Success of Direct-Acting, Antiviral-Based Therapy for Chronic Hepatitis C Is Not Affected by Type 2 Diabetes.

Chronic hepatitis C virus (HCV) is a risk factor for type 2 diabetes. In the era of interferon-based HCV therapy, type 2 diabetes was associated with decreased likelihood of sustained virologic response (SVR). Preliminary studies suggest that type 2 diabetes may not reduce the efficacy of regimens involving direct-acting antiviral (DAA) medications. We aimed to determine whether preexisting type 2 diabetes is associated with a reduced rate of SVR achieved 12 weeks after treatment of HCV with DAA-based regimens.

Effect of Treatment with Direct Acting Antiviral on Glycemic Control in Patients with Diabetes Mellitus and Chronic Hepatitis C

ABSTRACT Introduction and aim. The effect of the new direct acting antiviral drugs (DAAs) for chronic hepatitis C (HCV) on glycemic control is unknown. Materials and methods. We conducted a retrospective cohort study of patients who were treated for chronic HCV with direct-acting antiviral medications at a single academic institution between May 2013 and April 2016. Univariate analysis was performed comparing subjects pre- and post-treatment. Results. One hundred seventy-five consecutive adult patients were treated for chronic HCV and met enrollment criteria. The majority (80.8%) were genotype 1 and overall cohort sustained virologic response at week 12 (SVR12) was 97.8%. Thirty-one (18.5%) had diabetes mellitus (DM); twenty-six had pre- and post-treatment HbA1c values. Of these, 76.9% were male and 61.5% had cirrhosis. Ninety-six percent were prescribed sofosbuvir-based therapy and all but one (96.8%) achieved SVR12. Three patients were started on treatment despite meeting the definition for poorly controlled DM (HbA1c > 9 mg/dL). There was no significant difference when comparing pre-treatment (7.36 mg/dL, 95% CI 6.55-8.16) to post-treatment HbA1c (7.11 mg/dL, 95% CI 6.34-7.88, p = 0.268). Thirty-one percent of subjects required dose escalation or the initiation of insulin based therapy during treatment. Discussion. Although chronic HCV is associated with exacerbation of insulin resistance, our results showed HbA1c to be unaffected by eradication of chronic HCV with DAA in diabetic patients with and without cirrhosis. Paradoxically, almost 1/3 of patients required escalation of anti-diabetic therapy during treatment. Long-term studies are warranted to understand the relationship between HCV viral eradication and insulin metabolism.(AU)

Effect of Treatment with Direct Acting Antiviral on Glycemic Control in Patients with Diabetes Mellitus and Chronic Hepatitis C.

INTRODUCTION AND AIM: The effect of the new direct acting antiviral drugs (DAAs) for chronic hepatitis C (HCV) on glycemic control is unknown. MATERIALS AND METHODS: We conducted a retrospective cohort study of patients who were treated for chronic HCV with direct-acting antiviral medications at a single academic institution between May 2013 and April 2016. Univariate analysis was performed comparing subjects pre- and post-treatment. RESULTS: One hundred seventy-five consecutive adult patients were treated for chronic HCV and met enrollment criteria. The majority (80.8%) were genotype 1 and overall cohort sustained virologic response at week 12 (SVR12) was 97.8%. Thirty-one (18.5%) had diabetes mellitus (DM); twenty-six had pre- and post-treatment HbA1c values. Of these, 76.9% were male and 61.5% had cirrhosis. Ninety-six percent were prescribed sofosbuvir-based therapy and all but one (96.8%) achieved SVR12. Three patients were started on treatment despite meeting the definition for poorly controlled DM (HbA1c > 9 mg/dL). There was no significant difference when comparing pre-treatment (7.36 mg/dL, 95% CI 6.55-8.16) to post-treatment HbA1c (7.11 mg/dL, 95% CI 6.34-7.88, p = 0.268). Thirty-one percent of subjects required dose escalation or the initiation of insulin based therapy during treatment. DISCUSSION: Although chronic HCV is associated with exacerbation of insulin resistance, our results showed HbA1c to be unaffected by eradication of chronic HCV with DAA in diabetic patients with and without cirrhosis. Paradoxically, almost 1/3 of patients required escalation of anti-diabetic therapy during treatment. Long-term studies are warranted to understand the relationship between HCV viral eradication and insulin metabolism.

Transport mechanisms in the ammonium transporter family.

Ammonium transport is mediated by membrane proteins of the ubiquitous Amt/Rh family. Despite the availability of different X-ray structures that provide many insights on the ammonium permeation process, the molecular details of its mechanism remain controversial. The X-ray structures have revealed that the pore of the Amt and Rh proteins is characterized by a hydrophobic portion about 12A long in which electronic density was observed in crystallographic study of AmtB from Escherichia coli. This electronic density was initially only observed when crystals were grown in presence of ammonium salt and was thus attributed to ammonia (NH(3)) molecules, and lead the authors to suggest that the conduction mechanism in the Amt/Rh proteins involves the single-file diffusion of NH(3) molecules. However, other X-ray crystallography results and molecular mechanics simulations suggest that the pore of AmtB could also be filled with water molecules. The possible presence of water molecules in the pore lumen calls for a reassessment of the growing consensus that Amt/Rh proteins work as plain NH(3) channels. Indeed, functional experiments on plant ammonium transporters and rhesus proteins suggest a variety of permeation mechanisms including the passive diffusion of NH(3), the antiport of NH(4)(+)/H(+), the transport of NH(4)(+), or the cotransport of NH(3)/H(+). We discuss these mechanisms in light of some recent functional and simulation studies on the AmtB transporter and illustrate how they can be reconciled with the available high resolution X-ray data.

The Escherichia coli AmtB protein as a model system for understanding ammonium transport by Amt and Rh proteins.

The Escherichia coli ammonium transport protein (AmtB) has become the model system of choice for analysis of the process of ammonium uptake by the ubiquitous Amt family of inner membrane proteins. Over the past 6 years we have developed a range of genetic and biochemical tools in this system. These have allowed structure/function analysis to develop rapidly, offering insight initially into the membrane topology of the protein and most recently leading to the solution of high-resolution 3D structures. Genetic analysis has revealed a novel regulatory mechanism that is apparently conserved in prokaryotic Amt proteins and genetic approaches are also now being used to dissect structure/function relationships in Amt proteins. The now well-recognised homology between the Amt proteins, found in archaea, eubacteria, fungi and plants, and the Rhesus proteins, found characteristically in animals, also means that studies on E. coli AmtB can potentially shed light on structure/function relationships in the clinically important Rh proteins.

Complex formation between AmtB and GlnK: an ancestral role in prokaryotic nitrogen control.

Ammonium transport proteins belonging to the Amt family are ubiquitous in prokaryotes. In Escherichia coli, the AmtB protein and the associated P(II) signal transduction protein (GlnK) have recently been recognized as an ammonium sensory system that effectively couples the intracellular nitrogen regulation (Ntr) system to external changes in ammonium availability. Given the almost invariant coupling of AmtB and GlnK in bacteria and archaea it seems probable that these two proteins may constitute an ancestral nitrogen-responsive system that has been coupled with a variety of unrelated nitrogen regulatory processes, which are now found in prokaryotes. The multiplicity of P(II) proteins could therefore be considered to have evolved from an ancestral GlnK-like protein and to have subsequently been adapted to control many other aspects of nitrogen metabolism.

Molecular characterization of two ammonium transporters from the ectomycorrhizal fungus Hebeloma cylindrosporum.

Heterologous expression of the yeast triple Mep mutant has enabled the first molecular characterization of AMT/MEP family members in an ectomycorrhizal fungus. External hyphae, which play a key role in nitrogen nutrition of trees, are considered as the absorbing structure of the ectomycorrhizal symbiosis and therefore molecular studies on ammonium transport in hyphae are urgently needed. The kinetic properties of AMT2 and AMT3 from Hebeloma cylindrosporum were studied in Saccharomyces cerevisiae. Expression of HcAmts in the yeast triple Mep mutant restored ammonium retention within cells. The HcAmts did not complement the ammonium sensing defect phenotype of Mep2Delta cells during pseudohyphal differentiation. Northern blot analysis in H. cylindrosporum showed that the HcAMTs were up-regulated upon nitrogen deprivation and down-regulated by ammonium.

Ammonium and methylamine transport by the ectomycorrhizal fungus Paxillus involutus and ectomycorrhizas.

Using [(14)C]methylamine as an analogue of ammonium, the kinetics and the energetics of NH(4)(+) transport were studied in the ectomycorrhizal fungus, Paxillus involutus (Batsch) Fr. The apparent half-saturation constant (K(m)) and the maximum uptake rate (V(max)) for the carrier-mediated transport derived from the Eadie-Hofstee transformation were 180 µM and 380 nmol (mg dry wt)(-1) min(-1,) respectively. Both pH dependence and inhibition by protonophores indicate that methylamine transport in P. involutus was dependent on the electrochemical H(+) gradient. Both long-term and short-term uptake experiments were consistent with regulation of ammonium/methylamine transport processes by the presence of an organic nitrogen source. Analysis of methylamine uptake by different P. involutus isolates revealed no obvious trend in the uptake capacities in relation to N deposition at the collection site. Kinetic parameters were determined in P. involutus/Betula pendula (Roth.) axenic association and in detached mycorrhizal roots isolated from forest sites. Enhanced methylamine uptake in the presence of the fungal symbiont was demonstrated. Homogeneous V(max) values were found for axenic and detached mycorrhizas, whereas K(m) values showed greater variations.