Higher urine desmosine levels are associated with mortality in patients with acute lung injury

Desmosine is a stable breakdown product of elastin that can be reliably measured in urine samples. We tested the hypothesis that higher baseline urine desmosine would be associated with higher mortality in 579 of 861 patients included in the recent Acute Respiratory Distress Syndrome Network trial of lower tidal volume ventilation (1). We also correlated urine desmosine levels with indexes of disease severity. Finally, we assessed whether urine desmosine was lower in patients who received lower tidal volumes. Desmosine was measured by radioimmunoassay in urine samples from days 0, 1, and 3 of the study. The data were expressed as a ratio of urine desmosine to urine creatinine to control for renal dilution. The results show that higher baseline (day 0) urine desmosine-to-creatinine concentration was associated with a higher risk of death on adjusted analysis (odds ratio 1.36, 95% confidence interval 1.02-1.82, P=0.03). Urine desmosine increased in both ventilator groups from day 0 to day 3, but the average rise was higher in the 12-ml/kg predicted body weight group compared with the 6-ml/kg predicted body weight group (P=0.053, repeated-measures model). In conclusion, patients with acute lung injury ventilated with lower tidal volumes have lower urine desmosine levels, a finding that may reflect reduced extracellular matrix breakdown. These results illustrate the value of evaluating urinary biological markers that may have prognostic and pathogenetic significance in acute lung injury.     

Elevated levels of plasminogen activator inhibitor-1 in pulmonary edema fluid are associated with mortality in acute lung injury

The alveolar fibrinolytic system is altered in acute lung injury (ALI). Levels of the fibrinolytic protease inhibitor, plasminogen activator inhibitor-1 (PAI-1), are too low in bronchoalveolar lavage to address its prognostic significance. This study was performed to assess whether PAI-1 antigen in undiluted pulmonary edema fluid levels can identify patients with ALI and predict their outcome. PAI-1 antigen levels in both plasma and edema fluid were higher in ALI compared with hydrostatic edema, and edema fluid PAI-1 values identified those with ALI with high sensitivity and specificity. Both the high plasma and edema fluid PAI-1 antigen values were associated with a higher mortality rate and fewer days of unassisted ventilation in patients with ALI. Differences in PAI-1 activity were concordant with levels of PAI-1 antigen. Although the fibrin-derived alveolar D-dimer levels were strikingly similar in both groups, ALI patients had a higher relative proportion of D-monomer. In conclusion, PAI-1 levels in edema fluid and plasma identify those with ALI that have a poor prognosis. The data indicate that fibrin turnover in early ALI is a consequence of a rapid fibrinogen influx and fractional fibrinolytic inhibition.     

Sources of alveolar soluble TNF receptors during acute lung injury of different etiologies

Elevated soluble tumor necrosis factor-α receptor (sTNFR) levels in bronchoalveolar lavage fluid (BALF) are associated with poor patient outcome in acute lung injury (ALI). The mechanisms underlying these increases are unknown, but it is possible that pulmonary inflammation and increased alveolar epithelial permeability may individually contribute. We investigated mechanisms of elevated BALF sTNFRs in two in vivo mouse models of ALI. Anesthetized mice were challenged with intratracheal lipopolysaccharide or subjected to injurious mechanical ventilation. Lipopolysaccharide instillation produced acute intra-alveolar inflammation, but minimal alveolar epithelial permeability changes, with increased BALF sTNFR p75, but not p55. Increased p75 levels were markedly attenuated by alveolar macrophage depletion. In contrast, injurious ventilation induced substantial alveolar epithelial permeability, with increased BALF p75 and p55, which strongly correlated with total protein. BALF sTNFRs were not increased in isolated buffer-perfused lungs (devoid of circulating sTNFRs) subjected to injurious ventilation. These results suggest that lipopolysaccharide-induced intra-alveolar inflammation upregulates alveolar macrophage-mediated production of sTNFR p75, whereas enhanced alveolar epithelial permeability following mechanical ventilation leads to increased BALF p75 and p55 via plasma leakage. These data provide new insights into differential regulation of intra-alveolar sTNFR levels during ALI and may suggest sTNFRs as potential markers for evaluating the pathophysiology of ALI.     

Elevated CSF levels of TACE activity and soluble TNF receptors in subjects with mild cognitive impairment and patients with Alzheimer's disease

We recently reported that expression levels of tumor necrosis factor (TNF) receptors, TNFR1 and TNFR2, are significantly changed in the brains and cerebrospinal fluid (CSF) with Alzheimer's disease (AD). Moreover, we also found that, in an Alzheimer's mouse model, genetic deletion of TNF receptor (TNFR1) reduces amyloid plaques and amyloid beta peptides (Aβ) production through β-secretase (BACE1) regulation. TNF-α converting enzyme (TACE/ADAM-17) does not only cleave pro- TNF-α but also TNF receptors, however, whether the TACE activity was changed in the CSF was not clear. In this study, we examined TACE in the CSF in 32 AD patients and 27 age-matched healthy controls (HCs). Interestingly, we found that TACE activity was significantly elevated in the CSF from AD patients compared with HCs. Furthermore, we also assayed the CSF levels of TACE cleaved soluble forms of TNFR1 and TNFR2 in the same patients. We found that AD patients had higher levels of both TACE cleaved soluble TNFR1 (sTNFR1) and TNFR2 (sTNFR2) in the CSF compared to age- and gender-matched healthy controls. Levels of sTNFR1 correlated strongly with the levels of sTNFR2 (rs = 0.567-0.663, p < 0.01). The levels of both sTNFR1 and sTNFR2 significantly correlated with the TACE activity (rs = 0.491-0.557, p < 0.05). To examine if changes in TACE activity and in levels of cleaved soluble TNFRs are an early event in the course of AD, we measured these molecules in the CSF from 47 subjects with mild cognitive impairment (MCI), which is considered as a preclinical stage of AD. Unexpectedly, we found significantly higher levels of TACE activity and soluble TNFRs in the MCI group than that in AD patients. These results suggest that TACE activity and soluble TNF receptors may be potential diagnostic candidate biomarkers in AD and MCI.     

Elevated levels of soluble TNF receptors 1 and 2 correlate with Plasmodium falciparum parasitemia in pregnant women: potential markers for malaria-associated inflammation

Plasmodium falciparum-infected erythrocytes (IEs) sequester in the intervillous space (IVS) of the placenta causing placental malaria (PM), a condition that increases a woman's chances of having a low-birth-weight baby. Because IEs sequester, they frequently are not observed in peripheral blood smears, resulting in women with PM being misdiagnosed and thus not treated. Because sequestered IEs induce inflammation in the IVS, detection of inflammatory mediators in the peripheral blood may provide an approach for diagnosing PM. Two counterregulatory molecules, TNF-αR (TNFR) 1 and TNFR2, modulate the pathological effects of TNF-α. Levels of these soluble TNFRs (sTNFRs) are reported to be elevated in children with severe malaria, but it is unclear if they are increased in the peripheral blood of PM-positive women with asymptomatic infections. In this study, sTNFR levels were measured throughout the course of pregnancy, as well as at delivery, in women with asymptomatic infections and those who remained uninfected. Results showed that both sTNFRs were significantly increased in the peripheral blood of women with asymptomatic malaria (p < 0.0001) and were positively correlated with parasitemia (p < 0.0001 for sTNFR1 and p = 0.0046 for sTNFR2). Importantly, levels of sTNFR2 were elevated in the peripheral blood of women who were PM-positive but peripheral blood-smear negative (p = 0.0017). Additionally, sTNFR2 levels were elevated in the blood of malaria-positive women who delivered low-birth-weight babies. In vitro studies demonstrated that syncytiotrophoblasts were not a major source of sTNFR. These data suggest that sTNFR2 may be a valuable biomarker for detection of malaria-associated inflammation.     

Proteomic analysis of pulmonary edema fluid and plasma in patients with acute lung injury

Proteomics is the large-scale analysis of protein profiles. This approach has not yet been reported in the study of acute lung injury (ALI). This study details protein profiles in plasma and pulmonary edema fluid (EF) from 16 ALI patients and plasma and bronchoalveolar lavage fluid (BALF) from 12 normal subjects. More than 300 distinct protein spots were evident in the EF and BALF of both normal subjects and ALI patients. Of these, 158 were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In the plasma and EF protein profile of ALI patients, there were multiple qualitative changes. For instance, in all normal subjects, but in only one of the ALI patients, seven distinct surfactant protein A isoforms were evident. Nearly all ALI patients also had protein spots that indicate truncation or other posttranslational modifications. Several of these novel changes could serve as new biomarkers of lung injury.     

A key role of neurokinin 1 receptors in acute pancreatitis and associated lung injury

Earlier studies have shown that mice deficient in NK1 receptors or its ligand, substance P, are protected against acute pancreatitis and associated lung injury. In the current study, the protective effect of NK1 receptor blockage against acute pancreatitis and associated lung injury was investigated, using a specific receptor antagonist, CP-96345. Acute pancreatitis was induced in mice by intraperitoneal (i.p.) injections of caerulein. Substance P levels in plasma, pancreas, and lungs were found to be elevated in a caerulein dose-dependent manner. Mice treated with CP-96345, either prophylactically, or therapeutically, were protected against acute pancreatitis and associated lung injury as evident by attenuation in plasma amylase, pancreatic and pulmonary myeloperoxidase activities, and histological evidence of pancreatic and pulmonary injuries. Pulmonary microvascular permeability was also reduced as a result of CP-96345 treatment. These results point to a key role of NK1 receptors in acute pancreatitis and associated lung injury.     

Lung-derived soluble mediators are pathogenic in ventilator-induced lung injury

Ventilator-induced lung injury (VILI) due to high tidal volume (V(T)) is associated with increased levels of circulating factors that may contribute to, or be markers of, injury. This study investigated if exclusively lung-derived circulating factors produced during high V(T) ventilation can cause or worsen VILI. In isolated perfused mouse lungs, recirculation of perfusate worsened injury (compliance impairment, microvascular permeability, edema) induced by high V(T). Perfusate collected from lungs ventilated with high V(T) and used to perfuse lungs ventilated with low V(T) caused similar compliance impairment and permeability and caused a dose-dependent decrease in transepithelial electrical resistance (TER) across rat distal lung epithelial monolayers. Circulating soluble factors derived from the isolated lung thus contributed to VILI and had deleterious effects on the lung epithelial barrier. These data demonstrate transferability of an injury initially caused exclusively by mechanical ventilation and provides novel evidence for the biotrauma hypothesis in VILI. Mediators of the TER decrease were heat-sensitive, transferable via Folch extraction, and (following ultrafiltration, 3 kDa) comprised both smaller and larger molecules. Although several classes of candidate mediators, including protein cytokines (e.g., tumor necrosis factor-α, interleukin-6, macrophage inflammation protein-1α) and lipids (e.g., eicosanoids, ceramides, sphingolipids), have been implicated in VILI, only prostanoids accumulated in the perfusate in a pattern consistent with a pathogenic role, yet cyclooxygenase inhibition did not protect against injury. Although no single class of factor appears solely responsible for the decrease in barrier function, the current data implicate lipid-soluble protein-bound molecules as not just markers but pathogenic mediators in VILI.     

Increased plasma mannose binding lectin levels are associated with bronchiolitis obliterans after lung transplantation

Background

Long-term lung allograft survival is limited by bronchiolitis obliterans syndrome (BOS). Mannose binding lectin (MBL) belongs to the innate immune system, participates in complement activation, and may predispose to graft rejection. We investigated mannose binding (MBL) during cold ischemia and in tissue samples from explanted lungs with BOS, and assessed MBL and complement proteins in plasma post-lung transplantation relative to BOS staging.

Methods

MBL was detected by immunohistochemistry lung tissue at the time of cold ischemia and in samples with BOS. MBL was assayed in the peripheral blood of 66 lung transplant patients transplanted between 1990–2007.

Results

MBL localized to vasculature and basement membrane during cold ischemia and BOS. Patients further out post-lung transplant > 5 years (n = 33), had significantly lower levels of MBL in the blood compared to lung transplant patients < 5 years with BOS Op-3 (n = 17), 1738 ± 250 ng/ml vs 3198 ± 370 ng/ml, p = 0.027, and similar levels to lung transplant patients < 5 years with BOS 0 (n = 16), 1738 ± 250 ng/ml vs 1808 ± 345 ng/ml. MBL levels in all BOS 0 (n = 30) vs. all BOS Op-3 (n = 36) were 1378 ± 275 ng/ml vs. 2578 ± 390 ng/ml, p = 0.001, respectively. C3 plasma levels in BOS 0 (n = 30) vs. BOS Op-3 (n = 36) were 101 ± 19.8 mg/ml vs. 114 ± 25.2 mg/ml, p = 0.024, respectively.

Conclusions

MBL localizes within the lung during graft ischemia and BOS, higher levels of plasma MBL are associated with BOS Op-3 and < 5 years post-transplant, and higher level of plasma complement protein C3 was associated with BOS Op-3 clinical status. MBL may serve as a biomarker for poorer outcome post-lung transplantation.     

Elevated plasma nonesterified fatty acids are associated with deterioration of acute insulin response in IGT but not NGT

High concentrations of nonesterified fatty acids (NEFA) are a risk factor for developing type 2 diabetes in Pima Indians. In vitro and in vivo, chronic elevation of NEFA decreases glucose-stimulated insulin secretion. We hypothesized that high fasting plasma NEFA would increase the risk of type 2 diabetes by inducing a worsening of glucose-stimulated insulin secretion in Pima Indians. To test this hypothesis, fasting plasma NEFA concentrations, body composition, insulin action (M), acute insulin response (AIR, 25-g IVGTT), and glucose tolerance (75-g OGTT) were measured in 151 Pima Indians [107 normal glucose tolerant (NGT), 44 impaired glucose tolerant (IGT)] at the initial visit. These subjects, participants in ongoing studies of the pathogenesis of obesity and type 2 diabetes, had follow-up measurements of body composition, glucose tolerance, M, and AIR. In NGT individuals, cross-sectionally, high fasting plasma NEFA concentrations at the initial visit were negatively associated with AIR after adjustment for age, sex, percent body fat, and M (P = 0.03). Longitudinally, high fasting plasma NEFA concentrations at the initial visit were not associated with change in AIR. In individuals with IGT, cross-sectionally, high fasting plasma NEFA concentrations at the initial visit were not associated with AIR. Longitudinally, high fasting plasma NEFA concentrations at the initial visit were associated with a decrease in AIR before (P < 0.0001) and after adjustment for sex, age at follow-up, time of follow-up, change in percent body fat and insulin sensitivity, and AIR at the initial visit (P = 0.0006). In conclusion, findings in people with NGT indicate that fasting plasma NEFA concentrations are not a primary etiologic factor for beta-cell failure. However, in subjects who have progressed to a state of IGT, chronically elevated NEFA seem to have a deleterious effect on insulin-secretory capacity.     

Elevated levels of plasma lipofuscins in patients with chronic renal failure

The fluorescence excitation and emission spectra observed in plasma from patients with chronic renal failure were reproduced by the generation of soluble lipofuscins in normal plasma samples by incubation with mixtures of L-dopa, dopamine, L-norepinephrine, L-epinephrine, 3-hydroxy-DL-kynurenine and 3-hydroxy-anthranilic acid for 24 h at 37 degrees C. Relative fluorescence intensity measurements consistently showed elevated plasma levels of the soluble lipofuscins in chronic renal failure: the means (n = 27) were 73.9 +/- 33.4 (SD) and 71.1 +/- 14.8 at emissions 413 nm and 445 nm respectively, in contrast to those of normal plasma samples (n = 11), 18.2 +/- 5.3 and 23.1 +/- 5.6. The maximum or shoulder at approximately 413 nm represents soluble lipofuscin that can be generated from 3-hydroxyanthranilic acid and the maximum or shoulder at approximately 445 nm represents soluble lipofuscins derived from the precursors listed above and probably from other related precursors. Gravimetric measurements also showed elevated levels of melanins in the plasma samples of patients with chronic renal failure: 2.72 +/- 0.38 mg/ml (n = 16), as compared to normal values: 1.70 +/- 0.10 mg/ml (n = 6). In individual patients haemodialysis reduced the fluorescence intensities to a range of 65-99% and the melanin levels to a range of 86-99% of the pre-dialysis values.     

TNF-alpha, soluble TNF receptor and interleukin-6 plasma levels in the general population

The cytokines tumor necrosis factor-alpha (TNF-alpha), soluble TNF receptors p55 and p75, and interleukin 6 (IL-6) are involved in host defense against several microbiological agents, in the process of inflammation and also in body weight regulation. In the present study, we sought to assess the influence of age, gender, smoking, and body mass index on plasma levels of TNF-alpha, TNF receptors, and IL-6 in more than 550 adult subjects randomly selected from the Bavarian population. None of the cytokine parameters had a normal distribution and all distributions were significantly skewed. The cytokine plasma levels investigated increased significantly with age, while gender had a relatively weaker influence on the plasma levels. Plasma levels of TNF-alpha, TNF receptors, and IL-6 correlated significantly with the BMI. The study provides insights into factors influencing the cytokine levels investigated in a randomly chosen study sample.     

Elevated levels of plasma VEGF in patients with dengue hemorrhagic fever

Vascular endothelial growth factor (VEGF) can be produced by monocytes and endothelial cells. It plays important role in angiogenesis and vascular permeability. The phenomenon of extensive plasma leakage into various serous cavities of the body is a cardinal symptom of dengue hemorrhagic fever (DHF). This study was performed to investigate the role of VEGF in patients with DHF. Plasma samples collected from the 53 dengue fever (DF) patients (including 14 patients with DHF), and 5 additional subjects with non-dengue febrile illness as controls were tested for VEGF levels using commercial enzyme-linked immunosorbent assay (ELISA) kits. The results showed that median plasma levels of VEGF in the patients with DHF (54.6 pg ml(-1)) were significantly higher than those of DF (14.6 pg ml(-1)) and control group (27.1 pg ml(-1)) (P<0.05). In addition, VEGF levels in DF patients were not significantly different from those of control patients with non-dengue febrile illness (P=0.17). Multiple regression analysis was used to analyze the clinical variables independently associated with VEGF levels. The data showed that D-dimer levels were significantly associated with VEGF levels. In this study, plasma VEGF levels in patients with DHF were significantly higher than values from DF patients. The association between increased plasma VEGF levels and increased plasma D-dimer levels in the patients with dengue illness suggests that activation of the fibrinolytic system may play a role in VEGF production in the patients with DF.     

Low 1,5-anhydroglucitol levels are associated with long-term cardiac mortality in acute coronary syndrome patients with hemoglobin A1c levels less than 7.0%

Background

Diabetes mellitus is considered an important risk factor for cardiovascular diseases. High hemoglobin A1c (HbA1c) levels, which indicate poor glycemic control, have been associated with occurrence of cardiovascular diseases. There are few parameters which can predict cardiovascular risk in patients with well-controlled diabetes. Low 1,5-anhydroglucitol (1,5-AG) levels are considered a clinical marker of postprandial hyperglycemia. We hypothesized that low 1,5-AG levels could predict long-term mortality in acute coronary syndrome (ACS) patients with relatively low HbA1c levels.

Methods

The present study followed a retrospective observational study design. We enrolled 388 consecutive patients with ACS admitted to the cardiac intensive care unit at the Juntendo University Hospital from January 2011 to December 2013. Levels of 1,5-AG were measured immediately before emergency coronary angiography. Patients with early stent thrombosis, no significant coronary artery stenosis, malignancy, liver cirrhosis, a history of gastrectomy, current steroid treatment, moderately to severely reduced kidney function (estimated glomerular filtration rate < 45 ml/min/1.73 m²; chronic kidney disease stage 3B, 4, and 5), HbA1c levels ≥ 7.0%, and those who received sodium glucose co-transporter 2 inhibitor therapy were excluded.

Results

During the 46.9-month mean follow-up period, nine patients (4.5%) died of cardiovascular disease. The 1,5-AG level was significantly lower in the cardiac death group compared with that in the survivor group (12.3 ± 5.3 vs. 19.2 ± 7.7 µg/ml, p < 0.01). Kaplan–Meier survival analysis showed that low 1,5-AG levels were associated with cardiac mortality (p = 0.02). Multivariable Cox regression analysis showed that 1,5-AG levels were an independent predictor of cardiac mortality (hazard ratio 0.76; 95% confidence interval 0.41–0.98; p = 0.03).

Conclusion

Low 1,5-AG levels, which indicate postprandial hyperglycemia, predict long-term cardiac mortality even in ACS patients with HbA1c levels < 7.0%.

     

Elevated ghrelin plasma levels in patients with polycystic ovary syndrome.

Polycystic ovary syndrome is a common endocrine disorder in women. It is associated with hirsuitism, obesity, insulin resistance, abnormality in the growth hormone/insulin-like growth factor I (IGF-1) axis and polycystic ovaries. The etiology of PCOS has not been clarified. Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor. It is mainly secreted by stomach cells but has also been shown to be present in hypothalamus, pituitary, pancreas and gonads. Ghrelin is a regulator of energy homeostasis and GH secretion. The influence of ghrelin on insulin secretion and gonadal function is known. Since ghrelin may play an important role in pathophysiology of PCOS, we studied ghrelin levels in a group of 52 women with PCOS and in 16 women in a control group. Plasma levels of insulin, total testosterone, SHBG, LH, and FSH were also measured. In conclusion, PCOS women have higher ghrelin levels than controls. Ghrelin negatively correlates with BMI and insulin levels in PCOS group. A relation between ghrelin and SHBG was observed. Our data suggest that ghrelin could be the possible link in PCOS etiology.     

Perinatal mortality and morbidity associated with eclampsia.

Out of all the women who were delivered in Cardiff maternity units during 1965-74, 43 developed eclampsia, an incidence of 72/100 000 deliveries. The incidence in residents of Cardiff was 53/100 000 deliveries. None of the mothers with eclampsia died, but 10 of the 47 babies were lost, all but one having been born to women with antepartum eclampsia. The perinatal deaths were mainly associated with chronic placental insufficiency and preterm delivery. The extent to which the wide range of complex drug regimens used influenced perinatal outcome is not clear, although polypharmacy should be avoided. Because eclampsia is rare we advocate that its management should be planned and rehearsed and that a simple, standardised treatment regimen should be used. Failing placental function may be detected by monitoring fetal growth by ultrasound.     

Elevated plasma levels of endothelin are associated with the severity of sepsis and presence of shock in contrast to the levels of atrial natriuretic peptide

Immunoreactive endothelin (ETi) and atrial natriuretic peptide (ANPi) blood levels were measured by radioimmunoassay in patients with clinically defined sepsis. The interaction between these two peptides and their relation to circulatory shock and mortality were studied. All septic patients (n = 16) had significantly higher ETi (22.3 +/- 11.1 pg/ml) and ANPi (398.3 +/- 154.3 pg/ml) plasma concentrations compared to control subjects (ETi, 4.1 +/- 1.2; ANPi, 59.1 +/- 14.8 pg/ml; n = 13). ETi levels followed the severity of illness according to the APACHE II scoring system and were higher in patients who did not survive. ETi levels were significantly higher in the presence of shock and bacteraemia. Furthermore, ETi correlated well with plasma lactate (r = 0.83, p < 0.05), but not with renal function. ANPi levels did not show correlation with any of these determinants. Serial blood sampling, six consecutive days after admission, showed that ETi levels gradually decreased in normotensive patients in contrast to patients with septic shock. ANPi levels did not show systematic changes in time, and no relationship was observed between ETi and ANPi levels. These results suggest that plasma ETi levels are indicative for disease severity and might have prognostic significance. The role of ANPi during sepsis remains to be eludicated.     

High plasma leptin levels are associated with impaired diastolic function in patients with coronary artery disease

Background and aimsObese subjects have elevated leptin levels, which have been associated with increased risk of cardiovascular events. Because leptin has direct cellular effects on various tissues, we tested the hypothesis that leptin levels are associated with cardiac structure or function in patients with coronary artery disease (CAD).Methods and resultsThe study population consisted of 1 601 CAD patients, of whom 42% had type 2 diabetes mellitus. Plasma leptin was measured in fasted state and an echocardiography performed. Leptin levels were not related to LV dimensions or LV ejection fraction (NS for all), but higher leptin levels were associated with elevated E/E’ (9.43 vs. 11.94 in the lowest and the highest leptin quartile, respectively; p = 0.018 for trend). Correspondingly, a decreasing trend was observed in E/A (1.15 vs. 1.06; p = 0.037). These associations were independent of obesity and other relevant confounding variables.ConclusionWe conclude that elevated plasma leptin levels are associated with impaired left ventricular diastolic function in patients with CAD independently of obesity and other confounding variables. Leptin may be one of the mechanistic links explaining the development of congestive heart failure in obese subjects.     

Elevated plasma levels of soluble (pro)renin receptor in patients with obstructive sleep apnea syndrome: Association with polysomnographic parameters

(Pro)renin receptor ((P)RR) is a specific receptor for both renin and its precursor prorenin. (P)RR was shown to be involved in pathophysiology of cardiovascular and renal diseases. Soluble (pro)renin receptor (s(P)RR), which is generated by furin from full length (P)RR, is present in blood. The aim of the present study is to clarify the association of plasma s(P)RR levels and the severity of OSAS. Plasma levels of s(P)RR were measured by ELISA in 58 male patients diagnosed as OSAS based on polysomnography, and 14 age-matched male control subjects. Blood samples were obtained at 6:00 a.m. just after overnight polysomnography. Plasma s(P)RR levels were significantly higher in patients with OSAS (9.0 ± 2.0 ng/mL, mean ± SD) than in control subjects (7.4 ± 1.5 ng/mL) (P = 0.0026). Plasma s(P)RR levels showed a significant negative correlation with % stage rapid eye movement (REM) sleep (r = −0.377, p < 0.005), and significant positive correlations with % stage 1 (r = 0.374, p < 0.005), arousal index (r = 0.341, p < 0.01), apnea hypopnea index (AHI) (r = 0.352, p < 0.01) and desaturation index (r = 0.302, p < 0. 05). In 12 OSAS patients with AHI ≥20, plasma levels of s(P)RR were studied after 3-month treatment with nasal continuous positive airway pressure (nCPAP). Plasma s(P)RR levels were significantly decreased after the nCPAP treatment (p = 0.0016). The present study has shown for the first time elevated plasma s(P)RR levels in patients with OSAS. Plasma s(P)RR levels were associated with the severity of OSAS. Soluble (P)RR may serve as a plasma marker reflecting the severity of OSAS.