Combatting antimicrobial resistance via the cysteine biosynthesis pathway in bacterial pathogens.

Antibiotics are the cornerstone of modern medicine and agriculture, and rising antibiotic resistance is one the biggest threats to global health and food security. Identifying new and different druggable targets for the development of new antibiotics is absolutely crucial to overcome resistance. Adjuvant strategies that either enhance the activity of existing antibiotics or improve clearance by the host immune system provide another mechanism to combat antibiotic resistance. Targeting a combination of essential and non-essential enzymes that play key roles in bacterial metabolism is a promising strategy to develop new antimicrobials and adjuvants, respectively. The enzymatic synthesis of L-cysteine is one such strategy. Cysteine plays a key role in proteins and is crucial for the synthesis of many biomolecules important for defense against the host immune system. Cysteine synthesis is a two-step process, catalyzed by two enzymes. Serine acetyltransferase (CysE) catalyzes the first step to synthesize the pathway intermediate O-acetylserine, and O-acetylserine sulfhydrylase (CysK/CysM) catalyzes the second step using sulfide or thiosulfate to produce cysteine. Disruption of the cysteine biosynthesis pathway results in dysregulated sulfur metabolism, altering the redox state of the cell leading to decreased fitness, enhanced susceptibility to oxidative stress and increased sensitivity to antibiotics. In this review, we summarize the structure and mechanism of characterized CysE and CysK/CysM enzymes from a variety of bacterial pathogens, and the evidence that support targeting these enzymes for the development of new antimicrobials or antibiotic adjuvants. In addition, we explore and compare compounds identified thus far that target these enzymes.

A holistic view of cancer bioenergetics: mitochondrial function and respiration play fundamental roles in the development and progression of diverse tumors.

Since Otto Warburg made the first observation that tumor cells exhibit altered metabolism and bioenergetics in the 1920s, many scientists have tried to further the understanding of tumor bioenergetics. Particularly, in the past decade, the application of the state-of the-art metabolomics and genomics technologies has revealed the remarkable plasticity of tumor metabolism and bioenergetics. Firstly, a wide array of tumor cells have been shown to be able to use not only glucose, but also glutamine for generating cellular energy, reducing power, and metabolic building blocks for biosynthesis. Secondly, many types of cancer cells generate most of their cellular energy via mitochondrial respiration and oxidative phosphorylation. Glutamine is the preferred substrate for oxidative phosphorylation in tumor cells. Thirdly, tumor cells exhibit remarkable versatility in using bioenergetics substrates. Notably, tumor cells can use metabolic substrates donated by stromal cells for cellular energy generation via oxidative phosphorylation. Further, it has been shown that mitochondrial transfer is a critical mechanism for tumor cells with defective mitochondria to restore oxidative phosphorylation. The restoration is necessary for tumor cells to gain tumorigenic and metastatic potential. It is also worth noting that heme is essential for the biogenesis and proper functioning of mitochondrial respiratory chain complexes. Hence, it is not surprising that recent experimental data showed that heme flux and function are elevated in non-small cell lung cancer (NSCLC) cells and that elevated heme function promotes intensified oxygen consumption, thereby fueling tumor cell proliferation and function. Finally, emerging evidence increasingly suggests that clonal evolution and tumor genetic heterogeneity contribute to bioenergetic versatility of tumor cells, as well as tumor recurrence and drug resistance. Although mutations are found only in several metabolic enzymes in tumors, diverse mutations in signaling pathways and networks can cause changes in the expression and activity of metabolic enzymes, which likely enable tumor cells to gain their bioenergetic versatility. A better understanding of tumor bioenergetics should provide a more holistic approach to investigate cancer biology and therapeutics. This review therefore attempts to comprehensively consider and summarize the experimental data supporting our latest view of cancer bioenergetics.

Breastfeeding in women with diabetes: lower rates despite greater rewards. A population-based study.

AIMS: To explore intention to breastfeed and breastfeeding rates in hospital and on discharge across women with pre-gestational or gestational diabetes mellitus, or no diabetes. METHODS: A retrospective cohort analysis was conducted using data from four Ontario hospitals. Women who delivered a viable infant between 1 April 2008 and 31 March 2010 were included in the study. Unadjusted and adjusted odds ratios were calculated for each outcome measure and were used to compare the breastfeeding rates among women with and without diabetes. RESULTS: After controlling for potential confounders, women with insulin-treated diabetes were less likely to intend to breastfeed, when compared with women without diabetes (adjusted odds ratio 0.49, 95% CI 0.27-0.89). In hospital, women with insulin-treated diabetes were least likely to breastfeed (odds ratio 0.42, 95% CI 0.26-0.67), followed by women with non-insulin-treated diabetes (odds ratio 0.50, 95% CI 0.26-0.96) and women with gestational diabetes (odds ratio 0.77, 95% CI 0.68-0.87) when compared with women without diabetes. On discharge, women with insulin-treated diabetes were least likely to breastfeed (odds ratio 0.38, 95% CI 0.24-0.60), followed by women with gestational diabetes (odds ratio 0.75, 95% CI 0.66-0.85); rates of breastfeeding among women with non-insulin-treated diabetes were comparable on discharge with those of women without diabetes. Women seeking care from an antenatal provider other than a physician were 2-3 times more likely to breastfeed in hospital and on discharge. CONCLUSIONS: Women with insulin-treated diabetes had the poorest outcomes with respect to breastfeeding rates. Gestational and non-insulin-treated diabetes were associated with lower rates of breastfeeding in hospital, while gestational diabetes was additionally associated with lower breastfeeding rates on discharge.

Original sound compositions reduce anxiety in emergency department patients: a randomised controlled trial.

OBJECTIVE: To determine whether emergency department (ED) patients' self-rated levels of anxiety are affected by exposure to purpose-designed music or sound compositions with and without the audio frequencies of embedded binaural beat. DESIGN, SETTING AND PARTICIPANTS: Randomised controlled trial in an ED between 1 February 2010 and 14 April 2010 among a convenience sample of adult patients who were rated as category 3 on the Australasian Triage Scale. INTERVENTIONS: All interventions involved listening to soundtracks of 20 minutes' duration that were purpose-designed by composers and sound-recording artists. Participants were allocated at random to one of five groups: headphones and iPod only, no soundtrack (control group); reconstructed ambient noise simulating an ED but free of clear verbalisations; electroacoustic musical composition; composed non-musical soundtracks derived from audio field recordings obtained from natural and constructed settings; sound composition of audio field recordings with embedded binaural beat. All soundtracks were presented on an iPod through headphones. Patients and researchers were blinded to allocation until interventions were administered. State-trait anxiety was self-assessed before the intervention and state anxiety was self-assessed again 20 minutes after the provision of the soundtrack. MAIN OUTCOME MEASURE: Spielberger State-Trait Anxiety Inventory. RESULTS: Of 291 patients assessed for eligibility, 170 patients completed the pre-intervention anxiety self-assessment and 169 completed the post-intervention assessment. Significant decreases (all P < 0.001) in anxiety level were observed among patients exposed to the electroacoustic musical composition (pre-intervention mean, 39; post-intervention mean, 34), audio field recordings (42; 35) or audio field recordings with embedded bianaural beats (43; 37) when compared with those allocated to receive simulated ED ambient noise (40; 41) or headphones only (44; 44). CONCLUSION: In moderately anxious ED patients, state anxiety was reduced by 10%-15% following exposure to purpose-designed sound interventions. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN 12608000444381.

The effectiveness of implementing a reminder system into routine clinical practice: does it increase postpartum screening in women with gestational diabetes?

INTRODUCTION: During regular care, women with previous gestational diabetes mellitus (GDM) rarely receive the recommended screening test for type 2 diabetes, a 2-hour oral glucose tolerance test (OGTT), in the postpartum period. The current study examined whether the implementation of a reminder system improved screening rates. METHODS: Based on our previous randomized control trial, we implemented a postpartum reminder (letter or phone call) protocol into routine care at two of three clinical sites. We verified postpartum testing by searching hospital laboratory databases and by linking to the provincial physician service claims database. The primary outcome was the proportion of patients who underwent an OGTT within 6 months of delivery. RESULTS: Women who received care in a setting using a reminder system were more likely to receive an OGTT within 6 months postpartum (28%) compared with usual care (14%). The OGTT rates for both reminder groups were lower than that found in our randomized control trial (28% vs. 60%). CONCLUSION: Although the screening rates remain low, postpartum reminders doubled screening rates using the recommended test, the OGTT.

Changes in homocysteine levels during normal pregnancy.

OBJECTIVE: The objective of this study was to determine the changes in total plasma homocysteine concentration that occur during normal pregnancy. STUDY DESIGN: In this cross-sectional study homocysteine was measured in 155 normal women in the first, second, and third trimesters and in nonpregnant controls. In addition, albumin, serum B12, serum folate, and red blood cell folate concentrations were measured and correlated to homocysteine values. RESULTS: The mean homocysteine concentration (in micromoles per liter) was 5.6 (95% confidence interval 3.9-7.3) at 8-16 weeks' gestation, 4.3 (95% confidence interval 3.5-5.3) at 20-28 weeks' gestation, 5.5 (95% confidence interval 3.3-7.5) at 36-42 weeks' gestation, and 7.9 (95% confidence interval 6.2-9.6) in the nonpregnant control group. Homocysteine was significantly lower in all 3 trimesters of pregnancy compared with nonpregnant controls (P <.001). Homocysteine levels were directly correlated with albumin levels, which decreased during pregnancy. Homocysteine concentrations were decreased in subjects taking folic acid supplementation. CONCLUSION: Serum concentrations of homocysteine decrease during pregnancy. This occurs in association with the physiologic fall in albumin during pregnancy, as well as with folic acid supplementation.