Efficacy, safety, and tolerability of exenatide once weekly in patients with type 2 diabetes mellitus: an integrated analysis of the DURATION trials.

BACKGROUND AND AIM: Exenatide is a glucagon-like peptide-1 receptor agonist demonstrated to improve glycemic control with low hypoglycemia risk in patients with type 2 diabetes mellitus. The Diabetes Therapy Utilization: Researching Changes in A1C, Weight, and Other Factors Through Intervention With Exenatide Once Weekly (DURATION) program comprised 6 randomized, comparator-controlled, 24- to 30-week trials of exenatide once weekly (EQW), an extended-release formulation. This post hoc analysis pooled data from patients taking EQW across 6 trials to assess efficacy and safety in a large, varied patient population. MATERIALS AND METHODS: The intent-to-treat (ITT) population contained 1379 patients (baseline mean ± standard deviation glycated hemoglobin [HbA1c] levels of 8.4% ± 1.1%) who were treated with EQW over the course of 24 to 30 weeks. Changes from baseline in efficacy parameters for the ITT population and a completer population (1195 patients with ≥ 22 weeks of exposure) were evaluated. RESULTS: The ITT population experienced significant reductions from baseline (least-squares mean [95% CI]) in HbA1c levels (-1.4% [-1.5% to -1.4%]), fasting blood glucose levels (-36 mg/dL [-38.4 mg/dL to -33.8 mg/dL]), and body weight (-2.5 kg [-2.8 kg to -2.3 kg]) after 24 to 30 weeks of EQW treatment. Reductions in HbA1c and fasting blood glucose levels were observed across baseline HbA1c level strata; patients with higher baseline HbA1c levels experienced greater reductions. Treatment with EQW was associated with modest, significant reductions in blood pressure (systolic blood pressure, -2.8 mm Hg [-3.5 mm Hg to -2.1 mm Hg]; diastolic blood pressure, -0.8 mm Hg [-1.2 mm Hg to -0.4 mm Hg]), and fasting lipid levels (total cholesterol, -6.5 mg/dL [-8.2 mg/dL to -4.7 mg/dL]; low-density lipoprotein cholesterol, -3.9 mg/dL [5.3 mg/dL to -2.5 mg/dL]; and triglyceride [geometric least-squares mean percent change (95% CI)], -6% [-8% to -4%] levels). Similar reductions were observed in the completer population. Exenatide once weekly was generally well tolerated. Transient, mild-to-moderate gastrointestinal treatment-emergent adverse events and injection-site treatment-emergent adverse events were reported most frequently, but were seldom treatment limiting. No major hypoglycemic events were observed; minor hypoglycemic events occurred infrequently in patients not using a sulfonylurea. CONCLUSION: This post hoc analysis of > 1300 patients demonstrated that EQW was associated with significant reductions in HbA1c levels, body weight, blood pressure, and fasting lipid levels, with minimal hypoglycemia risk. Consistent with established safety profiles, EQW therapy was generally well tolerated. TRIAL REGISTRATION: www.ClinicalTrials.gov identifiers: NCT00308139, NCT00637273, NCT00641056, NCT00676338, NCT00877890, NCT01029886.

Endogenous GSK-3/shaggy regulates bidirectional axonal transport of the amyloid precursor protein.

Neurons rely on microtubule (MT) motor proteins such as kinesin-1 and dynein to transport essential cargos between the cell body and axon terminus. Defective axonal transport causes abnormal axonal cargo accumulations and is connected to neurodegenerative diseases, including Alzheimer's disease (AD). Glycogen synthase kinase 3 (GSK-3) has been proposed to be a central player in AD and to regulate axonal transport by the MT motor protein kinesin-1. Using genetic, biochemical and biophysical approaches in Drosophila melanogaster, we find that endogenous GSK-3 is a required negative regulator of both kinesin-1-mediated and dynein-mediated axonal transport of the amyloid precursor protein (APP), a key contributor to AD pathology. GSK-3 also regulates transport of an unrelated cargo, embryonic lipid droplets. By measuring the forces motors generate in vivo, we find that GSK-3 regulates transport by altering the activity of kinesin-1 motors but not their binding to the cargo. These findings reveal a new relationship between GSK-3 and APP, and demonstrate that endogenous GSK-3 is an essential in vivo regulator of bidirectional APP transport in axons and lipid droplets in embryos. Furthermore, they point to a new regulatory mechanism in which GSK-3 controls the number of active motors that are moving a cargo.

Molecular motor function in axonal transport in vivo probed by genetic and computational analysis in Drosophila.

Bidirectional axonal transport driven by kinesin and dynein along microtubules is critical to neuronal viability and function. To evaluate axonal transport mechanisms, we developed a high-resolution imaging system to track the movement of amyloid precursor protein (APP) vesicles in Drosophila segmental nerve axons. Computational analyses of a large number of moving vesicles in defined genetic backgrounds with partial reduction or overexpression of motor proteins enabled us to test with high precision existing and new models of motor activity and coordination in vivo. We discovered several previously unknown features of vesicle movement, including a surprising dependence of anterograde APP vesicle movement velocity on the amount of kinesin-1. This finding is largely incompatible with the biophysical properties of kinesin-1 derived from in vitro analyses. Our data also suggest kinesin-1 and cytoplasmic dynein motors assemble in stable mixtures on APP vesicles and their direction and velocity are controlled at least in part by dynein intermediate chain.

Move it or lose it: axis specification in Xenopus.

A long-standing question in developmental biology is how amphibians establish a dorsoventral axis. The prevailing view has been that cortical rotation is used to move a dorsalizing activity from the bottom of the egg towards the future dorsal side. We review recent evidence that kinesin-dependent movement of particles containing components of the Wnt intracellular pathway contributes to the formation of the dorsal organizer, and suggest that cortical rotation functions to align and orient microtubules, thereby establishing the direction of particle transport. We propose a new model in which active particle transport and cortical rotation cooperate to generate a robust movement of dorsal determinants towards the future dorsal side of the embryo.

GBP binds kinesin light chain and translocates during cortical rotation in Xenopus eggs.

In Xenopus, axis development is initiated by dorsally elevated levels of cytoplasmic beta-catenin, an intracellular factor regulated by GSK3 kinase activity. Upon fertilization, factors that increase beta-catenin stability are translocated to the prospective dorsal side of the embryo in a microtubule-dependent process. However, neither the identity of these factors nor the mechanism of their movement is understood. Here, we show that the GSK3 inhibitory protein GBP/Frat binds kinesin light chain (KLC), a component of the microtubule motor kinesin. Upon egg activation, GBP-GFP and KLC-GFP form particles and exhibit directed translocation. KLC, through a previously uncharacterized conserved domain, binds a region of GBP that is required for GBP translocation and for GSK3 binding, and competes with GSK3 for GBP. We propose a model in which conventional kinesin transports a GBP-containing complex to the future dorsal side, where GBP dissociates and contributes to the local stabilization of beta-catenin by binding and inhibiting GSK3.