Multiple roles of PPARα in brown adipose tissue under constitutive and cold conditions

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Abstract
Peroxisome proliferator‐activated receptor α (PPARα) is a member of the nuclear receptor family, regulating fatty acid degradation in many organs. Two‐dimensional SDS‐PAGE of brown adipose tissue (BAT) from PPARα‐null mice produced a higher‐density spot. Proteomic analysis indicated that the protein was pyruvate dehydrogenase β (PDHβ). To observe PDHβ regulation in BAT, the organ was stimulated by long‐term cold exposure, and the activities of associated enzymes were investigated. Histological and biochemical analyses of BAT showed a significant decrease in the triglyceride content in wild‐type mice and some degree of decrease in PPARα‐null mice on cold exposure. Analyses of molecules related to glucose metabolism showed that the expression of PDHβ is under PPARα‐specific regulation, and that glucose degradation ability may decrease on cold exposure. In contrast, analyses of molecules related to fatty acid metabolism showed that numerous PPARα/γ target molecules are induced on cold exposure, and that fatty acid degradation ability in wild‐type mice is markedly enhanced and also increases to same degree in PPARα‐null mice on cold exposure. Thus, this study proposes novel and multiple roles of PPARα in BAT.