Impairment of PGC-1alpha expression, neuropathology and hepatic steatosis in a transgenic mouse model of Huntington's disease following chronic energy deprivation

We investigated the ability of AMP-activated protein kinase (AMPK) to activate PPARgamma coactivator-1alpha (PGC-1alpha) in the brain, liver and brown adipose tissue (BAT) of the NLS-N171-82Q transgenic mouse model of Huntington's disease (HD). In the striatum of the HD mice, the baseline levels of PGC-1alpha, NRF1, NRF2, Tfam, COX-II, PPARdelta, CREB and ERRalpha mRNA and mitochondrial DNA (mtDNA), were significantly reduced. Administration of the creatine analog beta guanidinopropionic acid (GPA) reduced ATP and PCr levels and increased AMPK mRNA in both the cerebral cortex and striatum. Treatment with GPA significantly increased expression of PGC-1alpha, NRF1, Tfam and downstream genes in the striatum and cerebral cortex of wild-type (WT) mice, but there was no effect on these genes in the HD mice. The striatum of the untreated HD mice showed microvacuolation in the neuropil, as well as gliosis and huntingtin aggregates, which were exacerbated by treatment with GPA. GPA treatment produced a significant increase in mtDNA in the cerebral cortex and striatum of WT mice, but not in HD mice. The HD mice treated with GPA had impaired activation of liver PGC-1alpha and developed hepatic steatosis with accumulation of lipids, degeneration of hepatocytes and impaired activation of gluconeogenesis. The BAT in the HD mice showed vacuolation due to accumulation of neutral lipids, and age-dependent impairment of UCP-1 activation and temperature regulation. Impaired activation of PGC-1alpha, therefore, plays an important role in the behavioral phenotype, metabolic disturbances and pathology of HD, which suggests the possibility that agents that enhance PGC-1alpha function will exert therapeutic benefits in HD patients.