Association of plasma acylated ghrelin with blood pressure and left ventricular mass in patients with metabolic syndrome

Molecular and cellular mechanisms underlying the hepatoprotective role of ghrelin against NAFLD progression

The underlying mechanisms for the development and progression of nonalcoholic fatty liver disease (NAFLD) are complex and multifactorial. Within the last years, experimental and clinical evidences support the role of ghrelin in the development of NAFLD. Ghrelin is a gut hormone that plays a major role in the short-term regulation of appetite and long-term regulation of adiposity. The liver constitutes a target for ghrelin, where this gut-derived peptide triggers intracellular pathways regulating lipid metabolism, inflammation, and fibrosis. Interestingly, circulating ghrelin levels are altered in patients with metabolic diseases, such as obesity, type 2 diabetes, and metabolic syndrome, which, in turn, are well-known risk factors for the pathogenesis of NAFLD. This review summarizes the molecular and cellular mechanisms involved in the hepatoprotective action of ghrelin, including the reduction of hepatocyte lipotoxicity via autophagy and fatty acid β-oxidation, mitochondrial dysfunction, endoplasmic reticulum stress and programmed cell death, the reversibility of the proinflammatory phenotype in Kupffer cells, and the inactivation of hepatic stellate cells. Together, the metabolic and inflammatory pathways regulated by ghrelin in the liver support its potential as a therapeutic target to prevent NAFLD in patients with metabolic disorders.

Fasting and postprandial ghrelin changes in older and younger volunteers

BACKGROUND

Little evidence is available on how both forms of ghrelin change during the aging process. Most of the earlier studies measured only total ghrelin levels and mainly in the fasting state. This study aimed to assess periprandial changes of acylated and deacylated ghrelin (AG, DAG) in volunteers aged ≥65 and <65 years and to establish an association between both forms of ghrelin and nutritional status in older volunteers.

METHODS

Venous blood for serum AG and DAG assays were collected in sixty volunteers after an overnight fast and two hours after the consumption of a standard 300 kcal-mixed meal. In those aged 65 years or more nutritional status was assessed.

RESULTS

Levels of DAG and AG were lower in older compared to younger volunteers in the fasting state as well as postprandial. DAG levels after a meal decreased in older, but not in younger subjects. However, significantly higher levels of postprandial AG were found in subjects with a risk of malnutrition and those with reduced appetite in comparison to well-nourished ones. Interestingly, elderly subjects with the lowest insulin and BMI had the lowest fasting AG levels and subjects with too high BMI and hyperinsulinemia presented also the highest fasting AG levels.

CONCLUSIONS

In older subjects, levels of both forms of ghrelin were lower and differential postprandial AG and DAG responses were observed when compared to younger subjects.

Effects of a 12-Week Diet versus Diet plus Aerobic and Resistance Exercise Program on Acylated and Desacylated Ghrelin, and Ghrelin O-Acyltransferase in Adolescent Girls with Obesity

This study investigated the effects of a 12-week diet versus diet plus aerobic and resistance exercise programme on acylated ghrelin (AG), desacylated ghrelin (DAG), and ghrelin O-acyltransferase (GOAT) concentrations in girls with obesity. We randomised 30 adolescents with obesity to a 12-week aerobic and resistance exercise group (EG) or a control group (CG). At baseline and at 4, 8, and 12 weeks, we measured their body composition, lipid profile, glucose, AG, DAG, and GOAT concentrations. In the EG, the body fat percentage decreased by 2.37% and was significantly lower than that in the CG. The DAG concentrations significantly increased by 48.3% and 27.4% in the EG and CG, respectively. At 4, 8, and 12 weeks, DAG concentrations were significantly higher in the EG than in the CG. AG concentrations were higher at week 12 than at baseline in both groups. In both groups, the GOAT concentrations increased at weeks 8 and 12; however, no between-group differences were observed in the changes in GOAT concentrations. This study showed increased DAG concentrations and non-significant changes in AG and GOAT concentrations after a 12-week aerobic and resistance exercise programme in girls with obesity. These findings suggest that an aerobic and resistance exercise programme influences appetite-regulating hormones, mainly through changes in DAG concentrations.

Relationship between atrophic gastritis, serum ghrelin and body mass index

OBJECTIVE

Atrophic gastritis may affect circulating ghrelin levels and, indirectly, body mass index. The aim of this study was to investigate the relationship between atrophic gastritis, focusing on autoimmune atrophic gastritis and advanced stages of atrophic gastritis, serum ghrelin levels and BMI.

METHODS

Sixty-three patients, of whom 18 had autoimmune atrophic gastritis, 27 non-autoimmune antrum and corpus atrophic gastritis, and 18 non-atrophic gastritis or antrum-limited atrophic gastritis (control group) were assessed. All participants underwent endoscopy with multiple gastric biopsies. Atrophic gastritis was diagnosed by histology, classified according to the Updated Sydney System and staged by the Operative Link on Gastritis Assessment (OLGA) Classification. Total serum ghrelin, body weight and height were measured.

RESULTS

Compared with control patients (144.6 ± 111 pg/ml), mean serum level of total ghrelin was higher in patients with autoimmune atrophic gastritis (226.08 ± 243.03 pg/ml, P = 0.65) and lower in those with both antrum and corpus atrophic gastritis (74.51 ± 37.38 pg/ml, P = 0.12), although differences were not statistically significant. Serum ghrelin decreased in patients with advanced OLGA stages of atrophic gastritis. In non-obese patients BMI was significantly lower in those with both antrum and corpus atrophic gastritis than in control patients (23.1 ± 1.8 vs. 24.5 ± 1.6, P = 0.01), also after adjustment for age and sex (P = 0.02); BMI was positively correlated with serum total ghrelin (r = 0.51, P < 0.001).

CONCLUSION

Advanced stages of atrophic gastritis, but not autoimmune atrophic gastritis, seem to be associated with lower serum levels of ghrelin and lower BMI. In non-obese patients, BMI was positively correlated with total serum ghrelin.

[The «obesity paradox» and its degree of proof]

The article gives a critical assessment of the so-called obesity paradox. Methodological errors that occur in the organization of studies that studied the obesity paradox and the formation of comparison groups are highlighted. There are also examples of the disappearance of the obesity paradox when taking into account additional risk factors. The organization of prospective studies or more careful consideration of all currently known risk factors for cardiovascular diseases (CVD) will significantly improve the results of the study of the effect of overweight and obesity on mortality in patients with CVD. Thus, despite the biological possibility of the existence of a positive effect of adipose tissue in CVD, the presence of a large number of errors identified in the analysis of the work of researchers obesity paradox require to reconsider the existence of this phenomenon, it should be taken into account the possibility that the obesity paradox may be a consequence of improper design studies to investigate this phenomenon.

GHRL Gene Leu72Met Polymorphism and Type 2 Diabetes Mellitus: A Meta-Analysis Involving 8,194 Participants

Background: Although many studies indicate a positive correlation between GHRL gene Leu72Met polymorphism and an increased susceptibility to type 2 diabetes mellitus (T2DM), inconsistencies between independent studies still remain. Objective: Considering the inconsistencies between them, we have performed the current meta-analysis study. The objective of this study is to better examine the correlation of the GHRL gene Leu72Met polymorphism and T2DM. Methods: The current meta-analysis, involving 8,194 participants from 11 independent studies, was performed. A fixed effect model was used to evaluate the pooled odds ratios (ORs) and the corresponding 95% confidence intervals (95% CIs). Results: A significant association was found between T2DM and GHRL gene Leu72Met polymorphism under recessive (OR: 1.33, 95% CI: 1.01-1.76, P = 0.04), and homozygous genetic models (OR: 1.34, 95% CI: 1.01-1.78, P = 0.04) in the whole population. The correlation was more distinct in our subgroup analysis of the Chinese population under recessive (OR: 1.52, 95% CI: 1.07-2.15, P = 0.02), dominant (OR: 1.70, 95% CI: 1.38-2.10, P < 0.00001), additive (OR: 1.16, 95% CI: 1.02-1.33, P = 0.02), and homozygous genetic models (OR: 1.54, 95% CI: 1.07-2.20, P = 0.02). Conclusions: In short, GHRL gene Leu72Met polymorphism was significantly correlated with increased T2DM risk, particularly in the Chinese population. Individuals carrying the Met72 allele of GHRL Leu72Met gene polymorphism, particularly those of Chinese ancestry, may be more susceptible to developing T2DM disease.

One Year of Yoga Training Alters Ghrelin Axis in Centrally Obese Adults With Metabolic Syndrome

Introduction: Metabolic syndrome (MetS) is a multiplex cardiometabolic manifestation associated with type 2 diabetes mellitus and cardiovascular diseases. Yoga training has been shown to alleviate MetS. Recently, circulatory ghrelin profile was demonstrated to be associated with MetS. This study examined the effects of 1 year of yoga training on β-cell function and insulin resistance, and the involvement of metabolic peptides, including unacylated ghrelin (UnAG), acylated ghrelin (AG), obestatin, growth hormone (GH), and insulin, in the beneficial effects of yoga training in centrally obese adults with MetS. Methods: This was a follow up study, in which data of risk factors of MetS, physical performance tests [resting heart rate (HR), chair stand test (CS), chair sit and reach test (CSR), back scratch test (BS), and single leg stand tests (SLS)] and serum samples of 79 centrally obese MetS subjects aged 58 ± 8 years (39 subjects received 1-year yoga training and 40 subjects received no training) were retrieved for analyses. β-cell function and insulin resistance were examined by Homeostasis Model Assessment (HOMA). Circulating levels of UnAG, AG, obestatin, GH, and insulin were determined by enzyme-linked immunosorbent assay using fasting serum samples. Generalized estimating equation analysis and Mann-Whitney U-test were used to detect statistically significant differences between groups. Results: Waist circumference (WC) was significantly decreased after yoga intervention (control: +2%; yoga: -4%). Significant improvements in HR (control: +2%; yoga: -5%), CS (control: -1%; yoga: +24%), CSR left (control: worsen by 0.90 cm; yoga: improved by 4.21 cm), CSR right (control: worsen by 0.75 cm; yoga: improved by 4.28 cm), right side of BS (control: improved by 0.19 cm; yoga: improved by 4.31 cm), SLS left (control: -10%; yoga: +86%), and SLS right (control: -6%; yoga: +47%) were observed after 1-year yoga training. No significant difference was found between the two groups in insulin, HOMA indices, and disposition index. Yoga training significantly increased circulating GH (control: -3%; yoga: +22%), total circulating ghrelin (control: -26%; yoga: +13%), and UnAG (control: -27%; yoga: +14%), whereas decreased AG (control: -7%; yoga: -33%) and obestatin (control: +24%; yoga: -29%). Conclusion: One-year of yoga training modulated total ghrelin, UnAG, AG, obestatin, and GH while exerting beneficial effects on physical functions and central obesity in adults with MetS. The beneficial effects of yoga may be associated with the alteration of ghrelin gene product and GH.

Ghrelin suppresses cardiac fibrosis of post-myocardial infarction heart failure rats by adjusting the activin A-follistatin imbalance

Ghrelin, a growth hormone-releasing peptide, potentially improves cardiac function, but the mechanisms remain unclear. In the study, the rat heart failure (HF) model was established by ligating the left anterior descending coronary artery (LAD) and treated with ghrelin (100μg/kg, subcutaneous injection, bid); neonatal rat cardiomyocytes were cultured and stimulated with Ang II (0.1μM) and ghrelin(0.1μM) to explore the underlying mechanism of ghrelin in myocardial remodeling. Hemodynamic changes and serum brain natriuretic peptide (BNP) concentrations were measured to assess cardiac function. Left ventricular mass index (LVMI), hematoxylin and eosin (H&E) staining, and Masson's trichrome staining were performed to evaluate myocardial fibrosis. Interestingly, ghrelin significantly improved cardiac function by inhibiting fibrous tissue proliferation. To further explore the mechanisms by which ghrelin interferes with myocardial fibrosis, the levels of activin A (Act A) and its blocker-follistatin (FS) were examined by immunohistochemistry; Act A levels were significantly increased in the myocardial infarction (MI), and ghrelin administeration downregulated Act A expression. In contrast, FS expression showed no significant change in all experimental groups. Furthermore, ghrelin decreased Ang II-induced Act A expression with no effect on FS expression in primary rat cardiomyocytes in vitro (real-time quantitative PCR and ELISA). Thus, ghrelin corrected the Act A/FS imbalance. Finally, Act A treated cultured primary rat cardiac fibroblasts (CFs) showed increased proliferation [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay] and enhanced expressions of type I and type III collagen (Col I and Col III) (real-time quantitative PCR). These data suggest that ghrelin inhibits myocardial fibrosis, attenuates left ventricular remodeling, and eventually improves cardiac function by adjusting Act A/FS imbalance.

Sleeve Gastrectomy Decreases Body Weight, Whole-Body Adiposity, and Blood Pressure Even in Aged Diet-Induced Obese Rats

BACKGROUND

Aging and obesity are two conditions associated with increased risk of cardiovascular disease. Our aim was to analyze whether an advanced age affects the beneficial effects of sleeve gastrectomy on weight loss and blood pressure in an experimental model of diet-induced obesity (DIO).

METHODS

Young (6-month-old) and old (18-month-old) male Wistar DIO rats (n = 101) were subjected to surgical (sham operation and sleeve gastrectomy) or dietary interventions (pair-fed to the amount of food eaten by sleeve gastrectomized animals). Systolic (SBP), diastolic (DBP), and mean (MBP) blood pressure values and heart rate (HR) were recorded in conscious, resting animals by non-invasive tail-cuff plethysmography before and 4 weeks after surgical or dietary interventions.

RESULTS

Aging was associated with higher (P < 0.05) body weight and subcutaneous and perirenal fat mass as well as mild cardiac hypertrophy. Sleeve gastrectomy induced a reduction in body weight, whole-body adiposity, and serum total ghrelin in both young and old DIO rats. The younger group achieved a higher excess weight loss than the older group (164 ± 60 vs. 82 ± 17 %, P < 0.05). A significant (P < 0.05) decrease in insulin resistance, SBP, DBP, MBP, and HR without changes in heart weight was observed after sleeve gastrectomy independently of age.

CONCLUSION

Our results provide evidence for the effectiveness of sleeve gastrectomy without increased operative risk in body weight and blood pressure reduction even in aged animals via endocrine changes that go beyond the mere caloric restriction.

The Acylated/Unacylated Ghrelin Ratio Is Similar in Patients With Acromegaly During Different Treatment Regimens

BACKGROUND

Data on plasma acylated ghrelin (AG) and unacylated ghrelin (UAG) levels in acromegaly are limited. High AG/UAG ratios are linked with type 2 diabetes, obesity, and hyperphagia (e.g., in Prader-Willi syndrome).

OBJECTIVE

To assess fasting plasma AG and UAG levels, and the AG/UAG ratio in acromegaly patients receiving combination treatment of long-acting somatostatin analogs (LA-SSAs) and pegvisomant (PEGV; n = 60). We used as controls acromegaly patients whose disease was controlled with PEGV monotherapy and medically naïve patients with active acromegaly.

METHODS

Fasting venous blood samples were collected and directly stabilized to inhibit deacylation of AG. Plasma AG and UAG levels were determined by double-antibody sandwich enzyme immunoassay, and the AG/UAG ratio was calculated.

RESULTS

Plasma AG and UAG levels were significantly lower in patients with acromegaly receiving combination treatment [median, interquartile range (IQR): AG: 8.5 pg/mL, 2.9 to 21.1 pg/mL; UAG: 26.9 pg/mL, 11.2 to 42.1 pg/mL] compared with patients using PEGV alone [AG: 60.5 pg/mL (IQR, 58.8 to 77.4 pg/mL); UAG: 153.7 pg/mL (IQR, 127.3 to 196.0 pg/mL)] and medically naïve patients with acromegaly [AG: 24.0 pg/mL (IQR, 12.6 to 49.7 pg/mL); UAG: 56.3 pg/mL (IQR, 43.4 to 61.5 pg/mL)]. However, AG/UAG ratios were similar in all groups.

CONCLUSIONS

Although plasma AG and UAG are suppressed during combination treatment with LA-SSAs and PEGV, the AG/UAG ratio remained similar. This shows that SSAs decrease both AG and UAG levels, which suggests that they do not alter metabolism significantly in acromegaly patients.

Metabolic Syndrome is Associated with Lower Plasma Levels of Desacyl Ghrelin and Total Ghrelin in Asymptomatic Middle-aged Korean Men

BACKGROUND

Desacyl ghrelin is acylated by ghrelin O-acyltransferase (GOAT) and converted to acyl ghrelin. To date, little is known about the relationship among the levels of these two forms of ghrelin, GOAT level, and insulin resistance in Asian individuals. The purpose of this study was to determine the relationship between insulin resistance and the levels of plasma acyl ghrelin, desacyl ghrelin, and GOAT in asymptomatic middle-aged Korean men.

METHODS

This cross-sectional study evaluated 78 asymptomatic middle-aged Korean men with metabolic syndrome (MS). We examined the correlation between the plasma levels of acyl ghrelin, desacyl ghrelin, and GOAT and sociodemographic, dietary, anthropometric, and metabolic parameters, as well as the association between insulin resistance and plasma levels of acyl ghrelin, desacyl ghrelin, and GOAT.

RESULTS

The levels of desacyl ghrelin and total ghrelin were significantly lower in the MS group than in the non-MS group (P<0.017, P=0.01, respectively). HOMA-IR values showed a significant negative correlation with desacyl ghrelin (r=-0.271, P=0.017) and total ghrelin (r=-0.271, P=0.016) levels. Acyl ghrelin and GOAT were not significantly correlated with HOMA-IR, and no correlation was found between the plasma levels of the two ghrelin types and GOAT.

CONCLUSION

The plasma levels of desacyl ghrelin and total ghrelin in middle-aged Korean men with MS were lower than in those without MS. A significant negative correlation was observed between desacyl ghrelin level and HOMA-IR; however, no correlation was found between plasma levels of acyl ghrelin and GOAT and HOMA-IR.

Acylated and desacyl ghrelin are associated with hepatic lipogenesis, β-oxidation and autophagy: role in NAFLD amelioration after sleeve gastrectomy in obese rats

Bariatric surgery improves non-alcoholic fatty liver disease (NAFLD). Our aim was to investigate the potential role of ghrelin isoforms in the resolution of hepatic steatosis after sleeve gastrectomy, a restrictive bariatric surgery procedure, in diet-induced obese rats. Male Wistar rats (n = 161) were subjected to surgical (sham operation and sleeve gastrectomy) or dietary interventions [fed ad libitum a normal (ND) or a high-fat (HFD) diet or pair-fed]. Obese rats developed hepatosteatosis and showed decreased circulating desacyl ghrelin without changes in acylated ghrelin. Sleeve gastrectomy induced a dramatic decrease of desacyl ghrelin, but increased the acylated/desacyl ghrelin ratio. Moreover, sleeve gastrectomy reduced hepatic triglyceride content and lipogenic enzymes Mogat2 and Dgat1, increased mitochondrial DNA amount and induced AMPK-activated mitochondrial FFA β-oxidation and autophagy to a higher extent than caloric restriction. In primary rat hepatocytes, the incubation with both acylated and desacyl ghrelin (10, 100 and 1,000 pmol/L) significantly increased TG content, triggered AMPK-activated mitochondrial FFA β-oxidation and autophagy. Our data suggest that the decrease in the most abundant isoform, desacyl ghrelin, after sleeve gastrectomy contributes to the reduction of lipogenesis, whereas the increased relative acylated ghrelin levels activate factors involved in mitochondrial FFA β-oxidation and autophagy in obese rats, thereby ameliorating NAFLD.

Association of ghrelin with cardiometabolic risk factors in Iranian adolescents: the CASPIAN-III study

Introduction: Current evidence suggests that ghrelin could contribute to the development of metabolic syndrome (MetS) in adults, but limited experience exists in adolescents. This study aims to explore the association of ghrelin levels with the MetS components among Iranian adolescents.

Methods: In this case-control study, 32 adolescents with MetS and 148 healthy controls were selected randomly from the childhood and Adolescence Surveillance and Prevention of Adult Non communicable disease (CASPIAN-III) study. MetS was defined according to the Adult Treatment Panel III (ATP III) criteria modified for children and adolescents. Anthropometric measures (including body mass index [BMI], waist circumference [WC] and waist to height ratio [WHtR]), blood pressure (BP) and biochemical data (including fasting blood sugar [FBS], triglyceride [TG], high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], total cholesterol [TC] and gerlin) were measured.

Results: Total ghrelin level was significantly higher in students without MetS compared to those with MetS (748.89 ± 85.04 vs. 728.72 ± 90.36 [pg/mL]; P < 0.001). Significant negative correlations were seen between ghrelin levels and BMI, WC, WHtR, TG, and TC. Ghrelin had also relatively strong inverse correlations with FBS (r = −0.59, P< 0.001), LDL-C (r = −0.56, P < 0.001), and positive correlation with HDL-C (r = 0.60, P < 0.001). Compared with the children with MetS, in those without MetS, ghrelin was significantly associated with HDL-C and LDL-C. A decreasing trend was observed in the mean ghrelin level across increasing number of MetS components (P for trend <0.001).

Conclusion: We observed a relationship between ghrelin concentration and MetS components in adolescents.

RETRACTED: Ghrelin protects infarcted myocardium by induction of autophagy and AMP-activated protein kinase pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. It contains LM images in figure 2E, which were originally published in Nat. Comm. 6/2015, p. 1-14 (http://doi:10.1038/ncomms8388). Permission to reproduce this figure was not requested nor granted by the authors of the original article for its re-use. The authors of this article would like to apologize to all affected parties.

Serum ghrelin and prediction of metabolic parameters in over 20-year follow-up

Ghrelin is a peptide hormone from the stomach, with an ability to release growth-hormone from the pituitary. Numerous cross-sectional studies indicate that ghrelin also has a role in metabolic abnormalities, such as metabolic syndrome and type 2 diabetes, but evidence for long-term effect is scarce. We investigated, whether ghrelin concentration measured in middle age would predict the development or absence of metabolic disturbances subsequently. Study population consisted of 600 middle-aged persons, and the follow-up time was approximately 21 years. Plasma total ghrelin concentration was measured at the baseline, and divided to tertiles. Numerous anthropometric and other clinical measurements (including blood pressure), and laboratory test were made both at the baseline and at the follow-up. After the follow-up the prevalence of high systolic blood pressure according to MetS IDF-criteria was the lowest in the highest ghrelin tertile, and the highest in the first (p<0.03). When only subjects free of hypertension medication at baseline were considered, subjects belonging to the highest ghrelin tertile developed less new hypertension and high blood pressure according to IDF-criteria as well as medication for it during the follow-up (p<0.05). Although serum insulin levels were negatively correlated to ghrelin levels at both points in time (p<0.001 at baseline and p=0.003 at follow-up), plasma ghrelin concentration did not predict the development of abnormalities in glucose tolerance. The association with ghrelin and metabolic syndrome was lost during the follow-up. In conclusion, our results suggest high ghrelin to be protective against the development of hypertension in the long-term follow-up.

Plasma Levels of Acylated Ghrelin in Children with Pulmonary Hypertension Associated with Congenital Heart Disease

This study aims to estimate plasma levels of acylated ghrelin in children with pulmonary hypertension (PH) associated with congenital heart disease (CHD) and to correlate the levels of acylated ghrelin with endothelin-1 (ET-1), nitric oxide (NO), and clinical hemodynamic parameters. We investigated the plasma concentration of acylated ghrelin, ET-1, NO, and the hemodynamic parameters in 20 children with CHD, 20 children with PH-CHD, and 20 normal children. Plasma-acylated ghrelin and NO levels were significantly higher in CHD group than in control subjects (P < 0.001). Moreover, plasma-acylated ghrelin, ET-1, and NO levels were significantly elevated in PH-CHD group compared with the CHD group (P < 0.05). In PH-CHD children, plasma-acylated ghrelin levels correlated positively with pulmonary artery systolic pressure (PASP; r = 0.740, P < 0.001), pulmonary artery diastolic pressure (PADP; r = 0.613, P = 0.004), right ventricular systolic pressure (RVSP; r = 0.642, P = 0.002), mean pulmonary arterial hypertension (mPAP; r = 0.685, P = 0.001), right ventricle diameter (RVD; r = 0.473, P = 0.035), pulmonary artery trunk diameter (PAD; r = 0.613, P = 0.004), NO (r = 0.463, P = 0.04), and ET-1 (r = 0.524, P = 0.018). Plasma-acylated ghrelin levels were elevated both in CHD and in PH-CHD. Increased acylated ghrelin levels correlated positively with ET-1, NO, PASP, PADP, RVSP, mPAP, RVD, and PAD. Acylated ghrelin may be a new biomarker of PH-CHD.

Protective effects of desacyl ghrelin on diabetic cardiomyopathy

AIM

Diabetic cardiomyopathy is a specific complication of type 2 diabetes mellitus, which causes progressive cardiac dysfunction. Desacyl ghrelin has been preliminarily demonstrated to have beneficial effects on cardiovascular system and glucose metabolism, which are both related to diabetic cardiomyopathy. The aim of this study was to investigate the protective effects of desacyl ghrelin on cardiac dysfunction, cardiac fibrosis, and cellular autophagy in a type 2 diabetic mouse model.

MATERIALS AND METHODS

Fourteen- to eighteen-week-old db/db diabetic and db/+ non-diabetic mice were intraperitoneally treated with desacyl ghrelin at a dosage of 100 μg/kg for ten consecutive days. Ventricular fractional shortening was examined as an indicator of cardiac function by transthoracic echocardiography.

RESULTS

The presence of diabetic cardiomyopathy was evident by the reduction in fractional shortening shown in our examined db/db mice. Intriguingly, this reduction in fractional shortening was not observed in the hearts of db/db mice treated with desacyl ghrelin. Cardiac fibrosis (indicated by excessive collagen deposition, decreased by Adiponectin and Mmp13 expression, and up-regulated by Mmp8 expression) and impairment of autophagic signalling (indicated by decreases in Foxo3 and LC3 II-to-LC3 I ratio) were shown in the hearts of diabetic mice. All these cellular and molecular alterations were alleviated by desacyl ghrelin treatment. The key cardiac pro-survival cellular signals including AMPK, Akt, ERK1/2, and GSK3α/β were impaired in the diabetic hearts, but the administration of desacyl ghrelin attenuated these signalling impairments.

CONCLUSIONS

These results collectively demonstrate that desacyl ghrelin protects the heart against cardiac dysfunction in type 2 diabetic mice by inhibiting excessive collagen deposition and enhancing cardiac autophagic signalling via the pro-survival cellular AMPK/ERK1/2 signalling pathways.

Inverse association of des-acyl ghrelin with worksite blood pressure in overweight/obese male workers

BACKGROUND

Job strain, defined as a combination of high job demands and low job control, has been reported to elevate blood pressure (BP) during work. Meanwhile, a recent experimental study showed that ghrelin blunted the BP response to such mental stress. In the present study, we examined the hypothesis that des-acyl ghrelin may have some beneficial effects on worksite BP through modulating the BP response to work-related mental stress, i.e., job strain.

METHODS

Subjects were 34 overweight/obese male day-shift workers (mean age 41.7 ± 6.7 years). No subjects had received any anti-hypertensive medication. A 24-h ambulatory BP monitoring was recorded every 30 min on a regular working day. The average BP was calculated for Work BP, Morning BP, and Home BP. Job strain was assessed using the short version of the Japanese Job Content Questionnaire.

RESULTS

Des-acyl ghrelin showed significant inverse correlations with almost all BPs except Morning SBP, Morning DBP, and Home DBP. In multiple regression analysis, des-acyl ghrelin inversely correlated with Work SBP after adjusting for confounding factors. Des-acyl ghrelin was also negatively associated with BP changes from Sleep to Morning, Sleep to Work, and Sleep to Home.

CONCLUSIONS

Des-acyl ghrelin was inversely associated with Worksite BP, suggesting a unique beneficial effect of des-acyl ghrelin on Worksite BP in overweight/obese male day-shift workers.

Does des-acyl ghrelin improve glycemic control in obese diabetic subjects by decreasing acylated ghrelin levels?

OBJECTIVE

The objective of this study was to assess the effects of a continuous overnight infusion of des-acyl ghrelin (DAG) on acylated ghrelin (AG) levels and glucose and insulin responses to a standard breakfast meal (SBM) in eight overweight patients with type 2 diabetes. Furthermore, in the same patients and two additional subjects, the effects of DAG infusion on AG concentrations and insulin sensitivity during a hyperinsulinemic-euglycemic clamp (HEC) were assessed.

RESEARCH DESIGN AND METHODS

A double-blind, placebo-controlled cross-over study design was implemented, using overnight continuous infusions of 3 and 10  μg DAG/kg per h and placebo to study the effects on a SBM. During a HEC, we studied the insulin sensitivity.

RESULTS

We observed that, compared with placebo, overnight DAG administration significantly decreased postprandial glucose levels, both during continuous glucose monitoring and at peak serum glucose levels. The degree of improvement in glycemia was correlated with baseline plasma AG concentrations. Concurrently, DAG infusion significantly decreased fasting and postprandial AG levels. During the HEC, 2.5  h of DAG infusion markedly decreased AG levels, and the M-index, a measure of insulin sensitivity, was significantly improved in the six subjects in whom we were able to attain steady-state euglycemia. DAG administration was not accompanied by many side effects when compared with placebo.

CONCLUSIONS

DAG administration improves glycemic control in obese subjects with type 2 diabetes through the suppression of AG levels. DAG is a good candidate for the development of compounds in the treatment of metabolic disorders or other conditions with a disturbed AG:DAG ratio, such as type 2 diabetes mellitus or Prader-Willi syndrome.

Gender differences in ghrelin association with cardiometabolic risk factors in arab population

Ghrelin is a stomach produced hormone that has been shown to have protective role against development of CVD which is a leading cause of death in the Arab world. The objective of this study is to examine the gender difference in association between traditional CVD risk factors and plasma ghrelin among Arabs. 359 Arab residents in Kuwait participated in a cross-sectional survey (≥20 years old): 191 were females and 168 were males. Plasma level of ghrelin was assessed using Luminex-based assay. Ghrelin levels were significantly higher in females (935 ± 78 pg/mL) than males (763 ± 65 pg/mL) (P = 0.0007). Females showed inverse association with WC (r = -0.23, P = 0.001) and HbA1C (r = -0.19, P = 0.0102) as well as SBP (r = -0.15, P = 0.0383) and DBP (r = -0.16, P = 0.0230), respectively. Higher levels of ghrelin were shown to associate with increased insulin resistance, as measured by HOMAIR, in male Arab subjects (P-trend = 0.0202) but not in females. In this study we show that higher ghrelin level was negatively associated with measures of obesity, HbA1C, and blood pressure in females and positively associated with increased insulin resistance in Arab males.

Extraordinary level of hormone and number of ghrelin cells in the stomach and duodenum of an obese woman

Obesity is a major metabolic disorder, in which ghrelin plays a significant role. The objective of this study was to characterize the morphology of ghrelin cells in the stomach and duodenum and the levels of ghrelin and leptin in the serum of a 52-year-old obese woman. Material for the study was obtained from the stomachs and duodenum, of obese and control women. Each subject had been treated at the Intensive Care Unit of the Clinical University Hospital in Białystok, due to brain damage, due to primary cardiac arrest. After brain death was diagnosed and individual death was confirmed by doctors, stomach and duodenum samples were collected from each body. Paraffin sections were stained with hematoxylin and eosin and processed for immunolocalization of ghrelin. The density of ghrelin cells in each part of the gastrointestinal tract was estimated under a light microscope with a digital camera. Ghrelin-IR cells were also analyzed in terms of morphometric features such as length, width and area. The ghrelin and leptin concentrations in each blood sample were measured by ELISA. Immunohistochemical studies revealed a small number of ghrelin cells in the stomach and duodenum which did not reflect the high level of hormone. The obese woman had lower number of ghrelin cells in the stomach and duodenum and elevated ghrelin and leptin levels in serum. It can therefore be assumed that additional source of ghrelin and probably changes in activity of ghrelin o-acylotransferase, are responsible for the high concentration of ghrelin in the obese woman.

Novel molecular aspects of ghrelin and leptin in the control of adipobiology and the cardiovascular system

Ghrelin and leptin show opposite effects on energy balance. Ghrelin constitutes a gut hormone that is secreted to the bloodstream in two major forms, acylated and desacyl ghrelin. The isoforms of ghrelin not only promote adiposity by the activation of hypothalamic orexigenic neurons but also directly stimulate the expression of several fat storage-related proteins in adipocytes, including ACC, FAS, LPL and perilipin, thereby stimulating intracytoplasmic lipid accumulation. Moreover, both acylated and desacyl ghrelin reduce TNF-α-induced apoptosis and autophagy in adipocytes, suggesting an anti-inflammatory role of ghrelin in human adipose tissue. On the other hand, leptin is an adipokine with lipolytic effects. In this sense, leptin modulates via PI3K/Akt/mTOR the expression of aquaglyceroporins such as AQP3 and AQP7 that facilitate glycerol efflux from adipocytes in response to the lipolytic stimuli via its translocation from the cytosolic fraction (AQP3) or lipid droplets (AQP7) to the plasma membrane. Ghrelin and leptin also participate in the homeostasis of the cardiovascular system. Ghrelin operates as a cardioprotective factor with increased circulating acylated ghrelin concentrations in patients with left ventricular hypertrophy (LVH) causally related to LV remodeling during the progression to LVH. Additionally, leptin induces vasodilation by inducible NO synthase expression (iNOS) in the vascular wall. In this sense, leptin inhibits the angiotensin II-induced Ca(2+) increase, contraction and proliferation of VSMC through NO-dependent mechanisms. Together, dysregulation of circulating ghrelin isoforms and leptin resistance associated to obesity, type 2 diabetes, or the metabolic syndrome contribute to cardiometabolic derangements observed in these pathologies.

Ghrelin-Derived Peptides: A Link between Appetite/Reward, GH Axis, and Psychiatric Disorders?

Psychiatric disorders are often associated with metabolic and hormonal alterations, including obesity, diabetes, metabolic syndrome as well as modifications in several biological rhythms including appetite, stress, sleep-wake cycles, and secretion of their corresponding endocrine regulators. Among the gastrointestinal hormones that regulate appetite and adapt the metabolism in response to nutritional, hedonic, and emotional dysfunctions, at the interface between endocrine, metabolic, and psychiatric disorders, ghrelin plays a unique role as the only one increasing appetite. The secretion of ghrelin is altered in several psychiatric disorders (anorexia, schizophrenia) as well as in metabolic disorders (obesity) and in animal models in response to emotional triggers (psychological stress …) but the relationship between these modifications and the physiopathology of psychiatric disorders remains unclear. Recently, a large literature showed that this key metabolic/endocrine regulator is involved in stress and reward-oriented behaviors and regulates anxiety and mood. In addition, preproghrelin is a complex prohormone but the roles of the other ghrelin-derived peptides, thought to act as functional ghrelin antagonists, are largely unknown. Altered ghrelin secretion and/or signaling in psychiatric diseases are thought to participate in altered appetite, hedonic response and reward. Whether this can contribute to the mechanism responsible for the development of the disease or can help to minimize some symptoms associated with these psychiatric disorders is discussed in the present review. We will thus describe (1) the biological actions of ghrelin and ghrelin-derived peptides on food and drugs reward, anxiety and depression, and the physiological consequences of ghrelin invalidation on these parameters, (2) how ghrelin and ghrelin-derived peptides are regulated in animal models of psychiatric diseases and in human psychiatric disorders in relation with the GH axis.

Treatment of cachexia: melanocortin and ghrelin interventions

Cachexia is a condition typified by wasting of fat and LBM caused by anorexia and further endocrinological modulation of energy stores. Diseases known to cause cachectic symptoms include cancer, chronic kidney disease, and chronic heart failure; these conditions are associated with increased levels of proinflammatory cytokines and increased resting energy expenditure. Early studies have suggested the central melanocortin system as one of the main mediators of the symptoms of cachexia. Pharmacological and genetic antagonism of these pathways attenuates cachectic symptoms in laboratory models; effects have yet to be studied in humans. In addition, ghrelin, an endogenous orexigenic hormone with receptors on melanocortinergic neurons, has been shown to ameliorate symptoms of cachexia, at least in part, by an increase in appetite via melanocortin modulation, in addition to its anticatabolic and anti-inflammatory effects. These effects of ghrelin have been confirmed in multiple types of cachexia in both laboratory and human studies, suggesting a positive future for cachexia treatments.

The ghrelin O-acyltransferase-ghrelin system reduces TNF-α-induced apoptosis and autophagy in human visceral adipocytes

AIMS/HYPOTHESIS

Proinflammatory and proapoptotic cytokines such as TNF-α are upregulated in human obesity. We evaluated the association between ghrelin isoforms (acylated and desacyl ghrelin) and TNF-α in obesity and obesity-associated type 2 diabetes, as well as the potential role of ghrelin in the control of apoptosis and autophagy in human adipocytes.

METHODS

Plasma concentrations of the ghrelin isoforms and TNF-α were measured in 194 participants. Ghrelin and ghrelin O-acyltransferase (GOAT) levels were analysed by western-blot, immunohistochemistry and real-time PCR in 53 biopsies of human omental adipose tissue. We also determined the effect of acylated and desacyl ghrelin (10 to 1,000 pmol/l) on TNF-α-induced apoptosis and autophagy-related molecules in omental adipocytes.

RESULTS

Circulating concentrations of acylated ghrelin and TNF-α were increased, whereas desacyl ghrelin levels were decreased in obesity-associated type 2 diabetes. Ghrelin and GOAT were produced in omental and subcutaneous adipose tissue. Visceral adipose tissue from obese patients with type 2 diabetes showed higher levels of GOAT, increased adipocyte apoptosis and increased expression of the autophagy-related genes ATG5, BECN1 and ATG7. In differentiating human omental adipocytes, incubation with acylated and desacyl ghrelin reduced TNF-α-induced activation of caspase-8 and caspase-3, and cell death. In addition, acylated ghrelin reduced the basal expression of the autophagy-related genes ATG5 and ATG7, while desacyl ghrelin inhibited the TNF-α-induced increase of ATG5, BECN1 and ATG7 expression.

CONCLUSIONS/INTERPRETATION

Apoptosis and autophagy are upregulated in human visceral adipose tissue of patients with type 2 diabetes. Acylated and desacyl ghrelin reduce TNF-α-induced apoptosis and autophagy in human visceral adipocytes.

Ghrelin and toxicity: recent findings and future challenges

Ghrelin is a novel brain-gut peptide that plays various roles in mammals, including control of food intake and growth hormone release, as well as gastric motility and acid secretion in the gastrointestinal tract. It is mainly secreted by the gastric mucosa, but is also expressed in various other tissues. Different studies confirm the multiple biological roles of and possible protective effects of ghrelin. Multiple in vitro and in vivo studies support the powerful protective action of ghrelin against heart, gastric and liver injury. Moreover, ghrelin has been reported to be beneficial in renal tissue injury and excretory function after ischemia-reperfusion and to exert neuroprotective effects in cerebral ischemic regions. The aim of this review is to summarize and evaluate all the currently available in vivo and in vitro studies regarding the effects of ghrelin on tissue injury induced in different organs and tissues.

Transcriptional analysis of brown adipose tissue in leptin-deficient mice lacking inducible nitric oxide synthase: evidence of the role of Med1 in energy balance

Leptin and nitric oxide (NO) are implicated in the control of energy homeostasis. The aim of the present study was to examine the impact of the absence of the inducible NO synthase (iNOS) gene on the regulation of energy balance in ob/ob mice analyzing the changes in gene expression levels in brown adipose tissue (BAT). Double knockout (DBKO) mice simultaneously lacking the ob and iNOS genes were generated and the expression of genes involved in energy balance including fatty acid and glucose metabolism as well as mitochondrial genes were analyzed by microarrays. DBKO mice exhibited an improvement in energy balance with a decrease in body weight (P < 0.001), total fat pads (P < 0.05), and food intake (P < 0.05), as well as an enhancement in BAT function compared with ob/ob mice. To better understand the molecular events associated with this improvement, BAT gene expression was analyzed. Of particular interest, gene expression levels of the key subunit of the Mediator complex Med1 was upregulated (P < 0.05) in DBKO mice. Real-time PCR and immunohistochemistry further confirmed this data. Med1 is implicated in adipogenesis, lipid metabolic and biosynthetic processes, glucose metabolism, and mitochondrial metabolic pathways. Med1 plays an important role in the transcriptional control of genes implicated in energy homeostasis, suggesting that the improvement in energy balance and BAT function of the DBKO mice is mediated, at least in part, through the transcription coactivator Med1.

Ghrelin signaling in heart remodeling of adult obese mice

Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor (GHS-R), has been suggested to be associated to obesity, insulin secretion, cardiovascular growth and homeostasis. GHS-R has been found in most of the tissues, and among the hormone action it is included the regulation of heart energy metabolism. Therefore, hypernutrition during early life leads to obesity, induces cardiac hypertrophy, compromises myocardial function, inducing heart failure in adulthood. We examined ghrelin signaling process in cardiac remodeling in these obese adult mice. The cardiomyocytes (cmy) of left ventricle were analyzed by light microscopy and stereology, content and phosphorilation of cardiac proteins: ghrelin receptor (growth hormone secretagogue receptor 1a, GHSR-1a), protein kinase B (AKT and pAKT), phosphatidil inositol 3 kinase (PI3K), AMP-activated protein kinase (AMPK and pAMPK) and actin were achieved by Western blotting. GHSR-1a gene expression was analyzed by Real Time-PCR. We observed hyperglycemia and higher liver and visceral fat weight in obese when compared to control group. Obese mice presented a marked increase in heart weight/tibia length, indicating an enlarged heart size or a remodeling process. Obese mice had increased GHSR-1a content and expression in the heart associated to PI3K content and increased AKT content and phosphorylation. In contrast, AMPK content and phosphorylation in heart was not different between experimental groups. Ghrelin plasma levels in obese group were decreased when compared to control group. Our data suggest that remodeled myocardial in adult obese mice overnourished in early life are associated with higher phosphorylation of GHSR-1a, PI3K and AKT but not with AMPK.

Physiological roles of preproghrelin-derived peptides in GH secretion and feeding

Among the factors playing a crucial role in the regulation of energy metabolism, gastro-intestinal peptides are essential signals to maintain energy homeostasis as they relay to the central nervous system the informations about the nutritional status of the body. Among these factors, preproghrelin is a unique prohormone as it encodes ghrelin, a powerful GH secretagogue and the only orexigenic signal from the gastrointestinal tract and obestatin, a proposed functional ghrelin antagonist. These preproghrelin-derived peptides may contribute to balance energy intake, metabolism and body composition by regulating the activity of the GH/IGF-1 axis and appetite. Whereas the contribution of ghrelin has been well characterized, the role of the more recently identified obestatin, in this regulatory process is still controversial. In this chapter, we describe the contribution of these different preproghrelin-derived peptides and their receptors in the regulation of GH secretion and feeding. Data obtained from pharmacological approaches, mutant models and evaluation of the hormones in animal and human models are discussed.

Ghrelin PYY 3-36 serum changes in left ventricular hypertrophic, insulin-resistant, hypertensive obese patients

AIM

Hypertension is a major health problem and is usually associated with common conditions such as obesity, which contribute to clinical cardiac dysfunction. The role of energy homeostasis hormones such as ghrelin and PYY 3-36 in cardiovascular function remains incompletely understood. Therefore, the aim of our study was to explore the potential differences in concentrations of ghrelin forms and PYY 3-36 circulating in obese patients with grade 1 and grade 2 hypertension, with higher and lower BMI and without and with insulin resistance as well as to determine whether these hormones may be associated with left ventricular hypertrophy.

METHODS

A total of 142 adult subjects were studied in three subgroups: lean (BMI < 25 kg/m(2)) normotensive subjects and obese subjects (BMI 30.0-34.9 kg/m(2)), and obese subjects (BMI 35.0-39.9 kg/m(2)) under hypertensive treatment for at least 9 years. Fasting blood glucose, insulin, high-sensitivity C-reactive protein (hs-CRP), lipid profile, urinic acid, acylated ghrelin (A-Ghr), total ghrelin (T-Ghr), and PYY 3-36 were measured. Insulin resistance was determined by the homeostasis model assessment of insulin resistance (HOMA-IR). We also echocardiographically assessed left ventricular mass (LVM) index (LVMI = LVM/height(2.7)). We evaluated the association between plasma T-Ghr, A-Ghr, PYY 3-36 levels with LVMI and other measured factors using univariate and multivariate analysis.

RESULTS

There were significant differences between BMI, waist circumference (WC), LVMI, hs-CRP and A-Ghr/nonacylated ghrelin (NA-Ghr) ratio (in the two obese subgroups. There was no significant difference between T-Ghr, A-Ghr and PYY 3-36 levels between obese subgroups. T-Ghr and PYY 3-36 were significantly lower in obese patients than in the control group, whereas A-Ghr levels did not differ between obese and controls. A-Ghr/NA-Ghr ratio was significantly higher in patients with second-degree hypertension and BMI 35.0-39.9 kg/m(2) than in patients with first-degree hypertension and BMI 30.0-34.9 kg/m(2). There were negative associations between T-Ghr, NA-Ghr or PYY 3-36 and LVMI (r = -0.49, p = 0.0001; r = -0.47, p = 0.0001; or r = -0.18, p = 0.029, respectively) and positive association between A-Ghr/NA-Ghr ratio and LVMI (r = 0.3, p = 0.0003). T-Ghr and NA-Ghr, were associated negatively with fasting insulin (r = -0.31, p = 0.0025; and r = -0.36, p = 0.001, repectively), while A-Ghr/NA-Ghr ratio was positively associated with BMI and fasting insulin (r = 0.23, p = 0.041; r = 0.3, p = 0.0045, respectively). T-Ghr, A-Ghr, and NAGhr were also inversely related to HOMA-IR indices in obese patients (r = -0.43, p = 0.001; r = -0.32, p = 0.0359; r = -0.35, p = 0.001, respectively). In insulin-resistant obese subjects T-Ghr and NA-Ghr correlated negatively with HOMA-IR (r = -0.34, p = 0.0015; r = -0.28, p = 0.0116, respectively). LVMI was associated negatively with T-Ghr, NA-Ghr and PYY 3-36 (r = -0.49, p = 0.0001; r = -0.47, p = 0.0001; r = -0.18, p = 0.029, respectively). In addition, LVMI was positively associated with A-Ghr/NA-Ghr ratio (r = 0.30, p = 0.0003).

CONCLUSION

Plasma ghrelin forms and PYY 3-36 levels are associated with LVMI. These associations indicate a possible interaction between gut peptides and the cardiovascular system in hypertension and obesity.

Altered myocardial expression of ghrelin and its receptor (GHSR-1a) in patients with severe heart failure

Ghrelin is a peptide hormone mainly produced by the stomach, which strongly stimulates the release of growth hormone (GH) via the GH secretagogue receptor 1a (GHSR-1a) located in the hypothalamus. It has been reported to exert performance-enhancing effects on myocardial function, and as both ghrelin and GHSR-1a are expressed in myocardial tissues, the ghrelin system may have a direct GH-independent impact on cardiac function. We intended to investigate the expression of ghrelin and its receptor GHSR-1a in different myocardial areas of patients with chronic heart failure (CHF) as compared to heart-healthy subjects to better define the role of the ghrelin signaling system in the networks regulating cardiac function and its potential as a target for diagnosis and/or treatment of CHF. Myocardium biopsies of 12 patients undergoing heart transplantation and suffering from CHF were obtained. Expression of both ghrelin and GHSR-1a was assessed by means of immunohistochemistry and real-time PCR. Expression of ghrelin was significantly decreased in CHF hearts both in atrium and ventricles in comparison to the control hearts (p<0.05). The expression of the GHS-1a receptor was significantly increased in the CHF biopsies as compared to controls (p<0.05). No significant differences were found between the anatomical areas studied. Expression of myocardial ghrelin and GHSR-1a is directly associated with myocardial function: CHF hearts exhibit an impaired ghrelin production which might reflect maladaptive processes and an - probably compensatory - increase in GHSR-1a expression. These findings may open up new perspectives regarding the potential of ghrelin signaling as a target for pharmacological modulation.

Regulation of inducible nitric oxide synthase activity/expression in rat hearts from ghrelin-treated rats

The purpose of this study was to examine the effects of ghrelin on protein kinase B (Akt) and mitogen-activated protein kinase p42/44 (ERK1/2) activation as well as ghrelin effects on inducible nitric oxide (NO) synthase (iNOS; for gene Nos2) activity/expression in rat hearts. Male Wistar rats were treated with ghrelin (0.3 nmol/5 μl) or an equal volume of phosphate-buffered saline, injected every 24 h into the lateral cerebral ventricle for 5 days and 2 h after the last treatment the animals were sacrificed. Serum NO, L-arginine (L-Arg), and arginase activity were measured spectrophotometrically. For phosphorylation of Akt, ERK1/2, and iNOS protein expression, Western blot method was used. The expression of Nos2 mRNA was measured by the quantitative real-time polymerase chain reaction (qRT-PCR). Treatment with ghrelin significantly increased NO production in serum by 1.4-fold compared with control. The concentration of L-Arg was significantly higher in ghrelin-treated rats than in control while arginase activity was significantly lower in ghrelin-treated than in control hearts. Ghrelin treatment increased phosphorylation of Akt by 1.9-fold and ERK1/2 by 1.6-fold and increased iNOS expression by 2.5-fold compared with control. In addition, ghrelin treatment increased Nos2 gene expression by 2.2-fold as determined by qRT-PCR. These results indicate that ghrelin regulation of iNOS expression/activity is mediated via Akt/ERK1/2 signaling pathway. These results may be relevant to understanding molecular mechanisms underlying direct cardiovascular actions of ghrelin.

Ghrelin improves disturbed myocardial energy metabolism in rats with heart failure induced by isoproterenol

To explore the effects of ghrelin on disturbed myocardial energy metabolism during chronic heart failure (CHF). Rats were subcutaneously injected with isoproterenol (ISO) for 10 days with or without ghrelin for another 10 days. Enzyme immunoassay was to measure ghrelin concentrations. Compared with the control group, ISO-treated rats showed suppressed cardiac function with high ghrelin/GHS-R expressions. These rats also showed the decreases in food consumption and weight. The decreased levels of plasma glucose and myocardial glucogen, but the high lactate in blood and myocardium showed myocardial metabolic disturbance. Compared with the group given ISO alone, the rats with ghrelin (20 and 100 microg/kg/day) improved cardiac dysfunction and increased food intake by 13.5 and 14.2% (both P < 0.01), and rate of weight gain by 95% (P < 0.05) and 1.71-fold (P < 0.01), respectively. The plasma glucose were increased by 49.7 and 50.8% (both P < 0.01), and myocardial glucogen, by 40.5 and 51.7% (both P < 0.01), but blood lactate decreased by 1.56- and 1.96-fold (both P < 0.01), and myocardial lactate by 32.1 and 48.7% (both P < 0.05), respectively. Their MCT1 mRNA and protein expressions increased. The myocardial ghrelin/GHS-R pathway can be upregulated during CHF. The ghrelin can attenuate cardiac dysfunction and energy metabolic disturbance in CHF rats.