Based on the differences in metabolic activity observed between primary AEC2s from non-fibrotic and IPF lungs, and in conjunction with our previous report that AEC2s preferentially utilize lactate as a metabolic substrate [18], we next examined whether this metabolic shift in IPF AEC2s is associated with changes in LDH isoenzyme tetramer composition associated with forms favoring pyruvate to lactate conversion (Fig. 2; i.e., higher LDHA to LDHB subunit ratios and, therefore, more LDH4 and 5 forms of the active tetramers; illustrated in Fig. 2A). This evidence concerns the gene LDHA and idiopathic pulmonary fibrosis.