As diabetes accelerates NASH, a role for the growth factor, CTGF/CCN2, in NASH pathogenesis was investigated using anti-CTGF neutralising antibody intervention in a rodent diabetes model.
Methods: Male wild type C57BL/6 mice were fed Chow or high fat diet (HFD) for 15 weeks. Then some per group were randomly assigned low dose streptozotocin (STZ: 3x65mg/kg) to induce type 2 diabetes. Some mice from each group were treated with in-house generated rabbit anti-rhCTGF neutralising antibody (i.p. 150µg per mouse twice/week), for a subsequent 10 weeks. Normal rabbit IgG (150µg per mouse twice/week) was used as control.
Results: NASH developed in HFD plus diabetes (HFD+DM) across 10 weeks of diabetes (25 weeks’ study). Anti-CTGF neutralising antibody prevented collagen-I (~10 fold) and collagen-III (~7 fold) mRNA induction (p<0.05) and showed a trend to normalise collagen IV-α1, collagen-VI and FN mRNA induction in HFD+DM. The neutralising antibody also significantly prevented pro-inflammatory MCP-1 mRNA induction (4.2 fold, p<0.05) and showed a trend to normalise TNF-α, IL-1β and IL-6 mRNA in the HFD+DM group. At the protein level, collagen accumulation by PSR stain and collagen-I protein increases in HFD+DM, were prevented (55% for PSR and 45% for collagen-I) by anti-CTGF antibody (each P<0.05). Phosphorylation of the pro-fibrotic ERK signalling pathway in liver was prevented by the in vivo neutralising antibody (p<0.05). In addition, profiles of CCN members detected in the NASH model showed CCN1 mRNA level was induced (1.7 fold) in the HFD+DM model (p<0.05), CCN3 was down-regulated in HFD+DM at mRNA and protein level, whilst there was no dysregulation for CCN4, CCN5 or CCN6. CCN3 down-regulation was prevented by the anti-CTGF neutralising antibody (p<0.05).
In summary, this in vivo data indicates that CTGF/CCN2 is a molecular target in NASH exacerbated by high fat diet with diabetes, and that ERK signalling is implicated in this process.