In support of this notion, while being protective in X-ALD fibroblasts, increased SCD1 activity in multiple sclerosis (MS), Alzheimer’s disease (AD), and Parkinson’s disease (PD) is associated with the formation of disease-promoting microglia and neuronal dysfunction (see Sect. 3.2–3.4). This evidence concerns the gene SCD and early-onset autosomal dominant Alzheimer disease.