Adropin expression correlates with aging-related neuropathology in the human brain and improves neuroinflammation and cognitive function in aging mice

The putative secreted domain of adropin (residues 34-76) is sufficient for biological activity when administered by ip. injection to mice, inducing changes in mitochondrial fuel selection of skeletal muscle. To investigate whether adropin administered also regulates the brain transcriptome, RNA seq was used in 18-month-old male B6 mice treated with synthetic peptide at a dose previously shown to be effective. Mice were split into two weight matched groups, acclimated to handling and then treated with peptide (90 nmol/kg/d) suspended in 0.9% saline plus 0.1% BSA over 4 weeks. Controls were treated with diluent; injections were given daily at 0900h. Applying a cut-off using a fold-change (FC) >1.5 and a p-value of <0.05 identified a small number of responsive genes (84 upregulated, 172 downregulated). Gene enrichment analysis indicated that peptide treatment primarily changed the expression of genes involved in tissue morphogenesis (e.g. “pattern specification process”, “embryo development”, “animal morphogenesis”). Possibly related to increases in cellular proliferation and differentiation, there was also evidence for increases in large molecule synthesis. For example, RNA metabolism (“positive regulation of RNA biosynthetic process”; “positive regulation of transcription by RNA polymerase II”) and ‘macromolecule synthesis” were affected by treatment. C57BL mice were purchased at 18 months of age from Jackson Laboratories (Bar Harbor, ME). Mice were acclimated to local conditions for 2 wk and then divided into two weight matched groups (n=15/group). The mice were treated with 90 nmol/kg/d adropin ( ABClonal Science, 98.66% purity) suspended in 0.9% sterile saline with 0.1% BSA. The peptide was resuspended daily prior to injection and administered as a single ip. injection (0.1ml volume) at 0900h. Controls received saline diluent only. Mice were weighed daily; after 2 weeks of injections, mice were subjected to behavioral testing. Treatment continued during behavioral testing. At completion, mice were fasted for 6h. Blood glucose (tail snip) levels were recorded using a glucometer; blood samples were collected for analysis of measurement of insulin by ELISA (Ultra Sensitive Mouse Insulin ELISA kit, Crystal Chem USA, IL, USA). Brain tissue samples were collected and snap frozen using liquid nitrogen and subsequently used for RNA-Seq.