FFAR2 and early-onset autosomal dominant Alzheimer disease: Bicyclo[2.2.1]heptan-2-ol, 1,3,3-trimethyl-(fenchol), a terpene found in various plant oil extracts [43], has been demonstrated as a potent activator of free fatty acid receptor 2 (FFAR2) signaling, which may prevent the increase in amyloid-beta (Aβ)-stimulated neuronal toxicity in Alzheimer’s disease [44].