Effects of adiponectin transgenic expression in liver of nonalcoholic steatohepatitis model mice

We have previously reported that transgenic mice expressing nuclear sterol regulatory element-binding protein 1c (nSREBP-1c) in adipose tissue under the control of aP2 promoter, an inherited lipodystrophic model with insulin resistance and fatty liver, developed with age liver lesions similar to those of human nonalcoholic steatohepatitis (NASH). Because the spontaneous NASH model mice had marked hypoadiponectinemia, here we assessed the effect of adiponectin transgenically expressed in the liver of nSREBP-1c transgenic mice. The nSREBP-1c/adiponectin double-transgenic mice showed hepatic adiponectin production and restored circulating adiponectin levels. Both subtypes of adiponectin receptors proved to be expressed normally in the liver. Peroxisome proliferator-activated receptor-alpha was up-regulated in the double-transgenic mice. Histologic findings similar to those observed in the liver specimens of patients with NASH were observed in the livers from nSREBP-1c transgenic mice at the age of 30 weeks. In contrast, the NASH-like hepatic lesions were obviously attenuated in age-matched double-transgenic mice. Immunoreactivity of 8-hydroxy-2'-deoxyguanosine and proliferating cell nuclear antigen-positive cells were increased in nSREBP-1c transgenic mice, but not in the double-transgenic mice. Postload plasma glucose levels were significantly lower in the double-transgenic mice compared with nSREBP-1c transgenic mice, whereas serum leptin levels did not differ significantly in the 2 groups. These observations suggest that hypoadiponectinemia plays a key role in the pathogenesis of NASH associated with insulin resistance and may provide a clue to the novel therapy for human NASH.