Vasoconstrictor antagonism improves functional and structural vascular alterations and liver damage in rats with early NAFLD

Background & Aims

Intrahepatic vascular resistance is increased in early non-alcoholic fatty liver disease (NAFLD), potentially leading to tissue hypoxia and triggering disease progression. Hepatic vascular hyperreactivity to vasoconstrictors has been identified as an underlying mechanism. This study investigates vasoconstrictive agonism and antagonism in 2 models of early NAFLD and in non-alcoholic steatohepatitis (NASH).

Methods

The effects of endothelin-1 (ET-1), angiotensin II (ATII) and thromboxane A₂ (TxA₂) agonism and antagonism were studied by in situ ex vivo liver perfusion and preventive/therapeutic treatment experiments in a methionine-choline-deficient diet model of steatosis. Furthermore, important results were validated in Zucker fatty rats after 4 or 8 weeks of high-fat high-fructose diet feeding. In vivo systemic and portal pressures, ex vivo transhepatic pressure gradients (THPG) and transaminase levels were measured. Liver tissue was harvested for structural and mRNA analysis.

Results

The THPG and consequent portal pressure were significantly increased in both models of steatosis and in NASH. ET-1, ATII and TxA₂ increased the THPG even further. Bosentan (ET-1 receptor antagonist), valsartan (ATII receptor blocker) and celecoxib (COX-2 inhibitor) attenuated or even normalised the increased THPG in steatosis. Simultaneously, bosentan and valsartan treatment improved transaminase levels. Moreover, bosentan was able to mitigate the degree of steatosis and restored the disrupted microvascular structure. Finally, beneficial vascular effects of bosentan endured in NASH.

Conclusions

Antagonism of vasoconstrictive mediators improves intrahepatic vascular function. Both ET-1 and ATII antagonists showed additional benefit and bosentan even mitigated steatosis and structural liver damage. In conclusion, vasoconstrictive antagonism is a potentially promising therapeutic option for the treatment of early NAFLD.

Lay summary

In non-alcoholic fatty liver disease (NAFLD), hepatic blood flow is impaired and the blood pressure in the liver blood vessels is increased as a result of an increased response of the liver vasculature to vasoconstrictors. Using drugs to block the constriction of the intrahepatic vasculature, the resistance of the liver blood vessels decreases and the increased portal pressure is reduced. Moreover, blocking the vasoconstrictive endothelin-1 pathway restored parenchymal architecture and reduced disease severity.

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The transhepatic pressure gradient and thus portal pressure are increased in severe hepatic steatosis.

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Vasoconstrictor antagonists attenuate the transhepatic gradient to near normal in steatosis.

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Vasoconstrictor antagonists attenuate the transhepatic gradient in steatosis.

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Bosentan and valsartan attenuate increased transaminase levels in severe steatosis.

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Bosentan treatment decreases steatosis and restores the microvascular architecture.

Evaluation of Splenic Stiffness in Patients of Extrahepatic Portal Vein Obstruction Using 2D Shear Wave Elastography: Comparison with Intra-Operative Portal Pressure

BACKGROUND/AIMS

To compare splenic stiffness (SS) with intra-operative portal pressures (PPs) in patients of extrahepatic portal vein obstruction (EHPVO).

METHODS

Twenty-one patients (14 males; 7 females) of mean age 20.4 years with clinical and sonographic diagnosis of EHPVO were included in this approved prospective study. Endoscopy for esophageal varices (EV) was done in all patients followed by ultrasonographic 2D shear wave elastography (SWE) of spleen. Three values were taken at different areas of spleen avoiding major vessels and mean was calculated. Intra-operative PP was measured from an omental vein during proximal spleno-renal shunt surgery. The PP was compared and correlated with SS along with other parameters.

RESULTS

The mean SS was 46.04 ± 8.0 kPa and the mean PP was 33.29 ± 4.1 mmHg. There was no significant correlation between PP and SS (P = 0.61) and between grades of EV and SS (P = 0.38). Significant correlation was seen between grades of EV and PP (0.04). SS also did not show significant correlation with splenic size or duration of disease.

CONCLUSION

SS measured by 2D SWE did not correlate with PP and thus may not help in predicting gastrointestinal bleed in patients of EHPVO.