The role of trimethylamine N-oxide as a mediator of cardiovascular complications in chronic kidney disease.

Patients with chronic kidney disease (CKD) have an enhanced risk of cardiovascular (CV) morbidity and mortality when compared with age- and gender-matched individuals with normal kidney function. Trimethlyamine N-oxide (TMAO) is a gut-derived amine oxide that has been implicated in the causation of CV diseases. Plasma TMAO is cleared by the kidney, and TMAO levels are elevated in CKD. Experimental studies have identified pathogenic mechanisms by which TMAO may contribute to CV disease through dysregulation of lipid metabolism, enhanced macrophage foam cell formation, and platelet dysfunction. Safe and well-tolerated therapeutic interventions such as pre- and probiotics, which modify the gut microbiome, offer the opportunity for interventional studies. This review examines the pathogenicity of TMAO, its value as a biomarker, and its potential as a therapeutic target in the context of CKD.

Evidence that links loss of cyclooxygenase-2 with increased asymmetric dimethylarginine: novel explanation of cardiovascular side effects associated with anti-inflammatory drugs.

BACKGROUND: Cardiovascular side effects associated with cyclooxygenase-2 inhibitor drugs dominate clinical concern. Cyclooxygenase-2 is expressed in the renal medulla where inhibition causes fluid retention and increased blood pressure. However, the mechanisms linking cyclooxygenase-2 inhibition and cardiovascular events are unknown and no biomarkers have been identified. METHODS AND RESULTS: Transcriptome analysis of wild-type and cyclooxygenase-2(-/-) mouse tissues revealed 1 gene altered in the heart and aorta, but >1000 genes altered in the renal medulla, including those regulating the endogenous nitric oxide synthase inhibitors asymmetrical dimethylarginine (ADMA) and monomethyl-l-arginine. Cyclo-oxygenase-2(-/-) mice had increased plasma levels of ADMA and monomethyl-l-arginine and reduced endothelial nitric oxide responses. These genes and methylarginines were not similarly altered in mice lacking prostacyclin receptors. Wild-type mice or human volunteers taking cyclooxygenase-2 inhibitors also showed increased plasma ADMA. Endothelial nitric oxide is cardio-protective, reducing thrombosis and atherosclerosis. Consequently, increased ADMA is associated with cardiovascular disease. Thus, our study identifies ADMA as a biomarker and mechanistic bridge between renal cyclooxygenase-2 inhibition and systemic vascular dysfunction with nonsteroidal anti-inflammatory drug usage. CONCLUSIONS: We identify the endogenous endothelial nitric oxide synthase inhibitor ADMA as a biomarker and mechanistic bridge between renal cyclooxygenase-2 inhibition and systemic vascular dysfunction.

Reduced Renal Methylarginine Metabolism Protects against Progressive Kidney Damage.

Nitric oxide (NO) production is diminished in many patients with cardiovascular and renal disease. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis, and elevated plasma levels of ADMA are associated with poor outcomes. Dimethylarginine dimethylaminohydrolase-1 (DDAH1) is a methylarginine-metabolizing enzyme that reduces ADMA levels. We reported previously that a DDAH1 gene variant associated with increased renal DDAH1 mRNA transcription and lower plasma ADMA levels, but counterintuitively, a steeper rate of renal function decline. Here, we test the hypothesis that reduced renal-specific ADMA metabolism protects against progressive renal damage. Renal DDAH1 is expressed predominately within the proximal tubule. A novel proximal tubule-specific Ddah1 knockout (Ddah1(PT-/-)) mouse demonstrated tubular cell accumulation of ADMA and lower NO concentrations, but unaltered plasma ADMA concentrations. Ddah1(PT-/-) mice were protected from reduced kidney tissue mass, collagen deposition, and profibrotic cytokine expression in two independent renal injury models: folate nephropathy and unilateral ureteric obstruction. Furthermore, a study of two independent kidney transplant cohorts revealed higher levels of human renal allograft methylarginine-metabolizing enzyme gene expression associated with steeper function decline. We also report an association among DDAH1 expression, NO activity, and uromodulin expression supported by data from both animal and human studies, raising the possibility that kidney DDAH1 expression exacerbates renal injury through uromodulin-related mechanisms. Together, these data demonstrate that reduced renal tubular ADMA metabolism protects against progressive kidney function decline. Thus, circulating ADMA may be an imprecise marker of renal methylarginine metabolism, and therapeutic ADMA reduction may even be deleterious to kidney function.

LGI1 Encephalitis and IgG4-Related Disease: Rare Conditions Collide.

OBJECTIVES: Leucine-rich glioma-inactivated 1 (LGI1) encephalitis and IgG4-related disease (IgG4RD) have traditionally been regarded as 2 distinct disease entities. METHODS: We detail the presentation, investigations, and management of a patient who showed typical signs and symptoms of LGI1 encephalitis and also found to possess pancreatic changes and a serum profile in keeping with IgG4RD. RESULTS: Serum and CSF analyses at presentation showed a significant hyponatraemia (117 mmol/L), elevated IgG4 concentration (1.73 g/L), and the presence of LGI1 antibodies. MRI revealed symmetrical diffuse T2-weighted hyperintensity and mild swelling throughout both medial temporal lobes. CT of the chest, abdomen and pelvis revealed an edematous, bulky pancreas with loss of lobulation, typical for IgG4RD. A glucocorticoid weaning regimen was commenced, facilitated by 2 rituximab infusions, with the patient showing an effective treatment response. HLA testing confirmed the presence of HLA DRB1 and HLA DQB1 risk alleles. DISCUSSION: This case suggests that there may be shared mechanisms between LGI1 encephalitis and IgG4RD, supported by common risk HLA associations and treatment strategies/responses. To our knowledge, this represents the first instance that LGI1 encephalitis and IgG4RD have been reported in the same patient and emphasizes the continued development of our understanding of the wide range of IgG4-mediated conditions.

Gender Differences in Experiences and Expectations of Hemodialysis in a Frail and Seriously Unwell Patient Population.

Introduction: Surprisingly few studies have explored the experiences of seriously unwell people with kidney disease on hemodialysis therapy: we conducted a mixed-methods study to investigate gender differences in illness experience, symptom burden, treatment considerations or expectations in this cohort. Methods: Seriously unwell people on hemodialysis (1-year mortality risk of >20%) at 3 hospital-based units were invited to take part in a structured interview or to complete the same questions independently via a questionnaire. A total of 54 people took part (36 males, 18 females); data analysis was undertaken using a thematic approach. Results: "Desire to keep living" is the most important and basic thought process when starting dialysis. Fear also predominates influencing risk assessment and decision-making. Once fear is managed, there are physical, social, practical and emotional issues to rationalize, but choice only seems possible if shared decision-making is part of the consultation.Gender differences were seen in perceived hopes and expectations of treatment. Males were more likely to prioritize achievement of physical goals, with females prioritizing a wish to feel well. Both genders reported significantly higher symptom scores than their health care provider perceived, however this difference was more marked in females. Dialysis regret existed in >50% of participants and 6 out of 54 (11%) stated that they would have chosen no dialysis at all. Females were more likely to report feeling depressed (P = 0.001). Conclusion: Different genders approach treatment decisions and prioritize treatment expectations differently. Recognizing this will allow personalized care plans to be developed and improve the experiences of seriously unwell people with kidney disease.

Perceptions of Illness Severity, Treatment Goals, and Life Expectancy: The ePISTLE Study.

INTRODUCTION: A better understanding of factors influencing perceived life expectancy (PLE), interactions between patient prognostic beliefs, experiences of illness, and treatment behavior is urgently needed. METHODS: Case-notes at 3 hemodialysis units were screened: patients with ≥20% 1-year mortality risk were included. Patients and their health care professionals (HCPs) were invited to complete a structured interview or mixed-methods questionnaire. Four hundred eleven patient notes were screened. Seventy-seven eligible patients were approached and 51 were included. RESULTS: Patients predicted significantly higher life expectancies than HCPs (P < 0.0001). Documented cognitive impairment, gender, or increasing age did not affect 1- or 5-year PLE. PLE influenced priorities of care: one-fifth of patients who estimated themselves to have >95% 1-year survival preferred "care focusing on relieving pain and discomfort," compared with nearly three-quarters of those reporting a ≤50% chance of 1-year survival. Twenty of 51 (39%) patients believed transplantation was an option for them, despite only 4 being waitlisted at the time of the interview. Patients who thought they were transplant candidates were significantly more confident they would be alive at 1 and 5 years and to want resuscitation attempted. Cognitive impairment had no effect on perceived transplant candidacy. A high symptom burden was present and underrecognized by HCPs. High symptom burden was associated with significantly lower PLE at both 1 and 5 years, increased anxiety/depression scores, and treatment choices more likely to prioritize relief of suffering. CONCLUSION: There is a disparity between patient PLE and those of their HCPs. Severity of symptom burden and beliefs regarding PLE or transplant candidacy affect patient treatment preferences.

Recently published papers: renal support in acute kidney injury - is low dose the new high dose?

Despite 21st century definitions, the management of acute kidney injury remains steadfastly rooted in the 20th century with treatment being principally supportive. Protection from potential causative agents is an essential part of management and to that end protection against contrast-induced nephropathy has received yet more attention. When optimization of volume status, haemodynamic parameters, electrolyte and acid-base disturbances have failed we turn to renal replacement therapy. The time 'bought' on renal support gives a period for renal recovery but although renal replacement therapy is widely employed, many management issues remain unanswered, including the timing, duration and the dose of treatment. In contrast to respiratory support for acute lung injury, for example, there is a paucity of large randomized studies addressing these fundamental issues. We describe some recent studies focusing on these issues with the hope that they may lead to better treatment for our patients.

autoregulatory role of endothelium-derived nitric oxide (NO) on Lipopolysaccharide-induced vascular inducible NO synthase expression and function.

Nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) is responsible for sepsis-induced hypotension and plays a major contributory role in the ensuing multiorgan failure. The present study aimed to elucidate the role of endothelial NO in lipopolysaccharide (LPS)-induced iNOS expression, in isolated rat aortic rings. Exposure to LPS (1 mug/ml, 5 h) resulted in a reversal of phenylephrine precontracted tone in aortic rings (70.7 +/- 3.2%). This relaxation was associated with iNOS expression and NF-kappaB activation. Positive immunoreactivity for iNOS protein was localized in medial and adventitial layers of LPS-treated aortic rings. Removal of the endothelium rendered aortic rings resistant to LPS-induced relaxation (8.9 +/- 4.5%). Western blotting of these rings demonstrated an absence of iNOS expression. However, treatment of endothelium-denuded rings with the NO donor, diethylamine-NONOate (0.1 mum), restored LPS-induced relaxation (61.6 +/- 6.6%) and iNOS expression to levels comparable with arteries with intact endothelium. Blockade of endothelial NOS (eNOS) activation using geldanamycin and radicicol, inhibitors of heat shock protein 90, in endothelium-intact arteries suppressed both LPS-induced relaxation and LPS-induced iNOS expression (9.0 +/- 8.0% and 2.0 +/- 6.2%, respectively). Moreover, LPS treatment (12.5 mg/kg, intravenous, 15 h) of wild-type mice resulted in profound elevation of plasma [NO(x)] measurements that were reduced by approximately 50% in eNOS knock-out animals. Furthermore, LPS-induced changes in vascular reactivity and iNOS expression evident in wild-type tissues were profoundly suppressed in tissues taken from eNOS knockout animals. Together, these data suggest that eNOS-derived NO, in part via activation of NF-kappaB, regulates iNOS-induction by LPS. This study provides the first demonstration of a proinflammatory role of vascular eNOS in sepsis.