In this episode, we explore the role of Vitamin D in brain health, focusing on how its active form, calcitriol (1,25-dihydroxyvitamin D3), influences cognitive function and neuroprotection. We’ll discuss the synthesis of Vitamin D, its conversion into its active form, and its ability to cross the blood-brain barrier to exert effects on neurons and glial cells. Additionally, we will highlight how calcitriol regulates gene expression through Vitamin D Response Elements (VDREs), impacting inflammation, antioxidant defense, and neurotrophic support. Finally, we touch on the symptoms of low Vitamin D and the link to cognitive decline.
1. Introduction to Vitamin D and the Brain
- Forms of Vitamin D, synthesis, conversion/activation, and its role in the brain
- Vitamin D2 (ergocalciferol), plant-based sources like mushrooms
- Vitamin D3 (cholecalciferol), UVB radiation, animal-based foods
3. Synthesis and Conversion of Vitamin D3
- Synthesis in the skin: 7-dehydrocholesterol converts to pre-vitamin D3
- Conversion in the liver: 25-hydroxylase converts D3 to 25-hydroxyvitamin D (calcidiol)
- Final activation in the kidneys: 1-alpha-hydroxylase converts calcidiol to 1,25-dihydroxycholecalciferol (calcitriol), the active form
4. Calcitriol and the Blood-Brain Barrier
- Calcitriol’s lipophilic nature, crossing the BBB
- The structure and function of the blood-brain barrier
- How calcitriol diffuses across the BBB and reaches brain cells
5. Calcitriol's Role in the Brain
- Interaction with Vitamin D receptors (VDRs) in neurons and glial cells
- VDRs in key brain regions: hippocampus, prefrontal cortex, cerebellum, basal ganglia
- Binding of calcitriol to VDRs, conformational change, and formation of the VDR-RXR complex
6. Gene Regulation via Vitamin D Response Elements (VDREs)
- Overview of VDREs in promoter regions of genes
- Role of calcitriol in activating or repressing gene transcription
7. Impact on Inflammatory Responses
- VDREs in anti-inflammatory genes promote IL-10 expression
- Calcitriol’s role in reducing pro-inflammatory cytokines like IL-6 and TNF-alpha
- VDREs’ role in regulating genes that promote BDNF
- BDNF’s impact on neuron survival, growth, and synaptic connectivity
- VDREs influence the expression of glutathione peroxidase and superoxide dismutase (SOD)
- The role of these enzymes in defending neurons from oxidative stress
10. Brain Regions & Calcitriol
- Hippocampus: Learning, memory, neurogenesis, synaptic plasticity
- Prefrontal Cortex: Executive functions, mood regulation
- Cerebellum: Motor control, cognitive processing, calcium homeostasis
- Basal Ganglia: Movement regulation, protection of dopaminergic neurons
- Amygdala: Emotion processing, fear, anxiety, stress response
11. Interconnection of Brain Regions
- How Vitamin D’s effects on neurotransmitter regulation, anti-inflammatory action, and calcium homeostasis create a global protective effect.
- Recap of calcitriol’s cellular mechanisms and neuroprotective effects
- Symptoms of low Vitamin D
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