OGDH and Thiamine deficiency: Since vitamin B1 (thiamine) is essential for enzymatic activity of PDH and OGDH, thiamine deficiency decreases the activities of both PDH and OGDH (Figure 3), which is clinically characterized by increased plasma levels of pyruvate and lactate (Frohman and Day, 1949; Park and Gubler, 1969; Falder et al., 2010; Sweet and Zastre, 2013; Hernandez-Vazquez et al., 2016).