Serum resistin concentrations in growth hormone-deficient children during growth hormone replacement therapy

The "Adipo-Cerebral" Dialogue in Childhood Obesity: Focus on Growth and Puberty. Physiopathological and Nutritional Aspects

Overweight and obesity in children and adolescents are overwhelming problems in western countries. Adipocytes, far from being only fat deposits, are capable of endocrine functions, and the endocrine activity of adipose tissue, resumable in adipokines production, seems to be a key modulator of central nervous system function, suggesting the existence of an “adipo-cerebral axis.” This connection exerts a key role in children growth and puberty development, and it is exemplified by the leptin–kisspeptin interaction. The aim of this review was to describe recent advances in the knowledge of adipose tissue endocrine functions and their relations with nutrition and growth. The peculiarities of major adipokines are briefly summarized in the first paragraph; leptin and its interaction with kisspeptin are focused on in the second paragraph; the third paragraph deals with the regulation of the GH-IGF axis, with a special focus on the model represented by growth hormone deficiency (GHD); finally, old and new nutritional aspects are described in the last paragraph.

Comparison between euglycemic hyperinsulinemic clamp and surrogate indices of insulin sensitivity in children with growth hormone deficiency

OBJECTIVE

Data about the impact of growth hormone treatment (GHT) on insulin sensitivity in children are quite controversial, due to the different surrogate indices that have been used.

DESIGN

We evaluated insulin sensitivity through the euglycemic hyperinsulinemic clamp, considered the gold standard technique, in 23 children affected by growth hormone deficiency (GHD) at baseline and after 12months of GHT and in 12 controls with short stature at baseline, and we compared the clamp-derived index (M-value) with the most commonly used surrogate index of insulin sensitivity, as ISI Matsuda, and with circulating plasma markers of insulin sensitivity, as adiponectin and resistin levels.

RESULTS

At baseline, no significant difference in all metabolic parameters between GHD children and control subjects was found. After 12months of GHT, GHD children showed a significant increase in fasting insulin (p<0.001) and resistin (p=0.028) and a decrease in ISI Matsuda (p<0.001) and M-value (p<0.001), without significant change in fasting glucose, HbA1c and adiponectin. In GHD children, M-value showed a significant but weak correlation with ISI Matsuda (rho 0.418, p=0.047) at baseline, while no correlation with other parameters was found. After 12months of GHT, M-value did not show any significant correlation with any other metabolic parameter analyzed.

CONCLUSIONS

This study highlights the limit of the evaluation of insulin sensitivity performed through surrogate indices or circulating markers, which may lead to controversial data and do not correlate with the gold standard technique to evaluate insulin sensitivity.

Glucose Metabolism in Children With Growth Hormone Deficiency

BACKGROUND

The growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis has a fundamental impact on glucose metabolism. Therefore, both untreated GH deficiency (GHD) and GH treatment (GHT) may be associated with some metabolic alterations, although the abnormalities of glucose metabolism have been investigated by relatively few studies as main outcomes.

AIM

The present review summarizes the available data on glucose metabolism in children with GHD, providing an overview of the current state of the art in order to better clarify the real metabolic impact of GHD and GHT.

METHODS

Among all the existing studies, we evaluated all original studies that fulfilled our criteria for analysis reporting parameters of glucose metabolism as the primary or secondary objective.

RESULTS

The reported impact of GHD per se on glucose metabolism is quite homogeneous, with the majority of studies reporting no significant difference in metabolic parameters between GHD children and controls. Conversely, GHT proves to be more frequently associated with a subtle form of insulin resistance, while both fasting glucose and HbA1c levels remain almost always within the normal range.

CONCLUSION

The different methods to study glucose metabolism, the heterogeneity of the populations evaluated, the different doses of GH used together with the variable duration of follow-up may be responsible for discrepancy in the results. Long-term longitudinal studies having glucose homeostasis as their primary outcome are still needed in order better to clarify the real metabolic impact of GHD and GHT in children.

Resistin, visfatin, leptin and omentin are differently related to hormonal and metabolic parameters in growth hormone-deficient children

PURPOSE

The effect of growth hormone (GH) on adipose tissue and the role of adipokines in modulating metabolism are documented, but with discordant data. Our aim was to evaluate the impact of GH treatment on a series of selected adipokines known to have a metabolic role and poorly investigated in this setting.

METHODS

This is a prospective study. Thirty-one prepubertal children (25 M, 6 F; aged 8.5 ± 1.6 years) with isolated GH deficiency treated with GH for at least 12 months and 30 matched controls were evaluated. Auxological and metabolic parameters, insulin sensitivity indexes, leptin, soluble leptin receptor, adiponectin, visfatin, resistin, omentin, adipocyte fatty acid-binding protein and retinol-binding protein-4 were evaluated before and after 12 months of treatment.

RESULTS

At baseline, no significant difference in metabolic parameters was found between GHD children and controls, except for higher LDL cholesterol (p = 0.004) in the first group. At multivariate analysis, LDL cholesterol was independently associated with resistin (B 0.531; p = 0.002), while IGF-I was the only variable independently associated with visfatin (B 0.688; p < 0.001). After 12 months, a significant increase in fasting insulin (p = 0.008), Homa-IR (p = 0.007) and visfatin (p < 0.001) was found, with a concomitant decrease in LDL cholesterol (p = 0.015), QUICKI (p = 0.001), ISI Matsuda (p = 0.006), leptin (p = 0.015) and omentin (p = 0.003)]. At multivariate analysis, BMI was the only variable independently associated with leptin (B 0.485; p = 0.040).

CONCLUSIONS

GH treatment modifies adipokine secretion and the perturbation of some adipokine levels could contribute to the clinical and metabolic changes observed during the follow-up.

Isolated growth hormone deficiency (GHD) in childhood and adolescence: recent advances

The diagnosis of GH deficiency (GHD) in childhood is a multistep process involving clinical history, examination with detailed auxology, biochemical testing, and pituitary imaging, with an increasing contribution from genetics in patients with congenital GHD. Our increasing understanding of the factors involved in the development of somatotropes and the dynamic function of the somatotrope network may explain, at least in part, the development and progression of childhood GHD in different age groups. With respect to the genetic etiology of isolated GHD (IGHD), mutations in known genes such as those encoding GH (GH1), GHRH receptor (GHRHR), or transcription factors involved in pituitary development, are identified in a relatively small percentage of patients suggesting the involvement of other, yet unidentified, factors. Genome-wide association studies point toward an increasing number of genes involved in the control of growth, but their role in the etiology of IGHD remains unknown. Despite the many years of research in the area of GHD, there are still controversies on the etiology, diagnosis, and management of IGHD in children. Recent data suggest that childhood IGHD may have a wider impact on the health and neurodevelopment of children, but it is yet unknown to what extent treatment with recombinant human GH can reverse this effect. Finally, the safety of recombinant human GH is currently the subject of much debate and research, and it is clear that long-term controlled studies are needed to clarify the consequences of childhood IGHD and the long-term safety of its treatment.

Resistin in dairy cows: plasma concentrations during early lactation, expression and potential role in adipose tissue

Resistin is an adipokine that has been implicated in energy metabolism regulation in rodents but has been little studied in dairy cows. We determined plasma resistin concentrations in early lactation in dairy cows and investigated the levels of resistin mRNA and protein in adipose tissue and the phosphorylation of several components of insulin signaling pathways one week post partum (1 WPP) and at five months of gestation (5 MG). We detected resistin in mature bovine adipocytes and investigated the effect of recombinant bovine resistin on lipolysis in bovine adipose tissue explants. ELISA showed that plasma resistin concentration was low before calving, subsequently increasing and reaching a peak at 1 WPP, decreasing steadily thereafter to reach pre-calving levels at 6 WPP. Plasma resistin concentration was significantly positively correlated with plasma non esterified fatty acid (NEFA) levels and negatively with milk yield, dry matter intake and energy balance between WPP1 to WPP22. We showed, by quantitative RT-PCR and western blotting, that resistin mRNA and protein levels in adipose tissue were higher at WPP1 than at 5 MG. The level of phosphorylation of several early and downstream insulin signaling components (IRβ, IRS-1, IRS-2, Akt, MAPK ERK1/2, P70S6K and S6) in adipose tissue was also lower at 1 WPP than at 5 MG. Finally, we showed that recombinant bovine resistin increased the release of glycerol and mRNA levels for ATGL (adipose triglyceride lipase) and HSL (hormone-sensitive lipase) in adipose tissue explants. Overall, resistin levels were high in the plasma and adipose tissue and were positively correlated with NEFA levels after calving. Resistin is expressed in bovine mature adipocytes and promotes lipid mobilization in adipose explants in vitro.

Serum resistin and insulin-like growth factor-1 levels in patients with hypothyroidism and hyperthyroidism

Introduction. The aim of this study was to evaluate the serum levels of resistin and insulin-like growth factor-1 (IGF-1) and and also the potential relationship between thyroid function and levels of resistin and IGF-1 in hypothyroid and hyperthyroid patients. Methods. Fifteen cases of hypothyroid (HT), 16 of subclinically hypothyroid (SCHT), 15 of hyperthyroid (HrT), 15 of subclinically hyperthyroid (SCHrT), and 17 healthy individuals have been included in the study. Serum resistin levels were measured using enzyme-linked immunosorbent assay and IGF-1 and thyroid stimulating hormone (TSH) levels by chemiluminescence method. Results. Resistin levels in total HT group were significantly higher than in controls (12.66 ± 6.04 and 8.45 ± 2.90 ng/mL, resp.). In SCHrT subgroup resistin levels were significantly higher than those of controls (14.88 ± 7.73 and 8.45 ± 2.90 ng/mL, resp.). IGF-1 levels were significantly lower in total HT than in total HrT and control groups (117.22 ± 52.03, 155.17 ± 51.67, and 184.00 ± 49.73 ng/mL, resp.). Furthermore IGF-1 levels in HT subgroup were significantly lower compared to controls (123.70 ± 44.03 and 184 ± 49.73 ng/mL, resp.). In SCHT subgroup IGF-1 levels were significantly lower than those of control and SCHrT groups (111.11 ± 59.35, 184.00 ± 49.73, and 166.60 ± 47.87 ng/mL, resp.). There were significant correlations between IGF-1 and TSH in HT subgroup and between resistin and TSH in total HrT group. Conclusion. It was concluded that increased resistin levels are directly related to thyroid dysfunction, and GH/IGF-1 axis is influenced in clinically or subclinically hypothyroidism patients.

Effect of recombinant growth hormone on leptin, adiponectin, resistin, interleukin-6, tumor necrosis factor-α and ghrelin levels in growth hormone-deficient children

BACKGROUND

Treatment with GH promotes linear growth and decreases body fat in patients with isolated GH deficiency (GHD). However, few studies have analyzed how GH replacement modifies ghrelin levels and the adipokine profile and the relationship of these modifications with the metabolic changes.

AIMS

To analyze the eventual differences between serum levels of leptin, leptin soluble receptor (sOBR), resistin, adiponectin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), total (TG) and acylated ghrelin (AG) and lipid and glycemic profiles in children with GHD, as well as to determine the effect of GH replacement on these parameters during the first year of therapy.

SUBJECTS AND METHODS

Thirty pre-pubertal (Tanner stage I) GHD children and 30 matched controls were enrolled. Children with GHD were studied before and after 6 and 12 months of GH treatment. Weight, height, BMI, fasting glucose, insulin, lipid profile and serum levels of adipokines and ghrelin were studied at every visit. Adi - pokines, insulin and ghrelin levels were determined by using commercial radio- and enzymoimmunoassays.

RESULTS

At baseline children with GHD had significantly higher sOBR (p<0.01) and adiponectin (p<0.01) levels than controls. Treatment with GH resulted in a decline in leptin (p<0.05) and TG (p<0.001) levels, an increase of homeostasis model assessment index and restored IGF-I levels (p<0.001).

CONCLUSIONS

These data indicate that GH replacement has a negative effect on leptin levels and may also produce a slight unfavorable effect on carbohydrate metabolism. In addition, the changes observed in the adipokine profile appear to be independent of body mass index.

Biological effects of growth hormone on carbohydrate and lipid metabolism

This review will summarize the metabolic effects of growth hormone (GH) on the adipose tissue, liver, and skeletal muscle with focus on lipid and carbohydrate metabolism. The metabolic effects of GH predominantly involve the stimulation of lipolysis in the adipose tissue resulting in an increased flux of free fatty acids (FFAs) into the circulation. In the muscle and liver, GH stimulates triglyceride (TG) uptake, by enhancing lipoprotein lipase (LPL) expression, and its subsequent storage. The effects of GH on carbohydrate metabolism are more complicated and may be mediated indirectly via the antagonism of insulin action. Furthermore, GH has a net anabolic effect on protein metabolism although the molecular mechanisms of its actions are not completely understood. The major questions that still remain to be answered are (i) What are the molecular mechanisms by which GH regulates substrate metabolism? (ii) Does GH affect substrate metabolism directly or indirectly via IGF-1 or antagonism of insulin action?