Transcapillary Transport Research Articles

Mathematical model of oxygen, nutrient, and drug transport in tuberculosis granulomas.

Physiological abnormalities in pulmonary granulomas-pathological hallmarks of tuberculosis (TB)-compromise the transport of oxygen, nutrients, and drugs. In prior studies, we demonstrated mathematically and experimentally that hypoxia and necrosis emerge in the granuloma microenvironment (GME) as a direct result of limited oxygen availability. Building on our initial model of avascular oxygen diffusion, here we explore additional aspects of oxygen transport, including the roles of granuloma vasculature, transcapillary transport, plasma dilution, and interstitial convection, followed by cellular metabolism. Approximate analytical solutions are provided for oxygen and glucose concentration, interstitial fluid velocity, interstitial fluid pressure, and the thickness of the convective zone. These predictions are in agreement with prior experimental results from rabbit TB granulomas and from rat carcinoma models, which share similar transport limitations. Additional drug delivery predictions for anti-TB-agents (rifampicin and clofazimine) strikingly match recent spatially-resolved experimental results from a mouse model of TB. Finally, an approach to improve molecular transport in granulomas by modulating interstitial hydraulic conductivity is tested in silico.

Monoclonal Antibody Pharmacokinetics in Cynomolgus Monkeys Following Subcutaneous Administration: Physiologically Based Model Predictions from Physiochemical Properties.

An integrated physiologically based modeling framework is presented for predicting pharmacokinetics and bioavailability of subcutaneously administered monoclonal antibodies in cynomolgus monkeys, based on in silico structure-derived metrics characterizing antibody size, overall charge, local charge, and hydrophobicity. The model accounts for antibody-specific differences in pinocytosis, transcapillary transport, local lymphatic uptake, and pre-systemic degradation at the subcutaneous injection site and reliably predicts the pharmacokinetics of five different wild-type mAbs and their Fc variants following intravenous and subcutaneous administration. Significant associations were found between subcutaneous injection site degradation rate and the antibody's local positive charge of its complementarity-determining region (R = 0.56, p = 0.0012), antibody pinocytosis rate and its overall positive charge (R = 0.59, p = 0.00063), and antibody paracellular transport and its overall charge together with hydrophobicity (R = 0.63, p = 0.00096). Based on these results, population simulations were performed to predict the relationship between bioavailability and antibody local positive charge. In addition, model simulations were conducted to calculate the relative contribution of absorption pathways (lymphatic and blood), pre-systemic degradation pathways (interstitial and lysosomal), and the influence of injection site lymph flow on antibody bioavailability and pharmacokinetics. The proposed physiologically based modeling framework integrates fundamental mechanisms governing antibody subcutaneous absorption and disposition, with structured-based physiochemical properties, to predict antibody bioavailability and pharmacokinetics in vivo.

Minimal Physiologically-based Pharmacokinetic Model to Investigate the Effect of Charge on the Pharmacokinetics of Humanized anti-HCV-E2 IgG Antibodies in Sprague-Dawley Rats.

To develop a minimal physiologically-based pharmacokinetic (mPBPK) model in quantifying the relationships between the charge and pharmacokinetics (PK) of therapeutic monoclonal IgG antibody (TMAb). PK data used in this study were native IgG and five humanized anti-HCVE2-IgG antibodies in rats. Different models that related the effect of charge on interstitial distribution, transcapillary transport, and cellular uptake for FcRn-mediated metabolism were tested. External validation was conducted to assess if the charge-parameter relationships derived from rats could be used to predict the PK of TMAbs in mice. The final mPBPK model was used to construct the relationships between the FcRn binding and charge on the PK of TMAbs. Increasing the isoelectric point (pI) of IgG was associated with higher interstitial space distribution and cellular uptake. The transcapillary transport of IgG from plasma to interstitial space remains constant with pI values below 7.96 and then increased linearly with pI. The model-based simulation results suggested that improving the FcRn binding affinity can overcome the problems of low plasma/interstitial space exposures associated with TMAbs with higher pI values by reducing the FcRn-mediated metabolism and hence increasing drug exposure in the interstitial space that has close contact with many solid tumors. The final mPBPK model was developed and used to construct complex quantitative relationships between the pI/FcRn binding affinity and PK of TMAbs and such relationships are useful to select the discovery of a "sweet spot" of designing future generation of TMAbs with optimal PK properties to achieve desirable plasma and tissue drug exposures.

Морфологічні зміни головного мозку при діабетичній енцефалопатії

Метою наведеної роботи було вивчення морфологічних характеристик змін головного мозку у хворих із діабетичною енцефалопатією (ДЕ) на підставі дослідження аутопсійного матеріалу. Матеріали та методи. В роботі наведено результати 14 секційних спостережень. Середній вік хворих становив 51,0 ± 3,4 року. Шматочки мозку фіксували в розчині IHC Zink Fixative, виготовляли серійні парафінові зрізи товщиною 10 ± 1 мкм. Препарати фарбували гематоксиліном і еозином, конго рот, тіоніном за методом Ніссля, ставили ШИК-реакцію, імпрегнували нітратом срібла за методом Більшовського і хлоридом золота за Кахалем, проводили морфометричне дослідження за Г.Г. Автанділовим. Препарати досліджували на мікроскопі Olympus AX70 з цифровою камерою Olympus DP50. Мікрофотографування препаратів здійснювалося з використанням програми AnalysisPro 3.2. Результати. Основними цито-ангіоархітектонічними проявами ДЕ є дифузна альтерація базальних мембран і ендотелію судин мікроциркуляторного русла, меншою мірою — артеріол, внутрішньомозкових артерій і вен. Висока щільність (питомий обсяг) капілярної мережі при ДЕ морфологічно відображає картину капілярного паралітичного застою. Капілярний застій супроводжується стазом крові, збільшенням навколосудинного капілярного простору (простір Вірхова — Робіна), ширина якого є морфологічним еквівалентом лімфатичної дисциркуляції. Ранні морфологічні ушкодження стінок капілярів — потовщення і розщеплення основної мембрани з накопиченням ШИК-позитивних речовин, вогнищева проліферація ендотеліоцитів. До пізніх пошкоджень відносяться капілярний фіброз і гіаліноз, проліферація перицитів, що супроводжується різким порушенням транскапілярного транспорту. Порушення стріарної і радіарної цитоархітектоніки в I–IV шарах головного мозку, випадіння нейронів (нейрональні спустошення) проявляються вогнищевим випадінням гангліозних і пірамідальних клітин. Висновки. Ранніми зворотними морфологічними змінами нейронів є набухання нейронів (гідропічна дистрофія нервових клітин), вогнищевий гіперхроматоз. Незворотними структурними ушкодженнями нейронів є лізис ядра і ядерця з гомогенізацією цитоплазми, формування клітин-тіней, вакуолізація цитоплазми, перицелюлярний набряк, лізис відрост­ків у поєднанні з нейрофагією. Є характерним поєднання гострих альтернативних ушкоджень нейронів із хронічними (ішемічного характеру) — пікноз, зморщування ядер з вираженою атрофією цитоплазми.

Transcapillary transport of water, small solutes and proteins during hemodialysis

The semipermeable capillary walls not only enable the removal of excess body water and solutes during hemodialysis (HD) but also provide an essential mechanism for maintaining cardiovascular homeostasis. Here, we investigated transcapillary transport processes on the whole-body level using the three-pore model of the capillary endothelium with large, small and ultrasmall pores. The transcapillary transport and cardiovascular response to a 4-h hemodialysis (HD) with 2 L ultrafiltration were analyzed by simulations in a virtual patient using the three-pore model of the capillary wall integrated in the whole-body compartmental model of the cardiovascular system with baroreflex mechanisms. The three-pore model revealed substantial changes during HD in the magnitude and direction of transcapillary water flows through small and ultrasmall pores and associated changes in the transcapillary convective transport of proteins and small solutes. The fraction of total capillary hydraulic conductivity attributed to ultrasmall pores was found to play an important role in the transcapillary water transport during HD thus influencing the cardiovascular response to HD. The presented model provides a novel computational framework for a detailed analysis of microvascular exchange during HD and as such may contribute to a better understanding of dialysis-induced changes in blood volume and blood pressure.

The importance of the interstitium in peritoneal transport.

The peritoneal capillary exchange vessels are located within all the tissues which surround the peritoneal cavity and are separated from the peritoneal dialysis fluid by the tissue interstitium. The interstitium adds an additional barrier to transcapillary transport resistance and slows the diffusion of solutes from the blood to the dialysis fluid. The interstitium also alters the pressure environment of the blood capillary and has profound effects on water transport, causing fluid loss from the cavity to the body during dialysis.

Analysis of menstrual and reproductive function in women with infertility and varicose gonadic veins

The problem of reproductive health in Ukraine over the last decade has become very important. The greatest clinical interest is infertility, which is accompanied by a violation of the ovulatory function of the ovaries due to hypothalamic-pituitary-ovarian failure. Sustained anovulation for a long time, as well as the lack of adequate correction of menstrual disorders, lead to the development of endocrine-dependent gynecological diseases, the manifestation of which is primary or secondary infertility. Increased flow of venous blood through the ovarian veins is accompanied by phlebostasis and phlebohypertension in the venous sector of the internal genital organs. Increasing the viscosity and rheological properties of blood that occurs at the same time leads to a deterioration of transcapillary metabolism and transport of oxygen to tissues. In the ischemic ovary, degenerative changes in the follicular apparatus, yellow bodies, followed by spreading to all the ovarian structural elements, which leads to its atrophy and reduced functional properties. Considering the importance of venous blood flow in the development of hormonal imbalance as a result of a violation of the endocrine function of the ovaries, the purpose of our study was to assess the menstrual and reproductive function of infertile women against the background of varicose veins. The reproductive function of women with infertility and varicose changes in ovarian veins is represented by a significant percentage of unauthorized miscarriages (41.9%) in the period of pregnancy after 6 weeks (30.6%). In patients with varicose veins in the ovaries, there was a tendency to increase the duration of infertility compared with patients without varicose dilatation of ovarian veins, which may indirectly indicate more significant functional and structural changes in the reproductive organs. In women, both the primary and the comparator groups are predominantly the late and early menarche, but the rates in groups differ slightly in their direction in women with infertility and varicose veins in the ovaries, although they do not reach statistically significant values. The menstrual function of women in the main group is characterized by a regular menstrual cycle (77.5%), regular duration (43.6%) with excessive blood loss during menstruation (54.8%) and a duration of more than 6 days (50.1%) with acyclic uterine bleeding (37.1%), dysmenorrhea (56.4%) and premenstrual disorders (51.6%), which significantly impairs the quality of life of women. At the same time, the violation of the menstrual cycle in the form of its shortening of 16,1% and acyclic uterine bleeding — 6,5%, was gradually increasing with age and was statistically significant against women from the comparison group. Conclusion in the analysis of clinical characteristics, the more significant percentage of changes in the menstrual cycle, reproductive function in women with functional infertility and varicose veins of the ovary compared with patients with infertility without structural changes in ovarian veins indicates the significant importance of venous hemodynamics in the functional properties of the ovary.

Model of fluid and solute shifts during hemodialysis with active transport of sodium and potassium.

BackgroundMathematical models are useful tools to predict fluid shifts between body compartments in patients undergoing hemodialysis (HD). The ability of a model to accurately describe the transport of water between cells and interstitium (Jv,ISIC), and the consequent changes in intracellular volume (ICV), is important for a complete assessment of fluid distribution and plasma refilling. In this study, we propose a model describing transport of fluid in the three main body compartments (intracellular, interstitial and vascular), complemented by transport mechanisms for proteins and small solutes.MethodsThe model was applied to data from 23 patients who underwent standard HD. The substances described in the baseline model were: water, proteins, Na, K, and urea. Small solutes were described with two-compartment kinetics between intracellular and extracellular compartments. Solute transport across the cell membrane took place via passive diffusion and, for Na and K, through the ATPase pump, characterized by the maximum transport rate, JpMAX. From the data we estimated JpMAX and two other parameters linked to transcapillary transport of fluid and protein: the capillary filtration coefficient Lp and its large pores fraction αLP. In an Expanded model one more generic solute was included to evaluate the impact of the number of substances appearing in the equation describing Jv,ISIC.ResultsIn the baseline model, median values (interquartile range) of estimated parameters were: Lp: 11.63 (7.9, 14.2) mL/min/mmHg, αLP: 0.056 (0.050, 0.058), and JpMAX: 5.52 (3.75, 7.54) mmol/min. These values were significantly different from those obtained by the Expanded model: Lp: 8.14 (6.29, 10.01) mL/min/mmHg, αLP: 0.046 (0.038, 0.052), and JpMAX: 16.7 (11.9, 25.2) mmol/min. The relative RMSE (root mean squared error)averaged between all simulated quantities compared to data was 3.9 (3.1, 5.6) %.ConclusionsThe model was able to accurately reproduce most of the changes observed in HD by tuning only three parameters. While the drop in ICV was overestimated by the model, the difference between simulations and data was less than the measurement error. The biggest change in the estimated parameters in the Expanded model was a marked increase of JpMAX indicating that this parameter is highly sensitive to the number of species modeled, and that the value of JpMAX should be interpreted only in relation to this factor.

A Continuum Mechanics Model of Enzyme-Based Tissue Degradation in Cancer Therapies

We propose a mathematical model to describe enzyme-based tissue degradation in cancer therapies. The proposed model combines the poroelastic theory of mixtures with the transport of enzymes or drugs in the extracellular space. The effect of the matrix-degrading enzymes on the tissue composition and its mechanical response are accounted for. Numerical simulations in 1D, 2D and axisymmetric (3D) configurations show how an injection of matrix-degrading enzymes alters the porosity of a biological tissue. We eventually exhibit numerically the main consequences of a matrix-degrading enzyme pretreatment in the framework of chemotherapy: the removal of the diffusive hindrance to the penetration of therapeutic molecules in tumors and the reduction of interstitial fluid pressure which improves transcapillary transport. Both effects are consistent with previous biological observations.

Radiation treatment monitoring with DCE-US in CWR22 prostate tumor xenografts.

Longitudinal monitoring of potential radiotherapy treatment effects can be determined by dynamic contrast-enhanced ultrasound (DCE-US). To assess functional parameters by means of DCE-US in a murine subcutaneous model of human prostate cancer, and their relationship to dose deposition and time-frame after treatment. A special focus has been placed to evaluate the vascular heterogeneity of the tumor and on the most suitable data analysis approach that reflects this heterogeneity. In vivo DCE-US was acquired 24 h and 48 h after radiation treatment with a single dose of 7.5 Gy and 10 Gy, respectively. Tumor vasculature was characterized pixelwise using the Brix pharmacokinetic analysis of the time-intensity curves. Longitudinal changes were detected ( P < 0.001) at 24 h and 48 h after treatment. At 48 h, the eliminating rate constant of the contrast agent from the plasma, kel, was correlated ( P ≤ 0.05) positively with microvessel density (MVD; rτ = 0.7) and negatively with necrosis (rτ = -0.6) for the treated group. Furthermore, Akep, a parameter related to transcapillary transport properties, was also correlated to MVD (rτ = 0.6, P ≤ 0.05). DCE-US has been shown to detect vascular changes at a very early stage after radiotherapy, which is a great advantage since DCE-US is non-invasive, available at most hospitals, and is low in cost compared to other techniques used in clinical practice.

Two-Pore Minimum Physiologically-based Pharmacokinetic Model to Describe the Disposition of Therapeutic Monoclonal IgG Antibody in Humans.

The aim of this study was to develop a two-pore minimum physiologically-based pharmacokinetic (mPBPK) model in describing the pharmacokinetic (PK) of therapeutic monoclonal antibody (TMAb) in human subjects. PK data used in this study were endogenous/exogenous native IgG and two TMAbs (palivizumab and Motavizumab-YTE) in normal volunteer or familial hypercatabolic hypoproteinemia (FIHH) patient. Several important components were implemented to overcome the limitations of the early mPBPK model, e.g. two-pore model to describe the transcapillary transport of IgG from vascular to interstitial space. Six mPBPK models with different osmotic reflection coefficient (OFC) of transcapillary transport, endocytosis rates (ETR) and plasma clearance for the TMAbs/IgG were tested and the best model was selected using AICc values. The final model consisted of different OFC and ETR values for native IgG and TMAbs, supporting the hypothesis that the dynamics in the endosomal space had an important role in the compliant FcRn salvage mechanism to determine the clearance of TMAbs. The estimated FcRn concentration of FIHH subjects was 2.72μmol/l. The final two-pore mPBPK model has a better performance for native IgG than previously developed mPBPK model. The final two-pore mPBPK model not only overcome the limitations of the early mPBPK model but also has a better performance to describe the disposition of the IgG antibody in human subjects.

Modelling Transcapillary Transport of Fluid and Proteins in Hemodialysis Patients

BackgroundThe kinetics of protein transport to and from the vascular compartment play a major role in the determination of fluid balance and plasma refilling during hemodialysis (HD) sessions. In this study we propose a whole-body mathematical model describing water and protein shifts across the capillary membrane during HD and compare its output to clinical data while evaluating the impact of choosing specific values for selected parameters.MethodsThe model follows a two-compartment structure (vascular and interstitial space) and is based on balance equations of protein mass and water volume in each compartment. The capillary membrane was described according to the three-pore theory. Two transport parameters, the fractional contribution of large pores (αLP) and the total hydraulic conductivity (LpS) of the capillary membrane, were estimated from patient data. Changes in the intensity and direction of individual fluid and solute flows through each part of the transport system were analyzed in relation to the choice of different values of small pores radius and fractional conductivity, lymphatic sensitivity to hydraulic pressure, and steady-state interstitial-to-plasma protein concentration ratio.ResultsThe estimated values of LpS and αLP were respectively 10.0 ± 8.4 mL/min/mmHg (mean ± standard deviation) and 0.062 ± 0.041. The model was able to predict with good accuracy the profiles of plasma volume and serum total protein concentration in most of the patients (average root-mean-square deviation < 2% of the measured value).ConclusionsThe applied model provides a mechanistic interpretation of fluid transport processes induced by ultrafiltration during HD, using a minimum of tuned parameters and assumptions. The simulated values of individual flows through each kind of pore and lymphatic absorption rate yielded by the model may suggest answers to unsolved questions on the relative impact of these not-measurable quantities on total vascular refilling and fluid balance.

Human insulin dynamics in women: a physiologically based model.

Currently available models of insulin dynamics are mostly based on the classical compartmental structure and, thus, their physiological utility is limited. In this work, we describe the development of a physiologically based model and its application to data from 154 patients who underwent an insulin-modified intravenous glucose tolerance test (IM-IVGTT). To determine the time profile of endogenous insulin delivery without using C-peptide data and to evaluate the transcapillary transport of insulin, the hepatosplanchnic, renal, and peripheral beds were incorporated into the circulatory model as separate subsystems. Physiologically reasonable population mean estimates were obtained for all estimated model parameters, including plasma volume, interstitial volume of the peripheral circulation (mainly skeletal muscle), uptake clearance into the interstitial space, hepatic and renal clearance, as well as total insulin delivery into plasma. The results indicate that, at a population level, the proposed physiologically based model provides a useful description of insulin disposition, which allows for the assessment of muscle insulin uptake.

Abstract 2065: Magnetic resonance imaging with an iron oxide nanoparticle demonstrates the preclinical feasibility of predicting intratumoral uptake and activity of MM-398, a nanoliposomal irinotecan (nal-IRI)

Abstract Sustained intratumoral delivery of cytotoxic agents is a major challenge for effective cancer treatment, and motivated the development of MM-398, a stable nanoliposomal irinotecan (nal-IRI) with an extended plasma half-life and greater tumor deposition than free irinotecan. By using a systems pharmacology approach, we have previously shown that tumor deposition of nal-IRI and the subsequent conversion of irinotecan to the active metabolite, SN-38, by carboxylesterases are important determinants for nal-IRI activity in vivo. Ferumoxytol (FMX) is a 30nm iron-oxide, super-paramagnetic nanoparticle, known to be taken up by macrophages (as is nal-IRI), and for exhibiting magnetic resonance imaging properties. Since the size of a nanoparticle affects the rate of transcapillary transport significantly, we hypothesized that nal-IRI tumor biodistribution may be predicted by FMX-based MRI (Fe-MRI). Biodistribution and imaging studies were performed in mice bearing cell-line derived (A2780, HT29, A549) and patient-derived (pancreatic adenocarcinoma) tumor xenografts. The protocol consisted of a baseline MRI scan, i.v. injection of FMX (20mg/kg), and then i.v. injection of fluorescently labeled nal-IRI (10mg/kg) 24hr later. Mice were sacrificed 24hr and 72hr after nal-IRI injection, and irinotecan and SN-38 concentrations were determined in plasma, tumor, and tissues by HPLC analysis. The presence of FMX did not interfere with nal-IRI PK or biodistribution. Cellular distribution of liposomes within tumors was also not affected by FMX at up to 50mg/kg as measured by flow cytometry. Furthermore, immunohistochemistry showed that both liposomes and FMX were co-localized with tumor-associated macrophages. The drug metabolite measurements from tissue samples showed that the xenograft tumor models display wide ranges of nal-IRI deposition capacity (irinotecan concentrations at 24hr: ∼2,104 to 20,096ng/g). A2780 tumors displayed highest concentration of both iron (3.92 μg/ml) and irinotecan (9,466 ng/g) at 72hr after nal-IRI injection, whereas A549 tumors displayed lowest levels of both iron (0.23 μg/ml ) and irinotecan (436 ng/g). We observed a correlation between the tumor Fe-MRI signal and intratumoral levels of irinotecan 72hr after nal-IRI injection (R2=0.9, p&amp;lt;0.001). Furthermore, in vivo activity studies confirmed that xenograft models having higher intratumoral levels of irinotecan and SN-38 at 72hr showed greater tumor growth inhibition. In summary, preclinical studies demonstrate the potential of utilizing Fe-MRI as a potential diagnostic tool to identify patients with higher tumor permeability. Based on encouraging preclinical data, a pilot study in patients with advanced solid tumors with extensive Fe-MRI scanning and paired tumor biopsies (NCT # 01770353) is being conducted. Citation Format: Ashish V. Kalra, Joseph Spernyak, Jaeyeon Kim, Arnold Sengooba, Stephan Klinz, Nancy Paz, Jason Cain, Walid Kamoun, Ninfa Straubinger, Yang Qu, Sheryl Trueman, Eliel Bayever, Ulrik Nielsen, Daryl Drummond, Jonathan Fitzgerald, Robert Straubinger. Magnetic resonance imaging with an iron oxide nanoparticle demonstrates the preclinical feasibility of predicting intratumoral uptake and activity of MM-398, a nanoliposomal irinotecan (nal-IRI). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2065. doi:10.1158/1538-7445.AM2014-2065

Traversing the Barrier: A Journey of Insulin from Vascular Lumen into Skeletal Muscle

Copyright: © 2013 Wang H. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Plasma insulin must traverse the vascular endothelium to reach its major sites of action on myocytes and adipocytes. In study simultaneously measuring plasma and lymphatic insulin concentrations in normal, conscious dogs during euglycemic insulin clamps it was found that the steady-state plasma insulin concentration was consistently higher than lymph with a rough ratio of 3:2 during the basal period. In addition, while plasma insulin concentration rose quickly to reach the steady-state during the insulin clamp, the lymph insulin concentration rose very slowly indicating a barrier function of the vascular endothelium. Most importantly, this study showed that the dynamics of glucose disposal correlated very strikingly with the insulin concentration in lymph but not plasma, suggesting that trans-capillary insulin transport is a rate limiting step for peripheral insulin action [1]. Consistent with this, direct injection of insulin into canine skeletal muscle in vivo was recently noted to significantly hasten the onset of muscle glucose utilization compared with intravenously delivered insulin [2]. Multiple other studies also support such an important role of vascular endothelium during insulin clamp by measurement of the insulin concentration within skeletal muscle interstitium in humans and animals using either lymphatic sampling or microdialysis methods [3-7]. Results obtained using either method indicate that even after several hours of steady state hyperinsulinemia, muscle interstitial insulin concentration is only 40-50% of that in plasma and the time course for insulin-mediated glucose disposal during the euglycemic clamp correlates strongly with interstitial but not plasma insulin concentrations. Based on these findings, it has been estimated that slow trans-endothelial insulin transport may account for 30-40% of insulin resistance seen with human obesity or type-2 diabetes [3,8,9].

Hemodynamic actions of insulin: beyond the endothelium

BRIEF HISTORICAL OVERVIEW Insulin’s hemodynamic actions are being progressively unraveled over the last two decades (Baron, 1994; Clark, 2008). Originally, Baron et al (Laakso et al., 1990) reported insulin-mediated increase in total blood flow, suggesting an associated higher delivery of nutrients and insulin to target tissues. Nonetheless, the physiological meaning of that extensive hemodynamic action of insulin is controversial, given that lower insulin concentrations than those required to increase total blood flow, stimulate muscle glucose uptake (Yki-Jarvinen and Utriainen, 1998; Zhang et al., 2004). Afterward, a distinct vascular action of insulin was observed, which resulted in capillary recruitment (Rattigan et al., 1997). Such capillary recruitment occurs at physiological concentrations of insulin, precedes increases in total blood flow and is directly correlated to glucose uptake in skeletal muscle (Rattigan et al., 1997, 1999; Coggins et al., 2001). Provided that insulin transcapillary transport plausibly involves a predominant non-saturable process in skeletal muscle (Steil et al., 1996; Hamilton-Wessler et al., 2002; Majumdar et al., 2012), insulin-mediated capillary recruitment emerges as a crucial action of insulin, coupling vascular and metabolic physiology. An integrative pathophysiological view of the relationships between hemodynamic and metabolic functions of insulin has been presented in detail in previous reviews (Muniyappa et al., 2007; Clark, 2008; Muris et al., 2013). Likewise, it has been recognized a similar vascular and metabolic insulin-signaling via insulin receptor/phosphatidylinositol 3kinase (PI3K) pathways (Kim et al., 2006; Kubota et al., 2011), which are present in both endothelium and vascular smooth muscle (VSM), leading to nitric oxide synthase (NOS) activation, increased nitric oxide (NO) production and subsequent vasodilation (Zeng and Quon, 1996; Anfossi et al., 2002). Most previous research in this field has focused on insulin actions in and/or through the endothelium, assumed as the preponderant sensor/effector organ underlying the vascular effects of insulin (Muniyappa et al., 2007; Kubota et al., 2011). However, recently increased animal and human evidence suggests a leading hemodynamic role for the direct insulin action in VSM (Rossi et al., 2005; Newman et al., 2009; Montero et al., 2013a,c), thus requiring to reconsider widely held conceptions in this field.

Lipid-Induced Insulin Resistance Is Not Mediated by Impaired Transcapillary Transport of Insulin and Glucose in Humans

Increased lipid availability reduces insulin-stimulated glucose disposal in skeletal muscle, which is generally explained by fatty acid–mediated inhibition of insulin signaling. It remains unclear whether lipids also impair transcapillary transport of insulin and glucose, which could become rate controlling for glucose disposal. We hypothesized that lipid-induced insulin resistance is induced by inhibiting myocellular glucose uptake and not by interfering with the delivery of insulin or glucose. We measured changes in interstitial glucose and insulin in skeletal muscle of healthy volunteers during intravenous administration of triglycerides plus heparin or glycerol during physiologic and supraphysiologic hyperinsulinemia, by combining microdialysis with oral glucose tolerance tests and euglycemic-hyperinsulinemic clamps. Lipid infusion reduced insulin-stimulated glucose disposal by ∼70% (P < 0.05) during clamps and dynamic insulin sensitivity by ∼12% (P < 0.05) during oral glucose loading. Dialysate insulin and glucose levels were unchanged or even transiently higher (P < 0.05) during lipid than during glycerol infusion, whereas regional blood flow remained unchanged. These results demonstrate that short-term elevation of free fatty acids (FFAs) induces insulin resistance, which in skeletal muscle occurs primarily at the cellular level, without impairment of local perfusion or transcapillary transport of insulin and glucose. Thus, vascular effects of FFAs are not rate controlling for muscle insulin-stimulated glucose disposal.

Highlights of This Issue

Despite the initial effectiveness of current anti-androgens in disseminated prostate cancer, therapy resistance typically emerges after 18 months. The androgen receptor (AR), however, remains a therapeutics target because its activity is restored. Here, we describe the detection and characterization of a novel class of AR antagonists that inhibit the expression of androgen-regulated genes and reduce the proliferation of AR-positive prostate cancer cell lines. MEL-3 not only has an improved in vitro therapeutic profile compared to bicalutamide, but it also remains active on models of resistance to bicalutamide and hydroxyflutamide, which indicates that it might ensure follow-up treatment in these forms of therapy resistance.Reactivation of p53 and Induction of Tumor cell Apoptosis (RITA) is a promising compound for treatment of human cancer by reactivating the oncosuppressor p53. To explore RITA efficacy in Ewing's sarcoma, one of the most frequent bone cancers in adolescence, Di Conza and colleagues provided evidence that RITA is effective in reducing growth and tumorigenic potential of Ewing's sarcoma cells independently of p53. Particularly, RITA causes downregulation of IGF-1R, an important oncogenic mark of this tumor. This work suggests the possibility of RITA adopting an additional mechanism of action, expanding its field of application, and envisages the promising use of RITA derivative as a potential treatment for Ewing's sarcomas.There has been a renaissance in our understanding of the Warburg effect and the importance of the metabolic changes that accompany and help sustain cancer progression. Here, Katt and colleagues provide an expanded structure-activity relationship for 968, a novel inhibitor of glutaminase C that is a key enzyme responsible for satisfying the glutamine addiction of cancer cells. These studies now offer a new strategy for achieving the allosteric inhibition of this important metabolic enzyme and hopefully will help to inform future efforts toward developing more potent inhibitors and eventually improved cancer therapies.A bispecific antibody was engineered for use in pretargeted radioimmunotherapy, with radiometal chelate binding sites with affinity varying from KD = 10 pmol/L - 20 nmol/L, depending on the radiometal (177Lu vs. 111In) and the particular chelator (DOTA vs. Benzyl DOTA). This enabled determination of the effect of binding affinity on accumulation of the small molecule radiometal chelate in the tumor. KD &lt; 400 pM provides maximum label uptake, consistent with a simple mathematical model that predicts the required affinity for maximal uptake as a function of antigen expression level, transcapillary transport rate, and endocytosis rate.

Is endothelial-independent vascular reactivity compromised in obese subjects with metabolic syndrome?

to the editor: Schinzari et al. ([4][1]) compared the endothelial-dependent and -independent vasodilatory responses in controls and subjects with metabolic syndrome (MetSyn). The primary objective was to explore the integrity of the nitric oxide (NO) pathway and evaluate the effects of

Crossing Barriers From blood-to-brain and academia-to-industry

Crossing Barriers From blood-to-brain and academia-to-industry