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Global energy demand and environmental concerns have stimulated increasing efforts to produce carbon-neutral fuels directly from renewable resources. Microbially derived aliphatic hydrocarbons, the petroleum-replica fuels, have emerged as promising alternatives to meet this goal. However, engineering metabolic pathways with high productivity and yield requires dynamic redistribution of cellular resources and optimal control of pathway expression. Here we report a genetically encoded metabolic switch that enables dynamic regulation of fatty acids (FA) biosynthesis in Escherichia coli . The engineered strains were able to dynamically compensate the critical enzymes involved in the supply and consumption of malonyl-CoA and efficiently redirect carbon flux toward FA biosynthesis. Implementation of this metabolic control resulted in an oscillatory malonyl-CoA pattern and a balanced metabolism between cell growth and product formation, yielding 15.7- and 2.1-fold improvement in FA titer compared with the wild-type strain and the strain carrying the uncontrolled metabolic pathway. This study provides a new paradigm in metabolic engineering to control and optimize metabolic pathways facilitating the high-yield production of other malonyl-CoA–derived compounds.

Neurodegenerative diseases are among the most widespread diseases affecting humans, and the number of patients is only rising. Seaweed polysaccharide extracts show significant neuroprotective and reparative activities. Seaweed polysaccharides might provide the next big breakthrough in neurodegenerative disease treatment. This paper reviews the applications of seaweed polysaccharides as potential treatments of neurodegenerative diseases. The particular focus is on fucoidan, ulvan, and their derivatives as potential agents to treat Alzheimer’s disease. This review provides a critical update on the progress in this important research area.

Most growth factors are naturally occurring proteins, which are signaling molecules implicated in cellular multiple functions such as proliferation, migration and differentiation under patho/physiological conditions by interacting with cell surface receptors and other ligands in the extracellular microenvironment. Many of the growth factors are heparin-binding proteins (HBPs) that have a high affinity for cell surface heparan sulfate proteoglycans (HSPG). In the present study, we report the binding kinetics and affinity of heparin interacting with different growth factors, including fibroblast growth factor (FGF) 2,7,10, hepatocyte growth factor (HGF) and transforming growth factor (TGF β-1), using a heparin chip. Surface plasmon resonance studies revealed that all the tested growth factors bind to heparin with high affinity (with KD ranging from ~0.1 to 59 nM) and all the interactions are oligosaccharide size dependent except those involving TGF β-1. These heparin-binding growth factors also interact with other glycosaminoglycans (GAGs), as well as various chemically modified heparins. Other GAGs, including heparan sulfate, chondroitin sulfates A, B, C, D, E and keratan sulfate, showed different inhibition activities for the growth factor-heparin interactions. FGF2, FGF7, FGF10 and HGF bind heparin but the 2-O-sulfo and 6-O-sulfo groups on heparin have less impact on these interactions than do the N-sulfo groups. All the three sulfo groups (N-, 2-O and 6-O) on heparin are important for TGFβ-1-heparin interaction.

Background Intravenous fluids, an essential component of sepsis resuscitation, may paradoxically worsen outcomes by exacerbating endothelial injury. Preclinical models suggest that fluid resuscitation degrades the endothelial glycocalyx, a heparan sulfate-enriched structure necessary for vascular homeostasis. We hypothesized that endothelial glycocalyx degradation is associated with the volume of intravenous fluids administered during early sepsis resuscitation. Methods We used mass spectrometry to measure plasma heparan sulfate (a highly sensitive and specific index of systemic endothelial glycocalyx degradation) after 6 h of intravenous fluids in 56 septic shock patients, at presentation and after 24 h of intravenous fluids in 100 sepsis patients, and in two groups of non-infected patients. We compared plasma heparan sulfate concentrations between sepsis and non-sepsis patients, as well as between sepsis survivors and sepsis non-survivors. We used multivariable linear regression to model the association between volume of intravenous fluids and changes in plasma heparan sulfate. Results Consistent with previous studies, median plasma heparan sulfate was elevated in septic shock patients (118 [IQR, 113–341] ng/ml 6 h after presentation) compared to non-infected controls (61 [45–79] ng/ml), as well as in a second cohort of sepsis patients (283 [155–584] ng/ml) at emergency department presentation) compared to controls (177 [144–262] ng/ml). In the larger sepsis cohort, heparan sulfate predicted in-hospital mortality. In both cohorts, multivariable linear regression adjusting for age and severity of illness demonstrated a significant association between volume of intravenous fluids administered during resuscitation and plasma heparan sulfate. In the second cohort, independent of disease severity and age, each 1 l of intravenous fluids administered was associated with a 200 ng/ml increase in circulating heparan sulfate ( p  = 0.006) at 24 h after enrollment. Conclusions Glycocalyx degradation occurs in sepsis and septic shock and is associated with in-hospital mortality. The volume of intravenous fluids administered during sepsis resuscitation is independently associated with the degree of glycocalyx degradation. These findings suggest a potential mechanism by which intravenous fluid resuscitation strategies may induce iatrogenic endothelial injury.

Monkeypox virus (MPXV), a member of the Orthopoxvirus genus, has begun to spread into many countries worldwide. While the prevalence of monkeypox in Central and Western Africa is well-known, the recent rise in the number of cases spread through intimate personal contact, particularly in the United States, poses a grave international threat. Previous studies have shown that cell-surface heparan sulfate (HS) is important for vaccinia virus (VACV) infection, particularly the binding of VACV A27, which appears to mediate the binding of virus to cellular HS. Some other glycosaminoglycans (GAGs) also bind to proteins on Orthopoxviruses. In this study, by using surface plasmon resonance, we demonstrated that MPXV A29 protein (a homolog of VACV A27) binds to GAGs including heparin and chondroitin sulfate/dermatan sulfate. The negative charges on GAGs are important for GAG–MPXV A29 interaction. GAG analogs, pentosan polysulfate and mucopolysaccharide polysulfate, show strong inhibition of MPXV A29–heparin interaction. A detailed understanding on the molecular interactions involved in this disease should accelerate the development of therapeutics and drugs for the treatment of MPXV.

The thick mucus layer of the gut provides a barrier to infiltration of the underlying epithelia by both the normal microbiota and enteric pathogens. Some members of the microbiota utilise mucin glycoproteins as a nutrient source, but a detailed understanding of the mechanisms used to breakdown these complex macromolecules is lacking. Here we describe the discovery and characterisation of endo-acting enzymes from prominent mucin-degrading bacteria that target the polyLacNAc structures within oligosaccharide side chains of both animal and human mucins. These O-glycanases are part of the large and diverse glycoside hydrolase 16 (GH16) family and are often lipoproteins, indicating that they are surface located and thus likely involved in the initial step in mucin breakdown. These data provide a significant advance in our knowledge of the mechanism of mucin breakdown by the normal microbiota. Furthermore, we also demonstrate the potential use of these enzymes as tools to explore changes in O-glycan structure in a number of intestinal disease states. Epithelial cells that line the gut secrete complex glycoproteins that form a mucus layer to protect the gut wall from enteric pathogens. Here, the authors provide a comprehensive characterisation of endo-acting glycoside hydrolases expressed by mucin-degrading members of the microbiome that are able to cleave the O-glycan chains of a range of different animal and human mucins.

Complex carbohydrates (glycans) are major players in all organisms due to their structural, energy, and communication roles. This last essential role involves interacting and/or signaling through a plethora of glycan-binding proteins. The design and synthesis of glycans as potential drug candidates that selectively alter or perturb metabolic processes is challenging. Here we describe the first reported sulfur-linked polysaccharides with potentially altered conformational state(s) that are recalcitrant to digestion by heparanase, an enzyme important in human health and disease. An artificial sugar donor with a sulfhydryl functionality is synthesized and enzymatically incorporated into polysaccharide chains utilizing heparosan synthase. Used alone, this donor adds a single thio-sugar onto the termini of nascent chains. Surprisingly, in chain co-polymerization reactions with a second donor, this thiol-terminated heparosan also serves as an acceptor to form an unnatural thio-glycosidic bond (‘ S -link’) between sugar residues in place of a natural ‘ O -linked’ bond. S -linked heparan sulfate analogs are not cleaved by human heparanase. Furthermore, the analogs act as competitive inhibitors with > ~200-fold higher potency than expected; as a rationale, molecular dynamic simulations suggest that the S -link polymer conformations mimic aspects of the transition state. Our analogs form the basis for future cancer therapeutics and modulators of protein/sugar interactions. Heparin is a family of complex carbohydrates binding to proteins to modulate cell activities. Here the authors report the synthesis, and conformations simulations of S -linked hemi-A heparosan [GlcA-S-GlcNAc] n , a thio-glycosidic uncleavable polysaccharide, and test it as human heparanase inhibitor.

6’-Sialyllactose conjugated to polyamidoamine dendrimers at a well-defined valency and spacing can circumvent drug resistance and inhibit influenza A viruses. Rapid change 1 and zoonotic transmission to humans 2 have enhanced the virulence of the influenza A virus (IAV) 3 . Neutralizing antibodies fail to provide lasting protection from seasonal epidemics 1 , 4 . Furthermore, the effectiveness of anti-influenza neuraminidase inhibitors has declined because of drug resistance 5 . Drugs that can block viral attachment and cell entry independent of antigenic evolution or drug resistance might address these problems. We show that multivalent 6′-sialyllactose-polyamidoamine (6SL–PAMAM) conjugates, when designed to have well-defined ligand valencies and spacings, can effectively inhibit IAV infection. Generation 4 (G4) 6SL–PAMAM conjugates with a spacing of around 3 nm between 6SL ligands (S3–G4) showed the strongest binding to a hemagglutinin trimer (dissociation constant of 1.6 × 10 −7  M) and afforded the best inhibition of H1N1 infection. S3–G4 conjugates were resistant to hydrolysis by H1N1 neuraminidase. These conjugates protected 75% of mice from a lethal challenge with H1N1 and prevented weight loss in infected animals. The structure-based design of multivalent nanomaterials, involving modulation of nanoscale backbone structures and number and spacing between ligands, resulted in optimal inhibition of IAV infection. This approach may be broadly applicable for designing effective and enduring therapeutic protection against human or avian influenza viruses.

Septic patients frequently develop cognitive impairment that persists beyond hospital discharge. The impact of sepsis on electrophysiological and molecular determinants of learning is underexplored. We observed that mice that survived sepsis or endotoxemia experienced loss of hippocampal long-term potentiation (LTP), a brain-derived neurotrophic factor-mediated (BDNF-mediated) process responsible for spatial memory formation. Memory impairment occurred despite preserved hippocampal BDNF content and could be reversed by stimulation of BDNF signaling, suggesting the presence of a local BDNF inhibitor. Sepsis is associated with degradation of the endothelial glycocalyx, releasing heparan sulfate fragments (of sufficient size and sulfation to bind BDNF) into the circulation. Heparan sulfate fragments penetrated the hippocampal blood-brain barrier during sepsis and inhibited BDNF-mediated LTP. Glycoarray approaches demonstrated that the avidity of heparan sulfate for BDNF increased with sulfation at the 2-O position of iduronic acid and the N position of glucosamine. Circulating heparan sulfate in endotoxemic mice and septic humans was enriched in 2-O- and N-sulfated disaccharides; furthermore, the presence of these sulfation patterns in the plasma of septic patients at intensive care unit (ICU) admission predicted persistent cognitive impairment 14 days after ICU discharge or at hospital discharge. Our findings indicate that circulating 2-O- and N-sulfated heparan sulfate fragments contribute to septic cognitive impairment.

Abstract Rationale Degradation of the endothelial glycocalyx, a glycosaminoglycan (GAG)-rich layer lining the vascular lumen, is associated with the onset of kidney injury in animal models of critical illness. It is unclear if similar pathogenic degradation occurs in critically ill patients. Objectives To determine if urinary indices of GAG fragmentation are associated with outcomes in patients with critical illnesses such as septic shock or acute respiratory distress syndrome (ARDS). Methods We prospectively collected urine from 30 patients within 24 hours of admission to the Denver Health Medical Intensive Care Unit (ICU) for septic shock. As a nonseptic ICU control, we collected urine from 25 surgical ICU patients admitted for trauma. As a medical ICU validation cohort, we obtained serially collected urine samples from 70 patients with ARDS. We performed mass spectrometry on urine samples to determine GAG (heparan sulfate, chondroitin sulfate, and hyaluronic acid) concentrations as well as patterns of heparan sulfate/chondroitin sulfate disaccharide sulfation. We compared these indices to measurements obtained using dimethylmethylene blue, an inexpensive, colorimetric urinary assay of sulfated GAGs. Measurements and Main Results In septic shock, indices of GAG fragmentation correlated with both the development of renal dysfunction over the 72 hours after urine collection and with hospital mortality. This association remained after controlling for severity of illness and was similarly observed using the inexpensive dimethylmethylene blue assay. These predictive findings were corroborated using urine samples previously collected at three consecutive time points from patients with ARDS. Conclusions Early indices of urinary GAG fragmentation predict acute kidney injury and in-hospital mortality in patients with septic shock or ARDS. Clinical trial registered with www.clinicaltrials.gov (NCT01900275).