Centrally located GLP-1 receptors modulate gastric slow waves and cardiovascular function in ferrets consistent with the induction of nausea.

Glucagon-like peptide-1 (GLP-1) receptor agonists are indicated for the treatment of Type 2 diabetes and obesity, but can cause nausea and emesis in some patients. GLP-1 receptors are distributed widely in the brain, where they contribute to mechanisms of emesis, reduced appetite and aversion, but it is not known if these centrally located receptors also contribute to a modulation of gastric slow wave activity, which is linked causally to nausea. Our aim was to investigate the potential of the GLP-1 receptor agonist, exendin-4, administered into the 3rd ventricle to modulate emesis, feeding and gastric slow wave activity. Thermoregulation and cardiovascular parameters were also monitored, as they are disturbed during nausea. Ferrets were used as common laboratory rodents do not have an emetic reflex. A guide cannula was implanted into the 3rd ventricle for delivering a previously established dose of exendin-4 (10nmol), which had been shown to induce emesis and behaviours indicative of 'nausea'. Radiotelemetry recorded gastric myoelectric activity (GMA; slow waves), blood pressure and heart rate variability (HRV), and core temperature; food intake and behaviour were also assessed. Exendin-4 (10nmol, i.c.v.) decreased the dominant frequency of GMA, with an associated increase in the percentage of bradygastric power (lasting ~4h). Food intake was inhibited in all animals, with 63% exhibiting emesis. Exendin-4 also increased blood pressure (lasting ~24h) and heart rate (lasting ~7h), decreased HRV (lasting ~24h), and caused transient hyperthermia. None of the above parameters were emesis-dependent. The present study shows for the first time that gastric slow waves may be modulated by GLP-1 receptors in the brain through mechanisms that appear independent from emesis. Taken together with a reduction in HRV, the findings are consistent with changes associated with the occurrence of nausea in humans.

Insights into the central pathways involved in the emetic and behavioural responses to exendin-4 in the ferret.

BACKGROUND: GLP-1 receptor agonists are utilised for the treatment of Type-2 diabetes but can be associated with undesirable effects of nausea and vomiting. OBJECTIVES: To investigate the role of GLP-1 receptors in mechanisms of emesis, behaviours indicative of nausea (BIN) and food intake in the ferret. RESULTS: Exendin-4 (10 and 30nmol, i.c.v.) induced emesis, inhibited food intake, and increased the frequency of BIN. Increases in c-Fos in the brainstem, midbrain and forebrain occurred in animals exhibiting emesis; no activation of the brainstem occurred in animals not vomiting. Exendin-4 (10nmol, i.c.v.) when preceded by i.c.v. saline (15µl), was not emetic but induced BIN and inhibited food intake; exendin (9-39) (100nmol) reduced BIN only. c-Fos showed that consistent with the absence of emesis in saline/exendin-4 treated animals there was no increase in c-Fos in the brainstem, but it increased in midbrain and forebrain nuclei. Excepting the amygdala, exendin (9-39) was without efffect on the increases in c-Fos. Analysis of c-Fos data showed a positive linear relationship between midbrain and forebrain areas irrespective of the occurrence of emesis induced by exendin-4. In contrast, brainstem and midbrain c-Fos levels were positively correlated, but only in animals with emesis. CONCLUSIONS: The brainstem is critical for exendin-4-induced emesis but suppression of food intake and BIN involves more rostral brain sites. Exendin-4-induced BIN and c-Fos activation of the amygdala are sensitive to exendin (9-39), whereas the suppression of food intake is not implicating separate control mechanisms for emesis and BIN.

Differential hypoglycaemic, anorectic, autonomic and emetic effects of the glucagon-like peptide receptor agonist, exendin-4, in the conscious telemetered ferret.

BACKGROUND: Rodents are incapable of emesis and consequently the emetic potential of glucagon-like peptide-1 receptor (GLP-1R) agonists in studies designed to assess a potential blood glucose lowering action of the compound was missed. Therefore, we investigated if the ferret, a carnivore with demonstrated translation capability in emesis research, would identify the emetic potential of the GLP-1R agonist, exendin-4, and any associated effects on gastric motor function, appetite and cardiovascular homeostasis. METHODS: The biological activity of the GLP-1R ligands was investigated in vivo using a glucose tolerance test in pentobarbitone-anesthetised ferrets and in vitro using organ bath studies. Radiotelemetry was used to investigate the effect of exendin-4 on gastric myoelectric activity (GMA) and cardiovascular function in conscious ferrets; behaviour was also simultaneously assessed. Western blot was used to characterize GLP-1R distribution in the gastrointestinal and brain tissues. RESULTS: In anesthetised ferrets, exendin-4 (30 nmol/kg, s.c.) reduced experimentally elevated blood glucose levels by 36.3%, whereas the GLP-1R antagonist, exendin (9-39) (300 nmol/kg, s.c.) antagonised the effect and increased AUC0-120 by 31.0% when injected alone (P < 0.05). In animals with radiotelemetry devices, exendin-4 (100 nmol/kg, s.c.) induced emesis in 1/9 ferrets, but inhibited food intake and decreased heart rate variability (HRV) in all animals (P < 0.05). In the animals not exhibiting emesis, there was no effect on GMA, mean arterial blood pressure, heart rate, or core body temperature. In the ferret exhibiting emesis, there was a shift in the GMA towards bradygastria with a decrease in power, and a concomitant decrease in HRV. Western blot revealed GLP-1R throughout the gastrointestinal tract but exendin-4 (up to 300 nM) and exendin (9-39), failed to contract or relax isolated ferret gut tissues. GLP-1R were found in all major brain regions and the levels were comparable those in the vagus nerve. CONCLUSIONS: Peripherally administered exendin-4 reduced blood glucose and inhibited feeding with a low emetic potential similar to that in humans (11% vs 12.8%). A disrupted GMA only occurred in the animal exhibiting emesis raising the possibility that disruption of the GMA may influence the probability of emesis occurring in response to treatment with GLP-1R agonists.

Dose-dependent anti-inflammatory and neuroprotective effects of an ανß3 integrin-binding peptide.

Previous studies have shown that prevention of leukocyte infiltration by targeting integrins involved in transendothelial migration may suppress the clinical and pathological features of neuroinflammatory disease. This study was designed to investigate the effects of C16, an ανß3 integrin-binding peptide, in an acute experimental allergic encephalomyelitis (EAE) rat model. Multiple histological and immunohistochemical staining, electron microscopy observation, ELISA assay, Western blot, and magnetic resonance imaging (MRI) were employed to assess the degree of inflammation, axonal loss, neuronal apoptosis, white matter demyelination, and extent of gliosis in the brain and spinal cord of differently treated EAE models. The results showed that C16 treatment could inhibit extensive leukocyte and macrophage accumulation and infiltration and reduce cytokine tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) expression levels. A significantly lower clinical score at the peak time of disease was also demonstrated in the C16 treated group. Moreover, astrogliosis, demyelination, neuronal death, and axonal loss were all alleviated in C16 treated EAE animals, which may be attributed to the improvement of microenvironment. The data suggests that C16 peptide may act as a protective agent by attenuating inflammatory progression and thus affecting the expression of some proinflammatory cytokines during neuroinflammatory disease.

Serum proteomic patterns for gastric lesions as revealed by SELDI mass spectrometry.

SELDI mass spectrometry was used to investigate protein expression in sera of patients with gastric cancer and gastritis compared to normal volunteers. Differences in peak morphology and intensity were observed in regions of 5910 Da, 5084 Da, 6640 Da and 8691 Da. Patients with gastric cancer exhibited an up-regulation of the 5910 Da peak and a down-regulation of the 8691 Da peak compared to the healthy volunteers; there was also some bi-partitioning and tri-partitioning at the 5084 Da peak. When comparing the sera of these cancer patients with those of gastritis, the former had an up-regulation of the 5910 Da peak and a down-regulation of the 6640 Da peak. This is the first report showing that SELDI sera analysis may be useful in the screening of gastric lesions.

Action of ondansetron and CP-99,994 on cisplatin-induced emesis and locomotor activity in Suncus murinus (house musk shrew).

Species possessing the emetic reflex are useful for anti-emetic screening. Assessing the potential of novel drugs to simultaneously reduce nausea and emesis in animals is problematic, however. In the present studies, therefore, the behavioural repertoire of Suncus murinus in response to the emetic chemotherapeutic drug cisplatin was studied in an attempt to characterize behaviours (including spontaneous locomotor activity) that may be relevant to nausea status. Cisplatin at 30 mg/kg, intraperitoneal, induced a robust emetic response but did not induce novel behaviour and failed to affect spontaneous locomotor activity. Ondansetron at 3 mg/kg, subcutaneous, and CP-99,994 at 10 mg/kg, subcutaneous, reduced emesis by 98% and 40.7%, respectively. Both ondansetron and CP-99,994, however, were inactive in modifying spontaneous locomotor activity in either cisplatin-treated or normal animals. Results are discussed in relation to other animal models of nausea and emesis.

Internal limiting membrane staining with various concentrations of indocyanine green dye under air in macular surgeries.

PURPOSE: To determine the effective minimal concentration of indocyanine green (ICG) for staining the internal limiting membrane (ILM) under air in macular surgeries and to report the clinical outcome of these patients. DESIGN: Prospective, randomized clinical trial. METHODS: Consecutive cases of macular hole (17 cases) and epiretinal membrane (ERM) (11 cases) undergoing primary surgery with ICG-stained ILM peeling were randomized to receive one of the three concentrations (mg/ml) of ICG (1): 0.25, (2) 0.5, and (3) 1.25. The number of ICG injections, visual quality of the stained ILM, and time used for ILM peeling were recorded. Internal limiting membrane specimens were subsequently examined under electron microscopy. Preoperative and postoperative clinical data with fluorescein angiography were recorded. RESULTS: There was a significantly smaller number of eyes with poor ILM staining in the 1.25-mg/ml group compared with the 0.25- to 0.5-mg/ml group (Fisher exact test, P =.04). The mean time required for ILM peeling was 4.2 minutes (range, 2.0-8.1 minutes). There was no significant difference in the time required for ILM peeling among the three concentration groups (one-way analysis of variance, P =.18) or between the macular hole and ERM group (two-tailed t test, P =.34). No ICG toxicity was found clinically or angiographically, except in one suspected case with ERM formation at the edge of ILM peeling. Electron microscopy of ILM specimens did not reveal any retinal elements. CONCLUSIONS: 1.25-mg/ml ICG under air stains the macular ILM consistently well for its removal in macular surgeries. The safety of ICG-stained ILM peeling needs further evaluation.