Five-year efficacy and safety data of exenatide once weekly: long-term results from the DURATION-1 randomized clinical trial.

OBJECTIVE: To evaluate the 5-year efficacy and safety of once weekly exenatide. PATIENTS AND METHODS: The Diabetes Therapy Utilization: Researching Changes in A1C, Weight and Other Factors Through Intervention with Exenatide Once Weekly (DURATION-1) randomized clinical trial consisted of a 30-week controlled phase (2 mg of exenatide once weekly vs 10 µg of exenatide twice daily) with an open-ended uncontrolled extension (once weekly exenatide only) in patients with type 2 diabetes mellitus on background glucose-lowering therapies (April 15, 2006, through February 21, 2012). At week 30, patients initially receiving 10 µg of exenatide twice daily switched to 2 mg of exenatide once weekly. Study end points included changes from baseline in hemoglobin A1c, fasting plasma glucose, weight, lipids, and blood pressure. Long-term safety data included adverse events, liver and renal function, and heart rate. RESULTS: Of 258 extension-phase patients, 153 (59.3%) completed 5 years of treatment. Hemoglobin A1c levels were significantly and durably reduced from baseline (least-squares mean, -1.6%; 95% CI, -1.8% to -1.4%; vs -1.9% for exenatide once weekly at week 30), and 65 (43.9%) of 148 patients achieved hemoglobin A1c levels of less than 7.0%. Significant improvements in fasting plasma glucose level (-28.8 mg/dL; 95% CI, -36.2 to -21.5 mg/dL), weight (-3.0 kg; 95% CI, -4.6 to -1.3 kg), lipids, and diastolic blood pressure were observed, with minimal heart rate increase. Frequencies of nausea and injection-site reactions or nodules were decreased vs the initial 30-week controlled phase. Minor hypoglycemia occurred predominantly with sulfonylurea use, and no major hypoglycemia or new safety signals were observed. CONCLUSION: Long-term once weekly exenatide treatment was generally well tolerated with sustained glycemic improvement, weight reduction, and improved markers of cardiovascular risk in patients with type 2 diabetes. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00308139.

Baseline factors associated with glycemic control and weight loss when exenatide twice daily is added to optimized insulin glargine in patients with type 2 diabetes.

OBJECTIVE: To determine variables associated with glycemic and body weight responses when adding exenatide to basal insulin-treated type 2 diabetes. RESEARCH DESIGN AND METHODS: Exploratory subgroup analyses based on baseline A1C, disease duration, and BMI of a 30-week study comparing exenatide twice daily to placebo, added to optimized insulin glargine (intent-to-treat analysis: 137 exenatide; 122 placebo). RESULTS: Exenatide participants had greater A1C reductions compared with optimized insulin glargine alone, irrespective of baseline A1C (P < 0.001). Exenatide participants with longer diabetes duration and those with lower BMI had greater A1C reductions (P < 0.01). Exenatide participants lost more weight, regardless of baseline A1C or BMI (P < 0.05). Exenatide participants with longer diabetes duration lost the most weight (P < 0.001). CONCLUSIONS: Exenatide added to optimized basal insulin was associated with improved glycemic control and weight loss, irrespective of baseline A1C, diabetes duration, and BMI. Changes were evident in modestly obese patients and in those with longer diabetes duration.

Efficacy and tolerability of exenatide monotherapy over 24 weeks in antidiabetic drug-naive patients with type 2 diabetes: a randomized, double-blind, placebo-controlled, parallel-group study.

BACKGROUND: Evaluation of exenatide monotherapy in patients with type 2 diabetes may be of clinical interest based on improvements in glycemic control and weight that have been reported with the use of exenatide in combination with oral antidiabetic agents. OBJECTIVE: The aim of this study was to evaluate the efficacy and tolerability of exenatide monotherapy in patients with type 2 diabetes naive to antidiabetic agents and whose disease was inadequately controlled with diet and exercise alone. METHODS: This 24-week, double-blind, placebo-controlled, parallel-group study was conducted at 23 centers across the United States, Puerto Rico, Romania, Russia, and India. Patients aged >or=18 years with type 2 diabetes were randomly assigned to receive exenatide 5 microg, exenatide 10 microg, or placebo administered SC BID. Patients were instructed by investigators to maintain their individualized prestudy diet and exercise regimens throughout the study. Efficacy measures included: glycosylated hemoglobin (HbA(1c)); fasting serum glucose (FSG); 6-point self-monitored blood glucose; percentages of patients achieving HbA(1c) values or=1 treatment-emergent adverse event. Nausea was reported with the greatest incidence (5 microg, 3%; 10 microg, 13%; placebo, 0%; P = 0.010 for the combined exenatide group vs placebo). Most (88%) treatment-emergent adverse events were mild or moderate in intensity. Hypoglycemia was reported in 5%, 4%, and 1% of patients in the exenatide 5- and 10-microg and placebo groups, respectively (P = NS), with no incidents of severe hypoglycemia reported. CONCLUSIONS: In these patients with type 2 diabetes naive to treatment with antidiabetic agents, exenatide monotherapy was associated with improved HbA(1c), improved fasting and postprandial glucose control, reduced weight, improved beta-cell function (HOMA-B), and improved blood pressure, and was well tolerated. These results suggest that exenatide monotherapy may provide a viable treatment option beyond diet and exercise and support further study of exenatide monotherapy in antidiabetic drug-naive patients with type 2 diabetes.

Adenovirus-mediated overexpression of follistatin enlarges intact liver of adult rats.

Under normal physiologic conditions, liver size is under strict regulatory control. Activin, a member of the transforming growth factor beta (TGF-beta) superfamily, is expressed in the intact adult liver and is an inhibitor of hepatocyte growth. However, the exact role played by endogenous activin in maintaining the size of a normal adult liver has yet to be completely examined in vivo. Here, we report the development of an adenoviral vector (AdexCAFS288) that expressed human follistatin-288, which binds to activin and neutralizes its biologic activities. AdexCAGFP, a control virus, expressed green fluorescent protein. AdexCAFS288 effectively expressed follistatin-288, as measured both in HepG2 cell lysate and conditioned medium and blocked activin signaling and its biologic functions in vitro. Intraperitoneal injection of AdexCAFS288 in vivo resulted in significant liver growth (146% of control) in intact liver of adult male rats 12 days following treatment without significant dysfunctions. The increase in liver size was attributed to increased hepatocyte proliferation, as monitored by the mitotic index. Furthermore, there was a significant correlation between serum follistatin levels and liver weight. In conclusion, our results suggest that activin plays a critical role in maintaining optimal liver size and implicates the endogenous activin system as a therapeutic target in the treatment of liver disease.

Neuron-specific expression in vivo by defined transcription regulatory elements of the GnRH gene.

The GnRH-expressing neurons are the ultimate regulator of reproductive function. GnRH gene expression is limited to this small population of neurons in the hypothalamus. Transfections using 3 kb of the rat or mouse 5'-regulatory region provide specific gene expression in the hypothalamic cell line GT1-7. The combination of two elements, a 300-bp enhancer and a 173-bp promoter, recapitulates specificity in GT1-7 cells. It was not known whether these elements could specifically target gene expression throughout development in the whole animal. We demonstrate that the 3-kb rat GnRH regulatory region provides a higher degree of specificity than the equivalent mouse sequence in a mouse hypothalamic cell line. Moreover, combination of the enhancer and the promoter of the rat gene targets expression to GnRH neurons in transgenic mice in a developmentally appropriate manner. Transgene expression is regulated by activin A, a known activator of GnRH gene expression. In contrast, the enhancer on a heterologous promoter produces inappropriate expression in vivo. We conclude that the enhancer and promoter regions of the rat GnRH gene are necessary for targeted expression to hypothalamic neurons and are sufficient to confer regulated, cell type-specific expression to a reporter gene in vivo.

Effect of adenovirus-mediated overexpression of follistatin and extracellular domain of activin receptor type II on gonadotropin secretion in vitro and in vivo.

Activins are dimeric proteins that stimulate the synthesis and secretion of pituitary FSH by interacting with two classes of receptors, type I and type II, to initiate their intracellular signaling cascade. The extracellular domain of type II activin receptor (ActRII-ECD) contains all structural determinants sufficient for high affinity ligand binding. A soluble recombinant ActRII-ECD has been reported to attenuate FSH secretion from cultured rat anterior pituitary cells in response to exogenous activin A or endogenous activin B. Follistatin is a binding protein that acts as an extracellular factor to bind and inactivate activin. We constructed adenoviral vectors able to mediate expression of follistatin 288 (AdexCAFS288) and ActRII-ECD (AdexCAECD) and tested their biological activities both in vitro and in vivo. The data show that adenovirus-mediated overexpression of either ActRII-ECD or follistatin was able to attenuate FSH secretion by cultured rat anterior pituitary cells. However, AdexCAFS288 overexpression of follistatin was more effective than adenovirus-mediated overexpression of ActRII-ECD. In vivo, a single ip injection of AdexCAFS288 induced the expression of high levels of follistatin and resulted in the suppression of serum FSH levels in castrated male rats for up to 12 d postinjection. Infection with AdexCAFS288 had no effect on LH secretion in vitro or in vivo, demonstrating its selectivity. In conclusion, the results demonstrate the effectiveness of adenovirus-mediated overexpression of follistatin and ActRII-ECD to regulate FSH secretion and the potential of using this strategy as a tool to further define the critical role of activin/inhibin/follistatin circuitry in the modulation of the reproductive system.

The distribution of betaglycan protein and mRNA in rat brain, pituitary, and gonads: implications for a role for betaglycan in inhibin-mediated reproductive functions.

Betaglycan was reported by our laboratory to serve as an inhibin binding protein and to facilitate the antagonism of activin signaling. Although an accessory receptor for TGFbeta and inhibin, its distribution within reproductive tissues remains largely unexplored. Histochemical analyses reveal betaglycan protein and mRNA distributed throughout the rat reproductive axis. In the brain, betaglycan mRNA is localized in discrete regions of the forebrain and brain stem, including olfactory, septal, and hypothalamic nuclei. In the pituitary, moderate levels of betaglycan protein and mRNA were observed in the anterior and intermediate lobes. Betaglycan immunoreactivity was colocalized with all the pituitary cell subtypes, to the greatest extent with the gonadotrope population. In the gonads, betaglycan mRNA was localized in cellular compartments, coinciding with its protein for the most part. Moderate levels of mRNA were observed in ovarian granulosa cells, with lower expression in the thecal layer and the oocyte. In the testes, betaglycan mRNA was observed in the Leydig and tubule-specific germ cells. This is the first comprehensive report detailing the distribution of betaglycan in mammalian reproductive tissues. The present findings illustrate and support the hypothesis of a modulatory role for betaglycan in TGFbeta and/or inhibin effects in these tissues.