Zhi-Fu Guo

Different responses of circulating ghrelin, obestatin levels to fasting, re-feeding and different food compositions, and their local expressions in rats

Obestatin, a sibling of ghrelin derived from preproghrelin, opposes several physiological actions of ghrelin. Our previous study has demonstrated that both plasma ghrelin and obestatin levels were decreased significantly 2h after food intake in human. To further expand current knowledge, we investigated the temporal profiles of their levels in ad libitum fed rats, 48h fasted rats and 48h fasted rats refed 2h with a standard chow, crude fiber, 50% glucose or water, and their expressions in stomach, liver and pancreatic islets immunohistochemically. Plasma ghrelin and obestatin levels were measured by EIA. Plasma leptin, insulin and glucose levels were also evaluated. Both plasma ghrelin and obestatin levels increased significantly in fasted rats compared with ad libitum fed rats. The ingestion of standard chow produced a profound and sustained suppression of ghrelin levels, whereas plasma obestatin levels decreased significantly but recovered quickly. Intake of crude fiber or 50% glucose, however, produced a more profound and sustained suppression of obestatin levels, though they had relatively less impact on ghrelin levels. Plasma glucose was the only independent predictor of ghrelin levels, obestatin levels, and ghrelin to obestatin ratios. Obestatin immunoreactivity was detected in the fundus of stomach, liver and pancreatic islets, with roughly similar patterns of distribution to ghrelin. These data show quantitative and qualitative differences in circulating ghrelin and obestatin responses to the short-term feeding status and nutrient composition, and may support a role for obestatin in regulating metabolism and energy homeostasis.

Obestatin, obesity and diabetes

The high prevalence of obesity and diabetes will lead to higher rates of morbidity and mortality. It is well known that ghrelin plays a potential role in obesity and diabetes. Obestatin, a novel 23 amino acid amidated peptide encoded by the same gene that encodes ghrelin, was initially reported to have opposite actions to ghrelin in the regulation of food intake, emptying of the stomach and body weight. Recent work suggests that obestatin also regulate beta-cell survival and insulin secretion. The ghrelin-obestatin system is, therefore, a promising target for the developing of new drugs for the treatment of obesity and diabetes. This review summarizes the interrelationship between obestatin, obesity and diabetes.

Disturbance of circulating ghrelin and obestatin in chronic heart failure patients especially in those with cachexia

Plasma ghrelin was elevated in chronic heart failure (CHF) patients with cachexia. Obestatin, a sibling of ghrelin, opposes several actions of ghrelin. We, therefore, investigated plasma obestatin and ghrelin levels in patients with CHF. Total plasma ghrelin and obestatin levels were measured in 65 patients with CHF (22 with cardiac cachexia) and 15 controls. Ghrelin levels were significantly higher in patients with cachexia (1237.8+/-47.9 pg/ml) than those without cachexia (P=0.041) and controls (P<0.01). Obestatin levels correlated positively with ghrelin levels, and obestatin levels were significantly increased in patients with cachexia (282.3+/-13.0 pg/ml) than patients without cachexia and controls (both P<0.01). However, the ghrelin to obestatin ratios (4.5+/-0.2) were significantly lower in CHF patients with cachexia than controls (P<0.01). Ghrelin and ratio of ghrelin to obestatin were independent predictors of the development of cardiac cachexia. No association was found between ghrelin, obestatin and New York Heart Association functional class, brain natriuretic peptide. There was disturbance of circulating ghrelin and obestatin in the CHF patients especially those with cachexia, which may have a role in the pathogenesis of cardiac cachexia in CHF.

Plasma ghrelin and obestatin levels are increased in spontaneously hypertensive rats.

Obestatin, encoded by the same gene as ghrelin, was first described as a physiological opponent of ghrelin. We investigated fasting plasma ghrelin and obestatin levels in spontaneously hypertensive rats and Wistar-Kyoto rats. We found that ghrelin levels, obestatin levels and the ratio of ghrelin to obestatin were significantly higher in spontaneously hypertensive rats than Wistar-Kyoto rats. Systolic blood pressure and diastolic blood pressure were positively correlated; however, heart period and baroreflex sensitivity were negatively correlated with ghrelin levels. Systolic blood pressure was positively correlated, whereas baroreflex sensitivity was negatively correlated with obestatin levels. In addition, systolic blood pressure was a significantly independent variable of ghrelin levels, obestatin levels, and the ghrelin to obestatin ratio in a multiple regression analysis. Our data suggests that there is a disturbance of ghrelin and obestatin in the circulation of spontaneously hypertensive rats and the ghrelin/obestatin system might play a role in blood pressure regulation.

Association of obestatin with blood pressure in the third trimesters of pregnancy

Obestatin is a recently discovered 23-amino acid peptide encoded by the same gene that encodes ghrelin. It has been reported that there is a significant negative correlation between the plasma ghrelin concentration and systemic blood pressure in patients with pregnancy-induced hypertension. We investigated the plasma concentration of obestatin in 18 non-pregnant women, 18 normal pregnant women, and 15 patients with pregnancy-induced hypertension. The plasma concentrations of obestatin in these 3 groups of women were 63.4+/-9.5pg/ml, 38.1+/-6.3pg/ml, and 46.0+/-9.3pg/ml, respectively. In non-pregnant women, there was no correlation between the plasma obestatin concentration and the mean arterial pressure. However, there was a positive correlation between the plasma obestatin concentration and the mean arterial pressure in normal pregnant women and pregnant women with pregnancy-induced hypertension. These results suggest that obestatin may have some potential role in the regulation of blood pressure in normal pregnant women and women with pregnancy-induced hypertension.

Circulating ghrelin and ghrelin to obestatin ratio are low in patients with untreated mild-to-moderate hypertension.

Obestatin, encoded by the same gene as ghrelin, was first described as a physiological opponent of ghrelin. We investigated fasting plasma ghrelin and obestatin levels and ratio of ghrelin to obestatin in humans with untreated mild-to-moderate hypertension and humans with normal blood pressure. We found that the plasma concentration of ghrelin and the ratio of ghrelin to obestatin were significantly lower in hypertension group compared with control group (236.3±12.3 pg/ml vs 381.4±25.6 pg/ml, P<0.01; 0.89±0.06 vs 1.2±0.06, P<0.01). The plasma concentration of obestatin was lower in hypertension group compared with control group, but the difference between the two groups was not significant (276.2±15.1 pg/ml vs 325.4±25.8 pg/ml, P>0.05). In a multiple regression model, systolic blood pressure, triglyceride and obestatin were independent predictors of ghrelin (standardized coefficient=-0.332; P=0.019; standardized coefficient=-0.302; P=0.030; standardized coefficient=0.630; P<0.0005, respectively). In another multiple regression model, only ghrelin was an independent predictor of obestatin (standardized coefficient=0.861; P<0.0005). Both systolic blood pressure and triglyceride were independent predictors of ratio of ghrelin to obestatin (standardized coefficient=-0.385; P=0.033; standardized coefficient=-0.430; P=0.018, respectively). Our data suggests that there are disturbances of ghrelin and obestatin in the circulating plasma of humans and the ghrelin/obestatin system might play a role in blood pressure regulation.

Bolus intravenous injection of obestatin does not change blood pressure level of spontaneously hypertensive rat

Ghrelin, an endogenous ligand for the GH secretagogue receptor, has been shown to decrease arterial pressure. Obestatin, a sibling of ghrelin derived from preproghrelin, opposes several physiological actions of ghrelin. The aim of this study was to determine the effects of bolus intravenous injection of obestatin on blood pressure in spontaneously hypertensive rats. Three different dosages of obestatin (10, 50, and 100 microg/kg) and one dosage of ghrelin (10 microg/kg) were applied. The mean arterial pressure and heart period were continuously recorded for 30 min after injection of drugs. Baroreflex sensitivity was also investigated. In this study, we first demonstrated that intravenous injection of obestatin showed no significant effects on mean blood pressure (10 microg/kg: 113.8+/-2.0 mmHg vs. 114.4+/-1.6 mmHg; 50 microg/kg: 110+/-2.4 mmHg vs. 109+/-3.2 mmHg; 100 microg/kg: 115.9+/-1.5 mmHg vs. 115.8+/-2.4 mmHg; all P>0.05), heart period (10 microg/kg: 184.7+/-3.9 ms vs. 185.5+/-4.1ms; 50 microg/kg: 185.9+/-4.1 ms vs. 193.4+/-4.5 ms; 100 microg/kg: 137.7+/-4.5 ms vs. 143.9+/-5.6 ms; all P>0.05), or baroreflex sensitivity (10 microg/kg: 0.414+/-0.03 ms/mmHg vs. 0.442+/-0.02 ms/mmHg; 50 microg/kg: 0.453+/-0.04 ms/mmHg vs. 0.439+/-0.01 ms/mmHg; 100 microg/kg: 0.398+/-0.02 ms/mmHg vs. 0.401+/-0.01 ms/mmHg; all P>0.05), however, intravenous injection of ghrelin could decrease mean arterial pressure (115.9+/-1.5 mmHg vs. 108.6+/-3.6 mmHg, P<0.01) and increase heart period (132.4+/-2.8 ms vs. 152.6+/-7.4 ms, P<0.05), but did not change baroreflex sensitivity (0.36+/-0.009 ms/mmHg, P>0.05) in spontaneously hypertensive rats.

Endothelial enriched microRNAs regulate angiotensin II-induced endothelial inflammation and migration

The initial stage of atherosclerosis is characterised by recruitment of leukocytes to activate endothelial cells (ECs). MicroRNAs (miRNAs) are a class of 19 to 25 nucleotides, non-protein-coding RNAs that repress target gene expression by translational inhibition or mRNA degradation. The link between miRNA and endothelial functions is largely unknown. Northern blot showed that miR-155 and miR-221 were highly expressed in human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (VSMCs). Bioinformatics analysis proposed Ets-1, a key endothelial transcription factor for inflammation and tube formation, as a candidate target for miR-155 and miR-221/222 cluster. The effect was demonstrated by luciferase reporter assay and Western blot. By using Western blot, we also confirmed that angiotensin II type 1 receptor (AT1R) is a target of miR-155 in HUVECs. Quantitative PCR showed that Ets-1 and its downstream genes, including VCAM1, MCP1 and FLT1, were up-regulated in angiotensin II-stimulated HUVECs, and this effect was partially reversed by over-expression of miR-155 and miR-221/222. In addition, cell adhesion assay revealed over-expression of miR-155 and miR-221/222 effectively decreased the adhesion of Jurkat T cells to Ang II-stimulated HUVECs. Besides, by targeting AT1R, miR-155 can also decrease the HUVECs migration in response to Ang II. In summary, HUVECs highly expressed miR-155 may co-target AT1R and Ets-1 while miR-221/222 targets Ets-1, which indirectly regulate the expression of several inflammatory molecules of ECs, and therefore attenuate the adhesion of Jurkat T cells to activated HUVECs and reduce HUVECs migration. These findings present possible therapeutic targets in atherosclerosis.

Circulating obestatin is increased in patients with cardiorenal syndrome and positively correlated with vasopressin.

Obestatin regulates fluid and electrolyte homeostasis mainly by opposing the action of vasopressin (AVP). We measured plasma concentration of obestatin and AVP in patients with cardiorenal syndrome (CRS). Plasma AVP and obestatin concentration were measured in 34 patients with type II CRS. The data were compared to that in 31 patients with chronic kidney disease (CKD), 41 patients with chronic heart failure (CHF) and 30 healthy subjects. Obestatin was significantly higher in the patients with CRS (355.8 ± 85.1 pg/ml) than that in the healthy controls (212.3 ± 37.9 pg/ml, P<0.01), the patients with CKD (246.7 ± 34.3 pg/ml, P<0.01) and the patients with CHF (258.4 ± 112.1 pg/ml, P<0.01). AVP was also significantly higher in the patients with CRS (65.1 ± 36.0 pg/ml) than that in the healthy controls (38.5 ± 20.1 pg/ml, P<0.01), the patients with CKD (50.4 ± 24.8 pg/ml, P<0.01) and the patients with CHF (54.6 ± 16.3 pg/ml, P<0.01). Plasma concentration of obestatin was positively correlated with AVP plasma concentration in the overall analysis that included subjects from all disease categories (r = 0.219, P<0.05), but not within the CRS group. Plasma obestatin and vasopressin were elevated in patients with CRS. Plasma obestatin concentration seemed to be positively correlated with plasma AVP.

Successful catheter ablation of idiopathic premature ventricular contractions originating from the "right" ventricular outflow tract in a patient with dextrocardia and situs inversus viscerum.

Article history: Received 17 June 2015 Accepted 26 June 2015 Available online 2 July 2015 radiofrequency ablation with rare complications. However, after a review of the medical literature, and to our knowledge, there has been only one case report of catheter ablation of PVC in patients with dextrocardia and situs inversus published. Whats more, this is the first case of successful idiopathic “R”VOT-PVC ablation using a three-dimensional mapping system in an adult with dextrocardia and situs inversus viscerum. While the initial case of “R”VOT-PVC ablation in dextrocardia was reported by Bonnemeier et al. last A 65-year-old man was referred for catheter ablation of idiopathic premature ventricular contractions (PVC) because of severe palpitations for more than one year. No abnormality except for right-sided heart sounds was found in the physical examination and laboratory tests, which indicated likely dextrocardia. The chest radiogram and CT further confirmed it and abdominal ultrasound found situs inversus viscerum as well. Electrocardiogram indicated right axis deviation with an inversion of the electrical waves in I, aVR and aVL, as well as sustained ventricular bigeminy. The monomorphic PVC had left bundle branch block (LBBB) with inferior axis after V1–V6 inversed and positioned over the right chest (Fig. 1A). Transthoracic echocardiography revealed a normal “left” ventricular ejection fraction (LVEF 60%) without structural abnormality. The St. Jude Ensite 3000 mapping system was used to make a detailed electroanatomic map of his “right” ventricle. Activation mapping revealed the earliest site of ventricular activation 40 msec earlier than the QRS complex on surface electrocardiogram, which existed in the posterior septum of the “right” ventricular outflow tract (RVOT) (Fig. 2A). Pace mapping at this site showed a 12-lead match between paced beats and arrhythmia complexes. Radiofrequency ablation at this site resulted in PVC termination successfully (Fig. 2B–C) and no PVC could be induced by ventricular stimulation during the subsequent 30 min after the procedure, as well as for the rest of the hospital stay. There was no recurrence of PVC in subsequent 3 month follow-up according to the results of a 24 h-Holter.