Renal sodium retention during upright posture in preascitic cirrhosis

Sodium-glucose linked transporter 2 inhibitors in liver cirrhosis: Beyond their antidiabetic use

Type 2 diabetes mellitus (T2DM) and liver cirrhosis are clinical entities that frequently coexist, but glucose-lowering medication options are limited in cirrhotic patients. Sodium-glucose linked transporter 2 (SGLT2) inhibitors are a class of glucose-lowering medication that act independently of insulin, by causing glycosuria in the proximal convoluted tubule. In this review, we aimed to briefly present the main data and to provide insight into the pathophysiology and potential usefulness of SGLT2 inhibitors in cirrhotic patients with or without T2DM. SGLT2 inhibitors have been proven useful as antidiabetic treatment in patients with metabolic liver disease, with most robust data from patients with metabolic dysfunction-associated steatotic liver disease (MASLD), where they also showed improvement in liver function parameters. Moreover, it has been suggested that SGLT2 inhibitors may have effects beyond their antidiabetic action. Accordingly, they have exhibited cardioprotective effects, expanding their indication in patients with heart failure without T2DM. Since decompensated liver cirrhosis and congestive heart failure share common pathophysiological features, namely renin-angiotensin-aldosterone axis and sympathetic nervous system activation as well as vasopressin secretion, SGLT2 inhibitors could also be beneficial in patients with decompensated cirrhosis, even in the absence of T2DM.

Adaptive Mechanisms of Renal Bile Acid Transporters in a Rat Model of Carbon Tetrachloride-Induced Liver Cirrhosis

Background: Acute kidney injury (AKI) is common in advanced liver cirrhosis, a consequence of reduced kidney perfusion due to splanchnic arterial vasodilation and intrarenal vasoconstriction. It clinically manifests as hepatorenal syndrome type 1, type 2, or as acute tubular necrosis. Beyond hemodynamic factors, an additional mechanism may be hypothesized to explain the renal dysfunction during liver cirrhosis. Recent evidence suggest that such mechanisms may be closely related to obstructive jaundice. Methods: Given the not completely elucidated role of bile acids in kidney tissue damage, this study developed a rat model of AKI with liver cirrhosis induction by carbon tetrachloride (CCl₄) inhalation for 12 weeks. Histological analyses of renal and liver biopsies were performed at sacrifice. Organic anion tubular transporter distribution and apoptosis in kidney cells were analyzed by immunohistochemistry. Circulating and urinary markers of inflammation and tubular injury were assayed in 21 treated rats over time (1, 2, 4, 8, and 12 weeks of CCl₄ administration) and 5 controls. Results: No renal histopathological alterations were found at sacrifice. Comparing treated rats with controls, organic anion transporters were differentially expressed and localized. High serum bile acid values were detected in cirrhotic animals, while caspase-3 staining was negative in both groups. Increased levels of serum inflammatory and urinary tubular injury biomarkers were observed during cirrhosis progression, with a peak after 4 and 8 weeks of treatment. Conclusions: These findings suggest possible adaptive tubular mechanisms for bile acid transporters in response to cirrhosis-induced AKI.

Mechanisms of decompensation and organ failure in cirrhosis: From peripheral arterial vasodilation to systemic inflammation hypothesis

The peripheral arterial vasodilation hypothesis has been most influential in the field of cirrhosis and its complications. It has given rise to hundreds of pathophysiological studies in experimental and human cirrhosis and is the theoretical basis of life-saving treatments. It is undisputed that splanchnic arterial vasodilation contributes to portal hypertension and is the basis for manifestations such as ascites and hepatorenal syndrome, but the body of research generated by the hypothesis has revealed gaps in the original pathophysiological interpretation of these complications. The expansion of our knowledge on the mechanisms regulating vascular tone, inflammation and the host-microbiota interaction require a broader approach to advanced cirrhosis encompassing the whole spectrum of its manifestations. Indeed, multiorgan dysfunction and failure likely result from a complex interplay where the systemic spread of bacterial products represents the primary event. The consequent activation of the host innate immune response triggers endothelial molecular mechanisms responsible for arterial vasodilation, and also jeopardizes organ integrity with a storm of pro-inflammatory cytokines and reactive oxygen and nitrogen species. Thus, the picture of advanced cirrhosis could be seen as the result of an inflammatory syndrome in contradiction with a simple hemodynamic disturbance.

ANP-induced signaling cascade and its implications in renal pathophysiology

The balance between vasoconstrictor/sodium-retaining and vasodilator/natriuretic systems is essential for maintaining body fluid and electrolyte homeostasis. Natriuretic peptides, such as atrial natriuretic peptide (ANP), belong to the vasodilator/natriuretic system. ANP is produced by the conversion of pro-ANP into ANP, which is achieved by a proteolytical cleavage executed by corin. In the kidney, ANP binds to the natriuretic peptide receptor-A (NPR-A) and enhances its guanylyl cyclase activity, thereby increasing intracellular cyclic guanosine monophosphate production to promote natriuretic and renoprotective responses. In the glomerulus, ANP increases glomerular permeability and filtration rate and antagonizes the deleterious effects of the renin-angiotensin-aldosterone system activation. Along the nephron, natriuretic and diuretic actions of ANP are mediated by inhibiting the basolaterally expressed Na(+)-K(+)-ATPase, reducing apical sodium, potassium, and protein organic cation transporter in the proximal tubule, and decreasing Na(+)-K(+)-2Cl(-) cotransporter activity and renal concentration efficiency in the thick ascending limb. In the medullary collecting duct, ANP reduces sodium reabsorption by inhibiting the cyclic nucleotide-gated cation channels, the epithelial sodium channel, and the heteromeric channel transient receptor potential-vanilloid 4 and -polycystin 2 and diminishes vasopressin-induced water reabsorption. Long-term ANP treatment may lead to NPR-A desensitization and ANP resistance, resulting in augmented sodium and water reabsorption. In mice, corin deficiency impairs sodium excretion and causes salt-sensitive hypertension. Characteristics of ANP resistance and corin deficiency are also encountered in patients with edema-associated diseases, highlighting the importance of ANP signaling in salt-water balance and renal pathophysiology.

Review article: advances in the management of patients with cirrhosis and portal hypertension-related renal dysfunction

BACKGROUND

In cirrhosis, portal hypertension is associated with a spectrum of renal dysfunction that has significant implications for morbidity and mortality.

AIM

To discuss recent progress in the patho-physiological mechanisms and therapeutic options for portal hypertension-related renal dysfunction.

METHODS

A literature search using Pubmed was performed.

RESULTS

Portal hypertension-related renal dysfunction occurs in the setting of marked neuro-humoral and circulatory derangement. A systemic inflammatory response is a pathogenetic factor in advanced disease. Such physiological changes render the individual vulnerable to further deterioration of renal function. Patients are primed to develop acute kidney injury when exposed to additional 'hits', such as sepsis. Recent progress has been made regarding our understanding of the aetiopathogenesis. However, treatment options once hepatorenal syndrome develops are limited, and prognosis remains poor. Various strategies to prevent acute kidney injury are suggested.

CONCLUSION

Prevention of acute kidney injury in high risk patients with cirrhosis and portal hypertension-related renal dysfunction should be a clinical priority.

Activity with ambulation attenuates diuretic responsiveness in chronic heart failure

INTRODUCTION

We hypothesized that discharged heart failure (HF) patients could develop clinical congestion despite adhering to prescribed diuretics, because ambulation attenuates diuretic and natriuretic responsiveness.

METHODS

We studied 9 patients aged 57 ± 13 (mean ± SD) years with New York Heart Association functional class II-III symptoms and ejection fraction <40% (28 ± 7%) and receiving furosemide (≥80 mg/d [113 ± 53 mg/d]) plus renin-angiotensin system antagonists and beta-blockade. Inulin and p-amminohippuric acid were infused to estimate glomerular filtration rate (GFR) and renal plasma flow (RPF). Furosemide was administered intravenously at 75% of the usual oral morning dose. Participants were randomized to supine (90 minutes recumbancy) or upright (90 minutes sitting and treadmill walking) posture and assumed the other position on their second day. Primary outcome variables were urine volume and sodium excretion 90 minutes after furosemide.

RESULTS

On the upright, compared with the supine, day, urine volume (792 ± 484 vs 1,290 ± 503 mL; P = .02) and sodium (79 ± 55 vs 141 ± 61 mmol; P < .01) were attenuated, whereas plasma norepinephrine (4.4 ± 2.7 vs 2.3 ± 1.8 mmol/L; P = .01) and renin (327 ± 250% of supine; P < .01) were augmented. Urinary K+, mean pressure, GFR, and RPF were similar.

CONCLUSIONS

Activation of the sympathetic nervous system and renin-angiotensin axis by upright ambulation may attenuate diuresis and natriuresis by increasing proximal tubular reabsorption of sodium and water.

Calcium-dependent diuretic system in preascitic liver cirrhosis

BACKGROUND & AIMS

Extracellular Ca(++) activates cell membrane calcium-sensing receptors (CaRs), leading to renal tubule production of prostaglandins E(2) (PGE(2)), which decrease both sodium reabsorption in the thick ascending limb of Henle's loop and free-water reabsorption in collecting ducts.

AIMS & METHODS

To assess the activity of this diuretic system in experimental cirrhosis, we evaluated renal function, hormonal status, PGE(2) urinary excretion, and renal tissue concentrations of Na(+)-K(+)-2Cl(-) co-transporters (BSC-1) and CaRs in three groups of rats: one group of controls receiving 5% glucose solution (vehicle) intravenously and two groups of rats with CCl(4)-induced preascitic cirrhosis receiving either vehicle or 0.5mg i.v. Poly-l-Arginine (PolyAg), a CaR-selective agonist.

RESULTS

Compared to controls, cirrhotic rats showed reduced urine volume and sodium excretion (p<0.05). Western blot analysis revealed reduced CaRs and increased BSC-1 protein content in kidneys of cirrhotic rats compared with controls (all p<0.01). PolyAg-treated cirrhotic rats had their urine and sodium excretion returned to normal; PolyAg also increased renal plasma flow, PGE(2) urinary excretion, and free-water clearance in cirrhotic rats (all p<0.01 v. untreated cirrhotic animals).

CONCLUSIONS

In preascitic cirrhosis, sodium retention may be linked to down-regulation of renal CaRs and up-regulation of tubular sodium-retaining channels. Calcimimetic drugs normalize preascitic sodium retention.

PDEs1-5 activity and expression in tissues of cirrhotic rats reveal a role for aortic PDE3 in NO desensitization

Liver cirrhosis is associated with increased nitric oxide (NO) production in the vasculature. We have previously demonstrated that aorta from rats with liver cirrhosis have a reduced relaxant response to NO donors that is corrected by DMPPO, a PDE5-specific inhibitor. Vasodilator responses to DMPPO itself were also reduced in rings from cirrhotic rats. These results supported previous suggestions that upregulation of PDE5 in liver cirrhosis might contribute to renal sodium retention, and consequently modulate vascular reactivity in the context of increased NO production (Tahseldar-Roumieh et al. in Am. J. Physiol. Heart Circ. Physiol. 290, H481-H488, 2006). Here, we investigated the possible alteration in activity and expression of cyclic nucleotide phosphodiesterase PDE1-PDE5 in kidney and vascular tissues in rats 4 weeks after bile duct ligation. The kidney of rats with cirrhosis had increased activity of PDE1 and PDE4 but not PDE5, and increased expression of PDE1A. Unexpectedly and interestingly, there was no change in cirrhotic aorta PDE5, but an increase in PDE3 and PDE4 activity associated with increased expression of PDE3A and PDE3B. Cilostamide, a specific PDE3 inhibitor, corrected the decreased response to an NO donor in isolated aorta from cirrhotic rats, suggesting that the difference in response to NO donors was due to differences in PDE3-induced hydrolysis of cGMP or to cGMP-induced inhibition of PDE3, rather than to differences in PDE5 contribution. In conclusion, these changes in PDE isozymes could greatly contribute to NO desensitization and to the regulation of vascular and renal function in liver cirrhosis.

Hemodynamic alterations in liver cirrhosis

In cirrhotic patients, portal hypertension is often associated with a hyperdynamic circulatory syndrome, with high cardiac output and reduced systemic vascular resistance and arterial pressure. The hyperdynamic circulatory syndrome is due to arterial vasodilation that mainly occurs in the splanchnic circulation, while vascular resistance in the other circulatory districts is normal or increased, accordingly with the degree of portal hypertension, liver impairment and activation of the renin-aldosterone and sympathetic nervous system. The mechanism(s) leading to splanchnic vasodilation is unclear. A favored hypothesis translocation of intestinal bacteria and/or some their products, such as endotoxin, into the interstitial space in the splanchnic organs results in the local release of vasodilating factors such as nitric oxide, carbon monoxide and others.

Sodium retention and ascites formation in a cholestatic mice model: role of aldosterone and mineralocorticoid receptor?

Renal sodium retention in experimental liver cirrhosis originates from the distal nephron sensitive to aldosterone. The aims of this study were to (1) determine the exact site of sodium retention along the aldosterone-sensitive distal nephron, and (2) to evaluate the role of aldosterone and mineralocorticoid receptor activation in this process. Liver cirrhosis was induced by bile duct ligation in either adrenal-intact or corticosteroid-clamped mice. Corticosteroid-clamp was achieved through adrenalectomy and corticosteroid supplementation with aldosterone and dexamethasone via osmotic minipumps. 24-hours renal sodium balance was evaluated in metabolic cages. Activity and expression of sodium- and potassium-dependent adenosine triphosphatase were determined in microdissected segments of nephron. Within 4-5 weeks, cirrhosis induced sodium retention in adrenal-intact mice and formation of ascites in 50% of mice. At that time, sodium- and potassium-dependent adenosine triphosphatase activity increased specifically in cortical collecting ducts. Hyperaldosteronemia was indicated by increases in urinary aldosterone excretion and in sgk1 (serum- and glucocorticoid-regulated kinase 1) mRNA expression in collecting ducts. Corticosteroid-clamp prevented induction of sgk1 but not cirrhosis-induced sodium retention, formation of ascites and stimulation of sodium- and potassium-dependent adenosine triphosphatase activity and expression (mRNA and protein) in collecting duct. These findings demonstrate that sodium retention in cirrhosis is independent of hyperaldosteronemia and of the activation of mineralocorticoid receptor.

CONCLUSION

Bile duct ligation in mice induces cirrhosis which, within 4-5 weeks, leads to the induction of sodium- and potassium-dependent adenosine triphosphatase in cortical collecting ducts, to renal sodium retention and to the formation of ascites. Sodium retention, ascites formation and induction of sodium- and potassium-dependent adenosine triphosphatase are independent of the activation of mineralocorticoid receptors by either aldosterone or glucocorticoids.

Daily profile of circulating C-type natriuretic peptide in pre-ascitic cirrhosis and in normal subjects: relationship with renal function

OBJECTIVE

To investigate whether the C-type natriuretic peptide (CNP) has a role in the regulation of fluid and sodium homeostasis in normal subjects and in pre-ascitic cirrhotic patients.

MATERIAL AND METHODS

The daily profile of CNP plasma levels was assessed by serial measurements (0700 h, 0900 h, 1800 h, 2300 h) in 10 pre-ascitic cirrhotic outpatients (age 56+/-4 years) and in 10 age-matched healthy controls (54+/-2 years) on a normal sodium diet (150 mmol/day) while carrying on their usual activities (mobile from 0700 h to 2200 h), after an equilibration period of 5 days. Daily diuresis and natriuresis were also monitored.

RESULTS

Mean daily CNP was comparable in cirrhotic and healthy subjects (3.64+/-0.32 versus 3.20+/-0.20 pg/ml; p=0.139); CNP concentration showed a tendency towards a circadian fluctuation in healthy subjects (p=0.053) but not in patients (p=0.171). Mean daily CNP concentration significantly correlated with 24-h natriuresis (r=0.709; p=0.022) and urine volume (r=0.745; p=0.013) in patients but not in healthy subjects.

CONCLUSIONS

CNP plasma levels appear to play a role in the water-sodium balance regulation in patients with pre-ascitic cirrhosis.

Effects of a 7-day treatment with midodrine in non-azotemic cirrhotic patients with and without ascites

BACKGROUND/AIMS

Splanchnic arterial vasodilatation has been causally related with hyperdynamic circulation and impaired natriuresis in advanced cirrhosis and has also been suggested to be responsible for the subtle sodium retention in pre-ascitic cirrhosis. This study evaluated the effects of a 7-day treatment with the alpha1-adrenergic agonist midodrine in non-azotemic cirrhotic patients with and without ascites.

METHODS

Thirty-nine cirrhotic patients were studied at baseline and 7 days after administration of oral midodrine 10mg, t.i.d. (11 without and 12 with ascites) or placebo (8 without and 8 with ascites).

RESULTS

A significant increase in urine sodium excretion was noted after midodrine administration in patients without and with ascites, in line with significant increases in mean arterial pressure and systemic vascular resistance, and significant decreases in cardiac output and heart rate. Significant increases in glomerular filtration rate, filtration fraction, and urine volume and significant decreases in plasma renin activity and aldosterone were observed in patients with ascites. Placebo had no effect in any study group.

CONCLUSIONS

The administration of midodrine for 7 days improves systemic haemodynamics and sodium excretion in non-azotemic cirrhotic patients without or with ascites. In patients with ascites, but not in those without ascites, these effects are associated with a suppression of the activity of the renin-angiotensin-aldosterone system, suggesting that the increase in natriuresis is related to the improvement in the effective arterial blood volume.

Effect of potassium canrenoate, an anti-aldosterone agent, on incidence of ascites and variceal progression in cirrhosis

BACKGROUND & AIMS

Because aldosterone-dependent sodium and water retention contribute to portal hypertension, the safety and effect of an antialdosteronic drug (Kcanrenoate) have been evaluated on the occurrence of de novo appearance of ascites and the development of esophageal varices or the progression of small varices.

METHODS

Inclusion criteria were as follows: Child-Pugh A viral pre-ascitic cirrhosis, with either F1 esophageal varices or no varices, but endoscopic and/or ultrasound evidence of portal hypertension. Thirteen Italian Liver Units prospectively enrolled 120 patients randomized to receive double-blind either Kcanrenoate (100 mg/day; 66 patients) or placebo (54 patients). Endoscopy and sonography were performed at entry and at 52 weeks unless the patient developed ascites earlier, whereas laboratory examinations were performed at entry and every 3 months thereafter. An intention-to-treat analysis was performed, with each end point assessed by the Fisher exact test; the cumulative risk for the appearance of any end point was analyzed by the adjusted log-rank test (Tarone-Ware), with censoring for drop-outs.

RESULTS

The progression of variceal status or appearance of ascites, analyzed independently, was not significantly more frequent on placebo (24.1% and 9.2%, respectively) than on Kcanrenoate (12.1% and 1.5%, respectively), whereas the cumulative occurrence of end points was decreased on Kcanrenoate (17.6% vs 38.3% with placebo; P < .05, Tarone-Ware test). The incidence of adverse events was negligible and did not differ between groups.

CONCLUSIONS

This preliminary study shows that 100 mg/day of Kcanrenoate is well tolerated and does not reduce the individual incidence of ascites and/or the appearance or progression of esophageal varices in preascitc cirrhosis, but may decrease their 1-year cumulative occurrence.

Impaired 11 beta-hydroxysteroid dehydrogenase contributes to renal sodium avidity in cirrhosis: hypothesis or fact?

Exaggerated renal sodium retention with concomitant potassium loss is a hallmark of cirrhosis and contributes to the accumulation of fluid as ascites, pleural effusion, or edema. This apparent mineralocorticoid effect is only partially explained by increased aldosterone concentrations. I present evidence supporting the hypothesis that cortisol confers mineralocorticoid action in cirrhosis. The underlying molecular pathology for this mineralocorticoid receptor (MR) activation by cortisol is a reduced activity of the 11 beta-hydroxysteroid dehydrogenase type 2, an enzyme protecting the MR from promiscuous activation by cortisol in healthy mammalians.

The effect of single oral low-dose losartan on posture-related sodium handling in post-TIPS ascites-free cirrhosis

Post-TIPS ascites-free patients with cirrhosis and previous refractory ascites demonstrate subtle sodium retention when challenged with a high sodium load. This is also observed in pre-ascitic patients with cirrhosis. This phenomenon is dependent on an intrarenal angiotensin II (ANG II) mechanism related to the assumption of erect posture. We investigated whether similar mechanisms were involved in post-TIPS ascites-free patients, by studying 10 patients with functioning TIPS and no ascites. We measured the effect of changing from supine to erect posture on sodium excretion at baseline and after single oral low dose losartan (7.5 mg) which has been shown to blunt proximal and distal tubular sodium reabsorption in pre-ascites. At baseline, the assumption of erect posture produced a reduction in sodium excretion (from 0.30+/-0.06 to 0.13+/-0.02 mmol/min, P=.05), which was mainly due to an increase in proximal tubular reabsorption of sodium (PTRNa) (69.7+/-3.1% to 81.1+/-1.8%, P=.003). The administration of losartan resulted in a blunting of PTRNa (supine 69.7+/-3.1% to 63.9+/-3.9%, P=.01 and erect 81.1+/-1.8% to 73.8+/-2.4%, P=.01), accompanied by an increased distal tubular reabsorption of sodium in both postures, with no overall improvement in sodium excretion on standing. In conclusion, post-TIPS ascites-free patients with cirrhosis exhibit erect posture-induced sodium retention. We speculate that (1) this effect is partly mediated by the effect of ANG II on PTRNa and (2) that the inability of low dose losartan to block the erect posture-induced sodium retention may be related to the erect posture-induced rise in aldosterone which is unmodified by losartan.

A novel sodium overload test predicting ascites decompensation in rats with CCl4-induced cirrhosis

BACKGROUND/AIMS

We aimed to develop a non-invasive test to identify the initial alterations of sodium homeostasis and prospectively predict decompensation in preascitic cirrhotic rats.

METHODS

The sodium overload test (SOT) was performed in control (CT) and CCl4-induced cirrhotic rats (CH) by calculating the percentage of sodium excreted in the urine after NaCl oral administration (0.5 g/kg). Liver fibrosis was quantified by image cytometry.

RESULTS

From the 8th week of CCl4 intoxication, while the daily sodium balance did not change in CH and CT, SOT became significantly lower in the former (62.1+/-13.2 vs 78.8+/-13.2%; P=0.035). At sacrifice, ascites was only present in one animal. The degree of liver fibrosis correlated with SOT. In subsequent experiments, 17 cirrhotic rats developed ascites between the 9th and 14th weeks. SOT remained stable up to 3 weeks before ascites appearance, while it fell significantly to 35+/-19 and 26+/-21% at 2 and 1 week before ascites diagnosis, respectively. Nearly all the rats (95%) with a SOT<60% developed ascites within 3 weeks.

CONCLUSIONS

In preascitic cirrhotic rats, SOT unveils sodium metabolism abnormalities earlier than the daily sodium balance and prospectively predicts ascites appearance, identifying rats in a homogeneous stage of cirrhosis, which is essential in pathophysiological studies on sodium retention.

Cardiac, neuroadrenergic, and portal hemodynamic effects of prolonged aldosterone blockade in postviral child A cirrhosis

OBJECTIVES

The present study was designed to determine the effects of long-term antialdosterone treatment on cardiac structural and functional alterations, portal and systemic hemodynamic as well as adrenergic dysfunction characterizing Child A cirrhotic patients with F1 esophageal varices.

METHODS

Twenty-two Child A postviral preascitic cirrhotic patients were randomly allocated to 200 mg/day K-Canrenoate (13 patients, age 59.6 +/- 2.2 yr, mean + SEM) or no-drug treatment (9 patients, age 61.8 +/- 2.3) for a 6-month-period. Measurements, which included hepatic venous pressure gradient (HVPG), left ventricular wall thickness, left ventricular end-diastolic volume and diastolic function (LVWT, LVEDV, and E/A ratio, echocardiography), and muscle sympathetic nerve activity (MSNA, microneurography, peroneal nerve), were obtained at baseline and following 6 months of drug or no-drug treatment. Ten healthy age-matched subjects served as controls.

RESULTS

Cirrhotic patients were characterized by increased HVPG, LVWT, and MSNA values and by a depressed E/A ratio. K-Canrenoate treatment significantly reduced HVPG (from 15.3 +/- 1.0 to 13.8 +/- 0.8 mmHg, p < 0.05), LVWT (from 21.8 +/- 0.5 to 20.7 +/- 0.6 mm, p < 0.02), and LVEDV (from 99.2 +/- 7 to 86.4 +/- 6 ml, p < 0.01), leaving E/A ratio and MSNA almost unaltered. No significant change was observed in the untreated group of cirrhotic patients followed for 6 months without intervention.

CONCLUSIONS

These data provide evidence that aldosterone blockade by long-term K-Canrenoate administration improves hepatic hemodynamics by lowering HVPG and ameliorates cardiac structure and function by favoring a reduction in LVWT and LVEDV as well. They also show, however, that this therapeutic intervention neither improves left ventricular diastolic dysfunction nor exerts sympathoinhibitory effects.

Evidence of a dynamic aldosterone-independent distal tubular control of renal sodium excretion in compensated liver cirrhosis

BACKGROUND AND AIM

In preascitic cirrhosis increased sodium retention occurs in kidney distal tubule in spite of normal aldosterone plasma levels. No clearance technique can dissect the respective contribution to sodium retention exerted by Henle's loop, distal convoluted tubule and collecting duct, so we evaluated proximal and distal tubular sodium handling in preascites during two manoeuvres that temporarily increase aldosterone secretion.

METHODS

Ten patients with compensated cirrhosis and nine controls were studied in recumbency, during standing and after dopamine receptor blockade with metoclopramide through: 4 h renal clearances of sodium, potassium, lithium and creatinine; plasma levels of active renin and aldosterone.

RESULTS

Whilst comparable in recumbency, aldosterone levels significantly rose during standing and after metoclopramide in both groups. In patients, dopaminergic blockade caused a fall of distal sodium delivery (P < 0.01) but urinary sodium excretion was unchanged because the reabsorbed fraction of distal sodium delivery also fell (P < 0.03). Cirrhotic patients showed the same findings in the passage from recumbency to standing.

CONCLUSIONS

In preascitic cirrhosis, the distal tubular segments of the nephron are able to cope with decreases in tubular flow by reducing reabsorption at an aldosterone-independent site (possibly the loop of Henle).

Effects of tilting on central hemodynamics and homeostatic mechanisms in cirrhosis

Patients with cirrhosis have a hyperdynamic circulation and an abnormal blood volume distribution with central hypovolemia, an activated sympathetic nervous system (SNS) as well as the renin-angiotensin-aldosterone system (RAAS). As the hyperdynamic circulation in cirrhosis may be present only in the supine patient, we studied the humoral and central hemodynamic responses to changes with posture. Twenty-three patients with alcoholic cirrhosis (Child-Turcotte-Pugh classes A/B/C: 2/13/8) and 14 healthy controls were entered. Measurements of central hemodynamics and activation of SNS and RAAS were taken in the supine position, after 30 degrees head-down tilting, and after 60 degrees passive head-up tilting for a maximum of 20 minutes. After the head-up tilting, the central blood volume (CBV) decreased in both groups, but the decrease was significantly smaller in patients than in controls (-19% vs. -36%, P <.01). Central circulation time increased only in the patients (+30% vs. -1%, P <.01). The absolute increases in circulating norepinephrine and renin after head-up tilting were significantly higher in the patients than in the controls (P <.05 and P <.01, respectively). In patients with cirrhosis, changes in SNS and RAAS were related to changes in arterial blood pressure, systemic vascular resistance, heart rate, non-CBV, plasma volume, and arterial compliance. In conclusion, cardiovascular and humoral responses to changes in posture are clearly abnormal in patients with cirrhosis. Head-up tilting decreases the CBV less in patients with cirrhosis, and the results suggest a differential regulation of central hemodynamics in patients with cirrhosis.

Effects of tilting on central hemodynamics and homeostatic mechanisms in cirrhosis

Patients with cirrhosis have a hyperdynamic circulation and an abnormal blood volume distribution with central hypovolemia, an activated sympathetic nervous system (SNS) as well as the renin-angiotensin-aldosterone system (RAAS). As the hyperdynamic circulation in cirrhosis may be present only in the supine patient, we studied the humoral and central hemodynamic responses to changes with posture. Twenty-three patients with alcoholic cirrhosis (Child-Turcotte-Pugh classes A/B/C: 2/13/8) and 14 healthy controls were entered. Measurements of central hemodynamics and activation of SNS and RAAS were taken in the supine position, after 30 degrees head-down tilting, and after 60 degrees passive head-up tilting for a maximum of 20 minutes. After the head-up tilting, the central blood volume (CBV) decreased in both groups, but the decrease was significantly smaller in patients than in controls (-19% vs. -36%, P <.01). Central circulation time increased only in the patients (+30% vs. -1%, P <.01). The absolute increases in circulating norepinephrine and renin after head-up tilting were significantly higher in the patients than in the controls (P <.05 and P <.01, respectively). In patients with cirrhosis, changes in SNS and RAAS were related to changes in arterial blood pressure, systemic vascular resistance, heart rate, non-CBV, plasma volume, and arterial compliance. In conclusion, cardiovascular and humoral responses to changes in posture are clearly abnormal in patients with cirrhosis. Head-up tilting decreases the CBV less in patients with cirrhosis, and the results suggest a differential regulation of central hemodynamics in patients with cirrhosis.

Review article: pathogenesis and pathophysiology of hepatorenal syndrome--is there scope for prevention?

The hepatorenal syndrome (HRS) is a functional impairment of the kidneys in chronic liver disease caused by a circulatory failure. The prognosis is poor, particularly with type 1 HRS, but also type 2, and only liver transplantation is of lasting benefit. However, recent research into the pathophysiology of ascites and HRS has stimulated new enthusiasm in their prevention and treatment. Patients with HRS have hyperdynamic circulatory dysfunction with reduced arterial blood pressure and reduced central blood volume, owing to preferential splanchnic arterial vasodilatation. Activation of potent vasoconstricting systems, including the sympathetic nervous and renin-angiotensin-aldosterone systems, counteracts the arterial vasodilatation and leads to a pronounced renal vasoconstriction with renal hypoperfusion, a reduced glomerular filtration rate, and intense sodium-water retention. Thus prevention of HRS should seek to improve liver function, limit arterial hypotension and central hypovolaemia, and reduce renal vasoconstriction and the renal and interstitial pressures. Portal pressure can be reduced with beta-adrenergic blockers and transjugular intrahepatic portosystemic shunt (TIPS). Precipitating events, like infections, bleeding, and postparacentesis circulatory syndrome, should be treated to avoid further circulatory failure. Improvement in arterial blood pressure and central hypovolaemia can be achieved with vasoconstrictors, such as terlipressin (Glypressin), and plasma expanders such as human albumin. In the future endothelins, adenosine antagonists, long-acting vasoconstrictors, and antileukotriene drugs may play a role in preventing and treating HRS.

Pathogenesis of ascites and predictors of resistance to therapy

Ascites is one of the most frequent complications of cirrhosis. Its appearance is considered as the marker of the transition from the compensated to the decompensated stage of the disease. Appearance of ascites also has prognostic significance, as it causes a sharp drop in the expected survival rate. Portal hypertension is a sine qua-non for the development of ascites. Although no precise portal pressure threshold has been defined for the development of ascites, the latter rarely develops with portal pressures below 12 mmHg. In addition, in patients treated with interventions that markedly decrease portal pressure, such as surgical porta-caval shunts or transjugular intrahepatic portalsystemic shunts, a disappearance or a marked reduction of ascites can be observed. The currently most accepted theory of ascites formation is the so-called 'forward' theory. According to this theory, the development of ascites is related to the presence of severe sinusoidal portal hypertension, which causes marked splanchnic arterial vasodilation and a forward increase in the splanchnic production of lymph. Splanchnic arterial vasodilation also causes a significant reduction of the effective blood volume, leading to activation of sodium and water-retaining mechanisms. The retained sodium and water, however, while increasing total plasma volume, are unable to compensate for the reduced effective blood volume, initiating a vicious cycle. In the advanced stages of cirrhosis, the extreme underfilling of the arterial circulation leads to a maximal stimulation of the vasoconstrictor mechanisms which override the protective effect of renal vasodilator factors and cause renal vasoconstriction, further aggravating ascites and leading to functional renal insufficiency. Renal insufficiency is also one of the main causes of resistance to diuretic therapy. While several studies have investigated the predictors of survival in cirrhotic patients with ascites, this has not been done for the occurrence of resistance to therapy. However, as the mechanisms of refractoriness are associated with advanced disease and short survival, the models developed for predicting survival should be employed also to verify if they can exert such additional prediction.

Monitoring of transtubular potassium gradient in the diuretic management of patients with cirrhosis and ascites

BACKGROUND/AIMS

Aldosterone antagonists are the diuretics of first choice in the treatment of cirrhotic ascites. However, there is still no reliable clinical parameter to evaluate their efficacy. Transtubular potassium gradient (TTKG), the accurate indicator of aldosterone bioactivity, may serve as a guide for the proper use of the aldosterone antagonists.

METHODS

In 23 patients with cirrhotic ascites, the daily administered initial dosage of 100 mg of spironolactone was increased by 100 mg/day at intervals of 5 days until either diuresis commenced or TTKG fell below 3.0, the value indicating complete blockade of aldosterone bioactivity. For the non-responders with TTKG lower than 3.0, furosemide was given in addition to spironolactone.

RESULTS

Basal TTKG correlated significantly with plasma aldosterone concentration (r = 0.60, P = 0.002). Spironolactone induced the decrease of TTKG in 20 patients, from 5.3 +/- 0.5 to 2.9 +/- 0.2 (mean +/- SE, P < 0.001). A TTKG value of 3.0 could classify seven patients, who did not respond to low dose spironolactone, into two distinct groups at that time, indicating different further diuretic regimen. All patients achieved diuretic responses without complication by this TTKG-guided modification of diuretics.

CONCLUSIONS

TTKG may be a suitable guide for the diuretic management of cirrhotic ascites by accurately reflecting the effect of aldosterone antagonists.

Cardiovascular effects of canrenone in patients with preascitic cirrhosis

In patients with cirrhosis and portal hypertension, standing induces a reduction in cardiac index (CI) and an increase in systemic vascular resistance index. Our previous studies indicate that this abnormal hemodynamic response to standing is due to an altered myocardial function, because cirrhotic patients are unable to compensate for the reduced preload with an increase in left ventricular (LV) ejection fraction (EF) and stroke volume. To evaluate whether the cardiac dysfunction in cirrhosis is influenced by canrenone, an aldosterone antagonist, 8 patients with preascitic, nonalcoholic cirrhosis, and portal hypertension underwent echocardiographic assessment of LV function and systemic hemodynamics and determinations of plasma volume, urinary sodium excretion, and plasma renin activity (PRA), aldosterone (PAC), and norepinephrine (PNE) when on a 150-mmol/d-sodium diet (baseline), after 1 month on canrenone (100 mg/d) plus a 40-mmol/d-sodium diet and after 1 month on canrenone plus a 150-mmol/d-sodium diet. Echocardiographic evaluation was performed with the patient in the supine position and during active standing. At baseline, patients had high plasma volume and normal renal function, PRA, PAC, and PNE. CI, LVEF, and stroke volume index were also normal. Standing caused a significant reduction in CI and LVEF. After canrenone and either sodium diet, CI significantly decreased, and PRA and PNE increased in the supine position. On standing, LVEF and CI did not decrease further. Plasma volume significantly decreased only after low-sodium diet plus canrenone. In conclusion, canrenone normalizes the cardiac response to the postural challenge in patients with preascitic cirrhosis.

The mechanism of improved sodium homeostasis of low-dose losartan in preascitic cirrhosis

Renal sodium retention on standing is one aspect of the abnormal renal sodium handling in preascitic, well-compensated patients with cirrhosis. Recently, it has been shown that low doses (7.5 mg) of the angiotensin II (Ang II) receptor antagonist, losartan, can reverse renal sodium retention on high, 200-mmol sodium/d diet in these patients and restore them to sodium balance. Therefore, the effect of 7.5 mg of losartan on sodium excretion, when changing from supine to erect posture for 2 hours, was examined in 10 well-compensated patients with cirrhosis and 9 age- and sex-matched controls on the same sodium diet, under strictly controlled metabolic conditions. In contrast to control subjects, in whom sodium excretion was unaffected, single 7.5-mg doses of losartan again restored the preascitic patients with cirrhosis to sodium balance. In addition, it blunted the fall in erect posture- induced renal sodium excretion by a reduction in proximal and distal tubular reabsorption of sodium. These changes occurred without any significant changes in blood volumes, systemic and renal hemodynamics, or glomerular filtration rate (GFR) and filtered sodium load compared with controls, and despite activation of the systemic renin-angiotensin-aldosterone system, which was still within normal levels. In conclusion, the beneficial natriuretic effects of low-dose losartan on erect posture - induced sodium retention in preascitic cirrhosis supports the suggestion that the pathophysiology of sodium retention in preascites is in part caused by an intrarenal tubular effect of Ang II in that posture.

Evaluation of serum cystatin C concentration as a marker of renal function in patients with cirrhosis of the liver

BACKGROUND AND AIMS

Diagnosis of moderately impaired renal function is of particular importance in patients with cirrhosis of the liver. Whereas patients with a markedly impaired glomerular filtration rate can be diagnosed easily by elevated serum creatinine concentrations, moderately reduced renal function may be missed by this conventional parameter. Recently, cystatin C has been suggested as a sensitive marker of renal function, independent of sex or muscle mass. Therefore, the aim of this study was to investigate the value of serum cystatin C concentration for the detection of moderately impaired renal function.

METHODS

Ninety seven in-hospital patients with cirrhosis and a 24 hour creatinine clearance of at least 40 ml/min were investigated and divided into group 1 (creatinine clearance > or = 70 ml/min; n = 55) and group 2 (creatinine clearance 40-69 ml/min; n = 42).

RESULTS

Serum cystatin C concentrations (mean (SD): 1.31 (0.51) v 1.04 (0.34) mg/l (p = 0.008)) and creatinine concentrations (1.03 (0.52) v 0.86 (0.22) mg/100 ml (p=0.03)) were higher in group 2 than in group 1; there was no significant difference in urea concentrations. Receiver-operator characteristics (ROC) revealed a differential diagnostic advantage of cystatin C over creatinine and urea. At cut off concentrations of 1.0 mg/l, 0.9 mg/100 ml, and 28 mg/100 ml, respectively, cystatin C, creatinine, and urea exhibited 69%, 45%, and 44% sensitivity (p<0.05). As patients with a small muscle mass or reduced physical activity could be particularly prone to overestimation of their renal function, separate analyses were performed for the subgroups of female and Child-Pugh class C patients, respectively. In both groups, discrimination between patients with moderately impaired and normal renal function was best with cystatin C. In female patients, sensitivity of cystatin C (77.8%) was superior (p<0.05) to that of creatinine (38.9%) and urea (41.2%). In Child-Pugh C patients, the ROC curve was significantly better for cystatin C than for creatinine.

CONCLUSIONS

Serum cystatin C determination could be a valuable tool in patients with cirrhosis, particularly with Child-Pugh class C or in female patients, for early diagnosis of moderately impaired renal function.

CHF: circulatory homeostasis gone awry

The role of the renin-angiotensin-aldosterone system (RAAS) is integral to salt and water retention, particularly by the kidneys. Over time, positive sodium balance leads first to intra- and then to extravascular volume expansion, with subsequent symptomatic heart failure. This report examines the role of the RAAS in regulating a less well recognized component essential to circulatory homeostasis--central blood volume. The regulation of central blood volume draws on integrative cardiorenal physiology and a key role played by the RAAS in its regulation. In presenting insights into the role of the RAAS in regulating central blood volume, this review also addresses other sodium-retaining states with a predisposition to edema formation, such as cirrhosis and nephrosis.

Reduced activity of 11 beta-hydroxysteroid dehydrogenase in patients with cholestasis

Enhanced renal sodium retention and potassium loss in patients with cirrhosis is due to activation of mineralocorticoid receptors (MRs). Increased aldosterone concentrations, however, do not entirely explain the activation of MR in cirrhosis. Here, we hypothesize that cortisol activates MRs in patients with cholestasis. We present evidence that access of cortisol to MRs is a result of bile acid-mediated inhibition of 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2), an MR-protecting enzyme that converts cortisol to cortisone. Twelve patients with biliary obstruction and high plasma bile acid levels were studied before and after removal of the obstruction. The urinary ratio of (tetrahydrocortisol + 5 alpha-tetrahydrocortisol)/tetrahydrocortisone, a measure of 11 beta-HSD2 activity, decreased from a median of 1.91 during biliary obstruction to 0.78 at 4 and 8 weeks after removal of the obstruction and normalization of plasma bile acid concentrations. In order to demonstrate that bile acids facilitate access of cortisol to the MR by inhibiting 11 beta-HSD2, an MR translocation assay was performed in HEK-293 cells transfected with human 11 beta-HSD2 and tagged MR. Increasing concentrations of chenodeoxycholic acid led to cortisol-induced nuclear translocation of MR. In conclusion, 11 beta-HSD2 activity is reduced in cholestasis, which results in MR activation by cortisol.

The pathophysiologic basis for the treatment of cirrhotic ascites

Advances in the understanding of the pathophysiology of sodium retention and ascites formation in cirrhosis has helped improve the treatment of ascites in these patients. It is likely that further unraveling of these pathophysiologic changes will lead to the development of novel and better treatment options. For example, the development of aquaretic agents for the management of hyponatremia in cirrhosis may allow more effective use of diuretic therapy. The ultimate challenge is to use the understanding of the pathophysiology to develop new strategies to prevent the development of ascites in cirrhosis.

The hyperdynamic circulation in cirrhosis: an overview

The hyperdynamic circulation begins in the portal venous bed as a consequence of portal hypertension due to the increased resistance to flow from altered hepatic vascular morphology of chronic liver disease. Dilatation of the portal vein is associated with increased blood flow, as well as the opening up or formation of veno-venous shunts and splenomegaly. At the same time, portal hypertension leads to subclinical sodium retention resulting in expansion of all body fluid compartments, including the systemic and central blood volumes. This blood volume expansion is associated with vasorelaxation, as manifested by suppression of the renin--angiotensin--aldosterone system, initially only when the patient is in the supine position. Acute volume depletion in such patients results in normalisation of the hyperdynamic circulation, whilst acute volume expansion results in exaggerated natriuresis. As liver disease progresses and liver function deteriorates, the systemic hyperdynamic circulation becomes more manifest with activation of the renin--angiotensin--aldosterone system. The presence of vasodilatation in the presence of highly elevated levels of circulating vasoconstrictors may be explained by vascular hyporesponsiveness due to increased levels of vasodilators such as nitric oxide, as well as the development of an autonomic neuropathy. However, vasodilatation is not generalised, but confined to certain vascular beds, such as the splanchnic and pulmonary beds. Even here, the status may change with the natural history of the disease, since even portal blood flow may decrease and become reversed with advanced disease. The failure of these changes to reverse following liver transplantation may be due to remodelling and angiogenesis.

Nitric oxide may contribute to nocturnal hemodynamic changes in cirrhotic patients

OBJECTIVE

Patients with liver cirrhosis have a nocturnal worsening of hemodynamic parameters that has been associated with an increased risk of variceal bleeding at nighttime. The aim of this study was to investigate whether nitric oxide and cytokines are implicated in these hemodynamic changes.

METHODS

Ten cirrhotic patients and eight controls were studied. Mean blood pressure, heart rate, plasma norepinephrine, tumor necrosis factor alpha and interleukin-6 levels, and serum nitrite + nitrate levels were determined at 0800, 1600, and 2400 h. All determinations were performed in supine rest and at least 4 h after meals. In a second study, nitrite + nitrate levels were assessed in 10 cirrhotic patients before and after eating a standard meal.

RESULTS

Mean arterial pressure levels that were always lower in the patient group showed a nocturnal decrease in both groups of subjects. Heart rate values that were always higher in cirrhotic patients showed a nocturnal fall in controls, whereas cirrhotics maintained elevated values at nighttime. Norepinephrine levels were higher in cirrhotics and maintained similar values during the study, whereas controls had a significant nocturnal decrease. Nitrite + nitrate levels that were higher in cirrhotic patients showed a significant mean increase of 40% from morning (0800 h) to night (2400 h) in the patient group, whereas in controls no change was observed (p < 0.05). Tumor necrosis factor alpha and interleukin-6 levels did not change either in patients or controls during the entire period. Cirrhotic patients with or without ascites maintained a pattern of hemodynamic and biochemical changes similar to the pattern observed in the entire group of patients. Finally, no changes in serum nitrite + nitrate levels were observed in patients before and after eating the standard meal.

CONCLUSION

An increased nocturnal nitric oxide production might contribute to the hemodynamic changes observed in cirrhotic patients during nighttime.

Inhibition of 11beta-hydroxysteroid dehydrogenase by bile acids in rats with cirrhosis

Renal sodium retention and potassium loss occur early, in many instances in the preascitic state of cirrhosis, an observation that cannot be fully explained by increased aldosterone concentrations. We therefore hypothesize that 11beta-hydroxysteroid dehydrogenase 2 (11beta-HSD2), which protects mineralocorticoid receptors (MR) from glucocorticosteroids, is down-regulated in cirrhosis. Cirrhosis was induced by bile duct ligation in rats. The urinary ratio of (tetrahydrocorticosterone + 5alpha-tetrahydrocorticosterone)/ 11-dehydro-tetrahydrocorticosterone [(THB+5alpha-THB)/THA] was measured by gas chromatography. Cortical collecting tubules (CCT) were isolated by microdissection and used for measurements of the activity of 11beta-HSD2 by assessing the conversion of corticosterone to dehydrocorticosterone. The mRNA content of 11beta-HSD2 was determined by reverse-transcription polymerase chain reaction (RT-PCR) in CCTs. The urinary ratio of (THB+5alpha-THB)/THA increased concomitantly with the urinary excretion of bile acids following bile duct ligation. Chenodeoxycholic acid (CDCA) dose-dependently inhibited 11beta-HSD2 in CCT with a Ki of 19.9 micromol/L. Four weeks after bile duct ligation, 11beta-HSD2 activity was decreased in CCT, an observation preceded by a reduced mRNA content at weeks 2 and 3. In cirrhosis, the MR-protecting effect by 11beta-HSD2 is diminished, and therefore, endogenous glucocorticoids can induce MR-mediated sodium retention and potassium loss.

The renal sympathetic and renin-angiotensin response to lower body negative pressure in well-compensated cirrhosis

BACKGROUND & AIMS

Certain antinatriuretic hormonal systems may be involved in the subclinical sodium handling abnormality in preascitic cirrhosis. The aims of this study were to determine the following in preascitic cirrhosis: (1) basal activity of the renal sympathetic and renin-angiotensin systems and (2) the relationship between the response of these systems to lower body negative pressure and sodium excretion.

METHODS

Seven preascitic cirrhotic patients and 9 age- and sex-matched controls were studied on a 150 mmol sodium per day diet. Systemic and renal hemodynamics, renal neurohormonal secretion rates, and sodium excretion were assessed before, during increasing levels of, and after lower body negative pressure, each for 30 minutes.

RESULTS

Both groups responded with a significant decrease in central venous pressure (P < 0.01) that remained higher in the cirrhotics than in the controls throughout the study. Cirrhotics showed significant increases compared with controls in renal renin and angiotensin II secretion rates at -20 mm Hg of lower body negative pressure, which was associated with significant renal sodium retention (96 +/- 17 micromol/min vs. 218 +/- 21 micromol/min at baseline, P < 0.05), but there was no change in renal sympathetic activity.

CONCLUSIONS

In preascitic cirrhosis, sodium retention occurs in response to lower body negative pressure, which was associated with increased renal renin-angiotensin activity. Stimulation of the intrarenal renin-angiotensin system may be the initial renal pathophysiological change causing sodium retention in cirrhosis.

Upright posture decreases esophageal varices flow velocity in patients with cirrhosis

BACKGROUND/AIMS

Patients with cirrhosis tend to have esophageal variceal bleeding episodes at night, rather than during the day time. Since human beings carry on ordinary activities in the upright posture in the day time and are recumbent at night, we hypothesized that posture may be a factor related to a circadian variation of variceal bleeding. The aim of this study was to examine the effect of upright posture on esophageal varices hemodynamics in patients with cirrhosis.

METHODS

Nine patients with cirrhosis and esophageal varices were included in a crossover study performed on 2 separate days. On the non-endoscopic day, cardiac output, portal vein flow velocity, and superior mesenteric artery flow velocity were measured with percutaneous Doppler ultrasonography. Plasma renin activity and plasma norepinephrine concentrations were also determined. On the endoscopic day, in addition to the above measurements, esophageal varices flow velocity was measured using transesophageal Doppler ultrasonography. These measurements were performed in the supine position and 20 min after the assumption of the upright position.

RESULTS

On the non-endoscopic day, the upright posture significantly decreased cardiac output, portal vein flow velocity, and superior mesenteric artery flow velocity. Plasma renin activity and plasma norepinephrine concentration were significantly increased after assumption of the upright position. On the endoscopic day, similar hemodynamic and hormonal changes were observed. In addition, the upright posture significantly decreased esophageal varices flow velocity. Furthermore, the magnitude of the reduction in esophageal varices flow velocity (-42%) was significantly greater than that in portal vein flow velocity (-22%, p<0.01) and that in superior mesenteric artery flow velocity (-25%, p<0.01). Although the change in esophageal varices flow velocity was not significantly correlated with that in plasma renin activity (r=-0.28) and that in plasma norepinephrine concentration (r=-0.10), it was significantly correlated with the change in superior mesenteric artery flow velocity (r=0.73, p<0.05).

CONCLUSIONS

The upright posture decreases esophageal varices flow velocity mainly because of the reduction in splanchnic blood flow. This effect may contribute to a low prevalence of esophageal variceal bleeding in the day time in patients with cirrhosis.

Down-regulation of hepatic and renal 11 beta-hydroxysteroid dehydrogenase in rats with liver cirrhosis

BACKGROUND & AIMS

11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) enzymes are responsible for the interconversion of active 11 beta-hydroxycorticosteroids into inactive 11-ketoglucocorticosteroids and by that mechanism regulate the intracellular access of the steroids to the cognate receptor. A down-regulation of the shuttle of active to inactive glucocorticoids enhances access of glucocorticosteroids to both the glucocorticoid and the mineralocorticoid receptors. In liver cirrhosis, enhanced mineralocorticoid and glucocorticoid effects are observed. We therefore investigated the impact of liver cirrhosis after bile duct ligation on the transcription and activity of 11 beta-OHSD1 and 11 beta-OHSD2 in the corresponding tissues.

METHODS

Messenger RNA from 11 beta-OHSD1 and 11 beta-OHSD2 was assessed by reverse-transcription polymerase chain reaction; activity was assessed by measuring the interconversion of corticosterone to dehydrocorticosterone. The effect of bile and bile salts was determined using COS-1 cells transfected with 11 beta-OHSD1 or 11 beta-OHSD2.

RESULTS

In liver tissue, the messenger RNA ratios of 11 beta-OHSD1 to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) levels and, in kidney tissue, the ratios of 11 beta-OHSD2 to GAPDH levels decreased after induction of liver cirrhosis. The 11 beta-OHSD activities were correspondingly reduced. Bile and individual bile salts inhibited 11 beta-OHSD1 and 11 beta-OHSD2 oxidative activity in transfected COS-1 cells.

CONCLUSIONS

These findings indicate that in liver cirrhosis the mineralocorticoid and glucocorticoid receptor-protecting effects by the 11 beta-OHSD isoenzymes are down-regulated and that by the same mechanism the glucocorticoid and mineralocorticoid effects are enhanced.

Review: the controversy over the pathophysiology of ascites formation in cirrhosis

The pathogenesis of renal sodium retention and ascites formation in cirrhosis is a subject of much controversy. The generally accepted 'peripheral arterial vasodilatation hypothesis' seems to best explain the mechanism of sodium retention and other clinical findings, such as the hyperdynamic circulation of cirrhosis. However, recent data in pre-ascites and in early ascites do not seem to conform to the peripheral arterial vasodilatation hypothesis. Sodium handling abnormalities can be demonstrated in pre-ascitic cirrhosis when patients are challenged with a sodium load, in the absence of systemic vasodilatation or arterial underfilling. Therefore, an alternative hypothesis with a direct hepatorenal interaction, acting via sinusoidal portal hypertension and/or hepatic dysfunction as the affector mechanism, is proposed to be the initiating event in renal sodium retention in cirrhosis. The second and later process is the development of systemic arterial vasodilatation, possibly due to the presence of excess systemic vasodilators and/or decreased responsiveness of the vasculature to endogenous vasoconstrictors. This, in turn, will lead to a relatively underfilled circulation with consequent activation of neurohumoral systems, promoting further renal sodium retention as described by the peripheral arterial vasodilatation hypothesis and ultimately leading to ascites. When compensatory natriuretic mechanisms fail, refractory ascites develops and hepatorenal syndrome sets in. Thus, renal sodium retention in cirrhosis is the result of interplay of many factors, with direct hepatorenal interaction predominating in earlier stages of the cirrhotic process, while systemic vasodilatation becomes a more important pathogenetic factor as the disease progresses.