Higher Risk of Many Physical Health Conditions in Sexual Minority Men: Comprehensive Systematic Review and Meta-Analysis in Gay- and Bisexual-Identified Compared with Heterosexual-Identified Men

Purpose: The purpose of this study was to provide a systematic review and, where possible, meta-analysis on the prevalence of physical health conditions in sexual minority men (SMM, i.e., gay- and bisexual-identified men) compared with heterosexual-identified men. Methods: A systematic literature search in the databases MEDLINE, Embase, CENTRAL, CINAHL, and Web of Science was conducted on epidemiological studies on physical health conditions, classified in the Global Burden of Disease project and published between 2000 and 2021. Meta-analyses comparing odds ratios were calculated. Results: In total, 23,649 abstracts were screened, and 32 studies were included in the systematic review. Main findings were that (1) Largest differences in prevalence by sexual identity were found for chronic respiratory diseases, particularly asthma: overall, SMM were significantly almost 50% more likely to suffer from asthma than heterosexual men. (2) Evidence of higher prevalence was also found for chronic kidney diseases and headache disorders in gay men and for hepatitis B/C in both gay and bisexual men. (3) We found an overall trend that bisexual men were more affected by some of the physical health conditions compared with gay men (e.g., cardiovascular diseases, asthma). However, regarding cancer, headache disorders, and hepatitis, gay men were more affected. Conclusion: We found evidence of physical health disparities by sexual identity, suggesting more health issues in SMM. Since some of these findings rely on few comparisons or small samples of SMM only, this review is intended to be a vehement plea for routinely including sexual identity assessment in health research and clinical practice.

Dihydromyricetin ameliorates vascular calcification in chronic kidney disease by targeting AKT signaling

Vascular calcification is highly prevalent in chronic kidney disease (CKD), and is characterized by transdifferentiation from contractile vascular smooth muscle cells (VSMCs) into an osteogenic phenotype. However, no effective and therapeutic option to prevent vascular calcification is yet available. Dihydromyricetin (DMY), a bioactive flavonoid isolated from Ampelopsis grossedentata, has been found to inhibit VSMCs proliferation and the injury-induced neointimal formation. However, whether DMY has an effect on osteogenic differentiation of VSMCs and vascular calcification is still unclear. In the present study, we sought to investigate the effect of DMY on vascular calcification in CKD and the underlying mechanism. DMY treatment significantly attenuated calcium/phosphate-induced calcification of rat and human VSMCs in a dose-dependent manner, as shown by Alizarin Red S staining and calcium content assay, associated with down-regulation of osteogenic markers including type I collagen (COL I), Runt-related transcription factor 2 (RUNX2), bone morphogenetic protein 2 (BMP2) and osteocalcin (OCN). These results were further confirmed in aortic rings ex vivo. Moreover, DMY ameliorated vascular calcification in rats with CKD. Additionally, we found that AKT signaling was activated during vascular calcification, whereas significantly inhibited by DMY administration. DMY treatment significantly reversed AKT activator-induced vascular calcification. Furthermore, inhibition of AKT signaling efficiently attenuated calcification, which was similar to that after treatment with DMY alone, and DMY had a better inhibitory effect on calcification as compared with AKT inhibitor. The present study demonstrated that DMY has a potent inhibitory role in vascular calcification partially by inhibiting AKT activation, suggesting that DMY may act as a promising therapeutic candidate for patients suffering from vascular calcification.

Indoleamine 2,3-dioxygenase-1, a Novel Therapeutic Target for Post-Vascular Injury Thrombosis in CKD

BACKGROUND

CKD, characterized by retained uremic solutes, is a strong and independent risk factor for thrombosis after vascular procedures . Urem ic solutes such as indoxyl sulfate (IS) and kynurenine (Kyn) mediate prothrombotic effect through tissue factor (TF). IS and Kyn biogenesis depends on multiple enzymes, with therapeutic implications unexplored. We examined the role of indoleamine 2,3-dioxygenase-1 (IDO-1), a rate-limiting enzyme of kynurenine biogenesis, in CKD-associated thrombosis after vascular injury.

METHODS

IDO-1 expression in mice and human vessels was examined. IDO-1-/- mice, IDO-1 inhibitors, an adenine-induced CKD, and carotid artery injury models were used.

RESULTS

Both global IDO-1-/- CKD mice and IDO-1 inhibitor in wild-type CKD mice showed reduced blood Kyn levels, TF expression in their arteries, and thrombogenicity compared with respective controls. Several advanced IDO-1 inhibitors downregulated TF expression in primary human aortic vascular smooth muscle cells specifically in response to uremic serum. Further mechanistic probing of arteries from an IS-specific mouse model, and CKD mice, showed upregulation of IDO-1 protein, which was due to inhibition of its polyubiquitination and degradation by IS in vascular smooth muscle cells. In two cohorts of patients with advanced CKD, blood IDO-1 activity was significantly higher in sera of study participants who subsequently developed thrombosis after endovascular interventions or vascular surgery.

CONCLUSION

Leveraging genetic and pharmacologic manipulation in experimental models and data from human studies implicate IS as an inducer of IDO-1 and a perpetuator of the thrombotic milieu and supports IDO-1 as an antithrombotic target in CKD.

Expression of lactate dehydrogenase A and B isoforms in the mouse kidney

Cellular metabolic rates in the kidney are critical for maintaining normal renal function. In a hypoxic milieu, cells rely on glycolysis to meet energy needs, resulting in the generation of pyruvate and NADH. In the absence of oxidative phosphorylation, the continuation of glycolysis is dependent on the regeneration of NAD+ from NADH accompanied by the fermentation of pyruvate to lactate. This reaction is catalyzed by lactate dehydrogenase (LDH) isoform A (LDHA), whereas LDH isoform B (LDHB) catalyzes the opposite reaction. LDH is widely used as a potential injury marker as it is released from damaged cells into the urine and serum; however, the precise isoform-specific cellular localization of the enzyme along the nephron has not been characterized. By combining immunohistochemistry results and single-cell RNA-sequencing data on healthy mouse kidneys, we identified that LDHA is primarily expressed in proximal segments, whereas LDHB is expressed in the distal parts of the nephron. In vitro experiments in mouse and human renal proximal tubule cells showed an increase in LDHA following hypoxia with no change in LDHB. Using immunofluorescence, we observed that the overall expression of both LDHA and LDHB proteins decreased following renal ischemia-reperfusion injury as well as in the adenine-diet-induced model of chronic kidney disease. Single-nucleus RNA-sequencing analyses of kidneys following ischemia-reperfusion injury revealed a significant decline in the number of cells expressing detectable levels of Ldha and Ldhb; however, cells that were positive showed increased average expression postinjury, which subsided during the recovery phase. These data provide information on the cell-specific expression of LDHA and LDHB in the normal kidney as well as following acute and chronic kidney disease.NEW & NOTEWORTHY Cellular release of lactate dehydrogenase (LDH) is being used as an injury marker; however, the exact localization of LDH within the nephron remains unclear. We show that LDH isoform A is expressed proximally, whereas isoform B is expressed distally. Both subunit expressions were significantly altered in models of acute kidney injury and chronic kidney disease. Our study provides new insights into basal and postinjury renal lactate metabolism.

Urinary DPP4 correlates with renal dysfunction, and DPP4 inhibition protects against the reduction in megalin and podocin expression in experimental CKD

This study investigated the molecular mechanisms underlying the antiproteinuric effect of DPP4 inhibition in 5/6 renal ablation rats and tested the hypothesis that the urinary activity of DPP4 correlates with chronic kidney disease (CKD) progression. Experiments were conducted in male Wistar rats who underwent 5/6 nephrectomy (Nx) or sham operation followed by 8 wk of treatment with the DPP4 inhibitor (DPP4i) sitagliptin or vehicle. Proteinuria increased progressively in Nx rats throughout the observation period. This increase was remarkably mitigated by sitagliptin. Higher levels of proteinuria in Nx rats compared to control rats were accompanied by higher urinary excretion of retinol-binding protein 4, a marker of tubular proteinuria, as well as higher urinary levels of podocin, a marker of glomerular proteinuria. Retinol-binding protein 4 and podocin were not detected in the urine of Nx + DPP4i rats. Tubular and glomerular proteinuria was associated with the reduced expression of megalin and podocin in the renal cortex of Nx rats. Sitagliptin treatment partially prevented this decrease. Besides, the angiotensin II renal content was significantly reduced in the Nx rats that received sitagliptin compared to vehicle-treated Nx rats. Interestingly, both urinary DPP4 activity and abundance increased progressively in Nx rats. Additionally, urinary DPP4 activity correlated positively with serum creatinine levels, proteinuria, and blood pressure. Collectively, these results suggest that DPP4 inhibition ameliorated both tubular and glomerular proteinuria and prevented the reduction of megalin and podocin expression in CKD rats. Furthermore, these findings suggest that urinary DPP4 activity may serve as a biomarker of renal disease and progression.

Aortic Aneurysms, Chronic Kidney Disease and Metalloproteinases

Metalloproteinases (MPs) are proteolytic enzymes involved in extracellular matrix deposition, regulation of cellular signals of inflammation, proliferation, and apoptosis. Metalloproteinases are classified into three families: Matrix-MPs (MMPs), A-Disintegrin-and-Metalloprotease (ADAMs), and the A-Disintegrin-and-Metalloproteinase-with-Thrombospondin-1-like-Domains (ADAMTS). Previous studies showed that MPs are involved in the development of aortic aneurysms (AA) and, concomitantly, in the onset of chronic kidney disease (CKD). CKD has been, per se, associated with an increased risk for AA. The aim of this review is to examine the pathways that may associate MPs with CKD and AA. Several MMPs, such as MMP-2, -8, -9, and TIMP-1 have been shown to damage the AA wall and to have a toxic effect on renal tubular cells, leading to fibrosis. Similarly, ADAM10 and 17 have been shown to degrade collagen in the AA wall and to worsen kidney function via pro-inflammatory stimuli, the impairment of the Renin-Angiotensin-Aldosterone System, and the degradation of structural proteins. Moreover, MMP-2 and -9 inhibitors reduced aneurysm growth and albuminuria in experimental and human studies. It would be important, in the future, to expand research on MPs from both a prognostic, namely, to refine risk stratification in CKD patients, and a predictive perspective, likely to improve prognosis in response to targeted treatments.

Pharmacological inhibition of Vanin-1 is not protective in models of acute and chronic kidney disease

Oxidative stress is a key concept in basic, translational, and clinical research to understand the pathophysiology of various disorders, including cardiovascular and renal diseases. Although attempts to directly reduce oxidative stress with redox-active substances have until now largely failed to prove clinical benefit, indirect approaches to combat oxidative stress enzymatically have gained further attention as potential therapeutic strategies. The pantetheinase Vanin-1 is expressed on kidney proximal tubular cells, and its reaction product cysteamine is described to negatively affect redox homeostasis by inhibiting the replenishment of cellular antioxidative glutathione stores. Vanin-1-deficient mice were shown to be protected against oxidative stress damage. The aim of this study was to elucidate whether pharmacological inhibition of Vanin-1 protects mice from oxidative stress-related acute or chronic kidney injury as well. By studying renal ischemia-reperfusion injury in Col4α3-/- (Alport syndrome) mice and in vitro hypoxia-reoxygenation in human proximal tubular cells we found that treatment with a selective and potent Vanin-1 inhibitor resulted in ample inhibition of enzymatic activity in vitro and in vivo. However, surrogate parameters of metabolic and redox homeostasis were only partially and insufficiently affected. Consequently, apoptosis and reactive oxygen species level in tubular cells as well as overall kidney function and fibrotic processes were not improved by Vanin-1 inhibition. We thus conclude that Vanin-1 functionality in the context of cardiovascular diseases needs further investigation and the biological relevance of pharmacological Vanin-1 inhibition for the treatment of kidney diseases remains to be proven.

Kidney ACE2 expression: Implications for chronic kidney disease

Angiotensin-converting enzyme 2 (ACE2) has been implicated in the pathogenesis of chronic kidney disease (CKD) and is a membrane receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease (COVID-19), whereas transmembrane protease, serine 2 (TMPRSS2) is involved in viral attachment. Together, tissue expression of ACE2 and TMPRSS2 may determine infection. Sex, age, body mass index (BMI), and CKD are clinical risk factors for COVID-19 severity, but the relationships between kidney ACE2 and TMPRSS2 expression and these clinical variables are unknown. Accordingly, we obtained renal tubulointerstitial and glomerular microarray expression data and clinical variables from healthy living donors (HLD) and patients with CKD from the European Renal cDNA Bank. ACE2 expression was similar in the tubulointerstitium of the two groups, but greater in females than males in HLD (P = 0.005) and CKD (P < 0.0001). ACE2 expression was lower in glomeruli of CKD patients compared to HLD (P = 0.0002) and lower in males than females. TMPRSS2 expression was similar in the tubulointerstitium but lower in glomeruli of CKD patients compared to HLD (P < 0.0001). There was a strong relationship between ACE2 and TMPRSS2 expression in the glomerulus (r = 0.51, P < 0.0001). In CKD, there was a relationship between tubulointerstitial ACE2 expression and estimated glomerular filtration rate (r = 0.36, P < 0.0001) and age (r = -0.17, P = 0.03), but no relationship with BMI. There were no relationships between TMPRSS2 expression and clinical variables. Genes involved in inflammation (CCL2, IL6, and TNF) and fibrosis (COL1A1, TGFB1, and FN1) were inversely correlated with ACE2 expression. In summary, kidney expression of ACE2 and TMPRSS2 differs in HLD and CKD. ACE2 is related to sex and eGFR. ACE2 is also associated with expression of genes implicated in inflammation and fibrosis.

Arylesterase activity but not PCSK9 levels is associated with chronic kidney disease in type 2 diabetes

PURPOSE

Oxidative stress and dyslipidemia have been found to be associated with the progression of chronic kidney disease (CKD) in type 2 diabetes mellitus (T2DM) patients. Paraoxonase 1 (PON-1) activity, and proprotein convertase subtilisin kexin type 9 (PCSK9) levels play an important role regarding anti-oxidants, and lipid metabolism, respectively. The aim of this study was to investigate the association of PON-1 activity, and PCSK9 levels with CKD in T2DM.

METHODS

A total of 180 T2DM (87 CKD, and 93 non-CKD) with age-, and gender-matched subjects were recruited in this study. PON-1 activity was measured with two kinds of substrate: paraoxon for paraoxonase (PONase) activity and phenylacetate for arylesterase (AREase) activity. PCSK9 levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

AREase activity was significantly lower in CKD compared with non-CKD (225.53 ± 108.73 vs. 257.45 ± 106.12 kU/L, p = 0.044) in T2DM, whereas there was no significant difference in PONase activity and PCSK9 levels between CKD and non-CKD groups. In addition, multivariate logistic regression analysis showed that the lowest tertile of AREase increased the risk for CKD in T2DM (OR 3.251; 95% CI 1.333-7.926, p = 0.010), whereas PONase activity and PCSK9 levels were not associated with CKD in T2DM.

CONCLUSION

Reduced AREase activity can increase the risk for CKD in T2DM patients. AREase activity, but not PONase activity and PCSK9 levels, may be used as the biomarker for predicting the progression of CKD in T2DM.

Comparison of Serum Amylase and Lipase Levels between Predialysis and Maintenance Haemodialysis CKD Patients

This cross sectional study was done to compare serum levels of amylase and lipase between predialysis and maintenance haemodialysis chronic kidney disease (CKD) patients and also to find out their relationship between degrees of renal impairment in Mymensingh Medical College Hospital and National Institute of Kidney Diseases and Urology, Dhaka, Bangladesh from May 2016 to April 2017. A total of 80 patients were included purposively as study subjects and made into two groups namely predialysis CKD group comprising 50 patients and other as maintenance haemodialysis group comprising of 30 patients. Among the predialysis group majority of the CKD was caused by glomerulonephritis (48%) followed by diabetes (26%), HTN (2%) and large portion undiagnosed (24%) whereas in the haemodialysis group ESRD was caused by diabetes (46%) followed by glomerulonephritis (16%), HTN (13%) and undiagnosed (23%). This study showed that mean serum amylase (158±718U/L vs. 111±41U/L) did not significantly differ between study groups except being above reference level but serum lipase (739±888U/L vs. 434±214U/L) was significantly higher in the predialysis group. There was a correlation between rising serum creatinine with serum amylase and lipase.

Identification of dicarbonyl and L-xylulose reductase as a therapeutic target in human chronic kidney disease

An imbalance of nephroprotective factors and renal damaging molecules contributes to development and progression of chronic kidney disease (CKD). We investigated associations of renoprotective factor gene expression patterns with CKD severity and outcome. Gene expression profiles of 197 previously reported renoprotective factors were analyzed in a discovery cohort in renal biopsies of 63 CKD patients. Downregulation of dicarbonyl and L-xylulose reductase (DCXR) showed the strongest association with disease progression. This significant association was validated in an independent set of 225 patients with nephrotic syndrome from the multicenter NEPTUNE cohort. Reduced expression of DCXR was significantly associated with degree of histological damage as well as with lower estimated glomerular filtration rate and increased urinary protein levels. DCXR downregulation in CKD was confirmed in 3 publicly available transcriptomics data sets in the context of CKD. Expression of DCXR showed positive correlations to enzymes that are involved in dicarbonyl stress detoxification based on transcriptomics profiles. The sodium glucose cotransporter-2 (SGLT2) inhibitors canagliflozin and empagliflozin showed a beneficial effect on renal proximal tubular cells under diabetic stimuli-enhanced DCXR gene expression. In summary, lower expression of the renoprotective factor DCXR in renal tissue is associated with more severe disease and worse outcome in human CKD.

Glutathione deficiency alters the vitamin D-metabolizing enzymes CYP27B1 and CYP24A1 in human renal proximal tubule epithelial cells and kidney of HFD-fed mice

Chronic kidney disease (CKD) is a worldwide public health problem with an estimated prevalence of 8.2%. This study reports glutathione deficiency, excess oxidative stress, and altered vitamin D metabolism in the kidney of mice fed a high-fat diet (HFD). The levels of GCLC and GCLM gene expression were significantly downregulated and the protein carbonylation level, a hallmark of oxidative damage, was significantly increased in the kidney of HFD-fed mice. While the levels of VD-regulatory genes 1-alpha-hydroxylase (CYP27B1), VDR, and RXRα were significantly downregulated in the kidney of mice fed a HFD, those of 24-hydroxylase (CYP24A1) were significantly elevated. In vitro, GSH deficiency per se causes excess oxidative damage (protein carbonylation), and significantly decreases the levels of VD-regulatory genes (CYP27B1, VDR, and RXRα), but increases levels of CYP24A1 in human renal proximal tubule epithelial cells (RPTEC), similar to findings in the kidney of HFD-fed diabetic mice. L-cysteine supplementation restores GSH and prevents oxidative damage in RPTEC. These studies suggest a potential role of GSH precursor in reducing excess oxidative stress and renal injury that commonly accompanies obesity/diabetes.

Glucocorticoid activation by 11β-hydroxysteroid dehydrogenase enzymes in relation to inflammation and glycaemic control in chronic kidney disease: A cross-sectional study

OBJECTIVE

Patients with chronic kidney disease (CKD) have dysregulated cortisol metabolism secondary to changes in 11β-hydroxysteroid dehydrogenase (11β-HSD) enzymes. The determinants of this and its clinical implications are poorly defined.

METHODS

We performed a cross-sectional study to characterize shifts in cortisol metabolism in relation to renal function, inflammation and glycaemic control. Systemic activation of cortisol by 11β-HSD was measured as the metabolite ratio (tetrahydrocortisol [THF]+5α-tetrahydrocortisol [5αTHF])/tetrahydrocortisone (THE) in urine.

RESULTS

The cohort included 342 participants with a median age of 63 years, median estimated glomerular filtration rate (eGFR) of 28 mL/min/1.73 m2 and median urine albumin-creatinine ratio of 35.5 mg/mmol. (THF+5αTHF)/THE correlated negatively with eGFR (Spearman's ρ = -0.116, P = 0.032) and positively with C-reactive protein (ρ = 0.208, P < 0.001). In multivariable analysis, C-reactive protein remained a significant independent predictor of (THF+5αTHF)/THE, but eGFR did not. Elevated (THF+5αTHF)/THE was associated with HbA1c (ρ = 0.144, P = 0.008) and diabetes mellitus (odds ratio for high vs low tertile of (THF+5αTHF)/THE 2.57, 95% confidence interval 1.47-4.47). Associations with diabetes mellitus and with HbA1c among the diabetic subgroup were independent of eGFR, C-reactive protein, age, sex and ethnicity.

CONCLUSIONS

In summary, glucocorticoid activation by 11β-HSD in our cohort comprising a spectrum of renal function was associated with inflammation and impaired glucose control.

Association between renal dysfunction and metalloproteinase (MMP)-9 activity in hypertensive patients

BACKGROUND AND OBJECTIVE

Matrix metalloproteinases (MMPs) are involved in deleterious tissue remodeling associated with target organ damage in renal disease. The aim of this study was to study the association between renal dysfunction and activity of the inflammatory metalloproteinase MMP-9 in hypertensive patients with mild-moderate chronic kidney disease (CKD).

MATERIAL AND METHODS

Plasmatic active MMP-9, total MMP-9, tissue inhibitor of MMP-9 (TIMP-1), MMP-9/TIMP-1 ratio and MMP-9-TIMP-1 interaction were analyzed in 37 hypertensive patients distributed by estimated glomerular filtration rate (eGFR) in 3 groups:>90, 90-60 y 60-30mL/min/1.73 m².

RESULTS

Total MMP-9 was not different as eGFR declines. TIMP-1 was significantly increased in hypertensive patients with eGFR 60-30mL/min/1.73 m² (P<.01 versus>90mL/min/1.73 m²). This relates to the significant decrease in the interaction between MMP-9-TIMP-1 observed in patients with eGFR 60-30mL/min/1.73 m² (P<.01 versus>90mL/min/1.73 m²). Despite the systemic elevation of TIMP-1, active MMP-9 was significantly increased in hypertensive patients with eGFR 60-30mL/min/1.73 m² (P<.05 and P<0.01 versus>90 and 90-60mL/min/1.73 m², respectively). TIMP-1, active MMP-9 and MMP-9-TIMP-1 interaction significantly correlate with the decline in renal function, which was not observed with total MMP-9.

CONCLUSIONS

The progression of CKD, even in stages where the decline of renal function is still moderate, is associated with an increase in MMP-9 activity, which could be considered as a potential therapeutic target.

[Value of serum alkaline phosphatase for predicting 2-year fracture in patients with chronic kidney disease on dialysis]

OBJECTIVE

To explore the value of baseline serum alkaline phosphatase (ALP) for predicting 2-year fracture in patients with chronic kidney disease (CKD) on maintenance dialysis.

METHODS

A total of 139 patients with CKD undergoing maintenance dialysis in our hospital were enrolled in this study. According to the median serum ALP level, the patients were divided into high ALP and low ALP groups. The demographic and clinical data of the patients including dialysis duration, serum calcium level, serum phosphorus level, and serum intact parathyroid hormone level were recorded, and their bone mineral density of the femur and the lumbar spine was measured using dual energy X-ray absorptiometry. The patients were followed up for 2 years and fracture events were recorded. The risk factors of fracture were analyzed using logistic regression analysis, and their predictive value for fracture was analyzed using receiver-operating characteristic (ROC) curve.

RESULTS

The mean baseline serum ALP level was 132.55±167.68 U/L in these patients, significantly higher than that in the normal population (t=2.816, P=0.006). Baseline serum ALP level was negatively correlated with the bone mineral density of the lumbar spine (r=-0.203, P=0.006) and the femur (r=-0.196, P=0.021). Fractures occurred in 21 (15.1%) of the patients during the 2-year follow-up, and the fracture rate was significantly higher in patients with high ALP levels. Logistic regression analysis identified serum ALP level as an independent risk factor of fracture (OR: 1.010, P=0.001, 95%CI: 1.004-1.016). The areas under the ROC curve were 0.900 and 0.768 for serum ALP level and intact parathyroid hormone level in predicting 2-year fractures, respectively.

CONCLUSIONS

Serum ALP may serve as a good indicator for predicting 2-year fractures in patients with CKD on maintenance dialysis.

Dietary tetrahydrocurcumin reduces renal fibrosis and cardiac hypertrophy in 5/6 nephrectomized rats

Tetrahydrocurcumin (THC) is the principal metabolite of curcumin and has antioxidant properties. In the present investigation, the effect of THC on renal and cardiovascular outcomes was studied in rats with chronic kidney disease (CKD). CKD rats were randomized following 5/6 nephrectomy to a special diet for 9 weeks which contained 1% THC (CKD+THC group). Low-dose polyenylphosphatidylcholine was used as a lipid carrier to increase bioavailability. Endpoints included tail blood pressure, normalized heart weight, plasma and urine biochemical data, and kidney tissue analyses. CKD animals demonstrated increased proteinuria, decreased creatinine clearance, hypertension, and cardiac hypertrophy. The antioxidant proteins CuZn SOD and glutathione peroxidase were decreased in the remnant kidney, while apoptosis (caspase-3) and fibrosis (alpha-SM actin) were increased. Renal fibrosis was confirmed histologically on trichrome staining. These pathologic changes were ameliorated in the CKD+THC group with significant decrease in proteinuria, hypertension, and kidney fibrosis. THC therapy restored levels of CuZn SOD and glutathione peroxidase. Consistent with prior reports, dietary THC did not improve nuclear Nrf2 levels. In summary, dietary THC therapy improved expression of antioxidant proteins in the remnant kidney, decreased renal fibrosis and proteinuria, and ameliorated hypertension in 5/6 nephrectomized rats.

Targeting STUB1-tissue factor axis normalizes hyperthrombotic uremic phenotype without increasing bleeding risk

Chronic kidney disease (CKD/uremia) remains vexing because it increases the risk of atherothrombosis and is also associated with bleeding complications on standard antithrombotic/antiplatelet therapies. Although the associations of indolic uremic solutes and vascular wall proteins [such as tissue factor (TF) and aryl hydrocarbon receptor (AHR)] are being defined, the specific mechanisms that drive the thrombotic and bleeding risks are not fully understood. We now present an indolic solute-specific animal model, which focuses on solute-protein interactions and shows that indolic solutes mediate the hyperthrombotic phenotype across all CKD stages in an AHR- and TF-dependent manner. We further demonstrate that AHR regulates TF through STIP1 homology and U-box-containing protein 1 (STUB1). As a ubiquitin ligase, STUB1 dynamically interacts with and degrades TF through ubiquitination in the uremic milieu. TF regulation by STUB1 is supported in humans by an inverse relationship of STUB1 and TF expression and reduced STUB1-TF interaction in uremic vessels. Genetic or pharmacological manipulation of STUB1 in vascular smooth muscle cells inhibited thrombosis in flow loops. STUB1 perturbations reverted the uremic hyperthrombotic phenotype without prolonging the bleeding time, in contrast to heparin, the standard-of-care antithrombotic in CKD patients. Our work refines the thrombosis axis (STUB1 is a mediator of indolic solute-AHR-TF axis) and expands the understanding of the interconnected relationships driving the fragile thrombotic state in CKD. It also establishes a means of minimizing the uremic hyperthrombotic phenotype without altering the hemostatic balance, a long-sought-after combination in CKD patients.

Hydrogen sulfide-producing cystathionine γ-lyase is critical in the progression of kidney fibrosis

Cystathionine γ-lyase (CSE), the last key enzyme of the transsulfuration pathway, is involved in the production of hydrogen sulfide (H₂S) and glutathione (GSH), which regulate redox balance and act as important antioxidant molecules. Impairment of the H₂S- and GSH-mediated antioxidant system is associated with the progression of chronic kidney disease (CKD), characterized by kidney fibrosis and dysfunction. Here, we evaluated the role of CSE in the progression of kidney fibrosis after unilateral ureteral obstruction (UUO) using mice deficient in the Cse gene. UUO of wild-type mice reduced the expression of H₂S-producing enzymes, CSE, cystathionine β-synthase, and 3-mercaptopyruvate sulfurtransferase in the obstructed kidneys, resulting in decreased H₂S and GSH levels. Cse gene deletion lowered H₂S and GSH levels in the kidneys. Deleting the Cse gene exacerbated the decrease in H₂S and GSH levels and increase in superoxide formation and oxidative damage to proteins, lipids, and DNA in the kidneys after UUO, which were accompanied by greater kidney fibrosis, deposition of extracellular matrixes, expression of α-smooth muscle actin, tubular damage, and infiltration of inflammatory cells. Furthermore, Cse gene deletion exacerbated mitochondrial fragmentation and apoptosis of renal tubule cells after UUO. The data provided herein constitute in vivo evidence that Cse deficiency impairs renal the H₂S- and GSH-producing activity and exacerbates UUO-induced kidney fibrosis. These data propose a novel therapeutic approach against CKD by regulating CSE and the transsulfuration pathway.

MMP-2 and 9 in Chronic Kidney Disease

Gelatinases are members of the matrix metalloproteinase (MMPs) family; they play an important role in the degradation of the extracellular matrix (ECM). This effect is also crucial in the development and progression of chronic kidney disease (CKD). Its expression, as well as its activity regulation are closely related to the cell signaling pathways, hypoxia and cell membrane structural change. Gelatinases also can affect the development and progression of CKD through the various interactions with tumor necrosis factors (TNFs), monocyte chemoattractant proteins (MCPs), growth factors (GFs), oxidative stress (OS), and so on. Currently, their non-proteolytic function is a hot topic of research, which may also be associated with the progression of CKD. Therefore, with the in-depth understanding about the function of gelatinases, we can have a more specific and accurate understanding of their role in the human body.

IκB Kinase Inhibitor Attenuates Sepsis-Induced Cardiac Dysfunction in CKD

Patients with CKD requiring dialysis have a higher risk of sepsis and a 100-fold higher mortality rate than the general population with sepsis. The severity of cardiac dysfunction predicts mortality in patients with sepsis. Here, we investigated the effect of preexisting CKD on cardiac function in mice with sepsis and whether inhibition of IκB kinase (IKK) reduces the cardiac dysfunction in CKD sepsis. Male C57BL/6 mice underwent 5/6 nephrectomy, and 8 weeks later, they were subjected to LPS (2 mg/kg) or sepsis by cecal ligation and puncture (CLP). Compared with sham operation, nephrectomy resulted in significant increases in urea and creatinine levels, a small (P<0.05) reduction in ejection fraction (echocardiography), and increases in the cardiac levels of phosphorylated IκBα, Akt, and extracellular signal-regulated kinase 1/2; nuclear translocation of the NF-κB subunit p65; and inducible nitric oxide synthase (iNOS) expression. When subjected to LPS or CLP, compared with sham-operated controls, CKD mice exhibited exacerbation of cardiac dysfunction and lung inflammation, greater increases in levels of plasma cytokines (TNF-α, IL-1β, IL-6, and IL-10), and greater increases in the cardiac levels of phosphorylated IKKα/β and IκBα, nuclear translocation of p65, and iNOS expression. Treatment of CKD mice with an IKK inhibitor (IKK 16; 1 mg/kg) 1 hour after CLP or LPS administration attenuated these effects. Thus, preexisting CKD aggravates the cardiac dysfunction caused by sepsis or endotoxemia in mice; this effect may be caused by increased cardiac NF-κB activation and iNOS expression.

Dipeptidyl peptidase-4 inhibition in chronic kidney disease and potential for protection against diabetes-related renal injury

AIMS

Type 2 diabetes mellitus (T2DM) is associated with a high risk of chronic kidney disease (CKD). About 20% of patients with T2DM have CKD of stage ≥ 3; up to 40% have some degree of CKD. Beyond targeting all renal risk factors together, renin-angiotensin-aldosterone system blockers are to date the only effective mainstay for the treatment of diabetic kidney disease (DKD). Indeed, several potentially nephroprotective agents have been in use, which have been unsuccessful. Some glucose-lowering agents, including dipeptidyl peptidase-4 inhibitors (DPP-4i), have shown promising results. Here, we discuss the evidence that glucose lowering with DPP-4i may be an option for protecting against diabetes-related renal injury.

DATA SYNTHESIS

A comprehensive search was performed of the literature using the terms "alogliptin," "linagliptin," "saxagliptin," "sitagliptin," and "vildagliptin" for original articles and reviews addressing this topic. DPP-4i are an effective, well-tolerated treatment option for T2DM with any degree of renal impairment. Preclinical observations and clinical studies suggest that DPP-4i might also be a promising strategy for the treatment of DKD. The available data are in favor of saxagliptin and linagliptin, but the consistency of results points to the possible nephroprotective effect of DPP-4i. This property appears to be independent of glucose lowering and can potentially complement other therapies that preserve renal function. Larger prospective clinical trials are ongoing, which might strengthen these hypothesis-generating findings.

CONCLUSIONS

The improvement in albuminuria associated with DPP-4i suggests that these agents may provide renal benefits beyond their glucose-lowering effects, thus offering direct protection from DKD. These promising results must be interpreted with caution and need to be confirmed in forthcoming studies.

Role of Myeloperoxidase in Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) is a worldwide public health problem. Patients with CKD have a number of disorders in the organism, and the presence of oxidative stress and systemic inflammation in these patients is the subject of numerous studies. Chronic inflammation joined with oxidative stress contributes to the development of numerous complications: accelerated atherosclerosis process and cardiovascular disease, emergence of Type 2 diabetes mellitus, development of malnutrition, anaemia, hyperparathyroidism, and so forth, affecting the prognosis and quality of life of patients with CKD. In this review we presented the potential role of the myeloperoxidase enzyme in the production of reactive/chlorinating intermediates and their role in oxidative damage to biomolecules in the body of patients with chronic kidney disease and end-stage renal disease. In addition, we discussed the role of modified lipoprotein particles under the influence of prooxidant MPO intermediates in the development of endothelial changes and cardiovascular complications in renal failure.

Caspase-1 Plays a Critical Role in Accelerating Chronic Kidney Disease-Promoted Neointimal Hyperplasia in the Carotid Artery

To determine whether caspase-1 is critical in chronic kidney disease (CKD)-mediated arterial neointimal hyperplasia (NH), we utilized caspase(-/-) mice and induced NH in carotid artery in a CKD environment, and uremic sera-stimulated human vascular smooth muscle cells (VSMC). We made the following findings: (1) Caspase-1 inhibition corrected uremic sera-mediated downregulation of VSMC contractile markers, (2) CKD-promoted NH was attenuated in caspase(-/-) mice, (3) CKD-mediated downregulation of contractile markers was rescued in caspase null mice, and (4) expression of VSMC migration molecule αvβ3 integrin was reduced in caspase(-/-) tissues. Our results suggested that caspase-1 pathway senses CKD metabolic danger signals. Further, CKD-mediated increase of contractile markers in VSMC and increased expression of VSMC migration molecule αvβ3 integrin in NH formation were caspase-1 dependent. Therefore, caspase-1 is a novel therapeutic target for the suppression of CKD-promoted NH.

Increased rho kinase activity in mononuclear cells of dialysis and stage 3-4 chronic kidney disease patients with left ventricular hypertrophy: Cardiovascular risk implications

AIMS

Cardiovascular disease (CVD) is the leading cause of excess mortality in chronic kidney disease (CKD) and dialysis patients (DP) who have higher prevalence of left ventricular hypertrophy (LVH), the strongest predictor of CV events. Rho kinase (ROCK) activation is linked in hypertensive patients to cardiac remodeling while ROCK inhibition suppresses cardiomyocyte hypertrophy and, in a human clinical condition opposite to hypertension, its downregulation associates with lack of CV remodeling. Information on ROCK activation-LVH link in CKD and DP is lacking.

MATERIALS AND METHODS

Mononuclear cells (PBMCs) MYPT-1 phosphorylation, a marker of ROCK activity, and the effect of fasudil, a ROCK inhibitor, on MYPT-1 phosphorylation were assessed in 23 DPs, 13 stage 3-4 CKD and 36 healthy subjects (HS) by Western blot. LV mass was assessed by M-mode echocardiography.

KEY FINDINGS

DP and CKD had higher MYPT-1 phosphorylation compared to HS (p<0.001 and p=0.003). Fasudil (500 and 1000μM) dose dependently reduced MYPT-1 phosphorylation in DP (p<0.01). DP had higher LV mass than CKD (p<0.001). MYPT-1 phosphorylation was higher in patients with LVH (p=0.009) and correlated with LV mass both in DP and CKD with LVH (p<0.001 and p=0.006).

SIGNIFICANCE

In DP and CKD, ROCK activity tracks with LVH. This ROCK activation-LVH link provided in these CVD high-risk patients along with similar findings in hypertensive patients and added to opposite findings in a human model opposite to hypertension and in type 2 diabetic patients, identify ROCK activation as a potential LVH marker and provide further rationale for ROCK activation inhibition as target of therapy in CVD high-risk patients.

TNFα up-regulates COX-2 in chronic progressive nephropathy through nuclear accumulation of RelB and NF-κB2

OBJECTIVE

The pathogenesis of progressive nephropathies involves inflammatory factors. The inhibition of cyclooxygenase-2 (COX-2) can limit renal damage and inflammation. However, the mechanism of up-regulation of COX-2 in nephropathy is poorly defined.

MATERIALS AND METHODS

Here we found that tumor necrosis factor alpha (TNFα) was involved in expression of COX-2 in normal rat kidney (NRK) cell line.

RESULTS

TNFα stimulated COX-2 production in a time-dependent manner in NRK cells by inducing nuclear accumulation of RelB and nuclear factor kappa B2 (NF-κB2) and their association with COX-2 gene promoter. Depletion of IκB-inducing kinase alpha, a positive regulator of activation of p100 processing to active p52, attenuated TNFα-induced COX-2 production. Furthermore, TNFα induced COX-2 production and nuclear import in anti-thymocyte serum (ATS) nephropathy.

DISCUSSION AND CONCLUSION

These data suggest that TNFα-RelB/p52 pathway may be involved in the early stages of renal damage, in part by stimulating COX-2 and inflammatory responses.

Alkaline Phosphatase, iPTH and Bone Turnover Markers in Chinese Advanced Chronic Kidney Disease Patients

BACKGROUND

Clinicians may use several biochemical markers of bone turnover to assess or guide the care of patients with chronic kidney disease (CKD). The aims of this study are to describe changes and correlations of markers of bone remodeling in patients with different stages of CKD.

METHODS

A total of 317 Chinese patients with advanced CKD (stage 3-5) were enrolled. We measured serum levels of intact-parathyroid hormone (iPTH), N-terminal midfragment (N-MID) osteocalcin, procollagen type 1 amino-terminal propeptide (P1NP), β-isomerized C-terminal telopeptide (β-CTx), total alkaline phosphatase (ALP), and 25-hydroxyvitamin D (25[OH]D).

RESULTS

Levels of iPTH, N-MID osteocalcin, P1NP, and β-CTx and serum phosphorus were significantly different among patients with different stages of CKD. Serum levels of ALP and 25(OH)D were higher in hemodialysis (HD) patients than in peritoneal dialysis (PD) patients. Levels of ALP, osteocalcin, and P1NP were significantly higher in dialysis patients than in non-dialysis patients. Correlations between the levels of iPTH, ALP, N-MID os- teocalcin, P1NP, and β-CTx were statistically significant but weak. There was no correlation between 25(OH)D and iPTH or ALP.

CONCLUSIONS

Our results suggest that measurement of N-MID osteocalcin, P1NP, β-CTx, and iPTH may be useful for assessment of CKD-mineral bone disorder (MBD) in patients with CKD.

Necroptosis mediated by receptor interaction protein kinase 1 and 3 aggravates chronic kidney injury of subtotal nephrectomised rats

Necroptosis, an alternative mode of programmed cell death, has crucial pathophysiological roles in many diseases, but its effect on chronic kidney disease (CKD) is poorly understood. Therefore, we assessed necroptosis and its pathophysiological effects in a widely used remnant-kidney rat model. We found that necroptotic cell death and the highest level of receptor interaction protein kinase 1 (RIP1) and receptor interaction protein kinase 3 (RIP3), critical signalling molecules for necroptosis, appeared 8 weeks after subtotal nephrectomy (SNX) surgery. After treatment with Necrostatin-1 (Nec-1), renal function and renal pathologic changes were significantly improved; the overexpression of RIP1, RIP3, mixed lineage kinase domain-like (MLKL) and dynamin-related protein 1 (Drp1) was reduced; and necroptosis was inhibited. These results indicated that necroptosis mediated by RIP1 and RIP3 participates in the loss of renal cells of subtotal nephrectomised rats and might be one of main causes of the excessive loss of renal cells during the sustained progression of renal fibrosis.

Matrix metalloproteinases and peripheral arterial disease

It has been postulated that atherosclerosis should be considered as a chronic inflammatory process and peripheral arterial disease (PAD) is a manifestation of such an atherosclerotic vascular disease. Matrix metalloproteinases (MMPs) are significant circulating biomarkers which play a pivotal role in the initiation, progression and clinical manifestations of PAD. This review summarizes the current body of evidence with regard to the association between MMPs and PAD.

Renalase, kidney and cardiovascular disease: are they related or just coincidentally associated?

Cardiovascular diseases, including hypertension are the leading cause of death in the developed countries. Diabetes and chronic kidney disease became also more prevalent reaching almost the level of epidemy. Researchers are looking eagerly for the new risk and/or pathogenetic factors, as well as therapeutic option in these disease. It has been suggested that human kidney releases a protein named renalase into the bloodstream. It is supposed to be an enzyme which breaks down catecholamines in the blood circulation and regulate blood pressure. However, there were several doubts whether renalase exerts monoaminooxidase activity, or if it is monoaminooxidase at all. Recently, a hypothesis that it is also a cytokine was postulated. Studies on renalase polymorphisms in hypertension, cardiovascular disease or diabetes are inconsistent. Similarly, there are several discrepancies in the animal on the possible role of renalase in hypertension and cardiovascular diseases. Some studies report a protective role of renalase in acute kidney injury, whereas others showed that renalase levels were mainly dependent on kidney function, indicating rather a role of kidney in excretion of this substance. Moreover, validated assays are needed to evaluate renalase levels and activity. On one hand a deeper and more accurate link between renalase and cardiovascular diseases require further profound research, on the other hand whether or not renalase protein could be a new therapeutic target in these pathologies should also be considered. Whether renalase, discovered in 2005, might be a Holy Grail of hypertension, linking kidney and cardiovascular diseases, remains to be proven.

Axl tyrosine kinase protects against tubulo-interstitial apoptosis and progression of renal failure in a murine model of chronic kidney disease and hyperphosphataemia

Chronic kidney disease (CKD) is defined as the progressive loss of renal function often involving glomerular, tubulo-interstitial and vascular pathology. CKD is associated with vascular calcification; the extent of which predicts morbidity and mortality. However, the molecular regulation of these events and the progression of chronic kidney disease are not fully elucidated. To investigate the function of Axl receptor tyrosine kinase in CKD we performed a sub-total nephrectomy and fed high phosphate (1%) diet to Axl+/+ and Axl−/− mice. Plasma Gas6 (Axl' ligand), renal Axl expression and downstream Akt signalling were all significantly up-regulated in Axl+/+ mice following renal mass reduction and high phosphate diet, compared to age-matched controls. Axl−/− mice had significantly enhanced uraemia, reduced bodyweight and significantly reduced survival following sub-total nephrectomy and high phosphate diet compared to Axl+/+ mice; only 45% of Axl−/− mice survived to 14 weeks post-surgery compared to 87% of Axl+/+ mice. Histological analysis of kidney remnants revealed no effect of loss of Axl on glomerular hypertrophy, calcification or renal sclerosis but identified significantly increased tubulo-interstitial apoptosis in Axl−/− mice. Vascular calcification was not induced in Axl+/+ or Axl−/− mice in the time frame we were able to examine. In conclusion, we identify the up-regulation of Gas6/Axl signalling as a protective mechanism which reduces tubulo-interstitial apoptosis and slows progression to end-stage renal failure in the murine nephrectomy and high phosphate diet model of CKD.

Significance of serum peptidylarginine deiminase type 4 in ANCA-associated vasculitis

OBJECTIVE

To investigate the clinical significance of peptidylarginine deiminase type 4 (PAD4) in the pathogenesis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). To make a primary observation on the relationship of chronic bronchitis and bronchiectasis (CB) with the pathogenesis of AAV by PAD4.

METHODS

The sera from 13 patients with AAV, 13 patients with CB, 11 patients with rheumatoid arthritis (RA), 11 patients with primary chronic kidney disease (CKD) and 12 normal controls were collected. Serum PAD4 was detected using commercial ELISA kits. The serum levels of PAD4 were compared not only among the different groups but also between the activity and remission stage of the same disease. The associations between serum PAD4 and the Birmingham Vasculitis Activity Score (BVAS) of AAV were further investigated.

RESULTS

(1) The serum levels of PAD4 in patients with AAV, RA and CB at activity stage were all higher than that in the normal controls (P<0.001, respectively, α'=0.007). The serum level of PAD4 in patients with CB at remission stage and that in CKD group were not found elevated compared with the normal controls (P=0.02, P=0.085, respectively, α'=0.007). (2) At activity stage, among the groups of simple AAV, AAV with a long history of CB and CB without AAV, no significant difference was detected. While at remission stage among the 3 groups, the serum level of PAD4 was at the lowest level in CB group without AAV. (3) The serum level of PAD4 in some patients with CB without AAV were found still higher at remission stage. (4) The serum level of PAD4 in AAV with renal damage at activity stage was positively correlated with BVAS (the activity score of AAV, r=0.71, P=0.02).

CONCLUSION

PAD4 is involved in the pathogenesis of AAV. Whether some patients with CB might progress to AAV by the link with PAD4 still need further investigation.

[Molecular aspects of renal desease]

The review considers molecular mechanisms of chronic renal failure and cancer kidney disease. The most important molecules inducing inflammation are cytokines (MCP-1, TNFalpha, IFN-gamma, IL-1,6,8,18), matrix metalloproteinases MMP-2,3,9,14, tissue inhibitors of metalloproteinases (TIMPs) and grow factors (VEGF PDGE FGF). This signal molecules regulate the activity of immune cells and remodeling extracellular matrix (ECM) components taken place in inflammatory reactions, proliferation, apoptosis and also in the differentiation of kidney cells. On the basis of these data nowadays developed new highly selective approaches to diagnosis, prediction, estimation of efficiency of treatment of renal disease and creating of target drugs.

Liver enzymes serum levels in patients with chronic kidney disease on hemodialysis: a comprehensive review

We reviewed the literature regarding the serum levels of the enzymes aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transferase in patients with chronic kidney disease on hemodialysis with and without viral hepatitis. Original articles published up to January 2013 on adult patients with chronic kidney disease on hemodialysis were selected. These articles contained the words "transaminases" "aspartate aminotransferase" "alanine aminotransferase" "gamma glutamyl transferase," "liver enzymes", AND "dialysis" OR "hemodialysis". A total of 823 articles were retrieved. After applying the inclusion and exclusion criteria, 49 articles were selected. The patients with chronic kidney disease on hemodialysis had reduced serum levels of aminotransferases due to hemodilution, lower pyridoxine levels, or elevated homocysteine levels. The chronic kidney disease patients on hemodialysis infected with the hepatitis C virus also had lower aminotransferase levels compared with the infected patients without chronic kidney disease. This reduction is in part due to decreased viremia caused by the dialysis method, the production of a hepatocyte growth factor and endogenous interferon-α, and lymphocyte activation, which decreases viral action on hepatocytes. Few studies were retrieved on gamma-glutamyl transferase serum levels; those found reported that there were no differences between the patients with or without chronic kidney disease. The serum aminotransferase levels were lower in the patients with chronic kidney disease on hemodialysis (with or without viral hepatitis) than in the patients with normal renal function; this reduction has a multifactorial origin.

[The mysterious properties of renalase]

Renalase, a recently discovered protein participating in the catecholamine metabolism and belonging to oxidoreductases, possess also antihypertensive and cardioprotective properties, confirmed in several studies on animal models. In human, rat and mouse renalase is thought to be produced mainly by kidney, but increasing number of reports indicates that large quantities of this enzyme, depending on species, are produced by other organs, primarily heart and gonads. However, there are still many uncertainties regarding the mechanism of in vivo action of renalase. The discrepancies in the results of measurement of its concentration in patients with chronic kidney disease exist. Moreover, the site of production and the potential biological function of the renalase isoforms, except isoform 1, are still not determined.

Angiotensin-converting enzyme 2 activity in patients with chronic kidney disease

Background

Angiotensin-converting enzyme 2 (ACE2) is a novel regulator of the renin–angiotensin system that counteracts the adverse effects of angiotensin II. In heart failure patients, elevated plasma ACE2 activity predicted adverse events and greater myocardial dysfunction. We aimed to describe plasma ACE2 activity and its clinical associations in patients with kidney disease.

Methods

Patients recruited from a single centre comprised of chronic kidney disease Stage III/IV (CKD), haemodialysis patients and kidney transplant recipients (KTRs). Plasma ACE2 enzyme activity was measured using a fluorescent substrate assay in plasma, collected at baseline and stored at −80°C. Linear regression was performed in both males and females separately to determine the covariates associated with log-transformed ACE2.

Results

The median (interquartile range) plasma ACE2 activity in pmol/mL/min was 15.9 (8.4–26.1) in CKD (n = 59), 9.2 (3.9–18.2) in haemodialysis (n = 100) and 13.1 (5.7–21.9) in KTR (n = 80; P < 0.01). In male haemodialysis patients, ACE2 activity was 12.1 (6.8–19.6) compared with 4.4 (2.5–10.3) in females (P < 0.01). Log-transformed ACE2 plasma activity was associated with post-haemodialysis systolic blood pressure in females [β-coefficient 0.04, 95% confidence interval (95% CI) 0.01–0.06, P = 0.006]. In males, log-transformed ACE2 plasma activity was associated with B-type natriuretic peptide (β-coefficient 0.39, 95% CI 0.19–0.60, P < 0.001). Plasma ACE2 activity was not associated with mortality.

Conclusions

Plasma ACE2 activity is reduced in haemodialysis patients compared with CKD patients, and in female haemodialysis patients compared with male. The different associations of plasma ACE2 activity between male and female haemodialysis patients indicate that the role of ACE2 in cardiovascular disease may differ by gender.

Transglutaminase 2 accelerates vascular calcification in chronic kidney disease

BACKGROUND

Transglutaminase 2 (TGM2) is a calcium-dependent enzyme that can cross-link nearly all extracellular matrix (ECM) proteins and can facilitate cell-ECM interaction through integrins. Given the importance of the ECM in vascular calcification we tested the hypothesis that increased TGM2 activity may accelerate vascular calcification in chronic kidney disease (CKD).

METHODS

We utilized thoracic aortas and vascular smooth muscle cells (VSMC) from the Cy/+ rat, a model of progressive CKD that develops arterial calcification on a normal phosphorus diet, compared to normal rats.

RESULTS

VSMC isolated from CKD rats had increased expression and activity of TGM2 compared to cells from normal rats. The increased calcification and expression of alkaline phosphatase activity observed in VSMC from CKD rats compared to normal was inhibited in a dose-dependent manner with the TGM inhibitors cystamine and Z006. Matrix vesicles (MV) from CKD rat VSMC also had increased TGM2 expression and the calcification of MV on type I collagen could be inhibited with cystamine and accelerated by exogenous cross-linking of fibronectin or type I collagen with TGM2. Finally, the calcification of aorta rings from CKD rats in ex vivo cultures was inhibited with TGM2 inhibitor.

CONCLUSION

These data demonstrate a role of TGM2 in the pathogenesis of vascular calcification in CKD through enhancement of MV-ECM calcification.

An inhibitor of thrombin activated fibrinolysis inhibitor (TAFI) can reduce extracellular matrix accumulation in an in vitro model of glucose induced ECM expansion

Chronic kidney disease (CKD) is characterised by the pathological accumulation of extracellular matrix (ECM) proteins leading to progressive kidney scarring via glomerular and tubular basement membrane expansion. Increased ECM synthesis and deposition, coupled with reduced ECM breakdown contribute to the elevated ECM level in CKD. Previous pre-clinical studies have demonstrated that increased plasmin activity has a beneficial effect in the protein overload model of CKD. As plasmin activation is downregulated by the action of the thrombin activated fibrinolytic inhibitor (TAFI), we tested the hypothesis that inhibition of TAFI might increase plasmin activity and reduce ECM accumulation in an in vitro model of glucose induced ECM expansion. Treatment of NRK52E tubular epithelial cells with increasing concentrations of glucose resulted in a 40% increase in TAFI activity, a 38% reduction in plasmin activity and a subsequent increase in ECM accumulation. In this model system, application of the previously reported TAFI inhibitor UK-396082 [(2S)-5-amino-2-[(1-n-propyl-1H-imidazol-4-yl)methyl]pentanoic acid] caused a reduction in TAFI activity, increased plasmin activity and induced a parallel decrease in ECM levels. In contrast, RNAi knockdown of plasmin resulted in an increase in ECM levels. The data presented here indicate that high glucose induces TAFI activity, inhibiting plasmin activation which results in elevated ECM levels in tubular epithelial cells. The results support the hypothesis that UK-396082 is able to reduce TAFI activity, normalising plasmin activity and preventing excess ECM accumulation suggesting that TAFI inhibition may have potential as an anti-scarring strategy in CKD.

A comparative study of chronic kidney disease in dogs and cats: induction of cyclooxygenases

The present study investigated whether renal cyclooxygenase (COX) induction is associated with the severity of chronic kidney disease (CKD) in dogs and cats. The collected kidneys were examined histopathologically and immunohistochemically. The immunoreactivities of COX-1 and COX-2 were evaluated quantitatively, and the correlations to the plasma creatinine concentrations, glomerular size, glomerulosclerosis, interstitial fibrosis, and interstitial cell infiltration were evaluated statistically. Immunoreactivities for COX-1 were heterogeneously observed in the medullary distal tubules and collecting ducts; no correlations with the severity of renal damage were detected. Immunoreactivities for COX-2 were heterogeneously observed in the macula densa (MD) regions. In dogs, the percentage of COX-2-positive MD was significantly correlated with the glomerular size. In cats, glomeruli with COX-2-positive MD had significantly higher sclerosis scores than those with COX-2-negative MD. In conclusion, renal COX-2 is induced in canine and feline CKD, especially in relation to the glomerular changes.

[Remodeling of the cardiovascular system and development of chronic kidney disease in patients with metabolic syndrome and obesity: role of eNOS, subunit p22-phox of NADPH-oxidase and MTHFR genes]

AIM

To examine contribution of polymorphisms of genes of endothelial NO-synthase (eNOS), NADPH-oxidase and methylenetetrahydrofolate reductase (mTHFR) to development of remodeling of cardiovascular system and chronic disease of the kidneys (CDK) in patients with metabolic syndrome (mS) and obesity. MATERIAL AND METHODS. Standard clinical and device examinations were made and polymorphisms C242T of gene of subunit p22-phox of NADPH-oxidase, G894T of gene of eNOS and C677T of gene of MTHFR were studied in 66 MS patients (49 males and 17 females, age 19-62 years.

RESULTS

The presence of even one prognostically poor allele variants of the genes studied was registered in 83 examinees. The genotype 242TTp22-phox of NADPH-oxidase subunit was associated with the highest insulin resistance, allele 894T of gene eNOS- with reduced glomerular filtration rate and progression of left ventricular hypertrophy.

CONCLUSION

Polymorphism of the genes the products of which modulate endothelial function can be considered as potential predictors of severity of MS target organs impairment.

Serum metalloproteinases MMP-2, MMP-9, and metalloproteinase tissue inhibitors in patients are associated with arteriovenous fistula maturation

OBJECTIVE

Many vascular surgeons construct arteriovenous fistulas (AVFs) for hemodialysis access as the primary choice access. A significant number of AVFs fail to mature, however, leading to patient frustration and repeated operations. Metalloproteinase (MMP) activity, particularly MMP-2 and MMP-9, may be important for AVF maturation. We therefore sought to identify whether serum MMP levels could serve as a biomarker for predicting future successful AVF maturation.

METHODS

Blood was collected from patients with chronic renal insufficiency at the time of surgery for long-term hemodialysis access. Serum was separated from whole blood and ultracentrifuged at 1000g for 10 minutes. Serum aliquots were frozen at -80°C until used for analysis. Enzyme-linked immunosorbent assay was used to assay levels of MMP-2, MMP-9, and tissue inhibitor of metalloproteinase type 2 (TIMP-2), and TIMP type 4 (TIMP-4). Clinical end points were used to divide patients into failed and matured AVF groups. Successful maturation was considered in patients who had specific duplex findings or 1 month of successful two-needle cannulation hemodialysis. MMP/TIMP ratios were calculated as an index of the MMP axis activity because MMP activity parallels alterations in TIMP levels.

RESULTS

Of 20 enrolled patients, AVF maturation was successful in 13 and failed in 7. Serum levels of MMP-2/TIMP-2 were significantly higher in patients with matured AVFs vs levels in those that failed (P = .003). Similarly, a trend toward increased serum levels of MMP-9/TIMP-4 was found in patients with successful AVF (P = .06).

CONCLUSIONS

MMP-2 and TIMP-2 levels were different among patients whose AVF matured vs those who did not. Further follow-up studies to determine the predictability of AVF maturation using relative patient serum levels of MMP-2 and TIMP-2 should be performed.

Neutrophil gelatinase-associated lipocalin (NGAL) and matrix metalloproteinases as novel stress markers in children and young adults on chronic dialysis

Phenomena related to chronic kidney disease, such as atherosclerosis, aggravate with the introduction of dialysis. Matrix metalloproteinases (MMP) and factors modifying their activity, such as their tissue inhibitors (TIMP) or neutrophil gelatinase-associated lipocalin (NGAL), take part in the matrix turnover and the endothelial damage characteristic for atherogenesis. However, there are no data on the associations between these parameters and other known pro-atherogenic factors, or on the impact of various dialysis modalities on them. The aim of our study was to assess the serum concentrations of NGAL, MMP-7, MMP-9, and TIMP-1, as well as their correlations with human heat shock proteins (Hsp90α, anti-Hsp60), endothelial dysfunction (sE-selectin), and inflammation (hsCRP) in pediatric patients chronically dialyzed. Twenty-two children on automated peritoneal dialysis (APD), 17 patients on hemodialysis (HD) and 24 controls were examined. The serum concentrations of NGAL, MMP-7, MMP-9, TIMP-1, Hsp90α, anti-Hsp60, and sE-selectin were assessed by enzyme-linked immunosorbent assay (ELISA). The median values of NGAL, MMP-7, MMP-9, TIMP-1, and MMP-9/NGAL ratio were significantly elevated in all dialyzed children vs. controls and were higher in HD than in APD. The values of MMP-9/TIMP-1 and MMP-7/TIMP-1 ratios in the HD subjects were lower than those in the APD children. Hsp90α and anti-Hsp60 predicted the values of NGAL, MMPs, and TIMP-1. Additionally, sE-selectin was a predictor of NGAL levels, whereas NGAL predicted the MMP and TIMP-1 concentrations. The increased concentrations of examined parameters indicate the dysfunction of MMP/TIMP/NGAL system in the dialyzed children, more pronounced on hemodialysis. The discrepancies between dialysis modalities and correlations with heat shock proteins (HSPs) suggest that NGAL may be considered a novel stress protein, whereas MMP-7, MMP-9, and TIMP-1 may be regarded as indicators of stress response in the pediatric population on chronic dialysis.

Associations between the CYBA 242C/T and the MPO –463G/A Polymorphisms, Oxidative Stress and Cardiovascular Disease in Chronic Kidney Disease Patients

Genetic variations in the NADPH/MPO system in chronic kidney disease (CKD) patients might lead to altered activity of these enzymes, and thus to altered risk for oxidative stress (OS) and cardiovascular disease (CVD). We evaluated the impact of 242C/T CYBA and -463G/A MPO polymorphisms on OS and CVD mortality in stage 5 CKD patients starting dialysis. Two hundred and fifty-seven patients were genotyped using Pyrosequencing. Plasmalogen [dimethylacetal (DMA) 16/C16:0] was used as OS marker. CVD was assessed from patient history and clinical symptoms. Prevalence of CVD was higher (35%) in GG patients (MPO) compared to AG (26%) and AA (0%) patients (p < 0.01). Patients with CC genotype (CYBA) had lower levels of DMA 16/C16:0 (ratio 0.071 +/- 0.003) compared to TT patients (0.089 +/- 0.006; p < 0.05). These patients also had increased CVD mortality compared to CT and TT patients (chi(2) 2.19; p < 0.05). We conclude that genetic variations in the NADPH/MPO system are associated with OS, presence of CVD and CVD-related mortality in CKD patients.

Jejunal dopamine and Na,K-ATPase activity in early chronic renal insufficiency

AIM

The uninephrectomised and three-quarter nephrectomised (3/4nx) rats present dopamine-sensitive enhanced natriuresis. This is accompanied in uninephrectomised rats by a reduced jejunal Na(+),K(+)-ATPase activity with recovered sensitivity to inhibition by dopamine. The present study examined the jejunal Na(+),K(+)-ATPase activity and the role of dopamine in 3/4nx animals.

METHODS

Fourteen days after surgery, the L-amino acid decarboxylase activity (AADC) activity, the enzyme responsible for the synthesis of dopamine, and the Na(+),K(+)-ATPase activity, were determined in jejunal epithelial cells from 3/4nx and Sham rats. In addition, the effect of dopamine (1 micromol/L) on jejunal Na(+),K(+)-ATPase activity was evaluated in both groups.

RESULTS

The 3/4nx rats presented a reduced AADC activity in jejunal epithelial cells (V(max) in nmol/mg prot/15 min, 142 +/- 6 vs 190 +/- 10, P < 0.05). In addition, the jejunal Na(+),K(+)-ATPase activity was increased in 3/4nx rats (Pi release in nmol/mg prot/min, 137 +/- 1 vs 122 +/- 2, P < 0.05). However, dopamine was unable to inhibit the Na(+),K(+)-ATPase activity in jejunal epithelial cells from both 3/4nx and Sham animals.

CONCLUSIONS

In contrast to uninephrectomy, the jejunal Na(+),K(+)-ATPase activity is increased in 3/4nx rats and is not sensitive to inhibition by dopamine.

EFFECT OF CHRONIC RENAL INSUFFICIENCY ON HEPATIC AND RENAL UDP-GLUCURONYLTRANSFERASES IN RATS

Significant evidence exists regarding altered CYP450 enzymes in chronic renal insufficiency (CRI), although none exists for the phase II enzymes. The objective of this study was to investigate the effect of CRI on hepatic and renal UDP-glucuronyltransferase (UGT) enzymes. Three groups of rats were included: CRI induced by the 5/6th nephrectomy model, control, and control pair-fed (CPF) rats. UGT activities were determined in liver and kidney microsomes by the 3- and 17-glucuronidation of beta-estradiol (E2-3G and E2-17G), glucuronidation of 4-methylumbelliferone (4-MUG), and 3-glucuronidation of morphine (M3G). UGT isoforms responsible for these catalytic activities were screened using recombinant rat UGT1A1, UGT1A2, UGT1A3, UGT1A7, UGT2B2, UGT2B3, and UGT2B8. UGT protein levels were examined by Western blot analysis using polyclonal antibodies. There was no significant difference between CRI and CPF rats in hepatic and/or renal E2-3G (UGT1A1), E2-17G (UGT2B3), 4-MUG (UGT1A6), and M3G (UGT2B1) formation. Formation of E2-17G and 4-MUG in the liver and E2-3G and 4-MUG in the kidney was significantly reduced (p < 0.05) in CPF and CRI rats compared with control rats. The down-regulated glucuronidation activities were accompanied by corresponding reductions in protein content of specific UGT isoforms. These results suggest that CRI does not seem to influence the protein levels or catalytic activity of most of the major hepatic or renal UGT enzymes. The observed down-regulation of hepatic and renal UGTs in CRI and CPF rats could be caused by restricted food intake in these groups of rats.