Acylated ghrelin levels in pre-pubertal obese children at diagnosis and after weight reduction: effect of oral glucose ingestion

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.

Effect of oral glucose administration on rebound growth hormone release in normal and obese women: the role of adiposity, insulin sensitivity and ghrelin

Context

Metabolic substrates and nutritional status play a major role in growth hormone (GH) secretion. Uncovering the mechanisms involved in GH secretion following oral glucose (OG) administration in normal and obese patients is a pending issue.

Objective

The aim of this study was to investigate GH after OG in relation with adiposity, insulin secretion and action, and ghrelin secretion in obese and healthy women, to further elucidate the mechanism of GH secretion after OG and the altered GH secretion in obesity.

Participants and Methods

We included 64 healthy and obese women. After an overnight fast, 75 g of OG were administered; GH, glucose, insulin and ghrelin were obtained during 300 minutes. Insulin secretion and action indices and the area under the curve (AUC) were calculated for GH, glucose, insulin and ghrelin. Univariate and multivariate linear regression analyses were employed.

Results

The AUC of GH (μg/L•min) was lower in obese (249.8±41.8) than in healthy women (490.4±74.6), P=0.001. The AUC of total ghrelin (pg/mL•min) was lower in obese (240995.5±11094.2) than in healthy women (340797.5±37757.5), P=0.042. There were significant correlations between GH secretion and the different adiposity, insulin secretion and action, and ghrelin secretion indices. After multivariate analysis only ghrelin AUC remained a significant predictor for fasting and peak GH.

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.

Effect of obesity on linear growth

PURPOSE OF REVIEW

To describe our current understanding of the mechanisms involved in the regulation of linear growth in childhood obesity.

RECENT FINDINGS

The developmental origins hypothesis has focused on low birth weight individuals with subsequent obesity, identifying a cascade of neuroendocrine regulatory factors involved in the progressive increase in body fat and metabolic risk. Yet, tall stature is the common clinical outcome of childhood obesity. Recent data have expanded our understanding of environmental influences on developing systems. Here, we review the elements of neuroendocrine systems contributing to the integration of metabolic controls involved in growth regulation in the obese child with particular emphasis on growth hormone, ghrelin, insulin-like growth factors and insulin.

SUMMARY

Growth patterns of obesity during childhood are well described, documenting increased linear growth in early childhood associated with accelerated pubertal maturation resulting in normal adult height. Despite recent data suggesting that ghrelin and the growth hormone secretagogue receptor, as well as the insulin-like growth factors, their binding proteins and insulin have potential to be mediators of nutrient exposure and linear growth, it remains to be determined how these systems interrelate and determine growth. This is an area of ongoing investigation.

[Paediatric obesities: from childhood to adolescence]

Obesity, as in every western country, is currently the most prevalent chronic disease in childhood in Spain. This has led to obesity being one of the most common consultations in general paediatrics and, particularly, in paediatric endocrinology. Furthermore, obesity associated comorbidities are increasing in prevalence in children and adolescents. It is widely accepted that this increase in the prevalence of obesity is derived from an imbalance between energy intake and expenditure, associated to the lifestyle in western countries. However, there is increasing evidence of the role of individual and familial genetic background in the risk of developing obesity. The pathophysiological basis of the mechanisms responsible for the control of appetite and energy expenditure are being discovered on the basis of the increasing known cases of human monogenic, syndromic and endocrine obesity. Thus it is no longer appropriate to talk about obesity but rather about «obesities», as their pathophysiological bases differ and they require different diagnostic and management approaches. In 2011, the paediatrician must be aware of this issue and focus the clinical history and physical examination towards these specific clinical sign and symptoms, to better manage the available diagnostic and therapeutic resources when faced with a child with obesity.