Deletion of Alzheimer's Disease Risk Gene ABCA7 Alters White Adipose Tissue Development and Leptin Levels.

ATP-binding cassette A7 (ABCA7) is a genetic risk factor for late-onset Alzheimer's disease (AD). It belongs to a group of transporter genes that specializes in regulating lipid transport in the periphery as well as in the brain. ABCA7 has been implicated in a number of roles relating to AD pathology, including phagocytic clearance of amyloid-β peptides. We have discovered that deletion of ABCA7 in mouse causes a dramatic reduction in white adipose tissue (WAT) in female mice. WAT is important in AD context because it is the primary producer of leptin, which is a hormone that is known to modulate AD neuropathology. WAT in male Abca7-/- mice was not altered. The pathological link between ABCA7 and WAT that impacts on AD is unknown. Our transcription analysis revealed that lipin-1 expression was significantly upregulated in female Abca7-/- mice, indicating that ABCA7 affects WAT development. The circulating leptin level was significantly reduced in female Abca7-/- mice without any change in WAT leptin mRNA or protein expression, indicating that ABCA7 does not affect leptin production, but alters the circulating leptin level indirectly by affecting WAT development. Insulin is a key hormone that regulates WAT development, i.e., adipogenesis, and it was significantly reduced in female Abca7-/- mice. These data when put together suggest that ABCA7 plays a role in regulating WAT development and consequently circulating leptin levels, which are known to modulate AD neuropathology.