Brown adipose tissue (BAT) expresses both uncoupling protein-1 and -3 (UCP1, UCP3). Despite the role played by UCP1 in non-shivering thermogenesis is well established, the function of UCP3 has not received universal acceptance and is still under debate. In the present study we gain further insight into this aspect by evaluating the impact of the absence of UCP3 on BAT mitochondria functionality. We used wild type (WT) and UCP3 knockout (KO) female mice, housed at thermoneutrality. The lack of UCP3 did not influence mitochondrial respiration rate when using piruvate (+ malate) as respiratory substrate, while a significant reduction was observed when using glycerol-3-phosphate (G3P). When evaluating the kinetic response of the reactions involved in the oxidation of the G3P and in the formation of proton motive force to a change in membrane potential, we found an inhibition of the above reactions. No differences in the mitochondrial glycerol-3-phosphate dehydrogenase (mG3PDH) protein levels were observed between WT and KO mice, on the other hand, G3PDH in gel activity was significantly reduced in KO mice, thus indicating the involvement of a post-trasductional mechanism in such a reduction. In the presence of G3P as respiratory substrate, BAT mitochondria of KO mice showed an increase in the percentage of electrons that, during their transport by respiratory chain, leaks and reduces oxygen to superoxide; this process is also associated with a damage to mitochondrial membrane lipids as evident by the measured increase of lipid hydroperoxides levels. In addition, the expression of enzymes involved in the mitochondrial antioxidant defense such as superoxide dismutase -2 and catalase were significantly enhanced in KO mice. As a whole, these data indicate that the absence of UCP3 in BAT of mice housed at thermoneutrality influences mG3PDH activity and mitochondrial oxidative stress.
Absence of UCP3 impacts mitochondrial glycerol-3-phosphate dehydrogenase activity and enzymatic antioxidant capacity in brown adipose tissue of mice acclimated at thermoneutrality
Giuseppe Petito;Antonia Lanni;
2018
Abstract
Brown adipose tissue (BAT) expresses both uncoupling protein-1 and -3 (UCP1, UCP3). Despite the role played by UCP1 in non-shivering thermogenesis is well established, the function of UCP3 has not received universal acceptance and is still under debate. In the present study we gain further insight into this aspect by evaluating the impact of the absence of UCP3 on BAT mitochondria functionality. We used wild type (WT) and UCP3 knockout (KO) female mice, housed at thermoneutrality. The lack of UCP3 did not influence mitochondrial respiration rate when using piruvate (+ malate) as respiratory substrate, while a significant reduction was observed when using glycerol-3-phosphate (G3P). When evaluating the kinetic response of the reactions involved in the oxidation of the G3P and in the formation of proton motive force to a change in membrane potential, we found an inhibition of the above reactions. No differences in the mitochondrial glycerol-3-phosphate dehydrogenase (mG3PDH) protein levels were observed between WT and KO mice, on the other hand, G3PDH in gel activity was significantly reduced in KO mice, thus indicating the involvement of a post-trasductional mechanism in such a reduction. In the presence of G3P as respiratory substrate, BAT mitochondria of KO mice showed an increase in the percentage of electrons that, during their transport by respiratory chain, leaks and reduces oxygen to superoxide; this process is also associated with a damage to mitochondrial membrane lipids as evident by the measured increase of lipid hydroperoxides levels. In addition, the expression of enzymes involved in the mitochondrial antioxidant defense such as superoxide dismutase -2 and catalase were significantly enhanced in KO mice. As a whole, these data indicate that the absence of UCP3 in BAT of mice housed at thermoneutrality influences mG3PDH activity and mitochondrial oxidative stress.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
