Plasma levels of active and total ghrelin in renal failure: a relationship with GH/IGF-I axis

Plasma Ghrelin Levels in Children with Chronic Renal Failure on Peritoneal Dialysis

Objectives

Malnutrition and loss of appetite represent a serious problem in children with chronic renal failure. Ghrelin is a newly described hormone involved in control of growth hormone secretion, stimulation of food intake, and regulation of energy balance.

Methods

Plasma ghrelin levels were compared between 12 children on automated peritoneal dialysis (APD) and 9 children on conservative treatment of chronic renal failure. Eight healthy children matched for age and body mass index (BMI) served as a control group.

Results

Plasma ghrelin levels were similar in children on APD (698.3 ± 59.7 pg/mL) and children on conservative treatment (675.4 ± 41.9 pg/mL) compared to healthy controls (700.1 ± 24.7 pg/mL). There was no difference in plasma ghrelin levels in children with chronic renal failure regardless of the method of treatment (peritoneal dialysis vs conservative treatment). The plasma ghrelin index was similar in all three investigated groups: APD 40.2 ± 8.7 vs conservative treatment 39.1 ± 5.6 vs controls 41.0 ± 7.8 (pg/mL)/BMI (kg/m2). Plasma ghrelin levels did not correlate with age, duration of dialysis treatment, height, weight, BMI, creatinine and urea levels, adequacy parameters, or nightly glucose load.

Conclusion

Plasma ghrelin levels in children on APD were not different from levels in children on conservative treatment or healthy controls with comparable BMI. The persistent state of toxic influence of uremic end-products could be responsible for such a lack of correlation with anthropometrical parameters. Further studies on a larger group of children on APD are needed to clarify the effect of ghrelin on nutritional status in children with chronic renal failure.

Oral ghrelin receptor agonist MK-0677 increases serum insulin-like growth factor 1 in hemodialysis patients: a randomized blinded study

Background

Protein-energy wasting (PEW) in end-stage renal disease (ESRD) patients is associated with increased morbidity and mortality, but options for treatment are limited. Growth hormone (GH) increases insulin-like growth factor 1 (IGF-1), with improved nutritional parameters, but must be given subcutaneously and does not provide normal GH secretion patterns. MK-0677, an oral ghrelin receptor agonist (GRA), maintains normal GH secretion and increases lean body mass in normal subjects; it has not been studied in dialysis patients, an essential step in assessing efficacy and safety prior to clinical trials.

Methods

We performed a randomized crossover double-blind study in assessing the effect of MK-0677 versus placebo on IGF-1 levels, the primary outcome, in hemodialysis patients. In total, 26 subjects enrolled and 22 completed the 3-month crossover study.

Results

The geometric mean IGF-1 was 1.07-fold greater [95% confidence interval (CI) 0.89-1.27; P = 0.718] after placebo. In patients receiving MK-0677, the geometric mean IGF-1 were 1.76-fold greater (95% CI 1.48-2.10; P < 0.001) following MK-0677. When the data were adjusted for preintervention IGF-1 concentration, the ratio of geometric means (MK-0677 relative to placebo) for the pre- versus postintervention change in the IGF-1 was 1.65 (95% CI 1.33-2.04; P < 0.001). These data demonstrate a 65% greater increase (95% CI 33-104%) in IGF-1 in MK-0677-dosed subjects compared with placebo. There were no serious adverse effects attributable to MK-0677.

Conclusions

MK-0677 increased serum IGF-1 levels with minimal adverse effects in hemodialysis subjects. Studies are needed to evaluate whether long-term therapy with MK-0677 improves PEW, lean body mass, physical strength, quality of life and survival in CKD/ESRD patients.

Unacylated ghrelin and obestatin: promising biomarkers of protein energy wasting in children with chronic kidney disease

BACKGROUND

Impairment in orexigenic/anorexigenic hormone balance may be key in the pathogenesis of protein energy wasting in children with chronic kidney disease (CKD). Measurement of ghrelin and obestatin concentrations in children with CKD would help assess the potential contribution of these hormones to uremic protein energy wasting.

METHODS

This was a cross-sectional case-control study. Acylated and unacylated ghrelin and obestatin were measured in 42 children on conservative treatment (CT), 20 children on hemodialysis, 48 pediatric renal transplant (RTx) recipients and 43 controls (CTR) (mean age 11.9, range 5-20 years). Weight, height and bicipital, tricipital, subscapular and suprailiac folds were measured, and the body mass index-standard deviation score (BMI-SDS), percentage of fat mass and fat-free mass were calculated. Urea and creatinine were measured and the glomerular filtration rate (GFR) calculated.

RESULTS

Unacylated ghrelin level was higher in patients than controls (p = 0.0001), with the highest levels found in hemodialysis patients (p = 0.001 vs. CKD-CT, p = 0.0001 vs. RTx, p < 0.0001 vs. CTR). Obestatin level was significantly higher in patients on hemodialysis than those on conservative treatment, RTx recipients and controls (p < 0.0001 in each case). Unacylated ghrelin negatively correlated with weight-SDS (p < 0.0001), BMI-SDS (p = 0.0005) and percentage fat mass (p = 0.004) and positively correlated with percentage fat-free mass (p = 0.004). Obestatin concentration negatively correlated with weight-SDS (p = 0.007). Unacylated ghrelin and obestatin concentrations positively correlated with creatinine and urea and inversely with eGFR, even after adjustments for gender, age, puberty and BMI-SDS (p < 0.0001 for each model).

CONCLUSIONS

Unacylated ghrelin and obestatin, negatively related to renal function, seem to be promising inverse indicators of nutritional status in children with CKD. Potential therapeutic implications in terms of optimization of their removal in patients on hemodialysis could be hypothesized.

Fetuin-A and Ghrelin Levels in Children with End Stage Renal Disease and the Effect of a Single Hemodialysis Session on Them

BACKGROUND

Fetuin-A and ghrelin have been implicated in cardiovascular diseases and mortality among end stage renal disease patients. The exact mechanisms have not been fully elucidated. There is robust data supporting an association between ghrelin and various cardiovascular conditions, and some common processes such as inflammation, oxidative stress, and endoplasmic reticulum stress have been implicated.

AIM

This study was conducted to assay serum fetuin-A and ghrelin in chronic renal failure pediatric patients and to study changes in their level that may occur after a single hemodialysis.

MATERIAL AND METHODS

Forty nine pediatric patients suffering from ESRD on maintenance hemodialysis (HD), 20 patients with chronic renal failure (CRF) not on dialysis and 35 healthy subjects as control group were included. The mean age of the study population was 10.58 ± 3.94, 10.62 ± 3.24 and 10.61 ± 3.97 years respectively. Serum fetuin-A and plasma acyl ghrelin levels were measured by using ELISA method.

RESULTS

The present study revealed that predialysis serum fetuin-A level was significantly increased in pediatric HD patients compared with the normal population, while ghrelin levels were significantly reduced. Furthermore, serum levels of fetuin-A decreased significantly after a single HD session.

CONCLUSION

Our study concluded that fetuin-A and acyl ghrelin may play a role in inflammatory process among HD pediatric patients which may account for cardiovascular insults and mortality but their use as biochemical markers among ESRD pediatric patients have limitations due to wide fluctuations.

Phlorizin pretreatment reduces acute renal toxicity in a mouse model for diabetic nephropathy

Streptozotocin (STZ) is widely used as diabetogenic agent in animal models for diabetic nephropathy (DN). However, it is also directly cytotoxic to kidneys, making it difficult to distinguish between DN-related and STZ-induced nephropathy. Therefore, an improved protocol to generate mice for DN studies, with a quick and robust achievement of the diabetic state, without direct kidney toxicity is required. To investigate the mechanism leading to STZ-induced nephropathy, kidney damage was induced with a high dose of STZ. This resulted in delayed gastric emptying, at least partially caused by impaired desacyl ghrelin clearance. STZ uptake in the kidneys is to a large extent mediated by the sodium/glucose cotransporters (Sglts) because the Sglt inhibitor phlorizin could reduce STZ uptake in the kidneys. Consequently, the direct toxic effects in the kidney and the gastric dilatation were resolved without interfering with the β-cell toxicity. Furthermore, pancreatic STZ uptake was increased, hereby decreasing the threshold for β-cell toxicity, allowing for single low non-nephrotoxic STZ doses (70 mg/kg). In conclusion, this study provides novel insights into the mechanism of STZ toxicity in kidneys and suggests a more efficient regime to induce DN with little or no toxic side effects.

Association of plasma des-acyl ghrelin levels with CKD

BACKGROUND AND OBJECTIVES

There are no effective therapies for malnutrition in CKD/ESRD patients. This study hypothesized that ghrelin, an endogenous orexigenic hormone, would correlate with renal function and might suggest therapeutic interventions for CKD/ESRD malnutrition.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Fifty-one CKD and 15 hemodialysis patients were enrolled. Acyl ghrelin (AG) and des-acyl ghrelin (DG) were determined using separate two-site-specific assays. Leptin, insulin, growth hormone, insulin-link growth factor-1, C-reactive protein, TNF-α, and IL-6 were also measured.

RESULTS

Univariate correlation analyses showed that CKD stage was highly, positively correlated with the levels of preprandial and postprandial DG and positively correlated with TNF-α, IL-6, leptin, and age. Multivariate partial-correlation analyses showed that CKD was independently associated with the proportion of preprandial and postprandial DG, whereas TNF-α, IL-6, leptin, insulin, and age were not independently associated with either. Geometric mean (GM) preprandial and postprandial AG were comparable between CKD stages ≤2 and >2, whereas GM preprandial DG and postprandial DG were 1.95-fold and 2.17-fold greater, respectively, for CKD stage >2 versus stage ≤2. DG was the dominant form of ghrelin preprandially and postprandially for both CKD stages ≤2 and >2. Dialysis had no effect on AG, but reduced DG by 73% to levels even lower (GM 48.7 pg/ml) than those seen postprandially in CKD stage ≤2 patients (GM 77.0 pg/ml).

CONCLUSIONS

This study shows a strong and independent correlation of DG with CKD stage. Postprandial suppression of ghrelin is impaired with reduced renal function. Hemodialysis selectively removes DG but not AG.

The pharmacokinetics of acyl, des-acyl, and total ghrelin in healthy human subjects

BACKGROUND

Ghrelin stimulates GH secretion and regulates energy and glucose metabolism. The two circulating isoforms, acyl (AG) and des-acyl (DAG) ghrelin, have distinct metabolic effects and are under active investigation for their therapeutic potentials. However, there is only limited data on the pharmacokinetics of AG and DAG.

OBJECTIVES

To evaluate key pharmacokinetic parameters of AG, DAG, and total ghrelin in healthy men and women.

METHODS

In study 1, AG (1, 3, and 5 μg/kg per h) was infused over 65 min in 12 healthy (8 F/4 M) subjects in randomized order. In study 2, AG (1 μg/kg per h), DAG (4 μg/kg per h), or both were infused over 210 min in ten healthy individuals (5 F/5 M). Plasma AG and DAG were measured using specific two-site ELISAs (study 1 and 2), and total ghrelin with a commercial RIA (study 1). Pharmacokinetic parameters were estimated by non-compartmental analysis.

RESULTS

After the 1, 3, and 5 μg/kg per h doses of AG, there was a dose-dependent increase in the maximum concentration (C(max)) and area under the curve (AUC(0-last)) of AG and total ghrelin. Among the different AG doses, there was no difference in the elimination half-life, systemic clearance (CL), and volume of distribution. DAG had decreased CL relative to AG. The plasma DAG:AG ratio was ~2:1 during steady-state infusion of AG. Infusion of AG caused an increase in DAG, but DAG administration did not change plasma AG. Ghrelin administration did not affect plasma acylase activity.

CONCLUSIONS

The pharmacokinetics of AG and total ghrelin appears to be linear and proportional in the dose range tested. AG and DAG have very distinct metabolic fates in the circulation. There is deacylation of AG in the plasma but no evidence of acylation.

Ghrelin and cachexia in chronic kidney disease

Ghrelin is a growth hormone (GH) secretagogue and a potent orexigenic factor that stimulates feeding by interacting with hypothalamic feeding-regulatory nuclei. Its multifaceted effects are potentially beneficial as a treatment in human disease states. In both adult and pediatric chronic kidney disease (CKD) patients, decreased appetite plays a major role in wasting, which in turn is linked to morbidity and mortality; wasting has also been linked to high levels of leptin and proinflammatory cytokines. The beneficial effects of ghrelin treatment in CKD are potentially mediated by multiple concurrent actions, including the stimulation of appetite-regulating centers, anti-inflammatory effects, and direct kidney effects. Further evaluation of this appetite-regulating hormone in CKD is needed to confirm previous findings and to determine the underlying mechanisms.

Therapeutic applications of ghrelin to cachexia utilizing its appetite-stimulating effect

Ghrelin, which is a natural ligand for the growth hormone (GH)-secretagogue receptor (GHS-R), stimulates food intake in both animals and humans. Ghrelin is the only circulating hormone known to stimulate appetite in humans. Ghrelin also stimulates GH secretion and inhibits the production of anorectic proinflammatory cytokines. As GH is an anabolic hormone, protein stores are spared at the expense of fat during conditions of caloric restriction. Thus, ghrelin exhibits anti-cachectic actions via both GH-dependent and -independent mechanisms. Several studies are evaluating the efficacy of ghrelin in the treatment of cachexia caused by a variety of diseases, including congestive heart failure, chronic obstructive pulmonary disease, cancer, and end-stage renal disease. These studies will hopefully lead to the development of novel therapeutic applications for ghrelin in the future. This review summarizes the recent advances in this area of research.

Intrarenal ghrelin infusion stimulates distal nephron-dependent sodium reabsorption in normal rats

Ghrelin is a 28-amino acid peptide hormone that exerts powerful orexigenic effects. Ghrelin receptor expression has been reported in the kidney, but the role of ghrelin in the kidney is unknown. The present studies confirmed ghrelin receptor mRNA expression in the kidneys of normal Sprague Dawley rats (n=6) using reverse transcription polymerase chain reaction (PCR) and sequencing of the 588-bp PCR product. To test intrarenal ghrelin action, uninephrectomized rats received 3 cumulative 1-hour renal interstitial (RI) infusions of 5% dextrose in water (vehicle, n=21), ghrelin (n=10), ghrelin plus specific ghrelin receptor antagonist [D-Lys-3]-GHRP-6 (n=24), or [D-Lys-3]-GHRP-6 alone (n=32). Mean arterial pressure (MAP), urine sodium excretion rate (U(Na)V), glomerular filtration rate (GFR), fractional excretion of sodium (FE(Na)), and fractional excretion of lithium (FE(Li)) were calculated for each period. RI ghrelin infusion significantly decreased U(Na)V to 86 ± 4.9% (P<0.05), 74 ± 6.5% (P<0.01), and 62 ± 10% (P<0.01) of baseline during periods 1 to 3, respectively. Ghrelin also significantly decreased FE(Na) to 68 ± 11% (P<0.05), 57 ± 8.6% (P<0.001), and 59 ± 12% (P<0.01) of baseline, without changing GFR or FE(Li). Identical ghrelin infusions in the presence of [D-Lys-3]-GHRP-6 failed to permit reductions in U(Na)V or FE(Na). Following [D-Lys-3]-GHRP-6 infusion alone, U(Na)V increased from 0.06 ± 0.01 to 0.18 ± 0.03 μmol/min (P<0.0001). Concomitant increases in FE(Na) were also observed (0.23 ± 0.03% to 0.51 ± 0.06% [P<0.001]), without changes in MAP, GFR, or FE(Li). Together, these data introduce a novel intrarenal ghrelin-ghrelin receptor system, which, on activation, significantly increases Na(+) reabsorption at the level of the distal nephron.

Ghrelin for cachexia

Ghrelin, a natural ligand for the growth hormone (GH)-secretagogue receptor, is primarily produced in the stomach. Administration of ghrelin stimulates food intake and GH secretion in both animals and humans. Ghrelin is the only circulating hormone known to stimulate appetite in humans. As GH is an anabolic hormone, protein stores are spared at the expense of fat during conditions of caloric restriction. Ghrelin also inhibits the production of anorectic proinflammatory cytokines. Thus, ghrelin exhibits anti-cachectic actions via both GH-dependent and -independent mechanisms. Several studies are evaluating the efficacy of ghrelin in the treatment of cachexia caused by a variety of diseases, including congestive heart failure, chronic obstructive pulmonary disease, cancer, and end-stage renal disease. These studies will hopefully lead to the development of novel clinical applications for ghrelin in the future. These studies have also facilitated a better understanding of the molecular basis of the anti-catabolic effects of ghrelin. This review summarizes the recent advances in this area of research.

Plasma levels of acylated and total ghrelin in pediatric patients with chronic kidney disease

This cross-sectional study set out to compare total and acyl ghrelin levels in children with mild chronic kidney disease (CKD) undergoing conservative treatment (n = 19) with children with end-stage renal disease (ESRD) undergoing hemodialysis (n = 24), and with healthy controls (n = 20). The relationship between ghrelin levels and parameters of renal function, nutritional status, and selective hormones were investigated. ESRD patients had higher total ghrelin levels than those with mild CKD or control individuals. However, acyl ghrelin did not differ between groups, indicating that the excess circulating ghrelin was desacylated. Since desacyl ghrelin has been shown to inhibit appetite, increased levels might contribute to protein-energy wasting in pediatric renal patients. When all 43 renal patients were combined, multiple regression analysis found age and glomerular filtration rate (GFR) to be significant negative predictors of total ghrelin. Acyl ghrelin was influenced negatively by age and positively by energy intake. Acyl to total ghrelin ratio related positively to GFR and energy intake. The results indicate that total but not acyl ghrelin is influenced by low GFR in children with CKD and suggests that ghrelin activation may be impaired in these patients. Since energy intake is a positive predictor of acyl ghrelin, the physiological control of ghrelin secretion appears to be altered in pediatric renal patients.

Ghrelin and its potential in the treatment of eating/wasting disorders and cachexia

The gastrointestinal "hunger" hormone ghrelin is the only known circulating peripheral molecule with the ability to decrease body fat utilization and to increase body weight gain. Accordingly, due to ghrelin's effects to promote food intake while decreasing energy expenditure ghrelin may offer potential as a drug for treatment of eating/wasting disorders and cachexia. Therapeutic potential of ghrelin and ghrelin analogues to promote food intake and body weight gain was recently indicated in several clinical studies. The recent discovery of the ghrelin O-acyltransferase as the key enzyme responsible for ghrelin acylation has further deepened our understanding of ghrelin activation, thereby paving the way for more efficient targeting of the ghrelin pathway. Here, we summarize the current knowledge pertaining to the potential of the endogenous ghrelin system as a drug target for the treatment of eating/wasting disorders and cachexia.

Integrating GHS into the Ghrelin System

Oligopeptide derivatives of metenkephalin were found to stimulate growth-hormone (GH) release directly by pituitary somatotrope cells in vitro in 1977. Members of this class of peptides and nonpeptidyl mimetics are referred to as GH secretagogues (GHSs). A specific guanosine triphosphatate-binding protein-associated heptahelical transmembrane receptor for GHS was cloned in 1996. An endogenous ligand for the GHS receptor, acylghrelin, was identified in 1999. Expression of ghrelin and homonymous receptor occurs in the brain, pituitary gland, stomach, endothelium/vascular smooth muscle, pancreas, placenta, intestine, heart, bone, and other tissues. Principal actions of this peptidergic system include stimulation of GH release via combined hypothalamopituitary mechanisms, orexigenesis (appetitive enhancement), insulinostasis (inhibition of insulin secretion), cardiovascular effects (decreased mean arterial pressure and vasodilation), stimulation of gastric motility and acid secretion, adipogenesis with repression of fat oxidation, and antiapoptosis (antagonism of endothelial, neuronal, and cardiomyocyte death). The array of known and proposed interactions of ghrelin with key metabolic signals makes ghrelin and its receptor prime targets for drug development.

Ghrelin gene products and the regulation of food intake and gut motility

A breakthrough using "reverse pharmacology" identified and characterized acyl ghrelin from the stomach as the endogenous cognate ligand for the growth hormone (GH) secretagogue receptor (GHS-R) 1a. The unique post-translational modification of O-n-octanoylation at serine 3 is the first in peptide discovery history and is essential for GH-releasing ability. Des-acyl ghrelin, lacking O-n-octanoylation at serine 3, is also produced in the stomach and remains the major molecular form secreted into the circulation. The third ghrelin gene product, obestatin, a novel 23-amino acid peptide identified from rat stomach, was found by comparative genomic analysis. Three ghrelin gene products actively participate in modulating appetite, adipogenesis, gut motility, glucose metabolism, cell proliferation, immune, sleep, memory, anxiety, cognition, and stress. Knockdown or knockout of acyl ghrelin and/or GHS-R1a, and overexpression of des-acyl ghrelin show benefits in the therapy of obesity and metabolic syndrome. By contrast, agonism of acyl ghrelin and/or GHS-R1a could combat human anorexia-cachexia, including anorexia nervosa, chronic heart failure, chronic obstructive pulmonary disease, liver cirrhosis, chronic kidney disease, burn, and postsurgery recovery, as well as restore gut dysmotility, such as diabetic or neurogenic gastroparesis, and postoperative ileus. The ghrelin acyl-modifying enzyme, ghrelin O-Acyltransferase (GOAT), which attaches octanoate to serine-3 of ghrelin, has been identified and characterized also from the stomach. To date, ghrelin is the only protein to be octanylated, and inhibition of GOAT may have effects only on the stomach and is unlikely to affect the synthesis of other proteins. GOAT may provide a critical molecular target in developing novel therapeutics for obesity and type 2 diabetes.

Ghrelin and obestatin levels in end-stage renal disease

Malnutrition is fairly common in end-stage renal disease (ESRD) patients, persistent lack of appetite being a major symptom. Ghrelin and obestatin are two hormones that are involved in appetite and energy homeostasis. The present study examined ghrelin and obestatin levels in 24 ESRD patients undergoing haemodialysis and 24 age-matched healthy controls. Serum and saliva ghrelin and obestatin levels in the ESRD patients were significantly higher compared with controls, while saliva ghrelin and obestatin levels in all study participants were significantly higher than serum levels. Saliva ghrelin correlated with serum ghrelin and saliva obestatin correlated with serum obestatin in all study participants, although there was no correlation between ghrelin and obestatin levels. In conclusion, the results suggest that the kidneys may have a role in the metabolism and/or clearance of obestatin, as they do for ghrelin. Further studies are needed to determine if elevated levels of these hormones in ESRD patients contribute to the malnutrition that is common in these patients.

[Short stature in chronic kidney disease: physiopathology and treatment with growth hormone]

Growth failure is frequent and a clinically important issue in children with chronic kidney disease (CKD). Many factors contribute to impaired growth in these children, including abnormalities in the growth hormone (GH)--insulin-like growth factor 1 (IGF-1) axis, malnutrition, acidosis, renal bone disease and glucocorticoid associated treatment. The management of growth failure in children with CKD is complicated by the presence of other-disease related complications requiring medical intervention. Despite evidence of GH efficacy and safety in this population, this therapy is still underutilized. This review shows the impact, the causes and the treatment of growth failure in children with CKD.

Serum zinc, plasma ghrelin, leptin levels, selected biochemical parameters and nutritional status in malnourished hemodialysis patients

This study was performed to investigate the serum zinc (Zn), plasma ghrelin, leptin levels and nutritional status, and to evaluate the potential association between malnutrition and these investigated parameters in malnourished hemodialysis (HD) patients. Fifteen malnourished HD patients, aged 42.9 +/- 2.11 years, who underwent the HD for 46.44 +/- 7.1 months and 15 healthy volunteers, aged 41.0 +/- 2.17 years, were included in this study. The nutritional status of the subjects was determined by the subjective global assessment (SGA). Anthropometric measurements were taken by bioelectrical impedance after HD. Blood samples were collected for the analysis of zinc (Zn), ghrelin, leptin, and selected blood parameters. The HD patients consumed less energy and nutrients than controls. In HD patients, body weight, body mass index (BMI) (p < 0.001), basal metabolic rate (BMR), body fat, lean body mass (LBM), serum Zn, copper (Cu) (p < 0.05), sodium (Na) (p < 0.01), glucose (p < 0.05), albumin (p < 0.01), total cholesterol (p < 0.001), and ghrelin (p < 0.05) were lower whereas body water ratio (p < 0.001), serum potassium (K) (p < 0.01), inorganic phosphorous (Pi), blood urea nitrogen, creatinine (p < 0.001), and plasma insulin (p < 0.05) levels were higher than the controls. No difference existed between HD patients and controls regarding plasma leptin levels. There were positive correlations for body weight-fasting glucose and body weight-leptin (p < 0.05), body weight-BMI and body weight-LBM (p < 0.01); body fat-leptin (p < 0.05); BMI-fasting glucose, BMI-leptin, and BMI-body fat (p < 0.05); albumin-hemoglobin and albumin-insulin (p < 0.05). Negative correlation was found for SGA score-ghrelin (p < 0.05). Malnutrition in HD patients may result from inadequate energy and nutrient intake and low Zn and ghrelin levels. Zinc supplementation to the diets of HD patients may be of value to prevent the malnutrition.

The role of ghrelin and ghrelin analogues in wasting disease

PURPOSE OF REVIEW

The purpose of this review is to summarize recent studies that investigated the role of ghrelin and ghrelin analogs in wasting conditions.

RECENT FINDINGS

Numerous studies have demonstrated potential beneficial effects exerted by ghrelin in a number of diseases associated with wasting. Besides ghrelin's orexigenic effect, anabolic as well as anti-inflammatory activity mediated by ghrelin have been investigated in wasting conditions such as cancer, diabetes mellitus, malabsorptive diseases, chronic obstructive pulmonary disease, anorexia nervosa, renal failure, liver failure, and chronic heart failure. Encouraging results have been obtained from experimental studies and a few clinical trials using subcutaneous administration of ghrelin and ghrelin agonists in cachexia. In-vitro studies have shown ghrelin and des-acyl ghrelin biological activities on proliferation of tumor cells and abnormal tissues.

SUMMARY

The recent studies support the possible positive effects of ghrelin in therapeutic approaches and adjunct treatment of a number of diseases associated with wasting. Utilization of agonists of the ghrelin receptor growth hormone secretagogue-1a is a promising approach for clinical use. Randomized and placebo-controlled studies, including large number of patients are further required.

Local feedback loop of ghrelin-GH in the pig ovary: action on estradiol secretion, aromatase activity and cell apoptosis

Ghrelin is recognized as an important regulator of growth hormone (GH) secretion, food intake and a factor which controls reproduction. In the present studies, the effect of GH and insulin-like growth factor (IGF-I) on ghrelin synthesis and secretion and the effects of ghrelin on GH synthesis and secretion in cultured whole porcine follicles were studied. Ghrelin and GH levels were measured in the follicular wall and in the culture medium. Moreover, the action of combined treatment with ghrelin and GH on estradiol secretion, aromatase activity and cell apoptosis were examined. We demonstrated that ghrelin increased GH secretion but not GH synthesis by ovarian follicles. GH stimulated both ghrelin synthesis and secretion in the ovarian follicles. The increase in estradiol secretion, aromatase activity and the decrease in caspase-3 activity were noted in ghrelin alone- and ghrelin in combination with GH-treated cells. In culture treated with combination of both these hormones, all investigated parameters were similar to those noted in ghrelin alone-treated cells. In conclusion, our study provides novel evidence for the gonadal feedback loop between GH and ghrelin secretion in the ovary. However, results of the presented research suggest independent action of GH and ghrelin in the ovary.

Relationship between Leptin, Insulin Resistance, Insulin-like Growth Factor-1 and Insulin-like Growth Factor Binding Protein-3 in Patients with Chronic Kidney Disease

This study examined the relationship between leptin, insulin-like growth factor-1 (IGF-1), IGF binding protein-3 (IGFBP-3) and insulin resistance in patients with chronic kidney disease (CKD). Levels of leptin, insulin, IGF-1, IGFBP-3 and common routine parameters were measured in 45 patients (23 males and 22 females) with CKD and 45 healthy controls matched for age, gender and body mass index. IGF-1 and IGFBP-3 levels were measured using a two-site immunoradiometric assay. Leptin levels were measured using an enzyme-linked immunosorbent assay. A homeostasis model assessment computer-solved model was used to assess insulin resistance (HOMA-IR). Levels of serum leptin, insulin, IGF-1, IGFBP-3 and HOMA-IR were significantly increased in patients with CKD compared with healthy subjects, whereas fasting blood glucose was not significantly different between the two groups. In patients with CKD, the serum leptin level was significantly correlated with IGF-1, IGFBP-3 and HOMA-IR. In conclusion, this study suggests that there is an interaction between leptin, IGF-1, IGFBP-3 and insulin resistance in patients with CKD.

Emerging results of anticatabolic therapy with ghrelin

PURPOSE OF REVIEW

This review summarizes recent developments in research into anticatabolic therapies with ghrelin. Potential conditions in which ghrelin treatment may be useful include cachexia, anorexia and ageing. We highlight a number of intriguing basic topics related to the anticatabolic effects of ghrelin.

RECENT FINDING

Repeated administration of ghrelin to patients with congestive heart failure or chronic obstructive pulmonary disease improved appetite, body composition, muscle wasting and functional capacity in open-label pilot studies. An acute, randomized, placebo-controlled, crossover clinical trial of cancer patients with anorexia revealed marked increases in energy intake following treatment. The effects of ghrelin treatment in patients with anorexia nervosa are controversial. Basic research studies have extended our understanding of the upstream regulation of neuropeptide Y/agouti-related protein signalling and the central control of adipocyte metabolism. In addition, alterations in fat-free mass may play a role in ghrelin regulation.

SUMMARY

A number of studies are currently evaluating the anticatabolic effects of ghrelin in the treatment of various diseases, including cachexia, anorexia and age-related disorders. These studies will hopefully lead to the development of novel clinical applications for ghrelin treatment. These studies have also facilitated a better understanding of the molecular basis of the anticatabolic effects of ghrelin.

Association of acylated and nonacylated ghrelin with insulin sensitivity in overweight and obese postmenopausal women

OBJECTIVE

Ghrelin [acylated (AG) and nonacylated (NAG)] has been shown to play a pivotal role in the regulation of food intake and insulin sensitivity. It is presently unclear whether variation in insulin sensitivity is related to AG and NAG levels in obese individuals. To address this issue, we determined whether insulin-sensitive overweight or obese (ISO) and insulin-resistant overweight or obese (IRO) individuals display different total ghrelin (TotG), AG, and NAG profiles during a euglycemic/hyperinsulinemic clamp (EHC).

DESIGN

Eighty-nine nondiabetic overweight and obese postmenopausal women underwent EHC to evaluate insulin sensitivity. Body composition and blood lipid profiles were assessed. Subjects within the highest tertile of insulin sensitivity were described as ISO (n = 31), whereas those within the lowest tertile of insulin sensitivity were considered as IRO (n = 29). Plasma TotG, AG, and NAG profiles were assessed by RIA at 0, 60, 160, 170, and 180 min during the EHC.

RESULTS

TotG and NAG levels were significantly decreased for ISO and IRO individuals during the EHC, whereas only ISO subjects displayed a significant reduction of AG concentrations (P < 0.05). AG area under the curve value and the ratio of AG/NAG (fasting and area under the curve) were significantly decreased in ISO individuals. Furthermore, maximal reduction of TotG and AG concentrations was greater in ISO compared with IRO individuals (P < 0.05). Insulin sensitivity was significantly correlated with maximal reduction of TotG (r = 0.36; P < 0.01) and AG (r = 0.36; P < 0.05) concentrations.

CONCLUSION

The dysregulation of ghrelin secretion profiles during EHC is associated with insulin resistance. AG may contribute to the variation of insulin sensitivity in overweight or obese postmenopausal women.