Thierry Abribat

A placebo-controlled, dose-ranging study of a growth hormone releasing factor in HIV-infected patients with abdominal fat accumulation.

Objective:To investigate the effects of TH9507, a novel growth hormone releasing factor, on abdominal fat accumulation, metabolic and safety parameters in HIV-infected patients with central fat accumulation. Design and methods:Randomized, double-blind, placebo-controlled trial enrolling 61 HIV-infected patients with increased waist circumference and waist-to-hip ratio. Participants were randomized to placebo or 1 or 2 mg TH9507 subcutaneously, once daily for 12 weeks. The primary outcome was change in abdominal fat, assessed by dual energy X-ray absorptiometry and cross-sectional computerized tomography scan. Secondary endpoints included change in insulin-like growth factor-I (IGF-I), metabolic, quality of life, and safety parameters. Results:TH9507 resulted in dose-related physiological increases in IGF-I (P < 0.01 for 1 mg (+48%) and 2 mg (+65%) versus placebo). Trunk fat decreased in the 2 mg group versus placebo (0.8, −4.6 and −9.2%; placebo, 1 and 2 mg, respectively, P = 0.014 for 2 mg versus placebo), without significant change in limb fat. Visceral fat (VAT) decreased most in the 2 mg group (−5.4, −3.6 and −15.7%; placebo, 1 and 2 mg, respectively) but this change was not significant versus placebo. Subcutaneous fat (SAT) was preserved and did not change between or within groups. Lean body mass and the ratio of VAT to SAT improved significantly in both treatment groups versus placebo. Triglyceride and the cholesterol to high-density lipoprotein ratio decreased significantly in the 2 mg group versus placebo. Treatment was generally well tolerated without changes in glucose. Conclusions:TH9507 reduced truncal fat, improved the lipid profile and did not increase glucose levels in HIV-infected patients with central fat accumulation. TH9507 may be a beneficial treatment strategy in this population, but longer-term studies with more patients are needed to determine effects on VAT, treatment durability, and safety.

Unacylated ghrelin and obestatin increase islet cell mass and prevent diabetes in streptozotocin-treated newborn rats

The ghrelin gene products, namely acylated ghrelin (AG), unacylated ghrelin (UAG), and obestatin (Ob), were shown to prevent pancreatic beta-cell death and to improve beta-cell function under treatment with cytokines, which are major cause of beta-cell destruction in diabetes. Moreover, AG had been described previously to prevent streptozotocin (STZ)-induced diabetes in rats; however, the effect of either UAG or Ob has never been examined in this context. In the present study, we investigated the potential of UAG and Ob to increase islet beta-cell mass and to reduce diabetes at adult age in STZ-treated neonatal rats. One-day-old rats were injected with STZ and subsequently administered with either AG, UAG or Ob for 7 days. On day 70, plasma glucose levels, plasma and pancreatic insulin levels, pancreatic islet area and number, insulin and pancreatic/duodenal homeobox-1 (Pdx1) gene expression, and antiapoptotic BCL2 protein expression were determined. Similarly to AG, both UAG and Ob counteracted STZ-induced high glucose levels and improved plasma and pancreatic insulin levels, which were reduced by the diabetogenic compound. UAG and Ob increased islet area, islet number, and beta-cell mass with respect to STZ treatment alone. Finally, in STZ-treated animals, UAG and Ob up-regulated insulin and Pdx1 mRNA and increased the expression of BCL2 similarly to AG. Taken together, our results suggest that in STZ-treated newborn rats, UAG and Ob improve glucose metabolism and preserve islet cell mass, granting a therapeutic potential in medical conditions associated with impaired beta-cell function.

Effects of acute administration of acylated and unacylated ghrelin on glucose and insulin concentrations in morbidly obese subjects without overt diabetes

OBJECTIVEnTo investigate the effects of unacylated ghrelin (UAG) and co-administration of acylated ghrelin (AG) and UAG in morbid obesity, a condition characterized by insulin resistance and low GH levels.nnnDESIGN AND METHODnEight morbidly obese non-diabetic subjects were treated with either UAG 200 microg, UAG 100 microg in combination with AG 100 microg (Comb) or placebo in three episodes of 4 consecutive days in a double-blind randomized crossover design. Study medication was administered as daily single i.v. bolus injections at 0900 h after an overnight fast. At 1000 h, a standardized meal was served. Glucose, insulin, GH, free fatty acids (FFA) and ghrelin were measured up to 4 h after administration.nnnRESULTSnInsulin concentrations significantly decreased after acute administration of Comb only, reaching a minimum at 20 min: 58.2 + or - 3.9% of baseline versus 88.7 + or - 7.2 and 92.7 + or - 2.6% after administration of placebo and UAG respectively (P<0.01). After 1 h, insulin concentration had returned to baseline. Glucose concentrations did not change after Comb. However, UAG administration alone did not change glucose, insulin, FFA or GH levels.nnnCONCLUSIONnCo-administration of AG and UAG as a single i.v. bolus injection causes a significant decrease in insulin concentration in non-diabetic subjects suffering from morbid obesity. Since glucose concentration did not change in the first hour after Comb administration, our data suggest a strong improvement in insulin sensitivity. These findings warrant studies in which UAG with or without AG is administered for a longer period of time. Administration of a single bolus injection of UAG did not influence glucose and insulin metabolism.

Des-acyl ghrelin analogs prevent high-fat-diet-induced dysregulation of glucose homeostasis

There is clinical evidence that des‐acyl ghrelin (DAG) favorably modulates glucose and lipid metabolism, although its mode of action is unknown. A murine model of prediabetes was used to assess possible mechanisms of action for DAG and a newly developed bioactive analog, AZP531. C57BL/6J mice were infused with saline, DAG, or AZP531 continuously for 4 wk, and fed either normal diet (ND) or normal diet for 2 wk followed by a high‐fat diet (HFD) for 2 wk. Compared with mice in the ND group, HFD increased body and fat mass, caused glucose intolerance and insulin resistance, had proinflammatory effects in white adipose tissue, and caused lipid accumulation in brown adipose tissue. DAG and AZP531 treatment prevented HFD‐induced proinflammatory effects, stimulated expression of mitochondrial function markers in brown adipose tissue, and prevented development of a prediabetic metabolic state. AZP531 also prevented a HFD‐induced increase in acyl ghrelin levels. Our data indicate DAG analogs as potential treatment for the prevention of metabolic syndrome.—Delhanty, P. J. D., Huisman, M., Baldeon‐Rojas, L.Y., van den Berge, I., Grefhorst, A., Abribat, T., Leenen, P. J. M., Themmen, A. P. N., van der Lely, A.‐J. Des‐acyl ghrelin analogs prevent high‐fat diet‐induced dysregulation of glucose homeostasis. FASEB J. 27, 1690–1700 (2013). www.fasebj.org

Des-acyl ghrelin fragments and analogues promote survival of pancreatic β-cells and human pancreatic islets and prevent diabetes in streptozotocin-treated rats.

Des-acyl ghrelin, although devoid of binding to ghrelin receptor (GRLN), exerts many biological effects, including regulation of glucose and lipid metabolism. Indeed, des-acyl ghrelin promotes pancreatic β-cell and human islet cell survival and prevents diabetes in streptozotocin (STZ) treated rats. We investigated whether des-acyl ghrelin fragments excluding serine(3), which is essential for binding to GRLN, would display similar actions. Among the different compounds tested, des-acyl ghrelin((6-13)) and des-acyl ghrelin((6-13)) with alanine substitutions or cyclization, but not with d-amino acid substitutions, showed the best survival effect, similar to des-acyl ghrelin. Des-acyl ghrelin((6-13)) even prevented diabetes in STZ-treated rats and protected human circulating angiogenic cells from oxidative stress and senescence, similar to des-acyl ghrelin. These results suggest that not only full-length des-acyl ghrelin but also short des-acyl ghrelin fragments have clear beneficial effects on several tissues in vitro and in vivo.

The continuous infusion of acylated ghrelin enhances growth hormone secretion and worsens glucose metabolism in humans

Context: Acylated ghrelin (AG) has been discovered as a natural ligand of the GH secretagogue receptor type 1a and is now recognized as an important orexigenic factor. Besides stimulation of GH secretion and appetite, it exerts other central and peripheral actions including modulation of insulin secretion, glucose and lipid metabolism. Objective: To define the effects of the continuous iv infusion of AG in humans with particular attention to metabolic parameters. Materials and methods: We studied the effects of 16h (from 21:00 to 13:00 h) infusion of AG (0.5 μg/kg/h) or saline in 8 young volunteers who were provided with isocaloric balanced meals. GH, cortisol, insulin, glucose, free fatty acid (FFA), and ghrelin levels were assayed every 20 min. Results: AG infusion increased circulating total ghrelin to a steady state that was maintained over 16 h infusion of the peptide. With respect to saline, AG infusion significantly modified GH, Cortisol, insulin, and glucose profiles and decreased FFA area under the curve (p<0.01). AG increased GH pulse frequency and approximate entropy (p<0.05). AG enhanced the glucose response to both dinner (p<0.02) and breakfast (p<0.03). AG infusion blunted the early insulin response to dinner (p<0.03) but enhanced the second-phase insulin response to dinner and breakfast (p<0.05). Conclusions: The continuous exposure to AG in humans enhances somatotroph secretion but also worsens glucose metabolism, although it inhibits lipolysis. These findings in normal young volunteers are consistent with data from studies in animals and suggest that acylated ghrelin is likely to play a negative role in glucose metabolism.

In vitro and in vivo stability and pharmacokinetic profile of unacylated ghrelin (UAG) analogues

Ghrelin, an endocrine hormone predominantly produced by the stomach, exists in acylated and unacylated forms in the circulation. Unacylated ghrelin (UAG), the more abundant form in blood, possesses similar, independent or opposite physiological actions as acylated ghrelin (AG). AZP502, a linear 8-amino acid peptide from the central region of UAG (UAG(6-13)), and its full (AZP531) and partially (AZP533) cyclised derivatives, exhibit the same pharmacological profile as UAG both in vitro and in vivo, independently of AG receptor binding. We investigated the stability of these three fragments in vitro in human blood samples and in vivo after subcutaneous and intravenous injection in rats and dogs using liquid chromatography-mass spectrometry. In both species, AZP502 is rapidly degraded generating two major metabolites. Partial cyclisation of AZP502 and acylation at its N-terminus (AZP533 peptide) improves its stability in human plasma in vitro. Full cyclisation of AZP502 (AZP531 peptide) also completely protects the peptide from peptidase degradation in vitro in human blood samples. Moreover this cyclisation strongly improves the stability and the bioavailability of this peptide in vivo in both dogs and rats (mean bioavailability of 10-15% and 85-95% for AZP502 and AZP531 respectively). Taken together these results support the rationale for developing AZP531 as a long-acting UAG analogue for subcutaneous injection for the treatment of type 2 diabetes mellitus and other metabolic disorders.

Safety, tolerability, pharmacokinetics and pharmacodynamics of AZP‐531, a first‐in‐class analogue of unacylated ghrelin, in healthy and overweight/obese subjects and subjects with type 2 diabetes

To explore the safety, pharmacokinetics and pharmacodynamics in humans of the unacylated ghrelin analogue AZP‐531, designed to improve glycaemic control and reduce weight.

Differential mechanisms of asparaginase resistance in B-type acute lymphoblastic leukemia and malignant natural killer cell lines

Bacterial L-asparaginase (ASNase), hydrolyzing L-asparagine (Asn), is an important drug for treating patients with acute lymphoblastic leukaemia (ALL) and natural killer (NK) cell lymphoma. Although different native or pegylated ASNase-based chemotherapy are efficient, disease relapse is frequently observed, especially in adult patients. The neo-synthesis of Asn by asparagine synthetase (AsnS) following ASNase treatment, which involves the amino acid response and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathways, is believed to be the basis of ASNase-resistance mechanisms. However, AsnS expression has not emerged as an accurate predictive factor for ASNase susceptibility. The aim of this study was to identify possible ASNase sensitivity/resistance-related genes or pathways using a new asparaginase, namely a pegylated r-crisantaspase, with a focus on classic Asn-compensatory responses and cell death under conditions of Asn/L-glutamine limitation. We show that, for B-ALL cell lines, changes in the expression of apoptosis-regulatory genes (especially NFκB-related genes) are associated with ASNase susceptibility. The response of malignant NK cell lines to ASNase may depend on Asn-compensatory mechanisms and other cellular processes such as cleavage of BCL2A1, a prosurvival member of the Bcl-2 protein family. These results suggest that according to cellular context, factors other than AsnS can influence ASNase susceptibility.