Background: D-4F is an apolipoprotein-A1 mimetic peptide that improves stroke outcome in non-diabetic mice. In this study, we employ D-4F as a novel neurorestorative treatment for stroke in type 2 diabetic mice and investigate the ATP-binding cassette transporter (ABCA1) signaling pathway for treatment derived benefits.
Methods: Male BKS.Cg-m+/+Leprdb/J (db/db)-T2DM mice (2-3m) and brain specific ABCA1 knockdown (ABCA1-B/-B) and control ABCA1fl/fl mice induced with T2DM using a combination of high fat diet and low dose Streptozotocin, were subject to distal MCAo (dMCAo) and treated with or without D-4F (16mg/kg, oral) starting 24h after dMCAo daily for 14 days (n=8/group). Following neurological evaluation, animals were sacrificed at 14 days after stroke. FITC labeled D-4F was administered orally at 24h and 48h after dMCAo (n=6/group) to test if D-4F passes the blood brain barrier. Electron Microscopy was employed to evaluate myelination. Laser capture micro-dissection was employed to extract tissue from the ipsilateral corpus callosum to test ABCA1 gene expression.
Results: D-4F treatment in T2DM stroke mice significantly improves neurological function, increases axon density, arteriogenesis and angiogenesis in the ischemic boundary zone compared to non-treated T2DM stroke mice (p<0.05). FITC labeled D-4F passes the blood brain barrier and homes to ischemic brain regions. D-4F treatment in T2DM stroke mice significantly increases ABCA1 gene expression. D-4F co-localizes with blood vessels, oligodendrocytes, and ABCA1 positive cells, while ABCA1 co-localizes with neurons and endothelial cells in the ischemic brain. ABCA1-B/-B mice have significantly decreased myelination compared to ABCA1fl/fl mice in the white matter tracts of the corpus callosum. D-4F treatment significantly improves neurological functional outcome after stroke in T2DM-ABCA1-fl/fl mice but not in T2DM-ABCA1-/- mice, indicating that ABCA1 signaling is a key mediator of D-4F induced neurorestorative effects after T2DM stroke in mice.
Conclusions: D-4F treatment in T2DM mice subjected to stroke significantly improves stroke outcome, vascular and white matter remodeling which may be attributed, at least in part, to D-4F induced increased ABCA1 signaling activity.