Ghrelin in Growth and Development

Dietary Pharmacological Zinc and Copper Enhances Voluntary Feed Intake of Nursery Pigs

The objective of the three experiments herein were to characterize the effect of pharmacological zinc and copper concentrations on nursery pig feed intake, stomach ghrelin, energy and nutrient digestibility, and mineral retention in post-weaned pigs. In Expt. 1, 300 weaned pigs were allotted across three dietary treatments (n = 10 pens/treatment) and fed in two diet phases (P1 and P2) lasting 7 and 14 days, respectively. Treatments were: (1) Control diet with no pharmacological minerals in P1 and P2, CON; (2) CON + 3,000 mg/kg Zn and 200 mg/kg Cu (P1), no pharmacological minerals in P2, ZC-CON; and (3) CON + 3,000 mg/kg Zn and 200 mg/kg Cu (P1), CON + 2,000 mg/kg Zn and 200 mg/kg Cu (P2); ZC. Over the 21-day test period, ZC pigs had 15% higher ADG and 13–24% ADFI compared to the CON and ZC-CON pigs (P < 0.05). ZC-CON and ZC pig daily feed intakes were 29 and 73% higher by day 5 and 7 post-weaning, respectively, compared to the CON pigs (P < 0.0001). However, removing pharmacological minerals in P2 abruptly decreased ZC-CON daily feed intake within 24 h to similar intakes as the CON compared to the ZC pigs (0.17, 0.14, and 0.22 kg/d, respectively, P < 0.05). Dietary pharmacological minerals increased stomach fundus ghrelin-positive cells than CON pigs at day 7 (P = 0.005) and day 21 (P < 0.001). However, fasting plasma total and acyl-ghrelin concentrations did not differ from a control in response to zinc oxide daily drenching (Expt. 2). Expt. 3 showed that zinc and copper to have moderate to low retention; however, pharmacological zinc and copper diets increased zinc (P < 0.05) and copper retention (P = 0.06) after 28 days post-weaning compared to control pigs. Pharmacological zinc and copper did not improve digestible energy, metabolizable energy or nitrogen balance. Altogether, dietary pharmacological zinc and copper concentrations improve growth rates and mineral retention in nursery pigs. This improved performance may partially be explained by increased stomach ghrelin abundance and enhanced early feed intake in newly weaned pigs fed pharmacological concentrations of zinc and copper.

Blood Acylated Ghrelin Concentrations in Healthy Term Newborns: A Prospective Cohort Study

Objective

The effect of ghrelin, a growth hormone (GH) secretagogue on growth of neonates, has been studied in the past, but not fully clarified. We aimed to investigate the relationship between ghrelin and growth parameters at birth and at the age of three months in healthy term infants. Methodology. This was a prospective observational study carried out in a tertiary care hospital. Eighty-four infants born at gestational ages between 37 and 42 weeks and classified as term small for gestational age (SGA) and appropriate for gestational age (AGA) were included in the study. Estimation of acylated ghrelin (AG) concentrations was done in the cord blood at birth and in venous blood at the age of 3 months in all the infants. The correlation between AG concentrations and growth parameters at birth and at 3 months was studied.

Results

AG concentrations were significantly higher in SGA (236.16 ± 152.4 pg/ml) than AGA neonates (59.45 ± 20.95 pg/ml) at birth. Concentrations were observed to be negatively correlated with birth weight (r = −0.34, p value 0.03), birth length, and head circumference (r = −0.509 and -0.376, respectively) in SGA neonates. However, at 3 months, AG concentrations did not correlate with changes in anthropometric parameters in both the groups.

Conclusion

Cord acylated ghrelin concentrations are higher in SGA neonates, and the concentrations are inversely proportional to the birth weight. Hence, its role as a surrogate marker for intrauterine nutrition can be suggested. However, its concentrations do not correlate with anthropometric parameters in early postnatal growth, suggesting it may not have a direct role in postnatal growth.

A new understanding of GHSR1a--independent of ghrelin activation

Growth hormone secretagogue receptor 1a (GHSR1a), a member of the G protein-coupled receptor (GPCR) family, is a functional receptor of ghrelin. The expression levels and activities of GHSR1a are affected by various factors. In past years, it has been found that the ghrelin-GHSR1a system can perform biological functions such as anti-inflammation, anti-apoptosis, and anti-oxidative stress. In addition to mediating the effect of ghrelin, GHSR1a also has abnormally high constitutive activity; that is, it can still transmit intracellular signals without activation of the ghrelin ligand. This constitutive activity affects brain functions, growth and development of the body; therefore, it has profound impacts on neurodegenerative diseases and some other age-related diseases. In addition, GHSR1a can also form homodimers or heterodimers with other GPCRs, affecting the release of neurotransmitters, appetite regulation, cell proliferation and insulin release. Therefore, further understanding of the constitutive activities and dimerization of GHSR1a will enable us to better clarify the characteristics of GHSR1a and provide more therapeutic targets for drug development. Here, we focus on the roles of GHSR1a in various biological functions and provide a comprehensive summary of the current research on GHSR1a to provide broader therapeutic prospects for age-related disease treatment.

Circulating LEAP-2 is associated with puberty in girls

BACKGROUND/OBJECTIVES

Liver-expressed antimicrobial peptide 2 (LEAP-2) was recently identified as an endogenous non-competitive allosteric antagonist of the growth hormone secretagogue receptor 1a (GHSR1a). LEAP-2 blunts ghrelin-induced feeding and its plasma levels are modulated in response to nutritional status in humans. Despite the relevant role of ghrelin in childhood, puberty, and childhood obesity, the potential implication of LEAP-2 in these aspects remains totally unknown. We aimed to investigate the regulation of circulating plasma LEAP-2 in childhood and adolescent either lean or obese.

METHODS AND RESULTS

Plasma levels of LEAP-2 were analyzed in a cross-sectional study with lean and obese children and adolescents (n = 150). Circulating LEAP-2 levels were significantly higher in girls than in boys independently of whether they were obese or lean. In addition, LEAP-2 was significantly increased (p < 0.001) in pubertal than in prepubertal girls, while no changes were found in boys between both developmental stages. Moreover, in girls LEAP-2 was positively correlated with insulin, IGF-1, HOMA-IR and triglycerides and negatively with ghrelin. In boys, LEAP-2 was positively correlated with leptin and negatively with vitamin D levels.

CONCLUSION

This study reveals a sexual dimorphism in LEAP-2 levels in children and adolescents. These changes and the higher levels during puberty imply that LEAP-2 may contribute to some of the biological adaptations occurring during pubertal development in terms of food intake, energy balance, growth rate, and puberty onset. Future studies assessing LEAP-2 levels in longitudinal studies and its implications in growth rate, puberty onset, and reproductive hormones will help to understand the relevance of this hormone in this stage of life.

The influence of skeletal muscle on appetite regulation

INTRODUCTION

Fat-free mass, of which skeletal muscle is amajor component, correlates positively with energy intake at energy balance. This is due to the effects of metabolically active tissue on energy expenditure which in itself appears to signal to the brain adrive to eat to ensure cellular energy homeostasis. The mechanisms responsible for this drive to eat are unknown but are likely to be related to energy utilization. Here muscle imparts an indirect influence on hunger. The drive to eat is also enhanced after muscle loss secondary to intentional weight loss. The evidence suggests loss of both fat mass and skeletal muscle mass directly influences the trajectory and magnitude of weight regain highlighting their potential role in long-termappetite control. The mechanisms responsible for the potential direct drive to eat stemming from muscle loss are unknown.

AREAS COVERED

The literature pertaining to muscle and appetite at energy balance and after weight loss was examined. Aliterature search was conducted to identify studies related to appetite, muscle, exercise, and weight loss.

EXPERT OPINION

Understanding the mechanisms which link energy expenditure and muscle loss to hunger has the potential to positively impact both the prevention and the treatment of obesity.

Fermented soybean product (Cheonggukjang) improved some attributes of protein and growth hormone measurements in Sprague-Dawley rats

We hypothesized that the administration of Cheonggukjang (CKJ) would exert positive effects on factors implicated with growth in Sprague-Dawley (SD) rats. To test this hypothesis, we measured specific aspects of bone and organ growth in male SD rats that were treated for 6 weeks with 3 concentrations of CKJ. Although the CKJ extract contained high concentrations of flavonoids and phenolic compounds, no significant differences in body length, organ weights, or femur weight were detected between the CKJ- and vehicle-treated groups. However, thicknesses of the epiphyseal growth plate in the proximal femoral epiphysis and the compact bone in the linea aspera were broadest in the femur of the 2 CKJ-treated groups when compared with the vehicle-treated groups. Furthermore, the levels of growth hormone (GH) and calcium ion were higher in the sera of the high-concentration CKJ-treated groups, whereas the expression level of GH receptor was higher in muscle tissue of all CKJ-treated groups and in the liver tissue of the high-concentration CKJ-treated group. In the GH receptor downstream signaling pathway, the phosphorylation levels of Akt and Erk were expressed differently between liver and muscle tissues upon CKJ treatment. However, the phosphorylation level of STAT5 was very similar to the expression level of the GH receptor in all CKJ-treated groups. These results indicate that CKJ extract may increase the thickness of the epiphyseal growth plate and the compact bone of the femur, elevate GH secretion, and stimulate regulation of the GH receptor downstream signaling pathway in the liver and muscle tissues of SD rats.

The relationship between serum ghrelin and body composition with bone mineral density and QUS parameters in subjects with Rett syndrome

Several studies have reported that females with Rett's syndrome frequently have marked decreases in bone mineral density (BMD). However, the pathogenesis of impaired bone status in RTT girls remains controversial. This study aimed to investigate whether ghrelin, an orexigenic peptide secreted by the stomach, was associated with body composition parameters, bone mineral density and quantitative ultrasound (QUS) in girls with Rett's syndrome. In 123 Rett girls (13.6±8.2 years) and in 55 similar age range controls we evaluated ghrelin serum levels, 25OHD, quantitative ultrasound parameters at phalanxes by Bone Profiler-IGEA (amplitude dependent speed of sound: AD-SoS and bone transmission time: BTT), total body bone mineral density (BMD-WB) by Hologic QDR 4500. Whole body mineral content (BMC-WB), BMC-WB/height, fat mass (FM), fat percentage and lean mass (LM) were determined by using the same DXA device. We found that serum ghrelin levels were significantly higher in the Rett patients with respect to the control group (p<0.05). In Rett girls ghrelin serum levels were inversely correlated with both age (R(2)=0.17, p<0.001) and BMI (R(2)=0.14, p<0.001). Moreover, in Rett subjects the values of BMD-WB, BMC-WB, BMC-WB/height and QUS parameters were significantly lower than in control subjects. Fat mass and lean mass were lower in Rett subjects than in controls, but the difference reached the statistical significance only for lean mass. In Rett girls ghrelin serum levels were not predictors of bone status. Instead, we found that in Rett subjects, lean mass, age and 25OHD were significant independent predictors of BMC-WB/h, whereas both age and height were independent predictors of BMD-WB. Moreover, AD-SoS was predicted by age, fat percentage and height; while BTT was predicted only by height. In conclusion, our findings indicate that ghrelin levels were higher in Rett girls with respect to healthy controls, and negatively associated with both DXA and QUS parameters. However, in our study ghrelin was not found to be an independent predictor of bone mass, so supporting the hypothesis that ghrelin is elevated in Rett subjects in a compensatory manner.

The relationship of active ghrelin levels and intrauterine growth in preterm infants

OBJECTIVE

We examined the association of active ghrelin levels with birth weight, sex, and gestational age (GA) in small for GA (SGA) and appropriate for GA (AGA) preterm infants.

METHODS

Active ghrelin levels were measured by ELISA method during the first five postnatal days in 38 preterm SGA infants and 32 preterm AGA controls.

RESULTS

Active ghrelin levels were significantly higher in preterm SGA infants than in preterm AGA controls (P < 0.01). Active ghrelin levels in preterms with birth weight <1500 g were statistically higher than those over 1500 g. Active ghrelin levels in preterms ≤ 34 gestational weeks were similar to those over 34 weeks. A negative correlation was detected between active ghrelin levels and birth weight (r = -0.561, P < 0.0001) as well as GA (r = -0.449, P < 0.0001).

CONCLUSION

We found significantly higher active ghrelin levels in SGA preterms than those in AGA preterms and demonstrated a negative correlation between active ghrelin levels and birth weight in preterm infants. This was the first study showing a negative correlation between active ghrelin levels and birth weight in preterm infants.

Ghrelin in the fetal pancreas - a digital quantitation study

Ghrelin is a hormone produced by specialized neuroendocrine cells located in the fetal pancreas. In the adult, ghrelin has multiple effects, but in the fetus the role of ghrelin and the distribution of ghrelin-producing cells is not well documented. The aim of this study was to describe and quantitate the number of ghrelin positive cells in the pancreas during gestation. The material consisted of pancreatic tissue from 19 fetuses at different gestational ages. Immunohistochemical staining was performed, and the expression was quantitated using an automated digital image analysis system. The results showed ghrelin-producing cells as scattered single cells in ductular structures and acini throughout the gestation. From midgestation they were also found in the periphery of the islets as a rim of cells. A tendency towards a high ghrelin expression during early gestation and a stable expression from midgestation to term was observed. In conclusion, the effects of fetal ghrelin are not fully understood, but the varying distribution of ghrelin positive cells indicates different effects of ghrelin during development.

Developmental effects of ghrelin

Ghrelin is a pleiotropic hormone that was originally described as promoting feeding and stimulating growth hormone release in adults. A growing body of evidence suggests that ghrelin may also exert developmental and organizational effects during perinatal life. The perinatal actions of ghrelin include the regulation of early developmental events such as blastocyst development and perinatal growth. Moreover, alterations in perinatal ghrelin levels result in structural differences in various peripheral organs, such as the pancreas and gastrointestinal tract. Recent data have also suggested that ghrelin acts on appetite-related brain centers in early life. Together, these observations indicate that exposure to factors that alter how ghrelin impacts development may induce lasting effects on physiological regulation.

Ghrelin levels are reduced in Rett syndrome patients with eating difficulties

Most patients with Rett syndrome (RTT) have both gastrointestinal problems and somatic growth failure, including microcephaly. Ghrelin is a peptide hormone involved in growth hormone secretion, interdigestive motility, and feeding behavior. Plasma ghrelin assays have previously been described for other neurodevelopmental disorders. To examine the pathophysiology of RTT, we measured plasma levels of ghrelin in patients with RTT. A case-control study examining plasma levels of ghrelin, serum growth hormone, and insulin-like growth factor-1 (IGF-1) was performed on 27 patients with RTT and 53 controls. Plasma levels of total (T)- and octanoyl (O)-ghrelin were significantly lower in patients with RTT than in controls. Plasma levels of T-ghrelin correlated significantly with serum IGF-1 levels and head circumference. Significantly lower levels of plasma T-ghrelin and O-ghrelin were observed in RTT patients with eating difficulties, while lower levels of plasma T-ghrelin were observed in RTT patients with constipation, in comparison to patients without either of these symptoms. Alterations in plasma ghrelin levels may reflect various clinical symptoms and signs in RTT patients, including growth failure, acquired microcephalus, autonomic nerve dysfunction, and feeding difficulties. We describe the role of ghrelin in RTT and suggest this peptide as a novel biological marker in patients with RTT.

Ontogeny of ghrelin, obestatin, preproghrelin, and prohormone convertases in rat pancreas and stomach

The processing of preproghrelin in the stomach by prohormone convertase (PC) 1/3 produces ghrelin and possibly obestatin. In the neonate, the pancreas is also a major source of ghrelin. We compared the ontogeny of preproghrelin, ghrelin, obestatin, and PCs in the stomach and pancreas from rat embryos (day 21) and neonates (days 1, 6, 13, 21, and 28) by immunohistochemistry. In stomach, preproghrelin positive cells were present from embryonic day 21 and were in excess of ghrelin cells. The number of ghrelin positive cells progressively increased with age. When preproghrelin cells were immunoreactive for ghrelin, they were also immunoreactive for obestatin and PC1/3. In pancreas, we only found 0 to 2 preproghrelin positive cells per islet and each of these cells was also positive for ghrelin and obestatin. None of the ghrelin positive cells stained for insulin, but we observed ghrelin positive/glucagon negative and ghrelin positive/glucagon positive cells. Ghrelin positive cells contained PC1/3 or PC2. In summary, in stomach, an excess of preproghrelin positive cells compared with ghrelin/PC1/3 positive cells suggests that PC1/3 determines preproghrelin processing to ghrelin. In pancreas, the colocalization of PC1/3 or PC2 in ghrelin positive cells points to a role for both PCs in preproghrelin processing.

Postnatal weight and height growth velocities at different ages between birth and 5 y and body composition in adolescent boys and girls

BACKGROUND

Rapid weight gain in the first years of life is associated with adult obesity. Whether there are critical windows for this long-term effect is unclear.

OBJECTIVE

The objective was to study anthropometric measures in adolescence by sex according to weight and height growth velocities at different ages between birth and 5 y.

DESIGN

Anthropometric measures, including fat and fat-free mass by bipodal impedancemetry, were measured in 468 adolescents aged 8-17 y. We retrospectively collected early infancy data and individually estimated weight and height growth velocities in 69.4% of them using a mathematical model. Associations between birth variables, growth velocities, and anthropometric measures in adolescence were studied.

RESULTS

Weight growth velocity at 3 mo was associated with overweight (odds ratio for a 1-SD increase: 1.52; 95% CI: 1.04, 2.22), fat mass, and waist circumference in adolescence in both sexes and with fat-free mass in boys (r = 0.29, P < 0.001) but not in girls (r = -0.01, NS). Weight growth velocities after 2 y were associated with all anthropometric measures in adolescence, in both sexes. Between 6 mo and 2 y, weight growth velocities were significantly associated only with adolescent height in boys; in girls, associations with fat mass in adolescence were weaker.

CONCLUSION

Our results support the hypothesis of 2 critical windows in early childhood associated with the later risk of obesity: up to 6 mo and from 2 y onward. The study of the determinants of growth during these 2 periods is of major importance for the prevention of obesity in adolescence.

Ghrelin and acyl ghrelin in preterm infants and maternal blood: relationship with endocrine and anthropometric measures

OBJECTIVE

The objective of the present study was to examine the association of acylated and total ghrelin levels at birth in preterm infants with anthropometric features and with related hormones in infants and their mothers.

DESIGN

Prospective, descriptive study.

METHODS

In total 23 pregnant women and their 26 preterm infants were involved in the study (3 twin pregnancies; gestational age, 25-35 weeks). Maternal and umbilical vein blood samples were taken after the delivery. Serum acylated and total ghrelin, leptin, cortisol, insulin, GH, and glucose were determined.

RESULTS

The mean level of acylated ghrelin concentration was higher in the maternal than in the cord blood (P<0.01) and there was a significant correlation between the fetal and maternal acylated ghrelin levels (P<0.01). The total ghrelin concentration was higher in neonates than in mothers (P<0.01), but there was no correlation between them. The multivariate regression analysis for fetal acylated and maternal total ghrelin as dependent variables shows that the fetal acylated ghrelin has two independent predictors, the maternal acylated ghrelin (P<0.01) and the fetal cortisol (P<0.05), whereas the maternal total ghrelin has only one independent predictor, the maternal glucose (P<0.05).

CONCLUSIONS

These data provide the first evidence that umbilical cord acylated ghrelin concentrations are lower than in maternal blood and support the hypothesis that the acylation process in the fetus is partly affected by cortisol and the placenta may play a role in this process.

Ghrelin concentrations reflect body mass index rather than feeding status in obese girls

Ghrelin stimulates both appetite and secretion of growth hormone (GH). We hypothesized that fasting should increase ghrelin, thereby increasing GH concentrations in obesity. Eight obese girls underwent a 48-h fast, receiving 25% of calories for ideal body weight. Blood was obtained every 15 min for the last 24 h of the fast. Four months later, six obese girls had blood obtained in the fed state. Two additional obese and five lean girls had blood obtained in the fed state. Ghrelin was determined in 3-h pools. Mean ghrelin concentrations were 0.41 +/- 0.03 ng/mL for lean girls and 0.16 +/- 0.01 ng/mL in obese fed girls (p < 0.0001). Lean fed girls had diurnal variation of ghrelin whereas obese fed girls did not. Fasting neither increased ghrelin (0.18 +/- 0.01 ng/mL) nor restored diurnal variation. Ghrelin concentrations were related to the body mass index (BMI) SD score (SDS) (r = 0.45, p = 0.005). For the six obese girls who participated in both fasting and fed studies, change in mean ghrelin concentration between studies was related to change in BMI SDS but not fed or fasting state. Ghrelin concentrations are, thus, a function of BMI rather than feeding status in obese girls.

Circulating ghrelin levels in obese women: a possible association with hypertension

OBJECTIVE

The orexigenic hormone ghrelin induces weight gain by stimulating food intake. Ghrelin has been shown to modulate sympathetic activity, to exert vasodilative effects and to counterreact with leptin on both food intake and blood pressure. Of these two hormones, ghrelin levels are decreased in obesity, whereas leptin levels are increased. In this cross-sectional study, differences in serum ghrelin and leptin levels were examined in normotensive and hypertensive obese women.

MATERIAL AND METHODS

Sixty-one normotensive and hypertensive women were classified according to the body mass indices as follows: (a) 18 healthy subjects with BMI 21.5-27.5 kg/m(2); (b) 22 normotensive subjects with BMI 30-47 kg/m(2); (c) 21 hypertensive obese subjects (BMI 30-48 kg/m(2)) with systolic blood pressure > or =140 mmHg or diastolic blood pressure > or =90 mmHg. Anthropometric measurements including height, weight, BMI, waist and hip circumferences and blood pressure were recorded. The levels of ghrelin and leptin were determined in sera using the commercial ELISA kits.

RESULTS

In normotensive obese subjects, ghrelin levels were significantly lower than in controls (0.21+/-0.13 vs 0.60+/-0.3 ng/mL), whereas hypertensive obese women had elevated ghrelin levels (0.64+/-0.36 ng/mL). Ghrelin concentration was decreased despite the presence of hypertension in the patients who had BMIs above 35 kg/m(2). Leptin levels were significantly higher in both normotensive and hypertensive obese groups (19.54+/-11.19 and 21.61+/-12.7 ng/mL, respectively) than in controls (7.61+/-3.3 ng/mL), and were not affected by the presence of hypertension in obese subjects.

CONCLUSION

Ghrelin was positively associated with hypertension in obese women and this association was inversely influenced by the increase of BMI.

Ghrelin stimulates myocyte development

Ghrelin, a gastric peptide hormone, may regulate mesenchymal cell development. Here we show that ghrelin promotes myogenesis in vitro in the mouse myoblast cell line C2C12 cells. Cells expressing ghrelin demonstrated a significant increase in the differentiation of premyocytes into myocytes. The mean myogenic index in cells stably expressing ghrelin increased significantly relative to control cells (42 +/- 2% vs. 16 +/- 1%, p<0.05). Western blotting showed that expression of MHC protein was elevated in cells expressing ghrelin compared to control cells. MyoD expression increased after treatment of C2C12 cells with exogenous ghrelin (10(-7) M). The stimulatory effect of ghrelin on myogenesis was abolished by either replacement of the third amino acid serine with alanine or deletion of its first nine amino acids. This study demonstrated that ghrelin is a potent stimulator for myogenesis.

Ghrelin administration into tegmental areas stimulates locomotor activity and increases extracellular concentration of dopamine in the nucleus accumbens

Ghrelin stimulates appetite, increases food intake and causes adiposity by mechanisms that include direct actions on the brain. Previously, we showed that intracerebroventricular administration of ghrelin has stimulatory and dopamine-enhancing properties. These effects of ghrelin are mediated via central nicotine receptors, suggesting that ghrelin can activate the acetylcholine-dopamine reward link. This reward link consists of cholinergic input from the laterodorsal tegmental area (LDTg) to the mesolimbic dopamine system that originates in the ventral tegmental area (VTA) and projects to the nucleus accumbens. Given that growth hormone secretagogue receptors (GHSR-1A) are expressed in the VTA and LDTg, brain areas involved in reward, the present series of experiments were undertaken to examine the hypothesis that these regions may mediate the stimulatory and dopamine-enhancing effects of ghrelin, by means of locomotor activity and in vivo microdialysis in freely moving mice. We found that local administration of ghrelin into the VTA (1 microg in 1 microl) induced an increase in locomotor activity and in the extracellular concentration of accumbal dopamine. In addition, local administration of ghrelin into the LDTg (1 microg in 1 microl) caused a locomotor stimulation and an increase in the extracellular levels of accumbal dopamine. Taken together, this indicates that ghrelin might, via activation of GHSR-1A in the VTA and LDTg, stimulate the acetylcholine-dopamine reward link, implicating that ghrelin is a part of the neurochemical overlap between the reward systems and those that regulate energy balance.

Influence of hormones on osteogenic differentiation processes of mesenchymal stem cells

Bone development, regeneration and maintenance are governed by osteogenic differentiation processes from mesenchymal stem cells through to mature bone cells, which are directed by local growth and differentiation factors and modulated strongly by hormones. Mesenchymal stem cells develop from both mesoderm and neural crest and can give rise to development, regeneration and maintenance of mesenchymal tissues, such as bone, cartilage, muscle, tendons and discs. There are only limited data regarding the effects of hormones on early events, such as regulation of stemness and maintenance of the mesenchymal stem cell pool. Hormones, such as estrogens, vitamin D-hormone and parathyroid hormone, besides others, are important modulators of osteogenic differentiation processes and bone formation, starting off with fate decision and the development of osteogenic offspring from mesenchymal stem cells, which end up in osteoblasts and osteocytes. Hormones are involved in fetal bone development and regeneration and, in childhood, adolescence and adulthood, they control adaptive needs for growth and reproduction, nutrition, physical power and crisis adaptation. As in other tissues, aging in mesenchymal stem cells and their osteogenic offspring is accompanied by the accumulation of genomic and proteomic damage caused by oxidative burden and insufficient repair. Failsafe programs, such as apoptosis and cellular senescence avoid tumorigenesis. Hormones can influence the pace of such events, thus supporting the quality of tissue regeneration in aging organisms in vivo; for example, by delaying osteoporosis development. The potential for hormones in systemic therapeutic strategies is well appreciated and some concepts are approved for clinical use already. Their potential for cell-based therapeutic strategies for tissue regeneration is probably underestimated and could enhance the quality of tissue-engineering constructs for transplantation and the concept of in situ-guided tissue regeneration.

Relationship between ghrelin and anthropometrical, body composition parameters and testosterone levels in boys at different stages of puberty

The aim of this study was to investigate the relationships between fasting serum ghrelin concentration, anthropometrical and body composition data in boys at different pubertal stages. Sixty healthy non-obese Estonian schoolboys (10 to 18 yr) were divided into 3 groups based on Tanner classification--group I was prepubertal, group II included stages 2 and 3, and group III stages 4 and 5. Additionally, we analyzed subjects as a total group. Fasting ghrelin, leptin, testosterone, insulin and glucose were collected between 08:00 and 10:00 h. Body fat % and lean body mass (LBM) were determined by dual-energy X-ray absorptiometry. Fasting ghrelin decreased, while leptin and insulin did not change and testosterone increased during puberty. There was a negative correlation between serum ghrelin and testosterone concentrations in group II (r=-0.51, p<0.05) and in the total group (r=-0.59, p<0.001). Ghrelin was also related to body height, body mass and LBM in group II and total group also with body mass index in total group. Stepwise multiple regression analysis showed that body height from auxological, LBM from body composition and testosterone from biochemical data explained 38.1, 41.7 and 33.7% of the ghrelin variance in the total group, respectively. In conclusion, body height, LBM and serum testosterone are the major determinants of serum ghrelin among parameters studied. Negative correlation between serum ghrelin and testosterone concentrations indicates that ghrelin may also have a role in male pubertal development.

Obestatin, acylated and total ghrelin concentrations in the perinatal rat pancreas

BACKGROUND

Ghrelin and obestatin are encoded by the preproghrelin gene and originate from posttranslational processing of the preproghrelin peptide. The fetal rat pancreas contains acylated and desacylated ghrelin peptides, as well as growth hormone secretagogue receptor -1a mRNA. Acylated ghrelin inhibits insulin secretion. We investigated the plasma and tissue ontogeny of ghrelin and obestatin in the rat.

METHODS

We measured obestatin and acylated and total ghrelin concentrations in plasma, pancreas and stomach from rat fetuses (F20) and neonates at postnatal day (PN) 1, 6, 12 and 21).

RESULTS

Overall, obestatin concentrations were markedly lower than total ghrelin concentrations. In plasma, total ghrelin concentrations decreased abruptly after birth (p < 0.05), contrasting with a 3 times increase in the concentration of acylated ghrelin between F20 and PN1 (p < 0.05). In pancreas, total ghrelin and obestatin concentrations decreased progressively from PN1 to PN21 but acylated ghrelin concentrations increased 6-7 times from F20 (18 [6] pg/ml) to PN6 (122 [59] pg/ml). The percent of acylated ghrelin increased from 1.8 (0.6) at F20 to 39.7 (13.0) % of total ghrelin immunoreactivity at PN12 (p < 0.05). There were significant positive correlations between postnatal obestatin, acylated or total ghrelin and insulin concentrations in the pancreas (all p < 0.02, r(2) > 0.21) and between postnatal total ghrelin and obestatin (in pancreas, r(2) = 0.37) or acylated ghrelin (in stomach, r(2) = 0.27) (p < 0.001).

CONCLUSION

Ghrelin and obestatin are present in the perinatal pancreas where they could potentially affect insulin secretion.

The regulation of appetite

The worsening global obesity epidemic, particularly the increase in childhood obesity, has prompted research into the mechanisms of appetite regulation. Complex pathways modulate energy balance, involving appetite centres in the hypothalamus and brain stem, and hormonal signals of energy status released by the gut and by the periphery. Better understanding of appetite regulation improves understanding of the aetiology of obesity. Manipulation of this homoeostatic system offers potentially useful treatments for obesity.