Urinary D-serine level as a predictive biomarker for deterioration of renal function in patients with atherosclerotic risk factors.

BACKGROUND: D-serine, the enantiomer of L-serine, was identified in mammals 20 years ago. Although a close relationship between D-serine and renal dysfunction has been shown, the clinical implications of urinary D- and L-serine in humans are poorly understood. The aim of this study was to evaluate the relationship between urinary D- and L-serine with well-known renal biomarkers, and clarify the prognostic value of D- and L-serine for renal events. METHODS: This cross-sectional, prospective study included 65 patients with atherosclerotic risk factors, who were followed up for a median of 16 months. The primary endpoint was a composite of end-stage renal disease and a decline in estimated glomerular filtration rate (eGFR) ≥ 25% from baseline. RESULTS: Urinary D-serine concentrations showed a better correlation with eGFR than did urinary L-serine, whereas neither urinary D- nor L-serine correlated with tubular markers such as urinary liver-type fatty acid-binding protein and N-acetyl-beta-D-glucosaminidase. A Cox regression analysis revealed that low urinary D-serine levels were significantly associated with the primary endpoint after adjusting for confounding factors (hazard ratio 12.60; 95% confidence interval, 3.49-45.51). CONCLUSIONS: Urinary D-serine is associated with glomerular filtration and can be a prognostic biomarker of renal dysfunction in patients with atherosclerotic risk factors.

Adaptive servo-ventilation improves renal function in patients with heart failure.

BACKGROUND: Impaired cardiac function and sleep-disordered breathing (SDB) are associated with progression of chronic kidney disease (CKD) in heart failure (HF) patients. Adaptive servo-ventilation (ASV) therapy improves cardiac function in HF patients regardless of the SDB severity through hemodynamic support and prevention of repetitive hypoxic stress. This study was designed to test the hypothesis that ASV therapy improves renal function in HF patients with SDB. METHODS AND RESULTS: Of 59 consecutively enrolled HF patients, 43 with moderate-to-severe SDB underwent ASV therapy. HF patients were divided into the ASV-treated group (n = 27) and the non-ASV-treated group (n = 16). Estimated glomerular filtration rate (eGFR), echocardiographic parameters, and inflammatory biomarkers were measured before and 12 months after ASV initiation. Improvement in the eGFR was found in the ASV-treated group, but not in the non-ASV-treated group. There was a positive correlation between the increases in eGFR and left ventricular ejection fraction (r = 0.488, p = 0.001). The changes in high-sensitivity C-reactive protein were negatively correlated with change in the eGFR (r = -0.416, p = 0.006). CONCLUSIONS: ASV therapy could improve renal dysfunction in HF patients through hemodynamic support. Additionally, prevention of SDB with the use of ASV therapy could exert anti-inflammatory effects, which could contribute to the improvement of renal function in HF patients.

Short-term prognosis of adaptive servo-ventilation therapy in patients with heart failure.

BACKGROUND: This study tested the hypothesis that adaptive servo-ventilation (ASV) therapy improves the prognosis of heart failure (HF) patients, regardless of the severity of sleep-disordered breathing (SDB). METHODS AND RESULTS: 88 consecutive patients were divided into 4 groups based on ASV therapy and SDB severity. The incidence of HF, brain natriuretic peptide (BNP) levels, and left ventricular ejection fraction (LVEF) were followed for 12 months. Fewer HF events, together with an increase in LVEF and a decrease in BNP, occurred in ASV-treated patients with both non-to-mild and moderate-to-severe SDB. CONCLUSIONS: ASV therapy improves the short-term prognosis in HF-patients, regardless SDB severity.

Fluvastatin protects vascular smooth muscle cells against oxidative stress through the Nrf2-dependent antioxidant pathway.

OBJECTIVE: HMG-CoA reductase inhibitors (statins) have pleiotropic actions, including the ability to reduce vascular oxidative stress. Transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) is an important regulator of cellular oxidative stress. This study examined the role of Nrf2 in statin-mediated antioxidant effects in vascular smooth muscle cells. METHODS AND RESULTS: In cultured human coronary artery smooth muscle cells (hCASMCs), fluvastatin activated the nuclear translocation of Nrf2, as evaluated by Western blotting and immunocytochemical analyses. Nrf2-antioxidant response element (ARE) activity was measured with a luciferase assay after transfection of reporter plasmids containing AREs. Fluvastatin significantly increased the transcriptional activity of the ARE. Electromobility shift assays using an ARE probe detected a complex that was significantly increased in intensity by fluvastatin. Western blotting and luciferase assay revealed fluvastatin activated Nrf2 via the PI3K/Akt pathway. Statins upregulated the Nrf2-related antioxidant genes heme oxygenase-1, NAD(P)H quinone oxidoreductase-1, and glutamate-cysteine ligase modifier subunits. Inhibition of Nrf2 by siRNA reduced statin-induced upregulation of these antioxidant genes. Moreover, Nrf2 siRNA markedly reduced the cytoprotective effects of fluvastatin against H(2)O(2) administration in hCASMCs. CONCLUSIONS: Fluvastatin exerts cytoprotective effects against oxidative stress, inducing antioxidant genes through Nrf2/ARE in hCASMCs. These results suggest that the Nrf2/ARE pathway plays an important role in the regulation of statin-mediated antioxidant effects in vascular smooth muscle cells.

Beneficial effects of adaptive servo ventilation in patients with chronic heart failure.

BACKGROUND: Sleep-disordered breathing (SDB) is thought to be a state of inflammation caused by hypoxic stress. Whether adaptive servo ventilation (ASV) attenuates the inflammatory response and improves the cardiac function of patients with congestive heart failure (CHF) accompanied by SDB was not been investigated. METHODS AND RESULTS: Seventeen inpatients with New York Heart Association (NYHA) II or III underwent polysomnography. There was a positive correlation between the apnea hypopnea index and high-sensitivity C-reactive protein (hs-CRP) level (r=0.753, P=0.016). The patients were divided into ASV (n=10) and non-ASV groups (n=7), and CHF-parameters were measured before and after ASV treatment. Improvement was noted for the NYHA class in the ASV group but not in the non-ASV group. In contrast to the non-ASV group, the level of brain natriuretic peptide (BNP), ejection fraction, and hs-CRP levels in the ASV group significantly improved (BNP, 212.1 ± 181.2 to 77.3 ± 54.0 pg/ml [P<0.05]; ejection fraction, 43.5 ± 6.4 to 53.3 ± 6.1% [P=0.002]; hs-CRP, 0.85 ± 0.58 to 0.21 ± 0.19 mg/dl, [P=0.008]). The increase in ejection fraction was correlated with a decrease in the hs-CRP level (r=-0.753, P=0.001). CONCLUSIONS: Anti-inflammatory effects of ASV are important contributors for improving cardiac function in patients with CHF accompanied by SDB.