Pegvisomant increases intra-abdominal fat in patients with acromegaly: a pilot study

The acromegaly lipodystrophy

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are essential to normal growth, metabolism, and body composition, but in acromegaly, excesses of these hormones strikingly alter them. In recent years, the use of modern methodologies to assess body composition in patients with acromegaly has revealed novel aspects of the acromegaly phenotype. In particular, acromegaly presents a unique pattern of body composition changes in the setting of insulin resistance that we propose herein to be considered an acromegaly-specific lipodystrophy. The lipodystrophy, initiated by a distinctive GH-driven adipose tissue dysregulation, features insulin resistance in the setting of reduced visceral adipose tissue (VAT) mass and intra-hepatic lipid (IHL) but with lipid redistribution, resulting in ectopic lipid deposition in muscle. With recovery of the lipodystrophy, adipose tissue mass, especially that of VAT and IHL, rises, but insulin resistance is lessened. Abnormalities of adipose tissue adipokines may play a role in the disordered adipose tissue metabolism and insulin resistance of the lipodystrophy. The orexigenic hormone ghrelin and peptide Agouti-related peptide may also be affected by active acromegaly as well as variably by acromegaly therapies, which may contribute to the lipodystrophy. Understanding the pathophysiology of the lipodystrophy and how acromegaly therapies differentially reverse its features may be important to optimizing the long-term outcome for patients with this disease. This perspective describes evidence in support of this acromegaly lipodystrophy model and its relevance to acromegaly pathophysiology and the treatment of patients with acromegaly.

HOMA-IR in acromegaly: a systematic review and meta-analysis

PURPOSE

This review is aimed at examining whether the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) is higher in Caucasian, adult, treatment-naïve patients with acromegaly (ACRO) than in the reference population independently of diabetes presence and to evaluate the impact of treatment [surgery and somatostatin analogues (SSAs)] on its assessment.

METHODS

We systematically reviewed in PubMed and Web of Science from July 1985 to December 2019, registered with the code number CRD42020148737. The inclusion criteria comprised studies conducted in Caucasian adult treatment-naïve patients with active ACRO in whom HOMA-IR or basal insulin and glucose were reported. Three reviewers screened eligible publications, extracted the outcomes, and assessed the risk of biases.

RESULTS

Of 118 originally selected studies, 15 met the inclusion criteria. HOMA-IR was higher in ACRO than the reference population, with mean difference and (95% confidence intervals) of 2.04 (0.65-3.44), even in ACRO patients without diabetes, 1.89 (1.06-2.73). HOMA-IR significantly decreased after treatment with either surgery or SSAs - 2.53 (- 3.24- - 1.81) and - 2.30 (- 3.05- - 1.56); respectively. However, the reduction of HOMA-IR due to SSAs did not improve basal glucose.

CONCLUSION

HOMA-IR in treatment-naïve ACRO patients is higher than in the reference population, even in patients without diabetes. This finding, confirms that insulin resistance is an early event in ACRO. Our results also suggest that HOMA-IR is not an adequate tool for assessing insulin resistance in those patients treated with SSAs.

Body Composition Changes with Long-term Pegvisomant Therapy of Acromegaly

Context

In active acromegaly, the lipolytic and insulin antagonistic effects of growth hormone (GH) excess alter adipose tissue (AT) deposition, reduce body fat, and increase insulin resistance. This pattern reverses with surgical therapy. Pegvisomant treats acromegaly by blocking GH receptor (GHR) signal transduction and lowering insulin-like growth factor 1 (IGF-1) levels. The long-term effects of GHR antagonist treatment of acromegaly on body composition have not been studied.

Methods

We prospectively studied 21 patients with active acromegaly who were starting pegvisomant. Body composition was examined by whole body magnetic resonance imaging, proton magnetic resonance spectroscopy of liver and muscle and dual-energy x-ray absorptiometry, and endocrine and metabolic markers were measured before and serially during 1.0 to 13.4 years of pegvisomant therapy. The data of patients with acromegaly were compared with predicted and to matched controls.

Results

Mass of visceral AT (VAT) increased to a peak of 187% (1.56-229%) (P < .001) and subcutaneous AT (SAT) to 109% (–17% to 57%) (P = .04) of baseline. These remained persistently and stably increased, but did not differ from predicted during long-term pegvisomant therapy. Intrahepatic lipid rose from 1.75% to 3.04 % (P = .04). Although lean tissue mass decreased significantly, skeletal muscle (SM) did not change. IGF-1 levels normalized, and homeostasis model assessment insulin resistance and HbA1C were lowered.

Conclusion

Long-term pegvisomant therapy is accompanied by increases in VAT and SAT mass that do not differ from predicted, stable SM mass and improvements in glucose metabolism. Long-term pegvisomant therapy does not produce a GH deficiency-like pattern of body composition change.

Pegvisomant Improves Glucose Metabolism in Acromegaly: A Meta-Analysis of Prospective Interventional Studies

INTRODUCTION

Pegvisomant (PEG) in monotherapy or combined with somatostatin analogs (SSAs) is used to control acromegaly, improving metabolism. However, the metabolic changes induced by PEG have not been systematically reviewed.

OBJECTIVE

To address the following questions: does PEG or the combination of PEG and SSAs affect fasting plasma glucose (FPG), glycosylated Hb (HbA1c), glucose load (2-hour oral glucose tolerance test), insulin levels [fasting plasma insulin (FPI)], homeostatic model assessment of insulin resistance (HOMA-I), homeostatic model assessment of β-cell function, lipid profile, or body mass index? Are the effects disease-related or drug-related?

DATA SOURCES

Indexed databases up to January 2019.

STUDY SELECTION

Prospective interventional trials reporting glycometabolic outcomes under PEG or PEG plus SSAs for a minimum of 6 months.

DATA EXTRACTION

Three reviewers screened eligible publications (7248), three others extracted the outcomes, and all assessed the risk of biases.

DATA SYNTHESIS

Thirteen studies were included in the PEG and 5 in the PEG plus SSAs analysis (overall 550 subjects). PEG significantly decreased FPG [effect size (ES) -0.80 mmol/L (95% CI, -1.06 to -0.55); P = 0.000], HbA1c [ES -0.43% (95% CI, -0.56 to -0.31); P = 0.000], FPI [ES -5.31 mU/L (95% CI, -10.23 to -0.39); P = 0.034], and HOMA-I [ES -0.61 (95% CI, -1.17 to -0.04); P = 0.034]. Effects on FPG and FPI were not correlated to IGF-1 changes. The addition of PEG to SSAs mitigated the effects of SSAs on metabolism, producing an overall neutral effect.

CONCLUSIONS

Independently of disease control, PEG in monotherapy or combined with SSAs seems to improve glucose metabolism, reducing FPG, HbA1c, FPI, and HOMA-I.

Changes in metabolic parameters and cardiovascular risk factors after therapeutic control of acromegaly vary with the treatment modality. Data from the Bicêtre cohort, and review of the literature

CONTEXT

Untreated acromegaly is associated with increased morbidity and mortality due to malignant, cardiovascular, and cerebrovascular disorders. Effective treatment of acromegaly reduces excess mortality, but its impact on cardiovascular risk factors and metabolic parameters are poorly documented.

AIM

We analyzed changes in cardiovascular risk factors and metabolic parameters in patients receiving various treatment modalities.

PATIENTS AND METHODS

We retrospectively studied 96 patients with acromegaly, both at diagnosis and after IGF-I normalization following surgery alone (n = 51) or medical therapy with first generation somatostatin analogues (SSA, n = 23), or pegvisomant (n = 22). Duration of follow-up was 77 (42-161) months, 75 (42-112) months, and 62 (31-93) months, in patients treated with surgery alone, SSA, and pegvisomant, respectively. In all the cases except four, patients treated medically had underwent previous unsuccessful surgery.

RESULTS

IGF-I normalization was associated with increased body weight, decreased systolic blood pressure (SBP) in hypertensive patients, decreased fasting plasma glucose (FPG) and HOMA-IR and HOMA-B levels, increased HDL cholesterol (HDLc); whereas, LDL cholesterol (LDLc) was not significantly different. Plasma PCSK9 levels were unchanged in patients with available values. Cardiovascular and metabolic changes varied with the treatment modality: surgery, but not pegvisomant, had a beneficial effect on SBP; FPG decreased after surgery but increased after SSA; the decline in HOMA-IR was only significant after surgery; pegvisomant significantly increased LDLc and total cholesterol; whereas SA increased HDLc and had no effect on LDLc levels.

CONCLUSION

Treatments used to normalize IGF-I levels in patients with acromegaly could have differential effects on cardiovascular risk factors and metabolic parameters.

Runx2 overexpression compromises bone quality in acromegalic patients

Acromegalic patients, characterized by excessive secretion of GH and IGF-1, show a high fracture risk but bone mineral density is a poor predictor for bone fractures in these patients. The effects of an excess of GH/IGF1 on skeleton as well as on osteogenic progenitors, i.e. mesenchymal stem cells, have not been investigated in these patients. We aimed to elucidate the skeletal conditions of acromegalic patients by means of bone microarchitecture analysis and evaluation of MSCs osteogenic commitment. In particular, we performed histomorphometric analyses, and we quantified the expression levels of the osteogenic transcription factor RUNX2 in circulating MSCs. Our results showed an abnormal microarchitecture and demonstrated that bone impairment in acromegalic patients is associated with the upregulation of RUNX2 expression. Furthermore, osteoblastic activity was significantly reduced in patients under pharmacological treatment, compared to untreated patients. In conclusion, this study demonstrates the key role of RUNX2 gene overexpression in causing bone impairment in acromegalic patients. It also suggests a therapeutic approach for the improvement of bone quality, focused on the osteoblastic lineage rather than the inhibition of osteoclastic activity.

Pegvisomant in acromegaly: an update

BACKGROUND

In 2007, we published an opinion document to review the role of pegvisomant (PEG) in the treatment of acromegaly. Since then, new evidence emerged on the biochemical and clinical effects of PEG and on its long-term efficacy and safety.

AIM

We here reviewed the emerging aspects of the use of PEG in clinical practice in the light of the most recent literature.

RESULTS

The clinical use of PEG is still suboptimal, considering that it remains the most powerful tool to control IGF-I in acromegaly allowing to obtain, with a pharmacological treatment, the most important clinical effects in terms of signs and symptoms, quality of life and comorbidities. The number of patients with acromegaly exposed to PEG worldwide has become quite elevated and the prolonged follow-up allows now to deal quite satisfactorily with many clinical issues including major safety issues, such as the concerns about possible tumour (re)growth under PEG. The positive or neutral impact of PEG on glucose metabolism has been highlighted, and the clinical experience, although limited, with sleep apnoea and pregnancy has been reviewed. Finally, the current concept of somatostatin receptor ligands (SRL) resistance has been addressed, in order to better define the acromegaly patients to whom the PEG option may be offered.

CONCLUSIONS

PEG increasingly appears to be an effective and safe medical option for many patients not controlled by SRL but its use still needs to be optimized.

The Possible Role of mRNA Expression Changes of GH/IGF-1/Insulin Axis Components in Subcutaneous Adipose Tissue in Metabolic Disturbances of Patients With Acromegaly

We explored the effect of chronically elevated circulating levels of growth hormone (GH)/insulin-like-growth-factor-1 (IGF-1) on mRNA expression of GH/IGF-1/insulin axis components and p85alpha subunit of phosphoinositide-3-kinase (p85alpha) in subcutaneous adipose tissue (SCAT) of patients with active acromegaly and compared these findings with healthy control subjects in order to find its possible relationships with insulin resistance and body composition changes. Acromegaly group had significantly decreased percentage of truncal and whole body fat and increased homeostasis model assessment-insulin resistance (HOMA-IR). In SCAT, patients with acromegaly had significantly increased IGF-1 and IGF-binding protein-3 (IGFBP-3) expression that both positively correlated with serum GH. P85alpha expression in SCAT did not differ from control group. IGF-1 and IGFBP-3 expression in SCAT were not independently associated with percentage of truncal and whole body fat or with HOMA-IR while IGFBP-3 expression in SCAT was an independent predictor of insulin receptor as well as of p85alpha expression in SCAT. Our data suggest that GH overproduction in acromegaly group increases IGF-1 and IGFBP-3 expression in SCAT while it does not affect SCAT p85alpha expression. Increased IGF-1 or IGFBP-3 in SCAT of acromegaly group do not appear to contribute to systemic differences in insulin sensitivity but may have local regulatory effects in SCAT of patients with acromegaly.

The Impact of Adipose Tissue on Insulin Resistance in Acromegaly

Adipose tissue (AT) is recognized as key contributor to the systemic insulin resistance and overt diabetes seen in metabolic syndrome. Acromegaly is a disease characterized by excessive secretion of growth hormone (GH) and insulin-like growth factor I (IGF-I). GH is known both for its action on AT and for its detrimental effect on glucose metabolism and insulin signaling. In active acromegaly, while body fat deports are diminished, insulin resistance is increased. Early studies have demonstrated defects in insulin action, both at the hepatic and extrahepatic (i.e., muscle and fat) levels, in active disease. This review discusses recent data suggesting that AT inflammation, altered AT distribution, and impaired adipogenesis are potential mechanisms contributing to systemic insulin resistance in acromegaly.

Long-term effects of pegvisomant on comorbidities in patients with acromegaly: a retrospective single-center study

CONTEXT

The effect of pegvisomant on IGF1 levels in patients with acromegaly is well documented, but little is known of its long-term impact on comorbidity.

AIM

The aim of this retrospective study was to evaluate the effects of long-term pegvisomant therapy on cardiorespiratory and metabolic comorbidity in patients with acromegaly.

PATIENTS AND METHODS

We analyzed the long-term (up to 10 years) effect of pegvisomant therapy given alone (n=19, 45%) or in addition to somatostatin analogues and/or cabergoline (n=23, 55%) on echocardiographic, polysomnographic and metabolic parameters in respectively 42, 12 and 26 patients with acromegaly followed in Bicêtre hospital.

RESULTS

At the first cardiac evaluation, 20±16 months after pegvisomant introduction, IGF1 levels normalized in 29 (69%) of the 42 patients. The left ventricular ejection fraction (LVEF) improved significantly in patients whose basal LVEF was ≤60% and decreased in those whose LVEF was >70%. The left ventricular mass index (LVMi) decreased from 123±25 to 101±21 g/m(2) (P<0.05) in the 17 patients with a basal LVMi higher than the median (91 g/m(2)), while it remained stable in the other patients. Pegvisomant reduced the apnoea-hypopnea index and cured obstructive sleep apnea (OSA) in four of the eight patients concerned. Long-term follow-up of 22 patients showed continuing improvements in cardiac parameters. The BMI and LDL cholesterol level increased minimally during pegvisomant therapy, and other lipid parameters were not modified.

CONCLUSIONS

Long-term pegvisomant therapy not only normalizes IGF1 in a large proportion of patients but also improves cardiac and respiratory comorbidity.

Adipose Tissue Redistribution and Ectopic Lipid Deposition in Active Acromegaly and Effects of Surgical Treatment

CONTEXT

GH and IGF-I have important roles in the maintenance of substrate metabolism and body composition. However, when in excess in acromegaly, the lipolytic and insulin antagonistic effects of GH may alter adipose tissue (AT) deposition.

OBJECTIVES

The purpose of this study was to examine the effect of surgery for acromegaly on AT distribution and ectopic lipid deposition in liver and muscle.

DESIGN

This was a prospective study before and up to 2 years after pituitary surgery.

SETTING

The setting was an academic pituitary center.

PATIENTS

Participants were 23 patients with newly diagnosed, untreated acromegaly.

MAIN OUTCOME MEASURES

We determined visceral (VAT), subcutaneous (SAT), and intermuscular adipose tissue (IMAT), and skeletal muscle compartments by total-body magnetic resonance imaging, intrahepatic and intramyocellular lipid by proton magnetic resonance spectroscopy, and serum endocrine, metabolic, and cardiovascular risk markers.

RESULTS

VAT and SAT masses were lower than predicted in active acromegaly, but increased after surgery in male and female subjects along with lowering of GH, IGF-I, and insulin resistance. VAT and SAT increased to a greater extent in men than in women. Skeletal muscle mass decreased in men. IMAT was higher in active acromegaly and decreased in women after surgery. Intrahepatic lipid increased, but intramyocellular lipid did not change after surgery.

CONCLUSIONS

Acromegaly may present a unique type of lipodystrophy characterized by reduced storage of AT in central depots and a shift of excess lipid to IMAT. After surgery, this pattern partially reverses, but differentially in men and women. These findings have implications for understanding the role of GH in body composition and metabolic risk in acromegaly and other clinical settings of GH use.

Escape and lipodystrophy in acromegaly during pegvisomant therapy, a retrospective multicentre Spanish study

BACKGROUND

Pegvisomant is an effective treatment for acromegaly.

OBJECTIVE

To investigate escape (loss of biochemical control in patients previously controlled) and lipodystrophy in acromegalic patients treated with pegvisomant and to evaluate possible associations with clinical features.

PATIENTS AND METHODS

Multicentre retrospective study involving 19 Spanish centres.

RESULTS

Ninety-seven patients were included (59% women, mean age at diagnosis 42 ± 13 years, 80% macroadenomas); mean follow-up on pegvisomant was 5 ± 2·5 years, and 89 (92%) achieved normal IGF-1. Escape was reported in 30/89 (34%) of responders, after a mean treatment duration of 25 ± 21 months. The mean initial dose of pegvisomant was 11 ± 5 mg/day, and mean dose at escape was 14 ± 7 mg/day. Most patients (26/30, 87%) achieved control with dose increase (57%), additional medical treatment (3%) or both (27%). Mean new dose that controlled IGF-1 after escape was 20 ± 7 mg/day. Treatments associated were somatostatin analogues (SSA in 47%), cabergoline (CAB in 47%) and both (6%). Lipodystrophy was observed in 15 patients (13 females), mild in six, moderate in six, severe in three and persistent in four. Among patients with lipodystrophy, three escaped and three were nonresponders to pegvisomant. Four patients discontinued the drug, and four had dose reductions because of lipodystrophy. It tended to be more frequent in females (P = 0·06) and in patients treated with triple association SSA+CAB+PEG (P = 0·018). No relationship between escape and clinical variables was found, except prior CAB (P = 0·04) and metformin treatment (0·02) and grade of lipodystrophy (P = 0·02).

CONCLUSIONS

A significant proportion of patients treated with pegvisomant escaped (34%); however, the majority (87%) was easily controlled with either dose increase, further medical treatment or both. Lipodystrophy developed in 15%, mostly females, and influenced the response to treatment.

Therapy of acromegalic patients exacerbated by concomitant type 2 diabetes requires higher pegvisomant doses to normalise IGF1 levels

OBJECTIVE

Acromegaly is associated with an increased prevalence of glucose metabolism disorders. Clinically confirmed diabetes mellitus is observed in approximately one quarter of all patients with acromegaly and is known to have a worse prognosis in these patients.

DESIGN

Of 514 acromegalic patients treated with pegvisomant and recorded in the German Cohort of ACROSTUDY, 147 had concomitant diabetes mellitus. We analysed these patients in an observational study and compared patients with and without concomitant diabetes.

RESULTS

Under treatment with pegvisomant, patients with diabetes mellitus rarely achieved normalisation (64% in the diabetic cohort vs 75% in the non-diabetic cohort, P=0.04) for IGF1. Diabetic patients normalised for IGF1 required higher pegvisomant doses (18.9 vs 15.5 mg pegvisomant/day, P<0.01). Furthermore, those diabetic patients requiring insulin therapy showed a tendency towards requiring even higher pegvisomant doses to normalise IGF1 values than diabetic patients receiving only oral treatment (22.8 vs 17.2 mg pegvisomant/day, P=0.11).

CONCLUSIONS

Hence, notable interdependences between the acromegaly, the glucose metabolism of predisposed patients and their treatment with pegvisomant were observed. Our data support recent findings suggesting that intra-portal insulin levels determine the GH receptor expression in the liver underlined by the fact that patients with concomitant diabetes mellitus, in particular those receiving insulin therapy, require higher pegvisomant doses to normalise IGF1. It is therefore important to analyse various therapy modalities to find out whether they influence the associated diabetes mellitus and/or whether the presence of diabetes mellitus influences the treatment results of an acromegaly therapy.

Dissecting adipose tissue lipolysis: molecular regulation and implications for metabolic disease

Lipolysis is the process by which triglycerides (TGs) are hydrolyzed to free fatty acids (FFAs) and glycerol. In adipocytes, this is achieved by sequential action of adipose TG lipase (ATGL), hormone-sensitive lipase (HSL), and monoglyceride lipase. The activity in the lipolytic pathway is tightly regulated by hormonal and nutritional factors. Under conditions of negative energy balance such as fasting and exercise, stimulation of lipolysis results in a profound increase in FFA release from adipose tissue (AT). This response is crucial in order to provide the organism with a sufficient supply of substrate for oxidative metabolism. However, failure to efficiently suppress lipolysis when FFA demands are low can have serious metabolic consequences and is believed to be a key mechanism in the development of type 2 diabetes in obesity. As the discovery of ATGL in 2004, substantial progress has been made in the delineation of the remarkable complexity of the regulatory network controlling adipocyte lipolysis. Notably, regulatory mechanisms have been identified on multiple levels of the lipolytic pathway, including gene transcription and translation, post-translational modifications, intracellular localization, protein-protein interactions, and protein stability/degradation. Here, we provide an overview of the recent advances in the field of AT lipolysis with particular focus on the molecular regulation of the two main lipases, ATGL and HSL, and the intracellular and extracellular signals affecting their activity.

Short-term administration of pegvisomant improves hepatic insulin sensitivity and reduces soleus muscle intramyocellular lipid content in young adults with type 1 diabetes

CONTEXT

Data on the metabolic effects of GH derived from studies using GH suppression by pharmacological agents may not reflect selective actions.

OBJECTIVE

The purpose of this study was to evaluate the effects of GH antagonism on glucose and lipid metabolism using pegvisomant, a selective GH receptor antagonist in patients with type 1 diabetes (T1D).

DESIGN AND PARTICIPANTS

In a randomized, placebo-controlled, crossover study, 10 young adults with T1D were evaluated at baseline and after 4 weeks of treatment with either 10 mg of pegvisomant or placebo. The assessments included an overnight euglycemic steady state followed by a hyperinsulinemic euglycemic clamp and used glucose and glycerol cold stable isotopes.

OUTCOME MEASURES

Hepatic and peripheral insulin sensitivity (IS), lipid turnover, and intramyocellular lipid (IMCL) were measured.

RESULTS

Compared with placebo, pegvisomant treatment resulted in lower IGF-I levels (P < .001). During the overnight steady state, insulin requirements for euglycemia (P = .019), insulin levels (P = .008), and glucose production rates (Ra) (P = .033) were reduced. During the clamp study, glucose infusion rates (P = .031) increased and glucose Ra (P = .015) decreased whereas glucose disposal rates were unchanged. Free fatty acid levels were similar during the steady state but were lower during the clamp (P = .040) after pegvisomant. Soleus muscle IMCL decreased after treatment (P = .024); however, no change in tibialis anterior muscle was observed.

CONCLUSIONS

The study demonstrates that GH antagonism in T1D results in improved hepatic insulin sensitivity. Lack of consistent changes in free fatty acid levels may suggest a direct effect of GH on IS. Unchanged peripheral IS despite reductions in IMCL indicate that GH-induced alterations in IMCL may not be causally linked to glucose metabolism.

Construction of suppressor of cytokine signaling 2 (SOCS2) adenoviral overexpression vector and its impact on growth-hormone-induced lipolysis in swine primary adipocytes

We investigated the effect of overexpression suppressor of cytokine signaling 2 (SOCS2) on lipolysis in swine primary adipocytes (pAd) induced by growth hormone (GH). We constructed pAd-SOCS2 adenoviral overexpression vectors to infect HEK293 cells for virus packaging and propagation. Cultured swine primary adipocytes were infected with virus particles; after 48 h the infected adipocytes were treated with 500 ng GH/mL in the growth medium. Lipometabolism-related gene expressions were detected at 0, 0.25, 0.5, 1, 2, and 4 h, by measuring mRNA and protein levels. The pAd-SOCS2 overexpression vector was successfully constructed and the concentration of titrated virus was 1.2 x 10(9) PFU/mL. We found that virus infection significantly increased SOCS2 mRNA and protein levels in swine primary adipocytes. Overexpression of SOCS2 significantly inhibited the increase in fatty acid synthase, adipose triglyceride lipase mRNA, and protein expression at 0.5 h. However, after 0.5 h, this inhibition was not significant. We concluded that overexpression of SOCS2 inhibited the increase in lipolysis induced by GH in swine primary adipocytes; this could provide a basis for studies of lipometabolism.

Fat content in liver and skeletal muscle changes in a reciprocal manner in patients with acromegaly during combination therapy with a somatostatin analog and a GH receptor antagonist: a randomized clinical trial

CONTEXT

Pegvisomant is a GH antagonist, which is used for the treatment of acromegalic patients. It effectively blocks the hepatic and peripheral effects of GH, but transient elevations in circulating liver enzymes of unknown pathogenesis may occur, which seems to be more prevalent when the treatment is combined with a somatostatin analog (SA). Accumulation of intrahepatic lipid is a known cause of elevated liver enzymes, and there is evidence to suggest that GH impacts lipid content in liver and skeletal muscle.

OBJECTIVE

Our objective was to measure lipid content in liver and skeletal muscle in acromegalic patients before and after cotreatment with pegvisomant and SA as compared with SA monotherapy.

DESIGN

Eighteen acromegalic patients well controlled on SA monotherapy were randomized in a parallel study over 24 wk to 1) unchanged SA monotherapy, or 2) cotreatment with pegvisomant (15-30 mg twice a week) and SA (half the usual dosage).

SETTING

This was an investigator-initiated study in a single tertiary referral center.

MAIN OUTCOME MEASURES

Intrahepatic lipid (IHL) and intramyocellular lipid (IMCL) was assessed by ¹H magnetic resonance spectroscopy.

RESULTS

IHL increased in the cotreatment group compared with SA only (P = 0.002). The increase was positively correlated to weekly pegvisomant dose (r² = 0.52; P = 0.01). By contrast, IMCL decreased in the cotreatment group compared with SA only (P = 0.01). These changes related neither to insulin sensitivity nor inflammatory markers.

CONCLUSION

Cotreatment with pegvisomant and a reduced SA dose increase IHL and decrease IMCL compared with SA monotherapy. The clinical implications remain unclear, but increased IHL may be causally linked to the transient elevations in liver enzymes observed during pegvisomant treatment.

DG3173 (somatoprim), a unique somatostatin receptor subtypes 2-, 4- and 5-selective analogue, effectively reduces GH secretion in human GH-secreting pituitary adenomas even in Octreotide non-responsive tumours

OBJECTIVE

Somatostatin analogues (SSA) reduce autonomous GH secretion by activating somatostatin receptors (sst) 2 and 5 in 50-60% of acromegalic patients. However, by inhibiting insulin secretion these SSA reduce glucose tolerance. DG3173 is a novel SSA with additional binding to sst4 and low insulin-suppressing activity. We investigated the effect of DG3173, including its relation to specific tumour characteristics, on GH secretion in human somatotroph adenoma cell cultures (hSA) in comparison with Octreotide.

METHODS

Twenty-seven hSA were characterised immunohistochemically for their hormone- and sst-expression, granularity and pre-surgical therapy with SSA. GH was determined in supernatants of hSA treated with DG3173 or Octreotide in time- (n=6) and dose-response (n=21) experiments. A positive response was defined as GH suppression to below 80% of baseline.

RESULTS

In the dose-response experiments DG3173 suppressed GH secretion in more adenomas than Octreotide (10/21 vs 5/21), including 38% (6/16) of Octreotide non-responders. In responders the extent of GH suppression and IC(50) were comparable for both SSA. The response-rate of both SSA was higher in monohormonal vs bihormonal adenomas, yet GH declined similarly in both groups. Neither pre-surgical SSA (n=6) nor tumour morphology was related to the GH response. However, semi-quantitative analysis indicated a small but significant negative correlation between the GH response to Octreotide and the immunoreactivity scores of sst2 expression.

CONCLUSIONS

DG3173 equalled Octreotide in suppressing GH secretion in hSA. Since DG3173 suppressed GH in some Octreotide-non-responsive adenomas, its clinical effectiveness will be worth testing. Moreover, its reduced insulin-suppressive potency would make it a valuable alternative to Octreotide.

Medical therapy of acromegaly

This paper outlines the present status of medical therapy of acromegaly. Indications for permanent postoperative treatment, postirradiation treamtent to bridge the interval until remission as well as primary medical therapy are elaborated. Therapeutic efficacy of the different available drugs-somatostatin receptor ligands (SRLs), dopamine agonists, and the GH antagonist Pegvisomant-is discussed, as are the indications for and efficacy of their respective combinations. Information on their mechanism of action, and some pharmakokinetic data are included. Special emphasis is given to the difficulties to define remission criteria of acromegaly due to technical assay problems. An algorithm for medical therapy in acromegaly is provided.

Influence of pegvisomant on serum ghrelin and leptin levels in acromegalic patients

INTRODUCTION

Pegvisomant (peg) is a GH receptor antagonist. In de novo acromegalic patients with high GH levels, ghrelin and leptin levels are reduced, suggesting a direct GH-mediated effect. The aim of our study was to evaluate whether peg treatment in acromegalic patients may abolish the GH impact on ghrelin and leptin levels.

METHODS

Ghrelin, leptin and endogenous GH were measured in ten peg-treated acromegalic patients (three females/seven males, 47 years (28-57)), ten patients with active (act) and ten patients with inactive disease (inact) as well as in ten gender-, age- and body mass index (BMI)-matched healthy volunteers (controls). Endogenous GH was measured using a special in-house assay without interference by peg; total ghrelin and leptin were determined using a commercial RIA and an immunofluorometric in-house assay respectively.

RESULTS

Age and BMI did not differ significantly between groups. Endogenous GH was significantly higher in peg (6.3 μg/l (1.5-41)) and act (9.3 μg/l (1.7-70)) compared with controls (0.1 μg/l (0.1-3.1)) and inact (0.35 μg/l (0.1-2.0), P<0.001). Ghrelin was significantly higher in peg (232  ng/l (96-351)) compared with act (102 ng/l (33-232), P<0.01), whereas ghrelin was not significantly different between the other groups. Leptin was highest in controls (19 μg/l (4-57)) and lowest in act (6 μg/l (2-21)), but this difference did not reach significance.

CONCLUSION

Treatment with peg seems to disrupt the feedback loop of ghrelin and GH, leading to elevated ghrelin levels. Furthermore, peg therapy appears not to have a strong impact on leptin levels, as acromegalic patients with and without peg treatment showed similar leptin levels.

Adverse anthropometric risk profile in biochemically controlled acromegalic patients: comparison with an age- and gender-matched primary care population

GH and IGF-1 play an important role in the regulation of metabolism and body composition. In patients with uncontrolled acromegaly, cardiovascular morbidity and mortality are increased but are supposed to be normalised after biochemical control is achieved. We aimed at comparing body composition and the cardiovascular risk profile in patients with controlled acromegaly and controls. A cross-sectional study. We evaluated anthropometric parameters (height, weight, body mass index (BMI), waist and hip circumference, waist to height ratio) and, additionally, cardiovascular risk biomarkers (fasting plasma glucose, HbA1c, triglycerides, total cholesterol, HDL, LDL, and lipoprotein (a), in 81 acromegalic patients (58% cured) compared to 320 age- and gender-matched controls (ratio 1:4), sampled from the primary care patient cohort DETECT. The whole group of 81 acromegalic patients presented with significantly higher anthropometric parameters, such as weight, BMI, waist and hip circumference, but with more favourable cardiovascular risk biomarkers, such as fasting plasma glucose, total cholesterol, triglycerides and HDL levels, in comparison to their respective controls. Biochemically controlled acromegalic patients again showed significantly higher measurements of obesity, mainly visceral adiposity, than age- and gender-matched control patients (BMI 29.5 +/- 5.9 vs. 27.3 +/- 5.8 kg/m(2); P = 0.020; waist circumference 100.9 +/- 16.8 vs. 94.8 +/- 15.5 cm; P = 0.031; hip circumference 110.7 +/- 9.9 vs. 105.0 +/- 11.7 cm; P = 0.001). No differences in the classical cardiovascular biomarkers were detected except for fasting plasma glucose and triglycerides. This effect could not be attributed to a higher prevalence of type 2 diabetes mellitus in the acromegalic patient group, since stratified analyses between the subgroup of patients with acromegaly and controls, both with type 2 diabetes mellitus, revealed that there were no significant differences in the anthropometric measurements. Biochemically cured acromegalic patients pertain an adverse anthropometric risk profile, mainly because of elevated adiposity measurements, such as BMI, waist and hip circumference, compared to an age- and gender-matched primary care population.

Improved insulin sensitivity, preserved beta cell function and improved whole-body glucose metabolism after low-dose growth hormone replacement therapy in adults with severe growth hormone deficiency: a pilot study

AIMS/HYPOTHESIS

Growth hormone-deficient patients show deterioration of insulin sensitivity and beta cell function. High-dose growth hormone treatment often induces further impairment of insulin sensitivity, leading to an increase in insulin and glucose levels or even, in cases of preexisting beta cell defect, to overt diabetes. However, low-dose treatment may improve insulin sensitivity, although data in humans with detailed metabolic phenotyping are as yet not available. We postulated that long-term low-dose growth hormone replacement, restoring IGF-1 to the low-normal range, might beneficially affect glucose metabolism.

METHODS

We studied prospectively the metabolic responses to 24 and 48 weeks of growth hormone treatment in a small group of six adults with severe growth hormone deficiency (four men, two women; age 40-59 years; BMI 30.2 +/- 1 kg/m(2); mean growth hormone dose 0.3 +/- 0.04 mg/day). All participants underwent an oral glucose tolerance test, euglycaemic-hyperinsulinaemic clamp and hyperglycaemic-hyperinsulinaemic clamp plus i.v. L: -arginine on three occasions. Insulin sensitivity was measured by calculating the M value during the steady state of the euglycaemic-hyperinsulinaemic clamp. Insulin secretion and clearance were estimated from AUC(C-peptide), AUC(insulin) and their ratio at each phase of the hyperglycaemic-hyperinsulinaemic clamp.

RESULTS

Growth hormone significantly improved insulin sensitivity (M value 13.8 +/- 2.6 [baseline] vs 19.6 +/- 2.6 [24 weeks] and 23.7 +/- 1.9 [48 weeks] micromol kg(-1) min(-1); p < 0.01). Although the insulin response to glucose and arginine decreased slightly, the disposition index, integrating insulin sensitivity and secretion, significantly increased (p < 0.01), indicating an improvement in whole-body glucose metabolism. Insulin clearance was not affected during treatment (p > 0.05).

CONCLUSIONS/INTERPRETATION

Our data indicate that long-term low-dose growth hormone treatment may improve insulin sensitivity and whole-body glucose metabolism in adults with severe growth hormone-deficiency.

Biological effects of growth hormone on carbohydrate and lipid metabolism

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

Secondary diabetes associated with principal endocrinopathies: the impact of new treatment modalities

The secondary occurrence of type 2 diabetes with various hormonal diseases (e.g. pituitary, adrenal and/or thyroid diseases) is a recurrent observation. Indeed, impaired glucose tolerance (IGT) and overt diabetes mellitus are frequently associated with acromegaly and hypercortisolism (Cushing syndrome). The increased cardiovascular morbidity and mortality associated with acromegaly and Cushing syndrome may partly be a consequence of increased insulin resistance that normally accompanies hormone excess. Acromegalic patients are insulin resistant, both in the liver and in the periphery, displaying hyperinsulinemia and increased glucose turnover in the basal post-absorptive states. The prevalence of diabetes mellitus and that of IGT in acromegaly is reported to range 16-56%, whereas the degree of glucose tolerance seems correlated with circulating growth hormone (GH) levels, age, and disease duration. Moreover, a family history of diabetes and concomitant presence of arterial hypertension have been found to predispose to diabetes as well. GH has physiological effects on glucose metabolism, stimulating gluconeogenesis and lipolysis, which results in increased blood glucose and free fatty acid levels. Conversely, insulin-like growth factor 1 (IGF-I) enhances insulin sensitivity primarily on skeletal muscles. However, in acromegaly, increased IGF-I levels are unable to counteract the insulin-resistance status determined by GH excess. Therapy with somatostatin analogues (SSAs) induce control of GH and IGF-I excess in the majority of patients, but their inhibitory effect on pancreatic insulin secretion might complicate the overall effect of this treatment on glucose tolerance. Hypercortisolism produces visceral obesity, insulin resistance, and dyslipidemia that together with hypertension, hypercoagulability, and ventricular morphologic and functional abnormalities increase cardiovascular risk, and persist up to 5 years after resolution of hypercortisolism. Hypercortisolism leads to hyperglycaemia and reduced glucose tolerance, determines insulin resistance, stimulates hepatic gluconeogenesis and glicogenolisis. In Cushing syndrome the prevalence of diabetes varies between 20 and 50%, but probably this prevalence is underestimated, as not always an oral glucose tolerance test is performed in the presence of an apparently normal fasting glycaemia. Again, disease duration, rather than hormone levels, seems to be the major determinant in the occurrence of systemic complications in Cushing syndrome. Due to the impact they have on mortality and morbidity in both acromegaly and Cushing syndrome, these complications should be treated aggressively. In patients with neuroendocrine tumours (NETs) the occurrence of altered glucose tolerance may be due to a decreased insulin secretion, like it happens in patients who underwent pancreatic surgery and in those with pheochromocytoma, or to an altered counterbalance between hormones, such as in patients with glucagonoma and somatostatinoma. Moreover, SSAs represent a valid therapeutic choice in the symptomatic treatment of NETs, and also in this case the medical therapy of the primary disease, may have a significant impact on the prevalence of glucose metabolism imbalance. In thyroid disorders, an abnormal glucose tolerance may be principally encountered in hyperthyroidism. The pathogenesis is complex and scant data on prevalence and severity are found in the literature. Adequate treatment for glucose imbalance is mandatory in these peculiar patients in line with the American Diabetes Association and the European Association for the Study of Diabetes consensus statement. In particular, since traditional insulins have two features that may complicate therapy (absorption profiles, delayed onset of action and peak activity), the new insulin analogues could be of particular interest in the management of the secondary diabetes associated with endocrinopathies, considering the frailty of these patients. Indeed, it has been demonstrated that insulin glargine, given once daily, reduces the risk of hypoglycaemia compared with other formulations, and can facilitate a more aggressive insulin treatment in this class of patients.