Adiponectin, leptin, and erythrocyte sodium/lithium countertransport activity, but not resistin, are related to glucose metabolism in growth hormone-deficient adults

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.

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.

Growth hormone and the cardiovascular system

Growth hormone (GH) exerts its effects through insulin-like growth factor-1, and although ubiquitous in human tissues, it has a significant role in cardiovascular function. In recent years, there has been a great deal of interest in GH as an etiologic factor in many cardiovascular disease states. Acromegaly, a state of endogenous GH excess, results in myocardial hypertrophy and decreased cardiac performance with increased cardiovascular mortality. Additional insight into the role of excess GH on the cardiovascular system has been gained from data collected in athletes doping with GH. Likewise, GH deficiency is associated with increased mortality, possibly from the associated increase in atherosclerosis, lipid abnormalities, and endothelial dysfunction. However, further research is required to clarify the benefit of GH treatment in both deficient states and in heart failure patients.

Relationship of adiponectin to endogenous GH pulse secretion parameters in response to stimulation with a growth hormone releasing factor

OBJECTIVE

Obesity is associated with both reduced growth hormone (GH) and adiponectin. However, the relationship between adiponectin and parameters of endogenous GH secretion remains unknown. The aim of this study was to determine the relationship between total and high molecular weight (HMW) adiponectin and parameters of endogenous pulsatile GH secretion and the effects of tesamorelin, a synthetic GH releasing hormone (GHRH(1-44)), on total and HMW adiponectin.

DESIGN

A 2-week interventional study with tesamorelin was conducted at an academic medical center in 13 men with BMI 20-35 kg/m(2). Overnight frequent blood sampling and measurement of total and HMW adiponectin at baseline and after treatment were performed to assess the effects of augmenting endogenous pulsatile GH secretion.

RESULTS

Total, but not HMW, adiponectin was positively associated with log(10)Peak GH area (r=+0.73; P=0.005), basal GH secretion (r=+0.67; P=0.01), and total GH production (r=+0.57; P=0.04), but was not associated with the number of secretion events (P=0.85). Two-week treatment with tesamorelin increased endogenous GH release and IGF-1, but neither total (change -0.16±0.64; P=0.40), nor HMW (change +0.03±0.70; P=0.87) adiponectin changed significantly with treatment. Sub-analyses in overweight and obese men yielded similar results.

CONCLUSIONS

Our study demonstrates a strong relationship between specific parameters of endogenous GH pulsatility and adiponectin. However, short-term augmentation of GH pulsatility over 2-weeks does not change adiponectin. Therefore, the relationship between GH and adiponectin is most likely mediated by specific covariates related to adiposity or other factors.

Adipokine profile and urinary albumin excretion in isolated growth hormone deficiency

BACKGROUND

GH deficiency (GHD) is often associated with cardiovascular risk factors, including abdominal fat accumulation, hypercholesterolemia, and increased C-reactive protein. Despite the presence of these risk factors, adults with congenital lifetime isolated GHD (IGHD) due to an inactivating mutation in the GHRH receptor gene do not have premature atherosclerosis.

OBJECTIVE

The aim was to study the serum levels of adiponectin and leptin (antiatherogenic and atherogenic adipokine, respectively), and the urinary albumin excretion (UAE) in these IGHD individuals.

DESIGN AND PATIENTS

We conducted a cross-sectional study of 20 IGHD individuals (seven males; age, 50.8 +/- 14.6 yr) and 22 control subjects (eight males; age, 49.9 +/- 11.5 yr).

MAIN OUTCOME MEASURES

Anthropometric factors, body composition, blood pressure, serum adiponectin, leptin, and UAE were measured.

RESULTS

Adiponectin was higher [12.8 (7.1) vs. 9.7 (5) ng/ml; P = 0.041] in IGHD subjects, whereas no difference was observed in leptin [7.3 (6.3) vs. 9.3 (18.7 ng/ml] and UAE [8.6 (13.8) vs. 8.5 (11.1) microg/min].

CONCLUSIONS

Subjects with lifetime untreated IGHD have an adipokine profile with high adiponectin and normal leptin levels that may delay vascular damage and lesions of the renal endothelium.

The reduction in visceral fat mass in response to growth hormone is more marked in men than in oestrogen-deficient women

CONTEXT

Women with severe growth hormone (GH) deficiency have a less marked response to GH replacement than men. This has mostly been attributed to the attenuating effects of oestrogen replacement therapy.

OBJECTIVE

To study gender related differences in the response to GH treatment in men and postmenopausal women.

METHODS

Fifteen men and 15 age- and BMI-matched women with abdominal obesity (mean age: 58; range 51-64 years) were treated for one year with similar doses (0.47 vs. 0.51 mg/day) of GH. All women were postmenopausal not receiving oestrogen treatment. Insulin sensitivity was assessed using a hyperinsulinemic euglycemic clamp and body composition by computed tomography (CT) scans and from total body potassium, K(40).

RESULTS

Men and women were comparable at baseline in terms of waist circumference, IGF-1 and lipid levels. After one year of GH treatment, there was a 18% reduction in visceral adipose tissue (VAT) in men and a 5% reduction in women (P=0.0001 men vs. women). Although the magnitude of the difference was small, men increased more in thigh muscle mass (P<0.0001 vs. women). A reduction in thigh intermuscular adipose tissue (IMAT) and diastolic blood pressure was seen only in men (both p<0.05 vs. baseline). A decrease in LDL cholesterol, and an increase in serum insulin, was observed only in women (both p<0.05 vs. baseline).

CONCLUSION

Low dose GH treatment reduced VAT more markedly in men as compared with women. As all women were postmenopausal and oestrogen-deficient, this gender difference in responsiveness was not due to an antagonistic effect of oestrogen on peripheral GH action.

Peroxisome proliferator-activated receptor gamma agonism modifies the effects of growth hormone on lipolysis and insulin sensitivity

CONTEXT

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonists such as thiazolidinediones (TZDs) improve insulin sensitivity in type 2 diabetes mellitus (T2DM) through effects on fat metabolism whereas GH stimulates lipolysis and induces insulin resistance.

OBJECTIVE

To evaluate the impact of TZDs on fat metabolism and insulin sensitivity in subjects exposed to stable GH levels.

DESIGN

A randomized, placebo-controlled, double-blind parallel-group study including 20 GH-deficient patients on continued GH replacement therapy. The patients were studied before and after 12 weeks.

INTERVENTION

Patients received either pioglitazone 30 mg (N = 10) or placebo (N = 10) once daily for 12 weeks.

RESULTS

Adiponectin levels almost doubled during pioglitazone treatment (P = 0.0001). Pioglitazone significantly decreased basal free fatty acid (FFA) levels (P = 0.02) and lipid oxidation (P = 0.02). Basal glucose oxidation rate (P = 0.004) and insulin sensitivity (P = 0.03) improved in the patients who received pioglitazone treatment. The change in insulin-stimulated adiponectin level after pioglitazone treatment was positively correlated to the change in insulin-stimulated total glucose disposal (R = 0.69, P = 0.04).

CONCLUSION

The impact of GH on lipolysis and insulin sensitivity can be modified by administration of TZDs.

Effects of GH treatment in GH-deficient adults on adiponectin, leptin and pregnancy-associated plasma protein-A

OBJECTIVE

GH deficiency (GHD) in adults is associated with adverse effects on metabolism and increased cardiovascular risk. Pregnancy-associated plasma protein-A (PAPP-A) is a protease that promotes IGF-I availability in vascular tissues. PAPP-A levels appear to correlate with carotid intima-media thickness and have been proposed as an early predictor of cardiac events. The aim of our study was to evaluate PAPP-A levels in GHD adults at baseline and after GH replacement and correlate them with changes in body composition, lipid profile, glucose homeostasis, inflammatory markers and in leptin and adiponectin.

PATIENTS AND METHODS

Fourteen GHD adults were evaluated at baseline and after 1 year of GH therapy. All patients were compared at baseline with 28 age-, sex- and body mass index (BMI)-matched control subjects.

RESULTS

At baseline, GHD adults showed higher PAPP-A levels (P=0.03) and higher leptin (P=0.04), fibrinogen (P=0.002) and highly sensitive C-reactive protein (P=0.01) values than controls. Therapy with GH reduced PAPP-A (P=0.03) and fibrinogen levels (P=0.002) while increased BMI (P=0.01) and reduced waist-hip ratio (WHR; P=0.05) were observed. Insulin and homeostasis model assessment of insulin resistance index increased after treatment (P<0.004/P=0.007), without changes in leptin or adiponectin levels. PAPP-A values correlated positively with BMI and WHR and negatively with adiponectin before and after treatment, with no correlation with glucose homeostasis parameters, lipid profile or leptin.

CONCLUSIONS

Our study suggests that PAPP-A expression is increased in GHD adults, and that 1 year of GH replacement therapy is able to reduce PAPP-A levels in this population. However, further studies are required to determine whether this decrease correlates with an improvement in atherosclerosis.

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

We performed this study to examine whether the serum resistin concentrations in growth hormone (GH)-deficient (GHD) children are influenced by administration of GH and to assess the relationship between serum resistin and free fatty acid levels during GH replacement therapy. The study included 20 prepubertal GHD children (16 boys and 4 girls) who were treated with recombinant human GH (hGH). The serum levels of resistin, insulin-like growth factor I, free fatty acid (FFA), triglyceride, cholesterol and glucose levels, leukocyte counts, and hemoglobin A(1c) were measured at baseline and after 1 month of hGH treatment. The serum resistin levels after hGH therapy were significantly higher than the basal resistin levels (median [range], 6.2 [4.9-11.8] vs 5.6 [4.4-8.3] ng/mL; P < .05), whereas the serum FFA levels were unchanged before and after treatment (0.51 [0.34-0.76] vs 0.37 [0.24-0.60] mEq/L). No significant relationship was found between serum resistin and FFA levels after hGH therapy. Body mass index, serum triglyceride, cholesterol and glucose levels, leukocyte counts, and hemoglobin A(1c) showed no significant differences before and after hGH treatment. Our results suggest that elevated serum resistin levels after 1-month hGH therapy in GHD children are not associated with the GH-induced lipolysis as found in GHD adults during short-time hGH therapy.

The effects of recombinant human growth hormone (rhGH) supplementation on adipokines and C-reactive protein in obese subjects

OBJECTIVE

Obese subjects have functional growth hormone deficiency (GHD). Recombinant human GH (rhGH) treatment of pituitary GHD improves serum levels of leptin, adiponectin and C-reactive protein (CRP). This study was undertaken to determine whether these rhGH-induced changes occur in obese subjects during rhGH supplementation.

DESIGN

Randomized double-blind placebo-controlled trial of low-dose rhGH (200 microg/day for the first month, then 400 microg/day for men and 600 microg/day for women thereafter) or placebo supplementation as an adjuvant to a standard weight loss program.

SUBJECTS

Forty healthy obese subjects, 28 premenopausal menstruating women (35+/-7 SD years) and 12 men (37+/-6 years).

MEASUREMENTS

Body weight, BMI, body composition (assessed by dual energy X-ray absorptiometry [DEXA]), and serum levels of glucose, insulin, IGF-I, IGFBP-3, insulin resistance index (homeostasis modal assessment [HOMA]), leptin, CRP and adiponectin were performed at baseline and at 6 months.

RESULTS

For similar entry BMI values, women when compared with men had higher percent body fat (BF) (43.5+/-4.6% vs. 29.8+/-4.0%, p<0.001), higher leptin levels (16.9+/-8.4 microg/L vs. 4.2+/-3.0 microg/L, p<0.001), and higher CRP levels (13.8+/-16.8 mg/L vs. 2.4+/-3.2mg/L, p=0.04). Serum levels of leptin and CRP, but not adiponectin, correlated significantly with BF in both sexes. Recombinant human GH treatment increased levels of IGF-I Z-Score between baseline and 6 months (from -0.7+/-0.9 SD to 0.1+/-1.1 SD, p=0.01) and modestly decreased BF (from 38.4+/-7.8% to 35.6+/-7.5%, p=0.046). Despite increased IGF-I, there were no differences between rhGH and placebo with regard to changes in leptin, CRP, or adiponectin.

CONCLUSION

It is concluded that in obesity, although rhGH treatment significantly increases IGF-I and modestly reduces body fat, the lack of significant changes in serum leptin, adiponectin or CRP levels suggests that rhGH treatment does not have a significant effect on these serum markers of adiposity.

Effect of growth hormone therapy on serum adiponectin and resistin levels in short, small-for-gestational-age children and associations with cardiovascular risk parameters

BACKGROUND

Adiponectin and resistin are fat cell-derived hormones, which are thought to be respectively protective and disadvantageous with regard to the development of cardiovascular disease and diabetes mellitus type 2. Low birth weight has been associated with increased risks for the development of these diseases. In short, small-for-gestational-age (SGA) children, GH therapy has several positive effects regarding cardiovascular risk factors. On the other hand, concern has been expressed about the effects of GH therapy on insulin sensitivity.

METHODS

We measured adiponectin and resistin levels in 136 short prepubertal children born SGA and their association with cardiovascular risk parameters and growth factors. Also, we compared the levels with normal-statured controls. The effect of GH treatment was evaluated in 50 short SGA children vs. baseline and vs. an untreated sex- and age-matched SGA control group.

RESULTS

Short SGA children had similar adiponectin and lower resistin levels, compared with normal-statured controls. In GH-treated SGA children, neither adiponectin nor resistin levels changed significantly during 2 yr of GH treatment. Compared with untreated sex- and age-matched SGA controls, GH-treated SGA children had similar adiponectin and lower resistin levels. Adiponectin correlated inversely with age but not any cardiovascular risk parameter or growth factor. Higher IGF-I levels in GH-treated children were associated with lower resistin levels.

CONCLUSIONS

Compared with normal-statured controls, short prepubertal SGA children had similar adiponectin and lower resistin levels. Two years of GH treatment had no effect on their adiponectin and resistin levels.

Growth hormone deficiency, low levels of adiponectin, and unfavorable plasma lipid and lipoproteins

OBJECTIVE

To examine the impact of adolescent growth hormone deficiency (GHD) on circulating adiponectin levels and the relation between adiponectin, fasting insulin, plasma lipid, and lipoprotein levels.

STUDY DESIGN

Twelve children with GHD on GH treatment with a chronological age (CA) of 14.4 +/- 2.0 years and 12 untreated adolescents with GHD with a CA of 14.9 +/- 2.3 years were studied. Adiponectin concentrations were measured in all patients, and the association of adiponectin with fasting insulin, total, LDL, and HDL cholesterol, triglycerides, apolipoprotein A-1, and apolipoprotein B was evaluated. Twelve healthy adolescents served as control subjects.

RESULTS

Adiponectin levels were significantly lower in untreated GHD adolescents than in treated GHD subjects or in control subjects (P < .008). Total and LDL cholesterol, triglycerides, and Apo B concentrations were increased in untreated GHD adolescents, whereas HDL cholesterol levels were similar in all three groups. Insulin levels were significantly increased in treated GHD adolescents when compared with control subjects (P < .05) but similar to those with untreated GHD. Adiponectin was found to be negatively associated with body mass index, waist-to-hip ratio, and with Apo B, total cholesterol, triglycerides, and LDL cholesterol concentrations in untreated GHD adolescents, whereas a positive correlation between adiponectin and HDL cholesterol was noted in both untreated and treated GHD subjects. Adiponectin correlated inversely with fasting insulin levels in untreated and treated GHD adolescents.

CONCLUSIONS

GHD in adolescence is associated with low levels of adiponectin and with an unfavorable plasma lipid and lipoprotein profile. Our data suggest that treatment with GH may improve the abnormalities seen.

Serum ghrelin and leptin levels in adult growth hormone deficiency syndrome

BACKGROUND

In spite of the increasing information that has recently been accumulated on the involvement of ghrelin and leptin in the control of energy balance, the relationship between ghrelin and leptin and the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis in the pathological condition characterized by GH deficiency has been poorly clarified. Therefore, we performed this study to examine the correlation of the plasma levels of ghrelin and leptin with the anthropometric and biochemical markers in GH-deficient (GHD) adults as compared to their healthy cohorts.

METHODS

In 60 male adults (GHD; n = 12, healthy control; n = 48, average age: 54 years), we investigated the correlations between the serum leptin and ghrelin levels with the anthropometric and biochemical factors in the control group, as compared to the GHD patients. The diagnosis of GH deficiency was made when peak response for serum GH was <5 microg/L to a GH-provocative test (L-dopa test). All subjects underwent assessment of waist circumference, body mass index (BMI) and percentage body fat for their body composition. Plasma ghrelin, leptin, insulin, GH and IGF-1 were measured.

RESULTS

Groups were matched for age, BMI, waist circumference and percent of body fat. Ghrelin and leptin levels were not significantly different between the two groups. There was no correlation between the peak GH level or the GHAUC and the ghrelin concentrations in the GHD subjects. Plasma leptin correlated positively with percentage of body fat, total cholesterol and LDL-cholesterol, but it had no correlation with the peak GH or area under the curve for growth hormone (GHAUC) in the GHD subjects. Plasma ghrelin concentrations were not correlated with the biochemical and anthropometric markers in the subjects with GHD, and ghrelin showed no significant differences in the GHD and control subjects. Leptin concentrations were positively correlated with body fat, but they were not correlated with the levels of either IGF-1 or GH in the GHD patients.

CONCLUSIONS

It is possible that ghrelin concentrations appeared normal in the GHD subjects because of the opposing influences of increased adiposity, which reduce ghrelin secretion, and GHD, which may increase it. Further studies are needed to clarify these controversies about the relation of ghrelin and leptin with the GH and IGF-1 levels.