Peroxisome proliferator-activated receptors as regulators of lipid metabolism; tissue differential expression in adipose tissues during cold acclimatization and hibernation of jerboa ( Jaculus orientalis)

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Brown (BAT) and white (WAT) adipose tissues play a key role in the body energy balance orchestrated by the central nervous system. Hibernators have developed a seasonal obesity to respond to inhospitable environment. Jerboa is one of the deep hibernator originated from sub-desert highlands. Thus, this animal represents an excellent model to study cold adaptation mechanism. We report that the adipogenic factor PPARγ exhibits a differential expression between BAT and WAT at mRNA level. A specific induction was only seen in WAT of pre-hibernating jerboa. Interestingly, PPAR β/δ is specifically induced in BAT and brain of pre-hibernating jerboa, highlighting for the first time the possible key role of this ubiquitous isoform in the cold adaptation of this true hibernator. Inductions of PPARγ 2 in WAT and PPAR β/δ in BAT are blunted by a hypolipemic drug, the ciprofibrate. These changes may be correlated with hibernation arrest and death of treated jerboa. Mitochondrial acyl-CoA dehydrogenase and peroxisomal acyl-CoA oxidase activities in brown and white adipose tissues are decreased up to 85% during cold acclimatization (without food privation). These enzyme activities are subject to a strong induction in BAT and in WAT (3.4–7.5 fold) during the hibernation period. The BAT thermogenesis marker is also largely induced (~4 fold of UCP1 mRNA level) during pre-hibernation period. Unexpectedly, treatment with ciprofibrate deeply affects lipolysis in BAT by increasing acyl-CoA dehydrogenase activity (3.4 fold) and acyl-CoA oxidase at both activity and mRNA levels (2.8 and 3.8 fold, respectively) and enhances strongly UCP1 mRNA level (9.5 fold) during pre-hibernation.