Homocysteine-lowering therapy in renal disease

Hyperhomocysteinemia is a potential risk factor for vascular disease and is associated with endothelial dysfunction, a predictor of adverse cardiovascular events. Renal patients (end-stage renal failure (ESRF) and transplant recipients (RTR)) exhibit both hyperhomocysteinemia and endothelial dysfunction with increasing evidence of a causative link between the 2 conditions. The elevated homocysteine appears to be due to altered metabolism in the kidney (intrarenal) and in the uremic circulation ( extrarenal). This review will discuss 18 supplementation studies conducted in ESRF and 6 in RTR investigating the effects of nutritional therapy to lower homocysteine. The clinical significance of lowering homocysteine in renal patients will be discussed with data on the effects of B vitamin supplementation on cardiovascular outcomes such as endothelial function presented. Folic acid is the most effective nutritional therapy to lower homocysteine. In ESRF patients, supplementation with folic acid over a wide dose range ( 2 - 20 mg/day) either individually or in combination with other B vitamins will decrease but not normalize homocysteine. In contrast, in RTR similar doses of folic acid normalizes homocysteine. Folic acid improves endothelial function in ESRF patients, however this has yet to be investigated in RTR. Homocysteine-lowering therapy is more effective in ESRF patients than RTR.

Effects of cigarette smoking and exposure to cadmium and lead on phenotypic variability of hepatic CYP2A6 and renal function biomarkers in men

Effects of cigarette smoking and exposure to dietary cadmium (Cd) and lead (Pb) on urinary biomarkers of renal function and phenotypic variability of cytochrome P450 2A6 (CYP2A6) were investigated in a group of 96 healthy Thai men with mean age of 36.7 year (19-57 years). In non-smokers, Cd burden increased with age (r = 0.47, P < 0.001). In current smokers, Cd burden increased with both age (r = 0.45, P = 0.01) and number of cigarettes smoked per day (r = 0.32, P = 0.05). Cd-linked renal tubular dysfunction was seen in both smokers and non-smokers, but Pb-linked glomerular dysfunction was seen in smokers only, possibly due to more recent exposure to high levels of Cd and Pb, as reflected by 30-50% higher serum Cd and Pb levels in smokers than non-smokers (P < 0.05). Exposure to dietary Cd and Pb appeared to be associated with mild tubular dysfunction whereas dietary exposure plus cigarette smoking was associated with tubular plus glomerular dysfunction. Hepatic CYP2A6 activity in non-smokers showed a positive association with Cd burden (adjusted P = 0.38, P = 0.006), but it showed an inverse correlation with Pb (adjusted beta = -0.29, P = 0.003), suggesting opposing effects of Cd and Pb on hepatic CYP2A6 phenotype. In contrast, CYP2A6 activity in current smokers did not correlate with Cd or Pb, but it showed a positive correlation with serum ferritin levels (r = 0.45, P = 0.01). These finding suggest that Pb concentrations in the liver probably were too low to inhibit hepatic synthesis of heme and CYP2A6 and that the concurrent induction of hepatic CYP2A6 and ferritin was probably due to cigarette smoke constituents other than the Cd and Pb. (C) 2004 Elsevier Ireland Ltd. All rights reserved.

Renal and hepatic accumulation of cadmium and lead in the expression of CYP4F2 and CYP2E1

The present study examined accumulation of the metal toxins cadmium (Cd) and lead (Pb) in relation to the abundance of cytochrome P450 4F2 (CYP4F2), CYP2E1 and concentrations of zinc and copper in liver and kidney samples using immunoblotting coupled with metal analysis. The post mortem liver and kidney cortex samples were from 23 males and 8 females aged 3-89 years. All were Caucasians who had not been exposed to metals in the workplace. Average kidney cortex Cd load of 17.4 mu g/g w.w. was 17 times greater than average liver Cd load (1.1 mu g/g w.w.). In contrast, average kidney cortex Ph load of 0.09 mu g/g w.w. was two times lower than liver Pb load of 0.19 mu g/g w.w. Average Zn and Cu concentrations in the kidney cortex samples were 67% and 33% lower than those in the liver. Liver and kidney Cd loads, but not liver or kidney Ph loads, correlated positively with donors' age. After controlling for liver Cd load, an inverse correlation was seen between Zn and age (partial r = -0.39, P = 0.02), suggesting reduction in liver Zn levels in old age. Liver CYP2E1 protein abundance correlated with age-adjusted Cd load (partial r = 0.37, P = 0.02) whereas kidney CYP4172 protein abundance showed a positive correlation with age-adjusted Cd loads (partial r = 0.40, P = 0.02). These findings suggest that Cd may be an inducer of renal CYP4172 and hepatic CYP2E1 and that increased renal CYP4172 expression may implicate in Cd-linked renal tubular dysfunction and high blood pressure, involving CYP4F2-dependent arachidonic acid metabolism. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

Kidney dysfunction and hypertension: Role for cadmium, P450 and heme oxygenases?

Cadmium (Cd) is a metal toxin of continuing worldwide concern. Daily intake of Cd, albeit in small quantities, is associated with a number of adverse health effects which are attributable to distinct pathological changes in a variety of tissues and organs. In the present review, we focus on its renal tubular effects in people who have been exposed environmentally to Cd at levels below the provisional tolerable intake level set for the toxin. We highlight the data linking such low-level Cd intake with tubular injury, altered abundance of cytochromes P450 (CYPs) in the kidney and an expression of a hypertensive phenotype. We provide updated knowledge on renal and vascular effects of the eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and eicosatrienoic acids (EETs), which are biologically active metabolites from arachidonate metabolism mediated by certain CYPs in the kidney. We note the ability of Cd to elicit oxidative stress and to alter metal homeostasis notably of zinc which may lead to augmentation of the defense mechanisms involving induction of the antioxidant enzyme heme oxygenase-1 (HO-1) and the metal binding protein metallothionein (MT) in the kidney. We hypothesize that renal Cd accumulation triggers the host responses mediated by HO-I and MT in an attempt to protect the kidney against injurious oxidative stress and to resist a rise in blood pressure levels. This hypothesis predicts that individuals with less active HO-1 (caused by the HO-1 genetic polymorphisms) are more likely to have renal injury and express a hypertensive phenotype following chronic ingestion of low-level Cd, compared with those having more active HO-1. Future analytical and molecular epidemiologic research should pave the way to the utility of induction of heme oxygenases together with dietary antioxidants in reducing the risk of kidney injury and hypertension in susceptible people.

Folate supplementation fails to affect vascular function and carotid artery intima media thickness in cyclosporin A-treated renal transplant recipients

Background: Cyclosporin A (CsA)-treated renal transplant recipients (RTR) exhibit relative hyperhomocystinemia and vascular dysfunction. Folate supplementation lowers homocysteine and has been shown to improve vascular function in healthy subjects and patients with coronary artery disease. The aim of this study was to assess the effects of 3 months of folate supplementation (5 mg/day) on vascular function and structure in RTR. Methods: A double-blind, placebo-controlled crossover study was conducted in 10 CsA-treated RTR. Vascular structure was measured as carotid artery intima media thickness (IMT) and function was assessed as changes in brachial artery diameter during reactive hyperemia (RE) and in response to glyceryl trinitrate (GTN). Function data were analyzed as absolute and percent change from baseline and area under the diameter/time curve. Blood samples were collected before and after supplementation and analyzed for total plasma homocysteine, folate, vitamin B-12 and asymmetric dimethyl arginine (ADMA) in addition to regular measures of hemoglobin, hematocrit, mean corpuscular volume (MCV) and serum creatinine. Results: Folate supplementation significantly increased plasma folate by 687% (p < 0.005) and decreased homocysteine by 37% (p < 0.05) with no changes (p > 0.05) in vitamin B 12 or ADMA. There were no significant (p > 0.05) changes in vascular structure or function during the placebo or the folate supplementation phases; IMT; placebo pre mean +/- SD, 0.52 +/- 0.12, post 0.50 +/- 0.11; folate pre 0.55 +/- 0.17, post 0.49 +/- 10.20 mm 5% change in brachial artery diameter (RH, placebo pre 10 +/- 8, post 6 +/- 5; folate pre 9 +/- 7, post 7 +/- 5; GTN, placebo pre 18 +/- 10, post 17 +/- 9, folate pre 16 +/- 9, post-supplementation 18 +/- 8). Conclusion: Three months of folate supplementation decreases plasma homocysteine but has no effect on endothelial function or carotid artery IMT in RTR.

Effect of remote ischaemic preconditioning in cardiac dysfunction and end-organ injury following cardiac surgery with cardiopulmonary bypass in children: A translational approach investigating clinical outcome and myocardial molecular biology

Congenital heart disease (CHD) is the most common birth defect, causing an important rate of morbidity and mortality. Treatment of CHD requires surgical correction in a significant percentage of cases which exposes patients to cardiac and end organ injury. Cardiac surgical procedures often require the utilisation of cardiopulmonary bypass (CPB), a system that replaces heart and lungs function by diverting circulation into an external circuit. The use of CPB can initiate potent inflammatory responses, in addition a proportion of procedures require a period of aortic cross clamp during which the heart is rendered ischaemic and is exposed to injury. High O2 concentrations are used during cardiac procedures and when circulation is re-established to the heart which had adjusted metabolically to ischaemia, further injury is caused in a process known as ischaemic reperfusion injury (IRI). Several strategies are in place in order to protect the heart during surgery, however injury is still caused, having detrimental effects in patients at short and long term. Remote ischaemic preconditioning (RIPC) is a technique proposed as a potential cardioprotective measure. It consists of exposing a remote tissue bed to brief episodes of ischaemia prior to surgery in order to activate protective pathways that would act during CPB, ischaemia and reperfusion. This study aimed to assess RIPC in paediatric patients requiring CHD surgical correction with a translational approach, integrating clinical outcome, marker analysis, cardiac function parameters and molecular mechanisms within the cardiac tissue. A prospective, single blinded, randomized, controlled trial was conducted applying a RIPC protocol to randomised patients through episodes of limb ischaemia on the day before surgery which was repeated right before the surgery started, after anaesthesia induction. Blood samples were obtained before surgery and at three post-operative time points from venous lines, additional pre and post-bypass blood samples were obtained from the right atrium. Myocardial tissue was resected during the ischaemic period of surgery. Echocardiographic images were obtained before the surgery started after anaesthetic induction and the day after surgery, images were stored for later off line analysis. PICU surveillance data was collected including ventilation parameters, inotrope use, standard laboratory analysis and six hourly blood gas analysis. Pre and post-operative quantitation of markers in blood specimens included cardiac troponin I (cTnI) and B-type natriuretic peptide (BNP), inflammatory mediators including interleukins IL-6, IL-8, IL-10, tumour necrosis factor (TNF-α), and the adhesion molecules ICAM-1 and VCAM-1; the renal marker Cystatin C and the cardiovascular markers asymmetric dymethylarginine (ADMA) and symmetric dymethylarginine (SDMA). Nitric oxide (NO) metabolites and cyclic guanosine monophosphate (cGMP) were measured before and after bypass. Myocardial tissue was processed at baseline and after incubation at hyperoxic concentration during four hours in order to mimic surgical conditions. Expression of genes involved in IRI and RIPC pathways was analysed including heat shock proteins (HSPs), toll like receptors (TLRs), transcription factors nuclear factor κ-B (NF- κ-B) and hypoxia inducible factor 1 (HIF-1). The participation of hydrogen sulfide enzymatic genes, apelin and its receptor were explored. There was no significant difference according to group allocation in any of the echocardiographic parameters. There was a tendency for higher cTnI values and inotropic score in control patients post-operatively, however this was not statistically significant. BNP presented no significant difference according to group allocation. Inflammatory parameters tended to be higher in the control group, however only TNF- α was significantly higher. There was no difference in levels of Cystatin C, NO metabolites, cGMP, ADMA or SDMA. RIPC patients required shorter PICU stay, all other clinical and laboratory analysis presented no difference related to the intervention. Gene expression analysis revealed interesting patterns before and after incubation. HSP-60 presented a lower expression at baseline in tissue corresponding to RIPC patients, no other differences were found. This study provided with valuable descriptive information on previously known and newly explored parameters in the study population. Demographic characteristics and the presence of cyanosis before surgery influenced patterns of activity in several parameters, numerous indicators were linked to the degree of injury suffered by the myocardium. RIPC did not reduce markers of cardiac injury or improved echocardiographic parameters and it did not have an effect on end organ function; some effects were seen in inflammatory responses and gene expression analysis. Nevertheless, an important clinical outcome indicator, PICU length of stay was reduced suggesting benefit from the intervention. Larger studies with more statistical power could determine if the tendency of lower injury and inflammatory markers linked to RIPC is real. The present results mostly support findings of larger multicentre trials which have reported no cardiac benefit from RIPC in paediatric cardiac surgery.

Renal and cardiovascular effects of Bothrops marajoensis venom and phospholipase A(2)

Bothrops marajoensis is found in the savannah of Marajo Island in the State of Par S and regions of Amapa State, Brazil. The aim of the work was to study the renal and cardiovascular effects of the B. marajoensis venom and phospholipase A(2) (PLA(2)). The venom was fractionated by Protein Pack 5PW. N-terminal amino acid sequencing of sPLA(2) showed amino acid identity with other lysine K49sPLA(2)s of snake venom. B. marajoensis venom (30 mu g/mL) decreased the perfusion pressure, renal vascular resistance, urinary flow, glomerular filtration rate and sodium tubular transport. PLA(2) did not change the renal parameters. The perfusion pressure of the mesenteric bed did not change after infusion of venom. In isolated heart, the venom decreased the force of contraction and increased PP but did not change coronary flow. In the arterial pressure, the venom and PLA(2) decreased mean arterial pressure and cardiac frequency. The presence of atrial flutter and late hyperpolarisation reversed, indicating QRS complex arrhythmia and dysfunction in atrial conduction. In conclusion, B. marajoensis venom and PLA(2) induce hypotension and bradycardia while simultaneously blocking electrical conduction in the heart. Moreover, the decrease in glomerular filtration rate, urinary flow and electrolyte transport demonstrates physiological changes to the renal system. (C) 2009 Elsevier Ltd. All rights reserved.

Impaired Incretin Secretion And Pancreatic Dysfunction With Older Age And Diabetes.

To estimate the impact of aging and diabetes on insulin sensitivity, beta-cell function, adipocytokines, and incretin production. Hyperglycemic clamps, arginine tests and meal tolerance tests were performed in 50 non-obese subjects to measure insulin sensitivity (IS) and insulin secretion as well as plasma levels of glucagon, GLP-1 and GIP. Patients with diabetes and healthy control subjects were divided into the following groups: middle-aged type 2 diabetes (MA-DM), aged Type 2 diabetes (A-DM) and middle-aged or aged subjects with normal glucose tolerance (MA-NGT or A-NGT). IS, as determined by the homeostasis model assessment, glucose infusion rate, and oral glucose insulin sensitivity, was reduced in the aged and DM groups compared with MA-NGT, but it was similar in the MA-DM and A-DM groups. Insulinogenic index, first and second phase insulin secretion and the disposition indices, but not insulin response to arginine, were reduced in the aged and DM groups. Postprandial glucagon production was higher in MA-DM compared to MA-NGT. Whereas the GLP-1 production was reduced in A-DM, no differences between groups were observed in GIP production. In non-obese subjects, diabetes and aging impair insulin sensitivity. Insulin production is reduced by aging, and diabetes exacerbates this condition. Aging associated defects superimposed diabetic physiopathology, particularly regarding GLP-1 production. On the other hand, the glucose-independent secretion of insulin was preserved. Knowledge of the complex relationship between aging and diabetes could support the development of physiopathological and pharmacological based therapies.

The Effect Of Pelvic Floor Muscle Training Alone Or In Combination With Electrostimulation In The Treatment Of Sexual Dysfunction In Women With Multiple Sclerosis.

Sexual dysfunction (SD) affects up to 80% of multiple sclerosis (MS) patients and pelvic floor muscles (PFMs) play an important role in the sexual function of these patients. The objective of this paper is to evaluate the impact of a rehabilitation program to treat lower urinary tract symptoms on SD of women with MS. Thirty MS women were randomly allocated to one of three groups: pelvic floor muscle training (PFMT) with electromyographic (EMG) biofeedback and sham neuromuscular electrostimulation (NMES) (Group I), PFMT with EMG biofeedback and intravaginal NMES (Group II), and PFMT with EMG biofeedback and transcutaneous tibial nerve stimulation (TTNS) (Group III). Assessments, before and after the treatment, included: PFM function, PFM tone, flexibility of the vaginal opening and ability to relax the PFMs, and the Female Sexual Function Index (FSFI) questionnaire. After treatment, all groups showed improvements in all domains of the PERFECT scheme. PFM tone and flexibility of the vaginal opening was lower after the intervention only for Group II. All groups improved in arousal, lubrication, satisfaction and total score domains of the FSFI questionnaire. This study indicates that PFMT alone or in combination with intravaginal NMES or TTNS contributes to the improvement of SD.

Blockade Of Renin-angiotensin System Prevents Micturition Dysfunction In Renovascular Hypertensive Rats.

Association between hypertension and bladder symptoms has been described. We hypothesized that micturition dysfunction may be associated with renin-angiotensin system (RAS) acting in urethra. The effects of the anti-hypertensive drugs losartan (AT1 antagonist) and captopril (angiotensin-converting enzyme inhibitor) in comparison with atenolol (β1-adrenoceptor antagonist independently of RAS blockade) have been investigated in bladder and urethral dysfunctions during renovascular hypertension in rats. Two kidney-1 clip (2K-1C) rats were treated with losartan (30 mg/kg/day), captopril (50mg/kg/day) or atenolol (90 mg/kg/day) for eight weeks. Cystometric study, bladder and urethra smooth muscle reactivities, measurement of cAMP levels and p38 MAPK phosphorylation in urinary tract were determined. Losartan and captopril markedly reduced blood pressure in 2K-1C rats. The increases in non-voiding contractions, voiding frequency and bladder capacity in 2K-1C rats were prevented by treatments with both drugs. Likewise, losartan and captopril prevented the enhanced bladder contractions to electrical-field stimulation (EFS) and carbachol, along with the impaired relaxations to β-adrenergic-cAMP stimulation. Enhanced neurogenic contractions and impaired nitrergic relaxations were observed in urethra from 2K-1C rats. Angiotensin II also produced greater urethral contractions that were accompanied by higher phosphorylation of p38 MAPK in urethral tissues of 2K-1C rats. Losartan and captopril normalized the urethral dysfunctions in 2K-1C rats. In contrast, atenolol treatment largely reduced the blood pressure in 2K-1C rats but failed to affect the urinary tract smooth muscle dysfunction. The urinary tract smooth muscle dysfunction in 2K-1C rats takes place by local RAS activation irrespective of levels of arterial blood pressure.

Temporomandibular Dysfunction Post-craniotomy: Evaluation Between Pre- And Post-operative Status.

To identify risk factors associated with post-operative temporomandibular joint dysfunction after craniotomy. The study sample included 24 patients, mean age of 37.3 ± 10 years; eligible for surgery for refractory epilepsy, evaluated according to RDC/TMD before and after surgery. The primary predictor was the time after the surgery. The primary outcome variable was maximal mouth opening. Other outcome variables were: disc displacement, bruxism, TMJ sound, TMJ pain, and pain associated to mandibular movements. Data analyses were performed using bivariate and multiple regression methods. The maximal mouth opening was significantly reduced after surgery in all patients (p = 0.03). In the multiple regression model, time of evaluation and pre-operative bruxism were significantly (p < .05) associated with an increased risk for TMD post-surgery. A significant correlation between surgery follow-up time and maximal opening mouth was found. Pre-operative bruxism was associated with increased risk for temporomandibular joint dysfunction after craniotomy.

Urinary Tract Infection In Renal Transplant Recipients: Incidence, Risk Factors, And Impact On Graft Function.

Urinary tract infection (UTI) is the most common infection posttransplant. However, the risk factors for and the impact of UTIs remain controversial. The aim of this study was to identify the incidence of posttransplant UTIs in a series of renal transplant recipients from deceased donors. Secondary objectives were to identify: (1) the most frequent infectious agents; (2) risk factors related to donor; (3) risk factors related to recipients; and (4) impact of UTI on graft function. This was a retrospective analysis of medical records from renal transplant patients from January to December 2010. Local ethics committee approved the protocol. The incidence of UTI in this series was 34.2%. Risk factors for UTI were older age, (independent of gender), biopsy-proven acute rejection episodes, and kidneys from deceased donors (United Network for Organ Sharing criteria). For female patients, the number of pretransplant pregnancies was an additional risk factor. Recurrent UTI was observed in 44% of patients from the UTI group. The most common infectious agents were Escherichia coli and Klebsiella pneumoniae, for both isolated and recurrent UTI. No difference in renal graft function or immunosuppressive therapy was observed between groups after the 1-year follow-up. In this series, older age, previous pregnancy, kidneys from expanded criteria donors, and biopsy-proven acute rejection episodes were risk factors for posttransplant UTI. Recurrence of UTI was observed in 44%, with no negative impact on graft function or survival.

Taurine Supplementation Reduces Blood Pressure And Prevents Endothelial Dysfunction And Oxidative Stress In Post-weaning Protein-restricted Rats.

Taurine is a sulfur-containing amino acid that exerts protective effects on vascular function and structure in several models of cardiovascular diseases through its antioxidant and anti-inflammatory properties. Early protein malnutrition reprograms the cardiovascular system and is linked to hypertension in adulthood. This study assessed the effects of taurine supplementation in vascular alterations induced by protein restriction in post-weaning rats. Weaned male Wistar rats were fed normal- (12%, NP) or low-protein (6%, LP) diets for 90 days. Half of the NP and LP rats concomitantly received 2.5% taurine supplementation in the drinking water (NPT and LPT, respectively). LP rats showed elevated systolic, diastolic and mean arterial blood pressure versus NP rats; taurine supplementation partially prevented this increase. There was a reduced relaxation response to acetylcholine in isolated thoracic aortic rings from the LP group that was reversed by superoxide dismutase (SOD) or apocynin incubation. Protein expression of p47phox NADPH oxidase subunit was enhanced, whereas extracellular (EC)-SOD and endothelial nitric oxide synthase phosphorylation at Ser 1177 (p-eNOS) were reduced in aortas from LP rats. Furthermore, ROS production was enhanced while acetylcholine-induced NO release was reduced in aortas from the LP group. Taurine supplementation improved the relaxation response to acetylcholine and eNOS-derived NO production, increased EC-SOD and p-eNOS protein expression, as well as reduced ROS generation and p47phox expression in the aortas from LPT rats. LP rats showed an increased aortic wall/lumen ratio and taurine prevented this remodeling through a reduction in wall media thickness. Our data indicate a protective role of taurine supplementation on the high blood pressure, endothelial dysfunction and vascular remodeling induced by post-weaning protein restriction. The beneficial vascular effect of taurine was associated with restoration of vascular redox homeostasis and improvement of NO bioavailability.

Reduced Plasma Angiotensin Ii Levels Are Reversed By Hydroxyurea Treatment In Mice With Sickle Cell Disease.

Sickle cell disease (SCD) pathogenesis leads to recurrent vaso-occlusive and hemolytic processes, causing numerous clinical complications including renal damage. As vasoconstrictive mechanisms may be enhanced in SCD, due to endothelial dysfunction and vasoactive protein production, we aimed to determine whether the expression of proteins of the renin-angiotensin system (RAS) may be altered in an animal model of SCD. Plasma angiotensin II (Ang II) was measured in C57BL/6 (WT) mice and mice with SCD by ELISA, while quantitative PCR was used to compare the expressions of the genes encoding the angiotensin-II-receptors 1 and 2 (AT1R and AT2R) and the angiotensin-converting enzymes (ACE1 and ACE2) in the kidneys, hearts, livers and brains of mice. The effects of hydroxyurea (HU; 50-75mg/kg/day, 4weeks) treatment on these parameters were also determined. Plasma Ang II was significantly diminished in SCD mice, compared with WT mice, in association with decreased AT1R and ACE1 expressions in SCD mice kidneys. Treatment of SCD mice with HU reduced leukocyte and platelet counts and increased plasma Ang II to levels similar to those of WT mice. HU also increased AT1R and ACE2 gene expression in the kidney and heart. Results indicate an imbalanced RAS in an SCD mouse model; HU therapy may be able to restore some RAS parameters in these mice. Further investigations regarding Ang II production and the RAS in human SCD may be warranted, as such changes may reflect or contribute to renal damage and alterations in blood pressure.