group of IH of 2 km altitude (IH2). IH5 for 2 and 5d significantly decreased GH mRNA expression in the pituitary. The pituitary immunostaining GH was remarkably increased in groups of IH2 for 5, 10, and 15 d, and in groups of IH5 for 2, 5, and 10d. Immunostaining SS in ME was significantly reduced in group of IH2 for 5d, and in groups of IH5 for 2d and 5d. Pretreatments (s.c.) with SS antagonist (CSH) significantly reversed IH5-caused increase of immunostaining GH and reduction of mRNA levels in pituitary. CONCLUSIONS: IH may cause a short-term and recoverable suppression of GH release, and reduce GH mRNA expression in anterior pituitary, which may depend on the intensity and duration of the hypoxia. This suppression may be due to a modulation of hypoxia-activated SS.

Pepsinogen secretion in cholecystokinin-1 receptor-deficient rats.

We examined the roles of cholecystokinin (CCK)-2 receptors in the regulation of pepsinogen secretion in the CCK-1 receptor deficient Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Pepsinogen secretion was determined in fasted acute fistula OLETF and control Long-Evans Tokusima Otsuka (LETO) rats. Pepsinogen secretion in OLETF rats under basal conditions as well as in response to CCK-8 stimulation was significantly higher than that in LETO rats. CCK-1 receptor specific agonist ARL 15849 was unable to stimulate pepsinogen secretion in OLETF rats, whereas it elicited pepsinogen secretion in LETO rats to levels similar to those obtained with equimolar CCK-8 stimulation. CCK-2 receptor antagonist reduced basal pepsinogen secretion and completely abolished CCK-8-stimulated pepsinogen output in OLETF rats, whereas in LETO rats, it reduced basal pepsinogen secretion but augmented CCK-8-stimulated pepsinogen output. CCK-1 receptor antagonist loxiglumide also greatly decreased CCK-8-stimulated pepsinogen secretion in OLETF rat, which indicates that loxiglumide is not a specific CCK-1 receptor antagonist. Intravenous infusion of somatostatin antagonist significantly increased CCK-8-stimulated pepsinogen secretion in LETO rats, whereas it had no significant influence on CCK-8-stimulated pepsinogen secretion in OLETF rats. These results indicate that CCK-8 stimulates pepsinogen secretion via CCK-2 receptors in CCK-1 receptor deficient OLETF rats and that the higher CCK-8-stimulated as well as basal pepsinogen secretion in OLETF rats might result from an elimination of tonic inhibition by somatostatin that is released from D cells through mainly CCK-1 receptors.

Gly-Pro-Glu protects beta-amyloid-induced somatostatin depletion in the rat cortex.

The effect of Gly-Pro-Glu (GPE) on the somatostatinergic system of the temporal cortex in amyloid beta-peptide (Abeta) treated rats was investigated. Intracerebroventricular Abeta25-35 administration for 14 days (300 pmol/day) to ovariectomized rats produced a marked reduction in somatostatin (SRIF) content, SRIF receptor density and reduced the inhibitory effect of SRIF on adenylyl cyclase activity. I.p. injection of three doses (300 microg) of GPE on days 0, 6 and 12 resulted in a partial recovery of the parameters affected by Abeta25-35 administration. These results indicate that GPE may have an in vivo effect protecting the temporal cortical somatostatinergic system from Abeta insult.