Thrombosis Risk History and D-dimer Levels in Asymptomatic Individuals with Prader-Willi Syndrome

Individuals with Prader–Willi syndrome (PWS) may be at higher risk of developing blood clots as compared to the typical population, but this risk is poorly understood. It is also unclear if laboratory testing of D-dimer concentration might be useful to screen for thrombosis in PWS. Here, we surveyed the thrombosis history of 883 individuals with PWS and evaluated the D-dimer concentration in a subset of 214 asymptomatic individuals, ages 5–55. A history of at least one blood clot was reported by 3.6% of respondents. Thrombosis increased with age, but no significant difference was found on the basis of sex or family history. Genetic subtype was a significant factor when considering only those with a known subtype, and individuals with a history of edema had significantly more blood clots. In the D-dimer sub-study, ≈15% of participants had high D-dimer concentrations, and 3.7% had D-dimer values more than twice the normal upper limit. One participant with a high D-dimer result was found to have a blood clot. No significant differences in D-dimer results were found on the basis of age, sex, genetic subtype, family history of blood clots, edema history, or BMI. The D-dimer test does not appear to be a sensitive and specific screening tool for blood clots in asymptomatic individuals with PWS.

Impaired pulmonary defense against Pseudomonas aeruginosa in VEGF gene inactivated mouse lung

Repeated bacterial and viral infections are known to contribute to worsening lung function in several respiratory diseases, including asthma, cystic fibrosis, and chronic obstructive pulmonary disease (COPD). Previous studies have reported alveolar wall cell apoptosis and parenchymal damage in adult pulmonary VEGF gene ablated mice. We hypothesized that VEGF expressed by type II cells is also necessary to provide an effective host defense against bacteria in part by maintaining surfactant homeostasis. Therefore, Pseudomonas aeruginosa (PAO1) levels were evaluated in mice following lung-targeted VEGF gene inactivation, and alterations in VEGF-dependent type II cell function were evaluated by measuring surfactant homeostasis in mouse lungs and isolated type II cells. In VEGF-deficient lungs increased PAO1 levels and pro-inflammatory cytokines, TNFα and IL-6, were detected 24 h after bacterial instillation compared to control lungs. In vivo lung-targeted VEGF gene deletion (57% decrease in total pulmonary VEGF) did not alter alveolar surfactant or tissue disaturated phosphatidylcholine (DSPC) levels. However, sphingomyelin content, choline phosphate cytidylyltransferase (CCT) mRNA, and SP-D expression were decreased. In isolated type II cells an 80% reduction of VEGF protein resulted in decreases in total phospholipids (PL), DSPC, DSPC synthesis, surfactant associated proteins (SP)-B and -D, and the lipid transporters, ABCA1 and Rab3D. TPA-induced DSPC secretion and apoptosis were elevated in VEGF-deficient type II cells. These results suggest a potential protective role for type II cell-expressed VEGF against bacterial initiated infection.

One-year treatment with exenatide improves beta-cell function, compared with insulin glargine, in metformin-treated type 2 diabetic patients: a randomized, controlled trial

OBJECTIVE

Traditional blood glucose-lowering agents do not sustain adequate glycemic control in most type 2 diabetic patients. Preclinical studies with exenatide have suggested sustained improvements in beta-cell function. We investigated the effects of 52 weeks of treatment with exenatide or insulin glargine followed by an off-drug period on hyperglycemic clamp-derived measures of beta-cell function, glycemic control, and body weight.

RESEARCH DESIGN AND METHODS

Sixty-nine metformin-treated patients with type 2 diabetes were randomly assigned to exenatide (n = 36) or insulin glargine (n = 33). beta-Cell function was measured during an arginine-stimulated hyperglycemic clamp at week 0, at week 52, and after a 4-week off-drug period. Additional end points included effects on glycemic control, body weight, and safety.

RESULTS

Treatment-induced change in combined glucose- and arginine-stimulated C-peptide secretion was 2.46-fold (95% CI 2.09-2.90, P < 0.0001) greater after a 52-week exenatide treatment compared with insulin glargine treatment. Both exenatide and insulin glargine reduced A1C similarly: -0.8 +/- 0.1 and -0.7 +/- 0.2%, respectively (P = 0.55). Exenatide reduced body weight compared with insulin glargine (difference -4.6 kg, P < 0.0001). beta-Cell function measures returned to pretreatment values in both groups after a 4-week off-drug period. A1C and body weight rose to pretreatment values 12 weeks after discontinuation of either exenatide or insulin glargine therapy.

CONCLUSIONS

Exenatide significantly improves beta-cell function during 1 year of treatment compared with titrated insulin glargine. After cessation of both exenatide and insulin glargine therapy, beta-cell function and glycemic control returned to pretreatment values, suggesting that ongoing treatment is necessary to maintain the beneficial effects of either therapy.

Pseudomonas aeruginosa degrades pulmonary surfactant and increases conversion in vitro

Although it is known that surfactant lipids and proteins are altered in patients with Pseudomonas aeruginosa infections, the mechanisms and implications of these alterations are not clear. In this study, the effects of P. aeruginosa on the surfactant large aggregate fraction were examined using an in vitro surface area cycling model. Large aggregates were isolated from porcine bronchoalveolar lavage fluid and incubated with supernatants from P. aeruginosa cultures (PAO1, parent strain; PAO1-A1, lasA-negative mutant; PAO1-B1, elastase-negative mutant) or purified elastase. Amounts of surfactant protein (SP)-A and SP-B, phospholipid content, and large aggregate conversion were assessed. In addition, lipid degradation was assessed by incubating a mixture of radiolabeled phospholipids with P. aeruginosa supernatants. The results demonstrated that SP-A was degraded by PAO1 and PAO1-A1 supernatants, and by purified elastase. SP-B was degraded by PAO1 and PAO1-B1 supernatants, but not by elastase. P. aeruginosa supernatants degraded phospholipids, a process inhibited by ZnCl(2). P. aeruginosa supernatants and elastase increased conversion. The data suggest that protein degradation facilitates increased conversion, and that phospholipid degradation and conversion enhance degradation of surfactant proteins. In conclusion, P. aeruginosa secretes multiple virulence factors that cooperate to result in degradation of surfactant components and alteration of large aggregate conversion.

Pseudomonas aeruginosa protease IV degrades surfactant proteins and inhibits surfactant host defense and biophysical functions

Pulmonary surfactant has two distinct functions within the lung: reduction of surface tension at the air-liquid interface and participation in innate host defense. Both functions are dependent on surfactant-associated proteins. Pseudomonas aeruginosa is primarily responsible for respiratory dysfunction and death in cystic fibrosis patients and is also a leading pathogen in nosocomial pneumonia. P. aeruginosa secretes a number of proteases that contribute to its virulence. We hypothesized that P. aeruginosa protease IV degrades surfactant proteins and results in a reduction in pulmonary surfactant host defense and biophysical functions. Protease IV was isolated from cultured supernatant of P. aeruginosa by gel chromatography. Incubation of cell-free bronchoalveolar lavage fluid with protease IV resulted in degradation of surfactant proteins (SP)-A, -D, and -B. SPs were degraded in a time- and dose-dependent fashion by protease IV, and degradation was inhibited by the trypsin-like serine protease inhibitor Nalpha-p-tosyl-L-lysine-chloromethyl ketone (TLCK). Degradation by protease IV inhibited SP-A- and SP-D-mediated bacterial aggregation and uptake by macrophages. Surfactant treated with protease IV was unable to reduce surface tension as effectively as untreated surfactant, and this effect was inhibited by TLCK. We speculate that protease IV may be an important contributing factor to the development and propagation of acute lung injury associated with P. aeruginosa via loss of surfactant function within the lung.

Early surfactant administration protects against lung dysfunction in a mouse model of ARDS

Sepsis can predispose the lung to insults such as mechanical ventilation (MV). It was hypothesized that treating the lung with exogenous surfactant early in the development of sepsis will reduce the lung dysfunction associated with MV 18 h later. Mice underwent sham or cecal ligation and perforation (CLP) surgery. Immediately after surgery, mice were either untreated or given 100 mg/kg of bovine lipid extract surfactant intratracheally. Eighteen hours later, the lungs were removed and analyzed either immediately or following ventilation ex vivo for 2 h by an "injurious" mode of ventilation (20 ml/kg, 0 cm positive end-expiratory pressure). In nonventilated lungs, exogenous surfactant had no impact on compliance or IL-6 concentrations in the lungs. In the ventilated groups, the administered surfactant had a significant protective effect on the lung dysfunction induced by MV, but only in the CLP lungs. We conclude that administration of exogenous surfactant at the time of a systemic insult can protect the lung from the damaging effects of MV 18 h later.

Pulmonary surfactant and inflammation in septic adult mice: role of surfactant protein A

Surfactant alterations, alveolar cytokine changes, and the role of surfactant protein (SP)-A in septic mice were investigated. Sepsis was induced via cecal ligation and perforation (CLP). Septic and sham mice were euthanized at 0, 3, 6, 9, 12, 15, and 18 h after surgery. Mice deficient in SP-A and mice that overexpressed SP-A were euthanized 18 h after surgery. In wild-type, sham-operated mice, surfactant pool sizes were similar at all time points, whereas in the CLP groups there was a significant decrease in small-aggregate surfactant pool sizes beginning 6 h after CLP. Interleukin-6 concentrations in bronchoalveolar lavage fluid from septic animals increased from 6 to 18 h after surgery. Identical surfactant alterations and concentrations of cytokines were observed in septic mice that were SP-A deficient or that overexpressed SP-A. In conclusion, alterations of pulmonary surfactant and alveolar cytokines occur simultaneously, 6 h after a systemic insult. In addition, we did not detect a role for SP-A in regulating surfactant phospholipid pool sizes or pulmonary inflammation in septic mice.

Evaluation of alveolar surfactant aggregates in vitro and in vivo

In acute lung injury, a decrease in surface-active large aggregates and an increase in the less surface-active small surfactant aggregates are observed. The objective of the current study was to determine if the increase in small aggregates interfered with the function of large aggregates, thereby independently contributing to lung dysfunction. Isolated large aggregates, small aggregates, and large aggregate+small aggregate combinations were analysed for in vitro surface activity utilizing a pulsating bubble surfactometer. Subsequently, large aggregates, small aggregates, and large aggregate+ small aggregate combinations were administered to surfactant-deficient, adult Sprague-Dawley rats. Physiological parameters were measured during 1 h of ventilation. After sacrifice, the whole lung lavage was analysed for protein concentration, and surface activity of the recovered large aggregates. The minimum surface tension of the large aggregate+small aggregate preparations (10 mN x m(-1)) was significantly higher than large aggregates alone (1 mN x m(-1)), but lower than small aggregates alone (21 mN x m(-1) ) after 100 pulsations. In vivo, rats receiving large aggregates+small aggregates showed immediate increases in oxygenation, similar to animals given large aggregates, whereas animals given small aggregates and control animals maintained low oxygenation values. In conclusion, small aggregates interfered with large aggregates function in vitro, but this was not observed in vivo in this experimental model.

Surfactant treatment for ventilation-induced lung injury in rats: effects on lung compliance and cytokines

The objective of this study was to determine if exogenous surfactant therapy could prevent the harmful effects of ventilation at high tidal volumes without positive end-expiratory pressure (PEEP). Rats were randomized to either a nontreated control group (8 mL/kg 4 cm H2O PEEP), a nontreated injuriously ventilated group (20 mL/kg 0 cm H2O PEEP) or a treatment group of either 50 mg/kg, 50 mg/kg + 5% surfactant-associated protein A, 100 mg/kg exogenous surfactant followed by injurious ventilation. Isolated lungs from animals in all 5 groups were ventilated in a humidified box at 37 degrees C for 2 hours. Pressure-volume curves and light microscopy showed that surfactant treatment reduced the ventilation-induced lung injury (VILI). Inflammatory cytokines (tumor necrosis factor-alpha [TNFalpha], interleukin [IL]-1beta, and IL-6) in the lavage were significantly higher in injuriously ventilated lungs compared to the control group. However the 3 treatment groups had cytokine concentrations that were similar to the injuriously ventilated group. We conclude that surfactant treatment is beneficial in preventing VILI; however, it does not prevent the release of inrflammatory cytokines during mechanical ventilation.

Effects of ventilation on the surfactant system in sepsis-induced lung injury

The present study examined the effects of mechanical ventilation, with or without positive end-expiratory pressure (PEEP), on the alveolar surfactant system in an animal model of sepsis-induced lung injury. Septic animals ventilated without PEEP had a significant deterioration in oxygenation compared with preventilated values (arterial PO(2)/inspired O(2) fraction 316 +/- 16 vs. 151 +/- 14 Torr; P < 0.05). This was associated with a significantly lower percentage of the functional large aggregates (59 +/- 3 vs. 72 +/- 4%) along with a significantly reduced function (minimum surface tension 17.7 +/- 1.8 vs. 11.8 +/- 3.8 mN/m) compared with nonventilated septic animals (P < 0.05). Sham animals similarly ventilated without PEEP maintained oxygenation, percent large aggregates and surfactant function. With the addition of PEEP, the deterioration in oxygenation was not observed in the septic animals and was associated with no alterations in the surfactant system. We conclude that animals with sepsis-induced lung injury are more susceptible to the harmful effects of mechanical ventilation, specifically lung collapse and reopening, and that alterations in alveolar surfactant may contribute to the development of lung dysfunction.