Copper deficiency results in AMP-activated protein kinase activation and acetylCoA carboxylase phosphorylation in rat cerebellum

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 acetyl CoA carboxylase (ACC), the first enzyme in fatty acid biosynthesis. We hypothesize 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.

Perinatal Copper Deficiency Alters Rat Cerebellar Purkinje Cell Size and Distribution

“…This protocol was approved by the University of Minnesota Animal Care Committee. This paradigm is similar to previous recent work [20].…”

“…We have also observed similar regiospecific cortical necrosis (unpublished data). However, focus of the current experiments was on cerebellum to extend recent biochemical work on CuD rat pup cerebellum [20,38,39,49]. Furthermore, work in both brindled mice and humans with Menkes disease reported more severe changes in cerebellum than other regions [50,51].…”

“…Ataxia has long been associated with copper deficiency, but the underlying mechanisms for this behavior were controversial. Recent findings have characterized biochemical abnormalities in CuD rat cerebella consistent with abnormal mitochondria [20,38]. Interestingly, in vivo proton NMR did not detect any alteration in cerebellar levels of glutamate or GABA following copper deficiency [39].…”

“…Cytochrome c oxidase (CCO) is a mitochondrial copperdependent enzyme responsible for ATP synthesis and susceptible to copper restriction. Recent biochemical findings in cerebella of CuD rats on CCO function and expression confirm that cerebellum is a sensitive target of dietary copper limitation [19,20]. Both macular and brindled mice mutants also show reduced CCO activity [21,22].…”

Gestational-neonatal iron deficiency suppresses and iron treatment reactivates IGF signaling in developing rat hippocampus

“…Although iron deficiency is common to these perinatal nutrient deficiencies (4,50), the similarity of brain developmental defects suggests that hippocampal IGF signaling is likely impaired in all of these preclinical rodent models. In this regard, reduced IGF signaling may be a common mechanism underlying hypomyelination in thyroid, copper, and ID brains (4,6,17,31), abnormal neural differentiation in ID hippocampus (34,60), and lower granular cell number observed in the DG of the rodent model of perinatal nutrition insufficiency (8). Thus, targeting the IGF signaling pathway may lead to novel therapeutic strategies to prevent long-term neurological abnormalities associated with perinatal nutrient deficiencies.…”