Comparable Benefit of β-Blocker Therapy in Heart Failure Across Regions of the World: Meta-analysis of Randomized Clinical Trials

Background

There is a concern about geographical region heterogeneity regarding clinical benefit of β-blocker (BB) therapy in heart failure with reduced ejection fraction (HFrEF). This study sought to compare benefits of BB use within randomized controlled trials (RCTs) that enrolled patients with HFrEF from North America (NA) compared with other regions of the world (ROW).

Methods

We conducted a meta-analysis using MEDLINE, EMBASE, Cochrane Library, Web of Science, and Scopus (inceptions-December 2012) of BB RCTs stratified according to NA vs ROW. The primary end point was all-cause mortality and secondary end points were cardiovascular death, sudden death, death due to pump failure, and premature drug discontinuation. Summary odds ratios (ORs) and 95% confidence intervals (CIs) for each outcome were calculated with interaction terms for region. Two-sided P values were calculated with P < 0.05 considered significant.

Results

The analysis included 16 RCTs with 14,452 patients; 7 trials were conducted in NA and 9 trials in ROW with follow-up durations of 3-58 months. All-cause mortality was consistently reduced in NA (OR, 0.82; 95% CI, 0.71-0.96; P = 0.01) and ROW (OR, 0.76; 95% CI, 0.69-0.84; P < 0.001; P-interaction = 0.40). Overall and according to region, all secondary end points including premature drug discontinuation were also less with BB therapy (P-interactions all ≥ 0.10).

Conclusions

For the regions represented in the included trials, there is no evidence to suggest that geographic region is a significant moderator of clinical outcomes with BB therapy in HFrEF patients.     

Metabolic model for diversity-generating biosynthesis

A conventional metabolic pathway leads to a specific product. In stark contrast, there are diversity-generating metabolic pathways that naturally produce different chemicals, sometimes of great diversity. We demonstrate that for one such pathway, tru, each ensuing metabolic step is slower, in parallel with the increasing potential chemical divergence generated as the pathway proceeds. Intermediates are long lived and accumulate progressively, in contrast with conventional metabolic pathways, in which the first step is rate-limiting and metabolic intermediates are short-lived. Understanding these fundamental differences enables several different practical applications, such as combinatorial biosynthesis, some of which we demonstrate here. We propose that these principles may provide a unifying framework underlying diversity-generating metabolism in many different biosynthetic pathways.There are two fundamentally different types of metabolic pathways in living systems. The first are aimed to generate one or a few discrete chemicals; these comprise the majority of pathways. The second have evolved to produce large numbers of different metabolites (1, 2). Although perhaps fewer in number, this second class, which we will call “diversity generating” (DG), may be responsible for the majority of small molecules in living systems. A key difference is that the compounds produced in the latter generally have a more limited phylogenetic distribution.The metabolic pathways first elucidated were for the synthesis of essential metabolites found in all cells, such as amino acids, purines, or pyrimidines. These conventional metabolic pathways typically comprise multiple metabolic steps, with the intermediates generated in each step converted only to the final product of the pathway. DG pathways, however, do not yield a single final product. Each enzyme in a DG pathway has relaxed substrate specificity and is able to handle a variety of compounds, carrying out the same chemical transformation on different substrates.Previously, an evolutionary framework was developed to explain why some biosynthetic pathways produce many compounds (3–5). In this study we provide the first integrated overview, to our knowledge, of the multiple metabolic steps that comprise a DG biosynthetic pathway. We have uncovered striking differences in how this pathway differs from the canonical features of conventional pathways. Our results provide an initial framework for understanding how DG pathways are designed and how key features of such pathways diverge from the textbook model.We specifically examine the tru and related pat cyanobactin pathways (1, 6). These ribosomally synthesized and posttranslationally modified (RiPP) secondary metabolite pathways were identified in cyanobacterial symbionts of coral reef animals. Their expression required transfer to a model host, Escherichia coli (Fig. 1) (7). In nature, tru and pat accept a wide variety of hypervariable substrates, but the enzymes are essentially identical in sequence. The tru pathway is capable of synthesizing potentially millions of compounds with highly diverse structures (8). In tru, the first step is the ribosomal synthesis of the precursor peptide, TruE, which encodes the production of two different patellin products (Fig. 1 and SI Appendix, Fig. S1) (7). Many different natural and artificial TruE variants exist, encoding different products (“X” in Fig. 1). TruE is the substrate for TruD, which inserts heterocycles (9), and TruA, a protease that removes the leader sequence (10). The product of TruA is the substrate of protease TruG, which macrocyclizes the N and C termini (10). Finally, TruF1 installs one or more isoprene units on the mature macrocycle (11).Open in a separate windowFig. 1.Generation of chemical diversity by cyanobactin pathways. (A) Biosynthesis of cyanobactins by the tru pathway. The relationship between the precursor peptide recognition sequence and the relevant enzyme is shown by color. For example, the TruA protease recognition sequence is shown in blue. “X” indicates regions that can be highly variable. Because these elements are progressively cleaved during biosynthesis, the substrate for each ensuing enzymatic step is progressively different in structure (SI Appendix, Fig. S1). (B) Representative natural coral reef compounds produced in this study.Each enzyme has relaxed substrate specificity; thousands of derivatives have been synthesized (8, 12–14). At each ensuing biochemical step the substrates are increasingly different, because early substrates contain large conserved elements known as “recognition sequences,” which are progressively pared away in the course of biosynthesis and are not found in the products of the pathway (1, 15). Thus, late-stage enzymes encounter structurally divergent substrates, whereas the substrates of early-stage enzymes retain some conserved structural features.Although tru has been expressed in E. coli to produce many compounds, a limitation was low and variable yield. Common methods afforded only modest yield improvements (16). Here, while improving yield by nearly 30,000-fold from an initial ∼1 μg/L, we discovered principles that may be fundamental in DG pathways.     

Applicability of natural colourless topaz as a high-energy beam dosimeter

Thermoluminescence characteristics of colourless topaz collected from Pakistan were studied. The objective of this study was to design and develop a TL dosimeter for high-energy beams. Samples were irradiated with (60)Co, (137)Cs and linear accelerator (6 MV, 15 MV). Glow curves of the chips revealed four trapping levels at temperature ranges 71-82 °C (Peak 1), 173-185 °C (Peak 2), 197-210 °C (Peak 3) and 225-260 °C (Peak 4). Peak 4 is stable and rose linearly with increase of exposure levels. The TL response vs. exposure showed linear behaviour between 1 and 10(2) Gy. Initial fading is rapid in first 24 h and becomes 8% in next 19 days. The variation in response of the last 20th cycle with respect to the 1st cycle was found to be 4% with a maximum variation of 15% within all data points. The thermoluminescence response was observed to be higher at low energy. The chips remained mechanically intact during handling in all experiments. Topaz chips can effectively and efficiently be used as a TLD for high-energy beams.     

Retinal Phenotyping of Ferrochelatase Mutant Mice Reveals Protoporphyrin Accumulation and Reduced Neovascular Response

PurposeHeme depletion, through inhibition of ferrochelatase (FECH), blocks retinal and choroidal neovascularization. Both pharmacologic FECH inhibition and a partial loss-of-function Fech mutation (Fech^m1Pas) are associated with decreased neovascularization. However, the ocular physiology of Fech^m1Pas mice under basal conditions has not been characterized. Here, we aimed to characterize the retinal phenotype of Fech^m1Pas mice.MethodsWe monitored retinal vasculature at postnatal day 17, 2 months, and 6 months in Fech^m1Pas homozygotes, heterozygotes, and their wild-type littermates. We characterized Fech substrate protoporphyrin (PPIX) fluorescence in the eye (excitation = 403 nm, emission = 628 nm), retinal function by electroretinogram, visual acuity by optomotor reflex, and retinal morphology by optical coherence tomography and histology. We stained vasculature using isolectin B4 and fluorescein angiography. We determined endothelial sprouting of retinal and choroidal tissue ex vivo and bioenergetics of retinal punches using a Seahorse flux analyzer.ResultsFundi, retinal vasculature, venous width, and arterial tortuosity showed no aberrations. However, VEGF-induced retinal and choroidal sprouting was decreased in Fech^m1Pas mutants. Homozygous Fech^m1Pas mice had pronounced buildup of PPIX in the posterior eye with no damage to visual function, bioenergetics, and integrity of retinal layers.ConclusionsEven with a buildup of PPIX in the retinal vessels in Fech^m1Pas homozygotes, the vasculature remains normal. Notably, stimulus-induced ex vivo angiogenesis was decreased in Fech^m1Pas mutants, consistent with reduced pathologic angiogenesis seen previously in neovascular animal models. Our findings indicate that Fech^m1Pas mice are a useful model for studying the effects of heme deficiency on neovascularization due to Fech blockade.     

The correlation of antioxidant levels of breast cancer: A case controlled study

Many free radicles are implicated to activate a number of oncogenic signaling, cause damage to deoxyribonucleic acid and tumor suppressor genes, or promote expression of proto-oncogenes. Reduced level of antioxidants and increases oxidative stress markers are associated with the development of various types of cancer.This prospective study included 60 women who were grouped into equal groups. Patients group included 30 breast cancer women and control group consisting of 30 apparently healthy women. Both groups were compared regarding the serum levels of antioxidants biomarkers (vitamin C, ceruloplasmin, glutathione) and oxidative stress biomarkers, malondialdehyde (MDA), peroxynitrite, and gamma-glutamyl transferase.In regard to the antioxidant biomarkers, there was a significant difference between the patients and the controls regarding the levels of serum ceruloplasmin and glutathione, (P values .000) for each while vitamin C showed no significant correlation (P value .053), while regarding oxidative stress biomarkers, the correlation was significant for both peroxynitrite and MDA (P value .000 and .001) respectively, and not significant for gamma-glutamyl transferase (P value 1.00).Reduced level both ceruloplasmin and glutathione is seen in patients with breast cancer while vitamin C is not associated. Elevated levels of both peroxynitrite and MDA is seen in patients with breast cancer which may be used as serum markers for the early detection of breast cancer.