Transjugular intrahepatic portosystemic shunt-placement increases arginine/asymmetric dimethylarginine ratio in cirrhotic patients

Hepato-Cardio-Renal Syndrome

Hepatorenal syndrome has conventionally been regarded as a multisystem syndrome in which pathophysiologic pathways that link cirrhosis with impairment in kidney function are followed by dysfunction of several organs such as the heart. The advances in cardiac studies have helped diagnose more subtle cardiac abnormalities that would have otherwise remained unnoticed in a significant subset of patients with advanced liver disease and cirrhosis. Accumulating data suggests that in many instances, the cardiac dysfunction precedes and predicts development of kidney disease in such patients. These observations point to the heart as a key player in hepatorenal syndrome and challenge the notion that the cardiac abnormalities are either the consequence of aberrancies in hepatorenal interactions or have only minor effects. As such, the disturbances traditionally bundled within hepatorenal syndrome may indeed represent a hepatic form of cardiorenal syndrome whereby the liver affects the kidney in part through cardiorenal pathways (that is, hepato-cardio-renal syndrome).

Assessment of glomerular filtration rate in patients with cirrhosis: Available tools and perspectives

Renal dysfunction often complicates the course of liver disease, resulting in higher morbidity and mortality. The accurate assessment of kidney function in these patients is essential to early identify, stage and treat renal impairment as well as to better predict the prognosis, prioritize the patients for liver transplantation and decide whether to opt for simultaneous liver-kidney transplants. This review analyses the available tools for direct or indirect assessment of glomerular filtration rate, focusing on the flaws and strengths of each method in the specific setting of cirrhosis. The aim is to deliver a clear-cut view on this complex issue, trying to point out which strategies to prefer in this context, especially in the peculiar setting of liver transplantation. Moreover, a glance is given at future promising tools for glomerular filtration rate assessment, including new biomarkers and new equations specifically modelled for the cirrhotic population.

Hepatorenal Syndrome: A Way for Early and Accurate Diagnosis

BACKGROUND: Hepatorenal syndrome (HRS) is a devastating consequence of liver cirrhosis that is clinically categorized into two subtypes. Acute malfunction of renal role, as measured by an elevation in blood creatinine, significantly underestimates the loss in renal function in cirrhotic individuals; more accurate biomarkers are desperately required in cirrhotic patients. AIM: The present study set out to uncover new biomarkers for the early prediction of AKI in cirrhotic cases. A comprehensive panel of biomarkers was investigated to get a clear insight into the pathogenesis of HRS. PATIENTS AND METHODS: Participants in this study were 70 individuals from the hepatogastroenterology unit of the Theodor Bilharz Research Institute (TBRI). Detailed medical data and a physical examination were recorded. Three groups of patients have been identified; Group 1: 30 cases with compensated liver cirrhosis and normal kidney functions. Group 2: 20 cases with decompensated liver cirrhosis and normal kidney functions. Group 3: 20 cases with decompensated liver cirrhosis proved hepatorenal syndrome Type 2 h. The following biomarkers were detected in serum using the sandwich-ELISA method: Human L-arginine ELISA kit, human neutrophil gelatinase related lipocalin (NGAL), human noradrenaline (NA), human asymmetrical dimethylarginine (ADMA), human symmetric dimethylarginine (SDMA), human nitric oxide (NO), and human renin. RESULTS: There was a highly significant difference between Groups 1 and 2 in NITRIC and ADMA. Significant differences between Groups 2 and 3 in NGAL, noradrenalin, and SDMA were observed. There was a significant difference (Group 2 vs. Group 3) in renin, NITRIC, ADMA, and L-ARGININE. There was highly significant differentiation (Group 2 vs. Group 3) in NGAL, noradrenalin, and SDMA. There was highly significant variation as per odd ratio and confidence interval between (Group 3 vs. Group 2) in NGAL. CONCLUSION: Assessment of renal biomarkers in individuals with decompensated cirrhosis gives critical information on the etiology of AKI. Further, it may aid in the diagnosis and prognosis of AKI. Renin, NITRIC, ADMA, and L-ARGININE could be used as biomarkers to indicate HRS in individuals with advanced cirrhosis.

Serum Amyloid Beta42 Is Not Eliminated by the Cirrhotic Liver: A Pilot Study

Amyloid-beta (Aβ) deposition in the brain is the main pathological hallmark of Alzheimer disease. Peripheral clearance of Aβ may possibly also lower brain levels. Recent evidence suggested that hepatic clearance of Aβ42 is impaired in liver cirrhosis. To further test this hypothesis, serum Aβ42 was measured by ELISA in portal venous serum (PVS), systemic venous serum (SVS), and hepatic venous serum (HVS) of 20 patients with liver cirrhosis. Mean Aβ42 level was 24.7 ± 20.4 pg/mL in PVS, 21.2 ± 16.7 pg/mL in HVS, and 19.2 ± 11.7 pg/mL in SVS. Similar levels in the three blood compartments suggested that the cirrhotic liver does not clear Aβ42. Aβ42 was neither associated with the model of end-stage liver disease score nor the Child–Pugh score. Patients with abnormal creatinine or bilirubin levels or prolonged prothrombin time did not display higher Aβ42 levels. Patients with massive ascites and patients with large varices had serum Aβ42 levels similar to patients without these complications. Serum Aβ42 was negatively associated with connective tissue growth factor levels (r = −0.580, p = 0.007) and a protective role of Aβ42 in fibrogenesis was already described. Diabetic patients with liver cirrhosis had higher Aβ42 levels (p = 0.069 for PVS, p = 0.047 for HVS and p = 0.181 for SVS), which is in accordance with previous reports. Present analysis showed that the cirrhotic liver does not eliminate Aβ42. Further studies are needed to explore the association of liver cirrhosis, Aβ42 levels, and cognitive dysfunction.

Association of Asymmetric Dimethylarginine and Nitric Oxide with Cardiovascular Risk in Patients with End-Stage Liver Disease

BACKGROUND AND OBJECTIVES

Endothelial dysfunction has been proposed to be an underlying mechanism of the pronounced cardiovascular morbidity in end-stage liver disease (ESLD), but clinical evidence is still limited. In this study, we investigated the association of circulating levels of asymmetric dimethylarginine (ADMA) and nitric oxide (NO) with estimated cardiovascular risk in patients with ESLD awaiting liver transplantation.

MATERIALS AND METHODS

ADMA and NO levels were measured in the sera of 160 adult ESLD patients. The severity of hepatic dysfunction was assessed by the model for end-stage liver disease (MELD) score. The cardiovascular risk was estimated with the European Society of Cardiology Systematic Coronary Risk Estimation (SCORE) index, which was used to dichotomize patients in the subgroups depicting higher and lower cardiovascular risk.

RESULTS

Severe hepatic dysfunction (MELD ≥ 18) was present in 38% of the patients, and a higher cardiovascular risk was present in almost half of the patients (N = 74). ADMA and NO both significantly increased with the progression of liver disease and were independently associated with higher cardiovascular risk. Fasting glucose also independently predicted a higher cardiovascular risk, while HDL cholesterol and the absence of concomitant hepatocellular carcinoma were protective factors.

CONCLUSIONS

These results suggest a remarkable contribution of the deranged arginine/NO pathway to cardiovascular risk in patients with end-stage liver disease.

One-Carbon Metabolism in Fatty Liver Disease and Fibrosis: One-Carbon to Rule Them All

Nonalcoholic fatty liver disease (NAFLD) is a term used to characterize a range of disease states that involve the accumulation of fat in the liver but are not associated with excessive alcohol consumption. NAFLD is a prevalent disease that can progress to organ damage like liver cirrhosis and hepatocellular carcinoma. Many animal models have demonstrated that one-carbon metabolism is strongly associated with NAFLD. Phosphatidylcholine is an important phospholipid that affects hepatic lipid homeostasis and de novo synthesis of this phospholipid is associated with NAFLD. However, one-carbon metabolism serves to support all cellular methylation reactions and catabolism of methionine, serine, glycine, choline, betaine, tryptophan, and histidine. Several different pathways within one-carbon metabolism that play important roles in regulating energy metabolism and immune function have received less attention in the study of fatty liver disease and fibrosis. This review examines what we have learned about hepatic lipid metabolism and liver damage from the study of one-carbon metabolism thus far and highlights unexplored opportunities for future research.

New Developments in Hepatorenal Syndrome

Hepatorenal syndrome (HRS) continues to be one of the major complications of decompensated cirrhosis, leading to death in the absence of liver transplantation. Challenges in precisely evaluating renal function in the patient with cirrhosis remain because of the limitations of serum creatinine (Cr) alone in estimating glomerular filtration rate (GFR); current GFR estimating models appear to underestimate renal dysfunction. Newer models incorporating renal biomarkers, such as the Cr-Cystatin C GFR Equation for Cirrhosis appear to estimate measured GFR more accurately. A major change in the diagnostic criteria for HRS based on dynamic serial changes in serum Cr that regard HRS type 1 as a special form of acute kidney injury promises the possibility of earlier identification of renal dysfunction in patients with cirrhosis. The diagnostic criteria of HRS still include the exclusion of other causes of kidney injury. Renal biomarkers have been disappointing in assisting with the differentiation of HRS from prerenal azotemia and other kidney disorders. Serum metabolomic profiling may be a more powerful tool to assess renal dysfunction, although the practical clinical significance of this remains unclear. As a result of the difficulties of assessing renal function in cirrhosis and the varying HRS diagnostic criteria and the rigor with which they are applied, the precise incidence and prevalence of HRS is unknown, but it is likely that HRS occurs more commonly than expected. The pathophysiology of HRS is rooted firmly in the setting of progressive reduction in renal blood flow as a result of portal hypertension and splanchnic vasodilation. Progressive marked renal cortical ischemia in patients with cirrhosis parallels the evolution of diuretic-sensitive ascites to diuretic-refractory ascites and HRS, a recognized continuum of renal dysfunction in cirrhosis. Alterations in nitrous oxide production, both increased and decreased, may play a major role in the pathophysiology of this evolution. The inflammatory cascade, triggered by bacterial translocation and endotoxemia, increasingly recognized as important in the manifestation of acute-on-chronic liver failure, also may play a significant role in the pathophysiology of HRS. The mainstay of treatment remains vasopressor therapy with albumin in an attempt to reverse splanchnic vasodilation and improve renal blood flow. Several meta-analyses have confirmed the value of vasopressors, chiefly terlipressin and noradrenaline, in improving renal function and reversing HRS type 1. Other interventions such as renal replacement therapy, transjugular intrahepatic portosystemic shunt, and artificial liver support systems have a very limited role in improving outcomes in HRS. Liver transplantation remains the definitive treatment for HRS. The frequency of simultaneous liver-kidney transplantation has increased dramatically in the Model for End-stage Liver Disease era, with changes in organ allocation policies. This has resulted in a more urgent need to predict native kidney recovery from HRS after liver transplantation alone, to avoid unnecessary simultaneous liver-kidney transplantation.

Asymmetric Dimethylarginine and Hepatic Encephalopathy: Cause, Effect or Association?

The methylated derivative of l-arginine, asymmetric dimethylarginine (ADMA) is synthesized in different mammalian tissues including the brain. ADMA acts as an endogenous, nonselective, competitive inhibitor of all three isoforms of nitric oxide synthase (NOS) and may limit l-arginine supply from the plasma to the enzyme via reducing its transport by cationic amino acid transporters. Hepatic encephalopathy (HE) is a relatively frequently diagnosed complex neuropsychiatric syndrome associated with acute or chronic liver failure, characterized by symptoms linked with impaired brain function leading to neurological disabilities. The l-arginine—nitric oxide (NO) pathway is crucially involved in the pathomechanism of HE via modulating important cerebral processes that are thought to contribute to the major HE symptoms. Specifically, activation of this pathway in acute HE leads to an increase in NO production and free radical formation, thus, contributing to astrocytic swelling and cerebral edema. Moreover, the NO-cGMP pathway seems to be involved in cerebral blood flow (CBF) regulation, altered in HE. For this reason, depressed NO-cGMP signaling accompanying chronic HE and ensuing cGMP deficit contributes to the cognitive and motor failure. However, it should be remembered that ADMA, a relatively little known element limiting NO synthesis in HE, may also influence the NO-cGMP pathway regulation. In this review, we will discuss the contribution of ADMA to the regulation of the NO-cGMP pathway in the brain, correlation of ADMA level with CBF and cognitive alterations observed during HE progression in patients and/or animal models of HE.

Estimation of Glomerular Filtration Rate in Patients With Cirrhosis by Using New and Conventional Filtration Markers and Dimethylarginines

BACKGROUND & AIMS

Equations used to estimate glomerular filtration rate (GFR) are not accurate in patients with cirrhosis. We aimed to develop a new equation to estimate the GFR in subjects with cirrhosis and compare its performance with chronic kidney disease epidemiology collaboration (CKD-EPI) cystatin C and creatinine-cystatin C equations, which were derived in populations without cirrhosis.

METHODS

From 2010 through 2014, we measured GFR in 103 subjects with cirrhosis based on non-radiolabeled iothalamate plasma clearance. We measured blood levels of creatinine, cystatin C, β-trace protein, β2-microglobulin, L-arginine, and symmetric and asymmetric dimethylarginines simultaneously with GFR. Multivariate linear regression analysis was performed to develop models to estimate GFR. Overall accuracy, defined by the root mean square error (RMSE) of our newly developed model to estimate GFR, was compared with that of the CKD-EPI equations. To obtain an unbiased estimate of our new equation to estimate GFR, we used a leave-one-out cross-validation strategy.

RESULTS

After we considered all the candidate variables and blood markers of GFR, the most accurate equation we identified to estimate GFR included serum levels of creatinine and cystatin C, as well as patients' age, sex, and race. Overall, the accuracy of this equation (RMSE = 22.92) was superior to that of the CKD-EPI cystatin C equation (RMSE = 27.27, P = .004). Among subjects with cirrhosis and diuretic-refractory ascites, the accuracy of the equation we developed to estimate GFR (RMSE = 19.36) was greater than that of the CKD-EPI cystatin C (RMSE = 27.30, P = .003) and CKD-EPI creatinine-cystatin C equations (RMSE = 23.37, P = .004).

CONCLUSIONS

We developed an equation that estimates GFR in subjects with cirrhosis and diuretic-refractory ascites with greater accuracy than the CKD-EPI cystatin C equation or CKD-EPI creatinine-cystatin C equation.

The dimethylarginine (ADMA)/nitric oxide pathway in the brain and periphery of rats with thioacetamide-induced acute liver failure: Modulation by histidine

Hepatic encephalopathy (HE) is related to variations in the nitric oxide (NO) synthesis and oxidative/nitrosative stress (ONS), and asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases (NOSs). In the present study we compared the effects of acute liver failure (ALF) in the rat TAA model on ADMA concentration in plasma and cerebral cortex, and on the activity and expression of the ADMA degrading enzyme, dimethylarginine dimethylaminohydrolase (DDAH), in brain and liver. ALF increased blood and brain ADMA, and the increase was correlated with decreased DDAH activity in both brain and liver. An i.p. administration of histidine (His), an amino acid reported to alleviate oxidative stress associated with HE (100 mg/kg b.w.), reversed the increase of brain ADMA, which was accompanied by the recovery of brain DDAH activity (determined ex vivo), and with an increase of the total NOS activity. His also activated DDAH ex vivo in brain homogenates derived from control and TAA rats. ALF in this model was also accompanied by increases of blood cyclooxygenase activity and blood and brain TNF-α content, markers of the inflammatory response in the periphery, but these changes were not affected by His, except for the reduction of TNF-α mRNA transcript in the brain. His increased the total antioxidant capacity of the brain cortex, but not of the blood, further documenting its direct neuroprotective power.

Increased circulatory asymmetric dimethylarginine and multiple organ failure: bile duct ligation in rat as a model

Bile duct ligation (BDL)-treated rats exhibit cholestasis, increased systemic oxidative stress, and liver fibrosis, which ultimately lead to liver cirrhosis. Asymmetric dimethylarginine (ADMA) is a competitive inhibitor of nitric oxide synthase that can decrease the synthesis of nitric oxide. BDL rats have higher plasma and hepatic ADMA levels, which may be due to increased hepatic protein arginine methyltransferase-1 and decreased dimethylarginine dimethylaminohydrolase expression. BDL rats also exhibit renal and brain damage characterized by increased tissue ADMA concentrations. The increased plasma ADMA levels and multiple organ damages seen here are also observed following multiple organ failures associated with critical illness. This review discusses the dysregulation of ADMA in major organs in BDL rats and the role of increased ADMA in multiple organ damages.

Current concepts in the diagnosis and classification of renal dysfunction in cirrhosis

BACKGROUND

Renal dysfunction is one of the most common complications of cirrhosis with high morbidity and mortality.

SUMMARY

In subjects with cirrhosis, renal dysfunction can present either as a direct consequence of cirrhosis (e.g. hepatorenal syndrome type I and type II) or secondary to etiologies other than cirrhosis (chronic kidney disease due to diabetic nephropathy, prerenal azotemia), or patients with cirrhosis may have renal dysfunction resulting directly from cirrhosis and an underlying chronic kidney disease.

KEY MESSAGES

Given the challenges in the differential diagnosis of renal dysfunction and insufficient accuracy of serum creatinine and creatinine-based glomerular filtration rate estimating equations in cirrhosis, there is an urgent need for more accurate biomarkers of renal dysfunction in this population. This review will discuss novel concepts for the diagnosis and classification of renal dysfunction in cirrhosis to overcome at least some of the diagnostic and therapeutic challenges. Additionally, a new classification will be proposed for renal dysfunction in cirrhosis.

Portal vein omentin is increased in patients with liver cirrhosis but is not associated with complications of portal hypertension

BACKGROUND

Omentin is a visceral fat-derived adipokine associated with endothelium-dependent vasodilation. Impaired endothelial function is a major cause of portal hypertension in liver cirrhosis. The aim was to assess associations of omentin with systemic markers of endothelial function, namely arginine and asymmetric dimethylarginine (ADMA) and complications of portal hypertension in liver cirrhosis.

MATERIALS AND METHODS

Systemic omentin was measured by ELISA in portal venous serum (PVS), systemic venous serum (SVS) and hepatic venous serum (HVS) of 40 patients with liver cirrhosis and 10 liver-healthy controls. ADMA and arginine were determined in SVS of the patients by ELISA.

RESULTS

Omentin is elevated in PVS and tends to be increased in SVS and HVS of patients with liver cirrhosis compared with controls. Omentin is principally expressed in visceral fat, and PVS omentin tends to be higher than SVS levels. Lower HVS than PVS omentin suggests that omentin may be partly removed from the circulation by the liver. Omentin in serum is not associated with stages of liver cirrhosis defined by CHILD-POUGH or MELD score and is not affected in patients with ascites. HVS omentin tends to be reduced in patients with large varices compared with patients without/with small varices. Arginine/ADMA ratio is reduced in patients with massive ascites but is not associated with variceal size. Further, Arginine/ADMA ratio does not correlate with omentin.

CONCLUSION

Current data show that PVS omentin is increased in liver cirrhosis but is not associated with complications of portal hypertension.

Asymmetric dimethylarginine is strongly associated with cognitive dysfunction and brain MR spectroscopic abnormalities in cirrhosis

BACKGROUND & AIMS

Asymmetric dimethylarginine (ADMA) is an inhibitor of nitric oxide synthase that accumulates in liver disease and may contribute to hepatic encephalopathy (HE). We aimed at evaluating the association of ADMA with cognition and brain MR spectroscopy (MRS) in cirrhosis.

METHODS

Cirrhotic patients with/without prior HE and non-cirrhotic controls underwent cognitive testing and ADMA determination. A subgroup underwent brain MRS [glutamine/glutamate (Glx), myoinositol (mI), N-acetyl-aspartate (NAA) in parietal white, occipital gray, and anterior cingulated (ACC)]. Cognition and ADMA in a cirrhotic subgroup before and one month after transjugular intrahepatic portosystemic shunting (TIPS) were also tested. Cognition and MRS values were correlated with ADMA and compared between groups using multivariable regression. ADMA levels were compared between those who did/did not develop post-TIPS HE.

RESULTS

Ninety cirrhotics (MELD 13, 54 prior HE) and 16 controls were included. Controls had better cognition and lower ADMA, Glx, and higher mI compared to cirrhotics. Prior HE patients had worse cognition, higher ADMA and Glx and lower mI compared to non-HE cirrhotics. ADMA was positively correlated with MELD (r=0.58, p<0.0001), abnormal cognitive test number (r=0.66, p<0.0001), and Glx and NAAA (white matter, ACC) and negatively with mI. On regression, ADMA predicted number of abnormal tests and mean Z-score independent of prior HE and MELD. Twelve patients underwent TIPS; 7 developed HE post-TIPS. ADMA increased post-TIPS in patients who developed HE (p=0.019) but not in others (p=0.89).

CONCLUSIONS

A strong association of ADMA with cognition and prior HE was found independent of the MELD score in cirrhosis.

The transhepatic endotoxin gradient is present despite liver cirrhosis and is attenuated after transjugular portosystemic shunt (TIPS)

BACKGROUND

Translocation of gut-derived bacterial products such as endotoxin is a major problem in liver cirrhosis.

METHODS

To assess the hepatic clearance of bacterial products in individuals with cirrhosis, we tested concentrations of Gram-negative bacterial lipopolysaccharide (LPS), LPS-binding protein (LBP), and the precursor of nitric oxide (NO), L-arginine, in a cohort of 8 stable patients with liver cirrhosis before and after elective transjugular portosystemic shunt (TIPS) implantation, including central venous, hepatic venous, and portal venous measurements.

RESULTS

Using an adapted LPS assay, we detected high portal venous LPS concentrations (mean 1743 ± 819 pg/mL). High concentrations of LPS were detectable in the central venous blood (931 ± 551 pg/mL), as expected in persons with cirrhosis. The transhepatic LPS gradient was found to be 438 ± 287 pg/mL, and 25 ± 12% of portal LPS was cleared by the cirrhotic liver. After TIPS, central venous LPS concentrations increased in the hepatic and central veins, indicating shunting of LPS with the portal blood through the stent. This paralleled a systemic increase of L-arginine, whereas the NO synthase inhibitor asymmetric dimethylarginine (ADMA) remained unchanged, suggesting that bacterial translocation may contribute to the pathogenesis of circulatory dysfunction post-TIPS.

CONCLUSIONS

This study provides quantitative estimates of the role of the liver in the pathophysiology of bacterial translocation. The data indicate that the cirrhotic liver retains the capacity for clearance of bacterial endotoxin from the portal venous blood and that TIPS implantation attenuates this clearance. Thus, increased endotoxin concentrations in the systemic circulation provide a possible link to the increased encephalopathy in TIPS patients.