Design,synthesis and biological evaluation of leptin fragments

摘要

Leptin(Lep),a hormone mainly secreted by the white adipose tissue,is involved in the control of energy homeostasis.When signaling to the central nervous system,this protein plays an important role in food intake,reproductive and respiratory functions and weight maintenance.In an attempt to identify regions of the leptin molecule responsible for its important bioactivities,we synthesized and tested six peptides based on the three-dimensional structure of the protein:Ac-Lep_(23-47)-NH_2(I),Ac-Lep_(48-71)-NH_2(II),Ac-Lep_(72-88)-NH_2(III),Ac-Lep_(92-115)-NH_2(IV),Ac-[Ser~(117)]Lep_(116-140)-NH_2(V)and Ac-Lep_(141-164)-NH_2(VI).When injected intravenously,the fragments were unable to induce Fos immunoreactivity(Fos-ir)in rat hypothalamus as the recombinant human leptin did.CD studies showed that in solution fragments I,IV and VI exhibited similar structural,behavior to that presented in native leptin,while fragments III and V did not.Thus,no clear correlation between structure determined by CD and biological activity was found.For this reason,we decided to evaluate whether these fragments could be recognized by leptin receptors present in HP-75 cells.Their correspondent dimeric form,generated by a disulfide bridge formation,peptide [D-Leu~4]-OB3,introduced by Rozhavskaya-Arena et al as a reducer of body weight gain and food intake in ob/ob mice,and its analogue related to the human sequence were also synthesized and tested.