YKL-40 (chitinase-3-like protein 1) serum levels are associated with abdominal aortic calcification in hemodialysis patients.

BACKGROUND: Vascular calcification (VC) is highly prevalent and predicts cardiovascular mortality in dialysis patients. The mechanisms are still unclear. Inflammation is a well-known inducer of VC. YKL-40 has been suggested as a novel biomarker of inflammation and has been demonstrated to be associated with cardiovascular mortality in hemodialysis patients. This study aims to evaluate the relationship between serum YKL-40 and VC in hemodialysis (HD) patients. METHODS: A total of 109 HD patients and 31 healthy controls were enrolled in the study from September 2014 to December 2014. We evaluated the abdominal aortic calcification (AAC) score by plain X-ray films of the abdomen and measured serum YKL-40 concentrations using enzyme-linked immunosorbent assay. We also examined the relationship between YKL-40 levels and AAC scores in HD patients. RESULTS: Serum YKL-40 levels in HD patients were significantly higher than those in healthy controls [199.8 (144.8, 288.7) vs. 71.9 (52.8, 89.3) ng/ml; P < 0.001]. There was a tendency that YKL-40 levels in diabetic hemodialysis patients were higher than those in nondiabetic patients [217.8 (155.3, 335.8) vs. 192.9 (135.9, 274.4) ng/ml; P = 0.093]. A significant positive correlation was found between serum YKL-40 level and AAC score in these patients (r = 0.410, P = 0.003). Multiple regression analysis showed that Ln(YKL-40) was independently associated with AAC score in HD patients (P = 0.044). CONCLUSION: This study showed high serum YKL-40 concentrations in chronic HD patients and that YKL-40 was independently associated with increased AAC in hemodialysis patients.

Urotensin II Induces Mice Skeletal Muscle Atrophy Associated with Enhanced Autophagy and Inhibited Irisin Precursor (Fibronectin Type III Domain Containing 5) Expression in Chronic Renal Failure.

BACKGROUND/AIMS: Skeletal muscle atrophy is one of the main manifestations of protein energy wasting. We hypothesized that urotensin II (UII) can lead to skeletal muscle atrophy through upregulating autophagy and affecting Irisin precursor fibronectin type III domain containing 5 (FNDC5) expressions. METHODS: Three animal models (the sham operation, wild-type C57BL/6 mice with 5/6 nephrectomy, UII receptor (UT) gene knockout (UTKO) mice with 5/6 nephrectomy) were designed. Skeletal muscle weight, cross-sectional area (CSA) along with UII, FNDC5, LC3, and p62 expression were investigated. C2C12 cells were differentiated for up to 4 days into myotubes. These cells were then exposed to different UII concentrations (10-5 to 10-7 M) for 6-12 h and analyzed for the expressions of autophagic markers. These cells were also exposed to the same predetermined UII concentrations for 48-72 h and analyzed for the FNDC5 expression. Myotube diameter was measured. RESULTS: Upregulation of UII expression in skeletal muscle tissue was accompanied by reduced muscle weight and skeletal muscle CSA in the 2 posterior limbs, upregulated autophagy markers expression, and downregulated FNDC5 expression in 5/6 nephrectomy mice. The decrease of skeletal muscle weight, skeletal muscle CSA, downregulation of FNDC5 expression, and the upregulation of autophagy markers were inhibited in UTKO with 5/6 nephrectomy mice. Our in vitrostudy showed that UII could directly decrease myotube diameter, induce autophagy markers upregulation, and inhibit expression of FNDC5. When UII receptor gene was interfered by UT-specific siRNA, UII induced autophagy markers upregulation and FNDC5 downregulation were inhibited. CONCLUSION: We are the first to verify UII induces mice skeletal muscle atrophy associated with enhanced skeletal muscle autophagy and inhibited FNDC5 expression in chronic renal failure.

Lower Serum Irisin Levels Are Associated with Increased Vascular Calcification in Hemodialysis Patients.

BACKGROUND/AIMS: Vascular calcification, which involves an active cellular transformation of vascular smooth muscle cells into bone forming cells, is prevalent and predicts mortality in dialysis patients. Its mechanisms are complex and unclear. We presume that irisin, a newly identified myokine also may play roles in vascular calcification in hemodialysis patients. This study aims to evaluate serum irisin levels and establish their relation to vascular calcification and other parameters in hemodialysis patients. METHODS: A total of 150 patients on maintenance hemodialysis treatment and 38 age- and sex-matched healthy controls were enrolled in this cross-sectional study. Serum irisin concentrations were measured by ELISA. Vascular calcification was evaluated by abdominal aortic calcification scores. RESULTS: Serum irisin concentrations were significantly lower in hemodialysis patients than in controls [52.8 (22.0, 100.0) vs. 460.8 (434.8, 483.4) ng/ml, P<0.01]. In addition, irisin was negatively correlated with the parathyroid hormone level (P=0.01). The HD patients with vascular calcification showed significantly lower serum irisin concentrations [39.0 (21.7, 86.2) vs.79.0 (39.5, 130.2) ng/mL, P<0.01]. Compared with the group without vascular calcification multivariate logistic regression analyses revealed that serum irisin, HD vintage and age were significant independent determinant factors for vascular calcification in HD patients. CONCLUSION: Our results are the first to provide a clinical evidence of the association between serum irisin and vascular calcification in HD patients. Lower irisin levels, long-term hemodialysis and old ages are independent risk factors in HD patients.

Irisin is Associated with Urotensin II and Protein Energy Wasting in Hemodialysis Patients.

AIMS/INTRODUCTION: Irisin is a newly identified myokine which can promote energy expenditure. Urotensin II (UII) is identified as the most potent mammalian vasoconstrictor to date. Previous studies showed that UII can aggravate insulin resistance while irisin alleviate insulin resistance. Through this study, it is our aim to elucidate if UII can induce insulin resistance and also have an association with the irisin level in hemodialysis (HD) patients. MATERIALS AND METHODS: One hundred and twenty-eight patients on maintenance hemodialysis treatment and forty healthy subjects were enrolled in this study. Blood irisin concentrations and UII concentrations were measured by ELISA and RIA respectively. The body composition was analyzed by bioelectrical impedance. RESULTS: The serum irisin levels and UII levels were both significantly lower in HD patients in comparison to that of the healthy subjects. The serum irisin levels were lower in HD patients with protein energy wasting than those of the patients without protein energy wasting. The independent determinants of circulating Ln (irisin) (the natural logarithm of irisin) were UII lean body mass and patients with protein energy wasting. CONCLUSIONS: Our results are the first to provide the clinical evidence of the association among irisin, UII, and protein energy wasting. Our results hint that UII and protein energy wasting might inhibit the release or synthesis of irisin from skeletal muscles in HD patients.

Irisin levels are associated with urotensin II levels in diabetic patients.

AIMS/INTRODUCTION: Irisin is a newly identified myokine that can promote energy expenditure. Previous studies showed that circulating urotensin II (UII) levels were increased in diabetes, and UII could inhibit the glucose transport in skeletal muscle in diabetic mice and aggravated insulin resistance. We presumed that irisin levels are associated with UII in diabetic patients. MATERIALS AND METHODS: A total of 71 patients with type 2 diabetes and 40 healthy subjects were recruited. Blood and urinary irisin concentrations were measured by using enzyme-linked immunosorbent assay, and UII concentrations were measured by bioelectrical impedance analysis. Every participant's body composition was analyzed by bioelectrical impedance. RESULTS: The serum irisin levels were significantly lower in diabetic patients than that of controls, whereas serum UII levels were significantly higher in diabetic patients than that in that of controls. Serum irisin levels were negatively associated with circulating UII, hemoglobin A1c and the natural logarithm transformation of urinary albumin excretion, whereas serum irisin was positively associated with estimated glomerular filtration rate, and low-density lipoprotein cholesterol and urinary irisin were positively associated with urinary UII. Furthermore, circulating irisin is positively associated with muscle mass, whereas circulating UII is negatively associated with muscle mass in diabetic patients. Hemoglobin A1c and circulating UII are independent determinants of circulating irisin by multiple regression analysis. CONCLUSIONS: The present results provide the clinical evidence of an association between irisin and UII in diabetic patients. Hemoglobin A1c and circulating UII are independent determinants of circulating irisin. Our results hint that UII and high glucose might inhibit the release of irisin from skeletal muscle in diabetic patients.

[Up-regulation of intrarenal renin-angiotensin system contributes to renal damage in high-salt induced hypertension rats].

OBJECTIVE: To test the hypothesis that in a high-salt induced hypertension in normal rats, whether the changes of intrarenal renin-agiotensin system (RAS) play a critical role in renal damage and could be reflected by urinary angiotensinogen (AGT). METHODS: In the study, 27 normotensive male Wistar-Kyoto rats were divided into control group [0.3% (mass faction) NaCl in chow, n=9, NS], high-salt diet group [8% (mass faction) NaCl in chow, n=9, HS] and high-salt diet with Losartan group [8% (mass faction) NaCl in chow and 20 mg/(kg×d) Losartan in gavages, n=9, HS+L)], and were fed for six weeks. The blood pressure was monitored and urine samples were collected every 2 weeks. AGTs in plasma, kidney and urine were measured by ELISA kits. The renal cortex expression of mRNA and protein of AGT were measured by Real-time PCR and immunohistochemistry (IHC). The renin activity and ANG II were measured by radioimmunoassay (RIA) kits. RESULTS: Compared with NS, the systolic blood pressure (SBP) [(156 ± 2) mmHg vs. (133 ± 3) mmHg, P<0.05] increased significantly at the end of the 2nd week, and the urinary protein [(14.07 ± 2.84) mg/24 h vs. (7.62 ± 3.02) mg/24 h, P<0.05] increased significantly at the end of the 6th week in HS. Compared with HS, there was no significant difference in SBP (P>0.05) but the proteinuria [(9.69 ± 2.73) mg/24 h vs. (14.07 ± 2.84) mg/24 h, P<0.01] decreased significantly in HS+L. Compared with NS, there was no significant difference in the plasma renin activity, angiotensinogen and ANG II level in HS (P>0.05), but the renal cortex renin content [(8.72 ± 1.98) ng/(mL × h) vs. (4.37 ± 1.26) ng/(mL × h), P<0.05], AGT formation [(4.02 ± 0.60) ng/mg vs. (2.59 ± 0.42) ng/mg, P<0.01], ANG II level [(313.8 ± 48.76) pmol/L vs. (188.9 ± 46.95) pmol/L, P<0.05] were increased significantly in HS, and the urinary AGT and ANG II excretion rates increased significantly (P<0.05). Compared with HS, the plasma renin activity, angiotensinogen and ANG II level were significantly increased (P<0.05), but the renal cortex renin content, AGT formation, ANG II level significantly decreased (P<0.05), and the urinary AGT and ANG II excretion rates decreased significantly in HS+L (P<0.05). The urinary AGT excretion rates were positively correlated with the AGT level in the renal cortex (P<0.05). CONCLUSION: Up-regulation of intarenal RAS may contribute to renal damage in high-salt induced hypertension rats. Urinary AGT may reflect the status of intrarenal RAS.

Yohimbine protects against endotoxin-induced acute lung injury by blockade of alpha 2A adrenergic receptor in rats.

BACKGROUND: Alpha 2A adrenergic receptor (AR) is a subtype of α2 AR belonging to G protein-coupled receptors, and exerts a variety of biological effects. Recent studies have demonstrated that the α2A AR activation was closely related with inflammatory reaction. The present study aimed to investigate the influence of α2A AR antagonist, yohimbine, on the severity of endotoxin-induced acute lung injury in rats. METHODS: A total of 72 male Sprague-Dawley rats were randomly divided into three groups: control group, lipopolysaccharide (LPS) group and LPS + yohimbine group. Rats were intratracheally administrated with normal saline or LPS (300 µg), and the rats in the LPS + yohimbine group were treated with additional yohimbine (2 mg/kg, i.p) soon after LPS administration. Six, 24 and 48 hours after treatment, arterial blood gas analysis was carried out, and optical microscopy was performed to evaluate pathological changes in the lung, and lung injury score was assessed. The count of white blood cells in bronchoalveolar lavage fluid (BALF) was determined. The levels of norepinephrine, tumor necrosis factor (TNF)-α, interleukin (IL)-1ß and IL-6 in BALF were measured with enzyme-linked immunosorbent assay. Immunocytochemistry was performed for the detection of α2A AR on inflammatory cells in BALF. RESULTS: When compared with the control group, the oxygenation index in the LPS group was significantly decreased, and white blood cell count, the lung histopathological scores, levels of norepinephrine and IL-6 as well as α2A AR expression on inflammatory cells in the BALF were dramatically increased at different time points, and the concentrations of TNF-α and IL-1ß were also increased except at 48 hours after LPS administration. The oxygenation index decreased while white blood cell count in BALF and the lung histopathological scores were obviously increased in the LPS + yohimbine group. The level of norepinephrine in BALF was increased at each time interval in the LPS + yohimbine group, and so did the levels of TNF-α, IL-1ß and IL-6 at 6 and 48 hours after LPS administration respectively. When compared with the LPS group, the oxygenation index, white blood cell count, the lung histopathological scores and the level of IL-6 in the LPS + yohimbine group were significantly improved at each time interval, and the concentrations of TNF-α and IL-1ß were also lower at 24 hours of LPS administration (all P < 0.05). Correlation analysis indicated the level of norepinephrine was related to the levels of TNF-α, IL-1ß and IL-6 in the BALF and the lung histopathological scores (r = 0.703, r = 0.595, r = 0.487 and r = 0.688, respectively, P < 0.001) and the intensity scores of immunoreactivity to α2A AR on inflammatory cells were also associated with the levels of TNF-α, IL-1ß and IL-6 as well as the lung histopathologial scores (r = 0.803, r = 0.978, r = 0.716 and r = 0.808, respectively, P < 0.001). CONCLUSIONS: Yohimbine can inhibit TNF-α, IL-1ß and IL-6 overproduction and relieve the severity of pulmonary inflammation induced by endotoxin, which is maybe mediated by blockade of α2A AR on inflammatory cells.