Effects of GH on body composition and cardiovascular risk markers in young men with abdominal obesity

Growth hormone in pediatric chronic kidney disease: more than just height

Recombinant human growth hormone therapy, which was introduced in the 1980s, is now routine for children with advanced chronic kidney disease (CKD) who are exhibiting growth impairment. Growth hormone usage remains variable across different centers, with some showing low uptake. Much of the focus on growth hormone supplementation has been on increasing height because of social and psychological effects of short stature. There are, however, numerous other changes that occur in CKD that have not received as much attention but are biologically important for pediatric growth and development. This article reviews the current knowledge about the multisystem effects of growth hormone therapy in pediatric patients with CKD and highlights areas where additional clinical research is needed. We also included clinical data on children and adults who had received growth hormone for other indications apart from CKD. Ultimately, having robust clinical studies which examine these effects will allow children and their families to make more informed decisions about this therapy.

Growth Hormone Administration Improves Nonalcoholic Fatty Liver Disease in Overweight/Obesity: A Randomized Trial

CONTEXT

Overweight and obesity are associated with relative growth hormone (GH) deficiency, which has been implicated in the development of nonalcoholic fatty liver disease (NAFLD). NAFLD is a progressive disease without effective treatments.

OBJECTIVE

We hypothesized that GH administration would reduce hepatic steatosis in individuals with overweight/obesity and NAFLD.

METHODS

In this 6-month randomized, double-blind, placebo-controlled trial of low-dose GH administration, 53 adults aged 18 to 65 years with BMI ≥25 kg/m2 and NAFLD without diabetes were randomized to daily subcutaneous GH or placebo, targeting insulin-like growth factor 1 (IGF-1) to the upper normal quartile. The primary endpoint was intrahepatic lipid content (IHL) by proton magnetic resonance spectroscopy (1H-MRS) assessed before treatment and at 6 months.

RESULTS

Subjects were randomly assigned to a treatment group (27 GH; 26 placebo), with 41 completers (20 GH and 21 placebo) at 6 months. Reduction in absolute % IHL by 1H-MRS was significantly greater in the GH vs placebo group (mean ± SD: -5.2 ± 10.5% vs 3.8 ± 6.9%; P = .009), resulting in a net mean treatment effect of -8.9% (95% CI, -14.5 to -3.3%). All side effects were similar between groups, except for non-clinically significant lower extremity edema, which was more frequent in the GH vs placebo group (21% vs 0%, P = .02). There were no study discontinuations due to worsening of glycemic status, and there were no significant differences in change in glycemic measures or insulin resistance between the GH and placebo groups.

CONCLUSION

GH administration reduces hepatic steatosis in adults with overweight/obesity and NAFLD without worsening glycemic measures. The GH/IGF-1 axis may lead to future therapeutic targets for NAFLD.

Increased GH/IGF-I Axis Activity Relates to Lower Hepatic Lipids and Phosphor Metabolism

CONTEXT

Non-alcoholic fatty liver disease (NAFLD) is a leading causes of liver-related morbidity and mortality. While data on acromegaly, a state of chronic growth hormone (GH)/insulin-like growth factor I (IGF-I) excess, suggest an inverse relationship with intrahepatic lipid (IHL) content, less is known about the impact of the GH/IGF-I axis on IHL, lipid composition, and phosphor metabolites in individuals without disorders of GH secretion.

OBJECTIVE

The aim was to investigate the relation between activity of the GH/IGF-I axis and IHL content and phosphor metabolism.

METHODS

We performed a cross-sectional study in 59 otherwise metabolically healthy individuals (30 females), of which 16 met the criteria of NAFLD with IHL of ≥5.6%. The GH/IGF-I axis was evaluated in a fasting state and during an oral glucose tolerance test (OGTT). Insulin sensitivity was estimated by validated indices. IHL, lipid composition (unsaturation index), and phosphate metabolites were analyzed by using 1H/31P magnetic resonance spectroscopy.

RESULTS

In the overall cohort (40.6 ± 15 years; body mass index: 24.5 ± 3 kg/m2; IGF-I: 68.0 ± 17% upper limit of normal), fasting GH (R = -0.31; P = .02), GH during oral glucose tolerance test (R = -0.51; P < .01), and IGF-I (R = -0.28; P = .03) inversely correlated with IHL. GH levels during OGTT were significantly lower in NAFLD than in controls (47.7 [22; 143] ng/mL/min vs 16.8 [7; 32] ng/mL/min; P = .003). GH/IGF-I axis activity correlated with lipid composition and with phosphor metabolites. In multiple regression analysis, the GH/IGF-I axis activity was a strong predictor for IHL and lipid composition independent from insulin sensitivity.

CONCLUSION

GH/IGF-I axis activity impacts hepatic lipid and phosphate metabolism in individuals without disorders in GH secretion. Lower GH axis activity is associated with higher IHL and an unfavorable lipid composition, probably mediated by changes in hepatic energy metabolism.

Growth hormone and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a prevalent cause of liver disease and metabolic comorbidities. Obesity is strongly associated with NAFLD and is also a state of relative deficiency of growth hormone (GH). Evidence supports a role of reduced GH and insulin-like growth factor-1 (IGF-1) in NAFLD pathogenesis. Physiological actions of GH in the liver include suppression of de novo lipogenesis (DNL) and promotion of lipid beta-oxidation, and GH also appears to have anti-inflammatory actions. Physiologic actions of IGF-1 include suppression of inflammatory and fibrogenic pathways important in the evolution from steatosis to steatohepatitis and fibrosis. Rodent models of impaired hepatic GH signaling show the development of steatosis, sometimes accompanied by inflammation, hepatocellular damage, and fibrosis, and these changes are ameliorated by treatment with GH and/or IGF-1. In humans, individuals with GH deficiency and GH resistance demonstrate an increased prevalence of NAFLD compared to controls, with improvement in hepatic lipid, steatohepatitis, and fibrosis following GH replacement. As a corollary, individuals with GH excess demonstrate lower hepatic lipid compared to controls along with increased hepatic lipid following treatment to normalize GH levels. Clinical trials demonstrate that augmentation of GH reduces hepatic lipid content in individuals with NAFLD and may also ameliorate steatohepatitis and fibrosis. Taken together, evidence supports an important role for perturbations in the GH/IGF-1 axis as one of the pathogenic mechanisms of NAFLD and suggests that further study is needed to assess whether augmentation of GH and/or IGF-1 may be a safe and effective therapeutic strategy for NAFLD.

The Advantage of Growth Hormone Alone as an Adjuvant Therapy in Advanced Age and BMI ≥ 24 kg/m2 with In Vitro Fertilization Failure Due to Poor Embryo Quality

This study aimed to assess the effects of GH adjuvant therapy on the cumulative live birth rate in patients with poor embryo quality and to determine the characteristics of patients who are more responsive to GH. A retrospective cohort study was carried out in patients who have suffered from previous IVF failure due to poor embryonic development and underwent IVF with or without a 6-week pretreatment with GH in the subsequent cycle from January 2018 to December 2020. Clinical parameters including the cumulative live birth rate between the (-) GH and (+) GH groups were compared. Multivariate analysis was performed to ascertain associations between clinical parameters and cumulative live birth rate. Upon analysis of the clinical data from 236 IVF cycles, 84 patients received GH and 152 did not receive GH. In frozen embryo transfer cycles, compared with the (-) GH group, the implantation rate and live birth rate were significantly higher in the (+) GH group (p < 0.05). After adjusting for possible confounding factors, GH improved cumulative live birth per oocyte retrieval cycle by 1.96 folds (p = 0.032). Furthermore, when patients were subdivided based on age and BMI, a significant increase in the cumulative live birth rate was found in the (+) GH group of patients between 35 and 42 years old and BMI ≥ 24 kg/m², respectively (p < 0.05). GH may increase the live birth rate in women who experienced IVF failure because of poor embryonic development, particularly in obese patients and women with advanced age.

Ectopic lipid metabolism in anterior pituitary dysfunction

Over the past decades, adapted lifestyle and dietary habits in industrialized countries have led to a progress of obesity and associated metabolic disorders. Concomitant insulin resistance and derangements in lipid metabolism foster the deposition of excess lipids in organs and tissues with limited capacity of physiologic lipid storage. In organs pivotal for systemic metabolic homeostasis, this ectopic lipid content disturbs metabolic action, thereby promotes the progression of metabolic disease, and inherits a risk for cardiometabolic complications. Pituitary hormone syndromes are commonly associated with metabolic diseases. However, the impact on subcutaneous, visceral, and ectopic fat stores between disorders and their underlying hormonal axes is rather different, and the underlying pathophysiological pathways remain largely unknown. Pituitary disorders might influence ectopic lipid deposition indirectly by modulating lipid metabolism and insulin sensitivity, but also directly by organ specific hormonal effects on energy metabolism. In this review, we aim to I) provide information about the impact of pituitary disorders on ectopic fat stores, II) and to present up-to-date knowledge on potential pathophysiological mechanisms of hormone action in ectopic lipid metabolism.

The Role of the GH/IGF1 Axis on the Development of MAFLD in Pediatric Patients with Obesity

The anomalies of the Growth Hormone (GH)/Insulin-like Growth Factor-1 (IGF1) axis are associated with a higher prevalence of Metabolic Associated Fatty Liver Disease (MAFLD) and with a more rapid progression towards fibrosis, cirrhosis, and end-stage liver disease. A total of 191 adolescents with obesity [12−18 years] were consecutively enrolled between January 2014 and December 2020 and underwent liver biopsy to diagnose MAFLD severity. In all patients GH, IGF1 and Insulin-like Growth Factor-Binding Protein 3 (IGFBP3) were measured. Patients with inflammation and ballooning have significantly lower values of GH and IGF1 than those without (GH: 5.4 vs. 7.5 ng/mL; IGF1 245 vs. 284 ng/mL, p < 0.05). GH and IGF1 were also negatively correlated with fibrosis’ degree (r = −0.51, p = 0.001, and r = −0.45, p = 0.001, respectively). Only GH correlated with TNF-a (r = −0.29, p = 0.04) and lobular inflammation (r = −0.36, p = 0.02). At multivariate regression, both GH and IGF1 values, after adjustment for age, sex and BMI, were negatively associated with HOMA-IR but above all with fibrosis (GH→β = −2.3, p = 0.001, IGF1→β = −2.8, p = 0.001). Even in the pediatric population, a reduction of GH input in the liver directly promotes development of de novo hepatic lipogenesis, steatosis, fibrosis and inflammation. The possible role of recombinant GH administration in adolescents with obesity and severe MAFLD deserves to be studied.

Metabolic actions of the growth hormone-insulin growth factor-1 axis and its interaction with the central nervous system

The growth hormone/insulin growth factor-1 axis is a key endocrine system that exerts profound effects on metabolism by its actions on different peripheral tissues but also in the brain. Growth hormone together with insulin growth factor-1 perform metabolic adjustments, including regulation of food intake, energy expenditure, and glycemia. The dysregulation of this hepatic axis leads to different metabolic disorders including obesity, type 2 diabetes or liver disease. In this review, we discuss how the growth hormone/insulin growth factor-1 axis regulates metabolism and its interactions with the central nervous system. Finally, we state our vision for possible therapeutic uses of compounds based in the components of this hepatic axis.

The GH/IGF-1 Axis Is Associated With Intrahepatic Lipid Content and Hepatocellular Damage in Overweight/Obesity

CONTEXT

Obesity is a state of relative growth hormone (GH) deficiency, and GH has been identified as a candidate disease-modifying target in nonalcoholic fatty liver disease (NAFLD) because of its lipolytic and anti-inflammatory properties. However, the GH/IGF-1 axis has not been well characterized in NAFLD.

OBJECTIVE

We aimed to investigate serum GH and IGF-1 levels in relation to intrahepatic lipid content (IHL) and markers of hepatocellular damage and fibrosis in NAFLD.

METHODS

This cross-sectional study included 102 adults (43% women; age 19-67; BMI ≥ 25 kg/m2) without type 2 diabetes. IHL was measured by magnetic resonance spectroscopy; NAFLD was defined by ≥ 5% IHL. Peak-stimulated GH in response to GH releasing hormone and arginine was assessed as was serum IGF-1 (LC/MS).

RESULTS

There was no difference in mean age, BMI, or sex distribution in NAFLD vs controls. Mean (± SD) IHL was higher in NAFLD vs controls (21.8 ± 13.3% vs 2.9 ± 1.1%, P < 0.0001). Mean peak-stimulated GH was lower in NAFLD vs controls (9.0 ± 6.3 vs 15.4 ± 11.2 ng/mL, P = 0.003), including after controlling for age, sex, visceral adipose tissue, and fasting glucose. In a stepwise model, peak-stimulated GH predicted 14.6% of the variability in IHL (P = 0.004). Higher peak-stimulated GH was also associated with lower ALT. Higher serum IGF-1 levels were associated with lower risk of liver fibrosis by Fibrosis-4 scores.

CONCLUSION

Individuals with NAFLD have lower peak-stimulated GH levels but similar IGF-1 levels as compared to controls. Higher peak-stimulated GH levels are associated with lower IHL and less hepatocellular damage. Higher IGF-1 levels are associated with more favorable fibrosis risk scores. These data implicate GH and IGF-1 as potential disease modifiers in the development and progression of NAFLD.

Expression of IGF-1 receptor and GH receptor in hepatic tissue of patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

OBJECTIVE

The GH and IGF-1 axis is a candidate disease-modifying target in nonalcoholic fatty liver disease (NAFLD) given its lipolytic, anti-inflammatory and anti-fibrotic properties. IGF-1 receptor (IGF-1R) and GH receptor (GHR) expression in adult, human hepatic tissue is not well understood across the spectrum of NAFLD severity. Therefore, we sought to investigate hepatic IGF-1R and GHR expression in subjects with NAFLD utilizing gene expression analysis (GEA) and immunohistochemistry (IHC).

DESIGN

GEA (n = 318) and IHC (n = 30) cohorts were identified from the Massachusetts General Hospital NAFLD Tissue Repository. GEA subjects were categorized based on histopathology as normal liver histology (NLH), steatosis only (Steatosis), nonalcoholic steatohepatitis (NASH) without fibrosis (NASH F0), and NASH with fibrosis (NASH F1-4) with GEA by the Nanostring nCounter assay. IHC subjects were matched for age, body mass index (BMI), sex, and diabetic status across three groups (n = 10 each): NLH, Steatosis, and NASH with fibrosis (NASH F1-3). IHC for IGF-1R, IGF-1 and GHR was performed on formalin-fixed, paraffin-embedded hepatic tissue samples.

RESULTS

IGF-1R gene expression did not differ across NAFLD severity while IGF-1 gene expression decreased with increasing NAFLD severity, including when controlled for BMI and age. GHR expression did not differ by severity of NAFLD based on GEA or IHC.

CONCLUSIONS

IGF-1R and GHR expression levels were not significantly different across NAFLD disease severity. However, expression of IGF-1 was lower with increasing severity of NAFLD. Additional research is needed regarding the contribution of the GH/IGF-1 axis to the pathophysiology of NAFLD and NASH.

Growth Hormone and Insulin-Like Growth Factor 1 Regulation of Nonalcoholic Fatty Liver Disease

Patients with obesity have a high prevalence of nonalcoholic fatty liver disease (NAFLD), representing a spectrum of simple steatosis to nonalcoholic steatohepatitis (NASH), without and with fibrosis. Understanding the etiology of NAFLD is clinically relevant since NAFLD is an independent risk factor for diabetes and cardiovascular disease. In addition, NASH predisposes patients to the development of cirrhosis and hepatocellular carcinoma, and NASH cirrhosis represents the fastest growing indication for liver transplantation in the United States. It is appreciated that multiple factors are involved in the development and progression of NAFLD. Growth hormone (GH) and insulin-like growth factor 1 (IGF1) regulate metabolic, immune, and hepatic stellate cell function, and alterations in the production and function of GH is associated with obesity and NAFLD/NASH. Therefore, this review will focus on the potential role of GH and IGF1 in the regulation of hepatic steatosis, inflammation, and fibrosis.

Impact of GH administration on skeletal endpoints in adults with overweight/obesity

OBJECTIVE

Overweight/obesity is associated with relative growth hormone (GH) deficiency and increased fracture risk. We hypothesized that GH administration would improve bone endpoints in individuals with overweight/obesity.

DESIGN

An 18-month, randomized, double-blind, placebo-controlled study of GH, followed by 6-month observation.

METHODS

In this study, 77 adults (53% men), aged 18-65 years, BMI ≥ 25 kg/m2, and BMD T- or Z-score ≤ -1.0 were randomized to daily subcutaneous GH or placebo, targeting IGF1 in the upper quartile of the age-appropriate normal range. Forty-nine completed 18 months. DXA, volumetric quantitative CT, and high-resolution peripheral quantitative CT were performed.

RESULTS

Pre-treatment mean age (48 ± 12 years), BMI (33.1 ± 5.7 kg/m2), and BMD were similar between groups. P1NP, osteocalcin, and CTX increased (P < 0.005) and visceral adipose tissue decreased (P = 0.04) at 18 months in the GH vs placebo group. Hip and radius aBMD, spine and tibial vBMD, tibial cortical thickness, and radial and tibial failure load decreased in the GH vs placebo group (P < 0.05). Between 18 and 24 months (post-treatment observation period), radius aBMD and tibia cortical thickness increased in the GH vs placebo group. At 24 months, there were no differences between the GH and placebo groups in bone density, structure, or strength compared to baseline.

CONCLUSIONS

GH administration for 18 months increased bone turnover in adults with overweight/obesity. It also decreased some measures of BMD, bone microarchitecture, and bone strength, which all returned to pre-treatment levels 6 months post-therapy. Whether GH administration increases BMD with longer treatment duration, or after mineralization of an expanded remodeling space post-treatment, requires further investigation.

Effect of growth hormone therapy on liver enzyme and other cardiometabolic risk factors in boys with obesity and nonalcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has become the most common causes of liver disease in children and adolescents. Although several reports have confirmed the significant correlation between NAFLD and growth hormone (GH)-insulin-like growth factor 1(IGF-1) axis, no study further investigates whether or not recombinant human GH (rhGH) treatment can improve NAFLD in obese children.

METHODS

This study was a randomized, open-label study comprising 44 boys with obesity and NAFLD (11.76 ± 1.67 year) to evaluate the effects of 6 months of rhGH administration for boys with obesity and NAFLD. The subjects were randomized divided into treatment group (subjects with recombinant human GH (rhGH)) and control group for 6 months.

RESULTS

After 6 months, IGF-1 increased significantly during rhGH treatment, in comparison with the control group (582.45 ± 133.00 vs. 359.64 ± 129.00 ng/ml; p < 0.001). A significant reduction in serum alanine aminotransferase(ALT) (15.00 vs. 28.00 U/L; p = 0.001), aspartate aminotransferase(AST) (20.00 vs. 24.50U/L; p = 0.004), gamma glutamyl transferase(GGT) (14.50 vs. 28.50 U/L; p < 0.001) was observed in the GH-treated boys. In addition, the rhGH group showed a significant decrease in C reactive protein (CRP) (1.17 ± 0.76 vs. 2.26 ± 1.43 mg/L) and body mass index standard deviation scores (BMI SDS) (2.28 ± 0.80 vs. 2.71 ± 0.61) than the control group (p = 0.003, p = 0.049 respectively). GH treatment also reduced low density lipoprotein cholesterol (LDL-C) (2.19 ± 0.42 vs. 2.61 ± 0.66 mmol/L; p = 0.016) and increased high density lipoprotein cholesterol (HDL-C) (1.30 vs. 1.15 mmol/L; p = 0.005), and there were no changes in total cholesterol (TC), triglycerides (TG) and uric acid(UA) between the treatment group and the control group.

CONCLUSION

Our findings suggest that 6 months treatment with rhGH may be beneficial for liver enzyme and can improve obesity-related other cardiovascular and metabolic complications in boys with obesity and NAFLD.

Towards Understanding the Direct and Indirect Actions of Growth Hormone in Controlling Hepatocyte Carbohydrate and Lipid Metabolism

Growth hormone (GH) is critical for achieving normal structural growth. In addition, GH plays an important role in regulating metabolic function. GH acts through its GH receptor (GHR) to modulate the production and function of insulin-like growth factor 1 (IGF1) and insulin. GH, IGF1, and insulin act on multiple tissues to coordinate metabolic control in a context-specific manner. This review will specifically focus on our current understanding of the direct and indirect actions of GH to control liver (hepatocyte) carbohydrate and lipid metabolism in the context of normal fasting (sleep) and feeding (wake) cycles and in response to prolonged nutrient deprivation and excess. Caveats and challenges related to the model systems used and areas that require further investigation towards a clearer understanding of the role GH plays in metabolic health and disease are discussed.

Quantitative Imaging of Body Composition

Body composition refers to the amount and distribution of lean tissue, adipose tissue, and bone in the human body. Lean tissue primarily consists of skeletal muscle; adipose tissue comprises mostly abdominal visceral adipose tissue and abdominal and nonabdominal subcutaneous adipose tissue. Hepatocellular and myocellular lipids are also fat pools with important metabolic implications. Importantly, body composition reflects generalized processes such as increased adiposity in obesity and age-related loss of muscle mass known as sarcopenia.In recent years, body composition has been extensively studied quantitatively to predict overall health. Multiple imaging methods have allowed precise estimates of tissue types and provided insights showing the relationship of body composition to varied pathologic conditions. In this review article, we discuss different imaging methods used to quantify body composition and describe important anatomical locations where target tissues can be measured.

Insulin and Growth Hormone Balance: Implications for Obesity

Disruption of endocrine hormonal balance (i.e., increased levels of insulin, and reduced levels of growth hormone, GH) often occurs in pre-obesity and obesity. Using distinct intracellular signaling pathways to control cell and body metabolism, GH and insulin also regulate each other's secretion to maintain overall metabolic homeostasis. Therefore, a comprehensive understanding of insulin and GH balance is essential for understanding endocrine hormonal contributions to energy storage and utilization. In this review we summarize the actions of, and interactions between, insulin and GH at the cellular level, and highlight the association between the insulin/GH ratio and energy metabolism, as well as fat accumulation. Use of the [insulin]:[GH] ratio as a biomarker for predicting the development of obesity is proposed.

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.

HIV and antiretroviral therapy-related fat alterations

Early in the HIV epidemic, lipodystrophy, characterized by subcutaneous fat loss (lipoatrophy), with or without central fat accumulation (lipohypertrophy), was recognized as a frequent condition among people living with HIV (PLWH) receiving combination antiretroviral therapy. The subsequent identification of thymidine analogue nucleoside reverse transcriptase inhibitors as the cause of lipoatrophy led to the development of newer antiretroviral agents; however, studies have demonstrated continued abnormalities in fat and/or lipid storage in PLWH treated with newer drugs (including integrase inhibitor-based regimens), with fat gain due to restoration to health in antiretroviral therapy-naive PLWH, which is compounded by the rising rates of obesity. The mechanisms of fat alterations in PLWH are complex, multifactorial and not fully understood, although they are known to result in part from the direct effects of HIV proteins and antiretroviral agents on adipocyte health, genetic factors, increased microbial translocation, changes in the adaptive immune milieu after infection, increased tissue inflammation and accelerated fibrosis. Management includes classical lifestyle alterations with a role for pharmacological therapies and surgery in some patients. Continued fat alterations in PLWH will have an important effect on lifespan, healthspan and quality of life as patients age worldwide, highlighting the need to investigate the critical uncertainties regarding pathophysiology, risk factors and management.

Association between muscle mass and insulin sensitivity independent of detrimental adipose depots in young adults with overweight/obesity

BACKGROUND/OBJECTIVE

Less muscle mass has been associated with greater insulin resistance, but whether the association is independent of deleterious adipose depots in young adults with overweight/obesity who are at high risk for type 2 diabetes (T2DM) but are otherwise metabolically healthy is not known. The objective of this study was to determine whether muscle mass is independently associated with insulin sensitivity (IS) in young adults with overweight/obesity.

SUBJECTS/METHODS

Cross-sectional Clinical Research Center study of 132 adults, 21-45yo, BMI ≥ 25 kg/m² and metabolically healthy without T2DM. Primary independent variable: percent ideal appendicular lean mass (ALM) calculated as measured ALM divided by predicted ALM for age, weight, and height, calculated using validated NHANES data-based equation. Primary dependent variable: IS by Matsuda index.

RESULTS

Mean age was 34.3 ± 6.8 years, and mean BMI 35.8 ± 5.8 kg/m² (mean ± SD). Individuals in the highest % ideal ALM tertile had mean IS 45% higher than the lowest tertile [6.94 ± 0.85 vs 4.80 ± 0.56 (mean ± SEM), p = 0.008] (sex interaction p = 0.003). Men in the highest % ideal ALM tertile had mean IS twice the lowest tertile (5.47 ± 0.68 vs 2.68 ± 0.34, p = 0.001), which remained significant controlling for visceral/subcutaneous and intermuscular adipose tissue, and intramyocellular and intrahepatic lipids (p = 0.03). The association was not significant in women.

CONCLUSIONS

Muscle mass is associated with IS independent of detrimental adipose depots in young men with overweight/obesity, at risk for T2DM but currently metabolically healthy. Muscle mass relative to sex, age, weight, and height-specific norms may be used to ascertain individual T2DM risk associated with low muscle mass.

Effect of One-Year Growth Hormone Therapy on Cardiometabolic Risk Factors in Boys with Obesity

It has been recognized that people with obesity are more likely to have low growth hormone secretion. Recent studies have also confirmed that the abnormalities of the growth hormone/insulin-like growth factor 1 axis were associated with cardiovascular complications in people with obesity. However, little is known about whether recombinant human growth hormone therapy could improve cardiovascular and metabolic risks in obese children. This study aims to evaluate the effect of one-year growth hormone therapy on obesity-related comorbidities and to assess the safety in Chinese boys with obesity. Eighteen boys with obesity were treated with recombinant human growth hormone for one year. Anthropometric measurements, endocrine testing, and cardiovascular risk markers were performed in all obese boys in baseline, and follow-up visits were performed at 3 months, 6 months, 9 months, and one year, respectively. After one year of recombinant human growth hormone treatment, the body mass index standard deviation scores decreased (P < 0.001) and insulin-like growth factor 1 levels increased (P < 0.001). GH treatment also reduced low density lipoprotein cholesterol (P < 0.001), total cholesterol (P < 0.001), triglycerides (P=0.042), and alanine aminotransferase (P=0.027) when compared with the baseline. One-year of recombinant human growth hormone treatment could improve cardiometabolic risk markers, without adverse effects on glucose homeostasis in boys with obesity.

Osteonecrosis of Femoral Head is Associated with Congenital Multiple Pituitary Hormone Deficiency: Report of Three Cases and Literature Review

Objective: Pituitary hormones are critical for bone development and maturation. It is currently unknown whether congenital multiple pituitary hormone deficiency (CMPHD) is associated with osteonecrosis of femoral head (ONFH). Methods: Clinical presentations and hormonal profiles of three patients with CMPHD and ONFH were retrospectively described. The incidence of ONFH in this population was studied. Results: (1) Congenital hypopituitarism was diagnosed in three patients. Femoral epiphyseal fusion in these patients was markedly delayed, and they had very low bone mineral density. (2) Hip pain, which is the main presentation of ONFH, occurred at the age of 20-30 years. ONFH induced by excessive glucocorticoids was excluded. (3) The estimated incidence of ONFH was approximately 694:100,000. Conclusions: CMPHD, especially a lack of growth and sex hormones, may contribute to ONFH.

Increased pain and inflammatory sensitivity in growth hormone-releasing hormone (GHRH) knockout mice

Growth hormone (GH) and GH-releasing hormone (GHRH), in addition to metabolic and endocrine effects, play a role in the modulation of pain and inflammation. We aimed to elucidate the consequences of GHRH deficiency on acute nociceptive stimulation and on both acute and chronic inflammatory stimuli in a mouse model of GH deficiency. Mice with generalized ablation of the GHRH gene (GHRH knock out, GHRHKO, -/-) were compared to wild type (GHRH +/+) mice. Responsiveness to acute nociceptive stimulation and to acute inflammatory stimulation was evaluated by conventional hot plate apparatus and formalin test, respectively. We also evaluated responsiveness to colonic inflammation induced both in vivo, after dextran sodium sulfate (DSS) treatment, or ex vivo, by incubating colon segments with bacterial lipopolysaccaride (LPS). Macroscopical and histological examinations were performed, prostaglandin (PG) E₂ and 8-iso-PGF_2α levels and cyclooxigenase (COX)-2 and tumor necrosis factor (TNF)-α gene expression were measured. Compared to controls, -/- mice showed decreased response latency during the hot plate test, and increased licking/biting time in formalin test, particularly in the second phase of inflammation. DSS treated -/- mice showed a significant increase of colonic inflammation compared to controls. Moreover DSS treatment increased PGE₂ and 8-iso-PGF_2α levels, along with COX-2 and TNF-α gene expression more markedly in colon specimens of -/- mice compared to controls. LPS-induced PGE₂ and 8-iso-PGF_2α production from colonic segments incubated ex vivo was also increased in -/- mice. Generalized GHRH gene ablation increases sensitivity to thermal pain and both acute and persistent inflammatory stimuli in male mice.

Growth hormone controls lipolysis by regulation of FSP27 expression

Growth hormone (GH) has long been known to stimulate lipolysis and insulin resistance; however, the molecular mechanisms underlying these effects are unknown. In the present study, we demonstrate that GH acutely induces lipolysis in cultured adipocytes. This effect is secondary to the reduced expression of a negative regulator of lipolysis, fat-specific protein 27 (FSP27; aka Cidec) at both the mRNA and protein levels. These effects are mimicked in vivo as transgenic overexpression of GH leads to a reduction of FSP27 expression. Mechanistically, we show GH modulation of FSP27 expression is mediated through activation of both MEK/ERK- and STAT5-dependent intracellular signaling. These two molecular pathways interact to differentially manipulate peroxisome proliferator-activated receptor gamma activity (PPARγ) on the FSP27 promoter. Furthermore, overexpression of FSP27 is sufficient to fully suppress GH-induced lipolysis and insulin resistance in cultured adipocytes. Taken together, these data decipher a molecular mechanism by which GH acutely regulates lipolysis and insulin resistance in adipocytes.

Adult-Onset Hepatocyte GH Resistance Promotes NASH in Male Mice, Without Severe Systemic Metabolic Dysfunction

Nonalcoholic fatty liver disease (NAFLD), which includes nonalcoholic steatohepatitis (NASH), is associated with reduced GH input/signaling, and GH therapy is effective in the reduction/resolution of NAFLD/NASH in selected patient populations. Our laboratory has focused on isolating the direct vs indirect effects of GH in preventing NAFLD/NASH. We reported that chow-fed, adult-onset, hepatocyte-specific, GH receptor knockdown (aHepGHRkd) mice rapidly (within 7 days) develop steatosis associated with increased hepatic de novo lipogenesis (DNL), independent of changes in systemic metabolic function. In this study, we report that 6 months after induction of aHepGHRkd early signs of NASH develop, which include hepatocyte ballooning, inflammation, signs of mild fibrosis, and elevated plasma alanine aminotransferase. These changes occur in the presence of enhanced systemic lipid utilization, without evidence of white adipose tissue lipolysis, indicating that the liver injury that develops after aHepGHRkd is due to hepatocyte-specific loss of GH signaling and not due to secondary defects in systemic metabolic function. Specifically, enhanced hepatic DNL is sustained with age in aHepGHRkd mice, associated with increased hepatic markers of lipid uptake/re-esterification. Because hepatic DNL is a hallmark of NAFLD/NASH, these studies suggest that enhancing hepatocyte GH signaling could represent an effective therapeutic target to reduce DNL and treat NASH.

Sex differences in body composition and association with cardiometabolic risk

Background

Body composition differs between men and women, with women having proportionally more fat mass and men more muscle mass. Although men and women are both susceptible to obesity, health consequences differ between the sexes. The purpose of our study was to assess sex differences in body composition using anatomic and functional imaging techniques, and its relationship to cardiometabolic risk markers in subjects with overweight/obesity.

Methods

After written informed consent, we prospectively recruited 208 subjects with overweight/obesity who were otherwise healthy (94 men, 114 women, age 37 ± 10 years, BMI 35 ± 6 kg/m²). Subjects underwent dual-energy X-ray absorptiometry (DXA) and computed tomography (CT) for fat and muscle mass, proton MR spectroscopy (1H-MRS) for intrahepatic (IHL) and intramyocellular lipids (IMCL), an oral glucose tolerance test, serum insulin, lipids, and inflammatory markers. Men and women were compared by Wilcoxon signed rank test. Linear correlation and multivariate analyses between body composition and cardiometabolic risk markers were performed.

Results

Women and men were of similar mean age and BMI (p ≥ 0.2). Women had higher %fat mass, extremity fat, and lower lean mass compared to men (p ≤ 0.0005). However, men had higher visceral adipose tissue (VAT) and IMCL and higher age-and BMI-adjusted IHL (p < 0.05). At similar age and BMI, men had a more detrimental cardiometabolic risk profile compared to women (p < 0.01). However, VAT in women, and IMCL in men, were more strongly associated with cardiometabolic risk markers, while more lower extremity fat was associated with a more favorable cardiometabolic profile in women compared to men (p ≤ 0.03).

Conclusions

Although the male pattern of fat distribution is associated with a more detrimental cardiometabolic risk profile compared to women of similar age and BMI, VAT is more strongly associated with cardiometabolic risk markers in women, while IMCL are more detrimental in men. Lower extremity fat is relatively protective, in women more than in men. This suggests that detailed anatomic and functional imaging, rather than BMI, provides a more complete understanding of metabolic risk associated with sex differences in fat distribution.

The effect of growth hormone on bioactive IGF in overweight/obese women

OBJECTIVE

Overweight/obesity is characterized by decreased growth hormone (GH) secretion whereas circulating IGF-I levels are less severely reduced. Yet, the activity of the circulating IGF-system appears to be normal in overweight/obese subjects, as estimated by the ability of serum to activate the IGF-I receptor in vitro (bioactive IGF). We hypothesized that preservation of bioactive IGF in overweight/obese women is regulated by an insulin-mediated suppression of IGF-binding protein-1 (IGFBP-1) and IGFBP-2, and by suppression of IGFBP-3, mediated by low GH. We additionally hypothesized that increases in bioactive IGF would drive changes in body composition with low-dose GH administration.

DESIGN

Cross-sectional analysis and 3-month interim analysis of a 6-month randomized, placebo-controlled study of GH administration in 50 overweight/obese women without diabetes mellitus. Bioactive IGF (kinase receptor activation assay) and body composition (DXA) were measured.

RESULTS

Prior to treatment, IGFBP-3 (r = -0.33, p = 0.02), but neither IGFBP-1 nor IGFBP-2, associated inversely with bioactive IGF. In multivariate analysis, lower IGFBP-3 correlated with lower peak stimulated GH (r = 0.45, p = 0.05) and higher insulin sensitivity (r = -0.74, p = 0.003). GH administration resulted in an increase in mean serum IGF-I concentrations (144 ± 56 to 269 ± 66 μg/L, p < 0.0001) and bioactive IGF (1.29 ± 0.39 to 2.60 ± 1.12 μg/L, p < 0.0001). The treatment-related increase in bioactive IGF, but not total IGF-I concentration, predicted an increase in lean mass (r = 0.31, p = 0.03) and decrease in total adipose tissue/BMI (r = -0.43, p = 0.003).

CONCLUSIONS

Our data suggest that in overweight/obesity, insulin sensitivity and GH have opposing effects on IGF bioactivity through effects on IGFBP-3. Furthermore, increases in bioactive IGF, rather than IGF-I concentration, predicted GH administration-related body composition changes.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00131378.

Effects of recombinant human growth hormone administration on cardiovascular risk factors in obese children with relative growth hormone deficiency

Background

Based on the sample of obese children with relative growth hormone deficiency (GHD), the objective of our study was to determine the effects of rhGH treatment on cardiovascular risk factors, including body mass index (BMI), lipid levels and glucose metabolism index.

Methods

A total of 43 obese children with relative GHD were included in our final analysis. The obese subjects were divided into two groups: recombinant human growth hormone (rhGH) treatment group and untreated control group.

Results

After 6 months, subjects in the rhGH treatment group had significant reductions in BMI standard deviation scores (SDS) compared with controls (2.32 ± 0.85 vs. 2.80 ± 0.61; P = 0.041), and Insulin-like growth factor 1(IGF-1) level increased during rhGH treatment, in comparison with the control group (702.91 ± 246.03 vs. 348.30 ± 131.93 ng/mL, P < 0.001). GH treatment reduced low density lipoprotein cholesterol (LDL-C) (2.20 ± 0.45 vs. 2.63 ± 0.76 mmol/L, P = 0.027), aspartate aminotransferase (AST) (21.26 ± 5.72 vs. 32.30 ± 17.68 mmol/L, P = 0.006) as well as alanine aminotransferase (ALT) (16.70 ± 6.72 vs. 45.20 ± 46.62 mmol/L, P = 0.002), and increased high density lipoprotein cholesterol (HDL-C) (1.45 ± 0.40 vs. 1.19 ± 0.23 mmol/L, P = 0.016) levels compared with the control group.

Conclusion

RhGH treatment for 6 months on obese children with relative GHD reduces BMI SDS, stabilize IGF-1 levels, and exerts beneficial effects on blood lipid profiles and live enzyme compared with untreated control group. Moreover, GH administration has no significant effects on increased insulin resistance and no adversely effect on glucose homeostasis.

Hepatic lipid metabolism and non-alcoholic fatty liver disease in aging

Aging is associated with dysregulation of glucose and lipid metabolism. Various factors that contribute to the dysregulation include both modifiable (e.g. obesity, insulin resistance) and non-modifiable risk factors (age-associated physiologic changes). Although there is no linear relationship between aging and prevalence of non-alcoholic fatty liver disease, current data strongly suggests that advanced age leads to more severe histological changes and poorer clinical outcomes. Hepatic lipid accumulation could lead to significant hepatic and systemic consequences including steatohepatitis, cirrhosis, impairment of systemic glucose metabolism and metabolic syndrome, thereby contributing to age-related diseases. Insulin, leptin and adiponectin are key regulators of the various physiologic processes that regulate hepatic lipid metabolism. Recent advances have expanded our understanding in this field, highlighting the role of novel mediators such as FGF 21, and mitochondria derived peptides. In this review, we will summarize the mediators of hepatic lipid metabolism and how they are altered in aging.

Body Composition and Ectopic Lipid Changes With Biochemical Control of Acromegaly

CONTEXT

Acromegaly is characterized by growth hormone (GH) and insulinlike growth factor-1 (IGF-1) hypersecretion, and GH and IGF-1 play important roles in regulating body composition and glucose homeostasis.

OBJECTIVE

The purpose of our study was to investigate body composition including ectopic lipids, measures of glucose homeostasis, and gonadal steroids in patients with active acromegaly compared with age-, body mass index (BMI)-, and sex-matched controls and to determine changes in these parameters after biochemical control of acromegaly.

DESIGN

Cross-sectional study of 20 patients with active acromegaly and 20 healthy matched controls. Prospective study of 16 patients before and after biochemical control of acromegaly.

MAIN OUTCOME MEASURES

Body composition including ectopic lipids by magnetic resonance imaging/proton magnetic resonance spectroscopy; measures of glucose homeostasis by an oral glucose tolerance test; gonadal steroids.

RESULTS

Patients with active acromegaly had lower mean intrahepatic lipid (IHL) and higher mean fasting insulin and insulin area under the curve (AUC) values than controls. Men with acromegaly had lower mean total testosterone, sex hormone-binding globulin, and estradiol values than male controls. After therapy, homeostasis model assessment of insulin resistance, fasting insulin level, and insulin AUC decreased despite an increase in IHL and abdominal and thigh adipose tissues and a decrease in muscle mass.

CONCLUSIONS

Patients with acromegaly were characterized by insulin resistance and hyperinsulinemia but lower IHL compared with age-, BMI-, and sex-matched healthy controls. Biochemical control of acromegaly improved insulin resistance but led to a less favorable anthropometric phenotype with increased IHL and abdominal adiposity and decreased muscle mass.

GH administration decreases subcutaneous abdominal adipocyte size in men with abdominal obesity

OBJECTIVE

To investigate the effects of short-term GH administration on abdominal subcutaneous adipocyte size and CT attenuation in men with abdominal obesity.

DESIGN

6-week, randomized, double-blind, placebo-controlled study of GH (starting dose 2μg/kg/d) vs placebo of 15 abdominally obese men (mean age: 34±6years; mean BMI: 37.7±6.1kg/m², mean IGF-1 SDS: -1.9±0.5) who underwent abdominal subcutaneous adipose tissue (SAT) aspirations to determine adipocyte size, CTs for body composition and measures of glucose tolerance at baseline and 6weeks. GH dosing was titrated to target IGF-1 levels in the upper normal age-appropriate range.

RESULTS

GH administration decreased subcutaneous abdominal adipocyte size compared to placebo. Adipocyte size was positively associated with 120-min glucose and HOMA-IR and inversely associated with peak-stimulated GH and CT attenuation. CT attenuation of SAT was inversely associated with 120-min glucose and HOMA-IR and increased following GH administration.

CONCLUSION

In men with abdominal obesity, subcutaneous abdominal adipocyte size is positively associated with measures of impaired glucose tolerance and administration of GH at doses that raise IGF-1 levels within the normal range, decreases abdominal subcutaneous adipocyte size, suggesting that GH administration improves the health of adipose tissue. Clinical trials number: NCT00131378.

The Role of the Growth Hormone/Insulin-Like Growth Factor System in Visceral Adiposity

There is substantial evidence that the growth hormone (GH)/insulin-like growth factor (IGF) system is involved in the pathophysiology of obesity. Both GH and IGF-I have direct effects on adipocyte proliferation and differentiation, and this system is involved in the cross-talk between adipose tissue, liver, and pituitary. Transgenic animal models have been of importance in identifying mechanisms underlying these interactions. It emerges that this system has key roles in visceral adiposity, and there is a rationale for targeting this system in the treatment of visceral obesity associated with GH deficiency, metabolic syndrome, and lipodystrophies. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Short- and Long-Term Reproducibility of Intrahepatic Lipid Quantification by 1H-MR Spectroscopy and CT in Obesity

OBJECTIVE

This study aimed to assess short- and long-term reproducibility of intrahepatic lipid (IHL) quantification by proton magnetic resonance spectroscopy (H-MRS) and computed tomography (CT).

METHODS

Sixteen obese subjects underwent H-MRS using a single-voxel point-resolved single-voxel spectroscopy sequence at 3 T and noncontrast single-slice CT of the liver. Measurements were repeated after 6 weeks and 6 months. Clinical parameters (weight, activity, serum lipids) were collected. Short-term (baseline to 6 weeks) and long-term (baseline to 6 months) reproducibility of IHL was assessed by coefficient of variance (CV), SD, and intraclass correlation coefficient (ICC).

RESULTS

Short-term reproducibility and long-term reproducibility of H-MRS were as follows: CV, 5.9% to 18.8%; SD, 0.7 to 1.9; and ICC, 0.998 to 0.995 (95% confidence interval, 0.942-0.999). Short-term reproducibility and long-term reproducibility of CT were as follows: CV, 4.4% to 14.2%; SD, 2.4 to 8.7; and ICC, 0.766 to 0.982 (95% confidence interval, 0.271-0.994). There was no significant change in clinical parameters (P > 0.3).

CONCLUSIONS

Proton magnetic resonance spectroscopy and CT are reproducible methods for short- and long-term quantification of IHL content. Our results can guide sample size calculations for interventional and longitudinal studies.

The Association Between IGF-1 Levels and the Histologic Severity of Nonalcoholic Fatty Liver Disease

Objectives:

The mechanisms responsible for the development of nonalcoholic fatty liver disease (NAFLD) and progression to nonalcoholic steatohepatitis (NASH) are incompletely understood. Growing evidence suggests that growth hormone (GH) and insulin-like growth factor-1 (IGF-1) may have roles in the development and progression of NAFLD. We hypothesized that lower serum IGF-1 levels would be associated with increased liver fat accumulation, inflammation, and fibrosis in a group of meticulously phenotyped obese subjects with liver biopsies.

Methods:

A retrospective, cross-sectional study was performed at Massachusetts General Hospital, Boston, MA, USA and St. Mary's Hospital, Richmond, VA, USA. Liver biopsies were performed in 142 subjects during NAFLD work-up or bariatric surgery and were graded by a single, blinded pathologist. Main outcome measures included liver histology and serum IGF-1.

Results:

Mean age was 52±10 years and body mass index (BMI) was 43±9 kg/m². Mean serum IGF-1 was lower in subjects with lobular inflammation (112±47 vs. 136±57 ng/ml, P=0.01), hepatocyte ballooning (115±48 vs. 135±57 ng/ml, P=0.05), higher fibrosis stage (stage 2–4 vs. 0–1; 96±40 vs. 125±51 ng/ml, P=0.005), and NASH (109±45 vs. 136±57 ng/ml, P=0.002). All results remained significant after controlling for age, BMI, and a diagnosis of diabetes, and all but hepatocyte ballooning (trend, P=0.06) remained significant after excluding individuals with cirrhosis. Steatosis was not significantly associated with mean serum IGF-1 levels.

Conclusions:

Low serum IGF-1 levels are associated with increased histologic severity of NAFLD when rigorously controlled for age, BMI, the presence of diabetes, and after the exclusion of subjects with cirrhosis. Further investigation is warranted to determine the differential effects of GH and IGF-1 on the development and progression of NAFLD, which could further elucidate pathophysiology and identify therapeutic targets.

Growth Hormone Control of Hepatic Lipid Metabolism

In humans, low levels of growth hormone (GH) and its mediator, IGF-1, associate with hepatic lipid accumulation. In mice, congenital liver-specific ablation of the GH receptor (GHR) results in reductions in circulating IGF-1 and hepatic steatosis, associated with systemic insulin resistance. Due to the intricate relationship between GH and IGF-1, the relative contribution of each hormone to the development of hepatic steatosis is unclear. Our goal was to dissect the mechanisms by which hepatic GH resistance leads to steatosis and overall insulin resistance, independent of IGF-1. We have generated a combined mouse model with liver-specific ablation of GHR in which we restored liver IGF-1 expression via the hepatic IGF-1 transgene. We found that liver GHR ablation leads to increases in lipid uptake, de novo lipogenesis, hyperinsulinemia, and hyperglycemia accompanied with severe insulin resistance and increased body adiposity and serum lipids. Restoration of IGF-1 improved overall insulin sensitivity and lipid profile in serum and reduced body adiposity, but was insufficient to protect against steatosis-induced hepatic inflammation or oxidative stress. We conclude that the impaired metabolism in states of GH resistance results from direct actions of GH on lipid uptake and de novo lipogenesis, whereas its actions on extrahepatic tissues are mediated by IGF-1.

What Can We Learn from Interventions That Change Fat Distribution?

Epidemiological studies have illustrated convincingly that fat distribution is associated with cardiometabolic risk. Fat deposition preferentially in the lower body, commonly seen in premenopausal women, is associated with lower risk, while central obesity in men and postmenopausal women is associated with higher risk. Studies of the physiology and the tissue and cellular characteristics of different adipose tissue depots, visceral and abdominal, gluteal, and femoral subcutaneous, corroborate this idea. In this report, we chose to focus on interventions-surgical, hormonal, lifestyle, and pharmacological-that directly or indirectly affect fat distribution, seeking further evidence for its pathophysiological significance.

Growth hormone receptor expression in human gluteal versus abdominal subcutaneous adipose tissue: Association with body shape

OBJECTIVE

Growth hormone (GH) administration reduces abdominal, but not lower body, fat mass. To gain insight into the underlying mechanisms, this study examined the expression of the GH receptor (GHR) and some of its targets in abdominal and gluteal adipose tissue.

METHODS

GHR and GH targets in the lipolytic pathway were assessed (quantitative PCR/Western blotting) in adipose aspirates from premenopausal women [n = 15, age 26.9 ± 6.1 years, body mass index (BMI) 28.0 ± 6.8 kg/m(2) ] and men (n = 28, age 29.2 ± 7.0 years, BMI 26.9 ± 3.7 kg/m(2) ).

RESULTS

GHR mRNA expression was lower in the gluteal depot when compared with the abdominal depot (P = 0.01). Abdominal GHR correlated negatively with age and BMI, whereas gluteal GHR was associated with lower waist-to-hip ratio (WHR), that is, pear shape. In both sites, GHR mRNA correlated strongly with genes important for the regulation of lipolysis: adipose tissue triglyceride lipase (ATGL), hormone-sensitive lipase, perilipin, and CIDEA (all P < 0.001), independently of BMI, WHR, age, and sex. GHR protein was lower in the gluteal fat when compared with the abdominal fat (P = 0.03) and correlated with ATGL protein in the gluteal depot (P < 0.001).

CONCLUSIONS

GHR levels correlate with levels of lipases and lipid droplet-associated proteins crucial for lipolysis. Thus, higher GHR expression in the abdominal depot when compared with the gluteal depot may underlie the in vivo effect of GH to specifically reduce abdominal adipose tissue mass.

Association between adiposity and cognitive function in young men: Hormonal mechanisms

OBJECTIVE

To determine the association between adiposity, hormones, and cognition in young men with abdominal obesity.

METHODS

In this cross-sectional observational study, 53 nondiabetic men with abdominal obesity (mean body mass index, 37.3 kg/m(2) ; age, 22-45 years) and normal intelligence underwent detailed measures of body composition, hormonal profiles, and cognition. Age- and education-adjusted performance in five cognitive domains was examined.

RESULTS

Total fat percentage was negatively associated with visuospatial skills (P = 0.002) and visual memory (P = 0.012). Insulin resistance (homeostatic model assessment of insulin resistance) was also negatively associated with these domains (P = 0.05 and trend, P = 0.06, respectively). Total testosterone levels were negatively associated with executive function and verbal learning and memory (P = 0.04 for each), but free testosterone was not. Sex hormone-binding globulin (SHBG) was also inversely associated with performance in these domains (P = 0.015 and trend, P = 0.09, respectively). In a stepwise regression model including percentage fat, homeostatic model assessment of insulin resistance, SHBG, and free testosterone, SHBG was the only variable selected for executive function (P = 0.05) and showed a trend for verbal learning and memory (P = 0.09).

CONCLUSIONS

Adiposity and insulin resistance were associated with worse function in visual domains. An unexpected negative association is reported between SHBG and cognitive measures, which seemed to be independent of free testosterone levels.

Short- and long-term reproducibility of marrow adipose tissue quantification by 1H-MR spectroscopy

OBJECTIVE

To assess short- and long-term reproducibility of marrow adipose tissue (MAT) quantification by 1H-MR spectroscopy.

MATERIALS AND METHODS

Our study was IRB-approved and HIPAA compliant. Written informed consent was obtained. We studied 20 overweight/obese but otherwise healthy subjects (12 female, 8 male) with a mean age of 37 ± 6 years. All subjects underwent proton magnetic resonance spectroscopy (1H-MRS) of the fourth lumbar vertebral body using a single-voxel point-resolved spatially localized spectroscopy sequence without water suppression at 3 T. Measurements were repeated after 6 weeks and 6 months using identical scanning protocols. The following clinical parameters were collected, weight, BMI, exercise status, and trabecular bone mineral density (BMD), by quantitative computed tomography. Short- (baseline, 6 weeks) and long-term (baseline, 6 months) reproducibility of MAT was assessed by the coefficient of variance (CV), standard deviation (SD), and interclass correlation coefficients (ICCs). Short- and long-term changes in clinical parameters were assessed by paired t-test.

RESULTS

For short-term reproducibility between baseline and 6-week scans, the CV was 9.9 %, SD was 0.08, and ICC was 0.97 (95 % CI 0.94-099). For long-term reproducibility between baseline and 6-month scans, the CV was 12.0 %, SD was 0.10, and ICC was 0.95 (95 % CI 0.88 to 0.98). There was no significant short- or long-term change in clinical parameters (weight, BMI, exercise status, BMD) (p > 0.2).

CONCLUSION

1H-MRS is a reproducible method for short- and long-term quantification of MAT. Our results can guide sample size calculations for interventional and longitudinal studies.

Effects of growth hormone-releasing hormone on visceral fat, metabolic, and cardiovascular indices in human studies

Increased visceral adipose tissue (VAT) is associated with reductions in endogenous GH secretion, possibly as a result of hyperinsulinemia, increased circulating free fatty acid, increased somatostatin tone, and reduced ghrelin. Reduced GH may, in turn, further exacerbate visceral fat accumulation because of decreased hormone-sensitive lipolysis in this depot. Data from multiple populations demonstrate that both reduced GH and increased VAT appear to contribute independently to dyslipidemia, increased systemic inflammation, and increased cardiovascular risk. The reductions in GH in states of visceral adiposity are characterized by reduced basal and pulsatile GH secretion with intact pulse frequency. Treatment with GH-releasing hormone (GHRH) provides a means to reverse these abnormalities, increasing endogenous basal and pulsatile GH secretion without altering pulse frequency. This review describes data from HIV-infected individuals and individuals with general obesity showing that treatment with GHRH significantly reduces visceral fat, ameliorates dyslipidemia, and reduces markers of cardiovascular risk. Further research is needed regarding the long-term efficacy and safety of this treatment modality.

Relationship between serum IGF-1 and skeletal muscle IGF-1 mRNA expression to phosphocreatine recovery after exercise in obese men with reduced GH

CONTEXT

GH and IGF-1 are believed to be physiological regulators of skeletal muscle mitochondria.

OBJECTIVE

The objective of this study was to examine the relationship between GH/IGF-1 and skeletal muscle mitochondria in obese subjects with reduced GH secretion in more detail.

DESIGN

Fifteen abdominally obese men with reduced GH secretion were treated for 12 weeks with recombinant human GH. Subjects underwent (31)P-magnetic resonance spectroscopy to assess phosphocreatine (PCr) recovery as an in vivo measure of skeletal muscle mitochondrial function and percutaneous muscle biopsies to assess mRNA expression of IGF-1 and mitochondrial-related genes at baseline and 12 weeks.

RESULTS

At baseline, skeletal muscle IGF-1 mRNA expression was significantly associated with PCr recovery (r = 0.79; P = .01) and nuclear respiratory factor-1 (r = 0.87; P = .001), mitochondrial transcription factor A (r = 0.86; P = .001), peroxisome proliferator-activated receptor (PPAR)γ (r = 0.72; P = .02), and PPARα (r = 0.75; P = .01) mRNA expression, and trended to an association with PPARγ coactivator 1-α (r = 0.59; P = .07) mRNA expression. However, serum IGF-1 concentration was not associated with PCr recovery or any mitochondrial gene expression (all P > .10). Administration of recombinant human GH increased both serum IGF-1 (change, 218 ± 29 μg/L; P < .0001) and IGF-1 mRNA in muscle (fold change, 2.1 ± 0.3; P = .002). Increases in serum IGF-1 were associated with improvements in total body fat (r = -0.53; P = .04), trunk fat (r = -0.55; P = .03), and lean mass (r = 0.58; P = .02), but not with PCr recovery (P > .10). Conversely, increase in muscle IGF-1 mRNA was associated with improvements in PCr recovery (r = 0.74; P = .02), but not with body composition parameters (P > .10).

CONCLUSION

These data demonstrate a novel association of skeletal muscle mitochondria with muscle IGF-1 mRNA expression, but independent of serum IGF-1 concentrations.

The Insulin-Like Growth Factor System in Obesity, Insulin Resistance and Type 2 Diabetes Mellitus

The insulin-like growth factor (IGF) system, acting in concert with other hormone axes, is important in normal metabolism. In obesity, the hyperinsulinaemia that accompanies peripheral insulin resistance leads to reduced growth hormone (GH) secretion, while total IGF-I levels are relatively unchanged due to increased hepatic GH sensitivity. IGF-binding protein (IGFBP)-1 levels are suppressed in relation to the increase in insulin levels in obesity and low levels predict the development of type 2 diabetes several years later. Visceral adiposity and hepatic steatosis, along with a chronic inflammation, contribute to the IGF system phenotype in individuals with metabolic syndrome and type 2 diabetes mellitus, including changes in the normal inverse relationship between IGFBP-1 and insulin, with IGFBP-1 concentrations that are inappropriately normal or elevated. The IGF system is implicated in the vascular and other complications of these disorders and is therefore a potential therapeutic target.

Whole-body insulin sensitivity rather than body-mass-index determines fasting and post-glucose-load growth hormone concentrations

Background

Obese, non-acromegalic persons show lower growth hormone (GH) concentrations at fasting and reduced GH nadir during an oral glucose tolerance test (OGTT). However, this finding has never been studied with regard to whole-body insulin-sensitivity as a possible regulator.

Methods

In this retrospective analysis, non-acromegalic (NonACRO, n = 161) and acromegalic (ACRO, n = 35), non-diabetic subjects were subdivided into insulin-sensitive (IS) and –resistant (IR) groups according to the Clamp-like Index (CLIX)-threshold of 5 mg·kg⁻¹·min⁻¹ from the OGTT.

Results

Non-acromegalic IS (CLIX: 8.8±0.4 mg·kg⁻¹·min⁻¹) persons with similar age and sex distribution, but lower (p<0.001) body-mass-index (BMI = 25±0 kg/m², 84% females, 56±1 years) had 59% and 70%, respectively, higher (p<0.03) fasting GH and OGTT GH area under the curve concentrations than IR (CLIX: 3.5±0.1 mg·kg⁻¹·min⁻¹, p<0.001) subjects (BMI = 29±1 kg/m², 73% females, 58±1 years). When comparing on average overweight non-acromegalic IS and IR with similar anthropometry (IS: BMI: 27±0 kg/m², 82% females, 58±2 years; IR: BMI: 27±0 kg/m², 71% females, 60±1 years), but different CLIX (IS: 8.7±0.9 vs. IR: 3.8±0.1 mg·kg⁻¹·min⁻¹, p<0.001), the results remained almost the same. In addition, when adjusted for OGTT-mediated glucose rise, GH fall was less pronounced in IR. In contrast, in acromegalic subjects, no difference was found between IS and IR patients with regard to fasting and post-glucose-load GH concentrations.

Conclusions

Circulating GH concentrations at fasting and during the OGTT are lower in non-acromegalic insulin-resistant subjects. This study seems the first to demonstrate that insulin sensitivity rather than body-mass modulates fasting and post-glucose-load GH concentrations in non-diabetic non–acromegalic subjects.

Effects of recombinant human growth hormone (rhGH) administration on body composition and cardiovascular risk factors in obese adolescent girls

Background

Obesity is associated with a relative deficiency of growth hormone, which is predictive of greater visceral fat and markers of cardiovascular risk. The study’s purpose was to use recombinant human growth hormone (rhGH) as a physiologic probe to assess the effects of reversing obesity-related GH deficiency on body composition, cardiovascular risk markers, and insulin resistance.

Methods

22 obese girls 13–21 years old were followed for a randomized 6-month trial of rhGH vs. placebo/no treatment. At baseline and 6-months, DXA was performed for body composition, MRI to measure visceral, subcutaneous and total adipose tissue (VAT, SAT and TAT), and fasting blood drawn for IGF-1, inflammatory cardiovascular risk markers [soluble intercellular adhesion molecule (sICAM), high sensitivity CRP], lipids and HbA1C. An oral glucose tolerance test (OGTT) was performed. Twelve girls completed the 6-month visit. Baseline and mean 6-month change were compared between the groups using the Student t-test and the relationship between variables was determined through multiple regression analysis.

Results

After 6-months, the rhGH group maintained IGF-1 levels, and had decreases in total cholesterol (p = 0.03), sICAM-1 (p = 0.04) and HbA1C (p = 0.03) compared to placebo/no treatment. The rhGH group trended towards greater decreases in LDL and 2-hour OGTT glucose. Glucose tolerance did not worsen with rhGH administration.

Conclusions

Administering rhGH in small doses is able to stabilize IGF-1 levels in obesity. We have also shown that rhGH administration leads to an improvement in some markers of cardiovacular risk with without adversely affecting glucose tolerance.

Trial registration

Clinical Trial Registration Number: NCT01169103.

Overweight/Obese adults with pituitary disorders require lower peak growth hormone cutoff values on glucagon stimulation testing to avoid overdiagnosis of growth hormone deficiency

CONTEXT

Obesity is associated with diminished GH secretion, which may result in the overdiagnosis of adult GH deficiency (GHD) in overweight/obese pituitary patients. However, there are no body mass index (BMI)-specific peak GH cutoffs for the glucagon stimulation test (GST), the favored dynamic test for assessing adult GHD in the United States.

OBJECTIVE

The objective of the study was to determine a peak GH cutoff level for the diagnosis of adult GHD in overweight/obese individuals using the GST.

DESIGN

This was a retrospective, cross-sectional study.

SETTING

The study was conducted at Massachusetts General Hospital and Oregon Health and Science University.

METHODS

A total of 108 subjects with a BMI ≥ 25 kg/m(2) were studied: healthy controls (n = 47), subjects with total pituitary deficiency (TPD) (n = 20, ≥ 3 non-GH pituitary hormone deficiencies), and subjects with partial pituitary deficiency (PPD) (n = 41, 1-2 non-GH pituitary hormone deficiencies).

INTERVENTION

The intervention consisted of a standard 4-hour GST.

MAIN OUTCOME MEASURES

The main outcome measure was peak GH level on GST.

RESULTS

Using the standard peak GH cutoff of 3 ng/mL, 95% of TPD cases (19 of 20), 80% of PPD (33 of 41), and 45% of controls (21 of 47) were classified as GHD. In receiver-operator characteristic curve analysis (controls vs TPD), a peak GH value of 0.94 ng/mL provided the greatest sensitivity (90%) and specificity (94%). Using a peak GH cutoff of 1 ng/mL, 6% of controls (3 of 47), 59% of PPDs (24 of 41), and 90% of TPDs (18 of 20) were classified as GHD. BMI (R = -0.35, P = .02) and visceral adipose tissue (R = -0.32, P = .03) negatively correlated with peak GH levels in controls.

CONCLUSION

A large proportion of healthy overweight/obese individuals (45%) failed the GST using the standard 3 ng/mL GH cutoff. Overweight/obese pituitary patients are at risk of being misclassified as GHD using this cutoff level. A 1-ng/mL GH cutoff may reduce the overdiagnosis of adult GHD in overweight/obese patients.

Insulin-Like Growth Factor-I, Insulin-Like Growth factor Binding Protein-3 and Blood Hemoglobin Concentration in an Elderly Population

BACKGROUND

Insulin-like growth factor-I (IGF-I) serum level decreases with age, and this decrease may underlie hemoglobin (Hb) decrease. The objective of the study was to assess the relationship between IGF-I and insulin-like growth factor binding protein-3 (IGFBP-3) serum levels and Hb, after adjustment especially for major nutritional factors in an elderly population because IGF-I system depends on nutritional state, often impaired in the elderly.

METHODS

Hemoglobin concentration was tested for 672 participants evaluated during an outpatient geriatric assessment. IGF-I and IGFBP-3 serum levels were assessed by Enzyme Linked Immunosorbent Assay. The molar ratio of IGF-I/IGFBP-3 that reflects the bioavailable IGF-I was calculated. Levels of IGF-I and IGFBP-3 were plotted against quartiles of Hb. Final linear models for IGF-I, IGFBP-3 and ratio molar included factors that could modify the Hb level.

RESULTS

Mean age (SD) of the sample was 78.0 (8.5) years old and 32% were men. After adjustment for age and sex, IGF-I serum level, IGFBP-3 serum level and molar ratio significantly increased with increasing quartiles of Hb. After adjustment for age, gender, diabetes, albumin, pre-albumin, renal function, total cholesterol, angiotensin converting enzyme inhibitors and angiotensin II receptor blockers consumption, C-Reactive Protein, Hb was significantly associated and with IGF-I level (p = .002) and molar ratio (p = .02).

CONCLUSIONS

IGF-I serum level and IGF-I/IGFBP-3 molar ratio were associated with Hb in an elderly population, independently of nutritional biological parameters. Thus, the association between the IGF-I system and Hb merits further investigation to determine whether interventions that modulate circulating IGF-I or IGF-I/BP3 ratio might preserve Hb in the elderly.

No evidence of ectopic lipid accumulation in the pathophysiology of the acromegalic cardiomyopathy

CONTEXT

PATIENTS with acromegaly frequently display disturbances of glucose and lipid metabolism, which might contribute to their increased cardiovascular risk. Because insulin resistance and increased lipolysis have been linked to ectopic lipid deposition, altered lipid accumulation in the liver and the myocardium might contribute to metabolic and cardiac complications in these patients.

OBJECTIVE

The aim of this study was to investigate myocardial (MYCL) and hepatic lipid content (HCL), insulin sensitivity, and cardiac function in active acromegaly and after control of GH excess through transsphenoidal surgery.

PATIENTS

Ten patients with newly diagnosed acromegaly (ACRO_active) were compared with 12 healthy controls (CON), matched for age, body mass index, and gender. In seven patients GH excess was controlled, and they were compared with their active state.

METHODS

MYCL and HCL were assessed by (1)H-magnetic resonance spectroscopy, pericardial fat and cardiac function by (1)H-magnetic resonance imaging, and insulin sensitivity and secretion by an oral glucose tolerance test.

RESULTS

Although MYCL tended to be lower, HCL was significantly lower in ACRO_active compared with CON (HCL: 1.2% ± 1.2% vs 4.3% ± 3.5% of (1)H-magnetic resonance spectroscopy signal, P < .02). Parameters of systolic function and hypertrophy were significantly increased in ACRO_active compared with CON, as were insulin secretion and resistance. After the control of GH excess, HCL and MYCL remained unchanged, but pericardial fat was increased in the patients in whom GH excess was controlled (from 11.6 ± 5.5 to 14.7 ± 6.2 cm(2), P = .02).

CONCLUSION

Acromegaly represents a unique condition characterized by low myocardial and hepatic lipid content despite decreased insulin sensitivity, hyperinsulinemia, and hyperglycemia. Hence, ectopic lipid accumulation does not appear to contribute to cardiac morbidity, and increased lipid oxidation might counteract ectopic lipid accumulation in GH excess.

Insulin-like growth factors (IGF-I and -II): new actors in the development of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease worldwide, affecting 20-30% of adults and 3-10% of children in Western countries. The pathogenesis of NAFLD is considered to be multifactorial and factors such as insulin resistance, intrahepatic fat accumulation, oxidative stress, mitochondrial alterations, and stellate cell activation appear to substantially contribute to the development and progression of the disease. In this Editorial, we highlight some evidence suggesting a close link between NAFLD and growth hormone (GH)-IGF (insulin-like growth factor) axis.

The effects of tesamorelin on phosphocreatine recovery in obese subjects with reduced GH

CONTEXT

Few studies have assessed the relationship between GH and mitochondrial function.

OBJECTIVE

The objective of this study was to determine the effects of improving IGF-I using a GHRH analog, tesamorelin, on mitochondrial function assessed by phosphocreatine (PCr) recovery using (31)P magnetic resonance spectroscopy in obese adults with reduced GH.

DESIGN

A total of 39 obese men and women with reduced GH secretion as determined by GHRH-arginine stimulation tests underwent magnetic resonance spectroscopy as part of a 12-month, double-blind, randomized, placebo-controlled trial comparing tesamorelin vs placebo. PCr recovery after submaximal exercise was assessed at baseline and at 12 months.

RESULTS

At baseline, there were no differences in age, sex, race/ethnicity, and GH or PCr parameters between tesamorelin and placebo. After 12 months, tesamorelin treatment led to a significantly greater increase in IGF-I than did placebo treatment (change, 102.9±31.8 μg/L vs 22.8±8.9 μg/L, tesamorelin vs placebo; P=.02). We demonstrated a significant positive relationship between increases in IGF-I and improvements in PCr recovery represented as ViPCr (R=0.56; P=.01). The association between IGF-I and PCr recovery was even stronger among subjects treated with tesamorelin only (ViPCr: R=0.71; P=.03). This association remained significant after controlling for age, sex, race, ethnicity, and parameters of body composition and insulin sensitivity (all P<.05).

CONCLUSIONS

Increases in IGF-I from 12 months of treatment with tesamorelin were significantly associated with improvements in PCr recovery parameters in obese men and women with reduced GH secretion, suggestive of improvements in mitochondrial function.