Selection pressure drives the co-evolution of several lipid metabolism genes in mammals

Adipose tissue is an important endocrine organ and energy supplier. Its physiological effect on the regulation of the energy balance is considered an important factor underlying the evolution of mammals. To test whether the genes controlling lipid metabolism have undergone adaptive molecular change in the evolution of mammals, in this study, we used the orthologous gene sequences of 12 important lipid metabolism proteins (leptin, OB-RL, RXRA, RXRB, RXRG, PPARA, PPARB/D, PPARG, PNLIP, ADIPOQ, LPL and UCP1) from NCBI’s databases. We found evidence that 4 of the corresponding genes (leptin, ADIPOQ, PNLIP and PPARA) have undergone positive selection in their evolutionary history and that most adaptive changes occurred during the evolution of the super-clades Laurasiatheria (placentals) and suborders within Euarchontoglires (primates and rodents). Comparisons across sets of genes showed that in a third of cases, bursts of positive selection, more than would be expected by chance, occurred on corresponding branches. We propose that the positive selection drives adaptive changes in some lipid metabolism genes in or within Laurasiatheria and Euarchontoglires clades. Along with evidence from earlier studies, our results show that co-evolution among interacting lipid metabolism proteins has taken place.