Kostas Stylianou

Low serum testosterone, arterial stiffness and mortality in male haemodialysis patients

BACKGROUND In the general population, accumulating data support a link between low testosterone levels and mortality by all causes, but especially by cardiovascular disease (CVD). Also, accelerated arterial stiffness has been recognized as an important cardiovascular risk factor. Here, we explored the association between testosterone levels and risk of death in male haemodialysis (HD) patients, whose arterial system is characterized by generalized stiffening. METHODS In this three-centre prospective observational study, 111 male HD patients after completion of baseline assessment, including measurement of male sex hormones and pulse wave velocity (PWV), were followed up for CVD and all-cause mortality. RESULTS Of the 111 patients studied, 54 were found with and 57 without testosterone deficiency, defined as testosterone levels <8 nmol/L. During a median follow-up period of 37 months, 49 deaths occurred, 28 (57%) of which were caused by CVD. Testosterone deficiency patients had increased CVD and all-cause mortality {crude hazard ratio: 3.14 [95% confidence interval (CI), 1.21-8.16] and 3.09 (95% CI, 1.53-6.25), respectively}, even after adjustment for age, body mass index, serum albumin and C-reactive protein, prevalent CVD and HD vintage. The association of testosterone with CVD mortality, but not with all-cause mortality, was lost after adjusting for PWV, an index of arterial stiffness. Testosterone levels were inversely related to PWV (r = -0.441; P < 0.001). CONCLUSION We showed that testosterone deficiency in male HD patients is associated with increased CVD and all-cause mortality and that increased arterial stiffness may be a possible mechanism explaining this association.

The PI3K/Akt/mTOR pathway is activated in murine lupus nephritis and downregulated by rapamycin

BACKGROUND The mammalian target of rapamycin (mTOR) inhibitor, rapamycin, has been shown to inhibit the progression of murine lupus nephritis by virtue of its potent immunosuppressive properties. The phosphoinositol-3-kinase (PI3K)/Akt pathway is a major upstream activator of mTOR and has been implicated in the propagation of cancer and autoimmunity. However, the activation status of the PI3K/Akt/mTOR pathway in lupus nephritis has not been studied so far. METHODS In NZBW/F1 female mice, we examined the glomerular expression of Akt and mTOR by immunofluorescence and western blot. We also searched for specific phosphorylations of these kinases known to ensue during activation of the PI3K/Akt/mTOR pathway. In parallel, we examined the therapeutic role of rapamycin either before or after the development of overt lupus nephritis. RESULTS We found that in untreated mice, as opposed to healthy controls, Akt and mTOR were over-expressed and phosphorylated at key activating residues. Rapamycin prolonged survival, maintained normal renal function, normalized proteinuria, restored nephrin and podocin levels, reduced anti-dsDNA titres, ameliorated histological lesions, and reduced Akt and mTOR glomerular expression activation. CONCLUSIONS These results suggest that: (i) the PI3K/Akt/mTOR pathway is upregulated in murine lupus nephritis, thus justifying treatment with rapamycin; (ii) rapamycin not only blocks mTOR but also negatively regulates the PI3K/Akt/mTOR pathway; and (iii) rapamycin is an effective treatment of murine lupus nephritis. Examination of the PI3K/Akt/mTOR pathway may offer new insights into the pathogenesis of lupus nephritis in humans and may lead to more individualized and less toxic treatment.

Prolactin Levels, Endothelial Dysfunction, and the Risk of Cardiovascular Events and Mortality in Patients with CKD

BACKGROUND AND OBJECTIVES Both prolactin clearance and production are altered in CKD. In nonrenal populations, emerging evidence suggests that prolactin participates in the atherosclerotic process. Given the elevated cardiovascular risk of CKD, this study examined links between prolactinemia, vascular derangements, and outcomes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This observational study was conducted in two cohorts: one with 457 nondialyzed CKD patients (mean age 52±12 years; 229 men) with measurements of flow-mediated dilation (FMD) and carotid intima-media thickness and one with 173 hemodialysis patients (65±12 years; 111 men) with measurements of pulse wave velocity (PWV). Patients were followed for cardiovascular events (n=146, nondialyzed cohort) or death (n=79, hemodialysis cohort). RESULTS Prolactin levels increased along with reduced kidney function. Prolactin significantly and independently contributed to explain the variance of both FMD (in nondialyzed patients) and PWV (in hemodialysis patients), but not intima-media thickness. In Cox analyses, the risk of cardiovascular events in nondialyzed patients increased by 27% (hazard ratio [HR], 1.27; 95% confidence interval [95% CI], 1.17-1.38) for each 10 ng/ml increment of prolactin. Similarly, the risk for all-cause and cardiovascular mortality in hemodialysis patients increased by 12% (HR, 1.12; 95% CI, 1.06-1.17) and 15% (HR, 1.15; 95% CI, 1.08-1.21), respectively. This was true after multivariate adjustment for confounders and after adjustment within the purported causal pathway (FMD or PWV). CONCLUSIONS Prolactin levels directly associated with endothelial dysfunction/stiffness and with increased risk of cardiovascular events and mortality in two independent cohorts of CKD patients.

Evidence for Activation of the Unfolded Protein Response in Collagen IV Nephropathies

Thin-basement-membrane nephropathy (TBMN) and Alport syndrome (AS) are progressive collagen IV nephropathies caused by mutations in COL4A3/A4/A5 genes. These nephropathies invariably present with microscopic hematuria and frequently progress to proteinuria and CKD or ESRD during long-term follow-up. Nonetheless, the exact molecular mechanisms by which these mutations exert their deleterious effects on the glomerulus remain elusive. We hypothesized that defective trafficking of the COL4A3 chain causes a strong intracellular effect on the cell responsible for COL4A3 expression, the podocyte. To this end, we overexpressed normal and mutant COL4A3 chains (G1334E mutation) in human undifferentiated podocytes and tested their effects in various intracellular pathways using a microarray approach. COL4A3 overexpression in the podocyte caused chain retention in the endoplasmic reticulum (ER) that was associated with activation of unfolded protein response (UPR)-related markers of ER stress. Notably, the overexpression of normal or mutant COL4A3 chains differentially activated the UPR pathway. Similar results were observed in a novel knockin mouse carrying the Col4a3-G1332E mutation, which produced a phenotype consistent with AS, and in biopsy specimens from patients with TBMN carrying a heterozygous COL4A3-G1334E mutation. These results suggest that ER stress arising from defective localization of collagen IV chains in human podocytes contributes to the pathogenesis of TBMN and AS through activation of the UPR, a finding that may pave the way for novel therapeutic interventions for a variety of collagenopathies.

Incidence, Clinical, Microbiological Features and Outcome of Bloodstream Infections in Patients Undergoing Hemodialysis

Objectives: Infection is a common cause of death among hemodialysis patients. The study investigated incidence, risk factors, clinical features and outcome of bloodstream infections (BSIs) in haemodialysis patients. Methods: The records of haemodialysis patients from 1999 to 2005 were reviewed. Risk factors were investigated by multivariate analysis. Results: There were identified 148 bacteremic episodes, in 102 patients. The BSI rate was 0.52 per 1000 patient-days. Of the 148 episodes, 34 occurred in patients with permanent fistulae (0.18/1000 patient-days); 19 in patients with grafts (0.39/1000 patient-days); 28 in patients with permanent tunneled central catheters (1.03/1000 patient-days); and 67 in those with temporary-catheter (3.18/1000 patient-days). With fistula as reference, the BSI ratio was 1.84 with arteriovenous graft (P=.029), 4.85 with permanent central venous catheter (P<.001), and 14.88 with temporary catheter (P <.001). Catheter related were 41 episodes (28%). Gram positive organism were responsible for 96 episodes (65%), with S. aureus ( 55%) the most frequent, followed by S. epidermidis (26%) and Gram-negative for 36 (23%), with E. coli (39%) the most frequent. Infection was polymicrobial in 14 (9.5%). Diabetes (p<0.001), low serum albumin (p=0.040) and low hemoglobin (p<0.001) were significant risk factors. During hospitalization 18 patients (18%) died. Septic shock (p<0.001) and polymicrobial infection (p=0.041) were associated with in-hospital mortality. Conclusion: The risk of BSI in patients undergoing hemodialysis is related to the catheter type and vascular access. Septic shock and polymicrobial infection predispose to unfavourable outcome.

The role of serum magnesium and calcium on the association between adiponectin levels and all-cause mortality in end-stage renal disease patients.

Background Adiponectin (ADPN) is the most abundant adipocyte-specific cytokine that plays an important role in energy homeostasis by regulating lipid and glucose metabolism. Studies of the impact of ADPN on clinical outcomes have yielded contradictory results so far. Here, we examined the association of ADPN with serum magnesium (s-Mg) and calcium (s-Ca) levels and explored the possibility whether these two factors could modify the relationship between ADPN and all-cause mortality in patients with end-stage renal disease. Methodology/Principal Findings After baseline assessment, 47 hemodialysis and 27 peritoneal dialysis patients were followed- up for a median period of 50 months. S-Mg and s-Ca levels emerged as positive and negative predictors of ADPN levels, respectively. During the follow-up period 18 deaths occurred. There was a significant 4% increased risk for all-cause mortality for each 1-µg/ml increment of ADPN (crude HR, 1.04; 95% CI, 1.01–1.07), even after adjustment for s-Mg and s-Ca levels, dialysis mode, age, albumin and C-reactive protein. Cox analysis stratified by s-Mg levels (below and above the median value of 2.45 mg/dl) and s-Ca levels (below and above the median value of 9.3 mg/dl), revealed ADPN as an independent predictor of total mortality only in the low s-Mg and high s-Ca groups. Furthermore, low s-Mg and high s-Ca levels were independently associated with malnutrition, inflammation, arterial stiffening and risk of death. Conclusions/Significance The predictive value of ADPN in all-cause mortality in end-stage renal disease patients appears to be critically dependent on s-Mg and s-Ca levels. Conversely, s-Mg and s-Ca may impact on clinical outcomes by directly modifying the ADPN’s bioactivity.

Acute Renal Failure, Translocational Hyponatremia and Hyperkalemia following Intravenous Immunoglobulin Therapy

Background/Aims: Intravenous immunoglobulin (IVIG) therapy has been associated with renal adverse effects and electrolyte disturbances. Methods: We retrospectively evaluated a cohort of 66 unselected patients with idiopathic thrombocytopenic purpura, who received 140 courses of IVIG therapy. Acute renal failure (ARF), hyponatremia and hyperkalemia, as potential complications of IVIG therapy, were assessed from 100 IVIG courses with sufficient data for analysis. Results: Thirteen out of 100 (13%) IVIG courses in 10 (15%) patients were complicated with ARF. Risk factors included advanced age, pre-existing renal impairment, use of diuretics and the presence of diabetes mellitus. All patients recovered renal function 1–2 weeks after IVIG infusion. Serum sodium (sNa) fell by 5.7 and 2.7 mmol/l (p < 0.01) in patients with and without ARF, respectively. Correspondingly, serum potassium increased by 0.7 and 0.23 mmol/l (p < 0.01). There was a strong inverse correlation (r = –0.308; p < 0.01) between changes in sNa and creatinine. Changes in serum potassium could be independently predicted by changes in both sNa and creatinine (R2 = 0.11; p < 0.01). These data suggested that both hyponatremia and hyperkalemia were (a) due to the translocational effect of the osmotic load of sucrose, and (b) largely depended on the extent of IVIG nephropathy. Conclusion: In our series, ARF attributable to IVIG therapy, although not rare, was usually mild and fully reversible. High-risk patients were more susceptible to IVIG-related renal complications. Translocational hyponatremia and hyperkalemia following IVIG therapy, although unimportant in patients with normal renal function, may be of clinical significance in patients with severely compromised renal function, resulting in impaired sucrose excretion.

X-linked Alport syndrome in Hellenic families: phenotypic heterogeneity and mutations near interruptions of the collagen domain in COL4A5.

Demosthenous P, Voskarides K, Stylianou K, Hadjigavriel M, Arsali M, Patsias C, Georgaki E, Zirogiannis P, Stavrou C, Daphnis E, Pierides A, Deltas C, Hellenic Nephrogenetics Research Consortium. X‐linked Alport syndrome in Hellenic families: Phenotypic heterogeneity and mutations near interruptions of the collagen domain in COL4A5.

Arterial Stiffness Alterations during Hemodialysis: The Role of Dialysate Calcium

Background/Aims: We investigated the way dialysate calcium (dCa) level can influence arterial stiffness (AS), measured by stiffness index (SI), a surrogate of pulse wave velocity, and reflection index (RI), a measure of the amount of pulse wave reflection, derived by digital volume pulse (DVP). Methods: Fourteen hemodialysis (HD) patients underwent two consecutive midweek 4-hour HD treatments in randomized order with a low dCa concentration of 1.25 mmol/l (LdCa) and a high dCa concentration of 1.75 mmol/l (HdCa), respectively. Before HD and at 1-hour intervals during the subsequent 4-hour HD sessions, SI and RI measurements were obtained from DVP contour analysis. Blood pressure (BP) and heart rate (HR) were measured after each measurement of AS. Ionized serum calcium (iCa) was measured before HD and at 120 and 240 min into the HD session. Results: iCa increased and decreased by 15.3 and 5.4% in the HdCa and LdCa groups, respectively, at the end of HD. SI and RI increased by 5.7 and 6% in the HdCa group, respectively, whereas they remained unchanged in the LdCa group. The treatment effect and the time × treatment effect were significant for both indices (ANOVA). BP and HR changes did not differ between treatments. Conclusion: Contrary to LdCa, HdCa treatment induced a BP-independent, significant increase in measured AS parameters. In the long run, HD with LdCa, by reducing the incidence of HD-induced hypercalcemia, may have a beneficial role in minimizing the cardiovascular risk related to the intermittent, intradialytic increase in AS, inherent in the chronic use of HdCa.

Long-term complication rates and survival of peritoneal dialysis catheters: the role of percutaneous versus surgical placement.

Considerable controversy currently exists in the literature concerning the mode of catheter placement and its impact on the technical success of peritoneal dialysis (PD). We decided to compare the impact of the surgical versus the percutaneous insertion technique on peritoneal dialysis catheter (PDCs) complications and survival. Our study population comprised 152 patients in whom 170 PDCs were inserted between January 1990 and December 2007 at the main PD unit on the island of Crete. Eighty four catheters were surgically placed (S group) and 86 were placed percutaneously by nephrologists (N group). The total experience accumulated was 4997 patient‐months. The overall complications did not differ between the two groups. Only early leakage was more frequent in N group than S group (10.3 versus 1.9 episodes per 1000 patient‐months; p < 0.001). However, it was easily treated and did not constitute a cause of early catheter removal. Catheter survival was 91.1%, 80.7%, and 73.2%, in the S group versus 89.5%, 83.7%, and 83.7% for the N group at 1, 2, and 3 years, respectively (p = 0.2). Catheter survival has significantly increased over the last decade. Factors positively affecting PDC survival appeared to be the use of mupirocin for exit site care and the utilization of the coiled type of catheter, practices implemented mainly after 1999. Peritonitis‐free survival and patient survival were not associated with the mode of placement, while in Cox regression analysis, were longer in patients treated with automated PD. The placement mode did not affect PD outcomes. Percutaneous implantation proved a safe, simple, low cost, immediately available method for PDC placement and helped to expand our PD program.