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Insulin resistance and oxidative stress: Two therapeutic targets in non-alcoholic steatohepatitis

  • Cosmin Sebastian Voican
    Affiliations
    INSERM, U996, IPSIT, Clamart, F-92140, France

    Univ Paris-Sud, Faculté de médecine Paris-Sud, Kremlin-Bicêtre, F-94270, France
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  • Gabriel Perlemuter
    Correspondence
    Corresponding author. Address: Hôpital Antoine Béclère, Hépato-gastroentérologie, 157, rue de la Porte de Trivaux, 92141 Clamart Cedex, France. Tel.: +33 1 45 37 43 69; fax: +33 1 40 94 06 56.
    Affiliations
    INSERM, U996, IPSIT, Clamart, F-92140, France

    Univ Paris-Sud, Faculté de médecine Paris-Sud, Kremlin-Bicêtre, F-94270, France

    Assistance Publique – Hôpitaux de Paris, Hôpital Antoine Béclère, Service d’hépato-gastroentérologie, Clamart, F-92140, France
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Open AccessPublished:November 12, 2010DOI:https://doi.org/10.1016/j.jhep.2010.07.054

      Keywords

      Abbreviations:

      PPARγ (peroxisome proliferator-activated receptor gamma), O2 (oxygen), MRC (mitochondrial respiratory chain), ROS (reactive oxygen species), NF-κB (nuclear factor-kappa B), IκB (inhibitor of kappa B), TG (triglycerides), FFA (free fatty acids), M2 (M2 type macrophages), M1 (M1 type macrophages), TNF-α (tumor necrosis factor alpha), MCP-1 (monocyte chemoattractant protein 1)
      COMMENTARY ON: Pioglitazone, vitamin E, or placebo for non-alcoholic steatohepatitis. Sanyal AJ, Chalasani N, Kowdley kV, McCullough A, Diehl AM, Bass NM, Neuschwander-Tetri BA, Lavine JE, Tonascia J, Unalp A, Van Natta M, Clark J, Brunt EM, Kleiner DE, Hoofnagle JH, Robuck PR; NASH CRN. N Engl J Med 2010;362:1675–85. Copyright © [2010] Massachusetts Medical Society. All rights reserved. Abstract reprinted with permission from Massachusetts Medical Society [RY – 2011 – 1119].
      Abstract: Background & Aims: Non-alcoholic steatohepatitis is a common liver disease that can progress to cirrhosis. Currently, there is no established treatment for this disease.
      Methods: We randomly assigned 247 adults with non-alcoholic steatohepatitis and without diabetes to receive pioglitazone at a dose of 30mg daily (80 subjects), vitamin E at a dose of 800IU daily (84 subjects), or placebo (83 subjects), for 96weeks. The primary outcome was an improvement in histologic features of non-alcoholic steatohepatitis, as assessed with the use of a composite of standardized scores for steatosis, lobular inflammation, hepatocellular ballooning, and fibrosis. Given the two planned primary comparisons, p values of less than 0.025 were considered to indicate statistical significance.
      Results: Vitamin E therapy, as compared with placebo, was associated with a significantly higher rate of improvement in non-alcoholic steatohepatitis (43% vs. 19%, p=0.001), but the difference in the rate of improvement with pioglitazone as compared with placebo was not significant (34% and 19%, respectively; p=0.04). Serum alanine and aspartate aminotransferase levels were reduced with vitamin E and with pioglitazone, as compared with placebo (p<0.001 for both comparisons), and both agents were associated with reductions in hepatic steatosis (p=0.005 for vitamin E and p<0.001 for pioglitazone) and lobular inflammation (p=0.02 for vitamin E and p=0.004 for pioglitazone) but not with improvement in fibrosis scores (p=0.24 for vitamin E and p=0.12 for pioglitazone). Subjects who received pioglitazone gained more weight than did those who received vitamin E or placebo; the rates of other side effects were similar among the three groups.
      Conclusions: Vitamin E was superior to placebo for the treatment of non-alcoholic steatohepatitis in adults without diabetes. There was no benefit of pioglitazone over placebo for the primary outcome; however, significant benefits of pioglitazone were observed for some of the secondary outcomes. (ClinicalTrials.gov number, NCT00063622).
      Non-alcoholic fatty liver disease (NAFLD) is the liver manifestation of the metabolic syndrome and, therefore, a leading cause of chronic liver disease. Non-alcoholic steatohepatitis (NASH) is only a stage in the spectrum of NAFLD. Its prevalence is difficult to assess as only a liver biopsy can distinguish NASH from other stages of NAFLD, but it is estimated between 8% and 27% [
      • Perlemuter G.
      • Bigorgne A.
      • Cassard-Doulcier A.-M.
      • Naveau S.
      Nonalcoholic fatty liver disease: from pathogenesis to patient care.
      ]. Considering that up to one-quarter of patients with NASH may progress to end-stage liver disease in less than a decade, there is an urgent need for efficient therapeutic options as there is still no approved medication. Schematically, besides lifestyle interventions, two different kinds of medications may be used, according to the pathophysiology of NAFLD: drugs that will target insulin resistance and drugs that will directly target the liver inflammatory process; of note, some medications may act on both targets.
      The recent article by Sanyal et al. [
      • Sanyal A.J.
      • Chalasani N.
      • Kowdley K.V.
      • McCullough A.
      • Diehl A.M.
      • Bass N.M.
      • et al.
      Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis.
      ] provides precious data on the short-term efficacy and safety of pioglitazone and vitamin E, drugs that address major mechanisms of NASH pathogenesis. Glitazones (pioglitazone, rosiglitazone) are peroxisome proliferator-activated receptor gamma (PPARγ) agonists that improve insulin resistance through several pathways: induction of adiponectin production, inhibition of lipolysis, and reduction of free fatty acid supply to the liver, induction of adipocyte differentiation, which promotes fat redistribution from the liver toward the adipose tissue. PPARγ agonists also prime monocyte differentiation toward anti-inflammatory M2 macrophages, contributing to insulin sensitization and a reduction of adipose tissue and hepatic inflammation [
      • Bouhlel M.A.
      • Derudas B.
      • Rigamonti E.
      • Dièvart R.
      • Brozek J.
      • Haulon S.
      • et al.
      PPARγ activation primes human monocytes into alternative M2 macrophages with anti-inflammatory properties.
      ].
      Vitamin E is a lipophilic antioxidant whose in vivo effects are mainly attributed to free radical scavenging. Low levels of reactive oxygen species (ROS) can be produced by the mitochondrial respiratory chain (MRC) under physiological conditions. Free fatty acid (FFA) accumulation in the liver may increase mitochondrial ROS formation by inhibiting the MRC enzyme complexes. A defective hepatic MRC has been reported in NASH [
      • Perez-Carreras M.
      • Del Hoyo P.
      • Martin M.A.
      • Rubio J.C.
      • Martin A.
      • Castellano G.
      • et al.
      Defective hepatic mitochondrial respiratory chain in patients with nonalcoholic steatohepatitis.
      ] and elevated oxidative stress markers in the liver are correlated with hepatic inflammation and fibrosis [
      • Seki S.
      • Kitada T.
      • Yamada T.
      • Sakaguchi H.
      • Nakatani K.
      • Wakasa K.
      In situ detection of lipid peroxidation and oxidative DNA damage in non-alcoholic fatty liver diseases.
      ], suggesting the potential utility of antioxidants, such as vitamin E. (Fig. 1)
      Figure thumbnail gr1
      Fig. 1Glitazones and vitamin E in NASH. PPARγ activation by glitazones promotes adipocyte differentiation and FFA uptake and storage in the adipose tissue, leading to improved insulin sensitivity by reduction of tissue lipid levels (liver, muscle). PPARγ also modulates the production of adipokines, such as adiponectin, TNF-α, MCP-1, which further ameliorates insulin resistance. In the liver, PPARγ activation reduces proinflammatory cytokine production by transrepression of NF-κB target genes. PPARγ primes monocytes toward an anti-inflammatory M2 phenotype. Vitamin E scavenges ROS production by the MRC and prevents cellular damage and ROS-induced NF-κB activation. Arrows indicate stimulation, bars indicate inhibition.
      In a 2-year multicentric randomized placebo controlled study of patients with NAFLD without diabetes, Sanyal et al. [
      • Sanyal A.J.
      • Chalasani N.
      • Kowdley K.V.
      • McCullough A.
      • Diehl A.M.
      • Bass N.M.
      • et al.
      Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis.
      ] offers strong proof for the practical benefit of antioxidant therapy in NASH patients. Authors observed that vitamin E therapy (800 UI/day), as compared to placebo, was associated with a significantly higher rate of histological response (defined as an improvement of at least one point in the ballooning score, no increase in fibrosis score, and either a decrease in NAFLD activity score to 3 or less or a decrease of at least 2 points with at least a 1-point decrease in either lobular inflammation or steatosis score). Surprisingly, the comparison of pioglitazone therapy (30 mg/day) with placebo did not reach the level of significance for this primary outcome. Both pioglitazone and vitamin E significantly improved steatosis, lobular inflammation, and NAFLD activity score. The absence of improvement in the fibrosis score may be related to too short of a duration of the study, the low level of fibrosis at inclusion or a true lack of efficacy of the drugs. Vitamin E and pioglitazone discontinuation was associated with disease relapse suggesting the necessity for long-term treatment. The duration of treatment was not long enough to assess the efficacy and safety of a long-term therapeutic intervention.
      Table 1 summarizes the relevant randomized controlled studies on the efficacy of glitazones or vitamin E in NASH patients. The other studies have also demonstrated a reduction of hepatic steatosis with pioglitazone or rosiglitazone, while there were some discrepancies on their efficacy on liver inflammation [
      • Sanyal A.J.
      • Chalasani N.
      • Kowdley K.V.
      • McCullough A.
      • Diehl A.M.
      • Bass N.M.
      • et al.
      Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis.
      ,
      • Ratziu V.
      • Giral P.
      • Jacqueminet S.
      • Charlotte F.
      • Hartemann-Heurtier A.
      • Serfaty L.
      • et al.
      Rosiglitazone for nonalcoholic steatohepatitis: one-year results of the randomized placebo-controlled fatty liver improvement with rosiglitazone therapy (FLIRT) trial.
      ,
      • Belfort L.
      • Harrison S.A.
      • Brown K.
      • Darland C.
      • Finch J.
      • Hardies J.
      • et al.
      A placebo-controlled trial of pioglitazone in subjects with nonalcoholic steatohepatitis.
      ,
      • Dufour J.F.
      • Oneta C.M.
      • Gonvers J.J.
      • Bihl F.
      • Cerny A.
      • Cereda J.M.
      • et al.
      Randomized placebo-controlled trial of ursodeoxycholic acid with vitamin E in nonalcoholic steatohepatitis.
      ,
      • Aithal G.P.
      • Thomas J.A.
      • Kaye P.V.
      • Lawson A.
      • Ryder S.D.
      • Spendlove I.
      • et al.
      Randomized, placebo-controlled trial of pioglitazone in nondiabetic subjects with nonalcoholic steatohepatitis.
      ]. Glitazones failed to decrease liver fibrosis similarly to the study of Sanyal and colleagues [
      • Sanyal A.J.
      • Chalasani N.
      • Kowdley K.V.
      • McCullough A.
      • Diehl A.M.
      • Bass N.M.
      • et al.
      Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis.
      ]. Of note, the duration of studies might be too short to prove any effect on the fibrotic process. Nevertheless, despite the absence of improvement of fibrosis, no aggravation was observed [
      • Ratziu V.
      • Giral P.
      • Jacqueminet S.
      • Charlotte F.
      • Hartemann-Heurtier A.
      • Serfaty L.
      • et al.
      Rosiglitazone for nonalcoholic steatohepatitis: one-year results of the randomized placebo-controlled fatty liver improvement with rosiglitazone therapy (FLIRT) trial.
      ,
      • Belfort L.
      • Harrison S.A.
      • Brown K.
      • Darland C.
      • Finch J.
      • Hardies J.
      • et al.
      A placebo-controlled trial of pioglitazone in subjects with nonalcoholic steatohepatitis.
      ].
      Table 1Randomized controlled studies of glitazones and vitamin E for the treatment of patients with NASH.
      RM, Randomized controlled multicenter.
      RS, Randomized controlled single center.
      P, Placebo.
      Pi, Pioglitazone.
      E, Vitamin E.
      ALT, alanine aminotransferase.
      U, ursodeoxycholic acid.
      NA, not available.
      NS, not significant.
      p Values: comparison between treatment group and placebo/control group at the and of treatment.
      aPatients with improvement (%).
      bMean change in ALT level (U/L).
      cMean change in score.
      dPatients with normal ALT level at end of treatment (%).
      Overall, targeting insulin resistance with glitazones might be a useful therapeutic option for reducing hepatic steatosis and normalizing aminotransferase levels, although the available studies do not clearly demonstrate an improvement of liver inflammation and fibrosis.
      The study of Sanyal et al. [
      • Sanyal A.J.
      • Chalasani N.
      • Kowdley K.V.
      • McCullough A.
      • Diehl A.M.
      • Bass N.M.
      • et al.
      Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis.
      ] is the first one that shows an efficacy of vitamin E monotherapy versus placebo in patients with NASH. In a previous small study, the combination of vitamin E and ursodeoxycholic acid (UDCA) has demonstrated a significant improvement in aminotransferase levels, as compared with placebo, but also in steatosis and NAFLD activity index, as compared with values at inclusion; However, no improvement of liver inflammation and fibrosis has been observed [
      • Dufour J.F.
      • Oneta C.M.
      • Gonvers J.J.
      • Bihl F.
      • Cerny A.
      • Cereda J.M.
      • et al.
      Randomized placebo-controlled trial of ursodeoxycholic acid with vitamin E in nonalcoholic steatohepatitis.
      ]. Vitamin E treatment is associated with a strong safety profile (i.e. a low incidence of side effects) [
      • Sanyal A.J.
      • Chalasani N.
      • Kowdley K.V.
      • McCullough A.
      • Diehl A.M.
      • Bass N.M.
      • et al.
      Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis.
      ,
      • Nobili V.
      • Manco M.
      • Devito R.
      • Di Ciommo V.
      • Comparcola D.
      • Sartorelli M.R.
      • et al.
      Lifestyle intervention and antioxidant therapy in children with nonalcoholic fatty liver disease: a randomized, controlled trial.
      ]. This is an important aspect for NAFLD patients, and particularly for young patients, as the duration of treatment is long and treatment discontinuation is associated with disease relapse. The efficacy of vitamin E versus placebo for the treatment of children with NAFLD has not yet been proven, but a large 2-year randomised controlled multicenter study is ongoing [
      • Lavine J.E.
      • Schwimmer J.B.
      • Molleston J.P.
      • Scheimann A.O.
      • Murray K.F.
      • Abrams S.H.
      • et al.
      Treatment of nonalcoholic fatty liver disease in children: TONIC trial design.
      ]. Of note, a recent meta-analysis has suggested a slight but significant increase of mortality in subjects with long-term antioxidant supplementation and should be taken into consideration [
      • Bjelakovic G.
      • Nikolova D.
      • Gluud L.L.
      • Simonetti R.G.
      • Gluud C.
      Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis.
      ].
      Thus, the demonstration by Sanyal and colleagues [
      • Sanyal A.J.
      • Chalasani N.
      • Kowdley K.V.
      • McCullough A.
      • Diehl A.M.
      • Bass N.M.
      • et al.
      Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis.
      ] that vitamin E is superior to placebo in improving liver histology in NASH patients without diabetes provides further evidence for a role of other therapeutic approaches, besides the insulin sensitizers, in NASH management. In this context, other therapeutic options targeting the oxidative stress, such as l-carnitine [
      • Malaguarnera M.
      • Gargante M.P.
      • Russo C.
      • Antic T.
      • Vacante M.
      • Malaguarnera M.
      • et al.
      l-Carnitine supplementation to diet: a new tool in treatment of nonalcoholic steatohepatitis – a randomized and controlled clinical trial.
      ] or UDCA [
      • Ratziu V.
      • De Ledinghen V.
      • Oberti F.
      • Mathurin P.
      • Wartelle-Bladou C.
      • Renou C.
      • et al.
      A multicentric, double-blind, randomised controlled trial (RCT) of high dose of ursodeoxycholic acid in patients with non-alcoholic steatohepatitis (NASH) [abstract].
      ] have recently suggested, in preliminary studies, a potential benefit in NASH patients.
      Overall, this is the first study showing that two different targets should be considered to treat patients with NASH: insulin resistance with pioglitazone and liver inflammation through oxidative stress reduction with vitamin E. Studies are still needed to evaluate the long-term benefit of these drugs, in particular on the fibrotic process (i.e. do these drugs stop or improve liver fibrosis?) and the tolerance. Finally, as these drugs act on different but complementary targets, we can also wonder whether their association may potentiate their therapeutic benefits.

      Conflict of interest

      The authors who have taken part in this study declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.

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