During fasting, one of the mechanisms for the synthesis of glucose involves protein degradation, followed by the production and export of alanine from muscle tissue to liver. Alanine is metabolized by deamination and gluconeogenesis in the liver in the glucose-alanine cycle [55]. Since hepatic levels of alanine were lower in PPARα −/− mice, it was suggested that the enzymes controlling this cycle may be constitutively more active in PPARα −/− mice [54]. It should be noted that PPARα has a more general suppressive effect on the trans- and deamination of amino acids in rodents [56].
