Acute effects of nitric oxide synthase inhibition on systemic, hepatic, and renal hemodynamics in patients with cirrhosis and ascites

Dipeptidyl Peptidase-4 Inhibition Potentiates Stimulated Growth Hormone Secretion and Vasodilation in Women

BACKGROUND

Diminished growth hormone (GH) is associated with impaired endothelial function and fibrinolysis. GH-releasing hormone is the primary stimulus for GH secretion and a substrate of dipeptidyl peptidase-4. We tested the hypothesis that dipeptidyl peptidase-4 inhibition with sitagliptin increases stimulated GH secretion, vasodilation, and tissue plasminogen activator (tPA) activity.

METHODS AND RESULTS

Healthy adults participated in a 2-part double-blind, randomized, placebo-controlled, crossover study. First, 39 patients (29 women) received sitagliptin or placebo on each of 2 days separated by a washout. One hour after study drug, blood was sampled and then arginine (30 g IV) was given to stimulate GH. Vasodilation was assessed by plethysmography and blood sampled for 150 minutes. Following a washout, 19 of the original 29 women received sitagliptin alone versus sitagliptin plus antagonist to delineate GH receptor (GHR)- (n=5), nitric oxide- (n=7), or glucagon-like peptide-1 receptor- (n=7) dependent effects. Sitagliptin enhanced stimulated GH secretion (P<0.01 versus placebo, for 30 minutes) and free insulin-like growth factor-1 (P<0.001 versus placebo, after adjustment for baseline) in women. Vasodilation and tPA increased in all patients, but sitagliptin enhanced vasodilation (P=0.01 versus placebo) and increased tPA (P<0.001) in women only. GHR blockade decreased free insulin-like growth factor-1 (P=0.04 versus sitagliptin alone) and increased stimulated GH (P<0.01), but decreased vascular resistance (P=0.01) such that nadir vascular resistance correlated inversely with GH (rs=-0.90, P<0.001). GHR blockade suppressed tPA. Neither nitric oxide nor glucagon-like peptide-1 receptor blockade affected vasodilation or tPA.

CONCLUSIONS

Sitagliptin enhances stimulated GH, vasodilation, and fibrinolysis in women. During sitagliptin, increases in free insulin-like growth factor-1 and tPA occur via the GHR, whereas vasodilation correlates with GH but occurs through a GHR-independent mechanism.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01701973.

Renal effects of NO-inhibition in patients with cirrhosis vs. healthy controls: a randomized placebo-controlled crossover study

BACKGROUND

Nitric oxide (NO) is an important regulator of renal hemodynamics and sodium excretion. Systemic and splanchnic NO-synthesis is increased in liver cirrhosis contributing to the characteristic hyperdynamic circulation. The significance of renal NO in human cirrhosis is not clear.

AIMS

In order to clarify the role of NO in the regulation of renal hemodynamics and sodium excretion in human cirrhosis, we studied the effects of N(G)-monomethyl-L-arginine (L-NMMA) - a nonselective NO-inhibitor - on blood pressure (MAP), heart rate (HR), GFR, RPF, UNa × V, FENa, FELi and plasma levels of renin, angII, aldo, ANP, BNP and cGMP in 13 patients with cirrhosis (Child gr.A: 8; Child gr.B+C: 5) and 13 healthy controls.

METHODS

The study was randomized and placebo-controlled. Renal hemodynamics were assessed by measuring renal clearance of (51) Cr-EDTA and (125) I-Hippuran for GFR and RPF, respectively.

RESULTS

L-NMMA induced a similar, significant increase in MAP in both groups and a more pronounced relative decrease in HR in the CIR group (P = 0.0209, anova). L-NMMA did not change GFR in any group, but RPF decreased significantly in both groups, but most pronouncedly in CIR (P = 0.0478, anova). FENa decreased significantly in both groups after l-NMMA, but the response was again most pronounced in the CIR group (P = 0.0270, anova). All parameters remained stable after placebo. No significant differences were observed between the effects of L-NMMA in Child gr.A vs. Child gr. B+C patients.

CONCLUSION

The data supports the hypothesis that renal NO is enhanced in human cirrhosis.

Pathophysiology of ascites formation in liver cirrhosis

Liver cirrhosis has a high morbidity and poses a large threat to human health worldwide. In China, viral hepatitis, especially hepatitis B, is the main pathogenic factor of liver cirrhosis. Ascites formation in cirrhosis is the result of combined action of portal hypertension and liver function impairment, and it is the most prominent clinical manifestation of decompensated cirrhosis. The understanding of pathophysiology of ascites formation can help provide more accurate treatment of this condition so as to alleviate patients' mental and economic burdens.

Increased plasma nitric oxide, L-arginine, and arginase-1 in cirrhotic patients with progressive renal dysfunction

BACKGROUND AND AIMS

Increased levels of nitric oxide (NO) are hypothesized to contribute to renal dysfunction in patients with decompensated cirrhosis. In this study, we examined whether splanchnic and/or peripheral NO levels and L-arginine (L-Arg) correlate with progressive renal dysfunction in cirrhotics.

METHODS

Serum NO metabolites (NOx) and L-Arg were measured in: controls (n = 10); organ donors (n = 12); compensated cirrhotics (n = 17), cirrhotics with ascites (n = 25), refractory ascites (n = 11) or hepatorenal syndrome type II (HRS) (n = 11) and chronic renal failure patients (n = 18).

RESULTS

Plasma NOx and L-Arg levels rose progressively with worsening renal function in decompensated cirrhotics. Both NOx and L-Arg levels were highest in patients with HRS (P < 0.001 and P < 0.025, respectively). While there were no differences in NOx levels related to the site of sampling, L-Arg levels were lowest in hepatic venous blood. There were significant relationships of NOx and L-Arg with Model for End-Stage Liver Disease score and Child-Pugh scores (P < 0.04 and P < 0.01, respectively). Multivariate analysis showed a significant relationship between NOx, L-Arg and HRS.

CONCLUSION

Worsening renal function in decompensated cirrhosis is accompanied by progressive elevation in plasma NOx and L-Arg. These findings support the hypothesis that NO-mediated vasodilation is probably linked with the mechanism of progressive renal failure in decompensated cirrhotics.

Review: Vasoconstrictors for the treatment of portal hypertension

Vasoconstrictors have long been used in an attempt to mitigate the effects of portal hypertension. In this review, we discuss the current understanding of portal hypertension and the use of vasoconstrictors in the management of its sequlae, including variceal hemorrhage, hepatorenal syndrome, and paracentesis-induced circulatory dysfunction. Experimental and clinical evidence for the use of vasoconstrictors is considered, and several exciting recent developments are reviewed.

Advances in drug treatment of portal hypertension

Intrahepatic vascular resistance augmentation and portal blood flow increase are main mechanisms of portal hypertension. The former as an initial factor is mainly due to liver structure changes and motivity changes (reversible). It has been demonstrated that this reversible resistance can be reduced by 20%-30% with drugs. Portosystemic shunt or transjugular intrahepatic portosystemic shunt (TIPS) may induce many severe complications such as hepatic encephalopathy and stent re-obstruction. Therefore, researchers have performed plenty of experimental investigations about drug treatment of portal hypertension, and this article introduces their new advances in this field.

Effects of Shehuang Paste on hemodynamics, endotoxin, nitric oxide and endothelin-1 in patients with refractory cirrhotic ascites

OBJECTIVE

To explore the influence of Shehuang Paste (SHP) to the hemodynamics, endotoxin, nitric oxide (NO), and endothelin-1 (ET-1) in patients with refractory cirrhotic ascites.

METHODS

Fifty-nine cases of refractory cirrhotic ascites were randomly assigned to two groups, 32 cases in the treatment group and 27 cases in the control group. The basic treatment was the same for both groups, including liver protecting medicines, diuretics and supportive drugs, but SHP navel sticking was applied for the treatment group additionally once a day. A course of one month of treatment was applied and the general efficacy on ascites was observed by the end of the therapeutic course. Before and after the treatment, examinations by limulus lysate chromogenic test was conducted to measure plasma endotoxin content; colorimetry to measure plasma content of NO indirectly, radioimmunoassay to measure plasma ET-1 content; and color Doppler ultrasonography to measure the blood flow of portal vein and splenic vein. The relationship between the blood flow of portal vein and splenic vein and endotoxin, NO and ET-1 in the treatment group was analyzed as well.

RESULTS

The total effective rate on ascites was 84.4% in the treatment group, and 48. 1% in the control group, with significant difference shown between them (P<0.01). In the treatment group the blood flow of portal vein and splenic vein, contents of endotoxin, NO and ET-1 all got significantly reduced after treatment ( P<0.05 or P<0.01); while these indexes in the control group were not significantly changed ( P 0.05). Moreover, it was found that in the treatment group, the blood flow of portal vein and splenic vein had a positive correlation to the levels of NO, ET-1, and endotoxin, either before or after treatment.

CONCLUSION

Application of SHP navel sticking could clearly reduce the blood flow of portal vein and splenic vein, and lower the content of endotoxin, NO and ET-1. The blood flow of portal vein and splenic vein in the treatment group showed a positive correlation with the contents of endotoxin, NO and ET-1. liver cirrhosis, refractory ascites, vasoactive substance, hemodynamics

Clinical research on navel application of Shehuang Paste combined with Chinese herbal colon dialysis in treatment of refractory cirrhotic ascites complicated with azotemia

AIM: To explore the efficacy and mechanism of a novel therapeutic method of traditional Chinese medicine in patients with refractory cirrhotic ascites complicated with azotemia.

METHODS: Seventy-five cases of refractory cirrhotic ascites complicated with azotemia were randomly divided into 3 groups: comprehensive treatment (n = 29), simple treatment (n = 24), and control (n = 22). The basic treatment methods were the same in all groups, including liver protecting medicines, diuretics and supportive drugs. The control group underwent only the basic treatment. Shehuang Paste (SHP) was applied to the navels of the two treatment groups once a day for 30 d. Colon dialysis with Chinese herbs was administered to the comprehensive treatment group once every two days. Before and after treatment, we measured abdominal circumference, BUN, Cr, serum Na⁺, urine Na⁺/K⁺, liver function, endotoxin content, NO, and ET-1. Color Doppler ultrasonography was conducted to measure the portal vein blood flow.

RESULTS: The total effective rate for ascites was 72.4% in the comprehensive treatment group, 45.8% in the simple treatment, contrasting with 18.2% in the controls. Between the two treatment groups and the controls, there were significant differences in the effective rates (P < 0.01, and P < 0.05). There was also a significant difference (P < 0.05) between the two treatment groups. Measurements of Cr and BUN showed higher values for the treatment groups, with the comprehensive better than the simple group (P < 0.05). Sera Na, urine Na/K were different, P < 0.01 between pre- and post-treatment in the comprehensive group, and P < 0.05 in the simple group. The treatment groups’ endotoxin content was also significantly reduced (P < 0.01, and P < 0.05), with the comprehensive group better than the simple group (P < 0.05). Portal vein blood flow and NO content significantly reduced (P < 0.05), as did ET-1 content (P < 0.01). There were no significant changes in the control group (P > 0.05). The comprehensive treatment group’s pre- and post-treatment portal vein and splenic vein blood flows showed a positive correlation to NO, ET-1 and endotoxin contents.

CONCLUSION: When treating refractory cirrhotic ascites complicated with azotemia, Shehuang Paste combined with Chinese herbal dialysis is better than Shehuang Paste alone for ascites resolution, azotemia, and endotoxin elimination. However, both methods on their own were also effective for reducing portal and splenic vein blood flow, and lowering the contents of NO, ET-1 in the two treatment groups.

The role of nitric oxide in the pathogenesis of systemic and splanchnic vasodilation in cirrhotic rats before and after the onset of ascites

BACKGROUND

The role of nitric oxide (NO) in the pathogenesis of splanchnic arterial vasodilation in cirrhosis has been recently debated by some experimental studies.

AIMS

We investigated the role of NO in the pathogenesis of the splanchnic arterial vasodilation along the course of CCl(4)-induced experimental cirrhosis.

METHODS

We analyzed the effect on mean arterial pressure (MAP), cardiac output (CO), total peripheral resistance (TPR), and resistance in the superior mesenteric artery (RSMA), before and after the administration of a unspecific NO synthase (NOS) inhibitor (Nomega-nitro-L-arginine-methyl-ester, L-NAME) and a specific NOS2 inhibitor (L-N-(1-iminoethyl)-lysine, L-NIL) to cirrhotic rats with and without ascites, and to control rats. NOS2 and NOS3 protein expression was also assessed in systemic and splanchnic arteries of these animals.

RESULTS

L-NAME in cirrhotic rats markedly improved MAP, and TPR and decreased CO regardless of whether they had ascites or not. L-NIL did not produce any significant effect on systemic haemodynamics in control and cirrhotic rats. NOS3 overexpression in the aorta of cirrhotic animals paralleled the progression of the liver disease. L-NAME increased RSMA in cirrhotic rats, but this effect was much less intense in rats with ascites. L-NIL had an effect only on RSMA in rats with ascites, which was of a similar extent to that produced by L-NAME. Western blot experiment showed a faint overexpression of NOS3 in the mesenteric artery of cirrhotic rats with and without ascites and a clear induction of NOS2 only in the mesenteric artery of rats with ascites.

CONCLUSIONS

These results indicate that NO contributes significantly to the pathogenesis of arterial splanchnic circulation in the early stages of experimental cirrhosis but has only a minor role in its maintenance after the development of ascites. Furthermore, the expression of the different NOS isoforms varies along the course of the liver disease.

Pathophysiology and management of pediatric ascites

Ascites accumulation is the product of a complex process involving hepatic, renal, systemic, hemodynamic, and neurohormonal factors. The main pathophysiologic theories of ascites formation include the "underfill," "overflow," and peripheral arterial vasodilation hypotheses. These theories are not necessarily mutually exclusive and are linked at some level by a common pathophysiologic thread: The body senses a decreased effective arterial blood volume, leading to stimulation of the sympathetic nervous system, arginine-vasopressin feedback loops, and the renin-angiotensin-aldosterone system. Cornerstones of ascites management include dietary sodium restriction and diuretics. Spironolactone is generally tried initially, with furosemide added if clinical response is suboptimal. More refractory patients require large-volume paracentesis (LVP) accompanied by volume expansion with albumin. Placement of a transjugular intrahepatic portosystemic shunt is reserved for individuals with compensated liver function who require very frequent sessions of LVP. Peritoneovenous shunts are not used in contemporary ascites management. Liver transplantation remains the definitive therapy for refractory ascites. Although treatment of ascites fails to improve survival, it benefits quality of life and limits the development of such complications as spontaneous bacterial peritonitis.

Portal hypertension

Portal hypertension, the main complication of cirrhosis, is responsible for its most common complications: variceal hemorrhage, ascites, and portosystemic encephalopathy. Portal hypertension is the result of increased intrahepatic resistance and increased portal venous inflow. Vasodilatation (splanchnic and systemic) and the hyperdynamic circulation are hemodynamic abnormalities typical of cirrhosis and portal hypertension. Gastroesophageal varices result almost solely from portal hypertension, although the hyperdynamic circulation contributes to variceal growth and hemorrhage. Ascites results from sinusoidal hypertension and sodium retention, which, in turn, is secondary to vasodilatation and activation of neurohumoral systems. The hepatorenal syndrome represents the result of extreme vasodilatation, with an extreme decrease in effective blood volume that leads to maximal activation of vasoconstrictive systems, renal vasoconstriction, and renal failure. Spontaneous bacterial peritonitis is a potentially lethal infection of ascites that occurs in the absence of a local source of infection. Portosystemic encephalopathy is a consequence of both portal hypertension (shunting of blood through portosystemic collaterals) and hepatic insufficiency that result in the accumulation of neurotoxins in the brain. This review covers the recent advances in the pathophysiology and management of the complications of portal hypertension.

Nitric oxide in liver transplantation: pathobiology and clinical implications

The gaseous molecule nitric oxide is involved in a variety of liver transplant-relevant processes, including ischemia-reperfusion injury, acute cellular rejection, and circulatory changes characteristic of advanced liver disease. This review article focuses on new advances relating to the role of nitric oxide in these syndromes with an emphasis on pathobiology and potential clinical implications.