Correlation between serum carnosinase concentration and renal damage in diabetic nephropathy patients.

Diabetic nephropathy (DN) is one of the major complications of diabetes and contributes significantly towards end-stage renal disease. Previous studies have identified the gene encoding carnosinase (CN-1) as a predisposing factor for DN. Despite this fact, the relationship of the level of serum CN-1 and the progression of DN remains uninvestigated. Thus, the proposed study focused on clarifying the relationship among serum CN-1, indicators of renal function and tissue injury, and the progression of DN. A total of 14 patients with minimal changes disease (MCD) and 37 patients with DN were enrolled in the study. Additionally, 20 healthy volunteers were recruited as control. Further, DN patients were classified according to urinary albumin excretion rate into two groups: DN with microalbuminuria (n = 11) and DN with macroalbuminuria (n = 26). Clinical indicators including urinary protein components, serum carnosine concentration, serum CN-1 concentration and activity, and renal biopsy tissue injury indexes were included for analyzation. The serum CN-1 concentration and activity were observed to be the highest, but the serum carnosine concentration was the lowest in DN macroalbuminuria group. Moreover, within DN group, the concentration of serum CN-1 was positively correlated with uric acid (UA, r = 0.376, p = 0.026) and serum creatinine (SCr, r = 0.399, p = 0.018) and negatively correlated with serum albumin (Alb, r = - 0.348, p = 0.041) and estimated glomerular filtration rate (eGRF, r = - 0.432, p = 0.010). Furthermore, the concentration of serum CN-1 was discovered to be positively correlated with indicators including 24-h urinary protein-creatinine ratio (24 h-U-PRO/CRE, r = 0.528, p = 0.001), urinary albumin-to-creatinine ratio (Alb/CRE, r = 0.671, p = 0.000), urinary transferrin (TRF, r = 0.658, p = 0.000), retinol-binding protein (RBP, r = 0.523, p = 0.001), N-acetyl-glycosaminidase (NAG, r = 0.381, p = 0.024), immunoglobulin G (IgG, r = 0.522, p = 0.001), cystatin C (Cys-C, r = 0.539, p = 0.001), beta-2-microglobulin (ß2-MG, r = 0.437, p = 0.009), and alpha-1-macroglobulin (α1-MG, r = 0.480, p = 0.004). Besides, in DN with macroalbuminuria group, serum CN-1 also showed a positive correlation with indicators of fibrosis, oxidative stress, and renal tubular injury. Taken together, our data suggested that the level of CN-1 was increased as clinical DN progressed. Thus, the level of serum CN-1 might be an important character during the occurrence and progression of DN. Our study will contribute significantly to future studies focused on dissecting the underlying mechanism of DN.

Hypoxia-Inducible Factor Stabilizers in End Stage Kidney Disease: "Can the Promise Be Kept?"

Anemia is a common complication of chronic kidney disease (CKD). The prevalence of anemia in CKD strongly increases as the estimated Glomerular Filtration Rate (eGFR) decreases. The pathophysiology of anemia in CKD is complex. The main causes are erythropoietin (EPO) deficiency and functional iron deficiency (FID). The administration of injectable preparations of recombinant erythropoiesis-stimulating agents (ESAs), especially epoetin and darbepoetin, coupled with oral or intravenous(iv) iron supplementation, is the current treatment for anemia in CKD for both dialysis and non-dialysis patients. This approach reduces patients' dependence on transfusion, ensuring the achievement of optimal hemoglobin target levels. However, there is still no evidence that treating anemia with ESAs can significantly reduce the risk of cardiovascular events. Meanwhile, iv iron supplementation causes an increased risk of allergic reactions, gastrointestinal side effects, infection, and cardiovascular events. Currently, there are no studies defining the best strategy for using ESAs to minimize possible risks. One class of agents under evaluation, known as prolyl hydroxylase inhibitors (PHIs), acts to stabilize hypoxia-inducible factor (HIF) by inhibiting prolyl hydroxylase (PH) enzymes. Several randomized controlled trials showed that HIF-PHIs are almost comparable to ESAs. In the era of personalized medicine, it is possible to envisage and investigate specific contexts of the application of HIF stabilizers based on the individual risk profile and mechanism of action.

Proprotein convertase subtilisin/kexin type 9 and mortality in patients starting hemodialysis.

BACKGROUND: Cardiovascular events are the leading cause of death in end stage renal disease (ESRD), but traditional markers of dyslipidemia are not clearly associated with cardiovascular risk in this population. Proprotein Convertase Subtilsin/Kexin type 9 (PCSK-9) could be of interest as a novel cardiovascular risk marker in ESRD due to the emergence of lipid lowering therapy based on PCSK-9 inhibition. The aim of the present study was to investigate if the convertase PCSK-9 is a potential risk marker for mortality among patients starting haemodialysis treatment. MATERIALS AND METHODS: This is a cohort study of 265 patients starting haemodialysis between 1991-2009, with 3 years follow-up. The association between baseline PCSK-9 levels and mortality was assessed using Cox proportional hazards- and quantile regression models, with adjustment for potential confounders. RESULTS: PCSK-9 levels at initiation of haemodialysis were associated to mortality in multivariable adjusted analysis. PCSK-9 levels exhibited an U-shaped association to mortality. Inclusion of the quadratic term of PCSK-9 in regression modelling optimized model performance. At baseline, PCSK-9 levels had positive correlations to Davies comorbidity score, haemoglobin and C-reactive protein while negative correlations were found for high-density lipoprotein and total cholesterol. PCSK-9 levels were higher in statin users and patients with a history of cardiovascular disease. CONCLUSIONS: This study shows, for the first time, that the level of PCSK-9 is associated with all-cause mortality in haemodialysis patients, independently of a number of potential confounders.

Free circulating active elastase contributes to chronic inflammation in patients on hemodialysis.

Atherosclerosis and cardiovascular complications are prevalent among patients undergoing chronic hemodialysis (HD). In this population, peripheral polymorphonuclear leukocytes (PMNLs) are primed, releasing proinflammatory mediators such as elastase. Elastase is normally inhibited by a specific inhibitor, avoiding undesirable degradation of cellular and extracellular components. This study tested the hypothesis that in states of noninfectious inflammation, elastase is released by PMNLs and acts in an uncontrolled manner to inflict vascular damage. Blood was collected from patients undergoing HD and healthy controls (HC). PMNL intracellular and surface expressions of elastase were determined by quantitative real-time PCR, Western blotting, and flow cytometry. The elastase activity was evaluated using a fluorescent substrate. The levels of serum α1-antitrypsin (α1-AT), the natural elastase inhibitor, were determined by Western blot. Free active elastase was elevated in HD sera, whereas the levels of α1-AT were decreased compared with HC. The levels of the intracellular elastase enzyme and its activity were lower in HD PMNLs despite similar expression levels of elastase mRNA. Elastase binding to PMNL cell surface was higher in HD compared with HC. The increased circulating levels of free active elastase released from primed HD PMNLs together with the higher cell surface-bound enzymes and the lower levels of α1-AT result in the higher elastase activity in HD sera. This exacerbated elastase activity could lead to the endothelial dysfunction, as hypothesized. In addition, it suggests that free circulating elastase can serve as a new biomarker and therapeutic target to reduce inflammation and vascular complications in patients on hemodialysis.

Identification of a novel loss-of-function mutation of the GLA gene in a Chinese Han family with Fabry disease.

BACKGROUND: Fabry disease is an X-linked recessive lysosomal disorder caused by deficient enzymatic activity of α-galactosidase A (α-Gal A). The insufficient enzymatic activity leads to excessive accumulation of glycosphingolipids, the substrates of the enzyme, in lysosomes in organs and tissues. Mutations in the α-Gal A gene (GLA, Xq22) have been proven to be responsible for Fabry disease. METHODS: In this study, we report a four-generation pedigree with left ventricular hypertrophy and chronic renal failure that was diagnosed by sequencing the GLA gene. An over expression system was constructed to evaluate the function of the detected mutation. RESULTS: We identified a novel mutation in exon 6 of the GLA gene, p.Asn278Lys, which completely co-segregated with the disease phenotype. The protein level of α-Gal A was significantly lower in the variant group than in the wild-type group; additionally, the pharmacological chaperone 1-deoxy-galactonojirimycin (DGJ) effectively normalized the enzyme activity of α-Gal A and its decline at the protein level. CONCLUSIONS: This study is the first to report a novel loss-of-function mutation, p.Asn278Lys, in exon 6 of the GLA gene as a genetic aetiology for Fabry disease. In addition, we analysed the feasibility of DGJ as a therapeutic approach for this particular GLA mutation.

Microsomal Prostaglandin E Synthase-1-Derived PGE2 Inhibits Vascular Smooth Muscle Cell Calcification.

OBJECTIVE: Chronic administration of selective cyclooxygenase-2 (COX-2) inhibitors leads to an increased risk of adverse cardiovascular events, including myocardial infarction and stroke. Vascular smooth muscle cell (VSMC) calcification, a common complication of chronic kidney disease, is directly related to cardiovascular morbidity and mortality. Here, we tested whether specific COX-2 inhibition affects vascular calcification during chronic renal failure. APPROACH AND RESULTS: The COX-2-specific inhibitors NS398 and SC236 significantly increased high-phosphate (Pi)-induced VSMC calcification. Similarly, COX-2(-/-) VSMCs, COX-2(-/-) aortas rings treated with high Pi and adenine diet-induced COX-2(-/-) chronic renal failure mice displayed enhanced calcium deposition. Metabolomic analysis revealed the differential suppression of PGE2 production by COX-1- and COX-2-specific inhibitors in high-Pi-stimulated VSMCs, indicating the involvement of PGE2 during COX-2 inhibition-aggravated vascular calcification. Indeed, exogenous PGE2 reduced alkaline phosphatase activity, osteogenic transdifferentiation, apoptosis, and calcification of VSMCs. In accordance, downregulation of microsomal prostaglandin E synthase (mPGES)-1 in VSMCs, mPGES-1(-/-) aorta with high-Pi stimulation and mPGES-1(-/-) chronic renal failure mice resulted in enhanced vascular mineralization. Further applications of RNAi and specific antagonists for PGE2 receptors indicated EP4 may mediate PGE2-inhibited vascular calcification. CONCLUSIONS: Our data revealed the pivotal role of COX-2-mPGES-1-PGE2 axis in vascular calcification. The selective inhibition of COX-2 or mPGES-1 may increase the risk of calcification and subsequent adverse cardiovascular events during chronic renal failure.

Selective cathepsin S inhibition attenuates atherosclerosis in apolipoprotein E-deficient mice with chronic renal disease.

Chronic renal disease (CRD) accelerates the development of atherosclerosis. The potent protease cathepsin S cleaves elastin and generates bioactive elastin peptides, thus promoting vascular inflammation and calcification. We hypothesized that selective cathepsin S inhibition attenuates atherogenesis in hypercholesterolemic mice with CRD. CRD was induced by 5/6 nephrectomy in high-fat high-cholesterol fed apolipoprotein E-deficient mice. CRD mice received a diet admixed with 6.6 or 60 mg/kg of the potent and selective cathepsin S inhibitor RO5444101 or a control diet. CRD mice had significantly higher plasma levels of osteopontin, osteocalcin, and osteoprotegerin (204%, 148%, and 55%, respectively; P < 0.05), which were inhibited by RO5444101 (60%, 40%, and 36%, respectively; P < 0.05). Near-infrared fluorescence molecular imaging revealed a significant reduction in cathepsin activity in treated mice. RO5444101 decreased osteogenic activity. Histologic assessment in atherosclerotic plaque demonstrated that RO5444101 reduced immunoreactive cathepsin S (P < 0.05), elastin degradation (P = 0.01), plaque size (P = 0.01), macrophage accumulation (P < 0.01), growth differentiation factor-15 (P = 0.0001), and calcification (alkaline phosphatase activity, P < 0.01; osteocalcin, P < 0.05). Furthermore, cathepsin S inhibitor or siRNA significantly decreased expression of growth differentiation factor-15 and monocyte chemotactic protein-1 in a murine macrophage cell line and human primary macrophages. Systemic inhibition of cathepsin S attenuates the progression of atherosclerotic lesions in 5/6 nephrectomized mice, serving as a potential treatment for atherosclerosis in patients with CRD.

Effects of Chronic Renal Failure on Brain Cytochrome P450 in Rats.

Chronic renal failure (CRF) impedes renal excretion of drugs and their metabolism by reducing the expression of liver cytochrome P450 (P450). Uremic serum contains factors, such as parathyroid hormone (PTH), that decrease liver P450s. The P450s are also involved in the metabolism of xenobiotics in the brain. This study investigates: 1) the effects of CRF on rat brain P450, 2) the role of PTH in the downregulation of brain P450s in CRF rats, and 3) the effects of PTH on P450s in astrocytes. Protein and mRNA expression of P450s were assessed in the brain of CRF and control (CTL) rats, as well as from CTL or CRF rats that underwent parathyroidectomy (PTX) 1 week before nephrectomy. CYP3A activity was measured using 3-[(3, 4-difluorobenzyl) oxy]-5, 5-dimethyl-4-[4-methylsulfonyl) phenyl] furan-2(5H)-1 metabolism in brain microsomal preparation. CYP3A protein expression was assessed in primary cultured astrocytes incubated with serum obtained from CRF or CTL rats or with PTH. Significant downregulations (≥40%) of CYP1A, CYP2C11, and CYP3A proteins were observed in microsomes from CRF rat brains. CYP3A activity reduction was also observed. CYP3A expression and activity were unaffected in PTX-pretreated CRF rats. Serum of PTX-treated CRF rats had no impact on CYP3A levels in astrocytes compared with that of untreated CRF rats. Finally, PTH addition to normal calf serum induced a reduction in CYP3A protein similar to CRF serum, suggesting that CRF-induced hyperparathyroidism is associated with a significant decrease in P450 drug-metabolizing enzymes in the brain, which may have implications in drug response.

The angiotensin-I converting enzyme gene I/D variation contributes to end-stage renal disease risk in Chinese patients with type 2 diabetes receiving hemodialysis.

Whether the DD genotype of the angiotensin-I converting enzyme (ACE) I/D variation contributes to end-stage renal disease (ESRD) risk in type 2 diabetes mellitus (T2DM) remains controversial. Differences in study design, case and control definition, sample size and ethnicity may contribute to the discrepancies reported in association studies. We performed a case-control study to evaluate the association of the ACE I/D variation with ESRD risk in Chinese patients with T2DM receiving hemodialysis and analyzed the genotype-phenotype interaction. Unrelated Chinese patients (n = 432) were classified into the non-diabetic nephropathy (DN) control group (n = 222, duration of diabetes >10 years, no signs of renal involvement) and the DN-ESRD group (n = 210; ESRD due to T2DM, receiving hemodialysis). Polymerase chain reaction was used to genotype ACE I/D for all 432 subjects. The frequencies of the ID + DD genotypes were higher in the DN-ESRD group than non-DN control group (65.2 vs. 50.9 %; adjusted OR 1.98 (95 % CI, 1.31-3.00; P = 0.001). In the DN-ESRD group, the DD genotypic subgroup had significantly elevated HbA1c and diastolic blood pressure (DBP) compared to the II subgroup (both P < 0.05). The DD genotype of the ACE I/D variation may be associated with more elevated blood pressure and HbA1c, and therefore may predict the development, progression and severity of DN-ESRD in Chinese patients with T2DM undergoing hemodialysis.

Association of aspartate aminotransferase with mortality in hemodialysis patients.

BACKGROUND: Liver disease is a common comorbid condition in maintenance hemodialysis (MHD) patients and may be associated with poor survival. The relationship between aspartate aminotransferase (AST) and survival has not yet been addressed in these patients. We hypothesized that higher AST level is associated with higher death risk in MHD patients. METHODS: A 5-year (January 2007-December 2011) cohort of 109 718 MHD patients was studied in the USA in dialysis clinics where AST was measured in at least 50% of all outpatients in the baseline calendar quarter. Survival models were adjusted for demographic variables, and available clinical and laboratory surrogates of malnutrition-inflammation complex, and cubic survival splines were plotted. RESULTS: A linear association existed between baseline serum AST levels and mortality. Increasing AST of >20 IU/L was incrementally and almost linearly associated with higher death risk at all levels of adjustment. In fully adjusted models, AST levels of ≥40 IU/L were associated with the highest risk of mortality (hazard ratio: 1.46, 95% CI: 1.38-1.54). Low AST levels (<15 IU/L) were associated with increased death risk only in fully adjusted models examining hepatitis C virus-positive patients. CONCLUSIONS: Higher AST level of >20 IU/L is incrementally associated with higher mortality in MHD patients whereas AST in the 15-20 IU/L range is associated with the greatest survival. These findings suggest that the assessment of liver function and improving liver disease may confer survival benefit to MHD patients.

Na+-H+ exchanger-1 (NHE1) regulation in kidney proximal tubule.

The ubiquitously expressed plasma membrane Na(+)-H(+) exchanger NHE1 is a 12 transmembrane-spanning protein that directs important cell functions such as homeostatic intracellular volume and pH control. The 315 amino acid cytosolic tail of NHE1 binds plasma membrane phospholipids and multiple proteins that regulate additional, ion-translocation independent functions. This review focuses on NHE1 structure/function relationships, as well as the role of NHE1 in kidney proximal tubule functions, including pH regulation, vectorial Na(+) transport, cell volume control and cell survival. The implications of these functions are particularly critical in the setting of progressive, albuminuric kidney diseases, where the accumulation of reabsorbed fatty acids leads to disruption of NHE1-membrane phospholipid interactions and tubular atrophy, which is a poor prognostic factor for progression to end stage renal disease. This review amplifies the vital role of the proximal tubule NHE1 Na(+)-H(+) exchanger as a kidney cell survival factor.

Dialysis Modalities and HDL Composition and Function.

Lipid abnormalities may have an effect on clinical outcomes of patients on dialysis. Recent studies have indicated that HDL dysfunction is a hallmark of ESRD. In this study, we compared HDL composition and metrics of HDL functionality in patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) with those in healthy controls. We detected a marked suppression of several metrics of HDL functionality in patients on HD or PD. Compositional analysis revealed that HDL from both dialysis groups shifted toward a more proinflammatory phenotype with profound alterations in the lipid moiety and protein composition. With regard to function, cholesterol efflux and anti-inflammatory and antiapoptotic functions seemed to be more severely suppressed in patients on HD, whereas HDL-associated paraoxonase activity was lowest in patients on PD. Quantification of enzyme activities involved in HDL metabolism suggested that HDL particle maturation and remodeling are altered in patients on HD or PD. In summary, our study provides mechanistic insights into the formation of dysfunctional HDL in patients with ESRD who are on HD or PD.

Mammalian target of rapamycin signaling inhibition ameliorates vascular calcification via Klotho upregulation.

Vascular calcification (VC) is a major risk factor for cardiovascular mortality in chronic renal failure (CRF) patients, but the pathogenesis remains partially unknown and effective therapeutic targets should be urgently explored. Here we pursued the therapeutic role of rapamycin in CRF-related VC. Mammalian target of rapamycin (mTOR) signal was activated in the aortic wall of CRF rats. As expected, oral rapamycin administration significantly reduced VC by inhibiting mTOR in rats with CRF. Further in vitro results showed that activation of mTOR by both pharmacological agent and genetic method promoted, while inhibition of mTOR reduced, inorganic phosphate-induced vascular smooth muscle cell (VSMC) calcification and chondrogenic/osteogenic gene expression, which were independent of autophagy and apoptosis. Interestingly, the expression of Klotho, an antiaging gene that suppresses VC, was reduced in calcified vasculature, whereas rapamycin reversed membrane and secreted Klotho decline through mTOR inhibition. When mTOR signaling was enhanced by either mTOR overexpression or deletion of tuberous sclerosis 1, Klotho mRNA was further decreased in phosphate-treated VSMCs, suggesting a vital association between mTOR signaling and Klotho expression. More importantly, rapamycin failed to reduce VC in the absence of Klotho by using either siRNA knockdown of Klotho or Klotho knockout mice. Thus, Klotho has a critical role in mediating the observed decrease in calcification by rapamycin in vitro and in vivo.

Impact of physiological, pathological and environmental factors on the expression and activity of human cytochrome P450 2D6 and implications in precision medicine.

With only 1.3-4.3% in total hepatic CYP content, human CYP2D6 can metabolize more than 160 drugs. It is a highly polymorphic enzyme and subject to marked inhibition by a number of drugs, causing a large interindividual variability in drug clearance and drug response and drug-drug interactions. The expression and activity of CYP2D6 are regulated by a number of physiological, pathological and environmental factors at transcriptional, post-transcriptional, translational and epigenetic levels. DNA hypermethylation and histone modifications can repress the expression of CYP2D6. Hepatocyte nuclear factor-4α binds to a directly repeated element in the promoter of CYP2D6 and thus regulates the expression of CYP2D6. Small heterodimer partner represses hepatocyte nuclear factor-4α-mediated transactivation of CYP2D6. GW4064, a farnesoid X receptor agonist, decreases hepatic CYP2D6 expression and activity while increasing small heterodimer partner expression and its recruitment to the CYP2D6 promoter. The genotypes are key determinants of interindividual variability in CYP2D6 expression and activity. Recent genome-wide association studies have identified a large number of genes that can regulate CYP2D6. Pregnancy induces CYP2D6 via unknown mechanisms. Renal or liver diseases, smoking and alcohol use have minor to moderate effects only on CYP2D6 activity. Unlike CYP1 and 3 and other CYP2 members, CYP2D6 is resistant to typical inducers such as rifampin, phenobarbital and dexamethasone. Post-translational modifications such as phosphorylation of CYP2D6 Ser135 have been observed, but the functional impact is unknown. Further functional and validation studies are needed to clarify the role of nuclear receptors, epigenetic factors and other factors in the regulation of CYP2D6.

Decreased nuclear receptor activity and epigenetic modulation associates with down-regulation of hepatic drug-metabolizing enzymes in chronic kidney disease.

Patients with chronic kidney disease (CKD) require many medications. CYP2C and CYP3A drug-metabolizing enzymes play a critical role in determining the pharmacokinetics of the majority of prescribed medications. These enzymes are transcriptionally regulated by the nuclear receptors pregnane X receptor (PXR) and hepatic nuclear factor 4α (HNF-4α). Expression of CYP2C and CYP3A is decreased in CKD; however, the mechanisms by which this occurs is unknown. We induced CKD in rats by 5/6 nephrectomy and used chromatin immunoprecipitation (ChIP) to determine nuclear receptor- and epigenetic alteration-mediated differences in the promoter region of the CYP2C and CYP3A genes. RNA polymerase II and HNF-4α binding was decreased 76 and 57% in the CYP2C11 promotor and 71 and 77% in the CYP3A2 promoter, respectively (P<0.05). ChIP also revealed a 57% decrease in PXR binding to the CYP3A2 promoter in CKD rats (P<0.05). The decrease in PXR and HNF-4α binding was accompanied by diminished histone 4 acetylation in the CYP3A2 promoter (48%) and histone 3 acetylation in the CYP2C11 (77%) and CYP3A2 (77%) promoter loci for nuclear receptor activation (P<0.05). This study suggests that decreased nuclear receptor binding and histone acetylation may contribute to the mechanism of drug-metabolizing enzyme down-regulation and altered pharmacokinetics in CKD.

CYP3A5 polymorphism affects the increase in CYP3A activity after living kidney transplantation in patients with end stage renal disease.

AIMS: It has been reported that cytochrome P450 (CYP)3A activity increases significantly in patients with end stage renal disease (ESRD) after kidney transplantation, with wide interindividual variability in the degree of increase. The aim of this study was to evaluate the influence of CYP3A5 polymorphism on the increase in CYP3A activity after living kidney transplantation, by measuring the plasma concentration of 4ß-hydroxycholesterol. METHODS: This prospective study recruited 22 patients with ESRD who underwent a first living kidney allograft transplantation, comprising 12 patients with CYP3A5*1 allele (CYP3A5*1/*1 or *1/*3) and 10 patients without CYP3A5*1 allele (CYP3A5*3/*3). RESULTS: No significant difference in estimated glomerular filtration rate over time was observed between patients with the CYP3A5*1 allele and patients without the CYP3A5*1 allele, suggesting that the degrees of recovery in renal function after living kidney transplantation were similar in the two groups. However, plasma concentrations of 4ß-hydroxycholesterol on days 90 (57.1 ± 13.4 vs. 39.5 ± 10.8 ng ml(-1)) and 180 (55.0 ± 14.5 vs. 42.4 ± 12.6 ng ml(-1)) after living kidney transplantation were significantly higher in the presence of the CYP3A5*1 allele than in the absence of the CYP3A5*1 allele [P = 0.0034 (95% confidence interval of difference 6.55, 28.6) and P = 0.043 (95% confidence interval of difference 0.47, 24.8), respectively], suggesting that CYP3A activity may increase markedly associated with recovery of renal function in patients with the CYP3A5*1 allele. CONCLUSIONS: These findings suggest that the presence of the CYP3A5*1 allele contributes to marked elevation of CYP3A activity associated with recovery of renal function after kidney transplantation.

Chronic hypercalcaemia from inactivating mutations of vitamin D 24-hydroxylase (CYP24A1): implications for mineral metabolism changes in chronic renal failure.

BACKGROUND: Loss-of-function mutations of vitamin D-24 hydroxylase have recently been recognized as a cause of hypercalcaemia and nephrocalcinosis/nephrolithiasis in infants and adults. True prevalence and natural history of this condition are still to be defined. METHODS: We describe two adult patients with homozygous mutations and six related heterozygous carriers. Mineral and hormonal data in these patients were compared with that in 27 patients with stage 2-3 chronic kidney disease and 39 healthy adult kidney donors. RESULTS: Probands had recurrent nephrolithiasis, chronic hypercalcaemia with depressed parathyroid hormone (PTH) and increased 1,25(OH)(2)D levels; carriers had nephrolithiasis (two of six), hypercalciuria (two of six) and high or normal-high 1,25(OH)(2)D (four of four). Corticosteroids did not reduce plasma and urine calcium levels, but ketoconazole did, indicating that 1,25(OH)(2)D production is not maximally depressed despite coexisting hypercalcaemia, high 1,25(OH)(2)D and depressed PTH, and that 1,25(OH)(2)D degradation through vitamin D-24 hydroxylase is a regulator of plasma 1,25(OH)(2)D levels. Both probands had vascular calcifications and high bone mineral content. One developed stage 3b renal failure: in this patient 1,25(OH)(2)D decreased within normal limits as glomerular filtration rate (GFR) fell and PTH rose to high-normal values, yet hypercalcaemia persisted and the ratio of 1,25(OH)(2)D to GFR remained higher than normal for any degree of GFR. CONCLUSIONS: This natural model indicates that vitamin D-24 hydroxylase is a key physiologic regulator of calcitriol and plasma calcium levels, and that balanced reduction of 1,25(OH)(2)D and GFR is instrumental for the maintenance of physiologic calcium levels and balance in chronic kidney diseases.

Activation of mTOR contributes to foam cell formation in the radial arteries of patients with end-stage renal disease.

BACKGROUND: Our previous in-vivo and in-vitro studies demonstrated that inflammation accelerated the progression of atherosclerosis via the dysregulation of the low-density lipoprotein receptor (LDLr) pathway. The current study aimed to investigate the effects and their underlying mechanisms of inflammation on lipid accumulation in the radial arteries of endstage renal disease (ESRD) patients with arteriovenostomy. METHODS: 30 ESRD patients with arteriovenostomy were included. The patients were divided into two groups based on their plasma levels of C-reactive protein: a control (n = 16) and an inflamed group (n = 14). The expression of tumor necrosis factor-alpha (TNF-alpha) and monocyte chemotactic protein-1 of the radial arteries were increased in the inflamed group. Foam cell formation and lipid droplet accumulation were examined by hematoxylin and eosin (H & E) and Oil Red O staining. Intracellular cholesterol trafficking-related proteins were examined by immunohistochemistry and immunofluorescent staining. RESULTS: There was significant lipid accumulation in the radial arteries of the inflamed group compared with the control. Further analysis demonstrated that this accumulation was correlated with the increased protein expression of LDLr, sterol regulatory element-binding protein-2 (SREBP-2), and SREBP cleavageactivating protein (SCAP). Confocal microscopy showed that inflammation enhanced the translocation of SCAP escorting SREBP-2 from the endoplasmic reticulum to the Golgi, thereby activating LDLr gene transcription. Interestingly, upregulated LDLr expression was positively associated with the increased protein expression of mammalian target of rapamycin (mTOR), which had enhanced coexpression with SREBP-2. This finding suggests that the activation of mTOR may be involved in LDLr pathway disruption through the upregulation of SREBP-2 expression. CONCLUSION: Inflammation contributed to foam cell formation in the radial arteries of ESRD patients via the dysregulation of the LDLr pathway, which could be modulated by the activation of the mTOR pathway.

Effects of endothelial nitric oxide synthase gene on end stage renal disease progression in autosomal dominant polycystic kidney disease.

AIM: To investigate whether endothelial nitric oxide synthase (eNOS) gene associate with the progression of autosomal dominant polycystic kidney disease (ADPKD). METHODS: Databases of EMBASE, Pubmed, ISI, Ovid Database, Cochrane library and China National Knowledge Infrastructure were all searched. Associated studies about eNOS polymorphisms and ADPKD were analyzed by meta-analysis. RESULTS: A total of 11 studies with Glu298Asp and 4b/a polymorphisms were included. A allele of the 4b/a polymorphism increased the risk of end stage renal disease (ESRD) in ADPKD (odds ratio (OR) = 1.85, 95% confidence interval (CI) 1.17-2.94, P = 0.009). However, GG phenotype of Glu298Asp polymorphism neither decreased the ESRD risk (OR = 0.77, 95% CI 0.55-1.08, P = 0.13) nor affected the hypertension risk (OR = 1.04, 95% CI 0.66-1.66, P = 0.86). The GG phenotype carriers had later ESRD age compared with the T allele of Glu298Asp polymorphism (WMD = 2.39; 95% CI 1.32-3.46; P < 0.0001). Significant association was also found in Caucasians (WMD = 2.41; 95% CI 1.18-3.64; P = 0.0001). Subgroup analysis by gender indicated GG genotype carriers had older age of ESRD than T allele carriers in males (WMD = 4.51; 95% CI 3.95-5.08; P = 0.00001), but not in females. CONCLUSIONS: GG genotype of the Glu298Asp variant slowed the ESRD progression in ADPKD, while a allele carriers of the 4b/a variant increased the risk of ESRD. Variants of eNOS gene might play different roles in the ESRD progression in ADPKD.

Significant increase in plasma 4ß-hydroxycholesterol concentration in patients after kidney transplantation.

Several previous studies have shown that renal failure decreases not only renal elimination but also metabolic clearance of drugs, particularly those metabolized by CYP3A. However, whether recovery of renal function results in recovery of hepatic CYP3A activity remains unknown. In this study, we evaluated the effect of renal function on CYP3A activity after kidney transplantation in patients with end-stage renal disease (ESRD) by measuring the change in CYP3A activity using plasma concentration of 4ß-hydroxycholesterol as a biomarker. The study enrolled 13 patients with ESRD who underwent the first kidney allograft transplantation. Morning blood samples were collected before and 3, 7, 10, 14, 21, 30, 60, 90, 120, 150 and 180 days after kidney transplantation. Plasma concentration of 4ß-hydroxycholesterol was measured using GC-MS. Compared with before kidney transplantation, creatinine clearance increased significantly from day 3 after kidney transplantation and stabilized thereafter. Plasma concentration of 4ß-hydroxycholesterol was elevated significantly on days 90 and 180 after kidney transplantation. In conclusion, this study suggests the recovery of CYP3A activity with improvement in renal function after kidney transplantation in patients with ESRD.