The decreased growth hormone response to growth hormone releasing hormone in obesity is associated to cardiometabolic risk factors

Physiological response of endurance exercise as a growth hormone mediator in adolescent women's

OBJECTIVES

Overweight status decreases the growth hormone (GH) secretion, thus, increasing the risk factors for medical complications. However, proper exercise is reported to enhance GH and affect the energy balance. Therefore, exercise is proclaimed to be an accurate and engaging therapy to increase GH in preventing overweight. This study aims to investigate the physiological response of exercise in mediating the increase of GH secretion in female adolescents.

METHODS

22 overweight women aged 19-20 years old, with maximal oxygen consumption of 27-35 mL/kg/min, were selected as sample size. They were divided into three groups, namely (CONT, n=7) Control, (MIEE, n=7) Moderate-intensity interval endurance exercise, and (MCEE, n=8) Moderate-intensity continuous endurance exercise. The exercise was carried out by running for 30-35 min using treadmills with an intensity of 60-70% HR_max. The blood sampling for GH examination was carried out four times before exercise, 10 min, 6 h, and 24 h after exercise. The enzyme-linked immunosorbent assay (ELISA) was used to measure the GH and IGF-1 levels. The data analysis was carried out using a one-way ANOVA test, with a significance level of 5%.

RESULTS

The results of the one-Way ANOVA test suggested a significantly different average GH and IGF-1 before and after the exercise between the three groups (CON, MIEE, and MCEE) (p≤0.05).

CONCLUSIONS

MCEE increases the GH and IGF-1 levels more considerably than MIEE. Therefore, exercise is a mediator to increase GH and IGF-1 secretion in overweight individuals. Exercise could be a viable therapy for overweight people.

Association between overweight and growth hormone secretion in patients with non-functioning pituitary tumors

Introduction

Growth hormone (GH) deficiency (GHD) is often complicated by non-functioning pituitary tumors (NFPTs); however, its prevalence remains unclear because preoperative screening for GHD with provocative tests is not recommended. Accordingly, we attempted to clarify the characteristics of GHD in unoperated patients with NFPT.

Materials and methods

We retrospectively reviewed adult patients with non-functioning pituitary adenoma (NFPA) and Rathke’s cyst who underwent preoperative GH-releasing peptide-2 (GHRP-2) tests from January 2013 to December 2016. We investigated the association between peak GH response to GHRP-2 and background characteristics.

Results

Among 104 patients (85 NFPA and 19 Rathke’s cysts), 45 (43%) presented severe GHD, as diagnosed using GHRP-2 tests. Body mass index (β = -0.210, P = 0.007), free thyroxine (β = 0.440, P < 0.001), and tumor height (β = -0.254, P < 0.001) were significant variables for determining the peak GH response to GHRP-2 in multiple regression analyses. Overweight (odds ratio, 3.86; 95% confidence interval, 1.02–14.66) was significantly associated with severe GHD after adjustment for age, sex, creatinine, free thyroxine, tumor height and clinical diagnosis. The regression slopes between tumor height and peak GH response to GHRP-2 significantly differed between overweight patients and non-overweight individuals, as determined by analysis of covariance (P = 0.040). In the 48 patients who underwent postoperative GHRP-2 tests, severe postoperative GHD was significantly more common in overweight patients than non-overweight individuals (100% vs. 48%, P < 0.001).

Conclusion

We observed a negative synergistic effect between overweight and tumor size on GH secretion in patients with NFPTs, indicating that GH provocation tests for diagnosing underestimated GHD could be considered in overweight unoperated patients with large NFPTs.

Altered GH-IGF-1 Axis in Severe Obese Subjects is Reversed after Bariatric Surgery-Induced Weight Loss and Related with Low-Grade Chronic Inflammation

Endocrine disorders are common in obesity, including altered somatotropic axis. Obesity is characterized by reduced growth hormone (GH) secretion, although the insulin-like growth factor-1 (IGF-1) values are controversial. The aim of this study was to evaluate the effect of weight loss after bariatric surgery in the GH–IGF-1 axis in extreme obesity, in order to investigate IGF-1 values and the mechanism responsible for the alteration of the GH–IGF-1 axis in obesity. We performed an interventional trial in morbidly obese patients who underwent bariatric surgery. We included 116 patients (97 women) and 41 controls (30 women). The primary endpoint was circulating GH and IGF-1 values. Circulating IGF-1 values were lower in the obese patients than in the controls. Circulating GH and IGF-1 values increased significantly over time after surgery. Post-surgery changes in IGF-1 and GH values were significantly negatively correlated with changes in C-reactive protein (CRP) and free T4 values. After adjusting for preoperative body mass index (BMI), free T4 and CRP in a multivariate model, only CRP was independently associated with IGF-1 values in the follow-up. In summary, severe obesity is characterized by a functional hyposomatotropism at central and peripheral level that is progressively reversible with weight loss, and low-grade chronic inflammation could be the principal mediator.

Peak Growth Hormone Response to Combined Stimulation Test in 315 Children and Correlations with Metabolic Parameters

BACKGROUND/AIMS

Studies are lacking regarding the timing of peak growth hormone (PGH) response. We aim to elucidate the timing of PGH response to arginine and levodopa (A-LD) and evaluate the influence of body mass index (BMI) and other metabolic parameters on PGH.

METHODS

During growth hormone (GH) stimulation testing (ST) with A-LD, serum GH was measured at baseline and every 30 min up to 180 min. The PGH cut-off was defined as &amp;#x3c;10 ng/mL. IGF-1, IGF BP3, BMI, and metabolic parameters were obtained in a fasting state at baseline.

RESULTS

In the 315 tested children, stimulated PGH levels occurred at or before 120 min in 97.8% and at 180 min in 2.2%. GH area under the curve (AUC) positively correlated with PGH in all patients and with IGF-1 in pubertal males and females. BMI negatively correlated with PGH in all subjects. GH AUC negatively correlated with HOMA-IR and total cholesterol.

CONCLUSION

We propose termination of the GH ST with A-LD at 120 min since omission of GH measurement at 180 min did not alter the diagnosis of GH deficiency based on a cut-off of &amp;#x3c; 10 ng/mL. BMI should be considered in the interpretation of GH ST with A-LD. The relationships between GH AUC and metabolic parameters need further study.

Insulin-Like Growth Factors and Metabolic Syndrome in Obese Children

BACKGROUND/AIMS

Insulin-like growth factor (IGF)-I is related to cardiometabolic risk in adults, whereas the metabolic role of IGF-II is unclear. The aim of this study was to assess IGFs in obese children and correlate them with metabolic syndrome (MetS) components.

METHODS

This is a retrospective study including 574 obese children (11.34 ± 3.16 years). All subjects underwent complete anthropometry and biochemical assessment. In a subgroup of 136 subjects, body composition was evaluated. IGF-I was measured in 300 obese subjects and IGF-II in 77 obese and 15 lean children. 177 subjects were divided according to the presence of 1 or more MetS criteria: group 1, subjects with 1 MetS criterion; group 2, subjects with 2 components; and group 3, subjects with MetS diagnosis.

RESULTS

IGF-I, IGF-II, and IGF-I/insulin-like growth factor-binding protein-3 ratio were not different among subjects with an increasing number of MetS criteria and were not associated with single components of MetS as well as with body composition parameters. In children younger than 10 years, IGF-I directly correlated with high-density lipoprotein cholesterol (p < 0.005) even after controlling for confounders. IGF-II was significantly higher in obese children and correlated with parameters of insulin sensitivity (p < 0.05).

CONCLUSION

IGFs were neither related to MetS nor to body composition parameters in obese children. Further studies are needed to clarify the mechanisms underlying the relationship between IGF-II and insulin sensitivity.

Dipeptidyl Peptidase-4 Inhibition Potentiates Stimulated Growth Hormone Secretion and Vasodilation in Women

BACKGROUND

Diminished growth hormone (GH) is associated with impaired endothelial function and fibrinolysis. GH-releasing hormone is the primary stimulus for GH secretion and a substrate of dipeptidyl peptidase-4. We tested the hypothesis that dipeptidyl peptidase-4 inhibition with sitagliptin increases stimulated GH secretion, vasodilation, and tissue plasminogen activator (tPA) activity.

METHODS AND RESULTS

Healthy adults participated in a 2-part double-blind, randomized, placebo-controlled, crossover study. First, 39 patients (29 women) received sitagliptin or placebo on each of 2 days separated by a washout. One hour after study drug, blood was sampled and then arginine (30 g IV) was given to stimulate GH. Vasodilation was assessed by plethysmography and blood sampled for 150 minutes. Following a washout, 19 of the original 29 women received sitagliptin alone versus sitagliptin plus antagonist to delineate GH receptor (GHR)- (n=5), nitric oxide- (n=7), or glucagon-like peptide-1 receptor- (n=7) dependent effects. Sitagliptin enhanced stimulated GH secretion (P<0.01 versus placebo, for 30 minutes) and free insulin-like growth factor-1 (P<0.001 versus placebo, after adjustment for baseline) in women. Vasodilation and tPA increased in all patients, but sitagliptin enhanced vasodilation (P=0.01 versus placebo) and increased tPA (P<0.001) in women only. GHR blockade decreased free insulin-like growth factor-1 (P=0.04 versus sitagliptin alone) and increased stimulated GH (P<0.01), but decreased vascular resistance (P=0.01) such that nadir vascular resistance correlated inversely with GH (rs=-0.90, P<0.001). GHR blockade suppressed tPA. Neither nitric oxide nor glucagon-like peptide-1 receptor blockade affected vasodilation or tPA.

CONCLUSIONS

Sitagliptin enhances stimulated GH, vasodilation, and fibrinolysis in women. During sitagliptin, increases in free insulin-like growth factor-1 and tPA occur via the GHR, whereas vasodilation correlates with GH but occurs through a GHR-independent mechanism.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01701973.

Relationship between IGF-I Concentration and Metabolic Profile in Children with Growth Hormone Deficiency: The Influence of Children's Nutritional State as well as the Ghrelin, Leptin, Adiponectin, and Resistin Serum Concentrations

BACKGROUND

Some, however not all, children with growth hormone deficiency (GHD) reveal a tendency towards metabolic disorders. Insulin-like growth factor I (IGF-I) is the main mediator of GH anabolic effects.

OBJECTIVE

The aim of the study was to compare ghrelin, adiponectin, leptin, resistin, lipid, glucose, and insulin concentrations in GHD children, depending on the IGF-I bioavailability.

METHODS

The analysis comprised 26 children with GHD, aged 5.7-15.3 yrs. Fasting serum concentrations of IGF-I, IGFBP-3, ghrelin, leptin, adiponectin, resistin, lipids, glucose, and insulin were measured. The GHD children were divided into two subgroups: (1) with lower IGF-I/IGFBP-3 molar ratio and (2) with higher IGF-I/IGFBP-3 molar ratio. The control group consisted of 39 healthy children, aged 5.1-16.6 yrs, of normal height and body mass.

RESULTS

GHD children with lower IGF-I/IGFBP-3 molar ratio were found to have a significantly lower body mass and insulin and triglyceride concentrations, as well as significantly higher ghrelin and adiponectin concentrations than GHD children with higher IGF-I/IGFBP-3.

CONCLUSIONS

A better metabolic profile characterised GHD children with low IGF-I bioavailability. This phenomenon may be the result of high adiponectin and ghrelin concentrations in those children and their influence on adipose tissue, glucose uptake, and orexigenic axis.

Low insulin-like growth factor 1 is associated with low high-density lipoprotein cholesterol and metabolic syndrome in Chinese nondiabetic obese children and adolescents: a cross-sectional study

Background

Low serum high-density lipoprotein cholesterol (HDL-C) is an independent risk factor for developing cardiovascular disease. Insulin-like growth factor 1(IGF-1) levels have been proven to be positively associated with HDL-C, but few studies were based on the dataset of children or adolescents. The aim of this study is to investigate the relationship among IGF-1, HDL-C and the metabolic syndrome in Chinese nondiabetic obese children and adolescents.

Methods

As a cross-sectional study, this study includes 120 obese Chinese children and adolescents and 120 healthy ones. The obese subjects were divided into two groups based on using 1.03 mmol/L as a threshold value for HDL-C. Clinical examination and laboratory examinations were assessed for all participants.

Results

Obese subjects had significantly lower IGF-1SDS and higher Height SDS than those in the control group. Among 120 obese children and adolescents, 22 (18.3 %) subjects had an HDL-C level <1.03 mmol/L. IGF-1SDS was significantly lower (P = 0.001) in obese subjects with low HDL-C. According to the results of multivariate logistic regression analysis, IGF-1 SDS is significantly associated with low HDL-C(OR 0.518, 95 % CI 0.292–0.916; P = 0.024), after being adjusted for age, gender, pubertal status, BMI SDS, SBP, DBP, HOMR-IR, total cholesterol, low density lipoprotein-cholesterol, triglycerides, ALT and uric acid. In addition, IGF-1 SDS is significantly correlated with the level of serum HDL-C in study population (r = 0.19, P = 0.003). Based on logistic regression analysis with adjustment for age, gender and pubertal status, the increased IGF-1 SDS was associated with a decreased probability of metabolic syndrome (OR 0.555, 95 % CI 0.385–0.801; P = 0.002) and hypertriglyceridemia (OR 0.582, 95 % CI 0.395–0.856; P = 0.006), but no significant correlation with hypertension.

Conclusion

Obese children had lower IGF-1SDS and taller stature compared with the control group. Low levels of IGF-1 SDS were associated with low levels of HDL-C in chinese nondiabetic obese children and adolescents, independent of insulin resistance, as well as other traditional cardiovascular disease risk markers.

Growth hormone deficiency after childhood bone marrow transplantation with total body irradiation: interaction with adiposity and age

OBJECTIVE

Bone marrow transplantation with total body irradiation (BMT/TBI) has adverse effects on growth, growth hormone status and adiposity. We investigated the GH-IGF-I axis in relation to adiposity.

DESIGN

Cross-sectional case control study.

PATIENTS

BMT/TBI survivors (n = 22) and short stature control participants (n = 19), all GH-naïve or off GH treatment >3 months.

MEASUREMENTS

Auxology, DEXA scans and GH-IGF-I axis investigation: (i) 12-h overnight GH profiles; (ii) insulin tolerance test (ITT); and (iii) IGF-I generation test.

ANALYSIS

auto-deconvolution of GH profile data and comparison of quantitative parameters using ANOVA.

RESULTS

Eighty-two percent of BMT/TBI survivors had growth hormone deficiency (GHD) using ITT. GH profile area-under-the-curve (GH-AUC) was reduced in BMT/TBI survivors vs short stature control participants [geometric mean (range) 209 (21-825) vs 428 (64-1400) mcg/l/12 h, respectively, P = 0·007]. GHD was more marked in those who had additional cranial irradiation (CRT) [ITT peak 1·4 (0·2-3·0) vs TBI only 4·1 (1·1-14·8) mcg/l, P = 0·036]. GHD was more marked at the end of growth in BMT/TBI survivors vs short stature control participants (GH-AUC 551 (64-2474) vs 1369 (192-4197) mcg/l/12 h, respectively, P = 0·011) and more prevalent (9/11 vs 1/9, respectively, P = 0·005). GH profile data were consistent with ITT results in 80% of participants. IGF-I generation tests were normal. BMT/TBI survivors still demonstrated lower GH levels after adjustment for adiposity (fat-adjusted mean difference for GH-AUC 90·9 mcg/l/12 h, P = 0·025).

CONCLUSIONS

GHD was more prevalent in BMT/TBI survivors than expected for the CRT dose in TBI, worsened with time and persisted into adulthood. GHD could not be explained by adiposity. There was no evidence of GH neurosecretory dysfunction or resistance after BMT/TBI.

Integrative neurobiology of metabolic diseases, neuroinflammation, and neurodegeneration

Alzheimer's disease (AD) is a complex, multifactorial disease with a number of leading mechanisms, including neuroinflammation, processing of amyloid precursor protein (APP) to amyloid β peptide, tau protein hyperphosphorylation, relocalization, and deposition. These mechanisms are propagated by obesity, the metabolic syndrome and type-2 diabetes mellitus. Stress, sedentariness, dietary overconsumption of saturated fat and refined sugars, and circadian derangements/disturbed sleep contribute to obesity and related metabolic diseases, but also accelerate age-related damage and senescence that all feed the risk of developing AD too. The complex and interacting mechanisms are not yet completely understood and will require further analysis. Instead of investigating AD as a mono- or oligocausal disease we should address the disease by understanding the multiple underlying mechanisms and how these interact. Future research therefore might concentrate on integrating these by “systems biology” approaches, but also to regard them from an evolutionary medicine point of view. The current review addresses several of these interacting mechanisms in animal models and compares them with clinical data giving an overview about our current knowledge and puts them into an integrated framework.

Preliminary data on the relationship between circulating levels of Sirtuin 4, anthropometric and metabolic parameters in obese subjects according to growth hormone/insulin-like growth factor-1 status

BACKGROUND

The main components of GH/insulin-like growth factor (IGF)-1 axis and Sirtuin 4 (Sirt4), highly expressed in liver and skeletal muscle mitochondria, serve as active regulators of mitochondrial oxidative capacity with opposite functions. In obesity both GH/IGF-1 status and serum Sirt4 levels, likely mirroring its reduced mitochondrial expression, might be altered.

OBJECTIVE

To evaluate the association between circulating levels of Sirt4, body composition, metabolic parameters and cardio-metabolic risk profile in obese patients according to their different GH/IGF-1 status.

DESIGN

Cross-sectional study with measurement of serum Sirt4, GH after GH releasing hormone (GHRH)+Arginine test, IGF-1 and assessment of body composition, glucose and lipid metabolism in 50 class II-III obese subjects (BMI 35.6 to 62.1 kg/m(2)) and 15 normal weight subjects. Low GH secretion and IGF-1 were defined using pre-determined cutoff-points. The Homeostatic Metabolic Assessment of insulin resistance index and Visceral adiposity index were also calculated. The association of Sirt4 with peak stimulated GH and IGF-1, body composition, metabolic parameters and cardio-metabolic risk profile was assessed.

RESULTS

Serum Sirt4 was inversely related to anthropometric and metabolic parameters and positively related to peak GH and IGF-1. After adjusting for peak GH and IGF-1, the relationships between Sirt4 and BMI became not significant. At multiple regression analysis IGF-1 (p<0.001) was the independent predictor for Sirt4.

CONCLUSION

There was a close relationship between low IGF-1 and low serum Sirt4. This observation suggested that in obese patients, low GH/IGF-1 status was likely associated with a major compensatory decrease in circulating levels of Sirt4 to oppose to its negative regulator effect on mitochondrial oxidative capacity.

Impact of adult growth hormone deficiency on metabolic profile and cardiovascular risk [Review]

Adult growth hormone deficiency (GHD) is a well defined clinical condition, which is characterized by abnormal body composition, impaired physical activity and decreased quality of life. In addition, in recent years, growing interest has been shown towards cardiovascular risks in adult patients affected by GHD. In this regard, GHD is widely known to be associated with increased mortality, likely due to the increase of risk factors, such as central obesity, impaired lipid and glucose profiles and other less-known risk factors, such as inflammatory cytokines, endothelial dysfunction and oxidative stress. However, very few papers have recently discussed this topic. In this review, the aim is to clarify this issue by discussing evidence regarding the effects of adult GHD on metabolic and cardiovascular profiles.

Network identification of hormonal regulation

Relations among hormone serum concentrations are complex and depend on various factors, including gender, age, body mass index, diurnal rhythms and secretion stochastics. Therefore, endocrine deviations from healthy homeostasis are not easily detected or understood. A generic method is presented for detecting regulatory relations between hormones. This is demonstrated with a cohort of obese women, who underwent blood sampling at 10 minute intervals for 24-hours. The cohort was treated with bromocriptine in an attempt to clarify how hormone relations change by treatment. The detected regulatory relations are summarized in a network graph and treatment-induced changes in the relations are determined. The proposed method identifies many relations, including well-known ones. Ultimately, the method provides ways to improve the description and understanding of normal hormonal relations and deviations caused by disease or treatment.

Effects of growth hormone withdrawal in obese premenopausal women

OBJECTIVE

We previously reported improved body composition and cardiovascular risk markers plus a small decrease in glucose tolerance with GH administration vs placebo for 6 months to abdominally obese premenopausal women. The objective of this study was to determine whether the effects of GH treatment on cardiovascular risk markers, body composition and glucose tolerance in obese women persist 6 months after GH withdrawal.

DESIGN AND PATIENTS

Fifty abdominally obese premenopausal women completed a trial of rhGH vs placebo for 6 months; thirty-nine women completed a subsequent 6-month withdrawal observation period.

MEASUREMENTS

IGF-I, body composition by CT, (1) H-MRS and DXA, serum cardiovascular risk markers, oral glucose tolerance test (OGTT).

RESULTS

IGF-I standard deviation scores (SDS) within the GH group were -1.7 ± 0.1 (pretreatment),-0.1 ± 0.3 (after 6 months of GH) and -1.7 ± 0.1 (6 months post-GH withdrawal). Six months after GH withdrawal, total abdominal and subcutaneous adipose tissue, total fat, trunk fat, trunk/extremity fat, hsCRP, apoB, LDL, and tPA were higher than at the 6-month (GH discontinuation) timepoint (P ≤ 0.05). All body composition and cardiovascular risk markers that had improved with GH returned to baseline levels by 6 months after GH discontinuation, as did fasting and 2-h OGTT glucose levels.

CONCLUSION

The effects of GH administration to abdominally obese premenopausal women have a short time-course. The beneficial effects on body composition and cardiovascular risk markers, and the side effect of altered glucose tolerance returned to pretreatment levels after GH withdrawal. There was no suppression of endogenous IGF-I levels, which returned to baseline after GH withdrawal.

Increased adiposity and insulin correlates with the progressive suppression of pulsatile GH secretion during weight gain

Pathological changes associated with obesity are thought to contribute to GH deficiency. However, recent observations suggest that impaired GH secretion relative to excess calorie consumption contributes to progressive weight gain and thus may contribute to the development of obesity. To clarify this association between adiposity and GH secretion, we investigated the relationship between pulsatile GH secretion and body weight; epididymal fat mass; and circulating levels of leptin, insulin, non-esterified free fatty acids (NEFAs), and glucose. Data were obtained from male mice maintained on a standard or high-fat diet. We confirm the suppression of pulsatile GH secretion following dietary-induced weight gain. Correlation analyses reveal an inverse relationship between measures of pulsatile GH secretion, body weight, and epididymal fat mass. Moreover, we demonstrate an inverse relationship between measures of pulsatile GH secretion and circulating levels of leptin and insulin. The secretion of GH did not change relative to circulating levels of NEFAs or glucose. We conclude that impaired pulsatile GH secretion in the mouse occurs alongside progressive weight gain and thus precedes the development of obesity. Moreover, data illustrate key interactions between GH secretion and circulating levels of insulin and reflect the potential physiological role of GH in modulation of insulin-induced lipogenesis throughout positive energy balance.

[Endocrine function in obesity]

Obesity is associated to significant disturbances in endocrine function. Hyper insulinemia and insulin resistance are the best known changes in obesity, but their mechanisms and clinical significance are not clearly established. Adipose tissue is considered to be a hormone-secreting endocrine organ; and increased leptin secretion from the adipocyte, a satiety signal, is a well-established endocrine change in obesity. In obesity there is a decreased GH secretion. Impairment of somatotropic function in obesity is functional and may be reversed in certain circumstances. The pathophysiological mechanism responsible for low GH secretion in obesity is probably multifactorial. There are many data suggesting that a chronic state of somatostatin hypersecretion results in inhibition of GH release. Increased FFA levels, as well as a deficient ghrelin secretion, probably contribute to the impaired GH secretion. In women, abdominal obesity is associated to hyperandrogenism and low sex hormone-binding globulin levels. Obese men, particularly those with morbid obesity, have decreased testosterone and gonadotropin levels. Obesity is associated to an increased cortisol production rate, which is compensated for by a higher cortisol clearance, resulting in plasma free cortisol levels that do not change when body weight increases. Ghrelin is the only known circulating orexigenic factor, and has been found to be decreased in obese people. In obesity there is also a trend to increased TSH and free T3 levels.