Impaired adult hippocampal neurogenesis in a mouse model of familial hypercholesterolemia: A role for the LDL receptor and cholesterol metabolism in adult neural precursor cells

Daiane F. Engel, Anna N. Grzyb, Jade de Oliveira, Alexandra Pötzsch, Tara L. Walker, Patricia S. Brocardo, Gerd Kempermann, Andreza F. de Bem

Hypercholesterolemia, especially in its inherited form, is an important risk factor for the development of neurodegenerative diseases. Familial hypercholesterolemia (FH) is caused by genetic abnormalities predominantly in the low-density lipoprotein (LDL) receptor (LDLr) gene, resulting in an ineffective metabolism of LDL particles. However, it remains unclear whether the chronic exposure to high circulating cholesterol levels or the dysfunction of the LDLr as such contributes to the altered central nervous system function. Engel and colleagues explored if adult hippocampal neurogenesis might be involved in cognitive dysfunction associated with FH and found that that impairment in hippocampal neurogenesis might contribute to the behavioral phenotype in LDLr-/- mice.

Objective: In familial hypercholesterolemia (FH), mutations in the low-density lipoprotein (LDL) receptor (LDLr) gene result in increased plasma LDL cholesterol. Clinical and preclinical studies have revealed an association between FH and hippocampus-related memory and mood impairment. We here asked whether hippocampal pathology in FH might be a consequence of compromised adult hippocampal neurogenesis.

Methods: We evaluated hippocampus-dependent behavior and neurogenesis in adult C57BL/6JRj and LDLr−/− mice. We investigated the effects of elevated cholesterol and the function of LDLr in neural precursor cells (NPC) isolated from adult C57BL/6JRj mice in vitro.

Results: Behavioral tests revealed that adult LDLr−/− mice showed reduced performance in a dentate gyrus (DG)-dependent metric change task. This phenotype was accompanied by a reduction in cell proliferation and adult neurogenesis in the DG of LDLr−/− mice, suggesting a potential direct impact of LDLr mutation on NPC. Exposure of NPC to LDL as well as LDLr gene knockdown reduced proliferation and disrupted transcriptional activity of genes involved in endogenous cholesterol synthesis and metabolism. The LDL treatment also induced an increase in intracellular lipid storage. Functional analysis of differentially expressed genes revealed parallel modulation of distinct regulatory networks upon LDL treatment and LDLr knockdown.

Conclusions: Together, these results suggest that high LDL levels and a loss of LDLr function, which are characteristic to individuals with FH, might contribute to a disease-related impairment in adult hippocampal neurogenesis and, consequently, cognitive functions.