IDH2 and Alzheimer disease: Previous studies on post-mortem AD brains indicate reduced levels and/or activity of these key enzymes: PDH, αKGDH and IDH (Sorbi et al., 1983; Butterworth and Besnard, 1990; Mastrogiacoma et al., 1996; Gibson et al., 2000; Ko et al., 2001; Bubber et al., 2005), with PDH and αKGDH exhibiting the largest decreases in activity.