Cysteine Boosts Fitness Under Hypoxia-Mimicked Conditions in Ovarian Cancer by Metabolic Reprogramming

Among gynecologic malignancies, ovarian cancer is the third most prevalent and the most common cause of death, especially due to diagnosis at an advanced stage together with resistance to therapy. As a solid tumor grows, cancer cells in the microenvironment are exposed to regions of hypoxia, a selective pressure prompting tumor progression and chemoresistance. We have previously shown that cysteine contributes to the adaptation to this hypoxic microenvironment, but the mechanisms by which cysteine protects ovarian cancer cells from hypoxia-induced death are still to be unveiled. Herein, we hypothesized that cysteine contribution relies on cellular metabolism reprogramming and energy production, being cysteine itself a metabolic source. Our results strongly supported a role of xCT symporter in energy production that requires cysteine metabolism instead of hydrogen sulfide (H2S) per se. Cysteine degradation depends on the action of the H2S-synthesizing enzymes cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and/or 3-mercaptopyruvate sulfurtransferase (MpST; together with cysteine aminotransferase, CAT). In normoxia, CBS and CSE inhibition had a mild impact on cysteine-sustained ATP production, pointing out the relevance of CAT + MpST pathway. However, in hypoxia, the concomitant inhibition of CBS and CSE had a stronger impact on ATP synthesis, thus also supporting a role of their hydrogen sulfide and/or cysteine persulfide-synthesizing activity in this stressful condition. However, the relative contributions of each of these enzymes (CBS/CSE/MpST) on cysteine-derived ATP synthesis under hypoxia remains unclear, due to the lack of specific inhibitors. Strikingly, NMR analysis strongly supported a role of cysteine in the whole cellular metabolism rewiring under hypoxia. Additionally, the use of cysteine to supply biosynthesis and bioenergetics was reinforced, bringing cysteine to the plateau of a main carbon sources in cancer. Collectively, this work supports that sulfur and carbon metabolism reprogramming underlies the adaptation to hypoxic microenvironment promoted by cysteine in ovarian cancer.

Kinetic analysis of cystine uptake and inhibition pattern of sulfasalazine in A549 cells

Cystine/glutamate transporter (xCT) is an antiporter involved in cystine uptake and glutamate efflux. However, there are very few reports regarding the kinetic analysis of xCT for cystine uptake using cancer cell lines, as well as the inhibition pattern of sulfasalazine, an inhibitor of xCT, for cystine uptake. Therefore, the purpose of this study was to clarify the kinetics of xCT in A549 cells, human lung cancer cells, and to reveal the inhibition pattern of sulfasalazine. Cystine uptake occurred in a time-dependent manner, with linear cystine uptake observed for 5 min. Additionally, sulfasalazine inhibited cystine uptake in a concentration-dependent manner, presenting an IC₅₀ value of 24.7 ± 5.6 μM. Cystine uptake was saturated with increasing concentration, demonstrating K_m and V_max values of 179.4 ± 26.7 μM and 30.4 ± 2.3 nmol/min/mg protein, respectively. Moreover, during cystine uptake with sulfasalazine, K_m and V_max were >300 μM and 8.0 ± 1.5 nmol/min/mg protein, respectively, suggesting that sulfasalazine might demonstrate a mixed inhibition pattern. Furthermore, xCT siRNA decreased the xCT mRNA level and reduced cystine uptake. In conclusion, xCT was involved in the cystine uptake in A549 cells and sulfasalazine showed a mixed inhibition pattern to xCT.

Chronic Sulfasalazine Treatment in Mice Induces System xc - - Independent Adverse Effects

Despite ample evidence for the therapeutic potential of inhibition of the cystine/glutamate antiporter system x_c⁻ in neurological disorders and in cancer, none of the proposed inhibitors is selective. In this context, a lot of research has been performed using the EMA- and FDA-approved drug sulfasalazine (SAS). Even though this molecule is already on the market for decades as an anti-inflammatory drug, serious side effects due to its use have been reported. Whereas for the treatment of the main indications, SAS needs to be cleaved in the intestine into the anti-inflammatory compound mesalazine, it needs to reach the systemic circulation in its intact form to allow inhibition of system x_c⁻. The higher plasma levels of intact SAS (or its metabolites) might induce adverse effects, independent of its action on system x_c⁻. Some of these effects have however been attributed to system x_c⁻ inhibition, calling into question the safety of targeting system x_c⁻. In this study we chronically treated system x_c⁻ - deficient mice and their wildtype littermates with two different doses of SAS (160 mg/kg twice daily or 320 mg/kg once daily, i.p.) and studied some of the adverse effects that were previously reported. SAS had a negative impact on the survival rate, the body weight, the thermoregulation and/or stress reaction of mice of both genotypes, and thus independent of its inhibitory action on system x_c⁻. While SAS decreased the total distance travelled in the open-field test the first time the mice encountered the test, it did not influence this parameter on the long-term and it did not induce other behavioral changes such as anxiety- or depressive-like behavior. Finally, no major histological abnormalities were observed in the spinal cord. To conclude, we were unable to identify any undesirable system x_c⁻-dependent effect of chronic administration of SAS.

Urolithiasis in dogs: Evaluation of trends in urolith composition and risk factors (2006-2018)

BACKGROUND

Urolithiasis is a common and often recurrent problem in dogs.

OBJECTIVE

To evaluate trends in urolith composition in dogs and to assess risk factors for urolithiasis, including age, breed, sex, neuter status, urolith location, and bacterial urolith cultures.

SAMPLE POPULATION

A total of 10 444 uroliths and the dogs from which they were obtained.

METHODS

The laboratory database at the UC Davis Gerald V. Ling Urinary Stone Analysis Laboratory was searched for all urolith submissions from dogs between January 2006 and December 2018. Mineral type, age, breed, sex, neuter status, urolith location, and urolith culture were recorded. Trends were evaluated and variables compared to evaluate risk factors.

RESULTS

Calcium oxalate (CaOx) and struvite-containing uroliths comprised the majority of all submissions from dogs, representing 47.0% and 43.6%, respectively. The proportion of CaOx-containing uroliths significantly decreased from 49.5% in 2006 to 41.8% in 2018 (P = .006), with no change in the proportion of struvite-containing urolith submissions. Cystine-containing uroliths comprised 2.7% of all submissions between 2006 and 2018 and a significant nonlinear increase in this mineral type occurred over time (1.4% of all submissions in 2006 to 8.7% in 2018; P < .001). Of all cystine-containing uroliths, 70.3% were from intact male dogs. Age, breed, and sex predispositions for uroliths were similar to those previously identified.

CONCLUSIONS AND CLINICAL IMPORTANCE

Although calcium oxalate- and struvite-containing uroliths continue to be the most common uroliths submitted from dogs, a decrease in the proportion of CaOx-containing uroliths and an increase in the proportion of cystine-containing uroliths occurred during the time period evaluated.

A mTORC1-mediated cyst(e)ine sensing mechanism governing GPX4 synthesis and ferroptosis

Ferroptosis is a cell death mechanism triggered by lipid peroxidation. Our recent study linked cyst(e)ine availability with glutathione peroxidase 4 (GPX4) protein synthesis and ferroptosis mitigation via a Rag-mechanistic target of rapamycin complex 1 (mTORC1) axis, and proposed that co-targeting mTORC1 and ferroptosis is a promising strategy for cancer therapy.

The mTORC1-mediated activation of ATF4 promotes protein and glutathione synthesis downstream of growth signals

The mechanistic target of rapamycin complex 1 (mTORC1) stimulates a coordinated anabolic program in response to growth-promoting signals. Paradoxically, recent studies indicate that mTORC1 can activate the transcription factor ATF4 through mechanisms distinct from its canonical induction by the integrated stress response (ISR). However, its broader roles as a downstream target of mTORC1 are unknown. Therefore, we directly compared ATF4-dependent transcriptional changes induced upon insulin-stimulated mTORC1 signaling to those activated by the ISR. In multiple mouse embryo fibroblast and human cancer cell lines, the mTORC1-ATF4 pathway stimulated expression of only a subset of the ATF4 target genes induced by the ISR, including genes involved in amino acid uptake, synthesis, and tRNA charging. We demonstrate that ATF4 is a metabolic effector of mTORC1 involved in both its established role in promoting protein synthesis and in a previously unappreciated function for mTORC1 in stimulating cellular cystine uptake and glutathione synthesis.

Extremely rapid stone formation in cystinuria: look out for dietary supplements!

Cystinuria is an autosomal recessive disease characterized by recurrent nephrolithiasis. The prevention of new stones is based on diluting and alkalinizing urine, as well as a low salt and moderate protein intake. The avoidance of food rich in methionine (the precursor of cystine) is also advocated. We report the case of a young adult adherent to the preventative strategy who was stone-free and within months formed a large stone. This coincided with the recent intake of a dietary supplement containing both cystine and methionine. Patients and physicians should be aware of the potential harm of such supplements in patients with cystinuria.

Non-canonical Glutamate-Cysteine Ligase Activity Protects against Ferroptosis

Cysteine is required for maintaining cellular redox homeostasis in both normal and transformed cells. Deprivation of cysteine induces the iron-dependent form of cell death known as ferroptosis; however, the metabolic consequences of cysteine starvation beyond impairment of glutathione synthesis are poorly characterized. Here, we find that cystine starvation of non-small-cell lung cancer cell lines induces an unexpected accumulation of γ-glutamyl-peptides, which are produced due to a non-canonical activity of glutamate-cysteine ligase catalytic subunit (GCLC). This activity is enriched in cell lines with high levels of NRF2, a key transcriptional regulator of GCLC, but is also inducible in healthy murine tissues following cysteine limitation. γ-glutamyl-peptide synthesis limits the accumulation of glutamate, thereby protecting against ferroptosis. These results indicate that GCLC has a glutathione-independent, non-canonical role in the protection against ferroptosis by maintaining glutamate homeostasis under cystine starvation.

Identification and initial characterization of a potent inhibitor of ferroptosis

Ferroptosis is a form of iron-dependent cell death characterized by elevated lipid peroxides and reactive oxygen species (ROS). Glutathione (GSH) plays an essential role in scavenging ROS to maintain cell viability and acts as a cofactor of GSH peroxidase 4 (GPX4) that protects lipids from oxidation. We have previously described a novel class of small molecules that induce ferroptosis in certain types of cancer cells. These compounds induce ferroptosis by blocking the uptake of cystine required for GSH synthesis. Even though ferroptosis is a well-established form of cell death, signaling pathways that modulate this process are not known. Therefore, we used a panel of growth factors/kinase inhibitors to test effects on ferroptosis induced by our lead compound. We discovered that BMS536924, a dual inhibitor of insulin-like growth and insulin receptors, is a potent inhibitor of ferroptosis. Further investigation indicated that the anti-ferroptotic activity of BMS536924 does not lie in its ability to inhibit insulin signal transduction. Instead, we provide evidence that BMS536924 binds iron, an essential cofactor in ferroptosis. Our results suggest caution in interpreting the effects of BMS536924 in investigations of insulin signaling and uncover a novel ferroptosis inhibitor.

Dietary Cystine Ameliorates Defects in Spermatogenesis via Testosterone Production Induced by Protein Deficiency and Darkness in Rats

Nutrition and light-dark cycle influence rat testicular development. With 9% casein diet (low protein diet) under normal 12 h-12 h lighting cycles (9P), juvenile rat testes undergo normal growth. On the other hand, a low protein diet with constant darkness (D9P) results in a growth arrest of rat testes. Supplementation of cystine to the low protein diet under constant darkness (D9PC) had a tendency to increase testes weight, suggesting an improvement in growth suppression. Whether the growth suppression of testes in D9P is associated with suppression of spermatogenesis has not yet been shown. We aimed to determine the effect of a low protein diet and constant darkness with or without dietary cystine in testes using a histological technique. In the histological assessment, D9P testes showed a decreased number of seminiferous tubules with elongated spermatids, indicating a functional testicular defect in this group. However, cystine supplementation resulted in enhanced spermatogenesis versus control animals (D9PC vs. D9P) implying the importance of cystine to testicular development in this condition. Furthermore, serum testosterone concentration was increased in D9PC suggesting contribution of testosterone to ameliorate spermatogenesis. From these results, we conclude that cystine supplementation to a low protein diet under constant darkness promoted an increase in testosterone which in turn benefitted spermatogenesis.

Multiple Disulfide-Bonded States of Native Proteins: Estimate of Number Using Probabilities of Disulfide Bond Formation

The polypeptide backbone of proteins is held together by two main types of covalent bonds: the peptide bonds that link the amino acid residues and the disulfide bonds that link pairs of cysteine amino acids. Disulfide bonds form as a protein folds in the cell and formation was assumed to be complete when the mature protein emerges. This is not the case for some secreted human blood proteins. The blood clotting protein, fibrinogen, and the protease inhibitor, α2-macroglobulin, exist in multiple disulfide-bonded or covalent states in the circulation. Thousands of different states are predicted assuming no dependencies on disulfide bond formation. In this study, probabilities for disulfide bond formation are employed to estimate numbers of covalent states of a model polypeptide with reference to α2-macroglobulin. When disulfide formation is interdependent in a protein, the number of covalent states is greatly reduced. Theoretical estimates of the number of states will aid the conceptual and experimental challenges of investigating multiple disulfide-bonded states of a protein.

A Pilot Study for Investigation of Plasma Amino Acid Profile in Neurofibromatosis Type 1 Patients

BACKGROUND

Neurofibromatosis, also known as Von Recklinghausen disease, is a systemic and progressive genetic disease that primarily affects the skin, eyes, nervous system and bones. The disease can occur in a variety of ways and can vary from individuals. Metabolomic-based research using blood samples has enabled new diagnostic methods to be used in the diagnosis of various diseases, especially cancer. Among metabolites, profiling of plasma free amino acids (PFAA) is a promising approach because PFAAs bind all organ systems and play an important role in metabolism.

OBJECTIVE

This study aimed to determine the characteristics of PFAA profiles in neurofibromatosis patients and the possibility of using them for early detection and treatment of the disease.

METHOD

Patients with a diagnosis of Neurofibromatosis Type I confirmed by genetic analysis and healthy individuals of the same age group without any disease were included in the study. We analysed the nineteen plasma free amino acids (phenylalanine, proline, threonine, arginine, asparagine, cystine, valine, glutamate, tyrosine, serine, glutamine, glycine, tryptophane, leucine, lysine, methionine, isoleucine, aspartate and alanine) from neurofibromatosis Type I patients and control group by liquid chromatography tandem mass spectrometry (LC-MS/MS) in Metabolism Laboratory of Harran University Research and Application Hospital. The results of the plasma free amino acid levels were divided into 3 groups as essential, semi-essential and non-essential. The differences of amino acid levels between groups were determined.

RESULTS

Eight amino acid levels (methionine, arginine, cystine, glutamine, proline, asparagine, serine, aspartate) were significantly altered in patients with neurofibromatosis type 1. In essential amino acids, methionine levels were significantly higher in the patient group than the control group. While the levels of arginine and glutamine in semi-essential amino acids were statistically significantly higher in the patient group, a significant decrease was observed in cystine and proline levels compared to the control group's amino acid levels. In non-essential amino acids group, asparagine, serine and aspartate amino acid levels were significantly higher in the patient group compared to the control group.

CONCLUSION

The current research predicates that eight amino acids, nsmely methionine, arginine, cystine, glutamine, proline, asparagine, serine, aspartate can be considered to be valuable biomarkers for neurofibromatosis type I. This present study is the first to build models for neurofibromatosis Type I screening using plasma free amino acids and the amino acid profile will guide the predicting of the complications that may occur during the course of the disease.

Cystine transporter SLC7A11/xCT in cancer: ferroptosis, nutrient dependency, and cancer therapy

The cystine/glutamate antiporter SLC7A11 (also commonly known as xCT) functions to import cystine for glutathione biosynthesis and antioxidant defense and is overexpressed in multiple human cancers. Recent studies revealed that SLC7A11 overexpression promotes tumor growth partly through suppressing ferroptosis, a form of regulated cell death induced by excessive lipid peroxidation. However, cancer cells with high expression of SLC7A11 (SLC7A11^high) also have to endure the significant cost associated with SLC7A11-mediated metabolic reprogramming, leading to glucose- and glutamine-dependency in SLC7A11^high cancer cells, which presents potential metabolic vulnerabilities for therapeutic targeting in SLC7A11^high cancer. In this review, we summarize diverse regulatory mechanisms of SLC7A11 in cancer, discuss ferroptosis-dependent and -independent functions of SLC7A11 in promoting tumor development, explore the mechanistic basis of SLC7A11-induced nutrient dependency in cancer cells, and conceptualize therapeutic strategies to target SLC7A11 in cancer treatment. This review will provide the foundation for further understanding SLC7A11 in ferroptosis, nutrient dependency, and tumor biology and for developing novel effective cancer therapies.

Polyamine pathway activity promotes cysteine essentiality in cancer cells

Cancer cells have high demands for non-essential amino acids (NEAAs), which are precursors for anabolic and antioxidant pathways that support cell survival and proliferation. It is well-established that cancer cells consume the NEAA cysteine, and that cysteine deprivation can induce cell death; however, the specific factors governing acute sensitivity to cysteine starvation are poorly characterized. Here, we show that that neither expression of enzymes for cysteine synthesis nor availability of the primary precursor methionine correlated with acute sensitivity to cysteine starvation. We observed a strong correlation between efflux of the methionine-derived metabolite methylthioadenosine (MTA) and sensitivity to cysteine starvation. MTA efflux results from genetic deletion of methylthioadenosine phosphorylase (MTAP), which is frequently deleted in cancers. We show that MTAP loss upregulates polyamine metabolism which, concurrently with cysteine withdrawal, promotes elevated reactive oxygen species and prevents cell survival. Our results reveal an unexplored metabolic weakness at the intersection of polyamine and cysteine metabolism.

Ferroptosis of epithelial ovarian cancer: genetic determinants and therapeutic potential

Epithelial ovarian cancer (OVCA) is the most lethal gynecologic cancer. Current treatment for OVCA involves surgical debulking of the tumors followed by combination chemotherapies. While most patients achieve complete remission, many OVCA will recur and develop chemo-resistance. Whereas recurrent OVCA may be treated by angiogenesis inhibitors, PARP inhibitors, or immunotherapies, the clinical outcomes of recurrence OVCA are still unsatisfactory. One new promising anti-tumor strategy is ferroptosis, a novel form of regulated cell death featured by lipid peroxidation. In this review, we have summarized several recent studies on the ferroptosis of OVCA. Also, we summarize our current understanding of various genetic determinants of ferroptosis and their underlying mechanisms in OVCA. Furthermore, ferroptosis can be combined with other standard cancer therapeutics, which has shown synergistic effects. Therefore, such a combination of therapeutics could lead to new therapeutic strategies to improve the response rate and overcome resistance. By understanding the genetic determinants and underlying mechanisms, ferroptosis may have significant therapeutic potential to improve the clinical outcome of women with OVCA.

Cystinuria: clinical practice recommendation

Cystinuria (OMIM 220100) is an autosomal recessive hereditary disorder in which high urinary cystine excretion leads to the formation of cystine stones because of the low solubility of cystine at normal urinary pH. We developed clinical practice recommendation for diagnosis, surgical and medical treatment, and follow-up of patients with cystinuria. Elaboration of these clinical practice recommendations spanned from June 2018 to December 2019 with a consensus conference in January 2019. Selected topic areas were chosen by the co-chairs of the conference. Working groups focusing on specific topics were formed. Group members performed systematic literature review using MEDLINE, drafted the statements, and discussed them. They included geneticists, medical biochemists, pediatric and adult nephrologists, pediatric and adult urologists experts in cystinuria, and the Metabolic Nephropathy Joint Working Group of the European Reference Network for Rare Kidney Diseases (ERKNet) and eUROGEN members. Overall 20 statements were produced to provide guidance on diagnosis, genetic analysis, imaging techniques, surgical treatment (indication and modalities), conservative treatment (hydration, dietetic, alkalinization, and cystine-binding drugs), follow-up, self-monitoring, complications (renal failure and hypertension), and impact on quality of life. Because of the rarity of the disease and the poor level of evidence in the literature, these statements could not be graded. This clinical practice recommendation provides guidance on all aspects of the management of both adults and children with cystinuria, including diagnosis, surgery, and medical treatment.

The incorporation of cystine by the soluble carrier family 7 member 11 (SLC7A11) is a component of the redox regulatory mechanism in stallion spermatozoa†

Oxidative stress is considered a major mechanism causing sperm damage during cryopreservation and storage, and underlies male factor infertility. Currently, oxidative stress is no longer believed to be caused only by the overproduction of reactive oxygen species, but rather by the deregulation of redox signaling and control mechanisms. With this concept in mind, here, we describe for the first time the presence of the soluble carrier family 7 member 11 (SLC7A11) antiporter, which exchanges extracellular cystine (Cyss) for intracellular glutamate, in stallion spermatozoa, as well as its impact on sperm function using the specific inhibitor sulfasalazine. Spermatozoa incubated with Cyss exhibited an increased intracellular GSH content compared with controls (P < 0.01): 50% in fresh extended stallion spermatozoa and 30% in frozen-thawed spermatozoa. This effect was prevented by the addition of sulfasalazine to the media. Cystine supplementation also reduced the oxidation-reduction potential of spermatozoa, with sulfasalazine only preventing this effect on fresh spermatozoa that were incubated for 3 h at 37°C, but not in frozen-thawed spermatozoa. While sulfasalazine reduced the motility of frozen-thawed spermatozoa, it increased motility in fresh samples. The present findings provide new and relevant data on the mechanism regulating the redox status of spermatozoa and suggest that a different redox regulatory mechanism exists in cryopreserved spermatozoa, thus providing new clues to improve current cryopreservation technologies and treat male factor infertility.

Modelling of sulphur amino acid requirements and nitrogen endogenous losses in kittens

The objective of this study was to estimate the sulphur amino acid (methionine + cystine) requirements and nitrogen endogenous losses in kittens aged 150 to 240 d. Thirty-six cats were distributed in six treatments (six cats per treatment) consisting of different concentrations of methionine + cystine (M + C): T1, 6.5 g/kg; T2, 8.8 g/kg; T3, 11.3 g/kg; T4, 13.6 g/kg; T5, 16.0 g/kg; and control, 6.5 g/kg. Diets were formulated by serial dilution of T5 (a diet relatively deficient in M + C but containing high protein concentrations) with a minimal nitrogen diet (MND). Thus, crude protein and amino acid concentrations in diets T1-T5 decreased by the same factor. The control diet was the T1 diet supplemented with adequate concentrations of M + C (6.5 g/kg; 8.8 g/kg; 11.3 g/kg; 13.6 g/kg and 16.0 g/kg). All diets were based on ingredients commonly used in extruded cat diets. Digestibility assays were performed for the determination of nitrogen balance. Nitrogen intake (NI) and nitrogen excretion (NEX) results data were fitted with an exponential equation to estimate nitrogen maintenance requirement (NMR), theoretical maximum for daily nitrogen retention (NR_maxT), and protein quality (b). M + C requirements were calculated from the limiting amino acid intake (LAAI) equation assuming a nitrogen retention of 45 to 65% NR_maxT. The NMR of kittens aged 150, 195, and 240 d was estimated at 595, 559, and 455 mg/kg body weight (BW)^0.67 per day, respectively, and M + C requirements were estimated at 517, 664, and 301 mg/kg BW^0.67 per day, respectively.

Breaking a Couple: Disulfide Reducing Agents

Cysteine is present in a large number of natural and synthetic (bio)molecules. Although the thiol side chain of Cys can be in a free form, in most cases it forms a disulfide bond either with a second Cys (bridge) or with another thiol, as in the case of protecting groups. Efficient reduction of these disulfide bridges is a requirement for many applications of Cys-containing molecules in the fields of chemistry and biochemistry. Here we review reducing methods for disulfide bonds, taking into consideration the solubility of the substrates when selecting the appropriate reducing reagent.

Cysteines and Disulfide Bonds as Structure-Forming Units: Insights From Different Domains of Life and the Potential for Characterization by NMR

Disulfide bridges establish a fundamental element in the molecular architecture of proteins and peptides which are involved e.g., in basic biological processes or acting as toxins. NMR spectroscopy is one method to characterize the structure of bioactive compounds including cystine-containing molecules. Although the disulfide bridge itself is invisible in NMR, constraints obtained via the neighboring NMR-active nuclei allow to define the underlying conformation and thereby to resolve their functional background. In this mini-review we present shortly the impact of cysteine and disulfide bonds in the proteasome from different domains of life and give a condensed overview of recent NMR applications for the characterization of disulfide-bond containing biomolecules including advantages and limitations of the different approaches.

Cysteine/cystine-rich undenatured whey protein supplement in patients' pressure ulcers outcomes: an open label study

OBJECTIVE

The prevalence and costs associated with treating pressure ulcers (PU) are at high levels. Frequently, PUs heal slowly or not at all, which may be due to the patient's catabolic state which may include protein energy malnutrition. The objective of this open label clinical trial was to improve healing rates by providing patients with a patented, high-quality protein containing all essential amino acids to ensure positive nitrogen balance. An additional benefit of this protein is the delivery of bioavailable cysteine (cystine) to promote glutathione (GSH) synthesis which supports immune function and heightens antioxidant defences.

METHODS

Patients with category II, III and IV PUs were fed 20g BID whey protein dietary supplement for 16-120 days, without change in ongoing 'best practice' PU management and their progress recorded.

RESULTS

A total of 10 patients were recruited, with an average age of 77 years. Most had shown no improvement in healing for ≥2 months before treatment and usually had other complications including chronic obstructive pulmonary disease (COPD), diabetes and various cardiovascular diseases. There were a total of 23 PUs, with some patients having more than one. Of these, 44% (n=10) showed complete resolution 83% (n=19) had better than 75% resolution over the observation period. Healing rates ranged from 16.9-0.2cm²/month (healed PUs) and 60.0-1.6cm²/month for resolving PUs.

CONCLUSION

By providing the necessary amino acids to rebuild tissues and bioactive cysteine (cystine) to promote synthesis of intracellular GSH and positive nitrogen balance, improvement in PUs healing was achieved.

The Staphylococcus aureus Cystine Transporters TcyABC and TcyP Facilitate Nutrient Sulfur Acquisition during Infection

Staphylococcus aureus is a significant human pathogen due to its capacity to cause a multitude of diseases. As such, S. aureus efficiently pillages vital nutrients from the host; however, the molecular mechanisms that support sulfur acquisition during infection have not been established. One of the most abundant extracellular sulfur-containing metabolites within the host is cysteine, which acts as the major redox buffer in the blood by transitioning between reduced and oxidized (cystine) forms. We therefore hypothesized that S. aureus acquires host-derived cysteine and cystine as sources of nutrient sulfur during systemic infection. To test this hypothesis, we used the toxic cystine analogue selenocystine to initially characterize S. aureus homologues of the Bacillus subtilis cystine transporters TcyABC and TcyP. We found that genetic inactivation of both TcyA and TcyP induced selenocystine resistance. The double mutant also failed to proliferate in medium supplemented with cystine, cysteine, or N-acetyl cysteine as the sole sulfur source. However, only TcyABC was necessary for proliferation in defined medium containing homocystine as the sulfur source. Using a murine model of systemic infection, we observed tcyP-dependent competitive defects in the liver and heart, indicating that this sulfur acquisition strategy supports proliferation of S. aureus in these organs. Phylogenetic analyses identified TcyP homologues in many pathogenic species, implying that this sulfur procurement strategy is conserved. In total, this study is the first to experimentally validate sulfur acquisition systems in S. aureus and establish their importance during pathogenesis.

Exercise plasma metabolomics and xenometabolomics in obese, sedentary, insulin-resistant women: impact of a fitness and weight loss intervention

Insulin resistance has wide-ranging effects on metabolism, but there are knowledge gaps regarding the tissue origins of systemic metabolite patterns and how patterns are altered by fitness and metabolic health. To address these questions, plasma metabolite patterns were determined every 5 min during exercise (30 min, ∼45% of V̇o_2peak, ∼63 W) and recovery in overnight-fasted sedentary, obese, insulin-resistant women under controlled conditions of diet and physical activity. We hypothesized that improved fitness and insulin sensitivity following a ∼14-wk training and weight loss intervention would lead to fixed workload plasma metabolomics signatures reflective of metabolic health and muscle metabolism. Pattern analysis over the first 15 min of exercise, regardless of pre- versus postintervention status, highlighted anticipated increases in fatty acid tissue uptake and oxidation (e.g., reduced long-chain fatty acids), diminution of nonoxidative fates of glucose [e.g., lowered sorbitol-pathway metabolites and glycerol-3-galactoside (possible glycerolipid synthesis metabolite)], and enhanced tissue amino acid use (e.g., drops in amino acids; modest increase in urea). A novel observation was that exercise significantly increased several xenometabolites ("non-self" molecules, from microbes or foods), including benzoic acid-salicylic acid-salicylaldehyde, hexadecanol-octadecanol-dodecanol, and chlorogenic acid. In addition, many nonannotated metabolites changed with exercise. Although exercise itself strongly impacted the global metabolome, there were surprisingly few intervention-associated differences despite marked improvements in insulin sensitivity, fitness, and adiposity. These results and previously reported plasma acylcarnitine profiles support the principle that most metabolic changes during submaximal aerobic exercise are closely tethered to absolute ATP turnover rate (workload), regardless of fitness or metabolic health status.

Sulfur-Based Copolymeric Polyamidoamines as Efficient Flame-Retardants for Cotton

The polyamidoamine derived from N,N'-methylenebisacrylamide (M) and glycine (G), M-G, has been shown to be an effective flame-retardant (FR) for cotton in horizontal flame spread tests (HFST), extinguishing the flame at 5% add-on. Its activity was attributed to its intrinsic intumescence. In vertical flame spread tests (VFST), M-G failed to extinguish the flame even at 30% add-on. Conversely, in VFST, the polyamidoamine derived from M and cystine (C), M-C, inhibited cotton combustion at 16% add-on, but in HFST failed to extinguish the flame below 12% add-on. Its activity was ascribed to the release of sulfur-containing volatiles acting as radical scavengers. In this work, the FR effectiveness of M-Gm-Cn copolymers with different G/C ratio was compared with that of the M-G and M-C homopolymers and of M-G/M-C blends of the same compositions. In HFST, both copolymers and blends extinguished the flame. In particular, M-G50-C50 and (M-G/M-C)50/50 extinguished the flame, even at 7% add-on. In VFST, the copolymers with ≥50% M-C units, similar to M-C, inhibited cotton combustion at 16% add-on. At the same add-on, the M-G/M-C blends failed to extinguish the flame. It may be concluded that, in contrast to blends, copolymers combined the merits of both homopolymers in all tests.