Abstract
Copper (Cu) deficiency impairs cerebellar development including biosynthetic processes like myelination and synaptogenesis. The activity of cerebellar mitochondrial cuproenzyme cytochrome c oxidase is markedly lower in Cu deficient rat pups and is accompanied by higher lactate levels indicating mitochondrial inhibition. Cu deficiency impaired energy metabolism is thought to contribute to developmental delays, but specific mechanisms linking these phenomena have remained unexplored. AMP-activated protein kinase (AMPK) is a cellular energy sensor that is activated during mitochondrial inhibition and shuts down biosynthetic processes to help conserve cellular ATP levels. Activated AMPK phosphorylates and inhibits acetylCoA carboxylase (ACC), the first enzyme in fatty acid biosynthesis. We hypothesize that AMPK is activated and ACC inhibited in Cu deficient cerebella. Perinatal copper deficiency was studied in young rats in rapidly frozen cerebella. Compared to copper-adequate (Cu+) pups, copper-deficient (Cu-) pups were hypothermic, had lower brain copper levels and markedly higher cerebellar lactate. Concentration of phosphorylated AMPK (pAMPK), indicating AMPK activation, was robustly higher in Cu- cerebella of rat pups at two ages and in two separate experiments. Compared to Cu+ cerebella, pACC content was significantly higher in all Cu- samples. Mechanisms leading to AMPK activation remain elusive. Higher AMP/ATP ratios and increased reactive nitrogen species (RNS) can lead to AMPK activation. ATP and AMP concentrations were unaltered and nitric oxide metabolites and 3-nitrotyrosine peptide levels remained unchanged in Cu- cerebella. AMPK activation may explain how ATP levels can be maintained even with a severe mitochondrial loss of CCO function.