👤 Kelly Hartigan

Overexpression of the low-density lipoprotein receptor (LDLR) is known to decrease apolipoprotein E (APOE) levels and alleviate amyloid beta (Aβ) pathology. We hypothesized that inhibiting the Inducible Degrader of LDLR (IDOL), an enzyme that ubiquitinates LDLR for degradation, would increase endogenous LDLR levels and attenuate amyloid pathology. To investigate the cell-type-specific role of IDOL, we generated Idol conditional knockout mice on an Aβ-amyloidosis mouse model and performed biochemical, histological, and multi-omics analyses. We demonstrated that neuronal, but not microglial, Idol deletion reduced amyloid accumulation and altered brain LDLR and APOE levels, indicating the critical role of neuronal IDOL-LDLR in amyloid pathology. In addition, neuronal Idol deletion increased the levels of Reelin receptors important for synaptic function, and single-nuclei RNA sequencing revealed significant changes associated with synaptic organization. Neuronal IDOL, but not microglial IDOL, plays a key role in Alzheimer's disease pathogenesis by regulating the levels of brain APOE receptors. Neuronal, but not microglial, Idol deletion reduces amyloid burden and modulates brain APOE and LDLR levels. Deletion of neuronal Idol increases the levels of APOER2 and VLDLR, the Reelin receptors, in the brain. Single-nuclei RNA sequencing highlights the neuronal IDOL's impact on inhibitory neurons and synaptic organization. Targeting neuronal IDOL may provide multiple therapeutic benefits in Alzheimer's disease by modulating APOE receptors. Show less

Adipose tissue expansion requires growth and proliferation of adipocytes and the concomitant expansion of their stromovascular network. We have used an ex vivo angiogenesis assay to study the mechanisms involved in adipose tissue expansion. In this assay, adipose tissue fragments placed under pro-angiogenic conditions form sprouts composed of endothelial, perivascular, and other proliferative cells. We find that sprouting was directly stimulated by insulin and was enhanced by prior treatment of mice with the insulin sensitizer rosiglitazone. Moreover, basal and insulin-stimulated sprouting increased progressively over 30 weeks of high fat diet feeding, correlating with tissue expansion during this period. cDNA microarrays analyzed to identify genes correlating with insulin-stimulated sprouting surprisingly revealed only four positively correlating (Fads3, Tmsb10, Depdc6, and Rasl12) and four negatively correlating (Asph, IGFbp4, Ppm1b, and Adcyap1r1) genes. Among the proteins encoded by these genes, IGFbp4, which suppresses IGF-1 signaling, has been previously implicated in angiogenesis, suggesting a role for IGF-1 in adipose tissue expandability. Indeed, IGF-1 potently stimulated sprouting, and the presence of activated IGF-1 receptors in the vasculature was revealed by immunostaining. Recombinant IGFbp4 blocked the effects of insulin and IGF-1 on mouse adipose tissue sprouting and also suppressed sprouting from human subcutaneous adipose tissue. These results reveal an important role of IGF-1/IGFbp4 signaling in post-developmental adipose tissue expansion. Show less