Apolipoprotein E ε4 modulates astrocyte neuronal support functions in the presence of amyloid-β.
Rebecca M FleemanMadison K KuhnDennis C ChanElizabeth A ProctorPublished in: Journal of neurochemistry (2023)
Apolipoprotein E (APOE) is a lipid transporter produced predominantly by astrocytes in the brain. The ε4 variant of APOE (APOE4) is the strongest and most common genetic risk factor for Alzheimer's disease (AD). Although the molecular mechanisms of this increased risk are unclear, APOE4 is known to alter immune signaling and lipid and glucose metabolism. Astrocytes provide various forms of support to neurons, including regulating neuronal metabolism and immune responses through cytokine signaling. Changes in astrocyte function due to APOE4 may therefore decrease neuronal support, leaving neurons more vulnerable to stress and disease insults. To determine whether APOE4 alters astrocyte neuronal support functions, we measured glycolytic and oxidative metabolism of neurons treated with conditioned media from APOE4 or APOE3 (the common, risk-neutral variant) primary astrocyte cultures. We found that APOE4 neurons treated with conditioned media from resting APOE4 astrocytes had similar metabolism to APOE3 neurons treated with media from resting APOE3 astrocytes, but treatment with astrocytic conditioned media from astrocytes challenged with amyloid-β (Aβ), a key pathological protein in AD, caused APOE4 neurons to increase their basal mitochondrial and glycolytic metabolic rates more than APOE3 neurons. These changes were not due to differences in astrocytic lactate production or glucose utilization, but instead correlated with increased glycolytic ATP production and a lack of cytokine secretion in response to Aβ. Additionally, we identified that astrocytic cytokine signatures could predict basal metabolism on neurons treated with the astrocytic conditioned media. Together, these findings suggest that in the presence of Aβ, APOE4 astrocytes alter immune and metabolic functions that result in a compensatory increase in neuronal metabolic stress.
Keyphrases
- cognitive decline
- high fat diet
- spinal cord
- mild cognitive impairment
- immune response
- cerebral ischemia
- insulin resistance
- adipose tissue
- gene expression
- fatty acid
- heart rate
- dendritic cells
- spinal cord injury
- newly diagnosed
- brain injury
- toll like receptor
- heart rate variability
- weight loss
- metabolic syndrome
- blood glucose
- functional connectivity
- african american
- binding protein
- resting state
- combination therapy