Hydration Changes upon DNA Folding Studied by Osmotic Stress Experiments

AbstractThe thermal stability of nucleic acid structures is perturbed under the conditions that mimic the intracellular environment, typically rich in inert components and under osmotic stress. We now describe the thermodynamic stability of DNA oligonucleotide structures in the presence of high background concentrations of neutral cosolutes. Small cosolutes destabilize the basepair structures, and the DNA structures consisting of the same nearest-neighbor composition show similar thermodynamic parameters in the presence of various types of cosolutes. The osmotic stress experiments reveal that water binding to flexible loops, unstable mismatches, and an abasic site upon DNA folding are almost negligible, whereas the binding to stable mismatch pairs is significant. The studies using the basepair-mimic nucleosides and the peptide nucleic acid suggest that the sugar-phosphate backbone and the integrity of the basepair conformation make important contributions to the binding of water molecules to the DNA bases and helical grooves. The study of the DNA hydration provides the basis for understanding and predicting nucleic acid structures in nonaqueous solvent systems

The Effects of Molecular Crowding on the Structure and Stability of G-Quadruplexes with an Abasic Site

Both cellular environmental factors and chemical modifications critically affect the properties of nucleic acids. However, the structure and stability of DNA containing abasic sites under cell-mimicking molecular crowding conditions remain unclear. Here, we investigated the molecular crowding effects on the structure and stability of the G-quadruplexes including a single abasic site. Structural analysis by circular dichroism showed that molecular crowding by PEG200 did not affect the topology of the G-quadruplex structure with or without an abasic site. Thermodynamic analysis further demonstrated that the degree of stabilization of the G-quadruplex by molecular crowding decreased with substitution of an abasic site for a single guanine. Notably, we found that the molecular crowding effects on the enthalpy change for G-quadruplex formation had a linear relationship with the abasic site effects depending on its position. These results are useful for predicting the structure and stability of G-quadruplexes with abasic sites in the cell-mimicking conditions

Use of iGlarLixi for Management of Type 2 Diabetes in Japanese Clinical Practice : SPARTA Japan, a Retrospective Observational Study

Introduction: Many individuals with type 2 diabetes (T2D) experience suboptimal glycemic control. Treatment intensification options include fixed-ratio combination products containing a basal insulin and a glucagon-like peptide-1 receptor agonist, such as iGlarLixi (insulin glargine 100 U/mL and lixisenatide). This study aimed to provide real-world evidence of the effect of iGlarLixi in Japanese clinical practice. Methods: SPARTA Japan was a non-comparative, observational study conducted at 27 institutions in Japan. Anonymized individual-level data from adults with T2D receiving iGlarLixi in routine clinical practice were retrospectively collected. The primary study objective was to assess the impact of iGlarLixi on the change in glycated hemoglobin (HbA1c) at 6 months’ post-treatment initiation, with preplanned subanalyses to determine the influence of baseline characteristics. Secondary and exploratory endpoints included assessment of the proportion of individuals achieving HbA1c targets, change in body weight, and incidence and severity of hypoglycemia and gastrointestinal events. Results: The full analysis set included 432 individuals, with data available at 6 months for 426. Of the 432 individuals, the mean (SD) age at baseline was 61.6 (12.8) years and the majority had a T2D duration of ≥ 10 years [mean (SD) 13.3 (10.4) years]. At 6 months, HbA1c had significantly decreased versus baseline ( –0.85%; P < 0.0001), with a greater decrease in those aged < 65 years, with a shorter duration of T2D and higher baseline HbA1c. A significant increase in the proportion of participants achieving age-specific HbA1c versus baseline was observed. Mean body weight decreased by 0.5 kg (P = 0.0034 versus baseline). There were few hypoglycemia and gastrointestinal events (in individuals with HbA1c data); no severe hypoglycemic events were reported. Conclusions: The results of this real-world study indicate that iGlarLixi may improve glycemic control without serious adverse events in Japanese individuals with T2D who have suboptimal glycemic control on current treatment regimens and switch to iGlarLixi

Use of iGlarLixi for the Management of Type 2 Diabetes in Japanese Clinical Practice : Prior Treatment Subgroup Analysis of the SPARTA Japan Study

Introduction: iGlarLixi, a fixed-ratio combination of insulin glargine 100 U/mL and the glucagon-like peptide 1 receptor agonist (GLP-1 RA) lixisenatide, is one option for treatment intensification in individuals with type 2 diabetes (T2D) who are unable to achieve targeted glycaemic control with their current glucose-lowering agent. Real-world data on the impact of prior treatment on the effectiveness and safety of iGlarLixi may be useful to guide individualised treatment decisions. Methods: This analysis of the 6-month, retrospective, observational SPARTA Japan study compared glycated haemoglobin (HbA1c), body weight and safety for pre-specified subgroups defined by prior treatment: post oral antidiabetic agent (OAD), GLP-1 RA, basal insulin (BI) + OADs (BOT), GLP-1 RA + BI or multiple daily injections (MDI). The post BOT and MDI subgroups were further divided on the basis of prior dipeptidyl peptidase 4 inhibitor (DPP-4i) use, and the post MDI group was divided on the basis of whether participants continued bolus insulin. Results: Of the 432 participants in the full analysis set (FAS), 337 were included in this subgroup analysis. Across subgroups, mean baseline HbA1c ranged from 8.49% to 9.18%. iGlarLixi significantly (p < 0.05) reduced mean HbA1c from baseline in all but the post GLP-1 RA + BI group. At 6 months, these significant reductions ranged from 0.47% to 1.27%. Prior DPP-4i exposure had no impact on the HbA1c-lowering effect of iGlarLixi. Mean body weight decreased significantly in the FAS (0.5 kg) and the post BOT (1.2 kg) and MDI (1.5 and 1.9 kg) subgroups but increased in the post GLP-1 RA subgroup (1.3 kg). iGlarLixi treatment was generally well tolerated, with very few participants discontinuing because of hypoglycaemia or gastrointestinal events. Conclusion: In participants with suboptimal glycaemic control on various regimens, 6 months of iGlarLixi treatment improved HbA1c in all but one prior treatment subgroup (GLP-1 RA + BI), and was generally well tolerated

Regulation of DNA nucleases by molecular crowding

Here, we examined the effects of molecular crowding on the function, structure and stability of nucleases. We found that the hydrolysis of a 29-mer double-stranded DNA by the endonucleases DNase I and S1 nuclease was substantially enhanced by molecular crowding using polyethylene glycol (PEG); however, molecular crowding had little effect on hydrolysis by exo III and exo I exonucleases. Moreover, kinetic analysis showed that the maximum velocity for the reaction of DNase I at 25°C was increased from 0.1 to 2.7 μM/min by molecular crowding with 20% (w/v) PEG, whereas that of exonuclease I at 37°C decreased from 2.2 to 0.4 μM/min. In contrast, molecular crowding did not significantly affect the Michaelis constant of DNase I or exonuclease I. These results indicate that molecular crowding has different effects on the catalytic activities of exonucleases and endonucleases

Dynamic Analysis of Photosynthate Translocation Into Strawberry Fruits Using Non-invasive 11C-Labeling Supported With Conventional Destructive Measurements Using 13C-Labeling

In protected strawberry (Fragaria × ananassa Duch.) cultivation, environmental control based on the process of photosynthate translocation is essential for optimizing fruit quality and yield, because the process of photosynthate translocation directly affects dry matter partitioning. We visualized photosynthate translocation to strawberry fruits non-invasively with 11CO2 and a positron-emitting tracer imaging system (PETIS). We used PETIS to evaluate real-time dynamics of 11C-labeled photosynthate translocation from a 11CO2-fed leaf, which was immediately below the inflorescence, to individual fruits on an inflorescence in intact plant. Serial photosynthate translocation images and animations obtained by PETIS verified that the 11C-photosynthates from the source leaf reached the sink fruit within 1 h but did not accumulate homogeneously within a fruit. The quantity of photosynthate translocation as represented by 11C radioactivity varied among individual fruits and their positions on the inflorescence. Photosynthate translocation rates to secondary fruit were faster than those to primary or tertiary fruits, even though the translocation pathway from leaf to fruit was the longest for the secondary fruit. Moreover, the secondary fruit was 25% smaller than the primary fruit. Sink activity (11C radioactivity/dry weight [DW]) of the secondary fruit was higher than those of the primary and tertiary fruits. These relative differences in sink activity levels among the three fruit positions were also confirmed by 13C tracer measurement. Photosynthate translocation rates in the pedicels might be dependent on the sink strength of the adjoining fruits. The present study established 11C-photosynthate arrival times to the sink fruits and demonstrated that the translocated material does not uniformly accumulate within a fruit. The actual quantities of translocated photosynthates from a specific leaf differed among individual fruits on the same inflorescence. To the best of our knowledge, this is the first reported observation of real-time translocation to individual fruits in an intact strawberry plant using 11C-radioactive- and 13C-stable-isotope analyses