TDO2 and Hypoglycemia: It has been observed that mice deficient in KLF15 expression have more pronounced fasting-induced hypoglycemia due to defects in the availability of amino acid-catabolizing enzymes, such as alanine aminotransferase 1 (ALT1), proline dehydrogenase (ProDH), tryptophan 2,3-dioxygenase (TDO2) and 4-hydroxyphenylpyruvic acid dioxygenase (HPD) [62].