Ramy Younes1, Chiara Rosso1, Melania Gaggini2, Lavinia Mezzabotta1, Milena Marietti1, Fabrizia Carli2, Federico Salomone3, Emma Buzzigoli2, Gian Paolo Caviglia1, Chiara Barbieri2, Maria Lorena Abate1, Antonina Smedile1, Giorgio Maria Saracco1, Quentin M. Anstee4, Diana J. Leeming5, Amalia Gastaldelli1, Detlef Schuppan6, Elisabetta Bugianesi1
1. Department of Medical Sciences, University of Turin, Torino, Italy. 2. CNR, Institute of Clinical Physiology, Pisa, Italy.
3. Division of Gastroenterology, Ospedale Acireale, Catania, Italy. 4. Newcastle University, Newcastle Upon Tyne, United Kingdom. 5. Biomarkers and research, Nordic Bioscience, Herlev, Denmark.
6. Translational Immunology , University Medical Center, Mainz, Germany.
Background. Impaired lipid metabolism due to insulin resistance (IR) has been associated with liver damage in NAFLD, but the exact role of glucose metabolism is unclear. Procollagen type III is upregulated in the early development of liver fibrosis and its C-terminal neo-epitope (Pro-C3) is a non-invasive marker of fibrogenesis. We evaluated the association between sites of IR and
fibrogenesis/fibrosis.
Methods. We analyzed data from 34 non-diabetic NAFLD subjects who underwent tracer studies (6,6D2glucose and D5glycerol). Tracer enrichment was determined by GCMS. Hepatic IR was calculated from endogenous glucose production (Hep-IR), peripheral IR from glucose clearance (GC) and adipose tissue IR (AT-IR) from glycerol Ra. Plasma Pro-C3 levels were measured by competitive ELISA. Histology was scored according to Kleiner.
Results. Plasma Pro-C3 increased by BMI classes (12±4.5vs16.5±7.7vs28.2±14.7, p=0.020) and in relation to waist circumference (r=0.39, p=0.027). Pro-C3 levels correlated with AST and ALT (r=0.51, p=0.024 and 0.46, p=0.007), with insulin and C-peptide (r=0.52, p=0.002 and r=0.67, p<0.001) but not with FFA levels (r=0.19, p=0.299). The percentage of liver fat correlated with plasma insulin, C-peptide (r=0.53, p=0.001 and r=0.70, p<0.001) and Pro-C3 levels (r=0.57, p<0.001). Both AT-IR and Hep-IR were associated with liver fat (r=0.35, p=0.044 and r= 0.43, p=0.013 respectively). The stage of fibrosis was proportional to plasma levels of insulin (rs=0.46, p=0.007), C-peptide (rs=0.53, p=0.002), Pro-C3 (rs=0.65, p<0.001) and was inversely related to GC (rs= - 0.34, p=0.050).
Pro-C3 levels were inversely related to GC (r= -0.35, p=0.050) but not to Hep-IR and AT-IR. By using published Pro-C3 cut-offs, NAFLD at high risk of progression had higher insulin and C-peptide levels, liver fat and lower GC (Table 1). For the same cut-off, the ability of Pro-C3 to diagnose F≥3 using AUROC was 0.96 (CI 0.84-0.99; PPV 60, NPV 96); the AUROC for combined Pro-C3 and C-peptide further increased to 0.98 (CI 0.86-1; PPV 88, NPV 100).
Conclusions. In non-diabetic subjects with NAFLD, liver fibrosis and fibrogenesis are associated with insulin secretion and decreased glucose uptake in the muscle suggesting an important role of peripheral IR in the onset and progression of NASH.
Conclusions. In non-diabetic subjects with NAFLD, liver fibrosis and fibrogenesis are associated with increased insulin secretion by the pancreas and decreased glucose uptake by the muscle suggesting an important role of peripheral IR in the onset and progression of NASH.
Table 1. Pro-C3 < 20 ng/mL Pro-C3 ≥ 20 ng/mL BMI (kg/m2) 26,391 ± 3.6 29,681 ±2.4 0.0189 INSULIN (mU/mL) 10,8 ± 6.4 17,1 ± 7.1 0.0103 C-peptide (pmol/mL) 0,8 ± 0.2 1,3 ±0.2 0.0001 GC (ml/min * kg) 1,69 ± 0.29 1,41 ±0.15 0.0167 Hep-IR 102 ± 49 133 ± 74 0.1693 AT-IR 32 ± 21 36 ± 20 0.5178 FFA (mmol/L) 0,598 ±0.256 0,724 ± 0.266 0.1401
