Lymphatic Uptake of a Highly Lipophilic Protease Inhibitor Prodrug from a Lipid-Based Formulation is Limited by Instability in the Intestine

Dabigatran etexilate (DABE) is a lipophilic double alkyl ester prodrug of dabigatran (DAB) which is a serine protease inhibitor used clinically as an anticoagulant. Recently, translocation of serine protease enzymes, including trypsin, from the gut into the mesenteric lymph and then blood has been associated with organ failure in acute and critical illnesses (ACIs). Delivery of DABE into mesenteric lymph may thus be an effective strategy to prevent organ failure in ACIs. Most drugs access the mesenteric lymph in low quantities following oral administration, as they are rapidly transported away from the intestine via the blood. Here, we examine the potential to deliver DABE into the mesenteric lymph by promoting association with lymph lipid transport pathways via co-administration with a lipid-based formulation (LBF). A series of self-emulsifying LBFs were designed and tested in vitro for their potential to form stable DABE loaded emulsions and keep DABE solubilised and stable over time in simulated gastrointestinal conditions. The LBFs were found to form fine emulsions with a droplet size of 214 ± 30 nm and DABE was stable in the formulation. The stability of DABE in vitro in simulated intestinal conditions, plasma and lymph samples was also evaluated to ensure stability in collected samples and to evaluate whether the prodrug is likely to release active DAB. Ultimately, a highly uniform and stable self-emulsifying Type III A LBF of DABE was chosen for progression into in vivo studies in male Sprague Dawley rats to confirm the lymphatic uptake and plasma pharmacokinetics. Both in vitro and in vivo in plasma and lymph, DABE was rapidly converted to an intermediate and DAB. The main species present in vivo in both plasma and lymph was DAB and mass transport of DABE and DAB in lymph was minimal (∼0.5 % of dose). Importantly, the concentration of DABE in lymph was substantially (20-176 fold) higher than in plasma, supporting that if the prodrug were stable and did not convert to DAB in the intestine, it would be lymphatically transported. Future studies will therefore focus on optimizing the design of the prodrug and formulation to improve stability during absorption and further promote lymphatic uptake.

Computational fluid dynamic modeling of the lymphatic system: a review of existing models and future directions

Historically, research into the lymphatic system has been overlooked due to both a lack of knowledge and limited recognition of its importance. In the last decade however, lymphatic research has gained substantial momentum and has included the development of a variety of computational models to aid understanding of this complex system. This article reviews existing computational fluid dynamic models of the lymphatics covering each structural component including the initial lymphatics, pre-collecting and collecting vessels, and lymph nodes. This is followed by a summary of limitations and gaps in existing computational models and reasons that development in this field has been hindered to date. Over the next decade, efforts to further characterize lymphatic anatomy and physiology are anticipated to provide key data to further inform and validate lymphatic fluid dynamic models. Development of more comprehensive multiscale- and multi-physics computational models has the potential to significantly enhance the understanding of lymphatic function in both health and disease.

Investigation of Staphylococcus aureus Biofilm-Associated Toxin as a Potential Squamous Cell Carcinoma Therapeutic

Cancer therapies developed using bacteria and their components have been around since the 19th century. Compared to traditional cancer treatments, the use of bacteria-derived compounds as cancer therapeutics could offer a higher degree of specificity, with minimal off-target effects. Here, we explored the use of soluble bacteria-derived toxins as a potential squamous cell carcinoma (SCC) therapeutic. We optimized a protocol to generate Staphylococcus aureus biofilm-conditioned media (BCM), where soluble bacterial products enriched in the development of biofilms were isolated from a bacterial culture and applied to SCC cell lines. Bioactive components of S. aureus ATCC 29213 (SA29213) BCM display selective toxicity towards cancerous human skin SCC-12 at low doses, while non-cancerous human keratinocyte HaCaT and fibroblast BJ-5ta are minimally affected. SA29213 BCM treatment causes DNA damage to SCC-12 and initiates Caspase 3-dependent-regulated cell death. The use of the novel SA29213 bursa aurealis transposon mutant library led to the identification of S. aureus alpha hemolysin as the main bioactive compound responsible for the observed SCC-12-specific toxicity. The antibody neutralisation of Hla eradicates the cytotoxicity of SA29213 BCM towards SCC-12. Hla displays high SCC-12-specific toxicity, which is exerted primarily through Hla-ADAM10 interaction, Hla oligomerisation, and pore formation. The high target specificity and potential to cause cell death in a controlled manner highlight SA29213 Hla as a good candidate as an alternative SCC therapeutic.

Targeting Cx43 to Reduce the Severity of Pressure Ulcer Progression

In the skin, repeated incidents of ischemia followed by reperfusion can result in the breakdown of the skin and the formation of a pressure ulcer. Here we gently applied paired magnets to the backs of mice to cause ischemia for 1.5 h and then removed them to allow reperfusion. The sterile inflammatory response generated within 4 h causes a stage 1 pressure ulcer with an elevation of the gap junction protein Cx43 in the epidermis. If this process is repeated the insult will result in a more severe stage 2 pressure ulcer with a breakdown of the epidermis 2-3 days later. After a single pinch, the elevation of Cx43 in the epidermis is associated with the inflammatory response with an increased number of neutrophils, HMGB1 (marker of necrosis) and RIP3 (responsible for necroptosis). Delivering Cx43 specific antisense oligonucleotides sub-dermally after a single insult, was able to significantly reduce the elevation of epidermal Cx43 protein expression and reduce the number of neutrophils and prevent the elevation of HMGB1 and RIP3. In a double pinch model, the Cx43 antisense treatment was able to reduce the level of inflammation, necroptosis, and the extent of tissue damage and progression to an open wound. This approach may be useful in reducing the progression of stage 1 pressure ulcers to stage 2.

Kidney Lymphatics

Following significant advances in lymphatic biology, the important role of kidney lymphatics in kidney function and dysfunction is now being more fully appreciated. Kidney lymphatics begin in the cortex as blind-ended lymphatic capillaries and then coalesce into larger lymphatics that follow the main blood vessels out through the kidney hilum. Their function in draining interstitial fluid, macromolecules, and cells underpins their important role in kidney fluid and immune homeostasis. This article provides a comprehensive overview of recent and more established research findings on kidney lymphatics and the implications of these findings for kidney function and disease. The use of lymphatic molecular markers has greatly expanded our knowledge of the development, anatomy, and pathophysiology of kidney lymphatics. Significant recent discoveries include the diverse embryological source of kidney lymphatics, the hybrid nature of the ascending vasa recta, and the effects of lymphangiogenesis on kidney diseases such as acute kidney injury and renal fibrosis. On the basis of these recent advances, there is now an opportunity to link information from across multiple research disciplines to drive a new era of lymphatic-targeted therapies for kidney disease. © 2023 American Physiological Society. Compr Physiol 13:4945-4984, 2023.

The cisterna chyli: a systematic review of definition, prevalence, and anatomy

The cisterna chyli is a lymphatic structure found at the caudal end of the thoracic duct that receives lymph draining from the abdominal and pelvic viscera and lower limbs. In addition to being an important landmark in retroperitoneal surgery, it is the key gateway for interventional radiology procedures targeting the thoracic duct. A detailed understanding of its anatomy is required to facilitate more accurate intervention, but an exhaustive summary is lacking. A systematic review was conducted, and 49 published human studies met the inclusion criteria. Studies included both healthy volunteers and patients and were not restricted by language or date. The detectability of the cisterna chyli is highly variable, ranging from 1.7 to 98%, depending on the study method and criteria used. Its anatomy is variable in terms of location (vertebral level of T10 to L3), size (ranging 2-32 mm in maximum diameter and 13-80 mm in maximum length), morphology, and tributaries. The size of the cisterna chyli increases in some disease states, though its utility as a marker of disease is uncertain. The anatomy of the cisterna chyli is highly variable, and it appears to increase in size in some disease states. The lack of well-defined criteria for the structure and the wide variation in reported detection rates prevent accurate estimation of its natural prevalence in humans.

Vmeasur: A software package for experimental and clinical measurement of mesenteric lymphatic contractile function over an extended vessel length

OBJECTIVE

Conventionally, in vivo mesenteric lymphatic contractile function is measured using a high magnification transmission microscope (field of view 0.3-1.5 mm), which precludes visualization of extended lengths of vessels embedded in mesenteric fat. Existing software is not optimized for imaging at a low magnification using a contrast agent. We aimed to develop a simple and clinically transferable method for in situ visualization, image analysis, and quantitative assessment of mesenteric lymphatic contractile function over an extended area.

METHODS

Subserosal injection of various blue dyes was taken up by mesenteric lymphatics and visualized under a stereomicroscope (25×), allowing for video recording of 1.4 × 1.1 cm of intact mesentery. A new R package ("vmeasur") that combines multiple high-performance image analyses into a single workflow was developed. The edges of each vessel were determined by applying an automated threshold to each frame (with real-time manual verification). The vessel width at every point in each frame was plotted to provide contractile parameters over time and along the lymphatic vessel length.

RESULTS

Contractile parameters and their differences along the length of the vessel were accurately calculated in a rodent model. In a human mesenteric lymphatic, the algorithm was also able to measure changes in diameter over length.

CONCLUSION

This software offers a low cost, rapid, and accessible method to measure lymphatic contractile function over a wide area, showing differences in contractility along the length of a vessel. Because the presence of mesenteric fat has less of an impact on imaging, due to the use of an exogenous contrast agent, there is potential for clinical application.

Electrochemical Methods for the Analysis of Milk

The milk and dairy industries are some of the most profitable sectors in many countries. This business requires close control of product quality and continuous testing to ensure the safety of the consumers. The potential risk of contaminants or degradation products and undesirable chemicals necessitates the use of fast, reliable detection tools to make immediate production decisions. This review covers studies on the application of electrochemical methods to milk (i.e., voltammetric and amperometric) to quantify different analytes, as reported over the last 10 to 15 years. The review covers a wide range of analytes, including allergens, antioxidants, organic compounds, nitrogen- and aldehyde containing compounds, biochemicals, heavy metals, hydrogen peroxide, nitrite, and endocrine disruptors. The review also examines pretreatment procedures applied to milk samples and the use of novel sensor materials. Final perspectives are provided on the future of cost-effective and easy-to-use electrochemical sensors and their advantages over conventional methods.

The effect of respiration and body position on terminal thoracic duct diameter and the lymphovenous junction: An exploratory ultrasound study

The thoracic duct (TD) drains most of the body's lymph back to the venous system via its lymphovenous junction (LVJ), playing a pivotal role in fluid homeostasis, fat absorption and the systemic immune response. The respiratory cycle is thought to assist with lymph flow, but the precise mechanism underpinning terminal TD lymph flow into the central veins is not well understood. The aim of this study was to use ultrasonography (US) to explore the relationship between terminal TD lymph flow, the respiratory cycle, and gravity. The left supraclavicular fossa was scanned in healthy non-fasted volunteers using high-resolution (13-5 MHz) US to identify the terminal TD and the presence of a lymphovenous valve (LVV). The TD's internal diameter was measured in relation to respiration (inspiration vs. expiration) and body positioning (supine vs. Trendelenburg). The terminal TD was visualized in 20/33 (61%) healthy volunteers. An LVV was visualized in only 4/20 (20%) cases. The mean terminal TD diameter in the supine position was 1.7 mm (range 0.8-3.1 mm); this increased in full inspiration (mean 1.8 mm, range 0.9-3.2 mm, p < 0.05), and in the Trendelenburg position (mean 1.8 mm, range 1.2-3.1 mm, p < 0.05). The smallest mean terminal TD diameter occurred in full expiration (1.6 mm, range 0.7-3.1 mm, p < 0.05). Respiration and gravity impact the terminal TD diameter. Due to the challenges of visualizing the TD and LVJ, other techniques such as dynamic magnetic resonance imaging will be required to fully understand the factors governing TD lymph flow.

Mesenteric lymphatic dysfunction promotes insulin resistance and represents a potential treatment target in obesity

Visceral adipose tissue (VAT) encases mesenteric lymphatic vessels and lymph nodes through which lymph is transported from the intestine and mesentery. Whether mesenteric lymphatics contribute to adipose tissue inflammation and metabolism and insulin resistance is unclear. Here we show that obesity is associated with profound and progressive dysfunction of the mesenteric lymphatic system in mice and humans. We find that lymph from mice and humans consuming a high-fat diet (HFD) stimulates lymphatic vessel growth, leading to the formation of highly branched mesenteric lymphatic vessels that 'leak' HFD-lymph into VAT and, thereby, promote insulin resistance. Mesenteric lymphatic dysfunction is regulated by cyclooxygenase (COX)-2 and vascular endothelial growth factor (VEGF)-C-VEGF receptor (R)3 signalling. Lymph-targeted inhibition of COX-2 using a glyceride prodrug approach reverses mesenteric lymphatic dysfunction, visceral obesity and inflammation and restores glycaemic control in mice. Targeting obesity-associated mesenteric lymphatic dysfunction thus represents a potential therapeutic option to treat metabolic disease.

Lymphatic Contractile Function: A Comprehensive Review of Drug Effects and Potential Clinical Application

BACKGROUND

The lymphatic system and the cardiovascular system work together to maintain body fluid homeostasis. Despite that, the lymphatic system has been relatively neglected as a potential drug target and a source of adverse effects from cardiovascular drugs. Like the heart, the lymphatic vessels undergo phasic contractions to promote lymph flow against a pressure gradient. Dysfunction or failure of the lymphatic pump results in fluid imbalance and tissue oedema. While this can due to drug effects, it is also a feature of breast cancer-associated lymphoedema, chronic venous insufficiency, congestive heart failure and acute systemic inflammation. There are currently no specific drug treatments for lymphatic pump dysfunction in clinical use despite the wealth of data from pre-clinical studies.

AIM

To identify (1) drugs with direct effects on lymphatic tonic and phasic contractions with potential for clinical application, and (2) drugs in current clinical use that have a positive or negative side effect on lymphatic function.

METHODS

We comprehensively reviewed all studies that tested the direct effect of a drug on the contractile function of lymphatic vessels.

RESULTS

Of the 208 drugs identified from 193 studies, about a quarter had only stimulatory effects on lymphatic tone, contraction frequency and/or contraction amplitude. Of FDA-approved drugs, there were 14 that increased lymphatic phasic contractile function. The most frequently used class of drug with inhibitory effects on lymphatic pump function were the calcium channels blockers.

CONCLUSION

This review highlights the opportunity for specific drug treatments of lymphatic dysfunction in various disease states and for avoiding adverse drug effects on lymphatic contractile function.

The effects of Staphylococcus aureus biofilm conditioned media on 3T3 fibroblasts

Staphylococcus aureus (SA) is the most common bacterial species in chronic wounds. However, there is a lack of understanding of how SA secretions affect the cell biology during the healing process. We studied the effects of biofilm-secretions from SA strain SA29213 on 3T3 fibroblasts. SA29213 is a chronic wound isolate and widely used as a reference strain. We used a series of concentrations of biofilm-conditioned media (BCM) and found 100% BCM is lethal within 10 h. Cells survived in ≤75% BCM but the rate of closure in scratch wound assays was reduced. Treatment with 75% and 50% BCM caused fibroblasts to change shape and develop dendrite like processes. Prolonged treatment with 75% and 50% BCM reduced cell proliferation and increased the 4n deoxyribonucleic acid cell population with cell cycle arrest. There was also an elevation in the senescence marker beta galactosidase and the number of multinucleated cells. Shorter treatments with 75% and 50% SA BCM caused an increase in cell-cell adhesion and a redistribution of β-catenin from the cell membrane to the cytoplasm along with a change in the appearance and decrease in size of ZO-1, vinculin and paxillin structures. Fibroblasts in the edge of chronic wounds exposed to the secretions of SA may suffer similar effects such as induction of senescence, reduced proliferation and migration, which may contribute to the delayed healing of these chronic infected wounds.

Electrochemical Preparation of Poly(3,4-Ethylenedioxythiophene) Layers on Gold Microelectrodes for Uric Acid-Sensing Applications

Two different methods for the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) on gold electrodes are described, using electropolymerization of 3,4-ethylenedioxythiophene (EDOT) monomer in an aqueous and an organic solution. Cyclic voltammetry (CV) was used in the synthesis of PEDOT thin layers. Lithium perchlorate (LiClO4) was used as a dopant in both aqueous (aqueous/acetonitrile (ACN)) and organic (propylene carbonate (PC)) solvent systems. After the PEDOT layer was created in the organic system, the electrode surface was acclimatized by successive cycling in an aqueous solution for use as a sensor for aqueous samples. The use of an aqueous-based electropolymerization method has the potential benefit of removing the acclimatization step to have a shorter sensor preparation time. Although the aqueous method is more economical and environmentally friendly than the organic solvent method, superior PEDOT formation is obtained in the organic solution. The resulting PEDOT electrode surfaces were characterized by scanning electron microscopy (SEM), which showed the constant growth of PEDOT during electropolymerization from the organic PC solution, with rapid fractal-type growth on gold (Au) microelectrodes.

The Lymphovenous Junction of the Thoracic Duct: A Systematic Review of its Structural and Functional Anatomy

Background: The lymphovenous junction (LVJ) of the thoracic duct (TD) is the principle outlet of the lymphatic system. Interest in this junction is growing as its role in lymphatic outflow obstruction is being realized, and as minimally invasive procedures for accessing the terminal TD become more common. Despite the growing clinical significance of the LVJ, its precise form and function remain unclear. The aim of this article was to systematically review the literature surrounding the structure and function of the LVJ and its associated lymphovenous valve (LVV). Methods and Results: A systematic review of the structure and function of the LVJ and LVV was undertaken using the MEDLINE, Scopus, and Google Scholar databases. Human and animal studies up to November 2019, with no language or past date restriction, were included. Forty-six relevant articles were reviewed. The LVJ shows marked anatomical variation. A valve is frequently absent at the LVJ, but when present it displays numerous distinct morphologies. These include bicuspid semilunar, ostial, and flap-like structure. Other factors, such as functional platelet plugs, or the tangential/intramural course of the terminal TD across the vein wall, may work to prevent blood from entering the lymphatic system. Conclusions: The form and function of the LVJ remain unclear. Dedicated studies of this area in vivo are required to elucidate how this part of the body functions in both health and disease.

Intestinal Lymph Flow, and Lipid and Drug Transport Scale Allometrically From Pre-clinical Species to Humans

The intestinal lymphatic system transports fluid, immune cells, dietary lipids, and highly lipophilic drugs from the intestine to the systemic circulation. These transport functions are important to health and when dysregulated contribute to pathology. This has generated significant interest in approaches to deliver drugs to the lymphatics. Most of the current understanding of intestinal lymph flow, and lymphatic lipid and drug transport rates, comes from in vitro studies and in vivo animal studies. In contrast, intestinal lymphatic transport studies in human subjects have been limited. Recently, three surgical patients had cannulation of the thoracic lymph duct for collection of lymph before and during a stepwise increase in enteral feed rate. We compared these data to studies where we previously enterally administered controlled quantities of lipid and the lipophilic drug halofantrine to mice, rats and dogs and collected lymph and blood (plasma). The collected lymph was analyzed to compare lymph flow rate, triglyceride (TG) and drug transport rates, and plasma was analyzed for drug concentrations, as a function of enteral lipid dose across species. Lymph flow rate, TG and drug transport increased with lipid administration in all species tested, and scaled allometrically according to the equation A = aM ^E where A is the lymph transport parameter, M is animal body mass, a is constant and E is the allometric exponent. For lymph flow rate and TG transport, the allometric exponents were 0.84-0.94 and 0.80-0.96, respectively. Accordingly, weight normalized lymph flow and TG mass transport were generally lower in larger compared to smaller species. In comparison, mass transport of drug via lymph increased in a greater than proportional manner with species body mass with an exponent of ∼1.3. The supra-proportional increase in lymphatic drug transport with species body mass appeared to be due to increased partitioning of drug into lymph rather than blood following absorption. Overall, this study proposes that intestinal lymphatic flow, and lymphatic lipid and drug transport in humans is most similar to species with higher body mass such as dogs and underestimated by studies in rodents. Notably, lymph flow and lipid transport in humans can be predicted from animal data via allometric scaling suggesting the potential for similar relationships with drug transport.

High-resolution 3D imaging and topological mapping of the lymph node conduit system

The conduit network is a hallmark of lymph node microanatomy, but lack of suitable imaging technology has prevented comprehensive investigation of its topology. We employed an extended-volume imaging system to capture the conduit network of an entire murine lymph node (comprising over 280,000 segments). The extensive 3D images provide a comprehensive overview of the regions supplied by conduits, including perivascular sleeves and distinctive “follicular reservoirs” within B cell follicles, surrounding follicular dendritic cells. A 3D topology map of conduits within the T-cell zone showed homogeneous branching, but conduit density was significantly higher in the superficial T-cell zone compared with the deep zone, where distances between segments are sufficient for T cells to lose contact with fibroblastic reticular cells. This topological mapping of the conduit anatomy can now aid modeling of its roles in lymph node function, as we demonstrate by simulating T-cell motility in the different T-cell zones.

Extended-volume confocal imaging allowed 3D visualisation of the fine network of conduits within lymph nodes; the resulting map of conduit topology underscores structural differences between the deep and superficial T cell zone and identifies "follicular reservoirs" within B cell follicles that concentrate lymphoid fluid around follicular dendritic cells.

Therapeutic delivery to the peritoneal lymphatics: Current understanding, potential treatment benefits and future prospects

The interest in approaches to deliver therapeutics to the lymphatic system has increased in recent years as the lymphatics have been discovered to play an important role in a range of disease states such as cancer metastases, inflammatory and metabolic disease, and acute and critical illness. Therapeutic delivery to lymph has the potential to enhance treatment of these conditions. Currently much of the existing data explores therapeutic delivery to the lymphatic vessels and nodes that drain peripheral tissues and the intestine. Relatively little focus has been given to understanding the anatomy, function and therapeutic delivery to the peritoneal lymphatics. Gaining a better understanding of peritoneal lymphatic structure and function would contribute to the understanding of disease processes involving these lymphatics and facilitate the development of delivery systems to target therapeutics to the peritoneal lymphatics. This review explores the basic anatomy and ultrastructure of the peritoneal lymphatics system, the lymphatic drainage pathways from the peritoneum, and therapeutic and delivery system characteristics (size, lipophilicity and surface properties) that favour lymph uptake and retention after intraperitoneal delivery. Finally, techniques that can be used to quantify uptake into peritoneal lymph are outlined, providing a platform for future studies.

Detection of Neurotransmitters by Three-Dimensional Laser-Scribed Graphene Grass Electrodes

Carbon nanomaterials possess superb properties and have contributed considerably to the advancement of integrated point-of-care chemical and biological sensing devices. Graphene has been widely researched as a signal transducing and sensing material. Here, a grass-like laser-scribed graphene (LSG) was synthesized by direct laser induction on common polyimide plastics. The resulting LSG grass was employed as a disposable electrochemical sensor for the detection of three neurotransmitters, dopamine (DA), epinephrine (EP), and norepinephrine (NE), and in the presence of uric acid and ascorbic acid as potential interferants, using differential pulse voltammetry and cyclic voltammetry. The LSG grass sensor achieved sensitivities of 0.243, 0.067, and 0.110 μA μM^-1 for DA, EP, and NE, respectively, whereas the limits of detection were 0.43, 1.1, and 1.3 μM, respectively. The selectivity of LSG grass was excellent for competing biomarkers with high structural similarity (EP vs NE and EP vs DA). The exceptional performance of LSG grass for DA, EP, and NE detection holds a promising future for carbon nanomaterial sensors with unique surface morphologies.

Acute pancreatitis conditioned mesenteric lymph causes cardiac dysfunction in rats independent of hypotension

BACKGROUND

Critical illness including severe acute pancreatitis is associated with the multiple organ dysfunction syndrome. The "gut-lymph" hypothesis states that multiple organ dysfunction syndrome is due to release of toxic factors from the intestine into the mesenteric lymph. The aims of this study were to determine the effect of normotensive acute pancreatitis conditioned mesenteric lymph on cardiac function and whether external drainage of mesenteric lymph would protect the heart.

METHODS

Groups of normal rats and those with normotensive taurocholate induced acute pancreatitis, had either no lymphatic intervention or thoracic duct ligation and external drainage of mesenteric lymph. After 6 hours, the hearts were removed for ex vivo functional measurements, including cardiac output, ventricular contractility (+dP/dt), and relaxation (-dP/dt). In a second experiment, mesenteric lymph from normal rats and those with established acute pancreatitis was infused into ex vivo perfused normal working rat hearts to assess impact on cardiac function. Heart and lung tissues were collected for assessment of edema.

RESULTS

Significant cardiac dysfunction, denoted by decreased cardiac output (21%), contractility (37%), relaxability (23%), and increased cardiac tissue edema (2-fold), developed in rats with established acute pancreatitis and no lymphatic intervention compared with the control group (all P < .05). Strikingly this cardiac dysfunction and edema was normalized in acute pancreatitis rats that had undergone prior thoracic duct ligation and external drainage of mesenteric lymph. In the second experiment, infusion of acute pancreatitis conditioned mesenteric lymph resulted in an immediate and significant similar magnitude decrease in of cardiac output (17%), contractility (22%), and relaxation (27%) compared with the infusion of normal lymph (all P <.05).

CONCLUSION

Mesenteric lymph from normotensive acute pancreatitis animals caused significant cardiac dysfunction which could be prevented by thoracic duct ligation and external drainage of mesenteric lymph.

Changes in the extracellular matrix surrounding human chronic wounds revealed by 2-photon imaging

Chronic wounds are a growing problem worldwide with no effective therapeutic treatments available. Our objective was to understand the composition of the dermal tissue surrounding venous leg ulcers and diabetic foot ulcers (DFU). We used novel 2-photon imaging techniques alongside classical histology to examine biopsies from the edges of two common types of chronic wound, venous leg ulcers and DFU. Compared to normal intact skin, we found that collagen levels are significantly reduced throughout the dermis of venous leg ulcer biopsies and DFU, with a reduction in both fibril thickness and abundance. Both wound types showed a significant reduction in elastin in the upper dermis, but in DFU, the loss was throughout the dermis. Loss of extracellular matrix correlated with high levels of CD68- and CD18-positive leukocytes. 2-photon imaging of the extracellular matrix in the intact tissue surrounding a chronic wound with a hand-held device may provide a useful clinical indicator on the healing progression or deterioration of these wounds.

Sustained Release of Cx43 Antisense Oligodeoxynucleotides from Coated Collagen Scaffolds Promotes Wound Healing

Antisense oligodeoxynucleotides targeting the mRNA of the gap junction protein Cx43 promote tissue repair in a variety of different wounds. Delivery of the antisense drug has most often been achieved by a thermoreversible hydrogel, Pluronic F-127, which is very effective in the short term but does not allow for sustained delivery over several days. For chronic wounds that take a long time to heal, repeated dosing with the drug may be desirable but is not always compatible with conventional treatments such as the weekly changing of compression bandages on venous leg ulcers. Here the coating of collagen scaffolds with antisense oligonucleotides is investigated and a way to provide protection of the oligodeoxynucleotide drug is found in conjunction with sustained release over a 7 d period. This approach significantly reduces the normal foreign body reaction to the scaffold, which induces an increase of Cx43 protein and an inhibition of healing. As a result of the antisense integration into the scaffold, inflammation is reduced with the rate of wound healing and contracture is significantly improved. This coated scaffold approach may be very useful for treating venous leg ulcers and also for providing a sustained release of any other types of oligonucleotide drugs that are being developed.

Mitochondrial dysfunction in peripheral blood mononuclear cells in early experimental and clinical acute pancreatitis

BACKGROUND/OBJECTIVES

Mitochondrial dysfunction occurs in vital organs in experimental acute pancreatitis (AP) and may play an important role in determining severity of AP. However, obtaining vital organ biopsies to measure mitochondrial function (MtF) in patients with AP poses considerable risk of harm. Being able to measure MtF from peripheral blood will bypass this problem. Furthermore, whether mitochondrial dysfunction is detectable in peripheral blood in mild AP is unknown. Therefore, the objective was to evaluate peripheral blood MtF in experimental and clinical AP.

METHOD

Mitochondrial respiration was measured using high resolution oxygraphy in an experimental study in caerulein induced AP and in a separate study, in patients with mild AP. Superoxide, cytochrome c, mitochondrial membrane potential (ΔΨ) and adenine triphosphate (ATP) were also measured as other markers of MtF.

RESULTS

Even though some states of mitochondrial respiration were increased in both experimental and clinical AP, this did not lead to an increase in net ATP in patients with AP. The increased leak respiration in both studies was further proof of dyscoupled mitochondria. In the clinical study there were also features of mitochondrial dysfunction with increased leak flux control ratio, superoxide, ΔΨ and decreased cytochrome c.

CONCLUSION

There is evidence of mitochondrial dysfunction with dyscoupled mitochondria, increased superoxide and decreased cytochrome c in patients with mild acute pancreatitis. Further studies should now determine whether mitochondrial function alters with severity in AP and whether mitochondrial dysfunction responds to treatments.

Leptin Is Associated With Persistence of Hyperglycemia in Acute Pancreatitis: A Prospective Clinical Study

Adipokines have many homeostatic roles, including modulation of glucose metabolism, but their role in the pathophysiology of hyperglycemia associated with acute and critical illnesses in general, and acute pancreatitis (AP) in particular, is largely unknown. This study aimed to investigate the relationship between a panel of adipokines and hyperglycemia in the early course of AP, as well as the role of adipokines as predictors of AP severity.Adiponectin, leptin, omentin, resistin, and visfatin were measured on a daily basis in the first 72 hours after hospital admission. A first set of analyses was undertaken with admission glycemia stratified by severity, and a second set of analyses was undertaken based on persistence of early hyperglycemia. All of the analyses were adjusted for confounders.A total of 32 patients with AP were included in this study. None of the studied adipokines was significantly associated with glucose level on admission. Leptin was significantly (P = 0.003) increased in patients with persistent hyperglycemia. Adiponectin was significantly associated with the Acute Physiology and Chronic Health Evaluation II (APACHE II) score in patients with persistent hyperglycemia (P = 0.015), visfatin with APACHE II score in patients with persistent hyperglycemia (P = 0.014), and omentin with APACHE II score in all of the patients regardless of the presence or absence of hyperglycemia (P = 0.021).Leptin is significantly associated with persistent hyperglycemia in the early course of AP. Omentin has a potential to become an accurate predictor of AP severity.

Glicentin-related pancreatic polypeptide inhibits glucose-stimulated insulin secretion from the isolated pancreas of adult male rats

Peptides derived from the glucagon gene Gcg, for example, glucagon and glucagon‐like peptide 1 (GLP‐1), act as physiological regulators of fuel metabolism and are thus of major interest in the pathogenesis of diseases, such as type‐2 diabetes and obesity, and their therapeutic management. Glicentin‐related pancreatic polypeptide (GRPP) is a further, 30 amino acid Gcg‐derived peptide identified in human, mouse, rat, and pig. However, the potential glucoregulatory function of this peptide is largely unknown. Here, we synthesized rat GRPP (rGRPP) and a closely related peptide, rat GRPP‐like peptide (rGRPP‐LP), and investigated their actions in the liver and pancreas of adult male rats by employing isolated‐perfused organ preparations. Rat GRPP and rGRPP‐LP did not affect glucose output from the liver, but both elicited potent inhibition of glucose‐stimulated insulin secretion (GSIS) from the rat pancreas. This action is unlikely to be mediated by glucagon or GLP‐1 receptors, as rGRPP and rGRPP‐LP did not stimulate cyclic adenosine monophosphate (cAMP) production from the glucagon or GLP‐1 receptors, nor did they antagonize glucagon‐ or GLP‐1‐stimulated cAMP‐production at either receptor. GRPP and GRPP‐LP may be novel regulators of insulin secretion, acting through an as‐yet undefined receptor.

The action of mimetic peptides on connexins protects fibroblasts from the negative effects of ischemia reperfusion

Connexins have been proposed as a target for therapeutic treatment of a variety of conditions. The main approaches have been by antisense or small peptides specific against connexins. Some of these peptides enhance communication while others interfere with connexin binding partners or bind to the intracellular and extracellular loops of connexins. Here, we explored the mechanism of action of a connexin mimetic peptide by evaluating its effect on gap junction channels, connexin protein levels and hemichannel activity in fibroblast cells under normal conditions and following ischemia reperfusion injury which elevates Cx43 levels, increases hemichannel activity and causes cell death. Our results showed that the effects of the mimetic peptide were concentration-dependent. High concentrations (100-300 μM) significantly reduced Cx43 protein levels and GJIC within 2 h, while these effects did not appear until 6 h when using lower concentrations (10-30 μM). Cell death can be reduced when hemichannel opening and GJIC were minimised.

Summary: Connexin mimetic peptides can reduce the levels of connexin proteins in cells and can prevent the spread of cell death that occurs following ischemia reperfusion injury, which has therapeutic potential.

Low-dose copper infusion into the coronary circulation induces acute heart failure in diabetic rats: New mechanism of heart disease

Diabetes impairs copper (Cu) regulation, causing elevated serum Cu and urinary Cu excretion in patients with established cardiovascular disease; it also causes cardiomyopathy and chronic cardiac impairment linked to defective Cu homeostasis in rats. However, the mechanisms that link impaired Cu regulation to cardiac dysfunction in diabetes are incompletely understood. Chronic treatment with triethylenetetramine (TETA), a Cu²⁺-selective chelator, improves cardiac function in diabetic patients, and in rats with heart disease; the latter displayed ∼3-fold elevations in free Cu²⁺ in the coronary effluent when TETA was infused into their coronary arteries. To further study the nature of defective cardiac Cu regulation in diabetes, we employed an isolated-perfused, working-heart model in which we infused micromolar doses of Cu²⁺ into the coronary arteries and measured acute effects on cardiac function in diabetic and non-diabetic-control rats. Infusion of CuCl₂ solutions caused acute dose-dependent cardiac dysfunction in normal hearts. Several measures of baseline cardiac function were impaired in diabetic hearts, and these defects were exacerbated by low-micromolar Cu²⁺ infusion. The response to infused Cu²⁺ was augmented in diabetic hearts, which became defective at lower infusion levels and underwent complete pump failure (cardiac output = 0 ml/min) more often (P < 0.0001) at concentrations that only moderately impaired function of control hearts. To our knowledge, this is the first report describing the acute effects on cardiac function of pathophysiological elevations in coronary Cu²⁺. The effects of Cu²⁺ infusion occur within minutes in both control and diabetic hearts, which suggests that they are not due to remodelling. Heightened sensitivity to the acute effects of small elevations in Cu²⁺ could contribute substantively to impaired cardiac function in patients with diabetes and is thus identified as a new mechanism of heart disease.

Mitochondrial dysfunction in steatotic rat livers occurs because a defect in complex i makes the liver susceptible to prolonged cold ischemia

Steatotic livers are susceptible to cold ischemia, which is thought to be secondary to mitochondrial dysfunction. Ischemic preconditioning (IPC) has been reported to improve liver function in the setting of warm ischemia/reperfusion injury, but the effect of IPC on steatotic liver mitochondrial function (MF) with cold ischemia has not been previously evaluated. We aimed to evaluate MF with various severities of hepatic steatosis after various durations of cold ischemia storage with or without IPC. Male Sprague-Dawley rats were fed a normal diet or a high-fat/high-sucrose diet for 1, 2, or 4 weeks to induce mild (<30%), moderate (30%-60%), or severe (>60%) macrovesicular steatosis, respectively. Liver MF was tested with high-resolution respirometry after 1.5, 4, 8, 12, 18, and 24 hours of cold ischemia. Rats in each group (n = 10) underwent 10 minutes of IPC or no IPC before cold ischemia. The baseline (time 0) respiration was similar for lean and severely steatotic livers despite decreased mitochondrial complex I (C-I) activity in severely steatotic livers. Hepatic steatosis was associated with increased C-I-mediated leaks and decreased respiratory control ratios (RCRs) after cold ischemia. Mildly, moderately, and severely steatotic livers showed significantly lower RCRs after 8, 1.5, and 1.5 hours of cold ischemia, respectively, in comparison with lean livers. IPC restored RCRs in mildly steatotic livers to levels comparable to those in lean livers for up to 24 hours of cold ischemia via the attenuation of C-I-mediated leaks, but it had no beneficial effect on moderately and severely steatotic livers. In conclusion, steatotic livers exhibited apparent mitochondrial dysfunction through an alteration in C-I activity, and this made them more susceptible to prolonged cold ischemia. The clinically based IPC protocol used here restored MF in cases of mild hepatic steatosis by attenuating C-I-mediated leaks after prolonged cold ischemia, but it did work not in livers with moderate or severe steatosis.

Impact of ischaemic preconditioning on experimental steatotic livers following hepatic ischaemia-reperfusion injury: a systematic review

BACKGROUND

Steatotic livers are vulnerable to the deleterious effects of ischaemia-reperfusion injury (IRI) that occur after hepatic surgery. Ischaemic preconditioning (IPC) has been shown to abrogate the effects of IRI in patients undergoing hepatic surgery. Experimental studies have suggested that IPC may be beneficial in steatotic livers subjected to IRI.

OBJECTIVE

The aim of this systematic review was to evaluate the effects of IPC on steatotic livers following hepatic IRI in experimental models.

METHODS

An electronic search of the OVID Medline and EMBASE databases was performed to identify studies that reported clinically relevant outcomes in animal models of hepatic steatosis subjected to IPC and IRI.

RESULTS

A total of 1093 articles were identified, of which 18 met the inclusion criteria. There was considerable heterogeneity in the type of animal model, and duration and type of IRI. Increased macrovesicular steatosis (> 30%) was associated with a poor outcome following IRI. Ischaemic preconditioning was found to be beneficial in > 30% steatotic livers and provided for decreased histological damage, improved liver function findings and increased survival.

CONCLUSIONS

Experimental evidence supports the use of IPC in steatotic livers undergoing IRI. These findings may be applicable to patients undergoing liver surgery. However, clinical studies are required to validate the efficacy of IPC in this setting.

Relationship between the exocrine and endocrine pancreas after acute pancreatitis

AIM: To determine the prevalence and time course of pancreatic exocrine insufficiency in individuals with newly diagnosed prediabetes or diabetes mellitus after acute pancreatitis.

METHODS: Relevant literature cited in three major biomedical journal databases (EMBASE, MEDLINE, and Scopus) was reviewed independently by two authors. There were no language constraints but the search was limited to human studies. Studies included were cohort studies of adult patients who were discharged after an attack of acute pancreatitis. Patients were excluded if they were under 18 years of age or had a previous diagnosis of prediabetes or diabetes mellitus, pancreatic exocrine insufficiency, or chronic pancreatitis. The main outcome measure was the prevalence of concomitant pancreatic exocrine insufficiency in patients who were diagnosed with prediabetes and diabetes mellitus after an attack of acute pancreatitis. Subgroup analysis was conducted for patients who were diagnosed with prediabetes only and those who were diagnosed with diabetes mellitus only. Subgroup analysis looking at the time course of concomitant pancreatic exocrine and endocrine insufficiency was also conducted. Pooled prevalence and corresponding 95% confidence intervals were calculated for all outcome measures and P-values < 0.05 were deemed statistically significant.

RESULTS: Eight clinical studies comprising of 234 patients met all eligibility criteria. The pooled prevalence of newly diagnosed prediabetes or diabetes in individuals after acute pancreatitis was 43% (95%CI: 30%-56%). The pooled prevalence of pancreatic exocrine insufficiency in individuals after acute pancreatitis was 29% (95%CI: 19%-39%). The prevalence of concomitant pancreatic exocrine insufficiency in individuals with newly diagnosed prediabetes or diabetes was 40% (95%CI: 25%-55%). The prevalence of concomitant pancreatic exocrine insufficiency among individuals with prediabetes alone and diabetes mellitus alone was 41% (95%CI: 12%-75%) and 39% (95%CI: 28%-51%), respectively. Further analysis showed that the prevalence of concomitant pancreatic exocrine insufficiency in individuals with prediabetes or diabetes decreases over time after an attack of acute pancreatitis.

CONCLUSION: Pancreatic exocrine insufficiency occurs in 40% of individuals with newly diagnosed prediabetes or diabetes mellitus after acute pancreatitis. Further studies are needed to investigate the pathogenesis of diabetes in this setting.

The clinical relevance of obesity in acute pancreatitis: targeted systematic reviews

BACKGROUND

With the rising prevalence of obesity, its impact on the severity and outcome of acute pancreatitis remains an important consideration when managing obese patients with acute pancreatitis.

OBJECTIVE

To determine the clinical relevance of obesity in acute pancreatitis.

METHODS

A series of clinically relevant questions were framed which formed the basis of our literature search using PubMed and EMBASE databases. These related to acute pancreatitis severity, systemic inflammatory response, mortality, local and systemic complications. The search was restricted to human studies. Studies were classified according to the Oxford Centre for Evidence Based Medicine levels of evidence 1 for prognostic studies. Obesity was defined according to the guidelines of the World Health Organization. In keeping with studies included the binary classification (mild and severe) of acute pancreatitis was used.

RESULTS

Obesity is associated with an amplified systemic inflammatory response in acute pancreatitis and is a prognostic factor for mortality, local, systemic complications and severity in acute pancreatitis. Obesity was not found to be an independent prognostic factor for mortality and organ failure in patients with acute pancreatitis. It was evident that further studies are required to determine whether incorporating obesity into existing scoring systems improves severity prediction. Emerging evidence suggests that an obesity paradox is present in patients with acute pancreatitis.

CONCLUSION

This review demonstrates that obesity has a clinically relevant impact on the course and outcome of acute pancreatitis.

The pathogenic mechanism of diabetes varies with the degree of overexpression and oligomerization of human amylin in the pancreatic islet β cells

The aggregation of human amylin (hA) to form cytotoxic structures has been closely associated with the causation of type 2 diabetes. We sought to advance understanding of how altered expression and aggregation of hA might link β-cell degeneration with diabetes onset and progression, by comparing phenotypes between homozygous and hemizygous hA-transgenic mice. The homozygous mice displayed elevated islet hA that correlated positively with measures of oligomer formation (r=0.91; P<0.0001). They also developed hyperinsulinemia with transient insulin resistance during the prediabetes stage and then underwent rapid β-cell loss, culminating in severe juvenile-onset diabetes. The prediabetes stage was prolonged in the hemizygous mice, wherein β-cell dysfunction and extensive oligomer formation occurred in adulthood at a much later stage, when hA levels were lower (r=-0.60; P<0.0001). This is the first report to show that hA-evoked diabetes is associated with age, insulin resistance, progressive islet dysfunction, and β-cell apoptosis, which interact variably to cause the different diabetes syndromes. The various levels of hA elevation cause different extents of oligomer formation in the disease stages, thus eliciting early- or adult-onset diabetes syndromes, reminiscent of type 1 and 2 diabetes, respectively. Thus, the hA-evoked diabetes phenotypes differ substantively according to degree of amylin overproduction. These findings are relevant to the understanding of the pathogenesis and the development of experimental therapeutics for diabetes.

The diabetic rat kidney mediates inosituria and selective urinary partitioning of D-chiro-inositol

Diabetic nephropathy is a serious complication of diabetes mellitus with a pressing need for effective metabolic markers to detect renal impairment. Of potential significance are the inositol compounds, myo-inositol (MI), and the less abundant stereoisomer, D-chiro-inositol (DCI), which are excreted at increased levels in the urine in diabetes mellitus, a phenomenon known as inosituria. There is also a selective urinary excretion of DCI compared to MI. As the biological origins of altered inositol metabolism in diabetes mellitus are unknown, the aim of this study was to determine whether the diabetic kidney was directly responsible. Kidneys isolated from four-week streptozotocin-induced diabetic rats were characterized by a 3-fold reduction in glomerular filtration rate (GFR) compared to matched non-diabetic kidneys. When perfused with fixed quantities of MI (50 µM) and DCI (5 µM) under normoglycemic conditions (5 mM glucose), GFR-normalized urinary excretion of MI was increased by 1.7-fold in diabetic vs. non-diabetic kidneys. By comparison, GFR-normalized urinary excretion of DCI was increased by 4-fold. Perfusion conditions replicating hyperglycemia (20 mM glucose) potentiated DCI but not MI urinary excretion in both non-diabetic and diabetic kidneys. Overall, there was a 2.4-fold increase in DCI urinary excretion compared to MI in diabetic kidneys that was independent of glucose ambience. This increased urinary excretion of DCI and MI in diabetic kidneys occurred despite increased renal expression of the inositol transporters, sodium myo-inositol transporter subtype 1 and 2 (SMIT1 and SMIT2). These findings show that the diabetic kidney primarily mediates inosituria and altered urinary partitioning of MI and DCI. Urinary inositol levels might therefore serve as an indicator of impaired renal function in diabetes mellitus with wider implications for monitoring chronic kidney disease.

Diabetic cardiomyopathy is associated with defective myocellular copper regulation and both defects are rectified by divalent copper chelation

BACKGROUND

Heart disease is the leading cause of death in diabetic patients, and defective copper metabolism may play important roles in the pathogenesis of diabetic cardiomyopathy (DCM). The present study sought to determine how myocardial copper status and key copper-proteins might become impaired by diabetes, and how they respond to treatment with the Cu (II)-selective chelator triethylenetetramine (TETA) in DCM.

METHODS

Experiments were performed in Wistar rats with streptozotocin (STZ)-induced diabetes with or without TETA treatment. Cardiac function was analyzed in isolated-perfused working hearts, and myocardial total copper content measured by particle-induced x-ray emission spectroscopy (PIXE) coupled with Rutherford backscattering spectrometry (RBS). Quantitative expression (mRNA and protein) and/or activity of key proteins that mediate LV-tissue-copper binding and transport, were analyzed by combined RT-qPCR, western blotting, immunofluorescence microscopy, and enzyme activity assays. Statistical analysis was performed using Student's t-tests or ANOVA and p-values of < 0.05 have been considered significant.

RESULTS

Left-ventricular (LV) copper levels and function were severely depressed in rats following 16-weeks' diabetes, but both were unexpectedly normalized 8-weeks after treatment with TETA was instituted. Localized myocardial copper deficiency was accompanied by decreased expression and increased polymerization of the copper-responsive transition-metal-binding metallothionein proteins (MT1/MT2), consistent with impaired anti-oxidant defences and elevated susceptibility to pro-oxidant stress. Levels of the high-affinity copper transporter-1 (CTR1) were depressed in diabetes, consistent with impaired membrane copper uptake, and were not modified by TETA which, contrastingly, renormalized myocardial copper and increased levels and cell-membrane localization of the low-affinity copper transporter-2 (CTR2). Diabetes also lowered indexes of intracellular (IC) copper delivery via the copper chaperone for superoxide dismutase (CCS) to its target cuproenzyme, superoxide dismutase-1 (SOD1): this pathway was rectified by TETA treatment, which normalized SOD1 activity with consequent bolstering of anti-oxidant defenses. Furthermore, diabetes depressed levels of additional intracellular copper-transporting proteins, including antioxidant-protein-1 (ATOX1) and copper-transporting-ATPase-2 (ATP7B), whereas TETA elevated copper-transporting-ATPase-1 (ATP7A).

CONCLUSIONS

Myocardial copper deficiency and defective cellular copper transport/trafficking are revealed as key molecular defects underlying LV impairment in diabetes, and TETA-mediated restoration of copper regulation provides a potential new class of therapeutic molecules for DCM.

Newly diagnosed diabetes mellitus after acute pancreatitis: a systematic review and meta-analysis

BACKGROUND

Diabetes mellitus (DM) is common in the general population and it poses a heavy burden to society in the form of long-term disability, healthcare use and costs. The pancreas is a key player in glucose homeostasis, but the occurrence of newly diagnosed DM after acute pancreatitis (AP), the most frequent disease of the pancreas, has never been assessed systematically. The aim of this study was to conduct a systematic literature review to determine the prevalence and time course of DM and related conditions after the first attack of AP as well as the impact of covariates.

METHODS

Relevant literature cited in three electronic databases (Scopus, EMBASE and MEDLINE) was reviewed independently by two authors. The main outcome measures studied were newly diagnosed prediabetes, DM, or DM treated with insulin. Pooled prevalence and 95% CIs were calculated for all outcomes.

RESULTS

A total of 24 prospective clinical studies, involving 1102 patients with first episode of AP, met all the eligibility criteria. Prediabetes and/or DM was observed in 37% (95% CI 30% to 45%) individuals after AP. The pooled prevalence of prediabetes, DM and treatment with insulin after AP was 16% (95% CI 9% to 24%), 23% (95% CI 16% to 31%), and 15% (95% CI 9% to 21%), respectively. Newly diagnosed DM developed in 15% of individuals within 12 months after first episode of AP and the risk increased significantly at 5 years (relative risk 2.7 (95% CI 1.9 to 3.8)). A similar trend was observed with regard to treatment with insulin. The severity of AP, its aetiology, individuals' age and gender had minimal effect on the studied outcomes.

CONCLUSIONS

Patients with AP often develop prediabetes and/or DM after discharge from hospital, and have a greater than twofold increased risk of DM over 5 years. Further studies are warranted to determine the optimal strategy for its detection and whether the risk of developing DM after AP can be reduced.

Additive effect of pretransplant obesity, diabetes, and cardiovascular risk factors on outcomes after liver transplantation

The effects of pretransplant obesity, diabetes mellitus (DM), coronary artery disease (CAD), and hypertension (HTN) on outcomes after liver transplantation (LT) are controversial. Questions have also been raised about the appropriateness of the body mass index (BMI) for assessing obesity in patients with end-stage liver disease. Both issues have implications for organ allocation in LT. To address these questions, we undertook a cohort study of 202 consecutive patients (2000-2010) undergoing LT at a national center in New Zealand. BMI and body fat percentage (%BF) values (dual-energy X-ray absorptiometry) were measured before transplantation, and the methods were compared. The influence of pretransplant risk variables (including obesity, DM, CAD, and HTN) on the 30-day postoperative event rate, length of hospital stay, and survival were analyzed. There was agreement between the calculated BMI and the measured %BF for 86.0% of the study population (κ coefficient = 0.73, 95% confidence interval = 0.61-0.85), and this was maintained across increasing Model for End-Stage Liver Disease scores. Obesity was an independent risk factor for the postoperative event rate [count ratio (CR) = 1.03, P < 0.001], as was DM (CR = 1.4, P < 0.001). Obesity with concomitant DM was the strongest predictor of the postoperative event rate (CR = 1.75, P < 0.001) and a longer hospital stay (5.81 days, P < 0.01). Independent metabolic risk factors had no effect on 30-day, 1-year, or 5-year patient survival. In conclusion, BMI is an adequate tool for assessing obesity-associated risk in LT. Early post-LT morbidity is highest for patients with concomitant obesity and DM, although these factors do not appear to influence recipient survival.

Hepatic mitochondrial function analysis using needle liver biopsy samples

BACKGROUNDS AND AIM

Current assessment of pre-operative liver function relies upon biochemical blood tests and histology but these only indirectly measure liver function. Mitochondrial function (MF) analysis allows direct measurement of cellular metabolic function and may provide an additional index of hepatic health. Conventional MF analysis requires substantial tissue samples (>100 mg) obtained at open surgery. Here we report a method to assess MF using <3 mg of tissue obtained by a Tru-cut® biopsy needle making it suitable for percutaneous application.

METHODS

An 18G Bard® Max-core® biopsy instrument was used to collect samples. The optimal Tru-cut® sample weight, stability in ice-cold University of Wisconsin solution, reproducibility and protocol utility was initially evaluated in Wistar rat livers then confirmed in human samples. MF was measured in saponin-permeabilized samples using high-resolution respirometry.

RESULTS

The average mass of a single rat and human liver Tru-cut® biopsy was 5.60±0.30 and 5.16±0.15 mg, respectively (mean; standard error of mean). Two milligram of sample was found the lowest feasible mass for the MF assay. Tissue MF declined after 1 hour of cold storage. Six replicate measurements within rats and humans (n = 6 each) showed low coefficient of variation (<10%) in measurements of State-III respiration, electron transport chain (ETC) capacity and respiratory control ratio (RCR). Ischemic rat and human liver samples consistently showed lower State-III respiration, ETC capacity and RCR, compared to normal perfused liver samples.

CONCLUSION

Consistent measurement of liver MF and detection of derangement in a disease state was successfully demonstrated using less than half the tissue from a single Tru-cut® biopsy. Using this technique outpatient assessment of liver MF is now feasible, providing a new assay for the evaluation of hepatic function.

Protection of the heart by treatment with a divalent-copper-selective chelator reveals a novel mechanism underlying cardiomyopathy in diabetic rats

Background

Intracellular calcium (Ca²⁺) coordinates the cardiac contraction cycle and is dysregulated in diabetic cardiomyopathy. Treatment with triethylenetetramine (TETA), a divalent-copper-selective chelator, improves cardiac structure and function in patients and rats with diabetic cardiomyopathy, but the molecular basis of this action is uncertain. Here, we used TETA to probe potential linkages between left-ventricular (LV) copper and Ca²⁺ homeostasis, and cardiac function and structure in diabetic cardiomyopathy.

Methods

We treated streptozotocin-diabetic rats with a TETA-dosage known to ameliorate LV hypertrophy in patients with diabetic cardiomyopathy. Drug treatment was begun either one (preventative protocol) or eight (restorative protocol) weeks after diabetes induction and continued thereafter for seven or eight weeks, respectively. Total copper content of the LV wall was determined, and simultaneous measurements of intracellular calcium concentrations and isometric contraction were made in LV trabeculae isolated from control, diabetic and TETA-treated diabetic rats.

Results

Total myocardial copper levels became deficient in untreated diabetes but were normalized by TETA-treatment. Cardiac contractility was markedly depressed by diabetes but TETA prevented this effect. Neither diabetes nor TETA exerted significant effects on peak or resting [Ca²⁺]_i. However, diabetic rats showed extensive cardiac remodelling and decreased myofibrillar calcium sensitivity, consistent with observed increases in phosphorylation of troponin I, whereas these changes were all prevented by TETA.

Conclusions

Diabetes causes cardiomyopathy through a copper-mediated mechanism that incorporates myocardial copper deficiency, whereas TETA treatment prevents this response and maintains the integrity of cardiac structure and myofibrillar calcium sensitivity. Altered calcium homeostasis may not be the primary defect in diabetic cardiomyopathy. Rather, a newly-described copper-mediated mechanism may cause this disease.

Integration of scaffolds into full-thickness skin wounds: the connexin response

Scaffolds have been reported to promote healing of hard-to-heal wounds such as burns and chronic ulcers. However, there has been little investigation into the cell biology of wound edge tissues in response to the scaffolds. Here, we assess the impact of collagen scaffolds on mouse full-thickness wound re-epithelialisation during the first 5 days of healing. We find that scaffolds impede wound re-epithelialisation, inducing a bulbous thickening of the wound edge epidermis as opposed to the thin tongue of migratory keratinocytes seen in normal wound healing. Scaffolds also increase the inflammatory response and the numbers of neutrophils in and around the wound. These effects were also produced by scaffolds made of alginate in the form of fibers and microspheres, but not as an alginate hydrogel. In addition, we find the gap junction protein connexin 43, which normally down-regulates at the wound edge during re-epithelialisation, to be up-regulated in the bulbous epidermal wound edge. Incorporation of connexin 43 antisense oligodeoxynucleotides into the scaffold can be performed to reduce inflammation whilst promoting scaffold biocompatibility.

Treatment with a copper-selective chelator causes substantive improvement in cardiac function of diabetic rats with left-ventricular impairment

BACKGROUND

Defective copper regulation is implicated as a causative mechanism of organ damage in diabetes. Treatment with trientine, a divalent-copper-selective chelator, improves arterial and renal structure/function in diabetes, wherein it also ameliorates left-ventricular (LV) hypertrophy. However, direct in vivo evidence that trientine can improve cardiac function in heart failure has hitherto been lacking.

METHODS

To determine whether trientine treatment could improve in vivo outcome, we measured cardiac function in groups of trientine-treated diabetic (TETA-DIA), non-drug-treated diabetic (DIA) and sham-treated control (SHAM) rats, by using in vivo high-field cardiac magnetic-resonance imaging (cMRI) and an ex vivo isolated-perfused working heart method. Forty age-matched animals underwent a cMRI scan after which 12 were randomized to the SHAM group and 28 underwent streptozotocin-injection; of these, 25 developed stable diabetes, and 12 were then randomized to receive no treatment for 16 weeks (DIA) and the other 13 to undergo 8-weeks' untreated diabetes followed by 8-weeks' drug treatment (TETA-DIA). Animals were studied again by cMRI at 8 and 16 weeks following disease induction, and finally by measurement of ex vivo cardiac function.

RESULTS

After eight weeks diabetes, rats (DIA/TETA-DIA) had developed significant impairment of LV function, as judged by impairment of ejection fraction (LVEF), cardiac output (CO), and LV mass (LVM)/body-mass (all P < 0.001), as well as other functional indexes. LVEF, CO (both P < 0.001) and the other indexes deteriorated further at 16 weeks in DIA, whereas trientine (TETA-DIA) improved cardiac function by elevating LVEF and CO (both P < 0.001), and also partially reversed the increase in LVM/body-mass (P < 0.05). In ex vivo hearts from DIA, the CO response to increasing preload pressure was deficient compared with SHAM (P < 0.001) whereas the preload-CO relationship was significantly improved in TETA-DIA animals (P < 0.001).

CONCLUSIONS

Trientine treatment significantly improved cardiac function in diabetic rats with substantive LV impairment. These results implicate impaired copper regulation in the pathogenesis of impaired cardiac function caused by diabetic cardiomyopathy, and support ongoing studies of trientine treatment in patients with heart failure.

Early nasogastric tube feeding versus nil per os in mild to moderate acute pancreatitis: a randomized controlled trial

BACKGROUND & AIMS

Nasojejunal tube feeding is a standard of care in patients with predicted severe acute pancreatitis (AP) and several recent trials suggested that nasogastric tube feeding (NGT) is as safe and efficient as nasojejunal tube feeding in these patients. The aim was to investigate whether NGT presents any benefit to patients with mild to moderate AP.

METHODS

The study design was a randomized controlled trial. The patients in the intervention group received NGT within 24 h of hospital admission. The patients in the control group were on nil per os (NPO). The severity of acute pancreatitis was determined according to the new international multidisciplinary classification.

RESULTS

There were 17 patients randomly allocated to the NGT group and 18 to the NPO group. The visual analogue pain score decreased to a significantly greater extent in the NGT group (from median 9 (range 7-9) at baseline to 1 (0-3) at 72 h after randomization) compared with the NPO group (from 7 (5-9) to 3 (1-4) (p = 0.036). The number of patients not requiring opiates at 48 h after randomization was significantly different (p = 0.024) between NGT (9/17) and NPO (3/18). Oral food intolerance was observed in 1/17 patient in the NGT group and 9/18 patients in the NPO group (p = 0.004). The overall hospital stay in the NGT group was 9 (5-12) days as compared with 8.5 (6-13) days in the NPO group (p = 0.91).

CONCLUSIONS

NGT commenced within 24 h of hospital admission is well tolerated in patients with mild to moderate acute pancreatitis. Further, when compared with NPO, it significantly reduces the intensity and duration of abdominal pain, need for opiates, and risk of oral food intolerance, but not overall hospital stay.

Pharmacological characterization of rat amylin receptors: implications for the identification of amylin receptor subtypes

BACKGROUND AND PURPOSE

Amylin (Amy) is an important glucoregulatory peptide and AMY receptors are clinical targets for diabetes and obesity. Human (h) AMY receptor subtypes are complexes of the calcitonin (CT) receptor with receptor activity-modifying proteins (RAMPs); their rodent counterparts have not been characterized. To allow identification of the most clinically relevant receptor subtype, the elucidation of rat (r) AMY receptor pharmacology is necessary.

EXPERIMENTAL APPROACH

Receptors were transiently transfected into COS-7 cells and cAMP responses measured in response to different agonists, with or without antagonists. Competition binding experiments were performed to determine rAmy affinity.

KEY RESULTS

rCT was the most potent agonist of rCT((a)) receptors, whereas rAmy was most potent at rAMY(1(a)) and rAMY(3(a)) receptors. rAmy bound to these receptors with high affinity. Rat α-calcitonin gene-related peptide (CGRP) was equipotent to rAmy at both AMY receptors. Rat adrenomedullin (AM) and rAM2/intermedin activated all three receptors but were most effective at rAMY(3(a)) . AC187, AC413 and sCT(8-32) were potent antagonists at all three receptors. rαCGRP(8-37) displayed selectivity for rAMY receptors over rCT((a)) receptors. rAMY(8-37) was a weak antagonist but was more effective at rAMY(1(a)) than rAMY(3(a)) .

CONCLUSIONS AND IMPLICATIONS

AMY receptors were generated by co-expression of rCT((a)) with rRAMP1 or 3, forming rAMY(1(a)) and rAMY(3(a)) receptors, respectively. CGRP was more potent at rAMY than at hAMY receptors. No antagonist tested was able to differentiate the rAMY receptor subtypes. The data emphasize the need for and provide a useful resource for developing new CT or AMY receptor ligands as pharmacological tools or potential clinical candidates.

Targeting Cx43 and N-cadherin, which are abnormally upregulated in venous leg ulcers, influences migration, adhesion and activation of Rho GTPases

Background

Venous leg ulcers can be very hard to heal and represent a significant medical need with no effective therapeutic treatment currently available.

Principal Findings

In wound edge biopsies from human venous leg ulcers we found a striking upregulation of dermal N-cadherin, Zonula Occludens-1 and the gap junction protein Connexin43 (Cx43) compared to intact skin, and in stark contrast to the down-regulation of Cx43 expression seen in acute, healing wounds. We targeted the expression of these proteins in 3T3 fibroblasts to evaluate their role in venous leg ulcers healing. Knockdown of Cx43 and N-cadherin, but not Zonula Occludens-1, accelerated cell migration in a scratch wound-healing assay. Reducing Cx43 increased Golgi reorientation, whilst decreasing cell adhesion and proliferation. Furthermore, Connexin43 and N-cadherin knockdown led to profound effects on fibroblast cytoskeletal dynamics after scratch-wounding. The cells exhibited longer lamelipodial protrusions lacking the F-actin belt seen at the leading edge in wounded control cells. This phenotype was accompanied by augmented activation of Rac-1 and RhoA GTPases, as revealed by Förster Resonance Energy Transfer and pull down experiments.

Conclusions

Cx43 and N-cadherin are potential therapeutic targets in the promotion of healing of venous leg ulcers, by acting at least in part through distinct contributions of cell adhesion, migration, proliferation and cytoskeletal dynamics.

A simple and rapid method for identifying and semi-quantifying peptide hormones in isolated pancreatic islets by direct-tissue matrix-assisted laser desorption ionization time-of-flight mass spectrometry

We describe a new, simple, robust and efficient method based on direct-tissue matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry that enables consistent semi-quantitation of peptide hormones in isolated pancreatic islets from normal and diabetic rodents. Prominent signals were measured that corresponded to all the main peptide hormones present in islet-endocrine cells: (α-cells) glucagon, glicentin-related polypeptide/GRPP; (β-cells) insulin I, insulin II, C-peptide I, C-peptide II, amylin; (δ-cells) somatostatin-14; and (PP-cells), and pancreatic polypeptide. The signal ratios coincided with known relative hormone abundances. The method demonstrated that severe insulin deficiency is accompanied by elevated levels of all non-β-cell-hormones in diabetic rat islets, consistent with alleviation of paracrine suppression of hormone production by non-β-cells. It was also effective in characterizing hormonal phenotype in hemizygous human-amylin transgenic mice that express human and mouse amylin in approx. equimolar quantities. Finally, the method demonstrated utility in basic peptide-hormone discovery by identifying a prominent new Gcg-gene-derived peptide (theoretical monoisotopic molecular weight 3263.5 Da), closely related to but distinct from GRPP, in diabetic islets. This peptide, whose sequence is HAPQDTEENARSFPASQTEPLEDPNQINE in Rattus norvegicus, could be a peptide hormone whose roles in physiology and metabolic disease warrant further investigation. This method provides a powerful new approach that could provide important new insights into the physiology and regulation of peptide hormones in islets and other endocrine tissues. It has potentially wide-ranging applications that encompass endocrinology, pharmacology, phenotypic analysis in genetic models of metabolic disease, and hormone discovery, and could also effectively limit the numbers of animals required for such studies.

Connexins in wound healing; perspectives in diabetic patients

Skin lesions are common events and we have evolved to rapidly heal them in order to maintain homeostasis and prevent infection and sepsis. Most acute wounds heal without issue, but as we get older our bodies become compromised by poor blood circulation and conditions such as diabetes, leading to slower healing. This can result in stalled or hard-to-heal chronic wounds. Currently about 2% of the Western population develop a chronic wound and this figure will rise as the population ages and diabetes becomes more prevalent [1]. Patient morbidity and quality of life are profoundly altered by chronic wounds [2]. Unfortunately a significant proportion of these chronic wounds fail to respond to conventional treatment and can result in amputation of the lower limb. Life quality and expectancy following amputation is severely reduced. These hard to heal wounds also represent a growing economic burden on Western society with published estimates of costs to healthcare services in the region of $25B annually [3]. There exists a growing need for specific and effective therapeutic agents to improve healing in these wounds. In recent years the gap junction protein Cx43 has been shown to play a pivotal role early on in the acute wound healing process at a number of different levels [4-7]. Conversely, abnormal expression of Cx43 in wound edge keratinocytes was shown to underlie the poor rate of healing in diabetic rats, and targeting its expression with an antisense gel restored normal healing rates [8]. The presence of Cx43 in the wound edge keratinocytes of human chronic wounds has also been reported [9]. Abnormal Cx43 biology may underlie the poor healing of human chronic wounds and be amenable therapeutic intervention [7]. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.

A comprehensive classification of invasive procedures for treating the local complications of acute pancreatitis based on visualization, route, and purpose

BACKGROUND/AIMS

The lack of a system to classify invasive procedures to treat local complications of acute pancreatitis is an obstacle to comparing interventions. This study aimed to develop and validate a comprehensive multidisciplinary classification.

METHODS

Standardized terminology was used to develop a classification of procedures based on three key components: how the lesion is visualized, the route used during the procedure, and the procedure's purpose. Gastroenterologists, radiologists, and surgeons (n = 22) from three New Zealand centers independently classified 15 published technique descriptions. Inter-rater reliability was calculated for each component. The classification's clarity, ease of use, and potential to achieve its objectives were rated on a Likert scale.

RESULTS

The classification's clarity, ease of use, and potential to achieve its objectives had median scores of 4/5. Inter-rater reliability for visualization, route, and purpose components was substantial at 0.73 (95% CI 0.63-0.82), 0.79 (95% CI 0.70-0.87), and 0.64 (95% CI 0.53-0.74), respectively.

CONCLUSIONS

This article describes the development and validation of a comprehensive classification for the wide range of procedures used to treat the local complications of acute pancreatitis. It has substantial inter-rater reliability and high acceptability, which should enhance communication between clinicians and facilitate comparison between procedures.

Warming and humidification have no effect on oxidative stress during pneumoperitoneum in rats

Pneumoperitoneum is reported to induce oxidative stress due to the desiccative effect of cold, dry gas insufflation. The aim of this study is to compare the effect of warmed, humidified insufflation to standard gas, by measuring oxidative stress markers in a physiologically relevant animal model. Twenty male Wistar rats (330?650 g) were alternately assigned to the Warm Humidified group (WH, n = 10) and Control group (n = 10). All rats underwent pneumoperitoneum at 5 mmHg and a controlled flow rate for 110 min. The WH group received warmed (37?C) and humidified (98% Relative Humidity (RH)) gas and the control group received standard gas at room temperature (19?C) and 0% RH. At the end of pneumoperitoneum, samples of liver, kidney, pancreas, jejunum, and lung were excised. Levels of plasma and tissue malondialdehyde (MDA) and protein carbonyls (PC) were measured. Organ light microscopy was performed. There were no differences between groups for MDA or PC concentrations in plasma, liver, kidney, jejunum, or lung tissue. There were no differences in histological score between groups. Warming and humidification of pneumoperitoneum insufflation gas have no effect on measures of oxidative stress compared to non-warmed, non-humidified controls.