283-OR: Inadequate Hepatic Mitochondrial Adaptation in Patients with NASH Is Related to the Severity of Steatohepatitis and Fibrosis Stage

Dysfunctional mitochondrial function plays an important role in the progression of nonalcoholic steatohepatitis (NASH). Mitochondrial (mt) respiratory function assessed by oxidative phosphorylation/ OXPHOS (activated respiration with mt complex I [OXPHOS CI] and mt complex I + II [OXPHOS CI+II] substrates) and electron transport system capacity [ETC] were measured using high-resolution respirometry (Oroboros Oxygraph 2k). The aim of this study was to assess mitochondrial function in patients a) with vs. without NASH, and b) NASH with vs. without fibrosis. Liver tissue was obtained from 40 patients (age: 52 ± 12 yrs; BMI: 39.4 ± 8.4 kg/m²; HbA_1c: 6.9 ± 1.5%) with NAFLD and obesity or T2DM either by percutaneous liver biopsy (n=28) or during bariatric surgery (n=12). Patients with vs. without NASH (n=20 in each group) were more insulin resistant/ IR (HOMA-IR: 8.1 ± 4.2 vs. 4.5 ± 2.7 mg/dl x μU/ml; Adipo-IR: 10.4 ± 7.2 vs. 6.2 ± 3.8 mmol/L x µU/mL) and had higher OXPHOS CI+II (all p<0.05), likely an adaptation to IR and higher FFA flux to the liver. We then compared those with worse steatohepatitis (necroinflammation score/ NIS), divided as mild (n=16), moderate (n=15) or severe (n=9). Patients with moderate vs. mild NIS had increased mitochondrial respiration, expressed as pmol/(s x mg wet weight) (OXPHOS CI: 20.8 ± 4.8 vs. 16.4 ± 4.6; OXPHOS CI+II: 46.0 ± 11.4 vs. 31.3 ± 9.8; ETC: 60.5 ± 17.1 vs. 46.4 ± 15.2; all p<0.05). There was a trend for these parameters to decline with the most severe disease activity, that was significant when patients with NASH also had significant fibrosis vs. mild or no fibrosis (OXPHOS CI+II: 38.6 ± 7.8 vs. 49.8 ± 12.5, p=0.04; ETC: 50.3 ± 12.9 vs. 67.5 ± 16.1; p=0.02).

Conclusion: In patients with NASH vs. simple steatosis, there is an early hepatic mitochondrial adaptation to severe insulin resistance. This adaptation is impaired when disease activity worsens, being most evident once patients develop steatohepatitis with significant fibrosis.