Effects of the IGF-I/IGFBP-3 complex on GH and ghrelin nocturnal concentrations in low birth weight children

The impact of growth hormone replacement therapy on adipokines, but not upon ghrelin

BACKGROUND

Besides growth acceleration, growth hormone (GH) therapy of GH deficient (GHD) children improves body composition by decreasing body fat. This effect is due to GH interaction with lipid and carbohydrate metabolism, possibly also mediated by adipokines secreted by adipose tissue, and ghrelin. This study aimed to assess the impact of one-year GH replacement therapy on the metabolic profile, adipokines, and acylated/unacylated ghrelin of prepubertal children with GHD.

METHODS

Prospective observational study of 42 non-obese, prepubertal children with GHD followed up for twelve months. Mean lipid, carbohydrate, adipokine profiles, acylated/unacylated ghrelin, and body composition data before therapy onset were compared with measurements obtained after 6 and 12 months of GH therapy.

RESULTS

Total body fat content and body fat percentage decreased significantly, while the lipid profile improved over the study period in the 42 GHD children with a mean age of 9.2±2.6 years. The levels of leptin and unacylated ghrelin decreased significantly, whereas adiponectin and acylated ghrelin values increased after GH therapy. In regression analysis models, GH treatment (reflected by increased absolute values or standard deviations of IGF1) influences the variation of leptin and adiponectin, but not ghrelin, independently of body composition - lean or fat mass.

CONCLUSIONS

GH replacement therapy improves body composition, lipid, and adipokine profile in GHD children. Also, GH replacement therapy directly impacts leptin and adiponectin concentrations, independently of body composition. Further research is needed to identify the molecular mechanisms and metabolic pathways by which the GH/IGF1 axis influences adipokines secretion.

DHEAS and Human Development: An Evolutionary Perspective

Adrenarche, the post-natal rise of DHEA and DHEAS, is unique to humans and the African Apes. Recent findings have linked DHEA in humans to the development of the left dorsolateral prefrontal cortex (LDPFC) between the ages of 4-8 years and the right temporoparietal junction (rTPJ) from 7 to 12 years of age. Given the association of the LDLPFC with the 5-to-8 transition and the rTPJ with mentalizing during middle childhood DHEA may have played an important role in the evolution of the human brain. I argue that increasing protein in the diet over the course of human evolution not only increased levels of DHEAS, but linked meat consumption with brain development during the important 5- to-8 transition. Consumption of animal protein has been associated with IGF-1, implicated in the development of the adrenal zona reticularis (ZR), the site of DHEAS production. In humans and chimps, the zona reticularis emerges at 3-4 years, along with the onset of DHEA/S production. For chimps this coincides with weaning and peak synaptogenesis. Among humans, weaning is completed around 2 ½ years, while synaptogenesis peaks around 5 years. Thus, in chimpanzees, early cortical maturation is tied to the mother; in humans it may be associated with post-weaning provisioning by others. I call for further research on adrenarche among the African apes as a critical comparison to humans. I also suggest research in subsistence populations to establish the role of nutrition and energetics in the timing of adrenarche and the onset of middle childhood.

First-in-man study with a novel PEGylated recombinant human insulin-like growth factor-I

OBJECTIVE

This study is a first time assessment of safety and tolerability, pharmacokinetics, and pharmacodynamics of RO5046013 in human, in comparison with unmodified rhIGF-I.

DESIGN

The study was conducted as a single-center, randomized, double-blinded, placebo-controlled, single ascending dose, parallel group study in a clinical research unit in France. A total of 62 healthy volunteers participated in this clinical trial. RO5046013 was given as single subcutaneous injection, or as intravenous infusion over 48h, at ascending dose levels. The active comparator rhIGF-I was administered at 50μg/kg subcutaneously twice daily for 4days. Safety and tolerability, pharmacokinetics, and pharmacodynamics of RO5046013 were evaluated.

RESULTS

PEGylation resulted in long exposure to RO5046013 with a half-life of 140-200h. Exposure to RO5046013 increased approximately dose proportionally. RO5046013 was safe and well tolerated at all doses, injection site erythema after SC administration was the most frequent observed AE. No hypoglycemia occurred. Growth hormone (GH) secretion was almost completely suppressed with rhIGF-I administration, whereas RO5046013 caused only a modest decrease in GH at the highest dose given IV.

CONCLUSIONS

PEGylation of IGF-I strongly enhances half-life, reduces the negative GH feedback and hypoglycemia potential, and therefore offers a valuable alternative to rhIGF-I in treatment of relevant diseases.

Ghrelin - Physiological Functions and Regulation

Ghrelin is an orexigenic peptide predominantly secreted from the stomach and stimulates appetite and growth hormone (GH) release. Studies have provided evidence that ghrelin exercises a wide range of functions, including regulation of food intake and energy metabolism, modulation of cardiovascular function, stimulation of osteoblast proliferation and bone formation and stimulation of neurogenesis and myogenesis. In the gastrointestinal system, ghrelin affects multiple functions, including secretion of gastric acid, gastric motility and pancreatic protein output. Most of these functions have been attributed to the actions of acylated ghrelin. The balance among its secretion rate, degradation rate and clearance rate determines the circulating level of ghrelin. This review explains what ghrelin is, its physiological functions and the factors that influence its level.

Effects of prenatal ethanol exposure on postnatal growth and the insulin-like growth factor axis

AIMS

To study the effect of in-utero alcohol exposure on the insulin-like growth factor axis (IGF) and leptin during infancy and childhood, considering that exposed children may exhibit pre- and postnatal growth retardation.

METHODS

We prospectively identified heavily drinking pregnant women who consumed on average 4 or more drinks of ethanol per day (≥ 48 g/day) and assessed growth in 69 of their offspring and an unexposed control group of 83 children, measuring serum IGF-I (radioimmunoassay), IGF-II (immunoradiometric assay, IRMA), insulin-like growth factor-binding protein 3 (IGFBP-3) (IRMA) and leptin (IRMA) at 1 month and 1, 2, 3, 4, and 5 years of age.

RESULTS

IGF-II levels increased with age in both groups, but the rate of increase was significantly higher in exposed children, and levels were significantly higher in ethanol-exposed children at 3, 4, and 5 years of age. In exposed children, IGF-I levels were higher at 3 and 4 years and leptin levels were significantly lower at 1 and 2 years. Exposed subjects showed a much lower correlation between IGF-I and growth parameters than unexposed subjects.

CONCLUSION

Exposure to ethanol during pregnancy increases IGF-I and IGF-II and decreases leptin during early childhood. The increase in serum IGF-II concentrations in ethanol-exposed children suggests that this hormone should be explored as a potential marker for prenatal alcohol exposure.

Changes in IGF-I, IGFBP-3 and ghrelin levels after adenotonsillectomy in children with sleep disordered breathing

OBJECTIVE

The aim of this study was to determine the changes in insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3) and ghrelin levels following adenotonsillectomy (T&A) in children with sleep disordered breathing (SDB).

METHODS

Forty children (mean age 4.85+/-2.15 years) clinically diagnosed with adenotonsillar hypertrophy (ATH) related SDB were enrolled. All children underwent T&A. Serum levels of IGF-I, IGFBP-3 and ghrelin were measured before and 6 months after T&A.

RESULTS

Serum levels of IGF-I and IGFBP-3 were significantly higher after T&A (p<0.001). Serum ghrelin levels showed a significant decrease after T&A (p<0.001).

CONCLUSION

Children with ATH related SDB who underwent T&A showed significant increases in IGF-I and IGFBP-3 levels indicating an increase in diurnal growth hormone secretion as well as a significant decrese in ghrelin levels indicating an increased oral food intake in the postoperative period.

Ghrelin fluctuation, what determines its production?

Ghrelin, a 28 amino acid gut brain peptide, acts as an endogenous ligand for its receptor, the growth hormone secretagogue receptor, to exercise a variety of functions ranging from stimulation of growth hormone secretion, regulation of appetite and energy metabolism, and cell protection to modulation of inflammation. This review summarizes the advance in the regulation of ghrelin expression and secretion. We introduce the structure of ghrelin promoter, the processing and modification of ghrelin precursor, and the regulation mechanism in these processes. Then we discuss factors found to be important in the regulation of ghrelin production, including nutrients, hormones, and autonomic nervous system. Finally, we outline the alteration in the level of ghrelin in certain physiological and pathological status.

Ghrelin in small-for-gestational age (SGA) newborn babies: a cross-sectional study

BACKGROUND

Small-for-gestational newborn babies may have long-term metabolic consequences. Among the main hormones possibly involved in foetal growth regulation are the IGFs, IGFBPs and the recently described ghrelin.

OBJECTIVE

To examine the levels of desacyl-ghrelin, IGF-1, IGFBP-1 and IGFBP-3 in children Small-for-gestational age (SGA) and children adequate-for-gestational age (AGA).

DESIGN

This was a cross-sectional and comparative study.

SUBJECTS

We included 40 children SGA and 40 children AGA.

MEASUREMENTS

Blood sample was taken a week after birth and measuring hormonal levels were done by ELISA.

RESULTS

SGA babies had lower IGF-1, IGFBP-3 and leptin levels, but higher ghrelin and IGFBP-1 levels. Birth weight was associated independently with ghrelin and IGFBP-1 (negatively) and IGFBP-3 (positively). Ghrelin circulating levels were associated negative and independently with IGFBP-3 and triglycerides in the mother.

CONCLUSIONS

We interpreted these findings to indicate that diminished body weight in newborns induce different adaptive signals, some of them mediated by IGF-1/IGFBP-3, ghrelin or by IGFBP-1. This regulation is congruent with the proposed role of ghrelin to adaptation to under-nutrition favouring lipid accumulation. CONCyTEG grant number 05-16-K117-028.

Mecasermin rinfabate: rhIGF-I/rhIGFBP-3 complex: iPLEX

BACKGROUND

Mecasermin rinfabate (iPLEX), comprising rhIGF-I complexed to rhIGFBP-3, was developed in an attempt to prolong the half-life of IGF-I and potentially reduce side effects. It is administered as a once-daily subcutaneous injection. Treatment with rhIGF-I has been explored in a number of growth and endocrine disorders.

OBJECTIVE

To review the published literature regarding the pharmacokinetics, safety profile and clinical efficacy of Mecasermin rinfabate.

METHODS

A comprehensive search via the NCBI PubMed portal was performed using the search terms rhIGF-I/rhIGFBP-3 complex, iPLEX and Somatokine.

RESULTS

The effects of Mecasermin rinfabate have been explored in a number of clinical situations including diabetes, severe insulin resistance, osteopaenia, burns and growth hormone insensitivity syndrome, with outcomes similar to those of rhIGF-I alone.

CONCLUSIONS

The biological effects of Mecasermin rinfabate are largely similar to those previously reported with rhIGF-I. There are little published data pertaining to pharmacokinetic properties in human subjects, and the side effect profile appears similar to that of rhIGF-I alone.

Obesity: the hormonal milieu

PURPOSE OF REVIEW

Obesity has reached epidemic proportions throughout the world and poses significant health and economic burdens to both developed and developing societies. Most recent data from the NHANES study (2003-2004) report that 17.1% of US children are overweight and 32.2% of adults are obese, a significant increase compared with data obtained only 6 years earlier.

RECENT FINDINGS

The neurohormonal control of appetite, body composition, and glucose homeostasis is mediated by hormones secreted from adipose tissue, endocrine glands, and enteroendocrine cells, which converge at the vagus nerve, brainstem and hypothalamus to modulate complex interactions of neurotransmitters and central appetite-regulating peptides. These hormonal signals are tightly regulated to maintain body weight/adiposity within a narrow, individually defined range that may be further impacted by variables such as ingested calories, meal composition, and lifestyle.

SUMMARY

Clinical manifestations of obesity, the metabolic syndrome and impaired glucose tolerance reflect biochemical alterations in a complex hormonal milieu. Elucidation of these hormonal perturbations in obese patients has already provided novel pharmacologic treatments to improve weight management and address the metabolic sequelae of obesity. The remarkable redundancy of these hormones, however, and their interactions make a monopharmaceutical approach unlikely to be successful.

The role of ghrelin in the energy homeostasis of elderly people: a population-based study

OBJECTIVE

Ghrelin is a hormone secreted mainly in the stomach which stimulates appetite and food intake. Endocrine factors are among the causes of anorexia in elderly people. The main objective of the present study was to examine the effect of age on ghrelin levels in non-institutionalized elderly people.

DESIGN AND SETTING

Observational, cross-sectional, population-based study.

PARTICIPANTS

A random sample of men aged 70 yr or older was taken from the municipal census.

MEASUREMENTS

All participants underwent a physical examination which measured weight and height, grip strength, functional capacity (according to the Barthel Index) and nutritional status (according to the short form of the Mini Nutritional Assessment). Blood was taken for basic biochemical analysis, determination of somatotropic, corticotropic, and gonadotropic hormones, and for measurement of ghrelin and cholecystokinin.

RESULTS

152 men with a mean (SD) age of 76.7 (5.4) yr were recruited. Mean ghrelin levels were 1143 (401) pg/ml. A weak negative correlation was found between ghrelin levels and age (r=-0.16, p=0.057). Multiple linear regression analysis showed a significant and independent effect of age (beta=-12.1, p=0.049), body mass index (BMI) (beta=-22.0, p=0.021), and creatinine levels (beta=407.7, p=0.002) on ghrelin. No correlations with age and BMI were found for cholecystokinin.

CONCLUSIONS

There is a slight decrease in ghrelin levels with age in older men aged 70 yr or more, although the clinical relevance of this finding remains unclear.