Therapeutic efficacy of an angiotensin II receptor antagonist in patients with nonalcoholic steatohepatitis

Authors


Abstract

The therapeutic efficacy of angiotensin II receptor antagonist, losartan, was studied in patients with nonalcoholic steatohepatitis (NASH). Seven patients with both NASH and hypertension were treated with losartan (50 mg/d) for 48 weeks. Treatment with losartan resulted in a significant decrease in blood markers of hepatic fibrosis, plasma TGF-β1 and serum ferritin concentration concurrently with an improvement in serum aminotransferase levels. Histological assessment showed improvement of hepatic necroinflammation in five patients, reduction of hepatic fibrosis in four patients, and disappearance of iron deposition in two patients. No side effect of treatment was noted at any time during the study. In conclusion, the present data raise the possibility that an angiotensin II receptor antagonist may be therapeutically efficacious for NASH. (HEPATOLOGY 2004.)

Nonalcoholic steatohepatitis (NASH) is a distinct clinical entity characterized by varying degrees of progressive steatosis, lobular inflammation and fibrosis of the liver.1, 2 Although the causes of NASH are not well defined and several therapies including diet,3 antioxidants,4 and approaches that improve insulin resistance5 have been tried, no commonly accepted therapeutic protocol has yet been established. Recent studies have demonstrated a crucial role of angiotensin II in the pathogenesis of hepatic fibrosis,6 and this peptide has been shown to enhance insulin resistance and tissue iron deposition.7, 8 Administration of an antagonist of angiotensin II type 1 receptor has been shown to decrease hepatic fibrosis in rats.6 In the present study, the effects of losartan, a selective angiotensin II type I receptor antagonist, were investigated in patients with NASH.

Abbreviations

NASH, nonalcoholic steatohepatitis; HOMA-R, homeostasis model assessment-R; TGF-β1, transforming growth factor β1; HSC, hepatic stellate cell.

Patients and Methods

Eight patients (two men and six women), aged 41-65 (median 57) years, with both NASH and hypertension, were entered into this study. All patients consumed less than 40 g of alcohol per week. Four patients were obese (body mass index < 25), four had diabetes mellitus, four had hyperlipidemia, and one had hyperuricemia. At the time of the study, some of the patients had already been on medication, including benzodiazepines, calcium antagonists or anticoagulants for at least 12 months. These therapeutic regimens were not changed after the start of the study. None of the patients were taking any angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists before the study.

Baseline laboratory assessment revealed abnormally high serum transaminase and γ-glutamyl transpeptidase concentrations in all patients. Five patients showed high serum ferritin concentrations. Homeostasis model assessment (HOMA)-R was abnormally high in all patients. Liver biopsies were performed prior to entry the study, and revealed moderate to severe lobular steatosis, and various degrees of hepatic necroinflammation and fibrosis in all patients. In two patients, iron deposition in hepatocytes was noted (Table 1).

Table 1. Histological Changes in Patients With Nonalcoholic Steatohepatitis Treated With Losartan
PatientNecro-inflammation (Grade)Fibrosis (Stage)Hepatocellular Injury (Score)Mallory Bodies (Score)Iron Deposition in Hepatocytes
BeforeAfterBeforeAfterBeforeAfterBeforeAfterBeforeAfter
111211100+
211211111
321111100
421323210
521323211
632443310+
721333210

After baseline assessment, all patients were prescribed losartan, at a dose of 50 mg/d for 48 weeks. Serum biochemistry, blood pressure, and body weight were monitored at the beginning of the study regimen and thereafter every 4 weeks. Fasting serum insulin level was determined at the beginning and end of the study to calculate HOMA-R. Iron profiles, plasma transforming growth factor-β1 (TGF-β1) concentrations and blood markers of hepatic fibrosis, including serum hyaluronic acid, type IV collagen, and procollagen III N-terminal propeptide levels, were also monitored at weeks 12, 24, and 48. At the end of the study, liver biopsy was repeated. Hematoxylin & eosin, Azan and Perls' Prussian blue staining were performed on fixed histological sections. Two experienced hepatopathologists evaluated all liver biopsy specimens. Necroinflammation and fibrosis were graded,9 and degrees of hepatocellular injury and Mallory bodies were scored10 in a blinded fashion. Iron deposition in hepatocytes was also evaluated. The Ethical Committee of Asahikawa Medical College for Clinical Study approved all protocols, and informed consent was obtained from all patients.

Data are expressed as means ± SD. The Wilcoxon rank sum test was used to compare laboratory parameters and measurements obtained before, after the beginning of, and at the conclusion of the study.

Results

For personal reasons, one patient (female) was removed from the study 24 weeks after the start of losartan treatment. For purposes of this report, the data obtained from this one patient were excluded from presentation and statistical analysis.

After beginning losartan treatment, systemic arterial blood pressure significantly decreased in all patients. Body mass index was not changed (mean ± SD: pretreatment, 28.7 ± 5.6; week 48, 28.8 ± 5.5). Serum aspartate aminotransferase and alanine aminotransferase levels were significantly decreased at week 12, 24, and 48, and γ-glutamyl transpeptidase levels were significantly decreased by week 48, after beginning losartan treatment (Fig 1). Blood markers of hepatic fibrosis were also significantly reduced at week 12, 24, and 48, concurrent with reduction of plasma TGF-β1 concentration (Fig. 1). Although serum iron and hemoglobin levels were not changed, serum ferritin concentration was significantly decreased at week 12, 24, and 48 (mean ± SD: pretreatment, 198 ± 138; week 12, 142 ± 102*; week 24, 119 ± 89*; week 48, 102 ± 70*, *P < .05 vs. pretreatment). Measurements of lipid profiles, renal function, serum electrolytes, plasma renin activities, serum angiotensin II, and HOMA-R (mean ± SD: pretreatment, 3.11 ± 1.59; week 48, 3.36 ± 1.49) were unchanged during the course of the study.

Figure 1.

Changes of serum liver enzymes, blood markers of hepatic fibrosis, and plasma TGF-β1 levels in patients with nonalcoholic steatohepatitis after the losartan treatment. AST, aspartate aminotransferase; ALT, alanine aminotransferase; γ-GTP, γ-glutamyl transpeptidase; HA, hyaluronic acid; Collagen, type IV collagen 7S; P-III-P, procollagen III N-terminal propeptide. Mean ± SD. *P < .05 compared with respective pretreatment level.

Although the degree of lobular steatosis was unaffected by losartan treatment in all patients, hepatic necroinflammatory grade improved in five patients and fibrotic stage in four subjects. Degrees of hepatocellular injury and Mallory bodies had improved in three patients. In two patients in whom iron deposition in hepatocytes was detected in the baseline biopsy, such changes had disappeared by the end of the study (Table 1). The degree of hepatic pathology did not worsen during the course of the study in any patient, and no side effects of losartan treatment were noted.

Discussion

In the present study, we demonstrated that administration of an angiotensin II type 1 receptor antagonist significantly improved liver biochemical indices as well as hepatic necroinflammation. Although the pathogenesis of NASH has remained poorly understood, several pathogenic factors, such as insulin resistance,11 oxidative stress12 and proinflammatory cytokines13 are proposed. In the current study, since body weight and medications were not changed during the study, the influence of diet and drugs other than losartan on NASH can be excluded.

We also demonstrated that serum ferritin levels were significantly decreased, and hepatic iron deposition disappeared in two patients after losartan treatment. Hepatic iron overload is suggested to play a crucial role in the pathogenesis of NASH.14 Although the interaction between angiotensin II and hepatic iron overload has not been well defined, animal experiments have recently shown that chronic administration of angiotensin II induces iron deposition in the heart, leading to cardiac fibrosis, and that this effect is blocked by losartan administration.8 As in the heart, angiotensin II may provoke hepatic iron deposition, and losartan may inhibit this action. Angiotensin II has been reported to enhance insulin resistance, and this effect was reversed by angiotensin II receptor antagonist.7 However, HOMA-R did not change after losartan treatment in the present study, suggesting that this drug does not affect insulin resistance in NASH.

We also investigated the effect of losartan on the hepatic fibrosis of NASH. Blood markers of hepatic fibrosis and plasma TGF-β1 level significantly decreased and histological findings of hepatic fibrosis had improved with treatment in four patients. In chronic liver diseases, TGF-β1 plays a pivotal role in the progression of hepatic fibrosis.15 TGF-β1 produced from Kupffer cell and inflammatory cells activates hepatic stellate cell (HSC).16 Activated HSC produces TGF-β1 by itself, and large amounts of extra cellular matrix proteins.16 We have demonstrated that patients with NASH have elevated plasma TGF-β1 levels that are reversed by α-tocopherol.4 As in other chronic liver diseases, previous reports showed that HSC plays an important role in progression of hepatic fibrosis in NASH.17 Angiotensin II type 1 receptor is expressed in activated HSC, and angiotensin II enhances hepatic fibrosis through production of TGF-β1.6 Moreover, angiotensin II type I receptor antagonist inhibits the development of liver fibrosis in animal models.6 In the present study, we showed that losartan treatment reduced plasma TGF-β1 concentrations concurrently with improvement of blood markers of hepatic fibrosis and hepatic fibrotic stages in patients with NASH. Although the therapeutic mechanisms of losartan remain elusive, this drug may improve hepatic fibrosis at least partially through inhibition of HSC function and the production of TGF-β1.

In conclusion, inhibiting the action of angiotensin II by losartan results in the improvement of serum liver enzyme levels and hepatic necroinflammation in patients with NASH, with no untoward side effects. Losartan decreases blood markers of hepatic fibrosis, TGF-β1 levels, and hepatic fibrosis. These observations suggest that therapeutic use of an angiotensin II receptor antagonist is safe and efficacious for the treatment of NASH.

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