Correlation between fasting plasma ghrelin levels and age, body mass index (BMI), BMI percentiles, and 24-hour plasma ghrelin profiles in Prader-Willi syndrome

Do patients with Prader-Willi syndrome have favorable glucose metabolism?

Background

In recent years, more studies have observed that patients with Prader–Willi syndrome have lower insulin levels and lower insulin resistance than body mass index-matched controls, which may suggest protected glucose metabolism.

Method

The PubMed and Web of Science online databases were searched to identify relevant studies published in the English language using the terms “Prader–Willi syndrome” with “glucose”, “insulin”, “diabetes mellitus”, “fat”, “adipo*”, “ghrelin”, “oxytocin”, “irisin” or “autonomic nervous system”.

Results

The prevalence of impaired glucose intolerance, type 2 diabetes mellitus and some other obesity-associated complications in patients with Prader–Willi syndrome tends to be lower when compared to that in general obesity, which is consistent with the hypothetically protected glucose metabolism. Factors including adipose tissue, adiponectin, ghrelin, oxytocin, irisin, growth hormone and the autonomic nervous system possibly modulate insulin sensitivity in patients with Prader–Willi syndrome.

Conclusion

Although lower insulin levels, lower IR and protected glucose metabolism are widely reported in PWS patients, the causes are still mysterious. Based on existing knowledge, we cannot determine which factor is of utmost importance and what are the underlying mechanisms, and further research is in urgent need.

Epigenetics in Prader-Willi Syndrome

Prader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder that affects approximately 1 in 20,000 individuals worldwide. Symptom progression in PWS is classically characterized by two nutritional stages. Stage 1 is hypotonia characterized by poor muscle tone that leads to poor feeding behavior causing failure to thrive in early neonatal life. Stage 2 is followed by the development of extreme hyperphagia, also known as insatiable eating and fixation on food that often leads to obesity in early childhood. Other major features of PWS include obsessive-compulsive and hoarding behaviors, intellectual disability, and sleep abnormalities. PWS is genetic disorder mapping to imprinted 15q11.2-q13.3 locus, specifically at the paternally expressed SNORD116 locus of small nucleolar RNAs and noncoding host gene transcripts. SNORD116 is processed into several noncoding components and is hypothesized to orchestrate diurnal changes in metabolism through epigenetics, according to functional studies. Here, we review the current status of epigenetic mechanisms in PWS, with an emphasis on an emerging role for SNORD116 in circadian and sleep phenotypes. We also summarize current ongoing therapeutic strategies, as well as potential implications for more common human metabolic and psychiatric disorders.

Differential expression of the ghrelin-related mRNAs GHS-R1a, GHS-R1b, and MBOAT4 in Japanese patients with schizophrenia

OBJECTIVES

Ghrelin regulates appetite and also plays important roles in cognition and may be involved in vulnerability to SCZ.

METHODS

In this study, we measured mRNA expression of the ghrelin-related molecules, growth hormone secretagogue receptor 1a (GHS-R1a) and 1b (GHS-R1b), and the ghrelin activator, membrane bound O-acyltransferase 4 (MBOAT4). Peripheral leukocytes from Japanese patients with SCZ (n = 49; 23 males, 26 females; age = 61.8 ± 13.3 years) and controls (n = 50; 25 males, 25 females; age = 62.0 ± 14.3 years) were recruited according to their clinical information. We also studied the DNA methylation rates of these genes in DNA from leukocytes.

RESULTS

The mRNA expression of GHS-R1a was significantly decreased in SCZ (SCZ vs. control: 0.35 ± 0.081 vs. 1.00 ± 0.059, respectively, p = 0.007), but expression levels of GHS-R1b and MBOAT4 were significantly increased in SCZ (SCZ vs. control: 2.02 ± 0.91 vs. 1.00 ± 0.32, p = 0.023, 1.37 ± 0.21 vs. 1.00 ± 0.11, respectively, p = 0.014). No differences in methylation rates for any genes were found.

CONCLUSION

We conclude that opposite expression of GHS-R1a and GHS-R1b, and elevated MBOAT4 mRNA expression may reflect the mechanisms of SCZ.

Body composition, adipokines, bone mineral density and bone remodeling markers in relation to IGF-1 levels in adults with Prader-Willi syndrome

Background

In patients with Prader-Willi syndrome (PWS) body composition is abnormal and alterations in appetite regulating factors, bone mineral density and insulin-like growth factor-1 (IGF-1) levels have been described. Studies in PWS adults are limited. In this study, we investigated body composition, appetite regulating peptides, bone mineral density and markers of bone remodeling in an adult PWS population. Furthermore, we investigated the association between these different parameters and IGF-1 levels because of the described similarities with growth hormone deficient patients.

Methods

In this cross-sectional observational cohort study in a university hospital setting we studied fifteen adult PWS patients. Anthropometric and metabolic parameters, IGF-1 levels, bone mineral density and bone metabolism were evaluated. The homeostasis model assessment of insulin resistance (HOMA2-IR) was calculated. Fourteen healthy siblings served as a control group for part of the measurements.

Results

In the adult PWS patients, height, fat free mass, IGF-1 and bone mineral content were significantly lower when compared to controls; body mass index (BMI), waist, waist-to-hip ratio and fat mass were higher. There was a high prevalence of osteopenia and osteoporosis in the PWS patients. Also, appetite regulating peptides and bone remodelling markers were aberrant when compared to reference values. Measurements of body composition were significantly correlated to appetite regulating peptides and high-sensitive C-reactive protein (hs-CRP), furthermore HOMA was correlated to BMI and adipokines.

Conclusion

In adults with Prader-Willi syndrome alterations in body composition, adipokines, hs-CRP and bone mineral density were demonstrated but these were not associated with IGF-1 levels. Further investigations are warranted to gain more insight into the exact pathophysiology and the role of these alterations in the metabolic and cardiovascular complications seen in PWS, so these complications can be prevented or treated as early as possible.

Effects of exenatide on weight and appetite in overweight adolescents and young adults with Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is associated with hyperphagia and hyperghrelinemia with major morbidity because of obesity without effective medical treatment targeting hyperphagia. Exenatide (Byetta [synthetic Exendin-4]; AstraZeneca, Wilmington DE) is a GLP-1 receptor agonist which reduces appetite and weight and may be an effective treatment in PWS.

OBJECTIVE

The objective of this study is to determine the effect of a 6-month trial of exenatide on appetite, weight and gut hormones in youth with PWS.

METHODS

Ten overweight and obese subjects with PWS (13-25 years) were recruited for a 6-month open-label, non-randomized, longitudinal study conducted at Children's Hospital Los Angeles. Exenatide was given using standard diabetes dosing without dietary modifications. Weight, body mass index (BMI), truncal fat, appetite and plasma acylated ghrelin were measured over 6 months. Mixed meal tolerance tests were performed at 0 and 6 months.

RESULTS

Appetite scores significantly decreased from baseline (32.2 ± 8.7) after 1, 3 and 6 moths of treatment (27.5 ± 8.8, 25.4 ± 9.3, and 25.4 ± 7.2 respectively; p = 0.004). Hemoglobin A1c decreased significantly after treatment, but weight, BMI z-score and adiposity did not. There was no significant change in ghrelin.

CONCLUSIONS

This is the first longitudinal investigation of the effects of exenatide in subjects with PWS. It was effective in decreasing appetite, without change in weight or BMI in the short term. Larger, controlled, longer-term trials in patients with PWS are needed to confirm the efficacy and safety of exenatide and to evaluate whether its use might induce weight loss when given in conjunction with behavioural modification.

The Fragile X proteins Fmrp and Fxr2p cooperate to regulate glucose metabolism in mice

Fragile X syndrome results from loss of FMR1 expression. Individuals with the disorder exhibit not only intellectual disability, but also an array of physical and behavioral abnormalities, including sleep difficulties. Studies in mice demonstrated that Fmr1, along with its paralog Fxr2, regulate circadian behavior, and that their absence disrupts expression and cycling of essential clock mRNAs in the liver. Recent reports have identified circadian genes to be essential for normal metabolism. Here we describe the metabolic defects that arise in mice mutated for both Fmr1 and Fxr2. These mice have reduced fat deposits compared with age- and weight-matched controls. Several metabolic markers show either low levels in plasma or abnormal circadian cycling (or both). Insulin levels are consistently low regardless of light exposure and feeding conditions, and the animals are extremely sensitive to injected insulin. Glucose production from introduced pyruvate and glucagon is impaired and the mice quickly clear injected glucose. These mice also have higher food intake and higher VO2 and VCO2 levels. We analyzed liver expression of genes involved in glucose homeostasis and found several that are expressed differentially in the mutant mice. These results point to the involvement of Fmr1 and Fxr2 in maintaining the normal metabolic state in mice.

Increased acyl ghrelin but decreased total ghrelin and unacyl ghrelin in Chinese Han people with impaired fasting glucose combined with impaired glucose tolerance

We assessed the plasma acyl ghrelin (AG), unacyl ghrelin (UAG), and total ghrelin (TGhr) levels in Chinese adults with pre-diabetes and newly diagnosed diabetes mellitus (NDDM) after an oral glucose tolerance test (OGTT), and abdominal subcutaneous fat area and visceral fat area (VFA) were measured. Fasting AG level was increased in the impaired fasting glucose (IFG) combined with impaired glucose tolerance (IFG+IGT) and NDDM groups. AG, UAG, and TGhr levels were significantly decreased post-OGTT, and the decrements of 30-min AG, UAG, and TGhr post-OGTT were not significantly different among groups. UAG and TGhr levels did not differ significantly among the normal glucose tolerance (NGT), IFG and NDDM groups, but they decreased obviously in the IFG+IGT and impaired glucose tolerance (IGT) groups. The NDDM group had larger VFA than the NGT, IGT, and IFG+IGT groups, even after adjustment for height, it was still larger than the NGT group. The factors such as dyslipidemia and obesity which are prone to develop insulin resistance (IR) and decrease insulin sensitivity (IS) were negatively correlated with UAG and TGhr, positively with AG/UAG, while no correlations with AG. In terms of evaluating IS and IR, AG/UAG ratio may be superior in AG concentration. Our findings suggest that relative sufficiency of AG, the deficiency of TGhr and UAG are already present in IFG+IGT patients. We speculate that there is UAG resistance in severe hyperglycemia (diabetic state), which could produce elevated TGhr and UAG compared to IFG+IGT group. In the development of T2D, increase of VFA could be the initiating factor, leading elevated AG, reduced UAG, IR, decreased IS, and finally hyperglycemia.

Systematic review of ghrelin response to food intake in pediatric age, from neonates to adolescents

OBJECTIVE

Food intake and energy balance are regulated during the lifespan with critical changes in each specific period (infancy, adulthood, aging). Some of ghrelin's changes may contribute to the regulation of food intake and weight in children. We aimed to analyze the ghrelin response to feeding in lean or obese subjects from birth to adolescence.

METHODS

We searched PubMed, Scopus, Google Scholar, Cochrane, and EMBASE (December 1999 to February 2013) and identified 62 relevant articles, of which 29 were suitable to be included.

RESULTS AND CONCLUSIONS

Total ghrelin response to meals is particular, with refractoriness in neonates and lean children and an inhibition that starts from puberty. Total ghrelin levels are decreased after meals, irrespective of pubertal stages in obese children and adolescents. Conversely, total ghrelin is decreased after an oral glucose tolerance test in all ages, with the exception of neonates. Data on unacylated ghrelin response are scant but resemble those of total ghrelin. The acylated ghrelin response to meals or oral glucose tolerance test is discordant, although a precocious inhibition followed by a rise back is present in both lean and obese children. The post-feeding profile in children with Prader-Willi syndrome is also peculiar, with a conserved and deeper inhibition of all ghrelin forms.

A descriptive study of colorectal function in adults with Prader-Willi Syndrome: high prevalence of constipation

BACKGROUND

Some patients with Prader-Willi Syndrome (PWS) have symptoms of constipation, but bowel function in PWS has never been systematically evaluated. The aim of the present study was to describe colorectal function in PWS by means of validated techniques.

METHODS

Twenty-one patients with PWS (14 women, age 17-47 (median = 32)) were evaluated with the Rome III constipation criteria, stool diary, digital rectal examination, rectal diameter assessed from transabdominal ultrasound, and total gastrointestinal transit time (GITT) determined with radio-opaque markers. Results were compared with those of healthy controls.

RESULTS

Among PWS patients able to provide information for Rome III criteria, 8/20 (40%) fulfilled the criteria for constipation. Most commonly reported symptoms were a feeling of obstructed defecation (8/19, 42%), <3 defecations per week (8/17, 47%), straining during defecation (7/19, 37%) and lumpy or hard stools (6/19, 32%). Rectal diameter did not differ between PWS (median 3.56 centimeters, range 2.24-5.36) and healthy controls (median 3.42 centimeters, range 2.67-4.72) (p = 0.96), but more PWS patients (13/20; 65%) than healthy controls (3/25; 12%) (p < 0.001) had fecal mass in the rectum. Median GITT was 2.0 days (range 0.5-4.4) in PWS versus 1.6 (range 0.7-2.5) in the control group (p = 0.26). However, GITT was >3 days in 5/21 (24%) of PWS and none of the controls (p = 0.047).

CONCLUSION

Constipation is very common in PWS. Patients with PWS have an increased prevalence of prolonged GITT and palpable stools in the rectum at digital rectal examination.

Serum acylated ghrelin is negatively correlated with the insulin resistance in the CODING study

Objective

Ghrelin is a 28-amino acid orexigenic peptide synthesized mainly in the stomach. Acute administration of ghrelin has been found to decrease insulin secretion. However, little data is available regarding whether ghrelin contributes to the long-term regulation of insulin resistance at the population level. The aim of this study is to investigate the association between circulating ghrelin and insulin resistance in a large population based study.

Design

A total of 2082 CODING study (Complex Diseases in the Newfoundland population: Environment and Genetics) subjects were assessed. Subjects were of at least third generation Newfoundland descent, between the ages of 20 and 79 years, and had no serious metabolic, cardiovascular, or endocrine diseases. Ghrelin was measured with an Enzyme Immunoassay method. Insulin and fasting glucose were measured by Immulite 2500 autoanalyzer and Lx20 clinical chemistry analyzer, respectively. Homeostatic Model Assessment of β cell function (HOMA-β) and Insulin Resistance (HOMA-IR) and Quantitative Insulin-sensitivity Check Index (QUICKI) were used for measurement of insulin resistance.

Results

Partial correlation analyses showed a significant negative correlation between circulating ghrelin and insulin level and insulin resistance in the entire cohort and also in men and women separately. The aforementioned correlation was independent of age, percentage of trunk fat and HDL-cholesterol. According to menopausal status, only pre-menopausal women revealed negative correlations.

Conclusion

Our results suggest that except for postmenopausal women, high circulating ghrelin level is associated with lower insulin resistance in the general population.

Hypothalamic obesity in children

Hypothalamic obesity is an intractable form of obesity syndrome that was initially described in patients with hypothalamic tumours and surgical damage. However, this definition is now expanded to include obesity developing after a variety of insults, including intracranial infections, infiltrations, trauma, vascular problems and hydrocephalus, in addition to acquired or congenital functional defects in central energy homeostasis in children with the so-called common obesity. The pathogenetic mechanisms underlying hypothalamic obesity are complex and multifactorial. Weight gain results from damage to the ventromedial hypothalamus, which leads, variously, to hyperphagia, a low-resting metabolic rate; autonomic imbalance; growth hormone-, gonadotropins and thyroid-stimulating hormone deficiency; hypomobility; and insomnia. Hypothalamic obesity did not receive enough attention, as evidenced by rarity of studies in this group of patients. A satellite symposium was held during the European Congress of Obesity in May 2011, in Istanbul, Turkey, to discuss recent developments and concepts regarding pathophysiology and management of hypothalamic obesity in children. An international group of leading researchers presented certain aspects of the problem. This paper summarizes the highlights of this symposium. Understanding the central role of the hypothalamus in the regulation of feeding and energy metabolism will help us gain insights into the pathogenesis and management of common obesity.

Appetite hormones and the transition to hyperphagia in children with Prader-Willi syndrome

OBJECTIVE

Prader-Willi syndrome (PWS) is a genetic neurodevelopmental disorder with several nutritional phases during childhood proceeding from poor feeding, through normal eating without and with obesity, to hyperphagia and life-threatening obesity, with variable ages of onset. We investigated whether differences in appetite hormones may explain the development of abnormal eating behaviour in young children with PWS.

SUBJECTS

In this cross-sectional study, children with PWS (n=42) and controls (n=9) aged 7 months-5 years were recruited. Mothers were interviewed regarding eating behaviour, and body mass index (BMI) was calculated. Fasting plasma samples were assayed for insulin, leptin, glucose, peptide YY (PYY), ghrelin and pancreatic polypeptide (PP).

RESULTS

There was no significant relationship between eating behaviour in PWS subjects and the levels of any hormones or insulin resistance, independent of age. Fasting plasma leptin levels were significantly higher (mean ± s.d.: 22.6 ± 12.5 vs 1.97 ± 0.79 ng ml(-1), P=0.005), and PP levels were significantly lower (22.6 ± 12.5 vs 69.8 ± 43.8 pmol l(-1), P<0.001) in the PWS group compared with the controls, and this was independent of age, BMI, insulin resistance or IGF-1 levels. However, there was no significant difference in plasma insulin, insulin resistance or ghrelin levels between groups, though PYY declined more rapidly with age but not BMI in PWS subjects.

CONCLUSION

Even under the age of 5 years, PWS is associated with low levels of anorexigenic PP, as in older children and adults. Hyperghrelinaemia or hypoinsulinaemia was not seen in these young children with PWS. Change in these appetite hormones was not associated with the timing of the transition to the characteristic hyperphagic phase. However, abnormal and/or delayed development or sensitivity of the effector pathways of these appetitive hormones (for example, parasympathetic and central nervous system) may interact with low PP levels, and later hyperghrelinaemia or hypoinsulinaemia, to contribute to hyperphagia in PWS.

Ghrelin in mental health, sleep, memory

Ghrelin acts as a neuropeptide. It participates in sleep-wake regulation. After systemic ghrelin treatment nonREM sleep is promoted in male humans and mice. This effect is influenced by gender, time of administration and depression. Ghrelin does not modulate sleep in healthy women and during the early morning in male subjects. In depressed women REM sleep is diminished after ghrelin. In elderly men and depressed men sleep promotion by ghrelin was preserved. In rats after central ghrelin feeding and wakefulness increased. The nocturnal secretion pattern of cortisol, GH, LH, FSH and hypothalamo-pituitary-thyroid hormones are influenced by ghrelin. Furthermore ghrelin appears to be related to memory and to be involved in the pathophysiology of CNS disorders, particularly depression.

Ghrelin in obesity and endocrine diseases

Ghrelin shows orexigenic effect through its action on the hypothalamic appetite-regulating pathways, while in the periphery ghrelin increases adipose tissue accumulation and has a diabetogenic effect on the liver and pancreas. Adenosine monophosphate-activated protein kinase (AMPK) has been suggested as one of the mediators of ghrelin's effects. Plasma ghrelin levels are dependent on body mass index as well as food intake patterns. Ghrelin levels are in general reduced in obese individuals and in subjects with insulin resistance. In contrast to other forms of obesity, patients with Prader-Willi syndrome (PWS) display high levels of ghrelin, reduced visceral adiposity and relative hypoinsulinemia. Relationships between obesity and common genomic variants of GHRL and GHS-R genes have been studied. Ghrelin may have a role in the weight-reducing effect of bariatric surgery; however, this is a much debated issue. Altered ghrelin levels have also been observed in Cushing's syndrome and thyroid disease probably due to the secondary insulin resistance in these subjects.

WITHDRAWN: Ghrelin in obesity and endocrine diseases

The Publisher regrets that this article is an accidental duplication of an article that has already been published, doi:10.1016/j.mce.2011.02.011. The duplicate article has therefore been withdrawn.

Obese adolescents show impaired meal responses of the appetite-regulating hormones ghrelin and PYY

Ghrelin and peptide YY (PYY) stimulate hunger and satiety, respectively. The physiology of these hormones during normal meal intake remains unclear. This study was designed to compare the responses of these two hormones to meal intake between lean and obese Hispanic adolescents. A total of 10 obese and 7 lean Hispanic youth, aged 11-14 years, consumed two mixed meals, one small and one large, during which plasma measurements of active and total ghrelin and total PYY were obtained. Obese subjects tended to consume more calories during the small meal than lean subjects, although this did not reach statistical significance. Intake of the small meal significantly suppressed active ghrelin and stimulated PYY levels in the lean subjects, and these changes were further accentuated by the large meals. In obese subjects, the suppression of active ghrelin and stimulation of PYY by caloric intake were blunted. Interestingly, a paradoxical stimulation of active ghrelin levels was noted during the small meals in both lean and obese subjects. This stimulation was not seen during the larger meals in lean subjects, but remained present in the obese subjects. Thus, meal-related changes in active ghrelin and PYY are blunted in obese as compared to lean Hispanic subjects. This blunting could contribute to the development or worsening of obesity.

Correlation between hyperghrelinemia and carotid artery intima-media thickness in children with Prader-Willi syndrome

PURPOSE

Prader-Willi syndrome (PWS) is a genetic disorder characterized by childhood-onset obesity and endocrine dysfunction that leads to cardiovascular disability. The objective of the study is to assess the relationship between carotid intima-media thickness (IMT) and atherosclerotic risk factors.

MATERIALS AND METHODS

Twenty-seven PWS children and 24 normal controls were enrolled. Correlations of IMT with atherosclerotic risk factors were assessed.

RESULTS

IMTs in the PWS group did not differ from those in the controls (p = 0.172), although total ghrelin levels were higher in the PWS children (p = 0.003). The multivariate analysis revealed positive correlations between total ghrelin levels ( = 0.489, p = 0.046) and IMT in the PWS group and between body mass index-standard deviation score (BMI-SDS) ( = 0.697, p = 0.005) and IMT in the controls.

CONCLUSION

Considering the positive correlation of IMT with total ghrelin levels and the high level of ghrelin in PWS children, a further study is warranted to evaluate the role of elevated ghrelin on atherosclerosis for PWS.

Obesity and its relationship to addictions: is overeating a form of addictive behavior?

Obesity is a major public health problem and notoriously difficult to treat. There are many parallels between obesity/overeating and addictions to alcohol and drugs. This paper discusses similarities between obesity and addictive disorders, including common personality characteristics, disruptive behavior syndromes, and brain mechanisms. Although there are important differences between overeating and other addictive behaviors, an addiction model of overeating may effectively inform prevention and treatment of obesity.

Ghrelin vaccination decreases plasma MCP-1 level in LDLR(-/-)-mice

Ghrelin is a novel peptide hormone having growth hormone releasing activity and many endocrine and metabolic functions. In rats and pigs, ghrelin immunizations have recently been shown to induce an antibody response against ghrelin simultaneously with a decrease in body weight gain. Our aim was to test the role of ghrelin immunization on atherosclerosis and weight gain in mice. LDLR(-/-)-mice (n=36) were immunized with ghrelin-PADRE, PADRE alone and PBS and then placed on a high fat diet for 22 weeks. Weight gain and food intake were followed throughout the study. Acylated and total ghrelin, cytokines and MCP-1 were analyzed from plasma using commercial kits. Stomach ghrelin was assessed using qRT-PCR and immunohistochemistry. Atherosclerosis was determined from aorta and cross-sections at the end of study. Mice immunized with ghrelin-PADRE developed high plasma IgG titers to ghrelin simultaneously with a significant increase in plasma acylated and total ghrelin levels. Plasma MCP-1 levels decreased in mice immunized with ghrelin-PADRE compared to mice immunized with PADRE and PBS. There were no differences in atherosclerosis determined from aorta and cross-sections as well as in body weights and food intake in LDLR(-/-)-mice between the different immunization groups. Our data indicates that ghrelin-PADRE vaccination induces a strong exclusive IgG response to ghrelin and increases plasma acylated and total ghrelin levels in mice. Ghrelin vaccination decreases plasma MCP-1 levels even though no effects on developing signs of atherosclerosis or weight gain in mice were observed.

Influence of age, gender, and glucose tolerance on fasting and fed acylated ghrelin in Prader Willi syndrome

BACKGROUND & AIMS

Prader Willi syndrome (PWS) is a genetic syndrome characterized by hyperphagia, morbid obesity, relative hypoinsulinemia and normal insulin sensitivity. PWS presents higher total (TG) and acylated ghrelin (AG) levels. The cause of this increase as well as the modulation of ghrelin secretion in fasting and feeding in relation to other metabolic parameters and glucose tolerance in PWS is largely unknown.

METHODS

We studied TG and AG at fasting in PWS children (14) and adults (18). We also studied TG and AG response to a mixed standardized light breakfast (SLB) in PWS adults without (AD-GT) and with glucose intolerance (AD-GI) at OGTT.

RESULTS

TG and AG were higher in children than in adults (p<0.05). AG was higher in adult males (p<0.001). Fasting AG and AG/TG ratio were lower in AD-GI than in AD-GT (p<0.05). TG, but not AG, decreased in AD-GT (p<0.006), whereas AG, but not TG, increased in AD-GI (p<0.03) post-SLB. Fasting TG and AG were negatively predicted by fasting insulin (p<0.05). Post-SLB AG was positively predicted by glucose during OGTT (p<0.04).

CONCLUSIONS

Fasting and post-meal AG levels are influenced by glucose tolerance in PWS, suggesting that AG derangement might have a role in the development of glucose intolerance.

Energy homoeostasis: The roles of adipose tissue-derived hormones, peptide YY and Ghrelin

This review discusses the physiology of the hormones leptin, adiponectin, resistin, peptide YY, and ghrelin and how each of these contributes to energy homoeostasis, weight regulation, and the pathogenesis of obesity. The relationship these hormones have with insulin and insulin resistance is also discussed, and the potential therapeutic use of each of these hormones is also considered.

Ghrelin concentrations in Prader-Willi syndrome (PWS) infants and children: changes during development

BACKGROUND

Prader-Willi syndrome (PWS) is associated with failure to thrive in infancy and progressive hyperphagia and obesity in childhood. This progressive weight gain is associated with hyperghrelinaemia and increased insulin sensitivity. The role of ghrelin excess in the pathogenesis of obesity is unclear.

OBJECTIVE

To determine if high ghrelin levels precede the onset of obesity in young PWS children.

DESIGN AND METHODS

A cross-sectional study of 33 infants with PWS and 28 healthy control subjects (C). Fasting ghrelin and other satiety hormones were measured.

RESULTS

Median total serum ghrelin in young children with PWS trended higher, but did not differ significantly from those in C of similar age, weight-for-age z-score and sex. However, there was more variability in ghrelin concentrations of young PWS. Eleven of 33 PWS subjects had ghrelin levels greater than the 95th percentile for ghrelin values in the C subjects (> 2871 pg/ml). Six of the PWS subjects with high ghrelin levels had weight-for-age z-scores < 0. Ghrelin concentrations in PWS and C infants exceeded those in older children. In youngsters with PWS, leptin was higher, suggesting a relative excess of fat to lean body mass and plasma adiponectin was increased.

CONCLUSIONS

Young infants with PWS who have not yet developed hyperphagia or obesity have median fasting ghrelin levels similar to controls. However, a subset (33%) of young PWS is hyperghrelinaemic; approximately one-half of those with hyperghrelinaemia have BMI z-score < 0. The age-related decline in ghrelin is blunted in PWS.

Hyperghrelinemia precedes obesity in Prader-Willi syndrome

BACKGROUND

High plasma ghrelin levels have been reported in Prader-Willi syndrome (PWS). However, little is known about plasma ghrelin in these children during the first years of life characterized by a failure to thrive.

OBJECTIVE

The objective of the study was to investigate total plasma ghrelin levels in children with PWS and controls from 2 months to 17 years.

SUBJECTS AND METHODS

Forty children with PWS [24 boys, 16 girls, median age 3.6 yr, median body mass index (BMI) Z-score 0.3] were compared with 84 controls (57 boys, 27 girls, median age 4.2 yr median BMI Z-score 0.1). Children were then divided into two groups according to age and GH treatment.

RESULTS

Median plasma ghrelin levels were significantly higher in children with PWS, compared with controls at any age (568 vs. 173, P < 0.0001) and decreased with age in both groups (P < 0.0001). In the whole group of PWS, we found an inverse relationship between ghrelin and BMI Z-score, insulin, homeostasis model assessment insulin resistance index, leptin, and lean mass. Plasma ghrelin levels were higher in children with PWS than controls, both in the youngest children below 3 yr who were not receiving GH (771 vs. 233, P < 0.0001) and in the children older than 3 yr, all of whom were treated with GH (428 vs. 159, P < 0.0001).

CONCLUSIONS

Plasma ghrelin levels in children with PWS are elevated at any age, including during the first years of life, thus preceding the development of obesity.

[Therapeutical approach of obesity in Prader-Willi Syndrome]

Prader-Willi Syndrome (PWS) is a multisystemic genetic disease characterized by hypotonia, mental retardation, characteristic facial appearance, hyperphagia, and compulsive eating due to hypothalamic dysfunction. PWS is caused by loss of function of genes located in chromosome 15q11-q13, an area subject to genomic imprinting. Obesity is a major cause of increased morbidity and mortality among patients with PWS. The objective of this study was to analyze the therapeutic options available for the treatment of the obesity in PWS including pharmacological and surgical strategies.

Peptide YY, cholecystokinin, insulin and ghrelin response to meal did not change, but mean serum levels of insulin is reduced in children with Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a contiguous gene syndrome characterized by uncontrollable eating or hyperphagia. Several studies have confirmed that plasma ghrelin levels are markedly elevated in PWS adults and children. The study of anorexigenic hormones is of interest because of their regulation of appetite by negative signals. To study the pattern and response of the anorexigenic hormones such as cholecystokinin (CCK) and peptide YY (PYY) to a meal in PWS, we measured the plasma CCK, PYY, ghrelin and serum insulin levels in PWS patients (n=4) and in controls (n=4) hourly for a day, and analyzed hormone levels and hormonal responses to meals. Repeated measures of ANOVA of hormone levels demonstrated that only insulin levels decreased (p=0.013) and CCK (p=0.005) and ghrelin (p=0.0007) increased in PWS over 24 hr. However, no significant group x time interactions (ghrelin: p=0.89, CCK: p=0.93, PYY: p=0.68 and insulin: p=0.85) were observed; in addition, there were no differences in an assessment of a three-hour area under the curve after breakfast. These results suggest that the response pattern of hormones to meals in PWS patients parallels that of normal controls. In addition, the decrease of insulin levels over 24 hr, in spite of obesity and elevated ghrelin levels, suggests that the baseline insulin level, not the insulin response to meals, may be abnormal in patients with PWS.

Marked suppression of ghrelin concentration by insulin in Prader-willi syndrome

The plasma ghrelin has been reported to be elevated in Prader-Willi syndrome (PWS) and modulated by insulin. It was hypothesized that insulin might have a more pronounced effect on reducing plasma ghrelin in PWS patients, which would influence appetite. This study investigated the degree of ghrelin suppression using an euglycemic hyperinsulinemic clamp in children with PWS (n=6) and normal children (n=6). After a 90-min infusion of insulin, the plasma ghrelin level decreased from a basal value of 0.86+/-0.15 to 0.58+/-0.12 ng/mL in the controls, and from 2.38+/-0.76 to 1.12+/-0.29 ng/mL in children with PWS (p=0.011). The area under the curve below the baseline level over the 90 min insulin infusion was larger in children with PWS than in controls (-92.82+/-44.4 vs. -10.41+/-2.87 ng/mL/90 min) (p=0.011). The insulin sensitivity measured as the glucose infusion rate at steady state was similar in the two groups (p=0.088). The decrease in the ghrelin levels in response to insulin was more pronounced in the children with PWS than in the controls. However, the level of ghrelin was always higher in the children with PWS during the clamp study. This suggests that even though insulin sensitivity to ghrelin is well maintained, an increase in the baseline ghrelin levels is characteristic of PWS.

The effect of growth hormone on the response of total and acylated ghrelin to a standardized oral glucose load and insulin resistance in children with Prader-Willi syndrome

CONTEXT

Fasting levels of plasma ghrelins are grossly elevated in children with Prader-Willi syndrome (PWS). The cause of this elevation and the regulation of ghrelins in PWS is largely unknown. The regulatory role of individual nutritional components and of GH is not well characterized.

OBJECTIVE

We investigated the influence of GH on acylated (aGhr) and total ghrelin (tGhr) concentrations before and after an oral glucose load, and on insulin resistance in PWS children.

DESIGN, PATIENTS, AND INTERVENTIONS

In a clinical follow-up study, plasma ghrelins were measured during an oral glucose tolerance test, and parameters of insulin resistance were determined in 28 PWS children before and/or 1.18 (0.42-9.6) yr (median, range) after start of GH therapy (0.035 mg/kg body weight per day).

MAIN OUTCOME MEASURES

Fasting and postglucose concentrations of aGhr and tGhr and homeostasis model assessment 2 insulin resistance were the main outcome measures.

SETTING

The study was conducted in a single center (University Children's Hospital).

RESULTS

High fasting [1060 +/- 292 (sd) pg/ml; n = 12] and postglucose trough (801 +/- 303 pg/ml; n = 10) tGhr concentrations in GH-untreated PWS children were found to be decreased in the GH-treated group (fasting 761 +/- 247 pg/ml, n = 24, P = 0.006; postglucose 500 +/- 176 pg/ml, n = 20; P = 0.006). In contrast, aGhr concentrations and insulin resistance were not changed by GH treatment. Both aGhr and tGhr concentrations were decreased by oral carbohydrate administration, independent of the GH treatment status.

CONCLUSIONS

Our results indicate that, in PWS children, aGhr and tGhr are differentially regulated by GH.

Obestatin is not elevated or correlated with insulin in children with Prader-Willi syndrome

CONTEXT

Obestatin is a peptide hormone derived from the proteolytic cleavage of ghrelin preprohormone. In Prader-Willi syndrome (PWS), the levels of total ghrelin (TG) and acylated ghrelin (AG) are increased, and these hormones are regulated by insulin.

OBJECTIVE

Our objective was to analyze the changes in the obestatin levels after glucose loading and to characterize the correlations of obestatin with TG, AG, and insulin.

DESIGN

Plasma obestatin, TG, AG, and insulin levels were measured in PWS children (n = 15) and controls (n = 18) during an oral glucose tolerance test.

SETTING

All subjects were admitted to the Samsung Medical Center.

INTERVENTIONS

An oral glucose tolerance test was performed after an overnight fast.

MAIN OUTCOME MEASURES

The plasma levels of obestatin, TG, AG, and serum insulin were measured at 0, 30, 60, 90, and 120 min after glucose challenge, and areas under the curves (AUCs) were calculated.

RESULTS

No significant difference in AUC of the plasma obestatin was found between the PWS children and normal obese controls (P = 0.885), although AUC of AG (P = 0.002) and TG (P = 0.003) were increased in the PWS children. Moreover, There was a negative correlation between the AUC of AG and AUC of insulin both in PWS (r = -0.432; P = 0.049) and in controls (r = -0.507; P = 0.016). However, AUC of obestatin was not significantly correlated with AUC of insulin (in PWS, r = 0.168 and P = 0.275; in controls, r = -0.331 and P = 0.09).

CONCLUSIONS

Our results indicate that plasma obestatin is not elevated in PWS children and is not regulated by insulin both in PWS children and in obese controls.

The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review

Leptin and ghrelin are two hormones that have been recognized to have a major influence on energy balance. Leptin is a mediator of long-term regulation of energy balance, suppressing food intake and thereby inducing weight loss. Ghrelin on the other hand is a fast-acting hormone, seemingly playing a role in meal initiation. As a growing number of people suffer from obesity, understanding the mechanisms by which various hormones and neurotransmitters have influence on energy balance has been a subject of intensive research. In obese subjects the circulating level of the anorexigenic hormone leptin is increased, whereas surprisingly, the level of the orexigenic hormone ghrelin is decreased. It is now established that obese patients are leptin-resistant. However, the manner in which both the leptin and ghrelin systems contribute to the development or maintenance of obesity is as yet not clear. The purpose of this review is to provide background information on the leptin and ghrelin hormones, their role in food intake and body weight in humans, and their mechanism of action. Possible abnormalities in the leptin and ghrelin systems that may contribute to the development of obesity will be mentioned. In addition, the potentials of leptin and ghrelin as drug targets will be discussed. Finally, the influence of the diet on leptin and ghrelin secretion and functioning will be described.

Aging influences the level and functions of fasting plasma ghrelin levels: the POWIRS-Study

OBJECTIVE

Ghrelin, known for its orexigenic activity, also have functions such as vasodilation and a growth hormone releasing action. It is uncertain whether these functions change with increasing age. This study aimed to determine whether ghrelin levels differ between young and older women with different levels of obesity; and secondly whether the associations of ghrelin with metabolic syndrome (MS) components, adipocytokines, coagulation factors, and cortisol change with increasing age.

METHODS AND RESULTS

Caucasian women (N=107) were divided into young (19-29 years) and older groups (30-56 years). Fasting ghrelin, leptin, adiponectin, glucose, insulin, cortisol, fibrinogen and plasminogen activator inhibitor-1 (PAI-1) levels were determined. Blood pressure (BP), body mass index and waist circumferences were measured. Older lean women showed lower levels of ghrelin (p<0.05) than young lean women, with no differences regarding BP, obesity, lipids, adipokines or insulin resistance (IR). Ghrelin levels of older women remained constant with increasing obesity, but younger women showed significantly reduced ghrelin levels in obese groups. Only younger women showed significant correlations between ghrelin and leptin, adiponectin, fibrinogen and PAI-1 (adjusted for age, obesity and menstrual phase), whereas both age groups showed significant correlations with IR. In younger women factor analysis grouped ghrelin with coagulation factors and all MS components. In older women ghrelin was absent from the MS cluster, but was associated with lower BP, cortisol and IR.

CONCLUSIONS

Ghrelin levels were not significantly elevated in lean older women, and did not change with increased obesity in older women--as were observed in younger women. The functions of ghrelin also seem to change with increased age since only in young women ghrelin was associated with obesity, coagulation factors and leptin.

Ghrelin levels in young children with Prader-Willi syndrome

OBJECTIVE

To explore the hypothesis that high ghrelin levels contribute to obesity in Prader-Willi syndrome (PWS), we assessed whether the increased levels observed in older persons with PWS exist in very young children, before the onset of hyperphagia.

STUDY DESIGN

We measured ghrelin levels in nine children with PWS (17-60 months of age) and eight healthy control subjects of equivalent body mass index (BMI), age, and sex.

RESULTS

PWS and control groups had equivalent BMI (16.8 +/- 1.4 vs 16.1 +/- 0.9 kg/m(2), respectively; P = .24), age (37.8 +/- 15.4 vs 50.3 +/- 17.7 months; P = .14), and sex. PWS and control groups also had equivalent fasting levels of total ghrelin (787 +/- 242 vs 716 +/- 135 pg/mL, respectively; P = .24), bioactive ghrelin (102 +/- 35 vs 91 +/- 23 pg/mL; P = .45), insulin, and glucose. Ghrelin correlated negatively with BMI among controls (r = -0.760, P = .029) but not PWS (r = 0.015, P = .97).

CONCLUSIONS

Children <5 years of age with PWS, who had not yet developed hyperphagia or excessive obesity, had normal ghrelin levels, in contrast with the hyperghrelinemia of older, hyperphagic people with PWS. It is possible that ghrelin levels increase suddenly before hyperphagia develops.

Ghrelin and the short- and long-term regulation of appetite and body weight

Ghrelin, an acylated upper gastrointestinal peptide, is the only known orexigenic hormone. Considerable evidence implicates ghrelin in mealtime hunger and meal initiation. Circulating levels decrease with feeding and increase before meals, achieving concentrations sufficient to stimulate hunger and food intake. Preprandial ghrelin surges occur before every meal on various fixed feeding schedules and also among individuals initiating meals voluntarily without time- or food-related cues. Ghrelin injections stimulate food intake rapidly and transiently, primarily by increasing appetitive feeding behaviors and the number of meals. Preprandial ghrelin surges are probably triggered by sympathetic nervous output. Postprandial suppression is not mediated by nutrients in the stomach or duodenum, where most ghrelin is produced. Rather, it results from post-ingestive increases in lower intestinal osmolarity (information probably relayed to the foregut via enteric nervous signaling), as well as from insulin surges. Consequently, ingested lipids suppress ghrelin poorly compared with other macronutrients. Beyond a probable role in meal initiation, ghrelin also fulfills established criteria for an adiposity-related hormone involved in long-term body-weight regulation. Ghrelin levels circulate in relation to energy stores and manifest compensatory changes in response to body-weight alterations. Ghrelin crosses the blood-brain barrier and stimulates food intake by acting on several classical body-weight regulatory centers, including the hypothalamus, hindbrain, and mesolimbic reward system. Chronic ghrelin administration increases body weight via diverse, concerted actions on food intake, energy expenditure, and fuel utilization. Congenital ablation of the ghrelin or ghrelin-receptor gene causes resistance to diet-induced obesity, and pharmacologic ghrelin blockade reduces food intake and body weight. Ghrelin levels are high in Prader-Willi syndrome and low after gastric bypass surgery, possibly contributing to body-weight alterations in these settings. Extant evidence favors roles for ghrelin in both short-term meal initiation and long-term energy homeostasis, making it an attractive target for drugs to treat obesity and/or wasting disorders.

Serum ghrelin levels are enhanced in patients with epilepsy

PURPOSE

In patients with epilepsy, although many changes in the physiology of hormones in the neuroendocrine system can occur (especially in the sex hormones, for example), the causes of these changes have not been fully elucidated. There are also relations between seizure activity and stages of sleep. Ghrelin is the peptide hormone, which has been shown to affect both endocrine function and sleep. The purpose of this study was to evaluate serum levels of ghrelin in epilepsy patients.

METHODS

A total of 35 patients currently receiving antiepileptic drug therapy (of these patients, 20 had primary generalized seizure and 15 had partial seizure) were studied. The control group consisted of 30 healthy volunteers matched for age and gender. In all participants, serum levels of ghrelin, cholesterol and triglycerides were measured and body mass index (BMI) was determined. Patients with endocrine, immune or any other chronic diseases were excluded.

RESULTS

In the epilepsy patients, the mean serum ghrelin level was 158.81+/-55.97 pg/ml, and this was significantly higher than the control group's level of 93.43+/-21.33 pg/ml (p<0.001). In terms of serum cholesterol, triglycerides and BMI, no significant differences were found between the epilepsy patients and the control group (p>0.05).

CONCLUSIONS

The origin of higher serum ghrelin levels in epilepsy and their relation to seizures are not completely known. However, this elevation of serum ghrelin could contribute to the lengthening of NREM sleep in epilepsy patients, thereby playing a role in seizure occurrence. From another direction, high serum ghrelin levels could cause changes and/or dysfunction in hormone secretion and physiology via its effects on growth hormone, and thereby play a facilitating role in seizure occurrence.

Hyperghrelinemia does not accelerate gastric emptying in Prader-Willi syndrome patients

Prader-Willi syndrome (PWS) is the most common form of syndromic obesity associated with hyperphagia. Because ghrelin stimulates gastric motility in rodents, and PWS patients have 3- to 4-fold higher fasting plasma ghrelin concentrations than normal subjects, we hypothesized that hyperphagia associated with PWS may be partly explained by rapid gastric emptying due to the increased gastric motility caused by ghrelin. We determined gastric emptying times (GETs) and measured ghrelin levels in 11 PWS children and 11 age-, sex-, and body mass index-matched controls using a standard meal containing [(99m)Tc]diaminetriaminepentacetate. Median plasma ghrelin levels before (precibum) and after the GET study were higher in PWS patients than in controls (P = 0.004 and P = 0.001, respectively). Median percent gastric retentions at 90 min after the standard meal were 57.1% (range, 34.0-83.2%) in PWS patients and 40.2% (range, 27.2-60.2%) in controls (P = 0.03). In particular, precibum ghrelin concentrations were not significantly correlated with the rate of gastric emptying in PWS patients (P = 0.153; r = 0.461) or controls (P = 0.911; r = 0.048). Our results show that gastric emptying in PWS is reduced despite higher ghrelin levels, and that the voracious appetite associated with PWS is related to another mechanism.

Estrogen replacement therapy increases plasma ghrelin levels

Ghrelin is a novel peptide hormone that has GH releasing activity and also other endocrine and metabolic functions. The purpose of this study was to investigate the effects of estrogen replacement therapy on plasma active ghrelin levels in 64 hysterectomized postmenopausal women receiving peroral estrogen (PE) or transdermal estrogen therapy for 6 months. Active ghrelin was measured using commercial RIA. Estrogen therapy increased plasma active ghrelin from 479 +/- 118 to 521 +/- 123 pg/ml (P = 0.002) among all the study subjects. PE therapy increased plasma ghrelin levels from 465 +/- 99 to 536 +/- 104 pg/ml (P = 0.001). Transdermal estrogen therapy did not increase plasma ghrelin levels significantly (from 491 +/- 132 to 509 +/- 138 pg/ml; P = 0.332). The relative changes in plasma ghrelin levels were associated with the relative changes in serum estradiol concentrations (r = 0.299; P = 0.017). During the estrogen therapy, negative associations were found between plasma active ghrelin levels and several plasma lipids (total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, total triglycerides, and very low-density lipoprotein triglycerides). As a conclusion, estrogen replacement therapy increased active plasma ghrelin levels, particularly PE therapy. Additional studies are needed to determine the possible underlying mechanisms.

Ghrelin in Growth and Development

Exogenous administration of ghrelin increases caloric intake and stimulates growth hormone (GH) secretion, two effects that are mediated through binding of ghrelin to the GH secretagogue receptor (GHS-R). In addition, ghrelin is thought to inhibit adipogenesis by GHS-R-independent mechanisms. In adults, ghrelin is mainly produced by the stomach. In contrast, in the fetal and early postnatal period, ghrelin gene expression is abundant in the pancreas but not in the stomach. While knockout animal studies demonstrate that ghrelin is not required for perinatal development under normal nutritional conditions, the characteristics of ghrelin metabolism during fetal development suggest that ghrelin could contribute to the programming of mechanisms involved in energy balance, such as beta-cell maturation, orexigenic pathways and adipogenesis. In humans, ghrelin concentrations progressively decrease during childhood and adolescence, as well as with advancing puberty. In adolescents, similar to adults, ghrelin concentrations are inversely related to body mass index and to circulating insulin. One notable exception is the presence of elevated ghrelin concentrations in subjects with Prader-Willi syndrome, raising the possibility that ghrelin could be part of the etiology of excess food intake in this condition. These data raise a number of fascinating questions on the potential physiologic role of this hormone during growth and development.