Cost-effectiveness of second-line antihyperglycemic therapy in patients with type 2 diabetes mellitus inadequately controlled on metformin

Background:

Metformin is widely accepted as first-line pharmacotherapy for patients with type 2 diabetes mellitus when glycemic control cannot be achieved by lifestyle interventions alone. However, uncertainty exists regarding the optimal second-line therapy for patients whose diabetes is inadequately controlled by metformin monotherapy. Increased use of newer, more costly agents, along with the rising incidence of type 2 diabetes, carries significant budgetary implications for health care systems. We conducted this analysis to determine the relative costs, benefits and cost-effectiveness of options for second-line treatment of type 2 diabetes.

Methods:

We used the United Kingdom Prospective Diabetes Study Outcomes Model to forecast diabetes-related complications, quality-adjusted life-years and costs of alternative second-line therapies available in Canada for adults with type 2 diabetes inadequately controlled by metformin. We obtained clinical data from a systematic review and mixed treatment comparison meta-analysis, and we obtained information on costs and utilities from published sources. We performed extensive sensitivity analyses to test the robustness of results to variation in inputs and assumptions.

Results:

Sulphonylureas, when added to metformin, were associated with the most favourable cost-effectiveness estimate, with an incremental cost of $12 757 per quality-adjusted life-year gained, relative to continued metformin monotherapy. Treatment with other agents, including thiazolidinediones and dipeptidyl peptidase-4 inhibitors, had unfavourable cost-effectiveness estimates compared with sulphonylureas. These results were robust to extensive sensitivity analyses.

Interpretation:

For most patients with type 2 diabetes that is inadequately controlled with metformin monotherapy, the addition of a sulphonylurea represents the most cost-effective second-line therapy.Type 2 diabetes mellitus is a progressive disease typically treated in a stepwise fashion, beginning with lifestyle modification, followed by the addition of one or more oral antihyperglycemic drugs and, finally, administration of exogenous insulin. Metformin monotherapy is widely recommended as first-line pharmacotherapy,^1,2 given its favourable effects in controlling blood glucose and body weight, low risk of hypoglycemia, low cost and association with mortality benefit.³ Multiple second-line treatment strategies are available for patients in whom glycemic control has become inadequate. These approaches are typically used in addition to continued metformin therapy.^4,5 Numerous second-line agents are available in Canada, including older oral agents, such as sulphonylureas, and more recently introduced agents, such as thiazolidinediones and dipeptidyl peptidase-4 inhibitors.The large number of choices for second-line therapy has increased uncertainty regarding the optimal treatment pathway. Recent clinical practice guidelines, including those produced by the Canadian Diabetes Association¹ and by the American Diabetes Association and the European Association for the Study of Diabetes,² have suggested selecting from among several agents on the basis of their respective advantages and disadvantages. There has been a considerable increase in the use of newer, more costly oral antihyperglycemic agents, which has resulted in substantial increases in associated costs to patients and both public and private drug plans in Canada.⁴ In light of current therapeutic uncertainty, the large proportion of patients requiring second-line therapy over time^3,6 and the increasing prevalence of type 2 diabetes,⁷ the utilization and cost of second-line therapy are likely to continue to grow.Informed decisions regarding optimal prescribing and reimbursement of second-line agents by public and private health care payers requires information about clinical benefits, costs and cost-effectiveness.⁸ As part of a larger initiative to determine optimal prescribing of antihyperglycemic agents, we sought to determine the incremental cost-effectiveness of treatment with alternative second-line agents added to metformin in patients with type 2 diabetes no longer adequately controlled by metformin monotherapy.     

Distinct Roles for Rho Versus Rac/Cdc42 GTPases Downstream of Vav2 in Regulating Mammary Epithelial Acinar Architecture

Non-malignant mammary epithelial cells (MECs) undergo acinar morphogenesis in three-dimensional Matrigel culture, a trait that is lost upon oncogenic transformation. Rho GTPases are thought to play important roles in regulating epithelial cell-cell junctions, but their contributions to acinar morphogenesis remain unclear. Here we report that the activity of Rho GTPases is down-regulated in non-malignant MECs in three-dimensional culture with particular suppression of Rac1 and Cdc42. Inducible expression of a constitutively active form of Vav2, a Rho GTPase guanine nucleotide exchange factor activated by receptor tyrosine kinases, in three-dimensional MEC culture activated Rac1 and Cdc42; Vav2 induction from early stages of culture impaired acinar morphogenesis, and induction in preformed acini disrupted the pre-established acinar architecture and led to cellular outgrowths. Knockdown studies demonstrated that Rac1 and Cdc42 mediate the constitutively active Vav2 phenotype, whereas in contrast, RhoA knockdown intensified the Vav2-induced disruption of acini, leading to more aggressive cell outgrowth and branching morphogenesis. These results indicate that RhoA plays an antagonistic role to Rac1/Cdc42 in the control of mammary epithelial acinar morphogenesis.     

Regeneration of amputated zebrafish fin rays from de novo osteoblasts

Determining the cellular source of new skeletal elements is critical for understanding appendage regeneration in amphibians and fish. Recent lineage-tracing studies indicated that zebrafish fin ray bone regenerates through the dedifferentiation and proliferation of spared osteoblasts, with limited if any contribution from other cell types. Here, we examined the requirement for this mechanism by using genetic ablation techniques to destroy virtually all skeletal osteoblasts in adult zebrafish fins. Animals survived this injury and restored the osteoblast population within 2 weeks. Moreover, amputated fins depleted of osteoblasts regenerated new fin ray structures at rates indistinguishable from fins possessing a resident osteoblast population. Inducible genetic fate mapping confirmed that new bone cells do not arise from dedifferentiated osteoblasts under these conditions. Our findings demonstrate diversity in the cellular origins of appendage bone and reveal that de novo osteoblasts can fully support the regeneration of amputated zebrafish fins.     

Comparing Platforms for C. elegans Mutant Identification Using High-Throughput Whole-Genome Sequencing

Background

Whole-genome sequencing represents a promising approach to pinpoint chemically induced mutations in genetic model organisms, thereby short-cutting time-consuming genetic mapping efforts.

Principal Findings

We compare here the ability of two leading high-throughput platforms for paired-end deep sequencing, SOLiD (ABI) and Genome Analyzer (Illumina; “Solexa”), to achieve the goal of mutant detection. As a test case we used a mutant C. elegans strain that harbors a mutation in the lsy-12 locus which we compare to the reference wild-type genome sequence. We analyzed the accuracy, sensitivity, and depth-coverage characteristics of the two platforms. Both platforms were able to identify the mutation that causes the phenotype of the mutant C. elegans strain, lsy-12. Based on a 4 MB genomic region in which individual variants were validated by Sanger sequencing, we observe tradeoffs between rates of false positives and false negatives when using both platforms under similar coverage and mapping criteria.

Significance

In conclusion, whole-genome sequencing conducted by either platform is a viable approach for the identification of single-nucleotide variations in the C. elegans genome.     

In Toto Imaging of Dynamic Osteoblast Behaviors in Regenerating Skeletal Bone

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Bioprocess development for extracellular production of recombinant human interleukin-3 (hIL-3) in <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Human interleukin-3 (hIL-3) is a therapeutically important cytokine involved in the maturation and differentiation of various cells of the immune system. The codon-optimized hIL-3 gene was cloned in fusion with the N-terminus α-mating factor signal peptide of Saccharomyces cerevisiae under an inducible alcohol oxidase 1 (AOX1) and constitutive glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter. A Zeocin concentration up to 2000 mg/L was used to select hyper-producers. The shake flask cultivation studies in the Pichia pastoris GS115 host resulted a maximum recombinant hIL-3 expression level of 145 mg/L in the extracellular medium under the control of AOX1 promoter. The batch fermentation strategy allowed us to attain a fairly pure glycosylated hIL-3 protein in the culture supernatant at a final concentration of 475 mg/L with a high volumetric productivity of 4.39 mg/L/h. The volumetric product concentration achieved at bioreactor level was 3.28 folds greater than the shake flask results. The 6x His-tagged protein was purified using Ni–NTA affinity chromatography and confirmed further by western blot analysis using anti-6x His tag antibody. The glycosylation of recombinant hIL-3 protein was confirmed in a PNGase F deglycosylation reaction where it showed a molecular weight band pattern similar to E. coli produced non-glycosylated hIL-3 protein. The structural properties of recombinant hIL-3 protein were confirmed by CD and fluorescence spectroscopy where protein showed 40 % α-helix, 12 % β-sheets with an emission maxima at 343 nm. MALDI-TOF-TOF analysis was used to establish the protein identity. The biological activity of purified protein was confirmed by the human erythroleukemia TF-1 cell proliferation assay.     

Perceived Risk of Avian Influenza and Urbanization in Northern Vietnam

Decision-analytic models provide forecasts of how systems of interest will respond to management. These models can be parameterized using empirical data, but sometimes require information elicited from experts. When evaluating the effects of disease in species translocation programs, expert judgment is likely to play a role because complete empirical information will rarely be available. We illustrate development of a decision-analytic model built to inform decision-making regarding translocations and other management actions for the boreal toad (Anaxyrus boreas boreas), a species with declines linked to chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd). Using the model, we explored the management implications of major uncertainties in this system, including whether there is a genetic basis for resistance to pathogenic infection by Bd, how translocation can best be implemented, and the effectiveness of efforts to reduce the spread of Bd. Our modeling exercise suggested that while selection for resistance to pathogenic infection by Bd could increase numbers of sites occupied by toads, and translocations could increase the rate of toad recovery, efforts to reduce the spread of Bd may have little effect. We emphasize the need to continue developing and parameterizing models necessary to assess management actions for combating chytridiomycosis-associated declines.