On the mechanism of fasting-associated elevations in hypothalamic cyclo(His-Pro) content.
Potential mechanism(s) underlying the fasting-associated rise in hypothalamic cyclo(His-Pro) content was explored by examining the effects of 24-hour fasting on: (i) cyclo(His-Pro) synthesis from TRH, (ii) cyclo(His-Pro) metabolism, and (iii) cyclo (His-Pro) secretion by hypothalamic tissue in vitro. The data presented here show that none of these three variables were altered due to fasting. Two additional potential changes that could cause cyclo(His-Pro) elevations during fasting are suggested. These include an in vivo decrease in hypothalamic cyclo(His-Pro) secretion that may not be apparent in vitro, and/or an increase in the synthesis of cyclo(His-Pro) from a precursor(s) other than TRH.
D000626:Aminopeptidases / Q000378:metabolism; D000818:Animals; D002855:Chromatography, Thin Layer; D005215:Fasting; D007031:Hypothalamus / Q000032:analysis / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010456:Peptides, Cyclic / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism*; D010879:Piperazines / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism; D013997:Time Factors
D010456:Peptides, Cyclic; D010879:Piperazines; D013973:Thyrotropin-Releasing Hormone; D000626:Aminopeptidases; C015924:histidyl-proline diketopiperazine